A training-free iron-based high-entropy shape memory alloy and its preparation method

Abstract

The present application provides a training-free iron-based high-entropy shape memory alloy, which comprises, in terms of atomic content percentage: Fe content of 40-55%, Mn content of 25-35%, Co content of 8-12%, Cr content of 8-15%, and Si content of 6-14%. By setting the ratio of these elements, the shape memory alloy can have a higher shape memory effect, and the maximum recoverable strain in the cast state can reach 6.0%. At the same time, it has the characteristics of high strength and good plasticity. The iron-based high-entropy shape memory alloy provided by the present invention does not require training, has low cost, good mechanical properties, and excellent processing performance, and can obtain excellent recoverable strain within the provided composition range.

Description

Technical Field

[0001] The present invention mainly relates to the field of alloy materials, and in particular to a training-free iron-based high-entropy shape memory alloy and a preparation method thereof. Background Art

[0002] High-entropy alloys (HEAs) are novel multi-component metallic materials, typically composed of FCC, HCP, or a combination of the two. The resulting disordered solid solution structure imparts high configurational entropy and solid solution strengthening, resulting in superior performance compared to conventional metals in high-temperature creep, corrosion, and radiation resistance. As the stacking fault energy of an alloy decreases, the dominant deformation mechanism shifts from dislocation slip to mechanical twinning, and then to phase transformation. Reducing the stacking fault energy destabilizes the alloy structure. Under stress, dislocations expand into stacking faults, which then stack to form an HCP phase, manifesting as a stress-induced FCC to HCP phase transformation, also known as transformation-induced plasticity (TRIP). Upon heating, the HCP phase undergoes a reverse transformation, returning to the FCC phase. The HCP martensitic phase transformation and its reverse transformation constitute the mechanism by which iron-based shape memory alloys exhibit shape memory.

[0003] Shape memory alloys (SMAs) are a key component of smart materials, combining shape memory effects, sensing, and actuation. The SMA effect has been observed in a variety of alloy compositions, including NiTi- and Cu-based SMAs based on thermoelastic phase transitions and Fe-based SMAs based on non-thermoelastic phase transitions. NiTi-based SMAs have gained widespread commercial application due to their high recoverable strain, high strength, and good biocompatibility. However, NiTi-based SMAs suffer from poor machinability and high cost. Cu-based SMAs, on the other hand, suffer from weak shape memory stability, low strength, and short fatigue life. In contrast, Fe-based SMAs offer high stability, good strength and ductility, easy machining, and long fatigue life, all at a lower price than NiTi- and Cu-based SMAs. They are suitable for the manufacture of one-way components such as pipe sleeve joints and have found applications in smart building materials, civil engineering bridges, and petrochemicals. However, the recoverable strain of Fe-based SMAs is very low, typically only 2–3%. Summary of the Invention

[0004] In view of the above problems, the present application is proposed to provide a training-free iron-based high entropy shape memory alloy and a preparation method thereof that overcomes the above problems or at least partially solves the above problems, including:

[0005] A training-free iron-based high-entropy shape memory alloy comprises, in terms of atomic content percentage, 40-55% Fe, 25-35% Mn, 8-12% Co, 8-15% Cr and 6-14% Si.

[0006] Furthermore, the structure is FCC phase and HCP phase.

[0007] Furthermore, the Mn is electrolytic Mn with a purity higher than 99.5%.

[0008] Furthermore, the Fe is industrial pure Fe with a purity higher than 99.5%.

[0009] Furthermore, it also includes 0 to 1% of Sn in atomic percentage.

[0010] Furthermore, it further comprises 0-1% of Pb in atomic percentage.

[0011] Furthermore, it also includes 0 to 1% of nitrogen in atomic percentage.

[0012] A method for preparing a training-free iron-based high-entropy shape memory alloy comprises the following steps:

[0013] Mixing raw materials in proportion, wherein the raw materials include, in terms of atomic percentage, 40-55% Fe, 25-35% Mn, 8-12% Co, 8-15% Cr, and 6-14% Si;

[0014] vacuum melting the raw materials to obtain alloy ingots;

[0015] The alloy ingot is subjected to alloy suction casting to obtain a cast alloy plate.

