NiTiNb shape memory alloy and in-situ alloying preparation method and application thereof

Abstract

The invention discloses a NiTiNb shape memory alloy and an in-situ alloying preparation method and application thereof. The invention belongs to the technical field of additive manufacturing. The invention aims to solve the technical problems of composition segregation caused by large melting point difference of alloy elements and high reactivity of the elements at high temperature. The method comprises the following steps: firstly, carrying out three-dimensional modeling on a target component, and carrying out slicing treatment; a NiTi alloy wire and a pure Nb wire are used as printing wires, the wire feeding angle, the dry extension length and the relative positions of the double wires are set, the wire feeding angle of the pure Nb wire is larger than the wire feeding angle of the NiTi alloy wire, and the dry extension length of the pure Nb wire extending out of a wire guide nozzle to the center axis of an electron beam is larger than the dry extension length of the NiTi alloy wire extending out of the wire guide nozzle to the center axis of the electron beam; and finally, electron beam fuse wire additive manufacturing parameters are set, and 3D printing is conducted according to slicing data.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a NiTiNb shape memory alloy and an in-situ alloying preparation method and application thereof. Background Art

[0002] NiTi alloy has good biocompatibility, mechanical properties, damping capacity, corrosion resistance and elastic thermal effect. It is a very promising shape memory material and has important applications in aerospace, biomedicine, construction, solid-state refrigeration and other fields. However, with the improvement of material performance requirements in these fields, some limitations of pure NiTi alloy have gradually emerged, including narrow thermal hysteresis range, poor fatigue resistance, limited low-temperature performance and other problems, which restrict the further development of NiTi alloy. In order to solve the above problems, Nb element is introduced to improve the performance of NiTi alloy. The addition of Nb reduces the martensitic transformation temperature, expands the operating temperature range, and shows a large thermal hysteresis. In addition, by introducing rich soft and tough β-Nb phase into the NiTi matrix, the plastic deformation ability and fatigue resistance are enhanced, and the formation of passivation film on the alloy surface is promoted, which improves the corrosion resistance of the alloy. The good biocompatibility and non-toxicity of Nb also make NiTiNb alloy have broad prospects in biomedical applications.

[0003] However, it is quite challenging to manufacture NiTiNb alloys by conventional metallurgical techniques such as casting, mainly due to the large difference in the melting points of Ni (1726K), Ti (1941K) and Nb (2741K), and the high chemical reactivity of these elements at high temperatures. In addition, the poor machinability of NiTi-based alloys limits the forming of NiTiNb alloys to simple geometries.

[0004] In recent years, additive technology based on wire or powder has attracted much attention due to its ability to flexibly control composition and manufacture complex geometric components. However, studies have shown that in additive manufacturing processes using powder as raw materials, component performance is often heavily dependent on the quality of the powder, and the prepared components usually have a large number of pore inclusions, low density, uneven composition and other defects. In contrast, although arc additive technology using wire as raw material avoids dependence on powder quality, it is easy to introduce impurities such as O, C, and N because it works in a non-vacuum environment, resulting in the formation of harmful phases such as oxides and carbides in the components, which seriously damages the functional properties of the alloy. Summary of the invention

[0005] In order to overcome the above technical defects, the present invention provides a NiTiNb shape memory alloy and an in-situ alloying preparation method and application thereof.

[0006] The technical solution of the present invention is as follows:

[0007] One of the purposes of the present invention is to provide a method for preparing a NiTiNb shape memory alloy by in-situ alloying, the method being carried out according to the following steps:

[0008] S1: 3D modeling of the target component and slicing;

[0009] S2: Pre-process the printing wire and substrate, use NiTi alloy wire and pure Nb wire as printing wire, set the wire feeding angle, dry extension length and relative position of the two wires, where the wire feeding angle of pure Nb wire is greater than the wire feeding angle of NiTi alloy wire, and the dry extension length of pure Nb wire extending from the wire guide nozzle to the center axis of the electron beam is greater than the dry extension length of NiTi alloy wire extending from the wire guide nozzle to the center axis of the electron beam;

[0010] S3: Set the electron beam fuse additive manufacturing parameters and perform 3D printing according to the slice data.

