A La-Fe-Si-based magnetic refrigeration composite material based on SPS technology and its preparation method

Abstract

This invention discloses a La-Fe-Si based magnetic refrigeration composite material based on SPS technology and its preparation method. The method involves uniformly mixing La-Fe-Si based magnetic refrigeration material powder and micron-sized Fe powder, followed by high-temperature discharge plasma sintering to obtain a bulk magnetic refrigeration material. The sintering temperature is 1100-1300 K, and the pressure is 10-100 MPa. The La-Fe-Si based magnetic refrigeration material is (La... 1‑ x Ce x (Fe) y Co 1‑y ) 11‑z Si z The compound, wherein 0≤x≤0.4, 0≤y≤2, 1.0≤z≤1.6, has a particle size ≤100μm, and the micron-sized Fe powder has a particle size of 3-5μm. This invention effectively solves the problem of difficult molding of La-Fe-Si materials. Simultaneously, it greatly simplifies the process flow. The composite material prepared by the above method exhibits good magnetocaloric effect and excellent mechanical properties.

Description

Technical Field

[0001] This invention relates to a La-Fe-Si based magnetic refrigeration composite material, and more particularly to a bulk magnetic refrigeration material with high density and good magnetocaloric properties prepared by a short-time molding method, and the preparation method thereof. Background Technology

[0002] Refrigeration technology plays an irreplaceable role in human society, but traditional gas compression refrigeration technology suffers from drawbacks such as low efficiency, high energy consumption, and the potential for greenhouse effects due to the release of chlorofluorocarbon (CFC) refrigerants. Magnetic refrigeration technology, with its advantages of high efficiency, energy saving, environmental friendliness, and reliable operation, is considered the most promising technology to replace gas compression refrigeration. NaZn 13 La-Fe-Si based compounds are considered to be among the most promising room-temperature magnetic refrigeration materials due to their non-toxicity, continuously adjustable Curie temperature, large magnetic entropy change, and low cost.

[0003] LaFe with low silicon content 13-x Si x Compounds with (1.0 ≤ x ≤ 1.6) have been extensively studied due to their giant magnetocaloric effect. However, LaFe... 13-x Si x The disadvantages of (1.0≤x≤1.6) are also obvious: (1) It is difficult to form phases, and it is difficult to obtain nearly 100% NaZn in the alloy. 13 The 1:13 magnetocaloric phase (hereinafter referred to as the 1:13 phase) often requires heat treatment at above 1273K for several days or even weeks; (2) magnetic volume effect, LaFe 13-x Si x (1.0≤x≤1.6) The compound exhibits a first-order magnetic phase transition, which is usually accompanied by a strong magnetic volume effect, and is accompanied by a large thermal hysteresis and magnetic hysteresis; (3) intrinsic brittleness, LaFe 13-x Si x The material is difficult to process and shape, and during the magnetic circulation process, cracks will form and propagate due to its intrinsic brittleness; (4) The Curie temperature is low, which is not suitable for low-silicon content LaFe with giant magnetocaloric effect. 13-x Si x The Curie temperature of these alloys is generally below 210K; these issues limit their commercial application. However, due to LaFe... 13-x Si x The enormous potential of the (1.0≤x≤1.6) compound for magnetic refrigeration applications has attracted widespread attention from materials scientists in Guangdong.

[0004] Significant progress has been made in improving the phase formation or molding defects of LaFe, for example: 1) using rapid cooling technology (rapid melt quenching, rapid solidification) to improve the phase formation or molding defects of LaFe. 13-x Six The material's uniform structure can shorten the heat treatment phase formation time; 2) By referencing powder metallurgy, other materials with good mechanical properties can be mixed and high-density composite bulk materials can be formed through hot pressing sintering or spark plasma sintering (SPS) to improve mechanical properties. However, these research results can only improve certain properties. To simultaneously coordinate non-magnetic and magnetic properties, multiple different methods must be combined, which not only complicates the preparation process but also makes it difficult to improve the overall performance of the material. Regarding improving overall performance, most work focuses on adding sintering aids during powder metallurgy. However, the introduction of sintering aids usually leads to magnetic dilution, which deteriorates magnetocaloric properties. In addition, some sintering aids react with the 1:13 phase during sintering, producing impurity phases that are detrimental to mechanical properties, which need to be eliminated through subsequent long-term heat treatment. Therefore, the key issue is how to efficiently prepare La-Fe-Si based magnetic refrigeration materials that simultaneously possess large magnetic entropy changes and high mechanical properties. Summary of the Invention

