Effect of predeformation on the semisolid microstructure of Mg–9Al–0.6Zn alloy

The effect of predeformation on the semisolid microstructure of Mg–9Al–0.6Zn (AZ91D) alloy is investigated. The results indicate that finer, more globular semisolid microstructure was attained in more heavily deformed alloys after heat treatment at 560 °C for 20 min. Furthermore, the liquid islands in the grains also become less with the increase in the compression ratio. It is mainly because the microstructural evolution mechanisms are different in alloys with various compression ratios. The heavy predeformation leads to the occurrence of the recrystallization, and the amount of recrystallization increases with the increase of the compression ratio. These recrystallization grains can easily give rise to the small initial grains that evolve towards a globular and small morphology rapidly during isothermal heat treatment at semisolid temperature of 560 °C. Moreover, there are also no liquid islands in the final grains after evolution. In addition to the recrystallization evolution mechanism, there are two other microstructural evolution mechanisms—melting and combining of dendritic arms, which are both discussed in this paper. [Copyright &y& Elsevier]