A rare earth permanent magnet material with excellent temperature resistance and its preparation method

Abstract

The present invention relates to a rare earth permanent magnet material with excellent temperature resistance and a preparation method thereof. The rare earth permanent magnet material comprises a compound having the chemical formula (R (1‑x‑y) R' x Y y ) a Fe 100‑a‑b‑c‑d M b Ga c B d , the R element includes one or two of the rare earth elements neodymium and praseodymium, the R' element includes one or two of the rare earth elements dysprosium and terbium, and the M element includes one or more of cobalt, aluminum, copper, zirconium, and niobium; and 30≤a≤33, 0≤b≤3, 0<c≤0.6, 0.88≤d≤1, 0<x≤0.2, and 0<y≤0.2. The rare earth permanent magnet material of the present invention is based on the characteristics of the different metallurgical behaviors of rare earth elements in the 2:14:1 phase, and is prepared to have a grain structure with a gradient distribution of rare earth elements. The Y-rich region inside the grain provides good anisotropic field-temperature characteristics, the Nd / Pr-rich region in the middle of the grain maintains high remanence of the magnet, and the Dy / Tb-rich region in the epitaxial portion of the grain ensures high coercivity of the magnet. The permanent magnet material of the present invention has excellent temperature resistance and can solve the problem of magnet demagnetization failure in high-temperature applications.

Description

Technical Field

[0001] The present invention relates to the technical field of rare earth permanent magnet materials, and in particular to a rare earth permanent magnet material with excellent temperature resistance and a preparation method thereof. Background Art

[0002] Rare earth permanent magnets are based on intermetallic compounds formed by rare earth metals and transition metals. Neodymium iron boron permanent magnets are currently the most magnetic permanent magnet material and are widely used in automotive, air conditioning, wind power generation, defense, and aerospace applications. They are crucial functional materials supporting social progress. However, in certain specialized applications, such as electric vehicle drive motors, the high operating temperatures place higher demands on the heat resistance of permanent magnet materials.

[0003] The temperature resistance of NdFeB permanent magnet materials is closely related to their coercive force. Heavy rare earth elements such as Dy or Tb are usually added to increase the coercive force of the material, thereby increasing the operating temperature of the magnet. However, due to the high price of heavy rare earths and the fact that excessive addition will significantly reduce the remanence of the magnet, reducing the use of heavy rare earths in NdFeB permanent magnet materials has become a development trend. The coercive force of NdFeB magnets mainly comes from the magnetocrystalline anisotropy of the material. The stability of the magnetocrystalline anisotropy field with temperature changes has an important influence on the temperature resistance of the magnet. In the 2:14:1 series of rare earth permanent magnet materials, element Y has no 4f electrons, and Y2Fe 14 The magnetocrystalline anisotropy of B mainly comes from the Fe sublattice, Y2Fe 14 Y2Fe 2 shows different temperature characteristics from other rare earth compounds within a certain temperature range. Therefore, the temperature resistance of the magnet can be improved by adding Y to NdFeB permanent magnet materials. For example, CN 109637768 B discloses a yttrium-containing rare earth permanent magnet material and its preparation method. However, due to the Y2Fe 2 14 The magnetocrystalline anisotropy field of B is small, the coercive force of the magnet obtained by this solution is relatively small, and the absolute value of the coercive force temperature coefficient is relatively large, so the magnet cannot be used at higher temperatures. CN 101834045 B discloses a neodymium iron boron rare earth permanent magnet material with yttrium added and a manufacturing method thereof, the purpose of which is to reduce the amount of neodymium and praseodymium used, but the performance of the prepared magnet is relatively low. Summary of the Invention

[0004] In response to the problems existing in the prior art, the present invention provides a rare earth permanent magnet material with excellent temperature resistance and a preparation method thereof. The magnet material exhibits excellent temperature resistance and is particularly suitable for fields requiring high temperature stability of magnets.

[0005] In order to achieve the above object, the present invention provides a rare earth permanent magnet material, the rare earth permanent magnet material comprises a compound having the chemical formula (R (1-x-y) R' x Yy ) a Fe 100-a-b-c-d M b Ga c B d ,in:

[0006] The R element includes one or both of the rare earth elements neodymium and praseodymium, the R' element includes one or both of the rare earth elements dysprosium and terbium, and the M element includes one or more of cobalt, aluminum, copper, zirconium, and niobium; and 30≤a≤33, 0≤b≤3, 0<c≤0.6, 0.88≤d≤1, 0<x≤0.2, 0<y≤0.2.

