A La-Fe-Si based magnetic refrigeration regenerator and its preparation method

Abstract

This invention provides a La-Fe-Si based magnetic refrigeration regenerator and its preparation method, relating to the field of magnetic material preparation. The La-Fe-Si based magnetic refrigeration regenerator includes a La-Fe-Si based magnetic refrigeration regenerator block, within which multiple interconnected microchannels are arranged. The arrangement of the microchannels is selected from one of 90° straight arrangement, 45° staggered arrangement, or 60° staggered arrangement, and the diameter of the microchannels is 0.5–1.5 mm. This invention also discloses the preparation method of the above-mentioned La-Fe-Si based magnetic refrigeration regenerator. This invention involves direct mechanical drilling in the cast La-Fe-Si based alloy. The large amount of ductile α-Fe phase inside can prevent material breakage during processing. Compared with the prior art, the mechanical drilling method has high processing accuracy and does not introduce organic contaminants or discharge remelting zones on the inner surface of the channels, which is beneficial for obtaining excellent magnetocaloric effects.

Description

Technical Field

[0001] This invention belongs to the field of magnetic material preparation, and relates to a La-Fe-Si based magnetic refrigeration regenerator and its preparation method. Background Technology

[0002] Refrigeration is an essential technology in modern production and daily life, widely used in everyday life, medicine, scientific research, aerospace, and other fields. Currently, the commonly used refrigeration method achieves this through the volume expansion and compression of low-boiling-point alkanes, known as gas compression refrigeration. While this method has achieved widespread application, it suffers from drawbacks such as low refrigeration efficiency, environmental damage, and high noise levels. Magnetic refrigeration is a novel solid-state refrigeration technology. Its principle involves using a solid magnetic material as the working fluid, repeatedly applying / removing a magnetic field to cause heat release / absorption, thereby achieving refrigeration. Compared to traditional gas compression refrigeration, this method offers advantages in terms of high efficiency and environmental friendliness. Its theoretical refrigeration efficiency can reach 60% of the ideal Carnot cycle, far exceeding the 20%–40% of gas compression refrigeration. Furthermore, its working fluid is solid, and it does not produce greenhouse gases during use, making it more environmentally friendly.

[0003] Magnetic refrigeration materials are one of the core components of magnetic refrigeration technology. Among the magnetic refrigeration materials reported so far, those containing NaZn... 13 La-Fe-Si based alloys with a large magnetocaloric effect, easily adjustable Curie temperature, and low cost are among the most promising magnetic refrigeration materials. In magnetic refrigeration equipment, La-Fe-Si based regenerators with internal microchannels are beneficial for achieving efficient heat exchange between materials and fluids, thereby obtaining excellent refrigeration performance. However, this material is intrinsically brittle and has poor machinability. To address this, existing technologies often employ additive manufacturing to prepare microchannel bulk materials, such as the microchannel bulk materials prepared by laser additive manufacturing methods reported in the literature (Journal of Applied Physics, 2013, 114(4): 043907. and Applied Thermal Engineering, 2020: 115297.), but the inner walls of the channels are rough and the processing accuracy is poor. In addition to the work mentioned above, the applicant explored the use of electrical discharge drilling to prepare microchannels in previous work (Materialia, 2024, 33:102034.), and found that discharge remelting and contaminant adhesion affect the microchannel inner wall structure and composition, which is not conducive to improving magnetocaloric performance. Summary of the Invention

[0004] The purpose of this invention is to provide a La-Fe-Si based magnetic refrigeration regenerator. First, a block is cut from a La-Fe-Si based ingot, then a microchannel is prepared by mechanical drilling, and finally the microchannel block is heat-treated to obtain the regenerator.

[0005] The objective of this invention is achieved through the following technical solution: a La-Fe-Si based magnetic refrigeration regenerator, comprising a La-Fe-Si based magnetic refrigeration regenerator block, wherein a plurality of through-flow microchannels are provided within the La-Fe-Si based magnetic refrigeration regenerator block, wherein the arrangement of the microchannels is selected from one of 90° straight arrangement, 45° staggered arrangement or 60° staggered arrangement, and the diameter of the microchannels is 0.5 to 1.5 mm.

[0006] Compared with the prior art, the present invention adopts the above-mentioned microchannel diameter because small-sized channels are difficult to process, while excessively large channel sizes often cannot guarantee the acquisition of suitable porosity.

[0007] Another object of the present invention is to provide a method for preparing a La-Fe-Si based magnetic refrigeration regenerator, the method specifically comprising the following steps:

[0008] S1. Select a La-Fe-Si based alloy ingot, cut a block from the La-Fe-Si based alloy ingot using wire cutting, and grind and clean the surface.

[0009] S2. Microchannels are machined in the polished and cleaned block using a drilling machine to obtain a microchannel block;

[0010] S3. After heat treatment of the microchannel block obtained in step S2, a La-Fe-Si based magnetic refrigeration regenerator is obtained.

