Research On The Aluminum Foam Prepared By Extrusion Powder Of PCM

Aluminum foam is a new kind of porous materials, which contains a lot of bubbles after foaming process and with aluminum, aluminum alloy and aluminum matrix composite materials as raw materials. Because of the pore structure foamed by bubbles distributed in the metal phase, the aluminum foam have both the characteristics of the continuous phase of aluminum and the dispersed phase of pore, and rolls the functional and structural properties into one, so that it becomes one of the major research and development projects in the world's high-tech materials science field today.In this paper, the author has used the method of powder extrusion, with the pure Al powders as matrix materials, TiH₂ as the foaming agent, and adds 1 percent of Mg in the aluminum oxide particles to improve the wettability, through mixed-extrusion-foam process to prepare the aluminum foam. The effects of such process parameters as forming temperature, TiH₂ addition and the forming times on the aluminum foam density, porosity, pore structure were discussed in detail; Analysis of the mechanism of the effects of the mixed powder forming and the foaming behavior of preform prepared by different extrusion methods and loading carriers.As shown by experiments, a high quality aluminum foam with low density, high porosity, foam fully developed, thinner bubble walls and uniform pore structure should be made on conditions under the forming temperature is 670℃, the TiH₂ addition is 0.8%, the forming time is 270s. The hydrogen can not be effective controlled in the insulation process, so it was difficult to obtain high density precursors by direct extrusion method. But using the method of pre-pressing at 400MPa and then extruding at 400℃can effectively eliminate the effects of hydrogen, high density precursors can be obtained by this method. In foaming process, a large number of hydrogen escaped from the side surface of the precursor, which was prepared with copper cylinder or copper sheet as the powder loading carrier. So the expansion ability of the precursor decreased, the lowest density only g/cm3. When using precursor sheet as the powder loading carrier, an oxide layer can be formed on the surface of precursor in early stage of foaming. The presence of oxide layer limited the escape of hydrogen and improved the utilization of TiH₂. Aluminum foam with a polygons pore morphology prepared by this way has reached the lowest density g/cm³, and the average pore wall thickness only about 150μm.