The mechanical and thermal expansion behavior of an Al-Si alloy composite reinforced with potassium titanate whisker

Composites of aluminum-silicon (Al-12 wt.%Si) alloy reinforced with potassi um titanate whiskers were prepared by the squeeze casting process. The tens ile behavior, thermal expansion and dimensional stability of such composite s were investigated. Tensile tests showed that the tensile strength of the composites at room temperature is slightly inferior to that of the Al-12Si alloy However, potassium titanium whiskers exert a beneficial effect in imp roving the tensile strength of Al-12Si alloy at higher temperatures. Dilato metric measurements revealed that the coefficient of thermal expansion of A l-12Si alloy tends to decrease with increasing whisker content. Strain hyst eresis was observed in Al-12Si alloy and its composites subjected to therma l cycling. The thermal response curves indicated that the Al-12Si alloy exh ibits the largest thermal and residual plastic strains subjected to heating and cooling cycles between 50 and 280 degreesC. The Al-12Si alloy reinforc ed with 30 vol.% whiskers had little dimensional change owing to the absenc e of residual plastic strain. Finally, we conclude that the thermal strain response curves can be used to predict the thermal stability and failure of the structural materials on exposure to fluctuating temperature environmen ts. (C) 2000 Elsevier Science Ltd. All rights reserved.