Effects of excess silicon addition. on ductility of AL-0.95%M9 2 Si alloy

Abstract

The effects of the addition of 0.4% excess silicon to a balanced pseudobinary Al-0.95%Mg₂Si alloy have been investigated. It has been verified by means of observations of tensile and tear resistance properties that the excess Si is a significant embrittling agent in these alloys. The nature, size, and distribution of the grain boundary precipitate has been observed by lowkV scanning electron microscopy and the secondary X-rays produced by the particles have been analysed. This has shown that there is a significant amount of free Si present in the grain boundaries of the excess-Si alloy, but not in the balanced alloy. It has been postulated that this free Si contributes to the embrittlement exhibited by the excess-Si alloy when combined with the more continuous Mg₂Si precipitate present in the grain boundaries of this alloy.