CN113035558A - Thermal deformation neodymium iron boron magnet and preparation method thereof - Google Patents
Thermal deformation neodymium iron boron magnet and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a thermal deformation neodymium iron boron magnet and a preparation method thereof, wherein the method comprises the following steps: mixing the first alloy powder and the rapidly quenched Nd-Fe-B powder, and then sequentially carrying out cold pressing preforming, hot pressing sintering and thermal deformation to carry out doping grain boundary diffusion so as to obtain a doped thermal deformation magnet; then placing the second alloy on the surface of the doped thermal deformation magnet and heating to perform grain boundary diffusion so as to obtain a thermal deformation neodymium iron boron magnet; wherein the first alloy is Tb-Cu alloy or/and Dy-Cu alloy, and the second alloy is Nd-Cu alloy or/and Pr-Cu alloy. Therefore, the coercive force and the coercive force temperature stability of the thermal deformation neodymium iron boron magnet can be obviously improved.
Description
Technical Field
The invention belongs to the technical field of rare earth permanent magnet material preparation, and particularly relates to a thermal deformation neodymium iron boron magnet and a preparation method thereof.
Background
The neodymium iron boron material is widely applied to the fields of automobiles, aerospace, electronics, medical equipment and the like due to the excellent magnetic performance, particularly high magnetic energy product and high coercive force. In recent years, with the rapid development of new energy fields such as electric vehicles and wind power generation, the demand for the neodymium iron boron material is increasing day by day. Meanwhile, higher requirements are also put on the magnetic performance of the material. The heat-deformed Nd-Fe-B material is a third type of Nd-Fe-B except sintered Nd-Fe-B and bonded Nd-Fe-BThe material has the advantages of fine grain size, high density, excellent corrosion resistance and the like, and has received much attention from the industry and scientific research community in recent years. However, the grain boundary of the hot deformed magnet often has a large amount of ferromagnetic elements such as Fe and Co, so that the coercive force of the hot deformed Nd-Fe-B magnet is only 1.2-1.8T. In recent years, it has been proposed in the academia to improve the coercive force of a hot deformed magnet by a single diffusion method such as grain boundary diffusion or grain boundary doping. However, in the case of Tb-Cu alloy and Dy-Cu alloy, Tb and Dy tend to enter Nd in the magnet after alloy doping2Fe14B lattice, form (Nd, Tb)2Fe14B、(Nd,Dy)2Fe14B matrix phase, Tb2Fe14B and Dy2Fe14B ratio Nd2Fe14B has a higher anisotropy field, and thus the coercive force of the magnet can be significantly improved. However, it is because Tb and Dy tend to enter grain boundary Nd2Fe14In B crystal lattice, high ferromagnetic elements such as Fe and Co still exist at the crystal boundary of the thermal deformation magnet, so that the improvement of coercive force is limited.
Therefore, the existing grain boundary diffusion method is in need of improvement.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, one object of the present invention is to provide a thermal deformation neodymium iron boron magnet and a preparation method thereof, wherein the method for preparing the thermal deformation neodymium iron boron magnet can significantly improve the coercivity of the thermal deformation neodymium iron boron magnet and simultaneously reduce the temperature coefficient of the coercivity.
In one aspect of the invention, a method of making a thermally deformed neodymium-iron-boron magnet is provided. According to an embodiment of the invention, the method comprises:
(1) mixing the first alloy powder and the rapidly quenched Nd-Fe-B powder, and then sequentially carrying out cold pressing preforming, hot pressing sintering and thermal deformation to carry out doping grain boundary diffusion so as to obtain a doped thermal deformation magnet;
(2) placing the second alloy on the surface of the doped thermal deformation magnet and heating to perform grain boundary diffusion so as to obtain a thermal deformation neodymium iron boron magnet;
wherein the first alloy is Tb-Cu alloy or/and Dy-Cu alloy, and the second alloy is Nd-Cu alloy or/and Pr-Cu alloy.
