Fine-grained high-coercivity neodymium-iron-boron permanent magnet material and method for producing same

Abstract

The application discloses a fine-grain high-coercivity neodymium-iron-boron permanent magnet material and a preparation method thereof. The fine-grain high-coercivity neodymium-iron-boron permanent magnet material has a grain size of 2-5.5 microns and contains one or more of Zr, Ti and Nb. Zr, Ti and Nb are first combined with LRE to form an auxiliary alloy, then the main alloy is mixed with the auxiliary alloy to perform hydrogen crushing, airflow grinding, powder preparation and sintering treatment, so as to obtain the fine-grain high-coercivity neodymium-iron-boron permanent magnet material.

Description

Technical Field

[0001] This invention relates to the field of rare earth permanent magnets, and more particularly to a fine-grained, high-coercivity neodymium iron boron permanent magnet material and its preparation method. Background Technology

[0002] Sintered NdFeB permanent magnets are widely used in wind power generation, new energy vehicles, energy-saving air conditioners, industrial motors, and other fields. Improving the coercivity of magnets is a key focus for industrialization and research. However, with the soaring prices of heavy rare earth elements (Dy or Tb), simply adding heavy rare earth elements to improve magnet coercivity has become unsustainable. Studies have shown that refining the grain size of the matrix phase in NdFeB magnets is an important means to improve coercivity (K.Hono and H.Sepehri-Amin, Strategy for high-coercivity Nd–Fe–B magnets, Scripta Materialia 67(2012)530–535; WFLi, T.Ohkubo, K.Hono, M.Sagawa, The origin of coercivity decrease in fine grained Nd–Fe–B sintered magnets, Journal of Magnetism and Magnetic Materials 321(2009)1100–1105). The coercivity of the magnet increases with the refinement of the grain size, and the basic relationship is approximately Hcj=24-2.4ln(D 2 (D) represents the grain size. Since sintering NdFeB magnets involves processes such as melting, powder preparation, forming, and sintering, refining the grain size cannot rely solely on finer powder particles; it also requires preventing grain agglomeration and growth during sintering. If these issues are not addressed, finer powders are more prone to abnormal grain growth during high-temperature sintering, leading to deterioration of the magnet's coercivity and other properties.

[0003] In existing technologies, those skilled in the art typically add high-melting-point elements, such as Zr, Ti, or Nb, to distribute these elements on the main phase or grain boundaries, thereby preventing the powder from approaching and growing during sintering, thus refining the grain size. When the average powder particle size is 3 μm, the sintered magnet grain size can reach 7–8 μm, making controlling grain growth during sintering crucial.

[0004] These elements are typically added through smelting to prepare the initial NdFeB alloy. Numerous patents and documents indicate that these high-melting-point elements combine with boron (B) to form needle-like ZrB₂ or TiB₂ phases (RTB-based sintered magnets, JP 2016-164958). The presence of this phase causes boron segregation within the magnet, which in turn affects the intrinsic magnetic properties of the matrix phase Nd₂Fe. 14 A decrease in the proportion of the B phase leads to a reduction in the remanence of the magnet. This is especially true when the B content in the nominal composition of the magnet is slightly below a positive ratio of 2:14:1, which can cause performance instability and reduced remanence.

[0005] In another method, Zr or Ti powder is added to the NdFeB alloy powder; however, due to their high melting point, the sintered blank is difficult to be dense.

[0006] Therefore, it is necessary to develop a new method for adding high-melting-point elements to prepare fine-grained magnets, thereby improving the coercivity of the magnets. Structurally modifying and optimizing the magnets is a problem that needs to be solved in this field. Summary of the Invention

[0007] To overcome the above-mentioned defects of the prior art, this invention provides a fine-grained, high-coercivity sintered NdFeB permanent magnet material and its preparation method. In the preparation method, by changing the way high-melting-point elements are added, the high-melting-point elements are dispersed at the grain boundaries, thereby preventing grain growth during sintering, optimizing the microstructure of the magnet, and achieving the purpose of improving coercivity.

