Study of the Transformation of Uranium-Niobium Alloys With Low Niobium Concentrations, Tempered From the Gamma and Beta + Gamma 1 Regions and Then Annealed at Different Temperatures. Comparison With Uranium-Molybdenum Alloys; Etude des transformation des alliages uranium-niobium a faible teneur en niobium trempes depuis les domaines gamma et beta + gamma 1 puis revenus a differentes temperatures. Comparaison avec les alliages uranium-molybdene
- Nancy Univ., Lorraine (France)
The author shows that uranium-niobium alloys, like uranium-molybdenum alloys, tempered from the gamma region, give a martensitic phase with a structure deriving from that of alpha uranium by a slight contraction parallel to the axis [001], The critical cooling rate allowing the formation of this martensite is 80 deg. C/s at 750 deg. C. Retention of the beta phase of uranium-niobium alloys is particularly difficult, the critical retention rate being 700 deg. C/s at 668 deg. C for an alloy containing 2.5 at. per cent of Nb. This beta phase is completely converted to the alpha phase at room temperature in about 6 hours. The TTT curves of this beta alloy are effectively reduced to the lower branch of the lower 'C'. The beta phase conversion law is expressed as: 1-x = exp. (kt)n x being the degree of progression of the conversion, t the time, n an exponent no-varying with temperature and having approximately the value 2 for the alloy considered, k an increasing function of temperature. The activation energy of conversion is of the order of 14,600 cal/mole. Niobium is much less active than molybdenum as a stabiliser of beta uranium.
- Research Organization:
- Nuclear Studies Center of Bordeaux Gradignan, Saclay (France)
- Sponsoring Organization:
- US Atomic Energy Commission (AEC)
- NSA Number:
- NSA-18-024124
- OSTI ID:
- 4055160
- Report Number(s):
- CEA--2341
- Country of Publication:
- France
- Language:
- English
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