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Processing and characterization of extruded 2024 series of aluminum alloy
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 12479–12483
www.materialstoday.com/proceedings
ICMMM - 2017
PROCESSING AND CHARACTERIZATION OF EXTRUDED 2024 SERIES OF ALUMINUM ALLOY P. Ashwath1, J. Joel2, Prashantha kumar H.G3, M. Anthony Xavior 4*, Anubhav Goel 5, Tushar Nigam 6, Mohit Rathi 7 1,2,3,4,5,6,7
Manufacturing Department, School of Mechanical Engineering, VIT University, Vellore, India.
Abstract Aluminum alloy 2024 with granules size of 10 - 20 µm is extruded to a aluminum plate and heat treated. The extruded composite contains Reinforcements of Al2O3 of granular size of 10 µm, sic with size 10 µm and graphene with nano size is 10 µm wide and 10 nm thick. The extruded composites samples are fabricated initially by powder metallurgy route by using different weight percentage concentration such as 6% Sic, 6% Al2O3 and .25% graphene. Hot extrusion is carried out after microwave Sintering, the other extruded plate is microwave aged with heat treatment Conditions. The extruded heat treated plates are tested for mechanical characteristics and then compared with parent homogeneous AA 2024 alloy. The other Parameters and methods are used to analyze the mechanical properties of the composite material processed by microwave sintering. The parameters such as density, Hardness and tensile strength are evaluated. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
Keywords:Aluminium alloys, ceramic reinforcements, tensile strength, heat treatment, extrusion.
1. Introduction In recent years, Aluminium alloys have involved consideration of many researchers, engineers and inventors as a capable structural material in different industries like aerospace and automotive applications. Specially 2024 Al alloys which major alloying element is copper have been studied extensively because of their high strength to weight ratio, outstanding formability, high-quality age hardening behaviour and other mechanical properties[1]. But some of the mechanical properties such as comparatively less wear resistance with other aluminium alloys; have
* Corresponding Author: Email Address: [email protected]
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
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P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
reduced application of these materials processed by powder metallurgy. Adding reinforcements such as SiC and Al2O3 particles to these metal matrix leads to rise in the wear resistance of the composites [2]. Artificial Aging can considerably elevate the properties of some of the Aluminium alloys and its composites, especially 2xxx and 6xxx series alloys which are alloyed major elements are copper and magnesium. In exploration of aging kinetics, it has been revealed that the addition of ceramic particles as reinforcement to precipitation hardenable Aluminium alloys has different properties on precipitation of composite compared with pure aluminium alloy [3–5]. Even though the subsequent processing techniques such as powder metallurgy, extrusion can improve the reinforcement distribution, it is desirable to achieve a uniform distribution of the reinforcement particles in the powder itself [6–9], moreover, there were some explanations that it reduce or poses poor alteration in the aging kinetics and aging behaviour [10,11]. Cottu et al. [12] exposed that age-hardening kinetics of Al-Cu-Mg alloy of 10 wt. % SiC reinforced composite was improved by the occurrence of the reinforcement during heat treatment. They explained this by the plastic deformation induced during artificial aging due to the difference in coefficients of thermal expansion of matrix metal and reinforcement used. Thomas and King [13] stated that in powder metallurgy of aluminium alloy 2124 reinforced with SiC composites, the presence of reinforcement particles enables the nucleation which results in the decrease of the required time to achieve peak hardness. However, Pal et al. [14] revealed that in the Aluminium alloy composite reinforced with various percentages of SiC particles, the presence of reinforcing particles led to decelerated artificial aging kinetics. They recognized this behaviour to lower concentration of vacancies in the composites, inadequate dislocation density and wide-ranging interfacial segregation of alloying elements. Similar interpretations of the effect of the ceramic particles on the artificial aging kinetics were earlier made for Aluminium alloys reinforced with SiC and Al2O3 composites [15, 16]. Considering significance and wide aerospace applications of these materials, in this research the effect of artificial aging conditions on the presence of 6 wt% Al2O3 and 6 wt% SiC reinforcing particles on the artificial aging kinetics and behaviour of AA 2024 composite fabricated by powder Metallurgy technique followed by hot extrusion was investigated. 