Speaker: Zachary Trautt, Physics, GMU
Title: Intrinsic Grain Boundary Properties From Equilibrium Atomistic Simulations

Abstract: Grain boundaries are the primary components of the microstructures that form during processing of polycrystals and often determine the structure-property relation in these classes of materials. While engineering the grain boundary microstructure remains the goal of much of metal materials processing, current efforts remain severely handicapped due to the lack of a fundamental as well as quantitative understanding of thermodynamic and kinetic properties associated with these defects. Grain boundary properties are extracted via physical experiments and theoretical modeling & simulation. The benefits and drawbacks of each method will be reviewed. Atomistic simulations, specifically molecular dynamics, incorporate the atomic-scale mechanisms which are central to the understanding of grain boundary properties. The primary focus of this talk will be grain boundary mobility and free energy. The former is a measure of sensitivity of the defects to driving pressures while the latter is a measure of the energy stored in these defects. Due to the computational limitations of molecular dynamics, much of the past work has extracted these properties at driving pressures orders of magnitude higher than those occurring experimentally. This talk presents unique and efficient methods for extracting these properties in the zero driving pressure limit. We report a distinct driving pressure dependence of grain boundary mobility. Results for various boundary misorientations indicate that the mobility and free energy are quite anisotropic; yet the anisotropy cannot be reliably predicted by geometric criteria.

Time: Friday, Feb. 5, 2010, 1:30-2:30 p.m.

Place: Science and Tech I, Room 242

Department of Mathematical Sciences
George Mason University
4400 University Drive, MS 3F2
Fairfax, VA 22030-4444
Tel. 703-993-1460, Fax. 703-993-1491