Quantitative Phase-Field Modeling Microstructural Evolution of Fe-Cr: A GPU-Accelerated Study

Duplex stainless steel, which shows that strong general corrosion resistance and high strength, is widely used as a structural material in industrial fields. Although duplex steels show high performance in terms of mechanical properties, embrittlement caused by the α′ phase and sigma phase which reduces the integrity of structural materials. Therefore, it is important that selecting optimal alloy composition to prevent α′ phase and sigma phase precipitation.<br/>In the Fe-Cr system, it has α phase and α′ phase at about 800K or less, and has a sigma phase and α phase or a sigma phase and α′ phase at about 800K or more according to the alloy composition. The precipitation phenomenon in many studies through the spinodal decomposition process of α phase and α′ phase was simulated using the Cahn-Hilliard equation, and many simulations and experimental studies have been conducted on the sigma phase precipitation. However, a physical model that can simultaneously consider α-α′ spinodal decomposition and sigma phase precipitation through a single physical model has not yet been proposed. In this study, a simulation framework that can predict the microstructural change of Fe-Cr under a given temperature and composition is presented without prior assumptions.<br/>We simulate the behavior of precipitation for α′ phase and sigma phase using calculation of phase diagram(CALPHAD)-based phase-field model of Fe-Cr system. Also, we conduct quantitative analysis for microstructural characteristics such as average size, precipitate number density and phase fraction according to sigma phase transformation. Moreover, to improve numerical stability and to accelerate simulation, we applied methods that semi-implicit Fourier spectral method and compute unified device architecture(CUDA) parallelization.