Effect of a high magnetic field on solidification structure in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy

Accepted Manuscript Effect of a high magnetic field on solidification structure in directionally solidified NiAlCr(Mo)-Hf eutectic alloy Huan Liu, Weidong Xuan, Xinliang Xie, Jianbo Yu, Jiang Wang, Xi Li, Yunbo Zhong, Zhongming Ren, Hui Wang, Yinming Dai PII:

S0925-8388(17)34256-1

DOI:

10.1016/j.jallcom.2017.12.073

Reference:

JALCOM 44159

To appear in:

Journal of Alloys and Compounds

Received Date: 2 November 2016 Revised Date:

5 December 2017

Accepted Date: 7 December 2017

Please cite this article as: H. Liu, W. Xuan, X. Xie, J. Yu, J. Wang, X. Li, Y. Zhong, Z. Ren, H. Wang, Y. Dai, Effect of a high magnetic field on solidification structure in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy, Journal of Alloys and Compounds (2018), doi: 10.1016/j.jallcom.2017.12.073. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Effect of a high magnetic field on solidification structure in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy Huan Liua, Weidong Xuana, *, Xinliang Xiea, Jianbo Yua, Jiang Wanga, Xi Lia, Yunbo Zhonga, Zhongming Rena, **, Hui Wangb, Yinming Daib State Key Laboratory of Advanced Special Steel, Shanghai University, Shanghai 200072, PR China

b

Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, PR China

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a

* Corresponding Author. Tel.: +86-02156334042. E-mail: [email protected] (W.D. Xuan)

** Corresponding Author. Tel.: +86-02156331102. E-mail: [email protected] (Z.M. Ren)

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Abstract

The effect of a high magnetic field on the microstructure in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy was investigated experimentally. The obtained results indicated that the

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application of the magnetic field caused the degeneration of the regular lamellar eutectic structure and induced the columnar-to-equiaxed transition (CET) of eutectic dendrites. In addition, the magnetic field modified the macroscopic solid-liquid interface shape and decreased the volume fraction of the Heusler phase. Furthermore, the amplitude and distribution of the thermoelectric magnetic force (TEMF) and thermoelectric magnetic convection (TEMC) in NiAl-Cr(Mo) eutectic alloy during directional

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solidification under a high magnetic field were studied by numerical simulation at different scales. It was found that the abovementioned results should be attributed to the coupling effects between the TEMC and TEMF. Besides, present work may provide a new method for modification of eutectic

Keywords

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morphology during directional solidification under a high magnetic field.

1.

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High magnetic field; Directional solidification; Microstructure; NiAl-Cr(Mo) eutectic alloy; Introduction

Intermetallic compound NiAl has been recognized as a promising candidate for high temperature

structural materials due to its high melting point, low density, high thermal conductivity and excellent oxidation resistance [1-3]. However, the low room temperature toughness and poor elevated temperature strength have limited its commercial application [4]. Over the past decades, researchers have focused their attention on NiAl in-situ composites, which can improve the toughness and strength simultaneously [5-8]. In particular, directionally solidified NiAl-Cr(Mo) eutectic composite exhibits a good combination of room temperature fracture toughness (24.1 MPa√m) [6] and elevated temperature 1

ACCEPTED MANUSCRIPT strength (348 MPa at 1093 °C) [9]. To further improve the elevated temperature mechanical properties, alloying additions have been investigated based on NiAl-Cr(Mo) eutectic alloy [10]. It was found that an addition of a small amount of Hf could effectively improve the elevated temperature strength. However, the fracture toughness decreased significantly due to the precipitation of the Heusler phase (Ni2AlHf) at the NiAl/Cr(Mo) interface and eutectic cell boundary [11,12]. Furthermore, the addition

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of Hf changed the microstructure from planar eutectic to cellular/dendritic eutectic due to the enlarged constitutional undercooling, which was detrimental to the fracture toughness. Therefore, to improve the room temperature toughness of NiAl-Cr(Mo)-Hf eutectic alloy, it is necessary to modify the eutectic

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morphology and to optimize the distribution of the Heusler phase.

