Quantitative Phase-Field Simulation of Composition Partition and Separation Kinetics of Nanoscale Phase in Fe-Cr-Al Alloy

Phase separation of the Cr-enriched nanoscale α′ phase in the Fe-38 at.% Cr-10 at.% Al alloy is studied by utilizing phase-field simulation. The partition of elements in the α and α′ phases is clarified with the composition evolution through the α/α′ phase interface, and the separation kinetics is quantitatively investigated by the temporal evolution of the size and volume fraction of the α′ phase. Aluminum partitions into the Fe-enriched α phase and depletes in the α′ phase, and the partition coefficient decreases as the temperature changes from 720 K to 760 K for the steady-state coarsening stage. As the temperature increases, the initial change rate of the volume fraction of the α′ phase is faster, indicating an accelerated phase separation. At the coarsening stage, the average particle distance and coarsening rate constant of the α′ phase increase with increased temperature, and the ratio of the Ostwald ripening is dominating compared with coalescence coarsening. The element partition and kinetics evolution of the α′ phase with temperature are helpful for the morphology and property predication of nanoscale precipitates.