A high coercivity rare-earth-free MnAlM permanent magnet alloy and its preparation method

Abstract

The present invention discloses a high coercivity rare-earth-free MnAlM permanent magnet alloy. The nominal molecular formula of the high coercivity rare-earth-free MnAlM permanent magnet alloy is Mn<subgt;50+x< / subgt;Al<subgt;50-x-y< / subgt;M<subgt;y< / subgt>, where x = 0 to 3, y = 1 to 3, and M is Zn or W. The high coercivity rare-earth-free MnAlM permanent magnet alloy of the present invention not only has excellent machining properties and good corrosion resistance, but also has a low price, a simple preparation process, and does not require complex magnetic field treatment. The present invention also provides a method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy. By regulating the doping elements and the heat treatment process, the temperature coefficient of coercivity is changed from negative to positive. The process is simple and convenient, the production cost is low, and it is convenient for actual production and promotion.

Description

Technical Field

[0001] The present invention relates to a permanent magnet alloy, and more particularly to a high coercivity rare-earth-free MnAlM permanent magnet alloy and a preparation method thereof. Background Art

[0002] Permanent magnet materials play an important role in the production of modern industry and people's lives. Magnetic materials have a wide range of uses, such as in electroacoustics, magnetic memories, telecommunications, permanent magnet motors, and can also be used as memory elements, microwave elements, magnetic resonance equipment, etc. The magnetic properties of MnAl materials are higher than those of traditional hard ferrites and AlNiCo alloys, but lower than those of rare-earth permanent magnets. However, rare-earth resources are strategic resources, which are not only expensive but also cause serious environmental pollution during production, restricting the development of rare-earth materials. Rare-earth-free permanent magnet materials represented by MnAl are rich in resources, low in cost, strong in corrosion resistance, high in mechanical processing performance, etc., and thus have broad development prospects and have attracted strong interest from researchers around the world.

[0003] In 1958, Kono, Koch and others first reported rare-earth-free MnAl-based permanent magnet alloys (also known as τ-phase MnAl alloys). MnAl-based permanent magnet alloys have relatively high magnetocrystalline anisotropy (10 7 erg / cm 3 ), theoretical coercivity (30 - 40 kOe), theoretical density (5200 kg / m 3 ), theoretical maximum magnetic energy product (12 MGOe), excellent corrosion resistance and good machinability, and can be used for bulk permanent magnets and thin film devices. MnAl-based permanent magnet alloys have now been widely used in hybrid electric vehicles, wind power generation, alternative energy and some important fields.

[0004] The τ-phase of MnAl permanent magnet alloy is a metastable phase that is easily decomposed into non-magnetic γ2 (Al8Mn5) and β (Mn), and the APBs in the τ-phase are antiferromagnetic coupling regions, which are favorable nucleation sites for magnetization reversal, while other planar defects such as stacking faults and twins are pinning centers. In the Mn-poor region, Mn occupies the position of (0, 0, 0), and Al occupies the position of (1 / 2, 1 / 2, 1 / 2). For the Mn-rich region, Mn not only occupies the original position but also a part occupies the position of (1 / 2, 1 / 2, 1 / 2), thus generating antiferromagnetic coupling. Currently, the MnAl permanent magnet alloy with high-purity magnetic phase is mainly prepared by doping a small amount of other elements (such as C, Ga, Ti, Cu, B, Cr, Ni, etc.) in the MnAl alloy prepared by arc melting and melt spinning technology to increase the stability of the magnetic τ-phase.

