Method for controlling beta phase in weldable Ni3Al-based high-temperature alloy
By controlling the Fe and Cr content to regulate the β phase volume fraction, the poor weldability of Ni3Al-based superalloys during the welding process was solved, enhancing its application potential in high-temperature environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-09
- Publication Date
- 2026-04-10
AI Technical Summary
Existing Ni3Al-based superalloys suffer from problems such as hot cracking, elemental segregation, and joint softening during welding, resulting in poor weldability and limiting their application in the aerospace field.
By controlling the content of Fe and Cr elements and adjusting the volume fraction of the β phase, alloy melting is carried out in a vacuum arc melting furnace to form β phases with different volume fractions, thereby improving the weldability and mechanical properties of the alloy.
It significantly improves the weldability and mechanical properties of Ni3Al-based superalloys, enhancing their application potential in high-temperature environments.
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Figure CN121826410A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microstructure control technology for weldable Ni3Al-based superalloys, and in particular to a method for controlling the β phase in weldable Ni3Al-based superalloys. Background Technology
[0002] With the continuous advancement of the aerospace industry, the required operating temperature of engine turbine blades is becoming increasingly higher, even exceeding 1100℃, and their structures are becoming more complex. Generally, nickel-based alloys can operate at temperatures up to 1100℃, but with the rapid development of aviation technology, higher requirements have been placed on the operating temperature of high-temperature alloys. 1100℃ is no longer sufficient to meet the temperature demands of current and future aero-engines, thus necessitating the development of new high-temperature materials with better temperature resistance.
[0003] Ni3Al-based superalloys exhibit higher service temperatures (exceeding 1100℃) than conventional nickel-based superalloys, and also display a lower Ni / Al ratio compared to traditional nickel-based superalloys. This characteristic results in a significantly higher performance. The volume fraction of the strengthening phase can typically reach over 80 vol.%, thereby further improving its high-temperature mechanical properties. Moreover, Al is a light metal, so not only is the production cost low, but the density is also relatively low. Therefore, Ni3Al-based high-temperature alloys have become one of the most mature intermetallic compound high-temperature alloys currently being researched, and most promising for industrialization and use as important structural materials in the aerospace and civilian industries.
[0004] In the existing technology, problems such as poor weldability often cause hot cracking, elemental segregation, and joint softening in Ni3Al-based alloys during the welding process, which seriously hinders the further expansion of its engineering applications. Summary of the Invention
[0005] The purpose of this invention is to provide a method for controlling the β phase in a weldable Ni3Al-based superalloy. By adjusting the Fe and Cr content, the volume fraction of the β phase in the weldable Ni3Al-based superalloy is controlled, resulting in weldable Ni3Al-based superalloys with different volume fractions of β phase, thereby significantly improving the mechanical properties of the weldable Ni3Al-based superalloy.
[0006] To achieve the above objectives, the present invention provides a method for controlling the β phase in a weldable Ni-Al superalloy, comprising the following steps: S1. Based on the Ni-Al-Fe ternary phase diagram, clarify the relationship between the Fe element content and the volume fraction of the β phase, and obtain the theoretical basic amount of Fe element added when the β phase is formed. S2. When the β phase is generated, theoretically, the minimum amount of Fe added should be set as the base value. Using the controlled variable method, the amount of Fe added should be gradually increased and the proportion of Ni should be reduced. Alloy ratios with different Fe contents should be selected. S3. Based on the alloy ratio obtained in S2, batch and smelt the alloys to obtain weldable Ni3Al-based high-temperature alloys with different β phase volume fractions. S4. Based on the Ni-Al-Cr ternary phase diagram, clarify the relationship between the Cr element content and the volume fraction of the β phase, and obtain the theoretical basic amount of Cr element added when the β phase is formed. S5. Select one of the proportions in S2 as the base value, and use the controlled variable method to gradually increase the amount of Cr element added and decrease the proportion of Ni element, and select alloy proportions with different Cr element contents. S6. Based on the alloy ratio obtained in S5, batch and smelt the alloys to obtain weldable Ni3Al-based high-temperature alloys with different β phase volume fractions.
[0007] Preferably, in S1, the relationship between the Fe element content and the volume fraction of the β phase in the alloy is as follows: as the Fe element increases, the volume fraction of the β phase in the alloy increases accordingly.
