Fe-Al-Ta intermetallic compound alloy and preparation method thereof

Abstract

The invention discloses a Fe-Al-Ta intermetallic compound alloy and a preparation method thereof, and belongs to the technical field of Fe-Al intermetallic compound materials, the mass percent of Ta element in the Fe-Al-Ta intermetallic compound alloy is 5%-25%, a matrix of the alloy is Fe3Al nanocrystalline of a body-centered cubic structure, and a second phase is Fe2Ta. A base body of the alloy is a Fe3Al nanocrystalline structure of a body-centered cubic structure, a second phase is Fe2Ta, along with the change of the Ta element content, the form of the second phase is converted into a stripe-shaped and spherical eutectic structure from a disorderly-distributed needle-shaped structure, then the second phase is converted into a uniformly-distributed irregular shape, and the size of the second phase is greatly increased. The compressive strength of the Fe-Al-Ta intermetallic compound alloy prepared through the method can reach 1500 MPa, and the plasticity and toughness are also remarkably improved while the strength is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of Fe-Al series intermetallic compound materials, and in particular to a Fe-Al-Ta intermetallic compound alloy and a preparation method thereof. Background Art

[0002] Intermetallic compound materials have high specific strength, specific stiffness, excellent oxidation resistance, corrosion resistance, and outstanding high-temperature mechanical properties. They are widely used in aerospace, transportation, and other fields. In particular, Fe-Al intermetallic compound materials are expected to serve as a new generation of structural materials to replace nickel-based high-temperature alloys and nickel-containing stainless steel. However, due to their poor ductility and toughness at room temperature and their susceptibility to brittle fracture, they are difficult to machine and form. Brittle fracture is prone to catastrophic damage without warning in actual engineering applications. Therefore, how to improve the room-temperature ductility and toughness of Fe-Al intermetallic compounds and promote their early practical application in the field of engineering materials is an important topic that needs to be studied urgently. Summary of the Invention

[0003] The present invention provides an Fe-Al-Ta intermetallic compound alloy and a preparation method thereof, which effectively solves the technical problem that existing Fe-Al intermetallic compound materials have poor plasticity and toughness at room temperature and are prone to brittle fracture. The present invention utilizes iron oxide and aluminum powder to generate a thermite reaction to release heat to smelt the alloy, thereby obtaining an Fe-Al-Ta alloy material in which a relatively large nanocrystalline matrix and a micron-sized second phase coexist. The compressive strength of the Fe-Al-Ta intermetallic compound alloy prepared by the present invention can reach 1500 MPa, and the plasticity and toughness are also improved.

[0004] The first object of the present invention is to provide an Fe-Al-Ta intermetallic compound alloy, wherein the mass percentage of the Ta element in the alloy is 5% to 25%, the mass percentage of the Fe element is 64.62% to 81.85%, and the mass percentage of the Al element is 10.38% to 13.15%, totaling 100%.

[0005] The alloy comprises a matrix and a second phase dispersed in the matrix, the matrix is Fe3Al nanocrystal with a body-centered cubic structure, and the second phase is Fe2Ta.

[0006] As a preferred embodiment, the grain size of the Fe3Al nanocrystals is 10nm~60nm.

[0007] A second object of the present invention is to provide a method for preparing the above-mentioned Fe-Al-Ta intermetallic compound alloy, comprising the following steps: Iron oxide powder, aluminum powder and tantalum powder are ball-milled to obtain metal powder.

[0008] The metal powder is pressed into a green block, and the green block and an igniter are heated to 350° C. to 400° C. in a protective atmosphere. The igniter burns to excite the metal powder to generate a thermite reaction, thereby obtaining a Fe-Al-Ta intermetallic compound alloy.

[0009] As a preferred embodiment, in the Fe-Al-Ta intermetallic compound alloy, the mass percentage of Ta element is 5% to 25%, the mass percentage of Fe element is 64.62% to 81.85%, and the mass percentage of Al element is 10.38% to 64.62%, which is 100% in total.

[0010] As a preferred embodiment, the ignition agent accounts for 0.1% to 0.2% by mass of the metal powder.

[0011] As a preferred embodiment, a protective gas of 0.5MPa~1MPa is first introduced into the green block and the igniter, heated to 80℃~150℃, ventilated, and then a protective gas of 3MPa~6MPa is introduced. The green block and the igniter are heated to 350℃~400℃, and the igniter burns to excite the metal powder to produce a thermite reaction for 3h~6h.

