Paper number 135


Xicong Liu and Yongmin Si

Department of Materials Engineering and Applied Chemistry, National University of Defense Technology, 410073, Changsha, Hunan, P.R. of China

Summary The short-term tensile strengths at elevated temperatures were studied for Al2O3 short fibers reinforced two aluminum alloys, Al2O3/Al-7Si-0.6Mg and Al2O3/Al-5Si-3Cu-1Mg subjected to various heat treatments. Strengths of the composites decreased with elevated temperatures. However, the strengths were substantially higher than those of the unreinforced matrix alloys. The reasons for the improvement in strength were that the fibers carried on a part of loads, and that the fibers traversing grain boundaries reinforced the grain boundaries and hence resisted their sliding at elevated temperatures. Age-hardening effect was weakened with elevated temperature, especially for Al2O3/Al-5Si-3Cu-1Mg composite. Therefore, at all test temperatures, there was no great difference in strengths, and strengths decreased very gently with temperatures for the two composites subjected to temper treatment at 300oC for 200 hrs due to eliminating age hardening. After a treatment improved fiber/matrix interface bonding, the composites showed a higher strength than those subjected to age-hardening treatment.
Keywords Al2O3/Al alloy composite, high temperature strength, heat treatment, microstructure, interface bonding, squeeze-casting.

Theme : Metal Matrix Composites ; Thermo-mechanical behaviour

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