Phase transformation of metastable discontinuous precipitation products to equilibrium phases in U10Mo alloys

Abstract The discontinuous precipitation (DP) mechanism is prevalent in over 80 alloy systems. We report a new type of DP occurring along prior γ-UMo grain boundaries of an alloy of uranium with 10 wt% molybdenum (U10Mo) during annealing at 500 °C, forming alternate lamellae of Mo-enriched γ-UMo and α-U. During prolonged annealing, the metastable Mo-enriched γ-UMo lamellae gradually transform into a composite mixture of equilibrium γ′-U2Mo embedded in Mo-depleted γ-UMo. Using high resolution scanning transmission electron microscopy and atom probe tomography, a comprehensive description of the structural and compositional changes of the metastable lamellar DP product to near-equilibrium phases is provided.