[0016] Furthermore, the step of vacuum melting the raw materials to obtain the alloy ingot comprises:

[0017] placing the raw materials into a vacuum arc melting furnace, and evacuating the vacuum arc melting furnace;

[0018] purging the vacuum melting furnace with argon;

[0019] After filling with argon gas for protection, the raw materials are melted.

[0020] Furthermore, after the argon gas is filled for protection, the step of melting the raw materials comprises:

[0021] Filling with argon gas to protect the raw materials;

[0022] Melting the raw materials to obtain ingots, with the melting time being not less than 2 minutes;

[0023] Turning the ingot over and melting it again for not less than 2 minutes;

[0024] Repeat the flipping and melting operation 5 to 6 times.

[0025] This application has the following advantages:

[0026] In the embodiments of the present application, in order to address the shortcomings of low recoverable strain of iron-based shape memory alloys in the prior art, the present application provides a training-free iron-based high entropy shape memory alloy, which, in terms of atomic content percentage, includes: Fe content of 40-55%, Mn content of 25-35%, Co content of 8-12%, Cr content of 8-15%, and Si content of 6-14%. By setting the ratio of these elements, the shape memory alloy can have a higher shape memory effect, with the maximum recoverable strain in the cast state reaching 6.0%. At the same time, it has the characteristics of high strength and good plasticity. The iron-based high entropy shape memory alloy provided by the present invention does not require training, has low cost, good mechanical properties, and excellent processing performance, and can obtain excellent recoverable strain within the provided composition range. The present invention provides a simple preparation method for the high entropy shape memory alloy, which is simple to operate, has a short preparation cycle, does not require tedious heat treatment processes, and has low consumption costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for the description of the present application. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0028] Figure 1 This is a flowchart of the steps of a method for preparing a training-free iron-based high entropy shape memory alloy provided by one embodiment of the present invention;

[0029] Figure 2 Schematic diagram of the recovery angle of a training-free iron-based high entropy shape memory alloy provided by one embodiment of the present invention;

[0030] Figure 3 This is a diffraction curve diagram of a training-free iron-based high entropy shape memory alloy provided by one embodiment of the present invention;

[0031] Figure 4 This is a graph showing the recovery test results of a training-free iron-based high-entropy shape memory alloy provided by one embodiment of the present invention;

[0032] Figure 5 This is a graph showing the mechanical properties test results of a training-free iron-based high-entropy shape memory alloy provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0033] To make the objectives, features, and advantages of this application more readily apparent, the present application is further described below in conjunction with the accompanying drawings and specific embodiments. It is apparent that the embodiments described are only a portion of the embodiments of this application, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments in this application without inventive effort are also within the scope of protection of this application.

[0034] By analyzing the existing technology, the inventors found that by setting the elements and proportions of the shape memory alloy, the strength and plasticity of the memory alloy can be improved, and the recoverable strain can be increased, without the need for thermomechanical cycle training, making the iron-based shape memory alloy more widely used and more adaptable to work scenarios.

[0035] In the embodiments of the present application, in order to address the shortcomings of low recoverable strain of iron-based shape memory alloys in the prior art, the present application provides a training-free iron-based high entropy shape memory alloy, which, in terms of atomic content percentage, includes: Fe content of 40-55%, Mn content of 25-35%, Co content of 8-12%, Cr content of 8-15%, and Si content of 6-14%. By setting the ratio of elements, the shape memory alloy can have a higher shape memory effect, and the maximum recoverable strain in the casting state can reach 6.0%. At the same time, it has the characteristics of high strength and good plasticity. The iron-based high entropy shape memory alloy provided by the present invention has low cost, good mechanical properties, excellent processing performance, and can obtain excellent recoverable strain within the provided composition range.

[0036] In one embodiment of the present application, a training-free iron-based high-entropy shape memory alloy is provided, which, in terms of atomic content percentage, includes: an Fe content of 40-55%, a Mn content of 25-35%, a Co content of 8-12%, a Cr content of 8-15%, and a Si content of 6-14%.

