Heat treatment method for improving impact toughness of high-strength titanium alloy

Abstract

The invention discloses a heat treatment method for improving the impact toughness of a high-strength titanium alloy, and the high-strength and high-toughness titanium alloy is obtained by carrying out solution treatment and converter aging treatment on the high-strength titanium alloy through precise heat treatment parameter design. According to the heat treatment method, the process combination of solution treatment and converter aging treatment is adopted, and precise heat treatment parameter design is combined, so that the titanium alloy forms an alternately-arranged alpha lamella and beta phase microstructure, the number of fine lamella structure interfaces is increased, the crack propagation path is complicated, the impact fracture resistance of the high-strength titanium alloy is effectively improved, and the service life of the titanium alloy is prolonged. On the premise that the strength reduction amplitude is controlled to be within 100 MPa, the impact toughness is remarkably improved, and the high-strength steel plate is suitable for preparing equipment such as armored vehicle protective armors and naval vessel pressure-resistant shells.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy mechanical property strengthening, and in particular relates to a heat treatment method for improving the impact toughness of high-strength titanium alloy. Background Art

[0002] In the field of modern high-end manufacturing, high-strength titanium alloys with a room temperature tensile strength greater than 1200MPa have become core basic materials for cutting-edge industries such as aerospace and defense due to their excellent specific strength characteristics. In the aerospace field, they are widely used in high-temperature and high-pressure components such as aircraft engine compressor blades and casings, as well as aircraft fuselage frames and landing gear structures. These components need to withstand numerous complex aerodynamic loads and maintain high-strength load-bearing capacity while ensuring lightweight structures. In the defense field, it is a key material for equipment such as armored vehicle protective armor and ship pressure hulls, capable of withstanding high-intensity impact and penetration while ensuring the mobility of the equipment.

[0003] However, this "lightweight powerhouse" has significant performance shortcomings. Its impact toughness is generally low, and the impact energy of conventional high-strength titanium alloys is often limited to less than 20J. In the high-frequency vibration environment generated by the high-speed operation of aircraft engines, or at the moment when armored vehicles are hit by an explosion, the stress concentration inside the components can easily induce crack initiation. Due to insufficient impact toughness, these cracks cannot be effectively suppressed and will expand at an extremely fast rate, eventually leading to brittle fracture of the components. This performance defect greatly limits the further application and expansion of high-strength titanium alloys under high dynamic load conditions, and has become a key technical bottleneck restricting the performance improvement of related high-end equipment. Summary of the Invention

[0004] The present invention aims to overcome the shortcomings of the prior art by providing a heat treatment method for improving the impact toughness of high-strength titanium alloys. This heat treatment method utilizes a combined process of solution treatment and converter aging, combined with precise heat treatment parameter design. While maintaining a strength drop within 100 MPa, it achieves a significant improvement in impact toughness, resolving the issue of insufficient impact toughness in high-strength titanium alloys under high-strength service conditions.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a heat treatment method for improving the impact toughness of high-strength titanium alloy, characterized in that through precise heat treatment parameter design, the high-strength titanium alloy is subjected to solid solution treatment and converter aging treatment to obtain a high-strength and high-toughness titanium alloy.

[0006] The above-mentioned heat treatment method for improving the impact toughness of high-strength titanium alloy is characterized in that the temperature of the solid solution treatment is 10°C to 20°C below the β-transus temperature.

[0007] The present invention achieves the goal of primary α phase content ≤ 10% by controlling the temperature of the solution treatment to 10°C to 20°C below the β transition temperature, reducing the occupied β phase space and creating conditions for the uniform growth of the secondary lamellar α phase in the subsequent aging process.

[0008] The above-mentioned heat treatment method for improving the impact toughness of high-strength titanium alloy is characterized in that the converter aging treatment process is: after the solid solution treatment, the high-strength titanium alloy is transferred to the aging furnace, and then the heat treatment is carried out at the aging temperature; the aging temperature T1 is calculated by the following formula: ; Wherein, T1 is the aging temperature, in °C; T2 is the aging strengthening heat treatment temperature at which the high-strength titanium alloy has excellent strength-plasticity matching, in °C.

