High-strength titanium alloy and preparation method thereof

Abstract

The invention discloses a high-strength titanium alloy and a preparation method thereof. The preparation method is characterized by comprising the following steps: stretching and pre-deforming an annealed titanium alloy blank at room temperature; then the titanium alloy blank is electrically heated, and a constant tensile load is applied to the titanium alloy blank during electric heating; after the titanium alloy blank is rapidly heated to the solid solution temperature, rapid cooling is conducted, and a high-strength titanium alloy finished product is obtained; the method has the advantages that the titanium alloy material is firstly stretched and pre-deformed, more dislocation movement in the titanium alloy material can be triggered, grain refinement is promoted, grain size distribution of the titanium alloy is more uniform, and the tensile strength of the titanium alloy is enhanced; and then the titanium alloy blank is subjected to stretching loading, meanwhile, the temperature is rapidly increased to the solid solution temperature through electric heating, the solid solution treatment effect is achieved, the obdurability of the titanium alloy material is improved, elements in the titanium alloy are more evenly distributed, and the mechanical property of the titanium alloy material is improved.

Description

Technical Field

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

[0002] Titanium alloys are widely used in aerospace, energy, chemical industry and other fields due to their low density, high specific strength, corrosion resistance, high temperature resistance and other excellent properties. They are important high-end materials in the industrial field. However, in the preparation process of titanium alloys, due to factors such as phase change and organizational changes, their strength and other mechanical properties often decrease, which poses a great challenge to their reliability and safety in practical applications.

[0003] In the preparation process of titanium alloy, heat treatment is one of the main means to optimize its mechanical properties, especially through solution treatment, which can effectively regulate the microstructure of titanium alloy and enhance its strength, toughness and corrosion resistance. However, the traditional solution treatment method has a long heating time and holding time, which easily causes the residual stress and structural stress of the titanium alloy material to be large, resulting in deformation and cracking of the titanium alloy. The above problems seriously affect the strength and service life of titanium alloy, especially in applications under high-strength and high-temperature environments. Therefore, how to prepare titanium alloy materials with excellent mechanical properties is still a key technical problem that needs to be solved urgently. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a high-strength titanium alloy and a preparation method thereof, which can greatly shorten the heat treatment time in the preparation process of the titanium alloy and can also make the elements and grain size distribution in the titanium alloy more uniform, so as to improve its comprehensive mechanical properties.

[0005] The technical solution adopted by the present invention to solve the above technical problems is: a high-strength titanium alloy, the mass percentage of its components is: aluminum 5.8-6.5%, vanadium 3.9-4.3%, impurities ≤0.3%, and the rest is titanium.

[0006] A method for preparing a high-strength titanium alloy comprises the following specific steps: (1) 89.2-90.3% titanium sponge, 1.5-2.6% aluminum beans, and 7.8-8.6% vanadium aluminum alloy are mixed and pressed into an electrode block according to mass percentage, and the electrode block is melted by arc heating under a vacuum environment and dripped into a water-cooled copper crucible, and air-cooled to form a titanium alloy ingot; (2) heating the titanium alloy ingot to 1000-1050°C and performing upsetting and drawing to form a titanium alloy billet; (3) hot rolling the titanium alloy billet in a rolling mill for multiple passes and air cooling; (4) Annealing the titanium alloy blank; (5) stretching and pre-deforming the annealed titanium alloy billet at room temperature; (6) electrically heating the pre-deformed titanium alloy blank, and applying a constant tensile load to the titanium alloy blank during the electrical heating; (7) When the titanium alloy blank is rapidly heated to the solution temperature, it is rapidly cooled to obtain a titanium alloy product with high strength.

[0007] Furthermore, in the step (5), the titanium alloy blank is uniformly stretched by a tensile testing machine, and the tensile deformation is controlled to be 2% to 10%.

