Significantly extending the gradient layer and mechanical properties of Mg alloys by texture optimization

Considerable efforts have been made to prepare a thicker gradient layer, while the reported thickness of the gradient layer for Mg alloys is often below 700 µm. In this study, an ultrasonic surface rolling process (USRP) was employed to fabricate gradient layers in AZ31 hot-rolled plates. By changing the initial texture of the <i>c</i>-axes of the grains from a direction largely parallel to the compression direction of the USRP into that perpendicular to the compression direction, the thickness of the gradient layer obtained by the USRP at a static force of 140 N increased from approximately 500 µm to 2000 µm. This in turn doubled the strengthening effect of the gradient layer under tension along the rolling direction of the plates, without compromising the ductility. Further investigations revealed that extending the gradient layer by tailoring its initial texture is closely related to the activation of profuse {101¯2} twinning.