Effect of Temperature on the Wear Behavior of Al-7Si-TiB 2 In-Situ Composites
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THE Al-7Si alloys used as automotive components (cylinder blocks, cylinder heads, cylinder liners, engine piston, break drum, etc.) are exposed to elevated temperatures during service. The tribological behavior of these components at elevated temperatures is very important in the design aspect. Many researchers[1,2] had shown that the addition of ceramic reinforcement particulates improves the wear resistance of Al-Si alloy. Very few reports are available on the elevated temperature tribological behavior of Al-based MMCs. Martinez et al.[3] reported that the addition of SiC to Al-Si alloy improved the high-temperature wear resistance. They observed a critical temperature above which there was a transition from mild to severe wear, for both the composite and matrix alloy. The transition temperature for the composites was much higher than the matrix alloy. A similar transition was found in the 2XXX Al alloy and its composites by the same group.[4–6] Alpas and his group studied the high-temperature wear behavior of the 6XXX and A356 Al alloys and composites.[7,8] They also reported that the transition temperature of the composites is higher than the matrix alloy and the transition temperature decreased with the increase in the load. Wilson and Alpas[8] studied the high-temperature wear behavior of Al 6061-20 vol pct Al2O3 and A356-20 vol pct SiC alloys and composites. They found that the A356 alloy and composites S. KUMAR, PhD Student, V. SUBRAMANYA SARMA, Assistant Professor, and B.S. MURTY, Professor, are with the Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600 036, India. Contact e-mail: [email protected] Manuscript submitted April 1, 2008. Article published online November 14, 2008 METALLURGICAL AND MATERIALS TRANSACTIONS A
exhibited better high-temperature wear resistance when compared to the AA6061 alloy and its composites. The transition temperature for the A356 composites was in the range of 440 °C to 450 °C, which is much higher than that for the AA6061 composites whose transition temperature varied from 310 °C to 350 °C. They also studied the high-temperature wear performance of the hybrid composites (A356-20 vol pct SiC-10 vol pct graphite) and found that hybrid composites remained in the mild wear regime at the test temperature of 460 °C. Wu et al.[9] and Liu et al.[10] showed that the addition of fiber reinforcement to Al-12Si alloy increases the high-temperature wear resistance, but it is well known that the particle-reinforced Al MMCs have superior wear properties to the fiber-reinforced MMCs. Straffelini et al.[11] studied the influence of load and temperature on the dry sliding wear behavior of Al-SiCp composites against frictional materials. They found that at higher temperatures, the frictional materials softened and formed a layer on the Al-based MMC disc, which increased the wear resistance of the MMC disc. Korkut[12] studied the effect of reinforcement type (such as M7C3, SiC, SiFe, Al2O3, and SiFe-Al2O3) on the wear behavior of Al-based M
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