FeMnSi shape memory alloy additive manufacturing method based on wire extrusion

Abstract

The invention discloses a FeMnSi shape memory alloy additive manufacturing method based on wire extrusion, and belongs to the technical field of metal additive manufacturing. The raw material FeMnSi memory alloy powder and a binder are melted and mixed and then extruded, and a wire material is obtained; the binder comprises a stearic acid surfactant, a soluble thermoplastic elastomer, soluble low-density polyethylene and insoluble low-density polyethylene; and the wire is subjected to low-temperature 3D printing, a sample blank is obtained, after stress is eliminated, the binder is removed, sintering is conducted in reducing gas, and the compact FeMnSi shape memory alloy is obtained. According to the invention, by optimizing a binder system and through a multi-component synergistic effect, degreasing kinetic optimization is realized, the content of residual organic matters after debonding is greatly reduced, precise forming of a block is ensured, then relatively high relative density is achieved by sintering, the grain size is small, the tensile strength is stabilized in a range of 580-700 MPa, and the memory effect is good.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal additive manufacturing, and particularly relates to a FeMnSi shape memory alloy additive manufacturing method based on wire extrusion. BACKGROUND

[0002] The information disclosed in this BACKGROUND section is for the purpose of increasing the understanding of the background of the present application and should not be taken as an acknowledgement or any form of suggestion that this information forms prior art with respect to any country.

[0003] FeMnSi alloy is an iron-based shape memory alloy with broad application prospects, and has many excellent properties, such as high strength, high toughness, good corrosion resistance, fatigue resistance and radiation resistance. These properties make it have potential application value in the fields of aerospace, automobile, machinery, electronics, etc. In terms of preparation, the bulk material prepared by traditional casting-forging process has defects such as composition segregation and ingot shrinkage, and needs to increase rolling and homogenization heat treatment means for post-processing. With the rapid development of additive manufacturing technology, laser powder additive and electric arc additive technologies are tried to be applied to the preparation of FeMnSi alloy. Laser additive manufacturing has the advantages of high precision, but due to the extremely high energy density of laser, the instantaneous high-temperature molten pool (>2000℃) will intensify the volatilization of low-boiling-point element Mn, causing element segregation of FeMnSi alloy, incomplete γ→ε phase transition problem, and decline of material memory effect; and cause the shift of FeMnSi alloy phase transition temperature (As point), affecting the stability of shape memory effect. Therefore, it is urgent to develop a new preparation method of FeMnSi alloy to avoid the burning loss of alloy elements while obtaining high-precision alloy shape.

[0004] Although the material extrusion-based fused filament fabrication technology (such as FDM derived process) has the advantages of low equipment cost and high forming efficiency, it still faces key bottlenecks in the field of metal materials: the conventional binder system (such as paraffin-polyethylene-based) is prone to internal porosity (porosity >15% after debinding) during the debinding process, and the residual carbon content (>500ppm) will significantly reduce the density of the sintered body; more prominent is that in order to achieve sufficient sintering driving force, the traditional process needs to use high temperature sintering above 1300℃, which will cause abnormal grain growth (average grain size >50μm) in FeMnSi alloy, resulting in a decrease in tensile strength of the sintered material to below 400MPa.

[0005] Therefore, it is urgent to develop a FeMnSi alloy additive manufacturing process that takes into account the low-temperature sintering characteristics and high densification capability, which has become the key to breaking through the bottleneck of the material engineering application. SUMMARY

[0006] In order to solve the problems of the prior art, the purpose of the present application is to provide a FeMnSi shape memory alloy additive manufacturing method based on wire extrusion, which mixes raw material FeMnSi memory alloy powder with a binder, uses an extrusion method to obtain wire, and then uses low-melting-point 3D printing technology to prepare a part, and after removing the binder and high-temperature sintering, the required memory alloy part can be obtained. The present application uses a binder to bond the raw material FeMnSi memory alloy powder, and the 3D printing forming process is carried out at low temperature, which can effectively avoid the burning loss of alloy elements and reduce the mechanical properties of the alloy, and a high-precision part shape can be obtained.

