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doi: http://dx.doi.org/10.24018/ejers.2017.2.2.275 EJERS, European Journal of Engineering Research and Science Vol. 2, No. 2, February 2017

Production and Characterization of Amorphous Aluminum- for Aerospace Applications

Olayide R. Adetunji, Muyiwa L. Olukuade, Wojciech Simka, Maciej Sowa, Olanrewaju M. Adesusi and Iliyas K. Okediran

 confidence has been maintained ensuring their use in Abstract-The main objective of this research is to produce significant quantities for centuries to come [4]-[6]. and characterize amorphous Aluminum copper (Cu) alloy for The production of materials that enhance material service high strength applications. High grade of both Aluminum and life by combining high strength and toughness has posed copper ingots were charged to a ceramic mould and put in an challenges. However, high strength aluminum alloys have electric furnace in the ratio of 13:1 of Al and Cu respectively. The furnace temperature was set at 1300oC and after melting, gained wider acceptance as a result of its high strength-to- ingot was done using plastic mould with sprayed water weight ratio, as materials for fabrication of light weight to achieve rapid cooling. An amorphous or glassy structures. Gas tungsten arc welding (GTAW) and gas metal structure was produced from the ingot by super cooling arc welding (GMAW) processes are the most preferred o through preheating the cast rod to 600 C and rapid cooled by welding processes for high strength aluminum alloys [7]. water . The glassy alloy rods and Al control sample The thermoplastic forming process of amorphous were prepared for Scanning Electron Microscope (SEM), tensile and impact toughness characterizations. The results (metallic ) is as a result of the special softening showed SEM images of the Al-Cu alloy and pure Al samples. feature of metallic glasses when heated above their The ultimate tensile strengths for Al-Cu and Al samples were transition temperature (Tg) [8],[9]. Many organisations 399 and 330 kg/m2 respectively. Similarly, the impact strengths published more specific standards for the manufacture of obtained were 27.3 and 26.4 J. It can be concluded that glassy aluminum alloys, including the Society of Automotive phase Al-Cu alloy was produced with high ultimate tensile Engineers standards organisation, specifically its aerospace strength and impact toughness. The amorphous alloy produced is a good structural material for aerospace applications. standards subgroups [10]. Small length scales of patterns which range from some Index Terms – Aerospace; Alloy; Aluminum; Amorphous; 10nm to several millimetres can be made from metallic Characterization; Copper; Production; Strength. glasses [11]. The low magnetisation loss that characterises metallic glasses is explored for use in production of high and even higher frequency . However, I. INTRODUCTION amorphous steel exhibit some level of brittleness which matrix composites are commonly used in the poses difficulty in punching into motor lamination made design and manufacture of high-performance military with amorphous steel [12]. Synthesise of glasses in both aircraft and specified for some applications in commercial alloy classes by intense deformation of crystalline multilayer aircraft. Alloys of aluminum nonetheless find application as arrays represents a significant level of micro-structural the base materials for aircraft structural components where control that influences the structural performance and high strength to weight ratio is required such as the fuselage stability [13]. Duralinium was earlier developed and applied skin and wing [1]. The advent of metal aircraft which used to the structural parts of aircrafts and subsequently, various thin steel skins brought about a major advancement via the aluminum-copper alloys were developed based on the application of aluminum alloys in the aerospace industry features of Duralinium [14]. which is still on to date [2]. Copper is the principal element of copper alloys having The formation of aluminum oxide protective layer makes high resistance against . The common types of aluminum alloy keep their apparent surface shining in dry copper alloys are bronze which has tin as an important environment and on the other hand, wet environment alloying element and brass which has zinc as the alloying prompts galvanic corrosion when aluminum alloy is placed element. There is also based aluminum alloy composing in electrical contact with metal having higher resistance [3]. of 12% by weight of aluminum and having high strength Fabrication costs, design experience, established and insulating properties [15]. manufacturing methods and facilities are performance Toughness is the property of a material that defines its characteristics of aluminum alloys in which continued ability to resist fracture while undergoing plastic deformation, which requires a balance of strength and Published on February 18, 2017. ductility. When a material is stressed, the amount of energy O. R. Adetunji, M. L. Olukuade and O. M. Adesusi are with the Federal absorbed per unit volume of that material depicts its state of University of Agriculture, Abeokuta, Nigeria. (e-mail: [email protected], [email protected] and toughness [16]. Mathematically, f [email protected]). Toughness = energy/volume =  (1) W. Simka and M. Sowa are with Silesian University of Technology, 0 Gliwice, Poland. (e-mail: [email protected] and where ε = strain, εf= strain upon failure and σ = stress. [email protected]). I. K. Okediran is with Osun State University, Osogbo, Osun State, The unit is J/m3. Nigeria (e-mail: [email protected]).

