Phase-field simulation of lamellar structure formation in MoSi ₂/NbSi₂ duplex suicide

We conducted phase-field simulations of microstructural evolution in C11_b-MoSi₂ / C40-NbSi₂ dual phase alloy with and without Cr-addition to examine the factors responsible for the formation and stability of the lamellar structure on the basis of thermodynamics, micromechanics and first-principles calculations. The first principles calculation was used for evaluating the interfacial energy, segregation energy of solute Cr-atoms and lattice parameters of imaginary disilicides for estimating the effects of solute distribution on the lattice misfit. When both of lattice misfit and the anisotropy of interfacial energy is taken into account, a lamellar structure similar to that observed experimentally is formed. In the absence of Cr-addition, the straightness of lamellar structure decreased slightly. When an isotropic interfacial energy is assumed, lamellar structure is not formed. Instead, a microstructure with habit planes parallel to {1 0 1 1} plane of C40-phase is formed. Thus, the anisotropy of interfacial energy is crucial for the lamellar structure formation rather than the elastic energy due to lattice misfit.