A grain boundary diffusion material, a neodymium iron boron magnet, its preparation method and application

Abstract

This invention discloses a grain boundary diffusion material, a neodymium iron boron (NdFeB) magnet, its preparation method, and its applications. The grain boundary diffusion material for the NdFeB magnet comprises a diffusion matrix and a diffusion source. The diffusion source is the raw material to be diffused added during the grain boundary diffusion treatment. The diffusion matrix comprises the following components: LR: 29–30 wt.%, where LR is a light rare earth element; Cu: 0.15–0.5 wt.%; B: 0.99–1.05 wt.%; Fe: 67–70 wt.%; wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet. The diffusion source comprises Cu and Tb. The percentage of the mass of Cu in the NdFeB magnet to the total mass of the NdFeB magnet is greater than 0.5 wt.%. The NdFeB magnet prepared from the grain boundary diffusion material of this invention, under the premise of adding an equal amount of heavy rare earth elements, can significantly improve coercivity while maintaining essentially unchanged remanence.

Description

Technical Field

[0001] This invention relates to a grain boundary diffusion material, a neodymium iron boron magnet, its preparation method, and its application. Background Technology

[0002] Sintered Nd-Fe-B magnets, with their excellent magnetic flux density, are widely used in wind power generation, electronic communications, and new energy vehicles. However, their low coercivity and poor thermal stability lead to thermal demagnetization during high-temperature operation, limiting their application in high-temperature fields. Improving the coercivity and thermal stability of magnets has attracted increasing attention from researchers.

[0003] The *Chinese Journal of Rare Earths* reported a study on Tb diffusion at grain boundaries in sintered NdFeB magnets. 70 Cu 30 Thermal stability and microstructure study of the alloy (Zhou Toujun et al., Jiangxi Provincial Key Laboratory of Rare Earth Magnetic Materials and Devices, 2021.01.21). Commercially available sintered magnets (PrNd) were used. 29.25 Dy 1.62 Fe bal B 0.98 Co 0.83 M 0.59 (Mass fraction wt.%, M = Nb, Al, Cu, Zr, Ga) Using specific grain boundary diffusion sources and diffusion temperatures, a magnetic material with significantly improved coercivity and essentially unchanged remanence was obtained. This diffusion method resulted in a significant increase in the Nd-rich phase, with a more continuous and clear distribution. Simultaneously, (Nd,Tb)₂Fe was formed. 14 The core-shell structure encapsulates the grains, enhancing the demagnetizing coupling between adjacent grains and improving the coercivity of the magnet. Specifically, the coercivity increased from 17.37 kOe to 20.04 kOe, an increase of 15.4%. Simultaneously, both the temperature coefficient of coercivity and the temperature coefficient of remanence decreased significantly. Within the temperature range of 20–200 °C, the absolute value of the temperature coefficient of coercivity decreased from 0.454% / ℃ to 0.442% / ℃, and the temperature coefficient of remanence decreased from 0.124% / ℃ to 0.12% / ℃. However, the magnet material in this literature still has the following drawback: the increase in coercivity due to diffusion is only 2.67 kOe, which is relatively limited.

[0004] In traditional NdFeB preparation, a small amount of Cu addition significantly improves coercivity. However, for diffused products, when the Cu content in the diffusion matrix exceeds 0.5 wt%, the effect of grain boundary diffusion on improving coercivity is greatly reduced, while remanence is also decreased. Using a typical formulation design, the Cu content in the diffusion matrix is ​​directly designed to be greater than 0.5 wt.%, followed by Tb diffusion to achieve a high Cu content and prepare a high-performance 54SH grade product. In reality, when the Cu content exceeds 0.5 wt.%, the magnetic properties after Tb diffusion are difficult to meet the requirements of the 54SH grade.

[0005] Currently, there is a lack of a preparation process that can fully utilize the coercivity-enhancing effect of heavy rare earth elements. Summary of the Invention

[0006] This invention primarily addresses the deficiency in existing technologies where the addition of heavy rare earth elements in grain boundary diffusion processes yields relatively low improvements in coercivity. It provides a grain boundary diffusion material, a neodymium iron boron (NdFeB) magnet, its preparation method, and its applications. NdFeB magnets prepared using the grain boundary diffusion material of this invention, with the addition of an equal amount of heavy rare earth elements, exhibit significantly improved coercivity while maintaining essentially unchanged remanence.

[0007] The present invention mainly solves the above technical problems through the following technical solutions.

[0008] This invention provides a grain boundary diffusion material for neodymium iron boron magnets, comprising a diffusion matrix and a diffusion source, wherein the diffusion source is a raw material to be diffused added during grain boundary diffusion treatment;

[0009] The diffusion matrix comprises the following components:

[0010] LR: 29-30 wt.%, where LR is a light rare earth element;

[0011] Cu: 0.15–0.5 wt.%;

[0012] B: 0.99~1.05wt.%;

[0013] Fe: 67-70 wt.%; wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet;

[0014] The diffusion source includes Cu and Tb;

[0015] The percentage of Cu mass in the NdFeB magnet to the total mass of the NdFeB magnet is greater than 0.5 wt.%.

[0016] In this invention, those skilled in the art will know that the diffusion matrix generally refers to a magnetic material that can be directly subjected to grain boundary diffusion treatment, and is generally a sintered body.

