A method for efficiently regulating the structure and performance of titanium alloy by rapid electric heating process

Abstract

The application provides a method for efficiently regulating and controlling the structure and performance of titanium alloy by a rapid electric heating process. A pure resistance self-resistance heating full-process system without external force assistance is constructed. Through medium and low temperature short-time holding at 650-780 DEG C and temperature closed-loop control, the method is coupled with hot forming / straightening process on line to realize quantitative and customized regulation and control of titanium alloy beta transformation structure and grain size, significantly shortens the heat treatment period, effectively reduces the unit energy consumption, the residual stress of the product is less than or equal to 10 MPa, and the straightness is less than or equal to 0.5 mm / m, and is suitable for industrialized continuous heat treatment production of titanium alloy bars, wires, pipes and plates for aerospace fasteners, medical implant devices and marine engineering equipment.

Description

Technical Field

[0001] This application relates to a method for efficiently controlling the microstructure and properties of titanium alloys using a rapid electric heating process, belonging to the field of heat treatment technology for titanium and titanium alloy materials. Background Technology

[0002] Ti-6Al-4V alloy, as a typical α+β dual-phase titanium alloy, has become an irreplaceable basic material in aerospace fasteners, surgical implants, marine engineering pressure-bearing components, and core components of high-end energy equipment due to its high specific strength, excellent corrosion resistance, good biocompatibility, and fatigue resistance. Heat treatment, as the core process for regulating the microstructure and properties of titanium alloys, directly determines the grain size, phase composition, residual stress state, and final mechanical properties of titanium alloy products. It is a crucial step in ensuring product reliability and controlling production efficiency and manufacturing costs.

[0003] Currently, the industrial heat treatment of titanium alloys generally adopts the traditional in-furnace radiant heating method. Although this process is technically mature, it has many problems: First, titanium alloys have low thermal conductivity, requiring several hours of heating and holding time in the furnace to achieve uniform internal and external temperatures and sufficient phase transformation, resulting in long production cycles and low efficiency. Second, it consumes a lot of energy and has low energy utilization. Heating in the furnace requires simultaneous heating of the furnace chamber and tooling, resulting in significant heat loss through the furnace and workpiece removal. Third, prolonged exposure to high temperatures easily leads to severe oxidation of the titanium alloy surface and the formation of an oxygen-rich embrittlement layer, reducing the material's fatigue performance. Fourth, prolonged high-temperature holding can cause abnormal grain growth and poor microstructure uniformity, leading to large batch-to-batch fluctuations in the mechanical properties of the product, failing to meet the stringent requirements for material consistency in aerospace and high-end medical fields. Therefore, the inherent disadvantages of traditional furnace heat treatment in terms of "time-energy consumption-microstructure controllability" are becoming increasingly prominent, becoming one of the major bottlenecks restricting the efficient manufacturing of titanium alloys.

[0004] To address the aforementioned issues, Chinese invention patent CN113061823A discloses a heat treatment method for regulating residual stress in medical titanium alloy screw rods. This method achieves the elimination of residual stress in small-sized titanium alloy rods through rapid electro-mechanical coupling treatment combined with short-time high-temperature holding at 850℃ or 900℃. However, the core effect of this technical solution relies on the multi-field coupling effect of axial compressive stress and high current density electro-mechanical-thermal fields. Axial compressive stress needs to be applied at both ends of the mold. Without external force assistance, residual stress elimination and microstructure control cannot be achieved, resulting in high process complexity and making it unsuitable for continuous processing of long bars, wires, and plates. Secondly, this solution is only developed for small-sized bars and cannot meet the heat treatment requirements of large-sized and long-specification titanium alloy products in industrial production, severely limiting its engineering application scenarios. In addition, this solution lacks the ability to actively and quantitatively control the phase transformation behavior and grain size of titanium alloys, making it impossible to achieve customized optimization of material properties. The solution requires high-temperature two-phase region treatment, which easily leads to abnormal growth of the β phase and increased surface oxidation. It also requires a two-step cooling process, making the process complex and unable to be integrated online with processes such as hot straightening and hot stretching, making it difficult to adapt to continuous industrial production.

