Evolutions of Microstructure and Mechanical Properties in Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd Alloy

doi:10.1007/s40195-022-01509-0

Abstract

Abstract:

The evolution of the microstructure and mechanical properties of alloy system with nominally composition Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd (x = 0, 1.2, 2.4, 3.6, 4.8, 6) is evaluated based on computational phase diagram and corresponding experimental studies. The results show that grains are significantly refined with the increase of Gd content. The main phases of as-cast alloys are α-Mg, β-Li, AgLi₂Mg, and Mg₃Gd. With the increase of Gd content, the amounts of Mg₃Gd phase and β-Li phase have been increased. When the Gd content exceeds 3.6 wt%, Mg₃Gd phase precipitates in a form of the network at the grain boundaries. The precipitation of β-Li can be attributed to the competitive dissolution of Zn, Gd, and Li in Mg. Meanwhile, γ″ is formed after the addition of Gd, which grows and transforms into γ′ with the increase of Gd content. In solidification process, stacking faults are formed by solid transformation of partial α-Mg and Mg₃Gd. Eventually, with the synergistic effect of Mg₃Gd, β-Li, and γ″ (or γ′), as the Gd content increasing, the tensile strength of the alloy first increases, then decreases, and the elongation decreases. When the content of Gd is 4.8 wt%, the ultimate tensile strength and yield strength reach the maximum values of 227 MPa and 139 MPa, and the elongation is 18.1%, respectively.

Key words: Mg-Li-Zn-Gd alloy, Phase diagram, Microstructure evolution, Mechanical properties

Bing-Yu Qian, Rui-Zhi Wu, Jian-Feng Sun, Jing-Huai Zhang, Le-Gan Hou, Xiao-Chun Ma, Jia-Hao Wang, Hai-Ting Hu. Evolutions of Microstructure and Mechanical Properties in Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd Alloy[J]. Acta Metallurgica Sinica (English Letters), 2023, 36(2): 215-228.

Figures/Tables 15

Table 1 ICP-AES results of the alloy compositions (wt%)

Alloys	Gd	Zn	Li	Ag	Zr	Gd/Zn
Z1	-	1.02	5.53	0.40	0.004	0
Z2	1.18	1.10	5.50	0.51	0.003	1.07
Z3	2.29	1.08	5.57	0.49	0.003	2.12
Z4	3.63	1.03	5.43	0.42	0.003	3.52
Z5	4.67	0.97	5.31	0.51	0.002	4.81
Z6	5.84	1.05	5.38	0.51	0.002	5.56

Fig. 1 Representative engineering stress-strain curves of as-cast alloys a, mechanical properties of as-cast alloys b

Fig. 2 XRD patterns of as-cast alloys

Fig. 3 Optical micrographs of as-cast alloys Z1 a, Z2 b, Z3 c, Z4 d, Z5 e, and Z6 f, respectively

Table 2 Average grain size, volume fraction of β-Li, and second phase of as-cast alloys

Alloys	Z1	Z2	Z3	Z4	Z5	Z6
Average grain size (μm)	58.3 ± 4.8	38.9 ± 3.1	29.2 ± 2.8	25.9 ± 1.8	23.3 ± 1.4	16.7 ± 0.9
Volume fraction of β-Li (%)	12.7 ± 1.7	12.9 ± 1.2	12.4 ± 0.8	16.8 ± 1.6	19.4 ± 1.9	25.7 ± 2.3
Volume fraction of second phase (%)	-	3.1 ± 0.4	4.5 ± 0.6	9.4 ± 0.9	15.8 ± 1.2	21.9 ± 2.1

Fig. 4 SEM morphology of Z1 as-cast alloy a, TEM morphology and selected area electron diffraction (SAED) pattern of the second phase indicated by point 1 in SEM morphology b. c TEM morphology and SAED pattern the second phase in β-Li shown as point 2 in SEM morphology

Fig. 5 Microstructures of as-cast alloy Z2 a, Z3 b, partial magnification of alloy Z3 microstructure c, TEM morphology of the eutectic structure and the corresponding diffraction pattern d

Fig. 6 Microstructures of the as-cast alloys Z4 a, Z5 b, Z6 c

Fig. 7 TEM morphology of the as-cast Z6 alloy a, EDS mapping b, magnified view of the white-arrow position in TEM morphology c, the corresponding diffraction pattern d

Fig. 8 Schematic diagram of microstructure evolution with different Gd contents

Fig. 9 Vertical cross-sectional phase diagram of Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd alloy

Fig. 10 DSC curves of Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd alloy

