TA11 titanium alloy bar with high creep resistance and high fatigue performance and preparation method of TA11 titanium alloy bar

Abstract

The invention discloses a TA11 titanium alloy bar with high creep resistance and high fatigue performance and a preparation method of the TA11 titanium alloy bar, and belongs to the field of titanium alloy material processing. 2, the blank is subjected to multi-heating-number circulating forging; step 3, rolling a finished bar; and 4, surface treatment. By optimizing the proportion of the alpha stable element, the beta stable element and the trace strengthening element and carrying out multi-heating-number forging and finished product rolling to refine the alloy structure within the range above and below the phase transformation point temperature, the high fatigue performance of the TA11 alloy bar is achieved, meanwhile, the trace silicon element is introduced, the dispersion strengthening effect of silicide is utilized, and the high fatigue resistance of the TA11 alloy bar is achieved. Dislocation motion and grain growth are hindered, the high creep resistance of the TA11 alloy is achieved, and the creep resistance and the fatigue resistance of the TA11 alloy bar are synergistically improved.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy material processing technology, specifically relating to a TA11 titanium alloy bar with high creep resistance and high fatigue performance and its preparation method. Background Technology

[0002] TA11 titanium alloy (nominal composition Ti-8Al-1Mo-1V) is a near-α type high-temperature titanium alloy. Due to its low density, high elastic modulus, excellent vibration damping performance, and thermal stability, it is widely used in critical hot-end components such as compressor blades in aero-engines. However, with the development of aerospace technology, engine service temperatures and stress levels are constantly increasing. Traditional TA11 titanium alloys suffer from insufficient high-temperature creep resistance and short cyclic fatigue life, making them prone to creep deformation and fatigue fracture under long-term high-temperature stress, thus limiting their application in aero-engines.

[0003] Currently, existing technologies mainly improve alloy properties by adjusting heat treatment processes, such as adjusting the double annealing temperature and holding time. However, relying solely on heat treatment is insufficient to fundamentally improve the intrinsic properties of alloys. Furthermore, some improved processes only focus on high creep resistance without considering fatigue performance. In practical engineering applications, materials often bear the coupled effects of high-temperature creep loads and cyclic fatigue loads simultaneously, and high creep resistance alone is insufficient to meet the requirements of use under complex working conditions.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a TA11 titanium alloy bar with high creep resistance and high fatigue performance and its preparation method, so as to solve the problem that high creep resistance alone cannot meet the requirements of use under complex working conditions.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance improves the fatigue performance of TA11 alloy bars by optimizing the ratio of α-stabilizing elements, β-stabilizing elements and trace strengthening elements, and refining the alloy microstructure through multi-fire forging and finished product rolling within the range above and below the phase transformation point temperature. At the same time, the introduction of trace Si elements utilizes the dispersion strengthening effect of silicides to hinder dislocation movement and grain growth, thereby improving the creep resistance of TA11 alloy bars.

[0007] Furthermore, the chemical composition of the TA11 titanium alloy, by mass percentage, is as follows: Al: 6.3%~7.5%, Mo: 1.8%~2.8%, V: 0.9%~1.3%, Zr: 1.0%~1.5%, O: 0.05%~0.13%, Si: 0.07~0.15%, C: 0.005%~0.010%, Fe: 0.01%~0.02%, N≤0.03%, H≤0.0015%, with the balance being Ti and unavoidable impurity elements, wherein the total amount of impurity elements is less than 0.03%.

[0008] Furthermore, in the TA11 titanium alloy, 7.5wt.%≤[Al]eq≤8.3wt.%, 2.7wt.%≤[Mo]eq≤3.5wt.%, and 2.4≤[Al]eq / [Mo]eq≤3.0, to avoid the formation of excessive α2 phase and to balance the improvement of creep resistance and fatigue performance.

[0009] Specifically, in the aforementioned TA11 titanium alloy, the mass percentage of each component should fall within the range described above, and can be adjusted adaptively according to actual performance requirements. For example, the mass percentage of Al can be 6.3%, 6.4%, 6.5%, 6.6%, 6.8%, 7.0%, 7.2%, 7.3%, 7.5%, etc., and the mass percentage of Mo can be 1.8%, 2.0%, 2.2%, 2.4%, 2.6%, 2.8%, etc. Other elements will not be listed here. However, it should be emphasized that the components in the TA11 titanium alloy must also meet the following conditions: 7.5wt.%≤[Al]eq≤8.3wt.%, 2.7wt.%≤[Mo]eq≤3.5wt.%, and 2.4≤[Al]eq / [Mo]eq≤3.0.

[0010] Furthermore, the preparation method includes the following steps: Step 1, Ingot preparation: Prepare electrode blocks according to the proportion of the target alloy, and melt them by vacuum consumable arc melting to obtain TA11 titanium alloy ingots with dimensions of Φ640mm~Φ720mm; Step 2, Multi-cycle forging of billet: The TA11 titanium alloy ingot obtained in Step 1 is subjected to multi-cycle forging at the β phase transformation temperature T. β The billet A is forged in multiple furnace cycles within the upper and lower range to obtain a billet A with a size of Φ80mm~Φ90mm; Step 3, Finished bar rolling: The bar billet A obtained in Step 2 is rolled in one heat to obtain bar billet B with a size of Φ27mm~Φ42mm; Step 4, Surface treatment: Remove the surface defects and oxide scale from the billet B obtained in step 3 to obtain the target TA11 titanium alloy finished bar with dimensions of Φ25mm~Φ40mm.

