Numerical Simulations of Coarsening of Lamellar Structures: Applications to metallic alloys

Understanding the microstructural evolution in metallic alloys helps to control their properties and improve their performance in industrial applications. The emphasis of our study is the coarsening mechanisms of lamellar structures. Coarsening of lamellar structure is modeled numerically using Monte Carlo Potts method. The initial microstructure consists of alternating lamellae of phase A and phase B with the spacing proportional to their volume fraction. Faults are introduced to the lamellae to induce instability in the system. We find that an isotropic lamellar structure degenerates via edge spheroidization and termination migration into nearly equiaxed grains with a diameter which is 2 to 3 times larger than the original lamellar spacing. The duration of this process is comparable with the time it would take Ostwald ripening to produce grains of the same size. Eventually grain growth reaches the asymptotic regime of coarsening described by a power-law function of time. Lamellae with anisotropic grain boundaries coarsen more slowly and via discontinuous coarsening mechanism. This produces larger grains upon degeneration of lamellae. Discontinuous coarsening was observed in lamellar alloys as well as termination migration.