MODIFICATION OF Mg2Si MORPHOLOGY IN A Mg-3Si-3Sn ALLOY DURING ISOTHERMAL HEAT TREATMENT

摘要

The effects of different isothermal holding temperatures and times on the morphology of Chinese script shaped or fibriform eutectic Mg2Si phases in a Mg-3Si-3Sn alloy were investigated during isothermal heat treatment. With increasing heat treatment temperature, the spheroidizing time for the coarse eutectic Mg2Si phases is reduced dramatically. After isothermal heat treatment of 2 h at 550°C, the morphology of the eutectic Mg2Si transforms completely from the coarse Chinese script type and fibriform shape into fine, spherical shape with the lowest interface energies. The spheroidizing mechanism of the Chinese script shaped or fibriform eutectic Mg2Si particles seems to be attributed to the 'Rayleigh shape instability'.