A multi-alloy high-comprehensive-performance magnet and a preparation method thereof

Abstract

This invention discloses a multi-alloy high-performance magnet and its preparation method, which is made from Nd (chemical formula, mass percentage) a M 100‑a‑b‑c Fe b B c Alloys and (Nd) 1‑x RE x ) a M 100‑a‑b‑c Fe b B c The alloy forms a dual-phase alloy, which is combined with a hard auxiliary alloy Al-X-B, wherein 26≤a≤34, 60≤b≤68, 0.9≤c≤1.1, 0<x≤90, RE is one or more of the high-abundance rare earth elements La, Ce, and Y, M is one or more of the elements Zn, Ga, Co, Cu, Nb, Sn, and Mn, and X is one or more of the elements Ti, Hf, Zr, and Nb; the mass ratio of the dual-phase alloy to the hard auxiliary alloy is 1:0.002-2. The two main phase alloys are rapidly solidified and spun into alloy powder through hydrogen crushing and air jet milling, and then mixed with the hard auxiliary alloy powder, pressed into blocks, and sintered to prepare the magnet. This invention reduces the manufacturing cost of magnets and enables permanent magnets with dual-controlled addition of hard auxiliary alloy Al-X-B and multi-alloy processes to exhibit superior comprehensive performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rare earth permanent magnet materials, and particularly relates to a multi-alloy high-comprehensive-performance magnet and a preparation method thereof. BACKGROUND

[0002] Sintered neodymium-iron-boron magnets are widely used in the fields of permanent magnetic levitation track, aerospace, new energy vehicles, wind power generation, etc. due to their excellent magnetic properties. The requirement for the mechanical properties of the magnets is gradually increasing. However, due to the contradiction between the magnetic anisotropy and the mechanical anisotropy, it is difficult to guarantee good mechanical properties while having high magnetic properties.

[0003] With the diversification of the service conditions of Nd-Fe-B magnets, the demand for high-comprehensive-performance magnets with excellent magnetic properties and mechanical properties is gradually increasing. It is mentioned in patents CN102800454A, CN103545079A, CN105321644A and CN106357175A that the double-main-phase sintered magnets prepared by using the traditional sintering technology can weaken the magnetic dilution effect of high-abundance rare earths. It is mentioned in patents CN117144201A, CN115821119A and CN110184503A that a refiner is often used in aluminum alloy materials to refine the grains. The grain refinement has a very obvious effect on the microstructure of the Nd-Fe-B magnet and has a positive promoting effect on the magnetic properties and mechanical properties of the Nd-Fe-B magnet. The common research is to add high-melting-point elements such as Zr and Ti in the single main-phase magnetic powder to realize grain refinement, and these high-melting-point elements tend to gather at the grain boundaries, limiting the grain refinement effect of the high-melting-point elements. However, there are few descriptions of multi-alloy sintering technology for realizing grain refinement by adding hard auxiliary alloy Al-X-B powder and realizing the homogeneous distribution of the hard auxiliary alloy Al-X-B powder through the double-main-phase process, X being one or several of Ti, Hf, Zr and Nb. SUMMARY

[0004] The application aims to provide a multi-alloy high-comprehensive-performance magnet and a preparation technology thereof. Two main-phase magnetic powders and Al-X-B hard auxiliary alloy are mixed and pressed, X being one or several of Ti, Hf, Zr and Nb. The application aims to enhance the capillary effect of the grain boundaries and promote the homogeneous distribution of the high-melting-point Al-X-B hard phase in the grain boundaries through the mutual diffusion of rare earth elements formed by the concentration gradient of the main phase, enhance the grain refinement effect of the Al-X-B hard phase and the inhibition effect of crack propagation in the magnet fracture process, and prepare a multi-alloy high-comprehensive-performance magnet with excellent magnetic properties and mechanical properties.

