A method for inhibiting hard and brittle phases of a ti al alloy and improving plasticity at room temperature

Abstract

The application provides a kind of TiAl alloy hard brittle phase inhibition and room temperature plasticity promotion regulation method, it is related to TiAl alloy composition and deformation technical field.The regulation method is the method of combining composition design and organization regulation to prepare deformation TiAl alloy forgings, including smelting+machining, coating, vacuum heating, multi-step isothermal forging and cooling+demoulding.Compared with traditional TNM alloy, the alloy composition in the application greatly reduces the content of beta0 phase at room temperature, has obvious composition advantage.The application adopts vacuum isothermal forging technology to form TiAl alloy forgings in situ multi-step, the process flow is greatly shortened, the good product yield is greatly improved, and the manufacturing cost is greatly reduced.Compared with casting and conventional forging method, the method of the application improves the comprehensive mechanical properties of TiAl alloy, and avoids the deformation defects caused by high temperature oxidation and other problems.Therefore, the method proposed in the application has important commercial value.

Description

Technical Field

[0001] This invention relates to the technical field of TiAl alloy composition and deformation, and in particular to a method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys. The prepared TiAl alloy is used in the field of aerospace engine disk temperature-resistant components. Background Technology

[0002] Weight reduction is a perennial theme in the development of aerospace and weaponry. For every 1g reduction in the weight of an aero-engine, the aircraft can be reduced by 4-8g. TiAl alloys are a new generation of high-temperature, lightweight structural materials with excellent properties such as high melting point, low density (3.9-4.2g / cm3), high elastic modulus, high oxidation resistance, and high creep resistance, especially at temperatures between 650-900°C. C-TiAl alloys possess strength similar to Ni-based superalloys, but with lower density, showing promising development prospects in aerospace and engine fields. Currently, TiAl alloys have also seen initial applications abroad, such as in low-pressure turbine blades for aero-engines and turbocharger turbines for racing cars.

[0003] However, TiAl alloys, as a typical intermetallic compound material with intrinsic brittleness, have a combination of metallic and covalent bonds between atoms. In the long-range ordered structure of the alloy, there are fewer independent slip systems, a larger Burgers vector of superlattice dislocations, and lower ordered structural symmetry. This results in TiAl alloys having high room temperature brittleness and high processing difficulty, which hinders the development and engineering application of TiAl alloys.

[0004] Compositional control is one method to address the high brittleness and processing difficulty of TiAl alloys. Ti-43.5Al-4Nb-1Mo-0.1B (TNM) alloy is considered a classic composition suitable for hot working, but it contains a relatively high amount of β0 phase at room temperature, reducing the plasticity of the TiAl alloy. Furthermore, during service, ω0 phase precipitates within the β0 phase, reducing service life. Therefore, further optimization of the TNM alloy composition is needed to reduce the β0 content at room temperature while maintaining good hot working properties.

[0005] Choosing appropriate preparation and processing methods is also an effective means to improve the room temperature plasticity of TiAl alloys. Currently, the commonly used preparation processes for TiAl alloys are powder metallurgy and ingot metallurgy. Powder metallurgy is divided into pre-alloyed powder method and elemental powder method based on raw materials. When preparing TiAl alloys using pre-alloyed powder, non-equilibrium dendrites easily form within the powder microstructure, and the preparation of raw powder is difficult and costly. Elemental powder method is less expensive than pre-alloyed powder method, but it faces problems such as poor formability, uneven composition, and high oxygen content. Ingot metallurgy can produce large-size parts with low energy consumption and low cost, but the TiAl alloy microstructure is relatively coarse during casting, and after casting, the ingot is prone to porosity and compositional segregation, resulting in poor strength and plasticity. Therefore, TiAl alloys prepared by ingot metallurgy generally require hot working. Although TiAl alloy forgings prepared by high-temperature forging under atmospheric conditions have high mechanical properties, direct forging of as-cast TiAl alloys is prone to cracking. Meanwhile, to prevent temperature drop, the forging rate is generally fast, resulting in insufficient dynamic recrystallization after forging. This easily leads to the formation of residual lamellar layers, affecting the mechanical properties and microstructure uniformity of the forged TiAl alloy, making it difficult to meet the stringent service conditions of high-temperature engine components. Furthermore, the method of extruding and then forging involves a long process and makes it difficult to solve the oxidation problem.

[0006] Chinese patent CN119501499A discloses a low-cost, high-performance TiAl alloy engine blade manufacturing method, which employs precision casting and vacuum isothermal forging to prepare TiAl alloy blades. While this method results in a small machining allowance, the forging deformation is also small, which is not conducive to a significant improvement in the performance of the TiAl alloy. Furthermore, the microstructure obtained in this patent shows a large amount of β0 phase, which would impair the room-temperature plasticity of the TiAl alloy.

[0007] Chinese patent CN119426505 discloses a method for preparing titanium-aluminum intermetallic compound discs with uniform microstructure and properties, which uses a combination of hot extrusion and vacuum isothermal forging techniques to prepare TiAl alloy discs. Although hot extrusion refines the grains and improves hot working performance, the added hot extrusion step results in a long production cycle and high cost. Chinese patent CN112746232A employs hot isostatic pressing, hot extrusion, and annealing, which similarly increases the process flow and production cost.

[0008] Chinese patent CN116590637A discloses a method for improving the microstructure and properties of cast TiAl alloys, which involves heating cast TiAl alloy bars to 1300-1500 °C. Isothermal compression deformation (C) increases the plasticity of the alloy and prevents cracking. However, this method generally enters the α single-phase region, resulting in limited refinement and plasticity improvement effects on TiAl alloys. Furthermore, the excessively high temperature leads to high energy consumption and places higher demands on isothermal forging dies, increasing costs.

