Method for diffusion bonding of tc4 titanium alloy at low temperature based on double nanocrystallization and high-entropy alloy interlayer

Abstract

The application discloses a TC4 titanium alloy low-temperature diffusion welding method based on double nanocrystallization and high-entropy alloy interlayer and belongs to the technical field of welding. The application adopts ultrasonic rolling to process TC4 titanium alloy base material, obtains nanocrystallized TC4 titanium alloy base material, adopts a high-entropy alloy interlayer composed of Ti 35%, Zr 25%, Co 10%, Ni 10%, Cu 7%, Nb 10% and Y 3% and is nanocrystallized, finally, the nanocrystallized high-entropy alloy interlayer is arranged in the middle of the nanocrystallized TC4 titanium alloy base material to perform diffusion welding, and a TC4 titanium alloy welded joint is obtained. The application successfully connects the TC4 titanium alloy by using the nanocrystallized high-entropy alloy interlayer, the obtained weld is defect-free, and high-quality strong-tough diffusion connection of the TC4 titanium alloy is realized.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and specifically to a low-temperature diffusion welding method for TC4 titanium alloy based on a dual-nanoscale and high-entropy alloy interlayer. Background Technology

[0002] TC4 (Ti-6Al-4V) alloy, due to its low density, high specific strength, and excellent resistance to environmental corrosion, is irreplaceable in the manufacturing of key hot-end components for aero-engines. However, traditional diffusion welding processes face two major technical bottlenecks: first, insufficient interface matching between the intermediate layer material and the substrate easily leads to local unbonded defects and excessive thermomechanical deformation of the substrate; second, the dynamic recrystallization behavior of the base material under cyclic thermo-mechanical coupling loads severely restricts the high-temperature durability of the joints. Therefore, how to synergistically improve the performance of TC4 alloy and the compatibility of the joining system through material modification and interface optimization has become a critical technical bottleneck that urgently needs to be overcome in the current field of high-reliability aero-engine component manufacturing.

[0003] Currently, in the diffusion welding of TC4 titanium alloy, the literature "Lv Tao, Yang Wulin, Lin Peng, et al. Diffusion welding process of TC4 titanium alloy with Ni-based alloy as intermediate layer [J]. Welding Technology, 2011, 40(09):27-31.DOI:10.13846 / j.cnki.cn12-1070 / tg.2011.09.011." discloses a method using Ni-based intermediate layer (Ni 82 TC4 diffusion welding of CrSiB was achieved at welding temperatures of 940 ℃~1020 ℃ and holding times of 20~150 min. It can be seen that the required welding temperature is relatively high and the holding time is relatively long, which may lead to grain coarsening in the titanium alloy, thereby reducing the mechanical properties of the diffusion weld joint. Therefore, there is an urgent need for a method that can diffusion weld TC4 titanium alloy at low temperature conditions. Summary of the Invention

[0004] To address the shortcomings mentioned in the background technology, this invention proposes a low-temperature diffusion welding method for TC4 titanium alloy based on a dual-nanoscale and high-entropy alloy interlayer. Ultrasonic rolling treatment of the TC4 base material significantly reduces its surface roughness, thereby increasing the effective contact area, reducing interfacial gaps, and promoting atomic diffusion. This is achieved by introducing a nanoscale high-entropy alloy interlayer, Ti. 35 Zr 25 Co 10 Ni 10 Cu7Nb 10 Y3 promotes element diffusion at the joint interface. Meanwhile, the micro-pits generated on the material surface after ultrasonic rolling can be fully filled by the nano high-entropy intermediate layer, improving the uniformity of the interface contact.

[0005] To achieve the above objectives, this invention provides a low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer, comprising the following steps:

[0006] Step 1: Prepare nano-sized TC4 titanium alloy base material. The TC4 titanium alloy base material is treated with ultrasonic rolling to obtain a surface-nano-sized TC4 titanium alloy base material.

