A nano-twinned nickel-based alloy sheet and a preparation method thereof

Abstract

The present invention provides a nano-twinned nickel-based alloy sheet and a preparation method thereof. The microstructure of the nano-twinned nickel-based alloy sheet includes grains; there are nano-twins and dislocations inside the grains; the grains containing nano-twins in the nano-twinned nickel-based alloy sheet account for more than 80% of the total number of grains. The nano-twinned nickel-based alloy sheet has excellent comprehensive mechanical properties, with excellent yield strength, tensile strength and good elongation; the technological process of the preparation method is simple, the processing cost is low, the condition parameters are easy to control, large-size products can be prepared, and it can be directly used as engineering materials, having the prospect of large-scale industrial application.

Description

Technical Field

[0001] The present invention relates to the technical field of nanostructured metallic materials, and particularly to a nanotwinned nickel-based alloy sheet and a preparation method thereof. Background Art

[0002] Nickel and its alloys have excellent corrosion resistance, good strength and good plasticity, etc., and are an important class of corrosion-resistant structural materials, which are widely used in high-tech fields such as aviation, aerospace, nuclear power, ocean, petrochemical, etc., and play an important and even indispensable role. In chemical engineering applications, in order to increase the reaction rate, control the reaction direction, and increase the product yield, harsh reaction conditions such as high temperature, high pressure, and strong corrosion are required. For equipment serving under such extremely harsh conditions, its service life and safety factor are comprehensively determined by the properties such as the strength, plasticity, and corrosion resistance of the material. Therefore, improving the relevant properties of nickel-based alloys is the development trend in the field of materials.

[0003] The microstructure of a material directly determines the properties of the material. By introducing specific defects inside the material, such as solute atoms, dislocations, grain boundaries, second phases, etc., to hinder the movement of dislocations can improve the strength of the material. However, while traditional strengthening means improve the strength of the material, they inevitably cause a significant reduction in properties such as plasticity, stability, conductivity, and corrosion resistance. Therefore, improving the strength of nickel-based alloys while maintaining their workability and corrosion resistance is both a severe challenge faced by materials scientists and a bottleneck problem that needs to be solved in engineering applications.

[0004] A twin boundary is a special interface, and the atoms on both sides are arranged in a mirror-symmetric relationship, which is a low-energy coherent interface. Twin boundaries can not only effectively hinder the movement of dislocations and strengthen metallic materials, but also promote the multiplication and slip of dislocations through specific dislocation reactions, improving the plasticity and work hardening ability of metallic materials. Since the interfacial energy of twin boundaries is only one-tenth of that of ordinary grain boundaries, it has high stability, which helps to improve the corrosion resistance of materials. The crystal between adjacent twin boundaries forms twin lamellae, and the thickness of the twin lamellae can only show the strengthening effect on the material when it is at the nanometer level. Therefore, forming a high-density nanotwinned structure is a new way to obtain metallic materials with high strength, high plasticity and high corrosion resistance.

[0005] The ease of twin formation is highly correlated with the stacking fault energy of metallic materials. Metals with low stacking fault energy, such as copper (78 mJ / m 2 ) and silver (22 mJ / m 2 ) etc. are easy to form twin boundaries, while nickel (128 mJ / m 2 ) with a relatively high stacking fault energy is more difficult to form a high-density nanoscale twin structure. Nevertheless, through specific technical means, nickel-based metallic materials with a nanotwinned structure can be obtained.

[0006] CN101144172A discloses a nano-twinned nickel coating with high corrosion resistance and its preparation technology. The nano-twinned nickel coating is prepared by pulse electrodeposition technology, and its microstructure is composed of nearly equiaxed sub-micron grains with a size ranging from 200 nm to 800 nm. There is a high-density lamellar twin structure with different orientations inside the grains. The twin lamellae with the same orientation are parallel to each other. The thickness of the twin lamellae is mainly distributed in the range of 10 nm to 30 nm, and its length is 100 - 400 nm. This nano-twinned nickel coating not only exhibits excellent corrosion resistance, but also has high strength and high wear resistance.

[0007] CN107083560A discloses an ultra-high hardness refractory metal nanocrystalline coating and its preparation method. The nano-twinned pure nickel and nickel-based alloy coatings are prepared by direct current electrodeposition technology, reducing the average thickness of the twin lamellae and increasing the volume fraction of twins, and obtaining a nickel-based alloy coating with high strength, high corrosion resistance and high stability.

[0008] CN111850624A discloses a nano-twinned nickel with extremely small twin lamella thickness and ultra-high strength and its preparation. This patent uses electrodeposition technology to prepare nano-twinned nickel with a thickness of hundreds of microns to millimeters. Its microstructure is composed of columnar grains with a length of 200 - 3000 nm and a width of about 10 - 50 nm. Inside the columnar grains, there is a high-density and uniformly oriented lamellar twin structure. The thickness of the twin lamellae ranges from 0.5 to 10 nm, and the grains with twin structure can account for 100% of the entire sample grains. The microhardness of this material at room temperature can reach above 8.5 GPa, which is 1.5 - 2 times or more that of ordinary electroplated nano-nickel. After annealing at 250 °C for half an hour, the hardness increases to 9.6 GPa, and the structure coarsening temperature can reach above 350 °C, which is more than 150 °C higher than that of ordinary nanocrystalline nickel. This nanocrystalline coating can be applied to the wear-resistant protection of metal materials such as copper, nickel and their alloys, as well as stainless steel, and can also be applied to fields such as micro-mechanical systems.

