Electron beam wire feeding welding method for high-performance titanium alloy thick-wall component

Abstract

The invention discloses an electron beam wire feeding welding method for a high-performance titanium alloy thick-wall component, and belongs to the technical field of metal material welding. The method aims at solving the typical metallurgical defects such as composition segregation, air holes and incomplete penetration which are prone to occurring in the welding process. The method comprises the steps that firstly, a steep-edge V-shaped groove with a truncated edge is machined in the welded end face of base metal, and the steep-edge V-shaped groove is polished, soaked in acid and then washed with absolute ethyl alcohol; and step 2, fixing on a welding platform, and carrying out multi-layer and multi-pass electron beam wire feeding welding. According to the electron beam wire feeding welding method, a feasible and generalizable technical path is provided for high-quality welding of the high-performance titanium alloy thick-wall component, a theoretical basis and practical guidance are provided for structure regulation and performance optimization in the welding process, and the electron beam wire feeding welding method has important engineering application value and industrial popularization prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material welding, and in particular relates to an electron beam wire feeding welding method for high-performance titanium alloy thick-walled components. Background Art

[0002] Titanium alloys have been widely used in aerospace, shipbuilding, marine engineering, energy equipment, biomedicine and other fields due to their low density, high specific strength, excellent corrosion resistance and good welding adaptability. In recent years, with the rapid development of manufacturing technologies for high-end equipment such as nuclear submarines, submersibles, and aircraft, the demand for thick-walled titanium alloy structural parts has been increasing. The thickness of typical components has exceeded 10mm, and some key stress-bearing parts even reach more than 100mm, requiring reliable connection through welding. However, the welding process of thick-walled titanium alloys involves multiple challenges such as heat input control, microstructure regulation and residual stress suppression. Traditional welding methods are difficult to meet the stringent requirements of high-performance components for joint quality, density and service reliability. Therefore, the research on high-quality welding processes suitable for thick-walled titanium alloy structures has become a key technical direction that urgently needs to be broken through in this field.

[0003] Currently, tungsten inert gas welding (TIG), laser beam welding (LBW), and electron beam welding (EBW) are commonly used for welding thick-walled titanium alloys. Tungsten inert gas welding (TIG) requires a large groove angle and high heat input during welding, which can lead to significant weld deformation and residual stresses. Furthermore, the weld microstructure is prone to coarsening and metallurgical defects such as tungsten inclusions. This results in relatively low welding efficiency and makes it difficult to meet the requirements for joining high-quality, thick-walled structures. Laser beam welding (LBW), with its advantages of high energy density, low heat input, and fast welding speed, performs well in welding thin titanium alloy sheets. However, its penetration capability is limited in thick-walled components, and the penetration depth is insufficient for single-pass welding. Multi-pass welding is typically required, which can lead to problems such as lack of sidewall fusion, porosity, weld deformation, and residual stress concentration. Laser welding is also sensitive to the highly reflective surface of titanium alloys, resulting in a narrow processing window and poor process stability. Electron beam welding (EBW) has a higher energy density and excellent deep penetration ability. It can achieve one-time deep penetration welding at low heat input. The weld is narrow, the aspect ratio is large, and the heat-affected zone is small. It is suitable for the precision connection of high-performance titanium alloy components. However, traditional electron beam welding mostly adopts the self-melting method. There are large temperature gradients and extremely high cooling rates during the welding process, which can easily lead to uneven structure. In addition, metallurgical defects such as incomplete penetration and porosity are prone to occur at the root of the weld, thereby affecting the structural integrity and service performance of the joint. In addition, due to the lack of external filling means, it is difficult to achieve effective control of the molten pool composition, solidification process, grain morphology and phase structure, resulting in poor controllability of the joint structure. Alloying element segregation, grain coarsening, the formation of columnar crystals, brittle phases and other unfavorable structures, seriously restrict the mechanical properties and service reliability of the joint. This problem is particularly prominent in thick-walled high-performance titanium alloy structures. Summary of the Invention

[0004] Against this backdrop, the present invention proposes an electron beam wire-feed welding method for high-performance thick-walled titanium alloy components. This innovative method integrates a controllable wire-feed system with electron beam welding technology, leveraging the electron beam's high energy density and high vacuum environment. By incorporating a precisely adjustable wire-feed system, this method achieves coordinated control of the molten pool composition, solidification behavior, and microstructural evolution.

