ULTRASONIC EVALUATION OF HYDRIDE CONCENTRATION IN ZIRCONIUM-NIOBIUM ALLOYS

An ultrasonic method has been developed to observe the solid solubilit y phase transition of metallic hydride in zirconium-niobium alloy. Thi s measured the change in ultrasonic velocity with temperature as the s ample was cooled through the expected solid solubility temperature (SS T). At the SST, free hydrogen forms a hydride precipitate within the m etallic structure on cooling, and the temperature dependence of ultras onic velocity was seen to change at this temperature, for both longitu dinal and shear waves. These results were compared to those of thermal expansion, using a dilatometer, where again the SST could be estimate d. Analysis of the data indicates that both measurements could be used as the basis for a possible nondestructive estimation of hydrogen con tent in these alloys. (C) 1997 Elsevier Science B.V.