A method for preparing a super fine grain nickel-based alloy and an article thereof

Abstract

The application discloses a preparation method of ultra-fine-grain nickel-based alloy and an article thereof, and comprises the following steps: step 1, a vacuum induction + electroslag remelting smelting method is used to prepare an electroslag ingot; step 2, high-temperature homogenization diffusion annealing is performed on the electroslag ingot obtained in step 1; step 3, a fast forging machine is used to forge the electroslag ingot after homogenization into an intermediate blank of a required specification under the condition of 1100 DEG C and multiple times of forging; step 4, intermediate heat treatment is performed on the intermediate blank in step 3; and step 5, low-temperature multiple-time forging is performed on the intermediate blank after the intermediate heat treatment in step 4.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature alloy material manufacturing, specifically relating to a method for preparing ultrafine-grained nickel-based alloys and its products. Background Technology

[0002] Ultrafine-grained nickel-based alloys are much finer than conventional industrial alloys (typically ASTM 3-5 grade, or hundreds of micrometers). These materials are primarily suitable for critical components requiring extreme safety and durability, and needing to operate in low- to medium-temperature environments. For example, in the aerospace field, ultrafine grains significantly improve impact resistance and fracture toughness; in the nuclear and energy sectors, microcrack propagation is a critical risk, and ultrafine grains effectively inhibit crack propagation.

[0003] However, the following difficulties exist in producing ultrafine-grained nickel-based alloy materials:

[0004] 1. Inherent problems caused by high niobium content: The extremely high niobium content is the core of all the problems. It leads to severe solidification segregation, formation of brittle Laves phase, narrow homogenization and hot working windows, and sluggish recrystallization kinetics.

[0005] 2. The ongoing struggle between grain refinement and growth: Achieving ultrafine grains requires maintaining high pressure to suppress grain growth throughout the entire high-temperature processing and treatment process. This necessitates precise control of dynamic recrystallization during hot working, effective grain boundary pinning using second-phase particles during solution treatment, and avoiding any process deviations that could lead to abnormal grain growth.

[0006] 3. Multiple and narrow process windows: Homogenization, hot working, and solution treatment all face conflicting objectives and extremely narrow process parameter windows. Loss of control at any stage can lead to complete failure. The hot working temperature range for nickel-based superalloy bars is relatively narrow, only around 70℃. If the temperature is too low during hot working, a large number of unrecrystallized elongated grains will remain on the surface and near the surface. Simultaneously, the low temperature will cause residual cold deformation in the bar, resulting in the precipitation of a large amount of Widmanstätten-like second phase during subsequent heat treatment. If the heating temperature is increased, factors such as internal heating during hot working will cause the central grains of the bar to become excessively coarse, which is detrimental to mechanical properties. The dynamic recrystallization temperature of conventional grains in nickel-based superalloys is as high as 950℃ or more. The critical hot working temperature of large-size bars for aerospace applications is generally 1020℃, and its hot working temperature range is only 70℃, which is only about one-seventh of that of ordinary steel. The solution temperature of this alloy is generally 950-980℃, which is far lower than the static recrystallization temperature of conventional grains of 1010-1020℃. The grain and grain boundary structure of this alloy depends almost entirely on hot working.

[0007] 4. In the traditional single-phase forging process of nickel-based superalloy long products, the significant differences in temperature and strain at different locations lead to substantial variations in the precipitation of the second phase, resulting in significant differences in microstructure from the center to the edge. Even in die forgings with extremely short forging times, cold die microstructure exists on the surface, affecting the mechanical properties of the forging. Typically, the commonly used testing standard for large-diameter bars of this alloy is a center and R / 2 grain size finer than grade 4, with the edge not assessed. For small-diameter bars, a center grain size finer than grade 5 is required. However, a greater problem is that the surface, near-surface, and even near-R / 2 recrystallized grains are excessively fine, sometimes finer than grade 10, with a large amount of unrecrystallized primary elongated grains remaining. Simultaneously, an excessive amount of second phase precipitates in Widmanstätten form within the primary elongated grains remaining on the surface and near-surface. Summary of the Invention

[0008] The purpose of this invention is to address the problem that large-diameter nickel-based alloy bars easily exhibit defects such as mixed grains and coarse grains when produced by traditional forging methods, and that the microstructure varies significantly across different locations, leading to large fluctuations in mechanical properties. This invention provides a solution to this problem, and the specific technical solution is as follows:

[0009] A method for producing an ultrafine-grained nickel-based alloy includes the following steps:

[0010] Step 1: Prepare the required electroslag ingots using a vacuum induction + electroslag remelting smelting method;

[0011] Step 2: The electroslag ingots obtained in Step 1 are subjected to high-temperature homogenization diffusion annealing. The specific process is as follows: the resistance furnace is first heated to 1160±10℃ and held for 25 hours, then the furnace is heated to 1195±10℃ and held for 72 hours, the furnace is cooled to below 400℃, and the ingots are then air-cooled after being taken out of the furnace.

