Effect of Initial Grain Size on Dynamically Recrystallized Grain Size in AZ31 Magnesium Alloy

The effect of initial grain size on dynamically recrystallized grain size (DRX grain size) is examined in AZ31 magnesium alloy with four kinds of initial grain sizes. When the average grain size after the high-temperature compression test is plotted against Zenner-Hollomon parameter (Z-parameter), initial grain size dependence on DRX grain size appears only in the specimen with large initial grain size in the low Z region, but not in the specimen with small grain size or in high Z region. When the grain size measured only in recrystallized region is plotted against Z-parameter, initial grain size dependence on DRX grain size does not appear. From these results, it is concluded that there is no initial grain size dependence on DRX grain size when the DRX proceeds to some degree, because the DRX grain size becomes constant for a given Z-value. The initial grain size dependence on DRX grain size observed in the low Z region would be related to the rotation of basal plane perpendicular to the compression axis during deformation before the DRX grains have been developed sufficiently.