[0009] Chinese patent CN119162525A discloses a method for improving the strength and plasticity of TiAl alloy based on cooling and isothermal superposition deformation, including the following steps: subjecting a sample of TiAl alloy ingot to multiple axial compressions; heating the sample to a set temperature and holding it before each compression, and then compressing it; cooling to room temperature after each compression. However, this method requires repeated heating and cooling, which significantly reduces production efficiency. Secondly, the gradual decrease in hot working temperature promotes the α-to-γ phase transformation, inevitably reducing lamellar clusters, which is not conducive to improving the strength and plasticity of TiAl alloy. In addition, the patent uses small-sized samples, which are difficult to implement in actual production. Summary of the Invention

[0010] The main objective of this invention is to address the technical problems in existing TiAl alloy preparation technologies, such as small forging deformation, difficulty in effectively coordinating hot working and hot forging, poor synergistic improvement of strength, plasticity, and high temperature resistance, long process, high energy consumption, and high cost. Therefore, a method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys is proposed to solve the aforementioned problems.

[0011] The technical solution is as follows: A method for controlling the suppression of brittle phases and the enhancement of room temperature plasticity in TiAl alloys, comprising the following steps: S1. Smelting + Machining: TiAl alloy ingots are obtained by casting metallurgy according to the composition of TiAl alloy, and TiAl alloy preforms for vacuum isothermal forging are obtained by machining. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; S3. Vacuum heating: Place the coated TiAl alloy preform and coating mold from S2 into a vacuum isothermal forging equipment, close the hatch and start evacuating the vacuum. Once the vacuum level reaches the required level, start multi-stage heating and heat preservation to obtain the coated TiAl alloy preform and coating mold to be forged. S4. Multi-step isothermal forging: After vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated mold to be forged are subjected to in-situ multi-step isothermal forging. The temperature is maintained between each step until the required deformation of the final product is reached, and then the forging is ended to obtain the forged TiAl alloy component. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select the set cooling rate and cool it to room temperature in the furnace. Then demold and take out the cooled deformed TiAl alloy component as the final product.

[0012] Optionally, the TiAl alloy composition in S1, by atomic percentage, is: Al 44-48 at.%, Nb 3-6 at.%, Mo 0-0.6 at.%, B / C / Si / N 0-1.5 at.%, RE 0-2.1 at.%, with the balance being Ti and other unavoidable impurities.

[0013] Optionally, the smelting temperature of the ingot metallurgical method in S1 is 1600-1650°C. C, vacuum degree is 1 10 -3 -8 10 -3 Pa, argon atmosphere protection, melting times are 2-5 times, and the casting mold is a graphite / metal mold.

[0014] Optionally, the machining in S1 is a mechanical cutting process, and the TiAl alloy preform for vacuum isothermal forging is a cylindrical TiAl alloy preform with a length-to-diameter ratio of 1:1-1:2 and a diameter of 20-200mm.

[0015] Optionally, the mold in S2 is one or a combination of graphite mold, molybdenum alloy mold or high-temperature alloy mold, and the demolding material is graphite foil or boron nitride.

[0016] Optionally, the thickness of the release material coating on the TiAl alloy preform in S2 is 100-500 μm, and the thickness of the release material coating on the mold surface is 100-500 μm.

[0017] Optionally, the vacuum level required in S3 is 10. -3 -10 -1 Pa, then began to rise in stages, 800 The heating rate below C is 40-80°C. C / min, 800-1200 The heating rate at C is 10⁻⁴⁰ C / min, 1200 The heating rate above C is 2-20 C / min, final set temperature 1200-1400 C. After each heating stage, maintain the temperature for 5-30 minutes.

[0018] Optionally, the forging rate of in-situ multi-step isothermal forging in S4 is stably controlled between 0.001 and 0.01 s. -1 Between each step, the deformation amount of forging is 10-40%, the holding time between each step is 1-10 minutes, and the overall deformation amount of isothermal forging is 20-90%.

[0019] Optionally, in S5, the cooling rate can be set to 20-100. The temperature is set at C / min, and multiple cooling rate stages are set during the cooling process, with each stage held for 5-30 minutes.

[0020] Optionally, the diameter of the cooled deformed TiAl alloy component in S5 is 40-200 mm, and the height is 8-60 mm; the microstructure includes 5-30 vol.% α2(Ti3Al) phase, 60-95 vol.% γ(TiAl) phase, and <5 vol.% β phase. o (B2) phase; room temperature properties: tensile strength 700MPa, yield strength 600MPa, yield ratio 0.75-0.90, elongation after fracture 1%, with a strong plasticity of 0.5-2 GPa. % 800 C. High-temperature performance: tensile strength 500MPa, yield strength 400MPa, yield ratio 0.77-0.87, elongation after fracture 5%, with a strength-plasticity product of 10-20 GPa. %.

[0021] Technical principles of the invention: This invention proposes, firstly, to design a new composition suitable for forging and with low β0 content through compositional control. Specifically, the composition of the TNM alloy is optimized by increasing Al and decreasing Mo, resulting in a novel TiAl alloy suitable for hot working while containing a very small amount of β0 phase. Secondly, through vacuum isothermal forging technology, the as-cast TiAl alloy undergoes complete recrystallization in a direct in-situ multi-step forging process, producing a deformed TiAl alloy with a uniform and fine microstructure. This invention not only improves the plasticity of the TiAl alloy through compositional adjustment but also significantly enhances its overall mechanical properties through a single vacuum isothermal forging process. Furthermore, this invention simplifies the process flow and effectively reduces raw material and processing costs, possessing significant commercial value.

