Exfoliation corrosion of extruded Mg-Li-Ca alloy

doi:10.1016/j.jmst.2018.05.014

Abstract

Abstract:

Exfoliation on as-extruded Mg-1Li-1Ca magnesium alloy was investigated after an immersion in 3.5 wt% NaCl aqueous solution for 90, 120 and 150 days through optical microscope, digital camera, scanning electron microscope, electrochemical workstation, scanning Kalvin probe, X-ray diffraction and Fourier transform infrared spectroscope. The results demonstrated that exfoliation corrosion occurred on extruded Mg-1Li-1Ca alloy due to elongated microstructure parallel to surface, and delamination of lamellar structure resulted from galvanic effect and wedge effect. Skin layer with fine grains exhibited better corrosion resistance, whereas the interior with coarse grains and the intermetallic compound, Mg₂Ca particles existing in a fibrous structure, dispersed along grain boundaries and extrusion direction in a line. Furthermore, galvanic effect between Mg₂Ca particles and their neighboring α-Mg matrix facilitated dissolution of Mg₂Ca particles and α-Mg matrix; wedge effect was caused by formation of corrosion products. Exfoliation corrosion of extruded Mg-Li-Ca alloys might be a synergic effect of pitting corrosion, filiform corrosion, intergranular corrosion and stress corrosion. Finally, exfoliation corrosion mechanism was proposed.

Key words: Magnesium-lithium alloy, Exfoliation corrosion, Intermetallic compound, Extrusion, Microstructure

Zi-You Ding, Lan-Yue Cui, Rong-Chang Zeng, Yan-Bin Zhao, Shao-Kang Guan, Dao-Kui Xu, Cun-Guo Lin. Exfoliation corrosion of extruded Mg-Li-Ca alloy[J]. J. Mater. Sci. Technol., 2018, 34(9): 1550-1557.

Figures/Tables 10

Fig. 1. Schematic illustration of different sections of extruded Mg-1Li-1Ca.

Fig. 2. OM images: (a) longitudinal section, (b) transverse section; and SEM images: (c) longitudinal section, (d) transverse section of extruded Mg-1Li-1Ca.

Fig. 3. (a), (b) SEM images of second phase Mg2Ca and (c) EDS.

Table 1 Composition of spectrums at second phase detected by EDS, at.%/wt.%.

Element	Spectrum #1 at.%/wt.%	Spectrum #2 at.%/wt.%	Spectrum #3 at.%/wt.%
O	1.62/1.06	4.56/3.02	10.52/7.07
Mg	96.47/95.80	93.86/94.36	87.10/88.93
Ca	1.92/3.14	1.58/2.62	2.38/4.00

Fig. 4. Corrosion macro-morphology of extruded Mg-1Li-1Ca specimens immersed in 3.5 wt.% NaCl aqueous solution for 90 d (a), (b), and (c), 120 d (d) (e), 150 d (f), (g), (h).

Fig. 5. Optical micrographs of skin and interior zone of extruded Mg-1Li-1Ca alloy after immersion in 3.5 wt.% NaCl solution for 24 h: corrosion morphology of (a) transverse section, (b) (c) (d) longitudinal section.

Fig. 6. (a) Open circuit potential as a function of immersion time and (b) polarization curves of inner zone and outer layer of extruded Mg-1Li-1Ca alloy in 3.5 wt.% NaCl solution.

Fig. 7. Surface Volta potential maps: longitudinal section of extruded Mg-1Li-1Ca.

Fig. 8. Chemical components: (a) XRD patterns of substrate and corrosion products after specific treatments and (b) FT-IR patterns of corrosion debris: a, b, c and water-soluble corrosion products: d, e, f.

Fig. 9. Schematic illustrations of exfoliation corrosion mechanism: (a) macro-galvanic corrosion between skin layer and interior zone, (b) micro-galvanic corrosion between Mg2Ca and α-Mg, (c) wedge effect and hydrogen blistering during exfoliation corrosion, (d) pitting corrosion and filiform corrosion.

