Enhancing mechanical properties of Mg-Sn alloys by combining addition of Ca and Zn

摘要

We developed new wrought Mg-2Sn-1Ca wt.% (TX21) and Mg-2Sn-1Ca-2Zn wt.% (TXZ212) alloys with high strength and ductility simultaneously, produced by conventional casting, homogenization and indirect extrusion. A partial dynamically recrystallized microstructure, with the micron-ano-MgSnCa particles and G.P. zones dispersing, was obtained in TX21 alloy extruded at 260 ℃ (TX21-260). The TX21-260 alloy exhibited yield strength (YS) of 269 MPa, ultimate tensile strength (UTS) of 305 MPa, while those of the TX21 alloy extruded at 300 ℃ decreased to be 207 MPa and 230 MPa respectively. For TXZ212-260 alloy, on the other hand, MgSnCa, MgZnCa and MgZn_2 phases were observed, and the average grain size increased to be ～5 μm. The YS and UTS of TXZ212-260 alloy evolved to be 218 MPa and 285 MPa, and the elongation (EL) reached as high as 23%. The high strengths of TX21-260 alloy were expected due to the high number density of nano-MgSnCa phases, G.P. zones and ultra-fine grain size (～0.8 μm). The high EL of 23% in TXZ212-260 alloy was consistent with the high work-hardening rate, which was attributed to the larger grain size, more high angular grain boundaries, presence of more nano-particles and the weaker texture.