[0005] This invention addresses the problems of inherent brittleness of La-Fe-Si based magnetic refrigeration materials, poor overall performance of composite materials, and long production cycles and complex processes in traditional preparation methods. It proposes a method to improve the overall performance of La-Fe-Si based magnetic refrigeration bulk materials by using micron-sized Fe powder as a binder and employing high-temperature discharge plasma sintering rapid prototyping technology.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A La-Fe-Si based magnetic refrigeration composite material based on SPS technology and its preparation method are disclosed. The La-Fe-Si based magnetic refrigeration material powder (main phase particles) and micron-sized Fe powder (binder) are uniformly mixed and then sintered by high-temperature discharge plasma to obtain a composite magnetic refrigeration bulk material. The sintering temperature is 1100K~1300K, the pressure is 10~100MPa, and the particle size of the La-Fe-Si based magnetic refrigeration material is ≤100μm.

[0008] Preferably, the sintering temperature is 1123K-1273K.

[0009] Preferably, the particle size of the La-Fe-Si based magnetic refrigeration material powder is less than 100 μm.

[0010] Preferably, the La-Fe-Si based magnetic refrigeration material is (La 1-x Ce x (Fe) y Co 1-y ) 11-z Siz Compounds, where 0 ≤ x ≤ 0.4, 0 ≤ y ≤ 2, 1.0 ≤ z ≤ 1.6.

[0011] Preferably, the (La) 1-x Ce x (Fe) y Co 1-y ) 11-z Si z The compound is (La 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Compounds with a particle size of 45 μm ≤ 100 μm.

[0012] Preferably, the La-Fe-Si based magnetic refrigeration material is composed of α-Fe phase with a content of ≥70 wt.% and NaZn phase with a content of ≤10 wt.%. 13 The structure is 1:13 phase, with the remainder being rare earth-rich (La,Ce)1(Fe,Co)1Si1 phase (hereinafter referred to as the 1:1:1 phase). 1-x Ce x (Fe) y Co 1-y ) 11-z Si z Bulk materials.

[0013] Preferably, the La-Fe-Si based magnetic refrigeration material is composed of α-Fe phase with a content of ≥70 wt.% and NaZn phase with a content of ≤10 wt.%. 13 The structure is a 1:13 phase, with the remainder being a rare earth-rich La1Fe1Si1 phase (hereinafter referred to as the 1:1:1 phase). 1- x Ce x (Fe) y Co 1-y ) 11-z Si z Melt-quenched thin strip.

[0014] Preferably, the particle size of the Fe powder binder is 5 μm.

[0015] Preferably, the amount of Fe powder added as adhesive is 10 wt.%.

[0016] Preferably, the sintering heating rate is 100±50K / min, the pressure is 30-50MPa, and the holding time is 1-10min.

[0017] Preferably, the sintering and forming are all carried out under a vacuum degree <10. –4The process is carried out under Pa conditions. The temperature of the mold below 1273K is detected by thermocouples inside the furnace, while the temperature of the mold above 1273K is detected by infrared detectors.

[0018] The step of the discharge plasma sintering is as follows: (La) 1-x Ce x (Fe) y Co 1-y ) 11-z Si z The Fe powder mixture is loaded into a mold, which is then placed in a sintering furnace and pressure is applied at 30-50 MPa. The mold is rapidly heated to 1073-1273 K at a heating rate of 100±50 K / min, held at that temperature and pressure for 1-10 min, and then cooled in the furnace to below 373 K before depressurization. The resulting La-Fe-Si based composite magnetic refrigeration block is then demolded.