[0008] Preferably, in S1, when the β phase is formed, the theoretical minimum mass percentage of Fe element added is 8-10%.
[0009] Preferably, in S2, five alloy ratios with different Fe element contents are selected, and the mass percentage difference of Fe element content in each of the five alloy ratios is 0-2%. The alloy comprises the following components by weight percentage: 8-9% Al, 4-9% Cr, 0-2% Mo, 0-0.002% W, 0.01-0.1% C, 0.055% Mn, 0.009% Ti, 8-14% Fe, 0.055% Si, 0.018% B, 0.5-1.5% Hf, with the remainder being Ni.
[0010] Preferably, in S2, the alloy comprises the following components by weight percentage: 8-9% Al, 6-7% Cr, 0-2% Mo, 0-0.002% W, 0.01-0.1% C, 0.055% Mn, 0.009% Ti, 8-14% Fe, 0.055% Si, 0.018% B, 0.5-1.5% Hf, with the remainder being Ni.
[0011] Preferably, in S3, the smelting is as follows: Place the prepared raw materials into a vacuum arc melting furnace and evacuate to a vacuum level of 5×10⁻⁶.-3 After Pa, argon gas is introduced into the vacuum chamber until the chamber pressure is -0.05MPa, and the raw material is subjected to electric arc melting. In order to ensure the uniformity of alloy composition, the alloy ingots at each station are held for 0-10 minutes after complete melting, and the ingots are turned over and melted 9-10 times. The melting temperature is maintained between 1300-1500℃. After the melting is completed, the ingots are cooled with water-cooled copper molds.
[0012] Preferably, in S3, the volume fractions of the β phase in the weldable Ni3Al-based superalloys with different β phase volume fractions are 10-12%, 14-16%, 16.5-17.5%, 18-20%, and 21-23%, respectively.
[0013] Preferably, in S4, the relationship between the Cr element content and the volume fraction of the β phase in the alloy is as follows: as the Cr element increases, the volume fraction of the β phase in the alloy increases accordingly.
[0014] Preferably, in S4, when determining the formation of the β phase, the theoretical minimum mass percentage of Cr element added is 3.5-5%.
[0015] Preferably, in S5, five alloy ratios with different Cr content are selected, and the mass ratio difference of Cr content in each of the five alloy ratios is 0-2%. The alloy comprises the following components by weight percentage: 8-9% Al, 4-9% Cr, 0-2% Mo, 0-0.002% W, 0.01-0.1% C, 0.055% Mn, 0.009% Ti, 11-12% Fe, 0.055% Si, 0.018% B, 0.5-1.5% Hf, with the remainder being Ni.
[0016] Preferably, in S6, the smelting is as follows: Place the prepared raw materials into a vacuum arc melting furnace and evacuate to a vacuum level of 5×10⁻⁶. -3 After Pa, argon gas is introduced into the vacuum chamber until the chamber pressure is -0.05MPa, and the raw material is subjected to electric arc melting. In order to ensure the uniformity of alloy composition, the alloy ingots at each station are held for 1 minute after complete melting, and the ingots are flipped and melted 9-10 times. The melting temperature is maintained between 1450℃. After the melting is completed, the ingots are cooled with water-cooled copper molds.
[0017] Preferably, in S6, the β phase of the weldable Ni3Al-based superalloy with different β phase volume fractions are 9-11%, 12.5-14.5%, 15-16.5%, 17-19%, and 20-22%, respectively.
[0018] Therefore, the present invention employs the above-mentioned method for controlling the β phase in a weldable Ni3Al-based superalloy, and the beneficial effects are as follows: (1) The present invention improves the mechanical properties of the high-temperature alloy by adjusting the composition of the weldable Ni3Al-based high-temperature alloy to form β phases with different volume fractions.
[0019] (2) This invention effectively improves the phase composition and welding performance of Ni3Al-based superalloys by adding Fe and Cr components. Specifically, the addition of higher Cr components promotes the precipitation of the NiAl-β phase and also promotes the formation of spheroidal particles of different sizes within the β phase. -Cr precipitate phase precipitation, and the precipitated phase The Cr phase can improve the toughness and ductility of the β phase in the alloy to a certain extent; the addition of higher Fe components will not only promote... The precipitation of the phase will also promote the precipitation of the β phase in the alloy. Therefore, the increase of these two components will improve the machinability and weldability of the alloy to a certain extent, and enhance the mechanical properties of the high-temperature alloy.
