CN106653268B - The preparation method of high performance sintered Nd-Fe-B magnets and its product of preparation with crystal boundary sandwich construction - Google Patents

The preparation method of high performance sintered Nd-Fe-B magnets and its product of preparation with crystal boundary sandwich construction Download PDF

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CN106653268B
CN106653268B CN201611150742.8A CN201611150742A CN106653268B CN 106653268 B CN106653268 B CN 106653268B CN 201611150742 A CN201611150742 A CN 201611150742A CN 106653268 B CN106653268 B CN 106653268B
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rare earth
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张培
胡梅娟
吴敏
张雷
张鹏国
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Institute of Materials of CAEP
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    • 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
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    • 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
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    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
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    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/02—Compacting only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
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    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/10—Sintering only
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
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    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles
    • 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
    • H01F1/0576—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 pressed, e.g. hot working
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    • 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
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    • B22F3/24—After-treatment of workpieces or articles
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    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
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Abstract

The invention discloses a kind of preparation method of high performance sintered Nd Fe B magnets and its product of preparation with crystal boundary sandwich construction, purpose is to solve the problems such as existing method can not realize finely regulating to grain boundary structure, cause intercrystalline strengthening single effect, heavy rare earth serious waste of resources.Magnet multilayer grain boundary structure prepared by the present invention, the heavy rare earth shell layer for being distributed in main phase grain border has higher magnetocrystalline anisotropy field, therefore the magnetic domain reversion of the crystal boundary weakness zone in opposing magnetic field can be suppressed, and then improve the coercivity and high-temperature stability of magnet.Meanwhile heavy rare earth shell layer is only distributed in main phase grain border, is seldom diffused into principal phase and crystal boundary central area, heavy rare earth dosage can be greatly reduced, reduce magnet generation cost.In addition, in magnet of the present invention high potential crystal boundary central core formation, Grain-Boundary Phase and Nd can be reduced2Fe14The difference in Electrode Potential of B principal phases, reduces electrochemical corrosion driving force, hence it is evident that improve the corrosion resistance of magnet.

Description

The preparation method of high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction and Its product prepared
Technical field
The present invention relates to Material Field, especially permanent-magnet material field, is specially a kind of height with crystal boundary sandwich construction The preparation method of performance sintered nd-fe-b magnet and its product of preparation.
Background technology
Nd-Fe-B magnets have excellent magnetic property, have become most widely used Rare Earth Functional Materials.More than 30 The development in year, sintered nd-fe-b magnet have become essential material, quilt in social and economic construction and people's daily life It is widely used in the every field such as aerospace, generator, electronic computer, automobile, communication, medical instrument.Nd-Fe-B magnets Remanent magnetism and maximum magnetic energy product have reached the 97% and more than 93% of theoretical value respectively, but the coercivity of magnet is less than theoretical value Half, and the corrosion resistance of magnet is very poor, the two main problems become the widely applied maximum of sintered nd-fe-b magnet Limiting factor.
The principal phase of neodymium iron boron magnetic body is Nd2Fe14B hard magnetic phases, Grain-Boundary Phase are rich-Nd phase.Wherein, the component of Grain-Boundary Phase, structure Having with distribution on magnet magnetic property, corrosion resistance and mechanical performance obviously influences.
In recent years, as Oversea wind power generation, hybrid vehicle develop rapidly, and the support of national policy, it is right The demand of high thermal stability magnet will be increasing, and corrosion resistance to magnet and service life will also propose higher will Ask.
At present, researcher mainly added by alloying, the technology such as crystal boundary modified and grain boundary decision, realize to Grain-Boundary Phase Strengthen, so as to improve magnet performance.In terms of intercrystalline strengthening mechanism, the coercivity of magnet is improved, it is necessary on main phase grain border Form the heavy rare earth shell layer of a floor height magnetocrystalline anisotropy；The corrosion resistance of magnet is improved, to form high potential in crystal boundary Stablize Grain-Boundary Phase；The continuity of Grain-Boundary Phase is improved, it is necessary to reduce Grain-Boundary Phase fusing point, and improve its wetability with principal phase.