[0007] Optionally, 31≤a≤33; further, 0.01≤x≤0.1; further, 0.05≤y≤0.1; further, 0.2<c≤0.5.

[0008] Optionally, the compound consists of main phase grains and grain boundary phases distributed between the main phase grains, and the main phase grains have a tetragonal structure of 2:14:1.

[0009] Optionally, in the main phase grains, rare earth elements are distributed in a gradient, including at least a Y-rich region in the center of the grain, an R-rich region in the middle, and an R'-rich region in the epitaxial portion of the grain.

[0010] Optionally, the mass percentage of Y in the Y-rich region in the central portion of the grain is greater than 2% of the total mass percentage of Y in the compound. Furthermore, in the main phase grain, the mass percentage of R' in the R'-rich region in the epitaxial portion of the grain is greater than 10% of the total mass percentage of R' in the compound.

[0011] Optionally, the average grain size of the main phase grains in the compound is 4 to 8 microns.

[0012] On the other hand, a method for preparing the rare earth permanent magnet material is provided, comprising:

[0013] Press (R (1-x-y) R' x Y y ) a Fe 100-a-b-c-d M b Ga c B d The R' element is removed from the proportion or the increment of the R' element during the diffusion process is deducted, and the ingredients are prepared, and a flake alloy is obtained after melting and solidification to obtain a powder;

[0014] The obtained powder is subjected to orientation pressing under a magnetic field and then isostatic pressing to obtain a compact; the compact is sintered to obtain a dense magnet;

[0015] A layer of a single substance or compound containing one or two of the heavy rare earth elements Dy and Tb is attached to the surface of the magnet;

[0016] Vacuum heat treatment is performed to diffuse the heavy rare earth element into the interior of the magnet to obtain a rare earth permanent magnet material.

[0017] Optionally, the melting includes: melting the raw materials under vacuum and inert gas protection;

[0018] Solidification includes: casting onto a water-cooled rotating roller to solidify to obtain a sheet alloy;

[0019] The powder is prepared by hydrogen crushing and jet milling the flaky alloy to obtain the powder. The linear speed of the rotating roller is 0.8 to 1.2 m / s, and the thickness of the flaky alloy is 0.15 to 0.45 mm, and the spacing between the rare earth-rich phases of the flaky alloy is 2 to 5 microns.

[0020] Furthermore, after the flake alloy is pulverized by hydrogen crushing and air flow milling, the average particle size of the obtained powder is 2 to 3 microns.

[0021] Optionally, the orientation pressing comprises: filling the powder into a mold, and orientation pressing under a magnetic field of at least 1 T to obtain a green compact;

[0022] The isostatic pressing comprises: placing the green compact in an isostatic press and pressing the green compact at a pressure of at least 150 MPa to obtain a green compact with a density of 4 to 5 g / cm 3 ;

[0023] The compact sintering comprises: placing the compact in a sintering furnace for vacuum sintering at a temperature of 1020-1100°C for 2-6 hours, and tempering at a temperature of 450-650°C for 3-6 hours to obtain a dense sintered magnet with an average grain size of 4-8 microns.

[0024] Optionally, the weight of the heavy rare earth element attached to the surface of the magnet accounts for 0-5% of the weight of the magnet, preferably 0.3-3%.

[0025] Optional, vacuum heat treatment, vacuum degree ≤ 5×10 -3 Pa; the heat treatment temperature is 800℃~1000℃, and the heat treatment time is 4~12h; followed by tempering treatment at 450~600℃ for 1~8h.

[0026] The above technical solution of the present invention has the following beneficial technical effects:

[0027] (1) The rare earth permanent magnet material of the present invention is based on the characteristics of different metallurgical behaviors of rare earth elements in the 2:14:1 phase, and a grain structure with a gradient distribution of rare earth elements is prepared. The Y-rich region inside the grain provides good anisotropic field temperature characteristics, the Nd / Pr-rich region in the middle of the grain enables the magnet to maintain high remanence, and the Dy / Tb-rich region in the epitaxial part of the grain ensures high coercive force of the magnet. The permanent magnet material of the present invention has excellent temperature resistance and can solve the problem of demagnetization failure of magnets in high-temperature applications.

[0028] (2) The present invention forms a Dy / Tb-rich hard magnetic region in the epitaxial portion of the grain, thereby offsetting the effect of the reduction in the coercive force of the magnet caused by the addition of Y, and broadening the scope of application of the magnet.

