WO2024114167A1 - 一种烧结钕铁硼磁体及其制备方法 - Google Patents

一种烧结钕铁硼磁体及其制备方法 Download PDF

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Publication number
WO2024114167A1
WO2024114167A1 PCT/CN2023/125800 CN2023125800W WO2024114167A1 WO 2024114167 A1 WO2024114167 A1 WO 2024114167A1 CN 2023125800 W CN2023125800 W CN 2023125800W WO 2024114167 A1 WO2024114167 A1 WO 2024114167A1
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alloy
magnet
sintered ndfeb
diffusion
ndfeb magnet
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PCT/CN2023/125800
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English (en)
French (fr)
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李志学
曹利军
程言志
李绍芳
赵凯
杜飞
韩雪
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北京中科三环高技术股份有限公司
天津三环乐喜新材料有限公司
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Publication of WO2024114167A1 publication Critical patent/WO2024114167A1/zh

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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
    • 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

Definitions

  • the purpose of the present disclosure is to provide a sintered NdFeB magnet and a preparation method thereof, which can promote the diffusion of heavy rare earth elements to the central area of the sintered magnet in the grain boundary diffusion process, and further improve the comprehensive magnetic properties of the sintered NdFeB magnet.
  • the first aspect of the present disclosure provides a sintered NdFeB magnet, which comprises a main phase and a grain boundary phase, wherein the ratio of the average size of the main phase grains in the surface layer of the magnet to the average size of the main phase grains in the center region of the magnet is 1.05 to 1.35;
  • R is a rare earth element, and the rare earth element is Nd, or a combination of Nd and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb, Dy, Tb and Lu, based on the total weight of the sintered NdFeB magnet, the content of RE is 0.5-6.5wt%, and RE is Dy and/or Tb;
  • T is Fe, or Fe and Co, wherein the content of Fe in T is 80 wt % or more.
  • the grain boundary phase includes a triangular region grain boundary phase; among the triangular region grain boundary phases, the number of small-area triangular region grain boundary phases accounts for more than 80% of the total number of all the triangular region grain boundary phases; the small-area triangular region grain boundary phase is a triangular region grain boundary phase with an area less than 2.5 ⁇ m 2 .
  • the sum of the maximum magnetic energy product (BH) max and the intrinsic coercive force HcJ of the sintered NdFeB magnet is greater than 80; and the remanence Br is greater than 13KGs; the unit of the maximum magnetic energy product (BH) max is MGOe, and the unit of the intrinsic coercive force HcJ is KOe.
  • the ratio of the average size of the main phase grains in the surface layer of the magnet to the average size of the main phase grains in the central region of the magnet is 1.13-1.35; and the content of O in the sintered NdFeB magnet is less than 600 ppm.
  • a second aspect of the present disclosure provides a method for preparing a sintered NdFeB magnet, the method comprising the following steps:
  • the conditions of the initial diffusion heat treatment include: a temperature of 800 to 980° C. and a time of 6 to 12 hours;
  • the conditions of the low temperature diffusion heat treatment include: temperature of 850-950°C and time of 6-12h;
  • the temperature of the high-temperature diffusion heat treatment is lower than the temperature of the sintering treatment and 50 to 200° C. higher than the temperature of the low-temperature diffusion heat treatment, and the time is 2 to 8 hours;
  • the sintered NdFeB magnet substrate obtained in step S1 contains 28.9-32.5wt% of R, 0.87-0.93wt% of B, 0.3-0.55wt% of Ga, 0.10-0.65wt% of M and the balance of T;
  • R is a rare earth element, and the rare earth element is Nd, or a combination of Nd and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb, Dy, Tb and Lu, and the content of RE is 0.5-6.5wt% based on the total weight of the sintered NdFeB magnet substrate, and RE is Dy and/or Tb;
  • M is selected from at least one of Cu, Al, Zr, Nb, Mn, Mg, Si, Cr and Ti;
  • T is Fe, or Fe and Co, wherein the content of Fe in T is 80 wt % or more.
  • each diffusion process stage further comprises: before the low-temperature diffusion heat treatment, attaching a diffusion source containing RE on the surface of the sintered NdFeB magnet substrate after the high-temperature diffusion heat treatment.
  • the temperature of the high-temperature diffusion heat treatment is 96%-99% of the sintering temperature.
  • step S1 the sintered NdFeB magnet substrate is prepared by the following steps:
  • the obtained molded compact is sintered and mechanically processed in a vacuum environment or in a vacuum sintering furnace by introducing protective gas to obtain the sintered NdFeB magnet substrate.
  • a R1-T1-B-Ga-M1 main alloy quick-setting sheet and a R2-T2-M2 auxiliary alloy quick-setting sheet are prepared by a double alloy method;
  • the R1-T1-B-Ga-M1 main alloy quick-setting sheet comprises 28.9-32.5wt% of R1, 0.87-0.93wt% of B, 0.3-0.55wt% of Ga, 0.10-0.65wt% of M1 and the balance of T1;
  • R1 is a rare earth element, and the rare earth element is Nd, or a combination of Nd and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb, Dy, Tb and Lu; M1 is at least one selected from Cu, Al, Zr, Nb, Mn, Mg, Si, Cr and Ti; T1 is Fe or Fe and Co;
  • the content of RE1 in the R1-T1-B-Ga-M1 main alloy quick-setting sheet is 0.5-5.2wt%, and RE1 is Dy and/or Tb;
  • the R2-T2-M2 auxiliary alloy quick-setting sheet contains 60-85wt% of R2, 3.0-6.0wt% of M2 and the balance of T2;
  • R2 is selected from one or more of Nd, Pr, Dy and Tb
  • M2 is selected from at least one of Ga, Cu and Al
  • T2 is Fe, or Fe and Co
  • the content of RE2 in the R2-T2-M2 auxiliary alloy quick-setting sheet is 0-80wt%, and RE2 is Dy and/or Tb;
  • the thickness of the R1-T1-B-Ga-M1 main alloy quick-setting sheet and the R2-T2-M2 auxiliary alloy quick-setting sheet are independently 0.13-0.46 mm.
  • the rare earth elements are Nd and RE1, or the rare earth elements are a combination of Nd, RE1 and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb and Lu.
  • step S02 the method for preparing the alloy hydrogenated powder includes:
  • the main alloy quick-setting sheet R1-T1-B-Ga-M1 is subjected to hydrogen crushing treatment to obtain the main alloy hydrogenated powder
  • the R2-T2-M2 auxiliary alloy quick-setting sheet R2 is subjected to hydrogen crushing treatment to obtain the auxiliary alloy hydrogenated powder
  • the main alloy hydrogenated powder and the auxiliary alloy hydrogenated powder are mixed to obtain the alloy hydrogenated powder;
  • the mass content of the main alloy hydrogenated powder is more than 95%, and the mass content of the auxiliary alloy hydrogenated powder is less than 5%.
  • the diffusion source containing RE includes one or more of RE oxide, RE fluoride, RE single substance or RE alloy; in the diffusion source containing RE, the content of RE is 60-100wt%.
  • the third aspect of the present disclosure provides a sintered NdFeB magnet prepared by the method described in the second aspect, wherein the sum of the maximum magnetic energy product (BH) max and the intrinsic coercive force HcJ of the sintered NdFeB magnet is greater than 80; and the remanence Br is greater than 13KGs; the unit of the maximum magnetic energy product (BH) max is MGOe, and the unit of the intrinsic coercive force HcJ is KOe.
  • the small-area triangular region grain boundary phase content in the sintered NdFeB magnet disclosed in the present invention is high, the coercive force and remanence of the magnet are improved; and the grain size of the surface layer of the magnet is large, which is conducive to weakening the influence of the demagnetization coupling effect on the surface layer of the magnet.
  • the sintered NdFeB magnet disclosed in the present invention has relatively balanced remanence and intrinsic coercivity, and is a high-performance magnet with a further increased sum of maximum magnetic energy product and intrinsic coercivity.
  • the preparation method disclosed herein adopts a diffusion heat treatment including an N-stage diffusion process section, wherein the low-temperature diffusion heat treatment enables the heavy rare earth elements in the diffusion source to diffuse along the grain boundary of the substrate and effectively concentrate in a narrow range near the grain boundary to increase the coercivity HcJ of the magnet and reduce the loss of remanence Br; the high-temperature diffusion heat treatment process enables more heavy rare earth elements to diffuse toward the center without reducing the surface coercivity, thereby increasing the diffusion depth, forming a thicker high coercivity region, and improving the overall coercivity distribution.
  • the method disclosed herein can reduce the amount of rare earths used, is simple to operate, easy to control, and is suitable for production with large-scale mass production requirements.
  • FIG. 1 is a flow chart of a grain boundary diffusion process of a specific embodiment of the method for preparing a sintered NdFeB magnet disclosed in the present invention.
  • FIG. 2 is a SEM image of a sintered NdFeB magnet substrate before diffusion in a specific embodiment of the method for preparing a sintered NdFeB magnet disclosed in the present invention.
  • FIG 3 is a SEM image of the surface layer of a sintered NdFeB magnet prepared after diffusion in a specific embodiment of the method for preparing a sintered NdFeB magnet disclosed in the present invention.
  • FIG. 4 is a distribution diagram of the Tb element in the grains and grain edge + grain boundary phase at different depths from the magnet surface in a specific embodiment of the sintered NdFeB magnet disclosed in the present invention.
  • FIG5 is a test diagram of the average size of some grains of a sintered NdFeB magnet prepared after diffusion in a specific embodiment of the sintered NdFeB magnet disclosed in the present invention.
  • the first aspect of the present disclosure provides a sintered NdFeB magnet, which includes a main phase and a grain boundary phase, wherein the ratio of the average grain size of the main phase on the surface of the magnet to the average grain size of the main phase in the center region of the magnet is 1.05 to 1.35.
  • magnet surface refers to an area with a distance of ⁇ 35 ⁇ m from the magnet surface, and it is understood that this area is a collection of positions in the magnet with a distance of ⁇ 35 ⁇ m from any surface.
  • Magnetic center area refers to an area with a distance of ⁇ 500 ⁇ m from the magnet surface, wherein this area is a collection of positions in the magnet with a distance of ⁇ 500 ⁇ m from any surface.