[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0021] Figure 1 This is an alloy equilibrium phase diagram of Embodiment 1 and Embodiments 3-6 of the present invention, which describes a method for controlling the β phase in a weldable Ni3Al-based superalloy. Figure 2 These are OM morphology images of Embodiment 1 and Embodiments 3-6 of the method for controlling the β phase in a weldable Ni3Al-based superalloy according to the present invention, wherein (a) is Embodiment 3, (b) is Embodiment 1, (c) is Embodiment 4, (d) is Embodiment 5, and (e) is Embodiment 6; Figure 3 These are SEM images of Embodiment 1 and Embodiments 3-6 of the present invention, which describe a method for controlling the β phase in a weldable Ni3Al-based superalloy. (a) is the overall SEM image of Embodiment 3 at low magnification; (b) is an enlarged view of the β phase in Embodiment 3; (c) is an enlarged view of the dendritic trunk γ′+γ two-phase structure in Embodiment 3; (d) is the overall SEM image of Embodiment 1 at low magnification; (e) is an enlarged view of the β phase in Embodiment 1; (f) is an enlarged view of the dendritic trunk γ′+γ two-phase structure in Embodiment 1; and (g) is the SEM image of Embodiment 6. The overall morphology of Example 4 under low magnification SEM: (h) is an enlarged view of the β phase of Example 4; (i) is an enlarged view of the dendritic trunk γ′+γ two-phase structure of Example 4; (j) is the overall morphology of Example 5 under low magnification SEM; (k) is an enlarged view of the β phase of Example 5; (l) is an enlarged view of the dendritic trunk γ′+γ two-phase structure of Example 5; (m) is the overall morphology of Example 6 under low magnification SEM; (n) is an enlarged view of the β phase of Example 6; (o) is an enlarged view of the dendritic trunk γ′+γ two-phase structure of Example 6. Figure 4 The room temperature tensile stress-strain curves of Embodiment 1 and Embodiments 3-6 of the present invention are shown. Figure 5 This is the alloy equilibrium phase diagram of Embodiment 2 and Embodiments 7-10 of the present invention, which describes a method for controlling the β phase in a weldable Ni3Al-based superalloy. Figure 6 These are OM morphology images of Embodiment 2 and Embodiments 7-10 of the method for controlling the β phase in a weldable Ni3Al-based superalloy according to the present invention, wherein (a) is Embodiment 7, (b) is Embodiment 2, (c) is Embodiment 8, (d) is Embodiment 9, and (e) is Embodiment 10. Figure 7 These are SEM images of Embodiment 2 and Embodiments 7-10 of the present invention, which describe a method for controlling the β phase in a weldable Ni3Al-based superalloy. (a) is the overall SEM image of Embodiment 7 at low magnification; (b) is an enlarged view of the β phase in Embodiment 7; (c) is an enlarged view of the dendritic trunk γ′+γ two-phase structure in Embodiment 7; (d) is the overall SEM image of Embodiment 2 at low magnification; (e) is an enlarged view of the β phase in Embodiment 2; (f) is an enlarged view of the dendritic trunk γ′+γ two-phase structure in Embodiment 2; and (g) is an image of Embodiment 2. The overall morphology of Example 8 under low magnification SEM: (h) is an enlarged view of the β phase of Example 8; (i) is an enlarged view of the dendritic trunk γ′+γ two-phase structure of Example 8; (j) is the overall morphology of Example 9 under low magnification SEM; (k) is an enlarged view of the β phase of Example 9; (l) is an enlarged view of the dendritic trunk γ′+γ two-phase structure of Example 9; (m) is the overall morphology of Example 10 under low magnification SEM; (n) is an enlarged view of the β phase of Example 10; (o) is an enlarged view of the dendritic trunk γ′+γ two-phase structure of Example 10. Figure 8 These are the room temperature tensile stress-strain curves of Embodiment 2 and Embodiments 7-10 of the present invention, which describe a method for controlling the β phase in a weldable Ni3Al-based superalloy. Detailed Implementation
[0022] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.
[0023] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.
[0024] Example 1: A weldable Ni3Al-based superalloy contains the following components by weight percentage, as shown in Table 1.
