W-Cu液相烧结体系致密化行为的模拟

Simulation of densification process of W-Cu system during liquid-phase sintering

基于流体流动模型和液相烧结作用力模型,对液相烧结第一阶段中(液相生成与固相颗粒重排阶段)液相Cu对固相W颗粒的润湿情况及颗粒的重排和密实化行为进行模拟。本模型包含Navier-Stokes(N-S)方程、区分气-液两相流的VOF方程及颗粒所受作用力(毛细力和黏性力)方程。使用二维非定常分离隐式PISO算法求解N-S方程,描述流体流动行为;求解VOF方程以区分气-液两相流;根据颗粒所受作用力编制颗粒运动自定义程序,控制颗粒运动,描述固相颗粒在毛细力牵引及黏性力共同作用下的运动。分析烧结过程液相对固相颗粒的润湿行为及液相烧结第一阶段密实化规律。探讨润湿角、颗粒间距对毛细力大小的影响,并结合具体烧结模型研究烧结体系颗粒尺寸对密实化速度的影响及不同初始液固比与烧结体系最终孔隙率的关系。最终将模拟结果与理论分析结果进行对比,两者基本一致。

The computational fluid dynamics model and interaction force model were applied to simulating the first wetting and rearrangement stage and densification behavior of W-Cu liquid phase sintering system. Navier-Stokes equation, volume of fluid （VOF） equation and interaction force （capillary force and viscosity force） equation were all involved in the model. The Navier-Stokes equations of fluid phases （including liquid and gas phases） were solved by pressure implicit with splitting of operators （PISO） and the VOF model was used to distinguish flowing behavior between liquid and gas phases. The interaction force between solid and liquid was described by a published theoretical model. The movement of solid particles was calculated by a user defined program based on the interaction forces. The wetting behavior of liquid phase to solid particle during sintering process and densification behavior were studied. The effects of wetting angle and particle distance on capillary forces were investigated. The influences of particle size on densification rate and the initial liquid-solid ratio on the final porosity were both discussed. Finally, simulation results were compared with the published theoretical results. The results show that they agree well with each other.