Microstructure of reduced activation ferritic/martensitic steel after transformation super plasticity
Year: 2025
Type: article
Abstract: Reduced activation ferritic-martensitic (RAFM) steels are considered promising candidates as structural materials for fusion blankets. However, the poor processability of RAFM steels is one of the critical issues in their application to fusion blankets. To address the issue, a new material processing based on transformation super plasticity (TSP), a type of superplastic forming (SPF), has been investigated for advanced fusion engineering. Our previous studies have demonstrated that the total elongation of a RAFM steel (JLF-1) reached 170 % through tensile tests under constant load and cyclic heat treatment, suggesting that the TSP-type SPF can be used for the macroscopic deformation processing of RAFM steel. For the application of TSP-type SPF, it is essential to study the microstructure before and after TSP. In this study, the effect of cyclic heat treatment on the microstructure before and after deformation in tensile tests using the TSP was investigated. Microstructural TEM observation of M 23 C 6 and MX precipitates showed that only M 23 C 6 disappeared after tensile tests with cyclic and isothermal temperature and precipitated again by the following tempering. The results indicate that the MX alone remaining at the lath boundaries cannot inhibit the TSP creep deformation, and the combination of dissolution of M 23 C 6 at the block boundaries and cyclic phase transformation may enhance the TSP creep deformation. These results will contribute to the development of advanced processing technology for fusion blankets.
Source: Fusion Engineering and Design
Institution: National Institute for Fusion Science
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,810
OpenAlex ID: W4415630049