Research On Melting And Pushing Technology With Plasma Welding In NiTi Shape Memory Alloy

With the high energy plasma beam melt and push welding method, the weldingquality of the NiTi shape memory alloy wire is studied. The research is divided in thefollowing parts:The joint of the NiTi SMA wire plasma beam welding is researched. Simulatingthe HAZ, as the Ni3Ti and Ti₂Ni was existed, the tensile strength and shape memoryproperties of the simulated alloy is lower than original alloy.To keep the shape memory properties of the SMA wire, it has to remove thewelding line and reduce the width of the HAZ.Using the plasma beam melt and push welding method weld the SMA wire, thehigh energy plasma beam melt and push welding equipment system is partly designedand built. The parameters' influence of the welding joint is analyzed, and therelationship between parameters and the proper range of parameters are confirmed.The performance and microcosmic organization of the welding joints are analyzedafter heat treatment process. The characteristic and difference of the welding joint arediscussed and compared, such as phase, microstructure, tensile strength and ShapeMemory properties and Pseudo-Elasticity.With the heat treatment of 500℃×1h, the result shows that the tensile strengthof joints is 89ï¼…of the original alloy, and Shape Memory properties is 97.3ï¼…of theoriginal alloy.