Necklace-shaped heterostructure high-entropy alloy and preparation method thereof

Abstract

The present application relates to the field of materials, and provide a necklace-like heterostructure high-entropy alloy, the chemical composition range, in terms of atomic percentage, is: Co: 18-25%, Cr: 16-20%, Fe: 16-22%, Ni: 20-30%, Al: 3-6%, Ti: 2-5%, Mo: 0.1-0.8%, Ta: 0.1-0.5%. The preparation method of the necklace-like heterostructure high-entropy alloy, the process flow is: batching, induction melting, casting forming, homogenization, forging, cold deformation and two-step aging heat treatment; the melting process is sequentially placed in the crucible according to the melting point from low to high, the vacuum degree in the induction furnace is maintained within 0.8 Pa during the melting process, after the complete melting of other raw materials, the low melting point alloy such as Al and Ti is sequentially added into the crucible by the material hanging method. The present application has the advantages that the heterostructure high-entropy alloy can provide good comprehensive mechanical properties under complex working conditions, especially an excellent balance between strength and plasticity under high temperature environment. It provides a potential solution for the requirements of wide temperature range use, high strength and high plasticity in practical application.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of materials, in particular to a necklace-shaped heterostructure high-entropy alloy and a preparation method thereof. BACKGROUND

[0002] Since its first proposal in 2004, high-entropy alloys (HEAs) have become a research hotspot in the field of materials science. Unlike traditional alloys, high-entropy alloys are formed by mixing multiple elements in equal atomic ratios or approximately equal atomic ratios, resulting in a high-entropy solid solution. This unique design concept opens up broad prospects for the development of new alloy materials. With further research, heterostructure high-entropy alloys have gradually become an important research direction. By introducing different phases or microstructures into the material, the mechanical properties of the alloy can be effectively controlled, especially achieving a good balance between strength, plasticity and toughness.

[0003] The significant advantage of heterostructure high-entropy alloys lies in their ability to optimize the mechanical properties of the material through multiple interaction mechanisms. In particular, in the balance between strength and plasticity / toughness, heterostructures provide unique advantages. First, the different phases in the heterostructure alloy can significantly improve the strength of the alloy through interface strengthening, mutual pinning mechanisms and deformation coordination. Due to the different hardness and deformation behavior of different phases (or grain structures), the heterostructure can effectively enhance the tensile strength and compressive strength of the alloy through load transfer and dislocation hindering. In addition, each phase (or grain structure) in the heterostructure can also exhibit different plasticity and toughness characteristics according to specific environmental conditions and loading modes, giving the alloy stronger crack propagation resistance and better impact resistance.

[0004] In particular, in high-entropy alloys with face-centered cubic (FCC) structure, the alloy after introducing heterostructure not only can improve the strength through precipitation strengthening, but also can improve the plasticity and toughness. By precisely controlling the size and distribution of the heterostructure, micron to nanometer sized strengthening phases can be formed in the alloy, which significantly improve the yield strength of the alloy through particle strengthening effect, while maintaining good ductility and toughness. This enables heterostructure high-entropy alloys to maintain high strength while avoiding brittle fracture, improving their stability and reliability under complex working conditions. In addition, the interfaces and phase boundaries in the heterostructure alloy serve as the main source of deformation, which helps to maintain the mechanical properties of the material at high temperatures. The high-entropy effect and sluggish diffusion effect in high-entropy alloys not only make the alloy have good high-temperature stability, but also effectively slow down the growth of phase transformation and precipitated strengthening phases, thereby ensuring that the strength and plasticity of the alloy remain in good balance at high temperatures. These characteristics make heterostructure high-entropy alloys have broad application potential in high-temperature environments, especially in the fields of high-temperature bearing materials and fatigue-resistant materials.

[0005] Therefore, the heterogeneous structure high-entropy alloy can significantly improve the plasticity, toughness and fatigue resistance while improving the strength of the material, thereby providing new possibilities for various engineering applications, especially in high-temperature and complex working conditions, and exhibiting excellent performance that cannot be compared with traditional alloys. SUMMARY

[0006] The present application aims to provide a necklace-like heterogeneous structure high-entropy alloy and a preparation method thereof. The necklace-like heterogeneous structure high-entropy alloy is obtained by adding elements such as Al, Ti, Mo and Ta to a non-equiatomic FeCoCrNi high-entropy alloy and adopting special cold deformation and multi-step aging heat treatment. Due to the introduction of the necklace-like heterogeneous structure grains and nanoscale L12 structure intermetallic compounds, the necklace-like heterogeneous structure high-entropy alloy has excellent comprehensive mechanical properties in a wide temperature range and can be used as a structural material in a wide temperature range.

