Method for improving strength and plasticity of TB17 titanium alloy

Abstract

The invention relates to a method for improving the strength and plasticity of TB17 titanium alloy, in particular to a method for regulating and controlling structure precipitation of the TB17 titanium alloy based on solid solution and multi-stage aging treatment so as to improve the strength and plasticity of the TB17 titanium alloy, a four-scale lath structure is obtained in the TB17 titanium alloy, and by means of the structure characteristic, alloy plastic deformation can be coordinated, the alloy plasticity can be improved, and meanwhile the strength and plasticity of the TB17 titanium alloy can be improved. Dislocation motion is hindered, the alloy strength is improved, and the TB17 titanium alloy obtains excellent strength and plasticity matching performance. The obtained TB17 titanium alloy has the structure morphology with the four-scale characteristic and is composed of a small number of primary alpha phases, a large number of lath alpha phases and a beta matrix, mechanical property tests prove that the strength and plasticity matching of the TB17 titanium alloy is obviously optimized, and the plasticity can be obviously improved while high strength is obtained. According to the method, the purpose of regulating and controlling four-scale structure precipitation is achieved through optimized technological parameters, the mechanical property of the TB17 titanium alloy is improved, good strength and plasticity matching is achieved, and the method has high guiding significance for actual production.

Description

Technical Field

[0001] The invention relates to the technical field of improving the strength and plasticity of TB17 titanium alloy, and specifically to a method for improving the strength and plasticity of TB17 titanium alloy based on regulating microstructure precipitation. Background Art

[0002] After entering the new century, my country's aerospace industry has entered a stage of rapid development, the frequency of military equipment renewal has gradually accelerated, and the performance requirements for materials have also gradually increased. High-strength plastic titanium alloys, with excellent properties such as low density and high specific strength, can ensure a long service time in a high-intensity service environment, can meet the needs of lightweight and high-performance weapons and equipment, and stand out in the competition of new generation military materials. It has great potential to replace high-density materials such as ultra-high-strength steel and high-temperature alloys in service. It has been used to manufacture new generation aircraft high-load-bearing structural parts, fasteners, ultra-high-strength impact-resistant load-bearing components for space launch and landing systems, tank body protection structures, etc. In addition, high-strength plastic titanium alloys have both high strength and good plasticity and toughness, and also have important application prospects in the structural parts of hypersonic aircraft and cutting-edge weapons and equipment.

[0003] However, since titanium alloys belong to the category of metal materials, and the strength-plasticity matching of metal materials has always been a major problem restricting their development, titanium alloys also face the shortcoming of strength-plasticity matching. Although this type of alloy nominally needs to achieve high strength and high plasticity simultaneously, the existing strength-plasticity technology is still difficult to achieve in actual production and use while maintaining high strength and improving plasticity of this type of alloy. Therefore, for high-strength-plasticity titanium alloys, it is necessary to develop new strength-plasticity matching technologies to achieve the widespread application of high-strength-plasticity titanium alloys.

[0004] A method for improving the strength and plasticity of dual-structure titanium alloys is disclosed in the invention patent with the authorization announcement number CN 114351067 B. The method uses pulse current rapid heating technology to achieve controllable preparation of dual structures in TC21 titanium alloy, and further regulates the microstructure of the alloy through subsequent heat treatment, thereby significantly improving the strength and plasticity matching of dual-structure titanium alloys. This method is suitable for actual production, but the method is based on the theoretical basis of the influence of dual structures of titanium alloys on mechanical properties, and has little reference value for other structures, especially for high-strength titanium alloys, where the structures are mostly lamellar structures, and this method is obviously not applicable.

[0005] A method for preparing an ultra-high-strength and plastic TB8G titanium alloy is disclosed in the invention patent with publication number CN 118256760 A. This method uses TB8 titanium alloy as the matrix, introduces Si powder and adopts powder metallurgy to combine it, and uses isothermal heat treatment and temperature-controlled hot extrusion methods to precipitate dense and uniform nano-scale silicides in the crystal, and further adopts a double-stage aging treatment to regulate the heterogeneous cellular structure, while maintaining good plasticity while improving the room temperature strength of the material. This method can significantly improve the mechanical properties of TB8 titanium alloy, but the method has complex operating steps, great difficulty in implementation, low fault tolerance, high cost, and greater restrictions on other high-strength titanium alloys. The range of materials that can match it to meet the strong plasticity conditions described in the invention and thus play an enhanced plasticization role is relatively small.

