Ultrahigh strength Mg-Y-Ni alloys obtained by regulating second phases

doi:10.1016/j.jmst.2019.11.026

Abstract

Abstract:

Mg-Y-Ni alloys with different second phases were designed by changing Y/Ni atomic ratio from 1.5 to 0.5. The microstructure and mechanical properties of as-cast and as-extruded alloys were investigated. The as-cast Mg-Y-Ni alloy with Y/Ni ratio of 1.5 is composed of α-Mg and long period stacking ordered (LPSO) phase. When Y/Ni ratio is equal to 1, nanoscale lamellar γ' phase and eutectic Mg₂Ni phase are formed in addition to LPSO phase. As Y/Ni ratio decreases further, the amount of eutectic Mg₂Ni phase increases, while the amount of LPSO phase decreases. After extrusion, the LPSO and γ' phases are distributed along the extrusion direction, while eutectic Mg₂Ni phase is broken and dispersed in the as-extruded alloys. LPSO phase and Mg₂Ni phase in the alloys promote dynamic recrystallization (DRX) during extrusion, while γ' phase inhibits DRX. Consequently, the Mg96Y2Ni2 (at.%) alloy with LPSO phase and γ' phase as the main second phases shows the strongest basal texture after extrusion. The tensile yield strength of the as-extruded Mg-Y-Ni alloys increases first and then decreases with decreasing Y/Ni ratio. The as-extruded Mg96Y2Ni2 (at.%) alloy with Y/Ni = 1 exhibits excellent mechanical properties with tensile yield strength of 465 MPa, ultimate tensile strength of 510 MPa and elongation to failure of 7.2%, which is attributed to the synergistic effect of bulk LPSO phase and nanoscale γ' phase.

Key words: Mg-Y-Ni alloys, LPSO, γ' Phase, Mg₂Ni, Mechanical properties

S.Z. Wu, X.G. Qiao, M.Y. Zheng. Ultrahigh strength Mg-Y-Ni alloys obtained by regulating second phases[J]. J. Mater. Sci. Technol., 2020, 45: 117-124.

Figures/Tables 12

Table 1 Chemical compositions of Mg-Y-Ni alloys.

Alloys	Composition (at.%)	Composition (wt%)	Y/Ni ratio
Mg95Y3Ni2	Mg95.1Y3.0Ni1.9	Mg-9.8Y-4.2Ni	1.5
Mg96Y2Ni2	Mg96.1Y2.0Ni1.9	Mg-6.7Y-4.3Ni	1
Mg97Y1Ni2	Mg96.9Y1.1Ni2.0	Mg-3.7Y-4.6Ni	0.5

Fig. 1. XRD patterns of the as-cast Mg95Y3Ni2 alloy, Mg96Y2Ni2 alloy and Mg97Y1Ni2 alloy.

Fig. 2. SEM images of the as-cast Mg-Y-Ni alloys with different Y/Ni atomic ratios: (a) Mg95Y3Ni2 alloy; (b) Mg96Y2Ni2 alloy; (c) Mg97Y1Ni2 alloy.

Fig. 3. (a) TEM bright field image and selected area electron diffraction pattern and (b) corresponding composition of 18R-LPSO in Mg95Y3Ni2 alloy; (c) TEM bright field image and selected area electron diffraction pattern and (d) corresponding composition of Mg2Ni phase in Mg97Y1Ni2 alloy; (e) TEM bright field image, (f) HADDF-STEM image and (g) elemental mappings of γ' phase in Mg96Y2Ni2 alloy.

Table 2 Volume fraction of the main phases in the as-cast Mg-Y-Ni alloys.

Alloys	α-Mg	LPSO	Mg₂Ni
Mg95Y3Ni2	40.6	59.4	—
Mg96Y2Ni2	47.8	50.3	1.9
Mg97Y1Ni2	65.9	30.0	4.1

Table 3 EDS analysis of the matrix by SEM mapping in the as-cast Mg-Y-Ni alloys (at.%).

Alloys	Mg	Y	Ni
Mg95Y3Ni2	98.4 ± 0.3	1.2 ± 0.3	0.4 ± 0.1
Mg96Y2Ni2	98.5 ± 0.2	0.8 ± 0.1	0.7 ± 0.3
Mg97Y1Ni2	99.1 ± 0.4	0.4 ± 0.1	0.5 ± 0.2

Fig. 4. SEM images of (a) Mg95Y3Ni2 alloy, (b) Mg96Y2Ni2 alloy and (c) Mg97Y1Ni2 alloy after preheating at 420 °C for 15 min; (d) TEM bright field image and the HADDF-STEM images of (e) γ' and (f) 18R-LPSO in Mg96Y2Ni2 alloy after preheating.

