Information was provided about the use of in situ determined diffusion coefficients of Si for modeling of a brazed joint formation, i.e. formation of the equilibrium surface of a

molten Al+xSi alloy at the onset of solidification in the joint. Diffusion coefficients of Si were determined (within both the joint and/or residue zone) to analyze its migration across the clad–core interface of an Al brazing sheet, including both the period prior to reaching brazing temperature range, and the peak brazing temperature range. Subsequently, diffusion coefficients were used to predict the joint formation during brazing. Migration of Si was not uniform along the clad–core interface during brazing and depended, in addition to material characteristics and process parameters, on the vicinity of the joint zone. It was argued that, due to these alterations, the joint formation modeling must be performed by using in situ determined diffusion coefficients. The diffusion coefficients determined directly from electron probe microanalysis scans at different locations along the cladding sheet and within the joint zone differed between each other and when compared to the literature data. This variation influences the outcome of the residue formation modeling; hence the joint formation modeling may be affected. The relation between these phenomena was briefly discussed and quantitative data regarding diffusion coefficients, and in particular an approach to utilization of these data in modeling of joint formation, were provided.

Solid State Si Diffusion and Joint Formation Involving Aluminum Brazing Sheet. F.Gao, H.Zhao, D.P.Sekulic, Y.Qian, L.Walker: Materials Science and Engineering A, 2002, 337[1-2], 228-35