[0011] Furthermore, in step 2, the multi-cycle forging of the billet includes: Step 2.1, at T β The forging process involves two consecutive furnace forgings at +(60~130)℃, with a forging ratio of 1.3~2.0, followed by air cooling. Step 2.2, at T β The forging process involves two consecutive hot forging cycles at -20~40℃, with a forging ratio of 1.4~1.9. After forging, the metal is returned to the furnace at T. β After maintaining the temperature at +30~50℃ for 3~4 hours, air cool. Step 2.3, at T β The forging process involves two consecutive furnace forgings at -(30~50)℃, with a forging ratio of 1.3~1.6, followed by air cooling. Step 2.4, at T β The forging process involves two consecutive hot forging cycles at -30~50℃, with a forging ratio of 1.2~1.4. After forging, the metal is returned to the furnace at T. β After being heated to -(20~40)℃ and held for 1.5h~2h, it is air-cooled to finally obtain the billet A of the target size.

[0012] Furthermore, in step 3, the temperature is heated to the β phase transition temperature T. β The following conditions are met: holding time at 60℃~90℃ for 1.5h~2h, rolling deformation of 72.4%~91%, and finally obtaining bar billet B of the target size.

[0013] Specifically, in step 1, according to the actual proportion of the target titanium alloy, the required amount of sponge titanium and the addition methods and requirements of each intermediate alloy for a single electrode block are as follows: The sponge titanium has a particle size of 2.0 mm to 6.0 mm, and the impurity content meets the following requirements: 0.005% ≤ C ≤ 0.010%, N ≤ 0.003%, 0.01% ≤ Fe ≤ 0.02%, H ≤ 0.001%, Cl ≤ 0.01%, Sn ≤ 0.002%, and the range between the initial and retest results of oxygen element is ≤ 50 ppm, and the average value of the initial and retest results of aluminum element is 0.002% to 0.01%. Aluminum is introduced in the form of elemental aluminum; oxygen is introduced in the form of titanium dioxide, which must be kept dry and free of moisture. Vanadium is introduced in the form of a vanadium-aluminum alloy with a particle size of 1.0 mm to 2.5 mm and impurity content satisfying the following: C ≤ 0.025%, N ≤ 0.025%, Fe ≤ 0.15%, H ≤ 0.001%, and the range between the initial and retest results of vanadium is ≤ 3000 ppm; molybdenum is introduced in the form of an aluminum-molybdenum master alloy powder with a particle size ≤ 0.3 mm and impurity content satisfying the following: C ≤ 0.005%, N ≤ 0.005%, Fe ≤ 0.10%, H ≤ 0.001%, and the range between the initial and retest results of molybdenum is ≤ 2000 ppm; silicon is introduced in the form of a titanium-silicon master alloy with a particle size ≤ 2.0 mm. Zirconium is introduced in the form of sponge zirconium with a particle size ≤ 5.0 mm.

[0014] Specifically, the electrode manufacturing process is as follows: the above-mentioned raw materials that meet the specifications are put into a mixing cart and mixed by mechanical mixing for a period of not less than 60 seconds to ensure that the raw materials do not agglomerate and are mixed evenly; the mixed raw materials are pressed into electrode blocks, and the weight of a single electrode block is controlled between 30kg and 115kg; the pressed electrode blocks are left to stand at room temperature for 6h to 8h to release the internal stress generated during the pressing process; then the electrode blocks are placed in a vacuum-protected, argon-filled plasma welding box for welding operations to assemble them into consumable electrodes, wherein the argon filling pressure of the plasma welding box is ≥60000Pa and the argon purity is ≥99.99%.

[0015] Furthermore, in step 1, the prepared electrode block is subjected to three vacuum consumable arc melting processes. The crucible ratio of the crucibles used in each vacuum consumable arc melting process is less than 0.75 to avoid the generation of edge arcs.

[0016] Specifically, the three-stage vacuum self-consuming arc melting process is as follows: In the first melting stage, the vacuum level is controlled to be ≤1.0 Pa, the melting leakage rate ≤0.8 Pa / min, the melting current is 10kA~20kA, the melting voltage is 25V~40V, and the arc stabilizing current is 10A~30A. After melting, the ingot is cooled for 4h~6h, and the moisture-absorbing and blackened areas on the surface are polished. In the second melting stage, the vacuum level is controlled to be ≤0.8 Pa, the melting leakage rate ≤0.5 Pa / min, and the melting speed is 18kg / min~2 The melting speed is 5 kg / min, the melting voltage is 28V~40V, the arc stabilizing current is 15A~25A, and the cooling time after melting is 6h~9h. The melting process adopts the turning and welding melting method. For the third melting, the vacuum degree is controlled to be ≤0.7Pa, the melting leakage rate is ≤0.5Pa / min, the melting speed is 12kg / min~20kg / min, the melting voltage is 30V~40V, the arc stabilizing current is 8A~20A, and the head is purged with argon and cooled for 5h~8h after melting. The melting process adopts the turning and welding melting method. The ingots after the first and second melting need to be placed in an oven for heat preservation to prevent moisture absorption after being taken out of the furnace.

[0017] Specifically, in the vacuum self-consuming arc melting process, the values ​​of specific process parameters can be selected within the range according to the actual process requirements. For example, in the first melting process, the melting current can be selected as 11kA, 15kA, 20kA, etc., the melting voltage can be selected as 25V, 30V, 35V, 40V, etc., and the arc stabilizing current can be selected as 15A, 19A, 24A, etc. The values ​​of process parameters in the second and third melting processes are similar to those in the first melting process, and will not be repeated here.

