Layered isomorphic organization ni-ti shape memory alloy with wide phase transition temperature interval and preparation method and application thereof

Abstract

Layered heterogeneous structure NiTi shape memory alloy with wide phase transition temperature interval and preparation method and application thereof. The present application belongs to the field of shape memory alloy. The purpose of the present application is to overcome the technical problems of narrow phase transition temperature interval and insufficient high and low temperature performance of the existing NiTi shape memory alloy. The present application adopts electron beam wire deposition technology, and the heterogeneous double wires are alternately printed in the vertical direction in the unidirectional scanning mode to obtain the layered heterogeneous structure NiTi shape memory alloy. The present application prepares the layered heterogeneous structure NiTi shape memory alloy with good forming, dense structure and excellent performance by adjusting the printing parameters and setting the interlayer cooling time. The layered structure deposited by the heterogeneous double wires can change the content of Ni in the interlayer region, thereby widening the phase transition temperature interval and having good superelasticity at high temperature; in addition, the layered structure also has shape memory effect and good mechanical properties at room temperature.

Description

Technical Field

[0001] This invention belongs to the field of shape memory alloys, specifically relating to a layered heterostructure NiTi shape memory alloy with a wide phase transformation temperature range, its preparation method, and its applications. Background Technology

[0002] NiTi shape memory alloys are equiatomic or near-equiatomic alloys. When the Ni and Ti content differs, in addition to the NiTi phase, a second phase precipitates in the alloy, including Ti3Ni4, Ti2Ni3, TiNi3, and Ti2Ni. Near-equiatomic NiTi alloys exhibit shape memory effect, superelasticity, and high damping properties, which are essentially due to the non-diffusion thermoelastic martensitic phase transformation between the high-temperature parent phase B2 austenite and the low-temperature B19' martensite. Furthermore, NiTi shape memory alloys possess excellent mechanical properties, corrosion resistance, and biocompatibility, thus finding wide application in aerospace, construction, and biomedical fields.

[0003] Currently, conventional methods for preparing NiTi shape memory alloys include casting and machining, and powder metallurgy. Because Ti is a highly reactive metallic element, it readily reacts with elements such as C, N, and O during smelting or powder metallurgy to form compounds like TiC and Ti4Ni2O, leading to a decrease in the alloy's mechanical and functional properties. Furthermore, the unique shape memory effect and resistance to deformation of NiTi alloys, as well as work hardening during cold working, pose certain difficulties for machining the ingots. Powder metallurgy can achieve near-net-shape forming of complex NiTi alloy components, but due to the different diffusion coefficients of Ti and Ni, the formation of Ti2Ni and Ni3Ti compounds, and capillary effects, it is difficult to obtain dense NiTi solids. Moreover, the preparation process is complex, has a long production cycle, and is costly, which to some extent limits the preparation and application of large, complex NiTi shape memory alloy components. In addition, the aforementioned traditional forming processes are significantly lacking in flexibility regarding structural control. In contrast, additive manufacturing technology, characterized by point-to-point melting, line-to-line overlapping, and layer-to-layer deposition, can not only integrally form material components with complex geometries, but also synergistically advance alloying and processing, creating specific compositional and microstructural features at specific locations. Currently, the NiTi shape memory alloy components prepared using electron beam filament deposition technology are all limited to single-component filament deposition, exhibiting a narrow phase transformation temperature range, and their performance is still inferior to NiTi alloys prepared by traditional processes. Summary of the Invention

[0004] The purpose of this invention is to overcome the technical problems of narrow phase transformation temperature range and insufficient high-temperature and low-temperature performance of existing NiTi shape memory alloys. This invention provides a layered heterogeneous NiTi shape memory alloy with a wide phase transformation temperature range, its preparation method, and its application.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] One objective of this invention is to provide a method for preparing a layered heterostructure NiTi shape memory alloy with a wide phase transformation temperature range, the preparation method comprising the following steps:

[0007] Electron beam fused deposition technology was used, in a unidirectional scanning mode, to deposit Ti 50.5 Ni 49.5 Shape memory alloy wire and Ni 50.7 Ti 49.3 Shape memory alloy wires are printed alternately in the vertical direction to obtain a layered heterogeneous NiTi shape memory alloy.