[0011] It is further defined that in S2: the pre-treatment process includes polishing, cleaning by immersion in anhydrous ethanol and / or acetone, and constant temperature drying in a vacuum drying oven.

[0012] It is further defined that in S2: the diameter of the NiTi alloy wire used is 1.6 mm, the diameter of the pure Nb wire is 1.2 mm, and the substrate is a TA1 alloy plate.

[0013] It is further defined that in S2: the wire feeding angle of the NiTi alloy wire is 30-45°, the wire feeding angle of the pure Nb wire is 45-70°, the wire extension length from the wire guide nozzle to the center axis of the electron beam is 10-20 mm, the double wires are located on both sides of the electron beam, the vertical distance between the front end of the wire and the substrate is 2-5 mm, and in the direction perpendicular to the substrate, the intersection of the pure Nb wire and the NiTi wire is located 1-2 mm to the right of the center point of the electron beam, ensuring that the front end of the Nb wire is lower than the NiTi alloy wire, and the vertical distance between the front ends of the double wires is 1-6 mm.

[0014] Further definition, in S3: the printing process parameters are: acceleration voltage 60kV, focusing current 1030-1250mA, cathode current 24-28A, beam density 70-120mA, scanning mode is elliptical, amplitude X is 3-8mm, amplitude Y is 1-3mm, vacuum degree is 9.5×10 -3 Pa, the substrate movement speed is 280-400mm / min, and the movement path is a reciprocating straight line.

[0015] Further definition, in S3: interlayer cooling time 60-120s

[0016] It is further defined that in S3: the wire feeding speed ratio of the pure Nb wire to the NiTi alloy wire is 0.2-1.

[0017] It is further defined that in S3: the substrate is preheated before printing, specifically, the acceleration voltage is 60 kV, the beam current density is 20 mA, the movement speed is 500 mm / min, and the preheating is performed more than 5 times.

[0018] The second object of the present invention is to provide a NiTiNb shape memory alloy prepared according to the above method, wherein the Nb content in the alloy is 9-20 at.%.

[0019] The third object of the present invention is to provide a NiTiNb shape memory alloy prepared by the above method for use in the fields of aerospace, biomedicine, construction, and solid-state refrigeration.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The method of the present invention not only enables the NiTi alloy wire and the pure Nb wire to continuously and evenly transition into the molten pool at different wire feeding speeds through comprehensive regulation of the angle of the twin wires, the wire bundle spacing, and the dry extension length, thereby solving the problem of component segregation caused by the large difference in the melting points of the three elements, but also realizes the introduction of trace alloying of Nb into NiTi, thereby obtaining a component with high density and uniform composition.

[0022] (2) The method of the present invention effectively avoids the introduction of impurity elements during deposition under a vacuum environment, improves the forming purity of the component, and is beneficial to the stability of the functional characteristics of the component; at the same time, during the electron beam fuse additive process, the heat accumulation is obvious, and the cooling speed is slower than that of the arc fuse additive, so a uniform structure can be obtained.

[0023] (3) The method of the present invention can achieve the preparation of NiTiNb components with different target compositions by adjusting the wire feeding speed and wire diameter of the NiTi alloy wire and the pure Nb wire during the deposition process.

[0024] (4) The method of the present invention uses an electron beam as a heat source, making full use of the advantages of electron beam technology such as high power, high energy utilization and high deposition efficiency, and can achieve high-quality rapid forming of large and complex metal components, effectively solving the problem of large-size forming difficulties of NiTiNb shape memory alloy.