[0007] Step 2: Prepare a high-entropy alloy interlayer; the chemical composition of the high-entropy alloy interlayer, by mass percentage, consists of Ti 35%, Zr 25%, Co 10%, Ni 10%, Cu 7%, Nb 10%, and Y 3%;

[0008] Step 3: Prepare a nano-sized high-entropy alloy intermediate layer; use laser shock to obtain the nano-sized high-entropy alloy intermediate layer;

[0009] Step 4: Place the nano-sized high-entropy alloy intermediate layer between the upper and lower layers of nano-sized TC4 titanium alloy base material, and place the whole assembly in a vacuum diffusion welding furnace to perform diffusion welding using a segmented heating method to obtain a TC4 titanium alloy welded joint.

[0010] Preferably, in step 1, during the ultrasonic rolling process of TC4 titanium alloy base material, the frequency is 20kHz~40kHz, the amplitude is 5μm~20μm, the workpiece rotation speed is 300r / min, the feed speed is 0.05mm / r, the number of rolling processes is 4, and the static pressure is 110N~150N.

[0011] Preferably, the grain size of the nano-sized TC4 titanium alloy substrate is 170nm~250nm, and the surface roughness is 0.013μm~0.027μm.

[0012] Preferably, before ultrasonic rolling treatment of the TC4 titanium alloy base material in step 1, the TC4 titanium alloy base material is ground, polished, cleaned and dried.

[0013] Preferably, in the process of preparing the high-entropy alloy intermediate layer in step 2, Ti, Zr, Co, Ni, Cu, Nb, and Y metal powders with a purity greater than 99.9% are weighed according to the stated mass percentages, and the high-entropy alloy intermediate layer is prepared by arc melting.

[0014] Preferably, in step 3, before preparing the nano-sized high-entropy alloy intermediate layer, the high-entropy alloy intermediate layer is cut and polished so that the thickness of the high-entropy alloy intermediate layer is 0.1mm~0.2mm and the surface roughness is 0.015μm~0.02μm.

[0015] Preferably, in step 3, during the laser shock process of the high-entropy alloy intermediate layer, the laser energy is 7J-10J, the pulse width is 10ns-15ns, the number of shocks is 3-5, the pulse frequency is 5Hz, the spot size is 2mm, and the absorption layer used is aluminum foil.

[0016] Preferably, the grain size of the nano-sized high-entropy alloy intermediate layer is 200nm~300nm.

[0017] Preferably, in the diffusion welding process using segmented heating in step 4, the first stage involves heating from room temperature to 300°C at a heating rate of 10°C / min, and holding at 300°C for 10 minutes; the second stage involves heating from 300°C to 600°C at a heating rate of 10°C / min, and holding at 600°C for 10 minutes; the third stage involves heating from 600°C to a welding temperature of 750°C~800°C at a heating rate of 10°C / min, after which the heating process ends; finally, the welding temperature of 750°C~800°C is held for 30 minutes while applying a pressure of 0.5MPa~5MPa; after the holding period, the furnace is cooled to room temperature, the pressure is reduced to zero, and the welding is completed.

[0018] Preferably, the vacuum degree of the vacuum diffusion welding furnace is ≤5×10⁻⁶. -3 Pa.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] This invention employs ultrasonic rolling to strengthen the surface of TC4 titanium alloy, resulting in a surface nanocrystalline TC4 titanium alloy. Simultaneously, it utilizes a high-entropy alloy obtained through laser shock as an intermediate layer, providing more diffusion driving force and diffusion channels for atomic diffusion, thereby improving the overall quality of the TC4 titanium alloy joint. This invention introduces a nanocrystalline high-entropy alloy intermediate layer, Ti... 35 Zr 25 Co 10 Ni 10 Cu7Nb 10 Y3 promotes element diffusion at the joint interface. Meanwhile, the micro-pits generated on the material surface after ultrasonic rolling can be fully filled by the nano high-entropy intermediate layer, improving the uniformity of the interface contact.