[0012] As a preferred embodiment, the ball milling is as follows: according to a ball-to-material ratio of 1:2, ball milling beads are added to the iron oxide powder, aluminum powder and tantalum powder, and the ball milling is carried out at a speed of 150r / min~200r / min for 5h~8h. During the ball milling process, the ball milling is stopped for 5min~10min after 1h~2h.

[0013] As a preferred embodiment, the pressing is: pressing at 30 MPa to 60 MPa for 3 min to 10 min.

[0014] As a preferred embodiment, the particle size of the tantalum powder is 45 μm, and the purity of the iron oxide powder, aluminum powder and tantalum powder are 99.9%, 99.9% and 99.999% respectively.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides an Fe-Al-Ta intermetallic compound alloy, wherein the mass percentage of Ta in the alloy is 5% to 25%. The alloy comprises a matrix of Fe3Al nanocrystals with a body-centered cubic structure and a secondary phase of Fe2Ta. The matrix of the alloy, a body-centered cubic Fe3Al nanocrystal structure, has fine grains that increase grain boundary density, effectively hindering dislocation slip and improving the material's strength. Furthermore, the fine grains result in smaller strain differences within the grains and near the grain boundaries, resulting in more uniform deformation. This reduces the chance of cracking due to stress concentration, allowing the material to withstand greater deformation before fracture, thereby improving its plastic toughness. The dispersed second phase of Fe2Ta compensates for the nanocrystals' limited dislocation storage and weak strain hardening capacity, enhancing resistance to non-uniform deformation while also coordinating the plastic deformation process. As the Ta content changes, the morphology of the secondary phase changes from a disordered, needle-like structure to a eutectic structure with stripes and spheres, and then to a uniformly distributed, irregular shape with a significant increase in size. The compressive strength of the Fe-Al-Ta intermetallic compound alloy prepared by the present invention can reach 1500 MPa, and while the strength is improved, the plastic toughness is also significantly increased.

[0016] The present invention utilizes the heat released by the thermite reaction between iron oxide and aluminum powder to smelt the alloy. The large amount of heat released by the reaction causes the molten metal powder to be superheated. The Ta element fully diffuses in the liquid phase and interacts with Fe atoms to form nuclei and grow into the Fe2Ta phase. The iron oxide is then reduced by the aluminum powder to form Fe3Al and Al2O3. Since the byproduct Al2O3 has a low density and a high melting point, it floats to the surface of the superheated metal liquid and solidifies before the alloy. After complete cooling, the Al2O3 layer is knocked off to obtain an Fe-Al-Ta intermetallic compound alloy with a nanocrystalline matrix and a micron-sized secondary phase. The material can achieve a compressive strength of 1500MPa and also has improved plasticity and toughness.

[0017] The Vickers hardness, room temperature compression performance and three-point bending test of the Fe-Al-Ta intermetallic compound alloy prepared by the present invention were tested. The test conditions for Vickers hardness are: load 198g, holding time 15s. Compression specimen requirements: cylindrical with a diameter of 5mm and a height of 5mm. The indenter displacement speed is 0.3mm / min. After testing, the Vickers hardness value of the Fe-Al-Ta intermetallic compound alloy is 400HV0.1~500HV0.1, and the compressive strength is 1000MPa~1500MPa. The three-point bending specimen requirements: size 30mm×6mm×3mm, a crack groove with a size of 0.2mm×3mm is cut at the center of the specimen. The indenter loading speed is 0.05mm / min, and the specimen span is set to 24mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is the XRD pattern of the Fe-Al-Ta intermetallic compound alloy prepared in the present invention, wherein 0.wt% Ta is Comparative Example 1, 5.wt% Ta is Example 1, 10.wt% Ta is Example 2, 15.wt% Ta is Example 3, 20.wt% Ta is Example 4, and 25.wt% Ta is Example 5.

[0019] Figure 2 Figure 3 shows the SEM microstructure of the Fe-Al-Ta intermetallic compound alloy prepared in the present invention, wherein (a) is the SEM image of the sample with 5 wt% Ta content, (b) is the SEM image of the sample with 10 wt% Ta content, (c) is the SEM image of the sample with 15 wt% Ta content, (d) is the SEM image of the sample with 20 wt% Ta content, and (e) is the SEM image of the sample with 25 wt% Ta content.

[0020] Figure 3 This is the compressive true stress and true strain diagram of the Fe-Al-Ta intermetallic compound alloy prepared in the present invention, wherein 0.wt% Ta is Comparative Example 1, 5.wt% Ta is Example 1, 10.wt% Ta is Example 2, 15.wt% Ta is Example 3, 20.wt% Ta is Example 4, and 25.wt% Ta is Example 5.

