In this work, laser powder bed fusion (LPBF) was used to fabricate the equimolar AlCoCrFeNi high-entropy alloy. After heat treatment 4 hours at the temperature of 600 °C, 800 °C, 1000 °C, and 1200 °C, the phase composition, microstructure, residual stress, microhardness, and electrochemical corrosion properties in 3.5 wt pct NaCl solution were studied. Results indicate that the HEA was composed of mixed slender columnar and equiaxed crystals with a single BCC phase. After heat treatment over 800 °C, Al–Ni and Cr–Fe elements were, respectively, enriched, while the BCC single-phase transformed into FCC + BCC dual phases. The hardness and residual tensile stress exhibited fluctuations as the temperature increased. Electrochemical tests and elemental analysis showed that phase transition results in the corrosion-type transition from random pitting to Al–Ni phase-preferred corrosion. The higher heat treatment temperature, the coarser FCC microstructure, and the surface passivation film also changed. More Cr oxidation/hydroxide was generated on the surface, which made the passivation film denser and thicker, effectively suppressing selective corrosion to continuous expansion. This work indicated that 1200 °C heat treatment significantly enhanced the corrosion resistance of LPBF-prepared AlCoCrFeNi HEA.
Zhang et al. (Sat,) studied this question.