[0012] Step 3: Use a high-speed forging machine to perform high-temperature multi-fire forging on the homogenized electroslag ingot obtained in Step 2 to produce an intermediate billet of the required specifications, where high temperature refers to 1100℃.

[0013] Step 4: Perform intermediate heat treatment on the intermediate billet obtained in Step 3. The specific process is as follows: heat the billet to 880±10℃ in a resistance furnace, hold it for 40 hours, cool it in the furnace to below 600℃, and then air cool it after removing it from the furnace.

[0014] Step 5: Perform low-temperature multi-fire forging on the intermediate billet obtained in Step 4. Specifically, after intermediate heat treatment, the intermediate billet is held at 940±10℃ for 3 hours and repeatedly forged in multiple fires to form finished bars of the target size.

[0015] The steel ingot in step 1 has the following composition: ≤0.08wt%C, ≤0.35wt%Si, ≤0.35wt%Mn, ≤0.015wt%S, ≤0.015wt%P, ≤0.006wt%B, ≤0.3wt%Cu, ≤0.01wt%Mg, ≤1.0wt%Co, 17.0-21.0wt%Cr, 50.0-55.0wt%Ni, 2.80-3.30wt%Mo, 4.75-5.50wt%Nb, 0.65-1.15wt%Ti, 0.20-0.80wt%Al, and the balance Fe, as well as unavoidable impurities.

[0016] In this application, ultrafine-grained nickel-based alloy refers to a nickel-based alloy with an ultrafine grain structure.

[0017] Preferably, the protective atmosphere in step 1 is argon.

[0018] Preferably, the high-temperature multi-fire forging in step 3 involves 6-8 forging cycles.

[0019] Preferably, the number of forging cycles in step 5 is 3-5 times.

[0020] The ultrafine-grained nickel-based alloy prepared by the aforementioned method has the following composition: ≤0.08wt%C, ≤0.35wt%Si, ≤0.35wt%Mn, ≤0.015wt%S, ≤0.015wt%P, ≤0.006wt%B, ≤0.3wt%Cu, ≤0.01wt%Mg, ≤1.0wt%Co, 17.0-21.0wt%Cr, 50.0-55.0wt%Ni, 2.80-3.30wt%Mo, 4.75-5.50wt%Nb, 0.65-1.15wt%Ti, 0.20-0.80wt%Al, and the balance being Fe, along with unavoidable impurities. The alloy has a grain size grade of ASTM 9 or higher and uniform grain size. The second phase δ phase accounts for 3-5% of the total volume fraction of the alloy and is in the form of short rods and / or granules. When the second phase in an alloy is uniformly distributed in the matrix, it pins grain boundaries during hot working and heat treatment, hindering grain growth and resulting in uniform and fine grains. If there is no second phase or only a very small amount of second phase in the microstructure, the material will exhibit notch sensitivity. Furthermore, if the second phase content is excessive, it will consume too much Nb, reducing the amount of strengthening phase precipitates and leading to a decrease in material strength. Therefore, in this application, the second phase δ is designed to account for 3-5% of the total alloy volume fraction, resulting in uniform and fine grains, with the second phase precipitating in a suitable amount as short rods or granules, thereby obtaining an alloy with excellent comprehensive properties.

[0021] Furthermore, the second phase δ is δ-Ni3Nb.

[0022] The second phase, δ phase, accounts for 3-5% of the total volume fraction of the alloy. In any 10 randomly selected image fields magnified 1000 times, the relative standard deviation of the volume fraction of the needle-like δ phase is ± 5%.

[0023] When the second phase δ phase is short rod-shaped, its length is 4-6 μm and its aspect ratio is 3:1-5:1; when it is granular, the particle size is 1-2 μm.

