Technical Program
aging following characteristic evolution paths. The fine C1. Light Metals and Alloys- precipitation scenarios revealed in our studies are rather Aluminum: I different from previous understandings in the textbooks Symsposium Organizers: and literatures published thus far. Baiqing Xiong, GRINM Group Co. Ltd., China; Yoshihito 9:00-9:20(1217796) Kawamura, Kumamoto University, Japan; Young Min Kim, Korea Institute of Materials Science (KIMS), Japan; Jian-Feng Anisotropic Behavior and Related Deformation Nie, Monash University, Australia; Diran Apelian, Worceste Mechanism of Al/Mg/Al Clad Sheet Polytechnic Institute, USA Toko Tokunaga, Kumamoto university, Japan Tuesday AM Room: Presidium Conference Room In terms of energy and resource savings, Al and Mg August 20, 2019 Symsposium: C1 alloys are ideal materials for vehicles because of their low density and high recyclability. These attractive Chairs: characteristics lead to wide attention of using these Brajendra Mishr, Worcester Polytechnic Institute, alloys together in one component. The authors have United States developed a fabrication process of Al/Mg/Al clad sheet Jianghua Chen, Hunan University, China by hot extrusion and subsequent hot rolling. The sheet exhibited a significant tensile elongation of more than 8:30-9:00 Keynote (1233466) 700% at 300℃ and at 1.0×10-3s-1. No cracks were observed at the Al/Mg interface after the elongation.
Tuesday AM | August 20, 2019 AM | Tuesday Electron Microscopy for Aluminum Alloys as The large elongation of the sheet is classified into the Light-Weight Industry Materials superplasticity in terms of the elongation and the strain Jianghua Chen, Hunan University, China rate sensitivity. Considering the poor formability of Mg alloys, deep drawing process is known to be one of the Developments of high-strength aluminum alloys have best processes to manufacture thin-walled Mg alloy always faced a difficult problem: owing to their small parts. Thus, the Al/Mg/Al sheet can be deformed by deep size, the early-stage strengthening precipitates are drawing process by taking advantage of its superplastic difficult to characterize in terms of composition, structure characteristic. Formability by the deep drawing process and evolution. Here we employ atomic-resolution is significantly influenced by the anisotropy of materials. transmission electron microscopy (TEM) imaging and Therefore, in the present study, anisotropic behavior of first-principles energy calculations to address these the Al/Mg/Al sheet is investigated. To understand the problems. Recent years, we have investigated tens of behavior, the anisotropy was discussed in the light of the typical high strength aluminum alloys, such as 2xxx crystallographic orientation of the Al and the Mg alloy. (AlCu, AlCuMg and AlCuLiMg), 6xxx (AlMgSi and Pure Al (99.99%) and AZ80 Mg alloy (Mg-8.2Al-0.56Zn- AlMgSiCu) and 7xxx (AlZnMg and AlZnMgCu) alloys, 0.44Mn (mass%)) were used for the cladding and with different compositions and with varying thermal substrate layers, respectively. The Al/Mg/Al sheet was processes for understanding their property-structure- fabricated by hot extrusion followed by hot rolling. The process correlations. Using aberration-corrected high- processing temperature and the reduction ratio of the resolution TEM (HRTEM) and aberration-corrected materials were 290℃ and 90% for the extrusion, and scanning TEM (STEM), much of our attention has been 350℃ and 81% for the rolling, respectively. To investigate paid to revisit the strengthening precipitates in these the anisotropic behavior of the sheet, tensile tests were important alloys and to clarify the controversies left in conducted. The tensile specimens were wire-cut from the past about their precipitation behaviors. Our study the sheet to have 0, 45, and 90o between the tensile and demonstrates the followings: the rolling directions. Tensile tests were conducted at 25, (1) Atomic-resolution imaging in STEM can provide 200, 250, and 300℃, and at 1.0×10-2, 5.0×10-3, and straightforward structure models at the atomic-scale, 1.0×10-3s-1. Crystallographic orientations of the Al and whereas atomic-resolution imaging in HRTEM with the Mg alloy were investigated by Electron BackScatter rapid quantitative image simulation analysis can provide Diffraction (EBSD) before and after the tensile tests. the refined structures with high precision beyond the At room temperature, the highest elongation and resolution limitation of the microscope. The combination strength were obtained with the Al/Mg/Al sheet tensile- of the two techniques can be more powerful in solving tested in 90o direction at any strain rates. There was difficult structure problems in materials science. no big difference in elongation and strength in the (2) Most of the early-stage precipitates in aluminum samples tensile-tested in 0 and 45o directions. At alloys are highly dynamic in both composition and elevated temperatures, neither anisotropy in elongation structure. Typically, having their characteristic genetic nor strength was not observed in any specimens, and skeletons to guide their evolution, these dynamic the reasons for this result is considered as follows. In precipitates initiate, mature and grow with thermal 50 the Al/Mg/Al sheet, the Mg alloy is much thicker than the Al layers and therefore the Mg alloy dominated 356MPa, 321MPa and 13%, respectively. the deformation of the sheet. It is known that the Mg Compared with other wrought AZ31 alloy with alloy deformed with the grain boundary sliding during conventional fabrication methods such as ECAP, ARB, the superplastic deformation. Thus, the Al/Mg/Al sheet MDF and so on, the caliber rolling seems an idea deformed mainly with grain boundary sliding at elevated approaching for achievement of high-performance Tuesday AM | August 20, 2019 temperatures. Since the anisotropy is mainly arisen commercial Mg alloys. by dislocation slip, the Al/Mg/Al sheet did not show anisotropy in the present study. Consequently, there 9:40-10:00(1217866) was no anisotropy in the superplastic behavior of the Al/ Effect of Alloy Elements on Non-Basal Slips in Mg/Al sheet. Magnesium Single Crystals Shinji Ando, Kumamoto University, Japan / 9:20-9:40(1220375) Magnesium Research Center, Japan; Tomohiro Microstructural Evolution and Mechanical Hanada, Kosuke Hayashi, Kumamoto University, Properties of Mg Alloy Processed by Multi-Pass Japan / Graduate School of Science and Technology, Caliber Rolling Japan; Hiromoto Kitahara, Kumamoto University, Hui Yu, Saoda Fan, Xiaorui Dong, Hao Liu, Jianan Japan / Institute of Pulsed Power Science, Japan Qin, Mingxu Yang, Fuxing Yin, Hebei University of Technology, China Magnesiumand magnesium alloys are candidate materials for energy saving of transportation vehicles Magnesium alloys are the lightest structural metals, and devices due to their high specific strength and and have good physical and mechanical properties low density. However, the plasticity of magnesium at that make them extremely attractive for applications room temperature is poor since basal slip system, requiring lightweight materials. The global market for which is their main slip system, has limited number of magnesium alloys has steadily expanded in the past independent slip systems available to accommodate decade, stimulated by the strong demand from the applied plastic deformation. Therefore, activation of non- automobile and electronic industries for lightweight basal slip systems is necessary to show good ductility. magnesium components. In order to meet the demand Recently, effect of yttrium on ductility of magnesium and of new high-performance alloys and overcome technical discussion for activity of (c+a) pyramidal slips has been challenges, severe plastic deformation is becoming an reported. In this study, to investigate effects of yttrium effective way to manufacture high-performance and and other alloying elements, such as aluminium, zinc ultrafine-grained Mg alloy. and cerium, on non-basal slips, [11-20] tensile and A promising process to produce high strength wrought [0001] compression tests of magnesium alloy single magnesium bulk materials in a more cost-effective crystals were carried out at 77K, 293K and 473K. manner is multi-pass caliber rolling. Although this Specimen sizes of tensile test and compression tests process has been used for many typical traditional were 20 x 3 x 0.3mm3 and 6 x 3 x 3mm3, respectively. alloys such as steel and titanium alloy, the caliber rolling Cross head speed of both tests was 0.05mm/min. of Mg alloy is relatively new. Complex alloying effects on the deformation behaviour of In this study, the effect of various multi-pass reduction, magnesium in tension and compression were observed. caliber rolling temperature and rolling speed on the In compression tests of Mg-0.5Al, Mg-0.5Zn, Mg- microstructure, texture evolution and mechanical 0.5Y, Mg-1.45Al-0.15Zn and Mg-2.7Al-0.4Zn, second properties of caliber rolling AZ31 magnesium alloys order pyramidal slips (SPCS) were observed, and the were systematically studied by means of OM, SEM/ critical resolved shear stresses (CRSS) of SPCS sere EBSD, TEM and tensile tests. increased by alloying. In tensile tests of Mg - 0.052Ce, The results shown that the average grain size decreases SPCS was observed and the CRSS was decreased. In with accumulated strain/increased pass. As a result, the Mg-0.5Al, Mg-1.0Al and Mg-2.6Al-0.3Zn, the alloys were tensile yield strength, the ultimate tensile strength and yield due to {10-11} twin instead of SPCS. Mg-(0.6-0.9)Y compressive yield strength improved significantly with single crystals were yielded due to first order pyramidal reduction in anisotropy. However, the elongation was slip instead of SPCS, and showed high ductility than in firstly increased and then decreased. pure magnesium. (c+a) edge dislocation immobilization In addition, rolling speed has greater influence on the by thermal activation process following double cross microstructure of AZ31 magnesium alloy rather than the slip of (c+a) screw dislocation, have been proposed as rolling temperature. The smaller caliber rolling speed, deformation mechanism for SPCS in pure magnesium. the finer grain can be obtained. The optimal rolling Based on the mechanism, effect of alloying elements on parameters of AZ31 magnesium alloy are as follows: ductility of magnesium was discussed. rolling temperature: 350℃, the rolling speed: 0.2m/s, and the TYS, UTS, CYS and elongation were 320MPa, 51 Technical Program
10:00-10:20(1220726) low potential for scalability and poor castability. In this work, two existing metal-matrix nanocomposite Effect of Various Texture Components on the manufacturing processes showing promise to overcome Formability of Al Alloy AA5182 at the Plane Strain some of these obstacles were developed further: the Condition in-situ gas-liquid reaction, and self-propagating high- Zhenshan Liu, Jingwei Zhao, Kangcai Yu, Lei Fu, temperature synthesis. Composites reinforced with Pizhi Zhao, Chinalco Materials Application Research aluminum nitride and titanium carbide were produced, Institute Co. Ltd, China alloyed with several matrix compositions and squeeze cast. The in-situ gas-liquid reaction simply introduces During the stamping of automotive parts, the cracking nitrogen gas into liquid aluminum at a set temperature usually happens in the plane strain zone. This paper and a controlled flow rate, which allows the reaction studied the influence of grain orientation on the plane to form aluminum nitride nanoparticles. The SHS strain at the forming limit curve (FLC) in Al alloy AA5182, process uses fine titanium, carbon, copper oxide and utilized as automotive inner panel. To achieve different aluminum particles to cause the formation reaction for grain orientation distribution with the same grain size, titanium carbide. Insights into the effects of process cold rolled sheets are annealed at various approaches, design on microstructure and properties were gained, Continuous Annealing air furnace (CA), Salt Bath (SB), and potential process improvements and areas to focus and Box type Air furnace (BA). FLCs of these annealed future research have been identified. samples, which only difference in texture distribution, are tested along various directions with digital image 11:10-11:30(1221490) correlation technique. It is found that the plane strain at Tuesday AM | August 20, 2019 AM | Tuesday FLC, exactly speaking minimum major strain (FLCmin) Microstructure and Mechanical Properties of varies in the range from 0.191 to 0.208 for these annealed 2N/4N-Al Multi-Layered Metals Fabricated by ARB AA5182 sheets. The texture components in annealed and Subsequent Annealing Processes AA5182 sheet scatter far away to their ideal orientation. Xiaojuan Jiang, Chongqing University, China / Kyoto In the sample annealed with CA and SB (500℃×1min), University, Japan; Si Gao, Kyoto University, Japan; Q and random texture take the dominance; in the sample Ling Zhang, Guilin Wu, Chongqing University, China; annealed with BA (450℃×2 hours), Cube, Brass, R and XiaoXu Huang, Chongqing University, China / Q are the main texture components. This difference of Technical University of Denmark, Denmark; Nobuhiro texture components has limited effect on FLCmin, only Tsuji, Kyoto University, Japan / Kyoto University, 1% of it. FLCmin shows good linear relationship with Japan elongation, uniform elongation, work hardening index, but has no clear correlation with r value. Hence, r value Recent studies have showed that high strength with is not a suitable parameter to characterize the formability satisfactory tensile ductility can be achieved in metals during the stamping of automotive aluminum sheet. having multi-layered structures, which seems a promising way to overcome the strength and ductility 10:20-10:45 Tea Break trade-off relationship that is well-known to exist in metallic materials. However, the multi-layered metals that have been previously studied mostly composed of 10:45-11:10 Invited(1232643) deformed microstructures. Moreover, the mechanism In-Situ Processes for Production of Aluminum- of the obtained high strength and good tensile ductility Matrix Nanocomposites in multi-layered metals has not been fully clarified Brajendra Mishra, Jeremy Fedors, Worcester yet. Systematic study on multi-layered metals having Polytechnic Institute, United States deformed or recrystallized microstructures, as well as on relationship with their mechanical properties is still Increasing the mechanical properties of cast aluminum lacked. components at temperatures in the vicinity of 300℃will In the present study, the multi-layered Al having 2N-Al allow for lightweighting opportunities, especially in (99.2%wt) and 4N-Al (99.99%wt) alternate layers was automotive and aerospace applications. Metal-matrix fabricated by accumulative roll-bonding (ARB) process. nanocomposites show great promise in this regard, in the 6 cycles of ARB processes was applied on stacked 2N- form of aluminum as a matrix containing well-dispersed and 4N-Al sheets, and a multi-layered specimen having ceramic nanoparticles. These have been shown to retain totally 64 layers with the thickness of each 2N- or 4N- most of the ductility of the matrix alloy, while adding Al layer of around 15μm, was successfully fabricated. strength and stiffness at far lower reinforcement fractions The multi-layered specimen was then annealed for 30 than are required in microcomposites. Unfortunately, minutes at different temperatures ranging from 125℃to metal-matrix nanocomposites are plagued by issues 250℃ in order to systematically vary microstructures of which limit commercialization, such as high costs of the 2N- and 4N-Al layers. 52 production, issues with particle wetting and dispersion, SEM-EBSD measurements showed that ultra-fine grained microstructures were observed in both 2N-Al a scanning probe microscope (SPM). Since the peak and 4N-Al layers of the as-ARB processed specimen, of pile-up tends to be located in the outer direction of with mean grain sizes of 0.26μm and 0.79μm for 2N- the indentation under the low load condition where Al and 4N-Al, respectively. Upon subsequent annealing, the indentation depth is small, in addition to the plastic grain coarsening was observed in both layers, and displacement of the vertical component of the indenter, Tuesday AM | August 20, 2019 specimens having varieties of grain sizes were obtained. the plastic displacement of the tangential component Mechanical properties of the multi-layered specimens due to the dislocation motion contributes to the formation were studied by tensile test combining with digital image of pile-up. correlation (DIC) technique at room temperature. It was The cross-sectional structure just under the indentation found that the multilayered specimens exhibited better was observed with a transmission electron microscope combinations of strength and tensile elongation than (TEM). Regardless of the aging condition, the plastic monotonous 2N-Al or 4N-Al sheets subjected to the region showed a shape close to an ellipse, and as the same ARB and annealing processes. DIC measurements aging time increased, the size of the plastic region for revealed that the pronounced discontinuous yielding and the indentation decreased. The characteristic shape of associated severe strain localization usually observed in this plastic region is attributable to the dislocation motion monotonous UFG 2N-Al were effectively suppressed in occurring on the slip plane diagonal to the loading axis the multilayered UFG specimens. The reason for high and the size of the plastic region decreased due to strength and good tensile ductility of the multilayered the inhibition of dislocation movement by precipitation specimen is discussed in terms of suppression of strain strengthening. localization by plastic strain compatibility between hard The average stress and average strain in the plastic zone 2N-Al layers and soft 4N-Al layers. predicted by TEM observation results and the plastic work of nano-indentation showed good agreement with 11:30-11:50(1221923) the yield stress of the present alloy. Indentation Microstructure and Stress Analysis of Age-Hardenable 7050 Aluminum Alloy 11:50-12:10(1221940) Ryo Muramatsu, Shinji Muraishi, Shinji Kumai, Tokyo Impurity Effects on Mechanical Properties of Institute of Technology, Japan 1xxx Series Aluminum Thin Foils Toshihiro Hara, Daisuke Egusa, The University of The nano-indentation test is a simple method of Tokyo, Japan; Mami Mihara, Hiroki Tanaka, UACJ measuring the micro hardness and Young's modulus Corporation, Japan; Eiji Abe, The University of Tokyo, from the load-displacement response of the material Japan / National Institute for Materials Science, Japan surface by a micro-indenter. It is known that characteristic surface displacements such as pile-up and sink-in occur Commercial pure aluminium (Al) thin foils are used around the impression, but the shape of the plastic for various ways, e.g. packaging foods, electrodes region and the residual stress influence on the surface of lithium-ion battery, and electrolytic capacitor. displacement is not clear yet. Therefore, in this study, Commercial pure Al alloys inevitably contain impurities in order to investigate the relationship between plastic which mainly consist of Fe/Si. Mechanical properties of deformation behavior around the indentation by a nano- those Al alloys usually understood as in the view of work indentation and aging precipitation, we measured the hardening, however it is also accepted that distributions surface displacement around the indentation of the 7050 of Fe/Si elements also affect mechanical properties precipitation strengthened type aluminum alloy and of the alloys. There are reports on the distributions of observed the dislocation structure and the expansion of these impurities, e.g., precipitation on dislocations the plastic zone just under the indentation. or segregations around grain boundaries. Since the Iindentations were made by nano-indentation test behaviour seems to be depend on history of process, on loading 100 to 50000mgf on the an as-quench details are still unclear. We investigated microstructures (A.Q.) material subjected to solution treatment to of 1050 Al foils with/without inter annealing (denoted IA/ 7050 aluminum alloy, a quasi-aging and a peak aging NIA, hereafter), especially focusing on distributions of material subjected to aging treatment for 1 hour and Fe/Si elements. Based on tensile testing of the foils, it 10days at 120℃ after solution treatment. In the load- is found that elongations are remarkably different, 2.8% displacement curve in nano-indentation, the elastic for IA and 5.6% for NIA, although the work hardening recovery rate increased with increasing aging time. It is behaviours are almost same while the testing. This considered that fine precipitates due to age hardening result contradicts usual point of view, suggesting effect act as obstacles of dislocation lines, and the elastic field of Fe/Si elements on the properties. The states of Fe/ of these dislocations increased the elastic recovery rate Si elements within the foils were identified as Al13Fe4, of the impression surface. Al-Fe-Si ternary compounds and pure Si by XRD, SEM Surface displacement around the impression was and TEM observations. Volume fractions of each state measured with a laser scanning microscope (LSM) and were estimated by XRD profiles, showing that volume 53 Technical Program