[0037] It should be noted that the shape memory effect is based on the FCC□HCP phase transformation. Fe provides the foundation for the FCC austenite structure and the HCP martensite structure. Mn can reduce the stacking fault energy, but excessive Mn increases the alloy's stability and inhibits the phase transformation. Si not only reduces the stacking fault energy but also produces a solid solution strengthening effect, increasing the resistance to dislocation slip. However, excessive Si can make the alloy very brittle. Cr addition can improve corrosion resistance. Co also reduces the stacking fault energy without producing a strong solid solution effect, and serves as a partial Si replacement to improve the alloy's plasticity.

[0038] In a specific implementation, the training-free iron-based high entropy shape memory alloy is subjected to a bending test. During the bending test, a long strip of alloy with a thickness of d is pressed against a bending die with a diameter of D for 2 seconds and then released. The bending recovery temperature is selected to be 600-650°C, the processing time is 10-15 minutes, and the deformed HCP martensite is completely transformed into FCC austenite. The pre-deformation rate ε = d / (d+D) × 100%. The shape recovery rate η = (θ d -θ h ) / θ d × 100%, where θ d and θ h like Figure 2 As shown. Recoverable strain ε re =η×ε×100%. Substituting the test results into the formula for calculation, the bending recoverable strain can be calculated. The yield strength of the memory alloy is 173.5MPa, the tensile strength is 703.5MPa, the elongation after fracture is 30.8%, and the maximum recoverable strain is 6.0%.

[0039] In one embodiment of the present application, the structure is an FCC phase and an HCP phase.

[0040] The training-free iron-based high-entropy shape memory alloy is mainly composed of a face-centered cubic FCC phase and a hexagonal close-packed HCP phase.

[0041] In one embodiment of the present application, the Mn is electrolytic Mn with a purity higher than 99.5%.

[0042] In one embodiment of the present application, the Fe is industrial pure Fe with a purity higher than 99.5%.

[0043] In one embodiment of the present application, 0-1% Sn is further included in the alloy in terms of atomic percentage. The Sn element can provide corrosion resistance to the alloy, reduce the friction coefficient, and increase toughness.

[0044] In one embodiment of the present application, the present invention further includes 0-1% Pb in atomic percentage.

[0045] The addition of Pb can form a tin-lead alloy with Sn, so that the training-free iron-based high-entropy shape memory alloy has a small friction coefficient and good toughness, thermal conductivity and corrosion resistance.

[0046] In one embodiment of the present application, 0-1% of N is further included in atomic percentage.

[0047] It should be noted that N can penetrate into the alloy surface and form extremely stable nitrides with other elements, becoming a surface hardening and strengthening element.

[0048] Reference Figure 1, shows a method for preparing a training-free iron-based high entropy shape memory alloy provided in one embodiment of the present application, comprising the steps of:

[0049] S110, mixing raw materials in proportion, wherein the raw materials include, in terms of atomic percentage, 40-55% Fe, 25-35% Mn, 8-12% Co, 8-15% Cr, and 6-14% Si;

[0050] S120, vacuum melting the raw materials to obtain alloy ingots;

[0051] S130, performing alloy suction casting on the alloy ingot to obtain a cast alloy plate.

[0052] In an embodiment of the present application, a method for preparing a training-free iron-based high-entropy shape memory alloy is provided, comprising the steps of: mixing raw materials in proportion, wherein the raw materials comprise, by atomic percentage, 40-55% Fe, 25-35% Mn, 8-12% Co, 8-15% Cr, and 6-14% Si; vacuum melting the raw materials to obtain an alloy ingot; and S130, performing alloy suction casting on the alloy ingot to obtain an as-cast alloy plate. The present invention provides a simple method for preparing the high-entropy shape memory alloy, which is simple to operate, has a short preparation cycle, does not require a tedious heat treatment process, and has low consumption costs.

[0053] Next, a method for preparing a training-free iron-based high entropy shape memory alloy in this exemplary embodiment will be further described.

[0054] As described in step S110 above, raw materials are mixed in proportion, and the raw materials include, in terms of atomic content percentage, 40-55% Fe, 25-35% Mn, 8-12% Co, 8-15% Cr, and 6-14% Si.

