Thermal deformation neodymium-iron-boron magnet and preparation method thereof

Abstract

The invention discloses a thermal deformation neodymium-iron-boron magnet and a preparation method thereof, the component of the thermal deformation neodymium-iron-boron magnet is RaCobBcNidCueTfFebal, R is one or more rare earth elements taking Nd as an essential element, T is selected from one or two of Ti and Zr, a + b + c + d + e + f + bal = 100 (by atomic percent), 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. In the magnet, non-ferromagnetic grain boundary phases exist on the grain boundaries of the c surface and the ab surface of neodymium iron boron grains.

Description

Technical Field

[0001] The present application relates to the field of thermally deformed NdFeB magnets, and in particular, to a thermally deformed NdFeB magnet and a preparation method thereof. Background Art

[0002] The grain size of hot-deformed NdFeB magnets is one order of magnitude lower than that of sintered NdFeB magnets. Based on the relationship between coercive force and grain size, its coercive force is expected to be higher than 2.5T without heavy rare earth doping. However, the reality is that the coercive force of hot-deformed magnets does not show its potential advantage in grain size. There are two main reasons for this. One is that the distribution of grain boundary phases is anisotropic, that is, the grain boundary phases tend to appear on the c-plane of the anisotropic main phase grains, resulting in thicker grain boundaries on the c-plane and lower ferromagnetic element content, while the ab-plane grain boundaries are very thin and have a high ferromagnetic element content. This is due to the fact that Nd2Fe 14 Determined by the unit cell structure of B, the interface terminals of the c-plane in the unit cell are mainly Nd atoms, while the interface terminals of the ab-plane are almost all Fe atoms.

[0003] As we all know, the grain boundary phase is often a Nd-rich phase with a high Nd content, which is easier to combine with Nd atoms and thus exists in large quantities on the c-plane grain boundary. There has been no good solution to the problem of uneven distribution of grain boundary phases on the c-plane grain boundary and the ab-plane grain boundary in thermal deformation magnets. If the ab-plane grain boundary phase can be increased through composition design, the exchange coupling of adjacent main phase grains can be magnetically isolated on the c-plane grain boundary and the ab-plane grain boundary at the same time, thereby greatly improving the coercivity of the thermal deformation magnet. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, the purpose of the present invention is to provide a method for solving the uneven distribution of grain boundary phases in thermally deformed magnets, by designing the magnet formula composition and regulating the distribution of grain boundary phases in thermally deformed magnets, so as to achieve the formation of non-ferromagnetic thin-layer grain boundary phases on both the c-plane and ab-plane grain boundaries of the thermally deformed magnets. According to an embodiment of the present invention, an "amphiphilic element" Ni is introduced, which is easy to combine with both Nd and Fe elements, and finally forms non-ferromagnetic grain boundary phases on both the c-plane and ab-plane grain boundaries of NdFeB grains.

[0005] In one aspect of the present invention, the present invention provides a thermally deformed NdFeB magnet. According to an embodiment of the present invention, the composition of the magnet is R a Co b B c Ni d Cu e T f Fe bal, R 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 an embodiment of the present invention, the thermally 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 thermally deformed NdFeB magnet comprises 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.

[0008] According to an embodiment of the present invention, the grain boundary includes a triple grain boundary and a thin grain boundary between two grains, and the grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It can be distributed not only at the triple grain boundaries, but also exists in the 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 grain boundaries 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, which can effectively magnetically isolate the exchange coupling between adjacent main phase grains.

[0011] In another aspect of the present invention, the present invention also provides a method for preparing a thermally deformed NdFeB magnet. According to an embodiment of the present invention, the method comprises:

[0012] S1: According to R a Co b B c Ni d Cu e T f Fe balThis composition and ratio are mixed to obtain a material, wherein R is one or more rare earth elements with Nd as an essential element, T is one or both of Ti and Zr, and 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;

[0013] S2: Melting and strip-spinning the material to obtain a rapidly quenched thin strip;

[0014] S3: crushing and grinding the quenched thin strip to obtain quenched magnetic powder;

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

[0016] S5: processing the crystallized magnetic powder by hot pressing and sintering to obtain a hot pressed NdFeB magnet;

[0017] S6: Processing the hot pressed NdFeB magnet by using a thermal deformation technology or a reverse extrusion molding technology to obtain a thermally deformed NdFeB magnet.

