Low Temperature Ageing Behaviour of U-Nb $\alpha''$ Phase Alloys

Abstract

Ageing mechanisms of the U-5\,\%wtNb system have been investigated on samples exposed to temperatures of 150$\,^{\circ}$C for up to 5000\,hours. A variety of surface and bulk analytic techniques have been used to investigate phase, chemical and crystallographic changes. Characterisation of microstructural evolution was carried out through secondary electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and x-ray diffraction (XRD). This investigation suggests crystallographic defects such as twinning furthers the martensitic tendencies with ageing. Resizing of the lattice and shuffling of atoms results in a small progression from the $\alpha''$ towards the $\alpha'$ phase.