Non-sheath preparation method and application of Ti2AlNb-based alloy plate

Abstract

The invention discloses a non-sheath preparation method and application of a Ti2AlNb-based alloy plate, and belongs to the technical field of titanium alloy plate preparation. The invention relates to a non-sheath preparation method of a Ti2AlNb-based alloy plate, which comprises the following steps: smelting a Ti2AlNb alloy raw material to obtain a Ti2AlNb cast ingot, carrying out near-isothermal cogging forging on the Ti2AlNb cast ingot in a B2 phase region, and then carrying out near-isothermal multidirectional forging in an alpha < 2 + > B2 phase region to obtain a forged cake; and the forging cake is subjected to heat treatment in an alpha < 2 + > O + B2 phase region and an O + B2 phase region in sequence, then non-sheathed hot rolling is conducted in the alpha < 2 + > O + B2 phase region or the alpha < 2 + > B2 phase region, and the Ti2AlNb-based alloy plate is obtained. According to the method, the Ti2AlNb-based alloy plate which is good in surface quality, free of edge cracks, excellent in plate shape and excellent in mechanical property can be prepared under the condition of no wrapping sleeve.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy plate preparation, and in particular to a non-jacketed preparation method and application of a Ti2AlNb-based alloy plate. Background Art

[0002] In recent years, the aerospace industry has developed rapidly. In order to meet the high requirements of this field, high-temperature structural materials need to develop rapidly. Ti2AlNb alloy is a new intermetallic compound in recent years. It has the characteristics of low density, large elastic modulus, creep performance, oxidation resistance, strong high-temperature strength, fracture toughness and low density. It is one of the materials with great application potential. Therefore, the preparation of Ti2AlNb alloy sheet is very important to the aerospace industry.

[0003] However, the Ti2AlNb-based alloy prepared by the ingot metallurgical method has a coarse cast structure and poor mechanical properties, and cannot be directly used to form parts. It needs to be forged to refine the grains. Ti2AlNb-based alloy forging is mostly selected in the B2 single-phase region to prevent defects caused by large deformation resistance inside the billet during the forging process, thereby causing the forging to fail. However, after forging in the B2 phase region, the higher temperature will accelerate the migration speed of the grain boundary, causing the grains to grow further, which is not conducive to subsequent hot forming. In addition, due to the narrow hot working range of Ti2AlNb alloy and poor elongation, direct hot rolling causes the temperature drop rate of the plate to be fast, the deformation resistance increases sharply, the plastic deformation ability decreases accordingly, and the cracking tendency of the plate increases. Therefore, the sheet rolling of Ti2AlNb generally adopts the method of jacket rolling. However, the surface quality of the sheet prepared by jacket rolling is poor, and the jacket rolling process is complicated and the preparation cost is high, which is not conducive to the large-scale production of Ti2AlNb-based alloy sheets, and limits the utilization and development of materials. Therefore, it is urgent to find a high-quality and efficient preparation method for Ti2AlNb-based alloy sheets. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a Ti2AlNb-based alloy plate without a jacket and its application, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: a method for preparing a Ti2AlNb-based alloy plate without a jacket, comprising the following steps:

[0007] After smelting the Ti2AlNb alloy raw material, a Ti2AlNb ingot is obtained, the Ti2AlNb ingot is subjected to near-isothermal blanking forging in the B2 phase region, and then subjected to near-isothermal multi-directional forging in the α2+B2 phase region to obtain a forged cake;

[0008] The forged cake is heat treated in the α2+O+B2 phase region and the O+B2 phase region in sequence, and then hot rolled without a jacket in the α2+O+B2 phase region or the α2+B2 phase region to obtain the Ti2AlNb-based alloy plate.

[0009] Furthermore, the Ti2AlNb ingot comprises the following raw materials, in atomic percentage: Ti: 50-57%, Al: 18-25% and Nb: 22-27%.

[0010] Furthermore, the method for preparing the forging cake comprises the following steps:

[0011] The forging die is heated to 900-1000°C, and the Ti2AlNb ingot is kept in the B2 phase region for 20-50 minutes, and then subjected to large-reduction near-isothermal billet forging, with a reduction of 50-60%, a reduction rate of 0.5-2 mm / s, an axial direction, and one forging time; then, near-isothermal multi-directional forging is performed in the α2+B2 phase region, with a reduction of 40-50%, a reduction rate of 0.5-2 mm / s, and 3-6 forging times, each time the direction of the reduction is 90° to the previous one, and before each forging, the ingot is placed in a furnace and kept warm for 10-40 minutes to obtain a forged cake;

[0012] Furthermore, when preparing the forging cake, the temperature of the B2 phase region should be controlled within the range of 1040-1090°C;

[0013] Furthermore, when preparing the forging cake, the temperature of the α2+B2 phase region should be controlled within the range of 950-1060°C.

