Study on Microstructure Evolution of Deformed Low-Activation F/M Steel During Annealing

A new kind of high-chromium low-activation ferritic/martensitic steel (0.14C-11.06Cr-2.3W) as one of the most promising candidates for SCWR fuel cladding tube was designed and fabricated. The experimental steel after quenching-and-tempering heat treatment had a typical tempered martensitic structure. The specimens were cold-deformed by uniaxial compression to a reduction of 60% and then annealed at 750-820 ℃ for 10-720 min. The changes of matrix structure in prior cold-deformed lath martensite and softening behavior occured during annealing were investigated. The results show that the behaviors of recrystallization and austenite formation are changed by the prior deformation. The specimens without pre-deformation do not undergo recrystallization even when annealed at a rather high temperature. However, after receiving sufficiently large cold strains (60%), the deformed lath martensite easily recrystallizes. The austenite forms directly from the tempered lath martensite in the non-deformed lath martensite, when the lath martensite deforms to a reduction of 60%, the recrystallization occurs prior to austenite formation, the austenite nucleates and grows at the boundaries of completely recrystallized ferrite grains.