[0025] Table 1. Components and weights of weldable Ni3Al-based superalloy
[0026] A method for controlling the volume fraction of the β phase in a weldable Ni3Al-based superalloy includes the following steps: S1. According to the Ni-Al-Fe phase diagram, as the Fe content increases, the volume fraction of the β phase increases accordingly. Therefore, it is determined that the theoretical basic amount of Fe added during the formation of the β phase is 9.3%.
[0027] S2. When the β phase is formed, the minimum amount of Fe added is theoretically set as the base value. Using the controlled variable method, the amount of Fe added is gradually increased and the proportion of Ni is reduced. One of the selected alloy compositions is 8.9% Al, 6.95% Cr, 1.18% Mo, 0.002% W, 0.077% C, 0.055% Mn, 10.7% Fe, 0.055% Si, 0.018% B, 0.45% Hf, and the remainder is Ni.
[0028] S3. Prepare and melt the raw materials according to the determined alloy ratio. The alloy melting process involves placing the prepared raw materials into a vacuum arc melting furnace and evacuating it to a vacuum level of 5×10⁻⁶. -3 After Pa, argon gas is introduced into the vacuum chamber until the chamber pressure reaches -0.05 MPa, and the raw material is subjected to arc melting. Each alloy ingot at each station is held for 1 minute after complete melting. To ensure alloy composition uniformity, the ingots are flipped and melted 10 times, with the melting temperature maintained between 1450℃. After melting, the alloy is cooled with a water-cooled copper mold, yielding a weldable Ni3Al-based high-temperature alloy with a β-phase volume fraction of 15.93%.
[0029] Example 2: A weldable Ni3Al-based superalloy contains the following components by weight percentage, as shown in Table 2.
[0030] Table 2. Components and weights of weldable Ni3Al-based superalloys
[0031] A method for controlling the volume fraction of the β phase in a weldable Ni3Al-based superalloy includes the following steps: S1. According to the Ni-Al-Cr phase diagram, it is clear that as the Cr content increases, the volume fraction of the β phase increases accordingly. Therefore, it is determined that the theoretical basic amount of Cr added during the formation of the β phase is 3.95%.
[0032] S2. When the β phase is formed, theoretically, the minimum amount of Cr added is set as the base value. Using the controlled variable method, the amount of Cr added is gradually increased and the proportion of Ni is decreased. One alloy composition is selected as 8.9% Al, 4.95% Cr, 1.18% Mo, 0.002% W, 0.077% C, 0.055% Mn, 11.7% Fe, 0.055% Si, 0.018% B, 0.45% Hf, and the remainder is Ni.
[0033] S3. Prepare and melt the raw materials according to the determined alloy ratio. The alloy melting process involves placing the prepared raw materials into a vacuum arc melting furnace and evacuating it to a vacuum level of 5×10⁻⁶. -3 After Pa, argon gas is introduced into the vacuum chamber until the chamber pressure reaches -0.05 MPa, and the raw material is subjected to arc melting. Each alloy ingot at each station is held for 1 minute after complete melting. To ensure alloy composition uniformity, the ingots are flipped and melted 10 times, with the melting temperature maintained between 1450℃. After melting, the alloy is cooled with a water-cooled copper mold, yielding a weldable Ni3Al-based high-temperature alloy with a β-phase volume fraction of 10.55%.
[0034] Example 3: The difference from Example 1 is that the weight of Fe in the alloy is adjusted to 9.70 by weight percentage.
[0035] Example 4: The difference from Example 1 is that the weight of Fe in the alloy is adjusted to 11.70 by weight percentage.
[0036] Example 5: The difference from Example 1 is that the weight of Fe in the alloy is adjusted to 12.70 by weight percentage.
[0037] Example 6: The difference from Example 1 is that the weight of Fe in the alloy is adjusted to 13.70 by weight percentage.
[0038] Example 7: The difference from Example 2 is that the weight of Cr in the alloy is adjusted to 5.95 by weight percentage.
[0039] Example 8: The difference from Example 2 is that the weight of Cr in the alloy is adjusted to 6.95 by weight percentage.
[0040] Example 9: The difference from Example 2 is that the weight of Cr in the alloy is adjusted to 7.95 by weight percentage.
[0041] Example 10: The difference from Example 2 is that the weight of Cr in the alloy is adjusted to 8.95 by weight percentage.
