A method for phase transformation superplastic diffusion bonding of high-temperature titanium alloys

Abstract

This invention discloses a high-temperature titanium alloy phase change superplastic diffusion bonding method, belonging to the field of material welding technology. The bonding method is as follows: the surface of the high-temperature titanium alloy sample to be welded is pretreated and chemically etched sequentially, followed by magnetron co-sputtering to sputter a layer of iron-nickel composite film onto the surface, obtaining an intermediate sample. The intermediate sample is then annealed to obtain a sample to be welded with the iron-nickel composite film layer; the iron-nickel composite film accounts for 0.55%~0.80% of the mass of the high-temperature titanium alloy sample; the mass ratio of iron to nickel in the iron-nickel composite film is (70:30)~(90:10); the sample to be welded with the iron-nickel composite film layer is then welded through multiple cycles of heating and cooling within a preset temperature range using a phase change superplastic diffusion process. This phase change superplastic diffusion bonding method solves the technical problems of low efficiency and unstable mechanical properties of welds in traditional isothermal diffusion welding.

Description

Technical Field

[0001] This invention belongs to the field of materials welding technology, specifically relating to a method for phase transformation superplastic diffusion bonding of high-temperature titanium alloys. Background Technology

[0002] High-temperature titanium alloys (also known as heat-resistant titanium alloys or heat-resistant titanium alloys) are a class of titanium-based alloy materials specifically designed for high-temperature environments. Through optimized alloy composition (such as the addition of elements like aluminum, vanadium, and molybdenum) and heat treatment processes, they achieve significant properties such as high specific strength, low thermal conductivity, and excellent corrosion resistance. These alloys can operate stably for extended periods at temperatures ranging from 400°C to 600°C, while maintaining high instantaneous strength, endurance strength, and good creep resistance. Therefore, they are widely used in the aerospace field and play a crucial role in improving engine thrust-to-weight ratio and service performance. As aerospace vehicles become larger, more complex, and more integrated, diffusion welding, as a key joining process, has become an ideal choice to meet the stringent connection performance requirements of aircraft components due to its high-strength bonding capability, excellent sealing performance, feasibility for joining dissimilar materials, and high degree of automation.

[0003] Currently, after diffusion bonding of high-temperature titanium alloys, the weld interface often contains incompletely closed micropores, leading to discontinuous grain structure in the interface region. Therefore, the strength and elongation of the welded area are typically significantly lower than those of the base material. To address these technical problems, Chinese invention patent CN120395093A provides a welding method for titanium alloys. This method involves: pre-treating the surface of the titanium alloy to be welded; performing sandblasting and magnetron sputtering on the pre-treated surface to sputter a thin iron film; annealing the titanium alloy with the sputtered iron film in an argon atmosphere; and welding the annealed titanium alloy surface using a diffusion welding process. During welding, the diffusion welding temperature is 40°C to 50°C below the β-phase transformation temperature, and the welding time is 1 to 3 hours. Although this method addresses the issue of lower plasticity compared to the base material to some extent, the diffusion bonding process typically requires a long time and faces the risk of weld grain growth, which can impair overall mechanical properties.

[0004] Therefore, there is an urgent need to develop a novel diffusion bonding process to optimize the diffusion bonding properties of high-temperature titanium alloys. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-temperature titanium alloy phase transformation superplastic diffusion bonding method to solve the technical problems of low efficiency and unstable mechanical properties of traditional isothermal diffusion welding.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a method for phase transformation superplastic diffusion bonding of high-temperature titanium alloys, comprising the following steps:

[0008] S1: The surface of the high-temperature titanium alloy sample to be welded is pretreated and chemically etched sequentially, followed by magnetron co-sputtering to sputter a layer of iron-nickel composite film onto the surface of the high-temperature titanium alloy sample to be welded, thus obtaining an intermediate sample. The intermediate sample is then annealed to obtain a sample to be welded with an iron-nickel composite film layer. The iron-nickel composite film accounts for 0.55% to 0.80% of the mass of the high-temperature titanium alloy sample. The mass ratio of iron to nickel in the iron-nickel composite film is (70:30) to (90:10).

[0009] S2: The sample to be welded is coated with an iron-nickel composite film layer by repeatedly heating and cooling within a preset temperature range through a phase change superplastic diffusion process.

[0010] In one embodiment, the preprocessing process includes:

[0011] The surface of the high-temperature titanium alloy sample to be welded was ground with 2000#~3000# sandpaper, and the non-welding surface of the high-temperature titanium alloy sample was ground with 120#~200# sandpaper to remove oxide scale. Then, ultrasonic cleaning was performed with acetone and alcohol in sequence. Finally, silicate glass anti-oxidation paste was applied to the non-welding surface of the high-temperature titanium alloy sample.

[0012] In one embodiment, the chemical etching process includes:

[0013] The pretreated high-temperature titanium alloy sample was immersed in an etching solution, and then ultrasonically cleaned with alcohol and acetone in sequence.

[0014] In one embodiment, the corrosive solution is composed of hydrogen fluoride, nitric acid, and water, wherein the volume ratio of hydrogen fluoride, nitric acid, and water is 1:4:495~500; and the soaking time is 30s~45s.