[0029] (3) Y is a high-abundance rare earth element, and its price is much lower than that of Pr, Nd, Dy, Tb and other rare earth elements. The addition of Y can reduce the use of some precious rare earth elements such as Pr, Nd, Dy, Tb, and reduce the cost of permanent magnet materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the microstructure of the rare earth permanent magnet material of the present invention;

[0031] Figure 2 is a backscattered scanning electron microscope image of the final magnet of Example 1 of the present invention;

[0032] Figure 3 This is a backscattered scanning electron microscope image of the final magnet of Comparative Example 1. DETAILED DESCRIPTION

[0033] To make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0034] As analyzed in the background technology, the sintered NdFeB magnets prepared by the existing technology either cannot meet the high-temperature application requirements or are very expensive. In order to solve this problem, the present invention provides a rare earth permanent magnet material with excellent temperature resistance and a preparation method thereof.

[0035] The present invention provides a rare earth permanent magnet material, which comprises a compound having the chemical formula:

[0036] (R (1-x-y) R' x Y y ) a Fe 100-a-b-c-d M b Gac B d , wherein 30≤a≤33, 0≤b≤3, 0<c≤0.6, 0.88≤d≤1, 0<x≤0.2, 0<y≤0.2, R is one or both of the rare earth elements neodymium and praseodymium, R' is one or both of the rare earth elements dysprosium and terbium, Y is the rare earth element yttrium, M is one or more of the metal elements cobalt, aluminum, copper, zirconium, and niobium, Ga is the element gallium, and B is the element boron.

[0037] Rare earth elements play two roles in permanent magnet materials. First, they form a 2:14:1 tetragonal phase structure with Fe and B, which is the source of the material's permanent magnetic properties. Second, they form a continuous grain boundary phase with other elements at grain boundaries. This grain boundary phase is essential for ensuring that the coercivity of sintered NdFeB materials meets practical requirements. The total rare earth content must be appropriately controlled. If it is too low, the grain boundary rare earth-rich phase in the magnet will be insufficient, preventing high coercivity. If it is too high, the grain boundary phase will be excessive. Since grain boundary phases do not have permanent magnetism, excessive grain boundary phases will dilute the material's magnetic properties. Therefore, the total rare earth content is controlled within 30≤a≤33, preferably 31≤a≤33.

[0038] R' is one or both of dysprosium and terbium. The R' in the present invention is mainly added by performing grain boundary diffusion heat treatment on the magnet in the later stage. Since the formation energy of the 2:14:1 tetragonal phase of Dy and Tb is lower than that of Nd or Pr, Dy and Tb enter the surface layer of the 2:14:1 tetragonal phase grains through grain boundary diffusion, greatly improving the anisotropy field of the grain surface, and significantly improving the coercivity of the material. If the R' content is too low, the surface layer of the grain cannot form a clear magnetic hardening layer, and the coercivity is not significantly improved. If the R' content is too high, too much R' enters the interior of the grain, resulting in a decrease in the remanence of the magnet and an inability to form a three-layer internal grain structure, which will also significantly increase the material cost. Therefore, the appropriate content of R' is 0<x≤0.2, preferably 0.01≤x≤0.1.

[0039] Y is a rare earth element yttrium, which can easily form a 2:14:1 phase. 14 The saturation magnetization and anisotropy field of B are not as good as those of Nd2Fe 14 B is high, but below the Curie temperature, Y2Fe 14 The coercivity temperature coefficient of B is much greater than that of Nd2Fe 14B's coercive force temperature coefficient, therefore, replacing Nd or Pr with part of Y is beneficial to improving the temperature stability of permanent magnet materials. Y has a unique metallurgical behavior in the preparation process of sintered magnets. During the sintering process, the Y element tends to concentrate in the center of the grain. By utilizing this, a magnet with a core-shell grain structure rich in Y in the center can be prepared. As mentioned above, Dy and Tb are diffused through the grain boundaries to form a Dy / Tb-rich area on the surface of the grain, so that a three-layer grain structure with a Dy / Tb-rich surface, an Nd / Pr-rich middle layer, and a Y-rich center can be formed. The Y content should be appropriate. If the Y content is too low, the improvement in the coercive force temperature coefficient of the magnet is not significant, and the temperature resistance performance cannot be improved. Due to Y2Fe 14 The intrinsic magnetic properties of B are better than those of Nd2Fe 14 If the B content is low, and the Y content is too high, the remanence and coercivity of the magnet will be significantly reduced, and it will not meet the application requirements. Therefore, the Y content is controlled within 0<y≤0.2, preferably 0.05≤y≤0.1.

