TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal spin friction welding method added with transition layer

Abstract

The invention provides a TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal spin friction welding method added with a transition layer, and belongs to the technical field of spin friction welding. The method comprises the steps that an inverse hyperbolic sine constitutive equation is used for searching a material which has plastic deformation adaptability with a TC4 titanium alloy and a GH4169 high-temperature alloy in a parameter space at the same time to serve as a transition layer material; the method comprises the following steps: firstly, carrying out first-time rotary friction welding on a TC4 titanium alloy and a transition layer material (or carrying out GH4169 high-temperature alloy and the transition layer material); the transition layer material part is cut for the connector of the TC4 titanium alloy / transition layer material (or GH4169 high-temperature alloy / transition layer material), and the transition layer material h is larger than or equal to 10 mm and larger than or equal to 5 mm. And second-time rotary friction welding of the TC4 titanium alloy and the GH4169 high-temperature alloy is conducted through shortening amount (h is larger than or equal to 10 mm and larger than or equal to 5 mm) control, and connection of the TC4 titanium alloy / GH4169 high-temperature alloy dissimilar materials added with the transition layer is achieved. The problem of deformation incoordination caused by large high-temperature strength difference of dissimilar materials is solved.

Description

Technical Field

[0001] This invention belongs to the field of rotary friction welding technology, specifically relating to a rotary friction welding method for dissimilar metals such as TC4 titanium alloy / GH4169 high-temperature alloy with an added transition layer. Background Technology

[0002] In the aerospace field, dissimilar material joining technology has become crucial for achieving lightweight structures and optimized performance. Particularly in the compressor section of advanced aero-engines, the use of transition joints between TC4 titanium alloy and GH4169 high-temperature alloy can significantly reduce weight and improve efficiency. However, the significant differences in the physical and chemical properties of these two materials have made reliable joining a major technical challenge for the industry.

[0003] Existing technologies mainly employ brazing, diffusion welding, and friction welding, but all of them have inherent defects: Brazing and diffusion welding rely on high-temperature processes, making it difficult to avoid intense metallurgical reactions between titanium (Ti) and nickel (Ni), which generate a large amount of brittle intermetallic compounds. This leads to severe degradation of joint strength (typically below 200 MPa), failing to meet the load-bearing requirements of structural components. Although some technologies have attempted to use composite interlayers for hot-pressing connections to suppress these compounds, this method is complex, costly, and inefficient, making it difficult to achieve industrial-scale mass production.

[0004] Direct friction welding, as an efficient solid-state joining technology, can alleviate compound problems to some extent, but faces a more prominent challenge of "plastic deformation mismatch." Because GH4169 maintains extremely high high-temperature strength at welding temperatures, while TC4 titanium alloy is relatively soft, severe plastic deformation occurs only on the TC4 side during friction welding, while the GH4169 side remains almost undeformed. This mismatch manifests macroscopically as flash on the joint existing only on the TC4 side, and microscopically as incomplete welding and long cracks at the joint interface, drastically reducing joint strength and reliability. Existing solutions include preheating GH4169 before welding to soften it, which can partially improve the plastic deformation mismatch. However, the preheating process introduces additional energy consumption and process complexity, and the high-temperature environment may actually exacerbate the interdiffusion of Ti and Ni elements, generating a continuous Ni-Ti brittle compound layer at the interface. This significantly affects the mechanical properties (strength and ductility) of the interface, leading to brittle fracture of the joint. Therefore, there is still room for improvement in joint strength (approximately 500 MPa) and joint ductility.

