Study On The Properties And Brazing Process Of New Ge-doping Cesium Salt Aluminum Flux With Low Melting Point

In decades,in the field of joining aluminum alloys aided with cesium salt fluoride flux at the intermediate temperature,it is an important topic to develop a kind of original flux which is highly active,non-corrosive,insoluble in water and with a lower melting temperature.And there are two conventional methods to design and modify the properties,one is to develop new preparation and application methods,the other is to add the third or more salt in the matrix flux.In this paper,different forms,contents of germanium?Ge?element were added into the CsF-AlF₃ and KF-CsF-AlF₃?b45,mol ratio of CsF:AlF₃:KF is 48:48:4?fluxes respectively,properties of which like melting property,phase structures and spreadability were studied.And thus a newly original cesium salt flux with low melting point and high activity was found.The main research work and results of this paper are as follows:?1?Fluxes doped with active element Ge in the form of GeO₂??NH₄?₂GeF₆ based on CsF-AlF₃ matrix flux were prepared.Researches show that forms of Ge has no much effect on the melting property,phase structures and spreadability,while the content of Ge does.When the content of Ge comes up to 4 wt.%,the melting temperature decreases from 471?to around 430?and has a short melting range as well,below 10?.What's more,fluxes doped with more than 4 wt.%Ge perform with a high activity on 1060,2024,6061 aluminum alloys in 450⁴80?.While in temperature of 480⁵30?,fluxes doped with no more than 4 wt.%Ge show more activity on the 6061 aluminum alloy.?2?Fluxes doped with active element Ge in the form of GeO₂ based on KF-CsF-AlF₃?b45?matrix flux were prepared.Studies show that melting temperatures of newly-prepared fluxes do not change a lot whether element Ge is added or not,while it shortens the melting range to some extent because of reduction of the liquidus temperature.And when the content of Ge comes up to 4 wt.%,new fluxes have main phases of Cs₂GeF₆ and Cs₂KAl₃F₁₂,and some acicular morphology in the microstructure appears as well.But it's certain that adding element Ge into KF-CsF-AlF₃?b45?matrix flux has no improving effect for activity.?3?Low melting temperature cesium salt fluoride binary flux dopped with 4 wt.%Ge was utilized to braze 2024 and 6061 aluminum alloys with Zn-15Al brazing filler metal.It turns out that two aluminum alloys could be brazed successfully at480⁴90?,respectively.And both lap joints achieve excellent strength,with fractures occurred on the base material.