Solidification and phase transformations in brazed aluminium alloys used in automotive heat exchangers

摘要

This paper presents the modifications of the micro-structure of aluminium alloys after brazing (multilayer materials made up of modified AA3003 core clad on both faces with AA4343) with particular attention paid to the phase identification. Silicon diffusion coming from the residual melted cladding led to the formation of a 'band of dense precipitates' (BDP) in the core. In this area, the cubic α-Al(Fe,Mn)Si phase was obtained after solid state transformation. In the brazed joints and in the residual cladding, multiphase deposits of (Al), α-Al(Fe,Mn)Si and Si were observed. Thermo-dynamic calculations allowed the solidification sequence to be described in good agreement with the successive deposits observed in the brazed joint and in reasonable agreement with those observed in the residual cladding.