Fundamental Research On Technical Process Of Aluminum Foam Sandwich Preparation By Two Steps Foaming

Aluminum foam sandwich(AFS)panels have promising application prospects in automobile,military,aerospace industry for the excellent properties such as lightweight,high specific strength and stiffness,etc.Currently,the AFS panels are usually manufactured by gluing the cover sheets and the Al foam core using polymeric adhesives at home.By this means,the AFS panels have encountered some problems when used in high temperature environment,for example,the corrosion and failure of the adhesives.Powders cladding and rolling method is widely used abroad.In this way,even the fabricated AFS panels have a metallurgical bonding interface,they also have problems of high costs and poor pore structures.As a consequence,it is of great importance to explore a economical method to manufacture AFS panels with metallurgical bonding interface and uniform pore structures.In this study,foamable precursors were prepared based on the two step foaming method.AlSi12 alloy and foaming agent TiH2 were used as the raw materials.Mg and Ca were chosen to be the metal additives.SiC powders were the stabilizing agent.We studied the preparation of foamable precursors,hot pressing process for combination of steel/precursor with foaming process.Besides,the three-point bending tests were conducted by using the resulting AFS panels.The main conclusions are shown as follows:(1)When the foamable precursors were fabricated by using melting method,the porosities of the precursor decreased with increasing the contents of the SiC particles or decreasing the sizes of the SiC particles.(2)The three-layer composite consisting of foamable precursor and two steel cover sheets were fabricated by hot pressing under different processing parameters.The bonding between the Al coated steel and the precursor were mechanical bonding,while a firmly contacted interface could be observed between AlSi12 coated steel and the precursor except for some microcracks.(3)In the process of fabricating AFS panels,the A1 foams had low porosities and nonuniform pore structures within a short foaming time.While for a long foaming time,coalescence of the pores were performed,resulting a deterioration of the foam structure.Al foam with fine morphology and relatively high porosity could be obtained at the foaming time of 13min.(4)By examination of the bonding interfaces of the AFS panels,Fe2Al5?Fe2Al7Si intermetallic compounds with a thickness of 25 ?m were formed at diffusion layer between Al foam and the steel which was coated with AlSi12 alloy layer by cold spraying;By using the steel which was coated with A1 layer by cold spraying,Fe3Al7 intermetallic compounds were formed with a thickness of 3-5 pm;By using the steel which was coated with A1 layer by hot spraying,a Fe-Al intermetallic compounds with a thickness of 10?pm were formed at the diffusion layer.(5)The results of the three-point bending tests showed that the failure modes of the AFS panels were shear failure mode.The ultimate load is 9291.34N and the corresponding displacement is 1.114mm.