[0009] However, the coating is prone to crack and peel off under external force, so it is restricted in practical engineering applications. Moreover, the electrodeposition technology has a slow processing rate, high operation and maintenance costs, high equipment requirements, and complex process parameters, which is not conducive to large-scale production; most of the nano-twinned materials prepared by the electrodeposition method are thin film and thin sheet samples, with a significantly anisotropic microstructure, small product size, and are not suitable as engineering structural materials.

[0010] Severe plastic deformation techniques such as high-pressure torsion and surface mechanical attrition treatment are effective means for forming bulk nanocrystalline twin metals. However, due to the relatively high stacking fault energy, even under severe plastic deformation conditions with high strain rates and large strain amounts, few or only a small amount of nanoscale twins can be generated inside nickel-based alloys, while other defects such as dislocations, grain boundaries, and shear bands are formed in large quantities. Severe plastic deformation techniques rely on special processing equipment and have low processing efficiency, and thus cannot be popularized in industrial production at present. Meanwhile, the shape and size of the nanocrystalline twin metal materials formed by severe plastic deformation are limited and cannot meet the requirements for processing industrial equipment with larger sizes.

[0011] Therefore, developing a preparation method for high-density nanocrystalline twin nickel-based alloy sheets that can produce large-sized products and is suitable for industrial production is of great significance for the engineering applications of nickel-based alloys in high-end industrial fields. Summary of the Invention

[0012] In view of the problems existing in the prior art, the present invention provides a nanocrystalline twin nickel-based alloy sheet and a preparation method thereof. The grain interior of the nanocrystalline twin nickel-based alloy sheet has high-density nanoscale deformation twins and dislocations. The technological process of the preparation method is simple, the processing cost is low, the production efficiency is high, large-sized nanocrystalline twin nickel-based alloy sheets can be prepared, and it is suitable for large-scale industrial production.

[0013] To achieve this purpose, the present invention adopts the following technical solutions:

[0014] In a first aspect, the present invention provides a nanocrystalline twin nickel-based alloy sheet. The microstructure of the nanocrystalline twin nickel-based alloy sheet includes grains; there are nanoscale twins and dislocations inside the grains; the grains containing nanoscale twins in the nanocrystalline twin nickel-based alloy sheet account for more than 80% of the total number of grains.

[0015] There are nanoscale twins and dislocations inside the grains of the nanocrystalline twin nickel-based alloy sheet of the present invention. The appearance of nanoscale twins can not only effectively hinder the movement of dislocations and strengthen the nickel-based alloy sheet, but also promote the multiplication and slip of dislocations through specific dislocation reactions, enhancing the work hardening ability and plastic deformation ability of the nickel-based alloy sheet. The nanocrystalline twin nickel-based alloy sheet of the present invention has a relatively large size and can be directly used as an engineering structural material, having good industrial application prospects.

[0016] The grains containing nanoscale twins in the nanocrystalline twin nickel-based alloy sheet of the present invention account for more than 80% of the total number of grains, and can be, for example, 80%, 83%, 85%, 88%, 90% or 95%.

[0017] Preferably, the thickness of the nanocrystalline twin nickel-based alloy sheet is 1-4 mm, and can be, for example, 1 mm, 2 mm, 3 mm or 4 mm.

[0018] Preferably, the shape of the crystal grains is columnar.

[0019] Preferably, the length of the crystal grains is 10 - 30 μm, for example, it can be 10 μm, 12 μm, 15 μm, 20 μm, 25 μm or 30 μm.

[0020] Preferably, the width of the crystal grains is 3 - 20 μm, for example, it can be 3 μm, 5 μm, 7 μm, 10 μm, 15 μm or 20 μm.

[0021] Preferably, the nano-twins are nano-scale deformation twins.

[0022] Preferably, the nano-twins within the same crystal grain in the nano-twin nickel-based alloy sheet have the same orientation and penetrate the entire crystal grain.

[0023] Preferably, the lamellar thickness of the nano-twins is 1 - 20 nm, for example, it can be 1 nm, 3 nm, 5 nm, 7 nm, 10 nm, 15 nm or 20 nm.

[0024] Preferably, the nano-twins form twin clusters.

[0025] Preferably, the distance between the twin clusters is 0.3 - 3.5 μm, for example, it can be 0.3 μm, 0.4 μm, 0.5 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm, 1.7 μm, 2.0 μm, 2.2 μm, 2.5 μm, 2.8 μm, 3.0 μm, 3.3 μm or 3.5 μm.

