Production of Refined and Modified Closed-Cell Aluminum Foams by Melt-Foaming Method

Closed-cell A356 aluminum alloy foams refined and modified were successfully fabricated by using barite and calcium carbonate as thickening and foaming agents, respectively. A melt treatment consisting of adding master alloys of Al-5Ti-1B and Al-10Sr for refining the dendritic microstructure and modifying the primary eutectic silicon, respectively, were included in the foaming process. The microstructure and mechanical properties of the foams manufactured were analyzed and compared with foams produced without the refining and modifying treatments. The secondary dendritic arm spacing (SDAS) was determined by optical measurements. Lower SDAS values were obtained in foam regions closer to the mold walls due to the high solidification rate imposed during the cooling step and a decrease in the SDAS values for the foams produced with the addition of the Al-5Ti-1B master alloy was evident. Additionally, the addition of the Al-10Sr master alloy caused the formation of solid solution dendrites and a fine irregular fibrous form of silicon. Foams produced with the melt treatment exhibit a good combination of structure and mechanical properties. Therefore, the melt route established is a feasible way to improve foam performance where the lowest SDAS and the highest mechanical properties were obtained for the closed-cell foams produced.