[0005] In summary, developing a rapid heat treatment method for titanium alloys that features a short heat treatment cycle, low energy consumption, precise microstructure control, good performance stability, and scalability has become a key technical problem that urgently needs to be solved in the field of high-end titanium alloy manufacturing. Summary of the Invention

[0006] To address the aforementioned issues, a method for efficiently controlling the microstructure and properties of titanium alloys using a rapid electric heating process is provided. Through a rapid heating and short-term holding electric heating cycle, the heat treatment time is significantly shortened and energy consumption is reduced, while achieving efficient and controllable adjustment of the phase transformation microstructure, grain size, and residual stress state of the titanium alloy, and improving the microstructure uniformity and performance stability.

[0007] According to one aspect of this application, a method for efficiently controlling the microstructure and properties of titanium alloys using a rapid electric heating process is provided, comprising the following steps: (1) Pretreatment of titanium alloy products: Clean the surface of titanium alloy products and set conductive clamps at both ends of the products to form a stable power circuit; (2) Controllable rapid electric heating and heat preservation: A controllable current is applied to the pretreated titanium alloy product, and the material's self-resistance heating is used to rapidly raise the temperature to the set temperature and keep it warm. During the heating process, the temperature closed-loop control is achieved by adjusting the current parameters. (3) Controllable cooling and shaping: After the heat preservation is completed, the power supply is immediately stopped and the titanium alloy product is cooled to room temperature; (4) Hot forming / correction process coupling: Apply hot forming or correction treatment to titanium alloy products during the rapid electric heating stage or after the heat preservation is completed.

[0008] Optionally, the titanium alloy product is a Ti-6Al-4V titanium alloy product, and the product form is any one of bar, wire, tube or plate.

[0009] Optionally, in step (1), surface cleaning specifically involves removing the lubricant (molybdenum disulfide), impurities, and loose oxides remaining on the surface of the titanium alloy rod and wire after drawing deformation. The conductive clamp is tightly fitted to both ends of the rod and wire, with a contact resistance ≤5mΩ.

[0010] Specifically, removing residual lubricant (molybdenum disulfide), impurities, and loose oxides from the surface can prevent poor contact and clamping end breakage caused by surface impurities. At the same time, it can prevent loose oxides from further diffusing at high temperatures to form an oxygen-rich embrittlement layer, ensuring the surface quality and fatigue performance of the product. Limiting the contact resistance can effectively avoid local overheating, ablation, and adhesion caused by Joule heat concentration in the contact area, ensuring that the axial and radial temperature uniformity error of the titanium alloy product is ≤±5℃. This lays the foundation for the uniform and controllable phase transformation of the subsequent microstructure. At the same time, it avoids the ineffective loss of electrical energy caused by excessive contact resistance, further improving energy utilization efficiency.

[0011] Optionally, in step (2), the temperature is set to T=650~780℃ and the heat preservation time is t=10~180s.

[0012] Specifically, by limiting the temperature range of 650~780℃ to the α+β two-phase region of the Ti-6Al-4V alloy, the α / β phase transformation within this temperature range is in a controllable kinetic range. Combined with a short holding time of 10~180s, the long-range diffusion of alloying elements during the phase transformation process can be suppressed by rapid heating, making the nucleation rate of the β phase much greater than the growth rate. This allows for precise quantitative control of the volume fraction, size, and overall grain size of the β transformation structure. By strictly controlling the upper limit of the temperature to be below 800℃ and the holding time to be no more than 180s, problems such as abnormal β phase growth, grain coarsening, and increased surface oxidation caused by long-term high-temperature holding are avoided. This solves the inherent contradiction of existing electric heating processes that have to use high-temperature treatment to eliminate stress, which in turn leads to grain coarsening.

[0013] Optionally, in step (2), the temperature is set to T=700℃ and the heat preservation time is t=30s.

[0014] Optionally, in step (2), the heating rate of the titanium alloy product is controlled at 50~200℃ / s.