[0005] Currently, welding of titanium alloys / high-temperature alloys mainly involves brazing, diffusion welding with an intermediate layer, and friction welding that sacrifices a significant amount of TC4 titanium alloy base material. However, these methods offer limited improvement in joint performance, and the addition of an intermediate layer increases joint instability, while sacrificing a large amount of TC4 base material results in complex processes and high costs. Therefore, there is a need to develop a low-cost and simple welding process for welding TC4 titanium alloys and GH4169 high-temperature alloys. Summary of the Invention

[0006] The technical problem to be solved: To overcome the shortcomings of existing technologies, this invention provides a rotary friction welding method for dissimilar metals, TC4 titanium alloy / GH4169 high-temperature alloy, with an added transition layer. The method calculates parameters such as the thermal deformation activation energy and thermal diffusion rate of the materials using the inverse hyperbolic sine constitutive equation to identify a transition layer material that is compatible with both TC4 and GH4169 in terms of plastic deformation. A two-stage rotary friction welding process is employed (first welding TC4 / the transition layer, then welding GH4169 to form a TC4 / transition layer material / GH4169 composite joint). By using the transition layer as a "plastic deformation bridge," the problem of deformation incompatibility caused by the large difference in high-temperature strength between dissimilar materials is solved.

[0007] The technical solution of this invention is: a method for rotary friction welding of dissimilar metals, TC4 titanium alloy / GH4169 high-temperature alloy, with an added transition layer, comprising the following steps: Step 1: Screening transition layer materials based on the principle of plastic deformation adaptability: Collect the thermophysical parameters of TC4 titanium alloy, GH4169 high-temperature alloy and candidate transition layer materials, substitute them into the inverse hyperbolic sine constitutive equation, and calculate their temperature, stress and strain rate curves in the welding parameter space; by finding that the constitutive curves of the candidate transition layer materials and TC4 titanium alloy and GH4169 high-temperature alloy have a common solution domain within the set temperature, stress and strain rate range, the transition layer materials that can serve as plastic deformation adaptability bridges are screened out. Step 2: First rotational friction welding: The selected transition layer material is rotated and friction welded with TC4 titanium alloy to form a TC4 / transition layer primary joint; Alternatively, the selected transition layer material can be rotary friction welded to GH4169 high-temperature alloy to form a GH4169 high-temperature alloy / transition layer primary joint. Step 3: Joint processing: Process the outer side of the transition layer of the primary joint, retaining a transition layer with a thickness h of 5mm to 10mm; Step 4: Second Rotary Friction Welding: Rotate friction welding is performed on the transition layer end face of the processed TC4 / transition layer primary joint to GH4169 high-temperature alloy; or, rotation friction welding is performed on the transition layer end face of the processed GH4169 high-temperature alloy / transition layer primary joint to TC4 titanium alloy. The axial shortening during welding is controlled to be less than or equal to the thickness h, ultimately forming a TC4 alloy / transition layer / GH4169 high-temperature alloy composite joint. A further technical solution of the present invention is: in step 1, the inverse hyperbolic sine constitutive equation is:

[0008] In the formula, Let be the constitutive constant of the material. For stress, For strain rate, Q The activation energy is R, where R is the gas constant. T For temperature.

[0009] A further technical solution of the present invention is: in step 1, the constitutive curve is calculated and visualized by mathematical software, and the common solution domain refers to the coordinated plastic deformation that can occur between the transition layer material and TC4 titanium alloy and GH4169 high-temperature alloy under the same temperature, stress and strain rate parameters.

[0010] A further technical solution of the present invention is: the transition layer material is a metal material that has good plastic deformation compatibility with TC4 alloy and GH4169 high temperature alloy and can suppress the interdiffusion of Ti and Ni elements, preferably SUS321 stainless steel. A further technical solution of the present invention is: in step 2, the process parameters for the first rotary friction welding are: When the transition layer material is subjected to rotary friction welding with TC4 titanium alloy: the rotation speed is 600 RPM, the welding pressure is 300 MPa, the upsetting pressure is 350 MPa, and the axial shortening is controlled, with the axial shortening ≤ h. When the transition layer material is subjected to rotary friction welding with GH4169 high-temperature alloy, the rotation speed is 1100 RPM, the welding pressure is 150-200 MPa, the upsetting pressure is 1.5-2 times the welding pressure, and the axial shortening is ≤h.

