Preparation method of high-strength plastic Ti-Al-Nb alloy plate for aerospace craft

Abstract

The invention discloses a preparation method of a high-strength and high-plasticity Ti-Al-Nb alloy plate for an aerospace craft, which comprises the following steps: 1, sequentially heating, preserving heat and forging a Ti-Al-Nb alloy ingot at different temperatures to obtain a Ti-Al-Nb forged plate blank; secondly, the Ti-Al-Nb forged plate blank is rolled after being heated and subjected to heat preservation, and a Ti-Al-Nb alloy hot-rolled plate is obtained; and thirdly, the Ti-Al-Nb alloy hot-rolled plate is subjected to solid solution and aging treatment. According to the preparation method, the finished product is obtained by combining the forging and rolling process with the solid solution aging heat treatment, the preparation efficiency of the Ti-Al-Nb alloy is fully improved and the performance of the Ti-Al-Nb alloy plate is improved by strictly controlling the hot working and heat treatment parameters, so that the prepared Ti-Al-Nb alloy plate has relatively high plasticity and excellent comprehensive mechanical properties, and the prepared Ti-Al-Nb alloy plate is suitable for large-scale production. The method is suitable for aerospace and other fields.

Description

Technical Field

[0001] The invention relates to the technical field of nonferrous metal processing, and in particular to a method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for a spacecraft. Background Art

[0002] In the development and production of spacecraft, "weight reduction" can effectively improve the carrying capacity and work efficiency of spacecraft. At the same time, due to the harsh service conditions of aerospace engines themselves, the materials required for manufacturing them must not only have good room temperature performance, but also have excellent high temperature performance and good processing performance. At present, high-density nickel-based high-temperature alloy materials are mainly used in this field, but high density and large mass have become its obvious disadvantages. Although traditional titanium and titanium alloy materials are widely used in the aerospace field, they can only be used below 600℃ due to limited high-temperature oxidation resistance and creep resistance. Compared with traditional high-temperature titanium alloys, Ti-Al alloys have the characteristics of low density, high specific strength, and good oxidation resistance. They are important materials for high-temperature lightweight structural parts of aviation and aerospace above 650℃. Ti-Al-Nb alloy is an important branch of Ti-Al alloys. Its service temperature is 650℃~750℃, which solves the "thermal barrier" problem of 600℃ for traditional titanium alloys. It has good application prospects in the field of aerospace high-temperature structural materials, especially suitable for manufacturing hot end parts of aerospace engines, such as engine blades and turbine disks. However, the low plasticity, toughness and inherent brittleness of Ti-Al-Nb alloy as an intermetallic compound seriously limit the wide application of Ti-Al-Nb alloy. At the same time, the hot working window of Ti-Al-Nb-based alloy is narrow, its microstructure and properties are easily affected by temperature, and the performance of rolled plates is generally poor. Therefore, how to optimize the composition of Ti-Al-Nb-based alloy and improve its processing properties to improve the plasticity and machinability of Ti-Al-Nb, achieve strong plasticity strength-plasticity matching, and obtain high-performance Ti-Al-Nb-based alloy plates is still a problem that needs to be solved in the field of Ti-Al-Nb alloy plate preparation. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles in view of the deficiencies of the above-mentioned prior art. The present invention adopts a forging + rolling process combined with a solid solution aging heat treatment to obtain a finished product, and by strictly controlling the hot working and heat treatment parameters, the preparation efficiency of the Ti-Al-Nb alloy is fully improved, and the performance of the Ti-Al-Nb alloy plate is improved, so that the prepared Ti-Al-Nb alloy plate has high plasticity and excellent comprehensive mechanical properties, solving the problem of poor plasticity and high processing difficulty of the Ti-Al-Nb alloy plate in the prior art.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles, characterized in that the method comprises the following steps:

