The effect of laser welds on the thermomechanical fatigue of niti shape memory alloys

Welding and joining of NiTi based shape memory alloys (SMAs) is essential for their integration into an increasing variety of applications. The titanium elemental constituent significantly complicates joining, especially with dissimilar materials where brittle intermetallics are often formed. There have been a relatively small number of investigations of the welding of NiTi in similar and in dissimilar joints. Of these studies, a few have investigated the effect of similar welded joints on the pseudoelastic fatigue of NiTi. To the author's knowledge there are no investigations on the effect of joining on the fatigue of thermally actuated NiTi. The current work investigates the physical, thermomechanical fatigue and shape memory properties of welded shape memory wires. The welded NiTi wires successfully achieved 86% of the base metal ultimate tensile strength. The cycle lives of the welded wires that underwent thermomechanical fatigue were significantly less than the base metal.