Influence of the Y 2 O 3 Content and Temperature on the Mechanical Properties of Melt‐Grown Al 2 O 3 –ZrO 2 Eutectics

The effect of Y 2 O 3 content on the flexure strength of melt‐grown Al 2 O 3 –ZrO 2 eutectics was studied in a temperature range of 25°–1427°C. The processing conditions were carefully controlled to obtain a constant microstructure independent of Y 2 O 3 content. The rod microstructure was made up of alternating bands of fine and coarse dispersions of irregular ZrO 2 platelets oriented along the growth axis and embedded in the continuous Al 2 O 3 matrix. The highest flexure strength at ambient temperature was found in the material with 3 mol% Y 2 O 3 in relation to ZrO 2 (Y 2 O 3 ). Higher Y 2 O 3 content did not substantially modify the mechanical response; however, materials with 0.5 mol% presented a significant degradation in the flexure strength because of the presence of large defects. They were nucleated at the Al 2 O 3 –ZrO 2 interface during the martensitic transformation of ZrO 2 on cooling and propagated into the Al 2 O 3 matrix driven by the tensile residual stresses generated by the transformation. The material with 3 mol% Y 2 O 3 retained 80% of the flexure strength at 1427°C, whereas the mechanical properties of the eutectic with 0.5 mol% Y 2 O 3 dropped rapidly with temperature as a result of extensive microcracking.