[0015] In one embodiment, in the magnetron co-sputtering process, the target materials are high-purity iron and high-purity nickel targets with a purity of 99.99%, the sputtering gas is argon gas with a purity of 99.99%, the argon gas flow rate is 10 sccm to 30 sccm, the sputtering pressure is 0.8 Pa to 1.2 Pa, the sputtering power of the high-purity iron target is 120 W to 180 W, the sputtering power of the high-purity nickel target is 20 W to 80 W, the single deposition time is 40 s to 60 s, the number of depositions is 15 to 20, and the rotation speed of the surface of the high-temperature titanium alloy sample to be welded is 150 r / min to 200 r / min.

[0016] In one embodiment, the upper limit temperature of the preset temperature range is 40°C to 50°C below the selected β phase transition point temperature; the lower limit temperature of the preset temperature range is 800°C to 850°C.

[0017] When two high-temperature titanium alloy samples with different β-phase transformation temperatures are welded, the selected β-phase transformation temperature is the lowest β-phase transformation temperature among the high-temperature titanium alloy samples with different β-phase transformation temperatures.

[0018] In one embodiment, in the multiple cyclic heating and cooling, the total number of cycles is 20 to 30, the heating rate is 5°C / s to 10°C / s, and the cooling rate is 15°C / s to 20°C / s; in the multiple cyclic heating and cooling, the cooling method is argon gas blowing cooling.

[0019] In one embodiment, during the multiple cycles of heating and cooling, the single holding time for the upper limit temperature of the preset temperature range is 10s to 15s, and the single holding time for the lower limit temperature of the preset temperature range is 10s to 15s.

[0020] In one embodiment, the welding pressure is 1 MPa to 3 MPa; the welding process maintains constant pressure diffusion.

[0021] In one embodiment, the annealing atmosphere is argon atmosphere, the annealing temperature is 300℃~600℃, and the annealing time is 1h~3h.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] This invention discloses a high-temperature titanium alloy phase change superplastic diffusion bonding method. This method uses magnetron co-sputtering to deposit an iron-nickel composite film on the surface of a high-temperature titanium alloy sample to be welded. Subsequently, phase change superplastic diffusion bonding technology is used to achieve a tight bond at the interface by utilizing the phase change superplastic effect of the titanium alloy. This improves welding efficiency while more stably ensuring the overall mechanical properties of the material, meeting the development requirements of both speed and quality. In this method, an iron-nickel composite film is introduced as an intermediate layer on the surface of the high-temperature titanium alloy sample to be welded to improve the interfacial bonding properties. Combined with the phase change superplastic diffusion bonding process, welding efficiency is significantly improved, reducing the welding time to 0.5 to 1 hour and increasing the interfacial bonding strength. During superplastic deformation, the material surface is in a superplastic rheological state, which can improve the joint tightness and accelerate atomic diffusion. However, due to the short welding time of superplastic welding itself, it is not possible to effectively seal interfacial pores. Increasing the number of cycles will cause deformation in the joint area, impairing its creep and durability properties. Therefore, introducing an iron-nickel composite interlayer not only ensures welding efficiency but also promotes the formation of silicide solid solutions (such as (Ti,Zr)6Si3, (Ti,Zr)5Si3, and (Ti,Zr)3Si) by trace elements such as silicon in the titanium alloy at the interface, effectively improving joint strength. Moreover, by introducing an iron-nickel thin film through magnetron co-sputtering and employing a phase change superplastic diffusion bonding process, the titanium alloy interface can be tightly bonded, with its microstructure mainly consisting of acicular α and β phases. Compared with bonding methods that do not add an interlayer or only add an iron thin film as an interlayer, the alloy strength remains consistent with the base material, and the plasticity only decreases slightly. In a more specific joining method, the pretreated high-temperature titanium alloy sample's surface to be welded is first chemically etched to improve film adhesion. Then, a stable and reliable intermediate layer is formed through magnetron co-sputtering to improve interfacial bonding properties. Next, stress-relief annealing eliminates internal stress between the iron-nickel composite film and the surface to be welded, and promotes diffusion between the film and the titanium substrate. Finally, a phase transformation superplastic diffusion joining process is used to join the surfaces of the high-temperature titanium alloy sample together. After diffusion joining, the microstructure of the joint region mainly consists of primary α phase, β phase, and secondary α phase, with tight interfacial bonding. While ensuring the strength of the base material, there is no significant decrease in plasticity. Furthermore, this invention strictly controls the iron-nickel content in the magnetron co-sputtering, approximately 0.55% to 0.80% of the total mass. If the overall content is below this range, the interfacial voids are not sufficiently sealed; if it exceeds this range, brittle iron-nickel intermetallic compounds will form at the joint, impairing the joint's plasticity. Furthermore, based on the characteristics of the activation activity of superplastic phase transition atoms, this invention specifies the iron-nickel ratio, with the mass ratio of iron to nickel being (70:30) to (90:10). This is because excessive iron and nickel content will lead to the formation of brittle intermetallic compounds such as iron-titanium and nickel-titanium at the joint, impairing the overall performance.In summary, the high-temperature titanium alloy phase transformation superplastic diffusion bonding method provided by this invention has a short process time, and the resulting weld interface has a dense bond and complete grain structure, with mechanical properties comparable to those of the base material. Furthermore, this method is simple to operate and low in cost, making it suitable for large-scale production applications. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the phase change superplastic diffusion process used in this invention, involving cyclic heating and cooling within a preset temperature range.

[0025] Figure 2 The images show a comparison of the microstructure of the interface layer in Example 1 and Comparative Example 1 of the present invention. (a) is a microstructure of the joint region of the phase change superplastic welding in Example 1, and (b) is a microstructure of the joint region of the isothermal welding in Comparative Example 1.