[0017] In this invention, the content of LR in the diffusion matrix is ​​preferably 29.4 to 30 wt.%, for example 29.42 wt.%, 29.5 wt.%, 29.62 wt.%, 29.65 wt.%, 29.6 wt.%, 29.68 wt.%, 29.7 wt.%, or 29.73 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0018] In this invention, the LR can be conventional in the art, and generally may include one or more of Nd, Pr and PrNd alloys, preferably Nd, "Nd and Pr" or PrNd alloys.

[0019] When the LR is Nd, the Nd content is preferably 29.4–29.8 wt.%, for example 29.42 wt.%, 29.5 wt.%, 29.6 wt.%, 29.68 wt.%, 29.7 wt.%, or 29.73 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet. When the LR is Nd, the remanence is higher than that of Nd and Pr, as well as NdFeB magnet materials made of PrNd alloys.

[0020] When the LR is Nd and Pr, the Nd content is preferably 21-23 wt.%, for example 22.28 wt.%; the Pr content is preferably 6-8 wt.%, for example 7.43 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0021] When the LR is a PrNd alloy, the content of the PrNd alloy is preferably 29-30 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet; in the PrNd alloy, the mass ratio of Nd to Pr is, for example, 3:1.

[0022] In this invention, the Cu content in the diffusion matrix is ​​preferably 0.15 to 0.35 wt.%, for example 0.16 wt.%, 0.24 wt.%, 0.25 wt.%, or 0.34 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0023] In this invention, the content of B is preferably 0.99 to 1.03 wt.%, for example 0.99 wt.%, 1 wt.%, or 1.01 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0024] In this invention, the diffusion matrix may also contain additive elements conventional in the art, such as one or more of Al, Co, Ti and Tb.

[0025] When the diffusion matrix contains Al, the content of Al can be 0.2 to 0.4 wt.%, for example 0.3 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0026] When the diffusion matrix contains Co, the content of Co can be 0.5 to 1.5 wt.%, for example 1 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0027] When the diffusion matrix contains Ti, the content of Ti can be 0.1 to 0.2 wt.%, for example 0.15 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0028] When the diffusion matrix contains Tb, the content of Tb is preferably less than 1 wt.%, for example 0.8 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0029] In this invention, the inventors further discovered that when the diffusion matrix does not contain Al and Co, the coercivity of the NdFeB magnet obtained through the grain boundary diffusion treatment can be significantly improved.

[0030] Those skilled in the art will understand that the absence of Al in the diffusion matrix generally means that no additional Al is added during the preparation of the diffusion matrix. However, it is unavoidable to introduce less than 1 wt.% of Al during the preparation of the diffusion matrix, such as 0.06 wt.% or 0.07 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0031] In this invention, the Fe content in the diffusion matrix is ​​preferably 67-69 wt.%, for example 66.87 wt.%, 67.12 wt.%, 67.57 wt.%, 67.6 wt.%, 67.69 wt.%, 67.76 wt.%, 67.9 wt.%, 67.91 wt.%, or 68.03 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0032] In this invention, the content of Tb in the diffusion source can be conventional in the art, preferably 0.1 to 1.5 wt.%, for example 0.65 wt.%, 0.66 wt.%, 0.7 wt.%, 0.81 wt.%, 0.85 wt.%, 0.86 wt.%, 0.88 wt.%, or 1 wt.%, where wt.% refers to the ratio of the Tb content to the total mass of the NdFeB magnet.

[0033] In this invention, the Cu content in the neodymium iron boron magnet is preferably 0.51 to 0.65 wt.%, for example 0.51 wt.%, 0.52 wt.%, 0.55 wt.%, 0.61 wt.%, 0.62 wt.%, 0.63 wt.%, or 0.65 wt.%, where wt.% refers to the ratio of Cu content to the total mass of the neodymium iron boron magnet.

[0034] In this invention, the preparation method of the diffusion matrix can be conventional in the art and generally includes the following steps: the raw material composition of the diffusion matrix is ​​sequentially melted, crushed, shaped and sintered.

[0035] The melting temperature is preferably 1400–1550°C, for example, 1480°C, 1500°C, or 1520°C. Those skilled in the art will understand that in actual operation, the melting temperature may have an error of ±20°C.

[0036] Preferably, the thickness of the alloy sheet obtained after melting is 0.25–0.55 mm, for example, 0.3 mm. Those skilled in the art will understand that in actual operation, the thickness of the alloy sheet has an error of ±0.05 mm.

[0037] The pulverization process typically involves sequential hydrogen pulverization and air jet milling.

[0038] The particle size of the powder obtained after pulverization is, for example, 3 to 5 μm.

[0039] The forming process is generally performed using a magnetic field. The magnetic field strength for this magnetic forming is, for example, 1.6T or higher.

[0040] The sintering temperature is, for example, 1000–1100°C.

[0041] The sintering time is, for example, 4 to 6 hours.

[0042] In a specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 29.6 wt.%, Cu 0.24 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 67.69 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.88 wt.% and Cu 0.38 wt.%.

[0043] In one specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 29.68 wt.%, Cu 0.16 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 67.6 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.86 wt.% and Cu 0.49 wt.%.

[0044] In one specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 29.73 wt.%, Cu 0.34 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.07 wt.%, and Fe 67.57 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.85 wt.% and Cu 0.29 wt.%.

[0045] In a specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 29.7 wt.%, Cu 0.5 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 67.76 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.81 wt.% and Cu 0.02 wt.%.

