Effect of Ag on High-Temperature Oxidation Behavior of Mg-6.5Gd-5.6Y-0.1Nd-0.01Ce-0.4Zr Alloy

doi:10.1007/s40195-024-01732-x

Abstract

Abstract:

In this paper, the isothermal oxidation experiments were used to study the effect of Ag on the high-temperature oxidation behavior of Mg-6.5Gd-5.6Y-0.1Nd-0.01Ce-0.4Zr (wt%) alloy oxidized at 350 °C, 400 °C and 450 °C for 120 h. The results show that the oxidation weight gain of the alloy mainly occurs in the early oxidation stage (0-20 h). This reason attributes to the lack of protective oxide film and the rapid inward diffusion of oxygen through the macroscopic defects of the incomplete oxide film. When dense oxide films such as Y₂O₃, Gd₂O₃, and ZrO₂ form, they hinder the inward transport of oxygen ions and improve the high-temperature oxidation resistance of the alloy. In addition, the role of the Ag element at three temperatures is different. The addition of Ag mainly promotes the formation of eutectic phases such as Mg₃Gd, Mg₂₄Y₅, and Ag₂Gd, which reduces the content of Gd and Y elements in the alloy matrix, resulting in a decrease in the diffusion rate of Gd and Y elements during the oxidation process at 350 °C and 400 °C, and weakens the oxidation resistance of Ag-containing alloys. However, in the oxidation experiment at 450 °C, a large amount of eutectic phase is solid dissolved into the matrix, reducing the difference in element content. At this time, it is detected that the Ag element promoted the outward diffusion of Gd and Y elements, accelerating the formation of the oxide film. The oxidation resistance of Ag-containing alloys is improved.

Key words: Magnesium alloy, High-temperature oxidation, Thermogravimetric analysis, Gibbs free energy, Oxide film, Oxidation resistance

Shuang Guo, Tianyu Liu, Tianjiao Luo, Yingju Li, Xiaohui Feng, Qiuyan Huang, Ce Zheng, Cheng Zhu, Yuansheng Yang, Weirong Li, Feng Li. Effect of Ag on High-Temperature Oxidation Behavior of Mg-6.5Gd-5.6Y-0.1Nd-0.01Ce-0.4Zr Alloy[J]. Acta Metallurgica Sinica (English Letters), 2024, 37(11): 1843-1857.

Figures/Tables 18

Table 1 Actual composition of the alloy (wt%)

Samples	Gd	Y	Zr	Nd	Ce	Ag	Mg
0Ag	6.51	5.73	0.26	0.11	0.011	-	Bal.
1.0Ag	6.47	5.66	0.31	0.12	0.015	1.04	Bal.
1.5Ag	6.30	5.84	0.29	0.12	0.015	1.63	Bal.
2.0Ag	6.40	5.47	0.22	0.12	0.015	2.09	Bal.

Fig. 1 Microstructure of as-cast alloys: a 0Ag, b 1.0Ag, c 1.5Ag, d 2.0Ag

Fig. 2 XRD patterns of the as-cast alloys

Table 2 EDS data of 2.0Ag alloy (wt%)

Points	Mg	Gd	Y	Zr	Nd	Ag
A	95.26	1.51	2.53	0.00	0.00	0.70
B	56.40	23.59	15.24	0.28	0.92	3.57
C	29.38	13.68	55.28	1.29	0.00	0
D	48.69	11.55	11.67	24.79	0.19	3.11
E	59.75	30.17	6.99	0.15	0.57	2.37

Fig. 3 Oxidation weight gain curves of four alloys: a 350 °C, b 400 °C, c 450 °C

Fig. 4 Fitting curves of oxidation weight gain at different temperatures: a 350 °C, b 400 °C, c 450 °C

Table 3 Relevant data of fitting curves for four alloys at 350 °C, 400 °C and 450 °C