fraction of pure Si only was different between IA and NIA. We investigated distributions of pure Si by SEM- EDS/EBSD, resulting that almost pure Si exists along high-angle grain boundaries. Pure Si were few micro- meters in radius and their sizes were larger in IA foil. Based on the observations, we designed a mechanism of coarsening of pure Si on grain boundaries by Ostwald ripening during inter annealing process. Such coarsened pure Si on grain boundaries can be a candidate for initiation of fracture, which lead decrease in elongation. The validity of the above mechanism was investigated with SEM and TEM observations of samples before foil rolling. Tuesday AM | August 20, 2019 AM | Tuesday
54 Technical Program
describe and interpret the somewhat limited data C1. Light Metals and Alloys- available on the variation of solute levels in the matrix Aluminum: II throughout the precipitation sequence and the degree Symsposium Organizers: to which equilibrium solubility is approached or reached during ageing. The potential opportunities for alloy Baiqing Xiong, GRINM Group Co. Ltd., China; Yoshihito design will also be considered. Kawamura, Kumamoto University, Japan; Young Min Kim, Korea Institute of Materials Science (KIMS), Japan; Jian-Feng 14:00-14:20（1222349） Nie, Monash University, Australia; Diran Apelian, Worceste Polytechnic Institute, USA Effect of GP(I) and GP(II) Zones on Precipitation Microstructure and Hardness in A7050 Aluminum Tuesday PM Room: Presidium Conference Room Alloy by Means of Two Step Aging August 20, 2019 Symsposium: C1 Yuta Sano, Shinji Muraishi, Yohei Harada, Shinji Kumai, Tokyo Institute of Technology, Japan Chairs: Zhihui Li, GRIMAT Engineering Institute Co., Ltd., Steel fastener, bolts, nuts and screws, has been China widely used for mechanical joint of various different Malcolm Couper, Monash University, Australia metal parts, where the contact points of dissimilar metals by aluminum and steel acting as the site of 13:30-13:55 Invited(1225971) internal stress and corrosion due to the difference of material properties, elastic modulus, thermal expansion
Tuesday PM | August 20, 2019 PM | Tuesday The Relationship of Solid Solubility to the coefficient, corrosion resistance, etc. Furthermore, Precipitation Sequence in Aluminium Alloys during remelting process, impurity elements from steel Malcolm Couper, Monash University, Australia parts are inevitably incorporated into aluminum alloy, which reduces potential recyclability of aluminum alloy. The room temperature equilibrium solid solubility In present study, we have chosen A7050 aluminum alloy of many elements, or combinations of elements, in (Al-Mg-Zn based alloy) as the candidate of aluminum aluminium is very low. For binary aluminium alloys, the screw to achieve good mechanical fastening ability by highest room temperature equilibrium solubilities occur age-hardening. The precipitation sequence of Al-Zn-Mg for Ga (8at%) and Mg (2.3at%), followed by Zn (approx based alloy is as follows, 0.5at%), Li, and Ge, though for the latter, extrapolation → → → SSSS GP zone η' η (MgZn2) from higher temperature is required (e.g. Li, 3.3at%, Recently, existence of two types of GP zones are 500K; Ge, 0.2at%, 450K). Most other common additions reported in Al-Zn-Mg alloy, which are spherical GP(I) to aluminium have extrapolated room temperature zone and plate-shaped GP(II) zone on {111} plane. equilibrium solubilities of <0.01x at% with the highest However, contribution of different types of GP zones on being probably Ag (0.04at%) and Cu (0.02at%). In other age-hardening behavior is still unclear. Therefore, the cases the data is typically extrapolated from 500~800K. ageing treatment for the formation of different types of For ternary aluminium alloys, the solubility is sometimes GP zones and their roles in evolution microstructure reported to increase, for example Cu with addition of Zn and resultant hardness by η' phase was investigated (at 730K), or decrease, for example Mn with addition of by means of two step aging treatment at different Si or Zn. For Al-Mg-Si/Ge ternary alloys, the solubility is temperatures. TEM observation revealed that the reduced by the formation of the equilibrium phase (Mg Si 2 amount of {111} type GP (II) can be increased at the / Mg Ge) and further reduced by an excess of Mg. The 2 aging temperature ranging from 333 to 393K, where solubility of Ge at 650K is 2at in Al-Ge but in Al-Mg Ge % 2 conventional spherical GP(I) are simultaneously formed it reduces to 0.03at%Ge. For Al-Si at 650K it is 0.24at% with GP(II). but in Al-Mg Si it reduces to 0.12at Si. Solubilities at 2 % By conducting several different two step aging, where room temperature or normal ageing temperatures have preferential formation of GP (I) or GP (II) is expected at not been reported. the first step of aging with different temperatures (room Super-saturation of solute can be realised by rapid temperature, 333, 393, 423K) and subsequent second solidification or more commonly, by quenching a solid step aging at 423K, it is found that there exists no solution from a high temperature, typically within the significant difference in the peak hardness by the second alpha phase region, with the solution temperature step aging at 423K regardless of the preliminary formed as high as possible, but also recognising the need to GP zones. This implies that the effect of two different minimise the risk of incipient melting. The subsequent types of GP zones on the precipitation and hardening precipitation has been studied extensively, with the focus behavior of η' phase is similar by several different two on the precipitation sequence, including compositions step aging conditions in present study. and structures that results in age-hardening or other combinations of properties. This paper attempts to 92 14:20-14:40(1222448) and compositions. Intermetallic compounds that form after the start of the precipitation of (Al) accounts for Study of Deformation Mechanisms in Ma-Ca Alloy the particles at grain boundaries in as-cast alloys. by In-Situ EBSD and 3DXRD Primary phases formed earlier than the (Al) phase are
Gaoming Zhu, Leyun Wang, Xiaoqin Zeng, Shanghai either embedded within (Al) grains or pushed to grain Tuesday PM | August 20, 2019 Jiaotong University, China boundaries. Calculated compositions of the (Al) phase can be used for predicting the composition profile of The addition of a small amount of Ca improves the the (Al) matrix and account for its compositional micro- ductility of Mg alloys. However, the mechanism segregation. underlying this effect is not well understood. In this work, Secondly, thermodynamic calculations and DICTRA in-situ tensile tests of an extruded Mg-0.47 wt.%Ca alloy diffusion simulations are utilized to optimize the were conducted both in a scanning electron microscope processing temperature and holding time for subsequent equipped with electron backscattered diffraction (EBSD) homogenization and solution treatments. With detector and at a synchrotron X-ray beamline with three equilibrium stepping calculations, the temperature range dimensional X-ray diffraction (3DXRD) capability. EBSD- for heat treating a specific alloy can be preliminarily based slip trace analysis indicates strong activity of determined so that the particles at grain boundaries can prismatic slip and pyramidal slip in addition to basal be dissolved completely or to a large extent. DICTRA slip, and the fraction of non-basal slip increased with simulations help to evaluate the holding time, which is strain. Some transmission electron microscopy (TEM) needed for eliminating the composition segregation in experiments were performed at the strain of 8%,
is greatly affected by the presence of θ (Al2Cu) and S 16:35-16:55(1222317) (Al CuMg) phase along grain boundary. Specifically, 2 Prediction of Mechanical Properties for Al-Mn Cu-rich precipitates and intermetallics are known to Alloys Subjected to Prolonged Heating at High act as local cathodes, which facilitate oxygen reduction Temperatures reactions and ultimately drive anodic dissolution of the surrounding matrix material. The intergranular corrosion Nobuhiro Makii, Shoichi Hirosawa, Yokohama resistance of the alloy decreases with the increase of the National University, Japan content of Cu and Mg elements. The results also show that the corrosion resistance of 2024 alloy with lower Mg The mechanical strength of alloys decreases when content is significantly improved compare with the 2024 exposed to high temperatures, but the rate of the alloy with a more common composition (Cu to Mg mass decrease is generally very small under the conventional ratio of 2.9). Attempts are made to explain the observed service condition of products. Therefore, it is required corrosion behavior of the alloy of various contents of to predict in advance the definitive strength after a Cu and Mg elements. The research results can provide service for, for example, several decades. Temperature- theoretical guidance for the composition design of 2xxx accelerated test and full-annealing treatment test aluminum alloy with high corrosion resistance. are examples of such prediction methods, and highly expected to provide good estimates instead of the 15:20-16:10 Tea Break experimentally unmeasurable definitive strength. Al-Mn alloys are one of the aluminum alloys used for high- temperature components, but further improvement of 16:10-16:35 Invited(1234419) the strength and thermal stability is in great demand. Tuesday PM | August 20, 2019 PM | Tuesday As-Cast Microstructure and Its Evolution during In this study, powder metallurgy (PM) extrudes of Homogenization of a Novel High Alloying Al-Zn- Al-2.5mass%Mn (25M), Al-3.0mass%Mn (30M) and Mg-Cu Alloy Al-4.0mass%Mn (40M) with larger amounts of Mn Zhihui Li, Kai Wen, Xiwu Li, Hongwei Yan, Da Xu, than its solubility limit were newly developed by gas Yongan Zhang, GRIMAT Engineering Institute Co., atomization and cold isostatic press (CIP). And then LTD., China; Baiqing Xiong, GRIMAT Engineering the mechanical strength after prolonged exposure at Institute Co., LTD., China / GRINM Group Co., LTD., 373~673K (i.e., temperature-accelerated test above China a service temperature) or after controlled cooling at 1K/h from a solution treatment at 793K for 10h (i.e., The second phases in as-cast Al-Zn-Mg-Cu alloy could full-annealing treatment test) were compared to those dissolve into the matrix or undergo transformation of the conventional A3004-H112 Al-Mn alloy by means during homogenization treatment. The microstructure of tensile test and Vickers hardness measurement. of as-cast and as-homogenized alloy was investigated The obtained time–temperature–hardness curves by means of scanning electron microscope (SEM), by temperature-accelerated test showed that the transmission electron microscope (TEM), differential hardness of A3004-H112 monotonously decreases scanning calorimetry (DSC), hardness and electrical with increasing exposure time above 523K, but 25M, conductivity tests. AlZnMgCu phase in as-cast alloy 30M and 40M hardly decrease in hardness even when exposed at 573K for 10000h. The hardness decreases possessed a similar structure of MgZn2. A transformation of 25M, 30M and 40M after full-annealing treatment from AlZnMgCu phase to Al2CuMg phase occurred via a homogenization treatment at 380℃ while AlZnMgCu test were also very small compared to A3004-H112, phase directly dissolved into the matrix with no phase thus disallowing numerical analyses by, for example, transformation at 470℃. Homogenization temperature Larson-Miller parameter (LMP) and Arrhenius models influenced diffusion rates of Zn, Mg and Cu atoms to be worked. Such endurance of mechanical strength determined an obvious diffusion rate gap between Zn of newly developed PM extrudes was attributed to and Cu atoms for homogenizing at 380℃, leading to thermally stable Al6Mn dispersed phase, and thus the definitive microstructures after a prolonged service was a transformation to Al2CuMg phase. On the contrast, homogenizing at 470℃ gave rise to a small gap so as attempted to elucidate by a phase field simulation. The calculated little microstructural change in 40M even after to the AlZnMgCu phase dissolution. Abundant Al3Zr particles with small size and dispersive distribution a prolonged exposure at 573K was in good agreement generated in the alloy after two stage homogenization with the results of the two prediction methods concerning the excellent thermal stability of the extrude. treatment. Al3Zr particle showed a round shape with a first stage homogenization temperature of 400℃. When the first stage homogenization temperature varied from ℃ ℃ 400 to 450 , Al3Zr particles with blocky morphology appeared and its proportion enlarged. The formation of
blocky Al3Zr particle was speculated. 94 16:55-17:15(1222087) and more valuable in engineering application. Recently, there has been some literatures on the foam fill tubes Grain Refinement and Macrosegregation (FFTs) structures, concluding that using aluminum Behavior of Direct Chill Cast 2024 Aluminum foams as cores inside the metal tubes can improve Alloy under Intensive Melt Shearing the energy absorption of simple tubes. However, the Tuesday PM | August 20, 2019 Xudong Liu, Qingfeng Zhu, Rui Wang, Yubo Zuo, strength of the aluminum foam core was generally low. Northeastern University, China It was difficult to achieve synergetic deformation with the metal tube, and the interaction between foam and tube Grain refinement and improvement of macrosegregation can't be maximized. In this study, CNTs/Al composite are very important for direct chill (DC) casting of high foam filled 6061 aluminum alloy thin-walled tube was quality wrought aluminum alloy ingots. In this paper, prepared. The combination of CNTs/Al composite foam intensive melt shearing was introduced to refine the with tube was achieved by simple mechanical contact. as-cast structure and improved macrosegregation CNTs had high reinforcement efficiency owing to low during DC casting 2024 aluminum alloy. Intensive melt density, high modulus. The composite aluminum foam shearing was achieved by the application of a stator- fabricated by space-holder method had the consistent rotor high shearing device and was applied directly pore size and precise porosity. The addition of CNTs to the melt in the sump during DC casting process to and the controllable foam structure improved the control the as-cast structure and macrosegregation of deformation strength and stability of the composite 2024 aluminum alloy ingot with a diameter of 300mm. foam, respectively. Benefit from the properties of the Temperature measurement was carried out to study CNTs/Al composite foam, the CNTs/Al composite FFTs the temperature field during casting process and to structure showed high strength, certain toughness and understand the mechanism of the grain refinement excellent energy absorption properties. effect of intensive melt shearing on the DC casting The experiment studied the compressive deformation process. The experiment results show that intensive and energy absorption capability of the FFTs structure. melt shearing can reduce the cold folds, which make Due to the synergetic deformation between the CNTs/ the surface of ingot smooth. The thickness of the solid Al composite foam and alloy tube, CNTs/Al composite shell increases with the application of intensive melt FFTs structure exhibited more excellent properties shearing. After the application of intensive melt shearing, than that of the superposition of alloy tube and CNTs/ the grain structure is transformed from the mixture of Al composite foam. The plateau stress and energy columnar grains, feathery grains and coarse equiaxed absorption of composite structure were 57.4MPa and grains to fine equiaxed grains. The uniformity of as-cast 28.4MJ/m3, which were ~0.23 and ~0.87 times higher structure is also greatly improved. The intensive melt than that of the superposition of alloy tube and CNTs/ shearing shows a significant effect on the distribution of Al composite foam, respectively. More importantly, the elements. The negative macrosegregation in the center energy absorption efficiency of composite structure region of the ingot is obvious reduced. At the same time, was 1.23 times that of the superposition of tube and it has no obvious effect on the strong positive surface composite foam. Compared to pure aluminum FFTs segregation and negative subsurface segregation. In structure, CNTs/Al composite foam with high strength conventional DC casting process, the temperature of can significantly increase the plateau stress, energy the melt in the sump is high and the temperature field in absorption capacity of the FFTs structure. CNTs/Al the sump is non-uniform. During the DC casting process composite FFTs structure's plateau stress and energy with intensive melt shearing, the liquid melt from the absorption were ~0.51 and ~0.67 times higher than that launder is cooled with a high cooing rate directly to of pure aluminum FFTs structure, respectively. ℃ 2~4 below the liquidus and the temperature field in Generally, CNTs could improve foam's strength while the sump is quite uniform. This is believed results in the reducing its density. The CNTs/Al composite foam and enhanced heterogeneous nucleation and improved the tube deformed cooperatively, further preventing the foam survival of the nuclei. and tube from collapsing instantaneously, stabilizing the FFTs structure. The specific energy absorption and 17:15-17:35(1222115) specific strength of the FFTs structure were obviously Compressive Properties and Energy Absorption improved. of CNTs/Al Composite Foam Filled Aluminum Alloy Tubes Jiali Xu, Chunnian He, Naiqin Zhao, Tianjin University, China; Xudong Yang, Civil Aviation University of China, China
