Abstract No.:
5997

 Scheduled at:
Thursday, May 23, 2019, Saal Brüssel 11:00 AM
Development of brazing metals


 Title:
Influence of tin on the wetting behaviour of aluminum

 Authors:
Alexander Schmidt* / RWTH Aachen University, Germany
Kirsten Bobzin / Surface Engineering Institute, Aachen
Mehmet Öte/ Surface Engineering Institute, Aachen
Stefanie Wiesner/ Surface Engineering Institute, Aachen
Joachim Mayer/ Central Facility for Electron Microscopy, Aachen
Anke Aretz/ Central Facility for Electron Microscopy, Aachen

 Abstract:
Wetting is a primary challenge in brazing aluminum due to the low wettability of the alumina layer by the molten brazing filler metals. The alumina layer is formed instantaneously on the surface of aluminum when the base material is exposed to air before brazing and prevents an interaction between base material and filler metal. Thus, in order to achieve a metallurgical bond it is necessary to remove the alumina layer during the brazing process and to prevent a reoxidation of the base material. For this purpose, fluxes can be used when brazing aluminum. Most fluxes need to be removed after the brazing process due to their corrosive effect. Thus, there is a demand for developing flux-free aluminum brazing processes.

For the first time in literature, all stages of a successful aluminium brazing process including melting of the filler metal: 78Sn22Cu (wt. %), removal of the oxide scale without the use of any flux, and wetting of the base material could be observed in a large-chamber scanning electron microscope. In this case, it is assumed that tin infiltrates into the oxide scale via thermal induced cracks and subsequently removes it. Based on this, the focus of the current study is set on the influence of tin on the wetting behaviour of aluminum. In detail, the interactions between liquid tin and alumina resulting in the removal of the oxide scale and the wetting of the substrate are investigated. The mechanism of alumina layer removal and the subsequent wetting is analysed further. For this purpose, different tin containing alloys are produced and characterized by means of DSC and SEM analysis. Furthermore, wetting experiments with subsequent SEM analysis of the spreading pattern of the filler metal on the base material are carried out.


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