Microstructural Evolution and Interfacial Motion in Systems with Diffusion Barriers

The initial goal of this research program was to model and to simulate phase transformations in systems containing diffusion barriers. The modeling work included the development and testing of code to describe mass flow, the kinetics of phase formation, elastic deformation, and subsequent microstructural evolution occurring during interdiffusion. The primary simulation tools to be used were a class of diffuse interface methods described by the Cahn-Hilliard and phase field equations for the temporal and spatial evolution of the composition and deformation fields and other relevant phase variables. One-dimensional analytical solutions were also to be developed both to test the numerical methods and to establish connections to physical systems. During the early stages of the research program, two new areas of research related to systems with diffusion barriers were identified. The first area concerned phase formation and diffusional phase transformations in reacting systems subject to high electric current densities. Such high-current environments are common in lead-free solders, for example, and have important technological applications. The second area was an offshoot of the present work, and concerned theoretical modeling of phase evolution and cyclical amorphization of metallic alloys during ball milling