Volume 46 International Scientific Journal Archives Issue 2 published monthly by the
of Materials Science December 2010 World Academy of Materials The aluminum alloys of 6xxx group have been studied After artificial aging, a set of specimens were prepared for extensively because of their technological importance and tensile testing to study the effect of T6 heat treatments on and Engineering Pages 98-107 and Manufacturing Engineering exceptional increase in strength obtained by precipitation mechanical properties of the examined alloys. The specimens hardening. The 6xxx aluminium alloys are mostly used as were strained by tensile deformation on Instron TTF-1115 extruded products, as well as for construction and automotive servohydraulic universal tester at a constant rates at room application. The ease with which these alloys can be shaped, their temperature in according to standard PN-EN 10002-1:2004 [23]. low density, their very good corrosion and surface properties and Tensile properties (tensile and yield strength; elongation) were good weldability are factors that together with a low price these evaluated using round test specimens of 8 mm diameter and 65 Influence of chemical composition variation make them commercially very attractive. mm gauge length (according to ASTM E602-78T [24] standard). The precipitation of metastable precursors of the equilibrium A metallographic investigations were performed on the ȕ(Mg2Si) phase occurs in one or more sequences which are quite samples at as-cast state after homogenization treatment and and heat treatment on microstructure and complex. The precipitation sequence for 6xxx alloys, which is extrusion forging process. The microstructure of the alloys was generally accepted in the literature [11-13], is: observed using optical microscope - Nikon 300 on polished mechanical properties of 6xxx alloys SSSS ĺatomic clusters ĺGP zones ĺE''ĺ E'ĺ E (stable) sections etched in Keller solution containing 0.5 % HF in 50ml Some authors [8] consider the GP zones as GP1 zones while H2O. The surfaces of fracture of the damaged samples were the E'' is called a GP2 zone. The most effective hardening phase prepared to microscopic examination by scanning electron for this types of materials is E''. The medium strength AlMgSi microscopy (SEM). G. Mrówka-Nowotnik* aluminium alloys are commonly processed by extrusion. Their Department of Materials Science, Rzeszow University of Technology, extradubility depends to a large extent on chemical composition, ul. W. Pola 2, 35-959 Rzeszów, Poland casting condition and heat treatment parameters (eg. 3. Results and discussion * Corresponding author: E-mail address: [email protected] homogenization treatment) which determine the microstructure of the billet before extrusion. The microstructure of the 6061 alloy in as-cast state and after Received 10.09.2010; published in revised form 01.12.2010 homogenization is given in Fig. 1 - as an example of as-cast state of the investigated alloys. ABSTRACT 2. Material and experimental a) Purpose: The main task of this work was to study the effect a the precipitation hardening on the microstructure The investigation has been carried out on the commercial and mechanical properties of 6061, 6063 and 6082 aluminium alloys. 6061, 6063 and 6082 aluminum alloys. Chemical composition of Design/methodology/approach: In this paper differential scanning calorimetry (DSC) and hardness the alloys is indicated in Table 1. measurements have been utilized to study the effect of a precipitation hardening on the mechanical properties in 6xxx aluminium alloys. The mechanical (Rm and Rp0.2) and plastic (A, Z) properties of the examined alloys were evaluated Table 1. by uniaxial tensile test at room temperature. The microstructure was observed using optical microscope - Nikon 300, Chemical composition of the investigated alloys, %wt scanning electron microscope HITACHI S-3400 (SEM) in a conventional back-scattered electron mode. Alloy Si Mg Mn Cu Fe Zn Ni Cr Ti Findings: The results show that the microstructure and mechanical properties changes during artificial aging due 6061 0.78 1.07 0.15 0.35 0.16 0.042 0.007 0.35 0.029 a the precipitation strengthening process. Therefore, the parameters (time and aging temperature) of precipitation strengthening process that may lead to the most favourable mechanical properties of 6061, 6063 and 6082 alloys 6063 0.55 0.55 0.07 0.026 0.18 0.02 0.005 - 0.018 were determined. 6082 1.0 0.76 0.56 0.022 0.16 0.013 0.004 - 0.023 Practical implications: This paper is the part of previous author’s investigations which results in modification of the heat treatment parameters that may lead to the most favorable mechanical properties of 6xxx alloys. Originality/value: The paper has provided essential data about influence chemical composition and aging Thermal processing of the investigated alloys included a b) parameters on the microstructure and mechanical properties of 6061, 6063 and 6082 alloys. homogenization treatment and T6 heat treatment (artificially ageing after solution treatment). The temperature of Keywords: Metallic alloys; Microstructure; Mechanical properties; Heat tretmeant homogenization treatment of 6xxx alloys were determined on the Reference to this paper should be given in the following way: basis of literature data and calorimetric investigations. The samples G. Mrówka-Nowotnik, Influence of chemical composition variation and heat treatment on microstructure and in as-cast state were preheated in an induction furnace to mechanical properties of 6xxx alloys, Archives of Materials Science and Engineering 46/2 (2010) 98-107. temperature 575°C held for 72 hours and subsequently cooled to room temperature. Additionally all alloys were heated in a MATERIALS resistance furnace for 12 hours at 565°C and then quenched into a water. Subsequently the specimens were subjected to artificial aging at temperature 175oC up to 98 h. In order to determine an influence 1. Introduction technical 6xxx aluminium alloys contents of Si and Mg are in the of time on the kinetics of ageing the Brinell hardness was measured. 1. Introduction range of 0.5-1.2 wt%, usually with a Si/Mg ratio larger than one. DSC samples of the supersaturated 6061, 6063 and 6082 alloys
Besides the intentional additions, transition metals such as Fe and were investigated in SETARAM Setsys thermal analyzer fitted with The 6xxx-group contains magnesium and silicon as major Mn are always present. If Si content in Al alloys exceed the a scanning differential calorimeter module. The heat effects addition elements. These multiphase alloys belong to the group of amount that is necessary to form Mg Si phase, the remaining Si is associated with precipitation of GP zones and intermediate commercial aluminum alloys, in which relative volume, chemical 2 present in other phases, such as Al-Fe-Si and Al-Fe-Si-Mn metastable and stable strengthening phase E(Mg Si) were obtained composition and morphology of structural constituents exert 2 Fig. 1. Microstructure of examined 6061 alloy: a) as-cast state, particles [2,4,6-13]. by subtracting a super purity Al baseline run. o significant influence on their useful properties [1-22]. In the b) after homogenization at 575 C/72h
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The aluminum alloys of 6xxx group have been studied After artificial aging, a set of specimens were prepared for extensively because of their technological importance and tensile testing to study the effect of T6 heat treatments on exceptional increase in strength obtained by precipitation mechanical properties of the examined alloys. The specimens hardening. The 6xxx aluminium alloys are mostly used as were strained by tensile deformation on Instron TTF-1115 extruded products, as well as for construction and automotive servohydraulic universal tester at a constant rates at room application. The ease with which these alloys can be shaped, their temperature in according to standard PN-EN 10002-1:2004 [23]. low density, their very good corrosion and surface properties and Tensile properties (tensile and yield strength; elongation) were good weldability are factors that together with a low price these evaluated using round test specimens of 8 mm diameter and 65 make them commercially very attractive. mm gauge length (according to ASTM E602-78T [24] standard). The precipitation of metastable precursors of the equilibrium A metallographic investigations were performed on the ȕ(Mg2Si) phase occurs in one or more sequences which are quite samples at as-cast state after homogenization treatment and complex. The precipitation sequence for 6xxx alloys, which is extrusion forging process. The microstructure of the alloys was generally accepted in the literature [11-13], is: observed using optical microscope - Nikon 300 on polished SSSS ĺatomic clusters ĺGP zones ĺE''ĺ E'ĺ E (stable) sections etched in Keller solution containing 0.5 % HF in 50ml Some authors [8] consider the GP zones as GP1 zones while H2O. The surfaces of fracture of the damaged samples were the E'' is called a GP2 zone. The most effective hardening phase prepared to microscopic examination by scanning electron for this types of materials is E''. The medium strength AlMgSi microscopy (SEM). aluminium alloys are commonly processed by extrusion. Their extradubility depends to a large extent on chemical composition, casting condition and heat treatment parameters (eg. 3. ResultsResults andand discussion homogenization treatment) which determine the microstructure of the billet before extrusion. The microstructure of the 6061 alloy in as-cast state and after homogenization is given in Fig. 1 - as an example of as-cast state of the investigated alloys. 2. MaterialMaterial and experimentalexperimental a) The investigation has been carried out on the commercial 6061, 6063 and 6082 aluminum alloys. Chemical composition of the alloys is indicated in Table 1.
