A simultaneous improvement of both strength and ductility by Sn addition in as-extruded Mg-6Al-4Zn alloy

Commercial wrought Mg alloys normally contain low alloying contents to ensure good formability. In the present work, high-alloyed Mg-6Al-4Zn-xSn (x = 1, 2 and 3 wt.%, respectively) alloys were fabricated by extrusion. Hereinto, Sn was proven to play an effective contribution to simultaneous improvement in strength and ductility that are traditional trade-off features of synthetic materials. It was found that the average grain size of those alloys decreases significantly from ∼11 to ∼4 μm as a function of Sn contents increasing from 0 to 3 wt.%, while the amounts of Mg₂Sn and Mg₁₇Al₁₂ particles continuously increase. More importantly, the addition of Sn leads to the transformation of dominated deformation modes from {101¯2} extension twinning (1 wt.%) to pyramidal <c+a> slip (3 wt.%) during tensile tests along the extrusion direction at room temperature. The advantageous combination of ultimate tensile strength (∼366 MPa) and elongation (∼19 %) in Mg-6Al-4Zn-3Sn alloy is mainly attributed to the strong strain hardening ability induced by the enhanced activity of non-basal <c+a> slip. This work could provide new opportunities for the development of high-alloyed wrought Mg alloys with promising mechanical properties.