Uniform superplastic deformation method and device for multi-pass stirring friction processing of titanium alloy plate

Abstract

The invention discloses a uniform superplastic deformation method and device for a multi-pass stirring friction processed titanium alloy plate, and belongs to the technical field of titanium alloy superplastic deformation. The method comprises the following steps: firstly, optimizing friction stir processing parameters by adopting an iterative method combining numerical simulation and experiments to obtain optimized friction stir processing parameters, carrying out multi-pass friction stir processing on a titanium alloy plate by adopting the optimized friction stir processing parameters to obtain a fine-grain titanium alloy plate, and then carrying out superplastic deformation on the fine-grain titanium alloy plate to obtain the fine-grain titanium alloy plate. And in the deformation process, a plurality of cooling pipes and laser emitters are distributed along the multi-pass stirring friction machining area and the interface area to carry out micro-area rapid cooling and rapid heating regulation and control on the superplastic deformation process, so that uniform superplastic deformation of the titanium alloy plate subjected to multi-pass stirring friction machining is realized. According to the method for optimizing the stirring friction machining process parameters, the titanium alloy stirring friction machining process parameters are optimized in a numerical simulation mode, and the barrier that the stirring friction machining process parameters are selected through experience traditionally is broken through.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy superplastic deformation technology, specifically relating to a method and apparatus for uniform superplastic deformation of titanium alloy plates through multi-pass friction stir processing. Background Technology

[0002] Titanium alloys possess advantages such as high specific strength, non-magnetic properties, corrosion resistance, and high temperature resistance, making them widely used in aerospace, military industry, petrochemicals, and many other fields. However, due to their low elastic modulus, high yield strength ratio, and large deformation resistance, titanium alloys are difficult to process using conventional stamping, bending, and forging processes. These methods often result in anisotropy, cracking, wrinkling, and severe springback during forming, thus requiring heat forming.

[0003] Superplastic forming technology is a novel hot working technique developed by utilizing the excellent deformation properties of materials in a superplastic state. Under superplastic deformation conditions, materials can withstand large deformations without being destroyed, exhibit low deformation resistance, simple processes, and the ability to form complex shapes in a single operation, significantly improving material utilization and opening up new avenues for the plastic forming of difficult-to-deform materials. Therefore, superplastic forming technology has gradually become a common method in the field of titanium alloy hot working. Generally, the smaller the grain size of titanium alloys, the higher their superplastic properties. While intense plastic deformation techniques can significantly refine the grain size of titanium alloys, traditional intense plastic deformation techniques (such as equal channel angular extrusion, high-pressure torsion, and forging) are limited by mold structure and size, making it impossible to produce large-size, fine-grained titanium alloy sheets.

[0004] Friction stir machining (FSM) is a vigorous plastic deformation technique that is not limited by mold structure and size, and can produce large-sized fine-grained or even ultrafine-grained titanium alloy sheets. During FSM, process parameters directly affect the heat input to the processing zone, thus influencing the grain size. Excessive heat input leads to grain coarsening in the processing zone, which is detrimental to subsequent superplastic deformation. Insufficient heat input results in processing defects, leading to processing failure. Therefore, accurately selecting the optimal FSM process parameters is fundamental to the preparation of fine-grained titanium alloys. Furthermore, the preparation of large-sized fine-grained titanium alloy sheets typically requires multiple passes of friction stir machining. During this process, the microstructure at the interface between adjacent processing zones often differs from that at the center of the processing zone, easily leading to uneven deformation characteristics during the superplastic deformation of the fine-grained sheet, thus affecting its superplastic forming performance. Therefore, there is an urgent need to find a method that can achieve uniform superplastic deformation of titanium alloy sheets through multiple passes of friction stir machining. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and apparatus for uniform superplastic deformation of titanium alloy plates by multi-pass friction stir processing, so as to solve the problem of uneven superplastic deformation in the preparation of large-size titanium alloy plates by existing multi-pass friction stir processing.