[0042] Experimental testing: 1. Microstructure characterization of multiphase Ni3Al-based alloys with different Fe contents.
[0043] The effect of Fe content (with Ni as the equilibrium element) on the microstructure and properties of multiphase Ni3Al-based alloys was investigated. Experimental alloy compositions were designed by adjusting the Fe content, in which alloying elements such as Cr, Mo, W, and Hf were used for solid solution strengthening of the γ and γ′ phases. A certain amount of B and C elements were also added to the experimental alloy compositions. B element was used to improve grain boundary brittleness, and C element was used to form carbides or interstitial elements for strengthening. The mass percentage of the alloy design is shown in Table 3.
[0044] Table 3. Design chemical composition of multiphase Ni3Al-based alloys with different Fe contents
[0045] The effect of Fe element content on the main phase composition (γ′, β, and γ phases) of the alloy was calculated using J Mat Pro software thermodynamic simulation. The resulting equilibrium phase diagram is shown below. Figure 1 As shown in Table 3, the results indicate that as the Fe content increases, the volume fraction of the γ′ phase gradually decreases, while the volume fractions of the γ and β phases gradually increase. When the mass percentage of Fe is 13.7%, the β phase begins to appear. This is because when a large amount of Fe is added to the alloy, Fe will replace Ni atoms, which will not only promote the precipitation of the γ phase but also promote the precipitation of the β phase in the alloy. Using the composition designed in Table 3, the alloy prepared by vacuum arc melting furnace exhibits a relatively smooth surface without obvious cracks, bubbles, shrinkage cavities, or oxidation or corrosion marks. Therefore, overall, the casting of this batch of experimental alloy ingots was successful and meets the experimental requirements.
[0046] After cutting and polishing the above alloy ingots, the corresponding microstructures of as-cast multiphase Ni3Al-based alloys with different Fe element contents are as follows: Figure 2As shown, the as-cast microstructure of the alloy is a typical irregular dendritic structure. The predominantly light gray area represents the dendritic trunk structure (γ′ phase and γ phase), while the irregularly distributed dark gray areas are the interdendritic structure (β phase). Furthermore, the crystal size decreases with increasing Fe content. ImageJ software analysis revealed that the volume fractions of the β phase in the alloy were 11.57 vol.%, 15.93 vol.%, 16.59 vol.%, 19.07 vol.%, and 21.11 vol.%, respectively, with average β phase widths of 7.33 μm, 5.64 μm, 4.35 μm, 4.31 μm, and 3.22 μm for different Fe contents. In summary, it can be observed that with increasing Fe content, the volume fraction of the β phase in the multiphase Ni3Al-based alloy gradually increases, while its size gradually decreases. Figure 1 The calculated simulation results for the β phase in multiphase Ni3Al-based alloys are consistent.
[0047] SEM microstructures of as-cast multiphase Ni3Al-based alloys with different Fe contents are shown below. Figure 4 As shown, it can be observed that with the increase of Fe content, the types of phases in the alloy do not change significantly, but the volume fraction and size of each phase change more significantly. Figure 3 (a) Figure 3 (d) Figure 3 (g) in Figure 3 (j) and Figure 3 In the figure (m), the overall morphology of the alloys with different Fe contents under low magnification SEM is shown. It can be seen that the as-cast microstructure of the alloys is a typical irregular dendritic structure, and there are also a large number of continuous blocky phases at the grain boundaries. The continuous blocky phases are Cr. 23 C6. Figure 3 (b) Figure 3 (e) Figure 4 (h) in Figure 3 (k) and Figure 3 In the diagram, (n) represents magnified images of the β phase in cast multiphase Ni3Al-based alloys with different Fe contents. It can be seen that there is a thin coating layer outside the β phase with thicknesses of 0.48 μm, 0.42 μm, 0.27 μm, 0.22 μm, and 0.19 μm, respectively. The coating layer is a γ′-envelope phase. Figure 3 (c) Figure 3 (f) in Figure 4 (i) Figure 3 (l) and Figure 3(o) is an enlarged view of the dendritic γ′+γ two-phase microstructure of as-cast multiphase Ni3Al-based alloys with different Fe contents. It can be seen that the γ′ phase in the dendritic γ′+γ two-phase microstructure has a high cubicity, with average sizes of 0.305 μm, 0.198 μm, 0.142 μm, 0.111 μm, and 0.087 μm, respectively. The widths of the γ′ channels between the γ′ phases are relatively narrow, at 0.024 μm, 0.030 μm, 0.032 μm, 0.0396 μm, and 0.055 μm, respectively. In summary, it can be observed that with increasing Fe content, the width of the γ′-envelope phase and the size of the γ′ phase gradually decrease, while the γ channels gradually increase. This is because, after reaching a certain Fe content, Fe can replace Ni, promoting the precipitation of the γ phase and reducing the size of the γ′ phase.