[0021] This invention employs a diffusion welding method, which successfully connects TC4 titanium alloy at low temperature using a nano high-entropy alloy interlayer, and the resulting weld is defect-free, achieving a high-quality, strong and tough diffusion connection of TC4 titanium alloy. Attached Figure Description

[0022] Figure 1 This is a SEM image of the surface microstructure of the TC4 titanium alloy base material after laser shock in Example 1 of this invention.

[0023] Figure 2 This is a SEM image of the fracture morphology of the TC4 titanium alloy diffusion welded head in Example 1 of this invention. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] This invention provides a low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer, comprising the following steps:

[0026] Step 1: Prepare nano-sized TC4 titanium alloy base material. The TC4 titanium alloy base material is treated with ultrasonic rolling to obtain a surface-nano-sized TC4 titanium alloy base material.

[0027] This invention utilizes ultrasonic rolling to treat TC4 titanium alloy base material, significantly enhancing its stress and corrosion resistance. Furthermore, it forms a gradient hardening layer on the surface of the TC4 titanium alloy base material, progressing from the surface inwards. The grain size at the outermost surface of the hardening layer decreases, while the grain size increases with increasing distance from the outermost surface. This reduction in grain size significantly increases the grain boundary area, providing more atomic diffusion channels. Simultaneously, ultrasonic rolling greatly reduces the surface roughness of the base material, thereby increasing the effective contact area, reducing interfacial gaps, and promoting atomic diffusion.

[0028] Specifically, in step 1, during the ultrasonic rolling process of TC4 titanium alloy base material, the preferred frequency is 20kHz~40kHz, for example, 20kHz, 30kHz, or 40kHz; the preferred amplitude is 5μm~20μm, for example, 5μm, 10μm, 15μm, or 20μm; the workpiece rotation speed is 300r / min; the feed rate is 0.05mm / r; the number of rolling processes is 4; and the static pressure is 110N~150N.

[0029] Specifically, in step 1, the grain size of the nano-sized TC4 titanium alloy substrate is preferably 170nm~250nm, for example, it can be 170nm, 200nm, 220nm, or 250nm, and the surface roughness is 0.013μm~0.027μm.

[0030] Specifically, in step 1, before ultrasonically rolling the TC4 titanium alloy base material, the TC4 titanium alloy base material is first polished with 400#, 800#, 1500# and 2000# sandpaper in sequence and polished with a SiO2-H2O2 polishing machine. After that, it is ultrasonically cleaned for 10 minutes and then dried.

[0031] Step 2: Prepare a high-entropy alloy interlayer; the chemical composition of the high-entropy alloy interlayer, by mass percentage, consists of Ti 35%, Zr 25%, Co 10%, Ni 10%, Cu 7%, N 10%, and Y 3%;

[0032] This invention achieves synergistic performance optimization through a designed seven-element high-entropy alloy interlayer. The slow diffusion effect effectively suppresses the rapid segregation of some components, preventing the formation of coarse, brittle intermetallic compounds and promoting the formation of fine, dispersed reinforcing phases in the interface reaction layer. The multi-principal solid solution itself possesses excellent high-temperature stability and corrosion resistance, ensuring the long-term reliability of the joint under harsh environments. Ti and Zr, as matrix compatibility elements, with their crystal structures similar to TC4 alloys, ensure good structural matching and stability at the interface, effectively reducing the heterojunction interface energy. Co, Ni, and Cu, as melting point reducing elements, lower the solidus temperature of the system and, during the heating process... The intermediate layer undergoes a eutectic reaction with elements such as Ti and Zr, producing a low-melting-point eutectic phase at a lower temperature. This further lowers the solid-liquid phase temperature of the alloy, enabling the intermediate layer to possess excellent plasticity at a lower welding temperature. It can better fill interfacial gaps, significantly improve interfacial wettability, and promote pore healing. At the same time, its moderate diffusion rate avoids excessive growth of the interfacial reaction layer. Nb, as a β-phase stabilizer and grain refiner, diffuses to the interface side of the base material, stabilizing the β-Ti phase, refining the grains, and improving the strength and toughness of the interfacial region. Y, as a grain boundary purifying and antioxidant element, has extremely high oxygen affinity and preferentially reacts with interfacial oxygen to form stable oxides, effectively purifying grain boundaries and inhibiting interfacial oxidation embrittlement.

