Precipitates Morphology in Iron-Diluted U–Fe Alloys

Abstract

The morphology of U 6 Fe precipitates were investigated in the different allotropic states of uranium matrix. The morphology of c-U is equiaxed and the characteristic size is *65 lm. The excess dissolved iron in b-U precipitates discontinuously through a eutectoid reaction during cooling at the grain boundaries, while a-phase precipitates have a ''needle-like'' morphology (in many cases, aspect ratio )10) with a well-defined direction in the uranium matrix. This morphology may compensate for the large density differences of *9 % between a-U and U 6 Fe (*19 and *17.4 g/cm 3 , respectively) and the fact that precipitation takes place at relatively low temperatures. It was shown that U 6 Fe precipitates do not introduce new nucleation sites in b and a phases of uranium.