Abstract: Many future engineering systems will rely on high-performance metallic materials that are several times stronger and tougher than those in use today. In many situations, these superior properties will be desired in harsh environments, such as elevated temperatures, at high rates, and under irradiation. Nanolaminates, built from stacks of crystalline layers, each with nanoscale individual thicknesses, are proving to exhibit a composite of many of these target properties. Examples span from nanotwinned materials to biphase nanolaminates, comprised of alternating nano-thick layers that differ in orientation, chemistry and crystal structure. Studies on these materials report exceptional properties far beyond a volume average value of their constituents, such as strengths that are over five to ten times higher, hardness values that are several orders of magnitude higher, and unprecedented microstructural stability in harsh environments, such as irradiation, sudden impact, or elevated temperatures. While the combination of properties is clearly attractive, one roadblock to applying the nanolaminate concept to any general composite material system is their complex, highly anisotropic deformation behavior, making them less reliable than coarsely structured materials. Critical to designing the material nanostructure to achieve uniformity and reliability is understanding and predicting the strength properties of nanostructure materials based on known conditions and measurable variables, such as basic nanostructure size scales and chemical composition. Multiscale models for conventional coarse-grained materials have been in development for several decades, but analogous versions for nanostructured materials require extensions to explicitly account for the overriding dominance of internal boundaries on these microstructure/property relationships. The computational materials challenge lies in how to represent the discrete and statistical dislocation glide processes in nanostructured materials so that the profound influence of the fine nanoscale crystals can be properly replicated in simulation. In this talk, we will present recent examples of computational techniques and some unanticipated couplings between nanostructural size effects and microstructural evolution and strength that arise from their application.

Bio: Irene J. Beyerlein is a Professor at the University of California at Santa Barbara (UCSB) with a joint appointment in the Mechanical Engineering and Materials Departments. She currently holds the Robert Mehrabian Interdisciplinary Endowed Chair in the College of Engineering.