Microstructural evolution and behaviour of deuterium in a ferritic ODS 12 Cr steel annealed at different temperatures

In the present work, an ODS 12 Cr steel was characterized using Electron Microscopy techniques, in an as-received condition and after annealing treatments between 773 K and 1573 K. Results show a complex microstructure, with the presence of fine Y-Ti-O nanoparticles dispersed in the matrix. After annealing at 1573 K, the average diameter of Y-Ti-O nanoparticles increases from ~4 to ~7 nm and partial recrystallization occurs. The trapping behavior of deuterium in the steel in its as-received state and annealed at 1573 K was investigated. Samples were exposed to low-energy deuterium plasma and analyzed with thermal desorption spectroscopy, after waiting times of 1 day and 25 days. The samples measured 1 day after exposure released a higher total amount of deuterium than the ones measured after 25 days. The effect of waiting time is explained by the release of deuterium, at 300 K, from sites with low activation energy for detrapping, Ed. In the as-received condition, part of the deuterium detrapped at 300 K was re-trapped by high-Ed sites. For the samples in the annealed condition, the redistribution of deuterium from low-Ed to high-Ed sites was not observed, but the total amount of deuterium released was higher.