Alloys	Parameters	350 °C	400 °C	450 °C
0Ag	k	0.01123	0.01955	0.04146
	R²	0.98149	0.97764	0.9793
	c₁	1.00275	− 2.37847 × 10^-19	-
	c₂	− 6.14477 × 10^-4	− 2.92413 × 10^-4	-
	n	-	-	1.7366
1.0Ag	k	0.01207	0.02622	0.02395
	R²	0.96863	0.99493	0.97732
	c₁	0.66043	− 5.90181 × 10^-19	-
	c₂	0.00446	− 0.00596	-
	n	-	-	1.9203
1.5Ag	k	0.01295	0.03107	0.03625
	R²	0.97539	0.99865	0.98089
	c₁	0.51521	− 1.17842 × 10^-18	-
	c₂	0.00814	− 0.0114	-
	n	-	-	1.7805
2.0Ag	k	0.01972	0.03096	0.03356
	R²	0.9648	0.99245	0.98192
	c₁	1.41663	− 2.2075 × 10^-20	-
	c₂	− 0.00857	0.00579	-
	n	-	-	1.9368

Fig. 5 Three-dimensional morphology of surface oxide films on four alloys at different temperatures for 120 h

Fig. 6 Surface morphologies of four alloys oxidized at different temperatures for 120 h

Fig. 7 XRD patterns of four alloys after oxidation for 120 h at different temperatures: a 350 °C, b 400 °C, c 450 °C

Fig. 8 Cross-section morphologies and element distribution of four alloys oxidized at 350 °C for 120 h: a 0Ag, b 1.0Ag, c 1.5Ag, d 2.0Ag

Fig. 9 Cross-section morphologies and element distribution of four alloys oxidized at 400 °C for 120 h: a 0Ag, b 1.0Ag, c 1.5Ag, d 2.0Ag

Fig. 10 Cross-sectional morphologies and element distribution of four alloys after oxidation at 450 °C for 120 h: a 0Ag, b 1.0Ag, c 1.5Ag, d 2.0Ag

Table 4 Gibbs free energy of actual reactions at temperatures of 623 K, 673 K, and 723 K (J/mol)

Temperatures	ΔG_MgO	ΔG_Gd2O3	ΔG_Y2O3	ΔG_ZrO2
623 K	− 653,428.9	− 1,969,362.0	− 2,026,730.2	− 1,196,767.3
673 K	− 658,862.3	− 1,984,915.0	− 2,039,706.9	− 1,142,166.5
723 K	− 633,568.0	− 2,000,984.9	− 2,001,309.0	− 1,147,496.5

Fig. 11 Schematic diagram of the oxidation process

Fig. 12 Cross-sectional morphologies of four alloys oxidized for 120 h at different temperatures

Table 5 EDS analysis of the matrix of four alloys oxidized for 120 h at different temperatures (wt%)

Points	Mg	Gd	Y
P₁	92.49	3.47	4.04
P₂	93.63	3.00	3.37
P₃	94.43	2.77	2.80
P₄	94.79	2.63	2.58
P₅	90.89	4.96	4.16
P₆	91.78	4.25	3.96
P₇	92.54	3.89	3.57
P₈	92.90	3.51	3.59
P₉	88.59	6.36	5.05
P₁₀	88.36	6.22	5.42
P₁₁	89.02	5.34	5.64
P₁₂	89.49	5.38	5.13

Fig. 13 Microstructure cross-section scanning curves of four alloys oxidized for 120 h at different temperatures

