CN108517455B - Nanocrystalline rare earth permanent magnetic material with double-main-phase structure and preparation method thereof - Google Patents

Abstract

The invention discloses a _{nanocrystalline rare earth permanent} magnet material with a double main phase structure and a preparation method thereof. The magnetic Nd ₇₀ Cu ₃₀ powder is uniformly mixed in a certain proportion, and a nanocrystalline rare earth permanent magnet material with dual main phase structure is prepared by spark plasma sintering technology. The invention utilizes the quick-quenching alloy powder with hard magnetic properties and the non-magnetic rare-earth alloy powder to obtain a nanocrystalline rare-earth permanent magnet material with a double main phase structure, and improves the microstructure, magnetic properties and corrosion resistance of the permanent magnet. And make full use of the high abundance rare earth element Ce. In addition, the invention also has the characteristics of short sintering time and simple process flow, which effectively promotes the efficient and balanced utilization of rare earth resources.

Description

A kind of nanocrystalline rare earth permanent magnet material with dual main phase structure and preparation method thereof

technical field

The invention belongs to the field of rare earth permanent magnet materials, and particularly provides a nanocrystalline rare earth permanent magnet material with a double main phase structure and a preparation method thereof.

Background technique

Due to its excellent magnetic properties, Nd ₂ Fe ₁₄ B-type rare earth permanent magnet materials are widely used in wind power generation, consumer electronics, medical equipment, new energy vehicles, aerospace, rail transit and other fields. The widespread application of Nd-Fe-B magnets has led to a surge in global demand for low- and medium-abundance rare earth elements neodymium, praseodymium, dysprosium, and terbium. However, high-abundance rare-earth elements dominated by cerium (Ce) have not been widely used in rare-earth permanent magnets, resulting in a serious unbalanced utilization of rare-earth resources. From the perspective of raw material cost and national strategic security, the research and development of cost-effective high-abundance rare earth permanent magnets is imperative. Although the intrinsic magnetic properties of Ce ₂ Fe ₁₄ B compounds are inferior to those of Nd ₂ Fe ₁₄ B compounds, recent studies have shown that they still have the prospect of preparing hard magnetic properties of permanent magnet materials.

The unique microstructure characteristics and strong intergranular exchange coupling of nanocrystalline magnets make its temperature stability and fracture toughness better than traditional sintered magnets and bonded magnets. Therefore, nanocrystalline NdFeB magnets are the current research hotspot and the future development direction. Generally speaking, magnets with a dual-main phase structure have better magnetic properties than those with a single-main-phase structure. Therefore, the development of nanocrystalline Ce-Fe-B-based magnets with dual main phase structure can make full use of high-abundance rare earth Ce, reduce the cost of magnets, improve the cost performance of permanent magnets, and realize the efficient and balanced utilization of rare earth resources.

SUMMARY OF THE INVENTION

The purpose of the invention is to make full use of the high abundance rare earth Ce, and realize the dual main phase structure of the nanocrystalline Ce-Fe-B based magnet through the addition of the low melting point rare earth alloy, so as to further improve the magnetic properties of the magnet.

The technical scheme of the present invention is as follows:

A nanocrystalline rare earth permanent magnet material with dual main phase structure is characterized in that: the C _x Fe _{101-xyz By M z magnetic} powder with hard magnetic properties and the non-magnetic Nd ₇₀ Cu ₃₀ powder are in a mass ratio of 70 -95:5-30 is uniformly mixed, and nanocrystalline rare earth permanent magnet materials with dual main phase structure are prepared by spark plasma sintering technology; in C _x Fe _{101-xyz By M z magnetic} powder, M is Cu, Al, Ga, One or more of Nb, Zr and Hf elements, 11≤x≤20, 3≤y≤10, 0≤z≤3.

Wherein: in the Ce _x Fe _{101-xyz By M z magnetic} powder, part of the Fe element can be replaced by Co; part of the Nd element in the Nd ₇₀ Cu ₃₀ powder composition can be replaced by one of Pr, Dy, Tb, Ho, Gd or Various substitutions, part of the Cu element can be replaced by one or more of Al, Ga, and Zn.

The invention also provides a method for preparing the nanocrystalline rare earth permanent magnet material with dual main phase structure, which is characterized in that: using spark plasma sintering technology to prepare the nanocrystalline rare earth permanent magnet material with dual main phase structure, and spark plasma sintering The vacuum degree before and throughout the sintering process is less than 10Pa, the sintering temperature is 600-800°C, the sintering pressure is 20-100MPa, and the sintering time is 0-20min.

