High-entropy alloy with super-high mechanical properties under low temperature environment and preparation method thereof

Abstract

The application discloses a high-entropy alloy with super-high mechanical properties in a low-temperature environment and a preparation method thereof, wherein the alloy is a Co-Ni-Cr-Al-Ti (HfMoC) high-entropy alloy. The alloy is prepared through melting and casting, homogenization solid solution treatment, cold mechanical deformation treatment and aging heat treatment. After the cold mechanical deformation and the aging heat treatment, the prepared alloy is characterized by a fully recrystallized structure which can realize coupling of multiple toughening mechanisms. In the condition of liquid nitrogen temperature (77K), the uniform tensile plasticity of the prepared alloy plate can reach more than 10%, the yield strength can reach 2.30 GPa, and the tensile strength can reach 2.40 GPa, thereby realizing high combination of plasticity and strength.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-performance alloy material preparation, and provides a CoCrNiAlTi(HfMoC) high-entropy alloy with super-high mechanical properties at a liquid nitrogen temperature (77K) and a preparation method thereof. BACKGROUND

[0002] The aerospace, low-temperature superconducting and other national defense key fields urgently need to update and replace the structural materials with high mechanical properties in low-temperature environments. The high-toughness metal profiles are the key to preparing aerospace low-temperature fuel storage and transportation equipment, and specifically require good service performance, excellent stress corrosion resistance, excellent dimensional stability and good processing process at low-temperature conditions. At present, austenitic stainless steel (314LN), nickel-based alloy (GH4169) or cobalt-based alloy (GH159) are commonly used as manufacturing materials in engineering, but these traditional alloys have been optimized to the limit due to the inherent mutual exclusivity of strength and plasticity, and it is difficult to make further improvements, thereby severely restricting the improvement space of the preparation of low-temperature fuel storage and transportation special equipment.

[0003] In recent years, the high-entropy alloy fundamentally updates the design concept of traditional alloys, and has a broad application space in the low-temperature and ultra-low-temperature fields due to its high strength and plasticity, excellent toughness, outstanding stress corrosion resistance and radiation resistance and other advantages. The successful research and development of high-toughness high-entropy alloy profiles and other industrial products for low-temperature and other extreme environments has important significance for promoting the engineering application of high-entropy alloys, not only can significantly improve the technical advantages and independent support capabilities in related fields, but also has an important role in promoting the green and low-carbon development of the industry. In addition, the low-temperature high-toughness metal pipes, pumps, valves and other key components in the aerospace, low-temperature superconducting fields often also need to have excellent fatigue performance, radiation resistance, stress corrosion resistance and other multiple characteristics, and high-entropy alloys have obvious advantages in structural and functional integrated design, therefore, the research and development, application and preparation process optimization of new low-temperature ultra-high-strength high-entropy alloy industrial products are the top priority of the low-temperature application research of high-entropy alloys.

[0004] An important indicator for high-performance structural materials urgently needed in national defense key fields such as aerospace and low-temperature superconductivity is to have ultra-high yield strength and acceptable uniform plasticity (significant work hardening phenomenon during deformation). The increase of yield strength determines the carrying capacity, fatigue resistance and safety of structural materials. At present, although there are a few reports on ultra-high strength high-entropy alloys, the yield strength of most alloys is still below 1.5 GPa under liquid nitrogen low-temperature conditions, and the significant advantages of ultra-high strength and toughness high-entropy alloys in replacing traditional low-temperature engineering materials are not fully exhibited. Among them, the research team of Dai Lanhong of Institute of Mechanics, Chinese Academy of Sciences chose AlCoCrFeNi2.1 eutectic high-entropy alloy with lamellar structure, and the results are remarkable. They successfully prepared a kind of eutectic high-entropy alloy millimeter wire with unique gradient lamellar structure by designing multi-pass drawing process. The eutectic high-entropy alloy wire developed shows outstanding low-temperature (77K) strength and plasticity (fracture strength 2.52 GPa, uniform elongation 14.3%), but the profile obtained by the research is millimeter wire, and the application space is limited. Under this background, it is urgent to strengthen the basic research on high-entropy alloys and deeply explore the low-temperature performance potential of high-entropy alloys, so as to develop new low-temperature ultra-high strength high-entropy alloy plates and other profiles with significant performance advantages. SUMMARY

[0005] Therefore, the application provides a high-entropy alloy with ultra-high mechanical properties under low-temperature environment and a preparation method thereof to solve the problems in the prior art.

[0006] In one aspect, the application provides a high-entropy alloy with ultra-high mechanical properties under low-temperature environment, which comprises the following components according to atomic percentage: Cr: 10-15%, Ni: 22-28%, Al: 4-7%, Ti: 5-6%, Hf: 0.5-1%, Mo: 0.5-1%, C: 1-2%, and the balance is Co.

