Influence of Annealing Temperature on the Microstructure and Properties of Powder Metallurgy AlCoCrFeNi High‐Entropy Alloy

This study investigated the effects of annealing at 700–900°C on the microstructure and mechanical properties of powder metallurgy AlCoCrFeNi high‐entropy alloy. Annealing at 700°C preserved the single BCC phase, while annealing at 800°C induced phase transformation, forming a small amount of σ and FCC phases. Upon annealing at 900°C, the σ phase partially dissolved into the BCC matrix, the FCC phase content increased slightly. Additionally, annealing at 900°C induced lattice expansion in the alloy, thereby leading to an increase in the microstrain values. Annealing did not change the equiaxed grain morphology but modified intragranular microregions. Al–Ni‐rich dendritic areas increased and Cr‐rich interdendritic regions decreased. The annealing process does not effectively improve the relative density of the alloy. The hardness and wear resistance of the alloy exhibited a nonmonotonic trend—initially decreasing, then increasing to optimal values of 590.6 HV and 0.095 mm 3 ·(N·m) −1 , respectively, at 800°C, before finally decreasing again, with abrasive wear identified as the dominant mechanism throughout. The main strengthening mechanism after annealing was second‐phase (σ phase) strengthening. Appropriate annealing can tailor the alloy microstructure and optimize its hardness and wear resistance.