Preparation method of copper-based shape memory alloy by supersonic cold spraying solid-phase additive

Abstract

The application provides a preparation method of a copper-based shape memory alloy prepared by supersonic cold spraying solid-phase additive manufacturing. The method comprises the following steps: selecting dry CuZnAl powder as raw material for supersonic cold spraying solid-phase deposition, preheating the raw material in an inert gas atmosphere, and depositing the preheated raw material on a brass substrate by supersonic cold spraying solid-phase additive manufacturing to obtain a block-shaped copper-based shape memory alloy deposition body; the preheating temperature of the raw material is 200-350 DEG C, the inert gas pressure during the supersonic cold spraying solid-phase additive manufacturing is 2.5-5 MPa, and the inert gas temperature during the supersonic cold spraying solid-phase additive manufacturing is 400-700 DEG C. The application uses the supersonic cold spraying solid-phase additive manufacturing to prepare the block-shaped copper-based shape memory alloy for the first time, the deposition process temperature is low, the volatilization of Al element in the CuZnAl powder and the oxidation of the powder particles are avoided, the deposition body has fine grains due to the strong plastic deformation of the CuZnAl powder, and the high brittleness of the copper-based shape memory alloy is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal alloy material manufacturing, in particular to a preparation method of a supersonic cold spraying solid-phase additive copper-based shape memory alloy. BACKGROUND

[0002] The copper-based shape memory alloy has the advantages of excellent electrical / thermal conductivity, high density, high strength, high elastic modulus, high corrosion resistance, excellent super-elasticity, good machining performance and low cost, and has important application prospects in the fields of aerospace, biological medicine, electronic communication and energy chemical industry. At present, the copper-based shape memory alloy has achieved preliminary application in parts such as stents, orthotics, valves and adjusting devices. However, the phase transition temperature of the copper-based shape memory alloy is extremely susceptible to the composition, and the traditional melting process is easy to cause the composition change, reduce the phase stability, increase the shape recovery stress, cause the phase transition and strain recovery hysteresis, and seriously affect the shape memory performance. In addition, the coarse grain boundary of the sample prepared by the traditional process is extremely fragile under the influence of the high-elasticity anisotropy, narrows the plastic process window, shows high intergranular brittleness and low fatigue strength, and greatly limits its popularization and application.

[0003] In order to reduce the high intergranular brittleness and low fatigue strength of the copper-based shape memory alloy, the existing technology uses supersonic cold spraying to prepare the alloy material, because the supersonic cold spraying technology can realize the spraying of the coating on the metal surface under the condition of relatively low temperature. The coating is connected with the base material through mechanical embedding and local metallurgy, and the adhesion, uniformity and coating functionality of the coating are the core problems concerned in the preparation of the coating. Although the alloy material with the best adhesion, uniformity and coating functionality can be prepared by considering the above core problems in the preparation of the coating, the thickness of the prepared alloy material is limited, and the block alloy material is required for the preparation of parts such as stents, orthotics, valves and adjusting devices, so the alloy material prepared by the spraying of the coating on the metal surface is not suitable for the preparation of parts such as stents, orthotics, valves and adjusting devices. When the parts such as stents, orthotics, valves and adjusting devices are prepared, the block alloy material (deposition body) is required to have higher overall mechanical properties. Therefore, how to improve the overall comprehensive mechanical properties of the copper-based shape memory alloy deposition body is a key step to promote and expand the application of the copper-based shape memory alloy. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a preparation method of a supersonic cold spraying solid-phase additive copper-based shape memory alloy, which aims to solve the problems proposed in the technical background. The copper-based shape memory alloy prepared thereby can reduce the high brittleness of the copper-based shape memory alloy and improve the comprehensive mechanical properties of the copper-based shape memory alloy.

[0005] To solve the above-mentioned technical problems, the first solution provided by this invention is a method for preparing a copper-based shape memory alloy by supersonic cold spray solid-phase additive manufacturing, which is prepared by the following steps:

[0006] Dry CuZnAl powder was selected as the raw material for supersonic cold spray solid phase deposition. The raw material was preheated in an inert gas atmosphere. The preheated raw material was deposited on a pretreated brass substrate by supersonic cold spray solid phase additive manufacturing to obtain a bulk copper-based shape memory alloy deposit.