[0005] To achieve the above-mentioned purpose, the application provides the following technical scheme:

[0006] A multi-alloy high comprehensive performance magnet is formed by a double main phase alloy of a chemical formula of mass percentage of Nd a M 100-a-b-c Fe b B c alloy and a low-cost chemical formula of mass percentage of (Nd 1-x RE x ) a M 100-a-b-c Fe b B c alloy, wherein 26≤a≤34, 60≤b≤68, 0.9≤c≤1.1, 0

[0007] Preferably, the mass ratio of the double main phase alloy to the hard auxiliary alloy is 1:0.002-0.004.

[0008] Preferably, the hard auxiliary alloy Al-X-B has a chemical formula of mass percentage of AlX5B.

[0009] Considering the comprehensive cost and magnetic property, in the double main phase alloy, the mass ratio of the Nd a M 100-a-b-c Fe b B c alloy to the (Nd 1-x RE x ) a M 100-a-b-c Fe b B c alloy is preferably 1:0.5-4, and more preferably 1:1.

[0010] The present application adopts a conventional Nd a M 100-a-b-c Fe b B c main phase alloy and a (Nd 1-x RE x ) a M 100-a-b-c Fe b B cThe main phase alloy and nanoscale hard auxiliary alloy Al-X-B powder are mixed with each other, and the purposes are as follows: (1) using high-abundance rare earth RE to partially replace Nd in the Nd-Fe-B magnet, increasing the use amount of high-abundance rare earth in the magnet, reducing the manufacturing cost of the magnet, and relieving the problems of resource waste and environmental pollution caused by long-term accumulation of high-abundance rare earth; (2) forming two alloy main phases with significant difference in magnetic crystal anisotropy field, promoting the uniform distribution of Al-X-B at the grain boundary through the rare earth element migration of Nd and high-abundance rare earth elements between the two main phases, inhibiting the crack propagation when the magnet is fractured along the grain, and improving the mechanical properties of the magnet. The high-melting-point Al-X-B can also effectively refine the main phase grains, optimize the grain boundary, and inhibit the coupling effect of adjacent grains, so that the permanent magnet controlled by Al-X-B addition and double main phase process exhibits more excellent comprehensive performance.

[0011] The application also provides a preparation method of the above-mentioned multi-alloy high-comprehensive-performance magnet, comprising the following steps:

[0012] (1) preparing raw materials: preparing Nd a M 100-a-b-c Fe b B c and (Nd 1-x RE x ) a M 100-a-b-c Fe b B c alloy raw materials;

[0013] (2) rapid quenching and tape casting: placing the prepared raw materials into a melting rapid quenching furnace respectively to obtain Nd a M 100-a-b-c Fe b B c and (Nd 1-x RE x ) a M 100-a-b-c Fe b B c alloy rapid quenching tapes;

[0014] (3) hydrogen crushing: placing the two kinds of alloy rapid quenching tapes into hydrogen crushing tanks respectively to obtain coarse-grained alloy powder through hydrogen absorption and hydrogen desorption reactions;

[0015] (4) airflow milling: preparing the hydrogen crushing powder obtained in the step (3) under nitrogen, and using a sorting wheel to obtain alloy powder with a particle size of 2.6-3.1 microns;

[0016] (5) mixing and pressing: the hard alloy Al-X-B powder needs to control the particle size range of 10-500nm, the added mass percentage is 0.002-2%, and the two main phase magnetic powders and the hard alloy Al-X-B powder are mixed in a powder mixer for 10-20min under a protective atmosphere and pressed into a block, then sealed in a bag and cold isostatic pressed, the pressing pressure is 150-200MPa, and the pressing time is 0.01-5min;

[0017] (6) sintering: the block is sintered to obtain a completely dense Nd2Fe 14 B main phase and low-cost (Nd, RE)2Fe 14 B main phase and hard alloy phase composite sintered magnet.

[0018] Preferably, the step (2) alloy rapid solidification piece preparation method is: vacuumizing the rapid solidification furnace, after heating and baking the furnace, argon is introduced, the temperature of the crucible is refined to 1400-1600℃ by medium-frequency current, the alloy liquid is poured into a tundish, and is guided to a cold roller to cool and solidify into a rapid solidification piece, the rotating speed of the cold roller is 1.15-1.5m / s, the thickness of the rapid solidification piece is 0.25-0.4mm, and the cooling water temperature of the copper roller is 18-25℃.