[0008] Preferably, the printing process parameters are: accelerating voltage U = 60kV, focusing current I = 0. f 1000mA, wire feeding speed V F 3000 mm / min, beam current density I b 30-40mA, moving speed V T The speed is 300-400 mm / min, and the interlayer cooling time is set.

[0009] More preferably, beam current density I b It is 35mA.

[0010] More preferably, the moving speed V T The speed is 350 mm / min.

[0011] More preferably, the interlayer cooling time is 30 seconds.

[0012] Preferred, Ti 50.5 Ni 49.5 Shape memory alloy wire and Ni 50.7 Ti 49.3 The diameter of the shape memory alloy wire is 1mm.

[0013] Preferably, the dual-filament material is pretreated before use. The specific process is as follows: first, acid washing, then acetone soaking and cleaning to remove surface oil and impurities, and finally drying.

[0014] Preferably, the substrate is Ni. 50.8 Ti 49.2 .

[0015] More preferably, the substrate is pretreated before use. The specific process is as follows: first, sand the surface with sandpaper until it is smooth and clean, then wipe it with acetone to remove surface oil and impurities, and finally dry it.

[0016] Preferably, the vacuum level during printing is 7×10⁻⁶. -2 Pa.

[0017] Preferably, when printing, first use Ti 50.5 Ni 49.5 A layer of shape memory alloy wire is printed on a substrate, and after interlayer cooling, Ni is used. 50.7 Ti 49.3 The shape memory alloy wire is then printed in another layer, and this process is repeated alternately.

[0018] The second objective of this invention is to provide a NiTi shape memory alloy with a layered heterostructure obtained by the above method.

[0019] The third objective of this invention is to provide an application of the layered heterostructure NiTi shape memory alloy obtained by the above method in the fields of aerospace, construction, and biomedicine.

[0020] The significant advantages of this invention compared to existing technologies are:

[0021] This invention uses Ti 50.5 Ni 49.5 (at.%) alloy wire and Ni 50.7 Ti 49.3 Using (at.%) alloy wire as raw material, a layered heterogeneous NiTi shape memory alloy with good shape, dense microstructure, and excellent performance is prepared by electron beam fused wire deposition technology, following a path planned in CAD, through alternating dual-wire printing on a substrate. By adjusting printing parameters and setting interlayer cooling time, this invention offers the following advantages over existing technologies:

[0022] (1) The present invention can realize the rapid deposition of NiTi shape memory alloy. By adjusting the process parameters and interlayer cooling time, a NiTi shape memory alloy with good shape, dense structure and layered heterogeneous structure can be obtained.

[0023] (2) This invention uses heterogeneous twin-filament deposition of layered structures to change the Ni content in the interlayer region. Different Ni contents affect the phase transition point, thus widening the phase transition temperature range. A s and A fThe temperatures are 34.26℃ and 51.20℃ respectively, and it exhibits good superelasticity at high temperatures. In addition, it also has shape memory effect and good mechanical properties at room temperature, showing a tensile strength of 597.4 MPa and an elongation of 5.89%, and has obvious martensitic phase transformation characteristics, which are significantly better than NiTi alloys prepared by single wire.

[0024] (3) The method provided by the present invention can realize the integrated design and fabrication of NiTi alloy structure / function, and is expected to realize near-net-shape rapid prototyping of complex components;

[0025] (4) The preparation method provided by the present invention is applicable to the rapid preparation of other high-melting-point and high-activity alloys and the near-net-shape forming of complex heterogeneous components, so as to realize the rapid preparation of complex configurations with integrated structure and function. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the electron beam dual-wire melting deposition additive manufacturing process of the present invention;

[0027] Figure 2 The image shows a metallographic image of the layered heterostructure NiTi shape memory alloy obtained in Example 1, in a cross section perpendicular to the scanning direction; where the upper, middle, and lower sections correspond to different positions in the vertical direction.

