High-strength high-plasticity near-alpha high-temperature titanium alloy and preparation method thereof

Abstract

The invention discloses a high-strength and high-plasticity near-alpha high-temperature titanium alloy and a preparation method thereof, and belongs to the field of titanium alloy materials. The high-toughness near-alpha high-temperature titanium alloy composed of tiny alpha lamellas, residual beta between the lamellas and silicides is prepared through mechanical ball milling, sintering and solid solution aging treatment of raw material powder. After a powder metallurgy process of mechanical ball milling and sintering is carried out, solid solution is carried out at the temperature 10-40 DEG C above the beta / (alpha + beta) phase transformation point, then aging treatment is carried out, and the titanium alloy with high density, high component uniformity and high strength and toughness can be obtained. According to the high-strength and high-toughness titanium alloy, the tensile strength is 1050 MPa or above and the ductility is 14% or above at the room temperature, and the tensile strength is 650 MPa or above and the ductility is 10% or above at the temperature of 550 DEG C. The titanium alloy prepared through the method is excellent in performance, the process is simple and controllable, and the application range of the high-temperature titanium alloy prepared through powder metallurgy in the engineering field can be widened.

Description

Technical Field

[0001] The invention belongs to the field of high-temperature titanium alloy preparation, and particularly relates to a high-strength and high-plasticity near-alpha high-temperature titanium alloy and a preparation method thereof. Background Art

[0002] Titanium alloys are widely used in aerospace, petrochemical, biomedical and other fields due to their high specific strength, thermal strength and corrosion resistance. Based on the phase composition, titanium alloys can be divided into three categories, namely α-type, α+β-type and β-type. Among them, α-type titanium alloy has good high-temperature performance, stable structure and good welding performance, but low room temperature strength and insufficient plasticity. Based on this, in recent years, researchers have added less than 0.25% of β-stabilizing elements to α-type titanium alloys to prepare near-α-type titanium alloys, and obtained 8% to 15% of β or metal compounds in the annealed structure to improve room temperature performance and further improve high temperature performance. The highest long-term use temperature can reach above 550°C, making it the most commonly used high-temperature titanium alloy. Typical high-temperature titanium alloys such as IMI 834 (Ti-5.8Al-4Sn-3.5Zr-0.7Nb-0.5Mo-0.35Si-0.06C), Ti-1100 (Ti-6Al-2.75Sn-4Zr-0.4Mo-0.45Si), BT36 (Ti-6.2Al-2Sn-3.6Zr-0.7Mo-5W-0.15Si) and Ti600 (Ti-6Al-2.8Sn-4Zr-0.5Mo-0.4Si-0.1Y), etc. However, the preparation of near-α-type titanium alloys is mainly through vacuum melting into ingots, and then heat treatment after high-temperature ingot forging and fine forging or hot rolling. The entire production and preparation cycle is long, and the alloy elements are prone to segregation during the smelting process, which is not conducive to improving the performance of titanium alloys. At the same time, the high-temperature thermal deformation energy consumption is high, which makes the production cost of near-α-type high-temperature titanium alloys high. To this end, researchers proposed to prepare near-α-type high-temperature titanium alloys by combining powder metallurgy technology to simplify the process and reduce production costs. For example, the patent application document with application number 201811598566.3 discloses a near-α-type titanium alloy and its preparation and molding method. Powder metallurgy is used to eliminate segregation and avoid the impact of uneven composition. Combining hot extrusion molding can eliminate the defects of low density of powder metallurgy. At the same time, it can be molded in one time and directly extrude the final shape of the product to reduce the amount of subsequent processing; the subsequent vacuum annealing process will improve the stability of the alloy. However, during the high-temperature hot extrusion molding process, after the powder metallurgical billet is heated to a high temperature, it is easy to oxidize during the process of transferring to the hot extrusion die for extrusion, which makes it difficult to improve the plasticity of the prepared near-α-type titanium alloy, and the room temperature elongation remains below 12%.Based on this, the patent application document with application number 202011102497.X discloses a high-performance near-α high-temperature titanium alloy and its powder metallurgy preparation method. The near-α high-temperature titanium alloy is prepared by mixing powder + pressing into billets + sintering + extrusion forming + heat treatment. The elongation at room temperature can reach 14%. This method uses titanium hydride as raw material. The use of titanium hydride powder instead of pure titanium powder for hydrogenation and dehydrogenation can effectively reduce the oxygen content of the titanium alloy, thereby improving the performance. However, the solute hydrogen in the titanium alloy extruded rod has not yet completely escaped. Therefore, before annealing the titanium alloy extruded rod, it is necessary to first perform vacuum dehydrogenation in a high-temperature vacuum sintering furnace. The vacuum dehydrogenation heat treatment temperature is 600-800℃ for 4-14h. However, the high-temperature vacuum dehydrogenation treatment has high requirements for the vacuum of the equipment, and the vacuum degree needs to be controlled at 5×10. -3 Pa, this long-term high temperature and vacuum condition not only increases the complexity of the production process and equipment, but also increases the manufacturing cost. Therefore, how to provide a method for preparing near-α high-temperature titanium alloys by combining powder metallurgy technology, which can simplify the process and process, and prepare near-α high-temperature titanium alloys with high strength, high plasticity and excellent comprehensive mechanical properties under room temperature and high temperature (550℃) service environment, has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing a near-α high-temperature titanium alloy by combining powder metallurgy technology, which can simplify the process and flow, and prepare a near-α high-temperature titanium alloy with high strength, high plasticity and excellent comprehensive mechanical properties under room temperature and high temperature (550°C) service environment.