[0055] It should be noted that the shape memory effect is based on the FCC□HCP phase transformation. Fe provides the foundation for the FCC austenite structure and the HCP martensite structure. Mn can reduce the stacking fault energy, but excessive Mn increases the alloy's stability and inhibits the phase transformation. Si not only reduces the stacking fault energy but also produces a solid solution strengthening effect, increasing the resistance to dislocation slip. However, excessive Si makes the alloy very brittle. Cr addition can improve corrosion resistance. Co also reduces the stacking fault energy without producing a strong solid solution effect, replacing some Si to improve the alloy's plasticity. Sn can provide corrosion resistance, reduce the friction coefficient, and increase toughness.

[0056] As described in step S120 above, the raw materials are vacuum melted to obtain alloy ingots.

[0057] In one embodiment of the present invention, the specific process of "vacuum melting the raw materials to obtain the alloy ingot" in step S120 can be further explained in combination with the following description.

[0058] As described in the following steps, the raw materials are placed in a vacuum arc melting furnace, and the vacuum arc melting furnace is evacuated.

[0059] As described in the following steps, the vacuum melting furnace is purged with argon gas.

[0060] It should be noted that the purge operation begins by first starting the mechanical pump. When the vacuum drops below 5E0, close the mechanical pump valve. Then, start the molecular pump and open the molecular pump valve, setting the molecular pump speed to 27,000 rpm. Once the vacuum drops below 3E-3, close the molecular pump valve. Open the argon valve and fill with argon until the vacuum reaches between -0.08 and -0.05 MPa. This completes one purge. One or two purges are required to prevent alloy oxidation.

[0061] As described in the following steps, the raw materials are melted after being filled with argon gas for protection.

[0062] It should be noted that a vacuum melting furnace is used for melting, and after striking the arc with a current of 30 to 60 A, the current is increased to 150 to 350 A to perform arc melting on the alloy.

[0063] In one embodiment of the present invention, the specific process of the step of "smelting the raw materials after filling with argon gas for protection" can be further described in combination with the following description:

[0064] As described in the following steps, the raw materials were protected by filling with argon gas.

[0065] The raw materials are melted to obtain an ingot as described in the following steps, and the melting time is not less than 2 minutes. After striking an arc with a current of 30 to 60 A, the current is increased to 150 to 350 A to arc melt the alloy.

[0066] The ingot was flipped over and melted again for not less than 2 minutes as described in the following steps.

[0067] Repeat the flip melting operation 5 to 6 times as described in the following steps.

[0068] As described in step S130 above, the alloy ingot is subjected to alloy suction casting to obtain a cast alloy plate.

[0069] It should be noted that after smelting, a button-shaped alloy ingot is obtained. This button-shaped alloy ingot is placed on a plate-shaped suction casting mold of the desired size. The molten material is liquidized and rounded. The suction casting button is immediately pressed and the power is turned off, completing the high-entropy alloy preparation. After demolding, the cast alloy plate of the desired size is obtained.

[0070] In a specific implementation, a high entropy shape memory alloy is prepared, whose composition is, by atomic percentage, 47% Fe, 28.2% Mn, 9.4% Co, 9.4% Cr, and 6% Si.

[0071] Configuration principle: The raw materials selected are electrolytic Mn with a purity of over 99.5%, and industrial pure Fe, industrial pure Co, electrolytic Cr, and crystalline Si with a purity of over 99.95%. The raw materials are weighed according to the corresponding mass and placed in a vacuum arc melting furnace.

[0072] Gas Cleaning: After evacuating the chamber, fill it with argon to create a protective atmosphere to prevent oxidation. Start the mechanical pump and wait until the vacuum drops below 5E0. Close the mechanical pump valve. Start the molecular pump and open the molecular pump valve, setting the molecular pump speed to 27,000 rpm. Once the vacuum drops below 3E-3, close the molecular pump valve. Open the argon valve and fill it with argon until the vacuum reaches -0.06 MPa. This completes one gas clean.

[0073] Melting: After striking the arc with a current of 50A, increase the current to 200-250A to perform arc melting on the alloy. Each melting time should be more than 2 minutes.

[0074] The ingot was melted five times, and the alloy ingot was turned over between each melting to improve the uniformity of the alloy and obtain a button-shaped alloy ingot.

[0075] Vacuum casting: Select a copper casting mold with a size of 10×10×90mm. Place the button-shaped alloy ingot on top of the plate-shaped casting mold. Melt the material into liquid form and press the casting button. After cooling and demolding, the cast alloy plate is obtained.