[0014] Near-isothermal forging can ensure temperature stability during the forging process, preventing the increase in deformation resistance and forging failure caused by temperature drop. Multi-directional forging (by flattening the grains in different directions) can cause a large amount of dynamic recrystallization of the grains, achieving the effect of grain refinement. The use of temperature reduction forging can introduce the α2 phase through phase transformation to produce a pinning effect, achieving the effect of grain refinement.

[0015] The use of near-isothermal multi-directional forging can effectively eliminate internal defects, while avoiding performance degradation caused by coarse grains, which is beneficial to subsequent rolling forming.

[0016] Furthermore, the heat treatment method includes: performing a solution treatment in the α2+O+B2 phase region for 20 to 40 minutes, and then performing an aging treatment in the O+B2 phase region for 1.5 to 2.5 hours.

[0017] Furthermore, during heat treatment, the temperature of the α2+O+B2 phase region should be controlled within the range of 900°C to 1020°C;

[0018] Furthermore, during heat treatment, the temperature of the O+B2 phase region should be controlled within the range of 750-960°C.

[0019] The primary lath O phase and the secondary needle-shaped O phase are introduced through solution treatment and aging treatment respectively, achieving the effect of grain refinement. The microstructure that is beneficial to the subsequent hot rolling can be regulated through heat treatment, further ensuring the realization of the non-jacketed rolling process.

[0020] Open forging in the B2 phase region at a higher temperature and a larger reduction can avoid forging failure caused by defects inside the cast state. Large reduction can introduce more shear bands in the coarse grains so that more recrystallization bands can be generated in the subsequent heat preservation forging and the coarse grains can be separated to ensure the final grain refinement. After that, the temperature is lowered to the α2+B2 phase region for near-isothermal multi-directional forging, which can further refine the grains by flattening the grains and producing phase transformation, and introduce the α2 phase to prevent the subsequent growth of the refined grains. The solution aging heat treatment after forging precipitates the primary lath O phase and the secondary needle-shaped O phase in the organization respectively. The intervention of appropriate amounts of O phase and α2 phase can improve the problem of incoordination of deformation between α2 phase and B2 phase at high temperature to a certain extent, so that the three-phase organization has good mechanical properties at high temperature (i.e. rolling temperature). The α2 phase and O phase distributed at the grain boundary ensure the strength at the B2 grain boundary, and the O phase can improve the elongation at high temperature.

[0021] Furthermore, the method of hot rolling without jacket comprises: using ABAQUS finite element software to simulate the rolling temperature to determine the rolling temperature parameters, using an induction heating device to heat the roller to 480-530° C., and then performing hot rolling without jacket after keeping the roller in the α2+O+B2 phase region for 10-30 minutes, the linear speed of the roller is 0.1-0.2 m / s, the reduction is 20-30%, and the total reduction is 80-90%;

[0022] Alternatively, the rolling temperature parameters are determined by simulating the rolling temperature using ABAQUS finite element software, the rollers are heated to 480-530°C using an induction heating device, and then hot-rolled without a jacket after being kept in the α2+B2 phase region for 10-30 minutes, the linear speed of the rollers is 0.1-0.2 m / s, the reduction is 20-30%, and the total reduction is 80-90%.

[0023] Furthermore, during hot rolling without a jacket, the temperature of the α2+O+B2 phase region should be controlled within the range of 900-1020°C;

[0024] Furthermore, during hot rolling without jacketing, the temperature of the α2+B2 phase region should be controlled within the range of 950 to 1060°C.

[0025] The rolling temperature was selected to be α2+B2 two-phase region and α2+O+B2 three-phase region. After hot rolling in the B2 single-phase region, the coarse grains caused a significant decrease in strength and elongation, while the elongation dropped sharply due to the lack of B2 phase in the O+α2 phase hot rolling. After rolling in the α2+B2 two-phase region, the microstructure was the matrix of B2 phase and α2 phase. The pinning effect provided by the α2 phase reduced the grain growth and strengthened the grain boundary strength, which ultimately gave the plate good strength and excellent elongation. After hot rolling in the α2+O+B2 three-phase region, the O phase was introduced, which further improved the strength and slightly decreased the elongation, and its high-temperature performance was further optimized. After the plates were rolled at the two temperatures, high-performance plates could be obtained without post-rolling heat treatment, which was convenient for direct application and secondary cold rolling of the plates.