Researcher mainly realizes reinforcing to Grain-Boundary Phase by alloying addition and crystal boundary modified and reconstruct method, so that Improve the coercivity and corrosion resistance of Sintered NdFeB magnet.Based on pairing gold process, tight seminar utilizes Dy71.5Fe28.5 With Dy32.5Fe62Cu5.5Alloy has carried out Sintered NdFeB magnet crystal boundary modified.Research finds, the low melting point heavy rare earth of addition Crystal boundary modified alloy forms (Nd, Dy) in magnet sintering process2Fe14The heavy rare earth shell of B, the magnetocrystalline for improving crystal boundary are each Anisotropy field, so as to improve the coercivity of magnet.Yue et al. have studied nanometer Tb, Dy powder crystal circle addition to magnet coercivity Influence.When the additive amount of Tb is only 0.4 at.%, the coercivity of magnet brings up to 20 kOe or so from 12 kOe, together When remanent magnetism remain at 1.36 T, equally, nanometer Dy powder crystal boundary addition in the case of, be similarly formed uniform magnetic hardening Shell, coercitive raising effect are obvious.
Unliterary sword et al. have studied the crystal boundary modified influences to sintered nd-fe-b magnet corrosion resistance of MgO.The crystalline substance of magnet Boundary mutually forms the Nd-O-Fe-Mg phases of chemical property stabilization due to the addition of MgO, these stable phase integrated distributions are in crystal boundary, resistance Hinder propagation of the corrosion along rich-Nd phase, improve the chemical stability and electrochemical stability of Grain-Boundary Phase.Tight seminar uses Nd64Co36High potential alloyed powder carries out crystal boundary reconstruct to the neodymium iron boron main-phase alloy of low content of rare earth, and it is steady to form chemical property Fixed Grain-Boundary Phase, greatly reduces the potential difference between Grain-Boundary Phase and principal phase, while magnetic property is kept on magnetic greatly improved The intrinsic corrosion resistance of body.
At present, Grain-Boundary Phase is often studied its fusing point, magnetocrystalline anisotropy field and the change of corrosion potential as an entirety Change, can not realize the finely regulating to grain boundary structure, cause intercrystalline strengthening single effect, heavy rare earth serious waste of resources etc. to be asked Topic.
The content of the invention
At present, existing research is studied using Grain-Boundary Phase as an entirety, strengthens crystal boundary by different methods, The finely regulating to crystal boundary internal structure is not realized, so as to cause unnecessary waste.It is for example, brilliant in heavy rare earth alloy In boundary's modification and reconstruct, the formation of the heavy rare earth shell on main phase grain border can effectively improve magnet coercivity, and remaining big Part heavy rare earth element concentrates on crystal boundary central area, causes unnecessary waste.Meanwhile reconstructed in high potential alloy crystal boundary In magnet, grain boundaries form continuous stable Grain-Boundary Phase, and the intrinsic corrosion resistance of magnet greatly improved, but in order to reduce Cost, general high potential reconstruct in alloy and do not contain heavy rare earth element, so being lifted to coercivity little.
At present, it can not also realize and be substantially improved while neodymium iron boron magnetic body coercivity and corrosion resistance.Applicant studies After think, mainly due under current process conditions, crystal ingedient and structure can not realize finely regulating, can't be same for this Magnetic exchange coupling effect between the magnetic reversal farmland forming core field of time control combinations circle, grain boundary potentials and stability, and main phase grain.
