Effect of Foaming Time and Temperature on the Hardness of Al-Si-Cu-Mg Alloy Foam Cell Walls

Abstract

Al-Si-Cu-Mg alloy foams of different compositions and different cell morphologies were produced using the powder metallurgical method and by varying the foaming time and temperature during production. Hardness of the produced precursors and foams was measured using nanoindentation and micro indentation hardness measurement methods. Results obtained from both of the methods showed similar trend although the nanoindentation hardness of the specimens was consistently higher than the corresponding micro Vickers hardness. The precursor and foams obtained from Al-5wt.%Si-4wt.%Cu-4wt.%Mg (alloy 544) showed a higher hardness value than Al-3wt.%Si-2wt.%Cu-2wt.%Mg (alloy 322) precursor and foams made at the same foaming temperature and time because of their higher content of alloying elements. The hardness value of foam walls increased with the increase in foaming time at all foaming temperatures due to the increase of eutectic phase. Same density foams obtained from the same precursor but at different foaming temperatures were found to have different hardness values which indicate that local and global properties of foams with similar densities obtained from the same precursor will differ from each other if their foaming conditions are not the same
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