Microstructural and material property changes in severely deformed Eurofer-97

Kay Song; Guanze He; Abdallah Reza; Tamas Ungár; Phani Karamched; David Yang; Ivan Tolkachev; Kenichiro Mizohata; David E J Armstrong; Felix Hofmann

arXiv · 2308.07735

Microstructural and material property changes in severely deformed Eurofer-97

Kay Song·Guanze He·Abdallah Reza·Tamas Ungár·Phani Karamched·David Yang·Ivan Tolkachev·Kenichiro Mizohata·David E J Armstrong·Felix Hofmann

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Abstract

Severe plastic deformation changes the microstructure and properties of steels, which may be favourable for their use in structural components of nuclear reactors. In this study, high-pressure torsion (HPT) was used to refine the grain structure of Eurofer-97, a ferritic/ martensitic steel. Electron microscopy and X-ray diffraction were used to characterise the microstructural changes. Following HPT, the average grain size reduced by a factor of $\sim$ 30, with a marked increase in high-angle grain boundaries. Dislocation density also increased by more than one order of magnitude. The thermal stability of the deformed material was investigated via in-situ annealing during synchrotron X-ray diffraction. This revealed substantial recovery between 450 K - 800 K. Irradiation with 20 MeV Fe-ions to $\sim$ 0.1 dpa caused a 20% reduction in dislocation density compared to the as-deformed material. However, HPT deformation prior to irradiation did not have a significant effect in mitigating the irradiation-induced reductions in thermal diffusivity and surface acoustic wave velocity of the material. These results provide a multi-faceted understanding of the changes in ferritic/martensitic steels due to severe plastic deformation, and how these changes can be used to alter material properties.

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Kay Song, Guanze He, Abdallah Reza, Tamas Ungár, Phani Karamched, David Yang, Ivan Tolkachev, Kenichiro Mizohata, David E J Armstrong, Felix Hofmann. 2023-08-15. Microstructural and material property changes in severely deformed Eurofer-97. https://arxiv.org/abs/2308.07735

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