Table 1. Chemical composition of the investigated alloys, %wt Alloy Si Mg Mn Cu Fe Zn Ni Cr Ti 6061 0.78 1.07 0.15 0.35 0.16 0.042 0.007 0.35 0.029 6063 0.55 0.55 0.07 0.026 0.18 0.02 0.005 - 0.018 6082 1.0 0.76 0.56 0.022 0.16 0.013 0.004 - 0.023
Thermal processing of the investigated alloys included a b) homogenization treatment and T6 heat treatment (artificially ageing after solution treatment). The temperature of homogenization treatment of 6xxx alloys were determined on the basis of literature data and calorimetric investigations. The samples in as-cast state were preheated in an induction furnace to temperature 575°C held for 72 hours and subsequently cooled to room temperature. Additionally all alloys were heated in a resistance furnace for 12 hours at 565°C and then quenched into a water. Subsequently the specimens were subjected to artificial aging at temperature 175oC up to 98 h. In order to determine an influence technical 6xxx aluminium alloys contents of Si and Mg are in the of time on the kinetics of ageing the Brinell hardness was measured. 1. Introduction range of 0.5-1.2 wt%, usually with a Si/Mg ratio larger than one. DSC samples of the supersaturated 6061, 6063 and 6082 alloys
Besides the intentional additions, transition metals such as Fe and were investigated in SETARAM Setsys thermal analyzer fitted with The 6xxx-group contains magnesium and silicon as major Mn are always present. If Si content in Al alloys exceed the a scanning differential calorimeter module. The heat effects addition elements. These multiphase alloys belong to the group of amount that is necessary to form Mg Si phase, the remaining Si is associated with precipitation of GP zones and intermediate commercial aluminum alloys, in which relative volume, chemical 2 present in other phases, such as Al-Fe-Si and Al-Fe-Si-Mn metastable and stable strengthening phase E(Mg Si) were obtained composition and morphology of structural constituents exert 2 Fig. 1. Microstructure of examined 6061 alloy: a) as-cast state, particles [2,4,6-13]. by subtracting a super purity Al baseline run. o significant influence on their useful properties [1-22]. In the b) after homogenization at 575 C/72h
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G. Mrówka-Nowotnik
a) phase may occur. It is supposed that the very fine dispersed with a high Fe content (0.16%) eutectic melting of Al +E- Based upon the recent researches [1-3] one may conclude that precipitates shown in Figure 1b are particles of ȕ-Mg2Si phase. Mg2Si+E-Al5FeSioL+D’-Al8Fe2Si or Al +E-Mg2Si oL occurred E(Mg2Si) precipitates play crucial role in hardening of these During hot working of ingots, particles of intermetallic phases [8]. It can thus be concluded that the response to DSC heating of alloys. According to [11] et al [6-9] the volume fraction of GP are arranged in positions parallel to direction of plastic the present alloy independently of deformation agreed reasonably zones and E(Mg2Si) precipitates increase with alloy’s components deformation (along plastic flow direction of processed material) well with the precipitation sequence reported for AlMgSi alloys: content. which allows for the formation of the band structure (Fig. 2). As a Supersaturated solid solution SSSS ĺatomic clusters ĺGP zones So far it has been shown that the mechanical properties were result, the reduction of size of larger particles may takes place. ĺE''ĺ E'ĺ E (stable). highly influenced by the precipitates of a hardening E(Mg2Si) The accumulation of lattice defects in the material during hot As can be observed in Table 2, the main difference in the phase. Precipitates of this phase do not only affect mechanical extrusion forging process exerts a considerable influence on a precipitation patterns of the examined alloys is the temperature of properties. The strength is also influenced by the intermetallic structure formation. As a result, the strain hardening of the alloy the peaks. This discrepancies of the order few degree of celsius phases formed during solidification of the alloys. This is evidently takes place and, in consequence, an increase in mechanical can be explained in terms of chemical compositions of the alloys, related to the reactions that occur during solidification of the 6xxx properties occurred. similar explanation can be held for the sharpness of the peaks. type alloys between some alloying elements (Fe, Mn and Cr) and The DSC curves of the investigated 6xxx alloys obtained main 6xxx alloys components – silicon and magnesium. Their during calorimetric study of samples quenched immediately after formation have significant effect on decreasing volume fraction of Table 2. solution heat treatment and heated with scaning rate of 15K/min hardening precipitates of E(Mg Si) phase. Therefore decreasing in Temperature of the peaks obtained during heating at rate of 2 revealed a total of 9 anthalpic effects. Seven of them were the effectiveness of hardening via precipitates of this phase is 15oC/min for the 6xxx alloys immediately after solutionizing and b) exothermic (Fig. 3). observed. Treakner [25] suggested to utilize the equations by quenching which either volume fraction of hardening E(Mg Si) phase and Temperature of the peaks, oC 2 -120 Alloy excessive content of Si can be calculated using a chemical 4 1 2 3 4 5 6 7 8 9 composition of an alloy: 6063 6061 78.2 161.2 1762.1 267.7 304.0 363.0 500.4 530.2 577.3 6082 -140 6061 6063 83.6 161.4 196.9 283.0 310.0 - 484.0 525.6 581.8 Si in precipitates of Al(FeMn)Si type 5 6082 83.2 166.0 198.1 274.4 310.4 - 508.1 528.0 585.6 zf(Si) = 0.25 (%Fe + %Mn) (1) Si in E(Mg2Si) formed in reaction with Mg
Endo Exo -160 z (Si) = 0.578 (%Mg) (2) 6 In order to determine the influence of precipitation hardening m
3 E 2 conditions on the aging kinetic of the examined alloys, hardness (Mg2Si) phase content w(Mg2Si ) = (Mg) + zm(Si) (3) 7 remaining content of Si nf(Si) = (%Si) - zf(Si) (4) Heat flow, mW flow, Heat -180 1 measurements at specified time intervals were performed (see Table 3). excessive content of Si n(Si) = nf(Si) - zm(Si) (5)
8 -200 Table 3. Changes in the HB hardness of investigated alloys in relation of Table 4. 9 Calculated values of volume fraction of E(Mg Si) and of the c) time of aging at 175°C 2 -220 Alloy excessive silicon content in the investigated alloys (equations 1-5) 100 200 300 400 500 600 Time of ageing, h 6061 6063 6082 Alloy zf(Si) nf(Si) zm(Si) w(Mg2Si ) n(Si) Temperature, °C 0 55.4 35.8 55.3 6061 0.077 0.703 0.618 1.688 0.085
