Homogeneous solid solution heat treatment method for Ni3Al-based intermetallic compound alloy with high Al content

Abstract

The invention discloses a homogeneous solid solution heat treatment method for a high-Al-content Ni3Al-based intermetallic compound alloy, and belongs to the technical field of preparation and heat treatment of Ni3Al-based alloys. The problem that an existing Ni3Al-based intermetallic compound alloy with the high Al content is insufficient in strength and plasticity is solved. The chemical components of the Ni3Al-based intermetallic compound alloy comprise C, Al, Cr, Mo, W, Ti, Nb, B and the balance Ni and inevitable impurities, the solidus temperature of the Ni3Al-based intermetallic compound alloy is increased through homogeneous solid solution heat treatment, the structure homogenization of the Ni3Al-based high-temperature alloy reaches the best, the room-temperature tensile property of the alloy is remarkably improved, and compared with non-heat-treatment, the tensile property of the alloy is greatly improved. The room-temperature yield strength of the alloy subjected to homogeneous solution heat treatment is improved by 21.4%, the ultimate tensile strength is improved by 31.6%, and the ductility is increased by more than 4 times.

Description

Technical Field

[0001] This invention belongs to the field of Ni3Al-based alloy preparation and heat treatment technology, specifically relating to a homogeneous solid solution heat treatment method for Ni3Al-based intermetallic compound alloys with high Al content. Background Technology

[0002] In the development of nickel-based superalloys, continuously increasing the content of the γ' strengthening phase (Ni3Al) in the alloy is an effective way to improve the alloy's temperature resistance. Starting with the addition of 1.3 wt% Al to Nimonic 80A alloy in 1944, a series of cast nickel-based superalloys with Al content of 5.5%-6.0% were developed by the 1960s. The γ' phase content in nickel-based superalloys also increased from 12 vol% to about 60 vol%, resulting in an approximately 200°C increase in the temperature resistance of nickel-based superalloys. In the late 1960s, some alloys with Al content of 6.5%-8.0% appeared, the most representative being WAZ 20, NX-188, and WAZ16 alloys. These alloys had a total γ' phase content of up to 70%, representing early Ni3Al-based superalloys, and their high-temperature strength was the highest among alloys at the time. Compared to Ni-based superalloys, Ni3Al-based superalloys have higher Al and γ' strengthening phase content, lower density, and higher service temperatures. In foreign countries, Ni3Al-based alloys contain about 8.5% Al, such as the IC series alloys developed by Oak Ridge National Laboratory in the United States and the BKHA series alloys developed by the All-Russian Institute of Aeronautical Materials.

[0003] The as-cast γ' phase and eutectic structure formed in Ni3Al-based intermetallic alloys not only lead to severe dendritic segregation but also reduce the volume fraction of the effective γ' strengthening phase, directly affecting its high-temperature mechanical properties. Furthermore, due to the different dissolution temperatures of the γ' phase between the dendrites and dendrites in Ni3Al-based intermetallic alloys, the regions between the precipitates and the γ' phase are discontinuous. These locations are weak points under stress and contribute insufficiently to the alloy's strength. Therefore, to achieve optimal performance in Ni3Al-based intermetallic alloys, solution heat treatment is generally used to homogenize the alloy microstructure. An ideal solution heat treatment must completely dissolve the eutectic and coarse as-cast γ' precipitates and minimize dendritic segregation, resulting in the most homogeneous alloy composition possible. The goal is to obtain a relatively uniform and fine γ' strengthening phase throughout the entire Ni3Al-based intermetallic alloy microstructure during subsequent aging, which is the optimal microstructure for achieving excellent mechanical properties in Ni3Al-based intermetallic alloys.

