Rare earth Ce-based alloy rapid hardening sheet and preparation method thereof

Abstract

The invention provides a rare earth Ce-based alloy rapid hardening sheet and a preparation method thereof. The chemical formula of the rare earth Ce-based alloy rapid hardening sheet is REaFe100-a-b-c-dAlbBcMd, wherein 13.5 < = a < = 15, 1.2 < = b < = 2.0, 5.2 < = c < = 5.6, 0.1 < = d < = 5, and 6.5 < = (b + c) < = 7.5. The raw materials are smelted into molten liquid, and then the molten liquid is cast to a rotating copper roller through a tundish to be rapidly solidified. According to the method, elements such as Al and B in the alloy are cooperatively adjusted, crystal forming energy and free energy are modulated, competitive growth of a main phase crystal and a rare earth-rich phase is controlled, and directional growth of the crystal of the rare earth Ce-based alloy in the rapid hardening process is formed; the main phase grows in an oriented mode to form columnar crystals, the rare earth-rich phase is not gathered and is thinly distributed on the surfaces of the columnar crystals, and an ideal microstructure is obtained. The Ce content of the columnar crystal rapid hardening sheet is 60 wt.% or above of the total rare earth content, and a new technical approach is established for solving the overstock problem of the high-abundance rare earth Ce element.

Description

Technical Field

[0001] The invention relates to a rare earth Ce-based alloy quick-setting sheet and a preparation method thereof, belonging to the field of rare earth alloy material preparation. Background Art

[0002] The 4f electrons of rare earth elements have a large orbital radius and a strong spin-orbit coupling. The anisotropy generated by the crystal structure may lead to significant magnetic anisotropy. Therefore, rare earth element alloys and compounds may have high magnetocrystalline anisotropy fields and high coercivity. 14 B. Nd2Fe 14 B crystals have high magnetocrystalline anisotropy field, high coercivity, and high saturation magnetization intensity, and are widely used in modern science and life. However, the widespread use of (Nd, Pr)-Fe-B magnets results in a large consumption of rare earth elements Nd and Pr. In rare earth ores, La, Ce, Pr, Nd and other elements coexist, with Ce having the highest abundance. The large consumption of Nd and Pr results in a serious backlog of high-abundance rare earth Ce elements. Ce2Fe 14 Theoretically, B crystal has a larger coercive force and a higher saturation magnetization, but it is different from Nd2Fe 14 B crystal is different, Ce2Fe 14 The B crystal structure is unstable, making it difficult for crystals to grow in a directional manner during the melting, solidification, and crystallization processes. The rapidly solidified sheets obtained from the melting and solidification processes are essentially unable to form columnar (lamellar) crystals in terms of microstructure, and may even precipitate an α-Fe soft magnetic phase. This greatly complicates subsequent orientation pressing, resulting in poor orientation and difficulty improving magnetic properties. To improve the directional growth ability of crystals, it is generally necessary to add a large amount of rare earth elements such as Nd and Pr to Ce-Fe-B. The rare earth Ce content in commercial magnets generally does not exceed 50 wt.% of the total rare earth element content. The invention patent (application number 201610407554.2) discloses a low-cost rare earth iron boron permanent magnet and its preparation method. This method uses a method of increasing the B content in (Ce, RE)-Fe-B to improve the directional growth conditions and the ability to form columnar crystals during solidification and crystallization. However, the grains on the roller-attached surface of the Ce-Fe-B rapidly solidified sheets grow in a disorderly manner, and columnar crystals cannot form in 30% of the sheet area. At present, the utilization of Ce elements in the rare earth industry is far less than that of Nd and Pr elements. The increasingly serious problem of Ce element backlog has not been fundamentally solved, which is not conducive to the protection and balanced utilization of rare earth resources, and also brings great pressure to the storage of Ce elements. Summary of the Invention