[0026] Preferably, the distance between the nano-twins within the twin clusters is 30 - 100 nm, for example, it can be 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0027] In a second aspect, the present invention provides a method for preparing a nano-twin nickel-based alloy sheet as described in the first aspect, and the preparation method includes the following steps:

[0028] (1) The nickel-based alloy ingot is subjected to homogenization treatment to obtain a first nickel-based alloy sheet;

[0029] (2) After hot rolling the first nickel-based alloy sheet, it is quenched and cooled to obtain a second nickel-based alloy sheet;

[0030] (3) The second nickel-based alloy sheet is cold rolled to obtain a third nickel-based alloy sheet;

[0031] (4) The third nickel-based alloy sheet is subjected to annealing heat treatment under the conditions of 500°C to 700°C to obtain a nano-twinned nickel-based alloy sheet.

[0032] In the preparation method of the present invention, alloying combined with thermo-mechanical treatment is adopted to form a high-density nano-scale deformation twin structure inside the nickel-based alloy sheet, and a large-sized nano-twinned nickel-based alloy sheet is obtained, which can be directly used as an engineering structural material for processing to meet the requirements of industrial equipment. Among them, it is particularly crucial that the third nickel-based alloy sheet after cold rolling is subjected to annealing heat treatment under the conditions of 500°C to 700°C. If the annealing heat treatment temperature is too low, unnecessary and movable dislocations in the third nickel-based alloy sheet cannot be removed, and the work hardening ability and plastic deformation ability of the finally obtained nano-twinned nickel-based alloy sheet will decrease; if the annealing heat treatment temperature is too high, serious recrystallization phenomenon is likely to occur, and the number of nano-twins in the finally obtained nano-twinned nickel-based alloy sheet will decrease, thereby affecting the strength and hardness of the nano-twinned nickel-based alloy sheet. Moreover, the highest temperature of the annealing heat treatment in the present invention is only 700°C, which can save energy consumption and is beneficial to large-scale industrial production.

[0033] The temperature of the annealing heat treatment of the present invention is 500°C to 700°C, and for example, it can be 500°C, 530°C, 550°C, 600°C, 640°C, 650°C or 700°C.

[0034] Preferably, the nickel-based alloy ingot in step (1) contains 20wt% to 30wt% of cobalt element, and for example, it can be 20wt%, 22wt%, 25wt%, 28wt% or 30wt%.

[0035] The present invention further preferably uses a nickel-based alloy ingot containing 20wt% to 30wt% of cobalt element. The addition of cobalt can significantly reduce the stacking fault energy and play a role in solid solution strengthening.

[0036] Preferably, the nickel-based alloy ingot contains 10wt% to 15wt% of chromium element, and for example, it can be 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt%.

[0037] The present invention further preferably uses a nickel-based alloy ingot containing 10wt% to 15wt% of chromium element. The addition of chromium can also play a certain role in reducing the stacking fault energy and solid solution strengthening, but compared with cobalt element, the effect of reducing the stacking fault energy and solid solution strengthening is slightly worse.

[0038] The present invention further preferably provides that the nickel-based alloy ingot contains 20 wt% to 30 wt% of cobalt element and 10 wt% to 15 wt% of chromium element at the same time, which can reduce the stacking fault energy of the nickel-based alloy sheet, so that after the nickel-based alloy sheet is subjected to thermo-mechanical treatment, a high-density nanoscale deformed twin structure can be formed.

[0039] Preferably, the temperature of the homogenization treatment in step (1) is 1100 - 1500 °C, for example, it can be 1100 °C, 1150 °C, 1200 °C, 1250 °C, 1300 °C, 1400 °C or 1500 °C.

[0040] Preferably, the time of the homogenization treatment is 1 - 4 h, for example, it can be 1 h, 1.5 h, 2 h, 3 h, 3.5 h or 4 h.

[0041] Preferably, the homogenization treatment is carried out in a muffle furnace.

[0042] The homogenization treatment of the present invention is carried out under high temperature conditions. By maintaining the temperature for a long time, the casting stress, composition segregation and structural inhomogeneity in the actual crystal structure are eliminated or reduced, so as to improve the process performance of the nickel-based alloy ingot.

[0043] Preferably, the initial thickness of the first nickel-based alloy sheet in step (2) is 30 - 50 mm, for example, it can be 30 mm, 32 mm, 35 mm, 40 mm, 45 mm or 50 mm.

[0044] Preferably, the hot rolling is at least 5 passes.

[0045] Preferably, the reduction per pass in the hot rolling is 5 - 10 mm, for example, it can be 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm.

[0046] The present invention further preferably performs 5 passes of hot rolling, and the reduction of each pass of hot rolling is 10 mm, 8 mm, 6 mm, 6 mm and 5 mm respectively.

[0047] Preferably, the final rolling temperature of the hot rolling is ≥ 950 °C, for example, it can be 950 °C, 970 °C or 1000 °C.

[0048] Preferably, the quenching medium includes water.

[0049] Preferably, the quenching is cooled to room temperature.