[0008] Furthermore, in the step (6), the titanium alloy blank is heated by direct current, and the current density is controlled to be 8 to 30 A / mm 2 , the constant tensile load applied is 0~30MPa.

[0009] Furthermore, in the step (7), the solution temperature of the titanium alloy billet is 830-870° C., and rapid cooling is performed by water cooling.

[0010] Furthermore, the specific hot rolling process of the step (3) is as follows: the titanium alloy billet is heated to 900-950°C, and then 2-4 rough rolling passes are performed in a rolling mill, with a reduction ratio of 15-25% for each rough rolling pass, and then a single finish rolling pass is performed, with a reduction ratio of 10%, and air cooling is performed after the hot rolling is completed.

[0011] Furthermore, the specific annealing process of step (4) is: heating the titanium alloy billet to 700-800° C., keeping the temperature for 2 hours and then air cooling.

[0012] Compared with the prior art, the advantages of the present invention are: (1) This method performs pre-stretching deformation on the annealed titanium alloy material, which can induce more dislocation movement inside the titanium alloy material, promote grain refinement, make the grain size distribution of the titanium alloy more uniform, and enhance the tensile strength of the titanium alloy; (2) The titanium alloy blank is stretched and loaded while being quickly heated to the solution temperature by electric heating. This not only achieves the effect of solution treatment, but also significantly shortens the heat treatment time compared with traditional solution treatment, avoiding the phenomenon of grain growth caused by the titanium alloy being kept at high temperature for a long time, thereby improving the strength and toughness of the titanium alloy material, and making the elements in the titanium alloy more evenly distributed, thereby improving its mechanical properties, such as strength, hardness and corrosion resistance; (3) By adjusting the pre-deformation amount of the titanium alloy billet and the current density during electric heating, the content, size and distribution of the α and β phases in the titanium alloy material can be controlled, thus solving the problems of low process efficiency, uneven structure, grain growth and large residual stress in the preparation of conventional titanium alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a microstructure diagram of the titanium alloy product obtained in Example 3 of the present invention; Figure 2 This is a microstructure diagram of the titanium alloy product obtained in Example 6 of the present invention; Figure 3 This is a microstructure diagram of the titanium alloy product obtained in Example 9 of the present invention. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below with reference to the accompanying drawings.

[0015] Embodiment 1: A high-strength titanium alloy, wherein the mass percentage of each component is: aluminum 6.5%, vanadium 4.0%, impurities ≤ 0.3%, and the rest is titanium.

[0016] Embodiment 2: A high-strength titanium alloy, wherein the mass percentage of each component is: aluminum 6.2%, vanadium 4.14%, impurities ≤ 0.3%, and the rest is titanium.

[0017] Embodiment 3: The method for preparing the high-strength titanium alloy of the above embodiment 2 comprises the following specific steps: (1) 89.66% titanium sponge, 2.06% aluminum bean, and 8.28% vanadium aluminum alloy are mixed and pressed into an electrode block according to mass percentage, and the electrode block is melted by arc heating under a vacuum environment and dripped into a water-cooled copper crucible, and air-cooled to form a titanium alloy ingot; (2) heating the titanium alloy ingot to 1000°C and performing upsetting and drawing to form a titanium alloy billet; (3) The titanium alloy billet is heated to 920°C, and then subjected to three passes of rough rolling in a rolling mill, with a reduction rate of 20% for each pass, and then subjected to a single pass of finish rolling, with a reduction rate of 10%, and air cooling after hot rolling; (4) annealing the titanium alloy billet, specifically: heating the titanium alloy billet to 750°C, keeping the temperature for 2 hours, and then air cooling; (5) The annealed titanium alloy billet is uniformly stretched at room temperature using a tensile testing machine, and the tensile deformation is controlled to be 2%; (6) The pre-deformed titanium alloy billet is heated by direct current, and the current density is controlled to 11.34A / mm 2 , and applying a constant tensile load of 10 MPa to the titanium alloy billet while electrically heating; (7) When the titanium alloy billet is rapidly heated to 850°C, the power is turned off and the billet is rapidly water-cooled to room temperature to obtain a titanium alloy product with high strength.

