Abstract:

High-temperature pre-stretching experiments were carried out on the AZ31 Mg alloy at 723 K with strain levels of 2.54%, 6.48%, 10.92%, and 19.2% to alter the microstructure and texture for improving room-temperature formability. The results showed that the strain-hardening coefficient increased, while the Lankford value decreased. In addition, the Erichsen values of all pre-stretch sheets were enhanced compared with that of the as-received sheet. The maximum Erichsen value increased from 2.38 mm for the as-received sample to 4.03 mm for the 10.92%-stretched sample, corresponding to an improvement of 69.32%. This improvement was mainly attributed to the gradual increase in grain size, and the (0001) basal texture was weakened due to the activated non-basal slip as the high-temperature pre-stretching strain levels increased. The visco-plastic self-consistent analysis was performed on the as-received and high-temperature pre-stretched samples. Results confirmed the higher activity of the prismatic slip in 10.92%-stretched sample, leading to divergence and weakening of basal texture components. This results in an augmentation of the Schmid factor under different slip systems. Therefore, it can be concluded that high-temperature pre-stretching technology provided an effective method to enhance the formability of Mg alloy sheets.

Key words: High-temperature deformation, Grain growth, Magnesium alloys, Texture, Visco-plastic self-consistent modeling, Formability