A Ti65 alloy plate and preparation method thereof

Abstract

The present invention belongs to the field of titanium alloy processing, and specifically relates to a Ti65 alloy plate and a preparation method thereof. The preparation method mainly comprises the following steps: hot deformation-assisted homogenization treatment, fast-rate blanking in the single-phase region, low-temperature upsetting and high-temperature drawing reversing forging, slow-rate forging in the two-phase region, and gradient reversing rolling in the two-phase region. The high-magnification microstructure of the forged Ti65 alloy plate prepared by the present invention is a uniform equiaxed microstructure, with similar composition and microstructure in each region and good overall uniformity; the room temperature and high-temperature mechanical properties of the solution-aged alloy plate are excellent, showing near-isotropy, with the difference in transverse and longitudinal tensile strength not exceeding 15 MPa, and the difference in elongation not exceeding 2%.

Description

Technical Field

[0001] The invention belongs to the field of titanium alloy processing, and particularly relates to a Ti65 alloy plate and a preparation method thereof. Background Art

[0002] Ti65 alloy is a high-temperature titanium alloy developed in recent years by the Institute of Metal Research, Chinese Academy of Sciences based on Ti60 alloy. Its nominal composition is Ti-5.9Al-4.0Sn-3.5Zr-0.3Mo-0.4Si-0.3Nb-2.0Ta-1.0W-0.05C. It is designed for use at a temperature of 600-650°C. It is currently the most mature titanium alloy for high-temperature applications at 650°C. It has excellent thermal strength and thermal stability and is mainly used in hot-end components in the aerospace field.

[0003] As a 10-component titanium alloy, Ti65 alloy exhibits a higher resistance to deformation than other traditional high-temperature titanium alloys. This makes deformation difficult during production and preparation, making it more susceptible to processing damage such as cracks. Deformation parameters fluctuate widely across regions, making it difficult to effectively control microstructure uniformity. Furthermore, the difficulty in refining the original β grains of Ti65 alloy and the severe segregation of alloying elements such as W further degrade the alloy's processing performance and microstructure uniformity, adversely affecting the uniformity and stability of the alloy's mechanical properties. The preparation of Ti65 alloy sheet is particularly affected by these factors, resulting in large compositional fluctuations and significant microstructure differences across regions, leading to pronounced anisotropy in mechanical properties.

[0004] With the rapid development of the aerospace industry, the performance requirements for titanium alloys used in components operating in extreme environments are becoming increasingly stringent. Therefore, for highly alloyed titanium alloys with high deformation resistance, such as Ti65 alloy, a method that can fully control the alloy composition and microstructure uniformity during hot working is the key to optimizing alloy performance.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The object of the present invention is to provide a Ti65 alloy plate and a preparation method thereof; the method first effectively improves the composition uniformity of the alloy ingot through a hot deformation-assisted homogenization treatment, then obtains an alloy slab with uniform structure based on a reversing forging process of low-temperature upsetting and high-temperature drawing, and finally obtains a Ti65 alloy plate with good uniformity of composition, structure and mechanical properties by a simple single reversing rolling process.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for preparing a Ti65 alloy plate comprises the following steps:

[0009] S1. The alloy ingot is heated in the furnace to T1 temperature (10-30℃ above the β phase transformation point) for long-term heat preservation, and then heated to T2 temperature (60-100℃ above T1 temperature) for short-term heat preservation; after the heat preservation is completed, the ingot is taken out of the furnace and shaped into a square billet;

[0010] S2, the billet is returned to the furnace and heated to T2 temperature, and repeated upsetting is performed. After each upsetting, the billet is returned to the furnace and heated to T1 temperature, kept warm for a period of time, and then heated to T2 temperature; the billet is then stretched into an octagonal billet; then the billet is returned to the furnace and heated to T2 temperature, and after being taken out of the furnace, the billet is opened at a rapid rate and air-cooled after forging;

[0011] S3, the billet is returned to the furnace and heated to T3 temperature (80~30℃ below the β phase transformation point), first axially upset, then returned to the furnace and heated to T1 temperature, then taken out of the furnace and laterally stretched into an octagonal billet; then the billet is repeatedly upset and stretched at a slow rate at T3 temperature, with upsetting in the middle and then stretched in the opposite direction, and air-cooled after each forging; then the billet is returned to the furnace and heated to T3 temperature, taken out of the furnace and stretched into an alloy slab;

[0012] S4. The alloy slab is subjected to three-step rolling treatment in sequence: the first step is heating to a temperature of 55-25°C below the β phase transformation point, and then rolling along the length of the slab out of the furnace; the second step is heating to a temperature of 80-50°C below the β phase transformation point, and then rolling along the width of the slab out of the furnace; the third step is heating to a temperature of 60-30°C below the β phase transformation point, and then rolling along the width of the slab out of the furnace; after each rolling step, grinding, slitting, and air cooling to room temperature are performed; finally, after stress relief heat treatment and finishing machining, the Ti65 alloy plate is obtained.

