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

► The semisolid microstructure of Mg-9%Al-0.7%Si alloy is produced by the SIMA process. ► The α-Mg grain becomes globular and size decreases with the reduction ratio increase. ► The liquid islands in the grains become less with the reduction ratio increase. ► Mg2Si changed from Chinese script shape to globular shape by the SIMA process. ► Modification of Mg2Si is due to shifting of eutectic composition towards lower Si contents.