Grain size and texture dependence on mechanical properties, asymmetric behavior and low temperature superplasticity of ZK60 Mg alloy

The mechanical properties of ZK60 alloy were characterized as function of texture and grain size. An experimental methodology was designed by exploiting ECAP and annealing treatments on an extruded alloy, through which the individual effects of the mentioned parameters could be investigated. Microstructural observations revealed a significant grain refinement through ECAP processing, leading to an equiaxed ultrafine grain (UFG) structure with an average size of 500 nm. The initial extrusion fiber texture was gradually evolved into a new and more intense one featuring the preferential alignment of the basal planes along the ECAP shear planes with considerably higher intensity and Schmid factor. After annealing, the UFG structure was replaced by a structure close to that of the extruded condition. However, the basal texture orientation was only slightly modified. Tensile and compression tests at room temperature showed that regardless of grain size, fracture elongation and yield asymmetry were strongly influenced by basal texture orientation. Nevertheless, tensile tests at 200 degrees C showed that the flow stress was considerably texture dependent, whereas the fracture elongation was mainly dictated by the grain size.