Fabrication of Fibrous Bimaterial Composite by a Co-extrusion Process

Abstract

A repeated co-extrusion process was used to fabricate fibrous composites of both 11 vol%-zirconia/alumina composite and 11 vol%-alumina/zirconia composite. A bundle of feedrods composed of ordinary arranged alumina and zirconia green rods was co-extruded through a 6 : 1 reduction die. After the first co-extrusion, the individual pieces were bundled and co-extruded again, reducing the lateral size of each phase and multiplying the number of continuous monofilaments. The extrudates were pressureless sintered at 1600°C for 3 h after the decomposition of organic residuals. In both composites, first and second extrusion steps produced composites with cracks. Finally, a crack-free, high density alumina/zirconia composites could be obtained after third extrusion step, though the filaments were not found to be continuous. The fracture toughness of both the composites after third extrusion step was improved by introducing fine second phase filaments into the matrix.