[0026] Figure 3 The images show a comparison of the microstructure of the interface layer in Example 2 and Comparative Example 2 of the present invention. (a) is a microstructure of the joint region of the phase transformation superplastic welding in Example 2, and (b) is a microstructure of the joint region of the isothermal welding in Comparative Example 2.

[0027] Figure 4 The images show a comparison of the microstructure of the interface layer in Example 3 and Comparative Example 3 of the present invention. (a) is a microstructure of the joint region of the phase transformation superplastic welding in Example 3, and (b) is a microstructure of the joint region of the isothermal welding in Comparative Example 3.

[0028] Figure 5 The images show a comparison of the microstructure of the interface layer in Example 4 and Comparative Example 4 of the present invention. (a) is a microstructure of the joint region of the phase transformation superplastic welding in Example 4, and (b) is a microstructure of the joint region of the isothermal welding in Comparative Example 4. Detailed Implementation

[0029] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0030] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0031] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0032] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0033] Phase transformation superplasticity offers a new approach to address the shortcomings of existing diffusion bonding technologies, which typically require excessive time and are inefficient. Furthermore, prolonged time and high temperatures can lead to excessively large grain sizes in titanium alloys, negatively impacting plasticity. Phase transformation superplasticity refers to the excellent plastic deformation capacity of a material under specific temperature and stress conditions, and materials exhibiting solid-state phase transformation generally display this property. For titanium alloys, the temperature range required for diffusion bonding is similar to that of phase transformation superplastic forming, making it possible to integrate diffusion bonding and superplastic forming processes within a single thermal cycle. This enables the efficient manufacture of complex workpieces.

[0034] The core advantage of transformation superplastic diffusion bonding lies in the high plasticity induced in the material during the phase transformation process. Frequent phase transformations significantly activate surface atoms in the alloy, greatly increasing the diffusion rate. Simultaneously, the dynamic recrystallization phenomena accompanying the phase transformation (including transformation recrystallization and deformation recrystallization) further enhance the effect of grain boundary diffusion. However, frequent thermal cycling processes can easily generate brittle phases at the interface, impairing the material's durability and creep properties; moreover, lowering the diffusion temperature makes it difficult to achieve phase transformation, thus limiting the application of transformation superplasticity in high-temperature near-α titanium alloys.

[0035] To address this, the present invention introduces an intermediate layer at the interface, which can also improve the diffusion rate, promote interface healing, and further effectively reduce the diffusion bonding temperature. Furthermore, iron-nickel, as a fast-diffusion component in α-Ti, exhibits a diffusion coefficient in α-Ti that can reach up to 10 times that of titanium's self-diffusion coefficient. 3 ~10 5 This method can significantly increase the self-diffusion rate of trace elements within titanium alloys, promote the formation of solid solution phases such as silicides at the interface, and enhance interface strength. Based on the above mechanism, this invention employs a phase transformation superplastic diffusion bonding method with an added intermediate layer to achieve integrated forming of high-temperature titanium alloys, avoiding the problems of low diffusion welding rate, unstable weld mechanical properties, and weak strength of phase transformation superplastic welded joints in traditional methods.

[0036] Among them, magnetron co-sputtering, as a mature surface coating process, has advantages such as simple equipment operation, high deposition rate, and low cost, making it suitable for large-scale thin film preparation. More importantly, iron-nickel composite films deposited by magnetron co-sputtering can significantly optimize interfacial diffusion behavior, thereby effectively achieving workpiece bonding.

[0037] This invention provides a high-temperature titanium alloy phase change superplastic diffusion bonding method. An iron-nickel composite film is introduced as an intermediate layer onto the surface of a high-temperature titanium alloy sample to be welded via magnetron co-sputtering. Then, the samples coated with the iron-nickel composite film are bonded together using a phase change superplastic diffusion process. The specific steps are as follows:

[0038] Step 1: Pre-treat the surface of the high-temperature titanium alloy sample to be welded;

[0039] Step 2: Perform chemical etching on the surface of the pretreated high-temperature titanium alloy sample to be welded;

[0040] Step 3: Using magnetron co-sputtering, a layer of iron-nickel composite film is sputtered onto the surface of the high-temperature titanium alloy sample to be welded after chemical etching to obtain an intermediate sample; wherein, the iron-nickel composite film accounts for 0.55%~0.80% of the mass of the high-temperature titanium alloy sample; the mass ratio of iron to nickel in the iron-nickel composite film is (70:30)~(90:10).

[0041] Step 4: Anneal the intermediate sample under an argon atmosphere to obtain a sample to be welded with an iron-nickel composite thin film layer.

[0042] Step 5: The samples to be welded, coated with an iron-nickel composite thin film layer, are joined together by phase change superplastic diffusion.

[0043] The preprocessing process includes:

[0044] The surface of the high-temperature titanium alloy sample to be welded was ground with 2000#~3000# sandpaper, and the non-welding surface of the high-temperature titanium alloy sample was ground with 120#~200# sandpaper to remove oxide scale. Then, ultrasonic cleaning was performed with acetone and alcohol in sequence. Except for the surface to be welded, silicate glass anti-oxidation paste was then applied to the non-welding surface of the high-temperature titanium alloy sample.

