Study of the effect of heat treatment on corrosion property of the AlxCoCrFeNi high-entropy alloys (x = 0.3, 0.7, and 1) prepared by spark plasma sintering

Abstract

The effect of spark plasma assisted heat treatment (SPHT) on the corrosion property of Al0.3CoCrFeNi, Al0.7CoCrFeNi, and AlCoCrFeNi HEAs is studied in this paper. The Tafel and EIS measurement is adopted to determine how the corrosion resistance varies before and after SPHT. The Al0.3CoCrFeNi and Al0.7CoCrFeNi HEAs show an enhancement in corrosion resistance after SPHT as their corrosion current density (icorr) decreases and polarization resistance. The SPHTed Al0.7CoCrFeNi HEA features the best corrosion resistance as it has the lowest icorr of 7.1 × 10−10 A/cm2 and the highest polarization resistance of 139.89 kΩ·cm2. Nevertheless, SPHT damages the corrosion resistance of the AlCoCrFeNi HEA. The phase transition of FCC-B2 and BCC-FCC is revealed to benefit the corrosion resistance but the precipitation of the σ phase is found to damage corrosion resistance after SPHT. Cr is proven to be the most corrosion-resistant content while Al and Ni contents are easy to be corroded. The different particle size of the transformed phase decides their disparate effects on corrosion resistance as the micro-sized Cr-enriched phase increases the corrosion resistance by effectively covering the corrosion surface but the nano-sized Cr-enriched phase decreases the corrosion resistance by reducing the Cr contents in the neighboring matrix.