Microstructural evolution, mechanical properties and corrosion behavior of as-cast Mg-5Li-3Al-2Zn alloy with different Sn and Y addition

doi:10.1016/j.jmst.2020.07.029

Abstract

Abstract:

Influences of Sn and Y on the microstructure, mechanical properties, and corrosion behavior of as-cast Mg-5Li-3Al-2Zn (LAZ532) alloy were investigated. The addition of Sn and Y refines grains and results in the formation of Mg₂Sn and Al₂Y phases, thus improving the mechanical properties of alloy by second phase strengthening and grain refinement strengthening. As-cast LAZ532 alloy shows typical filiform corrosion morphology, and the addition of Sn and Y does not change the corrosion mode of alloy. As-cast LAZ532-0.8Sn-1.2Y alloy shows excellent mechanical properties with yield strength of 166.2 MPa, ultimate tensile strength of 228.6 MPa and elongation of 14.8 %, and exhibits the best corrosion resistance with the smallest corrosion current density and the lowest anodic dissolution rate.

Key words: Mg-Li alloy, Sn, Y, Mechanical properties, Corrosion behavior

Xiang Peng, Shihao Xu, Dehua Ding, Guanglan Liao, Guohua Wu, Wencai Liu, Wenjiang Ding. Microstructural evolution, mechanical properties and corrosion behavior of as-cast Mg-5Li-3Al-2Zn alloy with different Sn and Y addition[J]. J. Mater. Sci. Technol., 2021, 72: 16-22.

Figures/Tables 11

Table 1 Chemical composition of as-cast LAZ532-xSn-yY alloys.

Alloy number	Designed composition		Actual composition (wt.%)
Alloy number	Designed composition	Li	Al	Zn	Sn	Y	Mg
a	LAZ532	4.90	2.98	1.75	0	0	Bal.
b	LAZ532-1.6Sn-0.4Y	4.92	2.93	1.79	1.54	0.24	Bal.
c	LAZ532-1.2Sn-0.8Y	4.96	2.89	1.85	1.16	0.66	Bal.
d	LAZ532-0.8Sn-1.2Y	5.01	2.90	1.83	0.75	1.03	Bal.
e	LAZ532-0.4Sn-1.6Y	4.97	2.87	1.78	0.39	1.42	Bal.

Fig. 1. XRD patterns of the as-cast LAZ532-xSn-yY alloys: (a) x = 0, y = 0; (b) x = 1.6, y = 0.4; (c) x = 1.2, y = 0.8; (d) x = 0.8, y = 1.2; (e) x = 0.4, y = 1.6.

Fig. 2. SEM microstructures of the as-cast LAZ532-xSn-yY alloys: (a) x = 0, y = 0; (b) x = 1.6, y = 0.4; (c) x = 1.2, y = 0.8; (d) x = 0.8, y = 1.2; (e) x = 0.4, y = 1.6. The morphologies on the top right corner of (a-e) are enlarged views of the white dotted-line rectangular regions.

Table 2 EDS results of points marked by red cross in Fig. 2.

Point	Content (at.%)					Element ratio
Point	Mg	Al	Zn	Sn	Y	Mg/Sn	Al/Y
A	65.45	0.96	0.61	32.98	0.00	2:1	-
B	1.22	64.38	2.38	0.62	31.40	-	2:1
C	67.41	0.49	0.78	31.09	0.23	2:1	-
D	1.68	63.50	1.96	0.82	32.04	-	2:1

Fig. 3. Optical micrographs of the as-cast LAZ532-xSn-yY alloys: (a) x = 0, y = 0; (b) x = 1.6, y = 0.4; (c) x = 1.2, y = 0.8; (d) x = 0.8, y = 1.2; (e) x = 0.4, y = 1.6.

Fig. 4. Mechanical properties of the as-cast LAZ532-xSn-yY alloys: (a) tensile strength and elongation; (b) hardness.

Fig. 5. Fracture morphologies of the as-cast LAZ532-xSn-yY alloys: (a) x = 0, y = 0; (b) x = 1.6, y = 0.4; (c) x = 1.2, y = 0.8; (d) x = 0.8, y = 1.2; (e) x = 0.4, y = 1.6; (f) is the partial enlarged view of (d).

Fig. 6. Polarization curves of the as-cast LAZ532-xSn-yY alloys in 3.5 wt.% NaCl solution.

Table 3 Tafel fitting results of the as-cast LAZ532-xSn-yY alloys.

Alloy	E_corr (V vs SCE)	J_corr (A cm^-2)
LAZ532	-1.546	3.397 × 10^-4
LAZ532-1.6Sn-0.4Y	-1.616	4.646 × 10^-4
LAZ532-1.2Sn-0.8Y	-1.536	1.456 × 10^-4
LAZ532-0.8Sn-1.2Y	-1.526	9.304 × 10^-5
LAZ532-0.4Sn-1.6Y	-1.516	1.137 × 10^-4

Fig. 7. Hydrogen evolution of the as-cast LAZ532-xSn-yY alloys in 3.5 wt.% NaCl solution.

