High-nb-tial based composite material for powder metallurgy and preparation method thereof

Abstract

This invention provides a high-Nb-TiAl based composite material for powder metallurgy and its preparation method, relating to the technical fields of high-temperature TiAl alloy and composite material composition design and powder metallurgy. The chemical composition of the high-Nb-TiAl based composite material for powder metallurgy, by atomic percentage, is: Al 44-49 at.%, Nb 1-10 at.%, B 0.6-1.4 at.%, Si 0.1-0.3 at.%, with the balance being Ti and unavoidable impurity elements. The preparation method includes the following steps: raw material weighing and melting, atomization powder preparation, powder hot pressing sintering (including various pressure sintering methods such as hot isostatic pressing, induction hot pressing sintering, and spark plasma sintering), and heat treatment. This invention obtains a high-Nb-TiAl based composite material for high-temperature service through composition design, pre-alloyed powder preparation, and powder metallurgy hot pressing sintering. The prepared composite material exhibits excellent room temperature and high-temperature mechanical properties, further broadening the service temperature range of TiAl alloys. This invention is simple and easy to implement, with a convenient and flexible process flow, suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the technical field of composition design of high-temperature TiAl alloys and their composite materials and powder metallurgy, specifically to a high Nb-TiAl based composite material for powder metallurgy and its preparation method. Background Technology

[0002] TiAl alloys are considered the most promising lightweight structural materials for aerospace applications above 650°C due to their low density (about half that of nickel-based superalloys), high specific strength, and excellent high-temperature oxidation resistance. They have already been used to manufacture components such as low-pressure turbine blades for engines. However, their inherent room-temperature brittleness makes them extremely difficult to process and form. Furthermore, their strength drops sharply above 800°C, and their creep and oxidation resistance become insufficient, further limiting their application under extreme service conditions.

[0003] Composite processing, as an effective way to optimize the microstructure and room-temperature and high-temperature properties of TiAl alloys, has gradually become a research hotspot in the TiAl alloy field. Common composite processing methods include the addition of endogenous or exogenous ceramic particles, hard metal particles, or the construction of continuous fiber reinforcement. Endogenous boride and silicide ceramic particles are ideal composite processing methods for preparing TiAl-based composites due to their advantages such as dispersed distribution, grain refinement, high-temperature thermal stability, grain boundary pinning, and low cost. Among them, powder metallurgy is the mainstream method for preparing such composites. Compared with traditional casting methods, powder metallurgy can effectively avoid problems such as uneven distribution of reinforcing phases and severe interfacial reactions, achieving near-net-shape forming, which is particularly important for processing brittle materials. Addressing the urgent need for lightweight, heat-resistant, and high-strength and tough materials in aerospace and other fields, the preparation of high-Nb-TiAl-based composites using powder metallurgy combines the near-net-shape forming advantages of powder metallurgy with the design concept of strengthening and toughening composite materials, providing an effective way to solve the shortcomings of TiAl alloys.

[0004] Chinese patent CN116516212A discloses a method for preparing a high-temperature, high-strength high-Nb-TiAl alloy. The alloy composition requires the comprehensive addition of W, Si, and C to synergistically enhance the TiAl alloy's high-temperature strength. Although the composition design is simple and the melting method is convenient, it has technical defects such as compositional segregation, coarse microstructure, loose shrinkage cavities, and uneven distribution of reinforcing phases.

[0005] Chinese patent CN116516213A discloses a method for preparing a Si-containing high Nb-TiAl alloy. The high silicon content in the alloy composition can cause technical defects such as compositional segregation, uneven distribution of silicides, and coarsening and growth in the alloy prepared by two melting processes.

[0006] Chinese patent CN103820672A discloses a Cr and Mn alloyed β-phase solidified high Nb-TiAl alloy and its preparation method. Obviously, the composition design includes the addition of no more than 0.5% Cr and no more than 1% Mn. Although it can obtain a TiAl alloy with uniform and fine structure and no obvious segregation by centrifugal rotation casting, it has technical defects such as a high content of hard and brittle β / B2 phase, which is not conducive to room temperature plasticity.