[0005] The coercivity of currently prepared MnAl-based permanent magnets is relatively low, far lower than its theoretical value (30 - 40 kOe), leaving room for further improvement. In recent years, the research focus on MnAl-based alloys mainly revolves around the following two points: one is to explore what factors make it difficult to improve its coercivity; the other is how to obtain MnAl-based permanent magnets with both high coercivity and high saturation magnetization. Currently, in ingot samples, the coercivity is usually less than 1.0 kOe. Melt spinning and high-energy ball milling techniques are used to increase the coercivity of materials by refining grains / particles. However, in the ribbons prepared by melt spinning, the coercivity is usually less than 2.0 kOe. In the powders prepared by high-energy ball milling, the coercivity is usually less than 3.3 kOe, far lower than the theoretical value of coercivity. This is because although melt spinning can obtain ribbons with fine grains, the grain refinement leads to an increase in the intergranular exchange coupling effect, making it difficult to improve the coercivity. Similarly, although high-energy ball milling can prepare permanent magnet powders with fine particles, reducing the intergranular exchange coupling effect, ball milling often causes stacking faults in the magnetic phase and even amorphization of the magnetic phase, resulting in difficulty in improving the coercivity. F. Jime′nez-Villacorta et al. prepared Mn 55 Al 45 ribbons with both antiferromagnetic ε-phase and ferromagnetic τ-phase by melt spinning, and obtained a coercivity as high as 19 kOe at 10 K using antiferromagnetic / ferromagnetic exchange bias. However, this coercivity is obtained at a relatively low temperature. Currently, the coercivity of MnAl-based permanent magnet alloys obtained at room temperature is relatively low, and it is difficult to obtain both high saturation magnetization and high coercivity simultaneously. Moreover, there is relatively little research on improving the coercivity by generating a second antiferromagnetic phase in the MnAl system or even through antiferromagnetic / ferromagnetic exchange bias. SUMMARY OF THE INVENTION

[0006] The present invention aims to solve the above-mentioned technical problems existing in the prior art, and provides a high coercivity rare-earth-free MnAlM permanent magnet alloy with low production cost.

[0007] The present invention also provides a preparation method for a high coercivity rare-earth-free MnAlM permanent magnet alloy with simple process steps and strong operability.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A high coercivity rare-earth-free MnAlM permanent magnet alloy, the nominal molecular formula of the high coercivity rare-earth-free MnAlM permanent magnet alloy is Mn 50+x Al 50-x-y M y , where x = 0 - 3, y = 1 - 3, and M is Zn or W.

[0010] A preparation method of a high coercivity rare-earth-free MnAlM permanent magnet alloy, comprising the following steps:

[0011] (1) Batching

[0012] Configure raw materials according to the nominal molecular formula of the high coercivity rare-earth-free MnAlM permanent magnet alloy to obtain master alloy raw materials. In the present invention, Mn, Al, W, and Zn are selected as the raw materials of the permanent magnet alloy, which not only have excellent machining performance and good corrosion resistance, but also are low in price, have a simple preparation process, do not require complex magnetic field treatment, and are basically harmless to the human body and cause little environmental pollution during the production process; by regulating the doping elements and heat treatment process, the coercivity temperature coefficient is changed from negative to positive;

[0013] (2) Prepare MnAlM alloy ingot or MnAlM alloy strip

[0014] Use a non-consumable vacuum arc furnace to put the master alloy raw materials into a water-cooled copper crucible, evacuate and then fill with an inert gas as a protective gas, and repeatedly melt the alloy in an inert gas atmosphere, turning it over once for each melting to obtain a MnAlM alloy ingot with uniform composition; or polish the surface of the obtained MnAlM alloy ingot and put it into a quartz tube with small holes at the bottom, use a high-vacuum rapid quenching system, and adjust the size of the induction coil current in an inert gas atmosphere to completely melt the MnAlM alloy ingot in the quartz tube into a liquid state, and finally let it spray out and fall on a high-speed rotating water-cooled copper roller and be spun off to obtain a MnAlM alloy strip.

[0015] (3) Heat treatment

[0016] Polish the surface of the MnAlM alloy ingot and put it into a quartz tube, evacuate and seal it, and then perform heat treatment. After heat treatment, a high coercivity rare-earth-free MnAlM permanent magnet alloy ingot is obtained; or put the MnAlM alloy strip into a quartz tube, evacuate and seal it, and then perform heat treatment. After heat treatment, a high coercivity rare-earth-free MnAlM permanent magnet alloy strip is obtained. The alloy ingots and strips prepared by the preparation method of the present invention contain an antiferromagnetic γ phase and a magnetic τ phase. The hysteresis loop measured for the alloy containing the two phases at a temperature below the Néel temperature T N will exhibit an exchange bias phenomenon, and the coercivity temperature factor in the hysteresis loop measured at a temperature higher than the Néel temperature T N is positive, that is: the coercivity increases as the test temperature increases, and the presence of the antiferromagnetic phase will greatly increase the coercivity of the alloy.