Recently, high magnetic fields have been widely used in material processing. The effects of a high magnetic field on dendrite growth in single-phase alloys have been investigated [13-15]. It was found

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that the application of the magnetic field significantly affected the orientation, microsegregation, dendrite arm spacing and even gave rise to the columnar-to-equiaxed transition (CET) of the dendritic array. The influence of a high magnetic field on the eutectic growth in binary eutectic alloys has also been studied. The eutectic morphology changed remarkably under the magnetic field [16,17]. However, little work has been reported on the directional solidification of multicomponent eutectic alloys under a

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high magnetic field. The aim of the present work is twofold: first, the effect of a high magnetic field on solidification structure in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy was investigated; second, by studying the microstructure evolution, our understanding of the effect of the magnetic field

2.

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on the solidification structure in multicomponent eutectic alloys may be extended and deepened. Experimental procedures

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Alloy ingots with the nominal composition of Ni-33Al-28Cr-5.5Mo-0.5Hf (at.%) were prepared in a vacuum induction furnace. Cast samples were cut and enveloped in high-purity corundum tubes with an inner diameter and length of 10 mm and 200 mm, respectively, for the directional solidification. Fig. 1 shows the schematic of the experimental apparatus consisting of a static superconductor magnet and a Bridgman-Stockbarger-type furnace equipped with a pulling system and a temperature controller. The superconductor magnet can produce an axial static magnetic field with an adjustable intensity up to 6T. The furnace is made of nonmagnetic materials with a negligible effect on the field uniformity. A water-cooled cylinder containing liquid Ga-In-Sn metal (LMC) is used to cool down the specimens. The temperature gradient (90 K/cm in this study) was controlled by adjusting the temperature of the 2

ACCEPTED MANUSCRIPT furnace hot zone, which is insulated from the LMC by a refractory disc. The withdrawal velocity is controlled by a withdrawing device and could be continuously adjusted between 0.5 µm/s and 104 µm/s. During the experiment, the specimens were melted and directionally solidified in the Bridgman apparatus by drawing the crucible assembly at various speeds into the LMC cylinder. To observe the microstructure of the solid-liquid interface, quenching experiments were carried out by quickly

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withdrawing the crucible into the LMC cylinder.

The directionally solidified samples were cut along the longitudinal and transverse directions. After grinding and polishing, the specimens were etched with an 80% HCl + 20% HNO3 solution by

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volume. The microstructures were observed using an optical microscope (OM, Leica DM 6000M) and a scanning electron microscope (SEM, FEI Quanta 450) equipped with an energy dispersive spectroscopy (EDS, EDAX Octane Plus). The volume fraction of the Heusler phase was measured by

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Image-Pro Plus metallurgical analysis software. To ensure the accuracy, the measurement of area fraction was carried out at 30 sites on the transverse sections of each specimen, and the average values were reported. 3.

Results

dendrites

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3.1. Effect of a high magnetic field on the degeneration of the lamellar eutectic and the CET of eutectic

Fig. 2 shows the longitudinal structures near the solid-liquid interface in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy at various growth speeds with and without a 6 T high magnetic field. It

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can be observed that the microstructure without the magnetic field was typical cellular or dendritic eutectic. When the 6 T magnetic field was applied, the regular cellular/dendritic structure was

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destroyed and tended to transform into equiaxed grains at a low growth speed (i.e., 2 µm/s). Moreover, some freckles could be found below the solid-liquid interface. As the growth speed increased, the effect of the magnetic field became weak. The transverse microstructures in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy at various

growth speeds with and without a 6 T high magnetic field are shown in Fig. 3. In the absence of the magnetic field, the cellular and dendritic eutectic structure can be clearly observed. The eutectic colony consisted of NiAl matrix (dark), lamellar Cr(Mo) phase (gray) and the semi-continuously distributed white phase at the intercellular region, which was identified as the Heusler phase (Ni2AlHf) by EDS. The NiAl and Cr(Mo) plates exhibited a radially emanating pattern from the cell interior to its 3

ACCEPTED MANUSCRIPT boundaries. However, after the application of a strong magnetic field, the regular lamellar eutectic microstructure degenerated significantly at low growth speed. The Cr(Mo) phase showed an obvious tendency to spheroidization and coarsening. When the growth speed increased to 10 µm/s, only the intercellular region was destroyed. With further increase of the growth speed, the effect of the magnetic field on the eutectic microstructure became negligible.

