A method for efficiently preparing high-entropy alloy by using pulse current to accelerate L12 phase precipitation

Abstract

This invention discloses an efficient method for preparing high-entropy alloys that accelerates the rapid precipitation of the L12 phase, belonging to the field of alloy material technology. The method includes: selecting high-purity raw materials and obtaining a high-entropy alloy ingot using a dual process of vacuum induction melting and electroslag remelting; after homogenization treatment, hot forging, cold rolling, and water quenching, the sample is subjected to aging treatment, during which a pulsed current is intermittently applied to accelerate solute atom diffusion and promote the rapid precipitation of the L12 phase, thereby significantly shortening the aging time. The parameters of the single pulsed current are: current density 100-500 A / cm². 2 The frequency is 100-1000Hz, the pulse width is 10-300μs, and the treatment time is 10-300 seconds. This invention utilizes the electron wind effect and Joule heating effect of pulsed current to lower the diffusion energy barrier of solute atoms, accelerating the non-equilibrium diffusion process and shortening the aging time by more than 90% compared to traditional aging treatments. The process of this invention is simple, requires no complex equipment modification, and improves preparation efficiency while reducing energy consumption and manufacturing costs. It is suitable for the industrial preparation of high-entropy alloys and related high-temperature structural components.

Description

Technical Field

[0001] This invention belongs to the field of high-performance high-entropy alloy preparation technology, and specifically provides a method for efficiently preparing high-entropy alloys by intermittently applying pulsed current to accelerate the precipitation of L12 phase and shorten the aging time. Background Technology

[0002] With the rapid development of industries such as aerospace and energy, the market has created an urgent demand for high-temperature structural materials with excellent high-temperature mechanical properties. High-entropy alloys (HEAs), as a new type of alloy composed of multiple main elements, are considered important candidates for the next generation of high-temperature structural materials due to their outstanding high-temperature strength, fracture toughness, and oxidation resistance.

[0003] The L12 phase is an intermetallic compound with an ordered face-centered cubic (FCC) structure, such as γ'-Ni3Al. By rationally designing the composition and process of high-entropy alloys (HEAs), a high volume fraction of L12 precipitates coherent with the matrix can be introduced into the FCC matrix, thereby constructing a strengthening microstructure similar to nickel-based superalloys and significantly improving the mechanical properties of high-entropy alloys at both room temperature and high temperature. Typical high-entropy alloy systems, such as CoCrFeNi-based alloys, can form the L12 phase by adding elements such as Al, Ti, and Nb, achieving excellent strength-ductility matching.

[0004] In recent years, researchers have discovered that introducing L12-type intermetallic compounds (such as Ni3Al type) as reinforcing phases into high-entropy alloys (HEAs) can significantly improve the high-temperature strength and creep resistance of the alloys while maintaining good plasticity. Currently, in the Ni-15Co-18Cr-6Fe-1.5Mo-5.3Al-3.5Ti-0.6Nb alloy system, an aging process of 500-2000 hours is still required. The mechanical properties reach their best when the aging time reaches 1500 hours. While the yield strength is approximately 700 MPa and the tensile strength is approximately 785 MPa, the elongation increases to 13.6%, achieving a good balance between strength and plasticity. However, the excessively long traditional aging times result in long alloy preparation cycles, high energy consumption, and high costs, severely restricting its industrial application.

[0005] Pulsed current treatment, as a novel rapid heat treatment technology, has attracted widespread attention and has been applied in fields such as aluminum alloys and steel materials. Studies have shown that the electron wind effect generated by the electric pulse can accelerate atomic diffusion and promote the precipitation of strengthening phases; while the Joule heating effect can affect the phase transformation process and promote the growth of strengthening phases.

[0006] This invention applies pulsed current to the aging process of L12 phase-strengthened high-entropy alloys. By utilizing the electron wind effect and Joule heating effect of intermittently applied pulsed current to accelerate the rapid precipitation and growth of the L12 phase, the traditional aging process, which takes thousands of hours, is significantly shortened, thereby reducing energy consumption and greatly improving preparation efficiency. Summary of the Invention

[0007] This invention discloses an efficient method for preparing high-entropy alloys by intermittently applying pulsed current to accelerate the rapid precipitation and growth of the L12 phase, thereby solving the technical problems of excessively long aging time and low preparation efficiency required for L12 phase precipitation in existing technologies. The method of this invention specifically includes the following steps:

[0008] a. Select high-purity raw materials with a purity of not less than 99.9 wt.% and use a dual process of vacuum induction melting + electroslag remelting to obtain high-entropy alloy ingots;

[0009] b. Homogenize the high-entropy alloy ingot obtained in step a.

