Structural Characteristics And Mechanical Property Of A Closed-cell Aluminum Foam

Aiming at structure and property control, a closed cell aluminum foam with the same composition but different cell structures was prepared by air-foaming process. In order to understand the effect of processing parameters on cell structure, the foams were produced by changing air injection rate, foaming temperature and impeller speed during foaming process. Furthermore, plastic collapse strength, energy absorption and elastic modulus of the closed cell aluminum foam were studied in relation to cell structures.The results show that: the foam has a density range of 0.10 to 0.22 g/cm³ and the cell size varies from 4.0 to 11.0 mm. The cell size of the aluminum foam is increased with increasing air flow rate, while it is decreased as the impeller speed increases, and the density, node size and cell wall thickness of the aluminum foam are reduced the increase in cell size. The relation between foam density and cell size is expressed by ρ = 0.0278+0.3602e^-0.132d at a constant impeller speed of 600 rpm. Moreover the higher impeller speed produces smaller size cells with thicker cell wall and node size, which resulted in higher density foam in contrast to the foam with the same cell size prepared at lower impeller speed.The failure of the foam cells under compressive load progresses successively from the top or/and bottom to the mid-layer of the compression specimens, and no initial rupture of the foam cells is observed in the mid-height of the foam samples. When foam density increases from 0.11 to 0.22 g/cm³, the plastic collapse strength rises from 0.20 to 1.29 MPa, while the elastic modulus of the closed cell aluminum foam increases from 0.70 to 1.17 GPa. In contrast, the energy absorption of the foams decreases rapidly with increasing cell size. When the cell size increases from 4.7 to 10.1 mm, the energy absorption drops from over unity to 0.3 J/cm³. The normalized Yong's modulus of the closed cell aluminum foam is E*/E_s = 0.208 (ρ* /ρ_s), while the normalized strength of the foams, σ*/σ_s is expressed by σ*/σ_s=c (ρ*/ρ_s) where c is a density-dependent...