[0006] To achieve the above objectives, the present invention employs the following technical solution: A method for achieving uniform superplastic deformation of titanium alloy sheets through multi-pass friction stir processing includes the following steps: S1. By analyzing the actual and simulated friction stir machining process, the friction coefficient-actual temperature relationship curve is determined; and the optimized process parameters for friction stir machining are determined based on the friction coefficient-actual temperature relationship curve. S2, Based on optimized process parameters, the titanium alloy plate is subjected to friction stirring to obtain a fine-grained titanium alloy plate; S3, stretch the fine-grained titanium alloy plate until it reaches the set length; during the stretching deformation process, the strain of the processing area and the interface area of ​​the fine-grained titanium alloy plate is monitored by the strain monitoring system. If the difference between the two strains is greater than 10%, the area with the larger strain is cooled; if the difference between the two strains is 10%, the area with the larger strain is heated; if the difference between the two strains is less than 10%, heating or cooling is stopped.

[0007] A further improvement of the present invention is that: Preferably, in S1, the specific process for determining the friction coefficient-actual temperature relationship curve is as follows: S101, the actual temperature of the titanium alloy plate during the friction stir processing is measured by friction stir processing. S102, Numerical simulation of the friction stir processing of titanium alloy plates was performed to establish the friction coefficient-simulated temperature curve; S103, determine the intersection of the actual temperature and the friction coefficient-simulated temperature curve during the processing, and obtain the relationship between the friction coefficient and the actual temperature through the intersection; S104. In the numerical simulation model, the friction coefficient-actual temperature relationship is set to obtain the optimized process parameters for friction stir processing.

[0008] Preferably, in S101, the actual temperature of three points on the titanium alloy plate is measured.

[0009] Preferably, in S102, the friction coefficient is set to 0.1-1.5 during the numerical simulation.

[0010] Preferably, in S2, the optimized process parameters are: the number of multi-pass friction stirring processing passes is ≥3; the distance between the centers of adjacent passes is ≤ half the diameter of the stirring head tool shoulder.

[0011] Preferably, in S3, the fine-grained titanium alloy plate is heated and kept warm before undergoing superplastic tensile deformation.

[0012] Preferably, in S3, during the air blowing cooling process, the cooling medium is any one of air, argon, or carbon dioxide, and the flow rate of the cooling medium is 0.05-0.1 m / s.

[0013] Preferably, in S3, the heating process is carried out by laser heating, and the laser spot diameter during laser heating is ≤ 1 / 2 of the center distance between adjacent passes in the friction stir processing.

[0014] A system for achieving the above-mentioned method of uniform superplastic deformation of titanium alloy plates through multi-pass friction stir processing includes a stretching machine, a gas nozzle, a laser emitter, and a strain monitoring instrument; The gas nozzle is disposed around the processing area and interface area of ​​the stretched sample, the laser emitter outputs a laser spot in the processing area and interface area of ​​the stretched sample, and the strain monitor monitors the processing area and interface area of ​​the stretched sample. The stretching machine, gas nozzle, laser emitter, and strain monitor are all electrically connected to a control terminal.

[0015] Preferably, a portion of the strain monitoring instrument is installed in a high-temperature heating furnace, the gas nozzle is connected to a gas cylinder via a delivery pipe, the delivery pipe passes through a water cooler, and the water cooler is connected to a water tank.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for achieving uniform superplastic deformation of titanium alloy sheets through multi-pass friction stir processing. First, an iterative method combining numerical simulation and experimentation is used to optimize the friction stir processing parameters, thereby obtaining ultrafine-grained titanium alloy sheets through multi-pass friction stir processing that is most conducive to superplastic deformation. The optimized friction stir processing parameters are then used to perform multi-pass friction stir processing on the titanium alloy sheet to obtain fine-grained titanium alloy sheets. Subsequently, superplastic deformation is performed on these sheets. During the deformation process, multiple cooling pipes and laser emitters are distributed along the multi-pass friction stir processing zone and the interface zone to perform micro-area rapid cooling and heating control of the superplastic deformation process, thereby achieving uniform superplastic deformation of the titanium alloy sheet through multi-pass friction stir processing. The method for optimizing friction stir processing parameters proposed in this invention establishes a functional relationship between temperature and friction coefficient during the friction stir processing of titanium alloys. Numerical simulation is used to accurately predict the temperature field distribution during the friction stir processing of titanium alloys, and numerical simulation is used to optimize the friction stir processing parameters for titanium alloys, breaking through the barrier of traditional empirical selection of friction stir processing parameters. The ultrafine-grained titanium alloy prepared using optimized friction stir processing parameters has a grain size of less than 1 μm, providing a foundation for uniform superplastic deformation. Simultaneously, the micro-region rapid cooling and heating method and apparatus proposed in this invention can precisely control the coordinated and uniform superplastic deformation of the multi-pass friction stir processing zone and interface zone, significantly improving the superplastic properties of multi-pass friction stir processed titanium alloy sheets.