  • the sintered NdFeB magnet contains 29.2-32.5wt% R, 0.87-0.93wt% B, 0.3-0.55wt% Ga, 0.10-0.65wt% M and the balance T; preferably, the sintered NdFeB magnet contains 29.2-31.5wt% R, 0.88-0.92wt% B, 0.35-0.5wt% Ga, 0.1-0.4wt% M and the balance T.
  • R is a rare earth element
  • the rare earth element is Nd, or a combination of Nd and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb, Dy, Tb and Lu.
  • the content of RE is 0.5-6.5wt%, and RE is Dy and/or Tb; M is selected from at least one of Cu, Al, Zr, Nb, Mn, Mg, Si, Cr and Ti.
  • T is Fe, or Fe and Co, wherein the Fe content in T is greater than 80wt%.
  • the content of B can be 0.87wt%, 0.90wt%, 0.91wt%, 0.915wt%, 0.92wt%, 0.93wt%, or a value between any two of them;
  • the content of Ga can be 0.30wt%, 0.35wt%, 0.40wt%, 0.45wt%, 0.50wt%, 0.55wt%, or a value between any two of them;
  • the content of R can be 29.5wt%, 30.0wt%, 30.5wt%, 31.0wt%, 31.5wt%, or a value between any two of them;
  • the content of M can be 0.10wt%, 0.15wt%, 0.20wt%, 0.25wt%, 0.30wt%, 0.35wt%, 0.40wt%, or a value between any two of them.
  • the R content in the sintered NdFeB magnet is appropriate, which can avoid the precipitation of ⁇ -Fe phase during the cooling process of the alloy liquid during smelting, thereby reducing the remanence Br and coercivity HcJ of the sintered NdFeB magnet; and avoid excessive use of rare earth elements to cause waste of resources.
  • the sintered NdFeB magnet contains an appropriate content of B, which is conducive to the formation of the R2Fe14B main phase, avoids the formation of the R2T17 phase and causes the proportion of the main phase to decrease, and can further improve the coercivity HcJ and remanence Br of the magnet; and can avoid the formation of a B-rich phase at the grain boundary of the magnet, further improving the magnetic properties of the magnet.
  • the sintered NdFeB magnet contains an appropriate content of Ga, which can further improve the temperature coefficient, which is conducive to increasing the R-T-Ga phase formed by the magnet at high temperature, reducing the R2T17 phase, and further improving the coercivity HcJ and remanence Br.
  • the grain boundary phase of the sintered NdFeB magnet prepared in the present disclosure includes a triangular region grain boundary phase, and the number of small-area triangular region grain boundary phases accounts for more than 80% of the total number of all triangular region grain boundary phases.
  • the increase in the proportion of the number of small-area triangular region grain boundary phases can improve the intrinsic coercivity HcJ and remanence Br of the sintered NdFeB magnet; by adjusting the ratio of the average grain size of the surface layer of the magnet to the average grain size of the central region of the magnet, the distribution of the intrinsic coercivity HcJ can be improved.
  • a "small-area triangular region grain boundary phase” is a triangular region grain boundary phase with an area of less than 2.5 ⁇ m 2 .
  • the sum of the maximum magnetic energy product (BH) max and the intrinsic coercive force HcJ of the sintered NdFeB magnet prepared by the present invention is greater than 80; and the remanence Br is greater than 13KGs; the unit of the maximum magnetic energy product (BH) max of the magnet is MGOe, and the unit of the intrinsic coercive force HcJ is KOe.
  • the ratio of the average size of the main phase grains on the surface of the magnet to the average size of the main phase grains in the center area of the magnet is 1.13-1.35, for example, it can be 1.13, 1.15, 1.20, 1.25, 1.30, 1.35, or a value between any two of them.
  • the content of O in the sintered NdFeB magnet is less than 600 ppm, which is beneficial to maintain the main phase content, avoid the appearance of ⁇ -Fe phase, and further improve the coercive force HcJ of the magnet.
  • R is a rare earth element
  • the rare earth elements are Nd and RE
  • the rare earth element is a combination of Nd, RE and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb and Lu.
  • the content of RE is 0.5-6.5wt%
  • RE is Dy and/or Tb.
  • the second aspect of the present disclosure provides a method for preparing a sintered NdFeB magnet, the method comprising the following steps: S1, preparing a sintered NdFeB magnet substrate; S2, attaching a diffusion source containing RE on the surface of the sintered NdFeB magnet substrate, and then performing grain boundary diffusion treatment and tempering treatment; RE is Dy and/or Tb.
  • the thickness of the prepared sintered NdFeB magnet substrate can vary within a wide range. Specifically, the thickness of the sintered NdFeB magnet substrate in the magnetization direction is 1-15 mm, for example, 3 mm, 5 mm, 10 mm or 15 mm.
  • the "magnetization direction” refers to the diffusion source containing heavy rare earth elements from the surface of the sintered NdFeB magnet substrate to the sintered NdFeB magnet substrate. The direction of grain boundary diffusion inside the material. The concentration of heavy rare earth elements has a gradient in the thickness direction.
  • the "method for attaching a diffusion source containing RE" can adopt conventional technical means in the art, such as vacuum evaporation, immersion, magnetron sputtering, ion plating, etc., preferably magnetron sputtering.
  • the grain boundary diffusion treatment includes an initial diffusion heat treatment and N-level diffusion process sections, N ⁇ 1, and each level of the diffusion process section includes: high-temperature diffusion heat treatment and low-temperature diffusion heat treatment in sequence;
  • the conditions of the initial diffusion heat treatment include: a temperature of 800-980°C and a time of 6-12h;
  • the conditions of the low-temperature diffusion heat treatment include: a temperature of 850-950°C, for example, 850°C, 900°C, 950°C, or a value between any two of them, and a time of 6-12h, for example, 8h;
  • the temperature of the high-temperature diffusion heat treatment is lower than the temperature of the sintering treatment, and is 50-200°C higher than the temperature of the low-temperature diffusion heat treatment, and the time is 2-8h;
  • the temperature of the high-temperature diffusion heat treatment can be 50°C, 60°C, 80°C, 100°C, 120°C, 140°C
  • the sintered NdFeB magnet substrate obtained in step S1 contains 28.9-32.5wt% of R, 0.87-0.93wt% of B, 0.3-0.55wt% of Ga, 0.10-0.65wt% of M and the remainder of T; wherein R is a rare earth element, and the rare earth element is Nd, or a combination of Nd and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb, Dy, Tb and Lu, and the content of RE is 0.5-6.5wt% based on the total weight of the sintered NdFeB magnet substrate, and RE is Dy and/or Tb; M is selected from at least one of Cu, Al, Zr, Nb, Mn, Mg, Si, Cr and Ti; T is Fe, or Fe and Co, and the content of Fe in T is above 80wt%.
  • R is a rare earth element
  • the rare earth element is Nd, or a combination of N
  • the present disclosure adopts a diffusion heat treatment method including N-level diffusion process sections.
  • the diffusion process of the N-level diffusion process section can be carried out, for example, N ⁇ 2; in a specific embodiment of the present disclosure, the N-level diffusion is performed for more than 2 times, and each diffusion process section includes high-temperature diffusion heat treatment and low-temperature diffusion heat treatment in sequence.
  • Each diffusion process section also includes: before the low-temperature diffusion heat treatment, a diffusion source containing RE is attached to the surface of the sintered NdFeB magnet substrate after the high-temperature diffusion heat treatment.
  • the low-temperature diffusion causes the heavy rare earth elements in the diffusion source to diffuse along the substrate grain boundary and effectively concentrate in a very narrow range near the grain boundary; after the N-level diffusion heat treatment, the surface grains of the substrate magnet grow to a certain extent, and the larger grain size can reduce the number of grain boundary phases required to increase the demagnetization coupling between grains in the surface area of the magnet. Therefore, the heavy rare earth elements enriched in the surface grain boundary diffuse to the central area of the magnet, increasing the diffusion depth and forming a thicker high coercivity area. On the basis of not reducing the surface coercivity, the overall coercivity distribution is improved. At the same time, the high-temperature diffusion process promotes the generation of more liquid phases and produces more liquid phase channels, allowing the heavy rare earth elements enriched in the grain boundaries to further diffuse to the central area of the magnet, thereby increasing the diffusion depth.
  • the temperature of the high-temperature diffusion heat treatment is 96%-99% of the sintering temperature, preferably 96%, 96.5%, 97%, 97.5%, 98%, 98.5%, 99%, or a value between any two of them; before the high-temperature diffusion heat treatment, each diffusion process section also includes cooling to below 300°C, for example, 150-300°C; the heating rate of the high-temperature diffusion heat treatment is above 8°C/min, for example, 8-30°C/min.
  • the tempering treatment conditions include: the tempering temperature is 450-690°C, for example, 500-535°C; the time is 0.5-5h, for example, 2h; the method also includes rapid cooling after the tempering treatment, The sintered body is cooled to below 400°C; the rapid cooling rate may be 6-30°C/min, preferably 8-20°C/min.
  • the rapid cooling can effectively suppress the segregation of the ferromagnetic phase in the grain boundary phase, thereby improving the coercive force of the magnet.
  • the sintered NdFeB magnet substrate is prepared by the following steps: S01, placing the alloy raw material in a vacuum induction furnace for melting and casting to obtain an alloy quick-setting sheet; S02, subjecting the alloy quick-setting sheet to hydrogen crushing treatment to obtain an alloy hydrogenated powder; S03, subjecting the alloy hydrogenated powder to micro-crushing treatment to obtain an alloy micro-powder; S04, placing the alloy micro-powder in a magnetic field for orientation molding treatment, and then subjecting the obtained molded compact to a sintering treatment and mechanical processing treatment under a vacuum environment or in a vacuum sintering furnace by introducing a protective gas to obtain the sintered NdFeB magnet substrate.
  • a R1-T1-B-Ga-M1 main alloy quick-setting sheet and a R2-T2-M2 auxiliary alloy quick-setting sheet are prepared by a double alloy method;
  • the R1-T1-B-Ga-M1 main alloy quick-setting sheet contains 28.9-32.5wt% of R1, 0.87-0.93wt% of B, 0.3-0.55wt% of Ga, 0.10-0.65wt% of M1 and the remainder of T1;
  • R1 is a rare earth element, and the rare earth element is Nd, or a combination of Nd and at least one element in the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb, Dy, Tb and Lu
  • M1 is selected from at least one of Cu, Al, Zr, Nb, Mn, Mg, Si, Cr and Ti;
  • T1 is Fe or Fe and Co.
