29 Cocompaction or casting of two materials one leachable

Two powders, neither with a volume fraction below 25%, are mixed and compacted, forming double-connected structures of both phases. After consolidation one powder (e.g. salt) is leached out in a suitable solvent (Figure 2.9). Foams based on powder mixes of aluminum alloys with sodium chloride have successfully been made in large sections with uniform structures. The resulting cell shapes differ markedly from those of foams made by other methods. In practice the method is limited to producing materials with relative densities

Figure 2.9 (a) A bed of leachable particles (such as salt) is infiltrated with a liquid metal (such as aluminum or one of its alloys). (b) The particles are disolved in a suitable solvent (such as water) leaving an open-cell foam

Figure 2.9 (a) A bed of leachable particles (such as salt) is infiltrated with a liquid metal (such as aluminum or one of its alloys). (b) The particles are disolved in a suitable solvent (such as water) leaving an open-cell foam between 0.3 and 0.5. The cell size is determined by the powder particle size, and lies in the range 10 |im to 10 mm.

In an alternative but closely related process, a bed of particles of the leach-able material is infiltrated by liquid metal under pressure, and allowed to cool. Leaching of the particles again gives a cellular metallic structure of great uniformity.

0 0

Post a comment