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To elucidate the degeneration mechanism of the lamellar eutectic, the microstructure of directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy grown at 2 µm/s was investigated in detail. Fig. 4 shows the longitudinal structures at different positions with and without a 6 T magnetic field. It can

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be seen that the application of a high magnetic field did not disturb the lamellar structure near the solid-liquid interface. In fact, the lamellar structure disappeared after the solidification was completed.

process after the end of the solidification.

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This result indicated that the degeneration of the lamellar eutectic structure occurred during the cooling

3.2. Effect of a high magnetic field on the solid-liquid interface shape and the distribution of the Heusler phase

Fig. 5 shows the macroscopic solid-liquid interface morphologies and corresponding transverse structures at the periphery of the sample at the growth speed of 2 µm/s. In the case of no magnetic field,

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the solid-liquid interface shape was convex with obvious Hf segregation. This should be attributed to the thermo-solutal convection. The heavier species (in this case Hf) flowed down to the bottom of the protruding interface, resulting in a Heusler phase layer at the periphery of the sample, as shown in Fig.

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5(c). After the application of the 6 T magnetic field, the convex interface and the Heusler phase layer disappeared. The macroscopic interface shape became planar but uneven. This suggested that the

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thermo-solutal convection may be suppressed under a 6 T magnetic field. The effect of the magnetic field intensity on the solid-liquid interface shape was investigated. Fig.

6 shows the microstructures near the solid-liquid interface grown at 10 µm/s under various magnetic field intensities. It can be seen that a macroscopic planar interface and well-aligned columnar dendrites were obtained at the growth speed of 10 µm/s without the magnetic field. However, with the increasing magnetic field intensity the interface gradually became protruding. The protruding amplitude of the interface reached the maximum value under a 1 T magnetic field and then decreased with further increase of the magnetic field intensity. Moreover, the well-ordered columnar dendritic structure became irregular after the application of the magnetic field. 4

ACCEPTED MANUSCRIPT Fig. 7 shows the effect of a high magnetic field on the volume fraction of the Heusler phase at the eutectic cell boundary. It can be observed that the volume fraction of the Heusler phase decreased with the increasing growth speed. This is because as the growth speed increased, the Hf atom had less time to diffuse back to the matrix during the cooling after the end of the solidification. When the magnetic field was imposed, the Heusler phase fraction decreased at all growth speeds. The relationship between

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the volume fraction of the Heusler phase and the magnetic field intensity is presented in Fig. 7(b). As the magnetic field intensity increased, the fraction of the Heusler phase first decreased and then increased. The fraction of the Heusler phase reached its minimum when the field intensity was 2 T. Discussion

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4.

The experimental results described above indicated that the application of a high magnetic field destroyed the eutectic dendrites and caused the degeneration of the lamellar eutectic structure during

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the directional solidification at low growth speed. Moreover, the magnetic field had modified the solid-liquid interface shape and the distribution of the Heusler phase. Generally, two kinds of effects could affect the solidification microstructure during the directional solidification under a magnetic field. The first is the magnetization force arising from the magnetic crystalline anisotropy of a crystal. The second is the thermoelectric magnetic effect generated by the interaction between the thermoelectric

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current and the magnetic field. Since both NiAl and Cr(Mo) are weakly magnetic, the magnetization force is weak and negligible. Therefore, the above results should be mainly attributed to the thermoelectric magnetic effect.

dendrites

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4.1. Effect of a high magnetic field on the degeneration of lamellar eutectic and the CET of eutectic

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 produces a Seebeck It is well-known that in any material, a temperature gradient ∇

, where S is the thermoelectric power of the material. Considering that the two electromotive force S∇

eutectic phases and the liquid phase show a difference in thermoelectric power, this component can be regard as a thermocouple. Thus, a thermoelectric current will be generated around the interface. When a magnetic field is applied, the interaction between the thermoelectric current and magnetic field will produce a Lorentz force, which is known as thermoelectric magnetic force (TEMF). To investigate the distribution and magnitude of TEMF, numerical simulations were carried out using the commercial finite element code COMSOL Multiphysics (version 5.0.0.243). The simulation configuration was 2D. Both the solid and liquid regions were considered. Periodic boundary conditions 5