[0004] Although current research indicates that solution heat treatment can improve alloy properties, this conclusion is overly conceptual. In practical applications, heat treatment of Ni3Al-based intermetallic alloys does not necessarily refine grains or improve alloy performance. In recent years, various studies have explored the influence of solution heat treatment temperature on the microstructural stability and mechanical properties of Ni3Al-based intermetallic alloys, and have attempted to increase the initial melting temperature of Ni3Al-based intermetallic alloys by adjusting the stages of solution heat treatment. Results show that, using traditional microstructure homogenization methods, high-Al-content Ni3Al-based intermetallic alloys cannot be completely homogenized without the formation of localized melting regions. Therefore, it is crucial to maximize the solidus temperature and microstructure homogenization of Ni3Al-based intermetallic alloys without initial melting, ensuring their performance meets the practical engineering requirements of hot-end components in gas turbines and novel combined engines. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problem that existing high-Al-content Ni3Al-based intermetallic compound alloys suffer from insufficient strength and plasticity due to incomplete solid solution treatment, and to provide a homogeneous solid solution heat treatment method for high-Al-content Ni3Al-based intermetallic compound alloys.

[0006] The technical solution of the present invention is as follows: One objective of this invention is to provide a homogeneous solution heat treatment method for Ni3Al-based intermetallic compound alloys with high Al content, the method comprising the following steps: S1. Preheat the furnace to 150 ℃, then put in a Ni3Al-based intermetallic compound alloy with high Al content, and heat it to 1260 ℃ and hold for 2 h. S2, continue heating to 1275 ℃ and hold for 2 hours; S3. Continue heating to 1290 ℃ and hold for 2 hours; S4. Continue heating to 1300 ℃ and hold for 2 hours; S5. Continue heating to 1310 ℃ and hold for 6 hours; S6. Continue heating to 1315 ℃ and hold for 4 h. Then, remove the Ni3Al-based intermetallic compound alloy with high Al content and air cool to room temperature.

[0007] Further specified, the heating rate of the preheating and heating processes in S1-S6 is 10 ℃ / min, and the furnace temperature uniformity is ±1 ℃.

[0008] Further specifying, the chemical composition and mass percentage of the high Al content Ni3Al-based intermetallic compound alloy are as follows: C: 0.12-0.13%, Al: 8.8-8.9%, Cr: 4.9-5.1%, Mo: 2.2-2.3%, W: 2.9-3.1%, Ti: 1.6-1.7%, Nb: 1.0-2.0%, B: 0.012-0.016%, with the balance being Ni and unavoidable impurities.

[0009] Further specifying, Ni3Al-based intermetallic compound alloys contain a large number of coarse γ'-type alloys. m Eutectic phase.

[0010] Furthermore, the preparation method of Ni3Al-based intermetallic compound alloys with high Al content includes the following steps: S1. Weigh each raw material according to the chemical composition ratio of the high Al content Ni3Al-based intermetallic compound alloy, arrange each raw material in order, and preheat by heating. S2. After preheating, the process enters the molten metal stage. At the end of the molten metal stage, all raw materials are completely melted to form an alloy liquid. At the end of the molten metal stage, the temperature is raised to the refining temperature for refining. After refining, the alloy liquid is poured into an alloy ingot. After cooling to room temperature in the furnace, it is taken out to obtain a Ni3Al-based intermetallic compound alloy with high Al content.

[0011] To further specify, the order of the raw materials in S1 from top to bottom after being arranged in sequence is as follows: the top layer is metal Al and metal Ni with the same atomic ratio as metal Al, the middle layer is other raw materials besides metal Al and metal Ni, and the bottom layer is the remaining metal Ni.

[0012] Furthermore, the vacuum level during the placement of each raw material in S1 is <1 Pa.

[0013] Furthermore, the vacuum degree during the opening phase of S2 is <0.2 Pa, the vacuum degree during the refining process is <0.2 Pa, and the vacuum degree during the casting process is <0.2 Pa.

[0014] Furthermore, the refining temperature in S2 is 1450-1550 ℃, and the refining time is no less than 2 min.

