Fundamental Research On Preparation Of Aluminum Foam Sandwich

Aluminum foam sandwich(AFS) has been widely used in rail transit, aerospace industry and military equipment for the excellent performance of light weight, high specific strength, high specific stiffness and impact properties. Presently, AFS panel with in-situ bonded is mainly manufactured by rolling and glue bonding method at home and abroad. But the AFS prepared by gluing can’t resist high temperature or corrosion environment. Even the AFS with steel facesheet can be made by rolling, there will be lots of powder loss along the profile of the panel in the process of rolling leading to a low utilization of raw materials. What’s more, AFS panel is easy to be out of shape in the process of foaming. So it is of great significance to explore a brief process which suits the industrialization.In this paper, AFS was produced by powder metallurgy and the pure aluminum powder was used as the matrix. Mg and SiC powders were used as the additives. TiH2was the blowing agent. The influence of SiC on the stability of the aluminum foam was studied. The surface of the steel was treated by hot dipping with Al and Al-Si alloy. The precursor and the steel plate which was hot dipped were welding by solid-phase diffusion. Then AFS precursor was baked in a furnace for foaming. At last, the phase in the boundary was analyzed by SEM and EDS. The results were shown as below:(1) The phenomenon of coalescence, drainage and capillary are relieved by adding SiC in the precursor. When the content of SiC is10wt.%and foaming temperature is780℃, the Al-foam with uniform structure can be obtained.(2) The steel plate is treated by hot dipping with Al or Al-Si alloy coating. The thickness of the surface layer on the steel plate is increasing firstly, then decreasing with prolonging the holding time. The thickness of the diffusion layer showed a trend which is increasing at first and then keeping stable. A steel plate with thicker surface layer and thinner diffusion layer can be produced as the hot dipping temperature is720℃and the holding time is chosen to be5min. (3) By solid-phase diffusion bonding method, the steel plate and the precursor can be pre-welded with a metallurgical boundary. The hot pressing temperature is510℃and the heating rate is94℃/min. More than10min holding time and6MPa pressing pressure are also necessary. The surface of steel by hot dipped Al-Si alloy is superior to the steel hot dipped pure Al.(4) The AFS precursor which is manufactured by pre-welding the steel plates and the foamable precursor can be foamed to be AFS with metallurgical boundary. The thickness of the boundary is decreased with adding Si. The best hot pressing temperature is510℃and the holding time is15min. The heating rate and the pressure should be higher than94℃/min and6MPa, respectively.