[0007] It can be seen that although there are existing technologies for the composition design and smelting preparation of TiAl alloys, there are some technical defects to varying degrees.

[0008] While powder metallurgy can also be used to prepare TiAl alloys, it still has some technical shortcomings.

[0009] For example, Chinese patent CN111621659A discloses a method for preparing Ti2AlNb alloy by powder metallurgy, which not only requires the addition of vanadium and rare earth elements, but also has a very high niobium content, increasing the cost of alloy raw materials and the density of sintered billets.

[0010] Chinese patent CN116987921A discloses a fully lamellar network structure TiAl-based composite material and its preparation method. The method uses spherical TiAl pre-alloyed powder, metal powder and reinforcing powder as raw material powders. After high-energy ball milling, modified spherical TiAl alloy powder is obtained. After sieving, the composite material is obtained by three-stage temperature sintering. Obviously, the method has technical defects such as poor room temperature tensile plasticity of the prepared fully lamellar network structure.

[0011] Chinese patent CN117604313A discloses a high-Nb-content TiAl intermetallic compound porous material and its preparation method. The method involves mixing low-oxygen-content TiAl alloy coarse powder and high-oxygen-content ultrafine Nb powder, then packing the mixture into a stainless steel casing, vibrating it, evacuating it, sealing it, and then sequentially performing a first-stage hot isostatic pressing sintering at 850-950℃ and a second-stage hot isostatic pressing sintering at 1000-1150℃. Obviously, this method has technical defects such as excessively high oxygen content and poor mechanical properties.

[0012] In summary, how to obtain high-Nb-TiAl-based composite materials with excellent high-temperature mechanical properties and stable high-temperature microstructure through improvements in composition design and preparation methods, and the preparation methods thereof, are currently urgent technical challenges to be solved. Summary of the Invention

[0013] The technical problems to be solved by this invention are the low room temperature plasticity, limited high temperature resistance, oxidation and microstructure stability of existing TiAl alloys, and the difficulty in forming existing TiAl alloys due to their operating temperature not exceeding 650℃. This invention proposes a high Nb-TiAl based composite material for powder metallurgy and its preparation method. The technical solution is as follows:

[0014] A high Nb-TiAl-based composite material for powder metallurgy, wherein the chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 44-49 at.%, Nb 1-10 at.%, B 0.6-1.4 at.%, Si 0.1-0.3 at.%, with the balance being Ti and unavoidable impurity elements.

[0015] Optionally, the matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 5-80 μm. The matrix structure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

[0016] Optionally, the high Nb-TiAl based composite material for powder metallurgy, after high-temperature heat treatment followed by low-temperature heat treatment, exhibits a room temperature tensile strength of not less than 700 MPa, a yield strength of not less than 600 MPa, and an elongation after fracture of not less than 0.5%; a high-temperature tensile strength of not less than 600 MPa, a yield strength of not less than 500 MPa, and an elongation after fracture of not less than 1.5%; a high-temperature tensile strength of not less than 500 MPa, a yield strength of not less than 400 MPa, and an elongation after fracture of not less than 10%; and under creep conditions of 800℃ and 100 MPa, a creep life greater than 500 h and a minimum creep rate less than 8 × 10⁻⁶. -8 s -1 .

[0017] A method for preparing a high-Nb-TiAl based composite material for powder metallurgy, comprising the following preparation steps:

[0018] S1. Raw material weighing and smelting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder or aluminum-boron master alloy according to the above chemical composition ratio, and then use vacuum suspension smelting to fully smelt the raw materials of the above composition ratio to obtain the master alloy ingot.

[0019] S2, Atomization powder production: The master alloy ingot obtained in S1 is subjected to plasma rotating electrode atomization powder production or gas atomization powder production, and then the powder is sieved to obtain pre-alloyed powder with the required particle size for powder metallurgy.