  • the content of R1 can be 29.0wt%, 29.5wt%, 30.0wt%, 30.5wt%, 31.0wt%, 31.5wt%, 32.0wt%, 32.5wt%, or a value between any two of them;
  • the content of B can be 0.87wt%, 0.90wt%, 0.91wt%, 0.915wt%, 0.92wt%, 0.93wt%, or a value between any two of them;
  • the content of Ga can be 0.30wt%, 0.35wt%, 0.40wt%, 0.45wt%, 0.50wt%, 0.55wt%, or a value between any two of them.
  • the content of M1 can be 0.10wt%, 0.15wt%, 0.20wt%, 0.25wt%, 0.30wt%, 0.35wt%, 0.40wt%, 0.45wt%, 0.50wt%, 0.55wt%, 0.60wt%, 0.65wt%, or a value between any two of them.
  • the content of RE1 in the R1-T1-B-Ga-M1 main alloy quick-setting sheet is 0.5-5.2wt%
  • RE1 is Dy and/or Tb
  • the content of RE1 can be 0.5wt%, 1.0wt%, 1.5wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, or a value between any two of them.
  • the R2-T2-M2 auxiliary alloy quick-setting sheet contains 60-85wt% R2, 3.0-6.0wt% M2 and the balance T2; wherein R2 is selected from one or more of Nd, Pr, Dy and Tb, and M2 is selected from at least one of Ga, Cu and Al; T2 is Fe, or Fe and Co; in a preferred specific embodiment of the present disclosure, the content of R2 can be 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 85wt%, or a value between any two of them; the content of M2 can be 3.0wt%, 3.5wt%, 4.0wt%, 4.5wt%, 5.0wt%, 5.5wt%, 6.0wt%, or a value between any two of them.
  • the content of RE2 in the R2-T2-M2 auxiliary alloy quick-setting sheet is 0-80wt%, and RE2 is Dy and/or Tb; for example, the content of RE2 can be 10wt%, 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, or a value between any two of them.
  • the thickness of the R1-T1-B-Ga-M1 main alloy quick-setting sheet and the R2-T2-M2 auxiliary alloy quick-setting sheet are each independently 0.13-0.46 mm.
  • the rare earth element is Nd and RE1, or the rare earth element is Nd, RE1 A combination with at least one element from the following group: Y, La, Ce, Pr, Sm, Eu, Gd, Ho, Er, Tm, Yb and Lu.
  • the preparation method of the alloy hydrogenated powder includes: subjecting the R1-T1-B-Ga-M1 main alloy quick-setting sheet to hydrogen crushing treatment to obtain the main alloy hydrogenated powder, subjecting the R2-T2-M2 auxiliary alloy quick-setting sheet to hydrogen crushing treatment to obtain the auxiliary alloy hydrogenated powder, and then mixing the main alloy hydrogenated powder and the auxiliary alloy hydrogenated powder to obtain the alloy hydrogenated powder.
  • the mass content of the main alloy hydrogenated powder is more than 95%, and the mass content of the auxiliary alloy hydrogenated powder is less than 5%.
  • the mass content of the main alloy hydrogenated powder cannot be 100%, and the mass content of the auxiliary alloy hydrogenated powder cannot be 0%.
  • an additive in the fine grinding process of step S03, is further added, and the additive includes one or more of zinc stearate, calcium stearate and polyethylene glycol octane.
  • the D50 particle size of the obtained alloy micropowder can be 2-4.8 ⁇ m.
  • the density of the obtained molded green compact may be 3.9-4.6 g/cm 3 .
  • the sintering conditions include: a temperature of 950-1080°C, for example, 1046-1076°C; a time of 5-15h, for example, 8h; in a further embodiment, the vacuum degree in the vacuum sintering furnace is 10 -5 -10 -2 Pa, for example, 10 -2 Pa; in another further embodiment, a protective gas is introduced into the vacuum sintering furnace, and the protective gas pressure in the vacuum sintering furnace can be 5-20kPa, and the protective gas can be Ar gas.
  • the diffusion source containing RE includes one or more of RE oxide, RE fluoride, RE element or RE alloy; in the diffusion source containing RE, the content of RE is 60-100wt%.
  • the adhesion amount of RE is 0.1-1wt%, for example, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, or a value between any two of them; further preferably, the adhesion amount of RE in the N-stage diffusion process section decreases successively.
  • attachment amount refers to the weight increase percentage of the sintered NdFeB magnet after the diffusion source is attached in the initial diffusion and each stage of the diffusion process, based on the mass of the magnet substrate before diffusion.
  • the third aspect of the present disclosure provides a sintered NdFeB magnet prepared by the method described in the second aspect, wherein the sum of the maximum magnetic energy product (BH) max and the intrinsic coercive force HcJ of the sintered NdFeB magnet is greater than 80; and the remanence Br is greater than 13KGs; the unit of the maximum magnetic energy product (BH) max is MGOe, and the unit of the intrinsic coercive force HcJ is KOe.
  • the average grain size is analyzed by image analysis software (ImageProPlus is used for calculation in this paper) on the SEM test image of the magnet: a suitable magnification is selected so that the number of main phase grains in the field of view is greater than 200, a suitable scale is selected, and statistics are taken under three fields of view (one field of view in this paper) with the same distance from the surface and the same magnification, and the maximum distance in the same direction within the cross section of the main phase grains in the field of view is measured, for a total of more than 600 data points, and the average value of all the acquired data points is calculated to characterize the average grain size characteristics at this position.
  • image analysis software ImageProPlus is used for calculation in this paper
  • Test method for the percentage of small triangular grain boundary phase in the total number of all triangular grain boundary phases Test method: Image analysis The software (ImageProPlus was used for calculation this time) analyzes the SEM test image of the magnet, selects the appropriate magnification to make the field of view, selects the appropriate scale, relies on the contrast, selects the grain boundary phase under the field of view, statistically calculates the polygonal area of each grain boundary phase, and calculates the percentage of small-area triangular grain boundary phases in the total number of all triangular grain boundary phases.
  • the alloy raw material containing 1.8wt% Tb, 0.9wt% B, 0.11wt% Al, 0.12wt% Cu, 0.4wt% Ga, 27.4wt% PrNd and the balance Fe was made into a quick-setting sheet with a thickness of 0.23mm by a quick-setting process, and then finely pulverized by hydrogen crushing and jet milling to obtain NdFeB powder with a D50 of 3.0 ⁇ m.
  • the compact with a density of 3.9cm3 was obtained by orientation pressing under Ar protection, and the compact was placed in a vacuum of 10-2 Pa, sintering temperature of 1070 ° C for 8 hours to obtain a sintered NdFeB blank, through mechanical processing, a sintered NdFeB substrate with a thickness of 4mm ⁇ 10mm ⁇ 10mm in the magnetizing direction is obtained, and a diffusion source Tb is magnetron sputtered on the surface of the substrate with an attachment amount of 0.3wt%, and then an initial diffusion heat treatment is performed.
  • the initial diffusion heat treatment process is: keeping at 850 ° C for 8 hours and then cooling to 250 ° C; then a first-level grain boundary diffusion heat treatment is performed, the first-level grain boundary diffusion high-temperature heat treatment is performed under the conditions of keeping at 1030 ° C for 4 hours and then cooling to room temperature, and the diffusion source Tb is magnetron sputtered again with an attachment amount of 0.1wt%, and then a first-level grain boundary diffusion low-temperature heat treatment is performed.
  • the first-level grain boundary diffusion low-temperature heat treatment process is: keeping at 900 ° C for 8 hours, cooling to 510 ° C and tempering for 2 hours to obtain a sintered NdFeB magnet.
  • the alloy raw material containing 3.2wt% Tb, 2wt% Dy, 0.9wt% B, 0.1wt% Al, 0.12wt% Cu, 0.3wt% Ga, 0.02wt% Zr, 25wt% PrNd and the balance Fe was prepared into a quick-setting sheet with a thickness of 0.23mm by a quick-setting process, and then finely pulverized by hydrogen crushing and jet milling to obtain NdFeB powder with a D50 of 3.0 ⁇ m.
  • the green compact with a density of 4.1cm3 was obtained by orientation pressing under Ar protection, and the green compact was prepared under a vacuum degree of 10-2 Pa, sintering temperature of 1058 °C for 8h to obtain a sintered NdFeB blank, through mechanical processing, a sintered NdFeB substrate with a thickness of 5mm ⁇ 10mm ⁇ 10mm in the magnetizing direction is obtained, and a diffusion source Tb is magnetron sputtered on the surface of the substrate with an attachment amount of 0.3wt%, and then an initial diffusion heat treatment is performed.
  • the initial diffusion heat treatment process is: keeping warm at 850 °C for 8h and then cooling to 250 °C; then a first-level grain boundary diffusion heat treatment is performed, and the first-level grain boundary diffusion high-temperature heat treatment is carried out at 1038 °C for 3h and then cooled to room temperature, and the diffusion source Tb is magnetron sputtered again to attach The amount is 0.12wt%, and then the first level grain boundary diffusion low-temperature heat treatment is carried out.
  • the first level grain boundary diffusion low-temperature heat treatment process is: 850°C for 8h, cooling to 250°C; then the second level grain boundary diffusion heat treatment is carried out.
  • the second level grain boundary diffusion high-temperature heat treatment condition is 1040°C for 1.5h and then cooled to room temperature, and the diffusion source Tb is magnetron sputtered again with an attachment amount of 0.1wt%, and then the second level grain boundary diffusion low-temperature heat treatment is carried out.
  • the second level grain boundary diffusion low-temperature heat treatment process is 850°C for 8h, cooling to 500°C and tempering for 2h to obtain a sintered NdFeB magnet.
  • the alloy raw material containing 6.1wt% Tb, 0.92wt% B, 0.1wt% Al, 0.1wt% Cu, 0.4wt% Ga, 22.8wt% PrNd and the balance Fe was made into a quick-setting sheet with a thickness of 0.23mm by a quick-setting process, and then finely pulverized by hydrogen crushing and air flow milling to obtain NdFeB micropowder with a D50 of 3.0 ⁇ m. Under Ar protection, orientation pressing was performed to obtain a compact with a density of 4.1cm3 . The compact was sintered for 8h under the conditions of a vacuum of 10-2 Pa and a temperature of 1076°C to obtain a sintered NdFeB blank.
