A heat treatment method and application for improving the impact resistance of (α + β) titanium alloy

Abstract

The present invention relates to the technical fields of powder metallurgy and heat treatment, and provides a heat treatment method and application for improving the impact resistance of (α + β) titanium alloy, comprising the following steps: preparing a (α + β) titanium alloy blank; heating the (α + β) titanium alloy blank to T β -(100 - 180) °C for solution treatment, with the solution holding time ≤ 6 h; furnace cooling to T β -(100 - 180) °C, with the holding time ≤ 6 h; furnace cooling to T β -(200 - 300) °C, with the holding time ≤ 6 h; air cooling to room temperature; heating to T β -(350 - 450) °C, holding for ≤ 3 h and then air cooling to room temperature to obtain the treated (α + β) titanium alloy workpiece. Through the heat treatment of "solution + multi-stage cooling and holding + aging" of the present invention, precise regulation of multi-level α phase in the titanium alloy structure is realized, significantly improving the impact resistance of the titanium alloy material, which is applicable to the requirements of new-generation impact-resistant materials.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy and heat treatment, and specifically relates to a heat treatment method for improving the impact resistance of (α+β) titanium alloy and its application. Background Art

[0002] Titanium alloys have become the core materials for key components under penetration or impact resistance due to their high specific strength, good plasticity and toughness, excellent corrosion resistance and good processing performance. Based on the microstructural characteristics, titanium alloys can be divided into three types: α-type, β-type and (α+β)-type. Among them, (α+β) titanium alloys have attracted much attention in the field of impact resistance due to their wide range of strong-plastic matching and excellent impact resistance.

[0003] Traditional approaches to improving the impact resistance of titanium alloys mainly focus on composition optimization and forging process improvements, such as adding alloying elements such as Zr and Mo, or controlling the size of the primary α phase. However, these methods have disadvantages such as long design cycle, high trial and error cost, and strict requirements on equipment and process parameters, making it difficult to quickly respond to engineering needs. In recent years, the integration of powder metallurgy technology and hot isostatic pressing (HIP) technology has opened up a new direction for the preparation of titanium alloys: using (α+β) titanium alloy powder as raw material, near-net-shaped parts can be directly obtained through hot isostatic pressing. This process can effectively eliminate the internal pores of titanium alloys and achieve tissue homogenization, which greatly reduces the processing allowance compared with traditional forging processes. However, the fine control of the microstructure by subsequent heat treatment is still a key issue that needs to be broken through. In contrast, the traditional arc melting combined with forging method, when preparing titanium alloy bars and components, is mainly focused on solving the problems of composition uniformity and tissue uniformity.

[0004] As a core means of regulating material organization and performance, heat treatment can regulate the precipitation and distribution of α / β phases. However, the current heat treatment processes of (α+β) titanium alloys are mostly single solid solution + cooling or simple aging treatment, lacking segmented regulation of phase transformation dynamics in different temperature zones below the β transformation temperature. This results in coarse size and uneven distribution of the α phase, poor morphology of the β phase matrix precipitation phase, and inability to give full play to the synergistic toughening effect of the dual-phase organization. Especially under high strain rate impact loads, there is a technical gap in the fine regulation of organization, and it is difficult to achieve coordinated matching of strength, plasticity and toughness under dynamic / static conditions, which cannot meet actual use needs.

[0005] In addition, the application number is: 202311285661.9, and the publication date is: December 29, 2023. The patent title is: A heat treatment method and product for improving the dynamic properties of TA15 titanium alloy, mainly aiming at improving the dynamic properties of TA15 near-α titanium alloy. After solution treatment, it is slowly cooled to 550-650°C for aging treatment. The core lies in using a large number of equiaxed α phases to improve plasticity. However, this process is only applicable to specific composition systems, and the phase transformation mechanism in different temperature regions is not distinguished during the cooling process, and it is not applicable to (α+β) titanium alloy.

[0006] Therefore, there is an urgent need to develop a heat treatment method that is applicable to (α+β) titanium alloy and can effectively improve its impact resistance. Summary of the Invention

[0007] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a heat treatment method for improving the impact resistance of (α+β) titanium alloy. Through solution treatment and multi-stage cooling + heat preservation process, precise control of the microstructure of titanium alloy is realized, the impact resistance of titanium alloy materials is significantly improved, and the coordinated matching of strength-plasticity-toughness of titanium alloy materials under dynamic / static conditions is achieved.

