Ultrahigh-strength titanium alloy for aviation structural component

Abstract

The invention discloses an ultrahigh-strength titanium alloy for an aviation structural part. The ultrahigh-strength titanium alloy is prepared from the following components in percentage by mass: 5.5 wt%-6.2 wt% of Al, 3.5 wt%-4.2 wt% of V, 1.2 wt%-1.8 wt% of Mo, 0.8 wt%-1.2 wt% of Cr, 0.4 wt%-0.6 wt% of Fe, 0.08 wt%-0.12 wt% of Si, 0.05 wt%-0.15 wt% of rare earth elements, 0.1 wt%-0.3 wt% of Hf, 0.2 wt%-0.5 wt% of Ta, 0.005 wt%-0.015 wt% of B and the balance of Ti and inevitable impurities. The rare earth element is at least one of Nd and Er. The titanium alloy has the advantages of ultrahigh strength, good toughness, excellent temperature resistance and fatigue performance, reasonable preparation process and stable performance.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy materials technology, and in particular to an ultra-high strength titanium alloy for aerospace structural components. Background Technology

[0002] Titanium alloys possess excellent properties such as high melting point, high hardness, low density, high specific strength, and corrosion resistance, making them widely used in the manufacture of various structural components. In the aerospace industry, structural components must withstand complex loads and harsh environments, and their performance directly affects the safety and operational efficiency of aircraft. However, existing titanium alloy materials reveal numerous problems that urgently need to be addressed when facing the design requirements of next-generation aircraft.

[0003] In terms of strength, the room temperature tensile strength of traditional titanium alloys is mostly below 1000 MPa, making it difficult to withstand the enormous loads borne by advanced aerospace structural components. Current technology has yet to find an ideal solution for balancing toughness and strength. Some titanium alloys, in pursuit of high strength, often sacrifice toughness, making them highly susceptible to brittle fracture under sudden impact loads, posing a significant threat to the safe operation of aircraft. As aircraft speeds increase, structural components generate substantial heat during operation, leading to higher ambient temperatures. Existing titanium alloys struggle to maintain stable mechanical properties at higher temperatures. Fatigue performance is a key factor affecting the service life of aerospace structural components; existing titanium alloys, however, have limitations at 10... 7 The fatigue strength under cyclic loading is generally below 550 MPa. During long-term use, aerospace structural components are continuously subjected to cyclic loading. Low fatigue strength will cause fatigue cracks to appear prematurely, significantly shortening their service life and increasing maintenance costs and safety risks.

[0004] Furthermore, existing titanium alloy manufacturing processes have numerous shortcomings. For example, it is difficult to ensure compositional uniformity during smelting, leading to segregation; unreasonable forging process parameters result in coarse and uneven grains; and heat treatment processes cannot fully utilize the strengthening effects of alloying elements, resulting in poor performance stability of titanium alloys and making it difficult to meet the needs of large-scale industrial production. Additionally, current technologies rarely incorporate rare earth elements and special elements such as Hf, Ta, and B into titanium alloy compositions, failing to leverage their unique properties to improve the overall performance of titanium alloys.

[0005] To address the aforementioned issues, Chinese invention patent CN115772616B discloses an ultra-high-strength titanium alloy for aerospace structural components, composed of the following mass percentages: Al 4.0%–6.0%, Cr 4.0%–6.0%, (Mo+V) / Cr = (1–1.5):1, Zr 2.0%–4.0%, Nb 0.5%–1.5%, with the balance being Ti and unavoidable impurities. This invention's ultra-high-strength titanium alloy utilizes the fast eutectoid element Cr to achieve high strength and toughness. The addition of the isomorphous β-stabilizing element Mo+V, at a concentration 1–1.5 times that of Cr, significantly improves the alloy's hardenability. Simultaneously, it greatly suppresses the potential for inclusion or eutectoid reactions that may occur after adding large amounts of Al and Cr, preventing the formation of brittle intermetallic compounds and avoiding loss of plasticity. After heat treatment, the tensile strength is not less than 1500 MPa, making it suitable for manufacturing critical load-bearing components in aircraft fuselages, wings, and landing gear structures. However, it still has shortcomings in terms of toughness, temperature resistance, and fatigue performance.

