Method for preparing lattice-configuration magnetic shape memory alloy with excellent magnetic refrigeration performance through extrusion forming and two-stage degreasing

Abstract

The invention discloses a method for preparing lattice-configuration magnetic shape memory alloy with excellent magnetic refrigeration performance through extrusion forming and two-section type degreasing, and belongs to the technical field of metal material additive manufacturing. The problems that when an existing binder-related additive manufacturing method is used for preparing the magnetic shape memory alloy, the component stability is poor, and the time cost is high are solved. The method comprises the following steps: 1, preparing slurry; 2, printing; and 3, sintering. The method is used for preparing the lattice-configuration magnetic shape memory alloy with excellent magnetic refrigeration performance through extrusion forming and two-section type degreasing.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology for metallic materials. Background Technology

[0002] Modern society continues to face severe energy and environmental challenges. Refrigeration technology consumes approximately 20% of global electricity generation, and the problems of high-energy-consuming equipment such as air conditioners and refrigerators are becoming increasingly prominent. Although the market-dominant vapor compression refrigeration technology has been developing for over two centuries, it still suffers from inherent drawbacks such as an actual efficiency of only 30-40% of the Carnot cycle, high operating noise, difficulties in miniaturization, and reliance on greenhouse gas refrigerants. Against this backdrop, solid-state magnetic refrigeration technology based on the magnetocaloric effect, with its advantages of high energy efficiency and environmental friendliness, has become a cutting-edge research direction for solving energy and environmental problems, replacing traditional vapor compression refrigeration. The core efficiency of a solid-state magnetic refrigeration system depends on the performance of the solid refrigerant. An ideal material must produce a significant isothermal entropy change (ΔS) under varying magnetic fields. m ) and adiabatic temperature change (ΔT) ad It possesses high-efficiency heat exchange capabilities. Among numerous candidate materials, magnetic shape memory alloys, with their unique martensitic transformation, exhibit multifunctional properties such as shape memory effect, superelasticity, giant magnetocaloric effect, elastothermal effect, and multicaloric effect, and their operating temperature range covers room temperature, thus holding significant practical value in the field of solid-state refrigerators. Nickel-manganese-tin shape memory alloys, in particular, contain only low-cost, non-toxic elements, combining environmental friendliness and economy. Furthermore, incorporating cobalt into nickel-manganese-tin alloys can further enhance their magnetization performance. Therefore, the nickel-manganese-tin-cobalt alloy system has attracted considerable attention and is expected to become a breakthrough solid-state refrigerant in magnetocaloric refrigeration systems.

[0003] Achieving efficient magnetic refrigeration requires large magnetic entropy change, low hysteresis loss, and high thermal conductivity to enhance the magnetocaloric effect and heat exchange. Simultaneously, an optimal geometric structure with a high specific surface area is needed to enhance heat transfer. However, nickel-manganese-based alloys, as intermetallic compounds, exhibit inherent high brittleness, making them difficult to process into complex geometries, severely limiting their engineering applications.

[0004] Additive manufacturing technology, through its layer-by-layer printing strategy, offers advantages over traditional manufacturing in terms of rapid prototyping, complex structural design, and material processing costs, providing a new path to overcome the bottlenecks in processing brittle materials. Commonly used printing methods for magnetic shape memory alloys include: Laser Powder Bed Fusion, Binder Jetting, and Material Extrusion.

[0005] The authorized patent, CN116251963B, entitled "A Nickel-Manganese-Tin-Co Alloy with Room Temperature Magnetic Phase Transformation Properties and Its Efficient Additive Manufacturing Method and Application," prepared nickel-manganese-tin-cobalt alloy powder using a gas atomization method and then shaped the metal powder into bulk alloy parts using laser powder bed melting technology. However, this method failed to address the crack defects generated under non-equilibrium conditions, resulting in poor magnetic domain continuity and a low saturation magnetization of the alloy under a 5T magnetic field.

[0006] The authorized patent number CN117226107A, entitled "A Porosity-Controllable Additive Manufacturing Method for Nickel-Manganese-Tin-Co Alloy and Application of the Obtained Product," utilizes binder spraying to prepare nickel-manganese-tin-cobalt alloys. While this method avoids the problem of a second phase formation during short-time sintering, which leads to a decrease in magnetocaloric properties, the process is time-consuming, production costs are high, and the magnetocaloric properties of the obtained product still have room for improvement.