[0025] (5) The method of the present invention has wide applicability and is not limited to the preparation of NiTiNb shape memory alloys, but can also be applied to the preparation of other large-sized complex components with high activity, high melting point and different compositions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the spatial position during the preparation process of the NiTiNb shape memory alloy of the present invention;

[0027] Figure 2This is a physical picture of the NiTiNb shape memory alloy obtained in Example 1-3; Figure 2 (a) The wire feeding speed ratio of the two wires is: V Niti :V Nb =1:0.271, Figure 2 (b) The wire feeding speed ratio of the two wires is: V Niti :V Nb =1:0.43, Figure 2 (c) The wire feeding speed ratio of the two wires is: V Niti :V Nb =1:0.61;

[0028] Figure 3 The microstructure diagram of the intermediate stable region of the NiTiNb shape memory alloy obtained in Examples 1-3; wherein Figure 3 (a) The wire feeding speed ratio of the two wires is: V Niti :V Nb =1:0.271, Figure 3 (b) The wire feeding speed ratio of the two wires is: V Niti :V Nb =1:0.43, Figure 3 (c) The wire feeding speed ratio of the two wires is: V Niti :V Nb =1:0.61;

[0029] Figure 4 The microstructure diagram and element distribution diagram of the intermediate stable region of the NiTiNb shape memory alloy obtained in Example 1;

[0030] Figure 5 The microstructure diagram and element distribution diagram of the intermediate stable region of the NiTiNb shape memory alloy obtained in Example 2;

[0031] Figure 6 The microstructure diagram and element distribution diagram of the intermediate stable region of the NiTiNb shape memory alloy obtained in Example 3. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0034] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0035] Embodiment 1:

[0036] The method for preparing NiTiNb shape memory alloy by in-situ alloying in this embodiment comprises the following steps:

[0037] (1) 3D modeling of the target component and slicing;

[0038] (2) Pre-treating the printing filament and substrate; wherein the pre-treatment of the printing filament is as follows: grinding the surface of the filament with sandpaper to ensure that the surface of the filament is smooth and has no oxide layer; soaking and cleaning the polished filament with anhydrous ethanol; placing the cleaned filament in a vacuum drying oven and drying it at a constant temperature of 50° C. for 5 hours;

[0039] The pretreatment of the substrate is as follows: the surface of the substrate is polished with an angle grinder to ensure that the surface of the substrate is smooth and has no oxide layer; the polished substrate is soaked and cleaned with anhydrous ethanol and acetone in turn; the cleaned substrate is placed in a vacuum drying oven and dried at a constant temperature of 50°C for 5 hours;

[0040] (3) Using NiTi alloy wire and pure Nb wire as printing wire materials, setting the wire feeding angle, dry extension length and relative position of the two wires. Among them, the Ni element in the NiTi alloy wire accounts for 50.7at.%, and the diameter is 1.6mm; the purity of the pure Nb wire is ≥99.5%, and the diameter is 1.2mm; the substrate is a TA1 alloy plate with a size of 200mm×100mm×10mm;

[0041] The wire feeding angle of NiTi alloy wire is 35°, the wire feeding angle of pure Nb wire is 50°, the dry extension length of NiTi alloy wire from the wire guide nozzle to the center axis of electron beam is 10mm, the dry extension length of pure Nb wire from the wire guide nozzle to the center axis of electron beam is 15mm, the double wires are respectively located on both sides of the electron beam, the vertical distance between the front end of the wire and the substrate is 2mm, in the direction perpendicular to the substrate, the intersection of pure Nb wire and NiTi wire is located 1mm to the right of the center point of electron beam, ensuring that the pure Nb wire is 1mm below the NiTi alloy wire on the center line of the electron beam;

[0042] (4) Setting the parameters for electron beam fuse additive manufacturing, preheating the substrate before printing, specifically, the acceleration voltage is 60 kV, the beam current density is 20 mA, the movement speed is 500 mm / min, and preheating is performed 6 times;

[0043] 3D printing was performed according to the slice data, with a total of 25 layers printed, and the interlayer cooling time was 120s. The printing process parameters were: acceleration voltage 60kV, focusing current 1050mA, cathode current 27A, beam density 75mA, scanning mode was elliptical, amplitude X was 4mm, amplitude Y was 1mm, and vacuum degree was 9.5×10 -3 Pa, the substrate movement speed is 280 mm / min, the path of each layer is a straight line of 75 mm, and a reciprocating scanning printing method is adopted, that is, the end point of the first layer is the starting point of the second layer, and so on. The wire feeding speed ratio of pure Nb wire to NiTi alloy wire is 0.27.

