R-T-Al alloy particle, R-T-Al alloy secondary particle, preparation method and application

Abstract

The invention discloses an R-T-Al alloy particle, an R-T-Al alloy secondary particle, a preparation method and application, the R-T-Al alloy particle comprises R, T and Al, and the atomic ratio of R to T to Al is (1-1.1): (13-15.5); the atomic ratio of the T to the Al is (4.4-30): 1; the particle size of the R-T-Al alloy particles ranges from 10 micrometers to 1000 micrometers. The preparation method comprises the following steps: processing the base material by a plasma rotating electrode atomization method. The R-T-Al alloy particles are subjected to heat treatment, the R-T-Al alloy secondary particles are obtained, the R-T-Al alloy secondary particles comprise a main phase, and the main phase is an R (TAL) 13 type compound. The spherical particles of the R-T-Al alloy, which can be prepared by the method, have the advantages of high purity, high sphericity, uniform particle size and the like, and are simple in process, high in yield and low in cost; the R-T-Al alloy secondary particles obtained after heat treatment can keep an excellent magnetothermal effect, excellent mechanical properties, corrosion resistance and the like on the basis.

Description

Technical Field

[0001] The present invention relates to an R-T-Al alloy particle, an R-T-Al alloy secondary particle, a preparation method and an application thereof. Background Art

[0002] Magnetic refrigeration technology is a new type of solid-state refrigeration technology based on the magnetocaloric effect of magnetic materials, which has the advantages of high efficiency, energy conservation, environmental friendliness, strong reliability, etc., and can be used in fields such as cryophysics, medical equipment, household appliances, etc.

[0003] However, rare-earth-transition-metal-aluminum-based refrigeration materials still face some technical problems in the preparation and processing processes, such as: the conventional preparation process requires complex technological processes such as melting, heat treatment, hydrogen absorption, crushing, and processing and forming; and rare-earth-transition-metal-aluminum-based materials are prone to defects such as being fragile, oxidized, and stressed during the processing process, affecting their structure and performance.

[0004] How to overcome the above technical problems and develop a new type of R-T-Al alloy particle magnetic refrigeration material, which can maintain excellent magnetocaloric effect while solving the problems of complex preparation process and processing difficulty, is of great significance. Summary of the Invention

[0005] In order to solve the problems of complex preparation process, high processing difficulty, poor material stability and low cycle service life in the prior art, the present invention provides an R-T-Al alloy particle, an R-T-Al alloy secondary particle, a preparation method and an application thereof. The present invention can prepare spherical particles of R-T-Al alloy, which have the advantages of high purity, high sphericity, uniform particle size, etc., and the process is simple, the yield is high, and the cost is low; the R-T-Al alloy secondary particles obtained after heat treatment can maintain excellent magnetocaloric effect, as well as excellent mechanical properties, corrosion resistance, etc.

[0006] The object of the present invention is achieved by the following technical solutions.

[0007] In the first aspect, the present invention provides an R-T-Al alloy particle, which contains R, T and Al, and the atomic ratio of R to "T and Al" is (1-1.1):(13-15.5); the atomic ratio of T to Al is (4.4-30):1;

[0008] R is one or more of rare-earth metal elements; T is one or more of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), titanium (Ti), vanadium (V) and chromium (Cr);

[0009] The particle size of the R-T-Al alloy particle is 10-1000 μm.

[0010] In the present invention, the atomic ratio of the R to "the T and the Al" is preferably (1.03 - 1.05):(13 - 13.2) (within the scope of the independent claim).

[0011] In the present invention, when the T is at least 10.6, the corresponding maximum value of the Al is 2.4; when the T is at most 15, the corresponding minimum value of the Al is 0.5.

[0012] In the present invention, the atomic ratio of the T to the Al is preferably (11 - 12):(1 - 2) (within the scope of the independent claim), such as 11.5:1.5, 11.8:1.2, 11.6:1.6, 11.7:1.5 or 12:1.2.

[0013] In the present invention, the R may be one or more of scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu); preferably, the R at least includes lanthanum; for example, the R is lanthanum and cerium, lanthanum and praseodymium, "lanthanum, cerium and praseodymium" or "lanthanum, cerium, praseodymium and neodymium".

[0014] In some specific embodiments, the R is lanthanum and praseodymium. The atomic ratio of lanthanum and praseodymium may be (2 - 6):1, such as 0.84:0.21.

[0015] In some specific embodiments, the R is lanthanum, cerium and praseodymium. The atomic ratio of lanthanum, cerium and praseodymium may be (2 - 6):1:1, such as 0.63:0.21:0.21.

[0016] In some specific embodiments, the R is lanthanum, cerium, praseodymium and neodymium. The atomic ratio of lanthanum, cerium, praseodymium and neodymium may be (2 - 6):2:1:1, such as 0.63:0.21:0.105:0.105.

[0017] In the present invention, the T may be one or more of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), titanium (Ti), vanadium (V) and chromium (Cr); preferably, the T at least includes iron; for example, the T is iron, "iron and manganese", "iron and cobalt" or "iron, manganese and cobalt".

[0018] In some specific embodiments, the T is iron and manganese. The atomic ratio of iron and manganese may be (30 - 40):1, such as 11.2:0.3.

[0019] In some specific embodiments, the T is iron and cobalt. The atomic ratio of iron and cobalt may be (10 - 15):1, such as 11:0.8.

[0020] In certain specific embodiments, R is lanthanum, T is iron, and the atomic ratio of lanthanum, iron, and aluminum is (1.03 - 1.05):11.5:1.5, such as 1.05:11.5:1.5 or 1.03:11.5:1.5.

