Comportamiento en fractura de un eutéctico Al₂O₃/YAG crecido por solidificación direccional

Abstract

Esta investigación se ha centrado en el estudio de un eutéctico cerámico Al 2 O 3 /YAG fabricado por solidificación direccional mediante el método de Bridgman. Se han realizado ensayos de tenacidad de fractura por flexión en tres puntos y se ha medido el módulo de elasticidad entre temperatura ambiente y 1650 ºC. Así mismo se han utilizado dos velocidades de ensayo para analizar la influencia de la velocidad de deformación en el comportamiento en fractura. El comportamiento ha sido frágil hasta 1400 ºC, temperatura a partir de la cual comienzan a aparecer fenómenos plásticos. Estos se reducen o desaparecen cuando se aumenta la velocidad de deformación del material. Finalmente, el estudio se ha completado con el análisis de los mecanismos de deformación y rotura en el frente de la grieta. Palabras clave: Eutécticos cerámicos, solidificación direccional, propiedades mecánicas, fractura, microscopía electrónica de barrido, microscopía electrónica de transmisión. Fracture behaviour of a directionally solidified Al 2 O 3 /YAG eutecticThis investigation was aimed to analyse the mechanical behaviour of an eutectic ceramic Al 2 O 3 /YAG processed by directional solidification in a Bridgman furnace. Fracture toughness and young modulus were measured through three point bend tests from room temperature up to 1650 ºC. These tests were performed under stroke control using two different cross-head speeds to analyse the influence of strain rate on the fracture behaviour. The material was brittle up to 1400 ºC and plastic deformation was found at higher temperature. Plastic deformation was reduced, or even disappeared, when the strain rate was increased. Finally, the investigation was completed with the analysis of the deformation and fracture micromechanisms in the crack tip.

Fracture toughness and strength of Al2O3–Y3Al5O12 and Al2O3–Y3Al5O12–ZrO2 directionally solidified eutectic oxides up to 1900K

“…It should be noted that the ambient temperature fracture toughness determined with the technique described in Section 2 is equal to the one obtained with Vickers indentations 4 in binary Al 2 O 3 /YAG DSEO with the same microstructure and domain size. The fracture toughness of this material was insensitive to the temperature up to ≈1500 K and increased slightly beyond this point up to ≈ 4 MPa √ m at 1900 K. Such behavior is corresponds with the results reported by Ochiai et al 11 and Poza et al 27 in Al 2 O 3 /YAG DSEO grown by the Bridgman method with an interlamellar spacing above 20 m, indicating that the fracture toughness of this material is very insensitive to the microstructure. In addition, samples grown in air or nitrogen presented the same behavior.…”