A TiAl-based alloy, its preparation method and application

Abstract

The present invention provides a TiAl-based alloy, a preparation method thereof and an application thereof. In terms of weight percentage, the content of TiAl in the alloy is not less than 90%, and the content of B4C is not more than 10%. The present invention innovatively introduces and designs a multi-component blended quasi-continuous reticular reinforcement structure that combines boride and carbide in the TiAl-based alloy, that is, through the in-situ generation of boride and carbide, a quasi-continuous reticular reinforcement structure is constructed at the interface layer of the TiAl matrix unit. By utilizing the synergistic effect of boride and carbide, while stabilizing the quasi-continuous reticular reinforcement structure, the toughening of the matrix unit interface layer is realized, and through the optimized regulation of the multi-component blended quasi-continuous reticular reinforcement structure, a high-performance TiAl-based alloy with a tissue having capsule structure characteristics is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallic materials, and particularly relates to a TiAl-based alloy, a preparation method thereof, and an application thereof. Background Art

[0002] The lightweighting of high-performance structural materials is the key to improving the performance of aerospace engines, extending their service life, reducing energy consumption and costs, and directly determines the future sustainable development of the aerospace industry. TiAl-based alloys have the advantages of low density, high specific strength, excellent high-temperature oxidation resistance, and creep resistance. At the same time, their density is about half of that of nickel-based superalloys, making them the primary candidate materials to replace nickel-based superalloys for large-scale weight reduction in aerospace engines. Currently, the conventional service temperature of nickel-based superalloys is mostly above 1000°C, while the high-temperature strength of TiAl-based alloys is insufficient at this temperature, making it difficult to completely replace nickel-based superalloys to meet the performance requirements of the aerospace industry for high-temperature structural materials. Therefore, achieving a significant improvement in the high-temperature strength of TiAl-based alloys is crucial for promoting their wide application in the aerospace field.

[0003] To improve the mechanical properties of TiAl-based alloys, domestic and foreign researchers have introduced different types of second-phase reinforcements into the materials and achieved an improvement in the high-temperature ultimate strength of the materials by controlling the growth, distribution, and volume fraction of the reinforcements. Among them, rod-shaped and particulate in-situ self-generated carbide reinforcements have good self-lubricating properties, and the dispersed carbides can effectively improve the strength of TiAl-based alloys while coordinating their plastic deformation. However, the ability of carbides to pin the interface sliding at high temperatures is limited. At the same time, rod-shaped TiB reinforcements have high hardness and strength, which can effectively pin the interface sliding of the microstructure at high temperatures and inhibit the high-temperature creep of TiAl-based alloys. However, TiB is relatively brittle and is not conducive to improving the plasticity of the material. Therefore, it is necessary to further develop technical means that can balance the comprehensive mechanical properties of TiAl-based alloys. Summary of the Invention

[0004] The object of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a TiAl-based alloy, a preparation method thereof, and an application thereof. The present invention innovatively introduces and designs a multi-component blended quasi-continuous network reinforcement structure that combines borides and carbides in the TiAl-based alloy, that is, by in-situ self-generation of borides and carbides, a quasi-continuous network reinforcement structure is constructed at the interface layer of the TiAl matrix unit. By utilizing the synergistic effect of borides and carbides, while stabilizing the quasi-continuous network reinforcement structure, the toughening of the matrix unit interface layer is achieved, and through the optimization and regulation of the multi-component blended quasi-continuous network reinforcement structure, a high-performance TiAl-based alloy with a tissue structure featuring a capsule structure is obtained.

[0005] The technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a TiAl-based alloy. By weight percentage, the content of TiAl in the alloy is not less than 90%, and the content of B4C is not more than 10%.

[0007] Optionally, in the TiAl-based alloy, the content of TiAl is 100%.

[0008] Optionally, in the TiAl-based alloy, the content of B4C > 0%, and the balance is TiAl.

[0009] Preferably, in the TiAl-based alloy, the content of TiAl is 95%, and the content of B4C is 5%.

[0010] In a second aspect, the present invention provides a method for preparing a TiAl-based alloy. The content of TiAl in the alloy is 100%. The method for preparing the alloy includes: sintering spherical TiAl pre-alloyed powder at a certain temperature and pressure.

