Microstructure and corrosion behavior of Mg-Sc binary alloys in 3.5 wt.% NaCl solution

doi:10.1016/j.corsci.2020.108831

Corrosion Science

Volume 174, September 2020, 108831

https://doi.org/10.1016/j.corsci.2020.108831 Get rights and content

Highlights

•
Sc has a significant effect of refining grains of pure Mg.
•
Mg-Sc binary alloys show single-phase microstructure for Sc concentrations between 0.1−0.3 wt.%.
•
There are Mg-Sc precipitates in Mg-Sc binary alloys for higher Sc concentrations (0.5–1.5 wt.%).
•
The Sc additions obviously improve the corrosion resistance of pure Mg.
•
The corrosion rates of the Mg-Sc alloys firstly decrease and then increase with increasing Sc concentration.

Abstract

This paper studied the microstructure and corrosion behavior of Mg-xSc binary alloy (x = 0.1–1.5 wt.%) sheets. Sc has a significant effect of refining grains of Mg. The Mg-Sc binary alloys had a single-phase microstructure for Sc concentrations between 0.1−0.3 wt.%, while there were Mg-Sc precipitates for higher Sc concentrations. The Sc additions obviously improved the corrosion resistance of pure Mg due to the refinement of microstructure and the formation of a more protective corrosion products film. The corrosion rate firstly decreased and then increased with increasing Sc concentration. Mg-0.3Sc has the lowest corrosion rate.

Section snippets

Instruction

Magnesium (Mg) alloys have advantages of light weight, high specific strength and specific stiffness, good electromagnetic shielding, high damping capacity and excellent biocompatibility etc., which have attracted wide attention in manufacturing and medical field [[1], [2], [3], [4]]. Poor corrosion resistance is one of the major obstacles in the application of Mg alloys [5,6].

Alloying is a valid method to improve the corrosion resistance of Mg alloys [7,8]. However, Mg alloys often contain

Materials preparation

Mg-xSc binary alloys (x = 0, 0.1, 0.3, 0.5, 1.0 and 1.5 wt.%) were prepared from pure Mg (> 99.999 wt.%) and Mg-2Sc (wt.%) master alloy in an electric furnace under the protection of mixed CO₂ and SF₆ gas. The master alloy pieces were added to the melt at 720℃. The melt was mechanically stirred and held for 15 min to homogenize the alloy. The actual chemical composition of the Mg-xSc alloys was measured using a plasma-atomic emission spectrometer (ICP-AES) and the results are listed in Table 1.

Microstructures

Fig. 1 shows optical images and the grain size distribution of the Mg-xSc (x = 0, 0.1, 0.3, 0.5, 1.0 and 1.5 wt.%) alloys. The average grain size (AGS) of pure Mg was approximately 42.9 μm. The grains were significantly refined with addition of 0.1 wt.% Sc (24.6 um). The grains were further refined with increasing of Sc addition but the grain refinement effect is relatively not significant. Ultimately, the grain size was decreased to about 10.8 μm with addition of 1.5 wt.% Sc.

Fig. 2 shows EBSD

Effect of the microstructure

Grain size is an important factor affecting the corrosion resistance of Mg alloys. Grain refinement can improve the corrosion resistance of Mg alloys [[33], [34], [35]] for the following reasons. The grain boundary can act as a physical barrier to retard the spread of corrosion [36]. A small grain size is beneficial to form a continuous protective corrosion products film, which can effectively slow down corrosion [37]. In this study, pure Mg had coarse microstructure with grain size of about

Conclusions

1
Alloying with Sc significantly refined the grain size of pure Mg but the grain refinement was not significant with further increasing Sc concentration.
2
The Mg-xSc binary alloys showed a single-phase microstructure for Sc concentrations lower than 0.3 wt.%, but there were Mg-Sc phase precipitates in the alloys for Sc concentrations higher than 0.5 wt.%. The amount and size of the precipitates increased with increasing Sc concentration.
3
The alloying with Sc produced alloys with corrosion rates less

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time due to technical or time limitations.

CRediT authorship contribution statement

Cheng Zhang: Methodology, Formal analysis, Investigation, Writing - original draft, Writing - review & editing. Liang Wu: Conceptualization, Formal analysis, Writing - review & editing. Han Liu: Methodology, Investigation. Guangsheng Huang: Conceptualization, Formal analysis, Writing - review & editing. Bin Jiang: Conceptualization, Funding acquisition. Andrej Atrens: Formal analysis, Writing - review & editing. Fusheng Pan: Project administration, Funding acquisition.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by The National Key Research and Development Plan (2016YFB0301104), the National Natural Science Foundation of China (51671041, 51531002, 51971040, 51701029, and U1764253) and Natural Science Foundation of Chongqing (cstc2017jcyjBX0040), China Postdoctoral Science Foundation Funded Project (2017M620410, 2018T110942) and the Chongqing Postdoctoral Scientific Research Foundation (Xm2017010).

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Microstructure and corrosion behavior of Mg-Sc binary alloys in 3.5 wt.% NaCl solution

Highlights

Abstract

Section snippets

Instruction

Materials preparation

Microstructures

Effect of the microstructure

Conclusions

Data availability

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgements

Corros. Sci.

Prog. Mater. Sci.

Mater. Des.

Mater. Sci. Eng. C

J. Mater. Sci. Technol.

J. Alloys Compd.

Trans. Nonferrous Met. Soc. China

Mater. Sci. Eng. A

Mater. Des.

Electrochim. Acta

Mater. Lett.

J. Less Common Met.

Mater. Sci. Eng. A

Mater. Lett.

J. Alloys Compd.

Mater. Sci. Eng. A

J. Alloys Compd.

J. Alloys Compd.

J. Alloys Compd.

Corros. Sci.

Mater. Lett.

Mater. Sci. Eng. C