A method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling
By employing suspension induction melting and horizontal roll casting technology, combined with helium and argon flow rate control, the phase composition of Ti2AlNb thin strips can be controlled, solving the problems of complex processes and high costs in existing technologies, and improving production efficiency and material properties.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NORTHEASTERN UNIV CHINA
- Filing Date
- 2026-03-27
- Publication Date
- 2026-07-17
AI Technical Summary
Existing technologies for preparing Ti2AlNb thin strips involve complex processes, high costs, and long production cycles. Furthermore, it is difficult to achieve controllable adjustment of phase composition, especially the size and morphology of the O phase, during a one-step forming process.
Employing a vacuum chamber technology integrating suspension induction melting, horizontal strip casting, and four sets of spray guns, the solidification cooling and strip exit cooling rates are controlled in stages by adjusting the flow rates of helium and argon and the speed of the casting rolls. This simultaneously regulates the β/B2 phase matrix grains and the O phase, avoiding subsequent heat treatment.
A near-net-shape short-process preparation of Ti2AlNb thin strips was achieved, significantly reducing production energy consumption and cost. The grain size and O phase morphology are controllable, and the material has excellent mechanical properties, with tensile strength and elongation reaching 900~1400 MPa and 1~15%, respectively.
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Figure CN121911839B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metallurgical technology, specifically to a method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling. Background Technology
[0002] Against the backdrop of rapid iteration in aerospace and high-end equipment manufacturing towards lightweight, high-temperature resistance, and high reliability, traditional structural materials are no longer sufficient to meet performance requirements under extreme operating conditions. Ti2AlNb-based alloys, as a novel intermetallic compound material, through precise Al and Nb element ratios and microstructure control, inherit the excellent specific strength and corrosion resistance of titanium alloys while also possessing the lightweight advantages and high-temperature structural stability of aluminum alloys. Its operating temperature can stably reach 650~750℃, far exceeding that of conventional titanium alloys, making it one of the ideal candidate materials to replace high-temperature alloys and traditional titanium alloys.
[0003] Ti2AlNb thin strips, as an important application form of this alloy, have shown broad application prospects in core components such as aero-engine blades, spacecraft skins, and key load-bearing components of high-speed trains due to their thinness, high formability potential, and high structural design flexibility. Compared with bulk Ti2AlNb materials, thin strips can not only further reduce the weight of equipment and improve power efficiency, but also achieve complex shapes through plastic processing processes such as rolling and stamping, adapting to the integrated and precision design requirements of high-end equipment. However, Ti2AlNb alloys themselves have inherent problems such as low room temperature plasticity, narrow processing window, susceptibility to cracking during forming, and large springback. These problems are further amplified in the processing and application of thin strips, seriously restricting their industrialization. Therefore, there is an urgent need to develop Ti2AlNb thin strips with excellent comprehensive performance. Grain size and O phase morphology significantly affect the mechanical properties of Ti2AlNb thin strips, but their control often requires complex heat treatment processes.
[0004] Chinese invention patent CN117862230A proposes a method for preparing a high-strength aluminum / Ti2AlNb / high-strength aluminum three-layer composite plate by metastable rolling. This patent prepares a composite plate with the characteristics of high temperature resistance and lightweight by a three-step method of stacking and sealing, metastable heat treatment and rolling and post-rolling heat treatment. However, the process is complicated and the cost is high.
[0005] Chinese invention patent CN116803557A discloses a method for preparing Ti2AlNb-based alloy foil, relating to the field of Ti2AlNb-based alloy technology. The method involves first forging a Ti2AlNb-based alloy ingot in the α2+B2 phase region using multi-directional near-isothermal forging, followed by hot rolling in the α2+O+B2 phase region to obtain a Ti2AlNb-based alloy sheet. This sheet is then cold-rolled to obtain a cold-rolled foil, followed by short-time high-temperature annealing to obtain the final Ti2AlNb-based alloy foil. While this method has certain advantages by eliminating the need for stacking and prolonged heat treatment, the process still remains relatively complex due to the requirement of isothermal forging + hot rolling + cold rolling + short-time annealing.
[0006] Chinese invention patent CN115971492A discloses a Ti2AlNb alloy plate, its preparation method and application. The main feature of this patent is that it uses a hot isostatic pressing of Ti2AlNb pre-alloyed powder into a billet and then rolling it. With certain parameters, it can prepare a plate with a uniform and fine structure. However, the process and performance control are relatively complex. It requires hot isostatic pressing first, then rolling at a certain temperature, followed by heat preservation treatment.
[0007] Chinese invention patent CN120485675A proposes a heat treatment method to improve the microstructure uniformity and properties of dual-phase Ti2AlNb-based alloys. Specifically, it employs a heat treatment method combining dual solid solution synergistic regulation and graded aging strengthening. By controlling the size of the B2 / β matrix grains, and the size, morphology, and volume fraction of the α2 and O phases, different mechanical properties can be matched, resulting in a homogenized alloy microstructure and significantly improved mechanical properties. However, its microstructure control method (multi-stage heat treatment regime) is complex and time-consuming, which is not conducive to industrial production.