6063 0.062 0.487 0.318 0.868 0.169 Fig. 3. DSC trace of as-quenched samples of the examined 6xxx 0.5 70.9 36.9 64 aluminium alloys taken at a scan rate of 15oC/min 1 98.3 39 84.3 6082 0.177 0.823 0.439 1.199 0.384 1.5 106.3 52.6 101 Exothermic peaks 1 observed at the DSC curves are belived to 2 115.4 68.8 112.8 be responsible for the extensive clustering activity in this group of 3 116.6 73.1 113.2 Apart of quantitative determination of volume fraction of alloys. The exothermic peak 2 and 3 at approximetly 165°C was 4 118.5 81.2 118.3 E(Mg2Si) in 6061, 6063 and 6082 alloys, additional information linked to the formation of GP zones. GP zones dissolution 5 120 87.7 119 about excessive content of the main element of these alloys – Si occurred at ~ 187°C. The major exothermic peak 4 with a and Mg that take part (in the presence of Fe and Mn) in formation 6 121.5 91 122.6 maximum at 242°C is clearly linked with the precipitation of the of intermetallic phases were determined (Table 4). Previous principal hardening phase E”. E” precipitation is promoted by 8 125.3 88.8 121.7 works [2,26-28] and literature data [10-14] reveals that the precursor GP- zones [13]. The precipitation continued with the 10 127.2 89.7 123 presence of E(Mg2Si) phase and precipitates of intermetallic transformation of E” to the E’ phase producing neighbouring 12 123.3 92.5 120 phases containing Si, Fe and Mn play significant role in Fig. 2. Mictostructure of the examined alloys after hot extrusion: exothermic peak 5 with maximum at 331°C. 15 122.9 94.2 120 mechanical properties increasing. Fig. 4 shows the effect of a) 6063 alloy, b) 6082 alloy, c) 6061 alloy In 6061 aluminum alloy besides of E-Mg2Si phase 20 123 87.5 116.7 artificial aging time on hardness of 6061, 6063 and 6082 alloys. It precipitation of T-Al2Cu and Q(Al5Cu2Mg8Si6) phases can be 24 125.8 89 115 can clearly be seen that the hardness of examined alloys depends The revealed particles of the intermetallic phases were formed observed. The exothermic peak 6 with a maximum at 363°C is 30 124 91 119.7 on the chemical composition and aging time. The plots for all linked to the precipitation of the hardening phases T’ or Q’ during casting of the alloy. A typical as-cast microstructure of 35 126.6 91.3 122.1 alloys indicate that in all cases, the hardness initially increase 6xxx series aluminium alloys consisted of a mixture of Al Fe, The next two exothermic peaks 7 (428°C) and endothermic rapidly with the increase in aging time reaching the peak value, 3 48 128.7 88.6 115.5 ȕAlFeSi and Į-AlFeMnSi intermetallic phases distributed at cell peak 8 (528°C) are associated with the precipitation and after which hardness decrease. All of the investigated alloys 60 125.6 86.4 113.4 boundaries, accompanied sometimes with coarse Mg2Si (Fig. 1a). dissolution of the equilibrium E-Mg2Si phase respectively. On the reached maximum hardness after aging at 175°C – 128.7HB alloy During homogenization of the alloy at temperature 575qC, the DSC curve small endothermic peak with maximum at about 72 124.4 83 105.1 6061 for 48 hours, alloy 6063 –94.2HB for 15 hours and 6082 – transformation ȕ-AlFeSi phase in more spheroidal Į-Al(FeMn)Si 585°C was observed. On the basis of literature date in the alloy 98 122.2 81.4 100.9 123.0 HB for 10 hours) (see Table 3 and Fig. 4).
100 100 Archives of Materials Science and Engineering
Influence of chemical composition variation and heat treatment on microstructure and mechanical properties of 6xxx alloys
a) phase may occur. It is supposed that the very fine dispersed with a high Fe content (0.16%) eutectic melting of Al +E- Based upon the recent researches [1-3] one may conclude that precipitates shown in Figure 1b are particles of ȕ-Mg2Si phase. Mg2Si+E-Al5FeSioL+D’-Al8Fe2Si or Al +E-Mg2Si oL occurred E(Mg2Si) precipitates play crucial role in hardening of these During hot working of ingots, particles of intermetallic phases [8]. It can thus be concluded that the response to DSC heating of alloys. According to [11] et al [6-9] the volume fraction of GP are arranged in positions parallel to direction of plastic the present alloy independently of deformation agreed reasonably zones and E(Mg2Si) precipitates increase with alloy’s components deformation (along plastic flow direction of processed material) well with the precipitation sequence reported for AlMgSi alloys: content. which allows for the formation of the band structure (Fig. 2). As a Supersaturated solid solution SSSS ĺatomic clusters ĺGP zones So far it has been shown that the mechanical properties were result, the reduction of size of larger particles may takes place. ĺE''ĺ E'ĺ E (stable). highly influenced by the precipitates of a hardening E(Mg2Si) The accumulation of lattice defects in the material during hot As can be observed in Table 2, the main difference in the phase. Precipitates of this phase do not only affect mechanical extrusion forging process exerts a considerable influence on a precipitation patterns of the examined alloys is the temperature of properties. The strength is also influenced by the intermetallic structure formation. As a result, the strain hardening of the alloy the peaks. This discrepancies of the order few degree of celsius phases formed during solidification of the alloys. This is evidently takes place and, in consequence, an increase in mechanical can be explained in terms of chemical compositions of the alloys, related to the reactions that occur during solidification of the 6xxx properties occurred. similar explanation can be held for the sharpness of the peaks. type alloys between some alloying elements (Fe, Mn and Cr) and The DSC curves of the investigated 6xxx alloys obtained main 6xxx alloys components – silicon and magnesium. Their during calorimetric study of samples quenched immediately after formation have significant effect on decreasing volume fraction of Table 2. solution heat treatment and heated with scaning rate of 15K/min hardening precipitates of E(Mg Si) phase. Therefore decreasing in Temperature of the peaks obtained during heating at rate of 2 revealed a total of 9 anthalpic effects. Seven of them were the effectiveness of hardening via precipitates of this phase is 15oC/min for the 6xxx alloys immediately after solutionizing and b) exothermic (Fig. 3). observed. Treakner [25] suggested to utilize the equations by quenching which either volume fraction of hardening E(Mg Si) phase and Temperature of the peaks, oC 2 -120 Alloy excessive content of Si can be calculated using a chemical 4 1 2 3 4 5 6 7 8 9 composition of an alloy: 6063 6061 78.2 161.2 1762.1 267.7 304.0 363.0 500.4 530.2 577.3 6082 -140 6061 6063 83.6 161.4 196.9 283.0 310.0 - 484.0 525.6 581.8 Si in precipitates of Al(FeMn)Si type 5 6082 83.2 166.0 198.1 274.4 310.4 - 508.1 528.0 585.6 zf(Si) = 0.25 (%Fe + %Mn) (1) Si in E(Mg2Si) formed in reaction with Mg