[0011] A further technical solution of the present invention is: the axial shortening is selected as 5mm.

[0012] A further technical solution of the present invention is: in step 3, the end face of the processed transition layer is polished to make its surface roughness Ra≤0.8μm, and is cleaned with alcohol or acetone before welding.

[0013] A further technical solution of the present invention is: in step 4, the process parameters for the second rotary friction welding are: When the transition layer end face of the TC4 / transition layer primary joint is subjected to rotary friction welding with GH4169 high-temperature alloy: the rotation speed is 1100 RPM, the welding pressure is 150-200 MPa, and the upsetting pressure is 1.5-2 times the welding pressure. When the transition layer end face of the GH4169 high-temperature alloy / transition layer primary joint is subjected to rotary friction welding with TC4 titanium alloy: rotation speed 600RPM, welding pressure 300MPa, upsetting pressure 350MPa.

[0014] A TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal joint with an added transition layer, the joint having a three-layer composite structure, consisting of a TC4 titanium alloy layer, a transition layer and a GH4169 high-temperature alloy layer, which are bonded together by rotary friction welding. The transition layer is a metallic material that is compatible with both TC4 titanium alloy and GH4169 high-temperature alloy in terms of plastic deformation. It was selected and determined based on the fact that it shares a common plastic deformation region with both of them in the welding parameter space according to the inverse hyperbolic sine constitutive equation. The thickness of the transition layer is 5 mm to 10 mm; The interfaces between the TC4 titanium alloy layer and the transition layer, as well as the interfaces between the transition layer and the GH4169 high-temperature alloy layer, are densely bonded, suppressing the formation of a continuous brittle intermetallic compound layer in the Ni-Ti system, and the room temperature tensile strength of the joint is not less than 600 MPa.

[0015] Beneficial effects The beneficial effects of this invention are as follows: This invention introduces a transition layer with dual functions of "plastic deformation bridge" and "metallurgical barrier," and through a two-stage friction welding process, it physically blocks the direct contact between Ti in TC4 and Ni in GH4169, fundamentally inhibiting the formation of brittle intermetallic compounds. Furthermore, this transition layer exhibits plastic deformation compatibility with both base materials within the welding parameter space, enabling coordinated transfer of plastic deformation energy. This allows for sufficient and coordinated plastic flow on both the TC4 and GH4169 sides, completely eliminating interface cracks and incomplete welding defects caused by "plastic deformation mismatch." This synergistic effect increases the joint strength from less than 200 MPa using traditional methods to the 600 MPa level, achieving a significant performance improvement of over 300%. Specific effects are analyzed below: This invention is the first to introduce the hyperbolic sine constitutive equation into the material selection process for friction welding transition layers. By calculating the plastic deformation behavior of the material within the welding parameter space (temperature, stress, strain rate), the existence of a "plastic deformation fit zone" is used as the criterion for plastic deformation fit. This method transforms material selection from an experience-based "art" to a scientifically model-based "technology," greatly reducing the blind spots in material selection and R&D costs, and improving the success rate. The presence of the transition layer can significantly hinder the interdiffusion of Ni and Ti elements at the welding interface, effectively suppressing the formation of a continuous brittle phase in the Ni-Ti system, thereby significantly improving the joint strength. 3. The material selection method of this invention is not only applicable to the TC4 / GH4169 combination, but can also be extended to other soft / hard dissimilar metal combinations that are difficult to weld due to significant differences in physical and chemical properties (such as other titanium alloys / high-temperature alloys, aluminum / steel, etc.), providing a new and universal technical approach for a broad field of dissimilar material joining.