[0008] Chinese invention patent CN106637013A proposes a heat treatment method to improve the high-temperature strength of Ti2AlNb-based alloys, which includes pretreatment, solution treatment, quenching and aging treatment steps, and its performance control method is relatively complex.
[0009] Chinese invention patent CN108067596A discloses a method for preparing TiAl alloy slabs with uniform microstructure by thin strip casting and rolling. However, this method is specifically designed for the thin strip casting and rolling of TiAl alloys and cannot be directly applied to the preparation of Ti2AlNb alloys. The microstructure control in this method is achieved solely through casting and rolling process parameters and slow cooling treatment after strip exit. It lacks technical design to control the precipitation behavior of the O phase in the Ti2AlNb alloy, thus failing to achieve controllable adjustment of the phase composition of the Ti2AlNb alloy.
[0010] Chinese invention patent CN119710426A proposes a high-strength and high-plasticity Ti2AlNb-based alloy and its preparation method. The process route is vacuum melting and casting, homogenization treatment, hot rolling in the two-phase region, and subsequent quenching heat treatment. However, it cannot achieve one-step forming of Ti2AlNb thin strips from liquid metal. It still requires multiple hot working processes, resulting in a long production process. Its microstructure control depends on the hot deformation during hot rolling and the subsequent short-time quenching treatment.
[0011] In summary, existing technologies require forging, stacking, cold rolling, and heat treatment to obtain bulk / plate materials with controllable grain size and phase composition, making the preparation process complex and time-consuming. Furthermore, existing thin strip casting and rolling technologies are only applicable to the TiAl alloy system. The solidification phase transformation characteristics of TiAl alloys and Ti2AlNb alloys are fundamentally different, making it difficult to meet the requirements for preparing Ti2AlNb thin strips. Summary of the Invention
[0012] To address the current problems of long development cycles, high costs, and the need for heat treatment to control the microstructure of Ti2AlNb thin strips, the present invention aims to provide a method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling. This method achieves short flow length, low power consumption, and controllable phase composition preparation of Ti2AlNb thin strips. The phase composition and mechanical properties of the thin strip are controlled by injecting argon gas under two horizontal casting rolls, eliminating the need for complex heat treatment processes.
[0013] To achieve the above objectives, the technical solution of the present invention is as follows:
[0014] A method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling, comprising the following steps:
[0015] (1) Prepare alloy raw materials according to the set composition, and smelt to obtain alloy melt. Its composition by atomic percentage is: Al 18~25%, Nb 17~27%, and the balance is Ti;
[0016] (2) Install isostatic graphite side sealing plates in front of and behind the two horizontal casting rolls, rotate the horizontal casting rolls, and the pre-grinding speed of the casting rolls on the side sealing plates is 5~15 m / s, and the pre-grinding time of the side sealing plates is 20~60 min, so that the two side sealing plates and the two horizontally arranged internal water-cooled casting rolls are in close contact with each other, with a gap ≤0.1 mm.
[0017] (3) Evacuate the vacuum chamber, which is equipped with a suspension induction melting crucible, tundish, two horizontal casting rolls and four sets of spray guns, to a pressure of 10. -4 ~10 -2 Argon gas is introduced to 10000~45000 Pa to create a negative pressure, oxidation-free protective environment for the smelting and casting process;
[0018] (4) The smelting is carried out by suspension induction melting technology, and the melting temperature is 1400~2400 ℃ to obtain a uniform alloy melt.
[0019] (5) Helium gas is sprayed onto the roll surface of the two horizontal casting rolls using spray guns arranged with the same width as the roll surface, with a flow rate of 0~20 L / min on one side; Argon gas is sprayed onto the bottom of the two horizontal casting rolls using spray guns arranged with the same width as the Ti2AlNb thin strip, with a flow rate of 0~300 L / min on one side.
[0020] (6) Pour the melt in the suspension induction melting crucible into the intermediate ladle that has been preheated online to 1100~1250 ℃;
[0021] (7) The melt flows into the middle of the two horizontal casting rolls through the tundish nozzle, forming a molten pool between the casting rolls and the side sealing plate. The height of the molten pool is 3~160 mm, and the melt is evenly distributed.
[0022] (8) After the melt is solidified and cooled by two horizontal casting rolls and cooled by argon gas below, it solidifies to form a Ti2AlNb thin strip with a thickness of 1.0~3.0 mm and a controllable phase composition.
[0023] In the preparation method of Ti2AlNb thin strip with controllable phase composition based on thin strip casting and rolling, in step (3), the diameter of each spray gun is 1~5 mm and the spacing between adjacent spray guns is 10~15 mm.
[0024] In the preparation method of Ti2AlNb thin strip with controllable phase composition based on thin strip casting and rolling, in step (4), the suspension induction melting crucible is a water-cooled copper crucible, the heating temperature is controlled by the power of the induction coil, and the temperature value is measured by an infrared thermometer.
[0025] In the preparation method of Ti2AlNb thin strip with controllable phase composition based on thin strip casting and rolling, in step (5), the flow rate of helium gas injected by the spray gun is 1~20 L / min, and the flow rate of argon gas injected by the spray gun is 100~300 L / min.
