Phase field study of grain boundary effects on spinodal decomposition Original Research Article

We have developed a phase field model of a polycrystalline alloy by combining the Cahn–Hilliard model [J Chem Phys 28 (1958) 258] with a model of polycrystals due to Fan and Chen [Acta Mater 45 (1997) 3297]. We have used this model to study grain boundary (GB) effects on spinodal decomposition (SD) in two-dimensional (2D) systems. In binary A–B systems with constant atomic mobility, when the GB-energy (γα) of the A-rich α phase is lower than that (γβ) of the B-rich β phase, decomposition starts by enriching the GB with species A, setting off a composition wave that produces alternating α and β bands near the GB. Simultaneously, the grain interiors undergo normal SD. Thus, when decomposition ends, GB-bands coexist with grain interiors with spinodal microstructure. The number of GB bands is rationalized in terms of (γβ−γα) and the rate of SD in the grain interior. Further, during decomposition, grain growth is effectively suppressed.