[0006] It is evident that developing an ultra-high strength titanium alloy for aerospace structural components with ultra-high strength, good toughness, excellent temperature resistance and fatigue performance, and with a reasonable manufacturing process and stable performance meets market demand, has high market value and application prospects, and is of great significance to promoting the development of the titanium alloy materials field. Summary of the Invention

[0007] In view of the above problems, the purpose of this invention is to provide an ultra-high strength titanium alloy for aerospace structural components with ultra-high strength, good toughness, excellent temperature resistance and fatigue performance, and reasonable manufacturing process and stable performance.

[0008] To achieve the above objectives, the technical solution adopted by this invention is: an ultra-high strength titanium alloy for aerospace structural components, composed of the following components by mass percentage: Al: 5.5wt%-6.2wt%, V: 3.5wt%-4.2wt%, Mo: 1.2wt%-1.8wt%, Cr: 0.8wt%-1.2wt%, Fe: 0.4wt%-0.6wt%, Si: 0.08wt%-0.12wt%, rare earth elements: 0.05wt%-0.15wt%, Hf: 0.1wt%-0.3wt%, Ta: 0.2wt%-0.5wt%, B: 0.005wt%-0.015wt%, with the remainder being Ti and unavoidable impurities; the rare earth elements are at least one of Nd and Er.

[0009] Another object of the present invention is to provide a method for preparing the ultra-high strength titanium alloy for aerospace structural components, comprising the following steps:

[0010] Step S1, Raw material preparation: Select sponge titanium, high-purity aluminum ingots, vanadium-iron alloy, molybdenum bars, chromium blocks, iron wire, silicon wafers, rare earth metals, Hf blocks, Ta blocks, and B powder as raw materials, and strictly follow the component ratio for precise batching.

[0011] Step S2, Melting: Melting is carried out using a vacuum consumable arc furnace;

[0012] Step S3, Forging: Heat the smelted ingot to 60-80℃ above the β phase transformation point, hold it at that temperature for 2.5-2.8h, and then perform multiple precision forging passes;

[0013] Step S4, Heat treatment: The forged billet is subjected to double solution treatment and aging treatment to obtain ultra-high strength titanium alloy for aerospace structural parts.

[0014] Preferably, the smelting in step S2 includes a first smelting, a second smelting, a third smelting, and a fourth smelting.

[0015] Preferably, the vacuum degree of the first melting is controlled at 8.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 3200-3400A, the melting temperature is 1620-1680℃, and the melting time is 35-38min.

[0016] Preferably, the vacuum degree of the second melting is controlled at 4.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 2700-2900A, the melting temperature is 1580-1620℃, and the melting time is 30-32min.

[0017] Preferably, the vacuum degree of the third melting process is controlled at 2.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 2200-2400A, the melting temperature is 1530-1570℃, and the melting time is 25-28min.

[0018] Preferably, the vacuum degree of the fourth melting process is controlled at 1.0 × 10⁻⁶. -4 Below Pa, the arc starting current is 1800-2000A, the melting temperature is 1500-1520℃, and the melting time is 20-22min.

[0019] Preferably, the initial forging temperature in step S3 is 1050-1080℃, the deformation amount in the first pass is 12-13%, and the deformation amount in each subsequent pass gradually decreases by 0.5%. Water mist cooling is used between passes to 820-830℃ before the next forging pass is performed, and the total deformation amount is controlled at 70-75%. After forging is completed, a gradient cooling method is used, first air cooling to 600℃, and then furnace cooling to room temperature.