Endo Exo -160 z (Si) = 0.578 (%Mg) (2) 6 In order to determine the influence of precipitation hardening m
3 E 2 conditions on the aging kinetic of the examined alloys, hardness (Mg2Si) phase content w(Mg2Si ) = (Mg) + zm(Si) (3) 7 remaining content of Si nf(Si) = (%Si) - zf(Si) (4) Heat flow, mW flow, Heat -180 1 measurements at specified time intervals were performed (see Table 3). excessive content of Si n(Si) = nf(Si) - zm(Si) (5)
8 -200 Table 3. Changes in the HB hardness of investigated alloys in relation of Table 4. 9 Calculated values of volume fraction of E(Mg Si) and of the c) time of aging at 175°C 2 -220 Alloy excessive silicon content in the investigated alloys (equations 1-5) 100 200 300 400 500 600 Time of ageing, h 6061 6063 6082 Alloy zf(Si) nf(Si) zm(Si) w(Mg2Si ) n(Si) Temperature, °C 0 55.4 35.8 55.3 6061 0.077 0.703 0.618 1.688 0.085
6063 0.062 0.487 0.318 0.868 0.169 Fig. 3. DSC trace of as-quenched samples of the examined 6xxx 0.5 70.9 36.9 64 aluminium alloys taken at a scan rate of 15oC/min 1 98.3 39 84.3 6082 0.177 0.823 0.439 1.199 0.384 1.5 106.3 52.6 101 Exothermic peaks 1 observed at the DSC curves are belived to 2 115.4 68.8 112.8 be responsible for the extensive clustering activity in this group of 3 116.6 73.1 113.2 Apart of quantitative determination of volume fraction of alloys. The exothermic peak 2 and 3 at approximetly 165°C was 4 118.5 81.2 118.3 E(Mg2Si) in 6061, 6063 and 6082 alloys, additional information linked to the formation of GP zones. GP zones dissolution 5 120 87.7 119 about excessive content of the main element of these alloys – Si occurred at ~ 187°C. The major exothermic peak 4 with a and Mg that take part (in the presence of Fe and Mn) in formation 6 121.5 91 122.6 maximum at 242°C is clearly linked with the precipitation of the of intermetallic phases were determined (Table 4). Previous principal hardening phase E”. E” precipitation is promoted by 8 125.3 88.8 121.7 works [2,26-28] and literature data [10-14] reveals that the precursor GP- zones [13]. The precipitation continued with the 10 127.2 89.7 123 presence of E(Mg2Si) phase and precipitates of intermetallic transformation of E” to the E’ phase producing neighbouring 12 123.3 92.5 120 phases containing Si, Fe and Mn play significant role in Fig. 2. Mictostructure of the examined alloys after hot extrusion: exothermic peak 5 with maximum at 331°C. 15 122.9 94.2 120 mechanical properties increasing. Fig. 4 shows the effect of a) 6063 alloy, b) 6082 alloy, c) 6061 alloy In 6061 aluminum alloy besides of E-Mg2Si phase 20 123 87.5 116.7 artificial aging time on hardness of 6061, 6063 and 6082 alloys. It precipitation of T-Al2Cu and Q(Al5Cu2Mg8Si6) phases can be 24 125.8 89 115 can clearly be seen that the hardness of examined alloys depends The revealed particles of the intermetallic phases were formed observed. The exothermic peak 6 with a maximum at 363°C is 30 124 91 119.7 on the chemical composition and aging time. The plots for all linked to the precipitation of the hardening phases T’ or Q’ during casting of the alloy. A typical as-cast microstructure of 35 126.6 91.3 122.1 alloys indicate that in all cases, the hardness initially increase 6xxx series aluminium alloys consisted of a mixture of Al Fe, The next two exothermic peaks 7 (428°C) and endothermic rapidly with the increase in aging time reaching the peak value, 3 48 128.7 88.6 115.5 ȕAlFeSi and Į-AlFeMnSi intermetallic phases distributed at cell peak 8 (528°C) are associated with the precipitation and after which hardness decrease. All of the investigated alloys 60 125.6 86.4 113.4 boundaries, accompanied sometimes with coarse Mg2Si (Fig. 1a). dissolution of the equilibrium E-Mg2Si phase respectively. On the reached maximum hardness after aging at 175°C – 128.7HB alloy During homogenization of the alloy at temperature 575qC, the DSC curve small endothermic peak with maximum at about 72 124.4 83 105.1 6061 for 48 hours, alloy 6063 –94.2HB for 15 hours and 6082 – transformation ȕ-AlFeSi phase in more spheroidal Į-Al(FeMn)Si 585°C was observed. On the basis of literature date in the alloy 98 122.2 81.4 100.9 123.0 HB for 10 hours) (see Table 3 and Fig. 4).
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130 Table 5. a) a) 360 120 Mechanical properties of the examined alloys after T6 treatment 420 Mechanical properties Aging 390 110 Alloy R , R , A , Z, 330 time,h 0.2 m 5 100 MPa MPa % % 360 300 2 163.2 270.5 33.5 44.6 90 330 5 206.7 295.6 29.7 43.0 270 80 10 274.2 320.0 19.7 40.9 6061 300 240 70 24 326.5 353.9 15.2 42.1 , MPa K, ,
m 270 50 331.26 349.0 14.8 43.7 K,MPa ,
6061 m Hardness HB5/250 Hardness
, R , 210 60 6063 96 329.35 348.8 14.4 45.6 R 0.2 , R 0.2 240 6082 R0.2 0.2 50 2 128.5 202.3 25.1 75.4 R Rm R 180 R 5 257.0 275.6 16.1 51.8 210 K m 40 K 10 271.3 281.6 14.1 45.6 150 6063 180 30 30 269.2 289.9 12.1 40.4 1 10 100 50 267.5 290.4 13.9 35.5 150 120 log t, h 96 229.5 252.3 13.3 48.4 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 2 165.0 246.2 29.2 46.8 t, h Fig. 4. Variation of hardness with time of aging of investigated t, h 6 276.7 306.0 16.8 45.6 b) alloy at temperature of 175°C 10 299.9 338.1 15.9 40 b) 6082 50 30 314.9 333.7 15.4 40.3 80 It is well known that silicon and magnesium content has a 50 309.6 330.5 14.8 43.4 45 positive effect on mechanical properties after aging thus it is 96 282.0 298.3 13.0 44.8 70 A worth to determine the effect of Mg+Si concentration on the 40 5 Z behavior of 6xxx alloys during aging (Fig. 5). On the basic of the region of uniform plastic deformation 60 from the stress-strain curves of and a simple power – curve 35 50 relation: 30 n 130 V H = K (6) A5 , Z, % Z, , 5
25 % Z, , 40
Z 5 6082 the values of n (is the strain – hardening exponent) and K (is the A 125 strength coefficient) were determined. Additionaly on the basic of A 20 30 120 6061 the stress-strain curves Young modulus E, and m – “hardening
coefficient” from equation 7 was calculeted: 15 115 20 R R R 10 110 m 0.2 m (7) m 1 10 R0.2 R0.2 0 10 20 30 40 50 60 70 80 90 100 Max HB5/250 Max 105 0 10 20 30 40 50 60 70 80 90 100 were: R0.2 – yield strength, Rm – tensile strength (Tab. 6, Figs. 6-8). t, h y = 45,116x + 44,467 t, h 100 2 R = 0,998 c) c) Table 6. 0,7 95 The values of: E – Young modulus, K – strength coefficient, n – 0,6 6063 90 strain – hardening exponent and m – “hardening coefficient” 0,6 Aging 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 Alloy E/r K n m 0,5 Mg+Si, % time, h 0,5 2 68 538/1.0000 297.78 0.0957 0.67357 n 0,4 Fig. 5. Influence of different Mg + Si levels on the maximum 5 71 053/0.9999 337.60 0.08030 0.43028 n hardness of the examined alloys 10 70 470/0.9999 394.18 0.0601 0.18429 0,4 m 6061 m 24 71 155/0.9999 418.12 0.0367 0.08147 0,3
