Analysis of Phase and Structural Transformations in Ternary Systems by the Computer-Thermodynamic Methods: A Review

摘要

The latest accomplishments in the field of computer thermodynamics as applied to the diffusion transformations in multicomponent systems are reviewed. The methods of determining the driving forces for the diffusion of carbon and alloying elements upon phase transformations in ternary systems by finding the thermodynamic activity at all moving interfaces with the help of the construction of isothermal sections of phase diagrams are described. This approach allows one to qualitatively understand the mechanism and kinetics of solid-phase transformations without rigorously solving the diffusion equation. As an example, a number of complex diffusional transformations are considered, namely, the decomposition of the alloyed martensite by discontinuous precipitation; the decomposition of the M_(23)C_6 carbides upon heating according to the eutectoid reaction; the cementite decomposition during steel austenitizing by the widmanstatten-type reaction; the carbide transformation upon heating in situ; the austenite formation; and dissolution of the complex carbides. In a number of cases, it is shown how the thermodynamic and kinetic theories can be efficiently used to interpret phase transformations.