Thermo-kinetic modeling of Cu precipitation in α-Fe

Consistent and predictive simulation of precipitation in the Fe-Cu system is a complex task. So far, no comprehensive approach is reported in literature that is capable of reproducing simultaneously all fundamental precipitation parameters (phase fraction, mean radius and number density) within a single set of model parameters and over an extended range of temperatures. In the present paper, we address this problem and present a novel approach for simulation of Cu-precipitation based on CALPHAD-type Gibbs energies, a mean-field model for precipitate growth, advanced classical nucleation theory and a predictive model for interface energy calculation. For successful simulation, several physical mechanisms are accounted for in addition to conventional Kampmann-Wagner-based precipitation modeling to achieve a consistent evolution of precipitation parameters. These comprise of models for the transition from bcc to 9R to fcc structure, curvature and temperature effects on interfacial energy, particle coalescence as well as a thermodynamic reassessment of the Fe Cu system. We compare our results with experimental data as well as first-principles calculations from literature and, finally, predict a time-temperature-preci pitation (TTP) diagram that reproduces the experimental one well within the experimental scatter. (C) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.