[0013] Furthermore, in step S1, the long-term heat preservation time is (1.6-1.8)×D min, and the short-term heat preservation time is (0.03-0.05)×D min; wherein D is the diameter of the alloy ingot, in mm;

[0014] And / or, the billet is shaped into a square billet with a height-to-diameter ratio of 1.8 to 2.0 after being taken out of the furnace.

[0015] Further, in step S2, upsetting is repeated 2 to 3 times;

[0016] and / or, the deformation amount of each upsetting is 10-20%;

[0017] and / or, the final forging temperature after each upsetting is not lower than the β transformation point;

[0018] And / or, after each upsetting, the temperature is first raised to T1 in the furnace, and the holding time is (0.03~0.05)×H min, where H is the minimum thickness of the blank, in mm;

[0019] And / or, the billet is further drawn into an octagonal billet with a height-to-diameter ratio of 1.8 to 2.0.

[0020] Furthermore, in step S2, the rapid blanking is specifically performed by upsetting and pulling; the upsetting deformation amount of the upsetting and pulling is 50-60%;

[0021] And / or, the deformation rate of rapid blanking is 60~70 mm / s.

[0022] Furthermore, in step S3, the deformation amount of axial upsetting is 35-45%;

[0023] And / or, the octagonal billet is laterally drawn out of the furnace to have a height-to-diameter ratio of 1.8 to 2.0.

[0024] Furthermore, in step S3, the billet is subjected to a slow rate upsetting and drawing process at temperature T3 and repeated 3 to 4 times;

[0025] and / or, the upsetting deformation of each slow-speed upsetting and pulling operation is 45-55%;

[0026] And / or, the deformation rate of each slow-speed upsetting and drawing is 15~25 mm / s.

[0027] Furthermore, in step S3, the alloy slab is drawn out of the furnace to a thickness of 140-160 mm; the deformation amount of a single drawing is ≤30%.

[0028] Furthermore, in step S4, the cumulative deformations of the first step of length rolling, the second step of width rolling, and the third step of width rolling are 70-80%, 40-50%, and 30-40% respectively; and the deformation of each single pass is ≤10%;

[0029] and / or, the rolling rates of the first step of length rolling, the second step of width rolling, and the third step of width rolling are controlled within a range of 0.8-1.0 m / s;

[0030] And / or, the thickness of the prepared Ti65 alloy plate is 10-12 mm.

[0031] In addition, the present invention also provides a Ti65 alloy plate, which is prepared by the above-mentioned preparation method.

[0032] Furthermore, the Ti65 alloy plate has a uniform equiaxed microstructure in the forged state, and the difference in transverse tensile strength between room temperature (20-25°C) and 650°C in the solution-aged state does not exceed 15 MPa, and the difference in elongation does not exceed 2%; the difference in longitudinal tensile strength between room temperature and 650°C does not exceed 15 MPa, and the difference in elongation does not exceed 2%.

[0033] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0034] (1) The preparation method of the present invention utilizes a thermal deformation process during the homogenization and heat preservation process, which introduces a large number of dislocations into the alloy. These dislocations destroy the ordered structure of the crystal, thereby reducing the potential barrier for nearby atomic migration, which is beneficial for diffusion, especially for low-content alloying elements. Therefore, even refractory elements such as W with low self-diffusion coefficients can fully diffuse through the fast channels provided by dislocations, achieving effective homogenization of the alloy ingot and facilitating the control of microstructure uniformity during subsequent alloy processing.

[0035] (2) The use of fast rate and large deformation in the single-phase region can inhibit the dynamic recovery of the alloy, fully break up its cast structure and refine the β grains; combining the forging method of small deformation upsetting in the two-phase region + reversing drawing in the single-phase region, the inhibitory effect of α phase on the growth of β grains is fully utilized to further refine the β grains, while avoiding the occurrence of local temperature rise that destroys the uniformity of the alloy structure; during the forging process in the two-phase region, slow rate and large deformation are used to ensure that the lamellar α phase is fully recrystallized and spheroidized to obtain a uniform equiaxed structure.

[0036] (3) Based on the alloy slab with good composition and microstructure uniformity obtained through the above process, the target plate can be obtained by three-pass rolling and one-time reversal. The rolling process is simple and the processing loss is small. Combined with the optimized rolling parameters, the microstructure uniformity of the alloy is effectively controlled.

[0037] (4) The Ti65 alloy plate prepared by the method of the present invention has good composition uniformity, and the maximum difference in the content of all elements in each region does not exceed 0.03%; the microstructure is also good, and the high-magnification microstructure composition and morphology of each region are similar; at the same time, after solution aging treatment, the tensile properties at room temperature (20-25°C) and 650°C are nearly identical, with the difference in transverse and longitudinal tensile strength not exceeding 15 MPa, and the difference in elongation not exceeding 2%. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. Among them:

[0039] Figure 1 Schematic diagram of the sampling area for the composition and structure analysis of the Ti65 plate prepared in Example 1;

[0040] Figure 2 This is a metallographic image of the high-magnification microstructure of the Ti65 plate prepared in Example 1;

[0041] Figure 3 This is a metallographic image of the high-magnification microstructure of the Ti65 plate prepared in Example 2;

[0042] Figure 4This is a metallographic image of the high-magnification microstructure of the Ti65 plate prepared in Example 3;

[0043] Figure 5 This is a metallographic image of the high-magnification microstructure of the Ti65 plate prepared in Comparative Example 1. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. The process parameters for which specific conditions are not specified in the following examples are generally in accordance with conventional conditions.