[0026] The present invention realizes the non-jacket rolling of Ti2AlNb by a near-isothermal rolling method, optimizes and selects the appropriate rolling and roller temperature range by extracting and analyzing the temperature field results through ABAQUS finite element simulation, and then realizes the technical purpose of preparing Ti2AlNb-based alloy plates with high quality and high efficiency without a jacket by using the near-isothermal rolling technology. In addition, the near-isothermal rolling method can still ensure a good forming rate and mechanical properties of the rolled plate after avoiding the disadvantages of the cumbersome jacket rolling assembly process, which is conducive to the industrial large-scale production of Ti2AlNb-based alloy plates.

[0027] Furthermore, the unjacketed preparation method further includes, after the heat treatment and before the unjacketed hot rolling, grinding the plate and spraying an anti-oxidation coating.

[0028] The second technical solution of the present invention: a Ti2AlNb-based alloy plate prepared by the above-mentioned preparation method.

[0029] The third technical solution of the present invention: an application of the above-mentioned Ti2AlNb-based alloy sheet in the aerospace field.

[0030] The present invention discloses the following technical effects:

[0031] (1) The method of the present invention can prepare Ti2AlNb-based alloy plates with good surface quality, no edge cracks, excellent plate shape and excellent mechanical properties without a sheath.

[0032] (2) The present invention determines the rolling temperature parameters (roller temperature and rolling temperature) under the guidance of ABAQUS simulation, heats the rolls by an induction heating device, and successfully prepares Ti2AlNb-based alloy plates with excellent performance without the need for sheathing treatment, thus realizing an integrated control strategy of smelting-forging / heat treatment-near-isothermal rolling without sheathing-high-performance plates.

[0033] (3) The method of the present invention has the advantages of saving material costs, simplifying the process flow, reducing surface defects, improving plate quality, and improving production efficiency, and can realize large-scale production of Ti2AlNb-based alloy plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 is the phase diagram of Ti-22Al-xNb;

[0036] Figure 2 This is a schematic diagram of the temperature distribution profile of the plate during the near-isothermal rolling simulation using ABAQUS;

[0037] Figure 3 This is a microstructure morphology diagram of the forging blank obtained by heat treatment in step 3 of Example 1, wherein a is a low magnification and b is a high magnification;

[0038] Figure 4 This is a macroscopic morphology of the Ti2AlNb-based alloy plate prepared in Example 1;

[0039] Figure 5 The microstructure morphology of the Ti2AlNb-based alloy plate prepared in Example 1, wherein a is the BC image after EBSD treatment, and b is the phase image after EBSD treatment;

[0040] Figure 6 The mechanical property curves of the Ti2AlNb-based alloy plates prepared in Examples 1 to 4. DETAILED DESCRIPTION

[0041] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0042] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0043] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0044] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0045] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0046] The first aspect of the present invention provides a method for preparing a Ti2AlNb-based alloy plate without a jacket, comprising the following steps:

[0047] Step 1, smelting Ti2AlNb alloy raw material to obtain Ti2AlNb ingot;

[0048] In a specific embodiment of the present invention, the preparation method of the Ti2AlNb ingot includes: smelting the Ti2AlNb alloy raw material twice in a vacuum induction suspension melting furnace to obtain two small ingots, remelting the two small ingots to obtain a large ingot, and then remelting and casting the large ingot to obtain the Ti2AlNb ingot.

[0049] Due to the large porosity between the raw materials during the smelting process, the raw materials are smelted twice, and then the two small ingots are remelted to ensure uniform composition.

[0050] Melting in a vacuum induction levitation melting furnace can avoid crucible contamination and has the characteristics of controllable superheat and high melting efficiency.

[0051] In a specific embodiment of the present invention, the Ti2AlNb ingot includes the following raw materials, in atomic percentage: Ti: 50-57%, Al: 18-25% and Nb: 22-27%.

[0052] In a specific embodiment of the present invention, the Ti2AlNb alloy raw material includes titanium sponge, aluminum-niobium alloy and niobium particles.

[0053] Step 2, performing near-isothermal forging of the Ti2AlNb ingot in the B2 phase region, and then performing near-isothermal multi-directional forging in the α2+B2 phase region to obtain a forged cake.

[0054] In a specific embodiment of the present invention, the preparation method of the forging cake includes: heating the forging die to 900-1000°C, then keeping the Ti2AlNb ingot at 1040-1090°C in the B2 phase region for 20-50min, and then performing large reduction near-isothermal blanking forging, the reduction amount is 50-60%, the reduction rate is 0.5-2mm / s, the reduction direction is axial, and the number of forgings is 1 time; then performing near-isothermal multi-directional forging at 950-1060°C in the α2+B2 phase region, the reduction amount is 40-50%, the reduction rate is 0.5-2mm / s, the number of forgings is 3-6 times, each reduction direction is 90° with the previous one, and before each forging, it is placed in a furnace and kept warm for 10-40min to obtain a forging cake.

