Evaluation of composition region for peritectic coupled growth

The composition region for stable coupled peritectic growth is evaluated by means of extending Boettinger's analysis. Our present analysis demonstrates that there exists a critical composition between C_α (composition of primary α at peritectic equilibrium) and C_β (composition of peritectic β at peritectic equilibrium), i.e. C_crit, separating the peritectic plateau (between C_α and C_β) into two regions where coupled and banded growth regimes dominate between C_crit and C_β and between C_α and C_crit, respectively. The calculated critical composition, C_crit, is consistent with the observation in Ni-Al, Ti-Al and Sn-Cd peritectic systems. Effects of interfacial energies of constituent phases and convection on the separation of these two growth regimes are also discussed.