[0017] Preferably, in step (1), based on the mass of Mn in the master alloy raw materials, an additional 3-5% of Mn raw materials are added to the master alloy raw materials.

[0018] Preferably, in step (2), the inert gas is argon or helium.

[0019] Preferably, the number of melting times is 3 to 4 times.

[0020] Preferably, the specific process parameters of melting are as follows: the vacuum degree of the vacuum arc furnace is higher than 1×10 -3 Pa, the current intensity of the vacuum arc furnace is 45 - 55 A, and the melting time for each time is 3 min.

[0021] Preferably, the number of melting times is 3 to 4 times.

[0022] Preferably, in step (2), the linear velocity of the water-cooled copper roll is 5 - 30 m / s.

[0023] Preferably, in step (3), the specific steps of heat treatment of the MnAlM alloy ingot are as follows: put the MnAlM alloy ingot into a muffle furnace, the heat treatment temperature is 1150 - 1250 °C, and the heat treatment time is 16 - 20 h; after heat treatment, quickly put the MnAlM alloy ingot into ice water for quenching treatment. The high-vacuum high-temperature quenching process is used to obtain a high-temperature γ-phase with antiferromagnetism. At the same time, due to the high-vacuum sealed tube, the cooling rate of the alloy during the quenching process becomes slower, generating a magnetic τ-phase; the antiferromagnetic γ-phase separates the magnetic τ-phase grains, reducing the intergranular exchange coupling between the magnetic τ-phase grains, which is beneficial to the increase of the coercivity of the alloy.

[0024] Preferably, in step (3), the specific steps of heat treatment of the MnAlM alloy strip are as follows: put the MnAlM alloy strip into a muffle furnace, the heat treatment temperature is 1150 - 1250 °C, and the heat treatment time is 5 - 50 min; after heat treatment, quickly put the MnAlM alloy strip into an ice-water mixture for quenching treatment. The high-vacuum high-temperature quenching process is used to obtain a high-temperature γ-phase with antiferromagnetism. At the same time, due to the high-vacuum sealed tube, the cooling rate of the alloy during the quenching process becomes slower, generating a magnetic τ-phase; the antiferromagnetic γ-phase separates the magnetic τ-phase grains, reducing the intergranular exchange coupling between the magnetic τ-phase grains, which is beneficial to the increase of the coercivity of the alloy.

[0025] Therefore, the present invention has the following beneficial effects:

[0026] (1) The present invention selects Mn, Al, W, and Zn as the raw materials of the permanent magnet alloy. They not only have excellent mechanical processing performance and good corrosion resistance, but also are low in price, and the preparation process is simple, without the need for complex magnetic field treatment;

[0027] (2) The present invention adopts a high-vacuum high-temperature quenching process to obtain a high-temperature γ phase with antiferromagnetism. At the same time, due to the high-vacuum sealed tube, the cooling rate of the alloy during quenching becomes slower, generating a magnetic τ phase. The antiferromagnetic γ phase separates the magnetic τ phase grains, reducing the intergranular exchange coupling between the magnetic τ phase grains, which is beneficial to the increase of the coercivity of the alloy;

[0028] (3) The high-temperature heat treatment method adopted by MnAlW in the present invention generates an antiferromagnetic γ phase (AFM) and a ferromagnetic τ phase (FM). An exchange coupling will occur between the AFM phase and the FM phase grains, resulting in an exchange bias phenomenon;

[0029] (4) The present invention realizes the conversion of the temperature coefficient of coercivity from negative to positive by regulating the doping elements and the heat treatment process;

[0030] (5) The raw materials used in the present invention are basically harmless to the human body during the production process and cause little environmental pollution;

[0031] (6) The production and preparation process of the present invention is simple and convenient, with low production costs, and is convenient for actual production and promotion. Description of the Drawings

[0032] Figure 1 is the XRD pattern comparison diagram of the Mn 50 Al 49 W1 alloy ingot in Example 1 and the Mn 50 Al 48 W2 alloy ingot in Example 2.

[0033] Figure 2 is the XRD pattern comparison diagram of the high-coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy ingot in Example 1 and the high-coercivity rare-earth-free Mn 50 Al 48 W2 permanent magnet alloy ingot in Example 2.

[0034] Figure 3 is the hysteresis loop curve diagram of the high-coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy ingot measured under different temperature conditions.

