A method for preparing a TA15 alloy rod having high fatigue strength by synergistic control

Abstract

This invention relates to the field of high fatigue strength titanium alloy technology, specifically to a method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation. The method involves increasing the content of the main elements Al, Mo, V, and Zr, controlling the content of interstitial elements Fe, O, and C, and adding trace amounts of Nb to obtain a novel TA15 alloy composition. First, a 520mm TA15 alloy ingot is prepared by three vacuum arc remelting processes. Next, the TA15 alloy ingot is forged, and by reducing the forging temperature of the forming passes and increasing the deformation, a 180mm transfer bar is obtained. Subsequently, at the rolling temperature, by controlling the deformation between passes, the 180mm bar is rolled to a 65mm diameter in a single pass. Finally, within the range of 800-850℃, the 65mm bar is solution-treated to obtain a 65mm TA15 alloy bar. The 65mm TA15 alloy bar prepared by this invention has a uniform and fine primary α phase with a primary α phase content of 45~55%, a uniformly broken secondary α phase, and a smooth surface with a high cycle fatigue strength ≥698MPa.

Description

Technical Field

[0001] This invention belongs to the field of high fatigue strength titanium alloy technology, specifically relating to a method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation. Background Technology

[0002] Near-alpha type TA15 titanium alloy bars and forgings are widely used in aerospace load-bearing components, and their fatigue strength is a key factor affecting the service life of structural components. However, TA15 titanium alloy bars produced according to the nominal composition Ti-6.5Al-2Zr-1Mo-1V (all by mass fraction, wt.%) generally have a smooth high-cycle fatigue strength of no more than 600 MPa, which severely limits the service life of TA15 alloy components. The high-cycle fatigue strength of near-alpha type titanium alloys is affected by the morphology, content, and size of the primary and secondary alpha phases, all of which are closely related to the composition and microstructure of the titanium alloy. Generally, the high-cycle fatigue strength of titanium alloys increases with the increase of static tensile strength; however, simply increasing the tensile strength leads to rapid unstable propagation of fatigue cracks, which cannot meet the requirements of high-cycle loading.

[0003] Furthermore, the hypersonic flight environment of aircraft places higher demands on the fatigue performance of TA15 alloy. Currently, most TA15 alloys are produced in bars larger than 100mm in diameter, with very little production of smaller bars. Moreover, its high-cycle fatigue strength at Kt=1 and R=0.06 is approximately 520MPa, which cannot meet the requirement of a high-cycle fatigue strength >650MPa for 65mm TA15 alloy bars used in hypersonic aircraft.

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

[0005] The purpose of this invention is to provide a method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation. By optimizing the composition by appropriately increasing the content of main elements, controlling the content of interstitial elements, and adding trace amounts of Nb, and by using a hot working process strategy that reduces the forming temperature and increases the deformation amount, the composition ratio and microstructure of TA15 alloy are synergistically regulated. The aim is to obtain a near-α type titanium alloy with good strength and toughness matching. While ensuring sufficient strength, better plastic deformation can alleviate the fatigue crack propagation rate, thereby improving the high-cycle fatigue strength of TA15 alloy bars and providing material assurance for the service life of titanium alloys used in aerospace structural components.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a TA15 alloy bar with high fatigue strength, wherein the chemical composition of the TA15 alloy bar is as follows (by mass percentage):

[0008] Major elements: Al: 6.8-6.9%, Mo: 1.75-1.85%, V: 2.30-2.35%, Zr: 2.30-2.35%;

[0009] Interstitial elements: Fe: 0.15-0.20%, O: 0.115-0.130%, C: 0.01-0.02%;

[0010] Trace elements: Nb≤0.08%; the remainder is Ti and unavoidable impurity elements.

[0011] Furthermore, the TA15 alloy bar is a 65mm TA15 alloy bar.