2. Material and experimental method Metal matrix used is aluminium alloy 2024 of particle size 10 microns and reinforcement SiC, Al2O3 and graphene of particle size 10 microns and 10 nanometres. Chemical composition of aluminium alloy 2024 is illustrated in Table 1. SiC and Al2O3 is mixed using high energy ball mill. Ultrasonic liquid processor and ball milling is used to disperse reinforcements into the metal matrix. Initially, dispersion of Graphene is carried out through an ultrasonic dispersion method. Graphene with 0.25 weight percentage (0.25 weight %) were added into the acetone and sonicated for 60 min. Followed by ultrasonication, the mixtures are ball milled by adding aluminum alloy powders (AA 2024) separately followed by drying the powder mixtures in oven at 90ˑc for 48 hrs. The powders were mixed in a high energy planetary ball mill for 120 mins and 250 rpm. Green compacts thus produced are microwave sintered at 425oC for 120 min. After sintering the samples are hot extruded to flat plates at temperature 300oC. The extruded plates are solution treated at 425 oC and quenched samples are then shifted to microwave oven where the samples are aged at 193oC for 60 min and 120 min. The aged samples are then air cooled and the samples are prepared for testing. The aged extruded samples are subjected to micro structural analysis using scanning electron microscope to identify the effect of grain size on the mechanical properties and influence of aging mechanism. Hardness measurements were performed in Rockwell hardness tester with a ball indenter’s diameter of 2.5 mm and a load of 30 kgf. Table 1: Chemical composition of aluminium alloy 2024 Element 2024 Weight%
Cu
Mg
Si
Fe
Sn
Al
4.12
1.62
0.50
0.50
-
Remaining
The tensile strength of the samples is carried out in Instron testing machine. The tensile strength of the samples are correlated with the ceramic addition and the effect of the microwave sintering is studied.
P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
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3. Result and Discussion 3.1 Hardness testing: The samples sintered and prepared are tested for hardness in the Rockwell hardness testing machine. The Rockwell test determines the hardness by measuring the depth of the penetration of an indenter under a large load compared to the penetration made by an initial load. The extruded aged composite samples are polished on both the surfaces to maintain he sample surfaces equal. The samples are then loaded to the Rockwell testing machine with the load set to 30 kgf. Average of 10 readings is taken for each sample to avoid the discrepancy in the hardness measurement of the samples. The hardness results of the AA 2024 are tabulated in table 2. Table 2: Rockwell results (HR) comparison for AA 2024 AA 2024 S.No.
Reinforcement
Weight %
1
Graphene
2 3
As Sintered
1 Hr Aged
2 Hr Aged
0.25
67
74
82
SiC
6
71
80
87
Al2O3
6
75
83
92
The comparison between the reinforcements SiC, Al2O3 and graphene with AA 2024 clearly shows that Al2O3 has a better improved hardness than SiC and graphene because the copper percentage is higher in case of AA 2024. There is an increase in It can be seen that with increasing of the solution treating duration to 120 mins, the aging mechanism in the extruded samples and thus resulted in hardness improvement and UTS values as shown in table 3. It is understood that the solution treating duration for thorough dissolution of alpha precipitates particulates was inadequate for the samples solution treated for 60 min in a microwave furnace. The theory can be proved by locating much more dissolved precipitates in the matrix compared with the sample solution treated at 60 min. This can lead to type of reinforcement content in the metal matrix and will successively decrease the potential spots for precipitate formation. The samples aged for 60 min due to suitable solution treating duration, a considerable volume fraction of precipitates has dissolved. Therefore, the aging mechanism increases as the aging duration increases. In this study, the aging mechanism of the extruded composite compared between three different reinforcement materials is probably due to the existence of many matrix-particles interfaces in the composite, which are suitable zones for the precipitates to occupy and immovability of the precipitates. Table 3: UTS results and comparison for AA 2024 AA 2024 S.No.
Reinforcement
Weight %
1
Graphene
2 3
As Sintered
1 Hr Aged
2 Hr Aged
0.25
325.5
397.1
428.4
SiC
6
312.2
403.7
451.2
Al2O3
6
337.7
412.9
467.7
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P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
3.2 Microstructure Analysis: The extruded sample has been microwave aged after quenching to enable the growth of precipitates from a supersaturated solid solution which has rich copper contained alpha precipitates. The strength of the alloy has been greatly improved by precipitation hardening which is achieved my microwave processing. The 2nd phase is an intermetallic compound with a composition close to CuAl2. The depletion of Copper near the boundaries to these precipitates forms precipitation free zones (PFZ). SEM micrograph of AA 2024 reinforced with 6 wt% SiC and Al2O3 composite in as extruded condition are shown in fig 1 and fig 2 respectively. It can be seen that there is a considerable volume fraction of these precipitates in the matrix uniformly dispersed after extrusion process. It is important to note at high cooling rates (in this research about 425oC), the possibility of separation of the solutes and the formation of the intermediary copper rich precipitates during quenching and after quenching from solution treating temperature is improbable. Therefore the precipitates and their enrichment zones of precipitates in the micro structure and their presence was proved as the precipitates that have existed in the micro structure before the heat treatment process in the metal matrix, have not been dissolved during the solution treatment.