[0046] In a specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 29.6 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 68.03 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.65 wt.% and Cu 0.26 wt.%.

[0047] In a specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 29.5 wt.%, Tb 0.8 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 67.12 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.85 wt.% and Cu 0.27 wt.%.

[0048] In one specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 29.42 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B 1.01 wt.%, Al 0.3 wt.%, and Fe 66.87 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.7 wt.% and Cu 0.3 wt.%.

[0049] In a specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: Nd 22.28 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B 0.99 wt.%, Al 0.06 wt.%, and Fe 67.91 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.65 wt.% and Cu 0.28 wt.%.

[0050] In a specific embodiment of the present invention, the diffusion matrix is ​​composed of the following components: PrNd 29.7 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 67.9 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.66 wt.% and Cu 0.28 wt.%.

[0051] The present invention also provides a method for preparing the neodymium iron boron magnet, which includes the following steps: subjecting the diffusion matrix to grain boundary diffusion treatment using the diffusion source.

[0052] In this invention, the grain boundary diffusion treatment can be carried out in accordance with conventional methods in the art. Generally, after forming a diffusion source on the surface of the diffusion matrix, heat treatment is then performed.

[0053] In this invention, the heat treatment temperature in the grain boundary diffusion treatment is preferably 850–950°C, more preferably 910–930°C, for example 920°C.

[0054] In this invention, the heat treatment time can be conventional in the art, preferably 10 to 40 hours, for example 30 hours.

[0055] In this invention, the preferred method for forming the diffusion source is magnetron sputtering, that is, forming a diffusion film layer on the surface of the diffusion substrate, for example, first forming a Tb film layer or first forming a Cu film layer. Those skilled in the art will know that magnetron sputtering is simpler in process and less difficult to prepare the diffusion source compared to using TbCu alloy powder.

[0056] The present invention also provides a neodymium iron boron magnet, which is prepared by the above-described method for preparing neodymium iron boron magnets.

[0057] The present invention also provides a neodymium iron boron magnet, which comprises the following components:

[0058] LR: 29-30.0 wt.%, where LR is a light rare earth element;

[0059] Cu > 0.5 wt.%;

[0060] B: 0.99~1.05wt.%;

[0061] Fe: 67.0~70.0 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet;

[0062] The neodymium iron boron magnet also contains Tb;

[0063] The grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase with a width of 1–2.6 μm.

[0064] In this invention, the term "grain boundary phase" can be interpreted in the conventional sense, generally referring to the collective term for the regions formed by two-grain grain boundary phases and intergranular triangular regions. The two-grain grain boundary phase is generally the grain boundary phase between two main phase grains.

[0065] In this invention, those skilled in the art will know that the Cu-rich phase generally refers to a phase structure in which Cu enrichment can be visually observed through EPMA analysis, and the Cu content in the Cu-rich phase is more than 15 wt.% of the total mass of all elements in the region.

[0066] In this invention, the width of the Cu-rich phase generally refers to the average value of the short side dimension of the Cu-rich region observed by EPMA. The Cu-rich phase in this invention is generally irregular strip-shaped, that is, the short side dimension refers to the average value of the width of the irregular strip-shaped phase.

[0067] In this invention, the width of the Cu-rich phase is preferably 1 to 2 μm, for example 1.2 μm, 1.5 μm, 1.6 μm, 1.7 μm or 1.8 μm.

[0068] In this invention, the content of LR is preferably 29 to 29.5 wt.%, for example 29.05 wt.%, 29.12 wt.%, 29.20 wt.%, 29.21 wt.%, 29.27 wt.%, 29.30 wt.%, 29.33 wt.%, 29.34 wt.%, or 29.35 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0069] In this invention, the LR can be conventional in the art, and generally may include one or more of Nd, Pr and PrNd alloys, preferably Nd, "Nd and Pr" or PrNd alloys.

[0070] When the LR is Nd, the Nd content is preferably 29 to 29.5 wt.%, for example 29.05 wt.%, 29.12 wt.%, 29.20 wt.%, 29.21 wt.%, 29.27 wt.%, 29.30 wt.%, or 29.34 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0071] When the LR is Nd and Pr, the Nd content is preferably 21-23 wt.%, for example 22 wt.%; the Pr content is preferably 6-8 wt.%, for example 7.35 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0072] When the LR is a PrNd alloy, the content of the PrNd alloy is preferably 29-30 wt.%, for example 29.33 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0073] In this invention, the Cu content is preferably 0.51 to 0.65 wt.%, for example 0.51 wt.%, 0.52 wt.%, 0.53 wt.%, 0.55 wt.%, 0.61 wt.%, 0.62 wt.%, 0.63 wt.%, or 0.65 wt.%, where wt.% refers to the percentage of the total mass of the neodymium iron boron magnet.

[0074] In this invention, the content of B is preferably 0.99 to 1.03 wt.%, for example 0.99 wt.%, 1 wt.%, or 1.01 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0075] In this invention, the Fe content is preferably 67.0–69 wt.%, for example 67.33 wt.%, 67.88 wt.%, 67.94 wt.%, 68.06 wt.%, 68.04 wt.%, 68.26 wt.%, 68.27 wt.%, 67.48 wt.%, or 68.52 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0076] In this invention, the content of Tb is preferably 0.1 to 2 wt.%, for example 0.65 wt.%, 0.66 wt.%, 0.7 wt.%, 0.81 wt.%, 0.85 wt.%, 0.86 wt.%, 0.88 wt.%, or 1.65 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

[0077] In this invention, the neodymium iron boron magnet may also contain one or more additive elements conventional in the art, such as Al, Co and Ti.