According to the method for preparing the thermal deformation neodymium iron boron magnet, Tb-Cu alloy powder or/and Dy-Cu alloy powder and rapidly quenched Nd-Fe-B powder are mixed, and then cold pressing preforming, hot pressing sintering and thermal deformation are sequentially carried out to carry out doping grain boundary diffusion, so that the doped thermal deformation magnet can be obtained. In the process of doping grain boundary diffusion, Tb or/and Dy elements smoothly enter Nd2Fe14In B lattice, Tb or/and Dy partially replace the primary phase Nd2Fe14Nd in B, form (Nd, Tb)2Fe14B、(Nd,Dy)2Fe14And the core-shell structure improves the anisotropy field of the main phase, so that the coercive force of the magnet is improved. However, at the time, the grain boundary of the material still has high content of ferromagnetic elements, so that the coercive force of the magnet is improved to a limited extent, and in order to further improve the coercive force of the magnet, Nd-Cu alloy or/and Pr-Cu alloy is placed on the surface of the doped thermal deformation magnet and heated to carry out surface grain boundary diffusion. After the surface grain boundary is diffused, the nonmagnetic grain boundary phase in the magnet is obviously increased, the interaction between ferromagnetic matrix phases is effectively limited, and the coercive force of the magnet is further improved; meanwhile, the coercive force temperature coefficient is also obviously reduced. Therefore, compared with the single doping grain boundary diffusion or surface grain boundary diffusion mode in the prior art, the thermal deformation neodymium iron boron magnet is prepared by adopting the two-step grain boundary diffusion method of alloy doping grain boundary diffusion and alloy surface grain boundary diffusion, and the thermal deformation neodymium iron boron magnet with high coercivity and low coercivity temperature coefficient can be obtained.
In addition, the method for preparing the deformed ndfeb magnet according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, in step (1), the Tb-Cu alloy has the formula TbxCu100-xThe chemical formula of the Dy-Cu alloy is DyxCu100-x，50≤x≤85。
In some embodiments of the present invention, in the step (1), the first alloy powder accounts for 1 to 10% of the total weight of the rapidly quenched Nd-Fe-B powder. Thus, the heat-deformed neodymium-iron-boron magnet with high coercive force and low coercive force temperature coefficient can be obtained.
In some embodiments of the present invention, in step (1), the hot-pressing sintering is performed under vacuum or under inert atmosphere protection, and the vacuum condition is that the vacuum degree is not more than 10-2Pa, and the hot-pressing sintering temperature is 600-700 ℃. Thus, the heat-deformed neodymium-iron-boron magnet with high coercive force and low coercive force temperature coefficient can be obtained.
In some embodiments of the present invention, in step (1), the thermal deformation is performed under vacuum or inert atmosphere protection, and the vacuum condition is that the vacuum degree is not more than 10-2Pa, and the thermal deformation temperature is 675-800 ℃. Thus, the heat-deformed neodymium-iron-boron magnet with high coercive force and low coercive force temperature coefficient can be obtained.
In some embodiments of the invention, in step (2), the Nd — Cu alloy has a chemical formula of NdxCu100-xThe chemical formula of the Pr-Cu alloy is PrxCu100-x，50≤x≤85。
In some embodiments of the invention, in step (2), the second alloy is a powder or flake.
In some embodiments of the invention, in the step (2), the surface grain boundary diffusion process is performed under vacuum or inert atmosphere protection, and the vacuum condition is that the vacuum degree is not more than 10-2Pa, the diffusion temperature is 550-675 ℃, and the diffusion time is 20-60 minutes. Thus, the heat-deformed neodymium-iron-boron magnet with high coercive force and low coercive force temperature coefficient can be obtained.
In a second aspect of the invention, a thermally deformed neodymium iron boron magnet is provided. According to the embodiment of the invention, the thermal deformation neodymium iron boron magnet is prepared by adopting the method for preparing the thermal deformation neodymium iron boron magnet. Therefore, the hot deformed neodymium iron boron magnet has high coercive force and low coercive force temperature coefficient.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a schematic flow diagram of a method of preparing a thermally deformed neodymium-iron-boron magnet according to one embodiment of the present invention;
fig. 2 is a microstructure analysis of the thermally deformed neodymium-iron-boron magnet prepared in comparative examples 2 to 4 and example 2, wherein (a) in fig. 2 is a microstructure analysis of the magnet obtained in comparative example 2; fig. 2 (b) is a microstructure analysis of the magnet obtained in comparative example 3; fig. 2 (c) is a microstructure analysis of the magnet obtained in comparative example 4; fig. 2 (d) is a microstructure analysis of the magnet obtained in example 2.