[0019] This invention relates to a method for preparing alloy powder particles with suitable particle size (45-90μm) by mechanical grinding and screening, which are then uniformly mixed with Fe powder (5μm particle size) at a mass ratio of 9:1 and subjected to spark plasma sintering. During spark plasma sintering, the localized high temperature on the particle surface promotes element diffusion through the electric field, resulting in sintering and forming in a short time. This yields a La-Fe-Si based composite magnetic refrigeration block with a high content of 1:13 phase. This method significantly improves mechanical properties while maintaining good refrigeration capacity of the material and shortening the sample preparation cycle.

[0020] The method of this invention uses (La) 1-x Ce x (Fe) y Co 1-y ) 11-z Si z The compound particles are magnetocaloric materials, with micron-sized Fe powder as a binder, and are formed using high-temperature SPS technology. During the high-temperature SPS process, fine iron powder particles fill the (La)... 1-x Ce x (Fe) y Co 1-y ) 11-z Si zThe gaps between compound particles generate high local temperatures on the surface during sintering, forming a reliable metallurgical bond with the main phase particles, reducing material porosity, and thus obtaining a La-Fe-Si based room-temperature magnetic refrigeration bulk material with high density and excellent magnetocaloric properties. The high-temperature discharge plasma sintering (SPS) powder self-bonding technology for improving the performance of La-Fe-Si based magnetocaloric materials is a rapid powder consolidation technology that utilizes a high-current pulsed power supply to excite and promote the material's consolidation and reactive sintering process. During SPS sintering, the discharge plasma instantaneously generated when a DC pulsed current is applied to the electrodes activates the particle surface; the current flowing through the particles causes Joule heating within the sintered body, resulting in uneven temperature distribution and melting of the particle surface due to localized excessively high temperatures. Compared to hot pressing, SPS technology has significant advantages: uniform heating and rapid temperature rise; short sintering time, high production efficiency, and fine and uniform product structure; it almost maintains the natural state of the raw materials, forming a reliable metallurgical bond between particles, resulting in high-density bulk materials. Combining the La-Fe-Si based magnetic refrigeration tape obtained through composition design and melt quenching technology, the subsequent high-temperature SPS sintering process, driven by the addition of fine micron-sized iron powder particles, achieves powder bonding and molding. During the heating process, the decomposition of the 1:13 phase is minimized, and phase formation is rapid during the holding stage. After the holding stage, the material is rapidly cooled to room temperature. This effectively improves the density of the La-Fe-Si based magnetic refrigeration material and shortens the material preparation cycle while minimizing the reduction in the magnetic refrigeration capacity of the La-Fe-Si based magnetic refrigeration material. This simultaneously solves the problems of long sample preparation cycle and subsequent processing and molding, which are conducive to commercial application.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1) The material used in this invention is La-Fe-Si rapid-quenching strip that does not require heat treatment for phase formation. Utilizing the rapid heating advantage of spark plasma sintering technology, the decomposition of the 1:13 phase is effectively avoided, which facilitates subsequent phase formation. Furthermore, since the untreated strip contains a large amount of α-Fe phase, its good toughness helps maintain the integrity of the La-Fe-Si based alloy particles during sintering, avoiding particle breakage and resulting in uneven microstructure, thus improving the density of the bulk material.

[0023] 2) This invention selects different sintering temperatures for high-temperature discharge plasma sintering, and under different temperature conditions (La... 1-x Ce x (Fe) y Co 1-y ) 11-z Si zThe degree of alloy melting on the surface of the compound particles varies. As the SPS temperature increases, the melting of the alloy on the particle surface becomes more pronounced, thereby improving the metallurgical bonding between particles and contributing to increased density of the formed bulk material. Different SPS sintering temperatures also lead to variations in the latitude and longitude of the alloy during the sintering process. 1-x Ce x (Fe) y Co 1-y ) 11-z Si z The temperature of the compound particles varies. A suitable sintering temperature can promote the homogenization of the internal composition of the particles, achieving the purpose of phase formation. This solves the problems of long cycle and complex process in the traditional preparation method of La-Fe-Si based alloys, and effectively shortens the preparation cycle.

