1500 MPa-grade ultrahigh-strength high-plasticity titanium alloy for fasteners and preparation method thereof

Abstract

The 1500 MPa-grade ultrahigh-strength high-plasticity titanium alloy comprises, by mass, 3.50%-6.50% of Al, 3.00%-5.00% of Mo, 7.00%-9.00% of V, 3.0%-5.0% of Zr, 5.0%-7.0% of Cr and the balance Ti and inevitable impurities, an alloy ingot is subjected to cogging forging at the temperature of 1000-1200 DEG C, the finished product machining temperature is 750-850 DEG C, an alloy finished product is used after being subjected to 700-850 DEG C / WQ solid solution treatment and 400-600 DEG C / AC aging treatment, after the alloy is subjected to solid solution aging heat treatment, the alloy ingot is subjected to heat treatment, and the alloy ingot is subjected to heat treatment at the temperature of 800-800 DEG C and then subjected to heat treatment. The microstructure has the characteristics of fine crystal grains and multi-level structure, the ultrahigh strength-high plasticity performance matching can be realized, the room-temperature tensile strength Rm is greater than or equal to 1500 MPa, and the ductility is greater than or equal to 10%.

Description

Technical Field

[0001] This invention relates to the field of high-strength titanium alloys for fasteners, specifically to a 1500 MPa grade ultra-high strength and high ductility titanium alloy for fasteners and its preparation method. Background Technology

[0002] With the increasing sophistication of aircraft and the development of aerospace materials technology, higher requirements have been placed on the strength of titanium alloys used in fasteners. Developing ultra-high strength and high ductility titanium alloys for fasteners has become an inevitable choice for many countries. The successful production of ultra-high strength and high ductility titanium alloys for fasteners will enable my country to occupy a leading position in the field of aerospace metal materials. The upper limit of the strength of existing commercially available titanium alloys is around 1400 MPa. As the tensile strength approaches 1500 MPa, the ductility of the material decreases sharply. Manufacturing experience shows that when the ductility of the material is below ~9%, it will lead to difficulties in bolt manufacturing, low yield, and service safety risks. In the past few decades, researchers have proposed various strategies to address the discrepancy between the strength and ductility of titanium alloys, such as grain refinement, stress-induced phase transformation, twinning, and heterogeneous deformation-induced strengthening. However, a review of reported 1500 MPa-grade titanium alloys reveals that their elongation is still difficult to exceed 10%, which cannot meet the requirements of industrial production and mass application.

[0003] Therefore, developing an ultra-high strength and high plasticity titanium alloy for fasteners with a tensile strength ≥1500 MPa and an elongation ≥10% will have a positive promoting effect on the development of the aerospace field. Summary of the Invention

[0004] Therefore, it is necessary to provide an ultra-high strength and high plasticity titanium alloy for fasteners with a tensile strength ≥1500 MPa and an elongation ≥10% to address the aforementioned technical problems. This alloy has fine grains and a multi-level structure to achieve "ultra-high strength and high plasticity".

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a 1500 MPa grade ultra-high strength and high ductility titanium alloy for fasteners, which is composed of the following components by mass percentage: Al 3.50~6.50%, Mo 3.00~5.00%, V 7.00~9.00%, Zr 3.0~5.0%, Cr 5.0~7.0%, with the balance being Ti and unavoidable impurities.

[0006] Preferably, the ultra-high strength titanium alloy is composed of the following components in weight percentage: Al 4.00~6.00%, Mo 3.50~4.50%, V 7.50~8.50%, Zr 3.50~4.50%, Cr 5.50~6.50%, with the balance being Ti and unavoidable impurities.

[0007] The fastener described above uses a 1500 MPa grade ultra-high strength and high plasticity titanium alloy, which is used after being subjected to a solution treatment at 700-850℃ / WQ and an aging treatment at 400-600℃ / AC.

[0008] The aforementioned fastener uses a 1500 MPa grade ultra-high strength, high ductility titanium alloy, wherein the ultra-high strength titanium alloy, after heat treatment, has a room temperature tensile strength R... m ≥1500 MPa, elongation ≥10%.