[0045] The chemical etching process includes:

[0046] The surface of the pretreated high-temperature titanium alloy sample to be welded was immersed in the etching solution for 30s~45s, and then ultrasonically cleaned with alcohol and acetone in sequence.

[0047] The corrosive solution used consists of hydrogen fluoride, nitric acid, and water, with a volume ratio of 1:4:495~500.

[0048] The parameters of the magnetron co-sputtering process are as follows: the target materials are high-purity iron and high-purity nickel targets with a purity of 99.99%; the sputtering gas is argon gas with a purity of 99.99%; the argon gas flow rate is 10 sccm~30 sccm; the sputtering pressure is 0.8 Pa~1.2 Pa; the sputtering power of the high-purity iron target is 120 W~180 W; the sputtering power of the high-purity nickel target is 20 W~80 W; the single deposition time is 40 s~60 s; the number of depositions is 15~20; and the rotation speed of the surface of the high-temperature titanium alloy sample to be welded is 150 r / min~200 r / min.

[0049] The annealing process parameters are as follows: the atmosphere is argon atmosphere with a purity of 99.99%, the annealing temperature is 300℃~600℃, and the annealing time is 1h~3h.

[0050] The experimental equipment for the phase change superplastic diffusion process consists of a manual hydraulic press and a high-temperature resistance furnace. During connection operations, a butt-joint method is used for the joints.

[0051] like Figure 1 As shown, the phase change superplastic diffusion process involves welding through multiple cycles of heating and cooling within a preset temperature range. T max T is the upper limit temperature of the preset temperature range. min The lower limit temperature of the preset temperature range, n is the single cycle period, and N is the total number of cycles for heating and cooling.

[0052] The process parameters for the phase change superplastic diffusion are as follows:

[0053] The upper limit temperature T of the preset temperature range max The selected temperature range is 40℃~50℃ below the β phase transition temperature; the lower limit temperature T of the preset temperature range is... min The temperature range is 800℃ to 850℃. When welding two high-temperature titanium alloy samples with different β-phase transformation temperatures, the lowest β-phase transformation temperature among the samples is selected.

[0054] The total number of cycles N for cyclic heating and cooling is 20 to 30 times, and the heating rate v h The cooling rate v is 5℃ / s~10℃ / s. c The flow rate is 15℃ / s to 20℃ / s; during multiple cycles of heating and cooling, the cooling method is to blow in high-speed argon gas for air cooling, with an argon flow rate of 20000 sccm to 36600 sccm.

[0055] Within a single cycle n, the upper limit temperature T of the preset temperature range. max The single heat preservation time t is 10s~15s, and the lower limit temperature T of the preset temperature range is... min The single heat preservation time t is 10s~15s.

[0056] The welding pressure is 1 MPa to 3 MPa, and the entire welding process is constant pressure diffusion.

[0057] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0058] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0059] Example 1:

[0060] The material used in this embodiment is a 30×30×2mm Ti60 titanium alloy. The Ti60 titanium alloy is a near-α titanium alloy of Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si. The β phase transformation temperature of the Ti60 titanium alloy is 1034℃. The β phase transformation temperature of the Ti60 titanium alloy is selected as the selected β phase transformation point temperature.

[0061] This embodiment provides a method for phase transformation superplastic diffusion bonding of high-temperature titanium alloys, including the following steps:

[0062] Step 1): Grind the Ti60 titanium alloy surface to be welded with 3000# sandpaper, and grind the other non-welding surfaces with 120# sandpaper to remove the oxide layer. Then clean them with acetone and alcohol by ultrasonic cleaning. Apply anti-oxidation paste evenly to the non-welding surfaces.

[0063] Step 2): Immerse the surface to be welded in the etching solution for 30 seconds, then remove it and clean it with alcohol and acetone by ultrasonic cleaning in sequence; wherein, the volume ratio of hydrogen fluoride, nitric acid and water in the etching solution is 1:4:495;

[0064] Step 3): The Ti60 titanium alloy surface to be welded is subjected to magnetron co-sputtering treatment. The argon flow rate in the magnetron co-sputtering treatment is 10 sccm, the sputtering pressure is 0.8 Pa, the sputtering power of the high-purity iron target is 180 W, the sputtering power of the high-purity nickel target is 80 W, the single deposition time is 40 s, and the number of depositions is 15. After sputtering, the mass of the iron-nickel composite film on one side of the surface to be welded is 0.55% of the mass of the Ti60 titanium alloy to be welded on that side, and the mass of the iron-nickel composite film on the other side of the surface to be welded is 0.62% of the mass of the Ti60 titanium alloy to be welded on that side. The mass ratio of iron to nickel is approximately 70:30.

[0065] Step 4): Anneal the Ti60 titanium alloy to be welded in a tube furnace under an argon atmosphere. The annealing temperature is 300℃ and the annealing time is 3h. First, the temperature is increased to 290℃ at a rate of 10℃ / min, and then increased to 300℃ at a rate of 1℃ / min. After holding at the temperature, the furnace is cooled to room temperature.

[0066] Step 5): Perform phase transformation superplastic diffusion bonding on the Ti60 titanium alloy to be welded. The upper limit temperature for phase transformation superplastic diffusion bonding is T. max The lower limit temperature is 985℃, T. min The heating rate v is 850℃. h The cooling rate v is 5℃ / s. c The speed is 15℃ / s, and the upper limit temperature T is... max and lower limit temperature T min The single heat preservation time t is 15s, the total number of cycles N is 30, the cooling method is high-speed argon air cooling, the argon flow rate is 25000sccm, and the welding pressure is 1MPa.

