Sintered aluminum-nickel-cobalt magnet and preparation method thereof

Abstract

The invention provides a sintered aluminum-nickel-cobalt magnet and a preparation method thereof, and belongs to the field of permanent magnet alloy materials. The preparation method comprises the following steps: weighing required metal raw materials according to the component proportion, obtaining an alloy throwing sheet in a protective gas environment based on a vacuum melting-melt-spinning technology, crushing the alloy throwing sheet, adding an auxiliary agent, and pressing into a pressed blank; carrying out vacuum sintering on the pressed blank, cooling and discharging to obtain a sintered blank; and carrying out heat treatment on the sintered blank under the action of a magnetic field, then carrying out tempering treatment, and finally removing surface oxide skin to obtain the sintered aluminum-nickel-cobalt magnet. According to the preparation method, the preparation process is simplified, the oxygen content of the magnet is reduced, and the uniformity of magnet components is ensured; meanwhile, the magnet prepared through the method has good magnetic performance, for example, the prepared AlNiCo5 alloy has high residual magnetism, and the residual magnetism is 1.2 kGS or above; the coercive force of the AlNiCo8H alloy can be up to 170 kA / m or above.

Description

Technical Field

[0001] This invention relates to the field of permanent magnet alloy material preparation technology, specifically to a sintered aluminum-nickel-cobalt magnet and its preparation method. Background Technology

[0002] AlNiCo permanent magnet alloys have an irreplaceable position in environments with large temperature fluctuations and in precision instruments that have been in long-term service due to their high Curie temperature, low magnetic temperature coefficient, and long-term stability, as well as their excellent corrosion resistance and oxidation resistance.

[0003] The main methods for preparing AlNiCo permanent magnet alloys include casting and powder sintering. Among them, sintered magnets prepared by powder sintering consume less raw materials during manufacturing, have better mechanical properties than cast magnets, have a smooth surface, precise dimensions, and can be directly pressed into complex geometric shapes, reducing the need for subsequent machining. Therefore, they are widely used in industry.

[0004] Current traditional powder sintering methods typically use elemental powders such as Fe, Co, Ni, and Cu, and alloy powders such as CoAl, NbFe, and TiFe as raw materials. Elemental powders are expensive to purchase and require high-temperature hydrogen reduction before entering the mixing process, while alloy powders require smelting, crushing, and ball milling. This makes traditional powder sintering complex, time-consuming, and inherently dangerous. Furthermore, during the sintering process, elemental alloy powders (such as Cu) and alloy powders (such as TiFe) are highly susceptible to oxidation at high temperatures, which can compromise the magnetic properties of the final product. Products sintered using traditional methods also exhibit poor consistency in elemental composition across different parts, as well as lower density and compactness, affecting the overall magnetic properties of the product.

[0005] Chinese Patent Document Announcement No. CN115233111B discloses a high-performance powder-sintered AlNiCo magnetic material and its preparation method. The high-performance powder-sintered AlNiCo magnetic material comprises the following components by mass percentage: Al: 5-7wt%, Ni: 12-14wt%, Cu: 3-4wt%, Co: 36-38wt%, Nb: 0.5-0.8wt%, Ti: 5.5-7wt%, with the remainder being Fe. Cu, Ti, Fe, a portion of Co, and Nb metal raw materials are vacuum-melted and rapidly solidified to obtain sheet A; a portion of Al ingots and the remaining Co metal raw materials are vacuum-melted and rapidly solidified to obtain sheet B; the remaining Al and Ni are vacuum-melted and rapidly solidified to obtain sheet C. Sheets A, B, and C are all vacuum-annealed. Then, the three sheets are sequentially crushed, coarsely crushed, and finely ground using an air jet mill. 0.5wt% aluminum stearate is added, and the mixture is pressed into shape, followed by vacuum sintering, magnetic field heat treatment, and four-stage tempering. The remanence of this magnetic material is 0.855-865 kGS, the coercivity is 120-124 kA / m, and the magnetic energy product is 43.1-47.8 kJ / m. 3 However, there are issues with the remanence and coercivity, which need further improvement. Furthermore, the vacuum sintering process at 1330-1350℃ with a holding time of 4.5-6 hours presents a problem of long high-temperature holding times. Summary of the Invention

[0006] In view of this, the present invention provides a sintered AlNiCo magnet and its preparation method, which simplifies the preparation process, reduces the oxygen content of the magnet, and ensures the uniformity of the magnet composition. The magnet prepared by the present invention has good magnetic properties, such as the AlNiCo5 alloy having a high remanence of over 1.2 kGS; and the AlNiCo8H alloy having a coercivity of up to 170 kA / m.

[0007] To achieve the above objectives, the present invention provides a method for preparing sintered AlNiCo magnets, comprising the following steps: (1) Weigh the required metal raw materials according to the composition ratio, and obtain alloy sheets by vacuum melting-spinning technology under a protective gas environment; (2) After the alloy slabs are crushed, additives are added, and finally they are pressed into a compact; (3) Vacuum sinter the pressed billet, cool it and remove it from the furnace to obtain a sintered blank; (4) The sintered blank is heat-treated under the action of a magnetic field, then tempered, and finally the surface oxide scale is removed to obtain sintered aluminum nickel cobalt magnet.