Fig. 11 Schematic diagram of the solidification process of Z4 alloy

Fig. 12 Phase diagram of Mg-5Li-1Zn-0.5Ag-0.5Zr-xGd between 350 and 380 ℃

Fig. 13 TEM morphology, the corresponding diffraction pattern, and EDS mapping of γ″ a, TEM morphology of γ′ in Z3 alloy b, TEM morphology of γ′ in Z6 alloy c

References 44

[1]	D. Wang, S.J. Liu, R.Z. Wu, S. Zhang, H.J. Wu, J.H. Zhang, L.G. Hou, J. Alloys Compd. 881, 160663 (2021) DOI URL
[2]	J.H. Wang, L. Xu, R.Z. Wu, D. An, Z. Wei, J.X. Wang, J. Feng, J.H. Zhang, L.G. Hou, M.Z. Liu, J. Alloys Compd. 882, 160524 (2021) DOI URL
[3]	S.Y. Jin, X.C. Ma, R.Z. Wu, T.Q. Li, J.X. Wang, B. Krit, L.G. Hou, J.H. Zhang, G.X. Wang, Int. J. Miner. Metall. Mater. 29, 1453 (2022) DOI URL
[4]	P.D. Huo, F. Li, Y. Wang, R.Z. Wu, R.H. Gao, A.X. Zhang, Mater. Des. 219, 110696 (2022) DOI URL
[5]	F. Zhong, Y. Wang, R.Z. Wu, J. Zhang, L.G. Hou, M.L. Zhang, J. Alloys Compd. 831, 154765 (2020) DOI URL
[6]	S. Zhang, B. Sun, R.Z. Wu, Y. Zhou, Q. Wu, Mater. Lett. 312, 131680 (2022) DOI URL
[7]	M.D. Liu, Z. Zhang, R.Z. Wu, Y. Wang, Adv. Eng. Mater. 23, 2100530 (2021) DOI URL
[8]	M.M. Li, Z. Qin, Y. Yang, X.M. Xiong, G. Zhou, X.F. Cui, B. Jiang, X.D. Peng, F.S. Pan, Acta Metall. Sin. -Engl. Lett. 35, 867 (2022)
[9]	X.C. Ma, S.Y. Jin, R.Z. Wu, J.X. Wang, G.X. Wang, B. Krit, S. Betsofen, Trans. Nonferrous Met. Soc. China 31, 3228 (2021) DOI URL
[10]	Z.H. Liu, L. Wang, L.P. Wang, Y.C. Feng, F.W. Kang, B. Wang, S.Z. Li, C.S. Hu, J. Mater. Sci. 57, 15137 (2022) DOI URL
[11]	J.M. Meier, J. Caris, A.A. Luo, J. Magn. Alloys 10, 1401 (2022) DOI URL
[12]	A. Inoue, Y. Kawamura, M. Matsushita, K. Hayashi, J. Koike, J. Mater. Res. 16, 1894 (2001)
[13]	F.M. Lu, A.B. Ma, J.H. Jiang, D.H. Yang, Q. Zhou, Rare Met. 31, 303 (2012) DOI URL
[14]	J.S. Xie, J.H. Zhang, Z.H. You, S.J. Liu, K. Guan, R.Z. Wu, J. Wang, J. Feng, J. Magnes. Alloys 9, 41 (2021)
[15]	T.L. Zhang, T. Tokunaga, M. Ohno, M.L. Zhang, K. Matsuura, Acta Metall. Sin. -Engl. Lett. 32, 169 (2019)
[16]	J.X. Chen, L.L. Tan, X.M. Yu, K. Yang, J. Mater. Sci. Technol. 35, 503 (2019) DOI URL
[17]	Y. Zhang, J. Zhang, G.H. Wu, W.C. Liu, L. Zhang, W.J. Ding, Mater. Des. 66, 162 (2015) DOI URL
[18]	Q.M. Peng, N. Ma, H. Li, J. Rare Earths 30, 1064 (2012) DOI URL
[19]	X.Z. Jin, W.C. Xu, D.B. Shan, B. Guo, B.C. Jin, Mater. Des. 199, 109384 (2021) DOI URL
[20]	Y. Zhao, D.F. Zhang, J.Y. Xu, S.Y. Zhong, B. Jiang, F.S. Pan, Intermetallics 132, 107163 (2021) DOI URL
[21]	Y. Zhao, D. Zhang, R.J. Lei, P. Wang, J.K. Feng, X. Chen, B. Jiang, F.S. Pan, J. Mater, Res. Technol. 9, 12737 (2020)