[0020] Preferably, in step S4, the temperature of the first solution in the double solution treatment is 880-900℃, the holding time is 1.2-1.5h, and the solution is oil quenched; the temperature of the second solution in step S4 is 820-840℃, the holding time is 0.8-1.0h, and the solution is water quenched; the temperature of the aging treatment in step S4 is 480-520℃, the holding time is 5-5.5h, and the solution is air-cooled to room temperature.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The ultra-high strength titanium alloy for aerospace structural components disclosed in this invention constructs a "rare earth element (Nd / Er)-Hf-Ta-B" composite strengthening system, which works synergistically with basic elements such as Al, V, Mo, and Cr. Rare earth elements improve toughness by purifying the matrix (forming stable compounds with trace impurities) and refining grains (inhibiting grain growth); Hf can improve the high-temperature strength and oxidation resistance of titanium alloys, and synergistically enhance the heat resistance of alloys with other elements; Ta can significantly improve the high-temperature stability and strength of alloys, especially maintaining good performance at higher temperatures; B improves the strength and toughness of alloys by refining β grains, while also improving the casting performance of alloys. These elements work synergistically with elements such as Al, V, Mo, and Cr. Al forms fine intermetallic compounds with Si, which plays a dispersion strengthening role. V, Mo, and Cr improve the stability and toughness of the β phase. The combined effect of multiple elements achieves a synergistic improvement in strength, toughness, and temperature resistance without the deliberate addition of C, N, and O. This multi-element synergistic strengthening mechanism is not used in existing technologies.

[0023] (2) The ultra-high strength titanium alloy for aerospace structural components disclosed in this invention employs four-stage vacuum consumable arc melting, which, compared to traditional three-stage melting, further reduces the content of gases and impurities, especially strictly controlling the content of C, N, and O to ensure uniform distribution of rare earth elements, Hf, Ta, B, and other elements. The gradient deformation and gradient cooling processes during forging effectively refine the grain structure. The dual solution treatment + aging process allows the alloy elements to be fully dissolved and form a supersaturated solid solution. The aging treatment precipitates uniformly distributed fine strengthening phases (such as Ti3Al, Ti2Mo, etc.). The addition of Hf and Ta improves the high-temperature stability of the strengthening phases, and significantly improves the strength and temperature resistance of the alloy even without C, N, and O strengthening.

[0024] (3) The ultra-high strength titanium alloy for aerospace structural components disclosed in this invention, without the intentionally added C, N, and O, breaks through the performance constraints through synergistic optimization of composition and process, especially the introduction of rare earth elements, Hf, Ta, and B. The purification and grain refinement effects of rare earth elements and B improve strength while ensuring superior toughness; Hf and Ta improve the high-temperature stability of the alloy microstructure and strengthening phases, achieving excellent temperature resistance; the fine grain structure, uniform distribution of strengthening phases, and the effects of each element significantly improve fatigue performance, achieving a unified improvement in multiple properties, and with superior toughness. The β-phase stabilizing effect of Fe and the dispersion strengthening effect of Si complement each other: Fe ensures the balance of strength and toughness of the alloy at room temperature, while Si focuses on improving high-temperature performance. The combination of the two enables the alloy to meet the requirements of high-load components at room temperature, such as landing gear, and adapt to the use requirements of high-temperature environments, such as engine compartments. At the same time, the improved plasticity of Fe and the refined grain structure of Si work together to solve the problem of traditional high-strength titanium alloys being "strong but brittle".

[0025] (4) The ultra-high strength titanium alloy for aerospace structural components disclosed in this invention is composed of the following components by mass percentage: Al: 5.5wt%-6.2wt%, V: 3.5wt%-4.2wt%, Mo: 1.2wt%-1.8wt%, Cr: 0.8wt%-1.2wt%, Fe: 0.4wt%-0.6wt%, Si: 0.08wt%-0.12wt%, rare earth elements: 0.05wt%-0.15wt%, Hf: 0.1wt%-0.3wt%, Ta: 0.2wt%-0.5wt%, B: 0.005wt%-0.015wt%, with the remainder being Ti and unavoidable impurities; the rare earth elements are at least one of Nd and Er. Through the synergistic effect of the components, the product is endowed with ultra-high strength, good toughness, excellent temperature resistance, and fatigue performance. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0027] Example 1

[0028] An ultra-high strength titanium alloy for aerospace structural components is composed of the following components by weight percentage: Al: 5.5wt%, V: 3.5wt%, Mo: 1.2wt%, Cr: 0.8wt%, Fe: 0.4wt%, Si: 0.08wt%, rare earth elements: 0.05wt%, Hf: 0.1wt%, Ta: 0.2wt%, B: 0.005wt%, with the remainder being Ti and unavoidable impurities; the rare earth element is Nd.