[0021] Figure 4 is the yield strength σ of the Fe-Al-Ta intermetallic compound alloy prepared in the present invention 0.2 Figure, wherein 0.wt% Ta is comparative example 1, 5.wt% Ta is example 1, 10.wt% Ta is example 2, 15.wt% Ta is example 3, 20.wt% Ta is example 4, and 25.wt% Ta is example 5.

[0022] Figure 5 This is a Vickers hardness diagram of the Fe-Al-Ta intermetallic compound alloy material prepared in the present invention, wherein 0.wt% Ta is Comparative Example 1, 5.wt% Ta is Example 1, 10.wt% Ta is Example 2, 15.wt% Ta is Example 3, 20.wt% Ta is Example 4, and 25.wt% Ta is Example 5.

[0023] Figure 6 These are crack growth diagrams of the Fe-Al-Ta intermetallic compound alloy material prepared in the present invention, wherein (a), (b), and (c) are from Example 3, and (d), (e), and (f) are from Example 4.

[0024] Figure 7These are fracture morphologies of the Fe-Al-Ta intermetallic compound alloy material prepared in the present invention, and (a), (b), (c), and (d) are SEM images of Example 3 at different magnifications.

[0025] Figure 8 These are fracture morphologies of the Fe-Al-Ta intermetallic compound alloy material prepared in the present invention, and (a), (b), (c), and (d) are SEM images of Example 4 at different magnifications. DETAILED DESCRIPTION

[0026] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention is further described below with reference to specific examples, but the examples are not intended to limit the present invention. The following experimental and detection methods are conventional methods unless otherwise specified; the reagents and raw materials are commercially available unless otherwise specified.

[0027] Existing Fe-Al intermetallic compound materials have poor ductility and toughness at room temperature, making them prone to brittle fracture. This makes them difficult to machine and form, and brittle fracture can easily lead to catastrophic, unpredictable damage in practical engineering applications. To address these technical issues, the present invention provides an Fe-Al-Ta intermetallic compound alloy and a method for preparing the same.

[0028] The technical solution of the present invention is described in detail below.

[0029] The present invention first provides a Fe-Al-Ta intermetallic compound alloy, in which the mass percentage of the Ta element in the alloy is 5% to 25%, the mass percentage of the Fe element is 64.62% to 81.85%, and the mass percentage of the Al element is 10.38% to 13.15%, which is 100% in total.

[0030] The alloy comprises a matrix and a second phase dispersed in the matrix, the matrix is Fe3Al nanocrystal with a body-centered cubic structure, and the second phase is Fe2Ta.

[0031] In the above-mentioned technical solution, the Fe3Al nanocrystalline structure, with its body-centered cubic structure, boasts fine grains that increase grain boundary density, effectively hindering dislocation slip and enhancing the material's strength. Furthermore, the small strain differences between the grain interior and near the grain boundaries are minimal, resulting in more uniform deformation. This reduces the chance of cracking due to stress concentration, allowing the material to withstand greater deformation before fracture, improving its plastic toughness. The dispersed second phase, Fe2Ta, compensates for the nanocrystalline's limited dislocation storage and weak strain hardening capacity, enhancing resistance to non-uniform deformation while also harmonizing the plastic deformation process.

[0032] The present invention also provides a method for preparing the above-mentioned Fe-Al-Ta intermetallic compound alloy, comprising the following steps: Iron oxide powder, aluminum powder and tantalum powder are ball-milled to obtain metal powder.

[0033] The metal powder is pressed into a green block, and the green block and an igniter are heated to 350° C. to 400° C. in a protective atmosphere. The igniter burns to excite the metal powder to generate a thermite reaction, thereby obtaining a Fe-Al-Ta intermetallic compound alloy.

