CN117059357A - Neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain, and preparation method and application thereof - Google Patents

Neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain, and preparation method and application thereof Download PDF

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CN117059357A
CN117059357A CN202311043405.9A CN202311043405A CN117059357A CN 117059357 A CN117059357 A CN 117059357A CN 202311043405 A CN202311043405 A CN 202311043405A CN 117059357 A CN117059357 A CN 117059357A
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rare earth
heavy rare
iron
neodymium
boron
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范晓东
郭帅
丁广飞
闫阿儒
陈仁杰
郑波
曹帅
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Ningbo Institute of Material Technology and Engineering of CAS
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Ningbo Institute of Material Technology and Engineering of CAS
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/04—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials metals or alloys
    • H01F1/047—Alloys characterised by their composition
    • H01F1/053—Alloys characterised by their composition containing rare earth metals
    • H01F1/055—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5
    • H01F1/057—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B
    • H01F1/0571—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes
    • H01F1/0575—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together
    • H01F1/0577—Alloys characterised by their composition containing rare earth metals and magnetic transition metals, e.g. SmCo5 and IIIa elements, e.g. Nd2Fe14B in the form of particles, e.g. rapid quenched powders or ribbon flakes pressed, sintered or bonded together sintered
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
    • H01F41/0253—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets
    • H01F41/0293—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing permanent magnets diffusion of rare earth elements, e.g. Tb, Dy or Ho, into permanent magnets

Abstract

The application discloses a neodymium-iron-boron rare earth permanent magnet with a heavy rare earth element segregation structure in a crystal grain, and a preparation method and application thereof, and belongs to the field of magnetic materials. The raw materials of the neodymium-iron-boron rare earth permanent magnet consist of a main phase and an auxiliary phase, wherein the main phase is neodymium-iron-boron alloy, and the auxiliary phase is one or more selected from heavy rare earth hydride, heavy rare earth fluoride and heavy rare earth alloy; the magnet main phase crystal grain is provided with a heavy rare earth element segregation structure, wherein the heavy rare earth element diffuses into the main phase crystal grain to form a segregation layer and a heavy rare earth surface layer, the segregation layer is positioned on the inner side of the heavy rare earth surface layer, and the concentration of the heavy rare earth element is higher than that of the heavy rare earth surface layer. The neodymium-iron-boron rare earth permanent magnet has a heavy rare earth element segregation structure in a main phase grain, and the segregation occurs inside, namely, a segregation layer is positioned on the inner side of a heavy rare earth surface layer, so that the expansion of a magnetic domain wall to the inside of the grain in the reverse magnetization process can be prevented, the anti-demagnetization capability of the magnet is improved, and the coercive force of the magnet is improved.

Description

Neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain, and preparation method and application thereof
Technical Field
The application belongs to the technical field of magnetic materials, and particularly relates to a neodymium-iron-boron rare earth permanent magnet with a heavy rare earth element segregation structure in a crystal grain, and a preparation method and application thereof.
Background
The sintered NdFeB permanent magnet material has high coercivity and high magnetic energy product, so that the sintered NdFeB permanent magnet material is widely applied to various industries of national economy such as instruments and meters, microwave communication, wind power generation, electric automobiles and the like.
In general, the coercivity mechanism of sintered neodymium-iron-boron magnets is a nucleation mechanism. In the process of reverse magnetization of the magnet under the action of an external field, magnetic domains are reversely nucleated at weak positions of the anisotropic field of the crystal grains, and then magnetic domain walls rapidly move towards the inside of the crystal grains, so that the process of reverse magnetization is finally completed.
In order to improve the anti-demagnetizing capability of the grains in the magnet, a large number of researchers have adopted a heavy rare earth element strengthening scheme, developed a heavy rare earth element diffusion technology, such as a coating method to form a thin heavy rare earth element high anisotropic layer on the surface layer of the grains of the sintered neodymium-iron-boron magnet to prevent the movement of magnetic domain walls in the process of reverse magnetization.
Disclosure of Invention
The inventors found that: for such a magnet in which heavy rare earth elements are concentrated only on the surface layer of the grain (the concentration of heavy rare earth is less near the core of the grain), if the intensity of the applied magnetic field is sufficiently large, the magnetic domain of the low anisotropy field region inside the grain will instantaneously reverse in magnetization once the domain wall breaks through the surface layer high anisotropy layer, and the final coercivity of the magnet will be relatively low. If a heavy rare earth segregation layer with higher concentration can be formed on the inner side of the surface layer, the movement of the reverse magnetization domain to the inside of the magnet crystal grain can be prevented, and the anti-demagnetization capability and the coercive force of the magnet are improved.
Based on the above findings and knowledge, according to an embodiment of the present application, an object is to provide a neodymium iron boron rare earth permanent magnet having a heavy rare earth element segregation structure in a crystal grain, and a preparation method and application thereof. The neodymium-iron-boron rare earth permanent magnet has a heavy rare earth element segregation structure in a main phase grain, the concentration of a surface layer of the heavy rare earth element in the main phase grain of the magnet is low (heavy rare earth surface layer), the internal concentration is high (segregation layer), and the magnet with the grain of the structure can prevent a reverse magnetization domain from moving to the interior of the magnet and improve the anti-demagnetization capability and coercive force of the magnet.