[0012] Furthermore, the primary α phase of the TA15 alloy bar is uniformly distributed, the average equivalent circle diameter of the primary α phase is 2.1-7.5μm, the primary α phase content is 45-55%, the secondary α phase is uniformly broken, and the high-cycle fatigue strength is ≥698MPa.

[0013] In another aspect, the present invention also provides a method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation, comprising the following steps:

[0014] Step 1, Obtaining TA15 alloy ingots: Obtain TA15 alloy ingots with a diameter of φ520mm through three vacuum arc melting processes, and then homogenize them at a high temperature of 1170℃.

[0015] Step 2, billet forging: The TA15 alloy ingot is forged at a final forging temperature of 930-940℃, with a single forging deformation of 50-60%, to obtain a φ180mm transfer bar.

[0016] Step 3, Rolling: At a rolling temperature of 925-940℃, the φ180mm specification transfer bar is rolled into a φ65mm specification bar through multiple passes of incremental deformation rolling.

[0017] Step 4, solution treatment: The φ65mm bar is solution treated at 800-850℃ for 1.0-2.0h and then air-cooled to obtain TA15 alloy bar.

[0018] Further, in step 1, the main elements: Al, Mo, V, Zr, interstitial elements: Fe, O, C, and trace elements: Nb and Ti are weighed according to the mass percentage, and the electrode blocks are pressed on an 80MN hydraulic press. After plasma welding, the consumable electrode is welded, and then the TA15 alloy ingot with a φ520mm specification is obtained through three vacuum consumable arc melting processes.

[0019] Furthermore, the melting rate of the three-stage vacuum self-consuming arc melting is 5.0-7.5 kg / min.

[0020] Furthermore, in step 2, the forging is carried out on an 80MN high-speed forging machine, and the average equivalent circle diameter of the primary α phase in the φ180mm specification transfer bar is 7.0-10.5μm.

[0021] Furthermore, in step 3, the φ180mm specification transfer bar is subjected to a continuous deformation rolling process of 16 passes in one heat on a two-roll reversible rolling mill. In the continuous rolling process, the deformation amount of the first to fourth passes is 7.5-13%, the deformation amount of the fifth to seventh passes is 8-14%, the deformation amount of the eighth to 14th passes is 8-15%, and the deformation amount of the fifteenth to sixteenth passes is 15-25%.

[0022] Furthermore, the method can be used to prepare near-α type and (α+β) type titanium alloy rods.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. This invention aims to improve the high-cycle fatigue strength of TA15 alloy within the required composition range by the following methods: a) Appropriately increasing the content of the main elements Al, Mo, V, and Zr to change the [Al] equivalent and [Mo] equivalent of the TA15 alloy, and changing the primary α phase content to 45-55% through multi-element solid solution strengthening and matching the hot working process of "large deformation + low temperature forging" and "one-fire multi-pass + low temperature rolling", thereby improving the final fatigue strength; b) Based on the solid solubility of each interstitial element in the TA15 alloy, reasonably increasing the content of interstitial elements Fe, O, and C to exert the dual effect of solid solution strengthening and interstitial strengthening, and matching the hot working process of "large deformation + low temperature forging" and "one-fire multi-pass + low temperature rolling" to further improve fatigue strength; c) Adding a trace amount of the β-type element Nb in the form of a low-cost Ti-Nb master alloy to increase the content of β-transformation structure, balancing the relationship between strength and plasticity, and achieving a new type of TA15 alloy with coordinated strength and plasticity.

[0025] 2. This invention obtains 65mm TA15 alloy bars by controlling hot working processes such as forging temperature, rolling temperature, deformation amount and solution treatment. The primary α phase is uniform and fine (the average equivalent circle diameter of the primary α phase is 2.1-7.5μm), the primary α phase content is 45-55%, the secondary α phase is uniformly broken, and the high cycle fatigue strength is ≥698MPa.