[0017] This invention also discloses a device for multi-pass friction stir processing of titanium alloy sheets to achieve uniform superplastic deformation. The device mainly includes a tensile loading system, a high-temperature heating furnace, a cooling system, a laser heating system, an infrared temperature measurement system, and a strain monitoring system. The tensile loading system consists of a tensile machine and a control system. The high-temperature heating furnace is installed in a flat-push configuration at the rear of the tensile machine. The cooling system consists of a water cooler, a water tank, a gas cylinder, a delivery pipe, and a gas nozzle. The laser heating system consists of a laser emitter and a lifting support frame. The infrared temperature measurement system consists of an infrared thermometer and a lifting support frame. The strain monitoring system consists of a strain monitor and a lifting support frame. The tensile loading system, laser heating system, infrared temperature measurement system, and strain monitoring system are integrated into a control terminal using integrated software. This device achieves uniform superplastic deformation of titanium alloy sheets through multi-pass friction stir processing by controlling the local micro-area deformation of the sample during superplastic tensile deformation. The device has a simple structure, is easy to operate, and has a high degree of system integration. Furthermore, the device can be easily mounted on a conventional high-temperature tensile machine, with simple installation and no customization issues. Attached Figure Description

[0018] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram of the cross-section of a titanium alloy sheet processed by three-pass friction stirring according to the present invention; Figure 3 This is a schematic diagram of the cross-section of a titanium alloy sheet processed by multi-pass friction stir machining. Figure 4 This is a flowchart of the optimized friction stir processing parameters of the present invention; Figure (a) shows the relationship between the friction coefficient and temperature at a rotational speed of 100 r / min. (b) The figure shows the relationship between the coefficient of friction and temperature at a rotational speed of 200 r / min; (c) The figure shows the relationship between the friction coefficient and temperature at a rotational speed of 400 r / min; (d) The figure shows the relationship between temperature and experimental values; (e) The figure shows a temperature simulation diagram; Figure 5 This is a schematic diagram of the system structure of the present invention; Figure 6 This is a schematic diagram of the cooling gas nozzle structure; Among them, 1. stretching machine; 2. terminal; 3. high temperature heating furnace; 4. water cooler; 5. water tank; 6. gas cylinder; 7. conveying pipe; 8. gas nozzle; 9. laser emitter; 10. first lifting support; 11. infrared thermometer; 12. strain monitor; 13. second lifting support. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0020] As the background section points out, the traditional friction stir processing (FSM) method for preparing ultrafine-grained titanium alloys typically requires multiple sets of FSM parameters to process the alloy, followed by microstructure analysis of samples under different FSM parameters. This process not only demands extensive human experience but is also lengthy, costly, and prone to errors due to human experience, resulting in coarse microstructures in the processed samples, making it unsuitable for superplastic deformation. Furthermore, traditional FSM numerical simulations often assume a constant friction coefficient as the primary mechanism for heat generation. In reality, FSM is a vigorous plastic deformation technique involving complex material deformation and flow; therefore, its friction coefficient is not constant. Moreover, different materials will inevitably exhibit significant differences in their friction coefficients during FSM due to variations in material properties.

