EFFECT OF PROCESSING PARAMETERS ON SOLID-LIQUID INTERFACE OF Nb-Si BASE ALLOY FABRICATED BY ELECTROMAGNETIC COLD CRUCIBLE DIRECTIONAL SOLIDIFICATION
YAN Yuncheng1,2, DING Hongsheng1(), SONG Jinxia2, KANG Yongwang2, CHEN Ruirun1, GUO Jingjie1
1 National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001 2 Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095
Cite this article:
YAN Yuncheng, DING Hongsheng, SONG Jinxia, KANG Yongwang, CHEN Ruirun, GUO Jingjie. EFFECT OF PROCESSING PARAMETERS ON SOLID-LIQUID INTERFACE OF Nb-Si BASE ALLOY FABRICATED BY ELECTROMAGNETIC COLD CRUCIBLE DIRECTIONAL SOLIDIFICATION. Acta Metall Sin, 2014, 50(9): 1039-1045.
Nb-Si base alloys have attracted considerable attentions as the potential high temperature structural materials working in the service temperature range of 1200~1400 ℃ because of their high melting points (>1750 ℃), moderate densities (6.6~7.2 g/cm3) and excellent high temperature strength. However, the mismatching between room temperature fracture toughness and high temperature strength has limited their practical applications. Directional solidification (DS) and alloying have been proved to be the effective methods to overcome this critical issue. The DS processes used to prepare Nb-Si base alloys included Czochralski directional solidification in a copper crucible, electron beam directional solidification, optical floating zone melting, integrally directional solidification and electromagnetic cold crucible directional solidification (ECCDS). The previous studies focused on the effect of process parameters on microstructure and mechanical properties in the steady-state growth region (SSGR). However, the microstructure in the SSGR was controlled by the solid-liquid interface, and the solid-liquid interface was controlled by process parameters. Therefore, the study about the effect of process parameters on solid-liquid interface was very important. In this work, the master alloy with the nominal composition of Nb-22Ti-16Si-3Cr-3Al-2Hf (atomic fraction, %) was prepared by vaccum non-consumable arc-melting first, and then induction skull melting. The DS experiments were performed in the ECCDS device equipped with a square water cooled copper crucible (internal dimension: 26 mm×26 mm×120 mm) and a Ga-In alloy pool. There were three processing parameters in ECCDS including heating power of power supply, withdrawal rate and holding time. The DS ingots were prepared according to the orthogonal test (L9 (33)). Instability degree was defined as the ratio of the height of solid-liquid interface to the width of the DS ingot. The results showed that there were three macroscopic morphologies of solid-liquid interfaces; the increase of holding time, decrease of withdrawal rate and elevation of heating power were conducive to keeping the solid-liquid interface macroscopic morphology planar. With the increase of withdrawal rate, primary dendrite arm spacing (d1) and secondary dendrite arm spacing (d2) decreased gradually; with the increase of heating power, d1 and d2 increased gradually; with the increase of holding time, d1 and d2 increased first and then decreased. The higher withdrawal rate, lower heating power and less holding time were beneficial to refining the d1 and d2.
Table 1 Level factor table of orthogonal test L9 (33)
Specimen
P
v
t
Di
d1
d2
Oex-1
1
1
1
0.143
51.43
13.82
Oex-2
1
2
2
0.231
46.78
13.19
Oex-3
1
3
3
0.152
29.60
6.69
Oex-4
2
1
2
0.070
84.65
18.32
Oex-5
2
2
3
0.066
53.75
13.64
Oex-6
2
3
1
0.291
42.57
7.79
Oex-7
3
1
3
0.108
93.68
24.03
Oex-8
3
2
1
0.129
59.71
16.92
Oex-9
3
3
2
0.099
49.49
14.71
Table 2 Orthogonal test table and visual analysis of the measurement results