[0067] Example 2:

[0068] The materials used in this embodiment are Ti60 titanium alloy and Ti65 titanium alloy with a diameter of ø30×5mm. The Ti60 titanium alloy is a near-α titanium alloy of Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si, and the Ti65 titanium alloy is a near-α titanium alloy of Ti-5.9Al-4.0Sn-3.5Zr-0.3Mo-0.4Si-0.3Nb-2.0Ta-1.0W-0.05C10. The β-phase transformation temperature of the Ti60 titanium alloy is 1034℃, and the β-phase transformation temperature of the Ti65 titanium alloy is 1020℃. The β-phase transformation temperature of the Ti65 titanium alloy is selected as the selected β-phase transformation point temperature.

[0069] This embodiment provides a method for phase transformation superplastic diffusion bonding of high-temperature titanium alloys, including the following steps:

[0070] Step 1): Grind the surfaces of Ti60 and Ti65 titanium alloys to be welded with 2000# sandpaper, and grind the other non-welding surfaces with 200# sandpaper to remove the oxide layer. Then clean them with acetone and alcohol by ultrasonic cleaning. Apply anti-oxidation paste evenly to the non-welding surfaces.

[0071] Step 2): Immerse the surface to be welded in the etching solution for 35 seconds, then remove it and clean it with alcohol and acetone by ultrasonic cleaning in sequence; wherein, the volume ratio of hydrogen fluoride, nitric acid and water in the etching solution is 1:4:500.

[0072] Step 3): Magnetron co-sputtering was performed on the surfaces of Ti60 and Ti65 titanium alloys to be welded. The argon flow rate was 18 sccm, the sputtering pressure was 0.9 Pa, the sputtering power of the high-purity iron target was 160 W, the sputtering power of the high-purity nickel target was 70 W, the single deposition time was 45 s, and the number of depositions was 17. After sputtering, the mass of the iron-nickel composite film on the surface to be welded on the Ti60 titanium alloy side was 0.65% of the mass of the Ti60 titanium alloy on this side, and the mass of the iron-nickel composite film on the surface to be welded on the Ti65 titanium alloy side was 0.62% of the mass of the Ti65 titanium alloy on this side. The mass ratio of iron to nickel was approximately 74:26.

[0073] Step 4): Anneal the Ti60 titanium alloy and the Ti65 titanium alloy to be welded in a tube furnace under an argon atmosphere. The annealing temperature is 400℃ and the annealing time is 2h. First, the temperature is increased to 390℃ at a rate of 10℃ / min, and then increased to 400℃ at a rate of 1℃ / min. After holding at the temperature, the furnace is cooled to room temperature.

[0074] Step 5): Perform phase transformation superplastic diffusion bonding on the Ti60 titanium alloy and the Ti65 titanium alloy to be welded. The upper limit temperature for phase transformation superplastic diffusion bonding is T. max The lower limit temperature is 980℃. min The heating rate v is 830℃. h The cooling rate v is 7℃ / s. c The speed is 17℃ / s, and the upper limit temperature T is... max and lower limit temperature T min The single heat preservation time t is 12s, the total number of cycles N is 28, the cooling method is high-speed argon air cooling, the argon flow rate is 36000sccm, and the welding pressure is 2.5MPa.

[0075] Example 3:

[0076] The materials used in this embodiment are 20×30×4mm Ti65 titanium alloy and Ti175 titanium alloy. Ti65 titanium alloy is a near-α titanium alloy with a Ti-5.9Al-4.0Sn-3.5Zr-0.3Mo-0.4Si-0.3Nb-2.0Ta-1.0W-0.05C10 component. The β phase transformation temperature of Ti65 titanium alloy is 1020℃. Ti175 titanium alloy is an α+β titanium alloy with a Ti-6.5Al-2Sn-3.5Zr-4Mo-1W-0.2Si component. The β phase transformation temperature of Ti175 titanium alloy is 980℃. The β phase transformation temperature of Ti175 titanium alloy is selected as the β phase transformation point temperature.

[0077] This embodiment provides a method for phase transformation superplastic diffusion bonding of high-temperature titanium alloys, including the following steps:

[0078] Step 1): Grind the surfaces of Ti65 titanium alloy and Ti175 titanium alloy to be welded with 3000# sandpaper, and grind the other non-welding surfaces with 120# sandpaper to remove the oxide layer. Then clean them with acetone and alcohol by ultrasonic cleaning. Apply anti-oxidation paste evenly to the non-welding surfaces.

[0079] Step 2): Immerse the surface to be welded in the etching solution for 40 seconds, then remove it and clean it with alcohol and acetone by ultrasonic cleaning in sequence; wherein, the volume ratio of hydrogen fluoride, nitric acid and water in the etching solution is 1:4:495;

[0080] Step 3): Magnetron co-sputtering was performed on the surfaces of Ti65 and Ti175 titanium alloys to be welded. The argon flow rate was 25 sccm, the sputtering pressure was 1.1 Pa, the sputtering power of the high-purity iron target was 130 W, the sputtering power of the high-purity nickel target was 20 W, the single deposition time was 50 s, and the number of depositions was 18. After sputtering, the mass of the iron-nickel composite film on the surface to be welded on the Ti65 titanium alloy side was 0.80% of the mass of the Ti65 titanium alloy on this side, and the mass of the iron-nickel composite film on the surface to be welded on the Ti175 titanium alloy side was 0.76% of the mass of the Ti175 titanium alloy on this side. The mass ratio of iron to nickel was approximately 90:10.