The composite structures prepared by aluminum foam combined with other dense materials became more 95 9:00-9:20(1231962) C1. Light Metals and Alloys- Precipitation in Aluminium Alloys: Shake or Aluminum: III Bake? Symposium Organizers :
Christopher Hutchinson, Wenwen Sun, Yuman Wednesday AM | August 21, 2019 Baiqing Xiong, GRINM Group Co. Ltd., China; Yoshihito Zhu, Qi Zhang, Lingyu Wang, Xiang Gao, Monash Kawamura, Kumamoto University, Japan; Young Min Kim, University, Australia; Ross Marceau, Deakin Korea Institute of Materials Science (KIMS), Japan; Jian-Feng University, Australia Nie, Monash University, Australia; Diran Apelian, Worceste Polytechnic Institute, USA High strength Al alloys exploit solid state precipitation to tailor their mechanical response. This precipitation Wednesday AM Room: Presidium Conference Room requires two ingredients: a thermodynamic driving force August 21, 2019 Symsposium: C1 and atomic mobility. For a given alloy chemistry, the heat treatment (precipitation) temperature is chosen as Chairs: a compromise between having sufficient driving force JaeHwang Kim, Korea Institute of Industrial for precipitation and sufficient atomic mobility so that the Technology, Korea precipitation reaction occurs in a reasonable time and Yong Jiang, Central South University, China results in a 'not too coarse' precipitate distribution. It is this compromise that frames the competition between nucleation, growth and coarsening that constrains the 8:35-9:00 Invited(1241378) possible precipitate distributions and hence mechanical Formation Thermodynamics and Thermal responses. Stabilities of Coherent L12 Nano-Precipitates in In this presentation, we demonstrate a new approach Al-RE Alloys to precipitation hardening that does not use thermal Yong Jiang, Chaomin Zhang, Fuhua Cao, Yiren treatments and therefore allows independent control over Wang, Central South University, China the thermodynamic driving force and atomic mobility. This provides a means to fully alter the competition The thermal stabilities of nano-precipitates are critical between precipitate nucleation, growth and coarsening in determining the service temperature of metallic and new microstructures, with new combinations of alloys. Taking the Al-RE (rare earth) alloys as an properties are obtained. exemplary case, we performed intensive first-principles The approach uses small amplitude cyclic plasticity at investigations on solute segregation, coherent strains, room temperature as a means of continually pumping and formation energies of L12 nano-phase bulks and vacancies into the system to achieve atomic mobility interfaces. The following insights were obtained. Only under conditions of high thermodynamic driving force. matrix- dissolved solutes can strongly substitute the X The approach is self-regulating (in both space and sublattice sites in L12-Al3X. The Al3Er(L12)/Al3Zr(L12) particle size) and results in extremely uniform and fine- or Al3Sc(L12)/Al3Zr(L12) interface has nearly zero scale microstructures. The approach can be used either formation energy. Zr segregation to the Al/Al3Er(L12) as a new processing route for high strength Al alloys, or or Al/Al3Sc(L12) interface is in favor of forming a Zr- as a 'training' routine to improve the high cycle fatigue rich shell. Based on the classic nucleation theory, first- properties of precipitate strengthened Al alloys. Both principles energetics results were further employed to examples will be shown in this presentation. evaluate the precipitation thermodynamics and relative stabilities of various possible complex structures of L12 9:20-9:40(1234920) nano-phases, revealing that ternary L12-Al3(ErxZr1-x) Understanding Corrosion Mechanisms of or L12-Al3(ScxZr1-x) precipitates tend to form the Magnesium Alloys from a Microstructure Al Er-core+Al Zr-shell or the Al3Sc-core+Al Zr-shell 3 3 3 Perspective–A Review structure with a sharp core/shell interface. The effects Rongchang Cao, Shangdong University of Science of temperature and the Er/Zr or Sc/Zr atom ratio on the and Technology, China relative stabilities of these L12-phase nano-structures in Al were also discussed. Finally, all the results were Magnesium (Mg) alloys with low density and high specific combined to establish the thermal stability advantage strength, have attracted great attention for potential of core-shelled L12 nano-phases in Al alloys, which applications in 3C (Computer, Communication and can provide the fundamental understanding of diverse Customer electronic) products, aerospace, automobiles, experimental observations in the literatures. high speed rail and biodegradable materials. However, they are susceptible to corrosion in aggressive environments due to the lower potential of Mg. The poor corrosion resistance of Mg alloys restricts their 209 Technical Program
extensive applications. So far, understanding corrosion the key contribution to the working hardening capacity mechanisms of magnesium alloys have become a critical and plasticity. Additionally, the leftover stacking challenge. Alloying and subsequent processing lead to a faults nucleates low angle grain boundaries, and change in microstructure and corrosion behaviour. This then contribute to the enablement of the dynamic review reveals the cutting-edge advance in corrosion recrystallisation, resulting in significant grain refinement. and protection of magnesium alloys. Particularly, corrosion types (i.e. galvanic corrosion, pitting corrosion, 10:00-10:20(1235729) filiform corrosion, intergranular corrosion, exfoliation A Pressure-Driven Mould Filling Model of corrosion, stress corrosion and corrosion fatigue) and Aluminium Alloy Melt/Semi-Solid Slurry Based on mechanisms of magnesium alloys are disclosed and Rheological Behaviour discussed from a microstructure perspective. The Zhen Ma, Huarui Zhang, Fangfang Wang, Hu Zhang, discussion on the influence of microstructure (e.g. grain Beijing University of Aeronautics and Astronautic, size and texture, the size, morphology and distribution China of secondary phases or intermetallic compounds (quasi-crystals, long-period stacking ordered (LPSO) Pressure-driven mould filling ability of aluminium alloy structure), and dislocations, twins as well on corrosion melt/semi-solid slurry is of great significance in pressure is stressed. The relationship between the formation casting process such as low pressure die casting, high and degradation mechanism of chemical conversion pressure die casting and squeeze casting, and the coating, layered double hydroxides (LDH), and micro- rheological behaviour of the alloy has a crucial effect arc oxidation (MAO)/polymeric composite coating and on the mould filling ability according to fluid dynamics. the intermetallic compounds in Mg alloy substrates is Wednesday AM | August 21, 2019 AM | Wednesday In this paper, A356 alloy was employed as an example also probed. The methods with multi-perspectives to to clarify the rheological behaviour of aluminium alloy. characterize corrosion behaviour are proposed. The solid fraction and enthalpy change of A356 alloy during solidification was experimented by differential 9:40-10:00(1235077) scanning calorimeter, and the rheological behaviour Underlying Mechanisms for the Enhanced of the alloy in semi-solid state was investigated by Plasticity of Mg Alloys rotational rheometry. The rheological behaviour of the Suqin Zhu, Simon P. Ringer, The University of alloy obeyed the power law model and was effected by Sydney, Australia temperature. The stop of mould filling was thought to be attributed to pressure loss caused by viscosity during As the lightest structural metallic materials, Mg alloys flow of the melt/semi-solid slurry. The melt/semi-solid have been attracting more and more attention in slurry stopped filling when the pressure loss was equal science and engineering communities. However, the to the driving pressure. The steady-state rheological poor plasticity of the alloys greatly limits their industrial behaviour of the alloy in semi-solid state was modelled applications. We have developed a high strain-rate with shear rate and temperature as parameters. rolling (HSRR) process to effectively produce Mg alloys Pressure loss caused by viscous flow and heat transfer which possess attractive combinations of strength and between the alloy and the mould was calculated and ductility. During this thermomechanical process, the coupled during mould filling of the melt/semi-solid slurry. formability of Mg alloys is significantly improved, and A pressure-driven mould filling model of aluminium alloy untrafine-grained microstructure is obtained. melt/semi-solid slurry was established based on steady- Underlying fundamental mechanisms for the formability state rheological behaviour. The model was employed and microstructure evolution has been investigated. to predict the filling length of melt/semi-solid slurry in Electron backscatter diffraction (EBSD), transmission pressure casting process, and the results indicated Kikuchi diffraction (TKD) and conventional and high- that the model could provide a quantitative approach to resolution transmission electron microscopy (TEM) characterize the pressure-driven mould filling ability of were used in the study, which provided both statistical aluminium alloy melt/semi-solid slurry. and detailed atomic-level data for the same sample. In particular, the TKD and TEM observations were 10:20-10:45 Tea Break conducted at the same site of the specimen, enabling the integrated analysis of grain orientation and 10:45-11:10 Invited (1234989) crystallographic defects. The results shows that twinning and stacking faults Role of Nanoclusters in Two-Step and Multi-Step play a critical role during the HSRR process. The key Aging Behavior in Al-Mg-Si Alloys contribution to the enhanced plasticity is the formation JaeHwang Kim, Korea Institute of Industrial of stacking faults in the high-intensity twin segments. Technology, Korea The stacking faults interact with each other and form 210 perfect glissile non-basal slip dislocations, which is Weight reduction of automobile is required under consideration of CO2 emission and enhancement of easily developed into exfoliation corrosion. The IGC fuel efficiency. Al-Mg-Si alloys have been used for and exfoliation corrosion sensitivity from high to low is in automobile panel due to their good age-hardening the order of peak-aged state, solution treated state and response. Generally, two-step heat treatment such as over-aged state. In addition, the effect of PCG structure transportation at room temperature and baking process on exfoliation corrosion behavior was discussed as well. Wednesday AM | August 21, 2019 at around 170℃ for 1.2ks of Al sheets, is conducted for The inner fine elongated grains structure was slightly the production of Al panels. Nanoclusters formed during corroded compared with the outer PCG structure, and room temperature does not directly transform into the the longest crack was located at the boundary between strengthening β" phase during two-step aging at 170℃. the two structures. The macro-galvanic corrosion due This is called the negative effect of two-step aging to the difference of electrochemical properties between behavior in Al-Mg-Si alloys. the two structures is the main reason account for that In order to understand the effect of clustering during phenomenon. This work may help us to understand the room temperature on two-step aging behavior, influence mechanism of exfoliation corrosion behaviour in 2024 of natural aging time on two-step aging behavior aluminium alloy more intuitively. is investigated. Not only harmful but also useful nanoclusters are formed during natural aging, resulting 11:30-11:50(1235080) is 'three stages of two-step aging'. It is also confirmed Effects of Asymmetric Hot Rolling on Formability that even though the harmful cluster is formed during of 6061 Aluminium Alloy natural aging, the positive effect during two-step aging Mu Seob Jeong, Won Kee Chae, Jun Hyun Han, is confirmed through the 'atomic rearrangement' during Chungnam National University, Korea; Ho Joon Park, aging at 250℃. Hyundai-steel, Korea Effect of pre-aging and step-quenching on clustering formation and following artificial aging such as two- Because CO gas contained in automobile exhaust gas step and multi-step aging behavior is investigated 2 causes global warming, CO emission regulation for since nanoclusters are competitively formed during 2 automobiles is strengthened. Therefore, aluminum alloy, low temperature aging. Detrimental clusters, Cluster which is a lightweight material, has attracted attention (1) or Si-rich clusters, can be successfully suppressed as a next-generation automobile plate. by formation of Cluster (2). The two-step or multi-step Aluminum 6XXX alloy is widely used as automotive sheet aging behavior is discussed based on age-hardening material. It is made of Al-Mg-Si ternary system and small phenomena. amounts of Ti and Mn are added for grain refinement. The aluminum 6XXX alloy has a low formability of 60 ~70 11:10-11:30(1452155) % % compared to conventional automotive steel. Due to low Effects of Aging Treatment and Peripheral Coarse formability, it is difficult to produce a complicated shape Grain on the Exfoliation Corrosion Behavior and product. In addition, in order to improve the formability, Its Mechanism of 2024 Aluminium Alloy Using Aluminum product is made by warm forming at about SR-CT 300℃. And the strength of the product is lowered. The Shuangqing Sun, Fang Yi, Fengting Li, Xinyi Wang, age hardening to increase the strength lowered by warm Chunling Li, Songqing Hu, China University of forming raises the process cost. Petroleum, China After casting, the aluminum alloy has a low formability due to the strong development of <110>//ND texture. 2024 Al-Cu-Mg aluminium alloy has been widely utilized In addition, the average plastic strain ratio (r) of the in aircraft and vehicles industries due to its excellent cast aluminum 6xxx alloy is low as 0.7 to 0.8. Due to structural properties. However, 2024 aluminium alloy the low average plastic strain ratio, a defect called in certain aging states are vulnerable to exfoliation "earing" occurs during rolling. By applying shear stress, corrosion, which would greatly reduce its mechanical the average plastic strain ratio can be improved by properties and shorten the integrated service life. developing <111>//ND texture. However, due to work In this work, the exfoliation corrosion behavior of hardening during rolling, the elongation will decrease. In 2024 aluminium alloy in different aging states was this study, the effect of asymmetric rolling temperature investigated through exfoliation corrosion test, together on the texture of aluminum 6061 alloy is investigated. with SR-CT scan to achieve the 3D segementation of The formability of the alloy is evaluated. The texture of precipitated phases, corrosion cracks and corrosion the rolled Al alloy sheet was analyzed by XRD. products. The effect of aging treatment on exfoliation corrosion behavior were firstly studied. The results demonstrate that aging treatment has a significant effect on the distribution of the precipitated phase, and the precipitated phases continuously distributed along the grain boundary would contribute to IGC which is 211 Technical Program
11:50-12:10(1266797) Research on Heat Treatment Optimization of High Zn-Containing Al-Zn-Mg-Cu Alloy Kang Du, Chinalco Group, China
The effects of single-stage, dual-stage solution treatment and retrogression re-ageing treatment on redissolution of alloying elements and mechanical properties change of high Zn-containing Al-Zn-Mg-Cu alloy were investigated in this paper. Microstructure evolution, conductivity change and tensile property comparison were occupied to optimize the solution treatment parameters. According to the OM, SEM and EDS analysis, the secondary phases existing in extrusion are mainly T(AlZnMgCu) phase and Al7Cu2Fe phase with
a few of MgZn2 phase. The melting point of the alloy is 476℃by DSC test. According to the conductivity test and tensile property test results, dual-stage solution treatment lead to a better secondary phases solubility and better property stability than single-stage solution Wednesday AM | August 21, 2019 AM | Wednesday treatment. 460℃/2h+470℃/4h was recognize as optimal solution treatment parameter. The results also show that, dual-stage solution treatment has better solubility than single-stage solution treatment in the point of conductivity and AIMP view. The conductivity extremum could be as low as 15MS/m, and the AIMP value could goes down to 0.5J/g. RRA treatment leads to higher conductivity than traditional T6 heat treatment of the Al- Zn-Mg-Cu alloy. The highest tensile property in this alloy is 729MPa in ultimate strength and 10.3% in elongation. Dual-stage solution treatment also benefit the property improvement and stability for industrial production line than single-stage solution treatment.
