Effect of rolling path on microstructure and mechanical properties of GWZ731 magnesium alloy

In this study, the effects of unidirectional rolling and cross rolling on the microstructure and mechanical properties of magnesium alloys containing LPSO phase were investigated. The results show that compared with unidirectional rolling, cross rolling further improves the recrystallization degree of the alloy, effectively refines the alloy grains, and the bulk LPSO phase is broken more completely. The average grain size of the alloy decreases from 2.37 μm to 1.85 μm, and the fraction of low-angle grain boundaries increases from 53.9% to 59.3%. Cross rolling introduces kink bands in the structure while providing a large amount of deformation. As small-angle grain boundaries, they promote dynamic recrystallization. Cross rolling weakens the basal texture and changes the grain orientation of the alloy from "<0001>//ND" to "<10-10>//ND". The weakening of texture increases the Schmidt factor of basal slip, reduces the threshold of slip initiation, and improves the plasticity of the alloy. At the same time, the LPSO twist itself can effectively coordinate the strain difference between grains, inhibit the initiation and propagation of microcracks, and significantly improve the uniform deformation ability of the alloy. After cross rolling, the yield strength of the alloy under the synergistic effect of fine grain strengthening and dislocation strengthening is about 23 MPa higher than that of unidirectional rolling. The coordinated deformation of the kink band and the high proportion of broken LPSO phase achieves the synergistic improvement of the strength and plasticity of the alloy. Among them, the twist of LPSO phase is the core incentive to achieve simultaneous improvement of strength and plasticity.