[0040] M is one or more of the metal elements cobalt, aluminum, copper, zirconium, and niobium. Adding an appropriate amount of M metal can optimize the grain boundary structure and widen the process window, but the addition amount should not be too high, otherwise the magnetic dilution effect will be obvious. The appropriate amount of M is 0≤b≤3; the magnet contains a certain amount of Ga, which has two main functions. First, Ga can make the grain boundary have better fluidity. During the sintering process, the grain boundary phase can well wrap the grains, play a magnetic isolation role, and improve the coercive force of the magnet; second, Ga can lower the melting point of the grain boundary phase, which is beneficial to the subsequent grain boundary diffusion of Dy / Tb in the magnet and promotes the formation of a magnetic hardening layer on the surface of the grain. The Ga content is controlled at 0<c≤0.6, preferably 0.2≤c≤0.5. B is an essential element for the formation of the 2:14:1 phase. When the B content is high, the columnar crystal structure of the rapid-setting flake alloy is coarse, and a B-rich phase is generated at the grain boundaries of the sintered magnet, which impairs the magnetic properties of the magnet. If the B content is too low, it will easily lead to a decrease in the percentage of the main phase, resulting in deterioration of the magnetic properties of the magnet. In the present invention, the B content is controlled within 0.88≤d≤1.

[0041] The permanent magnetic material of the present invention belongs to the category of sintered NdFeB and is composed of main phase grains and grain boundary phases distributed between the main phase grains. The main phase grains have a tetragonal structure of 2:14:1.

[0042] The average grain size of the main phase grains of the permanent magnet material of the present invention is 4 to 8 microns. If the grain size exceeds 8 microns, the coercive force of the magnet is significantly reduced, and if the grain size is less than 4 microns, it is difficult to realize the process.

[0043] The present invention makes full use of the metallurgical behavior characteristics of elements such as Y, Dy, and Tb. In the main phase grains of the permanent magnet material, rare earth elements are distributed in a gradient to form three layers of regions with different components. Figure 1The Y-rich region in the center of the grain can provide good anisotropic field-temperature characteristics; the Nd / Pr-rich region in the middle of the grain enables the magnet to maintain high remanence; and the Dy / Tb-rich region in the epitaxial part of the grain forms a magnetic hardening layer to ensure high coercive force of the magnet.

[0044] Furthermore, in the main phase grains with a layered structure, the mass percentage of Y in the Y-rich region in the center of the grain is more than 2% higher than the total mass percentage of Y in the material composition. If it is less than 2%, it means that the distribution of Y in the magnet is relatively more uniform, which will cause the coercive force and magnetic energy product of the magnet to be relatively low, and the effect of the Y-rich region on improving the temperature coefficient of the coercive force of the magnet is not obvious; the mass percentage of Dy / Tb in the Dy / Tb-rich region in the epitaxial part of the grain is more than 10% higher than the total mass percentage of Dy / Tb in the material composition. If it is less than 10%, it means that the distribution of Dy / Tb in the magnet is relatively more uniform, which not only leads to insignificant magnetic hardening effect of the epitaxial layer of the grain, but also reduces the remanence of the magnet.

[0045] The present invention also provides a method for preparing a rare earth permanent magnet material, comprising the following steps:

[0046] (1) Press (R (1-x-y) R' x Y y ) a Fe 100-a-b-c-d M b Ga c B d The raw materials are melted in a crucible of a melting furnace under vacuum and inert gas protection, and then cast onto a water-cooled rotating roller to solidify to obtain a flake alloy, and the flake alloy is subjected to hydrogen crushing and air flow milling to obtain a powder;

[0047] (2) Orienting and pressing the obtained powder under a magnetic field, and then further isostatically pressing to obtain a compact; placing the compact in a sintering furnace for sintering to obtain a dense magnet;

[0048] (3) attaching a layer of a single substance or compound containing one or both of the heavy rare earth elements Dy and Tb to the surface of the magnet by coating, sputtering, electroplating, or other methods;

[0049] (4) The magnet containing surface attachments is subjected to vacuum heat treatment to diffuse the heavy rare earth elements into the interior of the magnet, thereby obtaining the rare earth permanent magnet material of the present invention.

