Micron-sized-thickness CrCoNi medium-entropy alloy ultra-thin strip and preparation process thereof

Abstract

The invention relates to a micron-sized-thickness CrCoNi medium-entropy alloy ultra-thin strip and a preparation process thereof, the atomic ratio of raw material cast ingots of the ultra-thin strip is Cr: Co: Ni = 1: 1: 1, the purity is greater than 99.9%, and the balance is inevitable impurity components; the complete preparation process of the CrCoNi medium-entropy alloy ultra-thin strip with the micron-grade thickness comprises the steps of homogenizing annealing, rough rolling, medium rolling, riveting, combined forming rolling, leveling and short-time and low-temperature annealing, and adopts the technology of synchronous rolling, asymmetrical rolling, combined forming rolling and low-temperature and short-time annealing. Excellent strength and plasticity can be achieved while ultrahigh ductility eta = 10000% can be achieved, and the CrCoNi ultra-thin strip with the micron-grade thickness can be efficiently produced on a large scale.

Description

Technical Field

[0001] This invention belongs to the field of medium-entropy alloy ultra-thin strip rolling technology, and specifically relates to a micron-thick CrCoNi medium-entropy alloy ultra-thin strip and its preparation process. Background Technology

[0002] With the rapid development of aerospace, electronic communications, micro-manufacturing, and new energy fields, the demand for high-performance ultra-thin metal strips is becoming increasingly urgent. Currently, the mainstream metal foils are mainly aluminum foil, copper foil, stainless steel foil, titanium alloy foil, nickel, and nickel alloy foil. CrCoNi medium-entropy alloys, with their high strength, excellent ductility, and corrosion resistance, have become an ideal choice for next-generation lightweight materials. Especially in applications such as flexible electronics, micro-sensors, and high-temperature components, the fabrication technology of micron-scale ultra-thin strips directly determines the ultimate performance of the materials.

[0003] However, traditional rolling processes face several bottlenecks in the preparation of ultra-thin strips: 1. High deformation resistance prevents further thinning after reaching the minimum rollable thickness during rolling. In existing technologies, asynchronous rolling can reduce the minimum rollable thickness by introducing shear strain, but achieving ultra-large deformation rolling, corresponding to a total reduction rate of 99% or higher, is difficult with conventional asynchronous rolling. In the production of micron-sized metal foils, the high work hardening rate during processing increases the difficulty of deformation, requiring multiple intermediate annealing processes, resulting in a cumbersome, inefficient, and environmentally unfriendly production process. For example, patent CN202111440700.9 describes the preparation of 0.10–0.16 mm ultra-thin strips of nickel-based high-temperature alloys using two intermediate annealing processes, a cumbersome and energy-intensive process. 2. Due to the prevalent size effect in ultra-thin strip rolling, the material strength decreases with decreasing thickness after exceeding the size effect threshold, ultimately leading to poor strength in ultra-thin strips. For example, in the paper "Excellent mechanical properties and strengthening mechanisms in ultrathin foils of CoCrNi medium-entropy alloy via accumulative rolling", the tensile strength of 77μm and 100μm CrCoNi ultrathin strips after accumulative rolling is only 1300MPa.

[0004] In summary, current research on the rolling of ultra-thin strips of medium / high entropy alloys is relatively lacking, which affects their large-scale industrial application. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention aims to provide a micron-thick CrCoNi medium-entropy alloy ultrathin strip and its preparation process. This preparation process uses synchronous rolling + asynchronous rolling + combined forming rolling + low temperature short-time annealing technology to prepare micron-thick CrCoNi ultrathin strip without intermediate annealing, and ensures its mechanical properties, thickness accuracy and surface roughness requirements.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A micron-thick CrCoNi medium-entropy alloy ultrathin strip, wherein the atomic ratio of the medium-entropy alloy is Cr:Co:Ni = 1:1:1, the purity is greater than 99.9%, and the balance is unavoidable impurity components; the raw material strip thickness of the entropy alloy ultrathin strip is 3-5 mm, and the finished product thickness is 0.03-0.05 mm.

[0008] This invention also provides a process for preparing a micron-thickness CrCoNi medium-entropy alloy ultrathin strip, which mainly includes the following steps:

[0009] S1: Homogenize and anneal a medium-entropy alloy strip with a thickness of 3-5 mm. The atomic ratio of the medium-entropy alloy is Cr:Co:Ni = 1:1:1, the purity is greater than 99.9%, and the balance is unavoidable impurity components.

[0010] S2: The homogenized annealed strip is subjected to rough rolling and intermediate rolling processes in sequence to reduce its thickness to 0.1-0.2 mm;

[0011] S3: The strip after intermediate rolling is trimmed, then riveted to the lead strip and rolled into an ultra-thin strip with a thickness of 0.03 to 0.05 mm.

