Fabrication and Properties of Porous Metals by Directional Solidification Under High Pressure of Hydrogen

Hideo Nakajima 

Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan

Abstract


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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Presentation: oral at High Pressure School 1999 (3rd), by Hideo Nakajima
See On-line Journal of High Pressure School 1999 (3rd)

Submitted: 2003-02-16 17:33
Revised:   2009-06-08 12:55