[0020] S3, Powder hot pressing sintering: The pre-alloyed powder of S2 is hot pressed and sintered to obtain a high Nb-TiAl based composite material blank with the required shape and size;

[0021] S4. High-temperature heat treatment / low-temperature heat treatment: High-temperature heat treatment is performed on the high Nb-TiAl matrix composite billet of S3 to regulate the matrix microstructure, or low-temperature heat treatment is performed to relieve stress and regulate the precipitation of the reinforcing phase, so as to obtain high Nb-TiAl matrix composites with different matrix microstructures.

[0022] Optionally, the master alloy ingot in S1 is of the following size. 50- Cylindrical blanks of 60mm × 300-600mm.

[0023] Optionally, the pre-alloyed powder obtained by sieving in S2 has a particle size of 5-300 μm and an oxygen content of less than 800 ppm.

[0024] Optionally, the powder metallurgy hot pressing sintering method in S3 includes any one of hot isostatic pressing, induction hot pressing sintering, spark plasma sintering, and other hot pressing sintering methods; the vacuum degree inside the sintering equipment or forming mold is less than 1×10⁻⁶. - 2 Pa or argon inert gas protection.

[0025] Optionally, the hot isostatic pressing sintering temperature in S3 is 1000-1400℃, the sintering pressure is 100-300MPa, and the sintering time is 0.5-6h; the sintering temperature of induction hot pressing sintering and spark plasma sintering is 1000-1450℃, the sintering pressure is 30-100MPa, and the sintering time is 10-120min.

[0026] Optionally, sintering in S3 requires a mold for a specific part shape, and demolding after sintering yields high Nb-TiAl based composite material parts.

[0027] Optionally, the S3 medium hot isostatic pressing mold is made of stainless steel; the induction hot pressing sintering and spark plasma sintering molds are made of graphite or carbon fiber.

[0028] Optionally, the high-temperature heat treatment + low-temperature heat treatment in S4 is carried out under vacuum or argon atmosphere protection; the temperature of the high-temperature heat treatment is 1250-1425℃, and the time of the high-temperature heat treatment is 0.5-72h; the temperature of the low-temperature heat treatment is 700-900℃, and the time of the low-temperature heat treatment is 2-24h; the cooling method includes at least one of furnace cooling, air cooling, water cooling and oil cooling.

[0029] Technical principles of the invention:

[0030] Composite processing, as an effective way to optimize the microstructure and room-temperature and high-temperature properties of TiAl alloys, has gradually become a research hotspot in the field of TiAl alloys. Common composite processing methods include the addition of endogenous or exogenous ceramic particles, hard metal particles, or the construction of continuous fiber reinforcement. Endogenous boride and silicide ceramic particles are ideal composite processing methods for preparing TiAl-based composite materials due to their advantages such as dispersed distribution, grain refinement, high-temperature thermal stability, grain boundary pinning, and low cost.

[0031] Powder metallurgy is the mainstream method for preparing these composite materials. Compared with traditional casting, powder metallurgy can effectively avoid problems such as uneven distribution of reinforcing phases and severe interfacial reactions, achieving near-net-shape forming, which is especially important for processing brittle materials.

[0032] Addressing the urgent need for lightweight, heat-resistant, and high-strength materials in aerospace and other fields, the preparation of high-Nb-TiAl based composite materials using powder metallurgy combines the near-net-shape advantages of powder metallurgy with the design concept of strengthening and toughening composite materials, providing an effective way to solve the shortcomings of TiAl alloys.

[0033] The above technical solution has at least the following advantages compared with the existing technology:

[0034] The above-mentioned solution proposes a high Nb-TiAl based composite material for powder metallurgy and its preparation method, which can solve the problems of low room temperature plasticity, limited high temperature resistance, oxidation and microstructure stability of existing TiAl alloys, as well as the technical problems of existing TiAl alloys having a service temperature not exceeding 650℃ and being difficult to form.