[0012] S4: After the ultra-thin strip is flattened, it is subjected to short-time low-temperature annealing to restore the material's plasticity; the short-time low-temperature annealing is performed under vacuum conditions at 650-680°C for 1 minute, with a heating rate of 8-10°C / min, followed by furnace cooling.

[0013] In one embodiment, the homogenization annealing is carried out in a heating furnace protected by high-purity argon gas at a temperature of 800–900°C for 1.5–2 hours, with the temperature rising along with the furnace at a rate of 8–10°C / min, and the cooling method is water quenching.

[0014] In one embodiment, the homogenized annealed strip is first rough rolled, then surface sanded and cleaned; the ultrathin strip is first cleaned before short-time low-temperature annealing.

[0015] The surface abrasion is performed using SiC abrasive belts on one side at a speed of 10–12 m / min. Two abrasive belts are used on each side, with mesh sizes of 400 and 800 mesh respectively. The abrasive belt abrasion pressure is 5–10 MPa. The cleaning before rough rolling uses a sodium hydroxide solution with a mass concentration of 5%–8%, and the cleaning before short-time low-temperature annealing uses a sodium hydroxide solution with a mass concentration of 3%–6%. The ultrasonic frequency for both cleaning processes is 40 kHz. After alkaline washing, the surface is rinsed with circulating water for 3–8 minutes, and the drying temperature is 50℃–70℃.

[0016] In one embodiment, the roughing rolling is to feed the strip into a four-high reversible rolling mill for synchronous rolling to thin the strip to 0.8-1.6 mm; the intermediate rolling is to cut the edges of the rough-rolled strip and then feed it into a four-high reversible rolling mill for asynchronous rolling to thin the strip to 0.1-0.2 mm.

[0017] In one embodiment, the working roll diameter of the four-roll reversible mill is 70-90 mm;

[0018] The roughing process involves a rolling force of 25–30 t, employing synchronous rolling to reduce the thickness of the strip from 3–5 mm to 0.8–1.6 mm. The single-pass reduction rate is 10%–15%, and the rolling lubricant and cooling medium has a kinematic viscosity of 8–10 mm. 2 / s of rolling oil;

[0019] The intermediate rolling mill uses a rolling force of 20–25 t and employs asynchronous rolling with a speed ratio of 1.2–1.3 to reduce the thickness of the strip from 0.8–1.6 mm to 0.1–0.2 mm. The single-pass rolling reduction rate is 10%–15%, and the rolling lubricating and cooling medium has a kinematic viscosity of 7–9 mm. 2 / s of rolling oil.

[0020] In one embodiment, the riveting is achieved by using rivets at intervals of 1.5 to 2 cm to securely connect the thin strip to the guide strip, with each rivet aligned in a straight line in the TD direction.

[0021] In one embodiment, the combined forming rolling process uses a four-high reversible rolling mill with work roll diameters of 70–90 mm. The rolling force during the rolling process is 15–20 t, and the tensile stress is 1 / 4–1 / 3 of the yield strength of a medium-entropy alloy strip with a thickness of 0.1–0.2 mm after intermediate rolling, i.e., 300–500 MPa. Asynchronous rolling with a speed ratio of 1.1–1.2 is used to reduce the strip thickness from 0.1–0.2 mm to 0.03–0.05 mm. The single-pass rolling reduction rate is 5%–10%, and the rolling lubricating and cooling medium has a kinematic viscosity of 6–8 mm. 2 / s of rolling oil.

[0022] In one embodiment, the mechanical properties of the CrCoNi ultra-thin strip after the combined forming and rolling process are: tensile strength of 1650-1800 MPa, yield strength of 1600-1700 MPa, and elongation of 1%-2%; the mechanical properties of the CrCoNi ultra-thin strip after the short-time low-temperature annealing are: tensile strength of 1100-1300 MPa, yield strength of 1000-1150 MPa, and elongation of 10%-14%.

[0023] In one embodiment, the leveling process is carried out using a leveling machine, with 1 to 3 leveling operations. The leveling process does not require rolling oil lubrication, the rolling force is 5 to 10t, and the tensile stress is 10 to 20% of the yield strength of the extremely thin strip with a thickness of 0.03 to 0.05 mm after combined forming and rolling, i.e., 160 to 340 MPa.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] (1) The micron-thickness CrCoNi medium-entropy alloy ultrathin strip disclosed in this invention and its preparation process adopt synchronous rolling + asynchronous rolling + combined forming rolling technology, which enables the strip to be thinned quickly while effectively controlling the good plate shape. It can improve the ultimate deformation capacity of the ultrathin strip without intermediate annealing and achieve ultra-high ductility of η=10000%.