[0024] 3) This invention adds fine micron-sized Fe powder as a sintering aid. Due to the good toughness and ductility of the fine micron-sized Fe powder particles, they can fully fill the (La) during the sintering process. 1-x Ce x (Fe) y Co 1-y ) 11-z Si z The gaps between the compound particles achieve the purpose of encapsulating the main phase particles, thereby greatly improving the mechanical properties of the sintered bulk material. Furthermore, iron powder and (La) 1-x Ce x (Fe) y Co 1-y ) 11-z Si z The interdiffusion of elements between compound particles does not lead to the formation of other alloy compounds that degrade the magnetic properties of the material, thus maximizing the magnetocaloric properties of the sintered bulk material and achieving excellent comprehensive performance in a shorter preparation time.

[0025] 4) This invention uses untreated La-Fe-Si based materials. During SPS sintering, localized high temperature and electric field assistance are used to promote element diffusion, achieving the desired shape and NaZn. 13 The simultaneous formation of the magnetocaloric phase (1:13 phase) greatly simplifies the process flow. Attached Figure Description

[0026] Figure 1 The SPS sintering temperatures in Examples 1-4 were 1123, 1173, 1223, and 1273 K, respectively (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 XRD pattern of / 10wt.%Fe magnetic refrigeration composite material.

[0027] Figure 2 The SPS sintering temperatures in Examples 1-4 were 1123, 1173, 1223, and 1273 K, respectively (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 A bar chart of phase content determined by refined XRD patterns in a 10wt.%Fe magnetic refrigeration composite material.

[0028] Figure 3a , Figure 3b , Figure 3c and Figure 3d The (La) samples from Examples 1 (sintered at 1123K), 2 (sintered at 1173K), 3 (sintered at 1223K), and 4 (sintered at 1223K) are respectively. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Backscattering image of a 10wt.%Fe magnetic refrigeration bulk material.

[0029] Figure 4 The SPS sintering temperatures in Examples 1-4 were 1123, 1173, 1223, and 1273 K, respectively (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Bar chart of experimental density and porosity of / 10wt.%Fe magnetic refrigeration composite material.

[0030] Figure 5 The SPS sintering temperatures in Examples 1-4 were 1123, 1173, 1223, and 1273 K, respectively (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 MT curves and dM / dT-T curves of / 10wt.%Fe magnetic refrigeration composite material.

[0031] Figure 6 The SPS sintering temperatures in Examples 1-4 were 1123, 1173, 1223, and 1273 K, respectively (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Magnetic entropy change-temperature relationship curve of / 10wt.%Fe magnetic refrigeration composite material.

[0032] Figure 7 The SPS sintering temperatures in Examples 1-4 were 1123, 1173, 1223, and 1273 K, respectively (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Stress-strain curve of / 10wt.%Fe magnetic refrigeration composite material. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the embodiments.

[0034] Example 1

[0035] A La-Fe-Si based magnetic refrigeration bulk material, the preparation method of which is as follows:

[0036] Step 1: Press (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The nominal composition of the alloy is as follows: raw materials are pure La (≥99.5 wt.%), Ce (≥99.5 wt.%), Fe (≥99.95 wt.%), Co (≥99.5 wt.%), and Si (≥99.95 wt.%) in bulk form, with the balance of La and Ce at 5 wt.% to compensate for the mass loss due to volatilization during the smelting process. The alloy is obtained through melt rapid quenching. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy strips;

[0037] Step 2: Take the untreated (La) obtained in Step 1 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Strip mechanical grinding and sieving were used to obtain powder with a particle size of 45-90 μm (La). 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy powder particles.

