Spinodal decomposition in polycrystalline alloys

Abstract

We have used a phase field model (a continuum equivalent of the Potts model) for studying spinodal decomposition (SD) in polycrystalline alloys. We show that the evolution of the microstructure is governed largely by the difference in the grain boundary energies γ gb of A-rich α and B-rich β phases. When γ gb α < γ gb β , the decomposition process is initiated with the formation of an α layer (band) at the grain boundary, and of a β layer on either side of it. In small grains, the entire grain is filled with two or three of these alternating α and β bands. In large grains, on the other hand, the microstructure exhibits a combination of GB-initiated bands and bicontinuous α and β regions in the grain interior produced by normal SD. During this decomposition process, grain growth is suppressed completely due to the pinning effect of the A-rich layer at the grain boundaries.