[0026] In the preparation method of Ti2AlNb thin strip with controllable phase composition based on thin strip casting and rolling, in steps (7) and (8), the speed of the casting roll is 10~25 m / s, the roll gap between the two horizontal casting rolls is 1~3 mm, and the casting and rolling force is 10~40 kN.
[0027] In the method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling, in step (8), the solidification cooling rate of the melt solidifying through the casting roll is 200~800 K / s, and the strip exit cooling rate of the Ti2AlNb thin strip is 50~200 K / s.
[0028] In the preparation method of Ti2AlNb thin strip with controllable phase composition based on thin strip casting and rolling, in step (8), the phase composition of Ti2AlNb thin strip is as follows by volume percentage: β / B2 phase accounts for 5~65%, α2 phase accounts for 3~20%, and O phase accounts for 15~90%.
[0029] In the preparation method of Ti2AlNb thin strip with controllable phase composition based on thin strip casting and rolling, in step (8), the solidification cooling rate is changed by adjusting the argon flow rate and the casting roll speed, and the grain size of the β / B2 phase is controlled within the range of 30~600 μm.
[0030] In the preparation method of Ti2AlNb thin strip with controllable phase composition based on thin strip casting and rolling, in step (8), the cooling rate of the strip is changed by adjusting the argon flow rate, and the size of the O phase is controlled to be 1~15 μm. The morphology of the O phase is adjusted between lath and needle.
[0031] The method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling, wherein the mechanical properties of the Ti2AlNb thin strips are: tensile strength R m The strength is 900~1400 MPa, and the elongation At is 1~15%.
[0032] The design concept of this invention is:
[0033] This invention breaks the industry's technical prejudice that the microstructure control of Ti2AlNb alloys must rely on subsequent heat treatment. It innovatively integrates suspension induction melting, two horizontal casting rolls for thin strip casting, and four sets of spray guns into a single vacuum chamber, constructing a short-process preparation system that integrates melting, casting, and graded cooling rate control. Based on the solidification phase transformation law of Ti2AlNb alloys, a two-stage gas-jet graded cooling rate control technology is employed: Helium gas is injected through spray guns of equal width to the roll surfaces of the two horizontal casting rolls to control the solidification cooling rate during the contact between the melt and the rolls, thereby achieving a wide range of controllable adjustment of the β / B2 phase matrix grain size; Argon gas is injected through spray guns of equal width to the Ti2AlNb thin strip below the rolls to control the cooling rate during the strip exit process, thereby achieving independent control of the size, morphology, and volume fraction of the O phase. By coordinating the flow rates of two gas streams with the casting and rolling process parameters, the microstructure and phase composition can be controlled simultaneously during the one-step casting and rolling of liquid metal into Ti2AlNb strips. No subsequent forging, rolling, or heat treatment processes are required, thus achieving a short-process, low-power, and near-net-shape preparation of Ti2AlNb strips with controllable phase composition.
[0034] Compared with the existing technology, the present invention has the following beneficial technical effects:
[0035] 1. This invention integrates induction melting, two horizontal casting rolls, and four sets of spray guns into a vacuum chamber, and performs one-step casting and rolling within the vacuum chamber. This enables the near-net-shape short-process preparation of Ti2AlNb thin strips, significantly simplifies the traditional Ti2AlNb thin strip preparation process, significantly reduces production energy consumption and costs, and effectively improves production efficiency.
[0036] 2. This invention uses a spray gun to spray helium gas with a controllable flow rate onto the roller surface, which can stably adjust the solidification and cooling rate of Ti2AlNb thin strips, thereby achieving control over the grain size of the β / B2 phase matrix of Ti2AlNb thin strips.
[0037] 3. This invention uses a spray gun to spray argon gas with a controllable flow rate below the casting roll, which can stably adjust the cooling rate of the Ti2AlNb thin strip, thereby achieving control over the size, morphology and content of the O phase in the Ti2AlNb alloy.
[0038] 4. This invention regulates the solidification and cooling rate of Ti2AlNb thin strips by adjusting the helium flow rate and the casting roll speed, thereby controlling the grain size of Ti2AlNb thin strips.
[0039] 5. This invention regulates the cooling rate of Ti2AlNb thin strips by adjusting the argon flow rate, thereby adjusting the size, morphology, and content of the O phase in Ti2AlNb and achieving flexible control of the phase composition.
[0040] 6. This invention eliminates the need for complex subsequent heat treatment processes, enabling the control of Ti2AlNb strip grain size, phase composition, and the size, morphology, and content of the O phase during the casting and rolling process, thereby achieving the matching of material mechanical properties.
[0041] 7. In this invention, the microstructure and phase composition of Ti2AlNb thin strips are highly controllable. By adjusting the solidification cooling rate, the grain size of the β / B2 phase can be controlled within the range of 30~600μm; by adjusting the strip exit cooling rate, the size of the O phase can be controlled within the range of 1~15μm, the morphology can be flexibly adjusted between lath and needle-like, and the volume fraction can be controlled within the range of 15~90%. At the same time, the volume fraction of the α2 phase can be stably controlled within the range of 3~20%, and the volume fraction of the β / B2 phase can be adjusted within the range of 5~65%.
