EA014583B1 - Composition for manufacturing caked permanent magnet, caked permanent magnet and method for producing thereof - Google Patents

Abstract

A composition for manufacturing caked a high-coercive field permanent magnet having a microstructure formed by a magnetically hard phaseseparated by a non-magnetic parting sized from 5 to 50 nm, being a mixture of powders of three alloys – a basic alloy A based on Nd-(Fe, Co)-B system in an amount of least 80 wt%, magnetic alloy-admixture based on compounds of light rare-earth element R and a transition metal T in an amount not exceeding 15 wt% and non-magnetic alloy-admixture A2 based on compounds of heavy rare-earth R with non-magnetic metalls M1 and/or M2 in an amount not exceeding 5 wt%; a permanent magnet produced on the base of said composition; and a method for producing caked high-coercive permanent magnet.

Description

Technical field

The present invention relates to the field of highly sintered sintered permanent magnets based on rare earth alloys, namely based on neodymium-iron-boron alloys. In particular, a composition is proposed for producing a sintered highly coercive permanent magnet having a microstructure formed by grains of the magnetically hard phase separated by a nonmagnetic interlayer of 5 to 50 nm in size, which is a mixture of the powders of three alloys - base alloy A based on the Yb-- (Fe, Co) system -B in an amount of not less than 80 wt.%, Quick-quenched magnetic alloy additive A1 based on compounds of light rare-earth element B and transition metal T in an amount of not more than 15 wt.% And non-magnetic alloy additive A2 based on compounds of the heavy rare-earth element B with non-magnetic metals M1 and / or M2 in an amount of not more than 5 wt.%; as well as a permanent magnet obtained on the basis of the specified composition, and a method for producing a sintered highly coercive permanent magnet.

State of the art

Permanent magnets based on a neodymium-iron-boron alloy with a main phase containing about 12 at.% N6, 5-7 at.% B and the rest - Fe (phase composition type W ₂ Fe1 ₄ V) are components of a wide variety of instruments and devices which are used in almost all areas of science and technology. In particular, permanent magnets based on this alloy due to their high magnetic characteristics, the main of which are the residual magnetization V _g , the coercive force H _s , magnetic energy (HV) _max , are used in electronics, electronic and computer technology, acoustics, such as drives and control devices of disk drives and printing devices, miniature speakers, focusing systems that require permanent magnets with high energy characteristics for their implementation. The level of magnetic properties of permanent magnets determines not only the service parameters of products, but also their weight and dimensions, which is especially important in the case of the use of such products in aerospace technology, microelectronics, computer technology, where the weight and small size of instruments and devices are crucial.

A new family of materials for permanent magnets based on alloys of the Νά-Fe-B system (in the general form B-T-B, where B is a rare-earth element, T is a transition metal, and B is boron) appeared in 1984 (see , for example, M. 8adata, 8. Rirtita, Ν. Todita. N. Uashasho. apb Ма. Ma1kiiga Ut Ma1epa1 Goth Regtapep! Madpe! Radek 2083-2087 (1984), incorporated herein by reference in its entirety) due to the discovery of the previously unknown highly anisotropic phase No. ₂ Fe1 ₄ V obtained by quenching from a liquid state alloys of the above system. Boron was introduced to increase the tendency of double alloys to amorphize, but it turned out that its presence leads to the formation of a previously unknown intermetallic compound ^ rPe ^ with an extremely high - record - saturation magnetization of 4πΙ ₈ (~ 16 kG) and a very high K1 magnetic anisotropy constant ( ~ 5.0 kJ / m ³ ). It was found that the new phase is equilibrium, has uniaxial magnetic anisotropy, and has a tetragonal crystal lattice. The intermetallic compound M ₂ Fe1 ₄ V served as the basis for the creation of permanent magnets with the highest values of magnetic energy (HV) _max (up to about 55 MGsec). Estimates have shown that the theoretical limit of magnitude (BH) _max is about 64 Mgsec and is the largest to date.

The main disadvantage of permanent magnets based on No.-Re-B is their relatively low, about 300 ° C, Curie temperature (T _s ) - the temperature above which the ferromagnetic properties disappear. With increasing temperature, the coercive force also decreases, i.e. demagnetizing field strength Н _с , at which the magnetic field induction is zero - a value characterizing the ability of a permanent magnet to maintain magnetic properties under demagnetization conditions (for example, at elevated temperatures). To overcome this problem, a relatively large number of solutions have been proposed to date. Thus, it is known from the prior art that in order to increase the coercive force of said permanent magnets, various in nature alloying additives are introduced in various amounts in relation to the main components at the stage of manufacturing the main alloy. One of these additives, widely known to date, is Co (see, for example, DR 59-64733). In DR 60-34005, to increase the coercive force, as well as the anisotropy of the main magnetic phase, it is proposed to add Oy and Tb as additional rare earth elements. From the documents DR 59-89401 and DR 64-7503 it is known that the coercive force can be increased by adding elements such as A1, Oa, 8p, Cu or Hell. Although these documents do not report any specific reasons for the increase in coercivity, the authors of the present invention suggest that this is due to a change in the physical properties of the intergranular boundary phase, a phase enriched in rare earth elements, such as the wettability of the enriched and main phases at elevated temperatures. Further, the addition of elements such as Τι, V, Cr, Ζτ,,, Mo, NG, and,, according to DR 62-23960, avoids the growth of the grains of the main phase during sintering and reduces the size of the resulting magnet structure, thereby contributing to an increase in coercivity .

