Microstructure Evolution of Alumina/Alumina Joint Bonded by Boron Oxide–Alumina Nonmetal Powder Interlayer

Abstract

Alumina was successfully joined to itself in air environment by B 2 O 3 + Al 2 O 3 powder mixture as the interlayer to synthesize aluminum borate whiskers in the joint. The microstructure evolution was analyzed by means of scanning electron microscope ( SEM ) and X‐ray diffraction ( XRD ). The possible mechanism of microstructure evolution was also discussed. The effects of parameters such as heating cycles and temperature on the microstructure as well as the 3‐point flexural strength of the joint were investigated. It was found that heating the specimen for several heating cycles instead of holding at a constant temperature for a long time can eliminate the voids among the whiskers to achieve a dense microstructure, and the phenomenon that higher temperatures can accelerate the reaction was also observed. The highest strength of the joint reaches 90.29 MP a with the heating temperature of 800°C after four heating cycles.