[0035] This invention, through rational design of the TiAl alloy composition, powder metallurgy, high-temperature heat treatment + low-temperature heat treatment, introduces borides and silicides into the matrix to form a fine and uniform ceramic phase composite structure. This results in a composite material with a room temperature tensile strength of not less than 700 MPa, a yield strength of not less than 600 MPa, and an elongation after fracture of not less than 0.5%; a high-temperature tensile strength of not less than 600 MPa, a yield strength of not less than 500 MPa, and an elongation after fracture of not less than 1.5% at 800℃; a high-temperature tensile strength of not less than 500 MPa, a yield strength of not less than 400 MPa, and an elongation after fracture of not less than 10% at 900℃; and a creep life greater than 500 hours and a minimum creep rate less than 8 × 10⁻⁶ h under creep conditions of 800℃ and 100 MPa. -8 s -1 It is a high Nb-TiAl based composite material with excellent comprehensive performance at both room temperature and high temperature.

[0036] The high Nb-TiAl based composite material of the present invention meets the requirements of strength, creep resistance and oxidation resistance of hot end components at service temperatures of 650-800℃. It can be applied to rotor components such as engine turbine blades and turbocharger turbines of automobile engines, and has great application and promotion value.

[0037] In summary, compared with traditional TiAl-based composite material preparation methods, the method of this invention obtains high-Nb-TiAl-based composite materials for high-temperature service through composition design, pre-alloyed powder preparation, and powder metallurgy hot pressing sintering. The prepared composite material has excellent room temperature and high-temperature mechanical properties, further broadening the service temperature range of TiAl alloys. The composition design of this invention is controllable, the production equipment and process are simple, the production cost is low, and the efficiency is high, which is conducive to large-scale industrial production and application. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a process flow diagram of a method for preparing a high Nb-TiAl based composite material for powder metallurgy according to the present invention. Detailed Implementation

[0040] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0041] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0042] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0043] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0044] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0045] A high Nb-TiAl-based composite material for powder metallurgy, wherein the chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 44-49 at.%, Nb 1-10 at.%, B 0.6-1.4 at.%, Si 0.1-0.3 at.%, with the balance being Ti and unavoidable impurity elements.

[0046] Specifically, the matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 5-80 μm. The matrix structure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperatures.

[0047] Specifically, the high Nb-TiAl based composite material for powder metallurgy, after high-temperature heat treatment followed by low-temperature heat treatment, exhibits a room temperature tensile strength of not less than 700 MPa, a yield strength of not less than 600 MPa, and an elongation after fracture of not less than 0.5%; at 800℃, its tensile strength is not less than 600 MPa, its yield strength is not less than 500 MPa, and its elongation after fracture is not less than 1.5%; at 900℃, its tensile strength is not less than 500 MPa, its yield strength is not less than 400 MPa, and its elongation after fracture is not less than 10%; under creep conditions of 800℃ and 100 MPa, its creep life is greater than 500 h, and its minimum creep rate is less than 8 × 10⁻⁶. -8 s -1 .

[0048] A method for preparing high Nb-TiAl based composite materials for powder metallurgy, wherein the method for preparing high Nb-TiAl based composite materials for powder metallurgy is combined with Figure 1 The preparation steps include the following:

[0049] S1. Raw material weighing and smelting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder or aluminum-boron master alloy according to the above chemical composition ratio, and then use vacuum suspension smelting to fully smelt the raw materials of the above composition ratio to obtain the master alloy ingot.

[0050] S2, Atomization powder production: The master alloy ingot obtained in S1 is subjected to plasma rotating electrode atomization powder production or gas atomization powder production, and then the powder is sieved to obtain pre-alloyed powder with the required particle size for powder metallurgy.

