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

Pawar, S., Slater, T.J.A., 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: 07 Mar 2022 14:00
URI: https://orca.cardiff.ac.uk/id/eprint/147199

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