[0008] The purpose of the present invention is solved by the following technical solutions:

[0009] In the first aspect, the present invention provides a hot isostatic pressing treatment method for preparing (α+β) titanium alloy billets, including the following steps: First, load (α+β) titanium alloy powder into a stainless steel sealed envelope, and then, under a vacuum degree ≤ 1×10 -3 Pa, heat the stainless steel sealed envelope with (α+β) titanium alloy powder to 850-950°C at a heating rate of 5-15°C / min, synchronously apply an argon pressure of 100-150 MPa, keep the temperature and pressure for 2-4 h, then cool it to room temperature with the furnace, and finally, remove the stainless steel sealed envelope to obtain (α+β) titanium alloy billets with a relative density ≥ 99.5%.

[0010] Furthermore, the (α+β) titanium alloy powder is prepared by plasma atomization method, and the powder particle size of the (α+β) titanium alloy powder ≤ 200 μm, the oxygen content ≤ 0.2 wt%, and the nitrogen content ≤ 0.05 wt%.

[0011] In the second aspect, the present invention provides a heat treatment method for improving the impact resistance of (α+β) titanium alloy, including the following steps:

[0012] Step 1: Prepare (α+β) titanium alloy billets based on the hot isostatic pressing treatment method for preparing (α+β) titanium alloy billets and determine the corresponding T β The T βis the β transformation temperature of the (α + β) titanium alloy blank. In (α + β) titanium alloy blanks with different compositions, the value of T β varies;

[0013] Step 2. Solution treatment: Heat the (α + β) titanium alloy blank to T β -(10 - 80) °C for solution treatment, and the solution holding time ≤ 6 h to obtain the first blank;

[0014] Step 3. First-stage cooling + holding treatment: Cool the first blank in the furnace to T β -(100 - 180) °C, and then carry out holding treatment with the holding time ≤ 6 h to obtain the second blank;

[0015] Step 4. Second-stage cooling + holding treatment: Cool the second blank in the furnace to T β -(200 - 300) °C, and then carry out holding treatment with the holding time ≤ 6 h to obtain the third blank;

[0016] Step 5. Third-stage cooling treatment: Air-cool the third blank to room temperature to obtain the fourth blank;

[0017] Step 6. Aging treatment: Heat the fourth blank to T β -(350 - 450) °C, after holding for ≤ 3 h, air-cool to room temperature to obtain the treated (α + β) titanium alloy part.

[0018] Furthermore, the (α + β) titanium alloy blank is prepared by the method of traditional vacuum arc melting combined with forging.

[0019] Furthermore, cool the first blank in the furnace to T β -(100 - 180) °C at a cooling rate of 5 - 15 °C / h.

[0020] Furthermore, cool the second blank in the furnace to T β -(200 - 300) °C at a cooling rate of 20 - 30 °C / h.

[0021] Furthermore, the (α + β) titanium alloy part is any one of TC4, TC17, TC18, TC19, TC21, TB6, Ti55531, TC4-DT, and other (α + β) titanium alloys.

[0022] In a third aspect, the present invention provides a method for preparing an impact-resistant titanium alloy bar or component by heat treatment, and the impact-resistant titanium alloy bar or component is used for structural components under penetration or impact-resistant working conditions.

[0023] Furthermore, the tensile strength of the impact-resistant titanium alloy bar or component is ≥980MPa, the yield strength is ≥930MPa, the impact energy is ≥35J, the dynamic plastic strain is ≥0.24, the dynamic rheological stress is ≥1580MPa, and the impact absorption energy is ≥400J·cm -3 , dynamic flow stress at 500℃≥1300MPa, dynamic plastic strain at 500℃≥0.26, impact absorption energy at 500℃≥300J·cm -3 .

[0024] The present invention achieves a significant improvement in the impact resistance of (α+β) titanium alloy through the synergistic effect of multi-stage precise temperature control process and organizational regulation mechanism, as shown in the following:

[0025] (1) The primary α phase (α p ) optimization control: By β -Precise solution treatment is carried out at (10~80)℃ to make part of α p Dissolved in the β matrix to form a supersaturated solid solution, followed by first stage furnace cooling to T β - (100~180) ℃, further controlling α p The size and content of the p Further homogenization eventually forms an equiaxed α with smaller size, uniform distribution and higher content. p , the equiaxed axis α p The average size is 5~12μm, and the volume fraction is greater than 30%. p Because the static load is evenly dispersed and a plastic deformation path is provided for the titanium alloy, the energy absorption of the titanium alloy under impact load is increased.