[0007] The technical scheme of the present application is as follows:

[0008] The necklace-like heterogeneous structure high-entropy alloy has a chemical composition range of Co: 18-25%, Cr: 16-20%, Fe: 16-22%, Ni: 20-30%, Al: 3-6%, Ti: 2-5%, Mo: 0.1-0.8% and Ta: 0.1-0.5% in terms of atomic percentage.

[0009] The preparation method of the necklace-like heterogeneous structure high-entropy alloy has the following process flow: batching, induction melting, casting forming, homogenization, forging, cold deformation and two-step aging heat treatment. The oxygen and nitrogen contents are controlled in the induction melting process to prevent the formation of brittle non-metallic inclusions. The raw materials are sequentially placed in the crucible according to the melting point from low to high. The vacuum degree in the induction furnace is maintained within 0.8 Pa during the melting process. After the other raw materials are completely melted, the low-melting-point alloy materials such as Al and Ti are sequentially added to the crucible by the hanging material method. After the raw materials are completely melted, electromagnetic stirring is repeated. The obtained ingot is subjected to homogenization and forging treatment.

[0010] The homogenization treatment temperature and time are 1200-1300℃ and ≥12h, respectively.

[0011] After the ingot is homogenized, it is subjected to forging treatment. The forging holding temperature is 1250℃, the initial temperature is 1190℃, the minimum temperature is 1080℃, and the ingot is repeatedly upset-drawn for more than 5 times. The final sample has a forging ratio of ≥5 and is air-cooled to room temperature after forging.

[0012] Before cold rolling / cold drawing / spinning, the forged sample is subjected to solid solution treatment. The specific process is as follows: solid solution treatment before cold deformation, 1125℃ for 60min, water cooling to room temperature; and cold deformation of the sample on the cold rolling / cold drawing / spinning equipment after the solid solution treatment:

[0013] (1) Cold rolling process: the cold rolling temperature is room temperature, the sample is subjected to multi-pass cold rolling treatment, the thickness change amount of each pass is 2mm, and the sample is cold rolled from 40mm to 20mm through 10 passes, and the total deformation amount is 50%;

[0014] (2) Cold drawing process: the cold drawing temperature is room temperature, the sample is subjected to multi-pass cold drawing treatment, the diameter change amount of each pass is 0.3mm, and the sample is cold drawn from 10mm to 7mm through 10 passes, and the total deformation amount is 51%;

[0015] (3) Swaging process: the swaging temperature is room temperature, the sample is subjected to multi-pass swaging treatment, the diameter change amount of each pass is 1mm, and the sample is swaged from 20mm to 10mm through 10 passes, and the total deformation amount is 75%; in order to ensure that the cold deformation is carried out at room temperature, the sample is cooled in water for 5s after each pass of deformation.

[0016] The aging process after cold deformation is as follows: the cold deformed sample is kept at 920 DEG C for 15min, then the sample is quickly placed in a holding furnace at 760 DEG C for 4h, and then water-cooled to room temperature.

[0017] After two-step aging, the alloy organization has a necklace-shaped grain distribution morphology, wherein the edge of the coarse grain is distributed with necklace-shaped fine grains, forming a surrounding type grain structure in which fine grains wrap coarse grains.

[0018] The room temperature tensile properties of the obtained necklace-shaped heterogeneous structure high-entropy alloy are as follows: the yield strength is greater than or equal to 1100MPa, the tensile strength is greater than or equal to 1400MPa, and the elongation is greater than or equal to 12%; the tensile mechanical properties at-196 DEG C are as follows: the yield strength is greater than or equal to 1400MPa, the tensile strength is greater than or equal to 1800MPa, and the elongation is greater than or equal to 12%; the tensile properties at 650 DEG C are as follows: the yield strength is greater than or equal to 1000MPa, the tensile strength is greater than or equal to 1100MPa, and the elongation is greater than or equal to 12%.