[0011] Furthermore, the control process of the sintering includes: the sintering process is protected by a protective gas, the sintering pressure is 40 - 60 MPa, the sintering temperature is 1150 - 1300 °C, the heating rate during sintering is 5 °C / min - 15 °C / min, and the sintering time is 0.5 - 2 h.

[0012] In a third aspect, the present invention provides another method for preparing a TiAl-based alloy. The content of B4C in the alloy is > 0% and ≤ 10%; the balance is TiAl. The method for preparing the alloy includes:

[0013] Step 1, proportioning spherical TiAl pre-alloyed powder and B4C powder according to the composition of the TiAl-based alloy;

[0014] Step 2, mixing and ball-milling the raw material powders;

[0015] Step 3, sintering the raw material powders after mixing and ball-milling.

[0016] Furthermore, the particle size of the spherical TiAl pre-alloyed powder is 105 μm - 125 μm, and the particle size of the B4C powder is ≤ 2 μm.

[0017] Furthermore, the control process of the mixing and ball-milling includes: the ball-to-powder ratio of the ball-milling beads to the raw material powders is 2 - 5:1; the ball-milling process is protected by a protective gas, the ball-milling speed is 100 - 300 rpm, and the ball-milling time is 1 - 10 h.

[0018] Preferably, the ball-milling beads are stainless steel ball-milling beads with a diameter of 5 - 20 mm.

[0019] Further, the control process of the sintering includes: the sintering process is protected by a protective gas, the sintering pressure is 40 - 60 MPa, the sintering temperature is 1150 - 1300 °C, the heating rate during sintering is 5 °C / min - 15 °C / min, and the sintering time is 0.5 - 2 h.

[0020] Fourthly, the present invention provides the application of the above-mentioned TiAl-based alloy in the preparation of high-temperature resistant materials.

[0021] Fifthly, the present invention provides a high-temperature resistant material, and the raw material composition includes the above-mentioned TiAl-based alloy.

[0022] Sixthly, the present invention provides the application of the above-mentioned high-temperature resistant material in the preparation of aircraft.

[0023] The present invention has the following beneficial effects compared with the prior art:

[0024] 1. The present invention introduces a reinforcement structure in which the reinforcements are distributed in a quasi-continuous network pattern in the TiAl-based alloy (as Figures 2 to 6 shown). According to the H-S theory of composite materials, the mechanical properties of the TiAl-based alloy with discontinuous network reinforcement can reach the upper limit of its theoretical value. When the spherical soft phase is surrounded by the hard phase to form a capsule structure, the material has the highest elastic modulus, which can maximize the reinforcement effect of the reinforcements and the toughening effect of the matrix, thereby improving the comprehensive mechanical properties of the material. Therefore, the present invention finally obtains an in-situ self-generated reinforcement structure in which the reinforcements are connected to the TiAl matrix units in a metallurgical bonding manner and are distributed in a quasi-continuous network pattern around the matrix units by controlling the growth, distribution, and volume fraction of the reinforcements. For an independent matrix unit, the reinforcements are in a capsule shape surrounding the matrix unit. Overall, the reinforcements are evenly distributed in a quasi-continuous network structure around the matrix unit to significantly improve the high-temperature mechanical properties of the TiAl-based alloy.

[0025] 2. A multi-component blended quasi-continuous network reinforcement structure with borides and carbides of different types and morphologies is designed and introduced in the TiAl-based alloy. Through the in-situ self-generation reaction of B4C and the TiAl matrix, a quasi-continuous network reinforcement structure is constructed at the interface layer of the matrix unit. Among them, the rod-shaped and granular in-situ self-generated carbide reinforcements have good self-lubricating properties, and their dispersed distribution can improve the strength of the TiAl-based alloy while coordinating the plastic deformation of the material. However, their ability to pin the interface sliding at high temperatures is limited. In addition, the rod-shaped TiB reinforcements have high hardness and strength, which can effectively pin the sliding of the tissue interface at high temperatures and inhibit the high-temperature creep of the TiAl-based alloy. However, TiB is brittle and is not conducive to the improvement of the plasticity of the material. In view of this, the present invention utilizes the synergistic effect between borides and carbides to stabilize the quasi-continuous network reinforcement structure while achieving the strengthening and toughening of the interface layer of the TiAl matrix unit, rather than providing a single strengthening or toughening effect, so as to achieve the synchronous improvement of the yield strength and ultimate strength of the material under high-temperature service conditions.

