Microstructure and mechanical properties of the Mg-2Si alloys prepared with fine Si powders as the raw materials were investigated by OM （optical microscope）

SEM （scanning electron microscope）

XRD （X-ray diffraction） and tensile testing. The results show that the primary Mg2Si particles are characterized by the fine polyhedral shape with size less than 10μm and length of eutectic Mg2Si rods is less than 100μm after fine silicon powders with size less than 48μm is added into the aluminum melt at 700℃ and holding for 3 min. Amounts of fine primary α-Mg phase and primary Mg2Si phase are precipitated from the aluminum melt during solidification as a result of many Si rich regions and Si-poor regions occurred in the melt with addition of Si powders

forming compact skeleton frame to divide the residual melt and restrain the growth of the eutectics

which is responsible for the improvement of mechanical properties.