[0019] Based on the FeCoCrNi high-entropy alloy matrix, the heterogeneous structure high-entropy alloy with excellent mechanical properties is developed through composition optimization and experimental exploration. First, by adding Al, Ti, Mo, Ta and other elements, the composition of the alloy is controlled and optimized, and the phase composition and microstructure are optimized. Through forging + special cold deformation + two-step aging treatment process, the alloy forms a necklace-shaped heterogeneous structure, which can effectively improve the strength of the alloy, and optimize the plasticity and toughness, so that the alloy can exhibit excellent comprehensive mechanical properties at low temperature, room temperature and high temperature.

[0020] The advantages and beneficial effects of the present application are:

[0021] The application creates conditions for subsequent regulation of necklace-shaped grain structure by introducing a large number of dislocations in the alloy while retaining the original equiaxed grain boundaries of the alloy through special cold deformation treatment methods including cold rolling, cold drawing and spinning. In this process, the accumulation of dislocations and the evolution of grain boundaries will provide a basis for subsequent microstructure regulation. Subsequently, a two-step heat treatment process of high temperature + low temperature is adopted to further regulate the microstructure of the alloy. In the high temperature stage, the original grain boundaries in the alloy are first formed by recrystallization fine grains, and the recrystallization in the grain is hindered by the L12 structure nanophase formed at the same time, thereby forming a necklace-shaped grain structure. Subsequently, in the low temperature stage, the volume fraction of the nanophase is further promoted by further promoting the precipitation of the nanophase. Through the above process, the necklace-shaped heterogeneous structure of small grains wrapping large grains is formed in the alloy. Through a series of precise process design and regulation, the final heterogeneous structure high-entropy alloy can provide good comprehensive mechanical properties under complex working conditions, especially excellent strength / plasticity balance under high temperature environment. This design idea provides a new direction for the development of high-performance alloy materials, and provides a potential solution for the wide temperature range use, high strength and high plasticity requirements in practical applications. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The low temperature-196 DEG C, room temperature 25 DEG C and high temperature 650 DEG C tensile curves of the sample of example 1 are shown in the figure;

[0023] Figure 2 The scanning electron microscope morphology of the sample of example 1 is shown in the figure;

[0024] Figure 3 The low temperature-196 DEG C, room temperature 25 DEG C and high temperature 650 DEG C tensile curves of the sample of example 2 are shown in the figure;

[0025] Figure 4 The scanning electron microscope morphology of the sample of example 2 is shown in the figure;

[0026] Figure 5 The low temperature-196 DEG C, room temperature 25 DEG C and high temperature 650 DEG C tensile curves of the sample of example 3 are shown in the figure;

[0027] Figure 6 The scanning electron microscope morphology of the sample of example 3 is shown in the figure;

[0028] Figure 7 The low temperature-196 DEG C, room temperature 25 DEG C and high temperature 650 DEG C tensile curves of the sample of example 4 are shown in the figure;

[0029] Figure 8 The scanning electron microscope morphology of the sample of example 4 is shown in the figure;

[0030] Figure 9 The transmission electron microscope morphology of the discontinuous precipitated nanophase in the sample of example 4 is shown in the figure;

[0031] Figure 10 EBSD results of the necklace-like grain of Example 4. DETAILED DESCRIPTION

[0032] The following examples will further illustrate the present application but do not limit the present application.

[0033] Example 1

[0034] The nominal composition of the alloy is, in atomic percentage: Fe: 20%, Co: 25%, Cr: 18%, Ni: 28%, Al: 4.6%, Ti: 4.0%, Mo: 0.2%, Ta: 0.2%. According to the atomic ratio of the composition, the raw materials are converted into mass percentage for batching, and each raw material is carefully polished to remove surface impurities. Then, according to the order of melting point from low to high, each alloy component is added to the crucible of the induction furnace in turn. The smelting process is carried out in a vacuum environment, maintaining the vacuum degree in the furnace at 0.2 Pa until the alloy raw materials are completely melted. Then, electromagnetic stirring is used for refining, and the refining time is 1 hour, and five times of skull remelting is carried out.