[0010] c. After homogenization, the sample is heated and then hot-forged, and then cold-rolled.

[0011] d. Subsequently, a solution treatment is performed, and the cold-rolled plate is water-quenched and cooled to retain the supersaturated solid solution matrix;

[0012] e. The solution-treated sample is subjected to aging treatment, and a pulsed current is intermittently applied during the aging treatment to accelerate the formation of the precipitated phase;

[0013] f. Finally, a high-entropy alloy sample is obtained.

[0014] In one specific embodiment, the composition of the high-entropy alloy in step a is Ni-(12-18wt.%)Co-(10-20wt.%)Cr-(1-10wt.%)Fe-(1-5wt.%)Mo-(5-10wt.%)Al-(1-5wt.%)Ti-(0.6-1wt.%)Nb.

[0015] In one specific implementation, the homogenization treatment in step b is carried out at a temperature of 1100-1300°C for 12-24 hours.

[0016] In one specific embodiment, the initial forging temperature in step c is 1000-1200℃, the final forging temperature is 800-1000℃, the relative deformation during forging is 50-80%, and the cold rolling is at room temperature (20-30℃) with a cold rolling deformation of 70-80%.

[0017] In one specific embodiment, the solution treatment temperature of the cold-rolled sheet in step d is 1000-1200℃, the time is 1-2h, and the water quenching is at room temperature (20-30℃).

[0018] In one specific embodiment, the aging treatment in step e is carried out at a temperature of 600-800℃ for a time of 10-200 hours. This results in an aging treatment time that is more than 90% shorter than that without the application of pulsed current. The parameters of the pulsed current are: current density 100-500 A / cm². 2 Frequency 100-1000Hz, pulse width 10-300μs, duration 10-300 seconds.

[0019] The mechanism of the pulsed current described in this invention is as follows: by utilizing the electron wind effect and Joule heating effect of pulsed current treatment, the traditional diffusion-controlled L12 phase precipitation and growth process, which requires 1000-2000 hours, is significantly shortened. Specifically, the mechanism is as follows: intermittent application of pulsed current creates a dynamic equilibrium between the instantaneous Joule heating generated and the constant temperature environment of the furnace. During the pulsed current application phase, the instantaneous Joule heating provides high activation energy; during the intermittent phase, precise temperature control of the furnace ensures that the sample remains within the ideal aging temperature range while promoting L12 phase precipitation. The electron wind effect significantly reduces the atomic diffusion activation energy, accelerating the migration rate of solute atoms such as Al, Ti, and Nb. Furthermore, the electromigration effect generated by the pulsed current promotes the segregation of solute atoms towards defects such as dislocations and grain boundaries, providing numerous nucleation sites for the L12 phase. The thermal stress during pulsed current treatment can also introduce point defects such as vacancies, further accelerating diffusion. Through the synergistic effect of the aforementioned multiple mechanisms, this effect significantly improves the nucleation rate and growth rate of the L12 phase during the aging treatment stage, enabling the L12 phase to precipitate and achieve the ideal volume fraction and distribution state in a shorter time. Compared with traditional aging treatment, this invention can shorten the aging time by more than 90%, thereby greatly improving the preparation efficiency.

[0020] Advantages of this invention:

[0021] 1. Significantly shortens aging time and improves preparation efficiency: This invention provides a method for preparing high volume fraction L12-strengthened high-entropy alloys by rapidly precipitating the L12 phase using pulsed current treatment, which greatly shortens the traditional aging time of 1000-2000 hours, significantly improves processing efficiency, and greatly reduces energy consumption and production costs.

