Vinod Kumar, G.S.; Charkraborty, M.; García-Moreno, F.; Banhart, J.: Foamability of MgAl2O4 (Spinel)-Reinforced Aluminum Alloy Composites. Metallurgical and Materials Transactions A 42 (2011), p. 2898-2908

A novel foamable aluminum alloy has been developed. It contains sub-micron-sized MgAl2O4 (spinel) particles that are generated in situ by a reaction of SiO2 with a molten Al-Mg alloy. The study involves an optimization of parameters such as Mg concentration, SiO2 particles size, and reaction time and shows that a composite containing MgAl2O4 particles as chief reinforcement in the matrix leads to effective foaming. Composites containing large sized transition phases and particle agglomerates in the matrix yield poor foam structure. The best foamable composite obtained contained 3.4 vol. pct of ultrafine (80 nm to 1 lm) MgAl2O4 particles uniformly distributed in an Al-Si alloy matrix. The corresponding metal foam contained 75 pct porosity and exhibited a uniform distribution of cells.