Coarsening of precipitate clusters in stress gradients

Abstract

Several recent theoretical studies and computer simulations have shown that a misfit strain and a uniform applied stress field can induce strong spatial correlations between precipitates during coarsening of two-phase microstructures. The sign and magnitude of the misfit strain and applied stress, and the difference in elastic constants between precipitate and matrix phases influence strongly the resultant microstructure. Most two-phase structural materials, including those used as a matrix in metal-matrix composites, experience external fields that are strongly position dependent owing to, for example, the mechanical loading conditions and system geometry, the polycrystalline nature of many materials, stress concentrators and thermal mismatch between fibers and a metal matrix. The presence of non-uniform external stress fields and stress gradients is also expected to affect microstructural evolution since the elastic field affects the thermodynamic stability of the phases. The scope of this work is to illustrate by computer simulation how such stress gradients can affect microstructural evolution during coarsening.