Welding method of titanium alloy

Abstract

The invention belongs to the technical field of material welding, and discloses a titanium alloy welding method which comprises the following steps: pretreating a to-be-welded surface of a titanium alloy; the pretreated to-be-welded surface is subjected to sand blasting treatment and magnetron sputtering treatment, and an iron film is sputtered on the to-be-welded surface; the titanium alloy with the to-be-welded surface sputtered with the iron film is subjected to annealing treatment in the argon atmosphere; and the to-be-welded surface of the sputtering iron film is welded through a diffusion welding process. According to the characteristic that the iron element can promote mutual diffusion of the titanium alloy, surface sand blasting, magnetron sputtering, stress relief annealing and diffusion welding processes are combined, so that the titanium alloy is tight in interface connection and complete in grain, the plasticity is not obviously reduced while the strength of the titanium alloy is kept, and the requirement for large-scale and integrated aero-engines can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of material welding and relates to a welding method for titanium alloy. Background Art

[0002] In many fields of modern industry, titanium alloy stands out with a series of excellent properties and becomes a key material attracting much attention. Titanium alloy has many advantages such as high specific strength, low thermal conductivity coefficient, and excellent corrosion resistance, and is widely used in the aerospace field. In the manufacture of engines of aerospace aircraft, the application of titanium alloy significantly improves the thrust-to-weight ratio and service ability of the engine. The engine can generate greater thrust, and its own weight is relatively light, which can improve the key performance such as the flight speed and climb rate of the aircraft. At the same time, it can operate stably for a long time under extreme working conditions such as high temperature, high pressure, and high-speed rotation.

[0003] With the rapid development of aerospace technology, aerospace aircraft are evolving towards large-scale, structurally complex, and integrated directions. As a common metal processing technology, diffusion welding has high joint strength, good sealing performance, high automation degree, and can connect a variety of materials, which can meet the high requirements of aircraft structures for joint strength.

[0004] Currently, after diffusion welding of titanium alloy, most of the interface connections at the welding part cannot be completely closed, which results in tiny gaps or defects at the welding interface. The interface grains are also incomplete, and the growth and arrangement of grains are affected by the welding process and cannot reach the grain state of the base material, making its strength and elongation lower than those of the base material. Insufficient strength causes premature fracture of the welding part when stressed, while low elongation results in insufficient toughness of the welding part when undergoing deformation and is prone to cracking. These problems severely limit the wider application of titanium alloy in the aerospace field, especially in key parts with extremely high requirements for structural strength and reliability. Therefore, a process is needed to optimize the weldability of titanium alloy and improve the strength and plasticity of the welding part. Summary of the Invention

[0005] The purpose of the present invention is to provide a welding method for titanium alloy to solve the problem that the strength and plasticity of the existing titanium alloy welding interface are both lower than those of the base material.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A welding method for titanium alloy, comprising: Pre-treating the surface of the titanium alloy to be welded; Performing sandblasting treatment and magnetron sputtering treatment on the pre-treated surface to be welded, and sputtering an iron thin film on the surface to be welded; Annealing the titanium alloy with an iron thin film sputtered on the surface to be welded in an argon atmosphere; The surface of the titanium alloy to be welded after annealing treatment is welded by diffusion welding process.

[0007] Furthermore, the pretreatment method is as follows: After grinding the surface of the titanium alloy to be welded with 3000# sandpaper, the titanium alloy is ultrasonically cleaned with acetone or ethanol.

[0008] Furthermore, during the sandblasting process, aluminum oxide is used as the abrasive for sandblasting.

[0009] Furthermore, during the sandblasting process, the sandblasting distance is 50 - 200 mm, the sandblasting angle is 90°, the pressure of the compressed air used for sandblasting is 0.3 - 0.6 MPa, and the sandblasting time is 1 - 5 min.

[0010] Furthermore, the target for the magnetron sputtering treatment is a high-purity iron target with a purity of 99.99%, and the gas for the magnetron sputtering treatment is argon with a purity of 99.99%.