The above object can be achieved by the following embodiments of the present application:
according to one aspect of the application, the neodymium-iron-boron rare earth permanent magnet with a heavy rare earth element segregation structure in the crystal grain provided by the application is prepared from a main phase and an auxiliary phase, wherein the main phase is an alloy containing neodymium-iron-boron; the auxiliary phase is one or more selected from the hydride of the heavy rare earth, the fluoride of the heavy rare earth and the alloy of the heavy rare earth; the magnet crystal grain is provided with a heavy rare earth element segregation structure, wherein the heavy rare earth element diffuses into the main phase crystal grain to form a segregation layer and a heavy rare earth surface layer, the segregation layer is positioned on the inner side of the heavy rare earth surface layer, and the concentration of the heavy rare earth element is higher than that of the heavy rare earth surface layer.
Optionally, the concentration of heavy rare earth elements of the meta-polymeric layer is increased by 0.1wt.% to 5wt.% as compared to the heavy rare earth surface layer.
Optionally, the thickness of the bias layer is 0.1 μm to 2 μm.
Optionally, the thickness of the heavy rare earth surface layer is 1-4 μm.
Optionally, in the hydride, fluoride and alloy of the heavy rare earth, the heavy rare earth is one or more of holmium (Ho), dysprosium (Dy), terbium (Tb), gadolinium (Gd), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc) and yttrium (Y).
Optionally, the heavy rare earth alloy is an alloy formed by the heavy rare earth and at least one selected from aluminum, gallium, copper and zinc.
Optionally, the heavy rare earth alloy has a composition expressed as: RE' b N’ c The method comprises the steps of carrying out a first treatment on the surface of the Wherein b ranges from 40 to 90; c ranges from 60 to 10; b+c=100; RE' is one or more of Ho, dy, tb, gd, er, tm, yb, lu, sc, Y; n' is one or more of Ga, al, cu, zn.
Optionally, the auxiliary phase consumption is 0.1% -20% of the total amount of the main phase and the auxiliary phase.
Optionally, the composition of the main phase is: RE (RE) α B β M γ N δ Fe 100-α-β-γ-δ The method comprises the steps of carrying out a first treatment on the surface of the Wherein, in terms of mass percent, alpha is more than or equal to 25 and less than or equal to 35,0.94, beta is more than or equal to 1.10,0 and less than or equal to gamma is more than or equal to 10, and delta is more than or equal to 0 and less than or equal to 10; RE is Nd or Nd and one or more selected from La, ce, pr, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, Y and Sc; b is boron element; fe is iron element; when γ+.0, M is one or more of Co, ni, mn, cr, cu, zn, ti, V, zr, nb; when δ+.0, N is one or more of Ga, al, sn, ge.
According to another aspect of the present application, the present application provides a method for preparing a neodymium-iron-boron rare earth permanent magnet having a heavy rare earth element segregation structure in a crystal grain, including: obtaining main phase magnetic powder and auxiliary phase powder; adding auxiliary phase powder into main phase magnetic powder and mixing; and (3) carrying out orientation molding, sintering and tempering treatment on the mixed material, wherein heavy rare earth elements diffuse into the main phase crystal grains to form a heavy rare earth surface layer and a bias aggregation layer, the bias aggregation layer is positioned at the inner side of the heavy rare earth surface layer, and the concentration of the heavy rare earth elements is higher than that of the heavy rare earth surface layer, so as to obtain the neodymium-iron-boron rare earth permanent magnet with the heavy rare earth element bias aggregation structure in the crystal grains.
Optionally, in the step of obtaining main phase magnetic powder and auxiliary phase powder, preparing the main phase magnetic powder by adopting a rapid hardening smelting, hydrogen breaking and air flow grinding method; when the auxiliary phase is an alloy of heavy rare earth, preparing auxiliary phase powder by adopting a quick setting smelting, hydrogen breaking and air flow grinding method or an induction smelting post-breaking method.
Optionally, sintering is performed under vacuum conditions; vacuum degree of 1X 10 -4 Pa～1×10 -2 Pa; the sintering temperature is 900-1200 ℃; the sintering time is 1 h-10 h.
Optionally, the tempering treatment adopts two-stage tempering treatment; the primary tempering temperature is 800-1000 ℃ and the time is 1-6 h; the secondary tempering temperature is 400-650 ℃ and the time is 1-6 h.
According to another aspect of the application, the neodymium-iron-boron rare earth permanent magnet with the heavy rare earth element segregation structure in the crystal grain is applied to instruments and meters, microwave communication, wind power generation and electric automobiles.
The beneficial effects are that: according to one embodiment of the application, one or more of heavy rare earth hydride, heavy rare earth fluoride and heavy rare earth alloy is adopted as an auxiliary phase, neodymium-iron-boron-containing alloy is adopted as a main phase, heavy rare earth elements in the auxiliary phase are diffused into crystal grains of the main phase to form a heavy rare earth surface layer, and then are continuously diffused and biased to form a bias layer with higher concentration than the heavy rare earth surface layer, a heavy rare earth element bias structure is formed in the crystal grains, the concentration of the heavy rare earth elements at the crystal grain surface layer is lower, the concentration of the inside of the crystal grains is higher, and a magnet with the crystal grain structure can prevent the expansion of magnetic domain walls into the crystal grains in the reverse magnetization process, so that the demagnetizing resistance and the coercive force of the magnet are improved, for example, the coercive force H of the magnet in the example cj ≥11.46kOe。
According to one embodiment of the application, the auxiliary phase powder of the hydride, fluoride and alloy containing heavy rare earth is added into the main phase magnetic powder of the alloy containing neodymium iron boron, after being uniformly mixed, the auxiliary phase is subjected to orientation molding, sintering and tempering heat treatment, so that the heavy rare earth elements decomposed by the auxiliary phase in the heat treatment process are diffused into the inside of main phase grains, the heavy rare earth elements are continuously diffused to the inner side of the heavy rare earth surface layer after forming the heavy rare earth surface layer at the surface layer of the grains and are subjected to segregation to form a higher concentration segregation layer, thereby obtaining the neodymium iron boron rare earth permanent magnet with a heavy rare earth element segregation structure in the grains, and the magnet can prevent the anti-magnetization domain from moving to the inside of the grains in the anti-magnetization process, and improve the anti-demagnetization capability and coercive force of the magnet. The neodymium-iron-boron rare earth permanent magnet can be applied to instruments and meters, microwave communication, wind power generation and electric automobiles.
