MORPHOLOGY OF PRECIPITATION IN ALLOYS OF URANIUM-ALUMINIUM AND URANIUM-IRON-ALUMINIUM

Transmission electron microscopy of thin foils has been used to investigate the precipitates formed when alloys of uranium-aluminium and uranium-iron-aluminium are quenched from the gamma phase and annealed in the alpha phase. In the ternary alloy comparatively large precipitates of U6Fe formed rapidly at grain boundaries. In both alloys the intragranular precipitates have been identified by selected area electron diffraction as UAl2, except in the early stages of ageing of the ternary alloy when most of the particles have been found to be of the ternary compound U(Fe,Al)2. Evidence for orientation relationships between these phases and the matrix is presented and the atomic rearrangements involved in their formation are discussed. The thin foil observations indicate that the majority of the particles are preferentially nucleated on dislocations. © 1969.