Effects of grain size, texture and twinning on mechanical properties and work-hardening behavior of AZ31 magnesium alloys

Rolled sheets with various microstructures and (0 0 0 2) pole intensities have been obtained successfully using conventional flat rolling (CFR), differential speed rolling (DSR) and heat treatment methods. The mechanical properties of AZ31 magnesium alloys with different grain sizes, basal texture intensities and twinning conditions were investigated at room temperature. It was found that the rolled sheets show good ductility when grain size is around 15 μm. Finer grains and random (0 0 0 2) basal intensity are hardly achieved simultaneously using both DSR-RS and CFR-AR processing methods in current study. In the determination of the rolling processing, it is important to consider preferred grain refinement or lowered basal texture intensity. Moreover, the influences of grain size, basal texture intensity and twinning conditions on work-hardening rate were examined as well. As grain size decreases, extrapolated work-hardening rate decreases; while basal texture intensity has little effect on it. On the other hand, twinning plays a vital role in decreasing work-hardening in plastic flow stage; while twin boundaries increase the work-hardening rate in easy glide stage and linear hardening stage. However, they drop faster than un-twinned samples in stage III when the true strain is higher than 0.06.

► Rolled sheets of AZ31 with different microstructures were obtained experimentally.
► Grain sizes in around 15 μm show the best ductility.
► The work-hardening rate decreases as average grain size decreases.
► (0 0 0 2) texture intensity has little effect on work-hardening rate.
► The work-hardening rate in plastic flow stage is strongly affected by twinning.