ACCEPTED MANUSCRIPT were given on the sidewall of the model. The electric current, including the contribution of the electric field, the liquid motion and the Seebeck effect, is described by Ohm’s Law:  − ∇   = σ  +  × 

(1)

where  is the current density, σ is the electric conductivity,  is the electric field,  is the velocity

current and the magnetic field:   =  × 

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 is the magnetic field intensity. The TEMF is generated by the interaction of the of the fluid flow and 

(2)

The physical properties used in the simulations are listed in Table 1. Figs. 8(a-c) show the distribution

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of the mesh, thermoelectric current and TEMF around the modeled liquid-solid interface under a 6 T magnetic field. Fig. 8(d) shows the maximal value of the TEMF acting on the solid as a function of the

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magnetic field intensity. It can be seen that the value of the TEMF increases linearly with the magnetic field intensity. At the temperature gradient of 90 K/cm, the maximum TEMF value under the 6 T magnetic field is on the order of 105 N/m3. The force then created a torque on the eutectic cell/dendrite. When the force increases to a critical value, the eutectic dendrite will be destroyed and the CET occurs. According to Ref. [23], a force of 105 N/m3 is sufficiently strong to break the cells/dendrites. Therefore,

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the CET at low speed should be attributed to the TEMF acting on the solid. Recent studies have found that the TEMF acting on the solid would generate stress and high density of dislocation pile-ups in both dendritic and eutectic structures [24,25]. It can be noticed that the TE current swirl and TEMF are remarkably localized around the phase interface. The force deforms

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the solid and generates a large number of dislocation tangles around the eutectic interface. As a result, the interface stays in a high-energy state, which would promote atom diffusion and decrease the

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thermal stability of eutectic structure. Moreover, the research of Sun et al. revealed that the application of a high magnetic field could increase the interfacial energy [26]. It is well-known that eutectic morphology is significantly influenced by the interfacial energy. Therefore, to minimize the interfacial energy of the system, the lamellar eutectic degenerated and tended to coarsening and spheroidization during the cooling process of the directional solidification. This may initiate a new approach for the modification of the eutectic morphology by directional solidification under a high magnetic field. 4.2. Effect of a high magnetic field on the solid-liquid interface shape and the distribution of the Heusler phase The TEMF appears in both the solid and liquid. The TEMF acting on the liquid will further 6

ACCEPTED MANUSCRIPT develop a fluid flow, which is called the thermoelectric magnetic convection (TEMC). The TEMC under various scales has been investigated in single-phase alloys [27]. It was found that the fluid velocity first increases as B1/2 in the weak magnetic field and then decreases as B−1 in the strong magnetic field. Consequently, there exists a maximum value of the fluid velocity when the TEMF is

 = 

/    

∇ 

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balanced with the electromagnetic braking force. The maximum velocity umax can be calculated as (3)

magnetic field intensity Bmax can be expressed as 

/

 !∇" = #  

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where  and  are the typical length scale and the density of liquid, respectively. The corresponding

(4)

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From Eqs. (3) and (4), it can be found that the maximum velocity of the TEMC is different for different scales. The corresponding value of Bmax increases with decreasing length scale. Here, we consider a two-phase eutectic cell/dendrite as a cell/dendrite. Figs. 9 (a) and (b) show the schematic diagram of TEMC at the macroscopic interface and at the eutectic cell/dendrite tip. It can be observed that a rotatory convection forms around the protruding interface and the tip of the eutectic

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cell/dendrite. Furthermore, since the centrifugal force generated by the rotating fluid is distributed unevenly in the radial direction, a secondary convection will be produced in the axial direction, as shown in Fig. 9(c) [28]. Numerical simulations were also carried out to investigate the distribution and

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magnitude of TEMC at different scales. The conditions in this simulation are similar to the one in the previous section, expect the geometry model is different. Both electric currents and fluid flow modules

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are selected. Details about the equation and corresponding boundary conditions can be found in Ref. [29]. The computed results are shown in Fig. 9(d-f). It can be observed that the TEMC first increases and then decreases due to the damping effect at high magnetic fields. The magnetic field intensities corresponding to the maximum velocity for the sample and dendrite scales are 0.03 T and 1 T, respectively.