[0050] The room temperature in the present invention is 20 - 30 °C, for example, it can be 20 °C, 21 °C, 22 °C, 23 °C, 24 °C, 25 °C, 26 °C, 27 °C, 28 °C, 29 °C or 30 °C.

[0051] Preferably, the second nickel-based alloy sheet is subjected to surface treatment before cold rolling.

[0052] Preferably, the surface treatment includes pickling and grinding and polishing carried out in sequence.

[0053] The present invention further preferably conducts surface treatment on the second nickel-based alloy sheet before cold rolling. The main purpose is to remove the surface oxides and rolling defects of the second nickel-based alloy sheet, so as to facilitate subsequent cold rolling treatment.

[0054] Preferably, in the cold rolling in step (3), the reduction per pass does not exceed 10% of the current thickness of the cold-rolled sheet in that pass. For example, it can be 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3% or 2%.

[0055] Preferably, the thickness of the third nickel-based alloy sheet is reduced by 45-55% compared with the second nickel-based alloy sheet. For example, it can be 45%, 46%, 48%, 50%, 52% or 55%.

[0056] Preferably, the time of the annealing heat treatment in step (4) is 5-30 min. For example, it can be 5 min, 7 min, 10 min, 15 min, 18 min, 20 min, 22 min, 25 min or 30 min.

[0057] Preferably, the annealing heat treatment is carried out in a muffle furnace.

[0058] The present invention further preferably conducts annealing heat treatment on the third nickel-based alloy sheet. On the one hand, as many nanotwins as possible are retained to maintain the high strength and high stability of the finally obtained nanotwinned nickel-based alloy sheet; on the other hand, the dislocation density is reduced as much as possible to improve the plasticity, workability and corrosion resistance of the finally obtained nanotwinned nickel-based alloy sheet.

[0059] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0060] (1) A nickel-based alloy ingot containing 20 wt% - 30 wt% of cobalt element and 10 wt% - 15 wt% of chromium element is subjected to homogenization treatment at 1100 - 1500 °C for 1 - 4 h to obtain a first nickel-based alloy sheet;

[0061] (2) The initial thickness of the first nickel-based alloy sheet is 30 - 50 mm. After at least 5 passes of hot rolling, it is quenched and cooled to room temperature to obtain a second nickel-based alloy sheet; the final rolling temperature of the hot rolling ≥ 950 °C; the reduction per pass in the hot rolling is 5 - 10 mm;

[0062] (3) The second nickel-based alloy sheet is cold-rolled to obtain a third nickel-based alloy sheet; in the cold rolling, the reduction per pass does not exceed 10% of the current thickness of the cold-rolled sheet in that pass; the thickness of the third nickel-based alloy sheet is reduced by 45-55% compared with the second nickel-based alloy sheet;

[0063] (4) The third nickel-based alloy sheet is annealed at 500°C - 700°C for 5 - 30 min to obtain a nano-twinned nickel-based alloy sheet.

[0064] Thirdly, the present invention provides an application of the nano-twinned nickel-based alloy sheet as described in the first aspect in the fields of aviation, aerospace, nuclear power, ocean or petrochemical industry.

[0065] The nano-twinned nickel-based alloy sheet of the present invention has a high-density nano-twinned structure, excellent mechanical properties, high strength and high corrosion resistance, and can be mass-produced industrially, and has a wide application in the fields of aviation, aerospace, nuclear power, ocean or petrochemical industry.

[0066] Compared with the prior art, the present invention has at least the following beneficial effects:

[0067] (1) The nano-twinned nickel-based alloy sheet provided by the present invention has a relatively large size and a high-density nano-twinned structure, excellent comprehensive mechanical properties, in which the yield strength can reach more than 900 MPa, and can reach more than 1200 MPa under better conditions, the tensile strength can reach more than 1100 MPa, and can reach more than 1250 MPa under better conditions, and the elongation can reach more than 7%, and can reach more than 15% under better conditions;

[0068] (2) The preparation method of the nano-twinned nickel-based alloy sheet provided by the present invention requires simple equipment, low processing cost, high production efficiency, and is suitable for large-scale industrial production;

[0069] (3) The preparation process of the nano-twinned nickel-based alloy sheet provided by the present invention is simple, the condition parameters are easy to control, it is convenient to control the microstructure of the nano-twinned nickel-based alloy sheet, and the product performance window is large. Description of the Drawings

[0070] Figure 1 It is a backscattered electron image of a scanning electron microscope of the microstructure of a nickel-based alloy ingot in Example 1 of the present invention.

[0071] Figure 2 It is a backscattered electron image of a scanning electron microscope of the second nickel-based alloy sheet in Example 1 of the present invention.

[0072] Figure 3 It is a comparison diagram of backscattered electron diffraction bands of the second nickel-based alloy sheet in Example 1 of the present invention.

[0073] Figure 4 This is the bright-field image of the transmission electron microscope of the second nickel-based alloy sheet in Example 1 of the present invention, with a magnification of 50,000.

[0074] Figure 5 This is the bright-field image of the transmission electron microscope of the second nickel-based alloy sheet in Example 1 of the present invention, with a magnification of 75,000.