Drawings
Fig. 1 is a schematic diagram of the formation of grains in a neodymium-iron-boron rare earth permanent magnet according to an embodiment of the present application.
FIG. 2 is a grain structure and elemental wire distribution diagram of a NdFeB rare earth permanent magnet of example 2 of the present application;
fig. 3 is a magnetic domain moving process and an element plane distribution diagram of embodiment 2 of the present application.
Detailed Description
The advantages and various effects of the present application will be more clearly apparent from the following description and examples of the present application. It is apparent that the detailed description and examples, while indicating the application, are intended to be illustrative of the application only, and not of the application. The following description of at least one exemplary embodiment or example is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments and examples, which are apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein, are intended to be within the scope of the application as claimed.
As described above, the present inventors recognized that: at present, in sintered NdFeB magnets, heavy rare earth elements are mainly concentrated and distributed on the surface layer of the crystal grains, the concentration is lower at the position closer to the core of the crystal grains, if the strength of an externally-added magnet is large enough, once a magnetic domain wall breaks through a surface layer high anisotropic layer, the magnetic domain of a low anisotropic field area inside the crystal grains can be instantaneously magnetized and reversed, and the final coercive force of the magnet is relatively low; the present application is based on this.
According to the neodymium-iron-boron rare earth permanent magnet with the heavy rare earth element segregation structure in the crystal grain, the raw materials consist of a main phase and an auxiliary phase, and the main phase is an alloy containing neodymium-iron-boron; the auxiliary phase is one or more selected from the hydride of the heavy rare earth, the fluoride of the heavy rare earth and the alloy of the heavy rare earth; the main phase crystal grain of the magnet has a heavy rare earth element segregation structure. Wherein, the heavy rare earth element diffuses into the main phase crystal grain to form a heavy rare earth surface layer and a segregation layer, the segregation layer is positioned at the inner side of the heavy rare earth surface layer, and the concentration of the heavy rare earth element in the segregation layer is higher than that of the heavy rare earth surface layer.
In the forming process of the neodymium-iron-boron rare earth permanent magnet, the following steps are adopted: the heavy rare earth element diffuses along the surface layer of the main phase crystal grain to the inside of the main phase crystal grain, and after the heavy rare earth surface layer is formed at the surface layer of the main phase crystal grain, the heavy rare earth element continues to diffuse inwards and is biased and gathered at the inner side of the heavy rare earth surface layer, so that a bias gathering layer is formed; it can be seen that the segregation layer is formed inside the heavy rare earth surface layer, that is, the segregation occurs inside the main phase grains but not at the main phase grain surface layer; a heavy rare earth element segregation structure with lower surface layer concentration and higher internal concentration is formed in the main phase crystal grains of the magnet; the magnet with the grain structure can prevent the expansion of magnetic domain walls to the inside of grains in the process of reverse magnetization, and improve the anti-demagnetizing capability and coercive force of the magnet.
According to the neodymium iron boron rare earth permanent magnet provided by an embodiment of the application, the concentration of heavy rare earth elements of the segregation layer is increased by 0.1wt.% to 5wt.%, such as 0.5wt.%, 0.1wt.%, 1.5wt.%, 2.0wt.%, 2.5wt.%, 3.0wt.%, 3.5wt.%, 4.0wt.%, 4.5wt.%, 5.0wt.% and the like, compared with the surface layer in the main phase grains. When the intensity of the externally applied magnetic field breaks through the surface layer greatly, the bias aggregation layer with higher concentration is formed on the inner side of the surface layer in a bias aggregation mode, so that the movement of the anti-magnetization domain to the inside of the magnet crystal grain is effectively prevented, and the anti-demagnetization capability and the coercive force of the magnet are improved.
According to the neodymium-iron-boron rare earth permanent magnet provided by the embodiment of the application, the thickness of the heavy rare earth surface layer in the crystal grains is 1-4 mu m. For example 1 μm, 2 μm, 3 μm, 4 μm, etc. The bias-focusing layer is positioned on the inner side of the heavy rare earth surface layer, that is, the heavy rare earth element is biased and focused at a position 1-4 mu m away from the outer boundary of the grain, so that the bias-focusing layer with the concentration higher than that of the heavy rare earth surface layer is formed.
According to the neodymium-iron-boron rare earth permanent magnet provided by one embodiment of the application, the thickness of the segregation layer in the main phase crystal grains is 0.1-2 μm, such as 0.1 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm and the like.
In the neodymium-iron-boron rare earth permanent magnet provided by the application, the main phase is an alloy containing neodymium-iron-boron. Optionally, the composition of the main phase is: RE (RE) α B β M γ N δ Fe 100-α-β-γ-δ The method comprises the steps of carrying out a first treatment on the surface of the Wherein, in terms of mass percent, alpha is more than or equal to 25 and less than or equal to 35,0.94, beta is more than or equal to 1.10,0 and less than or equal to gamma is more than or equal to 10, and delta is more than or equal to 0 and less than or equal to 10; RE is Nd, or Nd and one or more selected from La, ce, pr, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, Y and Sc; b is boron element; fe is iron element; m is one or more of Co, ni, mn, cr, cu, zn, ti, V, zr, nb; n is one or more of Ga, al, sn, ge.
