Inactive eutectoid element regulated alpha + beta type titanium alloy and preparation method thereof

Abstract

The invention relates to the field of titanium alloy materials, in particular to an inactive eutectoid element regulated alpha + beta type titanium alloy and a preparation method thereof. The titanium alloy comprises the following chemical components in percentage by mass: 5.0 to 7.0 percent of Al element, 2.0 to 4.0 percent of Nb element, 1.0 to 3.0 percent of Mo element, 1.0 to 3.0 percent of V element, 1.0 to 2.0 percent of Zr element, 0.5 to 3.0 percent of Fe element and the balance of Ti. The preparation process of the titanium alloy comprises the steps of electrode pressing, cast ingot preparation, high-temperature homogenization treatment, forging, rolling, solution treatment and aging treatment. The strength and toughness of the titanium alloy are adjusted by regulating and controlling the content of the non-active strong beta stable element Fe, the alpha + beta type high-strength and high-toughness titanium alloy with different strength levels is obtained, and the alpha + beta type high-strength and high-toughness titanium alloy can be widely applied to the important fields of aerospace, ocean engineering, weaponry, petrochemical engineering, automobile industry, biomedical treatment and the like.

Description

Technical Field

[0001] The invention relates to the field of titanium alloy materials, in particular to an α+β type titanium alloy regulated by inactive eutectoid elements and a preparation method thereof. Background Art

[0002] Titanium alloys are widely used in important fields such as aerospace, marine engineering, weapons and equipment, petrochemicals, automobile industry, and biomedicine due to their excellent specific strength, high corrosion resistance, and good high temperature resistance. With the increasing demand for equipment upgrades in aerospace, marine engineering, weapons and equipment, etc., higher requirements are placed on the performance of structural titanium alloy materials. However, it is difficult for existing titanium alloy materials to achieve a good balance between high strength and plasticity, especially some high-strength titanium alloys, due to the addition of a large amount of expensive high-priced elements such as molybdenum, chromium or vanadium, which increases costs and complicates processes, narrows the processing window, and increases the difficulty of material organization control.

[0003] At present, there are many high-strength and high-toughness titanium alloy grades at home and abroad (see Table 1). Among them, Ti-10-2-3 is a metastable β-type titanium alloy developed by the American Reactive Metals (RMI) Company in 1969. The alloy has good hardenability and good cold working ability in the solid solution state. It is used for high-strength aviation fasteners, but its mechanical properties are extremely sensitive to microstructure and heat treatment. Low-temperature aging easily produces brittle ω phase, which causes the plasticity of the alloy to drop sharply. BT22 is a near-β titanium alloy developed by the Soviet Union in 1974. It has high strength, high toughness, and good hardenability. It is used for aircraft landing gear, but the alloy heat treatment strengthening performance and toughness matching effect are not ideal. Ti-5553 and Ti55531 are another high-strength titanium alloy jointly developed by Russia based on the composition of BT22 titanium alloy. When the adjusted strength reaches 1500MPa, the elongation is only 3%, and the plasticity drops sharply, which cannot be used in practice. Therefore, the research and development of new high-strength and high-toughness titanium alloys is crucial to further exert the service performance of titanium alloy materials, and it is also the eternal theme of the development of structural titanium alloys.

[0004] Table 1 Research progress of high strength and high toughness titanium alloy

[0005] Summary of the invention

[0006] In view of the problem that the strength, plasticity, cost and process of titanium alloys cannot be taken into account at the same time, the purpose of the present invention is to provide an α+β type high-strength and high-toughness titanium alloy (Ti18) regulated by inactive eutectoid elements and a preparation method thereof, so as to improve the serviceability of structural titanium alloys, expand the process processing window of titanium alloy materials, and thus realize the engineering application of new materials.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] The invention discloses an α+β type titanium alloy regulated by inactive eutectoid elements. The chemical composition of the titanium alloy is, by mass percentage, 5.0% to 7.0% Al element, 2.0% to 4.0% Nb element, 1.0% to 3.0% Mo element, 1.0% to 3.0% V element, 1.0% to 2.0% Zr element, 0.5% to 3.0% Fe element, and the balance is Ti. The strength and toughness of the titanium alloy are adjusted by regulating the content of the inactive strong β stabilizing element Fe, so as to obtain α+β type high-strength and high-toughness titanium alloys with different strength levels.