[0022] The above technical solution has at least the following advantages compared with the existing technology: The above-mentioned solution proposes a method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys. This method can solve the technical problems existing in the preparation technology of TiAl alloys, such as small forging deformation, difficulty in effectively coordinating hot working and hot forging, poor effect of synergistic improvement of strength, plasticity and high temperature resistance, long process, high energy consumption and high cost.

[0023] The method of this invention reduces the content of the β0 phase at room temperature through compositional optimization design, increases Al and decreases Mo, and the resulting alloy has a medium Nb content, resulting in lower raw material costs compared to traditional TNM alloys and high Nb-TiAl alloys. Furthermore, the addition of small amounts of elements such as B, C, and Si can refine the microstructure and improve the high-temperature mechanical properties of the alloy.

[0024] This invention employs a three-stage heating and holding process, which enables rapid heating while ensuring uniform temperature within the billet.

[0025] The method of this invention uses in-situ multi-step isothermal forging with heat preservation between each step to promote the recrystallization of TiAl alloy, enhance the uniformity of the microstructure, and reduce the tonnage required for forging and the requirements for equipment.

[0026] The method of the present invention allows for selection of a set cooling rate and cooling to room temperature in the furnace, followed by demolding and removal. This facilitates control of grain size and interlamellar spacing as needed, while ensuring uniform microstructure.

[0027] In summary, compared with traditional methods, the method of this invention can prepare novel deformed TiAl alloy forgings by adjusting the TiAl alloy composition and performing a single vacuum isothermal forging. The resulting forgings have good macroscopic quality, uniform and fine microstructure, and excellent mechanical properties. The method has a simple process flow, does not require complex encapsulation or repeated heating, is easy to operate, has low cost, low energy consumption, and high efficiency, and is conducive to large-scale industrial production and promotion. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a macroscopic morphology image of a Ti-45.5Al-4Nb-0.5Mo-0.1B alloy forging prepared by a method for controlling the suppression of hard and brittle phases and improving room temperature plasticity of TiAl alloy according to Example 1 of the present invention. In this image, A is marked as the edge, B is marked as the 1 / 2 radius, and C is marked as the center. Figure 2This is a Ti-45.5Al-4Nb-0.5Mo-0.1B alloy forging prepared using a method for controlling the suppression of hard and brittle phases and improving room temperature plasticity in TiAl alloys according to Example 1 of the present invention. Figure 1 Microscopic tissue diagram at point A in the middle; Figure 3 This is a Ti-45.5Al-4Nb-0.5Mo-0.1B alloy forging prepared using a method for controlling the suppression of hard and brittle phases and improving room temperature plasticity in TiAl alloys according to Example 1 of the present invention. Figure 1 Microscopic tissue diagram at point B in the middle; Figure 4 This is a Ti-45.5Al-4Nb-0.5Mo-0.1B alloy forging prepared using a method for controlling the suppression of hard and brittle phases and improving room temperature plasticity in TiAl alloys according to Example 1 of the present invention. Figure 1 Microscopic tissue diagram at point C in the middle; Figure 5 This is a room temperature tensile curve of a Ti-45.5Al-4Nb-0.5Mo-0.1B alloy forging prepared by a method for controlling the suppression of hard and brittle phases and improving room temperature plasticity of TiAl alloy according to Example 1 of the present invention. Figure 6 This is a microstructure diagram of a Ti-45.5Al-4Nb-0.5Mo-0.1B-0.1Si alloy forging prepared by a method for controlling the suppression of hard and brittle phases and improving room temperature plasticity of TiAl alloy according to Example 2 of the present invention. Figure 7 This is a microstructure diagram of a Ti-45.5Al-4Nb-0.5Mo-0.1B-0.5Si-0.1C alloy forging prepared by a method for controlling the suppression of hard and brittle phases and improving room temperature plasticity of TiAl alloy according to Example 3 of the present invention. Detailed Implementation

[0030] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0031] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0032] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0033] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0034] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0035] A method for controlling the suppression of brittle phases and the enhancement of room temperature plasticity in TiAl alloys, comprising the following steps: S1. Smelting + Machining: TiAl alloy ingots are obtained by casting metallurgy according to the composition of TiAl alloy, and TiAl alloy preforms for vacuum isothermal forging are obtained by machining. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; S3. Vacuum heating: Place the coated TiAl alloy preform and coating mold from S2 into a vacuum isothermal forging equipment, close the hatch and start evacuating the vacuum. Once the vacuum level reaches the required level, start multi-stage heating and heat preservation to obtain the coated TiAl alloy preform and coating mold to be forged. S4. Multi-step isothermal forging: After vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated mold to be forged are subjected to in-situ multi-step isothermal forging. The temperature is maintained between each step until the required deformation of the final product is reached, and then the forging is ended to obtain the forged TiAl alloy component. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select the set cooling rate and cool it to room temperature in the furnace. Then demold and take out the cooled deformed TiAl alloy component as the final product.

[0036] Specifically, the TiAl alloy composition in S1, by atomic percentage, is: Al 44-48 at.%, Nb 3-6 at.%, Mo 0-0.6 at.%, B / C / Si / N 0-1.5 at.%, RE 0-2.1 at.%, with the balance being Ti and other unavoidable impurities.

[0037] Specifically, the smelting temperature for the ingot metallurgical method in S1 is 1600-1650 °C. C, vacuum degree is 1 10 -3 -8 10 -3 Pa, argon atmosphere protection, melting times are 2-5 times, and the casting mold is a graphite / metal mold.