[0044] (5) After printing, the vacuum chamber is cooled for 2 h and the vacuum pump group is turned off. The vacuum chamber is then opened to remove the component to obtain a Ni-Ti-9at.%Nb shape memory alloy.

[0045] Figure 2 (a) is a specific physical picture, which shows that the NiTiNb shape memory alloy is well formed on the pure Ti substrate. Figure 3 (a) is the microstructure diagram, from which it can be seen that at this wire feeding speed, the alloy is mainly composed of NiTi matrix and eutectic structure, with Ti2Ni particles dispersed in the middle. Figure 4 This is the element distribution diagram of the alloy at the wire feeding speed. It can be seen that the elements are evenly distributed without obvious segregation, and the preparation of NiTiNb shape memory alloy with uniform composition and stable organization is achieved.

[0046] Embodiment 2:

[0047] The method for preparing NiTiNb shape memory alloy by in-situ alloying in this embodiment comprises the following steps:

[0048] (1) 3D modeling of the target component and slicing;

[0049] (2) Pre-treating the printing filament and substrate; wherein the pre-treatment of the printing filament is as follows: grinding the surface of the filament with sandpaper to ensure that the surface of the filament is smooth and has no oxide layer; soaking and cleaning the polished filament with anhydrous ethanol; placing the cleaned filament in a vacuum drying oven and drying it at a constant temperature of 50° C. for 5 hours;

[0050] The pretreatment of the substrate is as follows: the surface of the substrate is polished with an angle grinder to ensure that the surface of the substrate is smooth and has no oxide layer; the polished substrate is soaked and cleaned with anhydrous ethanol and acetone in turn; the cleaned substrate is placed in a vacuum drying oven and dried at a constant temperature of 50°C for 5 hours;

[0051] (3) Using NiTi alloy wire and pure Nb wire as printing wire materials, setting the wire feeding angle, dry extension length and relative position of the two wires. Among them, the Ni element in the NiTi alloy wire accounts for 50.7at.%, and the diameter is 1.6mm; the purity of the pure Nb wire is ≥99.5%, and the diameter is 1.2mm; the substrate is a TA1 alloy plate with a size of 200mm×100mm×10mm;

[0052] The wire feeding angle of NiTi alloy wire is 40°, the wire feeding angle of pure Nb wire is 60°, the dry extension length of NiTi alloy wire from the wire guide nozzle to the center axis of electron beam is 12mm, the dry extension length of pure Nb wire from the wire guide nozzle to the center axis of electron beam is 18mm, the double wires are respectively located on both sides of the electron beam, the vertical distance between the front end of the wire and the substrate is 2mm, in the direction perpendicular to the substrate, the intersection of pure Nb wire and NiTi wire is located 1.4mm to the right of the center point of electron beam, ensuring that the pure Nb wire is 3mm below the NiTi alloy wire on the center line of the electron beam;

[0053] (4) Setting the parameters for electron beam fuse additive manufacturing, preheating the substrate before printing, specifically, the acceleration voltage is 60 kV, the beam current density is 20 mA, the movement speed is 500 mm / min, and preheating is performed 6 times;

[0054] 3D printing was performed according to the slice data, with a total of 25 layers printed, and the interlayer cooling time was 90s. The printing process parameters were: acceleration voltage 60kV, focusing current 1030mA, cathode current 27A, beam density 75mA, scanning mode was elliptical, amplitude X was 5mm, amplitude Y was 2mm, and vacuum degree was 9.5×10 -3 Pa, the substrate movement speed is 350mm / min, the path of each layer is a straight line of 75mm, and the reciprocating scanning printing method is adopted, that is, the end point of the first layer is the starting point of the second layer, and so on. The wire feeding speed ratio of pure Nb wire and NiTi alloy wire is 0.43.