[0035] Figure 4 is the hysteresis loop curve diagram of the high-coercivity rare-earth-free Mn 50 Al 48 W2 permanent magnet alloy ingot measured under different temperature conditions.

[0036] Figure 5 is the high-coercivity rare-earth-free Mn 50 Al 49Recovery curve graph of W1 permanent magnet alloy ingot measured at 300K temperature.

[0037] Figure 6 It is the high coercivity rare-earth-free Mn in Example 2 50 Al 48 Recovery curve graph of W2 permanent magnet alloy ingot measured at 300K temperature.

[0038] Figure 7 It is Mn in Example 3 50 Al 49 Comparison diagram of XRD patterns of Zn1 alloy ingot and Mn in Example 4 50 Al 48 Comparison diagram of XRD patterns of Zn2 alloy ingot.

[0039] Figure 8 It is the high coercivity rare-earth-free Mn in Example 3 50 Al 49 Comparison diagram of XRD patterns of Zn1 permanent magnet alloy ingot and high coercivity rare-earth-free Mn in Example 4 50 Al 48 Comparison diagram of XRD patterns of Zn2 permanent magnet alloy ingot.

[0040] Figure 9 It is the high coercivity rare-earth-free Mn in Example 3 50 Al 49 Hysteresis loop curve graph of Zn1 permanent magnet alloy ingot measured under different temperature conditions.

[0041] Figure 10 It is the high coercivity rare-earth-free Mn in Example 4 50 Al 48 Hysteresis loop curve graph of Zn2 permanent magnet alloy ingot measured under different temperature conditions.

[0042] Figure 11 It is the high coercivity rare-earth-free Mn in Example 3 50 Al 49 Recovery curve graph of Zn1 permanent magnet alloy ingot measured at 300K temperature.

[0043] Figure 12 It is the high coercivity rare-earth-free Mn in Example 4 50 Al 48 Recovery curve graph of Zn2 permanent magnet alloy ingot measured at 300K temperature. Specific implementation manners

[0044] The following further describes the present invention in conjunction with the accompanying drawings and specific implementation manners.

[0045] Example 1

[0046] (1) Batching

[0047] Pure manganese blocks, pure aluminum blocks and pure tungsten powder with a purity of not less than 99.9% are used to prepare the raw materials of the master alloy according to the nominal molecular formula Mn 50 Al 49 W1 of the high coercivity rare-earth-free MnAlM permanent magnet alloy. In addition, based on the mass of Mn in the master alloy raw materials, an additional 3% of pure manganese blocks are added to the master alloy raw materials.

[0048] (2) Preparation of MnAlM alloy ingots

[0049] Using a non-consumable vacuum arc furnace, the master alloy raw materials are placed in a water-cooled copper crucible. After evacuating the air, an inert gas (argon) is filled as a protective gas. The above processes of evacuating and filling the gas are repeated 3 times. The alloy is repeatedly melted 3 times in an inert gas atmosphere, and it is turned over once each time it is melted. The vacuum degree of the vacuum arc furnace is higher than 1*10 -3 Pa, the current intensity of the vacuum arc furnace is 45 A, and the melting time for each time is 3 min, obtaining a Mn 50 Al 49 W1 alloy ingot with uniform composition. The XRD pattern of the Mn 50 Al 49 W1 alloy ingot is as shown by curve (a) in Figure 1 .

[0050] (3) After polishing the surface of the Mn 50 Al 49 W1 alloy ingot, it is placed in a quartz tube, evacuated and sealed, and then heat-treated. After heat-treatment, the high coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy is obtained. The specific steps of the heat treatment of the Mn 50 Al 49 W1 alloy ingot are as follows: The Mn 50 Al 49 W1 alloy ingot is placed in a muffle furnace for heat treatment. The heat treatment temperature is 1150 °C, and the heat treatment time is 20 h; after heat treatment, the Mn 50 Al 49 W1 alloy ingot is quickly placed in ice water for quenching treatment.

[0051] The magnetic performance data of the high coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy ingot under different temperature conditions are shown in Table 1.

[0052] The XRD pattern of the high coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy ingot is as shown by curve (a) in Figure 2 .

[0053] High coercivity rare-earth-free Mn50 Al 49 The hysteresis loops measured for the W1 permanent magnet alloy ingot under different temperature conditions are as Figure 3 shown.

