Effect of Al2O3 particulates as reinforcement in age hardenable aluminium alloy composites

Abstract

This paper investigates the behaviour of aluminium based composites, reinforced with aluminium oxide particulates, manufactured using a powder processing route and various sintering times. It is found that a softening effect, compared with the monolithic material, coincides with migration of magnesium from the matrix to the matrix/reinforcement interface and to the specimen surface. The addition of 5 wt-%Si to the matrix alloy results in a retention of hardness in the specimens given short sinter times (0.5 and 1 h). This coincides with reduced migration of magnesium from the matrix. It is postulated that the excess silicon in the matrix results in sufficient magnesium being retained in the matrix during short sinter times to take part in the formation of Mg₂Si precipitates necessary for the hardening of the Al alloy 6061 matrix.