UC Irvine

Traditionally, grain boundary character in nanoscale materials has been tailored to maximize different types of mechanical behavior, whether it be exhibiting near-theoretical strengths or prolonging fracture by dramatically increasing a material’s ductility. As more complex systems develop for nuclear and other extreme environment applications, the need for these types of materials is quickly identified. Specifically, materials in a nuclear reactor need to be amended to extend their longevity to promote safety and reliable usage. One strategy for improving radiation tolerance is the design and control of internal interfaces in a material. Atomistic simulations can give insight into the foundational principles of grain boundary structure and formation.

Two comprehensive simulation models are developed to bridge this gap with respect to radiation tolerant interfaces and structural transitions in binary alloy systems. Firstly, the radiation damage of an ordered grain boundary is compared to a disordered amorphous intergranular film, to investigate how interface thickness and free volume impacts point defect recombination. Collision cascades are simulated and residual point defect populations are analyzed as a function of boundary type and primary knock on atom energy. Secondly, hybrid

Monte Carlo/molecular dynamics simulations are used to study segregation-induced intergranular film formation in Cu-Zr and Cu-Nb alloys. While Cu-Zr alloys form structurally disordered or amorphous films, second phases precipitate at the interfaces of Cu-Nb. Finally, the effect of free surfaces on dopant segregation and complexion formation is investigated for both alloys.