[0018] Furthermore, the invention also provides TA11 titanium alloy bars obtained using some or all of the preparation methods described above. The finished TA11 titanium alloy bars have a diameter of Φ25mm to Φ40mm, and exhibit a creep ductile elongation εp ≤ 0.083% after 100 hours of maintenance under stress conditions of 410MPa and 425℃. The fatigue cycle count under stress conditions of 325MPa and 355MPa at 20℃ is 1×10⁻⁶. 8 .

[0019] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: This invention improves the fatigue performance of TA11 alloy bars by optimizing the ratio of α-stabilizing elements (such as aluminum to increase the β-transformation temperature of the alloy, thereby enhancing high-temperature microstructure stability), β-stabilizing elements (such as vanadium and molybdenum to reduce the deformation resistance of the alloy and enhance forging plasticity), and trace strengthening elements (such as oxygen through trace interstitial solid solution). Furthermore, it refines the alloy microstructure through multi-stage forging and finished product rolling within the phase transformation temperature range (by combining multiple heating, repeated forging, and cyclic recrystallization to promote full recrystallization, eliminate stress, and make the microstructure denser, resulting in a more uniform and finer microstructure). The fatigue cycle count under 20℃ and 325MPa stress and 425℃ and 355MPa stress conditions can be increased to 1×10⁻⁶. 8 .

[0020] Meanwhile, this invention introduces trace amounts of silicon, utilizing the dispersion strengthening effect of silicides to hinder dislocation movement and grain growth, thereby improving the creep resistance of TA11 alloy. Under stress conditions of 425℃ and 410MPa, its creep plastic elongation εp ≤ 0.085% can be maintained for 100 hours.

[0021] Furthermore, this invention also avoids grain boundary embrittlement by controlling the content of impurity elements, controlling the smelting process, and adopting a highly homogenized ingot smelting process, thereby achieving a synergistic improvement in the creep resistance and fatigue performance of TA11 alloy bars. Attached Figure Description

[0022] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A flowchart illustrating a method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance, provided by this invention. Figure 2 This is a transverse microstructure diagram of the head of a Φ640mm TA11 alloy ingot provided in Embodiment 1 of the present invention; Figure 3 This is a single-value control chart of Al element content at 9 points laterally at the head and tail of a Φ640mm ingot provided in Embodiment 1 of the present invention. Figure 4 This is a single-value control chart of the Mo element content at 9 points laterally at the head and tail of a Φ640mm ingot provided in Embodiment 1 of the present invention. Figure 5This is a single-value control chart of Si element content at 9 points laterally at the head and tail of a Φ640mm ingot provided in Embodiment 1 of the present invention. Figure 6 This is a single-value control chart of Zr element content at 9 points in the transverse direction at the head and tail of a Φ640mm ingot provided in Embodiment 1 of the present invention; Figure 7 This is a single-value control chart of the O element content at 9 points laterally at the head and tail of a Φ640mm ingot provided in Embodiment 1 of the present invention. Figure 8 This is a single-value control chart of V element content at 9 points laterally at the head and tail of a Φ640mm ingot provided in Embodiment 1 of the present invention. Figure 9 This is a high-magnification microstructure image of the 25mm TA11 titanium alloy finished bar provided in Embodiment 1 of the present invention; Figure 10 This is a high-magnification microstructure image of the TA11 titanium alloy Φ30mm finished bar provided in Embodiment 2 of the present invention; Figure 11 This is a high-magnification microstructure image of the 40mm TA11 titanium alloy finished bar provided in Embodiment 3 of the present invention. Detailed Implementation

[0025] Exemplary embodiments will now be described in detail. The embodiments described below are not representative of all embodiments consistent with this invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0026] See Figure 1 As shown, the present invention provides a method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance. The preparation method includes: step 1, ingot preparation; step 2, billet multi-cycle forging; step 3, finished bar rolling; and step 4, surface treatment.

[0027] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] Example 1 This embodiment provides a method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance. The target composition of the TA11 titanium alloy is Al: 6.8%, Mo: 2.5%, V: 0.95%, Zr: 1.05%, O: 0.12%, Si: 0.10%, with the balance being Ti and unavoidable impurity elements. The total amount of impurity elements such as C, Fe, N, and H is less than 0.03%, and the [Al]eq / [Mo]eq ratio is 2.617.

[0029] The specific steps are as follows: Step 1: Ingot Preparation Based on the actual proportions of the target titanium alloy, calculate the amount of sponge titanium and each intermediate alloy required for a single electrode, including: The sponge titanium uses small particles with a particle size of 2.0mm~6.0mm. The impurity content meets the following requirements: 0.005%≤C≤0.010%, N≤0.003%, 0.01%≤Fe≤0.02%, H≤0.001%, Cl≤0.01%, Sn≤0.002%. Furthermore, the range between the initial and retest results of oxygen is ≤50ppm, and the average value of the initial and retest results of aluminum is ≤0.01%. Aluminum is introduced in the form of elemental aluminum; oxygen is introduced in the form of titanium dioxide, and the titanium dioxide must be kept dry and free of moisture. Vanadium is introduced in the form of a vanadium-aluminum alloy with a particle size of 1.0 mm to 2.5 mm and impurity content meeting the following requirements: C ≤ 0.025%, N ≤ 0.025%, Fe ≤ 0.15%, H ≤ 0.001%, and the range between the initial and retest results for vanadium is ≤ 3000 ppm. Molybdenum is introduced in the form of an aluminum-molybdenum master alloy powder with a particle size ≤ 0.3 mm and impurity content meeting the following requirements: C ≤ 0.005%, N ≤ 0.005%, Fe ≤ 0.10%, H ≤ 0.001%, and the range between the initial and retest results for molybdenum is ≤ 2000 ppm. Silicon is introduced in the form of a titanium-silicon master alloy with a particle size ≤ 2.0 mm. Zirconium was introduced in the form of sponge zirconium with a particle size ≤ 5.0 mm.