  • a sintered NdFeB substrate with a thickness of 15mm ⁇ 20mm ⁇ 20mm in the magnetizing direction was obtained by machining.
  • a diffusion source Tb with an attachment amount of 0.3wt% was magnetron sputtered on the surface of the substrate, and then Initial diffusion heat treatment, the initial diffusion heat treatment process is: keep warm at 950°C for 8h and then cool to 250°C; then perform the first level grain boundary diffusion heat treatment, the first level grain boundary diffusion high temperature heat treatment, the condition is to keep warm at 1040°C for 3h and then cool to room temperature, magnetron sputter diffusion source Tb again, the attachment amount is 0.12wt%, then perform the first level grain boundary diffusion low temperature heat treatment, the first level grain boundary diffusion low temperature heat treatment process is: keep warm at 950°C for 8h, cool to 250°C, then perform the second level grain boundary diffusion heat treatment, the second level grain boundary diffusion high temperature heat treatment, the condition is to keep warm at 1060°C for 1.5h and then cool to room temperature, magnetron
  • the alloy raw materials are divided into a main alloy and an auxiliary alloy.
  • the main alloy containing 0.4wt% Tb, 0.92wt% B, 0.19wt% Al, 0.16wt% Cu, 0.4wt% Ga, 28.5wt% PrNd alloy raw materials and the balance Fe and the auxiliary alloy containing 55wt% Tb, 2.1wt% Al, 0.9wt% Cu, 5wt% PrNd alloy raw materials and the balance Fe are respectively made into quick-setting sheets with a thickness of 0.23mm by quick-setting process and hydrogen-broken.
  • the main alloy hydrogenated powder: auxiliary alloy hydrogenated powder 99.6%: 0.4% are mixed to obtain alloy hydrogenated powder.
  • the alloy powder with a D50 particle size of 3.0 ⁇ m is prepared by air flow milling.
  • the compact with a density of 3.9cm3 is obtained by orientation pressing under Ar protection.
  • the compact is vacuum-broken at a degree of 10-2 Pa, temperature 1076 °C, sintering for 8h to obtain a sintered NdFeB blank, through machining, a sintered NdFeB substrate with a thickness of 3mm ⁇ 10mm ⁇ 10mm in the magnetizing direction is obtained, and a diffusion source Tb is magnetron sputtered on the surface of the substrate with an attachment amount of 0.3wt%, and then an initial diffusion heat treatment is performed, and the initial diffusion heat treatment process is: keeping at 850 °C for 8h and then cooling to 250 °C; then a first-level grain boundary diffusion heat treatment is performed, the first-level grain boundary diffusion high-temperature heat treatment condition is 1040 °C for 4h and then cooled to room temperature, and the diffusion source Tb is magnetron sput
  • the alloy raw materials are divided into a main alloy and an auxiliary alloy.
  • the main alloy containing 1wt% Tb, 0.91wt% B, 0.1wt% Al, 0.1wt% Cu, 0.4wt% Ga, 27.9wt% PrNd alloy raw materials and the balance Fe and the auxiliary alloy containing 55wt% Tb, 1wt% Al, 2wt% Cu, 5wt% PrNd alloy raw materials and the balance Fe are respectively made into quick-setting sheets with a thickness of 0.23 mm by quick-setting process and hydrogen-broken.
  • the alloy powder with a D50 particle size of 3.0 ⁇ m is prepared by air flow milling.
  • the compact with a density of 3.9 cm 3 is obtained by orientation pressing under Ar protection.
  • the compact is vacuum-broken at a degree of 10 -2 Pa, sintering temperature of 1070 ° C for 8 hours to obtain a sintered NdFeB blank, through machining, a sintered NdFeB substrate with a thickness of 4mm ⁇ 10mm ⁇ 10mm in the magnetizing direction is obtained, and a diffusion source Tb is magnetron sputtered on the surface of the substrate with an attachment amount of 0.3wt%, and then an initial diffusion heat treatment is performed.
  • the initial diffusion heat treatment process is: keeping at 850 ° C for 8 hours and then cooling to 250 ° C; then a first-level grain boundary diffusion heat treatment is performed, the first-level grain boundary diffusion high-temperature heat treatment is performed under the conditions of keeping at 1030 ° C for 4 hours and then cooling to room temperature, and the diffusion source Tb is magnetron sputtered again with an attachment amount of 0.1wt%, and then a first-level grain boundary diffusion low-temperature heat treatment is performed.
  • the first-level grain boundary diffusion low-temperature heat treatment process is: keeping at 900 ° C for 8 hours, cooling to 510 ° C and tempering for 2 hours to obtain a sintered NdFeB magnet.
  • the alloy raw materials are divided into a main alloy and an auxiliary alloy.
  • the main alloy containing 0.5wt% Tb, 0.92wt% B, 0.1wt% Al, 0.05wt% Cu, 0.4wt% Ga, 29.2wt% PrNd alloy raw materials and the balance Fe and the auxiliary alloy containing 60wt% Tb, 1.2wt% Al, 1.8wt% Cu, 10wt% PrNd alloy raw materials and the balance Fe are respectively made into quick-setting sheets with a thickness of 0.23mm by quick-setting process and hydrogen-broken.
  • the main alloy hydrogenated powder: auxiliary alloy hydrogenated powder 97%: 3% are mixed to obtain alloy hydrogenated powder.
  • the alloy powder with a D50 particle size of 3.0 ⁇ m is prepared by air flow milling.
  • the compact with a density of 4.0cm3 is obtained by orientation pressing under Ar protection.
  • the compact is vacuumed to 10-2 Pa, sintering temperature of 1046 °C for 8h to obtain a sintered NdFeB blank, through machining, a sintered NdFeB substrate with a thickness of 10mm ⁇ 10mm ⁇ 10mm in the magnetizing direction is obtained, and a diffusion source Tb is magnetron sputtered on the surface of the substrate with an attachment amount of 0.3wt%, and then an initial diffusion heat treatment is performed.
  • the initial diffusion heat treatment process is: keeping at 950 °C for 8h and then cooling to 250 °C; then a first-level grain boundary diffusion heat treatment is performed, and the first-level grain boundary diffusion high-temperature heat treatment is carried out at 1020 °C for 3h and then cooled to room temperature, and the diffusion source Tb is magnetron sputtered again to attach The amount is 0.12wt%, and then the first level grain boundary diffusion low-temperature heat treatment is carried out.
  • the first level grain boundary diffusion low-temperature heat treatment process is: keeping at 950°C for 8h, cooling to 250°C, and then carrying out the second level grain boundary diffusion heat treatment.
  • the second level grain boundary diffusion high-temperature heat treatment condition is to keep at 1030°C for 1.5h and then cool to room temperature, and magnetron sputtering diffusion source Tb again with an attachment amount of 0.1wt%, and then carrying out the second level grain boundary diffusion low-temperature heat treatment.
  • the second level grain boundary diffusion low-temperature heat treatment process is to keep at 950°C for 8h, cool to 525°C and temper for 2h to obtain a sintered NdFeB magnet.
  • the raw material ratio and the preparation method of the sintered NdFeB substrate in this comparative example 1 are the same as those in Example 4, with the only difference being that: the diffusion process method is different, and the surface of the prepared sintered NdFeB substrate is subjected to magnetron sputtering diffusion source Tb with an attachment amount of 0.4wt%, and then subjected to diffusion heat treatment at 850°C for 20h and then cooled to 535°C for tempering treatment for 2h to obtain a sintered NdFeB magnet.
  • the sintered NdFeB magnets prepared in Examples 1-6 and Comparative Example 1 were subjected to composition tests, magnetic property tests and SEM tests.
  • the composition of the sintered NdFeB magnets is shown in Table 1; the remanence Br, maximum magnetic energy product (BH) max and intrinsic coercive force HcJ of the sintered NdFeB magnets are shown in Table 2.
  • Example 4 The microstructure of Example 4 before and after grain boundary diffusion is tested, and the results are shown in FIG2 and FIG3 .
  • a test chart of the average size of some grains of the sintered NdFeB magnet prepared in Example 4 is shown in FIG5 .
  • Example 3 The distribution of the Tb element in Example 3 at different depths from the magnet surface in the grains, grain edges and grain boundary phases is tested, and the results are shown in FIG4 .
  • the magnetic properties of the sintered NdFeB magnet prepared by the method disclosed in the present invention are further improved, the sum of the maximum magnetic energy product (BH) max and the intrinsic coercive force HcJ is greater than 80; and the remanence Br>13KGs.