[0028] Figure 3 The phase transition behavior of the layered heterostructure NiTi shape memory alloy obtained in Example 1;

[0029] Figure 4 The tensile properties of the NiTi shape memory alloy with layered heterostructure obtained in Example 1 are shown. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0032] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used in the following embodiments, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such a composition, step, method, article, or apparatus.

[0033] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range. In this specification and claims, range definitions may be combined and / or interchanged, unless otherwise stated, these ranges include all subranges contained therein.

[0034] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0035] In this invention, "an embodiment" or "embodiment" refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments.

[0036] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0037] Example 1

[0038] Combination Figure 1 The preparation method of the layered heterostructure NiTi shape memory alloy with a wide phase transformation temperature range in this embodiment is carried out according to the following steps:

[0039] (1) Dual-wire pretreatment: First, Ti with a diameter of 1mm is pretreated with a dual-wire wire. 50.5 Ni 49.5 Shape memory alloy wire and Ni with a diameter of 1mm 50.7 Ti 49.3Shape memory alloy wire undergoes pickling to remove the surface oxide film, followed by acetone soaking and cleaning to ensure the integrity of the Ti alloy. 50.5 Ni 49.5 Shape memory alloy wire and Ni 50.7 Ti 49.3 The surface of the shape memory alloy wire is free of oil and impurities, and finally Ti is... 50.5 Ni 49.5 Shape memory alloy wire and Ni 50.7 Ti 49.3 The shape memory alloy wire was placed in a drying oven and kept at 60°C for 3 hours.

[0040] (2) Substrate pretreatment: First, sandpaper was used to treat the Ni substrate with dimensions of 150mm×100mm×20mm. 50.8 Ti 49.2 The substrate is polished until Ni is removed. 50.8 Ti 49.2 The substrate surface is smooth and clean; then, the surface is wiped with acetone to remove Ni. 50.8 Ti 49.2 Oil and impurities on the substrate surface; finally, Ni 50.8 Ti 49.2 The substrate was placed in a drying oven and kept at 60°C for 3 hours.

[0041] (3) Assembly: The pretreated Ti 50.5 Ni 49.5 Shape memory alloy wire and Ni 50.7 Ti 49.3 Shape memory alloy wires are respectively installed on the wire feeding mechanisms of the electron beam fused deposition equipment, and pretreated Ni... 50.8 Ti 49.2 The substrate is clamped onto the motion system within the vacuum chamber of the electron beam fused deposition equipment. The vacuum level of the electron beam fused deposition equipment vacuum chamber reaches the required operating level (7×10⁻⁶). -2 Print when Pa).

[0042] (4) Printing: Set the following processing parameters: accelerating voltage U is 60kV, focusing current I... f 1000mA, wire feeding speed V F 3000 mm / min, beam current density I b 35mA, moving speed V T The speed is 350 mm / min, the interlayer cooling time is 30 s, and the scanning mode is followed by using Ti. 50.5 Ni 49.5 Shape memory alloy wire in Ni 50.8 Ti 49.2 A layer is printed vertically on the substrate, and after interlayer cooling, Ni is used.50.7 Ti 49.3 The shape memory alloy wire continues to be printed in the vertical direction, alternating layers in this order until the vertical dimension is 45mm.

[0043] Figure 2 The metallographic profile of the deposited body perpendicular to the scanning direction is shown. The cross-sectional structure is predominantly columnar crystals along the construction direction, with localized equiaxed crystal regions (distinguished by blue lines). This is because in the electron beam dual-wire melting deposition additive manufacturing process of this invention, a 30-second dwell time is set between layers, which facilitates interlayer temperature transfer and cooling of the deposited body, promoting the formation of equiaxed crystals during the melting and solidification of new deposited layers due to localized quenching. Therefore, it can be concluded that the NiTi shape memory alloy manufactured by electron beam dual-wire melting deposition additive manufacturing in Example 1 of this invention exhibits a layered heterogeneous structure.