[0008] In a first aspect, the present invention provides a neodymium iron boron permanent magnet material containing element A, wherein element A is selected from at least one of Zr, Ti, and Nb, and the microstructure of the neodymium iron boron permanent magnet material includes a matrix phase (RE2Fe). 14 The matrix phase consists of phase B and grain boundary phases dispersed around the matrix phase. The grain boundary phases include rare earth elements and their compounds, elemental A, and AB2 compounds. The mass percentage of AB2 compounds in the grain boundary phases is less than 0.1%.

[0009] Preferably, to ensure the magnet has high saturation magnetization and magnetocrystalline anisotropy, RE contains R and R1. R contains at least one of Nd and Pr, or at least one of Nd or Pr. Alternatively, it may contain a small amount of R1, which is selected from one or more of La, Ce, Y, Dy, Tb, Ho, and Gd, facilitating composition adjustment and performance control for magnets with different application requirements. RE2Fe 14B is the matrix phase of the magnet, which plays a crucial role in magnetic properties. Br (remanence) is directly proportional to the volume fraction of the matrix phase, and a ratio of 88% to 95% is preferred. Too low a matrix phase proportion cannot provide high remanence, while too high a matrix phase content leads to a low content of grain boundary phases in the magnet, resulting in low coercivity. Therefore, preferably, the RE... x Fe y M z B n Alloy sheet and the LRE a Co b A 100-a-b The mixing weight ratio of the alloy sheets is RE x Fe y M z B n Alloy sheet: LRE a Co b A 100-a-b Alloy sheet = 90~99.5: 0.5~10.

[0010] Preferably, RE is prepared x Fe y M z B n In the alloy sheet, the rare earth element is one or more of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and Sc.

[0011] Grain size is crucial for achieving high coercivity. Simultaneously, the grain size needs to be maintained within a reasonable range. The optimal range is typically consistent with the width of the matrix phase and columnar crystals in the cast sheet. The width of the matrix phase in the cast sheet is approximately 2-5 μm. Within this grain size range, the original grain structure is preserved, preventing excessive grain growth during sintering. Therefore, the average particle size of the second powder in the alloy sheet is 1.5–3.5 μm. Furthermore, 10% of the second powder in the alloy sheet has a particle size <1.6 μm. Because fine powders have high reactivity, an excessively high proportion can easily lead to abnormal grain growth.

[0012] Controlling grain growth during sintering is key to grain size regulation. NdFeB liquid-phase sintering primarily involves liquid-phase precipitation followed by solid-phase sintering. Grain growth mainly occurs during solid-phase sintering. Distributing high-melting-point elements such as Zr, Ti, and Nb along the grain boundaries can prevent grain growth during solid-phase sintering. This is because the melting points of Zr, Ti, and Nb are around 1800℃, while the sintering temperature is approximately 1000-1100℃; these high-melting-point elements can prevent the formation of sintering necks during the sintering process.

[0013] Based on the above insights, the magnet manufacturing process is as follows:

[0014] Secondly, the present invention provides a method for preparing the above-mentioned fine-grained, high-coercivity NdFeB permanent magnet material, specifically including the following steps: Step S1, preparing RE x Fe y M z B n Alloy sheet:

[0015] RE contains R and R1, where R contains at least one of Nd and Pr; it may also contain a small amount of R1, which is selected from one or more of La, Ce, Y, Dy, Tb, Ho, and Gd, and M is one or more of Al, Cu, Ga, Co, and Sn; and by weight percentage, 28≤x≤31.5, 0.3≤z≤4, 0.80≤n≤0.97, and y=100-xzn;

[0016] Step S2: Preparation of LRE a Co b A 100-a-b Alloy, wherein the weight fraction of a ranges from 80 to 90 and the weight fraction of b ranges from 2 to 10;

[0017] Step S3, Preparation of hybrid alloy: The RE x Fe y M z B n Alloy sheet and the LRE a Co b A 100-a-b The alloy sheets are mixed to obtain a mixed alloy sheet;

[0018] Step S4: Preparation of the first alloy sheet powder: The mixed alloy sheet is subjected to hydrogen absorption and then dehydrogenation treatment to obtain the first alloy sheet powder;

[0019] Step S5: Prepare the second alloy sheet powder: Under nitrogen protection, the first alloy sheet powder is subjected to air jet milling to obtain the second alloy sheet powder;

[0020] Step S6: Preparation of compact: Under a nitrogen protective atmosphere, the second powder of the alloy sheet is oriented and pressed into shape under a magnetic field to obtain a compact;

[0021] Step S7: After vacuum sintering the pressed blank under vacuum, tempering and aging treatment are performed to obtain fine-grained, high-coercivity NdFeB permanent magnet material.