[0051] S3, Powder hot pressing sintering: The pre-alloyed powder of S2 is hot pressed and sintered to obtain a high Nb-TiAl based composite material blank with the required shape and size;

[0052] S4. High-temperature heat treatment / low-temperature heat treatment: High-temperature heat treatment is performed on the high Nb-TiAl matrix composite billet of S3 to regulate the matrix microstructure, or low-temperature heat treatment is performed to relieve stress and regulate the precipitation of the reinforcing phase, so as to obtain high Nb-TiAl matrix composites with different matrix microstructures.

[0053] Specifically, the master alloy ingot in S1 is of a certain size. 50- Cylindrical blanks of 60mm × 300-600mm.

[0054] Specifically, the pre-alloyed powder obtained by sieving in S2 has a particle size of 5-300 μm and an oxygen content of less than 800 ppm, which is required for powder metallurgy.

[0055] Specifically, the powder metallurgy hot pressing sintering method in S3 includes any one of hot isostatic pressing, induction hot pressing sintering, spark plasma sintering, and other hot pressing sintering methods; the vacuum degree inside the sintering equipment or forming mold is less than 1×10⁻⁶. - 2 Pa or argon inert gas protection.

[0056] Specifically, the sintering temperature of S3 medium hot isostatic pressing is 1000-1400℃, the sintering pressure is 100-300MPa, and the sintering time is 0.5-6h; the sintering temperature of induction hot pressing and spark plasma sintering is 1000-1450℃, the sintering pressure is 30-100MPa, and the sintering time is 10-120min.

[0057] In particular, sintering in S3 requires custom-made molds for specific part shapes. After sintering, demolding yields high Nb-TiAl based composite material parts.

[0058] Specifically, the S3 medium hot isostatic pressing mold is made of stainless steel; the induction hot pressing sintering and spark plasma sintering molds are made of graphite or carbon fiber.

[0059] Specifically, the high-temperature heat treatment and low-temperature heat treatment in S4 are carried out under vacuum or argon atmosphere protection; the temperature of the high-temperature heat treatment is 1250-1425℃, and the time of the high-temperature heat treatment is 0.5-72h; the temperature of the low-temperature heat treatment is 700-900℃, and the time of the low-temperature heat treatment is 2-24h; the cooling method includes at least one of furnace cooling, air cooling, water cooling and oil cooling.

[0060] Example 1

[0061] This embodiment provides a high Nb-TiAl-based composite material for powder metallurgy. The chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 45 at.%, Nb 8 at.%, B 1.4 at.%, Si 0.2 at.%, with the balance being Ti and unavoidable impurity elements.

[0062] A method for preparing high Nb-TiAl based composite materials for powder metallurgy, wherein the method for preparing high Nb-TiAl based composite materials for powder metallurgy is combined with Figure 1 The preparation steps include the following:

[0063] S1. Raw Material Weighing and Melting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder, or aluminum-boron master alloy according to the above chemical composition ratio. Then, use vacuum suspension melting to fully melt the raw materials according to the composition ratio to obtain the dimensional... Cylindrical master alloy ingot, 50mm × 600mm;

[0064] S2, Atomization Powdering: The master alloy ingot obtained in S1 is atomized by plasma rotating electrode and then the powder is sieved to obtain pre-alloyed powder with a particle size range of 45-150μm and an oxygen content of 410ppm.

[0065] S3. Powder Hot Press Sintering: The pre-alloyed powder of S2 is induction hot press sintered into shape. The vacuum degree inside the induction hot press sintering furnace is 5.3 × 10⁻⁶. -3 The sintering conditions were: Pa, sintering temperature: 1425℃, sintering pressure: 100MPa, sintering time: 15min, and cooling to room temperature in the furnace after sintering. The mold used was made of carbon fiber. Cylindrical high-Nb-TiAl based composite preform of 50mm×10mm.

