Mechanical anisotropy in the zirconia toughened alumina

The two kinds of the hydrothermally crystallised zirconia powders were used to toughen alumina matrix. The one composed of isometric crystallites of t etragonal symmetry, the other one of elongated monoclinic particles. In the sintered ZTA material either isometric or elongated particles form tetrago nal disk shaped inclusions. Zirconia inclusions originating from the elonga ted particles tend to arrange crystallographically on the uniaxial compacti on. This resulted in the material showing different ultrasonic wave velocit y, Young modulus, crack lengths and fracture toughness along directions per pendicular and parallel to the compaction force. An explanation of this phe nomenon is suggested. Zirconia inclusions originating from the powder compo sed of isometric crystallites lead to the material of isotropic mechanical properties. (C) 1999 Kluwer Academic Publishers.