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Abstract

本公开涉及一种烧结钕铁硼磁体及其制备方法，该磁体包括主相和晶界相，磁体表层的主相晶粒平均尺寸与磁体中心区域的主相晶粒平均尺寸的比为1.05～1.35；其中，所述磁体表层是指距磁体表面的距离≤35μm的区域；所述磁体中心区域是指距磁体表面的距离≥500μm的区域。该烧结钕铁硼磁体的最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs；所述最大磁能积(BH)max的单位为MGOe，所述内禀矫顽力HcJ的单位为KOe。

Description

一种烧结钕铁硼磁体及其制备方法
相关申请的交叉引用
本申请要求于2022年11月30日递交的申请号为202211528956.X的中国专利申请的优先权，在此引用上述中国专利申请的内容全文以作为本申请的一部分。
技术领域
本公开涉及稀土磁体领域，具体地，涉及一种烧结钕铁硼磁体及其制备方法。
背景技术
烧结钕铁硼磁体因其具有优异的综合磁性能，广泛应用于电子信息、医疗、交通运输、风力发电、航空航天等领域，且近年来随着我国大力发展清洁、绿色新能源相关规划及政策的推行，烧结钕铁硼磁体作为新能源产业链中的关键一环，其市场需求量不断增加，尤其是随着高速马达的发展以及在电动汽车领域的应用。
目前的烧结钕铁硼磁体提高磁体综合性能，通常采用两种方式：
一种方式为可在熔炼时配合原料添加重稀土元素Dy(Tb)，主相中的轻稀土元素(以Nd和Pr为主)被重稀土元素Dy(Tb)置换，通过提高晶粒各向异性场来提升矫顽力。CN103887028A公开了通过控制成分配方，在原料熔炼中添加2.0-13.5wt％的Dy和Tb元素，同时控制工艺条件，优化边界富稀土相和微观组织结构，从而获得(BH)max(MGOe)+HcJ(KOe)≥70的超高性能烧结钕铁硼磁体。
另一种方式为晶界扩散工艺，该工艺不仅能够保证磁体的剩磁，同时能够采用更低含量的重稀土制备出同传统直接合金化法制备的相同矫顽力的磁体，还能大幅提高磁体的综合磁性能。但是，目前的晶界扩散工艺主要依靠浓度梯度驱动重稀土扩散，由于磁体表层重稀土元素的浓度较高，而内部重稀土元素含量较低，导致扩散的有效扩散深度有限，且容易导致重稀土元素含量分布不均匀，进而影响磁体综合磁性能；同时由于扩散驱动力不足，对处理样品的尺寸要去严格，一般只能处理厚度小于5mm的薄片磁体。
因此，需要寻求一种晶界扩散方法，能够增加扩散深度，提高重稀土的利用率，克服目前晶界扩散工艺的局限性，同时显著提高磁体的综合磁性能。
发明内容
本公开的目的是提供一种烧结钕铁硼磁体及其制备方法，该方法能够促进晶界扩散工艺中重稀土元素向烧结磁体的中心区域扩散，进一步提高烧结钕铁硼磁体的综合磁性能。
为了实现上述目的，本公开第一方面提供一种烧结钕铁硼磁体，该磁体包括主相和晶界相，磁体表层的主相晶粒平均尺寸与磁体中心区域的主相晶粒平均尺寸的比为1.05～1.35；
其中，所述磁体表层是指距磁体表面的距离≤35μm的区域；所述磁体中心区域是指距磁体表面的距离≥500μm的区域；
所述烧结钕铁硼磁体中含有29.2-32.5wt％的R、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M以及余量的T；
其中，R为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、 La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu，以所述烧结钕铁硼磁体的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb；
M选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；
T为Fe，或者为Fe和Co，其中，T中的Fe的含量为80wt％以上。
可选地，所述晶界相包括三角区晶界相；所述三角区晶界相中，小面积三角区晶界相的个数占所有所述三角区晶界相总数的80％以上；所述小面积三角区晶界相为面积小于2.5μm2的三角区晶界相。
可选地，该烧结钕铁硼磁体的最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs；所述最大磁能积(BH)max的单位为MGOe，所述内禀矫顽力HcJ的单位为KOe。
可选地，所述磁体表层的主相晶粒平均尺寸与所述磁体中心区域的主相晶粒平均尺寸的比为1.13～1.35；所述烧结钕铁硼磁体中O的含量低于600ppm。
可选地，R为稀土元素，所述稀土元素为Nd和RE，或者所述稀土元素为Nd、RE与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb和Lu，以所述烧结钕铁硼磁体的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb。
本公开第二方面提供一种制备烧结钕铁硼磁体的方法，该方法包括如下步骤：
S1、制备烧结钕铁硼磁体基材；
S2、在所述烧结钕铁硼磁体基材表面附着含有RE的扩散源，然后进行晶界扩散处理和回火处理；RE为Dy和/或Tb；
其中，所述晶界扩散处理包括初始扩散热处理和N级扩散工艺段，N≥1，每级所述扩散工艺段依次包括：高温扩散热处理和低温扩散热处理；
所述初始扩散热处理的条件包括：温度为800～980℃，时间为6～12h；
所述低温扩散热处理的条件包括：温度为850～950℃，时间为6～12h；
所述高温扩散热处理的温度低于所述烧结处理的温度，且比所述低温扩散热处理的温度高50～200℃，时间为2～8h；
步骤S1得到的烧结钕铁硼磁体基材包含28.9-32.5wt％的R、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M以及余量的T；
其中，R为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu，以所述烧结钕铁硼磁体基材的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb；
M选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；
T为Fe，或者为Fe和Co，其中，T中的Fe的含量为80wt％以上。
可选地，每级所述扩散工艺段还包括：在所述低温扩散热处理之前，在所述高温扩散热处理后的烧结钕铁硼磁体基材表面附着含有RE的扩散源。
可选地，所述高温扩散热处理的温度为烧结温度的96％-99％。
可选地，在步骤S1中，采用如下步骤制备所述烧结钕铁硼磁体基材：
S01、将合金原料置于真空感应炉中熔炼和浇铸，得到合金速凝片；
S02、将所述合金速凝片进行氢破碎处理后，得到合金氢化粉；
S03、将所述合金氢化粉进行微粉碎处理后，得到合金微粉；
S04、将所述合金微粉置于磁场中进行取向成型处理后，将得到的成型的压坯在真空环境下或在真空烧结炉内通入保护气进行烧结处理和机械加工处理，得到所述烧结钕铁硼磁体基材。
可选地，在S01步骤中通过双合金法制备R1-T1-B-Ga-M1主合金速凝片和R2-T2-M2辅合金速凝片；
所述R1-T1-B-Ga-M1主合金速凝片包含28.9-32.5wt％的R1、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M1和余量的T1；
其中，R1为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu；M1选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；T1为Fe或者为Fe和Co；
所述R1-T1-B-Ga-M1主合金速凝片中RE1的含量为0.5-5.2wt％，RE1为Dy和/或Tb；
所述R2-T2-M2辅合金速凝片包含60-85wt％的R2、3.0-6.0wt％的M2以及余量的T2；
其中，R2选自Nd、Pr、Dy和Tb中的一种或几种，M2选自Ga、Cu和Al中的至少一种；T2为Fe、或者为Fe和Co；
所述R2-T2-M2辅合金速凝片中RE2的含量为0-80wt％，RE2为Dy和/或Tb；
所述R1-T1-B-Ga-M1主合金速凝片和所述R2-T2-M2辅合金速凝片的厚度各自独立地为0.13-0.46mm。
可选地，所述稀土元素为Nd和RE1，或者所述稀土元素为Nd、RE1与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb和Lu。
可选地，在步骤S02中，所述合金氢化粉的制备方法包括：
将R1-T1-B-Ga-M1主合金速凝片进行氢破碎处理后得到主合金氢化粉，将R2-T2-M2辅合金速凝片进行氢破碎处理后得到辅合金氢化粉，再将主合金氢化粉和辅合金氢化粉混合，得到所述合金氢化粉；
在所述合金氢化粉中，所述主合金氢化粉的质量含量为95％以上，所述辅合金氢化粉的质量含量为5％以下。
可选地，所述含有RE的扩散源包括RE的氧化物、RE的氟化物、RE的单质或RE的合金的一种或几种；所述含有RE的扩散源中，RE的含量为60-100wt％。
本公开第三方面提供第二方面所述的方法制备的烧结钕铁硼磁体，该烧结钕铁硼磁体的最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs；所述最大磁能积(BH)max的单位为MGOe，所述内禀矫顽力HcJ的单位为KOe。
通过上述技术方案，本公开的烧结钕铁硼磁体中的小面积三角区晶界相含量高，磁体的矫顽力和剩磁提高；并且磁体表层的晶粒尺寸较大，有利于削弱磁体表层区域受去磁耦合作用的影响，在 不降低表层矫顽力的基础上，使更多的重稀土元素向中心扩散，形成更厚的高矫顽力区域，改善整体的矫顽力分布。本公开的烧结钕铁硼磁体具有相对均衡的剩磁和内禀矫顽力，是最大磁能积和内禀矫顽力之和进一步增大的高性能磁体。
本公开的制备方法采用包括N级扩散工艺段的扩散热处理，其中低温扩散热处理能够使得扩散源中重稀土元素沿基材晶界扩散，且有效地集中在晶界附近较窄的范围内，以提高磁体的矫顽力HcJ，降低剩磁Br的损失；高温扩散热处理过程能够在表层矫顽力不降低的基础上，使更多的重稀土元素向中心扩散，提高扩散深度，形成更厚的高矫顽力区域，改善整体的矫顽力分布。本公开的方法能够降低稀土的用量，并且操作简单，易于控制，适用于大规模量产需求的生产。
本公开的其他特征和优点将在随后的具体实施方式部分予以详细说明。
附图说明
附图是用来提供对本公开的进一步理解，并且构成说明书的一部分，与下面的具体实施方式一起用于解释本公开，但并不构成对本公开的限制。在附图中：
图1是本公开制备烧结钕铁硼磁体的方法一种具体实施方式的晶界扩散工艺流程图。
图2是本公开制备烧结钕铁硼磁体的方法一种具体实施方式中扩散前烧结钕铁硼磁体基材的SEM图。
图3是本公开制备烧结钕铁硼磁体的方法一种具体实施方式中扩散后制备的烧结钕铁硼磁体表层的SEM图。