Although some of the above supplements do increase the coercive

- 1 014583 the strength of the obtained sintered magnets, the magnitude of the residual magnetization (or magnetic induction Br) and, as a result, the magnetic energy (BH) _max , irreversibly fall as a result of doping. The temperature coefficients of induction _Br and coercive force and a curtained _HcM have values, while the cost of the magnets due to the introduction of expensive and rare elements is greatly increased. The present invention provides a composition for producing sintered highly coercive permanent magnets without these disadvantages.

Currently, two main fundamentally different areas of the technology for the production of rare-earth permanent magnets from Νά-Her-B system alloys are being developed: based on single-crystal powders obtained by mechanical grinding of ingots, and on the basis of isotropic nano- and submicrocrystalline powders obtained by melt quenching technology.

The first of these technological schemes is based on the traditional method of powder metallurgy (sintering of powder billets), which includes technologies based on the production of single-crystal powders with an average grain size of about 1-10 microns. At the first stage, ingots are made by fusion of the starting components. Cast alloys are subjected to mechanical crushing and fine grinding. Anisotropic permanent magnets (monolithic and composite) are prepared from single-crystal powders obtained in this way. To create a crystalline texture, the powder is pressed in a magnetic field, due to which the single-crystal particles are oriented by the easy magnetization axes in the field direction. The final compaction of the blanks to obtain high-energy magnets is carried out either by mechanical methods (cold or hot pressing, isostatic compression, compacting by explosion) or by sintering. Moreover, the most common and effective method of compaction is sintering (liquid-phase or solid-phase). At the final stage of manufacturing, the sintered permanent magnets are subjected to special heat treatment, as a result of which an optimal microstructure is formed, which causes a highly coercive state to be obtained.

The second technological scheme for the manufacture of permanent magnets based on Νά-Her-B alloys includes technologies based on the production of powders by melt quenching (with the production of so-called quick-quenched alloys (BSS)). The crystallite size in the particles of rapidly quenched powder can be from 5 to about 400 nm, so that most of the crystallites are in a single domain state (the critical size of a single domain for compound No. ₂ Its ₁₄ V is about 300 nm). Due to the small grain size and lack of crystalline texture, the magnetic properties of the initial powder are isotropic. Permanent magnets made of isotropic BZS powders of the Νά-Her-V system by cold or hot pressing also have isotropic and, therefore, not extremely high magnetic properties and are unsuitable for producing sintered magnets. The predominant share of BZS powders produced on an industrial scale on the basis of No. _{2 of} Its ₁₄ V is used for the manufacture of isotropic permanent magnets on polymer bonds - magnetoplastics.

Compared to magnetoplastics, permanent sintered magnets have higher basic magnetic characteristics, temperature stability, and also find areas of application in which magnetoplastics cannot be used for one reason or another.

The closest in technical essence to the composition described in the present invention for producing a sintered permanent magnet is the composition proposed in RF patent No. 2174261. The known composition is intended to produce permanent magnets by the method of mixtures and allows to obtain a rare-earth permanent magnet having high magnetic induction and a maximum energy value works, and having a heterogeneous microstructure, which consists of three structural components: component A, representing grains of a magnetically solid phase of composition Y-T-B (where I, T and B are a rare-earth element, transition metal and boron, respectively), in an amount of not less than 85%, component Ό - a non-magnetic insulating layer in an amount of up to 10 vol.% and component C, a boundary magnetic hard layer in an amount of up to 5 vol.%.

The widespread use in permanent technology of record-breaking permanent magnets based on intermetallic compounds of rare-earth metals with iron, in particular based on Ее-Her-B alloys, stimulates an intensive search for new compositions of these highly coercive materials and the creation of non-traditional methods for their preparation.

Based on the analysis of the prior art, it would be desirable to provide a permanent sintered magnet having a high coercive force while maintaining a high level of residual induction and maximum energy product. At the same time, it is desirable that the said permanent magnet have high temperature stability, have good anticorrosion properties, and also is cheap in comparison with the known analogues.

Thus, it is an object of the present invention to provide a composition for producing a highly coercive sintered permanent magnet having the above improved properties.

- 2 014583

Another objective of the present invention is a method for producing a highly coercive sintered permanent magnet based on the above composition.

Finally, another object of the present invention is to provide an article in which a magnet having the above improved properties could be used.

Disclosure of invention

In a first aspect, the present invention provides a composition for producing a sintered highly coercive permanent magnet having a microstructure formed by grains of a magnetic hard phase separated by a nonmagnetic interlayer with a thickness of 5 to 50 nm, which is a mixture of powders of three alloys — base alloy A in an amount of at least 80 wt. %, quenched alloy additive A1 in an amount of not more than 15 wt.% and alloy additive A2 in an amount of not more than 5 wt.%, characterized in that:

a) alloy A is a basic ferromagnetic alloy based on the system No.- (Fe, Co) -B with an N6 content of at least 12 at.%, B from 5 to 7 at.%, possibly from 5 to 12 at.% of Co, the rest is Re;

b) magnetic alloy additive A1 is a low-melting alloy K-T based on compounds of a light rare-earth element K and a transition metal T, where K is N6 and / or Pr, and T is Co of the following composition:

N6 and / or Pr - not less than 40 wt.%, Co - the rest;

c) non-magnetic alloy-additive A2 is a low-melting ligature [K- (M1, M2)] based on compounds of the heavy rare-earth element K with non-magnetic metals M1 and / or M2, where K represents Oy and / or To, M1 and M2 independently selected from the group consisting of A1, Ca, 8c, Ιη, Cu, Hell, 81.