[0026] (2) The micron-thickness CrCoNi medium-entropy alloy ultrathin strip disclosed in this invention and its preparation process, through short-time low-temperature annealing, the CrCoNi medium-entropy alloy ultrathin strip obtains excellent strength and plasticity, and improves the efficiency of the annealing process.

[0027] (3) The micron-thickness CrCoNi medium-entropy alloy ultrathin strip disclosed in this invention and its preparation process can obtain ultrathin strip with excellent mechanical properties, high dimensional accuracy and smooth surface without changing the rolling mill or rolls or intermediate annealing. It has the advantages of simple process, high yield and energy efficiency. Attached Figure Description

[0028] Figure 1 This is a process flow diagram for preparing a micron-thick CrCoNi medium-entropy alloy ultrathin strip according to the present invention.

[0029] Figure 2 This is a schematic diagram of the metallographic structure of the CrCoNi medium-entropy alloy strip after homogenization annealing in Example 1 of the present invention.

[0030] Figure 3 This is an image of the CrCoNi medium-entropy alloy ultrathin strip obtained in Example 1 of the present invention.

[0031] Figure 4XRD comparison images of samples from the preparation of CrCoNi medium-entropy alloy ultrathin strips in Example 1 of this invention.

[0032] Figure 5 This is a comparison of the engineering stress-strain curves of the rolled and annealed states of the CrCoNi medium-entropy alloy ultrathin strip prepared in Example 1 of this invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention is described in detail below. This description is for illustrative and explanatory purposes only and should not be construed as limiting the scope of protection of the present invention in any way. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the basic concept of the present invention.

[0034] A micron-thick CrCoNi medium-entropy alloy ultrathin strip and its preparation process are disclosed. The chemical composition of the ultrathin strip is Cr, Co and Ni in equiatomic ratio, with a purity greater than 99.9%, and the balance being other unavoidable impurities. The thickness of the raw material strip is 3-5 mm, and the thickness of the finished product is 0.03-0.05 mm.

[0035] Reference Figure 1 The manufacturing process for the micron-thickness CrCoNi medium-entropy alloy ultrathin strip mainly includes: homogenization annealing, rough rolling, intermediate rolling, riveting, combined forming rolling, leveling, and short-time low-temperature annealing. It can further include grinding and cleaning before rough rolling, cleaning before short-time low-temperature annealing, and subsequent electrolytic polishing, finished product cleaning, and packaging. This process is energy-saving and highly efficient, achieving excellent strength and plasticity while breaking through the material's ultimate deformation capacity, enabling large-scale, efficient production of micron-thickness CrCoNi ultrathin strips. The following provides a detailed description of each step and its principle.

[0036] S1: Homogenization annealing process.

[0037] In this invention, a CrCoNi medium-entropy alloy strip with a thickness of 3-5 mm is first fed into an annealing furnace for homogenization heat treatment to eliminate compositional segregation of the material during the casting process. The entire annealing process is protected by high-purity argon gas to minimize material oxidation.

[0038] In the homogenization annealing process of this invention embodiment, CrCoNi medium-entropy alloy strips with an atomic ratio greater than 99.9% can be fed into a heating furnace protected by high-purity argon gas for annealing at 800-900°C for 1.5-2 hours, with the furnace temperature rising at a rate of 8-10°C / min, and the cooling method being water quenching.

[0039] S2: Frosted finish.

[0040] The strip obtained from S1 is surface-grinding, specifically a single-sided grinding process can be used, with 400-mesh and 800-mesh abrasive belts made of SiC.

[0041] In the sanding process of this invention embodiment, the sanding speed is 10-12 m / min, two sanding and polishing belts are used on one side, with a mesh size of 400 mesh and 800 mesh respectively, and the sanding pressure is 5-10 MPa. After the upper surface of the raw material is sanded and polished, the lower surface is sanded and polished. This step removes the oxide layer generated during annealing, ensuring a clean and smooth material surface, which is beneficial to improving the processing quality of subsequent cold rolling.

[0042] S3: Cleaning process.

[0043] The abraded strip is cleaned to remove the fine particles formed during abrasion.

[0044] In the cleaning process of this invention embodiment, a sodium hydroxide solution with a mass concentration of 5% to 8% is used. The ultrasonic frequency for cleaning is 40 kHz, followed by rinsing with circulating water for 3 to 8 minutes after alkaline washing, and drying at a temperature of 50°C to 70°C. Cleaning removes fine particulate residues generated during the abrasive process, ensuring a clean and dry material surface, which is beneficial for improving the quality of subsequent cold rolling processing.

