Dynamic anisotropic grain growth during superplasticity in Al-Mg-Mn alloy

The microstructural mechanisms of dynamic anisotropic grain growth during superplasticity in a quasi-single phase Al-Mg-Mn alloy were characterized. The tensile superplasticity with 320% elongation was mediated by grain boundary sliding accompanied by rigid grain rotation with a limited crystallographic slip. The deformed sample exhibited a bimodal microstructure. Some grains maintained their original size and equiaxed morphology during superplasticity, whereas the others became elongated more than twice in aspect ratio and were composed of equiaxed subgrains that were aligned in the tensile axis. These microstructural features were possibly attributed to a rotation-coupled grain coalescence accompanied by grain boundary sliding. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.