Enhanced corrosion resistance of Mg alloy ZK60 after processing by integrated extrusion and equal channel angular pressing

Orlov, Dmitry; Ralston, Kevin; Birbilis, Nick; Estrin, Yuri

doi:10.1016/j.actamat.2011.06.033

Cited by 264 publications

(135 citation statements)

References 33 publications

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“…A cross-sectional microscopic examination of the corrosion filaments formed on as-cast AZ31B will be required to confirm this hypothesis. Given that Zn metal and Zn-alloyed Mg have been shown to be more catalytic toward the cathodic HE reaction than pure Mg, 31,32 the sustained cathodic activity revealed by the SVET results in the present investigation of AZ31B-H24 could be attributed to the Zn-enriched layer at the base of the filaments. Although the Znenriched layer was observed to be present underneath a reasonably dense corrosion filament, the presence of through-thickness cracks in the filaments could provide pathways for the electrolyte to be in direct contact with the Zn-enriched surface.…”

Section: Discussionmentioning

confidence: 60%

On the Evolution of Cathodic Activity during Corrosion of Magnesium Alloy AZ31B in a Dilute NaCl Solution

Cano

Kish

McDermid

2015

J. Electrochem. Soc.

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Sequential potentiodynamic polarization and scanning vibrating electrode technique measurements were made on Mg alloy AZ31B immersed in dilute 0.05 M NaCl solution to corroborate the suspected role of noble metal (relative to Mg) solute enrichment at the filament/alloy interface in sustaining the cathodic activation exhibited by corrosion filaments. The electrochemical measurements revealed that the extent of cathodic activation (i.e. current density) measured over a corrosion filament was sustained with immersion time. This resulted in a continual increase in the total anodic current measured over the AZ31B surface as new filaments initiated and propagated. The sustained cathodic activation coupled with observations of zinc (Zn) enrichment at the filament/alloy interface during the life of a corrosion filament is argued to be indicative of a solute enrichment mechanism being a significant factor in this process. Mg and Mg alloys have been shown to be susceptible to the formation of laterally-spreading corrosion products, which tend to form thread-like "filaments" or radially-expanding "discs" in neutral-pH sodium chloride (NaCl) solutions with concentrations ranging from 0.01 M to 0.86 M. 1,5,9 to show that this behavior is driven by a "differential electrocatalytic" mechanism, whereby areas consumed by the corrosion products catalyze the cathodic hydrogen evolution (HE) reaction. The HE reaction has been proposed to be catalyzed by non-alloyspecific mechanisms including undissolved metallic Mg "chunks" and a significantly roughened surface film, 5,13 in addition to alloyspecific mechanisms including enrichment of noble (relative to Mg) alloy constituents. 5,9,14,15 However, a consensus has not been reached in the literature to date regarding the dominant source(s) of cathodic activity.Williams et al. 9 proposed that the main source of cathodic activation on corrosion filaments formed on as-cast Mg alloy AZ31B were Al-Mn intermetallic particles which were originally present in the alloy microstructure and were left behind as the Mg matrix phase was selectively dissolved. Al-Mn phases are well-known to promote cathodic activity in Mg alloys due to their higher corrosion potentials (ranging from −1.0 to −1.5 V SCE ) relative to α-Mg (−1.6 V SCE ).16 A subsequent transmission electron microscopy (TEM) investigation by Cano et al.12 provided physical evidence of Al-Mn particles embedded in the corrosion filaments formed on wrought AZ31B-H24 sheet. However, these intermetallic particles were found to be embedded in the intact surface film as well, casting reasonable doubt concerning the role played by these intermetallic particles in sustaining cathodic activation. In light of this, two alternative sources of cathodic activation were identified by Cano et al.: 12 (1) the MgO-based corrosion filament itself and (2) the metallic zinc (Zn)-enriched layer formed at the filament/alloy interface during prolonged immersion in the NaCl solution. The first of these sources is regarded as less likely due to the poor cathod...