[0033] Specifically, in the process of preparing the high-entropy alloy intermediate layer, Ti, Zr, Co, Ni, Cu, Nb, and Y metal powders with a purity greater than 99.9% are weighed according to the above-mentioned mass percentages and prepared by electric arc melting method to obtain the high-entropy alloy intermediate layer.

[0034] Step 3: Prepare a nano-sized high-entropy alloy interlayer; use laser shock to obtain a nano-sized high-entropy alloy interlayer.

[0035] Specifically, before preparing the nano-sized high-entropy alloy interlayer, the high-entropy alloy interlayer was cut into thin slices of 6mm×6mm×0.2mm using an electrical discharge wire cutter. The slices were then polished to 0.1mm using 400#, 800#, 1500# and 2000# sandpaper, respectively, resulting in a surface roughness of 0.015μm~0.02μm.

[0036] Specifically, in step 3, during the laser shock process of the high-entropy alloy interlayer, the laser energy is preferably 7J~10J, for example, 7J, 8J, 9J, or 10J; the pulse width is preferably 10ns~15ns, for example, 10ns, 11ns, 12ns, 13ns, 14ns, or 15ns; the number of shocks is preferably 3~5, for example, 3, 4, or 5; the pulse frequency is 5Hz; the spot size is 2mm; the absorption layer used is aluminum foil; and the grain size of the obtained nano-sized high-entropy alloy interlayer is preferably 200nm~300nm, for example, 200nm, 220nm, 240nm, 260nm, 280nm, or 300nm.

[0037] Step 4: Place the nano-sized high-entropy alloy intermediate layer between the upper and lower nano-sized TC4 titanium alloy base materials, and place the whole assembly in a vacuum diffusion welding furnace to perform diffusion welding using a segmented heating method to obtain the TC4 titanium alloy welded joint.

[0038] Specifically, in step 4, during the diffusion welding process using a segmented heating method, the first stage involves heating from room temperature to 300°C at a heating rate of 10°C / min, and holding at 300°C for 10 minutes; the second stage involves heating from 300°C to 600°C at a heating rate of 10°C / min, and holding at 600°C for 10 minutes; the third stage involves heating from 600°C to the welding temperature at a heating rate of 10°C / min, preferably 750°C to 800°C, for example, 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C, after which the heating process ends; finally, the welding temperature is maintained at 750°C to 800°C. Hold at ℃ for 30 minutes while applying a pressure of preferably 0.5MPa to 5MPa, such as 0.5MPa, 1.5MPa, 2.5MPa, 3.5MPa, or 5MPa. After holding at ℃, cool with the furnace to room temperature, and the pressure will return to zero, thus completing the welding process.

[0039] Specifically, the vacuum degree of the vacuum diffusion welding furnace is ≤5×10 -3 Pa.

[0040] In some embodiments of the present invention, the intermediate layer used in the present invention is a nano-high entropy alloy Ti. 35 Zr 25 Co 10 Ni10 Cu7Nb 10 Y3 nanomaterials possess high activity, low diffusion activation energy, and a high atomic diffusion coefficient, enabling them to lower the welding temperature in diffusion welding, thus allowing the base materials to be joined at a lower temperature and in a shorter time. The residual stress and lattice distortion energy generated by ultrasonic rolling provide sufficient driving force for atomic diffusion. The high-density grain boundaries of the nano-high-entropy alloy provide rapid diffusion channels for atomic diffusion and can form a finer grain structure at the welding interface. At the same time, it can also promote diffusion between atoms and enhance interface migration, making it easier for micropores at the interface to close. Compared with traditional intermediate layers, the unique high-entropy effect of the nano-high-entropy alloy intermediate leads to severe lattice distortion, generating extremely high lattice distortion energy, which provides more driving force for atomic diffusion.