n, m n, 0,3 50 71 566/0.9999 394.46 0.0281 0.04910 m n, The results in (Fig. 5) demonstrate that progress of silicon and 96 71 999/0.9999 406.93 0.03420 0.05907 0,2 magnesium content improves the maximum hardness in examined 2 63 256/0.9999 228.82 0.09592 0.56516 0,2 alloys. In 6082 aluminium alloy, with the highest concentration of 6 67 235/0.9999 303.74 0.0347 0.11250 silicon and magnesium the highest hardness in T6 state was 10 66 322/0.9999 326.5 0.0300 0.0984 0,1 0,1 6063 observed. 30 65 707/0.9999 324.12 0.0313 0.07534 The tensile (R and R ) and plastic properties (A, Z) of the 50 68 935/0.9999 320.63 0.0312 0.08544 0,0 m p0.2 0,0 0 10 20 30 40 50 60 70 80 90 100 aged alloy 6061, 6063 and 6082 are also strongly depend on the 96 69 735/0.9999 299.29 0.0444 0.09321 0 10 20 30 40 50 60 70 80 90 100 t, h chemical composition and an aging time at 175°C. The results of 2 84 672/0.9999 290.27 0.0957 0.45930 t, h the static tensile tests were summarized in Table 5. The increment 6 69 683/0.9999 362.66 0.0402 0.10494 10 70 568/0.9999 378.5 0.0398 0.0765 Fig. 6. Effect of time aging at 175°C a) on yield R0.2, tensile Rm alloys strength similarly to the observed increment in hardness 6082 Fig. 7. Effect of time aging at 175°C a) on yield R0.2, tensile Rm 30 71 287/0.9999 394.82 0.0336 0.05766 strength and strength coefficient K, b) elongation A5 and can be treated as the effects of initial formation of GP zones strength and strength coefficient K, b) elongation A5 and followed by precipitation of metastable particles of E” and E’ 50 66 871/1.0000 391.92 0.0368 0.07073 compression Z, c) n the strain – hardening exponent and m – compression Z, c) n the strain – hardening exponent and m – phases. 96 70 756/0.9999 348.66 0.0294 0.04954 “hardening coefficient” of 6061 alloy “hardening coefficient”of 6063 alloy
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Influence of chemical composition variation and heat treatment on microstructure and mechanical properties of 6xxx alloys
130 Table 5. a) a) 360 120 Mechanical properties of the examined alloys after T6 treatment 420 Mechanical properties Aging 390 110 Alloy R , R , A , Z, 330 time,h 0.2 m 5 100 MPa MPa % % 360 300 2 163.2 270.5 33.5 44.6 90 330 5 206.7 295.6 29.7 43.0 270 80 10 274.2 320.0 19.7 40.9 6061 300 240 70 24 326.5 353.9 15.2 42.1 , MPa K, ,
m 270 50 331.26 349.0 14.8 43.7 K,MPa ,
6061 m Hardness HB5/250 Hardness
, R , 210 60 6063 96 329.35 348.8 14.4 45.6 R 0.2 , R 0.2 240 6082 R0.2 0.2 50 2 128.5 202.3 25.1 75.4 R Rm R 180 R 5 257.0 275.6 16.1 51.8 210 K m 40 K 10 271.3 281.6 14.1 45.6 150 6063 180 30 30 269.2 289.9 12.1 40.4 1 10 100 50 267.5 290.4 13.9 35.5 150 120 log t, h 96 229.5 252.3 13.3 48.4 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 2 165.0 246.2 29.2 46.8 t, h Fig. 4. Variation of hardness with time of aging of investigated t, h 6 276.7 306.0 16.8 45.6 b) alloy at temperature of 175°C 10 299.9 338.1 15.9 40 b) 6082 50 30 314.9 333.7 15.4 40.3 80 It is well known that silicon and magnesium content has a 50 309.6 330.5 14.8 43.4 45 positive effect on mechanical properties after aging thus it is 96 282.0 298.3 13.0 44.8 70 A worth to determine the effect of Mg+Si concentration on the 40 5 Z behavior of 6xxx alloys during aging (Fig. 5). On the basic of the region of uniform plastic deformation 60 from the stress-strain curves of and a simple power – curve 35 50 relation: 30 n 130 V H = K (6) A5 , Z, % Z, , 5
25 % Z, , 40
Z 5 6082 the values of n (is the strain – hardening exponent) and K (is the A 125 strength coefficient) were determined. Additionaly on the basic of A 20 30 120 6061 the stress-strain curves Young modulus E, and m – “hardening coefficient” from equation 7 was calculeted: 15 115 20 R R R 10 110 m 0.2 m (7) m 1 10 R0.2 R0.2 0 10 20 30 40 50 60 70 80 90 100 Max HB5/250 Max 105 0 10 20 30 40 50 60 70 80 90 100 were: R0.2 – yield strength, Rm – tensile strength (Tab. 6, Figs. 6-8). t, h y = 45,116x + 44,467 t, h 100 2 R = 0,998 c) c) Table 6. 0,7 95 The values of: E – Young modulus, K – strength coefficient, n – 0,6 6063 90 strain – hardening exponent and m – “hardening coefficient” 0,6 Aging 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 1,9 Alloy E/r K n m 0,5 Mg+Si, % time, h 0,5 2 68 538/1.0000 297.78 0.0957 0.67357 n 0,4 Fig. 5. Influence of different Mg + Si levels on the maximum 5 71 053/0.9999 337.60 0.08030 0.43028 n hardness of the examined alloys 10 70 470/0.9999 394.18 0.0601 0.18429 0,4 m 6061 m 24 71 155/0.9999 418.12 0.0367 0.08147 0,3
n, m n, 0,3 50 71 566/0.9999 394.46 0.0281 0.04910 m n, The results in (Fig. 5) demonstrate that progress of silicon and 96 71 999/0.9999 406.93 0.03420 0.05907 0,2 magnesium content improves the maximum hardness in examined 2 63 256/0.9999 228.82 0.09592 0.56516 0,2 alloys. In 6082 aluminium alloy, with the highest concentration of 6 67 235/0.9999 303.74 0.0347 0.11250 silicon and magnesium the highest hardness in T6 state was 10 66 322/0.9999 326.5 0.0300 0.0984 0,1 0,1 6063 observed. 30 65 707/0.9999 324.12 0.0313 0.07534 The tensile (R and R ) and plastic properties (A, Z) of the 50 68 935/0.9999 320.63 0.0312 0.08544 0,0 m p0.2 0,0 0 10 20 30 40 50 60 70 80 90 100 aged alloy 6061, 6063 and 6082 are also strongly depend on the 96 69 735/0.9999 299.29 0.0444 0.09321 0 10 20 30 40 50 60 70 80 90 100 t, h chemical composition and an aging time at 175°C. The results of 2 84 672/0.9999 290.27 0.0957 0.45930 t, h the static tensile tests were summarized in Table 5. The increment 6 69 683/0.9999 362.66 0.0402 0.10494 10 70 568/0.9999 378.5 0.0398 0.0765 Fig. 6. Effect of time aging at 175°C a) on yield R0.2, tensile Rm alloys strength similarly to the observed increment in hardness 6082 Fig. 7. Effect of time aging at 175°C a) on yield R0.2, tensile Rm 30 71 287/0.9999 394.82 0.0336 0.05766 strength and strength coefficient K, b) elongation A5 and can be treated as the effects of initial formation of GP zones strength and strength coefficient K, b) elongation A5 and followed by precipitation of metastable particles of E” and E’ 50 66 871/1.0000 391.92 0.0368 0.07073 compression Z, c) n the strain – hardening exponent and m – compression Z, c) n the strain – hardening exponent and m – phases. 96 70 756/0.9999 348.66 0.0294 0.04954 “hardening coefficient” of 6061 alloy “hardening coefficient”of 6063 alloy