[0024] The room temperature properties of the alloy are: tensile strength ≥ 1400 MPa (σb) and yield strength ≥ 1090 MPa (σ0.2). In some embodiments, the tensile strength σb of the alloy is 1400 MPa, 1410 MPa, 1415 MPa, 1420 MPa, 1425 MPa, 1430 MPa, or 1435 MPa; in some embodiments, the yield strength σ0.2 of the alloy is 1090 MPa, 1100 MPa, 1110 MPa, 1120 MPa, 1130 MPa, or 1140 MPa.

[0025] This application firstly uses pretreatment to precipitate a large number of needle-like second phases in the microstructure. These second phases will break into granular forms during subsequent low-temperature repeated forging. These granular second phases can hinder grain growth during hot working, thereby refining the grains. The pre-precipitated second phases consume a large amount of Nb element, so even if there is cold deformation at the edges, a large amount of Widmanstätten-like second phase will not precipitate during subsequent heat treatment. Secondly, since the final product forging heating temperature is 940℃, the heating temperature is low, and the internal temperature rise during forging is relatively small, which can also avoid grain growth. At the same time, the grains will not grow excessively at this heating temperature, so they can be repeatedly forged at this temperature, which greatly improves the operability of the hot working process. Finally, through repeated reheating and forging, the grains can be repeatedly broken, which can significantly refine the grains.

[0026] The beneficial technical effects of this invention are as follows: First, the required intermediate billet is obtained by forging using a high-speed forging mill. Then, a large amount of second phase is precipitated in the intermediate billet through intermediate heat treatment. Subsequently, the billet is forged at a low temperature using a high-speed forging mill with multiple heats below the dissolution temperature of the second phase to obtain finished bars of the required specifications. Finally, the bars are solution treated at an appropriate heat treatment temperature according to relevant technical standards. This process allows the central grain size of the large-size alloy bars to be controlled to be finer than ASTM grade 9, and the microstructure at different locations is uniform. By adjusting the solution treatment temperature, different grain sizes can be obtained. The technical indicators of the bars after normal heat treatment fully meet the relevant domestic and international technical conditions. Compared with other methods, this process has the advantages of convenience, flexibility, and low cost, and can realize the "multi-purpose use" of this alloy. Attached Figure Description

[0027] Figure 1 This is a metallographic photograph of the edge of the intermediate billet obtained in step 4 of Embodiment 1 of the present invention after intermediate heat treatment;

[0028] Figure 2 The image shows a metallographic photograph of the intermediate billet obtained in step 4 of Embodiment 1 of the present invention at position 0.5R after intermediate heat treatment.

[0029] Figure 3 This is a metallographic photograph of the center position of the intermediate billet obtained in step 4 of Embodiment 1 of the present invention after intermediate heat treatment;

[0030] Figure 4 This is a metallographic photograph of the alloy edge position finally obtained in Example 1 of the present invention;

[0031] Figure 5 This is a metallographic photograph of the alloy at position 0.5R, which was finally obtained in Example 1 of the present invention.

[0032] Figure 6 This is a metallographic photograph of the center position of the alloy finally obtained in Example 1 of the present invention;

[0033] Figure 7 This is a metallographic photograph of the alloy edge position finally obtained in Example 2 of the present invention;

[0034] Figure 8 This is a metallographic photograph of the alloy at position 0.5R obtained in Example 2 of the present invention;

[0035] Figure 9 This is a metallographic photograph of the center position of the alloy finally obtained in Example 2 of the present invention;

[0036] Figure 10 This is a metallographic photograph of the alloy edge position finally obtained in Example 3 of the present invention;

[0037] Figure 11 This is a metallographic photograph of the alloy at position 0.5R, which was finally obtained in Example 3 of the present invention.

[0038] Figure 12 This is a metallographic photograph of the center position of the alloy finally obtained in Example 3 of the present invention;

[0039] Figure 13 Metallographic photograph of the edge of the alloy finally obtained in Comparative Example 1;

[0040] Figure 14 Metallographic photograph of the 0.5R position of the alloy finally obtained in Comparative Example 1;

[0041] Figure 15 Metallographic photograph of the center position of the alloy finally obtained in Comparative Example 1;

[0042] Figure 16 Metallographic photographs of the edge portion of the intermediate billet obtained in step 4 of Comparative Example 2 after intermediate heat treatment;

[0043] Figure 17 The image shows a metallographic photograph of the intermediate billet obtained in step 4 of Comparative Example 2 after intermediate heat treatment at position 0.5R.

