Composition-dependent brittleness and ductility of the multicomponent phase (Fe, Cr)23(C, B)6 in Fe–Cr–B–C alloys: First-principles calculations and modeling

Abstract

(Fe, Cr)23(C, B)6, as a strengthening phase in Fe–Cr–B–C alloys, has not been reported on the relationship between its properties and composition over the entire composition range. (Fe, Cr)23(C, B)6 tends to exhibit brittleness, which is difficult to regulate through traditional experiments. The mechanical properties of (Fe, Cr)23(C, B)6 phase in Fe–Cr–B–C alloy have been studied by first principles calculation. With the help of CALPHAD method, the distribution of elastic constant, modulus, hardness and fracture toughness in the whole component space was obtained, so that the suitable component with good wear resistance and strong toughness was obtained. The mechanical properties of (Fe, Cr)23(C, B)6 phase is better in the range of ∼0.4–0.6 at. % B and ∼0.5–0.7 at. % Cr. The mechanism of these differences is explained in terms of state density, bond length, population analysis and differential charge density, as the addition of boron and the increase in chromium content led to a significant increase in the formation of covalent bonds between metals and non-metals, in which these bonds play a decisive role. The combination of the first principles calculation and the CALPHAD model provides a feasible model for constructing the composition-property relationship of medium entropy compounds.