[0009] The α+β type titanium alloy regulated by the inactive eutectoid elements has a molybdenum equivalent range of 8 to 10.

[0010] The α+β type titanium alloy regulated by the inactive eutectoid elements is a 1300MPa grade α+β type high strength and high toughness titanium alloy, with a plasticity greater than or equal to 12% and an impact toughness greater than or equal to 50J / cm 2 ; Calculated by mass percentage, the chemical composition of the titanium alloy is: 6% to 6.5% Al element, 2.5% to 3.0% Nb element, 2.5% to 3.0% Mo element, 2.5% to 3.0% V element, 1.0% to 1.5% Zr element, 0.5% to 1.0% Fe element, and the balance is Ti.

[0011] The α+β type titanium alloy regulated by the inactive eutectoid elements is a 1500MPa grade α+β type high-strength medium-toughness titanium alloy, with a plasticity greater than or equal to 8% and an impact toughness greater than or equal to 30J / cm 2 ; Calculated by mass percentage, the chemical composition of the titanium alloy is: 6.5% Al element, 2.0% Nb element, 3.0% Mo element, 2.0% V element, 1.0% Zr element, 2.0% Fe element, and the balance is Ti.

[0012] The α+β type titanium alloy regulated by the inactive eutectoid elements is an α+β type ultra-high strength titanium alloy with a strength level of 1800MPa. The chemical composition of the titanium alloy is, by mass percentage, 6.5% Al element, 2.0% Nb element, 2.0% Mo element, 1.5% V element, 1.0% Zr element, 3.0% Fe element, and the remainder is Ti.

[0013] The α+β type titanium alloy regulated by the inactive eutectoid elements, the α+β type high strength and high toughness titanium alloy has a unique two-level fine structure microstructure. p The size of the phase is between 2 and 5 μm, and the secondary α s The width of the phase is between 20 and 50 nm.

[0014] The preparation method of the α+β type titanium alloy regulated by the inactive eutectoid elements comprises the following specific steps:

[0015] (1) Pressing electrode

[0016] Using titanium sponge, Al bean, AlV master alloy, AlMo master alloy, TiNb master alloy, TiFe master alloy and zirconium sponge as raw materials, the materials are prepared according to the alloy design composition and pressed into electrodes;

[0017] (2) Preparation of ingots

[0018] The electrode obtained in step (1) is used to perform vacuum consumable smelting three times to obtain an ingot;

[0019] (3) High temperature homogenization treatment

[0020] The qualified ingot obtained in step (2) is subjected to high temperature homogenization treatment at a temperature of T β +200℃, insulation time 12~24h;

[0021] (4) Forging

[0022] The ingot after step (3) is forged into a rod blank, and the blank forging temperature is T β +200℃, single phase forging temperature is T β +80℃, two-phase zone forging temperature is T β -50℃, finished product forging temperature is T β -80℃, the holding time of each forging process is 4 to 8h, and the final forging temperature is not less than 800℃;

[0023] (5) Rolling

[0024] The bar blank obtained in step (4) is rolled into a bar stock at a temperature T β The first hot rolling is carried out at -120℃, and the rolling deformation is 70-80%; at temperature T β The second hot rolling is carried out at -150℃, and the holding time is 2 to 6 hours;

[0025] (6) Solution treatment

[0026] The bar obtained in step (5) is kept in the two-phase region for water-cooling solid solution treatment at a holding temperature of T β -30~50℃, keep warm for 30min~1h, quickly cool to room temperature, and control the cooling rate between 25~200℃ / s;

[0027] (7) Aging treatment

[0028] The solid solution rod obtained in step (6) is subjected to aging treatment at a holding temperature of 450° C. to 600° C. for 4 to 24 hours, and then air-cooled to room temperature.

