Multi-Phase Structure Control and Interfacial Investigation of TiB2/Hypereutectic Al-Si Alloy

Abstract

The effect of the distribution of the primary phase Si and TiB2 particles in the hypereutectic Al-Si alloy was studied and found to be influenced by the cooling rate. Therefore, this article studies the effect of the cooling rate on the multi-phase structure of TiB2 particles in Al-20Si using a wedge-shaped mold. The sizes, shapes, and distribution of primary phase Si and TiB2 particles inside primary phase Si were observed through SEM. The effect of TiB2 particles on cracks in primary phase Si was studied using nanoindentation technology, and the interface relationship between primary Si and TiB2 was studied using TEM. Finally, based on the experimental results, the trapping mechanism of primary Si for TiB2 particles is discussed. The results indicate that the faster the cooling rate, the finer and more uniform the size distribution of the primary Si phase in the structure. TiB2 mostly exists as individual particles. Moreover, the pushing rate of the solid–liquid interface during solidification is faster, resulting in more TiB2 particles being engulfed by the primary Si phase.