[0005] Step 1: Forging

[0006] Step 101, the Ti-Al-Nb alloy ingot is subjected to peeling and sawing treatment, and then heated and kept at 100° C. to 150° C. above the phase transition point, and after being taken out of the furnace, the ingot is subjected to first-fire forging on a fast forging machine, and after forging, the ingot is air-cooled to obtain a first-fire forging ingot;

[0007] Step 102, heating and keeping the first forging blank obtained in step 101 at 100° C. above the phase change point, performing reforging above the phase change point on a fast forging machine after taking out of the furnace, and air cooling after forging to obtain the first reforging blank; the reforging above the phase change point is completed in 1 to 2 fires;

[0008] Step 103, heating and keeping the first reformed forging billet obtained in step 102 at 20°C to 40°C below the phase transformation point, performing reformed forging below the phase transformation point on a fast forging machine after being taken out of the furnace, and air cooling after forging to obtain a second reformed forging billet; the reformed forging below the phase transformation point is completed in 1 to 2 fires;

[0009] Step 104, heating and keeping the second forging blank obtained in step 103 at 80°C to 100°C below the phase transformation point, forging the blank on a fast forging machine after it is taken out of the furnace, and air cooling after forging to obtain a Ti-Al-Nb forging blank;

[0010] Step 2: Hot rolling

[0011] The surface of the Ti-Al-Nb forging slab obtained in step 104 is coated with a high temperature resistant protective coating, and after the protective coating is completely dried, the slab is placed in a heating furnace for heating and heat preservation treatment, and after being taken out of the furnace, the slab is rolled to obtain a Ti-Al-Nb alloy hot-rolled slab; the slab rolling is completed in 1 to 2 fires according to the target thickness of the Ti-Al-Nb alloy hot-rolled slab;

[0012] Step 3: Heat treatment

[0013] The hot-rolled Ti-Al-Nb alloy plate obtained in step 2 is subjected to solution treatment in an atmospheric furnace, and then subjected to aging treatment to obtain a high-strength and plastic Ti-Al-Nb alloy plate; the high-strength and plastic Ti-Al-Nb alloy plate has a tensile strength Rm≥1050MPa, a yield strength Rp0.2≥900MPa, and an elongation after fracture A≥13%.

[0014] The above-mentioned method for preparing a high-strength and ductile Ti-Al-Nb alloy plate for a spacecraft is characterized in that the Ti-Al-Nb alloy ingot in step 101 is composed of the following components in percentage by mass: Al 13% to 14%, Nb 35% to 38%, Mo 0.8% to 1.0%, N≤0.03%, H≤0.01%, O≤0.15%, and the remainder is Ti and unavoidable impurities.

[0015] The above-mentioned method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles is characterized in that a high-temperature resistant protective coating is applied on the surface of the forging object before each forging in step 1.

[0016] The above-mentioned method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles is characterized in that in the forging process described in step one, the deformation mode of each forging is two upsetting and two drawing, and the deformation amount of each forging is more than 115%.

[0017] The above-mentioned method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for a spacecraft is characterized in that, during the forging process described in step one, the heating and holding time of one fire forging is 0.4 to 0.7 times the diameter of the cylindrical Ti-Al-Nb alloy ingot, and the heating and holding time of each remaining fire forging is 0.6 times the thickness of the corresponding forging blank, and the unit of the heating and holding time is min, and the unit of the diameter and thickness is mm.

[0018] The above-mentioned method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles is characterized in that the rolling in step 2 is unidirectional rolling, and the deformation amount per fire is 60% to 80%, and the deformation amount per single pass is 10% to 15%.

