Abstract
A comprehensive computational study of elastic properties of cementite (Fe3C) and its alloyed counterparts (M3C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr2FeC and CrFe2C) having the crystal structure of Fe3C is carried out employing electronic density-functional theory (DFT), all-electron PAW pseudopotentials and the generalized gradient approximation for the exchange-correlation energy (GGA). Specifically, as a part of our systematic study of cohesive properties of solids and in the spirit of materials genome, following properties are calculated: (i) single-crystal elastic constants, Cij, of above M3Cs; (ii) anisotropies of bulk, Young’s and shear moduli, and Poisson’s ratio based on calculated Cijs, demonstrating their extreme anisotropies; (iii) isotropic (polycrystalline) elastic moduli (bulk, shear, Young’s moduli and Poisson’s ratio) of M3Cs by homogenization of calculated Cijs; and (iv) acoustic Debye temperature, θD, of M3Cs based on calculated Cijs. We provide a critical appraisal of available data of polycrystalline elastic properties of alloyed cementite. Calculated single crystal properties may be incorporated in anisotropic constitutive models to develop and test microstructure-processing-property-performance links in multi-phase materials where cementite is a constituent phase.
Highlights
Cementite (Fe3C) is a metastable phase in the binary Fe-C system
A comprehensive computational study of elastic properties of cementite (Fe3C) and its alloyed counterparts (M3C (M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr2FeC and CrFe2C) having the crystal structure of Fe3C is carried out employing electronic density-functional theory (DFT), all-electron projector-augmented wave (PAW) pseudopotentials and the generalized gradient approximation for the exchangecorrelation energy (GGA)
Equation of state (EOS) of binary of M3C The equation of state (EOS) parameters of M3C have been summarized in a recent publication.[49]
Summary
Cementite (Fe3C) is a metastable phase in the binary Fe-C system. Its alloyed counterparts (here, represented as M3C with M = Al, Co, Cr, Cu, Fe, Hf, Mn, Mo, Nb, Ni, Si, Ta, Ti, V, W, Zr, Cr2FeC and CrFe2C), though unstable or metastable, is ubiquitous in low-, medium- and high-carbon steels. It is well known that the morphology and kinetics of cementite precipitates have a tremendous influence on the mechanical properties of steels. These factors have been manipulated by adding one or more alloying elements in steels to obtain desired microstructures, and properties. The precipitation of cementite can significantly alter the subsequent precipitation of more stable carbides.[1,2,3,4] Besides structural steels, thermo-physical properties of iron carbides (including cementite) have received considerable attention as they are important constituents in earth’s core.[5,6,7]
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