Abstract
Effects of nitrogen on microstructure, shape recovery behavior and tensile property of Ti-Ni alloy weldments were investigated. A near-equiatomic Ti-Ni shape memory alloy was welded by a gas tungsten arc (GTA) welding technique under Ar-N2 welding atmosphere. The nitrogen absorbed into the weld metal increased with rising nitrogen partial pressure and welding current. Second phase particles were observed in the weld metal containing nitrogen. The second phase was identified as TiN by transmission electron microscopy. The shape recovery stress of the weldment was equivalent to that of the base material. As temperature of the weld metal decreased with increasing nitrogen content. Tensile strength of the alloy decreased by welding process, and the further reduction was observed for the weld metal absorbed nitrogen. Elongation also decreased by welding and rising nitrogen content.
