The influence of thermomechanical processing on the microstructure and mechanical properties of 13.5Cr ODS steels

Abstract

Reduced activation oxide dispersion strengthened (ODS) ferritic steels are the most promising structural materials for future fusion power plants and innovative fission nuclear reactors. The structure and mechanical properties of fine-grained 13.5% Cr ODS ferritic steels, processed by hot cross rolling to large strains of 70% and subsequent annealing have been investigated. The microstructure after hot cross rolling is partially recrystallized. The texture of the ODS ferritic steel after rolling and annealing has a sharp rotated cube ({100} 〈110〉) texture component. The γ-fiber component (〈111〉||normal direction) typical of recrystallized rolled ferritic steels is absent. Similar values of tensile strength are obtained for rolled samples regardless of the sample orientation in comparison with hot isostatically pressed samples whereas a substantial enhancement in total elongation (22%) is present at 500°C. Cross-rolled ODS steels represent an increase in upper shelf energy to 2J compared with hot isostatically pressed samples. The relatively poor toughness properties, compared to 9Cr ODS RAFM steel EUROFER ODS, can be attributed mainly to the absence of the γ-fiber texture component, bimodal grain size distribution and high amounts of interstitial impurities (O, N).