Texture and mechanical properties of ultrafine-grained Mg-3Al-1Zn alloy sheets prepared by high-ratio differential speed rolling

▶ The ultrafine grained AZ31 alloy with the mean grain size of 1 μm could be produced by feeding the cold AZ31 sheet to the hot rolls set at the speed ratio of 3 for a thickness reduction of 73% through the two-step rolling process. ▶ The analysis of texture characteristics suggested that the grain refining during the HRDSR process proceeded by continuous dynamic recrystallization. The basal texture intensity and the rotation of basal angles depended on amount of shear deformation and rolling temperature. ▶ Grain-size strengthening and basal-texture strengthening contribute to the high strength achieved after HRDSR. ▶ The ultrafine grained AZ31 showed a relatively large post-uniform elongation compared to the as-recieved one due to increased strain rate sensitivity exponent and suppressoin of inhomogeneous twinning. ▶ By annealing the ultrafine grained AZ31 properly, a bimodal grain size distribution could be obtained, leading to significant improvement of uniform elongation.