[0050] The linear speed of the rotating roller in step (1) is 0.8 to 1.2 m / s, the thickness of the obtained flaky alloy is 0.15 to 0.45 mm, and the spacing between the rare earth-rich phases of the obtained flaky alloy is 2 to 5 microns. After the flaky alloy is subjected to hydrogen crushing and air flow milling, the average particle size of the obtained powder is 2 to 3 microns.

[0051] The pressing process described in step (2) is as follows: the powder obtained in step (1) is filled into a mold, and oriented and pressed in a magnetic field of at least 1T, the green compact is taken out of the mold, and is placed in an isostatic press for further pressing at a pressure of at least 150MPa, and the green compact density is 4-5g / cm 3 The green compact obtained after isostatic pressing is placed in a sintering furnace for vacuum sintering to densify the magnet. The sintering temperature is 1020-1100°C for 2-6 hours. It is then tempered at 450-650°C for 3-6 hours to obtain a dense sintered magnet with an average grain size of 4-8 microns.

[0052] In step (3), the oxide layer on the surface of the sintered magnet is cleaned by cleaning or polishing before implementation. Then, a layer of a single substance or compound containing one or both of the heavy rare earth elements Dy and Tb is attached to the surface perpendicular to the orientation direction of the magnet by methods including but not limited to coating, sputtering, electroplating, etc. The attached amount is converted into the weight of Dy and Tb based on the weight of the attached substance, and accounts for 0-5% of the weight of the magnet, preferably 0.3-3%. If the attached amount is too small, the coercive force will not be significantly improved. If the attached amount increases and the coercive force reaches the limit, further increasing the attached amount will not have the effect of further improving the coercive force, resulting in waste and increased costs.

[0053] In step (4), the magnet that has undergone step (3) is subjected to vacuum heat treatment, and the vacuum degree of the heat treatment is ≤5×10 -3 Pa; the heat treatment temperature is 800℃~1000℃, and the heat treatment time is 4~12h; followed by tempering treatment at 450~600℃ for 1~8h.

[0054] Y2Fe 14 B、(Dy / Tb)2Fe 14 B and (Nd / Pr)2Fe 14 B has different intrinsic properties, namely Y2Fe 14 B's M s (saturation magnetization) and H a (Anisotropy field) is relatively low, but the coercivity temperature characteristic is good; (Dy / Tb)2Fe 14 B's M s Low, but H a Very high; and (Nd / Pr)2Fe 14B has a coercive force temperature characteristic deviation, but has a relatively balanced M s and H a Based on the characteristics of the 2:14:1 tetragonal structure of the above different rare earth elements, the present invention combines the different metallurgical behavior characteristics of elements such as Y, Dy, Tb, Nd, and Pr in the magnet preparation process to design and prepare a magnet material containing a layered grain structure, that is, a Y-rich region is formed in the center of the grain through the sintering process, while providing good anisotropic field-temperature characteristics, minimizing the effect of adding Y on the material M. s and H a The invention also reduces the effect of Y addition on the magnet's coercivity, forming an Nd / Pr-rich region in the middle of the grain to maintain high remanence. Furthermore, grain boundary diffusion forms a Dy / Tb-rich region in the epitaxial portion of the grain, increasing the anisotropy field at the grain surface and compensating for the effect of Y addition on the magnet's coercivity, ensuring high coercivity. The magnet material of the invention exhibits excellent temperature resistance and is particularly suitable for applications requiring high temperature stability.

[0055] The beneficial effects of the present application will be further illustrated below in conjunction with Examples and Comparative Examples. The described embodiments are only a part of embodiments of the present invention, rather than all embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The implementation conditions adopted in the following examples can be further adjusted according to actual needs, and unspecified implementation conditions are generally conditions in routine experiments.

[0056] Examples 1-10:

[0057] Industrial metals Nd, PrNd alloy, DyFe alloy, Tb, Y, commercial pure iron, FeB alloy, Ga, Co, Al, Cu, Zr, and Nb are selected as raw materials. The materials are weighed according to the desired composition shown in Table 1, excluding the R' element or the increase in R' during diffusion. The prepared raw materials are placed in a crucible in a melting furnace, evacuated to below 5 Pa, and filled with 0.05 MPa of high-purity argon as a protective atmosphere. The raw materials are melted by induction heating. The crucible is tilted when the molten steel temperature is 1380-1480°C, and the molten steel is cast onto the surface of a rotating water-cooled roller at a linear speed of 0.8-1.2 m / s. After cooling, the resulting alloy flakes have a thickness of 0.15-0.45 mm. The microstructure of the flakes is observed using a metallographic microscope, and the average spacing between the rare earth-rich phases is measured to be 2-5 microns. The alloy is subjected to conventional hydrogen crushing treatment and then nitrogen flow milling treatment to crush the flaky alloy into powder with an average particle size of 2 to 3 microns.