[0055] (5) After printing, the components were cooled in the vacuum chamber for 2 h and then the vacuum pump group was turned off. The vacuum chamber was then opened to take out the components, thereby obtaining a Ni-Ti-15at.%Nb shape memory alloy.

[0056] Figure 2 (b) is a specific physical picture, which shows that the NiTiNb shape memory alloy is well formed on the pure Ti substrate. Figure 3 (b) is the microstructure diagram, from which it can be seen that at this wire feeding speed, the alloy is mainly composed of NiTi matrix and eutectic structure, with Ti2Ni particles dispersed in the middle. Figure 5 This is the element distribution diagram of the alloy at the wire feeding speed. It can be seen that the elements are evenly distributed without obvious segregation, and the preparation of NiTiNb shape memory alloy with uniform composition and stable organization is achieved.

[0057] Embodiment 3:

[0058] The method for preparing NiTiNb shape memory alloy by in-situ alloying in this embodiment comprises the following steps:

[0059] (1) 3D modeling of the target component and slicing;

[0060] (2) Pre-treating the printing filament and substrate; wherein the pre-treatment of the printing filament is as follows: grinding the surface of the filament with sandpaper to ensure that the surface of the filament is smooth and has no oxide layer; soaking and cleaning the polished filament with anhydrous ethanol; placing the cleaned filament in a vacuum drying oven and drying it at a constant temperature of 50° C. for 5 hours;

[0061] The pretreatment of the substrate is as follows: the surface of the substrate is polished with an angle grinder to ensure that the surface of the substrate is smooth and has no oxide layer; the polished substrate is soaked and cleaned with anhydrous ethanol and acetone in turn; the cleaned substrate is placed in a vacuum drying oven and dried at a constant temperature of 50°C for 5 hours;

[0062] (3) Using NiTi alloy wire and pure Nb wire as printing wire materials, setting the wire feeding angle, dry extension length and relative position of the two wires. Among them, the Ni element in the NiTi alloy wire accounts for 50.7at.%, and the diameter is 1.6mm; the purity of the pure Nb wire is ≥99.5%, and the diameter is 1.2mm; the substrate is a TA1 alloy plate with a size of 200mm×100mm×10mm;

[0063] The wire feeding angle of NiTi alloy wire is 45°, the wire feeding angle of pure Nb wire is 65°, the dry extension length of NiTi alloy wire from the wire guide nozzle to the center axis of electron beam is 10mm, the dry extension length of pure Nb wire from the wire guide nozzle to the center axis of electron beam is 12mm, the double wires are respectively located on both sides of the electron beam, the vertical distance between the front end of the wire and the substrate is 2mm, in the direction perpendicular to the substrate, the intersection of pure Nb wire and NiTi wire is located 2mm to the right of the center point of electron beam, ensuring that the pure Nb wire is 4mm below the NiTi alloy wire on the center line of the electron beam;

[0064] (4) Setting the parameters for electron beam fuse additive manufacturing, preheating the substrate before printing, specifically, the acceleration voltage is 60 kV, the beam current density is 20 mA, the movement speed is 500 mm / min, and preheating is performed 6 times;

[0065] 3D printing was performed according to the slice data, with a total of 25 layers, and the interlayer cooling time was 60s. The printing process parameters were: acceleration voltage 60kV, focusing current 1050mA, cathode current 27A, beam density 75mA, scanning mode elliptical, amplitude X 6mm, amplitude Y 3mm, vacuum degree 9.5×10 -3Pa, the substrate movement speed is 400 mm / min, the path of each layer is a straight line of 75 mm, and the reciprocating scanning printing method is adopted, that is, the end point of the first layer is the starting point of the second layer, and so on. The wire feeding speed ratio of pure Nb wire and NiTi alloy wire is 0.61.

