The Effect of Ceramic Reinforcement on the Microstructure, Mechanical Properties and Tribological Behavior of Al-7.5Si-0.5Mg Alloy

摘要

In this investigation, A357 (Al-7.5%Si-0.5%Mg) alloy/Al_2O_3 composites with various weight fractions (4%, 8%, 10%) were prepared by using permanent mould casting. In addition, A357 alloys were cast for comparison purposes. Microstructure, hardness and tensile properties of these composites were evaluated and compared with as-cast alloy. In addition, tribological properties of these composites were evaluated using a Pin-on-Disc apparatus at a constant sliding velocity of 1m/s and pressure of 0.35 MPa. The microstructure of the composites shows homogenous distribution of Al_2O_3 plate-like particles in the Al matrix except in the A357/10%Al_2O_3 composite. The wear and mechanical properties of composites improve with increasing the weight percentage of Al_2O_3 upto 8% and then decreases. Particularly, mechanical properties of the A357/10%Al_2O_3 composite are lower than the alloy indicating that the critical weight fraction of Al_2O_3 reinforcement in the A357 alloy is 8%. Wear morphology studies show that higher wear rate in case of unreinforced specimen was associated with higher thickness of hardened layer and consequent delamination of wear debris from the surface which was confirmed by optical and scanning electron micrography. Whereas ductile and brittle mode of fracture is observed in Fractographic observation of composite. The present paper highlights the salient features of casting technique and characterization of aluminum alloy A357 and alumina metal matrix composite.