[0021] In certain specific embodiments, R is lanthanum and cerium, T is iron, and the atomic ratio of lanthanum, cerium, iron, and aluminum is (0.6 - 0.8):(0.2 - 0.4):(11.5 - 12):1.5, such as 0.735:0.315:11.5:1.5 or 0.735:0.315:11.7:1.5.

[0022] In certain specific embodiments, R is lanthanum and praseodymium, T is iron, and the atomic ratio of lanthanum, praseodymium, iron, and aluminum is (0.7 - 0.9):(0.1 - 0.3):(11.5 - 12):(1 - 1.5), such as 0.84:0.21:11.5:1.5 or 0.84:0.21:11.7:1.5.

[0023] In certain specific embodiments, R is lanthanum, T is iron and cobalt, and the atomic ratio of lanthanum, iron, cobalt, and aluminum is 1.05:(10.9 - 11.1):(0.7 - 0.9):1.2, such as 1.05:11:0.8:1.2 or 1.05:11.1:0.9:1.2.

[0024] In certain specific embodiments, R is lanthanum, T is iron and manganese, and the atomic ratio of lanthanum, iron, manganese, and aluminum is 1.05:(11.1 - 11.3):(0.2 - 0.4):1.5, such as 1.05:11.2:0.3:1.5 or 1.05:11.3:0.2:1.5.

[0025] In certain specific embodiments, R is lanthanum, cerium, and praseodymium, T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, iron, and aluminum is 0.63:0.21:0.21:11.5:1.5.

[0026] In certain specific embodiments, R is lanthanum, cerium, praseodymium, and neodymium, T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, neodymium, iron, and aluminum is 0.63:0.21:0.105:0.105:11.5:1.5.

[0027] In certain specific embodiments, R is lanthanum and cerium, T is iron and cobalt, and the atomic ratio of lanthanum, cerium, iron, cobalt, and aluminum is 0.84:0.21:11:0.8:1.2.

[0028] In certain specific embodiments, R is lanthanum and cerium, T is iron and manganese, and the atomic ratio of lanthanum, cerium, iron, manganese, and aluminum is 0.735:0.315:11.2:0.3:1.5.

[0029] In the present invention, the particle size of the R-T-Al alloy particles is preferably 34μm, 36μm, 125μm, 128μm, 132μm, 321μm, 322μm, 324μm, 548μm, 553μm, 558μm, 564μm, 566μm, 973μm, or 976μm.

[0030] In a second aspect, the present invention provides a method for preparing R-T-Al alloy particles, which includes the following steps: processing a substrate by a plasma rotating electrode atomization method;

[0031] The substrate contains R, T, and Al, and the atomic ratio of R to "T and Al" is (1 - 1.1):(13 - 15.5); the atomic ratio of T to Al is (4.4 - 30):1.

[0032] R is one or more of rare earth metal elements; T is one or more of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), titanium (Ti), vanadium (V), and chromium (Cr).

[0033] In the present invention, the shape, size, manufacturing method, etc. of the substrate can be conventional selections in the art.

[0034] In the present invention, the shape of the substrate can be a rod.

[0035] Among them, the diameter of the rod can be 5 - 150mm, preferably 30 - 75mm, such as 30mm, 50mm, or 75mm.

[0036] Among them, the surface roughness Ra of the rod may not be greater than 1.6μm.

[0037] Among them, the rod can be processed with corresponding threads according to the matching requirements of the feeding mechanism for continuous feeding in cooperation with the rod.

[0038] In the present invention, the substrate can be obtained commercially or by using conventional preparation methods in the art; the preparation of the substrate may include the following steps: melting and casting the raw materials to obtain an ingot; and then processing the ingot to form the substrate.

[0039] Among them, the preparation method of the ingot can be a vacuum intermediate frequency induction melting preparation process.

[0040] Among them, the shape of the cast mold can be selected as square or cylindrical according to actual size requirements. The material of the mold can be selected from copper mold or cast iron mold.

[0041] In the present invention, the substrate is placed as an electrode in a plasma rotating electrode atomization device during the preparation process and is atomized by plasma rotating electrode subsequently.

[0042] In the present invention, the plasma rotating electrode atomization method can be implemented in a conventional plasma rotating electrode atomization device. The plasma rotating electrode atomization method (PREP method) is a method for preparing metal powders based on the principle of high-speed rotation and centrifugal atomization of electrode rod materials. This method can prepare metal powders with low oxygen content, no adhesion, and high sphericity. Using the plasma rotating electrode atomization method to prepare the rare earth-transition metal-aluminum-based alloy spherical working medium material required for magnetic refrigeration technology maintains excellent magnetocaloric effect, has a high specific surface area and high heat transfer effect, and at the same time solves problems such as complex preparation process, high processing difficulty, poor material stability, and low cycle service life.

[0043] Among them, the plasma rotating electrode atomization device includes a rotating electrode and its sealing device, a feeding device, a plasma gun head, and a collector.

[0044] The rotating electrode and its sealing device are used to rotate the substrate at a certain speed. Due to the action of centrifugal force, the melted droplets naturally form spherical particles during the flight in the air. The rotating device also includes a sealing device, which can ensure that the electrode can rotate at a high speed, the feeding is smooth, and at the same time ensure the sealing effect of the cavity.

