Hot deformed neodymium-iron-boron magnet and method for producing the same

Abstract

The present application discloses a kind of hot deformation neodymium-iron-boron magnet and its preparation method, the composition of the hot deformation neodymium-iron-boron magnet is R a Co b B c Ni d Cu e T f Fe bal , R is one or more than one rare earth element with Nd as essential element, T is selected from one or both of Ti and Zr, a+b+c+d+e+f+bal=100 (in atomic percent), 13.5≤a≤16.5, 0.0≤b≤2.0, 5.2≤c≤5.6, 0.2≤d+e≤3.0, 0≤f≤0.2.In the magnet, the c face and ab face grain boundary of neodymium-iron-boron grain both exist non-ferromagnetic grain boundary phase.

Description

Technical Field

[0001] This application relates to the field of hot-deformable NdFeB magnets, specifically, this invention relates to a hot-deformable NdFeB magnet and its preparation method. Background Technology

[0002] The grain size of hot-deformed NdFeB magnets is an order of magnitude smaller than that of sintered NdFeB magnets. Based on the relationship between coercivity and grain size, its coercivity is expected to exceed 2.5T without heavy rare earth doping. However, in reality, the coercivity of hot-deformed magnets has not shown the potential advantage of their smaller grain size. This is mainly due to two reasons. First, the distribution of grain boundary phases is anisotropic, meaning that grain boundary phases tend to appear on the c-plane of the anisotropic main phase grains. This results in thicker grain boundaries on the c-plane with lower ferromagnetic element content, while the ab-plane grain boundaries are very thin with higher ferromagnetic element content. This is due to Nd2Fe 14 The cell structure of B determines that the interface terminations of the c-plane in its cell are dominated by Nd atoms, while the interface terminations of the ab-plane are almost entirely Fe atoms.

[0003] As is well known, grain boundary phases are often Nd-rich phases with high Nd content, which are more likely to combine with Nd atoms and thus exist in large quantities on c-plane grain boundaries. There has been no good solution to the problem of uneven distribution of grain boundary phases on c-plane and ab-plane grain boundaries in hot-deformable magnets. If the ab-plane grain boundary phase can be increased through compositional design, it is possible to achieve simultaneous magnetic isolation of exchange coupling between adjacent principal phase grains on both c-plane and ab-plane grain boundaries, thereby significantly improving the coercivity of hot-deformable magnets. Summary of the Invention

[0004] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the objective of this invention is to provide a method for solving the problem of uneven grain boundary phase distribution in hot-deformable magnets. By designing the magnet formulation composition, the distribution of grain boundary phases in the hot-deformable magnet is controlled, thereby achieving the formation of non-ferromagnetic thin-layer grain boundary phases on both the c-plane and ab-plane grain boundaries of the hot-deformable magnet. According to an embodiment of this invention, the amphiphilic element Ni is introduced. This element readily combines with both Nd and Fe elements, ultimately forming non-ferromagnetic grain boundary phases on both the c-plane and ab-plane grain boundaries of NdFeB grains.

[0005] In one aspect of the invention, a heat-deformable neodymium iron boron magnet is provided. According to an embodiment of the invention, the magnet's composition is R... a Co b B c Ni d Cu e T f Fe balR is one or more rare earth elements with Nd as an essential element, T is selected from one or both of Ti and Zr, a+b+c+d+e+f+bal=100 (in atomic percentage), 13.5≤a≤16.5, 0.0≤b≤2.0, 5.2≤c≤5.6, 0.2≤d+e≤3.0, 0≤f≤0.2.

[0006] According to embodiments of the present invention, the above-mentioned heat-deformed NdFeB magnet may further include at least one of the following additional technical features:

[0007] According to an embodiment of the present invention, the hot-deformed NdFeB magnet comprises a main phase grain and a grain boundary phase, wherein the grain boundary phase is NdFeB. 1-x-y-z Fe x Ni y Cu z , 0.2≤x+y+z≤0.4.