The finely regulating to grain boundary structure can not be realized for existing method, cause intercrystalline strengthening single effect, weight dilute Soil resource wastes the problems such as serious, there is provided a kind of preparation side of the high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction Method and its product of preparation.The present invention prepares the sintering with crystal boundary sandwich construction using pairing gold process and double sintering technology Neodymium iron boron magnetic body, by the finely regulating to grain boundary structure, realizes comprehensive raising of magnet magnetic property and corrosion resistance.This hair The magnet of bright preparation has heavy rare earth shell layer/high potential crystal boundary central core/heavy rare earth shell layer multi-layer grain boundary structure.Wherein, The heavy rare earth shell layer for being distributed in main phase grain border has higher magnetocrystalline anisotropy field, therefore can suppress in reverse magnetic The magnetic domain reversion of crystal boundary weakness zone in, and then improve the coercivity and high-temperature stability of magnet.Meanwhile heavy rare earth shell layer Main phase grain border is only distributed in, is seldom diffused into principal phase and crystal boundary central area, heavy rare earth dosage can be greatly reduced, reduces magnetic Body production cost.In addition, in magnet of the present invention high potential crystal boundary central core formation, Grain-Boundary Phase and Nd can be reduced2Fe14B principal phases Difference in Electrode Potential, reduce electrochemical corrosion driving force, hence it is evident that improve the corrosion resistance of magnet.
To achieve these goals, the present invention adopts the following technical scheme that：
The preparation method of high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction, includes the following steps：
（1）Prepare intermediate
By the neodymium iron boron principal phase powder of low content of rare earth and low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1yAfter mixing, obtain To the first mixture, the first mixture is heated to low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1yMore than fusing point, and heat Temperature is less than 1100 DEG C, neodymium iron boron main phase grain edge is formed the heavy rare earth shell layer of a floor height magnetocrystalline anisotropy, obtains Intermediate；
（2）Prepare product
By step（1）After the intermediate of preparation crushes, with low melting point high potential crystal boundary reconstruct alloyed powder R2mM2nMixing, obtains To the second mixture, after the second mixture is carried out magnetic field orientating shaping, it is sintered, is heat-treated successively, up to product.
The particle mean size of the neodymium iron boron principal phase powder of the low content of rare earth is less than 5 μm, and rare earth element content is less than 29 Wt.%, Nd2Fe14B phases proportion is more than 95 %.
The low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1yIn, R1 is one kind in lanthanide series metal Gd, Tb, Dy, Ho Or a variety of, the one or more in M1 O, F, H, Cu, Ni, Fe, Co, Sn, Ti, Nb, Zr, x, y are respectively the atom hundred of R1, M1 Fraction, the scope of x are 5 ~ 80, x and y's and be 100.
The low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1yFusing point be less than 900 DEG C.
The low melting point high potential crystal boundary reconstruct alloyed powder R2mM2nIn, R2 for lanthanide series metal La, Ce, Pr, Nd, Sm, Gd, One or more in Tb, Dy, Ho, M2 are the one or more in high standard electrode potential Ni metal, Ni, Fe, Co, and m, n divide Not Wei R2, M2 atomic percentage, m and n's and be 100, m scope be 5 ~ 80.
The low melting point high potential crystal boundary reconstruct alloyed powder R2mM2nFusing point be less than 900 DEG C.
The low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1y, low melting point high potential crystal boundary reconstruct alloyed powder R2mM2n Granularity for respectively 0.1-100 μm.
The step（2）In, after the second mixture is carried out magnetic field orientating shaping, it is sintered, sintering temperature 950- 1100 DEG C, sintering time 2-5h, two-stage heat treatment is then carried out, level-one heat treatment temperature is 850-950 DEG C, and soaking time is 1-5h, two level heat treatment temperature are 300-600 DEG C, soaking time 1-5h, up to product.
Using the product prepared by preceding method.
For foregoing problems, the present invention provides a kind of high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction Preparation method and its product of preparation, i.e., it is a kind of to improve sintered NdFeB comprehensively（Nd-Fe-B）Magnet magnetic property, corrosion resistance The Sintered NdFeB magnet with crystal boundary sandwich construction design and preparation method.
