LA91超塑性变形力学性能研究

LA91 dual phase Mg-Li alloy plate was used as the study object. Superplastic tensile tests were carried out at different temperatures (423, 473, 523, 573 and 623 K) and different strain rates (5×10^-4, 1.5×10^-3,4.5×10^-3and 1.35×10^-2 s^-1). The ture stress-strain curve was used to analyze the superplastic deformation behavior of LA91. The results show that when increasing the deformation temperature or decreasing the strain rate, the elongation of LA91 increases and the peak flow stress decreases from 250 to 30 MPa. The maximum elongation is 187.04% when the initial strain rate is 1.5×10^-3 s^-1 and the deformation temperature is 623 K, which shows obvious superplasticity. Based on the superplastic constitutive equation, it can be obtained that the strain rate sensitivity index of LA91 is 0.41 and the activation energy of deformation is 92.93 kJ•mol^-1, and the mechanism of superplastic deformation of LA91 is grain boundary sliding controlled by grain boundary diffusion. The results provide scientific basis for plastic processing and application of LA91 dual phase Mg-Li alloy plate.