[0022] Preferably, in step S1, RE is prepared using a rapid solidification and spinning process. x Fe y M z B n Alloy sheet.

[0023] Preferably, the cooling rate in the rapid solidification and spinning process is ≥100℃ / s.

[0024] Preferably, in step S3, the A content in the mixed alloy sheet is 0.1–0.6 wt.%.

[0025] Preferably, in step S4, the mixed alloy sheet is stirred while absorbing hydrogen, and the RE x Fe y M z B n Alloy sheet and the LRE a Co b A 100-a-b The alloy sheets are thoroughly mixed, and the hydrogen absorption and dehydrogenation process is carried out in two steps. The first step is to absorb hydrogen at 300-500℃, and then absorb hydrogen at 200-300℃, which is a process of first absorbing hydrogen at high temperature and then at low temperature. Finally, the hydrogen is dehydrogenated at 500-600℃.

[0026] Preferably, in step S5, the first powder of the alloy sheet is ground under a supersonic nitrogen gas flow.

[0027] Preferably, in step S6, the magnetic field strength is ≥1.5T.

[0028] Preferably, in step S6, before pressing and molding, the second powder of the alloy sheet is coated with an antioxidant and a lubricant for surface treatment.

[0029] Preferably, in step S6, the density of the pressed blank is ≥4.2 g / cm³. 3 .

[0030] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0031] This invention prepares RE x Fe y M z B n High-melting-point Zr, Ti, or Nb are not added to the alloy sheet (alloy T). This avoids the common practice of adding high-melting-point Zr, Ti, or Nb, as Zr, Ti, or Nb preferentially react with B to form acicular TiB2 or ZrB2 phases during the melting and cooling process, thus reducing the consumption of B element in the alloy and increasing RE2Fe in the matrix. 14 The proportion of B matrix phase is beneficial to improving the remanence of the magnet. At the same time, the present invention distributes these high melting point elements on the grain boundaries to prevent grain growth during sintering and control the grain size within 2-5.5 μm, thus ensuring the production of a high coercivity magnet.

[0032] The grain boundaries of neodymium iron boron magnets are key to improving coercivity. In step S3, LRE... a Cob A 100-a-b Alloys and RE x Fe y M z B n The alloy sheets are mixed, and the composition of this alloy is close to that of the grain boundaries in the matrix alloy. Adding it through this method allows the alloy to melt and distribute along the grain boundaries during mixing, powdering, and sintering, enhancing demagnetizing coupling and thus improving coercivity. Adding a small amount of Co improves the alloy's fracture characteristics and forms a ternary eutectic alloy, promoting the distribution of Zr, Ti, or Nb. However, excessive Co leads to the formation of soft magnetic cores, resulting in low coercivity. Too much Zr, Ti, or Nb also deteriorates the magnet's machinability. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of a method for preparing a fine-grained, high-coercivity NdFeB permanent magnet material according to the present invention.

[0034] Figure 2 Example 1: Scanning electron microscope image of the magnet;

[0035] Figure 3 Comparative Example 1: Scanned electron image of a magnet;

[0036] Figure 4 Comparison of particle size distribution curves of Example 1 and Comparative Example 1. Detailed Implementation

[0037] The present invention will now be described in detail and specifically through specific embodiments to enable a better understanding of the invention. However, the following embodiments do not limit the scope of the invention.

[0038] Example 1

[0039] This embodiment provides a fine-grained, high-coercivity neodymium iron boron permanent magnet material, the preparation method of which specifically includes the following steps:

[0040] Step S1: Preparation of Alloy A:

[0041] By weight percentage, alloy A is Pr 7.75 Nd 23.25 Al 0.3 Cu 0.2 Ga 0.3 B 0.93 Co1Fe 66.27 Alloy A is produced by a rapid solidification and strip spinning process, with a cooling rate of 1000℃ / s.

