What is the foaming agent for aluminium?
There are various main methods of aluminum foaming, including the melt foaming method, powder metallurgy foaming method and secondary foaming method.
Melt foaming method is a method to produce foam structure in liquid aluminum. The specific process is to add a viscosity increasing agent, such as silicon carbide or alumina, to the molten aluminum liquid in order to increase the viscosity of the aluminum liquid and hinder the bubbles from rising and merging too quickly. Subsequently, a foaming agent, such as titanium hydride or hydrogen zirconium hydride, is added to the liquid aluminum, and these foaming agents decompose at high temperatures to produce gases that cause the liquid aluminum to expand and foam. By controlling the amount of blowing agent added, the decomposition temperature and the viscosity of the aluminum liquid, the size and distribution of the gas bubbles can be adjusted, which in turn results in the aluminum foam with the desired structure. After cooling and solidification, closed-cell or open-cell aluminum foam material is made.
Powder metallurgy foaming method is to prepare aluminum foam on the basis of solid aluminum powder. First, the aluminum powder is mixed with a blowing agent and pressed under a certain pressure to make a dense prefabricated block. Subsequently, the prefabricated blocks are put into a heating furnace and heated to close to the melting point of aluminum, at which time the blowing agent starts to decompose, and the gas produced causes the prefabricated blocks to expand to form a porous structure. By adjusting the foaming temperature, time and density of the prefabricated blocks, the porosity and pore structure of the aluminum foam can be controlled. The powder metallurgy foaming method is suitable for preparing aluminum foam products with complex shapes and high porosity requirements.
The secondary foaming method combines the advantages of the melt foaming method and the powder metallurgy foaming method. It first adds viscosity increasing agent and foaming agent in the aluminum melt, mixes well and casts into the mold for rapid cooling and solidification to get the foaming precursor. When the precursor is heated to a certain temperature, the foaming agent begins to decompose and foam, and finally produce aluminum foam. This method can better control the pore structure and properties of aluminum foam through the two-step foaming process, and is suitable for preparing high-performance aluminum foam materials.
There are various methods of aluminum foaming, and each method has its unique process characteristics and scope of application. In practical application, the appropriate method can be selected according to the specific needs and conditions for the preparation of aluminum foam.