[0007] The application also provides a preparation method of a high-entropy alloy with ultra-high mechanical properties under low-temperature environment, comprising the following steps:

[0008] (1) preparing the alloy according to the above components and atomic percentage and casting into an ingot;

[0009] (2) uniformly treating the ingot to obtain a casting;

[0010] (3) solid solution heat treating the casting to obtain an alloy with single-phase structure;

[0011] (4) cold rolling the casting after solid solution heat treatment with a deformation of 70-90% to obtain a plate;

[0012] (5) The deformed plate is subjected to aging heat treatment to obtain a high-entropy alloy plate with ultra-high mechanical properties in a low-temperature environment.

[0013] Preferably, in step (2), the homogenization treatment is carried out at a temperature of 1150-1200℃ for 6-10 hours.

[0014] Further preferred, in step (3), the temperature of the solution heat treatment is 900-1100℃ and the time is 4-8h.

[0015] Further preferred, in step (5), the temperature of the aging heat treatment is 600-700℃ and the time is 24-100h.

[0016] The high-entropy alloy with ultra-high mechanical properties at low temperatures provided by this invention is based on a precipitation-strengthened CoCrNiAlTi high-entropy alloy, with the addition of high-melting-point elements such as Hf, Mo, and C, resulting in a breakthrough in the alloy's performance. The strong grain refinement and intragranular solid solution strengthening by high-melting-point elements such as Hf, Mo, and C significantly contribute to the improvement of yield strength. Furthermore, these high-melting-point elements not only accumulate at grain boundaries, improving interfacial bonding strength, but the high concentration of dissolved C within the grains during low-temperature deformation also promotes the formation of short-range ordered structures (SRO). This SRO caused by low-temperature deformation leads to severe lattice distortion within the grains, thereby significantly increasing the low-temperature yield strength.

[0017] The high-entropy alloy with ultra-high mechanical properties in low-temperature environments provided by this invention has a yield strength of up to 2.30 GPa at low temperature (77 K) with liquid nitrogen, and also has excellent work hardening ability (tensile elongation greater than 10%), with a tensile strength of up to 2.40 GPa. Attached Figure Description

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0019] Figure 1 The typical tensile curve of the alloy sheet of Example 1 at liquid nitrogen temperature;

[0020] Figure 2 This is a typical recrystallization microstructure diagram of the alloy sheet from Example 1. Detailed Implementation

[0021] The present invention will be further explained below with reference to specific implementation schemes, but this explanation does not limit the scope of the invention.

[0022] Although high-entropy alloys have significant advantages in developing ultra-high-strength alloys, the development of profiles with ultra-high strength and good plasticity at low temperatures remains a bottleneck. Utilizing microalloying with multiple elements to generate coupled strengthening and toughening mechanisms is an effective way to further address this challenge. This invention is based on a precipitation-strengthened CoCrNiAlTi high-entropy alloy, with the addition of high-melting-point elements such as Hf, Mo, and C, resulting in a breakthrough in the performance of this high-entropy alloy.

[0023] This invention provides a high-entropy alloy with ultra-high mechanical properties at low temperatures, comprising the following components by atomic percentage: Cr: 10-15%, Ni: 22-28%, Al: 4-7%, Ti: 5-6%, Hf: 0.5-1%, Mo: 0.5-1%, C: 1-2%, with the balance being Co.

[0024] This invention also provides a method for preparing high-entropy alloys with ultra-high mechanical properties at low temperatures, comprising the following steps:

[0025] (1) Prepare the alloy according to the above composition and atomic percentage and melt and cast it into an ingot;

[0026] (2) The ingot is homogenized to obtain a casting;

[0027] (3) The casting is subjected to solution heat treatment to obtain an alloy with a single-phase structure;

[0028] (4) The castings after solution heat treatment are subjected to cold rolling mechanical deformation with a deformation amount of 70-90% to be rolled into plates;

[0029] (5) The deformed plate is subjected to aging heat treatment to obtain a high-entropy alloy plate with ultra-high mechanical properties in a low-temperature environment.

[0030] As an improvement to the technical solution, in step (2), the homogenization treatment temperature is 1150-1200℃ and the time is 6-10h.

[0031] As an improvement to the technical solution, in step (3), the temperature of the solution heat treatment is 900-1100℃ and the time is 4-8h.

[0032] As an improvement to the technical solution, in step (5), the temperature of the aging heat treatment is 600-700℃ and the time is 24-100h.

