有外加相存在时Al-Si合金枝晶微观组织的数值模拟

对有外加SiC颗粒(SiCp)的Al-7.0%Si(质量分数)合金熔体凝固过程中球状颗粒与枝晶间相互作用,以及包含颗粒分布的微观组织形成过程进行了模拟研究.在热、溶质守恒的基础上考虑了溶质再分布、界面曲率以及各向异性的影响,并分别对颗粒、固相、液相以及固/液界面进行处理.建立了单个及多个颗粒与枝晶相互作用的数值模型,预测了单个颗粒与凝固界面之间的吞并/推移现象,并研究了颗粒附近枝晶生长的溶质浓度场、速度场以及界面形状,再现了多颗粒与多枝晶相互作用直至最终偏聚到枝晶间的过程.模拟结果表明:颗粒被推移时颗粒与界面的相互作用是一个非稳态的过程,但是在凝固速率较低的条件下可以按照稳态推移的模式进行处理.模拟得到的颗粒分布及微观组织与实验结果吻合较好.

Numerical simulation of dendrite microstructure for Al-Si alloy with additive phase

The interaction between spherical particles and dendrites,and the process of mi- crostructure formation including particle distribution for Al-7.0%Si(mass fraction)alloy with additive SiC particles were simulated.Based on heat and solute conservations,the solute redistribution,inter- face curvature and anisotropy were considered.Particle,solid,liquid as well as solid/liquid interface were treated respectively.The numerical models that describe the interaction between single parti- cle/multiple particles and dendrites were established.The engulfment/pushing phenomena between single particle and solidification interface were predicted,and solute concentration field and velocity field of the growing dendrites and solid/liquid interface shape close to particle were studied.The in- teraction process between multiple particles and dendrites,and the segregation of particles into the interdendrite regions were recurred.The simulated results show that the interaction between particles and advancing curved solid/liquid interfaces is non-steady state when the particle is pushed,while it can be treated as steady pushing mode when solidification velocity is lower than critical velocity.The simulated results of dendrite microstructure and particle distribution are in good agreement with the experimental ones.