Effect of Intermetallic Phases on Corrosion Initiation of AZ91 Alloy With Rare Earth Y Addition

doi:10.1016/j.jmst.2014.09.018

Abstract

Abstract: The effect of the rare earth (RE) element Y on the microstructure of AZ91 Mg alloy is investigated. A detailed description of the procedure of identifying the intermetallic phases containing Y in the AZ91 Mg alloy with 0.9 wt% Y addition is presented. The results shows that there are two different kinds of RE phases in scanning electron microscopy (SEM) images. Energy dispersive spectrum (EDS) analysis shows that one is rich in Y element and the other is rich in Mn element. According to the element mapping of electron probe microanalysis (EPMA), the element Al can be found not only in the β-Mg₁₇Al₁₂ phase but also in these two RE phases. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results further confirm one of the two RE phases is Al₂Y; the phase of Al₁₀Mn₂Y has just been determined by transmission electron microscopy (TEM) instead of XRD probably because it is scarce. The shapes of these two RE intermetallic phases are pretty similar. The 3D digital microscopy is employed to observe in-situ the effect of the β phase and the above two RE intermetallic phases on the corrosion initiation of the alloys. The results show that the corrosion attack of AZ91 Mg alloy without Y addition starts around the eutectic phase β-Mg₁₇Al₁₂. With the addition of 0.9 wt% Y, the two kinds of Y-rich intermetallic phases act as cathodic effect and α phase in the adjacent of them was activated and cathodic effect of the β-Mg₁₇Al₁₂ phase was inhibited.

Key words: Mg alloy, Yttrium, Intermetallic phase, Corrosion initiation

Li-na Zhang, Ruiling Jia, Dan Li, Wei Zhang, Feng Guo. Effect of Intermetallic Phases on Corrosion Initiation of AZ91 Alloy With Rare Earth Y Addition[J]. J. Mater. Sci. Technol., 2015, 31(5): 504-511.

Figures/Tables 8

SEM morphologies of the AZ91 alloy (a), the intermetallic phase containing Mn in AZ91 alloy (b), the AZ91 with 0.9%Y alloy (c) and the intermetallic phases containing Y (e), EDS results of the phase containing Mn in AZ91 alloy (d), the phase of spectrum 1 (f) and the phase of spectrum 2 (g) in Fig. 1(e).

XRD patterns of AZ91 alloy (a) and AZ91 alloy with 0.9%Y addition (b).

EPMA analysis: BSE image (a), mapping of Al element (b) of AZ91 alloy, and BSE image (c), mapping of Al element (d), mapping of Y element (e), mapping of Mn element (f) of AZ91 alloy with 0.9%Y.

TEM bright field image (a) and electro diffraction patterns of the upper intermetallic phase (b) and the lower intermetallic phase diffraction (c).

EDS results of the upper particle (a) and the lower particle (b) in Fig. 4(a).

Corresponding corrosion images of AZ91 alloy by 3D digital microscopy: (a) under the solution immersion for 15 min

