对现有的气孔与晶界相互作用的相场模型进行改进，提出了新形式的自由能密度函数，并采用了张量形式的扩散系数。分析了相场模型中唯象参数的选择依据，并讨论了模型中界面能和界面宽度等物理参数的影响因素。气孔和晶界相互作用的相场模拟结果表明：晶界的曲率是晶界移动的动力，而气孔是晶界移动的阻力；当气孔施加的最大阻力大于等于晶界移动的动力时，气孔会随晶界一起运动；而当气孔施加的最大阻力小于晶界移动的动力时，气孔与晶界分离。若气孔与晶界未发生分离，体系的演化将由晶界主导转变为气孔主导，演化速率显著下降。含气孔UO₂多晶体系的晶粒生长的相场模拟结果表明：气孔率越大，晶粒生长速率越慢；UO₂平均晶粒直径与时间成幂函数关系，幂指数随气孔率的增大而增大。

The grain boundary (GB) and average grain size considerably affect the properties of materials, such as the fracture strength, dielectric constant, and thermal conductivity. For instance, when subjected to irradiation at 1750 ℃, the swelling of the UO₂ pellets and the release of fission gas from them decrease significantly with the increasing average grain size. However, several second-phase particles, such as pores, are inevitably introduced into a material during the solid-phase sintering or neutron radiation processes. Therefore, studying the interaction between the pores and GBs is considerably important. In this study, a phase-field model of the interaction between the pores and GBs is developed. Subsequently, the free-energy density function was modified, where the diffusion coefficient was incorporated in the tensor form. In addition, the selection of the phenomenological parameters, such as the coefficient in the free-energy density function of the phase-field model, was analyzed, and the influencing factors of interface energy and interface width were discussed. The phase-field model simulation results of the interaction between the pores and GBs show that the curvature of GB was the major driving force associated with the movement of GB and that pores resisted the movement of GB. Accordingly, the pores moved together with the GBs when the maximum pinning force exerted by the pores was larger than the driving force produced by the curvature of GB; however, the pores and GBs separated in the opposite case, during which the GB moved much faster than pores. The results of the phase-field simulation of the grain growth of the pore-containing UO₂ show that the grain growth speed decreases with the increasing porosity. The average grain size of UO₂ is a power function of time, the exponent of which increases with the increasing porosity.