[0030] The above raw materials are fed into a mixing trolley and mechanically mixed for 60 seconds to ensure that the raw materials do not agglomerate and are mixed evenly. The mixed raw materials are pressed into trapezoidal electrode blocks, each weighing 35 kg. The diagonal length of the electrode blocks after being assembled in pairs is 350 mm. The pressed electrode blocks are left to stand at room temperature for 6 hours to release the internal stress generated during the pressing process. Then the electrode blocks are placed in a vacuum-protected, argon-filled plasma welding box for welding operations to assemble them into consumable electrodes. The argon filling pressure of the plasma welding box is 60,000 Pa, and the argon purity is ≥99.99%.

[0031] The prepared consumable electrode underwent three vacuum arc melting processes. The specific process conditions were as follows: For the first melting, the crucible diameter was Φ440mm, the vacuum degree was controlled to ≤1.0Pa, the melting leakage rate was ≤0.8Pa / min, the melting current was 13kA, the melting voltage was 32V, and the arc stabilizing current was 12A DC. After melting, the electrode was cooled for 4 hours, and the moisture-absorbing and blackened areas on the ingot surface were polished. The ingot was then placed in an oven for 10 hours of heat treatment. For the second melting, the crucible diameter was Φ560mm, the vacuum degree was controlled to ≤0.8Pa, and the melting leakage rate was ≤0.5Pa / min. The melting rate was 18 kg / min, the melting voltage was 34 V, the arc stabilizing current was 25 A, and the ingot was cooled for 6 hours after melting. The melting process used a turning-over welding method. The ingot was kept in an oven for 8 hours. The diameter of the crucible for the three-stage melting was Φ640 mm, the vacuum degree was controlled to be ≤0.7 Pa, the melting leakage rate was ≤0.5 Pa / min, the melting rate was 15 kg / min, the melting voltage was 35 V, the arc stabilizing current was 15 A, and the head was purged with argon and cooled for 5 hours after melting. The melting process used a turning-over welding method. The transverse macrostructure of the ingot head is as follows. Figure 2 As shown, the ranges of each component at the nine points on the horizontal axis from the beginning to the end are as follows: Figures 3-8 As shown, the uniformity of the elemental composition is good, with Al < 1500 ppm (e.g. Figure 3 As shown), Mo < 700 ppm (e.g. Figure 4 As shown), Si < 250 ppm (e.g. Figure 5 As shown), Zr < 700ppm (e.g. Figure 6 As shown), O < 280ppm (e.g. Figure 7 As shown), V < 800ppm (e.g. Figure 8 (As shown).

[0032] Step 2: Multi-cycle forging of billet The Φ640mm ingot 1 obtained in step 1, after being melted by three vacuum self-consuming arc melting processes, is heated at the β phase transformation temperature T. β The process involves multiple forging cycles within the upper and lower regions to obtain a Φ90mm billet A1. This is divided into four steps: Step 2.1: Perform two consecutive forging cycles, with the first cycle at temperature T. β +130℃, the temperature of the second firing is T β +80℃, forging ratio 1.3~1.8, air cooling after forging; Step 2.2, at T β The forging process involves two consecutive hot forging cycles at -40℃, with a forging ratio of 1.4 to 1.8. After forging, the metal is returned to the furnace to T. β After being heated to +50℃ for 3 hours, air-cooled. Step 2.3, at T β The forging process involves two consecutive furnace passes at -30℃, with a forging ratio of 1.3 to 1.5, followed by air cooling. Step 2.4, at T β The forging process involves two consecutive hot forging cycles at -30℃, with a forging ratio of 1.2 to 1.3. After forging, the metal is returned to the furnace to T. β After being heated to -20℃ and held for 2 hours, the billet A1 with a diameter of 90mm was obtained by air cooling. Step 3: Finished product rolling The Φ90mm billet A obtained in step 2 is subjected to a single continuous rolling process at a heating temperature T. β The temperature was set at -60℃ and held for 2 hours, and the rolling deformation was 91%, finally yielding a Φ27mm bar billet B1. Step 4, Surface Treatment The Φ27mm billet obtained in step 3 is subjected to peeling and polishing to remove surface defects and oxide scale, resulting in a TA11 titanium alloy Φ25mm finished bar (I), as shown below. Figure 9 As shown, the primary α phase content is above 80%, and the microstructure of the bar material in this embodiment is more uniform and finer.

[0033] The mechanical properties of the 25mm TA11 titanium alloy finished bar (I) obtained above were tested, as shown in Table 1. It can be seen that the creep plastic elongation εp ≤ 0.083% under 425℃ and 410MPa stress conditions for 100h, and the fatigue cycle count under 20℃ and 325MPa stress conditions and 425℃ and 355MPa stress conditions increased to 1.2×10 8 It is 10 times higher than the target requirement.