212 13:55-14:15(1233798) C1. Light Metals and Alloys- Effect of Heat Treatment on Hydrogen Aluminum: IV Embrittlement of an Al-10Zn-2.6Mg-1.6Cu-0.2Cr Symposium Organizers : Alloy Wednesday PM | August 21, 2019 Baiqing Xiong, GRINM Group Co. Ltd., China; Yoshihito Toshiaki Manaka, Mitsuharu Todai, National Institute Kawamura, Kumamoto University, Japan; Young Min Kim, of Technology, Niihama College, Japan Korea Institute of Materials Science (KIMS), Japan; Jian-Feng Nie, Monash University, Australia; Diran Apelian, Worceste Al-Zn-Mg-Cu alloys have been used as structural Polytechnic Institute, USA components due to their high strength. Large amounts of Zn and Mg elements additions increase strength, Wednesday PM Room: Presidium Conference Room but stress corrosion cracking (SCC) susceptibility also August 21, 2019 Symsposium: C1 increase. Crack propagation of SCC in the Al-Zn-Mg- Cu alloys is caused by hydrogen embrittlement. The Chairs: peak-aged Al-Zn-Mg-Cu alloys show a degradation of Shinji Muraishi, Tokyo institute of technology, ductility in humid air (HA) compared to dry nitrogen gas Japan (DNG) when tensile testing is conducted at a slow strain Cheng Liu, CHINALCO Materials Application rate. In humid air, hydrogen uptake occurs resulting Research Institute, China from the reaction of water vapor with aluminum fresh surface. Although many studies have been carried out to improve SCC susceptibility of these alloys, the 13:30-13:55 Invited (1385109) mechanism of hydrogen embrittlement has not been Prediction and Evaluation of Residual Stress in elucidated yet. In the present study, effect of heat Aircraft 7050 Thick Plates treatment on hydrogen embrittlement of an Al-Zn-Mg-Cu Cheng Liu, J. Q. Wang, H. L. Cao, G.M. Niu, alloy with high Zn content was investigated by tensile CHINALCO Materials Application Research Institute, testing at various strain rates from 10-6s-1 to 10-3s-1 in China humid air and dry nitrogen gas. The tensile test pieces were solution-treated at 470℃ for 1h, water-quenched To meet increasing demand on weight reduction and and followed by different aging treatments, natural structure performance, a large amount of integral aging, peak aging and overaging. The tensile strength structures are used in modern aircrafts. The integral in peak-aged sample was ~650MPa, larger than that structures are manufactured by machining aluminum of the commercial high strength 7075 aluminum alloy. thick plates. Residual stress in the aluminum thick The elongation of specimens in any aging condition plates could cause unacceptable structure distortion at a strain rate of 10-6s-1 was smaller in HA than in during and after machining. To get a better control on DNG due to hydrogen embrittlement. Fracture surface the residual stress in thick plates, we have worked observation revealed that intergranular fracture resulted on the following aspects: predicting residual stress in a loss of elongation in naturally aged and peak-aged evolution in key production steps including quenching specimens, while quasi-cleavage fracture was observed and stretching, developing and selecting on-site fast in over-aged specimens. Moreover, in naturally aged residual stress measurement method and setting-up a and peak-aged specimens, elongation decreased due residual stress internal control standard. Firstly a FEM to hydrogen embrittlement even at a strain rate of 10-3s-1. model was constructed to establish the relation among process parameters, residual stress and distortion. 14:15-14:35(1235140) After validation, the model was used to generate a Effect of Ti Addition on Microstructure Evolution, database containing key process parameters, residual Precipitation and Mechanical Properties of Al-Zn- stress and distortion. Based on the database, a software Mg-Cu-Zr Alloy tool was developed being able to in-line predict the Sang-Hwa Lee, Korea Institute of Materials Science residual stress based on actual process parameters. (KIMS), Korea / Yonsei University, Korea; Jae-Gil Based on the database, a very accurate residual stress Jung, Min-Seok Kim, Kwangjun Euh, Korea Institute measurement method was designed. In addition, of Materials Science (KIMS), Korea; Se-Hun Kim, ultrasonic method was also evaluated for suitability Korea Automotive Technology Institute (KATECH), for the onsite measurement. Then both methods were Korea; Sung-Hyuk Park, Kyungpook National University, used to measure a large number of thick plates as well Korea; Young-Kook Lee, Yonsei University, Korea many imported 7050 ones. From these measurements a company internal residual stress standard was set-up We investigate the effects of Ti addition on the for quality control purpose. microstructure evolution, precipitation and mechanical
properties of high strength Al–7.6Zn–2.6Mg–2.0Cu– 275 Technical Program
0.1Zr alloy during casting, extrusion and heat at various temperature and time, then NA at RT for two treatment. The microstructure evolutions of the alloys weeks (named as PA-NA). Next, the two kinds of NA were examined using scanning electron microscope specimens were AA at 170℃ for 6h (named as NA/ (SEM), electron back-scattered diffraction (EBSD), AA, PA-NA/AA, respectively). The unreinforced alloy and transmission electron microscope (TEM), and their was fabricated and heat treated by the same method mechanical properties were evaluated by hardness for comparison. Results from the hardness and tensile and tensile test at room temperature. The addition of test showed that the hardening response in PA-NA Ti causes the refinement of Al grain and agglomerated specimens was weaker than that in specimens without eutectic phases in the as-cast alloy. The Ti addition PA. Moreover, the strength of PA-NA/AA specimens increases the number of η-phase bands aligned along was higher than that of NA/AA specimens, and this extrusion direction by reducing their length and spacing. phenomenon is more obvious in the composite than in The Ti addition also causes the refinement of η-phase the unreinforced alloy. The most suitable PA process is particles present between the η-phase bands. In addition, 150℃, 10min. Transmission electron microscopy results the Ti addition increases the area fraction of dynamically reveal that the size of precipitates in NA/AA composite recrystallized (DRXed) grains formed during extrusion, was larger than that in PA-NA/AA composite. Calculation while it decreases the size of DRXed grains. During based on Orowan strengthening mechanism showed solution treatment of the extruded alloy at 450℃, the that the smaller precipitates size and higher precipitates addition of Ti causes the refinement of L12-structured density in PA-NA/AA composite could be responsible dispersoids by changing the chemical composition for higher strength. The phase transformation activation
from Al3Zr to Al3(Zr,Ti) as well as the formation of new energy was calculated according to the Avtami-Johnson- Al Mg Ti dispersoids. The Al Mg Ti dispersoids act Mehl (AJM) theory based on differential scanning
Wednesday PM | August 21, 2019 PM | Wednesday 18 3 2 18 3 2 as preferential nucleation sites of η precipitates during calorimetry. Results show that the dissolution activation artificial aging at 120℃. The kinetics of η' precipitation energy of clusters was much larger, but the precipitation in the matrix is accelerated by the addition of Ti. The activation energy was lower in PA-NA specimens than Ti-induced changes in the microstructure, dispersoids in NA specimens, which indicates that clusters formed and precipitates improve the strength and ductility of T6- during PA is more stable and can become favorable treated extruded alloy. nucleation sites for precipitates during AA, resulting in higher strength in PA-NA/AA specimens. The difference 14:35-14:55(1306919) of phase transformation activation energy between PA- NA specimens and NA specimens was more obvious in Influence of Pre-Aging and Natural Aging on the composite than that in the unreinforced alloy, leading Mechanical Property of SiC/6xxxAl Composite to the larger increment in strength between PA-NA/AA Shize Zhu, Shenyang National Laboratory for specimens and NA/AA specimens in the composite. Materials Science, Institute of Metal Research, Chinese Academy of Sciences, China / School of 14:55-15:15(1235313) Materials Science and Engineering, University of Science and Technology of China, China; Dong Effect of Excess Si on Age-Hardening Behaviour Wang, Bolv Xiao, Zongyi Ma, Shenyang National in Al-Mg2Si Cast Alloy Aged at 473K Laboratory for Materials Science, Institute of Metal Taiki Tsuchiya, Yuki Makita, Seungwon Lee, Seiji Research, Chinese Academy of Sciences, China Saikawa, Susumu Ikeno, Kenji Matsuda, University of Toyama, Japan Some aluminum matrix composites based on heat
treatable aluminum alloys, with poor ductility at artificial Al-Mg2Si alloy is age-hardening alloy and used for aging (AA) state, could be cold worked at natural aging structural materials. Metastable phase affects hardening (NA) state and service after AA. However, the cluster in this alloy. The alloy having higher Si content than
behavior during NA will increase the strength of NA quasi-binary Al-Mg2Si alloy is called as excess Si type composites and impair the hardening response during alloy. This alloy has higher peak hardness than quasi-
AA, which are adverse for the above strategy. In this binary Al-Mg2Si alloy by aging heat treatment. In our study, the pre-aging (PA) treatment was used to inhibit previous work, we researched age-hardening behavior the adverse influence of NA. The composite, with a in excess Si type aluminum alloy to know precipitation nominal composition of Al-1.2Mg-0.6Si-1.0Cu (in weight sequence. And recently, we are investigating age- fraction) and 17% (in volume fraction) SiC particles, was hardening behavior in Al-7mass%Si-0.3mass%Mg cast fabricated by powder metallurgy (PM) process then hot alloy to know precipitation sequence. Al-7mass%Si-
extruded to the bar. The extruded bar was solution treated 0.3mass%Mg alloy is considered to Al-0.5mol%Mg2Si- at 540℃ then water quenched to room temperature 6.4mol%Si alloy. So the aim of this work is to investigate (RT). The quenched specimens were subjected to two the effect of excess Si contents on age-hardening aging process: (i) NA at RT for two weeks. (ii) Pre-aging behavior and microstructure evolution in Al-Mg2Si 276 cast alloy. The samples with basic composition Al- by Peach-Koehler formula. According to simulation
0.5mol%Mg2Si were casted into iron mold. Then we results, dislocation interaction strongly depends on the measured temperature in cast and quenched into iced stress field and geometry of misfit precipitates, repulsive water when that temperature reached under 773K. The and attractive force are operated on the dislocations amount of Si addition in excess were 0.2mol%, 0.4mol%, laying on the primary slip plane, and simultaneous climb Wednesday PM | August 21, 2019 0.8mol%, 1.6mol%, 3.2mol% and 6.4mol%. We called force becomes significant when dislocation approaching samples as Base alloy, 0.2Si alloy, 0.4Si alloy, 0.8Si toward the misfit precipitates. Hardening ability of alloy, 1.6Si alloy, 3.2Si alloy and 6.4Si alloy, respectively. precipitate is discussed in terms of energy dissipation The samples were cut by diamond-cutter and polished. associated with dislocation motion We measured hardness of as-cast using micro-vickers hardness measurements (load:0.98N, holding time 15s) 16:35-16:55(1235469) and after that the samples were aged at 473K. The Microstructural Characteristics of the Stir Zone for effect of excess Si addition on microstructures were Friction Stir Processed 5083 Aluminum Alloys researched using transmission electron microscopy Tsutomu Ito, Toyama Prefectural University, Japan; (TEM, Topcon EM-002B). Takashi Mizuguchi, Ehime University, Japan Result of hardness tests, hardness of as-cast and peak- hardness increased with increasing Si content. The mechanical properties of crystalline metallic We performed TEM observation in Base alloy from materials can be enhanced by strengthening the grain [001]Al direction. There were two regions. One is small interior and grain boundaries, as described by the Hall- amount of precipitates region, another is large amount Petch relationship. The strengthening mechanisms for of precipitates region. Rod-shape precipitates along the grain interior include solid-solution strengthening, <100> direction were observed in both region. We precipitation/dispersion-strengthening, and work observed cross section of rod-shape precipitates more hardening; and the strengthening mechanism for the higher magnification. We measured lattice spacing and grain boundaries of the materials is grain boundary internal angle of precipitates. It was confirmed that strengthening, which depends on the grain sizes. precipitates was β'. We will report other observation Material strengthening is expected to affect weight results on the day. saving of various structural members by decreasing the thickness of the materials. Therefore, development 15:30-16:10 Tea Break of microstructure refinement processes through severe plastic deformation (SPD) techniques such as equal 16:10-16:35 Invited(1234351) channel angular pressing (ECAP), high pressure Micromechanics Based Precipitation Hardening torsion (HPT), and accumulative roll bonding (ARB) Analysis in Aluminum Alloys have been recently conducted in the laboratory scale. Shinji Muraishi, Jianbin Liu, Tokyo Institute of This study attempts to use friction stir processing Technology, Japan (FSP) as a microstructure refinement process. FSP is a microstructure refinement process that employs the Fine misfit precipitates in age-hardenable aluminum principles of friction stir welding (FSW), which is a solid- alloys has important roles in their excellent age- phase bonding process developed by the welding institute hardening ability by their interaction with dislocations, so (TWI) in the United Kingdom (UK) in 1991; this process the design of precipitation microstructure has attracted can be used to obtain fine-grained microstructures of ≤ much attention in many decades. Typical precipitation sizes 10μm through very few operations. The practical microstructure in peak hardness consists of GP-zones uses of FSW in various fields such as civil engineering, and meta-stable phase on certain habit planes in construction, railway, automotive, and aerospace have aluminum alloys, e.g. {001} GP zones and θ" plates in Al- been demonstrated. However, FSP, which is based on Cu alloys, {001} β" needles in Al-Mg-Si alloys, spherical the principles of FSW, is required the something ideas GP-zones and {111} η" in Al-Zn-Mg alloys, etc. such as the increasing method of microstructural refining Present study focused on the internal stress field of volume or use as selectively microstructural refinement precipitates with various different shapes and misfit because the volume permitted by microstructural strains to evaluate their roles in dislocation cutting and refinement depends on the tool geometry. Therefore, by-pathing manners in terms of numerical computation this study conducted a single-pass FSP using various based on micromechanical Green's function method. FSP conditions for the solid-solution strengthening type Stress field of misfit precipitates on certain habit 5083 aluminum alloy. This paper briefly reports the plane is reconstructed by homogeneous misfit strain microstructural characteristics formed in the stir zone, (eigenstrain) in precipitate (Eshelby inclusion method), and the area of stir zone. and dislocation motion vector on primary slip and cross- slip planes are predicted by force acted on the dislocation 277 Technical Program
16:55-17:15(1310475) 17:15-17:35(1235532) Online Prediction of Mg Alloys Melt Structure TEM Observation of Al-2.5wt%Li(-2.0wt%Cu) under Temperature and Electromagnetic (-2.0wt%Mg) Alloys Deformed by HPT (High Field Inducement by Electrical Resistivity and Pressure Torsion) Thermoelectric Power Seungwon Lee, Yuhei Haizuka,Taiki Tsuchiya, Seiji Qing Lan, Qichi Le, Ruizhen Guo, Jianfeng Zhang, Saikawa, Kenji Matsuda, Susumu Ikeno, University Northeastern University, China of Toyama, Japan; Zenji Horita, Kyushu University, Japan; Shoichi Hirosawa, Yokohama National In this paper, temperature-induced the electrical University, Japan resistivity and thermoelectric power variation of Mg-Gd binary alloys melt have been studied with four-point Severe plastic deformation (SPD) processes attracted probe technique, as well as the thermoelectric power of attention in recent years as a method of grain refinement. these two alloys melt at constant temperature induced High-pressure torsion (HPT) process can introduce a by alternating current (AC) electromagnetic fields. large amount of strain continuously compared to other It should be noticed that online electrical resistivity SPD processes. Al-Li alloys have low density and are and thermoelectric power provide the real-time and strengthened by dispersed fine precipitates through an continuous measurement for the melt structure during aging treatment, traditionally. They have been used as the temperature inducement or electromagnetic field aircraft materials. The intention of this research is to treatment process. In our research, the heating or cooling investigate the effect of Cu and Mg on Al-Li alloys on melt temperature is in the range of 580~720℃, and the grain refinement using HPT process and aging behavior Wednesday PM | August 21, 2019 PM | Wednesday melt is respectively under the liquid-solid mixed stae, using aging treatment. semi-solid stae and absolute liuqid stae. Both electrical In this research, three kinds of alloys (Al-2.5%Li, Al- resistivity and thermoelectric power show the invertibility 2.5%Li-2.0%Cu, Al-2.5%Li-2.0%Mg alloy in wt.%) during the heating and cooling process. The results also were prepared by casting. Alloys were subjected to a indicate that temperature-induced thermoelectric power homogenization treatment at 808K for 12h, then, they and electrical resistivity change occurs in the semi-solid were undergone hot-rolling to the thickness of 1.2mm. state, and temperature-induced change point attributes Disks with 10mm diameter were cut from the sheets to Gd content in magnesium alloys. using an electrical discharge machine (EDM). The discs On the other hand, the experimental constant were solution treated at 833K for 3.6ks at Ar atmosphere, temperature during the electromagnetic fields treatment then quenched into ice water. The solution treated is above the liquidus (640~730℃). The results show discs were subjected to HPT process under an applied that the thermoelectric power is strongly sensitive to pressure of 6GPa for 5 revolutions with a rotation speed the electromagnetic field, showing the sharp increment. of 1 rpm at room temperature. Aging treatments were Then thermoelectric power gets back to the initial conducted on the HPT-processed alloys at 423K for a value after turning off the electromagnetic field. Some total time period of up to 600ks. characteristic parameters of thermoelectric power The Micro Vickers hardness measurement was are extracted to indicate the melt structure variation conducted on a mechanically polished surface of the degree under the electromagnetic fields. The results disks. Each hardness measurement was performed show that the electromagnetic field induced the by using a load of 100g for 15s. After HPT process, characteristic parameters change occurs at different hardness increased significantly compared to as- experimental temperature, which attributes to the Gd quenched (asQ). During aging treatment, Al-Li-Cu and content in magnesium alloys. Furthermore, the effects Al-Li-Mg alloys reached peak aging at 0.48ks (8min), of electromagnetic field condition, such as the electrical however, Al-Li alloy did not change the hardness level current, electromagnetic field frequency and duty at the initial stage of aging, then hardness started to cycle, on the thermoelectric power of melt have also decrease. researched further. The microstructures of the disks were observed using a TOPCON EM-002B transmission electron microscope (TEM) operating at 120kV. The samples were thin disks electrochemically polished with a solution of 75vol.% methanol and 25vol.% nitric acid. In as-HPT sample, i.e.
no aging treatment, δ' (Al3Li) phase was observed. With an increase of aging time, it was possible to observe
the coarsened δ' phase in all alloys and T1 phase in Cu added alloy.
278 17:35-17:55(1234970) Integrated Development "High Entropy" Aluminum Alloys
Yu Zhong, Mohammad Asadikiya, Songge Yang, Wednesday PM | August 21, 2019 Libo Wang, Diran Apelian, Worcester Polytechnic Institute, USA
High entropy alloys have been greatly investigated in recent fifteen years due to their superior properties such as high strength, high hardness, high temperature softening resistance, etc. Meanwhile, the traditional aluminum alloys have attractive properties including light weight, high corrosion resistance, and high thermal conductivity, etc., it would be beneficial if a new alloy can be developed with the excellent properties of High entropy alloys and aluminum alloy combined. Especially, an "high entropy" concept alloy with the aluminum fcc matrix will be of great interests. In this project funded by Advanced Casting Research Center (ACRC) at Worcester Polytechnic Institute (WPI), the calculation of phase diagrams (CALPHAD) is combined with the experiments to design a multicomponent "high entropy" aluminum-rich alloy with fcc matrix. The "high entropy" concept borrowed from High entropy alloys shows a totally new composition region which has much higher entropy of mixing (delta Hmix) than the traditional aluminum alloys. In addition, the casting and heat treatment experiments with the CALPHAD proposed compositions are carried out. Especially the multiple-stage solutionization is carried out, which successfully avoided the commonly existed incipient melting phenomena. The final candidates show promising yield strength and ductility behavior.