[0038] Step 3: Weigh 0.8g of iron powder with a particle size of 5μm;

[0039] Step 4: Weigh 7.2g of powder with a particle size of 45-90μm (La). 0.8 Ce 0.2 )Fe 9.2 Co0.6 Si 1.2 alloy powder;

[0040] Step 5: Mix the powder for 30 minutes, then put the powder particles into a Φ15mm×12mm mold and pre-compact them.

[0041] Step 6: Using the sintering furnace program control, apply a pressure of 50MPa and heat the mold to 1123K at a heating rate of 100K / min. After the temperature stabilizes, hold the mold at that temperature for 5 minutes and then stop heating. Allow the mold to cool to room temperature and release the pressure. Then, remove the mold for demolding.

[0042] The Φ15mm×5mm (La) obtained through the above six steps 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 / 10wt.%Fe magnetic refrigeration composite block.

[0043] In Example 1, (La) was sintered by SPS at 1123K. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the XRD pattern of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 1 .

[0044] In Example 1, (La) was sintered by SPS at 1123K. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the phase content diagram of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 2 .

[0045] Figure 3a The (La) sintered by SPS at 1123K in the example 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2Backscattered image of a 10wt.% Fe magnetic refrigeration bulk material. During high-temperature discharge plasma sintering (SPS) at 1123K, the particles themselves exhibit discharge phenomena and generate localized high temperatures. Micron-sized Fe powder fills the voids in the main phase particles, forming a metallurgical bond between them. However, due to the relatively low SPS sintering temperature, atomic diffusion in the sample is uneven, the 1:13 phase content is low, and EDS analysis of different regions revealed the presence of two 1:13 phases (A and B) with different compositions. Furthermore, the α-Fe phase and La-rich phase were present in significant quantities, indicating insufficiently uniform diffusion.

[0046] In Example 1, (La) was sintered by SPS at 1123K. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the bar chart for the experimental density and porosity of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 4 .

[0047] In Example 1, (La) was sintered by SPS at 1123K. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 For the MT curve and dM / dT-T curve of the / 10wt.%Fe magnetic refrigeration bulk material, please refer to [reference]. Figure 5 .

[0048] In Example 1, (La) was sintered by SPS at 1123K. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The relationship between the magnetic entropy change and temperature of the / 10wt.%Fe magnetic refrigeration bulk material is shown in the curve. Figure 6 The maximum magnetic entropy of the sample under a 2T magnetic field change is ~2.57 J·kg⁻¹. -1 ·K -1 .

[0049] In Example 1, (La) was sintered by SPS at 1123K. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The stress-strain curve of the / 10wt.%Fe magnetic refrigeration bulk material is shown in [reference]. Figure 7 The sample exhibits good mechanical properties (maximum compressive strength) (~1140 MPa).

[0050] Example 2

[0051] A La-Fe-Si based magnetic refrigeration bulk material, the preparation method of which is as follows:

[0052] Step 1: Press (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The nominal composition of the alloy is as follows: raw materials are pure La (≥99.5 wt.%), Ce (≥99.5 wt.%), Fe (≥99.95 wt.%), Co (≥99.5 wt.%), and Si (≥99.95 wt.%) in bulk form, with the balance of La and Ce at 5 wt.% to compensate for the mass loss due to volatilization during the smelting process. The alloy is obtained through melt rapid quenching. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy strips;

[0053] Step 2: Take the untreated (La) obtained in Step 1 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Strip mechanical grinding and sieving were used to obtain powder with a particle size of 45-90 μm (La). 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy powder particles.

[0054] Step 3: Weigh 0.8g of iron powder with a particle size of 5μm;

[0055] Step 4: Weigh 7.2g of powder with a particle size of 45-90μm (La). 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 alloy powder;

[0056] Step 5: Mix the powder for 30 minutes, then put the powder particles into a Φ15mm×12mm mold and pre-compact them.