[0066] The matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy prepared in this embodiment is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 60 μm. The matrix microstructure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

[0067] The high Nb-TiAl based composite material for powder metallurgy prepared in this embodiment has a density of 99.6%, a room temperature tensile strength of 743 MPa, and an elongation after fracture of 0.9%; a high temperature tensile strength of 612 MPa at 800℃ with an elongation after fracture of 2.2%; a high temperature tensile strength of 565 MPa at 900℃ with an elongation after fracture of 17.7%; and a creep life greater than 500 h under creep conditions of 800℃ and 100 MPa, with a minimum creep rate of 2.6 × 10⁻⁶. -8 s -1 .

[0068] Comparative Example 1

[0069] Using the same preparation method as in Example 1, a Ti-45Al-8Nb (at.%) alloy was prepared. Its density was 99.5%, its room temperature tensile strength was 605 MPa with an elongation after fracture of 0.2%, its 800℃ tensile strength was 572 MPa with an elongation after fracture of 0.42%, and its 900℃ tensile strength was 538 MPa with an elongation after fracture of 0.47%. Creep tests at 800℃ and 100 MPa showed a creep life greater than 500 hours and a minimum creep rate of 6.2 × 10⁻⁶. -8 s -1 .

[0070] As can be seen from the combined results of Example 1 and Comparative Example 1, Comparative Example 1 uses a Ti-45Al-8Nb alloy, which, compared to Example 1, does not contain B and Si and does not form a composite material. Compared to Example 1, the alloy prepared in Comparative Example 1 has lower room temperature / high temperature strength and elongation after fracture, and a higher creep rate. This indicates that the room temperature and high temperature mechanical properties of the composite material are significantly improved compared to the uncomposite Ti-45Al-8Nb alloy.

[0071] Example 2

[0072] This embodiment provides a high Nb-TiAl-based composite material for powder metallurgy. The chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 45 at.%, Nb 8 at.%, B 1.1 at.%, Si 0.3 at.%, with the balance being Ti and unavoidable impurity elements.

[0073] A method for preparing high Nb-TiAl based composite materials for powder metallurgy, wherein the method for preparing high Nb-TiAl based composite materials for powder metallurgy is combined with Figure 1 The preparation steps include the following:

[0074] S1. Raw Material Weighing and Melting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder, or aluminum-boron master alloy according to the above chemical composition ratio. Then, use vacuum suspension melting to fully melt the raw materials according to the composition ratio to obtain the dimensional... Cylindrical master alloy ingots measuring 60mm × 600mm;

[0075] S2, Atomization powder production: The master alloy ingot obtained in S1 is atomized by plasma rotating electrode and then the powder is sieved to obtain pre-alloyed powder with a particle size range of less than 45μm required for powder metallurgy and an oxygen content of 670ppm.

[0076] S3. Powder Hot Press Sintering: The pre-alloyed powder of S2 is induction hot pressing sintered into shape. The vacuum degree inside the induction hot pressing sintering furnace is 8.2 × 10⁻⁶. -3 The sintering conditions were: Pa, sintering temperature: 1200℃, sintering pressure: 50MPa, sintering time: 60min, and cooling to room temperature in the furnace after sintering. The mold used was made of graphite. A cylindrical high-Nb-TiAl based composite preform measuring 40mm × 8mm;

[0077] The matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy prepared in this embodiment is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 10 μm. The matrix microstructure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

[0078] The high Nb-TiAl based composite material for powder metallurgy prepared in this embodiment has a density of 99.5%, a room temperature tensile strength of 733 MPa, and an elongation after fracture of 1.6%; a high temperature tensile strength of 607 MPa at 800℃ with an elongation after fracture of 2.8%; a high temperature tensile strength of 526 MPa at 900℃ with an elongation after fracture of 21.4%; and a creep life greater than 500 h under creep conditions of 800℃ and 100 MPa, with a minimum creep rate of 7.6 × 10⁻⁶. -8 s -1 .

