Semi-Empirical Parameterization of Interatomic Interactions and Kinetics of the Atomic Ordering in Ni-Fe-C Permalloys and Elinvars

Within the framework of the lattice-statics and static fluctuation-wave methods, the available energies of strain-induced interaction of interstitial-interstitial, interstitial-substitutional and substitutional-substitutional impurity atomic pairs are collected and analysed for f.c.c.-(Ni,Fe)-C solutions allowing for discrete atomic structure of the host-crystal lattice. The lattice spacings, elasticity moduli and/or quasi-elastic force parameters of the host-crystal lattice, and concentration coefficients of the dilatation of solid-solution lattice due to the respective solutes are selected as the input numerical experimental data used. The above-mentioned interaction energies prove to have non-monotonically decreasing and anisotropic dependences on discrete interatomic radius-vector, and themselves are strong and long-range. In all f.c.c.-(Ni,Fe)-base solutions, there is strain-induced attraction in many coordination shells. In general, the strain-induced interaction between impurity atoms in gamma-Fe is weaker than in alpha-Ni. The verification of applicability of the approximation of strain-induced interaction of impurities for f.c.c.-(Ni,Fe)-C alloys showed that it must be supplemented with additional short-range (electrochemical) repulsion in the first coordination shell. Nevertheless, in any case, the strain-induced interaction of impurity atoms must be taken into account for analysis of structure and properties of f.c.c.-(Ni,Fe)-base solutions. The Monte Carlo simulation procedures applied for constitution of a nanoscale Fe-C-austenite crystallite and based on analysis of the dependences of numbers of the different atomic configurations on C-C interatomic-interaction energies reveal correlation between the potential energy of such a modeling system and the numbers of iterations as well as Monte Carlo steps for the approach to constrained equilibrium.