摘要
Uniaxial tensile tests were carride out in the temperature range of 250-450℃ and the strain rate range of 0.7×10^-3^-1.4×10^-1s^-1 to evaluate the superplasticity of AZ31 Mg aloy .The threshold stress which characterizes the difficulty for grain boundary sliding was calculated at various temperature .The surface relieves of superplastically deformed specimens were observde by using a scanning elctronic microscops （SEM）.Results show that ,at the temperature of 400℃ and strain rate of 1.7×10^-3^-1,the strain rate sensitivity exponent ,i e,m value reaches 0.47 and the maximum elongation of 362.5% is achieved .Grain boundary sliding （GBS）is the primary deformation mechanism and characterized by a pronounced improvement in the homogeneity with increasing temperatures.A large number of filaments were formed at the end of deformation and intergranular cavities produced with the necking and fracture of filaments.Finally ,the model for the formation of intergranular cavities was proposed.
Uniaxial tensile tests were carride out in the temperature range of 250-450℃ and the strain rate range of 0.7×10^-3^-1.4×10^-1s^-1 to evaluate the superplasticity of AZ31 Mg aloy .The threshold stress which characterizes the difficulty for grain boundary sliding was calculated at various temperature .The surface relieves of superplastically deformed specimens were observde by using a scanning elctronic microscops （SEM）.Results show that ,at the temperature of 400℃ and strain rate of 1.7×10^-3^-1,the strain rate sensitivity exponent ,i e,m value reaches 0.47 and the maximum elongation of 362.5% is achieved .Grain boundary sliding （GBS）is the primary deformation mechanism and characterized by a pronounced improvement in the homogeneity with increasing temperatures.A large number of filaments were formed at the end of deformation and intergranular cavities produced with the necking and fracture of filaments.Finally ,the model for the formation of intergranular cavities was proposed.
