In situ structural characterization of laser welded NiTi shape memory alloys

Abstract

Preserving the shape memory effect (SME) and superelasticity (SE) in shape memory alloys (SMAs) after a joining process is of great importance. In this work Ni-rich NiTi SMAs were laser welded using a Nd:YAG laser in continuous mode. A detailed structural characterization was carried by means of X-ray diffraction (XRD). It was possible to observe the existence of a microstructural gradient from the base material (BM), which contained only austenite, through the heat affected zone (HAZ) and the fusion zone (FZ), where both zones contained austenite and martensite. The mechanical behavior under cyclic load/unload of the welded samples may be explained taking in consideration the structural information retrieved from the XRD analysis.