[0029] A method for preparing the ultra-high strength titanium alloy for aerospace structural components includes the following steps:

[0030] Step S1, Raw material preparation: Select sponge titanium, high-purity aluminum ingots, vanadium-iron alloy, molybdenum bars, chromium blocks, iron wire, silicon wafers, rare earth metals, Hf blocks, Ta blocks, and B powder as raw materials, and strictly follow the component ratio for precise batching.

[0031] Step S2, Melting: Melting is carried out using a vacuum consumable arc furnace;

[0032] Step S3, Forging: Heat the smelted ingot to 60°C above the β phase transformation point, hold it at the precise temperature for 2.5 hours, and then perform multiple precision forging passes;

[0033] Step S4, Heat treatment: The forged billet is subjected to double solution treatment and aging treatment to obtain ultra-high strength titanium alloy for aerospace structural parts.

[0034] The smelting process in step S2 includes a first smelting, a second smelting, a third smelting, and a fourth smelting; the vacuum degree of the first smelting is controlled at 8.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1620℃, and the melting time is 35 min; the vacuum degree of the second melting is controlled at 4.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1580℃, and the melting time is 30 min; the vacuum degree of the third melting is controlled at 2.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1530℃, and the melting time is 25 min; the vacuum degree of the fourth melting is controlled at 1.0×10⁻⁶. -4 Below Pa, the arc starting current is 1800A, the melting temperature is 1500℃, and the melting time is 20min.

[0035] The initial forging temperature in step S3 is 1050℃, the deformation amount in the first pass is 12%, and the deformation amount in each subsequent pass gradually decreases by 0.5%. Water mist cooling is used between passes to 820℃ before the next forging pass is performed, and the total deformation amount is controlled at 70%. After forging is completed, a gradient cooling method is used, first air cooling to 600℃, and then furnace cooling to room temperature.

[0036] The first solution in step S4 is at a temperature of 880℃ and a holding time of 1.2h, followed by oil quenching; the second solution in step S4 is at a temperature of 820℃ and a holding time of 0.8h, followed by water quenching; the aging treatment in step S4 is at a temperature of 480℃ and a holding time of 5h, followed by air cooling to room temperature.

[0037] Example 2

[0038] An ultra-high strength titanium alloy for aerospace structural components is composed of the following components by mass percentage: Al: 6.0 wt%, V: 4.0 wt%, Mo: 1.5 wt%, Cr: 1.0 wt%, Fe: 0.5 wt%, Si: 0.1 wt%, rare earth elements: 0.12 wt%, Hf: 0.2 wt%, Ta: 0.3 wt%, B: 0.01 wt%, with the remainder being Ti and unavoidable impurities; the rare earth elements are Nd and Er mixed in a mass ratio of 2:1.

[0039] A method for preparing the ultra-high strength titanium alloy for aerospace structural components includes the following steps:

[0040] Step S1, Raw material preparation: Select sponge titanium, high-purity aluminum ingots, vanadium-iron alloy, molybdenum bars, chromium blocks, iron wire, silicon wafers, rare earth metals, Hf blocks, Ta blocks, and B powder as raw materials, and strictly follow the component ratio for precise batching.

[0041] Step S2, Melting: Melting is carried out using a vacuum consumable arc furnace;

[0042] Step S3, Forging: Heat the smelted ingot to 65°C above the β phase transformation point, hold it at that temperature for 2.6 hours, and then perform multiple precision forging passes;

[0043] Step S4, Heat treatment: The forged billet is subjected to double solution treatment and aging treatment to obtain ultra-high strength titanium alloy for aerospace structural parts.