[0021] See Figure 1This invention discloses a method for achieving uniform superplastic deformation of titanium alloy sheets through multi-pass friction stir processing. The method includes performing multi-pass friction stir processing on the titanium alloy sheet using optimized parameters to obtain a fine-grained titanium alloy sheet, followed by superplastic deformation. During the deformation process, multiple cooling pipes and a laser emitter are distributed along the multi-pass friction stir processing zone and the interface zone to perform micro-area rapid cooling and heating control of the superplastic deformation process, thereby achieving uniform superplastic deformation of the titanium alloy sheet through multi-pass friction stir processing. The specific method for achieving uniform superplastic deformation of titanium alloy sheets through multi-pass friction stir processing is as follows: S1. By analyzing the actual and simulated friction stir machining process, the friction coefficient-actual temperature relationship curve is determined; and the optimized process parameters for friction stir machining are determined based on the friction coefficient-actual temperature relationship curve. S2, Based on optimized process parameters, friction stirring is performed to obtain a fine-grained titanium alloy plate; S3, stretch and deform the fine-grained titanium alloy plate until it reaches the set length; during the stretching and deformation process, the strain of the fine-grained titanium alloy plate in the friction stir processing zone and the interface zone is monitored by the strain monitoring system. If the difference between the two strains is greater than 10%, the area with large strain is cooled by blowing air. When the difference between the two strains is reduced to 10%, the area with large strain is heated. If the difference between the two strains is less than 10%, heating or cooling is stopped.

[0022] This invention proposes an iterative method combining numerical simulation and experimentation to accurately predict the temperature field distribution during friction stir machining (FSM) of titanium alloys. Numerical simulation is used to optimize the FSM process parameters, overcoming the shortcomings of traditional methods that rely on empirical selection. The optimized FSM parameters produce ultrafine-grained titanium alloys with grain sizes less than 1 μm, providing a foundation for uniform superplastic deformation. Furthermore, the proposed micro-area rapid cooling and heating method enables precise and coordinated uniform superplastic deformation of the interface and processing zones in multi-pass FSM processes, significantly improving the superplastic properties of multi-pass FSM-machined titanium alloy sheets.

[0023] The object of processing in this invention is a dual-phase titanium alloy plate, and fine-grained titanium alloy plate refers to a grain size of <10 μm.

[0024] See Figure 2 In S3, the specific objects of heating or cooling are the processing zone and interface zone generated during the friction stir machining process. The processing zone is the area where each pass of the friction stir machining process is located, and the interface zone is the interaction area between two passes of friction stir machining.

[0025] In some embodiments of the present invention, in S1, the process of optimizing the friction stir machining parameters is as follows: S101, the original titanium alloy sheet was processed using three sets of different friction stir processing parameters. Thermocouples were used to measure the temperature at at least three different locations in the processing area. Figure 3 As shown, these correspond to the edge and center areas of the processing zone, respectively; S102, numerical simulation of the friction stir processing of titanium alloys was performed, with friction coefficients selected from 0.1 to 1.5. Subsequently, the numerical simulation temperature at the measured location of the friction stir processing temperature was recorded. S103, the temperatures measured at different locations in the numerical simulation are plotted and analyzed. Simultaneously, the actual measured temperatures at different locations in the processing zone are plotted on this curve. Then, the intersection points of the measured temperatures at different processing zone locations and the curves are mathematically fitted to obtain the functional relationship between the temperature and the friction coefficient in the stirring friction processing zone. Figure 4 As shown; S104, by substituting the above-mentioned functional relationship between temperature and friction coefficient into the numerical simulation model, the peak temperature of the processing zone under different friction stir processing parameters can be accurately predicted. The smaller the peak temperature, the smaller the grain size of the fine-grained titanium alloy processed by friction stir.

[0026] In some embodiments of the present invention, in S2, among the optimized process parameters, the number of passes in the multi-pass friction stir processing is greater than or equal to 3; the distance between the centers of adjacent passes in the multi-pass friction stir processing is less than or equal to 1 / 2 of the diameter of the stirring head tool shoulder; the diameter of the stirring head tool shoulder in the multi-pass friction stir processing is 12-16 mm; the peak temperature in the processing zone is lower than 1 / 2 of the melting point of the titanium alloy material; after the multi-pass friction stir processing is completed, a superplastic deformation sample of the multi-pass friction stir processing is cut transversely along the processing zone, and the surface of the sample is polished smooth with sandpaper.