[0034]

[0035] Example 2 This embodiment provides a method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance. The target alloy composition is Al: 7.0%, Mo: 2.0%, V: 1.20%, Zr: 1.1%, O: 0.10%, Si: 0.08%, with the balance being Ti and unavoidable impurity elements. The total amount of impurity elements such as C, Fe, N, and H is less than 0.03%, and the [Al]eq / [Mo]eq ratio is 2.928.

[0036] The specific steps are as follows: Step 1: Ingot Preparation The weight of individual electrodes for sponge titanium and various intermediate alloys is calculated based on the target composition of the alloy ingot, where: The sponge titanium uses small particles with a particle size of 2.0~6.0mm. The impurity content meets the following requirements: 0.005%≤C≤0.010%, N≤0.003%, 0.01%≤Fe≤0.02%, H≤0.001%, Cl≤0.01%, Sn≤0.002%, and the range between the initial and retest results of oxygen element is ≤50ppm, and the average value of the initial and retest results of aluminum element is ≤0.01% (0.002%). Aluminum is introduced in the form of elemental aluminum; oxygen is introduced in the form of titanium dioxide, and the titanium dioxide must be kept dry and free of moisture. Vanadium is introduced in the form of a vanadium-aluminum alloy with a particle size of 1.0~2.5mm and impurity content meeting the following requirements: C≤0.025%, N≤0.025%, Fe≤0.15%, H≤0.001%, and the range between the initial and retest results of vanadium is ≤3000ppm; molybdenum is introduced in the form of an aluminum-molybdenum master alloy powder with a particle size ≤0.3mm and impurity content meeting the following requirements: C≤0.005%, N≤0.005%, Fe≤0.10%, H≤0.001%, and the range between the initial and retest results of molybdenum is ≤2000ppm; silicon is introduced in the form of a titanium-silicon master alloy with a particle size ≤2.0mm. Zirconium was introduced in the form of sponge zirconium with a particle size ≤ 5.0 mm.

[0037] The above raw materials are fed into a mixing trolley and mechanically mixed for 70 seconds to ensure that the raw materials do not agglomerate and are mixed evenly. The mixed raw materials are then pressed into trapezoidal electrode blocks, each weighing 38 kg. The diagonal length of the electrode blocks after being assembled in pairs is 365 mm. The pressed electrode blocks are left to stand at room temperature for 8 hours to release the internal stress generated during the pressing process. Subsequently, the electrode blocks are placed in a vacuum-protected, argon-filled plasma welding box for welding operations, and assembled into consumable electrodes. The argon pressure of the plasma welding box is 80,000 Pa, and the argon purity is ≥99.99%.

[0038] The prepared consumable electrode was subjected to three vacuum consumable arc melting processes. The specific process conditions were as follows: For the first melting, the crucible diameter was Φ440mm, the vacuum degree was controlled to ≤1.0Pa, the melting leakage rate was ≤0.8Pa / min, the melting current was 13kA, the melting voltage was 32V, and the arc stabilizing current was 12A DC. After melting, the electrode was cooled for 4 hours, and the moisture-absorbing and blackened areas on the ingot surface were polished. The ingot was then placed in an oven for 10 hours. For the second melting, the crucible diameter was Φ560mm, the vacuum degree was controlled to ≤0.8Pa, and the melting leakage rate was ≤0.5Pa / min. The melting speed was 18 kg / min, the melting voltage was 34 V, the arc stabilizing current was 25 A, and the melting was completed and cooled for 6 hours. The melting process adopted the turning and welding melting method. The ingot was placed in an oven for 8 hours of heat preservation. The diameter of the crucible for the three melting processes was Φ640 mm. The vacuum degree was controlled to be ≤0.7 Pa, the melting leakage rate was ≤0.5 Pa / min, the melting speed was 15 kg / min, and when 1000 kg remained, the melting speed was reduced to 12 kg. The melting voltage was 35 V, the arc stabilizing current was 18 A, and the head was purged with argon and cooled for 5 hours after melting. The melting process adopted the turning and welding melting method.

[0039] Step 2: Multi-cycle forging of billet The Φ640mm ingot 2 obtained in step 1, after three vacuum self-consuming arc melting processes, is heated at the β phase transformation temperature T. β The process involves multiple forging cycles within the upper and lower regions to obtain a Φ90mm billet A2. This is divided into four steps: Step 2.1: Perform two consecutive forging cycles, with the first cycle being T. β +100℃, second firing T β +80℃, forging ratio 1.3~1.8, air cooling after forging; Step 2.2, at T β The forging process involves two consecutive hot forging cycles at -20℃, with a forging ratio of 1.4 to 1.8. After forging, the metal is returned to the furnace to T. β After being heated to +40℃ and kept at that temperature for 3 hours, it was then air-cooled. Step 2.3, at T β The forging process involves two consecutive furnace passes at -40℃, with a forging ratio of 1.3 to 1.5, followed by air cooling. Step 2.4, at T β The forging process involves two consecutive hot forging cycles at -40℃, with a forging ratio of 1.2 to 1.3. After forging, the metal is returned to the furnace to T. β After being heated to -30℃ and held for 2 hours, the billet A2 with a diameter of 90mm was obtained by air cooling. Step 3: Finished product rolling The Φ90mm billet obtained in step 2 is subjected to a single continuous rolling process at a heating temperature T. β The temperature was set at -70℃ and held for 2 hours, and the rolling deformation was 87.4%, finally yielding a Φ32mm billet B2. Step 4, Surface Treatment The Φ32mm billet B2 obtained in step 3 is peeled and polished to remove surface defects and oxide scale, resulting in a TA11 titanium alloy Φ30mm finished bar (II). Figure 10 As shown, the primary α phase content is above 85%, and the microstructure of the bar material in this embodiment is more uniform and finer.

