The influence of Mg and Mn content on abnormal grain growth in AA5182 type alloys

The occurrence of abnormal grain growth (AGG) in AA5182 alloy during annealing imposes severe restrictions on processing parameters and deteriorates mechanical properties. In this work, we investigated the effect of chemical composition on the appearance of abnormal grain growth by varying Mg and Mn content in the range of composition limits for standard AA5182 alloy, 4.0-5.0% Mg, and 0.2-0.5% Mn, respectively. Thermo-mechanical processing of alloys included cold rolling with reductions ranging from 40 to 85%, followed by annealing in the temperature range from 350 to 520 °C. The results showed that the rise in alloying elements content drives the onset of abnormal grain growth toward higher temperatures. The increase in the cold rolling reduction degree promotes abnormal grain growth and lowers its onset temperature. Abnormal grain growth and grain boundary mobility showed strong anisotropy related to rod-like shape and alignment of Al6Mn(Fe) dispersoids through Zener pinning.