Study on the effect of double-sided laser welding of NiTi shape memory alloys wire

Abstract

NiTi shape memory alloys (SMAs) have essential applications in intelligent system design and development due to their flexibility in integration through welding or joining techniques. In this work, both single-sided laser welding and doublesided laser welding processes were used for the welding of NiTi SMAs wire. Then, the macro-morphology, microstructure, phase transformation behavior, mechanical performance, fracture surface characteristics, and cyclic tensile properties of the samples obtained under the two welding processes were investigated. The results showed that there were dendrites and equiaxed grains in the fusion zone (FZ) of the double-sided welding samples, without obvious welding defects. Although the phase transformation temperature in the FZ of the samples obtained by the two processes was significantly increased, the temperature rise of the double-sided welded samples was relatively lower. The tensile strength and elongation of the double-sided welded samples were higher, and all the samples had a ductile fracture. The residual strains of the 1st to 15th cycle tests revealed that the double-sided welded samples exhibited significant improvements in functional fatigue properties compared to the residual strains of the single-sided welded samples. The improved performance of laser-welded NiTi SMAs obtained from this work could benefit these alloys for welding integration applications in smart system design and production.