[0026] 3. This invention employs a single-fire, multi-pass continuous rolling process, with the rolling temperature controlled between 925-940℃ to obtain a high primary α-phase content. Through the uniform plastic deformation of the α-phase, the rapid instability and propagation of fatigue cracks are alleviated, thereby improving fatigue strength. Simultaneously, the single-fire continuous rolling directly from φ180mm to φ65mm, with a deformation of over 60%, fully breaks down the secondary α-phase, making it into a uniform short rod shape with a length-to-diameter ratio of (1.0±0.7):1. This can suppress the propagation of fatigue cracks, change the fatigue crack propagation path, alleviate rapid instability, and improve fatigue strength.

[0027] 4. In order not to damage the microstructure of the φ65mm rolled bar, the present invention adopts a short-time solution treatment at a relatively low temperature (800-850℃). This treatment is only used to eliminate residual stress in the rolled bar and does not change the microstructure, thus providing an intrinsic basis for high fatigue strength. Attached Figure Description

[0028] 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.

[0029] 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.

[0030] Figure 1 This is a flowchart of the method for preparing TA15 alloy bars with high fatigue strength by synergistic regulation according to the present invention;

[0031] Figure 2 This is a primary α-phase morphology diagram of the TA15 alloy bar with high fatigue strength prepared by this invention.

[0032] Figure 3 This is a secondary α-phase morphology diagram of the TA15 alloy bar with high fatigue strength prepared according to the present invention.

[0033] Figure 4 This is a macroscopic morphology image of the fatigue fracture surface of the TA15 alloy bar with high fatigue strength prepared by the present invention.

[0034] Figure 5 This is a microscopic image of the fatigue fracture surface of the TA15 alloy bar with high fatigue strength prepared according to the present invention. Detailed Implementation

[0035] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0036] 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.

[0037] This invention provides a TA15 alloy bar with high fatigue strength, the chemical composition by mass percentage of which is:

[0038] Major elements: Al: 6.8-6.9%, Mo: 1.75-1.85%, V: 2.30-2.35%, Zr: 2.30-2.35%;

[0039] Interstitial elements: Fe: 0.15-0.20%, O: 0.115-0.130%, C: 0.01-0.02%;

[0040] Trace elements: Nb≤0.08%; the remainder is Ti and unavoidable impurity elements.

[0041] The TA15 alloy rods provided by this invention exhibit a uniform distribution of the primary α phase, with an average equivalent circle diameter of 2.1~7.5μm and a primary α phase content of 45~55%. The secondary α phase is uniformly fragmented, resulting in a smooth high-cycle fatigue strength ≥698MPa. The secondary α phase is in the form of uniform short rods with a length-to-diameter ratio of (1.0±0.7):1.

[0042] This invention synergistically controls the preparation of high fatigue strength TA15 alloy φ65mm bars through both composition optimization and hot working process. Specifically:

[0043] 1) From the perspective of composition optimization: Within the composition range required by the current TA15 alloy grade, the content of the main elements Al, Mo, V, and Zr is appropriately increased. The objectives include: a) increasing the content of the main elements and slightly increasing the [Al] equivalent and [Mo] equivalent to improve strength through solid solution strengthening; b) although the content of the main elements Al, Mo, V, and Zr is increased, it is still kept within a reasonable range to meet the compositional uniformity control capability of industrial-grade large-size ingots (φ520mm). Furthermore, relying solely on increasing the content of the main elements, even at the maximum limit, is unlikely to meet the final high fatigue strength requirements. Further, this invention changes the traditional "low interstitial" paradigm by increasing the content of interstitial elements Fe, O, and C, leveraging the dual effects of solid solution strengthening and interstitial strengthening to achieve strength improvement. Of course, to balance the relationship between strength and plasticity, this invention innovatively adds trace amounts of the β-type element Nb to achieve a balance between strength and plasticity.

