Thermodynamic analysis of the aluminum alloy foaming process by melt route

A thermodynamic analysis was carried out to determine the stability compounds formed by the interaction between the molten alloy (A356 alloy) with a foaming agent (1, 2, 3 wt. % CaCO₃) and a thickening agent (1 wt. % Al₂O₃) for the production of closed-cell aluminum alloy foams. Stability phase diagrams were obtained to 973, 1073 and 1173 K and they showed the formation of the compounds MgAl₂O₄, CaAl₄O₇, Al₄C₃, and Al₄O₄C. Typical closed-cell foams of the A356 aluminum alloy were produced to the same conditions of the thermodynamic analysis. The structure of the foams produced was evaluated by SEM-EDS and Raman techniques. The stability compounds predicted are in good agreement with those determined experimentally. The compounds formed by the interaction between the particles and the melt were increased with the increase of the foaming agent and were located at the cell walls.