[0011] In one possible implementation, in step S1, the selected La-Fe-Si based alloy ingot contains a tough α-Fe phase, and the ingot can form NaZn after heat treatment. 13 Structural phase.

[0012] Compared with existing technologies, the selected La-Fe-Si based alloy contains a large amount of ductile α-Fe phase in its as-cast microstructure, which can ensure that the alloy has a certain degree of machinability, and the alloy can form NaZn after heat treatment. 13 The structural phase is thus obtained, thereby achieving a large magnetocaloric effect.

[0013] In one possible implementation, in step S1, the regenerator block is cube-shaped or disc-shaped.

[0014] In one possible implementation, the thickness of the regenerator block is 5 to 15 mm.

[0015] Compared with existing technologies, if the material thickness is too small, it is easy to break during drilling, while if the thickness is too large, the drilling may be eccentric.

[0016] In one possible implementation, the porosity of the microchannel block obtained in step S2 is 10-50%.

[0017] Compared with the prior art, the porosity of the present invention can meet the application scenarios of different magnetic refrigeration regenerators.

[0018] In one possible implementation, in step S3, the heat treatment is carried out under the protection of a high-purity inert gas, the heat treatment temperature is 1000-1250°C, and the heat treatment time is 1-7 days.

[0019] Compared with the prior art, the present invention uses the above-mentioned heat treatment parameters, which can cause a reaction to occur inside the material to generate a magnetocaloric phase.

[0020] In one possible implementation, in step S3, after the heat treatment, a hydrogenation treatment is performed, with the following parameters: temperature 300°C and time 5 hours.

[0021] Compared with the prior art, the present invention performs hydrogenation treatment after heat treatment, which can raise the Curie temperature of the regenerator material to near room temperature.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The method in this invention does not use any special equipment. The methods such as melting and casting, wire cutting, and drilling have all been industrialized. Therefore, the method is simple, efficient, suitable for large-scale production, and has high economic value.

[0024] 2. The method in this invention can flexibly adjust parameters such as the size of the regenerator and the size of the microchannel according to the design requirements of the refrigeration machine, which is beneficial for preparing magnetic working fluids suitable for different service conditions;

[0025] 3. Compared with electrical discharge drilling, the microchannel inner wall prepared by the method described in this invention does not have a discharge remelting zone or organic matter adhesion, which is beneficial to obtaining excellent magnetocaloric effect;

[0026] 4. Compared with laser additive manufacturing methods, the microchannels prepared by the method described in this invention have high dimensional accuracy. Attached Figure Description

[0027] Figure 1 This is a microstructure diagram of the alloy ingot in Example 1 of the present invention.

[0028] Figure 2 This is a physical image of the microchannel block prepared in Example 1 of the present invention.

[0029] Figure 3 This is a three-dimensional cross-sectional view and contour curve of the microchannel prepared in Example 1 of the present invention.

[0030] Figure 4 The images show actual microchannel blocks with different porosities prepared in Example 1 of this invention. Detailed Implementation

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. This specification and its embodiments are merely exemplary.

[0034] The technical effects of the present invention will be described below with reference to specific embodiments. The induction melting method described therein has been disclosed in patent CN105834407B. The specific scheme can be adjusted and optimized according to the actual situation.

[0035] Example 1

[0036] A LaFe 13.9 Si 1.4 The specific steps for preparing a magnetic refrigeration regenerator are as follows:

[0037] (1) Weigh the raw materials La, Fe and Si according to the composition ratio, and use the conventional vacuum induction melting method to obtain a plate-shaped ingot with a thickness of about 20 mm;

[0038] (2) Use wire cutting to cut an 8×8×8mm sample from the plate-shaped ingot. 3 10×10×10mm 3 The cube was sanded clean with sandpaper, then cleaned with alcohol and dried.

[0039] (3) Fix a 1mm diameter tungsten carbide drill bit on a bench drill press, and then drill an 8×8×8mm drill bit. 3 Holes were drilled in a 90° straight line arrangement on a cubic block, with a center-to-center distance of 2 mm between adjacent holes, controlling the porosity to approximately 11.0%; in a 10×10×10mm... 3 Holes were drilled in a 90° straight line pattern on the block, with the center-to-center distance between adjacent holes being 1.5–2 mm, controlling the porosity to be approximately 12.6%–28.3%; microchannel blocks of different sizes were obtained accordingly.

[0040] (4) The microchannel blocks of different sizes obtained in step (3) are sealed in glass tubes with argon protection and subjected to heat treatment at 1050℃ for 7 days, followed by water quenching to obtain heat-treated samples.

[0041] (5) Heat-treated samples of different sizes were hydrogenated at 300℃ for 5 hours and then furnace-cooled to room temperature. The hydrogen pressure was 2 bar, resulting in La-Fe-Si based magnetic refrigeration regenerators of different sizes.

[0042] Figure 1 The microstructure is that of a plate-shaped ingot, in which the dark phase is the tough α-Fe phase, which is beneficial to improving the machinability of the material.