[0034] To further improve the plasticity and toughness of the Fe-Al-Ta intermetallic compound, the Fe-Al-Ta intermetallic compound alloy comprises a Ta element percentage of 5% to 25%, a Fe element percentage of 64.62% to 81.85%, and an Al element percentage of 10.38% to 13.15%, totaling 100%. When Fe accounts for 81.85%, Al accounts for 13.15%, and Ta accounts for 5%, due to the low Ta content and large compositional supercooling, the Fe2Ta phase grows in a dendritic manner to form needles. This second phase morphology hinders dislocation movement and microcrack propagation, thereby improving strength and toughness. However, due to anisotropy and uneven distribution, the mechanical properties of the material vary in local areas. In addition, the tips of the needle-shaped second phase may form crack initiation points, resulting in reduced strength and toughness of the material. When Fe accounts for 77.54%, Al accounts for 12.46%, and Ta accounts for 10%, the Fe2Ta phase forms a eutectic stripe-like second phase with distinct eutectic cluster boundaries. The fine interlamellar spacing increases the interphase area, hindering dislocation motion and thus improving strength. Eutectic lamellae facilitate crack deflection and branching during propagation, dissipating more energy and enhancing toughness. When Fe accounts for 73.23%, Al accounts for 11.77%, and Ta accounts for 15%, the eutectic clusters further expand and interconnect. The connected eutectic clusters form a network-like distribution uniformly within the matrix, further enhancing the reinforcing effect of the second phase and homogenizing the plastic deformation process. The eutectic cluster boundaries are arc-shaped, reducing the influence of crack initiation at low-angle phase interfaces. When Fe accounts for 68.92%, Al accounts for 11.08%, and Ta accounts for 20%, the stripe-like second phase within the eutectic clusters transforms into fine spherical shapes. Grain boundary sliding in the nanocrystalline matrix and dislocation motion of the micron-sized second phase contribute to crack deflection. The synergistic effect of these mechanisms contributes to improved overall mechanical properties. When Fe accounts for 64.62%, Al accounts for 10.38%, and Ta accounts for 25%, the Ta content is too high, exceeding the eutectic composition point of the Fe-Al-Ta alloy, and the eutectic reaction no longer occurs. The size of the formed Fe2Ta second phase increases, and the precipitation strengthening effect increases the strength of the material. However, the appearance of sharp phase interfaces with small angles makes the matrix more easily torn during plastic deformation, resulting in a decrease in plastic toughness. In short, by changing the alloy component ratio, when the Fe2Ta second phase exists in a eutectic structure, especially a spherical eutectic structure, the synergistic improvement effect on the strength and toughness of the material is more significant.

[0035] To produce an alloy with the desired properties, the igniter accounts for 0.1% to 0.2% by mass of the metal powder. Elements such as sulfur, potassium, and nitrogen contained in the igniter can easily form defects in the alloy, reducing material properties. Lower igniter contents may not effectively stimulate the thermite reaction, preventing the desired alloy from being produced.

[0036] It should be noted that a protective gas of 0.5 MPa to 1 MPa is first introduced into the green block and the igniter, heated to 80°C to 150°C, ventilated, and then a protective gas of 3 MPa to 6 MPa is introduced, and the green block and the igniter are heated to 350°C to 400°C. The combustion of the igniter excites the metal powder to produce a thermite reaction for 3h to 6h.

[0037] To ensure thorough mixing of the raw materials, the ball milling process involves adding ball milling beads to the iron oxide powder, aluminum powder, and tantalum powder at a ball-to-material ratio of 1:2, and milling at a speed of 150 to 200 rpm for 5 to 8 hours. After 1 to 2 hours of ball milling, pause for 5 to 10 minutes.

[0038] To further enhance the alloy's strength, the pressing process is performed at 30-60 MPa for 3-10 minutes. Low pressing pressures and short pressing times can result in loose compaction of the pressed billet, causing the introduced shielding gas to disperse the metal powder, preventing the desired alloy from being obtained. High pressing pressures and long pressing times can reduce the activity of the metal powder, potentially preventing or interrupting the thermite self-propagating reaction.

[0039] It should be noted that the particle size of the tantalum powder is micron-level, and the purity of the iron oxide powder, aluminum powder and tantalum powder are 99.9%, 99.9% and 99.999% respectively.

[0040] The present invention will be described in detail below through the following examples and comparative examples.

[0041] Example 1 A method for preparing a Fe-Al-Ta intermetallic compound alloy comprises the following steps: Weigh 1004.9g of iron oxide powder, 452.205g of aluminum powder, and 42.972g of tantalum powder, divide the weighed powders into 6 equal parts and put them into ball mills respectively. Add about 125g of ball milling beads to each ball mill and stir evenly. Place the ball mill in a planetary ball mill and mill for 6h. Then sieve the mixed reaction materials with a sieve and put them into a stainless steel mold. Use a hydraulic press to keep the pressure at 50MPa for 5min. Then stack the pressed green blocks in a copper crucible and place 2g of induction on top of the green blocks. The copper crucible containing the embryo block and the ignition agent is placed in the reaction vessel and 1MPa argon is introduced. When the temperature rises to 120°C, the outlet valve is opened to completely discharge the gas in the reaction vessel to achieve the purpose of ventilation, and then 4.5MPa argon is introduced again. When the temperature rises to 262°C, the reaction materials react with each other. At this time, the gas pressure reaches 10MPa. After the reaction is complete, the heating equipment is turned off, and after cooling to room temperature with the furnace, it is taken out and the aluminum oxide impurities are knocked out to obtain the Fe-Al-Ta intermetallic compound alloy.