[0055] Before each forging pass, the ingot and the pad in direct contact with the ingot during forging are heated to the specified temperature respectively, and forging is performed after keeping them warm. This can ensure the forging temperature, make the forging more uniform, and reduce the cracking of the forgings.

[0056] When forging in the B2 phase region, the temperature increases and the deformation resistance decreases. Therefore, controlling a larger reduction can ensure grain refinement while preventing internal defects from causing forging failure.

[0057] Step 3, heat treating the forging cake in the α2+O+B2 phase region and the O+B2 phase region to obtain a forging blank.

[0058] In a specific embodiment of the present invention, the preparation method of the forging blank includes: first subjecting the forging cake to a solution treatment at 900°C to 1020°C in the α2+O+B2 phase region for 20 to 40 minutes, then subjecting the forging cake to an aging treatment at 750 to 960°C in the O+B2 phase region for 1.5 to 2.5 hours, and then furnace cooling.

[0059] The forging cake is first solution treated in the α2+O+B2 phase region to precipitate the lath O phase, and then aged in the O+B2 phase region to precipitate an appropriate amount of needle-shaped O phase.

[0060] The microstructure of the forging blank is composed of matrix B2 phase, a large amount of primary lath O phase and secondary needle-shaped O phase and α2 phase distributed at the grain boundaries.

[0061] A large amount of fine O phase helps to improve the high-temperature yield strength and elongation in room temperature and high-temperature tensile tests. The B2 phase ensures plasticity, while the pinning effect of the α2 phase ensures that the grains do not further coarsen.

[0062] Step 4, hot rolling the forging blank without jacket in the α2+O+B2 phase region or the α2+B2 phase region to obtain a Ti2AlNb-based alloy plate.

[0063] In a specific embodiment of the present invention, the method of unclad hot rolling includes: using ABAQUS finite element software to simulate the rolling temperature to determine the rolling temperature parameters, using an induction heating device to heat the roll to 480-530°C, and then keeping the forging blank at 900-1020°C in the α2+O+B2 phase region for 10-30 minutes before performing unclad hot rolling (unclad near-isothermal hot rolling), the linear speed of the roll is 0.1-0.2 m / s, the reduction is 20-30%, and the total reduction is 80-90%.

[0064] Alternatively, ABAQUS finite element software is used to simulate the rolling temperature to determine the rolling temperature parameters, the rolls are heated to 480-530°C using an induction heating device, and then the forged billet is kept at 950-1060°C (α2+B2 phase region) for 10-30 minutes before being hot rolled without a jacket (nearly isothermal hot rolling without a jacket), the linear speed of the rolls is 0.1-0.2 m / s, the reduction is 20-30%, and the total reduction is 80-90%.

[0065] After the first rolling, the plate is returned to the furnace for insulation for 10 to 30 minutes to ensure the rolling temperature of the plate and prevent the plate from cracking during rolling. After the insulation is completed, rolling is carried out again with a reduction of 20 to 30%. This process is repeated, and air cooling is carried out after rolling. After cooling to room temperature, a hot-rolled plate is obtained.

[0066] The microstructure of the Ti2AlNb-based alloy sheet is composed of an elongated B2 phase and an α2 phase distributed along the grain boundaries, and the grain size is about 30 μm.

[0067] Using the temperature of O+B2 phase region for hot rolling will generate too many laths and needle-shaped O phases, which is not conducive to the room temperature plasticity of the alloy plate; using the temperature of B2 single phase region will cause the B2 phase grains to grow and form a coarse grain structure which is not conducive to the mechanical properties of the plate; therefore, the optimal hot rolling temperature is selected as 970~1030℃, that is, the partial temperature phase region of α2+O+B2 and α2+B2. The pinning effect of α2 on B2 phase can inhibit the growth of grains, and at the same time, an appropriate amount of O phase can be introduced, which is beneficial to the high temperature plasticity of the plate.

[0068] The heating temperature of the roll is determined by the guidance of the finite element simulation results of ABAQUS. The thermal simulation found that the rolling temperature is in the stable zone of 940-1050℃, and the initial temperature of the plate during the rolling process without a sheath is 1020℃. When the roll temperature is 500℃, the plate temperature is about 970℃ during the rolling process without a sheath. When the roll temperature drops to 450℃, the plate temperature drops to about 940℃, falling into the instability zone. When the roll temperature rises to 550℃, the plate temperature drops to about 980℃, the heating rate slows down significantly, and the effect is not obvious. For economic and environmental considerations, the roll temperature is selected to be 480-530℃, and the roll temperature can make the temperature uniform during hot rolling, ensure the uniformity of the organization, prevent edge cracking during rolling, and enable the hot-rolled plate to obtain excellent mechanical properties without heat treatment, realizing the process of high-performance hot preparation of Ti2AlNb-based alloy plates without sheaths.