[0007] In order to achieve the above-mentioned purpose, the technical scheme of the present application is: The first aspect of the present application provides a FeMnSi shape memory alloy additive manufacturing method based on wire extrusion, comprising: Preparation of raw material FeMnSi memory alloy powder; After the raw material FeMnSi memory alloy powder is mixed with the binder and then extruded, wire is obtained; the binder comprises a stearic acid surfactant, a soluble thermoplastic elastomer, soluble low-density polyethylene, and insoluble low-density polyethylene; The wire is 3D printed to obtain a sample embryo, after stress relief, the binder is removed, and sintering is carried out in a reducing gas to obtain a FeMnSi shape memory alloy.

[0008] The present application optimizes the binder system, proposes to use a stearic acid surfactant, a soluble thermoplastic elastomer as a toughening agent, and a binder system compounded with soluble low-density polyethylene (LDPE) and insoluble LDPE. The system realizes the optimization of debinding kinetics through the synergistic effect of multiple components. The stearic acid surfactant is adsorbed on the surface of the metal powder during the melt blending stage, reduces the interfacial energy, and increases the volume fraction of the powder to more than 62 vol%; the soluble thermoplastic elastomer and the soluble LDPE are dissolved first during the solvent debinding stage, forming continuous through channels (channel diameter ~ 1-5 μm), which improves the debinding rate of the insoluble LDPE skeleton; the insoluble LDPE maintains the bending strength of the wire at room temperature > 15 MPa by adjusting the molecular weight, and the subsequent low-temperature sintering and organic solvent dissolution can greatly reduce the content of residual organic matter after debinding. After the above step-by-step removal of various binders, the formed FeMnSi printed product still maintains the original shape, but the binder affecting the diffusion and bonding between the powders is basically cleaned up, and a dense body is formed by the diffusion between the powders during the final sintering process. When the sintered body is sintered at a relatively low temperature (relative to the laser additive temperature), it can achieve a relatively high relative density, small grain size, and stable tensile strength in the range of 580-700 MPa.

[0009] In addition, the binder system is formed by low-temperature 3D printing, avoids fluctuations in components caused by excessively high temperatures, is sintered and densified in a reducing gas, effectively avoids burning loss of Mn elements, and reduces the probability of formation of carbide inclusions in the epsilon phase, thereby ensuring the stability of the shape recovery rate. The present application provides a reliable process basis for low-temperature additive manufacturing of high-performance shape memory alloys through the physical dissolution-thermal decomposition step-by-step debinding mechanism.

[0010] In some embodiments of the present application, the raw material FeMnSi memory alloy powder comprises 12-18 wt% Mn, 5-6 wt% Si, 6-10 wt% Cr, 3-6 wt% Ni, 0.1-0.2 wt% C, and the balance is Fe.

[0011] It can be understood that the raw material FeMnSi memory alloy powder is prepared by a conventional preparation method in the art. For example, the element alloy powder or intermediate alloy with the same element ratio is mixed sufficiently, refined in a vacuum melting furnace, and prepared into a powder by a vacuum atomization powdering method to obtain the raw material FeMnSi memory alloy powder.

[0012] In some embodiments of the present application, the mass ratio of the raw material FeMnSi memory alloy powder to the binder is: raw material FeMnSi memory alloy powder: stearic acid surfactant: soluble thermoplastic elastomer: soluble low-density polyethylene (LDPE): insoluble low-density polyethylene (50-70):(2-7):(5-25):(10-20):(5-20).

[0013] It can be understood that the term "soluble" refers to the solubility of the material in the solvent used in the solvent debinding stage (such as cyclohexane impregnation). In the present application, the soluble thermoplastic elastomer refers to a thermoplastic elastomer that can be dissolved in the solvent used in the solvent debinding stage. Similarly, the soluble low-density polyethylene refers to a low-density polyethylene that can be dissolved in the solvent used in the solvent debinding stage, and the insoluble low-density polyethylene refers to a low-density polyethylene that cannot be dissolved in the solvent used in the solvent debinding stage.

[0014] The present application does not limit the specific type of stearic acid surfactant, and any stearic acid surfactant that can be dissolved in the solvent in the debinding stage can be used, such as stearic acid surfactant SA180, stearic acid surfactant SA1845 (Clariant), stearic acid Loxiol G22 (Wincell), nano-stearic acid HSt-ER (Kao), etc.