[0009] The present invention controls the aging temperature T1 to be increased by 20°C to 30°C on the basis of the aging strengthening heat treatment temperature at which the alloy has excellent matching of strength and plasticity. The essence is to alleviate the adverse effect of the increase in solid solution temperature on tensile plasticity by compensating for the microstructure during the aging stage. For example, the aging strengthening heat treatment temperature at which the Ti5321 alloy achieves excellent matching of strength and plasticity is 570°C. The aging temperature of the Ti5321 alloy of the present invention is selected to be 590°C to 600°C. For example, the aging strengthening heat treatment temperature at which the Ti1300 alloy achieves excellent matching of strength and plasticity is 540°C. The aging temperature of the Ti1300 alloy of the present invention is selected to be 570°C.

[0010] The above-mentioned heat treatment method for improving the impact toughness of high-strength titanium alloy is characterized in that the aging strengthening heat treatment temperature of the high-strength titanium alloy with excellent matching of strength and plasticity is 500°C~600°C.

[0011] The above-mentioned heat treatment method for improving the impact toughness of high-strength titanium alloy is characterized in that the duration of the heat preservation treatment is 4h~6h.

[0012] Compared with the prior art, the present invention has the following advantages: 1. The heat treatment method of the present invention adopts the process combination of "solution treatment + converter aging treatment" and combines it with precise heat treatment parameter design to achieve a significant leap of 40% to 50% in the impact toughness of high-strength titanium alloy while controlling the strength reduction within 100 MPa.

[0013] 2. The traditional "solution + air cooling + aging" process usually selects 30℃~60℃ below the β-transformation temperature. Within this temperature range, the alloy can retain a certain large-sized primary α phase, and the phase content is usually more than 20%. Although it is beneficial to plasticity, it is easy to form a "strong-weak phase interface" with the secondary α phase after aging, becoming a weak point for impact fracture. The present invention selects a solution temperature of 10℃~20℃ below the β-transformation temperature, which reduces the size of the residual primary α phase from the micron level of the traditional process to the submicron level, and the content is also reduced to less than 10%. Under the present invention, compared with the more primary α phase, the primary α phase after solid solution has a more significant advantage in reducing the space occupied by the β phase. This continuous and open β phase space provides a physical basis for the long-distance uniform growth of the secondary lamellar α phase during subsequent aging, avoiding the problem of "the β phase cells are too small, resulting in limited lamellar growth" in the traditional process; the subsequent converter aging treatment forms an alternating "α lamellar + β phase" microstructure, the fine lamellar organization interface increases, and the crack propagation path is complicated, thereby improving the impact fracture resistance of the high-strength titanium alloy.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the microstructure diagram of the high-strength and high-toughness Ti5321 alloy in Example 1 of the present invention.

[0016] Figure 2 This is the microstructure diagram of the high-strength Ti5321 alloy of comparative example 1 of the present invention. DETAILED DESCRIPTION

[0017] Example 1 The heat treatment method of the Ti5321 alloy in this embodiment is as follows: the Ti5321 alloy is placed in a solution furnace, subjected to solution treatment at 850°C for 1 hour, then transferred to an aging furnace, subjected to aging treatment at 600°C for 6 hours, and air-cooled to obtain a high-strength and high-toughness Ti5321 alloy; the aging strengthening heat treatment temperature of the Ti5321 alloy, which has excellent strength and plasticity, is 570°C.

[0018] The high strength and high toughness Ti5321 alloy obtained in this embodiment was subjected to microscopic analysis. Figure 1 As shown in the figure, the high-strength and high-toughness Ti5321 alloy forms a microstructure of α-lamellae + β-phase, and the number of fine lamellar organization interfaces increases, which complicates the crack propagation path, thereby improving the impact fracture resistance of the high-strength titanium alloy.

[0019] Comparative Example 1 The heat treatment method of the Ti5321 alloy in this comparative example is as follows: the Ti5321 alloy is placed in a solid solution furnace, subjected to solid solution treatment at 800°C for 1 hour, and then air-cooled, and then subjected to aging treatment at 570°C for 4 hours, and then air-cooled to obtain a high-strength Ti5321 alloy.