[0029] In the preparation method of the α+β type titanium alloy regulated by the inactive eutectoid elements, in step (2), the ingot is required to be melted uniformly with a small current density to prevent the segregation of the iron element, ultrasonic flaw detection is performed after peeling, and the riser is cut off from the ingot, and the β transformation temperature is determined by metallographic method.

[0030] In the method for preparing the α+β type titanium alloy controlled by the inactive eutectoid elements, in step (4), grinding treatment is performed after each sequence of forging to ensure that the deformation of each sequence of forging is 50% to 70%.

[0031] In the method for preparing the α+β type titanium alloy regulated by the inactive eutectoid elements, in step (5), grinding treatment is performed after each rolling sequence, and peeling treatment is performed after the last rolling sequence.

[0032] The design concept of the present invention is

[0033] The present invention adjusts the strength and toughness of the new titanium alloy by adding different contents of inactive eutectoid element Fe to the titanium alloy. The ability of the inactive eutectoid element Fe to stabilize the β phase is stronger than that of V, Mo, Cr, and Mn. The diffusion rate of the Fe element is the fastest and can meet the diffusion conditions of amplitude modulation decomposition to achieve microstructure regulation. In addition, the resource is abundant and the cost is low. The molybdenum equivalent is regulated by controlling the content of the Fe element, and the hardenability is increased, so that the alloy forms different contents of primary equiaxed α phase and α″ martensite phase and nano-sized ω phase after solution treatment, and then the α″ martensite phase and nano-sized ω phase are transformed into micro-nano secondary α phase through aging treatment. The two-level fine structure microstructure makes the alloy have high strength and high toughness characteristics. At the same time, the increase of the Fe element can reduce the c / a ratio of the titanium alloy, increase the slip system, reduce the high-temperature rheological stress, and expand the hot processing window of the material. The alloy has good plastic forming ability above 700°C. In order to avoid Fe-rich segregation to produce β spots, the present invention adopts 0.25-1 mm small particle TiFe master alloy and simultaneously adopts a small current uniform melting and rapid solidification method to control the ingot segregation.

[0034] The advantages and beneficial effects of the present invention are:

[0035] 1. Different from the microstructure of existing engineering titanium alloys, due to the extremely fast diffusion coefficient of Fe element, Ti18 titanium alloy can form a unique double-level fine structure microstructure feature. The double-level size refers to the α phase with both micron and nanometer levels. The primary α p The size of the phase is between 2 and 5 μm, and the secondary α s The width of the phase is between 20 and 50 nm.

[0036] 2. The method of the present invention is used to adjust the strength and toughness of the new titanium alloy by adding different contents of the inactive eutectoid element Fe to the titanium alloy. The inactive eutectoid element Fe has a stronger ability to stabilize the β phase than V, Mo, Cr, and Mn, and is rich in resources and low in cost. By controlling the content of Fe element to adjust the molybdenum equivalent, the alloy hardenability can be increased and the grains can be refined.

[0037] 3. The method of the present invention can be used to prepare titanium alloy bars, wires, plates, etc.

[0038] 4. The method of the present invention can be used to prepare α+β titanium alloy (Ti18) with high strength and high toughness, which can be widely used in many important fields such as aerospace, marine engineering, weapon equipment, petrochemical industry, automobile industry and biomedicine. β Water-cooled solution treatment is carried out at -30 to 50°C, and the holding time is 30min to 1h. Aging is carried out at 450 to 600°C, and the holding time is 4 to 24h, and then air-cooled to room temperature. According to the content of Fe element, high-strength and high-toughness titanium alloy with strength level ranging from 1300 to 1800MPa can be obtained.