[0015] Specifically, this heating rate range can effectively suppress long-range diffusion of elements at the α-phase grain boundaries and abnormal growth of the β-phase during the heating process, ensuring uniform nucleation of the β-phase in the α-phase matrix, and achieving grain refinement and microstructure homogenization. When the heating rate is below 50℃ / s, long-range diffusion of alloying elements will occur during the heating process, and the β-phase will preferentially grow at the grain boundaries to form a coarse Widmanstätten structure, losing the grain refinement advantage of rapid electric heating. When the heating rate is above 200℃ / s, it is easy to cause excessive radial and axial temperature differences in the product, uneven phase transformation of the microstructure, and the risk of temperature overshoot exceeding the 800℃ safety limit.

[0016] Optionally, in step (3), the cooling method can be any one of air cooling, gas cooling or water cooling.

[0017] Optionally, in step (4), the hot forming or straightening process is hot stretching or hot straightening, applying 1% to 3% plastic deformation to the titanium alloy product.

[0018] Specifically, this application couples rapid electric heating with hot stretching / hot straightening processes online. Utilizing the low rheological stress of titanium alloys in the hot state of 650~780℃, a small plastic deformation of 1%~3% can effectively promote the annihilation and rearrangement of dislocations. While regulating the microstructure, it further releases residual stress, reducing the residual stress of the product to below 4.77MPa. At the same time, it achieves precise optimization of the product's straightness, ultimately controlling the straightness to within 0.3mm / m, far superior to the existing technology's level of 1mm / m. The 1%~3% deformation range avoids the problems of insufficient stress release and poor straightening effect caused by too small a deformation, while also preventing the problems of work hardening and uneven microstructure deformation caused by too large a deformation. The thermal cycle of rapid electric heating forms a synergistic effect, realizing the simultaneous completion of microstructure performance regulation, residual stress elimination, and shape accuracy optimization in a three-in-one manner, eliminating the need for subsequent additional straightening processes and significantly shortening the production process.

[0019] Optionally, the treated titanium alloy product has a controllable β-transformation volume fraction in the range of 7.34% to 16.67%, an adjustable β-phase size in the range of 0.41 to 1.15 μm², and an average grain size controlled in the range of 4.66 to 12.29 μm².

[0020] Optionally, the treated titanium alloy products have a room temperature tensile strength fluctuation range of ≤2.5% and a post-fracture elongation fluctuation range of ≤5%; the treated titanium alloy products have an axial residual stress of ≤10MPa and a straightness of ≤0.5mm / m.

[0021] In this application, room temperature refers to 25°C.

[0022] The beneficial effects of this application include, but are not limited to: 1. This application achieves heating and short-term holding of titanium alloy within 10 to 180 seconds through rapid electric heating, shortening the processing cycle by 30 to 900 times compared to traditional in-furnace heat treatment (2.5h = 9000s). The core process (700℃ × 30 s) improves the processing efficiency by more than 150 times, and can effectively control the phase transformation and microstructure reconstruction process in a much shorter cycle than traditional processes.

[0023] 2. This application establishes an engineering-reusable process window centered on electric heating temperature (650–780℃) and holding time (10–180 s). By controlling the upper limit (T<800℃, t≤180 s), the risks of excessive softening at high temperatures, coarsening of the microstructure, and aggravated surface oxidation are suppressed from the source. Within the process window, the β-variant microstructure size can be controlled within the range of 0.41–1.15 μm², the volume fraction within the range of 7.34%–16.67%, and the grain size within the range of 4.66–12.29 μm². The tensile strength fluctuation of the product is ≤2.5%, and the elongation fluctuation is ≤5%, which significantly improves the process stability, repeatability, and fault tolerance.

[0024] 3. This application achieves direct heating of the material itself (with an electrical energy utilization rate of over 85%), reducing heat conduction loss and ineffective heating. The unit energy consumption is reduced by more than 80% compared to traditional in-furnace heat treatment (from 8.6 kWh / kg to 1.1 kWh / kg). At the same time, short-term high-temperature exposure controls the surface oxide layer thickness to within 3 μm (compared to 12 μm in traditional in-furnace heat treatment), reducing the degree of oxidation by 75%. This effectively improves surface quality and adaptability to subsequent processing, providing effective support for the green manufacturing and low-carbon processing of titanium alloys.