[0042] X-ray diffraction analysis shows that the Fe-Al-Ta intermetallic compound alloy prepared in Example 1 has a body-centered cubic Fe3Al matrix and a close-packed hexagonal Fe2Ta reinforcement phase. Scanning electron microscopy results show that the Fe2Ta reinforcement phase is irregularly distributed in the matrix in the form of strips and particles. The Vickers hardness of the material is 452.6HV0.1, and the yield strength σ 0.2 It is 717MPa.

[0043] Example 2 A method for preparing a Fe-Al-Ta intermetallic compound alloy comprises the following steps: Weigh 973.28g of iron oxide powder, 437.98g of aluminum powder, and 87.864g of tantalum powder, divide the weighed powders into 6 equal parts and put them into ball mills respectively. Add about 125g of ball milling beads to each ball mill and stir evenly. Put the ball mill into a planetary ball mill and mill for 6h. Then sieve the mixed reaction materials with a sieve and put them into a stainless steel mold. Use a hydraulic press to keep the pressure at 50MPa for 5min. Then stack the pressed green blocks in a copper crucible, place 2g of igniter on the top of the green blocks, and A copper crucible containing the embryonic block and the ignition agent is placed in a reaction vessel and 1 MPa argon is introduced. When the temperature rises to 120°C, the outlet valve is opened to completely discharge the gas in the reaction vessel to achieve the purpose of ventilation. Then 4.5 MPa argon is re-introduced. When the temperature rises to 278.5°C, a reaction occurs between the reactants. At this time, the gas pressure reaches 10.1 MPa. After the reaction is complete, the heating equipment is turned off, and after cooling to room temperature with the furnace, it is taken out and the alumina impurities are knocked out to obtain the Fe-Al-Ta intermetallic compound alloy.

[0044] X-ray diffraction analysis shows that the Fe-Al-Ta intermetallic compound alloy prepared in Example 2 has a body-centered cubic Fe3Al matrix and a close-packed hexagonal Fe2Ta reinforcement phase. Scanning electron microscopy results show that the Fe2Ta reinforcement phase is a striped eutectic structure with obvious eutectic cell boundaries. The Vickers hardness of the material is 437.1HV0.1, and the yield strength σ 0.2 It is 854MPa.

[0045] Example 3 A method for preparing a Fe-Al-Ta intermetallic compound alloy comprises the following steps: Weigh 941.287g of iron oxide powder, 423.624g of aluminum powder, and 134.974g of tantalum powder, divide the weighed powders into 6 equal parts and put them into ball mills respectively. Add about 125g of ball milling beads to each ball mill and stir evenly. Place the ball mill in a planetary ball mill and mill for 6h. Then sieve the mixed reaction materials with a sieve and put them into a stainless steel mold. Use a hydraulic press to keep the pressure at 50MPa for 5min. Then stack the pressed green blocks in a copper crucible and place 2g of ignition on the top of the green blocks. The copper crucible containing the embryo block and the ignition agent is placed in the reaction vessel and 1MPa argon is introduced. When the temperature rises to 120°C, the outlet valve is opened to completely discharge the gas in the reaction vessel to achieve the purpose of ventilation. Then 4.5MPa argon is introduced again. When the temperature rises to 284°C, the reactants react with each other. At this time, the gas pressure reaches 10.6MPa. After the reaction is complete, the heating equipment is turned off, and after cooling to room temperature with the furnace, it is taken out and the aluminum oxide impurities are knocked out to obtain the Fe-Al-Ta intermetallic compound alloy.

[0046] X-ray diffraction analysis shows that the Fe-Al-Ta intermetallic compound alloy prepared in Example 3 has a Fe3Al matrix with a bcc structure and a Fe2Ta reinforcement phase with an hcp structure. Scanning electron microscopy results show that the eutectic cells have further expanded and are evenly distributed in a network inside the matrix. The eutectic cells have a striped structure. The Vickers hardness of the material is 462.2HV0.1, and the yield strength σ 0.2 It is 926MPa.