[0076] The casting was cut by a medium-speed wire cutting machine to obtain the dumbbell-shaped tensile parts and bent strips for the test. The tensile parts were polished to 2000 mesh using SiC sandpaper.

[0077] The prepared iron-based high entropy shape memory alloy was subjected to X-ray diffraction, and the diffraction curve was obtained as shown in the attached figure. Figure 3 As shown in Example 1, the phase composition is mainly FCC phase.

[0078] The mechanical properties of this embodiment were tested according to the requirements of GB / T228.1-2010 "Tension test of metallic materials Part 1: Room temperature test method". The results are shown in the attached figure. Figure 5 As shown in Example 1, the yield strength is 150.4 MPa, the tensile strength is 579.1 MPa, and the elongation after break is 32.2%.

[0079] The bending recovery effect of this embodiment was tested under different pre-strain conditions. The bent samples with different pre-strain were kept at 600℃ for 10 minutes to allow them to fully recover. The results are shown in the attached figure. Figure 4 As shown in Example 1, the maximum recoverable strain of the alloy material is 2.2%.

[0080] In another specific implementation, a high entropy shape memory alloy is prepared, whose composition is, by atomic percentage, 46% Fe, 27.6% Mn, 9.2% Co, 9.2% Cr, and 8% Si.

[0081] Prepare raw materials: Select electrolytic Mn with a purity of 99.5% or higher, and industrial-purity Fe, industrial-purity Co, electrolytic Cr, and crystalline Si with a purity of 99.95% or higher. Weigh the raw materials according to the corresponding mass and place them in a vacuum arc melting furnace.

[0082] Gas Cleaning: After evacuating the chamber, fill it with argon to create a protective atmosphere to prevent oxidation. Start the mechanical pump and wait until the vacuum drops below 5E0. Close the mechanical pump valve. Then, start the molecular pump and open the molecular pump valve, setting the molecular pump speed to 27,000 rpm. Once the vacuum drops below 3E-3, close the molecular pump valve. Open the argon valve and fill it with argon until the vacuum reaches -0.07 MPa. This completes one gas clean.

[0083] Melting: After striking the arc with a current of 45A, increase the current to 210-260A to perform arc melting on the alloy. Each melting time should be more than 2 minutes.

[0084] The ingot was melted six times, and the alloy ingot was turned over between each melting to improve the uniformity of the alloy and obtain a button-shaped alloy ingot.

[0085] Vacuum casting: Select a copper casting mold with a size of 10×10×90mm. Place the button-shaped alloy ingot on top of the plate-shaped casting mold. Once the molten material is liquid, press the casting button. After cooling and demolding, the cast alloy plate is obtained.

[0086] The casting was cut by a medium-speed wire cutting machine to obtain the dumbbell-shaped tensile parts and bent strips for the test. The tensile parts were polished to 2000 mesh using SiC sandpaper.

[0087] The prepared iron-based high entropy shape memory alloy was subjected to X-ray diffraction, and the diffraction curve was obtained as shown in the attached figure. Figure 3 As shown in Example 2, the phase composition is mainly FCC phase and HCP phase.

[0088] The mechanical properties of this embodiment were tested according to the requirements of GB / T 228.1-2010 "Metallic materials - Tensile tests - Part 1: Room temperature test methods". The results are shown in the attached figure. Figure 5As shown in Example 2, the yield strength is 163.6 MPa, the tensile strength is 501.5 MPa, and the elongation after break is 19.2%.

[0089] The bending recovery effect of this embodiment was tested under different pre-strain conditions. The bent samples with different pre-strain were kept at 600℃ for 15 minutes to allow them to fully recover. The results are shown in the attached figure. Figure 4 As shown in Example 2, the maximum recoverable strain of the alloy material is 3.3%.

[0090] In another specific implementation, a high entropy shape memory alloy is configured with a composition of 45% Fe, 27% Mn, 9% Co, 9% Cr, and 10% Si in atomic percentage.

[0091] Prepare raw materials: Select electrolytic Mn with a purity of 99.5% or higher, and industrial-purity Fe, industrial-purity Co, electrolytic Cr, and crystalline Si with a purity of 99.95% or higher. Weigh the raw materials according to the corresponding mass and place them in a vacuum arc melting furnace.