(b) the solution is soaked up by filter papers after immersion for 15 min

References

[1] H.Y. Wu, F.Z. Lin, Mater. Sci. Eng. A , 527 (2010), pp. 1194-1199
[2] T. Bhattacharjee, C.L. Mendis, K. Oh-ishi, Mater. Sci. Eng. A , 575 (2013), pp. 231-240
[3] C. Zhong, M.F. He, L. Liu, Y.T. Wu, Y.J. Chen, Y.D. Deng, B. Shen, W.B. Hu, J. Alloy. Compd. , 504 (2010), pp. 377-381
[4] C. Zhong, M.F. He, L. Liu, Y.J. Chen, B. Shen, Y.T. Wu, Y.D. Deng, W.B. Hu, Surf. Coat. Technol. , 205 (2010), pp. 2412-2418
[5] C. Zhong, F. Liu, Y.T. Wu, J.J. Le, L. Liu, M.F. He, J.C. Zhu, W.B. Hu, J. Alloy. Compd. , 520 (2012), pp. 11-21
[6] J.J. Le, L. Liu, F. Liu, Y.D. Deng, C. Zhong, W.B. Hu, J. Alloy. Compd. , 610 (2014), pp. 173-179
[7] H. Tang, Z. Cheng, J. Liu, Mater. Sci. Eng. A , 550 (2012), pp. 11-21
[8] J. Patel, K. Morsi, J. Alloy. Compd. , 540 (2012), pp. 100-106
[9] G. Wu, Y. Fan, H. Gao, Mater. Sci. Eng. A , 408 (2005), pp. 255-263
[10] S. Wei, Y. Chen, Y. Tang, Mater. Sci. Eng. A , 508 (2009), pp. 59-63
[11] J.H. Jun, J.M. Kim, B.K. Park, J. Mater. Sci. , 40 (2005), pp. 2659-2661
[12] J. Zhang, L.P. Chen, Y. Ai, Foundry Technol. , 27 (2006), pp. 47-49
[13] J.H. Zhang, X.D. Niu, X. Qiu, J. Alloy. Compd. , 471 (2009), pp. 322-330
[14] F. Wang, Y. Wang, P.L. Mao, Trans. Nonferrous Met. Soc. China , 20 (2010), pp. 311-317
[15] H. Ma, Corros. Sci. Prot. , 23 (2011), pp. 223-227
[16] T.J. Luo, Y.S. Yang, Y.J. Li, Electrochim. Acta , 54 (2009), pp. 6433-6437
[17] M.L. Liu, L. Liu, Mater. Heat Treat. , 39 (2010), pp. 61-63
[18] Z. Tian, D.P. Zhang, H.Y. Wang, H. Du, D.X. Tang, J. Meng, L.L. Rokhlin, J. Chin, Rare Earth Soc. , 26 (2008), pp. 729-734
[19] R.L. Jia, M. Zhang, L.N. Zhang, W. Zhang, F. Guo, J. Alloy. Compd. , Accepted.
[20] Y. Wang, M. Xia, Z. Fan, X. Zhou, G.E. Thompson, Intermetallics , 18 (2010), pp. 1683-1689
[21] J.H. Zhang, X.D. Niu, X. Qiu, K. Liu, C.M. Nan, D.X. Tang, J. Meng, J. Alloy. Compd. , 471 (2009), pp. 322-330
[22] M. Jonsson, D. Thierry, N. LeBozec, Corros. Sci. , 48 (2006), pp. 1193-1208
[23] F. Andreatta, I. Apachitei, A.A. Kodentsov, J. Dzwonczyk, Electrochim. Acta , 51 (2006), pp. 3551-3557
[24] A. Pardo, M.C. Merino, A.E. Coy, F. Viejo, R. Arrabal, S. Feliu Jr., Eletrochim. Acta , 53 (2008), pp. 7890-7902
[25] R. Arrabal, E. Matykina, A. Pardo, M.C. Merino, K. Paucar, M. Mohedano, P. Casajus, Corros. Sci. , 55 (2012), pp. 351-362
[26] J. Chen, J.Q. Wang, E.H. Han, J.H. Dong, W. Ke, Electrochim. Acta , 52 (2007), pp. 3299-3309
[27] A.E. Coy, F. Viejo, P. Skldon, G.E. Thompson, Corros. Sci. , 52 (2010), pp. 3896-3906
[28] T. Zhang, Y. Yang, Y.W. Shao, G.Z. Meng, F.H. Wang, Electrochim. Acta , 54 (2009), pp. 3915-3922
[29] H. Wang, J. Xie, K.P. Yan, M. Duan, Y. Zuo, Corros. Sci. , 51 (2009), p. 181185
[30] G.T. Burstein, C. Liu, R.M. Souto, S.P. Vines, Corros. Eng. Sci. Technol. , 39 (2004), pp. 25-30