Method for ultrasonic assisted arc additive manufacturing of high performance ti-ni-fe shape memory alloys

Abstract

The application discloses a method for ultrasonic-assisted electric arc additive manufacturing of high-performance Ti-Ni-Fe shape memory alloy, which comprises the following steps: placing a welding torch above a substrate, feeding a nickel welding wire to a lower part of a tungsten electrode of the welding torch, melting the nickel welding wire under the action of a pulse direct current arc and depositing the nickel welding wire on the substrate to form a pure nickel transition layer on an arc cladding area of the substrate; placing the welding torch above the pure nickel transition layer, forming an alloy layer on the pure nickel transition layer by the welding torch to obtain high-tensile-strength Ti-Ni-Fe shape memory alloy, wherein the method for forming each alloy layer comprises the following steps: applying ultrasonic waves to the substrate, feeding a titanium welding wire, a nickel welding wire and an iron welding wire to the lower part of the tungsten electrode of the welding torch at the same time, melting the titanium welding wire, the nickel welding wire and the iron welding wire under the action of the pulse direct current arc and depositing the titanium welding wire, the nickel welding wire and the iron welding wire on the pure nickel transition layer. The high-tensile-strength Ti-Ni-Fe shape memory alloy has a limit tensile strength of 755.6 MPa in the horizontal direction and an anisotropy of 3%.

Description

Technical Field

[0001] This invention belongs to the field of shape memory alloy technology, and specifically relates to a method for ultrasonic-assisted arc additive manufacturing of high-performance Ti-Ni-Fe shape memory alloys. Background Technology

[0002] Titanium-nickel-iron (Ti-Ni-Fe) alloys possess unique shape memory (SME) and superelasticity (SE) properties under extreme low-temperature environments. They have the ability to remember their original shape within a specific temperature range and automatically recover after large deformations under external forces, making them highly promising for applications in aerospace hydraulic pipelines, cryogenic sensors, and other fields. Electrical arc additive manufacturing (WAAM), a method based on arc welding technology, uses molten metal wire to build up components layer by layer, enabling the production of high-strength, large-sized metal parts. WAAM offers significant advantages such as high manufacturing efficiency, low cost, and high material utilization, making it particularly suitable for manufacturing large metal structural components in aerospace, marine engineering, automotive, and energy sectors. However, the WAAM process is prone to problems such as compositional segregation, coarse microstructure, and significant anisotropy, which limit the performance and applications of additive components. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for ultrasonic-assisted arc additive manufacturing of high tensile strength Ti-Ni-Fe shape memory alloys.

[0004] Another object of the present invention is to provide a high tensile strength Ti-Ni-Fe shape memory alloy obtained by the above method.

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

[0006] A method for ultrasonic-assisted arc additive manufacturing of high tensile strength Ti-Ni-Fe shape memory alloys includes the following steps:

[0007] Step 1, First Arc Additive Manufacturing: The welding torch is placed above the substrate. Under an inert gas atmosphere, the nickel (Ni) welding wire is fed to the lower part of the tungsten electrode of the welding torch through the wire feeding mechanism. The nickel (Ni) welding wire melts and is deposited on the substrate under the action of the pulsed DC arc, forming a pure nickel transition layer with a thickness of 1.5~2 mm on the arc cladding area of ​​the substrate.

[0008] In step 1, the wire feeding speed of the nickel (Ni) welding wire is 1200~1500 mm / min.

[0009] In step 1, the welding speed is 100~120 mm / min, the welding torch oscillation width is 8~10 mm, and the welding current is 80~120 A.

[0010] Step 2, Second Arc Additive Manufacturing: The welding torch is placed above the pure nickel transition layer, and at least 20 alloy layers are formed on the pure nickel transition layer by the welding torch to obtain a high tensile strength Ti-Ni-Fe shape memory alloy. The method for forming each alloy layer includes: applying ultrasound to the substrate in an inert gas atmosphere, and feeding titanium (Ti) welding wire, nickel (Ni) welding wire and iron (Fe) welding wire simultaneously into the lower part of the tungsten electrode of the welding torch through a wire feeding mechanism. The titanium (Ti) welding wire, nickel (Ni) welding wire and iron (Fe) welding wire melt and deposit on the pure nickel transition layer under the action of a pulsed DC arc.