[0015] The second objective of this invention is to provide a Ni3Al-based intermetallic compound alloy with high Al content obtained by the above-mentioned homogeneous solution heat treatment method. The alloy has an ultimate tensile strength ≥750 MPa, an elongation ≥11.5%, and a yield strength ≥550 MPa at room temperature.

[0016] The beneficial effects of this invention are as follows: This invention, through processes such as composition design, vacuum smelting, and homogeneous solution heat treatment, improves the solidus temperature of high-Al-content Ni3Al-based intermetallic compound alloys to 1315-1320 °C, optimizes the microstructure homogenization of these alloys, and significantly improves their room-temperature tensile properties and strength compared to existing technologies. This invention also offers the following advantages: (1) Without adding rare and dispersed metal elements, this invention achieves synergistic optimization of the microstructure and macroscopic mechanical properties of the alloy by rationally designing the alloy composition and controlling the parameters of homogeneous solution heat treatment. This significantly improves the room temperature tensile properties of the Ni3Al-based intermetallic compound alloy. After homogeneous solution heat treatment, the room temperature yield strength of the alloy is not less than 550 MPa, the room temperature tensile strength is not less than 750 MPa, and the elongation is not less than 11.5%.

[0017] (2) The alloy of the present invention is free of rare dispersed elements such as Re, Ru, Hf, and Y. It uses vacuum melting and vacuum casting technology to manufacture Ni3Al-based intermetallic compound alloy castings, which directly reduces the cost of the alloy from the perspective of raw materials and preparation process. Using the homogeneous solid solution heat treatment process parameters provided by the present invention, Ni3Al-based intermetallic compound alloys with good room temperature mechanical properties are successfully prepared. The homogeneous solid solution heat treatment method of the present invention is simple, can meet the actual large-scale production needs, and is easy to produce high-performance Ni3Al-based intermetallic compound alloys.

[0018] (3) In the traditional preparation process of Ni3Al-based intermetallic compound alloys, in order to obtain a high volume fraction of γ' strengthening phase, a large amount of Al element is often added to the alloy. However, this also leads to the formation of many insoluble phases and eutectics in the alloy, which increases the difficulty of subsequent heat treatment and has an adverse effect on the performance of the alloy. Although the Ni3Al-based intermetallic compound alloy of the present invention has a high Al content, the coarse γ' phase formed in the as-cast structure of the Ni3Al-based intermetallic compound alloy can be removed through the homogeneous solid solution heat treatment process. m The eutectic phase fully dissolves back into the matrix, allowing the strengthening phase γ' in the heat-treated alloy to fully dissolve. Ⅰ The phase volume fraction is as high as 88.1%, which improves the room temperature plasticity and strength of Ni3Al-based intermetallic compound alloys. Attached Figure Description

[0019] Figure 1 Dimensions of the metal mold used in Example 1 and Comparative Example 1, and dimensions of the ingot shape of Comparative Example 1; (a) Dimensions of the metal mold, (b) Dimensions of the ingot shape; Figure 2 The equilibrium phase and its mass fraction of the as-cast sample of Comparative Example 1 in the range of 500-1400 °C; Figure 3 SEM images of the as-cast and homogeneous solution-treated specimens prepared for Comparative Examples 1-5 and Example 1: (a) Comparative Example 1; (b) Comparative Example 2; (c) Comparative Example 3; (d) Comparative Example 4; (e) Comparative Example 5; (f) Example 1. Figure 4 Tensile stress-strain curves at room temperature for the as-cast specimens and homogeneous solution-treated specimens prepared for Comparative Example 1 and Example 1; Figure 5 SEM images of the fracture surfaces of the cast specimens and homogeneous solution-treated specimens prepared in Comparative Example 1 and Example 1 after tensile testing at room temperature; (a) Comparative Example 1, (b) Example 1, (c) is an enlarged view of the white rectangle in (a), (d) is an enlarged view of the white rectangle in (b), (e) is an enlarged view of the white rectangle in (c), and (f) is an enlarged view of the white rectangle in (d). Detailed Implementation