[0019] Preferably, the step (3) hydrogen absorption and dehydrogenation reaction method is: vacuumizing the hydrogen breaking tank, absorbing hydrogen at room temperature for 1.2-2.0h under a hydrogen pressure of 0.5-0.7MPa, and dehydrogenating at 480-520℃ for 2.5-3.5h.

[0020] Preferably, in the step (4) airflow milling process, the rotating speed of the sorting wheel is 4300-4500r / min.

[0021] The present application utilizes powder metallurgy technology to prepare Nd a M 100-a-b-c Fe b B c and (Nd 1-x RE x ) a M 100-a-b-c Fe b B cTwo different types of rapid solidification flakes, and under the protection of argon, through hydrogen breaking and airflow grinding and mixing with hard alloy Al-X-B to make mixed multi-alloy magnetic powder, after liquid phase sintering, sintered magnets with two types of main phases are obtained, two types of alloy main phases with significant difference in magnetic crystal anisotropy field, the concentration gradient formed by the concentration difference of Nd and high-abundance rare earth elements in the two alloys promotes the uniform distribution of Al-X-B at the grain boundary, and inhibits the expansion of intergranular fracture cracks during the fracture process, and the inhibition of abnormal grain growth of high-melting-point Al-X-B also acts on the main phase grains, optimizes the grain boundary, and inhibits the coupling effect of adjacent grains, so that the permanent magnet with the addition of hard auxiliary alloy Al-X-B and the double regulation of the double main phase process exhibits more excellent comprehensive performance. The sintered magnet density, the uniformity of the mixed powder and the particle size control of the hard auxiliary alloy Al-X-B are the key to preparing high-comprehensive-performance magnets.

[0022] Compared with the prior art, the beneficial effects of the present application are:

[0023] (1) The high-abundance rare earth RE is used to partially replace Nd in the Nd-Fe-B magnet, which increases the amount of high-abundance rare earth in the magnet, reduces the manufacturing cost of the magnet, and alleviates the problems of resource waste and environmental pollution caused by long-term overstock of high-abundance rare earth;

[0024] (2) Two types of alloy main phases with significant difference in magnetic crystal anisotropy field are formed, the concentration gradient formed by the concentration difference of Nd and high-abundance rare earth elements in the two alloys promotes the uniform distribution of Al-X-B at the grain boundary, and inhibits the expansion of intergranular fracture cracks during the fracture process, and the inhibition of abnormal grain growth of high-melting-point Al-X-B also acts on the main phase grains, optimizes the grain boundary, and inhibits the coupling effect of adjacent grains, so that the permanent magnet with the addition of hard auxiliary alloy Al-X-B and the double regulation of the double main phase process exhibits more excellent comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The figure is a single main phase magnet Al-X-B (black needle-shaped) enrichment diagram;

[0026] Figure 2 The figure is a schematic diagram of the core-shell structure of the interdiffusion of rare earth elements between the main phases of the double main phase magnet, which promotes the homogenization process of Al-X-B. DETAILED DESCRIPTION

[0027] The following further detailed description is made in conjunction with specific embodiments, and the examples given are only to illustrate the present application, not to limit the scope of the present application.

[0028] Example 1

[0029] (1) The main phase A is prepared according to the mass percentage of Nd 31 Ga0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 and main phase B: (Nd 0.7 Ce 0.3 ) 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 .

[0030] (2) Put the configured main phase A and main phase B into a smelting rapid solidification furnace respectively, vacuumize to 5x10 -3 Pa, heat to 400℃, then introduce high-purity argon (the argon volume content is 99.999%), heat the crucible to 1500℃ by medium-frequency current for 4 min, pour the alloy liquid into a tundish, guide to a cold roller to cool and solidify into a rapid solidification piece, the cold roller rotation speed is 1.3 m / s, the rapid solidification piece thickness is 0.28 mm;