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G. Mrówka-Nowotnik
360 a) The yield strength Rp0.2 (Fig. 9) and the tensile strength Rm a) (Fig. 10) increases with time of aging, however a significant 350 390 increase in mechanical properties was achieved during aging for 340 360 the first 20 hours. Further heating causes a steady increase of yield strength Rp0.2 , tensile strength Rm and strength coefficient 330
330 m K. After achieving the maximum values of R , R and K 6061 0.2 m 320 300 continuously decreases with the time of aging were observed. The , max R max , 310
highest yield strength Rp0.2 (Fig. 9) and tensile strength Rm 0.2 6082 270 , K,MPa , (Fig. 10) was achieved in 6061 alloy (Tables 5, 6). 300
m 6063 R max
, R , R 240 0.2 R0.2 290 0.2 340 Rm R Rm 210 K 320 280 300 270 180 280 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 150 Mg Si, % 260 2 0 10 20 30 40 50 60 70 80 90 100 240
t, h Fig. 11. Influence of different Mg2Si levels on maximum on yield , MPa , 220 0.2 strength Rp0.2 and tensile strength Rm of the investigated alloys aged b) 50 R 200 at 175°C b) 6061 180 45 6063 35 6082 160 40 140 6061 30 6063 35 120 6082 0 20 40 60 80 100 30 t, h 25 , % % , 5 A5 , Z, % Z, , 5 25 Z A Fig. 9. Effect of aging time on yield strength Rp0.2 of the alloys aged at 175°C 20 20
Elongation A Elongation 360 15 15
10 330 10
0 10 20 30 40 50 60 70 80 90 100 t, h 300 0 20 40 60 80 100 t, h c) 0,5 270 c)
MPa , Fig. 12. Effect of aging time on elongation A5 of the investigated m
R alloys aged at 175°C 240 0,4 6061 6063 80 6082 210 75 n 6061 0,3 6063 m 70 6082 180 0 20 40 60 80 100 65 n, m n, 0,2 t, h 60
Fig. 10. Effect of aging time on tensile strength Rm of the alloys 55 0,1 aged at 175°C 50 Compression % Z, The highest tensile strength Rm was recorded for 6061 45 0,0 aluminium alloy with the maximum concentration of Mg2Si 40 0 10 20 30 40 50 60 70 80 90 100 (Table 4, Fig. 11). One can see that, tensile strength Rm of 6061 t, h alloy is higher by about 60 MPa compared to the 6063 alloy with 35 0 20 40 60 80 100 the minimum concentration of Mg2Si (Tables 4, 5 and Fig. 8. Effect of time aging at 175°C a) on yield R0.2, tensile Rm Figs. 6, 7, 10). It is worth to mention that 6061 possess the best t, h strength and strength coefficient K, b) elongation A5 and plastic properties after aging at 175°C (Figs. 12, 13). As we can Fig.14. Tensile fracture surface of the investigated alloys: a) 6061, compression Z, c) n the strain – hardening exponent and m – Fig. 13. Effect of aging time on compression Z of the investigated b) 6063, c) 6082 after solid solution treatment and artificial aging see on Fig. 12 the highest elongation A5 was observed in 6061 “hardening coefficient” of 6082 alloy alloy, and the worst in 6063 alloy. alloys aged at 175°C at 175°C
104 104 Archives of Materials Science and Engineering
Influence of chemical composition variation and heat treatment on microstructure and mechanical properties of 6xxx alloys
360 a) The yield strength Rp0.2 (Fig. 9) and the tensile strength Rm a) (Fig. 10) increases with time of aging, however a significant 350 390 increase in mechanical properties was achieved during aging for 340 360 the first 20 hours. Further heating causes a steady increase of yield strength Rp0.2 , tensile strength Rm and strength coefficient 330
330 m K. After achieving the maximum values of R , R and K 6061 0.2 m 320 300 continuously decreases with the time of aging were observed. The , max R max , 310 highest yield strength Rp0.2 (Fig. 9) and tensile strength Rm 0.2 6082 270 , K,MPa , (Fig. 10) was achieved in 6061 alloy (Tables 5, 6). 300 m 6063 R max
, R , R 240 0.2 R0.2 290 0.2 340 Rm R Rm 210 K 320 280 300 270 180 280 0,8 0,9 1,0 1,1 1,2 1,3 1,4 1,5 1,6 1,7 1,8 150 Mg Si, % 260 2 0 10 20 30 40 50 60 70 80 90 100 240 t, h Fig. 11. Influence of different Mg2Si levels on maximum on yield , MPa , 220 0.2 strength Rp0.2 and tensile strength Rm of the investigated alloys aged b) 50 R 200 at 175°C b) 6061 180 45 6063 35 6082 160 40 140 6061 30 6063 35 120 6082 0 20 40 60 80 100 30 t, h 25 , % % , 5 A5 , Z, % Z, , 5 25 Z A Fig. 9. Effect of aging time on yield strength Rp0.2 of the alloys aged at 175°C 20 20
Elongation A Elongation 360 15 15
10 330 10
0 10 20 30 40 50 60 70 80 90 100 t, h 300 0 20 40 60 80 100 t, h c) 0,5 270 c)
MPa , Fig. 12. Effect of aging time on elongation A5 of the investigated m
R alloys aged at 175°C 240 0,4 6061 6063 80 6082 210 75 n 6061 0,3 6063 m 70 6082 180 0 20 40 60 80 100 65 n, m n, 0,2 t, h 60
Fig. 10. Effect of aging time on tensile strength Rm of the alloys 55 0,1 aged at 175°C 50 Compression % Z, The highest tensile strength Rm was recorded for 6061 45 0,0 aluminium alloy with the maximum concentration of Mg2Si 40 0 10 20 30 40 50 60 70 80 90 100 (Table 4, Fig. 11). One can see that, tensile strength Rm of 6061 t, h alloy is higher by about 60 MPa compared to the 6063 alloy with 35 0 20 40 60 80 100 the minimum concentration of Mg2Si (Tables 4, 5 and Fig. 8. Effect of time aging at 175°C a) on yield R0.2, tensile Rm Figs. 6, 7, 10). It is worth to mention that 6061 possess the best t, h strength and strength coefficient K, b) elongation A5 and plastic properties after aging at 175°C (Figs. 12, 13). As we can Fig.14. Tensile fracture surface of the investigated alloys: a) 6061, compression Z, c) n the strain – hardening exponent and m – Fig. 13. Effect of aging time on compression Z of the investigated b) 6063, c) 6082 after solid solution treatment and artificial aging see on Fig. 12 the highest elongation A5 was observed in 6061 “hardening coefficient” of 6082 alloy alloy, and the worst in 6063 alloy. alloys aged at 175°C at 175°C
Volume 46 Issue 2 December 2010 105
G. Mrówka-Nowotnik