[0007] The preheating temperature of the raw materials is 200℃~350℃, the inert gas pressure during supersonic cold spray solid phase additive manufacturing is 2.5MPa~5MPa, and the inert gas temperature during supersonic cold spray solid phase additive manufacturing is 400℃~700℃.

[0008] Preferably, the particle size of CuZnAl powder is 15μm to 53μm.

[0009] This is because CuZnAl powder with a particle size in the range of 15μm to 53μm can achieve the required deposition rate while maintaining the flowability of CuZnAl powder. However, as the particle size of CuZnAl powder increases, the critical velocity required for particle deposition increases, the deposition efficiency decreases, and CuZnAl powder particles become less likely to deposit. Conversely, when the particle size of CuZnAl powder decreases, its flowability decreases.

[0010] Preferably, the drying temperature of CuZnAl powder is 80℃~120℃, and the drying time of CuZnAl powder is 1h~2h.

[0011] The powder to be dried may contain moisture or other volatile substances. These substances evaporate and expand during the deposition process, increasing the critical velocity of powder particle deposition. This results in insufficient deformation of powder particles under the same process conditions, leading to a decrease in coating density and an increase in porosity, which in turn increases the grain size of the alloy material.

[0012] Drying CuZnAl powder at temperatures below this range will not achieve the desired drying effect, while drying CuZnAl powder at excessively high temperatures may cause oxidation of the CuZnAl powder and deteriorate the performance of the deposit.

[0013] Preferably, the weight percentage of each component in the CuZnAl powder is: 65wt.% to 75wt.% Cu, 19wt.% to 28wt.% Zn and 2wt.% to 7wt.% Al.

[0014] Preferably, the brass substrate pretreatment is that the brass substrate is ultrasonically cleaned in acetone with a volume concentration of 15% to 20% at 40°C to 60°C for 10 min to 30 min, then is sandblasted with corundum of 100 meshes to 300 meshes, the sandblasting pressure during sandblasting is 0.2 MPa to 0.7 MPa, and the residual corundum sand particles on the surface of the brass substrate are blown clean with compressed air after sandblasting, thereby completing the pretreatment of the brass substrate.

[0015] The brass substrate pretreatment can improve the bonding force between the deposited body and the brass substrate, is helpful to improve the bonding between the particles in the deposited body, and further improves the density of the deposited body.

[0016] Preferably, the spraying distance during the supersonic cold spraying solid-phase additive manufacturing is 20 mm to 40 mm, the spraying gun moving speed during the supersonic cold spraying solid-phase additive manufacturing is 200 mm / s to 500 mm / s, and the powder feeding gas during the supersonic cold spraying solid-phase additive manufacturing is nitrogen with a purity of 99.5% to 99.9%.

[0017] Preferably, the preheated raw material during the supersonic cold spraying solid-phase additive manufacturing is deposited and printed on the pretreated brass substrate in a Z shape, and the mechanical hand is retreated by 80 µm to 200 µm after depositing a layer.

[0018] The spraying distance during the supersonic cold spraying solid-phase deposition process is directly related to the speed of the particles. Generally, the spraying distance is 20 mm to 40 mm, the mechanical hand is retreated by 80 µm to 200 µm after depositing a layer, mainly because the thickness of the deposited layer is usually 80 µm to 200 µm, and the retreat can ensure that the spraying distance of each layer is the same. The process parameters during the deposition process are kept stable.

[0019] Preferably, the inert gas is nitrogen with a purity of 99.5% to 99.9%. The inert gas commonly used during the supersonic cold spraying solid-phase additive manufacturing can be nitrogen or helium, and the nitrogen is selected in the present application mainly because of its wide source and low price, which is suitable for industrial production.

[0020] The second implementation scheme provided in the present application is to provide a preparation method of a supersonic cold spraying solid-phase additive copper-based shape memory alloy, and a block-shaped copper-based shape memory alloy is prepared.