[0019] The above-mentioned method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for a spacecraft is characterized in that the temperature of the solid solution treatment in step three is 900°C to 950°C, and the insulation time is 90min to 120min; the temperature of the aging treatment is 650°C to 720°C, the insulation time is 8h to 10h, and the cooling method is air cooling.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. From the perspective of processing technology-heat treatment, the present invention adopts forging + rolling process combined with solid solution aging heat treatment to obtain the finished product. By strictly controlling the hot working and heat treatment parameters, the preparation efficiency of Ti-Al-Nb alloy is fully improved, and the performance of Ti-Al-Nb alloy plate is improved. The prepared Ti-Al-Nb alloy plate has uniform structure, stable performance, high strength-plasticity matching, and good comprehensive mechanical properties.

[0022] 2. The present invention adds Mo element to replace part of Nb element in Ti-Al-Nb alloy, which effectively refines the structure, improves the creep resistance and high temperature performance of the alloy without affecting the yield strength and plasticity of the alloy, and helps to improve the processing performance and comprehensive mechanical properties of Ti-Al-Nb alloy.

[0023] 3. The present invention can preheat the forging anvil and hammer by applying a high-temperature resistant protective coating on the surface of the forging object before each forging, thereby effectively avoiding cooling of the surface of the forged object during the forging process, ensuring its processing performance, and reducing cracking behavior during alloy processing; at the same time, the high-temperature resistant protective coating is converted into a glassy state at high temperature and adheres to the alloy surface, which slows down the oxidation and cracking of the alloy during the forging process, and is beneficial to slowing down the surface cooling phenomenon during the transportation of the alloy from the heating furnace to the forging anvil; in addition, compared with the general forging method, each forging of the present invention can complete a maximum of 2 to 3 upsetting processes, and the forging deformation is larger, the blank is fully deformed, and the preparation efficiency is improved.

[0024] 4. The present invention follows the principle of large deformation in few passes, adopts a rolling method with large plastic deformation, controls the deformation of a single rolling pass to 10% to 15%, and quickly completes the rolling process under high temperature conditions. On the one hand, the preparation efficiency is improved, and on the other hand, the internal distortion energy of the Ti-Al-Nb alloy hot-rolled plate structure is increased through large plastic deformation, providing fine-grained plates for the next step of heat treatment; in addition, the present invention controls the rolling process parameters and the rolling temperature, so that the Ti-Al-Nb alloy hot-rolled plate undergoes large plastic deformation while avoiding local stress concentration that causes cracking or large rolling temperature reversal, thereby ensuring the smooth progress of the rolling process and improving the yield rate.

[0025] 5. The high-strength and plastic Ti-Al-Nb alloy plate prepared by the present invention has a tensile strength Rm≥1050MPa, a yield strength Rp0.2≥900MPa, and an elongation after fracture A≥13% at room temperature, which meets the application requirements in aerospace and other fields such as aerospace engines, rocket thrusters, etc.

[0026] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the preparation method of the high-strength and plastic Ti-Al-Nb alloy plate.

[0028] Figure 2 This is the metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in Example 1 of the present invention.

[0029] Figure 3 This is the metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in Example 2 of the present invention.

[0030] Figure 4 This is the metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in Example 3 of the present invention.

[0031] Figure 5 This is the metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in Example 4 of the present invention. DETAILED DESCRIPTION

[0032] Example 1

[0033] like Figure 1 As shown, this embodiment includes the following steps:

[0034] Step 1: Forging

[0035] Step 101, the Ti-Al-Nb alloy ingot is peeled and sawed to obtain a cylindrical Ti-Al-Nb alloy ingot with a diameter of Φ340 mm, and a high-temperature resistant protective coating is brushed on the surface of the cylindrical Ti-Al-Nb alloy ingot, and then the ingot is placed in a heating furnace and heated and kept at 100° C. above the phase transition point for 136 minutes, and immediately taken out of the furnace and forged on a fast forging machine for single-fire forging, the deformation method is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 125%, and air cooling is performed after the forging is completed to obtain a single-fire forging billet with a size of side length × length of □300 mm×L mm; the Ti-Al-Nb alloy ingot is composed of the following components in percentage by mass: Al 13%, Nb 35%, Mo0.8%, N≤0.03%, H≤0.01%, O≤0.15%, and the balance is Ti and unavoidable impurities;