Figure 14 shows the fracture surface of the specimen of [3] M. Warmuzek, J. Sieniawski, A. Gazda, G. Mrówka, [18] L.A. DobrzaĔski, W. Borek, R. Maniara, Influence of the [23] PN-EN 10002-1+AC1. Metals. Standard method of tensile investigated 6xxx aluminum alloy in the peak aged condition after Analysis of phase formation in AlFeMnSi alloy with crystallization condition on Al-Si-Cu casting alloys test at room temperature. static tensile test. variable content of Fe and Mn transition elements, Materials structure, Journal of Achievements in Materials and [24] ASTM E602-78T. Tentative method for Sharp-notch tension SEM observation of fracture processes in the sample with the Engineering 137 (2003) 821-824. Manufacturing Engineering 18 (2006) 211-214. testing with cylindral specimens. highest tensile stress, confirmed that fracture initiates within void [4] M. WierzbiĔska, J. Sieniawski, Effect of morphology of [19] M. Kciuk, The structure, mechanical properties and [25] F.O. Traekner, Factors Affecting the Physical Characteristics clusters as a result of a sequence of void nucleation, void growth, eutectic silicon crystals on mechanical properties and corrosion resistance of aluminium AlMg1Si1 alloy, Journal of Aluminium Magnesium Silicon Alloy Extrusions. Proc. of and void coalescence. Figure 5 presents the classical ductile clevage fractuce toughnessof AlSi5Cu1 alloy, Journal of of Achievements in Materials and Manufacturing 2nd Int. Aluminium Technology Seminar, Atlanta 1 (1977) profile with existence of dimples with different sizes which can be Achievements in Materials and Manufacturing Engineering Engineering 16 (2006) 51-56 339-347. related to the presence of the two population of voids. Inside the 14 (2006) 217-220. [20] M. Czechowski, Fatigue life of friction stir welded Al-Mg [26] G. Mrówka-Nowotnik, J. Sieniawski, Influence of heat dimples the presence of different particles are visible. Large [5] S. Zajac, B. Bengtsson , Ch. Jönsson, Influence of cooling alloys, Proceeding of the 13th International Scientific treatment on the micrustructure and mechanical properties of dimples around hard intermetallic D(Al8Fe2Si) and E(Al5FeSi) after homogenization and reheating to extrusion on Conference on Achievements in Mechanical and Materials 6005 and 6082 aluminium alloys, Journal of Materials precipitates and also smaller ones around dispersive hardening E- extrudability and final properties of AA 6063 and AA 6082 Engineering" AMME'2005, Gliwice – Wisáa, 2005, 83-86. Processing Technology 162-163 (2005) 367-372. Mg2Si Al2Cu and Į-Al(FeMn)Si precipitates were formed. alloys, Materials Science Forum 396-402 (2002) 675-680. [21] L.A. DobrzaĔski, R. Maniara, M. KrupiĔski, J.H. [27] G. Mrówka-Nowotnik, J. Sieniawski M. WierzbiĔska, [6] M. Warmuzek, G. Mrówka-Nowotnik, J. Sieniawski, Sokolowski, Microstructure and mechanical properties of Analysis of intermetallic particles in AlSi1MgMn Influence of the heat treatment on the precipitation of the AC AlSi9CuX alloys, Journal of Achievements in Materials aluminium alloys, Journal of Achievements in Materials and intermetallic phases in commercial AlMn1FeSi alloy, and Manufacturing Engineering 24/2 (2007) 51-54. Manufacturing Engineering 20 (2007) 155-158. 4. ConclusionConclusions Journal of Materials Processing Technology 157-158 (2004) [22] M. Kciuk, S. Tkaczyk, Structure, mechanical properties and [28] G. Mrówka-Nowotnik, J. Sieniawski, A. Nowotnik, Tensile 624-632. corrosion resistance of AlMg5 and AlMg1Si1 alloys, properties and fracture toughness of heat treated 6082 alloy, x It was found that the mechanical properties of the 6xxx series [7] R.A. Siddiqui, H.A. Abdullah, K.R. Al.-Belushi, Influence Journal of Achievements in Materials and Manufacturing Journal of Achievements in Materials and Manufacturing aluminium alloys in the T6 tempers are strongly depend on of aging parameters on the mechanical properties of 6063 Engineering 21/1 (2007) 51-54. Engineering 17 (2006) 105-108. the chemical composition and an aging time at 175°C. The aluminium alloy, Journal of Materials Processing degree of strengthening depends on the extent of E” Technology 102 (2000) 234-240. precipitation which increases with increasing Mg and Si [8] N.C.W. Kuijpers, W.H. Kool, P.T.G. Koenis, K.E. Nilsen, content in the chemical composition of the alloys. I. Todd, S. van der Zwaag, Assessment of diffrent x The highest mechanical properties connected with a good techniques for quantification of Į-Al(FeMn)Si and ȕ-AlFeSi plastic properties was achieved for 6061 alloy with the highest intermetallics in AA 6xxx alloys, Materials Characterization concentration of alloying elements Mg, Si, Cu, Mn and Fe. In 49 (2003) 409-420. 6061 aluminium alloy besides of E-Mg2Si strengthening phase [9] G. Sha, K. O’Reilly, B. Cantor, J. Worth, R. Hamerton, the precipitation of T-Al2Cu and Q(Al5Cu2Mg8Si6) phases can Growth related phase selection in a 6xxx series wrought Al be present. alloy, Materials Science and Engineering A304-306 (2001) x Observation fracture surface (SEM) specimens after static 612-616. tensile test showed that cracking of the examined alloys begin [10] A.K. Gupta, D.J. Lloyd, S.A. Court, Precipitation hardening by nucleation and growth of voids. The sites of heterogenic in Al-Mg-Si alloys with and without excess Si, Materials nucleation of voids are the precipitates of intermetallic phases. Science and Engineering A316 (2001) 11-17. Subsequent decohesion process initially proceeded at the [11] G.A. Edwards, K. Stiller, G.L. Dunlop, M.J. Couper, The interface between matrix and particle. precipitation sequence in Al-Mg-Si alloys, Acta Materialia 46/11(1998) 3893-3904. [12] W.F. Miao, D.E. Laughlin, Precipitation hardening in Acknowledgements aluminum alloy 6022, Scripta Materialia 40/7 (1999) 873-878. [13] G. Biroli, G. Caglioti, L. Martini, G. Riontino, Precipitation This work was carried out with the financial support of the kinetics of AA4032 and AA6082 a comparison based on Ministry of Science and Information Society Technologies under DSC and TEM, Scripta Materialia 39/2 (1998) 197-203. grant No. N507 3828 33. [14] Z. Li, A.M. Samuel, C. Rayindran, S. Valtierra, H.W. Doty, Parameters controlling the performance of AA319-type alloys: Part II. Impact properties and fractography, Materials Science and Engineering A367 (2004) 111-122. References [15] G. Mrówka - Nowotnik, J. Sieniawski, A. Nowotnik, Tensile properties and fracture toughness of heat treated 6082 alloy, [1] S. Karabay, M. Zeren, M. Yilmaz, Investigation of extrusion Journal of Achievements in Materials and Manufacturing ratio effect on mechanical behaviour of extruded alloy AA- Engineering 17 (2006) 105-108. 6101 from the billets homogenised-rapid quenched and as- [16] M. WierzbiĔska, J. Sieniawski, Effect of morfology of cast conditions, Journal of Materials Processing Technology eutectuc silicon crystals on mechanical properties and 160 (2004) 138-147. cleavage fracture toughness of AlSi5Cu1 alloy, Journal of [2] G. Mrówka-Nowotnik, J. Sieniawski, Influence of heat Achievements in Materials and Manufacturing Engineering treatment on the microstructure and mechanical properties of 14 (2006) 31-36. 6005 and 6082 aluminium alloys, Proc. Int. Conf. [17] L.A. DobrzaĔski, R. Maniara, J.H. Sokoáowski, The effect "Achievements in Mechanical & Materials Engineering", of cast Al-Si-Cu alloy solidification rate on alloy thermal Gliwice – Wisáa, 2005, 447-450. characteristic, Journal of Achievements in Materials and Manufacturing Engineering 17 (2006) 217-220.
