Effect of Zr on the microstructure of corrosion resistant ODS steels

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Radiation-resistant steels are essential for the development of next-generation fission and future fusion energy systems. The incorporation of nano-particles in metallic matrices by powder metallurgy processing is widely employed for the development of radiation-resistant steels, and continues to be the subject of intense research worldwide. The two most critical properties of these materials for application in these future reactor designs are the maintenance of high strength at temperatures above the softening point of conventional steels and the reduction in sensitivity to radiation-induced He embrittlement. Oxide dispersion strengthened (ODS) steels show considerable promise in both properties. The distribution, chemistry and shape of the oxide nanoparticles, and their influence on the matrix chemistry and irradiation response, play a crucial role in many of the improved properties. However, there is considerable disagreement in the literature on the nature of these nanoparticles as a function of alloy chemistry and manufacturing process, and the precise mechanisms by which they respond to irradiation damage. There is also a requirement to develop new ODS steels with improved corrosion resistance specifically for fuel cladding materials for closed fuel cycles. Recently, high Cr ODS steels with Al additions have been developed for use in highly corrosive environments, but their high-temperature strength is poor. First principles calculations by one of the partners indicate that adding Zr to these alloys may refine and increase the number density of oxide particles by forming Y-Zr-O phases. We predict that this would improve the high temperature strength while maintaining the improved corrosion resistance and irradiation performance. It is this prediction that we wish to test in this new project.