[0008] The preparation method of this invention, under a protective gas environment, is based on vacuum melting-spinning technology. Specifically, it involves first evacuating the vacuum, then introducing a protective gas, and then performing melting-spinning. That is, melting is first performed under high vacuum followed by melting in a protective gas atmosphere such as an inert gas. This avoids high-temperature oxidation and impurity inclusions in the alloy. The rapid solidification using vacuum melting-spinning effectively avoids elemental segregation phenomena in traditional methods, resulting in alloy sheets with uniform composition. The oxygen content of the sintered AlNiCo magnets prepared by this invention is less than 1500 ppm. Moreover, this invention directly produces metal sheets from all metal raw materials together, eliminating the need for grouping the metals for sheet preparation and for vacuum annealing, thus simplifying the preparation process.

[0009] In the preparation method of the present invention, the alloy powder obtained after the alloy sheet is crushed has a uniform composition and melting point, which avoids the large difference in melting points of various metal / alloy powders in the traditional preparation method, and the uneven composition and deformation caused by specific gravity segregation during the sintering process.

[0010] In step (2), the additive is a lubricant.

[0011] Based on the above improvements, combined with vacuum sintering, magnetic field heat treatment, and tempering, it is beneficial to improve the magnetic properties of sintered AlNiCo magnets.

[0012] Further, in step (3), the vacuum sintering method includes: heating from room temperature to 400-500℃ at a rate of 3-10℃ / min and holding for 10-60 min; heating to 650-800℃ and holding for 60-180 min; heating to 1100-1250℃ and holding for 10-60 min; heating to 1250-1400℃ and holding for 60-180 min.

[0013] Based on ensuring that the sintered AlNiCo magnet has good magnetic properties, the preparation method of the present invention requires only 60 to 180 minutes of holding at 1330 to 1340°C during the vacuum sintering process. Compared with the existing literature CN115233111B which requires 4.5 to 5 hours of holding, the holding time at high temperature is significantly reduced, which is beneficial to saving production costs.

[0014] Further, in step (2), the alloy slab is crushed into coarse powder of 50~200μm and fine powder of 4~10μm. The coarse powder and fine powder are mixed evenly at a mass ratio of 0.2~5:1. Additives are added during the mixing process, and finally the mixture is pressed into a compact.

[0015] The two fine powders are mixed evenly in a ratio of 0.2 to 5:1. This combination of coarse and fine powders improves the compressibility and shape retention, while also increasing the density to over 98% and reaching 7.2 g / cm³. 3The above. If only the alloy wafers are crushed into coarse powder of 50~200μm, and the compact is also made entirely of coarse powder, the density and compactness of the prepared sintered AlNiCo magnets will decrease, with a density of around 7g / cm³. 3 It is around 96%, with a density of less than 98%.

[0016] Furthermore, the additive is aluminum stearate, and the amount of aluminum stearate added is 0.1~2.0 wt.% of the total mass of coarse and fine powders. Adding aluminum stearate is beneficial for pressing coarse and fine powders into blanks.

[0017] Further, in step (2), the alloy slabs are mechanically crushed into coarse powder. Part of the coarse powder is refined into coarse powder by ball milling, and the other part is refined into fine powder by air jet milling. In the ball milling, the ball-to-material ratio is 10:1 to 50:1, the ball mill speed is 50-250 rpm, and the ball milling time is 3-50 h to obtain coarse powder of 50-200 μm. In the air jet milling, the grinding chamber weight is 3-10 kg, the grinding chamber pressure is 450-700 kPa, and the sorting speed is 1500-4500 rpm to obtain fine powder of 4-10 μm.

[0018] Further, in step (4), the method of heat treatment under the action of a magnetic field includes: preheating the sintered blank at 600~850℃ for 20~60 min, then dissolving it at 1200~1300℃ for 10~50 min, followed by air cooling for 0.2~5 min, then cooling it to below 600℃ or holding it at 750~850℃ for 15~60 min in a magnetic field of 2000~10000 Gs, and then air cooling it to room temperature in a magnetic field.

[0019] Further, in step (4), the method of heat treatment under the action of a magnetic field includes: preheating the sintered blank at 620~750℃ for 20~50 min, then dissolving it at 1250~1300℃ for 25~40 min, followed by air cooling for 0.5~3 min, then cooling it to below 600℃ or holding it at 760~800℃ for 25~40 min in a magnetic field of 3000~8000 Gs, and then air cooling it to room temperature in a magnetic field.

[0020] Furthermore, in step (4), the tempering process includes: gas pressure ≤ 10 -1 Under Pa or protective gas protection conditions, the furnace is held at 630~680℃ for 1~6 h, at 600~620℃ for 3~10 h, at 570~590℃ for 5~20 h, and at 500~560℃ for 10~30 h, and then cooled to room temperature with the furnace.

[0021] Furthermore, in step (4), the tempering process includes: gas pressure ≤ 10 -1Under Pa or protective gas protection conditions, the furnace is held at 645~670℃ for 1.5~5 h, at 600~615℃ for 3~7 h, at 570~580℃ for 5~12 h, and at 500~540℃ for 10~20 h, and then cooled to room temperature with the furnace.

[0022] Furthermore, in step (1), the method of vacuum melting-spinning technology includes: first evacuating to a vacuum level of 2×10⁻⁶. -2 Below Pa, then a protective gas is introduced to 5-5×10 Pa. 4 Pa, the metal raw materials are smelted; wherein the smelting power is 10-200 kW, the holding time is 10-100 min, and the molten steel is obtained at a temperature of 1550~1850℃; then the molten steel is poured onto a water-cooled roller for rapid quenching, the roller speed is 20-100 rpm, and the resulting alloy slabs are 0.1~0.8 mm thick, with an oxygen content of less than 500 ppm, and the crystal structure of the alloy slabs is a body-centered cubic structure.

