In 1970s, Kaufman and Bernstein summarized the general features of computer numerical calculation of multicomponent phase equilibrium thermodynamics, by means of polynomial expressions of the Gibbs free energy, and they created the CALPHAD group (Coupling of Phase Diagrams and Thermochemistry). CALPHAD group aims to promote computational thermodynamics through development of models to (i) critical assessment of experimental and computed data and their incorporation into self-consistent databases, (ii) represent thermodynamic properties for various phases which permit prediction of properties of multicomponent systems, and (iii) development of software to improve understanding of various industrial and technological processes. Besides software for performing thermodynamic modeling, there are today several programs to modeling kinetics of diffusion controlled phase transformations. These kinetic programs are interfaced with programs for performing thermodynamic simulations as well as with kinetic databases. In this work, several case studies about numerical modeling of thermal as well as thermochemical processing of steels are reported. The analyzed case studies are brief descriptions of theoretical and experimental research works which are being carried out in the Metallurgical and Materials Engineering Department, University of São Paulo. It is shown the processing parameter optimization during: high-alloy steel nitriding, TRIP steel thermal processing, CrN and Cr2N thermal synthesis from chromium powder, solution annealing of stainless steels, and primary-carbide decomposition during heat treatment of tool steels.
CALPHAD; computational thermodynamics; numerical modeling; heat treatments