[0036] Step 102, brushing a high temperature resistant protective coating on the surface of the first fire forging blank obtained in step 101, then putting it into a heating furnace and heating it at 100° C. above the phase change point for 180 minutes, immediately taking it out of the furnace and performing reforming forging above the phase change point on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 125%, after forging, air cooling is performed, and the first reformed forging blank with a size of side length × length of □300mm×Lmm is obtained;

[0037] Step 103, brushing a high temperature resistant protective coating on the surface of the first modified forging billet obtained in step 102, then putting it into a heating furnace and heating and keeping it at 20° C. below the phase change point for 180 minutes, immediately taking it out of the furnace and performing modified forging below the phase change point on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 125%, after forging, air cooling is performed, and the second modified forging billet with a size of side length × length of □300mm×Lmm is obtained;

[0038] Step 104, coating the surface of the second modified forging blank obtained in step 103 with a high temperature resistant protective coating, then placing it in a heating furnace and heating it at 80° C. below the phase transition point for 180 minutes, immediately taking it out of the furnace and forging it on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of the upsetting and drawing forging is 125%, and air cooling is performed after the forging is completed to obtain a Ti-Al-Nb forging blank;

[0039] Step 2: Hot rolling

[0040] The Ti-Al-Nb forging slab obtained in step 104 is subjected to milling treatment to remove surface defects of the slab, and a high-temperature resistant protective coating is applied on the surface. After the protective coating is completely dried, the slab is placed in a heating furnace for heating and heat preservation treatment at 1020° C. for 120 minutes, and then immediately taken out of the furnace for plate rolling. The plate rolling is one-pass unidirectional rolling, and the deformation amount of one pass is 60%, and the deformation amount of a single pass is 10%, to obtain a Ti-Al-Nb alloy hot-rolled plate with a thickness×width×length of δ30mm×423mm×Lmm;

[0041] Step 3: Heat treatment

[0042] The Ti-Al-Nb alloy hot-rolled plate obtained in step 2 is subjected to solution treatment at 900°C for 90 minutes in an atmospheric annealing furnace, air-cooled after being taken out of the furnace, and then subjected to aging treatment at 650°C for 8 hours, air-cooled after being taken out of the furnace, to obtain a Ti-Al-Nb alloy plate.

[0043] According to tests, the tensile strength of the Ti—Al—Nb alloy plate prepared in this embodiment at room temperature is Rm=1147 MPa, the yield strength is Rp0.2=984 MPa, and the elongation after fracture is A=17%.

[0044] Figure 2 The metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in this embodiment is shown in FIG. Figure 2 It can be seen that the microstructure of the Ti-Al-Nb alloy plate after heat treatment is composed of α2 phase, O phase and matrix phase, and the microstructure is uniform.

[0045] Example 2

[0046] like Figure 1 As shown, this embodiment includes the following steps:

[0047] Step 1: Forging

[0048] Step 101, the Ti-Al-Nb alloy ingot is peeled and sawed to obtain a cylindrical Ti-Al-Nb alloy ingot with a diameter of Φ330 mm, and a high-temperature resistant protective coating is brushed on the surface of the cylindrical Ti-Al-Nb alloy ingot, and then the ingot is placed in a heating furnace and heated and kept at 150° C. above the phase transition point for 230 minutes, and immediately taken out of the furnace and subjected to single-fire forging on a fast forging machine, wherein the deformation mode is two upsetting and two drawing, and the deformation amount of the upsetting and drawing forging is 130%, and air cooling is performed after the forging is completed to obtain a single-fire forging billet with a size of side length × length of □300 mm × L mm; the Ti-Al-Nb alloy ingot is composed of the following components in percentage by mass: Al 14%, Nb 38%, Mo 1.0%, N≤0.03%, H≤0.01%, O≤0.15%, and the remainder is Ti and unavoidable impurities;

