| Aluminum foam sandwich(AFS)panels is a new kind of laminated composite which composed of Al foam and dense cover sheets.It not only has the properties of lightweight,heat insulation,damping and sound absorption?but also shows good intensity and bending property.While,as a new kind material,the manufacture process of AFS has some inevitable disadvantages and deficiency.For example,when the Al foam and the cover sheet are bonded by gluing,the interface usually has a low bonding strength and the glue is easily to lose for aging.Although the AFS by metallurgically bonded can overcome the above problems,the Al alloy which is commonly used as the cover sheet becomes soften and deforming during the foaming process.Besides,the center Al foam usually has a poor pore structure.The application of AFS has been limited seriously by such problems.Based on the characteristics of preparation process of Al foam,this paper perfects the manufacture process of powder metallurgy(PM)method and the Formgrip method,and the foamable precursors are fabricated by these two methods.Then the precursor and the steel cover sheets are bonded to be a "sandwich-like" laminated composite by hot pressing technology.Finally,the metallurgically bonded AFS can be manufactured by foaming of the bonded composite.In addition,we have also design a experiment apparatus for the preparation of large-scale AFS,providing a reliable' experimental basis and thinking for the industrial application.The main research contents includes:(1)In the study of preparation of Al foams by PM method,the foamable precursor is fabricated by uniaxial and bidirectional cold pressing.By contrast of the two samples,the former one is denser and the density distribution is more homogeneous.A rapid foaming can be carried out by using a foaming mold.Ceramic particle SiC,element Mg and Sn are helpful to improve the uniformity,stability,and the expansion ratio of the A1 foam.(2)In the study of Formgrip method,the influence of the process parameters such as the stirring time,temperature,and the treatment of TiH2 on the foamability of Al foams are revealed.By optimizing the process parameters and improving the equipments,the size of the precursor is increased efficiently.These lay a good foundation for the manufacture of large-scale AFS panels.(3)The surface treatment technologies of steel cover sheet are studied,and they are suitable for preparing AFS panels.The steel cover sheet is aluminized by hot dipping and cold spraying,resulting to metallurgical bonding and mechanical bonding between the two substrates,respectively.The optimized hot pressing parameters such as temperature,time,and pressure are ensured.The cover sheet and the foamable precursor can be bonded before foaming.The influence of hot pressing on the foamability of the precursor fabricated by two different techniques is discussed,and the bonding condition of steel/Al foam is also analyzed.(4)The possibility of preparing large-scale AFS panel by PM and Formgrip method is investigated by foaming experiments.The results show that when using PM method,the surface of Al foam is oxidized seriously,inhibiting the diffusion bonding between the samples.For the Formgrip method,the seperated A1 foams become an entire one.The interface between the Al foams is disappeared.The foamable precursor prepared by Formgrip method is more suitable for the manufacture of large-scale AFS panel.The mechanical behavior and failure mode of the metallurgically bonded AFS is examined by three-point bending experiments.By contrast,the metallurgically bonded AFS has better bonding strength and damping property than that of the glued AFS. |
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