Microstructure evolution and mechanical properties of plasma sprayed AlCoCrFeNi2.1 eutectic high-entropy alloy coatings

In this work, AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) coatings were prepared by atmospheric plasma spraying (APS) and the evolution of the eutectic structure during annealing of 600, 800 and 1000 °C and the correlation with mechanical properties was revealed. Results showed that the sprayed EHEA consisted of BCC (AlNi) + FCC (FeCoNi) bi-phase as nanoscale eutectic stripes. Annealing changed BCC to B2 and FCC due to the enrichment and depletion of Al and the optimal hardness was achieved after 600 °C annealing attributed to the formation of hard phase B2 and the narrowing of arranged stripes; Due to expansion of plastic FCC, the optimal elasticity was obtained after annealing at 1000 °C, which provides the basis for achieving the best combination of mechanical performances by heat treatment.