Spinodal decomposition in fine grained materials

[摘要] 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 (ð‘�??) in our model has an order parameter ($eta_i$) associated with it; $eta_i$ has a value of unity inside the ð‘�?�th grain, decreases smoothly through the grain boundary region to zero outside the grain. For a symmetric alloy of composition, ð‘�? = 0.5, our results show that microstructural evolution depends largely on the difference in the grain boundary energies, $gamma_{gb}$, of A-rich (ð›�?) and B-rich (ð›�?) phases. If $gamma^{alpha}_{gb}$ is lower, we find that the decomposition process is initiated with an ð›�? 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 ð›�? 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.

[学科分类] 材料工程

[关键词] Spinodal decomposition;grain boundary effects;phase field models.