Effect of growth rate on rod spacing and undercooling of Bridgman-grown Si-TaSi₂ eutectic in situ composite

Directionally solidified Si-6 wt.%TaSi₂ eutectic alloy has been studied to characterize the variation of inter-rod spacing at different growth rates (V = 6-200 μm/s) with a constant temperature gradient (210 K/cm). Statistical distributions of inter-rod spacings at each solidification rate are determined. It is confirmed that the relationship between inter-rod spacing and solidification rate obeys the Magnin-Kurz model, and the theoretical value of λa2V = 5435.6 μm³/s (λ_a is the average inter-rod spacing) approximately equals to the experimental value of λa2V^1.06 = 5343.6 μm^3.06/s. For the Si-TaSi ₂ system, the operating parameter φ is a function of the solidification rate due to the transition of the TaSi₂ phase from facet to nonfacet, and as the solidification rate increases the kinetic undercooling cannot be ignored.