Abstract:

Closed-cell metal foams are commercially available and are mainly used in light weight and energy absorption applications. A lot of research has been conducted on the production of Al foams using conventional blowing agents like TiH2, CaCO3, etc. The use of Mg based blowing agent (Mg, Al50Mg50, for example) is a relatively new concept. This type of blowing agents yields cheaper foams with fewer defects and higher strength compared to conventional blowing agents. However, there is a major drawback in this type of blowing agent – the need to use a high amount of Mg. Till date the minimum amount of Mg used is 15 wt.% for foaming Al alloys. This results in the formation of a high amount of intermetallic making the foams brittle compared to the foams produced by using conventional blowing agents.

In this study, we investigated the effect of Mg content on the Al- Si-Mg alloy foams produced by powder metallurgy route. Mg content was varied in Al-Si13-Mgx (x = 2.5, 5, 10, 15 wt.%) alloys. The foams were subjected to structural (macro and micro) and mechanical characterization. It was observed that 5 wt.% of Mg results in comparable expansion and a higher strength compared to that achieved by using 15 wt.% Mg. This is because of a relatively small number of defects in the former foams. Foams produced using 10 wt.% of Mg showed the highest strength, but less expansion and ductility compared to the foams produced using 5 wt.% Mg. The ductility of foams decreased with Mg content because of an increase in the amount of intermetallic. The strength of the foams containing 5 wt.% Mg was improved by subjecting them to heat treatments. It can be concluded that the use of 5 and 10 wt.% Mg results in foams with better properties compared to 15 wt.% Mg.