Structural Insights in the β to α Phase Transformation of the U–1 wt.%Ga–0.2 wt.%Fe Alloy

β-U could be metastably retained at room temperature when alloyed with various elements such as gallium. Since iron is a common impurity, we investigated two different kinetic processes which occurs simultaneously; one is the β → α transformation and the other is the precipitation of the U₆Fe phase from the iron dilute U(Ga)–Fe alloy. Furthermore, we determined the solubility of iron and gallium solubility in quenched uranium from 800 to 720 °C (γ and β phase regions, respectively). It was shown that the β → α phase transformation is sluggish and has a character of massive transformation. The retention from the β phase region does not fully stabilize β phase, and α phase is also formed during quenching, while the γ-quenched sample remains metastable at room temperature, and only high-temperature heat treatment transforms β to α. The precipitates found in the system are U₆Fe and U₂Ga₃, no ternary intermetallics were detected, and the morphology of the precipitates does not depend on the heat treatment course. The gallium and iron contents found in the γ- and β-quenched samples are X_Ga= 0.72 wt% X_Fe= 0.18 wt% and X_Ga= 0.42 wt% X_Fe= 0.06 wt%, respectively. The different gallium contents in the γ and β explain the differences in the β → α phase transformation kinetics. Quenching U–Ga alloys (above the solubility limit of gallium) from the γ region stabilizes β-U better than quenching from the β region.