[0042] Step S2, Preparation of Alloy B:

[0043] By weight percentage, alloy B is Pr 85 Nd5Ti5Co4; Alloy B is also produced by rapid solidification and strip spinning process, with a cooling rate of 1100℃ / s.

[0044] Step S3: Mix alloy A and alloy B in a weight ratio of 95:5 to obtain a mixed alloy sheet;

[0045] Step S4: The mixed alloy sheet is subjected to hydrogen absorption at 330℃ and then at 220℃, followed by dehydrogenation treatment at 550℃ to obtain the first alloy sheet powder. The hydrogen pressure is 0.1MPa. The alloy is stirred while absorbing hydrogen at a speed of 10 rpm. Alloy A and Alloy B are thoroughly mixed to prevent the alloy from recombinizing during the dehydrogenation process.

[0046] Step S5: The first alloy sheet powder obtained in step S4 is ground under a supersonic nitrogen gas flow to obtain the second alloy sheet powder with an average particle size of 2.93 μm, of which 10% of the particles are below 1.46 μm. The particle size distribution diagram is shown in the figure. Figure 4 ;

[0047] Step S6: Before pressing, add antioxidants and lubricants to modify the surface of the powder. Under a nitrogen protective atmosphere, orient the second powder of the alloy sheet under a magnetic field with a magnetic field strength of 2T to obtain a pressed blank with a density of 4.4 g / cm³. 3 ;

[0048] Step S7: Sinter the pressed compact under vacuum, with a sintering vacuum degree of 5×10⁻⁶. -3 Pa, the sintering process conditions are 1070℃, 6h; after sintering, tempering treatment is performed at 900℃×2h+540℃×4h to obtain fine-grained high-coercivity NdFeB permanent magnet material with an average grain size of 5.13μm.

[0049] The obtained magnets were processed into Φ10mm×10mm sample columns for magnetic property testing. The main test items were remanence (Br) and intrinsic coercivity (Hcj). Simultaneously, the samples were polished, etched with 3% nitric acid alcohol, and then the metallographic structure was tested, and the grain size was analyzed. The analysis results are shown in Table 1-2.

[0050] Example 2

[0051] This embodiment provides a fine-grained, high-coercivity neodymium iron boron permanent magnet material, the preparation method of which specifically includes the following steps:

[0052] Step S1: Preparation of Alloy A:

[0053] By weight percentage, alloy A is Nd 29 Al 0.1 Cu 0.2 Co1.5 B1Fe 68.2 Alloy A is produced by a rapid solidification and strip spinning process, with a cooling rate of 1500℃ / s.

[0054] Step S2, Preparation of Alloy B:

[0055] By weight percentage, alloy B is Pr 89 Zr8Co3; Alloy B is also produced by rapid quenching process, with a cooling rate of 10000℃ / s;

[0056] Step S3: Mix alloy A and alloy B in a weight ratio of 97:3 to obtain a mixed alloy sheet;

[0057] Step S4: The mixed alloy sheet is subjected to hydrogen absorption at 350°C and then at 200°C, followed by dehydrogenation treatment at 580°C to obtain the first alloy sheet powder. The hydrogen pressure is 0.12 MPa. The alloy is stirred while absorbing hydrogen, and the stirring speed is 12 rpm. Alloy A and alloy B are fully mixed to prevent the alloy from recombinizing during the dehydrogenation process.

[0058] Step S5: The first alloy sheet powder obtained in step S4 is ground under a supersonic nitrogen gas flow to obtain the second alloy sheet powder with an average particle size of 3.01 μm, of which 10% of the particles are below 1.53 μm.

[0059] Step S6: Before pressing, add antioxidants and lubricants to modify the surface of the powder. Under a nitrogen protective atmosphere, orient the second powder of the alloy sheet under a magnetic field with a magnetic field strength of 2T to obtain a pressed blank with a density of 4.3 g / cm³. 3 ;

[0060] Step S7: Sinter the pressed compact under vacuum, with a sintering vacuum degree of 8×10⁻⁶. -3 Pa, the sintering process conditions are 1060℃ for 8h; after sintering, tempering treatment is carried out at 900℃ for 3h + 520℃ for 4h to obtain fine-grained NdFeB permanent magnet material with an average grain size of 5.42μm.