[0045] It is easy to understand that S2 and S3 are optimized choices of the present invention. In some cases where the requirements are not high, one or both of these two steps can be omitted.

[0046] S4: Rough rolling process.

[0047] The cleaned strip is then rolled synchronously. In this embodiment, a four-roll reversible rolling mill is used to reduce the strip thickness from 3-5 mm to 0.8-1.6 mm through roughing rolling.

[0048] The working roll diameter of the four-roll reversible rolling mill of this invention is 70-90 mm. The roll diameter is related to the minimum rollable thickness; in this embodiment, 80 mm is selected. During roughing, the rolling force is 25-30 t. Synchronous rolling is used to reduce the thickness of the strip from 3-5 mm to 0.8-1.6 mm. The single-pass rolling reduction rate is 10%-15%, and the rolling lubrication and cooling medium has a kinematic viscosity of 8-10 mm. 2 The presence of rolling oil at a rate of / s improves the surface quality of the strip, which is beneficial for subsequent intermediate rolling. During the roughing stage, the material's deformation resistance is relatively low; simultaneous rolling can achieve a high reduction rate while ensuring a flat material shape.

[0049] S5: Intermediate rolling process.

[0050] After the strip is rough-rolled by S4, it is trimmed and then asynchronously rolled. In this embodiment, this step still uses a four-roll reversible mill to further reduce the thickness of the strip to 0.1-0.2 mm.

[0051] Furthermore, in the intermediate rolling process of this embodiment of the invention, the mill is still a four-high reversible rolling mill, and the work roll diameter is still 80mm. During the intermediate rolling process, the rolling force is 20-25t, and asynchronous rolling with a speed ratio of 1.2-1.3 is used to reduce the thickness of the strip from 0.8-1.6mm to 0.1-0.2mm. The single-pass rolling reduction rate is 10%-15%, and the rolling lubrication and cooling medium has a kinematic viscosity of 7-9mm. 2 As the rolling mill thins out, the material thickness decreases, and the kinematic viscosity of the rolling oil should also decrease appropriately. As cold rolling progresses, the material becomes increasingly difficult to deform; by introducing shear strain through asynchronous rolling, rapid reduction can be achieved.

[0052] S6: Riveting process.

[0053] In order to carry out the next step of tensioned asynchronous rolling, the strip rolled in S5 is trimmed and then riveted to the lead strip.

[0054] Furthermore, in the riveting process of this embodiment of the invention, 5*4mm rivets are used at intervals of 1.5 to 2cm to firmly rivet the thin strip and the guide strip. Each rivet is in a straight line in the TD direction to ensure that the tension is evenly distributed on the CrCoNi ultrathin strip and the guide strip, and to avoid stress concentration.

[0055] S7: Combined forming rolling process.

[0056] The strip after S6 riveting is subjected to tension asynchronous rolling to further reduce the strip thickness to 0.03-0.05 mm, thus obtaining an ultra-thin strip.

[0057] Furthermore, in the combined forming rolling process of this embodiment, the mill is still a four-high reversible mill, the work roll diameter is still 80mm, the rolling force during the rolling process is 15-20t, and the tensile stress is 1 / 4 to 1 / 3 of the yield strength of the medium-entropy alloy strip with a thickness of 0.1-0.2mm after intermediate rolling, i.e., 300-500MPa. Asynchronous rolling with a speed ratio of 1.1-1.2 is used to reduce the thickness of the 0.1-0.2mm strip to 0.03-0.05mm, with a single-pass rolling reduction rate of 5%-10%. This combined forming rolling involves negative roll gap rolling, which can easily lead to edge waviness and even strip breakage in experiments without lubricating oil. Moreover, the addition of rolling lubricating oil can improve the surface quality of the strip. A suitable rolling lubricating oil viscosity can form a continuous oil film between the roll gaps, maintaining a stable rolling effect. This invention selects a rolling lubrication and cooling medium with a kinematic viscosity of 6-8mm. 2 / s of rolling oil.

[0058] The mechanical properties of the CrCoNi ultra-thin strip after this step of combined forming and rolling are: tensile strength of 1650-1800 MPa, yield strength of 1600-1700 MPa, and elongation of 1%-2%. This is because the deformation zone of the ultra-thin strip is simultaneously subjected to compressive stress, tensile stress, and shear stress, making it easier to reach the deformation conditions.

[0059] S8: Leveling process.

[0060] The ultra-thin strip after S7 assembly and rolling is leveled using a leveling machine.

