Formation and Evolution of Stray Grains on Remelted Interface in the Seed Crystal During the Directional Solidification of Single-Crystal Superalloys Assisted by Vertical Static Magnetic Field
SU Zhenqi1,2, ZHANG Congjiang1,2, YUAN Xiaotan1,2, HU Xingjin1,2, LU Keke1,2, REN Weili1,2(), DING Biao1,2(), ZHENG Tianxiang1,2, SHEN Zhe1,2, ZHONG Yunbo1,2, WANG Hui3, WANG Qiuliang3
1School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China 2State Key Laboratory of Advanced Special Steel, Shanghai University, Shanghai 200444, China 3Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
Cite this article:
SU Zhenqi, ZHANG Congjiang, YUAN Xiaotan, HU Xingjin, LU Keke, REN Weili, DING Biao, ZHENG Tianxiang, SHEN Zhe, ZHONG Yunbo, WANG Hui, WANG Qiuliang. Formation and Evolution of Stray Grains on Remelted Interface in the Seed Crystal During the Directional Solidification of Single-Crystal Superalloys Assisted by Vertical Static Magnetic Field. Acta Metall Sin, 2023, 59(12): 1568-1580.
Nickel-based superalloys, especially single-crystal (SC) ones, have long been recognized as important materials for turbine blades used in aerospace and gas engines. Static magnetic fields are effective at controlling the material forming. The use of static magnetic fields during solidification has evolved as a sophisticated approach for efficiently controlling the microstructures and mechanical performance of metallic materials. In recent years, studies have shown that static magnetic fields have a complex effect on dendrites in SC superalloys. However, the mechanism of static magnetic fields regulating stray grains on remelted interface needs to be investigated further. This work studied the generation of stray grains near the seed remelted zone and the evolution mechanism during the directional solidification of the SC superalloy assisted by a magnetic field by tracing the solidification microstructure. The stray grains of large orientation that deviated from the <001> direction appeared on the remelted zone interface of the solidification microstructure when the magnetic field was applied, accompanied by the formation of a large-angle grain boundary (LAGB). Most of the stray grains were distributed at the sample edge. The increase in magnetic field intensity and pulling speed increased the number of stray grains and the length of the LAGB. As the solidification progressed, the large-orientation stray grains and the LAGBs were eliminated at a fast speed and evolved into small-orientation dendrites. During the following solidification, the orientation of the dendrites became even smaller and the evolution speed decreased sharply. The increase in withdrawal speed intensified the evolution process. The stray grains formed in the remelted zone can be attributed to the twisting dendrite by the thermoelectric magnetic force. The distribution of more stray grains around the sample was caused by the circulation from thermoelectric magnetic convection at the macroscopic scale.
Fund: National Natural Science Foundation of China(51871142);Independent Research and Development Project of State Key Laboratory of Advanced Special Steel, Shanghai Key Laboratory of Advanced Ferrometallurgy, Shanghai University(SKLASS 2021-Z08);Science and Technology Commission of Shanghai Municipality(19DZ2270200)
Fig.1 Single-crystal (SC) superalloy prepared by the seed crystal (a) and the magnified image in the red box in Fig.1a (b) (20 and 50 mm indicate the lengths of the used seed crystal and the master alloy rods, respectively. 0, 5, 15, 25, and 35 mm indicate the observed positions of the across section. The red box indicates the area where the remelted zone of the seed crystal. The white- and green-dotted lines show the positions of the fully remelted interface and the partially remelted interface, respectively)