[0026] 3. The present invention realizes the synchronous introduction of multi-component boride and carbide reinforcements through the in-situ self-generation of micron-scale B4C. By using the special crystal structure and bonding mode of B4C, the combination process of B and C atoms with Ti and Al atoms is regulated, effectively solving the problems of agglomeration precipitation and coarsening of borides, and promoting the embedding of borides and carbides in the form of whiskers into the TiAl matrix unit, improving the integrity and connectivity of the TiAl matrix unit. Description of the Drawings

[0027] Figure 1 is the SEM comparison image of the spherical TiAl pre-alloy powder and the spherical TiAl pre-alloy powder with B4C powder embedded on the surface prepared by low-energy ball milling in Example 1. Among them, Figure (a) is the SEM image of the spherical TiAl pre-alloy powder, and Figure (b) is the SEM image of the spherical TiAl pre-alloy powder with B4C powder embedded on the surface prepared by low-energy ball milling.

[0028] Figure 2 is the SEM image of the microstructure of the TiAl-based alloy with a multi-component blended quasi-continuous network reinforcement structure prepared in Example 1.

[0029] Figure 3 is the SEM image of the microstructure of the TiAl-based alloy with a multi-component blended quasi-continuous network reinforcement structure prepared in Example 2.

[0030] Figure 4 is the SEM image of the microstructure of the TiAl-based alloy with a multi-component blended quasi-continuous network reinforcement structure prepared in Example 3.

[0031] Figure 5This is a 10-fold magnified SEM image of the microstructure of the TiAl-based alloy with a multi-component blended quasi-continuous network reinforcement structure prepared in Example 3.

[0032] Figure 6 This is an SEM image of the microstructure of the TiAl-based alloy with a multi-component blended quasi-continuous network reinforcement structure prepared in Example 4.

[0033] Figure 7 This is an SEM image of the TiAl-based alloy microstructure prepared in Example 6.

[0034] Figure 8 The graphs are compression mechanical property curves at 800° C. for the TiAl-based alloys with a multi-component blended quasi-continuous network reinforcement structure prepared in Examples 1 to 6. DETAILED DESCRIPTION

[0035] In the description of the present invention, it should be noted that if specific conditions are not specified in the examples, the experiments were carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used, if the manufacturer is not specified, are all conventional products that can be purchased commercially.

[0036] The present invention innovatively introduces and designs a multi-component blended quasi-continuous network reinforcement structure with both borides and carbides in TiAl-based alloys. That is, through the in-situ self-generation of borides and carbides, a quasi-continuous network reinforcement structure is constructed in the interface layer of the TiAl matrix unit. The synergistic effect of borides and carbides is utilized to stabilize the quasi-continuous network reinforcement structure while achieving the toughening of the matrix unit interface layer. By optimizing and regulating the multi-component blended quasi-continuous network reinforcement structure, a high-performance TiAl-based alloy with a capsule structure characteristic organization is obtained.

[0037] The preparation method of the B4C-doped TiAl-based alloy of the present invention comprises the following steps:

[0038] Step 1, TiAl pre-alloyed powder and B4C powder are mixed according to the composition of TiAl-based alloy;

[0039] Step 2: ball milling the raw material powder; the control process of the mixed ball milling includes: the ball-to-material ratio of ball milling beads to raw material powder is 2 to 5:1; the ball milling process is protected by protective gas, the ball milling speed is 100 to 300 rpm, and the ball milling time is 1 to 10 hours; the ball milling beads are stainless steel ball milling beads with a diameter of 5 to 20 mm;

[0040] Step 3, sintering the mixed ball-milled raw material powder. The sintering control process includes: the sintering process adopts protective gas protection, the sintering pressure is 40-60 MPa, the sintering temperature is 1150-1300°C, the heating rate during sintering is 5°C / min-15°C / min, and the sintering time is 0.5-2h.

