Characterization of Al2O3/Al/Al2O3 Joints with Ti+Cr Interlayer

Abstract

Joints of Al 2 O 3 /Al/Al 2 O 3 are formed by liquid-state bonding of alumina substrates covered with thin Ti+Cr film of 380 nm thickness using an Al interlayer of 30 µm at 973 K under a vacuum of 0.2 mPa applied for 5 minutes and at a pressure of 0.01 MPa. The bond strength of the joints is examined by a four-point bend testing at room temperature, coupled with optical, scanning and transmission electron microscopy. Results show that introduction of the thin Ti+Cr film layer: (i) improves plasticity in the metal layer of Al 2 O 3 /Al/Al 2 O 3 joints, (ii) has positive effect on structure transformation in the interface and leads to fabrication of reliable metal-ceramic joints. Information obtained from the wetting characteristics of liquid Al on alumina substrate coated by thin Ti+Cr film indicates that the contact angle can be reduced to even less than 60°. Microstructural investigations of the interface of Al 2 O 3 /Ti+Cr/Al/Ti+Cr/Al 2 O 3 joints carried out by SEM and TEM techniques indicated that the precipitates of intermetallic phases rich in both Ti and Cr as well as Al 2 O 3 were formed at the Al/Al 2 O 3 interface, which influenced strengthening of these joints. Hence a conclusion can be drawn that the interface structure influences the mechanical durability increase in Al/Al 2 O 3 joints.