Structural evolution of ZA27 alloy during semi-solid isothermal heat treatment

The structural evolution of ZA27 alloy modified by element Zr was studied during semi-solid isothermal heat treatment, and its transformation mechanism was also discussed. The results indicate that the primary a phase changes from equiaxed grains to spherical grains gradually at semi-solid temperature of 460 degreesC. With increasing isothermal time, the eutectic between boundaries of a phase diffuses toward a phase, and the primary equiaxed grain arms merge and boundaries tend to disappear to form near particle grains. Further, the eutectic left on a boundaries melts to make the near particle grains separate, and form spherical structure at last.