Interaction and arrangement of nitrogen and carbon atoms in fcc γ-iron

Abstract

A Mössbauer effect measurement has been done for Fe−N, Fe−Al−C and Fe−Ni−C austenite in order to study the interaction between the interstitial atoms and their distribution among the octahedral sites of the fcc lattice, together with the influence of Al and Ni atoms. The spectra for Fe−N and Fe−Al−C austenite are decomposed into three components; one singlet γ₀, and two sets of doublet γ₁ and γ₂, with different quadrupole splittings, while no γ₂ component is found in the spectrum for Fe−Ni−C. By analyzing the component ratio in each spectrum, it is concluded that, in Fe−N and Fe−Al−C, the interaction between 2nd nearest neighboring nitrogen or carbon atoms is attractive, and is repulsive between 1st nearest for Fe−N, and that the interaction between 2nd nearest atoms is repulsive for Fe−Ni−C. By measuring the spectra of Fe−Ni−C in magnetic field, the sign of EFG for most of the γ₁ component is determined to be negative.