[0041] In Step 2 above, the ball milling time determines whether the distribution of B4C is uniform. The longer the ball milling time, the more uniform the distribution of B4C, and the more uniform the distribution of the finally formed reinforcement. The ball milling speed determines the adhesion effect of B4C. If the ball milling speed is too high, the spherical TiAl pre-alloy powder will be broken, which is not conducive to the formation of a regular quasi-continuous network reinforcement structure. If the ball milling speed is too low, B4C will accumulate and be unevenly distributed, forming aggregated large-sized reinforcements during the in-situ self-generation reaction process, which is also not conducive to the formation of an ideal quasi-continuous network reinforcement structure. Under load conditions, cracks will form at the aggregated large-sized reinforcements, leading to premature fracture of the material.

[0042] In Step 3 above, if the sintering temperature is too high, the grain size in the TiAl matrix will be too large, and even overburning and melting will occur, making it impossible to form a quasi-continuous network reinforcement structure and deteriorating the mechanical properties of the material. If the sintering temperature is too low, the densification degree of the material will be insufficient, and pores will form at the interface, deteriorating the mechanical properties of the material. If the sintering time is too long, the grain size in the TiAl matrix will be too large, deteriorating the mechanical properties of the material. If the sintering time is too short, the in-situ self-generated reinforcements do not have enough time to grow, making it difficult to form whiskers to firmly pin the TiAl matrix unit interface, reducing the interface bonding force and deteriorating the mechanical properties of the material.

[0043] The following further elaborates on the present invention in conjunction with the accompanying drawings and specific embodiments to help those skilled in the art have a more complete, accurate, and in-depth understanding of the inventive concept and technical solution of the present invention. The protection scope of the present invention includes but is not limited to the following embodiments. Any modification made to the details and forms of the technical solution of the present invention without departing from the spirit and scope of the present application falls within the protection scope of the present invention.

[0044] Example 1

[0045] This example provides a TiAl-based alloy with a quasi-continuous network reinforcement structure, including the following components by weight percentage: 99.95% of TiAl and 0.05% of B4C. Its preparation method includes the following steps.

[0046] Step 1, weighing materials. According to the component weight percentage of 99.95% of TiAl and 0.05% of B4C described in Claim 1, spherical TiAl pre-alloy powder and B4C powder are respectively weighed as raw materials.

[0047] Step 2, ball milling. First, the weighed spherical TiAl pre-alloy powder and B4C powder are put into the ball milling tank, and stainless steel ball milling beads are put into the ball milling tank according to a ball-to-material ratio of 5:1. Then, the ball milling tank is locked through a locking device, and the inside of the ball milling tank is evacuated by a vacuum pump until the internal air pressure of the ball milling tank reaches 10 -2MPa, stop vacuum pumping, and fill the ball milling tank with high-purity argon until the internal pressure of the ball milling tank is atmospheric pressure, then stop filling with high-purity argon; finally, place the ball milling tank in the ball mill and lock it in place, and perform low-energy ball milling at a ball milling speed of 200 rpm for 1 h. The SEM image of the spherical TiAl pre-alloy powder with B4C powder embedded on its surface prepared by low-energy ball milling is as Figure 1 (b) shown, Figure 1 (a) also gives the SEM image of the spherical TiAl pre-alloy powder before ball milling. It can be seen that obvious grain morphology can be seen on the surface of the TiAl pre-alloy powder before ball milling, and the surface is bright. After a suitable low-energy ball milling process, the B4C powder is evenly wrapped and embedded on the surface of the spherical TiAl pre-alloy powder;

[0048] Step 3, sintering. Put the ball milled mixed powder in step 2 into a graphite mold, place the mold in a hot press sintering furnace, and perform hot press sintering under the conditions of 1200 °C / 50 MPa / 1 h, then cool it to room temperature with the furnace, take out the mold after opening the furnace, and obtain a TiAl-based alloy with a multi-component co-mixed quasi-continuous network reinforcement structure. The SEM image of the microstructure is as Figure 2 shown. It can be seen that boride and carbide reinforcements with different morphologies are evenly distributed in a quasi-continuous network at the interface layer of the TiAl matrix unit, and the TiAl matrix unit has good integrity and connectivity.

[0049] Furthermore, the particle size of the spherical TiAl pre-alloy powder in step 1 is 105 μm to 125 μm, and the particle size of the B4C powder is ≤2 μm.

