Joining aluminium/nicalon composite by diffusion bonding

Abstract

The joining of aluminium/Nicalon composite has been investigated by diffusion bonding under pressure using metal interlayers. Bond strengths have been measured using a simple shear jig and the joint microstructures characterised by electron microscopy and electron-probe microanalysis. Using interlayers of copper and copper-silver alloy, joints were readily formed at 550 and 510°C, respectively, as a result of the formation of eutectic liquid which helped to disrupt the oxide film on the aluminium matrix and promote metal diffusion across the joint interface. In the case of copper, however, oxidation at the edge of the interlayer limited the bonded area to ∼80%. Using an interlayer of aluminium alloy (2124), a temperature of 500°C was sufficient to produce a satisfactory joint with ∼100% bonded area, in this case the aluminium oxide film being disrupted by reaction with magnesium in the alloy interlayer. The shear strength of all bonded specimens was ∼50 MPa, with failure occurring mainly through the adjacent composite rather than at the joint interface.