Optimization of Mg Blowing Agent Content for Foaming Aluminum

Abstract: Mg-based blowing agents exhibit the potential to yield aluminum foams with better structure and properties than those achieved by using conventional blowing agents. However, all the studies to date used a high amount of such blowing agents (e.g., 15 wt pct Mg) for foaming aluminum. In this study, we investigate the minimum amount of Mg blowing agent required for foaming. Al-Si13-MgX (X = 2.5–15 wt pct) alloy foams were produced employing the powder metallurgy route where Mg acted as the blowing agent. The macro- and microstructure of the foams were analyzed using X-ray tomography, microscopy, and X-ray diffraction. The foams were subjected to hardness and compression tests to evaluate their mechanical properties. Deformation behavior was studied in situ by monitoring the foam surface during the compression test. For the first time to our knowledge, the present study established that 5 wt pct of Mg is sufficient to achieve foam expansion similar to that achieved by 15 wt pct Mg. Moreover, the structural and mechanical properties of the 5 wt pct Mg-containing foams were much superior to the 15 wt pct Mg-containing foams. However, the highest strength was obtained using 10 wt pct of Mg. Many cracks were observed at the early deformation stages of 10 and 15 wt pct Mg-containing foams. We correlate the Mg content with the structure, properties, and deformation behavior of the foams. Graphical abstract: [Figure not available: see fulltext.].