[0075] Figure 6 This is the backscattered electron image of the scanning electron microscope of the third nickel-based alloy sheet in Example 1 of the present invention.

[0076] Figure 7 This is the backscattered electron image of the scanning electron microscope of the nanocrystalline twin nickel-based alloy sheet in Example 1 of the present invention.

[0077] Figure 8 This is the comparison diagram of backscattered electron diffraction bands of the nanocrystalline twin nickel-based alloy sheet in Example 1 of the present invention.

[0078] Figure 9 This is the backscattered electron image of the scanning electron microscope of the nanocrystalline twin nickel-based alloy sheet in Example 4 of the present invention.

[0079] Figure 10 This is the comparison diagram of backscattered electron diffraction bands of the nanocrystalline twin nickel-based alloy sheet in Example 4 of the present invention. Detailed implementation mode

[0080] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific implementation modes.

[0081] The present invention will be further described in detail below. However, the following examples are only simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention is subject to the claims.

[0082] Example 1

[0083] This embodiment provides a method for preparing a nanocrystalline twin nickel-based alloy sheet, and the preparation method includes the following steps:

[0084] (1) A nickel-based alloy ingot containing 30 wt% of cobalt element and 15 wt% of chromium element is homogenized in a muffle furnace at 1200 °C for 2 h to obtain a first nickel-based alloy sheet;

[0085] (2) The initial thickness of the first nickel-based alloy sheet is 40 mm. After 5 passes of hot rolling, the final thickness of the first nickel-based alloy sheet is 5 mm, and it is water-quenched to room temperature to obtain the second nickel-based alloy sheet; the final rolling temperature of the hot rolling is 950 °C; the reduction per pass in the hot rolling is 10 mm, 8 mm, 6 mm, 6 mm, and 5 mm respectively;

[0086] (3) After the second nickel-based alloy sheet is pickled and polished in sequence, it is cold-rolled to obtain the third nickel-based alloy sheet; the reduction per pass in the cold rolling does not exceed 10% of the current thickness of the cold-rolled sheet in that pass; the thickness of the third nickel-based alloy sheet is reduced by 50% compared with the second nickel-based alloy sheet;

[0087] (4) The third nickel-based alloy sheet is annealed at 500 °C for 15 min in a muffle furnace to obtain a nano-twinned nickel-based alloy sheet.

[0088] In this embodiment, the backscattered electron image of the microstructure of the nickel-based alloy ingot obtained by scanning electron microscopy is as Figure 1 shown. The nickel-based alloy ingot has coarse irregular-shaped grains, and the average grain size is 258.9 ± 23.5 μm. There are no significant microcrystalline defects such as dislocations and twins inside the grains.

[0089] In this embodiment, the backscattered electron image of the second nickel-based alloy sheet obtained by scanning electron microscopy is as Figure 2 shown. The second nickel-based alloy sheet has relatively fine equiaxed grains, and the average grain size is 7.4 ± 1.4 μm. Coarse annealing twins are formed inside the grains.

[0090] In this embodiment, the backscattered electron diffraction band contrast diagram of the second nickel-based alloy sheet is as Figure 3 shown. There are few internal defects in the second nickel-based alloy sheet, and the annealing twin boundaries with a relatively high coherency degree are the main microstructures inside the grains.

[0091] In this embodiment, the bright-field image of the second nickel-based alloy sheet obtained by transmission electron microscopy, with a magnification of 50,000, is as Figure 4 shown, and with a magnification of 75,000, is as Figure 5 shown. Combining Figure 4 and Figure 5 it can be known that there are trace amounts of short dislocations and stacking faults across the grains inside the second nickel-based alloy sheet, and the thickness of the annealing twin lamellae is 0.4 - 1 μm.

[0092] In this embodiment, the backscattered electron image of the third nickel-based alloy sheet obtained by scanning electron microscopy is as Figure 6As shown, the grains in the third nickel-based alloy sheet are significantly elongated along the rolling direction, and a large number of nano-scale deformation twins penetrating the grains are generated inside more than 90% of the grains.

[0093] In this embodiment, the backscattered electron image of the nano-twinned nickel-based alloy sheet by scanning electron microscope is as Figure 7 shown. The nano-twinned nickel-based alloy sheet is composed of columnar grains, and the deformation twins crossing the grains widely exist inside the grains.

[0094] In this embodiment, the backscattered electron diffraction band contrast diagram of the nano-twinned nickel-based alloy sheet is as Figure 8 shown. The length of the columnar grains of the nano-twinned nickel-based alloy sheet is 10 - 30 μm, the width is 3 - 20 μm, and high-density nano-scale deformation twins exist inside more than 90% of the grains.