[0038] Specifically, in S1, the machining is a mechanical cutting process, resulting in a cylindrical TiAl alloy preform for vacuum isothermal forging with a length-to-diameter ratio of 1:1 to 1:2 and a diameter of 20-200 mm.

[0039] Specifically, in S2, the mold is one or a combination of graphite mold, molybdenum alloy mold or high-temperature alloy mold, and the demolding material is graphite foil or boron nitride.

[0040] Specifically, the thickness of the release material coating on the TiAl alloy preform in S2 is 100-500 μm, and the thickness of the release material coating on the mold surface is 100-500 μm.

[0041] Specifically, the vacuum level required in S3 is 10. -3 -10 -1 Pa, then began to rise in stages, 800 The heating rate below C is 40-80°C. C / min, 800-1200 The heating rate at C is 10⁻⁴⁰ C / min, 1200 The heating rate above C is 2-20 C / min, final set temperature 1200-1400 C. After each heating stage, maintain the temperature for 5-30 minutes.

[0042] Optionally, the forging rate of in-situ multi-step isothermal forging in S4 is stably controlled between 0.001 and 0.01 s. -1 Between each step, the deformation amount of forging is 10-40%, the holding time between each step is 1-10 minutes, and the overall deformation amount of isothermal forging is 20-90%.

[0043] Optionally, in S5, the cooling rate can be set to 20-100. The temperature is set at C / min, and multiple cooling rate stages are set during the cooling process, with each stage held for 5-30 minutes.

[0044] Optionally, the diameter of the cooled deformed TiAl alloy component in S5 is 40-200 mm, and the height is 8-60 mm; the microstructure includes 5-30 vol.% α2(Ti3Al) phase, 60-95 vol.% γ(TiAl) phase, and <5 vol.% β phase. o (B2) phase; room temperature properties: tensile strength 700MPa, yield strength 600MPa, yield ratio 0.75-0.90, elongation after fracture 1%, with a strong plasticity of 0.5-2 GPa. % 800 C. High-temperature performance: tensile strength 500MPa, yield strength 400MPa, yield ratio 0.77-0.87, elongation after fracture 5%, with a strength-plasticity product of 10-20 GPa. %.

[0045] Example 1

[0046] This embodiment discloses a method for controlling the suppression of brittle phases and the enhancement of room temperature plasticity in a TiAl alloy. The TiAl alloy composition is Ti-45.5Al-4Nb-0.5Mo-0.1B. The method for controlling the suppression of brittle phases and the enhancement of room temperature plasticity in the TiAl alloy includes the following steps: S1. Smelting + Machining: Based on the TiAl alloy composition, TiAl alloy ingots are obtained using the ingot metallurgical method, and then smelted in a magnetic levitation vacuum levitation melting furnace at a melting temperature of 1600°C. C, vacuum degree is 2.3 10 -3 Under argon atmosphere protection, the melting process was carried out twice, and finally the mixture was poured into a cylindrical graphite mold to obtain TiAl alloy ingots. TiAl alloy preforms for vacuum isothermal forging were obtained by machining. The machining was wire cutting and milling. The TiAl alloy preforms for vacuum isothermal forging were cylindrical with a length-to-diameter ratio of 1:1 and a diameter of 30 mm. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; the mold is a graphite mold and the release material is boron nitride; the thickness of the release material coating on the TiAl alloy preform is 200μm and the thickness of the release material coating on the mold surface is 300μm. S3. Vacuum Heating: Place the coated TiAl alloy preform and coating mold from S2 into the vacuum isothermal forging equipment, close the hatch, and begin vacuuming until the vacuum level reaches the required 10. -1 After Pa, multi-stage heating and holding begins, with an initial heating rate of 40°C. C / min, heating up to 800 Hold at temperature C for 10 minutes, then change the heating rate to 30°C. C / min, heating to 1200 Hold at temperature C for 20 minutes, then change the heating rate to 10. C / min, continue heating to 1260 C, hold for 5 minutes to obtain the coated TiAl alloy preform to be forged and the coating mold to be forged; S4. Multi-step isothermal forging: After the vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated die to be forged are subjected to in-situ multi-step isothermal forging. The forging rate is stably controlled between 0.001-0.005 s. -1 In the first step, the forging deformation is 40%, and the holding time is 2 minutes. In the second step, the forging deformation is 40%, and the overall deformation is 64%. The forging is then completed, and the forged TiAl alloy component is obtained. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select and set the cooling rate to 20. Cool down to 1000 C / min C, hold at this temperature for 10 minutes, then cool to room temperature at the maximum cooling rate of the equipment. After that, demold and remove the cooled deformed TiAl alloy component as follows: Figure 1 The final product shown has good surface quality and is free of cracks. Its edge microstructure morphology is as follows: Figure 2 As shown, the microstructure morphology at 1 / 2 radius is as follows Figure 3 As shown, the central microstructure morphology is as follows Figure 4 As shown.

[0047] The cooled deformed TiAl alloy component prepared in this embodiment has a size of Φ50. The microstructure, measuring 12 mm, comprises 90.0% γ phase, 9.6% α2 phase, and 0.4% β0 phase by volume. Figure 5 As shown, the room temperature properties are: tensile strength of 806.7 MPa, yield strength of 675.1 MPa, yield ratio of 0.84, elongation after fracture of 1.9%, and strength-ductility product of 1.5 GPa. % 800 C. High-temperature properties: Tensile strength is 628.2 MPa, yield strength is 476.2 MPa, yield ratio is 0.76, elongation after fracture is 30.2%, and strength-ductility product is 19.0 GPa. %.