[0044] 2) Forging and rolling: The purpose of forging and rolling the compositionally optimized TA15 alloy is threefold: to achieve uniform and fine primary α phase, a primary α phase content of 45-55%, and uniform fragmentation of secondary α phase. To achieve these three goals, the measures taken include: a) reducing the forging temperature of the φ180mm transfer bar and increasing the deformation amount to obtain a billet with a fine microstructure; b) In the critical rolling process, this invention adopts a single-fire, multi-pass continuous rolling process with the rolling temperature controlled between 925-940℃ to obtain a higher primary α phase content. Through uniform plastic deformation of the α phase, the rapid instability and propagation of fatigue cracks are mitigated, thereby improving fatigue strength. At the same time, the single-fire continuous rolling directly from φ180mm to φ65mm, with a deformation amount exceeding 60%, fully breaks down the secondary α phase, making it into a uniform short rod shape, which can inhibit the propagation of fatigue cracks, change the fatigue crack propagation path, mitigate rapid instability, and improve fatigue strength.

[0045] 3) Heat treatment control: In order not to damage the microstructure of the φ65mm rolled bar, the present invention adopts a low-temperature short-time solution treatment, which is only used to eliminate residual stress in the rolled bar without changing the microstructure, thus providing an intrinsic basis for high fatigue strength.

[0046] See Figure 1-5 As shown, the present invention provides a method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation, comprising the following steps:

[0047] Step 1: Obtain TA15 alloy ingot.

[0048] Specifically, firstly, the TA15 titanium alloy is batched according to the mass percentage of each chemical component, where Al: 6.8-6.9%; Mo: 1.75-1.85%; V: 2.30-2.35%; Zr: 2.30-2.35%; Fe: 0.15-0.20%; O: 0.115-0.130%; C: 0.01-0.02%; Nb≤0.08%; the remainder being Ti and unavoidable impurities. Then, the electrode blocks are pressed on an 80MN hydraulic press, followed by plasma welding and consumable electrode welding. After three vacuum consumable arc melting processes, a 5-ton φ520mm new TA15 alloy ingot with uniform composition is obtained, which is then homogenized at 1170℃. The melting rate of the three vacuum consumable arc melting processes is 5.0-7.5 kg / min.

[0049] Step 2, forging the billet.

[0050] Specifically, TA15 alloy ingots are forged on an 80MN high-speed forging mill. The final forging temperature is 930-940℃, and the deformation is 50-60%, resulting in φ180mm transfer bars with uniform and fine microstructure. The average equivalent circle diameter of the primary α phase in the obtained φ180mm transfer bars is 7.0-10.5μm.

[0051] Step 3, rolling.

[0052] At a rolling temperature of 925-940℃, φ180mm transfer bars are rolled to φ65mm in one pass on a 650 two-roll reversible mill. The deformation per pass increases or decreases systematically, with the overall deformation per pass...

[0053] The deformation amount shows a gradually increasing trend. Specifically, φ180mm specification transfer bar is processed into φ65mm specification bar through 16 consecutive passes of incremental deformation rolling on a two-roll reversible rolling mill. The deformation amount of the first 4 passes is 7.5-13%, the deformation amount of the 5th-7th passes is 8-14%, the deformation amount of the 8th-14th passes is 8-15%, and the deformation amount of the 15th-16th passes is 15-25%. More specifically, the deformation amount is 7.5% for the first pass, 13% for the second pass, 10% for the third pass, 10% for the fourth pass, 14% for the fifth pass, 12% for the sixth pass, 8% for the seventh pass, 15% for the eighth pass, 10% for the ninth pass, 11% for the tenth pass, 12% for the eleventh pass, 9% for the twelfth pass, 9% for the thirteenth pass, 8% for the fourteenth pass, 15% for the fifteenth pass, and 25% for the sixteenth pass.

[0054] Step 4, solution treatment.

[0055] After solution treatment at 800-850℃ for 1.0-2.0h, 65mm diameter TA15 alloy bars are air-cooled to obtain 65mm diameter TA15 alloy bars with uniform and fine primary α phase, primary α phase content of 45-55%, uniform secondary α phase fragmentation, and smooth high-cycle fatigue strength ≥698MPa.