[0050] Furthermore, the diameter of the stainless steel ball milling beads in step 2 is 5 mm, and the step of evacuating and then filling with argon needs to be repeated 3 times to ensure that the air in the ball milling tank is exhausted to the greatest extent.

[0051] Furthermore, the hot press sintering in step 3 is carried out under the protection of an argon atmosphere, and the heating rate during sintering is 10 °C / min.

[0052] Example 2

[0053] This example provides a TiAl-based alloy with a quasi-continuous network reinforcement structure, which includes the following components by weight percentage: 99.90% of TiAl, 0.10% of B4C. Its preparation method includes the following steps.

[0054] Step 1, weighing. According to the component weight percentages of 99.9% of TiAl and 0.1% of B4C in claim 1, weigh the spherical TiAl pre-alloy powder and B4C powder respectively as raw materials;

[0055] Step 2, ball milling. First, put the weighed spherical TiAl pre-alloy powder and B4C powder into the ball milling tank, and put stainless steel ball milling beads into the ball milling tank according to a ball-to-material ratio of 5:1; then lock the ball milling tank through the locking device, and use a vacuum pump to evacuate the inside of the ball milling tank until the air pressure inside the ball milling tank reaches 10 -2 MPa, stop evacuating, and fill the ball milling tank with high-purity argon until the air pressure inside the ball milling tank is atmospheric pressure, then stop filling with high-purity argon; finally, put the ball milling tank into the ball mill and lock it in place, and carry out low-energy ball milling at a ball milling speed of 200 rpm for 1 h;

[0056] Step 3, sintering. Put the ball-milled mixed powder in Step 2 into a graphite mold, put the mold into a hot pressing sintering furnace, and carry out hot pressing sintering under the conditions of 1200 °C / 50 MPa / 1 h, then cool it to room temperature with the furnace, take out the mold after opening the furnace, and obtain a TiAl-based alloy with a quasi-continuous network reinforcement structure. The SEM image of the microstructure is as Figure 3 shown. It can be seen that the alloy has a quasi-continuous network reinforcement structure composed of multi-element boride and carbide reinforcements.

[0057] Furthermore, the particle size of the spherical TiAl pre-alloy powder in Step 1 is 105 μm to 125 μm, and the particle size of the B4C powder is ≤ 2 μm.

[0058] Furthermore, the diameter of the stainless steel ball milling beads in Step 2 is 5 mm, and the step of filling argon after evacuation is repeated 3 times to ensure that the air in the ball milling tank is exhausted to the greatest extent.

[0059] Furthermore, the hot pressing sintering in Step 3 is carried out under the protection of an argon atmosphere, and the heating rate of sintering is 10 °C / min.

[0060] Example 3

[0061] This example provides a TiAl-based alloy with a quasi-continuous network reinforcement structure, which includes the following components by weight percentage: 99.50% of TiAl, 0.50% of B4C. Its preparation method includes the following steps.

[0062] Step 1, weighing materials. According to the component weight percentages of 99.5% of TiAl and 0.5% of B4C described in Claim 1, weigh spherical TiAl pre-alloy powder and B4C powder respectively as raw materials;

[0063] Step 2, ball milling. First, put the weighed spherical TiAl pre-alloy powder and B4C powder into the ball milling tank, and put stainless steel ball milling beads into the ball milling tank according to a ball-to-material ratio of 5:1; then lock the ball milling tank through the locking device, and use a vacuum pump to evacuate the inside of the ball milling tank until the air pressure inside the ball milling tank reaches 10 -2MPa, stop vacuum pumping, and fill the ball milling tank with high-purity argon until the internal pressure of the ball milling tank reaches atmospheric pressure, then stop filling with high-purity argon; finally, place the ball milling tank in the ball mill and lock it in place, and perform low-energy ball milling at a ball milling speed of 200 rpm for 1.5 h.

[0064] Step 3, sintering: Put the ball-milled mixed powder in step 2 into a graphite mold, place the mold in a hot pressing sintering furnace, and perform hot pressing sintering under the conditions of 1200 °C / 50 MPa / 1 h, then cool it in the furnace to room temperature. After opening the furnace, take out the mold to obtain a TiAl-based alloy with a quasi-continuous network reinforcement structure. The SEM image of the microstructure is as Figure 4 and Figure 5 shown. It can be seen that the alloy has a quasi-continuous network reinforcement structure, and the reinforcements in this structure present a whisker form, that is, borides and carbides are embedded in the TiAl matrix unit in the form of whiskers.

