Microstructure Characteristics and Mechanical Properties of Nb-17Si-23Ti Ternary Alloys Fabricated by In Situ Reaction Laser Melting Deposition

doi:10.1007/s40195-017-0619-y

Abstract

Abstract:

Fabrication of ternary Nb-17Si-23Ti alloys was attempted by in situ reaction laser melting deposition (LMD) with dual powder feeding method from Nb-28 at.% Ti powder mixture and pure Si powder. The microstructures of the as-deposited alloys were examined with scanning electronic microscope, and the phase constituents were analyzed by X-ray energy-dispersive spectrometer and X-ray diffraction. Furthermore, the effect of laser power on microstructure characteristics, microhardness and indentation fracture toughness was also investigated. The in situ reaction LMD process resulted in remarkable refinement of the microstructure. The as-deposited samples mainly consisted of Nb_SS, metastable (NbTi)₃Si and Ti-rich Nb_SS. With the increase in the laser power from 1000 to 2000 W, the Nb_SS morphology changed from discontinuous dendritic to near equiaxed, but the Ti-rich Nb_SS phase tended to vanish. Furthermore, with the increase in the laser power, the microhardness of as-deposited samples increased from 822 to 951 HV, while the indentation fracture toughness was improved from 12.3 to 14.1 MPa m^1/2. The corresponding mechanism is also discussed.

Key words: Nb-Si-Ti alloys, Laser melting deposition, Microstructure, Mechanical properties, In situ reaction

Wei Liu, Hua-Ping Xiong, Neng Li, Shao-Qing Guo, Ren-Yao Qin. Microstructure Characteristics and Mechanical Properties of Nb-17Si-23Ti Ternary Alloys Fabricated by In Situ Reaction Laser Melting Deposition[J]. Acta Metallurgica Sinica (English Letters), 2018, 31(4): 362-370.

Figures/Tables 10

Fig. 1 SEI micrographs of the Nb powder a, Si powder b, Ti powder c

Table 1 Fabrication parameters of LMD for the Nb-17Si-23Ti ternary alloys

Fabrication parameters	Values
Laser spot diameter (mm)	0.8
Scanning speed (mm min^-1)	600
Hatch spacing (mm)	0.5
Distance of substrate to laser focus point (mm)	0
Si powder feed rate (g min^-1)	0.45
Nb + Ti powder mixture feed rate (g min^-1)	7
Laser power (W)	1000, 2000

Fig. 2 Schematics of LMD with dual powder feeding method a, and scanning path of laser beam b

Fig. 3 Macro-photos and the cross-sectional optical metallographs of the as-deposited Nb-Si-Ti alloy specimens fabricated by LMD with 1000 W a-c, 2000 W b-d laser power, respectively

Table 2 Relative density, O and N contents, and chemical composition of the as-deposited Nb-Si-Ti alloys

Samples	A (1000 W)	B (2000 W)
Relative density (%)	98.3	99.4
O content (ppm)	111	143
N content (ppm)	35	68
Composition (at.%)	Nb-16.9Si-23.4Ti	Nb-16.2Si-22.9Ti

Fig. 4 X-ray diffraction patterns for the as-deposited Nb-17Si-23Ti samples fabricated by LMD using 1000 and 2000 W laser power, respectively

Fig. 5 BSE images of the as-deposited Nb-17Si-23Ti alloys fabricated by LMD with the laser power of 1000 W a, b, 2000 W c, d, respectively. Insert in d is an enlarged image

Table 3 Elemental atomic concentration for the constituent phases of as-deposited Nb-17Si-23Ti alloys

Samples	Phase contrast	Si (at.%)	Nb (at.%)	Ti (at.%)	Deduced phase
A (1000 W)	Bright	3.01	67.32	29.67	Nb_SS
	Gray	27.22	58.87	13.91	(NbTi)₃Si
	Dark	3.25	50.93	45.82	Ti-rich Nb_SS
B (2000 W)	Bright	4.45	61.26	34.29	Nb_SS
B (2000 W)	Gray	23.86	57.80	18.34	(NbTi)₃Si

Fig. 6 Vickers hardness and indentation fracture toughness of as-deposited Nb-17Si-23Ti samples

Fig. 7 BSE images of the hardness indentation a, b, and the cracks at the tips of hardness indentation c, d on the as-deposited samples fabricated by LMD with 1000 W a-c, 2000 W b-d laser power, respectively