[0081] Step 4): Anneal the Ti65 titanium alloy and Ti175 titanium alloy to be welded in a tube furnace under an argon atmosphere. The annealing temperature is 500℃ and the annealing time is 1h. First, the temperature is increased to 490℃ at a rate of 10℃ / min, and then increased to 500℃ at a rate of 1℃ / min. After holding at the temperature, the furnace is cooled to room temperature.

[0082] Step 5): Perform phase transformation superplastic diffusion bonding on the Ti65 titanium alloy and the Ti175 titanium alloy to be welded. The upper limit temperature for phase transformation superplastic diffusion bonding is T. max The lower limit temperature is 940℃, T. minThe heating rate v is 800℃. h The cooling rate v is 10℃ / s. c The speed is 20℃ / s, and the upper limit temperature T is... max and lower limit temperature T min The single heat preservation time t is 10s, the total number of cycles N is 23, the cooling method is high-speed argon air cooling, the argon flow rate is 20000sccm, and the welding pressure is 3MPa.

[0083] Example 4:

[0084] The materials used in this embodiment are ø40×5mm Ti60 titanium alloy and Ti175 titanium alloy. The Ti60 titanium alloy is a near-α titanium alloy of Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.3Si, and the β phase transformation temperature of the Ti60 titanium alloy is 1034℃. The Ti175 titanium alloy is an α+β titanium alloy of Ti-6.5Al-2Sn-3.5Zr-4Mo-1W-0.2Si, and the β phase transformation temperature of the Ti175 titanium alloy is 980℃. The β phase transformation temperature of the Ti175 titanium alloy is selected as the β phase transformation point temperature.

[0085] This embodiment provides a method for phase transformation superplastic diffusion bonding of high-temperature titanium alloys, including the following steps:

[0086] Step 1): Grind the surfaces of Ti60 titanium alloy and Ti175 titanium alloy to be welded with 3000# sandpaper, and grind the other non-welding surfaces with 120# sandpaper to remove the oxide layer. Then clean them with acetone and alcohol by ultrasonic cleaning. Apply anti-oxidation paste evenly to the non-welding surfaces.

[0087] Step 2): Immerse the surface to be welded in the etching solution for 45 seconds, then remove it and clean it with alcohol and acetone by ultrasonic cleaning in sequence; wherein, the volume ratio of hydrogen fluoride, nitric acid and water in the etching solution is 1:4:495;

[0088] Step 3): Magnetron co-sputtering was performed on the surfaces of Ti60 and Ti175 titanium alloys to be welded. The argon flow rate was 30 sccm, the sputtering pressure was 1.2 Pa, the sputtering power of the high-purity iron target was 120 W, the sputtering power of the high-purity nickel target was 45 W, the single deposition time was 60 s, and the number of depositions was 20. After sputtering, the mass of the iron-nickel composite film on the surface to be welded on the Ti60 titanium alloy side was 0.63% of the mass of the Ti60 titanium alloy on this side, and the mass of the iron-nickel composite film on the surface to be welded on the Ti75 titanium alloy side was 0.64% of the mass of the Ti75 titanium alloy on this side. The mass ratio of iron to nickel was approximately 80:20.

[0089] Step 4): Anneal the Ti60 titanium alloy and Ti175 titanium alloy to be welded in a tube furnace under an argon atmosphere. The annealing temperature is 600℃ and the annealing time is 3h. First, the temperature is increased to 590℃ at a rate of 10℃ / min, and then increased to 600℃ at a rate of 1℃ / min. After holding at the temperature, the furnace is cooled to room temperature.

[0090] Step 5): Perform phase transformation superplastic diffusion bonding on the Ti60 titanium alloy and the Ti175 titanium alloy to be welded. The upper limit temperature for phase transformation superplastic diffusion bonding is T. max The lower limit temperature is 930℃. min The heating rate v is 800℃. h The cooling rate v is 8℃ / s. c The speed is 18℃ / s, and the upper limit temperature T is... max and lower limit temperature T min The single heat preservation time t is 10s, the total number of cycles N is 20, the cooling method is high-speed argon air cooling, the argon flow rate is 36600sccm, and the welding pressure is 2.8MPa.

[0091] Comparative Example 1

[0092] The isothermal diffusion bonding method provided in this comparative example has the same steps 1) to 4) as the phase change superplastic diffusion bonding method provided in Example 1. The difference is that in step 5), the isothermal diffusion bonding is carried out at a temperature of 985°C, and the remaining reaction conditions are the same as in Example 1, so as to obtain the isothermal diffusion bonded titanium alloy welded workpiece.

[0093] Table 1

[0094] Comparison of room temperature tensile properties of titanium alloy welded workpieces in Example 1 and Comparative Example 1

[0095]

[0096] Mechanical properties of the welded workpieces were tested, and the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 1 were compared with those prepared in Comparative Example 1 by isothermal diffusion bonding at 985℃. The results are shown in Table 1. It can be seen that the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 1 have better strength and plasticity than those prepared in Comparative Example 1 by isothermal diffusion bonding. The tensile strength reaches 1134 MPa, the yield strength is 980 MPa, and the elongation is 7.26%, showing excellent comprehensive mechanical properties.