[0015] The present application does not limit the specific type of soluble thermoplastic elastomer, and the thermoplastic elastomer that can be dissolved in the solvent during the debinding stage can be used, for example, styrene-based thermoplastic elastomer (TPS), hydrogenated styrene-butadiene block copolymer (Kraton G1652), hydrogenated styrene-isoprene-styrene block copolymer (SEPS), thermoplastic polyester elastomer (TPEE), etc.

[0016] Further, in order to improve the debinding effect and increase the density of the sintered body, the weight average molecular weight of the insoluble low-density polyethylene is preferably 20,000-30,000. The insoluble LDPE is controlled by molecular weight (weight average molecular weight Mw=20,000-30,000), and under the premise of maintaining the room temperature bending strength of the wire >15 MPa, the content of residual organic matter after debinding can be <0.3 wt%.

[0017] The present application does not limit the specific type of soluble low-density polyethylene, and the low-density polyethylene that can be dissolved in the solvent during the debinding stage can be used, for example, Dow LDPE 2102TN00, ExxonMobil LD165, Dow 722, Borealis LD0860, etc.

[0018] The present application does not limit the specific type of insoluble low-density polyethylene, and the low-density polyethylene that cannot be dissolved in the solvent during the debinding stage and meets the required molecular weight can be used, for example, Dow LDPE 2047K, SABIC2100TN00, LyondellBasell 2420K, Total 1012FE, etc.

[0019] In some embodiments of the present application, the melt mixing is stirring mixing in a protective gas, the temperature is 170-220℃, and the time is 20-60 min. It can be understood that the temperature of the melt mixing mainly depends on the melting point of the binder, and within the temperature range and stirring time, the raw material FeMnSi memory alloy powder and the binder can be fully mixed, and the interfacial bonding force between the binder and the raw material FeMnSi memory alloy powder is improved.

[0020] In some embodiments of the present application, the temperature of the extrusion is 110-140℃.

[0021] The melt mixture is extruded by an extruder, and the extrusion temperature of the extruder is controlled at 110-140℃. Within this temperature range, the composition of the obtained wire can be uniform; the diameter fluctuation rate of the wire can be low, and the surface can be defect-free (such as cracks); the bending strength of the obtained wire can be guaranteed, and its fracture can be avoided.

[0022] In some embodiments of the present application, the diameter of the wire is 1.6-2.0 mm.

[0023] It can be understood that the diameter of the wire directly determines the microstructure integrity and macroscopic performance stability of the FeMnSi alloy by regulating the material transport kinetics and energy distribution gradient. Controlling the diameter in the range of 1.6-12.0 mm can maximize the advantages of low-temperature sintering process, realize high density, low sintering loss, and strong toughness of the additive manufacturing effect, and provide reliable guarantee for high-precision forming of complex shape memory components.

[0024] In some embodiments of the present application, the stress relief is heating the sample blank at 110-130℃ for 10-30 min.

[0025] It can be understood that during the 3D printing process, the material is accumulated layer by layer, which will produce residual stress due to temperature gradient and cooling speed. These stresses may cause the blank to deform and crack, affecting the subsequent forming and sintering process. Therefore, stress relief by heat treatment is necessary. By eliminating residual stress, the dimensional stability is improved. The dimensional accuracy, sintering activity and functional characteristics of the FeMnSi alloy additive manufacturing component are significantly improved. Stress relief at the above-mentioned temperature and time can realize high strength, high recovery rate and low defect precision manufacturing of shape memory alloy, and provide technical support for key scenes such as aerospace precision actuators.

[0026] In some embodiments of the present application, the binder removal includes heating and removing the binder in an organic solvent and sintering and removing the binder in a protective gas.

[0027] The present application adopts a physical dissolution-thermal decomposition step-by-step debinding mechanism. First, the organic solvent is used to remove stearic acid, soluble thermoplastic elastomer and soluble low-density polyethylene in the sample blank, forming a continuous through channel, improving the debinding rate of the insoluble low-density polyethylene skeleton by more than 3 times. The insoluble low-density polyethylene is sintered and removed from the binder in a protective gas, greatly reducing the content of residual organic matter after debinding. After sintering, the sample blank reaches a high relative density, improving the density of the alloy, and providing a reliable process basis for low-temperature additive manufacturing of high-performance shape memory alloys.

