The preparation technique for a high silicon magnesium alloy ASE640 was explored. Different addition forms of silicon element to magnesium melt were compared and the master alloy method was selected. In addition, microstructure and phase structure of this alloy were investigated with optical microscope, scan electronic microscope and X ray diffraction meter. The dissolution rate of Si in magnesium melt was discussed. It shows that the smaller the primary silicon strips in the master alloy are, the higher the dissolution rate and the less dissolution time are. The experimental results show that in as cast ASE640 alloy a lot of Mg 2Si intermetallic compound particles are found and they present the shape of Chinese characters. However, the mechanical properties at room temperature and creep properties at elevated temperature are decreased for the coarse Mg 2Si grains. The Mg 2Si grains can be refined by hot extrusion and dispersed uniformly in the matrix, which may efficiently improve the mechanical properties of the alloy.
