Preparation of Non-Dendritic Microstructure of AZ31 Alloy Using Isothermal Heat Treatment of the Refined Billet

Abstract

Semisolid metal forming (SSF) has been regarded as a potential process to shape the wrough Mg alloy base on the thixotropy and low deformation resistance of non-dendritic semisolid slurry. Therefore, it is necessary to develop the slurry production method of wrought Mg alloy as most current researches are focused on the cast alloy. In this paper, the AZ31 billet was refined by the self-inoculation method, and the partialy remelt method was employed to produce the non-dendritic microstructure. Results indicate that both the morphology and size of the primary Mg phase in AZ31 were refined by the grain refining treatment. When the billet were reheated under 595°C and 610°C with different holding times, the morphology of primary Mg phase undergo an evolution pattern from rosette or tiny dendritic to spherical, and with the prolonged holding time, the size of primary Mg phase increased and the shape turn to irregular. Moreover, the result show that the high holding temperature shorten the evolution time from irregular to spherical and the deteriorative grains obtained earlier compared to the low holding temperature.