[0023] Further, in step (1), the method of vacuum melting-spinning technology is as follows: first, evacuate to 2×10 -2 Below Pa, then a protective gas is introduced to 10. 2 -2×10 4 Pa involves melting metal raw materials at a power of 40-130 kW and holding for 15-40 minutes to obtain molten steel at a temperature of 1650-1800℃. The molten steel is then poured onto a water-cooled roller for rapid quenching at a speed of 50-80 rpm, resulting in alloy slabs with a thickness of 0.3-0.65 mm, an oxygen content of less than 500 ppm, and a body-centered cubic crystal structure.

[0024] Furthermore, in step (1), the metal raw material has a purity of ≥99%, and its shape is one or more of metal sheets, metal ingots, and metal rods, and its composition may be elemental or / and alloy.

[0025] Furthermore, in step (2), the pressure for pressing the compact is 3~15 T.

[0026] A sintered AlNiCo magnet is prepared using the aforementioned preparation method.

[0027] Furthermore, the sintered AlNiCo magnet comprises the following components by mass percentage: 5-10% Al, 12-15% Ni, 25-40% Co, 0-10% Ti, Cu≤5%, 0-1% Nb, and the balance being Fe.

[0028] Furthermore, the sintered AlNiCo8 or AlNiCo8H alloy comprises the following components by mass percentage: 6-9% Al, 12-15% Ni, 35-40% Co, 5-9.5% Ti, 1-4% Cu, 0-1% Nb, and the balance being Fe. Alternatively, the sintered aluminum-nickel-cobalt magnet may be an AlNiCo5 alloy comprising the following components by mass percentage: 6-9% Al, 12-15% Ni, 25-30% Co, 1-4% Cu, 0-1% Nb, and the balance being Fe.

[0029] AlNiCo5 alloy, through the above-mentioned component content settings, exhibits high remanence, exceeding 1.2 kGS.

[0030] Furthermore, the sintered AlNiCo8 or AlNiCo8H alloy comprises the following components by mass percentage: 8% Al, 14% Ni, 37-40% Co, 6-9.5% Ti, 3% Cu, 0.5% Nb, and the balance being Fe.

[0031] The above-mentioned component content settings give the AlNiCo8 alloy high coercivity, which is above 140 kA / m.

[0032] The protective gas in this application is an inert gas, argon, helium, or a mixture of both.

[0033] The above-described technical solution of the present invention has at least the following beneficial effects: (1) In the preparation method of the present invention, the alloy sheet is directly crushed and mixed with additives before the subsequent pressing, sintering and other steps are carried out. This avoids the relatively dangerous hydrogen reduction step of elemental powder in the traditional method. It also eliminates the more complicated melting-crushing-ball milling steps and mixing steps of elemental powder and binary alloy powder required for the preparation of binary alloy powder in the traditional method. This can significantly improve production efficiency and shorten the production cycle.

[0034] (2) In traditional preparation methods, elemental alloy powders (such as Cu) and binary alloy powders (such as TiFe) are easily oxidized in high-temperature environments, forming oxide inclusions in the magnet and thus affecting the magnet's performance. In this preparation method, AlNiCo alloy powder with strong oxidation resistance can be directly obtained, which can effectively reduce the oxygen content in the final product. The oxygen content of the sintered AlNiCo magnet is less than 1500ppm, which helps to improve the magnet's performance.

[0035] (3) The sintered AlNiCo magnets prepared by this invention have high remanence (above 1.2 kGS) in type 5 AlNiCo magnets (AlNiCo5 alloy) and high coercivity (above 170 kA / m) in type 8 AlNiCo magnets (AlNiCo8H alloy), and the magnets have good magnetic properties. Moreover, the elemental composition of each part of the entire magnet is relatively consistent, ensuring the uniformity of the magnetic properties of each part of the magnet. Attached Figure Description

[0036] Figure 1 The XRD pattern of the alloy sheet obtained in Example 1; Figure 2 This is a statistical diagram showing the thickness distribution of the alloy sheet obtained in Example 1. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0038] Example 1 This embodiment describes eight methods for preparing sintered AlNiCo magnets.

[0039] A method for preparing a sintered AlNiCo magnet includes the following steps: (1) The raw material of 50kg metal ingot, by weight percentage, has the following composition: 7% Al, 13% Ni, 35% Co, 6% Ti, 3% Cu, 0.5% Nb, and the balance Fe. The metal ingot raw material is placed in an induction melting crucible and evacuated to 10°C. -2 Pa, stop evacuation and purge with argon protective gas to 10. 2 Pa; adjust the heating power to 80 kW, wait for the metal in the crucible to completely melt, and hold for 20 min to obtain a molten metal at approximately 1650℃; set the rotation speed of the water-cooled copper roller to 55 rpm, pour the molten metal onto it, and alloy flakes can be obtained in the collection tray below the copper roller, such as Figure 1 XRD results indicate that the crystal structure of the alloy wafers is a body-centered cubic phase. Figure 2 Thickness statistics of the alloy sprue show that its thickness is 0.3~0.65mm, and the oxygen content of the sprue is only 306 ppm as measured by an oxygen analyzer.