Fig. 5. SEM images of the as-extruded Mg-Y-Ni alloys with different Y/Ni atomic ratios along extrusion direction: (a) Mg95Y3Ni2 alloy; (b) Mg96Y2Ni2 alloy; (c) Mg97Y1Ni2 alloy.

Fig. 6. (a-c) IPF images and (d-i) inverse pole ?gures of as-extruded alloys along extrusion direction: (a, d, g) Mg95Y3Ni2 alloy; (b, e, h) Mg96Y2Ni2 alloy; (c, f, i) Mg97Y1Ni2 alloy; (d-f) non-DRXed + DRXed regions and (g-i) DRXed regions.

Table 4 DRX ratio and DRXed grain size of as-extruded Mg-Y-Ni alloys.

Alloys	α-Mg (%)	Non-DRXed (%)	DRXed (%)	DRX ratio (%)	Grain diameter (μm)
Mg95Y3Ni2	40.6	10.1	30.5	75.2	3.70 ± 1.36
Mg96Y2Ni2	47.8	23.1	24.7	51.7	0.67 ± 0.20
Mg97Y1Ni2	65.9	10.6	55.3	83.9	0.83 ± 0.46

Fig. 7. SEM images observed from the position of (a-c) 10 mm and (d) 0 mm below the die-entrance of partially extruded alloys: (a) Mg95Y3Ni2 alloy; (b) Mg96Y2Ni2 alloy; (c, d) Mg97Y1Ni2 alloy.

Fig. 8. (a) Tensile stress-strain curves of the as-extruded Mg-Y-Ni alloys, (b) mechanical properties of the as-extruded Mg-Y-Ni alloys with decreasing Y/Ni atomic ratio and (c) comparison of tensile properties of the as-extruded Mg-Y-Ni alloys and other high strength Mg alloys containing RE.

