Radiation resistance in alloys by solute-defect trapping

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

NON-TECHNICAL ABSTRACT: Materials used in current nuclear reactors cannot meet key requirements of the advanced designs proposed for future reactors. In particular, their resistance to radiation damage is insufficient. We investigate here one approach to increase materials radiation resistance, where small additions of carefully selected alloying elements are used to drastically slow down the kinetics of evolution of these materials. The approach takes advantage of the large body of accurate data now available to the community from high-throughput atomistic calculations to screen the most promising alloying elements. The research proposes to employ state-of-the-art nanoscale experiments to validate this approach in a copper matrix, for which antimony has been pre-selected as a promising alloying element. The work also aims at determining whether this material design approach can be combined with another one, relying on the spontaneous formation of precipitates at the nanoscale, thus resulting in extreme radiation resistance. The research will provide education for two graduate students and several undergraduate students, with an emphasis on advanced materials synthesis and characterization techniques, and atomistic modeling. Special effort will be made to recruit female and underrepresented minority students. The research will be integrated with education to further develop and implement active learning techniques. TECHNICAL ABSTRACT: This fundamental research program examines a strategy for designing single phase materials resistant to radiation damage by using small alloying additions of solutes that trap point defects so as to increase point defect mutual recombination over their elimination at sinks. While this strategy has been considered in the past, and yielded encouraging results, it has not received widespread attention in large part because no reliable method was available to select the best solutes to trap point defect. The proposed research takes advantage of recent modeling advances to overcome these limitations. Specifically, for a Cu matrix, using first principles calculations to calculate solute-point defect interactions, and self-consistent mean-field theory to calculate defect and solute transport coefficients, Sb was identified as one of these promising solutes. The experimental program measures directly the relative rate of recombination over sink elimination during irradiation of dilute Cu-Sb alloys from the broadening and the drift of thin marker layers placed at strategic positions in a Cu thin film bounded by Nb layers, the Cu/Nb interfaces providing near perfect sinks for point defect elimination. These broadenings and shifts are measured at the nanoscale using atom probe tomography (APT) and analytical scanning transmission electron microscopy (TEM). In addition this approach is implemented for imparting radiation resistance to alloys that self-organizes under irradiation, such as Cu-Fe, so as to further extend their stability under irradiation. By combining the two approaches, point defect trapping and compositional patterning, radiation resistance can be achieved in a vastly extended domain of irradiation conditions. The experimental program is complemented by atomistic KMC simulations to support the data analysis and to explore the potential impact of simplifications made during the solute screening stage. The impact of the program is broadened by offering research opportunities to undergraduates and by integrating research with education through computational modules in courses taught by the PIs. Active engagement is also offered to develop, assess, and spread active learning techniques.