[0045] The feeding device is used to feed the alloy substrate into the cavity at a certain feeding speed, form a continuous arc with the plasma gun head, and remain in the gas flow of the arc. The feeding device can feed single rods, can also feed continuously, and can also achieve continuous feeding through the threaded connection of the rod materials.

[0046] The plasma gun head sprays plasma gas flow towards the substrate, causing the end face part of the substrate to melt and splash out with the rotation of the rotating electrode, forming droplet particles; as the substrate rotates, the end face of the substrate melts, droplets splash, and the feeding device continuously feeds, so that the atomization process continues. For the purpose of protecting the equipment device, the electrode formed by the substrate will not be completely consumed, and a remaining section of the stock head stops atomization. The cross-section of the substrate corresponding to the center of the plasma gun head is continuously adjustable from the center to the edge position.

[0047] The chamber of the collector, due to the droplet splashing generated by the rotation of the rotating electrode, is approximately spatially symmetric and can be circular or conical. Its width can be 100 - 2000 mm, its diameter can be 1000 - 4000 mm, and its edge can be arc-shaped. Its inner wall is preferably made of a non-stick material, such as smooth stainless steel. The bottom of the collector can be provided with an outlet, which can be connected to an independent storage tank for collecting R-T-Al alloy particles. A baffle valve that can be opened and closed can be provided above the outlet, enabling continuous feeding, continuous discharging, and continuous atomization.

[0048] In the present invention, in the plasma rotating electrode atomization method, the working current and the rotation speed of the substrate are determined by obtaining a product with a specific particle size; the working parameters of other components can be conventional selections in the art.

[0049] In the present invention, in the plasma rotating electrode atomization method, the working current can be 500 - 4000 A. The working current can vary in the radial direction of the cross-section of the substrate.

[0050] Preferably, at the central position of the cross-section of the substrate, the working current is 800 - 3000 A, such as 800 A, 1400 A, 1600 A, 2100 A, or 2600 A.

[0051] Preferably, at the one-quarter diameter position of the cross-section of the substrate, the working current is 600 - 3000 A, such as 600 A, 800 A, 900 A, 1100 A, or 1400 A. Herein, the "one-quarter diameter position of the cross-section" starts from the center or the edge of the cross-section.

[0052] In the present invention, in the plasma rotating electrode atomization method, the rotation speed of the substrate can be 500 - 30000 rpm, preferably 1500 - 26000 rpm, such as 1500 rpm, 2500 rpm, 4000 rpm, 12000 rpm, or 26000 rpm.

[0053] In the present invention, in the plasma rotating electrode atomization method, the feeding speed of the substrate can be 0.1 - 10 mm / s, preferably 1 - 5 mm / s, such as 1.5 mm / s.

[0054] In the present invention, the plasma rotating electrode atomization method can be carried out in an inert gas environment. The inert gas environment is beneficial for arc ignition. The spherical droplets fly and solidify in the inert gas environment. The inert gas environment can protect the spherical droplets from oxidation. At the same time, through the heat transfer and heat exchange of the inert gas, the speed of the droplets solidifying into spheres during flight is accelerated, the flight distance is shortened, and R-T-Al alloy particles are formed. The inert environment is beneficial for reducing the volume, weight, and cost of the equipment.

[0055] Among them, the inert gas environment can be argon and / or helium.

[0056] Among them, the oxygen content in the inert gas environment is less than or equal to 50 ppm, and more preferably the oxygen content is less than or equal to 5 ppm.

[0057] Among them, the air pressure of the inert gas environment is preferably maintained at 0.05 - 0.3 MPa; more preferably 0.1 - 0.2 MPa, such as 0.12 MPa.

[0058] In the present invention, in the plasma rotating electrode atomization method, the vacuum degree in the atomization chamber can be ≤1×10 -2 Pa;

[0059] In the present invention, in the plasma rotating electrode atomization method, the oxygen content in the atomization chamber can be ≤50 ppm, preferably ≤5 ppm.

[0060] In the present invention, the relative purity of the substrate can be ≥99 wt%, preferably ≥99.5 wt%.

[0061] In a third aspect, the present invention provides an R-T-Al alloy particle prepared by the preparation method as described above.

[0062] In the present invention, the prepared R-T-Al alloy particles have a high sphericity.

[0063] In the present invention, the yield of the prepared R-T-Al alloy particles can be 75 wt% or more, where the yield of the R-T-Al alloy particles = total mass of the R-T-Al alloy particles / mass of the complete R-T-Al alloy rod electrode that has completed machining but has not been atomized.

[0064] In a fourth aspect, the present invention provides an R-T-Al alloy secondary particle, which contains R, T, and Al, and the atomic ratio of R to "T and Al" is (1 - 1.1):(13 - 15.5); the atomic ratio of T to Al is (4.4 - 30):1;

[0065] R is one or more of rare earth metal elements; T is one or more of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), titanium (Ti), vanadium (V), and chromium (Cr);

[0066] The R-T-Al alloy secondary particle contains a main phase, and the main phase is an R(TAl) 13 type compound.

[0067] In the present invention, the R-T-Al alloy secondary particles may further contain a heterogeneous phase, and the heterogeneous phase is dispersedly distributed in the matrix phase; the heterogeneous phase may include at least one of T element, R element, R-T compound, and R1T1Al1-type compound; preferably, the heterogeneous phase further includes α-iron phase.

[0068] Among them, the heterogeneous phase may include T element. In the R-T-Al alloy secondary particles, a part of T atoms will form R(TAl) 13 type compound as the matrix phase, and T element is dispersed as the heterogeneous phase in the matrix phase. The matrix phase mainly provides magnetocaloric effect performance, and the presence of an appropriate amount of heterogeneous phase can improve the mechanical properties of the material.