[0092] Gas Cleaning: After evacuating the chamber, fill it with argon to create a protective atmosphere to prevent oxidation. Start the mechanical pump and wait until the vacuum drops below 5E0. Close the mechanical pump valve. Start the molecular pump and open the molecular pump valve, setting the molecular pump speed to 27,000 rpm. Wait until the vacuum drops below 3E-3, then close the molecular pump valve. Open the argon valve and fill it with argon until the vacuum reaches -0.05 MPa. Repeat this process twice.

[0093] Melting: After striking the arc with a current of 55A, increase the current to 220-270A to perform arc melting on the alloy. Each melting time should be more than 2 minutes.

[0094] The ingot was melted five times, and the alloy ingot was turned over between each melting to improve the uniformity of the alloy and obtain a button-shaped alloy ingot.

[0095] Vacuum casting: Select a copper casting mold with a size of 10×10×90mm. Place the button-shaped alloy ingot on top of the plate-shaped casting mold. Once the molten material is liquid, press the casting button. After cooling and demolding, the cast alloy plate is obtained.

[0096] The casting was cut by a medium-speed wire cutting machine to obtain the dumbbell-shaped tensile parts and bent strips for the test. The tensile parts were polished to 2000 mesh using SiC sandpaper.

[0097] The prepared iron-based high entropy shape memory alloy was subjected to X-ray diffraction, and the diffraction curve was obtained as shown in the attached figure. Figure 3 As shown in Example 3, the phase composition is mainly FCC phase and HCP phase.

[0098] The mechanical properties of this embodiment were tested according to the requirements of GB / T 228.1-2010 "Metallic materials - Tensile tests - Part 1: Room temperature test methods". The results are shown in the attached figure. Figure 5 As shown in Example 3, the yield strength is 173.5 MPa, the tensile strength is 703.5 MPa, and the elongation after break is 30.8%.

[0099] The bending recovery effect of this embodiment was tested under different pre-strain conditions. The bent samples with different pre-strain were kept at 600℃ for 10 minutes to allow them to fully recover. The results are shown in the attached figure. Figure 4 As shown in Example 3, the maximum recoverable strain of the alloy material is 6.0%.

[0100] In another specific implementation, the configured composition is a high entropy shape memory alloy with an Fe content of 44%, a Mn content of 26.4%, a Co content of 8.8%, a Cr content of 8.8%, and a Si content of 12% by atomic percentage.

[0101] Prepare raw materials: Select electrolytic Mn with a purity of 99.5% or higher, and industrial-purity Fe, industrial-purity Co, electrolytic Cr, and crystalline Si with a purity of 99.95% or higher. Weigh the raw materials according to the corresponding mass and place them in a vacuum arc melting furnace.

[0102] Gas Cleaning: After evacuating the chamber, fill it with argon to create a protective atmosphere to prevent oxidation. Start the mechanical pump and wait until the vacuum drops below 5E0. Close the mechanical pump valve. Run the molecular pump and open the molecular pump valve, setting the molecular pump speed to 27,000 rpm. Wait until the vacuum drops below 3E-3, then close the molecular pump valve. Open the argon valve and fill it with argon until the vacuum reaches -0.06 MPa. Repeat this process twice.

[0103] Melting: After striking the arc with a current of 52A, increase the current to 180-270A to perform arc melting on the alloy. Each melting time should be more than 2 minutes.

[0104] The ingot was melted six times, and the alloy ingot was turned over between each melting to improve the uniformity of the alloy and obtain a button-shaped alloy ingot.

[0105] Vacuum casting: Select a copper casting mold with a size of 10×10×90mm. Place the button-shaped alloy ingot on top of the plate-shaped casting mold. Once the molten material is liquid, press the casting button. After cooling and demolding, the cast alloy plate is obtained.

[0106] The casting was cut by a medium-speed wire cutting machine to obtain the dumbbell-shaped tensile parts and bent strips for the test. The tensile parts were polished to 2000 mesh using SiC sandpaper.

[0107] The prepared iron-based high entropy shape memory alloy was subjected to X-ray diffraction, and the diffraction curve was obtained as shown in the attached figure. Figure 3 As shown in Example 4, the phase composition is mainly FCC phase and HCP phase.