[0035] The cast ingot after smelting will undergo the following hot working and heat treatment process:

[0036] (1) Homogenization treatment: 1200℃ for 12h;

[0037] (2) Forging: the initial forging temperature is 1190℃, and 5 times of repeated upsetting and drawing is carried out, and then the cast ingot is forged into a round bar, and the forging ratio is 5, and after forging, it is naturally cooled to room temperature;

[0038] (3) Solution treatment: 1125℃ for 60min, and then water cooled to room temperature immediately;

[0039] (5) Aging treatment: the above cold-drawn alloy is aged at 920℃ for 15min, and then the alloy is placed in a muffle furnace at 760℃ for 4h, and then water cooled to room temperature.

[0040] The alloy after aging treatment is processed into samples, and its tensile mechanical properties at low temperature-196℃, room temperature 25℃ and high temperature 650℃ are tested respectively, and metallographic observation is carried out on the test samples. The tensile curve is shown in Figure 1 Table 1 shows the test results of yield strength, tensile strength and elongation. The microstructure is shown in Figure 2

[0041] Example 2

[0042] ​The nominal composition of the alloy is, in atomic percentage: Fe: 20%, Co: 25%, Cr: 18%, Ni: 28%, Al: 4.6%, Ti: 4.0%, Mo: 0.2%, Ta: 0.2%. According to the atomic ratio of the composition, the raw materials are converted into mass percentage for batching, and each raw material is carefully polished to remove surface impurities. Subsequently, in order of low to high melting point, each alloy component is sequentially added to the crucible of the induction furnace. The smelting process is carried out in a vacuum environment, maintaining the vacuum degree in the furnace at 0.2 Pa until the alloy raw materials are completely melted. Subsequently, electromagnetic stirring is used for refining, and the refining time is 1 hour, and five times of skull remelting are carried out.

[0043] The cast ingot after smelting will undergo the following hot working and heat treatment process:

[0044] (1) Homogenization treatment: 1250℃ for 12h;

[0045] (2) Forging: The initial forging temperature is 1190℃, and 5 times of repeated upsetting and drawing are carried out, and then the cast ingot is forged into a round bar, and the forging ratio is 5, and the forged bar is naturally cooled to room temperature;

[0046] (3) Solution treatment: 1125℃ for 60min, and then water cooled to room temperature immediately;

[0047] (4) Cold working treatment: After solution treatment, the alloy is cold rolled and deformed, and the specific scheme is: taking a plate with a thickness of 40mm from the round bar after solution treatment, rolling it to a thickness of 20mm in 10 passes, with a total deformation of 50%, and a deformation of 2mm per pass. After each pass, the sample is placed in water for 5s to ensure that each deformation is carried out at room temperature.

[0048] (5) Aging treatment: the cold rolled alloy is aged at 920℃ for 15min, and then placed in a 760℃ muffle furnace for 4h, and then water cooled to room temperature.

[0049] The alloy after aging treatment is processed into samples, and its tensile mechanical properties at low temperature-196℃, room temperature 25℃ and high temperature 650℃ are tested, and metallographic observation is carried out on the test samples. The tensile curve is shown in Figure 3 , and the test results of yield strength, tensile strength and elongation are shown in Table 1. The microstructure is shown in Figure 4 .

[0050] Example 3

[0051] The nominal composition of the alloy is, in atomic percentage: Fe: 20%, Co: 25%, Cr: 18%, Ni: 28%, Al: 4.6%, Ti: 4.0%, Mo: 0.2%, Ta: 0.2%. According to the atomic ratio of the composition, the raw materials are converted into mass percentage for batching, and each raw material is carefully polished to remove surface impurities. Subsequently, in order of low to high melting point, each alloy component is sequentially added to the crucible of the induction furnace. The smelting process is carried out in a vacuum environment, maintaining a vacuum degree of 0.2 Pa in the furnace until the alloy raw materials are completely melted. Subsequently, electromagnetic stirring is used for refining, and the refining time is 1 hour, and five times of skull remelting are carried out.