[0006] The invention patent with publication number CN 117904557 A discloses a thermomechanical processing method for synergistically improving the strength and plasticity of β-type titanium alloy. This method significantly refines the material grains and accumulates a large number of deformation defects by superimposing multiple cold deformation-rapid temperature rise and fall cycles, and then adjusts the microstructure through aging and precipitates a large number of fine lamellar structures inside the grains. Through the combined action of multiple mechanisms such as solid solution strengthening, fine grain strengthening, and phase transformation strengthening, the synergistic strength and plasticity are greatly improved. However, since this method requires multiple cold deformation-rapid temperature rise and fall, the implementation process is complicated and has high process requirements, making it unsuitable for actual production.

[0007] In the invention patent with the authorization announcement number CN 101435063 B, a heat treatment process for improving the plasticity of cold-formed β-titanium alloy after aging is disclosed. The process first ages the β-titanium alloy after solutionization and cold deformation at a normal aging temperature for a short time, and then appropriately increases the aging temperature for a short time to partially eliminate the deformation defects such as dislocations remaining from the cold deformation through the high-temperature recovery mechanism, thereby restoring the plasticity of the material while ensuring the strength of the alloy, and shortening the aging time. This heat treatment process improves plasticity by increasing the aging temperature to partially alleviate the cold deformation defects through high-temperature recovery, but its effect on strength is not obvious.

[0008] The journal "Forging and Stamping" published a paper titled "Process Experiments to Improve the Strength-Plasticity Matching of TC21 Titanium Alloy Forgings" in the 15th issue of 2022. This paper improves the quasi-β forging process, and uses the air cooling time after quasi-β heating to have a significant effect on the microstructure. Extending the air cooling time can make the basketweave structure more broken, which can significantly improve the plasticity of TC21 titanium alloy forgings and improve the strength of the forgings. This process improvement is simple and suitable for actual production, but it is only for basketweave structures and not for other structures.

[0009] The journal "Rare Metal Materials and Engineering" published a paper titled "Study on the Evolution of High-Temperature Deformation Microstructure and Strength-Plasticity of TC25G Titanium Alloy" in Volume 52, Issue 12 in December 2023. The paper conducted heat treatment tests on TC25G titanium alloy bars with different deformation amounts. The increase in deformation amount corresponds to the spheroidization process of the lamellar α phase in the microstructure. After the α phase is fully spheroidized, the microstructure dominated by equiaxed structure makes the alloy have better plasticity. The best high-temperature strength-plasticity match is achieved by controlling the degree of spheroidization of the lamellar α phase. The method in this paper is simple, but the degree of spheroidization of the lamellar α phase must be strictly controlled, the actual operation has a small error tolerance, and this method is to improve strength-plasticity at high temperatures and is not suitable for room temperature.

[0010] The technical solutions of the prior art mentioned above all have shortcomings such as inapplicable organization, large alloy restrictions, and insignificant improvement effects. Compared with TB17 titanium alloy, the restrictions are extremely large or even inapplicable, which leads to an increase in production costs and a decrease in production efficiency in order to enhance the strength-plasticity matching of TB17 titanium alloy in the actual production process to achieve the purpose of increasing service life. Therefore, it is necessary to conduct research on the improvement of the strength-plasticity of TB17 titanium alloy, and to improve the strength-plasticity matching of TB17 titanium alloy by regulating the organization precipitation behavior during heat treatment. This is of great significance for improving the service life of TB17 titanium alloy and expanding the application range of TB17 titanium alloy. Summary of the invention

[0011] In order to overcome a series of shortcomings of existing strong plasticization technology, such as small organizational applicability and large alloy usage restrictions, and to optimize the strong plasticization matching mechanism of TB17 titanium alloy, the present invention proposes a method for improving the strength and plasticity of TB17 titanium alloy.

