• H Ramanarayan

Articles written in Bulletin of Materials Science

• Spinodal decomposition in fine grained materials

We have used a phase field model to study spinodal decomposition in polycrystalline materials in which the grain size is of the same order of magnitude as the characteristic decomposition wavelength ($\lambda_{SD}$). In the spirit of phase field models, each grain (𝑖) in our model has an order parameter ($\eta_i$) associated with it; $\eta_i$ has a value of unity inside the 𝑖th grain, decreases smoothly through the grain boundary region to zero outside the grain. For a symmetric alloy of composition, 𝑐 = 0.5, our results show that microstructural evolution depends largely on the difference in the grain boundary energies, $\gamma_{gb}$, of A-rich (𝛼) and B-rich (𝛽) phases. If $\gamma^{\alpha}_{gb}$ is lower, we find that the decomposition process is initiated with an 𝛼 layer being formed at the grain boundary. If the grain size is sufficiently small (about the same as $\lambda_{SD}$), the interior of the grain is filled with the 𝛽 phase. If the grain size is large (say, about 10 $\lambda_{SD}$ or greater), the early stage microstructure exhibits an A-rich grain boundary layer followed by a B-rich layer; the grain interior exhibits a spinodally decomposed microstructure, evolving slowly. Further, grain growth is suppressed completely during the decomposition process.

• Bulletin of Materials Science

Volume 43, 2020
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