Bond strength and microstructure investigation of Al2O3/Al/Al2O3 joints with surface modification of alumina by titanium

Joints of Al2O3/Al/Al2O3 are formed by liquid-state bonding of alumina substrates covered with thin titanium film of 800 nm thickness using an Al interlayer of 30 or 300 μm at 973 K under a vacuum of 0.2 mPa for 5 min and an applied 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: (i) bonding occurs due to the formation of a reactive interface on the metal side of the joint with the presence of Al3Ti precipitates (ii) a decrease in Al layer thickness leads to stronger Al2O3/Al/Al2O3 bonds accompanied by a change of both the distribution of reaction products (Al3Ti) in the region of the interface and the failure surface characteristics.