[0079] Comparative Example 2

[0080] Using the same preparation method as in Example 2, a Ti-45Al-8Nb-0.3Si (at.%) alloy was prepared. Its density was 99.5%, its room temperature tensile strength was 588 MPa with an elongation after fracture of 1.2%, its tensile strength at 800℃ was 465 MPa with an elongation after fracture of 0.61%, and its tensile strength at 900℃ was 326 MPa with an elongation after fracture of 31.3%. Creep tests at 800℃ and 100 MPa showed a creep life greater than 500 hours and a minimum creep rate of 9.4 × 10⁻⁶ h. -8 s -1 .

[0081] It can be seen from the combined results of Example 2 and Comparative Example 2 that Comparative Example 2 uses a Ti-45Al-8Nb-0.3Si alloy, which does not contain B compared to Example 1. Compared to Example 2, the alloy prepared in Comparative Example 2 has lower room temperature / high temperature strength and elongation after fracture, and a higher creep rate. This indicates that the composite material formed by introducing B has significantly improved room temperature and high temperature mechanical properties compared to the Ti-45Al-8Nb-0.3Si alloy without B composite.

[0082] Example 3

[0083] This embodiment provides a high Nb-TiAl-based composite material for powder metallurgy. The chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 45 at.%, Nb 8 at.%, B 1.0 at.%, Si 0.1 at.%, with the balance being Ti and unavoidable impurity elements.

[0084] A method for preparing high Nb-TiAl based composite materials for powder metallurgy, wherein the method for preparing high Nb-TiAl based composite materials for powder metallurgy is combined with Figure 1 The preparation steps include the following:

[0085] S1. Raw Material Weighing and Melting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder, or aluminum-boron master alloy according to the above chemical composition ratio. Then, use vacuum suspension melting to fully melt the raw materials according to the composition ratio to obtain the dimensional... Cylindrical master alloy ingot, 50mm × 600mm;

[0086] S2, Atomization Powdering: The master alloy ingot obtained in S1 is atomized by plasma rotating electrode to produce powder, and then the powder is sieved to obtain pre-alloyed powder with a particle size range of 45-150μm and an oxygen content of 480ppm required for powder metallurgy.

[0087] S3. Powder Hot Pressing Sintering: The pre-alloyed powder of S2 is filled into a stainless steel mold, vacuum-sealed, and then hot isostatically pressed (HIP) to form the mold. The HIP sintering temperature is 1200℃, the sintering pressure is 300MPa, and the sintering time is 120min. After sintering, the mold is cooled to room temperature in the furnace to obtain the dimensional... Cylindrical high-Nb-TiAl based composite preform, 50mm × 100mm;

[0088] S4. High-temperature heat treatment: The high Nb-TiAl-based composite material blank of S3 was subjected to high-temperature heat treatment at 1320℃ for 10 min and then cooled to room temperature in the furnace to obtain a high Nb-TiAl-based composite material with a near-lamellar microstructure.

[0089] The matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy prepared in this embodiment is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 65 μm. The matrix microstructure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

[0090] The high Nb-TiAl based composite material for powder metallurgy prepared in this embodiment has a density of 99.8%, a room temperature tensile strength of 730 MPa, an elongation after fracture of 1.1%, a high temperature tensile strength of 603 MPa at 800℃ with an elongation after fracture of 2%, a high temperature tensile strength of 552 MPa at 900℃ with an elongation after fracture of 15.3%, and a creep life of more than 500 h under creep conditions of 800℃ and 100 MPa, with a minimum creep rate of 3.2 × 10⁻⁶. -8 s -1 .

[0091] Example 4

[0092] This embodiment discloses a high Nb-TiAl-based composite material for powder metallurgy. The chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 45 at.%, Nb 8 at.%, B 1.2 at.%, Si 0.2 at.%, with the balance being Ti and unavoidable impurity elements.

