Microstructural regulation and specific strength optimization of lightweight porous eutectic high-entropy alloys by thermal treatment

Porous metallic materials, offering a unique combination of lightweight characteristics and mechanical load-bearing capability, have demonstrated great potential in aerospace, energy conversion, and multifunctional structural applications. In this study, a triple-phase eutectic high-entropy alloy (EHEA) with the composition Co₁₈Cr₁₈Fe₁₈Ni₂₆Al₁₀Nb₁₀ was employed as the precursor for fabricating stable porous structures via a chemical dealloying process. Prior to dealloying, the as-cast alloy was subjected to annealing at 750 °C, 900 °C, and 1050 °C to induce microstructural evolution with varying phase scales and distributions, thereby influencing subsequent pore formation behavior. A comprehensive characterization was conducted to evaluate the effects of annealing on microstructure evolution, dealloying depth, ligament size, and room-temperature compressive performance. Among the tested conditions, the sample annealed at 900 °C exhibited an optimized combination of structural integrity and mechanical performance after dealloying, achieving a high specific strength of 177.25 kN·m/kg while maintaining a low density of 5.65 g/cm³. This work establishes an effective strategy for tuning porous architecture and mechanical properties through thermal treatment, providing new insights and experimental evidence for the development of high-performance porous high-entropy alloys.