Al Alloy Foam With Foaming Mechanism

The foam aluminum alloy is one kind of new structure function material. It obtained the great progress until recent years. Its application has already involved astronautics aviation, the transportation, the electron, the war industry, different high tech and the general industry domain because of its light quality, flame-resistant, the high energy absorption and so on. Melting bubble method perpetrating foam aluminum alloy is one of the most industrialization al production in the future because its production craft is relatively simple, the cost is low. Therefore foam aluminum material has the extremely broad market prospect.The paper elaborated with ZL102 (Al-Si₁₂), as the substrate material, Ca makes the viscosity-increasing agent, composite alkali-metal carbonate makes the foaming agent, with Melting bubble method to prepare the foam aluminum alloy. The foaming process was studied by experimental analysis.The result showed that: foaming agent reached its decompositional peak near the melting temperature of 650℃, and the decompositional range is narrow, in line with foaming agents conditions to make aluminum foam .After metal Ca was joined in aluminum melt, the produced intermetallic compound CaAl₄ and CaAl₂ can be moisted and wraped to increase viscosity and can also gather the aluminum to cause the bubble stabilization. When the design's four-agitation wheel was carried, the melt can run in the radial flowing and the axial motion which caused the foaming agent distributing evenly.The technical parameters of foam temperature,stirring time, holding time ,amount of viscosity increasing agent and foaming agent were adjusted to identify the beneficial controlling scope for foaming effect so that we can design five factors four levels orthogonal experiments to obtain the preliminary optimized craft parameter: foaming temperature 680℃, foaming agent 2.5%, viscosity increasing agent 2.5%, stirring time 2.0 mim, holding time 4.0 mint.The theory was stduied in the process of foaming, according to thermodynamics process ,we discussed the foaming agent decomposed, the bubble shaped nucleus and growed up initially, obtained thermodynamics condition to demonstrate the trend of bubble evolvement.Meanwhile, according to dynamics process, considering the influence of every stage to the bubble structure and property ,we establised the foaming konetics equation (dr)/(dt)=(RT)/(4πr²p)n₀(dα)/(dt).The evolution showed that bubble's growth rate(dr/dt) is a function offoaming agent decomposed rate(dn/dt),and bubble's radius will increase with increasing amount of CO₂, the bubble growed in constant temperature mainly, and the foaming agent that attached to the bubble surface released CO₂ to make bubble bigger and bigger.