[0043] Figure 2 It is 8×8×8mm 3 A photograph of the actual object after drilling holes in the block, from Figure 2 It can be seen that the sample remained intact after drilling, without any fragmentation or breakage.

[0044] Figure 3 It is 8×8×8mm 3 Three-dimensional cross-sectional view and contour curve of microchannels after drilling of the block, from Figure 3 It can be seen that the microchannels did not show obvious blockage and were basically circular.

[0045] Figure 4 For 10×10×10mm with different porosities 3 Microchannel blocks, from Figure 4 It can be seen that samples with different porosities can be obtained using the method of this invention.

[0046] Example 2

[0047] A LaFe 11.0 Co 0.8 Si 1.2 The specific steps for preparing a magnetic refrigeration regenerator are as follows:

[0048] (1) Weigh La, Fe, Co and Si raw materials according to the component ratio, and use conventional vacuum induction melting method to obtain plate-shaped ingots with a thickness of about 20 mm;

[0049] (2) Use wire cutting to cut a round block with a diameter of 25mm and a thickness of 8mm from the plate-shaped ingot, and use sandpaper to clean the surface of the block and then clean it with alcohol and blow it dry.

[0050] (3) Fix a 1mm diameter tungsten carbide drill bit on a drilling machine, and then drill holes in the block in a staggered manner at 60°. The center distance between adjacent circular holes is 2mm, and the porosity is controlled to be about 19.4%, thus obtaining a microchannel block.

[0051] (4) The microchannel block was sealed in a glass tube with argon protection and subjected to heat treatment at 1050℃ for 3 days and then water quenched to obtain a La-Fe-Si based magnetic refrigeration regenerator.

[0052] Example 3

[0053] A LaFe 11.6 Si 1.4 The specific steps for preparing a magnetic refrigeration regenerator are as follows:

[0054] (1) Weigh the raw materials La, Fe and Si according to the component ratio, and obtain the ingot by conventional vacuum induction melting method;

[0055] (2) Use wire cutting to cut a 10×10×10mm sample from the ingot. 3 The cube was sanded clean with sandpaper, then cleaned with alcohol and dried.

[0056] (3) Fix a 0.8mm diameter tungsten carbide drill bit on a bench drill press, and then drill holes in the block in a 90° straight line manner. The center distance between adjacent circular holes is about 1.6mm, and the porosity is controlled to be about 12.6%, thus obtaining a microchannel block.

[0057] (4) The microchannel block is sealed in a glass tube with argon protection and subjected to heat treatment at 1050℃ for 7 days, followed by water quenching.

[0058] (5) The heat-treated sample was hydrogenated at 300℃ for 5h and then furnace-cooled to room temperature. The hydrogen pressure was 2 bar to obtain a La-Fe-Si based magnetic refrigeration regenerator.

[0059] As can be seen from the above results, the method in this invention does not use any special equipment, and the methods such as melting and casting, wire cutting, and drilling have all been industrialized. Therefore, the method is simple, efficient, suitable for large-scale production, and has high economic value.

[0060] While the present invention has been disclosed above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and all such changes and modifications will fall within the scope of protection of the present invention.

Claims

1. A method for preparing a La-Fe-Si based magnetic refrigeration regenerator, characterized in that, The La-Fe-Si based magnetic refrigeration regenerator includes a La-Fe-Si based magnetic refrigeration regenerator block, and a plurality of through microchannels are provided in the La-Fe-Si based magnetic refrigeration regenerator block. The arrangement of the microchannels is selected from one of 90° straight arrangement, 45° staggered arrangement or 60° staggered arrangement, and the diameter of the microchannels is 0.5 to 1.5 mm. The preparation method of the La-Fe-Si based magnetic refrigeration regenerator specifically includes the following steps: S1. Select a La-Fe-Si based alloy ingot, cut a block from the La-Fe-Si based alloy ingot using wire cutting, and grind and clean the surface. S2. Microchannels are machined in the polished and cleaned block using a drilling machine to obtain a microchannel block; S3. After heat treatment of the microchannel block obtained in step S2, a La-Fe-Si based magnetic refrigeration regenerator is obtained. In step S1, the selected La-Fe-Si based alloy ingot contains a tough α-Fe phase, and the ingot can form NaZn after heat treatment. 13 structural phase; In step S1, the shape of the regenerator block is a cube or a disc. In step S1, the thickness of the regenerator block is 5-15 mm.

2. The method for preparing the La-Fe-Si based magnetic refrigeration regenerator as described in claim 1, characterized in that, In step S2, the porosity of the microchannel block obtained is 10-50%.

3. The method for preparing the La-Fe-Si based magnetic refrigeration regenerator as described in claim 1, characterized in that, In step S3, the heat treatment is carried out under the protection of high-purity inert gas, the temperature of the heat treatment is 1000-1250℃, and the heat treatment time is 1-7 days.

4. The method for preparing the La-Fe-Si based magnetic refrigeration regenerator as described in claim 1, characterized in that, In step S3, after heat treatment, hydrogenation is performed. The parameters for hydrogenation are as follows: temperature is 300℃ and time is 5h.

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