High-rigidity TC4 titanium alloy and preparation method thereof

Abstract

The present invention discloses a high-rigidity TC4 titanium alloy and a preparation method thereof. The high-rigidity TC4 titanium alloy comprises a TC4 matrix and Al2O3 particles dispersed within the TC4 matrix. The Al2O3 particles have a particle size of less than 500 nm and a volume fraction of 0.9 to 1.2% in the high-rigidity TC4 titanium alloy. The high-rigidity TC4 titanium alloy has an elastic modulus of 126 to 142 GPa. By adding Al2O3 particles and uniformly distributing them within the matrix material, the present invention achieves a dispersion strengthening effect, thereby improving the steel strength of the TC4 titanium alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy preparation, and in particular to a high-rigidity TC4 titanium alloy and a preparation method thereof. Background Art

[0002] TC4 (Ti-6Al-4V) alloy, as a duplex titanium alloy, has become the most widely used and promoted titanium alloy due to its excellent comprehensive performance and processing characteristics. Especially in the aviation field, it can replace traditional steel materials and significantly reduce the weight of aircraft.

[0003] However, TC4 titanium alloy's inherent stiffness is relatively low, only about 50% of that of steel, severely limiting its application in critical load-bearing structural components. Therefore, as aircraft continue to demand greater weight reduction, reliability, and longevity, there is an urgent need to develop new TC4 titanium alloy preparation methods that can overcome stiffness limitations and meet the performance requirements of primary load-bearing structures. Summary of the Invention

[0004] The main purpose of the present invention is to provide a high-rigidity TC4 titanium alloy and a preparation method thereof, so as to solve the problem of low rigidity of existing TC4 titanium alloy.

[0005] According to one aspect of the present invention, a high-rigidity TC4 titanium alloy is proposed, comprising: a TC4 matrix and Al2O3 particles dispersed in the TC4 matrix, wherein the particle size of the Al2O3 particles is less than 500 nm, and in the high-rigidity TC4 titanium alloy, the volume fraction of the Al2O3 particles is 0.9-1.2%, and the elastic modulus of the high-rigidity TC4 titanium alloy is 126-142 GPa.

[0006] According to one embodiment of the present invention, the particle size of the Al2O3 particles is 200-500 nm.

[0007] According to another aspect of the present invention, a method for preparing a high-rigidity TC4 titanium alloy is proposed, comprising: sequentially smelting, forging and annealing raw materials to obtain the high-rigidity TC4 titanium alloy; wherein the raw materials contain sponge titanium, vanadium aluminum alloy, aluminum, titanium dioxide, ferrotitanium alloy and Al2O3 particles, the particle size of the Al2O3 particles is less than 500nm, and the volume fraction of the Al2O3 particles in the raw materials is 0.9-1.2%.

[0008] According to one embodiment of the present invention, the Al2O3 particles are obtained by ball milling in a high-energy ball mill, and the particle size of the Al2O3 particles is 200-500 nm.

[0009] According to one embodiment of the present invention, the smelting includes: sequentially mixing, pressing, and welding the raw materials to form an electrode, and smelting the electrode using a vacuum consumable smelting method.

[0010] According to one embodiment of the present invention, magnetic stirring is performed during the smelting process.

[0011] According to one embodiment of the present invention, forging includes: adopting an 8-fire forging forming process, the insulation temperature of the billet before forging is 1130-1170℃, 1080-1120℃, 1030-1070℃, 980-1020℃, 940-980℃, 940-980℃, 940-980℃, and 940-980℃, and the insulation time is not less than 4 hours; the first 7 fires are forging with two piers and two draws, the piercing deformation is 30-50%, and the drawing height-to-diameter ratio is 1.7-2.0; the 8th fire is drawing to a round bar with a predetermined diameter.

[0012] According to one embodiment of the present invention, the annealing includes: performing an annealing treatment at 750° C. for 2 hours.

[0013] According to one embodiment of the present invention, the elastic modulus of the high-rigidity TC4 titanium alloy is 126-142 GPa.

[0014] In the high-rigidity TC4 titanium alloy and its preparation method according to an embodiment of the present invention, Al2O3 particles are added and uniformly distributed in the matrix material to achieve a dispersion strengthening effect, thereby improving the steel strength of the TC4 titanium alloy. DETAILED DESCRIPTION

[0015] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in conjunction with specific embodiments.

[0016] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. Subsequent embodiments will not explain this one by one.

[0017] The inventors of this application recognized that dispersion strengthening refers to a material strengthening method that involves adding hard particles to a homogeneous material. If the compound is distributed as dispersed particles or granules within the solid solution grains, it can significantly improve the alloy's strength and rigidity. Furthermore, the finer and more dispersed the particles, the better the strengthening effect. The inventors further recognized that high-hardness Al2O3 particles have a high melting point, exceeding 2000°C, and will not melt during the smelting process, thus ensuring that the composition of the TC4 alloy matrix remains unchanged. Based on this understanding, the present invention proposes the embodiments described below.