[0007] Nickel-manganese-based magnetic shape memory alloys are highly sensitive to composition, microstructure, and phase transformation behavior, making direct application in extrusion additive manufacturing processes difficult. Specifically, the multifunctional properties of magnetic shape memory alloys are highly dependent on martensitic phase transformation, making them extremely sensitive to trace component shifts, porosity distribution, and second-phase precipitation. Furthermore, the organic binders used in material extrusion can easily introduce carbon residues during the debinding stage, leading to the formation of a non-magnetic γ-phase, which adversely affects the material's phase transformation stability and magnetocaloric properties. In addition, existing processes are time-consuming and energy-intensive, hindering large-scale applications. Therefore, achieving stable composition, controllable microstructure, and excellent magnetocaloric properties in magnetic shape memory alloys while ensuring efficient extrusion forming remains a crucial research direction for researchers. Summary of the Invention

[0008] This invention aims to address the problems of poor compositional stability and high time costs in existing binder-related additive manufacturing methods for preparing magnetic shape memory alloys. It provides a method for preparing lattice-structured magnetic shape memory alloys with excellent magnetic cooling performance through extrusion molding and two-stage debinding.

[0009] A method for preparing lattice-structured magnetic shape memory alloys with excellent magnetic refrigeration properties by extrusion molding and two-stage debinding is carried out according to the following steps:

[0010] I. Preparation of the slurry:

[0011] First, nickel-manganese-tin-cobalt alloy powder was prepared by gas atomization. The nickel-manganese-tin-cobalt alloy powder, sodium alginate solution, surfactant aqueous solution and microcrystalline cellulose were mixed to obtain a mixture. The mixture was then ball-milled to obtain nickel-manganese-tin-cobalt alloy slurry.

[0012] II. Printing:

[0013] Under the conditions of substrate temperature of 305K~315K, printing needle inner diameter of 0.24mm~0.30mm, extrusion pressure of 0.12MPa~0.25MPa and printing speed of 4mm / s~8mm / s, nickel manganese tin cobalt alloy paste is used to perform multi-layer printing on the substrate surface to obtain nickel manganese tin cobalt lattice components.

[0014] The nickel-manganese-tin-cobalt lattice component is a grid structure composed of multiple interleaved stacked layers;

[0015] III. Sintering:

[0016] Nickel-manganese-tin-cobalt lattice components, manganese powder, and sponge titanium are loaded into a quartz tube. The quartz tube is then evacuated and protected with argon gas, and finally sealed to obtain a sealed quartz tube. The sealed quartz tube is placed in a tube furnace and heated to 773K~973K at a rate of 8K / min~10K / min, and held at 773K~973K for 15min~30min. Then, the temperature is increased to 1228K~1238K at a rate of 8K / min~10K / min, and held at 1228K~1238K for 1h~2h. Finally, it is cooled at a rate of 15K / min~25K / min, thus completing the extrusion molding and two-stage debinding process to prepare a lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance.

[0017] The beneficial effects of this invention are:

[0018] This invention utilizes magnetic shape memory alloys printed by material extrusion additive manufacturing as the refrigerant. Leveraging the high degree of freedom in this process and combining it with a printing paste exhibiting good extrusion stability, the invention designs the formed structure and interlayer configuration based on magnetocaloric performance requirements. This results in a nickel-manganese-tin-cobalt lattice structure that facilitates heat transfer and mass migration, providing a stable structural foundation for subsequent processes. The high-specific-surface-area nickel-manganese-tin-cobalt lattice component is then vacuum-sealed in a quartz tube for segmented debinding and sintering. This approach synergistically enhances material performance from multiple levels, including structural design, heat treatment path, and composition control.

[0019] During the 773K~973K holding stage for 15min~30min, the binder is decomposed and smoothly discharged through the regular lattice structure and through-channels constructed by the material extrusion molding, avoiding the retention of decomposition products inside the material and the formation of carbon residue or local component enrichment. This process maintains the stability of the green body structure while avoiding the risk of γ-phase precipitation caused by impurity residue or chemical inhomogeneity, thereby improving the magnetic entropy change of the material. During the 1228K~1238K holding stage for 1h~2h, densification treatment is carried out after thorough degreasing. By shortening the high-temperature exposure time of the sample, the volatilization of manganese in the material is reduced, improving the component loss caused by long degreasing in the traditional one-step sintering process, and further stabilizing the martensitic phase transformation behavior. Through the synergistic effect of the above high specific surface area structural design and segmented degreasing sintering process, this invention effectively suppresses the precipitation of non-magnetic second phase while simultaneously improving the compositional stability and microstructure uniformity, enabling the nickel-manganese-tin-cobalt magnetic shape memory alloy to exhibit excellent room-temperature magnetocaloric cooling capacity. In addition, this process route reduces the overall sintering time and energy consumption, improves the success rate of preparation and process repeatability, and takes into account the reliability and economy of the production process while ensuring performance, thus showing good prospects for engineering applications. Attached Figure Description

[0020] Figure 1 A photograph of the nickel-manganese-tin-cobalt lattice component prepared in step two of Example 1;

[0021] Figure 2 The image shows the surface morphology of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1.

[0022] Figure 3 This is a photograph of the surface morphology of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1 after polishing.

