Interaction of solute atoms in austenite

The energies of strain-induced (elastic) interaction of CC and N-N pairs are calculated for austenite while taking into account the discrete atomic structure of the host lattice. This interaction is strong, long-range, oscillating, and anisotropic. Generally, the strain-induced interaction in austenite is weaker than in ferrite. The verification of applicability of the model of strain-induced interaction for carbon and nitrogen in austenite by means of calculation of interstitial activity shows that the model must be supplemented by the calculation of additional repulsion in the first coordination shell. The obtained energies of C-C interaction, including repulsion in the first shell, are used to determine the interaction energies between substitutional Si, Ni, Cu, Co, Zn, AL Mn, W, Cr, Mo, V, Nb, Ti, and carbon atoms in the first coordination shell. It is determined that the calculated interaction energies clearly depend on the employed model for C-C interaction. The obtained energies of carbon-substitutional interaction may be regarded as being more precise than previously calculated due to taking into account the long-range C-C interaction. Both elastic and 'chemical' interactions essentially contribute to the C-s interaction energy in austenite.