[0022] 2. Significantly reduces energy consumption and production costs, enhancing application feasibility: Traditional aging processes require holding the alloy at 750℃ for 1500 hours, resulting in enormous energy consumption, long equipment downtime, and high production costs. This invention employs pulsed current processing, with highly concentrated energy input and extremely short processing time, significantly reducing total energy consumption. It also reduces the usage time and maintenance costs of high-temperature equipment, offering significant economic benefits and making it applicable to high-entropy alloys and other high-performance metal alloys.

[0023] 3. Improved mechanical properties, suitable for high-temperature applications: The high-entropy alloy prepared by this invention exhibits uniform and dispersed L12 phase precipitation, maintaining a good coherent relationship with the matrix. Compared to traditional aging processes, it significantly shortens the aging time without sacrificing the material's mechanical properties, achieving a good balance between strength and plasticity. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0025] Example 1

[0026] High-purity raw materials with a purity of not less than 99.9 wt.% were selected, and a high-entropy alloy ingot was obtained using a dual process of vacuum induction melting and electroslag remelting. Its composition (wt.%) was: Ni-(16wt.%)Co-(16wt.%)Cr-(7wt.%)Fe-(1.8wt.%)Mo-(5.8wt.%)Al-(3.2wt.%)Ti-(1.0wt.%)Nb. The alloy ingot was homogenized at 1250℃ for 24 hours and then furnace-cooled to room temperature. The homogenized sample was then heated to 1150℃ for hot forging, with an initial forging temperature of 1150℃ and a final forging temperature of 900℃, resulting in a relative deformation of 60%. After hot forging, the ingot was air-cooled to room temperature and then cold-rolled (room temperature 25℃), with a relative deformation of 80%. The cold-rolled sheet was solution-treated at 1100℃ for 2 hours, followed immediately by water quenching to room temperature (25℃). The solution-treated sample was then aged at 750℃ for 48 hours. A pulsed current was applied at the start of aging and every 12 hours (for a total of 3 times). The pulsed current parameters were: current density 450 A / cm². 2 The frequency was 800 Hz, the pulse width was 50 μs, and the treatment time was 60 seconds. Compared with the condition without pulsed current (which requires 500 hours to achieve the same degree of precipitation), the treatment time was reduced by 90%.

[0027] Example 2

[0028] High-purity raw materials with a purity of not less than 99.9 wt.% were selected, and a high-entropy alloy ingot was obtained using a dual process of vacuum induction melting and electroslag remelting. Its composition (wt.%) was: Ni-(15 wt.%), Co-(18 wt.%), Cr-(6 wt.%), Fe-(1.5 wt.%), Mo-(5.3 wt.%), Al-(3.5 wt.%), Ti-(0.6 wt.%), Nb. The alloy ingot was homogenized at 1250℃ for 24 hours and then furnace-cooled to room temperature. The homogenized sample was then heated to 1150℃ for hot forging, with an initial forging temperature of 1150℃ and a final forging temperature of 900℃, resulting in a relative deformation of 60%. After hot forging, the ingot was air-cooled to room temperature and then cold-rolled (room temperature 25℃), with a relative deformation of 80%. The cold-rolled sheet was solution-treated at 1100℃ for 2 hours, followed immediately by water quenching to room temperature (25℃). The solution-treated samples were then aged at 700℃ for 72 hours. A pulsed current was applied at the start of aging and every 24 hours (for a total of 3 times). The pulsed current parameters were: current density 300 A / cm². 2 The frequency was 1000 Hz, the pulse width was 100 μs, and the treatment time was 120 seconds. Ultimately, compared with the condition without pulsed current (which requires 1000 hours to achieve the same level of precipitation), the treatment time was reduced by 93% for the same level of precipitation.