[0040] (2) The alloy slabs are first mechanically crushed into coarse powder. Then, a portion of the coarse powder is ball-milled at a ball-to-material ratio of 30:1, a ball milling speed of 200 rpm, and a ball milling time of 15 h to obtain coarse powder. The other portion of the coarse powder is subjected to an air jet mill at a milling chamber pressure of 650 kPa, a sorting speed of 3000 rpm, and a milling chamber weight of 5 kg to obtain fine powder. The coarse powder and fine powder are mixed in a 1:1 ratio, and then 0.5 wt.% of aluminum stearate is added based on the total weight of the alloy powder (coarse powder and fine powder) and mixed evenly to obtain a mixed powder. The mixed powder is then pressed under a pressure of 6 T to obtain a cylindrical blank with a size of Φ10×10 mm.

[0041] (3) The obtained compact is placed in a vacuum sintering furnace for sintering, with a vacuum degree of 10. -2 Pa, the sintering process is as follows: the temperature is increased from room temperature to 420℃ at a rate of 5℃ / min and held for 40 min; the temperature is increased to 700℃ at a rate of 5℃ / min and held for 150 min; the temperature is increased to 1200℃ at a rate of 1℃ / min and held for 40 min; the temperature is increased to 1340℃ at a rate of 4℃ / min and held for 120 min; then the furnace is cooled to room temperature to obtain the sintered blank. (4) The sintered blank is then subjected to magnetic field heat treatment. The heat treatment regime is as follows: the blank is placed in a resistance furnace at 650°C for 35 min, then the blank is transferred to a resistance furnace at 1290°C for 40 min for solidification, then the blank is taken out and air-cooled for 1 min, then the blank is transferred to a magnetic field with an intensity of 4000 Gs and kept at 780°C for 25 min, and then air-cooled to room temperature in the magnetic field. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 5 × 10⁻⁶. -2 Under Pa conditions, the furnace is held at 645℃ for 1.5 h, 610℃ for 4.5 h, 575℃ for 6 h, and 510℃ for 16 h, and then cooled to room temperature in the furnace. The sintered AlNiCo magnet is obtained by grinding to remove the surface oxide scale.

[0042] Example 2 This embodiment describes five methods for preparing AlNiCo magnets, with corresponding adjustments made to the component content.

[0043] A method for preparing a sintered AlNiCo magnet includes the following steps: (1) Weigh 100 kg of a metal ingot raw material with a composition of 8% Al, 15% Ni, 25% Co, 4% Cu, 0.2% Nb, and the balance Fe, and place it in an induction melting crucible. Evacuate to 100°C. -3 Pa, stop evacuation and purge with argon protective gas to 10. 3Pa. Adjust the heating power to 70 kW, wait for the metal in the crucible to completely melt, and hold for 35 min to obtain a molten metal at approximately 1700°C. Set the rotation speed of the water-cooled copper roller to 60 rpm, pour the superheated molten metal onto it, and obtain an alloy strip in the collection tray below the copper roller; (2) The alloy slabs are first mechanically crushed into coarse powder. Then, a portion of the coarse powder is ball-milled at a ball-to-material ratio of 20:1, a ball milling speed of 250 rpm, and a ball milling time of 20 h to obtain coarse powder. The other portion of the coarse powder is subjected to an air jet mill at a milling chamber pressure of 600 kPa, a sorting speed of 2200 rpm, and a milling chamber weight of 7 kg to obtain fine powder. The coarse powder and fine powder are mixed in a 2:1 ratio, and then 0.7 wt.% aluminum stearate of the total weight of alloy powder is added to the mixer and mixed evenly to obtain a mixture. The mixture is then pressed under a pressure of 7.5 T to obtain a cylindrical blank with a size of Φ15×20 mm. (3) The obtained compact is placed in a vacuum sintering furnace for sintering, with a vacuum degree of 3×10 -2 Pa, the sintering process is as follows: the temperature is increased from room temperature to 480℃ at a rate of 4℃ / min and held for 20 min; the temperature is increased to 700℃ and held for 120 min; the temperature is increased to 1150℃ and held for 50 min; the temperature is increased to 1330℃ and held for 140 min; then the furnace is cooled to room temperature to obtain the sintered blank. (4) The sintered blank is then subjected to magnetic field heat treatment. The heat treatment regime is as follows: the sintered blank is placed in a resistance furnace at 700°C for 20 min to preheat, then the blank is transferred to a resistance furnace at 1300°C for 30 min to solidify, then the blank is taken out and air-cooled for 0.5 min, then the blank is transferred to a magnetic field with an intensity of 6000 Gs, wrapped with heat insulation cotton and air-cooled to below 600°C, then the heat insulation cotton is removed and air-cooled to room temperature in the magnetic field. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 2×10⁻⁶. -2 Under Pa conditions, the furnace was kept at 660℃ for 3 h, 615℃ for 4 h, 580℃ for 5 h, and 540℃ for 10 h, and then cooled to room temperature with the furnace. After grinding to remove the surface oxide scale, sintered aluminum-nickel-cobalt magnets can be obtained.