[0027] In some embodiments of the present invention, in step S3, the heating equipment is started and heated to the target deformation temperature before the fine-grained titanium alloy plate is stretched to the set length; the superplastic deformation sample is fixed with a clamp, and then the superplastic deformation sample is placed in a high-temperature heating furnace for 5-10 minutes; after the heat preservation is completed, the load loading system is started to perform superplastic tensile deformation at a constant strain rate.

[0028] In some embodiments of the present invention, in step S3, the load loading system is activated to perform superplastic tensile deformation at a constant strain rate. Simultaneously, a strain monitoring system monitors the deformation characteristics of the multi-pass friction stir processing zone and the interface zone of the superplastic deformation sample. When the strain difference between adjacent processing zones and the interface zone exceeds 10%, the cooling system is activated to rapidly cool the micro-area with larger strain using cooling pipe gas nozzles, lowering its local temperature. At this time, the micro-area with smaller strain gradually deforms. When the difference in deformation between the micro-area with smaller strain and the micro-area with larger strain decreases to 10%, the cooling system is turned off and the laser heating system is activated to rapidly heat the micro-area with larger strain to the same temperature as the high-temperature furnace, ensuring a consistent temperature across the entire superplastic deformation sample. When the strain difference between adjacent processing zones and the interface zone is less than 10%, the cooling system and the laser heating system remain off. This repeated regulation of the multi-pass friction stir processing of the titanium alloy processing zone and the interface zone coordinates the deformation, achieving uniform superplastic deformation.

[0029] Preferably, the cooling medium in the cooling process is any one of air, argon or carbon dioxide, and the flow rate of the cooling medium is 0.05-0.1 m / s.

[0030] To achieve the above method, a second aspect of the present invention discloses a multi-pass friction stir processing system for uniform superplastic deformation of titanium alloy plates. The system includes a stretching machine 1, a gas nozzle 8, a laser emitter 9, and a strain monitor 12. The gas nozzle 8 is positioned next to the processing area and interface area of ​​the stretched sample. The laser emitter 9 outputs a laser spot at the processing area and interface area of ​​the stretched sample. The strain monitor 12 monitors the processing area and interface area of ​​the stretched sample. The stretching machine 1, the gas nozzle 8, the laser emitter 9, and the strain monitor 12 are all electrically connected to a control terminal 2.

[0031] It should be understood that the superplastic deformation system described above can be designed according to the site environment, as long as it can achieve the corresponding functions and ensure rapid cooling and heating during the stretching process.

[0032] See Figure 5 In some embodiments of the present invention, a specific structure of a multi-pass friction stir processing system for uniform superplastic deformation of titanium alloy plates is disclosed. This system includes a tensile loading system, a high-temperature heating furnace 3, a cooling system, a laser heating system, an infrared temperature measurement system, and a strain monitoring system. These systems can be integrated into a terminal 2 and controlled via the terminal 2.

[0033] Specifically, the tensile loading system consists of a tensile machine 1 and a control terminal 2, which is the main device for superplastic deformation. The high-temperature heating furnace 3 adopts a flat-push structure and is installed at the rear of the tensile machine 1. The center height of the high-temperature heating furnace 3 is kept at the same height as the superplastic deformation sample. The main function of the high-temperature heating furnace 3 is to heat the superplastic deformation sample.

[0034] The high-temperature heating furnace 3 is an annular heating furnace, including an inner ring wall and an outer ring wall. The middle part of the inner ring wall is a support device, and heating resistance wires are installed in both the inner and outer ring walls.

[0035] The cooling system consists of a water cooler 4, a water tank 5, a gas cylinder 6, a delivery pipe 7, and a gas nozzle 8. The delivery pipe 7 and the gas nozzle 8 are installed inside the high-temperature heating furnace. The outlet end of the delivery pipe 7 is connected to the gas nozzle 8, and the inlet end of the delivery pipe 7 is connected to the gas cylinder 6. The delivery pipe 7 passes through the water cooler 4, and the water cooler 4 is connected to the water tank 5. During the cooling process, the water cooler 4, the gas cylinder 6, and the water tank 5 serve as auxiliary devices. Their main function is to cool the gas in the gas cylinder 6. While the gas is being sprayed out through the gas nozzle 8, the gas in the gas cylinder 6 is cooled by the water in the water cooler 4 as it passes through the water cooler 4.