[0008] According to an embodiment of the present invention, the grain boundaries include triple grain boundaries and thin grain boundaries between two grains, wherein the grain boundary phase is Nd. 1-x-y-z Fe x Ni y Cu z It can be found not only at the three-pointed grain boundaries, but also in thin grain boundaries.

[0009] According to an embodiment of the present invention, the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is distributed on both c-plane and ab-plane grain boundaries.

[0010] According to an embodiment of the present invention, the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is a non-ferromagnetic grain boundary phase. It can effectively magnetically isolate the exchange coupling between adjacent principal phase grains.

[0011] In another aspect, the present invention also provides a method for preparing a hot-deformed neodymium iron boron magnet. According to an embodiment of the present invention, the method includes:

[0012] S1: According to R a Co b B c Ni d Cu e T f Fe balThe components and proportions are mixed to obtain the material, where R is one or more rare earth elements with Nd as an essential element, and T is selected from one or both of Ti and Zr. The formula is a+b+c+d+e+f+bal=100 (in atomic percentage), 13.5≤a≤16.5, 0.0≤b≤2.0, 5.2≤c≤5.6, 0.2≤d+e≤3.0, and 0≤f≤0.2.

[0013] S2: The material is smelted and spun to obtain a rapid quenching thin strip;

[0014] S3: The rapidly quenched thin strip is crushed and ground to obtain rapidly quenched magnetic powder;

[0015] S4: Perform crystallization treatment on the rapidly quenched magnetic powder to obtain crystallized magnetic powder;

[0016] S5: The crystallized magnetic powder is processed by hot pressing sintering to obtain a hot-pressed NdFeB magnet;

[0017] S6: The hot-pressed NdFeB magnet is processed using hot deformation technology or reverse extrusion molding technology to obtain a hot-deformed NdFeB magnet.

[0018] According to embodiments of the present invention, the above method may further include at least one of the following additional technical features:

[0019] According to an embodiment of the present invention, the hot pressing temperature in the hot pressing sintering method is 540℃-650℃.

[0020] According to an embodiment of the present invention, the heat distortion temperature in the heat distortion technology or reverse extrusion molding technology is 570℃-750℃.

[0021] According to an embodiment of the present invention, the hot-deformed NdFeB magnet comprises a main phase grain and a grain boundary phase, wherein the grain boundary phase is NdFeB. 1-x-y-z Fe x Ni y Cu z , 0.2≤x+y+z≤0.4.

[0022] According to an embodiment of the present invention, the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is distributed on both c-plane and ab-plane grain boundaries.

[0023] According to an embodiment of the present invention, the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is a nonferromagnetic grain boundary phase.

[0024] According to embodiments of the present invention, a method for preparing a hot-deformed neodymium iron boron magnet is disclosed. According to embodiments of the present invention, the method includes the following steps:

[0025] 1) Proportion the materials according to the nominal composition of the design, focusing on controlling the relative content of elements such as Nd, Fe, B, Ni, and Cu.

[0026] 2) Melt and spin the material according to the composition designed in step 1) to obtain a rapid quenching thin strip with the predetermined composition;

[0027] 3) The rapidly quenched thin strip is crushed and ground to obtain rapidly quenched magnetic powder;

[0028] 4) Crystallize the rapidly quenched magnetic powder;

[0029] 5) Hot-pressed NdFeB magnets with fine grains are prepared from magnetic powder using a hot-pressing sintering method. The hot-pressing temperature is 540℃-650℃.

[0030] 6) Anisotropic heat-deformed NdFeB magnets are prepared using hot deformation or reverse extrusion molding processes. The heat deformation temperature is 570℃-750℃.

[0031] According to embodiments of the present invention, the hot-deformed NdFeB magnets disclosed in the present invention, or the hot-deformed NdFeB magnets prepared by the method according to embodiments of the present invention, exhibit non-ferromagnetic grain boundary phases Nd on both the ab and c planes. 1-x-y- z Fe x Ni y Cu z It can effectively magnetically isolate adjacent main phase grains, prevent the expansion of reverse magnetic domains, and improve coercivity.

