Microstructure and flexure creep behaviour of SiC-particle reinforced Al 2O 3 matrix composites

Abstract

The flexure creep behaviour of monolithic Al 2O 3 and 10 vol% SiC-particle reinforced Al 2O 3 matrix composites was investigated in air atmosphere at 1160 to 1400 °C and under a stress of 40 to 125 MPa. Two kinds of SiC particles with different particle sizes and oxygen contents were used in the composites, one having an average size of 0.6 μm with 1.7 vol% SiO 2 impurities and the other of average size 2.7 μm with 3.4 vol% SiO 2 impurities. Compared with the creep behaviour of monolithic Al 2O 3 the strain rate of the composites with 0.6 μm SiC particles did not decrease; however, the composites with 2.7 μm SiC particles exhibited excellent creep resistance. Microstructure analysis showed that the Al 2O 3 grains in the composites with 0.6 μm SiC particles were mainly equiaxed with most of the SiC particles lying at the grain boundaries or triplegrain junctions, whereas the grain features of the composites with 2.7 μm SiC particles were irregular and elongated and most of the SiC particles were entrapped into Al 2O 3 matrix grains. It was revealed that the entrapment of 2.7 μm SiC particles into Al 2O 3 matrix grains was related to the high SiO 2 impurity content on SiC particle surfaces, and the change of grain morphology and the good high-temperature oxidation resistance were responsible for the creep resistance increase of the composites with 2.7 μm SiC particles.