In the neodymium-iron-boron rare earth permanent magnet provided by the application, the auxiliary phase is one or more selected from the hydride of heavy rare earth, the fluoride of heavy rare earth and the alloy of heavy rare earth. Wherein, the heavy rare earth refers to one or more of holmium (Ho), dysprosium (Dy), terbium (Tb), gadolinium (Gd), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc) and yttrium (Y). For example, fluoride of holmium fluoride of heavy rare earth (HoF x ) Fluoride of dysprosium (DyF) x ) Terbium fluoride (TbF) x ) Etc. The hydride of the heavy rare earth may be a hydride of holmium (HoH x ) Hydrides of dysprosium (DyH) x ) Terbium hydride (TbH) x ) Etc.
In addition, the alloy of the heavy rare earth refers to an alloy formed by the heavy rare earth and other metal elements. The heavy rare earth can be one or more of holmium (Ho), dysprosium (Dy), terbium (Tb), gadolinium (Gd), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc) and yttrium (Y). The other metal element may be one or more selected from aluminum (Al), gallium (Ga), copper (Cu), zinc (Zn), etc., for example, an aluminum alloy of heavy rare earth, an aluminum gallium alloy of heavy rare earth, etc. More specifically, for example, an aluminum gallium alloy of holmium (HoAlGa), an aluminum gallium alloy of dysprosium (DyAlGa), an aluminum gallium alloy of terbium (TbAlGa), or the like may be mentioned. When the alloy of heavy rare earth is used as an auxiliary phase, in the high-temperature treatment process, alloy elements such as Al, ga and the like in the auxiliary phase can flow along the grain boundary of the magnet to dilute ferromagnetism of the grain boundary phase, and finally, a continuous and uniform non-magnetic thin-wall grain boundary phase is formed, so that the microstructure of the magnet can be optimized to a certain extent, and the coercive force of the magnet is improved.
In an alternative embodiment, the composition of the heavy rare earth alloy may be expressed as: RE' b N’ c The method comprises the steps of carrying out a first treatment on the surface of the Wherein b isThe circumference is 40 to 90 percent; c ranges from 60 to 10; and b+c=100; RE' is one or more of holmium (Ho), dysprosium (Dy), terbium (Tb), gadolinium (Gd), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu), scandium (Sc) and yttrium (Y); n' can be one or more of metal elements such as Ga, al, cu, zn and the like; such as ternary alloys of heavy rare earth elements with Al and Ga elements, and the like. When N' is plural, the sum of c and b is 100, and the ratio of the metal elements is not limited, but may be 1:1 or the like when two kinds are used.
The inventors found that: under the condition of taking the neodymium iron boron alloy as a main phase, by adopting the hydride, fluoride and alloy of the heavy rare earth as auxiliary phases, the auxiliary phases decompose heavy rare earth atoms under the action of high temperature in the heat treatment process of the magnet, migrate into crystal lattices of main phase grains and are biased towards the inner side of a surface layer, and a heavy rare earth bias structure with low surface layer concentration and high bias layer concentration between the surface layer and a core is formed in the neodymium iron boron main phase grains.
According to the preparation method of the neodymium-iron-boron rare earth permanent magnet with the heavy rare earth element segregation structure in the crystal grain, provided by the embodiment of the application, the following steps are adopted: comprising the following steps: step S1, preparing main phase magnetic powder and auxiliary phase powder; step S2, mixing main phase magnetic powder and auxiliary phase powder; s3, carrying out orientation molding on the mixed materials to obtain a magnet green body; and S4, performing heat treatment on the magnet green body, wherein in the heat treatment process, heavy rare earth elements in the auxiliary phase diffuse into the main phase crystal grains, a heavy rare earth surface layer is formed at the surface layer of the main phase crystal grains, and continuously diffuse inwards and perform segregation on the inner side of the heavy rare earth surface layer, so that a segregation layer with the concentration higher than that of the heavy rare earth surface layer is formed, and a neodymium-iron-boron rare earth permanent magnet with a heavy rare earth element segregation structure in the crystal grains is obtained.
Fig. 1 schematically illustrates a schematic diagram of the formation of grains in a neodymium-iron-boron rare earth permanent magnet according to an embodiment of the present application. As shown in fig. 1, the main phase and the auxiliary phase are mixed, sintered and tempered after orientation molding, so that a magnet with the grain structure shown in fig. 1 can be obtained; the crystal grain can be divided into three areas, the outermost area is an area containing heavy rare earth elements and is called a heavy rare earth-rich shell layer, the center is a core area, the area between the heavy rare earth-rich shell layer and the core is an area where heavy rare earth elements are concentrated, and the area contains heavy rare earth elements with higher concentration and is called a heavy rare earth-rich concentrated layer.
The forming principle is as follows: after the main phase and the auxiliary phase are fully mixed, the main phase and the auxiliary phase are subjected to orientation molding and heat treatment, the auxiliary phase is melted and decomposed to obtain heavy rare earth elements in the heat treatment process, the heavy rare earth elements gradually penetrate into the main phase along the surface layer of crystal grains, and are concentrated in the main phase, so that a heavy rare earth surface layer with lower concentration and a concentrated layer positioned at the inner side of the heavy rare earth surface layer are formed; the core is very low in heavy rare earth concentration or the heavy rare earth element does not enter the region, so that the core is the main phase core. It can be seen that the heavy rare earth element is biased in the main phase crystal grain, specifically, the heavy rare earth surface layer is formed at the surface layer of the main phase crystal grain, and then the heavy rare earth element is continuously biased in the inner side of the heavy rare earth surface layer to form a bias polymerization layer. The heavy rare earth element presents gradient distribution in the main phase crystal grains: the concentration of the main phase crystal grain surface layer is lower, the concentration of the main phase crystal grain surface layer near the core is higher, and the heavy rare earth element segregation structure is formed. The magnet with the grain structure can prevent the expansion of the magnetic domain wall to the inside of the grain in the process of reverse magnetization, improve the demagnetizing resistance of the magnet, finally improve the coercive force of the magnet and improve the thermal stability of the magnet, and is an effective scheme for obtaining the high-performance neodymium iron boron magnet.
