Growth rate effect on colony formation in directional solidification of Al₂O₃/YAG/ZrO₂

Abstract

Mechanical properties of Al 2 O 3 /Y 3 Al 5 O 12 /ZrO 2 ternary eutectic ceramics are strongly affected by structural defects as pores or colonies. Experimental investigation of the microstructure of this ternary composite indicates that the colonies are generally observed when the solidification occurs at high rates. In this work, the influence of the growth rate on the solid-liquid interface shape and formation of colonies in directional solidification of Al 2 O 3 /Y 3 Al 5 O 12 /ZrO 2 by Bridgman, Edge-defined Film-fed Growth (EFG), and Czochralski (Cz) methods is numerically and experimentally investigated. Numerical modeling of the Bridgman growth process shows large curvatures of the solid-liquid interface when the pulling rate is increased up to 80 mm/h. The ingots solidified at rates between 5 and 80 mm/h exhibit colony type microstructure. The analysis of EFG growth of ceramic ribbons reveals less curved solid-liquid interfaces in this system. Numerical modeling shows significant increase in the interface curvature with increasing pulling rate. The microstructure of ribbons grown at pulling rates between 6 and 12 mm/h exhibits colonies only for the ingots solidified at higher rate. Simula-

Cracking mechanism in laser directed energy deposition of melt growth alumina/aluminum titanate ceramics

“…3,4 More importantly, the addition of binders and sintering aids sacrifices the purity and density of ceramics, which severely affects their excellent performance in practical production. The development and application of directional solidification techniques, including the Bridgman method, 5 micro-pulling method, 6 laser floating zone method, 7 and the edge-defined film-fed growth, 8 have simplified the preparation process to a certain extent. Unfortunately, the problems of low preparation efficiency and difficulty in preparing complex structures arising from equipment and technical limitations still plague the industrial application of ceramics.…”