Microstructure evolution and local strengthening mechanisms in CoCrFeMnNi high entropy alloy joints reinforced with Inconel 625

In the fusion-based welding processes, filler materials are commonly used to adjust and improve the composition of the fusion zone with the aim of optimizing both microstructure and mechanical properties. However, in the field of welding high entropy alloys, the influence of different filler materials on the microstructure and mechanical response is still scarce, owing to the yet incipient usage of welding technologies for these novel, advanced engineering alloys. To bridge this knowledge gap, Inconel 625 filler wire was used during gas metal arc welding of the well-known CoCrFeMnNi high entropy alloy. To systematically analyze the microstructure evolution and mechanical properties of the welded joints, multiscale characterization techniques were employed. It is shown that the different regions of the welded joint possess distinct microstructural features due to the weld thermal cycle, which is further compounded in the fusion zone by the introduction of the filler material. The use of Inconel 625 filler promotes a solid solution strengthening effect in the fusion zone and became the main contributor to the yield strength of this region (302 MPa (via solid solution strengthening) vs 478 MPa (yield stress from tensile experiments). Since Hall-Petch strengthening is predominant in both base material and heat affected zone, but not on the fusion zone due to the large grain structure that developed, the addition of Inconel 625 filler demonstrates to be a feasible approach to increase the typically low fusion zone strength. By coupling microstructural characterization with mechanical property analysis, aided by the calculation of the strengthening mechanisms, we unveil processing, microstructure, property relationships, providing a broader basis for the widespread application of gas metal arc welding for high entropy alloys.

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Funding Information: JS and JPO acknowledge Fundação para a Ciência e a Tecnologia (FCT - MCTES) for its financial support via the project UID/00667/2020 (UNIDEMI). JS and JPO acknowledges the funding of CENIMAT/i3N by national funds through the FCT-Fundação para a Ciência e a Tecnologia, I.P., within the scope of LA/P/0037/2020, UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication – i3N. JS acknowledges the China Scholarship Council for funding the Ph.D. grant (CSC NO. 201808320394). This work was supported by the National Research Foundation of Korea (NRF) with a grant funded by the Korea government (MSIP) (NRF-2021R1A2C3006662). 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-20210899 EC. The research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. Publisher Copyright: © 2025 The Authors

Palavras-chave

CoCrFeMnNi high entropy alloy Digital image correlation Gas metal arc welding Inconel 625 Mechanical testing Strengthening mechanisms Synchrotron X-ray diffraction Thermodynamic calculations General Materials Science Condensed Matter Physics Mechanics of Materials Mechanical Engineering