When the main phase magnetic powder is obtained: the main phase magnetic powder is obtained by firstly preparing ingredients according to the components of the main phase, mixing the prepared main phase raw materials, carrying out quick setting smelting on the mixture to obtain an alloy cast sheet, firstly carrying out hydrogen breaking on the alloy cast sheet to obtain coarse powder, and then carrying out air flow grinding on the coarse powder.
When the auxiliary phase powder is obtained: for heavy rare earth alloys, a rapid solidification smelting-hydrogen crushing-jet milling process may be employed, comprising: firstly, preparing ingredients according to the components of auxiliary phases, mixing the prepared metal raw materials, carrying out quick setting smelting on the mixture to obtain alloy cast pieces, carrying out hydrogen breaking on the alloy cast pieces to obtain coarse powder, and carrying out air flow grinding on the coarse powder to obtain auxiliary phase powder. It can also be obtained by induction smelting-mechanical crushing method, including: the auxiliary phase powder is obtained by firstly preparing ingredients according to the auxiliary phase components, mixing the prepared metal raw materials, firstly carrying out induction smelting on the mixture, and then mechanically crushing and/or ball milling. Whereas for heavy rare earth hydrides or heavy rare earth fluorides: directly purchasing.
In an alternative embodiment, in step S1, the particle size of the prepared main phase magnetic powder is about 2 to 4 μm. The particle size of the auxiliary phase magnetic powder is about 1.5-4.5 mu m. By adopting the main phase magnetic powder and the auxiliary phase powder with the particle size range, the subsequent orientation molding can be more facilitated, so as to obtain the density of more than 6g/cm 3 Is more beneficial to the migration process of heavy rare earth elements at grain boundaries in the heat treatment process, so that the heavy rare earth elements penetrate into a main phase lattice to form an internal segregation layer.
In an alternative embodiment, in step S2, the auxiliary phase powder is added to the main phase magnetic powder in a mass percentage of 0.1% to 20% of the total amount of the main phase and the auxiliary phase. For example, the additive is added in a mass percentage of 0.1%, 0.5%, 1%, 3%, 5%, 7%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, etc. The auxiliary phase powder is added into the main phase according to the proportion, so that under the condition that heavy rare earth elements form a heavy rare earth surface layer at the surface layer of the main phase crystal grain, a higher concentration bias aggregation layer is formed at the inner side of the heavy rare earth surface layer, the high heavy rare earth concentration bias aggregation layer has high magnetic crystal anisotropy field, the movement of a reverse magnetization domain in the crystal grain in the demagnetizing process can be prevented, the effect similar to domain wall pinning can be achieved, and the coercive force of a magnet is improved, in this way, the finally obtained neodymium-iron-boron permanent magnet can be enabled to be positioned in the B r Sum (BH) max Increase H without excessive decrease cj . Furthermore, the inventors have found that if the addition amount of the auxiliary phase is too high, for example, higher than 20wt.%, excessive heavy rare earth elements are introduced into the magnet, and the residual magnetization of the magnet is greatly reduced due to antiferromagnetic coupling between the heavy rare earth elements and Fe; when the addition amount of the auxiliary phase is too low, for example, less than 0.1wt.%, the amount of heavy rare earth element in the magnet is too small, a high-concentration segregation layer cannot be formed in the grains, and the heavy rare earth element segregation structure cannot be provided, so that the effect of preventing the movement of the reverse magnetization domain in the grains in the demagnetizing process is achievedAnd (5) fruits.
In an alternative embodiment, in the step S3, during the orientation molding, the mixed powder is subjected to magnetic field orientation molding in a molding press, wherein the orientation magnetic field is more than or equal to 1.6T, and the magnet green compact is obtained.
In addition, optionally, isostatic pressing treatment can be adopted after the magnetic field orientation molding, the isostatic pressing treatment pressure can be more than or equal to 150MPa, and the green density of the magnet can be further improved through the isostatic pressing treatment.
In an alternative embodiment, in step S4, the magnet green body is sintered under vacuum, and a two-stage tempering treatment is adopted to obtain the neodymium-iron-boron rare earth permanent magnet. Alternatively, the vacuum degree is 1×10 -4 Pa～1×10 -2 Pa may be, for example, 1×10 -4 、1×10 -3 、1×10 -2 Pa, and the like. Optionally, the sintering temperature is 900-1200 ℃; the sintering time is 1 h-10 h. For example, the sintering temperature may be 900 ℃, 950 ℃, 1000 ℃, 1050 ℃, 1100 ℃, 1150 ℃, 1200 ℃, etc. The sintering time can be 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, etc. Optionally, during the two-stage tempering treatment, the primary tempering temperature is 800-1000 ℃ and the primary tempering time is 1-6 h. For example, the primary tempering temperature is 800 ℃, 810 ℃, 820 ℃, 830 ℃, 840 ℃, 850 ℃, 860 ℃, 870 ℃, 880 ℃, 890 ℃, 900 ℃, 910 ℃, 920 ℃, 930 ℃, 940 ℃, 950 ℃, 1000 ℃, and the like. The primary tempering time is 1h, 2h, 3h, 4h, 5h, 6h and the like. The secondary tempering temperature is 400-650 ℃ and the time is 1-6 h. For example, the secondary tempering temperature is 400 ℃, 420 ℃, 440 ℃, 460 ℃, 480 ℃, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 650 ℃, etc. The secondary tempering time is 1h, 2h, 3h, 4h, 5h and 6h. And under the condition, the magnet green body is subjected to heat treatment, so that the heavy rare earth elements decomposed by the auxiliary phase in the heat treatment process are more favorable, the temperature environment is fully utilized, the heavy rare earth elements can be effectively diffused into the main phase grains in the treatment time, and the heavy rare earth elements are concentrated in the grains, so that a heavy rare earth element concentrated layer with higher concentration is formed.
