Synergistic effect of Gd and Ce on enhancement of mechanical properties of as-extruded Mg-Sn-Zn alloys

The effects of incorporating dilute Gd and Ce on the microstructure and mechanical properties of Mg-0.5Sn-0.3Zn (TZ00, wt%) alloys are systematically revealed. The results indicate that the co-addition of 0.3 wt% Gd and 0.3 wt% Ce can significantly reduce the grain size from 40.8 μm to 12.0 μm, enhance dynamic recrystallization, and attenuate the intensity of basal texture. Furthermore, plenty of micron- and nano-scale (Gd, Ce)MgSn phases are precipitated. In comparison with the TZ00 alloy, the Mg-0.5Sn-0.3Zn-0.3Gd-0.3Ce alloy (TZGE0000, wt%) displays synergistic improvements in strength and ductility. The corresponding tensile yield strength (TYS), ultimate tensile strength (UTS), and elongation (EL) are 214.1 MPa, 297.4 MPa, and 23.5 %, respectively. The primary reason for this strength improvement is the combined effects of grain refinement and (Gd, Ce)MgSn nano-phase strengthening, while the ductility enhancement is mainly due to the refined grain size, weakened basal texture, increased activation of prismatic slip and {10−12} tensile twinning. Additionally, relative Visco-Plastic Self-Consistent (VPSC) simulations confirm that the combined addition of Gd and Ce can promote the activation of non-basal slip and {10−12} tensile twinning during the deformation process. In more detail, basal and prismatic slips are the primary deformation mechanisms during tensile loading, together with a minor occurrence of {10−12} tensile twinning and pyramidal slip coordination deformations. Conversely, {10−12} tensile twinning predominates during the compression deformation.