Enhanced strength-ductility synergy of directed energy deposited Mg-3.0Nd-0.2Zn-0.3Zr alloy via micro-alloying with Ce

Grain size and texture can be controlled to improve the strength and ductility of magnesium rare-earth (Mg-RE) alloys by alloying. Directed energy deposition-arc (DED-arc) is a typical sub-rapid solidification process that contributes to the modification of the microstructure. In this paper, a series of novel Mg-3.0Nd-0.2Zn-0.3Zr-xCe (NZ30K-xCe) alloys with different Ce contents (0, 0.1, 0.3, 0.5 wt.%) were prepared by DED-arc. The results show that the experimental alloys have lower porosity (≤0.11 %). After adding 0.1 wt.% Ce, the average grain size decreases from 98.9 ± 5.7 µm to 49.8 ± 1.0 µm, and the texture is significantly weakened. Further additions of Ce (0.3 and 0.5 wt.%) do not lead to significant alterations in the average grain size and texture intensity when compared with the NZ30K-0.1Ce alloy. Grain refinement is related to the constitutional supercooling, and the texture weakening is connected to the solid solubility of Ce in the Mg matrix. The ultimate tensile strength and elongation of NZ30K-0.1Ce alloy are 37.2 % and 61.3 % higher than those of NZ30K alloy. Grain refinement and texture weakening are the reasons for the better strength-ductility of NZ30K-0.1Ce alloy.