Longitudinal cross-section microstructure of growth striation in Al₂O₃/Y₃Al₅O₁₂/ZrO₂ directionally solidified eutectic ceramic prepared by laser floating zone

Periodic growth striations with a width of 380μm are observed in Al₂O₃/Y₃Al₅O₁₂/ZrO₂ ternary directionally solidified eutectic ceramic prepared by laser floating zone. It is found that the microstructure of the growth striations exhibits disparate growth characteristics. The direct experimental evidence of the formation of the microstructure of the growth striations is obtained through examining the solid-liquid interface. The lamellar coarsening of the growth striations is related to the nucleation of Al₂O₃ particles and their engulfment by the extended Y₃Al₅O₁₂ phase. The mechanism accounting for this phenomenon is explained by considering eutectic growth behavior under mutative condition induced by oscillatory convection.