A method for improving shape memory effect stability of 3D printed FeMnSi series alloy during multiple deformations

Abstract

The application discloses a method for improving shape memory effect stability of 3D printing FeMnSi series alloy in multiple deformations, which comprises the following steps: 1, micron FeMnCoCrNiSi pre-alloy powder is mixed with nano SiO2 powder at room temperature to obtain mixed powder; 2, the mixed powder is printed into a printed part with stable shape memory effect by using a metal powder bed selective laser melting 3D printing process. The application adds nano SiO2 in the 3D printing FeMnSi series shape memory alloy, so that a large number of nano SiO2 particle strengthening phases are distributed on the boundary of the cellular structure in the printed part during the printing and solidification process, thereby limiting the development of intracellular dislocations into larger slip bands, inhibiting the accumulation of residual plastic deformation of the FeMnSi series shape memory alloy printed part in the repeated deformation process, thereby greatly inhibiting the attenuation of the shape memory effect, and improving the engineering application value of the FeMnSi series shape memory alloy.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing technology, specifically relating to a method for improving the stability of shape memory effect during multiple deformations of FeMnSi alloys in 3D printing. Background Technology

[0002] FeMnSi-based shape memory alloys exhibit a significant shape memory effect, the mechanism of which involves a deformation-induced fcc-hcp phase transformation and a subsequent hcp-fcc phase transformation upon heating, ultimately leading to the restoration of the original shape. With a room temperature bending pre-strain of 5%, the recoverable strain after heating can reach 2.5%–3%. Furthermore, its low-temperature strength is significantly higher than that of NiTi shape memory alloys. Therefore, it holds promise as a reusable intelligent load-bearing, energy storage, and buffer element for applications in aerospace, robotics, and other fields under low-temperature environments.

[0003] Because intelligent load-bearing, energy storage, and buffering components typically require complex geometries or porous structures, conventional casting and rolling processes are insufficient for fabricating such components. Therefore, selective laser melting (SLM) 3D printing with greater manufacturing freedom is needed to manufacture FeMnSi-based shape memory alloy intelligent load-bearing, energy storage, and buffering components with complex structures. Currently, there are reports of 3D printing FeMnSi-based shape memory alloys, which exhibit good shape memory effects with only a low number of deformations. However, when the number of deformations increases significantly, such as from 10 to 50 times, the shape memory effect decreases substantially. This is because, with increasing deformation counts, the cellular boundaries in the printed part are insufficient to confine dislocation slip to the extracellular space, resulting in a significant increase in dislocation density. This leads to severe micro-regional residual plastic deformation within the matrix. Since this plastic deformation cannot be recovered during subsequent heating, it significantly reduces the shape memory effect.

[0004] Therefore, the shape memory effect of existing FeMnSi alloys exhibits poor stability after repeated use. In practical engineering applications, materials often undergo multiple deformation-recovery processes, thus necessitating improvements in the stability of the shape memory effect of existing FeMnSi alloys during repeated use. Summary of the Invention

[0005] The technical problem this invention aims to solve is to address the shortcomings of the prior art by providing a method to improve the stability of the shape memory effect during repeated deformation of 3D-printed FeMnSi alloys. This method involves adding nano-SiO2 to the 3D-printed FeMnSi shape memory alloy, resulting in a large distribution of nano-SiO2 particles as a reinforcing phase at the boundaries of the cellular structure during printing and solidification. This enhances the cell walls' resistance to dislocation slip, thereby suppressing the accumulation of residual plastic deformation in the printed FeMnSi shape memory alloy parts during repeated deformation. This solves the problem of shape memory effect attenuation in FeMnSi shape memory alloys and improves their engineering application value.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for improving the stability of shape memory effect during multiple deformations of FeMnSi alloys in 3D printing, characterized in that the method includes the following steps: Step 1: Mix micron-sized FeMnCoCrNiSi pre-alloyed powder with nano-sized SiO2 powder by rotary mixing at room temperature to obtain a mixed powder; Step 2: Using selective laser melting 3D printing technology, the mixed powder obtained in Step 1 is printed into a shape memory effect stable printed part.