[0032] According to embodiments of the present invention, compared to currently common heat-deformed NdFeB magnets, the present invention has at least one of the following beneficial effects:

[0033] 1) In this invention, Ni, an amphiphilic element, was selected as one of the foreign additive elements of the magnet. Cu, a low melting point alloying element, was also selected to reduce the melting point of the grain boundary phase, so that the grain boundary phase can be distributed more evenly on the ab and c plane grain boundaries of the NdFeB grains.

[0034] 2) By controlling the relative contents of Nd, Fe, B, Ni, and Cu elements in the raw materials, the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It can be distributed relatively evenly on the ab and c plane grain boundaries of the magnet, thereby effectively magnetically isolating adjacent grains and improving coercivity.

[0035] 3) Compared with the magnetic powder commonly used to prepare hot-deformed NdFeB magnets, the formulation designed in this invention omits Ga and instead adds Ni and Cu elements, which can reduce the cost of raw materials. Attached Figure Description

[0036] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0037] Figure 1 This is a model diagram of the ideal grain boundary phase distribution in the designed hot-deformed NdFeB magnet. Detailed Implementation

[0038] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the application is described and illustrated below with reference to the accompanying drawings and embodiments. Obviously, the described exemplary embodiments are only a part of the embodiments of this invention, and not all examples. All other examples obtained by those skilled in the art based on the examples in this invention without inventive effort are within the protection scope of this invention.

[0040] Obviously, the accompanying drawings described below are merely an ideal model demonstration of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without any inventive effort. Furthermore, it is understood that although the effort involved in such a development process may be lengthy, for those skilled in the art related to the content disclosed in this application, any changes to the design, manufacturing, or production methods based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of this application.

[0041] The present invention will now be described in detail with reference to an exemplary embodiment. However, it should be noted that this embodiment is not a limitation of the present invention. Equivalent changes or substitutions in composition or process made by those skilled in the art based on these embodiments are all within the protection scope of the present invention.

[0042] Exemplary Implementation Examples

[0043] The nominal composition of the alloy is selected as (Nd, Pr). 15 Co 1.5 B 5.4 Ni 0.6 Cu 0.6 Ti 0.1 Febal (at.%), materials are proportioned according to the nominal component ratio.

[0044] The prepared alloy raw materials (Nd, Pr) 15 Co 1.5 B 5.4 Ni 0.6 Cu 0.6 T 0.1 Fe bal The ingot is placed in a vacuum arc melting furnace or induction melting furnace and repeatedly melted 5 times under the protection of an argon atmosphere to fully alloy the ingot. After cooling, an alloy ingot is obtained.

[0045] The obtained alloy ingot is coarsely crushed and placed in a quartz tube of a vacuum rapid quenching furnace. Under the protection of an argon atmosphere, the melt is rapidly quenched to obtain the desired rapid quenched thin strip. The diameter of the quartz tube opening is 0.8 mm, the distance from the roller surface is 1 mm, and the roller speed is 25 m / s.

[0046] Rapidly quenched thin strips are crushed, ground, and then screened to obtain rapidly quenched magnetic powder with a particle size of 100-350μm.

[0047] The rapidly quenched magnetic powder is crystallized at 560℃, and the crystallized rapidly quenched magnetic powder is used as raw material for hot pressing and hot deformation processes.

[0048] Powder was added to a cemented carbide mold with an inner diameter of 10 mm and a height of 50 mm. The diameter and length of the upper and lower pressure heads were 9.8 mm and 40 mm, respectively. The assembled female mold, pressure heads, and base were placed in a vacuum hot press furnace. The furnace was heated until the vacuum degree reached 10... -3 The powder was hot-pressed and sintered at a temperature of 570℃ and a loading pressure of 300 MPa for 2 minutes. After hot-pressing and sintering, the sample was cooled in the furnace. After the sample cooled to room temperature, it was demolded and removed. A dense, isotropic hot-pressed sample with a height of 14 mm and a diameter of 9.8 mm was obtained.

