Effect of high magnesium content on microstructure of Al-7Si alloy

Abstract

A new class of ternary Al-7Si-xMg alloys was developed with improved microstructure consisting of fine spheroidal Mg2Si and eutectic Si particles dispersed in ?-Al. The studies show that Mg and Sr have a modification effect on eutectic Si and Mg2Si particles respectively. In alloys with high Mg, a combination of Sr addition followed by T6 treatment resulted in a fine and spheroidal eutectic mixture of Si and Mg2Si. It was concluded that 2 wt% Mg is optimum to obtain a minimum amount of coarse Mg2Si particles in the Al-7Si-xMg system as well as modify the eutectic Si particles. Furthermore, the hardness of Al-7Si-xMg alloys with and without Sr addition is comparable with those of in-situ Al-7Si-TiB2 composites indicating that they can be used as an alternative for the composites for wear resistant applications.�2013 Published by Elsevier B.V.