This paper reports on investigations by Hütte Klein‐Reichenbach and LKR in the course of the development of a new processing technique for cellular aluminum, to produce net shape parts of foamed aluminum via the melt route by gas injection. The foaming depends on the interaction between the blowing gas, the ceramic particles, and the melt. The stabilization of the foam by different particle contents in interaction with air, oxygen and nitrogen as blowing gas has been investigated for some matrix alloys with respect to the processing parameters. The resulting cell structure is characterized by computed X‐ray tomography, light optical and scanning electron, as well as high resolution Auger electron microscopy. The microstructure of the cell walls is presented as well as the achieved pore size and the local mass density distribution.

The foaming of aluminum melt of LKR‐Austria is investigated. The foaming was performed in a furnace chamber at adiabatic conditions to keep the foam in liquid state. The foams were taken out from the chamber after 1, 10 and 100 min isothermal holding time and cooled in air or quenched in water. The final cellular structure depends on the following parameters: particle (composition, shape and size, volume fraction), gas (composition and purity), the particle‐surface interactions, matrix alloy composition and temperature of foaming.Metallographical examinations are carried out after freezing the foamed melt by the help of Scanning Electron Microscopy. The cell wall thickness, the particle distribution and the existing phases are determined. Transmission Electron Microscopy and Auger Electron Spectroscopy are used to analyze the surface skin of the cells and to determine the oxide layer thickness depending on the different foaming gases.An equipment called High Temperature Maximum Bubble Pressure Tensiometer (HTMBPT) was built to measure the apparent surface tension of the particle‐stabilized melt. Semi quantitative description of the experimental phenomena are presented.

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Metal foams were produced by blowing gas into aluminium alloy melts. The effect of oxygen content of the blowing gas on composition and structure of the inner surface of the foam cells is studied by varying gas composition from argon, nitrogen and air to pure oxygen. Scanning Electron Microscopy, Auger Electron Spectroscopy and Transmission Electron Microscopy are used to analyse the surfaces. Initially particle‐free melts are pre‐treated by bubbling air through them after which a certain degree of foam stability is achieved. The oxidation products are characterised by microscopy on such foams.

Metal foams are quite a challenge to materials scientists due to their difficult manufacturing. In all processes the foam develops in the liquid or semiliquid state. Liquid-metal foams are complex fluids which contain liquid metals, solid particles and gas bubbles at the same time. An X-ray transparent furnace was developed to monitor liquid metal foam evolution. Aluminium foams - similar to the commercial Metcomb foams - were produced by feeding argon or air gas bubbles into an aluminium composite melt. The foam evolution was observed in-situ by X-ray radioscopy under normal gravity. Drainage and rupture were evaluated during the 5 min foam decay and 2 min solidification. Argon blown foams showed significant drainage and cell wall rupture during the first 20 s of foam decay. Air blown foams were stable and neither drainage nor rupture occurred. We demonstrated the feasibility of experiments during parabolic flight or drop tower campaigns. However, the development of a foam generator for low gravity is needed.