[0061] Furthermore, in this embodiment of the invention, the leveling process involves 1 to 3 leveling passes using a leveling machine. The leveling process does not require rolling oil lubrication, the rolling force is 5 to 10 tons, and the tensile stress is 10 to 20% of the yield strength of the ultra-thin strip with a thickness of 0.03 to 0.05 mm after combined forming and rolling, i.e., 160 to 340 MPa. This process ensures the final product thickness accuracy while further improving the flatness of the strip.

[0062] S9: Cleaning process.

[0063] The ultra-thin strip after S8 flattening is cleaned.

[0064] In the cleaning process of this invention embodiment, a sodium hydroxide solution with a mass concentration of 3% to 6% is used. The ultrasonic frequency for cleaning is 40 kHz, followed by alkaline washing and rinsing with circulating water for 3 to 8 minutes. The drying temperature is 50°C to 70°C. Cleaning removes fine particulate residues generated during the abrasive process, ensuring a clean and dry material surface, which is beneficial for improving the quality of subsequent processing.

[0065] It is easy to understand that S9 is an optimized option of the present invention, and this step can be omitted in some situations where the requirements are not high.

[0066] S10: Short-time low-temperature annealing process.

[0067] After cleaning the S9, the ultra-thin strip is subjected to short-time low-temperature annealing to restore the material's plasticity. To avoid surface oxidation, a vacuum annealing furnace can be used for annealing under high vacuum.

[0068] Furthermore, in the short-time low-temperature annealing process of this embodiment of the invention, annealing is performed in a vacuum annealing furnace at 650-680°C for 1 min, preferably 650°C; the heating rate is 8-10°C / min, preferably 10°C / min, and the material is cooled in the furnace. The mechanical properties of the annealed CrCoNi ultrathin strip are: tensile strength of 1100-1300 MPa, yield strength of 1000-1150 MPa, and elongation of 10%-14%.

[0069] S11: Electropolishing process.

[0070] Electrolytic polishing was performed on the ultra-thin strip after S11 sandblasting to further reduce the surface roughness to 0.0025–0.005 μm.

[0071] S12: Finished product inspection and packaging.

[0072] It is easy to understand that S11 and S12 are optimized options of the present invention. In some cases where the requirements are not high, one or both of these steps can be omitted.

[0073] The following are some specific embodiments of the present invention.

[0074] Example 1:

[0075] A micrometer-thick CrCoNi medium-entropy alloy ultrathin strip and its preparation process include the following steps:

[0076] Step 1: Homogenization Annealing Process: First, CrCoNi medium-entropy alloy raw materials with a purity greater than 99% and a thickness of 3mm are fed into an annealing furnace for homogenization heat treatment. This eliminates compositional segregation that occurred during the casting process. High-purity argon gas is used throughout the annealing process to minimize material oxidation. The annealing temperature is 900℃, the time is 1.5 hours, and the temperature is increased with the furnace at a rate of 10℃ / min. The cooling method is water quenching. The metallographic structure of the CrCoNi strip after homogenization annealing is as follows: Figure 2 As shown, a uniform equiaxed crystal structure of ~170μm is obtained, which improves the plasticity of the material, makes the deformation more uniform and coordinated, and is conducive to achieving thinner thickness.

[0077] Step 2: Grinding Process: The raw material obtained from S1 is subjected to surface grinding using a single-sided grinding process. The abrasive belt mesh sizes are 400 mesh and 800 mesh, and the abrasive belt material is SiC. The grinding speed is 10m / min, and two single-sided grinding and polishing passes are performed. The abrasive belt grinding pressure is 6MPa. After the upper surface of the raw material is ground and polished, the lower surface is ground and polished.

[0078] Step 3: Cleaning Process: The raw material after grinding is cleaned to remove the fine particles formed during grinding. A 7% sodium hydroxide solution is used as the alkaline solution, the ultrasonic frequency is 40 kHz, and the drying temperature is 60℃. Alkaline cleaning helps reduce the surface roughness of the strip, thereby improving the processing quality of subsequent cold rolling.

[0079] Step 4: Rough Rolling Process: The cleaned raw material is fed into a four-high reversible rolling mill for roughing. The work roll diameter is 80mm, and the rolling force during the rolling process is 25t. Synchronous rolling is used to reduce the thickness of the 3mm raw material to 0.85mm. The single-pass rolling reduction rate is 14.3%. The rolling lubricating and cooling medium has a kinematic viscosity of 9mm. 2 / s of rolling oil.

[0080] Step 5: Intermediate Rolling Process: After edge trimming following S4 rough rolling, the strip is fed into a four-high reversible mill for asynchronous rolling to further reduce the material thickness. The work roll diameter is 80mm, the rolling force is 20t, and asynchronous rolling with a speed ratio of 1.3 is used to reduce the thickness of the 0.85mm strip to 0.1mm. The single-pass rolling reduction rate is 14.7%, and the rolling lubricating and cooling medium has a kinematic viscosity of 8mm. 2 / s of rolling oil.