[0078] When the neodymium iron boron magnet contains Al, the content of Al can be 0.2 to 0.4 wt.%, for example 0.3 wt.%, where wt.% is the percentage of the total mass of the neodymium iron boron magnet.

[0079] When the neodymium iron boron magnet contains Co, the content of Co can be 0.5 to 1.5 wt.%, for example 1 wt.%, where wt.% is the percentage of the total mass of the neodymium iron boron magnet.

[0080] Wherein, when the neodymium iron boron magnet contains Ti, the content of Ti can be 0.1 to 0.2 wt.%, for example 0.15 wt.%, where wt.% is the percentage of the total mass of the neodymium iron boron magnet.

[0081] In this invention, the neodymium iron boron magnet preferably does not contain Al and Co. As mentioned above, "Al-free" generally means that the Al content is below 0.1 wt.%, for example, 0.06 wt.% or 0.07 wt.%, where wt.% is the percentage of the total mass of the neodymium iron boron magnet.

[0082] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 29.34 wt.%, Tb 0.88 wt.%, Cu 0.62 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.07 wt.%, and Fe 67.94 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, the width of which is 1.2 μm.

[0083] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 29.21 wt.%, Tb 0.86 wt.%, Cu 0.65 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.07 wt.%, and Fe 68.06 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, and the width of the Cu-rich phase is 1 μm.

[0084] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 29.27 wt.%, Tb 0.85 wt.%, Cu 0.63 wt.%, Ti 0.15 wt.%, B 0.99 wt.%, Al 0.07 wt.%, and Fe 68.04 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, and the width of the Cu-rich phase is 1.8 μm.

[0085] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 29.2 wt.%, Tb 0.81 wt.%, Cu 0.52 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 68.26 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, and the width of the Cu-rich phase is 2.5 μm.

[0086] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 29.12 wt.%, Tb 0.65 wt.%, Cu 0.51 wt.%, Ti 0.15 wt.%, B 0.99 wt.%, Al 0.06 wt.%, and Fe 68.52 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, and the width of the Cu-rich phase is 1.5 μm.

[0087] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 29.3 wt.%, Tb 1.65 wt.%, Cu 0.52 wt.%, Ti 0.15 wt.%, B 0.99 wt.%, Al 0.06 wt.%, and Fe 67.33 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, the width of which is 1.5 μm.

[0088] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 29.05 wt.%, Tb 0.7 wt.%, Cu 0.55 wt.%, Ti 0.15 wt.%, Co 1 wt.%, B 1.01 wt.%, Al 0.3 wt.%, and Fe 67.24 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, and the width of the Cu-rich phase is 1.7 μm.

[0089] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: Nd 22wt.%, Pr 7.35wt.%, Tb 0.65wt.%, Cu 0.53wt.%, Ti 0.15wt.%, B 0.99wt.%, Al 0.06wt.%, and Fe 68.27wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, and the width of the Cu-rich phase is 1.6μm.

[0090] In a specific embodiment of the present invention, the neodymium iron boron magnet is composed of the following components: PrNd 29.33 wt.%, Tb 0.66 wt.%, Cu 0.53 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 68.27 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, and the width of the Cu-rich phase is 1.5 μm.

[0091] The present invention also provides an application of the neodymium iron boron magnet as a material for preparing permanent magnet motors.

[0092] The permanent magnet motor is, for example, an air conditioner compressor or a general-purpose servo motor.

[0093] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0094] The reagents and raw materials used in this invention are all commercially available.

[0095] The positive and progressive effects of this invention are as follows: NdFeB magnets made using grain boundary diffusion materials of NdFeB magnets can significantly improve coercivity while maintaining remanence essentially unchanged under the premise of adding an equal amount of heavy rare earth elements, thus obtaining high-performance NdFeB magnets (e.g., grade 54SH). Attached Figure Description

[0096] Figure 1 EPMA analysis of the neodymium iron boron magnet in Example 4.

[0097] Figure 2 EPMA analysis of the neodymium iron boron magnet in Example 5.

[0098] Figure 3 EPMA analysis of the neodymium iron boron magnet in Example 7. Detailed Implementation

[0099] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0100] Example 1

[0101] (1) Preparation of diffusion matrix

[0102] According to the formula in Table 1, the raw materials of each component are mixed and then melted in an induction furnace at a temperature of 1500±20℃. The mixture is then rapidly quenched and spun into sheet alloys with a thickness of 0.3±0.05mm. These sheets are then hydrogen-crushed and pulverized into powder of 3-5μm using an air jet mill. The powder is then shaped under a magnetic field strength of 1.6T or higher and sintered at 1000-1100℃ for 4-6 hours to obtain bulk NdFeB permanent magnets. The bulk NdFeB permanent magnets are then cut into sheet substrates for grain boundary diffusion.

[0103] (2) Grain boundary diffusion treatment

[0104] The NdFeB magnets were obtained by magnetron sputtering followed by heat treatment to achieve grain boundary diffusion. The weight of the film added by magnetron sputtering was 1.26 wt.% (this weight is the total mass of Tb and Cu in the diffusion source). The heat treatment temperature in the grain boundary diffusion process was 920℃ and the time was 30h.