Detailed Description
The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In a first aspect of the invention, a method of making a thermally deformed neodymium-iron-boron magnet is presented. According to an embodiment of the invention, with reference to fig. 1, the method comprises:
s100: mixing the first alloy powder and the rapidly quenched Nd-Fe-B powder, and then sequentially carrying out cold pressing preforming, hot pressing sintering and thermal deformation to carry out doped grain boundary diffusion
In the step, an alloy ingot of a first alloy with uniform components is smelted, an alloy thin strip of the first alloy is prepared by a rapid quenching method, the alloy thin strip is crushed by a ball mill to obtain micron-sized first alloy powder, and then the first alloy powder and the rapidly quenched Nd-Fe-B powder are mixed and subjected to cold pressing preforming, hot pressing sintering and thermal deformation in sequence to carry out doping grain boundary diffusion, so that the doped thermal deformation magnet can be obtained. Wherein the first alloy is Tb-Cu alloy or/and Dy-Cu alloy, specifically, the first alloy is Tb-Cu alloy, or the first alloy is Dy-Cu alloyThe gold, or the first alloy, is a mixture of a Tb-Cu alloy and a Dy-Cu alloy, and the mixing ratio of the Tb-Cu alloy and the Dy-Cu alloy is not particularly limited, and can be selected by those skilled in the art according to actual needs. The inventors have found that, in the above-mentioned grain boundary diffusion process, Tb or/and Dy elements smoothly enter Nd2Fe14In B lattice, Tb or/and Dy partially replace the primary phase Nd2Fe14Nd in B, form (Nd, Tb)2Fe14B、(Nd,Dy)2Fe14And the core-shell structure improves the anisotropy field of the main phase, so that the coercive force of the magnet is improved. The above rapid quenching method is a conventional method for producing an alloy thin strip in the art.
Further, the chemical formula of the Tb-Cu alloy is TbxCu100-xThe chemical formula of the Dy-Cu alloy is DyxCu100-xX is more than or equal to 50 and less than or equal to 85. Preferably, the Tb-Cu alloy has the formula Tb70Cu30The chemical formula of the Dy-Cu alloy is Dy70Cu30。
The first alloy powder may account for 1% to 10% of the total weight of the first alloy powder and the rapidly quenched Nd — Fe — B powder, and specifically may account for 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or the like. The inventor finds that if the addition amount of the first alloy powder is too small, the coercivity improvement effect of the prepared thermal deformation neodymium iron boron magnet is not obvious; if the addition amount of the first alloy powder is too much, the storage amount of the heavy rare earth element Dy/Tb in the earth crust is far lower than that of the light rare earth element Nd, the market price of the heavy rare earth element Dy/Tb is far higher than that of the light rare earth element Nd, and the raw material cost for preparing the magnet can be increased due to the addition of a large amount of Dy/Tb.
Further, the cold pressing pressure of the cold pressing preforming is 350-450 MPa, preferably 400MPa, and the pressure maintaining time is 1-5 min; meanwhile, the hot-pressing sintering is carried out under the protection of vacuum or inert atmosphere, the hot-pressing pressure is 350-450 MPa, preferably 400MPa, the hot-pressing sintering temperature is 600-700 ℃, the pressure maintaining time is 1-20 min, and if the vacuum hot-pressing sintering is carried out, the vacuum degree is not more than 10-2Pa; in addition, the thermal deformation is carried out under the protection of vacuum or inert atmosphere, the thermal deformation temperature is 675-800 ℃, and if the thermal deformation process is carried outIn vacuum atmosphere, the vacuum degree is not more than 10-2Pa。
S200: placing the second alloy on the surface of the doped thermal deformation magnet and heating for surface grain boundary diffusion
In the step, the surface of the doped thermal deformation magnet obtained in the step S100 is polished clean, and then the second alloy is placed on the surface of the doped thermal deformation magnet and heated to perform surface grain boundary diffusion, so that the thermal deformation neodymium iron boron magnet can be obtained. The second alloy is Nd-Cu alloy or/and Pr-Cu alloy, specifically, the second alloy is Nd-Cu alloy, or the second alloy is Pr-Cu alloy, or the second alloy is a mixture of Nd-Cu alloy and Pr-Cu alloy, and the mixing ratio of Nd-Cu alloy and Pr-Cu alloy is not particularly limited, and can be selected by those skilled in the art according to actual needs. The inventors found that after the surface grain boundary diffusion of the second alloy, the nonmagnetic grain boundary phase in the magnet is significantly increased, which effectively limits the interaction between the ferromagnetic matrix phases, so that the coercivity of the magnet is further improved, and at the same time, the coercivity temperature coefficient is also significantly reduced. The second alloy ingot is crushed into powder to cover the surface of the doped thermal deformation magnet or the second alloy ingot is cut into slices to be placed on the surface of the doped thermal deformation magnet, and the second alloy ingot is ensured to be in direct contact with the doped thermal deformation magnet to form a diffusion couple; the above surfaces are the upper and lower surfaces perpendicular to the direction of easy magnetization of the doped thermal deformation magnet.