[0041] The present invention will be further described below with reference to the embodiments.

[0042] Example 1

[0043] This embodiment provides a low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer, including the following steps:

[0044] Step 1: The TC4 titanium alloy base material was successively polished with 400#, 800#, 1500# and 2000# sandpaper and polished with a SiO2-H2O2 polishing machine. After that, it was ultrasonically cleaned for 10 minutes and dried. The TC4 titanium alloy base material was then ultrasonically rolled. The ultrasonic generator was started at a frequency of 30kHz and an amplitude of 10μm. The workpiece rotation speed was 300r / min, the feed speed was 0.05mm / r, the rolling process was performed 4 times, and the static pressure was 150N. The resulting TC4 titanium alloy base material with a nano-surface was obtained. The nano-surfaced TC4 titanium alloy base material was then cut into 5mm×10mm×4mm cuboids using an EDM wire cutter.

[0045] Step 2: Prepare the high-entropy alloy intermediate layer Ti using the electric arc melting method. 35 Zr 25 Co 10 Ni 10 Cu7Nb 10 Y3; The chemical composition of the high-entropy alloy interlayer, by mass percentage, consists of Ti 35%, Zr 25%, Co 10%, Ni 10%, Cu 7%, Nb 10%, and Y 3%; The high-entropy alloy interlayer is cut into thin slices of 6mm × 6mm × 0.2mm using an electrical discharge wire cutting machine, and then polished to 0.1mm using 400#, 800#, 1500#, and 2000# sandpaper respectively.

[0046] Step 3: Use a 1064nm Nd:YAG laser to laser-shock the high-entropy alloy intermediate layer. The laser energy is 7J, the pulse width is 10ns, the number of shocks is 3, the pulse frequency is 5Hz, the spot size is 2mm, and the absorption layer used is aluminum foil to obtain a nano-sized high-entropy alloy intermediate layer.

[0047] Step 4: Place the nano-high entropy alloy intermediate layer between the upper and lower layers of nano-TC4 titanium alloy base material to obtain a sandwich structure of TC4-nano-high entropy alloy-TC4. Place the entire structure in a vacuum diffusion welding furnace and perform diffusion welding using a segmented heating method. The first segment heats the material from room temperature to 300℃ at a heating rate of 10℃ / min and holds it at 300℃ for 10 min. The second segment heats the material from 300℃ to 600℃ at a heating rate of 10℃ / min and holds it at 600℃ for 10 min. The third segment heats the material from 600℃ to the welding temperature of 750℃ at a heating rate of 10℃ / min, and then the heating is completed. Finally, the material is held at the welding temperature of 750℃ for 30 min while applying a pressure of 1.5MPa. After the holding period, the material is cooled to room temperature with the furnace, and the pressure is reduced to zero. The welding is then complete.

[0048] The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this embodiment reached 562 MPa, and the port morphology of the joint is as follows. Figure 2 As shown; the microstructure of the TC4 titanium alloy base material after ultrasonic rolling strengthening is as follows. Figure 1 As shown, its microhardness is 376 HV.

[0049] Example 2

[0050] This embodiment provides a low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer. The steps are basically the same as in Embodiment 1, except that in step 2, the high-entropy alloy interlayer is prepared by arc melting and cut into 6mm × 6mm × 0.2mm thin slices using an EDM wire cutter. These slices are then polished to 0.15mm using 400#, 800#, 1500#, and 2000# sandpaper, respectively. The welding temperature in step 4 is 770℃, and the remaining steps are the same as in Embodiment 1. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this embodiment reaches 483MPa.