[0039] 5. The titanium alloy prepared by the method described in the present invention can reduce the c / a ratio of the titanium alloy, increase the slip system, reduce the high-temperature flow stress, and expand the hot processing window of the material due to the increase of Fe element. The Ti18 alloy has good plastic forming ability above 700°C, which can reduce the processing and manufacturing cost and expand the engineering application field of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is the XRD phase analysis spectrum in hot rolling state, solid solution state and solid solution aging state.

[0041] Figure 2 It is a multi-scale composite microstructure under solid solution aging state.

[0042] Figure 3 The stress-strain curves of high-strength and high-toughness titanium alloys with different strength levels obtained with different contents of Fe elements.

[0043] Figure 4 This is the stress-strain curve of 1300MPa grade high-strength and high-toughness titanium alloy at different temperatures. DETAILED DESCRIPTION

[0044] In the specific implementation process, the present invention adopts an α+β type high-strength and high-toughness titanium alloy (Ti18) regulated by an inactive eutectoid element, adds 5wt% to 7wt% of Al element and 1.0wt% to 2.0wt% of Zr element, strengthens the α phase, not only improves the critical shear stress of α-Ti dislocation slip, but also enables the sliding of the column and the base surface to start at the same time, which can simultaneously improve the yield strength and fracture toughness of the alloy. Then, 1.0wt% to 3.0wt% of V, 1.0wt% to 3.0wt% of Mo and 2.0wt% to 4.0wt% of Nb, which are isomorphous β stabilizing elements, are added to reduce the martensitic transformation temperature, improve the stability of the β phase, enhance the critical induced stress of the martensitic phase transformation, exert the TRIP and TWIP effects of the titanium alloy, and improve the plasticity of the titanium alloy. Finally, the strength and toughness of the new titanium alloy are regulated by regulating the content of the inactive strong β-stabilizing element Fe. The mass ratio of the Fe element is regulated in the range of 0.5wt% to 3.0wt%. High-strength and high-toughness titanium alloys of different strength levels can be obtained according to the content of the Fe element. The addition of the inactive eutectoid element iron can greatly reduce the high-temperature deformation resistance, increase the hardenability, expand the hot working process window, reduce the number of hot working passes, and reduce the hot working process cost. The addition of the inactive eutectoid element iron can also refine the grain size, and can also regulate the strength of the titanium alloy between 1000MPa and 1800MPa while maintaining good plasticity. In order to avoid the generation of β spots due to Fe-rich segregation, the present invention uses 0.25-1mm small-particle TiFe intermediate alloys, and uses a small current uniform melting and rapid solidification method to control the segregation of the ingot.

[0045] In order to make the purpose, technical solution and effect of the present application clearer and more explicit, the present application is further described in detail below with reference to the accompanying drawings and examples.

[0046] The specific examples and comparative examples illustrate and explain the present application, but should not be used to limit the scope of the present application. Examples 1 to 3 are alloys prepared by appropriately adjusting the Fe content and Mo equivalent according to the preparation steps in the invention content.

[0047] Embodiment 1:

[0048] An α+β type high-strength and high-toughness titanium alloy (Ti18-1) with a strength level of 1300MPa and a low content of inactive eutectoid element Fe is used. The chemical composition and mass percentage of the titanium alloy are: 6.5% Al element, 3.0% Nb element, 3.0% Mo element, 3.0% V element, 1.0% Zr element, 1.0% Fe element, and the remainder is Ti; the molybdenum equivalent is 8, and the phase transition point test temperature is 955±5℃.

[0049] In this embodiment, the preparation steps of the α+β type high-strength and high-toughness titanium alloy (Ti18-1) regulated by the inactive eutectoid elements are as follows:

[0050] (1) Pressing electrodes: Using titanium sponge, Al bean, AlV master alloy, AlMo master alloy, TiNb master alloy, TiFe master alloy, and zirconium sponge as raw materials, the ingredients are prepared according to the alloy design composition and pressed into electrodes.