[0042] 8. The Ti2AlNb thin strip prepared by this invention has excellent comprehensive mechanical properties. The thickness of the thin strip can be stably controlled between 1.0 and 3.0 mm, the tensile strength Rm can reach 900 to 1400 MPa, and the elongation At can reach 1 to 15%. It takes into account both the high strength and good plasticity of the material, and fundamentally solves the problems of easy cracking and poor formability of Ti2AlNb thin strips in traditional processing. Attached Figure Description
[0043] Figure 1 This is a schematic diagram of the Ti2AlNb ribbon fabrication process. The figures are labeled as follows: 1-vacuum chamber, 2-water-cooled copper crucible, 3-intermediate ladle, 4-first gas pipeline and spray gun assembly, 5-second gas pipeline and spray gun assembly, 6-melt, 7-third gas pipeline and spray gun assembly, 8-casting roll, 9-fourth gas pipeline and spray gun assembly, 10-Ti2AlNb ribbon.
[0044] Figure 2 This is the X-ray diffraction (XRD) pattern from Example 1. Detailed Implementation
[0045] In the specific implementation process, the present invention proposes a method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling, which is carried out according to the following steps: (1) Smelting alloy melt according to the set composition, the composition of which is: Al 18~25%, Nb 17~27%, and the balance is Ti; (2) Installing isostatic graphite side sealing plates in front of and behind the horizontal casting roll, rotating the horizontal casting roll at a speed of 5~15 m / s; pre-grinding the side sealing plates for 20~60 min, so that the two side sealing plates and the two horizontally arranged internal water-cooled casting rolls are in close contact with each other, with a gap ≤0.1 mm. (3) Evacuating the vacuum chamber to 10 -4 ~10 -2 Pa, high-purity argon gas is introduced to 10000~45000Pa to create a negative pressure and oxidation-free protective environment for the melting and casting process; (4) Suspension induction melting technology is used for melting, and the melt heating temperature is 1400~2400 ℃ to obtain a uniform and highly clean alloy melt; (5) Helium gas is sprayed onto the roll surface of the two horizontal casting rolls using a spray gun with the same width as the roll surface, with a single-sided flow rate of 0~20 L / min; Argon gas is sprayed onto the bottom of the two horizontal casting rolls using a spray gun with the same width as the Ti2AlNb thin strip, with a single-sided flow rate of 0~300 L / min; (6) The melt in the water-cooled copper crucible is quickly tilted into the tundish that has been preheated online to 1100~1250 ℃; (7) The melt flows into the middle of the two horizontal casting rolls through the tundish nozzle, forming a molten pool between the casting rolls and the side sealing plate, with a molten pool height of 3~160 mm, the melt is evenly distributed; (8) after the melt is rapidly solidified and cooled by two horizontal casting rolls and rapidly cooled by argon gas exiting the strip below, it quickly solidifies to form a Ti2AlNb thin strip with a thickness of 1.0~3.0 mm and a controllable phase composition.
[0046] like Figure 1As shown, the production equipment for Ti2AlNb thin strip includes a vacuum chamber 1, a water-cooled copper crucible 2, an intermediate ladle 3, a first gas pipeline and spray gun assembly 4, a second gas pipeline and spray gun assembly 5, a melt 6, a third gas pipeline and spray gun assembly 7, a casting roll 8, and a fourth gas pipeline and spray gun assembly 9. The water-cooled copper crucible 2, the intermediate ladle 3, and the casting roll 8 are arranged sequentially from top to bottom in the vacuum chamber 1. Alloy melting, casting, casting and rolling forming, and cooling rate control are all completed in this vacuum chamber 1.
[0047] The water-cooled copper crucible 2 completes the vacuum suspension melting and composition homogenization of Ti, Al, and Nb raw materials, providing Ti2AlNb alloy melt 6 with qualified temperature and composition for subsequent casting and rolling processes. The tundish 3 stabilizes the melt casting flow rate and homogenizes the melt temperature, avoiding the direct impact of melt 6 on the casting roll 8 and causing violent fluctuations in the molten pool. At the same time, online preheating prevents excessive temperature drop and premature solidification during the melt casting process, ensuring the continuous stability of the two casting rolls casting and rolling processes. The casting roll 8 consists of two counter-rotating synchronously and horizontally arranged internal water-cooled casting rolls. The two casting rolls 8 and the front and rear isostatic graphite side sealing plates together form a closed molten pool. The high-temperature alloy melt quickly contacts the surface of the casting roll 8 in the molten pool and solidifies rapidly. At the same time, it completes the rolling deformation with the rotation of the casting roll, realizing the one-step forming of liquid metal into Ti2AlNb thin strip.
[0048] The first gas pipe and spray gun assembly 4 corresponds to the upper surface of one casting roll 8, and the third gas pipe and spray gun assembly 7 corresponds to the upper surface of another casting roll 8. The spray guns of the first gas pipe and spray gun assembly 4 and the third gas pipe and spray gun assembly 7 are arranged with the same width as the casting roll surface. Helium gas is delivered through the gas pipe and sprayed onto the casting roll surface. By adjusting the helium gas flow rate, the heat exchange efficiency of the interface between the casting roll and the melt can be flexibly controlled, thereby controlling the solidification and cooling rate of the melt, and finally achieving a wide range of controllable adjustment of the β / B2 phase matrix grain size.