[0021] Compared with the prior art, the present application has the beneficial effects that:

[0022] The preparation method of the copper-based shape memory alloy deposited by the supersonic cold spray solid-phase additive manufacturing method provided by the application first uses the supersonic cold spray solid-phase additive manufacturing method to prepare the bulk copper-based shape memory alloy, the deposition process temperature is low in the supersonic cold spray solid-phase additive manufacturing method, the volatilization of the Al element in the CuZnAl powder and the oxidation of the powder particles are avoided, the gas temperature is controlled at 400-700 DEG C to ensure that the powder particles are sufficiently softened and plastically deformed and the particle temperature does not exceed the recrystallization temperature, the deformed particles are not recrystallized and grown in a large area, the control of the gas pressure and temperature can make the powder particle speed (> 800 m / s) exceed the deposition critical speed (~ 700 m / s), due to the strong plastic deformation of the CuZnAl powder, the deposited body has fine grains, the high brittleness of the copper-based shape memory alloy is reduced, and the comprehensive mechanical properties are improved.

[0023] In the preparation method of the copper-based shape memory alloy deposited by the supersonic cold spray solid-phase additive manufacturing method provided by the application, the preheating of the CuZnAl powder can effectively supplement the insufficient heating of the powder particles in the gas, make the particles sufficiently soften, improve the plastic deformation ability of the powder impacting the substrate, significantly reduce the porosity of the deposited body, increase the deposition efficiency of the powder, and improve the comprehensive performance of the deposited body.

[0024] In the preparation method of the copper-based shape memory alloy deposited by the supersonic cold spray solid-phase additive manufacturing method provided by the application, the inert gas pressure in the supersonic cold spray solid-phase additive manufacturing process increases the flow velocity of the inert gas flow at the outlet and the speed of the powder particles, affects the deposition efficiency of the powder particles, the density and strength of the deposited body, and improves the comprehensive performance of the deposited body.

[0025] The method of the application expands the preparation process of the copper-based shape memory alloy, and has important application value in the manufacturing and remanufacturing of important parts in the fields of aerospace, biological medicine, electronic communication and energy chemical industry. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The scanning electron microscope image of the microstructure of the bulk copper-based shape memory alloy deposited body in Example 9 of the application.

[0027] Figure 2 The surface image of the bulk copper-based shape memory alloy deposited body in Example 9 of the application. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] The inventors find that the characteristics of high strain rate (>10 3 s-1) and low temperature deposition of the cold spraying solid phase deposition make the particles severely deform, the dislocation density at the interface greatly increases, the crystal grains are difficult to grow, and a nanocrystalline or submicron crystalline structure is formed. In addition, the powder preheating can effectively soften the particles, effectively maintain the original chemical composition of the deposited body, refine the crystal grains, and improve the interlayer metallurgical bonding and the overall mechanical properties of the deposited body, which is of great significance to expand the forming process and application range of copper-based shape memory alloys.

[0030] Therefore, the present application provides a preparation method of a supersonic cold spraying solid phase additive copper-based shape memory alloy. The copper-based shape memory alloy prepared by the method can reduce the high brittleness of the copper-based shape memory alloy, and achieve the purpose of improving the comprehensive mechanical properties of the copper-based shape memory alloy.

[0031] It should be noted that when a numerical range is involved in the present application, both endpoints of each numerical range and any number between the two endpoints can be selected. Since the steps and methods used in the embodiments 1 to 11 are the same, in order to avoid repetition, the preferred embodiments are described in the present application, but the present application is not limited thereto, but can also be implemented in other ways within the scope of the technical solutions defined in the appended claims.

[0032] The technical solutions of the present application will be further illustrated in the form of specific examples.