[0108] The mechanical properties of this embodiment were tested according to the requirements of GB / T 228.1-2010 "Metallic materials - Tensile tests - Part 1: Room temperature test methods". The results are shown in the attached figure. Figure 5 As shown in Example 4, the yield strength is 239.6 MPa, the tensile strength is 539.6 MPa, and the elongation after break is 11.8%.

[0109] The bending recovery effect of this embodiment was tested under different pre-strain conditions. The bent samples with different pre-strain were kept at 600℃ for 12 minutes to allow them to fully recover. The results are shown in the attached figure. Figure 4 As shown in Example 4, the maximum recoverable strain of the alloy material is 4.4%.

[0110] In another specific implementation, a high entropy shape memory alloy is configured with a composition of 43% Fe, 27% Mn, 9% Co, 9% Cr, 8% Si, and 1% Sn in atomic percentage.

[0111] Prepare raw materials: Select electrolytic Mn with a purity of 99.5% or higher, and industrial-purity Fe, industrial-purity Co, electrolytic Cr, crystalline Si, and industrial-purity Sn with a purity of 99.95% or higher. Weigh the raw materials according to the corresponding mass and place them in the vacuum arc melting furnace.

[0112] Gas Cleaning: After evacuating the chamber, fill it with argon to create a protective atmosphere to prevent oxidation. Start the mechanical pump and wait until the vacuum drops below 5E0. Close the mechanical pump valve. Start the molecular pump and open the molecular pump valve, setting the molecular pump speed to 27,000 rpm. Wait until the vacuum drops below 3E-3, then close the molecular pump valve. Open the argon valve and fill it with argon until the vacuum reaches -0.05 MPa. Repeat this process twice.

[0113] Melting: After striking the arc with a current of 55A, increase the current to 220-270A to perform arc melting on the alloy. Each melting time should be more than 2 minutes.

[0114] The ingot was melted five times, and the alloy ingot was turned over between each melting to improve the uniformity of the alloy and obtain a button-shaped alloy ingot.

[0115] Vacuum casting: Select a copper casting mold with a size of 10×10×90mm. Place the button-shaped alloy ingot on top of the plate-shaped casting mold. Once the molten material is liquid, press the casting button. After cooling and demolding, the cast alloy plate is obtained.

[0116] The casting was cut by a medium-speed wire cutting machine to obtain the dumbbell-shaped tensile parts and bent strips for the test. The tensile parts were polished to 2000 mesh using SiC sandpaper.

[0117] X-ray diffraction analysis of the prepared iron-based high entropy shape memory alloy showed that the phase composition was mainly FCC phase and HCP phase.

[0118] The mechanical properties of this embodiment were tested according to the requirements of GB / T 228.1-2010 "Tensile tests on metallic materials - Part 1: Room temperature test methods", and the yield strength was 172.8 MPa, the tensile strength was 611.7 MPa, and the elongation after fracture was 19.5%.

[0119] The bending recovery effect of this embodiment was tested under different pre-strain conditions. The bent samples with different pre-strains were kept at 600° C. for 10 minutes to allow them to fully recover. The maximum recoverable strain of the alloy material was 7.2%.

[0120] In another specific implementation, the configuration composition is a high entropy shape memory alloy with an Fe content of 43%, a Mn content of 27%, a Co content of 9%, a Cr content of 9%, a Si content of 8%, a N content of 1%, a Sn content of 1%, and a Pb content of 1% by atomic percentage.

[0121] Prepare raw materials: Select electrolytic Mn with a purity of 99.5% or higher, and industrial-grade Fe, industrial-grade Co, electrolytic Cr, crystalline Si, industrial-grade Sn, and industrial-grade Pb with a purity of 99.95% or higher. Weigh the raw materials according to the corresponding mass and place them in a vacuum arc melting furnace.

[0122] Gas Cleaning: After evacuating the chamber, fill it with argon to create a protective atmosphere to prevent oxidation. Start the mechanical pump and wait until the vacuum drops below 5E0. Close the mechanical pump valve. Start the molecular pump and open the molecular pump valve, setting the molecular pump speed to 27,000 rpm. Wait until the vacuum drops below 3E-3, then close the molecular pump valve. Open the argon valve and fill it with argon until the vacuum reaches -0.05 MPa. Repeat this process twice.

