Method for obtaining mosaic structure in TC18 titanium alloy
By introducing a deformation heat treatment process of mosaic structure into TC18 titanium alloy, the problem of insufficient strength in aerospace bearing structural parts is solved, and the strength and plasticity are significantly improved, meeting the high performance requirements of aerospace bearing structural parts.
Patent Information
- Application Number
- CN202510434384.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-08
- Publication Date
- 2025-07-08
AI Technical Summary
The existing heat treatment process of TC18 titanium alloy is difficult to meet the high performance requirements of aerospace load-bearing structural parts, especially in large load-bearing structural parts of aircraft landing gear, the traditional solid solution and aging process cannot significantly improve its strength and plasticity.
By adopting the deformation heat treatment process, mosaic tissue is introduced into the TC18 titanium alloy, including compression of 810-870℃, cooling to room temperature at 30-50℃/s for 4 hours, aged at 540-600℃ for 4 hours, forming a nano-scale αs phase, and using crystal defects and deformed tissue during thermal deformation to achieve tissue structure strengthening and precipitation strengthening.
Significantly improve the strength of TC18 titanium alloy, increase the tensile strength by more than 240MPa, and maintain high plasticity, the formed mosaic structure effectively hinders dislocation slip and improves the comprehensive mechanical properties of the alloy.
Smart Images
Figure CN120272841A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of alloy heat treatment, and particularly relates to a method for obtaining a mosaic structure in TC18 titanium alloy Background Art
[0002] In the process of rapid development of the aerospace field, the requirements for the performance of the materials used are constantly increasing. Especially, the service conditions of aerospace load-bearing structural components are extremely harsh, and their stability requirements far exceed those of ordinary manufacturing industries. TC18 titanium alloy has excellent properties such as excellent hardenability, good corrosion resistance, good weldability, and high specific strength. It is an important material in the fields of aerospace, chemical medical devices, ocean engineering, and oil exploration, etc. Especially in the aerospace field, it is often used as the manufacturing material for key components, such as manufacturing large load-bearing structural components like aircraft fuselages and landing gears, etc.
[0003] At present, the main strengthening strategy of TC18 titanium alloy is solution treatment plus aging heat treatment. Although this processing technology is more convenient and simple, and the performance of the original material can be optimized only through heat treatment. For example, the highest tensile strength and total elongation obtained by solution treatment plus aging in the two-phase region are 1300 MPa and 5.6% respectively. However, it is far from enough for the performance requirements of aerospace load-bearing components. Moreover, the processing technology of aircraft landing gears mainly focuses on die forging, which involves hot deformation. Therefore, in the basic research on applying TC18 titanium alloy as a large load-bearing structural component to aircraft landing gears, hot deformation should be taken into account. And some researchers have found that the strength and plasticity of titanium alloy after aging after hot deformation in the α+β two-phase region are better than those after aging after hot deformation in the β single-phase region. This thermomechanical treatment process refines the grains of the alloy during hot deformation, and at the same time, the αs and αp precipitated during aging form α phases with different scales. The synergistic effect of this heterogeneous structure on mechanical properties will greatly improve its strength while ensuring the plasticity of the alloy. Therefore, based on the above theory, the present invention designs a new process to introduce multi-scale α phases and nano-α phases into the crystal structure of TC18 titanium alloy to form a mosaic structure, making it have excellent mechanical properties. Summary of the Invention
[0004] Aiming at the deficiencies of the prior art, the present invention provides a method for obtaining a mosaic structure in TC18 titanium alloy to achieve the improvement of the strength of TC18 titanium alloy
[0005] To achieve the above objectives, the present invention is realized through the following technical solutions
[0006] The present invention discloses a method for obtaining a mosaic structure in TC18 titanium alloy. The TC18 titanium alloy cylindrical specimen is heated at 810-870 °C for 0.01-10 s -1After compression by 60%, cooled to room temperature at 30 - 50 °C / s, aged at 540 - 600 °C for 4 h, and then air-cooled to room temperature.
[0007] Preferably, the TC18 titanium alloy cylindrical specimen is heated to 810 - 870 °C for 0.01 - 1 s -1 Compressed by 60% to refine the grains, increasing the β-phase interface and generating a large number of defects.
[0008] Preferably, cooled to room temperature at 30 - 50 °C / s to retain the deformed structure and crystal defects formed during the hot deformation process.
[0009] Preferably, after aging at 540 - 600 °C for 4 h, α s phase nucleates and grows at places with high dislocation density to form a mosaic structure.
[0010] The present invention has the following beneficial effects:
[0011] 1. The present invention adopts a thermomechanical treatment process, introducing a mosaic structure to strengthen the titanium alloy in two different ways, achieving a significant increase in the strength of the TC18 titanium alloy. The two strengthening mechanisms are precipitation strengthening and microstructure strengthening. By precipitating a large number of nano-scale αs phases, its strength is improved. At the same time, introducing the mosaic structure can also optimize its strength.
[0012] 2. The above thermomechanical treatment process adopted by the present invention precipitates a large number of nano αs phases to increase the alloy strength. Cooled to room temperature at 30 - 50 °C / s, retaining the deformed structure and crystal defects formed during the hot deformation process, effectively utilizing the defects during the hot deformation process to successfully introduce a mosaic structure during the aging process to further strengthen the alloy, ultimately resulting in a significant increase in the strength of the TC18 titanium alloy. BRIEF DESCRIPTION OF THE DRAWINGS
[0013] Figure 1 It is a TEM analysis diagram of the TC18 titanium alloy after thermomechanical treatment; (a) The hot compression process is at 840 °C for 0.1 s -1 , and the aging process is at 600 °C for 4 h; (b) An enlarged view of the mosaic αs phase in Figure (a);
[0014] Figure 2 It is a schematic diagram of the thermomechanical treatment process;
[0015] Figure 3 It is the test result of mechanical properties. DETAILED DESCRIPTION OF THE INVENTION
[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.