[0049] The hot-pressed sample was placed in a female mold with an inner diameter of 25 mm and a height of 30 mm. The upper and lower pressure rods used with the female mold were both 24.8 mm in diameter and 35 mm in length. The assembled mold was then placed in a vacuum hot press furnace, and the vacuum level was increased to 10... -3 The sample was hot-pressed and deformed at a temperature of 670℃. Once the sample height decreased by 72%, the hot deformation was complete, resulting in an anisotropic hot-deformed magnet. The sample was then removed after the furnace cooled to room temperature.

[0050] It should be noted that since the lowest eutectic point temperature of the Nd-Ni system is 540℃ and that of the Nd-Cu system is 520℃, the temperatures selected for the hot pressing and hot deformation processes are relatively low.

[0051] Figure 1 This is a model diagram of the ideal microstructure of a hot-deformed NdFeB magnet prepared according to the designed magnet composition and fabrication process. From... Figure 1 As can be seen, each face of the main phase grain is continuously wrapped by the grain boundary phase, and the c-plane grain boundary is slightly thicker than the ab-plane grain boundary phase.

[0052] In addition, Ti exists in the magnet in the form of TiB2. This phase is widely distributed in the form of dispersed and dot-like precipitates on the grain boundaries and inside the main phase grains of the magnet. Most of the TiB2 phase is distributed on the grain boundaries, which can inhibit grain boundary migration and grain growth to a certain extent, thereby refining uniform grains and preventing the formation of abnormally large grains.

[0053] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0054] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A heat-deformable neodymium iron boron magnet, characterized in that, The composition of the heat-deformed NdFeB magnet is R. a Co b B c Ni d Cu e T f Fe bal R represents one or more rare earth elements with Nd as an essential element, T is selected from one or both of Ti and Zr, a+b+c+d+e+f+bal=100 (in atomic percentage), 13.5 ≤ a ≤ 16.5, 0.0≤b≤2.0, 5.2≤c≤5.6, 0.2≤d+e≤3.0, 0≤f≤0.2; the hot-deformed NdFeB magnet contains a main phase grain and a grain boundary phase, the grain boundary phase being Nd 1-x-y-z Fe x Ni y Cu z , 0.2≤x+y+z≤0.4; the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is distributed on both c-plane and ab-plane grain boundaries; the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is a nonferromagnetic grain boundary phase.

2. A method for preparing a hot-deformed NdFeB magnet, characterized in that, include: S1: According to R a Co b B c Ni d Cu e T f Fe bal The components and proportions are mixed to obtain the material, where R is one or more rare earth elements with Nd as an essential element, and T is selected from one or both of Ti and Zr. The formula is a+b+c+d+e+f+bal=100 (in atomic percentage), 13.5 ≤ a ≤ 16.5, 0.0≤b≤2.0, 5.2≤c≤5.6, 0.2≤d+e≤3.0, and 0≤f≤0.

2. S2: The material is smelted and spun to obtain a rapid quenching thin strip; S3: The rapidly quenched thin strip is crushed and ground to obtain rapidly quenched magnetic powder; S4: Perform crystallization treatment on the rapidly quenched magnetic powder to obtain crystallized magnetic powder; S5: The crystallized magnetic powder is processed by hot pressing sintering to obtain a hot-pressed NdFeB magnet; S6: The hot-pressed NdFeB magnet is processed using hot deformation technology or reverse extrusion molding technology to obtain a hot-deformed NdFeB magnet. The hot-deformed NdFeB magnet contains a main phase grain and a grain boundary phase, wherein the grain boundary phase is Nd. 1-x-y- z Fe x Ni y Cu z 0.2≤x+y+z≤0.4, the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z The Nd grain boundary phase is distributed on both the c-plane and ab-plane grain boundaries. 1-x-y-z Fe x Ni y Cu z It is a nonferromagnetic grain boundary phase.

3. The method according to claim 2, characterized in that, The hot pressing temperature in the hot pressing sintering method is 540 ℃-650 ℃.

4. The method according to claim 2, characterized in that, The heat distortion temperature in the aforementioned heat distortion technology or reverse extrusion molding technology is 570 ℃-750 ℃.

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