[0011] In step 2, the method of applying ultrasound includes: bringing the ultrasonic vibrating head into contact with the substrate surface (the area where the pure nickel transition layer has not been formed); moving the ultrasonic vibrating head and the welding torch synchronously in the same direction, with an ultrasonic amplitude of 20~60 µm.

[0012] In step 2, a load of 100N (vibrational additional force) is applied to the substrate by an ultrasonic vibrating head.

[0013] In step 2, the wire feeding speed of titanium (Ti) welding wire is 1050 mm / min, the wire feeding speed of nickel (Ni) welding wire is 660 mm / min, and the wire feeding speed of iron (Fe) welding wire is 50 mm / min.

[0014] In step 2, the welding speed is 100~120 mm / min, the welding torch oscillation width is 8~10 mm, and the welding current is 80~120 A.

[0015] In step 2, the ultrasonic power is 1500 W and the ultrasonic frequency is 20 kHz.

[0016] In step 2, the thickness of each alloy layer is 2 mm.

[0017] The high tensile strength Ti-Ni-Fe shape memory alloy obtained by the above method.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The high tensile strength Ti-Ni-Fe shape memory alloy prepared by this invention has an ultimate tensile strength of 755.6 MPa in the horizontal direction, an elongation at break of 7.5% in the horizontal direction, and an anisotropy of 3%. The high ultimate tensile strength can improve the load-bearing capacity and overload resistance of the shape memory alloy, while the smaller anisotropy can reduce the problem of local failure caused by uneven stress in the shape memory alloy. Attached Figure Description

[0020] Figure 1The images show the physical images of the Ti-Ni-Fe shape memory alloys prepared in Comparative Examples 1 and 2, where (a) is a physical image of the Ti-Ni-Fe shape memory alloy prepared in Comparative Example 2, and (b) is a physical image of the Ti-Ni-Fe shape memory alloy prepared in Comparative Example 1.

[0021] Figure 2 The images show the morphology of the high tensile strength Ti-Ni-Fe shape memory alloys prepared in Examples 1-3. (a) is the microscopic appearance of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1; (b)-(c) are SEM images of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1; (d) is the microscopic appearance of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2; (e)-(f) are SEM images of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2; (g) is the microscopic appearance of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 3; and (h)-(i) are SEM images of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 3.

[0022] Figure 3 The results of tensile property tests are as follows: (a) is the tensile curve of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1; (b) is the tensile curve of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2; (c) is the tensile curve of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 3; and (d) is the ultimate tensile strength in the horizontal direction, the ultimate tensile strength in the vertical direction, and the anisotropy corresponding to Examples 1 to 3.

[0023] Figure 4 A schematic diagram of a method for manufacturing high tensile strength Ti-Ni-Fe shape memory alloys using ultrasonic-assisted arc additive manufacturing. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0025] In the following embodiments, the substrate is a Q235A substrate (250×100×5 mm). Before use, the oxides on the surface of the Q235A substrate are removed with 120-grit sandpaper, and then the oil and dirt on the surface of the Q235A substrate are wiped off with alcohol.

[0026] This embodiment uses a tungsten inert gas (GTAW) welding torch from Wuxi Gutu Welding Equipment Co., Ltd. as the arc heat source, and the welding power source is a pulsed DC type. The GTAW torch includes a welding torch and a wire feeding mechanism. During operation, the welding torch reciprocates, meaning it moves from the arc initiation point to the arc termination point.

[0027] Ti welding wire: grade TA1, diameter 1.2 mm; Ni welding wire: grade ER-Ni, diameter 1.2 mm; Fe welding wire: grade ER-Fe, diameter 1.2 mm.

[0028] Argon: purity 99.999%.