[0026] (2) The secondary α phase (α s ) is oriented to precipitate by cooling to T in the second stage. β - (200~300) ℃, through furnace cooling, α is precisely controlled s The precipitation thickness is only 0.05~1.2μm, forming a thin sheet or needle-shaped α s The two-phase structure is evenly distributed in the β matrix. s / β interface structure can consume more impact energy through interface slip and plastic deformation, thus inhibiting the rapid expansion of cracks.

[0027] (3) The tertiary α phase (α t ) directional precipitation regulation: by heating to T during failure treatment β- (350~450)°C, by controlling the directional precipitation of α t , the volume fraction of α t is less than 10%, effectively compensating for the insufficient strength of the titanium alloy caused by slow cooling, and at the same time will not have an obvious impact on the plasticity and toughness of the titanium alloy, thus achieving the regulation goal of high strength and high toughness of the titanium alloy.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. For (α + β) titanium alloys with different compositions, the present invention proposes a regulation process of process segmentation and control of cooling rate in different temperature regions below the β transformation temperature corresponding to the (α + β) titanium alloy: controlling the cooling rate in segments below T β (such as furnace cooling, rapid furnace cooling, air cooling combination), solution treatment and multi-stage cooling and heat preservation process, accurately controlling the precipitation behavior and distribution state of the α phase in the (α + β) titanium alloy, forming a "high-content equiaxed α p uniform distribution + lamellar controllable thickness α s precipitation + small amount of α t " organizational structure, that is, the multi-stage α regulation technology, to achieve the coordinated matching of strength-plasticity-toughness of the (α + β) titanium alloy.

[0030] 2. The heat treatment method of the present invention can significantly improve the impact resistance of the (α + β) titanium alloy material. After testing, its impact toughness is increased by more than 20% compared with the traditional method.

[0031] 3. The heat treatment method provided by the present invention is applicable to high-impact-resistant titanium alloy materials under penetration or impact-resistant working conditions, and has a wide application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings here are incorporated into the specification and form a part of the specification, and are used together with the specification to explain the principle of the present invention.

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0034] Figure 1 is the phased process diagram of the heat treatment method for improving the impact resistance of the (α + β) titanium alloy provided by the present invention;

[0035] Figure 2 is the microstructure morphology diagram of the titanium alloy after heat treatment in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] Here, exemplary embodiments will be described in detail, and examples thereof are shown in the accompanying drawings. When the following description refers to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. On the contrary, they are merely examples consistent with some aspects of the present invention detailed in the appended claims.

[0037] 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.

[0038] As Figure 1 shown, the present invention provides a heat treatment method for improving the impact resistance of (α + β) titanium alloy, including the following steps:

[0039] Step 1, prepare a (α + β) titanium alloy blank.

[0040] Obtain a (α + β) titanium alloy blank through hot isostatic pressing and determine its corresponding T β . Among them, the specific process of hot isostatic pressing is as follows: First, load the (α + β) titanium alloy powder into a stainless steel sealed envelope, and then, under a vacuum degree ≤ 1×10 -3 Pa, heat the stainless steel sealed envelope with the (α + β) titanium alloy powder to 850 - 950°C at a heating rate of 5 - 15°C / min, synchronously apply an argon pressure of 100 - 150 MPa, keep the temperature and pressure for 2 - 4 h, then cool to room temperature with the furnace, and finally, remove the stainless steel sealed envelope to obtain a (α + β) titanium alloy blank with a relative density ≥ 99.5%.

[0041] Prepare (α + β) titanium alloy powder by plasma atomization method. The powder particle size of the prepared (α + β) titanium alloy powder is ≤ 200 μm, the oxygen content is ≤ 0.2 wt%, and the nitrogen content is ≤ 0.05 wt%; use the prepared (α + β) titanium alloy powder as raw material to prepare a (α + β) titanium alloy blank.

[0042] It is also possible to prepare a (α + β) titanium alloy blank by the traditional vacuum arc melting combined with forging method.

[0043] The obtained (α + β) titanium alloy blank prepared above is a (α + β) titanium alloy bar and component. Through hot isostatic pressing, internal tissue defects of the (α + β) titanium alloy can be eliminated and homogenized.

[0044] In addition, T β is the β transformation temperature of the titanium alloy blank. Among (α + β) titanium alloy blanks with different compositions, T βFor example, the β transformation temperature T of TA1 / TA2 titanium alloy is β The temperature range is between 885 and 900°C. This temperature is a key parameter that determines the evolution of the titanium alloy microstructure and subsequent processing technology. When the (α+β) titanium alloy billet is hot worked or heat treated, T β It can serve as an important basis for dividing different phase regions, and further guide process operations to ensure ideal material properties.

[0045] Step 2: Solution treatment.