106 106 Archives of Materials Science and Engineering
Figure 14 shows the fracture surface of the specimen of [3] M. Warmuzek, J. Sieniawski, A. Gazda, G. Mrówka, [18] L.A. DobrzaĔski, W. Borek, R. Maniara, Influence of the [23] PN-EN 10002-1+AC1. Metals. Standard method of tensile investigated 6xxx aluminum alloy in the peak aged condition after Analysis of phase formation in AlFeMnSi alloy with crystallization condition on Al-Si-Cu casting alloys test at room temperature. static tensile test. variable content of Fe and Mn transition elements, Materials structure, Journal of Achievements in Materials and [24] ASTM E602-78T. Tentative method for Sharp-notch tension SEM observation of fracture processes in the sample with the Engineering 137 (2003) 821-824. Manufacturing Engineering 18 (2006) 211-214. testing with cylindral specimens. highest tensile stress, confirmed that fracture initiates within void [4] M. WierzbiĔska, J. Sieniawski, Effect of morphology of [19] M. Kciuk, The structure, mechanical properties and [25] F.O. Traekner, Factors Affecting the Physical Characteristics clusters as a result of a sequence of void nucleation, void growth, eutectic silicon crystals on mechanical properties and corrosion resistance of aluminium AlMg1Si1 alloy, Journal of Aluminium Magnesium Silicon Alloy Extrusions. Proc. of and void coalescence. Figure 5 presents the classical ductile clevage fractuce toughnessof AlSi5Cu1 alloy, Journal of of Achievements in Materials and Manufacturing 2nd Int. Aluminium Technology Seminar, Atlanta 1 (1977) profile with existence of dimples with different sizes which can be Achievements in Materials and Manufacturing Engineering Engineering 16 (2006) 51-56 339-347. related to the presence of the two population of voids. Inside the 14 (2006) 217-220. [20] M. Czechowski, Fatigue life of friction stir welded Al-Mg [26] G. Mrówka-Nowotnik, J. Sieniawski, Influence of heat dimples the presence of different particles are visible. Large [5] S. Zajac, B. Bengtsson , Ch. Jönsson, Influence of cooling alloys, Proceeding of the 13th International Scientific treatment on the micrustructure and mechanical properties of dimples around hard intermetallic D(Al8Fe2Si) and E(Al5FeSi) after homogenization and reheating to extrusion on Conference on Achievements in Mechanical and Materials 6005 and 6082 aluminium alloys, Journal of Materials precipitates and also smaller ones around dispersive hardening E- extrudability and final properties of AA 6063 and AA 6082 Engineering" AMME'2005, Gliwice – Wisáa, 2005, 83-86. Processing Technology 162-163 (2005) 367-372. Mg2Si Al2Cu and Į-Al(FeMn)Si precipitates were formed. alloys, Materials Science Forum 396-402 (2002) 675-680. [21] L.A. DobrzaĔski, R. Maniara, M. KrupiĔski, J.H. [27] G. Mrówka-Nowotnik, J. Sieniawski M. WierzbiĔska, [6] M. Warmuzek, G. Mrówka-Nowotnik, J. Sieniawski, Sokolowski, Microstructure and mechanical properties of Analysis of intermetallic particles in AlSi1MgMn Influence of the heat treatment on the precipitation of the AC AlSi9CuX alloys, Journal of Achievements in Materials aluminium alloys, Journal of Achievements in Materials and intermetallic phases in commercial AlMn1FeSi alloy, and Manufacturing Engineering 24/2 (2007) 51-54. Manufacturing Engineering 20 (2007) 155-158. 4. Conclusion Journal of Materials Processing Technology 157-158 (2004) [22] M. Kciuk, S. Tkaczyk, Structure, mechanical properties and [28] G. Mrówka-Nowotnik, J. Sieniawski, A. Nowotnik, Tensile 624-632. corrosion resistance of AlMg5 and AlMg1Si1 alloys, properties and fracture toughness of heat treated 6082 alloy, x It was found that the mechanical properties of the 6xxx series [7] R.A. Siddiqui, H.A. Abdullah, K.R. Al.-Belushi, Influence Journal of Achievements in Materials and Manufacturing Journal of Achievements in Materials and Manufacturing aluminium alloys in the T6 tempers are strongly depend on of aging parameters on the mechanical properties of 6063 Engineering 21/1 (2007) 51-54. Engineering 17 (2006) 105-108. the chemical composition and an aging time at 175°C. The aluminium alloy, Journal of Materials Processing degree of strengthening depends on the extent of E” Technology 102 (2000) 234-240. precipitation which increases with increasing Mg and Si [8] N.C.W. Kuijpers, W.H. Kool, P.T.G. Koenis, K.E. Nilsen, content in the chemical composition of the alloys. I. Todd, S. van der Zwaag, Assessment of diffrent x The highest mechanical properties connected with a good techniques for quantification of Į-Al(FeMn)Si and ȕ-AlFeSi plastic properties was achieved for 6061 alloy with the highest intermetallics in AA 6xxx alloys, Materials Characterization concentration of alloying elements Mg, Si, Cu, Mn and Fe. In 49 (2003) 409-420. 6061 aluminium alloy besides of E-Mg2Si strengthening phase [9] G. Sha, K. O’Reilly, B. Cantor, J. Worth, R. Hamerton, the precipitation of T-Al2Cu and Q(Al5Cu2Mg8Si6) phases can Growth related phase selection in a 6xxx series wrought Al be present. alloy, Materials Science and Engineering A304-306 (2001) x Observation fracture surface (SEM) specimens after static 612-616. tensile test showed that cracking of the examined alloys begin [10] A.K. Gupta, D.J. Lloyd, S.A. Court, Precipitation hardening by nucleation and growth of voids. The sites of heterogenic in Al-Mg-Si alloys with and without excess Si, Materials nucleation of voids are the precipitates of intermetallic phases. Science and Engineering A316 (2001) 11-17. Subsequent decohesion process initially proceeded at the [11] G.A. Edwards, K. Stiller, G.L. Dunlop, M.J. Couper, The interface between matrix and particle. precipitation sequence in Al-Mg-Si alloys, Acta Materialia 46/11(1998) 3893-3904. [12] W.F. Miao, D.E. Laughlin, Precipitation hardening in Acknowledgements aluminum alloy 6022, Scripta Materialia 40/7 (1999) 873-878. [13] G. Biroli, G. Caglioti, L. Martini, G. Riontino, Precipitation This work was carried out with the financial support of the kinetics of AA4032 and AA6082 a comparison based on Ministry of Science and Information Society Technologies under DSC and TEM, Scripta Materialia 39/2 (1998) 197-203. grant No. N507 3828 33. [14] Z. Li, A.M. Samuel, C. Rayindran, S. Valtierra, H.W. 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