[0004] In a first aspect, the present invention provides a method for preparing a near-α titanium alloy, comprising the following preparation steps:

[0005] S1. Providing a raw material powder, wherein the composition of the raw material powder includes, by mass percentage, Al: 5.7-7.0%, Sn: 2-5.5%, Zr: 1.5-4.5%, Mo: 0.3-1.3%, Nb: 0.8-4.5%, Y: 0-0.5%, Si: 0.25-0.55%, and the balance is Ti;

[0006] S2. The raw powders are mixed, and the raw powders are mixed uniformly by ball milling to obtain a mixed powder;

[0007] S3. Sintering the mixed powder, sintering the mixed powder to prepare a titanium alloy block;

[0008] S4. Heat treatment: subjecting the titanium alloy block to solid solution aging treatment to prepare a near-α titanium alloy.

[0009] Optionally, in step S1, the composition of the raw material powder includes, by mass percentage: Al: 5.7-7.0%, Sn: 3.5-5.5%, Zr: 3.2-4.2%, Mo: 0.3-1.2%, Nb: 0.8-4.2%, Y: 0-0.4%, Si: 0.25-0.55%, and the remainder is Ti.

[0010] Optionally, in step S1, the raw material powder includes at least one of a single substance powder or an alloy powder of the component, and the powder particle size of the single substance powder or the alloy powder is 1 to 150 μm; and / or,

[0011] In step S2, the ball milling is carried out in a protective atmosphere, the rotation speed of the ball mill is 250-800 r / min, and the ball milling time is 2-60 h.

[0012] Optionally, in step S3, the sintering is performed by spark plasma sintering in a vacuum or protective atmosphere, with a heating rate of 50 to 150° C. / min, a sintering temperature of 1000 to 1300° C., a sintering holding time of 5 to 30 min, and a sintering pressure of 40 to 80 MPa; and / or,

[0013] In step S4, the solution temperature is 10-40°C above the β-transus temperature, the solution time is 0.5-6h, the aging temperature is 500-800°C, and the aging time is 2-10h.

[0014] Optionally, in step S3, the sintering is performed by spark plasma sintering in a vacuum or protective atmosphere, with a heating rate of 50 to 150° C. / min, a sintering temperature of 1080 to 1280° C., a sintering holding time of 5 to 30 min, and a sintering pressure of 40 to 80 MPa; and / or,

[0015] In step S4, the solution temperature is 10-40°C above the β-transus temperature, the solution time is 0.5-6h, the aging temperature is 550-650°C, and the aging time is 2-10h.

[0016] Optionally, the microstructure of the near-α titanium alloy prepared in step S4 is a fine α lamellae structure and dispersed particles distributed between the fine α lamellae, the thickness of the α lamellae structure is between 50nm and 2.5μm, and the dispersed particles are residual β phase and silicide phase, wherein the volume fraction of the α lamellae structure accounts for more than 90% of the total volume.

[0017] Optionally, the thickness of the α-lamellar tissue is between 50 nm and 1 μm.

[0018] Optionally, the original β grain size of the near-α titanium alloy prepared in step S4 is 5 to 50 μm.

[0019] Optionally, the near-α titanium alloy prepared in step S4 has a room temperature tensile strength of more than 1050 MPa, a room temperature elongation of more than 14%, a tensile strength at 550° C. of more than 650 MPa, and an elongation at 550° C. of more than 10%.

[0020] In a second aspect, the present invention provides a near-α titanium alloy obtained by the aforementioned preparation method of the near-α titanium alloy.

[0021] In summary, the present invention has at least one of the following beneficial effects:

[0022] 1. The present invention provides a method for preparing a near-α titanium alloy. The mechanical ball milling process performed before sintering helps to improve the uniformity of mechanical mixing of alloy elements, promote the reduction of sintering temperature and shorten the time required for sintering, reduce preparation energy consumption, and at the same time, the improvement of component uniformity is conducive to improving the uniformity of alloy structure, thereby improving the comprehensive mechanical properties of the alloy at room temperature and high temperature.