[0046] Specifically, the (α+β) titanium alloy blank prepared in step 1 is placed in a heating furnace and heated to T β -(10~80)℃ solid solution treatment, solid solution holding time ≤6h, to obtain the first blank. β -Precise solution treatment is carried out at (10~80)℃ to make part of the α in the (α+β) titanium alloy billet structure p Dissolved in the β matrix to form a supersaturated solid solution.

[0047] Step 3: First stage cooling + heat preservation treatment.

[0048] Specifically, the first blank is furnace cooled to T at a cooling rate of 5-15°C / h. β - (100~180) ℃, followed by heat preservation treatment, the heat preservation time is ≤ 6h, and the second billet is obtained. The internal α of the first billet is further controlled by furnace cooling operation. p The size and content of the p Further homogenization eventually forms an equiaxed α with smaller size, uniform distribution and higher content. p , due to the equiaxed α p The static load is evenly dispersed and a plastic deformation path of the first blank is provided, thereby increasing the energy absorption of the titanium alloy blank under impact load.

[0049] Step 4: Second stage cooling + heat preservation treatment.

[0050] Specifically, the furnace is cooled to T at a cooling rate of 20-30°C / h. β - (200~300) ℃, followed by heat preservation treatment, the heat preservation time is ≤ 6h, and the third blank is obtained. Through the furnace cooling operation, the internal α s The precipitation thickness forms a thin sheet or needle-shaped α s The two-phase structure is evenly distributed in the β matrix. s / β interface structure can consume more impact energy through interface slip and plastic deformation, thus inhibiting the rapid expansion of cracks.

[0051] Step 5. Cooling treatment in the third stage.

[0052] Specifically, the third blank is air-cooled to room temperature to obtain the fourth blank.

[0053] Step 6. Aging treatment.

[0054] Specifically, the fourth blank is heated to T β -(350 - 450) °C. After holding for ≤ 3 h, it is air-cooled to room temperature to obtain the treated (α + β) titanium alloy part. By heating the fourth blank to T β -(350 - 450) °C, through the directional precipitation regulation of α t in the titanium alloy structure, the insufficient strength of the (α + β) titanium alloy caused by slow cooling is effectively compensated, and at the same time, the plasticity and toughness of the (α + β) titanium alloy are not significantly affected, thereby achieving the regulation goal of high strength and high toughness of the (α + β) titanium alloy.

[0055] The treated (α + β) titanium alloy part is any one of TC4, TC17, TC18, TC19, TC21, TB6, Ti55531, TC4-DT and other (α + β) titanium alloys.

[0056] Through the heat treatment method provided by the present invention, impact-resistant titanium alloy bars or components can be prepared. The prepared impact-resistant titanium alloy bars or components can be used for structural parts under penetration or impact conditions. The tensile strength of the impact-resistant titanium alloy bars or components prepared by the heat treatment method of the present invention is ≥ 980 MPa, the yield strength is ≥ 930 MPa, the impact work is ≥ 35 J, the dynamic plastic strain is ≥ 0.24, the dynamic flow stress is ≥ 1580 MPa, the impact absorption energy is ≥ 400 J·cm -3 , the dynamic flow stress at 500 °C is ≥ 1300 MPa, the dynamic plastic strain at 500 °C is ≥ 0.26, and the impact absorption energy at 500 °C is ≥ 300 J·cm -3 .

[0057] In order to verify the beneficial effects brought by the preparation method of the present invention, it is further described through the following examples and comparative examples. Example 1

[0058] This example provides a heat treatment method for improving the impact resistance of TC4 titanium alloy, including the following steps:

[0059] Step 1. Obtain a TC4 titanium alloy blank by hot isostatic pressing.

[0060] The process of hot isostatic pressing is as follows: First, load the TC4 titanium alloy powder into a stainless steel sealed envelope. Then, under a vacuum degree ≤ 1×10 -3Under a pressure of Pa, the stainless-steel sealed envelope containing TC4 titanium alloy powder was heated to 900°C at a heating rate of 5°C / min, while simultaneously applying an argon pressure of 120 MPa. After holding for 3 h under constant temperature and pressure, it was cooled to room temperature in the furnace. Finally, the stainless-steel sealed envelope was removed to obtain a TC4 titanium alloy blank with a relative density ≥99.5%, and the corresponding T was determined. β , T β = 990°C.

[0061] Step 2. Solution treatment: The TC4 titanium alloy blank was heated to T β - 10°C = 980°C for solution treatment, and held at a constant temperature for 2 h to obtain the first blank.