[0018] According to an embodiment 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°C-650°C.

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

[0021] According to an embodiment of the present invention, the thermally deformed NdFeB magnet comprises 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.

[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 grain boundaries 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 non-ferromagnetic grain boundary phase.

[0024] According to an embodiment of the present invention, the present invention discloses a method for preparing a thermally deformed NdFeB magnet. According to an embodiment of the present invention, the method comprises the following steps:

[0025] 1) Material proportioning is carried out according to the designed nominal composition, with emphasis on regulating the relative contents of elements such as Nd, Fe, B, Ni, and Cu.

[0026] 2) melting and spinning the strip according to the composition designed in step 1) to obtain a rapidly quenched thin strip with a predetermined composition;

[0027] 3) crushing and grinding the rapidly quenched thin strip to obtain rapidly quenched magnetic powder;

[0028] 4) Performing crystallization treatment on the rapidly quenched magnetic powder;

[0029] 5) The magnetic powder is prepared into an isotropic hot-pressed NdFeB magnet with fine grains by hot-pressing sintering method at a hot-pressing temperature of 540°C-650°C.

[0030] 6) Using a thermal deformation process or a reverse extrusion molding process to prepare anisotropic thermally deformed NdFeB magnets with a thermal deformation temperature of 570°C-750°C.

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

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

[0033] 1) In the present invention, the "amphiphilic element" Ni is selected as one of the external additive elements of the magnet, and Cu, a low melting point alloying element, is selected to lower the melting point of the grain boundary phase, so that the grain boundary phase can be more evenly distributed on the ab-plane and c-plane grain boundaries of the NdFeB grains.

[0034] 2) By adjusting the relative contents of Nd, Fe, B, Ni, and Cu 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-plane and c-plane grain boundaries of the magnet, thereby effectively magnetically isolating adjacent grains and improving coercive force.

[0035] 3) Compared with the common magnetic powder used to prepare hot-deformed NdFeB magnets, the Ga element is abandoned in the formula composition designed by the present invention, and Ni and Cu elements are added instead, which can reduce the cost of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0039] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments. Obviously, the exemplary embodiments described are only part of the embodiments of the present invention, not all examples. Based on the examples in the present invention, all other examples obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0040] Obviously, the drawings described below are only an ideal model demonstration of the present application. For ordinary technicians in this field, the present application can also be applied to other similar scenarios based on these drawings without creative work. In addition, it can also be understood that although the efforts made in this development process may be lengthy, for ordinary technicians in this field related to the content disclosed in this application, some changes in design, manufacturing or production based on the technical content disclosed in this application are just conventional technical means, and should not be understood as the content disclosed in this application is insufficient.

[0041] The present invention is described in detail below with reference to an exemplary embodiment, but it should be noted that this embodiment is not a limitation of the present invention, and equivalent changes or substitutions in components and processes made by ordinary technicians in the field according to these embodiments are all within the protection scope of the present invention.

[0042] EXAMPLE EMBODIMENTS

[0043] Select the nominal alloy composition as (Nd, Pr) 15 Co 1.5 B 5.4 Ni 0.6 Cu 0.6 Ti 0.1 Febal (at.%), and mix materials according to the nominal composition 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 an induction melting furnace and repeatedly melted 5 times under the protection of an argon atmosphere to fully alloy the ingot, and then cooled to obtain an alloy ingot.

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

[0046] The quick-quenching thin strip is crushed and ground to screen out quick-quenching magnetic powder with a particle size of 100-350 μm.

[0047] The quick-quenching magnetic powder is crystallized at 560°C, and the crystallized quick-quenching magnetic powder is used as the raw material for hot pressing and hot deformation processes.