[0023] 2. The present invention adopts spark plasma sintering technology to prepare high-strength and tough titanium alloy. Compared with other powder metallurgy technologies, it has the advantages of uniform heating, fast heating rate, short sintering time, high production efficiency, etc., and can quickly obtain high-density alloy materials.

[0024] 3. The present invention adopts relatively high content of Al, Sn and Zr elements, which has the characteristics of high aluminum equivalent, improves the strength of the alloy, and improves the high temperature strength and creep resistance of the alloy by adding Nb, Mo and Si. The alloy elements in multiple specific proportions work together to significantly refine the lamellar structure of the titanium alloy, which plays a role in better organization refinement and high temperature performance enhancement.

[0025] 4. The present invention uses solution aging treatment, heats in the β single phase region during solution, so that the original β grain boundary is destroyed during the phase change process, the primary grain boundary α phase is suppressed, and the α lamellae in the grain become thinner and shorter, and the α bundle size becomes smaller; the size of the secondary α phase is adjusted by the aging process, so that the alloy has high strength and plasticity.

[0026] 5. The present invention adopts spark plasma sintering and solution aging treatment to obtain a high-strength and tough near-α high-temperature titanium alloy, whose room temperature strength is above 1050MPa, the room temperature elongation is above 14%, the tensile strength at 550°C is above 650MPa, and the elongation at 550°C is above 10%; preferably, the tensile strength at room temperature is above 1150MPa and the elongation is above 19%, the high-temperature strength at 550°C is above 790MPa and the elongation is above 18%, which well meets the application standards of high-temperature titanium alloys in aerospace and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1is the XRD spectrum of the near-α titanium alloy prepared in Examples 1, 2, and 4 of the present invention;

[0028] Figure 2 (a) room temperature tensile stress-strain curve and (b) 550°C tensile stress-strain curve of the near-α titanium alloy prepared in Example 1 of the present invention;

[0029] Figure 3 (a) metallographic structure diagram and (b) backscattered electron morphology diagram of the near-α titanium alloy prepared in Example 1 of the present invention;

[0030] Figure 4 are the metallographic structure diagram of the near-α titanium alloy prepared in (a) Example 2 and (b) Example 4 of the present invention;

[0031] Figure 5 is the metallographic structure diagram of the near-α titanium alloy prepared in Example 11 of the present invention;

[0032] Figure 6 It is the metallographic structure diagram of the near-α titanium alloy prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0033] The present invention provides a high-strength and high-plasticity near-α high-temperature titanium alloy and a preparation method thereof. In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] In recent years, near-α titanium alloys have become a research hotspot for high-temperature titanium alloys due to their good high-temperature mechanical properties, creep resistance and corrosion resistance, and have become one of the most widely used types of high-temperature titanium materials in the aerospace field. Near-α titanium alloys mainly rely on the solid solution strengthening of the α phase by α-stabilizing elements to ensure the thermal strength of high-temperature titanium alloys, while combining trace β-stabilizing elements (β stability coefficient is less than 0.25%) to achieve comprehensive regulation of thermal stability, creep, fatigue and other properties. The inventors have discovered in the long-term research process that by further accurately controlling the alloying element composition and ratio of the titanium alloy, combined with ball milling, sintering and post-solid solution aging treatment processes, a high-strength and high-plasticity near-α high-temperature titanium alloy with extremely fine α lamellae, residual β dispersed between the lamellae and silicide can be prepared. The present invention is obtained on the basis of this research.

[0035] In some embodiments of the present invention, a method for preparing a near-alpha titanium alloy comprises the following preparation steps:

[0036] S1. Providing a raw material powder, wherein the composition of the raw material powder includes, by mass percentage, Al: 5.7-7.0%, Sn: 2-5.5%, Zr: 1.5-4.5%, Mo: 0.3-1.3%, Nb: 0.8-4.5%, Y: 0-0.5%, Si: 0.25-0.55%, and the balance is Ti;

[0037] S2. The raw powders are mixed, and the raw powders are mixed uniformly by ball milling to obtain a mixed powder;

[0038] S3. Sintering the mixed powder, sintering the mixed powder to prepare a titanium alloy block;

[0039] S4. Heat treatment: subjecting the titanium alloy block to solid solution aging treatment to prepare a near-α titanium alloy.