[0081] Step 6: Riveting process: In order to carry out the next step of asynchronous rolling under tension, after the strip in S5 is trimmed, it is riveted to the lead strip with 5*4mm rivets at intervals of 1.5cm. The rivets are all in a straight line in the TD direction to ensure that the tension is evenly distributed on the CrCoNi ultra-thin strip and the lead strip and to avoid stress concentration.

[0082] Step 7: Combined Forming Rolling Process: The S6 riveted strip is subjected to tension asynchronous rolling to reduce the material thickness to the target thickness. The mill is a four-high reversible mill with a work roll diameter of 80mm. The rolling force during the rolling process is 16t, and the tensile stress is 450MPa. Asynchronous rolling with a speed ratio of 1.2 is used to reduce the thickness of the strip from 0.1mm to 0.03mm. The single-pass rolling reduction rate is 8.75%, and the rolling lubricating and cooling medium has a kinematic viscosity of 7mm. 2 The rolling oil at a rate of / s produces CrCoNi ultra-thin strip with the following mechanical properties after rolling: tensile strength 1725MPa, yield strength 1680MPa, and elongation 1.36%. The finished CrCoNi ultra-thin strip is shown below. Figure 3 As shown, the XRD patterns of samples with different deformation amounts during the rolling process are as follows. Figure 4 As shown, the rolling process maintains a single FCC phase structure.

[0083] Step 8: Leveling process: The strip after S7 assembly and rolling is leveled three times using a leveling machine. No rolling oil lubrication is required during the leveling process. The rolling force is 5t and the tensile stress is 200MPa.

[0084] Step 9: Cleaning Process: The ultra-thin S8 strip after leveling is cleaned to remove dirt and rolling oil from the surface during the rolling process. A 6% sodium hydroxide solution is used as the alkaline solution, the ultrasonic frequency is 40kHz, and the drying temperature is 70℃.

[0085] Step 10: Short-time low-temperature annealing process: The ultra-thin strip after S9 cleaning undergoes short-time low-temperature annealing to achieve excellent strength and plasticity. To avoid surface oxidation, a vacuum annealing furnace is used for annealing under high vacuum. The annealing temperature is 650℃, the annealing time is 1 min, the heating rate is 10℃ / min, and it is cooled in the furnace. The mechanical properties of the annealed CrCoNi ultra-thin strip are: tensile strength 1173 MPa, yield strength 1014 MPa, and elongation 13.4%. The stress-strain curves of the rolled and annealed CrCoNi ultra-thin strips are shown below. Figure 5 As shown.

[0086] Step 11: Electrolytic polishing process: Electrolytic polishing is performed on the ultra-thin strip after S11 abrasive polishing to further reduce the surface roughness to 0.003μm;

[0087] Step 12: Finished product inspection and packaging.

[0088] The rolling process parameters are shown in Table 1.

[0089] Table 1. Rolling process parameters involved in Example 1

[0090] Cold rolling process Number of rolling processes Rolling speed (m / s) Thickness after rolling (mm) Deformation Rough rolling 5 0.03 0.85 71.67％ intermediate rolling 6 0.02 0.1 88.24％ Combined forming rolling 8 0.01 0.03 70％

[0091] Example 2:

[0092] A micrometer-thick CrCoNi medium-entropy alloy ultrathin strip and its preparation process include the following steps:

[0093] Step 1: Homogenization Annealing Process: First, the CrCoNi medium-entropy alloy raw material with a purity greater than 99% and a thickness of 5mm is fed into the annealing furnace for homogenization heat treatment, which can eliminate the compositional segregation of the material during the casting process. The entire annealing process is protected by high-purity argon gas to minimize material oxidation. The annealing temperature is 900℃, the time is 2h, the furnace temperature is increased at a rate of 10℃ / min, and the cooling method is water quenching.

[0094] Step 2: Grinding Process: The raw material obtained from S1 is subjected to surface grinding using a single-sided grinding process. The abrasive belts are 400 mesh and 800 mesh, and the belt material is SiC. The grinding speed is 12m / min, and two single-sided grinding and polishing passes are performed. The abrasive belt grinding pressure is 8MPa. After the upper surface of the raw material is ground and polished, the lower surface is ground and polished.

[0095] Step 3: Cleaning Process: The raw material after abrasion is cleaned to remove the fine particles formed during abrasion. A 6% sodium hydroxide solution is used as the alkaline solution, the ultrasonic frequency is 40kHz, and the drying temperature is 50℃.

