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.