NiMnGa Wires Produced by the In Rotating Water Melt-Spinning Technique

Abstract. Ferromagnetic shape memory alloys NiMnGa alloys have trigged great interest for their high to 10% magnetic-field-induced strain which are expected for actuators, sensors and dampers. However, the intrinsic brittleness of NiMnGa alloys limited theirs applications. Recently, more attentions are put on NiMnGa particles/polymer composite materials. As the properties of the NiMnGa/polymer composites were largely decided by the NiMnGa particles, Ni₅₅Mn_20.6Ga_24.4 wires were made by the in rotating water melt-spinning technique and its related properties were also studied by SEM, XRD, DSC and VSM. NiMnGa wires exhibit the microstructure of “bamboo” shape in the axial direction and single crystal in the radial direction. The phase transformation temperature of wires was similar to the bulk alloys which remains martensite at room temperature. The crystal structure of wires presents non-moderated martensite and has preferred orientation at (622). The magnetization curves of the axial direction of NiMnGa wires were different to that of radial direction.

Keywords: NiMnGa, shape memory alloys, in rotating water melt-spinning, crystal structure, martensitic transformation