Particle reinforced AA 6061 and A359 aluminium alloys under cyclic thermal loading conditions

Abstract

The thermal cycling creep characteristics of aluminium matrix composites AA 6061+22 vol.-%Al₂O₃particles and A359+20 vol.-%SiC particles were analysed with respect to the dependence of the behaviour on the applied external stress and on different heat treatment conditions. The specimens were thermally cycled using a triangular waveform between 50 and 300°C with dwell times of 3 s at the minimum and maximum temperatures. An enhanced lifetime was found for reinforced aluminium alloy 6061 compared with A359+20 vol.-%SiC and it was found that overaging of the matrix prior to the thermal cycling experiments increases the creep rates significantly in both composites. The determination of the true, thermally compensated strain revealed a much higher in cycle strain evolution in A359+20 vol.-%SiC. Reverse creep during the cooling sequence was observed in both composites where it depends on the applied stress.