[0033] Embodiment 1

[0034] A preparation method of a supersonic cold spraying solid phase additive copper-based shape memory alloy, comprising the following steps:

[0035] Step 1: CuZnAl powder with an average particle size of 37 μm prepared by a gas atomization method is selected as a raw material for supersonic cold spraying solid phase deposition, and the morphology and particle size distribution of the raw material are as shown in Figure 1 and Figure 2 Before spraying, the powder raw material is placed in a drying oven at 90℃ for 120 min, and after drying, the raw material is added to a powder feeder.

[0036] Step 2: After the brass substrate is cleaned ultrasonically in acetone with a volume fraction of 20% at a temperature of 50℃ for 30 min, the brass substrate is sandblasted at 0.6 MPa using corundum with an average particle size of 300 mesh, and the residual corundum particles on the surface are blown off using compressed air. The pretreated brass substrate is then fixed by a tool.

[0037] Step 3: After the brass substrate is fixed, the CuZnAl powder used as raw material in the powder feeder is preheated at 300℃. The nitrogen gas pressure for supersonic cold spraying solid-phase additive manufacturing is set to 4 MPa, the nitrogen gas temperature is set to 500℃, the spraying distance is set to 20 mm, and the moving speed of the spray gun is set to 300 mm / s. After the parameters are set, the preheated CuZnAl powder is sent out by nitrogen gas with a purity of 99.5% to 99.9%, and deposited and printed on the brass substrate in a Z shape. When the Z shape is deposited and printed, the mechanical hand retreats 100 μm after depositing a layer, and the bulk copper-based shape memory alloy deposition body is completed.

[0038] Embodiment Case 2

[0039] The difference between this embodiment and embodiment 1 is that the CuZnAl powder raw material is dried in a drying oven at 70℃ for 60 min before spraying in step 1.

[0040] Embodiment Case 3

[0041] The difference between this embodiment and embodiment 1 is that the CuZnAl powder raw material is dried in a drying oven at 120℃ for 120 min before spraying in step 1.

[0042] Embodiment Case 4

[0043] The difference between this embodiment and embodiment 1 is that the average particle size of the corundum used for sandblasting in step 2 is 150 mesh at 0.4 MPa.

[0044] Embodiment Case 5

[0045] The difference between this embodiment and embodiment 1 is that the preheating temperature of the CuZnAl powder in step 3 is 250℃.

[0046] Embodiment Case 6: The difference between this embodiment and embodiment 1 is that the preheating temperature of the CuZnAl powder in step 3 is 350℃.

[0047] Embodiment Case 7

[0048] The difference between this embodiment and embodiment 1 is that the nitrogen gas pressure for supersonic cold spraying solid-phase additive manufacturing in step 3 is 2.5 MPa.

[0049] Embodiment Case 8

[0050] The difference between this embodiment and embodiment 1 is that the nitrogen gas pressure during the supersonic cold spray solid phase additive manufacturing in step 3 is 5.0 MPa.

[0051] Embodiment 9

[0052] The difference between this embodiment and embodiment 1 is that the preheating temperature of the CuZnAl powder in step 3 is 350℃, the nitrogen gas pressure during the supersonic cold spray solid phase additive manufacturing is 5 MPa, the nitrogen gas temperature during the supersonic cold spray solid phase additive manufacturing is 700℃, and wherein Figure 1 The scanning electron microscope image of the microstructure of the bulk copper-based shape memory alloy deposited body prepared in this embodiment is shown in Figure 8, from which it can be seen that the deposited body is dense and has no visible pores, and the deposited particles are fully deformed. Figure 1 Figure 2 The surface image of the bulk copper-based shape memory alloy deposited body of this embodiment is shown in Figure 9.

[0053] Embodiment 10

[0054] The difference between this embodiment and embodiment 1 is that the nitrogen gas temperature during the supersonic cold spray solid phase additive manufacturing in step 3 is 600℃.

[0055] Embodiment 11

[0056] The difference between this embodiment and embodiment 1 is that the preheating temperature of the CuZnAl powder in step 3 is 350℃, the nitrogen gas pressure during the supersonic cold spray solid phase additive manufacturing is 5 MPa, the nitrogen gas temperature during the supersonic cold spray solid phase additive manufacturing is 700℃, and the moving speed of the spray gun is 500 mm / s. After depositing a layer in a Z shape, the robot is retracted by 150 μm.