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0021] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0022] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0023] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. The materials, reagents, methods, and instruments used, unless otherwise specified, are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0025] Example 1 The preparation method of the high-Al-content Ni3Al-based intermetallic compound alloy in this embodiment is carried out according to the following steps: (1) The following components and weight percentages are used for batching: C: 0.13%, Al: 8.86%, Cr: 5.04%, Mo: 2.24%, W: 3.06%, Ti: 1.67%, Nb: 1.76%, B: 0.016%, with the balance being Ni and unavoidable impurities; the batching process is carried out by adding the burn-off mass to the intended batching mass according to the burn-off rate of each element, wherein the burn-off rate of element B is 0.25wt%, the burn-off rate of elements Al and Mo is 0.02wt%, the burn-off rate of elements Cr and W is 0.01wt%, the burn-off rate of element C is 0.07wt%, and the burn-off rate of element Ti is 0.1wt%; Ni, Al, C, Cr, Mo, W, Ti, Nb, and B elements with a purity of not less than 99.95% are selected as raw materials. Each raw material is cleaned with anhydrous ethanol before melting and then dehydrogenated after drying: that is, placed in a muffle furnace at room temperature and heated to 450°C at a heating rate of 10°C / min. Hold at ℃ for 1 hour, then cool to below 100 ℃ and air cool to ensure the high quality of the prepared alloy; (2) Smelting: The smelting equipment used is an industrial-grade three-chamber vacuum induction furnace, model ZG-005LB. The three-chamber vacuum induction furnace consists of a charging chamber, a casting chamber, a smelting chamber and an operating table. The raw materials are placed in the melting furnace in the following order: all metallic Al and metallic Ni with the same atomic ratio as Al are placed on top; the middle layer contains all raw materials except metallic Al and metallic Ni; and the bottom layer contains the remaining metallic Ni. This process of placing the raw materials is called the filling period. Then, the temperature is raised to 800 ℃ for preheating for 10 min. After preheating, the raw materials begin to melt, which also marks the beginning of the opening period. During this period, the raw materials continue to melt until they are completely melted to form an alloy liquid. After the opening period, the temperature of the alloy liquid is rapidly increased to 1500 ℃ at a rate of 60 ℃ / s and held for 120 s, i.e., refining for 120 s, to ensure that the high-melting-point elements W, Nb, and Mo are fully melted and kept uniform. After refining, the alloy liquid is held at 1480 ℃ until it is poured within 20 s, resulting in a size of 64 mm × 90 mm × 120 mm. Ni3Al-based alloy ingots with high Al content (mm); to minimize the residual H, O, N and other gaseous elements, the vacuum degree during the filling period is less than 1 Pa, and the vacuum degree during the opening, refining and casting periods is less than 0.2 Pa. The dimensions of the metal mold and the shape of the alloy ingot in this step are as follows: Figure 1As shown in the diagram. In this process, the first step involves melting Al; the second step involves an exothermic reaction between the liquid Al and the top-layer Ni; the third step involves the molten droplets moving under gravity, contacting the alloying elements in the center of the crucible, and the alloying elements dissolving into the Ni3Al droplets to form a Ni3Al-based ingot. Continuous induction heating is maintained during the formation of the Ni3Al droplets and the Ni3Al-based alloy ingot to ensure the reaction continues; finally, a high-Al-content Ni3Al-based alloy ingot is formed at the bottom of the crucible. (3) The Ni3Al-based alloy ingot with high Al content obtained after casting is cooled to room temperature in the casting chamber at a rate of 0.3 ℃ / s to obtain a Ni3Al-based intermetallic compound alloy with high Al content, which is recorded as a cast sample.

