Tensile properties of flanged NiTi pin fabricated by laser rod end melting and immediate flange processing

To achieve a joining of Nickel-Titanium alloys to components that are resistant to heat, stress and corrosion, a process chain called laser rod end melting with immediate flange processing has been proved as a promising alternative to conventional joining and laser welding. A laser beam melts the end of a NiTi wire to a melt droplet, immediately reshaped to a flange, connected to the rest wire as a flanged pin. Considering that tensile properties of laser-welded NiTi alloys can be improved by appropriate process parameters and post-weld heat treatment, this approach has potential to be applied on the flanged pins, which was systematically investigated in this study. Despite the earlier fracture of the flanged pin than the base material, the laser process had a negligible influence on the tensile behavior of the pin under the different parameter combinations. However, the relative position of the pin in the flange had to be carefully concerned during the fabrication. Except the laser power, laser-scan speed and delay time, the flange height led to an apparent change of the tensile strength. Besides the laser process, the post heat treatment improved the tensile strength of the flanged pin. It modified not only the hardness distribution in the flanged pin but also the tensile behavior under loading. This study revealed the mechanism determining the tensile behavior of the flanged pin for superelastic application.