There are two Curie temperature transition points in the prepared magnet, that is, there are dual main phases in the magnet. By changing the composition and addition amount of Nd ₇₀ Cu ₃₀ powder, the purpose of regulating the Curie temperature of the magnet can be achieved. At the same time, the grain size of the main phase in the obtained magnet is at the nanometer level, and nanoparticles with a size of 10-15 nm are dispersed at the grain boundary.

The preparation method of the nanocrystalline rare earth permanent magnet material with dual main phase structure of the present invention is characterized in that the specific steps are as follows:

1. The elements Ce, Fe, B, and M _are proportioned according to Ce _x Fe _101-xyz By M _z , and some Fe elements in the composition can also be replaced by Co elements; put the prepared raw materials into the electric arc furnace, in argon gas Smelting in an atmosphere to obtain a master alloy ingot, and preparing a rapidly quenched alloy strip by means of rapid melt quenching, and crushing the alloy strip into powder under the protection of the atmosphere;

2. The elements Nd and Cu are proportioned according to Nd ₇₀ Cu _30. Some Nd elements in the composition can be replaced by Pr, Dy, Tb, Ho, Gd, etc., and some Cu elements can be replaced by Al, Ga, Zn, etc.; Put it into an electric arc furnace, smelt in an argon atmosphere to obtain a master alloy ingot, and prepare a rapidly quenched alloy strip by means of rapid melt quenching, and crush the alloy strip into powder under the protection of the atmosphere;

③. _Mix the C _x Fe _101-xyz By M _z powder and the Nd ₇₀ Cu ₃₀ powder uniformly in a certain proportion, pour it into a graphite mold, and use a spark plasma sintering device to make a nanocrystalline magnet with a dual main phase structure. The sintering temperature is 600～800℃, the sintering pressure is 20～100MPa, and the sintering time is 0～20min;

Generally speaking, the double main phase structure magnet is obtained by using two kinds of powder materials with hard magnetic properties. The present invention uses a kind of powder material with hard magnetic properties and a kind of non-magnetic rare earth alloy to mix, using the spark plasma rapid sintering technology The nanocrystalline dual main phase permanent magnets were prepared. There are two main phases of RE ₂ Fe ₁₄ B with different compositions in the magnet at the same time, and the controllable adjustment of the second Curie transition point of the magnet can be realized by controlling the addition type and amount of the low-melting rare earth alloy. The invention improves the microstructure of the permanent magnet, has high density and strong corrosion resistance, and fully utilizes the high-abundance rare earth element Ce. In addition, the invention also has the characteristics of short sintering time and simple process flow, which effectively promotes the efficient and balanced utilization of rare earth resources.

Description of drawings

Figure 1 is the M-T curve of the Ce-Fe-B-based spark plasma sintered magnet without adding rare earth alloy.

Figure 2 is the M-T curve of 20wt.% NdCu-added Ce-Fe-B-based spark plasma sintered magnet.

Fig. 3 is the TEM morphology of spark plasma sintered magnet.

Detailed ways

The present invention will be further described in detail below with reference to the embodiments of the drawings, but the present invention is not limited to these embodiments, and the following embodiments are only for illustrative purposes and should not be used to limit the scope of the present invention and the claims.

Example 1

The elements Ce, Fe, B, Nb, Cu, Ga, and Co are proportioned according to Ce ₁₇ Fe _74.5 Co ₂ B ₆ Nb _0.5 Cu _0.5 Ga _0.5 , and the prepared raw materials are put into the arc melting furnace and placed in an argon atmosphere. The master alloy ingot is obtained by smelting, and the rapidly quenched alloy strip is prepared by a strip machine, wherein the roll speed is 19m/s, and the alloy strip is broken into powder under the protection of argon; the elements Nd and Cu are classified according to Nd ₇₀ Cu ₃₀ Proportion, put the prepared raw materials into an electric arc furnace, smelt in an argon atmosphere to obtain alloy ingots, and prepare rapidly quenched alloy strips by means of melt rapid quenching, wherein the roll speed of the strip machine is 30m /s, crush the alloy ribbon into powder in the glove box; under argon protection, the Ce ₁₇ Fe _74.5 Co ₂ B ₆ Nb _0.5 Cu _0.5 Ga _0.5 powder and the Nd ₇₀ Cu ₃₀ powder are uniformly mixed in a mass ratio of 95:5. The mixed powder is poured into a graphite mold, and the magnet is produced by rapid sintering by spark plasma sintering equipment. The vacuum degree before sintering and the whole sintering process is less than 10Pa, the sintering temperature is 650℃, the sintering pressure is 50MPa, and the sintering time is 2min.

