Microstructure and phase stability of C-doped AlCoCrFeNi2.1 eutectic high-entropy alloys at 600 °C

The AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) presents a promising balance between high strength and ductility, with its excellent mechanical properties maintained up to 600–700 °C. C doping has been shown to further enhance its strength. However, the phase stability of the alloy remains uncertain. This study evaluated the microstructure and phase stability of both the as-cast AlCoCrFeNi2.1 EHEA and its C-doped counterpart, (AlCoCrFeNi2.1)97C3, at 600 °C. After 20 days of annealing, the eutectic structure of the AlCoCrFeNi2.1 EHEA exhibited slight coarsening in localized areas without phase decomposition. In contrast, the C-doped alloy developed needle-like and granular precipitates within the BCC phase. •The microstructure and phase stability of AlCoCrFeNi2.1 EHEA at 600 ℃ are examined.•The stability of its C-doped variant, (AlCoCrFeNi2.1)97C3, is assessed.•Microstructure evolution, phase changes, and relevant mechanisms are identified.