Nondestructive Evaluation of Ductile to Brittle Transition Temperature for Martensitic Steels Based on Magnetic Measurements

Interest in magnetic nondestructive evaluation (NDE) methods for nuclear reactors materials to quantify material embrittlement and ensure reactor safety is increased. In this paper, ductile–brittle transition temperature (DBTT) and temperature dependence of the coercive field (\(H_{C})\) and magnetization (M) of martensitic steels (F82H, Eurofer97, SCRAM, T91 and cold rolled T91 steels) were investigated from 100 to 350 K to non-destructively evaluate their DBTT. Results show that a characteristic temperature in both ln(\(H_{C})\) and d(lnM)/d(1/T) vs temperature curves coincides well with the corresponding DBTT measured by Charpy impact test. The curves decrease linearly above and below DBTT respectively, the absolute slope above DBTT is larger than that below. The phenomenon is closely related to the different motion status and the pinning strength of dislocations and magnetic domain wall in the ductile and brittle regions. Results indicate the magnetic evaluation method could be a promising technique with good reproducibility and high sensitivity to evaluate DBTT of martensitic steels used in nuclear reactors.