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

Author of the article:ZHANG Ang1 , LI Chuangming1 , SU Dongbo1 , DU Jinglian2 , LIU Feng2 , JIANG Bin1

Author's Workplace：1. National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044, China; 2. State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China

Key Words：magnesium alloy; gas porosity; bubble dynamics; obstacle; phase-field simulation

Abstract：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.