[0005] The method of the present invention effectively improves the uniformity of weld composition and the density of the structure, and effectively suppresses typical metallurgical defects such as composition segregation, porosity, and incomplete penetration that are prone to occur during welding, thereby significantly improving the metallurgical quality and service reliability of the weld joint. The method of the present invention uses Ti-6Al-4V alloy forged plate as the base material and selects Ti-6Al-4V alloy wire with matching composition as the filler material. By precisely controlling the wire filling speed and wire feeding position, the dynamic coupling of heat input and material compensation during welding is achieved, ensuring the stability and weld quality during the welding process. With the help of the small, stable, high-energy molten pool formed by the electron beam, the method of the present invention promotes the rapid solidification and refinement of the structure while improving the fluidity and filling capacity of the metal.

[0006] By systematically controlling key parameters such as acceleration voltage, beam current, welding speed, wire feeding rate, and groove morphology, we conducted in-depth research on the influence mechanism of various variables on weld microstructure evolution and joint mechanical properties, established a process-microstructure-performance relationship model for electron beam wire feeding welding of titanium alloys, and clarified the optimal process window for different component structures and thickness ranges. It is worth emphasizing that this method shows excellent flexibility and stability in terms of structural adaptability and thickness range. In theory, it is suitable for welding titanium alloys with no thickness restrictions, and is particularly suitable for the connection needs of complex structures and large key components. The welded joints show excellent comprehensive performance in terms of strength, plasticity, toughness, density, etc., and can meet the extremely stringent requirements of application scenarios such as aerospace, shipbuilding, and marine equipment for material connection quality.

[0007] In summary, the electron beam wire feeding welding method proposed in the present invention not only provides a feasible and popularizable technical path for high-quality welding of high-performance titanium alloy thick-walled components, but also provides a theoretical basis and practical guidance for microstructure regulation and performance optimization during welding. It has important engineering application value and industrial promotion prospects.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: The object of the present invention is to provide an electron beam wire feeding welding method for high performance titanium alloy thick wall components, comprising the following steps: Step 1: Form a V-shaped groove with a blunt edge on the welded end face of the base material, polish it, soak it in acid, and then rinse it with anhydrous ethanol; Step 2: Then fix it on the welding platform and perform multi-layer and multi-pass electron beam wire feeding welding. It is further defined that the groove angle of the V-shaped groove is 10° to 30°, the blunt edge thickness is 2 mm, and the gap is ≤ 2 mm.

[0009] The process parameters for multi-layer and multi-pass electron beam welding are further defined as follows: acceleration voltage of 50 kV to 70 kV, beam current of 50 mA to 100 mA, focusing current of 950 mA to 1050 mA, welding speed of 400 mm / min to 1000 mm / min, wire feeding speed of 800 mm / min to 1600 mm / min, and chamber vacuum of less than 5 × 10 -2 Pa; in terms of forming parameters, the single layer height is 0.5mm~0.8mm, the layer width is 10mm~12mm, and the overlapping width between passes is controlled at 1mm~3mm.

[0010] It is further defined that the alloy wire has a diameter of 1.6 mm.

[0011] It is further defined that a front wire feeding mode is adopted, that is, the wire is located in front of the electron beam, and the two are located in the same horizontal plane; the wire feeding direction is at a 45° angle to the welding direction, and the relative distance between the front end of the wire feeding and the center of the molten pool is controlled at 1~4mm.

[0012] It is further defined that the parent material is a Ti-6Al-4V alloy wrought plate.

[0013] Further defined, Ti-6Al-4V alloy wire.

[0014] It is further defined that, in terms of mass percentage, the composition of the alloy wire is: Al: 6 wt.%, V: 4 wt.%, and the remainder is Ti.

[0015] It is further defined that the pickling solution used is prepared by 2% to 4% hydrofluoric acid (HF), 30% to 40% nitric acid (HNO3) and deionized water (H2O) by volume fraction.

[0016] It is further defined that before use, the alloy wire is placed in a drying oven at 60° C. for constant temperature drying.