[0058] Table 1 Composition of the cast alloys in Examples 1-10

[0059]

[0060] In a nitrogen atmosphere, the obtained powder is filled into a press mold and oriented and pressed in a magnetic field of at least 1 to 2 T. The green compact is removed from the mold and placed in an isostatic press for further pressing at a pressure of 150 to 250 MPa to obtain a density of 4 to 5 g / cm 3 The green compact obtained after isostatic pressing is placed in a sintering furnace for vacuum sintering to densify the magnet. The sintering temperature is 1020-1100°C for 2-6 hours. It is then tempered at 450-650°C for 3-6 hours to obtain a dense sintered magnet. The average grain size of the magnet measured by metallographic microscope is 4-8 microns.

[0061] The oxide layer on the surface of the resulting magnet is cleaned by cleaning or polishing. A layer of a single substance or compound containing one or both of the heavy rare earth elements Dy and Tb is then deposited perpendicular to the magnet's orientation using known methods, including but not limited to coating, sputtering, and electroplating. The deposited amount, calculated as the ratio of the weight of Dy and Tb to the weight of the magnet, is shown in Table 2.

[0062] Table 2 Proportions of heavy rare earth attached to the magnet surface in Examples 1-10

[0063]

[0064]

[0065] The magnets with heavy rare earth elements attached to their surfaces were subjected to vacuum heat treatment, evacuated to 5×10⁻³Pa or less, at a temperature of 800°C to 1000°C for 4 to 12 hours. The temperature was then lowered to 450°C to 600°C for tempering, which lasted for 1 to 8 hours. This resulted in a magnet with high temperature resistance. The average composition of the final magnets, as determined by ICP testing, is shown in Table 3.

[0066] Table 3 Composition of the final magnets in Examples 1-10

[0067] wt% Nd Pr Dy Tb Y B Co Al Cu Ga Zr Nb Fe Example 1 18.68 5.25 0.00 3.18 4.78 0.92 0 0 0 0.30 0 0 bal. Example 2 5.56 23.02 0.48 1.21 2.68 0.88 1.00 0.25 0.15 0.50 0 0 bal. Example 3 0 26.05 0.98 0.50 2.90 0.90 1.00 0.50 0.15 0.45 0.12 0.10 bal. Example 4 22.49 0.00 0.00 1.50 6.01 0.92 0 0 0.20 0.20 0.12 0 bal. Example 5 25.47 5.44 0.00 0.32 1.62 0.90 1.50 0 0.20 0.10 0 0 bal. Example 6 16.12 3.98 0.00 6.21 4.61 0.95 2.00 0.15 0 0.60 0.12 0.10 bal. Example 7 21.01 5.24 0.00 1.55 3.12 0.98 0 0 0 0.50 0.12 0.10 bal. Example 8 17.80 5.07 3.04 0.00 4.55 0.90 2.00 0 0 0.30 0 0 bal. Example 9 13.12 12.04 0.6 0.95 5.11 0.91 2.00 0 0.15 0.10 0.12 0 bal. Example 10 21.54 5.38 0.00 2.52 2.02 1.00 0 0.10 0.15 0.20 0 0.20 bal.

[0068] The magnetic properties of the magnets prepared above were measured using a NIM-500C permanent magnet material measurement system. The magnetic properties of the magnets were tested at room temperature (20°C) and high temperature (150°C). The coercive force and coercive force temperature coefficient results are shown in Table 4. The magnets exhibited excellent high-temperature properties.

[0069] Table 4 Coercive force and temperature coefficient of the final magnets in Examples 1-10 at 20°C and 150°C

[0070]

[0071] Conduct microstructure observation and micro-area element analysis on the final magnet. Figure 2 is a scanning electron microscope image (backscattered) of the final magnet in Example 1, Figure 2 The figure shows that a single grain contains three contrasts, indicating that there are three distinct compositional regions within the same grain. The compositions of the outermost Dy / Tb-rich region (+1) and the central Y-rich region (+2) were tested. Similar tests were performed on Examples 2-10, and the results are summarized in Table 5.