[0007] The aforementioned method for improving the stability of the shape memory effect during multiple deformations of FeMnSi alloys in 3D printing is characterized in that the micron-sized FeMnCoCrNiSi pre-alloy powder in step one is composed of the following mass fractions: Co 1%~3%, Si 5%~6%, Mn 10%~18%, Cr 9%~12%, Ni 4%~6%, with the balance being Fe. In this invention, by controlling the alloy composition, especially controlling the mass fraction of Co to 1%~3%, the fcc phase is directly generated during the printing process without the bcc-fcc phase transformation, which effectively promotes the formation of cellular structures. Nano-SiO2 can only effectively limit dislocation accumulation and improve the stability of the shape memory effect when distributed at the boundaries of the cellular structures.

[0008] The method described above for improving the stability of shape memory effect during multiple deformations of FeMnSi alloys in 3D printing is characterized in that the average particle size of the micron-sized FeMnCoCrNiSi pre-alloyed powder in step one is 25μm~35μm. This invention ensures the effectiveness of 3D printing by controlling the average particle size of the micron-sized FeMnCoCrNiSi pre-alloyed powder.

[0009] The aforementioned method for improving the stability of the shape memory effect during multiple deformations of 3D-printed FeMnSi alloys is characterized in that the average particle size of the nano-SiO2 powder in step one is 200nm~500nm. This invention, by controlling the average particle size of the nano-SiO2 powder, prevents its agglomeration and enhances its cell wall strengthening effect, thereby improving the stability of the shape memory effect. It avoids the shortcomings of excessively low average particle size leading to significant agglomeration of nanoparticles, and also prevents excessively high average particle size resulting in too few nanoparticles, which reduces the cell wall strengthening effect and causes stress concentration due to excessively large size, thus reducing the stability of the shape memory effect.

[0010] The method described above for improving the stability of the shape memory effect during multiple deformations of 3D-printed FeMnSi alloys is characterized in that the mass content of nano-SiO2 powder in the mixed powder in step one is 0.5%~1.5%. This invention, by controlling the amount of nano-SiO2 powder added, ensures the effect of strengthening the cell wall, improves the stability of the shape memory effect, and prevents insufficient cell wall strengthening due to too low a content, thus reducing the instability of the shape memory effect. It also prevents excessively high a content, which could lead to nanoparticle agglomeration, stress concentration, and further reduce the stability of the shape memory effect.

[0011] The aforementioned method for improving the stability of the shape memory effect during multiple deformations of FeMnSi alloys in 3D printing is characterized by the laser power being 200W~380W and the scanning speed being 800mm / s~1000mm / s in the selective laser melting 3D printing process of the metal powder bed in step two. This invention effectively promotes uniform particle distribution and avoids keyhole defects by controlling the parameters of the 3D printing process, thereby improving the stability of the shape memory effect and preventing keyhole defects or insufficient particle agglomeration caused by excessively high or low energy.

[0012] The aforementioned method for improving the shape memory effect stability of 3D-printed FeMnSi alloys during multiple deformations is characterized by processing the shape memory effect-stable printed part, as described in step two, into alloy wires. After 50 deformations, the shape recovery rate of the alloy wires decreases by less than 10%. In this invention, processing the printed part into alloy wires for shape memory effect stability testing, and after 50 deformations, the shape recovery rate of the alloy wires decreases by less than 10%, thus improving the shape memory effect stability of 3D-printed FeMnSi alloys during multiple deformations.

[0013] Compared with the prior art, the present invention has the following advantages: 1. This invention proposes adding nano-SiO2 to FeMnSi shape memory alloys for 3D printing. This results in a large number of nano-SiO2 particles distributed as reinforcing phases at the boundaries of the cellular structure in the printed part during the 3D printing solidification process. Since the SiO2 phase is a ceramic phase, it is not easily cut by dislocations, thus significantly improving the cell wall's resistance to dislocation slip. This limits the accumulation and development of intracellular dislocations into larger slip bands during deformation, thereby inhibiting the accumulation of residual plastic deformation in FeMnSi alloy printed parts during repeated deformation. This significantly suppresses the attenuation of the shape memory effect and improves the engineering application value of FeMnSi shape memory alloys.

[0014] 2. The nano-SiO2 powder used in this invention has a high bonding force between Si and O elements, and is not easily decomposed into the matrix during the printing process. It does not affect the shape memory effect of the matrix itself. It only limits the development of intracellular dislocations through its strengthening effect on the cell wall, and greatly inhibits the accumulation of micro-area plastic deformation after multiple deformations. Therefore, it effectively improves the stability of the shape memory effect of 3D printed FeMnSi alloy parts when used multiple times.

[0015] 3. This invention effectively promotes uniform particle distribution and avoids keyhole defects by controlling the parameters of the 3D printing process, thereby improving the stability of the shape memory effect.

