Irradiation hardening and ductility loss of Eurofer97 steel variants after neutron irradiation to ITER-TBM relevant conditions

• Published in: Fusion engineering and design 2021-12, Vol.173 (NA), p.112935, Article 112935
• Main Authors: Bhattacharya, Arunodaya, Chen, Xiang, Graening, Tim, Geringer, Josina W., Reed, Jordan, Henry, Jean, Pilloni, Luciano, Terentyev, Dmitry, Puype, Athina, Byun, Thak Sang, Katoh, Yutai, Rieth, Michael, Zinkle, Steven J.
• Format: Article
• Language: English
• Subjects: Diamond pyramid hardness; Ductility; Elongation; Eurofer97 steel; Ferritic stainless steels; fracture; Irradiation-hardening; Low temperature; Martensitic stainless steels; MATERIALS SCIENCE; Necking; Neutron irradiation; NUCLEAR PHYSICS AND RADIATION PHYSICS; Plastic instability; Reduction; Reduction in area; Steel; Strain hardening; Tensile properties; Tensile stress; True stress; Work hardening; Yield strength; Yield stress
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2021.112935

•Neutron irradiations cause hardening, ductility loss and strain hardening capacity reduction in Eurofer97 steel variants (∼3 dpa, 300 °C).•Post-necking ductility mainly contributes to the irradiated tensile elongation, with mostly ductile failures.•RA decreases after irradiation, and the irradiation-induced yield stress increase and loss in RA appear to be inversely correlated.•RAFM steel designing should target a large separation between plastic-instability stress and yield stress. Ten Eurofer97 steel variants, produced by non-standard fabrication-processing routes and modified alloying chemistries, were studied by neutron irradiations in the high flux isotope reactor. The irradiations were performed to ITER-TBM relevant conditions of ∼255–350 °C, 2.94–3.24 dpa. We quantified the irradiation-induced degradation of the steels using mechanical property tests. All the steels suffered from irradiation hardening, where a significant increase in Vickers microhardness and yield stress (σYS) occurred, accompanied with severe loss of tensile elongation. The extent of hardening was material dependent. For Tirr = 300±30 °C, most steels showed σYS increase in the range of ∼30% to as high as ∼66%, except for a low temperature tempered steel with σYS increase below 15%. Despite large losses in elongation, most failures were ductile. Significant post-necking ductility was retained with reduction in area (RA) between 65–75%, but