[0096] Step 4: Rough Rolling Process: The cleaned raw material is fed into a four-high reversible rolling mill for roughing. The work roll diameter is 80mm, and the rolling force during the rolling process is 30t. Synchronous rolling is used to reduce the thickness of the 5mm raw material to 1.6mm. The single-pass rolling reduction rate is 13.6%. The rolling lubricating and cooling medium has a kinematic viscosity of 10mm. 2 / s of rolling oil.

[0097] Step 5: Intermediate Rolling Process: After edge trimming following S4 rough rolling, the strip is fed into a four-high reversible mill for asynchronous rolling to further reduce the material thickness. The work roll diameter is 80mm, the rolling force during the rolling process is 25t, and asynchronous rolling with a speed ratio of 1.3 is used to reduce the thickness of the 1.6mm strip to 0.2mm. The single-pass rolling reduction rate is 12.5%, and the rolling lubricating and cooling medium has a kinematic viscosity of 9mm. 2 / s of rolling oil.

[0098] Step 6: Riveting process: In order to carry out the next step of asynchronous rolling under tension, after the strip in S5 is trimmed, it is riveted to the lead strip with 5*4mm rivets at intervals of 1.5cm. The rivets are all in a straight line in the TD direction to ensure that the tension is evenly distributed on the CrCoNi ultra-thin strip and the lead strip and to avoid stress concentration.

[0099] Step 7: Combined Forming Rolling Process: The S6 riveted strip is subjected to tension asynchronous rolling to reduce the material thickness to the target thickness. The mill is a four-high reversible mill with a work roll diameter of 80mm. The rolling force during the rolling process is 18t, and the tensile stress is 400MPa. Asynchronous rolling with a speed ratio of 1.2 is used to reduce the thickness of the 0.15mm strip to 0.05mm. The single-pass rolling reduction rate is 9.5%, and the rolling lubricating and cooling medium has a kinematic viscosity of 7mm. 2 The mechanical properties of the rolled CrCoNi ultrathin strip after rolling with rolling oil of / s are: tensile strength 1710MPa, yield strength 1629MPa, and elongation 1.5%.

[0100] Step 8: Leveling process: The strip after S7 assembly and rolling is leveled twice using a leveling machine. No rolling oil lubrication is required during the leveling process. The rolling force is 7t and the tensile stress is 250MPa.

[0101] Step 9: Cleaning Process: The ultra-thin S8 strip after leveling is cleaned to remove dirt and rolling oil from the surface. A 6% sodium hydroxide solution is used as the alkaline solution, the ultrasonic frequency is 40kHz, and the drying temperature is 60℃.

[0102] Step 10: Short-time low-temperature annealing process: The ultra-thin strip after S9 cleaning is subjected to short-time low-temperature annealing to achieve excellent strength and plasticity. To avoid surface oxidation, a vacuum annealing furnace is used for annealing under high vacuum. The annealing temperature is 650℃, the annealing time is 1min, the heating rate is 10℃ / min, and the strip is cooled in the furnace. The mechanical properties of the annealed CrCoNi ultra-thin strip are: tensile strength of 1213MPa, yield strength of 1078MPa, and elongation of 11.8%.

[0103] Step 11: Electrolytic polishing process: Electrolytic polishing is performed on the ultra-thin strip after S11 abrasive polishing to further reduce the surface roughness to 0.003μm;

[0104] Step 12: Finished product inspection and packaging.

[0105] The rolling process parameters are shown in Table 2.

[0106] Table 2 shows the rolling process parameters involved in Example 2.

[0107] Cold rolling process Number of rolling processes Rolling speed (m / s) Thickness after rolling (mm) Deformation Rough rolling 5 0.03 1.6 68％ intermediate rolling 7 0.02 0.2 87.5％ Combined forming rolling 10 0.01 0.05 75％

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A micrometer-thick CrCoNi medium-entropy alloy ultrathin strip, characterized in that, The atomic ratio of this medium-entropy alloy is Cr:Co:Ni = 1:1:1, the purity is greater than 99.9%, and the balance is unavoidable impurity components; the raw material strip thickness of this medium-entropy alloy ultra-thin strip is 3-5 mm, and the finished product thickness is 0.03-0.05 mm.