[0003] In response to the shortcomings of the existing technology for preparing Ce-based alloy quick-setting sheets, the present invention controls the composition of the Ce-based alloy, modulates the main phase crystal formation energy and free energy through methods such as the coordinated adjustment of Al and B elements, modulates the distribution of the intercrystalline phase, enhances the wettability of the intercrystalline rare earth-rich phase, improves the competitive growth conditions of the main phase crystal and the intercrystalline phase, establishes a crystal directional growth technology for Ce-based alloys during the melting and quick-setting process, and provides a rare earth Ce-based alloy quick-setting sheet and a preparation method to solve the difficult problem of microstructure control of Ce-based alloy quick-setting sheets and solve the practical problem of serious backlog of Ce elements.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A rare earth Ce-based alloy quick-setting sheet, the composition of which in atomic percentage is RE a Fe 100-a-b-c-d Al b B c M d , where 13.5≤a≤15, 1.2≤b≤2.0, 5.2≤c≤5.6, 0.1≤d≤5, and 6.5≤(b+c)≤7.5;

[0006] RE is one or more of the rare earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, wherein the Ce content is 60 wt.%-100 wt.% of the total rare earth element content;

[0007] M is an added element, including one or more of Co, Cu, Ga, Zr, Ti, Nb, V, Cr, Mn, Ni, Zn, Mo, Sn, and Ag;

[0008] The rare earth Ce-based alloy rapid solidification sheet obtained by melting and rapid solidification using this component ratio is mainly composed of a main phase and an intergranular phase at the microscopic level, with no α-Fe impurity phase. The main phase grains basically grow in a direction and form columnar crystals, and the rare earth-rich intergranular phase is thinly distributed on the surface of the columnar crystals.

[0009] The method for preparing the rare earth Ce-based alloy quick-setting sheet comprises the following steps:

[0010] (1) Weighing each element according to the composition of the rare earth Ce-based alloy to obtain a raw material mixture;

[0011] (2) adding the raw material mixture into the crucible of the induction melting rapid solidification furnace, evacuating to 0.1 Pa, then heating to 600-900 ° C, maintaining this temperature and vacuum for 5-25 minutes, then filling with argon, and electrically heating under the argon protective atmosphere until the mixture melts into liquid, and maintaining the molten state for 3-10 minutes;

[0012] (3) The molten liquid is cast through a tundish onto a water-cooled copper roller at a linear speed of 0.5-3 m / s. After air cooling for 45-120 min, the furnace door is opened to discharge the material, and a rare earth Ce-based alloy quick-setting sheet with an average thickness of 0.2-0.5 mm is obtained.

[0013] Beneficial effects of the present invention:

[0014] (1) The present invention controls and adjusts the composition of Ce-based alloys and modulates the synergistic effect of elements such as Al and B. The Al element can enter the main phase to replace Fe or B, and can also be distributed in the intergranular phase. When the Al element enters the main phase, the main phase crystal formation energy is reduced, the entropy is increased, the free energy is reduced, the main phase crystal structure is more stable, and no soft magnetic phase α-Fe is precipitated. At the same time, the wettability of the intergranular rare earth-rich phase is enhanced, and the adverse effect of the intergranular phase on the directional growth of the main phase is weakened, so that the main phase crystal can grow in a directional manner. On this basis, a quick-setting sheet with columnar crystals and non-aggregated rare earth-rich intergranular phases is prepared. There is no soft magnetic phase α-Fe in the quick-setting sheet. In this way, the magnet's easy magnetization axis orientation is good in the subsequent magnet preparation process, and higher magnetic properties can be obtained.

[0015] (2) Due to Ce2Fe 14 The crystal structure of B is unstable. In order to obtain columnar crystals and inhibit the precipitation of α-Fe impurity phase, Ce2Fe 14 Expensive rare earth Nd elements are added to B to improve the stability of the crystal structure and increase the content of columnar crystals. The present invention modulates the synergistic effect of elements such as Al and B, and can obtain an ideal microstructure of columnar crystals in the thickness direction of the quick-setting sheet without adding rare earth Nd. Therefore, the present invention uses a large amount of rare earth Ce, and the Ce content of the columnar crystal quick-setting sheet formed can reach 100wt.% of the total amount of rare earth elements. Other rare earth elements such as Nd, Pr, Gd, Dy, Tb can be used in small amounts or even without using them to obtain columnar crystal quick-setting sheets of rare earth permanent magnet materials. The present invention can not only significantly reduce the cost of magnets, but also establish a new technical approach to solve the backlog of Ce elements and the balanced utilization of rare earth elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a scanning electron microscope image of the cross section of the quick-setting sheet in Example 1.