[0072] Table 5 Element distribution ratios in different regions of the final magnet grains in Examples 1-10

[0073]

[0074] Comparative Example 1-2

[0075] Industrial metal Nd, praseodymium-neodymium alloy, metal Y, industrial pure iron, ferroboron alloy, metal Ga, Co, Al, Cu, and Zr were selected as raw materials and weighed according to the desired composition in Table 6. The subsequent casting, powdering, pressing, and sintering were carried out according to the steps and processes in Examples 1-10. The magnet of Comparative Example 1 was completed after sintering. The magnet of Comparative Example 2 was prepared by magnetron sputtering after sintering and surface cleaning, with 1.14% of the magnet weight being attached to the sintered and surface-cleaned magnet. The magnet was then vacuumed to 5×10 -3 Pa and below, heat treated at 890°C for 8 hours, then cooled to 520°C for tempering for 4 hours to obtain the final magnet of Comparative Example 2. The final magnet compositions of Comparative Examples 1-2 measured by ICP are summarized in Table 7.

[0076] Table 6 Composition of the cast alloy in Comparative Example 1-2

[0077] wt% Nd Pr Y B Co Al Cu Ga Zr Fe Comparative Example 1 18.40 4.90 6.20 0.88 1.00 0.25 0.15 0.50 0.12 bal. Comparative Example 2 25.60 5.90 0.00 0.90 1.50 0.00 0.20 0.20 0.12 bal.

[0078] Table 7 Final magnet composition of Comparative Examples 1-2

[0079] wt% Nd Pr Tb Y B Co Al Cu Ga Zr Fe Comparative Example 1 18.32 4.88 0.00 6.14 0.88 1.00 0.25 0.15 0.50 0.12 bal. Comparative Example 2 25.56 5.86 1.02 0.00 0.90 1.50 0.00 0.20 0.20 0.12 bal.

[0080] The magnetic properties of the magnets prepared in Example 1-2 were measured using a NIM-500C permanent magnet material measurement system. The magnetic properties of the magnets were tested at room temperature (20°C) and high temperature (150°C). The coercive force and coercive force temperature coefficient results are shown in Table 8.

[0081] Table 8 Coercive force and temperature coefficient of the final magnets in Comparative Examples 1-2 at 20°C and 150°C

[0082]

[0083] The magnet of Comparative Example 1 was subjected to microstructural observation. Figure 3 This is a scanning electron microscope image (backscattered) of the final magnet in Comparative Example 1. The image shows that the grains present a two-layer core-shell structure.

[0084] From the coercive force and temperature coefficient test results of the embodiments and comparative examples, it can be seen that the appropriate addition of Y, combined with the grain boundary diffusion of Dy\Tb, forms a multi-layer gradient structure inside the grains, which significantly improves the coercive force temperature coefficient of the magnet. In addition, the addition of Y instead of Nd and Pr can also significantly reduce material costs.

[0085] In summary, the present invention relates to a rare earth permanent magnet material with excellent temperature resistance and a preparation method thereof, wherein the rare earth permanent magnet material comprises a compound having the chemical formula (R (1-x-y) R' x Y y ) a Fe 100-a-b-c-d M b Ga c B d , the R element includes one or two of the rare earth elements neodymium and praseodymium, the R' element includes one or two of the rare earth elements dysprosium and terbium, and the M element includes one or more of cobalt, aluminum, copper, zirconium, and niobium; and 30≤a≤33, 0≤b≤3, 0<c≤0.6, 0.88≤d≤1, 0<x≤0.2, and 0<y≤0.2. The rare earth permanent magnet material of the present invention is based on the characteristics of the different metallurgical behaviors of rare earth elements in the 2:14:1 phase, and is prepared to have a grain structure with a gradient distribution of rare earth elements. The Y-rich region inside the grain provides good anisotropic field-temperature characteristics, the Nd / Pr-rich region in the middle of the grain maintains high remanence of the magnet, and the Dy / Tb-rich region in the epitaxial portion of the grain ensures high coercivity of the magnet. The permanent magnet material of the present invention has excellent temperature resistance and can solve the problem of magnet demagnetization failure in high-temperature applications.

[0086] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or illustrative of the principles of the present invention and do not constitute limitations of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included within the scope of protection of the present invention. In addition, the appended claims are intended to cover all variations and modifications that fall within the scope and metes and bounds of the appended claims, or equivalents thereof.

