Microstructure and Wear Behavior of Squeeze Cast7075 Al-Al{sub}2O{sub}3 particle composites

摘要

Different percentages of Al{sub]2O{sub}3 particles were introduced into 7075 Al alloy to produce composites by using a vortex technique. Microstructure of cast composites showed some amount of porosities and sites of Al{sub}2O{sub}3 particles clustering; these are especially at high volume fraction of Al{sub}2O{sub}3 particles. Different squeeze pressures were applied to the cast composites during solidification to reduce porosities and particle clusters. Microstructure examinations of squeeze cast composites showed remarkable grain refining compared with that of the matrix alloy. As the volume fraction of particles and applied squeeze pressure were increased, the hardness was increased linearly. This increase was related to the modified structure and decrease of the porosity. The effect of particle volume fraction and squeeze pressure on the dry sliding wear of the composites were studied. Experiments were performed at loads of 10 and 30 N and a sliding speed of 1 m/s using a pin-ring apparatus. As the particle volume fraction and squeeze pressure were increased the wear resistance of the composite was improved compared with that of the monolithic alloy because the Al{sub}2O{sub}3 particles acted as load bearing constituents.