Project Scope
Emily’s research investigates castable nanostructured alloys (CNAs), a class of reduced activation ferritic martensitic (RAFM) steel specifically engineered to: 1) decrease the amount of long-lived radioactive material from a nuclear power plant by following reduced activation alloying guidelines and 2) meet the harsh conditions in a fusion nuclear reactor environment, including irradiation, high temperature, stress, and exposure to the coolant. Previous RAFM steel generations exhibit insufficient creep strength above ~550 – 600°C, limiting the achievable thermal efficiency of a nuclear reactor. Therefore, CNAs aim to improve creep strength through compositional and microstructural optimization by computational thermodynamics and thermomechanical treatments. The main alloy design principle of CNAs is to encourage a high number density of the relatively stable, nanosized MX (M=Ta, Ti, V and X=C, N) precipitates. Preliminary results suggest CNAs exhibit an order of magnitude increase in MX precipitate number density, as well as superior thermal creep strength compared to other leading RAFM steels. However, the microstructural features and mechanisms responsible for thermal creep strength have not been investigated in CNAs. Due to the nanoscale microstructural strengthening features in CNAs, such as precipitates, sub-grains, and dislocations, the proposed work involves employing advanced electron microscopy techniques, mainly using a transmission electron microscope (TEM), to characterize the CNA microstructure after creep rupture. The objective of this work is to use model CNAs to correlate the contribution of various microstructural features to creep strength, aiding alloy design for CNAs as well as structural materials more broadly.