Insight into the complex coupled growth behavior of Al2O3/YAG eutectic ceramic based on the evolutions of microstructure and crystallographic texture

Abstract

Clarifying the dependence of microstructure and crystallographic texture on growth kinetics is critical concerns for mechanical properties prediction in complex faceted eutectic growth. In this study, we present the comprehensive investigations of microstructure and crystallographic texture characteristic in directionally solidified Al2O3/YAG eutectic that rely on its coupled growth mechanism. The growth mechanism of eutectic spacing is also well depicted by the Magnin-Kurz (MK) model associated with morphological criteria for branching in faceted phase. As increasing the solidification rate (10 µm/s∼200 µm/s), the regularization tendency for irregular three-dimensional interpenetrated (TDI) structure in geometric category is stronger. Whereas, the enhanced kinetic undercooling increases the misorientation and interfacial energy, which is attributed to the fact that the growth kinetics is more dominant than the minimum interface energy in this work. Additionally, the fluctuation tendency of eutectic spacing and crystallographic orientation with the solidification rate is diametrically opposite. The colony structure consisting of coupled irregular eutectic is formed by the planar interface instability, and its formation mechanism is revealed by the misorientation distribution. This comprehensive research contributes to the design of high-performance eutectic ceramics considering the influence of microstructural features and crystallographic growth modes.