Fig 1: SEM Micrographs of AA 2024 MMC’s with 6 wt% SiC extruded
Fig 2: SEM Micrographs of AA 2024 MMC’s aged 6 wt% Al2O3 extruded
P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
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CONCLUSION: The aging kinetic mechanism of AA 2024 on extruded composite reinforced with 6 wt% of silicon carbide (SiC), alumina (Al2O3) and graphene particles was studied after solution treating at 425oC for 120 min and aged for 60 min and 120 mins. Copper rich beta precipitates such as CuAl2and CuMgAl2 phases are formed after microwave aging. Extrude sample after powder metallurgy processing of AA 2024 exhibited good mechanical properties. Graphene, Al2O3 and SiC as reinforcement performed convincingly in improving the composites strength after the extrusion process. 6. References: [1]
Kacar H, Atik E, Meric C. The effect of precipitation-hardening conditions on wear behaviours at 2024 aluminium wrought alloy. J Mater Proc Tech2003;142:762–6. [2] Guo J, Yuan X. The aging behavior of SiC/Gr/6061 Al composite in T4 and T6 treatments. Mater Sci Eng A 2009;499:212–4. [3] Bekheet NE, Gadelrab RM, Salah MF, Abdel-Azim AN. The effects of aging on the hardness and fatigue behavior of 2024 Al alloy/SiC composites. Mater Des 2002;23:1539. [4] Nieh TG, Karlak RF. Aging characteristics of B4C-reinforced 6061 aluminum. Scripta Metall 1984;18:25–8. [5] Christman T, Suresh S. Microstructural development in an aluminum alloy-SiC whisker composite. Acta Metall 1988;36:1691–704. [6] Suresh S, Christman T, Sugimura Y. Accelerated aging in cast Al alloy-SiC particulate composites. Scripta Metall 1989;23:1599–602. [7] Lu L, Lai MO, Su Y, Teo HL, Feng CF. In situ TiB2 reinforced Al alloy composites. Scripta Mater 2001;45:1017–23. [8] Li W, Long JP, Jing S, Shen BL, Gao SJ, Tu MJ. Aging characteristics of short mullite fiber reinforced Al–4.0Cu–1.85Mg metal matrix composite. J Mater EngPerform 2003;12:19–22. [9] Janowski GM, Pletka BJ. The effect of particle size and volume fraction on the aging behavior of a liquid-phase sintered SiC/aluminum composite. MetalMater Trans 1995;26A:3027–35. [10] Cottu JP, Coudere JJ, Viguier B, Bernard L. Influence of SiC reinforcement on precipitation and hardening of a metal matrix composite. J Mater Sci1992;27:3068–74. [11] Dutta I, Bourell DL. A theoretical and experimental study of aluminum alloy 6061-SiC metal matrix composite to identify the operative mechanism foraccelerated aging. Mater Sci Eng A 1989;112:67–77. [12] Appendino P, Badini C, Marino F, Tomasi A. 6061 aluminum alloy-SiC particulate composite: a comparison between aging behavior in T4 and T6treatment. Mater Sci Eng A 1991;135:275–9. [13] Pal S, Mitra R, Bhanuprasad VV. Aging behaviour of Al–Cu–Mg alloy-SiC composites. Mater Sci Eng A 2008;480:496–505. [14] Daoud A, Reif W. Influence of Al2O3 particulate on the aging response of A356 Al-based composites. J Mater Proc Tech 2002;123:313–8. [15] Abdel-Azim AN, Shash Y, Mostafa SF, Younan A. Aging behaviour of 2024-Al alloy reinforced with Al2O3 particles. J Mater Proc Tech 1995;55:140–5. [16] Skibo M, Morris PL, Lloyd DJ. In: Fishman SG, Dhirngra AK, editors. Cast reinforced composites. ASM International; 1988. p. 257–61
ScienceDirect Materials Today: Proceedings 5 (2018) 12479–12483
www.materialstoday.com/proceedings
ICMMM - 2017
PROCESSING AND CHARACTERIZATION OF EXTRUDED 2024 SERIES OF ALUMINUM ALLOY P. Ashwath1, J. Joel2, Prashantha kumar H.G3, M. Anthony Xavior 4*, Anubhav Goel 5, Tushar Nigam 6, Mohit Rathi 7 1,2,3,4,5,6,7
Manufacturing Department, School of Mechanical Engineering, VIT University, Vellore, India.
