Phase evolution and thermal stability of AlCoCrFe high entropy alloy with carbon as unsolicited addition from milling media

Phase evolution and thermal stability of AlCoCrFe high entropy alloy with unsolicited carbon from the milling media were investigated. A single BCC phase was evolved during mechanical alloying, and BCC/B2 phases with Cr-rich M23C6 carbide was observed after spark plasma sintering. Unsolicited carbon during milling has led to the formation of M23C6 secondary phase after sintering. The alloy exhibits a very high hardness of 1050 ± 20 HV1 and excellent phase stability. The hardness reduction after annealing at 900 °C for 600 h is less than 10%, indicating excellent resistance to anneal softening.