Further, the chemical formula of the Nd-Cu alloy is NdxCu100-xThe chemical formula of the Pr-Cu alloy is PrxCu100-xX is more than or equal to 50 and less than or equal to 85. Preferably, the Nd-Cu alloy has a chemical formula of Nd70Cu30The chemical formula of the Pr-Cu alloy is Pr70Cu300。
Further, the surface grain boundary diffusion process is carried out under the protection of vacuum or inert atmosphere, the diffusion temperature is 550-675 ℃, the diffusion time is 20-60 minutes, and if the surface grain boundary diffusion is carried out in vacuum, the vacuum degree is not more than 10-2Pa。
The inventor finds that the doped thermal deformation magnet can be obtained by mixing Tb-Cu alloy powder or/and Dy-Cu alloy powder with rapidly quenched Nd-Fe-B powder, and then sequentially carrying out cold pressing preforming, hot pressing sintering and thermal deformation to carry out doping grain boundary diffusion. In the process of doping grain boundary diffusion, Tb or/and Dy elements smoothly enter Nd2Fe14In B lattice, Tb or/and Dy partially replace the primary phase Nd2Fe14Nd in B, form (Nd, Tb)2Fe14B、(Nd,Dy)2Fe14And the core-shell structure improves the anisotropy field of the main phase, so that the coercive force of the magnet is improved. However, at this time, a high content of ferromagnetic elements still exists at the grain boundary of the material, so that the coercivity of the magnet is improved to a limited extent. In order to further improve the coercive force of the magnet, Nd-Cu alloy or/and Pr-Cu alloy is placed on the surface of the doped thermal deformation magnet and heated for surface grain boundary diffusion, after the surface grain boundary diffusion, nonmagnetic grain boundary phases in the magnet are obviously increased, interaction among ferromagnetic matrix phases is effectively limited, the coercive force of the magnet is further improved, and meanwhile, the coercive force temperature coefficient is also obviously reduced. Therefore, compared with the single doping grain boundary diffusion or surface grain boundary diffusion mode in the prior art, the thermal deformation neodymium iron boron magnet is prepared by adopting the two-step grain boundary diffusion method of alloy doping grain boundary diffusion and alloy surface grain boundary diffusion, and the thermal deformation neodymium iron boron magnet with high coercivity and low coercivity temperature coefficient can be obtained.
In a second aspect of the invention, a thermally deformed neodymium iron boron magnet is provided. According to the embodiment of the invention, the thermal deformation neodymium iron boron magnet is prepared by adopting the method for preparing the thermal deformation neodymium iron boron magnet. Therefore, the hot deformed neodymium iron boron magnet has high coercive force and low coercive force temperature coefficient. It should be noted that the features and advantages described above for the method of manufacturing the thermally deformed ndfeb magnet are also applicable to the thermally deformed ndfeb magnet, and are not described herein again.
The scheme of the invention will be explained with reference to the examples. It will be appreciated by those skilled in the art that the following examples are illustrative of the invention only and should not be taken as limiting the scope of the invention. The examples, where specific techniques or conditions are not indicated, are to be construed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.