[0069] By using an induction heating device to heat the rolls, the temperature drop of the sheet during the non-cladding rolling process is similar to that of the cladding rolling process, and the non-cladding rolling of the Ti2AlNb-based alloy sheet can be achieved through near-isothermal hot rolling. In addition, the uniform temperature of the sheet during the rolling process ensures the uniformity of the structure, which can effectively prevent edge cracking during the rolling process, and the sheet after hot rolling obtains excellent mechanical properties without heat treatment. This method can also make it possible for Ti2AlNb-based alloy sheets to achieve industrial large-scale production.

[0070] In a specific embodiment of the present invention, it also includes that after the heat treatment and before the un-jacketed hot rolling, the forging blank is wire-cut to a plate with a thickness of 5 to 10 mm, and then the plate is polished and sprayed with an anti-oxidation coating.

[0071] The cutting chamfer size of the controlled wire cutting is R4mm, which can prevent stress concentration and cracking at the sharp corners during hot rolling of the plate.

[0072] In a specific embodiment of the present invention, the thickness of the Ti2AlNb-based alloy plate is 0.9-1.3 mm.

[0073] In a specific embodiment of the present invention, the spray thickness of the anti-oxidation coating is 0.05 mm to 0.1 mm.

[0074] Spraying anti-oxidation coating can prevent the surface of Ti2AlNb alloy sheet from being excessively oxidized.

[0075] The second aspect of the present invention provides a Ti2AlNb-based alloy plate prepared by the above preparation method.

[0076] The third aspect of the present invention provides an application of the above-mentioned Ti2AlNb-based alloy sheet in the aerospace field.

[0077] The phase diagram of Ti-22Al-xNb is shown in Figure 1 ; ABAQUS simulation of the temperature distribution of the plate during near-isothermal rolling is shown in the cross-sectional diagram Figure 2 .

[0078] Example 1

[0079] A method for preparing a Ti2AlNb-based alloy plate without a jacket:

[0080] Step 1: according to the atomic ratio of Ti: 53%, Al: 22%, Nb: 25%, titanium sponge, high-purity niobium and aluminum-niobium alloy are put into a crucible placed in a vacuum induction suspension melting furnace twice (2.3 kg each time, a total of 4.6 kg), and argon is backfilled for melting after vacuuming; the raw materials are first baked at a power of 100 kW for 1 minute, and then the power is increased until the raw materials are red hot around and then kept warm for 2 minutes until the center of the raw materials is red, and the power is increased again until droplets appear around the raw materials and then kept warm for 2 minutes. At this time, the raw materials gradually melt. After the raw materials are completely melted, the power is increased to make the melt temperature reach 50°C above the melting point of the alloy, and the temperature is kept for 10 minutes. The melt is stirred under electric stirring. The composition is uniform under the action of the action, and two small ingots are obtained as the crucible cools; the two small ingots are then remelted once, and a large ingot is obtained as the crucible cools; the large ingot is remelted and poured, the inner diameter of the pouring mold is 75 mm, the shrinkage cavities of the poured ingot are cut off and the surface defects are removed, and finally a Ti2AlNb ingot with a diameter of 73 mm and a height of 90 mm is obtained, the actual composition is Ti-22Al-25Nb, the B2 phase temperature is 1055-1090°C, the α2+B2 phase temperature is 1010-1055°C; the α2+O+B2 phase temperature is 930-1010°C; the O+B2 phase temperature is 750-930°C.

[0081] Step 2, heating the forging die to 990°C, and then keeping the Ti2AlNb ingot at 1060°C in the B2 phase region for 30 minutes, and then performing large-reduction near-isothermal forging, with a reduction of 55%, a reduction rate of 1 mm / s, an axial direction, and 1 forging number; then performing near-isothermal multi-directional forging at 1010°C in the α2+B2 phase region, with a reduction of 45% for each forging, a reduction rate of 1 mm / s, and 3 forging times. Each reduction direction is 90° to the previous one, and before each forging, it is placed in a furnace and kept warm for 30 minutes to obtain a forging cake with a size of 135×75×40 mm.

[0082] Step 3, first subjecting the forging cake to a solution treatment at 950°C in the α2+O+B2 phase region for 30 min, and then subjecting it to an aging treatment at 800°C in the O+B2 phase region for 2 h, followed by furnace cooling, wire cutting into a plate with a thickness of 7 mm, and cutting and chamfering with a chamfer size of R4 mm. Subsequently, the plate is ground and polished using a grinder to grind out fresh metal, and a 0.1 mm thick Al2O3 anti-oxidation coating is sprayed to obtain a forging blank.