Now let us consider the effect of TEMC on the solid-liquid interface shape. The magnetic field flattened the macroscopic convex interface at 2 µm/s. This is typically due to the damping of the thermo-solutal convection. As we can conclude from the computed results, the convection at the sample scale can be easily suppressed by a high magnetic field. At the growth speed of 10 µm/s, the interface shape changed from planar to protruding with increasing magnetic field for B < 1 T. Since the 7

ACCEPTED MANUSCRIPT TEMC at the sample scale is damped by the magnetic field, the modification of the solid-liquid interface shape should be mainly attributed to the TEMC at the eutectic dendrite scale. The rotatory convection at the tips of each cell/dendrite further induces a secondary convection near the solid-liquid interface (see Fig. 9(c)). The secondary convection tends to drive the heavier solute to the periphery of the sample. Since the solidification temperature decreases in the solute rich regions, the solidification

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temperature for the Hf-rich melt near the crucible wall is lower that at the centerline, leading to a protruding solid-liquid interface. Upon the further increase of the field intensity, the TEMC velocity at the dendrite scale decreases, and the interface becomes macroscopically planar but rough. The change

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in the interface shape is in good agreement with the change in the TEMC at the eutectic dendrite scale. The experimental results also revealed that the application of the magnetic field decreased the volume fraction of the Heusler phase, which means that the magnetic field decreased the

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microsegregation during the directional solidification. Microsegregation is affected significantly by the partition coefficient. The influence of a strong magnetic field on the equilibrium partition coefficient has been investigated by Li with the obtained results suggesting that the change in the equilibrium partition coefficient under a 10 T strong magnetic field is negligible [30]. However, the actual solidification always proceeds under non-equilibrium condition. Thus, the effective partition coefficient

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rather than the equilibrium partition coefficient is the key variable. As is well-known, the effective partition coefficient is remarkably influenced by fluid flow. The interdendritic TEMC in the mushy zone will promote the solute mixing and decrease the thickness of the solute boundary layer. This leads

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to the decrease of the effective partition coefficient. Additionally, the secondary convection could bring the solute into the liquid. Therefore, the application of magnetic field decreased the fraction of the

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interdendritic Heusler phase. Moreover, during the cooling process of directional solidification, the Hf atoms rejected in the intercellular region diffuse back into the NiAl matrix. The crystal defects generated by the TEMF acting on the solid provide a fast path for atom transport, which is beneficial for diffusion [31]. The acceleration of the back-diffusion process will further decrease the fraction of the Heusler phase. 5.

Conclusions The effect of an axial strong magnetic field on the solidification structure in directionally

solidified NiAl-Cr(Mo)-Hf eutectic alloy was investigated. The main results are summarized as follows: 8

ACCEPTED MANUSCRIPT 1. The regular lamellar eutectic structure grown at 2 µm/s degenerated significantly when the magnetic field was imposed. The Cr(Mo) phase tended to spheroidization and coarsening during the cooling process. This is due to the decreased thermal stability caused by TEMF acting on the eutectic during the solidification. 2. The application of the magnetic field destroyed the dendritic array and induced the CET of

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eutectic dendrites at low growth speed. This is attributed to the TEMF acting on the eutectic dendrites. 3. The macroscopic solid-liquid interface shape changed from planar to protruding, and then to planar but uneven. The modification of the solid-liquid interface shape should be attributed to the

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TEMC at the eutectic dendrite scale and the secondary convection.

4. The volume fraction of the Heusler phase decreased after the application of the magnetic field. This may be attributed to the decrease of the effective partition coefficient caused by the interdendritic

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TEMC. Acknowledgements

This work was supported by the National Natural Science Foundation of China (Nos. 51604172, 51690162, U1560202), the United Innovation Program of Shanghai Commercial Aircraft Engine (AR910, AR911), and the Shanghai Science and Technology Committee Grant (Nos. 13521101102,

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14521102900). References

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ACCEPTED MANUSCRIPT Table Caption Table 1 Physical properties of NiAl-Cr(Mo) eutectic alloy.

