Microstructure evolution and mechanical properties in a gas tungsten arc welded Fe42Mn28Co10Cr15Si5 metastable high entropy alloy

Shen, Jiajia; Agrawal, Priyanka; Rodrigues, Tiago A.; Lopes, J. G.; Schell, N.; He, Jingjing; Zeng, Zhi; Mishra, Rajiv S.; Oliveira, J. P.

http://hdl.handle.net/10362/154392

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Weldability studies on high entropy alloys are still relatively scarce, delaying the deployment of these materials into real-life applications. Thus, there is an urgent need for in-depth studies of the weldability of these novel advanced engineering alloys. In the current work, an as-cast Fe42Mn28Co10Cr15Si5 metastable high entropy alloy was welded for the first time using gas tungsten arc welding. The weld thermal cycle effect on the microstructure evolution over the welded joint was examined using electron microscopy in combination with electron backscatter diffraction, synchrotron X-ray diffraction analysis, and thermodynamic calculations. Furthermore, tensile testing and hardness mapping were correlated with the microstructure evolution. The microstructure evolution across the joint is unveiled, including the origin of the ε-h.c.p. phase at different locations of the material. Different strengthening effects measured throughout the joint are associated with the weld thermal cycle and resulting microstructure. A synergistic effect of smaller grain size of the ε-h.c.p. phase in the fusion zone, overturns the reduced volume fraction of this phase, increasing the local strength of the material. Moreover, the brittle nanosized σ phase was also found to play a critical role in the joints’ premature failure during mechanical testing.

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Funding Information: JS, JGL and JPO acknowledge Fundação para a Ciência e a Tecnologia (FCT - MCTES) for its financial support via the project UID/00667/2020 (UNIDEMI). JS acknowledges the China Scholarship Council for funding the Ph.D. grant (CSC NO. 201808320394). The authors acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Beamtime was allocated for proposal I-20220492 EC. Publisher Copyright: © 2023 The Authors

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FeMnCoCrSi Gas tungsten arc welding Mechanical testing Metastable high entropy alloys Synchrotron X-ray diffraction Thermodynamic calculations General Materials Science Condensed Matter Physics Mechanics of Materials Mechanical Engineering