Effect of Al content on the microstructure and mechanical properties of Mg-5wt%Sn-xAl as-cast alloys

Abstract

Microstructure and mechanical properties of Mg-5wt.% Sn-xAl as-cast alloys were studied, for the Al content ranged from 0.5 to 3.0wt.%. It was found that Al element was mainly distributed in Mg17Al12 phase in as-cast alloys, and its increase rose the Mg17Al12 phase share. There were no ternary phases in these alloys. Only two forms of Mg2Sn and Mg17Al12 phases were detected, namely (i) Mg17Al12 phase attached to the end of Mg2Sn phase and (ii) Mg2Sn phase enclosed by Mg17Al12 phases. The grain sizes of these alloys got refined with the growing content of Al element, and 1.5wt% Al content corresponded to the grain size of 33.5um. As for the mechanical properties, the ultimate tensile and yield strengths of the alloys were improved at larger contents of Al. The Mg-5wt.%Sn-3.0wt% alloy had the highest ultimate tensile and yield strengths of 212 and 167MPa, respectively, while Mg-5wt.%Sn-1.5wt%Al alloy had the best elongation of 16.5%.