Fatigue behaviour of SiC-particulate-reinforced aluminium alloy composites with different particle sizes at elevated temperatures

Fully reversed axial fatigue tests have been performed at 150 °C (423 K) and 250 °C (523 K) using smooth specimens of SiC-particulate-reinforced aluminium alloy composites with different particle sizes at a constant wt.% of SiC particles. Regardless of particle size, fatigue strength decreased with increasing temperature with a remarkable reduction at 250 °C. The particle size dependence of fatigue strength was clearly seen at ambient temperature, while became small at 150 °C and almost disappeared at 250 °C. Crack initiation depended on temperature and particle size and small crack growth rates were an order faster at 250 °C than at ambient temperature and 150 °C in all materials studied. It was indicated that the softening and associated loss in strength of the matrix at elevated temperatures were the primary causes for the observed temperature and particle size dependence of fatigue behaviour.