Micro-Resistance Spot Welding of 55.8wt% Ni-Ti Crossed Wires

Nitinol alloys are an excellent material for various applications not only because they exhibit high strength and high ductility but also because of their pseudoelasticity, shape memory, and biocompatible properties. Currently, Nitinol alloys are being used extensively in medical device applications. As demand for more sophisticated medical equipments grow, alternate processing methods are required. Welding is a key fabrication process used in the manufacture of medical devices. However, Nitinol welding is still not well understood and further research is required before its full potential can be realized in practical applications. The current study details the mechanical properties of micro-resistance spot welding (MRSW) of Nitinol crossed wires. Joint performance was tested using a micro-tensile tester, expressed in joint breaking force and also by micro-hardness tests. Results showed the joint breaking force increased with increasing peak current. Optical microscopy coupled with micro-hardness results showed the grain growth and recrystallization in the weld metal induced local softening.