Fig.1 OM images of S/L interface (H is the vertical distance from the highest point of the S/L interface to the straight line)
(a) Oex-2 (b) Oex-4 (c) Oex-5
Fig.2 Tendency chart of the instability degree of S/L interface
Level / range
P
v
t
k1
0.175
0.107
0.188
k2
0.142
0.142
0.133
k3
0.112
0.181
0.109
Range
0.063
0.074
0.079
Table 3 Visual analysis of Di
Fig.3 OM image of S/L interfaces of Oex-4 sample
Fig.4 Tendency chart of the primary dendrite arm spacing of primary Nbss
Level / range
P
v
t
u1
42.60
76.59
51.24
u2
60.32
53.41
60.31
u3
67.63
40.55
59.01
Range
25.02
36.03
9.07
Table 4 Visual analysis of d1 of the primary Nbss at S/L interface
Level / range
P
v
t
w1
11.23
18.72
12.84
w2
13.25
14.58
15.41
w3
18.55
9.73
14.79
Range
7.32
8.99
2.56
Table 5 Visual analysis of d2 of the primary Nbss at S/L interface
Fig.5 Tendency chart of the secondary dendrite arm spacing of primary Nbss
Fig.6 Lateral heat transfer schematic of electromagnetic cold crucible directional solidification (1—water-cooled copper crucible, 2—skin layer, 3—skull border determined by heat transfer, 4—molten pool, 5—directional solidification texture. d and d represent the depth of skin layer and the thickness of skull, respectively)
[1]
Bewlay B P, Jackson M R, Zhao J C, Subramanian P R, Mendiratta M G, Lewandowski J J. MRS Bull, 2003; 28: 646
[2]
Bewlay B P, Jackson M R, Zhao J C, Subramanian P R. Metall Mater Trans, 2003; 34A: 2043
[3]
Subramanian P, Mendiratta M, Dimiduk D. JOM, 1996; 48: 33
[4]
Bewlay B P, Jackson M R, Lipsitt H A. Metall Mater Trans, 1996; 27A: 3801
[5]
Mendiratta M G, Lewandowski J J, Dimiduk D M. Metall Trans, 1991; 22: 1573
[6]
Li Y L, Ma C L, Zhang H, Miura S. Mater Sci Eng, 2011; A528: 5772
[7]
Tian Y X, Guo J T, Cheng G M, Sheng L Y, Zhou L Z, He L L, Ye H Q. Mater Des, 2009; 30: 2274
[8]
Sekido N, Kimura Y, Miura S, Wei F G, Mishima Y. J Alloys Compd, 2006; 425: 223
[9]
Sha J B, Hirai H, Tabaru T, Kitahara A, Ueno H, Hanada S. Metall Mater Trans, 2003; 34A: 85
[10]
Bewlay B P, Jackson M R, Lipsitt H A. J Phase Equilib, 1997; 18: 264
[11]
Guan P, Guo X P, Ding X, Zhang J, Gao L, Kusabiraki K. Acta Metall Sin (Engl Lett), 2004; 17: 450
[12]
Guo X P, Gao L M. J Aeron Mater, 2006; 26(3): 47
(郭喜平, 高丽梅. 航空材料学报, 2006; 26(3): 47)
[13]
Kang Y W. PhD Dissertation, Beijing Institute of Aeronautical Materials, 2008
(康永旺. 北京航空材料研究院博士学位论文, 2008)
[14]
Wu M L, Wang Y Y, Li S S, Jiang L W, Han Y F. Int J Mod Phys, 2010; 24B: 2964
[15]
Kim W Y, Tanaka H, Kasama A, Hanada S. Intermetallics, 2001; 9: 827
[16]
Sekito Y, Miura S, Ohkubo K, Mohri T, Sakaguchi N, Watanabe S, Kimura Y, Mishima Y. Mater Res Soc Symp Proc, 2009; 1128: 38
[17]
Guo H S, Guo X P. Scr Mater, 2011; 64: 637
[18]
Yao C F, Guo X P, Guo H S. Acta Metall Sin, 2008; 44: 579
(姚成方, 郭喜平, 郭海生. 金属学报, 2008; 44: 579)
[19]
He Y S, Guo X P, Guo H S, Sun Z P. Acta Metall Sin, 2009; 45: 1035
(何永胜, 郭喜平, 郭海生, 孙志平. 金属学报, 2009; 45: 1035)
[20]
Wang Y, Guo X P. Acta Metall Sin, 2010; 46: 506
(王 勇, 郭喜平. 金属学报, 2010; 46: 506)
[21]
Yan Y C, Ding H S, Kang Y W, Song J X. Mater Des, 2014; 55: 450
[22]
Yan Y C, Ding H S, Song J X. Proc Eng, 2012; 27: 1033
[23]
Nie G, Ding H S, Chen R R, Guo J J, Fu H Z. Mater Des, 2012; 39: 350
[24]
Ding H S, Nie G, Chen R R, Guo J J, Fu H Z. Mater Des, 2012; 41: 108
[25]
Li Y Y,Hu C R. Experiment Design and Data Processing. 2nd Ed., Beijing: Chemical Industry Press, 2008: 124
(李云雁,胡传荣. 试验设计与数据处理. 第二版, 北京: 化学工业出版社, 2008: 124)
[26]
Wang Y L, Guo J J, Fu H Z. J Harbin Inst Technol, 2008; 40: 1808
(王艳丽, 郭景杰, 傅恒志. 哈尔滨工业大学学报, 2008; 40: 1808)
[27]
Zhou Y H,Hu Z Q,Jie W Q. Solidification Technology. Beijing: Machinery Industry Press, 1998: 155
(周尧和,胡壮麒,介万齐. 凝固技术. 北京: 机械工业出版社, 1998: 155)
[28]
Hu H Q. Metal Solidification Principle. 2nd Ed., Beijing: Machinery Industry Press, 2007: 108