This method mainly includes herein below：（1）By the way that neodymium iron boron principal phase powder and the low melting point weight of low content of rare earth is dilute Native crystal boundary reconstruct alloyed powder mixing, heat treatment, in Nd2Fe14The weight that B main phase grains edge forms a floor height magnetocrystalline anisotropy is dilute Native shell layer, up to intermediate；（2）Principal phase powder with heavy rare earth shell layer is crushed（After the intermediate prepared crushes）, And mixed with low melting point high potential crystal boundary reconstruct alloyed powder, then be molded through magnetic field orientating, and after sintering, being heat-treated, prepare Sintered NdFeB magnet with heavy rare earth shell layer/high potential crystal boundary central core/heavy rare earth shell layer multi-layer grain boundary structure.
In the present invention, low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1yThe side quickly cooled down using melting and rejection tablet Method, under low content of rare earth, obtains Nd as much as possible2Fe14B principal phases, then by the way that hydrogen is quick-fried average is obtained with airflow milling method Particle size is less than 5 μm of principal phase powder.
Low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1y, low melting point high potential crystal boundary reconstruct alloyed powder R2mM2nMaking When standby, according to enthalpy of mixing between alloy phase diagram, element and elemental standards electrode potential, two kinds of crystal boundaries for designing low melting point reconstruct alloy Component, alloy pig is prepared using vacuum arc melting or vacuum induction melting, followed by modes such as ball milling or airflow millings By alloy breaks down into granularity be 0.1-100 μm of powder.
In the present invention, low rare earth principal phase powder is uniformly mixed with low melting point heavy rare earth crystal boundary reconstruct alloyed powder, and is reconstructing More than powder fusing point carry out vacuum heat so that crystal boundary reconstruct powder fusing, and be evenly distributed on around main phase grain, it is being heat-treated During react with principal phase, generate magnetocrystalline anisotropy field higher heavy rare earth shell layer, and then improve magnet coercivity, Prepare intermediate.
The intermediate of preparation is broken into powder again, and alloyed powder R2 is reconstructed with low melting point high potential crystal boundarymM2nIt is uniformly mixed Close, be molded afterwards by magnetic field orientating, sintered at 950-1100 DEG C and keep the temperature 2-5 it is small when, then carried out at 850-950 DEG C Level-one heat treatment 1-5 it is small when, then at 300-600 DEG C two level heat treatment 1-5 it is small when, after cooling, obtain product.In this process In, low melting point high potential grain boundary alloys can melt, and be distributed at crystal boundary center, greatly reduce the current potential of principal phase and Grain-Boundary Phase Difference, improves magnet corrosion resistance.
In conclusion applicant on the basis of studying for a long period of time, by the finely regulating to grain boundary structure, realizes magnet Comprehensive performance is obviously improved, and has in-depth study to its Physiochemical mechanism.The present invention is based on pairing gold process and two Secondary sintering technology, forms the thin heavy rare earth shell of high magnetocrystalline anisotropy on main phase grain border, and in crystal boundary central area shape Stablize Grain-Boundary Phase into high potential, prepare brilliant with heavy rare earth shell layer/high potential crystal boundary central core/heavy rare earth shell layer multi-layer The neodymium iron boron magnetic body of boundary's structure, reaches while the coercivity and corrosion resistance of neodymium iron boron magnetic body is improved, weight is greatly reduced The purpose of rare-earth usage.
As shown in Figure 1, 2, the essence to crystal boundary internal structure is realized compared to traditional Sintered NdFeB magnet, the present invention Fine tuning control so that heavy rare earth element is only distributed in the heavy rare earth shell of high magnetocrystalline anisotropy, and crystal boundary center is mainly then High potential stablizes Grain-Boundary Phase.In Fig. 1, core Nd2Fe14B principal phases, the edge of core is richness Nd Grain-Boundary Phases.