[0044] Comparative Example 1 This comparative example is basically the same as Example 1, except that: according to the same formula as Example 1, CoAl alloy powder, NbFe alloy powder, and TiFe alloy powder, based on the Al, Nb, and Ti content ratios, were weighed respectively, wherein the CoAl alloy contained 75% Co, the NbFe alloy contained 40% Nb by mass, and the TiFe alloy contained 25% Ti. Then, the remaining required weights of Fe, Co, Ni, and Cu elemental powders were weighed. The elemental powders were placed in a hydrogen reduction furnace at 600°C for 4 hours and then cooled to room temperature with the furnace. The treated metal elemental powders and alloy powders were placed in a mixer, and 0.5 wt.% of aluminum stearate was added to the mixture. The mixture was then pressed under 6 T pressure to obtain a cylindrical blank with dimensions of Φ10×10 mm. The resulting compact was placed in a vacuum sintering furnace for sintering at a vacuum degree of 3 × 10⁻⁶. -2 Pa, the sintering process is as follows: the temperature is increased from room temperature to 480℃ at a rate of 4℃ / min and held for 20 min; the temperature is increased to 700℃ at a rate of 7℃ / min and held for 120 min; the temperature is increased to 1150℃ at a rate of 2℃ / min and held for 50 min; the temperature is increased to 1330℃ at a rate of 2℃ / min and held for 140 min; then the furnace is cooled to room temperature to obtain the sintered blank. The sintered blank was then subjected to magnetic field heat treatment. The heat treatment regime was as follows: the sintered blank was placed in a resistance furnace at 700°C for 20 min to preheat, then the blank was transferred to a resistance furnace at 1300°C for 30 min to solidify, then the blank was taken out and air-cooled for 0.5 min, and then the blank was transferred to a magnetic field with an intensity of 6000 Gs to cool to room temperature. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 2×10⁻⁶. -2 Under Pa conditions, the furnace was kept at 660℃ for 3 h, 615℃ for 4 h, 580℃ for 5 h, and 540℃ for 10 h, and then cooled to room temperature with the furnace. After grinding to remove the surface oxide scale, sintered aluminum-nickel-cobalt magnets can be obtained.

[0045] Table 1 Oxygen content of sintered AlNiCo magnets

[0046] The elemental composition of the upper, middle and lower parts of the magnet was tested using inductively coupled plasma spectrometry (ICP). As shown in Table 2, the elemental composition of each part of Comparative Example 1 differs greatly, while the elemental composition of each part of Example 1 is similar and also close to the nominal composition, indicating that the elemental composition of the magnet prepared by the present invention has good consistency.

[0047] Table 2. Elemental composition results of sintered aluminum-nickel-cobalt magnets

[0048] Example 3 The composition includes 7.5% Al, 13% Ni, 36% Co, 5.5% Ti, 3% Cu, 0% Nb, and the balance is Fe.

[0049] (1) Weigh 110 kg of metal ingot raw materials according to the formula, place them in an induction melting crucible, and evacuate to 100°C. -2 Pa, stop evacuation and purge with argon protective gas to 2 × 10⁻⁶. 4 Pa; adjust the heating power to 100 kW, wait for the metal in the crucible to melt completely, and keep it at the temperature for 30 min to obtain a molten metal at about 1700℃; set the rotation speed of the water-cooled copper roller to 50 rpm, pour the molten metal onto it, and obtain alloy splatters in the collection tray below the copper roller.

[0050] (2) The alloy slabs are first mechanically crushed into coarse powder. Then, a portion of the coarse powder is ball-milled at a ball-to-material ratio of 40:1, a ball milling speed of 150 rpm, and a ball milling time of 15 h to obtain coarse powder. The other portion of the coarse powder is subjected to an air jet mill at a milling chamber pressure of 700 kPa, a sorting speed of 2500 rpm, and a milling chamber weight of 5 kg to obtain fine powder. The coarse powder and fine powder are mixed in a 1:1 ratio, and then 0.7 wt.% of aluminum stearate is added according to the total weight of the alloy powder (coarse powder and fine powder) and mixed evenly to obtain a mixed powder. The mixed powder is then pressed under a pressure of 7 T to obtain a cylindrical blank with a size of Φ10×10 mm.

[0051] (3) The obtained compact is placed in a vacuum sintering furnace for sintering, with a vacuum degree of 2×10⁻⁶. -2 Pa, the sintering process is as follows: the temperature is increased from room temperature to 470℃ at a rate of 5℃ / min and held for 30 min; the temperature is increased to 750℃ and held for 180 min; the temperature is increased to 1180℃ and held for 60 min; the temperature is increased to 1350℃ and held for 180 min; then the temperature is cooled to room temperature in the furnace to obtain the sintered blank. (4) The sintered blank is then subjected to magnetic field heat treatment. The heat treatment regime is as follows: the blank is placed in a resistance furnace at 700°C for 50 min, then the blank is transferred to a resistance furnace at 1300°C for 30 min to solidify, then the blank is taken out and air-cooled for 1.5 min, then the blank is transferred to a magnetic field with an intensity of 6000 Gs and held at 760°C for 40 min, and then air-cooled to room temperature in the magnetic field. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 2×10⁻⁶. -2Under Pa conditions, the furnace is held at 660℃ for 2 h, 600℃ for 6 h, 580℃ for 10 h, and 500℃ for 20 h, and then cooled to room temperature in the furnace. The sintered aluminum-nickel-cobalt magnet is obtained by grinding to remove the surface oxide scale.

[0052] Example 4 The composition includes 8% Al, 14% Ni, 37% Co, 6% Ti, 3% Cu, 0.5% Nb, and the balance Fe.