Proposed according to the present invention, the composition allows to obtain a sintered permanent magnet having a significantly higher coercive force compared to known analogues and having a wider range of temperature stability and maximum operating temperature. So in a preferred embodiment, the sintered permanent magnet according to the present invention has a higher coercive force while maintaining a high level of magnetic induction and maximum energy product.

The development of the above composition consisting of three alloys - base alloy A and additive alloys A1 and A2, and the practical preparation of sintered permanent magnets with high coercive force were based on the laws and methods of optimal alloying and microstructure formation by the method of mixtures (see, for example, patent RF 2174261, fully incorporated into the present description by reference).

Based on a detailed study of the fine structure of sintered permanent magnets, without wishing to be bound by any particular theory, the authors of the present invention suggested that in order to achieve high coercive forces, it is necessary to create a material in which the grains of the main magnetically solid phase No. ₂ Re ₁₄ V are separated continuous thin intergranular layer with a thickness of 5-50 nm, preferably 5-10 nm - nanophase. This interlayer can be enriched in rare-earth metal and therefore non-magnetic, which provides magnetic isolation of the grains of the main phase and prevents the formation of magnetization reversal nuclei and the movement of the domain wall during magnetization reversal.

Experimental studies have shown that this particular layer plays a large role in the formation of a highly coercive state and in achieving high values of the energy product. The formation of such an interlayer, as well as the management of its chemical composition, structural, and then electronic and magnetic properties, is impossible without the use of nanotechnology. Such a structure can be formed only with a certain chemical composition using nanostructured alloys-additives, using a whole range of technological measures, as well as subsequent special heat treatment. All this together allows you to control the properties of this intergranular layer on a nanoscale and determines the unique properties of the final product, a sintered permanent magnet based on Νά-Re-B.

As noted above, the coercive properties of materials based on intermetallic compound No. ₂ Re ₁₄ V are largely determined by intergranular layers of the phase enriched in rare-earth metal, in particular neodymium with a thickness of 5-10 nm. By optimizing (by doping) the thickness of the intergranular phase layers, the coercive force (N _cM ) of the material can be increased, however, in this case, the residual induction (V _g ) can decrease, which will lead to a decrease in the energy product of the magnet. Therefore, it is necessary to optimize the thickness of the intergranular phase so that the maximum value of residual induction is maintained. In particular, the authors of the present invention have shown that to fulfill the above conditions, the thickness of the non-magnetic layer should be from 5 to 50 nm.

The present invention proposes the use of innovative technology to change the structure and other properties of the intergranular phase by introducing nanostructured additives into the material. In the general case, additives should affect the thickness and structure of the intergranular phase during its formation and meet the following requirements:

- 3 014583 additives must be brittle and grind no worse than the base alloy, so that during grinding the grains of the main phase Νά are reliably surrounded _; Εθ |. · | Β, the additives should act on the intergranular nanophase and the boundary region of the main phase, therefore, the amount of additives should be ~ 1–20 wt%, the additives should be relatively low-melting, so that they can easily interact (dissolve) with the nanophase during sintering and at the same time, to modify the boundary region of the main phase (due to diffusion processes) with the given elements, the additives should be more resistant to oxidation in the powder redistribution process than the intergranular nanophase.

The most fully specified requirements are satisfied by nanostructured rare-earth intermetallic compounds obtained by fast hardening (fast-cured alloys - BZS) and having a grain size of 50-200 nm. The nanocrystallinity of the alloy-additive structure provides, firstly, increased corrosion resistance of the alloy-additive powder to oxidation during grinding and mixing with the main alloy and, secondly, the small particle size of the alloy powder (alloy-additive composition corresponds to intermetallic compounds with increased brittleness) and the necessary uniformity of the distribution of its particles in the billet.

Additive alloys based on compounds of heavy rare-earth metals (for example, Oy, Tb) with non-magnetic metals (for example, A1, Ca, 8c, Ιη, Cu, δί, Ad) serve to increase the anisotropy field of the surface layers of grains of the main magnetically solid phase. During sintering, these alloying elements diffuse from the intergranular phase enriched in heavy rare-earth metals introduced through the additive alloy into the grains of the main phase Ш ₂ Рс _{| 4} V. Forming (under the optimal sintering regime) narrow surface regions with a high content of Оу or ТЬ ( (ΝάΌ.νΚΡοΜΒ or (Oi, Tb) ₂ Pe ₁₄ V), characterized by increased magnetocrystalline anisotropy.The optimal width of such regions is comparable to the width of domain walls in NάBeV alloys and lies in the range of 10–20 nm. The regions serve as an energy barrier preventing the displacement of the domain walls of the magnetization reversal nuclei formed on defects concentrated along the grain boundaries of the main phase.

Thus, the use of the above components of the composition, allows to obtain the final product - sintered permanent magnet NάBeV with high magnetic and operational characteristics.

Summarizing the above, in order to achieve the claimed technical result, in particular, providing a composition for obtaining a permanent highly coercive sintered magnet, the inventors were guided by the following.

First, alloying in order to increase the coercive force of sintered magnets from alloys of the Νά-Be-B system was carried out directionally, while minimizing its negative effect on the energy characteristics of magnets.