Fig.2 Macroscopic morphologies of cross sections at the positions of 0 mm (a1-c1), 15 mm (a2-c2), and 35 mm (a3-c3) prepared by directional solidification under different magnetic fields at the pulling rate of 20 μm/s (B —magnetic field) (a1-a3) 0 T (b1-b3) 0.5 T (c1-c3) 1 T
Fig.3 EBSD inverse pole figures (IPFs) of cross sections at the positions of 0 mm (a1-c1), 15 mm (a2-c2), and 35 mm (a3-c3) prepared by directional solidification under the magnetic fields of 0 T (a1-a3), 0.5 T (b1-b3), and 1 T (c1-c3) at the pulling rate of 20 μm/s (Red, green, and blue curves in the figures represent the grain boundaries of 2°-5°, 5°-15°, and 15°-65°, respectively)
Fig.4 Maximum dendrite orientations at different solidification distances (a) and the percentages of dendrite orientation deviation from <001> more than 20° (b)
Fig.5 Grain boundary lengths of different angles at different solidification distances under the magnetic fields of 0 T (a), 0.5 T(b), and 1 T (c) (For clarity, the grain boundary length data in the figures are represented by integers)
Fig.6 Macroscopic morphologies of cross section at the directional-solidification lengths of 0 mm (a1-c1), 15 mm (a2-c2), and 35 mm (a3-c3) under 0.5 T magnetic field at the pilling rates of 20 μm/s (a1-a3), 50 μm/s (b1-b3), and 100 μm/s (c1-c3)
Fig.7 EBSD IPFs of cross sections at the directional-solidification lengths of 0 mm (a1-c1), 15 mm (a2-c2), and 35 mm (a3-c3) under 0.5 T magnetic field (The red, green, and blue curves in the figures represent the grain boundaries of 2°-5°, 5°-15°, and 15°-65°, respectively) (a1-a3) 20 μm/s (b1-b3) 50 μm/s (c1-c3) 100 μm/s
Fig.8 Length distribution statistics of dendrite grain boundaries at different locations after 0.5 T magnetic field solidification at the pulling rates of 20 μm/s (a), 50 μm/s (b), and 100 μm/s (c) (For clarity, the grain boundary length data in the figures are represented by integers)
Fig.9 Quenching interface morphologies under 0.5 T magnetic field (a) 0.5 T remelted quenching interface (b) 0.5 T quenched after pulling down at 20 μm/s for 5 mm
Fig.10 Computing domain and its meshing (a) computational domains including liquid, solid, and cellular liquid-solid interfaces (b) cross section, taken from the white curve area in Fig.10a
Fig.11 Distribution of thermoelectric current (a1, b1) and thermoelectro-magnetic force (a2, b2) at the liquid-solid interface of the cellar crystal under different magnetic fields (The red arrows represent the directions of the current) (a1, a2) 0.5 T (b2, b2) 1 T
Fig.12 Flow field structures of the transverse (a1-c1) and longitudinal (a2-c2) sections in the melt under the magnetic fields of 0 T (a1, a2), 0.5 T (b1, b2), and 1 T (c1, c2) (The cross section was taken at 4.5 mm from the tip of the cell)
Fig.13 Schematics of competitive growth of bi-crystal including converging (a1-a3) and diverging (b1-b3) at different angles deviating from the direction of <001> (The red and blue dendrites represent the favorable dendrites (A small deviation from the <001> direction) and the unfavorable dendrites (a large deviation from the <001> direction), respectively)(a1, b1 and a3, b3) the favorable dendrites are in the same or the opposite orientation as the unfavorable dendrite, respectively (a2, b2) the favorable dendrite is parallel to the direction of heat flow
Fig.14 Schematics of solute-enrichment-layer interaction in dendrite front in unusual overgrowth of converging bi-crystal model (Different color curves represent the isoconcentration contour) (a) converging type shown in Fig.13a2 (b) converging type shown in Fig.13a3
1
