The limits of solid state foaming

Elzey, D. M.; Wadley, H.N.G.

doi:10.1016/s1359-6454(00)00395-5

Cited by 68 publications

(59 citation statements)

References 13 publications

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“…Powder metallurgy is essentially based on the sintering of a green compact produced from powders or fibers. 1,2) In more advanced technologies, pores are created by the entrapment of gas contained in a powder compact, 3) by the use of spaceholding filler materials or hollow spheres, 4) and by the foaming of metal powder slurries. 5) A typical method in use of casting enables to produce lotus-type porous metals.…”

Section: Introductionmentioning

confidence: 99%

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Development of a New Method for Manufacturing Iron Foam Using Gases Generated by Reduction of Iron Oxide

et al. 2007

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A new method for manufacturing iron foam using CO and CO 2 as foaming gases was studied. This method consists of three stages: (1) mixing powders of pure iron, graphite, and hematite; (2) preparing the precursor by cold pressing the mixed powders; and (3) foaming by heating the precursor at temperatures between the liquidus and solidus in the Fe-C binary system. Molten iron containing carbon is foamed by gases generated by a reduction reaction. Optimizations of both the composition of the precursor and the heating conditions are required to produce the iron foam with high porosity. It was found that the content and powder size of hematite in the precursor significantly affect the porosity and pore diameter of the iron foam. Iron foam with a porosity of 55% and average pore diameter of around 500 mm is obtained by heating the precursor of Fe-3.1 mass%C-1.0 mass%Fe 2 O 3 at 1543 K.

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Section: Introductionmentioning

confidence: 99%

“…Then, the precursor is heated, and it expands and foams as the metal matrix melts. Aluminum foam with a density of 0.069-0.54 g/cm 3 is obtained by these methods, and it has high energy and sound absorbabilities. However, aluminum foam is very expensive, although it has excellent properties.…”

Section: Introductionmentioning

confidence: 99%

Development of a New Method for Manufacturing Iron Foam Using Gases Generated by Reduction of Iron Oxide

et al. 2007

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“…[10] The gas entrapment method is not described for nickel, copper, or their alloys, so a direct comparison is not available, but the lack of an allotropic transformation will prevent this type of technique from being applied to accelerate expansion. Furthermore, the porosity is not dependent on creating an initial pore pressure, but the mechanisms and limits on expansion by gas entrapment [49] do provide some valuable insights as both methods are dependent on plastic flow of the matrix.…”

Section: Matrix Effects On Porositymentioning

confidence: 99%

Solid State Foaming of Nickel, Monel, and Copper by the Reduction and Expansion of NiO and CuO Dispersions

et al. 2018

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Nickel and its alloys are useful in a range of applications, and nickel foams have increased in popularity for functional applications, such as electrodes. Despite their versatility and interest for burgeoning technologies, there is only one well-developed method for producing porous nickel commercially. This work introduces a simple method for creating porosity in nickel and Monel (70% Ni, 30% Cu) that results in sub-micron to micron-scale pores and grains. This is accomplished by creating oxide dispersions in the metallic matrix and then reducing those oxides at elevated temperature to form pores. It is found that nickel and Monel reach maximum porosity at 800 C withMonel reaching a higher overall porosity (33% vs. 25% for Ni), whereas Cu exhibited 40% porosity under the same conditions. Varied matrix and oxide pairings are examined microstructurally, and the effects of matrix strength, oxide chemistry, and other factors are considered to determine factors in pore development. Uniquely, this method produces pores within individual metallic particles, so this porosity can be added to other powder methods of solid state foaming to enhance the performance in functional applications.

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“…During the manufacturing procedure of closed-cell cellular metals with gas injection (air, CO 2 , O 2 , Ar) the gas in pores can reach up to 1200 K and 100 MPa according to Elzey et al [24] and Öchsner et al [25]. After solidification and cooling down it can be assumed that the gas is trapped in the base material for a certain time.…”

Section: Pore Fillersmentioning

confidence: 99%

“…Under compressive loading the pore gas pressure increases due to cell deformation, thus contributing to structure stiffness increase up to the point of base material yielding. This results in the collapse of intercellular walls and increase of the material structure porosity [24]. Öchsner et al have shown a strong effect on the yield stress due to varying pore gas pressure under quasi-static loading and isothermal conditions.…”

Section: Pore Fillersmentioning

confidence: 99%