[0061] The magnetic properties and average grain size were analyzed using the method described in Example 1. The results are shown in Tables 1-2.

[0062] Example 3

[0063] This embodiment provides a fine-grained, high-coercivity neodymium iron boron permanent magnet material, the preparation method of which specifically includes the following steps:

[0064] Step S1: Preparation of Alloy A:

[0065] By weight percentage, alloy A is Nd 29 Al0.1 Cu 0.2 B1Co 1.5 Dy 0.4 B1Fe 67.8 Alloy A is produced by a rapid solidification and strip spinning process, with a cooling rate of 900℃ / s.

[0066] Step S2, Preparation of Alloy B:

[0067] By weight percentage, alloy B is Pr 90 Zr8Co2; Alloy B is also produced by rapid quenching process, with a cooling rate of 10000℃ / s;

[0068] Step S3: Mix alloy A and alloy B in a weight ratio of 94:6 to obtain a mixed alloy sheet;

[0069] Step S4: The mixed alloy sheet is subjected to hydrogen absorption at 360°C and then at 230°C, followed by dehydrogenation at 580°C to obtain the first alloy sheet powder. The hydrogen pressure is 0.15 MPa. The alloy is stirred while absorbing hydrogen, and the stirring speed is 8 rpm. Alloy A and Alloy B are fully mixed to prevent the alloy from recombinizing during the dehydrogenation process.

[0070] Step S5: The first alloy sheet powder obtained in step S4 is ground under a supersonic nitrogen gas flow to obtain the second alloy sheet powder with an average particle size of 2.65 μm, of which 10% of the particles are below 1.35 μm.

[0071] Step S6: Before pressing, add antioxidants and lubricants to modify the surface of the powder. Under a nitrogen protective atmosphere, orient the second powder of the alloy sheet under a magnetic field with a magnetic field strength of 2T to obtain a pressed blank with a density of 4.3 g / cm³. 3 ;

[0072] Step S7: Sinter the pressed compact under vacuum, with a sintering vacuum degree of 2×10⁻⁶. -3 Pa, the sintering process conditions are 1040℃, 8h; after sintering, tempering treatment is performed at 900℃×3h+480℃×4h to obtain fine-grained high-coercivity NdFeB permanent magnet material with an average grain size of 4.93μm.

[0073] The magnetic properties and average grain size were analyzed using the method described in Example 1. The results are shown in Tables 1-2.

[0074] Comparative Example 1

[0075] This comparative example provides a fine-grained, high-coercivity neodymium iron boron permanent magnet material, the preparation method of which specifically includes the following steps:

[0076] Step A1: Preparation of the main alloy sheet:

[0077] By weight percentage, the main alloy is Pr 11.61 Nd 22.34 Al 0.29 Cu 0.19 Ga 0.29 B 0.88 Co 1.15 Fe 62.96 Ti 0.25 The main alloy is produced by a rapid solidification and strip spinning process, with a cooling rate of 1000℃ / s.

[0078] Step A2: The main alloy sheet is subjected to hydrogen absorption at 330℃ and then dehydrogenation at 550℃ to process the main alloy sheet into powder. The hydrogen pressure is 0.1MPa. The main alloy sheet is stirred while absorbing hydrogen, and the stirring speed is 10 rpm.

[0079] Step A3: The powder obtained in step A2 is ground under a supersonic nitrogen gas flow to obtain an average particle size of 3.25 μm, of which 10% of the particles are below 1.61 μm.

[0080] Step A4: Before pressing, add antioxidants and lubricants to modify the surface of the powder. Under a nitrogen protective atmosphere, orient and press the powder obtained in step A3 under a magnetic field with a magnetic field strength of 2T to obtain a compact with a compact density of 4.4 g / cm³. 3 ;

[0081] Step A5: Sinter the pressed blank obtained in step A4 under vacuum, with a sintering vacuum degree of 5 × 10⁻⁶. -3 Pa, the sintering process is 1070℃ for 6h; after sintering, it is tempered at 900℃ for 2h + 540℃ for 4h to obtain NdFeB permanent magnet material with an average grain size of 7.36μm.

