Atomic and grain level modeling of polycrystal deformation

Modeling of superplastic deformation mechanisms is carried out in two different scales of atoms and grains. The length scale, computational methods at each level are introduced. In the grain level modeling, a micromechanical model is developed from the constituent grain level to the level of polycrystalline bulk materials, to study the stress-strain rate relations. Using this approach, the influence of temperature and grain size on the high-temperature deformation behavior of superplastic materials are predicted over a wide range of strain rates. In the atomistic simulation, interatomic potentials using Embedded Atom Method (EAM) are used in conjunction with molecular statics and dynamic calculations. Atomistic simulations are performed on a series of grain boundary structures in aluminum, and the energies associated with each of their equilibrium configurations are computed. The equilibrium grain boundary structures are obtained using energy minimization technique. The temperature and applied stress effects on grain boundary sliding (GBS) and migration are analyzed in details by using molecular dynamics calculations.