Role of Nd content in synergistically regulating microstructure and enhancing mechanical properties of wire arc additive manufactured Mg-3Al alloys

Mg-3Al-xNd (x = 0, 1, 2, 3 wt%) alloys were fabricated by wire arc additive manufacturing (WAAM). The effects of Nd content on the microstructure and room temperature mechanical properties were systematically investigated. Results indicate that Nd addition significantly modifies the phase constitution, suppresses the formation of the Mg₁₇Al₁₂ phase, and promotes the precipitation of Al₂Nd and Al₁₁Nd₃ intermetallic compounds. At 1% Nd, the grains are slightly coarser, as Nd content rises to 2% and 3%, abundant coarse Al₂Nd phases act as effective heterogeneous nucleation sites, which markedly refine the average grain size from 45.3 μm to 20.2 μm. Nd addition enhances both the strength and ductility of the alloys synchronously. With Nd content increased to 3%, the ultimate tensile strength, yield strength, and elongation reach 249 ± 2.1 MPa, 115 ± 1.7 MPa, and 18.1 ± 0.5%, which correspond to improvements of 12.5%, 17%, and 23% compared with the Nd-free alloy, respectively. The enhanced strength mainly originates from grain-refinement strengthening and second-phase (Al₂Nd, Al₁₁Nd₃) strengthening, while the improved plasticity could be attributed to grain refinement promoting the spatial uniformity of deformation, along with weakened texture contributing to the activation of more potential slip systems. The combined positive effects of these two factors on plasticity are highly likely to outweigh the adverse influence of second‑phase particles. This study verifies that proper Nd addition combined with WAAM enables microstructure refinement of Mg-Al based alloys, thereby achieving additively manufactured magnesium alloys with balanced strength and ductility.