[0049] Step 102, brushing a high temperature resistant protective coating on the surface of the first fire forging blank obtained in step 101, then putting it into a heating furnace and heating and keeping it at 100° C. above the phase change point for 180 minutes, immediately taking it out of the furnace and performing reforming forging above the phase change point on a fast forging machine, the deformation mode is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 138%, air cooling is performed after the forging is completed, and the heating and keeping, upsetting and drawing forging, and air cooling process are repeated once to obtain a first reformed forging blank with a size of side length × length of □300mm×Lmm;

[0050] Step 103, brushing a high temperature resistant protective coating on the surface of the first modified forging billet obtained in step 102, then putting it into a heating furnace and heating and keeping it at 40° C. below the phase change point for 180 minutes, immediately taking it out of the furnace and performing modified forging below the phase change point on a fast forging machine, the deformation mode is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 132%, air cooling is performed after the forging is completed, and the heating and keeping, upsetting and drawing forging, and air cooling processes are repeated once to obtain a second modified forging billet with a size of side length × length of □300mm×Lmm;

[0051] Step 104, coating the surface of the second modified forging blank obtained in step 103 with a high temperature resistant protective coating, then placing it in a heating furnace and heating it at 100° C. below the phase transition point for 180 minutes, immediately taking it out of the furnace and forging it on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 122%, and air cooling is performed after forging to obtain a Ti-Al-Nb forging blank;

[0052] Step 2: Hot rolling

[0053] The Ti-Al-Nb forging slab obtained in step 104 is subjected to milling treatment to remove surface defects of the slab, and a high-temperature resistant protective coating is applied on the surface. After the protective coating is completely dried, the slab is placed in a heating furnace for heating and heat preservation treatment at 1020° C. for 120 minutes, and then immediately taken out of the furnace for plate rolling. The plate rolling is one-pass unidirectional rolling, and the deformation amount of one pass is 80%, and the deformation amount of a single pass is 15%, to obtain an intermediate hot-rolled plate with a thickness×width×length of δ30 mm×430 mm×L mm;

[0054] The intermediate hot-rolled plate is polished, and a high-temperature resistant protective coating is applied on the surface. After the protective coating is dried, it is placed in a heating furnace for heating and heat preservation at 1010° C. for 40 minutes, and then immediately taken out of the furnace for plate rolling. The plate rolling is one-pass unidirectional rolling, and the deformation amount of one pass is 73%, and the deformation amount of a single pass is 15%, to obtain a Ti-Al-Nb alloy hot-rolled plate with a thickness×width×length of δ8mm×430mm×Lmm;

[0055] Step 3: Heat treatment

[0056] The Ti-Al-Nb alloy hot-rolled sheet obtained in step 2 is subjected to solution treatment by being kept at 950°C for 120 minutes in an atmospheric annealing furnace, air-cooled after being taken out of the furnace, and then subjected to aging treatment by being kept at 720°C for 10 hours, air-cooled after being taken out of the furnace, to obtain a Ti-Al-Nb alloy sheet.

[0057] According to tests, the tensile strength of the Ti—Al—Nb alloy plate prepared in this embodiment at room temperature is Rm=1072 MPa, the yield strength is Rp0.2=917 MPa, and the elongation after fracture is A=23%.

[0058] Figure 3 The metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in this embodiment is shown in FIG. Figure 3 It can be seen that the microstructure of the Ti-Al-Nb alloy plate after heat treatment is composed of α2 phase, O phase and matrix phase, and the microstructure is uniform.