[0044] Figure 18 This is a metallographic photograph of the center position of the intermediate billet obtained in step 4 of Comparative Example 2 after intermediate heat treatment. Detailed Implementation

[0045] Example 1

[0046] The ultrafine nickel-based alloy was prepared according to the following steps:

[0047] Step 1: Referring to the elemental content of the raw materials listed in Table 1, prepare steel ingots with a diameter of Ф430mm using vacuum induction + electroslag remelting (VIM+ESR) smelting technology, which can also be called electroslag ingots.

[0048] Step 2: High-temperature homogenization diffusion annealing of electroslag ingots. The specific process is as follows: the resistance furnace is first heated to 1160±10℃ and held for 25 hours, then the furnace is heated to 1195±10℃ and held for 72 hours, the furnace is cooled to below 400℃, and the ingots are then air-cooled.

[0049] Step 3: Use a high-speed forging machine to forge the homogenized electroslag ingot in multiple passes at 1100℃ to form an octagonal intermediate billet of 420mm.

[0050] Step 4: Perform intermediate heat treatment on the intermediate billet. The specific process is as follows: heat to 880±10℃ in a resistance furnace, hold for 40 hours, furnace cool to below 600℃, and air cool after removal from the furnace. At this time, the alloy microstructure is as follows: Figure 1-3 As shown, by Figure 1-3 It can be seen that a large number of needle-like second phases appear in different positions of the alloy, and the delta phase in the central region almost covers the entire grain.

[0051] Step 5: After intermediate heat treatment, the intermediate billet is held at 940±10℃ for 3 hours and repeatedly forged in multiple furnaces to form a finished bar with a diameter of Ф260mm.

[0052] The 260mm diameter rods prepared by the above process, after solution treatment at 980℃ for 60min, exhibited uniform grain structure at different locations, with the second phase distributed uniformly in granular form. The average grain size was approximately ASTM grade 9. The grain structure was as follows: Figure 4-6 As shown.

[0053] Example 2

[0054] Step 1: Referring to the elemental content of the raw materials listed in Table 1, prepare electroslag ingots with a diameter of 430 mm using vacuum induction + electroslag remelting (VIM+ESR) smelting technology.

[0055] Step 2: High-temperature homogenization diffusion annealing of electroslag ingots. The specific process is as follows: the resistance furnace is first heated to 1160±10℃ and held for 25 hours, then the furnace is heated to 1195±10℃ and held for 72 hours, the furnace is cooled to below 400℃, and the ingots are then air-cooled.

[0056] Step 3: Use a high-speed forging machine to perform high-temperature multi-fire forging on the homogenized electroslag ingot to produce an octagonal intermediate billet with a diameter of 420mm.

[0057] Step 4: Perform intermediate heat treatment on the intermediate billet. The specific process is as follows: heat the billet to 880±10℃ in a resistance furnace, hold it for 40 hours, cool it in the furnace to below 600℃, and then air cool it after removing it from the furnace.

[0058] Step 5: The intermediate billet after intermediate heat treatment is subjected to low-temperature multi-fire forging. The heating temperature is 940±10℃, the holding temperature is 3 hours, and the billet is repeatedly forged in the furnace to form a finished bar with a diameter of Ф240mm.

[0059] The 240mm diameter rods prepared by the above process, after solution treatment at 980℃ for 60min, showed no abnormal structures such as mixed grains or coarse grains. The grain structure was uniform across different locations, with the second phase distributed uniformly in granular form. The average grain size was approximately ASTM 9.5. The grain structure is shown in the attached figure. Figure 7-9 As shown.

[0060] Example 3

[0061] Step 1: Referring to the elemental content of the raw materials listed in Table 1, prepare Ф430mm electroslag ingots using vacuum induction + electroslag remelting (VIM+ESR) smelting technology.

[0062] Step 2: High-temperature homogenization diffusion annealing of electroslag ingots. The specific process is as follows: the resistance furnace is first heated to 1160±10℃ and held for 25 hours, then the furnace is heated to 1195±10℃ and held for 72 hours, the furnace is cooled to below 400℃, and the ingots are then air-cooled.

