Preparation And Characterization Of NiCoMnSn/Cu Composite Materials

In the present paper,Ni41Co9-xMn40Sn10Fex(x=0,1,2,3) (at.%) ferromagnetic alloys were prepared. Some of them were ball milled to powders and then filled into Cu tubes, which were rolled to obtain sheet-like samples. Optical microscope, scanning electron microscope, X-ray diffraction technique, differential scanning calorimeter, compression testing and PPMS were employed to investigate the influence of Fe element on the martensitic transformations,microstructures, mechanical properties and magnetic properties of Ni41Co9-xMn40Sn10Fex(x=0,1,2,3) alloy systematically.The influences of rolling processes on martensitic transformations, mechanical properties of the composite were studied.The results demonstrated that martensitic transformation temperatures and the microstructure in Ni41Co9-xMn40Sn10Fex(x=0,1,2,3) alloys were significantly affected by Fe content. At room temperature,the microstructure of Ni41Co9-xMn40Sn10Fex(x=0,1) alloys is single-phase, i.e., only martensite exists. In Ni41Co9-xMn40Sn10Fex(x=2,3) alloys, the microstructure consists of martensite phase and the second phases. The volume fraction of the second phases increases with increasing Fe content. As compared with the matrix, the second phase is rich in Co and Fe while poor in Sn content. The martensitic transformation temperatures and the Curie temperature decrease with the increase of Fe content, which can be due to the combination effects of the change of valence electron concentration (e/a) and the presence of second phases.The addition of Fe could significantly improve the mechanical properties when the content of Fe exceeds 2at.%. For 3at.% Fe content, the fracture strength and the maximum strain are up to 1269MPa and 20.8%,respectively. The fracture mechanism changes from intergranular crack to the transgranular cleavage crack. The increase of second phase and the change of fracture type result in the improvement of mechanical properties.Magnetization curves show that only in Ni41Co7Mn40Sn10Fe2 alloy could martensitic reverse transformation be induced by a magnetic field of 20kOe. Other three samples do not exhibit magnetic-field induced reverse transformation. In comparision, no magnetic-field induced reverse transformation is found for all ball-milled powder samples. In addition,After ball-milling the martensitic transformation temperatures,enthalpy and magnetic properties are decreased.Mechanical properties of NiCoMnSn/Cu composities are greatly dependent on the processing parameters including the size of Cu tube and the rolling thickness. Their stress-strain behavior exhibit different characteristics from conventional alloys.