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 (∼6 μm) decreases gradually due to continuous activation of 〈c + a〉 slip, while that for twinning-mediated grains (∼41 μm) decreases rapidly because of the combined action of 〈c + a〉 slip, contraction twinning ({101¯1}〈101¯2〉) and extension twinning ({101¯2}〈101¯1¯〉).