[0049] A second gas pipe and spray gun assembly 5 and a fourth gas pipe and spray gun assembly 9 are respectively set on both sides of the Ti2AlNb thin strip 10 near the casting roll 8. The spray guns of the second gas pipe and spray gun assembly 5 and the fourth gas pipe and spray gun assembly 9 are arranged with the same width as the Ti2AlNb thin strip 10. Argon gas is delivered through the gas pipes and sprayed onto the surface of the Ti2AlNb thin strip 10 that has just detached from the casting roll 8. By adjusting the argon gas flow rate, the cooling rate of the Ti2AlNb thin strip can be stably controlled, thereby controlling the precipitation kinetics of the O phase and realizing the control of the size, morphology and volume fraction of the O phase.
[0050] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.
[0051] Example 1
[0052] In this embodiment, a method for preparing Ti-22Al-25Nb thin strips with controllable phase composition based on thin strip casting and rolling specifically includes the following steps:
[0053] 1. Using metallic Ti (99.9wt%), Al (99.9wt%), and Nb (99.9wt%) as raw materials, weigh the raw materials according to the nominal composition, with atomic percentages of Ti 53%, Al 22%, and Nb 25%, for a total mass of 10 kg.
[0054] 2. Install side sealing plates before and after the horizontal casting roll, rotate the horizontal casting roll, and the pre-grinding speed of the casting roll is 10 m / s; the pre-grinding time of the side sealing plates is 30 min, so that the two side sealing plates and the two horizontal casting rolls are in close contact with a gap of 0.1 mm.
[0055] 3. Place the raw materials into the water-cooled copper crucible in order of their melting points, close the vacuum chamber, and evacuate to a pressure of 10. -2 Pa.
[0056] 4. Purge the vacuum chamber with high-purity argon gas (99.999% volume purity) to 45000 Pa. Use induction melting technology to melt the raw materials into a homogeneous melt. Hold at this temperature for 5 minutes, then turn off the power and allow the furnace to cool to room temperature.
[0057] 5. Open the vacuum chamber, flip the ingot in the water-cooled copper crucible, and place it back into the water-cooled copper crucible. Remelt the ingot to ensure uniform composition. During the second melting, hold the ingot at that temperature for 5 minutes after it has completely melted.
[0058] 6. Adjust the gap between the horizontal casting rolls to 2 mm and the roll speed to 20 m / s. Inject helium gas onto the surface of the casting rolls at a flow rate of 20 L / min, and simultaneously inject argon gas below the casting rolls at a flow rate of 300 L / min. Then, directly tilt the water-cooled copper crucible and pour the alloy molten metal into the graphite tundish. The molten metal flows from the tundish nozzle to the space between the two horizontal water-cooled rolls, and rapidly forms a strip under the rapid cooling effect of the casting rolls. The thickness of the Ti2AlNb strip is approximately 2 mm.
[0059] like Figure 2 As shown in the X-ray diffraction (XRD) pattern in Example 1, Ti2AlNb thin strips with the target strengthening phase O phase as the main component, combined with the toughening phase B2 phase and containing a small amount of stable α2 phase were successfully prepared without subsequent heat treatment. The microstructure and phase composition of Ti2AlNb alloy were controlled in situ by adjusting the cooling rate.
[0060] In this embodiment, the phase composition of the Ti2AlNb ribbon, by volume percentage, is approximately 30% β / B2 phase, approximately 4% α2 phase, and approximately 66% O phase. The grain size of the Ti2AlNb ribbon is approximately 30~80 μm, with lamellar O phase accounting for approximately 1 / 4 and acicular O phase accounting for approximately 3 / 4. The mechanical properties of the Ti2AlNb ribbon are: tensile strength R... m It has a strength of approximately 1400 MPa and an elongation of approximately 14%.
[0061] Example 2
[0062] In this embodiment, a method for preparing Ti-22Al-25Nb thin strips with controllable phase composition based on thin strip casting and rolling specifically includes the following steps:
[0063] 1. Using metallic Ti (99.9wt%), Al (99.9wt%), Nb (99.9wt%), and AlNb2O (99.9wt%) as raw materials, weigh the raw materials according to the nominal composition, with an atomic percentage of Ti 53%, Al 22%, and Nb 25%, and weigh two portions of the raw materials, each weighing 10 kg.
[0064] 2. Install side sealing plates before and after the horizontal casting roll, rotate the horizontal casting roll, and the pre-grinding speed of the casting roll is 10 m / s; the pre-grinding time of the side sealing plates is 30 min, so that the two side sealing plates and the two horizontal casting rolls are in close contact with a gap of 0.1 mm.
[0065] 3. Place the raw materials into the water-cooled copper crucible in order of their melting points, close the vacuum chamber, and evacuate to a pressure of 10. -2 Pa.
[0066] 4. Purge the vacuum chamber with high-purity argon gas (99.999% volume purity) to 45000 Pa. Use induction melting technology to melt the raw materials into a homogeneous melt. Hold at this temperature for 5 minutes, then turn off the power and allow the furnace to cool to room temperature.