[0048] Comparative Example 1

[0049] The method of the present invention is used to prepare deformed TNM alloy forgings. The specific steps are consistent with those of Example 1. After forging, a disc with good quality and no cracks is obtained, similar to that of Example 1. However, the volume fraction of β0 phase in its microstructure is higher than 6%, and the elongation after fracture at room temperature is only 0.63%. Compared with Example 1, the room temperature plasticity is lower, making it difficult to machine into irregularly shaped high-temperature resistant parts for engines.

[0050] Comparative Example 2

[0051] Ti-45.5Al-4Nb-0.5Mo-0.1B alloy ingots were obtained using the same ingot metallurgical method as in Example 1. The ingots were then forged using a conventional cladding forging method. The heating process parameters were consistent with Example 1, with a 10-minute holding time between the two forging steps. All other parameters, including the cooling stage, were also identical. After forging, the uncladding revealed a central depression in the forging, and the microstructure showed poor uniformity. Compared to Example 1, this process is more complex and produces lower-quality forgings.

[0052] Example 2

[0053] This embodiment describes a method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in a TiAl alloy. The TiAl alloy composition is Ti-45.5Al-4Nb-0.5Mo-0.1B-0.1Si. The method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in the TiAl alloy includes the following steps: S1. Smelting + Machining: Based on the TiAl alloy composition, TiAl alloy ingots are obtained using the ingot metallurgical method, and then smelted in a magnetic levitation vacuum levitation melting furnace at a melting temperature of 1600°C. C, vacuum degree is 2.3 10 -3 Under argon atmosphere protection, the melting process was carried out twice, and finally the mixture was poured into a cylindrical graphite mold to obtain TiAl alloy ingots. TiAl alloy preforms for vacuum isothermal forging were obtained by machining. The machining was wire cutting and milling. The TiAl alloy preforms for vacuum isothermal forging were cylindrical with a length-to-diameter ratio of 1:1 and a diameter of 50 mm. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; the mold is a graphite mold and the release material is boron nitride; the thickness of the release material coating on the TiAl alloy preform is 200μm and the thickness of the release material coating on the mold surface is 100μm. S3. Vacuum Heating: Place the coated TiAl alloy preform and coating mold from S2 into the vacuum isothermal forging equipment, close the hatch, and begin vacuuming until the vacuum level reaches the required 10. -1 After Pa, multi-stage heating and holding begins, with an initial heating rate of 40°C. C / min, heating up to 800 Hold at temperature C for 10 minutes, then change the heating rate to 30°C. C / min, heating to 1200 Hold at temperature C for 20 minutes, then change the heating rate to 10. C / min, heating to 1300 Hold at temperature C for 20 minutes, then change the heating rate to 5. C / min, continue heating to 1340 C, hold for 5 min; to obtain the coated TiAl alloy preform to be forged and the coating mold to be forged; S4. Multi-step isothermal forging: After the vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated die to be forged are subjected to in-situ multi-step isothermal forging. The forging rate of each step is stably controlled at 0.005-0.01s. -1 Between these points, the deformation is 20%, and the holding time is 5 minutes. This process is repeated 4 times, and the final deformation is about 60%. The forging is then completed, and the forged TiAl alloy component is obtained. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select and set the cooling rate to 30. Cool down to 1000 C / min C, hold at this temperature for 30 minutes, then cool to room temperature at the maximum cooling rate of the equipment. Afterwards, demold and remove the cooled TiAl alloy component. Its microstructure morphology is as follows: Figure 6 As shown.

[0054] The cooled deformed TiAl alloy component prepared in this embodiment has a size of Φ80. The sample was 20 mm thick. Its microstructure consisted of 82.5% γ phase, 17.4% α2 phase, and 0.1% β0 phase by volume. Room temperature properties: tensile strength 703.9 MPa, yield strength 607.7 MPa, yield ratio 0.86, elongation after fracture 1.0%, and strength-ductility product 0.7 GPa. % 800 C. High-temperature properties: Tensile strength is 613.2 MPa, yield strength is 529.3 MPa, yield ratio is 0.86, elongation after fracture is 27.3%, and strength-ductility product is 16.7 GPa. %.