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Section: Discussionmentioning

confidence: 60%

On the Evolution of Cathodic Activity during Corrosion of Magnesium Alloy AZ31B in a Dilute NaCl Solution

Cano

Kish

McDermid

2015

J. Electrochem. Soc.

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“…Corrosion behavior has been investigated on UFG materials fabricated mainly by processing of SPD such as ECAP, ARB, HPT for aluminum and its alloy, [87][88][89][90][91][92][93]120,121,143,[150][151][152][153]156,[158][159][160][161][162][163][164][165][166][167][168][169][170][171] magnesium and its alloy, 34,72,[115][116][117]122,123,154,157,[172][173][174][175][176][177][178][179] copper and its alloy, 6,[96][97][98]…”

Section: General Descriptionmentioning

confidence: 99%

Corrosion of Ultrafine Grained Materials by Severe Plastic Deformation, an Overview

Miyamoto

2016

Mater. Trans.

114

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Corrosion of ultra ne grain (UFG) materials by severe plastic deformation (SPD) is reviewed in light of the existing literature and microstructural change. Fortunately, by holistic survey of the literature, it seems likely that grain re nement by SPD, while enhancing mechanical properties, does not compromise the overall corrosion resistance, and in many case, improve it in comparison with coarse-grained counterparts, although there are some contradictory results within the same materials and same environment. The degree of impact of UFG formation on corrosion is highest in stainless steels followed by aluminum and magnesium alloys whereas it is relatively marginal in pure copper and titanium. The effect of UFG formation by SPD on corrosion is imparted by not only grain re nement, but also other microstructural change occurring commonly in SPD in general and unique to each speci c SPD method. In this review, an attention is paid speci cally to the former case, and this includes shuf ing or redistribution of chemical inhomogeneity into a ner scale, deformation-induced grain boundaries and high internal stress stemming from these grain boundaries. The literature on stress corrosion cracking (SCC) of UFG materials are de nitely insuf cient to nd the general trends, more studies are waited.

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“…They observed a rather smooth surface with a smaller penetration rate at grain boundaries and thus considerable improvement in intergranular corrosion. For SPD materials, corrosion behavior such as general [10][11][12][13][14][15][16][17][18][19][20], intergranular [21][22][23] and pitting corrosion [21,[24][25][26][27][28][29][30][31][32] of UFG aluminum and aluminum alloy [17,21,22,24,25,[29][30][31][32], copper and copper alloy [11,15,19,28] as well as stainless steels [10,12,18,23,27] and magnesium [13,14,16,20] processed by SPD, and corrosive environment dependence [33][34]…”

Section: Introductionmentioning

confidence: 99%

Effects of Strain Energy and Grain Size on Corrosion Resistance of Ultrafine Grained Fe-20%Cr Steels with Extremely low C and N Fabricated by ECAP

Rifai

Miyamoto

Fujiwara

2015

International Journal of Corrosion

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Effect of strain energy and grain size on corrosion resistance of ultrafine grained (UFG) Fe-20%Cr steels with extremely low C and N fabricated by equal channel angular pressing (ECAP) was investigated. UFG structures of initial grain size of 144 nm exhibited the typical three-stage softening comprising recovery, recrystallization, and grain growth. Potentiodynamic polarization measurements were carried out with a conventional three-electrode cell to evaluate pitting potential. Pitting potential in 1000 mol⋅m −3 NaCl solution was nobler in UFG state, but pitting potential started to decrease monotonously at lower temperature compared to hardness. The degradation of corrosion resistance in the early stage of annealing is attributed to stability change of passivation by recovery of dislocation structures inside grains and in nonequilibrium grain boundaries. We therefore conclude that nobler potentials of UFG states were realized by not only grain size reduction but also defective deformation-induced UFG.

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Enhanced corrosion resistance of Mg alloy ZK60 after processing by integrated extrusion and equal channel angular pressing

Cited by 264 publications

References 33 publications

On the Evolution of Cathodic Activity during Corrosion of Magnesium Alloy AZ31B in a Dilute NaCl Solution

On the Evolution of Cathodic Activity during Corrosion of Magnesium Alloy AZ31B in a Dilute NaCl Solution

Corrosion of Ultrafine Grained Materials by Severe Plastic Deformation, an Overview

Effects of Strain Energy and Grain Size on Corrosion Resistance of Ultrafine Grained Fe-20%Cr Steels with Extremely low C and N Fabricated by ECAP

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