| Interest in microstructural evolution of polycrystalline materials stems from the multiplicity of interrelated phenomena that contribute to this evolution, and from the impact that such phenomena have on the performance and reliability of these materials, especially in applications such as microelectronic devices.; In this work, a continuum field formulation developed to study this type of phenomena is presented. The formulation accounts fully for the coupling between mechanical behavior, self diffusion, electric effects and interface migration. Each phenomenon being modeled is treated as a coupled initial and boundary value problem, consisting of these four component problems. Atomic-level mechanisms are taken into consideration while developing the thermodynamic basis of the formulation, from which the constitutive relations are derived.; The computational framework used to solve the resulting coupled field equations is described in detail. This framework is built around a staggered solution scheme in which the finite element method is used to solve each governing differential equation individually. Additional computational techniques utilized in the implementation are also discussed. Examples of these include the level set method, a least-squares projection/smoothing technique and a modified form of the Galerkin/least-squares stabilization method.; To study the problem of void nucleation in polycrystals, the stability of the atom-vacancy system is examined closely. A thermodynamic instability which could lead to spinodal decomposition of this system is identified. The amplications of this result in the context of void nucleation are explored and its relation to classical nucleation theory is realized. All quantities needed to calculate void formation rates are obtained from the coupled field calculations in a consistent mannen As expected, the results indicate that a high tensile stress can lead to void nucleation in the presence of impurities.; The problem of grain-boundary migration is also treated. The level set method is used successfully to track the moving boundary without remeshing. Thermodynamic driving forces for boundary migration arising from boundary curvature, stress-driven diffusion and electromigration are accounted for. In this case also, the strongly coupled nature of the problem is captured, the calculations remain stable and physically-meaningful results are obtained. |
