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 & sdot;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.