Small specimen fracture toughness tests of HT-9 steel irradiated with protons

A method to evaluate the fracture toughness, using the recrysatallization technique and a small punch test, has been developed on miniaturized specimens of ferritic/martensitic steel HT-9. The recrystallization technique, to measure the plastic strain region formed with crack extension in precracked disk-shaped compact tension (DCT) specimens, made it possible to drop and acoustic emission measurements were also applied to detect the crack extension together with load/displacement curves in DCT specimens. The small punch tests demonstrated a clear ductile-brittle fracture energy transition behavior and good ductile-brittle transition temperature (DBTT) correlation with the Charpy V-notch tests results. The effect of proton irradiation and/or hydrogen charging on the fracture behavior of HT-9 was observed. (orig.)