[0045] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0047] It should be noted that the T1 temperature in the present invention is 10-30°C above the β phase transition point, the T2 temperature is 60-100°C above the T1 temperature, and the T3 temperature is 80-30°C below the β phase transition point.

[0048] The "β phase transition point" refers to the critical temperature at which the α phase (close-packed hexagonal structure) and the β phase (body-centered cubic structure) transform into each other during heating or cooling. The β phase transition point of Ti65 alloy is approximately 1040°C.

[0049] According to a first aspect of the present invention, a Ti65 alloy plate and a preparation method thereof are provided. The preparation method has the following synergistic effects: first, a homogenization treatment assisted by hot deformation in a single-phase region is performed, that is, multiple small deformation upsettings are performed during the homogenization and heat preservation process before the ingot is opened, thereby introducing a large number of dislocations and promoting element diffusion (especially refractory elements such as W), providing a compositionally uniform ingot for subsequent slab preparation, and facilitating the regulation of slab microstructure uniformity during the preparation process; then, a fast-rate large-deformation opening is performed in the single-phase region to break up the as-cast microstructure and refine the β grains; a combination of low-temperature (two-phase region) axial upsetting and high-temperature (single-phase region) lateral drawing is performed to fully utilize the inhibitory effect of the α phase on β grain growth to further refine the β grains while avoiding local temperature rise that damages the microstructure uniformity of the alloy; a slow-rate large-deformation forging is performed in the two-phase region to ensure sufficient recrystallization and spheroidization of the lamellar α phase to obtain a uniform equiaxed microstructure; and finally, a three-stage gradient reversing rolling is performed to effectively regulate the uniformity of the alloy microstructure and avoid processing damage such as cracks. Through the synergistic effect of hot deformation-assisted homogenization treatment, fast-rate blanking in the single-phase zone, low-temperature upsetting and high-temperature drawing reversing forging, slow-rate forging in the two-phase zone, and gradient reversing rolling in the two-phase zone, the whole process control of Ti65 alloy plates from composition homogenization to organization optimization is achieved, and finally finished plates with good composition and organization uniformity are obtained.

[0050] The specific technical solutions of the present invention are as follows:

[0051] Step (1) heating the alloy ingot to 10-30°C (T1 temperature) above the β phase transformation point and holding the temperature for a long time, then continuing to heat the ingot to 60-100°C (T2 temperature) above the T1 temperature and holding the temperature for a short time, after which the ingot is taken out of the furnace and shaped into a square billet with a height-to-diameter ratio of about 1.8-2.0, and returning the hot billet to the furnace after forging and heating it to the T2 temperature;

[0052] Step (2) the alloy billet is taken out of the furnace and subjected to rough deformation, the deformation amount is controlled at 10% to 20%, the final forging temperature is not lower than the β phase transformation point, the hot material is returned to the furnace after forging, and the temperature is kept at T1 for a period of time and then raised to T2; repeat step (2) 2 to 3 times;

[0053] Step (3) the alloy billet is taken out of the furnace and drawn into an octagonal billet with a height-to-diameter ratio of about 1.8 to 2.0, returned to the furnace and heated to T2 temperature, taken out of the furnace and subjected to a rapid upsetting and drawing process with the deformation controlled at 50% to 60%, and air-cooled after forging;

[0054] Step (4) heating the alloy billet to 80-30°C below the β phase transformation point (T3 temperature), taking it out of the furnace and performing axial upsetting, controlling the deformation amount to 35%-45%, returning the hot material to the furnace and heating it to T1 temperature, taking it out of the furnace and laterally stretching it into an octagonal billet with a height-to-diameter ratio of about 1.8-2.0;

[0055] Step (5) heating the alloy billet to T3 temperature, upsetting and drawing at a slow rate after taking it out of the furnace, controlling the deformation amount to 45%~55%, and air cooling after forging; repeating step (5) 3~4 times, upsetting in the middle fire and then reversing and drawing; if the number of repetitions is 3 times, then upsetting in the second period and then reversing and drawing; if the number of repetitions is 4 times, then upsetting in the third period and then reversing and drawing.

[0056] In step (6), the alloy billet is heated to a temperature of T3, and is drawn out of the furnace to a slab having a thickness δ of about 140 to 160 mm. The deformation of a single drawing does not exceed 30%, and the difference between the cumulative deformation in the length direction and the width direction of the slab does not exceed 10%. Specifically, the cumulative deformation when the billet is drawn to the target slab length is A, and the cumulative deformation when it is drawn to the target slab width is B, and A-B≤10%.