[0048] 2. Room temperature tensile properties of multiphase Ni3Al-based alloys with different Fe contents.
[0049] The room temperature tensile properties of multiphase Ni3Al-based alloys with different Fe contents were tested. The room temperature tensile stress-strain curves and tensile data are shown below. Figure 5 As shown in Table 4.
[0050] Table 4. Room temperature tensile properties of as-cast multiphase Ni3Al-based alloys with different Fe components
[0051] Depend on Figure 5 As shown in Table 4, the room temperature tensile curves of as-cast multiphase Ni3Al-based alloys with different Fe contents exhibit similar trends. The flow stress initially increases rapidly with increasing strain, then decreases rapidly after reaching a peak. With increasing Fe content, the tensile strength of the corresponding alloy samples first decreases and then increases, reaching a maximum of 843.7 MPa when the Fe content is 13.7%. The elongation of the samples first decreases, then increases, and finally decreases, reaching a maximum of 22.3% when the Cr content is 12.7%. This is because when the Fe content in Ni3Al is ≤15%, Fe mainly plays a solid solution strengthening role by replacing Ni and Al atoms in the γ' phase. Adding Fe can significantly improve the room temperature tensile strength of Ni3Al alloys.
[0052] In summary, the alloy of Example 1 has superior performance.
[0053] 3. Microstructure characterization of multiphase Ni3Al-based alloys with different Cr contents.
[0054] The effect of Cr content (Ni as the equilibrium element) on the microstructure and properties of multiphase Ni3Al-based alloys was investigated. Experimental alloy compositions were designed by adjusting the Cr content, in which alloying elements such as Fe, Mo, and W were used for solid solution strengthening of the γ and γ′ phases. A certain amount of B and C elements were added to the alloy. B was used to improve grain boundary brittleness, and C was used to form carbides or interstitial elements for strengthening. The atomic mass percentages of the alloy designs are shown in Table 5.
[0055] Table 5. Design chemical composition of multiphase Ni3Al-based alloys with different Cr contents
[0056] The effect of Cr component changes on the main phase composition (γ′, β, and γ phases) of the alloy was calculated using thermodynamic simulation with JMat Pro software. The equilibrium phase diagram is shown below. Figure 6 As shown in the figure, according to the calculation results, the volume fraction of the γ′ phase gradually decreases with the increase of Cr content, and the volume fraction of the γ phase first increases and then decreases. When the mass percentage of Cr is 10.7%, the β phase begins to precipitate, and its volume fraction increases with the increase of Cr content. This is because the increase of Cr content not only reduces the volume fraction of the γ′ phase, but also promotes the precipitation of a large amount of the β phase. In addition, Cr, as a γ phase forming element, is mainly dissolved in the γ phase, but the solid solubility of Cr in the γ phase is limited, and the solid solution strengthening effect is also weak. Therefore, the volume fraction of the γ phase first increases and then decreases, and finally tends to level off. Based on the design composition shown in Table 5, alloys were prepared using a vacuum arc melting furnace as shown in the figure. Figure 7 As shown, the surface of the experimental alloy ingots is relatively smooth, without obvious cracks, bubbles, shrinkage cavities, or traces of oxidation or corrosion. Therefore, overall, the casting of this batch of experimental alloy ingots was successful and meets the experimental requirements.
