Effect of Welding Speed on Phase Transformation and Mechanical Properties of Laser-Welded NiTi Shape Memory Alloy

Abstract

In this research work, the butt joint of 0.5 mm sheet thickness NiTi–NiTi shape memory alloy (SMA) is welded using a 2-kW fibre laser machine. The effect of scanning speed on phase transformation and mechanical properties was investigated. The DSC analysis of base material and welded joints results less variations in austenite and martensite temperature phase transformation because during laser welding process there was not the presence of new phases in the weld zone (WZ) such as Ni3Ti or Ti3Ni4 because of which the chemical composition of Ni and Ti was not altered. This confirms the functionality of the material is preserved even after the welding process. The hardness analysis results that the increase of welding speed yields low heat input in weld metal which causes the increase of hardness values with an increase in welding speed. Microscopic investigations revealed the welded samples have negligible heat-affected zone. The flexibility in joining and retaining NiTi SMA's pseudoelastic characteristics through laser welding finds extensive applications as orthodontic wires, adaptive nozzles and seismic application. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.