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Ni-Mn-Ga合金激光粉末床熔融成形工艺及磁性能

Laser powder bed fusion process and magnetic properties of Ni-Mn-Ga alloy

  • 摘要: 文中通过激光粉末床熔融(laser powder bed fusion,L-PBF)技术,结合热处理工艺优化策略,探索新型制造方案以实现功能性Ni-Mn-Ga合金及其复杂构件的可控制备. 结果表明,激光加工制造过程中产生了气孔、裂纹和未熔合等缺陷,裂纹主要源于快速凝固引起的大热应力. 在优化的工艺区间内,成功制备致密度97.5%以上的成形件,材料在环境温度为295 ~ 301 K时表现为L21有序奥氏体结构. 经均匀化、有序化和去应力退火热处理后,材料成分均匀性有所提高,相变温度区间变窄,相变特征温度的提高约为20 K,磁化强度显著提高. 热处理态材料在环境温度下表现为L21有序奥氏体和五层调制(5 M)马氏体结构的混合物相. 磁感应强度为5 T磁场下,热处理态材料在温度为300 K的饱和磁化强度可达到65.8(A·m2)/kg. L-PBF能够制备功能性 Ni-Mn-Ga磁性形状记忆合金.

     

    Abstract: 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. L-PBF can fabricate functional Ni-Mn-Ga magnetic shape memory alloys.

     

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