Study On The Performance Of Five Layer Composite Brazing Aluminum Foil By Pre-tension

Because the aluminum alloy has the advantages of high specific strength,excellent heat transfer performance,rich reserves and low cost,it has been widely used in the field of heat exchanger.All Aluminizing of heat exchanger has become an inevitable trend of development.Its manufacturing must be accomplished through brazing,but the problems of corrosion and strength in the process of brazing have a great influence on the safe use of materials.There-fore,it is urgent to study aluminum alloy composites with higher performance and corrosion resistance.In this paper,taking the five layers of composite brazed aluminum foil as the research object.The advantages of five layers of material relative to the traditional three layer materi-als in mechanical properties and corrosion resistance are compared and analyzed,and the changes of the mechanical properties and the corrosion resistance of the five layers of the material after brazing are studied.The following conclusions are shown:1)By adding a layer of barrier layer between the traditional three layer brazed aluminum foil,with no influence on the brazing performance,more Mg elements can be added to the core layer to improve the mechanical properties of the material,and the barrier layer can ef-fectively reduce the diffusion of the Si element in the brazing layer,thus reducing the corro-sion phenomenon.2)The size of the main precipitates Al₈₅Mn₁₅?Al₆₅Cu₆Fe₉Mn₂₀?Al_0.5Fe_0.5Si is slightly reduced and the density is increased slightly after the five layer material is prestretched at2.5%and 5%,and the grain structure of the material after 2.5%pre-tension after brazing is the finer,and the density of the material AlCuMg is maximum after 5%pretension after brazing,so the mechanical properties are greatly improved.After 2.5%pre-tension,the tensile strength reaches the maximum of 218.2MPa,and the yield strength reaches the maximum of105.5MPa after 5%pre-tension.While the size of the main precipitated phase in the material is greatly reduced and the density increases after 7.5%and 10%pre-tension,but the aging hardening phase of AlCuMg decreases or even disappears,and the recrystallization incom-plete to make the grain large,which makes the mechanical properties of the material lower after brazing.When the material passes through the 10%pre-tension,the yield strength and tensile strength of the material after brazing are the lowest,achieved 67.9MPa and 189.1MPa respectively.3)With the increase of pre deformation degree,the corrosion resistance of materials first decreased,then increased and then decreased.Among them,2.5%pre-tension material has serious grain boundary corrosion,and its corrosion resistance is the worst.The deepest pene-tration rate after welding is 20.5%.The corrosion resistance of the 5%and 7.5%pre-tension materials has been greatly improved,and the best corrosion resistance of the 7.5%pre-tension material and the depth after welding is 15.1%.After 10%pre-tension,the corrosion resistance of the material is slightly reduced,but it is better than that of the material without pre-tension.The deepest penetration rate after welding is 16.3%.4)The effect of pre tension on the mechanical properties and corrosion resistance of the five layer brazed aluminum foil after welding is considered.The material after 5%pre-tension can not only improve the corrosion resistance of the material,but also improve the mechani-cal properties of the material,which is the best pre deformation degree of the material.