钛合金氧化钇铸型凝胶注模成形缺陷模拟与控制

Simulation and Control of Forming Defects in Gel Casting of Yttria-Stabilized Ceramic Molds for Titanium Alloy

摘要:

针对钛合金闭式叶轮一体化氧化钇陶瓷铸型凝胶注模过程中气泡滞留缺陷导致金属铸件瘤状凸起的问题，本文构建Carreau非牛顿粘度模型和VOF两相瞬态充型的预测与调控框架。通过实验流变数据拟合获得氧化钇浆料 Carreau 模型（相对误差 <5%），并复现充型过程气泡生成和滞留的时空演化，模拟得到的滞留位置与陶瓷铸型 CT 空洞及钛合金铸件CT瘤状凸起在叶轮/底部区域呈高度空间对应。研究表明：适中充型速度为0.05 m/s可显著降低滞留体积；底注式充型结构可基本消除叶轮区滞留；在此基础上施加水平振动（50 Hz，1 mm）后气泡滞留完全消除。基于模拟优化制备的陶瓷铸型经扫描验证，叶轮内部气泡滞留消除。研究为复杂钛合金构件的凝胶注模铸型提供了缺陷预测与主动调控的理论框架。

Abstract:

To address nodular protrusions on titanium-alloy closed impellers caused by gas entrapment during gelcasting of integrated Y?O? (yttria) ceramic molds, this work establishes a predictive and control framework that couples a Carreau non-Newtonian viscosity model with a transient two-phase VOF filling solver. Rheological experiments are fitted to obtain the Carreau parameters for the yttria slurry (relative error < 5%), enabling time–space reconstruction of bubble generation–migration–entrapment throughout filling. The simulated entrapment locations exhibit strong spatial correspondence with computed-tomography (CT) voids in ceramic molds and nodular defects on Ti-alloy castings at both the impeller and bottom regions. Parametric studies indicate that a moderate filling velocity of 0.05 m·s?1 markedly reduces trapped-gas volume; a bottom-fill configuration essentially eliminates entrapment in the impeller region; and, on this basis, applying horizontal vibration (50 Hz, 1 mm) during and after filling removes the remaining bubbles. Ceramic molds fabricated with the optimized parameters were verified by scanning, confirming the disappearance of gas entrapment within the impeller. The study provides a reusable framework for defect prediction and active process control in gelcasting of complex Ti-alloy components.