[0105] The formulations of the diffusion matrix and the diffusion sources during grain boundary diffusion treatment in Examples 1-9 and Comparative Example 1 are shown in Table 1 below. The preparation steps and process parameters of Examples 2-9 and Comparative Example 1 are the same as those in Example 1.

[0106] Table 1

[0107]

[0108] Note: The composition of the diffusion matrix in Table 1 was measured using high-frequency inductively coupled plasma optical emission spectrometry (ICP-OES). PrNd alloy refers to Nd to Pr alloy with a mass ratio of 3:1.

[0109] Wherein, " / " indicates that the element is not present. In the diffusion matrix, the content of each component is a percentage of its mass relative to the total mass of the NdFeB magnet. The total mass of the diffusion matrix does not include unavoidable impurities introduced during the preparation process, such as C and O. However, less than 0.08 wt.% of Al in the diffusion matrix is ​​introduced from non-Al raw materials. In the diffusion source, the mass content of Tb and Cu refers to the percentage of Tb and Cu's mass relative to the total mass of the NdFeB magnet, respectively.

[0110] Example 1

[0111] 1. Composition determination of neodymium iron boron magnets prepared in Examples 1-9 and Comparative Example 1

[0112] The measurements were performed using a high-frequency inductively coupled plasma optical emission spectrometer (ICP-OES). The test results are shown in Table 2 below.

[0113] Table 2 (Unit: wt.%)

[0114] PrNd Nd Pr Tb Dy Cu Nb Ti Co B Al Fe Comparative Example 1 / 29.28 / 1.00 / 0.61 / 0.15 / 1.01 0.07 67.88 Example 1 / 29.34 / 0.88 / 0.62 / 0.15 / 1.00 0.07 67.94 Example 2 / 29.21 / 0.86 / 0.65 / 0.15 / 1.00 0.07 68.06 Example 3 / 29.27 / 0.85 / 0.63 / 0.15 / 0.99 0.07 68.04 Example 4 / 29.20 / 0.81 / 0.52 / 0.15 / 1.00 0.06 68.26 Example 5 / 29.12 / 0.65 / 0.51 / 0.15 / 0.99 0.06 68.52 Example 6 / 29.30 / 1.65 / 0.52 / 0.15 / 0.99 0.06 67.33 Example 7 / 29.05 / 0.70 / 0.55 / 0.15 1.00 1.01 0.3 67.24 Example 8 / 22.00 7.35 0.65 / 0.53 / 0.15 / 0.99 0.06 68.27 Example 9 29.33 / / 0.66 / 0.53 / 0.15 / 1.00 0.06 68.27

[0115] Note: The content of each component is a percentage of the mass of each component to the total mass of the NdFeB magnet. Testing revealed a decrease in the Nd content of the NdFeB magnet, which may be due to the grain boundary diffusion treatment being a heat treatment process, causing a small amount of rare earth elements to volatilize from the diffusion matrix.

[0116] 2. Magnetic property test

[0117] The magnetic properties of neodymium iron boron magnets were tested using a PFM pulsed BH demagnetization curve testing device at room temperature (20°C).

[0118] The magnetic performance test results of five products from the same batch of neodymium iron boron magnets in Example 1 at 20°C are shown in Table 3 below.

[0119] Table 3

[0120] Br(kGs) Hcj(kOe) HcB(kOe) (BH)max(MGOe) HK(kOe) 1 14.43 20.48 13.84 49.96 17.48 2 14.41 20.20 13.82 49.83 17.40 3 14.46 20.38 13.92 50.25 17.69 4 14.45 20.45 13.88 50.08 17.79 5 14.46 20.16 13.91 50.28 17.70

[0121] As can be seen from Table 3, the magnetic properties of products from the same batch in this invention are uniform and the stability is good.

[0122] The average magnetic properties of Example 1 are shown in Table 4 below. Other examples used the same testing method, and the final average magnetic properties are shown in Table 4 below.

[0123] Table 4

[0124]

[0125]

[0126] Note: RTB magnets refer to neodymium iron boron magnets.

[0127] As can be seen from the data in the table above, by using the diffusion method of the present invention, adding a specific amount of Cu to the diffusion matrix, and adding a specific amount of Tb during grain boundary diffusion treatment, combined with the specific diffusion matrix of the present invention, the increase in coercivity is more significant compared to the scheme of only adding Tb during grain boundary diffusion. The inventors also conducted a study during the research and development process where all Cu was added during grain boundary diffusion, but the increase in coercivity was comparable to Comparative Example 1 and did not reach the level of the present invention.

[0128] Furthermore, based on the above-mentioned scheme, the present invention has discovered neodymium iron boron magnets with superior magnetic properties. For example, comparing Examples 1-3, it can be seen that when the Cu content in the diffusion matrix is ​​0.16 wt.% or 0.24 wt.%, the coercivity improvement value can reach more than 10 kOe compared to a Cu content of 0.34 wt.%. For example, in Example 7, compared to other examples, Al and Co were additionally added, but the coercivity improvement value only reached 8.72 kOe.

