Micromagnetic nondestructive evaluation of microstructural evolution for structural materials

It is essential for both integrity assurance and remaining life assessment of power plant to know the damage state of the structural materials. The microstructural evolution and solute segregation induced in a thermal or radiational environment frequently produce severe degradation of the mechanical properties of steel. Current nondestructive evaluation methods are mainly for the detection and characterization of flaws and cracks, not for the evaluation of the time-dependent changes in microstructural features. The measurement of Barkhausen noise (BN) and structure-sensitive magnetic properties is a promising potential tool responding sensitively to changes in internal microstructural features as well as stresses in ferromagnetic materials. The microstructural evolution of the 12% Cr steels during various heat treatments is closely related to the degradation states of nuclear structural materials. At this investigation, the mechanical properties like hardness and the microstructural evolution were nondestructively evaluated by the measurements of structure-sensitive magnetic properties and BN for the degradation states of nuclear structural material