Recent progress of R&D activities on reduced activation ferritic/martensitic steel (CLF-1)

Ferritic/martensitic (F/M) steels have been proposed as important candidates for structural materials of nuclear reactors due to their good mechanical properties and radiation resistance. Compared with traditional normalizing and tempering (N&T) or quenching and tempering (Q&T) processes, recent studies have shown that a quenching and partitioning (Q&P) process can significantly improve the strength of steels due to the multi-phase microstructure. In this study, we developed a Q&P process that significantly improved the ultimate tensile strength/yield strength of a modified 9Cr–2WVTa steel from ~752 MPa/~644 MPa to ~1210 MPa/~927 MPa at room temperature, maintaining a total elongation of ~21.4%. Additionally, the strength of the steel at elevated temperatures (25–600 °C) was significantly improved by the Q&P process. The strengthening effect is attributed to the combined effects of the different microstructure characteristics, i.e., more solute carbon atoms within the matrix, higher dislocation density in the martensite, refined structural units (martensite packets/ultra-fine martensite laths) and finer precipitates (M23C6, MX, and θ-carbide). The relationship between the microstructures resulted from the two processes and the corresponding mechanical properties has also been comparatively discussed, which provides guidelines for tailoring the microstructure and mechanical properties of F/M steels by a Q&P process.

Comparative study on the microstructure and mechanical properties of a modified 9Cr–2WVTa steel by normalizing-tempering and quenching-partitioning treatments

Potential application of Laser Solid Forming Technology for fabrication of breeding blanket

Microstructure and mechanical properties of thick CLF-1 reduced activation steel weld joint made by electron beam welding joint

Heat treatment optimization of China low-activation ferritic/martensitic steel with cerium addition

The effects of heat treatment parameters on microstructure and mechanical properties of reduced activation ferritic/martensitic(RAFM) steels were investigated by microhardness test,microstructure observation and tensile test at room temperature.The feasible heat treatment process was determined.The results show that good microstructure and mechanical properties of the steel were obtained after solution treated at 980 ℃ for 45 min and tempered at 740 ℃ for 90 min,that the tensile strength was 760 MPa and the elongation was 19.5%,which could satisfy its working need.The recrystallization temperature was about 780 ℃,the transformation temperature from α phase region to α and γ two-phase region was about 820 ℃,γ single-phase region temperature was slightly higher than 920 ℃.

Chen Ji-ming

Papers

Heat Treatment Process for CLF-1 Reduced Activation Ferritic/Martensitic Steel