[0011] Furthermore, during the magnetron sputtering process, the sputtering current is 60 - 80 mA, the sputtering gas pressure is 8 - 20 Pa, the single sputtering deposition time is 40 - 60 s, and the number of sputtering depositions is 5 - 10 times.

[0012] Furthermore, the mass of the iron thin film sputtered on the surface to be welded is 0.35% - 0.6% of the mass of the titanium alloy.

[0013] Furthermore, the purity of the argon atmosphere for the annealing treatment is 99.99%.

[0014] Furthermore, during the annealing process, the annealing temperature is 300 - 600 °C, and the annealing time is 1 - 3 h.

[0015] Furthermore, during the welding process, the temperature of the diffusion welding process is 40 - 50 °C below the β-phase transformation temperature, the welding time is 1 - 3 h, and the welding pressure is 2 - 10 MPa.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a welding method for titanium alloy. First, after pretreatment, the surface to be welded of the titanium alloy is sandblasted to improve the film adhesion. Subsequently, an iron film is introduced as an intermediate layer on the surface to be welded of the titanium alloy through magnetron sputtering process. Then, stress relief annealing treatment is carried out to eliminate the internal stress of the titanium alloy, promote the diffusion between the iron film and the titanium alloy base material. Finally, the surfaces to be welded of the titanium alloy are welded together through diffusion welding process. The operation of the present invention is simple and the cost is relatively low. By combining surface sandblasting, magnetron sputtering, stress relief annealing and diffusion welding processes, surface sandblasting can roughen the surface of the titanium alloy and improve the film adhesion; magnetron sputtering can obtain a suitable intermediate layer and improve the interface connection property; stress relief annealing treatment can eliminate the internal stress between the iron film and the titanium alloy base material, make the structure uniform, and promote the diffusion between the iron film and the titanium alloy base material, further improving the adhesion of the iron film and preventing it from falling off; finally, the diffusion layer obtained through the diffusion welding process has complete grains, and the structure is mainly composed of acicular α-phase and β-phase distributed alternately, making the interface connection of the titanium alloy tight. After welding, the titanium alloy of the present invention can maintain the strength of the titanium alloy base material while the plasticity does not decrease significantly, can meet the requirements of the large-scale and integrated development of aero-engines, can be used on a large scale, and has broad application prospects.

[0017] Further, the present invention uses an iron film as the intermediate layer. As a fast diffusion element in α-Ti, the diffusion rate of iron is 10 3 , 5 , ,

[0020] , ,

[0019] , ,

[0018] ~10 5 times that of the self-diffusion rate of α-Ti. When the titanium alloy contains iron element, it can improve the self-diffusion ability of the titanium alloy and enhance the interface bonding ability of the titanium alloy. At the same time, as a strong β-phase stabilizing element, the small amount of iron element present in the α-type titanium alloy can reduce the β / α phase transformation temperature, expand the β-phase region, improve the plasticity of the welded part of the titanium alloy, and reduce the tendency of welding cracks.

[0018] Further, the present invention uses aluminum oxide for sandblasting treatment on the surface to be welded after pretreatment. The rough surface formed after sandblasting treatment provides good mechanical biting conditions between the iron film and the titanium alloy, and can improve the adhesion of the iron film on the surface to be welded of the titanium alloy.

[0019] Further, the present invention conducts magnetron sputtering treatment on the surface to be welded after sandblasting treatment, which can form a uniform and dense iron film on the surface of the titanium alloy. The presence of the iron film can promote the diffusion and combination between atoms, improve the interface combination state, enhance the bonding force of the welded joint, and improve the strength of the welded joint. At the same time, the magnetron sputtering instrument is simple and convenient to use, the target sputtering deposition rate is relatively fast, and the cost is relatively low, which can realize large-scale coating preparation.

[0020] Furthermore, the titanium alloy after sputtering an iron thin film on the surface to be welded in the present invention is subjected to annealing treatment, which can eliminate the internal stress between the iron thin film and the titanium alloy base material, promote the diffusion between each other, improve the interface connection property after coating, and further reduce the welding temperature and shorten the welding time. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0022] Figure 1 Schematic diagram of titanium alloy welding according to the present invention.

