Nanoparticle Capture During Directional Solidification of Nano-Sized SiC Particle-Reinforced AZ91D Composites

The capture/push behavior of a particle in front of a solidification interface was analyzed theoretically and experimentally in this work. Van der Waals force, viscous force, and force due to interfacial energy played important roles in the particle capture/push process. Directional solidification experiments were conducted with nano-sized SiC particle-reinforced AZ91D composites to observe the distribution of nanoparticles in different solidification morphologies under varied cooling rates. When the composite solidified with plane manner, the nanoparticles could be captured by the solidification front and distributed uniformly in the matrix. When solidified with columnar or equiaxial manners, the nanoparticles could be captured by the solidification front but distributed uniformly only in the grain boundary as a result of the difference in interfacial energy and wettability between SiC/alpha-Mg and SiC/eutectic phase. Theoretical prediction of particle capture was in agreement with the experiment results.