[0062] Step 3. First-stage cooling + holding treatment: The first blank was cooled in the furnace at a cooling rate of 5°C / h to T β - 100°C = 890°C, and then held for 2 h to obtain the second blank.

[0063] Step 4. Second-stage cooling + holding treatment: The second blank was cooled in the furnace at a cooling rate of 20°C / h to T β - 200°C = 790°C, and then held for 2 h to obtain the third blank.

[0064] Step 5. Third-stage cooling treatment: The third blank was air-cooled to room temperature to obtain the fourth blank.

[0065] Step 6. Aging treatment: The fourth blank was heated to T β - 450°C = 540°C, held for 3 h, and then air-cooled to room temperature to obtain the treated TC4 titanium alloy.

[0066] The TC4 titanium alloy structure obtained by the heat treatment method of this example is as Figure 2 shown. Example 2

[0067] This example provides a heat treatment method for improving the impact resistance of TC21 titanium alloy, including the following steps:

[0068] Step 1. Obtain a TC21 titanium alloy blank by hot isostatic pressing.

[0069] The process of hot isostatic pressing is as follows: First, load the TC21 titanium alloy powder into a stainless-steel sealed envelope, and then, under a vacuum degree ≤1×10 -3Under a pressure of Pa, the stainless-steel sealed envelope containing TC21 titanium alloy powder was heated to 850°C at a heating rate of 5°C / min, while simultaneously applying an argon pressure of 150 MPa. After holding the temperature and pressure for 4 h, it was cooled to room temperature in the furnace. Finally, the stainless-steel sealed envelope was removed to obtain a TC21 titanium alloy blank with a relative density ≥99.5%, and its corresponding T β , T β = 965°C.

[0070] Step Two, solution treatment: The TC21 titanium alloy blank was heated to T β - 10°C = 955°C for solution treatment, and the solution was held for 2 h to obtain the first blank.

[0071] Step Three, first-stage cooling + holding treatment: The first blank was furnace-cooled to T β - 100°C = 865°C at a cooling rate of 5°C / h, and then subjected to a holding treatment for 2 h to obtain the second blank.

[0072] Step Four, second-stage cooling + holding treatment: The second blank was furnace-cooled to T β - 200°C = 765°C at a cooling rate of 20°C / h, and then subjected to a holding treatment for 2 h to obtain the third blank.

[0073] Step Five, third-stage cooling treatment: The third blank was air-cooled to room temperature to obtain the fourth blank.

[0074] Step Six, aging treatment: The fourth blank was heated to T β - 375°C = 590°C, held for 2 h, and then air-cooled to room temperature to obtain the treated TC21 titanium alloy. Example 3

[0075] This example provides a heat treatment method for improving the impact resistance of TC19 titanium alloy, including the following steps:

[0076] Step One, prepare a TC19 titanium alloy blank by using the traditional vacuum arc melting combined with forging method, and determine its corresponding T β , T β = 960°C.

[0077] Step Two, solution treatment: The TC19 titanium alloy blank was heated to T β - 50°C = 910°C for solution treatment, and the solution was held for 4 h to obtain the first blank.

[0078] Step Three, first-stage cooling + holding treatment: The first blank was furnace-cooled to T β - 150°C = 810°C at a cooling rate of 10°C / h, and then subjected to a holding treatment for 4 h to obtain the second blank.

[0079] Step 4. Second-stage cooling + heat preservation treatment: Cool the second blank in the furnace at a cooling rate of 25 °C / h to T β - 250 °C = 710 °C, and then carry out heat preservation treatment for 4 h to obtain the third blank.

[0080] Step 5. Third-stage cooling treatment: Air-cool the third blank to room temperature to obtain the fourth blank.

[0081] Step 6. Aging treatment: Heat the fourth blank to T β - 350 °C = 610 °C, after heat preservation for 2 h, air-cool it to room temperature to obtain the treated TC19 titanium alloy. Example 4

[0082] This example provides a heat treatment method for improving the impact resistance of TC17 titanium alloy, including the following steps:

[0083] Step 1. Obtain a TC17 titanium alloy blank by hot isostatic pressing.

[0084] The process of hot isostatic pressing is as follows: First, load the TC17 titanium alloy powder into a stainless steel sealed envelope, and then, under a vacuum degree ≤ 1×10 -3 Pa, heat the stainless steel sealed envelope with TC17 titanium alloy powder to 880 °C at a heating rate of 10 °C / min, synchronously apply an argon pressure of 130 MPa, after heat preservation and pressure holding for 3 h, cool it in the furnace to room temperature, finally, remove the stainless steel sealed envelope to obtain a TC17 titanium alloy blank with a relative density ≥ 99.5%, and determine its corresponding T β , T β = 895 °C.

