Influence of grain size on strain rate sensitivity in rolled Mg-3Al-3Sn alloy at room temperature

The strain rate sensitivity (SRS) of a rolled Mg-3Al-3Sn (AT33) alloy increased with decreasing grain size at room temperature, owing to a change in the deformation mechanism from dislocation-dominated to twinning-mediated. Moreover, as deformation proceeds the SRS for slip-dominated grains (similar to 6 mu m) decreases gradually due to continuous activation of < c + a > slip, while that for twinning-mediated grains (similar to 41 mu m) decreases rapidly because of the combined action of < c + a > slip, contraction twinning ({10 (1) over bar1} < 10 (1) over bar2 >) and extension twinning ({10 (1) over bar2} < 10 (1) over bar(1) over bar >). (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.