[0056] To verify the beneficial effects of the preparation method of the present invention, the following examples and comparative examples are provided for further explanation.

[0057] Example 1

[0058] A method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation includes the following steps:

[0059] Step 1: First, the TA15 titanium alloy is batched according to the mass percentage of its chemical composition: Al: 6.8%; Mo: 1.75%; V: 2.30%; Zr: 2.30%; Fe: 0.15%; O: 0.115%; C: 0.01%; Nb: 0.08%; the remainder being Ti and unavoidable impurities. Then, the electrode blocks are pressed on an 80MN hydraulic press, followed by plasma welding and consumable electrode welding. After three vacuum consumable arc melting processes, a 5-ton φ520mm new TA15 alloy ingot with uniform composition is obtained, which is then homogenized at 1170℃.

[0060] Step 2: The TA15 alloy ingot with uniform composition is forged on an 80MN high-speed forging machine. The forging temperature of the final forming heat is 930℃ and the deformation is 50%, resulting in a φ180mm transfer bar with uniform and fine structure.

[0061] Step 3: At a rolling temperature of 925℃, the φ180mm specification transfer bar is rolled to φ65mm specification in 16 passes on a 650 two-roll reversible rolling mill, with the deformation amount increasing or decreasing regularly in each pass.

[0062] Step 4: After solution treatment at 800℃ for 1.0h, the φ65mm bar is air-cooled to obtain a φ65mm TA15 alloy bar with uniform and fine primary α phase, primary α phase content of 45%, uniform secondary α phase fragmentation, smooth high-cycle fatigue strength of 698MPa.

[0063] Example 2

[0064] A method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation includes the following steps:

[0065] Step 1: First, the TA15 titanium alloy is batched according to the mass percentages of its chemical composition: Al: 6.85%; Mo: 1.80%; V: 2.30%; Zr: 2.35%; Fe: 0.18%; O: 0.12%; C: 0.015%; Nb: 0.08%; the remainder being Ti and unavoidable impurities. Then, the electrode blocks are pressed on an 80MN hydraulic press, followed by plasma welding and consumable electrode welding. After three vacuum consumable arc melting processes, a 5-ton, φ520mm new TA15 alloy ingot with uniform composition is obtained, which is then homogenized at 1170℃.

[0066] Step 2: The TA15 alloy ingot with uniform composition is forged on an 80MN high-speed forging machine. The forging temperature of the final forming heat is 935℃ and the deformation is 55%, resulting in a φ180mm transfer bar with uniform and fine structure.

[0067] Step 3: At a rolling temperature of 930℃, the φ180mm specification transfer bar is rolled to φ65mm specification in 16 passes on a 650 two-roll reversible rolling mill, with the deformation amount increasing or decreasing regularly in each pass.

[0068] Step 4: After solution treatment at 800℃ for 2.0h, the φ65mm bar is air-cooled to obtain a φ65mm TA15 alloy bar with uniform and fine primary α phase, primary α phase content of 50%, uniform secondary α phase fragmentation, smooth high-cycle fatigue strength of 700MPa.

[0069] Example 3

[0070] A method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation includes the following steps:

[0071] Step 1: First, the TA15 titanium alloy is batched according to the mass percentages of its chemical composition: Al: 6.9%; Mo: 1.85%; V: 2.35%; Zr: 2.35%; Fe: 0.20%; O: 0.125%; C: 0.02%; Nb: 0.08%; the remainder being Ti and unavoidable impurities. Then, the electrode blocks are pressed on an 80MN hydraulic press, followed by plasma welding and consumable electrode welding. After three vacuum consumable arc melting processes, a 5-ton φ520mm new TA15 alloy ingot with uniform composition is obtained, which is then homogenized at 1170℃.

[0072] Step 2: The TA15 alloy ingot with uniform composition is forged on an 80MN high-speed forging machine. The forging temperature of the final forming heat is 940℃ and the deformation is 60%, resulting in a φ180mm transfer bar with uniform and fine structure.

