Nickel-based alloy with heterogeneous structure and gamma '-phase composite structure and preparation method of nickel-based alloy

Abstract

The invention discloses a nickel-based alloy with a heterogeneous structure and a gamma'phase composite structure and a preparation method of the nickel-based alloy, and relates to the technical field of nano-structure metal materials. The nickel-based alloy with a heterogeneous structure and a gamma'phase composite structure is prepared by adopting a solution treatment-cold rolling-annealing process, and the nickel-based alloy structure contains heterogeneous structures with different grain sizes and also contains a large number of gamma 'precipitated phases. The treated nickel-based alloy mainly comprises residual deformation structures, recrystallization and nanocrystals, the yield strength of the treated nickel-based alloy reaches up to 1600 MPa, the yield strength of the treated nickel-based alloy is improved by 50%-100% compared with that of untreated nickel-based alloy, the uniform elongation of the treated nickel-based alloy is 10%-14%, and the high strength-plasticity ratio is achieved. The preparation method provided by the invention is simple and convenient, has low requirements on equipment, and is convenient for large-scale industrial production and application.

Description

Technical Field

[0001] The present invention relates to the technical field of nanostructured metal materials, and in particular to a nickel-based alloy having a heterogeneous structure and a γ′ phase composite structure and a preparation method thereof. Background Art

[0002] Nickel-based alloys have good comprehensive characteristics such as good fatigue resistance and corrosion resistance at high temperatures, and are widely used in aerospace, nuclear power and other fields. With the development of industry, the demand for high-strength and high-toughness metal materials continues to increase, which is often achieved by optimizing the organizational structure. The main phase structures in nickel-based alloys are γ phase and γ′ phase. Different strengthening elements are often added during the smelting process. These alloying elements generally play the role of solid solution strengthening and second phase strengthening, but may change the physical and chemical properties of the alloy, and the cost is relatively high. Due to the limited solid solution strengthening effect of solution atoms, the material properties of solid solution-strengthened nickel-based alloys are difficult to further improve. In order to obtain a better strength-plasticity ratio of the material, it is necessary to find a better process to obtain a better structure. The heterogeneous structure is to improve the strength and plasticity of the material by introducing grains of different sizes. This method is simple and low-cost.

[0003] Du X, Li W, Chang H, et al. Dual heterogeneous structures lead to ultrahigh strength and uniform ductility in a Co-Cr-Ni medium-entropy alloy [J]. Nature Communications, 2020, 11 (1): 2390. Du et al. used rolling and two-step annealing to treat NiCoCr alloy and obtained a heterogeneous structure of coarse grains (10-30 μm) and ultrafine grains (0.5-2 μm), accompanied by a large amount of precipitated phases (100 nm). The strength of the alloy was as high as 2.2 GPa and the uniform elongation was 13%.

[0004] Literature Liu X, Zhang M, Ma Y, et al. Achieving ultrahigh strength in CoCrNi-based medium-entropy alloys with synergistic strengthening effect [J]. Materials Science and Engineering: A, 2020, 776: 139028. Liu et al. used mechanical heat treatment process to 0.1 Mo 0.1By controlling the microstructure, an incompletely recrystallized structure was obtained. The tensile strength of the alloy reached 1304MPa and the uniform elongation reached 22%.

[0005] Literature Zhang C, Macdonald BE, Guo F, et al. Cold-workable refractory complex concentrated alloys with tunable microstructure and good room-temperature tensile behavior[J]. Scripta Materialia, 2020, 188: 16-20. Zhang et al. regulated the NbTaTi-based refractory alloy by mechanical heat treatment and obtained a layered heterogeneous structure composed of fine grains and coarse grains. Compared with the homogeneous sample, the yield strength of the structural alloy was increased by 20% to 620MPa.

[0006] Plastic deformation technology can refine grains and thus improve the strength of materials, but the improvement in strength often comes at the expense of plasticity. This drawback can be alleviated through specific heat treatment conditions. Mechanical heat treatment is simple, efficient, and has a wide range of applications. It is one of the main methods for preparing nanometal materials. Summary of the invention

[0007] The object of the present invention is to provide a nickel-based alloy having a heterogeneous structure and a γ′ phase composite structure and a preparation method thereof, wherein the nickel-based alloy is refined to different sizes so as to have higher strength and more superior service performance.

