Microscopic Mechanisms of Deformation in Amorphous Solids

Mo Li Associate Professor School of Materials Science and EngineeringGeorgia Institute of Technology While the fundamental deformation mechanisms in crystalline materials, namely, the dislocation-based process, have long been understood and put into use, our understanding of the microscopic deformation mechanisms in amorphous solids still remains in its infancy despite tremendous efforts made in the past forty years. Amorphous solids contribute to a large fraction of materials used today, including metallic glasses and amorphous semiconductors, granular matters, and many geological materials. They are characterized by metastability and the lack of long-range order, which poses great challenges for experimentalists as well as theorists to have a detailed understanding of how deformation occurs at the atomic or molecular level. In this talk, I will give a brief introduction to the mechanical properties of amorphous solids and in particular, metallic glasses with special emphasis on shear localization or shear banding. I will present the results from extensive atomistic modeling of the changes in the local atomic structure, volume, and mechanical properties in several model systems subjected to various external loadings. The results led us to the establishment of a new model, an extended Ginzburg-Landau theory. We conclude, from these studies, that the microscopic deformation mechanism in amorphous metals is through the process starting from local volume change and then local shear softening to the final breakdown. The implications derived from this study and its applications to other disordered systems such as granular matters and nanocrystalline materials will be briefly mentioned. --------------------------------------------------------------------------------Mo Li received his Ph.D. in applied physics in 1994 from California Institute of Technology. He joined Morgan Stanley & Co. in New York after a brief stays as a postdoctoral fellow at Caltech and the Argonne National Laboratory. From 1998 to 2001 he was an assistant professor at the Johns Hopkins University. Currently he is an associate professor at Georgia Institute of Technology. His research focuses on mechanical properties of amorphous solids and nano-scaled materials, phase transitions in metastable systems, interfaces, and statistical physics and its applications. The approaches used in his research are a blend of those from statistical physics, solid state physics, materials science, metallurgy, mechanics and computational methods. His research focuses on algorithm development, simulation, and theoretical analysis.

Location: Stauffer Science Lecture Hall, Rm 102

Audiences: Everyone Is Invited

Contact: April Mundy