[0052] The cast ingot after smelting will undergo the following hot working and heat treatment process:

[0053] (1) Homogenization treatment: 1200℃ for 12h;

[0054] (2) Forging: The initial forging temperature is 1190℃, and 5 times of repeated upsetting and drawing are carried out, and then the cast ingot is forged into a round bar, and the forging ratio is 5, and the forged bar is naturally cooled to room temperature;

[0055] (3) Solution treatment: 1125℃ for 60min, and then water cooled to room temperature immediately;

[0056] (4) Cold working treatment: After solution treatment, the alloy is deformed by room temperature cold drawing, and the specific scheme is: taking a plate with a thickness of Φ10mm from the round bar after solution treatment, and cold drawing to a diameter of 7.0mm in 10 passes (the diameter changes by 0.3mm in each pass). After the end of each pass, the sample is placed in water for 5s to ensure that each pass is deformed at room temperature.

[0057] (5) Aging treatment: The cold-drawn alloy is aged at 920℃ for 15min, and then placed in a 760℃ muffle furnace for 4h, and then water cooled to room temperature.

[0058] The alloy after aging treatment is processed into samples, and its tensile mechanical properties at low temperature-196℃, room temperature 25℃ and high temperature 650℃ are tested, and metallographic observation is carried out on the test samples. The tensile curve is shown in Figure 5 , and the test results of yield strength, tensile strength and elongation are shown in Table 1. The microstructure morphology is shown in Figure 6 .

[0059] Example 4

[0060] The nominal composition of the alloy is, in atomic percentage: Fe: 20%, Co: 25%, Cr: 18%, Ni: 28%, Al: 4.6%, Ti: 4.0%, Mo: 0.2%, Ta: 0.2%. According to the atomic ratio of the composition, the raw materials are converted into mass percentage for batching, and each raw material is carefully polished to remove surface impurities. Subsequently, in order of low to high melting point, each alloy component is sequentially added to the crucible of the induction furnace. The smelting process is carried out in a vacuum environment, maintaining a vacuum degree of 0.2 Pa in the furnace until the alloy raw materials are completely melted. Subsequently, electromagnetic stirring is used for refining, and the refining time is 1 hour, and five times of skull remelting is carried out.

[0061] The cast ingot after smelting will undergo the following heat processing and heat treatment process:

[0062] (1) Homogenization treatment: 1200℃ for 12h;

[0063] (2) Forging: The initial forging temperature is 1190℃, and 5 times of repeated upsetting and drawing is carried out, and then the cast ingot is forged into a round bar, and the forging ratio is 5, and the forged bar is naturally cooled to room temperature;

[0064] (3) Solution treatment: 1125℃ for 60min, and then water cooled to room temperature immediately;

[0065] (4) Cold working treatment: After solution treatment, the alloy is deformed by room temperature rotary forging, and the specific scheme is: taking a plate with a thickness of Φ20mm from the round bar after solution treatment, rotary forging to a diameter of 10mm in 10 passes, and the diameter changes by 1mm in each pass. After each pass, the sample is cooled in water for 5s to ensure that each pass is deformed at room temperature.

[0066] (5) Aging treatment: The above cold-drawn alloy is aged at 920℃ for 15min, and then placed in a 760℃ muffle furnace for 4h, and then water cooled to room temperature.

[0067] The alloy after aging treatment is processed into samples, and the tensile mechanical properties at low temperature-196℃, room temperature 25℃ and high temperature 650℃ are tested, and metallographic observation is carried out on the test samples. The tensile curve is shown in Figure 7 Table 1, and the yield strength, tensile strength and elongation test results are shown in Table 1. The microstructure is shown in Figure 8

[0068] The low temperature-196℃, room temperature 25℃ and high temperature 650℃ mechanical properties of the final heat treated samples of Examples 1, 2, 3 and 4 are shown in Table 1.

[0069] Table 1 Low temperature-196℃, room temperature 25℃ and high temperature 650℃ mechanical properties

[0070] ​

[0071] As can be seen from Table 1, the non-equivalent atom ratio high-entropy alloy of the present application, by alloying Al, Ti, Mo, Ta, forms a plurality of nanophases of different sizes, so that the alloy obtains comprehensive mechanical properties at low temperature-196℃, room temperature 25℃ and high temperature 650℃. The traditional processing and heat treatment process (Example 1) has an equiaxed crystal structure, and a large number of lamellar nanophases are formed near the grain boundary after aging. This nanophase is a discontinuous precipitated nanophase, which has the same crystal structure (L12 structure) as the internal spherical nanophase, as shown in Figure 9 The formation of a large number of grain boundary nanophases significantly promotes the brittleness of the alloy at intermediate temperature (600-800℃), resulting in an elongation of less than 10%.