1 doi: http://dx.doi.org/10.24018/ejers.2017.2.2.275 EJERS, European Journal of Engineering Research and Science Vol. 2, No. 2, February 2017

The metallographic structure of an amorphous metal is of 13:1 of Al and Cu respectively. The furnace temperature that of a non- which mimics the structure of glass- was set at 1300oC, Copper was first poured to the heated like. Unlike common glasses with typical insulating furnace under a closed atmosphere via the hopper the property, amorphous metals have good electrical temperature was held constant to ensure proper melting, conductivity [17]. They can be produced in a number of stirrer was engaged as aluminum was fed to the furnace ways including extremely rapid cooling, physical vapour consecutively. Simultaneously, stirring of the mixture deposition, solid-state reaction, ion irradiation, and continued for proper formation of the ingot to be produced, mechanical alloying [18]. ingot casting was done using plastic mould with sprayed Metallic glasses undergo heterogeneous deformation by water to achieve rapid cooling. An amorphous metal or formation of shear bands which is due to shear instability glassy structure was produced from the ingot by super causing them to fail catastrophically [19]. Unusual cooling through preheating the cast rod to 600oC and rapid uniformity in fracture strengths of metallic glasses, around cooled by water quenching. The glassy alloy rods and Al 2% of strain, is controlled by the flow stress making failure control sample were prepared for Scanning Electron in metallic glasses an intrinsic process. This phenomenon Microscope (SEM), Energy Dispersive X-ray (EDX), tensile opposes the state of fracture strength in crystalline material and impact toughness characterizations. which depends on the material preparation [20]. Tensile yield strengths and higher elastic strain limits of III. RESULTS AND DISCUSSION amorphous metals are higher than polycrystalline metal The results obtained are contained in Figs. 1-3, and alloys while their ductility and fatigue strengths are lower Tables I-II. SEM image and EDX of the Al-Cu alloy and Al [21]. The non-crystalline structure of amorphous metal control sample are contained in Figs. 1 and 2 while Tables I which is free from defects such as that places and II showed the Elemental composition of the samples. limitation on crystalline alloys strength, gives its higher Table III contained the result of impact, hardness and tensile strength. ultimate tensile properties of the alloy as compared with Entropy difference between crystal and under-cooled melt pure Aluminum control sample. could not be ruled out, the difference in entropy which is a function of temperature, between the super cooled liquid and that of its stable crystal experiences a decline [22]. Liquids cooled below their transition temperature without crystallising exhibit lower entropy more than the crystalline phase. This temperature attained by passing crystallisation is regarded as the Kauzmann paradox [23]. A resolution of this popular paradox is the assumption that liquids super cooled at this temperature must undergo a phase transition to ideal glasses before the entropy of the super cooled liquid decrease below that of the crystal [24]. This transition temperature is defined as the calorimetric ideal temperature Toc [25] as given in (2).

Tg  Toc as dT/dt  0 (2)

(a) The change in configuration of glass within the transition temperature range occurs slowly with time towards the equilibrium structure [26]. The thermodynamic driving force, as provided by Gibbs free energy principle of minimisation is necessary for the ultimate physical change. Glass structure equilibrium is attained speedily at temperatures high than Tg (T > Tg). Contrarily, at significantly lower temperatures, glass configuration remains sensibly stable over lengthy periods of time [27]. The uniqueness of this work is the addressing of the challenge of both high strength and toughness through production of amorphous materials. This research therefore, elucidated the production and characterization of amorphous Aluminum copper alloy for high strength applications especially in aerospace. (b)