The present invention is measured, test result indicates that, the formation of heavy rare earth shell layer substantially increases the magnetic of Grain-Boundary Phase Anisotropic crystalline fieldH A, and then improve the coercivity of magnetH cj；The formation of high potential crystal boundary central core substantially reduces crystal boundary Phase and Nd2Fe14The potential difference of B principal phases, i.e. electrochemical corrosion driving force, and then improve the corrosion resistance of magnet.The present invention The Sintered NdFeB magnet with crystal boundary sandwich construction, at room temperature coercivity can reach 19 more than kOe, heavy rare earth additive amount Less than 1 wt.%；Corrosion potential in 3.5 wt.% sodium-chloride water solutions is higher than -0.75V, at 120 DEG C, 2 atmospheric pressure and In the environment of 100% relative humidity, weight loss when corrosion 96 is small is less than 0.7mg/cm2。
The present invention prepares the multilayer grain boundary structure met the requirements, and to prepare and use in magnet by finely regulating During, the stability of the sandwich construction is effectively maintained, significantly improves the magnetic property and corrosion resistance of magnet, heavy rare earth dosage Less than equal coercivity commercialization magnet, there is higher application value and economic value.
Brief description of the drawings
Examples of the present invention will be described by way of reference to the accompanying drawings, wherein：
Fig. 1 is traditional Sintered NdFeB magnet structure diagram.
Fig. 2 is product structure schematic diagram prepared by the present invention.
Embodiment
All features disclosed in this specification, or disclosed all methods or during the step of, except mutually exclusive Feature and/or step beyond, can combine in any way.
Any feature disclosed in this specification, unless specifically stated, can be equivalent by other or with similar purpose Alternative features are replaced.I.e., unless specifically stated, each feature is an example in a series of equivalent or similar characteristics .
Embodiment 1
（1）Prepare the neodymium iron boron principal phase powder of low content of rare earth
First prepare the Nd-Fe-B principal phase powder of low content of rare earth, component Nd12.3FebalB6.1.It is quick using melting and rejection tablet The method of cooling, is made neodymium iron boron rapid hardening thin slice.Then, by the way that hydrogen is quick-fried and air-flow grinding process, obtaining average particle size particle size is about 3.8 μm of principal phase powder.
（2）Prepare crystal boundary reconstruct alloy
According to enthalpy of mixing between alloy phase diagram, element, design low melting point heavy rare earth crystal boundary reconstruct alloying component, it is desirable in alloy Containing more heavy rare earth element, while fusing point is relatively low, can be melted in heat treatment process and be evenly distributed on main phase grain week Enclose.
Inventor selects Dy-Fe binary eutectic point components Ds y71.5Fe28.5（Atomic percent）Reconstructed as heavy rare earth crystal boundary Alloy（That is low melting point heavy rare earth crystal boundary reconstruct alloy）, its fusing point is 890 DEG C.Afterwards, selected according to the standard electrode potential of element The binary eutectic point component Nd of Nd-Co is selected64Co36（Atomic percent）Alloy is reconstructed as high potential crystal boundary（I.e. low melting point is high Current potential crystal boundary reconstructs alloy）, its fusing point is 566 DEG C.Then, two kinds of crystal boundaries are prepared for by electric arc melting and reconstruct alloy pig, and The alloy powder that granularity is about 1.7 μm is prepared by ball milling.
（3）Prepare product
Principal phase powder and heavy rare earth alloy powder Dy prepared by step 171.5Fe28.5Uniformly after mixing, at 980 DEG C, Vacuum Heat Handle 2 it is small when, obtain intermediate.By the mixed-powder after heat treatment（The intermediate obtained）It is broken, scattered, and and high potential Alloyed powder Nd64Co36Uniformly mixing；Wherein, low rare earth principal phase powder：Heavy rare earth grain boundary alloys powder：The matter of high potential grain boundary alloys powder Amount is than being 97:1:2.After mixed powder, magnetic field orientating shaping is carried out under 1.6 T, 200 MPa；Afterwards, sintering 4 is small at 1075 DEG C When, then when heat treatment 2 is small at 890 DEG C, when then heat treatment 2 is small at 400 DEG C, being made has the heavy rare earth shell layer/height electric The neodymium iron boron magnetic body of position crystal boundary central core/heavy rare earth shell layer multi-layer grain boundary structure.