[0129] 3. Characterization of microstructure

[0130] Neodymium iron boron magnets from Examples 1-9 and Comparative Example 1 were fabricated into metallographic surfaces. An electron probe microanalysis (EPMA) device was used to scan the metallographic surface products, generating secondary electrons and X-rays through the interaction of electrons and X-rays. The morphology of the samples was observed using the secondary electron signals. Qualitative and quantitative analysis of the elements in the samples was performed by measuring the wavelength and intensity of the X-rays. For the measurement of the width of the Cu-rich phase: an EMA surface scan was used, and the short side dimension of the Cu-rich phase at the grain boundary was calibrated using the device's built-in scale tool. Figure 1 The image shows the EPMA analysis of the neodymium iron boron magnet in Example 4. (As shown...) Figure 2 The image shows the EPMA analysis of the neodymium iron boron magnet in Example 5. (As shown...) Figure 3 The EPMA analysis of the NdFeB magnet in Example 7 is shown. Al is diffusely distributed, while Co is abundant at the grain boundaries. Specific test results are shown in Table 5 below.

[0131] Table 5

[0132] Width (μm) of Cu-rich phase Comparative Example 1 3.0 Example 1 1.2 Example 2 1.0 Example 3 1.8 Example 4 2.5 Example 5 1.5 Example 6 1.5 Example 7 1.7 Example 8 1.6 Example 9 1.5

[0133] Note: The width of the Cu-rich phase refers to the average of the short side dimensions of the Cu-rich region observed by EPMA. For example, if the Cu-rich region is elongated, then the average of the short side dimensions is the average of the width of the elongated region.

[0134] Combining Table 5 and Table 1, it can be seen that the width of the Cu-rich phase at the grain boundary is positively correlated with the Cu content added to the substrate.

[0135] The experimental comparisons above revealed that in Example 4, a large amount of Cu was distributed at the grain boundaries, with a small amount distributed within the main phase grains. The high Cu content at the grain boundaries resulted in coarser grain boundaries, which reduced the proportion of the main phase and decreased remanence. Simultaneously, the coarser grain boundaries reduced the demagnetizing coupling effect of heavy rare earth elements diffusing into the substrate grain boundaries, thus reducing the effect of Tb diffusion into the substrate and consequently lowering the increase in coercivity. In Example 5, although the total Cu content was the same, a smaller amount of Cu was distributed at the grain boundaries, which was more conducive to grain boundary continuity and improved coercivity.

Claims

1. A grain boundary diffusion material for neodymium iron boron magnets, characterized in that, It includes a diffusion matrix and a diffusion source, wherein the diffusion source is the raw material to be diffused added during grain boundary diffusion treatment; The diffusion matrix comprises the following components: LR: 29~30 wt.%, where LR is Nd; Cu: 0.15~0.34 wt.%; B: 0.99~1.05wt.%; Fe: 67~69 wt.%; wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; The diffusion source includes Cu and Tb, and the content of Tb is 0.65~0.88 wt.%; the percentage of the mass of Cu in the NdFeB magnet to the total mass of the NdFeB magnet is 0.51~0.65 wt%.

2. The grain boundary diffusion material of the NdFeB magnet as described in claim 1, characterized in that, The diffusion matrix is ​​a sintered body; And / or, in the diffusion matrix, the Cu content is 0.15~0.25 wt.%; And / or, in the diffusion matrix, the content of B is 0.99~1.03 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet; And / or, in the diffusion source, the content of Tb is 0.65–0.88 wt%; And / or, the percentage of the mass of Cu in the NdFeB magnet to the total mass of the NdFeB magnet is 0.51~0.65 wt.%; And / or, the diffusion matrix further includes one or more of Al, Co, and Ti; Alternatively, the diffusion matrix does not contain Co.

3. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, In the diffusion matrix, the Nd content is 29.4~29.8 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet.

4. The grain boundary diffusion material of the NdFeB magnet as described in claim 3, characterized in that, The Nd content is 29.42 wt.%, 29.5 wt.%, 29.6 wt.%, 29.68 wt.%, 29.7 wt.%, or 29.73 wt.%.

5. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, The Cu content is 0.16 wt.%, 0.24 wt.%, or 0.25 wt.%.

6. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, In the diffusion matrix, the content of B is 0.99 wt.%, 1 wt.%, or 1.01 wt.%.

7. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, The Fe content is 67.33 wt.%, 67.88 wt.%, 67.94 wt.%, 68.06 wt.%, 68.04 wt.%, 68.26 wt.%, 68.27 wt.%, 67.48 wt.%, or 68.52 wt.%.

8. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, The Tb content is 0.65 wt.%, 0.66 wt.%, 0.7 wt.%, 0.81 wt.%, 0.85 wt.%, 0.86 wt.%, or 0.88 wt.%.

9. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, The percentage of the mass of Cu in the neodymium iron boron magnet to the total mass of the neodymium iron boron magnet is 0.51 wt.%, 0.52 wt.%, 0.55 wt.%, 0.61 wt.%, 0.62 wt.%, 0.63 wt.%, or 0.65 wt.%.

10. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, When the diffusion matrix contains Al, the content of Al is 0.2~0.4 wt.% or less than 0.1 wt.%.

11. The grain boundary diffusion material of the NdFeB magnet as described in claim 10, characterized in that, The content of Al is 0.06 wt.%, 0.07 wt.%, or 0.3 wt.%.

12. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, When the diffusion matrix contains Co, the content of Co is 0.5~1.5 wt.%.

