Beilby layers on crystal surfaces

Vlasov, A. D.; Rez, Jiří; Fil'chenkov, M. L.

doi:10.1002/crat.2170230908

Cited by 16 publications

(12 citation statements)

References 6 publications

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“…11 The temperature increases arising from a periodic contact of the abrasive with the crystal surface. 25 It is likely that both shear stresses and temperature increases can lead to the formation of this disordered layer. This will be discussed in more detail in the future.…”

Section: Discussionmentioning

confidence: 99%

Mechanism of Localized Breakdown of 7000 Series Aluminum Alloys

Wang

Frankel

Jiang

et al. 2013

J. Electrochem. Soc.

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The localized breakdown behavior of AA7055 alloy, and an Al-Zn-Mg alloy having no Cu, with different tempers was studied in 3.5 wt% NaCl solution by an in situ observation system during polarization. Three potentials at which the current increased rapidly were found for AA7055-T6 (peak-aged) samples. The first breakdown potential corresponded to the transient dissolution of an active surface layer formed during surface preparation by abrading with grinding paper. The second potential at which the current increased rapidly was associated with crevice corrosion and was not a true breakdown potential. The second breakdown potential was associated with pitting of the underlying bulk alloy. However, no surface layer attack and a single breakdown potential were observed for AA7055-T73 (over-aged) samples and for the Cu-free Al-Zn-Mg samples in the peak-aged condition. All three samples contained surface layers consisting of nano-grains with the solute-rich bands formed by surface preparation. Both the Zn-rich bands in the surface layer and the Cu content in matrix solid solution of the underlying bulk alloy are responsible for surface layer attack. The change in pitting potential with over-aged tempers could be rationalized based on the Cu content in the matrix. Precipitation-hardenable aluminum alloys are main structural materials for aircrafts due to their high strength-to-density ratio. The AlZn-Mg(-Cu) alloys form precipitates following the general precipitation sequence of supersaturated solid solution, GP zones, metastable η , and stable η.1,2 Metastable η phase is believed to be the main hardening phase and responsible for the peak hardening in Al-ZnMg(-Cu) alloys.2 The equilibrium phase η has the hexagonal structure of MgZn 2 , but Al and Cu can substitute for Zn, and the stoichiometry of this phase can be described as Mg(Zn,Al,Cu) 2 in Cu containing 7××× series Al alloys.3,4 Aging treatments produce changes in the morphology, chemistry, size and density of precipitates and the composition of the solid solution. In the past decade, much research effort has been put into evaluating the composition of nanoscale precipitates in Al alloys due to the development of advanced characterization tools such as atom probe tomography (APT).2,5-7 Sha and Cerezo studied the chemistry evolution of the early-stage precipitates in 7050 Al alloy using transmission electron microscopy (TEM) and APT.2 Marlaud and Deschamps investigated the composition of precipitates and the solid solution in Al-Zn-Mg-Cu alloys in peak-aged and over-aged conditions by combining APT and systematic anomalous small-angle X-ray scattering (ASAXS) techniques.7 This microstructural information has also facilitated a better understanding of corrosion behavior in 7××× series Al alloys with different heat treatments.The localized breakdown behavior of 7××× series Al alloys has been studied extensively. 4,[8][9][10][11][12] The anodic polarization curve for 7×××-T6 Al alloys in NaCl solution exhibits two breakdown potentials. However, only one breakdown pot...

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Section: Discussionmentioning

confidence: 99%

Mechanism of Localized Breakdown of 7000 Series Aluminum Alloys

Wang

Frankel

Jiang

et al. 2013

J. Electrochem. Soc.

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“…The main purpose of this procedure was to obtain a smooth surface while also etching lightly to dissolve the amorphous layer (Beilby layer) left on the surface by mechanical polishing. [15] The average grain size of the specimens was 20 to 50 lm.…”

Section: Methodsmentioning

confidence: 99%

Thickness of Anodic Titanium Oxides as a Function of Crystallographic Orientation of the Substrate

Diamanti

Pedeferri

Schuh

2008

Metall Mater Trans A

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This work deals with the anodization-driven oxidation of titanium, studied as a function of the crystallographic orientation of the crystal grains of the substrate. On a polycrystalline surface, different colors appear on the surface after anodization under galvanostatic conditions at a fixed potential. The color of the oxides on individual grains is correlated to an independent set of reflectometry data relating color to thickness, to infer the approximate thickness of the oxide layer grown on each grain in the polycrystal. These data are further related to the crystallographic orientation of each grain as assessed by electron backscatter diffraction measurements. It is shown that crystallographic orientations close to (0001) lead to relatively slower oxidation as compared with inclined orientations.

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“…In contrast to polishing, etching with KCN/O 2 is a chemical dissolution process that also proceeds predominantly at energetically favored, i. e., less coordinated, surface structures like edges, steps, kinks, grain boundaries or other so-called active sites, [45] and generally removes what is known in metal machining as the "Beilby layer". [46][47][48] Emanating from already crystalline surfaces, temporary chemical etching will accentuate the present orientation of individual grains (see Figure 10a). But based on this highly ordered state, electrochemical dissolution rates of surface gold atoms are low and therefore their concentration near the electrode surface.…”

Section: Discussion: Interrelation Of Surface Morphology and Electrocmentioning

confidence: 90%

“…From all this follows, that the process behind peak A3 is very likely the oxidation of highly ordered crystalline areas and faces. In contrast to polishing, etching with KCN/O 2 is a chemical dissolution process that also proceeds predominantly at energetically favored, i. e., less coordinated, surface structures like edges, steps, kinks, grain boundaries or other so‐called active sites, and generally removes what is known in metal machining as the “Beilby layer” . Emanating from already crystalline surfaces, temporary chemical etching will accentuate the present orientation of individual grains (see Figure a).…”

Section: Discussion: Interrelation Of Surface Morphology and Electmentioning

confidence: 92%

Electrochemical Formation of Gold Nanoparticles on Polycrystalline Gold Electrodes during Prolonged Potential Cycling

et al. 2017

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The voltammetric behavior of polycrystalline gold electrodes in 0.1 M sulfuric acid and the influence of prolonged repetitions of oxidation and reduction cycles at different scan rates on the surface morphology was studied. Slow (0.1 V s−1) as well as fast (1.0 V s−1) scan rates lead to an intense roughening of the electrode surface and the formation of a variety of different crystalline particles on it. These crystallites, their formation, and the influence of surface pretreatment were investigated with electrochemical methods, X‐ray diffraction measurements, and scanning electron microscopy. Additionally, an interpretation of the changing electrochemical signals of polycrystalline gold during prolonged potential cycling is given.

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Beilby layers on crystal surfaces

Cited by 16 publications

References 6 publications

Mechanism of Localized Breakdown of 7000 Series Aluminum Alloys

Mechanism of Localized Breakdown of 7000 Series Aluminum Alloys

Thickness of Anodic Titanium Oxides as a Function of Crystallographic Orientation of the Substrate

Electrochemical Formation of Gold Nanoparticles on Polycrystalline Gold Electrodes during Prolonged Potential Cycling

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