[0069] Among them, the heterogeneous phase may include R atoms, and R atoms contribute to the formation of R(TAl) 13 type compound. Because the formation of this compound is relatively demanding, once the easily oxidized R atoms react with oxygen and are partially consumed or form compounds with Al and are partially consumed, the amount of R atoms is insufficient, so an appropriate amount can exist.

[0070] In a fifth aspect, the present invention provides a method for preparing R-T-Al alloy secondary particles, which includes the following steps: heat-treating the R-T-Al alloy particles as described above.

[0071] In the present invention, the temperature of the heat treatment may be 850 - 950 °C.

[0072] In the present invention, the time of the heat treatment may be 12 - 48 h.

[0073] In some specific embodiments, the time of the heat treatment may be extended to 7 - 14 days.

[0074] In the present invention, the equipment and method of the heat treatment may be a conventional choice in the art, such as a high-vacuum sintering furnace or vacuum-packaging into a quartz tube or tantalum tube.

[0075] In the present invention, after the heat treatment, cooling may be carried out.

[0076] Among them, the cooling method may be a conventional choice in the art, such as rapid air cooling with argon, water quenching, ice-water quenching, or liquid nitrogen quenching.

[0077] In a sixth aspect, the present invention provides an R-T-Al alloy secondary particle prepared by the preparation method as described above.

[0078] In a seventh aspect, the present invention provides the application of the R-T-Al alloy secondary particle as described above as a magnetic refrigeration material in the field of solid-state refrigeration.

[0079] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention. The reagents and raw materials used in the present invention are all commercially available.

[0080] The positive and progressive effects of the present invention are as follows:

[0081] (1) The R-T-Al alloy particles provided by the present invention have the advantages of high sphericity, smooth surface, uniform particle size distribution, and no obvious defects. Based on the R-T-Al alloy particles, the obtained secondary R-T-Al alloy particles have good magnetocaloric performance, excellent mechanical properties, corrosion resistance, etc., while maintaining high sphericity, smooth surface, and uniform particle size distribution.

[0082] (2) The preparation method provided by the present invention has relatively simple process, without the need for complex equipment and operations; no additional separation and purification processes are required; and the particle size distribution can be regulated by adjusting parameters such as the rotation speed and working current of the equipment to meet different application requirements and the yield is relatively high. Specific Embodiments

[0083] The present invention will be further illustrated below by way of examples, but the present invention is not limited to the scope of the described examples. The experimental methods without specific conditions noted in the following examples are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0084] Example 1

[0085] La 1.03 Fe 11.5 Al 1.5 The preparation of alloy particles includes the following steps:

[0086] (1) The raw materials of lanthanum, iron, and aluminum with a relative purity of more than 99 wt% are proportioned according to the atomic ratio of 1.03:11.5:1.5, and a lanthanum-iron-aluminum alloy ingot is prepared by vacuum induction melting and casting. The casting mold is a cast iron mold, and the mold shape can be selected as a cylindrical shape according to the actual size requirements;

[0087] (2) The ingot is machined into a lanthanum-iron-aluminum alloy rod with a diameter of 30 mm by mechanical processing, and the surface roughness Ra is not greater than 1.6 μm;

[0088] (3) The lanthanum-iron-aluminum alloy rod is fixed to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center of the cross-section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth, and also ensures a good sealing effect;

[0089] (4) The chamber of the plasma rotating electrode equipment is evacuated, and the vacuum degree reaches 1×10 -2Below Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5 ppm;

[0090] (5) Close the valve between the vacuum pump and the chamber, open the valve of the inert gas, and fill the vacuum chamber of the plasma rotating electrode device with high-purity argon gas to keep the pressure in the chamber at 0.12 MPa;

[0091] (6) Turn on the power supply and adjust the parameters of the plasma rotating electrode device. The feeding speed of the rod is 1.5 mm / s; the rotation speed of the rotating device is 26,000 rpm; the working current of the device is 800 A;

[0092] (7) After the plasma gun head and the electrode are arced, spray the plasma gas flow through the plasma gun onto the lanthanum-iron-aluminum alloy rod electrode to melt the end face part of the alloy rod and splash it out with the rotation of the electrode to form droplets of lanthanum-iron-aluminum alloy;

[0093] (8) Make the droplets naturally form a spherical shape during flight through the centrifugal force of the rotating device and the surface tension of the droplets; as the electrode rotates, the end face melts, the droplets splash, and the feeding device continuously feeds, so that the atomization process continues;

[0094] (9) Make the droplets rapidly solidify during flight through the cooling effect of the inert gas to form lanthanum-iron-aluminum alloy balls. The inert gas also helps to arc;

[0095] (10) Collect the lanthanum-iron-aluminum alloy particles through a collector.

[0096] The spherical lanthanum-iron-aluminum alloy particles prepared in this example have a high sphericity, a smooth surface, no obvious defects, a controllable particle size distribution, D50 is 36 μm, and the yield of lanthanum-iron-aluminum alloy balls is 78 wt%.