[0016] 4. This invention enables low-cost and high-efficiency welding of dissimilar metals such as TC4 titanium alloy / GH4169 high-temperature alloy, which are difficult to weld, and can achieve industrialized mass production. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a friction welding machine for implementing a rotary friction welding method for dissimilar metals, specifically TC4 titanium alloy / GH4169 high-temperature alloy with an added transition layer, in an embodiment of the present invention. Figure 2 This is a schematic diagram of two friction welding operations with a transition layer added in an embodiment of the present invention; Figure 3 This is the result of combining the constitutive equations of the TC4 titanium alloy / GH4169 high-temperature alloy base material and the transition layer material in the embodiments of the present invention; Figure 4 This is a friction welding sample with a transition layer added in an embodiment of the present invention; Figure 5 This is the cross-sectional morphology of the connector in an embodiment of the present invention; Figure 6 The figure shows the tensile test curve of the joint in an embodiment of the present invention. Detailed Implementation The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0018] In recent years, dissimilar material joining technology has gradually become one of the most critical and challenging technologies in the welding field. It can not only effectively reduce structural weight and energy consumption but also fully utilize the advantages of different materials, thus providing appropriate functionality for specific applications. Existing welding technologies for dissimilar materials such as TC4 titanium alloy / GH4169 high-temperature alloy mainly include brazing, diffusion welding, and friction welding. Brazing relies on the high-temperature melting of the filler metal, which spreads and wets the joint of the base materials, eventually forming a unified joint. Brazing of TC4 titanium alloy / GH4169 high-temperature alloy generally suffers from low joint strength. This is because the filler metal itself has relatively low strength, inferior to titanium alloys and high-temperature alloys. More importantly, the high-temperature brazing process still inevitably produces brittle intermetallic compounds. For diffusion welding, element diffusion at high temperatures still leads to the formation of a brittle and hard intermetallic compound layer at the interface, resulting in low weld strength (less than 200 MPa) and limited application value. Adding an intermediate layer can improve this, but this leads to unstable interface formation and low welding efficiency. Friction welding itself has advantages such as high welding efficiency, low cost, environmental friendliness, and high energy conversion rate, making it suitable for large-scale automated industrial production. However, due to the significant difference in high-temperature strength between the two metals, a "plastic deformation mismatch" phenomenon occurs during friction welding. Macroscopically, this manifests as plastic deformation occurring only on the TC4 side, forming flash. In terms of interface formation, it manifests as long cracks and incomplete fusion along the interface direction in the post-weld joint, significantly affecting the joint's mechanical properties. Solving the "plastic deformation mismatch" problem in the friction welding process of titanium alloys / high-temperature alloys would greatly expand the application range of TC4 titanium alloy / GH4169 high-temperature alloy.

[0019] Based on this, this invention develops a rotary friction welding method for dissimilar metals, TC4 titanium alloy / GH4169 high-temperature alloy, with an added transition layer. It also provides a new approach for rotary friction welding of other soft / hard alloy dissimilar materials. This method introduces the concept of plastic deformation compatibility. First, by calculating the constitutive equations of different materials, a mathematical expression of the plastic deformation compatibility concept is obtained and expressed using a three-dimensional visualization curve. Materials possessing plastic deformation compatibility with both TC4 titanium alloy and GH4169 high-temperature alloy are sought as transition layer materials. Adding a transition layer material not only solves the "plastic deformation mismatch" problem at the TC4 / GH4169 alloy interface during welding but also hinders the interdiffusion of Ti and Ni elements, suppresses the formation of brittle and hard intermetallic compounds, and significantly improves the welding strength of both materials. It also has the advantages of simple process and low cost, making it suitable for industrial mass production. Furthermore, this method can be applied to other soft / hard alloy combinations (except for TC4 titanium alloy / GH4169 high-temperature alloy combinations). The specific technical solution is as follows: Step 1: Screening transition layer materials based on the principle of plastic deformation adaptability: Thermophysical parameters of TC4 titanium alloy, GH4169 high-temperature alloy and candidate transition layer materials are collected, substituted into the inverse hyperbolic sine constitutive equation, and their three-dimensional curves of temperature, stress and strain rate in the welding parameter space are calculated; by finding that the constitutive curves of candidate transition layer materials and TC4 titanium alloy and GH4169 high-temperature alloy have a common solution domain within the set temperature, stress and strain rate range, transition layer materials that can serve as plastic deformation adaptability bridges are screened. Step 2: First rotational friction welding: The selected transition layer material is rotated and friction welded with TC4 titanium alloy to form a TC4 / transition layer primary joint; Alternatively, the selected transition layer material can be rotary friction welded to GH4169 high-temperature alloy to form a GH4169 high-temperature alloy / transition layer primary joint. Step 3: Joint processing: Process the outer side of the transition layer of the primary joint, retaining a transition layer with a thickness h of 5mm to 10mm; Step 4: Second Rotary Friction Welding: Rotate friction welding is performed on the transition layer end face of the processed TC4 / transition layer primary joint to GH4169 high-temperature alloy; or, rotation friction welding is performed on the transition layer end face of the processed GH4169 high-temperature alloy / transition layer primary joint to TC4 titanium alloy. The axial shortening during welding is controlled to be less than or equal to the thickness h, ultimately forming a TC4 alloy / transition layer / GH4169 high-temperature alloy composite joint.