[0031] (3) Put the alloy rapid solidification piece into a hydrogen breaking tank respectively, vacuumize to 1x10 -3 Pa, absorb hydrogen at 0.6 MPa hydrogen pressure at room temperature for 1.5 h, dehydrogenate at 500℃ for 3 h, prepare a coarse-grained alloy powder after the hydrogen absorption and dehydrogenation reaction;

[0032] (4) Under high-purity nitrogen (the nitrogen volume content is 99.999%), the hydrogen breaking powder is prepared by airflow mill sorting wheel rotation speed 4300 r / min, the average particle size is 2.8 μm;

[0033] (5) Mix main phase A and main phase B according to 1:1 mass ratio, and mix the magnetic powder and 100 nm particle size hard auxiliary alloy AlTi5B (atomic ratio) powder according to 1:0.0023 mass ratio under vacuum drying, and press into a 25x25x25 mm block under high-purity nitrogen protection, then isostatic pressing, the pressing pressure is 200 MPa, the pressure holding time is 5 min;

[0034] (6) Put the block into a graphite box and put it into a tube-type sintering furnace, vacuumize to 1x10 -3 Pa, heat and sinter to prepare a dense (Nd 0.85 Ce 0.15 ) 31 Ti 0.2 Ga 0.1 Co 0.3 Al 0.02 Cu 0.2 B 0.94 Fe 67.24 multi-alloy magnet.

[0035] (7) For comparative example, the same composition single main phase magnetic powder (Nd 0.85 Ce 0.15 ) 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 and hard alloy AlTi5B powder with 100 nm particle size were mixed to prepare single main phase magnets by the same preparation process.

[0036] The sintered magnets were cut into cylindrical samples with a diameter D of 10 mm and a height of 10 mm, and rectangular cuboid samples with dimensions of 5x6x22 mm by wire cutting and inner circle cutting, respectively. The magnetic properties and bending strength were measured using a NIM-2000HF rare earth permanent magnet measuring device and a universal testing machine. The performance is shown in Table 1.

[0037] Example 2

[0038] (1) The main phase A: Nd 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 and the main phase B: (Nd 0.7 Ce 0.3 ) 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 .

[0039] (2) The prepared main phase A and main phase B were placed in a smelting rapid solidification furnace, respectively, and vacuumed to 5x10 -3 Pa, and then high-purity argon was introduced after the furnace was heated to 400℃. The temperature of the crucible was heated to 1500℃ by medium-frequency current for 4 min. The alloy liquid was poured into a tundish and guided to a cold roller for cooling and rapid solidification into a rapid solidification piece. The rotation speed of the cold roller was 1.3 m / s, and the thickness of the rapid solidification piece was 0.28 mm.

[0040] (3) The alloy rapid solidification piece was placed in a hydrogen breaking tank, respectively, and vacuumed to 1x10 -3 Pa, and then hydrogen was absorbed at 0.6 MPa hydrogen pressure at room temperature for 1.5 h, and dehydrogenation was carried out at 500℃ for 3 h. Coarse grain alloy powder was prepared after the hydrogen absorption and dehydrogenation reactions.

[0041] (4) The hydrogen breaking powder was separated by airflow mill under high-purity nitrogen, with a separation wheel rotation speed of 4300 r / min, to obtain an average particle size of 2.8 μm.

[0042] (5) Main phase A and main phase B are mixed in a mass ratio of 1:1, and the magnetic powder and hard auxiliary alloy AlZr5B (atomic ratio) powder with a particle size of 100 nm are mixed in a ratio of 1:0.0025 under vacuum drying and pressed into a 25x25x25mm block under the protection of high-purity nitrogen, followed by isostatic pressing, pressing pressure 200 MPa, holding time 5 min.

[0043] (6) The block is loaded into a graphite box and placed in a tube sintering furnace, vacuumed to 1x10 -3 Pa, sintered at high temperature to obtain dense (Nd 0.85 Ce 0.15 ) 31 Zr 0.21 Ga 0.1 Co 0.3 Cu 0.2 Al 0..01 B 0.95 Fe 67.23 alloy magnet.

