Abstract
Effects of oxygen on microstructure, shape recovery behavior and tensile properties were investigated for Ti-Ni shape memory alloy weldments. Gas tungsten arc (GTA) welding technique was applied for the alloy under controlled Ar-O2 welding atmospheres. The oxygen content in the weld metal increased with rising oxygen partial pressure and welding current. Many second phase particles were observed in the weld metal which had absorbed oxygen. The second phase was identified as Ti, Ni2O by transmission electron microscopy. Shape recovery behavior was measured for the temperature range of 283 to 372 K. The shape recovery stress of weldment at the 372 K gave equivalent value to that of the base material, however, As temperature of the weld metal decreased with increasing oxygen content. Tensile strength and elongation of the weldment decreased by welding and with increasing oxygen content.