Abstract Aluminum alloy 2024 with granules size of 10 - 20 µm is extruded to a aluminum plate and heat treated. The extruded composite contains Reinforcements of Al2O3 of granular size of 10 µm, sic with size 10 µm and graphene with nano size is 10 µm wide and 10 nm thick. The extruded composites samples are fabricated initially by powder metallurgy route by using different weight percentage concentration such as 6% Sic, 6% Al2O3 and .25% graphene. Hot extrusion is carried out after microwave Sintering, the other extruded plate is microwave aged with heat treatment Conditions. The extruded heat treated plates are tested for mechanical characteristics and then compared with parent homogeneous AA 2024 alloy. The other Parameters and methods are used to analyze the mechanical properties of the composite material processed by microwave sintering. The parameters such as density, Hardness and tensile strength are evaluated. © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
Keywords:Aluminium alloys, ceramic reinforcements, tensile strength, heat treatment, extrusion.
1. Introduction In recent years, Aluminium alloys have involved consideration of many researchers, engineers and inventors as a capable structural material in different industries like aerospace and automotive applications. Specially 2024 Al alloys which major alloying element is copper have been studied extensively because of their high strength to weight ratio, outstanding formability, high-quality age hardening behaviour and other mechanical properties[1]. But some of the mechanical properties such as comparatively less wear resistance with other aluminium alloys; have
* Corresponding Author: Email Address: [email protected]
2214-7853 © 2017 Elsevier Ltd. All rights reserved. Selection and/or Peer-review under responsibility of International Conference on Materials Manufacturing and Modelling (ICMMM - 2017).
12480
P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
reduced application of these materials processed by powder metallurgy. Adding reinforcements such as SiC and Al2O3 particles to these metal matrix leads to rise in the wear resistance of the composites [2]. Artificial Aging can considerably elevate the properties of some of the Aluminium alloys and its composites, especially 2xxx and 6xxx series alloys which are alloyed major elements are copper and magnesium. In exploration of aging kinetics, it has been revealed that the addition of ceramic particles as reinforcement to precipitation hardenable Aluminium alloys has different properties on precipitation of composite compared with pure aluminium alloy [3–5]. Even though the subsequent processing techniques such as powder metallurgy, extrusion can improve the reinforcement distribution, it is desirable to achieve a uniform distribution of the reinforcement particles in the powder itself [6–9], moreover, there were some explanations that it reduce or poses poor alteration in the aging kinetics and aging behaviour [10,11]. Cottu et al. [12] exposed that age-hardening kinetics of Al-Cu-Mg alloy of 10 wt. % SiC reinforced composite was improved by the occurrence of the reinforcement during heat treatment. They explained this by the plastic deformation induced during artificial aging due to the difference in coefficients of thermal expansion of matrix metal and reinforcement used. Thomas and King [13] stated that in powder metallurgy of aluminium alloy 2124 reinforced with SiC composites, the presence of reinforcement particles enables the nucleation which results in the decrease of the required time to achieve peak hardness. However, Pal et al. [14] revealed that in the Aluminium alloy composite reinforced with various percentages of SiC particles, the presence of reinforcing particles led to decelerated artificial aging kinetics. They recognized this behaviour to lower concentration of vacancies in the composites, inadequate dislocation density and wide-ranging interfacial segregation of alloying elements. Similar interpretations of the effect of the ceramic particles on the artificial aging kinetics were earlier made for Aluminium alloys reinforced with SiC and Al2O3 composites [15, 16]. Considering significance and wide aerospace applications of these materials, in this research the effect of artificial aging conditions on the presence of 6 wt% Al2O3 and 6 wt% SiC reinforcing particles on the artificial aging kinetics and behaviour of AA 2024 composite fabricated by powder Metallurgy technique followed by hot extrusion was investigated. 