[0057] Step (7) heating the alloy slab to a temperature of 55-25°C below the β phase transformation point, taking it out of the furnace and rolling it along the length (rolling along the slab drawing length direction), with a cumulative deformation of 70%-80%, a single-pass deformation of no more than 10%, grinding and slitting after rolling, and air cooling to room temperature;

[0058] Step (8) heating the alloy slab to a temperature of 80-50°C below the β phase transformation point, taking it out of the furnace and rolling it along the width (rolling along the slab width direction), with a cumulative deformation of 40%-50%, and a single-pass deformation of no more than 10%, grinding and slitting it after rolling, and air cooling it to room temperature;

[0059] Step (9) heating the alloy slab to a temperature of 60-30°C below the β phase transformation point, taking it out of the furnace and rolling it along the width (rolling along the slab width direction), with a cumulative deformation of 30%-40%, and a single-pass deformation of no more than 10%, grinding and slitting it after rolling, and air cooling it to room temperature;

[0060] Step (10) is to obtain a finished Ti65 alloy plate with a thickness of 10 to 12 mm through stress relief heat treatment and finishing machining. Preferably, the slab is heated to 700°C and kept at this temperature for 2 hours for stress relief heat treatment.

[0061] It should be noted that, in the present invention, “upsetting” and “drawing” without mentioning a specific direction refer to axial upsetting, which is the most common upsetting direction in this field.

[0062] In the above preparation method, as a preferred embodiment, in step S1, the long-term holding time is (1.6-1.8)×D min, and the short-term holding time is (0.03-0.05)×D min; wherein D is the diameter of the alloy ingot, in mm;

[0063] In the above preparation method, as a preferred embodiment, in step (2), after each upsetting, the temperature is first raised to T1 in the furnace, and the holding time is (0.03~0.05)×H min, where H is the minimum thickness of the blank, in mm; more preferably, the insulation coefficient after the first deformation is 0.03 mm / min, the second is 0.04 mm / min, and the third and subsequent times is 0.05 mm / min.

[0064] In the above preparation method, as a preferred embodiment, in step (3), the deformation rate of the fast rate-upsetting-pulling is 60-70 mm / s; preferably, in step (5), the deformation rate of the slow rate-upsetting-pulling is 15-25 mm / s.

[0065] In the above preparation method, as a preferred embodiment, the rolling rate in steps (7) to (9) is controlled at 0.8 to 1.0 m / s, and the furnace is allowed to be reheated during rolling.

[0066] According to a second aspect of the present invention, a Ti65 alloy plate is provided, produced by the preparation method described in the first aspect. The Ti65 alloy plate produced by this method exhibits good compositional uniformity, with the maximum difference in all element contents across regions not exceeding 0.03%. It also exhibits good structural uniformity, with similar high-magnification microstructure and morphology across regions. Furthermore, the tensile properties at room temperature (20-25°C) and at 650°C are nearly identical, with the difference in transverse and longitudinal tensile strength not exceeding 15 MPa, and the difference in elongation not exceeding 2%.

[0067] The present invention will be described in detail below with reference to the accompanying drawings and embodiments of the present invention. Each example is provided by way of explanation of the present invention and does not limit the present invention. In fact, it will be clear to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature shown or described as part of one embodiment can be used in another embodiment to produce yet another embodiment. Therefore, it is intended that the present invention encompasses such modifications and variations within the scope of the appended claims and their equivalents.

[0068] Example 1

[0069] Example 1: A Ti65 alloy ingot with a size of Φ500×1260 mm and an alloy composition of Ti-5.7Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.0Ta-0.9W (wt.%) was selected. The β-phase transition point of the alloy was approximately 1040°C. The specific implementation steps were as follows:

[0070] Step 1) heating the alloy ingot to 1070°C and holding it for 800 minutes, then continuing to heat it to 1170°C and holding it for 15 minutes. After the holding period, the ingot is taken out of the furnace and shaped into a square billet (500 mm thick × 990 mm long) with an aspect ratio of about 2.0. After forging, the hot billet is returned to the furnace and heated to 1170°C.

[0071] Step 2) The alloy billet is subjected to upsetting deformation after removal from the furnace, with a deformation amount of 20% and a final forging temperature of not less than 1040°C. After forging, the hot material is returned to the furnace and kept at 1070°C for 15-20 minutes before being heated to 1170°C. Step 2) is repeated twice, with the return and holding times adjusted to 20-25 minutes and 30-35 minutes, respectively.

[0072] Step 3) The alloy billet is drawn out of the furnace into an octagonal billet with a height-to-diameter ratio of about 2.0, returned to the furnace and heated to 1170°C, and then quickly upset and drawn out of the furnace with a deformation of 60% and a deformation rate of 70 mm / s. After forging, it is air-cooled.