Secondly, since the properties of the magnetically solid phase M ₂ Be ₁₄ V deteriorate with almost any doping, minimal modification was assumed in the process of determining the composition of the base alloy. In particular, only with the aim of improving the corrosion characteristics, improving the melting conditions and crystallization of the alloy ingots, it was allowed to replace up to 5 wt% Be with Co, as well as a slight excess Νά compared to the stoichiometric composition (up to 2.5 wt%). Thus, in a preferred embodiment of the present invention, the main phase in the base alloy A is the stoichiometric phase of W ₂ Be ₁₄ B or W ₂ (Be, Co) ₁₄ V.

Thirdly, additive alloys were chosen in such a way that the requirements of the principles of minimizing the oxygen content in rare-earth permanent magnets, reliable magnetic isolation of the grains of the main magnetically solid phase, the formation of a high gradient of the anisotropy field on the surface of grains No. ₂ Be ₁₄ V, and sufficient mechanical the strength of the finished magnet.

In accordance with these requirements, in terms of their influence and chemical composition, additive alloys were divided into two groups:

(1) compensating low-melting two-component magnetic alloys, representing a low-melting BT alloy based on compounds of a light rare-earth element B and a transition metal T, where B is Νά and / or Pr, and T is Co of the following composition: Νά and / or Rg - not less than 40 wt.%, Co - the rest. Compensating low-melting alloys-additives provide the formation of an insulating and bonding layer between the grains of the main magnetically solid phase, and are also an effective conductive medium that provides directional redistribution of alloying components;

(2) fusible ligatures based on non-magnetic alloys and compounds of heavy rare-earth metals with non-magnetic metals M1 and / or M2, where B is Oy and / or To, M1 and M2 are independently selected from the group including A1, Ca, 8c, Ιη Cu 81 and Hell having a composition of intermetallic compounds (including Laves phases) with stoichiometry В ₂ М ₇ , ВМ ₃ , ВМ ₂ , ВМ, В ₂ М, В ₆ М ₂₃ and designed, in particular, to increase the anisotropy field of surface layers grains of the main magnetically solid phase. In a preferred embodiment of the invention, said alloys are

- 4 014583 alloys based on two-component alloys B-Ca, B-Si, as well as a three-component alloy B-Si-81. This additive is of fundamental importance to achieve a technical result, since its type, as well as the amount of alloys in the mixture, determine the level of coercive force of the obtained sintered permanent magnets and can vary widely depending on the purpose of the magnets. In a preferred embodiment of the present invention, the amount of said additive is not more than 5% by weight.

In one preferred embodiment of the invention, alloy A2 is an alloy based on B-Ca compounds, where B is Oy and / or Tb, and the composition of the main phases of said alloy corresponds to compounds selected from the group consisting of BCa, BCa ₂ , BCa ₃ , BCa <5, B2Ca5, B5Ca ₃ .

In yet another preferred embodiment of the invention, alloy A2 is an alloy based on B-Cu compounds, where B is Oy and / or Tb, and the main phase alloy of said alloy corresponds to BCi ₂ and BCi ₅ , and it is preferred that the amount of component B amounted to at least 40 wt.%.

In another preferred embodiment of the invention, alloy A2 is an alloy based on compounds B-Cu-81, where B is Oy and / or Tb, and the composition of the main phases of said alloy corresponds to compounds selected from the group consisting of BCi81, BCi ₂ 81 ₂ , VzSits814, VbSi818, Vo.5Si1.5811.5, VzSibz814.

It should be noted that the introduction of additive alloys affects one or another, depending on the needs, characteristic or property of the magnets or their selected combination, for example, anisotropy field, corrosion resistance, density, and also provides a uniform distribution of certain alloying components in volume magnet.

In a second aspect, the present invention provides a method for producing a sintered highly coercive permanent magnet, comprising independently preparing alloys A, A1 and A2;

preliminary crushing of alloys A, A1 and A2 to obtain powders whose particle size is not more than 100 microns;

mixing said alloy powders to form a mixture in which the content of A, A1 and A2 is not less than 80%, not more than 15% and not more than 5%, respectively;

fine grinding the specified mixture to obtain a composition, the particle size of which is not more than 3 microns;

compiling the resulting composition in a magnetic field with a strength of at least 0.9-1 MA / m to obtain a workpiece of the desired shape;

sintering the obtained preform at a temperature of 1000-1150 ° C for 2-10 hours;

heat treatment of the sintered billet at T 450-650 ° C, characterized in that

a) alloy A is a basic ferromagnetic alloy based on the Lyb- (Fe, Co) -B system with an N6 content of at least 12 at.%, B from 5 to 7 at.%, possibly from 5 to 12 at.% of Co, the rest is Re;

b) the magnetic alloy additive A1 is a low-melting alloy BT based on compounds of the light rare-earth element B and transition metal T, where B represents N6 and / or Pr, and T represents Co of the following composition: N6 and / or Pr - not less than 40 wt.%, Co - the rest;

c) non-magnetic alloy-additive A2 is a low-melting ligature [B- (M1, M2)] based on the compounds of the heavy rare-earth element B with non-magnetic metals M1 and / or M2, where B is Oy and / or Tb, M1 and M2 independently selected from the group consisting of A1, Ca, 8c, Ιη, Cu, Hell, 81.

The inventive method for producing a sintered highly coercive permanent magnet according to the present invention is based on the idea of forming the required level of properties by creating a mechanical mixture (composition) of at least three alloys significantly differing in composition and physical properties. The introduction of additive alloys aims to influence one or another, depending on the needs, characteristic or property of the magnets or their selected combination, for example, anisotropy field, corrosion resistance, density, and also to provide the necessary distribution of certain alloying components over the volume of the magnet.