[0057] Step 6: Using the sintering furnace program control, apply a pressure of 50MPa and heat the mold to 1173K at a heating rate of 100K / min. After the temperature stabilizes, hold the mold at that temperature for 5 minutes and then stop heating. Allow the mold to cool to room temperature and release the pressure. Then, remove the mold for demolding.

[0058] The Φ15mm×5mm (La) obtained through the above six steps0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 / 10wt.%Fe magnetic refrigeration composite block.

[0059] In Example 2, (La) sintered by SPS at 1173K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the XRD pattern of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 1 .

[0060] In Example 2, (La) sintered by SPS at 1173K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the phase content diagram of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 2 .

[0061] Figure 3b The (La) sintered by SPS at 1173K in the example 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Backscattered image of a 10wt.% Fe magnetic refrigeration bulk material. During high-temperature discharge plasma sintering at 1173K, the particles themselves exhibit discharge phenomena and generate localized high temperatures. Iron powder fills the voids in the main phase particles, forming a metallurgical bond between them. Compared to the sample of Example 1, the uneven atomic diffusion in the sample is improved due to the increased sintering temperature, and the content of the 1:13 phase further increases. EDS analysis of the composition in different regions revealed the presence of two 1:13 phases (A and B) with different compositions. Furthermore, the amounts of α-Fe and La-rich phases decreased, indicating that atomic diffusion is relatively more uniform than in Example 1, but further diffusion is still needed.

[0062] In Example 2, (La) sintered by SPS at 1173K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the bar chart for the experimental density and porosity of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 4 .

[0063] In Example 2, (La) sintered by SPS at 1173K 0.8Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The MT curve and dM / dT-T curve of the / 10wt.%Fe magnetic refrigeration bulk material are shown in [reference]. Figure 5 .

[0064] In Example 2, (La) sintered by SPS at 1173K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The relationship between the magnetic entropy change and temperature of the / 10wt.%Fe magnetic refrigeration bulk material is shown in the curve. Figure 6 The maximum magnetic entropy of the sample under a 2T magnetic field change is ~4.10 J·kg⁻¹. -1 ·K -1 .

[0065] In Example 2, (La) sintered by SPS at 1173K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The stress-strain curve of the / 10wt.%Fe magnetic refrigeration bulk material is shown in [reference]. Figure 7 The sample exhibits good mechanical properties (maximum compressive strength) (~1149 MPa).

[0066] Example 3

[0067] A La-Fe-Si based magnetic refrigeration bulk material, the preparation method of which is as follows:

[0068] Step 1: Press (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The nominal composition of the alloy is as follows: raw materials are pure La (≥99.5 wt.%), Ce (≥99.5 wt.%), Fe (≥99.95 wt.%), Co (≥99.5 wt.%), and Si (≥99.95 wt.%) in bulk form, with the balance of La and Ce at 5 wt.% to compensate for the mass loss due to volatilization during the smelting process. The alloy is obtained through melt rapid quenching. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy strips;

[0069] Step 2: Take the untreated (La) obtained in Step 1 0.8 Ce 0.2 )Fe9.2 Co 0.6 Si 1.2 Strip mechanical grinding and sieving were used to obtain powder with a particle size of 45-90 μm (La). 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy powder particles.

[0070] Step 3: Weigh 0.8g of iron powder with a particle size of 5μm;

[0071] Step 4: Weigh 7.2g of powder with a particle size of 45-90μm (La). 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 alloy powder;

[0072] Step 5: Mix the powder for 30 minutes, then put the powder particles into a Φ15mm×12mm mold and pre-compact them.

[0073] Step 6: Using the sintering furnace program control, apply a pressure of 50MPa and heat the mold to 1223K at a heating rate of 100K / min. After the temperature stabilizes, hold the mold at that temperature for 5 minutes and then stop heating. Allow the mold to cool to room temperature and release the pressure. Then, remove the mold for demolding.

[0074] The Φ15mm×5mm (La) obtained through the above six steps 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 / 10wt.%Fe magnetic refrigeration composite block.

