Processing and characterization of alumina wire by controlled fracture forming process: (I) forming behavior and evolution of green microstructure

The forming behavior of the Al₂O₃ wire on the route of the controlled fracture forming (CFF) process, and the evolution of its green microstructure with respect to particle size and pore morphology are investigated. Results indicate that the 98% reduction in area is required to form the wire with high relative density ( ~ 77% theoretical density) as well as homogeneous green microstructure. The intense compressive stress or strain resulted from the plastic deformation of the metal sheath material crushed the agglomerates or the larger grains in the presintered billet, and the flow and rearrangement of these constituent particles resulted in the elimination of the larger pores with coordination number more than 12. Because of the smaller particles and the homogeneous pore distribution, the formed wire can achieve full densification, which implies that the CFF process has a potential to fabricate the ceramic wire reinforced metal matrix composites.