An Investigation on Grain Growth in a Commercial Al–Mg Alloy

Alloy AA5182 contains coarse constituent particles and submicron dispersoids. While the former may cause particle stimulated nucleation (PSN) during primary recrystallization, the fine dispersoids may ‘arrest’ grain growth during subsequent annealing. Abnormal grain growth was observed after dissolution/coarsening of the dispersoids. Mainly S [{123}〈634〉] grains, but also some Brass [{011}〈112〉] and Cu [{112}〈111〉] grains, were observed to grow abnormally. Both the grain size and the grain boundary character distribution (GBCD) possibly played a role in the selection of the grains for abnormal grain growth. A dramatic increase in the number fraction of extremely low angle (1−5°) boundaries was observed with annealing, the increase being more at 470°C (when dispersoids were stable and grain growth was arrested more effectively) than at 500°C/530°C (when inhibition to grain growth was less). The nature of the CSL boundaries did not change significantly with annealing time/temperature.