Fig. 8. (a, b) Corrosion morphologies of the as-cast (a) LAZ532 and (b) LAZ532-0.8Sn-1.2Y alloys immersed in 3.5 wt.% NaCl solution for 1 h; (c-g) corrosion morphologies of the LAZ532-xSn-yY alloys immersed in 3.5 wt.% NaCl solution for 37 h: (c) x = 0, y = 0; (d) x = 1.6, y = 0.4; (e) x = 1.2, y = 0.8; (f) x = 0.8, y = 1.2; (g) x = 0.4, y = 1.6; (h) sketch map of filiform corrosion for Mg-Li alloys [19]. The morphologies on the top right corner of (c-g) are enlarged views of the white dotted-line rectangular regions.

References 26

[1]	W. Xu, N. Birbilis, G. Sha, Y. Wang, J.E. Daniels, Y. Xiao, M. Ferry, Nat. Mater. 14 (2015) 1229-1235. DOI URL
[2]	X. Peng, G.H. Wu, L. Xiao, H. Ji, J. Zhang, W.B. Zou, Z.Q. Li, W.C. Liu, Prog. Nat. Sci. Mater. Int. 29 (2019) 103-109. DOI URL
[3]	Q. Xiang, R.Z. Wu, M.L. Zhang, J. Alloys. Compd. 477 (2009) 832-835. DOI URL
[4]	H.Y. Ha, J.Y. Kang, J. Yang, C.D. Yim, B.S. You, Corros. Sci. 102 (2016) 355-362. DOI URL
[5]	H.Y. Ha, J.Y. Kang, S.G. Kim, B. Kim, S.S. Park, C.D. Yim, B.S. You, Corros. Sci. 82 (2014) 369-379. DOI URL
[6]	X.B. Liu, D.Y. Shan, Y.W. Song, R.S. Chen, E.H. Han, Electrochim. Acta 56 (2011) 2582-2590. DOI URL
[7]	W.C. Liu, S. Feng, J. Zhao, G.H. Wu, W.J. Ding, J. Mater. Sci. Technol. 34 (2018) 2256-2262. DOI URL
[8]	J. Zhao, J. Zhang, W.C. Liu, G.H. Wu, L. Zhang, Mater. Sci. Eng. A 650 (2016) 240-247. DOI URL
[9]	M. Gu, G.L. Wei, J. Zhao, W.C. Liu, G.H. Wu, Mater. Sci. Technol. 33 (2017) 864-869. DOI URL
[10]	R. Islam, M. Haghshenas, J. Magnesium Alloys 7 (2019) 203-217. DOI URL
[11]	J.Q. Li, Z.K. Qu, R.Z. Wu, M.L. Zhang, Mater. Sci. Eng. A 527 (2010) 2780-2783. DOI URL
[12]	F. Zhong, H.J. Wu, Y.L. Jiao, R.Z. Wu, J.H. Zhang, L.G. Hou, M.L. Zhang, J. Mater. Sci. Technol. 39 (2020) 124-134. DOI URL
[13]	J. Yang, J.L. Wang, L.D. Wang, Y.M. Wu, L.M. Wang, H.J. Zhang, Intermetallics 17 (2009) 104-108. DOI URL
[14]	Y.H. Sun, R.C. Wang, C.Q. Peng, Y. Feng, Mater. Sci. Eng. A 733 (2018) 429-439. DOI URL
[15]	H. Ji, X. Peng, X.L. Zhang, W.C. Liu, G.H. Wu, L. Zhang, W.J. Ding, J. Alloys. Compd. 791 (2019) 655-664. DOI URL
[16]	G.X. Luo, G.Q. Wu, S.J. Wang, R.H. Li, Z. Huang, J. Mater. Sci. 41 (2006) 5556-5558. DOI URL
[17]	Y. Jiang, Y.A. Chen, D. Fang, L. Jin, Mater. Sci. Eng. A 641 (2015) 256-262. DOI URL
[18]	H.M. Liu, Y.G. Chen, Y.B. Tang, S.H. Wei, G. Niu, J. Alloys. Compd. 440 (2007) 122-126. DOI URL
[19]	Y.W. Song, D.Y. Shan, R.S. Chen, E.H. Han, Corros. Sci. 51 (2009) 1087-1094. DOI URL
[20]	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) 14-22. DOI URL
[21]	M.C. Lin, C.Y. Tsai, J.Y. Uan, Corros. Sci. 51 (2009) 2463-2472. DOI URL
[22]	S. Manivannan, S.P.K. Babu, S. Sundarrajan, J.Mater. Eng. Perform. 24 (2015) 1649-1655.
[23]	S. Jin, D. Zhang, X.P. Lu, Y. Zhang, L.L. Tan, Y. Liu, Q. Wang, J. Mater. Sci. Technol. 47 (2020) 190-201. DOI URL
[24]	N.N. Aung, W. Zhou, Corros. Sci. 52 (2010) 589-594. DOI URL
[25]	B. Jiang, Q. Xiang, A. Atrens, J. Song, F. Pan, Corros. Sci. 126 (2017) 374-380. DOI URL
[26]	F.M. Xu, L. Luo, L. Xiong, Y. Liu, J. Magnesium Alloys 8 (2020) 480-492. DOI URL