Microstructural evolution and phase stability in Nb-containing interstitial Fe-Mn-Co-Cr-C high-entropy alloys

The influence of Nb on phase stability and microstructural evolution in an interstitial Fe-Mn-Co-Cr-C high-entropy alloy was investigated using in-situ synchrotron X-ray diffraction (SXRD) during laser melting. Scheil-Gulliver simulations predict the formation of σ and γ-f.c.c. phases in all three alloys, along with NbC in Nb-containing compositions. SXRD confirmed the presence of most predicted phases, but the σ phase was absent. Nb promotes crystallite refinement and increases dislocation density, though excessive additions reduce refinement efficiency due to solubility limits and secondary phase formation. Furthermore, Nb addition also enhances ε-h.c.p. phase formation by reducing stacking fault energy through NbC-induced carbon depletion. Analysis of intensity peak evolution reveals that Nb alters preferred grain orientations, reducing {111}γ intensity while enhancing {220}γ, leading to a more isotropic grain distribution. Overall, Nb plays a key role in phase selection, microstructure refinement, and preferred orientation evolution, allowing the tailored microstructure of high-entropy alloys via rapid solidification.

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Funding Information: I. A. B. Moura acknowledges Fundação para a Ciência e Tecnologia (FCT – MCTES) for funding the PhD grant (2021.08034.BD). JS and JPO acknowledge the funding by national funds from FCT - Fundação para a Ciência e a Tecnologia, I.P., in the scope of the project's LA/P/0037/2020, UIDP/50025/2020 and UIDB/50025/2020 of the Associate Laboratory Institute of Nanostructures, Nanomodelling and Nanofabrication – i3N. P.F.R. acknowledges funding by FCT – Fundação para a Ciência e a Tecnologia, under projects UID/00285 - Centre for Mechanical Engineering, Materials and Processes, LA/P/0112/2020 and CAPES - Novação - 99999.011943/2013–00. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science user facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02–06CH11357. The present study was developed in the scope of the Project “Agenda ILLIANCE” [C644919832–00000035 | Project n° 46], financed by PRR – Plano de Recuperação e Resiliência under the Next Generation EU from the European Union. Publisher Copyright: © 2025 The Author(s)

Palavras-chave

Interstitial high entropy alloys Multicomponent solidification Rapid solidification Solidification microstructure Synchrotron radiation General Materials Science