[0020] The high strength Ti5321 alloy obtained in this comparative example was subjected to microscopic analysis. Figure 2 As shown, the microstructure of the high-strength Ti5321 alloy is significantly reduced in the interface of the fine lamellar structure compared with Example 1, indicating that the impact fracture resistance is lower than that of the high-strength and high-toughness Ti5321 alloy obtained in Example 1.

[0021] Example 2 The heat treatment method of the Ti5321 alloy in this embodiment is as follows: the Ti5321 alloy is placed in a solution furnace, subjected to solution treatment at 840°C for 1 hour, then transferred to an aging furnace, subjected to aging treatment at 590°C for 4 hours, and air-cooled to obtain a high-strength and high-toughness Ti5321 alloy.

[0022] Example 3 The heat treatment method of the Ti5321 alloy in this embodiment is as follows: the Ti5321 alloy is placed in a solution furnace, subjected to solution treatment at 845°C for 1 hour, then transferred to an aging furnace, subjected to aging treatment at 595°C for 5 hours, and air-cooled to obtain a high-strength and high-toughness Ti5321 alloy.

[0023] Example 4 The heat treatment method of the Ti1300 alloy in this embodiment is as follows: the Ti1300 alloy is placed in a solution furnace, subjected to solution treatment at 810°C for 1 hour, then transferred to an aging furnace, subjected to aging treatment at 570°C for 4 hours, and air-cooled to obtain a high-strength and high-toughness Ti1300 alloy; the aging strengthening heat treatment temperature for the Ti1300 alloy to achieve excellent matching of strength and plasticity is 540°C.

[0024] Comparative Example 2 The heat treatment method of the Ti1300 alloy in this comparative example is as follows: the Ti1300 alloy is placed in a solution furnace, subjected to solution treatment at 760°C for 1 hour, then transferred to an aging furnace, subjected to aging treatment at 540°C for 4 hours, and air-cooled to obtain a high-strength Ti1300 alloy.

[0025] The tensile properties and impact properties of the alloys obtained in Examples 1-4 and Comparative Examples 1-2 were tested. The results are shown in Table 1.

[0026] Table 1 Performance test results

[0027] As shown in Table 1, the high strength and high toughness Ti5321 alloys after heat treatment in Examples 1 to 3 are lower than those in Comparative Example 1 in terms of tensile strength σb and yield strength σ 0.2 The tensile strength of the high-strength and high-toughness Ti1300 alloy after heat treatment in Example 4 is σ lower than that in Comparative Example 2. b and yield strength σ 0.2 The heat treatment method of the present invention can achieve a significant leap in the impact toughness of high-strength titanium alloy on the basis of controlling the strength reduction within 100 MPa.

[0028] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A heat treatment method for improving the impact toughness of high-strength titanium alloy, characterized in that: Through precise heat treatment parameter design, high-strength titanium alloy is subjected to solid solution treatment and converter aging treatment to obtain high-strength and high-toughness titanium alloy.

2. A heat treatment method for improving the impact toughness of high-strength titanium alloy according to claim 1, characterized in that: The temperature of the solution treatment is 10°C to 20°C below the β-transus temperature.

3. A heat treatment method for improving the impact toughness of high-strength titanium alloy according to claim 1, characterized in that: The converter aging treatment process is as follows: after solution treatment, the high-strength titanium alloy is transferred to an aging furnace, and then subjected to a holding treatment at an aging temperature; the aging temperature T1 is calculated by the following formula: ； Wherein, T1 is the aging temperature, in °C; T2 is the aging strengthening heat treatment temperature at which the high-strength titanium alloy has excellent strength-plasticity matching, in °C.

4. A heat treatment method for improving the impact toughness of high-strength titanium alloy according to claim 3, characterized in that: The high-strength titanium alloy has excellent matching strength and plasticity, and the aging strengthening heat treatment temperature is 500°C to 600°C.

5. The heat treatment method for improving the impact toughness of high-strength titanium alloy according to claim 3, characterized in that: The duration of the heat preservation treatment is 4h~6h.

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