ODS steels are primary candidates for Gen IV nuclear fission reactors and nuclear fusion applications. This research aims to conduct systematic fracture toughness experiments from RT to 700°C using small size C(T) specimens. The fracture toughness of ODS steels at RT and at high temperature is an important information for reactor component safety. Also, sufficient fracture toughness is needed during hot forming and handling of ODS steels.
The fracture behavior strongly depends on the final microstructure of the material. The final microstructure is in turn dependent on the manufacturing method which was used to produce the material. Since ODS steels are manufactured by powder metallurgy and contains oxide particles, its microstructure is slightly different than conventional steels. Characterization of the microstructure using TEM, SEM, EDS and EBSD throws more light on the microstructure-mechanical properties relation. Texture or anisotropy in microstructure due to manufacturing processes like hot rolling and hot extrusion greatly influence the fracture behavior. Secondary crack formation during fracture toughness testing, which could be detrimental for nuclear reactor components, depends on factors such has porosity, grain size, texture and local ductility of the material.
Various fracture toughness testing methods such as Unloading Compliance and Normalization method are used and compared. JR curves of ODS steels from different production methods are determined and compared. Small scale CT specimen are used because of the challenges faced in the mass production of ODS steels. Differences in Normalization and Unloading compliance method are also studied w.r.t small scale specimen and their usability is explored at temperatures up to 700°C.