Figure Captions

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Fig. 1. Schematic illustration of the Bridgman solidification apparatus in a superconductor magnet.

Fig. 2. Longitudinal structures near the solid-liquid interface in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy at various growth speeds without and with a 6 T magnetic field: (a and

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e) 2 µm/s; (b and f) 10 µm/s; (c and g) 20 µm/s and (d and h) 50 µm/s.

Fig. 3. Transverse structures in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy at various

µm/s and (g and h) 50 µm/s.

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growth speeds without and with a 6 T magnetic field: (a and b) 2 µm/s; (c and d) 10 µm/s; (e and f) 20

Fig. 4. Longitudinal microstructures at different positions in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy grown at 2 µm/s without and with a 6 T magnetic field: (a and b) near the solid-liquid interface; (c and d) 3 cm below the solid-liquid interface.

Fig. 5. Microstructures near the solid-liquid interface in directionally solidified NiAl-Cr(Mo)-Hf

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eutectic alloy grown at 2 µm/s without and with a 6 T magnetic field: (a and b) longitudinal structures; (c and d) corresponding transverse structures at the periphery of the sample. Fig. 6. Microstructures near the solid-liquid interface in directionally solidified NiAl-Cr(Mo)-Hf

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eutectic alloy grown at 10 µm/s under various magnetic field intensities: (a) 0 T; (b) 0.1 T; (c) 0.5 T; (d) 1 T; (e) 2 T and (f) 6 T.

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Fig. 7. Effect of a high magnetic field on the volume fraction of the Heusler phase in directionally solidified NiAl-Cr(Mo)-Hf eutectic alloy: (a) volume fraction of the Heusler phase as a function of the growth speed with and without a 6 T magnetic field; (b) volume fraction of the Heusler phase as a function of the magnetic field intensities at the growth speed of 10 µm/s. Fig. 8. Simulation of TE current and TEMF near the liquid-solid interface during directional solidification of the NiAl-Cr(Mo) eutectic under a high magnetic field: (a) mesh for the numerical simulation; (b) thermoelectric current arrows near the interface; (c) distribution of TEMF acting on the solid and liquid near the liquid-solid interface under a 6 T magnetic field (in N/m3); and (d) maximum value of the TEMF acting on the solid as a function of the magnetic field intensity. 12

ACCEPTED MANUSCRIPT Fig. 9. Schematic diagram and numerical simulation of TEMC at different scales: (a) schematic diagram of the TEMC on the scale of the sample; (b) schematic diagram of the TEMC on the scale of eutectic cell/dendrite; (c) secondary convection near the interface; (d) distribution of TEMC on the scale of the sample at 0.03 T (in m/s); (e) distribution of TEMC on the scale of eutectic cell/dendrite at 1 T (in m/s); and (f) maximum values of the TEMC velocity as a function of the magnetic field

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intensity at different scales.

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ACCEPTED MANUSCRIPT Table 1 Properties

Magnitude µV·K-1

-5.1 [18]

Thermoelectric power of solid Cr(Mo)

µV·K-1

5.7 [19]

Thermoelectric power of liquid

µV·K-1

-38 [20]

Electrical conductivity of solid NiAl

Ω-1·m-1

Electrical conductivity of solid Cr(Mo)

Ω-1·m-1

Electrical conductivity of liquid

Ω-1·m-1

Temperature gradient

K·cm-1

Viscosity

Pa·s

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Thermoelectric power of solid NiAl

11.1×106 [18] 2.5×106 [19]

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0.67×106 [21] 90

5.69×10-3 [22]

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Fig. 9

ACCEPTED MANUSCRIPT Highlights The lamellar eutectic degenerated at low growth speed under a high magnetic field.




Magnetic field induced columnar to equiaxed transition of eutectic dendrites.




The fraction of Heusler phase decreased after the magnetic field is applied.




This work may initiate a new method to modify eutectic morphology.

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