The process of obtaining sintered permanent magnets Νά-Pe-B begins with the smelting of these alloys and their crystallization in metal molds. In this case, the base alloy A can be prepared using standard powder metallurgy technology, while the additive alloys are obtained by rapid quenching from the melt.

The conditions that must be met by the base alloy can be formulated as follows:

the base alloy should have a very narrow particle size distribution (particle size is about 1-10 microns, preferably not more than 3 microns);

each particle of the main phase ^ ₂ Re ₁₄ V of the base alloy should be as single-crystal as possible;

- 5 014583 to exclude the possibility of preserving primary α-Fe crystals in the base alloy (due to the incompleteness of the peritectic reaction of the formation of a magnetically hard phase Νά ₂ ^ ₁₄ Β in the process of smelting the base alloy), which do not allow achieving high values of coercive force, as well as the formation of the required amount boundary phase, providing magnetic isolation of grains ΝΦ ^ .- Β. it is necessary that the base alloy be slightly enriched in neodymium (its total content should be at least 14 at.%) compared with stoichiometry Νά ₂ ^ ₁₄ Β (~ 12.8 at.%).

In a preferred embodiment, the base alloy based on the Νά-Fe-B system is obtained by accelerated crystallization from a melt (or, in other words, κΐτίρ sakyid - a term widely used in English literature). This method consists in crystallization of the melt on the surface of a rotating water-cooled wheel with a given surface rotation speed. Thus obtained alloy is a cup with a thickness of 0.2 to 0.4 mm and is in the optimal phase-structural state. The matrix phase in each grain is phase No. ₂ Re ₁₄ V, and the enriched Νά phase is represented by a large number of precipitates elongated in a direction parallel to the direction of the main crystalline phase, as well as along all grain boundaries.

To improve the quality of the base alloy, the introduction of the hydrogen embrittlement stage (ΗΌΌΒ treatment) was very fruitful. The effectiveness of this process obviously depends on the ability of the alloys to reversibly absorb and liberate hydrogen during the hydrogen treatment of ingots. When carrying out this stage, there is no risk of the formation of bicrystalline particles during the preparation of the base alloy, which subsequently avoids problems with texturing the resulting powder. Thus, as a result of the introduction of this stage, it is possible to significantly increase the uniformity of the microstructure of the main alloy, significantly improve its properties and the manufacturability of the process as a whole.

Alloys of additives A1 and A2 can be obtained by the method of rapid quenching from melts described in detail in the source Kekalo IB, Menushenkov VP, Course of lectures MISiS, Moscow, 2000, fully incorporated into this description by reference. In the production of BSS, it is possible to use at least three varieties of the melt quenching method. In the first case, the melt spinning method is applied to a rapidly swirling metal roll, which results in the formation of tape fragments with a thickness of 10 to 50 μm and a width of 0.5 to 1.5 mm, which are in an amorphous or nanocrystalline state. In the second, the melt is ejected onto the inner surface of the rotating metal cylinder (the method of centrifugation), as a result of which the melt has a longer contact with the surface of the crystallizer than during spinning, which leads to an increase in the quenching rate and to a more uniform structure of BZS flakes. In the third - the centrifugal spraying method, small drops of the melt hit at high speed against the surface of the crystallizer-cooler, which is used as a metal screen. BSS obtained by the indicated method are characterized by a more constant particle size distribution, uniform distribution of alloy components in the powder particles, and a better uniformity of the structure of the particles themselves. To prevent oxidation, the process of quenching from the melt is carried out in vacuum or in an atmosphere of inert gas.

After smelting and crystallization, the resulting alloys are pre-crushed to a particle size of not more than 100 microns, and then mixed in the specified proportion to obtain a mixture. The mass ratio of powders of alloys A, A1, A2 in the resulting mixture is not less than 80%, not more than 15% and not more than 5%, respectively, and is set to ensure that the microstructure of subsequently sintered magnets is close to ideal.

The resulting mixture is subjected to fine dry or wet grinding using ball mills, jet mills or atritors in a controlled gas atmosphere to obtain a powder, the average particle size of which is not more than 3 microns. It will be obvious to a person skilled in the art that the step of mixing the powders of said alloys to form the composition can be carried out after preliminary grinding of each of the powders individually.

In order to obtain a high degree of particle orientation carried out at the stage of powder compaction, particles having dimensions of several micrometers need to report a sufficiently strong torque, which is achieved in orienting magnetic fields with a voltage of at least 0.9-1 MA / m. Moreover, in the process of pressing it is very important to ensure good mechanical contact between the powder particles, i.e. to ensure the maximum density of the permanent blanks of billet magnets in order to prevent particles from turning relative to each other and a corresponding decrease in the degree of magnetic texture in the blanks until the process of final compaction during sintering is completed. Typically, permanent magnet billets are obtained by pressing using transverse (perpendicular) or longitudinal (axial) patterns. The longitudinal pattern (ΑΌΡ) of the pressing allows you to get magnets of various shapes with small allowances for grinding, however, the degree of orientation is relatively low, only 86-88%. With a transverse pattern (ΤΏΡ), the resulting degree of texture is higher, 90-93%, however, the number of possible forms of magnets, I get

- 6 014583 in this way is not large, moreover, the allowances for grinding are also noticeably greater than in the previous case. In a preferred embodiment, isostatic pressing in a rubber sleeve (ΚΙΡ-pressing) is used (see Nagata X., Sagawa M. Ideal technology for producing sintered magnets ΝάΕεΒ - In the collection of materials from the Russian-Japanese seminar Materials Science and Metallurgy. Advanced Technologies and Equipment. MISIS -LUAS 1ps. Moscow, MISiS, March 25, 2003, pp. 105-113, fully incorporated into this description by reference). In the K1P method, a thin-walled rubber mold with a cavity for filling with powder is placed in a metal matrix. The powder-filled mold is then compressed using the upper and lower punches, and under such pseudo-isostatic conditions a compact is formed. The most important advantage of this method compared to traditional pressing in molds when producing Νά-Her-B sintered magnets is that the degree of orientation of the powder in the billet can reach an almost limit value, with a texture degree of up to 98% or more.