[0026] This embodiment continues the homogeneous solution heat treatment process on the as-cast sample. The specific process is as follows: S1: Preheat a high-temperature box-type resistance heating furnace with a furnace temperature uniformity of ±1℃ to 150℃, then place the as-cast sample in the furnace, raise the temperature to 1260℃ and hold for 2 hours; S2: Continue heating to 1275 ℃ and hold for 2 hours; S3: Continue heating to 1290 ℃ and hold for 2 hours; S4: Continue heating to 1300 ℃ and hold for 2 hours; S5: Continue heating to 1310 ℃ and hold for 6 hours; S6: Continue heating to 1315 ℃ and hold for 4 h, then take out the sample and air cool to room temperature, and record it as SSHT 4 sample; The heating rate during the heat treatment process was 10 °C / min.

[0027] Comparative Example 1 The difference between this comparative example and Example 1 is that after obtaining the as-cast sample, no homogeneous solution heat treatment process was carried out. The remaining operations and process parameters are the same as those in Example 1.

[0028] Comparative Example 2 The difference between this comparative example and Example 1 is that, to prevent the initial melting of the high-Al-content Ni3Al-based intermetallic compound alloy, a single-stage solution heat treatment process was performed on the as-cast sample at a temperature close to but below the solidus (1295.35 °C). Specifically, the high-temperature box-type resistance furnace with a temperature uniformity of ±1 °C was preheated to 150 °C, and then the as-cast sample was placed inside. The temperature was increased to 1294 °C at a rate of 10 °C / min and held for 4 hours. The sample was then removed and air-cooled to room temperature, and this was designated as the SHT state sample. All other operations and process parameters were the same as in Example 1.

[0029] Comparative Example 3 The difference between this comparative example and Example 1 is that the homogeneous solution heat treatment process performed on the as-cast sample is as follows: S1. Preheat a high-temperature box-type resistance heating furnace with a temperature uniformity of ±1℃ to 150℃, then place the as-cast sample in the furnace and heat it to 1260℃ for 2 hours; S2, continue heating to 1275 ℃ and hold for 2 hours; S3. Continue heating to 1290 ℃ and hold for 2 hours; S4. Continue heating to 1300 ℃ and hold for 2 h; remove the alloy and air cool to room temperature, and record it as SSHT 1 state sample; The heating rate during the heat treatment process was 10 °C / min, and the remaining operations and process parameters were the same as in Example 1.

[0030] Comparative Example 4 The difference between this comparative example and Example 1 is that the homogeneous solution heat treatment process performed on the as-cast sample is as follows: S1. Preheat the high-temperature box-type resistance heating furnace with a furnace temperature uniformity of ±1℃ to 150℃, then put in the as-cast sample, raise the temperature to 1260℃ and hold for 2 hours. S2, continue heating to 1275 ℃ and hold for 2 hours; S3. Continue heating to 1290 ℃ and hold for 2 hours; S4. Continue heating to 1300 ℃ and hold for 2 hours; S5. Continue heating to 1310 ℃ and hold for 2 hours; S6. Continue heating to 1315 ℃ and hold for 2 h. Then remove the alloy and air cool it to room temperature. This is recorded as the SSHT 2 state sample. The heating rate during the heat treatment process was 10 °C / min, and the remaining operations and process parameters were the same as in Example 1.

[0031] Comparative Example 5 The difference between this comparative example and Example 1 is that the homogeneous solution heat treatment process performed on the as-cast sample is as follows: S1. Preheat the high-temperature box-type resistance heating furnace with a furnace temperature uniformity of ±1℃ to 150℃, then put in the as-cast sample, raise the temperature to 1260℃ and hold for 2 hours. S2, continue heating to 1275 ℃ and hold for 2 hours; S3. Continue heating to 1290 ℃ and hold for 2 hours; S4. Continue heating to 1300 ℃ and hold for 2 hours; S5. Continue heating to 1310 ℃ and hold for 2 hours; S6. Continue heating to 1315 ℃ and hold for 2 hours; S7. Continue heating to 1320 ℃ and hold for 2 h. Then remove the alloy and air cool it to room temperature. This is recorded as the SSHT 3-state sample. The heating rate during the heat treatment process was 10 °C / min, and the remaining operations and process parameters were the same as in Example 1.