[0051] (2) Preparation of ingots. The electrode obtained in step (1) is used for three vacuum consumable melting to obtain an ingot. The ingot casting requires a low current density (40-45 kA / m 2 ) is uniformly melted. Ultrasonic flaw detection is performed after peeling, and the riser is cut off from the ingot. At the same time, the β transformation temperature is determined by metallographic method to be 955±5℃.

[0052] (3) High-temperature homogenization treatment: The qualified ingot obtained in step (2) is subjected to high-temperature homogenization treatment, with the temperature selected being 1155° C. and the holding time being 24 h.

[0053] (4) Forging. The ingot treated in step (3) is forged into a billet, with a billet forging temperature of 1155±5°C and a holding time of 8h, a single-phase forging temperature of 1035±5°C and a holding time of 6h, a two-phase forging temperature of 905±5°C and a holding time of 4h, a finished product forging temperature of 875±5°C and a holding time of 4h, a final forging temperature of not less than 800°C, and a return to the furnace is allowed to be no more than twice. Grinding treatment is performed after each sequence of forging to ensure that the deformation of each sequence of forging is 60%.

[0054] (5) Rolling. The bar blank obtained in step (4) is subjected to the first hot rolling at a temperature of 835±5°C, with a rolling deformation of 75%; the second hot rolling is carried out at a temperature of 805±5°C, with a holding time of 2h. After rolling, the bar blank is subjected to peeling and polishing.

[0055] (6) Heat treatment. The bar obtained in step (5) was subjected to water-cooling solution treatment at 920°C for 1 hour. Aging was performed at 500±5°C for 4 hours, and then air-cooled to room temperature to obtain a tensile strength of 1367MPa, a yield strength of 1277MPa, an elongation of 12.4%, a cross-sectional shrinkage of 53%, and an impact toughness of 58.8J / cm 2 High-strength and high-toughness titanium alloy.

[0056] Embodiment 2:

[0057] An α+β type high-strength and high-toughness titanium alloy (Ti18-2) with a strength level of 1500MPa and a medium content of inactive eutectoid element Fe is used. The chemical composition and mass percentage of the titanium alloy are: 6.5% Al element, 2.0% Nb element, 3.0% Mo element, 2.0% V element, 1.0% Zr element, 2.0% Fe element, and the remainder is Ti; the molybdenum equivalent is 9, and the phase transition point test temperature is 945±5℃.

[0058] In this embodiment, the preparation steps of the α+β type high-strength and high-toughness titanium alloy (Ti18-1) regulated by the inactive eutectoid elements are as follows:

[0059] (1) Pressing electrodes: Using titanium sponge, Al bean, AlV master alloy, AlMo master alloy, TiNb master alloy, TiFe master alloy, and zirconium sponge as raw materials, the ingredients are prepared according to the alloy design composition and pressed into electrodes.

[0060] (2) Preparation of ingots. The electrode obtained in step (1) is used for three vacuum consumable melting to obtain an ingot. The ingot casting requires a low current density (40-45 kA / m 2 ) is uniformly melted. Ultrasonic flaw detection is performed after peeling, and the riser is cut off from the ingot. At the same time, the β transformation temperature is determined by metallographic method to be 945±5℃.

[0061] (3) High-temperature homogenization treatment: The qualified ingot obtained in step (2) is subjected to high-temperature homogenization treatment at a temperature of 1145° C. and a holding time of 24 h.