[0055] Example 3

[0056] This embodiment discloses a method for controlling the suppression of brittle phases and the enhancement of room temperature plasticity in a TiAl alloy. The TiAl alloy composition is Ti-45.5Al-4Nb-0.5Mo-0.1B-0.5Si-0.1C. The method for controlling the suppression of brittle phases and the enhancement of room temperature plasticity in the TiAl alloy includes the following steps: S1. Smelting + Machining: Based on the TiAl alloy composition, TiAl alloy ingots are obtained using the ingot metallurgical method, and then smelted in a magnetic levitation vacuum levitation melting furnace at a melting temperature of 1650°C. C, vacuum degree is 2.2 10-3 Under argon atmosphere protection, the melting process was carried out 4 times, and finally the mixture was poured into a cylindrical graphite mold to obtain TiAl alloy ingots. TiAl alloy preforms for vacuum isothermal forging were obtained by machining. The machining was wire cutting and milling. The TiAl alloy preforms for vacuum isothermal forging were cylindrical with a length-to-diameter ratio of 1:2 and a diameter of 50 mm. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; the mold is a graphite mold and the release material is boron nitride; the thickness of the release material coating on the TiAl alloy preform is 200μm and the thickness of the release material coating on the mold surface is 100μm. S3. Vacuum Heating: Place the coated TiAl alloy preform and coating mold from S2 into the vacuum isothermal forging equipment, close the hatch, and begin vacuuming until the vacuum level reaches the required 10. -1 After Pa, multi-stage heating and holding begins, with an initial heating rate of 40°C. C / min, heating up to 800 Hold at temperature C for 10 minutes, then change the heating rate to 10. C / min, heating to 1200 Hold at temperature C for 30 minutes, then change the heating rate to 5. C / min, heating to 1300 Hold at temperature C for 30 minutes, then continue heating at a rate of 5. C / min, temperature increased to 1330 C, hold for 10 min; to obtain the coated TiAl alloy preform to be forged and the coating mold to be forged; S4. Multi-step isothermal forging: After the vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated die to be forged are subjected to in-situ multi-step isothermal forging. The forging rate of each step is stably controlled at 0.002-0.005s. -1 Between these points, the deformation is 20%, and the holding time is 10 minutes. This process is repeated 3 times, and the final deformation is about 50%. The forging is then completed, and the forged TiAl alloy component is obtained. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select and set the cooling rate to 30. Cool down to 1200 °C / min C, keep warm for 30 minutes, then set the cooling rate to 20. Cool down to 900°C / min C, hold at this temperature for 10 minutes, then cool to room temperature at the maximum cooling rate of the equipment. Afterwards, demold and remove the cooled TiAl alloy component. Its microstructure morphology is as follows: Figure 7 As shown.

[0057] The cooled deformed TiAl alloy component prepared in this embodiment has a size of Φ70. The sample was 50 mm thick. The microstructure consisted of 83.2% γ phase, 16.7% α2 phase, and 0.1% β0 phase by volume. Room temperature properties: tensile strength 735.8 MPa, yield strength 604.7 MPa, yield ratio 0.82, elongation after fracture 1.8%, and strength-ductility product 1.3 GPa. % 800 C. High-temperature properties: Tensile strength is 643.3 MPa, yield strength is 550.2 MPa, yield ratio is 0.86, elongation after fracture is 18.2%, and strength-ductility product is 11.7 GPa. %.

[0058] Example 4

[0059] This embodiment describes a method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in a TiAl alloy. The TiAl alloy composition is Ti-46.5Al-4Nb-0.2Mo-0.1B-0.01Y. The method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in the TiAl alloy includes the following steps: S1. Smelting + Machining: Based on the TiAl alloy composition, TiAl alloy ingots are obtained using the ingot metallurgical method, and then smelted in a magnetic levitation vacuum levitation melting furnace at a melting temperature of 1600°C. C, vacuum degree is 5.0 10 -3 Under argon atmosphere protection, the melting process was carried out three times, and finally the mixture was poured into a cylindrical graphite mold to obtain TiAl alloy ingots. TiAl alloy preforms for vacuum isothermal forging were obtained by machining. The machining was wire cutting and milling. The TiAl alloy preforms for vacuum isothermal forging were cylindrical with a length-to-diameter ratio of 1:1.5 and a diameter of 30 mm. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; the mold is a graphite mold and the release material is boron nitride; the thickness of the release material coating on the TiAl alloy preform is 200μm and the thickness of the release material coating on the mold surface is 200μm. S3. Vacuum Heating: Place the coated TiAl alloy preform and coating mold from S2 into the vacuum isothermal forging equipment, close the hatch, and begin vacuuming until the vacuum level reaches the required 10. -1 After Pa, multi-stage heating and holding begins, with an initial heating rate of 60°C. C / min, heating up to 800 Hold at temperature C for 10 minutes, then change the heating rate to 35°C. C / min, heating to 1200 Hold at temperature C for 10 minutes, then change the heating rate to 15. C / min, heating to 1300 Hold at temperature C for 10 minutes to obtain a preform of coated TiAl alloy to be forged and a coating mold to be forged. S4. Multi-step isothermal forging: After the vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated die to be forged are subjected to in-situ multi-step isothermal forging. The forging rate of each step is stably controlled at 0.005-0.01s. -1 Between these points, the deformation amount is 41%, and the holding time is 5 minutes. This process is repeated 3 times, and the final deformation amount is about 80%. The forging is then completed, and the forged TiAl alloy component is obtained. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select and set the cooling rate to 20. Cool down to 1000 C / min C, keep warm for 30 minutes, then cool to room temperature at the maximum cooling rate of the equipment, and then demold and remove the cooled TiAl alloy component.

[0060] The cooled deformed TiAl alloy component prepared in this embodiment has a size of Φ67. The sample was 9 mm thick. The microstructure consisted of 90.7% γ phase, 9.1% α2 phase, and 0.2% β0 phase by volume. Room temperature properties: tensile strength 777.8 MPa, yield strength 655.1 MPa, yield ratio 0.84, elongation after fracture 1.6%, and strength-ductility product 1.2 GPa. % 800 C. High-temperature properties: Tensile strength is 610.6 MPa, yield strength is 504.3 MPa, yield ratio is 0.83, elongation after fracture is 20.5%, and strength-ductility product is 12.5 GPa. %.