[0020] The present invention also proposes a TC4 titanium alloy / GH4169 high temperature alloy dissimilar metal joint with an added transition layer. The joint is a three-layer composite structure, which is formed by a TC4 titanium alloy layer, a transition layer and a GH4169 high temperature alloy layer in sequence through rotary friction welding. The transition layer is a metallic material that is compatible with both TC4 titanium alloy and GH4169 high-temperature alloy in terms of plastic deformation. It was selected and determined based on the fact that it shares a common plastic deformation region with both of them in the welding parameter space according to the inverse hyperbolic sine constitutive equation. The thickness of the transition layer is 5 mm to 10 mm; The interfaces between the TC4 titanium alloy layer and the transition layer, as well as the interfaces between the transition layer and the GH4169 high-temperature alloy layer, are densely bonded, suppressing the formation of a continuous brittle intermetallic compound layer in the Ni-Ti system, and the room temperature tensile strength of the joint is not less than 600 MPa.

[0021] The above technical solution will be further analyzed below with reference to the accompanying drawings and examples: In one embodiment, a rotary friction welding method for dissimilar metals of TC4 titanium alloy / GH4169 high-temperature alloy with an added transition layer is described: SUS321 stainless steel is used as a transition layer to connect TC4 titanium alloy and GH4169 high-temperature alloy.

[0022] 1. Preparation of experimental materials Base materials: TC4 titanium alloy and GH4169 nickel-based high-temperature alloy, both of which are bars with a diameter of φ25 mm and a length of 100 mm.

[0023] Candidate transition layer material: SUS321 austenitic stainless steel, also in the form of bars with a diameter of φ25 mm.

[0024] Pretreatment: All materials' weldable ends are machined on a lathe to ensure flatness, with a surface roughness Ra ≤ 0.8 μm. The ends are then ultrasonically cleaned with anhydrous ethanol to remove oil and impurities, and dried for later use.

[0025] 2. Selection of transition layer materials (Step 1) Theoretical screening: Thermal deformation activation energy (Q), thermal diffusivity, and thermal conductivity, among other physical properties, were collected from TC4, GH4169, and SUS321 and substituted into parameters suitable for describing a wide range of stresses (0–600 MPa) and strain rates (0–100 s⁻¹). -1 In the inverse hyperbolic sine constitutive equation with respect to temperature (0.7–0.9 Tm):

[0026] In the formula, Let be the constitutive constant of the material. For stress, For strain rate, Q The activation energy is R, where R is the gas constant. T For temperature.