[0040] In some embodiments of the present invention, in step S1, the composition of the raw material powder includes, by mass percentage, Al: 5.7-7.0%, Sn: 3.5-5.5%, Zr: 3.2-4.2%, Mo: 0.3-1.2%, Nb: 0.8-4.2%, Y: 0-0.4%, Si: 0.25-0.55%, and the balance is Ti; Optionally, the composition of the raw material powder includes, by mass percentage, Al: 5.7-7.0%, Sn: 3.5-5.5%, Zr: 3.2-4.2%, Mo: 0.3-1.2%, Nb: 0.8-4.2%, Y: 0-0.4%, Si: 0.25-0.55%, and the balance is Ti. r: 3.2-4.2%, Mo: 0.5-1.2%, Nb: 0.8-3.2%, Y: 0-0.4%, Si: 0.25-0.55%, and the balance is Ti; further optionally, the composition of the raw material powder includes, by mass percentage, Al: 5.7-7.0%, Sn: 3.5-5.5%, Zr: 3.2-4.2%, Mo: 0.5-1.2%, Nb: 0.8-3.2%, Y: 0-0.2%, Si: 0.25-0.55%, and the balance is Ti. Ti; Further optionally, the composition of the raw material powder includes by mass percentage: Al: 5.7-7.0%, Sn: 3.5-5.5%, Zr: 3.2-4.2%, Mo: 0.5-1.2%, Nb: 0.8-3.2%, Y: 0-0.1%, Si: 0.25-0.55%, and the balance is Ti; Further optionally, the composition of the raw material powder includes by mass percentage: Al: 5.7-7.0%, Sn: 3.5-5.5%, Zr: 3 .2~3.6%, Mo: 0.5~1.2%, Nb: 0.8~2.4%, Y: 0~0.1%, Si: 0.25~0.55%, and the balance is Ti; further optionally, the composition of the raw material powder includes, by mass percentage, Al: 5.7~6.7%, Sn: 3.8~4.5%, Zr: 3.3~3.6%, Mo: 0.8~1.2%, Nb: 0.8~1.2%, Y: 0~0.1%, Si: 0.3~0.4%, and the balance is Ti.

[0041] In some embodiments of the present invention, the raw powder includes at least one of a single powder or an alloy powder of the component, and the powder particle size of the single powder or the alloy powder is 1 to 150 μm; optionally, the raw powder is a single powder of the component; optionally, the powder particle size is 1 to 100 μm, further optionally, the powder particle size is 1 to 75 μm, further optionally, the powder particle size is 1 to 45 μm.

[0042] In some embodiments of the present invention, in step S2, the ball milling is carried out in a protective atmosphere, optionally, the protective atmosphere is nitrogen or argon, and further optionally, the protective atmosphere is argon; the rotation speed of the ball mill is 250-800r / min, optionally, the rotation speed of the ball mill is 300-500r / min; the ball milling time is 2-60h, optionally, the ball milling time is 4-40h, and further optionally, the ball milling time is 10-30h; the ball-to-material ratio is 5-30:1, optionally, the ball-to-material ratio is 8-20:1, and further optionally, the ball-to-material ratio is 8-16:1.

[0043] In some embodiments of the present invention, in step S3, the sintering is performed by spark plasma sintering in a vacuum or protective atmosphere, with a heating rate of 50 to 150°C / min, a sintering temperature of 1000 to 1300°C, a sintering holding time of 5 to 30min, and a sintering pressure of 40 to 80MPa. Optionally, the sintering temperature is 1080 to 1280°C, and further optionally, the sintering temperature is 1100 to 1200°C, and the sintering time is 5 to 15min. Optionally, the vacuum degree is lower than 100Pa, and further optionally, the vacuum degree is lower than 50Pa. Optionally, the protective atmosphere is argon, so that the pressure in the cavity of the spark plasma sintering furnace is not higher than 20kPa relative to the atmospheric pressure; optionally, argon is continuously introduced during the sintering process, and the flow rate of argon is 200ml / min to 800ml / min. Optionally, the sintering pressure is 50 to 70MPa.

[0044] In some embodiments of the present invention, in step S4, the solution temperature is 10-40°C above the β transition temperature, the solution time is 0.5-6h, the aging temperature is 500-800°C, and the aging time is 2-10h. Optionally, the solution temperature is 15-30°C above the β transition temperature, and the solution time is 1-4h. Optionally, the aging temperature is 550-650°C, and the aging time is 2-6h.

[0045] In some embodiments of the present invention, the microstructure of the near-α titanium alloy prepared in step S4 is a fine α lamella structure and dispersed particles distributed between the fine α lamellae, the thickness of the α lamella structure is between 50nm and 2.5μm, and the dispersed particles are residual β phase and silicide phase, wherein the volume fraction of the α lamella structure accounts for more than 90% of the total volume of the near-α titanium alloy. Optionally, the thickness of the α lamella structure is between 50nm and 1μm, and further optionally, the thickness of the α lamella structure is between 50nm and 450nm. Optionally, the volume fraction of the α lamella structure accounts for more than 95% of the total volume of the near-α titanium alloy.

[0046] In some embodiments of the present invention, the original β grain size of the near-α titanium alloy prepared in step S4 is 5 to 50 μm; optionally, the original β grain size is 5 to 35 μm, and further optionally, the original β grain size is 5 to 30 μm.

