Microstructural evaluation and mechanical behaviour of dissimilar niti-stainless steel joints welded by micro gas tungsten arc welding

• Published in: Materials chemistry and physics 2019-02, Vol.224, p.137-147
• Main Authors: Oliveira, M.J.C., Melo, R.H.F., Maciel, T.M., de Araújo, C.J.
• Format: Article
• Language: English
• Subjects: Austenitic stainless steels; Chemical composition; Diamond pyramid hardness; Dissimilar metals; Dissimilar welding; Gas tungsten arc welding; Heat treating; Intermetallic compounds; Mechanical properties; Metal sheets; Metallurgy; Microstructure; Morphology; Nickel base alloys; Nickel compounds; Nickel titanides; NiTi; Organic chemistry; Post-weld heat treatment; Shape memory alloys; Stainless steel; Superalloys; Tensile tests; Titanium compounds; Weld metal; Welded joints
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2018.12.013

In this work, the microstructure and mechanical behaviour of dissimilar nickel-titanium (NiTi) shape memory alloy (SMA) and AISI 304 stainless steel (SS) thin sheets welded by micro gas tungsten arc welding (GTAW) using NiTi and Inconel 625 as filler metals were studied. The influence of a post-weld heat treatment was also elucidated. The obtained dissimilar NiTi-304SS joints were characterized by optical and scanning electronic microscopy, tensile tests and the Vickers hardness. After welding, the joints exhibited a heterogeneous weld zone due to the formation of intermetallic elements along with embrittlement of the weld metal. For non-heat treated joints, partial diluted zones with distinct morphology, chemical composition and hardness were formed. It was possible to increase the mechanical strength of the joint up to 286 MPa by using an intermediate layer of Inconel 625 at the junction between dissimilar metals and by applying heat treatment for stress relief. [Display omitted] •Dissimilar NiTi-AISI 304 joints were welded by micro GTAW.•The joints' mechanical behaviour is influenced by Inconel 625 use.•The M25IC welded joint presented a UTS of 286 MPa and elongation of 4.5%.