[0012] The specific process of the present invention is:

[0013] Step 1: Forging TB17 titanium alloy bar:

[0014] TB17 titanium alloy billet is obtained by forging.

[0015] When forging the TB17 titanium alloy bar, the original TB17 titanium alloy bar is placed in a heating furnace at 20 to 40° C. below the phase transition point and preheated for 60 to 120 minutes; after preheating, the temperature is raised with the furnace at a heating rate of 9° C. / s to 5 to 15° C. below the phase transition point for heating and forging.

[0016] The heating coefficient of the original rod of the TB17 titanium alloy is 0.7 min / mm.

[0017] The total deformation amount of the original bar of the TB17 titanium alloy is 30-40%.

[0018] Step 2: Solution treatment of the forged TB17 titanium alloy billet:

[0019] The heating furnace was heated at a heating rate of 9°C / s until the temperature in the furnace reached 30-40°C below the phase transition point. The obtained TB17 titanium alloy billet was placed in a heating furnace at a constant temperature of 30-40°C below the phase transition point for 2-4 hours; after the insulation, the TB17 titanium alloy billet was taken out and cooled to room temperature in air. The TB17 titanium alloy billet after solid solution treatment was obtained.

[0020] Step 3, multi-level aging treatment:

[0021] The TB17 titanium alloy blank after the solution treatment is subjected to a multi-stage aging treatment.

[0022] The multi-stage aging treatment is a three-stage aging treatment, and the specific process is:

[0023] The first stage aging treatment: heat the heating furnace to 600-650°C, put the solution treated billet into the heating furnace and keep it warm for 1-2 hours. After the insulation, turn off the power of the heating furnace and let the billet cool down to 500-550°C with the furnace.

[0024] When the billet is cooled to 500-550°C in the furnace, the second stage treatment is carried out; the heating furnace is powered on, and the temperature of the heating furnace is maintained at 500-550°C, so that the billet is kept warm for 2-3 hours; after the insulation is completed, the heating furnace is powered off, and the billet is cooled to 450°C with the furnace.

[0025] When the billet is cooled to 450°C in the furnace, the third stage effect treatment is carried out; the heating furnace is powered on, the temperature is set to 450°C, and the billet is kept in the 450°C heating furnace for 3 hours. After the insulation is completed, the billet is taken out and cooled to room temperature in the air.

[0026] During the multi-stage aging treatment, the heating rate of the heating furnace is 9°C / s.

[0027] The multi-stage aging treatment of the TB17 titanium alloy billet after the solid solution treatment is completed to obtain the TB17 titanium alloy with improved strength and plasticity.

[0028] The obtained TB17 titanium alloy has a four-scale characteristic microstructure, which is primary α phase + coarse lath α phase + fine lath α phase + nano-lath α phase.

[0029] The primary α phase is 5-10 μm, the coarse lath α phase is 1-2 μm, the fine lath α phase is 0.1-0.3 μm, and the nano lath α phase is 50-100 nm.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] TB17 titanium alloy is a high-strength titanium alloy independently developed by my country, but there are many limitations in the actual production process with the existing strong plasticity technology. Traditional strong plasticity methods mostly focus on improving the strong plasticity of the alloy by regulating equiaxed structure and secondary phase precipitation through solution treatment or solution + single-stage aging treatment, but there is a problem that the strength improvement is not obvious, or even the strength is reduced when the plasticity of the alloy is significantly improved. In addition, other methods for improving the strong plasticity of titanium alloys proposed at this stage are slightly complicated, and problems such as high cost and low yield rate will occur in the actual production process. Therefore, in order to avoid similar problems, the present invention is based on solution + multi-stage aging treatment to regulate the precipitation of TB17 titanium alloy organization, and then improve the method of strong plasticity of TB17 titanium alloy. A four-scale lath organization is obtained in TB17 titanium alloy, and this organizational feature can achieve coordinated alloy plastic deformation to improve alloy plasticity while hindering dislocation movement to improve alloy strength, so that TB17 titanium alloy obtains excellent strong plasticity matching performance.