[0047] In some embodiments of the present invention, the room temperature tensile strength of the near-α titanium alloy prepared in step S4 is above 1050MPa, the room temperature elongation is above 14%, the tensile strength at 550°C is above 650MPa, and the elongation at 550°C is above 10%; optionally, the room temperature tensile strength of the prepared near-α titanium alloy is above 1150MPa, the room temperature elongation is above 14%, the tensile strength at 550°C is above 650MPa, and the elongation at 550°C is above 10%; optionally, the room temperature tensile strength of the prepared near-α titanium alloy is above 1150MPa, the room temperature elongation is above 15%, the tensile strength at 550°C is above 690MPa, and the elongation at 550°C is above 14% or more; Optionally, the room temperature tensile strength of the prepared near-α titanium alloy is above 1150MPa, the room temperature elongation is above 15%, the tensile strength at 550℃ is above 720MPa, and the elongation at 550℃ is above 14%; Optionally, the room temperature tensile strength of the prepared near-α titanium alloy is above 1150MPa, the room temperature elongation is above 18%, the tensile strength at 550℃ is above 780MPa, and the elongation at 550℃ is above 14%; Optionally, the room temperature tensile strength of the prepared near-α titanium alloy is above 1150MPa, the room temperature elongation is above 19%, the tensile strength at 550℃ is above 780MPa, and the elongation at 550℃ is above 18%.

[0048] The present invention is further described in detail below with reference to specific examples and comparative examples. Unless otherwise specified, the raw materials of the present invention can be obtained from commercial sources.

[0049] Example 1

[0050] Example 1 provides a method for preparing a high-strength and high-plasticity near-α titanium alloy, and the specific preparation steps are as follows:

[0051] S1. Provide raw material powder, weigh the raw material powder according to the ratio, the composition of the raw material powder includes by mass percentage: Al is 6%, Sn is 4%, Zr is 3.5%, Mo is 1.0%, Nb is 1.0%, Si is 0.35%, and the balance is Ti. The source of each component is a single powder, the purity of each single powder is not less than 99.9wt%, and the particle size distribution of each single powder is 3 to 45μm;

[0052] S2. Mix the raw powders, and mix the raw powders evenly by ball milling to obtain a mixed powder. The specific operation is as follows: according to the ball-to-material ratio of 10:1, put the grinding balls and the raw powders into a ball milling jar, and then introduce argon gas for protection, and place the ball milling jar on a planetary ball mill, and perform mechanical ball milling at a speed of 400r / min for a total of 24h. After the ball milling is completed, the obtained mixed powder is placed in an argon protection atmosphere for standby use;

[0053] S3. Sintering the mixed powder, the mixed powder is subjected to spark plasma sintering to prepare a titanium alloy block, the specific operation is as follows: after the mixed powder is filled into a mold in an argon protective atmosphere, the mold is placed in a spark plasma sintering device for rapid vacuum treatment, and the sintering process is: control the vacuum degree to be lower than 20Pa, the sintering pressure is 50MPa, the temperature is increased to 1200℃ at 100℃ / min, and the temperature is kept for 10min, and then cooled to room temperature with the furnace, taken out and demolded to prepare a titanium alloy block;

[0054] S4. Heat treatment, subjecting the titanium alloy block to solid solution aging treatment to prepare a near-α titanium alloy, the specific operation is as follows: placing the titanium alloy block in T β The alloy was solution treated at 600℃ (1080℃) for 2h and cooled by water quenching. The alloy was then aged at 600℃ for 4h and cooled to room temperature to obtain the near-α titanium alloy sample S-1.

[0055] The near-α titanium alloy sample S-1 prepared in Example 1 was tested by X-ray diffractometer (XRD), and its XRD pattern is as follows: Figure 1 As shown, from Figure 1 It can be seen that only the diffraction peak of α-Ti is detected in the sample S-1 prepared in Example 1, indicating that the matrix phase of the prepared near-α titanium alloy is α-Ti.

[0056] The Vickers hardness of sample S-1 was tested using a Vickers hardness tester. After the sample surface was ground and polished, the Vickers hardness was measured in accordance with GB / T4340.1-2024. The pressure was 1 kg and the holding time was 10 s. The Vickers hardness of sample S-1 was measured to be 435 HV1.0.

[0057] The room temperature and high temperature (550°C) tensile properties of sample S-1 were tested using an MTS universal mechanical testing machine. The test was carried out with reference to GB / T228.1-2021. The room temperature stress-strain curve of sample S-1 was measured as follows: Figure 2 As shown in (a), the room temperature tensile strength of sample S-1 is measured to be 1185MPa, and the elongation is 19.8%; the high temperature test temperature is 550℃, and the high temperature stress-strain curve of sample S-1 is measured as follows Figure 2As shown in (b), the high temperature (550°C) tensile strength was measured to be 790 MPa and the elongation was 18.6%.

