Transient liquid phase diffusion bonding under a temperature gradient: modelling of the interface morphology

Imposing a temperature gradient when transient liquid phase (TLP) diffusion bonding results in reliable joints with shear strengths as high as those of the parent material (e.g. aluminium-based alloys and composites). The key feature of this new method relies on the formation of non-planar interfaces as a consequence of morphological instability at the solid/liquid interface during solidification of the liquid layer (normally with a eutectic composition) at the bonding temperature. A model is proposed in this paper which is capable of predicting interface morphology and the bonding conditions which result in the formation of non-planar bond lines when using this new bonding method. The results of model provide an insight to the nature of the solidification process. The proposed model was verified experimentally when bonding pure aluminium and also an aluminium alloy (6082) using copper interlayers.