[0018] An embodiment of the present invention proposes a high-rigidity TC4 titanium alloy, which includes: a TC4 matrix and Al2O3 particles dispersed in the TC4 matrix, wherein the particle size of the Al2O3 particles is less than 500nm, and in the high-rigidity TC4 titanium alloy, the volume fraction of the Al2O3 particles is 0.9~1.2%, and the elastic modulus of the high-rigidity TC4 titanium alloy is 126~142GPa.

[0019] In embodiments of the present invention, high-melting-point, high-hardness Al2O3 particles are incorporated and uniformly distributed throughout the matrix material, achieving a dispersion strengthening effect. This effectively hinders grain boundary movement during deformation, thereby increasing the strength of the TC4 titanium alloy. The use of nanoscale Al2O3 particles with a particle size of less than 500 nm further enhances the dispersion strengthening effect. A volume fraction of 0.9 to 1.2% Al2O3 particles prevents insufficient strengthening from occurring with too few particles and damage to the TC4 matrix structure from excessive amounts.

[0020] In some embodiments, the Al2O3 particles have a particle size of 200 to 500 nm. Al2O3 particles with a particle size of 200 to 500 nm can be easily prepared by a high-energy ball mill.

[0021] The present invention also proposes a method for preparing a high-rigidity TC4 titanium alloy, comprising: smelting, forging and annealing raw materials in sequence to obtain the high-rigidity TC4 titanium alloy; wherein the raw materials contain sponge titanium, vanadium aluminum alloy, aluminum, titanium dioxide, titanium-iron alloy and Al2O3 particles, the particle size of the Al2O3 particles is less than 500nm, and in the raw materials, the volume fraction of the Al2O3 particles is 0.9~1.2%.

[0022] In some embodiments, the Al2O3 particles are obtained by ball milling in a high-energy ball mill, and the particle size of the Al2O3 particles is 200 to 500 nm. High-energy ball milling can be used to refine purchased Al2O3 powder to obtain nano-sized Al2O3 particles. During operation, the Al2O3 powder can be placed in a carbide ball milling jar, which is tightened in an argon atmosphere, and then ball milled using a high-energy ball mill. The dispersion strengthening effect gradually increases as the size of the incorporated particles decreases, so using high-energy ball milling to prepare nano-sized Al2O3 particles can improve the dispersion strengthening effect.

[0023] In some embodiments, smelting includes: sequentially mixing, pressing, and welding the raw materials to form an electrode, and smelting the electrode using a vacuum consumable smelting method. An automatic weighing system can be used to weigh the titanium sponge, Al particles, and AlV55 alloy to a specified weight, and an electronic scale can be used to manually weigh the TiO2, ferro-titanium alloy, and Al2O3 particles. A mixer is used to mix the weighed raw materials, and then a press is used to press the electrode. After the electrode is pressed, the electrode block is welded in a vacuum plasma welding box. After the electrode is dried, the vacuum consumable smelting method is used to perform three smeltings.

[0024] In some embodiments, magnetic stirring is performed during the smelting process to ensure uniform distribution of chemical elements and Al2O3 particles, thereby achieving a dispersion strengthening effect.

[0025] In some embodiments, forging includes: using an 8-fire forging process, with the billet holding temperatures before forging being 1130-1170°C, 1080-1120°C, 1030-1070°C, 980-1020°C, 940-980°C, 940-980°C, 940-980°C, and 940-980°C, with a holding time of not less than 4 hours; the first 7 fires are performed with two piercings and two drawing, with a piercing deformation of 30-50% and a drawing height-to-diameter ratio of 1.7-2.0; the eighth fire is drawn to a round bar of a predetermined diameter (e.g., 150-300 mm in diameter), and multiple remelting is allowed during this period. Before forging, the ingot obtained after smelting can be peeled and sawn at the head and tail. In an embodiment of the present invention, the forging process increases the number of high-temperature drawing cycles, performing four drawing cycles at temperatures above 1000°C, to ensure the dispersed distribution of Al2O3 particles and further enhance the dispersion strengthening effect. In other embodiments, other forging processes may also be employed. For example, the number of forging cycles may be varied based on actual conditions, and the holding temperature, holding time, roughing deformation, drawing length-to-diameter ratio, and the number of drawing cycles per cycle may be adaptively adjusted.

[0026] In some embodiments, the annealing step includes performing an annealing process at 750° C. for 2 hours.

[0027] In some embodiments, the high-rigidity TC4 titanium alloy has an elastic modulus of 126 to 142 GPa. By incorporating Al2O3 particles, the present invention can produce large-scale forged TC4 titanium alloy bars with a dispersed distribution of fine hard second phases in the matrix. Compared to undoped TC4 titanium alloy forged bars, the stiffness of the bars is significantly improved, with the elastic modulus, for example, being increased from 93 to 105 GPa to 126 to 142 GPa.