[0017] Figure 2 This is a scanning electron microscope image of the cross section of the quick-setting sheet of comparative example 1. DETAILED DESCRIPTION

[0018] The specific embodiments of the present invention are further described in detail below with reference to the examples.

[0019] Example 1

[0020] A rare earth Ce-based alloy quick-setting sheet, the chemical formula of which is composed of Ce in atomic percentage: 14 Fe77.9 Co 0.5 Cu 0.1 5Al 1.6 Ga 0.1 Zr 0.15 Ti 0.1 B 5.5 (i.e., Ce is 14 at.%, Fe is 77.9 at.%, Co is 0.5 at.%, Cu is 0.15 at.%, Al is 1.6 at.%, Ga is 0.1 at.%, Zr is 0.15 at.%, Ti is 0.1 at.%, and B is 5.5 at.%).

[0021] The preparation method comprises the following steps:

[0022] (1) Weighing each element according to the composition of the rare earth Ce-based alloy to prepare a raw material mixture;

[0023] (2) The prepared rare earth Ce-based alloy mixture is placed in the crucible of an induction melting rapid solidification furnace, evacuated to 0.1 Pa, and then heated to 800°C. This temperature and vacuum are maintained, and argon is filled in after 10 minutes. Under the protective atmosphere of argon, electric heating is performed until all raw materials are melted into liquid, and the molten state is maintained for 5 minutes. The melt is refined to ensure uniform alloying of the raw materials.

[0024] (3) The molten liquid was cast through a tundish onto a water-cooled copper roller at a linear speed of 1 m / s. After air cooling for 60 min, the furnace door was opened to discharge the material, and a rare earth Ce-based alloy quick-setting sheet with a thickness of about 0.3 mm was obtained.

[0025] The obtained rare earth Ce-based alloy rapid solidification sheet forms columnar crystals from the free surface to the roller surface. Figure 1 As shown, the microstructure of this rare earth Ce-based alloy quick-setting sheet is primarily composed of a main phase and an intergranular phase, with no α-Fe impurity. The main phase grains grow in a largely directional pattern, and a thin rare earth-rich intergranular phase is distributed on the surface of the columnar crystals. This rare earth Ce-based alloy quick-setting sheet conforms to the microstructure of the current national standard GB / T 29655-2013 for NdFeB quick-setting sheet alloys. The Ce content in this rare earth Ce-based alloy quick-setting sheet is 100% of the total rare earth content. Compared to NdFeB quick-setting sheet alloys, this alloy avoids the use of expensive rare earth elements such as neodymium (Nd) and utilizes Ce more efficiently, not only reducing costs but also establishing a new technological approach for the balanced utilization of rare earth elements.

[0026] Example 2

[0027] A rare earth Ce-based alloy quick-setting sheet, the chemical formula of which is Ce 14 Fe 78 Co 0.5 Cu 0.15 Al 1.2 Ga 0.4 Zr 0.15Ti 0.1 B 5.5 .

[0028] The preparation method comprises the following steps:

[0029] (1) Weighing each element according to the composition of the rare earth Ce-based alloy to prepare a raw material mixture;

[0030] (2) The prepared rare earth Ce-based alloy mixture is placed in the crucible of an induction melting rapid solidification furnace, evacuated to 0.1 Pa, and then heated to 800°C. This temperature and vacuum are maintained, and argon is filled in after 10 minutes. Under the protective atmosphere of argon, electric heating is performed until all raw materials are melted into liquid, and the melt is kept in the molten state for 5 minutes to refine the melt. The purpose is to ensure uniform alloying of the raw materials.

