Study On Fabrication Of Aluminum Foam Sandwich By Rolling Method Using Aluminum Panels As Facesheet

Closed-cell aluminum foam sandwich(AFS)panel is a kind of composite material with both structural and functional performance.They have the advantages of lightweight,high energy absorption,good electromagnetic shielding,sound insulation and noise reduction performance etc.They are widely applied in aviation,rail transit,automobile and other fields.At present,the preparation of aluminum foam sandwich panels are mainly by glue-binding and powder metallurgy.However,the glue-bonding AFS panels with low interface bonding strength,easily leads to the separation of core and panels at high temperature.AFS panels by powder metallurgy with a metallurgical bonding interface can overcome the disadvantages of glue-bonding AFS,bute the high costs and complex process limited the industrialization.Therefore,it is of great importance to explore a economical method to get AFS panels with metallugical bonding interface.(1)In this research,foamable precursors were prepared based on the two step foaming method.Al-Si alloy and foaming agent TiH2 were used as the raw materials.The precursor and aluminum panel are bonded by hot-rolling method.And the interface between coversheet and precursor core was characterized by micro-analysis and the mechanical property was tested through tensile test.In addition,this paper studied the effects systematically of foaming temperature and foaming time on the foaming process.Then the micro-analysis of the foamed interface is carried out.Besides,the three-point bending tests are conducted by using the AFS panels.The main conclusions are shown as follows:(2)The hot rolling process is under 450℃ and the holding time is 100 min.The rolling speed is 0.1 m·s-1 and the rolling is divided into 4 passes,and the reduction rate of each pass is 22%.After each pass of rolling,put the AFS back to the furnace and hold for 30 min.The total thickness can changed from 26 mm to 9.6 mm.By comparing the metallography before and after rolling,it is found that the grain phase is distributed along the rolling direction.After rolling,the interface between precursor and panel is smooth,and part of the elements from precursor are diffused into the panel.The tensile test shows that the samples are brittle fracture and the interface of the precursor and panel still combined well.(3)The handmade steel mold could help to achieve rapid and horizontal limited foaming.The ideal foaming process parameters in this research should be 720℃ of foaming temperature and 270 s of foaming time.Meanwhile the idea AFS with aluminum panel’s density is 1.48 g·cm-3,porosity is 48%,expansion rate is 76%.After foaming process,the interface can be metallurgical bond.(4)Through the three-point bending of AFS,it can be seen that the AFS with merged pores,the two wings of the core layer are destroyed by shear force.Mean while the core layer and panels are also destroyed by shear force.The appearance of AFS after the fracture looks like "butterfly".The AFS with circular and evenly distributed pores,only appeared the core layer and panels destroyed by shear force.However,all appearances of fracture still have a metallurgical bonding interface.