Normal and abnormal grain growth in magnesium: Experimental observations and simulations

Commercial purity as-cast magnesium was hot rolled and subsequently annealed at different temperatures in order to investigate its grain growth behavior and link it to the texture evolution. Annealing at an intermediate temperature of 220 °C gave rise to abnormal grain growth with a few grains reaching a grain diameter 10 times larger than the mean. Increasing the annealing temperature to 350 °C yielded normal grain growth. Both types of grain growth revealed a strengthening of the (0001) 11 2 - 0 texture component. It is hypothesized that a dislocation density gradient after recrystallization grants (0001) 11 2 - 0 grains a size advantage during early stages of growth. The type of growth will be, however, determined by the mobility of the present grain boundaries and triple junction drag, which are strongly dependent on the annealing temperature. The above hypothesis of the interplay between these parameters was explored through curvature- and residual dislocation-density-gradient-driven grain growth simulations using a formerly developed level-set approach. The simulation outcome suggests that application of such a modeling approach in microstructure studies of magnesium can provide valuable new insights into the problem of grain growth and associated texture evolution.