[0028] In some embodiments of the present application, the binder is removed in an organic solvent at a temperature of 40-60℃; The sintering temperature is 450-500℃, and the holding time is 3-5 h.

[0029] This invention does not limit the specific type of solvent used in the solvent debinding process, as long as it can degrease the raw materials. Examples include cyclohexane, n-heptane, cyclohexane-ethanol mixture, and supercritical carbon dioxide. The soluble components in the adhesive are thoroughly removed through impregnation in the solvent, resulting in a rapid debinding rate at 40-60°C.

[0030] This invention utilizes thermal decomposition at 450-500℃ to thoroughly remove the adhesive, resulting in more complete removal at this temperature. Specifically, the sample can be placed in an atmosphere furnace for thermal debonding. First, a protective gas is introduced, and the sample is heated to 450-500℃ at a heating rate of 0.5-2℃ / min. After holding at this temperature for 3-5 hours, thermal debonding is complete.

[0031] In some embodiments of the present invention, the sintering temperature is 1200-1300℃, and the holding time is 2-4 h. It is understood that sintering at this temperature can improve the density of the FeMnSi shape memory alloy, reduce the loss of manganese, and ensure the forming accuracy of the resulting alloy.

[0032] The beneficial effects of this invention are as follows: This invention provides a method for additive manufacturing of FeMnSi shape memory alloys based on filament extrusion. By optimizing the binder system, a binder system is proposed using stearic acid (SA) as a surfactant, a soluble thermoplastic elastomer as a toughening agent, and synergistically combining soluble low-density polyethylene (LDPE) and insoluble LDPE. This system achieves optimized debinding kinetics through the synergistic effect of multiple components. SA adsorbs onto the surface of the metal powder during the melt blending stage, reducing interfacial energy and increasing the powder volume fraction to over 62 vol%. The soluble thermoplastic elastomer and soluble LDPE dissolve first during the solvent debinding stage, forming continuous, interconnected channels (channel diameter ~1-5 μm), increasing the debinding rate of the insoluble LDPE skeleton. The insoluble LDPE maintains a room temperature flexural strength >15 MPa for the filaments by controlling the molecular weight. Subsequent low-temperature sintering and organic solvent dissolution significantly reduce the residual organic matter content after debinding. After removing various binders in the above steps, the FeMnSi printed product still retains its original shape. However, the binders that affect the diffusion and bonding between powders are basically removed. In the final sintering process, the diffusion between powders is used to form a dense body. The sintered body can achieve a high relative density (>98%) when sintered at a relatively low temperature (relative to the laser additive temperature). The relative density is small (less than 10 μm), and the tensile strength is stable in the range of 580-700 MPa.

[0033] Furthermore, this binder system is formed by low-temperature 3D printing, avoiding compositional fluctuations caused by excessively high temperatures. It undergoes densification through sintering in a reducing gas environment, effectively preventing the loss of Mn elements and reducing the probability of carbide inclusions in the ε phase, thus ensuring the stability of the shape recovery rate (recovery rate decay <3% after 50 thermal cycles). This invention provides a reliable process basis for the low-temperature additive manufacturing of high-performance shape memory alloys through a stepwise debonding mechanism of physical dissolution and thermal decomposition. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0035] Example 1 A method for additive manufacturing of FeMnSi shape memory alloys based on wire extrusion includes the following steps: (1) Preparation of FeMnSi shape memory alloy powder Metal powders with a weight ratio of 5 wt% Ni, 8.5 wt% Cr, 15.5 wt% Mn, 5.2 wt% Si, and the balance being Fe were mixed, wherein the iron powder was a low-carbon iron alloy powder with a carbon content of 0.12%, to obtain FeMnSi alloy powder.