[0023] Figure 4 Comparison diagram of chemical composition of lattice-configuration magnetic shape memory alloys prepared in step three of Examples 1 and Comparative Experiments 1 to 4;

[0024] Figure 5 The room temperature XRD pattern of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1;

[0025] Figure 6 The image shows the EBSD characterization of the lattice-configuration magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1.

[0026] Figure 7 The isofield magnetization curve of the lattice-configuration magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1;

[0027] Figure 8 The isothermal magnetization curve of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1 is shown.

[0028] Figure 9 The isothermal magnetic entropy change curve of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1;

[0029] Figure 10 This is a schematic diagram of the structure of the multilayer printed nickel-manganese-tin-cobalt lattice component in step two of the present invention;

[0030] Figure 11 The thermogravimetric curve of the nickel-manganese-tin-cobalt lattice component prepared in step two of Example 1. Detailed Implementation

[0031] Specific implementation method one, combined with Figure 10 Detailed description: This embodiment describes a method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration properties through extrusion molding and two-stage debinding. It is carried out according to the following steps:

[0032] I. Preparation of the slurry:

[0033] First, nickel-manganese-tin-cobalt alloy powder was prepared by gas atomization. The nickel-manganese-tin-cobalt alloy powder, sodium alginate solution, surfactant aqueous solution and microcrystalline cellulose were mixed to obtain a mixture. The mixture was then ball-milled to obtain nickel-manganese-tin-cobalt alloy slurry.

[0034] II. Printing:

[0035] Under the conditions of substrate temperature of 305K~315K, printing needle inner diameter of 0.24mm~0.30mm, extrusion pressure of 0.12MPa~0.25MPa and printing speed of 4mm / s~8mm / s, nickel manganese tin cobalt alloy paste is used to perform multi-layer printing on the substrate surface to obtain nickel manganese tin cobalt lattice components.

[0036] The nickel-manganese-tin-cobalt lattice component is a grid structure composed of multiple interleaved stacked layers;

[0037] III. Sintering:

[0038] Nickel-manganese-tin-cobalt lattice components, manganese powder, and sponge titanium are loaded into a quartz tube. The quartz tube is then evacuated and protected with argon gas, and finally sealed to obtain a sealed quartz tube. The sealed quartz tube is placed in a tube furnace and heated to 773K~973K at a rate of 8K / min~10K / min, and held at 773K~973K for 15min~30min. Then, the temperature is increased to 1228K~1238K at a rate of 8K / min~10K / min, and held at 1228K~1238K for 1h~2h. Finally, it is cooled at a rate of 15K / min~25K / min, thus completing the extrusion molding and two-stage debinding process to prepare a lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance.

[0039] In this specific embodiment, the substrate temperature is 305K~315K to promote interlayer bonding strength. The nickel-manganese-tin-cobalt slurry is loaded into a plastic syringe equipped with a replaceable conical needle at the end, with an inner diameter of 0.24mm~0.30mm. To ensure stable slurry extrusion and forming quality, the extrusion pressure is 0.12MPa~0.25MPa, and the printing speed is 4mm / s~8mm / s. Online back pressure compensation and pulse voltage stabilization ensure the consistency of the extruded filament diameter, keeping instantaneous flow fluctuations within the range of -3%~3%.

[0040] In this specific embodiment, the addition of manganese powder can compensate for the loss of manganese elements under high-temperature sintering; titanium has an extremely strong oxygen adsorption capacity, and the addition of sponge titanium can absorb residual oxygen while providing a channel for degreasing gas; a high-temperature flame gun is used to seal the pipe opening.

[0041] In this specific embodiment, a sealed quartz tube is placed in a tube furnace. First, the temperature is increased to 773K~973K at a rate of 8K / min~10K / min and held for 15min~30min to complete the decomposition of the binder and partial degreasing, thereby avoiding the risk of γ second phase formation. Then, the temperature is increased again at a rate of 8K / min~10K / min. This heating rate can effectively avoid the accumulation of thermal stress and the generation of cracks in the pores caused by excessively rapid heating. The temperature is increased to 1228K~1238K and held for 1h~2h to achieve complete degreasing, reduce the volatilization of manganese in the material, achieve densification of the pores, and control the closed porosity in the pores to within 3%. Finally, the tube is cooled at a rate of 15K / min~25K / min.

[0042] This specific embodiment proposes a material extrusion additive manufacturing method by selecting a suitable nickel-manganese-tin-cobalt alloy powder slurry to print a porous billet with a high specific surface area and a lattice structure. Through a vacuum two-stage debinding and sintering process, the binder is removed in stages and the pore edges are densified. At the same time, crack defects in the pore edges and the generation of a second phase that is detrimental to the magnetic refrigeration performance are avoided. A magnetic shape memory alloy with excellent room temperature magnetic refrigeration performance is prepared, and the heat dissipation efficiency is improved by increasing the specific surface area.