[0097] See Figure 2 In example (a), the phase transformation superplastic diffusion-bonded titanium alloy welded workpiece prepared in Example 1 shows a tight connection in the phase transformation superplastic welded joint area, with no obvious welding defects such as voids found. See also... Figure 2 In Comparative Example 1 (b), the isothermal diffusion bonded titanium alloy welded workpiece showed fine pore defects in the joint area due to insufficient welding time.

[0098] Comparative Example 2

[0099] The isothermal diffusion bonding method provided in this comparative example has the same steps 1) to 4) as the phase change superplastic diffusion bonding method provided in Example 2. The difference is that in step 5), the isothermal diffusion bonding is carried out at a temperature of 980°C, and the remaining reaction conditions are the same as in Example 2, so as to obtain the isothermal diffusion bonded titanium alloy welded workpiece.

[0100] Table 2

[0101] Comparison of room temperature tensile properties of titanium alloy welded workpieces in Example 2 and Comparative Example 2

[0102]

[0103] Mechanical properties of the welded workpieces were tested, and the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 2 were compared with those prepared in Comparative Example 2 by isothermal diffusion bonding at 980℃. The results are shown in Table 2. It can be seen that the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 2 have better strength and plasticity than those prepared in Comparative Example 2 by isothermal diffusion bonding. The tensile strength reaches 1024 MPa, the yield strength is 943 MPa, and the elongation is 6.49%, showing excellent comprehensive mechanical properties.

[0104] See Figure 3 In example (a), the phase transformation superplastic diffusion-bonded titanium alloy welded workpiece prepared in Example 2 exhibits a tight connection in the phase transformation superplastic welded joint area, with no obvious welding defects such as voids found. See also... Figure 3 In Comparative Example 2 (b), the isothermal diffusion bonded titanium alloy welded workpiece showed fine pore defects in the joint area due to insufficient welding time.

[0105] Comparative Example 3

[0106] The isothermal diffusion bonding method provided in this comparative example has the same steps 1) to 4) as the phase change superplastic diffusion bonding method provided in Example 3. The difference is that in step 5), the isothermal diffusion bonding is carried out at a temperature of 940°C, and the remaining reaction conditions are the same as in Example 3, so as to obtain the isothermal diffusion bonded titanium alloy welded workpiece.

[0107] Table 3

[0108] Room temperature tensile properties of titanium alloy welded workpieces in Example 3 and Comparative Example 3

[0109]

[0110] Mechanical properties of the welded workpieces were tested, and the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 3 were compared with those prepared in Comparative Example 3 by isothermal diffusion bonding at 940℃. The results are shown in Table 3. It can be seen that the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 3 have better strength and plasticity than those prepared in Comparative Example 3 by isothermal diffusion bonding. The tensile strength reaches 1005 MPa, the yield strength is 932 MPa, and the elongation is 6.35%, showing excellent comprehensive mechanical properties.

[0111] See Figure 4 In example (a), the phase transformation superplastic diffusion-bonded titanium alloy welded workpiece prepared in Example 3 shows a tight connection in the phase transformation superplastic welded joint area, with no obvious welding defects such as voids found. See also... Figure 4 In Comparative Example 3 (b), the isothermal diffusion bonded titanium alloy welded workpiece showed fine pore defects in the joint area due to insufficient welding time.

[0112] Comparative Example 4

[0113] The isothermal diffusion bonding method provided in this comparative example has the same steps 1) to 4) as the phase change superplastic diffusion bonding method provided in Example 4. The difference is that in step 5), the isothermal diffusion bonding is carried out at a temperature of 930°C, and the remaining reaction conditions are the same as in Example 4, so as to obtain the isothermal diffusion bonded titanium alloy welded workpiece.

[0114] Table 4

[0115] Room temperature tensile properties of titanium alloy welded workpieces in Example 4 and Comparative Example 4

[0116]

[0117] Mechanical properties of the welded workpieces were tested, and the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 4 were compared with those prepared in Comparative Example 4 by isothermal diffusion bonding at 930℃. The results are shown in Table 4. It can be seen that the phase change superplastic diffusion-bonded titanium alloy welded workpieces prepared in Example 4 have better strength and plasticity than those prepared in Comparative Example 4 by isothermal diffusion bonding. The tensile strength reaches 1045 MPa, the yield strength is 951 MPa, and the elongation is 6.52%, showing excellent comprehensive mechanical properties.

[0118] See Figure 5In example (a), the phase transformation superplastic diffusion-bonded titanium alloy welded workpiece prepared in Example 4 exhibits a tight connection in the phase transformation superplastic welded joint area, with no obvious welding defects such as voids found. See also... Figure 5 In Comparative Example 4 (b), the isothermal diffusion bonded titanium alloy welded workpiece showed fine pore defects in the joint area due to insufficient welding time.

[0119] Comparative Example 5

[0120] In the high-temperature titanium alloy phase change superplastic diffusion bonding method provided in this comparative example, steps 1) to 2) and 4) to 5) are the same as steps 1) to 2) and 4) to 5) in the phase change superplastic diffusion bonding method provided in Example 4. The difference is that in step 3), only an iron-nickel composite film with a mass ratio of iron to nickel of 95:5 is used, and the remaining reaction conditions are the same as in Example 4, so as to obtain a titanium alloy welded workpiece with phase change superplastic diffusion bonding.