References

[1]	G.L. Song, A. Atrens, Adv. Eng. Mater., 1(2010), pp. 11-33
[2]	X.J. Wang, D.K. Xu, R.Z. Wu, X.B. Chen, Q.M. Peng, L. Jin, Y.C. Xin, Z.Q. Zhang, Y. Liu, X.H. Chen, G. Chen, K.K. Deng, H.Y. Wang, J. Mater. Sci. Technol., 32(2018), pp. 245-247
[3]	M.P. Staiger, A.M. Pietak, J. Huadmai, G. Dias, Biomaterials, 27(2006), pp. 1728-1734
[4]	F. Witte, Acta Biomater., 6(2010), pp. 1680-1692
[5]	R.C. Zeng, L. Sun, Y.F. Zheng, H.Z. Cui, E.H. Han, Corros. Sci., 79(2014), pp. 69-82
[6]	Y. Zou, L.H. Zhang, Y. Li, H. Wang, J. Liu, P.K. Liaw, H. Bei, Z. Zhang, J. Alloys Compd., 736(2018), pp. 2625-2633
[7]	Z.L. Zhao, Z.W. Sun, W. Liang, Y.D. Wang, L.P. Bian, Mater. Sci. Eng. A, 702(2017), pp. 206-217
[8]	Y. Zou, L.H. Zhang, Y. Li, H.T. Wang, J.B. Liu, P.K. Liaw, H.B. Bei, Z.W. Zhang, J. Alloys Compd., 736(2018), pp. 2626-2633
[9]	H.W. Dong, F.S. Pan, B. Jiang, R.H. Li, X.Y. Huang, Mater. Des., 65(2015), pp. 42-49
[10]	R.H. Li, B. Jiang, Z.J. Chen, F.S. Pan, Chin. J. Nonferrous Metals, 27(2017), pp. 1118-1124
[11]	S.S. Nene, Y. Estrin, B.P. Kashyap, N. Prabhu, T. Al-Samman, B.J.C.Luthringer, R. Willumeit, Adv.Biomater. Dev. Med., 1(2015), pp. 32-36
[12]	Q. Xiang, B. Jiang, Y.X. Zhang, X.B. Chen, J.F. Song, J.Y. Xu, L. Fang, F.S. Pan, Corros. Sci., 119(2017), pp. 14-22
[13]	C.Q. Li, D.K. Xu, X.B. Chen, B.J. Wang, R.Z. Wu, E.H. Han, N. Birbilis, Electrochim. Acta, 260(2018), pp. 55-64
[14]	R.L. Liu, J.R. Scully, G. Williams, N. Birbilis, Electrochim. Acta, 260(2018), pp. 184-195
[15]	B. Jiang, Q. Xiang, A. Atrens, J.F. Song, F.S. Pan, Corros. Sci., 126(2017), pp. 374-380
[16]	R.C. Zeng, W. Dietzel, R. Zettler, W.M. Gan, X.X. Sun, Trans. Nonferrous Met. Soc. China, 24(2014), pp. 3060-3069
[17]	L.Y. Cui, X.T. Li, R.C. Zeng, S.Q. Li, E.H. Han, L. Song, Front. Mater. Sci. China, 11(2017), pp. 1-12
[18]	L.Y. Cui, R.C. Zeng, S.K. Guan, W.C. Qi, F. Zhang, S.Q. Li, E.H. Han, J. Alloys Compd., 695(2016), pp. 2464-2476
[19]	R.C. Zeng, W.C. Qi, F. Zhang, H.Z. Cui, Y.F. Zheng, Prog. Nat. Sci. Mater. Int., 24(2014), pp. 492-499
[20]	Y.W. Song, D.Y. Shan, E.H. Han, J. Mater. Sci. Technol., 33(2017), pp. 954-960
[21]	Y.W. Song, D.Y. Shan, R.S. Chen, E.H. Han, Corros. Sci., 51(2009), pp. 1087-1094
[22]	G.L. Makar, J. Kruger, Metall. Rev., 38(1993), pp. 138-153
[23]	R.C. Zeng, K.U. Kainer, C. Blawert, W. Dietzel, J. Alloys Compd., 509(2011), pp. 4462-4469
[24]	T. Marlaud, B. Malki, C. Henon, A. Deschamps, B. Baroux, Corros. Sci., 53(2011), pp. 3139-3149
[25]	G.S. Peng, K.H. Chen, S.Y. Chen, H.C. Fang, Trans. Nonferrous Metal. Soc., 22(2012), pp. 803-809
[26]	M.J. Robinson, N.C. Jackson, Br. Corros. J., 34(1999), pp. 45-49
[27]	D.J. Kelly, M.J. Robinson, Corrosion, 49(1993), pp. 787-795
[28]	T. Morishige, H. Doi, T. Goto, E. Nakamura, T. Takenaka, Mater. Trans., 54(2013), pp. 1863-1866
[29]	F. Witte, V. Kaese, H. Haferkamp, E. Switzer, A. Meyer-Lindenberg, C.J. Wirth, H. Windhagen, Biomaterials, 26(2005), pp. 3557-3563
[30]	Y.H. Zou, R.C. Zeng, Q.Z. Wang, L.J. Liu, X.U. Qian, C. Wang, Z.W. Liu, Front. Mater. Sci., 10(2016), pp. 281-289
[31]	R.C. Zeng, X.X. Sun, Y.W. Song, F. Zhang, S.Q. Li, H.Z. Cui, E.H. Han, Trans Nonferrous Metal. Soc., 23(2013), pp. 3293-3299
[32]	L.Y. Cui, R.C. Zeng, Y.X. Yang, D.D. Sun, S.Q. Li, F. Zhang, E.H. Han, J. Mater. Sci. Technol., 33(2017), pp. 971-986
[33]	R.C. Zeng, K.U. Kainer, C. Blawert, W. Dietzel, J. Alloys Compd., 509(2011), pp. 4462-4469
[34]	M.J. Robinson, Corros. Sci., 23(1983), pp. 887-899
[35]	N.T. Kirkland, N. Birbilis, J. Walker, T. Woodfield, G.J. Dias, M.P. Staiger, J. Biomed. Mater. Res. Part B, 95(2010), pp. 91-100
[36]	B. Denkena, A. Lucas, Cirp Ann. -Manuf. Technol., 56(2007), pp. 113-116
[37]	T. Marlaud, B. Malki, A. Deschamps, B. Baroux, Corros. Sci., 53(2011), pp. 1394-1400
[38]	S.S. Nene, B.P. Kashyap, N. Prabhu, Y. Estrin, T. Al-Samman, J. Mater. Sci., 50(2015), pp. 3041-3050
[39]	L.F. Hou, M. Raveggi, X.B. Chen, W.Q. Xu, K.J. Laws, Y.H. Wei, M. Ferry, N. Birbilis, J. Electrochem. Soc., 163(2016), pp. C324-C329
[40]	R.C. Zeng, Y. Hu, S.K. Guan, H.Z. Cui, E.H. Han, Corros. Sci., 86(2014), pp. 171-182