[0044] The smelting process in step S2 includes a first smelting, a second smelting, a third smelting, and a fourth smelting; the vacuum degree of the first smelting is controlled at 8.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1640℃, and the melting time is 36 min; the vacuum degree of the second melting is controlled at 4.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1590℃, and the melting time is 30.5 min; the vacuum degree of the third melting is controlled at 2.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1540℃, and the melting time is 26 min; the vacuum degree of the fourth melting is controlled at 1.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 1850A, the melting temperature is 1505℃, and the melting time is 20.5min.

[0045] The initial forging temperature in step S3 is 1060℃, the deformation amount in the first pass is 12.3%, and the deformation amount in each subsequent pass gradually decreases by 0.5%. Water mist cooling is used between passes to 823℃ before the next forging pass is performed, and the total deformation amount is controlled at 72%. After forging is completed, a gradient cooling method is used, first air cooling to 600℃, and then furnace cooling to room temperature.

[0046] The first solution in step S4 is performed at a temperature of 885°C for 1.3 hours, followed by oil quenching; the second solution in step S4 is performed at a temperature of 825°C for 0.9 hours, followed by water quenching; the aging treatment in step S4 is performed at a temperature of 490°C for 5.2 hours, followed by air cooling to room temperature.

[0047] Example 3

[0048] An ultra-high strength titanium alloy for aerospace structural components is composed of the following components by mass percentage: Al: 6.2 wt%, V: 4.2 wt%, Mo: 1.8 wt%, Cr: 1.2 wt%, Fe: 0.6 wt%, Si: 0.12 wt%, rare earth elements: 0.15 wt%, Hf: 0.3 wt%, Ta: 0.5 wt%, B: 0.015 wt%, with the remainder being Ti and unavoidable impurities; the rare earth elements are Nd and Er mixed in a mass ratio of 4:1.

[0049] A method for preparing the ultra-high strength titanium alloy for aerospace structural components includes the following steps:

[0050] Step S1, Raw material preparation: Select sponge titanium, high-purity aluminum ingots, vanadium-iron alloy, molybdenum bars, chromium blocks, iron wire, silicon wafers, rare earth metals, Hf blocks, Ta blocks, and B powder as raw materials, and strictly follow the component ratio for precise batching.

[0051] Step S2, Melting: Melting is carried out using a vacuum consumable arc furnace;

[0052] Step S3, Forging: Heat the smelted ingot to 70°C above the β phase transformation point, hold it at that temperature for 2.7 hours, and then perform multiple precision forging passes;

[0053] Step S4, Heat treatment: The forged billet is subjected to double solution treatment and aging treatment to obtain ultra-high strength titanium alloy for aerospace structural parts.

[0054] The smelting process in step S2 includes a first smelting, a second smelting, a third smelting, and a fourth smelting; the vacuum degree of the first smelting is controlled at 8.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1650℃, and the melting time is 36.5 min; the vacuum degree of the second melting is controlled at 4.0 × 10⁻⁶. -4The arc ignition current is below Pa, the melting temperature is 1600℃, and the melting time is 31 min; the vacuum degree of the third melting is controlled at 2.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1550℃, and the melting time is 26.5 min; the vacuum degree of the fourth melting is controlled at 1.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 1900A, the melting temperature is 1510℃, and the melting time is 21min.

[0055] The initial forging temperature in step S3 is 1065℃, the deformation amount in the first pass is 12.5%, and the deformation amount in each subsequent pass gradually decreases by 0.5%. Water mist cooling is used between passes to 825℃ before the next forging pass is performed, and the total deformation amount is controlled at 73%. After forging is completed, a gradient cooling method is used, first air cooling to 600℃, and then furnace cooling to room temperature.