[0029] Comparative Example 1

[0030] A method for arc additive manufacturing of Ti-Ni-Fe shape memory alloy includes: placing a welding torch above a substrate (the substrate is not preheated and its bottom is naturally cooled), and forming 20 alloy layers (each alloy layer is 2 mm thick, and the welding torch is raised 2 mm after each alloy layer is deposited) on the arc cladding area of ​​the substrate to obtain Ti-Ni-Fe shape memory alloy. The method for forming each alloy layer includes: feeding Ti welding wire, Ni welding wire, and Fe welding wire separately and simultaneously into the lower part of the tungsten electrode of the welding torch through three wire feeding mechanisms under an argon atmosphere (argon flow rate of 15 L / min). The Ti welding wire, Ni welding wire, and Fe welding wire melt and deposit on the substrate under the action of a pulsed DC arc. The wire feeding speed of the Ti welding wire is 1050 mm / min, the wire feeding speed of the Ni welding wire is 660 mm / min, the wire feeding speed of the Fe welding wire is 50 mm / min, the welding speed is 120 mm / min, and the welding stroke is 100 mm / min. mm, welding torch oscillation width is 8 mm, welding current is 120 A;

[0031] After each alloy layer is deposited, it is allowed to cool for 120 seconds before the next alloy layer is deposited, i.e., the interlayer cooling time is 120 seconds.

[0032] Comparative Example 2

[0033] A method for arc additive manufacturing of Ti-Ni-Fe shape memory alloys includes the following steps:

[0034] Step 1: Place the substrate on the worktable, turn off the wire feed, and allow the welding torch to travel empty without arcing to complete the trajectory simulation test. Then, place the welding torch above the substrate (the substrate is not preheated and the bottom is naturally cooled). Under an argon atmosphere (argon flow rate of 15 L / min), feed the Ni welding wire to the lower part of the tungsten electrode of the welding torch through the wire feed mechanism. The Ni welding wire melts and deposits on the substrate under the action of a pulsed DC arc (wire feed speed of 1500 mm / min). A pure nickel transition layer with a thickness of 2 mm is formed on the arc cladding area of ​​the substrate. The welding speed is 120 mm / min, the welding stroke is 100 mm, the welding torch oscillation width is 10 mm, and the welding current is 120 A.

[0035] Step 2: Place the welding torch above the pure nickel transition layer (the substrate is not preheated and the bottom is naturally cooled). Form 20 alloy layers on the pure nickel transition layer using the welding torch (each alloy layer is 2 mm thick, and the welding torch is raised 2 mm after each layer is deposited) to obtain a Ti-Ni-Fe shape memory alloy. The method for forming each alloy layer includes: feeding Ti welding wire, Ni welding wire, and Fe welding wire into the lower part of the tungsten electrode of the welding torch simultaneously through three wire feeding mechanisms under an argon atmosphere (argon flow rate of 15 L / min). The Ti welding wire, Ni welding wire, and Fe welding wire melt and deposit on the pure nickel transition layer under the action of a pulsed DC arc. The wire feeding speed of Ti welding wire is 1050 mm / min, the wire feeding speed of Ni welding wire is 660 mm / min, the wire feeding speed of Fe welding wire is 50 mm / min, the welding speed is 120 mm / min, the welding stroke is 100 mm, the welding torch oscillation width is 8 mm, and the welding current is 120 A.

[0036] In this process, after the pure nickel transition layer is deposited, it is allowed to stand and cool for 120 seconds before the first alloy layer is deposited. After each alloy layer is deposited, it is allowed to stand and cool for 120 seconds before the next alloy layer is deposited. That is, the interlayer cooling time is 120 seconds.

[0037] Physical images of the Ti-Ni-Fe shape memory alloys prepared in Comparative Examples 1 and 2 are shown below. Figure 1 As shown, (a) is a physical image of the Ti-Ni-Fe shape memory alloy prepared in Comparative Example 2, and (b) is a physical image of the Ti-Ni-Fe shape memory alloy prepared in Comparative Example 1. Figure 1It can be seen that the Ti-Ni-Fe shape memory alloys prepared in Comparative Examples 1 and 2 all formed a single-wall structure. Comparative Example 2, due to the formation of a pure nickel transition layer, exhibited good fusion between the alloy layer and the substrate, with no macroscopic cracks. In contrast, Comparative Example 1 showed obvious macroscopic cracks between the alloy layer and the substrate. NiTi2 intermetallic compounds exist between the alloy layer and the substrate, and due to their high coefficient of thermal expansion, they are prone to cracking during static cooling. The presence of the pure nickel transition layer prevents direct contact between the alloy layer and the substrate and provides a high concentration of Ni, allowing Ti to preferentially form a tough NiTi intermetallic compound with Ni. This fundamentally inhibits the excessive formation of NiTi2 intermetallic compounds and effectively prevents the generation of hot cracks during additive manufacturing. When a pure Ti transition layer, a pure Cu transition layer, or a NiTi alloy transition layer is formed on the substrate, macroscopic hot cracks of varying degrees appear. Therefore, forming a pure nickel transition layer on the substrate is the optimal choice.