[0061] Example 5

[0062] This embodiment describes a method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in a TiAl alloy. The TiAl alloy composition is Ti-45.5Al-4Nb-0.2Mo-0.1B. The method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in the TiAl alloy includes the following steps: S1. Smelting + Machining: Based on the TiAl alloy composition, TiAl alloy ingots are obtained using the ingot metallurgical method, and then smelted in a magnetic levitation vacuum levitation melting furnace at a melting temperature of 1650°C. C, vacuum degree is 2.3 10 -3 Under argon atmosphere protection, the melting process was carried out twice, and finally the mixture was poured into a cylindrical graphite mold to obtain TiAl alloy ingots. TiAl alloy preforms for vacuum isothermal forging were obtained by machining. The machining was wire cutting and milling. The TiAl alloy preforms for vacuum isothermal forging were cylindrical with a length-to-diameter ratio of 1:1 and a diameter of 30 mm. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; the mold is a graphite mold and the release material is boron nitride; the thickness of the release material coating on the TiAl alloy preform is 200μm and the thickness of the release material coating on the mold surface is 100μm. S3. Vacuum Heating: Place the coated TiAl alloy preform and coating mold from S2 into the vacuum isothermal forging equipment, close the hatch, and begin vacuuming until the vacuum level reaches the required 10. -1 After Pa, multi-stage heating and holding begins, with an initial heating rate of 40°C. C / min, heating up to 800 Hold at temperature C for 10 minutes, then change the heating rate to 30°C. C / min, heating to 1200 Hold at temperature C for 20 minutes, then change the heating rate to 10. C / min, continue heating to 1330 C, hold for 5 minutes to obtain the coated TiAl alloy preform to be forged and the coating mold to be forged; S4. Multi-step isothermal forging: After the vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated die to be forged are subjected to in-situ multi-step isothermal forging. The forging rate of each step is stably controlled at 0.001-0.005s. -1 Between these points, the deformation is 20%, and the holding time is 5 minutes. This process is repeated 4 times, and the final deformation is about 60%. The forging is then completed, and the forged TiAl alloy component is obtained. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select and set the cooling rate to 20. Cool down to 900°C / min C, keep warm for 30 minutes, then cool to room temperature at the maximum cooling rate of the equipment, and then demold and remove the cooled TiAl alloy component.

[0063] The cooled deformed TiAl alloy component prepared in this embodiment has a size of Φ50. The microstructure, measuring 12 mm in diameter, comprises 87.6% γ phase, 12.0% α2 phase, and 0.4% β0 phase by volume. Room temperature properties include a tensile strength of 794.0 MPa, a yield strength of 698.7 MPa, a yield ratio of 0.88, an elongation after fracture of 1.7%, and a strength-ductility product of 1.3 GPa. % 800 C. High-temperature properties: tensile strength is 635.9 MPa, yield strength is 528.2 MPa, yield ratio is 0.83, elongation after fracture is 25.9%, and strength-ductility product is 16.5 GPa. %.

[0064] Example 6

[0065] This embodiment describes a method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in a TiAl alloy. The TiAl alloy composition is Ti-47.5Al-4Nb-0.1Mo-0.1B. The method for controlling the suppression of brittle phases and the enhancement of room-temperature plasticity in the TiAl alloy includes the following steps: S1. Smelting + Machining: Based on the TiAl alloy composition, TiAl alloy ingots are obtained using the ingot metallurgical method, and then smelted in a magnetic levitation vacuum levitation melting furnace at a melting temperature of 1650°C. C, vacuum degree is 2.3 10 -3 Under argon atmosphere protection, the melting process was carried out twice, and finally the mixture was poured into a cylindrical graphite mold to obtain TiAl alloy ingots. TiAl alloy preforms for vacuum isothermal forging were obtained by machining. The machining was wire cutting and milling. The TiAl alloy preforms for vacuum isothermal forging were cylindrical with a length-to-diameter ratio of 1:1 and a diameter of 30 mm. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; the mold is a graphite mold and the release material is boron nitride; the thickness of the release material coating on the TiAl alloy preform is 200μm and the thickness of the release material coating on the mold surface is 100μm. S3. Vacuum Heating: Place the coated TiAl alloy preform and coating mold from S2 into the vacuum isothermal forging equipment, close the hatch, and begin vacuuming until the vacuum level reaches the required 10. -1 After Pa, multi-stage heating and holding begins, with an initial heating rate of 40°C. C / min, heating up to 800 Hold at temperature C for 10 minutes, then change the heating rate to 30°C. C / min, heating to 1200 Hold at temperature C for 20 minutes, then change the heating rate to 10. C / min, continue heating to 1360 C, hold for 5 minutes to obtain the coated TiAl alloy preform to be forged and the coating mold to be forged; S4. Multi-step isothermal forging: After the vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated die to be forged are subjected to in-situ multi-step isothermal forging. The forging rate of each step is stably controlled at 0.001-0.005s. -1 Between these points, the deformation is 20%, and the holding time is 5 minutes. This process is repeated 4 times, and the final deformation is about 60%. The forging is then completed, and the forged TiAl alloy component is obtained. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select and set the cooling rate to 20. Cool down to 1000 C / min C, keep warm for 30 minutes, then cool to room temperature at the maximum cooling rate of the equipment, and then demold and remove the cooled TiAl alloy component.

[0066] The cooled deformed TiAl alloy component prepared in this embodiment has a size of Φ50. The sample is 12 mm thick, and its microstructure consists of 91.2% γ phase and 8.8% α2 phase by volume. Room temperature properties: tensile strength 784.7 MPa, yield strength 673.9 MPa, yield ratio 0.86, elongation after fracture 1.6%, and strength-ductility product 1.3 GPa. % 800 C. High-temperature properties: Tensile strength is 510.9 MPa, yield strength is 402.5 MPa, yield ratio is 0.79, elongation after fracture is 33.2%, and strength-ductility product is 17.0 GPa. %.

[0067] The above-mentioned solution proposes a method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys. This method can solve the technical problems existing in the preparation technology of TiAl alloys, such as small forging deformation, difficulty in effectively coordinating hot working and hot forging, poor effect of synergistic improvement of strength, plasticity and high temperature resistance, long process, high energy consumption and high cost.

