Amit Misra
Director, Center for Materials at Irradiation and Mechanical Extremes, an Energy Frontier Research Center, Fellow, Los Alamos National Laboratory

Defect-Interface Interactions in Metallic Nanolayered Composites

Location: EBII Room 1231

Monday, March 11th 2013 - 11:00 am

The interaction of defects (vacancies, interstitials, dislocations) with interfaces (grain boundaries, interphase boundaries) plays a key role in the mechanical response of materials. In materials where the spacing between interfaces is on the order of a few to a few tens of nanometers, the material properties are dominated by defect-interface interactions as opposed to defect-defect interactions in the bulk.

We have used physical vapor deposition to synthesize nanolayered composites such as Cu-Nb that are used as model systems to explore the interaction of interphase boundaries with defects introduced via plastic deformation or ion irradiation. The results of these experimental studies are integrated with atomistic modeling and dislocation theory to provide insight on the unprecedented combination of properties achieved in certain nanolayered composites such as ultra-high flow strengths, high plastic flow stability, high fatigue strength, high thermal stability, high sink strength for radiation-induced point defects and trapping of helium in the form of stable clusters at interfaces. The results on "bottom-up" synthesized model systems are compared with "top down" accumulative roll bonding (ARB) processed bulk Cu-Nb nanolayered composites. A quantification of the defect-interface interactions as well as the processing-interface structure relationship allows the development of materials design concepts with controlled interface structures in nanocomposites to achieve tailored response in engineering applications.

North Carolina State University