Effect of crystal orientation on corrosion behavior of directionally solidified Mg-4 wt% Zn alloy

doi:10.1016/j.jmst.2017.06.009

Abstract

Abstract:

Microstructure and crystallographic orientation of directionally solidified Mg-4 wt% Zn alloy were characterized by X-ray computed tomography (XCT) and electron backscatter diffraction (EBSD) in this study. Results reveal that Mg-4 wt% Zn alloy with dendritic microstructure exhibits typical {0002} basal texture along growth direction. Based on this, the effect of grain orientation on corrosion behavior of directionally solidified Mg-4 wt% Zn alloy in 0.9 wt% NaCl solution was investigated. Result shows that {0002} oriented planes have better corrosion resistance than {11\(\overline{2}\)0} and {10\(\overline{1}\)0} ones, which is attributed to a synergistic effect of surface energy, atomic packing density and the stability of oxidation film.

Key words: Mg-4 wt% Zn alloy, Directional solidification, Crystal orientation, Corrosion resistance

Hongmin Jia, Xiaohui Feng, Yuansheng Yang. Effect of crystal orientation on corrosion behavior of directionally solidified Mg-4 wt% Zn alloy[J]. J. Mater. Sci. Technol., 2018, 34(7): 1229-1235.

Figures/Tables 12

Fig. 1. Schematic of selection of samples.

Fig. 2. XCT micrographs of directionally solidified Mg-4 wt%Zn alloy: (a) 3D; (b) LD; (c) TD.

Fig. 3. EBSD images of directionally solidified Mg-4 wt% Zn alloy: (a) LD; (b) TD.

Fig. 4. Polarization curves of directionally solidified Mg-4 wt% Zn alloy with different crystal orientations immersed in 0.9 wt% NaCl solution.

Table 1 Electrochemical parameters of Mg-4 wt%Zn alloy with different crystal orientations measured in 0.9 wt% NaCl solution derived from polarization curves.

Sample	E_pt (V_SCE)	σ₁	E_corr (V_SCE)	σ₂	i_corr (μA cm^-2)	σ₃
LD	-1.301	0.0594	-1.391	0.0489	35.9	0.1784
TD	-1.365	0.0685	-1.442	0.0755	50.1	0.1218

Fig. 5. EIS spectra of directionally solidified Mg-4 wt.% Zn alloy with different crystal orientations immersed in 0.9 wt% NaCl solution: (a) Nyquist plots; (b) Bode plots of ?Z? with frequency; (c) Bode plots of phase angle with frequency; (d) equivalent circuit of EIS spectra.

Table 2 Fitting electrochemical parameters of EIS spectra.

Sample	R_s (Ω cm²)	R_ct (kΩ cm²)	CPE_ct		R_f (kΩ cm²)	CPE_f
			Q_ct (μF sⁿ cm^-2)	n		Q_f (μF sⁿ cm^-2)	n
LD	96.5	13.6	1.25	0.93	9.27	87.8	0.71
TD	97.1	10.4	1.48	0.81	6.64	104.7	0.80

Fig. 6. (a) Hydrogen volume evolution, (b) corrosion rate and (c) weight loss of directionally solidified Mg-4 wt%Zn alloy with different crystal orientations immersed in 0.9 wt% NaCl solution for 48 h.

Fig. 7. Corrosion surfaces of directionally solidified Mg-4 wt%Zn alloy for samples LD (a, c) and TD (b, d) after immersion in 0.9 wt% NaCl solution for 48 h with (a, b) and removing (c, d) corrosion products.

Fig. 8. Corrosion CLSM morphologies of directionally solidified Mg-4 wt%Zn alloy after immersion in 0.9 wt% NaCl solution for 48 h: (a) LD; (b) TD.

Fig. 9. Morphologies showing distribution of secondary phases in LD (a) and TD (b) samples.

Fig. 10. XPS profiles of LD (a) and TD (b) samples with different orientations after immersion in 0.9 wt% NaCl solution for 48 h.

References

[1]	B.L. Mordlike, T. Ebert, Mater. Sci. Eng. A 302 (2001) 37-45.
[2]	G.L. Song, Adv. Eng. Mater. 7(2005) 563-586.
[3]	G.L. Song, Corros. Sci. 49(2007) 1696-1701.
[4]	A. Pardo, M.C. Merino, A.E. Coy, R. Arrabal, F. Viejo, E. Matykina, Corros. Sci. 50(2008) 823-834.
[5]	Y.W. Song, E.H. Han, D.Y. Shan, C.D. Yim, B.S. You, Corros. Sci. 65(2012)322-330.
[6]	M. Mandal, A.P. Moon, G. Deo, Corros. Sci. 78(2014) 172-182.
[7]	A. Pardo, M.C. Merino, A.E. Coy, F. Viejo, R. Arrabal, S. Feliú Jr., Electrochim.Acta 53 (2008) 7890-7902.
[8]	X. Li, X.M. Liu, S.L. Wu, K.W.K.Yeung, Y.F. Zheng, P.K. Chu, Acta Biomater. 45(2016) 2-30.
[9]	G.L. Song, Adv. Mater. Res. 29(2007) 95-98.
[10]	M. Liu, D. Qiu, M.C. Zhao, G.L. Song, A. Atrens, Scr. Mater. 58(2008) 421-424.
[11]	G.L. Song, Z.Q. Xu, Corros. Sci. 63(2012) 100-112.
[12]	G.L. Song, R. Mishra, Z.Q. Xu, Electrochem. Commun. 12(2010) 1009-1012.
[13]	G.L. Song, Z.Q. Xu, Corros. Sci. 54(2012) 97-105.
[14]	R.L. Xin, Y.M. Luo, A.L. Zuo, J.C. Gao, Q. Liu, Mater. Lett. 72(2012) 1-4.
[15]	Q.T. Jiang, X.M. Ma, K. Zhang, Y.T. Li, X.G. Li, Y.J. Li, M.L. Ma, B.R. Hou, J.Magnes. Alloys 3 (2015) 309-314.
[16]	K.S. Shin, M.Z. Bian, N.D. Nam, J. Miner. Met.Mater. Soc. 64(2012) 664-670.
[17]	K. Hagihara, M. Okubo, M. Yamasaki, T. Nakano, Corros. Sci. 109(2016) 68-85.
[18]	H.M. Jia, X.H. Feng, Y.S. Yang, Mater. Sci. Forum 816 (2015) 411-417.
[19]	H.M. Jia, X.H. Feng, Y.S. Yang, J. Magnes. Alloys 3 (2015) 247-252.
[20]	Y.W. Song, E.H. Han, D.Y. Shan, C.D. Yim, B.S. You, Corros. Sci. 60(2012)238-245.
[21]	H.M. Jia, X.H. Feng, Y.S. Yang, Acta Metall, Sin. (Engl. Lett.) (2017) (accepted).
[22]	G.L. Song, Corros. Sci. 52(2010) 455-480.
[23]	B.Q. Fu, W. Liu, Z.L. Li, Appl. Surf. Sci. 255(2009) 9348-9357.
[24]	C.N. Cao, Principles of Electrochemistry of Corrosion, second ed., ChemicalIndustry Press, Beijing, 2004, pp. 52-67.
[25]	G. Brail, C. Blanc, N. Pébérz, J. Electrochem. Soc.. 148(2001) B489-B496.
[26]	M. Taheri, M. Danaie, J.R. Kish, J. Electrochem. Soc.. 161(2014) C89-C94.