[0008] The technical solution to achieve the purpose of the present invention is:

[0009] A nickel-based alloy with a heterogeneous structure and a γ′ phase composite structure. The components of the nickel-based alloy raw material are measured by atomic percentage (at.%) as follows: Ni: 50.5-55.5%, Co: 19.8-21.58%, Cr: 16.1-19.8%, Al: 4.1-5.0%, Ti: 3.1-3.9%, Mo: 0.9-1.70%, Fe: 0.65-1.2%, W: 0.4-0.6%, Zr: 0.04-0.09%, C: 0.03-0.06%, and B: 0.02-0.06%.

[0010] Preferably, the microstructure of the nickel-based alloy mainly consists of residual deformation microstructure, recrystallization, nanocrystals and γ′ phase, and the yield strength of the nickel-based alloy reaches up to 1600 MPa.

[0011] Preferably, in the microstructure of the nickel-based alloy, the recrystallization size is 1-3 μm, the nanocrystal size is 20-100 nm, and the γ′ phase size is 40-400 nm.

[0012] A method for preparing the above nickel-based alloy, the specific steps are as follows:

[0013] (1) cutting a nickel-based alloy ingot into block samples by wire cutting, performing a solid solution treatment on the block nickel-based alloy to be treated, and obtaining a nickel-based alloy with a uniform structure by air cooling;

[0014] (2) Before rolling, the surface oxide layer of the nickel-based alloy with uniform structure is removed, and continuous rolling is performed until the deformation exceeds 50%;

[0015] (3) The nickel-based alloy after the rolling process is annealed.

[0016] Preferably, in step (1), the solution treatment process is: placing the nickel-based alloy in a heating furnace at 1100° C. and keeping it warm for 6 hours.

[0017] Preferably, in step (2), the rolling process adopts a double-roll mill with a roll diameter of 400 mm and a rolling speed of 0.021 m / s. By adjusting the rolling passes and the pressure of each pass, the rolling deformation is controlled at 50-90%, preferably 60-80%, and the pressure of each rolling pass is 0.2-0.5 mm.

[0018] Preferably, in step (3), the annealing process is: placing the cold-rolled nickel-based alloy into a heating furnace, keeping it at 800°C for 30 hours and then air-cooling it, and then keeping it at 600°C for 6 hours and then air-cooling it.

[0019] Compared with the prior art, the present invention has the following significant advantages:

[0020] (1) The present invention can prepare a nickel-based alloy with a heterogeneous structure and a γ′ phase composite structure, the microstructure of which can be precisely controlled by controlling the number of rolling passes and the amount of pressure in each pass as well as the heat treatment process, and the preparation effect is stable.

[0021] (2) Rolling is usually divided into hot rolling and cold rolling according to the temperature. The hot rolling process consumes a lot of energy and has a high production cost. In addition, the surface quality of the processed alloy material is poor. The cold rolling process can avoid the above defects of the hot rolling process.

[0022] (3) The preparation method provided by the present invention is simple, has low requirements on equipment, and is convenient for large-scale industrial production and application.

[0023] (4) For typical solid solution strengthened nickel-based alloys, the strength is difficult to further improve due to the limited solid solution strengthening effect of solution atoms. The present invention retains the solid solution strengthening effect of the nickel-based alloy itself without changing the chemical composition of the material. At the same time, the strength of the nickel-based alloy is improved to 1200-1600MPa by refining the grains and changing the microstructure. The uniform elongation is 10.1%-15%, thereby achieving a higher strength-to-plasticity ratio.

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is an EBSD microstructure image of the heterogeneous structure in the nickel-based alloy with 60% rolling deformation in the embodiment.

[0026] Figure 2 3 is a transmission electron microscope image of the heterogeneous structure in the nickel-based alloy with 60% rolling deformation in the embodiment.

[0027] Figure 3 3 is a transmission electron microscope image of nanocrystals in a nickel-based alloy with a rolling deformation of 60% in the embodiment.

[0028] Figure 4 Comparison of yield strength of examples, rolled treated and untreated nickel-based alloys.

[0029] Figure 5 It is a schematic diagram of the principle of the rolling and annealing treatment described in the present invention. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0031] The present invention adopts a solution treatment-cold rolling-annealing process preparation method to prepare a high-strength nickel-based alloy with heterogeneous structure and γ′ phase composite structure. First, the nickel-based alloy is subjected to solution treatment at 1100°C for 6 hours, and then air-cooled to obtain a nickel-based alloy with uniform structure. Then, a double-roll mill is used with a roll diameter of 400mm, a rolling speed of 0.021m / s, and a rolling pressure of 0.2-0.5mm per pass to roll the nickel-based alloy. Figure 5As shown in the figure, according to the principle of constant volume, the rolling process is to bite the nickel-based alloy with the relatively rotating rollers. The nickel-based alloy enters between the rollers and is subjected to the rolling force of the rollers, causing the nickel-based alloy to undergo plastic deformation, resulting in an increase in length, a decrease in thickness, and a slight increase in width. The deformation of the nickel-based alloy is controlled by controlling the rolling passes, and the nickel-based alloy is subjected to multiple rolling processes until the deformation of the nickel-based alloy reaches the required amount. The structure is optimized by using the heat treatment process, and the rolled nickel-based alloy is placed in a furnace at 800°C for 30 hours and then air-cooled, and then kept at 600°C for 6 hours and then air-cooled.

