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Crystallographic effects on the corrosion of twin roll cast AZ31 Mg alloy sheet

Pawar, S., Slater, T.J.A. ORCID: https://orcid.org/0000-0003-0372-1551, Burnett, T.L., Zhou, X., Scamans, G.M., Fan, Z., Thompson, G.E. and Withers, P.J. 2017. Crystallographic effects on the corrosion of twin roll cast AZ31 Mg alloy sheet. Acta Materialia 133 , pp. 90-99. 10.1016/j.actamat.2017.05.027

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Abstract

The influence of crystal orientation on the corrosion behaviour of twin roll cast (TRC) AZ31 Mg alloy sheet has been investigated using correlative microscopy and immersion testing in 3.5% NaCl. Corrosion initiates as a consequence of the microgalvanic coupling between cathodic intermetallic phases, including sub-micron sized, rosette-shaped Al8Mn5 particles, β-Mg17(Al,Zn)12 phase and the Mg matrix. Subsequent development of lateral filiform-like corrosion fronts are observed running along the dendrite arms whilst being constrained by the Al- and Zn-rich interdendritic boundaries. Prolonged immersion showed variable corrosion depths across the surface. By correlating with EBSD analysis, it was confirmed that the corrosion depth is considerably higher in α-Mg grains with non-basal planes on the surface. The severity of attack suffered by α-Mg grains with non-basal planes on the surface is on average twice that for grains with basal or near-basal with planes on the surface. At the same time, corroded α-Mg grains with basal planes on the surface display nanoscale, canyon-like corrosion features developing into the alloy perpendicularly. A mechanism has been proposed to explain the sequential corrosion events.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Additional Information: This is an open access article under the terms of the CC-BY license.
Publisher: Elsevier
ISSN: 1359-6454
Date of First Compliant Deposit: 7 March 2022
Date of Acceptance: 15 May 2017
Last Modified: 15 May 2023 02:25
URI: https://orca.cardiff.ac.uk/id/eprint/147199

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