Guo J T. The current situation of application and development of superalloys in the fields of energy industry[J]. Acta Metall. Sin., 2010, 46: 513
doi: 10.3724/SP.J.1037.2009.00860
Zhang J, Huang T W, Liu L, et al. Advances in solidification characteristics and typical casting defects in nickel-based single crystal superalloys[J]. Acta Metall. Sin., 2015, 51: 1163
doi: 10.11900/0412.1961.2015.00448
Ren N, Panwisawas C, Li J, et al. Solute enrichment induced dendritic fragmentation in directional solidification of nickel-based superalloys[J]. Acta Mater., 2021, 215: 117043
doi: 10.1016/j.actamat.2021.117043
6
Zhang J, Wang L, Wang D, et al. Recent progress in research and development of nickel-based single crystal superalloys[J]. Acta Metall. Sin., 2019, 55: 1077
D'Souza N, Newell M, Devendra K, et al. Formation of low angle boundaries in Ni-based superalloys[J]. Mater. Sci. Eng., 2005, A413-414: 567
8
Zhou Y Z. Formation of stray grains during directional solidification of a nickel-based superalloy[J]. Scr. Mater., 2011, 65: 281
doi: 10.1016/j.scriptamat.2011.04.023
9
Yang X L, Dong H B, Wang W, et al. Microscale simulation of stray grain formation in investment cast turbine blades[J]. Mater. Sci. Eng., 2004, A386: 129
10
Meng X B, Lu Q, Li J G, et al. Modes of grain selection in spiral selector during directional solidification of nickel-base superalloys[J]. J. Mater. Sci. Technol., 2012, 28: 214
doi: 10.1016/S1005-0302(12)60044-9
11
Li Y F, Liu L, Huang T W, et al. The process analysis of seeding-grain selection and its effect on stray grain and orientation control[J]. J. Alloys Compd., 2016, 657: 341
doi: 10.1016/j.jallcom.2015.09.249
12
Hu S S, Yang W C, Li Z R, et al. Formation mechanisms and control method for stray grains at melt-back region of Ni-based single crystal seed[J]. Prog. Nat. Sci., 2021, 31: 624
doi: 10.1016/j.pnsc.2021.07.004
13
Hallensleben P, Schaar H, Thome P, et al. On the evolution of cast microstructures during processing of single crystal Ni-base superalloys using a Bridgman seed technique[J]. Mater. Des., 2017, 128: 98
doi: 10.1016/j.matdes.2017.05.001
14
Zhang T, Ren W L, Dong J W, et al. Effect of high magnetic field on the primary dendrite arm spacing and segregation of directionally solidified superalloy DZ417G[J]. J. Alloys Compd., 2009, 487: 612
doi: 10.1016/j.jallcom.2009.08.025
15
Dong J W, Ren Z M, Ren W L, et al. Effect of horizontal magnetic field on the microstructure of directionally solidified Ni-based superalloy[J]. Acta Metall. Sin., 2010, 46: 71
Ren W L, Lu L, Yuan G Z, et al. The effect of magnetic field on precipitation phases of single-crystal nickel-base superalloy during directional solidification[J]. Mater. Lett., 2013, 100: 223
doi: 10.1016/j.matlet.2013.03.023
17
Xuan W D, Song G, Duan F M, et al. Enhanced creep properties of nickel-base single crystal superalloy CMSX-4 by high magnetic field[J]. Mater. Sci. Eng., 2021, A803: 140729
18
Li Q D, Shen J, Qin L, et al. Effect of traveling magnetic field on freckle formation in directionally solidified CMSX-4 superalloy[J]. Mater. Process. Technol., 2019, 274: 116308
doi: 10.1016/j.jmatprotec.2019.116308
19
Xuan W D, Ren Z M, Li C J. Effect of a high magnetic field on microstructures of Ni-based superalloy during directional solidification[J]. J. Alloys Compd., 2015, 620: 10
doi: 10.1016/j.jallcom.2014.09.114
20
Zhang K L, Li Y J, Yang Y S. Influence of the low voltage pulsed magnetic field on the columnar-to-equiaxed transition during directional solidification of superalloy K4169[J]. J. Mater. Sci. Technol., 2020, 48: 9
doi: 10.1016/j.jmst.2020.02.009
21
Ren W L, Niu C L, Ding B, et al. Improvement in creep life of a nickel-based single-crystal superalloy via composition homogeneity on the multiscales by magnetic-field-assisted directional solidification[J]. Sci. Rep., 2018, 8: 1452
