Figure 4: Relative compressive strength, and , plotted against relative density, , for different kinds of hydride (F1, F3, F4, and F7–F12) and carbonate (F2, F5, F6, F13, and F14) kinds of Al/Al alloy foams performed with (F1–F3, F5, F7, F9, F11, and F13) and without (F4, F6, F8, F10, F12, and F14) Ca additive: (a) Al-foams processed with Al (F1 and F2) and Al-foams of Al-Zn-Mg alloy (F11–F14); (b) Al-foams of Al alloys such as Al-7Si (F3–F6), Al-1Mg-0.6Si (F7 and F8), and Al-5Mg (F9 and F10).