After measured, the obtained neodymium iron boron magnetic body with multilayer grain boundary structure of the present embodiment, its coercivity are 19.18 KOe, corrosion potential of the magnet in 25 DEG C, 3.5 wt.% sodium chloride solutions are -0.753 V；Magnet is at 120 DEG C, 2 atmospheric pressure It is 0.47 mg/cm with weight loss when corrosion 96 is small in the environment of 100% relative humidity2。
Embodiment 2
（1）Prepare the Nd-Fe-B principal phase powder of low content of rare earth
First prepare the Nd-Fe-B principal phase powder of low content of rare earth, component Nd12.3FebalB6.1.It is quick using melting and rejection tablet The method of cooling, is made neodymium iron boron rapid hardening thin slice.Then, by the way that hydrogen is quick-fried and air-flow grinding process, obtaining average particle size particle size is about 3.8 μm of principal phase powder.
（2）Prepare crystal boundary reconstruct alloy
According to enthalpy of mixing between alloy phase diagram, element, design low melting point heavy rare earth crystal boundary reconstruct alloying component, it is desirable in alloy Containing more heavy rare earth element, while fusing point is relatively low, can be melted in heat treatment process and be evenly distributed on main phase grain week Enclose.
Inventor selects Dy-Fe binary eutectic point components Tb71.5Fe28.5（Atomic percent）Reconstructed as heavy rare earth crystal boundary Alloy.Afterwards, the binary eutectic point component Nd of Nd-Co is have selected according to the standard electrode potential of element64Co36（Atomic percent Than）Alloy is reconstructed as high potential crystal boundary, its fusing point is 566 DEG C.Then, two kinds of crystal boundary reconstruct are prepared for by electric arc melting to close Ingot, and the alloy powder that granularity is about 1.7 μm is prepared by ball milling.
（3）Prepare product
By step（1）The principal phase powder and heavy rare earth alloy powder Tb of preparation71.5Fe28.5After uniformly mixing, at 980 DEG C, Vacuum Heat Handle 2 it is small when, obtain intermediate.Mixed-powder after heat treatment is crushed, is disperseed, and with high potential alloyed powder Nd64Co36 Even mixing；Wherein；Low rare earth principal phase powder：Heavy rare earth grain boundary alloys powder：The mass ratio of high potential grain boundary alloys powder is 96:2:2.It is mixed After powder, magnetic field orientating shaping is carried out under 1.6 T, 200 MPa；Afterwards, when sintering 4 is small at 1080 DEG C, then the heat at 890 DEG C Handle 2 it is small when, then at 400 DEG C heat treatment 2 it is small when, be made have heavy rare earth shell layer/high potential crystal boundary central core/weight it is dilute The neodymium iron boron magnetic body of native shell layer multi-layer grain boundary structure.
After measured, the neodymium iron boron magnetic body manufactured in the present embodiment with multilayer grain boundary structure, its coercivity are 23.33 KOe, corrosion potential of the magnet in 25 DEG C, 3.5 wt.% sodium chloride solutions are -0.796 V；Magnet is at 120 DEG C, 2 atmospheric pressure It is 0.53 mg/cm with weight loss when corrosion 96 is small in the environment of 100% relative humidity2。
Embodiment 3
（1）Prepare the neodymium iron boron principal phase powder of low content of rare earth
First prepare the Nd-Fe-B principal phase powder of low content of rare earth, component Nd12.3FebalB6.1.It is quick using melting and rejection tablet The method of cooling, is made neodymium iron boron rapid hardening thin slice.Then, by the way that hydrogen is quick-fried and the method for airflow milling, average particle size particle size is obtained about For 3.8 μm of principal phase powder.
（2）Prepare crystal boundary reconstruct alloy
According to enthalpy of mixing between alloy phase diagram, element, design low melting point heavy rare earth crystal boundary reconstruct alloying component, it is desirable in alloy Containing more heavy rare earth element, while fusing point is relatively low, can be melted in heat treatment process and be evenly distributed on main phase grain week Enclose.