[0043] The beneficial effects of this specific implementation method are:

[0044] This embodiment utilizes magnetic shape memory alloys printed by material extrusion additive manufacturing as the refrigerant. Taking advantage of the high degree of freedom in this process and combining it with a printing paste exhibiting good extrusion stability, the formed structure and interlayer configuration are specifically designed based on magnetocaloric performance requirements. This results in a nickel-manganese-tin-cobalt lattice structure that facilitates heat transfer and mass migration, providing a stable structural foundation for subsequent processes. The high specific surface area nickel-manganese-tin-cobalt lattice component is then vacuum-sealed in a quartz tube for segmented debinding and sintering. This approach synergistically enhances material performance from multiple levels, including structural design, heat treatment path, and composition control.

[0045] During the 773K~973K holding stage for 15min~30min, the binder is decomposed and discharged smoothly through the regular lattice structure and through-channels constructed by the material extrusion molding, avoiding the retention of decomposition products inside the material and the formation of carbon residue or local component enrichment. This process maintains the stability of the green body structure while avoiding the risk of γ-phase precipitation caused by impurity residue or chemical inhomogeneity, thereby improving the magnetic entropy change of the material. During the 1228K~1238K holding stage for 1h~2h, densification treatment is carried out after thorough degreasing. By shortening the high-temperature exposure time of the sample, the volatilization of manganese in the material is reduced, improving the component loss caused by long degreasing in the traditional one-step sintering process, and further stabilizing the martensitic phase transformation behavior. Through the synergistic effect of the above high specific surface area structural design and segmented degreasing sintering process, this embodiment effectively suppresses the precipitation of non-magnetic second phase while simultaneously improving the compositional stability and microstructure uniformity, enabling the nickel-manganese-tin-cobalt magnetic shape memory alloy to exhibit excellent room-temperature magnetocaloric cooling capacity. In addition, this process route reduces the overall sintering time and energy consumption, improves the success rate of preparation and process repeatability, and takes into account the reliability and economy of the production process while ensuring performance, thus showing good prospects for engineering applications.

[0046] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the chemical formula of the nickel-manganese-tin-cobalt alloy powder mentioned in step one is Ni. 41 Mn 43 Sn 10Co6; the particle size of the nickel-manganese-tin-cobalt alloy powder mentioned in step one is ≤15μm. Everything else is the same as in specific embodiment one.

[0047] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in the following ways: the concentration of the sodium alginate solution in step one is 3wt%~8wt%; the surfactant aqueous solution in step one is a 20wt%~40wt% Pronic F-127 aqueous solution; the mass ratio of the nickel-manganese-tin-cobalt alloy powder to the sodium alginate solution in step one is 1:(0.08~0.12); the mass ratio of the nickel-manganese-tin-cobalt alloy powder to the surfactant aqueous solution in step one is 1:(0.01~0.02); the mass ratio of the nickel-manganese-tin-cobalt alloy powder to microcrystalline cellulose in step one is 1:(0.02~0.04). Everything else is the same as in Specific Implementation Method One or Two.

[0048] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the ball milling described in step one is carried out as follows: using zirconia balls with a diameter of 4mm to 6mm as grinding balls, the mixture is ball-milled for 1.5h to 2h under the conditions of a ball-to-material mass ratio of (4~7):1 and a rotation speed of 1100r / min to 1300r / min to obtain a nickel-manganese-tin-cobalt alloy slurry. The rest is the same as in Specific Implementation Methods One to Three.

[0049] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the viscosity of the nickel-manganese-tin-cobalt alloy slurry described in step one is 5 × 10⁻⁶ at room temperature. 3 Pa•s ~7×10 3 Pa.s. Other aspects are the same as in specific embodiments one through four.

[0050] In this specific embodiment, the viscosity of the slurry at room temperature is 5 × 10⁻⁶. 3 ~7×10 3 Pa•s can quickly recover its viscoelastic modulus after extrusion, ensuring that the interlayer overlay does not collapse, thus achieving stable forming for subsequent printing.

[0051] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the substrate mentioned in step two is an alumina plate covered with a plastic film. Everything else is the same as in Specific Implementation Methods One to Five.

[0052] In this specific embodiment, the substrate is an alumina plate covered with a plastic film, which ensures uniform shrinkage of the printed parts during the drying process and avoids interface warping.

[0053] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: during the printing process in Step Two, the temperature of the printing chamber is 295K~303K, and the relative humidity of the printing chamber is 30%~50%. Everything else is the same as Specific Implementation Methods One to Six.

[0054] This specific embodiment uses a custom-designed material extrusion 3D printing device equipped with an air pump, a precision pressure regulator, and a temperature-controlled printing chamber. The printing chamber temperature is maintained at 295K~303K, and the relative humidity is controlled at 30%~50% to stabilize the slurry rheological behavior.