[0032] The nickel-based alloy undergoes severe plastic deformation after rolling, the grains are refined, and a large number of dislocations are accumulated. The microstructure size of the nickel-based alloy needs to be deformed by more than 50% to reach the nanometer level. At this time, the microstructure is mainly nanocrystalline. After annealing, recrystallization occurs, the dislocation density is reduced, the recrystallization size is 1 to 3μm, the nanocrystalline size is 20 to 100nm, and the γ′ phase size is 40 to 400nm. This structure can significantly improve the strength of the nickel-based alloy and thus improve its service performance. The yield strength of the nickel-based alloy reaches 1200 to 1600MPa.

[0033] Example

[0034] A nickel-based alloy with high yield strength containing dislocation, recrystallization and nanocrystals is obtained by solution treatment-cold rolling-annealing. The chemical elements in the nickel-based alloy are measured by atomic percentage (at.%) as follows: Ni: 51.5%, Co: 20.1%, Cr: 17.6%, Al: 4.6%, Ti: 3.3%, Mo: 1.4%, Fe: 1.0%, W: 0.4%, Zr: 0.04%, C: 0.05%, B: 0.05%.

[0035] According to the above ratio, the nickel-based alloy ingot obtained by smelting is cut into block materials with a size of 10mm×15mm×50mm by electric spark wire cutting. The nickel-based alloy sample to be treated is placed in a high-temperature furnace and kept at 1100°C for 6 hours for solution treatment.

[0036] After the solution treatment, the surface of the nickel-based alloy is polished smooth before rolling, and the surface oxide layer is removed before rolling. The rolling speed is 0.021m / s, and the pressure of each rolling pass is 0.2mm. In order to offset the elastic recovery of the nickel-based alloy during the deformation process, after 20-24 rolling passes, the rolling deformation is guaranteed to be 60%.

[0037] The cold-rolled nickel-based alloy is placed in a heating furnace, kept at 800°C for 30 hours and then air-cooled, and then kept at 600°C for 6 hours and then air-cooled for annealing.

[0038] The recrystallized region in the nickel-based alloy obtained in this embodiment is wrapped with residual deformed structure, such as Figure 1 This is the EBSD microstructure image of the heterogeneous structure in the nickel-based alloy with a rolling deformation of 60%. At the same time, there is a nanocrystalline structure in the nickel-based alloy. There are a large number of dislocations and stacking faults in the nanocrystalline. The average grain size of the nanocrystalline is 49.3nm, and the average structural size of the recrystallized grain is 1.5μm. Figure 2 Transmission electron microscope image of recrystallization in a nickel-based alloy after 60% rolling deformation and annealing. Figure 3 Transmission electron microscope image of nanocrystals in a nickel-based alloy with 60% rolling deformation and annealing. Figure 4 The yield strength of the nickel-based alloy in the embodiment is compared with that of the rolled and untreated nickel-based alloys. The yield strength of the nickel-based alloy reaches 1461MPa, which is 1.8 times that of the untreated nickel-based alloy. The uniform elongation is 12.1%, achieving a higher strength-plasticity ratio. The rolling and annealing treatments significantly refine the grains of the nickel-based alloy, improve the grain structure, and increase the strength of the nickel-based alloy.

[0039] Comparative Example 1

[0040] Literature Wu YZ, Zhang ZY, Juan L, et al. Preparation of high-mechanical-property medium-entropy CrCoNi alloy by asymmetric cryorolling [J]. Transactions of Nonferrous Metals Society of China, 2022, 32 (5): 1559-1574. Wu et al. conducted asymmetric cold rolling and annealing of CrCoNi alloy at different temperatures. The results show that the strength of the asymmetric cold-rolled alloy reaches above 1.6 GPa. After annealing at 1073K, its strength remains at 1 GPa and its elongation is close to 60%. The average grain size of the asymmetric rolled alloy is 466 nm, and most of the grain sizes are concentrated between 300 and 399 nm. The refinement effect of this method is not as good as that of the present invention, and this treatment process has high requirements on equipment. The present invention only requires a traditional double-roll mill, and the production cost is low.

