Superplastic Deformation Behavior of Hot-rolled AZ31 Magnesium Alloy Sheet at Elevated Temperatures

1IntroductionAs a typical wrought magnesiumalloy,AZ31alloyhas a wide prospect for applications inthe fields of auto-mobiles,electronic appliances and aeronautic facili-ties1,2].However,due to the hexagonal close-packed(HCP)structure of magnesium,the ductility of AZ31al-loy at roomtemperature is rather poor,which greatly re-stricts its applications in structural fields3-5].Owing tothe activation of non-basal slip system6],the ductility ofMg alloycan be significantlyimproved at elevatedtem…

Superplastic deformation behavior of hot-rolled AZ31 magnesium alloy sheet at elevated temperatures

Uniaxial tensile tests were carried out in the temperature range of 250–450°C and the strain rate range of 0.7×10⁻³–1.4×10⁻¹ s⁻¹ to evaluate the superplasticity of AZ31 Mg alloy. The threshold stress which characterizes the difficulty for grain boundary sliding was calculated at various temperatures. The surface relieves of superplastically deformed specimens were observed by using a scanning electronic microscope (SEM). Results show that, at the temperature of 400°C and strain rate of 0.7×10⁻³s⁻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 integranular cavities were produced with the necking and fracture of filaments. Finally, the model for the formation of intergranular cavities was proposed.