[0023] Figure 2 Graph of the change of pressure with time during the welding process according to the present invention.

[0024] Figure 3 Line scan diagram of the interface diffusion layer of Example 1 according to the present invention.

[0025] Figure 4 Line scan diagram of the interface diffusion layer of Example 2 according to the present invention.

[0026] Figure 5 Line scan diagram of the interface diffusion layer of Example 3 according to the present invention.

[0027] Figure 6 Line scan diagram of the interface diffusion layer of Example 4 according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To enable those skilled in the art to understand the features and effects of the present invention, the following is a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art for the present invention. When there is a conflict, the definition in this specification shall prevail.

[0029] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0030] In this document, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of a numerical range or percentage range should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0031] In this document, for the sake of concise description, all possible combinations of all technical features in each embodiment or example are not described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as within the scope described in this specification.

[0032] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0033] Conventional instruments and equipment in the art are used in the following embodiments. For the experimental methods without specific conditions indicated in the following embodiments, they are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise specified, commercially available products are used, and their specifications are the conventional specifications in the art.

[0034] The present invention will be further described in detail below with reference to the accompanying drawings: The present invention provides a welding method for titanium alloy, which specifically includes the following steps: Step 1: Pretreat the surface to be welded of the titanium alloy. After grinding with 3000# sandpaper, ultrasonically clean the titanium alloy with acetone or ethanol.

[0035] Step 2: Use a microjet micro sandblaster, select aluminum oxide as the abrasive, and rough-treat the surface to be welded of the pretreated titanium alloy to improve the film adhesion of the surface to be welded.

[0036] During the sandblasting process, the sandblasting distance is 50 - 200 mm, the sandblasting angle is 90°, the pressure of the compressed air used for sandblasting is 0.3 - 0.6 MPa, and the sandblasting time is 1 - 5 min.

[0037] Step 3: Through the magnetron sputtering process, a layer of iron film is sputtered on the surface of the titanium alloy to be welded. The target material for magnetron sputtering treatment is a high-purity iron target with a purity of 99.99%, and the gas for magnetron sputtering treatment is argon with a purity of 99.99%. During the magnetron sputtering process, the sputtering current is 60 - 80 mA, the sputtering gas pressure is 8 - 20 Pa, the single sputtering deposition time is 40 - 60 s, and the sputtering deposition times is 5 - 10 times. After sputtering is completed, the mass of the iron film sputtered on the surface to be welded is 0.35% - 0.6% of the mass of the titanium alloy.

[0038] Step 4: Anneal the titanium alloy with an iron film sputtered on the surface to be welded in an argon atmosphere with a purity of 99.99%. During the annealing process, the annealing temperature is 300 - 600 °C, and the annealing time is 1 - 3 h.

[0039] Step 5: Connect the surfaces to be welded of the annealed titanium alloy together through the diffusion welding process, as Figure 1 shown.

[0040] During welding, the temperature of the diffusion welding process is 40 - 50 °C below the β-phase transformation temperature, the welding time is 1 - 3 h, and the welding pressure is 2 - 10 MPa.

[0041] As Figure 2 shown, during the heating stage, the pressure increases from 0 to P1 within t1 time, during the heat preservation stage, the pressure P1 increases to P2 within t2 time, during the cooling stage, the pressure is P2 and decreases to P3 within t3 time. After the temperature reaches room temperature, the pressure decreases from P3 to 0. Among them, P1, P2, and P3 are 60%, 100%, and 30% of the total pressure P respectively, the range of t1 is 10 min ≤ t1 ≤ 0.1t 升 , the range of t2 is 3 min ≤ t2 ≤ 0.1t 保 , the range of t3 is 20 min ≤ t3 ≤ 50 min, where, t 升 represents the time used in the heating stage, and t 保 represents the heat preservation stage time.

