Ni-Mn-Ga 合金激光粉末床熔融成形工艺及磁性能

Laser powder bed fusion (L-PBF) technology combined with optimized heat treatment strategies was used to explore a new manufacturing scheme to achieve the controllable fabrication of functional Ni-Mn-Ga alloys and complex components. The results show that defects including porosity, cracks, and lack-of-fusion are generated during laser processing, with cracks primarily originating from significant thermal stresses induced by rapid solidification. Within the optimized process interval, parts with a density of more than 97.5% are successfully prepared, and the materials showed L2₁-ordered austenite structure at the ambient temperature of 295~301 K. After homogenization, ordering, and stress-relief annealing treatments, the material demonstrates improved compositional homogeneity, narrowed phase transformation temperature interval, elevated phase transition characteristic temperatures by approximately 20 K, and significantly enhanced magnetization. At ambient temperature, the material exhibits a mixed phase comprising L2₁-ordered austenite and five-layered modulated (5M) martensite structures. Under a magnetic field with a magnetic induction intensity of 5 T, the heat-treated material achieves a saturation magnetization of 65.8 (A·m²)/kg at 300 K. LPBF can fabricate functional Ni-Mn-Ga magnetic shape memory alloys.