[0047] Example 4 A method for preparing a Fe-Al-Ta intermetallic compound alloy comprises the following steps: Weigh 907.536g of iron oxide powder, 408.35g of aluminum powder, and 184.318g of tantalum powder, divide the weighed powder into 6 equal parts and put them into ball mills respectively. Add about 125g of ball milling beads to each ball mill and stir evenly. Place the ball mill in a planetary ball mill and ball mill for 6 hours. Then, sieve the mixed reaction materials with a sieve and put them into a stainless steel mold. Use a hydraulic press to maintain a pressure of 50MPa for 5 minutes. Then, stack the pressed green blocks in a copper crucible and place 2g of igniter on the top of the green blocks. A copper crucible containing the embryonic block and the ignition agent is placed in a reaction vessel and 1 MPa argon is introduced. When the temperature rises to 120°C, the outlet valve is opened to completely discharge the gas in the reaction vessel to achieve the purpose of ventilation. Then 4.5 MPa argon is re-introduced. When the temperature rises to 272°C, a reaction occurs between the reactants. At this time, the gas pressure reaches 9.7 MPa. After the reaction is complete, the heating equipment is turned off, and the crucible is cooled to room temperature with the furnace. Then, the crucible is taken out and the aluminum oxide impurities are knocked out to obtain a Fe-Al-Ta intermetallic compound alloy.

[0048] X-ray diffraction analysis showed that the Fe-Al-Ta intermetallic compound alloy prepared in Example 4 has a Fe3Al matrix with a bcc structure and a Fe2Ta reinforcement phase with an hcp structure. Scanning electron microscopy results showed that the eutectic cells almost completely covered the matrix, and the eutectic structure changed from stripes to spherical and distributed densely and evenly. The diameter of the spherical particles was about 1 μm. The Vickers hardness of the material was 483.4 HV0.1, and the yield strength σ 0.2 It is 1192 MPa.

[0049] Example 5 A method for preparing a Fe-Al-Ta intermetallic compound alloy comprises the following steps: Weigh 871.45g of iron oxide powder, 392.15g of aluminum powder, and 235.98g of tantalum powder. Divide the weighed powders into 6 equal parts and place them in ball mills. Add about 125g of ball milling beads to each ball mill and stir evenly. Place the ball mill in a planetary ball mill and mill for 6h. Then sieve the mixed reaction materials with a sieve and place them in a stainless steel mold. Use a hydraulic press to maintain a pressure of 50MPa for 5min. Then stack the pressed green blocks in a copper crucible and place 2g of igniter on top of the green blocks. A copper crucible containing the embryonic block and the ignition agent is placed in a reaction vessel and 1 MPa argon is introduced. When the temperature rises to 120°C, the outlet valve is opened to completely discharge the gas in the reaction vessel to achieve the purpose of ventilation. Then 4.5 MPa argon is re-introduced. When the temperature rises to 245°C, a reaction occurs between the reactants. At this time, the gas pressure reaches 8.3 MPa. After the reaction is complete, the heating equipment is turned off, and after cooling to room temperature with the furnace, the crucible is taken out and the aluminum oxide impurities are knocked out to obtain a Fe-Al-Ta intermetallic compound alloy.

[0050] X-ray diffraction analysis shows that the Fe-Al-Ta intermetallic compound alloy prepared in Example 4 has a Fe3Al matrix with a bcc structure and a Fe2Ta reinforcement phase with an hcp structure. Scanning electron microscopy results show that the morphology of the Fe2Ta reinforcement phase has changed again, with a significantly larger size and an irregular shape, and the eutectic structure has disappeared. The Vickers hardness of the material is 465.5 HV0.1, and the yield strength σ 0.2 It is 1175MPa.

[0051] In order to further illustrate the effect of the present invention, the present invention also provides a comparative example, as follows: Comparative Example 1 Compared with Example 1, the difference is that Ta powder is not added.