[0058] The microstructure of sample S-1 was examined by metallographic microscope and scanning electron microscope (SEM). Figure 3 As shown, from Figure 3 It can be seen that the microstructure of sample S-1 includes fine α-lamellar structure and a large number of fine dispersed particles. In the backscattered magnified image, it can be clearly seen that the fine dispersed particles are distributed between the fine α-lamellae. The fine dispersed particles are residual β-phase and silicide phase. According to ImageJ statistics, the volume fraction of the dispersed particles is 3.5%, the thickness of the α-lamellae is mainly distributed between 50nm and 450nm, and the volume fraction is 96.5%. The original β grain size is mainly distributed between 5 and 30μm. This extremely fine nano-α-lamellae + a large number of fine dispersed particles + fine grains give the alloy excellent room temperature and high temperature strength and plasticity.

[0059] Embodiments 2 to 4

[0060] The difference between Examples 2 to 4 and Example 1 is that, in step S1 of Examples 2 to 4, the raw material powder is provided, and the Nb content is 2.0wt%, 3.0wt%, and 4.0wt% by mass percentage, respectively; the remaining preparation steps are the same as those of Example 1, and samples S-2, S-3, and S-4 are prepared. The room temperature and high temperature (550°C) mechanical properties of the samples of Examples 2 to 4 are tested by the same test method as that of Example 1, and the results are shown in Table 1. As can be seen from Table 1, with the increase of Nb content, the hardness and room temperature tensile strength of the alloy gradually increase, but the high temperature tensile strength gradually decreases, and the room temperature plasticity of the alloy tends to decrease with the increase of Nb elements, but the comprehensive mechanical properties of the alloy are still maintained at a high level, the room temperature tensile strength is maintained between 1150 and 1300MPa, the room temperature elongation is maintained between 17% and 21%, the high temperature (550°C) tensile strength is maintained between 690 and 800MPa, and the high temperature (550°C) elongation is maintained between 14% and 19%. The alloy metallographic structures of Example 2 and Example 4 are as follows: Figure 4 (a) and (b), combined with the alloy microstructure of Example 1 ( Figure 3 ), it can be seen that with the increase of Nb content, the thickness of the α lamellae structure tends to increase, from 0.3-0.9 μm of the α lamellae thickness in Example 2 to 0.4-1.1 μm of the α lamellae thickness in Example 4; in addition, the original β grain size increases from 5-35 μm in Example 2 to 7-45 μm in Example 4, also slightly growing.

[0061] Table 1. Room temperature and high temperature mechanical properties of near-α titanium alloys of Examples 2 to 4

[0062]

[0063] Example 5

[0064] The difference between Example 5 and Example 1 is that in step S1 of Example 5, the raw material powder has a Sn content of 2% and a Zr content of 1.5%, and the remaining preparation steps are the same as those of Example 1, to prepare sample S-5. The room temperature and high temperature mechanical properties of the sample of Example 5 were tested using the same test method as that of Example 1, and the results are shown in Table 2. It can be seen from Table 2 that the low Sn and Zr contents lead to a significant decrease in the strength and plasticity of the alloy.

[0065] Table 2. Room temperature and high temperature mechanical properties of near-α titanium alloy of Example 5

[0066]

[0067]

[0068] Embodiments 6 to 8

[0069] The difference between Examples 6 to 8 and Example 1 is that, in step S1 of Examples 6 to 8, the raw material powder is provided, and the Zr content is increased to 4wt% by mass percentage, and the Y content is 0wt%, 0.1wt%, and 0.3wt% respectively; the remaining preparation steps are the same as those of Example 1, and near-α titanium alloy samples S-6, S-7, and S-8 are prepared. The room temperature and high temperature mechanical properties of the samples of Examples 6 to 8 are tested by the same test method as in Example 1, and the results are shown in Table 3. It can be seen from Table 3 that the increase in Zr content improves the solid solution strengthening effect of the α phase and can slightly increase the room temperature strength of the alloy, but is not conducive to the plasticity and high temperature strength of the alloy. The addition of Y is beneficial to improving the plasticity of the alloy, but the strength of the alloy is slightly reduced.

[0070] Table 3. Room temperature and high temperature mechanical properties of near-α titanium alloys of Examples 6 to 8

[0071]

[0072] Embodiments 9-10

[0073] The difference between Examples 9 and 10 and Example 1 is that in step S3 of Examples 9 and 10, the spark plasma sintering temperatures are 1100°C and 1000°C respectively during the sintering of the mixed powder; the remaining preparation steps are the same as those of Example 1, and near-α titanium alloy samples S-9 and S-10 are prepared. The room temperature and high temperature mechanical properties of the samples of Examples 9 and 10 are tested using the same test method as that of Example 1, and the results are shown in Table 4. It can be seen from Table 4 that the room temperature strength increases slightly as the sintering temperature decreases, but is not conducive to the plasticity and high temperature tensile strength of the alloy.