[0082] The magnetic properties and average grain size were analyzed using the method described in Example 1. The results are shown in Tables 1-2.

[0083] Comparative Example 2

[0084] This comparative example provides a fine-grained, high-coercivity neodymium iron boron permanent magnet material, the preparation method of which specifically includes the following steps:

[0085] Step A1: Preparation of the main alloy sheet:

[0086] By weight percentage, the main alloy is Pr 2.67 Nd 28.13 Al 0.10 Cu 0.19 B 0.97 Zr 0.24 Fe 66.15 Co1.55 The main alloy is produced by a rapid solidification and strip spinning process, with a cooling rate of 900℃ / s.

[0087] Step A2: The main alloy sheet is subjected to hydrogen absorption at 330℃ and then dehydrogenation at 550℃ to process the main alloy sheet into powder. The hydrogen pressure is 0.12MPa. The main alloy sheet is stirred while absorbing hydrogen, and the stirring speed is 12 rpm.

[0088] Step A3: The powder obtained in step A2 is ground under a supersonic nitrogen gas flow to obtain an average particle size of 3.04 μm, of which 10% of the particles are below 1.58 μm.

[0089] Step A4: Before pressing, add antioxidants and lubricants to modify the surface of the powder. Under a nitrogen protective atmosphere, orient and press the powder obtained in step A3 under a magnetic field with a magnetic field strength of 2T to obtain a compact with a compact density of 4.4 g / cm³. 3 ;

[0090] Step A5: Sinter the pressed blank obtained in step A4 under vacuum, with a sintering vacuum degree of 8 × 10⁻⁶. -3 Pa, the sintering process is 1060℃ for 8h; after sintering, it is tempered at 900℃ for 3h + 520℃ for 4h to obtain NdFeB permanent magnet material with an average grain size of 6.13μm.

[0091] The magnetic properties and average grain size were analyzed using the method described in Example 1. The results are shown in Tables 1-2.

[0092] Comparative Example 3

[0093] This comparative example provides a fine-grained, high-coercivity neodymium iron boron permanent magnet material, the preparation method of which specifically includes the following steps:

[0094] Step A1: Preparation of the main alloy sheet:

[0095] By weight percentage, the main alloy is Pr 5.40 Nd 27.26 Al 0.09 Cu 0.19 B 0.94 Zr 0.48 Dy 0.38 Co 1.53 Fe 63.73

[0096] The main alloy is produced by a rapid solidification and strip spinning process, with a cooling rate of 900℃ / s.

[0097] Step A2: The main alloy sheet is subjected to hydrogen absorption at 330℃ and then dehydrogenation at 550℃ to process the main alloy sheet into powder. The hydrogen pressure is 0.1MPa. The main alloy sheet is stirred while absorbing hydrogen, and the stirring speed is 8 rpm.

[0098] Step A3: The powder obtained in step A2 is ground under a supersonic nitrogen gas flow to obtain an average particle size of 2.63 μm, of which 10% of the particles are below 1.45 μm.

[0099] Step A4: Before pressing, add antioxidants and lubricants to modify the surface of the powder. Under a nitrogen protective atmosphere, orient and press the powder obtained in step A3 under a magnetic field with a magnetic field strength of 2T to obtain a compact with a compact density of 4.4 g / cm³. 3 ;

[0100] Step A5: Sinter the pressed blank obtained in step A4 under vacuum, with a sintering vacuum degree of 2×10⁻⁶. -3 Pa, the sintering process is 1040℃ for 8h; after sintering, it is tempered at 900℃ for 3h + 480℃ for 4h to obtain NdFeB permanent magnet material with an average grain size of 5.62μm.

[0101] The magnetic properties and average grain size were analyzed using the method described in Example 1. The results are shown in Tables 1-2.

