Effect of ceramic particle addition on the foaming behavior, cell structure and mechanical properties of P/M AlSi7 foam

The effects of SiC addition on the foaming behavior and compressive properties of AlSi7 metal foams were studied. Elemental powders of Al, Si, SiC and TiH2 were mixed, hot compacted and foamed at temperatures between 750 and 810 degrees C. The role of SiC volume fraction up to 10 vol.% and its particle size (3, 8 and 16 mu m) was investigated. It was found that the foaming behavior of AlSi7 alloy, i.e. the maximum foam expansion and its stability, depends on the size and volume fraction of SiC particles. Increasing the amount of the ceramic particles and/or decreasing the particle size leads to less melt drainage whilst the cell structure becomes non-uniform. This is attributed to the effect of the ceramic particles on the viscosity of the aluminum melt and the cell wall thinning rate. Here, it was noticed that the effect of SiC addition is closely related to the temperature used for the foaming process. Also, a slight degradation in the mechanical properties under compressive load was observed. Better foamability with improved stability and proper mechanical properties were obtained in AlSi7-3 vol.% SiC (3 mu m) precursor foamed at 810 degrees C. (c) 2006 Elsevier B.V. All rights reserved.