Microstructural and Tribological Properties of A356 Al-Si Alloy Reinforced with Al2O3 Particles

In the present study, the effect of the Al2O3 particles (average size of 12 mu m, 3 and 10 wt.%) reinforcement on the microstructure and tribological properties of Al-Si alloy (A356) was investigated. Composites were produced by applying compocasting process. Tribological properties of unreinforced alloy and composites were studied, using pin-on-disc tribometer, under dry sliding conditions at different specific loads and sliding speed of 1 m/s. Microhardness measurements, optical microscope and scanning electron microscope were used for microstructural characterization and investigation of worn surfaces and wear debris. During compocasting of A356 alloy, a transformation from a typical dendritic primary alpha phase to a non-dendritic rosette-like structure occurred. Composites exhibited better wear resistance compared with unreinforced alloy. Presence of 3 wt.% Al2O3 particles in the composite material affected the wear resistance only at specific loads up to 1 MPa. The wear rate of composite with 10 wt.% Al2O3 particles was nearly two order of the magnitude lower than the wear rate of the matrix alloy. Dominant wear mechanism for all materials was adhesion, with others mechanisms: oxidation, abrasion and delamination as minor ones.