[0027] The constitutive curves of the three components in the same parameter space (temperature-stress-strain rate) were calculated and plotted using Matlab software in three dimensions (see [link]). Figure 3In the figure, the red-represented TC4 titanium alloy and the blue-represented GH4169 high-temperature alloy show no overlap in stress, strain rate, and temperature parameters across the entire welding parameter space (stress mapped to welding pressure, strain rate mapped to welding rotation speed). This indicates that the two base materials do not undergo joint plastic deformation at the same temperature. This phenomenon suggests that TC4 titanium alloy and GH4169 high-temperature alloy lack plastic deformation compatibility, resulting in continuous plastic deformation on the TC4 side during welding, while the GH4169 side remains undeformed. Based on the above analysis, a region should be identified within the welding parameter space where a transition material intersects with both TC4 titanium alloy and GH4169 high-temperature alloy. Subsequently, it should be determined whether the transition layer material possesses plastic deformation compatibility with both TC4 titanium alloy and GH4169 high-temperature alloy. For example... Figure 3 In the image representation, both SUS321 stainless steel and TC17 titanium alloy have two overlapping regions of base materials. However, the difference lies in their compatibility. SUS312 stainless steel exhibits the same temperature, stress, and strain rate overlap with both TC4 titanium alloy and GH4169 high-temperature alloy within the welding parameter space, making it a suitable transition layer material. In contrast, TC17 titanium alloy only undergoes common plastic deformation with GH4169 high-temperature alloy at a minimum of 1650K, exceeding the parameter space of friction welding, thus making it unsuitable as a transition layer material.

[0028] Screening Result Judgment: Visualization results show that the constitutive curve of SUS321 stainless steel is approximately at 1073K (800℃), with a stress range of 200-400MPa and a strain rate of 10-50s, compared to the curves of TC4 titanium alloy and GH4169 high-temperature alloy. -1 Temperature approximately 1473 K (1200 °C), stress range 100–200 MPa, strain rate 1–20 s -1 There exists a suitable common solution domain (i.e., curve intersection) within the parameter region. This indicates that within this friction welding process window, SUS321 can undergo coordinated plastic deformation with TC4 titanium alloy and GH4169 high-temperature alloy, possessing the "plastic deformation adaptability" required as a transition layer. Therefore, SUS321 was selected as the transition layer material in this embodiment.

[0029] 3. First rotational friction welding: Welding TC4 to SUS321 (perform step 2) Clamping: Clamp the TC4 titanium alloy bar to the fixed end of the friction welding machine, and clamp the SUS321 stainless steel bar to the rotating end.

[0030] Welding parameter settings and execution: Speed: 600 RPM; Welding pressure: 300 MPa; Upsetting pressure: 350 MPa; Control mode: Axial shortening control, set shortening amount to 5mm Start the welding machine to complete the welding process. After welding, the workpiece is allowed to cool naturally in the air, forming a TC4 titanium alloy / SUS321 primary joint.

[0031] 4. Joint processing and preparation (proceed with step 3) The excess length was removed from one side of the SUS321 using a wire EDM machine, precisely preserving a transition layer thickness of 5 mm.

[0032] When selecting the thickness of the transition layer, it is necessary to consider that an excessively thick transition layer will result in a larger shrinkage during the second friction welding, leading to increased material loss and friction welding time, thus increasing costs and interface brittleness. Conversely, an excessively thin transition layer will damage the original TC4 / transition layer material welding interface, causing direct contact between TC4 and GH4169, thereby negating the purpose of adding the transition layer. Based on the above analysis, it is recommended to control the intermediate layer thickness within the range of 10 mm ≥ h ≥ 5 mm.

[0033] The retained SUS321 end face was re-machined to ensure a smooth surface with a roughness Ra ≤ 0.8μm, then cleaned with ethanol and dried in preparation for the second welding.

[0034] 5. Second rotary friction welding: Welding of SUS321 and GH4169 high-temperature alloys (step 4) Clamping: Clamp the above-processed TC4 titanium alloy / SUS321 connector on the fixed end of the welding machine (SUS321 end facing outwards), and clamp the GH4169 high temperature alloy bar on the rotating end.