[0036] (2) Preparation of extruded filaments (the following are mass ratios) FeMnSi alloy powder, stearic acid surfactant SA1801, styrene-based thermoplastic elastomer (TPS), partially soluble low-density polyethylene (Dow LDPE 2102TN00) and insoluble low-density polyethylene (Dow LDPE 2047K) were mixed in a mass ratio of 55:3:20:15:12 and then stirred and melted in a container under argon protection at a temperature of 195℃ for 30 min.

[0037] The molten mixture is extruded using an extruder, with the extrusion temperature controlled at 120℃ and the diameter of the filament controlled at 1.6 mm.

[0038] The wire was tested and found to have a bending strength of 32 MPa at room temperature.

[0039] (3) 3D part printing and stress relief treatment The above-mentioned filament was printed using a thermoplastic 3D printer to obtain the desired shape. Printing parameters were: nozzle diameter 0.4 mm, nozzle temperature 220℃, substrate temperature 60℃, printing speed 200 mm / min, and layer height 0.2 mm. After the 3D printed part was prepared, it underwent stress relief treatment in an oven at 110℃ for 30 minutes.

[0040] (4) Solvent debinding The 3D printed samples were solvent debonded in cyclohexane at 40°C and 60°C for three hours each using a magnetic stirrer at 10 rpm.

[0041] (5) Hot debonding and sintering The samples subjected to solvent debinding were placed in an atmosphere furnace for thermal debinding. Argon gas was first introduced, and the temperature was raised to 460°C at a rate of 1°C per minute. This temperature was maintained for 34 hours to complete thermal debinding. Then, the temperature was raised to 1300°C, and hydrogen gas was introduced. This temperature was maintained for 3 hours to complete thermal sintering and densification, yielding the FeMnSi shape memory alloy. Final performance: The final sample has a tensile strength of 600 MPa, a memory effect of 2%, and a phase transition point of 320℃.

[0042] Example 2: Low limiting composition alloy (Mn 12%, Cr 6%, Ni 3%) A method for additive manufacturing of FeMnSi shape memory alloys based on wire extrusion includes the following steps: (1) Preparation of FeMnSi shape memory alloy powder Take high-purity iron powder (balance), 12% metallic manganese powder (purity 99.7%), 6.7% ferrosilicon powder (Si 75%), 9.2% ferrochrome powder (Cr 65%), and 3% nickel powder, and obtain Fe-12Mn-5Si-6Cr-3Ni-0.15C alloy powder (D90=50 μm) by mechanical alloying treatment (argon protection, ball milling for 8 hours at 300 rpm).

[0043] (2) Preparation of extruded filaments The alloy powder, stearic acid surfactant SA1845 (Clariant), hydrogenated styrene-butadiene block copolymer (Kraton G1652), partially soluble LDPE (ExxonMobil LD165) and insoluble LDPE (SABIC 2100TN00) were mixed in a mass ratio of 60:3:18:12:7 and then stirred and melted in a container under argon protection at a temperature of 195°C for 30 min.

[0044] The mixture is melt-blended at 115°C using a twin-screw extruder, extruded into 1.8 mm diameter filaments, cooled, wound, and stored.

[0045] Tests showed that the filament has a bending strength of 35 MPa at room temperature.

[0046] (3) 3D printing and stress relief Using an FDM printer (0.4 mm nozzle): nozzle temperature 210℃ / substrate temperature 65℃; printing speed 180 mm / min, layer thickness 0.15 mm; after printing the honeycomb structure, stress relief was performed in a 100℃ oven for 45 min.

[0047] (4) Solvent debinding Debinding was performed in stages using n-heptane solvent: debinding at low speed (8 rpm) for 4 hours at 40℃; and debinding with ultrasonic assistance (40kHz) at 60℃ for 2 hours.

[0048] (5) Hot debonding and sintering Thermal debonding was achieved by heating to 450℃ at 0.5℃ / min and holding for 40 hours under an argon atmosphere; sintering was then achieved by switching to hydrogen and heating to 1280℃ at 5℃ / min and holding for 4 hours, resulting in a low-limit composition alloy (Mn 12%, Cr 6%, Ni 3%).

[0049] Final performance: tensile strength 590 MPa, memory effect 1.9%, phase transition temperature 290℃ (DSC test).

