REPOSITORY > RESULTS

Abstract

Aluminium foams are prospective class of cell materials that offer a variety of applications in fields such as lightweight structures or crash-energy management. Due to interesting combination of physical and mechanical properties, such as high stiffness at low density, high impact energy absorption, flame and heat resistance, sound absorption, aluminium foams are usually used in aircraft and aerospace industries, for armoured vehicles, in car and shipbuilding industries, in civil engineering, as well as in biomedical industry.
Production of aluminum foams by the powder-metallurgy process depends on preparation of pre-cursors. In general, pre-cursors consist of compacted metallic powder that is sintered at pre-determined temperature. Due to high temperature of sintering, foaming agent decomposes into a solid component that is built into the matrix material, and a gas component that causes foaming of the matrix material. Powder metallurgy is method for making close-cell foams and it is the best selection, especially for production of net-shape parts, providing excellent quality of end products.
In presented work, powders, precursors and foams, made from different metallic powders (Al 99.7 % purity, AlSi12 alloy) with different foaming agents (TiH2, CaCO3, CaMg(CaCO3)2), were examined with light and electron microscopy. Density of porous material, size and distribution of pores was determined. Further, SEM/EDS analyses of distribution of single elements in cellular walls were also made. Results of characterization of single pre-cursors and obtained foams were mutually compared.
Special attention was devoted to precursor preparation prepared by different compacting techniques and comparison of green densities of precursors on foaming effect was made. Foaming effect, size and distribution of pores, were checked with precursors made with various fractions of different blowing agents. Differences in volumes of precursors during heating were observed in heating microscope. Also AES analyses of oxides on the surface of powder particles and on the surface of pore walls were made for better understanding of foam stability.
Results of analyses and of materials characterization during all the three steps of the powder–metallurgy foaming process (powders, precursors and foams) have revealed the most important parameters in aluminium foams preparation and the influence of foaming agents on foaming process and stability of foams.