图4是本公开烧结钕铁硼磁体一种具体实施方式中Tb元素距离磁体表面不同深度处在晶粒及晶粒边缘+晶界相中的分布图。
图5是本公开烧结钕铁硼磁体一种具体实施方式中扩散后制备的烧结钕铁硼磁体的部分晶粒平均尺寸的测试图。
具体实施方式
以下结合附图对本公开的具体实施方式进行详细说明。应当理解的是，此处所描述的具体实施方式仅用于说明和解释本公开，并不用于限制本公开。
本公开第一方面提供一种烧结钕铁硼磁体，该磁体包括主相和晶界相，磁体表层的主相晶粒平均尺寸与磁体中心区域的主相晶粒平均尺寸的比为1.05～1.35。
本公开中，“磁体表层”是指距磁体表面的距离≤35μm的区域，可以理解的是，该区域为磁体中距离任意表面的距离≤35μm的位置的集合。“磁体中心区域”是指距磁体表面的距离≥500μm的区域，其中，该区域为磁体中距离任意表面的距离≥500μm的位置的集合。
在本公开的一种具体实施方式中，烧结钕铁硼磁体中含有29.2-32.5wt％的R、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M以及余量的T；优选地，烧结钕铁硼磁体中含有29.2-31.5wt％的R、0.88-0.92wt％的B、0.35-0.5wt％的Ga、0.1-0.4wt％的M以及余量的T。其中，R为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu，以所述烧结钕铁硼磁体的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb；M选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一 种；T为Fe，或者为Fe和Co，其中，T中的Fe的含量为80wt％以上。在本公开的一种优选的具体实施方式中，B的含量可以为0.87wt％、0.90wt％、0.91wt％、0.915wt％、0.92wt％、0.93wt％，或者为它们中任意两者之间的数值；Ga的含量可以为0.30wt％、0.35wt％、0.40wt％、0.45wt％、0.50wt％、0.55wt％，或者为它们中任意两者之间的数值；R的含量可以为29.5wt％、30.0wt％、30.5wt％、31.0wt％、31.5wt％，或者为它们中任意两者之间的数值；M的含量可以为0.10wt％、0.15wt％、0.20wt％、0.25wt％、0.30wt％、0.35wt％、0.40wt％，或者为它们中任意两者之间的数值。
上述实施方式中，烧结钕铁硼磁体中R的含量适宜，能够避免熔炼时合金液冷却的过程中析出α-Fe相，从而降低烧结钕铁硼磁体的剩磁Br和矫顽力HcJ；且避免稀土元素用量过多造成资源的浪费。烧结钕铁硼磁体中包含适宜含量的B，有利于形成R2Fe14B主相，避免生成R2T17相而导致主相的比例降低，能够进一步提高磁体的矫顽力HcJ和剩磁Br；并且能够避免在磁体晶界处形成富B相，进一步改善了磁体的磁性能。烧结钕铁硼磁体中包含适宜含量的Ga，能够进一步改善温度系数，利于增加磁体在高温下形成的R-T-Ga相，减少R2T17相，从而进一步提高矫顽力HcJ和剩磁Br。
本公开制备的烧结钕铁硼磁体的晶界相包括三角区晶界相，且小面积三角区晶界相的个数占所有三角区晶界相总数的80％以上，小面积三角区晶界相的个数的比例增加，能够提高烧结钕铁硼磁体的内禀矫顽力HcJ和剩磁Br；通过调整磁体表层的晶粒平均尺寸与磁体中心区域的晶粒平均尺寸之比，能够改善内禀矫顽力HcJ的分布。本公开中，“小面积三角区晶界相”为面积小于2.5μm2的三角区晶界相。
由本公开制备的烧结钕铁硼磁体的最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs；磁体的最大磁能积(BH)max的单位为MGOe，内禀矫顽力HcJ的单位为KOe。
在本公开的一种优选的具体实施方式中，磁体表层的主相晶粒平均尺寸与磁体中心区域的主相晶粒平均尺寸的比为1.13～1.35，例如可以为1.13、1.15、1.20、1.25、1.30、1.35，或者为它们中任意两者之间的数值。
在本公开的一种具体实施方式中，烧结钕铁硼磁体中O的含量低于600ppm，利于保持主相含量、避免出现α-Fe相，进一步提高磁体的矫顽力HcJ。
在本公开中的一种实施方式中，R为稀土元素，所述稀土元素为Nd和RE，或者所述稀土元素为Nd、RE与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb和Lu，以所述烧结钕铁硼磁体的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb。
本公开第二方面提供一种制备烧结钕铁硼磁体的方法，该方法包括如下步骤：S1、制备烧结钕铁硼磁体基材；S2、在所述烧结钕铁硼磁体基材表面附着含有RE的扩散源，然后进行晶界扩散处理和回火处理；RE为Dy和/或Tb。
本公开中，步骤S1中，制备的烧结钕铁硼磁体基材的厚度可以在较大的范围内变化，具体地，烧结钕铁硼磁体基材的充磁方向的厚度为1-15mm，例如为3mm、5mm、10mm或15mm。其中，“充磁方向”指的是含重稀土元素的扩散源从烧结钕铁硼磁体基材的表面向烧结钕铁硼磁体基 材内部晶界扩散的方向。重稀土元素的浓度在厚度方向具有梯度。“附着含有RE的扩散源方法”可以采用本领域常规的技术手段，例如可以采用真空蒸镀法、浸渍法、磁控溅射法、离子镀法等方式，优选采用磁控溅射方法。
在本公开的一种具体实施方式中，所述晶界扩散处理包括初始扩散热处理和N级扩散工艺段，N≥1，每级所述扩散工艺段依次包括：高温扩散热处理和低温扩散热处理；所述初始扩散热处理的条件包括：温度为800～980℃，时间为6～12h；所述低温扩散热处理的条件包括：温度为850～950℃，例如可以为850℃、900℃、950℃，或者为它们中任意两者之间的数值，时间为6～12h，例如可以为8h；所述高温扩散热处理的温度低于烧结处理的温度，且比所述低温扩散热处理的温度高50～200℃，时间为2～8h；在本公开的一种优选的具体实施方式中，所述高温扩散热处理的的温度比低温扩散热处理的温度可以高50℃、60℃、80℃、100℃、120℃、140℃、160℃、180℃、200℃，或者为它们中任意两者之间的数值。
在本公开的一种具体实施方式中，步骤S1得到的烧结钕铁硼磁体基材包含28.9-32.5wt％的R、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M以及余量的T；其中，R为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu，以所述烧结钕铁硼磁体基材的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb；M选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；T为Fe，或者为Fe和Co，其中，T中的Fe的含量为80wt％以上。
本公开采用了包括N级扩散工艺段的扩散热处理的方法，根据烧结钕铁硼磁体成分特征和性能需要，优选地，可进行N级扩散工艺段的扩散过程，例如N≥2；在本公开的一种具体实施方式中，N级扩散为2次以上，每级扩散工艺段依次包括高温扩散热处理和低温扩散热处理。每级所述扩散工艺段还包括：在所述低温扩散热处理之前，在所述高温扩散热处理后的烧结钕铁硼磁体基材表面附着含有RE的扩散源。其中低温扩散使得扩散源中重稀土元素沿基材晶界扩散，且有效地集中在晶界附近很窄的范围内；经过N级扩散热处理，基材磁体的表层晶粒发生一定程度的长大，更大的晶粒尺寸可以使得在磁体表层区域内所需的增加晶粒间去磁耦合作用的晶界相数量减少，因此，富集在表层晶界中的重稀土元素向磁体中心区域扩散，提高了扩散深度，形成更厚的高矫顽力区域。在不降低表层矫顽力的基础上，改善整体的矫顽力分布。同时，高温扩散过程促进更多液相生成，产生更多的液相通道，使得富集在晶界内的重稀土元素进一步向磁体中心区域扩散，提高扩散深度。
在本公开的一种具体实施方式中，高温扩散热处理的温度为烧结温度的96％-99％，优选可以为96％、96.5％、97％、97.5％、98％、98.5％、99％，或者为它们中任意两者之间的数值；在进行高温扩散热处理之前，每级扩散工艺段还包括，降温至低于300℃，例如为150～300℃；高温扩散热处理的升温速率为8℃/min以上，例如为8～30℃/min。在上述优选的高温扩散热处理温度范围内，进一步有利于主相转变为液相，生成均匀核壳，避免晶粒异常长大，进一步改善磁体性能。
在本公开的一种具体实施方式中，步骤S2中，回火处理的条件包括：回火温度为450-690℃，例如可以为500-535℃；时间为0.5-5h，例如可以为2h；该方法还包括回火处理后进行快速冷却， 将烧结体冷却至400℃以下；快速冷却速率可以为6-30℃/min，优选为8-20℃/min。上述优选的实施方式中，通过快速冷却可以有效抑制晶界相中铁磁性相的偏析，进而提高磁体的矫顽力。
在本公开的一种具体实施方式中，在步骤S1中，采用如下步骤制备所述烧结钕铁硼磁体基材：S01、将合金原料置于真空感应炉中熔炼和浇铸，得到合金速凝片；S02、将所述合金速凝片进行氢破碎处理后，得到合金氢化粉；S03、将所述合金氢化粉进行微粉碎处理后，得到合金微粉；S04、将所述合金微粉置于磁场中进行取向成型处理后，将得到的成型的压坯在真空环境下或在真空烧结炉内通入保护气进行烧结处理和机械加工处理，得到所述烧结钕铁硼磁体基材。
在本公开的一种具体实施方式中，在S01步骤中通过双合金法制备R1-T1-B-Ga-M1主合金速凝片和R2-T2-M2辅合金速凝片；所述R1-T1-B-Ga-M1主合金速凝片包含28.9-32.5wt％的R1、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M1和余量的T1；其中，R1为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu；M1选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；T1为Fe或者为Fe和Co。
在本公开的一种优选的具体实施方式中，R1的含量可以为29.0wt％、29.5wt％、30.0wt％、30.5wt％、31.0wt％、31.5wt％、32.0wt％、32.5wt％，或者为它们中任意两者之间的数值；B的含量可以为0.87wt％、0.90wt％、0.91wt％、0.915wt％、0.92wt％、0.93wt％，或者为它们中任意两者之间的数值；Ga的含量可以为0.30wt％、0.35wt％、0.40wt％、0.45wt％、0.50wt％、0.55wt％，或者为它们中任意两者之间的数值。M1的含量可以为0.10wt％、0.15wt％、0.20wt％、0.25wt％、0.30wt％、0.35wt％、0.40wt％、0.45wt％、0.50wt％、0.55wt％、0.60wt％、0.65wt％，或者为它们中任意两者之间的数值。
