Title: Atomistic Simulations of Grain Boundaries and Nanocrystalline Metals

Speaker: Dr. Garritt J. Tucker, The Georgia Institute of Technology, Atlanta, GA

Date/Time: Tuesday, November 9, 2010, 9:30 am Mountain Time       

Location: CSRI Building/Room 90 (Sandia NM)

Brief Abstract: The potential for improvement in numerous functional properties of nanostructured materials as compared to traditional materials have led to increased interest throughout the scientific community. However, many challenges still exist to accurately understand and characterize fundamental structure/property relationships that dictate material behavior. Therefore, computational methods such as atomistic simulations have been leveraged to explore nanoscale phenomena and provide insight about influential processes and critical accommodation mechanisms. In this research, atomistic simulations are used to explore grain boundaries and deformation processes in nanocrystalline materials. Heterogeneous dislocation nucleation is seen as a major accommodation mechanism in nanocrystalline metals, where grain boundary structure and free volume migration are important factors when determining defect nucleation. Additional grain boundary mediated processes, such as boundary migration, sliding, and shear shuffling are also influential mechanisms in nanocrystalline metals and will be investigated by simulation as well. Apart from these interfacial-mediated processes, multi-scale relationships persist and significantly affect functional material behavior. Thus, innovative multi-scale modeling methods have been created over the last decade with the objective of bridging length and time scales, and also to uncover vital structure/property relationships affecting material properties. However, crucial grain boundary behavior in nanocrystalline materials is not usually captured nor included in their development. To address this disconnect, we have formulated volume-averaged kinematic metrics from continuum mechanics to analyze data from atomistic simulations of grain boundaries and nanocrystalline plasticity. The results are encouraging and show structure dependent deformation and microrotation fields emerging from the nanostructure. It might also now be possible using these continuum metrics to resolve the contributions and filter the role of various competing accommodation mechanisms during the deformation of nanocrystalline metals.

CSRI POC: Richard Lehoucq, 505-845-8929