279 9:00-9:20(1220357) C1. Light Metals and Alloys- Role of Subgrain Stripe in the Exfoliation Aluminum: V Corrosion Behavior of Al-4.6Mg-3.1wt%Zn Alloy Symposium Organizers :
Qingwei Ding, Di Zhang, Jishan Zhang, University Tuesday AM | August 20, 2019 Baiqing Xiong, GRINM Group Co. Ltd., China; Yoshihito of Science and Technology Beijing, China; Linzhong Kawamura, Kumamoto University, Japan; Young Min Kim, Zhuang, University of Science and Technology Korea Institute of Materials Science (KIMS), Japan; Jian-Feng Beijing, China / TaTa Steel, 1970 CA Ijmuiden, Nie, Monash University, Australia; Diran Apelian, Worceste Canada Polytechnic Institute, USA
Thursday AM Room: Presidium Conference Room As a kind of inhomogeneous microstructure generated August 22, 2019 Symsposium: C1 during dynamic recovery after plastic deformation, subgrain stripe has a significant effect on the properties of high alloying aluminum alloys. However, few attentions Chairs: have been paid on the effect of exfoliation corrosion Sri Lathabai, Shanghai Jiao Tong University, (EXCO) behavior. In this study, the effect of subgrain Australia stripe on the EXCO behavior of Al-4.6Mg-3.1wt%Zn Kenji Matsuda, University of Toyama, Japan alloy has been elucidated. The studied alloy sheets have been solid solution treated at 495℃ for 50min and 8:35-9:00 Invited(1235812) 1440min before artificial aging treatment respectively to Existence of Two Phases in Al-Zn-Mg Alloys obtain the microstructures with different volume fractions Containing Cu of subgrain stripe. Then the EXCO test of both status Kenji Matsuda, University of Toyama, Japan samples were carried out in the test solution for different immersing times. The observations showed that both We have proposed the existance of the universal clusters samples were suffered with corrosion, but the corrosion in age-hardenable aluminum alloys, for example, Al-Cu- rate of the sample with abundant subgrain stripes in its Mg, Al-Mg-Si, and Al-Zn-Mg alloys. The effect of Cu- microstructure was much faster than the other sample addition on age-hardening and precipitation in Al-Zn-Mg with lower volume fraction of subgrain stripes, so alloys has been investigated by hardness measurement, that the final EXCO rating was much higher after 48h tensile test, High Resolution Transmission Electron corrosion. These phenomena were also proved by the Microscopy (HRTEM) and Annular Dark Field Scanning electrochemical analysis that the sample with higher Transmission Electron Microscopy (HAADF-STEM) volume fraction of subgrain stripe in its microstructure techniques. Higher hardness, strength, and lower has more than twice of the corrosion current compared elongation were caused by increasing amount of Zn + to the other sample. To reveal the mechanism of the Mg because of increased number density of precipitates. difference mentioned above, the interfaces of the Cu addition also provided even higher peak hardness, samples after EXCO test were divided into two groups strength, and lower elongation. The alloy containing and observed under electron backscattered diffraction highest Cu content had fine precipitates of GPB-II and transmission electron microscopy respectively. zones or the second clusters which we proposed, in the One is the normal grain boundary and the other special precipitate free zones (PFZs) and the matrix, together interface is defined as the interface between subgrain with η'/η in the matrix from the early stage of aging. Two stripe and the normal grain. It was proposed that the regions have been confirmed as the PFZs: (i) nearest to higher residual stresses and strains were generated at grain boundary about 70nm in width and (ii) conventional the special interface than that of normal grain boundary PFZ about 400nm in width which can be confirmed by in the studied alloy. This kind of special interface acted conventional TEM. The conventional PFZ contains fine as a fast track for the propagation of corrosion during precipitates consisting of GPB-II zones or the second the EXCO test, which accelerated the corrosion rate of clusters, even for 2 minutes of aging at 473K which were the alloy. not present in the PFZ nearest to grain boundaries. The fine precipitates, GPB-II zones or the second clusters 9:20-9:40(1221704) in the conventional PFZ and the matrix disappeared at Differences in Microstructure and Mechanical overaged condition. Characteristics of Al Alloy Sheet Containing RE Element Produced by Strip and Direct Chill Casting Seonghyeon Yoo, Heon Kang, Hojun Park, Namhoon Goo, Hyundai-steel, Korea
Aluminum alloy has been spotlighted as a light-weight 7 Technical Program
structural material in automotive industry and its catastrophic result. Therefore, extensive attention was application to sheet material for vehicle has recently attracted to advance the understanding of localized been expanded due to environmental regulation and corrosion behaviour in aluminium alloys to ensure the reduction weight of automotive. Among the Al alloys, transportation safety. heat-treatable Al 6000 series alloy has been most In the present work, the correlation between studied for vehicle because it has sufficient ductility stored energy distributions with localized corrosion after solution treatment and high strength after a baking development in AA2024-T351, 2A97-T8 and AA6082-T6 process. The Al 6000 series alloy sheet requires high aluminium alloys was investigated. Scanning and plasticity and uniform formability to form complex shape transmission electron microscopes were employed to and alloy design and processes are being studied to characterize the corrosion morphology of aluminium satisfy these properties. alloys. Electron backscatter diffraction analysis was Recently, rare earth metals (RE) which were mainly conducted at the localized corrosion site to correlate used in Mg alloys, are used as the Al alloy element stored energy distribution to the development of localized because the RE element can improve the strength and corrosion. It is revealed that localized corrosion occurs plasticity of Al alloy by refinement and sphericalization in aluminium alloys in forms of intergranular attack and of eutectic and secondary phases. The general methods crystallographic pitting, which tends to occur in the of producing aluminum alloys are D.C (direct chill) regions with higher levels of stored energies in all three casting and strip casting. For D.C casting, the Al alloy alloys, suggesting that region with higher stored energy sheet produced through many process such as casting, exhibiting higher localized corrosion susceptibility and grinding, heat-treatment, hot rolling and cold rolling. In vice versa.
Tuesday AM | August 20, 2019 AM | Tuesday other hand, the strip casting has several advantages The correlation between stored energy distribution and such as low process cost and minimized hot rolling localized corrosion development may be associated process result that it is possible to control the texture with the combined effect between thermodynamic rather than D.C casting. stability and precipitation behaviour during the In this study, the Al alloy containing RE element (Ce, thermomechanical process of aluminium alloys. La) with high formability were designed for automotive sheet in lab-scale. Furthermore, the Al alloy sheet also 10:00-10:20(1235125) produced using the conventional D.C casting and strip Liquid Phase Separation of Ternary Al-Sn- casting in pilot-scale. The microstructure and texture Cu Immiscible Alloy within Three Orthogonal of produced Al alloy sheets by lab and pilot-scale Ultrasounic Field processes analyzed using a OM (optical microscope), Wei Zhai, Bingbo Wei, Northwestern Polytechincal SEM (scanning electron microscope) and EBSD University, China (electron backscattered diffraction). The tensile test conducted using a UTM (universal testing machine) Applying power ultrasound during solidification based on ASTM standards. The mechanical properties has proven to be an effective way to improve the of the produced Al alloy sheet improved compare to microstructure and enhance the mechanical properties conventional Al alloy. The strengthening mechanism of metal alloys. The most popular way for introducing of the RE element and effects of strip and D.C casting ultrasound is to insert a vibrating ultrasonic horn into processes on mechanical properties and texture of Al the solidifying liquid alloys. However, the disadvantage alloy sheet will be more detail discussed. of this one dimensional ultrasound method is that the
ultrasonic effects are always confined to a limited 9:40-10:00(1234531) volume, beyond which weak or even no influence on the The Correlation between Stored Energy on microstructures takes place. Localized Corrosion Development of Aluminium To overcome the disadvantage of one dimensional Alloys ultrasound, in the present work, we propose firstly by Xinxin Zhang, Huazhong University of Science numerical simulation that the employment of three and Technology, China / University of Manchester, orthogonal ultrasounds can greatly enhance the sound United Kingdom; Zehua Dong, Huazhong University pressure level and enlarge the cavitation volume which of Science and Technology, China; Xiaorong Zhou, may strengthen the effect of ultrasounds on the resultant University of Manchester, United Kingdom microstructure. Then, we experimentally apply three orthogonal ultrasounds during the liquid phase separation High strengthen aluminium alloy was widely used as process of ternary Al71.9Sn20.4Cu7.7 immiscible alloy. structural components of transportation industry due to In contrast to the layered structure caused by the large its high strengthen weight ratio and low manufacturing density difference between the two immiscible liquid (Al) cost. However, high strengthen aluminium alloys and (Sn) phases, a uniform microstructure consisting of were not immune to localized corrosion, especially in fine secondary (Sn) phase dispersed on Al-rich matrix is 8 chloride-containing environment, which could lead to fabricated in the whole alloy sample with a large size of 30mm×30mm×100mm. Theoretical analyses indicate of high strength, high electrical conductivity and that the coupled effect of three ultrasounds promotes light density, graphene reinforced aluminum matrix the sound pressure level and consequently enlarges composites has attracted great attention in recent the cavitation zone within the alloy melt. The strong years due to the excellent mechanical and electrical shockwaves produced by cavitation prevent the (Sn) performance of graphene. Aluminum matrix composites Tuesday AM | August 20, 2019 droplets from coalescence, and keep them suspended reinforced with graphene nanoplatelets (GNPs) were in the parent Al-rich liquid phase. This accounts for the prepared by continuous casting and subsequent rolling. formation of homogeneous composite structures. Thus The ultimate tensile strength of Al-0.2wt.% GNPs the introduction of three orthogonal ultrasounds is an composites was about 36.8% higher than that of pure effective way to suppress the macrosegregation caused Al with the same casting and rolling process with the by liquid phase separation and produce bulk immiscible conductivity of the composites decreased slightly, alloys with uniform structures. indicating that interface scattering between Al and GNPs is very limited. The investigation results show that Al- 10:20-10:45 Tea Break GNPs composite is potential for high strength and high conductivity application. Better understanding of the interface is the key to achieving graphene/Al composites 10:45-11:10 Invited(1234400) with superior performance. To investigate the phase Corrosion Behaviour of Additively Manufactured composition and interface bonding between Al matrix AlSi10Mg Aluminium Alloy and GNPs and evolution of interface structure during Sri Lathabai, Kishore Venkatesan, Paul White, David deformation, graphene nanoplatelets and Al matrix in Ritchie, Aaron Seeber, Avi Ben David, Mark Greaves, Al-GNPs composites prepared by ball milling, spark ZSIRO, Australia plasma sintering (SPS) and subsequent hot extrusion. High resolution transmission electron microscopy Additive Manufacturing (AM) has emerged as a vital (HRTEM) was used for interface observation. Tensile tool in the rapid fabrication of metal components in tests were carried out on as-SPSed and as-extruded various engineering applications. AM involves the GNPs/Al composites to evaluate the interface strength. 5-layered interfaces Al/Al O /GNPs/Al O /Al were building of a part directly from its CAD file, in a layer 2 3 2 3 by layer manner. In Selective Laser Melting (SLM), a observed in the as-SPSed composites and some fresh powder bed is selectively melted using a laser beam, GNPs/Al interfaces formed after hot extrusion and led to the formation of 7-layered interfaces Al/Al O /GNPs/Al/ in accordance with the sliced CAD file. Steep thermal 2 3 GNPs/Al O /Al. No evidence of Al C were found in the gradients, directional heat extraction, repeated thermal 2 3 4 3 cycles induced by the layer by layer melting all result interface. However, stacking faults were observed in the in unique microstructures in the AM built materials, Al matrix near the interfaces resulted from high stress resulting in mechanical and functional properties that formed during SPS. Individual GNPs engulfed inside the can be quite different from those of conventionally built Al grains was observed after extrusion, indicating the good wetting between Al with amorphous Al O layer on counter parts. In this paper, we present the results 2 3 of an investigation into the corrosion behaviour of the surface and GNPs. The composite deformation and load transfer across the interfaces contributed by the AlSi10Mg aluminium alloy produced by SLM in NaCl solutions and compare the results with those of a die- multilayered structure were confirmed by strengthening analysis. cast AlSi10Mg alloy. Potentiodynamic tests, polarisation testes and immersion tests were conducted to examine the effects of the build orientation, surface finish. The 11:20-11:40(1222232) corroded surfaces were examined by X-ray diffraction High Strength, High Ductility 7xxx Series and scanning electron microscopy to determine the Aluminum Alloys type of corrosion products and to gain insights into the Hojun Park, Heon Kang, Seonghyeon Yod, Nam corrosion mechanism. The efficacy of a diamond-like Hoon Goo, Hyundai-steel, Korea carbon coating on the as-built surface on enhancing the corrosion resistance of AlSi Mg was investigated 10 Aluminum demand for automobile industry has been rising recently due to the increasing demand 11:10-11:20(1300781) for light weight of automobile bodies. Technological Interfaces in Graphene Reinforced Aluminum developments have been actively carried out to Matrix Composites overcome the limitations of mechanical properties Haiyan Gao, Min Li, Jun Wang, Baode Sun, Shanghai and productivity of automobile aluminum sheets and Jiao Tong University, China to secure economical applicability. In the case of automobile bumper beams, 6xxx series and 7xxx series Facing with the urgent demand for conductive materials aluminum alloys are mainly used. In recent years, study 9 Technical Program
has been carried out to increase the productivity through the rolling process by improving the formability of alloys due to the preference of 7xxx series (Al-Zn-Mg) alloys with higher yield strength. Al-Zn-Mg has a disadvantage in that it has difficulty in cold forming because of its high strength but lack of ductility. In this study, by adding Cu and Si elements to Al-Zn-Mg alloy, the alloys with yield strength of 340MPa or more and elongation of 15% or more were developed under T6 condition to secure high strength and high ductility. Through the thermodynamic simulation, the phase composition, amount and the solidification behavior were predicted, and the sheet was fabricated through rolling process after gravity casting. The effects of additive elements on the microstructure of homogenization, solution treatment and artificial aging were analyzed and mechanical properties and formability were evaluated. Optimum heat treatment conditions for improving the yield strength and elongation were derived
by controlling the precipitation behavior of the MgZn2,
Al2Cu, Mg2Si and other phases and the microstructures Thursday AM | August 22, 2019 AM | Thursday such as grain size and crystal structure. In addition, Alloys were fabricated by twin roll casting (TRC) process and direct chill cast (DC) process, and the properties and microstructure were compared and evaluated. The mechanical properties were evaluated by tensile strength and the microstructure was analyzed by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscattered diffusion (EBSD) and transmission electron microscopy (TEM) .
