Energy absorption in closed-cell Al-Zn-Mg-Ca-Ti foam

Cellular metallic foams have interesting potential for impact energy absorption. In this study, modification of solid in a closed-cell Al-Ca-Ti foam was carried out, adding the strengthening elements of Zn and Mg for enhancement of energy absorption. Samples with dimensions of 100 x 100 x 100 mm(3) were examined at a dynamic strain rate corresponding to the crashing speed of automobiles. The compression deformation behavior of the Al-7Zn-0.5Mg-1.5Ca-1.5Ti (by mass%) foam was found to be different from that of the original Al-1.5Ca-1.5Ti (by mass%) foam. Plateau stress could be effectively enhanced with the combined effect of strengthening solid alloy and increasing the aspect ratio of cell wall thickness against cell edge length. Plateau stress of the modified foam was independent of strain rate, while the stress in Al-Ca-Ti foam exhibited a certain strain rate sensitivity. Plateau strain, designated as the strain where the compressive stress reached 1.5 times higher value than the yield stress, was also enhanced by the present modification. As a result, absorption energy was also effectively enhanced but was independent of strain rate as a result of the present modification.