[0032] The heat treatment method proposed in the present invention obtains a microstructure with four-dimensional characteristics in the TB17 titanium alloy. Figure 1 To illustrate, magnify the tissue 1000 times Figure 1 (a) shows that the TB17 titanium alloy structure consists of a small amount of primary α phase, a large amount of lath α phase and β matrix. Figure 1 In (b), the size of the primary α phase is about 5 to 10 μm, and the size of the coarse lath α phase is about 1 to 2 μm. Figure 1 In (c), the size of the fine lath α phase is about 0.1-0.3 μm, and the size of the nano lath α phase is about 50-100 nm. After the mechanical properties of each embodiment of the organizational morphology of the four-scale characteristics obtained by the present invention are tested, the results are shown in Table 1, and it is found that the strength-plasticity matching of the TB17 titanium alloy has been significantly optimized, and the plasticity can be significantly improved while obtaining higher strength.

[0033] The present invention is relatively simple to operate, and specifically proposes conditions for formulating a heat treatment process, provides specific process parameter range limits, and achieves the purpose of regulating the precipitation of four-scale structures. The mechanical properties of the TB17 titanium alloy are improved through the structure, and a better strength-plasticity matching is achieved. The present invention solves the problem of the lack of strength-plasticity matching technology for TB17 titanium alloy, and is easy to operate and has a low production cost, which has a high guiding significance for actual production.

[0034] Table 1 Strength and plasticity parameters of TB17 titanium alloy in various embodiments

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a scanning electron microscope micrograph of the TB17 titanium alloy sample prepared in Example 1 of the present invention; wherein, Figure 1 a is the tissue after magnification 1000 times, Figure 1 b is the tissue after magnification 5000 times, Figure 1 c is the tissue after magnification 50,000 times.

[0037] Figure 2 This is a scanning electron microscope micrograph of the TB17 titanium alloy sample prepared in Example 2 of the present invention; wherein, Figure 2 a is the tissue after magnification 1000 times, Figure 2 b is the tissue after magnification 5000 times, Figure 2 c is the tissue after magnification 50,000 times.

[0038] Figure 3 This is a scanning electron microscope micrograph of the TB17 titanium alloy sample prepared in Example 3 of the present invention; wherein, Figure 3 a is the tissue after magnification 1000 times, Figure 3 b is the tissue after magnification 5000 times, Figure 3 c is the tissue after magnification 50,000 times.

[0039] Figure 4 It is a flow chart of the present invention. DETAILED DESCRIPTION

[0040] The present invention is a method for improving the strength and plasticity of TB17 titanium alloy, and its technical scheme will be described in detail through three embodiments.

[0041] The specific process of the present invention is:

[0042] Step 1, forging of TB17 titanium alloy bar:

[0043] The original bar of TB17 titanium alloy is placed in a heating furnace with a set temperature of 20 to 40°C below the phase transformation point for preheating for 60 to 120 minutes, and then the temperature is raised to 5 to 15°C below the phase transformation point at a heating rate of 9°C / s for forging. The heating coefficient is 0.7min / mm. The total deformation is 30 to 40% compared with the original bar, and a TB17 titanium alloy billet is obtained.

[0044] Step 2, solution treatment of TB17 titanium alloy billet:

[0045] The specific process of the solution treatment is to heat the heating furnace to 30-40°C below the phase transition point at a heating rate of 9°C / s. The TB17 titanium alloy billet is placed in a heating furnace heated to 30-40°C below the phase transition point and kept warm for 2-4 hours. After the insulation is completed, the billet is taken out and cooled to room temperature in air. A TB17 titanium alloy billet that has undergone solution treatment is obtained.

[0046] Step 3, multi-level aging treatment:

[0047] Performing multi-stage aging treatment on the TB17 titanium alloy blank after the solution treatment;

[0048] The multi-stage aging treatment is a three-stage aging treatment, and the specific process is:

[0049] Heat the heating furnace at a heating rate of 9°C / s until the temperature in the furnace reaches 600-650°C. Place the solution treated billet in a heating furnace at 600-650°C and keep it warm for 1-2 hours. After the insulation, turn off the power of the heating furnace and allow the billet to cool down to 500-550°C along with the furnace.

[0050] When the blank cools down to 500-550℃, the heating furnace is powered on to keep the temperature at 500-550℃ for 2-3h. After the insulation, the heating furnace is powered off to cool down the blank to 450℃.