[0065] Furthermore, the particle size of the spherical TiAl pre-alloy powder in step 1 is 105 μm to 125 μm, and the particle size of the B4C powder is ≤2 μm.

[0066] Furthermore, the diameter of the stainless steel ball milling beads in step 2 is 5 mm, and the step of evacuating and then filling with argon is repeated 3 times to ensure that the air in the ball milling tank is exhausted to the greatest extent.

[0067] Furthermore, the hot pressing sintering in step 3 is carried out under the protection of an argon atmosphere, and the heating rate during sintering is 10 °C / min.

[0068] Example 4

[0069] This example provides a TiAl-based alloy with a quasi-continuous network reinforcement structure, which includes the following components by weight percentage: 95.00% of TiAl and 5.00% of B4C. Its preparation method includes the following steps.

[0070] Step 1, weighing: Weigh spherical TiAl pre-alloy powder and B4C powder as raw materials according to 95% of TiAl and 5% of B4C in the component weight percentage described in claim 1.

[0071] Step 2, ball milling: First, put the weighed spherical TiAl pre-alloy powder and B4C powder into the ball milling tank, and put stainless steel ball milling beads into the ball milling tank according to a ball-to-material ratio of 5:1; then lock the ball milling tank through the locking device, and use a vacuum pump to evacuate the inside of the ball milling tank until the internal pressure of the ball milling tank reaches 10 -2MPa, stop vacuum pumping, and fill the ball milling tank with high-purity argon gas until the internal pressure of the ball milling tank reaches atmospheric pressure, then stop filling with high-purity argon gas; finally, place the ball milling tank in the ball mill and lock it in place, and perform low-energy ball milling at a ball milling speed of 200 rpm for 8 h;

[0072] Step 3, sintering: Put the ball-milled mixed powder in step 2 into a graphite mold, place the mold in a hot press sintering furnace, and perform hot press sintering under the conditions of 1200 °C / 50 MPa / 1 h, then cool it to room temperature with the furnace, take out the mold after opening the furnace, and obtain a TiAl-based alloy with a quasi-continuous network reinforcement structure. The SEM image of the microstructure is as Figure 6 shown. It can be seen that boride and carbide reinforcements with different morphologies are distributed in a quasi-continuous network at the interface of the TiAl matrix unit.

[0073] Furthermore, the particle size of the spherical TiAl pre-alloy powder in step 1 is 105 μm to 125 μm, and the particle size of the B4C powder is ≤ 2 μm.

[0074] Furthermore, in step 2, the diameter of the stainless steel ball milling beads is 5 mm, and the step of evacuating and then filling with argon gas is repeated 3 times to ensure that the air in the ball milling tank is exhausted to the greatest extent.

[0075] Furthermore, the hot press sintering in step 3 is carried out under the protection of an argon gas atmosphere, and the heating rate during sintering is 10 °C / min.

[0076] Example 5

[0077] This example provides a TiAl-based alloy with a quasi-continuous network reinforcement structure, which includes the following components by weight percentage: 90.00% of TiAl and 10.00% of B4C. Its preparation method includes the following steps.

[0078] Step 1, weighing: According to the component weight percentage of 90% of TiAl and 10% of B4C as described in claim 1, respectively weigh spherical TiAl pre-alloy powder and B4C powder as raw materials;

[0079] Step 2, ball milling: First, put the weighed spherical TiAl pre-alloy powder and B4C powder into the ball milling tank, and put stainless steel ball milling beads into the ball milling tank according to a ball-to-material ratio of 5:1; then lock the ball milling tank through the locking device, and use a vacuum pump to evacuate the inside of the ball milling tank until the internal pressure of the ball milling tank reaches 10 -2 MPa, stop vacuum pumping, and fill the ball milling tank with high-purity argon gas until the internal pressure of the ball milling tank reaches atmospheric pressure, then stop filling with high-purity argon gas; finally, place the ball milling tank in the ball mill and lock it in place, and perform low-energy ball milling at a ball milling speed of 200 rpm for 8 h;

[0080] Step 3, sintering: Put the milled mixed powder in Step 2 into a graphite mold, place the mold in a hot-pressing sintering furnace, conduct hot-pressing sintering under the conditions of 1200 °C / 50 MPa / 1 h, then cool it in the furnace to room temperature, take out the mold after opening the furnace, and obtain a TiAl-based alloy with a quasi-continuous network-reinforced structure.

