Study On Vacuum Foaming Preparation Of Foamed Aluminum Core Sandwich

AFS is composited with aluminum foam core and metal panel, which has low density, high damping, high strength, high energy absorption and electromagnetic shielding properties. It solves the aluminum foam’s shortcoming of low strength for a great extent.The interface connection is not ideal between the aluminum foam core and the surface layer in AFS, the mechanical properties are restricted by the way of interface combination, therefore, this paper presents a new kind of Near-Net-Shape preparion way of AFS-vacuum foaming technique, and the preparation of AFS by vacuum foaming method was studied, the main results are shown as following:(1) AFS with thickness 20-35mm was successfully prepared by vacuum foaming method based on Al-Si12-Ca3 alloy. The AFS layer thickness was 0.5-1mm, uniform structure of cell, the pore size was 2.5-7mm, the binding mode of surface layer and foam core is metallurgical combination.(2) The melt which contained initial pore that can be vacuum foaming was preparated and obtained the optimal initial pore preparation process parameters:0.3% TiH2 content, melt temperature 630℃, stirring speed 2000r/min, stirring time 120s.The melt was under the action of vacuum filling and foaming, obtained the best vacuum foaming process:vacuum is 10Pa, vacuum foaming time is 30s.(3) The AFS prepared by vacuum foam has been tensile tested and three point bending tested. The results showed that the porosity has great influence on its tensile strength and bending strength. Along with the increase of porosity (75% to 85%), the tensile strength decreased from 18.89MPa to 10.73MPa, the bending strength decreased from 16.20MPa to 8.73MPa. In the same pore diameter or porosity, the AFS’s tensile strength and three point bending strength were improved 24.6% and 13.67% respectively than the aluminum foam core.(4) The initial pore nucleation mode was inhomogeneous nucleation, the nucleation rate was proportional to H2 concentration and the number of nuclei. Under the action of vacuum, pressure difference between bubble internal and vacuum tank is the power of bubble expansion, the faster the vacuum tank pressure reduces, the faster the bubble expands. In the whole process of bubble expansion, the expansion rate of the bubble is slow firstly and then fast.(5)The outside bubble wall of the melt foam under the vacuum expansion effect and the mould effect, adjacent cell walls squeeze each other which make it polygonization and planarization, the melt first solidified in the mold surface crust formed surface layer, obtain AFS by natural cooling lastly.