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The energies of strain-induced (elastic) interaction of pairs of substitutional atoms and host atom displacements around a substitutional atom are calculated for Al, Ag, Au, Cu, Ni, Pd, Cr, u-Fe, Mo, Nb, Ta, V, and W taking into account the discrete atomic structure of the host lattice. The elastic constants, Born-von Karman constants of the host lattice, and coefficients of the concentration expansion of the solid solution lattice due to substitutional atoms are the numerical parameters used. A computer calculation is carried out in the general form appropriate for any substitutional atoms in these metals. The energies of strain-induced interaction of substitutional atoms are of the same order as the 'chemical' interaction energy and should be taken into account during computer simulation of structure and properties of the substitutional solid solutions.

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~TRODUCTIONThe scientific school of G. V. Kurdyumov has investigated the problem of martensite transformations from a very wide viewpoint. One direction of the research is the study of interatomic interactions and their effect on the structure of the phases and the thermodynamics of the phase transformations [I]. This direction has been developed by A. G. . He has created a theory of strain (elastic, due to deformation of the crystal lattice around the dissolved atoms) interaction within the framework of the model of a discrete crystal lattice. By now the energy of paired strain interaction has been computed for many metals with b.c.c. [4][5][6][7][8][9][10][11][12], f.c.c. [8-10, 13, 14], and hexagonal [15] lattices. The elastic (strain) interaction of carbon and nitrogen atoms in ferrite was considered in [2,4]. The energy of elastic (strain) interaction of carbon and nitrogen atoms in austenite was computed in [16] using a simplified form of the dynamic matrix of the f.c.c, crystal lattice of ),-Fe and only some of the available experimental data on the phonon spectrum.Information on the interaction between carbon atoms in austenite is traditionally obtained from the concentration dependence of the thermodynamic activity of carbon a c measured at various temperatures [17][18][19][20][21]. There are reliable experimental data on the activity of carbon [22 -28]. However, they have been analyzed within the framework of the model of carbon-carbon atomic interaction in the first or first two coordination spheres. At the same time, it is well known that elastic (strain) interaction in interstitial solid solutions is long-range [2, 3] and the interaction distance substantially exceeds two coordination spheres. Despite the limitations of the model of paired interatomic interaction it is useful for solving many problems, in particular, for analyzing thermodynamic properties and phase transformations. As has been mentioned above, there are virtually no realiable published data on the strain (elastic) interaction of carbon and nitrogen atoms in austenite, although such information is i Moscow State Academy of Instrumentation and Information Science, Moscow, Russia.very important for understanding the behavior of austenite and phase transformations in steels. In this connection, we posed the problem 2 of computing the energy of C -C interaction more accurately and using the model of long-range strain interaction to describe the thermodynamic activity of carbon in austenite. ELASTIC (STRAIN) INTERACTION OF INTERSTITIAL ATOMSIn order to compute the energy of paired strain interaction of interstitial carbon atoms at octahedral interstices of the f.c.c, crystal lattice of iron we used the method of lattice statics as formulated by A. G. Khachaturyan [2, 3]. The distortions created in the crystal lattice by interstitial atoms are described by the concentration coefficient of expansion of the crystal lattice U 0 :where c is the atomic fraction of interstitial atoms, a is the period of the crystal lattice of austenite, and a 0 i...

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