[0048] The powder was added into a carbide die 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 die, pressure head and base were placed in a vacuum hot press furnace. When the vacuum in the furnace chamber reached 10 -3 Pa and the temperature reaches 570℃, the powder is hot pressed and sintered, the loading pressure is 300MPa, and the action time is 2 minutes. After the hot pressing and sintering is completed, the sample is cooled with the furnace, and the hot pressed sample is demolded and taken out after the sample cools to room temperature. A dense isotropic hot pressed sample with a height of 14mm and a diameter of 9.8mm is obtained.

[0049] The hot pressing sample is placed in a female mold with an inner diameter of 25 mm and a height of 30 mm. The upper and lower pressing rods used in conjunction with the female mold have a diameter of 24.8 mm and a length of 35 mm. The assembled mold is placed in a vacuum hot pressing furnace and the vacuum degree is 10 -3 Pa, and then the hot pressed sample is thermally deformed after the temperature reaches 670℃. When the sample height drops by 72%, the thermal deformation is completed, and anisotropic hot deformed magnets are obtained. The sample is taken out after the furnace temperature cools to room temperature.

[0050] It should be pointed out that since the lowest eutectic temperature of the Nd-Ni system is 540°C and the lowest eutectic temperature of the Nd-Cu system is 520°C, the temperature of the hot pressing and hot deformation process is selected to be relatively low.

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

[0052] In addition, the Ti element exists in the magnet in the form of TiB2, which is widely distributed on the grain boundaries and inside the main phase grains of the magnet in the form of dispersed and point-like precipitation phases. 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 coarse grains.

[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0054] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A thermally deformed NdFeB magnet, characterized in that: The composition of the magnet is R a Co b B c Ni d Cu e T f Fe bal , R 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.

2. The thermally deformed NdFeB magnet according to claim 1, characterized in that: The thermally deformed NdFeB magnet comprises main phase grains and grain boundary phases, wherein the grain boundary phase is Nd 1-x-y-z Fe x Ni y Cu z , 0.2≤x+y+z≤0.

4.

3. The thermally deformed NdFeB magnet according to claim 2, characterized in that: The grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is distributed on both c-plane grain boundaries and ab-plane grain boundaries.

4. The thermally deformed NdFeB magnet according to claim 3, characterized in that: The grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is a non-ferromagnetic grain boundary phase.

5. A method for preparing a thermally deformed NdFeB magnet, characterized in that: include: S1: According to R a Co b B c Ni d Cu e T f Fe bal This composition and ratio are mixed to obtain a material, wherein R is one or more rare earth elements with Nd as an essential element, T is one or both of Ti and Zr, and 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; S2: Melting and strip-spinning the material to obtain a rapidly quenched thin strip; S3: crushing and grinding the quenched thin strip to obtain quenched magnetic powder; S4: performing a crystallization treatment on the rapidly quenched magnetic powder to obtain crystallized magnetic powder; S5: processing the crystallized magnetic powder by hot pressing and sintering to obtain a hot pressed NdFeB magnet; S6: Processing the hot pressed NdFeB magnet by using a thermal deformation technology or a reverse extrusion molding technology to obtain a thermally deformed NdFeB magnet.

6. The method according to claim 5, characterized in that The hot pressing temperature in the hot pressing sintering method is 540°C-650°C.

7. The method according to claim 5, characterized in that The heat deformation temperature in the heat deformation technology or the reverse extrusion molding technology is 570°C-750°C.

8. The method according to claim 5, characterized in that The thermally deformed NdFeB magnet comprises main phase grains and grain boundary phases, wherein the grain boundary phase is Nd 1-x-y-z Fe x Ni y Cu z , 0.2≤x+y+z≤0.

4.

9. The method according to claim 5, characterized in that The grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is distributed on both c-plane grain boundaries and ab-plane grain boundaries.

10. The method according to claim 5, characterized in that The grain boundary phase Nd 1-x-y-z Fe x Ni y Cu z It is a non-ferromagnetic grain boundary phase.

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