[0059] Example 3

[0060] like Figure 1 As shown, this embodiment includes the following steps:

[0061] Step 1: Forging

[0062] Step 101, the Ti-Al-Nb alloy ingot is peeled and sawed to obtain a cylindrical Ti-Al-Nb alloy ingot with a diameter of Φ330 mm, and a high-temperature resistant protective coating is brushed on the surface of the cylindrical Ti-Al-Nb alloy ingot, and then the ingot is placed in a heating furnace and heated and kept at 120° C. above the phase transition point for 180 minutes, and immediately taken out of the furnace and subjected to one-fire forging on a fast forging machine, wherein the deformation mode is two upsetting and two drawing, and the deformation amount of the upsetting and drawing forging is 130%, and air cooling is performed after the forging is completed to obtain a one-fire forging billet with a size of side length × length of □300 mm × L mm; the Ti-Al-Nb alloy ingot is composed of the following components in percentage by mass: Al 13.5%, Nb 37%, Mo0.9%, N≤0.03%, H≤0.01%, O≤0.15%, and the remainder is Ti and unavoidable impurities;

[0063] Step 102, brushing a high temperature resistant protective coating on the surface of the first fire forging blank obtained in step 101, then putting it into a heating furnace and heating it at 100° C. above the phase change point for 180 minutes, immediately taking it out of the furnace and performing reforming forging above the phase change point on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 136%, after forging, air cooling is performed, and the first reformed forging blank with a size of side length × length of □300mm×Lmm is obtained;

[0064] Step 103, brushing a high temperature resistant protective coating on the surface of the first modified forging billet obtained in step 102, then putting it into a heating furnace and heating and keeping it at 30° C. below the phase change point for 180 minutes, immediately taking it out of the furnace and performing modified forging below the phase change point on a fast forging machine, the deformation mode is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 128%, air cooling is performed after the forging is completed, and the heating and keeping and modified forging below the phase change point and air cooling process are repeated once to obtain a second modified forging billet with a size of side length × length of □300mm×Lmm;

[0065] Step 104, coating the surface of the second modified forging blank obtained in step 103 with a high temperature resistant protective coating, then placing it in a heating furnace and heating it at 90° C. below the phase transition point for 180 minutes, immediately taking it out of the furnace and forging it on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of the upsetting and drawing forging is 130%, and air cooling is performed after the forging is completed to obtain a Ti-Al-Nb forging blank;

[0066] Step 2: Hot rolling

[0067] The Ti-Al-Nb forging slab obtained in step 104 is subjected to milling treatment to remove surface defects of the slab, and a high-temperature resistant protective coating is brushed on the surface. After the protective coating is completely dried, it is placed in a heating furnace for heating and heat preservation treatment at 1000° C. for 120 minutes, and immediately taken out of the furnace for plate rolling. The plate rolling is one-pass unidirectional rolling, and the deformation amount of one pass is 70%, and the deformation amount of a single pass is 12.5%, to obtain a Ti-Al-Nb alloy hot-rolled plate with a thickness×width×length of δ30mm×430mm×Lmm;

[0068] Step 3: Heat treatment

[0069] The Ti-Al-Nb alloy hot-rolled plate obtained in step 2 is subjected to solution treatment at 925°C for 105 minutes in an atmospheric annealing furnace, air-cooled after being taken out of the furnace, and then subjected to aging treatment at 700°C for 9 hours, air-cooled after being taken out of the furnace, to obtain a Ti-Al-Nb alloy plate.

[0070] According to tests, the tensile strength of the Ti—Al—Nb alloy plate prepared in this embodiment at room temperature is Rm=1065 MPa, the yield strength is Rp0.2=910 MPa, and the elongation after fracture is A=19%.

[0071] Figure 4 The metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in this embodiment is shown in FIG. Figure 4 It can be seen that the microstructure of the Ti-Al-Nb alloy plate after heat treatment is composed of α2 phase, O phase and matrix phase, and the microstructure is uniform.

