Influence of Zn on the microstructure and mechanical properties of Mg-Gd-Zr alloy

Here, the microstructure and mechanical properties are investigated for the designed Mg-4Gd-0.5Zr-xZn (x = 0, 0.2, 0.5, 1.0 and 1.5 wt%) alloys with special emphasis on the effect of Zn. The results show that the designed Mg-4Gd-0.5Zr-xZn alloys exhibit the exceptional ductility. Among them, the Mg-4Gd-0.5Zr-1.0Zn and Mg-4Gd-0.5Zr-1.5Zn alloys show the elongation to fracture as high as 35.2% and 32.5%. Furthermore, a good strength-ductility balance is achieved in the alloys, which is basically ascribed to the grain refinement, texture softening and the precipitation of Zn-containing second phases. As Zn content increases from 0 to 1.5 wt%, the grain sizes of the extruded Mg-Gd-Zr-Zn alloys decrease from 6.02 to 3.05 μm, while the maximum texture intensity decreases from 11.13 to 5.24 m.r.d. Moreover, the Zn 2 Zr 3 and Mg 3 Zn 3 Gd 2 precipitates, which exhibit the completely coherent and semi-coherent orientation relationship with Mg matrix, are induced by the addition of Zn. These coherent and semi-coherent precipitates lead to noticeable strengthening effect and are not easy to become the source of crack, contributing to the high ductility in Mg-4Gd-0.5Zr-1.0Zn and Mg-4Gd-0.5Zr-1.5Zn. • The designed Mg-4Gd-0.5Zr-xZn (x = 0, 0.2, 0.5, 1.0 and 1.5 wt%) alloys all exhibit the exceptional ductility. • The Mg-4Gd-0.5Zr-1.0Zn and Mg-4Gd-0.5Zr-1.5Zn alloys exhibit a good strength-ductility balance. • The orientation relationship between the precipitates and Mg matrix was studied.