[0057] After the above alloy ingots are cut and polished, the corresponding OM microstructure of the multiphase Ni3Al-based alloy is as follows: Figure 6 As shown, the as-cast microstructure of the alloy is a typical irregular dendritic structure. The predominantly light gray area represents the dendritic trunk structure (γ′ phase and γ phase), while the irregularly distributed dark gray areas are the interdendritic structure (β phase). Furthermore, the crystal size decreases with increasing Cr content. ImageJ software analysis revealed that the volume fractions of the β phase in the alloy were 10.55 vol.%, 14.06 vol.%, 16.41 vol.%, 17.39 vol.%, and 20.20 vol.%, respectively. The average widths of the β phase with different Cr contents were 5.65 μm, 4.40 μm, 4.35 μm, 4.23 μm, and 4.15 μm, respectively. With increasing Cr content, the volume fraction of the β phase in the multiphase Ni3Al-based alloy gradually increases, while its size gradually decreases. Figure 6 The calculated simulation results for the β phase in multiphase Ni3Al-based alloys are consistent.
[0058] Microstructures of as-cast multiphase Ni3Al-based alloys with different Cr contents as shown in the corresponding SEM images. Figure 7 As shown, it can be observed that with the increase of Cr content, the types of phases in the alloy do not change significantly, but the quantity and size of each phase change more significantly. Figure 7 (a) Figure 7 (d) Figure 7 (g) in Figure 7 (j) and Figure 7 In the figure, (m) represents the overall SEM morphology of alloys with different Cr contents at low magnification. It can be seen that the as-cast microstructure of the alloys is a typical irregular dendritic structure, and there are also a large number of continuous blocky phases at the grain boundaries. According to the literature and the experimental results in the previous section, the continuous blocky phases are Cr. 23 C6. Figure 7 (b) Figure 7 (e) Figure 7 (h) in Figure 7 (k) and Figure 7 In the diagram, (n) represents magnified images of the β phase in cast multiphase Ni3Al-based alloys with different Fe contents. It can be seen that there is a thin coating layer outside the β phase with thicknesses of 0.66 μm, 0.48 μm, 0.27 μm, 0.24 μm, and 0.15 μm, respectively. Based on literature review and previous experimental results, it is known to be the γ′-envelope phase. Figure 7 (c) Figure 7 (f) in Figure 7 (i) Figure 7 (l) and Figure 7 (o) is an enlarged view of the dendritic γ′+γ two-phase structure of as-cast multiphase Ni3Al-based alloys with different Cr content. It can be seen that the γ′ phase in the dendritic γ′+γ two-phase structure has a high cubicity, which increases with the increase of Cr content. The average size of the cubic γ′ phase is 0.285 μm, 0.195 μm, 0.142 μm, 0.119 μm and 0.095 μm, respectively. The width of the γ channel phase between the γ′ phases is relatively narrow, which is 0.019 μm, 0.024 μm, 0.032 μm, 0.036 μm and 0.039 μm, respectively. In summary, with the increase of Cr content, the width of the coating layer (γ′-envelope phase) and the size of the γ′ phase gradually decrease, the γ channel gradually increases, and the cubicity of the cubic γ′ phase gradually increases. This is because Cr, as a γ phase forming element, is mainly dissolved in the γ phase, which has the effect of reducing the size of the γ′ phase and increasing the cubicity of the γ′ phase.
[0059] 4. Room temperature tensile properties of multiphase Ni3Al-based alloys with different Cr content.
[0060] The room temperature tensile properties of as-cast multiphase Ni3Al-based alloys with different Cr contents were tested. The room temperature tensile stress-strain curves and tensile data are shown below. Figure 8 As shown in Table 6.
[0061] Table 6. Room temperature tensile properties of as-cast multiphase Ni3Al-based alloys with different Cr components
[0062] Depend on Figure 8 As shown in Table 6, the room temperature tensile curves of as-cast multiphase Ni3Al-based alloys with different Cr contents exhibit similar trends. The flow stress initially increases rapidly with increasing strain, then decreases rapidly after reaching a peak. With increasing Cr content, the tensile strength of the multiphase Ni3Al-based alloy samples with different Cr contents first increases and then decreases, reaching a maximum of 800.2 MPa at a Cr content of 7.95%. The elongation of the samples also shows a similar trend, reaching a maximum of 26.8% at a Cr content of 5.95%. This is because the addition of higher Cr content in the Ni3Al-based high-temperature alloy promotes the precipitation of the β phase, as well as the precipitation of spheroidal α-Cr precipitates of different sizes within the β phase. Furthermore, the precipitated α-Cr phase can improve the toughness and ductility of the β phase within the alloy to a certain extent. In conclusion, the optimal composition for multiphase Ni3Al-based alloys with different Fe and Cr components is 11.70Fe-5.95Cr.
