Phase-Field-Crystal Modeling of Polycrystalline Plasticity: A Window into Defect-Mediated Phenomena in between Particle and Discrete Dislocation Dynamics
Alain Karma (Northeastern University)
Computational Materials Design via Multi-scale Modeling
Wed 1:30 - 2:50
Barus-Holley 190
The phase-fi?eld crystal (PFC) model has attracted considerable attention during the past decade for its potential application to model the complex evolution of polycrystalline structures on di?ffusive time scales. Those time scale are not generally accessible by molecular dynamics (MD) simulations. At the other extreme, conventional continuum models of plasticity such as discrete dislocation dynamics (DDD) permit to access much larger length and time scales but rely on assumptions to handle dislocation reactions and high-angle grain boundaries. The PFC method lies in between those two extremes. It reproduces semi-quantitatively basic equilibrium properties such as grain boundary energy and elastic constants. It also naturally describes elementary dynamical processes such as dislocation glide and climb and dislocation reactions. However, the quantitative validity of this approach to realistically model the evolution of polycrystalline materials, beyond equilibrium properties, remains largely unexplored. In this talk, I will discuss conceptual challenges in formulating PFC dynamical equations that represent a physically plausible coarse-graining in time of discrete particle systems. I will discuss progress made to formulate such equations guided by detailed comparisons of PFC and MD simulations conducted primarily in controlled bicrystalline geometries. The results shed new light on complex mechanisms that mediate the shear-coupled motion and sliding of individual GBs over a large range of GB bicrystallography, as well as the stress-driven evolution of multigrain structures. They provide a glimpse into a wealth of phenomena that lie in between MD and DDD.