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Ying Zeng,Xunfei Xiong,Xiaoying Qian,Dabiao Xia,Xin Shang,Bin Jiang,Dongdi Yin 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.7
Significant tension-compression (T–C) yield asymmetry in common wrought Mg alloys hinders their widespread applications. A double extrusion process with variable speed and partially substituted yttrium (Y) (2 wt%) for Sn was proposed to improvethe T–C asymmetry of Mg–2.5Sn (wt%) alloy, and then to explore the critical grain size parameter for T–C symmetry. Theresult showed that the individual double extrusion or partial substitution of Sn by Y slightly refined the grains of Mg–2.5Snalloy (from ~ 42.5 μm to 35.5 μm and 31.2 μm, respectively), along with the improved T–C asymmetry (CYS/TYS) from0.44 to 0.51 and 0.75, respectively. When combining the above two factors, the double-extruded Mg–Sn–Y alloys obtainedfine grains with ~ 8.8 μm and gained a T–C yield symmetry (CYS/TYS = 1.01). By tailoring the extrusion speed from theprevious 1.2 mm/s to 2 mm/s, the grain size of double-extruded Mg–Sn–Y further deduced to ~ 5.6 μm and turned to be areversed T–C asymmetry (CYS/TYS) of 1.37. The refined grain size combined with weakened texture led to a decreasedactivation or even inhibition of tension twinning and increased activation of non-basal slip, which might be the main reasonfor the improved or even reversed T–C asymmetry in double-extruded Mg–0.5Sn–2Y.