Effect of thermo-mechanical processing on microstructure and mechanical properties of U – Nb – Zr alloys: Part 1 - U–6 wt. % Nb –6 wt. % Zr

Abstract The present work is part of an extended investigation on U - Nb - Zr alloys and investigates the effect of mechanical processing routes on microstructure of U - 6 wt. % Nb - 6 wt. % Zr alloy, through X-ray diffraction and scanning electron microscopy. Mechanical properties are determined using microhardness and simple bending tests and correlated with the developed microstructures. The results show that processing sequence, in particular the inclusion of a 1000 °C heat treatment step, affects significantly the microstructure and mechanical properties of this alloy. Microstructural characterization shows the presence of large amounts of primary γ-Nb-Zr rich precipitates. Simple bending tests show that sample ductility does not correlate necessarily with hardness and that the key factor appears to be the amount of the γ-Nb-Zr precipitates. Samples with a monoclinic α ″ cellular microstructure, although not strictly ductile, showed the largest allowed strains-before-break, pointing out to the macroscopic observation of superelasticity.