[0055] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the grid spacing of the grid structure described in step two is 0.75mm~1.10mm, the diameter of the grid lines is 0.28mm~0.35mm, and the channels of the grid structure are vertically interconnected; the layer height of each layer in the nickel-manganese-tin-cobalt lattice component described in step two is 0.20mm~0.28mm, and each layer is composed of multiple parallel lines, with a rotation angle of 60°~90° between adjacent layers. Everything else is the same as in Specific Implementation Methods One to Seven.

[0056] In this specific embodiment, the rotation angle between adjacent layers is set to 60~90° to regulate pore connectivity and increase specific surface area.

[0057] In this specific embodiment, the diameter of the grid lines is controlled between 0.28 mm and 0.35 mm by pressure-velocity coupling.

[0058] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in the following ways: the mass ratio of manganese powder to nickel-manganese-tin-cobalt lattice components in step three is 1:(0.8~1.2); the mass ratio of manganese powder to sponge titanium in step three is 1:(0.2~0.4); the particle size of the manganese powder in step three is 15μm~53μm; the porosity of the sponge titanium in step three is 70%~85%; in the sealed quartz tube in step three, the manganese powder is located 2cm~4cm from the bottom of the quartz tube, the nickel-manganese-tin-cobalt lattice components are located 7cm~10cm above the manganese powder, and the sponge titanium is located 5cm~7cm above the nickel-manganese-tin-cobalt lattice components, and the nickel-manganese-tin-cobalt lattice components are pressed tightly against the inner wall of the tube using a magnet. Everything else is the same as in Specific Implementation Methods One to Eight.

[0059] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One through Nine in that: the vacuuming and argon gas introduction in step three is specifically performed as follows: first, vacuum for 5 to 10 minutes to achieve a vacuum level of 10 inside the quartz tube. -4 The pressure was reduced to below 1 Pa, then high-purity argon gas at 1 atmosphere was reinflated. This process of evacuation and argon reinflating was repeated multiple times. Finally, 3 × 10⁻⁶ Pa was introduced. 3Pa~5×10 3 Pa is protected with high-purity argon gas; the purity of the high-purity argon gas is 99.999%. Other aspects are the same as in specific embodiments one through nine.

[0060] The beneficial effects of the present invention are verified using the following embodiments:

[0061] Example 1:

[0062] A method for preparing lattice-structured magnetic shape memory alloys with excellent magnetic refrigeration properties by extrusion molding and two-stage debinding is carried out according to the following steps:

[0063] I. Preparation of the slurry:

[0064] First, nickel-manganese-tin-cobalt alloy powder was prepared by gas atomization. The nickel-manganese-tin-cobalt alloy powder, sodium alginate solution, surfactant aqueous solution and microcrystalline cellulose were mixed to obtain a mixture. The mixture was then ball-milled to obtain nickel-manganese-tin-cobalt alloy slurry.

[0065] II. Printing:

[0066] Under the conditions of substrate temperature of 313K, printing needle inner diameter of 0.30mm, extrusion pressure of 0.20MPa and printing speed of 8mm / s, nickel manganese tin cobalt alloy paste was used to perform multi-layer printing on the substrate surface to obtain nickel manganese tin cobalt lattice components.

[0067] The nickel-manganese-tin-cobalt lattice component is a grid structure composed of multiple interleaved stacked layers;

[0068] III. Sintering:

[0069] A nickel-manganese-tin-cobalt lattice component, manganese powder, and sponge titanium were loaded into a quartz tube. The quartz tube was then evacuated and protected with argon gas, and finally sealed to obtain a sealed quartz tube. The sealed quartz tube was placed in a tube furnace and heated to 873 K at a rate of 10 K / min, and held at 873 K for 20 min. Then, the temperature was increased to 1233 K at a rate of 10 K / min, and held at 1233 K for 1 h. Finally, the temperature was cooled at a rate of 20 K / min to obtain a lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration properties.

[0070] The chemical formula of the nickel-manganese-tin-cobalt alloy powder mentioned in step one is Ni. 41 Mn 43 Sn 10 Co6; the particle size of the nickel-manganese-tin-cobalt alloy powder mentioned in step one is 5μm~15μm.

[0071] The concentration of the sodium alginate solution mentioned in step one is 5 wt%; the surfactant aqueous solution mentioned in step one is a 30 wt% Pluronic F-127 aqueous solution; the mass ratio of the nickel-manganese-tin-cobalt alloy powder to the sodium alginate solution mentioned in step one is 110:10; the mass ratio of the nickel-manganese-tin-cobalt alloy powder to the surfactant aqueous solution mentioned in step one is 110:1.5; the mass ratio of the nickel-manganese-tin-cobalt alloy powder to microcrystalline cellulose mentioned in step one is 110:2.2.

[0072] The ball milling described in step one is specifically carried out according to the following steps: using zirconia balls with a diameter of 5 mm as grinding balls, the mixture is ball-milled for 2 hours at a ball-to-material mass ratio of 5:1 and a rotation speed of 1100 r / min to obtain a nickel-manganese-tin-cobalt alloy slurry; the viscosity of the nickel-manganese-tin-cobalt alloy slurry at room temperature is 6 × 10⁻⁶. 3 Pa•s.