[0054] High coercivity rare-earth-free Mn 50 Al 49 The recovery curve graph measured for the W1 permanent magnet alloy ingot at a temperature of 300K is as Figure 5 shown.

[0055] Example 2

[0056] The difference between Example 2 and Example 1 lies in that: the nominal molecular formula of the high coercivity rare-earth-free MnAlM permanent magnet alloy is Mn 50 Al 48 W2, the current intensity of the vacuum arc furnace is 55A, smelting is carried out 4 times, the heat treatment temperature is 1200 °C, and the heat treatment time is 18h. The rest is exactly the same as in Example 1.

[0057] Mn 50 Al 48 The XRD pattern of the W2 alloy ingot is as the curve (b) in Figure 1 shown.

[0058] Mn 50 Al 48 The magnetic property data of the W2 permanent magnet alloy ingot under different temperature conditions are shown in Table 1.

[0059] High coercivity rare-earth-free Mn 50 Al 48 The XRD pattern of the W2 permanent magnet alloy ingot is as the curve (b) in Figure 2 shown.

[0060] High coercivity rare-earth-free Mn 50 Al 48 The hysteresis loops measured for the W2 permanent magnet alloy ingot under different temperature conditions are as Figure 4 shown.

[0061] High coercivity rare-earth-free Mn 50 Al 48 The recovery curve graph measured for the W2 permanent magnet alloy ingot at a temperature of 300K is as Figure 6 shown.

[0062] Table 1 Magnetic property data of Mn 50 Al 49 W1 and Mn 50 Al 48 W2 alloy bulk samples

[0063]

[0064] By Figure 1 and Figure 2 comparison, it can be seen that from Figure 2 there is a τ-MnAl phase, diffraction peaks of β and γ phases can be seen, and the proportion of the γ phase increases, indicating that heat treatment increases the content of the antiferromagnetic γ phase.

[0065] As can be seen from Table 1, the remanent magnetization decreases with the increase of the test temperature, and the coercivity increases with the increase of the test temperature between 150K and 400K. The temperature coefficient is used to represent the thermal stability in magnetic materials, and the remanent magnetization temperature coefficient (α) and the coercivity temperature coefficient (β) represent its stability, Mn 50 Al 48 For the alloy ingot after heat treatment of Mn -1 Al -1 .

[0066] Example 3

[0067] Compared with Example 1, the difference in Example 3 is that pure manganese blocks, pure aluminum blocks and pure zinc blocks with a purity of not less than 99.9% are used to configure the raw materials according to the nominal molecular formula Mn 50 Al 49 Zn1 of the high coercivity rare earth-free MnAlM permanent magnet alloy to obtain the master alloy raw materials, and the rest are exactly the same as in Example 1.

[0068] Mn 50 Al 49 The XRD pattern of the Mn Figure 7 Al

[0069] Zn1 alloy ingot is shown as curve (a) in 50 Al 49 . The magnetic property data of the high coercivity rare earth-free Mn

[0070] Al 50 Al 49 Zn1 alloy ingot at different temperature conditions are shown in Table 2. Figure 8 The XRD pattern of the high coercivity rare earth-free Mn

[0071] Al 50 Al 49 Zn1 alloy ingot is shown as curve (a) in Figure 9 .

[0072] The hysteresis loop measured for the high coercivity rare earth-free Mn 50 Al 49 Zn1 alloy ingot at 300K temperature is shown inFigure 11 as shown

[0073] Example 4

[0074] Compared with Example 2, Example 4 is different in that pure manganese blocks, pure aluminum blocks, and pure zinc blocks with a purity of not less than 99.9% are used to prepare the raw materials of the master alloy according to the nominal molecular formula Mn 50 Al 48 Zn2 of the high coercivity rare-earth-free MnAlM permanent magnet alloy, and the rest is exactly the same as Example 2.