[0073] Step 3: At a rolling temperature of 940℃, the φ180mm specification transfer bar is rolled to φ65mm specification in 16 passes on a 650 two-roll reversible rolling mill, with the deformation amount increasing or decreasing regularly in each pass.

[0074] Step 4: After solution treatment at 850℃ for 1.5h, the φ65mm bar is air-cooled to obtain a φ65mm TA15 alloy bar with uniform and fine primary α phase, primary α phase content of 55%, uniform secondary α phase fragmentation, smooth high-cycle fatigue strength of 705MPa.

[0075] Table 1 shows the room temperature tensile properties and impact toughness of the φ65mm TA15 alloy bar obtained in Example 3.

[0076]

[0077] Table 2 shows the smooth high-cycle fatigue strength of the φ65mm TA15 alloy bar obtained in Example 3.

[0078]

[0079] Example 3 is the optimal embodiment of the present invention. The TA15 alloy bar with high fatigue strength prepared according to Example 3 has a primary α phase content as high as 55%, and has good strength and toughness matching and a smooth high-cycle fatigue strength of 705 MPa. This is closely related to the composition ratio and hot working process of the new TA15 alloy. Specifically: (1) The content of the main element, interstitial element and Nb element of the TA15 alloy in Example 3 is at the upper limit required by the present invention for the TA15 alloy bar. It includes Al and O elements for stabilizing the α phase, Mo, V, Fe, C, Nb elements for stabilizing the β phase and the neutral element Zr. The elements interact with each other, and solid solution strengthening and interstitial strengthening play a role at the same time. In addition, the addition of interstitial elements and trace Nb elements can coordinate plastic deformation, so that the TA15 alloy bar of Example 3 exhibits the room temperature tensile strength and impact toughness shown in Table 1. (2) In Example 3, the forging temperature of the φ180mm transfer bar forming process was 940℃ and the deformation was 60%, which ensured the uniformity and fineness of the microstructure of the transfer bar. Subsequent rolling at 940℃ further increased deformation and promoted finer microstructure, resulting in a uniformly spheroidized, regularly shaped, and finely sized primary α phase, such as... Figure 2 As shown; under the combined action of forging and rolling, the large plastic deformation causes the secondary α phase of the TA15 alloy bar to be fully broken down, exhibiting... Figure 3The short rod shape shown hinders the propagation path of fatigue cracks, enabling the high-cycle fatigue strength of the TA15 alloy rod of the present invention to reach 705 MPa as shown in Table 2. (3) After high-cycle fatigue, the macroscopic fracture surface of the TA15 alloy rod in Example 3 exhibits three distinct characteristic regions, such as Figure 4 As shown, from right to left, these are the fatigue crack initiation zone, fatigue crack propagation zone, and instantaneous fracture zone. Figure 5 The microscopic characteristics of the fatigue fracture surface of the TA15 alloy bar show that dense and fine fatigue bands exist in the fatigue crack propagation zone, which is a typical fracture feature of high fatigue strength titanium alloys. In addition, obvious dimples were observed in the instantaneous fracture zone, indicating that the high fatigue strength TA15 alloy bar provided by the present invention has good plastic deformation ability. While ensuring strength, it alleviates the premature concentration and unstable propagation of fatigue cracks, thus ensuring the fatigue strength of the high fatigue strength TA15 alloy bar of the present invention.

[0080] The high-cycle fatigue strengths achieved by the TA15 alloy bars prepared in Examples 1 and 2 were 698 MPa and 700 MPa, respectively. Although these were slightly lower than the high-cycle fatigue strength of Example 3, they still met the requirement that the high-cycle fatigue strength of 650 MPa for φ65mm TA15 alloy bars used in hypersonic aircraft should be greater than 650 MPa.

