PM processing of Al-Al₂O₃ composites and their characterisation

Abstract

Aluminium based composites containing 5 to 20 vol.-%Al₂O₃ as the reinforcing phase were synthesised by powder metallurgy. The process consisted of blending aluminium powder with Al₂O₃ powder followed by hot compaction and hot extrusion. The microstructural features, mechanical properties and wear characteristics of the composites were investigated with variation in volume fraction of Al₂O₃ phase. The results indicated a continuous increase in yield and ultimate tensile strength with a marked decrease in ductility of the composites arising from increased Al₂O₃ content. High temperature tensile test data revealed that the strength of the base material Al and composite materials containing 5 and 15%Al₂O₃ decreased with increase in temperature. However, the rate of strength reduction was higher for the extruded compact of unreinforced aluminium than the composites. Lower wear rates were observed in the composite materials than the unreinforced aluminium compacts. An increase in Al₂O₃ content led to a decrease in wear rate of composites under the applied load of 5-35 N and a range of sliding velocity from 0·25 to 1·5 m s^-1. The reasons for improvement in strength and wear behaviour of composite materials are discussed in light of their microstructural features.