Microstructure characterization of Friction Stir Spot Welded TRIP steel

Publication: Research - peer-reviewConference article – Annual report year: 2012

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Transformation Induced Plasticity (TRIP) steels have not yet been successfully joined by any welding technique. It is desirable to search for a suitable welding technique that opens up for full usability of TRIP steels. In this study, the potential of joining TRIP steel with Friction Stir Spot Welding (FSSW) is investigated. The aim of the study is to investigate whether acceptable welds can be produced, and additionally, to obtain an understanding of the microstructural changes during welding. The microstructure was investigated with a combination of microscopical techniques with the aim of identifying the transformations occurring during welding. Reflected light microscopy, scanning electron microscopy, and electron backscatter diffraction were among the methods applied for detailed investigations. The microstructure adjacent to the welds can generally be subdivided in two thermo-mechanically affected zones (TMAZ), and two heat-affected zones (HAZ). The dual behavior of the microstructure in the zones is related to the two transition temperatures in steel: A1 and A3. In parts of the TMAZ the microstructure contains ultra fine-grained ferrite. This finding parallels the observation in thermo-mechanically processed steels, where severe deformation at elevated temperatures is used to produce ultra fine-grained microstructures. Several possible transformation mechanisms could in principle explain the development of ultra fine-grained ferrite, e.g. dynamic recrystallization, strain-induced ferrite transformation and dynamic recovery. © (2012) Trans Tech Publications, Switzerland.
Original languageEnglish
JournalAdvanced Materials Research
Issue number275-280
Pages (from-to)275-280
StatePublished - 2012
Event7th International Conference on Processing and Manufacturing of Advanced Materials : THERMEC 2011 Supplement - Quebec City, QC


Conference7th International Conference on Processing and Manufacturing of Advanced Materials : THERMEC 2011 Supplement
CityQuebec City, QC
Period01/01/2011 → …
CitationsWeb of Science® Times Cited: No match on DOI


  • Microstructure characterization, Scanning electron microscopy, Electron backscatter diffraction, Reflective light microscopy, Friction stir spot welding, TRIP steel
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