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Abstract:
Equiatomic AlCoCrFeNi high-entropy alloy (HEA) and its rhenium-modified variant (AlCoCrFeNi–1 at% Re) were synthesized via mechanical alloying followed by hot pressing. This study demonstrates that minor, classical alloying with only 1 at% Re significantly enhances mechanical and thermal stability without altering the base processing route. Both alloys exhibited a dual-phase FCC–BCC structure with M₂₃C₆ carbides. Rhenium promoted Cr–Re solid solution formation during milling, refined the post-sintering microstructure, improved densification, and modified lattice parameters. The Re-containing alloy showed nearly a threefold increase in flexural strength at room temperature and moderate improvements in tensile strength at room and elevated temperatures (750–900 °C). Dilatometry and post-deformation XRD analyses revealed temperature-induced phase evolution. The Re-modified alloy exhibited smoother thermal expansion behavior and improved high-temperature stability. The principal advantage of this investigation lies in demonstrating that a minor Re addition effectively enhances the strength and microstructural stability of mechanically alloyed and hot-pressed HEAs without complex processing modifications.

Keywords:
Mechanical alloying, Rhenium, High-entropy alloys, High-temperature tests, Hot-pressing