Interfacial reaction mechanism between Y-containing DD5 alloy and Al₂O₃ ceramic during directional solidification process

This study systematically investigated the influence of varying yttrium(Y) additions on the interfacial reaction mechanism between the DD5 superalloy melt and Al₂O₃-based ceramic molds during directional solidification. The analysis revealed the formation of a complex multilayer reaction layer at the alloy-ceramic interface. The interfacial products changed from CaO·6Al₂O₃ to a mixture of various yttrium oxides after Y was added. As the reaction time increased, the sequence of interfacial reaction products observed on the surface of Y-containing alloys progressed as follows: Y₂O₃, Y₄Al₂O₉, YAlO₃, and ultimately Y₃Al₅O₁₂. Increasing the Y additions promoted the formation of a reaction layer with a higher atomic percentage of Y. The interfacial reaction process between the DD5 superalloy and Al₂O₃-based ceramic molds involved ceramic decomposition and diffusion, Y element diffusion and displacement reactions, Al₂O₃ dissolution and further diffusion of the Al element. This process resulted in the formation of different yttrium-aluminum oxides and related to the bidirectional erosion of the Y₂O₃. These interfacial reactions significantly contributed to the consumption of Y element within the alloy.