[0042] The following further elaborates on the present invention through specific embodiments: Embodiment 1: The material used in this embodiment is a Ti60 titanium alloy with dimensions of 50 * 50 * 2 mm. The Ti60 titanium alloy is a near-α titanium alloy of Ti - 5.8A1 - 4Sn - 3.5Zr - 0.7Nb - 0.5Mo - 0.3Si, and the β-phase transformation temperature is 1035 ± 5 °C.

[0043] Step 1): After grinding the surface to be welded of the Ti60 titanium alloy with 3000# sandpaper, ultrasonically clean the Ti60 titanium alloy with acetone; Step 2) Sandblast the surface of the Ti60 titanium alloy to be welded. Use aluminum oxide as the abrasive for sandblasting. The pressure of the compressed air used for sandblasting is 0.3 MPa, the sandblasting distance is 50 mm, the sandblasting angle is 90°, and the sandblasting time is 1 min; Step 3) Perform magnetron sputtering treatment on the surface of the Ti60 titanium alloy to be welded. The sputtering gas pressure is 20 Pa, the sputtering current is 80 mA, the single - time sputtering deposition time is 60 s, and the number of sputtering depositions is 5 times. After sputtering, the mass of the iron thin film on one side of the surface to be welded is 0.35% of the mass of the titanium alloy on this side, and the mass of the iron thin film on the other side of the surface to be welded is 0.43% of the mass of the titanium alloy on this side; Step 4) Anneal the Ti60 titanium alloy to be welded in a tube furnace under an argon atmosphere. The temperature is 300 °C. First, heat it at a rate of 10 °C / min to 290 °C, and then heat it at a rate of 1 °C / min to 300 °C, hold for 2 h, and then cool it to room temperature with the furnace; Step 5) Perform diffusion welding on the Ti60 titanium alloy. The welding temperature is selected as 980 °C, and the pressure is 4 MPa. First, heat it at a rate of 10 °C / min to 970 °C, and then heat it at a rate of 1 °C / min to 980 °C, hold for 1 h. During the heating stage, the pressure rises from 0 to 2.4 MPa in 15 min. During the holding stage, the pressure rises from 2.4 MPa to 4 MPa in 4 min. During the cooling stage, the pressure drops from 4 MPa to 1.2 MPa in 30 min. After cooling to room temperature with the furnace, the pressure drops to 0.

[0044] Perform mechanical property tests on the welded Ti60 titanium alloy and compare it with the Ti60 titanium alloy base material. The results are shown in Table 1. It can be seen that the strength of the welded Ti60 titanium alloy in Example 1 of the present invention is higher than that of the Ti60 titanium alloy base material. The tensile strength reaches 1170 MPa, and the yield strength reaches 984 MPa. At the same time, the plasticity is slightly lower than that of the Ti60 titanium alloy base material, and the elongation is 7.26%, showing excellent comprehensive mechanical properties. Figure 3 This is the line - scan diagram of the interfacial diffusion layer of the welded Ti60 titanium alloy in Example 1. From Figure 3 it can be seen that the weld interface is complete without defects. The grains around the weld are refined. The Fe element diffuses along the welding interface to both sides, and the diffusion width is 20 μm. The surface Fe promotes the bonding of the welding interface.

[0045] Table 1 Room - temperature tensile properties of the welded Ti60 titanium alloy in Example 1

[0046] Example 2: The materials used in this embodiment are Ti60 titanium alloy and Ti65 titanium alloy with dimensions of 30*30*10 mm. Among them, Ti60 titanium alloy is a near-α titanium alloy of Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si, and Ti65 titanium alloy is a 10-component near-α titanium alloy of Ti-5.9Al-4.0Sn-3.5Zr-0.3Mo-0.4Si-0.3Nb-2.0Ta-1.0W-0.05C. The β-phase transformation temperature of Ti60 titanium alloy is 1035 ± 5 °C, and the β-phase transformation temperature of Ti65 titanium alloy is 957 ± 5 °C.