[0097] Example 2

[0098] Metal alloy La 0.735 Ce 0.315 Fe 11.5 Al 1.5 Preparation of spherical particles includes the following steps:

[0099] (1) Charge the raw materials of lanthanum, cerium, iron, and aluminum with a relative purity of more than 99 wt% according to the atomic ratio of 0.735:0.315:11.5:1.5, and prepare a lanthanum-cerium-iron-aluminum alloy ingot by vacuum induction melting. Select a cast iron mold for casting, and the mold shape can be selected as a cylindrical shape according to the actual size requirements;

[0100] (2) Process the ingot into a lanthanum-cerium-iron-aluminum alloy rod with a diameter of 50 mm by mechanical processing, and the surface roughness Ra is not greater than 1.6 μm;

[0101] (3) Fix the lanthanum-cerium-iron-aluminum alloy rod to the rotating device of the plasma rotating electrode equipment as the electrode, align the center of the cross-section at one end of the alloy rod with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also enables smooth feeding and ensures good sealing effect;

[0102] (4) Evacuate the chamber of the plasma rotating electrode equipment. When the vacuum degree reaches below 1×10 -2 Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5 ppm;

[0103] (5) Close the valve between the vacuum pump and the chamber, open the valve of the inert gas, and fill the vacuum chamber of the plasma rotating electrode equipment with high-purity argon gas to keep the air pressure in the chamber at 0.12 MPa;

[0104] (6) Turn on the power supply, adjust the parameters of the plasma rotating electrode equipment. The feeding speed of the rod is 1.5 mm / s, the rotational speed of the rotating device is 12,000 rpm; the working current of the equipment is 2,100 A;

[0105] (7) After the plasma gun head and the electrode are arced, spray the plasma gas flow through the plasma gun onto the lanthanum-cerium-iron-aluminum alloy rod electrode to melt the end face part of the alloy rod and splash it out with the rotation of the electrode to form droplets of lanthanum-cerium-iron-aluminum alloy;

[0106] (8) Make the droplets naturally form spherical shapes during flight through the centrifugal force of the rotating device and the surface tension of the droplets; as the electrode rotates, the end face melts, the droplets splash, and the feeding device continuously feeds, so that the atomization process continues;

[0107] (9) Make the droplets rapidly solidify during flight through the cooling effect of the inert gas to form lanthanum-cerium-iron-aluminum alloy balls. The inert gas also helps to initiate the arc;

[0108] (10) Collect the lanthanum-cerium-iron-aluminum alloy balls through the collector.

[0109] The lanthanum-cerium-iron-aluminum alloy balls prepared in this example have high sphericity, smooth surfaces, no obvious defects, controllable particle size distribution, D50 is 132 μm, and the recovery rate of the lanthanum-cerium-iron-aluminum alloy balls is 79 wt%.

[0110] Example 3

[0111] Metal alloy La 0.84 Pr 0.21 Fe 11.5 Al 1.5 The preparation of spherical particles includes the following steps:

[0112] (1) preparing lanthanum, praseodymium, iron and aluminum raw materials with a relative purity of more than 99 wt % according to an atomic ratio of 0.84:0.21:11.5:1.5, and preparing lanthanum-praseodymium-iron-aluminum alloy ingots by vacuum induction melting and casting, and selecting a cast iron mold for the casting mold, and the mold shape can be cylindrical according to actual size requirements;

[0113] (2) machining the ingot into a lanthanum-praseodymium-iron-aluminum alloy rod with a diameter of 75 mm and a surface roughness Ra of no more than 1.6 μm;

[0114] (3) A lanthanum-praseodymium-iron-aluminum alloy rod is fixed to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center of the cross section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth and ensures a good sealing effect;

[0115] (4) Evacuate the chamber of the plasma rotating electrode equipment to a vacuum degree of 1×10 -2 Pa, monitor the oxygen content in the chamber to ensure that the oxygen content in the chamber is less than or equal to 5ppm;

[0116] (5) Close the valve between the vacuum pump and the chamber, open the inert gas valve, and fill the vacuum chamber of the plasma rotating electrode equipment with high-purity argon gas to maintain the gas pressure in the chamber at 0.12 MPa;

[0117] (6) Turn on the power and adjust the parameters of the plasma rotating electrode equipment. The feeding speed of the rod is 1.5 mm / s, the speed of the rotating device is 4000 rpm, and the working current of the equipment is 2600 A.

[0118] (7) After the plasma gun head and the electrode are arced, a plasma gas flow is sprayed toward the lanthanum-praseodymium-iron-aluminum alloy rod electrode through the plasma gun, so that the end surface of the alloy rod is partially melted and splashed out with the rotation of the electrode to form droplets of lanthanum-praseodymium-iron-aluminum alloy;

[0119] (8) The centrifugal force of the rotating device and the surface tension of the droplets make the droplets naturally form a spherical shape during flight; the electrode rotates, the end surface melts, the droplets splash, and the pushing device continuously feeds, so that the atomization process continues;

[0120] (9) The inert gas cools the droplets rapidly during flight to form lanthanum-praseodymium-iron-aluminum alloy balls. The inert gas also helps in starting the arc.

[0121] (10) The lanthanum-praseodymium-iron-aluminum alloy balls are collected by a collector.

[0122] The spherical lanthanum praseodymium iron aluminum alloy balls prepared in this example have high sphericity, smooth surfaces, no obvious defects, controllable particle size distribution, a D50 of 324 μm, and a recovery rate of the lanthanum praseodymium iron aluminum alloy balls of 78 wt%.

