Laser welding of nickel-titanium (NiTi) shape memory alloys

Nickel-titanium (NiTi) shape memory alloys (SMAs) with outstanding shape memory and superelasticity effects are interesting candidates for a multitude of applications ranging from small-scale structures, such as microsensors and stents, to large-scale components used in aviation and automotive industries. After a mechanical deformation, SMAs can resume their initial shape which makes them an ideal candidate material to be used in smart components for various applications. A practical method for joining similar and dissimilar NiTi SMAs is laser welding. However, the thermal effect associated with the laser welding procedure influences the transformation temperature of the welded parts that will significantly impact their super elasticity and/or shape memory effect characteristics. This chapter deals with the microstructural, metallurgical, and mechanical investigations of the laser welding process as well as suggesting effective methods to improve the functionality of the welded parts of NiTi alloys.