[0009] The fasteners of the present invention are prepared using a 1500 MPa grade ultra-high strength and high ductility titanium alloy through the following steps: Step 1: Mix sponge titanium, aluminum granules, aluminum-vanadium alloy, molybdenum-vanadium-aluminum-titanium alloy, pure chromium particles and sponge zirconium to form an electrode, and then perform three vacuum consumable arc melting processes to obtain an alloy ingot. Step 2: The alloy ingot from Step 1 is forged at 900–1300℃ (preferably 1050–1150℃) (forging deformation of 40–80%), then rolled at 750–850℃ (preferably 780–820℃) (deformation of 60–95%), and then drawn at 650–750℃ (preferably 680–720℃) (deformation of 20–80%) to obtain the finished alloy product; Step 3: The alloy product from Step 2 is subjected to solution treatment at 700–850℃ / WQ (preferably 760–800℃) followed by aging heat treatment at 400–600℃ / AC (preferably 450–550℃). The solution treatment time is 0.5–4 hours (preferably 1–2 hours), and the aging treatment time is 6–14 hours (preferably 8–12 hours). After heat treatment, the tensile strength R of the alloy is... m ≥1500 MPa, elongation ≥10%.

[0010] WQ refers to water cooling, and AC refers to air cooling.

[0011] The beneficial effects of this invention are:

[0012] (1) In terms of composition design, the present invention obtains a multi-level structure through reasonable element matching and heat treatment process.

[0013] (2) In terms of deformation process, the present invention obtains fine-grained structure through a large plastic deformation process.

[0014] (3) In terms of heat treatment process, the present invention develops high-temperature solid solution water cooling treatment, which can be adapted to continuous water quenching furnaces for industrial production, so as to realize the stable mass production of bolt fasteners.

[0015] (4) The ultra-high strength titanium alloy of the present invention has a tensile strength R after heat treatment. mWith a strength of ≥1500 MPa and an elongation of ≥10%, it exhibits a good match between "ultra-high strength and high plasticity". Attached Figure Description

[0016] Figure 1 This is a scanning electron microscope (SEM) image of the microstructure of the ultra-high strength and high ductility titanium alloy rod obtained in Example 1. As can be seen from the image, the alloy grains are fine, and the microstructure consists of fine equiaxed α grains, long lamellar α grains, and short rod α grains.

[0017] Figure 2 This is a scanning electron microscope (SEM) image of the microstructure of a conventional TB9 titanium alloy bar obtained in Comparative Example 1. As can be seen from the image, the microstructure consists of β grains and intragranular precipitated lamellar α-structure. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Example 1

[0019] Step 1: Sponge titanium, aluminum briquettes, aluminum-vanadium alloy, molybdenum-vanadium-aluminum-titanium alloy, pure chromium particles, and sponge zirconium are mixed and pressed into electrodes. After three vacuum consumable arc melting processes, an alloy ingot (ingot shape and size is φ330 mm rod) is obtained. The alloy ingot is composed of the following components by mass percentage: Al 5.40%, V 8.09%, Mo 4.25%, Zr 3.86%, Cr 5.95%, with the balance being Ti and unavoidable impurities <0.05% (e.g., one or more of Mg, Ca, etc.). Step 2: The alloy ingot from Step 1 is forged at 1150℃ (held for 2 hours, forging deformation is 60%), then rolled at 800℃ with a deformation of 92.9% (the rolled billet shape and size is φ16 mm bar), and then drawn at 720℃ with a deformation of 68.4% (the drawn billet shape and size is φ9 mm bar), to obtain the finished alloy product; Step 3: Perform a solution treatment at 770℃ / WQ (1.5 hours) followed by an aging heat treatment at 500℃ / AC (10 hours) on the alloy product from Step 2.

[0020] According to the testing (referring to the national standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature", the mechanical properties of the obtained titanium alloy bars were determined), the tensile strength R of the heat-treated ultra-high strength titanium alloy prepared in this embodiment was [missing information]. m =1570 MPa, elongation =13%. Example 2

[0021] Step 1: Sponge titanium, aluminum briquettes, aluminum-vanadium alloy, molybdenum-vanadium-aluminum-titanium alloy, pure chromium particles, and sponge zirconium are mixed and pressed into electrodes. After three vacuum consumable arc melting processes, an alloy ingot (ingot shape and size is φ330 mm rod) is obtained. The alloy ingot is composed of the following components by mass percentage: Al 5.40%, V 8.09%, Mo 4.25%, Zr 3.86%, Cr 5.95%, with the balance being Ti and unavoidable impurities <0.05% (e.g., one or more of Mg, Ca, etc.). Step 2: The alloy ingot from Step 1 is forged at 1150℃ (held for 2 hours, forging deformation is 60%), then rolled at 800℃ with a deformation of 92.9% (the rolled billet shape and size is φ16 mm bar), and then drawn at 720℃ with a deformation of 68.4% (the drawn billet shape and size is φ9 mm bar), to obtain the finished alloy product; Step 3: Perform a solution treatment at 770℃ / WQ (1.5 hours) followed by an aging heat treatment at 520℃ / AC (10 hours) on the finished alloy product from Step 2.