[0121] The phase change superplastic diffusion-bonded titanium alloy welded workpiece prepared in this comparative example showed a significant decrease in plasticity compared to the phase change superplastic diffusion-bonded titanium alloy welded workpiece prepared in Example 4. It was found that there were large unsealed pores at the joint. This was due to the formation of brittle iron-titanium compounds and the short welding time, which did not allow enough time for diffusion.

[0122] Comparative Example 6

[0123] In the high-temperature titanium alloy phase change superplastic diffusion bonding method provided in this comparative example, steps 1) to 2) and 4) to 5) are the same as steps 1) to 2) and 4) to 5) in the phase change superplastic diffusion bonding method provided in Example 4. The difference is that in step 3), only an iron-nickel composite film with a mass ratio of iron to nickel of 65:35 is used, and the remaining reaction conditions are the same as in Example 4, so as to obtain a titanium alloy welded workpiece with phase change superplastic diffusion bonding.

[0124] The phase change superplastic diffusion-bonded titanium alloy welded workpiece prepared in this comparative example showed a significant decrease in plasticity compared to the phase change superplastic diffusion-bonded titanium alloy welded workpiece prepared in Example 4. It was found that there were large unsealed pores at the joint. This was due to the formation of brittle iron-titanium compounds and brittle nickel-titanium compounds, and the short welding time, which did not allow enough time for diffusion.

[0125] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method of high temperature titanium alloy phase transformation superplastic diffusion bonding, characterized in that, The method comprises the following steps: S1: sequentially performing pretreatment and chemical etching treatment on the surface to be welded of the high-temperature titanium alloy sample, then performing magnetron co-sputtering treatment, sputtering a layer of iron-nickel composite film on the surface to be welded of the high-temperature titanium alloy sample to obtain an intermediate sample, and then performing annealing treatment on the intermediate sample to obtain the surface to be welded plated with the layer of iron-nickel composite film; the iron-nickel composite film accounts for 0.55% to 0.80% of the mass of the high-temperature titanium alloy sample; the mass ratio of iron to nickel in the iron-nickel composite film is (70:30) to (90:10); S2: welding the surface to be welded plated with the layer of iron-nickel composite film through a phase transition superplastic diffusion process in a preset temperature range by multiple cycles of heating and cooling; in the multiple cycles of heating and cooling, the total cycle number of the cycles of heating and cooling is 20 to 30, the heating rate is 5 to 10 ℃ / s, and the cooling rate is 15 to 20 ℃ / s; in the multiple cycles of heating and cooling, the cooling mode is argon blowing air cooling; in the multiple cycles of heating and cooling, the single holding time of the upper limit temperature of the preset temperature range is 10 to 15 s, and the single holding time of the lower limit temperature of the preset temperature range is 10 to 15 s; the upper limit temperature of the preset temperature range is 40 to 50 ℃ below the selected beta phase transition point temperature; and the lower limit temperature of the preset temperature range is 800 to 850 ℃; when two high-temperature titanium alloy samples with different beta phase transition point temperatures are welded, the selected beta phase transition point temperature is the lowest beta phase transition point temperature among the high-temperature titanium alloy samples with different beta phase transition point temperatures.

2. The high temperature titanium alloy phase transformation superplastic diffusion bonding method according to claim 1, characterized in that, The pretreatment process comprises the following steps: the surface to be welded of the high-temperature titanium alloy sample is ground with 2000# to 3000# sandpaper, the non-welding surface of the high-temperature titanium alloy sample is ground with 120# to 200# sandpaper to remove the oxide skin, then the surface to be welded of the high-temperature titanium alloy sample is ultrasonically cleaned with acetone and alcohol in sequence, and finally silicate glass anti-oxidation paste is coated on the non-welding surface of the high-temperature titanium alloy sample.

3. The high temperature titanium alloy phase transformation superplastic diffusion bonding method of claim 1, wherein, The chemical etching treatment process comprises the following steps: the surface to be welded of the high-temperature titanium alloy sample after the pretreatment is immersed in an etching liquid, and then ultrasonically cleaned with alcohol and acetone in sequence.

4. The high temperature titanium alloy phase transformation superplastic diffusion bonding method according to claim 3, wherein, The etching liquid is composed of hydrogen fluoride, nitric acid and water, and the volume ratio of the hydrogen fluoride, the nitric acid and the water is 1:4:495 to 500; the immersion time is 30 to 45 s.

5. The high temperature titanium alloy phase transformation superplastic diffusion bonding method of claim 1, wherein, In the magnetron co-sputtering treatment, the target material is a high-purity iron target and a high-purity nickel target with a purity of 99.99%, the sputtering gas is argon with a purity of 99.99%, the flow rate of the argon is 10 to 30 sccm, the sputtering gas pressure is 0.8 to 1.2 Pa, the sputtering power of the high-purity iron target is 120 to 180 W, the sputtering power of the high-purity nickel target is 20 to 80 W, the single deposition time is 40 to 60 s, the deposition number is 15 to 20, and the rotation speed of the surface to be welded of the high-temperature titanium alloy sample is 150 to 200 r / min.

6. The high temperature titanium alloy phase transformation superplastic diffusion bonding method of claim 1, wherein, The welding pressure is 1 to 3 MPa; and the welding process maintains constant pressure diffusion.

7. The high temperature titanium alloy phase transformation superplastic diffusion bonding method according to claim 1, wherein, The atmosphere of the annealing treatment is an argon atmosphere, the annealing temperature of the annealing treatment is 300-600 DEG C, and the annealing time of the annealing treatment is 1-3 hours.

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