[0017] In one embodiment, the method of the present invention comprises the following steps: Step 1: Select a 150mm × 50mm × 30mm Ti-6Al-4V alloy forged plate as the base material, with the alloy composition being: Al: 6wt.%, V: 4wt.%, with the remainder being Ti. Before welding, the base material's welding area is CNC machined to obtain a groove morphology that meets the requirements for electron beam wire feeding welding. The groove used is a steep V-shaped groove with blunt edges. The specific parameters are as follows: groove angle of 10° to 30°, blunt edge thickness of 0 to 2mm, and gap ≤ 2mm. This groove shape facilitates the stable formation of the molten pool and the full fusion of the filler wire, while also providing geometric protection to avoid defects such as electron beam penetration or incomplete penetration.

[0018] Step 2: The machined, grooved Ti-6Al-4V alloy forged sheet undergoes surface pretreatment to further remove surface oil, scale, and other impurities. This ensures a clean, active metal surface in the weld zone, facilitating a high-quality weld joint. The specific treatment process involves first sanding the groove surface and adjacent areas uniformly with sandpaper to remove any surface oxide film. The base metal is then immersed in an acid pickling solution. The pickling solution is a mixture of 2% to 4% hydrofluoric acid (HF), 30% to 40% nitric acid (HNO3), and deionized water (H2O) by volume. The base metal is immersed in this pickling solution for 3 to 10 minutes to thoroughly remove oil, scale, and other contaminants from the titanium alloy surface. After pickling, the base metal surface is immediately rinsed with anhydrous ethanol to remove any residual acid before welding.

[0019] Step 3: The filler material used is a 1.6mm diameter Ti-6Al-4V alloy wire with an alloy composition of 6 wt.% Al, 4 wt.% V, and the remainder Ti. Before use, the alloy wire is dried in a 60°C drying oven for 4 hours. This step removes moisture and impurities from the wire surface, ensuring stable filler material performance during welding and preventing weld defects caused by moisture.

[0020] Step 4: First, use a special fixture to fix the surface-treated and grooved Ti-6Al-4V alloy forged plate on the welding platform to ensure that the base material is accurately positioned and without deformation. Then, set the electron beam welding program according to the process requirements and perform multi-layer and multi-pass electron beam wire feeding welding operations. Figure 1 Figure 2 is a schematic diagram of the electron beam wire feeding welding process for high-performance titanium alloy thick-walled components. The multi-layer and multi-pass electron beam welding process parameters used are as follows: acceleration voltage of 50kV to 70kV, beam current of 50mA to 100mA, focusing current of 950mA to 1050mA, welding speed of 400mm / min to 1000mm / min, wire feeding speed of 800mm / min to 1600mm / min, and chamber vacuum of less than 5×10 -2 In terms of forming parameters, the single layer height is 0.5mm~0.8mm, the layer width is 10mm~12mm, and the overlap width between passes is controlled at 1mm~3mm.

[0021] The present invention provides an electron beam wire feeding welding method for high-performance titanium alloy thick-walled components, which has significant advantages over traditional welding methods (such as TIG welding and laser welding). Electron beam wire feeding welding uses a small molten pool and rapid solidification mechanism through high energy density, high vacuum environment and precise heat input control, and can effectively avoid problems such as excessive expansion of the heat-affected zone and coarse weld structure, while reducing common defects in the welding process, such as porosity, incomplete penetration and cracks. This significantly improves the metallurgical quality of the weld joint, and also improves the density and mechanical properties of the weld. In addition, compared with electron beam autogenous welding, the present invention can accurately control the wire feeding speed and position by introducing a controllable wire feeding mechanism, thereby flexibly selecting filler wires of different compositions, achieving the purpose of composition optimization design and customized design of weld performance. By adopting multi-pass and multi-layer welding path planning to ensure sufficient fusion between layers and passes, and combining a small molten pool with a rapid solidification mechanism, the weld structure can be effectively refined and evenly distributed from top to bottom, significantly reducing the risk of typical defects such as porosity and incomplete penetration at the weld root, thereby comprehensively improving the structural integrity and service reliability of the weld joint.

[0022] Compared with the prior art, the present invention has the following beneficial effects: (1) Relying on the high energy density, high vacuum environment and precise heat input control of electron beam welding, combined with a small molten pool and rapid solidification mechanism, it can effectively reduce the scope of the heat affected zone, inhibit the coarsening of the weld structure, and significantly reduce the risk of typical defects such as porosity, incomplete penetration and lack of fusion, thereby improving the metallurgical quality of the weld joint.

