Dislocation Loop Evolution in Ni-Based fcc Model Alloys by In-Situ Self-Ion Irradiation at High Temperatures

Austenitic Stainless Steels (ASSs) are foreseen as cladding material for next generation reactors even though their swelling under irradiation will limit the fuel burnup. Solute elements, such as titanium and carbon, efficiently reduce this swelling but the mechanism is still ambiguous.<br/>Here we focus on the effect of a progressive addition of titanium on the microstructure evolution of nickel at small irradiation dose and on the loop interaction during irradiation. Nickel is considered as a model alloy for ASSs (same crystallographic structure). Pure Ni and nickel alloyed with various percentages of titanium (x ranging from 0.4% to 1.2% by mass), are <i>in-situ</i> irradiated at 450°C and 510°C within a Transmission Electron Microscope using the JANNuS-Orsay facility.<br/>The in-situ microstructural evolution and dislocation loop characteristics are finely analyzed in function of specimen composition and doses. We reveal a strong impact of micro-alloying on microstructure: loop nature, growth rate, formation thickness, density, Burgers vector and mobility. A direct correlation of Frank loop morphology and nature is observed. Finally, a temperature-dependent critical Ti content for Frank loop nature is highlighted and discussed.