Microstructures and properties of capacitor discharge welded joint of TiNi shape memory alloy and stainless steel

Microstructures and properties of capacitor discharge welded (CDW) joint of TiNi shape memory alloy (SMA) and stainless steel (SS) were studied. The fracture characteristics of the joint were analyzed by means of scanning electron microscope (SEM). Microstructures of the joint were examined by means of optical microscope and SEM. The results showed that the tensile strength of the inhomogeneous joint (TiNi-SS joint) was low and the joint was brittle. Because TiNi SMA and SS melted, a brittle as-cast structure and compound were formed in the weld. The tensile strength and the shape memory effect (SME) of TiNi-SS joint were strongly influenced by the changes of composition and structure of the weld. Measures should be taken to prevent defects from forming and extruding excessive molten metal in the weld for improving the properties of TiNi-SS joint.