Effect of laser welding parameters on the austenite and martensite phase fractions of NiTi

TitleEffect of laser welding parameters on the austenite and martensite phase fractions of NiTi
Publication TypeJournal Article
Year of Publication2016
AuthorsOliveira JP, Braz Fernandes FM, Miranda RM, Schell N, Ocaña JL
JournalMaterials Characterization
KeywordsAustenite, Austenitic transformations, Compositional variation, Functional properties, Laser beam welding, Laser welding parameters, Local transformations, Martensite, NiTi shape memory alloys, Phase fractions, Phase transitions, Rietveld refinement, Shape memory alloys(SMA), Shape memory effect, Synchrotron radiation, Synchrotron x ray diffraction, Synchrotrons, Welding, X ray diffraction

Although laser welding is probably the most used joining technique for NiTi shape memory alloys there is still a lack of understanding about the effects of laser welding parameters on the microstructural induced changes: in both the heat affected and fusion zones martensite may be present, while the base material is fully austenitic. Synchrotron X-ray diffraction was used for fine probing laser welded NiTi joints. Through Rietveld refinement the martensite and austenite phase fractions were determined and it was observed that the martensite content increases towards the weld centreline. This is related to a change of the local transformation temperatures on these regions, which occurs due to compositional variation in those regions. The martensite phase fraction in the thermally affected regions may have significant implications on functional properties on these joints. © 2016 Elsevier Inc.