[0102] Table 1. Component parameters (mass fraction) of the examples and comparative examples

[0103] Alloy A Alloy B A:B Example 1 <![CDATA[Pr 7.75 Nd 23.25 Al 0.3 Cu 0.2 Ga 0.3 B 0.93 Co1Fe 66.27 ]]> <![CDATA[Pr 85.5 Nd 5.5 Ti5Co4]]> 95:5 Example 2 <![CDATA[Nd 29 the 0.1 With 0.2 B1Co 1.5 B1Fe 68.2 ]]> <![CDATA[Pr 89 Zr8Co3]]> 97:3 Example 3 <![CDATA[Nd 29 It 0.1 Cu 0.2 B1Co 1.5 To 0.4 B1Fe 67 .8]]> <![CDATA[Pr 90 Zr8Co2]]> 94:6 Comparative Example 1 <![CDATA[Pr 11.61 Nd 22.34 Al 0.29 Cu 0.19 Ga 0.29 B 0.88 Co 1.15 Faith 62.96 To 0.25 ]]> Comparative Example 2 <![CDATA[Pr 2.67 Nd 28.13 Al 0.1 Cu 0.19 B 0.97 Zr 0.24 Faith 66.15 Co 1.55 ]]> Comparative Example 3 <![CDATA[Pr 5.40 Nd 27.26 Al 0.09 Cu 0.19 B 0.94 Zr 0.48 Of 0.38 Mutual 1.53 Fe 63.73 ]]>

[0104] Table 2 Comparison of preparation process parameters between the examples and comparative examples

[0105]

[0106] Table 3 Comparison of magnetic performance data between comparative examples and embodiments.

[0107] Coercivity Hcj(kOe) Remanence Br (kGs) Example 1 22.67 12.85 Example 2 18.92 14.16 Example 3 24.53 12.73 Comparative Example 1 21.38 12.74 Comparative Example 2 17.85 13.92 Comparative Example 3 21.87 12.61

[0108] In Example 1 and Comparative Example 1, using the same nominal composition and powder particle size, and subjected to the same sintering temperature, the data in Tables 1 and 2 show that adding a small amount of Pr-Nd-Ti-Co auxiliary alloy refined the grain size from 7.36 μm to 5.13 μm, resulting in a significant grain size refinement and an increase in the coercivity (Hcj) of the magnet by 1.29 kOe. It can be seen that when 10% of the powder particles are larger than 1.6 μm, grain growth is easily caused, and the particle size distribution is as follows... Figure 4 As shown. Figure 2The microstructure of Example 1 shows a uniform distribution of grain boundary phases, fine grains, and no needle-like TiB2 phases appearing at the grain boundaries. Figure 3 To compare the microstructure of Example 1, needle-like TiB2 phases can be observed in the grain boundary regions. Based on the area fraction comparison, the proportion of the needle-like phase is greater than 0.1%, reducing the volume fraction of the matrix phase. From the difference in remanence between Example 1 and Comparative Example 1, it can be seen that the remanence (Br) of the magnet with the auxiliary alloy is slightly higher than that of the magnet with Ti added to the main alloy. This is mainly because adding Ti to the main alloy produces a large amount of TiB2 phase, reducing the volume fraction of the matrix phase. However, by adding a Pr-Nd-Ti-Co auxiliary alloy, after powder sintering, Ti is mainly distributed on the grain boundaries, without the presence of TiB2 phase, thus avoiding the consumption of B content and the resulting reduction in the volume fraction of the matrix phase. Simultaneously, the Ti distribution on the grain boundaries inhibits grain growth during sintering.

[0109] Data from Example 2 and Comparative Example 2 show that by adding a Pr-Zr-Co auxiliary alloy, the grain size of the magnet after sintering was refined from 6.13 μm to 5.42 μm. Simultaneously, the coercivity of the magnet was improved, and the remanence was higher than that of the magnet with Zr added to the main alloy. High-magnification scanning electron microscopy analysis also revealed the presence of fibrous phases such as ZrB2 at the triangular grain boundaries.

[0110] The data results for Example 3 and Comparative Example 3 are the same as those for Example 2 and Comparative Example 2. Adding a larger amount of Pr-Zr-Co auxiliary alloy significantly improves the coercivity of the magnet.

[0111] The data above shows that the method of adding high-melting-point alloys in this invention can effectively reduce grain size, improve the coercivity of the magnet, reduce the formation of needle-like TiB2 phases, and improve remanence, thus solving the problem of improving coercivity by refining grains in the field of permanent magnets.