[0083] The microstructure morphology of the forging blank is shown in Figure 3 , where (a) is low magnification and (b) is high magnification.

[0084] Step 4, using ABAQUS finite element software to simulate the rolling temperature to determine the rolling temperature parameters, using an induction heating device to heat the roll to 500°C, hot rolling the forged billet at 1020°C in the α2+B2 phase region, keeping warm for 20 minutes before each hot rolling to ensure uniform temperature before rolling, the reduction per pass is 23±0.3%, the linear speed of the roll is 0.15m / s, the number of rolling passes is 7, the final total reduction is 84±0.2%, and the thickness is 1.10-1.13mm; air cooling is used for cooling, and the Ti2AlNb-based alloy sheet is obtained after cooling to room temperature.

[0085] The macroscopic morphology of Ti2AlNb based alloy sheet is shown in Figure 4 ; The microstructure morphology of Ti2AlNb-based alloy sheet is shown in Figure 5 , Figure 5 In the figure, a is the BC diagram after EBSD treatment, and b is the phase diagram after EBSD treatment; the mechanical properties curve of Ti2AlNb-based alloy sheet is shown in Figure 6 .

[0086] The tensile strength of the Ti2AlNb-based alloy plate prepared in this embodiment is 1070 MPa, and the elongation is 8%.

[0087] Example 2

[0088] The same as Example 1, the only difference is that step 4 is specifically as follows: heating the rolling roller to 500°C, and then hot rolling the forging billet at 990°C in the α2+O+B2 phase region, keeping warm for 20 minutes before each hot rolling to ensure uniform temperature before rolling, the reduction in each pass is 23±0.1%, the linear speed of the rolling roller is 0.15m / s, the number of rolling passes is 7, the total reduction is 84±0.2%, and the final thickness is 1.10~1.13mm.

[0089] Mechanical properties curve of Ti2AlNb based alloy sheet is shown in Figure 6 .

[0090] The tensile strength of the Ti2AlNb-based alloy plate prepared in this embodiment is 1200 MPa, and the elongation is 6%.

[0091] Example 3

[0092] A method for preparing a Ti2AlNb-based alloy plate without a jacket:

[0093] Step 1 is the same as Example 1, except that the actual atomic ratio of Ti, Al and Nb is 55% Ti, 18% Al and 27% Nb. The B2 phase temperature is 1040-1090°C, the α2+B2 phase temperature is 1020-1040°C, the α2+O+B2 phase temperature is 955-1020°C and the O+B2 phase temperature is 750-955°C.

[0094] Step 2, heating the forging die to 990°C, and then keeping the Ti2AlNb ingot at 1090°C in the B2 phase region for 40 minutes, and then performing large-reduction near-isothermal forging, with a reduction of 60%, a reduction rate of 2 mm / s, an axial direction, and 1 forging time; then performing near-isothermal multi-directional forging at 1030°C in the α2+B2 phase region, with a reduction of 50% for each forging pass, a reduction rate of 1 mm / s, and 3 forging times. Each reduction direction is 90° to the previous one, and before each forging, it is placed in a furnace and kept warm for 40 minutes to obtain a forging cake with a size of 135×75×40 mm.

[0095] Step 3, first subjecting the forging cake to a solution treatment at 970°C in the α2+O+B2 phase region for 20 min, then subjecting it to an aging treatment at 850°C in the O+B2 phase region for 1.5 h, then furnace cooling, wire cutting into a plate with a thickness of 7 mm, cutting and chamfering, and the chamfering size is R4 mm, and then using a grinder to grind and polish the above-mentioned plate to grind out fresh metal, and spraying a 0.05 mm thick Al2O3 anti-oxidation coating to obtain a forging blank.

[0096] Step 4, using ABAQUS finite element software to simulate the rolling temperature to determine the rolling temperature parameters, using an induction heating device to heat the roll to 480°C, hot rolling the forged billet at 1030°C in the α2+B2 phase region, keeping warm for 30 minutes before each hot rolling to ensure uniform temperature before rolling, the reduction per pass is 24±0.1%, the linear speed of the roll is 0.1m / s, the number of rolling passes is 7, the final total reduction is 85.4±0.2%, and the final thickness is 1.00-1.02mm; air cooling is used for cooling, and the Ti2AlNb-based alloy sheet is obtained after cooling to room temperature.

[0097] Mechanical properties curve of Ti2AlNb based alloy sheet is shown in Figure 6 .