References 40

[1]	Z. Yu, C. Xu, J. Meng, S. Kamado, Mater. Sci. Eng. A 703 (2017) 348-358.
[2]	R.G. Li, J.F. Nie, G.J. Huang, Y.C. Xin, Q. Liu, Scr. Mater. 64 (2011) 950-953.
[3]	T. Homma, N. Kunito, S. Kamado, Scr. Mater. 61 (2009) 644-647.
[4]	C. Xu, M.Y. Zheng, S.W. Xu, K. Wu, E.D. Wang, S. Kamado, G.J. Wang, X.Y. Lv, Mater. Sci. Eng. A 547 (2012) 93-98.
[5]	C. Xu, T. Nakata, X.G. Qiao, M.Y. Zheng, K. Wu, S. Kamado, Sci. Rep. 7 (2017) 43391.
[6]	S. Wu, J. Zhang, Z. Zhang, C. Xu, K. Nie, X. Niu, Mater. Sci. Eng. A 648 (2015) 134-139.
[7]	T. Itoi, R. Ichikawa, M. Hirohashi, Mater. Sci.Forum 706-709 (2012) 1176-1180.
[8]	D. Qin, J. Wang, Y. Chen, R. Lu, F. Pan, Mater. Sci. Eng. A 624 (2015) 9-13.
[9]	H. Liu, F. Xue, J. Bai, J. Zhou , J. Mater. Eng. Perform. 22 (2013) 3500-3506.
[10]	K. Xu, S. Liu, D. Huang, Y. Du , J. Mater. Sci. 53 (2018) 9243-9257.
[11]	X. Yang, S. Wu, S. Lü, L. Hao, X. Fang , J. Alloys. Compd. 726 (2017) 276-283.
[12]	S.M. Zhu, R. Lapovok, J.F. Nie, Y. Estrin, S.N. Mathaudhu, Mater. Sci. Eng. A 692 (2017) 35-42.
[13]	S.Q. Luo, A.T. Tang, B. Jiang, H.W. Dong, W. Wei, F.S. Pan, Mater. Sci. Forum 898 (2017) 172-178.
[14]	T. Itoi, K. Takahashi, H. Moriyama, M. Hirohashi, Scr. Mater. 59 (2008) 1155-1158.
[15]	H.S. Jiang, M.Y. Zheng, X.G. Qiao, K. Wu, Q.Y. Peng, S.H. Yang, Y.H. Yuan, J.H. Luo, Mater. Sci. Eng. A 684 (2017) 158-164.
[16]	Y.M. Zhu, K. Oh-ishi, N.C. Wilson, K. Hono, A.J. Morton, J.F. Nie, Metall. Mater. Trans. A 47 (2015) 927-940.
[17]	Y.M. Zhu, A.J. Morton, M. Weyland, J.F. Nie, Acta Mater. 58 (2010) 464-475.
[18]	J.F. Nie, K. Oh-ishi, X. Gao, K. Hono, Acta Mater. 56 (2008) 6061-6076.
[19]	Z. Wang, Q. Luo, S. Chen, K.-C. Chou, Q. Li, J. Alloys. Compd. 649 (2015) 1306-1314.
[20]	M. Jiang, S. Zhang, Y. Bi, H. Li, Y. Ren, G. Qin, Intermetallics 57 (2015) 127-132.
[21]	K. Yamashita, T. Itoi, M. Yamasaki, Y. Kawamura, E. Abe , J. Alloys. Compd. 788 (2019) 277-282.
[22]	K. Kishida, K. Nagai, A. Matsumoto, A. Yasuhara, H. Inui, Acta Mater. 99 (2015) 228-239.
[23]	D. Egusa, E. Abe, Acta Mater. 60 (2012) 166-178.
[24]	Q. Dong, Z. Luo, H. Zhu, L. Wang, T. Ying, Z. Jin, D. Li, W. Ding, X. Zeng , J. Mater. Sci. Technol. 34 (2018) 1773-1780.
[25]	J. Zhang, Y. Dou, G. Liu, Z. Guo, Comput. Mater. Sci. 79 (2013) 564-569.
[26]	Q. Zhang, L. Fu, T.W. Fan, B.Y. Tang, L.M. Peng, W.J. Ding, Phys. B 416 (2013) 39-44.
[27]	C. Xu, G.H. Fan, T. Nakata, X. Liang, Y.Q. Chi, X.G. Qiao, G.J. Cao, T.T. Zhang, M. Huang, K.S. Miao, M.Y. Zheng, S. Kamado, H.L. Xie, Metall. Mater. Trans. A 49 (2018) 1931-1947.
[28]	J.D. Robson, D.T. Henry, B. Davis, Acta Mater. 57 (2009) 2739-2747.
[29]	K. Hagihara, N. Yokotani, Y. Umakoshi, Intermetallics 18 (2010) 267-276.
[30]	C. Xu, T. Nakata, X. Qiao, M. Zheng, K. Wu, S. Kamado, Sci. Rep. 7 (2017) 40846.
[31]	Y.B. Chun, J. Geng, N. Stanford, C.H.J. Davies, J.F. Nie, M.R. Barnett, Mater. Sci. Eng. A 528 (2011) 3653-3658.
[32]	M. Yamasaki, K. Hashimoto, K. Hagihara, Y. Kawamura, Acta Mater. 59 (2011) 3646-3658.
[33]	M. Yamasaki, K. Hashimoto, K. Hagihara, Y. Kawamura, Mater. Sci.Forum 654-656 (2010) 615-618.
[34]	L.B. Tong, X.H. Li, H.J. Zhang, Mater. Sci. Eng. A 563 (2013) 177-183.
[35]	T. Itoi, T. Suzuki, Y. Kawamura, M. Hirohashi, Mater. Trans. 51 (2010) 1536-1542.
[36]	Z. Zhang, X. Liu, Z. Wang, Q. Le, W. Hu, L. Bao, J. Cui, Mater. Des. 88 (2015) 915-923.
[37]	J. Wang, L. Wang, G. Zhu, B. Zhou, T. Ying, X. Zhang, Q. Huang, Y. Shen, X. Zeng, H. Jiang, Metall. Mater. Trans. A 49 (2018) 5382-5392.
[38]	G. Garces, P. Perez, S. Cabeza, S. Kabra, W. Gan, P. Adeva, Metall. Mater. Trans. A 48 (2017) 5332-5343.
[39]	W.W. Jian, G.M. Cheng, W.Z. Xu, H. Yuan, M.H. Tsai, Q.D. Wang, C.C. Koch, Y.T. Zhu, S.N. Mathaudhu, Mater. Res. Lett. 1 (2013) 61-66.
[40]	Z.T. Li, X.G. Qiao, C. Xu, S. Kamado, M.Y. Zheng, A.A. Luo , J. Alloys. Compd. 792 (2019) 130-141.