Spark Plasma Sintering of Al2O3-SiC Ceramics. Study of the Microstructure and Properties

The features of spark plasma sintering of submicron Al2O3 powders with different contents (0, 0.5, 1.5, 5 vol %) of beta-SiC nanoparticles have been studied. The microstructure and hardness of Al2O3 + 5 vol % SiC ceramics obtained by sintering Al2O3 powders with beta-SiC particles of various types (nanoparticles, submicron particles, fibers) have been studied. Sintering was carried out at heating rates (V-h) from 10 to 700 degrees C/min. The sintering process of Al2O3 + SiC ceramics with low heating rates (V-h = 10-50 degrees C/min) has a complex three-stage character, with a flat area in the temperature range of 1200-1300 degrees C. At high heating rates (V-h > 250 degrees C/min), the usual three-stage character of sintering is observed. The analysis of temperature dependences of compaction was carried out using the Young-Cutler model; it was found that the kinetics of powder sintering is limited by the intensity of grain boundary diffusion. It is shown that the dependence of the hardness of Al2O3 + SiC ceramics on V(h )has a nonmonotonic character, with a maximum. In the case of pure alumina, an increase in V(h )leads to a monotonic decrease in hardness.