[0066] (5) After printing, the vacuum chamber is cooled for 2 h and the vacuum pump group is turned off. The vacuum chamber is then opened to remove the component to obtain a Ni-Ti-20at.%Nb shape memory alloy.

[0067] Figure 2 (c) is a specific physical picture, which shows that the NiTiNb shape memory alloy is well formed on the pure Ti substrate. Figure 3 (c) is the microstructure diagram, from which it can be seen that at this wire feeding speed, the alloy is mainly composed of NiTi matrix and eutectic structure, with Ti2Ni particles dispersed in the middle. Figure 6 This is the element distribution diagram of the alloy at the wire feeding speed. It can be seen that the elements are evenly distributed without obvious segregation, and the preparation of NiTiNb shape memory alloy with uniform composition and stable organization is achieved.

[0068] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. An in-situ alloying preparation method of NiTiNb shape memory alloy, It is characterized in that The method: S1: 3D modeling of the target component and slicing; S2: Pre-process the printing wire and substrate, use NiTi alloy wire and pure Nb wire as printing wire, set the wire feeding angle, dry extension length and relative position of the two wires, where the wire feeding angle of pure Nb wire is greater than the wire feeding angle of NiTi alloy wire, and the dry extension length of pure Nb wire extending from the wire guide nozzle to the center axis of the electron beam is greater than the dry extension length of NiTi alloy wire extending from the wire guide nozzle to the center axis of the electron beam; S3: Set the electron beam fuse additive manufacturing parameters and perform 3D printing according to the slice data.

2. The method according to claim 1, It is characterized in that S2: Pretreatment process: polishing, cleaning by immersion in anhydrous ethanol and / or acetone, and constant temperature drying in a vacuum drying oven.

3. The method according to claim 1, It is characterized in that In S2: the diameter of the NiTi alloy wire used is 1.6 mm, the diameter of the pure Nb wire is 1.2 mm, and the substrate is a TA1 alloy plate.

4. The method according to claim 1, It is characterized in that In S2: the wire feeding angle of the NiTi alloy wire is 30-45°, the wire feeding angle of the pure Nb wire is 45-70°, the wire extension length from the wire guide nozzle to the center axis of the electron beam is 10-20 mm, the double wires are located on both sides of the electron beam, the vertical distance between the front end of the wire and the substrate is 2-5 mm, and in the direction perpendicular to the substrate, the intersection of the pure Nb wire and the NiTi wire is located 1-2 mm to the right of the center point of the electron beam, ensuring that the front end of the Nb wire is lower than the NiTi alloy wire, and the vertical distance between the front ends of the double wires is 1-6 mm.

5. The method according to claim 1, It is characterized in that In S3, the printing process parameters are: acceleration voltage 60 kV, focusing current 1030-1250 mA, cathode current 24-28 A, beam density 70-120 mA, scanning mode is elliptical, amplitude X is 3-8 mm, amplitude Y is 1-3 mm, vacuum degree is 9.5×10 -3 Pa, the substrate movement speed is 280-400mm / min, and the movement path is a reciprocating straight line.

6. The method according to claim 1, It is characterized in that In S3: inter-layer cooling time 60-120s.

7. The method according to claim 1, It is characterized in that In S3: the wire feeding speed ratio of pure Nb wire to NiTi alloy wire is 0.2-1.

8. The method according to claim 1, It is characterized in that In S3: the substrate is preheated before printing, specifically, the acceleration voltage is 60 kV, the beam current density is 20 mA, the movement speed is 500 mm / min, and the preheating is performed for more than 5 times.

9. The NiTiNb shape memory alloy prepared by the method according to any one of claims 1 to 8, It is characterized in that The Nb content in the alloy is 9-20 at.%.

10. Application of the NiTiNb shape memory alloy according to claim 9 in the fields of aerospace, biomedicine, construction, and solid-state refrigeration.

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