[0123] Example 4

[0124] Metal alloy La 1.05 Fe 11 Co 0.8 Al 1.2 The preparation of spherical particles includes the following steps:

[0125] (1) Ingredients of lanthanum, iron, cobalt, and aluminum raw materials with a relative purity of more than 99 wt% are proportioned according to an atomic ratio of 1.05:11:0.8:1.2, and a lanthanum iron cobalt aluminum alloy ingot is prepared by vacuum induction melting and casting. The casting mold is a cast iron mold, and the mold shape can be selected as a cylindrical shape according to actual size requirements;

[0126] (2) The ingot is machined into a lanthanum iron cobalt aluminum alloy rod with a diameter of 50 mm by mechanical processing, and the surface roughness Ra is not greater than 1.6 μm;

[0127] (3) The lanthanum iron cobalt aluminum alloy rod is fixed to the rotating device of the plasma rotating electrode equipment as an electrode, so that the center of the cross-section of one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also makes the feeding smooth, and also ensures a good sealing effect;

[0128] (4) The chamber of the plasma rotating electrode equipment is evacuated, and the vacuum degree is below 1×10 -2 Pa. The oxygen content in the chamber is monitored to ensure that the oxygen content in the chamber is less than or equal to 5 ppm;

[0129] (5) The valve between the vacuum pump and the chamber is closed, the valve of the inert gas is opened, and high-purity argon is filled into the vacuum chamber of the plasma rotating electrode equipment to keep the air pressure in the chamber at 0.12 MPa;

[0130] (6) The power is turned on, and the parameters of the plasma rotating electrode equipment are adjusted. The feeding speed of the rod is 1.5 mm / s, the rotation speed of the rotating device is 2500 rpm; the working current of the equipment is 1600 A;

[0131] (7) After the plasma gun head and the electrode are arced, a plasma gas flow is sprayed from the plasma gun onto the lanthanum iron cobalt aluminum alloy rod electrode, so that the end face part of the alloy rod melts and splashes out with the rotation of the electrode to form droplets of the lanthanum iron cobalt aluminum alloy;

[0132] (8) The droplets naturally form spheres during flight through the centrifugal force of the rotating device and the surface tension of the droplets; as the electrode rotates, its end face melts, the droplets splash, and the feeding device continuously feeds, enabling the atomization process to continue;

[0133] (9) The droplets rapidly solidify during flight through the cooling effect of the inert gas to form lanthanum-iron-cobalt-aluminum alloy spheres. The inert gas also helps to initiate the arc;

[0134] (10) The lanthanum-iron-cobalt-aluminum alloy spheres are collected by a collector.

[0135] The lanthanum-iron-cobalt-aluminum alloy spheres prepared in this example have a high sphericity, a smooth surface, no obvious defects, a controllable particle size distribution, a D50 of 564 μm, and a recovery rate of the lanthanum-iron-cobalt-aluminum alloy spheres of 79 wt%.

[0136] Example 5

[0137] Metal alloy La 1.05 Fe 11.2 Mn 0.3 Al 1.5 The preparation of spherical particles includes the following steps:

[0138] (1) The raw materials of lanthanum, iron, manganese, and aluminum with a relative purity of more than 99 wt% are proportioned according to an atomic ratio of 1.05:11.2:0.3:1.5, and a lanthanum-iron-manganese-aluminum alloy ingot is prepared by vacuum induction melting and casting. The casting mold is a cast iron mold, and the mold shape can be selected as a cylindrical shape according to actual size requirements;

[0139] (2) The ingot is machined into a lanthanum-iron-manganese-aluminum alloy rod with a diameter of 50 mm by mechanical processing, and the surface roughness Ra is not greater than 1.6 μm;

[0140] (3) The lanthanum-iron-manganese-aluminum alloy rod is fixed to the rotating device of the plasma rotating electrode equipment as an electrode, and the center of the cross-section at one end of the alloy rod is aligned with the center of the plasma gun head. The sealing device of the electrode not only ensures the high-speed rotation function, but also enables smooth feeding and ensures a good sealing effect;

[0141] (4) The chamber of the plasma rotating electrode equipment is evacuated to a vacuum of less than 1×10 -2 Pa, and the oxygen content in the chamber is monitored to ensure that the oxygen content in the chamber is less than or equal to 5 ppm;

[0142] (5) The valve between the vacuum pump and the chamber is closed, the valve of the inert gas is opened, and high-purity argon is filled into the vacuum chamber of the plasma rotating electrode equipment to keep the air pressure in the chamber at 0.12 MPa;

[0143] (6) Turn on the power supply and adjust the parameters of the plasma rotating electrode equipment. The feeding speed of the rod is 1.5 mm / s, and the rotational speed of the rotating device is 1500 rpm; the working current of the equipment is 1400 A;

[0144] (7) After the plasma gun head and the electrode are arced, inject a plasma gas flow through the plasma gun towards the lanthanum-iron-manganese-aluminum alloy rod electrode, causing the end face part of the alloy rod to melt and splash out with the rotation of the electrode, forming droplets of lanthanum-iron-manganese-aluminum alloy;

[0145] (8) Make the droplets naturally form spheres during flight through the centrifugal force of the rotating device and the surface tension of the droplets; as the electrode rotates, the end face melts, the droplets splash, and the feeding device continuously feeds, enabling the atomization process to continue;

[0146] (9) Make the droplets rapidly solidify during flight through the cooling effect of the inert gas, forming lanthanum-iron-manganese-aluminum alloy spheres. The inert gas also helps with arcing;

[0147] (10) Collect the lanthanum-iron-manganese-aluminum alloy spheres through a collector.

[0148] The lanthanum-iron-manganese-aluminum alloy spheres prepared in this example have a high sphericity, a smooth surface, no obvious defects, a controllable particle size distribution, D50 is 973 μm, and the yield of the lanthanum-iron-manganese-aluminum alloy spheres is 77 wt%.