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the cellular structure of the alloy blocks obtained in Embodiment 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0018] Example 1 This embodiment includes the following steps: Step 1: Micron-sized FeMnCoCrNiSi pre-alloyed powder and nano-sized SiO2 powder are mixed by rotary mixing at room temperature to obtain a mixed powder. The micron-sized FeMnCoCrNiSi pre-alloyed powder consists of the following components by mass fraction: Co 3%, Si 6%, Mn 18%, Cr 12%, Ni 6%, with the balance being Fe, and an average particle size of 35 μm. The average particle size of the nano-sized SiO2 powder is 500 nm. The mass content of nano-sized SiO2 powder in the mixed powder is 1.5%. Step 2: Using selective laser melting 3D printing technology, the mixed powder obtained in Step 1 is printed into a shape memory stable part with a length × width × height of 100mm × 10mm × 10mm; in the selective laser melting 3D printing technology, the scanning linewidth is 80μm, the laser beam diameter is 80μm, the laser power is 380W, and the scanning speed is 1000mm / s; Step 3: Cut the printed part obtained in Step 2 to obtain an alloy wire with a diameter of 1mm.

[0019] Comparative Example 1 This comparative example includes the following steps: Step 1: Using a selective laser melting 3D printing process, micron-sized FeMnCoCrNiSi pre-alloyed powder is printed into a part with dimensions of 100mm × 10mm × 10mm (length × width × height). The micron-sized FeMnCoCrNiSi pre-alloyed powder is composed of the following mass fractions: Co 3%, Si 6%, Mn 18%, Cr 12%, Ni 6%, with the balance being Fe, and an average particle size of 35μm. In the selective laser melting 3D printing process, the scanning linewidth is 80μm, the laser beam diameter is 80μm, the laser power is 380W, and the scanning speed is 1000mm / s. Step 2: Cut the printed part obtained in Step 1 to obtain an alloy wire with a diameter of 1mm.

[0020] The alloy wires obtained in Example 1 and Comparative Example 1 were subjected to 50 repeated shape memory effect tests, with a pre-strain of 5% for both. The stability of the shape memory effect was tested (test method reference: "YS / T 1307.2-2019 Test Method for Memory Performance of Nickel-Titanium Shape Memory Alloys Part 2: Bending Test Method"). The shape memory effect at different numbers of deformations is shown in Table 1. The results show that the shape memory effect of the alloy wire obtained in Example 1 is relatively stable after multiple deformations. Even after 50 deformations, the shape recovery rate of the alloy wire only decreases by 9% (calculated by (64-58)÷64×100%), which does not affect the actual engineering application effect. The shape memory effect of the alloy wire obtained in Comparative Example 1 decreases significantly after multiple deformations. After 50 deformations, the shape recovery rate of the alloy wire decreases by 55%, which seriously affects the actual engineering application.

[0021] Table 1

[0022] Figure 1 This is a schematic diagram of the cellular structure of the alloy blocks obtained in Embodiment 1 and Comparative Example 1 of the present invention. The left side of the diagram represents Comparative Example 1, and the right side represents Embodiment 1. Figure 1As can be seen, in Comparative Example 1, dislocations formed multiple slip bands, which significantly reduced the shape memory effect. In Example 1, nano-SiO2 powder was added. During the solidification process of 3D printing, a large number of nano-SiO2 particles were distributed at the boundaries of the cellular structure in the printed part to strengthen the phase. Since the SiO2 phase is a ceramic phase, it is not easily cut by dislocations, thus greatly improving the cell wall's resistance to dislocation slip. This limits the accumulation of intracellular dislocations during deformation, preventing them from forming larger slip bands. This inhibits the accumulation of residual plastic deformation during repeated deformation of the printed part, thereby significantly suppressing the attenuation of the shape memory effect.

[0023] Example 2 This embodiment includes the following steps: Step 1: Micron-sized FeMnCoCrNiSi pre-alloyed powder and nano-sized SiO2 powder are mixed by rotary mixing at room temperature to obtain a mixed powder. The micron-sized FeMnCoCrNiSi pre-alloyed powder consists of the following components by mass fraction: Co: 1%, Si: 5%, Mn: 10%, Cr: 9%, Ni: 4%, balance Fe, with an average particle size of 25 μm. The average particle size of the nano-sized SiO2 powder is 200 nm. The mass content of nano-sized SiO2 powder in the mixed powder is 0.5%. Step 2: Using selective laser melting 3D printing technology, the mixed powder obtained in Step 1 is printed into a shape memory stable part with a length × width × height of 100mm × 10mm × 10mm; in the selective laser melting 3D printing technology, the scanning linewidth is 80μm, the laser beam diameter is 80μm, the laser power is 200W, and the scanning speed is 800mm / s; Step 3: Cut the printed part obtained in Step 2 to obtain an alloy wire with a diameter of 1mm.