[0032] Figure 2 (a) shows the equilibrium phase and its mass fraction in the as-cast sample obtained in Comparative Example 1 within the range of 500-1400 °C. Figure 2 (b) is Figure 2 (a) Enlarged view of the area indicated by the black dashed line. The figure shows that the complete dissolution temperature of the γ' phase is 1309.71℃; within the range of 500-1309.71℃, the mass fraction of the γ' phase gradually decreases with increasing temperature. The solidus curve of the as-cast sample (…) T solidus The temperature was 1295.35 ℃, which is lower than the complete dissolution temperature of the γ' phase. Since the preparation methods of Comparative Example 1 and Example 1 for the high Al content Ni3Al-based intermetallic compound alloy are exactly the same, the solidus lines of the as-cast sample in Example 1 ( T solidus The temperature was also 1295.35 ℃. This means that it is impossible to completely dissolve the γ' phase in the as-cast sample without initial melting. Therefore, for as-cast samples, it is necessary to continuously increase the solidus temperature of the as-cast sample through homogeneous solution heat treatment, ultimately achieving the precipitation of the as-cast γ' phase and the formation of coarse γ' phases. m The purpose is to achieve complete resolution of the eutectic and improve microstructure segregation.

[0033] Figure 3 SEM images of Comparative Examples 1-5 and Example 1, Figure 3 The upper right insets in (a)-(d) and (f) show the microstructure of the γ+γ' two-phase region at higher magnification. The white arrows in the figures represent γ'. m Eutectic, the blue arrow represents the as-cast γ' phase, and the orange arrow represents the γ' phase that precipitates again after the as-cast γ' phase has been dissolved. Ⅰ Phase, the red arrow indicates the initial melting structure.

[0034] Figure 3(a) is the SEM image of Comparative Example 1. It can be seen that elemental segregation during solidification results in a typical dendritic structure in the as-cast alloy sample. The as-cast γ' phase and eutectic structure formed in the Ni3Al-based intermetallic compound alloy not only lead to severe dendritic segregation but also reduce the volume fraction of the effective γ' strengthening phase, directly affecting its high-temperature mechanical properties. Furthermore, due to the different dissolution temperatures of the γ' phase in the dendritic region and between dendrites, the region between the precipitated phase and the γ' phase is discontinuous. These locations are weak areas under stress and contribute insufficiently to the alloy's strength. Therefore, to further improve the alloy's performance, solution heat treatment is used to homogenize the alloy microstructure, maximally dissolve the eutectic and coarse as-cast γ' phase, and maximally improve dendritic segregation.

[0035] Figure 3 (b) is the SEM image of Comparative Example 2. When the Ni3Al-based intermetallic compound alloy is subjected to the SHT heat treatment regime, the as-cast γ' portion of the dendrite trunk region dissolves back, but γ' m However, no obvious changes were observed. If the solution temperature was further increased, the alloy underwent initial melting. This indicates that simply increasing the solution temperature cannot achieve complete solution treatment of the alloy; a suitable homogeneous solution heat treatment process must be used to treat the as-cast alloy sample.

[0036] Depend on Figure 3 (c) is the SEM image of Comparative Example 3. It can be seen that no initial melting occurred after the Ni3Al-based intermetallic compound alloy underwent homogeneous solution heat treatment using the SSHT 1 process, indicating that step-heating can indeed increase the solidus temperature of the alloy; at this point, the solidus temperature of the alloy is >1300 ℃. The microstructure of the alloy consists of residual γ' m Eutectic and Reprecipitated γ+γ' Ⅰ Composed of two-phase regions. γ' Ⅰ The phase has a relatively regular cubic shape. However, the alloy is not completely dissolved.