2. Material and experimental method Metal matrix used is aluminium alloy 2024 of particle size 10 microns and reinforcement SiC, Al2O3 and graphene of particle size 10 microns and 10 nanometres. Chemical composition of aluminium alloy 2024 is illustrated in Table 1. SiC and Al2O3 is mixed using high energy ball mill. Ultrasonic liquid processor and ball milling is used to disperse reinforcements into the metal matrix. Initially, dispersion of Graphene is carried out through an ultrasonic dispersion method. Graphene with 0.25 weight percentage (0.25 weight %) were added into the acetone and sonicated for 60 min. Followed by ultrasonication, the mixtures are ball milled by adding aluminum alloy powders (AA 2024) separately followed by drying the powder mixtures in oven at 90ˑc for 48 hrs. The powders were mixed in a high energy planetary ball mill for 120 mins and 250 rpm. Green compacts thus produced are microwave sintered at 425oC for 120 min. After sintering the samples are hot extruded to flat plates at temperature 300oC. The extruded plates are solution treated at 425 oC and quenched samples are then shifted to microwave oven where the samples are aged at 193oC for 60 min and 120 min. The aged samples are then air cooled and the samples are prepared for testing. The aged extruded samples are subjected to micro structural analysis using scanning electron microscope to identify the effect of grain size on the mechanical properties and influence of aging mechanism. Hardness measurements were performed in Rockwell hardness tester with a ball indenter’s diameter of 2.5 mm and a load of 30 kgf. Table 1: Chemical composition of aluminium alloy 2024 Element 2024 Weight%
Cu
Mg
Si
Fe
Sn
Al
4.12
1.62
0.50
0.50
-
Remaining
The tensile strength of the samples is carried out in Instron testing machine. The tensile strength of the samples are correlated with the ceramic addition and the effect of the microwave sintering is studied.
P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
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3. Result and Discussion 3.1 Hardness testing: The samples sintered and prepared are tested for hardness in the Rockwell hardness testing machine. The Rockwell test determines the hardness by measuring the depth of the penetration of an indenter under a large load compared to the penetration made by an initial load. The extruded aged composite samples are polished on both the surfaces to maintain he sample surfaces equal. The samples are then loaded to the Rockwell testing machine with the load set to 30 kgf. Average of 10 readings is taken for each sample to avoid the discrepancy in the hardness measurement of the samples. The hardness results of the AA 2024 are tabulated in table 2. Table 2: Rockwell results (HR) comparison for AA 2024 AA 2024 S.No.
Reinforcement
Weight %
1
Graphene
2 3
As Sintered
1 Hr Aged
2 Hr Aged
0.25
67
74
82
SiC
6
71
80
87
Al2O3
6
75
83
92
The comparison between the reinforcements SiC, Al2O3 and graphene with AA 2024 clearly shows that Al2O3 has a better improved hardness than SiC and graphene because the copper percentage is higher in case of AA 2024. There is an increase in It can be seen that with increasing of the solution treating duration to 120 mins, the aging mechanism in the extruded samples and thus resulted in hardness improvement and UTS values as shown in table 3. It is understood that the solution treating duration for thorough dissolution of alpha precipitates particulates was inadequate for the samples solution treated for 60 min in a microwave furnace. The theory can be proved by locating much more dissolved precipitates in the matrix compared with the sample solution treated at 60 min. This can lead to type of reinforcement content in the metal matrix and will successively decrease the potential spots for precipitate formation. The samples aged for 60 min due to suitable solution treating duration, a considerable volume fraction of precipitates has dissolved. Therefore, the aging mechanism increases as the aging duration increases. In this study, the aging mechanism of the extruded composite compared between three different reinforcement materials is probably due to the existence of many matrix-particles interfaces in the composite, which are suitable zones for the precipitates to occupy and immovability of the precipitates. Table 3: UTS results and comparison for AA 2024 AA 2024 S.No.
Reinforcement
Weight %
1
Graphene
2 3
As Sintered
1 Hr Aged
2 Hr Aged
0.25
325.5
397.1
428.4
SiC
6
312.2
403.7
451.2
Al2O3
6
337.7
412.9
467.7
12482
P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
3.2 Microstructure Analysis: The extruded sample has been microwave aged after quenching to enable the growth of precipitates from a supersaturated solid solution which has rich copper contained alpha precipitates. The strength of the alloy has been greatly improved by precipitation hardening which is achieved my microwave processing. The 2nd phase is an intermetallic compound with a composition close to CuAl2. The depletion of Copper near the boundaries to these precipitates forms precipitation free zones (PFZ). SEM micrograph of AA 2024 reinforced with 6 wt% SiC and Al2O3 composite in as extruded condition are shown in fig 1 and fig 2 respectively. It can be seen that there is a considerable volume fraction of these precipitates in the matrix uniformly dispersed after extrusion process. It is important to note at high cooling rates (in this research about 425oC), the possibility of separation of the solutes and the formation of the intermediary copper rich precipitates during quenching and after quenching from solution treating temperature is improbable. Therefore the precipitates and their enrichment zones of precipitates in the micro structure and their presence was proved as the precipitates that have existed in the micro structure before the heat treatment process in the metal matrix, have not been dissolved during the solution treatment.
