A variety of porous metal microstructure can be produced by utilizing gas solubility gap in between liquid and solid.Higher pressure gas atmosphere enhances the solubility of gas atoms in liquid phase predominantly. Porous metals such copper, nickel and iron was fabricated by directional solidification in the mixture gas of hydrogen and argon at high pressure to 2 MPa. The pore growth direction is controlled by the directional solidification; columnar pore configuration and radial pore configuration can be synthesized by this method. The pore size is controlled by the cooling rate, the heating temperature of melt, the ratio of the mixture gas and the pressure, whose diameter ranges from 5 mm to 5 mm. Porous metals with unique pore size is fabricated at an eutectic composition in the metal-gas eutectic reaction. The maximum porosity is about 70%. Internal friction and mechanical property of the porous copper were investigated. The internal friction increases on the porous copper. The mechanical property is remarkably dependent on the pore growth direction. The specific strength of the specimen with columnar pore structure grown in the tensile direction does not change up to 40% porosity. The detailed results will be presented as functions of the control parameters such as the heating temperature of melt, the ratio of the mixture gas, the pressure and the purity of copper. The theory on pore nucleation and growth will be given. Furthermore, possible applications of the porous metals and alloys to various structural and functional practical materials will be also mentioned.
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