[0075] Mn 50 Al 48 The XRD pattern of the Mn Figure 7 Al

[0076] Zn2 alloy ingot is as shown by curve (b) in 50 Al 48 Table 2 shows the magnetic property data of the high coercivity rare-earth-free Mn

[0077] Zn2 permanent magnet alloy ingot under different temperature conditions. 50 Al 48 The XRD pattern of the high coercivity rare-earth-free Mn Figure 8 Zn2 permanent magnet alloy ingot is as shown by curve (b) in

[0078] The hysteresis loop of the high coercivity rare-earth-free Mn 50 Al 48 Zn2 permanent magnet alloy ingot measured under different temperature conditions is as shown in Figure 10 as shown

[0079] The demagnetization curve of the high coercivity rare-earth-free Mn 50 Al 48 Zn2 permanent magnet alloy ingot measured at temperature of 300K is as shown in Figure 12 as shown

[0080] Table 2 Magnetic property data of Mn 50 Al 49 Zn1 and Mn 50 Al 48 Zn2 alloy bulk samples

[0081]

[0082] Example 5

[0083] Compared with Example 1, Example 5 is different in that:

[0084] (2) The obtained Mn 50 Al 49After the surface of the W1 alloy ingot is polished, it is placed in a quartz tube with small holes at the bottom. Using a high-vacuum rapid quenching system, in an inert gas atmosphere, by adjusting the magnitude of the induction coil current, the Mn in the quartz tube 50 Al 49 The W1 alloy ingot is completely melted into a liquid state, and finally it is ejected and landed on a high-speed rotating water-cooled copper roller, and then spun off. The linear velocity of the water-cooled copper roller is 10 m / s, obtaining Mn 50 Al 49 W1 alloy thin strip;

[0085] (3) Heat treatment

[0086] Put the Mn 50 Al 49 W1 alloy thin strip into the quartz tube, evacuate and seal it, and then conduct heat treatment. After heat treatment, the high coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy thin strip is obtained. The specific steps for heat treatment of the Mn 50 Al 49 W1 alloy thin strip are as follows: Put the Mn 50 Al 49 W1 alloy thin strip into a muffle furnace. The heat treatment temperature is 1150 °C, and the heat treatment time is 15 min; after heat treatment, quickly put the Mn 50 Al 49 W1 alloy thin strip into an ice-water mixture for quenching treatment.

[0087] The magnetic properties of the high coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy thin strip obtained in Example 5 are similar to those of the high coercivity rare-earth-free Mn 50 Al 49 W1 permanent magnet alloy ingot obtained in Example 1, so they will not be elaborated here.

[0088] Example 6

[0089] The difference between Example 6 and Example 2 is that:

[0090] (2) After the obtained Mn 50 Al 48 The surface of the W2 alloy ingot is polished and placed in a quartz tube with small holes at the bottom. Using a high-vacuum rapid quenching system, in an inert gas atmosphere, by adjusting the magnitude of the induction coil current, the Mn in the quartz tube 50 Al 48 The W2 alloy ingot is completely melted into a liquid state, and finally it is ejected and landed on a high-speed rotating water-cooled copper roller, and then spun off. The linear velocity of the water-cooled copper roller is 20 m / s, obtaining Mn 50 Al 42 W2 alloy thin strip;

[0091] (3) Heat treatment

[0092] Put Mn 50 Al 42 The Mn-Al-W2 alloy strip is put into a quartz tube, vacuum-sealed, and then heat-treated. After heat treatment, the high coercivity rare-earth-free Mn-Al-W2 permanent magnet alloy strip is obtained. 50 Al 42 W2 permanent magnet alloy strip, Mn 50 Al 42 The specific steps for heat-treating the Mn-Al-W2 alloy strip are as follows: Put the Mn-Al-W2 alloy strip into a muffle furnace, the heat treatment temperature is 1200 °C, and the heat treatment time is 20 min; after heat treatment, quickly put the Mn-Al-W2 alloy strip into an ice-water mixture for quenching treatment. 50 Al 42 W2 alloy strip into the muffle furnace, the heat treatment temperature is 1200 °C, and the heat treatment time is 20 min; after heat treatment, quickly put the Mn-Al-W2 alloy strip into an ice-water mixture for quenching treatment. 50 Al 42 W2 alloy strip into an ice-water mixture for quenching treatment.

[0093] The magnetic properties of the high coercivity rare-earth-free Mn-Al-W2 permanent magnet alloy strip obtained in Example 6 are similar to those of the high coercivity rare-earth-free Mn-Al-W2 permanent magnet ingot obtained in Example 2, so they will not be elaborated here. 50 Al 42 W2 permanent magnet alloy strip and the magnetic properties of the high coercivity rare-earth-free Mn-Al-W2 permanent magnet ingot obtained in Example 2 are similar, so they will not be elaborated here. 50 Al 42 W2 permanent magnet alloy ingot, so it will not be elaborated here.