[0063] Step 3: Use a high-speed forging machine to perform high-temperature multi-fire forging on the homogenized electroslag ingot to produce an octagonal intermediate billet with a diameter of 420mm.

[0064] Step 4: Perform intermediate heat treatment on the intermediate billet. The specific process is as follows: heat the billet to 880±10℃ in a resistance furnace, hold it for 40 hours, cool it in the furnace to below 600℃, and then air cool it after removing it from the furnace.

[0065] Step 5: The intermediate billet after intermediate heat treatment is subjected to low-temperature multi-fire forging at a heating temperature of 940±10℃ and held for 3 hours. It is then repeatedly forged in the furnace to form a finished bar with a diameter of 210mm.

[0066] The 210mm diameter rods prepared using the above process, after solution treatment at 980℃ for 60min, exhibited uniform grain structure at different locations, without the presence of unrecrystallized primary elongated grains or Widmanstätten-like second phase. The second phase was uniformly distributed in granular form, with an average grain size of approximately ASTM grade 10. The grain structure is shown in the attached figure. Figure 10-12 As shown.

[0067] Comparative Example 1

[0068] Step 1: Referring to the elemental content of the raw materials listed in Table 1, prepare electroslag ingots with a diameter of 430 mm using vacuum induction + electroslag remelting (VIM+ESR) smelting technology.

[0069] Step 2: High-temperature homogenization diffusion annealing of electroslag ingots. The specific process is as follows: the resistance furnace is first heated to 1160±10℃ and held for 25 hours, then the furnace is heated to 1195±10℃ and held for 72 hours, the furnace is cooled to below 400℃, and the ingots are then air-cooled.

[0070] Step 3: The homogenized electroslag ingot is subjected to high-temperature multi-fire forging using a high-speed forging mill to produce bars with a diameter of 240mm. The specific process is as follows:

[0071] First heating: heating temperature 1120℃, holding time 1.5h, steel ingot upsetting to a diameter of 555mm;

[0072] Second heating: heating temperature 1080℃, holding time 1.5h, Φ555mm billet drawn to a diameter of 460mm;

[0073] Third heating: heating temperature 1050℃, holding time 1.5h, Φ460mm billet drawn to diameter 370mm;

[0074] Fourth heating: heating temperature 1020℃, holding time 1.5h, Φ370mm billet drawn to a diameter of 300mm;

[0075] Fifth heat: Heating temperature 1000℃, holding time 1.5h, while wrapping the surface with insulation cotton to prevent surface temperature drop, and drawing the 300mm diameter billet to a diameter of 240mm.

[0076] The nickel-based alloy bars with a diameter of 240 mm, prepared using conventional processes, exhibited a double-grained microstructure at the edges after solution treatment at 980℃ for 60 min. Large, unrecrystallized grains were surrounded by a ring of smaller, recrystallized grains, while the average grain size at the center and 0.5R was approximately ASTM 6.5. This non-uniform microstructure is detrimental to mechanical properties and easily leads to uneven mechanical performance. (The grain structure appears to be...) Figure 13-15 As shown.

[0077] Comparative Example 2

[0078] Unlike Example 1, step 4 involves intermediate heat treatment of the intermediate billet. Specifically, the billet is heated to 880±10℃ in a resistance furnace, held for 20 hours, furnace cooled to below 600℃, and then air-cooled. The resulting metallographic image of the alloy is shown below. Figure 16-18 As shown, by Figure 16-18 It is known that the delta phase in the central region did not grow to cover the entire grain, and the grain will definitely grow during the subsequent forging process, so the grain size of the final product will not meet ASTM level 9.

[0079] Table 1. Raw material composition of nickel-based alloy bars in Examples 1-3 and Comparative Examples 1-2

[0080]

[0081] The properties of the alloy bars prepared in Examples 1-3 and Comparative Example 1 were tested using the test methods in GJB713-89 standard. The test results are shown in Table 2.