[0044] The phase transition behavior of the layered heterostructure NiTi shape memory alloy fabricated by electron beam dual-wire melting deposition additive manufacturing in Example 1 of this invention is as follows: Figure 3 As shown in the figure, As and Af are 34.26℃ and 51.20℃, respectively. This indicates that the layered heterogeneous NiTi shape memory alloy manufactured by electron beam dual-wire melting deposition additive manufacturing of the present invention has good superelasticity under high-temperature service conditions. At the same time, multiple peaks overlapped during the heating process and multiple phase transition peaks appeared during the cooling process. This is because Ti-rich / Ni-rich alloy wires were printed alternately during the printing process, and the Ni content affects the phase transition point, resulting in different phase transition temperatures in different regions. This further illustrates that the NiTi shape memory alloy manufactured by electron beam dual-wire melting deposition additive manufacturing in Example 1 of the present invention has a layered heterogeneous structure.

[0045] also, Figure 4 The room temperature tensile properties of the layered heterostructure NiTi shape memory alloy obtained in Example 1 are shown. Figure 4 As shown, the layered heterostructure NiTi shape memory alloy manufactured by electron beam dual-wire melting deposition additive manufacturing of the present invention has excellent mechanical properties at room temperature, with tensile strength and elongation of 597.4 MPa and 5.89%, respectively.

[0046] In summary, the additive manufacturing method provided by this invention can realize the preparation of NiTi shape memory alloys with layered heterogeneous structures. By adjusting the process parameters and interlayer cooling time, NiTi shape memory alloys with good forming, dense structure and layered heterogeneous structure can be obtained. This method is of great value for reducing production costs, shortening processing flow, and designing NiTi shape memory alloy parts with complex microstructures. It can also be extended to the near-net-shape forming of other high-melting-point and high-activity alloys, realizing the rapid preparation of structure-function integration of complex configurations.

[0047] The above description is merely a preferred embodiment of the present invention. These specific embodiments are different implementations based on the overall concept of the present invention, and the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing a lamellar heterostructured NiTi shape memory alloy having a wide phase transition temperature interval, characterized in that, The following steps are followed: Ti 50.5 Ni 49.5 shape memory alloy wire and Ni 50.7 Ti 49.3 shape memory alloy wire are printed alternately in the vertical direction to obtain a layered heterogeneous structure NiTi shape memory alloy, wherein, during printing, the Ti 50.5 Ni 49.5 shape memory alloy wire is used to print a layer on the substrate, after interlayer cooling, the Ni 50.7 Ti 49.3 shape memory alloy wire is used to print another layer, and the above process is repeated alternately, the beam current density I b is 35 mA, and the moving speed V T is 350 mm / min. A s and A f are 34.26°C and 51.20°C, respectively.

2. The method of claim 1, wherein, The printing process parameters are: accelerating voltage U is 60 kV, focusing current I f is 1000 mA, wire feeding speed V F is 3000 mm / min, and the interlayer cooling time is set.

3. The method of claim 2, wherein, The interpass cooling time is 30 s.

4. The method of claim 1, wherein, Ti 50.5 Ni 49.5 Shape memory alloy wires and Ni 50.7 Ti 49.3 The diameter of the shape memory alloy wires was 1 mm.

5. The method of claim 1, wherein, Substrate is Ni 50.8 Ti 49.2 .

6. The method of claim 1, wherein, The vacuum during printing was 7 x 10 -2 Pa.

7. Layered hysterecograhically textured NiTi shape memory alloy obtained by the method according to any one of claims 1-6.

8. Use of the layered hysterecograhically textured NiTi shape memory alloy obtained by the method according to any one of claims 1-6 in the aerospace, construction or biomedical fields.

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