[0052] A method for preparing an Fe-Al intermetallic compound alloy comprises the following steps: Weigh 1034.48 g of iron oxide powder and 465.52 g of aluminum powder, divide the weighed powder into 6 equal parts and put them into ball mills respectively. Add about 125 g of ball milling beads to each ball mill and stir evenly. Place the ball mill in a planetary ball mill and ball mill for 6 hours. Then, sieve the mixed reaction materials with a sieve and put them into a stainless steel mold. Use a hydraulic press to maintain a pressure of 50 MPa for 5 minutes. Then, stack the pressed green blocks in a copper crucible and place 2 g of igniter on the top of the green blocks. A copper crucible containing the embryonic block and the ignition agent is placed in a reaction vessel and 1 MPa argon is introduced. When the temperature rises to 120°C, the outlet valve is opened to completely discharge the gas in the reaction vessel to achieve the purpose of ventilation. Then 4.5 MPa argon is re-introduced. When the temperature rises to 286°C, a reaction occurs between the reactants. At this time, the gas pressure reaches 10.0 MPa. After the reaction is complete, the heating equipment is turned off, and after cooling to room temperature with the furnace, the crucible is taken out and the aluminum oxide impurities are knocked out to obtain the Fe-Al intermetallic compound alloy.

[0053] The properties of the Fe-Al-Ta intermetallic compound alloys prepared in Examples 1 to 5 and the Fe-Al intermetallic compound alloy provided in Comparative Example 1 were tested, and the results are as follows.

[0054] Figure 1 The XRD pattern of the Fe-Al-Ta intermetallic compound alloy prepared in the present invention, wherein 0.wt% Ta is comparative example 1, 5.wt% Ta is example 1, 10.wt% Ta is example 2, 15.wt% Ta is example 3, 20.wt% Ta is example 4, and 25.wt% Ta is example 5. Figure 1 It can be seen that the Ta element mainly precipitates at the grain boundaries to form Fe2Ta phase, and has no effect on the matrix organization and crystal structure of Fe3Al nanocrystalline.

[0055] Figure 2 The SEM microstructure of the Fe-Al-Ta intermetallic compound alloy prepared by the present invention, wherein (a) is the SEM image of the sample with 5 wt% Ta content, (b) is the SEM image of the sample with 10 wt% Ta content, (c) is the SEM image of the sample with 15 wt% Ta content, (d) is the SEM image of the sample with 20 wt% Ta content, and (e) is the SEM image of the sample with 25 wt% Ta content. Figure 2 It can be seen that with the change of Ta content, the morphology of the second phase has undergone a significant change, among which the synergistic improvement effect of the fine spherical second phase on the material strength and toughness at 20.wt% Ta content is the most significant.

[0056] Figure 3The true stress and true strain diagram of the Fe-Al-Ta intermetallic compound alloy prepared by the present invention, wherein 0.wt% Ta is comparative example 1, 5.wt% Ta is example 1, 10.wt% Ta is example 2, 15.wt% Ta is example 3, 20.wt% Ta is example 4, and 25.wt% Ta is example 5. Figure 3 It can be seen that the addition of Ta improves the strength of the Fe-Al intermetallic alloy to varying degrees. The compressive strength of the material increases with increasing Ta content, but decreases at a Ta content of 25%, which is related to the disappearance of the eutectic structure. In terms of plasticity and toughness, the deformation capacity of the material increases to varying degrees at 5% to 20% Ta content. Samples with 10%, 15%, and 20% Ta content maintain high strength without failure even after a true strain of 50%. At 25% Ta content, the plasticity and toughness of the material decreases significantly, with instability and failure occurring at a true strain of 15%. This indicates that the large, irregularly shaped Fe2Ta second phase is detrimental to the plasticity and toughness of the Fe-Al intermetallic alloy.

[0057] Figure 4 is the yield strength σ of the Fe-Al-Ta intermetallic compound alloy prepared in the present invention 0.2 Figure, where 0.wt% Ta is comparative example 1, 5.wt% Ta is example 1, 10.wt% Ta is example 2, 15.wt% Ta is example 3, 20.wt% Ta is example 4, and 25.wt% Ta is example 5. Figure 4 It can be seen that the yield strength of samples with different compositions shows an upward trend with the increase of Ta content. Compared with the 0.wt%Ta comparative example 1, the yield strength σ 0.2 The highest increase was 95.4%.

[0058] Figure 5 The Vickers hardness diagram of the Fe-Al-Ta intermetallic compound alloy material prepared by the present invention, wherein 0.wt% Ta is comparative example 1, 5.wt% Ta is example 1, 10.wt% Ta is example 2, 15.wt% Ta is example 3, 20.wt% Ta is example 4, and 25.wt% Ta is example 5. Figure 5 It can be seen that the addition of Ta improves the Vickers hardness of the material.

