Fabrication of aluminum foams by using CaCO3 foaming agent

Abstract

Since TiH2 is widely used as a foaming agent to generate gas bubbles in the melt, but it has some disadvantages and difficulties that studying another foaming agent instead TiH2 is of great interest. In this work, pure aluminum foams were produced by a foam melting method using CaCO3 as a foaming agent. In this regard, the process parameters were optimized to fabricate the homogeneous foam based on its structure. The effect of Ca addition on the density and porosity of foams has been investigated. In addition, the influence of CaCO3 as a foaming agent and stirring speed on density and porosity has been studied. The mechanical response of the foam obtained at optimum condition was evaluated by uniaxial compression test. The results showed that by adding 1.5 wt% Ca, a uniform structure and an optimum viscosity can be achieved with a maximum porosity of 70% and minimum density of 0.8 g cm−3. Moreover, it was found that by increasing the amount of CaCO3 up to 2 wt% and increasing of the stirring speed up to 2000 rpm, the porosity increased and the size of cells decreased. The optimum values for Ca amount, CaCO3 value, and stirring speed was found as 1.5 wt%, 1 wt%, and 1400 rpm, respectively. The produced foam at optimum condition had a density of 0.9 g cm−3 with spherical cell morphology, and revealed compressive strength of 8 MPa and energy absorption of 1.12 kJ. It was successfully concluded that CaCO3 can be used as a foaming agent instead of TiH2 to produce aluminum foams in order to reduce the cost of manufacture, density of foam, and generation of harmful and H2 gas.