[0098] The tensile strength of the Ti2AlNb-based alloy plate prepared in this embodiment is 1080 MPa, and the elongation is 9%.

[0099] Example 4

[0100] A method for preparing a Ti2AlNb-based alloy plate without a jacket:

[0101] Step 1 is the same as Example 1, except that the actual atomic ratio of Ti, Al and Nb is 55% Ti, 19% Al and 26% Nb. The B2 phase temperature is 1045-1090°C, the α2+B2 phase temperature is 1010-1045°C, the α2+O+B2 phase temperature is 960-1010°C and the O+B2 phase temperature is 750-960°C.

[0102] Step 2, heat the forging die to 990°C, then keep the Ti2AlNb ingot at 1080°C in the B2 phase region for 40 minutes for large-reduction near-isothermal forging, with a reduction of 60%, a reduction rate of 0.5 mm / s, an axial direction, and 1 forging time; then perform near-isothermal multi-directional forging at 1015°C in the α2+B2 phase region, with a reduction of 40% for each forging pass, a reduction rate of 1 mm / s, 3 forging times, each reduction direction is 90° to the previous one, and keep it in a furnace for 40 minutes before each forging to obtain a forging cake with a size of 135×75×40 mm.

[0103] Step 3, first subjecting the forging cake to a solution treatment at 970°C in the α2+O+B2 phase region for 40 min, and then subjecting it to an aging treatment at 750°C in the O+B2 phase region for 2.5 h, followed by furnace cooling, and wire cutting into a plate with a thickness of 7 mm, and cutting and chamfering, with a chamfer size of R4 mm, and then using a grinder to grind and polish the plate to obtain fresh metal, and spraying a 0.05 mm thick Al2O3 anti-oxidation coating to obtain a forging blank.

[0104] Step 4, using ABAQUS finite element software to simulate the rolling temperature to determine the rolling temperature parameters, using an induction heating device to heat the roll to 530°C, hot rolling the forged billet at 1030°C in the α2+B2 phase region, keeping warm for 30 minutes before each hot rolling to ensure uniform temperature before rolling, the reduction per pass is 24±0.1%, the linear speed of the roll is 0.1m / s, the number of rolling passes is 7, the total reduction is 85.4±0.2%, and the final thickness is 1.00-1.02mm; air cooling is used for cooling, and the Ti2AlNb-based alloy sheet is obtained after cooling to room temperature.

[0105] Mechanical properties curve of Ti2AlNb based alloy sheet is shown in Figure 6 .

[0106] The tensile strength of the Ti2AlNb-based alloy plate prepared in this embodiment is 1000 MPa and the elongation is 10%.

[0107] Comparative Example 1

[0108] The same as Example 1, the only difference is that step 3 is specifically: cutting the forging cake into a plate with a thickness of 7 mm, cutting and chamfering, the chamfering size is R4 mm, then using a grinder to grind and polish the above plate to grind out fresh metal, spraying Al2O3 anti-oxidation coating with a thickness of 0.1 mm, and obtaining a forging blank.

[0109] The hot-rolled plate has serious edge cracks.

[0110] Comparative Example 2

[0111] The same as Example 1, the only difference is that the temperature of the rolling roller in step 4 is 450°C. After simulation, the temperature of the plate during rolling is about 980°C, which falls into the instability zone of thermal simulation.

[0112] The plate after hot rolling showed more cracking.

[0113] Comparative Example 3

[0114] The same as Example 1, the only difference is that in step 4, specifically: using ABAQUS finite element software to simulate the rolling temperature to determine the rolling temperature parameters, using an induction heating device to heat the roller to 500°C, hot rolling the forging billet at 1060°C in the B2 phase region, keeping warm for 20 minutes after each hot rolling, ensuring that the temperature is uniform before rolling, the reduction per pass is 23±0.3%, the linear speed of the roller is 0.15m / s, the rolling passes are 7 passes, the total reduction is 84±0.2%, and the final thickness is 1.10-1.13mm; air cooling is used for cooling, and the Ti2AlNb-based alloy plate is obtained after cooling to room temperature.

[0115] The tensile strength of the Ti2AlNb-based alloy plate prepared in this comparative example is only 600 MPa, and the elongation is only 2%.

[0116] Comparative Example 4

[0117] The same as Example 1, the only difference is that in step 4, specifically: using ABAQUS finite element software to simulate the rolling temperature to determine the rolling temperature parameters, using an induction heating device to heat the roller to 500°C, hot rolling the forging billet at 900°C in the O+B2 phase region, keeping warm for 20 minutes after each hot rolling, ensuring that the temperature is uniform before rolling, the reduction per pass is 23%±0.3%, the linear speed of the roller is 0.15m / s, the number of rolling passes is 7, the total reduction is 84±0.2%, and the final thickness is 1.10~1.13mm; air cooling is used for cooling, and the Ti2AlNb-based alloy plate is obtained after cooling to room temperature.