[0051] Example 3

[0052] This embodiment provides a low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer. The steps are basically the same as in Embodiment 1, except that in step 2, the high-entropy alloy interlayer is prepared by arc melting and cut into 6mm × 6mm × 0.2mm thin slices using an EDM wire cutter without grinding. The welding temperature in step 4 is 800℃, and the remaining steps are the same as in Embodiment 1. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this embodiment reaches 514MPa.

[0053] Example 4

[0054] This embodiment provides a low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer. The steps are basically the same as in Embodiment 1, except that the welding temperature in step 4 is 750 ℃ ​​and the pressure is 5 MPa. The remaining steps are the same as in Embodiment 1. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this embodiment reaches 512 MPa.

[0055] Example 5

[0056] This embodiment provides a low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer. The steps are basically the same as in Embodiment 1, except that the welding temperature in step 4 is 780 ℃ and the pressure is 1.5 MPa; the rest is the same as in Embodiment 1. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this embodiment reaches 489 MPa.

[0057] Comparative Example 1

[0058] This comparative example provides a low-temperature diffusion welding method for TC4 titanium alloy based on a high-entropy alloy interlayer. The steps are basically the same as those in Example 1, except that ultrasonic rolling treatment of the TC4 titanium alloy base material is not performed in step 1. The remaining steps are the same as those in Example 1.

[0059] Because the ultrasonic rolling process was missing in this comparative example, the stress resistance and corrosion resistance of the TC4 titanium alloy base material were reduced. Furthermore, during the diffusion welding process, the contact area between the TC4 titanium alloy base material and the high-entropy alloy intermediate layer was reduced, and gaps existed at the interface between them. This reduced the atomic diffusion rate during the diffusion welding process. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this comparative example was 338 MPa, which was significantly lower than that in Example 1.

[0060] Comparative Example 2

[0061] This comparative example provides a low-temperature diffusion welding method for TC4 titanium alloy based on a high-entropy alloy interlayer. The steps are basically the same as those in Example 1, except that the high-entropy alloy interlayer in step 3 is not subjected to laser shock, while the remaining steps are the same as those in Example 1.

[0062] Because this comparative example lacks the laser shock step, the activation energy of the intermediate layer decreases, and the element diffusion is insufficient, resulting in a significant decrease in its mechanical properties. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this comparative example is 396 MPa, which is significantly lower than that of Example 1.

[0063] Comparative Example 3

[0064] This comparative example provides a low-temperature diffusion welding method for TC4 titanium alloy based on dual nano-sizing and a high-entropy alloy interlayer. The steps are basically the same as those in Example 1, except that in step 2, an arc melting method is used to prepare the high-entropy alloy interlayer. The chemical composition of the prepared high-entropy alloy interlayer is composed of Ti 55%, Zr 32%, Nb 10%, and Y 3% by mass percentage. The remaining steps are the same as those in Example 1.

[0065] The high-entropy alloy intermediate layer in this comparative example does not contain melting-reducing elements Co, Ni, and Cu. However, at the welding temperature of Example 1, complete welding could not be achieved. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this comparative example is 375 MPa, which is significantly lower than that of Example 1.

[0066] Comparative Example 4

[0067] This comparative example provides a low-temperature diffusion welding method for TC4 titanium alloy based on dual nano-sizing and a high-entropy alloy interlayer. The steps are basically the same as those in Example 1, except that in step 2, an arc melting method is used to prepare the high-entropy alloy interlayer. The chemical composition of the prepared high-entropy alloy interlayer is composed of Ti 35%, Zr 30%, Co 10%, Ni 15%, Cu 7%, and Y 3% by mass percentage; the rest is the same as in Example 1.

