No abstract

Al2O3–cBN has received considerable attention in the field of ceramic cutting tools due to its high hardness, high wear resistance, and low cost, but poor interfacial bonding affects the performance of the composite. In this study, a novel hot‐forging process was used to prepare high‐performance Al2O3–cBN composites using Ti(C,N) as a binder. The evolution of the morphology, phase, and microstructure of the hot‐forged Al2O3–Ti(C,N)–cBN composites was determined, and the mechanical properties were measured. The relative density of the composites increases significantly after hot forging, and the deformation of the composites increases with the hot‐forging temperature. The highest performing Al2O3–Ti(C,N)–cBN composite was prepared by hot forging at 1600°C and has a hardness of 20 GPa, a bending strength of 647 MPa and a fracture toughness of 5.37 MPa m1/2, which are superior to those of a directly hot‐pressed sintered composite. However, at hot‐forging temperatures higher than 1700°C, Al5O6N and TiB2 are formed in the composite. In the composite hot forged at 1800°C, serrated grain boundaries promote the strength and toughness of the composite to 877 MPa and 6.76 MPa m1/2, respectively. Therefore, the novel hot‐forging process is expected to enhance material properties.

The densification behaviors of MgO-doped-Al 2 O 3 ceramics in the flashing stage and the steady stage were investigated using the classic kinetic model. The results show that the most densification of MgO-doped Al 2 O 3 was completed during the flashing stage. The densification mechanism transferred from particle rearrangement resulted from Columbic force among particles under the effect of electrical field in the flashing stage to the lattice diffusion in the steady stage. Therefore, the densification rate in the steady stage dramatically decreased. Additionally, the estimated densification activation energy in the steady stage of flash sintering is 396 kJ/mol, much lower than the activation densification of lattice diffusion measured from conventional sintering, likely due to the effect of electric field/current-induced point defects on the diffusion.