Evolution of twins and texture and its effects on mechanical properties of AZ31 magnesium alloy sheets under different rolling process parameters

In order to investigate the dependence of microstructure and mechanical properties on the rolling process parameters, AZ31 magnesium alloy sheets with different grain sizes, basal texture intensities and twinning types were obtained using hot rolling at various temperatures and reductions. The volume fractions of the extension, contraction and secondary twins in the as-rolled sheets depend on the grain size. The highest volume fractions of three types of twins are obtained at 523 K under the reduction of 10% when the average grain size value is the maximum. The critical reductions for complete dynamic recrystallization are 30% at 523 K and 40% at 473 K. The increase of yield strength is ascribed to both grain-refinement strengthening and basal texture strengthening at the first stage. When the grain size does not decrease with increasing the reduction, the yield strength is mainly influenced by the texture weakening.