10 Technical Program
14:00-14:20(1222670) C1. Light Metals and Alloys- Effects of Ultrasonic Treatment on Microstructure Aluminum: VI and Mechanical Properties of Mg-6Zn-0.5Y-2Sn Symsposium Organizers: Magnesium Alloys Baiqing Xiong, GRINM Group Co. Ltd., China; Yoshihito Zhihui Xing, Gaozhan Zhao, Ming Li, Jianquan Tao, Kawamura, Kumamoto University, Japan; Young Min Kim, Zhiwei Huang, No.59 Institute of China Ordnance Korea Institute of Materials Science (KIMS), Japan; Jian-Feng Industry, China; Hansong Xue, College of Materials Nie, Monash University, Australia; Diran Apelian, Worceste Science and Engineering, Chongqing University, Polytechnic Institute, USA China
Thursday PM Room: Presidium Conference Room In this paper, the effects of melt ultrasonic treatment on August 22, 2019 Symsposium: C1 the microstructure and mechanical properties of Mg- 6Zn-0.5Y-2Sn magnesium alloy was studied by means Chairs: of ultrasonic vibration treatment with different powers Timothy Langan, Clean TeQ, United States ( 0W, 300W, 500W and 700W) during solidification process of Mg-6Zn-0.5Y-2Sn magnesium alloy. The 13:30-13:55 Invited (1235843) results show that the appropriate ultrasonic treatment can not only improve the microstructure of the as-cast Precipitation of Stable Sc-Containing Dispersoids and extruded experimental alloys, but also significantly in High Strength Aluminum Alloys Thursday PM | August 22, 2019 Thursday PM | improve their mechanical properties. Timothy Langan, Clean TeQ, United States The microstructure of the as-cast Mg-6Zn-0.5Y-2Sn
alloy is mainly consisted of α-Mg phase, MgZn2 phase, Scandium, the most potent alloying element that can MgSnY phase, Mg2Sn phase and I-phase (Mg3Zn6Y, be added to aluminum, has been shown to improve with small amount). With the application of ultrasonic performance of alloys in a number of ways including; treatment, the small amount I-phase and the existed i) refining grain size during solidification, ii) reducing coarse dendrites microstructure nearly disappear, and or eliminating recrystallization in wrought product, iii) with the increase of the ultrasonic treatment power, the precipitation of very potent stable coherent disperdoids coarse dendrites microstructure is gradually changed and iv) enhanced nucleation of strengthening phases into roundish equiaxed grains. And the morphologies (e.g., refined distribution of theta prime phase in Al-Cu of MgZn2 phase, MgSnY phase and Mg2Sn phase are alloys). Early work by Willey at Alcoa demonstrated transformed from coarse, semi-continuous and non- that modified heat treatment schedules can be used to uniform to fine, discontinuous, uniform and dispersive. enhance strengthening in Sc-containing alloys. This talk When the ultrasonic treatment power is 700W, the best will review the recent development of heat treatments ultimate tensile strength (245.6MPa) and elongation designed to optimize precipitation of stable Sc-containing (20.2%) of Mg-6Zn-0.5Y-2Sn alloy are obtained, the best dispersoids in commercial aluminum alloys. Work will 0.2% tensile yield strength (83.0MPa) is achieved when be highlighted that elucidates the effects of alloying the power is 500W. Compared with the untreated alloy, and trace elements in commercial alloys on nucleation, the best 0.2% tensile yield strength, ultimate tensile growth and stability of these dispersoids. Specifically strength and elongation are improved by 43.1%, 30.2% looking at interactions with Cu in Al-Cu 2xxx alloys; and 66.9%, respectively. Mg in Al-Zn-Mg 7xxx and Al-Mg 5xxx; and Si in Al-Si- The microstructure of the as-extruded Mg-6Zn-0.5Y-2Sn Mg 6xxx. Results of advanced characterization studies alloy is mainly consisted of α-Mg phase, MgSnY phase have been used to guide these efforts. Work shows that and Mg2Sn phase. After 700W ultrasonic treatment, the interactions between Sc, vacancies and other alloying microstructure of the as-extruded Mg-6Zn-0.5Y-2Sn alloy elements impacts nucleation of both the Sc-containing is mainly consisted of α-Mg phase and MgSnY phase. dispersoids and strengthening phases. Approaches to The MgSnY phase is fine, dispersive and uniform. The incorporate heat treat schedules designed to precipitate Mg2Sn phase has been broken into fine and dispersive Sc-dispersoids into conventional heat treat schedules particles and dissolved into α-Mg matrix significantly. used to homogenize commercial alloys will also be The average recrystal grain size reduces from about discussed. 21μm to 15μm. When the ultrasonic treatment power is 300W, the best 0.2% tensile yield strength (178.8MPa) is achieved. When the ultrasonic treatment power is 500W, the best elongation (19.6%) is achieved. When the ultrasonic treatment power is 700W, the best tensile strength (327.7MPa) is achieved. Compared with the untreated alloy, the best 0.2% tensile yield strength, 28 ultimate tensile strength and elongation are improved by 7.2%, 12.3% and 74.3%, respectively. 14:40-15:00(1222686) Influence of Continuous Pulsed Current Treatment 14:20-14:40(1221370) on the Dynamic Behavior of Mg/Al Composite Microstructural Investigation of High Strength Plate Fabricated by Explosive Welding
Self-Piercing Riveted Joints of Different Car Body Xiaoqing Cao, Xuewen Zhang, Xinxiao Zhu, Xiaolei Thursday PM | August 22, 2019 Aluminum Alloys Cui, Peng Lin, Taiyuan university of technology, China Ebad Bagherpour, Yan Huang, Zhongyun Fan, Brunel Centre for Advanced Solidification Technology In recent decades, the research and preparation of (BCAST), Brunel University London, United Kingdom laminated metal composite plates have attracted wide attention of scholars and experts due to their excellent Self-piercing riveting (SPR) as a solid-state joining physical, chemical and mechanical properties by technology has extended its application in the taking into account the characteristics of its member automobile industry in recent years, mostly in the metal materials. The preparation of Mg/Al laminated joining of car body aluminum sheets. A number of composite plates with lightweight, high strength and investigations have been carried out to study the effect corrosion resistance which has both advantages of of the rivet, die and process parameters including components metals and achieves the complementary material stacks on the joint quality either by physical and optimum properties has attracted much attention. experiment or computer simulation. However, most Explosive welding has high bonding strength, relatively investigations have been able to focus only on the thin di usion layer, no porosity and other defects. But effect of a limited rivet and die conditions and process there is a little work reported on the dynamic behavior of parameters. In particular, the characteristic features of Mg/Al composite plates especially the one fabricated by microstructures around the joint and their dependence explosive welding. In this study, Mg/Al composite plate on the rivet and die conditions and process parameters, was prepared by explosive welding with good bonding which are important to understand material behavior strength. After explosive welding, Mg/Al composite is during the joining process, optimize process parameters usually heat treated (annealing) to eliminate high residual and improve joint quality, are not considered in these stress from explosive wave, but this process will cause investigations. In the present work, a comprehensive brittle intermetallic compounds between magnesium investigation is conducted to study the performance of alloy and aluminum alloy and damaged the property of the SPR process for car body aluminum alloys including the composite plate. Continuous pulse current treatment AA6111, AA6082, AC170, and RC5754. A wide range is an useful way to reduce the detriment according some of rivet and die conditions and process parameters researchers work. The magnesium plate and Mg/Al are tested under various stacks between similar and composite plastic fabricate by explosive welding were dissimilar aluminum alloy sheets with different thickness. treated by continuous pulsed current with different current Shear and peel tests are performed to evaluate the joint density respectively, and their dynamic behavior under mechanical properties. The microstructures of typical different strain rates were tested by Hopkinson pressure joints are examined by optical microscopy, scanning bar test system to indicate the effect of pulsed current electron (SEM) microscopy and electron back-scatter treat. To clarify the mechanism of pulsed current treat, diffraction (EBSD), and material flow pattern during the microstructure change before and after continuous joining is characterized accordingly with much higher pulsed current treatment of magnesium and Mg/Al accuracy than that from low magnification observations. composites were observed by OM, SEM, EBSD. The Also, the effect of riveting on the texture of the sheets results showed that Mg/Al composite plate by explosive was investigated. It was confirmed that the area around welding has better response under dynamic condition the outer wall of the tail of the rivet in the lower sheet compared with magnesium plate under both conditions, exhibited the highest deformation and possibly tolerated i.e. with and without continuous pulsed treatment. The the highest tensile stress. Besides, the best conditions results will help to widen the use of magnesium alloy in of joining for the various car body aluminum alloys were collision condition such as automobile buffer beam and defined in order to achieve the best combination of peel weapons. and shear strengths.
29 Technical Program
15:00-15:20(1233808) that the addition of graphene has a certain shielding effect on corrosion. But in the previous study, graphene The Microstructure, Tensile Properties and Wear is disordered in the coating, so gaps existing between Behavior of High-Speed DC Cast Al-16%Mg Si 2 graphene will still cause corrosion. In this study, a Composite composite interfacial layer of graphene and hydrophobic Dongtao Wang, Haitao Zhang, Soochow University, polymer was prepared on the aluminum alloy substrate China / Northeastern University, China; Jianzhong after microarc oxidation, and the corrosion resistance Cui, Northeastern University, China; Hiromi Nagaumi, of the metal was studied. Through the interaction Soochow University, China between cations of polyelectrolyte and graphene, and the hydrophobic interaction between graphene and In this paper, the improved cooling system was used for hydrophobic polymer, strong binding strength between the high-speed DC casting. The high-speed DC casting the microarc oxidation layer and the graphene/polymer of Al-16 Mg Si billet (106mm diameter) was achieved % 2 layer is established, and thus the superhydrophobic to increase the casting speed to 300mm/min. The properties are obtained. Moreover, microarc oxidation results showed that when the casting speed increased layer and superhydrophobic graphene/polymer layer from 50mm/min to 300mm/min, primary Mg Si particles 2 provide double protection for aluminum alloy and became finer and its average size was reduced from the corrosion resistance is improved. Firstly, PDDA 22μm to 10μm, the average spacing of primary Mg Si 2 aqueous solution and PVDF dissolved in of DMF phases decreased from 53μm to 15μm, the size solution were prepared. And graphene immersed in difference of primary Mg2Si phase decreased also and 10mL of deionized water and vigorous stirred to form Thursday PM | August 22, 2019 Thursday PM | its distribution became more uniform at the different homogeneous dispersions. Then, the sample was billet positions. With the increase in casting speed, immersed in PDDA solution, and washed by deionized the morphology of primary Mg Si transformed from 2 water and dried. Then, the sample was immersed in irregular shape to regular and polyhedral shapes, the graphene dispersion and PVDF solution respectively, eutectic Mg Si transformed from lamellar shape to short 2 and dried when taken out, and we get the first layer. rod-like shape and the spacing of the eutectic Mg Si 2 Then repeating precious step for n times (n=1,2,3,4,5). decreases from 2.1μm to 0.5μm. The solid solubility of And we get MAO/G/PVDFn specimens. The surface Mg and Si in α-Al increased according to the change characterization of aluminum alloy and MAO ceramic of diffraction peak angle of α-Al in XRD. The hardness, layer and MAO/G/PVDF film were investigated by tensile strength and elongation of the Al-16 Mg Si % 2 SEM (JEOL JSM-7500, Japan) with an accelerating billet improved with the increase in casting speed. The voltage of 20kV. The chemical composition of allium wear tests showed that the mass loss, wear rate and alloy substrate, MAO ceramic layer, and MAO/G/PVDF friction coefficient of Al-16 Mg Si billet decrease with % 2 film was detected by X-ray diffraction technic (Rigaku the increase of the casting speed. The refinement and Ultima IV) and Raman spectra analysis. Contact angle morphology transformation of primary Mg Si particles at 2 measurements: CAs of the samples were measured on the high casting speed (300mm/min) is the major factor an SL200KS machine at ambient temperature. A water for the improvement of tensile and wear properties in the droplet (about 5μL) was dropped carefully onto the Al-16 Mg Si composite. % 2 prepared surface. CA was adopted as the average value of three to five measurements at different positions of 15:20-16:10 Tea Break one sample. The electrochemical corrosion test was performed on electrochemical station (CS series) by three-electrodes system in 0.05mol/L NaCl solution. The 16:10-16:30(1234630) prepared sample with size of 1cm2 was used as work Superhydrophobic Film with Ordered electrode, SCE was used as conference electrode, and Arrangement of Graphene for Protection of MAO platinum was used as assistance electrode. Ceramic layer Against Corrosion Tianlu Li, Fei Chen, Li Li, Beijing Institute of 16:50-17:10(1235072) Petrochemical Technology, China The Preparation of Al-V Alloy and Its Characteristics Superhydrophobic materials have extensive research and many applications in the fields of self-cleaning, Yihan Liu, Northeastern University, China antifouling, microfluidics transportation, drag reduction With the development of aviation, national defense, high- and corrosion protection. In the field of corrosion speed train and other vehicles, the aluminum alloys have resistance, the preparation of superhydrophobic film on changed rapidly in high technology areas. Vanadium— the metal surface can separate metal surface from the the vital national strategic metal resources—has been external corrosion environment, and so it is a simple and widely used in the aluminum alloy, which become an effective corrosion prevention method. Research shows 30 important means to improve the microstructure and properties of alloy. welded joint, the fatigue failure mainly originated from In this study, the liquid aluminum reduction smelting the specimen surface or near surface at 106 ~ 108 process is selected to produce Al alloy containing low cycles, while their fatigue cracks initiated in subsurface content of V. The influence of V on the microstructure, or internal area where inclusion defects were found exist mechanical properties and corrosion resistance of in crack nucleation sites at high cycle numbers close to Thursday PM | August 22, 2019 Al-V alloys was studied by optical microscopy (OM), 109 cycles. And by observing microstructures of post- Scanning electronic microscopy (SEM), mechanical fatigued specimens, the slip and twining were activated properties testing and electrochemical workstation. The during the fatigue testing process, and played important results reveal as follow: roles in fatigue life of both AZ31 magnesium alloy and (1) It is possible for smelting process to produce Al-V its welded joint. ℃ alloy. When smelting temperature is 1150 and V2O5 addition amount is 5.5% and hold time is 6h the liquid 17:30-17:50 (1235639) aluminum reduction smelting process is able to produce TEM Observation of Al-7Si-0.4Mg Casting Alloy Al-V alloy, and the V content is about 4.5%. Extracted by the Thermal Phenol Method (2) As-cast alloy is composed of α-Al, Al21V2 and Al45V7. Makita Yuki, Tsuchiya Taiki, Seungwon Lee, Saikawa The high temperature nonstationary phase Al45V7 all Seji, Ikeno Susumu, Matsuda Kenji, University of become Al21V2 after homogenization treatment. Toyama, Japan (3) The mechanical properties of Al-V alloy indict that: The addition of V can clearly improve the hardness, Al-Si alloys have been used as casting materials for tensile strength and yield strength. But the elongation is automobile parts. Al-Si-Mg alloys enhance its ductility decreased obviously. and castability due to formation of metastable phase (Mg2Si). Moreover, it is effective for increasing both 17:10-17:30 (1235710) strength and corrosion resistance with Mg addition. Study on Ultrahigh-Frequency Fatigue Behaviors However, precipitation sequence is not clear in T5 of As-Extruded AZ31 Magnesium Alloy and Its (casting + aging treatment) process. The aim of this Friction Welded Joint research is to estimate mechanical properties and Yuwenxi Zhang, Gaofeng Quan, Mingyang Zhou, to classify precipitates by micro Vickers hardness Southwest Jiaotong University, China measurement and transmission electron microscopy (TEM) of Al-7%Si-0.4%Mg (mass%) alloy in T5 condition. Magnesium alloys are expanding into more critical Al-7%Si-0.4%Mg alloy was fabricated by casting using applications in aerospace, automotive and rail Fe Y-block mold, then, alloy was cooled in the mold as is transportation industries with their excellent properties. to 773K, and quenched into cold water. Specimens were And these structural components, including their welding taken from mold bottom were used in this research. After parts, inevitably withstanding low and dynamic loading casting, artificial aging was carried out. Micro Vickers in service. So it is necessary to understand high even hardness measurement was conducted using Mitutoyo ultrahigh cycles fatigue properties of magnesium alloys HV-101 (load: 0.98N, duration time:15s). Microstructure and their welded joints. This work aim to investigate the observation were conducted the samples of aged using ultrahigh frequency fatigue behaviors of as-extruded AZ31 scanning ion microscopy (SIM, HITACHI FB-2100), magnesium alloy and its continuous drive friction welded SEM (HITACHI S-3500H) and TEM (TOPCON EM-002B joint via ultrasonic fatigue test at a resonance frequency operated at 120kV). Micro Vickers hardness values of 20kHz and a stress ratio of R = −1. Microstructure were decreased and time to reach to peak-aging was analysis, mechanical performance testing and SEM shortened. Eutectic Si and α-Al matrix were observed fracture surface characterization were performed to by SIM aged at 473K for 7.2ks. Particles size of ~50nm explain the mechanism underlying crack initiation in AZ31 were observed only far from eutectic Si. Uneven magnesium base alloy and welded joint. precipitates occurred depending from eutectic Si. With The results showed that under ultrahigh frequency fatigue close inspection of TEM images and SAED pattern, Si, condition, AZ31 magnesium alloys have conventional β", preprogram precipitate and Type-A precipitates were fatigue characteristics, and all of these specimens only observed in the peak-aged samples by analysis results have conditioned fatigue limits. The conditioned fatigue of HR-TEM images and SAED patterns. We analyzed limits of as-extruded AZ31 base alloy at 109 cycles is Type-A precipitates in detail by the thermal phenol 90MPa, higher than that of its welded joints 61MPa, method. We got SAED patterns and EDS analysis which is not corresponding to their ultimate tensile results from a number of rod-shaped precipitates and strength, 209MPa and 255MPa respectively, while the analyzed SAED patterns. We can make stereographic tensile strength of friction welded joint is close to that of projection of diffraction pattern of Type-A precipitates. base material. The ratio of endurance limit at one billion The chemical composition of Type-A precipitates were cycles to the tensile strength (σ−1/σb) is 0.33, belonging proven Mg: Al: Si= 1: 4: 5 from EDS analysis result in to moderate fatigue strength. In both base alloy and this alloys. 