We have selected Dy-Fe binary eutectics point components D y71.5Fe28.5（Atomic percent）Reconstructed as heavy rare earth crystal boundary Alloy, its fusing point are 890 DEG C.Afterwards, the binary eutectic point component of Nd-Co is have selected according to the standard electrode potential of element Nd65Ni35（Atomic percent）Alloy is reconstructed as high potential crystal boundary, its fusing point is 535 DEG C.Then, prepared by electric arc melting Two kinds of crystal boundaries reconstruct alloy pigs, and the alloy powder that granularity is about 1.7 μm prepared by ball milling.
（3）Prepare product
By step（1）The Nd-Fe-B principal phases powder and heavy rare earth alloy powder Dy of preparation71.5Fe28.5Uniformly after mixing, at 980 DEG C Under, when vacuum heat 2 is small, obtain intermediate.Mixed-powder after heat treatment is crushed, is disperseed, and with high potential alloyed powder Nd65Ni35Uniformly mixing；Wherein, low rare earth principal phase powder：Heavy rare earth grain boundary alloys powder：The mass ratio of high potential grain boundary alloys powder is 96:1:3.After mixed powder, magnetic field orientating shaping is carried out under 1.6 T, 200 MPa；Afterwards, when sintering 4 is small at 1075 DEG C, then When heat treatment 2 is small at 890 DEG C, when then heat treatment 2 is small at 500 DEG C, being made has in heavy rare earth shell layer/high potential crystal boundary The neodymium iron boron magnetic body of central layer/heavy rare earth shell layer multi-layer grain boundary structure.
After measured, the neodymium iron boron magnetic body manufactured in the present embodiment with multilayer grain boundary structure, its coercivity are 19.97 KOe, corrosion potential of the magnet in 25 DEG C, 3.5 wt.% sodium chloride solutions are -0.750 V；Magnet is at 120 DEG C, 2 atmospheric pressure It is 0.42 mg/cm with weight loss when corrosion 96 is small in the environment of 100% relative humidity2。
Embodiment 4
First prepare the Nd-Fe-B principal phase powder of low content of rare earth, component Nd12.3FebalB6.1.It is quick using melting and rejection tablet The method of cooling, is made neodymium iron boron rapid hardening thin slice.Then, by the way that hydrogen is quick-fried and air-flow grinding process, obtaining average particle size particle size is about 3.8 μm of principal phase powder.
（2）Prepare crystal boundary reconstruct alloy
According to enthalpy of mixing between alloy phase diagram, element, design low melting point heavy rare earth crystal boundary reconstruct alloying component, it is desirable in alloy Containing more heavy rare earth element, while fusing point is relatively low, can be melted in heat treatment process and be evenly distributed on main phase grain week Enclose.
We have selected Dy-Fe binary eutectics point components D y71.5Fe28.5（Atomic percent）Reconstructed as heavy rare earth crystal boundary Alloy, its fusing point are 890 DEG C.Afterwards, the Nd of more high potential is have selected according to the standard electrode potential of element30Co65Cu5（Atom Percentage）Alloy is reconstructed as high potential crystal boundary, its fusing point is 605 DEG C.Then, two kinds of crystal boundary weights are prepared for by electric arc melting Structure alloy pig, and the alloy powder that granularity is about 1.7 μm is prepared by ball milling.
（3）Prepare product
By step（1）The Nd-Fe-B principal phases powder and heavy rare earth alloy powder Dy of preparation71.5Fe28.5Uniformly mixing, at 980 DEG C When vacuum heat 2 is small, intermediate is obtained.By the mixed-powder after heat treatment（The intermediate obtained）It is broken, scattered, and with High potential alloyed powder Nd30Co65Cu5Uniformly mixing；Wherein, low rare earth principal phase powder：Heavy rare earth grain boundary alloys powder：High potential crystal boundary closes The mass ratio of bronze is 97:1:2.After mixed powder, magnetic field orientating shaping is carried out under 1.6 T, 200 MPa；Afterwards, at 1075 DEG C Sinter 4 it is small when, then at 890 DEG C heat treatment 2 it is small when, then at 400 DEG C heat treatment 2 it is small when, be made there is heavy rare earth shell The neodymium iron boron magnetic body of layer/high potential crystal boundary central core/heavy rare earth shell layer multi-layer grain boundary structure.
