A Semi-Empirical Parameterization of Interatomic Interactions Based onthe Statistical-Thermodynamic Analysis of the Data on Radiation Dif-fraction and Phase Equilibria in F.C.C.-Ni-Fe Alloys

摘要

Using both the statistical-thermodynamics methods within the scope of the self-consistent field approximation and the diffraction data on coherent (or diffuse) scattering of X-rays (or thermal neutrons) from (dis)ordered f.c.c.-Ni—Fe alloys of various compositions, the estimation of interatomic interactions (including their magnetic contribution) and their temperature—concentration dependences were obtained. Based on the static concentration-wave representation, the expressions for configuration free energies of L1_2-Ni_3Fe-type permalloy, L1_0-NiFe-type elinvar and L1_2-Fe_3Ni-type invar were analyzed, considering explicit expressions for configuration entropies of atomic and magnetic subsystems with their configuration internal energies. Phase diagram of a system at issue was plotted within the field of the presence of f.c.c.-Ni—Fe alloys; their phase boundaries, equilibrium (static) properties near critical points (order parameter, etc.), and possible microstructures developed by composition-controlled magnetic transitions and/or order—disorder constant-composition solid—solid phase transformations were discussed. The obtained results were compared with available experimental data.