Effect of solid solution treatment on semisolid microstructure of dendritic zinc alloy ZA27.

The effect of solid solution treatment on semisolid microstructure of a Zn alloy ZA27 with developed dendrites was investigated and a new approach to produce non-dendritic semisolid microstructure available for thixoforming was developed. The results indicated that a semisolid microstructure with small and spherical primary particles could be obtained when the alloy with developed dendrites was solution treated for 3 h at 370°C and then partially remelted at a semisolid temperature of 460°C. This method could not only overcome some inevitable shortcomings resulting from using some present popular approaches, but also simplify the procedure of thixoforming. Too short or too long solution treatment duration could increase the shape factor, size and inhomogeneity of the primary particles. All of these microstructural changes were attributed to the dendrite coalescence and phase transformation which occurred during solid solution treatment. [ABSTRACT FROM AUTHOR]