大尺寸薄壁变截面 ZTA15 钛合金铸件在航空发动机异形、变截面喷管部件中具有广泛应用前景，但其铸造过程易受壁厚参数影响，导致充型不匀、温度分布失衡及凝固缺陷等问题。 基于此，采用 ProCAST 软件对不同壁厚条件下 ZTA15 钛合金铸件的浇注充型过程、温度场、速度场及凝固过程进行数值模拟仿真研究。结果表明，2.0 mm 薄壁铸件充型速度过快，易形成涡流和气孔；8.0 mm 厚壁铸件凝固时间延长，增加缩孔风险；3.5 mm 壁厚下铸件的温度场分布均匀，凝固序列合理，温降首先从米字型横浇道和第一层加强筋开始，后期大平面薄壁表面冷却加速。 所有壁厚铸件内部均存在缩松缩孔，主要集中于中心浇道与米字型横浇道的连接处及加强筋椭圆短轴壁厚区域，这些缺陷源于局部冷却速率差异，导致热应力集中。 大平面薄壁表面不存在明显孤立液相区，表明优化浇注速度和时间可有效抑制缺陷。

Large-scale thin-walled variable-section ZTA15 titanium alloy castings hold significant application potential in the manufacture of complex, variable-section nozzle components for aeroengines. However, the casting process is highly sensitive to wall thickness parameters, leading to issues such as uneven mold filling, imbalanced temperature distributions, and solidification defects. ProCAST software was employed to conduct numerical simulations of the pouring and filling process, temperature field, velocity field, and solidification behavior of ZTA15 titanium alloy castings with different wall thicknesses (i.e., 2.0, 3.5, and 8.0 mm). The results reveal that the 2.0 mm thick-walled castings exhibit excessive filling velocity, resulting in vortex and porosity defects. The 8.0 mm thick-walled castings experience prolonged solidification time, increasing the risk of shrinkage cavities. In contrast, the 3.5 mm wall thickness yields a uniform temperature field and areasonable solidification sequence, with initial cooling occurring at the cross-shaped runner and the first layer of reinforcing ribs, followed by accelerated cooling of the large flat thin-walled surface in the later stages. Shrinkage porosity and cavities are observed across all wall thicknesses, primarily concentrated at the junction of the central sprue and the cross-shaped runner, as well as in the thicker regions near the reinforcing ribs. These defects are attributed to localized variations in cooling rates, leading to thermal stress concentration. No significant isolated liquid phase regions are found on the large flat thin-walled surfaces, indicating that optimizing the pouring velocity and time can effectively mitigate defects.