13. The grain boundary diffusion material of the NdFeB magnet as described in claim 12, characterized in that, The content of Co is 1 wt.%.

14. The grain boundary diffusion material of the NdFeB magnet as described in claim 2, characterized in that, When the diffusion matrix contains Ti, the content of Ti is 0.1~0.2 wt.%.

15. The grain boundary diffusion material of the NdFeB magnet as described in claim 14, characterized in that, The content of Ti is 0.15 wt.%.

16. The grain boundary diffusion material of the NdFeB magnet as described in any one of claims 2 to 15, characterized in that, The method for preparing the diffusion matrix includes the following steps: sequentially melting, pulverizing, molding and sintering the raw material composition of the diffusion matrix; The melting temperature is 1400~1550℃; the thickness of the alloy sheet obtained after melting is 0.25~0.5mm. The pulverization process involves sequential hydrogen pulverization and air jet milling. Wherein, the forming is magnetic field forming; The sintering temperature is 1000~1100℃; The sintering time is 4 to 6 hours.

17. The grain boundary diffusion material of the NdFeB magnet as described in claim 16, characterized in that, The melting temperature is 1480℃, 1500℃ or 1520℃.

18. The grain boundary diffusion material of the NdFeB magnet as described in claim 16, characterized in that, The thickness of the alloy sheet obtained after melting is 0.3 mm.

19. The grain boundary diffusion material of the NdFeB magnet as described in claim 16, characterized in that, The particle size of the powder obtained after pulverization is 3~5μm.

20. The grain boundary diffusion material of the NdFeB magnet as described in claim 16, characterized in that, The magnetic field strength for the magnetic field shaping is above 1.6T.

21. The grain boundary diffusion material of the NdFeB magnet as described in any one of claims 16 to 20, characterized in that, The diffusion matrix is ​​composed of the following components: Nd 29.6 wt.%, Cu 0.24 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 67.69 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the diffusion source is Tb 0.88 wt.% and Cu 0.38 wt.%. Alternatively, the diffusion matrix may consist of the following components: Nd 29.68 wt.%, Cu 0.16 wt.%, Ti 0.15 wt.%, B1 wt.%, Al 0.06 wt.%, and Fe 67.6 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; and the diffusion source may be Tb 0.86 wt.% and Cu 0.49 wt.%. Alternatively, the diffusion matrix may consist of the following components: Nd 29.73 wt.%, Cu 0.34 wt.%, Ti 0.15 wt.%, B1 wt.%, Al 0.07 wt.%, and Fe 67.57 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; and the diffusion source may be Tb 0.85 wt.% and Cu 0.29 wt.%. Alternatively, the diffusion matrix may consist of the following components: Nd 29.7 wt.%, Cu 0.5 wt.%, Ti 0.15 wt.%, B1 wt.%, Al 0.06 wt.%, and Fe 67.76 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; and the diffusion source may be Tb 0.81 wt.% and Cu 0.02 wt.%. Alternatively, the diffusion matrix may consist of the following components: Nd 29.6 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B1 wt.%, Al 0.06 wt.%, and Fe 68.03 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; and the diffusion source may be Tb 0.65 wt.% and Cu 0.26 wt.%. Alternatively, the diffusion matrix may consist of the following components: Nd 29.42 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B 1.01 wt.%, Al 0.3 wt.%, and Fe 66.87 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; and the diffusion source may be Tb 0.7 wt.% and Cu 0.3 wt.%. Alternatively, the diffusion matrix may consist of the following components: Nd 22.28 wt.%, Cu 0.25 wt.%, Ti 0.15 wt.%, B 0.99 wt.%, Al 0.06 wt.%, and Fe 67.91 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; and the diffusion source may be Tb 0.65 wt.% and Cu 0.28 wt.%.

22. A method for preparing a neodymium iron boron magnet, characterized in that, It includes the following steps: The diffusion matrix as described in any one of claims 1 to 21 is subjected to grain boundary diffusion treatment using the diffusion source as described in any one of claims 1 to 21; In the grain boundary diffusion treatment, the heat treatment temperature is 850~950℃; In the grain boundary diffusion treatment, the heat treatment time is 10~40h; The diffusion source is formed by magnetron sputtering.

23. The method for preparing a neodymium iron boron magnet as described in claim 22, characterized in that, The heat treatment temperature is 910~930℃.

24. The method for preparing a neodymium iron boron magnet as described in claim 22, characterized in that, The heat treatment temperature is 920℃, and the heat treatment time is 30h.

25. A neodymium iron boron magnet prepared by the method for preparing neodymium iron boron magnets as described in any one of claims 22 to 24.

26. A neodymium iron boron magnet prepared using a grain boundary diffusion material of a neodymium iron boron magnet as described in any one of claims 1 to 25, characterized in that, It includes the following components: LR: 29~30.0 wt.%, where LR is Nd; Cu: 0.51 wt%~0.65 wt%; B: 0.99~1.05wt.%; Fe: 67.0~69.0 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; The neodymium iron boron magnet also contains Tb; The grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase with a width of 1~1.8 μm.