[0073] The substrate mentioned in step two is an alumina plate covered with a plastic film.

[0074] During the second step of the printing process, the temperature in the printing chamber is 300K and the relative humidity in the printing chamber is 40%.

[0075] The mesh spacing of the mesh structure described in step two is 0.8 mm, the diameter of the mesh line is 0.3 mm, and the channels of the mesh structure are vertically connected; the layer height of each layer in the nickel-manganese-tin-cobalt lattice component described in step two is 0.20 mm, and each layer is composed of multiple parallel lines, with a rotation angle of 90° between adjacent layers.

[0076] In step three, the mass ratio of manganese powder to nickel-manganese-tin-cobalt lattice components is 1:1; the mass ratio of manganese powder to sponge titanium is 1:0.2; the particle size of manganese powder in step three is 15μm~53μm; the porosity of sponge titanium raw material in step three is 80%; in the sealed quartz tube in step three, the manganese powder is located 4cm from the bottom of the quartz tube, the nickel-manganese-tin-cobalt lattice components are located 10cm above the manganese powder, and the sponge titanium is located 5cm above the nickel-manganese-tin-cobalt lattice components. The nickel-manganese-tin-cobalt lattice components are pressed tightly against the inner wall of the tube using a magnet.

[0077] Step 3, which involves evacuating the vacuum and introducing argon gas, is specifically performed as follows: First, evacuate the vacuum for 10 minutes to achieve a vacuum level of 2 × 10⁻⁶ inside the quartz tube. -5 Pa, then refill with 1 atmosphere of high-purity argon gas, repeating the vacuuming and argon refilling process multiple times, finally filling with 5 × 10 Pa. 3 Pa is protected with high-purity argon gas; the purity of the high-purity argon gas is 99.999%.

[0078] Comparative Experiment 1: This embodiment differs from Embodiment 1 in that step 1 is performed at a temperature of 1213K for 1 hour. Everything else is the same as in Embodiment 1.

[0079] Comparative Experiment 2: This example differs from Example 1 in that in step one, the temperature is maintained at 1223K for 1 hour. Everything else is the same as in Example 1.

[0080] Comparative Experiment 3: This example differs from Example 1 in that in step one, the temperature is maintained at 1243K for 1 hour. Everything else is the same as in Example 1.

[0081] Comparative Experiment 4: This example differs from Example 1 in that in step one, the temperature is maintained at 1253K for 1 hour. Everything else is the same as in Example 1.

[0082] Figure 1 The image shows a photograph of the nickel-manganese-tin-cobalt lattice component prepared in step two of Example 1. As can be seen from the image, the nickel-manganese-tin-cobalt lattice component prepared by material extrusion has high forming quality and does not have problems such as collapse or obvious boundary blurring.

[0083] Figure 2 The image shows the morphology of the lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1. As can be seen from the image, there are a small number of uniformly distributed pores on the surface, and careful observation reveals that the pores are mainly concentrated at the grain boundaries. The overall density can be obtained as 95.2% by Archimedes' displacement method, with an open porosity of about 3.4% and a closed porosity of about 1.4%.

[0084] Figure 3 The image shows the surface morphology of the lattice-structured magnetic shape memory alloy with excellent magnetic cooling performance prepared in step three of Example 1 after polishing. As can be seen from the image, after the sample is vibrated and polished, the proportion of irregularly shaped connected pores is low, and most of them are circular closed pores, while there are uniformly distributed micropores.

[0085] And by Figure 2 and Figure 3 It can be seen that after sintering, neither the original surface nor the polished surface has any crack defects.

[0086] Figure 4This is a comparison of the chemical composition of the lattice-configured magnetic shape memory alloys prepared in step three of Examples 1 and Comparative Experiments 1 to 4. By comparing the samples sintered and densified at 1213K~1253K, it was found that the chemical composition of the sample sintered at 1233K in Example 1 was stable, especially the Mn element, with a loss of less than 0.2%. Segmented degreasing followed by short-time high-temperature sintering reduced Mn evaporation. As the temperature gradually increased beyond this range, the Mn content loss was significant, reaching a maximum of approximately 0.7%, corresponding to the precipitation of the second phase. Since the second phase does not participate in the martensitic phase transformation, this affects the final magnetocaloric properties of the material. Therefore, during the high-temperature sintering stage, the sample sintered in Example 1 balanced the compositional loss with the density change.

[0087] Figure 5 The room temperature XRD pattern of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1 is shown in the figure. The figure shows that there is a single L21 ordered austenite phase with the space group Fm-3m (225) in the sintered sample. This phase has superlattice diffraction peaks such as (200), (220), (400) and (422).