[0073] Step 4) The alloy billet is heated to 1010°C, removed from the furnace and subjected to axial upsetting with a deformation of 45%. The hot billet is then returned to the furnace and heated to 1070°C, removed from the furnace and laterally elongated into an octagonal billet with a height-to-diameter ratio of approximately 2.0.

[0074] Step 5) The alloy billet is heated to 1010°C, taken out of the furnace, and subjected to a slow rate of upsetting and drawing, with a deformation amount of 55% and a deformation rate of 25 mm / s. After forging, the billet is air-cooled; Step 5) is repeated 4 times, and during the third repetition, the upsetting is reversed by 90° and drawn;

[0075] Step 6) The alloy billet is heated to 1010°C, taken out of the furnace and drawn into a slab with a thickness of about 150 mm. The deformation of a single drawing is 25% to 30%, and the difference between the cumulative deformation in the width direction and the length direction of the slab is about 10%.

[0076] Step 7) heating the alloy slab to 1015°C, rolling it out of the furnace along the length, with a cumulative deformation of 70% and a single-pass deformation of 8% to 10%. After rolling, grinding and slitting are performed, and air cooling is performed to room temperature.

[0077] Step 8) heating the alloy slab to 990°C, rolling it along the width of the slab after it is taken out of the furnace, with a cumulative deformation of 50% and a single-pass deformation of 8% to 10%. After rolling, the slab is ground and cut, and then air-cooled to room temperature.

[0078] Step 9) heating the alloy slab to 1010°C, rolling it along the width of the slab after it is taken out of the furnace, with a cumulative deformation of 40% and a single-pass deformation of 8% to 10%. After rolling, the slab is ground and cut, and then air-cooled to room temperature.

[0079] Step 10) The slab is heated to 700°C and kept at this temperature for 2 hours for stress relief heat treatment, and then subjected to finishing machining and other steps to obtain a finished Ti65 alloy plate with a thickness of 12 mm.

[0080] Samples were taken from each area of ​​the Ti65 alloy plate prepared in Example 1 (e.g. Figure 1 As shown in Table 1, it can be found that the maximum difference in the content of all elements in each area does not exceed 0.03%, and the composition uniformity is good. Samples were taken from plate areas 4 and 5 for tissue analysis, as shown in Table 1. Figure 2 As shown in Table 2, the microstructures of the two regions are essentially identical, and the high-magnification microstructures are uniform, equiaxed, and exhibit good structural uniformity. Mechanical properties of the plates after solution aging treatment were analyzed, as shown in Table 2. The differences in transverse and longitudinal tensile strength at room temperature and 650°C do not exceed 15 MPa, and the differences in elongation do not exceed 2%, demonstrating near-isotropy.

[0081] Table 1 Chemical composition of Ti65 alloy plate in Example 1 (wt.%)

[0082]

[0083] Table 2 Mechanical properties of Ti65 alloy plate in Example 1

[0084]

[0085] Among them, R m is the tensile strength, R p0.2 is the yield strength, A is the elongation after fracture, and Z is the reduction of area. Composition analysis tests are conducted in accordance with GB / T 4698, room temperature tensile tests are conducted in accordance with GB / T 228.1-2021, and high temperature tensile tests are conducted in accordance with GB / T 228.2-2015.

[0086] Example 2

[0087] Example 2: The specifications of the Ti65 alloy ingot are: Φ600×1650 mm, the alloy composition is Ti-5.7Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.0Ta-0.9W (wt.%), and the β phase transition point of the alloy is about 1040°C. The specific implementation steps are as follows:

[0088] Step 1) heating the alloy ingot to 1050°C and holding it for 900 minutes, then continuing to heat it to 1150°C and holding it for 30 minutes. After the holding period, the ingot is taken out of the furnace and shaped into a square billet (640 mm thick × 1135 mm long) with a height-to-diameter ratio of about 1.8. After forging, the hot billet is returned to the furnace and heated to 1150°C.

[0089] Step 2) The alloy billet is subjected to upsetting deformation after removal from the furnace, with a deformation amount of 10% and a final forging temperature of not less than 1040°C. After forging, the hot material is returned to the furnace and kept at 1050°C for 20-25 minutes before being heated to 1150°C. Step 2) is repeated three times, wherein the return to the furnace and holding time are adjusted to 25-30 minutes, 35-40 minutes, and 40-45 minutes, respectively.

[0090] Step 3) The alloy billet is drawn out of the furnace into an octagonal billet with a height-to-diameter ratio of about 1.8, returned to the furnace and heated to 1150°C, and then quickly upset and drawn out of the furnace with a deformation of 50% and a deformation rate of 60 mm / s. After forging, it is air-cooled.

[0091] Step 4) The alloy billet is heated to 960°C, removed from the furnace and subjected to axial upsetting with a deformation of 35%. The hot billet is then returned to the furnace and heated to 1050°C, removed from the furnace and laterally elongated into an octagonal billet with a height-to-diameter ratio of approximately 1.8.

