Accelerated growth of oxide film on aluminium alloys under steam: Part I: Effects of alloy chemistry and steam vapour pressure on microstructure

Din, Rameez Ud; Gudla, Visweswara Chakravarthy; Jellesen, Morten Stendahl; Ambat, Rajan

doi:10.1016/j.surfcoat.2015.06.059

Cited by 30 publications

(18 citation statements)

References 37 publications

(47 reference statements)

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“…3) shows additional effect of water vapour and sodium chloride ions on the oxide film growth. It leads to more intensive crack formation and healing and, consequently, increases the hindered contraction factor that in agreement with known data on aluminium oxidation and corrosion [17][18][19][20].…”

Section: Resultssupporting

confidence: 89%

Irreversible Thermal Expansion of Replicated Aluminium Foam

Finkelstein¹,

Husnullin²

2018

Acta Metall Slovaca

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Irreversible thermal expansion of large items made of the replicated aluminium foam was detected during the extraction of soluble filler from Al-NaCl composite. Sources of the phenomenon were investigated The expansion discovered was caused by incomplete contraction of the porous metal due to the oxidation of its internal porous surface in air and water mediums during thermal cycling. Significant influence of oxide film defects on the expansion process was shown. The information about irreversible thermal expansion dependence on temperature of the extraction process and metal foam pore size was collected. Measurements of expansion dynamics showed its finite character. It was also noted that the expansion is limited by the thermal expansion coefficient of an alloy used. Finally, correction coefficients were obtained that, being applied to nominal sizes of a porous item, compensates the expansion.Keywords: aluminium, replicated foam, alumina film, micro-cracks, contraction, thermal expansion IntroductionThe effect of irreversible three-dimensional expansion of items was detected at the stage of soluble filler extraction during the manufacturing process of commercial replicated aluminum foam at Composite Materials LLC (Kirovgrad, Russia) [1]. Replicated aluminum foam technology involves mechanical treatment to final shape before the filler dissolving from the casting body. This treatment was applied during the process of mold fabrication for expandable polystyrene (EPS) molding with an overall dimension of 850 mm. Control measurement, performed by the customer, showed the overall dimension of 854 mm, not 850 mm, and the product was rejected. It was checked that the dimensional non-compliance was not a mistake at the machining process but the consequence of the filler extraction in accordance with the adopted manufacture technology. The case of the expansion was not identified by the other researchers of the replicated aluminum foam technology [2,3,4,5] due to insignificant sizes of laboratory specimens (not over 200 mm). In this case extraction of the filler is not a difficult task and may be realized within the mode of water external convection at room temperature. Such extraction process is ineffective if sizes of a casting are large, as mentioned above. Non-soluble aluminum hydroxide is formed in the pores while casting is immersed into water for a long time. The hydroxide blocks the process of the filler extraction. A casting is to be heated up to 200-300°С before immersion into the water in order to form a gap between the metal surface and the filler particles [5].Also formation of the gap is used for acceleration of wax model removing from the ceramic molds in the investment casting process [6].

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Section: Resultssupporting

confidence: 89%

Irreversible Thermal Expansion of Replicated Aluminium Foam

Finkelstein¹,

Husnullin²

2018

Acta Metall Slovaca

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“…As iron containing intermetallic particles shifts the corrosion potential of aluminium alloys to nobler side, the coverage of these cathodic intermetallic particles by the formed oxide film may shift the corrosion potential to negative side. Pitting potential is significantly affected by the increased steam pressure in the treatment, and it is assumed to be due to the compactness of the oxide film at high vapour pressure [38]. Pre-treatment 1 followed by pressurised steam treatment showed inferior corrosion resistance as compared to pre-treatment 2, which can be related to the removal of some intermetallic phases and the better coverage of intermetallic particles at high vapour pressure of steam [38].…”

Section: Discussionmentioning

confidence: 99%

“…Pitting potential is significantly affected by the increased steam pressure in the treatment, and it is assumed to be due to the compactness of the oxide film at high vapour pressure [38]. Pre-treatment 1 followed by pressurised steam treatment showed inferior corrosion resistance as compared to pre-treatment 2, which can be related to the removal of some intermetallic phases and the better coverage of intermetallic particles at high vapour pressure of steam [38]. The presence of different intermetallic phases in aluminium matrix makes the surface prone to localised corrosion [42][43][44].…”

Section: Discussionmentioning

confidence: 99%

Accelerated growth of oxide film on aluminium alloys under steam: Part II: Effects of alloy chemistry and steam vapour pressure on corrosion and adhesion performance

Din

Bordo

Jellesen

et al. 2015

Surface and Coatings Technology

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“…The sheets have been mechanically polished with 6 μm, 3 μm, and 1 μm diamond paste and stored in a desiccator for 24 hours at room temperature to allow the formation of a homogeneous oxide layer before exposing the samples to the test environment. Chemical pretreatments to remove the Mechanically Deformed Layer (MDL) have been omitted deliberately to avoid the enrichment or depletion of alloying elements and dissolution of IMPs on the sample surface that would affect the characteristics of the surface layer …”

Section: Methodsmentioning

confidence: 99%

“…This treatment creates a thick boehmite (γ‐AlOOH) coating that reinforces the barrier properties of the native passive layer and improves the adhesion of organic coatings. For alloys, the process parameters must be controlled carefully to avoid heterogeneous growth of the surface layer around intermetallic phases (IMPs) …”

Section: Passive Layer On Aluminium Exposed To Water or Water Vapourmentioning

confidence: 99%

Evolution of surface characteristics of two industrial 7xxx aluminium alloys exposed to humidity at moderate temperature

Schwarzenböck

Hack

Kolb

et al. 2019

Surface & Interface Analysis

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This study analyses the evolution of surface characteristics of two industrial high‐strength 7xxx aluminium alloys with a focus on alloy composition and environmental parameters. Based on storage and transport conditions of as‐machined products, the effect of humidity—as liquid and vapour phase—on the natural oxide layer has been studied. The evolution of the natural oxide layer has been analysed by scanning electron microscopy and X‐ray photoelectron spectroscopy. The growth behaviour of the surface layer is dominated by environmental conditions, while microgalvanic activity depends mainly on the alloys' chemical composition and differs significantly for tested alloys. Scanning transmission electron microscopy images demonstrated that the long‐term exposure at moderate temperatures affects the microstructure near the surface, which differs for the analysed alloy compositions. An anomalous precipitation of zinc‐rich particles at the surface and along the precipitate‐free zone is observed for the alloy with higher Zn/Mg ratio and lower Cu content.

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Accelerated growth of oxide film on aluminium alloys under steam: Part I: Effects of alloy chemistry and steam vapour pressure on microstructure

Cited by 30 publications

References 37 publications

Irreversible Thermal Expansion of Replicated Aluminium Foam

Irreversible Thermal Expansion of Replicated Aluminium Foam

Accelerated growth of oxide film on aluminium alloys under steam: Part II: Effects of alloy chemistry and steam vapour pressure on corrosion and adhesion performance

Evolution of surface characteristics of two industrial 7xxx aluminium alloys exposed to humidity at moderate temperature

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