The mechanical properties of two uranium alloys and their role in the oxidation of the alloys

The creep and tensile properties of two uranium alloys (U-21 at.% Nb and U-16.6 at. % Nb-5.6 at. % Zr) were determined in the temperature range 750–900°C. The creep data were fitted to an equation of the form $$\dot \varepsilon = k\sigma ^n$$ exp (-Q/RT)which in turn was used to calculate stresses in oxidizing alloy specimens on the basis of elongation measurements made on the specimens during oxidation. The variation of the average stress in the oxide and in the substrate metal is given as a function of time. The details of the mechanism by which stresses are generated during the oxidation of the alloys are discussed. Comparisons of the relative creep and oxidation rates of the alloys with the stress levels observed during oxidation lead to the conclusion that at least for certain specimen geometries the differences in the mechanical properties of the oxide scales and of the parent alloys account in large measure for the differences in the oxidation characteristics of the alloys.