Influence of porosity on fatigue resistance of cast SiC particulate-reinforced Al-Si alloy composite

The effect of cast pores on cyclic deformation and fatigue behavior of cast aluminum 9% silicon alloy (Al-Si) reinforced with 20% SIC particles was in vestigated experimentally by comparing with its extruded counterpart. The c ast composite experiences cyclic strain softening under low applied cyclic strain at which level there is no macroscopic plastic strain. It is found t hat the elastic modulus and yield stress of the cast composite are fairly c lose to that of the extruded composite; however, the extrusion process cons iderably enhances the ductility, fracture strength and fatigue life of the composite. The cyclic strain softening and poor low cycle fatigue resistanc e of cast composites are mainly attributed to the existence of porosity in the cast composites. A fatigue life prediction. based on modeling large siz e pores in cast composites as pre-existing cracks, agrees well with the exp erimental results of the cast composite. (C) 2000 Elsevier Science S.A. All rights reserved.