There are two Curie transition points in the magnet, which are T _c1 =438K and T _c2 =457K respectively, indicating that there are two hard magnetic main phases in the magnet, with a double main phase structure.

Comparative ratio

The elements Ce, Fe, B, Nb, Cu, Ga, and Co are proportioned according to Ce ₁₇ Fe _74.5 Co ₂ B ₆ Nb _0.5 Cu _0.5 Ga _0.5 , and the prepared raw materials are put into the arc melting furnace and placed in an argon atmosphere. Smelting to obtain a master alloy ingot, and preparing a rapidly quenched alloy strip through a strip machine, wherein the roll speed is 19m/s, and the alloy strip is broken into powder under the protection of argon; Ce ₁₇ Fe _74.5 Co ₂ B ₆ Nb The _0.5 Cu _0.5 Ga _0.5 powder was poured into a graphite mold, and the magnet was prepared by rapid sintering by spark plasma sintering equipment. The vacuum degree before sintering and the whole sintering process is less than 10Pa, the sintering temperature is 650℃, the sintering pressure is 50MPa, and the sintering time is 2min.

The MT curve of the magnet without rare earth alloy is shown in Figure 1. There is one Curie transition point in Fig. 1, which is T _c =443K, indicating that there is only one main phase in the magnet. Compared with Example 1, it can be seen that after the addition of the non-magnetic rare earth alloy, the Nd element diffuses into the interior of the main phase crystal grains, resulting in the formation of a dual main phase structure.

Example 2

The difference from Example 1 is that Ce ₁₇ Fe _74.5 Co ₂ B ₆ Nb _0.5 Cu _0.5 Ga _0.5 powder and Nd ₇₀ Cu ₃₀ powder are uniformly mixed in a mass ratio of 90:10. The mixed powder is poured into a graphite mold, and the magnet is produced by rapid sintering by spark plasma sintering equipment. Before spark plasma sintering and during the whole sintering process, the vacuum degree is less than 10Pa, the sintering temperature is 750℃, the sintering pressure is 30MPa, and the sintering time is 3min.

There are two Curie transition points in the magnet, which are T _c1 =439K and T _c2 =493K respectively, indicating that there are two hard magnetic main phases in the magnet, with a double main phase structure.

Example 3

The difference from Example 1 is that Ce ₁₇ Fe _74.5 Co ₂ B ₆ Nb _0.5 Cu _0.5 Ga _0.5 powder and Nd ₇₀ Cu ₃₀ powder are uniformly mixed in a mass ratio of 80:20. The mixed powder is poured into a graphite mold, and the magnet is produced by rapid sintering by spark plasma sintering equipment. Before spark plasma sintering and the whole sintering process, the vacuum degree is less than 10Pa, the sintering temperature is 800℃, the sintering pressure is 50MPa, and the sintering time is 1min.

The magnet MT curve is shown in Figure 2. There are two Curie transition points in the magnet, respectively T _c1 =440K and T _c2 =508K, indicating that there are two hard magnetic main phases in the magnet at the same time, with a dual main phase structure. Figure 3 is a TEM image of the magnet. It can be seen from the figure that all the grains in the magnet are nanoscale, and the grain boundaries between the main phase grains are dispersed with nanoparticles with a size of 10-15nm.

Example 4

The difference from Example 1 is that Ce ₁₇ Fe _74.5 Co ₂ B ₆ Nb _0.5 Cu _0.5 Ga _0.5 powder and Nd ₇₀ Cu ₃₀ powder are uniformly mixed in a mass ratio of 70:30. The mixed powder is poured into a graphite mold, and the magnet is produced by rapid sintering by spark plasma sintering equipment. Before spark plasma sintering and during the whole sintering process, the vacuum degree is less than 10Pa, the sintering temperature is 650℃, the sintering pressure is 50MPa, and the sintering time is 2min.

There are two Curie transition points in the magnet, which are T _c1 =439K and T _c2 =504K respectively, indicating that there are two hard magnetic main phases in the magnet, with a double main phase structure.

