Mechanisms of lamellar structure formation and Cr interfacial segregation in C11b-MoSi2/C40-NbSi2 dual phase silicide verified by a phase-field simulation incorporating elastic inhomogeneity

We developed a phase-field model of C11b-MoSi2/C40-NbSi2 duplex silicide incorporating elastic inhomogeneity, and simulated microstructure formation and interface segregation. We examined the effect of elastic inhomogeneity on the morphology, volume fraction of the C11b-precipitate, stress distribution, and solute partitioning. In the simulations, parameters evaluated by first-principles calculation are used for the experimentally unknown parameters. The lamellar structure was not formed in the case incorporating the elastic strain energy only and ignoring the anisotropy of the interfacial energy. When the anisotropy of the interfacial energy was taken into account, the lamellar structure was formed parallel to (0 0 0 1)C40 as observed in the experiment. It was also found that the elastic strain energy changes the equilibrium concentrations by >0.2 at%, but the difference between the equilibrium concentrations in homogeneous and inhomogeneous systems was <0.1 at%. The interfacial segregation was also hardly affected by the elastic inhomogeneity. These results confirm that elastic inhomogeneity can be neglected in the simulation of MoSi2/NbSi2 lamellar silicide.