[0050] Example 3: Median composition alloy (Mn 15%, Cr 8%, Ni 4.5%) A method for additive manufacturing of FeMnSi shape memory alloys based on wire extrusion includes the following steps: (1) Preparation of FeMnSi powder Powder preparation by atomization: Fe-15Mn-5.5Si-8Cr-4.5Ni-0.18C raw material was vacuum melted (1600℃) and then atomized to obtain spherical powder (oxygen content <300 ppm, D50=35 μm).

[0051] (2) Preparation of extruded filaments The atomized alloy powder, stearic acid Loxiol G22 (Evonik), SEPS elastomer (Kuraray 4055), partially soluble LDPE (Dow 722) and insoluble LDPE (LyondellBasell 2420K) were mixed in a mass ratio of 55:5:20:13:7 and then stirred and melted in a container under argon protection at a temperature of 195℃ for 30 min.

[0052] Extruding 1.6 mm filaments at 125℃, with a surface roughness Ra≤3.2 μm.

[0053] The wire was tested and found to have a bending strength of 28 MPa at room temperature.

[0054] (3) 3D printing and stress relief Printing parameters: Nozzle 225℃ / substrate 75℃, layer thickness 0.1 mm; 80% fill rate for printing mesh structures; stress relief treatment: 110℃×30 min.

[0055] (4) Solvent debinding Cyclohexane-ethanol (7:3, volume ratio) mixed solvent gradient debinding: soaking at 40℃ for 6 hours and then shaking at 60℃ for 3 hours to debind.

[0056] (5) Hot debonding and sintering Thermal debonding was achieved by heating to 460℃ at a rate of 2℃ / min and holding for 30 hours in argon atmosphere. Sintering was then completed at 1300℃ for 3 hours in hydrogen atmosphere (relative density 98.7%).

[0057] Final properties: tensile strength 645MPa, memory effect 2.4%, phase transition point 325℃.

[0058] Example 4: High limiting composition (Mn 18%, Cr 10%, Ni 6%) A method for additive manufacturing of FeMnSi shape memory alloys based on wire extrusion includes the following steps: (1) Preparation of FeMnSi powder Fe-18Mn-6Si-10Cr-6Ni-0.20C powder was prepared by plasma rotating electrode atomization (PREP): the particle size distribution was 15-53 μm and the sphericity was >95%; the carbon content was finely controlled by manganese carbide.

[0059] (2) Preparation of extruded filaments PREP alloy powder, nano stearic acid HSt-ER (Kao), TPEE elastomer (Teknor MD-445), partially soluble LDPE (Borealis LD0860) and insoluble LDPE Total 1012FE were mixed in a mass ratio of 68:4:15:8:5 and then stirred and melted in a container under argon protection at a temperature of 195℃ for 30 min.

[0060] A 2.0 mm thick filament is formed at 130°C using a high-torque extruder.

[0061] Tests showed that the filament has a bending strength of 40 MPa at room temperature.

[0062] (3) 3D printing and stress relief Industrial-grade FDM equipment parameters: 0.6 mm nozzle, 240℃ / 100℃ substrate; printing speed 5 mm / s, layer thickness 0.25 mm.

[0063] Stress relief treatment: 120℃ × 20 minutes.

[0064] (4) Solvent debinding Supercritical carbon dioxide degreasing (pressure 15 MPa, temperature 60℃) for 8 hours resulted in a degreasing rate >99.2%.

[0065] (5) Hot debonding and sintering Direct sintering in an argon-hydrogen mixture (1:4, volume ratio): debinding at 500℃ for 10 hours, densification at 1280℃ for 2 hours.

[0066] Final properties: tensile strength 695 MPa, memory effect 3.2%, phase transition temperature 365℃.

[0067] Comparative Example 1 A method for additive manufacturing of FeMnSi shape memory alloy based on wire extrusion differs from Example 4 in that: PREP alloy powder, TPEE elastomer (Teknor MD-445), partially soluble LDPE (Borealis LD0860), and insoluble LDPE Total 1012FE are mixed in a mass ratio of 68:19:8:5 and then stirred and melted in a container under argon protection at a temperature of 195°C for 30 min. The remaining steps are completely consistent with those of Example 4.