[0056] The first solution in step S4 is performed at a temperature of 890°C for 1.4 hours, followed by oil quenching; the second solution in step S4 is performed at a temperature of 830°C for 0.9 hours, followed by water quenching; the aging treatment in step S4 is performed at a temperature of 500°C for 5.3 hours, followed by air cooling to room temperature.

[0057] Example 4

[0058] An ultra-high strength titanium alloy for aerospace structural components is composed of the following components by weight percentage: Al: 5.8 wt%, V: 3.8 wt%, Mo: 1.6 wt%, Cr: 1.1 wt%, Fe: 0.55 wt%, Si: 0.11 wt%, rare earth elements: 0.15 wt%, Hf: 0.25 wt%, Ta: 0.4 wt%, B: 0.012 wt%, with the remainder being Ti and unavoidable impurities; the rare earth element is Er.

[0059] A method for preparing the ultra-high strength titanium alloy for aerospace structural components includes the following steps:

[0060] Step S1, Raw material preparation: Select sponge titanium, high-purity aluminum ingots, vanadium-iron alloy, molybdenum bars, chromium blocks, iron wire, silicon wafers, rare earth metals, Hf blocks, Ta blocks, and B powder as raw materials, and strictly follow the component ratio for precise batching.

[0061] Step S2, Melting: Melting is carried out using a vacuum consumable arc furnace;

[0062] Step S3, Forging: Heat the smelted ingot to 75°C above the β phase transformation point, hold it at that temperature for 2.7 hours, and then perform multiple precision forging passes;

[0063] Step S4, Heat treatment: The forged billet is subjected to double solution treatment and aging treatment to obtain ultra-high strength titanium alloy for aerospace structural parts.

[0064] The smelting process in step S2 includes a first smelting, a second smelting, a third smelting, and a fourth smelting; the vacuum degree of the first smelting is controlled at 8.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1670℃, and the melting time is 37.5 min; the vacuum degree of the second melting is controlled at 4.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1610℃, and the melting time is 31.5 min; the vacuum degree of the third melting is controlled at 2.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1560℃, and the melting time is 27.5 min; the vacuum degree of the fourth melting is controlled at 1.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 1950A, the melting temperature is 1515℃, and the melting time is 21.5min.

[0065] The initial forging temperature in step S3 is 1075℃, the deformation amount in the first pass is 12.8%, and the deformation amount in each subsequent pass gradually decreases by 0.5%. Water mist cooling is used between passes to 828℃ before the next forging pass is performed, and the total deformation amount is controlled at 74%. After forging is completed, a gradient cooling method is used, first air cooling to 600℃, and then furnace cooling to room temperature.

[0066] The first solution in step S4 is performed at a temperature of 895°C for 1.4 hours, followed by oil quenching; the second solution in step S4 is performed at a temperature of 835°C for 0.95 hours, followed by water quenching; the aging treatment in step S4 is performed at a temperature of 510°C for 5.4 hours, followed by air cooling to room temperature.

[0067] Example 5

[0068] An ultra-high strength titanium alloy for aerospace structural components is composed of the following components by mass percentage: Al: 5.6 wt%, V: 3.6 wt%, Mo: 1.3 wt%, Cr: 0.9 wt%, Fe: 0.45 wt%, Si: 0.09 wt%, rare earth elements: 0.09 wt%, Hf: 0.15 wt%, Ta: 0.25 wt%, B: 0.008 wt%, with the remainder being Ti and unavoidable impurities; the rare earth elements are Nd and Er mixed in a mass ratio of 2:1.

[0069] A method for preparing the ultra-high strength titanium alloy for aerospace structural components includes the following steps:

[0070] Step S1, Raw material preparation: Select sponge titanium, high-purity aluminum ingots, vanadium-iron alloy, molybdenum bars, chromium blocks, iron wire, silicon wafers, rare earth metals, Hf blocks, Ta blocks, and B powder as raw materials, and strictly follow the component ratio for precise batching.