[0024] Example 3 This embodiment includes the following steps: Step 1: Micron-sized FeMnCoCrNiSi pre-alloyed powder and nano-sized SiO2 powder are mixed by rotary mixing at room temperature to obtain a mixed powder. The micron-sized FeMnCoCrNiSi pre-alloyed powder consists of the following components by mass fraction: Co 2%, Si 5.5%, Mn 15%, Cr 11%, Ni 5%, with the balance being Fe, and an average particle size of 30 μm. The average particle size of the nano-sized SiO2 powder is 350 nm. The mass content of nano-sized SiO2 powder in the mixed powder is 1.0%. Step 2: Using selective laser melting 3D printing technology, the mixed powder obtained in Step 1 is printed into a shape memory stable part with a length × width × height of 100mm × 10mm × 10mm; in the selective laser melting 3D printing technology, the scanning linewidth is 80μm, the laser beam diameter is 80μm, the laser power is 300W, and the scanning speed is 900mm / s; Step 3: Cut the printed part obtained in Step 2 to obtain an alloy wire with a diameter of 1mm.

[0025] The alloy wires obtained in Examples 2 and 3 were subjected to 50 repeated shape memory effect tests, with a pre-strain of 5% for both. The stability of the shape memory effect was tested (test method reference: "YS / T 1307.2-2019 Test Method for Memory Performance of Nickel-Titanium Shape Memory Alloys Part 2: Bending Test Method"). The shape memory effect at different numbers of tests is shown in Table 2. The results show that the alloy wire obtained in Example 2 has a relatively stable shape memory effect during multiple deformations. Even after 50 deformations, the shape recovery rate of the alloy wire only decreases by 10%, which does not affect the actual engineering application effect. The alloy wire obtained in Example 3 also has a relatively stable shape memory effect during multiple deformations. Even after 50 deformations, the shape recovery rate of the alloy wire only decreases by 9.5%, which does not affect the actual engineering application effect.

[0026] Table 2

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for improving the stability of shape memory effect during multiple deformations of 3D-printed FeMnSi alloys, characterized in that, The method includes the following steps: Step 1: Mix micron-sized FeMnCoCrNiSi pre-alloyed powder with nano-sized SiO2 powder at room temperature to obtain a mixed powder; Step 2: Using selective laser melting 3D printing technology, the mixed powder obtained in Step 1 is printed into a shape memory effect stable printed part.

2. The method for improving the stability of shape memory effect during multiple deformations of 3D printed FeMnSi alloys according to claim 1, characterized in that, The micron FeMnCoCrNiSi pre-alloyed powder mentioned in step one is composed of the following components by mass fraction: Co 1%~3%, Si 5%~6%, Mn 10%~18%, Cr 9%~12%, Ni 4%~6%, with the balance being Fe.

3. The method for improving the stability of shape memory effect during multiple deformations of 3D-printed FeMnSi alloys according to claim 1, characterized in that, The average particle size of the micron-sized FeMnCoCrNiSi pre-alloyed powder mentioned in step one is 25μm~35μm.

4. The method for improving the stability of shape memory effect during multiple deformations of 3D printed FeMnSi alloys according to claim 1, characterized in that, The average particle size of the nano-SiO2 powder mentioned in step one is 200nm~500nm.

5. The method for improving the stability of shape memory effect during multiple deformations of 3D printed FeMnSi alloys according to claim 1, characterized in that, The mass content of nano-SiO2 powder in the mixed powder in step one is 0.5%~1.5%.

6. The method for improving the stability of shape memory effect during multiple deformations of 3D printed FeMnSi alloys according to claim 1, characterized in that, In step two, the laser power in the selective laser melting 3D printing process for metal powder beds is 200W~380W, and the scanning speed is 800mm / s~1000mm / s.

7. The method for improving the stability of shape memory effect during multiple deformations of 3D printed FeMnSi alloys according to claim 1, characterized in that, The shape memory effect stabilized printed part described in step two is processed into alloy wire. After 50 deformations, the shape recovery rate of the alloy wire decreases by less than 10%.

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