[0059] Figure 6Figures (a), (b), and (c) show SEM images of crack propagation in a 15 wt% Ta-content sample during a bending test. The eutectic lamellar structure hinders crack propagation, causing the crack tip to ultimately stop at the eutectic cell boundary, indicating that the presence of the second phase in the 15 wt% Ta-content sample improves the material's fracture toughness. Figures (d), (e), and (f) show SEM images of crack propagation in a 20 wt% Ta-content sample during a bending test. The crack propagates in a zigzag pattern along the eutectic cell boundary. This is because the resistance to crack propagation from the fine, dense spherical second phase is much higher than that from the lamellar second phase at the eutectic cell boundary. The curved crack propagation increases the crack propagation path, resulting in increased resistance to crack propagation and improved fracture toughness.

[0060] Figure 7 These SEM images of the fracture surface of a 15 wt% Ta-containing sample after bending fracture at different magnifications show a stepped or layered structure. This is because the second phase of the eutectic layer hinders the crack, allowing the crack to propagate between different layers within the material, resulting in delamination and the formation of a stepped fracture. At higher magnifications, the torn second phase and phase interfaces can be observed.

[0061] Figure 8 These are SEM images of the fracture morphology of the sample with 20.wt% Ta content after bending fracture at different magnifications. Since the crack preferentially breaks at the lamellar secondary phase at the boundary of the eutectic group, the step-like morphology and torn eutectic lamellar structure can be seen, indicating that for the alloy with this composition ratio, the spherical eutectic structure has a greater hindering effect on crack propagation. The crack propagates in the lamellar secondary phase at the boundary of the eutectic group and cannot penetrate into the interior of the spherical eutectic structure group.

[0062] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A Fe-Al-Ta intermetallic compound alloy, characterized in that: The mass percentage of the Ta element in the alloy is 5% to 25%, the mass percentage of the Fe element is 64.62% to 81.85%, and the mass percentage of the Al element is 10.38% to 13.15%, which totals 100%; The alloy comprises a matrix and a second phase dispersed in the matrix, the matrix is Fe3Al nanocrystal with a body-centered cubic structure, and the second phase is Fe2Ta.

2. The Fe-Al-Ta intermetallic compound alloy according to claim 1, characterized in that The grain size of the Fe3Al nanocrystals is 10nm~60nm.

3. A method for preparing the Fe-Al-Ta intermetallic compound alloy according to claim 1 or 2, characterized in that: The following steps are involved: Ball milling iron oxide powder, aluminum powder and tantalum powder to obtain metal powder; The metal powder is pressed into a green block, and the green block and an igniter are heated to 350° C. to 400° C. in a protective atmosphere. The igniter burns to excite the metal powder to generate a thermite reaction, thereby obtaining a Fe-Al-Ta intermetallic compound alloy.

4. The method for preparing the Fe-Al-Ta intermetallic compound alloy according to claim 3, wherein: In the Fe-Al-Ta intermetallic compound alloy, the mass percentage of the Ta element is 5% to 25%, the mass percentage of the Fe element is 64.62% to 81.85%, and the mass percentage of the Al element is 10.38% to 13.15%, which totals 100%.

5. The method for preparing the Fe-Al-Ta intermetallic compound alloy according to claim 3, wherein: The igniter accounts for 0.1% to 0.2% of the mass percentage of the metal powder.

6. The method for preparing the Fe-Al-Ta intermetallic compound alloy according to claim 3, wherein: First, a protective gas of 0.5MPa~1MPa is introduced into the green block and the igniter, heated to 80℃~150℃, ventilated, and then a protective gas of 3MPa~6MPa is introduced. The green block and the igniter are heated to 350℃~400℃, and the igniter burns to excite the metal powder to produce a thermite reaction for 3h~6h.

7. The method for preparing the Fe-Al-Ta intermetallic compound alloy according to claim 3, wherein: The ball milling is as follows: adding ball milling beads to the iron oxide powder, aluminum powder and tantalum powder according to a ball-to-material ratio of 1:2, ball milling at a rotation speed of 150 r / min to 200 r / min for 5 h to 8 h, and stopping for 5 min to 10 min after 1 h to 2 h of ball milling.

8. The method for preparing the Fe-Al-Ta intermetallic compound alloy according to claim 3, wherein: The pressing is as follows: pressing at 30 MPa to 60 MPa for 3 min to 10 min.

9. The method for preparing the Fe-Al-Ta intermetallic compound alloy according to claim 3, wherein: The particle size of the tantalum powder is micron-level, and the purity of the iron oxide powder, aluminum powder and tantalum powder are 99.9%, 99.9% and 99.999% respectively.

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