Mechanical properties of directionally solidified Al2O3-ZrO2(Y2O3) eutectics

The relationship between microstructure and mechanical properties was studi ed in Al2O3-ZrO2 eutectic rods. The material, produced by directional solid ification using the laser-heated float zone method, was formed mainly of co lonies consisting of a fine interpenetrating or ordered network of ZrO2 and alpha -Al2O3 surrounded by a thick boundary region that contained pores an d other defects. The flexure strength of the eutectic rods was excellent (> 1.1 GPa) owing to the small critical defect size and the high toughness (7 .8 MPa rootm). No microstructural changes were observed after about 1 h of exposure at 1700 K, and the eutectic oxide maintained a very high strength up to this temperature. The nature of the critical defects that led to frac ture, the toughening micromechanisms, and the differences between the longi tudinal and transverse strength are discussed in the light of the microstru ctural features of the material. (C) 2001 Elsevier Science B.V. All rights reserved.