Fig. 1. (a) SEM image of Al-Cu alloy (b) EDX of Al-Cu alloy II. MATERIALS AND METHODS High grade Aluminum and copper ingots were washed dried, and surface cleaned with abrasive paper, and charged to a ceramic mould and put in an electric furnace in the ratio

2 doi: http://dx.doi.org/10.24018/ejers.2017.2.2.275 EJERS, European Journal of Engineering Research and Science Vol. 2, No. 2, February 2017

TABLE II: PROCESSING ELEMENTAL COMPOSITION OF ALUMINUM CONTROL SAMPLE Element Element Element Confidence Concentration Number Symbol Name 13 Al Aluminum 100.0 75.9 8 O Oxygen 100.0 23.3 33 As Arsenic 100.0 0.8

TABLE III: PROCESSING IMPACT, HARDNESS AND ULTIMATE TENSILE STRENGTH OF SAMPLES. Ultimate tensile strength Sample Impact strength (joule) Hardness value (Brinell) AV AV A B C AV A B C G A B C G G 405 402 390 399

Al-alloy 26.2 28.1 27.6 27.3 172 170 168 170 340 330 320 330

Aluminum 26.2 26 26.4 26.2 46 41 45 44

The properties of Amorphous Al-Cu alloy that enhances its suitability for aerospace applications include light weight (a) 3 (3.013 g/cm ), high strength to weight ratio, higher values of impact toughness, hardness and ultimate tensile strength as compared to commercial Aluminum (Table III). In addition, it has good thermal and corrosion properties. The mechanism of strengthening is by substitutional solid solution since copper is large enough to replace the aluminum in the lattice positions. The strength of the Al-Cu alloy is dependent on the ease with which dislocations can be moved by increasing the stress τ (as expressed below) that impedes the motion of dislocations [13].

1/2 * 3 (b)  = Gb c (3) Fig. 2. (a) SEM image and (b) EDX of Aluminum control sample Where c = Cu atoms concentration, G = shear modulus, b 450 = Burger’s vector magnitude, and ϵ = lattice strain due to 400 Cu. The SEM image of the Al-Cu amorphous alloy contained 350 the matrix of both Aluminum and intermetallic compound of 300 Al and Cu. The EDX pattern also confirmed the glassy 250 phase of the alloy. The elemental composition from Table I also confirmed the presence of Cu in the alloy. The results 200 Alcu 150 of the mechanical properties of the alloy in comparison with Al that of control sample showed significant improvement in 100 hardness and ultimate tensile strength of the alloy as shown Test units(J,HR,N/sq.m) Test 50 in Fig. 2. The results obtained were in agreement with the 0 findings of researches conducted [11], [14]. Impact Hardness UTS The production and characterization of amorphous Al-Cu Mechanical properties alloy enhanced its suitability for aerospace applications, as the choice of both metals and the processes involved make the glassy phase formation possible. The characterisation of Fig. 3. Plot of strength values of experimental samples the alloy elucidated the aerospace properties in for precipitate formation that enhanced the strength, hardness TABLE I: PROCESSING ELEMENTAL COMPOSITION OF AL-CU ALLOY Element Element Element Confidence Concentration and corrosion resistance. Number Symbol Name In aerospace applications, high strength to weight ratio is 13 Al Aluminum 100.0 75.9 required to ensure delivery of large components as payload 8 O Oxygen 100.0 23.3 increases. Also, good thermal stability, weight saving and 33 As Arsenic 100.0 0.5 better corrosion resistance are essentials especially for 11 Na Sodium 100.0 1.7 aircraft wing and fuselage skin materials. The amorphous 29 Cu Copper 100.0 1.6 Al-Cu alloy possessed these properties thus making it suitable for aerospace applications.

3 doi: http://dx.doi.org/10.24018/ejers.2017.2.2.275 EJERS, European Journal of Engineering Research and Science Vol. 2, No. 2, February 2017