[0149] Example 6

[0150] Except for different raw materials, the other conditions are the same as those in Example 2. See Table 1 below for details.

[0151] Example 7

[0152] Except for different raw materials, the other conditions are the same as those in Example 3. See Table 1 below for details.

[0153] Example 8

[0154] Except for different raw materials, the other conditions are the same as those in Example 4. See Table 1 below for details.

[0155] Example 9

[0156] Except for different raw materials, the other conditions are the same as those in Example 4. See Table 1 below for details.

[0157] Example 10

[0158] Except for different raw materials, the other conditions are the same as those in Example 1. See Table 1 below for details.

[0159] Example 11

[0160] Except for different raw materials, the other conditions are the same as those in Example 4. See Table 1 below for details.

[0161] Example 12

[0162] Except for the different raw materials, the other conditions are the same as those in Example 2. See Table 1 below for details.

[0163] Example 13

[0164] Except for the different raw materials, the other conditions are the same as those in Example 3. See Table 1 below for details.

[0165] Example 14

[0166] Except for the different raw materials, the other conditions are the same as those in Example 4. See Table 1 below for details.

[0167] Example 15

[0168] Except for the different raw materials, the other conditions are the same as those in Example 5. See Table 1 below for details.

[0169] Table 1 Raw materials, conditions and results in Examples 1 - 15

[0170]

[0171] It can be seen from Table 1 that the R-T-Al alloy particles provided by the present invention have the advantages of high sphericity, smooth surface, uniform particle size distribution, and no obvious defects.

[0172] Example 16

[0173] The R-T-Al alloy particles in Examples 1 - 15 are heat-treated to obtain secondary R-T-Al alloy particles. Among them, the heat treatment temperature is 850 - 950 °C; the heat treatment time is 12 - 48 h, and it can also be extended to 7 - 14 days.

[0174] The obtained secondary R-T-Al alloy particles contain the main phase - R(TAl) 13 type compounds. On the basis of maintaining high sphericity, smooth surface and uniform particle size distribution, they have good magnetocaloric performance, as well as excellent mechanical properties, corrosion resistance, etc.

[0175] The above embodiments are only the preferred embodiments of the present invention, and are only used to explain the present invention, rather than limiting the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit and essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. An R-T-Al alloy particle, characterized in that, It contains R, T and Al, and the atomic ratio of R to "T and Al" is (1 - 1.1):(13 - 15.5); the atomic ratio of T to Al is (4.4 - 30):1; R is one or more of rare earth metal elements; T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; The particle size of the R-T-Al alloy particles is 10 - 1000 μm.

2. The R-T-Al alloy particles according to claim 1, wherein The atomic ratio of R to "T and Al" is (1.03 - 1.05):(13 - 13.2); and / or, the atomic ratio of T to Al is (11 - 12):(1 - 2), such as 11.5:1.5, 11.8:1.2, 11.6:1.6, 11.7:1.5 or 12:1.2; and / or, R is one or more of scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium; preferably, R includes at least lanthanum; for example, R is lanthanum and cerium, lanthanum and praseodymium, "lanthanum, cerium and praseodymium" or "lanthanum, cerium, praseodymium and neodymium"; and / or, T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; preferably, T includes at least iron; for example, T is iron, "iron and manganese", "iron and cobalt" or "iron, manganese and cobalt"; Preferably, R and T satisfy any one of the following conditions; (1) R is lanthanum and praseodymium; the atomic ratio of lanthanum and praseodymium is more preferably (2 - 6):1, such as 0.84:0.21; (2) R is lanthanum, cerium and praseodymium; the atomic ratio of lanthanum, cerium and praseodymium is more preferably (2 - 6):1:1, such as 0.63:0.21:0.21; (3) R is lanthanum, cerium, praseodymium and neodymium; the atomic ratio of lanthanum, cerium, praseodymium and neodymium is more preferably (2 - 6):2:1:1, such as 0.63:0.21:0.105:0.105; (4) T is iron and manganese; the atomic ratio of iron and manganese is more preferably (30 - 40):1, such as 11.2:0.3; (5) T is iron and cobalt; the atomic ratio of iron and cobalt is more preferably (10 - 15):1, such as 11:0.8; (6) R is lanthanum, T is iron, and the atomic ratio of lanthanum, iron and aluminum is (1.03 - 1.05):11.5:1.5, such as 1.05:11.5:1.5 or 1.03:11.5:1.5; (7) R is lanthanum and cerium, T is iron, and the atomic ratio of lanthanum, cerium, iron and aluminum is (0.6 - 0.8):(0.2 - 0.4):(11.5 - 12):1.5, such as 0.735:0.315:11.5:1.5 or 0.735:0.315:11.7:1.5; (8) R is lanthanum and praseodymium, T is iron, and the atomic ratio of lanthanum, praseodymium, iron and aluminum is (0.7 - 0.9):(0.1 - 0.3):(11.5 - 12):(1 - 1.5), such as 0.84:0.21:11.5:1.5 or 0.84:0.21:11.7:1.5; (9) The R is lanthanum, the T is iron and cobalt, and the atomic ratio of lanthanum, iron, cobalt and aluminum is 1.05:(10.9 - 11.1):(0.7 - 0.9):1.2, such as 1.05:11:0.8:1.2 or 1.05:11.1:0.9:1.2; (10) The R is lanthanum, the T is iron and manganese, and the atomic ratio of lanthanum, iron, manganese and aluminum is 1.05:(11.1 - 11.3):(0.2 - 0.4):1.5, such as 1.05:11.2:0.3:1.5 or 1.05:11.3:0.2:1.5; (11) The R is lanthanum, cerium and praseodymium, the T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, iron and aluminum is 0.63:0.21:0.21:11.5:1.5; (12) The R is lanthanum, cerium, praseodymium and neodymium, the T is iron, and the atomic ratio of lanthanum, cerium, praseodymium, neodymium, iron and aluminum is 0.63:0.21:0.105:0.105:11.5:1.5; (13) The R is lanthanum and cerium, the T is iron and cobalt, and the atomic ratio of lanthanum, cerium, iron, cobalt and aluminum is 0.84:0.21:11:0.8:1.2; (14) The R is lanthanum and cerium, the T is iron and manganese, and the atomic ratio of lanthanum, cerium, iron, manganese and aluminum is 0.735:0.315:11.2:0.3:1.5; And / or, the particle size of the R-T-Al alloy particles is 34μm, 36μm, 125μm, 128μm, 132μm, 321μm, 322μm, 324μm, 548μm, 553μm, 558μm, 564μm, 566μm, 973μm or 976μm.