[0081] In summary, this invention provides a method for preparing TA15 alloy bars with high fatigue strength through synergistic regulation. Within the required composition range of TA15 alloy, by altering the proportions of main elements, interstitial elements, and trace elements, and by controlling hot working processes such as forging temperature, rolling temperature, deformation amount, and solution treatment, TA15 alloy bars with a φ65mm specification exhibiting good strength and toughness matching and a smooth high-cycle fatigue strength of 700MPa can be obtained. Furthermore, the composition optimization and synergistic regulation method of hot working processes involved in this invention provides technical support for improving the fatigue strength of near-α and (α+β) type titanium alloy bars used in aerospace structural components.

[0082] 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.

[0083] 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 TA15 alloy rods with high fatigue strength through synergistic regulation, characterized in that, The chemical composition (by mass percentage) of the TA15 alloy bar is as follows: Major elements: Al: 6.8-6.9%, Mo: 1.75-1.85%, V: 2.30-2.35%, Zr: 2.30-2.35%; Interstitial elements: Fe: 0.15-0.20%, O: 0.115-0.130%, C: 0.01-0.02%; Trace elements: Nb≤0.08%; the remainder is Ti and unavoidable impurity elements; The method includes the following steps: Step 1, Obtaining TA15 alloy ingots: Obtain TA15 alloy ingots with a diameter of φ520mm through three vacuum arc melting processes, and then homogenize them at a high temperature of 1170℃. Step 2, billet forging: The TA15 alloy ingot is forged at a final forging temperature of 930-940℃, with a single forging deformation of 50-60%, to obtain a φ180mm transfer bar. Step 3, Rolling: At a rolling temperature of 925-940℃, the φ180mm specification transfer bar is rolled into a φ65mm specification bar through multiple passes of incremental deformation rolling. Step 4, solution treatment: The φ65mm bar is solution treated at 800-850℃ for 1.0-2.0h and then air-cooled to obtain TA15 alloy bar.

2. The method for preparing TA15 alloy rods with high fatigue strength by synergistic regulation according to claim 1, characterized in that, The primary α phase of the TA15 alloy bar is uniformly distributed, with an average equivalent circle diameter of 2.1-7.5 μm and a primary α phase content of 45-55%. The secondary α phase is uniformly broken, and the high-cycle fatigue strength is ≥698 MPa.

3. The method for preparing TA15 alloy rods with high fatigue strength by synergistic regulation according to claim 1, characterized in that, In step 1, the main elements Al, Mo, V, and Zr, interstitial elements Fe, O, and C, and trace elements Nb and Ti are mixed according to the mass percentage. The electrode blocks are then pressed on an 80MN hydraulic press, followed by plasma welding to complete the consumable electrode welding. Finally, the electrodes undergo three vacuum consumable arc melting processes to obtain a 5-ton TA15 alloy ingot with a diameter of 520mm.

4. The method for preparing TA15 alloy rods with high fatigue strength by synergistic regulation according to claim 1, characterized in that, The melting rate of the three-stage vacuum self-consuming arc melting is 5.0-7.5 kg / min.

5. The method for preparing TA15 alloy rods with high fatigue strength by synergistic regulation according to claim 1, characterized in that, In step 2, the billet forging is carried out on an 80MN high-speed forging machine, and the average equivalent circle diameter of the primary α phase in the φ180mm specification transfer bar is 7.0-10.5μm.

6. The method for preparing TA15 alloy rods with high fatigue strength by synergistic regulation according to claim 1, characterized in that, In step 3, the φ180mm specification transfer bar is subjected to 16 consecutive passes of incremental deformation rolling on a two-roll reversible rolling mill. In the continuous rolling process, the deformation amount of the first to fourth passes is 7.5-13%, the deformation amount of the fifth to seventh passes is 8-14%, the deformation amount of the eighth to 14th passes is 8-15%, and the deformation amount of the fifteenth to sixteenth passes is 15-25%.

7. The method for preparing TA15 alloy rods with high fatigue strength by synergistic regulation according to claim 1, characterized in that, The method can be used to prepare near-α type and (α+β) type titanium alloy rods.

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