Control of Interfacial Reaction in the Dissimilar Joints Using Shape Memory Alloy Thin Wires for the Fabrication of Medical Devices Inserted in Blood Vessel

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In order to investigate the applicability of laser micro welding to the fabrication of medical devices, Ti-Ni based shape memory alloy biomaterials wires were micro spot melted by using YAG laser.By the optimization of laser conditions such as laser power or pulse duration, sound spot melted wires free from any defects were prepared and the width of the melted metal was reduced to about 0.2mm for the 0.15mm diameter wires. Compared with the 5U5304 wires, melting of shape memory alloy wires needed more precise control of laser conditions although it needed smaller power input.Melted metal exhibited a rapidly quenched microstructure. The spot melted wires showed 70% of tensile strength and almost the same super-elastic behavior compared with base materials. Besides, it was confirmed by immersion test and by measurement of anodic polarization curve that NT-E4 wires still retain a sound corrosion resistance in a quasi biological environment by laser spot melting.Crosswise or parallel joints was also successfully prepared by laser spot welding of wires, suggesting the laser micro welding is applicable to the fabrication of biomedical devices.