Modification of Mg2Si morphology in Mg–9%Al–0.7%Si alloy by the SIMA process

Abstract

The effect of predeformation on the semisolid microstructure of Mg–9%Al–0.7%Si alloy produced by the strain induced melt activation (SIMA) process was studied. Experimental results indicated that a non-dendritic microstructure could be obtained by the SIMA process in the alloy. With the reduction ratio varying from 0% to 30%, the volume fraction of liquid gradually enlarged from 37.26vol.% to 48.28vol.%, and the morphology of α-Mg grains transformed from dendritic shape to spherical shape, with a size of 52.16μm. Also, the liquid islands in the grains become less with the increase of the reduction ratio. In addition, the eutectic Mg2Si phase transformed from Chinese script shape to globular shape during the isothermal heat treatment. A possible reason of the modification of Mg2Si morphology is the shifting of the eutectic composition of the liquid towards lower silicon contents with increasing Al content.