NiTi shape memory alloys are considered one the most important metallic materials in modern medical technology. In addition to their unique properties, they are characterized by excellent biocompatibility, thus making them perfectly suitable for both implants and surgical instruments. However, these advantages are accompanied by comparatively high material costs and poor workability. To improve the cost-effectiveness and manufacturing conditions of new products, particularly in the medical sector, there is rising interest in the joining of structural and functional materials, e.g., by dissimilar welding, that ultimately enables the fabrication of functionally-graded components. Titanium is a promising material for dissimilar joints with NiTi, as it also features exceptional biocompatibility and can consequently be used for similar applications. However, dissimilar fusion welding of NiTi to titanium is associated with the formation of extremely brittle intermetallic compounds, which severely limit the weldability.

In the present study, pure niobium is applied as a filler material in a NiTi/Nb/Ti butt-joint configuration and welded using a pulsed laser beam source. Variations of process parameters, e.g., pulse duration, are applied and subsequently correlated with the microstructural evolution in the weld metal. It is demonstrated that the intermixing of niobium significantly improves the chemical compatibility and, thus, the weldability compared to joints without filler materials. Furthermore, excellent mechanical properties can be achieved through the use of optimized parameters, allowing the welded parts to fully utilize the superelastic stress plateau of NiTi. As niobium is also biocompatible, the results offer the potential to be adopted in future medical technology applications.