[0094] Example 7

[0095] The difference between Example 7 and Example 3 is as follows:

[0096] (2) Grind the surface of the obtained Mn-Al-Zn1 alloy ingot and put it into a quartz tube with small holes at the bottom. Use a high-vacuum rapid quenching system. In an inert gas atmosphere, adjust the magnitude of the induction coil current to completely melt the Mn-Al-Zn1 alloy ingot in the quartz tube into a liquid state, and finally let it spray out and fall on a high-speed rotating water-cooled copper roller and be thrown out. The linear velocity of the water-cooled copper roller is 15 m / s to obtain the Mn-Al-Zn1 alloy strip; 50 Al 49 Zn1 alloy ingot, and adjust the magnitude of the induction coil current in an inert gas atmosphere to completely melt the Mn-Al-Zn1 alloy ingot in the quartz tube into a liquid state, and finally let it spray out and fall on a high-speed rotating water-cooled copper roller and be thrown out. The linear velocity of the water-cooled copper roller is 15 m / s to obtain the Mn-Al-Zn1 alloy strip; 50 Al 49 Zn1 alloy ingot completely melts into a liquid state, and finally let it spray out and fall on a high-speed rotating water-cooled copper roller and be thrown out. The linear velocity of the water-cooled copper roller is 15 m / s to obtain the Mn-Al-Zn1 alloy strip; 50 Al 49 Zn1 alloy strip;

[0097] (3) Heat treatment

[0098] Put the Mn-Al-Zn1 alloy strip into a quartz tube, vacuum-sealed, and then heat-treated. After heat treatment, the high coercivity rare-earth-free Mn-Al-Zn1 permanent magnet alloy strip is obtained. 50 Al 49 Zn1 alloy strip into a quartz tube, vacuum-sealed, and then heat-treated. After heat treatment, the high coercivity rare-earth-free Mn-Al-Zn1 permanent magnet alloy strip is obtained. 50 Al 49 Zn1 permanent magnet alloy strip, Mn 50 Al49 The specific steps for heat-treating the Zn1 alloy thin strip are as follows: Mn 50 Al 49 Put the Zn1 alloy thin strip into a muffle furnace, the heat-treatment temperature is 1200 °C, and the heat-treatment time is 20 min; after heat-treatment, Mn 50 Al 49 Quickly put the Zn1 alloy thin strip into an ice-water mixture for quenching treatment.

[0099] The magnetic properties of the high coercivity rare-earth-free Mn 50 Al 49 Zn1 permanent magnet alloy thin strip obtained in Example 7 are similar to those of the high coercivity rare-earth-free Mn 50 Al 49 Zn1 permanent magnet alloy ingot, so they will not be elaborated here.

[0100] Example 8

[0101] The difference between Example 8 and Example 4 is as follows:

[0102] (2) After grinding the surface of the obtained Mn 50 Al 48 Zn2 alloy ingot, put it into a quartz tube with small holes at the bottom, and use a high-vacuum rapid quenching system. In an inert gas atmosphere, adjust the magnitude of the induction coil current to completely melt the Mn 50 Al 48 Zn2 alloy ingot in the quartz tube into a liquid state, and finally let it spray out and fall on a high-speed rotating water-cooled copper roller, spin it out, the linear velocity of the water-cooled copper roller is 20 m / s, to obtain the Mn 50 Al 49 Zn1 alloy thin strip;

[0103] (3) Heat treatment

[0104] Put the Mn 50 Al 48 Zn2 alloy thin strip into a quartz tube, evacuate and seal it, and then conduct heat treatment. After heat treatment, the high coercivity rare-earth-free Mn 50 Al 48 Zn2 permanent magnet alloy thin strip is obtained. The specific steps for heat-treating the Mn 50 Al 48 Zn2 alloy thin strip are as follows: Put the Mn 50 Al 48 Zn2 alloy thin strip into a muffle furnace, the heat-treatment temperature is 1200 °C, and the heat-treatment time is 20 min; after heat treatment, quickly put the Mn 50 Al 48 Zn2 alloy thin strip into an ice-water mixture for quenching treatment.