[0053] (1) Weigh out 60 kg of metal ingot raw materials according to the formula, place them in an induction melting crucible, and evacuate to 4 × 10⁻⁶ kg. -3 Pa, stop evacuation and purge with argon protective gas to 2 × 10⁻⁶. 4 Pa; adjust the heating power to 100 kW, wait for the metal in the crucible to melt completely, and keep it at the temperature for 35 minutes to obtain a molten metal at about 1750°C; set the rotation speed of the water-cooled copper roller to 75 rpm, pour the molten metal onto it, and alloy splatters can be obtained in the collection tray below the copper roller.

[0054] (2) The alloy slabs were first mechanically crushed into coarse powder. Then, a portion of the coarse powder was ball-milled at a ball-to-material ratio of 35:1, a ball milling speed of 150 rpm, and a ball milling time of 20 h to obtain coarse powder. The other portion of the coarse powder was subjected to an air jet mill at a milling chamber pressure of 600 kPa, a sorting speed of 3500 rpm, and a milling chamber weight of 6 kg to obtain fine powder. The coarse powder and fine powder were mixed in a ratio of 4:1, and then 0.7 wt.% of aluminum stearate was added according to the total weight of the alloy powder (coarse powder and fine powder) and mixed evenly to obtain a mixed powder. The mixed powder was then pressed under a pressure of 12 T to obtain a cylindrical blank with a size of Φ10×20 mm.

[0055] (3) The obtained pressed blank is placed in a vacuum sintering furnace for sintering, with a vacuum degree of 5×10 -3 Pa, the sintering process is as follows: the temperature is increased from room temperature to 480℃ at a rate of 4℃ / min and held for 40 min; the temperature is increased to 800℃ and held for 120 min; the temperature is increased to 1200℃ and held for 50 min; the temperature is increased to 1340℃ and held for 140 min; then the furnace is cooled to room temperature to obtain the sintered blank. (4) The sintered blank is then subjected to magnetic field heat treatment. The heat treatment regime is as follows: the blank is placed in a resistance furnace at 730°C for 40 min, then the blank is transferred to a resistance furnace at 1260°C for 35 min for solidification, then the blank is taken out and air-cooled for 3 min, then the blank is transferred to a magnetic field with an intensity of 4000 Gs and held at 770°C for 30 min, and then air-cooled to room temperature in the magnetic field. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 2×10⁻⁶. -2 Under Pa conditions, the furnace is held at 655℃ for 4 h, 610℃ for 6 h, 575℃ for 10 h, and 500℃ for 18 h, and then cooled to room temperature in the furnace. The sintered aluminum-nickel-cobalt magnet is obtained by grinding to remove the surface oxide scale.

[0056] Example 5 This embodiment describes a method for preparing AlNiCo8H magnets, with corresponding adjustments made to the component content.

[0057] The composition includes 8% Al, 14% Ni, 40% Co, 9.5% Ti, 3% Cu, 0.5% Nb, and the remainder Fe.

[0058] (1) Weigh out 80 kg of metal ingot raw materials according to the formula, place them in an induction melting crucible, and evacuate to 8 × 10⁻⁶. -3 Pa, stop evacuation and purge with argon protective gas to 7 × 10⁻⁶. 3 Pa; adjust the heating power to 130 kW, wait for the metal in the crucible to melt completely, and keep it at the temperature for 40 minutes to obtain a molten metal at about 1800℃; set the rotation speed of the water-cooled copper roller to 70 rpm, pour the molten metal onto it, and alloy splatters can be obtained in the collection tray below the copper roller.

[0059] (2) The alloy slabs were first mechanically crushed into coarse powder. Then, a portion of the coarse powder was ball-milled at a ball-to-material ratio of 30:1, a ball milling speed of 200 rpm, and a ball milling time of 11 h to obtain coarse powder. The other portion of the coarse powder was subjected to an air jet mill at a milling chamber pressure of 550 kPa, a sorting speed of 3300 rpm, and a milling chamber weight of 7 kg to obtain fine powder. The coarse powder and fine powder were mixed in a 3:1 ratio, and then 0.3 wt.% of aluminum stearate was added based on the total weight of the alloy powder (coarse powder and fine powder) and mixed evenly to obtain a mixed powder. The mixed powder was then pressed under a pressure of 10 T to obtain a cylindrical blank with dimensions of Φ15×20 mm.

[0060] (3) The obtained pressed blank is placed in a vacuum sintering furnace for sintering, with a vacuum degree of 9×10⁻⁶. -3 Pa, the sintering process is as follows: the temperature is increased from room temperature to 500℃ at a rate of 5℃ / min and held for 30 min; the temperature is increased to 780℃ and held for 100 min; the temperature is increased to 1180℃ and held for 60 min; the temperature is increased to 1330℃ and held for 160 min; then the furnace is cooled to room temperature to obtain the sintered blank. (4) The sintered blank is then subjected to magnetic field heat treatment. The heat treatment regime is as follows: the blank is placed in a resistance furnace at 750°C for 30 min, then the blank is transferred to a resistance furnace at 1290°C for 30 min for solidification, then the blank is taken out and air-cooled for 3 min, then the blank is transferred to a magnetic field with an intensity of 5000 Gs and held at 800°C for 25 min, and then air-cooled to room temperature in the magnetic field. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 4 × 10⁻⁶. -2 Under Pa conditions, the furnace is held at 670℃ for 3 h, 610℃ for 7 h, 570℃ for 12 h, and 510℃ for 15 h, and then cooled to room temperature in the furnace. The sintered aluminum-nickel-cobalt magnet is obtained by grinding to remove the surface oxide scale.