Example 1
Step 1: tb with uniform components is smelted by Tb, Nd and Cu metals with the purity of more than 99.9 percent70Cu30And Nd70Cu30Casting ingot of the alloy and preparing Tb by adopting a rapid quenching method70Cu30Alloy and Nd70Cu30Alloy thin strip of alloy, then using ball mill to make Tb70Cu30Crushing the thin strip to obtain micron Tb70Cu30Alloying the powder with Nd70Cu30Cutting the alloy ingot into Nd70Cu30A sheet;
step 2: tb is to be70Cu30Mixing the alloy powder with rapidly quenched Nd-Fe-B powder (Tb)70Cu30The alloy powder accounts for 2 percent of the total weight of the Nd-Fe-B powder, and the Nd-Fe-B powder is mixed and sequentially subjected to cold pressing preforming (the cold pressing pressure is 400MPa, the pressure maintaining time is 2min), hot pressing sintering (the hot pressing pressure is 400MPa, the hot pressing temperature is 600 ℃, the pressure maintaining time is 20min, and the vacuum degree is 5 multiplied by 10-3Pa) and heat distortion (heat distortion temperature 675 ℃ C., vacuum degree of 5X 10-3Pa) carrying out doping grain boundary diffusion to obtain a doped thermal deformation magnet;
and step 3: cooling the doped thermal deformation magnet to room temperature, polishing the surface of the doped thermal deformation magnet, and then polishing the Nd prepared in the step (1)70Cu30Placing the alloy sheet on the surface of the doped heat-deformed magnet, heating, and performing surface grain boundary diffusion treatment (diffusion temperature is 600 deg.C, diffusion time is 30 min, and vacuum degree is 5 × 10)-3Pa), and performing surface grain boundary diffusion to obtain the thermal deformation neodymium iron boron magnet.
Example 2
Step 1: tb with uniform components is smelted by Tb, Nd and Cu metals with the purity of more than 99.9 percent70Cu30And Nd70Cu30Casting ingot of the alloy and preparing Tb by adopting a rapid quenching method70Cu30Alloy thin strip of alloy, then using ball mill to make Tb70Cu30Crushing the thin strip to obtain micron Tb70Cu30Alloying the powder with Nd70Cu30Cutting the alloy ingot into Nd70Cu30A sheet;
step 2: tb is to be70Cu30Mixing the alloy powder with rapidly quenched Nd-Fe-B powder (Tb)70Cu30The alloy powder accounts for 5 percent of the total weight of the Nd-Fe-B powder, and the Nd-Fe-B powder is mixed and sequentially subjected to cold pressing preforming (the cold pressing pressure is 400MPa, the pressure maintaining time is 2min), hot pressing sintering (the hot pressing pressure is 400MPa, the hot pressing temperature is 600 ℃, the pressure maintaining time is 20min, and the vacuum degree is 5 multiplied by 10-3Pa) and heat distortion (heat distortion temperature 675 ℃ C., vacuum degree of 5X 10-3Pa) carrying out doping grain boundary diffusion to obtain a doped thermal deformation magnet;
and step 3: cooling the doped thermal deformation magnet to room temperature, polishing the surface of the doped thermal deformation magnet, and then polishing the Nd prepared in the step (1)70Cu30Placing the alloy sheet on the surface of the doped heat-deformed magnet, heating, and performing surface grain boundary diffusion treatment (diffusion temperature is 600 deg.C, diffusion time is 30 min, and vacuum degree is 5 × 10)-3Pa), and performing surface grain boundary diffusion to obtain the thermal deformation neodymium iron boron magnet.
Comparative example 1
Sequentially carrying out cold pressing preforming (the cold pressing pressure is 400MPa, the pressure maintaining time is 2min) and hot pressing sintering (the hot pressing pressure is 400MPa, the hot pressing temperature is 600 ℃, the pressure maintaining time is 20min, and the vacuum degree is 5 multiplied by 10-3Pa) and heat distortion (heat distortion temperature 675 ℃ C., vacuum degree of 5X 10-3Pa) to obtain the thermal deformation neodymium iron boron magnet.
