Study on Preparation and Reaction Mechanism of B4C/β-Sialon/SiC/Al2O3 Composite Powder

B4C, Si, Al, and gamma-Al2O3 were used as raw materials, formed beta-Sialon and SiC in situ by solid-state reaction for preparation of B4C composite powder. beta-Sialon and SiC grains are uniformly and dispersedly distributed in the composite powder. The effects of the molar ratio of raw materials, nitridation temperature and soaking time for the phase composition, and microstructure of the composite powder were studied. When the molar ratio of B4C and Si is 2: 3, the composite powder with columnar beta-Sialon grains growing alternately can be prepared after nitridation at 1500 degrees C for 4 h. The liquid phase formed by the melting of Si at high temperature promoted the dissolution of B4C and the formation of SiC. When the nitridation temperature was increased or the soaking time was prolonged, the gas phase volatilization of Si and Al was intensified, SiC and AlN whiskers tend to be formed in the composite powder.