[0105] The high coercivity rare-earth-free Mn 50 Al 48 Zn2 permanent magnet alloy strip performance is similar to that of the high coercivity rare-earth-free Mn 50 Al 48 Zn2 permanent magnet alloy ingot, so it will not be elaborated here.

[0106] The above-described embodiments are only a preferred solution of the present invention, and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A rare-earth-free MnAlM permanent magnetic alloy with high coercivity, characterized in that, The nominal molecular formula of the high coercivity rare-earth-free MnAlM permanent magnet alloy is Mn 50+x Al 50-x-y M y , where x = 0 to 3, y = 1 to 3, and M is Zn or W; The alloy comprises a high-temperature γ phase having antiferromagnetism obtained by a high-vacuum high-temperature quenching process, wherein the cooling rate of the alloy slows down during the quenching process to generate a magnetic τ phase; the antiferromagnetic γ phase separates the magnetic τ phase grains; Exchange coupling occurs between the antiferromagnetic γ phase and the ferromagnetic τ phase grains, resulting in exchange bias.

2. A method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy as described in claim 1, characterized in that, The following steps are involved: (1) Ingredients Prepare raw materials according to the nominal molecular formula of the high coercive force rare earth-free MnAlM permanent magnet alloy to obtain a master alloy raw material; (2) Preparation of MnAlM alloy ingots or MnAlM alloy strips A non-consumable vacuum arc furnace is used to place the master alloy raw material into a water-cooled copper crucible, which is then evacuated and filled with an inert gas as a protective gas. The alloy is repeatedly smelted in an inert gas atmosphere, and the ingot is turned over after each smelting to obtain a MnAlM alloy ingot with uniform composition. Alternatively, the surface of the obtained MnAlM alloy ingot is polished and then placed in a quartz tube with a small hole at the bottom. A high vacuum rapid quenching system is used to completely melt the MnAlM alloy ingot in the quartz tube into a liquid state by adjusting the current of the induction coil in an inert gas atmosphere. Finally, the ingot is ejected and falls onto a high-speed rotating water-cooled copper roller and is thrown out to obtain a MnAlM alloy thin strip. (3) Heat treatment The surface of the MnAlM alloy ingot is polished and then placed in a quartz tube, which is vacuum-sealed and then heat-treated to obtain a high-coercivity rare-earth-free MnAlM permanent magnet alloy ingot; or a MnAlM alloy ribbon is placed in a quartz tube, which is vacuum-sealed and then heat-treated to obtain a high-coercivity rare-earth-free MnAlM permanent magnet alloy ribbon.

3. The method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 2, characterized in that, In step (1), based on the mass of Mn in the master alloy raw material, 3 to 5% of Mn raw material is additionally added to the master alloy raw material.

4. The method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 2, characterized in that, In step (2), the inert gas is argon or helium.

5. The method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 2 or 4, characterized in that, The smelting times are 3 to 4 times.

6. The method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 5, characterized in that, The specific process parameters for smelting are as follows: the vacuum degree of the vacuum arc furnace is higher than 1*10 -3 Pa, the current intensity of the vacuum arc furnace is 45 - 55 A, and the smelting time for each time is 3 min.

7. The method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 6, wherein, The smelting times are 3 to 4 times.

8. The method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 2, characterized in that, In step (2), the linear speed of the water-cooled copper roller is 5 to 30 m / s.

9. The preparation method of the high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 2, characterized in that, In step (3), the specific steps of heat treatment of the MnAlM alloy ingot are: placing the MnAlM alloy ingot in a muffle furnace, the heat treatment temperature is 1150-1250°C, and the heat treatment time is 16-20h; after the heat treatment, the MnAlM alloy ingot is quickly placed in ice water for quenching.

10. The method for preparing a high coercivity rare-earth-free MnAlM permanent magnet alloy according to claim 2, characterized in that, In step (3), the specific steps of heat treating the MnAlM alloy strip are as follows: placing the MnAlM alloy strip in a muffle furnace, the heat treatment temperature is 1150-1250°C, and the heat treatment time is 5-50 minutes; after the heat treatment, the MnAlM alloy strip is quickly placed in an ice-water mixture for quenching.

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