Ostwald Ripening in Elastically Stressed Solids

9707073在无弹性应力的情况下，界面能是金属合金加工过程中析出粗化的主要驱动力。结果是，平均颗粒尺寸随时间单调增加，大颗粒以牺牲小颗粒为代价生长。相反，在弹性应力存在的情况下，颗粒会经历反向粗化，其中小颗粒以牺牲大颗粒为代价生长，并在固体中发生大规模的颗粒迁移。两相混合物相对于粗化的完全稳定是可能的。在这项研究中，从实验和理论两个方面研究了弹性应力固体的粗化过程。实验工作集中在弹性应力固体中粗化过程的两个主要方面：(1)在较大的平均颗粒尺寸范围内的粗化动力学，从小平均颗粒尺寸，其中界面能是系统中的主要能量，到大颗粒尺寸，其中弹性应力是系统中的主要能量，以及(2)L中颗粒的三维形态和空间排列经历了粗化阶段。理论上的努力是为了预测一个统计上很大的粒子系统的演化，其中粒子的形态和位置以与系统中的弹性场和扩散场一致的方式演化。这项工作应该能够确定统计平均量，如描述粗化动力学和粗化过程中微结构发展的时间幂定律的指数和幅度。该理论将用于使用将在实验中测量的参数来预测粗化动力学。该理论将是足够现实的，这些预测可以作为抗粗化的共格合金的发展的指导。***

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. * **