Simultaneous improvement in strength and ductility of extruded Mg alloy via novel closed forging extrusion
(1. College of Materials Science and Engineering, Chongqing University, Chongqing 400044, China;
2. National Engineering Research Center for Mg Alloys, Chongqing University, Chongqing 400044, China;
3. School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China;
4. Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick, V94 T9PX, Ireland;
5. School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China)
2. National Engineering Research Center for Mg Alloys, Chongqing University, Chongqing 400044, China;
3. School of Metallurgy and Materials Engineering, Chongqing University of Science and Technology, Chongqing 401331, China;
4. Bernal Institute, Department of Chemical Sciences, University of Limerick, Limerick, V94 T9PX, Ireland;
5. School of Materials Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China)
Abstract: A novel continuous plastic process employed on AZ31 Mg alloy called closed forging extrusion (CFE) was presented. The optical microscopy, scanning electron microscopy, electron back-scatter diffraction and tensile and compressive tests were employed to investigate the microstructure evolution and strengthening mechanism. The results indicated that the CFE-process can promote dynamic recrystallization (DRX), eliminate the coarsen unDRXed grain regions, refine the grains effectively, and improve the strength, plasticity and anisotropy of the alloy. The grain refinement was mainly attributed to the stress, which facilitated the nucleation of recrystallization and refined the microstructure via the CFE. The fully DRXed ultrafine grained structure improved the strength and plasticity simultaneously. After 60 s closed forging and continuous extrusion, the alloy exhibits relatively high TYS, UTS, CYS, elongation and yield asymmetry of 305 MPa, 337 MPa, 295 MPa, 27% and 0.97, respectively.
Key words: Mg alloys; extrusion; mechanical properties