[0044] (7) For comparison, a single main phase magnet is prepared using the same composition of magnetic powder (Nd 0.85 Ce 0.15 ) 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 and 100 nm particle size hard auxiliary alloy AlZr5B powder are mixed, and the same preparation process is used to prepare a single main phase magnet.

[0045] The sintered magnet is cut into a cylinder with a diameter D of 10 mm and a height of 10 mm, and a 5x6x22mm rectangular test sample by wire cutting and inner circle cutting, respectively, and the magnetic properties and bending strength are detected by NIM-2000HF rare earth permanent magnet measuring device and universal testing machine, and the performance is shown in Table 1.

[0046] Example 3

[0047] (1) Main phase A: Nd 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 and main phase B: (Nd 0.7 Ce 0.3 ) 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 are prepared in mass percentage.

[0048] (2) Put the configured main phase A and main phase B into the smelting rapid solidification furnace respectively, vacuumize to 5x10 -3 Pa, and then introduce high-purity argon gas. Heat the crucible to 1500℃ by medium-frequency current for 4 min. Pour the alloy liquid into the tundish, and guide it to the cold roller to cool and solidify into a rapid solidification piece. The rotating speed of the cold roller is 1.3 m / s, and the thickness of the rapid solidification piece is 0.28 mm.

[0049] (3) Put the alloy rapid solidification piece into the hydrogen decrepitation pot respectively, vacuumize to 1x10 -3 Pa, and then absorb hydrogen at 0.6 MPa hydrogen pressure at room temperature for 1.5 h, and dehydrogenate at 500℃ for 3 h. After the hydrogen absorption and dehydrogenation reaction, the coarse-grained alloy powder is prepared.

[0050] (4) Under high-purity nitrogen gas, the hydrogen decrepitation powder is prepared by airflow mill sorting wheel rotating speed of 4300 r / min, and the average particle size is 2.8 μm.

[0051] (5) Mix the main phase A and the main phase B according to the mass ratio of 1:1, and mix the magnetic powder and the 100 nm particle size hard auxiliary alloy AlHf5B (atomic ratio) powder according to the ratio of 1:0.0036 under vacuum drying, and press into a 25x25x25 mm block under high-purity nitrogen protection. Then, isostatic pressing is carried out, the pressing pressure is 200 MPa, and the pressure holding time is 5 min.

[0052] (6) Put the block into a graphite box and put it into a tube-type sintering furnace, vacuumize to 1x10 -3 Pa, and then heat and sinter to prepare a dense (Nd 0.85 Ce 0.15 ) 31 Hf 0.31 Ga 0.1 Co 0.3 Cu 0.2 Al 0.01 B 0.96 Fe 67.12 alloy magnet.

[0053] (7) In order to compare the example, the same component single main phase magnetic powder (Nd 0.85 Ce 0.15 ) 31 Ga 0.1 Co 0.3 Cu 0.2 B 0.93 Fe 67.47 and the 100 nm particle size hard auxiliary alloy AlHf5B powder are mixed, and a single main phase magnet is prepared by the same preparation process.

[0054] The sintered magnets were cut into cylindrical samples with diameter D of 10 mm and height of 10 mm and cuboid samples with length of 5x6x22 mm by wire cutting and inner circle cutting respectively, and the magnetic properties and bending strength were detected by NIM-2000HF rare earth permanent magnet measuring device and universal testing machine, and the properties are shown in Table 1.

[0055] Table 1 Magnetic properties and bending strength of magnets prepared by different methods (SMP is single main phase process, and DMP is double main phase process)

[0056]

[0057]

[0058] It can be seen from the results of the examples that the magnets prepared by Al-X-B addition and double main phase double adjustment have more excellent comprehensive properties than those prepared by single main phase process. The reasons are shown in Figure 1 and Figure 2 , SMP single main phase process is shown in Figure 1 , and Al-X-B (black needle-like) exists in the single main phase magnets. In Figure 2 , DMP double main phase process, the mutual diffusion of rare earth elements between the main phases of the double main phase magnets forms the core-shell structure and promotes the homogenization of Al-X-B.

