  A phase-field study has been conducted to obtain an understanding of the
formation mechanism of the script lamellar pattern of MoSi2/Mo5Si3 eutectic
composite, which is a promising candidate for high-temperature structural
application. The spacing of the lamellar pattern in the simulation results
shows good agreement with that of experimental observations and analytical
solutions under three growth rates: 10 mm/h, 50 mm/h, and 100 mm/h. The
discontinuity of Mo5Si3 rods, in contrast to the regular eutectic with a
continuous pattern, is claimed to be caused by the instability of the
solid-liquid interface. In this study, the implementation of Mo5Si3 nucleation
over the solid-liquid interface has been proposed and successfully reproduced
the characteristic of discontinuity. A highly random and intersected lamellar
pattern similar to that observed in the ternary MoSi2/Mo5Si3 eutectic alloyed
with 0.1at% Co has been obtained in simulation owing to the increase in the
frequency of nucleation. In addition, it has been demonstrated that the
inclination of the Mo5Si3 rod can be reproduced by taking into account the
strong relaxation of lattice strain energy, which is generally considered to be
negligible in eutectic reaction, as the result of the formation of
ledge-terrace structure.
