气孔缺陷及含障碍物的气泡动力学三维相场模拟研究

Gas Porosity Defect and Three-Dimensional Phase-Field Simulation of Bubble Dynamics in a Microchannel with Obstacle

镁合金铸造过程中气孔缺陷难以避免,而气孔源于未从金属液中逸出的气泡。本文以Mg-Al合金为研究对象,分析了铸态Mg-30%Al(质量分数)合金的气孔缺陷特征。通过将气泡在熔体中的动力学行为抽象为在含障碍物微通道内的动力学行为,以及采用保守相场-格子玻尔兹曼模型,研究了气泡在含障碍物微通道内的演变规律。通过引入形状参数对气泡形状进行量化,研究了障碍物尺寸对气泡动力学的影响。结果表明,随着障碍物宽度的增大,气泡会由被障碍物分裂变为被阻挡,并在后续上升过程中,呈现不同的动力学特征。

Gas porosity, which is difficult to avoid during the solidification of magnesium alloys, originates from gas bubbles that do not escape from the melt. In this work, the gas porosity defect in the Mg-30%Al(mass fraction) alloy is characterized, and the bubble dynamics in the melt are investigated by abstracting such dynamics as bubble rising behavior in a microchannel with the obstacle. A conservative phase-field lattice-Boltzmann model is employed to solve the bubble dynamics, and two shape parameters are introduced to characterize the bubble shape. The effect of the obstacle width on the bubble dynamics is quantified. The results show that the bubble changes from being split by the obstacle to being blocked with increasing obstacle width and presents different dynamic characteristics in the subsequent rising process.