According to the preparation method provided by the embodiment of the application, neodymium iron boron magnetic powder is adopted as a main phase, the hydride, fluoride or alloy of heavy rare earth is adopted as an auxiliary phase material, the adding proportion of the main phase and the auxiliary phase is optimized, and the process of 'mixed post-orientation molding-heat treatment' is adopted, so that the process parameters are further optimized, the heavy rare earth elements decomposed by the auxiliary phase in the heat treatment process are more beneficial to gradually permeate into the main phase crystal grains along the surface layers of the main phase crystal grains, the bias aggregation layer of the heavy rare earth elements is formed in the crystal grains of the magnet, and finally the obtained magnet can effectively prevent the movement of the anti-magnetization domain into the crystal grains in the anti-demagnetization capability and the coercive force of the magnet. In addition, in the preparation process, a liquid curing agent is not needed, and auxiliary phases are not needed to be prepared into diffusion liquid, so that the process is further simplified, the introduction of other miscellaneous phases is reduced, and the production cost of the magnet is reduced.
According to the application, the neodymium-iron-boron rare earth permanent magnet with the heavy rare earth element segregation structure in the crystal grain can be applied to instruments and meters, microwave communication, wind power generation and electric automobiles.
The present application will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the application are shown. Unless otherwise indicated, all starting materials in the examples of the present application were purchased commercially.
Example 1
Obtaining main phase magnetic powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain main-phase magnetic powder;
the chemical formula of the main phase component: (Nd) 0.7 Y 0.3 ) 13.80 Fe 79.82 Al 0.24 Cu 0.10 B 6.04 (at％)；
Obtaining auxiliary alloy powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain auxiliary alloy powder;
the chemical formula of the auxiliary alloy is as follows: ho 76 Al 12 Ga 12 (wt.％)；
Preparation: adding the prepared auxiliary alloy powder into main phase magnetic powder according to the mass percentage of 3% of the total amount, uniformly mixing, performing magnetic field orientation molding to prepare a green body, then placing the green body into a high-vacuum sintering furnace for high-temperature sintering and tempering treatment, and finally obtaining the neodymium-iron-boron magnet with the element segregation structure in the crystal grains.
The specific sintering and tempering process comprises the following steps: vacuum degree of 1X 10 -4 Pa, sintering temperature is 1070 ℃, and sintering heat preservation time is 4h; the primary tempering temperature is 900 ℃, and the heat preservation time is 2 hours; the secondary tempering temperature is 500 ℃, and the heat preservation time is 2 hours.
The prepared magnet is placed in an open-circuit PFM permanent magnet material measuring system, and the magnetic performance is measured as follows: b (B) r ＝13.07kGs，H cj ＝11.46kOe，(BH) max ＝41.32MGOe。
Example 2
Obtaining main phase magnetic powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain main-phase magnetic powder;
the chemical formula of the main phase component: (Nd) 0.7 Y 0.3 ) 13.80 Fe 79.82 Al 0.24 Cu 0.10 B 6.04 (at％)；
Obtaining auxiliary alloy powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain auxiliary alloy powder;
the chemical formula of the auxiliary alloy is as follows: ho 76 Al 12 Ga 12 (wt.％)。
Preparation: adding the prepared auxiliary alloy powder into main phase magnetic powder according to the mass percentage of 7% of the total amount, uniformly mixing, performing magnetic field orientation molding to prepare a green body, and then placing the green body into a high-vacuum sintering furnace for high-temperature sintering and tempering treatment to finally obtain the neodymium-iron-boron magnet with the element segregation structure in the grains.
The specific sintering and tempering process comprises the following steps: vacuum degree of 1X 10 -4 Pa, sintering temperature is 1090 ℃, and sintering heat preservation time is 4h; the primary tempering temperature is 900 DEG CThe heat preservation time is 2 hours; the secondary tempering temperature is 500 ℃, and the heat preservation time is 2 hours.
The prepared magnet is placed in an open-circuit PFM permanent magnet material measuring system, and the magnetic performance is measured as follows: b (B) r ＝11.45kGs，H cj ＝13.74kOe，(BH) max ＝31.63MGOe。
Fig. 2 is a grain structure and elemental line scan of example 2. In fig. 2b, the ordinate indicates the element concentration; the distribution of Nd, Y and Ho element lines is sequentially from top to bottom. The shell layer refers to a crystal grain surface layer, and the region is diffused with heavy rare earth elements and can be called as a heavy rare earth element-rich shell layer; the core refers to the central area of the crystal grain and is also the main phase crystal grain core, and the heavy rare earth in the core area is little or even the heavy rare earth can not reach the area; the eccentric layer is positioned between the shell layer and the core, and heavy rare earth elements are eccentric in the area.