[0067] 5. Open the vacuum chamber, flip the ingot in the water-cooled copper crucible, and place it back into the water-cooled copper crucible. Remelt the ingot to ensure uniform composition. During the second melting, hold the ingot at that temperature for 5 minutes after it has completely melted.
[0068] 6. Adjust the gap between the horizontal casting rolls to 2 mm. For the first batch of raw material, adjust the roll speed to 10 m / s; for the second batch of raw material, adjust the roll speed to 15 m / s. Inject helium gas onto the surface of the casting rolls at a flow rate of 20 L / min, and simultaneously inject argon gas below the casting rolls at a flow rate of 300 L / min. Then, directly tilt the water-cooled copper crucible and pour the alloy molten metal into the graphite tundish. The molten metal flows from the tundish nozzle to the space between the two horizontal water-cooled rolls, rapidly forming a strip under the rapid cooling effect of the casting rolls. The Ti2AlNb strip is approximately 2 mm thick.
[0069] In this embodiment, the Ti2AlNb ribbon phase composition, by volume percentage, is approximately 30% β / B2 phase, approximately 4% α2 phase, and approximately 66% O phase. For the first batch of raw material, the Ti2AlNb ribbon grain size is approximately 150~200 μm, with lamellar O phase accounting for approximately 1 / 4 and acicular O phase accounting for approximately 3 / 4; for the second batch of raw material, the Ti2AlNb ribbon grain size is approximately 80~150 μm, with lamellar O phase accounting for approximately 1 / 4 and acicular O phase accounting for approximately 3 / 4. For the first batch of raw material, the tensile strength R... m The tensile strength is approximately 1000 MPa, and the elongation At is approximately 3%; for the second raw material, the tensile strength R m It has a strength of approximately 1050 MPa and an elongation of approximately 6%.
[0070] Example 3
[0071] In this embodiment, a method for preparing Ti-22Al-25Nb thin strips with controllable phase composition based on thin strip casting and rolling specifically includes the following steps:
[0072] 1. Using metallic Ti (99.9wt%), Al (99.9wt%), and Nb (99.9wt%) as raw materials, weigh the raw materials according to the nominal composition, with an atomic percentage of Ti 53%, Al 22%, and Nb 25%, and weigh two portions of the raw materials, each weighing 10 kg.
[0073] 2. Install side sealing plates before and after the horizontal casting roll, rotate the horizontal casting roll, and the pre-grinding speed of the casting roll is 10 m / s; the pre-grinding time of the side sealing plates is 30 min, so that the two side sealing plates and the two horizontal casting rolls are in close contact with a gap of 0.1 mm.
[0074] 3. Place the raw materials into the water-cooled copper crucible in order of their melting points, close the vacuum chamber, and evacuate to a pressure of 10. -2 Pa.
[0075] 4. Purge the vacuum chamber with high-purity argon gas (99.999% volume purity) to 45000 Pa. Use induction melting technology to melt the raw materials into a homogeneous melt. Hold at this temperature for 5 minutes, then turn off the power and allow the furnace to cool to room temperature.
[0076] 5. Open the vacuum chamber, flip the ingot in the water-cooled copper crucible, and place it back into the water-cooled copper crucible. Remelt the ingot to ensure uniform composition. During the second melting, hold the ingot at that temperature for 5 minutes after it has completely melted.
[0077] 6. Adjust the gap between the horizontal casting rolls to 2 mm and the roll speed to 20 m / s. For the first batch of raw material, no helium gas was injected onto the surface of the casting rolls; for the second batch of raw material, helium gas was injected onto the surface of the casting rolls at a flow rate of 10 L / min. Simultaneously, argon gas was injected below the casting rolls at a flow rate of 300 L / min. Then, the water-cooled copper crucible was tilted directly, and the alloy melt was poured into the graphite tundish. The molten metal flowed from the tundish nozzle to the space between the two horizontal water-cooled rolls, and under the rapid cooling effect of the casting rolls, it quickly formed a strip. The thickness of the Ti2AlNb strip was approximately 2 mm.
[0078] In this embodiment, the phase composition of the Ti2AlNb ribbon, by volume percentage, is approximately 30% β / B2 phase, approximately 4% α2 phase, and approximately 66% O phase. For the first batch of raw material, the grain size of the Ti2AlNb ribbon is approximately 300~600 μm, with lamellar O phase accounting for approximately 1 / 4 and acicular O phase accounting for approximately 3 / 4; for the second batch of raw material, the grain size of the Ti2AlNb ribbon is approximately 100~250 μm, with lamellar O phase accounting for approximately 1 / 4 and acicular O phase accounting for approximately 3 / 4. For the first batch of raw material, the mechanical properties of the Ti2AlNb ribbon are: tensile strength R... m The tensile strength is approximately 920 MPa, and the elongation at is approximately 1.5%; for the second raw material, the tensile strength R... m It has a strength of approximately 1100 MPa and an elongation of approximately 6% at.
[0079] Example 4
[0080] In this embodiment, a method for preparing Ti-22Al-25Nb thin strips with controllable phase composition based on thin strip casting and rolling specifically includes the following steps:
[0081] 1. Using metallic Ti (99.9wt%), Al (99.9wt%), and Nb (99.9wt%) as raw materials, weigh the raw materials according to the nominal composition, with an atomic percentage of Ti 53%, Al 22%, and Nb 25%, and weigh two portions of the raw materials, each weighing 10 kg.
