Effect of the volume fraction of SiC on the microstructure and creep behavior of hot pressed Al2O3/SiC composites

Al2O3/SiC composites containing different volume fractions (3, 5, 10, 15, and 20 vol%) of SiC particles have been fabricated by mixing alumina and silicon carbide powders, followed by hot pressing at the temperature 1740 °C for 1 h under the pressure of 30 MPa and in the atmosphere of Ar. The effect of the volume fraction of SiC on the microstructure and creep behavior of the composites was investigated and possible creep mechanisms were discussed. The creep behavior of the composites at temperatures up to 1350 °C, and mechanical load up to 200 MPa, i.e. under conditions which were more severe than those reported previously, was studied, and compared to the monolithic Al2O3 reference. The microstructure and creep behavior of the Al2O3/SiC microcomposites was significantly influenced by the volume fraction of SiC particles and the average size of the alumina matrix grains. When compared to monolithic Al2O3, the creep resistance of the Al2O3/SiC composites was markedly improved, especially in the materials with 10 vol% of SiC. Long loading time before mechanical failure suggested grain boundary sliding and cavitation controlled creep behavior. The enhanced creep resistance was attributed to grain boundary pinning by the intergranular SiC nanoparticles.