[0022] According to the testing (referring to the national standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature", the mechanical properties of the obtained titanium alloy bars were determined), the tensile strength R of the heat-treated ultra-high strength titanium alloy prepared in this embodiment was [missing information]. m =1539 MPa, elongation =12.5%. Example 3

[0023] Step 1: Sponge titanium, aluminum briquettes, aluminum-vanadium alloy, molybdenum-vanadium-aluminum-titanium alloy, pure chromium particles, and sponge zirconium are mixed and pressed into electrodes. After three vacuum consumable arc melting processes, an alloy ingot (ingot shape and size is φ330 mm rod) is obtained. The alloy ingot is composed of the following components by mass percentage: Al 4.42%, V 8.10%, Mo 4.28%, Zr 3.87%, Cr 6.00%, with the balance being Ti and unavoidable impurities <0.05% (e.g., one or more of Mg, Ca, etc.). Step 2: The alloy ingot from Step 1 is forged at 1150℃ (held for 2 hours, forging deformation is 60%), then rolled at 800℃ with a deformation of 92.9% (the rolled billet shape and size is φ16 mm bar), and then drawn at 720℃ with a deformation of 68.4% (the drawn billet shape and size is φ9 mm bar), to obtain the finished alloy product; Step 3: Perform a solution treatment at 720℃ / WQ (1.5 hours) followed by an aging heat treatment at 480℃ / AC (10 hours) on the finished alloy product from Step 2.

[0024] According to the testing (referring to the national standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature", the mechanical properties of the obtained titanium alloy bars were determined), the tensile strength R of the heat-treated ultra-high strength titanium alloy prepared in this embodiment was [missing information]. m =1560 MPa, elongation =12%. Example 4

[0025] Step 1: Sponge titanium, aluminum briquettes, aluminum-vanadium alloy, molybdenum-vanadium-aluminum-titanium alloy, pure chromium particles, and sponge zirconium are mixed and pressed into electrodes. After three vacuum consumable arc melting processes, an alloy ingot (ingot shape and size is φ330 mm rod) is obtained. The alloy ingot is composed of the following components by mass percentage: Al 4.42%, V 8.10%, Mo 4.28%, Zr 3.87%, Cr 6.00%, with the balance being Ti and unavoidable impurities <0.05% (e.g., one or more of Mg, Ca, etc.). Step 2: The alloy ingot from Step 1 is forged at 1150℃ (held for 2 hours, forging deformation is 60%), then rolled at 800℃ with a deformation of 92.9% (the rolled billet shape and size is φ16 mm bar), and then drawn at 720℃ with a deformation of 68.4% (the drawn billet shape and size is φ9 mm bar), to obtain the finished alloy product; Step 3: Perform a solution treatment at 720℃ / WQ (1.5 hours) followed by an aging heat treatment at 500℃ / AC (10 hours) on the finished alloy product from Step 2.

[0026] According to the testing (referring to the national standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature", the mechanical properties of the obtained titanium alloy bars were determined), the tensile strength R of the heat-treated ultra-high strength titanium alloy prepared in this embodiment was [missing information]. m =1513 MPa, elongation =14%.

[0027] Comparative Example 1 Step 1: Sponge titanium, aluminum briquettes, aluminum-vanadium alloy, molybdenum-vanadium-aluminum-titanium alloy, pure chromium particles, and sponge zirconium are mixed and pressed into electrodes. After three vacuum consumable arc melting processes, an alloy ingot (ingot shape and size is φ330 mm rod) is obtained. The alloy ingot is composed of the following components by mass percentage: Al 3.44%, V 8.02%, Mo 4.08%, Zr 3.85%, Cr 6.04%, with the balance being Ti and unavoidable impurities <0.05% (e.g., one or more of Mg, Ca, etc.). Step 2: Forge the alloy ingot from Step 1 at 1150℃ (hold for 2 hours, forging deformation is 60%), then roll at 800℃ with a deformation of 92.9% (the rolled billet shape and size is φ16 mm), then draw at 720℃ with a deformation of 72.8% (the drawn billet shape and size is φ8.35 mm), and finally cold draw at 770℃ / 1h / WQ to φ5.9 mm to obtain the finished alloy product; Step 3: Perform aging heat treatment at 530℃ / AC on the alloy product from Step 2 (for 6 hours).