[0095] Example 2

[0096] This embodiment provides a preparation method of a nano-twinned nickel-based alloy sheet. The preparation method includes the following steps:

[0097] (1) A nickel-based alloy ingot containing 20 wt% of cobalt element and 10 wt% of chromium element is homogenized in a muffle furnace at 1100 °C for 4 h to obtain a first nickel-based alloy sheet;

[0098] (2) The initial thickness of the first nickel-based alloy sheet is 30 mm. After 5 passes of hot rolling, it is cooled to room temperature by water quenching to obtain a second nickel-based alloy sheet; the final rolling temperature of the hot rolling is 980 °C; the reduction per pass in the hot rolling is 5 mm;

[0099] (3) After the second nickel-based alloy sheet is pickled and polished in sequence, it is cold-rolled to obtain a third nickel-based alloy sheet; the reduction per pass in the cold rolling does not exceed 10% of the current thickness of the cold-rolled sheet in this pass; the thickness of the third nickel-based alloy sheet is reduced by 50% compared with the second nickel-based alloy sheet;

[0100] (4) The third nickel-based alloy sheet is annealed in a muffle furnace at 700 °C for 5 min to obtain a nano-twinned nickel-based alloy sheet.

[0101] The length of the columnar grains of the nano-twinned nickel-based alloy sheet prepared in this embodiment is 10 - 21 μm, the width is 4 - 12 μm, and high-density nano-scale deformation twins exist inside more than 80% of the grains.

[0102] Example 3

[0103] This embodiment provides a preparation method of a nano-twinned nickel-based alloy sheet. The preparation method includes the following steps:

[0104] (1) A nickel-based alloy ingot containing 25 wt% cobalt element and 13 wt% chromium element is homogenized in a muffle furnace at 1500 °C for 1 h to obtain a first nickel-based alloy sheet;

[0105] (2) The initial thickness of the first nickel-based alloy sheet is 50 mm. After 5 passes of hot rolling, it is water quenched to room temperature to obtain a second nickel-based alloy sheet; the final rolling temperature of the hot rolling is 1000 °C; the reduction per pass in the hot rolling is 10 mm, 10 mm, 10 mm, 8 mm, and 8 mm respectively;

[0106] (3) After the second nickel-based alloy sheet is pickled and polished in sequence, it is cold rolled to obtain a third nickel-based alloy sheet; the reduction per pass in the cold rolling does not exceed 10% of the current thickness of the cold rolled sheet in that pass; the thickness of the third nickel-based alloy sheet is reduced by 50% compared with the second nickel-based alloy sheet;

[0107] (4) The third nickel-based alloy sheet is annealed in a muffle furnace at 600 °C for 30 min to obtain a nano-twinned nickel-based alloy sheet.

[0108] The grains of the nano-twinned nickel-based alloy sheet prepared in this example are all columnar deformed grains, with a length of 10 - 30 μm and a width of 5 - 18 μm. The grains containing nano-twins account for more than 87% of the total number of grains, and there are a large number of dislocation structures inside the grains.

[0109] Example 4

[0110] This example provides a method for preparing a nano-twinned nickel-based alloy sheet. The preparation method is the same as that of Example 1 except that the annealing temperature in step (4) is 700 °C.

[0111] The backscattered electron image of the nano-twinned nickel-based alloy sheet in this example by scanning electron microscope is as Figure 9 shown. The nano-twinned nickel-based alloy sheet is composed of columnar grains and a small amount of equiaxed grains. Deformed twins across the grains widely exist inside the columnar grains, and only a small amount of coarse annealing twins exist inside the equiaxed grains.

[0112] The band contrast diagram of the backscattered electron diffraction of the nano-twinned nickel-based alloy sheet in this example is as Figure 10 shown. The columnar grains of the nano-twinned nickel-based alloy sheet have a length of 10 - 30 μm and a width of 3 - 20 μm. The average grain size of the equiaxed grains is 3.78 ± 1.72 μm, and more than 80% of the grains have high-density nano-scale deformed twins inside.

[0113] Example 5

[0114] This embodiment provides a method for preparing a nano-twinned nickel-based alloy sheet. Except that the nickel-based alloy ingot in step (1) only contains 15 wt% of chromium element, the rest are the same as those in Embodiment 1.

[0115] The columnar grain length of the nano-twinned nickel-based alloy sheet prepared in this embodiment is 13 - 34 μm, the width is 6 - 23 μm, and the grains containing nano-twins account for more than 75% of the total number of grains, but there are only trace amounts of nano-scale deformation twins inside the grains.

[0116] Embodiment 6

[0117] This embodiment provides a method for preparing a nano-twinned nickel-based alloy sheet. Except that the nickel-based alloy ingot in step (1) only contains 30 wt% of cobalt element, the rest are the same as those in Embodiment 1.

[0118] The columnar grain length of the nano-twinned nickel-based alloy sheet prepared in this embodiment is 11 - 30 μm, the width is 5 - 20 μm, the grains containing nano-twins account for more than 90% of the total number of grains and there are a large number of dislocation structures inside the columnar grains.

[0119] Comparative Example 1

[0120] This comparative example provides a highly corrosion-resistant nano-twinned nickel coating and its preparation technology disclosed in Patent CN101144172A. This patent uses pulse electrodeposition technology to prepare a nano-twinned nickel coating, and its microstructure is composed of nearly equiaxed sub-micron grains of 200 nm to 800 nm.