References

[1]	B.P. Bewlay, M.R. Jackson, P.R. Subramanian, J.C. Zhao, Metall. Mater. Trans. A 34, 2043 (2003)
[2]	M.R. Jackson, B.P. Bewlay, R.G. Rowe, D.W. Skelly, H.A. Lipsitt, JOM 48, 39 (1996)
[3]	C.M. Liu, H.M. Wang, S.Q. Zhang, H.B. Tang, A.L. Zhang, J. Alloys Compd. 583, 162(2014)
[4]	J.C. Zhao, J.H. Westbrook, MRS Bull. 28, 622(2003)
[5]	W.Y. Kim, H. Tanaka, A. Kasama, S. Hanada, Intermetallics 9, 827 (2001)
[6]	N. Sekido, Y. Kimura, S. Miura, F. Wei, Y. Mishima, J. Alloys Compd. 425, 223(2006)
[7]	T. Fei, Y. Yu, C. Zhou, J. Sha, Mater. Des. 116, 92(2017)
[8]	K.S. Chan, Mater. Sci. Eng., A 329, 513 (2002)
[9]	J. Sha, C. Yang, J. Liu, Scr. Mater. 62, 859(2010)
[10]	T. Murakami, S. Sasaki, K. Ichikawa, A. Kitahara, Intermetallics 9, 621 (2001)
[11]	Y. Wang, X. Guo, Y. Qiao, Mater. Des. 116, 461(2017)
[12]	K. Zelenitsas, P. Tsakiropoulos, Mater. Sci. Eng. A 416, 269 (2006)
[13]	J. Geng, P. Tsakiropoulos, G. Shao, Mater. Sci. Eng. A 441, 26 (2006)
[14]	B.P. Bewlay, M.R. Jackson, R.R. Bishop, J. Phase Equilib. 19, 577(1998)
[15]	J. Sha, H. Hirai, H. Ueno, T. Tabaru, A. Kitahara, S. Hanada, Metall. Mater. Trans. A 34, 85 (2003)
[16]	X. Li, H. Chen, J. Sha, H. Zhang, A 527, 6140 (2010)
[17]	B.P. Bewlay, M.R. Jackson, J.C. Zhao, P.R. Subramanian, M.G. Mendiratta, J.J. Lewandowski, MRS Bull. 28, 646(2003)
[18]	B. Guo, X. Guo, Mater. Sci. Eng. A 617, 39 (2014)
[19]	W. Liu, J. Sha, Mater. Des. 111, 301(2016)
[20]	E.M. Lawrence, J. Mater. Sci. Technol. 32, 987(2016)
[21]	G.P. Dinda, A.K. Dasgupta, J. Mazumder, Mater. Sci. Eng. A 509, 98 (2009)
[22]	R. Dicks, F. Wang, X. Wu, J. Mater. Process. Technol. 209, 1752(2009)
[23]	R.R. Dehoff, P.M. Sarosi, P.C. Collins, L.F. Hamish, J.M. Michael, MRS Online Proc. Libr. 753, 2(2011)
[24]	Y. Guo, L. Jia, S. Sun, B. Kong, J. Liu, H. Zhang, Mater. Des. 109, 37(2016)
[25]	A.G. Evans, E.A. Charles, J. Am. Ceram. Soc. 59, 371(1976)
[26]	J.L. Yu, K.F. Zhang, Scr. Mater. 59, 714(2008)
[27]	M.G. Mendiratta, J.J. Lewandowski, D.M. Dimiduk, Metall. Trans. A 22, 1573 (1991)
[28]	K. Zelenitsas, P. Tsakiropoulos, Intermetallics 13, 1079 (2005)
[29]	L. Su, L. Jia, Y. Feng, H. Zhang, S. Yuan, H. Zhang, Mater. Sci. Eng. A 560, 672 (2013)
[30]	K.A. Jackson, J.D. Hunt, A.I.M.E. Met, Soc. Trans. 236, 1129(1966)
[31]	C.T. Lynch, J.P. Kershaw, (CRC Press, Boca Raton 1972), p. 121
[32]	Y. Li, S. Miura, K. Ohsasa, C. Ma, H. Zhang, Intermetallics 19, 460 (2011)
[33]	N. Hansen, Scr. Mater. 51, 801(2004)
[34]	L. Wang, N. Wang, W.J. Yao, Y.P. Zheng, Acta Mater. 88, 283(2015)
[35]	M.C. Flemings, Metall. Trans. A 5, 2121 (1974)
[36]	H. Attar, K.G. Prashanth, L.C. Zhang, M. Calin, I.V. Okulov, S. Scudino, C. Yang, J. Eckert, J. Mater. Sci. Technol. 31, 1001(2015)
[37]	Y. Li, D. GU, Mater. Des. 63, 856(2014)
[38]	H. Liao, W. Huang, Q. Wang, F. Jia, J. Mater. Sci. Technol. 30, 146(2014)
[39]	Y.J. Liang, X. Cheng, H.M. Wang, Acta Mater. 118, 17(2016)
[40]	K. Arafune, A. Hirata, J. Cryst. Growth 197, 811 (1999)
[41]	E. Guo, S.S. Singh, C. Mayer, X. Meng, Y. Xu, L. Luo, M. Wang, N. Chawla, J. Alloys Compd. 704, 89(2017)