High-temperature plastic behaviour of Al2O3–Y3Al5O12 directionally solidified eutectics

Al2O3–Y3Al5O12 eutectic rods grown by the laser floating zone method at 25, 350 and 750 mm/h have been studied by means of constant strain rate and constant stress compressive tests. Creep exponents were in the range n 1.9–3, and the activation energy was 720 ± 20 kJ/mol for rods grown at 350 mm/h. The experimental results indicate that to explain creep behaviour in these materials the bulk diffusion contribution to creep must be considered. We propose a creep model based on the isostrain approach to explain the plastic behaviour, attending to the interphase spacing. The model successfully predicts stress exponents, activation energy and load transfer effects within experimental error.