The Influence of Oxide Interphases on the Toughness of the Interface Between a-Al sub(2)O sub(3) and Ni(Al) Intermetallic

The effects of a reaction interlayer on the fracture toughness of an interface between a-Al sub(2)O sub(3) and a g'-Ni sub(3)Al intermetallic has been assessed. The interfaces have been fabricated by diffusion-bonding, subject to O chemical potentials that result in the formation of a thin (120 nm) interlayer. High-resolution characterization has revealed that the interlayer consists of mixed oxide-metallic phases, consistent with phase equilibrium for the system. The interface toughness has been measured as, sub(I)-6 J-m super(2), much lower than that for interfaces between Ni alloys and a-Al sub(2)O sub(3). Spectra obtained from the fracture surfaces indicate that the oxide-containing interphases are present on both, consistent with the low toughness.