[0018] Embodiment 4: The other steps are the same as those of Embodiment 3, except that in step (5), the tensile deformation of the titanium alloy blank is 4%.

[0019] Embodiment 5: The other steps are the same as those of Embodiment 3, except that in step (5), the tensile deformation of the titanium alloy blank is 6%.

[0020] Embodiment 6: The other steps are the same as those of Embodiment 3, except that in step (6), when direct current heating is applied to the pre-deformed titanium alloy blank, the current density is controlled to be 15.79 A / mm 2 .

[0021] Embodiment 7: The other steps are the same as those of Embodiment 6, except that in step (5), the tensile deformation of the titanium alloy blank is 4%.

[0022] Embodiment 8: The other steps are the same as those of Embodiment 6, except that in step (5), the tensile deformation of the titanium alloy blank is 6%.

[0023] Embodiment 9: The other steps are the same as those of Embodiment 3, except that in step (6), when direct current heating is applied to the pre-deformed titanium alloy blank, the current density is controlled to be 20.24 A / mm 2 .

[0024] Embodiment 10: The other steps are the same as those of Embodiment 9, except that in step (5), the tensile deformation of the titanium alloy blank is 4%.

[0025] Embodiment 11: The other steps are the same as those of Embodiment 9, except that in step (5), the tensile deformation of the titanium alloy blank is 6%.

[0026] Comparative Example: Steps (1) to (4) are the same as those in Example 3, except that the annealed titanium alloy billet is placed in a box-type resistance furnace for conventional solution treatment at a solution temperature of 850°C, kept at this temperature for 30 minutes, and then taken out for water quenching.

[0027] The titanium alloy products prepared in the above nine embodiments and comparative examples were tested for comprehensive mechanical properties, and the results are shown in the following table: Tensile deformation <![CDATA[Current density (A / mm 2 ).]]> Tensile strength (MPa) Yield strength (MPa) Embodiment 3 2% 11.34 996.83 948.26 Embodiment 4 4% 11.34 1013.02 961.44 Embodiment 5 6% 11.34 1018.55 954.36 Embodiment 6 2% 15.79 984.21 920.01 Embodiment 7 4% 15.79 997.77 936.59 Embodiment 8 6% 15.79 1007.85 907.78 Embodiment 9 2% 20.24 975.44 873.14 Embodiment 10 4% 20.24 982.48 919.42 Embodiment 11 6% 20.24 1003.79 926.51 Comparative Example / / 891.13 826.38 It can be seen from the table that the tensile strength and yield strength of the titanium alloy product prepared by this method are much greater than those of the titanium alloy obtained by traditional solid solution treatment, with the maximum tensile strength increased by 14.29% and the maximum yield strength increased by 16.34%. It can also be seen that the titanium alloy product prepared by this method has a tensile deformation of 6% and a current density of 11.34 A / mm 2When the tensile deformation is 4% and the current density is 11.34 A / mm 2 , the yield strength is the highest, reaching 961.44MPa; this proves that this method can effectively regulate the tensile strength and yield strength of titanium alloy materials.

[0028] In addition, microstructure tests were performed on the titanium alloy products prepared in Example 3, Example 6 and Example 9, and the results were as follows: Figure 1 The microstructure diagram of the titanium alloy of Example 3 is shown. The size of the equiaxed α grains (shown in red circles) in the finished titanium alloy is about 41.26 μm. Figure 1 It can be seen that after rapid heating with direct current, an α→β phase transformation occurs; and after rapid water cooling, the high-temperature β phase transforms into lamellar martensite (as shown in the yellow circle in the figure), which significantly improves the dislocation slip resistance. Compared with titanium alloys treated with traditional solid solution treatment, its tensile strength is increased by 11.86% and its yield strength is increased by 14.45%.