[0062] (4) Forging. The ingot treated in step (3) is forged into a billet, with a billet forging temperature of 1145±5°C and a holding time of 8h, a single-phase forging temperature of 1025±5°C and a holding time of 6h, a two-phase forging temperature of 895±5°C and a holding time of 4h, a finished product forging temperature of 865±5°C and a holding time of 4h, a final forging temperature of not less than 800°C, and a return to the furnace is allowed to be no more than twice. Grinding treatment is performed after each sequence of forging to ensure that the deformation of each sequence of forging is 60%.

[0063] (5) Rolling. The bar blank obtained in step (4) is subjected to the first hot rolling at a temperature of 825±5°C, with a rolling deformation of 75%; and the second hot rolling is carried out at a temperature of 795±5°C, with a holding time of 2h. After rolling, the bar blank is subjected to peeling and polishing.

[0064] (6) Heat treatment. The bar obtained in step (5) was subjected to water-cooling solution treatment at 910°C for 1 hour. Aging was performed at 500±5°C for 4 hours, and then air-cooled to room temperature to obtain a tensile strength of 1551MPa, a yield strength of 1470MPa, an elongation of 8.5%, a cross-sectional shrinkage of 30%, and an impact toughness of 35.5J / cm 2 High-strength and medium-toughness titanium alloy.

[0065] Embodiment 3:

[0066] An α+β type high-strength and high-toughness titanium alloy (Ti18-3) with a strength level of 1800MPa and a high content of inactive eutectoid element Fe is used. The chemical composition and mass percentage of the titanium alloy are: 6.5% Al element, 2.0% Nb element, 2.0% Mo element, 1.5% V element, 1.0% Zr element, 3.0% Fe element, and the remainder is Ti; the molybdenum equivalent is 10, and the phase transition point test temperature is 930±5℃.

[0067] In this embodiment, the preparation steps of the α+β type high-strength and high-toughness titanium alloy (Ti18-1) regulated by the inactive eutectoid elements are as follows:

[0068] (1) Pressing electrodes: Using titanium sponge, Al bean, AlV master alloy, AlMo master alloy, TiNb master alloy, TiFe master alloy, and zirconium sponge as raw materials, the ingredients are prepared according to the alloy design composition and pressed into electrodes.

[0069] (2) Preparation of ingots. The electrode obtained in step (1) is used for three vacuum consumable melting to obtain an ingot. The ingot casting requires a low current density (40-45 kA / m 2 ) is uniformly melted. Ultrasonic flaw detection is performed after peeling, and the riser is cut off from the ingot. At the same time, the β transformation temperature is determined by metallographic method to be 930±5℃.

[0070] (3) High-temperature homogenization treatment: The qualified ingot obtained in step (2) is subjected to high-temperature homogenization treatment at a temperature of 1120° C. and a holding time of 24 h.

[0071] (4) Forging. The ingot treated in step (3) is forged into a billet, with a billet forging temperature of 1120±5°C and a holding time of 8h, a single-phase forging temperature of 1005±5°C and a holding time of 6h, a two-phase forging temperature of 880±5°C and a holding time of 4h, a finished product forging temperature of 850±5°C and a holding time of 4h, a final forging temperature of not less than 800°C, and a return to the furnace is allowed to be no more than twice. Grinding treatment is performed after each sequence of forging to ensure that the deformation of each sequence of forging is 60%.

[0072] (5) Rolling. The bar blank obtained in step (4) is subjected to the first hot rolling at a temperature of 810±5°C, with a rolling deformation of 75%; the second hot rolling is carried out at a temperature of 780±5°C, with a holding time of 2h. After rolling, the bar blank is subjected to peeling and polishing.

[0073] (6) Heat treatment. The bar obtained in step (5) was subjected to water-cooling solution treatment at a temperature of 895±5°C for 1 hour. Aging was performed at 500±5°C for 4 hours, and then air-cooled to room temperature to obtain a tensile strength of 1870MPa, a yield strength of 1803MPa, an elongation of 4.5%, a cross-sectional shrinkage of 5%, and an impact toughness of 13.5J / cm2 Ultra-high strength titanium alloy.