As can be seen from fig. 2 b: the heavy rare earth element Ho has an obvious segregation layer in the interior of the crystal grains; the concentration of Ho element in the core area is very low, the concentration at the bias aggregation layer is rapidly increased, and the concentration of Ho element in the bias aggregation layer is gradually reduced to be gentle from the bias aggregation layer to the shell layer. In addition, as can be seen from FIG. 2b, the thickness of the shell layer, i.e., the thickness of the heavy rare earth surface layer, is about 2 to 3.5 μm, and the thickness of the bias layer is about 0.5 to 1.5. Mu.m.
Fig. 3 is a graph showing a domain wall moving process and an elemental plane according to example 2. Wherein, (a 1) to (a 11) are migration processes of magnetic domain walls under different externally applied magnetic fields, and (b 1) to (b 5) are element plane distribution diagrams of Fe, nd, ho, Y of the corresponding regions.
As can be seen from fig. 3: the position indicated by the arrow is the position where the magnetic domain is blocked in the moving process, and the position is the position where the Ho element segregation layer is located (the Ho element segregation layer is located between the surface layer and the core of the crystal grain), so that the heavy rare earth Ho element segregation layer in the crystal grain can be judged to block the migration of the magnetic domain wall into the magnet, the anti-demagnetizing capability of the crystal grain is improved, and the coercive force of the magnet is further improved.
Example 3
Obtaining main phase magnetic powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain main-phase magnetic powder;
the chemical formula of the main phase component: (Pr, nd) 2 Fe 14 B(at％)；
Obtaining auxiliary alloy powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain auxiliary alloy powder;
the chemical formula of the auxiliary alloy is as follows: ho 76 Al 12 Ga 12 (wt.％)；
Preparation: adding the prepared auxiliary alloy powder into main phase magnetic powder according to the mass percentage of 7% of the total amount, uniformly mixing, performing magnetic field orientation molding to prepare a green body, and then placing the green body into a high-vacuum sintering furnace for high-temperature sintering and tempering treatment to finally obtain the neodymium-iron-boron magnet with the element segregation structure in the grains.
The specific sintering and tempering process comprises the following steps: vacuum degree of 1X 10 -4 Pa, sintering temperature is 1080 ℃, and sintering heat preservation time is 4 hours; the primary tempering temperature is 900 ℃, and the heat preservation time is 2 hours; the secondary tempering temperature is 500 ℃, and the heat preservation time is 2 hours.
The prepared magnet is placed in an open-circuit PFM permanent magnet material measuring system, and the magnetic performance is measured as follows: b (B) r ＝12.08kGs，H cj ＝19.20kOe，(BH) max ＝35.01MGOe。
Example 4
Obtaining main phase magnetic powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain main-phase magnetic powder;
the chemical formula of the main phase component: (Nd) 0.7 Y 0.3 ) 13.80 Fe 79.82 Al 0.24 Cu 0.10 B 6.04 (at％)；
Obtaining auxiliary phase powder: directly purchasing.
Auxiliary phase: hydrides of dysprosium (DyH) x )。
Preparation: adding the prepared auxiliary alloy powder into main phase magnetic powder according to the mass percentage of 3% of the total amount, uniformly mixing, performing magnetic field orientation molding to prepare a green body, then placing the green body into a high-vacuum sintering furnace for high-temperature sintering and tempering treatment, and finally obtaining the neodymium-iron-boron magnet with the element segregation structure in the crystal grains.
The specific sintering and tempering process comprises the following steps: vacuum degree of 1X 10 -4 Pa, sintering temperature is 1090 ℃, and sintering heat preservation time is 4h; the primary tempering temperature is 900 ℃, and the heat preservation time is 2 hours; the secondary tempering temperature is 500 ℃, and the heat preservation time is 2 hours.
The prepared magnet is placed in an open-circuit PFM permanent magnet material measuring system, and the magnetic performance is measured as follows: b (B) r ＝13.20kGs，H cj ＝14.52kOe，(BH) max ＝42.21MGOe。
The difference from example 1 is that: auxiliary phase DyH x The damage to the remanence of the magnet after the addition is smaller than that of the HoAlGa alloy in the embodiment 1, the improvement effect on the coercive force is higher than that of the HoAlGa alloy, and the maximum magnetic energy product of the final magnet is improved.
Example 5
Obtaining main phase magnetic powder: mixing the metal raw materials according to the proportion, performing quick setting smelting on the mixture to obtain alloy cast sheets, performing hydrogen breaking on the alloy cast sheets to obtain coarse powder, and performing air flow grinding on the coarse powder to obtain main-phase magnetic powder;
the chemical formula of the main phase component: (Nd) 0.7 Y 0.3 ) 13.80 Fe 79.82 Al 0.24 Cu 0.10 B 6.04 (at％)；
Obtaining auxiliary phase powder: directly purchasing.
The auxiliary phase is as follows: terbium fluoride (TbF) x )。
Preparation: adding the prepared auxiliary alloy powder into main phase magnetic powder according to the mass percentage of 3% of the total amount, uniformly mixing, performing magnetic field orientation molding to prepare a green body, then placing the green body into a high-vacuum sintering furnace for high-temperature sintering and tempering treatment, and finally obtaining the neodymium-iron-boron magnet with the element segregation structure in the crystal grains.
The specific sintering and tempering process comprises the following steps: vacuum degree of 1X 10 -4 Pa, sintering temperature is 1090 ℃, and sintering heat preservation time is 4h; the primary tempering temperature is 900 ℃ and the heat preservation time is long2h; the secondary tempering temperature is 500 ℃, and the heat preservation time is 2 hours.
