Study On The Brazing Process And Mechanical Behavior Of The Foamed Aluminum/Aluminum Sandwich Panel

Foamed aluminum has characteristics of both metal and porous structure.Due to its superior properties such as high specific strength,specific stiffness,and energy absorption and heat insulation,it has broad application prospects in the fields of aerospace,aviation,transportation,and automobile industries.And it is considered as one of the most promising new structural and functional materials in the future.Sandwich material made of foamed aluminum and metal panel composite is a new type of lightweight structural material with great application value.This article innovatively studied the preparation of foamed aluminum/aluminum sandwich panels by vacuum brazing,focusing on the brazing mechanism and process parameters?brazing temperature and holding time?on the bonding layer in foamed aluminum/aluminum sandwich panels.With the influence of performance and optimization of process parameters,the bending mechanical behavior of foamed aluminum/aluminum sandwich panels prepared by brazing was studied.A foamed aluminum/aluminum sandwich panel was prepared by vacuum brazing method.The influence of brazing temperature and holding time on the quality of brazing joint bonding layer was studied.Within the modern analysis methods such as OM,SEM and EDS,the phase composition,morphology,distribution characteristics and element diffusion law of the multi-component alloy at the brazing seam interface of the sandwich panel were analyzed to determine the best welding process parameters of the foam aluminum/aluminum sandwich panel.The results show that the brazed joints of foamed aluminum/aluminum sandwich panels are mainly divided into four parts:aluminum plate base metal zone,single phase??Al?solid solution zone,weld center zone and aluminum foam matrix.Among them,the microstructure of the weld center zone mainly consists of??Al?solid solution,massive CaAl₂Si₂ compound and skeletal CaAl₄.When the welding temperature is 605?615? for 30 min,or the welding temperature is 625? for 20 min,the element diffusion occurs between the base metal and the brazing filler metal,forming a good metallurgical bond and brittleness in the bonding layer,and the distribution of CaAl₂Si₂ compounds is uniform and small;when the brazing temperature is further increased,or the holding time is prolonged,the matrix material will produce the phenomenon of coarse grains,which reduces the metallurgical bonding performance of the brazing seam joints.When the soldering temperature is low or the holding time is short,the plate/core cannot form a good metallurgical bond,of which the bonding interface is relatively flat,and the CaAl₂Si₂ compound is accumulated.A quasistatic three-point bending experiment was performed on foamed aluminum/aluminum sandwich panels prepared under different brazing processes.The bending performance,bending deformation behavior and failure modes of the brazing foam aluminum/aluminum sandwich panels were studied.The results show that there are three main failure modes of foamed aluminum/aluminum sandwich panels under bending load,which are cracking failure of the bonding layer,cracking failure of the core shear-bonding layer and panel yield failure;When the brazing temperature is within 605?625? and the holding time is within 10?30 min,an excellent metallurgical bonding layer can be formed between the panel and the core layer.The prepared foamed aluminum/aluminum sandwich panel's failure mode is panel yield failure,and it has the overall high bending performance,of which the maximum bending strength up to 67.97MPa;When the brazing temperature is low and the holding time is short,the strength between the panel and the core layer is low,and the board/core cracking phenomenon is easy to occur.The maximum bending strength of the sandwich panel is low,generally under 52.7 MPa;When the brazing temperature is too high and the holding time is too long,the microstructure of the panel is coarse,resulting in a reduction in the overall mechanical properties,thereby reducing the maximum bending strength of the sandwich panel.