Contribution to the uranium–gallium phase diagram

Uranium-rich gallium alloys were studied by metallography, electron microscopy, X-ray diffraction and differential thermal analysis. Gallium additions allow retaining metastable β-uranium alloys at ambient temperature. The solubility of Ga in the high temperature uranium phases was determined by WDS, reaches 8 at.% at 800 °C in Uγ and 1.2 at.%, in Uβ at 720 °C. The presence of the Ga5U3 compound, structure type Pd5Pu3, was confirmed.Moderate mechanical stresses at room temperature promote the transformation of the metastable Uβ alloys into Uα′ by a shear-like transformation. The latter is a Ga-containing metastable variant of the room temperature equilibrium uranium allotrope. The matastable structure ultimately reverts to the equilibrium Uα and releases excess Ga by precipitation of the U3Ga5 compound in the form of thin platelets.