[0061] Example 6 This embodiment is basically the same as Embodiment 2, except that the composition is 8% Al, 15% Ni, 27% Co, 4% Cu, 0.2% Nb, and the balance Fe. (1) 90 kg of metal raw materials according to the composition formula were placed in an induction melting crucible. A vacuum of 8 × 10⁻⁶ was applied. -3 Pa, stop evacuation and purge with argon protective gas to 7 × 10⁻⁶. 3 Pa. Adjust the heating power to 40 kW, wait for the metal in the crucible to completely melt, and hold for 45 min to obtain a molten metal at approximately 1650°C. Set the rotation speed of the water-cooled copper roller to 80 rpm, pour the superheated molten metal onto it, and obtain an alloy strip in the collection tray below the copper roller; (2) The alloy slabs are first mechanically crushed into coarse powder. Then, a portion of the coarse powder is ball-milled at a ball-to-material ratio of 50:1, a ball milling speed of 80 rpm, and a ball milling time of 30 h to obtain coarse powder. The other portion of the coarse powder is subjected to an air jet mill at a milling chamber pressure of 650 kPa, a sorting speed of 2500 rpm, and a milling chamber weight of 6 kg to obtain fine powder. The coarse powder and fine powder are mixed in a 3:1 ratio, and then 0.4 wt.% aluminum stearate of the total weight of alloy powder is added to the mixer and mixed evenly to obtain a mixture. The mixture is then pressed under a pressure of 9 T to obtain a cylindrical blank with a size of Φ10×15 mm. (3) The obtained compact is placed in a vacuum sintering furnace for sintering, with a vacuum degree of 2×10⁻⁶. -2 Pa, the sintering process is as follows: the temperature is increased from room temperature to 440℃ at a rate of 5℃ / min and held for 45 min; the temperature is increased to 750℃ and held for 100 min; the temperature is increased to 1200℃ and held for 60 min; the temperature is increased to 1370℃ and held for 170 min; then the furnace is cooled to room temperature to obtain sintered blanks. (4) The sintered blank is then subjected to magnetic field heat treatment. The heat treatment regime is as follows: the sintered blank is placed in a resistance furnace at 750°C for 40 min, then the blank is transferred to a resistance furnace at 1270°C for 25 min for solidification, then the blank is taken out and air-cooled for 1 min, then the blank is transferred to a magnetic field with an intensity of 8000 Gs, wrapped with heat insulation cotton and air-cooled to below 600°C, then the heat insulation cotton is removed and air-cooled to room temperature in the magnetic field. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 6 × 10⁻⁶. -2 Under Pa conditions, the furnace was kept at 650℃ for 5 h, 610℃ for 3 h, 570℃ for 10 h, and 520℃ for 20 h, and then cooled to room temperature with the furnace. After grinding to remove the surface oxide scale, sintered aluminum-nickel-cobalt magnets can be obtained.

[0062] Example 7 The composition is 6% Al, 13% Ni, 27% Co, 4% Cu, 0.2% Nb, and the balance Fe.

[0063] (1) 150 kg of metal raw materials according to the composition formula were placed in an induction melting crucible. A vacuum of 2 × 10⁻⁶ was applied. -2 Pa, stop evacuation and purge with argon protective gas to 4 × 10⁻⁶. 4 Pa. Adjust the heating power to 80 kW, wait for the metal in the crucible to completely melt, and hold for 15 min to obtain a molten metal at approximately 1600°C. Set the rotation speed of the water-cooled copper roller to 65 rpm, pour the superheated molten metal onto it, and obtain an alloy strip in the collection tray below the copper roller; (2) The alloy slabs were first mechanically crushed into coarse powder. Then, a portion of the coarse powder was ball-milled at a ball-to-material ratio of 35:1, a ball milling speed of 150 rpm, and a ball milling time of 16 h to obtain coarse powder. The other portion of the coarse powder was subjected to an air jet mill at a milling chamber pressure of 700 kPa, a sorting speed of 2900 rpm, and a milling chamber weight of 9 kg to obtain fine powder. The coarse powder and fine powder were mixed at a ratio of 0.8:1, and then 1 wt.% aluminum stearate of the total weight of the alloy powder was added to the mixer and mixed evenly to obtain a mixture. The mixture was then pressed under a pressure of 12 T to obtain a cylindrical blank with a size of Φ20×25 mm. (3) The obtained compact is placed in a vacuum sintering furnace for sintering, with a vacuum degree of 10. -3 Pa, the sintering process is as follows: the temperature is increased from room temperature to 490℃ at a rate of 5℃ / min and held for 55 min; the temperature is increased to 700℃ and held for 150 min; the temperature is increased to 1180℃ and held for 45 min; the temperature is increased to 1380℃ and held for 150 min; then the temperature is cooled to room temperature in the furnace to obtain the sintered blank. (4) The sintered blank is then subjected to magnetic field heat treatment. The heat treatment regime is as follows: the sintered blank is placed in a resistance furnace at 620°C for 40 min, then the blank is transferred to a resistance furnace at 1250°C for 35 min for solidification, then the blank is taken out and air-cooled for 1 min, then the blank is transferred to a magnetic field with an intensity of 3000 Gs, wrapped with insulation cotton and air-cooled to below 600°C, then the insulation cotton is removed and air-cooled to room temperature in the magnetic field. Then, a multi-stage tempering process is performed, with the tempering regime being: at a pressure of 2×10⁻⁶. -2 Under Pa conditions, the furnace is held at 655℃ for 4 h, 615℃ for 5 h, 580℃ for 8 h, and 510℃ for 15 h, and then cooled to room temperature in the furnace. The sintered aluminum-nickel-cobalt magnet is obtained by grinding to remove the surface oxide scale.

