Long-term properties of reduced activation ferritic/martensitic steels for fusion reactor blanket system

Thermal aging properties of reduced activation ferritic/martensitic steel F82H was researched. The aging was performed at temperature ranging from 400 degrees C to 650 degrees C up to 100,000 h. Microstructure, precipitates, tensile properties, and Charpy impact properties were carried out on aged materials. Laves phase was found at temperatures between 550 and 650 degrees C and M(6)C type carbides were found at the temperatures between 500 and 600 degrees C over 10,000 h. These precipitates caused degradation in toughness, especially at temperatures ranging from 550 degrees C to 650 degrees C. Tensile properties do not have serious aging effect, except for 650 degrees C, which caused large softening even after 10,000h. Increase of precipitates also causes some degradation in ductility, but it is not critical. Large increase in ductile-to-brittle transition temperature was observed in the 650 degrees C aging. It was caused by the large Laves phase precipitation at grain boundary. Lives precipitates at grain boundary also degrades the upper-shelf energy of the aged materials. These aging test results indicate F82H can be used up to 30,000 h at 550 degrees C. (C) 2011 Elsevier B.V. All rights reserved.