References 32

[1]	N.Y. Liu, Z.Y. Zhang, L.M. Peng, W.J. Ding, Mater. Sci. Eng. A 627, 223 (2015)
[2]	J.J. Wang, A.B. Phillion, G.M. Lu, J. Alloys Compd. 609, 290 (2014)
[3]	J.J. Wang, Z.M. Zhang, A.B. Phillion, S.Z. Shang, G.M. Lu, J. Mater. Res. 31, 2482 (2016)
[4]	X.S. Xia, Q. Chen, Z.D. Zhao, M.L. Ma, X.G. Li, K. Zhang, J. Alloys Compd. 623, 62 (2015)
[5]	B.L. Mordike, T. Ebert, Mater. Sci. Eng. A 302, 37 (2001)
[6]	N.J. Kim, Mater. Sci. Technol. 30, 1925 (2014)
[7]	W.F. Mo, L. Zhang, G.H. Wu, Y. Zhang, W.C. Liu, C.L. Wang, Mater. Des. 63, 729 (2014)
[8]	J. Wang, J. Meng, D.P. Zhang, D.X. Tang, Mater. Sci. Eng. A 456, 78 (2007)
[9]	H.R.J. Nodooshan, W.C. Liu, G.H. Wu, R. Alizadeh, R. Mahmudi, W.J. Ding, J. Alloys Compd. 619, 826 (2015)
[10]	J.F. Nie, X. Gao, S.M. Zhu, Scr. Mater. 53, 1049 (2005)
[11]	H.R.J. Nodooshan, W.C. Liu, G.H. Wu, Y. Rao, C.X. Zhou, S.P. He, W.J. Ding, R. Mahmudi, Mater. Sci. Eng. A 615, 79 (2014)
[12]	S.M. He, X.Q. Zeng, L.M. Peng, X. Gao, J.F. Nie, W.J. Ding, J. Alloys Compd. 427, 316 (2007)
[13]	J.N. Yu, W.D. Jian, B.Z. Xiao, Acta Metall. Sin. -Engl. Lett. 36, 295 (2023)
[14]	K. Yamada, H. Hoshikawa, S. Maki, T. Ozaki, Y. Kuroki, S. Kamadoa, Y. Kojimaa, Scr. Mater. 61, 636 (2009)
[15]	L.M. Peng, J.W. Chang, X.W. Guo, A. Atrens, W.J. Ding, Y.H. Peng, J. Appl. Electrochem. 39, 913 (2009)
[16]	Y. Zhang, Y.J. Wu, L.M. Peng, P.H. Fu, F. Huang, W.J. Ding, J. Alloys Compd. 615, 703 (2014)
[17]	X. Gao, J.F. Nie, Scr. Mater. 58, 619 (2008)
[18]	H. Zhou, Q.D. Wang, J. Chen, B. Ye, W. Guo, Trans. Nonferrous Met. Soc. 22, 1891 (2012)
[19]	Y. Zhang, T. Alam, B. Gwalani, W. Rong, R. Banerjee, L.M. Peng, Phil. Mag. Lett. 96, 212 (2016)
[20]	S. Najafi, R. Mahmudi, J. Magnes. Alloy. 8, 1109 (2020) DOI
[21]	Y. Chen, J.C. Pang, S.X. Li, Z.F. Zhang, Acta Metall. Sin. -Engl. Lett. 35, 1117 (2022)
[22]	Y. Yang, L. Peng, P. Fu, B. Hu, W. Ding, J. Alloys Compd. 485, 245 (2009)
[23]	J.X. Zheng, Z.Y. Luo, L. Tan, B. Chen, Microsc. Microanal. 22, 1244 (2016)
[24]	J. Askill, Tracer diffusion data for metals, alloys, and simple oxides (Springer, Berlin, 2012)
[25]	L. Wu, Z. Yang, J. Alloys Compd. 626, 194 (2015)
[26]	F. Czerwinski, JOM 64, 1477 (2012)
[27]	Q.Y. Tan, A. Atrens, N. Mo, M.X. Zhang, Corros. Sci. 112, 734 (2016)
[28]	D.J. Young, High-temperature oxidation and corrosion of metals (Elsevier, New York, 2008)
[29]	X.M. Wang, W.D. Wu, Y.J. Tang, X.Q. Zeng, S.S. Yao, J. Alloys Compd. 474, 499 (2009)
[30]	J.W. Liu, Y. Li, F.H. Wang, Oxid. Met. 71, 319 (2009)
[31]	X.W. Yu, B. Jiang, J.J. He, B. Liu, F.S. Pan, J. Alloys Compd. 749, 1054 (2018)
[32]	J.F. Fan, C.H.L. Yang, G. Han, S. Fang, W.D. Yang, B.S. Xu, J. Alloys Compd. 509, 2137 (2011)