[0036] The laser heating system consists of a laser emitter 9 and a first lifting support 10. The main function of the laser emitter 9 is to locally heat different micro-regions of the superplastic deformation sample. The lifting structure of the first lifting support 10 facilitates the vertical adjustment of the laser emitter. The laser emitter's spot diameter is less than half the distance between the centers of adjacent passes in multi-pass friction stir machining, and the laser emitter is mounted on the lifting support frame.

[0037] The infrared temperature measurement system consists of an infrared thermometer 11 and a second lifting bracket 13. Its main function is to synchronously monitor the temperature distribution at different locations in the deformation zone of the superplastic deformation sample.

[0038] The strain monitoring system consists of a strain monitor 12 and a lifting support frame 13. Its main function is to monitor the strain at different locations in the deformation zone of the superplastic deformation specimen. The lifting structure facilitates the vertical adjustment of the strain monitor 12.

[0039] The cooling pipe is made of high-temperature resistant metal and consists of a delivery pipe 7 and a gas nozzle 8. (See attached image.) Figure 6The cooling gas nozzle 8 is frustum-shaped, and its outlet consists of multiple microporous structures. The gas nozzle 8 is located at the end of the delivery pipe 7. The diameter of the cooling gas nozzle 8 is the distance between the centers of adjacent passes in the multi-pass friction stir machining process. This design allows for cooling of the corresponding passes. The angle between the axis of the gas nozzle 8 and the surface of the superplastic tensile specimen is 90°, and the distance between the outer end face of the gas nozzle 8 and the surface of the superplastic deformed specimen is less than 5 mm, ensuring sufficient cooling of the superplastic deformed specimen. The cooling gas nozzle 8 is frustum-shaped, and its outlet consists of multiple microporous structures.

[0040] The number of cooling tubes is consistent with the number of interface zones in the multi-pass stirring friction processing zone contained in the deformation zone of the superplastic deformation specimen, and the flow rate of each cooling tube can be controlled independently; all cooling tubes pass through water cooler 4 and can be cooled.

[0041] The specific working process of this device is as follows: Step 1: Push the high-temperature heating furnace 3 horizontally to the initial position behind the stretching machine 1, start the control terminal 2, set the target temperature of the high-temperature heating furnace and start heating, and set the superplastic deformation strain rate. Step 2: After the temperature of the high-temperature heating furnace rises to the target temperature, the superplastic deformation sample is loaded onto the fixture of the tensile machine 1. Step 3: Push the high-temperature heating furnace horizontally to the center of the stretching machine, ensuring that the superplastic deformation sample is in the center of the high-temperature heating furnace and keep it at the temperature for 5-10 minutes. Step 4: Adjust the position of the cooling gas nozzle 8 to ensure that one cooling gas nozzle is distributed at each corresponding position in the processing zone and interface zone of the multi-pass stirring friction in the deformation zone of the superplastic deformation sample, and keep the distance between the cooling gas nozzle 8 and the surface of the superplastic deformation sample less than 5 mm. Step 5: Adjust the position of the laser emitter 9 to ensure that the corresponding positions of each processing zone and interface zone in the deformation zone of the superplastic deformation sample after multiple stirring frictions are aligned with the laser emitter 9. Step 6: After the superplastic deformation sample has finished being kept at a constant temperature, start the tensile loading. During the loading process, simultaneously start the strain monitoring system and the infrared temperature measurement system to achieve automatic adjustment of the laser heating system and the cooling system. Step 7: After the superplastic deformation sample breaks, turn off the tensile machine 1, the high-temperature heating furnace 3, the strain monitoring system and the infrared temperature measurement system.