Next, the obtained preforms are sintered at temperatures of 1000-1150 ° C for the required time (about 2-10 hours) and heat treated in the temperature range of 450-650 ° C. As a result of heat treatment (annealing), the coercive force can be increased, as a rule, from 5 to 50%.

The resulting sintered magnet based on the above composition, on the one hand, has unique properties from the point of view of its use as a highly coercive permanent magnet, due to its microstructure formed by grains of the magnetic hard phase separated by a nonmagnetic interlayer with a thickness of 5 to 50 nm on the other hand, it can be susceptible to corrosion, in particular, due to the rather easy penetration of hydrogen deep into the material along grain boundaries, as a result of which various hydrides are formed with highly reactive rare-earth metal neodymium, which can lead to a deterioration in its basic magnetic characteristics. To overcome the above problems, protective coatings are optionally applied to the surface of said magnet.

In particular, for coating the sintered magnets obtained, the galvanic method is used, with which protective layers of metals selected from the group consisting of nickel, zinc, copper, gold, as well as their possible combinations, are formed on the surface of the magnets. In a preferred embodiment, the method of microarc oxidation (MAO) is used, based on the fact that when a high-density current passes through the interface, the magnet surface is an electrolyte, the electric field strength at the interface becomes higher than its dielectric strength, as a result of which breakdowns occur on the treated surface - microplasma discharges with high local temperatures and pressures. As a result of the action of microplasma discharges on the surface of the magnet, a nanostructured layer is formed, consisting of oxides of elements that make up the components and constitute the electrolyte. The composition of the forming layer can be varied by the selection of the MAO process mode and the electrolyte composition. The forming coatings are characterized by high hardness, corrosion resistance and wear resistance, high adhesion to the contact surface on which the coatings are formed, and also high electrical strength. In particular, the operating temperature of the obtained sintered magnet coated is from 150 to 200 ° C. The high characteristics of the coating are determined by the unique properties of the nanostructured transition layer arising between the oxide layer and the surface of the magnet. In some embodiments of the invention, the resulting coating may be a coating consisting of a working layer of a-A1 ₂ O ₃ oxide lying on a nanostructured sublayer containing γ-Α1 ₂ Ο ₃ and A1 oxide particles ranging in size from 10 to 500 nm, preferably from 50 up to 100 nm.

The sintered highly coercive permanent magnets obtained as a result of the described method can find application in various industrial products and devices. Among other things, the above magnets will find application in high-performance magnetic separators with a strong and weak field, electromagnetic automatic gas valves, as well as in any other products and devices where there is a need to create a high magnetic field without involving energy costs.

Examples

The experimental procedure and samples.

Alloys of the desired compositions were smelted from pure components in a vacuum induction furnace in an atmosphere of purified argon. In this case, the base four-component alloys | (Νά- (Οο.Οο) -Β | were obtained by melt crystallization (81 mol%) and contained from 12 to 15 at.% С. The ingots of the base alloys were homogenized at temperatures of 1050-1070 ° C in for 24 h, and then subjected to S-treatment, including hydrogen peroxidation of the alloys at room temperature, as well as subsequent partial vacuum dehydrogenation in the temperature range 400-500 ° C. Alloys are additives in the crystalline state, which were used as ligatures [Pr - Co], and | K (M1, M2)], where K = Tb and / and and Iu, M1 and M2 are independently selected from the group consisting of A1, 6a, 8c, 1H, Cu, Ag, δΐ, prepared by rapid quenching from rasplva and depending on the composition homogenized

- 7 014583 in the temperature range of 600-900 ° C for 4-10 hours. After homogenization of the additive alloys and hydrogen embrittlement of the base alloys, the ingots were preliminarily crushed in an inertial cone crusher in a nitrogen atmosphere to obtain powders with a particle size of not more than 100 μm.

Fine grinding of alloy mixtures taken in the required proportion was carried out in a ball mill in the environment of isopropyl alcohol. Suspensions of alloy powders in isopropyl alcohol (average particle size of 3-4 μm) were pressed in a magnetic field with a strength of at least 960 kA / m, oriented perpendicular to the direction of application of the pressing pressure. Depending on the chemical composition of the permanent blank, the billet of permanent magnets was sintered at temperatures of 1080–1120 ° C for 2 hours. After measuring the hysteresis characteristics of the permanent magnets in the sintered state, they were heat treated in the temperature range of 500–600 ° C for 1 hour. At the final stage in examples 1 and 2 (see below), nickel and copper coatings were applied to the surface of the obtained magnets, respectively, using the galvanic method. In example 3, the microarc oxidation method was applied with a nanostructured coating based on aluminum oxide (A1 ₂ O ₃ ).

The results of the experiments.

