Ultrasonic Nondestructive Characterisation of Nuclear Materials

Ultrasonic non-destructive evaluation (NDE) technique is a versatile and sensitive tool for structural/microstructural and defect characterisation of materials. An indigenous experimental set-up developed in the authors’ laboratory is used for online ultrasonic velocities and attenuation measurement over a wide range of temperatures from room temperature to 1100 K. The measured ultrasonic parameters such as ultrasonic velocities and derived elastic constants are used to assess changes in microstructural features as a function of temperatures. The first order differentials of the temperature dependent ultrasonic parameters are used to reveal the precise information about the structural/phase transitions. In the present investigation, ultrasonic longitudinal velocity measurements carried out in β-quenched Zircaloy-2 specimens in the temperature range of 298 to 623 K clearly reveal formation of intermetallic precipitates from the β-quenched martensite phase. It is observed that the first order differential plots of variation in ultrasonic velocity as function of temperature is an effective tool in predicting the temperatures at which the structural changes take place. In addition, the fatigue and the creep-fatigue damages in AISI 316 stainless steel are correlated with on-line ultrasonic velocity measurements, particularly made at elevated temperatures. The results reveal that in-situ high temperature ultrasonic measurements enable assessment of creep and fatigue damage with high sensitivity.