X-ray diffraction study of δ-stabilized plutonium alloys under pressure

Previous extensive studies of the δ → α′-phase transformation induced by temperature and/or by pressure in δ-stabilized plutonium alloys indicate strong dependence on parameters such as solute type, solute distribution, chemical impurities, kinetics, thermodynamic path….The present paper reports results obtained on two Pu–2.3at.%Ga binary alloys differing by solute homogenization treatment and studied under pressure by in situ by X-ray diffraction in diamond anvil cells. The γ′-phase appears as an intermediate phase during the δ → α′-phase transformation. In cored samples, unexpanded α′-phase is formed at the beginning of the transformation, from domains with low solute content, and expanded α′-phase subsequently forms (from domains with higher solute content) as the transformation progresses with the pressure increase.