Influence of foaming temperature and time on the hardness of cellular AI-Si-Cu-Mg alloys

Micro Vickers hardness was measured on the cell wall of AI-Si-Cu-Mg alloy foams having different compositions and subjected to different foaming temperature and period of time during production. The powder metallurgical route was utilized to obtain aluminium alloy foam. AI-5%Si-4%Cu-4%Mg-l%TiH₂ alloy precursor showed higher hardness value than AI-3%Si-2%Cu-2%Mg-l %TiH₂ alloy because of higher alloying element. The hardness value was increased with the increase of foaming period of time at all foaming temperatures while foams having same composition but higher foaming temperature showed higher hardness value regardless of material. These might be due to the fine eutectic grain size effect. Local hardness of foams at α-AI grain boundaries and junctions of multiple grains were found to be higher than that inside the α-Al grains. Higher hardness value of eutectic phase and accumulation of eutectic phase near grain boundaries are responsible for this higher hardness value at α-Al grain boundaries.