Comparative example 2
Step 1: tb with uniform components is smelted by Tb, Nd and Cu metals with the purity of more than 99.9 percent70Cu30And Nd70Cu30Casting ingot of the alloy and preparing Tb by adopting a rapid quenching method70Cu30Alloy thin strip of alloy, howeverThen utilizes the ball mill to pair Tb70Cu30Crushing the thin strip to obtain micron Tb70Cu30Alloying powder;
step 2: tb is to be70Cu30Mixing the alloy powder with rapidly quenched Nd-Fe-B powder (Tb)70Cu30The alloy powder accounts for 2 percent of the total weight of the Nd-Fe-B powder, and the Nd-Fe-B powder is mixed and sequentially subjected to cold pressing preforming (the cold pressing pressure is 400MPa, the pressure maintaining time is 2min), hot pressing sintering (the hot pressing pressure is 400MPa, the hot pressing temperature is 600 ℃, the pressure maintaining time is 20min, and the vacuum degree is 5 multiplied by 10-3Pa) and heat distortion (heat distortion temperature 675 ℃ C., vacuum degree of 5X 10-3Pa) carrying out doped grain boundary diffusion to obtain the thermal deformation neodymium iron boron magnet.
Comparative example 3
Step 1: tb with uniform components is smelted by Tb, Nd and Cu metals with the purity of more than 99.9 percent70Cu30And Nd70Cu30Casting ingot of the alloy and preparing Tb by adopting a rapid quenching method70Cu30Alloy thin strip of alloy, then using ball mill to make Tb70Cu30Crushing the thin strip to obtain micron Tb70Cu30Alloying powder;
step 2: tb is to be70Cu30Mixing the alloy powder with rapidly quenched Nd-Fe-B powder (Tb)70Cu30The alloy powder accounts for 5 percent of the total weight of the Nd-Fe-B powder, and the Nd-Fe-B powder is mixed and sequentially subjected to cold pressing preforming (the cold pressing pressure is 400MPa, the pressure maintaining time is 2min), hot pressing sintering (the hot pressing pressure is 400MPa, the hot pressing temperature is 600 ℃, the pressure maintaining time is 20min, and the vacuum degree is 5 multiplied by 10-3Pa) and heat distortion (heat distortion temperature 675 ℃ C., vacuum degree of 5X 10-3Pa) carrying out doped grain boundary diffusion to obtain the thermal deformation neodymium iron boron magnet.
Comparative example 4
Step 1: tb with uniform components is smelted by Tb, Nd and Cu metals with the purity of more than 99.9 percent70Cu30And Nd70Cu30Casting ingot of the alloy and preparing Tb by adopting a rapid quenching method70Cu30Alloy thin strip of alloy, then using ball mill to make Tb70Cu30Crushing the thin strip to obtain micron Tb70Cu30Alloying powder;
step 2: tb is to be70Cu30Mixing the alloy powder with rapidly quenched Nd-Fe-B powder (Tb)70Cu30The alloy powder accounts for 10% of the total weight of the Nd-Fe-B powder, and the Nd-Fe-B powder is mixed and sequentially subjected to cold pressing preforming (the cold pressing pressure is 400MPa, the pressure maintaining time is 2min), hot pressing sintering (the hot pressing pressure is 400MPa, the hot pressing temperature is 600 ℃, the pressure maintaining time is 20min, and the vacuum degree is 5 multiplied by 10-3Pa) and heat distortion (heat distortion temperature 675 ℃ C., vacuum degree of 5X 10-3Pa) carrying out doped grain boundary diffusion to obtain the thermal deformation neodymium iron boron magnet.
The magnetic performance of the thermally deformed neodymium-iron-boron magnets prepared in the examples 1-2 and the comparative examples 1-4 was tested, the testing equipment was a comprehensive physical property measuring instrument, the testing temperature range was 298K-453K, and the testing field strength was 0-6T- (-6T) -6T. The coercive force temperature coefficient of the magnet is calculated from the coercive force variation value in the temperature range. The performance test results are shown in table 1:
TABLE 1 magnetic Property test results of thermally deformed NdFeB magnets prepared in examples 1 to 2 and comparative examples 1 to 4
| Magnetic property | Example 1 | Example 2 | Comparative example 1 | Comparative example 2 | Comparative example 3 | Comparative example4 |
| Remanence Br(T) | 1.1 | 1.0 | 1.45 | 1.35 | 1.25 | 1.13 |
| Coercive force Hcj(T) | 2.7 | 3.1 | 1.3 | 1.8 | 2.4 | 3.1 |
Taking example 2 as an example, the absolute value of the coercivity temperature coefficient was calculated to be 0.34%/deg.c.