[0040] The mechanical properties of the 30mm TA11 titanium alloy finished bar (II) obtained above were tested, as shown in Table 2. It can be seen that its creep plastic elongation εp ≤ 0.078% after 100h under stress conditions of 425℃ and 410MPa, and the fatigue cycle count under stress conditions of 20℃ and 325MPa and 425℃ and 355MPa is increased to 1.2×10⁻⁶. 8 It is 10 times higher than the target requirement.

[0041]

[0042] Example 3 This embodiment provides a method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance. The target alloy composition is Al: 7.0%, Mo: 2.3%, V: 0.98%, Zr: 1.40%, O: 0.07%, Si: 0.15%, with the balance being Ti and unavoidable impurity elements. The total amount of impurity elements such as C, Fe, N, and H is less than 0.03%, and the [Al]eq / [Mo]eq ratio is 2.700.

[0043] The specific steps are as follows: Step 1: Ingot Preparation Based on the actual proportions of the target titanium alloy, calculate the amount of sponge titanium and each intermediate alloy required for a single electrode, including: The sponge titanium uses small particles: the particle size is 2.0~6.0mm, and the impurity content meets the following requirements: 0.005%≤C≤0.010%, N≤0.003%, 0.01%≤Fe≤0.02%, H≤0.001%, Cl≤0.01%, Sn≤0.002%, and the range of the initial and retest results of oxygen element is ≤50ppm, and the average value of the initial and retest results of aluminum element is ≤0.01% (0.002%). Aluminum is introduced in the form of elemental aluminum; oxygen is introduced in the form of titanium dioxide, and the titanium dioxide must be kept dry and free of moisture. Vanadium is introduced in the form of a vanadium-aluminum alloy with a particle size of 1.0~2.5mm and impurity content meeting the following requirements: C≤0.025%, N≤0.025%, Fe≤0.15%, H≤0.001%, and the range between the initial and retest results of vanadium is ≤3000ppm; molybdenum is introduced in the form of an aluminum-molybdenum master alloy powder with a particle size ≤0.3mm and impurity content meeting the following requirements: C≤0.005%, N≤0.005%, Fe≤0.10%, H≤0.001%, and the range between the initial and retest results of molybdenum is ≤2000ppm; silicon is introduced in the form of a titanium-silicon master alloy with a particle size ≤2.0mm. Zirconium was introduced in the form of sponge zirconium with a particle size ≤ 5.0 mm.

[0044] The above raw materials are fed into a mixing trolley and mechanically mixed for 70 seconds to ensure that the raw materials do not agglomerate and are mixed evenly. The mixed raw materials are then pressed into trapezoidal electrode blocks, each weighing 110 kg. The diagonal length of the electrode blocks after being assembled in pairs is 420 mm. The pressed electrode blocks are left to stand at room temperature for 8 hours to release the internal stress generated during the pressing process. Subsequently, the electrode blocks are placed in a vacuum-protected, argon-filled plasma welding box for welding operations, and assembled into consumable electrodes. The argon filling pressure of the plasma welding box is 80,000 Pa, and the argon purity is ≥99.99%.

[0045] The prepared consumable electrode was subjected to three vacuum consumable arc melting processes. The specific process conditions were as follows: For the first melting, the crucible diameter was Φ560mm, the vacuum degree was controlled to ≤1.0Pa, the melting leakage rate was ≤0.8Pa / min, the melting current was 16kA, the melting voltage was 34V, the arc stabilizing current was 15A DC, and after melting, the electrode was cooled for 6 hours. Moisture-absorbing and blackened areas on the ingot surface were polished, and the ingot was placed in an oven for 12 hours. For the second melting, the crucible diameter was Φ640mm, the vacuum degree was controlled to ≤0.8Pa, the melting leakage rate was ≤0.5Pa / min, and the melting speed was... The melting rate was 20 kg / min, the melting voltage was 36 V, the arc stabilizing current was 20 A, and the melting was cooled for 6.5 h after melting. The melting process adopted the turning and welding melting method. The ingot was placed in an oven for 10 h of heat preservation. The diameter of the crucible for the three melting processes was Φ720 mm, the vacuum degree was controlled to be ≤0.7 Pa, the melting leakage rate was ≤0.5 Pa / min, the melting speed was 20 kg / min, and when 1500 kg remained, the melting speed was reduced to 18 kg, the melting voltage was 36 V, the arc stabilizing current was 20 A, and the head was purged with argon and cooled for 6 h after melting. The melting process adopted the turning and welding melting method.