31 C1-2: Effect of Heating Rate on Microstructure C1. Light Metals and Alloys-Alumi- and Mechanical Properties of Al 7055 Alloy num (1268347) Symsposium Organizers: Seunggyu Choi, Seok-Jae Lee, Chonbuk National Baiqing Xiong, GRINM Group Co. Ltd., China; Yoshihito University, Korea Kawamura, Kumamoto University, Japan; Young Min Kim, Korea Institute of Materials Science (KIMS), Japan; Jian-Feng Nowadays, 7xxx aluminum alloys has been widely Nie, Monash University, Australia; Diran Apelian, Worceste used as structural materials that requires high strength Polytechnic Institute, USA in automotive, aircraft, and defense industries. A precipitation hardening is a key strengthening August 19-21, 2019 mechanism to improve the strength in 7xxx Al alloys. Posters Room: Exhibition Area (3rd Floor) The characteristics of precipitates such as mean particle size, volume fraction, average distance among particles, total number of particles, and so on could be C1-1: Finite Element Analysis of Residual Stress controlled during an artificial T6 aging treatment after with Quenching Rate of 6061 Aluminum Alloy a solid solution treatment. Even though the same T6 (1235741) aging condition was adopted, the mechanical properties GyuSeok Lim, SukCheol Kwon, HwaYoung Woo, of the aged 7xxx Al alloys might be different depending Chungnam National University, Korea; JongHyeon on the solid solution treatment. Previous studies Lee, Chungnam National University, Korea / Rapidly reported that the chemical composition of matrix and Solidified Materials Research Center, Korea / the condition of precipitates are influenced by solid Graduate school of Energy Science and Technology, solution temperature, cooling rate, etc. which resulted Korea in the variation of mechanical properties. In the present study, we investigated the influence of heating rate on Aluminum (Al) alloy is an important material for mechanical properties of Al 7055 alloy. The dissolution the environmentally friendly industry including the and formation kinetics of precipitates existed in the automobile industry and the aerospace industry sample before the solid solution treatment were affected because of its light weight, good processability and depending on the heating rate because the dissolution high noble strength. The 6061 aluminum alloy, in which and formation of precipitate particles are diffusional magnesium (Mg) and silicon (Si) are added to aluminum controlled. A dilatometric test was carried out to control as an alloy element, is a precipitation hardening type the heating rates in the solid solution treatment. The alloy and has a relatively high strength and excellent mechanical properties were evaluated using hardness corrosion resistance. In order to achieve precipitation test and compressive test while the microstructural hardening, solution treatment is essential, and if features were observed by XRD, OM, and TEM. thermal deformation occurs at a stage of holding and quenching at a high temperature, a large residual stress C1-3: Effect of AlP in Aluminum System Alloys is generated inside the specimen. This causes distortion AA365(1216896) during subsequent machining and reduces the precision Yiyang Zhao, Satoru Ishihara, Seiji Saikawa, of the part. Therefore, in order to increase the precision University of Toyama, Japan; Hisao Kazuta, University of the component, it is important to minimize the residual of Toyama (Present: NIDEC CORPORATION), stress generated during quenching and to analyze the Japan; Susumu Ikeno, University of Toyama, Japan residual stress distribution in the aluminum alloy. This study simulated the quenching of Al 6061 alloy billets From the perspective of protecting the atmosphere, in using finite element method. The thermal flow and the automotive industry, attempts have been made to residual stress distribution were calculated by varying convert iron-based materials for automotive parts into the cooling rate through water temperature change aluminum, aluminum, magnesium, and resins with low during quenching. From these results, it is expected specific gravity to reduce the weight of the body to reduce that it will provide guidelines for the change of residual carbon dioxide emissions and improve fuel economy. stress due to quenching of aluminum alloy and improve AA365 alloy is applied to automobile parts because it the reliability and mechanical properties of the material. is easier to recycle, cheap and environmentally friendly than resin. As a result of, it has been widely used for automobile road wheels, suspension arms. We investigated the effect of AlP on the microstructure of Al-10mass%Si-Mg system alloy by using different purity aluminum (to reduce the nucleation frequency of AlP caused by P content). In DTA cooling curve of using low purity Al-10mass%Si-0.8mass%Mg alloy, we 39 Technical Program
observed unknown peak. The peak was researched Aim of this research is to investigate the influence of with quench at any temperature during solidification. homogenization treatment on microstructure of Al- Mg- In the result, it was found that the peak occured by Si alloys. Two kinds of samples were prepared; (1) non- growth of plate-like eutectic Si phase formed with AlP homogenization and (2) homogenizing treatment at 848K as the heterogenius nucleation site. In this study, has for 7.2ks. Microstructure evolution was investigated investigated influence of P content on AA365 alloy by each alloy using optical microscope (OM), electron using different purity aluminum. In order to do this, we probe micro analyzer (EPMA) and transmission electron used 2N alloy and 5N alloy that different of P content microscope (TEM) at 120kV. In non-homogenization due to investigate effect of AlP was prepared. Aluminum sample, the contrast thought of as dispersoids and of commercial purity (2N 99.7mass%) or high purity precipitates around dispersoids mainly are observed. (5N 99.999mass%) was melted with crucible made by In homogenized sample, the contrast thought of as alumina in electric resistant furnace. For investigation dispersoids, equilibrium phase and precipitates are of the solidification sequence, measured crystallization observed. Precipitates are not seen very often around temperature and quenched microstructure. The result big dispersoids and equilibrium. TEM observation from
Posters of this study, supercooling at about 2℃ was observed the [100]Al direction, it was possible to observe rod-like only in 5N alloy. And a plate-like Si phase have formed precipitation and their cross sectional plane. Rod-like AlP as a core was only observed at 2N material at any precipitation have orientation relationship with matrix; temperature. Further, before the Al-Si binary eutectic parallel to the <100>Al direction. reaction, the number of the plate-like Si phases in the 2N material increases, and the number of the plate-like C1-5: Effect of Cold-Rolling on Aging Behavior Si phases increases and the behavior increases. of Al-Cu-Mg Alloy with Different Cu/Mg Ratio (1222335) C1-4: Microstructure Observation of Al- Masaki Matsumoto, Graduate school of Science and 1.6mass%Mg2Si Alloy with and without Engineering for Education, University of Toyama, Homogenization (1222168) Japan; Taiki Tsuchiya, Seungwon Lee, Kenji Matsuda, Takara Umezawa, Graduate school of Science and Graduate School of Science and Engineering for Engineering for Education, University of Toyama, Research, University of Toyama, Japan; Ken-ichi Japan; Taiki Tsuchiya, Seungwon Lee, Kenji Matsuda, Ikeda, Division of Materials Science and Engineering Graduate school of Science and Engineering for Faculty of Engineering, Hokkaido University, Japan; research, University of Toyama, Japan; Ken-ichi Tomoyuki Homma, Department of Mechanical Ikeda, Division of Materials Science and Engineering, Engineering, Nagaoka University of Technology, Faculty of Engineering, Hokkaido University, Japan; Japan; Susumu Ikeno, University of Toyama, Japan Tomoyuki Homma, Department of Mechanical Engineering, Nagaoka University of Technology, Al-Cu-Mg alloys are known as 2xxx series aluminium Japan; Susumu Ikeno, University of Toyama, Japan alloys which is represented by the duralumin and super duralumin, and it is widely used in aerospace and Al-Mg-Si alloys (6xxx Al alloy series) are one of age- transportation industries due to its excellent mechanical hardenable aluminum alloys. The precipitation sequence properties. It has been reported that mechanical can be described as follows: Super Saturated Solid properties of 2xxx series aluminium alloys can be Solution (ssss) → clusters / GP zones → needle shaped enhanced by cold-rolling before aging. The precipitation β"/ Parallelogram type precipitates → rod shaped β'/ sequence for Al-Cu-Mg alloys is generally described Type A / Type B / Type C precipitates → plate shaped as followed as: S.S.S.S.→ G.P. Zone→ metastable → → β (Mg2Si) precipitates. Al- Mg- Si alloys are extensively θ' phase stable θ phase or S.S.S.S. G.P.B. used in chassis part of window frames, automotive and Zone→ metastable S' phase → stable S phase. The high-speed train, due to their high strength-to-weight precipitation sequence of this alloy series is related with ratio, high ductility, good extrudability and excellent the Cu/Mg ratio. In addition, many studies on the high corrosion resistance by anodizing. These chassis are concentration side as represented by the A2024 alloy usually produced by extrusion process. But the speed have been made, but few studies are dealt with aging of extrusion is restricted by occurring cracks that is precipitation behaviour in the cold rolling before aging called "pick-up fault" with increasing extrusion speed. on the low concentration side. Therefore, the purpose It is reported that pick-up fault could be reduced by of this research is to investigate the effect of cold-rolling homogenization treatment. However, the reports are on age hardening behaviour of low concentration Al-Cu- few about effect of homogenization treatment against Mg alloys with different Cu/Mg ratio (Cu/Mg=1, 3) aged Al- Mg- Si alloys without impurities. It is known that initial at 473K. In this study, four types of cold-rolling before microstructure can influence to extruded microstructure artificial aging were used: these are 0%, 10%, 30%, by casting microstructure, for example segregation 60%. To estimate mechanical properties, Micro Vickers of alloying elements, dendrites and dispersoids. hardness measurement was conducted. Microstructure 40 observation was carried out using TEM. Samples for Ag added alloy at the initial stage and peak hardness microstructure observation was prepared by twin-jet condition was remarkably increased compared to Base electropolishing method. As the result of Micro Vickers alloy. In the case of over-aged condition, β' phase, A hardness measurement, the Micro Vickers hardness of type and β phase were observed in Ag added alloy. β' cold-rolled samples was increased and the aging time phases with different a-axis were found. A type existed to peak-hardness was shortened with the increase of on grain boundary. Interplanar spacing of A type in the thickness after cold-rolling. The aging time to peak- Ag added alloy was no change compared to A type in hardness was shortened with the increase of Cu/Mg the Base alloy. ratio. As the result of t Microstructure observation, the number density of S' phases and θ' phase in cold-rolling C1-7: Effect of Homogenization on the Microstruc- samples was increased. The reason why the precipitation ture in an Excess Silicon Al-Mg-Si Alloy (1222365) Posters process was promoted is that the dislocations what is Shuaishuai Qin, Graduate school of Science and introduced by cold-rolling would be the nucleation site Engineering for Education, Japan; Taiki Tsuchiya, of the precipitation. Seungwon Lee, Kenji Matsuda, Graduate School of Science and Engineering for Research, University C1-6: Influence of Ag Addition on Microstructure of Toyama, Japan; Susumu Ikeno, Professor of of Al-Mg-Ge Alloy (1222344) Emeritus, University of Toyama Shu Umemura, Graduate school of Science and Engineering for Education, Japan; Taiki Tsuchiya, Widely used Al-Mg-Si(6XXX) alloys usually need an Seungwon Lee, Kenji Matsuda, Graduate school of extrusion process. Before extrusion, the as-casted Science and Engineering for Research, University of billets often require a homogenization treatment, Toyama, Japan; Ken-ichi Ikeda, Division of Materials because homogenized billets not only extrude easier Science and Engineering, Faculty of Engineering, and faster and give better surface finish than cast Hokkaido University, Japan; Tomoyuki Homma, billets, but also can make the as-cast billet capable Department of Mechanical Engineering, Nagaoka of undergoing extensive plastic deformation without University of Technology, Japan; Susumu Ikeno, cracking and local melting. Despite there are detailed University of Toyama, Japan studies of how homogenization affect extrudability in the Al–Mg–Si alloys, less attention was focused on the Several reports are available about a substitution for effect of homogenization on the final microstructure after Si to Ge in Al-Mg-Si alloy can improve its mechanical artificial aging. property by aging treatment at relatively high In the present work, we used Al-0.33at%Mg-0.67at%Si temperatures. Precipitation sequence of Al-0.43%Mg- alloy to investigate how homogenization affects the final 0.20%Ge (mol.%) alloy is suggested to S.S.S.S → microstructure. The as-cast microstructure is typical Cluster → G.P. zone → Random type → Parallelogram dendritic structure. The temperature of homogenization type, β" → β', A type → β. is 575℃ and the samples were held for 2h, then the It is known that Ag addition on Al-Mg-Si alloys can samples were cooled in air and furnace, respectively. enhance their mechanical properties and age- After homogenization, optical microscope(OM) showed hardenability due to increase of precipitates. Also, it is that the predominant phase formed in the matrix is rod- reported that Ag addition can precipitate β' Ag which has like, the length of the rod-like precipitates in furnace- smaller a-axis than β' phase. Ag enters the composition cooling samples is longer than in air-cooling, however, of β' phase, shrinking its hexagonal network from there are many boundaries can be found in the grains a=0.715nm in the Ag-free phase to a=0.69nm, while of air-cooling samples after homogenization, at the the c direction remains the same 0.405nm. β' Ag phase same time, the rod-like precipitates trend to distribute has Al, Mg, Si and Ag in its composition. Further, β' along these boundaries. In order to identify these Ag phase has a space group different from β' phase. precipitates and boundaries, TEM observation was The aim of this research is to understand the effect of conducted by using Topcon, EM-002B with accelerated Ag on aging behavior and mechanical property on Al- voltage of 120kV, according to the diffraction patterns, Mg-Ge-Ag alloy. Chemical compositions of alloys are these precipitates were β', and also, many low angle Al-0.43%Mg-0.20%Ge (Base alloy) and Al-0.47%Mg- grain boundaries were observed in air-cooling samples 0.23%Ge-0.23%Ag (Ag added alloy) (mol.%). Aging after homogenization. After one hour of solution heat treatment was carried out at 423K, 473K, 523K. treatment, few particles can be observed in air-cooling Vickers microhardness measurement was conducted samples, however, there are many particles remained to estimate the mechanical properties of alloys. TEM in the matrix of no-homogenization samples. Moreover, observation was conducted by using Topcon, EM-002B the average grain size is also calculated and the no- with accelerated voltage of 120kV. Ag added alloy homogenization samples exhibit the finest grains. showed a significant increment of hardness at the initial Finally, artificial aging treatment was carried out at 473K, stage of aging. The number density of precipitates in the the hardness was measured and no-homogenization 41 Technical Program
group exhibits the lowest peak-hardness. Under peak C1-9: Characterizations of the Microstructural aging condition, TEM observation revealed that the and Tensile Properties of Al-9Si-0.3Fe-0.15Mn precipitates in no-homogenization samples are coarser Alloy with Ti and V Additions(1222590) than the homogenized samples. Zeze Xiao, Kazuhiro Matsugi, Zhefeng Xu, Taishi Matsuoka, Tomoshi Uomi, Hirohshima University, C1-8: Influence of P Content in Crystallization Japan; Nobuyuki Oda, Hironobu Kominato, Behavior of Pseudo-Binary Al-Mg2Si(1222524) Hirohshima University, Japan / Mazda Motor Arisa Osugi, Hisao Kazuta, Satoru Ishihara, Corporation, Japan; Yasuo Uosaki, Mazda Motor University of TOYAMA, Japan; Susumu Ikeno, Corporation, Japan Professor emeritus at University of TOYAMA, Japan; Seiji Saikawa, University of TOYAMA, Japan The effects of 0.2wt% Ti and 0.2wt% V additions on the Al-9Si-0.3Fe-0.15Mn base alloy were investigated for In recent years, weight reduction of vehicle body has development of low-cost alloys which could be used been required in the automobile industry because for the as-cast applications. It was found that the grain
Posters of protection of the environment. The application of size of α−Al phase in the base, 0.2wt% Ti and 0.2wt% aluminium alloy have been expanded in the auto parts. V addition alloys measured by image analysis were Al-Mg-Si alloy has both of good strength and high 43.7μm, 53.7μm and 30.1μm, respectively. Dendritic ductility without heat treatment, which is attracting structures were observed in the base and 0.2wt% V attention as new die-cast alloy. However, the castability addition alloy. The secondary dendrite arm spacing in in this alloy is inferior to other aluminum alloy. 0.2wt% V addition alloy was 31.1μm, which was smaller In our previous study, the castability of Al-2~6%Mg- than that of the base alloy. The microstructure of the 1~3%Si system alloy. As a result, the composition that base alloy exhibited the α−Al, flake-like Si eutectic and hot-tear decresed was Al-6%Mg-3%Si alloy, because a small amount of the intermetallic compounds, such as
the composition of this alloy was close to pseudo-binary the polyhedral-shaped Al15(Mn, Fe)3Si2 compound and
eutectic of Al-Mg2Si. In addition, it is found that hot- rod-shaped β-Al5(Fe, Mn)Si compound. The introduction tearing was not occurred in the case of 0.04%Sr addition of 0.2wt% Ti to base alloy resulted in the formation of
to Al-6%Mg-3%Si alloy. Eutectic Mg2Si phase of Sr-free Al3Ti compound, which distributed in the eutectic region.
alloy was observed plate-like Mg2Si having AlP nuclei. The polyhedral-shaped Al15(Mn, Fe, V)3Si2 compound
On the other hands, Eutectic Mg2Si phase of 0.04%Sr and rod-shaped β-Al5(Fe, Mn, V)Si compound appeared addition alloy was the remarkable refinement and not in the 0.2wt% V addition alloy. The liquidus temperature present plate-like Mg Si. was increased by the addition of 0.2wt% Ti and 0.2wt% In this study, for the purpose of clarifying the V, which led to the promotion of the segregation degree
crystallization behavior of plate-like Mg2Si phase with AlP in the α−Al phase and Si eutectic region. Three alloys
as the nucleus, Al-6%Mg-3%Si alloy the crystallization showed the same levels in tensile properties (σ0.2 :
behavior was investigated in detail. 79 ~ 83MPa, σUTS : 148.7 ~ 152.8MPa and εf : 5.6%~ 2N alloys and 5N alloys that different of P content 6.3%), which correlated to segregation degree at the due to investigate effect of AlP was prepared. The as-cast condition. The effect of 0.2wt% Ti and 0.2wt% target compositions were Al-6%massMg-3mass%Si. V additions on tensile properties were discussed in the The melt was held at any temperature and time, and view of the characteristic microstructural. The findings of the tissue was frozen by quenching in water. The this study can benefit and contribute to developing a new quenching specimens were polished with sandpaper, Al-9Si series alloys for as-cast applications intended for buffed with 1μm diamond paste and etched in a 0.5%HF lightweight materials for the automobiles. solution. The microstructures were observed by optical microscope and the average diameter and number of
plate-like Mg2Si phases were investigated. The plate-
like Mg2Si phase formed with AlP as the heterogeneous nucleation site was observed only in 2N alloy. In the case of 5N, no such nuclei existed, there were very fine lamellar eutectic phase. In the case of the molten metal was held for a long time, the number of plate-like Mg2Si phases decreased.