Example 1. Shows the changes in the energy characteristics and coercive force of sintered permanent magnets as a result of the directed action on the N6-enriched boundary phase of the base alloy of ferromagnetic alloys of additives based on Pr and paramagnetic based on Eu6a alloys.

In the table. Figure 1 shows the hysteresis properties (H _C1 , (HV) _max ) of the investigated series of sintered permanent magnets from three-component alloy mixtures, the composition of which in general is determined by the formula:

(100-x-y) wt.% A + x wt.% A1 + y wt.% A ₂ , where A is the basic ferromagnetic four-component alloy Ν6- (Εο.ί.'ο) -Β. A1 -. Two-component ferromagnetic alloy [Pr-Co], 3.1 wt% and A ₂ -. Fusible two-component ligation SchU Oa], y = 1-3 wt%, the coercive force determines the magnitude of the phase with the stoichiometric composition, a differential scanning calorimetry and X-ray phase analysis of the type EuSa, Oy6a ₂ , Oy6a ₃ , Pu6a <5, Oy ₂ 6a ₅ , Oy ₅ 6a ₃ . In the table. Figure 1 shows the hysteresis characteristics of sintered permanent magnets from the investigated mixtures of alloys (100-x-y) A + xA1 + yA2.

Table 1

Mass % Sintered state After annealing Oh sa WG-Co Na, KE (HV) _t and _x MGSE On CE (VN) _takh , MGSE 2 one 21.17 42.68 24.21 42.15 3 one 23.45 40.93 25.68 43.80 2 2 22.21 42.15 24.62 43.09 3 2 23.75 40.22 26.45 42.88 one 3 20.81 43.56 21.89 43,44 2 3 22.79 42.10 25.24 41.79

kGf = 0.1 T; 1 kOe = 79.6 kA / m; 1 MGsec = 7.96 kJ / m ³

Example 2. In the table. Figure 2 shows the hysteretic properties (H _C1 , (BH) _max ) of the investigated series of sintered permanent magnets from three-component alloy mixtures, the composition of which in general is determined by the formula (100-xy) wt.% A + wt.% A1 + wt. % A2, where A - basic quaternary alloy ferromagnetic №- (Her, Co) -B, A1 -. two-component ferromagnetic alloy [Pr-Co] 1-3 wt% and A ₂ - A two-component ligation fusible [Th-Si], y = 1-3 wt.%, Determining the value of the coercive force with stoichiometric phase compositions determined by the differential scanning calorie method metrics and X-ray phase analysis of the type Tlci ₂ and Tlci5.

As can be seen from the above examples, the maximum properties are observed for magnets from heterogeneous mixtures when, along with Pr, an additive containing Tb is introduced into the alloys. Given the laws of the influence of heavy P3M on the properties of sintered magnets, it can be assumed that this is due to the formation of a highly anisotropic layer on the surface of grains No. ₂ (Eg, Co) 14B and a corresponding increase in the gradient of the anisotropy field. In the table. Figure 2 shows the hysteresis characteristics of sintered permanent magnets from the investigated alloy mixtures (100-x-y) A + xA1 + yA ₂ .

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table 2

Mass % Sintered state After annealing T-si WG-Co N _th (HV) _tx MGsE Na, KE (HV) _tx MGsE one one 19.75 44.12 22.71 43.52 2 one 24.21 41.17 27.21 43.05 one 2 22.69 41.19 23.55 40.70 2 2 24.75 36.62 27.90 42.59 one 3 20.87 42.51 21.83 42.46 2 3 28.46 35.15 29.82 43.51

Example 3. In the table. Figure 3 shows the hysteretic properties (H _C1 , (HV) _max ) of the investigated series of sintered permanent magnets from three-component alloy mixtures, the composition of which in general is determined by the formula:

(100 - x - y) mass,% A + x mass,% A1 + y mass,% A ₂ , where A is the basic ferromagnetic four-component alloy Yb- (Te, Co) -B, A1 is a ferromagnetic two-component alloy [Pr- Co] 1-3 wt.% And A ₂ - fusible three-component ligature [Iu - Cu - 81], y = 1-3 wt.%, Which determines the value of coercive force with phase compositions determined by the method of differential scanning calorimetry and X-ray phase analysis of the type IuSi81 , IuSi ₂ 81 ₂ O ^{33 Si} b3814.

Table 3

Mass % Sintered state After annealing Oh - C - 3Ϊ WG-Co Нс !, кЭ (HV) _tx MGsE Na, KE (HV) _tx MGsE 2 one 20.45 41.30 23.15 41.31 3 one 22.50 39.22 25.26 41.69 2 2 21.05 41.22 23.50 42.12 3 2 22.11 41.10 24.10 40.13 one 3 19.95 42.47 20.32 42.36 2 3 21.71 40.12 22.68 42.55

The obtained experimental data clearly indicate the effectiveness of the proposed model of the structure of highly coercive permanent magnets based on alloys of the Lyb- (Fe, Co) -B system, as well as the completeness of the system of basic principles underlying it. The concrete examples demonstrate the advantages of the composition according to the present invention for producing sintered highly coercive permanent magnets and the effectiveness of the method for producing sintered magnets based on it. In contrast to traditional ideas and approaches to the choice of the composition of the components of mixtures, the necessity of choosing alloys that differ significantly in their composition and physicochemical characteristics, as well as the high efficiency of non-magnetic alloys based on dysprosium and terbium, are emphasized. Each of the additive alloys in such a system, depending on the purpose of the developed magnets, must fulfill a well-defined, predetermined function. In addition, the research results show that the obtained magnets have improved corrosion properties compared with similar properties of magnets from three-component alloys of the Ее-Her-B system.