Fig 1: SEM Micrographs of AA 2024 MMC’s with 6 wt% SiC extruded
Fig 2: SEM Micrographs of AA 2024 MMC’s aged 6 wt% Al2O3 extruded
P. Ashwath et al. / Materials Today: Proceedings 5 (2018) 12479–12483
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CONCLUSION: The aging kinetic mechanism of AA 2024 on extruded composite reinforced with 6 wt% of silicon carbide (SiC), alumina (Al2O3) and graphene particles was studied after solution treating at 425oC for 120 min and aged for 60 min and 120 mins. Copper rich beta precipitates such as CuAl2and CuMgAl2 phases are formed after microwave aging. Extrude sample after powder metallurgy processing of AA 2024 exhibited good mechanical properties. Graphene, Al2O3 and SiC as reinforcement performed convincingly in improving the composites strength after the extrusion process. 6. References: [1]
Kacar H, Atik E, Meric C. The effect of precipitation-hardening conditions on wear behaviours at 2024 aluminium wrought alloy. J Mater Proc Tech2003;142:762–6. [2] Guo J, Yuan X. The aging behavior of SiC/Gr/6061 Al composite in T4 and T6 treatments. Mater Sci Eng A 2009;499:212–4. [3] Bekheet NE, Gadelrab RM, Salah MF, Abdel-Azim AN. The effects of aging on the hardness and fatigue behavior of 2024 Al alloy/SiC composites. Mater Des 2002;23:1539. [4] Nieh TG, Karlak RF. Aging characteristics of B4C-reinforced 6061 aluminum. Scripta Metall 1984;18:25–8. [5] Christman T, Suresh S. Microstructural development in an aluminum alloy-SiC whisker composite. Acta Metall 1988;36:1691–704. [6] Suresh S, Christman T, Sugimura Y. Accelerated aging in cast Al alloy-SiC particulate composites. Scripta Metall 1989;23:1599–602. [7] Lu L, Lai MO, Su Y, Teo HL, Feng CF. In situ TiB2 reinforced Al alloy composites. Scripta Mater 2001;45:1017–23. [8] Li W, Long JP, Jing S, Shen BL, Gao SJ, Tu MJ. Aging characteristics of short mullite fiber reinforced Al–4.0Cu–1.85Mg metal matrix composite. J Mater EngPerform 2003;12:19–22. [9] Janowski GM, Pletka BJ. The effect of particle size and volume fraction on the aging behavior of a liquid-phase sintered SiC/aluminum composite. MetalMater Trans 1995;26A:3027–35. [10] Cottu JP, Coudere JJ, Viguier B, Bernard L. Influence of SiC reinforcement on precipitation and hardening of a metal matrix composite. J Mater Sci1992;27:3068–74. [11] Dutta I, Bourell DL. A theoretical and experimental study of aluminum alloy 6061-SiC metal matrix composite to identify the operative mechanism foraccelerated aging. Mater Sci Eng A 1989;112:67–77. [12] Appendino P, Badini C, Marino F, Tomasi A. 6061 aluminum alloy-SiC particulate composite: a comparison between aging behavior in T4 and T6treatment. Mater Sci Eng A 1991;135:275–9. [13] Pal S, Mitra R, Bhanuprasad VV. Aging behaviour of Al–Cu–Mg alloy-SiC composites. Mater Sci Eng A 2008;480:496–505. [14] Daoud A, Reif W. Influence of Al2O3 particulate on the aging response of A356 Al-based composites. J Mater Proc Tech 2002;123:313–8. [15] Abdel-Azim AN, Shash Y, Mostafa SF, Younan A. Aging behaviour of 2024-Al alloy reinforced with Al2O3 particles. J Mater Proc Tech 1995;55:140–5. [16] Skibo M, Morris PL, Lloyd DJ. In: Fishman SG, Dhirngra AK, editors. Cast reinforced composites. ASM International; 1988. p. 257–61