Properties of cast austenitic materials for light water reactors
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文摘
Primary piping elbows of light water reactors are made of cast austeno-ferritic materials (grade CF8 or CF8M) which are susceptible to embrittlement by thermal ageing in service. Ageing kinetics depends on chromium content and on the temperature. The effect of ageing on mechanical properties is determined by the decreasing of Charpy-U energy. It is shown that the rupture of such aged material comes from a combination of cleavage of the ferrite and shearing or ductile tearing of austenite ligaments. The fracture toughness is determined by J-R curves, which exhibit a large scatter related to the solidification macrostructure of the steel. It is shown that J-R curves are independent of the geometry of the specimens.