[0059] Although the present application has been disclosed as above with examples, it is not intended to limit the protection scope of the present application, and any modification and decoration made by those skilled in the art without departing from the concept and scope of the present application shall fall within the protection scope of the present application.

Claims

1. A multi-alloy high-performance magnet, characterized in that: It is composed of Nd with a chemical formula and a mass percentage of 100%. a M 100-a-b- c Fe b B c Alloys and (Nd) 1-x RE x ) a M 100-a-b-c Fe b B c The alloy forms a dual-phase alloy, which is composited with a hard auxiliary alloy Al-XB, wherein 26≤a≤34, 60≤b≤68, 0.9≤c≤1.1, 0<x≤90, RE is one or more of the high-abundance rare earth elements La, Ce, and Y, M is one or more of the elements Zn, Ga, Co, Cu, Nb, Sn, and Mn, and X is one or more of the elements Ti, Hf, Zr, and Nb; the mass ratio of the dual-phase alloy to the hard auxiliary alloy is 1:0.002-0.004, and the Nd a M 100-a-b-c Fe b B c Alloys and (Nd) 1-x RE x ) a M 100-a-b-c Fe b B c The mass ratio of the alloy is 1:0.5-4, and the atomic ratio of each element in the hard auxiliary alloy Al-XB is AlX5B.

2. A method for preparing a multi-alloy high-performance magnet according to claim 1, comprising the following steps: (1) Preparation of raw materials: Preparation of Nd a M 100-a-b-c Fe b B c and (Nd 1-x RE x ) a M 100-a-b-c Fe b B c Alloy raw materials; (2) Rapid solidification and strip casting: The prepared raw materials are placed into a rapid solidification furnace to produce Nd. a M 100-a-b-c Fe b B c and (Nd 1- x RE x ) a M 100-a-b-c Fe b B c Alloy quick-setting tablets; (3) Hydrogen crushing: The two types of alloy quick-condensing sheets are placed into the hydrogen crushing tank respectively, and coarse-particle alloy powder is obtained through hydrogen absorption and dehydrogenation reactions. (4) Airflow milling: The hydrogen-crushed powder obtained in step (3) is processed into alloy powder with a particle size of 2.6-3.1 μm under nitrogen protection using a sorting wheel; (5) Mixing and pressing: The particle size of the hard auxiliary alloy Al-XB powder is controlled at 10-500nm, and the mass percentage of the powder added is 0.002-0.004%. Under a protective atmosphere, the two main phase magnetic powders and the hard auxiliary alloy Al-XB powder are mixed in a powder mixer for 10-20min and pressed into blocks. Then, the blocks are sealed in bags and subjected to cold isostatic pressing at a pressing pressure of 150-200MPa and a pressing time of 0.01-5min. (6) Sintering: The bulk material is sintered to obtain dense Nd2Fe containing high magnetic anisotropy. 14 B main phase and low-cost (Nd,RE)2Fe 14 Composite sintered magnets consisting of B main phase and hard auxiliary alloy phase.

3. The preparation method according to claim 2, characterized in that, The preparation method of the alloy quick-solidification sheet in step (2) is as follows: the quick-solidification furnace is evacuated, and after heating and baking the furnace, argon gas is introduced. The crucible is heated to 1400-1600℃ by medium frequency current for refining. The alloy liquid is poured into the intermediate ladle and guided to the cold roller for cooling and quick solidification into quick-solidification sheets. The rotation speed of the cold roller is 1.15-1.5m / s, the thickness of the quick-solidification sheet is 0.25-0.4mm, and the temperature of the copper roller cooling water is 18-25℃.

4. The preparation method according to claim 2, characterized in that, The hydrogen absorption and dehydrogenation reaction method in step (3) is as follows: the hydrogen tank is broken and a vacuum is drawn, hydrogen is absorbed at room temperature under a hydrogen pressure of 0.5-0.7MPa for 1.2-2.0h, and hydrogen is dehydrogenated at 480-520℃ for 2.5-3.5h.

5. The preparation method as described in claim 2, characterized in that: In step (4), during the air jet milling process, the sorting wheel speed is 4300-4500 r / min.

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