Example 5

The difference from Example 1 is that the Ce ₂₀ Fe ₇₁ B ₈ Nb _0.5 Cu _0.5 Ga _1.0 powder and the Nd ₇₀ Cu ₃₀ powder are uniformly mixed in a mass ratio of 80:20. The mixed powder is poured into a graphite mold, and the magnet is produced by rapid sintering by spark plasma sintering equipment. The vacuum degree before spark plasma sintering and the whole sintering process is less than 10Pa, the sintering temperature is 650℃, the sintering pressure is 50MPa, and the sintering time is 2min.

There are two Curie transition points in the magnet, indicating that there are two hard magnetic main phases in the magnet, with a double main phase structure.

Example 6

The difference from Example 1 is that Ce ₁₈ Fe ₇₃ B ₈ Zr _0.5 Al _0.5 Ga _1.0 powder and Dy ₇₀ Cu ₃₀ powder are uniformly mixed in a mass ratio of 85:15. The mixed powder is poured into a graphite mold, and the magnet is produced by rapid sintering by spark plasma sintering equipment. Before spark plasma sintering and during the whole sintering process, the vacuum degree is less than 10Pa, the sintering temperature is 650℃, the sintering pressure is 40MPa, and the sintering time is 5min.

There are two Curie transition points in the magnet, indicating that there are two hard magnetic main phases in the magnet, with a double main phase structure.

Example 7

The difference from Example 1 is that Ce ₂₀ Fe ₇₁ B ₈ Zr _0.5 Cu _0.5 Al _1.0 powder and Pr ₇₀ Cu ₃₀ powder are uniformly mixed in a mass ratio of 90:10. The mixed powder is poured into a graphite mold, and the magnet is produced by rapid sintering by spark plasma sintering equipment. Before spark plasma sintering and during the whole sintering process, the vacuum degree is less than 10Pa, the sintering temperature is 600℃, the sintering pressure is 100MPa, and the sintering time is 3min.

There are two Curie transition points in the magnet, indicating that there are two hard magnetic main phases in the magnet, with a double main phase structure.

The above-mentioned embodiments are only intended to illustrate the technical concept and characteristics of the present invention, and the purpose thereof is to enable those who are familiar with the art to understand the content of the present invention and implement them accordingly, and cannot limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included within the protection scope of the present invention.

Claims (5)

1. a nanocrystalline rare earth permanent magnet material with dual main phase structure is characterized in that: by mass ratio of the C _x Fe 10 _{-xyz By M z magnetic} powder with hard magnetic properties and the non-magnetic Nd ₇₀ Cu ₃₀ powder It is 70-95:5-30 uniformly mixed, and the nanocrystalline rare earth permanent magnet material with dual main phase structure is prepared by spark plasma sintering technology; Wherein C _x Fe _{101-xyz By M z magnetic} powder, M is one or more of Cu, Al, Ga, Nb, Zr, Hf elements, 11≤x≤20, 3≤y≤10, 0≤z ≤3; The vacuum degree before spark plasma sintering and the whole sintering process is less than 10Pa, the sintering temperature is 600-800℃, the sintering pressure is 20-100MPa, and the sintering time is 0-20min. 2 . The nanocrystalline rare earth permanent magnet material with dual main phase structure according to claim 1 , wherein: in the C _x Fe _{101 -xyz By M z magnetic} powder, part of the Fe element is replaced by Co. 3 . 3. according to the nanocrystalline rare earth permanent magnet material of the described double main phase structure of claim 1, it is characterized in that: part of Nd element in Nd ₇₀ Cu ₃₀ powder composition is composed of one of Pr, Dy, Tb, Ho, Gd or Various substitutions, part of the Cu element is replaced by one or more of Al, Ga, and Zn. 4. according to the nanocrystalline rare earth permanent magnet material of the described dual main phase structure of claim 1, it is characterized in that: there are two Curie temperature transition points in the obtained magnet, by changing the composition and the addition amount of Nd ₇₀ Cu ₃₀ powder, can To achieve the purpose of regulating the Curie temperature of the magnet. 5. according to the nanocrystalline rare earth permanent magnet material of the described double main phase structure of claim 1, it is characterized in that: in the obtained magnet, the main phase grain size is in nanometer level, and the nanometer size of 10-15nm is dispersed at the grain boundary. particles.

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