[0047] Step 1) After grinding the surfaces to be welded of Ti60 titanium alloy and Ti65 titanium alloy with 3000# sandpaper, clean Ti60 titanium alloy and Ti65 titanium alloy ultrasonically with ethanol. Step 2) Perform sandblasting on the surfaces to be welded of Ti60 titanium alloy and Ti65 titanium alloy. Use aluminum oxide as the sandblasting material. The pressure of the compressed air used for sandblasting is 0.4 MPa, the sandblasting distance is 100 mm, the sandblasting angle is 90°, and the sandblasting time is 3 min. Step 3) Perform magnetron sputtering treatment on the surfaces to be welded of Ti60 titanium alloy and Ti65 titanium alloy respectively. The sputtering gas pressure is 15 Pa, the sputtering current is 60 mA, the single sputtering deposition time is 60 s, and the sputtering deposition times are 10 times. After sputtering, the mass of the iron thin film on the surface to be welded of Ti60 titanium alloy is 0.52% of the mass of Ti60 titanium alloy, and the mass of the iron thin film on the surface to be welded of Ti65 titanium alloy is 0.47% of the mass of Ti65 titanium alloy. Step 4) Anneal the Ti60 titanium alloy and Ti65 titanium alloy to be welded in a tubular furnace under an argon atmosphere at a temperature of 400 °C. First, heat up to 390 °C at a rate of 10 °C / min, and then heat up to 400 °C at a rate of 1 °C / min. Keep the temperature for 3 h, and then cool down to room temperature with the furnace. Step 5) Diffusion-weld Ti60 titanium alloy and Ti65 titanium alloy. The welding temperature is selected as 910 °C, and the pressure is 10 MPa. First, heat up to 900 °C at a rate of 10 °C / min, and then heat up to 910 °C at a rate of 1 °C / min. Keep the temperature for 3 h. During the heating stage, the pressure rises from 0 to 6 MPa in 30 min. During the holding stage, the pressure rises from 6 MPa to 10 MPa in 7 min. During the cooling stage, the pressure drops from 10 MPa to 3 MPa in 40 min. After cooling down to room temperature with the furnace, the pressure drops to 0.

[0048] The mechanical properties of the welded Ti60 titanium alloy and Ti65 titanium alloy were tested and compared with the base metals of Ti60 titanium alloy and Ti65 titanium alloy. The results are shown in Table 2. It can be seen that the strength of the welded Ti60 titanium alloy and Ti65 titanium alloy in Example 2 of the present invention is slightly lower than that of the Ti65 titanium alloy base metal, but significantly higher than that of the Ti60 titanium alloy base metal. The tensile strength is 1250 MPa, reaching 99.7% of the tensile strength of the Ti65 titanium alloy base metal. The yield strength is 1143 MPa. At the same time, the plasticity is between that of the Ti60 titanium alloy and the Ti65 titanium alloy, and the elongation is 8.49%, showing excellent comprehensive mechanical properties. Figure 4 This is the line scan diagram of the interface diffusion layer of the welded Ti60 titanium alloy and Ti65 titanium alloy in Example 2. From Figure 4 it can be seen that the weld interface is complete without defects. The grains around the weld are refined. The Fe element diffuses to both sides along the welding interface, and the diffusion width is 22 μm. The surface Fe promotes the combination of the welding interface.

[0049] Table 2 Room temperature tensile properties of the welded Ti60 titanium alloy and Ti65 titanium alloy in Example 2

[0050] Example 3: The material used in this example is a 30*30*4 mm Ti65 titanium alloy. The Ti65 titanium alloy is a 10-component near-α titanium alloy of Ti-5.9Al-4.0Sn-3.5Zr-0.3Mo-0.4Si-0.3Nb-2.0Ta-1.0W-0.05C, and the β-phase transformation temperature is 957 ± 5 °C.