[0038] Examples 1-3

[0039] A method for ultrasonic-assisted arc additive manufacturing of high tensile strength Ti-Ni-Fe shape memory alloys includes the following steps:

[0040] Step 1: Place the substrate on the worktable, turn off the wire feed, and allow the welding torch to travel empty without arcing to complete the trajectory simulation test. Then, place the welding torch above the substrate (the substrate is not preheated and the bottom is naturally cooled). Under an argon atmosphere (argon flow rate of 15 L / min), feed the Ni welding wire to the lower part of the tungsten electrode of the welding torch through the wire feed mechanism. The Ni welding wire melts and deposits on the substrate under the action of a pulsed DC arc (wire feed speed of 1500 mm / min). A pure nickel transition layer with a thickness of 2 mm is formed on the arc cladding area of ​​the substrate. The welding speed is 120 mm / min, the welding stroke is 100 mm, the welding torch oscillation width is 10 mm, and the welding current is 120 A.

[0041] Step 2: Place the welding torch above the pure nickel transition layer substrate (the substrate is not preheated and the bottom is naturally cooled). Form 20 alloy layers on the pure nickel transition layer using the welding torch (each alloy layer is 2 mm thick; after each layer is deposited, the welding torch is raised 2 mm), obtaining a high tensile strength Ti-Ni-Fe shape memory alloy. The method for forming each alloy layer includes: applying ultrasound to the substrate in an argon atmosphere (argon gas (99.999%) flow rate of 15 L / min); feeding Ti, Ni, and Fe welding wires simultaneously into the lower part of the tungsten electrode of the welding torch using three wire feeding mechanisms; melting and depositing the Ti, Ni, and Fe welding wires on the pure nickel transition layer under the action of a pulsed DC arc. The method of applying ultrasound includes: Figure 4As shown, the ultrasonic vibrating head of the ultrasonic vibration device is brought into contact with the substrate surface (the area where the pure nickel transition layer has not been formed). A load of 100 N (vibrational additional force) is applied to the substrate through the ultrasonic vibrating head. The ultrasonic vibrating head and the welding torch move synchronously and in the same direction through a three-axis motion control system. The wire feeding speed of Ti welding wire is 1050 mm / min, the wire feeding speed of Ni welding wire is 660 mm / min, the wire feeding speed of Fe welding wire is 50 mm / min, the welding speed is 120 mm / min, the welding stroke is 100 mm, the welding torch swing width is 8 mm, the welding current is 120 A, the ultrasonic power of the ultrasonic vibration device is 1500 W, the ultrasonic frequency is 20 kHz, and the ultrasonic amplitude is X µm. The value of X is shown in Table 1.

[0042] In this process, after the transition layer is deposited, it is allowed to cool for 120 seconds before the first alloy layer is deposited. After each alloy layer is deposited, it is allowed to cool for 120 seconds before the next alloy layer is deposited. That is, the interlayer cooling time is 120 seconds.

[0043] Table 1

[0044]

[0045] In the high tensile strength Ti-Ni-Fe shape memory alloys prepared in Examples 1-3, the atomic ratio of Ti, Ni, and Fe elements is 50:46.5:3.5.