[0085] Step 2. Solution treatment: Heat the TC17 titanium alloy blank to T β - 50 °C = 845 °C for solution treatment, with solution heat preservation for 4 h to obtain the first blank.

[0086] Step 3. First-stage cooling + heat preservation treatment: Cool the first blank in the furnace at a cooling rate of 10 °C / h to T β - 150 °C = 745 °C, and then carry out heat preservation treatment for 4 h to obtain the second blank.

[0087] Step 4. Second-stage cooling + heat preservation treatment: Cool the second blank in the furnace at a cooling rate of 25 °C / h to T β - 250 °C = 645 °C, and then carry out heat preservation treatment for 4 h to obtain the third blank.

[0088] Step 5. Third-stage cooling treatment: Air-cool the third blank to room temperature to obtain the fourth blank.

[0089] Step Six, Aging Treatment: Heat the fourth billet to T β - 405°C = 490°C, after holding for 1 h, air cool to room temperature to obtain the treated TC17 titanium alloy. Example 5

[0090] This example provides a heat treatment method for improving the impact resistance of TB6 titanium alloy, including the following steps:

[0091] Step One, Obtain a TB6 titanium alloy billet by hot isostatic pressing.

[0092] The process of hot isostatic pressing is as follows: First, load the TB6 titanium alloy powder into a stainless steel sealed envelope, then, under a vacuum degree ≤ 1×10 -3 Pa, heat the stainless steel sealed envelope with the TB6 titanium alloy powder to 860°C at a heating rate of 10°C / min, simultaneously apply an argon pressure of 140 MPa, after holding and pressurizing for 2.5 h, cool with the furnace to room temperature, finally, remove the stainless steel sealed envelope to obtain a TB6 titanium alloy billet with a relative density ≥ 99.5%, and determine its corresponding T β , T β = 805°C.

[0093] Step Two, Solution Treatment: Heat the TB6 titanium alloy billet to T β - 50°C = 755°C for solution treatment, hold for 4 h for solution treatment to obtain the first billet.

[0094] Step Three, First - stage Cooling + Holding Treatment: Cool the first billet with the furnace at a cooling rate of 10°C / h to T β - 150°C = 655°C, then carry out holding treatment, hold for 4 h to obtain the second billet.

[0095] Step Four, Second - stage Cooling + Holding Treatment: Cool the second billet with the furnace at a cooling rate of 25°C / h to T β - 250°C = 555°C, then carry out holding treatment, hold for 4 h to obtain the third billet.

[0096] Step Five, Third - stage Cooling Treatment: Air - cool the third billet to room temperature to obtain the fourth billet.

[0097] Step Six, Aging Treatment: Heat the fourth billet to T β - 355°C = 450°C, after holding for 1 h, air cool to room temperature to obtain the treated TB6 titanium alloy. Example 6

[0098] This example provides a heat treatment method for improving the impact resistance of TC18 titanium alloy, including the following steps:

[0099] Step 1: Obtain a TC18 titanium alloy blank by hot isostatic pressing.

[0100] The process of hot isostatic pressing is as follows: First, load the TC18 titanium alloy powder into a stainless steel sealed envelope. Then, under a vacuum degree ≤ 1×10 -3 Pa, heat the stainless steel sealed envelope with the TC18 titanium alloy powder to 920 °C at a heating rate of 15 °C / min, simultaneously apply an argon pressure of 110 MPa, keep the temperature and pressure for 3.5 h, then cool it to room temperature with the furnace, and finally, remove the stainless steel sealed envelope to obtain a TC18 titanium alloy blank with a relative density ≥ 99.5%, and determine its corresponding T β , T β = 870 °C.

[0101] Step 2: Solution treatment: Heat the TC18 titanium alloy blank to T β - 80 °C = 790 °C for solution treatment, keep the solution for 6 h to obtain the first blank.

[0102] Step 3: First-stage cooling + heat preservation treatment: Cool the first blank with the furnace at a cooling rate of 15 °C / h to T β - 180 °C = 690 °C, then carry out heat preservation treatment for 6 h to obtain the second blank.

[0103] Step 4: Second-stage cooling + heat preservation treatment: Cool the second blank with the furnace at a cooling rate of 25 °C / h to T β - 300 °C = 570 °C, then carry out heat preservation treatment for 6 h to obtain the third blank.

[0104] Step 5: Third-stage cooling treatment: Air-cool the third blank to room temperature to obtain the fourth blank.