[0092] Step 5) The alloy billet is heated to 960°C, taken out of the furnace, and subjected to a slow rate of upsetting and drawing, with a deformation of 45% and a deformation rate of 15 mm / s. After forging, the billet is air-cooled; Step 5) is repeated three times, and during the second upsetting, the direction is reversed by 90° and drawn;

[0093] Step 6) The alloy billet is heated to 960°C, taken out of the furnace and drawn into a slab with a thickness of approximately 140 mm. The deformation of the slab during a single drawing is 25% to 30%, and the difference between the cumulative deformation in the width direction and the length direction is approximately 8%.

[0094] Step 7) heating the alloy slab to 985°C, rolling it out of the furnace along the length, with a cumulative deformation of 80% and a single-pass deformation of 8% to 10%. After rolling, grinding and slitting are performed, and air cooling is performed to room temperature.

[0095] Step 8) heating the alloy slab to 960°C, rolling it along the width of the slab after it is taken out of the furnace, with a cumulative deformation of 40% and a single-pass deformation of 8% to 10%. After rolling, the slab is ground and cut, and then air-cooled to room temperature.

[0096] Step 9) heating the alloy slab to 980°C, rolling it along the width of the slab after it is taken out of the furnace, with a cumulative deformation of 30% and a single-pass deformation of 8% to 10%. After rolling, the slab is ground and cut, and then air-cooled to room temperature.

[0097] Step 10) The slab is heated to 700°C and kept at this temperature for 2 hours for stress relief heat treatment, and then subjected to finishing machining and other steps to obtain a finished Ti65 alloy plate with a thickness of 10 mm.

[0098] Samples were taken from each area of ​​the Ti65 alloy plate prepared in Example 2 (e.g. Figure 1As shown in Table 3, it can be found that the maximum difference in the content of all elements in each area does not exceed 0.03%, and the composition uniformity is good. Samples were taken from plate areas 4 and 5 for tissue analysis, as shown in Table 3. Figure 3 As shown in Table 4, the microstructures of the two regions are essentially identical, and the high-magnification microstructures are uniform, equiaxed, and exhibit good structural uniformity. Mechanical properties of the plates after solution aging treatment were analyzed, as shown in Table 4. The differences in transverse and longitudinal tensile strengths at room temperature and 650°C do not exceed 15 MPa, and the differences in elongation do not exceed 2%, demonstrating near-isotropy.

[0099] Table 3 Chemical composition of Ti65 alloy plate in Example 2 (wt.%)

[0100]

[0101] Table 4 Mechanical properties of Ti65 alloy plate in Example 2

[0102]

[0103] Example 3

[0104] Example 3: The specifications of the Ti65 alloy ingot are: Φ450×1080 mm, the alloy composition is Ti-5.7Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.0Ta-0.9W (wt.%), and the β phase transition point of the alloy is about 1040°C. The specific implementation steps are as follows:

[0105] Step 1) heating the alloy ingot to 1060°C and holding it for 810 minutes, then continuing to heat it to 1120°C and holding it for 20 minutes. After the holding period, the ingot is taken out of the furnace and shaped into a square billet (455 mm thick and 825 mm long) with a height-to-diameter ratio of about 1.8. After forging, the hot billet is returned to the furnace and heated to 1120°C.

[0106] Step 2) The alloy billet is subjected to upsetting deformation after removal from the furnace, with a deformation amount of 15% and a final forging temperature of not less than 1040°C. After forging, the hot material is returned to the furnace and kept at 1060°C for 15-20 minutes before being heated to 1120°C. Step 2) is repeated twice, wherein the return to the furnace and holding time are adjusted to 20-25 minutes and 25-30 minutes respectively.

[0107] Step 3) The alloy billet is drawn out of the furnace into an octagonal billet with a height-to-diameter ratio of about 1.8, returned to the furnace and heated to 1120°C, and then quickly upset and drawn out of the furnace with a deformation of 50% and a deformation rate of 60 mm / s. After forging, it is air-cooled.

[0108] Step 4) The alloy billet is heated to 990°C, removed from the furnace and subjected to axial upsetting with a deformation of 40%. The hot billet is then returned to the furnace and heated to 1060°C, removed from the furnace and laterally elongated into an octagonal billet with a height-to-diameter ratio of approximately 1.8.

[0109] Step 5) The alloy billet is heated to 990°C, taken out of the furnace, and subjected to a slow rate of upsetting and drawing, with a deformation amount of 50% and a deformation rate of 15 mm / s. After forging, the billet is air-cooled; Step 5) is repeated 4 times, and during the third repetition, the upsetting is reversed by 90° and drawn;

[0110] Step 6) The alloy billet is heated to 990°C, taken out of the furnace and drawn into a slab with a thickness of approximately 150 mm. The deformation of the slab during a single drawing is 25% to 30%, and the difference between the cumulative deformation in the width direction and the length direction is approximately 8%.

