Aluminium is cast together with crystal salt into the desired shape and afterwards the salt is washed out. The salt grains and their contact points are thus replaced by pores. This is how porous aluminium is produced.
Thanks to the high strength and low weight, foamed metals are gaining importance as industrial material. Because of the large internal surface area and good thermal conductivity, foamed metals are used in the automotive industry and heat engineering.
Metal foams are usually made of aluminium or aluminium alloys, although it is also possible to foam copper, zinc or lead.
Manufacturing technologies for metal foams:
– Metal powder or metal chips are mixed with titanium hydride or other explosive agents and heated above the melting point of the metal, thereby releasing gaseous hydrogen so that the mixture foams.
– Gas is injected into the molten metal, after cooling the porous structure remains.
The main difficulties in the production of metal foams are to find the right combination of metal and explosive agent and heating them up in the right time to the correct temperature, as this is the only way of obtaining the desired result. In doing so, it is practically unpredictable how porosity, pore size and distribution of pores will be.
For these reasons, porous Aaluminium, with its simple manufacturing technology, is the valuable alternative. The broad range of precisely defined pore sizes can differentiate the application accurately. Extra strong cast interfaces between porous and non-porous parts opens up a wide range of different applications.
Porous Aluminium has following main advantages over metal foams:
– control of volume porosity
– control of pore sizes
– control of pore distribution / homogeneous structure