[0042] The basic principle of the method and apparatus of this invention is to obtain optimal stirring friction process parameters through a precise optimization method, thereby refining the grain size of the titanium alloy as much as possible, providing a foundation (internal conditions for superplastic deformation) for fully utilizing the superplastic deformation of fine-grained titanium alloy sheets. Simultaneously, the invention employs a micro-area rapid cooling and heating device system to regulate the uneven deformation of micro-areas in the multi-pass stirring friction processing of the fine-grained titanium alloy sheet during superplastic deformation, achieving coordinated deformation of the processing zone and the interface zone, thus achieving overall uniform deformation. The principle of micro-area rapid cooling and heating utilizes the different grain boundary slip caused by varying temperatures in local micro-areas of the sample, thereby achieving overall uniform deformation of the sample.

[0043] The present invention will be further described below with reference to the embodiments: Example 1: Step 1: Three sets of friction stir machining process parameters (human empirical parameters: machining speed of 80 mm / min, and rotation speeds of 100 r / min, 200 r / min, and 400 r / min respectively) were used to machine the β-rich α+β titanium alloy. The temperature at the center of the machining area, the forward shoulder position, and the backward shoulder position was measured. Figure 3 Simultaneously, the Deform simulation software was used to numerically simulate the three sets of friction stir processing parameters. During the numerical simulation, friction coefficients ranging from 0.1 to 1.5 were selected to calculate and obtain the simulated temperature values ​​of P1-P3. Curves were plotted for the simulated temperature values ​​of P1-P3 under the three sets of friction stir processing parameters. At the same time, the measured temperature values ​​of P1-P3 under the three sets of friction stir processing parameters were plotted onto the corresponding parameter curves, and their intersection with the curves was used to obtain the abscissa of different points. Figure 4 (a-4c) The intersection points of the simulated curves and measured temperatures of P1-P3 under the three sets of friction stir processing parameters are extracted and plotted as follows: Figure 4 As shown in Figure d, the relationship between the friction coefficient and temperature during the friction stir processing of titanium alloys is obtained. Substituting this curve into the Deform simulation software, the temperature field distribution under arbitrary friction stir processing parameters can be accurately obtained. Selecting appropriate friction stir processing parameters such that the temperature in the processing zone is less than or equal to half the melting point of the titanium alloy is considered the optimal parameter for friction stir processing of titanium alloys.

[0044] Step 2: Perform three passes of friction stir processing on the titanium alloy using the above-mentioned optimal friction stir processing parameters. Figure 5 The stirring tool has a shoulder diameter of 12 mm and a center-to-center distance of 6 mm between adjacent passes. After three passes of friction stirring are completed, a superplastic deformation specimen is cut along the cross-section of the plate. The deformation zone of the superplastic deformation specimen includes three processing zones and two interface zones. The superplastic deformation specimen is polished smooth with sandpaper.

[0045] Step 3: Push the high-temperature heating furnace horizontally to the initial position behind the stretching machine, start the control terminal, set the target temperature of the high-temperature heating furnace to 800℃ and start heating, and set the superplastic deformation strain rate to 1×10 -3 s -1 After the high-temperature furnace temperature rises to 800℃, the superplastic deformation sample is loaded onto the clamps of the tensile testing machine. The high-temperature furnace is then pushed horizontally to the center of the tensile testing machine, ensuring the superplastic deformation sample is in the center of the furnace and held at that temperature for 10 minutes. The position of the cooling gas nozzles is adjusted to ensure that one cooling gas nozzle is distributed at each of the three processing zones and two interface zones corresponding to the three passes of stirring friction in the deformation zone of the superplastic deformation sample, and that the distance between the cooling gas nozzles and the surface of the superplastic deformation sample is less than 5 mm. The position of the laser emitter is adjusted to ensure that the corresponding positions of each processing zone and interface zone in the multi-pass stirring friction in the deformation zone of the superplastic deformation sample are aligned with the laser emitter. After the superplastic deformation sample has finished holding at that temperature, the tensile loading is started. During the loading process, the strain monitoring system and infrared temperature measurement system are simultaneously activated to achieve automatic adjustment of the laser heating system and the cooling system. The laser emitter spot diameter is 6 mm, the cooling medium in the cooling tube is argon gas, and the flow rate of the cooling medium is 0.08 m / s. After the superplastic deformation sample fractures, the tensile loading system, high-temperature heating furnace, strain monitoring system, and infrared temperature measurement system are turned off.