After measured, the neodymium iron boron magnetic body manufactured in the present embodiment with multilayer grain boundary structure, its coercivity are 20.14 KOe, corrosion potential of the magnet in 25 DEG C, 3.5 wt.% sodium chloride solutions are -0.711 V；Magnet is at 120 DEG C, 2 atmospheric pressure It is 0.40 mg/cm with weight loss when corrosion 96 is small in the environment of 100% relative humidity2。
The invention is not limited in foregoing embodiment.The present invention, which expands to, any in the present specification to be disclosed New feature or any new combination, and disclose any new method or process the step of or any new combination.

Claims (7)

1. the preparation method of the high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction, it is characterised in that including following step Suddenly：
（1）Prepare intermediate
By the neodymium iron boron principal phase powder of low content of rare earth and low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1yAfter mixing, is obtained One mixture, low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1 is heated to by the first mixturexM1yIt is more than fusing point, and heating-up temperature Less than 1100 DEG C, neodymium iron boron main phase grain edge is formed the heavy rare earth shell layer of a floor height magnetocrystalline anisotropy, obtain centre Body；
（2）Prepare product
By step（1）After the intermediate of preparation crushes, with low melting point high potential crystal boundary reconstruct alloyed powder R2mM2nMixing, obtains the Two mixtures, after the second mixture is carried out magnetic field orientating shaping, are sintered, are heat-treated, up to product successively；
In the neodymium iron boron principal phase powder of the low content of rare earth, rare earth element content is less than 29 wt.%；
The low melting point heavy rare earth crystal boundary reconstruct alloyed powder R1xM1yIn, R1 is one kind or more in lanthanide series metal Gd, Tb, Dy, Ho Kind, the one or more in M1 O, F, H, Cu, Ni, Fe, Co, Sn, Ti, Nb, Zr, x, y are respectively the atomic percent of R1, M1 Number, the scope of x are 5 ~ 80, x and y's and be 100；
The low melting point high potential crystal boundary reconstruct alloyed powder R2mM2nIn, R2 for lanthanide series metal La, Ce, Pr, Nd, Sm, Gd, Tb, One or more in Dy, Ho, M2 are the one or more in high standard electrode potential Ni metal, Ni, Fe, Co, and m, n are respectively The atomic percentage of R2, M2, m and n's and be 100, m scope be 5 ~ 80.
2. the preparation method of the high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction according to claim 1, it is special Sign is that the particle mean size of the neodymium iron boron principal phase powder of the low content of rare earth is less than 5 μm, Nd2Fe14B phases proportion is more than 95 %。
3. the preparation method of the high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction according to claim 1, it is special Sign is that the low melting point heavy rare earth crystal boundary reconstructs alloyed powder R1xM1yFusing point be less than 900 DEG C.
4. the preparation method of the high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction according to claim 1, it is special Sign is that the low melting point high potential crystal boundary reconstructs alloyed powder R2mM2nFusing point be less than 900 DEG C.
5. the preparation method of the high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction according to claim 1, it is special Sign is that the low melting point heavy rare earth crystal boundary reconstructs alloyed powder R1xM1y, low melting point high potential crystal boundary reconstruct alloyed powder R2mM2n's Granularity is 0.1-100 μm respectively.
6. the preparation of the high performance sintered Nd-Fe-B magnets with crystal boundary sandwich construction according to claim any one of 1-5 Method, it is characterised in that the step（2）In, after the second mixture is carried out magnetic field orientating shaping, it is sintered, sintering temperature Spend for 950-1100 DEG C, sintering time 2-5h, then carry out two-stage heat treatment, level-one heat treatment temperature is 850-950 DEG C, is protected The warm time is 1-5h, and two level heat treatment temperature is 300-600 DEG C, soaking time 1-5h, up to product.
7. using the product prepared by any one of preceding claims 1 ~ 6 the method.
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