[0075] In Example 3, (La) sintered by SPS at 1223K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the XRD pattern of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 1 .

[0076] In Example 3, (La) sintered by SPS at 1223K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the phase content diagram of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 2 .

[0077] Figure 3c The (La) sintered by SPS at 1223K in the example 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Backscattered image of a 10wt.% Fe magnetic refrigeration bulk material. During high-temperature discharge plasma sintering at 1223K, the particles themselves exhibit discharge phenomena and generate localized high temperatures. Fe powder fills the voids in the main phase particles, forming a metallurgical bond between them. Compared to the sample in Example 2, due to the further increase in sintering temperature, the uneven atomic diffusion in the sample is significantly improved, and the 1:13 phase content is higher. EDS analysis of the composition in different regions revealed that the 1:13 phase composition in the sample is relatively uniform, the La-rich phase disappears, and the amount of α-Fe phase further decreases, indicating that atomic diffusion is basically complete at this point, and the sample has a relatively uniform microstructure. However, a small amount of lanthanum oxide was found at the particle boundaries between the main phase and the iron powder. This is because the particle surface melts due to excessively high local temperatures after the sintering temperature is increased. The 1:13 phase partially decomposes to generate α-Fe and lanthanum-rich liquid phases. The lanthanum-rich liquid phase is oxidized, but its small quantity has little impact on the alloy properties.

[0078] In Example 3, (La) sintered by SPS at 1223K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the bar chart for the experimental density and porosity of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 4 .

[0079] In Example 3, (La) sintered by SPS at 1223K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The MT curve and dM / dT-T curve of the / 10wt.%Fe magnetic refrigeration bulk material are shown in [reference]. Figure 5 .

[0080] In Example 3, (La) sintered by SPS at 1223K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The relationship between the magnetic entropy change and temperature of the / 10wt.%Fe magnetic refrigeration bulk material is shown in the curve. Figure 6 The maximum magnetic entropy of the sample under a 2T magnetic field change is ~6.65 J·kg⁻¹. -1 ·K -1 .

[0081] In Example 3, (La) sintered by SPS at 1223K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The stress-strain curve of the / 10wt.%Fe magnetic refrigeration bulk material is shown in [reference]. Figure 7 The mechanical properties (maximum compressive strength) of the sample decreased compared to Examples 1 and 2 (~980 MPa).

[0082] Example 4

[0083] A La-Fe-Si based magnetic refrigeration bulk material, the preparation method of which is as follows:

[0084] Step 1: Press (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The nominal composition of the alloy is as follows: raw materials are pure La (≥99.5 wt.%), Ce (≥99.5 wt.%), Fe (≥99.95 wt.%), Co (≥99.5 wt.%), and Si (≥99.95 wt.%) in bulk form, with the balance of La and Ce at 5 wt.% to compensate for the mass loss due to volatilization during the smelting process. The alloy is obtained through melt rapid quenching. 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy strips;

[0085] Step 2: Take the untreated (La) obtained in Step 1 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Strip mechanical grinding and sieving were used to obtain powder with a particle size of 45-90 μm (La). 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Alloy powder particles.

[0086] Step 3: Weigh 0.8g of iron powder with a particle size of 5μm;

[0087] Step 4: Weigh 7.2g of powder with a particle size of 45-90μm (La). 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 alloy powder;

[0088] Step 5: Mix the powder for 30 minutes, then put the powder particles into a Φ15mm×12mm mold and pre-compact them.

[0089] Step 6: Using the sintering furnace program control, apply a pressure of 50MPa and heat the mold to 1273K at a heating rate of 100K / min. After the temperature stabilizes, hold the mold at that temperature for 5 minutes and then stop heating. Allow the mold to cool to room temperature and release the pressure. Then, remove the mold for demolding.

[0090] The Φ15mm×5mm (La) obtained through the above six steps 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 / 10wt.%Fe magnetic refrigeration composite block.