[0035] Welding parameter settings and execution: Speed: 1100 RPM; Welding pressure: 150 MPa; Upsetting pressure: 300 MPa; Control mode: Axial shortening control, with a set shortening amount of 5 mm. Start the welding machine and complete the welding. After welding, the workpiece cools naturally, and finally a TC4 / SUS321 / GH4169 three-layer composite dissimilar metal joint is obtained.

[0036] 6. Joint performance and microstructure inspection To verify the effectiveness of this embodiment, the obtained assembly was subjected to the following tests: Macroscopic morphological observation: such as Figure 4 and Figure 5As shown, the joint is well formed, and obvious flash is produced on both the TC4 side and the GH4169 side, indicating that plastic deformation occurs in a coordinated manner on both sides, and the problem of "plastic deformation mismatch" has been successfully solved.

[0037] Microstructure analysis: Metallographic observation and EDS line scanning analysis were performed on the cross-section of the joint. The results showed that the TC4 / SUS321 interface and the SUS321 / GH4169 interface were densely bonded, without a continuously distributed brittle intermetallic compound layer. The SUS321 transition layer effectively blocked the interdiffusion of Ti and Ni elements.

[0038] To verify the effectiveness of this method, this embodiment provides a specific implementation case. The experimental materials used were TC4 titanium alloy / SUS321 stainless steel / GH4169 high-temperature alloy. A welding method with an added transition layer material was used to achieve the connection between the TC4 titanium alloy and the GH4169 high-temperature alloy. The experimental results (joint macroscopic morphology, joint tensile test curve) and actual data are shown below. Figure 1-6 As can be seen, the TC4 titanium alloy / GH4169 high-temperature alloy joint welded by this method improves the "plastic deformation mismatch" problem. The difficult-to-deform GH4169 high-temperature alloy undergoes significant plastic deformation, making the deformation of GH4169 high-temperature alloy and TC4 titanium alloy more coordinated. This welding method significantly improves the welding strength, enabling the joint strength to reach the 600MPa level.

[0039] Comparative example (traditional direct friction welding) On the same equipment, without adding any transition layer, an attempt was made to directly friction weld TC4 titanium alloy and GH4169 high-temperature alloy. Using optimized parameters (including increased rotation speed and pressure), macroscopic cracks appeared along the interface in the weld joint. Tensile testing showed that its strength was less than 150 MPa, and brittle fracture occurred at the interface. Microstructural analysis revealed a large amount of Ti-Ni intermetallic compounds at the interface. This comparison fully demonstrates the effectiveness and necessity of this invention in solving the core technical problem.

[0040] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for transition layer added TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding, characterized in that, The method comprises the following steps: Step 1: screening of transition layer material based on plastic deformation adaptability principle: collecting the thermophysical parameters of TC4 titanium alloy, GH4169 high-temperature alloy and candidate transition layer material, substituting into the inverse hyperbolic sine constitutive equation, calculating the temperature, stress and strain rate curves of the transition layer material in the welding parameter space; by finding that the constitutive curves of the candidate transition layer material, TC4 titanium alloy and GH4169 high-temperature alloy all have a common solution domain in the set temperature, stress and strain rate range, the transition layer material that can serve as a plastic deformation adaptability bridge is screened out; Step 2: first rotary friction welding: the screened transition layer material is rotary friction welded with TC4 titanium alloy to form a TC4 / transition layer primary joint; or the screened transition layer material is rotary friction welded with GH4169 high-temperature alloy to form a GH4169 high-temperature alloy / transition layer primary joint; Step 3: joint processing: processing the outside of the transition layer of the primary joint to retain a transition layer with a thickness h of 5-10 mm; Step 4: second rotary friction welding: rotary friction welding the transition layer end face of the processed TC4 / transition layer primary joint with GH4169 high-temperature alloy; or rotary friction welding the transition layer end face of the processed GH4169 high-temperature alloy / transition layer primary joint with TC4 titanium alloy; The welding axial shortening amount is controlled to be less than or equal to the thickness h, and finally a TC4 alloy / transition layer / GH4169 high-temperature alloy composite joint is formed. In the step 1, the inverse hyperbolic sine constitutive equation is:

