The phase equilibria and thermodynamic properties of the U–Nb system were investigated through experiments and thermodynamic modeling. In the experiments, a series of samples with different content of Nb were prepared by arc melting. The Nb content covers the entire composition range of the U–Nb binary system. After solidification, the samples were annealed and then analyzed by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimeter and neutron diffraction. The equilibrium phases, including γ₁ (U-rich bcc), αU, and γ₂ (U-depleted bcc), were determined in detail from the experimental characterization. The occurrence of the invariant reaction γ₁→ αU + γ₂ was confirmed, and the reaction temperature and composition were accurately identified. Moreover, the experimental findings clarify the dispute between the Dwight and Terekhov theories regarding the phase region (i.e., whether the phase region is αU + γ₁ or βU + γ₂). Furthermore, the U–Nb phase diagram was reassessed by incorporating the present experimental data and previously published reliable experimental data from the literature. A set of self-consistent thermodynamic parameters were developed using CALPHAD (Calculation of phase diagrams), and the calculations reasonably agree with the experimental observations.

通过实验和热力学模型研究了U–Nb系统的相平衡和热力学性质。在实验中，通过电弧熔化制备了一系列具有不同Nb含量的样品。Nb的含量涵盖了U–Nb二元体系的整个成分范围。固化后，将样品退火，然后通过X射线衍射，扫描电子显微镜，能量色散X射线光谱，差示扫描量热仪和中子衍射进行分析。平衡相，其中γ ₁（U-富BCC），αU，和γ ₂（U-耗尽BCC），在从实验表征细节进行了测定。不变反应的发生γ ₁ →αU+γ ₂确认，并准确鉴定反应温度和组成。此外，实验结果澄清有关的相位区域的德怀特和捷列霍夫理论之间的争议（即，相位区域是否为αU+γ ₁或βU+γ ₂）。此外，通过结合目前的实验数据和先前从文献中发表的可靠实验数据，重新评估了U–Nb相图。使用CALPHAD（相图的计算）开发了一组自洽的热力学参数，并且这些计算与实验观察值合理地吻合。