STRUCTURAL TRANSFORMATIONS IN U3SI

X-ray diffraction analysis has been used to examine the phase change introduced in U3Si thermally, by irradiation at 60°C and by plastic deformation. Short irradiation exposures (burnup ≤ 0.12 × 10-3% of all atoms) and plastic deformation modified the room temperature structure of U3Si, be tetragonal, to a disordered fcc structure, while heating above 756 ± 5 °C caused an allotropic transformation to an ordered fcc structure of the Cu3Au type. Lattice parameter determinations indicated that the irradiation-induced phase transformation was accompanied by a volume increase of 0.6%. Further irradiation resulted in a nearly complete destruction of the diffraction pattern as the U3Si became amorphous. The damage introduced by irradiation or by plastic deformation annealed in the range 250-500 °C with a complete recovery to the bc tetragonal structure. © 1969.