The Role of Oxidation in Blowing Particle‐Stabilised Aluminium Foams

Liquid metal foam can be generated by creating gas inside a liquid or semi‐liquid metallic melt which has been pre‐treated in a suitable way. Such foams are self‐supporting disordered structures in complete analogy to aqueous foams. The stabilisation mechanism of metallic foams is still not fully understood. In order to facilitate discussion of foam stabilisation the various methods for making such foams are classified with respect to the mode of gas generation and the type of melt used for foaming. Metal foams can be produced by gas injection from an external source or by in‐situ nucleation of gas bubbles in the melt for which various possibilities are known. Melts amenable to foaming range from almost pure molten alloys to melts to which particles have been added, formed by in‐situ reactions or which have been already present in the solid precursor prior to melting. Some of the available experimental evidence for the action of stabilising particles in metallic foams is presented. It is found that although stabilisation seems to be based on the presence of a solid constituent in all the foaming processes, the mechanisms might vary. At present the nature of stabilisation is not yet fully understood and many questions remain open.

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“…As a rule, internal gas formation makes it easier to create a stable foam than external gas injection. [17] …”

Section: Direct Foaming Of Meltsmentioning

confidence: 99%

Metal Foams: Production and Stability

2006

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“…Generally, the formation of oxide layer is considered to be primary responsible both for ef cient inhibition of cell coalescence 4,12) and retention of ne cell structure. 6,8) The ways proposed to explain the role of oxide layer on cell face surface in terms of its effect on foam stability were summarised.…”

Section: Stabilizing Effect Of Clustered Oxide Network/parti-mentioning

confidence: 99%

“…8) Former phenomenon is currently associated with an additional stabilisation effect of oxide skin formed on surface of cell faces via the reaction of liquid Al with oxidizing CO 2 gas. 5,6,[8][9][10][11][12][13] Although the results related to in situ monitoring of foam formation from powder compacts being produced with TiH 2 foaming agent have been published, [14][15][16][17][18][19][20][21] formation of foams created from powder compacts with CaCO 3 as gas source has not yet been systematically assessed by in situ experiments. 22) The present paper is aimed at in situ analysis of foam formation and stability at heating Al-based powder compacts with CaCO 3 by comparison with those prepared with TiH 2 .…”

Section: Introductionmentioning

confidence: 99%

Effect of CaCO<sub>3</sub> Foaming Agent at Formation and Stabilization of Al-Based Foams Fabricated by Powder Compact Technique

2017

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The paper presents the results obtained by in situ observation of Al-based foams formation at heating of powder compacts with calcium carbonate (CaCO 3 ) by comparing with those prepared with conventional titanium hydride (TiH 2 ). Foamable precursors comprising powder of either pure aluminium or AlZnMg-alloy were used for detailed investigation of foam evolution and stability. High temperature X-ray furnace was applied for in situ visualization of foam formation. It was identi ed that expansion and stability of foams with CaCO 3 are much superior to those with TiH 2 . Distribution and size of solid inclusions (network of oxide remnants, particles of foaming agent, secondary reaction products, and solid oxide skin) in the cell wall materials of studied foams as well as relevant wetting data were determined to clarify the difference in foams stability. Improved stability of foams with CaCO 3 is explained on the base of stabilizing models developed by Kaptay by assuming an interfacial force, the disjoining pressure, which ef ciency is variable and dependent on the distribution and wetting behaviour of the clustered oxide network/solid particles in foamy melt.

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“…Stabilization of bubbles is due to segregation of particles to the bubble surfaces. If aluminum melt does not contain micrometer-sized particles, such particles can be created in-situ by bubbling air through the melt [8]. Foam stability can be increased by using Al2O3 instead of SiC, because of increased cell wall thickness.…”

Section: Introductionmentioning

confidence: 99%

“…Method Blowing oxygen melt AlSi7Fe1 solves these two problems at same time. Modification of aluminum alloys by introducing Al2O3 particles also was described for metal foam and metal matrix composites [6][7][8][9][10][11][12]. Formation of oxide shell even under argon cannot be avoided due to residual oxygen traces in gas.…”

Section: Introductionmentioning

confidence: 99%

MICROSTRUCTURES, MECHANICAL PROPERTIES INGOT AlSi7Fe1 AFTER BLOWING OXYGEN THROUGH MELT

Finkelstein¹,

Чикова²,

Schaefer³

2017

Acta Metall Slovaca

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The new technology of producing ingot of AlSi7Fe1 high-strength is described. This new technology consists in saturation of melt with hydrogen, with further blowing with oxygen. Studied the microstructure, phase composition and mechanical properties of ingot after blowing oxygen of melt and ingot obtained with the traditional method. Have suggested that in liquid aluminum alloy AlSi7Fe1 because of blowing with oxygen arise refractory particles Al2O3. These particles Al2O3 further in crystallization serve as a modifier of the microstructure of ingot. Mostly observed modifications of eutectic phases. Thus saturation of melt with hydrogen, with further blowing with oxygen provides an increased tensile strength of ingot AlSi7Fe1.

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The Role of Oxidation in Blowing Particle‐Stabilised Aluminium Foams

Cited by 85 publications

References 16 publications

Metal Foams: Production and Stability

Metal Foams: Production and Stability

Effect of CaCO<sub>3</sub> Foaming Agent at Formation and Stabilization of Al-Based Foams Fabricated by Powder Compact Technique

MICROSTRUCTURES, MECHANICAL PROPERTIES INGOT AlSi7Fe1 AFTER BLOWING OXYGEN THROUGH MELT

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