[0028] In summary, in the technical solution of the present invention, Al2O3 particles are added to construct a dispersed hard second phase, thereby improving the stiffness of the TC4 titanium alloy; and combined with magnetic stirring during the smelting process and thermal deformation during the forging process, the Al2O3 particles are evenly distributed in the matrix material, achieving a dispersion strengthening effect.

[0029] The following describes the specific examples and comparative examples.

[0030] Example 1

[0031] The high-strength TC4 titanium alloy was prepared according to the following steps:

[0032] Step 1: Place Al2O3 powder in a carbide ball mill and secure the mill in an argon atmosphere. Then, use a high-energy ball mill to mill the powder to obtain Al2O3 particles with a size distribution of 200 to 500 nm.

[0033] Step 2: Use an automatic weighing system to weigh the specified weight of sponge titanium (small particle size above grade 0), Al particles, and AlV55 alloy respectively, and use an electronic scale to manually weigh TiO2, titanium-iron alloy, and Al2O3 particles, where the volume fraction of Al2O3 particles is 1.0%. A mixer is used to mix the weighed raw materials, and then a press is used to press the electrode. After the electrode is pressed, the electrode block is welded in a vacuum plasma welding box. After the electrode is dried, a vacuum consumable smelting method is used for 3 smeltings. Magnetic stirring is applied during the smelting process to ensure that the chemical elements and Al2O3 particles are evenly distributed.

[0034] Step 3: Before forging, the steel bars prepared in Step 2 are peeled and sawn at the ends. An eight-fire forging process is used, with the pre-forging holding temperatures set at 1150°C, 1100°C, 1050°C, 1000°C, 960°C, 960°C, 960°C, and 960°C, for five hours. The first seven fires involve two forgings and two drawing cycles, with a roughing deformation of 40% and a drawing height-to-diameter ratio of 1.9. The eighth fire draws the bars to Φ300mm, allowing for multiple remelting cycles.

[0035] Step 4: The rods prepared in step 3 are annealed at 750°C for 2 hours.

[0036] Comparative Example 1

[0037] The difference between Comparative Example 1 and Example 1 is that the volume fraction of Al2O3 particles is 0%, and the other contents are the same as those of Example 1.

[0038] The elastic modulus of the TC4 titanium alloy bars obtained in Example 1 and Comparative Example 1 was tested. The elastic modulus of the forged bar obtained in Example 1 was measured to be 126-142 GPa, which was much higher than the 93-105 GPa of the forged bar obtained in Comparative Example 1.

[0039] The tensile properties of the TC4 titanium alloy bars obtained in Example 1 and Comparative Example 1 were tested. The test data are shown in Table 1. The measured values ​​are the average values ​​of two tests.

[0040] Table 1: Room temperature tensile properties of Φ300mm TC4 forging bar

[0041]

[0042] According to Table 1, the tensile strength σ of the forged rod obtained in Example 1 b and yield strength σ 0.2 There is a slight increase, and the section elongation A and section shrinkage Z do not change significantly.

[0043] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the disclosure of the embodiments of the present invention (including the claims) is limited to these examples. Within the spirit of the embodiments of the present invention, the technical features of the above embodiments or different embodiments may be combined, and there are many other variations of the different aspects of the embodiments of the present invention described above, which are not provided in detail for the sake of clarity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the embodiments of the present invention should be included within the scope of protection of the embodiments of the present invention.

Claims

1. A method for preparing high-rigidity TC4 titanium alloy, characterized in that: The high-rigidity TC4 titanium alloy includes a TC4 matrix and Al2O3 particles dispersed in the TC4 matrix. The method includes: sequentially smelting, forging, and annealing raw materials to obtain the high-rigidity TC4 titanium alloy. The raw materials include sponge titanium, vanadium-aluminum alloy, aluminum, titanium dioxide, ferrotitanium alloy, and Al2O3 particles. The Al2O3 particles have a particle size of 200 to 500 nm, and the volume fraction of the Al2O3 particles in the raw materials is 0.9 to 1.2%. The smelting comprises: sequentially mixing, pressing, and welding the raw materials to form electrodes, and smelting the electrodes using a vacuum consumable smelting method; The forging process includes: adopting an 8-fire forging forming process, the insulation temperature of the billet before forging is 1130-1170℃, 1080-1120℃, 1030-1070℃, 980-1020℃, 940-980℃, 940-980℃, 940-980℃, 940-980℃, and 940-980℃, and the insulation time is not less than 4h; the first 7 fires of forging are performed with two piers and two draws, the pier deformation is 30-50%, and the drawing height-to-diameter ratio is 1.7-2.0; the 8th fire is drawn to a round bar with a predetermined diameter.

2. The method according to claim 1, characterized in that Magnetic stirring was performed during the melting process.

3. The method according to claim 1, characterized in that The annealing process includes performing an annealing process at 750° C. for 2 hours.

4. The method according to claim 1, wherein The elastic modulus of the high-rigidity TC4 titanium alloy is 126-142 GPa.

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