[0025] 4. The method described in this application is applicable to various forms of titanium alloy products, including bars, wires, tubes, and plates. It is particularly suitable for rapid online heat treatment and stress release of long-sized products. It can be integrated with straightening, hot stretching, and continuous processing production lines, providing a systematic method and theoretical basis for rapid parameter selection, stable preparation, and performance customization in engineering projects. It has significant engineering application value and broad prospects for industrial promotion. Attached Figure Description

[0026] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 Examples 1-8 in this application show the trend of grain size change with temperature and holding time. Figure 2 The comparative example 1 in this application is a statistical characterization diagram of the EBSD grain size microstructure. Detailed Implementation

[0027] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of skill in the art. The reagents and raw materials used in this invention are readily available through conventional means, and unless otherwise specified, they shall be used in accordance with conventional methods in the art or as per the product instructions. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described in this patent are for illustrative purposes only.

[0029] 1. Experimental materials and equipment All the Ti-6Al-4V titanium alloy hot-rolled bars used in the embodiments and comparative examples of this invention were prepared by three-stage vacuum arc remelting, and their composition met the requirements of GB / T 3620.1-2016 standard. The specific composition was as follows: Al: 5.96%~6.23%; V: 3.75%~4.23%; Fe: 0.15%~0.18%; O: 0.11%~0.13%; C: 0.006%~0.025%; N: 0.0030%~0.0069%; with the balance being titanium. The wire has an initial diameter of Φ5.5mm, a length of 2000mm, an average grain size of 12.82μm in its original state, a β phase volume fraction of 5.6%, an average β phase size of 0.38μm², an axial residual stress of 68MPa, and a straightness of 1.2mm / m.

[0030] The experimental equipment includes: a thyristor DC power supply (output power 0~50kW, current accuracy ±1A), copper conductive clamps (adjustable contact area), an infrared thermometer (temperature range 300~1200℃, accuracy ±1℃, sampling frequency 100Hz), a hydraulic hot stretching and straightening integrated machine (maximum tensile force 10t, deformation control accuracy ±0.1%), and a box-type resistance furnace (temperature control accuracy ±5℃).

[0031] The testing equipment includes: FEI Quanta 650F scanning electron microscope with EBSD probe, INSTRON5982 universal testing machine, X-ray residual stress analyzer, and surface roughness profiler.

[0032] 2. General testing standards and methods Tissue characterization: Grain size, β phase volume fraction and size were analyzed using EBSD technology with a test step size of 0.5 μm. The test area for each sample was no less than 500 μm × 500 μm, and the number of grains was no less than 1000. Mechanical property testing: GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Test at room temperature" was followed. The gauge length of the tensile specimen was 50 mm, the tensile rate was 2 mm / min, and 5 parallel specimens were tested in each group. The average value was taken and the fluctuation range was calculated. Residual stress detection: X-ray diffraction was used, following GB / T 7704-2017 "Nondestructive Testing - X-ray Stress Measurement Method". The detection location was the midpoint of the bar's axial direction, and the average value of three different circumferential locations was taken. Straightness inspection: A laser straightness measuring instrument is used to inspect the straightness of the entire length of the bar, with an accuracy of ±0.01mm / m; Oxide layer thickness detection: The morphology of the oxide layer on the cross section of the bar was observed by metallography, and the oxide layer thickness at 5 different locations was measured and the average value was taken; Energy consumption monitoring: The total power consumption of heat treatment of a single bar is recorded using an electricity meter, and the energy consumption per unit product (kWh / kg) is calculated.

[0033] Example 1 The steps are as follows: (1) Pretreatment of titanium alloy products: Take Φ5mm×2000mm hot-rolled Ti-6Al-4V wire, use alcohol ultrasonic cleaning to remove residual lubricant on the surface, and use sandpaper to polish to remove loose oxides on the surface; install copper conductive clamps at both ends of the wire to ensure that the clamps are tightly attached to the end face of the rod. The actual contact resistance is 3.2mΩ, forming a stable power circuit.

[0034] (2) Controllable rapid electric heating and heat preservation: Start the DC power supply, apply a controllable current to the bar, control the heating rate to 100℃ / s, rapidly heat up to 700℃, adjust the current to keep the temperature stable, and keep it warm for 30s; during the heating process, the temperature data is collected in real time by an infrared thermometer to realize closed-loop temperature control, and the temperature fluctuation range is controlled within ±5℃.

