In situ observation of the growth and Ostwald ripening of spherical second phase domains in a solid is reported. It was found that at relatively low (3%) volume fractions of coarsening phase, diffusional interactions between particles were sufficiently strong to alter significantly the individual particle coarsening rates from the theoretical predictions of Lifshitz and Slyozov and Wagner (LSW). As a result, the LSW theory was found to be an inadequate description of the coarsening behavior of this low volume fraction system. In addition, particle migration in the solid matrix during coarsening was observed. These experimental particle migration results were found to be qualitatively consistent with a theoretical analysis of particle motion due to interparticle diffusion interactions or nonuniform matrix concentration fields. The generality of the mechanism responsible for the particle migration implies that particle motion, and thus a time-dependent spatial correlation function, during coarsening will occur to some extent in all systems undergoing first order phase transformations.
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