[0037] The SEM image of Comparative Example 4 is as follows Figure 3 As shown in (d), even after further increasing the homogeneous solution heat treatment temperature to 1315 °C, the alloy still did not initially melt. This indicates that using the SSHT 2 heat treatment regime, the solidus line of the Ni3Al-based intermetallic compound alloy is further increased to above 1315 °C. γ' Ⅰ The cubicity of the phase did not change significantly, but the size increased, although residual γ' remained in the alloy. m Eutectic exists.

[0038] The SEM image of Comparative Example 5 is as follows Figure 3As shown in (e), it can be seen that the Ni3Al-based intermetallic compound alloy undergoes initial melting after the SSHT 3 heat treatment. This indicates that after the SSHT 2 treatment, the solidus temperature of the alloy is between 1315℃ and 1320℃.

[0039] Therefore, based on the SSHT 2 heat treatment regime of Comparative Example 4, the holding time of the Ni3Al-based intermetallic compound alloy at 1310 °C was extended to 6 h, and the holding time at 1315 °C was extended to 4 h, i.e., Example 1, and its SEM image is shown below. Figure 3 As shown in (f), the alloy did not undergo initial melting; at this point, the solidus temperature of the alloy was >1315 ℃. The γ' that re-precipitated after re-dissolution... Ⅰ Phase size continues to increase. Coarse γ' phases are found in the alloy. m The eutectic almost completely dissolved back into the matrix, with residual γ' m The volume fraction of the eutectic is 1.8%, γ' Ⅰ The volume fraction was 88.1%, and the alloy achieved maximum microstructure homogeneity. contrast Figure 3 As can be seen from the alloy microstructures of the six states, only the homogeneous solution heat treatment process of Example 1 can ensure that the solidus temperature is increased the most without initial melting of the alloy, thus reducing the coarse γ' m The eutectic dissolves back into the matrix, thereby maximizing the solid solution of the alloy, ultimately resulting in as-cast γ' precipitates and coarse γ' precipitates. m The purpose is to fully re-dissolve the eutectic and improve the microstructure segregation.

[0040] Figure 4 The figures show the tensile stress-strain curves at room temperature for the homogeneous solution-treated and cast specimens obtained in Example 1 and Comparative Example 1. It can be seen that the room temperature ultimate tensile strength of the homogeneous solution-treated specimen of Example 1 is 767.8 MPa, the yield strength is 554.5 MPa, and the elongation is 11.9%, while the ultimate tensile strength of the cast specimen of Comparative Example 1 is 582.5 MPa, the yield strength is 455.8 MPa, and the elongation is 2.7%. The homogeneous solution-treated specimen of Example 1 exhibits significantly superior room temperature tensile properties compared to the cast specimen of Comparative Example 1, especially in terms of elongation, which is more than four times greater.