[0017] Unless otherwise specified, the technical means used in the implementation examples are conventional means well known to those skilled in the art.
[0018] As Figure 2 shown, the present invention discloses a method for obtaining a mosaic structure in TC18 titanium alloy, and the process is as follows:
[0019] (1) A TC18 titanium alloy cylindrical specimen with a diameter of Φ8mm and a length of 12mm is compressed by 60% at 810°C to 870°C and a strain rate of 0.01 to 0.1 s -1 on a Gleeble-3800 thermo-mechanical simulator, and finally cooled to room temperature at 30 - 50°C / s to form a partially deformed structure, with a large number of recrystallized grains and equiaxed primary phases (α p ) with a micron size. During this treatment process, the titanium alloy can refine grains after large deformation. Cooling to room temperature at 30 - 50°C / s retains the deformed structure and crystal defects formed during the hot deformation process, preparing for the precipitation of nano-scale α s phase during subsequent aging treatment. This structure has a good promoting effect on the strength of the titanium alloy, and different hot compression processes can obtain different α p phases: the higher the hot compression temperature, the lower the content of α p and the fewer the deformed structures; the higher the hot compression rate, the larger the defects generated in the alloy and the more the deformed grains.
[0020] (2) Then it is placed in a box furnace at 540 - 600°C for aging for 4 h, and finally air-cooled to precipitate a large number of nano-scale α s phases arranged in a disorderly manner like "mosaic". The nucleation and growth of nano-scale α s phases form a mosaic morphology and are uniformly distributed in the β matrix.
[0021] In the present invention, the micron-scale α phase formed during the hot compression part will ensure that the plasticity of the alloy will not be lost too much while the strength is improved. At the same time, the large deformation treatment will generate a large number of defects in the alloy, and the cooling rate of 30 - 50°C / s can retain the deformed structure and crystal defects during the hot deformation process, which is helpful for the precipitation of α s phase during the next heat treatment process. In the aging treatment part, a large number of uniformly fine nano-scale α s phases will precipitate in the β phase matrix. Due to the large number of defects generated in the alloy by large deformation, αs The meeting grows along different directions to form a mosaic structure, seriously hindering the slip of dislocations and increasing its strength.
[0022] Based on the solution-aging process, the present invention performs hot compression on TC18 alloy above the recrystallization temperature and below the phase transformation temperature, dissolving small-sized α p grains, refining β grains, consuming a large number of dislocations through recrystallization to transform deformed grains into equiaxed grains, cooling to room temperature at 30-50 °C / s, retaining the deformed structure and crystal defects formed during the hot deformation process, providing favorable conditions for the precipitation of α s phase during aging, and finally forming a large number of randomly arranged morphological features, achieving a significant increase in strength compared with the traditional solution aging heat treatment process.
[0023] Based on the above method, when the hot compression process is 840 °C, 0.1 s -1 , the compression is 60%, the cooling rate is 30-50 °C / s, and the aging process is 600 °C, 4 h, the TEM analysis diagram of the TC18 titanium alloy after thermomechanical treatment is as Figure 1 shown; the results show that: in the aging treatment part, a large number of uniformly fine nanoscale αs phases will precipitate in the β-phase matrix (such as Figure 1 a), due to a large amount of deformation generating a large number of defects in the alloy, the αs phase will grow along different directions to form a mosaic morphology (such as Figure 1 b), seriously hindering the slip of dislocations and increasing its strength.
[0024] Based on the above method, when the hot compression process is 840 °C, 0.1 s -1 , and the aging process is 540-600 °C, 4 h, the mechanical property results are as Figure 3 shown, and the results show that: as the aging temperature increases, the tensile strength and yield strength of this alloy continuously decrease, and the elongation gradually increases. Compared with the highest tensile strength (1300 MPa) obtained by the traditional process of TC18 titanium alloy under the process of 750 °C / 30 min / air cooling + 600 °C / 6 h (solution-aging), the tensile strength of the TC18 alloy of the present invention has increased by more than 240 MPa.
[0025] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.
Claims
1. A method for obtaining a mosaic structure in TC18 titanium alloy, characterized in that: The TC18 titanium alloy cylindrical specimens were compressed by 60% at 810 - 870 °C for 0.01 - 10 s, cooled to room temperature at 30 - 50 °C / s, aged at 540 - 600 °C for 4 h, and then air-cooled to room temperature. -1 After that, they were cooled to room temperature at 30 - 50 °C / s, aged at 540 - 600 °C for 4 h, and then air-cooled to room temperature.
2. A method for obtaining a mosaic structure in TC18 titanium alloy according to claim 1, characterized in that: Compress the TC18 titanium alloy cylindrical specimen at 810 - 870 °C for 0.01 - 1 s -1 by 60% to refine the grains, increase the β-phase interfaces, and generate a large number of defects.
3. The cooling rate of the TC18 titanium alloy according to claim 1 after hot deformation is characterized in that: Cool to room temperature at 30 - 50 °C / s, retaining the deformed structure and crystal defects formed during the hot deformation process.
4. A method for obtaining a mosaic structure in TC18 titanium alloy according to claim 1, characterized in that: After aging at 540-600 °C for 4 h, α s phase nucleates and grows where the dislocation density is high, forming a mosaic structure.