[0031] (3) The molten liquid was cast through a tundish onto a water-cooled copper roller at a linear speed of 1 m / s. After air cooling for 60 min, the furnace door was opened to discharge the material, and a rare earth Ce-based alloy quick-setting sheet with a thickness of about 0.3 mm was obtained.

[0032] The resulting rare earth Ce-based alloy rapid-setting sheet is primarily composed of a main phase and an intergranular phase, devoid of α-Fe impurities. The main phase grains grow in a generally directional pattern, forming columnar crystals, with a thin rare earth-rich intergranular phase distributed on the columnar crystal surfaces. This rare earth Ce-based alloy rapid-setting sheet contains 100% rare earth Ce. Compared to NdFeB rapid-setting sheet alloys, it avoids the use of expensive rare earth elements such as neodymium (Nd).

[0033] Example 3

[0034] A rare earth Ce-based alloy quick-setting sheet, the chemical formula is Ce 12.5 Gd 1.5 Fe 78 Co 0.5 Cu 0.15 Al 1.7 Zr 0.15 Ti 0.1 B 5.4 .

[0035] The preparation method comprises the following steps:

[0036] (1) Weighing each element according to the composition of the rare earth Ce-based alloy to prepare a raw material mixture;

[0037] (2) The prepared rare earth Ce-based alloy mixture is placed in the crucible of an induction melting rapid solidification furnace, evacuated to 0.1 Pa, and then heated to 800°C. This temperature and vacuum are maintained, and argon is filled in after 10 minutes. Under the protective atmosphere of argon, electric heating is performed until all raw materials are melted into liquid, and the melt is kept in the molten state for 5 minutes to refine the melt. The purpose is to ensure uniform alloying of the raw materials.

[0038] (3) The molten liquid was cast through a tundish onto a water-cooled copper roller at a linear speed of 1 m / s. After air cooling for 60 min, the furnace door was opened to discharge the material, and a rare earth Ce-based alloy quick-setting sheet with a thickness of about 0.3 mm was obtained.

[0039] The resulting rare earth Ce-based alloy rapid-setting sheet is primarily composed of a main phase and an intergranular phase, devoid of α-Fe impurities. The main phase grains grow directionally and form columnar crystals, with a thin rare earth-rich intergranular phase distributed on the columnar crystal surfaces. The Ce content of this rare earth Ce-based alloy rapid-setting sheet is 88.1 wt.% of the total rare earth content. Compared to NdFeB rapid-setting sheet alloys, this alloy avoids the use of expensive rare earth elements such as neodymium (Nd), efficiently utilizing Ce, reducing costs and establishing a new technical approach for achieving balanced utilization of rare earth resources.

[0040] Comparative Example 1

[0041] A rare earth Ce-based alloy quick-setting sheet, the composition of which is Ce in atomic percentage 14 Fe 78.5 Co 0.5 Cu 0.15 Al 0.9 Ga 0.1 Zr 0.15 Ti 0.1 B 5.6 .

[0042] The preparation method is the same as that in Example 1.

[0043] Compared to Example 1, the alloy in Comparative Example 1 contains 0.9 at.% Al, lower than the 1.6 at.% Al content in Example 1, and does not meet the Al atomic percentage requirement of 1.2 ≤ b ≤ 2.0 in this application. The rare earth elements in Comparative Example 1 are all Ce, resulting in a small amount of Al incorporating into the main phase lattice. This leads to a low melting point, low binding energy, and relatively low mixing entropy of the main phase crystal structure, resulting in an unstable main phase crystal structure. Furthermore, the wettability of the rare earth-rich phase with the main phase is poor, resulting in competitive growth of the rare earth-rich phase that disrupts the directional growth of the main phase crystal.