[0081] Further, the particle size of the spherical TiAl pre-alloy powder in Step 1 is 105 μm - 125 μm, and the particle size of the B4C powder is ≤ 2 μm.

[0082] Further, the diameter of the stainless steel milling balls in Step 2 is 5 mm, and the step of evacuating and then filling with argon is repeated 3 times to ensure that the air in the milling tank is exhausted to the greatest extent.

[0083] Further, the hot-pressing sintering in Step 3 is carried out under the protection of an argon atmosphere, and the heating rate during sintering is 10 °C / min.

[0084] Example Six

[0085] This example provides a dense TiAl-based alloy with a duplex structure matrix, which includes the following components by weight percentage: 100.00% of TiAl. Its preparation method includes the following steps.

[0086] Put the weighed TiAl pre-alloy powder into a graphite mold, place the mold in a hot-pressing sintering furnace, conduct hot-pressing sintering under the conditions of 1200 °C / 50 MPa / 1 h, then cool it in the furnace to room temperature, take out the mold after opening the furnace to obtain a dense TiAl-based alloy with a duplex structure matrix. The SEM image of the microstructure is as Figure 7 shown. It can be seen that the combination between the TiAl matrices in the sintered structure is dense, and the TiAl-based alloy structure presents a duplex structure, but there is no quasi-continuous network-reinforced structure in the structure.

[0087] Further, the particle size of the spherical TiAl pre-alloy powder in the step is 105 μm - 125 μm.

[0088] Further, the hot-pressing sintering in the step is carried out under the protection of an argon atmosphere, and the heating rate during sintering is 10 °C / min

[0089] Conduct a compression performance test on the TiAl-based alloys prepared in Examples One to Six under the condition of a temperature of 800 °C. The high-temperature compression performance curve is as Figure 8 shown, and the detailed results are shown in Table 1.

[0090] Table 1

[0091]

[0092] In summary, the present invention has the following technical advantages:

[0093] 1. The present invention introduces a reinforcement structure with quasi-continuous network distribution of reinforcements in the TiAl-based alloy (as Figures 2 to 6 shown). According to the H-S theory of composite materials, the mechanical properties of the TiAl-based alloy with discontinuous network reinforcement can reach the upper limit of its theoretical value. When the spherical soft phase is surrounded by the hard phase to form a capsule structure, the material has the highest elastic modulus, which can maximize the strengthening effect of the reinforcement and the toughening effect of the matrix, thereby improving the comprehensive mechanical properties of the material. Therefore, the present invention controls the growth, distribution, and volume fraction of the reinforcement, and finally obtains in-situ self-generated reinforcements that are connected to the TiAl matrix units in a metallurgical bonding manner and are uniformly distributed in a quasi-continuous network around the matrix units. For an independent matrix unit, the reinforcement is in a capsule shape and wraps around the matrix unit. Overall, the reinforcement is uniformly distributed in a quasi-continuous network structure around the matrix unit, significantly improving the high-temperature mechanical properties of the TiAl-based alloy.

[0094] 2. The present invention designs and introduces a multi-component blended quasi-continuous network reinforcement structure with different types and morphologies of borides and carbides in the TiAl-based alloy. Through the in-situ self-generation reaction of B and C elements with the TiAl matrix, a quasi-continuous network reinforcement structure is constructed at the interface layer of the matrix unit. Among them, the rod-shaped and granular in-situ self-generated carbide reinforcements have good self-lubricating properties, and their dispersion distribution can improve the strength of the TiAl-based alloy while coordinating the plastic deformation of the material. However, their ability to pin the interface sliding at high temperatures is limited. In addition, the rod-shaped TiB reinforcement has high hardness and strength, which can effectively pin the interface sliding of the microstructure at high temperatures and inhibit the high-temperature creep of the TiAl-based alloy. However, TiB is relatively brittle and is not conducive to improving the plasticity of the material. In view of this, the present invention utilizes the synergistic effect between borides and carbides to stabilize the quasi-continuous network reinforcement structure and achieve the strengthening and toughening of the interface layer of the matrix unit, rather than providing a single strengthening or toughening effect, so as to simultaneously improve the yield strength and ultimate compressive strength of the material under high-temperature service conditions.