[0068] The final properties of the resulting alloy are: tensile strength 550 MPa, memory effect 2.2%, and phase transformation temperature 392℃.

[0069] Comparative Example 2 A method for additive manufacturing of FeMnSi shape memory alloy based on wire extrusion differs from Example 4 in that: PREP alloy powder, nano-stearic acid HSt-ER (Kao), partially soluble LDPE (Borealis LD0860), and insoluble LDPE Total 1012FE are mixed in a mass ratio of 68:19:8:5 and then stirred and melted in a container under argon protection at a temperature of 195°C for 30 min. The remaining steps are completely consistent with those of Example 4.

[0070] The final properties of the resulting alloy are: tensile strength 570 MPa, memory effect 1.9%, and phase transformation temperature 372℃.

[0071] Comparative Example 3 A method for additive manufacturing of FeMnSi shape memory alloy based on wire extrusion differs from Example 4 in that PREP alloy powder, nano-stearic acid HSt-ER (Kao), TPEE elastomer (Teknor MD-445), and insoluble LDPETotal 1012FE are mixed in a mass ratio of 68:4:15:13 and then stirred and melted in a container under argon protection at a temperature of 195°C for 30 min. The remaining steps are completely consistent with those of Example 4.

[0072] The final properties of the resulting alloy are: tensile strength 563 MPa, memory effect 2.1%, and phase transformation temperature 388℃.

[0073] Comparative Example 4 A method for additive manufacturing of FeMnSi shape memory alloy based on wire extrusion differs from Example 4 in that PREP alloy powder, nano-stearic acid HSt-ER (Kao), TPEE elastomer (Teknor MD-445), and partially soluble LDPE (Borealis LD0860) are mixed in a mass ratio of 68:4:15:13 and then stirred and melted in a container under argon protection at a temperature of 195°C for 30 min. The remaining steps are completely consistent with those of Example 4.

[0074] The final properties of the resulting alloy are: tensile strength 557 MPa, memory effect 1.8%, and phase transformation temperature 391℃.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for additive manufacturing of FeMnSi shape memory alloy based on wire extrusion, characterized in that, include: Preparation of raw material: FeMnSi shape memory alloy powder; The FeMnSi shape memory alloy powder is melt-mixed with a binder and then extruded to obtain a filament; the binder includes stearic acid surfactant, soluble thermoplastic elastomer, soluble low-density polyethylene and insoluble low-density polyethylene; The filament was 3D printed to obtain a sample blank. After stress relief, the binder was removed, and the sample was sintered in a reducing gas to obtain a FeMnSi shape memory alloy.

2. The method as described in claim 1, characterized in that, The raw material FeMnSi shape memory alloy powder comprises 12-18 wt% Mn, 5-6 wt% Si, 6-10 wt% Cr, 3-6 wt% Ni, 0.1-0.2 wt% C, and the balance is Fe.

3. The method as described in claim 1, characterized in that, The mass ratio of raw material FeMnSi shape memory alloy powder to binder is: raw material FeMnSi shape memory alloy powder: stearic acid surfactant: soluble thermoplastic elastomer: soluble low-density polyethylene: insoluble low-density polyethylene is (50-70): (2-7): (5-25): (10-20): (5-20).

4. The method as described in claim 1, characterized in that, The melting and mixing process involves stirring in a protective gas at a temperature of 170-220°C for 20-60 minutes.

5. The method as described in claim 1, characterized in that, The extrusion temperature is 110-140℃.

6. The method as described in claim 1, characterized in that, The diameter of the filament is 1.6-2.0 mm.

7. The method as described in claim 1, characterized in that, The stress relief is achieved by heating the sample embryo at 110-130℃ for 10-30 min.

8. The method as described in claim 1, characterized in that, The binder removal includes removing the binder by heating in an organic solvent and removing the binder by sintering in a protective gas.

9. The method as described in claim 8, characterized in that, Remove the adhesive in an organic solvent at a temperature of 40-60℃; The sintering temperature is 450-500℃, and the holding time is 3-5 h.

10. The method as described in claim 1, characterized in that, The sintering process is carried out at a temperature of 1200-1300℃ for 2-4 hours.