[0044] Figure 1 This is a scanning electron microscope image of a cross-section of the rapidly solidified sheet from Example 1. The gray portion in the image represents the primary phase, Ce-(Fe, Al, B) crystals, while the brighter portion represents the rare earth-rich phase. Most of the primary phase appears as lamellar columnar crystals, a result of the directional growth of Ce-(Fe, Al, B) crystals into columnar crystals. The rare earth-rich phase is relatively thin, mostly in straight lines, thinly distributed on the surface of the columnar crystals, separating the primary phase.

[0045] Figure 2 This is a scanning electron microscope image of the cross section of the quick-setting sheet of comparative example 1. The gray part in the figure is the main phase Ce2Fe 14B crystal, the brighter part is the rare earth-rich phase. The main phase grains failed to grow in a directional manner, no columnar crystals were formed, the rare earth-rich phase aggregated, and the ideal microstructure could not be obtained. Compared with the quick-setting sheet of Comparative Example 1, Example 1 controls the composition of the Ce-based alloy and modulates the synergistic effect of elements such as Al and B. Due to the entry of the Al element into the main phase, the main phase crystal formation energy is reduced, entropy is increased, free energy is reduced, the main phase crystal structure is more stable, and no soft magnetic phase α-Fe is precipitated. At the same time, the wettability of the intergranular rare earth-rich phase is enhanced, and the adverse effect of the intergranular phase on the directional growth of the main phase is weakened. The rare earth-rich phase does not aggregate and is thinly distributed on the surface of the columnar crystal, thereby obtaining an ideal microstructure.

[0046] The above embodiments are only for the purpose of illustrating the present invention clearly and are not intended to limit the embodiments. For those skilled in the art, other equivalent or similar variations can be made based on the concept of the present invention, and such variations are all within the scope of protection of the present invention.

Claims

1. A rare earth Ce-based alloy quick-setting sheet, characterized in that: The composition of the Ce-based alloy quick-setting sheet in atomic percentage is RE a Fe 100-a-b-c-d Al b B c M d , where 13.5≤a≤15, 1.2≤b≤2.0, 5.2≤c≤5.6, 0.1≤d≤5, and 6.5≤(b+c)≤7.5; RE is one or more of the rare earth elements La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, wherein the Ce content is 60 wt.%-100 wt.% of the total rare earth element content; M is an additional element, including one or more of Co, Cu, Ga, Zr, Ti, Nb, V, Cr, Mn, Ni, Zn, Mo, Sn, and Ag.

2. The method for preparing the rare earth Ce-based alloy quick-setting sheet according to claim 1, wherein: The following steps are involved: (1) Weighing each element according to the composition of the rare earth Ce-based alloy to obtain a raw material mixture; (2) Add the raw material mixture into the crucible of the induction melting rapid solidification furnace, evacuate to 0.1 Pa, then heat to 600-900 ° C, maintain this temperature and vacuum for 5-25 minutes, then fill with argon, and heat under the argon protective atmosphere until the mixture melts into liquid, and maintain the molten state for 3-10 minutes; (3) The molten liquid is cast through a tundish onto a water-cooled copper roller at a linear speed of 0.5-3 m / s. After air cooling for 45-120 min, the furnace door is opened to discharge the material, and a rare earth Ce-based alloy quick-setting sheet with an average thickness of 0.2-0.5 mm is obtained.

3. The method for preparing the rare earth Ce-based alloy quick-setting sheet according to claim 2, wherein: Step (2) is: adding the raw material mixture into the crucible of the induction melting rapid solidification furnace, evacuating to 0.1 Pa, then heating to 800 ° C, maintaining this temperature and vacuum for 10 minutes, then filling with argon, and electrically heating under an argon protective atmosphere until the mixture melts into a liquid, and maintaining the molten state for 5 minutes.

4. The method for preparing the rare earth Ce-based alloy quick-setting sheet according to claim 2, wherein: Step (3) is: casting the molten liquid through the tundish onto a water-cooled copper roller with a linear speed of 1 m / s, opening the furnace door to discharge the material after air cooling for 60 minutes, and obtaining a rare earth Ce-based alloy quick-setting sheet with an average thickness of 0.3 mm.

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