Superplastic deformation behavior of the as-extruded AZ110 magnesium alloy with La-rich Mish metal addition

Tensile test at high temperature and electron backscatter diffraction (EBSD) techniques were combined to investigate the deformation behavior and microstructure evolution of the as-extruded AZ110 magnesium alloy with La-rich Mish Metal addition (AZ110LC for short). The stretching temperature and strain rate have great effect on the flow stress of the alloy. The flow stress rapidly reaches the peak stress and then decreases with further deformation until the fracture. The maximum elongation of the alloy is 840% under 573 K and 1.7 × 10−4s−1. The excellent superplasticity ascribes to the refinement of microstructure and the distribution of sub-structures of the as-extruded AZ110LC alloy. Moreover, the strain rate sensitivity coefficient of the as-extruded AZ110LC alloy is 0.41 and the active energy is 87 kJ/mol under 523 K and 4.2 × 10−4s-1 indicating that the deformation mechanism of the alloy is GBS. Finally, the shapes and fraction of cavities closed to tensile fracture have a great influence on the elongation of the tensile samples at different strain rates under 573 K. The formation and growth of the cavities can effectively relax the stress concentration and can effectively coordinate and compensate the GBS mechanism in superplastic deformation of the alloy.