[0064] Comparative Example 2 This comparative example is basically the same as Example 1, except that the powder is not mixed with gas milling, but the other processes are the same. That is, in step (2), the alloy slabs are first mechanically crushed into coarse powder, and the coarse powder is ball-milled with a ball-to-material ratio of 30:1, a ball milling speed of 200 rpm, and a ball milling time of 15 h to obtain coarse powder. 0.5 wt.% of aluminum stearate is added to the coarse powder and mixed evenly to obtain a mixed powder. Then, the mixed powder is pressed under a pressure of 6 T to obtain a compact with a size of Φ10×10 mm.

[0065] Table 3. Magnetic property test results of sintered AlNiCo magnets

[0066] The sintered AlNiCo magnets prepared in Examples 2, 5, and 6 are all AlNiCo5 magnets with high remanence, above 1.2 kGS. The sintered AlNiCo magnets prepared in Examples 1, 3, 4, and 5 are all AlNiCo magnets of type 8, with the AlNiCo8H magnet in Example 5 having the highest coercivity of over 170 kA / m.

[0067] As shown in Table 4, compared with Comparative Example 2, Example 1 showed improved density and compactness, with the compactness reaching over 98%. Therefore, the preparation method of this invention based on vacuum melting-spinning technology-coarse and fine powder pressing is beneficial for improving the density and compactness of the magnet.

[0068] Table 4 Density and packing density of sintered AlNiCo magnets

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the implementation of the invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a sintered AlNiCo magnet, characterized in that, Includes the following steps: (1) Weigh the required metal raw materials according to the composition ratio, and obtain alloy sheets by vacuum melting-spinning technology under a protective gas environment; (2) After the alloy slabs are crushed, additives are added and they are pressed into blanks; (3) Vacuum sinter the pressed billet, cool it and remove it from the furnace to obtain a sintered blank; (4) The sintered blank is heat-treated under the action of a magnetic field, then tempered, and finally the surface oxide scale is removed to obtain sintered aluminum nickel cobalt magnet.

2. The preparation method according to claim 1, characterized in that, In step (3), the vacuum sintering method includes: heating from room temperature to 400-500℃ at a rate of 3-10℃ / min and holding for 10-60 min; heating to 650-800℃ and holding for 60-180 min; heating to 1100-1250℃ and holding for 10-60 min; heating to 1250-1400℃ and holding for 60-180 min.

3. The preparation method according to claim 1 or 2, characterized in that, In step (2), the alloy slab is crushed into coarse powder of 50~200μm and fine powder of 4~10μm. The coarse powder and fine powder are mixed evenly at a mass ratio of 0.2~5:

1. Additives are added during the mixing process, and finally the mixture is pressed into a compact.

4. The preparation method according to claim 3, characterized in that, The additive is aluminum stearate, and the amount of aluminum stearate added is 0.1~2.0 wt.% of the total mass of coarse and fine powder.

5. The preparation method according to claim 1 or 2, characterized in that, In step (4), the heat treatment under the action of a magnetic field includes: preheating the sintered blank at 600~850℃ for 20~60 min, then dissolving it at 1200~1300℃ for 10~50 min, followed by air cooling for 0.2~5 min, then cooling it to below 600℃ or holding it at 750~850℃ for 15~60 min in a magnetic field of 2000~10000 Gs, and then air cooling it to room temperature in a magnetic field.

6. The preparation method according to claim 1 or 2, characterized in that, In step (4), the tempering process is as follows: gas pressure ≤ 10 -1 Under Pa or protective gas protection conditions, the furnace is held at 630~680℃ for 1~6 h, at 600~620℃ for 3~10 h, at 570~590℃ for 5~20 h, and at 500~560℃ for 10~30 h, and then cooled to room temperature with the furnace.

7. The preparation method according to claim 1 or 2, characterized in that, In step (1), the vacuum melting-spinning technique is as follows: first, evacuate to 2×10 -2 Below Pa, then a protective gas is introduced to 5-5×10 Pa. 4 Pa involves smelting and rapidly solidifying metal raw materials.

8. A sintered AlNiCo magnet, characterized in that: Prepared using the preparation method described in any one of claims 1-7.

9. A sintered aluminum-nickel-cobalt magnet according to claim 8, characterized in that: It includes the following components by mass percentage: 5-10% Al, 12-15% Ni, 25-40% Co, 0-10% Ti, Cu≤5%, 0-1% Nb, and the balance being Fe.

10. A sintered AlNiCo magnet according to claim 2, characterized in that, The sintered AlNiCo8 or AlNiCo8H alloy comprises the following components by mass percentage: 6-9% Al, 12-15% Ni, 35-40% Co, 5-9.5% Ti, 1-4% Cu, 0-1% Nb, and the balance being Fe. Alternatively, the sintered aluminum-nickel-cobalt magnet may be an AlNiCo5 alloy comprising the following components by mass percentage: 6-9% Al, 12-15% Ni, 25-30% Co, 1-4% Cu, 0-1% Nb, and the balance being Fe.

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