[0074] See also Figures 1 to 4 .like Figure 1 As shown, the XRD phase analysis spectra in the hot-rolled state, solid solution state, and solid solution aging state in Example 1 of the present invention are as follows: Figure 1 It can be seen that a large number of α″ and ω unstable phases are formed in the solid solution state. Figure 2 As shown, the multi-scale composite structure in the solid solution aging state in Example 1 of the present invention has both micron-scale and nano-scale α phases, and the primary α p The size of the phase is between 2 and 5 μm, and the secondary α s The width of the phase is between 20 and 50 nm. Figure 3 As shown, the stress-strain curves of high-strength and high-toughness titanium alloys with different strength levels obtained by different contents of Fe elements after solid solution aging treatment in Examples 1, 2, and 3 of the present invention are shown in FIG. Figure 3 It can be seen that as the Fe content increases from 1% to 3%, the tensile strength level increases from 1300MPa to 1800MPa, the elongation decreases from 12.4% to 4.5%, and the tensile strength reaches 1800MPa, but still has a certain plasticity. Figure 4 As shown, the stress-strain curves of the 1300MPa high-strength and high-toughness titanium alloy at different temperatures in Example 1 of the present invention are as follows: Figure 4 It can be seen that as the temperature increases, the flow stress of the alloy becomes lower. When the temperature reaches above 700°C, the stress is only below 100MPa and the strain reaches more than 75%.

[0075] Table 2 Mechanical properties of Examples 1 to 3

[0076]

[0077] Table 3 High temperature mechanical properties of Example 1

[0078]

[0079] It can be seen from the results in Table 2 and Table 3 that the alloys in Examples 1 to 3 have relatively high tensile strength, yield strength and certain plasticity.

[0080] The results of the examples show that the addition of inactive eutectoid elements to the titanium alloy of the present invention is beneficial to retain the β phase to room temperature under the eutectoid composition, and it is not easy to generate a compound phase. The inactive eutectoid elements include iron, manganese, chromium, etc. Among them, the diffusion rate of iron is the fastest, which meets the diffusion conditions of spinodal decomposition, but the problem of element segregation during the smelting process increases the difficulty of engineering. The advantage of the present invention is to optimize the smelting process and the way of adding iron, and use titanium-iron intermediate alloy to avoid the problem of easy enrichment of iron in the liquid phase due to its fast diffusion rate. At the same time, the smelting parameters are adjusted to form a small molten pool, reduce the solidification temperature gradient, shorten the dendrite spacing, and thus overcome local component segregation. Because the diffusion rate of the inactive eutectoid element iron is extremely fast, a micro-region structure with different components but coherent crystals of 10 to 20 nm can be formed, thereby refining the grains and microstructures, and the strength of the titanium alloy can also be regulated between 1000MPa and 1800MPa. The present invention is used to obtain an α+β type titanium alloy that has both high strength and high toughness and has a double-level α phase, thereby improving the serviceability of the structural titanium alloy and expanding the process window of the titanium alloy material, thereby realizing the engineering application of the new material.

[0081] The above description is only an implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. An α+β type titanium alloy regulated by inactive eutectoid elements, characterized in that: The chemical composition of the titanium alloy is as follows, by mass percentage: 5.0% to 7.0% Al element, 2.0% to 4.0% Nb element, 1.0% to 3.0% Mo element, 1.0% to 3.0% V element, 1.0% to 2.0% Zr element, 0.5% to 3.0% Fe element, and the balance is Ti; the strength and toughness of the titanium alloy are adjusted by regulating the content of the inactive strong β-stabilizing element Fe, and α+β type high-strength and high-toughness titanium alloys of different strength levels are obtained.

2. The α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 1, characterized in that: The molybdenum equivalent range is 8 to 10.