[0118] During the hot rolling process, the roll bounces greatly and cracks occur when the actual reduction is 30%.

[0119] Effect Example 1

[0120] Changes in forging temperature, post-forging heat treatment, hot rolling temperature and roller temperature parameters all significantly affect the grain structure and mechanical properties of the plate. Direct cold roll rolling will cause cracking and deterioration of the plate performance. When the roller temperature is less than 500°C, the plate is prone to edge cracks and has poor performance. Too high or too low rolling temperature will lead to poor performance, and the best rolling phase region is α2+O+B2 and α2+B2 phase region. The average grain size of the plate is not the only parameter that determines the performance change, and it needs to be analyzed and discussed in combination with phase ratio, organizational morphology, etc. The four process parameters listed in the embodiment can all produce plates with excellent mechanical properties.

[0121] Table 1 Grain and performance statistics of Ti2AlNb-based alloy plates prepared in different embodiments and comparative examples

[0122] Average grain size (μm) Tensile strength(MPa) Elongation(%) Example 1 102 1070 8.2 Example 2 32 1200 6.3 Example 3 25 1080 10.1 Example 4 46 1000 9.2 Comparative Example 1 59 1397 1.8 Comparative Example 2 73 1202 3.7 Comparative Example 3 830 600 2.7 Comparative Example 4 257 849 1.8

[0123] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a Ti2AlNb-based alloy sheet without a jacket, characterized in that: The following steps are involved: After smelting the Ti2AlNb alloy raw material, a Ti2AlNb ingot is obtained, the Ti2AlNb ingot is subjected to near-isothermal blanking forging in the B2 phase region, and then subjected to near-isothermal multi-directional forging in the α2+B2 phase region to obtain a forged cake; The forged cake is heat treated in the α2+O+B2 phase region and the O+B2 phase region in sequence, and then hot rolled without a jacket in the α2+O+B2 phase region or the α2+B2 phase region to obtain the Ti2AlNb-based alloy plate.

2. The method for preparing the non-encapsulated product according to claim 1, characterized in that: The Ti2AlNb ingot comprises the following raw materials, in terms of atomic percentage: Ti: 50-57%, Al: 18-25% and Nb: 22-27%.

3. The method for preparing the non-encapsulated product according to claim 1, characterized in that: The preparation method of the forging cake comprises the following steps: The forging die is heated to 900-1000°C, and the Ti2AlNb ingot is kept in the B2 phase region and then subjected to near-isothermal blanking forging, with a reduction of 50-60%, a reduction rate of 0.5-2 mm / s, an axial direction, and one forging time; then, near-isothermal multi-directional forging is performed in the α2+B2 phase region, with a reduction of 40-50%, a reduction rate of 0.5-2 mm / s, and 3-6 forging times, each time the direction of the reduction is 90° to the previous one, and before each forging, the ingot is placed in a furnace for heat preservation to obtain a forged cake; And / or, the temperature of the B2 phase region is 1040-1090°C; And / or, the temperature of the α2+B2 phase region is 950-1060°C.

4. The method for preparing the non-encapsulated product according to claim 1, characterized in that: The heat treatment method comprises: performing a solution treatment in the α2+O+B2 phase region for 20 to 40 minutes, and then performing an aging treatment in the O+B2 phase region for 1.5 to 2.5 hours; And / or, the temperature of the α2+O+B2 phase region is 900°C to 1020°C; And / or, the temperature of the O+B2 phase region is 750-960°C.

5. The method for preparing the non-encapsulated product according to claim 1, characterized in that: The method of non-cladding hot rolling comprises: performing non-cladding hot rolling after heat preservation in the α2+O+B2 phase region, the linear speed of the roller is 0.1-0.2 m / s, the reduction is 20-30%, and the total reduction is 80-90%; or performing non-cladding hot rolling after heat preservation in the α2+B2 phase region, the linear speed of the roller is 0.1-0.2 m / s, the reduction is 20-30%, and the total reduction is 80-90%; And / or, the temperature of the α2+O+B2 phase region is 900°C to 1020°C; And / or, the temperature of the α2+B2 phase region is 950-1060°C.

6. The method for preparing the non-encapsulated product according to claim 1, characterized in that: It also includes grinding the plates and spraying anti-oxidation coating after heat treatment and before hot rolling without jacketing.

7. A Ti2AlNb-based alloy plate prepared by the preparation method according to any one of claims 1 to 6.

8. Application of the Ti2AlNb-based alloy sheet material according to claim 7 in the aerospace field.

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