[0072] Example 4

[0073] like Figure 1 As shown, this embodiment includes the following steps:

[0074] Step 1: Forging

[0075] Step 101, the Ti-Al-Nb alloy ingot is peeled and sawed to obtain a cylindrical Ti-Al-Nb alloy ingot with a diameter of Φ330 mm, and a high-temperature resistant protective coating is brushed on the surface of the cylindrical Ti-Al-Nb alloy ingot, and then the ingot is placed in a heating furnace and heated and kept at 120° C. above the phase transition point for 180 minutes, and immediately taken out of the furnace and subjected to single-fire forging on a fast forging machine, wherein the deformation mode is two upsetting and two drawing, and the deformation amount of the upsetting and drawing forging is 130%, and air cooling is performed after the forging is completed to obtain a single-fire forging billet with a size of side length × length of 300 mm × L mm; the Ti-Al-Nb alloy ingot is composed of the following components in percentage by mass: Al 13.8%, Nb 36%, Mo0.85%, N≤0.03%, H≤0.01%, O≤0.15%, and the remainder is Ti and unavoidable impurities;

[0076] Step 102, brushing a high temperature resistant protective coating on the surface of a fire forging blank obtained in step 101, then putting it into a heating furnace and heating and keeping it at 100° C. above the phase change point for 180 minutes, immediately taking it out of the furnace and performing reforging above the phase change point on a fast forging machine, the deformation mode is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 136%, air cooling is performed after forging, and the heating and keeping and reforging above the phase change point and air cooling process are repeated once to obtain a first reforging forging blank with a size of side length × length □300mm×Lmm;

[0077] Step 103, brushing a high temperature resistant protective coating on the surface of the first modified forging billet obtained in step 102, then putting it into a heating furnace and heating and keeping it at 25° C. below the phase change point for 180 minutes, immediately taking it out of the furnace and performing modified forging below the phase change point on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of upsetting and drawing forging is 128%, after forging, air cooling is performed, and the second modified forging billet with the size of side length × length of □300mm×Lmm is obtained;

[0078] Step 104, coating the surface of the second modified forging blank obtained in step 103 with a high temperature resistant protective coating, then placing it in a heating furnace and heating it at 85° C. below the phase transition point for 180 minutes, immediately taking it out of the furnace and forging it on a fast forging machine, the deformation method is two upsetting and two drawing, and the deformation amount of the upsetting and drawing forging is 128%, and air cooling is performed after the forging is completed to obtain a Ti-Al-Nb forging blank;

[0079] Step 2: Hot rolling

[0080] The Ti-Al-Nb forging slab obtained in step 104 is subjected to milling treatment to remove surface defects of the slab, and a high-temperature resistant protective coating is brushed on the surface. After the protective coating is completely dried, it is placed in a heating furnace for heating and heat preservation treatment at 1000° C. for 120 minutes, and immediately taken out of the furnace for plate rolling. The plate rolling is one-pass unidirectional rolling, and the deformation amount of one pass is 65%, and the deformation amount of a single pass is 14%, to obtain a Ti-Al-Nb alloy hot-rolled plate with a thickness×width×length of δ35mm×430mm×Lmm;

[0081] Step 3: Heat treatment

[0082] The Ti-Al-Nb alloy hot-rolled sheet obtained in step 2 is subjected to solution treatment by being kept at 940°C for 110 minutes in an atmospheric annealing furnace, air-cooled after being taken out of the furnace, and then subjected to aging treatment by being kept at 680°C for 10 hours, air-cooled after being taken out of the furnace, to obtain a Ti-Al-Nb alloy sheet.

[0083] According to tests, the Ti—Al—Nb alloy plate prepared in this embodiment has a tensile strength Rm=1165 MPa, a yield strength Rp0.2=950 MPa, and an elongation after fracture A=18% at room temperature.

[0084] Figure 5 The metallographic structure diagram of the Ti-Al-Nb alloy plate prepared in this embodiment is shown in FIG. Figure 5 It can be seen that the microstructure of the Ti-Al-Nb alloy plate after heat treatment is composed of α2 phase, O phase and matrix phase, and the microstructure is uniform.

