Aluminum foams are very effective porous materials for the absorption of sound, the absorption of impact energy and vibration, electromagnetic protection and, in addition, they are not flammable and remain stable at high temperature. They are also recyclable and non-polluting and offer a combination of physical, mechanical, thermal and acoustic properties characteristic of a homogeneous material. All these characteristics mean that they have important applications in different sectors such as automotive, aerospace, naval and construction.
In this area, the research group “Engineering and Materials Science” belonging to the Higher Technical School of Industrial Engineers of the UPM has managed to manufacture (*) these foams using calcium carbonate, which has considerably reduced its final price and enables a greater number of uses than you already have.
Aluminum foam is a relatively isotropic, highly porous metallic material with a random distribution of pores within the structure. The pores, essentially spheroidal, (open or closed) occupy 50% to 90% of the total volume. The mechanical and physical properties strongly depend on the density, which varies in the range of 0.4 to 0.8 g / cm 3(floating in the water).
About Aluminum foams Manufacture:
The manufacture of aluminum foams is possible because this element in liquid state allows the introduction of gas bubbles that are trapped inside. Under normal conditions, gas bubbles introduced into a liquid metal tend to reach the surface very quickly due to their lower density. But an increase in the viscosity of the molten metal and an adequate modification of the pressure and temperature conditions can hinder the migration of the gas and temporarily stabilize its permanence inside the molten metal until it is solidified. This requires some means of gas generation, either by the addition of foaming agents or by the injection of gases (air, nitrogen, argon, dioxide or carbon monoxide).
The most used foaming agent for aluminium alloys is titanium hydride, due to the high specific volume of hydrogen and the rapid kinetics in its decomposition reaction. However, it is a material that, in addition to being expensive, is dangerous when handled.
To avoid these problems, UPM researchers have managed to manufacture SAF aluminum using calcium carbonate as a foaming agent. It decomposes inside the molten aluminium alloy releasing monoxide and carbon dioxide. These reactive gases, under conditions of agitation, form bubbles as well as aluminium oxide, calcium oxide and other complex metal oxides that stabilize the liquid metal. This modifies its viscosity and the energy of the surface of the molten metal and prevents the union of the bubbles and the drainage of the liquid.
Usages of the Aluminum foams:
The alusion foam thus obtained has been stable in a wide range of compositions, which allows the obtaining of materials of different geometries and properties.
The manufacture of aluminium foam in a continuous process with this foamed can allow a significant reduction in costs as it is a cheaper component than titanium hydride or other higher-cost foamers. A lower cost product can multiply the already numerous applications of these materials.
