Tensile and Fracture Toughness Properties of EUROFER ODS ("EU Batch" - 6 mm Plate) in the Unirradiated Condition

In the EU, the most advanced approach for the breeding blankets envisages the use of oxide-dispersion strengthened (ODS) steels to achieve service temperatures as high as 650 °C, that is 100 °C higher than the current operating limit for conventional reduced-activation ferritic/martensitic (RAFM) steels such as EUROFER. Within the EFDA Long Term Programme task TTMS-006, several versions of EUROFER ODS have been produced and investigated; the most recent one, denominated "EU batch", is presently being characterized by several European labs in the unirradiated condition. SCK•CEN has performed tensile tests in the range -150 to 650 °C and fracture toughness tests in the ductile-to-brittle transition region, using sub-size specimens extracted from a section of the 6 mm plate supplied by FZK Karlsruhe. These results will also serve as a baseline for the characterization of the mechanical properties after irradiation in IRFUMA-5M (300 °C, 2 dpa). In general, it has been found that the tensile behaviour of the "EU batch" is similar to previous versions of EUROFER ODS and better than the standard EUROFER, in terms of both strength and ductility. On the other hand, fracture toughness in the unirradiated condition is much worse than the standard EUROFER; the reference temperature lies just above room temperature (32 °C), whereas for the non-ODS material we had previously measured To = -112 °C.