[0068] The high-entropy alloy interlayer in this comparative example does not contain element Nb, which reduces the shear strength of the joint. The shear strength of the TC4-nanosized high-entropy alloy-TC4 joint obtained in this comparative example is 457 MPa, which is significantly lower than that of Example 1.

[0069] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0070] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0071] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A low-temperature diffusion welding method for TC4 titanium alloy based on a dual-nanoscale and high-entropy alloy interlayer, characterized in that, Includes the following steps: Step 1: Prepare nano-sized TC4 titanium alloy base material. The TC4 titanium alloy base material is treated with ultrasonic rolling at a frequency of 20kHz~40kHz, an amplitude of 5μm~20μm, a workpiece rotation speed of 300r / min, a feed rate of 0.05mm / r, and 4 rolling passes. The static pressure is 110N~150N. This yields a nano-sized TC4 titanium alloy base material with a grain size of 170nm~250nm and a surface roughness of 0.013μm~0.027μm. Step 2: Prepare a high-entropy alloy interlayer; the chemical composition of the high-entropy alloy interlayer, by mass percentage, consists of Ti 35%, Zr 25%, Co 10%, Ni 10%, Cu 7%, Nb 10%, and Y 3%; the thickness of the high-entropy alloy interlayer is 0.1 mm to 0.2 mm, and the surface roughness is 0.07 μm to 0.12 μm; Step 3: Prepare a nano-sized high-entropy alloy intermediate layer; use laser shock to obtain a nano-sized high-entropy alloy intermediate layer with a grain size of 200nm~300nm; Step 4: Place the nano-sized high-entropy alloy intermediate layer between the upper and lower layers of nano-sized TC4 titanium alloy base material, and place the entire assembly in a vacuum diffusion welding furnace for diffusion welding using a segmented heating method to obtain a TC4 titanium alloy welded head. During the segmented heating diffusion welding process, the first stage involves heating from room temperature to 300℃ at a heating rate of 10℃ / min, and holding at 300℃ for 10 minutes; the second stage involves heating from 300℃ to 600℃ at a heating rate of 10℃ / min, and holding at 600℃ for 10 minutes; the third stage involves heating from 600℃ to a welding temperature of 750℃~800℃ at a heating rate of 10℃ / min, and then ending the heating; finally, hold at the welding temperature of 750℃~800℃ for 30 minutes, while applying a pressure of 0.5MPa~1.5MPa; after the holding period, cool with the furnace to room temperature, and the pressure returns to zero, completing the welding.

2. The low-temperature diffusion welding method for TC4 titanium alloy based on a dual-nanoscale and high-entropy alloy interlayer according to claim 1, characterized in that, Before ultrasonic rolling treatment of the TC4 titanium alloy base material in step 1, the TC4 titanium alloy base material is ground, polished, cleaned and dried.

3. The low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer according to claim 1, characterized in that, In step 2, during the preparation of the high-entropy alloy intermediate layer, Ti, Zr, Co, Ni, Cu, Nb, and Y metal powders with a purity greater than 99.9% are weighed according to the stated mass percentages and prepared by arc melting.

4. The low-temperature diffusion welding method for TC4 titanium alloy based on a dual-nanoscale and high-entropy alloy interlayer according to claim 1, characterized in that, In step 3, before preparing the nano-sized high-entropy alloy intermediate layer, the high-entropy alloy intermediate layer is cut and polished.

5. The low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer according to claim 1, characterized in that, In step 3, during the process of using laser to shock the high-entropy alloy intermediate layer, the laser energy is 7J~10J, the pulse width is 10ns~15ns, the number of shocks is 3~5, the pulse frequency is 5Hz, the spot size is 2mm, and the absorption layer used is aluminum foil.

6. The low-temperature diffusion welding method for TC4 titanium alloy based on a dual nano-sized and high-entropy alloy interlayer according to claim 1, characterized in that, The vacuum degree of the vacuum diffusion welding furnace is ≤5×10⁻⁶. -3 Pa.

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