2. The method for TC4 titanium alloy / GH4169 superalloy dissimilar metal rotary friction welding with transition layer according to claim 1, characterized in that: In the step 1, the constitutive curves are calculated and visualized by mathematical software, and the common solution domain refers to that the transition layer material, TC4 titanium alloy and GH4169 high-temperature alloy can all undergo coordinated plastic deformation under the same temperature, stress and strain rate parameters. wherein is the material's constitutive constant, is the stress, is the strain rate, Q is the activation energy, R is the gas constant, T is the temperature.

3. The method for TC4 titanium alloy / GH4169 superalloy dissimilar metal rotary friction welding with transition layer according to claim 2, characterized in that: The transition layer material is a metal material that has good plastic deformation adaptability with TC4 alloy and GH4169 high-temperature alloy and can inhibit the mutual diffusion of Ti and Ni elements, and is preferably SUS321 stainless steel.

4. The method for TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding with transition layer according to claim 1, characterized in that: In the step 2, the process parameters of the first rotary friction welding are:

5. The method for TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding with transition layer according to claim 1, characterized in that: When the transition layer material is rotary friction welded with TC4 titanium alloy: rotational speed 600 RPM, welding pressure 300 MPa, upset pressure 350 MPa, axial shortening amount control, axial shortening amount ≤h; When the transition layer material is rotary friction welded with GH4169 high-temperature alloy: rotational speed 1100 RPM, welding pressure 150-200 MPa, upset pressure is 1.5-2 times the welding pressure, axial shortening amount ≤h. The axial shortening amount is selected to be 5 mm.

6. The method for TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding with transition layer according to claim 5, characterized in that: In the step 3, the processed transition layer end face is polished to have a surface roughness Ra≤0.8 μm, and is cleaned with alcohol or acetone before welding.

7. The method for TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding with transition layer according to claim 1, characterized in that: In the step 4, the process parameters of the second rotary friction welding are:

8. The method for TC4 titanium alloy / GH4169 high-temperature alloy dissimilar metal rotary friction welding with transition layer according to claim 1, characterized in that: ​ When the transition layer end face of the TC4 / transition layer primary joint is rotationally friction welded with the GH4169 high-temperature alloy: rotation speed 1100 RPM, welding pressure 150-200 MPa, and upset pressure 1.5-2 times the welding pressure; When the transition layer end face of the GH4169 high-temperature alloy / transition layer primary joint is rotationally friction welded with the TC4 titanium alloy: rotation speed 600 RPM, welding pressure 300 MPa, and upset pressure 350 MPa.

9. A TC4 titanium alloy / GH4169 superalloy dissimilar metal joint with a transition layer, prepared by the method of claim 1-8; characterized in that, The joint body is a three-layer composite structure, sequentially comprising a TC4 titanium alloy layer, a transition layer, and a GH4169 high-temperature alloy layer, which are solid-phase combined by rotationally friction welding; The transition layer is a metallic material that has plastic deformation compatibility with both the TC4 titanium alloy and the GH4169 high-temperature alloy, and is screened and determined based on the fact that it has a common plastic deformation region with both of them in the welding parameter space according to the inverse hyperbolic sine constitutive equation; The thickness of the transition layer is 5-10 mm; The interfaces between the TC4 titanium alloy layer and the transition layer and between the transition layer and the GH4169 high-temperature alloy layer are both combined densely, continuous brittle intermetallic compound layers of the Ni-Ti system are inhibited from being formed, and the room-temperature tensile strength of the joint body is not less than 600 MPa.

Images