Theoretical Calculation and Analysis of Coherent Interfacial Energy between B1-Type Carbides and FCC Iron Matrix

Abstract

The valence electron structures (VES) of unit cells of the FCC iron matrix (γ) and B1-type carbides (ξ) in γ-Fe-M-C alloy systems (M=Nb, Ti, and V) were calculated using the empirical electron theory of solids and molecules (EET). Based on the results, the coherent interfacial energy between B1-type carbides and FCC iron matrix in γ-Fe-M-C alloy system was calculated and analyzed by combining EET and the discrete lattice plane-nearest neighbor broken bond (DLP-NNBB) method with covalent bond energy. The results showed that the solid solution strengthening effect was produced by the solute phase boundary segregation of the alloy elements at the γ/ξ interface, which enhanced the covalent bond network. The Nb alloy system had the largest segregation effect in γ-Fe-M-C alloy system. Moreover, the γ/ξ interfacial energy varies with different alloy elements over the range of 0.4-1.3 J/m2, and the γ-Fe-Nb-C alloy system has the largest coherent interfacial energy.The proposed theoretical method is consistent with the theoretical values calculated using other models, as well as empirical values. This indicates that the method proposed in this work is feasible for providing theoretical analysis and guidance.