[0035] (3) Controllable cooling and shaping: After the heat preservation is completed, immediately stop the power supply and air cool the bar to room temperature.

[0036] (4) Coupling of thermoforming / straightening processes: After the heat preservation is completed and before cooling to room temperature, the filament is immediately transferred to the hydraulic straightening machine and a 2% hot straightening deformation is applied to complete the shape accuracy optimization.

[0037] Examples 2-8 This embodiment is a parameter verification implementation scheme for different temperatures and holding times. The only difference from Embodiment 1 is that: Examples 2-4: In step 2, the rapid electric heating set temperatures are 650℃, 750℃, and 780℃, respectively; Examples 5-8: In step 2, the corresponding holding times are 10 s, 60 s, 120 s, and 180 s, respectively. The remaining pretreatment, cooling, and hot straightening steps and process parameters are completely consistent with those in Example 1.

[0038] Example 9 The only difference from Example 1 is that in step (4), during the rapid electric heating and heat preservation stage, 2% axial thermal stretching deformation is applied to the wire. After the heat preservation is completed, the stretching is stopped and the wire is air-cooled to room temperature. No subsequent separate straightening process is required.

[0039] Comparative Example 1 This comparative example uses a traditional in-furnace heat treatment process. The specific steps are as follows: Take Ti-6Al-4V hot-rolled wire of the same specifications as in Example 1, put it into a box-type resistance furnace, set the heating temperature to 950 ℃, hold it at that temperature for 2 h, and then cool it to room temperature with the furnace; no online straightening or small deformation is applied.

[0040] Comparative Example 2 The only difference from Example 1 is that: Ti-6Al-4V titanium alloy wire of the same specifications as in Example 1 is selected, and the self-resistance current rapid heating method is adopted; the heating temperature is set to 850 ℃, held for 30 s, and air-cooled to room temperature; and 2% hot stretching is applied.

[0041] Comparative Example 3 The only difference from Example 1 is that: Ti-6Al-4V titanium alloy rods of the same specifications as in Example 1 are selected, and a self-resistance current rapid heating method is adopted; the heating temperature is set to 700 ℃, held for 300 s, and air-cooled to room temperature; and a 2% hot stretching is applied.

[0042] Comparative Example 4 The only difference from Example 1 is that in step (1), the clamping force of the conductive fixture is adjusted so that the contact resistance is 8.5mΩ; the remaining steps and process parameters are completely consistent with Example 1.

[0043] Experimental Example 1. Comparison of organizational control effects The tissue characterization results of each embodiment and comparative example are shown in Table 1.

[0044] Table 1 Comparison of microstructure parameters of Ti-6Al-4V alloys prepared by different processes

[0045] As shown in Table 1, the titanium alloy products treated by the method specified in this application can achieve continuous and precise control of the β phase volume fraction in the range of 7.34% to 16.67%, the β phase size in the range of 0.41 to 1.15 μm², and the average grain size in the range of 4.66 to 12.29 μm². The repeatability error of the microstructure control is ≤8%, which fully meets the performance customization requirements of different application scenarios.

[0046] And by Figure 1 As can be seen from the figure, the synergistic effect of heating temperature and holding time on the average grain size of Ti-6Al-4V alloy during rapid electric heating is clearly shown. Under short holding time (10~30s), the average grain size of the alloy first decreases and then increases with the increase of heating temperature. The grains continue to refine in the range of 650~700℃, reaching the refinement peak at 700℃, with the average grain size dropping to 8.56μm². When the temperature continues to rise to 750~780℃, the rapid growth of the β phase drives the grain size to gradually increase. Under long holding time (60~180s), the average grain size of the alloy continues to increase with the increase of heating temperature. The high temperature environment accelerates the atomic diffusion inside the alloy, further aggravating the grain coarsening process. Within the low-temperature range of 650~700℃, the average grain size of the alloy first decreases and then increases with the extension of holding time. 30s is the optimal holding time for grain refinement. After 60s, the grains begin to grow slowly. In the high-temperature range of 750~780℃, the grain size continues to increase with the extension of holding time, with no grain refinement range. Overall, 700℃×30s is the optimal parameter combination for this rapid electric heating process. Under this parameter, the grain refinement effect is the most significant, with a grain size refinement of 33.2% compared to the original state. This pattern is due to the synergistic effect of the Joule heating effect and the non-thermal effect of the electron wind in rapid electric heating, which effectively suppresses the long-range diffusion of alloying elements, making the nucleation rate of the β phase much higher than the growth rate.