[0091] In Example 4, (La) sintered by SPS at 1273K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the XRD pattern of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 1 .

[0092] In Example 4, (La) sintered by SPS at 1273K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the phase content diagram of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 2 .

[0093] Figure 3d The (La) sintered by SPS at 1273K in the example 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2Backscattered image of a 10wt.% Fe magnetic refrigeration bulk material. During high-temperature discharge plasma sintering at 1273K, the particles themselves exhibit discharge phenomena and generate localized high temperatures. Fe powder fills the voids in the main phase particles, forming a metallurgical bond between the particles, resulting in a dense bulk structure. Compared to the sample in Example 3, the sintering temperature was too high, leading to coarsening of the α-Fe phase in the main phase particles. This is because the excessively high sintering temperature caused localized high temperatures on the surface of the main phase particles, resulting in further decomposition of the 1:13 phase. The 1:13 phase content decreased compared to Example 3, while the α-Fe phase content increased. Simultaneously, a small amount of lanthanum oxide was found at the particle boundary between the main phase and the iron powder. This is due to the high sintering temperature causing the particle surface to melt due to localized high temperatures. The 1:13 phase partially decomposed to generate the α-Fe phase and a lanthanum-rich liquid phase. The lanthanum-rich liquid phase was oxidized, but its small quantity had little impact on the alloy properties.

[0094] In Example 4, (La) sintered by SPS at 1273K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 See the bar chart for the experimental density and porosity of the / 10wt.%Fe magnetic refrigeration bulk material. Figure 4 .

[0095] In Example 4, (La) sintered by SPS at 1273K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The MT curve and dM / dT-T curve of the / 10wt.%Fe magnetic refrigeration bulk material are shown in [reference]. Figure 5 .

[0096] In Example 4, (La) sintered by SPS at 1273K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The relationship between the magnetic entropy change and temperature of the / 10wt.%Fe magnetic refrigeration bulk material is shown in the curve. Figure 6 The maximum magnetic entropy of the sample under a 2T magnetic field change is ~6.17 J·kg⁻¹. -1 ·K -1 .

[0097] In Example 4, (La) sintered by SPS at 1273K 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The stress-strain curve of the / 10wt.%Fe magnetic refrigeration bulk material is shown in [reference]. Figure 7 The mechanical properties (maximum compressive strength) of the sample were improved compared to Example 3 (~992 MPa).

Claims

1. A method for preparing La−Fe−Si-based magnetic refrigeration composite materials based on SPS technology, characterized in that, La−Fe−Si-based magnetic refrigeration material powder and micron-sized Fe powder were uniformly mixed and then sintered using high-temperature discharge plasma sintering to prepare a bulk magnetic refrigeration material. The sintering temperature was 1223-1273 K, and the pressure was 10-100 MPa. The La−Fe−Si-based magnetic refrigeration material is (La−Fe−Si-based magnetic refrigeration material) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The compound has a particle size of 45-100 μm, and the micron-sized Fe powder has a particle size of 3-5 μm; The (La) 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 The compound is NaZn with a content ≤100wt.% 13 1:13 phase (La) with a morphological structure 0.8 Ce 0.2 )Fe 9.2 Co 0.6 Si 1.2 Rapidly quenched strip; The mass ratio of the La−Fe−Si-based magnetic refrigeration material powder to the micron-sized Fe powder is (80~99):(1~20).

2. The preparation method according to claim 1, characterized in that, The La−Fe−Si-based magnetic refrigeration material powder has a particle size of 45-90μm, and the amount of micron-sized Fe powder added is 10 wt.%.

3. The preparation method according to claim 1 or 2, characterized in that, The sintering heating rate is 100±50 K / min, the pressure is 30-50MPa, and the holding time is 1-10min.

4. The preparation method according to claim 3, characterized in that, The sintering process is carried out under a vacuum degree <10. –4 The experiment was conducted under Pa conditions.

5. The La−Fe−Si-based magnetic refrigeration composite material prepared by the method according to any one of claims 1 to 4.

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