Influence of texture on superplastic behavior of friction stir processed ZK60 magnesium alloy

Commercial ZK60 extruded plate was subjected to friction stir processing (FSP). A fine-grained structure 2.9 μm in grain size with uniformly distributed fine second-phase particles and predominant high-angle grain boundaries of 97% was obtained. A strong basal fiber texture with the (0002) planes roughly surrounding the tool pin surface was developed in the FSP ZK60 alloy. The FSP ZK60 alloy exhibited superplastic behavior at 225-325 °C in both the transverse direction (TD) and longitudinal direction (LD), with the superplastic elongation in the LD being higher than that in the TD. A maximum elongation of 1390% was obtained at 300 °C and 3×10−4 s−1 in the LD. The existence of texture was found to influence the superplastic flow stress and plasticity. The texture had a minor influence on the flow stress, due to the texture weakening during superplastic deformation. However, the anisotropy of plasticity existed at all temperatures and strain rates, as a result of the activation of different slip systems in different tensile directions.