Strength at the nanoscale: fundamental mechanisms of plasticity in nano-structured materials

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Metallic alloys are useful for engineering applications largely due to their high strength.  Recently, materials scientists have discovered that this strength is further enhanced by so-called "nano-structured materials".  These are often the same alloys as conventional metals, but with special microstructural features refined to the nanometer-scale.  One finds, however, that the primary mechanisms governing strength and ductility are different in nano-structured materials than in conventional ones.  This new physics is not well understood, but occurs on length scales accessible to both modern atomistic simulation and nano-experiments.  It is a unique regime where a direct link between simulation and experimentation is possible.       Strength is of fundamental importance in almost every application.  Making a material stronger means we can make structures lighter, more energy efficient, safer, or faster.  Applications range from sporting goods to fuel-efficient cars to aircraft.  Even in non-structural applications like micro-electronics, improved strength can improve the robustness of the circuitry or permit further reductions in chip sizes.     The proposed work will make use of advanced computer modeling techniques, where recent progress makes possible a "virtual materials laboratory".  With these tools, detailed "virtual experiments" can be performed to test materials, permitting a level of control and detail that is often impossible to achieve in a real experiment.  We can also study model materials that may not actually exist, but provide a direct test of hypotheses regarding important features or mechanisms in real materials.       The goal of this modeling is to unravel the details of the mechanisms of strength and ductility, and specifically to determine the key differences in behaviour between conventional materials and nano-structured materials.  Ultimately, the research will help guide the design of materials with improved mechanical properties.