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 potassium titanate whiskers were prepared by the squeeze casting process. The tensile behavior, thermal expansion and dimensional stability of such composites 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 improving the tensile strength of Al-12Si alloy at higher temperatures. Dilatometric measurements revealed that the coefficient of thermal expansion of Al-12Si alloy tends to decrease with increasing whisker content. Strain hysteresis was observed in Al-12Si alloy and its composites subjected to thermal cycling. The thermal response curves indicated that the Al-12Si alloy exhibits the largest thermal and residual plastic strains subjected to heating and cooling cycles between 50 and 280°C. The Al-12Si alloy reinforced with 30 vol.% whiskers had little dimensional change owing to the absence 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 environments. (C) 2000 Elsevier Science Ltd. All rights reserved.