IV. CONCLUSION [12] S. R. Ning, J. Gao and Y. G. Wang. “Review on Applications of Low Loss Amorphous Metals in Motors,” Advanced Materials Research, Having carried out experimental work on production and 129-131; 2010. characterization of amorphous Al-Cu alloy for aerospace [13] J. Q. Wang, Y. H. Liu, S. Imhoff, N. Chen, D. V. Louzguine-Luzgin application, the followings can be concluded; and A. Takeuchi. “Enhance the Thermal Stability and Glass Forming Ability of Al-based Metallic Glass by Ca Minor-alloying,” The Al-Cu alloy produced was glassy in nature as it was Intermetallics, 29:35-40, 2012. confirmed by the EDX pattern obtained from SEM http://dx.doi.org/10.1016/j.internet.2012.04.009 examination of the sample. [14] D. T. Packer, Building Victory: Aircraft Manufacturing in the Los Angeles Area in the World War II, CA, Cypress, 2013, p.39,87,118. The SEM image of the sample showed a matrix of Al ISBN 978-0-9897906-0-4 background with Al and Cu intermetallic compounds as [15] O. Yoshihira. “Novel Fe – Al Alloys and Method of Producing the precipitates. same,” Free Patent Online, Application no 11/815946, 2009. [16] M. Ipek, I. H. Selv, F. Findik, O. Torkul and I. H. Cedimogly. “An The mechanical properties of the Al-Cu alloy got showed Expert System Based Material Selection Approach to superior properties of impact toughness, hardness values and Manufacturing,” Material and Design, 47: 331-340, 2013. doi: Ultimate tensile strengths as compared with the control 10.1016/j.matdes.2012.11.060 [17] https://en.wikipedia.org/wiki/Amorphous_metal sample of pure Al. [18] A. Moridi, S. M. Hassani-Gangara, M. Guagliano and M. Dao. “Cold Therefore, Amorphous Al-Cu Alloy is a suitable material Spray Coating: Review of Material Systems and Fracture for aerospace application which makes this work Perspective,” Surface Engineering, 36(6): 369-395, 2014. doi:10.1179/1743294414Y.0000000270 commercially viable. [19] M. E. Kassner, K. Smith and V. Eliason. “Creep in Amorphous Metals,” Journal of Material Research and Technology, 4(1):100- FUNDING 107, 2015. http://dx.doi.org/10.1016/j.mrt.2014.11.003 [20] T. Egami, T. Iwashita and W. Dmowski. “Mechanical Properties of This research did not receive any specific grant from Metallic Glasses,” Metals, 3: 77-113, 2013. doi: 10.339/met3010077 funding agencies in the public, commercial, or not-for-profit [21] A. Russel and K. L. Lee. Structure property Relations in Nonferrous sectors. metals, John Wiley & sons, 2000, p.92. [22] P. G. Debenedetti, T. M. Truskett and C. P. Lewis. “Theory of Super- cooled Liquids and Glasses: Energy Landscape and Statistical ACKNOWLEDGMENT Geometry Perspective,” Advances in Chemical Engineering, 28: 21- 79, 2014. The authors express their gratitude to the management [23] C. A. Becker, J. Agren, M. Barrico, Q. Chen, S. A. Decterov, U. R. and staff of Federal Institute of Industrial Research, Oshodi Kattner, J. H. Perepezko, G. R. Pottlacher and M. Selleby. (FIIRO) for the assistance rendered in carrying out the “Thermodynamic Modelling of Liquids: CALPHAD Approaches and Contribution from Statistical Physics,” Physics Status Solid, 25(1): experimental work. Similarly, they are equally grateful to 33-52, 2001. doi: 10.1002/pssb.201350149 the staff of Faculty of Chemistry, Silesian University of [24] G. Zhang, F. H. Stillinger and S. Torquato. “The Perfect Glass Technology, Gliwice, Poland for carrying out SEM of the Paradigm: Disordered Hyperuniform Glasses Down to Absolute Zero,” Statistical Mechanics, 1-14, 2016. doi:10.1038/srep36963 samples. [25] D. Q. M. Craig, P. G. Royall, V. L. Kett and M. L. Hopton. “The Relevance of the Amorphous State to Pharmaceutical Dosage REFERENCES Forms: Glass Drugs and Freeze Dried Systems,” International Journal of Pharmaceutics, 179: 179-207. [1] E. A. Starke and J. T. Staley. “Application of Modern [26] https://en.wikipedia.org/wiki/Glass_transition Aluminum Alloys to Aircraft,” Prog. Aerospace Sci., 32: 131-172, [27] I. M. Kalogeras. Glass-Transition Phenomena in Polymer Blends: 1996. Encyclopaedia of Polymer Blends, Wiley-VCH Verlag GmbH &Co. [2] Significant Developments in Structures & Materials since 1866, KGaA, 2016, 134 p. Royal Aeronautical Society. 2016. http://www.aerosociety.com. [3] M. A. Bolude, O. S. Sanni and W. A. Ayoola. “Effect of Copper Olayide R. Adetunji is a senior lecturer and Ag. Addition on the Corrosion and Mechanical Properties of 6063 HOD of the Department of Mechanical Engineering, Aluminum Alloy in 1 Molar Brine Solution,” Journal of Material Federal University of Agriculture, Abeokuta, Ogun Science and Engineering A3(4): 278-282, 2013. State, Nigeria. He has several published papers in [4] O. R. Adetunji, O. J. Akinyemi, S. I. Kuye, and E. O. Dare. reputable journals. His research interests are in the “Corrosion Performance of Al-Zn Coated Steel in Tomato, Orange area of corrosion engineering, energy materials, and Pineaple Juices,” Corrosion and Protection, 59(3):66-69, 2016. material characterization and nano-technology. http://www.ochronaprzedkoroza.pl, doi:10.15199/40.2016.3.2 [email protected] [5] N. S. Barekar and B. K. Dhindaw. “Twin-Roll casting of aluminum [email protected]. alloys-an overview,” Materials and Manufacturing Processes, 29(6): 651-661, 2014. doi:10.1080/10426914.2014.912307 Muyiwa L. Olukuade is a M. Eng. Student of the [6] K. F. Jin and J. F. Loffler. “Bulk Metallic glass formation in Zr-Cu- Department of Mechanical Engineering, Federal Fe-Al alloys,” Applied Physics Letters, 86(24), 241909-241911, 2005. University of Agriculture, Abeokuta, Ogun State, doi:10.1063/1.1948513 Nigeria. His research interests are in the area of [7] V. Balasubramanian, V. Ravisankar and G. Madhusudham Reddy. material characterization and development. “Effect of Postweld Aging Treatment on Fatigue Behaviour of Pulsed [email protected] Current Welded AA7075 Aluminum Alloy Joints,” Journal of Material Engineering and Performance, 17(2), 224 – 233, 2008. doi:10.1007/s11665-007-9129-9