[0023] (2) The introduction of precise and controllable wire feeding technology allows for flexible selection of filler wires with different compositions, enabling optimized control of weld composition and customized design of performance. This method is theoretically applicable to the welding of titanium alloys of various thicknesses and has excellent engineering adaptability, especially for the high-reliability connection requirements of complex structures and large key components.

[0024] (3) The use of multi-pass and multi-layer welding process, combined with a small molten pool and a rapid solidification mechanism, can effectively ensure the uniformity of the weld structure from top to bottom, avoid common defects such as pores and incomplete penetration at the weld root, and further improve the overall structural quality and long-term service reliability of the joint.

[0025] For a deeper understanding of the features and technical contents of the present invention, please refer to the detailed description and drawings attached hereto. It should be noted that the drawings are provided for illustrative purposes only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the electron beam wire feeding welding process for high-performance titanium alloy thick-walled components; Figure 2The microstructure of the welded joint in Example 1; Figure 3 The microstructure of the welded joint in Example 2; Figure 4 This is the micromorphology of the welded joint in Example 3. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to specific embodiments. These embodiments will help those skilled in the art further understand the present invention, but should not be construed as limiting the present invention. It should be noted that, without departing from the scope of the present invention, a number of variations and improvements may be made by those skilled in the art. These all fall within the scope of protection of the present invention.

[0028] The raw materials and equipment required for the present invention can be purchased through commercial channels.

[0029] Example 1: Step 1: A 150mm × 50mm × 30mm wrought Ti-6Al-4V alloy plate was selected as the base material. The alloy composition was: Al: 6 wt.%, V: 4 wt.%, with the remainder being Ti. Before welding, the base material's weld area was CNC machined to obtain a groove profile suitable for electron beam wire welding. The groove used was a steep V-shaped groove with a blunt edge, with the following parameters: a groove angle of 20° and a blunt edge thickness of 2mm.

[0030] Step 2: The machined, grooved Ti-6Al-4V alloy forged sheet undergoes surface pretreatment to further remove surface oil, scale, and other impurities. This ensures a clean, active metal surface in the weld zone, facilitating a high-quality weld joint. The specific treatment process involves first sanding the groove surface and adjacent areas uniformly with sandpaper to remove any surface oxide film. The base metal is then immersed in an acid pickling solution composed of 4% hydrofluoric acid (HF), 40% nitric acid (HNO3), and deionized water (H2O) by volume. The base metal is immersed in this pickling solution for 5 minutes to thoroughly remove surface contamination such as oil, scale, and other contaminants. Following pickling, the base metal surface is immediately rinsed with anhydrous ethanol to remove any residual acid before welding.

[0031] Step 3: The filler material used is a 1.6mm diameter Ti-6Al-4V alloy wire with an alloy composition of 6 wt.% Al, 4 wt.% V, and the remainder Ti. Before use, the alloy wire is dried in a 60°C drying oven for 4 hours. This step removes moisture and impurities from the wire surface, ensuring stable filler material performance during welding and preventing weld defects caused by moisture.

[0032] Step 4: First, a special fixture is used to fix the surface-treated and grooved Ti-6Al-4V alloy forged plate on the welding platform to ensure that the base material is accurately positioned and free of deformation. Subsequently, the electron beam welding program is set according to the process requirements, and multi-layer and multi-pass electron beam wire feeding welding operations are performed. The welding process parameters used are as follows: acceleration voltage of 60kV, beam current of 70mA, focusing current of 1030mA, welding speed of 600mm / min, wire feeding speed of 1300mm / min, and chamber vacuum of less than 5×10 -2 In terms of forming parameters, the single layer height is 0.8m, the layer width is 10mm, and the overlap width between passes is controlled at 2mm.

[0033] This embodiment uses a front-feed wire mode, where the wire is positioned in front of the electron beam and in the same horizontal plane. The wire feed direction forms a 45° angle with the welding direction, and the relative distance between the wire feed front and the center of the molten pool is controlled at 2 mm.

[0034] The micromorphology of the welded joints was observed by optical microscopy and scanning electron microscopy. Figure 2 As shown in the figure, the weld cross-section shows good weld quality. The weld zone microstructure is primarily composed of lath martensite α′ phase, with an average lath thickness of 0.97 μm. The weld joint has a yield strength of 841 MPa, a tensile strength of 897 MPa, and a weld coefficient of 0.89.