[0046] Step 2: Multi-cycle forging of billet The Φ720 ingot 3 obtained in step 1 through three vacuum self-consuming arc melting processes is then forged in a furnace multiple times above and below the β phase transformation point to obtain a Φ80mm billet A3. This process is divided into four steps: Step 2.1: Perform two consecutive forging cycles, with the first cycle being T. β +120℃, second fire T β +60℃, forging ratio 1.5~2.0, air cooling after forging; Step 2.2, at T β The forging process involves two consecutive hot forging cycles at -30℃, with a forging ratio of 1.5 to 1.9. After forging, the metal is returned to the furnace to T. β After being heated to +30℃ and kept at that temperature for 4 hours, it was then air-cooled. Step 2.3, at T β The forging process involves two consecutive furnace passes at -50℃, with a forging ratio of 1.4 to 1.6, followed by air cooling. Step 2.4, at T β The forging process involves two consecutive hot forging cycles at -50℃, with a forging ratio of 1.3 to 1.4. After forging, the metal is returned to the furnace to T. β After being heated to -40℃ and held for 1.5 hours, it was air-cooled to obtain a bar billet A3 with a diameter of 80mm. Step 3: Finished product rolling The Φ80mm billet obtained in step 2 is subjected to a single continuous rolling process at a heating temperature T. β The temperature was reduced to -90℃ and held for 1.5 hours. The rolling deformation was 72.4%, and finally a Φ42mm bar billet B3 was obtained. Step 4, Surface Treatment The Φ42mm billet B3 obtained in step 3 is subjected to peeling and polishing to remove surface defects and oxide scale, resulting in a TA11 titanium alloy Φ40mm finished bar (III). Figure 11 As shown, the primary α phase content is above 82%, and the tissue is uniform and fine.

[0047] The mechanical properties of the 40mm TA11 titanium alloy finished bar (III) obtained above were tested, as shown in Table 3. It can be seen that its creep plastic elongation εp ≤ 0.078% after 100h under stress conditions of 425℃ and 410MPa, and the fatigue cycle count under stress conditions of 20℃ and 325MPa and 425℃ and 355MPa is increased to 1.2×10⁻⁶. 8 It is 10 times higher than the target requirement.

[0048]

[0049] Comparative Example 1 Based on Example 2, this comparative example provides a method for preparing TA11 titanium alloy bars, which differs from Example 2 in that the billet undergoes a multi-stage forging process: Step 2.1: Perform two consecutive forging cycles, with the first cycle at temperature T. β +150℃, hold for 8 hours, the temperature of the second firing is T.β +100℃, hold for 2 hours, forging ratio 1.9, air cool after forging; Step 2.2, at T β The forging process involves a single continuous forging at -30℃, holding at that temperature for 6 hours, with a forging ratio of 1.6. After forging, the material is returned to the furnace to T. β After being heated to +50℃ and kept at that temperature for 4 hours, it was then air-cooled. Step 2.3, at T β The forging process involves four consecutive furnace passes at -60℃, with a holding time of 6 hours. The forging ratio is 1.2, followed by air cooling.

[0050] The mechanical properties of the 40mm TA11 titanium alloy finished bar (IV) obtained above were tested. The creep plastic elongation εp ≤ 0.086% after 100h under stress conditions of 425℃ and 410MPa. In contrast, the creep plastic elongation εp ≤ 0.078% of the 30mm TA11 titanium alloy finished bar (II) in Example 2 after 100h under stress conditions of 425℃ and 410MPa was improved by about 9.30%.

[0051] Comparative Example 2 Based on Example 3, this comparative example provides a method for preparing TA11 titanium alloy bars, which differs from Example 3 in that the nominal proportions of the ingots are different: The target alloy composition is Al: 7.8%, Mo: 1.1%, V: 0.98%, O: 0.09%, with the balance being Ti and unavoidable impurity elements. The total amount of impurity elements such as C, Fe, N, and H is less than 0.03%. The impurity element content and particle size in the sponge titanium and each intermediate alloy are consistent with those in Example 3.

[0052] The 40mm TA11 titanium alloy finished bar (V) obtained above was subjected to mechanical property testing. Its creep plastic elongation εp ≤ 0.106% after 100 hours under stress conditions of 425℃ and 410MPa, and its fatigue cycle count under stress conditions of 20℃ and 325MPa and 425℃ and 355MPa is 1.3 × 10⁻⁶. 7 In Example 3, the TA11 titanium alloy Φ40mm finished bar (III) maintained a creep plastic elongation εp ≤ 0.078% for 100 hours under stress conditions of 425℃ and 410MPa, and the fatigue cycle count increased to 1.2×10⁻⁶ under stress conditions of 20℃ and 325MPa and 425℃ and 355MPa respectively. 8 Compared with Comparative Example 2, the creep plasticity and fatigue cycle number in Example 3 were increased by approximately 26.4% and 10 times, respectively.

[0053] In summary, the method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance provided by this invention, compared with traditional multi-fire cycle forging or conventional methods without optimized element ratios and the introduction of silicon, produces TA11 titanium alloy bars with high creep resistance and high fatigue performance. This substantially solves the technical problem that high creep resistance alone cannot meet the requirements of complex working conditions. The fatigue cycle count of this TA11 titanium alloy bar can be increased to 1×10⁻⁶ under both 20℃ and 325MPa stress and 425℃ and 355MPa stress conditions. 8 The creep plastic elongation εp ≤ 0.083% after 100h under stress conditions of 425℃ and 410MPa.

[0054] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0055] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing TA11 titanium alloy bars with high creep resistance and high fatigue performance, characterized in that, By optimizing the ratio of α-stabilizing elements, β-stabilizing elements, and trace strengthening elements, and refining the alloy microstructure through multi-pass forging and finished product rolling within the range above and below the phase transformation point temperature, the fatigue performance of TA11 alloy bars is improved. At the same time, by introducing trace amounts of Si elements and utilizing the dispersion strengthening effect of silicides, dislocation movement and grain growth are hindered, thereby improving the creep resistance of TA11 alloy bars.