[0112] The specific embodiments of the present invention have been described in detail above, but they are merely examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, all equivalent transformations and modifications made without departing from the spirit and scope of the present invention should be covered within the scope of the present invention.

Claims

1. A neodymium-iron-boron permanent magnetic material, characterized in that, The neodymium-iron-boron permanent magnet material contains an A element selected from at least one of Zr, Ti and Nb, and a microstructure of the neodymium-iron-boron permanent magnet material includes a matrix phase RE2Fe 14 A B phase, and a grain boundary phase dispersed around the matrix phase, wherein the grain boundary phase contains rare earth elements and compounds thereof, elemental A and an AB2 compound, and the mass ratio of the AB2 compound in the grain boundary phase is less than 0.1%. The RE2Fe 14 In the B phase, RE contains R and R1, R contains at least one of Nd and Pr, R1 is selected from one or more of La, Ce, Y, Dy, Tb, Ho and Gd, the volume content of the RE2Fe 14 The volume content of the B phase in the Nd-Fe-B permanent magnet material is 88% to 95%, and R / (R+R1)≥70%. The preparation method of the neodymium-iron-boron permanent magnet material comprises the following steps: Step S1, preparing RE x Fe y M z B n alloy sheet: RE contains R and R1, R contains at least one of Nd and Pr, R1 is selected from one or more of La, Ce, Y, Dy, Tb, Ho, and Gd; M is one or more of Al, Cu, Ga, Co, and Sn; B is boron; wherein, in terms of weight percentage, 28≤x≤31.5, 0.3≤z≤4, 0.80≤n≤0.97, and y=100-x-z-n; Step S2, preparing LRE a Co b A 100-a-b alloy, LRE is selected from one or both of Pr or Nd; Step S3, preparing mixed alloy: mixing the RE x Fe y M z B n alloy pieces and the LRE a Co b A 100-a-b alloy pieces to obtain mixed alloy pieces; wherein the RE x Fe y M z B n alloy pieces and the LRE a Co b A 100-a-b The mixed weight ratio of the alloy pieces is RE x Fe y M z B n alloy pieces: LRE a Co b A 100-a-b alloy pieces = 90~99.5: 0.5~10; the total mass of Zr or Ti or Nb in the final magnet accounts for 0.1-0.6% of the mass of the magnet; the LRE a Co b A 100-a-b , wherein the weight fraction of a ranges from 80~90, and the weight fraction of b ranges from 2~10.

2. The NdFeB permanent magnetic material according to claim 1, characterized in that, The RE2Fe 14 The grain size of the B phase is 2-5.5 μm.

3. The Nd-Fe-B permanent magnet material according to claim 1, characterized in that, The preparation method further comprises the following steps: Step S4: preparing alloy sheet first powder: hydrogen absorption and dehydrogenation treatment is performed on the mixed alloy sheet to obtain alloy sheet first powder; Step S5: preparing alloy sheet second powder: airflow grinding treatment is performed on the alloy sheet first powder under nitrogen protection to obtain alloy sheet second powder; Step S6: preparing a compact: the alloy sheet second powder is oriented and pressed under a magnetic field in a nitrogen protection atmosphere to obtain a compact; Step S7: vacuum sintering is performed on the compact under vacuum, and then tempering and aging treatment are performed to obtain a fine-grained high-coercivity neodymium-iron-boron permanent magnet material.

4. The Nd-Fe-B permanent magnet material according to claim 3, characterized in that, The hydrogen absorption and dehydrogenation treatment process is performed in two steps: first, hydrogen absorption is performed at 300-500 DEG C, and then hydrogen absorption is performed at 200-300 DEG C; high-temperature hydrogen absorption is performed first, and then low-temperature hydrogen absorption is performed; and then dehydrogenation is performed at 500-600 DEG C.

5. The Nd-Fe-B permanent magnet material according to claim 3, characterized in that, The average particle size of the alloy sheet second powder is 1.5-3.5 mu m; wherein the particle size of 10% of the alloy sheet second powder is <1.6 mu m.

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