3. The α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 1, characterized in that: α+β type high strength and high toughness titanium alloy with strength level of 1300MPa, plasticity greater than or equal to 12%, impact toughness greater than or equal to 50J / cm 2 ; Calculated by mass percentage, the chemical composition of the titanium alloy is: 6% to 6.5% Al element, 2.5% to 3.0% Nb element, 2.5% to 3.0% Mo element, 2.5% to 3.0% V element, 1.0% to 1.5% Zr element, 0.5% to 1.0% Fe element, and the balance is Ti.

4. The α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 1, characterized in that: α+β type high-strength and medium-toughness titanium alloy with a strength level of 1500MPa, plasticity greater than or equal to 8%, and impact toughness greater than or equal to 30J / cm 2 ; Calculated by mass percentage, the chemical composition of the titanium alloy is: 6.5% Al element, 2.0% Nb element, 3.0% Mo element, 2.0% V element, 1.0% Zr element, 2.0% Fe element, and the balance is Ti.

5. The α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 1, characterized in that: The α+β type ultra-high strength titanium alloy with a strength level of 1800MPa has the following chemical compositions by mass percentage: 6.5% Al element, 2.0% Nb element, 2.0% Mo element, 1.5% V element, 1.0% Zr element, 3.0% Fe element, and the remainder Ti.

6. The α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 1, characterized in that: α+β type high strength and high toughness titanium alloy has a unique two-level fine structure microstructure. p The size of the phase is between 2 and 5 μm, and the secondary α s The width of the phase is between 20 and 50 nm.

7. A method for preparing the α+β type titanium alloy controlled by the inactive eutectoid elements according to any one of claims 1 to 6, characterized in that: The specific steps are as follows: (1) Pressing electrode Using titanium sponge, Al bean, AlV master alloy, AlMo master alloy, TiNb master alloy, TiFe master alloy and zirconium sponge as raw materials, the materials are prepared according to the alloy design composition and pressed into electrodes; (2) Preparation of ingots The electrode obtained in step (1) is used to perform vacuum consumable smelting three times to obtain an ingot; (3) High temperature homogenization treatment The qualified ingot obtained in step (2) is subjected to high temperature homogenization treatment at a temperature of T β +200℃, insulation time 12~24h; (4) Forging The ingot after step (3) is forged into a rod blank, and the blank forging temperature is T β +200℃, single phase forging temperature is T β +80℃, two-phase zone forging temperature is T β -50℃, finished product forging temperature is T β -80℃, the holding time of each forging process is 4 to 8h, and the final forging temperature is not less than 800℃; (5) Rolling The bar blank obtained in step (4) is rolled into a bar stock at a temperature T β The first hot rolling is carried out at -120℃, and the rolling deformation is 70-80%; at temperature T β The second hot rolling is carried out at -150℃, and the holding time is 2 to 6 hours; (6) Solution treatment The bar obtained in step (5) is kept in the two-phase region for water-cooling solid solution treatment at a holding temperature of T β -30~50℃, keep warm for 30min~1h, quickly cool to room temperature, and control the cooling rate between 25~200℃ / s; (7) Aging treatment The solid solution rod obtained in step (6) is subjected to aging treatment at a holding temperature of 450° C. to 600° C. for 4 to 24 hours, and then air-cooled to room temperature.

8. The method for preparing the α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 7, characterized in that: In step (2), the ingot is required to be melted uniformly with a small current density to prevent segregation of the iron element. After peeling, ultrasonic flaw detection is performed, and the riser of the ingot is cut off. At the same time, the β-transformation temperature is determined by metallographic method.

9. The method for preparing the α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 7, characterized in that: In step (4), grinding treatment is performed after each forging sequence to ensure that the deformation amount of each forging sequence is 50% to 70%.

10. The method for preparing the α+β type titanium alloy controlled by the inactive eutectoid elements according to claim 7, characterized in that: In step (5), grinding treatment is performed after each rolling sequence, and peeling treatment is performed after the last rolling sequence.

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