27. The neodymium iron boron magnet as described in claim 26, characterized in that, The percentage of the mass of Cu in the Cu-rich phase to the total mass of all elements in the Cu-rich phase is greater than 15 wt.%. And / or, the width of the Cu-rich phase is 1~2 μm; And / or, the Cu content is 0.51~0.65 wt.%, where wt.% refers to the percentage of the total mass of the NdFeB magnet; And / or, the content of B is 0.99~1.03 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet; And / or, the Tb content is 0.1~0.88 wt.%, where wt.% is the percentage of the total mass of the NdFeB magnet; And / or, the neodymium iron boron magnet further includes one or more of Al, Co and Ti; Alternatively, the neodymium iron boron magnet does not contain Co.

28. The neodymium iron boron magnet as described in claim 27, characterized in that, The width of the Cu-rich phase is 1.2 μm, 1.5 μm, 1.6 μm, 1.7 μm or 1.8 μm.

29. The neodymium iron boron magnet as described in claim 27, characterized in that, The Nd content is 29~29.5 wt.%.

30. The neodymium iron boron magnet as described in claim 29, characterized in that, The Nd content is 29.05 wt.%, 29.12 wt.%, 29.20 wt.%, 29.21 wt.%, 29.27 wt.%, 29.30 wt.%, or 29.34 wt.%.

31. The neodymium iron boron magnet as described in claim 27, characterized in that, The Cu content is 0.51 wt.%, 0.52 wt.%, 0.53 wt.%, 0.55 wt.%, 0.61 wt.%, 0.62 wt.%, 0.63 wt.%, or 0.65 wt.%.

32. The neodymium iron boron magnet as described in claim 27, characterized in that, The content of B is 0.99 wt.%, 1 wt.%, or 1.01 wt.%.

33. The neodymium iron boron magnet as described in claim 27, characterized in that, The Fe content is 67.33 wt.%, 67.88 wt.%, 67.94 wt.%, 68.06 wt.%, 68.04 wt.%, 68.26 wt.%, 68.27 wt.%, 67.48 wt.%, or 68.52 wt.%.

34. The neodymium iron boron magnet as described in claim 27, characterized in that, The Tb content is 0.65 wt.%, 0.66 wt.%, 0.7 wt.%, 0.81 wt.%, 0.85 wt.%, 0.86 wt.%, or 0.88 wt.%.

35. The neodymium iron boron magnet as described in claim 27, characterized in that, When the neodymium iron boron magnet contains Al, the content of Al is 0.2~0.4 wt.% or less than 0.1 wt.%.

36. The neodymium iron boron magnet as described in claim 35, characterized in that, The content of Al is 0.06 wt.%, 0.07 wt.%, or 0.3 wt.%.

37. The neodymium iron boron magnet as described in claim 27, characterized in that, When the neodymium iron boron magnet contains Co, the content of Co is 0.5~1.5 wt.%.

38. The neodymium iron boron magnet as described in claim 37, characterized in that, The content of Co is 1 wt.%.

39. The neodymium iron boron magnet as described in claim 27, characterized in that, When the neodymium iron boron magnet contains Ti, the content of Ti is 0.1~0.2 wt.%.

40. The neodymium iron boron magnet as described in claim 39, characterized in that, The content of Ti is 0.15 wt.%.

41. The neodymium iron boron magnet as described in any one of claims 27 to 40, characterized in that, The neodymium iron boron magnet is composed of the following components: Nd 29.34 wt.%, Tb 0.88 wt.%, Cu 0.62 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.07 wt.%, and Fe 67.94 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the neodymium iron boron magnet; the grain boundary phase of the neodymium iron boron magnet includes a Cu-rich phase, the width of which is 1.2 μm; Alternatively, the NdFeB magnet is composed of the following components: Nd 29.21 wt.%, Tb 0.86 wt.%, Cu 0.65 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.07 wt.%, and Fe 68.06 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the grain boundary phase of the NdFeB magnet includes a Cu-rich phase, the width of which is 1 μm; Alternatively, the NdFeB magnet is composed of the following components: Nd 29.27 wt.%, Tb 0.85 wt.%, Cu 0.63 wt.%, Ti 0.15 wt.%, B 0.99 wt.%, Al 0.07 wt.%, and Fe 68.04 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the grain boundary phase of the NdFeB magnet includes a Cu-rich phase with a width of 1.8 μm; Alternatively, the NdFeB magnet is composed of the following components: Nd 29.2 wt.%, Tb 0.81 wt.%, Cu 0.52 wt.%, Ti 0.15 wt.%, B 1 wt.%, Al 0.06 wt.%, and Fe 68.26 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the grain boundary phase of the NdFeB magnet includes a Cu-rich phase with a width of 2.5 μm; Alternatively, the NdFeB magnet is composed of the following components: Nd 29.12 wt.%, Tb 0.65 wt.%, Cu 0.51 wt.%, Ti 0.15 wt.%, B 0.99 wt.%, Al 0.06 wt.%, and Fe 68.52 wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the grain boundary phase of the NdFeB magnet includes a Cu-rich phase, the width of which is 1.5 μm; Alternatively, the NdFeB magnet is composed of the following components: Nd 29.05wt.%, Tb 0.7wt.%, Cu 0.55wt.%, Ti 0.15wt.%, Co 1wt.%, B 1.01wt.%, Al 0.3wt.%, and Fe 67.24wt.%, where wt.% is the percentage of the mass of each component to the total mass of the NdFeB magnet; the grain boundary phase of the NdFeB magnet includes a Cu-rich phase with a width of 1.7μm.

42. An application of the neodymium iron boron magnet as described in any one of claims 25 to 41 as a material for preparing permanent magnet motors.

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