[0041] Figure 5 These are fracture surface scan images of the homogeneous, solution-treated, and as-cast specimens obtained in Example 1 and Comparative Example 1, taken at different observation scales after being stretched at room temperature. From a macroscopic scale... Figure 5 As seen in (a) and (b), both specimens exhibit brittle fracture with almost no necking. At the microscopic scale, the fracture modes of the two specimens differ. The fracture morphology of the as-cast specimen is as follows: Figure 5As shown in (c) and (e), the surface has a polyhedral shape resembling rock candy or rock, with a strong three-dimensional effect, no traces of plastic deformation, and cracks initiating and propagating along the grain boundaries. This fracture mode is intergranular fracture. Figure 5 (d) and (f) show the fracture morphology of the homogeneous solid solution sample. Obvious "serpentine slip" marks were observed on the fracture surface. The microstructure of the fracture surface consists of densely packed equiaxed micropores and a very small number of cleavage surfaces. γ' can also be seen inside the pits. Ⅰ The fracture mode is micropore fracture. Micropore aggregation fracture is a type of ductile fracture that occurs during the formation, growth, and aggregation of micropores within the material. This fracture mode is accompanied by significant plastic deformation, and the fracture morphology exhibits a dark gray fibrous appearance, indicating that the material absorbed a large amount of energy before fracture. The crack propagation rate is slower than that of intergranular fracture. Therefore, due to its ductile characteristics, micropore fracture exhibits better plasticity than intergranular fracture. In other words, the alloy after homogeneous solid solution treatment in Example 1 has better plasticity than that in Comparative Example 1.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A homogeneous solution heat treatment method for a Ni3Al-based intermetallic compound alloy with high Al content, characterized in that, The method includes the following steps: S1. Preheat the furnace to 150 °C, then put in a Ni3Al-based intermetallic compound alloy with high Al content, and heat it to 1260 °C and hold for 2 h. S2, continue heating to 1275 ℃ and hold for 2 hours; S3. Continue heating to 1290 ℃ and hold for 2 hours; S4. Continue heating to 1300 ℃ and hold for 2 hours; S5. Continue heating to 1310 ℃ and hold for 6 hours; S6. Continue heating to 1315 ℃ and hold for 4 h. Then, remove the Ni3Al-based intermetallic compound alloy with high Al content and air cool to room temperature.

2. The homogeneous solution heat treatment method according to claim 1, characterized in that, The heating rate for both the preheating and heating processes in S1-S6 is 10 ℃ / min.

3. The homogeneous solution heat treatment method according to claim 1, characterized in that, The chemical composition and mass percentage of the high-Al-content Ni3Al-based intermetallic compound alloy are as follows: C: 0.12-0.13%, Al: 8.8-8.9%, Cr: 4.9-5.1%, Mo: 2.2-2.3%, W: 2.9-3.1%, Ti: 1.6-1.7%, Nb: 1.0-2.0%, B: 0.012-0.016%, with the balance being Ni and unavoidable impurities.

4. The homogeneous solution heat treatment method according to claim 3, characterized in that, The preparation method of Ni3Al-based intermetallic compound alloys with high Al content includes the following steps: S1. Weigh each raw material according to the chemical composition ratio of the high Al content Ni3Al-based intermetallic compound alloy, arrange each raw material in order, and preheat by heating. S2. After preheating, the process enters the molten metal stage. At the end of the molten metal stage, all raw materials are completely melted to form an alloy liquid. At the end of the molten metal stage, the temperature is raised to the refining temperature for refining. After refining, the alloy liquid is poured into an alloy ingot. After cooling to room temperature in the furnace, it is taken out to obtain a Ni3Al-based intermetallic compound alloy with high Al content.

5. The homogeneous solution heat treatment method according to claim 4, characterized in that, In S1, the order of the raw materials from top to bottom after being arranged in sequence is as follows: the top layer is metal Al and metal Ni with the same atomic ratio as metal Al, the middle layer is other raw materials except metal Al and metal Ni, and the bottom layer is the remaining metal Ni.

6. The homogeneous solution heat treatment method according to claim 4, characterized in that, The vacuum level during the placement of each raw material in S1 is <1 Pa.

7. The homogeneous solution heat treatment method according to claim 4, characterized in that, The vacuum degree during the opening period in S2 is <0.2 Pa.

8. In the homogeneous solution heat treatment method according to claim 4, the vacuum degree of the refining process in S2 is <0.2 Pa, and the vacuum degree of the casting process is <0.2 Pa.

9. The homogeneous solution heat treatment method according to claim 4, characterized in that, The refining temperature in S2 is 1450-1550 ℃, and the refining time is no less than 2 min.

10. A Ni3Al-based intermetallic compound alloy with high Al content after being treated by the homogeneous solution heat treatment method according to any one of claims 1-9, characterized in that, The alloy has an ultimate tensile strength of ≥750 MPa, an elongation of ≥11.5%, and a yield strength of ≥550 MPa at room temperature.

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