[8] A. Inoue, F. Kong, S. Zhu, C. T. Liu and F. Al-Marzouki. “Development and Applications of Highly Functional Al-based Wojciech Simka is an Associate Professor in the Materials by use of Metastable Phases,” Materials Result, 18(6), Department of Inorganic, Analitical and Electro- 2015. Sao Carlos; http://dx.doi.org/10.1590/1516-1439.058815 chemistry, Chemistry Faculty, Silesian University of [9] Z. Wang, R. T. Qu, S. Scudino, B. A. Sun, K. G. Prashanth, D. V. Technology, Gliwice, Poland. His research interests Louzguine-Luzgin, M. W. Chen, Z. F. Zhang and J. Eckert. “Hybrid are in the area of material characterization, Nano-structured Aluminum Alloy with Super-High Strength,” Asia electrochemistry, advance materials, biochemistry Materials, 7, 2015. e229; doi: 10.1038/am.2015.129 and corrosion. [10] Society of Automobile Engineers, Aerospace Council Report, 2009. [email protected] [11] G. Kumar, H. X. Tang and J. Schroers. “Nano-moulding with

amorphous metals” Nature, 457(7231): 868-872, 2009.

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Maciej Sowa is a Ph.D. student in the Department of Inorganic, Analytical and Electro-chemistry, Chemistry Faculty, Silesian University of Technology, Gliwice, Poland. His research interests are in the area of material characterization, electrochemistry, advance materials, biochemistry and corrosion. [email protected]

Olanrewaju M. Adesusi is a Ph.D. student in Department of Mechanical Engineering, Federal University of Agriculture, Abeokuta, Ogun State, Nigeria. His research interests are in the area of material characterization, cutting fluid, machine tools and bio-resources. [email protected]

Iliyas K. Okediran is a Ph.D. holder and a lecturer in the Department of Mechanical Engineering, Osun State University, Osogbo, Osun State, Nigeria. His research interests are in the area of materials and iron and steel production. [email protected]

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