3. A method for preparing R-T-Al alloy particles, characterized in that, It includes the following steps: Processing the substrate by the plasma rotating electrode atomization method; The substrate contains R, T and Al, and the atomic ratio of R to "T and Al" is (1 - 1.1):(13 - 15.5); the atomic ratio of T and Al is (4.4 - 30):1; The R is one or more of rare earth metal elements; the T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium.

4. The method for preparing the R-T-Al alloy particles according to claim 3, characterized in that, The shape of the substrate is a bar; the diameter of the bar is preferably 5 - 150mm, more preferably 30 - 75mm, such as 30mm, 50mm or 75mm; the surface roughness Ra of the bar is preferably not more than 1.6μm; the bar is preferably a bar with processed threads; And / or, the preparation of the substrate includes the following steps: obtaining an ingot by melting and casting the raw materials; then processing the ingot to form the substrate; the preparation method of the ingot is preferably the vacuum intermediate frequency induction melting preparation process; the shape of the casting mold is preferably square or cylindrical; the material of the mold is preferably a copper mold or a cast iron mold; And / or, the plasma rotating electrode atomization method is implemented in a plasma rotating electrode atomization device; the plasma rotating electrode atomization device preferably includes a rotating electrode and its sealing device, a pushing device, a plasma gun head and a collector; And / or, in the plasma rotating electrode atomization method, the condition parameters satisfy one or more of the following: (1) The working current is 500 - 4000 A; preferably, the working current satisfies any one of the following: (1-1) At the central position of the cross-section of the substrate, the working current is 800 - 3000 A, such as 800 A, 1400 A, 1600 A, 2100 A or 2600 A; (1-2) At the one-quarter diameter position of the cross-section of the substrate, the working current is 600 - 3000 A, such as 600 A, 800 A, 900 A, 1100 A or 1400 A; (2) The rotation speed of the substrate is 500 - 30000 rpm, preferably 1500 - 26000 rpm, such as 1500 rpm, 2500 rpm, 4000 rpm, 12000 rpm or 26000 rpm; (3) The feeding speed of the substrate is 0.1 - 10 mm / s, preferably 1 - 5 mm / s, such as 1.5 mm / s; (4) It is carried out in an inert gas environment; the inert gas environment is preferably argon and / or helium; the oxygen content in the inert gas environment is preferably less than or equal to 50 ppm, more preferably, the oxygen content is less than or equal to 5 ppm; the pressure of the inert gas environment is preferably maintained at 0.05 - 0.3 MPa; more preferably 0.1 - 0.2 MPa, such as 0.12 MPa; (5) The vacuum degree in the atomization chamber ≤ 1×10 -2 Pa; (6) The oxygen content in the atomization chamber ≤ 50 ppm, preferably ≤ 5 ppm; And / or, the relative purity of the substrate ≥ 99 wt%, preferably ≥ 99.5 wt%.

5. A R-T-Al alloy particle, characterized in that, It is prepared by the method for preparing R-T-Al alloy particles as described in claim 3 or 4.

6. A secondary particle of R-T-Al alloy, characterized in that, It contains R, T and Al, and the atomic ratio of R to "T and Al" is (1 - 1.1):(13 - 15.5); the atomic ratio of T to Al is (4.4 - 30):1; The R is one or more of rare earth metal elements; the T is one or more of iron, manganese, cobalt, nickel, copper, titanium, vanadium and chromium; The secondary particles of the R-T-Al alloy contain a main phase, and the main phase is R(TAl) 13 type compound.

7. A method for preparing secondary particles of an R-T-Al alloy, characterized in that, It includes the following steps: Heat-treat the R-T-Al alloy particles as described in any one of claims 1, 2 and 5.

8. The preparation method of the R-T-Al alloy secondary particles according to claim 7, characterized in that, The temperature of the heat treatment is 850 - 950 °C; And / or, the time of the heat treatment satisfies any one of the following: (1)12-48h； (2) 7 - 14 days; And / or, after the heat treatment, cooling is carried out; the cooling method is preferably rapid air cooling with argon, water quenching, ice water quenching or liquid nitrogen quenching.

9. A secondary particle of an R-T-Al alloy, characterized in that, It is prepared by the method for preparing R-T-Al alloy secondary particles as described in claim 3 or 4.

10. Application of an R-T-Al alloy secondary particle as described in claim 6 or 9 as a magnetic refrigeration material in the field of solid-state refrigeration.

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