Mg powder can be used both as alloying element and blowing agent for foaming Al alloys. The use of Mg based blowing agents yields aluminium foams with better structure and properties than that achieved by using conventional blowing agents (such as TiH2). All the previous studies have reported the usage of high amount of Mg based blowing agents, which increases the brittleness and oxidation of the foams. However, there have not been any attempt to reduce the Mg content. Also, till date, AlMg15Cu10 alloy, foamed using Mg based blowing agent, was used in most of the studies. Hence this thesis work was conducted to explore the alternate Al alloys for foaming using Mg based blowing agent, and also to investigate the possibility of reducing Mg content in order to improve the ductility of such foams.
In this study, as-received Mg powder was used as blowing agent. Initially, Al-Mg-X10 (X = Cu, Zn, Si) alloys were foamed using Mg blowing agent. Among these three alloys, Al-Mg-Si alloy foams exhibited superior properties compared to Cu and Zn containing alloy foams. Therefore, optimisation of Mg blowing agent content was performed using Al-Mg-Si alloy foams by varying Mg amount from 2.5 to 15 wt.%. It was observed that 5 wt.% Mg was sufficient to produce lightweight foams with desirable properties. On the other hand, 10 wt.% Mg containing foams exhibited the highest strength, albeit having high density. In a subsequently study, heat treatment of Al-Si-Mg foams (with 5 wt.% Mg) was performed, which revealed an enhancement in foam strength due to heat treatment. Finally, hot deformation studies were carried out on Al-Mg-Si alloy precursors containing 5 and 10 wt. % Mg to assess the deformability of these alloy precursors. A high deformability of the precursors is essential for producing these foams at an industrial scale. The deformability of 5 wt.% Mg containing precursors was found to be comparable to an alloy used for manufacturing aluminium foam sandwich in industrial scale.