[0046] In this embodiment, fine-grained titanium alloy plates with an average grain size of less than 1 μm were prepared using optimized friction stir processing parameters. The heating temperature was 800℃ and the strain rate was 1×10⁻⁶. -3 s -1 Under deformation conditions, after being regulated by the device of the present invention, the fine-grained titanium alloy plate obtained uniform superplastic deformation, and its superplastic elongation at break was greater than 800%.

[0047] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, "above" or "below" a second feature may include direct contact between the first and second features, or it may include contact between the first and second features not being in direct contact but through another feature between them.

[0048] In the description of this invention, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher horizontal level than the second feature.

[0049] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," 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, the 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.

[0051] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet material, characterized by, The method comprises the following steps: S1, determining the friction coefficient-actual temperature curve through the actual processing process and simulation process of the friction stir processing, and determining the optimized process parameters of the friction stir processing through the friction coefficient-actual temperature curve; S2, performing the friction stir processing on the titanium alloy plate based on the optimized process parameters to obtain the fine-grained titanium alloy plate; S3, performing the tensile deformation on the fine-grained titanium alloy plate until the fine-grained titanium alloy plate is stretched to the set length; During the tensile deformation, the strain monitoring system is used to monitor the strains of the processing zone and the interface zone of the fine-grained titanium alloy plate, if the difference between the two strains is greater than 10%, the area with larger strain is cooled, if the difference between the two strains is 10%, the area with larger strain is heated, and if the difference between the two strains is less than 10%, the heating or cooling is stopped.

2. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet according to claim 1, wherein In S1, the specific process of determining the friction coefficient-actual temperature curve is as follows: S101, measuring the actual temperature of the titanium alloy plate during the friction stir processing of the titanium alloy plate; S102, performing the numerical simulation on the process of the friction stir processing of the titanium alloy plate to establish the friction coefficient-simulated temperature curve; S103, determining the intersection point of the actual temperature and the friction coefficient-simulated temperature curve, and obtaining the friction coefficient-actual temperature relationship through the intersection point; S104, setting the friction coefficient-actual temperature relationship in the numerical simulation model to obtain the optimized process parameters of the friction stir processing.

3. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet according to claim 2, wherein In S101, the actual temperatures of three points on the titanium alloy plate are measured.

4. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet as claimed in claim 2, wherein In S102, during the numerical simulation process, the friction coefficient is set to 0.1-1.

5.

5. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet as claimed in claim 1, wherein, In S2, the optimized process parameters are as follows: the number of passes of the multi-pass friction stir processing is greater than or equal to 3; and the distance between the centers of adjacent passes is less than or equal to half of the diameter of the tool shaft shoulder of the friction stir processing tool.

6. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet as claimed in claim 1, wherein, In S3, the fine-grained titanium alloy plate is heated and kept warm before the superplastic tensile deformation.

7. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet as claimed in claim 1, wherein, In S3, during the air cooling process, the cooling medium is any one of air, argon or carbon dioxide, and the flow rate of the cooling medium is 0.05-0.1 m / s.

8. A method of uniform superplastic deformation of a multi-pass friction stir processed titanium alloy sheet as claimed in claim 1, wherein, In S3, the heating process is performed by laser heating, and the laser spot diameter during the laser heating process is less than or equal to 1 / 2 of the distance between the centers of adjacent passes of the friction stir processing.

9. A system for implementing the method of uniform superplastic deformation of titanium alloy sheet by multi-pass friction stir processing as claimed in any one of claims 1 to 8, wherein, The stretching machine (1), the gas nozzle (8), the laser emitter (9) and the strain monitor (12) are all connected with the control terminal (2) through electrical signals. A part of the strain monitor (12) is arranged in the high-temperature heating furnace (3), the gas nozzle (8) is connected with the gas cylinder (6) through the conveying pipe (7), the conveying pipe (7) passes through the water cooler (4), and the water cooler (4) is connected with the water tank (5). ​ 10. The system of claim 9, wherein, ​

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