[0046] The sample was cut along its thickness using an electrical discharge wire cutter, and then polished sequentially with sandpaper of grits 120, 200, 400, 600, 800, 1000, 1500, and 3000 to obtain a uniform unidirectional textured surface. First, it was polished for 20 minutes with a diamond polishing compound (purchased from Zhejiang Airuipu Instrument Co., Ltd., with diamond particles of 1.5~2.5 μm). Then, it was polished with a silica suspension (obtained by mixing water and silica polishing liquid purchased from Guangdong Heraeus Industrial Co., Ltd., with a water-to-silica polishing liquid volume ratio of 4:1) until the surface was mirror-like and free of marks. Etching was performed using Kroll reagent (a mixture of hydrofluoric acid (HF), nitric acid (HNO3), and water, with a mass ratio of 1:3:46): the sample was immersed in Kroll reagent for 40 ± 10 s, followed by washing with anhydrous ethanol and drying to obtain the test sample, which was then subjected to microstructure analysis (analysis of grain boundary morphology and precipitate distribution). Microstructure analysis was performed using an optical microscope (OM) and a Quanta FEG 250 field emission scanning electron microscope (SEM). The sample was one of the high tensile strength Ti-Ni-Fe shape memory alloys prepared in Examples 1-3. The results are as follows: Figure 2 As shown. Figure 2 (a) shows the microscope appearance of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1. Figure 2 (b) to (c) are SEM images of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1, wherein (b) has a magnification of 5000x and (c) has a magnification of 10000x. Figure 2 (d) shows the microscope appearance of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2. Figure 2 (e) to (f) are SEM images of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2, wherein (e) has a magnification of 5000x and (f) has a magnification of 10000x. Figure 2 (g) is the microscope appearance of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 3. Figure 2 (h) to (i) are SEM images of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 3, wherein (h) has a magnification of 5000x and (i) has a magnification of 10000x.

[0047] Depend on Figure 2As can be seen from (a) to (c), the microstructure of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1 exhibits a coexistence of coarse columnar crystals and equiaxed crystals extending along the deposition direction; from Figure 2 (d) to (f) it was observed that the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2 exhibits a transition characteristic from columnar to equiaxed crystals (CET), showing a mixed structure of equiaxed crystals and residual columnar crystals; Figure 2 (g) to (i) it was observed that the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 3 completely transformed into a uniformly distributed equiaxed crystal structure, and the grain size was significantly refined. When the ultrasonic amplitude increased from 20µm to 60µm, the microstructure changed from a coexistence of coarse columnar crystals and equiaxed crystals to uniform equiaxed crystals, indicating that the uniformity of the microstructure was significantly improved, which is beneficial to isotropy.

[0048] Tensile properties of the samples were tested using a WDW-100 electronic universal testing machine: tensile properties in the horizontal (H) and vertical (V) directions were tested separately, with a loading rate of 0.5 mm / min. The sample was one of the high tensile strength Ti-Ni-Fe shape memory alloys prepared in Examples 1-3. When the sample was the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1, the tensile curves obtained were as follows. Figure 3 As shown in (a), the horizontal axis represents elongation at break, and the vertical axis represents tensile strength; when the sample is the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2, the tensile curve obtained is as follows. Figure 3 As shown in (b); when the sample is the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 3, the tensile curve obtained is as follows. Figure 3 As shown in (c). Based on Figure 3 The tensile curve of (a) yields the ultimate tensile strength (UTS) in the horizontal direction corresponding to Example 1. H ) and ultimate tensile strength in the vertical direction (UTS) V Based on this UTS H and UTS V The anisotropy (k) of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 1 was calculated; based on Figure 3 The tensile curve of (b) yields the ultimate tensile strength (UTS) in the horizontal direction corresponding to Example 2. H ) and ultimate tensile strength in the vertical direction (UTS) V Based on this UTS H and UTS V The anisotropy (k) of the high tensile strength Ti-Ni-Fe shape memory alloy prepared in Example 2 was calculated; based on Figure 3The ultimate tensile strength (UTS H in the horizontal direction corresponding to Example 3 was obtained from the tensile curve of (c), and the ultimate tensile strength (UTS V in the vertical direction. Based on this UTS H and UTS V , the anisotropy (k) of the high-tensile-strength Ti-Ni-Fe shape memory alloy prepared in Example 3 was calculated. The ultimate tensile strength (UTS H in the horizontal direction, the ultimate tensile strength (UTS V in the vertical direction, and the anisotropy (k) corresponding to Examples 1-3 were plotted in Figure 3 of (d). Figure 3 In (d), the left vertical coordinate is the ultimate tensile strength, and the right vertical coordinate is the anisotropy. The formula for calculating the anisotropy (k) is:

[0049] .