[0051] When the blank is cooled to 450℃, the heating furnace is powered on to keep the temperature at 450℃ for 3h. After the insulation, the blank is taken out and cooled to room temperature in the air.

[0052] At this point, the heat treatment of the TB17 titanium alloy billet is completed. Through the heat treatment, a microstructure with four-scale characteristics is obtained: a primary α phase of about 5 to 10 μm + a coarse lath α phase of about 1 to 2 μm + a fine lath α phase of about 0.1 to 0.3 μm + a nano-lath α phase of 50 to 100 nm, which improves the strength and plasticity of the TB17 high-strength titanium alloy.

[0053] Table 2 Process parameters of each embodiment

[0054]

Claims

1. A method for improving the strength and plasticity of TB17 titanium alloy, characterized in that: The specific process is: Step 1: Forging TB17 titanium alloy bar: A TB17 titanium alloy billet is obtained by forging; Step 2: Solution treatment of the forged TB17 titanium alloy billet: The heating furnace is heated at a heating rate of 9°C / s until the temperature in the furnace reaches 30-40°C below the phase transition point; the obtained TB17 titanium alloy billet is placed in a heating furnace at a constant temperature of 30-40°C below the phase transition point and kept warm for 2-4 hours; after the end of the heat preservation, the TB17 titanium alloy billet is taken out and cooled to room temperature in air; and the TB17 titanium alloy billet after the solid solution treatment is obtained; Step 3, multi-level aging treatment: Performing multi-stage aging treatment on the TB17 titanium alloy blank after the solution treatment; The multi-stage aging treatment is a three-stage aging treatment, and the specific process is: The first stage aging treatment: heating the heating furnace to 600-650°C, placing the solution treated billet in the heating furnace for 1-2 hours of insulation, and then powering off the heating furnace after insulation to allow the billet to cool to 500-550°C with the furnace; When the billet is cooled to 500-550°C in the furnace, a second stage treatment is performed; The heating furnace is powered on, and the temperature of the heating furnace is maintained at 500-550°C, and the blank is kept warm for 2-3 hours; after the insulation is completed, the heating furnace is powered off, and the blank is cooled to 450°C along with the furnace; When the billet is cooled to 450°C in the furnace, the third stage aging treatment is carried out; the heating furnace is powered on, the temperature is set to 450°C, and the billet is kept warm in the 450°C heating furnace for 3 hours. After the insulation, the billet is taken out and cooled to room temperature in the air; the multi-stage aging treatment of the TB17 titanium alloy billet after the solution treatment is completed to obtain the TB17 titanium alloy with improved strength and plasticity.

2. The method for improving the strength and plasticity of TB17 titanium alloy as claimed in claim 1, characterized in that: When forging the TB17 titanium alloy bar, the original TB17 titanium alloy bar is placed in a heating furnace at 20 to 40° C. below the phase transition point and preheated for 60 to 120 minutes; after preheating, the temperature is raised with the furnace at a heating rate of 9° C. / s to 5 to 15° C. below the phase transition point for heating and forging.

3. The method for improving the strength and plasticity of TB17 titanium alloy as claimed in claim 1, characterized in that: The heating coefficient of the original rod of the TB17 titanium alloy is 0.7 min / mm.

4. The method for improving the strength and plasticity of TB17 titanium alloy as claimed in claim 1, characterized in that: The total deformation amount of the original bar of the TB17 titanium alloy is 30-40%.

5. The method for improving the strength and plasticity of TB17 titanium alloy as claimed in claim 1, characterized in that: During the multi-stage aging treatment, the heating rate of the heating furnace is 9°C / s.

6. The method for improving the strength and plasticity of TB17 titanium alloy as claimed in claim 1, characterized in that: The obtained TB17 titanium alloy has a four-scale characteristic microstructure, which is primary α phase + coarse lath α phase + fine lath α phase + nano-lath α phase.

7. The method for improving the strength and plasticity of TB17 titanium alloy as claimed in claim 6, characterized in that: The primary α phase is 5-10 μm, the coarse lath α phase is 1-2 μm, the fine lath α phase is 0.1-0.3 μm, and the nano lath α phase is 50-100 nm.

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