[0111] Step 7) heating the alloy slab to 1010°C, rolling it out of the furnace along the length, with a cumulative deformation of 80% and a single-pass deformation of 8% to 10%. After rolling, grinding and slitting are performed, and air cooling is performed to room temperature.

[0112] Step 8) heating the alloy slab to 980°C, rolling it out of the furnace along the width, with a cumulative deformation of 45% and a single-pass deformation of 8% to 10%. After rolling, grinding and slitting are performed, and air cooling is performed to room temperature.

[0113] Step 9) heating the alloy slab to 990°C, rolling it along the width of the slab after it is taken out of the furnace, with a cumulative deformation of 30% and a single-pass deformation of 8% to 10%. After rolling, the slab is ground and cut, and then air-cooled to room temperature.

[0114] Step 10) The slab is heated to 700°C and kept at this temperature for 2 hours for stress relief heat treatment, and then subjected to finishing machining and other steps to obtain a finished Ti65 alloy plate with a thickness of 12 mm.

[0115] Samples were taken from each area of ​​the Ti65 alloy plate prepared in Example 3 (e.g. Figure 1 As shown in Table 5, it can be found that the maximum difference in the content of all elements in each area does not exceed 0.03%, and the composition uniformity is good. Samples were taken from plate areas 4 and 5 for tissue analysis, as shown in Table 5. Figure 4 As shown in Table 6, the microstructures of the two regions are essentially identical, and the high-magnification microstructures are uniform, equiaxed, and exhibit good structural uniformity. Mechanical properties of the plates after solution aging treatment were analyzed, as shown in Table 6. The differences in transverse and longitudinal tensile strength at room temperature and 650°C do not exceed 15 MPa, and the differences in elongation do not exceed 2%, demonstrating near-isotropic properties.

[0116] Table 5 Chemical composition of Ti65 alloy plate in Example 3 (wt.%)

[0117]

[0118] Table 6 Mechanical properties of Ti65 alloy plate in Example 3

[0119]

[0120] Comparative Example 1

[0121] Comparative Example 1: The specifications of the Ti65 alloy ingot are: Φ500×1185 mm, the alloy composition is Ti-5.7Al-4.0Sn-3.5Zr-0.5Mo-0.4Si-0.3Nb-1.0Ta-0.9W (wt.%), and the β phase transition point of the alloy is about 1040°C. The specific implementation steps are as follows:

[0122] Step 1) heating the alloy ingot to 1170°C in a furnace and holding the temperature for 16 hours, then performing upsetting and drawing after removal from the furnace, with a deformation amount of 60% and a deformation rate of 60 mm / s, and air cooling after forging;

[0123] Step 2) heating the alloy billet to 1070°C, performing upsetting and drawing after removal from the furnace, with a deformation amount of 45% and a deformation rate of 50 mm / s, followed by air cooling after forging; repeating step 2) once;

[0124] Step 3) The alloy billet is heated to 1010°C, and after being taken out of the furnace, the billet is subjected to upsetting and drawing, with a deformation amount of 40% and a deformation rate of 45 mm / s. After forging, the billet is air-cooled; Step 3) is repeated 4 times, and after the second repetition, the forging direction is reversed;

[0125] Step 4) heating the alloy billet to 1010°C, taking it out of the furnace and drawing it into a slab with a thickness of about 150 mm, with a single drawing deformation of 25% to 30%;

[0126] Step 5) heating the alloy slab to 1015°C, rolling it out of the furnace and rolling it along the length to a cumulative deformation of 60%, grinding and slitting it after rolling, and air cooling it to room temperature;

[0127] Step 6) heating the alloy slab to 1015°C, rolling the slab along the width of the slab out of the furnace to a cumulative deformation of 55%, grinding and slitting the slab after rolling, and air cooling the slab to room temperature;

[0128] Step 7) heating the alloy slab to 1015°C, rolling it along the width of the slab after it is taken out of the furnace, with a cumulative deformation of 50%, grinding and slitting it after rolling, and air cooling it to room temperature;

[0129] Step 8) The slab is heated to 700°C and kept at this temperature for 2 hours for stress relief heat treatment, and then subjected to finishing machining and other steps to obtain a finished Ti65 alloy plate with a thickness of 12 mm.

[0130] Samples were taken from each area of ​​the Ti65 alloy plate prepared in Comparative Example 1 (e.g. Figure 1As shown in Table 7, it can be found that the maximum difference in the content of some elements in each area is more than 0.1%, and the composition uniformity is poor compared with Examples 1 to 3. Samples of plate areas 4 and 5 were taken for tissue analysis, as shown in Table 7. Figure 5 As shown in Table 8, significant microstructural differences can be observed between the two regions, with the primary α phase also unevenly distributed, and the microstructural uniformity is also poor compared to Examples 1 to 3. Mechanical property analysis of the plate after solution aging treatment reveals that the maximum difference in transverse and longitudinal tensile strength between room temperature and 650°C exceeds 40 MPa, and the maximum difference in elongation exceeds 5%, indicating anisotropy.