[22]	B.B. Yang, C.Y. Shi, X.J. Ye, J.W. Teng, R.L. Lai, Y.J. Cui, D.K. Guan, H.W. Cui, Y.P. Li, A. Chiba, Underlying slip/twinning activities of Mg-xGd alloys investigated by modified lattice rotation analysis. J. Magn. Alloys (2021). https://doi.org/10.1016/j.jma.2021.06.008 DOI
[23]	H.W. Miao, H. Huang, S.H. Fan, J.Y. Tan, Z.C. Wang, W.J. Ding, G.Y. Yuan, Mater. Des. 196, 109122 (2020) DOI URL
[24]	J. Zhao, B. Jiang, Y. Yuan, Q.H. Wang, M. Yuan, A.T. Tang, G.S. Huang, D.F. Zhang, F.S. Pan, J. Mater. Res. Technol. 95, 20 (2021)
[25]	J.M. Meier, J.S. Miao, S.M. Liang, J. Zhu, C. Zhang, J. Caris, A.A. Lou, J. Magn. Alloys 10, 689 (2021) DOI URL
[26]	B.B. Dong, X. Che, Z.M. Zhang, J.M. Yu, M. Mu, J. Alloys Compd. 853, 157066 (2021) DOI URL
[27]	B.Q. Xu, J.P. Sun, Z.Q. Yang, J. Han, Y.T. Fu, J.H. Jiang, A.B. Ma, J. Mater. Res. Technol. 9, 13616 (2020) DOI URL
[28]	S. Zhang, G.Y. Yuan, C. Lu, W.J. Ding, J. Alloys Compd. 509, 3515 (2011) DOI URL
[29]	L.R. Xiao, X.F. Chen, H.Y. Ning, P. Jiang, Y. Liu, B. Chen, D.D. Ying, H. Zhou, Y.T. Zhu, Unexpected high-temperature brittleness of a Mg-Gd-Y-Ag alloy. J. Magn. Alloys (2021). https://doi.org/10.1016/j.jma.2021.06.018 DOI
[30]	Z.J. Yu, L.L. Liu, A. Mansoor, K. Liu, S.B. Li, W.B. Du, J. Alloys Compd. 864, 158826 (2021) DOI URL
[31]	J.F. Nie, K. Oh-ishi, X. Gao, K. Hono, Acta Mater. 56, 6061 (2008) DOI URL
[32]	H. Okamoto, J. Phase Equilib. Diffus. 38, 70 (2017) DOI URL
[33]	P. Li, D.H. Hou, E.H. Han, R.S. Chen, Z.W. Shan, Acta Metall. Sin. -Engl. Lett. 33, 1477 (2020)
[34]	L.P. Wang, L.P. Bian, Y.L. Zhao, H.H. Zeng, W. Liang, X.G. Zhao, Rare Metal Mat. Eng. 47, 3223 (2018). ((In Chinese))
[35]	H.B. Xie, H.C. Pan, Y.P. Ren, S.N. Sun, L.Q. Wang, H. Zhao, B.S. Liu, X.X. Qi, G.W. Qin, Cryst. Growth Des. 18, 5866 (2018) DOI URL
[36]	J.K. Zheng, C.Y. Zhu, Z. Li, Mater. Lett. 238, 66 (2019) DOI URL
[37]	W. Rong, Y.J. Wu, Y. Zhang, M. Sun, J. Chen, L.M. Peng, W.J. Ding, Mater. Charact. 126, 1 (2017) DOI URL
[38]	K. Saito, M. Nishijima, K. Hiraga, Mater. Trans. 51, 1712 (2010) DOI URL
[39]	K. Saito, A. Yasuhara, K. Hiraga, J. Alloys Compd. 509, 2031 (2011)
[40]	Y.M. Zhu, K. Ohishi, N.C. Wilson, K. Hono, A.J. Morton, J.F. Nie, Metall. Mater. Trans. A 47, 927 (2015) DOI URL
[41]	S.Z. Wu, X.G. Qiao, S.H. Qin, Y.Q. Chi, M.Y. Zheng, Mater. Sci. Eng. A 831, 142198 (2022) DOI URL
[42]	W.B. Luo, Z.Y. Xue, W.M. Mao, H. Yu, Mater. Res. Express 6, 0965a4 (2019) DOI URL
[43]	Q. Zhang, W.C. Liu, G.H. Wu, L. Zhang, W.J. Ding, Acta Metall. Sin. -Engl. Lett. 33, 1505 (2020)
[44]	H. Liu, H. Huang, J.P. Sun, C. Wang, X.H. Chen, Acta Metall. Sin. -Engl. Lett. 32, 269 (2019)