Obtaining high strength and high plasticity in a Mg-3Al-1Zn plate using pre-tension and annealing treatments

In the present study, the usage of recovery structure to obtain a combination of the high strength and high plasticity in a Mg-3Al-1Zn plate was reported. The influence of pre-tension at different temperatures (25 °C, 150 °C and 200 °C) and subsequent annealing (175 °C for 6 h) on the microstructure, texture and mechanical properties during re-tension was systematically studied. Our results show that the as-used pre-tension plus annealing process can effectively improve the yield strength, especially the one with pre-tension at 150 °C and annealing at 175 °C for 6 h can increase the yield strength by 61 MPa, meanwhile retain a similar elongation (12.4%) to the initial plate (13.0%). A preferred distribution of prismatic planes with 〈10-10〉//TD exists in both the pre-tensioned samples and the annealed ones. It is found that this preferred distribution hardly varies the SF and the activity of prismatic 〈a〉 slip during re-tension, and eventually does not contribute to enhancing the yield strength or reducing the plasticity. TEM results show that the annealing of sample pre-tensioned at 150 °C develops many dislocation walls together with many areas with a quite low dislocation density. This type of recovery structure mainly accounts for the high strength and high plasticity in the pre-tensioned and annealed samples.