[0121] The grain size of the nano-twinned nickel coating obtained in this comparative example is much smaller than that of the nano-twinned nickel-based alloy sheets in Embodiments 1 - 8. However, pulse electrodeposition technology cannot produce large-sized thick sheets and cannot be directly processed and used as engineering structural materials.

[0122] Comparative Example 2

[0123] This comparative example provides a method for preparing a nano-twinned nickel-based alloy sheet. Except that the annealing heat treatment temperature in step (4) is 400 °C, the rest are the same as those in Embodiment 1.

[0124] Comparative Example 3

[0125] This comparative example provides a method for preparing a nano-twinned nickel-based alloy sheet. Except that the annealing heat treatment temperature in step (4) is 800 °C, the rest are the same as those in Embodiment 1.

[0126] The yield strength, tensile strength, and elongation of the above embodiments and comparative examples were measured by quasi-static tensile experiments, and the results are shown in Table 1.

[0127] Table 1

[0128]

[0129]

[0130] It can be seen from Table 1 that the following points can be obtained:

[0131] (1) From Examples 1 to 6, it can be seen that the preparation method of the nanoscale twin nickel-based alloy sheet provided by the present invention can obtain a nickel-based alloy sheet with a high-density nanoscale twin structure, and its comprehensive mechanical properties are excellent. The yield strength can reach more than 900 MPa, and can reach more than 1200 MPa under better conditions. The tensile strength can reach more than 1100 MPa, and can reach more than 1250 MPa under better conditions. The elongation can reach more than 7%, and can reach more than 15% under better conditions;

[0132] (2) It can be seen by comprehensively implementing Example 1 and Examples 5 to 6 that in step (1) of Example 1, the nickel-based alloy ingot contains 30 wt% of cobalt element and 15 wt% of chromium element. Compared with the nickel-based alloy ingot in step (1) of Example 5 that only contains 15 wt% of chromium element and the nickel-based alloy ingot in step (1) of Example 6 that only contains 30 wt% of cobalt element, the grains containing nano-twins in the nano-twinned nickel-based alloy sheet prepared in Example 1 account for more than 90% of the total number of grains, the yield strength is above 1278 MPa, the tensile strength is 1283 MPa, and the elongation is 18%. Moreover, the distance between twin clusters is 0.3 - 3.5 μm, and the distance between nano-twins within the twin clusters is 30 - 100 nm. For the nano-twinned nickel-based alloy sheet prepared in Example 5, although the grains containing nano-twins account for only more than 75% of the total number of grains, the yield strength and tensile strength are slightly reduced, being 1260 MPa and 1280 MPa respectively, while the elongation is significantly reduced, only being 7.5%. The main reason is that the nickel-based alloy ingot only contains 15 wt% of chromium element. After cold rolling and annealing heat treatment steps, the distance between twin clusters is 2 - 3.5 μm, and the distance between nano-twins within the twin clusters is 90 - 100 nm, thus affecting the elongation of the finally obtained nano-twinned nickel-based alloy sheet. For the nano-twinned nickel-based alloy sheet prepared in Example 6, although the grains containing nano-twins account for more than 90% of the total number of grains, the same as in Example 1, the yield strength and tensile strength are significantly reduced, being 1150 MPa and 1170 MPa respectively, and the elongation is also reduced to 11%. The main reason is that the nickel-based alloy ingot only contains 30 wt% of cobalt element. After cold rolling and annealing heat treatment steps, the distance between twin clusters is 0.7 - 1.8 μm, and the distance between nano-twins within the twin clusters is 35 - 95 nm, thus resulting in the reduction of the yield strength, tensile strength, and elongation of the finally obtained nano-twinned nickel-based alloy sheet. This shows that the present invention limits the nickel-based alloy ingot to contain 20 wt% - 30 wt% of cobalt element and 10 wt% - 15 wt% of chromium element, which can make the nano-twinned nickel-based alloy sheet have a large number of grains containing nano-twins and excellent comprehensive mechanical properties;

[0133] (3) It can be seen from a comprehensive comparison of Example 1 with Comparative Examples 2 to 3 that the annealing temperature in step (4) of Example 1 is 500 °C. Compared with the annealing temperatures in step (4) of Comparative Examples 2 to 3, which are 400 °C and 800 °C respectively, the grains containing nano-twins in the nano-twin nickel-based alloy sheet prepared in Example 1 account for more than 90% of the total number of grains, the yield strength is above 1278 MPa, the tensile strength can reach 1283 MPa, and the elongation is 18%. For the nano-twin nickel-based alloy sheet prepared in Comparative Example 2, the yield strength, tensile strength, and elongation all decreased to a certain extent, being 1173 MPa, 1216 MPa, and 9% respectively. For the nano-twin nickel-based alloy sheet prepared in Comparative Example 3, the yield strength is only 410 MPa, the tensile strength is only 780 MPa, but the elongation increased significantly, being 75%. Thus, it is shown that by annealing at a temperature of 500 - 700 °C, a nano-twin nickel-based alloy sheet with excellent yield strength, tensile strength, and good elongation can be prepared.