[0033] The high-entropy alloy with ultra-high mechanical properties at low temperatures provided by this invention is based on a precipitation-strengthened CoCrNiAlTi high-entropy alloy, with the addition of high-melting-point elements such as Hf, Mo, and C, resulting in a breakthrough in performance. The strong grain refinement and intragranular solid solution strengthening by high-melting-point elements such as Hf, Mo, and C significantly contribute to the improvement of yield strength. Furthermore, these high-melting-point elements not only accumulate at grain boundaries, improving interfacial bonding strength, but the high concentration of dissolved C within the grains during low-temperature deformation also promotes the formation of short-range ordered structures (SRO). This SRO caused by low-temperature deformation leads to severe lattice distortion within the grains, thereby significantly increasing the low-temperature yield strength.

[0034] Example 1

[0035] Formulated into Co 40 Ni 27 Cr 15 Al5Ti5 Hf 0.5 Mo 0.5 C2 (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1200℃ for 6 h, and then solution treated at 1000℃ for 8 h. It was then cold-rolled at room temperature with a deformation of approximately 70%, followed by aging at 625℃ for 24 h to obtain alloy sheets.

[0036] At liquid nitrogen temperature of 10 -3 s -1 The alloy sheet was stretched at a stretching rate of 12%, with a tensile strength of 2410 MPa and a yield strength of 2310 MPa. Figure 1 The figure shows a typical tensile curve of the alloy sheet at liquid nitrogen temperature. Figure 2 This is a typical recrystallization microstructure diagram of the alloy sheet.

[0037] Example 2

[0038] Formulated into Co 45 Ni 22 Cr 10 Al5Ti5 Hf 0.5 Mo 0.5 C2 (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1150℃ for 10 h, and then solution treated at 900℃ for 8 h. It was then cold-rolled at room temperature with a deformation of approximately 90%, followed by aging at 650℃ for 36 h to obtain alloy sheet.

[0039] At liquid nitrogen temperature of 10 -3 s -1The alloy sheet was stretched at a stretching rate of 11.5%, with a tensile strength of 2400 MPa and a yield strength of 2290 MPa.

[0040] Example 3

[0041] Formulated into Co 40 Ni 28 Cr 15 Al4Ti6 Hf 0.5 Mo 0.5 C1 (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1200℃ for 10 h, and then solution treated at 1100℃ for 4 h. It was then cold-rolled at room temperature with a deformation of approximately 80%, followed by aging at 700℃ for 100 h to obtain alloy sheet.

[0042] At liquid nitrogen temperature of 10 -3 s -1 The alloy sheet was stretched at a stretching rate of 13%, with a tensile strength of 2390 MPa and a yield strength of 2290 MPa.

[0043] Example 4

[0044] Formulated into Co 40 Ni 27 Cr 13 An Al7Ti5Hf1Mo1C1 (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1200℃ for 6 h, and then solution treated at 1000℃ for 8 h. It was then cold-rolled at room temperature with a deformation of approximately 80%, followed by aging at 600℃ for 100 h to obtain alloy sheets.

[0045] At liquid nitrogen temperature of 10 -3 s -1 The alloy sheet was stretched at a stretching rate of 13.5%, with a tensile strength of 2420 MPa and a yield strength of 2350 MPa.

Claims

1. A method for preparing high-entropy alloys with ultra-high mechanical properties at low temperatures, characterized in that: The high-entropy alloy with ultra-high mechanical properties at low temperatures comprises the following components by atomic percentage: Cr: 10-15%, Ni: 22-28%, Al: 4-7%, Ti: 5-6%, Hf: 0.5-1%, Mo: 0.5-1%, C: 1-2%, with the balance being Co; The preparation method of the high-entropy alloy with ultra-high mechanical properties under low temperature conditions includes the following steps: (1) Prepare the alloy according to the stated composition and melt and cast it into an ingot; (2) The ingot is homogenized to obtain a casting; (3) The casting is subjected to solution heat treatment to obtain an alloy with a single-phase structure; (4) The castings after solution heat treatment are subjected to cold rolling mechanical deformation with a deformation amount of 70-90% to be rolled into plates; (5) The deformed plate is subjected to aging heat treatment to obtain a high-entropy alloy plate with ultra-high mechanical properties in a low-temperature environment, wherein the aging heat treatment temperature is 600-700℃ and the time is 24-100h.

2. The method for preparing a high-entropy alloy with ultra-high mechanical properties at low temperatures according to claim 1, characterized in that: In step (2), the homogenization treatment is carried out at a temperature of 1150-1200℃ for 6-10 hours.

3. The method for preparing a high-entropy alloy with ultra-high mechanical properties at low temperatures according to claim 1, characterized in that: In step (3), the solution heat treatment temperature is 900-1100℃ and the time is 4-8 h.

Images