Forming and microstructure control of ceramic/metal composite wires

The Al₂O₃/SUS 304 (JIS) and Al₂O₃/β-Ti alloy composite wires have been formed on the route of the controlled fracture forming (CFF) process. Factors affecting the forming limit of the composite wires and the morphology of the as-formed Al₂O₃ core are investigated. The forming limit is significantly dependent on the initial area ratio (IAR) of the metal sheath to the ceramic billet and more than 3.0 of IAR is required to form the composite wires without cracking or fracturing the metal sheaths. The pre-sintered billets and the metals with high fracture strength are favorable to increase the relative density and to improve the particle morphology of the as-formed Al₂O₃ core. The mechanisms for the densification and the morphological improvement are considered as follows: the compressive stress that results from the plastic deformation of the metal sheaths during the cold forming process is continuously applied to the Al₂O₃ core, making its particles refined and rearranged and resulting in homogenous microstructure as well as high relative density.