Nd microalloying significantly enhances precipitation strengthening of Mg-Gd-Y-Zn-Zr alloy

Compositional optimization demonstrates greater commercial feasibility than complex processing routes for enhancing magnesium (Mg) alloy performance in industrial applications. This study proposes a metallurgical strategy of Nd microalloying (0.2 wt%), which significantly enhances the age hardening response of Mg-Gd-Y-Zn-Zr base alloy and increases its peak-aged yield strength from 352 MPa to 407 MPa. Microstructural analysis reveals that Nd addition induces negligible alterations in the macroscopic deformation structure, confirming that the improvement in yield strength is predominantly attributed to precipitation strengthening. First principles calculations have demonstrated the dual mechanism of Nd microalloying on aging precipitates. Nd microalloying promotes precipitation nucleation by lowering the formation energy of of beta" and beta' phases. Simultaneously, it suppresses beta' growth by increasing the elastic strain energy at the beta'/alpha(Mg) interface. Consequently, the Nd containing alloy exhibits a higher number density and reduced size of beta' phases. The calculation results demonstrate that high-density refined beta' in the Nd containing alloy is more likely to exert resistance to basal <a> slip by activating the dislocation-shearing mechanism, thereby enabling Nd microalloying to increase the yield strength of the peak-aged alloy by 55 MPa with only slight loss of ductility.