[0071] Step S2, Melting: Melting is carried out using a vacuum consumable arc furnace;

[0072] Step S3, Forging: Heat the smelted ingot to 80°C above the β phase transformation point, hold it at the precise temperature for 2.8 hours, and then perform multiple precision forging passes;

[0073] Step S4, Heat treatment: The forged billet is subjected to double solution treatment and aging treatment to obtain ultra-high strength titanium alloy for aerospace structural parts.

[0074] The smelting process in step S2 includes a first smelting, a second smelting, a third smelting, and a fourth smelting; the vacuum degree of the first smelting is controlled at 8.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1680℃, and the melting time is 38 min; the vacuum degree of the second melting is controlled at 4.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1620℃, and the melting time is 32 min; the vacuum degree of the third melting is controlled at 2.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1570℃, and the melting time is 28 min; the vacuum degree of the fourth melting is controlled at 1.0 × 10⁻⁶. -4 The arc starting current is below Pa, the melting temperature is 1520℃, and the melting time is 22min.

[0075] The initial forging temperature in step S3 is 1080℃, the deformation amount in the first pass is 13%, and the deformation amount in each subsequent pass gradually decreases by 0.5%. Water mist cooling is used between passes to 830℃ before the next forging pass is performed, and the total deformation amount is controlled at 70-75%. After forging is completed, a gradient cooling method is used, first air cooling to 600℃, and then furnace cooling to room temperature.

[0076] The first solution in step S4 is performed at a temperature of 900℃ for 1.5 hours, followed by oil quenching; the second solution in step S4 is performed at a temperature of 840℃ for 1 hour, followed by water quenching; the aging treatment in step S4 is performed at a temperature of 520℃ for 5.5 hours, followed by air cooling to room temperature.

[0077] Comparative Example 1

[0078] An ultra-high strength titanium alloy for aerospace structural components is basically the same as that in Example 2, except that it is composed of the following components by mass percentage: Al: 6.0 wt%, V: 4.0 wt%, C: 0.05 wt%, N: 0.03 wt%, O: 0.15 wt%, with the remainder being Ti and unavoidable impurities.

[0079] Comparative Example 2

[0080] An ultra-high strength titanium alloy for aerospace structural components is basically the same as that in Example 2, except that it does not contain Hf, Ta, or B.

[0081] To further illustrate the unexpected positive technical effects achieved by the ultra-high strength titanium alloy products for aerospace structural components in the various embodiments of the present invention, relevant performance tests were conducted on the ultra-high strength titanium alloys for aerospace structural components manufactured in each example. The test results are shown in Table 1, and the test methods are as follows:

[0082] (1) Tensile properties: Tensile properties were tested in accordance with the methods in GB / T 228.1-2021 and GB / T 228.2-2015.

[0083] (2) Impact toughness test: The test was conducted in accordance with GB / T 229-2007 "Charpy Pendulum Impact Test Method for Metallic Materials". U-notch specimens (size 10mm×10mm×55mm, notch depth 2mm) were used and tested on an impact testing machine (model: JB-300B). Each sample was tested 5 times and the average value was taken.

[0084] (3) Fatigue strength test: The test was conducted in accordance with GB / T 3075-2008 "Methods for Controlling Axial Force in Fatigue Testing of Metallic Materials". A rotary bending fatigue testing machine (model: QBG-100) was used. The specimens were smooth cylindrical specimens (diameter 8mm, gauge length 50mm), stress ratio R = -1, frequency 50Hz, and the test was performed at 10... 7 Fatigue strength was tested under cyclic loading, with each sample tested 5 times and the average value taken.

[0085] Table 1. Performance test results of ultra-high strength titanium alloys used in aerospace structural components.

