期刊
ACTA MATERIALIA
卷 133, 期 -, 页码 90-99出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.actamat.2017.05.027
关键词
Automotive sheet; Mg-Al alloy; Micro-galvanic corrosion; Mg dissolution
资金
- TARF-LCV [EP/I038616/1]
- LATEST2 Programme Grant [EP/H020047/1]
- European Research Council Advanced Grant [695638]
- EPSRC [EP/M010619, EP/K004530, EP/F007906, EP/F028431]
- EPSRC [EP/N007638/1, EP/M010619/1, EP/J021229/1] Funding Source: UKRI
- Engineering and Physical Sciences Research Council [EP/N007638/1, EP/J021229/1] Funding Source: researchfish
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, beta-Mg-17(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 alpha-Mg grains with non-basal planes on the surface. The severity of attack suffered by alpha-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 alpha-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. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd.
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