INTERFACIAL REACTIONS AND ADHESION STRENGTH OF METAL CERAMIC COMPOSITES/

The interfacial fracture energy of Ti/Al2O3 composites was measured wi th and without a diffusion barrier at different bonding temperatures b y using four-point bending tests. It was found that the interfacial fr acture energy increases with increasing bonding temperature up to 950 degrees C. When the bonding temperature was further raised to 1000 deg rees C, the interfacial fracture energy drops. The decrease of the int erfacial fracture energy is due to the formation of the continuous int ermetallic compound, Ti3Al, at the interface between Ti and Al2O3. By using a diffusion barrier, the interfacial fracture energy decreases f rom 25.4 to near 0 J/m(2) and 32.9 to 8.7 J/m(2) for applied bonding t emperatures of 800 and 900 degrees C, respectively, This is because th e diffusion barrier reduced the diffusion of Al across the interface a nd into the Ti, thereby preventing a strong chemical bond at the inter face. For the composite bonded at 900 degrees C, the crack propagation was found to occur at the interface between the Ti and Al2O3 The inte rfacial failure was found to be in the Ti3Al reaction layer for the co mposite processed at 1000 degrees C. With a diffusion barrier, the cra ck propagation path follows several interfaces, Evaluation of the proc essing temperature on the mechanical properties of the Ti was also obt ained by using a nanoindentation technique.