[0074] Table 4. Room temperature and high temperature mechanical properties of near-α titanium alloys of Examples 9 to 10

[0075]

[0076]

[0077] Embodiment 11

[0078] The difference between Example 11 and Example 1 is that in step S4. of Example 11, in the heat treatment, the aging temperature is 800°C; the remaining preparation steps are the same as those of Example 1, and a near-α titanium alloy sample S-11 is prepared. The room temperature and high temperature mechanical properties of the sample of Example 1 were tested using the same test method as in Example 1, and the hardness of the sample S-11 was measured to be 415HV1.0, the room temperature tensile strength was 1160MPa, the room temperature elongation was 14.2%, the 550°C tensile strength was 650MPa, and the 550°C elongation was 11.5%. Using the same test method as in Example 1, the alloy metallographic structure of Example 11 was measured as follows: Figure 5 As shown in the figure, due to the high aging temperature, the size of the α sheet increases to 0.5-2 μm, resulting in a significant decrease in the room temperature and high temperature plasticity of the alloy, but it is still a ductile fracture.

[0079] Example 12

[0080] The difference between Example 12 and Example 1 lies in that, in step S3 of Example 12, during the sintering of the mixed powder, the sintering process is as follows: the vacuum degree is controlled to be lower than 20 Pa, and then high-purity argon is filled in so that the pressure in the furnace chamber of the spark plasma sintering furnace is not higher than 20 kPa relative to the atmospheric pressure, the sintering pressure is 50 MPa, the temperature is increased to 1200°C at 100°C / min, and the temperature is kept for 10 minutes. Then, the furnace is cooled to room temperature, and the titanium alloy block is prepared after being taken out and demolded. The remaining preparation steps are the same as those in Example 1, and a near-α titanium alloy sample S-12 is prepared.

[0081] Example 13

[0082] The difference between Example 13 and Example 1 lies in that, in step S3 of Example 13, during the sintering of the mixed powder, the sintering process is as follows: the vacuum degree is controlled to be lower than 20Pa, and then high-purity argon is filled in to make the argon in the furnace chamber flow, and high-purity argon is continuously replenished for protection during the sintering process, the argon flow rate is adjusted to 400ml / min, the sintering pressure is 50MPa, the temperature is increased to 1200℃ at 100℃ / min, and the mixture is kept warm for 10min. Then, the mixture is cooled to room temperature with the furnace, taken out and demolded to obtain a titanium alloy block. The remaining preparation steps are the same as those in Example 1, and a near-α titanium alloy sample S-13 is prepared.

[0083] Embodiment 14

[0084] The difference between Example 14 and Example 1 is that in step S4. of Example 14, during the heat treatment, the titanium alloy block is placed in T β The solution treatment was carried out in a heat treatment furnace at +40°C (1100°C) for 2 hours, and the cooling method was water quenching. The remaining preparation steps were the same as those in Example 1, and a near-α titanium alloy sample S-14 was prepared.

[0085] Embodiment 15

[0086] The difference between Example 15 and Example 1 is that in step S4 of Example 15, in the heat treatment, the aging temperature is 600°C, the aging time is 4 hours, then the temperature is raised to 700°C, the aging is continued for 2 hours, and finally the furnace is cooled to room temperature; the remaining preparation steps are the same as in Example 1, and a near-α titanium alloy sample S-15 is prepared.

[0087] Comparative Examples 1 to 3

[0088] The difference between Comparative Examples 1 to 3 and Example 1 is that in step S1 of Comparative Examples 1 to 3, the Mo content in the raw material powder is increased to 1.5wt%, 2.0wt%, and 2.5wt.%, respectively; the remaining preparation steps are the same as Example 1, and samples C-1, C-2, and C-3 are prepared. The room temperature and high temperature mechanical properties of the samples of Comparative Examples 1 to 3 were tested using the same test method as Example 1. The results are shown in Table 5. It can be seen from Table 5 that the increase in Mo content can significantly improve the room temperature and high temperature strength of the alloy, but the plasticity of the alloy is significantly reduced. The alloy metallographic structure diagram of Comparative Example 3 is shown in Figure 6 As shown in the figure, the Mo content is too high, resulting in a significant increase in the thickness of the α sheet size to 0.35-0.8 μm, and a large amount of primary α phase is precipitated at the grain boundary, resulting in a significant increase in the brittleness of the alloy.

[0089] Table 5. Room temperature and high temperature mechanical properties of near-α titanium alloys of comparative examples 1 to 3

[0090]

[0091] Comparative Example 4

[0092] The difference between Comparative Example 4 and Example 1 is that in step S1. of Comparative Example 4, the Nb content in the raw material powder is increased to 5wt.%; the remaining preparation steps are the same as those of Example 1, and sample C-4 is prepared. The room temperature and high temperature mechanical properties of the sample of Comparative Example 4 are tested by the same test method as that of Example 1, and the results are shown in Table 6. It can be seen from Table 6 that when the Nb content is increased to 5wt.%, the room temperature strength of the alloy is further increased, but the high temperature strength of the alloy is reduced, and the plasticity of the alloy is significantly reduced.

