Effect of Cu and Sn additions on the cellular structure of Al–Si–Mg alloys foaming at low temperature (≤600 °C)

Low-temperature foaming is essential for the preparation of aluminum foam sandwich (AFS) using the powder metallurgy method. It ensures that the AFS panels, which are made of aluminum alloy plates, are not melted when the core layer is foamed. Therefore, the core material for the AFS should be an alloy with a low melting temperature, and it exhibits a better cellular structure and improved mechanical properties after foaming. In this study, foaming experiments were performed on Al–Si–Mg alloys at low temperature (≤600 °C) and the effect of Cu and Sn addition to the cellular structure of aluminum foams was analyzed. The results show that alloys composed of Al, Mg and Si benefit from the addition of Sn and Cu by reducing the pore size and foaming temperature, respectively. In particular, the observed cellular structure with uniform pore size could be the result of the needle intermetallic phase Al2Cu formation in the cell wall. This intermetallic phase possible stabilized the bubble pores when Cu and Sn were added together. However, cracks were detected in the cell wall. They gradually increased and expanded with increasing Si content in the alloy, thus reducing the quasi-static axial compression strength of the aluminum foam. Furthermore, it was more difficult for the foamable precursor to achieve compaction when the Si content was increased to 10 wt%. The findings of the study show that AlMg4Si6Cu4Sn4 has better cellular structure and mechanical properties after foaming at 600 °C for 15 min.