doi: 10.1038/s41598-018-19800-5
pmid: 29362394
22
Xuan W D, Liu H, Lan J, et al. Effect of a transverse magnetic field on stray grain formation of Ni-based single crystal superalloy during directional solidification[J]. Metall. Mater. Trans., 2016, 47B: 3231
23
Xuan W D, Liu H, Li C J, et al. Effect of a high magnetic field on microstructures of Ni-based single crystal superalloy during seed melt-back[J]. Metall. Mater. Trans., 2016, 47B: 828
24
Xuan W D, Lan J, Liu H, et al. Effects of a high magnetic field on the microstructure of Ni-based single-crystal superalloys during directional solidification[J]. Metall. Mater. Trans., 2017, 48A: 3804
25
Yuan X T, Zhou T, Ren W L, et al. Nondestructive effect of the cusp magnetic field on the dendritic microstructure during the directional solidification of nickel-based single crystal superalloy[J]. J. Mater. Sci. Technol., 2021, 62: 52
doi: 10.1016/j.jmst.2020.05.059
26
Liu C L, Su H J, Zhang J, et al. Effect of electromagnetic field on microstructure of Ni-based single crystal superalloys[J]. Acta Metall. Sin., 2018, 54: 1428
Li Y J, Teng Y F, Feng X H, et al. Effects of pulsed magnetic field on microsegregation of solute elements in a Ni-based single crystal superalloy[J]. J. Mater. Sci. Technol., 2017, 33: 105
doi: 10.1016/j.jmst.2015.12.021
28
Niu C L, Ren W L, Ding B, et al. The change of mushy-zone length of a nickel-based single-crystal superalloy during the static-magnetic-field-assisted directional solidification[J]. Cryst. Res. Technol., 2018, 53: 1700187
doi: 10.1002/crat.v53.6
29
Liu Q. EBSD technique and its applications in materials science[J]. Chin. J. Stereol. Image Anal., 2005, 10: 205
Xu W L, Wang F, Ma D X, et al. Sliver defect formation in single crystal Ni-based superalloy castings[J]. Mater. Des., 2020, 196: 109138
doi: 10.1016/j.matdes.2020.109138
31
Ren Z M, Lei Z S, Li C J, et al. New study and development on electromagnetic field technology in metallurgical processes[J]. Acta Metall. Sin., 2020, 56: 583
doi: 10.11900/0412.1961.2019.00373
Wang J, Fautrelle Y, Ren Z M, et al. Thermoelectric magnetic force acting on the solid during directional solidification under a static magnetic field[J]. Appl. Phys. Lett., 2012, 101: 251904
doi: 10.1063/1.4772510
33
Dahle A K, Arnberg L. Development of strength in solidifying aluminium alloys[J]. Acta Mater., 1997, 45: 547
doi: 10.1016/S1359-6454(96)00203-0
34
Khine Y Y, Walker J S. Thermoelectric magnetohydrodynamic effects during Bridgman semiconductor crystal growth with a uniform axial magnetic field[J]. J. Cryst. Growth, 1998, 183: 150
doi: 10.1016/S0022-0248(97)00394-1
35
Ma D X. Freckle formation during directional solidification of complex castings of superalloys[J]. Acta Metall. Sin., 2016, 52: 426
Walton D, Chalmers B. The origin of the preferred orientation in the columnar zone of ingots[J]. Trans. Am. Inst. Min. Metall. Eng., 1959, 215: 447
37
Zhou Y Z, Volek A, Green N R. Mechanism of competitive grain growth in directional solidification of a nickel-base superalloy[J]. Acta Mater., 2008, 56: 2631
doi: 10.1016/j.actamat.2008.02.022
38
Hu S S, Liu L, Cui Q W, et al. Converging competitive growth in bi-crystal of Ni-based superalloy during directional solidification[J]. Acta. Metall. Sin., 2016, 52: 897
Guo C W, Takaki T, Sakane S, et al. Overgrowth behavior at converging grain boundaries during competitive grain growth: A two-dimensional phase-field study[J]. Int. J. Heat Mass Transfer, 2020, 160: 120196
doi: 10.1016/j.ijheatmasstransfer.2020.120196
40
Zhou Y Z, Jin T, Sun X F. Structure evolution in directionally solidified bicrystals of nickel base superalloys[J]. Acta Metall. Sin., 2010, 46: 1327
doi: 10.3724/SP.J.1037.2010.01327