[0050] It can be seen from Figure 3 that the ultimate tensile strength of the high-tensile-strength Ti-Ni-Fe shape memory alloy (ultrasonic amplitude of 20 µm) prepared in Example 1 in the horizontal direction was 682.6 MPa, the elongation at break in the horizontal direction was 6.9%, and the anisotropy was 6%; the ultimate tensile strength of the high-tensile-strength Ti-Ni-Fe shape memory alloy (ultrasonic amplitude of 40 µm) prepared in Example 2 in the horizontal direction was 750.3 MPa, the elongation at break in the horizontal direction was 7.1%, and the anisotropy was 3.4%; the ultimate tensile strength of the high-tensile-strength Ti-Ni-Fe shape memory alloy (ultrasonic amplitude of 60 µm) prepared in Example 3 in the horizontal direction was 755.6 MPa, the elongation at break in the horizontal direction was 7.5%, and the anisotropy decreased to 3%. The high-tensile-strength Ti-Ni-Fe shape memory alloy prepared in Example 3 had the best comprehensive mechanical properties, laying a foundation for its engineering application in the construction of functional structure integration.

[0051] The tensile properties of the Ti-Ni-Fe shape memory alloy of Comparative Example 2 were tested using a WDW-100 type electronic universal testing machine. When testing, the loading rate was set to 0.5 mm / min, and the ultimate tensile strength in the horizontal direction was obtained as 631 MPa, the elongation at break was 5.5%, and the anisotropy was 13.7%.

[0052] There were obvious macroscopic cracks between the alloy layer and the substrate in the Ti-Ni-Fe shape memory alloy of Comparative Example 1, and the tensile properties could not be tested.

[0053] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A method for ultrasonic-assisted arc additive manufacturing of high tensile strength Ti-Ni-Fe shape memory alloy, characterized in that, Includes the following steps: Step 1, First Arc Additive Manufacturing: The welding torch is placed above the substrate. Under an inert gas atmosphere, the nickel welding wire is fed to the lower part of the tungsten electrode of the welding torch through the wire feeding mechanism. The nickel welding wire melts and is deposited on the substrate under the action of the pulsed DC arc, forming a pure nickel transition layer with a thickness of 1.5~2 mm on the arc cladding area of ​​the substrate. Step 2, Second Arc Additive Manufacturing: The welding torch is placed above the pure nickel transition layer, and at least 20 alloy layers are formed on the pure nickel transition layer by the welding torch to obtain a high tensile strength Ti-Ni-Fe shape memory alloy. The method for forming each alloy layer includes: applying ultrasound to the substrate in an inert gas atmosphere, feeding titanium welding wire, nickel welding wire and iron welding wire simultaneously into the lower part of the tungsten electrode of the welding torch through a wire feeding mechanism, and melting and depositing the titanium welding wire, nickel welding wire and iron welding wire on the pure nickel transition layer under the action of pulsed DC arc.

2. The method according to claim 1, characterized in that, In step 2, the method of applying ultrasound includes: bringing the ultrasonic vibrating head into contact with the substrate surface; moving the ultrasonic vibrating head and the welding torch synchronously in the same direction, with an ultrasonic amplitude of 20~60 µm.

3. The method according to claim 1, characterized in that, In step 2, the wire feeding speed of titanium welding wire is 1050 mm / min, the wire feeding speed of nickel welding wire is 660 mm / min, and the wire feeding speed of iron welding wire is 50 mm / min.

4. The method according to claim 1, characterized in that, In step 2, the ultrasonic power is 1500 W and the ultrasonic frequency is 20 kHz.

5. The method according to claim 1, characterized in that, In step 1, the wire feeding speed of the nickel welding wire is 1200~1500 mm / min.

6. The method according to claim 1, characterized in that, In step 2, the welding speed is 100~120 mm / min and the welding current is 80~120 A.

7. The method according to claim 1, characterized in that, In step 1, the welding speed is 100~120 mm / min and the welding current is 80~120 A.

8. The high tensile strength Ti-Ni-Fe shape memory alloy obtained by the method according to any one of claims 1 to 7.

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