[0088] Figure 6 The image shows the EBSD characterization of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1. It can be seen that the sample has an equiaxed crystal structure with uniform grain orientation. The inverse pole figure results indicate that there is no obvious texture in the sample, the grain orientation tends to be evenly distributed, and the overall structure is isotropic. Further statistical analysis of the grain size shows that the grain size distribution is uniform, approximately following a normal distribution, with an average grain size of 7.49 μm. Furthermore, the sintered samples are dominated by large-angle grain boundaries.

[0089] Figure 7 The isofield magnetization curves of the lattice-configuration magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1 are shown. Its phase transformation parameters are shown in Table 1. Its martensitic phase transformation temperature is near room temperature, indicating significant potential for room-temperature magnetic refrigeration. The phase transformation exhibits good uniformity, with a phase transformation width of only 14 K. Under a 0.02 T magnetic field, the phase transformation hysteresis is only 24 K, and this small hysteresis helps improve the reversible cycling performance of the magnetocaloric effect. Under a 5 T magnetic field, the inverse martensitic saturation magnetization difference of the material is 93.4 A•m. 2 •kg -1 It is significantly higher than that of magnetic shape memory alloys prepared by most existing additive manufacturing methods.

[0090] Table 1. Phase transition parameters of the lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1.

[0091]

[0092] Figure 8 The isothermal magnetization curve of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1 is shown. Figure 9 The isothermal magnetic entropy change curves of the lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance prepared in step three of Example 1 are shown. As the test temperature decreases, the slope of the magnetization curve in the magnetization test continuously decreases. This is because at low temperatures, the sample is in a martensite phase with low structural symmetry, making it more difficult to magnetize than austenite. Therefore, as the martensite content increases, the slope of the magnetization curve decreases. At 299 K, with an applied magnetic field strength of 5 T, a maximum of 103.3 A•m was obtained. 2 The magnetization is [value] / kg. The magnetic field induces a magnetic transformation from weakly magnetic martensite to ferromagnetic austenite, therefore ΔS [value]. m It is a positive value. As the magnetic field increases, ΔS m The peak temperature decreases, which is consistent with the trend of the martensitic transformation temperature shifting with changes in the magnetic field. Since some martensite cannot transform into austenite under a magnetic field of 5T, ΔS... m The peak value increases continuously with increasing magnetic field, but does not saturate. Using Maxwell's relation, the maximum ΔS occurs when the magnetic field changes by 5.0 T and the temperature is 294 K. m The value reaches 22.6 J / (kg•K). The refrigeration operating temperature range is wide at 18.1 K. The calculated refrigeration capacity (RC) is 344.8 J / kg, corresponding to a temperature range of 285.6 K to 300.1 K, which is close to room temperature, indicating that this alloy has great application potential in room temperature magnetic refrigeration. The hysteresis loss is determined by the area between magnetization and demagnetization on the integral isothermal magnetization curve. The average hysteresis loss AHL is 182.2 J / kg. After deducting this, the effective refrigeration capacity RC under a 5.0 T magnetic field is calculated. eff It is 161.6 J / kg.

[0093] Figure 11 The thermogravimetric curve (TGA) of the nickel-manganese-tin-cobalt lattice component prepared in step two of Example 1 is shown in the figure. As can be seen from the figure, when the green blank is heated to 373K~693K, the binder undergoes a pyrolysis reaction, resulting in a maximum overall mass reduction of 0.74%, at which point the binder completely decomposes. In the environment of 693K~1144K, the sample weight recovers somewhat due to the reaction of manganese with oxygen in the air to produce manganese oxide. When the temperature is above 1144K, the sample weight decreases again due to the evaporation of manganese at high temperatures. The TGA curve indirectly verifies the rationality of the temperature and time selection for different stages of segmented debinding.

Claims

1. A method for preparing lattice-structured magnetic shape memory alloys with excellent magnetic refrigeration properties through extrusion molding and two-stage debinding, characterized in that... It is done in the following steps: I. Preparation of the slurry: First, nickel-manganese-tin-cobalt alloy powder was prepared by gas atomization. The nickel-manganese-tin-cobalt alloy powder, sodium alginate solution, surfactant aqueous solution and microcrystalline cellulose were mixed to obtain a mixture. The mixture was then ball-milled to obtain nickel-manganese-tin-cobalt alloy slurry. II. Printing: Under the conditions of substrate temperature of 305K~315K, printing needle inner diameter of 0.24mm~0.30mm, extrusion pressure of 0.12MPa~0.25MPa and printing speed of 4mm / s~8mm / s, nickel manganese tin cobalt alloy paste is used to perform multi-layer printing on the substrate surface to obtain nickel manganese tin cobalt lattice components. The nickel-manganese-tin-cobalt lattice component is a grid structure composed of multiple interleaved stacked layers; III. Sintering: Nickel-manganese-tin-cobalt lattice components, manganese powder, and sponge titanium are loaded into a quartz tube. The quartz tube is then evacuated and protected with argon gas, and finally sealed to obtain a sealed quartz tube. The sealed quartz tube is placed in a tube furnace and heated to 773K~973K at a rate of 8K / min~10K / min, and held at 773K~973K for 15min~30min. Then, the temperature is increased to 1228K~1238K at a rate of 8K / min~10K / min, and held at 1228K~1238K for 1h~2h. Finally, it is cooled at a rate of 15K / min~25K / min, thus completing the extrusion molding and two-stage debinding process to prepare a lattice-configured magnetic shape memory alloy with excellent magnetic refrigeration performance.

2. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration performance by extrusion molding and two-stage debinding according to claim 1, characterized in that... The chemical formula of the nickel-manganese-tin-cobalt alloy powder mentioned in step one is Ni. 41 Mn 43 Sn 10 Co6; the particle size of the nickel-manganese-tin-cobalt alloy powder mentioned in step one is ≤15μm.

3. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration properties by extrusion molding and two-stage debinding according to claim 1, characterized in that... The concentration of the sodium alginate solution mentioned in step one is 3wt%~8wt%; the surfactant aqueous solution mentioned in step one is a 20wt%~40wt% Pronic F-127 aqueous solution; the mass ratio of the nickel-manganese-tin-cobalt alloy powder to the sodium alginate solution mentioned in step one is 1:(0.08~0.12); the mass ratio of the nickel-manganese-tin-cobalt alloy powder to the surfactant aqueous solution mentioned in step one is 1:(0.01~0.02); the mass ratio of the nickel-manganese-tin-cobalt alloy powder to microcrystalline cellulose mentioned in step one is 1:(0.02~0.04).

4. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration properties by extrusion molding and two-stage debinding according to claim 1, characterized in that... The ball milling described in step one is carried out in the following steps: using zirconia balls with a diameter of 4mm to 6mm as grinding balls, the mixture is ball milled for 1.5h to 2h under the conditions of a ball-to-material mass ratio of (4 to 7):1 and a rotation speed of 1100r / min to 1300r / min to obtain a nickel-manganese-tin-cobalt alloy slurry.

5. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration properties by extrusion molding and two-stage debinding according to claim 1, characterized in that... The viscosity of the nickel-manganese-tin-cobalt alloy slurry described in step one at room temperature is 5 × 10⁻⁶. 3 Pa•s ~7×10 3 Pa•s.

6. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration performance by extrusion molding and two-stage debinding according to claim 1, characterized in that... The substrate mentioned in step two is an alumina plate covered with a plastic film.

7. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration properties by extrusion molding and two-stage debinding according to claim 1, characterized in that... During the second step of the printing process, the temperature of the printing chamber is 295K~303K, and the relative humidity of the printing chamber is 30%~50%.

8. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration performance by extrusion molding and two-stage debinding according to claim 1, characterized in that... The mesh spacing of the mesh structure described in step two is 0.75mm~1.10mm, the diameter of the mesh lines is 0.28mm~0.35mm, and the channels of the mesh structure are vertically connected; the layer height of each layer in the nickel-manganese-tin-cobalt lattice component described in step two is 0.20mm~0.28mm, and each layer is composed of multiple parallel lines, with a rotation angle of 60°~90° between adjacent layers.

9. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration performance by extrusion molding and two-stage debinding according to claim 1, characterized in that... In step three, the mass ratio of manganese powder to nickel-manganese-tin-cobalt lattice components is 1:(0.8~1.2); the mass ratio of manganese powder to sponge titanium is 1:(0.2~0.4); the particle size of manganese powder in step three is 15μm~53μm; the porosity of sponge titanium in step three is 70%~85%; in the sealed quartz tube in step three, the manganese powder is located 2cm~4cm from the bottom of the quartz tube, the nickel-manganese-tin-cobalt lattice components are located 7cm~10cm above the manganese powder, and the sponge titanium is located 5cm~7cm above the nickel-manganese-tin-cobalt lattice components, and the nickel-manganese-tin-cobalt lattice components are pressed tightly against the inner wall of the tube using a magnet.

10. The method for preparing a lattice-structured magnetic shape memory alloy with excellent magnetic refrigeration properties by extrusion molding and two-stage debinding according to claim 1, characterized in that... Step 3, which involves evacuating the vacuum and introducing argon gas, is specifically performed as follows: First, evacuate the vacuum for 5 to 10 minutes to achieve a vacuum level of 10 inside the quartz tube. -4 The pressure was reduced to below 1 Pa, then high-purity argon gas at 1 atmosphere was reinflated. This process of evacuation and argon reinflating was repeated multiple times. Finally, 3 × 10⁻⁶ Pa was introduced. 3 Pa~5×10 3 Pa is protected with high-purity argon gas; the purity of the high-purity argon gas is 99.999%.

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