Interstitial carbide synergistically strengthening high-entropy alloy CoCrFeNiV0.5Cx

Abstract

A series of high-entropy alloy CoCrFeNiV0.5Cx (x = 0.01, 0.02, 0.03 and 0.04) with low C content was fabricated. The alloys were hot rolled, homogenized, cold rolled and annealed for treatment processes. The structure and mechanical properties of the alloy were studied. The formation process of different interstitial carbides and their role in the alloy were discussed. In the original state, these alloys all exhibit single-phase FCC structure, after annealing at different temperatures, a large number of M7C3-type interstitial carbides are produced at temperatures of 700 °C and above. The yield strengths (σy) of CoCrFeNiV0.5C0.02 and CoCrFeNiV0.5C0.03 alloys annealed at 700 °C are 1339.7 MPa and 1264.6 MPa, respectively, with excellent performance. In the transmission analysis of CoCrFeNiV0.5C0.02, a new type of interstitial carbides, namely non-stoichiometric interstitial carbides MxCy, were found. This interstitial carbide promotes the formation of fractured dimples during tensile fracture, and increases the alloy's plasticity without losing strength. The addition of interstitial carbon atoms in the FCC matrix high-entropy alloy synergistic effects of forming two different carbides, and the improved performance of the alloy were investigated. A variety of different carbides are introduced into the alloy through post-cold-rolling heat treatment to further strengthen the alloy, which provides new ideas for the practicality of high-entropy alloys.