[0072] The present application proposes a customized cold deformation + two-step aging process to obtain a necklace-shaped heterogeneous grain structure, as shown in Figure 10 While maintaining high comprehensive mechanical properties at low temperature and room temperature, the tensile strength of the alloy at 650℃ is more than 1100MPa, and the elongation is more than 10%. The necklace-shaped heterogeneous structure and a large number of internal nanophases significantly improve the comprehensive mechanical properties of the alloy at low temperature, room temperature and high temperature.

[0073] The remaining matters of the present application are known technologies.

[0074] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A necklace-like heterostructure high-entropy alloy, characterized in that: The necklace-like heterogeneous structure high-entropy alloy has a chemical composition range of Co: 18-25%, Cr: 16-20%, Fe: 16-22%, Ni: 20-30%, Al: 3-6%, Ti: 2-5%, Mo: 0.1-0.8%, and Ta: 0.1-0.5% in terms of atomic percentage.

2. The method for preparing the necklace-like heterostructure high-entropy alloy of claim 1, characterized in that: The process flow is: batching, induction smelting, casting forming, homogenization, forging, cold deformation and two-step aging heat treatment; the oxygen and nitrogen contents are controlled in the induction smelting process to prevent the formation of brittle non-metallic inclusions; the smelting process is sequentially placed in the crucible according to the melting point from low to high, the vacuum degree in the induction furnace is maintained within 0.8 Pa during the smelting process, and after the complete melting of other raw materials, repeated electromagnetic stirring is carried out; the obtained ingot is homogenized and forged; The homogenization treatment temperature and time are 1200-1300℃ and ≥12 h, respectively; the ingot is subjected to forging treatment after homogenization, the forging holding temperature is 1250℃, the initial temperature is 1190℃, the minimum temperature is 1080℃, and the ingot is repeatedly upset-drawing for more than 5 times; the final sample has a forging ratio of ≥5 and is air-cooled to room temperature after forging; Before cold deformation, the forged sample is subjected to solid solution treatment, and the specific process is: solid solution treatment before cold deformation, 1125℃ for 60 min, water cooling to room temperature; after solid solution treatment, the sample is subjected to cold deformation on a cold rolling / cold drawing / spinning equipment: (1) Cold rolling process: the cold rolling temperature is room temperature, the sample is subjected to multi-pass cold rolling treatment, the thickness change of each pass is 2mm, and after 10 passes, the sample is cold rolled from 40mm to 20mm, and the total deformation is 50%; (2) Cold drawing process: the cold drawing temperature is room temperature, the sample is subjected to multi-pass cold drawing treatment, the diameter change of each pass is 0.3mm, and after 10 passes, the sample is cold drawn from 10mm to 7mm, and the total deformation is 51%; (3) Spinning process: the spinning temperature is room temperature, the sample is subjected to multi-pass spinning treatment, the diameter change of each pass is 1mm, and after 10 passes, the sample is spun from 20mm to 10mm, and the total deformation is 75%; to ensure that the cold deformation is carried out at room temperature, the sample is cooled in water for 5s after each deformation; the cold deformed sample is heated at 920℃ for 15 min, then quickly placed in a holding furnace at 760℃ for 4h, and then water-cooled to room temperature.

3. The method for preparing the necklace-like heterostructure high-entropy alloy according to claim 2, characterized in that: After two-step aging, the alloy has a necklace-like grain distribution morphology, in which fine grains are distributed around the edges of coarse grains, forming a surrounding type grain structure in which fine grains wrap coarse grains.

4. The method for preparing the necklace-like heterostructure high-entropy alloy according to claim 2, characterized in that: The obtained necklace-like heterogeneous structure high-entropy alloy has room temperature tensile properties of yield strength ≥1100 MPa, tensile strength ≥1400 MPa, and elongation ≥12%; -196℃ tensile mechanical properties of yield strength ≥1400 MPa, tensile strength ≥1800 MPa, and elongation ≥12%; and 650℃ tensile properties of yield strength ≥1000 MPa, tensile strength ≥1100 MPa, and elongation ≥12%.

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