There is a significant demand for the discovery of advanced materials that can survive high temperature and high-dose radiations for next generation nuclear reactors. Under these operating conditions, a large number of metallic materials develop voids that result in embrittlement and consequent failure. Void swelling occurs as radiation induces atomic defects that migrate elsewhere leaving clusters of vacant positions behind. These vacancy clusters form voids and grow continuously. The principal investigators' initial study shows just the opposite phenomenon, however: that is, voids in metals with existing nanoscale pores shrink rather than expand during radiation. This research will investigate this phenomenon and may add radically to the understanding of fundamental mechanisms of radiation damage mitigation. A positive outcome will enhance the design of radiation tolerant nanoporous materials for advanced nuclear energy systems. In this project, special effort will be made to recruit female and other minority students. Additionally, collaborations with scientists at Argonne National Laboratories and Los Alamos National Laboratory will offer graduate students summer research experience at premier national labs.
The goal of this project is to understand, via a combination of modeling and experiments, the fundamental mechanisms through which deliberately introduced nanovoids in nanoporous metallic materials can absorb and eliminate radiation induced point defects, and ultimately curtail void swelling significantly and alleviate radiation embrittlement. The innovative concepts put forward here are the possibility of utilizing nanovoids and their stress field to trap, store and annihilate various defect species associated with radiation damage, and restore the capability to absorb defects continuously. Furthermore, nanoporous metals may have enhanced plasticity in comparison to radiation embrittlement frequently observed in bulk fully-dense counterparts. This study integrates in situ radiation experiments with phase field modeling to investigate the kinetics of void swelling, and combine in situ nanomechanical testing with dislocation dynamics modeling to explore mechanics and plasticity of irradiated nanoporous metals.