[0029] Figure 2 The microstructure diagram of the titanium alloy of Example 6 is shown. The size of the equiaxed α grains (shown in red circles) in the finished titanium alloy is about 43.78 μm. Figure 2 It can be seen that: although the α grains of Example 6 are coarser than those of Example 3, the α grain content is higher than that of Example 3, so the strength of the titanium alloy product is still close to that of Example 3. Compared with the titanium alloy treated by traditional solid solution treatment, its tensile strength is increased by 10.45% and the yield strength is increased by 11.37%, and the strengthening effect is still obvious.

[0030] Figure 3 The microstructure diagram of the titanium alloy of Example 9 is shown. The size of the equiaxed α grains (shown in red circles) in the finished titanium alloy is about 44.67 μm. Figure 3 It can be seen that: the excessively high current density leads to local heat accumulation, the α phase coarsening and the martensite content decreases, so the comprehensive strength is slightly lower than that of Examples 3 and 6. However, compared with the titanium alloy treated by traditional solid solution treatment, its tensile strength is still increased by 9.46% and the yield strength is increased by 5.66%.

[0031] The protection scope of the present invention includes but is not limited to the above embodiments, and its protection scope is subject to the claims. Any replacement, deformation, and improvement of the technology that can be easily thought of by technicians in this field shall fall within the protection scope of the present invention.

Claims

1. A high-strength titanium alloy, characterized in that The mass percentage of its components is: aluminum 5.8-6.5%, vanadium 3.9-4.3%, impurities ≤0.3%, and the rest is titanium.

2. A method for preparing a high-strength titanium alloy, characterized in that The specific steps include: (1) 89.2-90.3% titanium sponge, 1.5-2.6% aluminum beans, and 7.8-8.6% vanadium aluminum alloy are mixed and pressed into an electrode block according to mass percentage, and the electrode block is melted by arc heating under a vacuum environment and dripped into a water-cooled copper crucible, and air-cooled to form a titanium alloy ingot; (2) heating the titanium alloy ingot to 1000-1050°C and performing upsetting and drawing to form a titanium alloy billet; (3) hot rolling the titanium alloy billet in a rolling mill for multiple passes and air cooling; (4) Annealing the titanium alloy blank; (5) stretching and pre-deforming the annealed titanium alloy billet at room temperature; (6) electrically heating the pre-deformed titanium alloy blank, and applying a constant tensile load to the titanium alloy blank during the electrical heating; (7) When the titanium alloy blank is rapidly heated to the solution temperature, it is rapidly cooled to obtain a titanium alloy product with high strength.

3. The method for preparing a high-strength titanium alloy according to claim 2, characterized in that: In the step (5), the titanium alloy blank is uniformly stretched by a tensile testing machine, and the tensile deformation is controlled to be 2% to 10%.

4. The method for preparing a high-strength titanium alloy according to claim 2, characterized in that: In the step (6), the titanium alloy blank is heated by direct current, and the current density is controlled to be 8 to 30 A / mm 2 , the constant tensile load applied is 0~30MPa.

5. The method for preparing a high-strength titanium alloy according to claim 2, characterized in that: In the step (7), the solution temperature of the titanium alloy billet is 830-870°C, and the billet is rapidly cooled by water cooling.

6. The method for preparing a high-strength titanium alloy according to claim 2, characterized in that: The specific hot rolling process of step (3) is as follows: the titanium alloy billet is heated to 900-950°C, and then 2-4 rough rolling passes are performed in a rolling mill, with a reduction ratio of 15-25% for each rough rolling pass, and then a single finish rolling pass is performed, with a reduction ratio of 10%, and air cooling is performed after the hot rolling is completed.

7. The method for preparing a high-strength titanium alloy according to claim 2, characterized in that: The specific annealing process of step (4) is as follows: heating the titanium alloy blank to 700-800°C, keeping the temperature for 2 hours and then air cooling.

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