[0047] Depend on Figure 2As can be seen, the figure shows the EBSD grain size statistical characterization of the Ti-6Al-4V alloy after treatment with the conventional furnace heat treatment process in Comparative Example 1. Comparative Example 1 was treated with the conventional furnace heat treatment process of 950℃ for 2 hours without online hot forming or straightening. Its microstructure exhibits typical defects of the conventional heat treatment process. The alloy grains are extremely coarse and have very poor uniformity. The average grain size is as high as 25.68 μm², which is 3 times the grain size after the optimal process of this application. A large number of coarse Widmanstätten structures appear in the microstructure, the β phase grows abnormally and is extremely unevenly distributed, the degree of intragranular distortion is severe, the recrystallization ratio is extremely low, and the microstructure consistency and stability are extremely poor. In contrast, the Ti-6Al-4V alloy treated with the rapid electric heating process of this application... The alloy grains are fine, equiaxed, and uniformly distributed, with an average grain size controlled within the range of 4.66~12.29 μm². The β phase is dispersed and uniformly distributed, with no coarse Widmanstätten structure formed. The repeatability error of the microstructure control is ≤8%. The recrystallization process is sufficient and the dislocation density is low, resulting in minimal fluctuations in mechanical properties. This figure provides a direct comparison that highlights the inherent drawbacks of traditional furnace heat treatment, such as grain coarsening and microstructure inhomogeneity caused by prolonged high-temperature holding. It also fully verifies that the rapid electric heating combined with short-time holding process of this application can suppress abnormal grain growth from the source, achieve precise quantitative control of the β-transformation microstructure and grain size of titanium alloys, and effectively solve the core technical problems of low production efficiency, poor microstructure controllability, and large fluctuations in product performance in traditional heat treatment processes.

[0048] 2. Comparison of residual stress, shape accuracy, and surface quality The residual stress, straightness, and oxide layer thickness test results for each embodiment and comparative example are shown in Table 2.

[0049] Table 2 Comparison of residual stress, shape accuracy, and surface quality of Ti-6Al-4V alloys prepared by different processes

[0050] As shown in Table 2, the titanium alloy products treated by the method specified in this application can achieve an axial residual stress of ≤10MPa and a straightness of ≤0.5mm / m, demonstrating excellent performance.

[0051] The core solution of this application is to construct a highly efficient thermal cycle of "rapid heating-short holding-controllable cooling" using self-resistive current heating. This fully leverages the high energy efficiency and high response of direct heating of the material itself. By establishing a controllable matching relationship between the electric heating temperature T, the holding time t, and the electrical parameters (current density / power), a parameter-microstructure-property rapid mapping and parameter selection method for engineering applications is formed. This achieves efficient and stable control of the microstructure and properties of titanium alloys while significantly shortening heat treatment time, reducing energy consumption, and mitigating oxidation. The specific design concept is as follows: (1) By heating the material to 650-780℃ within seconds to minutes and holding it for a short time (10-180s), the synergistic effect of Joule heating and the non-thermal effect of “electron wind” is utilized to enable the titanium alloy to complete the α / β phase-related phase transformation and microstructure reconstruction within a time scale much shorter than that of traditional furnace heat treatment (more than 2.5h). Compared with the original TC4 alloy β phase volume fraction of 5.6% and size of 0.38μm², this method can achieve rapid control of β transformation microstructure volume fraction in the range of 7.34%-16.67% and size in the range of 0.41-1.15μm². At the same time, by suppressing abnormal grain growth caused by long-term holding, the average grain size can be controlled within the range of 4.66-12.29μm². Among them, the 700℃×30s process can refine the grain to 8.56μm² (33.2% refinement compared to the original 12.82μm²).