在本公开的一种具体实施方式中，所述R1-T1-B-Ga-M1主合金速凝片中RE1的含量为0.5-5.2wt％，RE1为Dy和/或Tb；例如RE1的含量可以为0.5wt％、1.0wt％、1.5wt％、2.0wt％、2.5wt％、3.0wt％、3.5wt％、4.0wt％、4.5wt％、5.0wt％，或者为它们中任意两者之间的数值。
在本公开的一种具体实施方式中，所述R2-T2-M2辅合金速凝片包含60-85wt％的R2、3.0-6.0wt％的M2以及余量的T2；其中，R2选自Nd、Pr、Dy和Tb中的一种或几种，M2选自Ga、Cu和Al中的至少一种；T2为Fe、或者为Fe和Co；在本公开的一种优选的具体实施方式中，R2的含量可以为60wt％、65wt％、70wt％、75wt％、80wt％、85wt％，或者为它们中任意两者之间的数值；M2的含量可以为3.0wt％、3.5wt％、4.0wt％、4.5wt％、5.0wt％、5.5wt％、6.0wt％，或者为它们中任意两者之间的数值。
在本公开的一种优选的具体实施方式中，所述R2-T2-M2辅合金速凝片中RE2的含量为0-80wt％，RE2为Dy和/或Tb；例如RE2的含量可以为10wt％、20wt％、30wt％、40wt％、50wt％、60wt％、70wt％、80wt％，或者为它们中任意两者之间的数值。
在本公开中一种具体实施方式中，所述R1-T1-B-Ga-M1主合金速凝片和所述R2-T2-M2辅合金速凝片的厚度各自独立地为0.13-0.46mm。
在本公开的一种具体实施方式中，所述稀土元素为Nd和RE1，或者所述稀土元素为Nd、RE1 与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb和Lu。
在本公开的一种具体实施方式中，在步骤S02中，所述合金氢化粉的制备方法包括：将R1-T1-B-Ga-M1主合金速凝片进行氢破碎处理后得到主合金氢化粉，将R2-T2-M2辅合金速凝片进行氢破碎处理后得到辅合金氢化粉，再将主合金氢化粉和辅合金氢化粉混合，得到所述合金氢化粉。在本公开的一种具体实施方式中，合金氢化粉中，主合金氢化粉的质量含量为95％以上，辅合金氢化粉的质量含量为5％以下，在本公开中，主合金氢化粉的质量含量不可以为100％，辅合金氢化粉的质量含量不可以为0％。
在本公开的一种具体实施方式中，步骤S03的微粉碎处理中，还加入添加剂，添加剂包括硬脂酸锌、硬脂酸钙和聚乙二醇辛烷中的一种或几种。得到的合金微粉的D50粒径可以为2-4.8μm。
在本公开的一种具体实施方式中，步骤S04中，得到的成型的压坯的密度可以为3.9-4.6g/cm3。
在本公开的一种具体实施方式中，步骤S04中，烧结的条件包括：温度为950-1080℃，例如可以为1046-1076℃；时间为5-15h，例如可以为8h；进一步的一种实施方式，真空烧结炉内的真空度为10-5-10-2Pa，例如可以为10-2Pa；进一步的另一种实施方式，真空烧结炉内通入保护气，真空烧结炉内的保护气压力可以为5-20kPa，保护气可以为Ar气。
在本公开的一种具体实施方式中，所述含有RE的扩散源包括RE的氧化物、RE的氟化物、RE的单质或RE的合金的一种或几种；所述含有RE的扩散源中，RE的含量为60-100wt％。
在本公开的一种具体实施方式中，晶界扩散处理初始扩散热处理及每级扩散工艺段中，以扩散前烧结钕铁硼磁体基材的总质量为基准，RE的附着量为0.1-1wt％，例如为0.4wt％、0.5wt％、0.6wt％、0.7wt％、0.8wt％、0.9wt％，或者为它们中任意两者之间的数值；进一步优选地，N级扩散工艺段的RE附着量依次减小。
本公开中，“附着量”为在初始扩散及每一级扩散工艺段中，以扩散前磁体基材质量为基准，附着扩散源后烧结钕铁硼磁体的增重百分含量。
本公开第三方面提供第二方面所述的方法制备的烧结钕铁硼磁体，该烧结钕铁硼磁体的最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs；所述最大磁能积(BH)max的单位为MGOe，所述内禀矫顽力HcJ的单位为KOe。
下面通过实施例来进一步说明本公开，但是本公开并不因此而受到任何限制。
在本公开的下述实施例和对比例中：
晶粒平均尺寸采用图像分析软件(本次采用ImageProPlus进行计算)对磁体的SEM测试图像进行分析：选定合适的放大倍数使视野下主相晶粒数量＞200，选定合适标尺，将距离表面相同距离、相同放大倍数的三个视野下(本次为1个视野下)进行统计，测量视野下主相晶粒截面内相同方向上的最大距离，共计＞600个数据点，计算所有获取数据点的平均值，以此表征该位置下晶粒平均尺寸特征。
小面积三角区晶界相占所有三角区晶界相总数百分比的测试方法：测试方法：采用图像分析 软件(本次采用ImageProPlus进行计算)对磁体的SEM测试图像进行分析，选定合适的放大倍数使视野下，选定合适的标尺，依靠衬度，选出视野下的晶界相，统计计算每个晶界相的多边形面积，并计算小面积三角区晶界相占所有三角区晶界相总数百分比。
实施例1
将含有1.8wt％Tb、0.9wt％B、0.11wt％Al、0.12wt％Cu、0.4wt％Ga、27.4wt％PrNd合金原料以及余量的Fe，采用速凝工艺制成厚度为0.23mm速凝片，经氢破、气流磨微粉碎制成D50为3.0μm的钕铁硼微粉，在Ar保护下取向压制获得密度为3.9cm3的压坯，在真空度为10-2Pa、温度为1070℃的条件烧结8h获得烧结钕铁硼毛坯，通过机械加工，得到充磁方向的厚度为4mm×纵10mm×横10mm的烧结钕铁硼基材，在基材表面磁控溅射扩散源Tb，附着量为0.3wt％，然后进行初始扩散热处理，初始扩散热处理工艺为：850℃保温8h后冷却至250℃；然后进行第一级晶界扩散热处理，第一级晶界扩散高温热处理，条件为1030℃保温4h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.1wt％，然后进行第一级晶界扩散低温热处理，第一级晶界扩散低温热处理工艺为：900℃保温8h，冷却至510℃回火处理2h，制得烧结钕铁硼磁体。
实施例2
将含有3.2wt％Tb、2wt％Dy、0.9wt％B、0.1wt％Al、0.12wt％Cu、0.3wt％Ga、0.02wt％Zr、25wt％PrNd合金原料以及余量的Fe，采用速凝工艺制成厚度为0.23mm速凝片，经氢破、气流磨微粉碎制成D50为3.0μm的钕铁硼微粉，在Ar保护下取向压制获得密度为4.1cm3的压坯，在真空度为10-2Pa、温度为1058℃的条件下烧结8h获得烧结钕铁硼毛坯，通过机械加工，得到充磁方向的厚度为5mm×纵10mm×横10mm的烧结钕铁硼基材，在基材表面磁控溅射扩散源Tb，附着量为0.3wt％，然后进行初始扩散热处理，初始扩散热处理工艺为：850℃保温8h后冷却至250℃；然后进行第一级晶界扩散热处理，第一级晶界扩散高温热处理，条件为1038℃保温3h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.12wt％，然后进行第一级晶界扩散低温热处理，第一级晶界扩散低温热处理工艺为：850℃保温8h，冷却至250℃；然后进行第二级晶界扩散热处理，第二级晶界扩散高温热处理，条件为1040℃保温1.5h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.1wt％，然后进行第二级晶界扩散低温热处理，第二级晶界扩散低温热处理工艺为850℃保温8h，冷却至500℃回火处理2h，制得烧结钕铁硼磁体。
实施例3
将含有6.1wt％Tb、0.92wt％B、0.1wt％Al、0.1wt％Cu、0.4Ga wt％、22.8wt％PrNd合金原料以及余量的Fe，采用速凝工艺制成厚度为0.23mm速凝片，经氢破、气流磨微粉碎制成D50为3.0μm的钕铁硼微粉，在Ar保护下取向压制获得密度为4.1cm3的压坯，在真空的为10-2Pa、温度为1076℃的条件下烧结8h获得烧结钕铁硼毛坯，通过机加工，得到充磁方向的厚度为15mm×纵20mm×横20mm的烧结钕铁硼基材，在基材表面磁控溅射扩散源Tb，附着量为0.3wt％，然后进行 初始扩散热处理，初始扩散热处理工艺为：950℃保温8h后冷却至250℃；然后进行第一级晶界扩散热处理，第一级晶界扩散高温热处理，条件为1040℃保温3h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.12wt％，然后进行第一级晶界扩散低温热处理，第一级晶界扩散低温热处理工艺为：950℃保温8h，冷却至250℃，然后进行第二级晶界扩散热处理，第二级晶界扩散高温热处理，条件为1060℃保温1.5h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.1wt％，然后进行第二级晶界扩散低温热处理，第二级晶界扩散低温热处理工艺为950℃保温8h，冷却至520℃回火处理2h，制得烧结钕铁硼磁体。
实施例4
将合金原料分为主合金和辅合金，将含有0.4wt％Tb、0.92wt％B、0.19wt％Al、0.16wt％Cu、0.4wt％Ga、28.5wt％PrNd合金原料以及余量的Fe的主合金和含有55wt％Tb、2.1Al wt％、0.9Cu wt％、5wt％PrNd合金原料以及余量的Fe辅合金，分别采用速凝工艺制成厚度为0.23mm速凝片并经氢破，按照主合金氢化粉：辅合金氢化粉＝99.6％：0.4％进行混合，得到合金氢化粉，经气流磨制备D50粒径为3.0μm的合金微粉，在Ar保护下取向压制获得密度为3.9cm3的压坯，在真空度为10-2Pa、温度为1076℃的条件下烧结8h获得烧结钕铁硼毛坯，通过机加工，得到充磁方向的厚度为3mm×纵10mm×横10mm的烧结钕铁硼基材，在基材表面磁控溅射扩散源Tb，附着量为0.3wt％，然后进行初始扩散热处理，初始扩散热处理工艺为：850℃保温8h后冷却至250℃；然后进行第一级晶界扩散热处理，第一级晶界扩散高温热处理，条件为1040℃保温4h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.1wt％，然后进行第一级晶界扩散低温热处理，第一级晶界扩散低温热处理工艺为：850℃保温8h，冷却至535℃回火处理2h，制得烧结钕铁硼磁体。
实施例5
将合金原料分为主合金和辅合金，将含有1wt％Tb、0.91wt％B、0.1wt％Al、0.1wt％Cu、0.4wt％Ga、27.9wt％PrNd合金原料以及余量的Fe的主合金和含有55wt％Tb、1wt％Al、2wt％Cu、5wt％PrNd合金原料以及余量的Fe的辅合金，分别采用速凝工艺制成厚度为0.23mm速凝片并经氢破，按照主合金氢化粉：辅合金氢化粉＝99％：1％进行混合，得到合金氢化粉，经气流磨制备D50粒径为3.0μm的合金微粉，在Ar保护下取向压制获得密度为3.9cm3的压坯，在真空度为10-2Pa、温度为1070℃的条件下烧结8h获得烧结钕铁硼毛坯，通过机加工，得到充磁方向的厚度为4mm×纵10mm×横10mm的烧结钕铁硼基材，在基材表面磁控溅射扩散源Tb，附着量为0.3wt％，然后进行初始扩散热处理，初始扩散热处理工艺为：850℃保温8h后冷却至250℃；然后进行第一级晶界扩散热处理，第一级晶界扩散高温热处理，条件为1030℃保温4h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.1wt％，然后进行第一级晶界扩散低温热处理，第一级晶界扩散低温热处理工艺为：900℃保温8h，冷却至510℃回火处理2h，制得烧结钕铁硼磁体。