[0028] According to the testing (referring to the national standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature", the mechanical properties of the obtained titanium alloy bars were determined), the tensile strength R of the heat-treated ultra-high strength titanium alloy prepared in this embodiment was [missing information]. m =1321 MPa, elongation =13.5%.

[0029] Comparative Example 2 Step 1: Sponge titanium, aluminum briquettes, aluminum-vanadium alloy, molybdenum-vanadium-aluminum-titanium alloy, pure chromium particles, and sponge zirconium are mixed and pressed into electrodes. After three vacuum consumable arc melting processes, an alloy ingot (ingot shape and size is φ330 mm rod) is obtained. The alloy ingot is composed of the following components by mass percentage: Al 3.44%, V 8.02%, Mo 4.08%, Zr 3.85%, Cr 6.04%, with the balance being Ti and unavoidable impurities <0.05% (e.g., one or more of Mg, Ca, etc.). Step 2: Forge the alloy ingot from Step 1 at 1150℃ (hold for 2 hours, forging deformation is 60%), then roll at 800℃ with a deformation of 92.9% (the rolled billet shape and size is φ16 mm bar), then draw at 720℃ with a deformation of 81.9% (the drawn billet shape and size is φ6.8 mm bar), and finally cold draw at 770℃ / 1h / WQ to φ5.9 mm to obtain the finished alloy product; Step 3: Perform solution treatment at 770℃ / WQ (1 hour) + aging heat treatment at 560℃ / AC (6 hours) on the finished alloy product from Step 2.

[0030] According to the testing (referring to the national standard GB / T 228.1-2010 "Metallic materials, tensile testing - Part 1: Test at room temperature", the mechanical properties of the obtained titanium alloy bars were determined), the tensile strength R of the heat-treated ultra-high strength titanium alloy prepared in this embodiment was [missing information]. m =118 1MPa, elongation =21%.

[0031] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A 1500 MPa grade ultra-high strength and high ductility titanium alloy for fasteners, characterized in that, This ultra-high strength and high plasticity titanium alloy is composed of the following components by mass percentage: Al 3.50~6.50%, Mo 3.00~5.00%, V 7.00~9.00%, Zr 3.0~5.0%, Cr 5.0~7.0%, with the balance being Ti and unavoidable impurities.

2. The titanium alloy according to claim 1, characterized in that, The ultra-high strength and high plasticity titanium alloy is composed of the following components by mass percentage: Al 4.00~6.00%, Mo 3.50~4.50%, V 7.50~8.50%, Zr 3.50~4.50%, Cr 5.50~6.50%, with the balance being Ti and unavoidable impurities.

3. The titanium alloy according to claim 1, characterized in that, The ultra-high strength and high plasticity titanium alloy product is obtained by solution treatment at 700-850℃ / WQ + aging treatment at 400-600℃ / AC (preferably 450-550℃) on the titanium alloy. The solution treatment time is 0.5-4 hours (preferably 1-2 hours), and the aging treatment time is 6-14 hours (preferably 8-12 hours).

4. The titanium alloy according to claim 1, characterized in that, The room temperature tensile strength R of the ultra-high strength and high ductility titanium alloy after heat treatment m ≥1500 MPa, elongation ≥10%.

5. A method for preparing the titanium alloy according to any one of claims 1-4, characterized in that, Step 1: Prepare alloy ingot bars with the required composition; Step 2: The alloy ingot from Step 1 is forged at 1000-1200℃ (preferably 1050-1150℃) (forging deformation of 40-80%), then rolled at 750-850℃ (preferably 780-820℃) (deformation of 60-95%), and then drawn at 650-750℃ (preferably 680-720℃) (deformation of 20-80%) to obtain the finished alloy product; Step 3: The alloy product from Step 2 is subjected to solution treatment at 700-850℃ / WQ (preferably 760-800℃) + aging heat treatment at 400-600℃ / AC (preferably 450-550℃). The solution treatment time is 0.5-4 hours (preferably 1-2 hours), and the aging treatment time is 6-14 hours (preferably 8-12 hours) to obtain an ultra-high strength and high plasticity titanium alloy.

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