[0052] (2) By setting upper limits for temperature and time (T<800℃, t≤180s), and coordinating with closed-loop temperature control and local protection measures, process risks are reduced from the source: When the temperature exceeds 800℃, excessive softening of the material leads to an increase of more than 30% in tensile necking, an increase in β phase size to more than 1.85μm², and a surface oxide layer thickness of 9.6μm (2.1 times that within the process window); when the holding time exceeds 180s, the grain size increases by 15% to 20% compared to 180s, and the tensile strength decreases by more than 5%. Within the process window of this invention, the tensile strength fluctuation of TC4 alloy is ≤2.5% (1049~1076 MPa), the elongation fluctuation is ≤5% (7.96%~11.44%), and the repeatability error of β transformation microstructure size and volume fraction control is ≤8%.

[0053] (3) Utilizing the electric heating characteristic of "direct energy conversion within the material body" (electric energy utilization rate of over 85%), this method can be integrated online with hot straightening, hot stretching and other processes. By combining 2% hot stretching with electric heating, the residual stress of TC4 bar can be reduced from 68MPa in the traditional process to below 4.77MPa, and the straightness can be optimized to within 0.3mm / m. At the same time, the heating and holding time is significantly shortened (the total processing time is shortened by more than 97% compared with the traditional in-furnace heat treatment), and the unit energy consumption is reduced by more than 80% (the energy consumption of traditional in-furnace heat treatment is 8.6 kWh / kg, while this method is only 1.1 kWh / kg), providing a process path that can be promoted for the efficient manufacturing of titanium alloys.

[0054] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for efficiently controlling the microstructure and properties of titanium alloys using a rapid electric heating process, characterized in that, Includes the following steps: (1) Pretreatment of titanium alloy products: Clean the surface of titanium alloy products and set conductive clamps at both ends of the products to form a stable power circuit; (2) Controllable rapid electric heating and heat preservation: A controllable current is applied to the pretreated titanium alloy product, and the material's self-resistance heating is used to rapidly raise the temperature to the set temperature and keep it warm. During the heating process, the temperature closed-loop control is achieved by adjusting the current parameters. (3) Controllable cooling and shaping: After the heat preservation is completed, the power supply is immediately stopped and the titanium alloy product is cooled to room temperature; (4) Hot forming / correction process coupling: Apply hot forming or correction treatment to titanium alloy products during the rapid electric heating stage or after the heat preservation is completed.

2. The method according to claim 1, characterized in that, The titanium alloy product is a Ti-6Al-4V titanium alloy product, and the product form is any one of the following: bar, wire, tube or plate.

3. The method according to claim 1, characterized in that, In step (1), surface cleaning specifically involves removing the lubricant, impurities, and loose oxides remaining on the surface of the titanium alloy rod and wire after drawing deformation. The conductive clamp is tightly fitted to both ends of the product, with a contact resistance ≤5mΩ.

4. The method according to claim 1, characterized in that, In step (2), the temperature is set to T=650~780℃ and the heat preservation time is t=10~180s.

5. The method according to claim 4, characterized in that, In step (2), the temperature is set to T=700℃ and the holding time is t=30s.

6. The method according to claim 1, characterized in that, In step (2), the heating rate of the titanium alloy product is controlled at 50~200℃ / s.

7. The method according to claim 1, characterized in that, In step (3), the cooling method is any one of air cooling, gas cooling or water cooling.

8. The method according to claim 1, characterized in that, In step (4), the hot forming or straightening treatment is hot stretching or hot straightening, which applies 1% to 3% plastic deformation to the titanium alloy product.

9. The method according to claim 1, characterized in that, The treated titanium alloy products exhibit a controllable β-transformation volume fraction ranging from 7.34% to 16.67%, with β-phase sizes ranging from 0.41 to 1.15 μm. 2 Adjustable within a certain range, with the average grain size controlled between 4.66 and 12.29 μm. 2 Within the range.

10. The method according to claim 1, characterized in that, The treated titanium alloy products have an axial residual stress ≤10MPa and a straightness ≤0.5mm / m.

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