PREPARATION OF SIC CERAMICS WITH UNIFORML Y DISPERSED SIC PLATELETS BY MECHANICAL ALLOYING PROCESS

To improve the fracture toughness of sintered bodies, a method for in- situ dispersion of SiC platelets was studied. A mechanically alloyed p owder mixture consisting of Si, C, B and W (the mixing ratio was Si/C= 1/1 in molar ratio, and 3 mass% C, 3 mass% B and 5 mass% W were added as sintering additives) was sintered above 2100 degrees C in Ar atmosp here. By using the mechanical alloyed powder mixture, ceramics reinfor ced with beta-SiC platelet in length of 100 mu m and thickness of 5 mu m, was obtained. Two possible mechanisms of the formation of a beta-S iC platelet have been proposed; (a) W and B in the SiC phase are super saturated by mechanical alloying process, (b) W-B phase is separated f rom the SiC phase during sintering, and then, SiC platelets grow. A W- containing compound formed in the reaction sintered SiC suppresses the phase transition from beta-SiC to alpha-SiC.