[0068] The method of this invention reduces the content of the β0 phase at room temperature through compositional optimization design, increases Al and decreases Mo, and the resulting alloy has a medium Nb content, resulting in lower raw material costs compared to traditional TNM alloys and high Nb-TiAl alloys. Furthermore, the addition of small amounts of elements such as B, C, and Si can refine the microstructure and improve the high-temperature mechanical properties of the alloy.

[0069] This invention employs a three-stage heating and holding process, which enables rapid heating while ensuring uniform temperature within the billet.

[0070] The method of this invention uses in-situ multi-step isothermal forging with heat preservation between each step to promote the recrystallization of TiAl alloy, enhance the uniformity of the microstructure, and reduce the tonnage required for forging and the requirements for equipment.

[0071] The method of the present invention allows for selection of a set cooling rate and cooling to room temperature in the furnace, followed by demolding and removal. This facilitates control of grain size and interlamellar spacing as needed, while ensuring uniform microstructure.

[0072] In summary, compared with traditional methods, the method of this invention can prepare novel deformed TiAl alloy forgings by adjusting the TiAl alloy composition and performing a single vacuum isothermal forging. The resulting forgings have good macroscopic quality, uniform and fine microstructure, and excellent mechanical properties. The method has a simple process flow, does not require complex encapsulation or repeated heating, is easy to operate, has low cost, low energy consumption, and high efficiency, and is conducive to large-scale industrial production and promotion.

[0073] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0074] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0075] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0076] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys, characterized in that, The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in the TiAl alloy includes the following steps: S1. Smelting + Machining: TiAl alloy ingots are obtained by casting metallurgy according to the composition of TiAl alloy, and TiAl alloy preforms for vacuum isothermal forging are obtained by machining. S2, Coating with release material: A release material is uniformly coated on the surface of the TiAl alloy preform and the mold in S1 to obtain a coated TiAl alloy preform and a coated mold; S3. Vacuum heating: Place the coated TiAl alloy preform and coating mold from S2 into a vacuum isothermal forging equipment, close the hatch and start evacuating the vacuum. Once the vacuum level reaches the required level, start multi-stage heating and heat preservation to obtain the coated TiAl alloy preform and coating mold to be forged. S4. Multi-step isothermal forging: After vacuum heating treatment in S3, the coated TiAl alloy preform to be forged and the coated mold to be forged are subjected to in-situ multi-step isothermal forging. The temperature is maintained between each step until the required deformation of the final product is reached, and then the forging is ended to obtain the forged TiAl alloy component. S5, Cooling + Demolding: After the multi-step isothermal forging in S4, select the set cooling rate and cool it to room temperature in the furnace. Then demold and take out the cooled deformed TiAl alloy component as the final product.

2. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, The TiAl alloy composition in S1, by atomic percentage, is: Al 44-48 at.%, Nb 3-6 at.%, Mo 0-0.6 at.%, B / C / Si / N 0-1.5 at.%, RE 0-2.1 at.%, with the balance being Ti and other unavoidable impurities.

3. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, The smelting temperature for the ingot metallurgical method in S1 is 1600-1650°C. C, vacuum degree is 1 10 -3 -8 10 -3 Pa, argon atmosphere protection, melting times are 2-5 times, and the casting mold is a graphite / metal mold.

4. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, In S1, machining is performed by mechanical cutting, resulting in a cylindrical TiAl alloy preform for vacuum isothermal forging with a length-to-diameter ratio of 1:1 to 1:2 and a diameter of 20-200 mm.

5. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, In S2, the mold is one or a combination of graphite mold, molybdenum alloy mold or high-temperature alloy mold, and the demolding material is graphite foil or boron nitride.

6. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, The thickness of the release material coating on the TiAl alloy preform in S2 is 100-500μm, and the thickness of the release material coating on the mold surface is 100-500μm.

7. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, The vacuum level required in S3 is 10. -3 -10 -1 Pa, then began to rise in stages, 800 The heating rate below C is 40-80°C. C / min, 800-1200 The heating rate at C is 10⁻⁴⁰ C / min, 1200 The heating rate above C is 2-20 C / min, final set temperature 1200-1400 C. After each heating stage, maintain the temperature for 5-30 minutes.

8. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, In S4, the forging rate of in-situ multi-step isothermal forging is stably controlled within 0.001-0.01 s. -1 Between each step, the deformation amount of forging is 10-40%, the holding time between each step is 1-10 minutes, and the overall deformation amount of isothermal forging is 20-90%.

9. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, In S5, select to set the cooling rate to 20-100. The temperature is set at C / min, and multiple cooling rate stages are set during the cooling process, with each stage held for 5-30 minutes.

10. The method for controlling the suppression of hard and brittle phases and the improvement of room temperature plasticity in TiAl alloys according to claim 1, characterized in that, The cooled deformed TiAl alloy components in S5 have a diameter of 40-200 mm and a height of 8-60 mm; the microstructure includes 5-30 vol.% α2(Ti3Al) phase, 60-95 vol.% γ(TiAl) phase, and <5 vol.% β phase. o (B2) phase; room temperature properties: tensile strength 700MPa, yield strength 600MPa, yield ratio 0.75-0.90, elongation after fracture 1%, with a strong plasticity of 0.5-2 GPa. % 800 C. High-temperature performance: tensile strength 500MPa, yield strength 400MPa, yield ratio 0.77-0.87, elongation after fracture 5%, with a strength-plasticity product of 10-20 GPa. %.

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