[0082] Table 2. Room temperature properties of alloy bars prepared in Examples 1-3 and Comparative Example 1

[0083]

[0084] As shown in Table 2, the alloys prepared in Examples 1-3 of this invention exhibit superior performance in terms of yield strength, tensile strength, and hardness. This is due to the alloy's ultra-fine, uniform grain structure, exceeding ASTM grade 9. Through the Hall-Page mechanism, a high-density grain boundary barrier is formed, significantly hindering dislocation movement and providing the alloy with extremely high basic yield strength, tensile strength, and hardness. This is the primary factor that surpasses the performance of traditional coarse-grained alloys. Simultaneously, the 3-5% volume fraction of short rod-shaped / granular δ phase contributes additional strength and hardness to the alloy. The specific volume fraction and morphology have been optimized to maximize the strengthening effect while avoiding the embrittlement problems that may be caused by excessive or improperly shaped δ phase. The δ phase provides precipitation strengthening, but as a brittle phase, it sacrifices some plasticity potential. Under ultra-high strength, the material often exhibits brittle fracture characteristics. Therefore, the elongation and reduction of area are not significantly improved, indicating that the alloy design has reached the extreme of "high strength and high hardness," which typically meets the requirements of aerospace and other applications with extremely high load-bearing capacity and a certain degree of redundancy in fracture toughness.

Claims

1. A method for preparing an ultrafine-grained nickel-based alloy, characterized in that, Includes the following steps: Step 1: Electroslag ingots are prepared using a vacuum induction + electroslag remelting method. The protective atmosphere for the electroslag remelting process is argon. The composition of the electroslag ingots is: ≤0.08wt%C, ≤0.35wt%Si, ≤0.35wt%Mn, ≤0.015wt%S, ≤0.015wt%P, ≤0.006wt%B, ≤0.3wt%Cu, ≤0.01wt%Mg, ≤1.0wt%Co, 17.0-21.0wt%Cr, 50.0-55.0wt%Ni, 2.80-3.30wt%Mo, 4.75-5.50wt%Nb, 0.65-1.15wt%Ti, 0.20-0.80wt%Al, and the balance Fe, as well as unavoidable impurities. Step 2: The electroslag ingots obtained in Step 1 are subjected to high-temperature homogenization diffusion annealing. The specific process is as follows: the resistance furnace is first heated to 1160±10℃ and held for 25 hours, then the furnace is heated to 1195±10℃ and held for 72 hours, the furnace is cooled to below 400℃, and the ingots are then air-cooled after being taken out of the furnace. Step 3: Using a high-speed forging mill, the electroslag ingot obtained in Step 2 is forged in multiple passes at 1100℃ to form an intermediate billet of the required specifications. Step 4: Perform intermediate heat treatment on the intermediate billet obtained in Step 3. The specific process is as follows: heat the billet to 880±10℃ in a resistance furnace, hold it for 40 hours, cool it in the furnace to below 600℃, and then air cool it after removing it from the furnace. Step 5: Perform low-temperature multi-fire forging on the intermediate billet obtained in Step 4. Specifically, after intermediate heat treatment, the intermediate billet is held at 940±10℃ for 3 hours and repeatedly forged in multiple fires to form finished bars of the target size.

2. The method for preparing the ultrafine-grained nickel-based alloy according to claim 1, characterized in that, In step 3, the forging process involves 6-8 forging passes.

3. The method for preparing the ultrafine-grained nickel-based alloy according to claim 1, characterized in that, In step 5, the number of times the forging process involves repeated furnace forging is 3-5 times.

4. An ultrafine-grained nickel-based alloy prepared by the method according to any one of claims 1-3, comprising: ≤0.08wt%C, ≤0.35wt%Si, ≤0.35wt%Mn, ≤0.015wt%S, ≤0.015wt%P, ≤0.006wt%B, ≤0.3wt%Cu, ≤0.01wt%Mg, ≤1.0wt%Co, 17.0-21.0wt%Cr, 50.0-55.0wt%Ni, 2.80-3.30wt%Mo, 4.75-5.50wt%Nb, 0.65-1.15wt%Ti, 0.20-0.80wt%Al, and the balance being Fe, and unavoidable impurities, characterized in that... The ultrafine-grained nickel-based alloy has a grain size grade of ASTM 9 or higher and uniform grains; the second phase δ phase in the alloy accounts for 3-5% of the total volume fraction of the alloy and is in the form of short rods or / and granules.

5. The ultrafine-grained nickel-based alloy according to claim 4, characterized in that, When the second phase δ phase is short rod-shaped, its aspect ratio is 3:1-5:1; when it is granular, the particle size is 1-2 μm.

6. The ultrafine-grained nickel-based alloy according to claim 4 or 5, characterized in that, The room temperature properties of the alloy are: tensile strength ≥1400MPa for σb and yield strength ≥1090MPa for σ0.2.

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