[0134] In summary, the preparation method of a nano-twin nickel-based alloy sheet provided by the present invention can prepare a nano-twin nickel-based alloy sheet with excellent comprehensive mechanical properties. Moreover, the technological process of the preparation method is simple, the processing cost is low, the condition parameters are easy to control, large-size products can be prepared, and it can be directly used as engineering materials, having the prospect of large-scale industrial application.

[0135] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a nano-twinned nickel-based alloy sheet, characterized in that, the microstructure of the nano-twinned nickel-based alloy sheet contains grains; there are nano-twins and dislocations inside the grains; the grains containing nano-twins in the nano-twinned nickel-based alloy sheet account for more than 80% of the total number of grains; the shape of the grains is columnar; the length of the grains is 10 - 30 μm; the width of the grains is 3 - 20 μm; the nano-twins inside the same grain in the nano-twinned nickel-based alloy sheet have the same orientation and penetrate the entire grain; the nano-twins form twin clusters; the preparation method includes the following steps: (1) The nickel-based alloy ingot is subjected to homogenization treatment to obtain the first nickel-based alloy sheet; the nickel-based alloy ingot contains 20wt% - 30wt% of cobalt element; the nickel-based alloy ingot contains 10wt% - 15wt% of chromium element; (2) The first nickel-based alloy sheet is hot-rolled and then quenched and cooled to obtain the second nickel-based alloy sheet; (3) The second nickel-based alloy sheet is cold-rolled to obtain the third nickel-based alloy sheet; (4) The third nickel-based alloy sheet is subjected to annealing heat treatment at 500°C - 700°C to obtain the nano-twinned nickel-based alloy sheet.

2. The preparation method according to claim 1, characterized in that, the thickness of the nano-twinned nickel-based alloy sheet is 1 - 4 mm.

3. The preparation method according to claim 1, characterized in that, the lamellar thickness of the nano-twins is 1 - 20 nm.

4. The preparation method according to claim 1, characterized in that, the distance between the twin clusters is 0.3 - 3.5 μm.

5. The preparation method according to claim 1, characterized in that, the distance between the nano-twins within the twin cluster is 30 - 100 nm.

6. The preparation method according to claim 1, characterized in that, the temperature of the homogenization treatment in step (1) is 1100 - 1500°C.

7. The preparation method according to claim 1, characterized in that, the time of the homogenization treatment is 1 - 4 h.

8. The preparation method according to claim 1, characterized in that, the initial thickness of the first nickel-based alloy sheet in step (2) is 30 - 50 mm.

9. The preparation method according to claim 1, characterized in that, the hot rolling is at least 5 passes.

10. The preparation method according to claim 1, characterized in that, the reduction per pass in the hot rolling is 5 - 10 mm.

11. The preparation method according to claim 1, characterized in that, the final rolling temperature of the hot rolling ≥ 950°C.

12. The preparation method according to claim 1, characterized in that, the quenching is cooled to room temperature.

13. The preparation method according to claim 1, characterized in that, the reduction per pass in the cold rolling in step (3) does not exceed 10% of the current thickness of the cold-rolled sheet in that pass.

14. The preparation method according to claim 1, characterized in that, the thickness of the third nickel-based alloy sheet is reduced by 45 - 55% compared with the second nickel-based alloy sheet.

15. The preparation method according to claim 1, characterized in that, the time of the annealing heat treatment in step (4) is 5 to 30 min.

16. The preparation method according to claim 1, characterized in that, the preparation method comprises the following steps: (1) A nickel-based alloy ingot containing 20 wt% to 30 wt% of cobalt element and 10 wt% to 15 wt% of chromium element is subjected to homogenization treatment at 1100 to 1500 °C for 1 to 4 h to obtain a first nickel-based alloy sheet; (2) The initial thickness of the first nickel-based alloy sheet is 30 to 50 mm. After being hot-rolled for at least 5 passes, it is quenched and cooled to room temperature to obtain a second nickel-based alloy sheet; the final rolling temperature of the hot rolling is ≥950 °C; the reduction per pass in the hot rolling is 5 to 10 mm; (3) The second nickel-based alloy sheet is cold-rolled to obtain a third nickel-based alloy sheet; the reduction per pass in the cold rolling does not exceed 10% of the current thickness of the cold-rolled sheet in this pass; the thickness of the third nickel-based alloy sheet is reduced by 45 to 55% compared with the second nickel-based alloy sheet; (4) The third nickel-based alloy sheet is subjected to annealing heat treatment at 500 °C to 700 °C for 5 to 30 min to obtain a nanocrystalline twin nickel-based alloy sheet.

17. Application of a nanocrystalline twin nickel-based alloy sheet obtained by the preparation method of a nanocrystalline twin nickel-based alloy sheet according to any one of claims 1 to 16 in the fields of aviation, aerospace, nuclear power, ocean or petrochemical industry.

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