Improving tensile properties of Mg-Sn-Zn magnesium alloy sheets using pre-tension and ageing treatment

A hot rolled and annealed Mg-5Sn-2Zn sheet was subjected to pre-tension and ageing treatment, and the microstructural evolution and mechanical property were carefully examined in this study. The as-annealed sheet exhibited an intense basal texture with bimodal grains, moderate yield strength and excellent elongation to failure. Samples directly aged at 150 degrees C for 48 h exhibited a small increment (similar to 10 MPa) in yield strength. In contrast, the yield strength was obviously improved by 48 MPa in RD and 49 MPa in TD through 3% pre-tension and ageing treatment. Moreover, the strength can be further increased by increasing pre-strain. Detailed microstructural characterization revealed that pre-tension refined the Mg2Sn precipitates and increased the number density, in addition, dense dislocation and a few twins were retained after ageing treatment. The pronounced improvement of yield strength was mainly ascribed for combination of the increased precipitation hardening of Mg2Sn and dislocation strengthening and the weakness of texture strengthening. (C) 2017 Elsevier B.V. All rights reserved.