铀铌合金的显微组织和相结构与铌含量和热处理制度密切相关。通过定量金相法对不同热处理制度下铀铌合金的显微组织和相结构演化进行了表征和分析。结果表明：淬火铀铌合金为单相过饱和固溶体，随铌含量增加，其相结构变化依次为正交、单斜、四方结构，显微组织形貌变化依次为针状、板条、等轴晶粒；慢冷铀铌合金为富铌（γ_1-2）和贫铌（α'）片层交替组成的珠光体；马氏体组织退火时优先沿奥氏体晶界发生胞状分解，分解组织也为富铌和贫铌片层交替组成的珠光体，分解动力学符合JMAK方程。

Microstructure and phase structure of uranium-niobium alloys are closely related to the niobium content and heat treatment process. The microstructure and phase structure evolution of uranium-niobium alloys under different heat treatment conditions were characterized and analyzed by quantitative metallography. The results show that quenched uranium-niobium alloy was single-phase supersaturated solid solution, and the phase structure transformed from the orthogonal to monoclinic and tetragonal structure with the increase of niobium content, the microstructure changed in the acicular, lath and equiaxed grains sequence. Slow-cooled uranium-niobium alloy was pearlite composed of niobium-rich (γ_1-2) and niobium-poor (α') alternating lamellae. Cellular decomposition occurred preferentially along austenite boundaries during the annealing in martensitic structure, and the decomposed structure was pearlite composed of niobium-rich and niobium-poor lamellae as well. The decomposition kinetics can be well described by the JMAK equation.