Processing of brass open-cell foam by silica-gel beads replication

Cellular metals can be produced by several routes, including molten metal infiltration of a leachable bed of solid particles, also known as space holder. The space holder is usually a mineral salt (i.e. NaCl) with relatively low melting point, but this is a limitation for processing high melting point metals and alloys. This work introduces the use of amorphous SiO2 (silica-gel) particles as space holder and wet solutions of hydrofluoric acid (HF) as solvent for Cu-based open-cell foams production. Commercial grade CW614N brass (solidification interval: 880–895 °C) was successfully foamed through the proposed route, resulting in open-cell foams having relative density ≈0.30 and almost spherical cell morphology. Because of the high chemical stability of SiO2 particles no interaction with the metallic system during liquid infiltration has been found. On the other hand, due to the corrosion resistance of that alloy to HF attack there has been no evidence of damage on the treated alloys.