The role of Gd on the microstructural evolution and mechanical properties of Mg-3Nd-0.2Zn-0.5Zr alloy

This work was undertaken to investigate the specific role of element Gd on the microstructural evolution and mechanical properties of Mg-3Nd-0.2Zn-0.5Zr alloy. It is noticeable that, as the Gd content increases, the average grain size of as-cast alloys is continuously reduced, accompanied by the main secondary phases changing from Mg12Nd to Mg3Gd. Tensile tests reveal that addition of Gd (1.5?4.5 wt%) could lead to substantial enhancements of alloy strength (25?70 MPa) and an excellent combination of strength and ductility is obtained in the alloy with 4.5 wt% Gd addition (YS = 200 MPa, UTS = 343 MPa, EL = 5.4%). Microstructure characterization indicates that the improved solid-solution strengthening effect originated from increasing Gd additions plays a key role in the significant strength improvements obtained in as-quenched alloys. HAADF-STEM observations suggest that Gd is highly enriched in the dominantly disc-like prismatic ??phases, leading to the strongly enhanced precipitation kinetics and greatly augmented volume fraction of ??phase. A quantitative microstructural comparison of peakaged specimens indicates that the significant strength enhancements should be primarily derived from the denser dispersion of ??phases with higher aspect radio arising from Gd addition.

Automated summary

This study investigates the specific role of Gd element on the microstructural evolution and mechanical properties of Mg-3Nd-0.2Zn-0.5Zr alloy. It is found that increasing Gd content leads to reduced grain size and substantial enhancements in alloy strength. Microstructure characterization shows that the improved solid-solution strengthening effect from Gd additions plays a key role in the significant strength improvements obtained in the as-quenched alloys.