[0035] Example 2: Step 1: A 150mm × 50mm × 30mm wrought Ti-6Al-4V alloy plate was selected as the base material. The alloy composition was: Al: 6 wt.%, V: 4 wt.%, with the remainder being Ti. Before welding, the base material's weld area was CNC machined to obtain a groove profile suitable for electron beam wire welding. The groove used was a steep V-shaped groove with a blunt edge, with the following parameters: a groove angle of 20° and a blunt edge thickness of 2mm.

[0036] Step 2: The machined, grooved Ti-6Al-4V alloy forged sheet undergoes surface pretreatment to further remove surface oil, scale, and other impurities. This ensures a clean, active metal surface in the weld zone, facilitating a high-quality weld joint. The specific treatment process involves first sanding the groove surface and adjacent areas uniformly with sandpaper to remove any surface oxide film. The base metal is then immersed in an acid pickling solution composed of 4% hydrofluoric acid (HF), 40% nitric acid (HNO3), and deionized water (H2O) by volume. The base metal is immersed in this pickling solution for 5 minutes to thoroughly remove surface contamination such as oil, scale, and other contaminants. Following pickling, the base metal surface is immediately rinsed with anhydrous ethanol to remove any residual acid before welding.

[0037] Step 3: The filler material used is a 1.6mm diameter Ti-6Al-4V alloy wire with an alloy composition of 6 wt.% Al, 4 wt.% V, and the remainder Ti. Before use, the alloy wire is dried in a 60°C drying oven for 4 hours. This step removes moisture and impurities from the wire surface, ensuring stable filler material performance during welding and preventing weld defects caused by moisture.

[0038] Step 4: First, a special fixture is used to fix the surface-treated and grooved Ti-6Al-4V alloy forged plate on the welding platform to ensure that the base material is accurately positioned and free of deformation. Subsequently, the electron beam welding program is set according to the process requirements, and multi-layer and multi-pass electron beam wire feeding welding operations are performed. The welding process parameters used are as follows: acceleration voltage of 60kV, beam current of 80mA, focusing current of 1030mA, welding speed of 600mm / min, wire feeding speed of 1300mm / min, and chamber vacuum of less than 5×10 -2 In terms of forming parameters, the single layer height is 0.6m, the layer width is 10.5mm, and the overlap width between passes is controlled at 2mm.

[0039] This embodiment uses a front-feed mode, meaning the wire is positioned in front of the electron beam, and both are located in the same horizontal plane. The wire feed direction forms a 45° angle with the welding direction, and the relative distance between the wire tip and the center of the weld pool is controlled to be 1-4 mm.

[0040] The micromorphology of the welded joints was observed by optical microscopy and scanning electron microscopy. Figure 3As shown in the figure, the weld cross-section shows good weld quality. The microstructure of the weld zone is primarily composed of lath martensite α′ phase, with an average lath thickness of 0.98 μm. The weld joint has a yield strength of 864 MPa, a tensile strength of 905 MPa, and a weld coefficient of 0.90.

[0041] Example 3: Step 1: A 150mm × 50mm × 30mm wrought Ti-6Al-4V alloy plate was selected as the base material. The alloy composition was: Al: 6 wt.%, V: 4 wt.%, with the remainder being Ti. Before welding, the base material's weld area was CNC machined to obtain a groove profile suitable for electron beam wire welding. The groove used was a steep V-shaped groove with a blunt edge, with the following parameters: a groove angle of 20° and a blunt edge thickness of 2mm.

[0042] Step 2: The machined, grooved Ti-6Al-4V alloy forged sheet undergoes surface pretreatment to further remove surface oil, scale, and other impurities. This ensures a clean, active metal surface in the weld zone, facilitating a high-quality weld joint. The specific treatment process involves first sanding the groove surface and adjacent areas uniformly with sandpaper to remove any surface oxide film. The base metal is then immersed in an acid pickling solution composed of 4% hydrofluoric acid (HF), 40% nitric acid (HNO3), and deionized water (H2O) by volume. The base metal is immersed in this pickling solution for 5 minutes to thoroughly remove surface contamination such as oil, scale, and other contaminants. Following pickling, the base metal surface is immediately rinsed with anhydrous ethanol to remove any residual acid before welding.