[0105] Step 6: Aging treatment: Heat the fourth blank to T β - 350 °C = 520 °C, keep the temperature for 0.5 h, then air-cool it to room temperature to obtain the treated TC18 titanium alloy. Example 7

[0106] This example provides a heat treatment method for improving the impact resistance of Ti55531 titanium alloy, including the following steps:

[0107] Step 1: Obtain a Ti55531 titanium alloy blank by hot isostatic pressing.

[0108] The process of hot isostatic pressing is as follows: First, load the Ti55531 titanium alloy powder into a stainless steel sealed envelope. Then, under a vacuum degree ≤ 1×10 -3Under a pressure of [[Pa]], the stainless-steel sealed envelope containing Ti55531 titanium alloy powder was heated to 950 °C at a heating rate of 15 °C / min, and an argon pressure of 100 MPa was applied simultaneously. After holding the temperature and pressure for 2 h, it was cooled to room temperature in the furnace. Finally, the stainless-steel sealed envelope was removed to obtain a Ti55531 titanium alloy blank with a relative density ≥ 99.5%, and its corresponding T β , T β = 835 °C.

[0109] Step 2. Solution treatment: The Ti55531 titanium alloy blank was heated to T β - 80 °C = 755 °C for solution treatment, and the solution was held for 6 h to obtain the first blank.

[0110] Step 3. First-stage cooling + holding treatment: The first blank was cooled in the furnace at a cooling rate of 15 °C / h to T β - 180 °C = 655 °C, and then holding treatment was carried out for 6 h to obtain the second blank.

[0111] Step 4. Second-stage cooling + holding treatment: The second blank was cooled in the furnace at a cooling rate of 30 °C / h to T β - 300 °C = 535 °C, and then holding treatment was carried out for 6 h to obtain the third blank.

[0112] Step 5. Third-stage cooling treatment: The third blank was air-cooled to room temperature to obtain the fourth blank.

[0113] Step 6. Aging treatment: The fourth blank was heated to T β - 355 °C = 480 °C, held for 1.5 h, and then air-cooled to room temperature to obtain the treated Ti55531 titanium alloy. Example 8

[0114] This example provides a heat treatment method for improving the impact resistance of TC4-DT titanium alloy, including the following steps:

[0115] Step 1. Obtain a TC4-DT titanium alloy blank by hot isostatic pressing.

[0116] The process of hot isostatic pressing is as follows: First, load the TC4-DT titanium alloy powder into a stainless-steel sealed envelope, and then, under a vacuum degree ≤ 1 × 10 -3 Pa, the stainless-steel sealed envelope containing TC4-DT titanium alloy powder was heated to 940 °C at a heating rate of 15 °C / min, and an argon pressure of 120 MPa was applied simultaneously. After holding the temperature and pressure for 3 h, it was cooled to room temperature in the furnace. Finally, the stainless-steel sealed envelope was removed to obtain a TC4-DT titanium alloy blank with a relative density ≥ 99.5%, and its corresponding T β , T β= 980 °C.

[0117] Step 2. Solution treatment: Heat the TC4-DT titanium alloy blank to T β -80 °C = 900 °C for solution treatment, keep the temperature for 6 hours to obtain the first blank.

[0118] Step 3. First-stage cooling + heat preservation treatment: Cool the first blank in the furnace at a cooling rate of 15 °C / h to T β -180 °C = 800 °C, then carry out heat preservation treatment for 6 hours to obtain the second blank.

[0119] Step 4. Second-stage cooling + heat preservation treatment: Cool the second blank in the furnace at a cooling rate of 30 °C / h to T β -300 °C = 680 °C, then carry out heat preservation treatment for 6 hours to obtain the third blank.

[0120] Step 5. Third-stage cooling treatment: Air-cool the third blank to room temperature to obtain the fourth blank.

[0121] Step 6. Aging treatment: Heat the fourth blank to T β -355 °C = 625 °C, after keeping the temperature for 1.5 hours, air-cool to room temperature to obtain the treated TC4-DT titanium alloy. Comparative Example 1

[0122] This Comparative Example 1 provides a double annealing treatment process for TC4 titanium alloy to obtain the treated TC4 titanium alloy.

[0123] To highlight the beneficial effects brought by the heat treatment method of the present invention, Examples 1-8 and Comparative Example 1 are compared in terms of tensile strength, yield strength, elongation after fracture, reduction of area, impact work, dynamic plastic strain, dynamic flow stress, impact absorption energy, and dynamic properties at 500 °C (dynamic plastic strain, dynamic flow stress, and impact absorption energy) of these titanium alloy properties.

