Diffusion behavior of silicon at interface of Al clad sheet and joint formation

The diffusion behavior of silicon in the brazing clad sheet was studied. It is interesting to notice that the residue clad appears after the brazing process, regardless of the brazing conditions. Diffusion coefficients of silicon during its migration across the clad-core interface of an Al brazing sheet, both prior to brazing temperature and at the peak brazing temperature, are determined directly from EPMA (electron probe microanalysis) scans at different locations along the cladding sheet and within the joint zone. Subsequently, the diffusion coefficients were used to predict the residue clad layer formation during brazing. Migration of silicon during brazing depends, in addition to material characteristics and process parameters, on the vicinity of the joint zone. From the analysis of the residue clad layer, the joint topology could be predicted based on the minimum potential energy principle. The deduced results may be utilized to study the thermal integrate of brazed joint.