Enhancement of thermal shock resistance of Al2O3–MgAl2O4 composites by controlling the content and distribution of spinel phase

Abstract

Herein, the Al2O3–MgAl2O4 composites were prepared using magnesite as variate and bauxite and alumina as main raw materials through a solid oxide reaction at 1500 °C. The content and distribution of MgAl2O4 on Al2O3–MgAl2O4 composites were adjusted with the aim of altering the microstructure and mechanical property, thereby enhancing their thermal shock resistance. The studies observed that by adding 5 wt% magnesite, a limited amount of MgAl2O4 particles can be generated, partially distributing on the microstructure; thus, the crack's propagation cannot be hinder with ease, which leads to a more limited residual strength ratio (68.97%). When 10 wt% of magnesite is added, the solid-solution (Mg1-xAl2x/3)Al2O4 is formed, and the apparent growth and wide distribution of spinel grains is induced, which pins the propagated front crack and enhances the toughening mechanism. The essential fracture path is altered from the predominantly transgranular mode to the mostly intergranular mode, and the residual strength ratio attains the highest value (94.36%).