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arXiv · 2604.08770

Pressure-stabilized dual-BCC polymorphism in a rhenium-based high-entropy alloy

Raimundas Sereika·Andrew D. Pope·Hunter Kantelis·Caleb M. Knight·Kallol Chakrabarty·Yogesh K. Vohra
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Abstract

Accessing metastable structural states in high-entropy alloys offers a promising route to tailor material properties, yet the use of high pressure to engineer such states remains underexplored. Here, we report the pressure-driven synthesis of a unique metastable dual-BCC microstructure in a near-equimolar ReNbTiZrHf alloy. Starting from an ambient two-phase mixture of hexagonal (C14-derived) and body-centered cubic (BCC) phases, compression induces a selective, diffusionless transformation of the hexagonal constituent into a second, crystallographically distinct BCC polymorph, while the original BCC phase remains stable. Upon decompression, the pressure-induced BCC phase is kinetically trapped, yielding a dual-BCC state that is inaccessible via conventional thermal processing. The pressure-stabilized BCC polymorph is Re-enriched and inherits the exceptional stiffness of its hexagonal parent (bulk modulus ~290 GPa), creating a composite microstructure with pronounced elastic and mechanical contrast relative to the softer original BCC matrix (~180 GPa). These findings demonstrate that pressure can effectively navigate the flat free-energy landscapes of chemically complex alloys, establishing a robust pathway for polymorph engineering and metastable phase design in refractory HEAs.

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Raimundas Sereika, Andrew D. Pope, Hunter Kantelis, Caleb M. Knight, Kallol Chakrabarty, Yogesh K. Vohra. 2026-04-09. Pressure-stabilized dual-BCC polymorphism in a rhenium-based high-entropy alloy. https://doi.org/10.1103/8smt-nygp

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