Ostwald Ripening in Elastically Stressed Solids

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9707073 Voorhees Interfacial energy is the primary driving force for the precipitate coarsening processing metal alloys in the absence of elastic stresses. As a result, the average particle size increases monotonically with time, and large particles grow at the expense of small particles. In contrast, in the presence of elastic stress, particles can undergo inverse coarsening where small particles grow at the expense of large particles, and large-scale particle migration occurs in the solid. Complete stabilization of the two-phase mixture with respect to coarsening may be possible. In this research the coarsening process is examined in elastically stressed solids both experimentally and theoretically. The experimental effort focuses on two major unexplored aspects of the coarsening process in elastically-stressed solids: (1) the kinetics of the coarsening over a wide range of average particle sizes, from small average particle sizes, where the interfacial energy is the dominant energy in the system, to large particle sizes, where the elastic stress is the dominant energy in the system, and (2) the three-dimensional morphology and spatial arrangement of particles in the l ate stages of coarsening. The theoretical effort is directed toward predicting the evolution of a statistically large system of particles where the particle morphologies and locations evolve in a manner that is consistent with the elastic and diffusion fields in the system. This effort should allow the determination of statistically averaged quantities such as the exponents and amplitudes of the temporal power laws that describe the coarsening kinetics as well as the development of the microstructure during coarsening. %%% The theory will be used to predict the coarsening kinetics using parameters that will be measured in the experiments. The theory will be sufficiently realistic that the predictions can serve as a guide to the development of coarsening-resistant coherent alloys. * **