Texture Controls of Self-Constructive Tri-layered Composites

Abstract

Alumina-based composite containing 1vol%NiAl has been fabricated to study the toughening mechanism due to the oxidation-derived metamorphic layer on the surface. The development of the network structure substituting the boundary of the matrix-Al₂O₃ with the oxidation product NiAl₂O₄ induces enhanced crack deflection to improve the fracture toughness and strength from 3.6MPa･m^1/2 and 539MPa (as-sintered) to 6.4 MPa･m^1/2 and 701MPa at the oxidation time of 5h. However, excess oxidation causes the diffusion of the surface oxidation products into the bulk. The disappearance of the network structure results in the decrease of the toughness and strength.