[0086] project room temperature tensile strength Tensile strength at 400℃ Impact toughness <![CDATA[10 7 Sub-cycle fatigue strength]]> unit MPa MPa <![CDATA[J / cm 2 ]]> MPa Example 1 1550 1500 92 800 Example 2 1660 1600 80 860 Example 3 1750 1710 71 900 Example 4 1600 1560 85 830 Example 5 1580 1550 82 820 Comparative Example 1 1050 950 46 590 Comparative Example 2 1500 1420 70 750

[0087] As can be seen from Table 1, the ultra-high strength titanium alloy for aerospace structural components disclosed in this invention exhibits superior mechanical properties, high-temperature resistance, impact toughness, and fatigue resistance compared to the comparative product. The combined addition of Hf, Ta, and B is beneficial for improving these properties.

[0088] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Anyone skilled in the art can readily implement the present invention based on the above description. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention using the disclosed technical content are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. An ultra-high strength titanium alloy for aerospace structural components, characterized in that, It is composed of the following components in weight percentage: Al: 5.5wt%-6.2wt%, V: 3.5wt%-4.2wt%, Mo: 1.2wt%-1.8wt%, Cr: 0.8wt%-1.2wt%, Fe: 0.4wt%-0.6wt%, Si: 0.08wt%-0.12wt%, rare earth elements: 0.05wt%-0.15wt%, Hf: 0.1wt%-0.3wt%, Ta: 0.2wt%-0.5wt%, B: 0.005wt%-0.015wt%, with the remainder being Ti and unavoidable impurities; the rare earth elements are at least one of Nd and Er.

2. A method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 1, characterized in that, Includes the following steps: Step S1, Raw material preparation: Select sponge titanium, high-purity aluminum ingots, vanadium-iron alloy, molybdenum bars, chromium blocks, iron wire, silicon wafers, rare earth metals, Hf blocks, Ta blocks, and B powder as raw materials, and strictly follow the component ratio for precise batching. Step S2, Melting: Melting is carried out using a vacuum consumable arc furnace; Step S3, Forging: Heat the smelted ingot to 60-80℃ above the β phase transformation point, hold it at that temperature for 2.5-2.8h, and then perform multiple precision forging passes; Step S4, Heat treatment: The forged billet is subjected to double solution treatment and aging treatment to obtain ultra-high strength titanium alloy for aerospace structural parts.

3. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 2, characterized in that, The smelting process in step S2 includes a first smelting, a second smelting, a third smelting, and a fourth smelting.

4. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 3, characterized in that, The vacuum level for the first melting process was controlled at 8.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 3200-3400A, the melting temperature is 1620-1680℃, and the melting time is 35-38min.

5. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 3, characterized in that, The vacuum level during the second melting process is controlled at 4.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 2700-2900A, the melting temperature is 1580-1620℃, and the melting time is 30-32min.

6. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 3, characterized in that, The vacuum level during the third melting process was controlled at 2.0 × 10⁻⁶. -4 Below Pa, the arc ignition current is 2200-2400A, the melting temperature is 1530-1570℃, and the melting time is 25-28min.

7. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 3, characterized in that, The vacuum level for the fourth melting process is controlled at 1.0 × 10⁻⁶. -4 Below Pa, the arc starting current is 1800-2000A, the melting temperature is 1500-1520℃, and the melting time is 20-22min.

8. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 2, characterized in that, The initial forging temperature in step S3 is 1050-1080℃, the deformation amount in the first pass is 12-13%, and the deformation amount in each subsequent pass gradually decreases by 0.5%. Water mist cooling is used between passes to 820-830℃ before the next forging pass is carried out. The total deformation amount is controlled at 70-75%. After forging is completed, a gradient cooling method is used, first air cooling to 600℃, and then furnace cooling to room temperature.

9. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 2, characterized in that, In step S4, the temperature of the first solution in the double solution process is 880-900℃, the holding time is 1.2-1.5h, and the solution is quenched in oil. In step S4, the temperature of the second solution in the double solution process is 820-840℃, the holding time is 0.8-1.0h, and the solution is quenched in water.

10. The method for preparing ultra-high strength titanium alloy for aerospace structural components according to claim 2, characterized in that, The aging treatment in step S4 is carried out at a temperature of 480-520℃, with a holding time of 5-5.5 hours, followed by air cooling to room temperature.