Successful integration of NiTi shape memory alloys (SMAs) into a growing range of applications relies on the development of suitable welding and joining techniques. Adoption of welded NiTi SMAs in actuators based on the functional properties presented by these alloys requires the characterization of the functional fatigue of the welded joints. The functional fatigue behavior of NiTi-Cu dissimilar welded joints was investigated in this work. The influence of Nd:YAG laser welding parameters on the microstructure and joint break force were also analyzed. The superelasticity (SE) of the dissimilar joints was analyzed by load/unload cycling tests and the influence of maximum applied load was assessed and compared with the NiTi base material. The effect of the number of cycles on the irrecoverable strain, which develops during the cycling tests, was also investigated. The results show that the stress induced transformation between austenite and martensite is gradually restricted by the plastic deformation generated during the cyclic deformation: the higher the applied load the higher the irrecoverable strain presented by the welded joints. Additionally, the accumulated irrecoverable strain of the NiTi-Cu dissimilar welded specimens accumulates progressively during mechanical cycling.
- Mechanical fatigue
- NiTi shape memory alloy