Microstructure and mechanical properties of Al 2O 3–TiC–4vol.%Co composites prepared from cobalt coated powders

Abstract

Al 2O 3–TiC–4vol.%Co composite was fabricated by hot pressing cobalt-coated Al 2O 3 and TiC powders. A chemical electroless method for cobalt deposition on the surface of ceramic powders was used. Microstructure and mechanical properties of the Al 2O 3–TiC–4vol.%Co composite were compared with that of conventional Al 2O 3–TiC composite. Cobalt phase was uniformly dispersed in the matrix, especially along the interfaces between Al 2O 3 and TiC grains, which inhibited the grain growth of the matrix. The fracture mode changed from intergranular to a mixture of intergranular and transgranular type. Overall improvement in fracture toughness (7.8 ± 0.8 Mpa m 1/2) and bending strength (782 ± 60 Mpa) was obtained in the composite, which should be attributed to the improved crack bridging and crack deflection after interfacial modification. And no obvious decrease in hardness was found in the Al 2O 3–TiC–4vol.%Co composite. The sinterability, homogeneity and fracture behavior appear to be significantly improved due to the application of cobalt coated powders.