Effect of Sm additions on the microstructure and corrosion behavior of magnesium alloy AZ91

•Sm additions to AZ91 alloys resulted in Al2Sm formation and microstructural alteration of β phase.•AZ91-Sm alloys revealed relatively lower mass loss and hydrogen evolution compared to AZ91 alloy.•The localised electrochemical property of the alloys with varying pH was uniquely revealed.•AZ91-Sm al...

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Bibliographic Details
Published in:Corrosion science 2019-04, Vol.149, p.144-152
Main Authors: Hu, Z., Liu, R.L., Kairy, S.K., Li, X., Yan, H., Birbilis, N.
Format: Article
Language:English
Subjects:
Alkaline corrosion
Aluminum
Corrosion
Corrosion effects
Intermetallics
Magnesium
Magnesium base alloys
Manganese
Microstructure
Morphology
Phase transitions
Polarisation
Samarium
Scanning electron microscopy
SEM
TEM
Transmission electron microscopy
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Summary:•Sm additions to AZ91 alloys resulted in Al2Sm formation and microstructural alteration of β phase.•AZ91-Sm alloys revealed relatively lower mass loss and hydrogen evolution compared to AZ91 alloy.•The localised electrochemical property of the alloys with varying pH was uniquely revealed.•AZ91-Sm alloys exhibited less localised corrosion relative to AZ91 alloys. Of the alloying additions to magnesium to date, samarium (Sm) has not been widely studied. Herein, the effect of Sm on the microstructure and corrosion of AZ91 (Mg-9Al-1Zn-0.4 Mn in wt.%) were investigated using scanning and transmission electron microscopy, electrochemical measurements, mass loss, and hydrogen collection. Results reveal preferential segregation of Sm with aluminium, leading to the formation of Al2Sm. Formation of Al2Sm in AZ91 resulted in a morphology change of β-Mg17Al12 phase, from a coarse, mesh structure, to a fine short rod structure – reducing the overall β-Mg17Al12 phase area fraction. Microelectrochemical tests were also employed to rationalise the corrosion observed.
ISSN:0010-938X
1879-0496
DOI:10.1016/j.corsci.2019.01.024