[0124] The performance data of the (α + β) titanium alloys obtained in Examples 1-8 by the heat treatment method of the present invention and the titanium alloy obtained by double annealing in Comparative Example 1 are shown in Table 1:

[0125] Table 1 Performance data of the treated titanium alloy

[0126]

[0127] As can be seen from Table 1, the tensile strength of the (α + β) titanium alloy obtained by the heat treatment method of the present invention is ≥ 980 MPa, the yield strength is ≥ 930 MPa, the impact work is ≥ 35 J, the dynamic plastic strain is ≥ 0.24, the dynamic flow stress is ≥ 1580 MPa, and the impact absorption energy is ≥ 400 J·cm -3, the dynamic plastic strain at 500 °C ≥ 0.26, the dynamic flow stress at 500 °C ≥ 1300 MPa, and the impact energy absorption at 500 °C ≥ 300 J·cm -3 .

[0128] However, the tensile strength, yield strength, dynamic plastic strain, dynamic flow stress, impact energy absorption, and the dynamic flow stress at 500 °C of the titanium alloy obtained by the treatment method of Comparative Example 1 are all less than those of Examples 1-8 of the present invention; only the elongation after fracture, reduction of area, and the dynamic plastic strain at 500 °C are slightly greater than those of some embodiments of the present invention.

[0129] This further proves that the heat treatment method provided by the present invention can significantly improve the impact resistance of titanium alloy materials, has strong process compatibility, is applicable to a variety of titanium alloy systems, does not require complex equipment modification, has excellent service performance, and has significantly better impact resistance than traditional processes under high-speed impact, meeting the material requirements for a new generation of penetration or impact-resistant working conditions.

[0130] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0131] 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 only limited by the appended claims.

Claims

1. A heat treatment method for improving the impact resistance of (α + β) titanium alloy, characterized in that, It includes the following steps: Step 1. Prepare an (α+β) titanium alloy blank based on the hot isostatic pressing method and determine the corresponding T β ; Step 2. Solution treatment: Heat the (α + β) titanium alloy blank to T β -(10 - 80) °C for solution treatment, with the solution holding time ≤ 6 h to obtain the first blank; Step 3. First-stage cooling + heat preservation treatment: Cool the first blank in a furnace to T β -(100 - 180)°C, then carry out heat preservation treatment with a heat preservation time ≤ 6 h to obtain the second blank; Step 4. Second-stage cooling + heat preservation treatment: Cool the second blank in a furnace to T β -(200 - 300)°C, then carry out heat preservation treatment with the heat preservation time ≤ 6 h to obtain the third blank; Step Five, Cooling Treatment in the Third Stage: Air-cool the third blank to room temperature to obtain the fourth blank; Step VI, aging treatment: Heat the fourth blank to T β -(350 - 450) °C, after holding for ≤ 3 h, air cool to room temperature to obtain the treated (α + β) titanium alloy part.

2. The heat treatment method for improving the impact resistance of (α + β) titanium alloy according to claim 1, characterized in that, The (α + β) titanium alloy blank is prepared by the method of combining traditional vacuum arc melting and forging.

3. The heat treatment method for improving the impact resistance of (α+β) titanium alloy according to claim 1, characterized in that, Cool the first blank in a furnace at a cooling rate of 5-15 °C / h to T β -(100-180) °C.

4. The heat treatment method for improving the impact resistance of (α + β) titanium alloy according to claim 1, characterized in that, Cool the second blank in a furnace at a cooling rate of 20 to 30 °C / h to T β -(200 to 300) °C.

5. The heat treatment method for improving the impact resistance of (α + β) titanium alloy according to claim 1, characterized in that, The (α + β) titanium alloy part is any one of TC4, TC17, TC18, TC19, TC21, TB6, Ti55531, and TC4-DT titanium alloy.

6. A method for preparing an impact-resistant titanium alloy bar or component by using the heat treatment method according to any one of claims 1-5, characterized in that, The impact-resistant titanium alloy bar or component is used for structural components under penetration or impact conditions.

7. The method for preparing an impact-resistant titanium alloy bar or component by the heat treatment method according to claim 6, characterized in that, The tensile strength of the impact-resistant titanium alloy bar or component is ≥980 MPa, the yield strength is ≥930 MPa, the impact energy is ≥35 J, the dynamic plastic strain is ≥0.24, the dynamic flow stress is ≥1580 MPa, and the impact absorption energy is ≥400 J·cm -3 , the dynamic flow stress at 500°C is ≥1300 MPa, the dynamic plastic strain at 500°C is ≥0.26, and the impact absorption energy at 500°C is ≥300 J·cm -3 .

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