Precipitation Behavior of Carbide and its Effect on the Mechanical Properties of a Novel Fe60Co10Cr10Ni10Mo5V5 Medium-Entropy Alloy

Carbide precipitates are effective for improving the strength and stability of high-entropy alloys. In this work, novel-designed Fe60Co10Cr10Ni10Mo5V5 medium-entropy alloys (MEAs) containing 1 wt.% carbon were prepared by vacuum arc melting followed by solid solution treatment and aging. The effects of aging on the microstructure and mechanical properties of the MEAs were investigated. The results showed that the microstructure of the solution-treated alloy was comprised of the face-centered cubic (FCC) matrix, coarse M2C/MC carbides, and tiny fine undissolved MC precipitates distributed on the grain boundaries and inside the grains. A high number density of cube-shaped MC precipitates, with an approximate mean size of 24 nm precipitate within the FCC matrix in the case of aging at 800°C for 2 h, contribute to the highest hardness and tensile strength of the sample without sacrificing its elongation. With increasing aging temperature and time, the size of the MC precipitates increased while their volume fraction decreased. The strengthening effect can be attributed to the combination of the precipitation strengthening and solid solution strengthening.