Tailoring good combinations between strength and ductility in novel Mg-5Sn-2Al-1Zn alloy via different hot extrusion processes
(School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China)
Abstract: A novel Mg-5Sn-2Al-1Zn (TAZ521) alloy was prepared. Direct extrusion (DE) and extrusion-shearing (ES) processes were performed on the alloy to improve its strength and ductility. The microstructure evolution, texture evolution, and strengthening mechanisms of as-homogenized and as-extruded alloy were investigated by XRD, SEM, TEM, EBSD, and tensile tests. The results showed that the mechanical properties of the DE-processed alloy were improved. However, the alloy exhibited a bimodal microstructure consisting of coarse grains and fine DRXed grains. After the ES process, the microstructure became more uniform and a good combination of strength and ductility was achieved. The TYS, UTS, and EL were 212 MPa, 303 MPa, and 21.7%, respectively. Grain refinement and pinning effect by Mg2Sn precipitates play an important role in the enhancement of strength. Additionally, the improvement of ductility is attributed to the weak basal fiber texture and the activation of non-basal slip.
Key words: Mg-Sn-Al-Zn alloys; extrusion-shearing; grain refinement; mechanical properties; texture evolution