As shown in Table 1, as can be seen from the comparison of the test results of examples 1 to 2 with comparative example 1, Tb was compared with the undoped thermomechanical magnet70Cu30The coercive force of the alloy-doped magnet is obviously improved. As can be seen from comparison of the test results of examples 1 to 2 and comparative examples 2 to 4, when Nd was applied to the alloy-doped magnet70Cu30After the alloy is diffused, the coercive force of the magnet is further improved in a large range. Meanwhile, high-temperature magnetic performance tests show that the absolute value of the coercive force temperature coefficient of the two-step diffusion magnet is greatly reduced. The microstructure analysis revealed that Tb (FIG. 2 (a) is the microstructure analysis of the magnet obtained in comparative example 2, (b) in FIG. 2 is the microstructure analysis of the magnet obtained in comparative example 3, (c) in FIG. 2 is the microstructure analysis of the magnet obtained in comparative example 4, (d) in FIG. 2 is the microstructure analysis of the magnet obtained in example 2)70Cu30Of alloy-doped magnetsThe grain boundary phase contains a very high ferromagnetic phase content, which severely limits further improvement of the coercivity of the magnet; when Nd is carried out on the doped magnet70Cu30After the alloy is diffused, the nonmagnetic grain boundary phase in the magnet is obviously increased, the interaction between ferromagnetic matrix phases is effectively limited, and the coercive force of the magnet is obviously improved. In conclusion, the coercivity and the coercivity temperature stability of the thermal deformation magnet can be remarkably improved by the two-step grain boundary diffusion provided by the invention.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
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, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (9)
1. A method of making a thermally deformed neodymium iron boron magnet, comprising:
(1) mixing the first alloy powder and the rapidly quenched Nd-Fe-B powder, and then sequentially carrying out cold pressing preforming, hot pressing sintering and thermal deformation to carry out doping grain boundary diffusion so as to obtain a doped thermal deformation magnet;
(2) placing the second alloy on the surface of the doped heat deformation magnet and heating to perform surface grain boundary diffusion so as to obtain a heat deformation neodymium iron boron magnet;
wherein the first alloy is Tb-Cu alloy or/and Dy-Cu alloy, and the second alloy is Nd-Cu alloy or/and Pr-Cu alloy.
2. The method according to claim 1, wherein in step (1), the Tb-Cu alloy has a chemical formula of TbxCu100-xThe chemical formula of the Dy-Cu alloy is DyxCu100-x，50≤x≤85。
3. The method according to claim 1, wherein in step (1), the first alloy powder accounts for 1 to 10% of the total weight of the rapidly quenched Nd-Fe-B powder.
4. The method according to claim 1, wherein in the step (1), the hot-pressing sintering is carried out under vacuum or under the protection of inert atmosphere, and the vacuum condition is that the vacuum degree is not more than 10-2Pa, and the hot-pressing sintering temperature is 600-700 ℃.
5. The method according to claim 1, wherein in the step (1), the thermal deformation is carried out under vacuum or under inert atmosphere protection, and the vacuum condition is that the vacuum degree is not more than 10-2Pa, and the thermal deformation temperature is 675-800 ℃.
6. The method according to claim 1, wherein in step (2), the Nd-Cu alloy has a chemical formula of NdxCu100-xThe chemical formula of the Pr-Cu alloy is PrxCu100-x，50≤x≤85。
7. The method of claim 1, wherein in step (2), the second alloy is a powder or flake.
8. The method of claim 1, wherein in step (2), the step (2) is performed by a computerThe surface grain boundary diffusion process is carried out under the protection of vacuum or inert atmosphere, and the vacuum condition is that the vacuum degree is not more than 10-2Pa, the diffusion temperature is 550-675 ℃, and the diffusion time is 20-60 minutes.
9. A thermally deformable NdFeB magnet, characterized in that it is prepared by the method of any one of claims 1 to 8.
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