[0063] Therefore, the present invention adopts the above-mentioned method for controlling the β phase in a weldable Ni-Al system high-temperature alloy. By adjusting the Fe element content and the Cr element content, the volume fraction of the β phase in the weldable Ni3Al-based high-temperature alloy is controlled, and weldable Ni3Al-based high-temperature alloys with different volume fractions of β phase are obtained, thereby significantly improving the mechanical properties of the weldable Ni3Al-based high-temperature alloy.
[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.
Claims
1. A method for controlling the β phase in a weldable Ni3Al-based superalloy, characterized in that, Includes the following steps: S1. Based on the Ni-Al-Fe ternary phase diagram, clarify the relationship between the Fe element content and the volume fraction of the β phase, and obtain the theoretical basic amount of Fe element added when the β phase is formed. S2. When the β phase is generated, theoretically, the minimum amount of Fe added should be set as the base value. Using the controlled variable method, the amount of Fe added should be gradually increased and the proportion of Ni should be reduced. Alloy ratios with different Fe contents should be selected. S3. Based on the alloy ratio obtained in S2, batch and smelt the alloys to obtain weldable Ni3Al-based high-temperature alloys with different β phase volume fractions. S4. Based on the Ni-Al-Cr ternary phase diagram, clarify the relationship between the Cr element content and the volume fraction of the β phase, and obtain the theoretical basic amount of Cr element added when the β phase is formed. S5. Select one of the proportions in S2 as the base value, and use the controlled variable method to gradually increase the amount of Cr element added and decrease the proportion of Ni element, and select alloy proportions with different Cr element contents. S6. Based on the alloy ratio obtained in S5, batch and smelt the alloys to obtain weldable Ni3Al-based high-temperature alloys with different β phase volume fractions.
2. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S1, the relationship between the Fe element content and the volume fraction of the β phase in the alloy is as follows: as the Fe element increases, the volume fraction of the β phase in the alloy increases accordingly.
3. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S1, when the β phase is formed, theoretically the minimum mass percentage of Fe added is 8-10%.
4. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S2, five alloy ratios with different Fe element contents were selected. The difference in the mass percentage of Fe element content among the five alloy ratios with different Fe element contents was 0-2%. The alloy comprises the following components by weight percentage: 8-9% Al, 6-7% Cr, 0-2% Mo, 0-0.002% W, 0.01-0.1% C, 0.055% Mn, 0.009% Ti, 8-14% Fe, 0.055% Si, 0.018% B, 0.5-1.5% Hf, with the remainder being Ni.
5. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S3, the smelting is as follows: Place the prepared raw materials into a vacuum arc melting furnace and evacuate to a vacuum level of 5×10⁻⁶. -3 After Pa, argon gas is introduced into the vacuum chamber until the chamber pressure is -0.05MPa, and the raw materials are subjected to electric arc melting. After the alloy ingots at each station are completely melted, they are held for 0-10 minutes, then flipped for melting. The melting temperature is maintained between 1300-1500℃, and the materials are cooled by water after melting.
6. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S3, different The volume fractions of the β phase in the weldable Ni3Al-based superalloys are 10-12%, 14-16%, 16.5-17.5%, 18-20%, and 21-23%, respectively.
7. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S4, the relationship between the Cr content and the volume fraction of the β phase in the alloy is as follows: as the Cr content increases, the volume fraction of the β phase in the alloy increases accordingly.
8. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S4, when determining the formation of the β phase, the theoretical minimum mass percentage of Cr element added is 3.5-5%.
9. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S5, five alloy ratios with different Cr content were selected. The mass ratio of Cr content in each of the five alloy ratios with different Cr content differed by 0-2%. The alloy comprises the following components by weight percentage: 8-9% Al, 4-9% Cr, 0-2% Mo, 0-0.002% W, 0.01-0.1% C, 0.055% Mn, 0.009% Ti, 11-12% Fe, 0.055% Si, 0.018% B, 0.5-1.5% Hf, with the remainder being Ni.
10. The method for controlling the β phase in a weldable Ni3Al-based superalloy according to claim 1, characterized in that, In S6, different The β phase of the weldable Ni3Al-based superalloys by volume fraction is 9-11%, 12.5-14.5%, 15-16.5%, 17-19%, and 20-22%, respectively.