[0093] Table 6. Room temperature and high temperature mechanical properties of near-α titanium alloy of comparative example 4

[0094]

[0095] Comparative Example 5

[0096] The difference between Comparative Example 5 and Example 1 is that, in step S1 of Comparative Example 5, the raw material powder has a Zr content of 5wt%; the remaining preparation steps are the same as those of Example 1, and sample C-5 is prepared. The room temperature and high temperature mechanical properties of the sample of Comparative Example 5 are tested by the same test method as that of Example 1, and the results are shown in Table 7. It can be seen from Table 7 that the increase of Zr content to 5wt% further improves the strength of the alloy, and the plasticity of the alloy is significantly reduced.

[0097] Table 7. Room temperature and high temperature mechanical properties of near-α titanium alloy of comparative example 5

[0098]

[0099] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a near-α titanium alloy, characterized in that: The method comprises the following preparation steps: S1. Providing a raw material powder, wherein the composition of the raw material powder includes, by mass percentage, Al: 5.7-7.0%, Sn: 2-5.5%, Zr: 1.5-4.5%, Mo: 0.3-1.3%, Nb: 0.8-4.5%, Y: 0-0.5%, Si: 0.25-0.55%, and the balance is Ti; S2. The raw powders are mixed, and the raw powders are mixed uniformly by ball milling to obtain a mixed powder; S3. Sintering the mixed powder, sintering the mixed powder to prepare a titanium alloy block; S4. Heat treatment: subjecting the titanium alloy block to solid solution aging treatment to prepare a near-α titanium alloy.

2. The method for preparing a near-α titanium alloy according to claim 1, characterized in that: In step S1, the composition of the raw material powder includes, by mass percentage, Al: 5.7-7.0%, Sn: 3.5-5.5%, Zr: 3.2-4.2%, Mo: 0.3-1.2%, Nb: 0.8-4.2%, Y: 0-0.4%, Si: 0.25-0.55%, and the balance is Ti.

3. The method for preparing a near-α titanium alloy according to claim 1 or 2, characterized in that: In step S1, the raw material powder includes at least one of a single substance powder or an alloy powder of the component, and the powder particle size of the single substance powder or the alloy powder is 1 to 150 μm; and / or, In step S2, the ball milling is carried out in a protective atmosphere, the rotation speed of the ball mill is 250-800 r / min, and the ball milling time is 2-60 h.

4. The method for preparing a near-α titanium alloy according to claim 1 or 2, characterized in that: In step S3, the sintering is performed by spark plasma sintering in a vacuum or protective atmosphere, with a heating rate of 50 to 150° C. / min, a sintering temperature of 1000 to 1300° C., a sintering holding time of 5 to 30 min, and a sintering pressure of 40 to 80 MPa; and / or, In step S4, the solution temperature is 10-40°C above the β-transus temperature, the solution time is 0.5-6h, the aging temperature is 500-800°C, and the aging time is 2-10h.

5. The method for preparing a near-α titanium alloy according to claim 4, characterized in that: In step S3, the sintering is performed by spark plasma sintering in a vacuum or protective atmosphere, with a heating rate of 50 to 150° C. / min, a sintering temperature of 1080 to 1280° C., a sintering holding time of 5 to 30 min, and a sintering pressure of 40 to 80 MPa; and / or, In step S4, the solution temperature is 10-40°C above the β-transus temperature, the solution time is 0.5-6h, the aging temperature is 550-650°C, and the aging time is 2-10h.

6. The method for preparing a near-α titanium alloy according to claim 1 or 2, characterized in that: The microstructure of the near-α titanium alloy prepared in step S4 is a fine α lamella structure and dispersed particles distributed between the fine α lamellae, the thickness of the α lamella structure is between 50nm and 2.5μm, and the dispersed particles are residual β phase and silicide phase, wherein the volume fraction of the α lamella structure accounts for more than 90% of the total volume.

7. The method for preparing a near-α titanium alloy according to claim 6, characterized in that: The thickness of the α-lamellar tissue is between 50 nm and 1 μm.

8. The method for preparing a near-α titanium alloy according to claim 6, characterized in that: The original β grain size of the near-α titanium alloy prepared in step S4 is 5-50 μm.

9. The method for preparing a near-α titanium alloy according to claim 1 or 2, characterized in that: The near-α titanium alloy prepared in step S4 has a room temperature tensile strength of more than 1050 MPa, a room temperature elongation of more than 14%, a tensile strength at 550° C. of more than 650 MPa, and an elongation at 550° C. of more than 10%.

10. A near-alpha titanium alloy obtained by the preparation method of the near-alpha titanium alloy according to any one of claims 1 to 9.

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