Mechanical Properties of Liquid Phase Sintered SiC Materials by the Addition of Unimodal and Bimodal Particles

Abstract

Both the mechanical properties and probability distribution of liquid phase sintered SiC (LPS-SiC) materials were investigated, based on a detailed analysis of their microstructures. In particular, the effect of the starting sizes of SiC particles on the characterization of LPS-SiC materials was evaluated. LPS-SiC materials were fabricated with a constant applied pressure, using a complex powder of different sized SiC particles. Two types of initial SiC powders used for the fabrication of LPS-SiC materials were a unimodal SiC single powder with the average particle size of 0.3 μm, and a bimodal SiC powder mixture with average particle sizes of 0.3 μm and 30 nm, respectively. A complex powder of Al2O3 and Y2O3 particles was also utilized as an additive material for the consolidation of the LPS-SiC materials. The characterization of the LPS-SiC materials was performed using microstructural observation, three-point bending test and micro Vickers hardness test. The LPS-SiC materials containing the unimodal SiC powder exhibited a good sintered density of about 3.11 g/cm3 and a low porosity of about 5.4%. The bimodal mixture of different SiC particles did not significantly affect the sintered density of LPS-SiC materials. However, LPS-SiC materials containing the bimodal SiC powder exhibited an average flexural strength about 630 MPa higher than that of unimodal SiC powder, accompanied by the creation of fine SiC grains in the range of about 0.2~1.4 μm. The LPS-SiC materials exhibited a similar hardness level of about 2200 Hv regardless of the starting SiC powders. The bimodal SiC powder also produced a higher shape parameter and variability in hardness in the Weibull statistical analysis. Key words: silicon carbide, liquid phase sintering, initial SiC particle size, grain size, weibull distribution, mechanical property