Phase characterization of the gamma decomposition of the U3Zr9Nb solid solution alloy during isothermal treatments at 300 deg C: preliminary work

Alloys of uranium with the composition of U3Zr9Nb have been investigated at CDTN. Investigations have shown that the metallurgical structures of uranium-rich alloys containing zirconium or niobium were quite similar to the structure of uranium alloys containing transitions metals. It has been known that additions of niobium and zirconium improve the properties of the uranium base alloys. In our work the starting materials were uranium of technical purity with about 500 ppm of metallic impurities, zirconium of purity 99.8 % and niobium of purity 99.9 %. Vacuum induction melting of these alloys were cast into ingots. The ingots were annealed and homogenized at 1000 deg C/24 hours in vacuum of < 10-4 Torr, and cooled at a rate of 3 deg C/min to room temperature. These uranium alloys were then reheated to gamma phase at about 800 deg C, for 1 hour. After quenching in a tin bath at 300 deg C samples were subjected to aging treatments in the range from about 4 minutes to 48 hours. Th samples were characterized by X-ray diffraction, metallographic examination, quantitative analysis using energy dispersive X-ray spectrometry and Vickers microhardness test. The results of quenching samples from 800 deg C and aging to 300 deg C have not revealed phase decompositions of the gamma cubic phase into martensitic phases. (author)