2. The method for preparing a TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 1, characterized in that, The TA11 titanium alloy has the following chemical composition by mass percentage: Al: 6.3%~7.5%, Mo: 1.8%~2.8%, V: 0.9%~1.3%, Zr: 1.0%~1.5%, O: 0.05%~0.13%, Si: 0.07~0.15%, C: 0.005%~0.010%, Fe: 0.01%~0.02%, N≤0.03%, H≤0.0015%, with the balance being Ti and unavoidable impurity elements, wherein the total amount of impurity elements is less than 0.03%.

3. The method for preparing a TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 2, characterized in that, In the TA11 titanium alloy, 7.5wt.%≤[Al]eq≤8.3wt.%, 2.7wt.%≤[Mo]eq≤3.5wt.%, and 2.4≤[Al]eq / [Mo]eq≤3.

0.

4. The method for preparing a TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 3, characterized in that, The preparation method specifically includes the following steps: Step 1, Electrode Block and Ingot Preparation: Electrode blocks are prepared according to the proportion of the target alloy and then melted by vacuum arc melting to obtain TA11 titanium alloy ingots with dimensions of Φ640mm~Φ720mm. Step 2, Multi-cycle forging of billet: The TA11 titanium alloy ingot obtained in Step 1 is subjected to multi-cycle forging at the β phase transformation temperature T. β The billet A is forged in multiple furnace cycles within the upper and lower range to obtain a billet A with a size of Φ80mm~Φ90mm; Step 3, Finished bar rolling: The bar billet A obtained in Step 2 is rolled in one heat to obtain bar billet B with a size of Φ27mm~Φ42mm; Step 4, Surface treatment: Remove the surface defects and oxide scale from the billet B obtained in Step 3 to obtain the target TA11 titanium alloy finished bar with dimensions of Φ25mm~Φ40mm.

5. The method for preparing a TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 4, characterized in that, In step 2, the multi-fire cycle forging of the billet specifically includes: Step 2.1, at T β The forging process involves two consecutive furnace forgings at +(60~130)℃, with a forging ratio of 1.3~2.0, followed by air cooling. Step 2.2, at T β The forging process involves two consecutive hot forging cycles at -20~40℃, with a forging ratio of 1.4~1.

9. After forging, the metal is returned to the furnace at T. β After maintaining the temperature at +30~50℃ for 3~4 hours, air cool. Step 2.3, at T β The forging process involves two consecutive furnace forgings at -(30~50)℃, with a forging ratio of 1.3~1.6, followed by air cooling. Step 2.4, at T β The forging process involves two consecutive hot forging cycles at -30~50℃, with a forging ratio of 1.2~1.

4. After forging, the metal is returned to the furnace at T. β After being heated to -(20~40)℃ and held for 1.5h~2h, it is air-cooled to finally obtain the billet A of the target size.

6. The method for preparing a TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 4, characterized in that, In step 3, the temperature is heated to the β phase transition point T. β The following conditions are met: holding time at 60℃~90℃ for 1.5h~2h, rolling deformation of 72.4%~91%, and finally obtaining bar billet B of the target size.

7. The method for preparing a TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 4, characterized in that, In step 1, according to the actual proportions of the target titanium alloy, the required amount of sponge titanium and the addition methods and requirements of each intermediate alloy for a single electrode block are as follows: Titanium is introduced in the form of sponge titanium with a particle size of 2.0 mm to 6.0 mm. The impurity content meets the following requirements: 0.005% ≤ C ≤ 0.010%, N ≤ 0.003%, 0.01% ≤ Fe ≤ 0.02%, H ≤ 0.001%, Cl ≤ 0.01%, Sn ≤ 0.002%, and the range between the initial and retest results of oxygen is ≤ 50 ppm. The average value of the initial and retest results of aluminum is 0.002% to 0.01%. Aluminum is introduced in the form of elemental aluminum; oxygen is introduced in the form of titanium dioxide. Vanadium is introduced in the form of a vanadium-aluminum alloy with a particle size of 1.0 mm to 2.5 mm and impurity content satisfying the following: C ≤ 0.025%, N ≤ 0.025%, Fe ≤ 0.15%, H ≤ 0.001%, and the range between the initial and retest results of vanadium is ≤ 3000 ppm; molybdenum is introduced in the form of an aluminum-molybdenum master alloy powder with a particle size ≤ 0.3 mm and impurity content satisfying the following: C ≤ 0.005%, N ≤ 0.005%, Fe ≤ 0.10%, H ≤ 0.001%, and the range between the initial and retest results of molybdenum is ≤ 2000 ppm; silicon is introduced in the form of a titanium-silicon master alloy with a particle size ≤ 2.0 mm. Zirconium is introduced in the form of sponge zirconium with a particle size ≤ 5.0 mm.

8. The method for preparing a TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 4, characterized in that, In step 1, the prepared electrode block is subjected to three vacuum consumable arc melting processes, and the crucible ratio of the crucibles used in each vacuum consumable arc melting process is less than 0.

75.

9. A TA11 titanium alloy bar with high creep resistance and high fatigue performance, characterized in that, The TA11 titanium alloy rod is obtained based on the TA11 titanium alloy rod preparation method according to any one of claims 1 to 8.

10. A TA11 titanium alloy bar with high creep resistance and high fatigue performance according to claim 9, characterized in that, The finished TA11 titanium alloy bars have a diameter of Φ25mm to Φ40mm. Under stress conditions of 425℃ and 410MPa, their creep ductile elongation εp ≤ 0.083% after 100 hours. The fatigue cycle count under stress conditions of 20℃ and 325MPa, and 425℃ and 355MPa, is 1×10⁻⁶. 8 .

Images