High-Porosity Closed-Cell Aluminum Foams Produced by Melting Method Without Stabilizer Particles

Abstract

Closed-cell A356 aluminum foams have been produced by the addition of calcium carbonate (CaCO3) powder as a foaming agent to the molten aluminum without any stabilizer particles. The foaming process is performed by the addition of 2.5–3.5 wt% CaCO3 and has relative density ranges of 0.12–0.44 and cell sizes of 1.5–3.1 mm with uniform cell structures. The foaming stabilizing mechanism and effect of foaming conditions such as the amount of foaming agent, casting holding and mixing time at the furnace on the foamed samples were investigated. The stabilizing mechanism is because of the foaming gas (CO2)/melt reaction during the foaming procedure and producing some solid particles such as CaO, Al2O3 and MgO. The optimum foamed aluminum with uniform cell size distribution was obtained at 4-min mixing time and 10-min holding time with 3 wt% CaCO3 foaming agent. The porosity of aluminum foam increased as the holding time increased from 60 to 86%. Also, the average cell size increased from 1.5 to 3.1 mm when the amount of CaCO3 increased from 2.5 wt% to 3.5 wt%, respectively.