[0051] Step 1) After grinding the surface of the Ti65 titanium alloy to be welded with 3000# sandpaper, ultrasonically clean the Ti65 titanium alloy with ethanol. Step 2) Perform sandblasting on the surface of the Ti65 titanium alloy to be welded. Use aluminum oxide as the sandblasting material. The compressed air pressure used for sandblasting is 0.5 MPa, the sandblasting distance is 140 mm, the sandblasting angle is 90°, and the sandblasting time is 4 min. Step 3) Perform magnetron sputtering on the surface of the Ti65 titanium alloy to be welded. The sputtering gas pressure is 8 Pa, the sputtering current is 65 mA, the single sputtering deposition time is 55 s, and the sputtering deposition times are 8 times. After sputtering, the mass of the iron thin film on one side of the surface to be welded is 0.55% of the mass of the titanium alloy on this side, and the mass of the iron thin film on the other side of the surface to be welded is 0.54% of the mass of the titanium alloy on this side. Step 4) Anneal the Ti65 titanium alloy to be welded in a tube furnace under an argon atmosphere at a temperature of 500 °C. First, heat it to 490 °C at a rate of 10 °C / min, and then heat it to 500 °C at a rate of 1 °C / min. Keep it at this temperature for 1 h, and then cool it to room temperature in the furnace. Step 5) Perform diffusion welding on the Ti65 titanium alloy. The welding temperature is selected as 900 °C, and the pressure is 2 MPa. First, heat it to 890 °C at a rate of 10 °C / min, and then heat it to 900 °C at a rate of 1 °C / min. Keep it at this temperature for 2 h. During the heating stage, the pressure rises from 0 to 1.2 MPa in 7 min. During the holding stage, the pressure rises from 1.2 MPa to 2 MPa in 3 min. During the cooling stage, the pressure drops from 2 MPa to 0.6 MPa in 33 min. After cooling to room temperature in the furnace, the pressure drops to 0.

[0052] Test the mechanical properties of the welded Ti65 titanium alloy and compare them with the Ti65 titanium alloy base material. The results are shown in Table 3. It can be seen that the strength of the Ti65 titanium alloy after welding in Example 3 of the present invention is close to that of the Ti65 titanium alloy base material. The tensile strength is 1243 MPa, the yield strength is 1145 MPa, and the elongation is 7.52%, showing excellent comprehensive mechanical properties and plasticity. Figure 5 This is the line scan diagram of the interface diffusion layer of the Ti65 titanium alloy after welding in Example 3. From Figure 5 it can be seen that the weld interface is complete without defects. The grains around the weld are refined. The Fe element diffuses along the welding interface to both sides, and the diffusion width is 25 μm. The surface Fe promotes the bonding of the welding interface.

[0053] Table 3 Room temperature tensile properties of the Ti65 titanium alloy after welding in Example 3

[0054] Example 4: The material used in this example is a 40*40*5 mm Ti175 titanium alloy. Among them, the Ti175 alloy is an α + β titanium alloy of Ti-6.5Al-2Sn-3.5Zr-4Mo-1W-0.2Si-0.9W, and the β-phase transformation temperature is 985 ± 5 °C.

[0055] Step 1) After grinding the surface to be welded of the Ti175 titanium alloy with 3000# sandpaper, ultrasonically clean the Ti175 titanium alloy with acetone. Step 2) Perform sandblasting on the surface to be welded of the Ti175 titanium alloy. Use aluminum oxide as the sandblasting material. The compressed air pressure used for sandblasting is 0.6 MPa, the sandblasting distance is 200 mm, the sandblasting angle is 90°, and the sandblasting time is 5 min. Step 3) Magnetron sputtering is carried out on the surface of the Ti175 titanium alloy to be welded. The sputtering pressure is 15 Pa, the sputtering current is 60 mA, the single sputtering deposition time is 40 s, and the sputtering deposition times is 10 times. After sputtering, the mass of the iron thin film on one side of the surface to be welded is 0.60% of the mass of the titanium alloy on this side, and the mass of the iron thin film on the other side of the surface to be welded is 0.57% of the mass of the titanium alloy on this side; Step 4) The Ti175 titanium alloy to be welded is annealed in a tube furnace under an argon atmosphere at a temperature of 600 °C. First, it is heated to 590 °C at a rate of 10 °C / min, and then heated to 600 °C at a rate of 1 °C / min, and held for 1 h, and then cooled to room temperature with the furnace; Step 5) The Ti175 titanium alloy is diffusion welded. The welding temperature is selected as 940 °C and the pressure is 10 MPa; First, it is heated to 930 °C at a rate of 10 °C / min, and then heated to 940 °C at a rate of 1 °C / min, and held for 2 h. During the heating stage, the pressure is increased from 0 to 6 MPa in 25 min. During the holding stage, the pressure is increased from 6 MPa to 10 MPa in 6 min. During the cooling stage, the pressure is decreased from 10 MPa to 3 MPa in 45 min. After cooling to room temperature with the furnace, the pressure is decreased to 0.