实施例6
将合金原料分为主合金和辅合金，将含有0.5wt％Tb、0.92wt％B、0.1wt％Al、0.05wt％Cu、0.4wt％Ga、29.2wt％PrNd合金原料以及余量的Fe的主合金和含有60wt％Tb、1.2wt％Al、1.8wt％Cu、10wt％PrNd合金原料以及余量的Fe的辅合金，分别采用速凝工艺制成厚度为0.23mm速凝片并经氢破，按照主合金氢化粉：辅合金氢化粉＝97％：3％进行混合，得到合金氢化粉，经气流磨制备D50粒径为3.0μm的合金微粉，在Ar保护下取向压制获得密度为4.0cm3的压坯，在真空度为10-2Pa、温度为1046℃的条件下烧结8h获得烧结钕铁硼毛坯，通过机加工，得到充磁方向的厚度为10mm×纵10mm×横10mm的烧结钕铁硼基材，在基材表面磁控溅射扩散源Tb，附着量为0.3wt％，然后进行初始扩散热处理，初始扩散热处理工艺为：950℃保温8h后冷却至250℃；然后进行第一级晶界扩散热处理，第一级晶界扩散高温热处理，条件为1020℃保温3h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.12wt％，然后进行第一级晶界扩散低温热处理，第一级晶界扩散低温热处理工艺为：950℃保温8h，冷却至250℃，然后进行第二级晶界扩散热处理，第二级晶界扩散高温热处理，条件为1030℃保温1.5h后冷却至室温，再次磁控溅射扩散源Tb，附着量为0.1wt％，然后进行第二级晶界扩散低温热处理，第二级晶界扩散低温热处理工艺为950℃保温8h，冷却至525℃回火处理2h，制得烧结钕铁硼磁体。
对比例1
本对比例1的原料配比及烧结钕铁硼基材制备方法同实施例4，区别仅在于：扩散工艺方法不同，制备得到的烧结钕硼基材表面磁控溅射扩散源Tb，附着量为0.4wt％，然后在850℃扩散热处理保温20h后冷却至535℃回火处理2h，制得烧结钕铁硼磁体。
测试例
将实施例1-6和对比例1制备得到的烧结钕铁硼磁体进行组成测试、磁性能测试和SEM测试，烧结钕铁硼磁体的成分如表1所示；烧结钕铁硼磁体的剩磁Br、最大磁能积(BH)max、内禀矫顽力HcJ如表2所示。
测试的实施例4的晶界扩散前、晶界扩散后的微观组织，结果如图2、图3所示。
实施例4中制备的烧结钕铁硼磁体的部分晶粒平均尺寸的测试图如图5所示。
测试的实施例3的Tb元素距离磁体表面不同深度处在晶粒及晶粒边缘和晶界相中的分布，结果如图4所示。
表1烧结钕铁硼磁体成分表

表2
由本公开的方法制备的烧结钕铁硼磁体的磁性能得到进一步提升，最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs。
以上结合附图详细描述了本公开的优选实施方式，但是，本公开并不限于上述实施方式中的具体细节，在本公开的技术构思范围内，可以对本公开的技术方案进行多种简单变型，这些简单变型均属于本公开的保护范围。
另外需要说明的是，在上述具体实施方式中所描述的各个具体技术特征，在不矛盾的情况下，可以通过任何合适的方式进行组合，为了避免不必要的重复，本公开对各种可能的组合方式不再另行说明。
此外，本公开的各种不同的实施方式之间也可以进行任意组合，只要其不违背本公开的思想，其同样应当视为本公开所公开的内容。

Claims (14)

  1. 一种烧结钕铁硼磁体，该磁体包括主相和晶界相，其特征在于，磁体表层的主相晶粒平均尺寸与磁体中心区域的主相晶粒平均尺寸的比为1.05～1.35；
    其中，所述磁体表层是指距磁体表面的距离≤35μm的区域；所述磁体中心区域是指距磁体表面的距离≥500μm的区域；
    所述烧结钕铁硼磁体中含有29.2-32.5wt％的R、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M以及余量的T；
    其中，R为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu，以所述烧结钕铁硼磁体的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb；
    M选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；
    T为Fe，或者为Fe和Co，其中，T中的Fe的含量为80wt％以上。
  2. 根据权利要求1所述的烧结钕铁硼磁体，其中，所述晶界相包括三角区晶界相；所述三角区晶界相中，小面积三角区晶界相的个数占所有所述三角区晶界相总数的80％以上；所述小面积三角区晶界相为面积小于2.5μm2的三角区晶界相。
  3. 根据权利要求1所述的烧结钕铁硼磁体，其中，该烧结钕铁硼磁体的最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs；所述最大磁能积(BH)max的单位为MGOe，所述内禀矫顽力HcJ的单位为KOe。
  4. 根据权利要求1所述的烧结钕铁硼磁体，其中，所述磁体表层的主相晶粒平均尺寸与所述磁体中心区域的主相晶粒平均尺寸的比为1.13～1.35；
    所述烧结钕铁硼磁体中O的含量低于600ppm。
  5. 根据权利要求1所述的烧结钕铁硼磁体，其中，R为稀土元素，所述稀土元素为Nd和RE，或者所述稀土元素为Nd、RE与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb和Lu，以所述烧结钕铁硼磁体的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb。
  6. 一种制备烧结钕铁硼磁体的方法，其特征在于，该方法包括如下步骤：
    S1、制备烧结钕铁硼磁体基材；
    S2、在所述烧结钕铁硼磁体基材表面附着含有RE的扩散源，然后进行晶界扩散处理和回火处理；RE为Dy和/或Tb；
    其中，所述晶界扩散处理包括初始扩散热处理和N级扩散工艺段，N≥1，每级所述扩散工艺段依次包括：高温扩散热处理和低温扩散热处理；
    所述初始扩散热处理的条件包括：温度为800～980℃，时间为6～12h；
    所述低温扩散热处理的条件包括：温度为850～950℃，时间为6～12h；
    所述高温扩散热处理的温度低于烧结处理的温度，且比所述低温扩散温度高50～200℃，时间为2～8h；
    步骤S1得到的烧结钕铁硼磁体基材包含28.9-32.5wt％的R、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M以及余量的T；
    其中，R为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu，以所述烧结钕铁硼磁体基材的总重量为基准，RE的含量为0.5～6.5wt％，RE为Dy和/或Tb；
    M选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；
    T为Fe，或者为Fe和Co，其中，T中的Fe的含量为80wt％以上。
  7. 根据权利要求6所述的方法，其特征在于，每级所述扩散工艺段还包括：在所述低温扩散热处理之前，在所述高温扩散热处理后的烧结钕铁硼磁体基材表面附着含有RE的扩散源。
  8. 根据权利要求6或7所述的方法，其中，所述高温扩散热处理的温度为烧结温度的96％-99％。
  9. 根据权利要求6所述的方法，其中，在步骤S1中，采用如下步骤制备所述烧结钕铁硼磁体基材：
    S01、将合金原料置于真空感应炉中熔炼和浇铸，得到合金速凝片；
    S02、将所述合金速凝片进行氢破碎处理后，得到合金氢化粉；
    S03、将所述合金氢化粉进行微粉碎处理后，得到合金微粉；
    S04、将所述合金微粉置于磁场中进行取向成型处理后，将得到的成型的压坯在真空环境下或在真空烧结炉内通入保护气进行烧结处理和机械加工处理，得到所述烧结钕铁硼磁体基材。
  10. 根据权利要求9所述的方法，其中，在S01步骤中通过双合金法制备R1-T1-B-Ga-M1主合金速凝片和R2-T2-M2辅合金速凝片；
    所述R1-T1-B-Ga-M1主合金速凝片包含28.9-32.5wt％的R1、0.87-0.93wt％的B、0.3-0.55wt％的Ga、0.10-0.65wt％的M1和余量的T1；
    其中，R1为稀土元素，所述稀土元素为Nd，或者为Nd与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb、Dy、Tb和Lu；M1选自Cu、Al、Zr、Nb、Mn、Mg、Si、Cr和Ti中的至少一种；T1为Fe或者为Fe和Co；
    所述R1-T1-B-Ga-M1主合金速凝片中RE1的含量为0.5-5.2wt％，RE1为Dy和/或Tb；
    所述R2-T2-M2辅合金速凝片包含60-85wt％的R2、3.0-6.0wt％的M2以及余量的T2；
    其中，R2选自Nd、Pr、Dy和Tb中的一种或几种，M2选自Ga、Cu和Al中的至少一种；T2 为Fe、或者为Fe和Co；
    所述R2-T2-M2辅合金速凝片中RE2的含量为0-80wt％，RE2为Dy和/或Tb；
    所述R1-T1-B-Ga-M1主合金速凝片和所述R2-T2-M2辅合金速凝片的厚度各自独立地为0.13-0.46mm。
  11. 根据权利要求10所述的方法，其中，所述稀土元素为Nd和RE1，或者所述稀土元素为Nd、RE1与下组中至少一种元素的组合：Y、La、Ce、Pr、Sm、Eu、Gd、Ho、Er、Tm、Yb和Lu。
  12. 根据权利要求9所述的方法，其中，在步骤S02中，所述合金氢化粉的制备方法包括：
    将R1-T1-B-Ga-M1主合金速凝片进行氢破碎处理后得到主合金氢化粉，将R2-T2-M2辅合金速凝片进行氢破碎处理后得到辅合金氢化粉，再将主合金氢化粉和辅合金氢化粉混合，得到所述合金氢化粉；
    在所述合金氢化粉中，所述主合金氢化粉的质量含量为95％以上，所述辅合金氢化粉的质量含量为5％以下。
  13. 根据权利要求6所述的方法，其中，所述含有RE的扩散源包括RE的氧化物、RE的氟化物、RE的单质或RE的合金的一种或几种；
    所述含有RE的扩散源中，RE的含量为60-100wt％。
  14. 采用权利要求6～13中任意一项所述的方法制备的烧结钕铁硼磁体，其特征在于，该烧结钕铁硼磁体的最大磁能积(BH)max与内禀矫顽力HcJ的数值之和大于80；且剩磁Br＞13KGs；所述最大磁能积(BH)max的单位为MGOe，所述内禀矫顽力HcJ的单位为KOe。
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