[0123] Melting: After striking the arc with a current of 55A, increase the current to 220-270A to perform arc melting on the alloy. Each melting time should be more than 2 minutes.

[0124] The ingot was melted five times, and the alloy ingot was turned over between each melting to improve the uniformity of the alloy and obtain a button-shaped alloy ingot.

[0125] Vacuum casting: Select a copper casting mold with a size of 10×10×90mm. Place the button-shaped alloy ingot on top of the plate-shaped casting mold. Once the molten material is liquid, press the casting button. After cooling and demolding, the cast alloy plate is obtained.

[0126] The casting was cut by a medium-speed wire cutting machine to obtain the dumbbell-shaped tensile parts and bent strips for the test. The tensile parts were polished to 2000 mesh using SiC sandpaper.

[0127] X-ray diffraction analysis of the prepared iron-based high entropy shape memory alloy showed that the phase composition was mainly FCC phase and HCP phase.

[0128] The mechanical properties of this embodiment were tested according to the requirements of GB / T 228.1-2010 "Tensile tests on metallic materials - Part 1: Room temperature test methods". The yield strength was 163.4 MPa, the tensile strength was 609.8 MPa, and the elongation after fracture was 20.8%.

[0129] The bending recovery effect of this embodiment was tested under different pre-strain conditions. The bent samples with different pre-strains were kept at 600° C. for 10 minutes to allow them to fully recover. The maximum recoverable strain of the alloy material was 5.4%.

[0130] Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0131] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or terminal device. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or terminal device that includes the element.

[0132] The above is a detailed introduction to a training-free iron-based high-entropy shape memory alloy and its preparation method provided by the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for general technical personnel in this field, based on the ideas of the present application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for preparing a training-free iron-based high entropy shape memory alloy, characterized in that: The invention relates to a novel alloy comprising, in atomic percentages, 40-55% Fe, 25-35% Mn, 8-12% Co, 8-15% Cr, and 6-14% Si. The alloy comprises an FCC phase and an HCP phase, and the shape memory effect is based on the FCC+HCP phase transformation. The Fe element serves as the basis for providing the FCC austenite structure and the HCP martensite structure. Mn can reduce stacking fault energy. Si can reduce stacking fault energy and also produce a solid solution strengthening effect to increase the resistance to dislocation slip. Cr can improve corrosion resistance. Co also reduces stacking fault energy without producing a strong solid solution effect. The raw materials are vacuum melted to obtain an alloy ingot. The alloy ingot is subjected to alloy suction casting to obtain a cast alloy plate, and the maximum recoverable strain in the cast state reaches 6.0%. placing the raw materials into a vacuum arc melting furnace, and evacuating the vacuum arc melting furnace; and washing the vacuum melting furnace with argon gas; The gas washing process is to start the mechanical pump first, and when the vacuum degree drops below 5E0, close the valve of the mechanical pump, run the molecular pump, and then open the molecular pump valve. The molecular pump speed is set to 27000rpm. When the vacuum degree value drops below 3E-3, close the molecular pump valve; open the argon valve to fill in argon gas. After the vacuum degree reaches -0.07 MPa and argon gas is filled in for protection, the raw materials are melted; after the arc is struck at a current of 45 A, the current is increased to 210-260 A to perform arc melting on the alloy.

2. The preparation method according to claim 1, characterized in that The Mn is electrolytic Mn with a purity higher than 99.5%.

3. The preparation method according to claim 1, characterized in that The Fe is industrial pure Fe with a purity higher than 99.5%.

4. The preparation method according to claim 1, characterized in that It also contains 0 to 1 atomic % of Sn.

5. The preparation method according to claim 1, characterized in that It also contains 0 to 1 atomic % of Pb.

6. The preparation method according to claim 1, characterized in that It also contains 0 to 1 atomic % of N.

7. The preparation method according to claim 1, characterized in that The step of melting the raw materials after filling with argon gas for protection includes: filling with argon gas to protect the raw materials; melting the raw materials to obtain ingots, with the melting time being not less than 1 minute; turning over the ingots and melting them again for not less than 2 minutes; repeating the turning and melting operation 5 to 6 times.

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