[0041] Comparative Example 2

[0042] In the document Popov V, Popova E, Kuznetsov D, et al. Evolution of Ni structure under ECAP and DCAP and further annealing [C]. Materials Science Forum, 2017: 1507-1512., Popov et al. used equal channel composite extrusion technology (ECAP) to process pure Ni, and refined the grain size to between 200-300nm, and the microhardness was increased from the initial 1300MPa to 2500MPa. This process has an obvious effect on grain refinement, but has high requirements on process equipment and is difficult to carry out batch production, which is not as wide as the applicability of the present invention.

[0043] Comparative Example 3

[0044] In the document Nurislamova G, Islamgaliev RK, Valiev R. Microstructure and mechanical properties of pure nickel processed by severe plastic deformation [C]. Materials Science Forum, 2006: 579-584., Nurislamova et al. used high pressure torsion technology (HPT) to perform severe plastic deformation on pure Ni, and obtained an equiaxed grain structure with a grain size of about 170 nm, and its tensile strength was as high as 1100 MPa, which was 5 times that of the untreated sample, but its plasticity decreased by 80%. This process can quickly refine the grains, but it is difficult to obtain a heterogeneous structure, and high pressure must be applied during the preparation process, which has extremely high requirements on equipment, and is not as simple and convenient as the present invention.

[0045] The results show that the microstructure of the solution treated-cold rolled-annealed nickel-based alloy proposed by the present invention is mainly composed of residual deformation structure, recrystallization, nanocrystal and γ′ phase, with a recrystallization size of 1 to 3 μm, a nanocrystal size of 20 to 100 nm, and a γ′ phase size of 40 to 400 nm. The yield strength of the treated nickel-based alloy reaches 1200 to 1600 MPa, which is 50% to 100% higher than the yield strength of the untreated nickel-based alloy. The preparation method provided by the present invention is simple, has low equipment requirements, and can stably prepare nickel-based alloys with heterogeneous structures and γ′ phase composite structures, which is convenient for large-scale industrialization.

Claims

1. A nickel-based alloy having a heterogeneous structure and a γ' phase composite structure, characterized in that: The composition of the nickel-based alloy raw material is measured in atomic percentage as follows: Ni: 50.5-55.5%, Co: 19.8 ~ 21.58%, Cr: 16.1 ~19.8%, Al: 4.1 ~ 5.0%, Ti: 3.1 ~3.9%, Mo: 0.9 ~ 1.70%, Fe: 0.65 ~ 1.2%, W: 0.4 ~ 0.6%, Zr: 0.04 ~ 0.09%, C: 0.03 ~ 0.06%, B: 0.02 ~ 0.06%.

2. The nickel-based alloy according to claim 1, wherein The microstructure of the nickel-based alloy mainly consists of residual deformation structure, recrystallization, nanocrystals and γ' phase, and the maximum yield strength of the nickel-based alloy reaches 1600 MPa.

3. The nickel-based alloy according to claim 1, wherein The microstructure of the nickel-based alloy has a recrystallized size of 1-3 μm, a nanocrystalline size of 20-100 nm, and a γ' phase size of 40-400 nm.

4. A method for preparing the nickel-based alloy according to any one of claims 1 to 3, characterized in that: The specific steps are as follows: (1) The nickel-based alloy ingot is cut into block samples by wire cutting, solution treated, and air cooled to obtain a nickel-based alloy with uniform structure; (2) The surface oxide layer is removed before rolling, and the nickel-based alloy is continuously rolled in succession until the deformation exceeds 50%; (3) Annealing the nickel-based alloy after rolling.

5. The method according to claim 4, characterized in that In step (1), the solution treatment process is: placing the nickel-based alloy in a heating furnace at 1100°C and keeping it warm for 6 hours.

6. The method according to claim 4, characterized in that In step (2), the rolling process adopts a twin-roll mill with a roll diameter of 400 mm and a rolling speed of 0.021 m / s. By adjusting the rolling passes and the pressure of each pass, the rolling deformation is controlled to be 50-90%, preferably 60-80%, and the rolling pressure of each pass is 0.2-0.5 mm.

7. The method according to claim 4, characterized in that In step (3), the annealing process is as follows: the rolled nickel-based alloy is placed in a heating furnace, kept at 800°C for 30 h, and then air-cooled, and then kept at 600°C for 6 h, and then air-cooled.

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