Claims (13)

CLAIM 1. The composition for producing a sintered permanent highly coercive magnet having a microstructure formed by grains of the magnetic hard phase separated by a non-magnetic interlayer with a thickness of 5 to 50 nm, which is a mixture of powders of three alloys - base alloy A in an amount of at least 80 wt.%, Quick-quenched alloy - additive A1 in an amount of not more than 15 wt.% and alloy additive A2 in an amount of not more than 5 wt.%, characterized in that: a) alloy A is a basic ferromagnetic alloy based on the system No.- (Eg, Co) -B with an N6 content of at least 12 at.%, B from 5 to 7 at.%, possibly from 5 to 12 at.% of Co, the rest is Her; b) the magnetic alloy-additive A1 is a low-melting alloy Y-T based on compounds of the light rare-earth element I and transition metal T, where I is N6 and / or Pr, and T is Co of the following composition: N6 and / or Pr - not less than 40 wt.%, Co - the rest; - 9 014583 c) non-magnetic alloy additive A2 is a low-melting ligature [B- (M1, M2)] based on the compounds of the heavy rare-earth element B with non-magnetic metals M1 and / or M2, where B is Oy and / or Tb, M1 and M2 independently selected from the group including A1, Ca, Ze, Ιη, Cu, Hell, δΐ. 2. The composition according to claim 1, characterized in that alloy A2 is an alloy based on compounds B-Ca, where B is Oy and / or Tb, and the composition of the main phases of this alloy corresponds to compounds selected from the group consisting of BCa, BCa ₂ , BCa ₃ , BCa ₆ , B ₂ Ca ₅ , B ₅ Ca ₃ . 3. The composition according to claim 2, characterized in that the amount of Ca in the A2 alloy is from 50 to 60 wt.% (Corresponds to the phase of the stoichiometric composition BCA ₂ ). 4. The composition according to claim 1, characterized in that the alloy A2 is an alloy based on compounds B-Cu, where B represents Oy and / or Tb, and the composition of the main phases of this alloy corresponds to compounds BCi ₂ and BCi ₅ . 5. The composition according to claim 4, characterized in that the amount of B is at least 40 wt.%. 6. The composition according to claim 1, characterized in that the alloy A2 is an alloy based on compounds B-Cu-δί, where B is Oy and / or Tb, and the composition of the main phases of this alloy corresponds to compounds selected from the group including VSiZts Ksi ₂ З | ₂ . In ₃ SICZs, In ₆ Ci ₈ Zy, VO.5Si1.5Zts.5, VzzSi6zZ ^ 4. 7. The composition according to any one of claims 1 to 6, characterized in that the main phase in alloy A is a stoichiometric phase of W ₂ Re ₁₄ V or W ₂ (Re, Co) ₄₄ V. 8. The composition according to any one of claims 1 to 6, characterized in that the mixture is a single crystal powder with a particle size of not more than 3 microns. 9. The composition according to any one of claims 1 to 6, characterized in that alloy A is obtained by accelerated crystallization from a melt (δΐτϊρ sakypd), and alloys A1 and A2 are obtained by melt quenching methods selected from the group comprising spinning, centrifugation, centrifugal spraying and melt rolling. 10. Sintered permanent high-coercive magnet having a microstructure formed by grains of the magnetically solid phase, separated by a non-magnetic layer with a thickness of 5 to 50 nm, obtained on the basis of the composition according to any one of claims 1 to 9. 11. The sintered permanent high-coercive magnet of claim 10, wherein the coercive force of said magnet is not less than 20 kOe. 12. The sintered permanent high-coercive magnet according to claim 10 or 11, characterized in that the maximum energy product (BH) _{max of} said permanent magnet is not less than 40 MGsec. 13. A method of obtaining a sintered highly coercive permanent magnet according to claims 10-12, comprising the independent preparation of alloys A, A1 and A2; preliminary crushing of alloys A, A1 and A2 to obtain powders whose particle size is not more than 100 microns; mixing said alloy powders to form a mixture in which the content of A, A1 and A2 is not less than 80%, not more than 15% and not more than 5%, respectively; fine grinding the specified mixture to obtain a composition, the particle size of which is not more than 3 microns; compacting the resulting composition in a magnetic field with a strength of at least 0.9-1 MA / m to obtain a workpiece of the desired shape; sintering the obtained preform at a temperature of 1000-1150 ° C for 2-10 hours; heat treatment of the sintered billet at T 450-650 ° C, characterized in that: a) alloy A is a basic ferromagnetic alloy based on the Lyb- (Fe, Co) -B system with an N6 content of at least 12 at.%, B from 5 to 7 at.%, possibly from 5 to 12 at.% of Co, the rest is Re; b) the magnetic alloy additive A1 is a low-melting alloy BT based on compounds of the light rare-earth element B and transition metal T, where B represents N6 and / or Pr, and T represents Co of the following composition: N6 and / or Pr - not less than 40 wt.%, Co - the rest; c) non-magnetic alloy additive A2 is a low-melting ligature [B- (M1, M2)] based on the compounds of the heavy rare-earth element B with non-magnetic metals M1 and / or M2, where B is Oy and / or Tb, M1 and M2 independently selected from the group comprising A1, Ca, Zc, Ιη, Cu, Hell, δΐ. 4 ^ 8) Eurasian Patent Organization, EAPO Russia, 109012, Moscow, Maly Cherkassky per., 2