Claims

1. A rare earth permanent magnet material, characterized in that: Rare earth permanent magnet materials contain compounds with the chemical formula (R (1-x-y) R' x Y y ) a Fe 100-a-b-c-d M b Ga c B d ,in: The R element includes one or both of the rare earth elements neodymium and praseodymium, the R' element includes one or both of the rare earth elements dysprosium and terbium, and the M element includes one or more of cobalt, aluminum, copper, zirconium, and niobium; And 30≤a≤33, 0≤b≤3, 0<c≤0.6, 0.88≤d≤1, 0<x≤0.2, 0<y≤0.2; The compound is composed of main phase grains and grain boundary phases distributed between the main phase grains, and the main phase grains have a tetragonal structure of 2:14:1; In the main phase grains, rare earth elements are distributed in a gradient, including at least a Y-rich region in the center of the grain, an R-rich region in the middle, and an R'-rich region in the epitaxial portion of the grain; In the main phase grains, the mass percentage of Y in the Y-rich region in the center of the grain is higher than the total mass percentage of Y in the compound by more than 2%; In the main phase grains, the mass percentage of R' in the R'-rich region of the epitaxial portion of the grain is higher than the total mass percentage of R' in the compound by more than 10%.

2. The rare earth permanent magnet material according to claim 1, characterized in that 31≤a≤33; 0.01≤x≤0.1; 0.05≤y≤0.1; 0.2<c≤0.

5.

3. The rare earth permanent magnet material according to claim 1 or 2, characterized in that: The average grain size of the main phase grains in the compound is 4 to 8 microns.

4. A method for preparing the rare earth permanent magnet material according to any one of claims 1 to 3, characterized in that: include: Press (R (1-x-y) R' x Y y ) a Fe 100-a-b-c-d M b Ga c B d The R' element is removed from the proportion or the increment of the R' element during the diffusion process is deducted, and the ingredients are mixed, and a flake alloy is obtained after melting and solidification to obtain a powder; The obtained powder is subjected to orientation pressing under a magnetic field and then isostatic pressing to obtain a compact; the compact is sintered to obtain a dense magnet; A layer of a single substance or compound containing one or both of the heavy rare earth elements dysprosium and terbium is attached to the surface of the magnet; Vacuum heat treatment is performed to diffuse the heavy rare earth element into the interior of the magnet to obtain a rare earth permanent magnet material.

5. The method for preparing rare earth permanent magnet material according to claim 4, characterized in that: Melting includes: melting the raw materials under vacuum and inert gas protection; Solidification includes: casting onto a water-cooled rotating roller to solidify to obtain a sheet alloy; The powder is prepared by hydrogen crushing and air flow grinding the flake alloy to prepare the powder.

6. The method for preparing rare earth permanent magnet material according to claim 5, characterized in that: The linear speed of the rotating roller is 0.8-1.2 m / s, the thickness of the obtained sheet alloy is 0.15-0.45 mm, and the rare earth-rich phase spacing of the sheet alloy is 2-5 microns.

7. The method for preparing rare earth permanent magnet material according to claim 5, characterized in that: After the flake alloy is pulverized by hydrogen crushing and air flow grinding, the average particle size of the obtained powder is 2 to 3 microns.

8. The method for preparing a rare earth permanent magnet material according to any one of claims 4 to 7, characterized in that: Orientation pressing includes: filling powder into a mold, and orienting and pressing in a magnetic field greater than 1T to obtain a green compact; The isostatic pressing comprises: placing the green compact in an isostatic press and pressing the green compact at a pressure of at least 150 MPa to obtain a green compact with a density of 4 to 5 g / cm 3 ; The compact sintering comprises: placing the compact in a sintering furnace for vacuum sintering at a temperature of 1020-1100°C for 2-6 hours, and tempering at a temperature of 450-650°C for 3-6 hours to obtain a dense sintered magnet with an average grain size of 4-8 microns.

9. The method for preparing a rare earth permanent magnet material according to any one of claims 4 to 7, characterized in that: The weight of the simple substance or compound of heavy rare earth elements Dy and / or Tb attached to the surface of the magnet accounts for 0.3-3% of the weight of the magnet.

10. The method for preparing rare earth permanent magnet material according to claim 9, characterized in that: The vacuum degree during the vacuum heat treatment is ≤5×10 -3 Pa; the heat treatment temperature is 800℃~1000℃, and the heat treatment time is 4~12h; followed by tempering treatment at 450~600℃ for 1~8h.

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