42 C1-10: Investigation of H Effect into Solid Solution creating vacancy rich clusters as seeds of nucleation. Decomposition in an Al-Zn-Mg Alloy System (1222654) C1-11: Effects of Homogenizing Treatment on Artenis Bendo, Graduate School of Science and Dispersive Precipitates and Recrystallized Grains Engineering for Education, University of Toyama, of Si-Bearing Al-Mg Alloys (1231910) Japan; Taiki Tsuchiya, Seungwon Lee, Kenji Cheng Guo, Haitao Zhang, Zibin Wu, Ping Wang, Matsuda, Katsuhiko Nishimura, Norio Nunomura, Baomian Li, Jianzhong Cui, Northeastern University, Graduate School of Science and Engineering for China; Hiromi Nagaumi, Soochow University, China Research, University of Toyama, Japan; Hiroyuki Toda, Kazuyuki Shimizu, Department of Mechanical In this research, microstructural evolutions of Si-bearing Engineering, Kyushu University, Japan; Tomohito Al-Mg alloys were investigated in detail by optical Posters Tsuru, Masatake Yamaguchi, Japan Atomic Energy microscope (OM), scanning electronic microscope Agency, Japan (SEM), energy dispersive spectrum (EDS) and transmission electronic microscope (TEM). For the as-
Hydrogen (H), the basic element on the periodic table, cast alloy, the microstructures consist of Mg2Si, Al6(Mn, is researched in material science and material physic for Fe) and Al12(Mn, Fe)3Si phases. The amount of the its applications and deteriorating effects. H interaction primary phase increased with the content of Si. In the with microstructural defects such as vacancies, homogenization process, the dimension, distribution and defects, dislocations, grain boundaries and interphase quantity of the dispersoids were influenced significantly boundaries in crystalline materials is an area of by the temperature and time of heat treatment. The research for its implications in mechanical and physical precipitates of the two-step homogenized samples properties. Reports of ten-fold enhanced diffusion were higher density and better dispersed distribution in Ni-Cu diffusion couples and lattice contraction in than the single homogenized samples. For the two- numerous metals when subjected to H atmosphere in step homogenization heat treatment, the purpose of high pressures and temperatures, suggests of strong the first step homogenization was to precipitate β' atomic H interaction with point defects. In this regard, (Mg2Si) from the supersaturated solid solution. The possible H effect into precipitation phenomena in Al- fine-scale β' phases decomposed into Si-rich "u-phase" Zn-Mg alloy system is investigated. Samples were H at the subsequent high-temperature homogenization charged immediately after quenching from solid solution stage, which provided nucleation sites for dispersed treatment. Hardness tests showed an inconsiderably α-Al (Mn, Fe) Si. The volume fraction of the dispersed slight shift of age-hardening curve to shorter ageing zone of the two-step homogenized samples increased time in H-charged and aged samples. Transmission as well as the dispersoid free zone (DFZ) decreased Electron Microscopy (TEM) was employed for comparing with that of single homogenizing. By microstructure investigation during ageing treatment comparing the volume fraction of the precipitates under to provide insight into microstructure decomposition. different homogenization conditions, the optical phase Investigation directions were [110]Al, [100]Al and [112] distribution was obtained when the alloy homogenized Al. Precipitation density and morphology did not show at 235℃/6h+580℃/8h. any consistent difference between H-charged and H-free The dispersive precipitates can restraint the samples, due to hindering of accurate measurement recrystallization of the alloy effectively in the hot because of thicknesses variations of investigated working and annealing process. After rolling, the regions. However, high resolution transmission electron dispersed α-Al (Mn, Fe) Si played the role of pinning (HRTEM) images along [110]Al revealed that regions dislocations and hindering the migration of grain rich in high aspect ratio GP-II zones were observed in boundary and sub-boundary. The alloy which processed H-charged and aged samples, and were absent in the by two-step homogenizing had finer grain size than number of HRTEM images analyzed for H-free ones. the single homogenized sample. Besides, the amount They had a heterogenous ditribution in Al matrix, with of the precipitates increased with the content of Si in regions rich and absent in these zones. High aspect the process of homogenization. So the grain size of ratio GP-II zones are reported to be occasionally the alloys decreased with the increasing of Si after observed in samples which were solid solution treated annealing. The strengths of the two-step homogenized at temperature higher than 450℃ indicating a strong alloys were higher than those of the single homogenized depence on vancancy concetration. Higher probability alloys, as the dispersed precipitates plays an important of observing these zones in hydrogen charged and aged role in the plastic deformation process. samples is probably related to H-point defect interaction and H previously reported effect on vacancy formation and stabilization. Higher presence of high aspect ratio GP-II zones neccesitates a higher presence of vacancies which are required for clustering on {111}Al planes and 43 Technical Program
C1-12: Additional Interface Strengthening in S.S.S.S.→GP zones→β", Parallelogram-type→Type-A, Aluminum alloy Laminated Plate with Bimodal Type-B, Type-C→β, Si Distribution of Grain Size(1234812) However, the correlation between the microstructures Taiqian Mo, Zejun Chen, Chongqing university, China and hardness in Al-Si-Mg alloys have not been clarified. The casting was done using metal permanent Y-mold. The objective of the present study is to obtain aluminum The alloy was cooled in the mold as is. The demolding alloy laminated plate with high yield strength and good carried out at the temperature of 473K, then, Y-block ductility through a multiscale coarse/ultrafine-grained was quenched into ice water. Specimens were taken design, fabricated by the difference in recrystallization from the mold bottom were used in this research. of constituent metals using different strain path and After casting, artificial aging was carried out at the 3 annealing processes. Experimental results showed selected temperatures (423K, 473K and 523K). Micro that, with increasing annealing temperature, where Vickers hardness measurement was conducted using pronounced grain coarsening of the 1100Al layers Mitutoyo HV-101 (load: 0.98N, duration time:15s). occurs, but for the 7075Al layers the change in The microstructures were observed by OM (Olympus
Posters grain structures is not obvious. The difference in BX51M), SEM (HITACHI S-3500H) and TEM (TOPCON recrystallization degree of two alloys results in the EM-002B operated at 120kV). SEM specimens were producing of the bimodal distribution of grain size in conducted deep etching. TEM specimens aged in a whole laminated plate. Moreover, in order to analyze silicone oil bath at 473K were cut from the ingot by the the effect of strain incompatibility on the mechanical precision cutter and thinned by the single jet electro- properties, laminated plates with different properties of polishing technique. Electrolytes were 10% perchloric constituent layers were comparatively studied. Results acid-ethanol solution and 25% nitric acid-methanol. showed that the cross rolling, compared with direct Micro Vickers hardness measurement of Al-7%Si- rolling, give rises to somewhat more effective mechanical 0.3%Mg alloy demolded and aged at 473K shows properties improvement after annealing treatment due that reaches peak hardness at 6ks. TEM observation to higher strain incompatibility across the interface. For showed that the precipitate density around eutectic Si the different processes, the difference in flow properties was lower Si in the case of aged at 473K for 6ks. The between the constituent layers plays an important role in selected area electron diffraction (SAED) patterns were interface strengthening mechanism. During tensile test, in agreement with Type-A precipitate and Si. high density of geometrically necessary dislocations (GNDs) were observed to distribute in the interface due C1-14: Effect of Microstructure on Discharge to the mechanical incompatibility across the interface. Performance of Al-0.8Sn-0.05Ga-0.9Mg-1.0Zn The high yield strength of the plate with multi-scale (wt%) Alloy as Anode for Seawater Activated grain structure is attributed to back stress strengthening Battery(1235320) associated with the formation of geometrically necessary Zibin Wu, Haitao Zhang, Cheng Guo, Jing Zou, Ke dislocations and the good ductility results from the high Qin, Ban Chunyan, Jianzhong Cui, Northeastern strain hardening rate during plastic deformation. University, China
C1-13: Aging Behavior of Al-7%Si-0.3%Mg The discharge behavior of Al-0.8Sn-0.05Ga-0.9Mg- Casting Alloy Demolded at 473K in T5 Process at 1.0Zn (wt%) alloys in as-cast, homogenized and annealed 473K (1235299) states was investigated through potentiodynamic Keigo Muro, Taiki Tsuchiya, Seungwon Lee, Seji polarization, electrochemical impedance spectroscopy, Saikawa, Susumu Ikeno, Kenji Matsuda, University galvanostatic discharge, and battery test in 3.5wt% NaCl of Toyama, Japan solution. An influence mechanism of rolling process on anode discharge performance is proposed. Results Al-Si-Mg cast alloys are widely used in automotive suggest that the mechanism can explain properly that industry to produce components and parts (i.e. engine rolling and subsequent annealing improves the discharge cylinders) at lower cost. These alloys have excellent properties of the Al-0.8Sn-0.05Ga-0.9Mg-1.0Zn (wt%) castability and good strength to weight ratio. Where alloy. The results indicate that rolling and subsequent dimensional accuracy is concerned, industrial Al-Si- annealing can greatly improve the microstructure of Mg cast alloys (i.e. A357, A356) are in many cases the Al-0.8Sn-0.05Ga-0.9Mg-1.0Zn (wt%) alloy, thereby performed T5 heat treatment (Artificial aging after improving its electrochemical performance. The 400℃ casting). Artificial aging treatment is carried out at annealed Al-0.8Sn-0.05Ga-0.9Mg-1.0Zn (wt%) alloy temperatures above ambient, typically in the range exhibits stronger discharge activity than the as-cast, of 423~473K. The precipitates in Al-Si-Mg alloys is homogenized and 150℃ annealed ones, attributed to presumed to correspond with excess Si-type Al-Mg-Si more grain boundaries being activated as a reaction alloys. The precipitation sequence of excess Si-type Al- channel. The 400℃ annealed Al-0.8Sn-0.05Ga-0.9Mg- 1.0Zn (wt%) alloy show higher anodic efficiency than 44 Mg-Si alloys is known to be as follows: the as-cast and homogeneous ones because of the C1-16: Effect of Hydrogen on Age Hardening more uniform distribution of Sn in the aluminum matrix. in Al-Zn-Mg Alloy Containing Low Zn/Mg Ratio Moreover, the discharge capacitance (2514.23 mAh·g-1) (1235703) and anodic efficiency ((84.37 ± 0.72)%) of the seawater Kengo Takamoto, Artenis Bendo, Kazuyuki Shimizu, activated battery using the 400℃ annealed Al-0.8Sn- Graduate School of Science and Engineerign for 0.05Ga-0.9Mg-1.0Zn (wt%) alloy is higher than those Education, University of Toyama, Japan; Taiki with magnesium alloys, and the peak power density Tsuchiya, Seungwon Lee, Kenji Matsuda, Katsuhiko -2 (61.3mW·cm ) of the battery is close to the seawater Nishimura, Norio Nunomura, Graduate school of activated battery with pure Mg, Mg-Li-Al-Ce-Y and Mg- Science and Engineering for Research, University of Al-Pb anodes. Toyama, Japan; Hiroyuki Toda, Kyosuke Hirayama, Hongye Gao, Department of Mechanical Engineering, Posters C1-15: Residual Stress Analysis of 7075 Kyusyu University, Japan; Masatake Yamaguchi, Aluminum Billet with Cooling Rate(1235700) Ken-ichi Ebihara, Mitsuhiro Itakura, Tomohito Tsuru, HwaYoung Woo, Sukcheol Kwon, Gyu-Seok Lim, Japan Atomic Energy Agency, Japan; Susumu Ikeno, Department of Materials Science and Engineering, University of Toyama, Japan Chungnam National University, Korea; Jong- Hyeon Lee, Department of Materials Science and 7xxx series alloy (Al-Zn-Mg alloy) has a high strength Engineering, Chungnam National University, Korea compared to other Al alloys due to its good age / Rapidly Solidified Materials Research Center, hardenability. The precipitation sequence of this series Chungnam National University, Korea / Graduate alloy is known to be as follows: School of Energy Science and Technology, S.S.S.S. → G.P.zone → η', T' → η, T Chungnam National University, Korea This series alloy also has problems about high stress corrosion crack susceptibility, it is considered that Aluminum alloys are widely used in many structural the cause is due to the propagation of hydrogen materials and industrial fields due to their high strength embrittlement. Behavior of the hydrogen embrittlement and corrosion resistance. The properties vary depending mechanism is revealing, but that in Al alloy isn't still on the content and type of the alloy element, and completely understood. We propose that elucidating aluminum alloys having suitable physical properties are behavior of hydrogen in the alloy plays a major role for used depending on the use. Among aluminum alloys, solving this problem. In this work, we use 2 types alloy 7075 aluminum is a precipitation-hardening aluminum which hydrogen charged Al-Zn-Mg alloy and not charged alloy containing zinc and magnesium as alloying same alloy. We investigated the aging behavior and the elements, and has the highest strength. Especially, type of precipitate of hydrogen charged sample and not 7075 aluminum is used in aircraft structure, mold tools, charged by means of hardness tests and transmission gears and shafts, mechanical equipment and fixture electron microscopy (TEM) microstructure observations. where high strength and corrosion resistance are We prepared Al-Zn-Mg alloy by casting. The chemical required. However, for precipitation hardening, internal composition is Al-1.8mol.%Zn-3.5mol.%Mg. Solution residual stress due to cooling rate difference occurs in heat treatment was conducted at 748K for 3.6ks, and the process of quenching after solution treatment. This then quenched in cold water. Hydrogen charging to the residual stress impairs the accuracy of the product during alloy was conducted by electron discharge machining. the subsequent processing and poses a risk of stability. We call the hydrogen charged sample "EDM" and not In this study, Ansys simulation program was used to charged sample "NoEDM". Micro-Vickers hardness was calculate the cooling rate of aluminum billet depending measured using Mitutoyo HM-101 (load: 0.98N, holding on the temperature of cooling media and the geometry. time 15s). TEM (Topcon EM-002B) observation was The residual stress was measured and compared with conducted under the accelerated voltage of 120kV. calculation data. The correlation between processing The result that Micro-Vickers hardness test of aged at parameters and residual stress was mathematically 393K, EDM had higher maximum hardness and shorter derived. From the results obtained, we expect to reduce time to reach it compared with NoEDM. The results from the cost of the process for removing residual stress by selected area electron diffraction (SAED), both of EDM optimizing the machining parameters. and NoEDM had the same diffraction spots reported
as η', η1, η4, T' phases in Al-Zn-Mg alloys. And the TEM bright field image of EDM showed that it had more precipitation ratio of η' phase and less that of T' phase than NoEDM sample.
45 Technical Program
C1-17: Effect of Different Aging Treatments on not been known. In this study, the influence of Si content Microstructure and Mechanical Properties of on the age hardening behavior of Al-Si-Mg based alloy Extruded 7136 Aluminum Alloy(1258401) was investigated by varying Si content from 4 to 10 Huiyan Li, Yue Ma, Beijing University of Aeronautics mass%. and Astronautics Alloys with target compositions of Al-4mass%Si- 0.3mass%Mg, Al-7mass%Si-0.3mass%Mg and Al- The retrogression and reaging (RRA) is an emerging 10mass%Si-0.3mass%Mg were cast. Based on the hot treatment technology that addresses many classic target compositions, pure Al, Al-20 mass% Si and shortcomings of more traditional aging treatment Al-10mass%Mg ingots were weighed and melted at a processes. In this work, the microstructure evolution of temperature of 993K with an electric furnace. After the the extruded 7136 aluminum alloy under different aging melting, Al-10mass%Sr alloy was added to the melt treatments were investigated via optical microscopy in an amount of 0.012 to 0.015% in order to improve (OM)，scanning electron microscope (SEM) and eutectic silicon structure and the Ar gas was supplied to transmission electron microscope (TEM). Meanwhile, the melt for the degasification. The melt was cast into a
Posters the mechanical properties and conductivity of the alloy copper mold having a Y block shaped cavity, when the during the different aging were studied by tensile testing, melt and the mold temperatures were 973K and 453K, hardness testing and electrical conductivity testing. respectively. After the pouring, when the temperature of When the number of RRA treatment was less than 3, the cast alloys decreased to 773K, the cast alloys were matrix precipitates (Mpt) grew up moderately, while released from the casting mold and were immediately grain boundaries precipitates (GBP) gradually became water-quenched. After the water-quenching, test coarser, and the width of the precipitate free zone specimens with dimensions of 10mm×12mm×2.5mm (PFZ) increased. As a result, the electrical conductivity were cut out within 1.8ks from the obtained casting at increased gradually over the cycle times due to the room temperature. Solution treatment was carried out decreased of the electron scattering centres which for 36.0ks at 813K. Vickers hardness was measured were closely related to the localized strain fields and the using a micro hardness testing machine under a load of solute concentration in the matrix. 16.29% enhancement 2.94N at a load time of 10s. in conductivity was achieved after 3 RRA treatment. The microstructure of the as-cast alloys was consisted Furthermore, the fine GP zone and the η' phase in the of primary crystallized α-Al and secondary crystallized crystal kept the ultimate tensile strength and hardness of eutectic phases. Amount of the eutectic phase increased the material at a high level (705MPa, 217HV). However, with increasing Si content. In addition, the value of the when the number of RRA treatment reached 4, the age hardening ΔHV also increased with increasing Si significantly coarsened matrix precipitates result in a content. It is considered that the amount of the area of dramatic decline in the tensile strength and hardness. the interface between the eutectic Si and the α-Al matrix The intrinsic mechanism of the influence of the multiple phase influences the age hardening behavior. RRA treatment on the microstructure, mechanical property, and the electrical conductivity was discussed. C1-19: Effect of SiC Particles Addition on RRA treatment on aluminum alloy was confirmed to Morphology of Primary Si Crystal in Hypereutectic be a simple and effective way to significantly improve Al-Si Alloy(1233943) the electrical conductivity while maintaining its tensile Masayuki Mizumoto, Takuto Hayashi, Satoru strength. Nishikawa, Iwate University, Japan
C1-18: Effect of Silicon Content on Age Hardening Hypereutectic Al-Si alloys are applied to piston and Behavior in Hypoeutectic Al-Si-Mg System Alloy cylinder block in engine due to their excellent abrasion (1222650) resistance, high temperature strength and low thermal Satoru Ishihara, Hisao Kazuta, Seiji Saikawa, expansion. In the present work, the effect of SiC University of TOYAMA, Japan; Susumu Ikeno, particles addition on the morphology of primary Si Professor emeritus at University of Toyama, Japan crystal in hypereutectic Al-Si alloy was investigated. SiC particles (mean particle size: 17μm) were added In the automobile industry, lightweight materials in the form of MMC (40vol% SiC particles/Al alloy are needed to improve fuel economy. Especially Al- composite). Hypereutectic Al-40wt%Si ally was melted 7mass%Si-0.3mass%Mg system alloy is widely used for and held at 1273K. MMC (1~10wt%) was added into aluminum die-casting alloys having excellent mechanical the alloy melt and held for predetermined time. When properties and castability. For these alloys, T6 heat MMC was added more than 5wt%, the morphology of treatment is applied for the purpose of improving the primary Si crystal was changed from coarse needle-like mechanical properties. However, there are few reports to fine polygonal shape and the primary Si crystal size on age hardening behavior of Al-Si-Mg cast alloys, and was decreased to less than half of that observed in the specimen without MMC addition. Most of SiC particles 46 the effect of Si content on age hardening behavior has