Thermophysical investigations of the uranium–zirconium alloy system

• Published in: Journal of alloys and compounds 2014-10, Vol.611, p.355-362
• Main Authors: Ahn, Sangjoon, Irukuvarghula, Sandeep, McDeavitt, Sean M.
• Format: Article
• Language: English
• Subjects: Alloy systems; Annealing; Cross-disciplinary physics: materials science; rheology; Differential scanning calorimetry; Exact sciences and technology; Materials science; Phase diagram; Phase diagrams; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Phase diagrams of metals and alloys; Phase transformation enthalpy; Phase transformation temperature; Phase transformations; Physics; Thermogravimetric analysis; Transformations; Uranium base alloys; Uranium–zirconium alloy; Zirconium
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2014.05.126

•Phase transformation temperatures and enthalpies of U–0.1, 2, 5, 10, 20, 30, 40, and 50wt% Zr alloys were measured using DSC–TGA.•The phase transformation of the (α-U, γ2) phase to the (β-U, γ2) phase at ∼662°C was not evident in Zr-rich (>10wt%) U–Zr alloys.•The absence of the phase transformation is rather consistent with the older U–Zr phase diagram that was experimentally assessed in the 1950s.•The current U–Zr binary alloy phase diagram may need to be revisited regarding the determination of the range of the (β, γ2) phase zone. The solid phase transformation behavior of uranium–zirconium (U–Zr) alloys (U–0.1, 2, 5, 10, 20, 30, 40, and 50wt% Zr) was observed using differential scanning calorimetry (DSC) with thermogravimetric analysis (TGA). The phase transformation temperatures and enthalpies were measured from the alloys annealed at 600°C for 72, 168, and 672h. The observations indicated distinctive mismatches between the measured data and the existing U–Zr alloy phase diagram. Most notably, the phase transformation of the (α-U, γ2) phase to the (β-U, γ2) phase at ∼662°C was not evident in Zr-rich (>10wt%) U–Zr alloys, while only two phase transformations were evident in the U–10Zr and U–20Zr alloys compared to the three isotherm lines extended over the two compositions in the current phase diagram. The absence of the phase transformation is rather consistent with the older U–Zr phase diagram that was experimentally assessed in the 1950s. This observation may lead to the conclusion that the (β-U, γ2) phase region is not correctly represented in the Zr-rich portion, or the hyper-monotectoid region, of the current U–Zr alloy phase diagram. It is evident that the phase diagram needs to be experimentally revisited to provide more reliable information for the development of metallic nuclear fuel performance models, if such models are to include phase-relevant effects, such as fuel constituent redistribution and fission gas swelling.