[0029] Example 3

[0030] High-purity raw materials with a purity of not less than 99.9 wt.% were selected, and a high-entropy alloy ingot was obtained using a dual process of vacuum induction melting and electroslag remelting. Its composition (wt.%) was: Ni-(18 wt.%), Co-(15 wt.%), Cr-(8 wt.%), Fe-(2 wt.%), Mo-(6 wt.%), Al-(2.5 wt.%), Ti-(0.7 wt.%), Nb. The alloy ingot was homogenized at 1300℃ for 12 hours and then furnace-cooled to room temperature. The homogenized sample was then heated to 1200℃ for hot forging, with an initial forging temperature of 1200℃ and a final forging temperature of 1000℃, resulting in a relative deformation of 50%. After hot forging, the ingot was air-cooled to room temperature and then cold-rolled (room temperature 30℃) with a relative deformation of 80%. The cold-rolled sheet was solution-treated at 1200℃ for 1 hour, followed immediately by water quenching to room temperature (30℃). The solution-treated samples were then aged at 650℃ for 72 hours. A pulsed current was applied three times, starting at the beginning of aging and every 24 hours thereafter. The pulsed current parameters were: current density 500 A / cm². 2 The treatment time was 95% shorter than that under conditions without pulsed current (requiring 1500 hours to achieve the same level of precipitation). The frequency was 100 Hz, the pulse width was 300 μs, and the treatment time was 300 seconds.

[0031] Example 4

[0032] High-purity raw materials with a purity of not less than 99.9 wt.% were selected, and a high-entropy alloy ingot was obtained using a dual process of vacuum induction melting and electroslag remelting. Its composition (wt.%) was: Ni-(12 wt.%), Co-(20 wt.%), Cr-(5 wt.%), Fe-(1 wt.%), Mo-(5 wt.%), Al-(4 wt.%), Ti-(0.8 wt.%), Nb. The alloy ingot was homogenized at 1200℃ for 24 hours and then furnace-cooled to room temperature. The homogenized sample was then heated to 1100℃ for hot forging, with an initial forging temperature of 1100℃ and a final forging temperature of 850℃, resulting in a relative deformation of 70%. After hot forging, the ingot was air-cooled to room temperature and then cold-rolled (room temperature 25℃), with a relative deformation of 75%. The cold-rolled sheet was solution-treated at 1150℃ for 1.5 hours, followed immediately by water quenching to room temperature (25℃). The solution-treated samples were then subjected to aging treatment at 600℃ for 120 hours. A pulsed current was applied at the start of aging and every 30 hours (a total of 4 times). The pulsed current parameters were: current density 350 A / cm². 2 The treatment time was 94% shorter than that under conditions without pulsed current (requiring 2000 hours to achieve the same level of precipitation). The frequency was 500 Hz, the pulse width was 150 μs, and the treatment time was 180 seconds.

Claims

1. A method for efficiently preparing high-entropy alloys by accelerating the precipitation of the L12 phase, characterized in that... Includes the following steps: a. Select high-purity raw materials with a purity of not less than 99.9 wt.% and use a dual process of vacuum induction melting + electroslag remelting to obtain high-entropy alloy ingots; b. Homogenize the high-entropy alloy ingot obtained in step a. c. After homogenization, the sample is heated and then hot-forged, and then cold-rolled. d. Subsequently, a solution treatment is performed, and the cold-rolled plate is water-quenched and cooled to retain the supersaturated solid solution matrix; e. The solution-treated sample is subjected to aging treatment, and a pulsed current is applied during the aging treatment to accelerate the formation of the precipitated phase; f. Finally, a high-entropy alloy sample is obtained.

2. The preparation method according to claim 1, wherein the composition of the high-entropy alloy is Ni-(12-18wt.%)Co-(10-20wt.%)Cr-(1-10wt.%)Fe-(1-5wt.%)Mo-(5-10wt.%)Al-(1-5wt.%)Ti-(0.6-1wt.%)Nb.

3. The preparation method according to claim 1, wherein the homogenization treatment is carried out at a temperature of 1100-1300℃ for 12-24 hours.

4. The preparation method according to claim 1, wherein the initial forging temperature is 1000-1200℃, the final forging temperature is 800-1000℃, and the relative deformation during forging is 50-80%; the cold rolling is at room temperature, and the relative deformation during cold rolling is 70-80%.

5. The preparation method according to claim 1, wherein the solution treatment temperature of the cold-rolled sheet is 1000-1200℃, the time is 1-2h, and the water quenching is at room temperature (20-30℃).

6. The preparation method according to claim 1, wherein the aging treatment temperature is 600-800℃ and the aging time is 10-200h; the aging treatment time is shortened by more than 90% compared with the aging treatment without pulsed current; the parameters of the single pulsed current are: current density 100-500A / cm². 2 Frequency 100-1000Hz, pulse width 10-300μs, duration 10-300 seconds.

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