[0043] Step 3: The filler material used is a 1.6mm diameter Ti-6Al-4V alloy wire with an alloy composition of 6 wt.% Al, 4 wt.% V, and the remainder Ti. Before use, the alloy wire is dried in a 60°C drying oven for 4 hours. This step removes moisture and impurities from the wire surface, ensuring stable filler material performance during welding and preventing weld defects caused by moisture.

[0044] Step 4: First, a special fixture is used to fix the surface-treated and grooved Ti-6Al-4V alloy forged plate on the welding platform to ensure that the base material is accurately positioned and free of deformation. Subsequently, the electron beam welding program is set according to the process requirements, and multi-layer and multi-pass electron beam wire feeding welding operations are performed. The welding process parameters used are as follows: acceleration voltage of 60kV, beam current of 90mA, focusing current of 1030mA, welding speed of 600mm / min, wire feeding speed of 1300mm / min, and chamber vacuum of less than 5×10-2 In terms of forming parameters, the single layer height is 0.5m, the layer width is 12mm, and the overlap width between passes is controlled at 2mm.

[0045] This embodiment uses a front-feed wire mode, where the wire is positioned in front of the electron beam and in the same horizontal plane. The wire feed direction forms a 45° angle with the welding direction, and the relative distance between the wire feed front and the center of the molten pool is controlled at 2 mm.

[0046] The micromorphology of the welded joints was observed by optical microscopy and scanning electron microscopy. Figure 4 As shown in the figure, the weld cross-section shows good weld quality. The microstructure of the weld zone is primarily composed of lath martensite α′ phase, with an average lath thickness of 1.14 μm. The weld joint has a yield strength of 787 MPa, a tensile strength of 836 MPa, and a weld coefficient of 0.83.

[0047] Table 1 Room temperature tensile properties of welded joints

[0048] The above describes in detail the specific embodiments of the present invention. It should be noted that the present invention is not limited to the specific embodiments described above. Without departing from the scope of protection defined by the claims, those skilled in the art can make various modifications or variations, and these modifications or variations are all technical solutions of the present invention.

Claims

1. A method for electron beam wire feeding welding of high performance titanium alloy thick wall components, characterized in that: The following steps are involved: Step 1: Form a V-shaped groove with a blunt edge on the welded end face of the base material, polish it, soak it in acid, and then rinse it with anhydrous ethanol; Step 2: Then fix it on the welding platform and perform multi-layer and multi-pass electron beam wire feeding welding.

2. The method according to claim 1, characterized in that The groove angle of the V-shaped groove is 10°~30°, the blunt edge thickness is 2mm, and the gap is ≤2mm.

3. The method according to claim 1, characterized in that The process parameters of multi-layer and multi-pass electron beam welding are as follows: acceleration voltage of 50 kV to 70 kV, beam current of 50 mA to 100 mA, focusing current of 950 mA to 1050 mA, welding speed of 400 mm / min to 1000 mm / min, wire feeding speed of 800 mm / min to 1600 mm / min, and chamber vacuum of less than 5 × 10 -2 Pa; in terms of forming parameters, the single layer height is 0.5mm~0.8mm, the layer width is 10mm~12mm, and the overlapping width between passes is controlled at 1mm~3mm.

4. The method according to claim 1, characterized in that The alloy wire diameter is 1.6 mm.

5. The method according to claim 1, characterized in that: The front wire feeding mode is adopted, the wire feeding direction is at a 45° angle to the welding direction, and the relative distance between the front end of the wire feeding and the center of the molten pool is controlled at 1mm~4mm.

6. The method according to claim 1, characterized in that The base material is Ti-6Al-4V alloy forged plate.

7. The method according to claim 6, characterized in that Ti-6Al-4V alloy wire.

8. The method according to claim 7, characterized in that: The composition of the alloy wire is as follows, by mass percentage: Al: 6 wt.%, V: 4 wt.%, and the remainder is Ti.

9. The method according to claim 1, characterized in that: The pickling solution used is prepared by volume fraction of 2% to 4% hydrofluoric acid, 30% to 40% nitric acid and deionized water.

10. The method according to claim 1, characterized in that: Before use, the alloy wire was placed in a drying oven at 60°C for constant temperature drying.

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