DIMENSIONAL STABILITY OF ALUMINUM MATRIX COMPOSITES REINFORCED WITH POTASSIUM TITANATE WHISKERS UNDER THERMAL CYCLING CONDITION

Aluminum matrix composites reinforced with potassium titanate whiskers were prepared by squeezing casting process. The thermal expansion and dimensional stability of such composites were investigated. Dilatometric measurements revealed that the coefficient of thermal expansion of ZL109 alloy tends to decrease with increasing whiskers content. Strain hysteresis was observed in the matrix alloy and its composites subjected to repeated thermal cycling between 50℃~280℃. Thermal cycling curves indicated that ZL109 alloy exhibits the largest thermal and residual plastic strain. The composite reinforced with 30vol% whiskers had little dimensional change owing to the absence of residual strain. Thermal cycling curves were categorized into three types and explained by the theory of plastic strain in the matrix. Finally, it is concluded that the thermal cycling curves can be used to predict the dimensional thermal stability and failure of the structural materials on exposure to fluctuating temperature environments.