[0085] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles, characterized in that: The method comprises the following steps: Step 1: Forging Step 101, the Ti-Al-Nb alloy ingot is subjected to peeling and sawing treatment, and then heated and kept at 100° C. to 150° C. above the phase transition point, and after being taken out of the furnace, the ingot is subjected to first-fire forging on a fast forging machine, and after forging, the ingot is air-cooled to obtain a first-fire forging ingot; Step 102, heating and keeping the first forging blank obtained in step 101 at 100° C. above the phase change point, performing reforging above the phase change point on a fast forging machine after taking out of the furnace, and air cooling after forging to obtain the first reforging blank; the reforging above the phase change point is completed in 1 to 2 fires; Step 103, heating and keeping the first reformed forging billet obtained in step 102 at 20°C to 40°C below the phase transformation point, performing reformed forging below the phase transformation point on a fast forging machine after being taken out of the furnace, and air cooling after forging to obtain a second reformed forging billet; the reformed forging below the phase transformation point is completed in 1 to 2 fires; Step 104, heating and keeping the second forging blank obtained in step 103 at 80°C to 100°C below the phase transformation point, forging the blank on a fast forging machine after it is taken out of the furnace, and air cooling after forging to obtain a Ti-Al-Nb forging blank; Step 2: Hot rolling The surface of the Ti-Al-Nb forging slab obtained in step 104 is coated with a high temperature resistant protective coating, and after the protective coating is completely dried, the slab is placed in a heating furnace for heating and heat preservation treatment, and after being taken out of the furnace, the slab is rolled to obtain a Ti-Al-Nb alloy hot-rolled slab; the slab rolling is completed in 1 to 2 fires according to the target thickness of the Ti-Al-Nb alloy hot-rolled slab; Step 3: Heat treatment The hot-rolled Ti-Al-Nb alloy plate obtained in step 2 is subjected to solution treatment in an atmospheric furnace, and then subjected to aging treatment to obtain a high-strength and plastic Ti-Al-Nb alloy plate; the high-strength and plastic Ti-Al-Nb alloy plate has a tensile strength Rm≥1050MPa, a yield strength Rp0.2≥900MPa, and an elongation after fracture A≥13%.

2. The method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles according to claim 1, characterized in that: The Ti-Al-Nb alloy ingot in step 101 is composed of the following components in percentage by mass: Al 13%-14%, Nb 35%-38%, Mo 0.8%-1.0%, N≤0.03%, H≤0.01%, O≤0.15%, and the remainder is Ti and unavoidable impurities.

3. The method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles according to claim 1, characterized in that: Before each forging in step 1, a high temperature resistant protective coating is applied on the surface of the forging object.

4. The method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles according to claim 1, characterized in that: In the forging process described in step 1, the deformation mode of each forging is two upsetting and two drawing, and the deformation amount of each forging is more than 115%.

5. The method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles according to claim 1, characterized in that: During the forging process described in step 1, the heating and holding time of one fire forging is 0.4 to 0.7 times the diameter of the cylindrical Ti-Al-Nb alloy ingot, and the heating and holding time of each remaining fire forging is 0.6 times the thickness of the corresponding forging blank. The unit of the heating and holding time is min, and the unit of the diameter and thickness is mm.

6. The method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles according to claim 1, characterized in that: The rolling in step 2 is unidirectional rolling, and the deformation amount in each pass is 60% to 80%, and the deformation amount in a single pass is 10% to 15%.

7. The method for preparing a high-strength and plastic Ti-Al-Nb alloy plate for aerospace vehicles according to claim 1, characterized in that: The temperature of the solution treatment in step three is 900°C to 950°C, and the insulation time is 90min to 120min; the temperature of the aging treatment is 650°C to 720°C, and the insulation time is 8h to 10h, and the cooling method is air cooling.

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