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

This paper investigates the behaviour of aluminium based composites, reinfo rced with aluminium oxide particulates, manufactured using a powder process ing route and various sintering times. It is found that a softening effect, compared with the monolithic material, coincides with migration of magnesi um from the matrix to the matrix/reinforcement interface and to the specime n surface. The addition of 5 wt-%Si to the matrix alloy results in a retent ion 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 p ostulated that the excess silicon in the matrix results in sufficient magne sium 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. MST/4559.