[0057] Comparative Example 1

[0058] The difference between this comparative example and embodiment 1 is that the CuZnAl powder used as the raw material for the supersonic cold spray solid phase deposition is not dried.

[0059] Comparative Example 2

[0060] The difference between this comparative example and embodiment 1 is that the CuZnAl powder used as the raw material in step 3 is not preheated.

[0061] The above embodiments 1-11 and comparative examples 1-2 can all prepare bulk copper-based shape memory alloys. The bulk copper-based shape memory alloy samples deposited in embodiments 1, 5, 7, 11 and comparative examples 1-2 are selected for performance evaluation.

[0062] Experimental results ​

[0063] 1) Deposits density and grain size

[0064] The bulk copper-based shape memory alloy samples deposited in Examples 1, 5, 7, 11, and Comparative Examples 1-2 were all sampled by wire cutting. Each wire-cut sample was then sequentially polished with sandpaper of 180, 600, 800, 1200, and 1500 grit, followed by mirror polishing. Scanning electron microscopy (SEM) images of the mirror-polished samples were then obtained. The porosity of the obtained SEM images was characterized using the image method in ImageJ software. This image method measures the coating porosity by dividing the number of pixels occupied by the pores by the total area of ​​pixels. To ensure accuracy and reproducibility, multiple measurements were taken from different parts of the bulk copper-based shape memory alloy sample, and the average value was calculated. Table 1 shows the density and grain size values ​​of the bulk copper-based shape memory alloy samples deposited in Examples 1, 5, 7, 11, and Comparative Examples 1-2.

[0065] Table 1 Density and grain size of copper-zinc-aluminum shape memory alloys deposited using different deposition processes

[0066] Parameter Density of the deposited body (%) Average grain size of the deposited body (pm) Example 1 99.1±0.3 1.3 Example 5 95±0.8 2.1 Example 7 98±0.5 1.8 Example 11 99.4±0.3 1.2 Comparative Example 1 97±0.5 2.3 Comparative Example 2 92±1.2 3.8

[0067] A comparison of Example 1 and Comparative Example 1 in Table 1 shows that the density of the deposit in Example 1 is greater than that in Comparative Example 1, while the average grain size of the deposit in Example 1 is smaller than that in Comparative Example 1. This is because undried CuZnAl powder may contain moisture or other volatile substances. These substances volatilize and expand during deposition, increasing the critical velocity for powder particle deposition. Consequently, under the same process conditions, the powder particles deform insufficiently, resulting in decreased coating density, increased porosity, and increased average grain size.

[0068] Comparing Examples 1, 5, and 2, it can be seen that, compared to Example 5, lowering the preheating temperature of CuZnAl powder in Example 1 leads to a decrease in the density of the deposited body and an increase in the average grain size. Furthermore, compared to Comparative Example 2, the density of the unpreheated CuZnAl powder deposited in Examples 1 and 5 is lower than that in Examples 1 and 5, while the average grain size is larger. This is because:

[0069] The preheating of CuZnAl powder and the increase of the preheating temperature of CuZnAl powder can effectively compensate for the insufficient heating of powder particles in the gas, so that the particles are fully softened, the plastic deformation ability of the particles impacting the substrate is improved, the porosity of the deposited body is significantly reduced, the deposition efficiency of the powder is increased, and the comprehensive performance of the deposited body is improved. However, it should be noted that for easily oxidized materials, the preheating temperature should not be too high to prevent the formation of oxides and nitrides on the surface of the powder particles, which will affect the subsequent deposition of the particles and the performance of the deposited body.

