1963•OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information)Requires access
STUDIES OF THE SYSTEM ZIRCALOY-2-NIOBIUM-OXYGEN
A.E. Bibb, J.R. Fascia
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Abstract
The additions of niobium and oxygen to Zircaloy-2 were found to increase the mechanical strength at temperatures up to --500 deg C. Hardness variations produced by recrystallization of 16 to 20% cold-worked Zircaloy-2--niobium - oxygen alloys were foumd to be masked by variations caused by annealing-induced structural changes involving omega formatiom. High-temperature x-ray, dialatometer, and differential-thermal-analysis studies were used to investigate the phase relationships in these alloys. The monotectoid temperature in the pseudotermary diagram of Zircaloy-2-- niobium was determined as 605 deg C. Oxygen had no apparent effect on this temperature. The maximum solubility of niobium in Zircaloy-2 was found to be below 2.5 wt.% niobium for all alloys containing between 700 and 3500 ppm oxygem. Isothermal sections of the pseudoternary phase uiagram for Zircaloy-2-- niobium-- oxygen for specific temperatures in the range 800 to 1600 deg C are presented and discussed. (auth)