[0131] Table 7 Chemical composition of Ti65 alloy plate in Comparative Example 1 (wt.%)

[0132]

[0133] Table 8 Mechanical properties of Ti65 alloy plate in Comparative Example 1

[0134]

[0135] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a Ti65 alloy plate, characterized in that: The following steps are involved: S1, heating the alloy ingot to T1 temperature for long-term heat preservation, and then heating to T2 temperature for short-term heat preservation; After the insulation is completed, the billet is taken out of the furnace and shaped into a square billet; S2, the billet is returned to the furnace and heated to T2 temperature, and repeated upsetting is performed. After each upsetting, the billet is returned to the furnace and heated to T1 temperature, kept warm for a period of time, and then heated to T2 temperature; the billet is then stretched into an octagonal billet; then the billet is returned to the furnace and heated to T2 temperature, and after being taken out of the furnace, the billet is opened at a rapid rate and air-cooled after forging; S3, the billet is returned to the furnace and heated to T3 temperature, first axially upsetting, then returned to the furnace and heated to T1 temperature, and then taken out of the furnace and laterally stretched into an octagonal billet; then the billet is repeatedly subjected to slow upsetting and stretching at T3 temperature, with upsetting in the middle and then reversing and stretching, and air cooling after each forging; then the billet is returned to the furnace and heated to T3 temperature, and taken out of the furnace and stretched into an alloy slab; S4. The alloy slab is subjected to three-step rolling treatment in sequence: the first step is heating to a temperature of 55-25°C below the β phase transformation point, and then rolling along the length of the slab out of the furnace; the second step is heating to a temperature of 80-50°C below the β phase transformation point, and then rolling along the width of the slab out of the furnace; the third step is heating to a temperature of 60-30°C below the β phase transformation point, and then rolling along the width of the slab out of the furnace; after each rolling step, grinding, slitting, and air cooling to room temperature are performed; finally, after stress relief heat treatment and finishing machining, the Ti65 alloy plate is obtained.

2. The method for preparing the Ti65 alloy plate according to claim 1, wherein: In step S1, the long-term holding time is (1.6-1.8)×D min, and the short-term holding time is (0.03-0.05)×D min; wherein D is the diameter of the alloy ingot, in mm; And / or, the billet is shaped into a square billet with a height-to-diameter ratio of 1.8 to 2.0 after being taken out of the furnace.

3. The method for preparing the Ti65 alloy plate according to claim 1, wherein: In step S2, upsetting is repeated 2 to 3 times; and / or, the deformation amount of each upsetting is 10-20%; and / or, the final forging temperature after each upsetting is not lower than the β transformation point; And / or, after each upsetting, the temperature is first raised to T1 in the furnace, and the holding time is (0.03~0.05)×H min, where H is the minimum thickness of the blank, in mm; And / or, the billet is further drawn into an octagonal billet with a height-to-diameter ratio of 1.8 to 2.

0.

4. The method for preparing the Ti65 alloy plate according to claim 1, wherein: In step S2, the rapid blanking process is specifically performed by upsetting and pulling; the upsetting deformation of the upsetting and pulling process is 50-60%. And / or, the deformation rate of rapid blanking is 60~70 mm / s.

5. The method for preparing the Ti65 alloy plate according to claim 1, wherein: In step S3, the deformation amount of axial upsetting is 35~45%; And / or, the octagonal billet is laterally drawn out of the furnace to have a height-to-diameter ratio of 1.8 to 2.

0.

6. The method for preparing the Ti65 alloy plate according to claim 1, wherein: In step S3, the billet is subjected to a slow rate of upsetting and drawing at temperature T3, and the number of repetitions is 3 to 4 times; and / or, the upsetting deformation of each slow-speed upsetting and pulling operation is 45-55%; And / or, the deformation rate of each slow-speed upsetting and drawing is 15~25 mm / s.

7. The method for preparing the Ti65 alloy plate according to claim 1, wherein: In step S3, the alloy slab is drawn out of the furnace to a thickness of 140-160 mm; the deformation of a single drawing is ≤30%.

8. The method for preparing the Ti65 alloy plate according to claim 1, wherein: In step S4, the cumulative deformation of the first step of length rolling, the second step of width rolling, and the third step of width rolling are 70-80%, 40-50%, and 30-40% respectively; the deformation of each single pass is ≤10%; and / or, the rolling speeds of the first step of length rolling, the second step of width rolling, and the third step of width rolling are controlled within a range of 0.8-1.0 m / s; And / or, the thickness of the prepared Ti65 alloy plate is 10-12 mm.

9. A Ti65 alloy plate, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. The Ti65 alloy plate according to claim 9, characterized in that: The Ti65 alloy plate has a uniform equiaxed microstructure in the forged state, and the difference in transverse tensile strength between room temperature and 650°C in the solution-aged state does not exceed 15 MPa, and the difference in elongation does not exceed 2%; the difference in longitudinal tensile strength between room temperature and 650°C does not exceed 15 MPa, and the difference in elongation does not exceed 2%.

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