[0082] 2. Install side sealing plates before and after the horizontal casting roll, rotate the horizontal casting roll, and the pre-grinding speed of the casting roll is 10 m / s; the pre-grinding time of the side sealing plates is 30 min, so that the two side sealing plates and the two horizontal casting rolls are in close contact with a gap of 0.1 mm.
[0083] 3. Place the raw materials into the water-cooled copper crucible in order of their melting points, close the vacuum chamber, and evacuate to a pressure of 10. -2 Pa.
[0084] 4. Purge the vacuum chamber with high-purity argon gas (99.999% volume purity) to 45000 Pa. Use induction melting technology to melt the raw materials into a homogeneous melt. Hold at this temperature for 5 minutes, then turn off the power and allow the furnace to cool to room temperature.
[0085] 5. Open the vacuum chamber, flip the ingot in the water-cooled copper crucible, and place it back into the water-cooled copper crucible. Remelt the ingot to ensure uniform composition. During the second melting, hold the ingot at that temperature for 5 minutes after it has completely melted.
[0086] 6. Adjust the gap between the horizontal casting rolls to 2 mm and the roll speed to 20 m / s. Inject helium gas onto the surface of the casting rolls at a flow rate of 20 L / min. Simultaneously, inject argon gas below the casting rolls at a flow rate of 150 L / min for the first batch of raw material; do not inject argon gas for the second batch. Then, directly tilt the water-cooled copper crucible and pour the alloy molten metal into the graphite tundish. The molten metal flows from the tundish nozzle to the space between the two horizontal water-cooled rolls, rapidly forming a strip under the rapid cooling effect of the casting rolls. The Ti2AlNb strip is approximately 2 mm thick.
[0087] In this embodiment, the phase composition of the Ti2AlNb ribbon, by volume percentage, is approximately 30% β / B2 phase, approximately 4% α2 phase, and approximately 66% O phase. The grain size of the Ti2AlNb ribbon is approximately 30~80 μm. For the first raw material, the phase composition of the alloy, by volume percentage, is approximately 25% β / B2 phase, approximately 4% α2 phase, and approximately 71% O phase, with lamellar O phase accounting for approximately 1 / 2 and acicular O phase accounting for approximately 1 / 2. For the second raw material, the phase composition of the alloy, by volume percentage, is approximately 10% β / B2 phase, approximately 4% α2 phase, and approximately 86% O phase, with lamellar O phase accounting for approximately 3 / 4 and acicular O phase accounting for approximately 1 / 4. For the first raw material, the mechanical properties of the Ti2AlNb ribbon are: tensile strength R... m The tensile strength is approximately 1300 MPa, and the elongation At is approximately 8%. For the second raw material, the mechanical properties of the Ti2AlNb ribbon are: tensile strength R... m It has a strength of approximately 1150 MPa and an elongation of approximately 4%.
[0088] Example 5
[0089] In this embodiment, a method for preparing Ti-25Al-17Nb thin strips with controllable phase composition based on thin strip casting and rolling specifically includes the following steps:
[0090] 1. Using metallic Ti (99.9wt%), Al (99.9wt%), and AlNb20 master alloy (99.9wt%) as raw materials, weigh the raw materials according to the nominal composition, with atomic percentages of Ti 58%, Al 25%, and Nb 17%, for a total mass of 10 kg.
[0091] 2. Install side sealing plates before and after the horizontal casting roll, rotate the horizontal casting roll, and the pre-grinding speed of the casting roll is 5 m / s; the pre-grinding time of the side sealing plates is 60 min, so that the two side sealing plates and the two horizontal casting rolls are in close contact with a gap of 0.1 mm.
[0092] 3. Place the raw materials into the water-cooled copper crucible in order of their melting points, close the vacuum chamber, and evacuate to a pressure of 10. -3 Pa.
[0093] 4. Purge the vacuum chamber with high-purity argon gas to 35000 Pa (volume purity 99.999%), and use suspension induction melting technology to melt the raw materials into a homogeneous melt. Hold at this temperature for 5 minutes, then turn off the power and allow the furnace to cool to room temperature.
[0094] 5. Open the vacuum chamber, flip the ingot in the water-cooled copper crucible, and place it back into the water-cooled copper crucible. Remelt the ingot to ensure uniform composition. During the second melting, hold the ingot at that temperature for 5 minutes after it has completely melted.
[0095] 6. Adjust the gap between the horizontal casting rolls to 1.5 mm and the roll speed to 20 m / s. Inject helium gas onto the surface of the casting rolls at a flow rate of 20 L / min, and simultaneously inject argon gas below the casting rolls at a flow rate of 300 L / min. Then, directly tilt the water-cooled copper crucible and pour the alloy molten metal into the graphite tundish. The molten metal flows from the tundish nozzle to the space between the two horizontal water-cooled rolls, and rapidly forms a strip under the rapid cooling effect of the casting rolls. The thickness of the Ti2AlNb strip is approximately 1.5 mm.