[0070] It can be seen from Comparative Example 1, Example 5 and Example 11 that the density of the deposited body of Example 11 is greater than that of the deposited bodies of Examples 1 and 5, and the average grain size of the deposited body of Example 11 is smaller than that of the deposited bodies of Examples 1 and 5. This is because: the nitrogen gas pressure during supersonic cold spraying solid phase additive (the pressure of the working gas) and the nitrogen gas temperature during supersonic cold spraying solid phase additive are important factors affecting the supersonic cold spraying solid phase deposition. High working gas temperature promotes the increase of the temperature of the powder particles themselves, increases the impact speed of the particles, reduces the critical deposition speed of the particles, and thus reduces the porosity of the deposited body, improves the deposition efficiency and the strength of the deposited body. The increase of the working gas pressure increases the flow rate of the nitrogen gas flow at the outlet and the speed of the powder particles. In summary, the temperature and pressure of the working gas are key parameters for supersonic cold spraying solid phase additive, and the two interact with each other, directly affecting the deposition efficiency of the powder particles, the density and strength of the deposited body.

[0071] The preparation method of the supersonic cold spraying solid phase additive copper-based shape memory alloy provided by the present application first uses supersonic cold spraying solid phase additive to prepare bulk copper-based shape memory alloy. The deposition process temperature in the supersonic cold spraying solid phase additive manufacturing is low, which avoids the volatilization of Al element in the CuZnAl powder and the oxidation of the powder particles. Since the CuZnAl powder has strong plastic deformation, the bulk copper-based shape memory alloy deposited body prepared has fine grains, reduces the high brittleness of the bulk copper-based shape memory alloy, and improves the comprehensive mechanical properties thereof.

[0072] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations.

Claims

1. A method for the production of a super sonic cold sprayed solid phase additive manufactured copper based shape memory alloy, characterized in that, Preparation steps are as follows: Dry CuZnAl powder is selected as raw material for supersonic cold spraying solid phase deposition, and the raw material is preheated in inert gas atmosphere, and the preheated raw material is deposited on pretreated brass substrate by supersonic cold spraying solid phase additive manufacturing to obtain bulk copper-based shape memory alloy deposition body. The preheating temperature of the raw material is 200-350℃, the inert gas pressure during supersonic cold spraying solid phase additive manufacturing is 2.5-5MPa, and the inert gas temperature during supersonic cold spraying solid phase additive manufacturing is 400-700℃.

2. A method of making a super sonic cold sprayed solid phase additive manufactured copper based shape memory alloy as claimed in claim 1, wherein, The particle size of CuZnAl powder is 15-53μm.

3. The method of claim 1, wherein the copper-based shape memory alloy is prepared by a cold spray process at a supersonic speed. The drying temperature of CuZnAl powder is 80-120℃, and the drying time of CuZnAl powder is 1-2h.

4. The method of claim 1, wherein the method is characterized by: The weight percentage of each component in CuZnAl powder is 65-75wt.% Cu, 19-28wt.% Zn and 2-7wt.% Al.

5. The method of claim 1, wherein the copper-based shape memory alloy is prepared by a cold spray process at a supersonic speed. The pretreatment of brass substrate is ultrasonic cleaning of brass substrate in 15-20vol.% acetone at 40-60℃ for 10-30min, then sandblasting with 100-300 mesh corundum, the sandblasting pressure is 0.2-0.7MPa, and then blowing the residual corundum sand on the surface of brass substrate with compressed air to complete the pretreatment of brass substrate.

6. The method of claim 1, wherein the copper-based shape memory alloy is prepared by a cold spray process at a supersonic speed. The spraying distance during supersonic cold spraying solid phase additive manufacturing is 20-40mm, the gun moving speed during supersonic cold spraying solid phase additive manufacturing is 200-500mm / s, and the powder feeding gas during supersonic cold spraying solid phase additive manufacturing is nitrogen with purity of 99.5-99.9%.

7. The method of claim 6, wherein the copper-based shape memory alloy is prepared by a cold spray process at a supersonic speed. The preheated raw material during supersonic cold spraying solid phase additive manufacturing is deposited on the pretreated brass substrate in Z shape.

8. The method of claim 1, wherein the copper-based shape memory alloy is prepared by a cold spray process at a supersonic speed. The inert gas is nitrogen with purity of 99.5-99.9%.

9. A bulk copper-based shape memory alloy prepared by the method of any one of claims 1-8.

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