[0095] 3. The present invention realizes the synchronous introduction of multi-component boride and carbide reinforcements through the in-situ self-generation of micron-sized B4C. By utilizing the special crystal structure and bonding mode of B4C, the combination process of B and C atoms with Ti and Al atoms is regulated, effectively solving the problems of aggregation precipitation and coarsening of borides, and promoting the embedding of borides and carbides into the TiAl matrix units in the form of whiskers, improving the integrity and connectivity of the matrix units.

[0096] 4. The present invention utilizes the low-energy ball milling technology under the protection of a high-purity argon gas atmosphere to uniformly embed micron-sized B4C powder on the surface of spherical TiAl pre-alloy powder while not damaging the surface morphology of the spherical TiAl pre-alloy powder, which helps to obtain a complete quasi-continuous network reinforcement structure, greatly avoids the oxidation of the raw material powder, and reduces the danger and cost during the ball milling process.

[0097] 5. The present invention introduces B and C elements through micron-sized B4C and utilizes the in-situ self-generation of B and C elements to synergistically introduce multi-component blended borides and carbides. Among them, micron-sized B4C effectively reduces the introduction cost of B and C elements from the raw materials and improves the introduction efficiency of B and C elements; the borides and carbides formed in-situ by B and C have good compatibility with the TiAl matrix, similar expansion coefficients, and are firmly and stably combined with the matrix, which helps to improve the mechanical properties of the material.

[0098] 6. The present invention can control the volume fraction of the reinforcement by changing the weight percentage of micron-sized B4C, control the distribution of the reinforcement by regulating the low-energy ball milling process parameters, and control the types of the reinforcement by regulating the composition of the spherical TiAl pre-alloy powder and the sintering process parameters, and finally realize the optimized regulation of the multi-component blended quasi-continuous network reinforcement structure.

[0099] The above-described embodiments merely represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but should not be construed as limiting the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A TiAl-based alloy, characterized in that: In the TiAl-based alloy by weight percentage, the content of TiAl is 90 - 99.95%, and the content of B4C is 0.05 - 10%; the TiAl-based alloy has a regular quasi-continuous reticular reinforcement structure; The preparation method of the TiAl-based alloy includes: Step 1, proportion the spherical TiAl pre-alloy powder and B4C powder according to the composition of the TiAl-based alloy; Step 2, perform ball milling on the raw material powders; Step 3, sinter the ball-milled raw material powders; Among them, the rotation speed of the ball milling is 100 - 300 rpm, and the ball milling time is 1 - 10 h; The sintering temperature is 1150 - 1300 °C, and the time is 0.5 - 2 h.

2. The preparation method of a TiAl-based alloy according to claim 1, characterized in that: The preparation method of the TiAl-based alloy includes: Step 1, proportion the spherical TiAl pre-alloy powder and B4C powder according to the composition of the TiAl-based alloy; Step 2, perform ball milling on the raw material powders; Step 3, sinter the ball-milled raw material powders; Among them, the rotation speed of the ball milling is 100 - 300 rpm, and the ball milling time is 1 - 10 h; The sintering temperature is 1150 - 1300 °C, and the time is 0.5 - 2 h.

3. The preparation method of a TiAl-based alloy according to claim 2, characterized in that: The control process of the sintering includes: the sintering process is protected by a protective gas, the sintering pressure is 40 - 60 MPa, the sintering temperature is 1150 - 1300 °C, the heating rate during sintering is 5 °C / min - 15 °C / min, and the sintering time is 0.5 - 2 h.

4. Application of the TiAl-based alloy according to claim 1 or the TiAl-based alloy obtained by the preparation method according to claim 2 or 3 in the preparation of high-temperature resistant materials.

5. A high-temperature resistant material, characterized in that: The raw material composition of the high-temperature resistant material includes the TiAl-based alloy according to claim 1 or the TiAl-based alloy obtained by the preparation method according to claim 2 or 3.

6. Application of the high-temperature resistant material according to claim 5 in the preparation of aircraft.

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