[0096] In this embodiment, the phase composition of the Ti2AlNb ribbon, by volume percentage, is approximately 7% β / B2 phase, approximately 20% α2 phase, and approximately 73% O phase. The grain size of the Ti2AlNb ribbon is approximately 30~80 μm, with lamellar O phase accounting for approximately 1 / 2 and acicular O phase accounting for approximately 1 / 2. The mechanical properties of the Ti2AlNb ribbon are: tensile strength R... m It has a strength of approximately 1400 MPa and an elongation of approximately 1% at.
[0097] The results show that this invention directly prepares Ti2AlNb strips by thin strip casting and rolling, solving the problems of lengthy process flow, long production cycle, high energy consumption and preparation cost in the existing Ti2AlNb strip preparation technology. It also breaks through the technical limitation that the control of Ti2AlNb alloy grain size, phase composition and O phase characteristics must rely on complex subsequent forging, rolling and multi-step heat treatment processes, and cannot be completed simultaneously in the forming process. At the same time, it solves the problems of low room temperature plasticity of Ti2AlNb alloy itself, easy cracking of thin strips and low yield in traditional processing, providing a new technical route for the preparation of Ti2AlNb alloy thin strips.
Claims
1. A method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling, characterized in that, Follow these steps: (1) Prepare alloy raw materials according to the set composition, and smelt to obtain alloy melt. Its composition by atomic percentage is: Al 18~25%, Nb 17~27%, and the balance is Ti; (2) Install isostatic graphite side sealing plates in front of and behind the two horizontal casting rolls, rotate the horizontal casting rolls, and the pre-grinding speed of the casting rolls on the side sealing plates is 5~15 m / s, and the pre-grinding time of the side sealing plates is 20~60 min, so that the two side sealing plates and the two horizontally arranged internal water-cooled casting rolls are in close contact with each other, with a gap ≤0.1 mm. (3) Evacuate the vacuum chamber, which is equipped with a suspension induction melting crucible, tundish, two horizontal casting rolls and four sets of spray guns, to a pressure of 10. -4 ~10 -2 Argon gas is introduced to 10000~45000 Pa to create a negative pressure and oxidation-free protective environment for the melting and casting process, and a short-process preparation system integrating melting, casting and rolling, and graded cooling rate control is constructed. (4) The smelting is carried out using the suspension induction melting technology, and the melting temperature is 1400~2400 ℃ to obtain a uniform alloy melt. (5) Helium gas is sprayed onto the roll surface of the two horizontal casting rolls using spray guns arranged with the same width as the roll surface, with a flow rate of 1~20 L / min on one side; Argon gas is sprayed onto the bottom of the two horizontal casting rolls using spray guns arranged with the same width as the Ti2AlNb thin strip, with a flow rate of 100~300 L / min on one side. (6) Pour the melt in the suspension induction melting crucible into the intermediate ladle that has been preheated online to 1100~1250 ℃; (7) The melt flows into the middle of the two horizontal casting rolls through the tundish nozzle, forming a molten pool between the casting rolls and the side sealing plate. The height of the molten pool is 3~160 mm, and the melt is evenly distributed. (8) After the melt is solidified and cooled by two horizontal casting rolls and cooled by argon gas at the bottom, it solidifies to form a Ti2AlNb thin strip with a thickness of 1.0~3.0 mm and a controllable phase composition. The solidification cooling rate of the melt through the casting rolls is 200~800 K / s, and the cooling rate of the Ti2AlNb thin strip at the bottom is 50~200 K / s. The solidification cooling rate is changed by adjusting the argon gas flow rate and the casting roll speed, and the grain size of the β / B2 phase is controlled within the range of 30~600 μm. The size of the O phase is controlled within the range of 1~15 μm by adjusting the argon gas flow rate and the cooling rate at the bottom. μm, the O phase morphology is adjusted between lath and needle-like; through the coordinated matching of two gas flow rates and casting and rolling process parameters, the microstructure and phase composition are simultaneously controlled during the one-step casting and rolling of liquid metal into Ti2AlNb thin strips. The phase composition of Ti2AlNb thin strips, by volume percentage, is 5~65% β / B2 phase, 3~20% α2 phase, and 15~90% O phase. No subsequent forging, rolling, or heat treatment processes are required, realizing the short-process, low-power, and near-net-shape preparation of Ti2AlNb thin strips with controllable phase composition.
2. The method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling according to claim 1, characterized in that, In step (3), the diameter of each spray gun is 1~5 mm, and the distance between adjacent spray guns is 10~15 mm.
3. The method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling according to claim 1, characterized in that, In step (4), the suspended induction melting crucible is a water-cooled copper crucible, and the heating temperature is controlled by the power of the induction coil. The temperature value is measured by an infrared thermometer.
4. The method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling according to claim 1, characterized in that, In steps (7) and (8), the speed of the casting roll is 10~25 m / s, the gap between the two horizontal casting rolls is 1~3 mm, and the casting force is 10~40 kN.
5. The method for preparing Ti2AlNb thin strips with controllable phase composition based on thin strip casting and rolling according to claim 1, characterized in that, The mechanical properties of Ti2AlNb thin strips are: tensile strength R m The strength is 900~1400 MPa, and the elongation At is 1~15%.