Influence of grain size on the compressive deformation of wrought Mg-3Al-1Zn

The influence of the grain size on the flow stress of extruded Mg-3Al-1Zn tested in compression is examined. Samples with grain sizes varying between 3 and 23 mum were prepared by altering the extrusion conditions. Compression testing of the extruded bar was carried out at temperatures between ambient and 200 degreesC. Twinning dominated the deformation at lower temperatures but this gave way to slip dominated flow when the temperature was raised. For tests carried out at intermediate temperatures, a similar transition was observed when the grain size was reduced. The transition was accompanied by a change in flow curve shape and Hall-Petch slope. The peak stresses achieved when twinning dominated the deformation were up to 100 MPa greater than those seen when slip dominated the flow. Critical grain sizes marking the twinning-slip transition were identified and these are described in terms of the deformation conditions. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.