The prepared magnet is placed in an open-circuit PFM permanent magnet material measuring system, and the magnetic performance is measured as follows: b (B) r ＝13.11kGs，H cj ＝16.73kOe，(BH) max ＝43.73MGOe。
The difference from example 1 is that: auxiliary phase TbF x The damage to the remanence of the magnet after the addition is smaller than that of the HoAlGa alloy in the embodiment 1, the improvement effect on the coercive force is higher than that of the HoAlGa alloy, and the maximum magnetic energy product of the final magnet is improved.
While the application has been described in terms of preferred embodiments, it will be understood by those skilled in the art that various changes and modifications can be made without departing from the scope of the application, and it is intended that the application is not limited to the specific embodiments disclosed.

Claims (12)

1. The neodymium-iron-boron rare earth permanent magnet with the heavy rare earth element segregation structure in the crystal grain is characterized in that the raw material consists of a main phase and an auxiliary phase, wherein the main phase is an alloy containing neodymium-iron-boron; the auxiliary phase is one or more selected from the hydride of the heavy rare earth, the fluoride of the heavy rare earth and the alloy of the heavy rare earth; the magnet crystal grain is provided with a heavy rare earth element segregation structure, wherein the heavy rare earth element diffuses into the main phase crystal grain to form a segregation layer and a heavy rare earth surface layer, the segregation layer is positioned on the inner side of the heavy rare earth surface layer, and the concentration of the heavy rare earth element is higher than that of the heavy rare earth surface layer.
2. The neodymium-iron-boron rare earth permanent magnet having a heavy rare earth element segregation structure in crystal grains according to claim 1, wherein the concentration of the heavy rare earth element of the segregation layer is increased by 0.1wt.% to 5wt.% as compared to the heavy rare earth surface layer.
3. The neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain according to claim 1, wherein the thickness of the segregation layer is 0.1 μm-2 μm.
4. The neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain according to claim 1, wherein the thickness of the heavy rare earth surface layer is 1-4 μm.
5. The neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in the crystal grain according to claim 1, wherein,
the heavy rare earth is one or more of Ho, dy, tb, gd, er, tm, yb, lu, sc, Y in the heavy rare earth hydride, the heavy rare earth fluoride and the heavy rare earth alloy;
the heavy rare earth alloy is an alloy formed by the heavy rare earth and at least one selected from aluminum, gallium, copper and zinc.
6. The neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain according to claim 1, wherein the composition of the alloy of heavy rare earth is expressed as: RE (RE) ， b N ， c ；
Wherein b ranges from 40 to 90; c ranges from 60 to 10; b+c=100;
RE ， is one or more of Ho, dy, tb, gd, er, tm, yb, lu, sc, Y;
N ， is one or more of Ga, al, cu, zn.
7. The neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain according to claim 1, wherein the auxiliary phase amount is 0.1% -20% of the total amount of main phase and auxiliary phase.
8. The neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grains according to claim 1, wherein the composition of the main phase is: RE (RE) α B β M γ N δ Fe 100-α-β-γ-δ ；
Wherein, in terms of mass percent, alpha is more than or equal to 25 and less than or equal to 35,0.94, beta is more than or equal to 1.10,0 and less than or equal to gamma is more than or equal to 10, and delta is more than or equal to 0 and less than or equal to 10;
RE is Nd, or Nd and one or more selected from La, ce, pr, pm, sm, eu, gd, tb, dy, ho, er, tm, yb, lu, Y and Sc; b is boron element; fe is iron element;
when γ+.0, M is one or more of Co, ni, mn, cr, cu, zn, ti, V, zr, nb;
when δ+.0, N is one or more of Ga, al, sn, ge.
9. A method for producing a neodymium-iron-boron rare earth permanent magnet having a heavy rare earth element segregation structure in a crystal grain according to any one of claims 1 to 8, comprising:
obtaining main phase magnetic powder and auxiliary phase powder; mixing main phase magnetic powder and auxiliary phase powder;
and (3) carrying out orientation molding on the mixed materials to obtain a magnet green body, carrying out sintering and tempering treatment on the magnet green body, and diffusing heavy rare earth elements into main phase grains to form a heavy rare earth surface layer and a segregation layer, wherein the segregation layer is positioned at the inner side of the heavy rare earth surface layer and has the concentration of the heavy rare earth higher than that of the heavy rare earth surface layer, so as to obtain the neodymium-iron-boron rare earth permanent magnet with the heavy rare earth element segregation structure in the grains.
10. The method according to claim 9, wherein in the step of obtaining the main phase magnetic powder and the auxiliary phase powder, the main phase magnetic powder is prepared by a rapid solidification smelting, hydrogen breaking and air flow grinding method; when the auxiliary phase is an alloy of heavy rare earth, preparing auxiliary phase powder by adopting a quick setting smelting, hydrogen breaking and air flow grinding method or an induction smelting post-breaking method.
11. The method according to claim 9, wherein the sintering is performed under vacuum, the degree of vacuum being 1X 10 -4 Pa～1×10 -2 Pa; the sintering temperature is 900-1200 ℃; the sintering time is 1-10 h;
the tempering treatment adopts two-stage tempering treatment; the primary tempering temperature is 800-1000 ℃ and the time is 1-6 h; the secondary tempering temperature is 400-650 ℃ and the time is 1-6 h.
12. Use of a neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in a crystal grain according to any one of claims 1-8 in instruments and meters, microwave communication, wind power generation and electric vehicles.
CN202311043405.9A 2023-08-18 2023-08-18 Neodymium-iron-boron rare earth permanent magnet with heavy rare earth element segregation structure in crystal grain, and preparation method and application thereof Pending CN117059357A (en)

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