[0056] The mechanical properties of the welded Ti175 titanium alloy are tested and compared with the Ti175 titanium alloy base material. The results are shown in Table 4. It can be seen that the strength and plasticity of the welded Ti175 titanium alloy in Example 4 of the present invention are both close to those of the Ti175 titanium alloy base material. The tensile strength reaches 1254 MPa, which is 98.8% of the Ti175 titanium alloy base material. The yield strength reaches 1034 MPa, and the elongation rate is 12.26%, showing excellent comprehensive mechanical properties. Figure 6 This is the line scan diagram of the interface diffusion layer of the Ti175 titanium alloy welded in Example 4. From Figure 6 it can be seen that the weld interface is complete without defects. The grains around the weld are refined. The Fe element diffuses along the welding interface to both sides, and the diffusion width is 25 μm. The surface Fe promotes the combination of the welding interface.

[0057] Table 4 Room temperature tensile properties of the Ti175 titanium alloy welded in Example 4

[0058] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A welding method for a titanium alloy, characterized in that, Including: Pre-treat the surface of the titanium alloy to be welded; Perform sandblasting treatment and magnetron sputtering treatment on the pre-treated surface to be welded, and sputter an iron thin film on the surface to be welded; Anneal the titanium alloy with an iron thin film sputtered on the surface to be welded in an argon atmosphere; Weld the surface to be welded of the annealed titanium alloy by diffusion welding process.

2. A welding method for a titanium alloy according to claim 1, characterized in that, The method of the pre-treatment is: Grind the surface of the titanium alloy to be welded with 3000# sandpaper, and then ultrasonically clean the titanium alloy with acetone or ethanol.

3. A welding method for a titanium alloy according to claim 1, characterized in that, In the sandblasting treatment, alumina is used as the sandblast.

4. A welding method for a titanium alloy according to claim 1, characterized in that, In the sandblasting treatment, the sandblasting distance is 50 - 200 mm, the sandblasting angle is 90°, the pressure of the compressed air used for sandblasting is 0.3 - 0.6 MPa, and the sandblasting time is 1 - 5 min.

5. A welding method for a titanium alloy according to claim 1, characterized in that, The target material for the magnetron sputtering treatment is a high-purity iron target with a purity of 99.99%, and the gas for the magnetron sputtering treatment is argon with a purity of 99.99%.

6. A welding method for a titanium alloy according to claim 1, characterized in that, In the magnetron sputtering treatment, the sputtering current is 60 - 80 mA, the sputtering gas pressure is 8 - 20 Pa, the single sputtering deposition time is 40 - 60 s, and the sputtering deposition times are 5 - 10 times.

7. A welding method for a titanium alloy according to claim 1, characterized in that, The mass of the iron thin film sputtered on the surface to be welded is 0.35% - 0.6% of the mass of the titanium alloy.

8. A welding method for a titanium alloy according to claim 1, characterized in that, The purity of the argon atmosphere for the annealing treatment is 99.99%.

9. A welding method for a titanium alloy according to claim 1, characterized in that, In the annealing treatment, the annealing temperature is 300 - 600 °C, and the annealing time is 1 - 3 h.

10. A welding method for a titanium alloy according to claim 1, characterized in that, In the welding, the temperature of the diffusion welding process is 40 - 50 °C below the β-phase transformation temperature, the welding time is 1 - 3 h, and the welding pressure is 2 - 10 MPa.

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