对重力作用下Al-Si/SiC颗粒系统二维凝固过程的数值模拟

论文采用多相流模型对重力作用下Al Si 7% (质量分数 ) /SiC颗粒功能梯度材料二维凝固过程进行了数值模拟 .计算了在不含颗粒、含有小尺寸颗粒和含有大尺寸颗粒几种不同条件下颗粒和液相的运动 ,产生的宏观偏析 ,共晶合金在晶体中所占比例 ,以及最终的颗粒分布 .结果表明 ,颗粒和糊状区的存在会使液态金属的流动阻力增大 ,流速降低 ,产生的宏观偏析减弱 .在含有小尺寸颗粒的情况下 ,液相和颗粒运动速度很小 ,大部分区域保持初始颗粒体积分数不变 .在含有大尺寸颗粒的情况下 ,颗粒沉降速度很快 ,在底部形成颗粒堆积区 ,在上部形成颗粒体积分数为零区 .

Numerical Simulation of Al-Si/SiC Particle System Two Dimension Solidification Processing by Gravity Casting

A multiphase model has been developed and applied to two-dimensional solidification processing of Al-7 wet pct Si/SiC particles Fgm. Macroscopic transport equations were written for each phase, with unknown parameters modeled through supplementary relations. Particle segregation, liquid metal flow, species macrosegregation , eutectic fraction and final macroscopic particle distribution were modeled in various systems with or without particles. Results indicate that convection during solidification is substantially reduced in the presence of particles due to the relatively large interfacial drag exerted on the liquid by the particles and stationary mush. Species macrosegregation is also reduced. For small particles, fewer particles settle prior to entrapment since the drag is relatively high. In contrast, large particles result in a large amount of settling and packing which leads to large denuded zone and packed zone in the casting.