The dynamics of precipitate evolution in elastically stressed solids

Elastic stress, generated by the misfit between particles and matrix, has prominent effects on the dynamics of the microstructural development in phase transformation process for many two-phase mixtures.;The study of the elastic field around a single particle with energy extremizing shape, which comes from the examination of particle morphology bifurcation diagram, provides a basis of comparison when considering the multiparticle problem. The effects of the elastic field on the development of particle morphology is then demonstrated by the evolution of an initially misoriented isolated particle. Two particle calculation where the morphology of each particle can evolve in accordance with the diffusion and elastic field in an elastically anisotropic system is examined. The total energy of the system, which is the sum of the elastic energy and the interfacial energy, is also determined through numerical integration. These energetic calculations not only confirm the dynamics of precipitate evolution by computer simulation but also provide explanations of the coarsening mechanism. Finally inverse coarsening is found in a three particle system.;The interaction between one or more dislocations and a precipitate is examined experimentally and theoretically. The theoretical calculations assumes that the particle evolves by the diffusion of mass, but does not make any a priori assumptions on the shape of the precipitate. The elastic interaction between the precipitate and dislocation is found can induce the precipitate to migrate through the solid either towards or away from the dislocation. In addition, the elastic interaction between the precipitate and a polygonized grain boundary was found to induce significant changes in the morphology of the precipitate. In an effort to verify the theoretical calculational experiments illustrating the morphological evolution of precipitates near polygonized grain boundaries in the Fe-Al system were performed. The particle morphologies found in these experiments are qualitatively consistent with the theory.