2. A process for preparing ultrathin CrCoNi medium-entropy alloy strips with a thickness of micrometers, characterized in that, Includes the following steps: S1: Homogenize and anneal a medium-entropy alloy strip with a thickness of 3-5 mm. The atomic ratio of the medium-entropy alloy is Cr:Co:Ni = 1:1:1, the purity is greater than 99.9%, and the balance is unavoidable impurity components. S2: The homogenized annealed strip is subjected to rough rolling and intermediate rolling processes in sequence to reduce its thickness to 0.1-0.2 mm; S3: The strip after intermediate rolling is trimmed, then riveted to the lead strip and rolled into an ultra-thin strip with a thickness of 0.03 to 0.05 mm. S4: After the ultra-thin strip is flattened, it is subjected to short-time low-temperature annealing to restore the material's plasticity; the short-time low-temperature annealing is performed under vacuum conditions at 650-680°C for 1 minute, with a heating rate of 8-10°C / min, followed by furnace cooling.

3. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 2, characterized in that, The homogenization annealing is carried out in a heating furnace protected by high-purity argon gas at a temperature of 800-900℃ for 1.5-2 hours. The furnace temperature is increased at a rate of 8-10℃ / min, and the cooling method is water quenching.

4. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 2, characterized in that, Before rough rolling the homogenized annealed strip, the surface is first sanded and cleaned; before short-time low-temperature annealing of the ultra-thin strip, it is first cleaned. The surface abrasion is performed using SiC abrasive belts on one side at a speed of 10–12 m / min. Two abrasive belts are used on each side, with mesh sizes of 400 and 800 mesh respectively. The abrasive belt abrasion pressure is 5–10 MPa. The cleaning before rough rolling uses a sodium hydroxide solution with a mass concentration of 5%–8%, and the cleaning before short-time low-temperature annealing uses a sodium hydroxide solution with a mass concentration of 3%–6%. The ultrasonic frequency for both cleaning processes is 40 kHz. After alkaline washing, the surface is rinsed with circulating water for 3–8 minutes, and the drying temperature is 50℃–70℃.

5. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 2, characterized in that, The roughing process involves feeding the strip into a four-high reversible mill for synchronous rolling, thinning the strip to 0.8–1.6 mm; the intermediate rolling process involves trimming the edges of the rough-rolled strip and then feeding it into a four-high reversible mill for asynchronous rolling, thinning the strip to 0.1–0.2 mm.

6. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 5, characterized in that, The working roll diameter of the four-roll reversible rolling mill is 70-90 mm; The roughing process involves a rolling force of 25–30 t, employing synchronous rolling to reduce the thickness of the strip from 3–5 mm to 0.8–1.6 mm. The single-pass reduction rate is 10%–15%, and the rolling lubricant and cooling medium has a kinematic viscosity of 8–10 mm. 2 / s of rolling oil; The intermediate rolling mill uses a rolling force of 20–25 t and employs asynchronous rolling with a speed ratio of 1.2–1.3 to reduce the thickness of the strip from 0.8–1.6 mm to 0.1–0.2 mm. The single-pass rolling reduction rate is 10%–15%, and the rolling lubricating and cooling medium has a kinematic viscosity of 7–9 mm. 2 / s of rolling oil.

7. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 2, characterized in that, The riveting is achieved by using rivets at intervals of 1.5 to 2 cm to firmly connect the thin strip to the guide strip, with each rivet aligned in a straight line in the TD direction.

8. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 2, characterized in that, The combined forming rolling process uses a four-high reversible mill with work roll diameters of 70–90 mm. The rolling force during the rolling process is 15–20 t, and the tensile stress is 1 / 4–1 / 3 of the yield strength of a medium-entropy alloy strip with a thickness of 0.1–0.2 mm after intermediate rolling, i.e., 300–500 MPa. Asynchronous rolling with a speed ratio of 1.1–1.2 is used to reduce the thickness of the strip from 0.1–0.2 mm to 0.03–0.05 mm. The single-pass rolling reduction rate is 5%–10%, and the rolling lubricating and cooling medium has a kinematic viscosity of 6–8 mm. 2 / s of rolling oil.

9. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 2 or 8, characterized in that, The mechanical properties of the CrCoNi ultra-thin strip after the combined forming and rolling process are: tensile strength of 1650-1800 MPa, yield strength of 1600-1700 MPa, and elongation of 1%-2%; the mechanical properties of the CrCoNi ultra-thin strip after the short-time low-temperature annealing are: tensile strength of 1100-1300 MPa, yield strength of 1000-1150 MPa, and elongation of 10%-14%.

10. The preparation process of the micron-thickness CrCoNi medium-entropy alloy ultrathin strip according to claim 2, characterized in that, The leveling process is carried out using a leveling machine, with 1 to 3 leveling operations. No rolling oil lubrication is required during the leveling process. The rolling force is 5 to 10 t, and the tensile stress is 10 to 20% of the yield strength of the extremely thin strip with a thickness of 0.03 to 0.05 mm after combined forming and rolling, i.e., 160 to 340 MPa.

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