[0093] A method for preparing high Nb-TiAl based composite materials for powder metallurgy, wherein the method for preparing high Nb-TiAl based composite materials for powder metallurgy is combined with Figure 1 The preparation steps include the following:

[0094] S1. Raw Material Weighing and Melting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder, or aluminum-boron master alloy according to the above chemical composition ratio. Then, use vacuum suspension melting to fully melt the raw materials according to the composition ratio to obtain the dimensional... Cylindrical master alloy ingot, 50mm × 600mm;

[0095] S2, Atomization Powdering: The master alloy ingot obtained in S1 is atomized by plasma rotating electrode and then the powder is sieved to obtain pre-alloyed powder with a particle size range of 45-150μm and an oxygen content of 452ppm.

[0096] S3. Powder Hot Pressing Sintering: The pre-alloyed powder of S2 is filled into a stainless steel mold, vacuum-sealed, and then hot isostatically pressed (HIP) to form the mold. The HIP sintering temperature is 1270℃, the sintering pressure is 270MPa, and the sintering time is 240min. After sintering, the mold is cooled to room temperature in the furnace to obtain the dimensional... Cylindrical high-Nb-TiAl based composite preform, 50mm × 100mm;

[0097] S4. High-temperature heat treatment: The high Nb-TiAl-based composite material blank of S3 was subjected to high-temperature heat treatment at 1340℃ for 60 min and then air-cooled to room temperature to obtain a high Nb-TiAl-based composite material with a full lamellar microstructure.

[0098] The matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy prepared in this embodiment is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 80 μm. The matrix microstructure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

[0099] The high Nb-TiAl based composite material for powder metallurgy prepared in this embodiment has a density of 99.9%, a room temperature tensile strength of 682 MPa, an elongation after fracture of 0.5%, a high temperature tensile strength of 548 MPa at 800℃ with an elongation after fracture of 1.7%, a high temperature tensile strength of 507 MPa at 900℃ with an elongation after fracture of 14.2%, and a creep life of more than 500 h under creep conditions of 800℃ and 100 MPa, with a minimum creep rate of 1.3 × 10⁻⁶. -8 s -1 .

[0100] Example 5

[0101] This embodiment provides a high Nb-TiAl-based composite material for powder metallurgy. The chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 45 at.%, Nb 8 at.%, B 1.3 at.%, Si 0.1 at.%, with the balance being Ti and unavoidable impurity elements.

[0102] A method for preparing high Nb-TiAl based composite materials for powder metallurgy, wherein the method for preparing high Nb-TiAl based composite materials for powder metallurgy is combined with Figure 1 The preparation steps include the following:

[0103] S1. Raw Material Weighing and Melting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder, or aluminum-boron master alloy according to the above chemical composition ratio. Then, use vacuum suspension melting to fully melt the raw materials according to the composition ratio to obtain the dimensional... Cylindrical master alloy ingot, 50mm × 600mm;

[0104] S2, Atomization Powdering: The master alloy ingot obtained in S1 is atomized by plasma rotating electrode and then the powder is sieved to obtain pre-alloyed powder with a particle size range of less than 45μm required for powder metallurgy and an oxygen content of 655ppm.

[0105] S3. Powder Hot Pressing Sintering: The pre-alloyed powder of S2 is sintered by spark plasma sintering. The vacuum degree inside the spark plasma sintering furnace is 5.1 × 10⁻⁶. -3 The sintering conditions were: Pa, sintering temperature: 1280℃, sintering pressure: 100MPa, sintering time: 10min, and cooling to room temperature in the furnace after sintering. The mold used was made of carbon fiber. A cylindrical high-Nb-TiAl based composite preform measuring 30mm × 6mm;

[0106] The matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy prepared in this embodiment is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 47 μm. The matrix structure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

[0107] The high Nb-TiAl based composite material for powder metallurgy prepared in this embodiment has a density of 99.5%, a room temperature tensile strength of 752 MPa, and an elongation after fracture of 1.8%; a high temperature tensile strength of 635 MPa at 800℃ with an elongation after fracture of 3%; a high temperature tensile strength of 580 MPa at 900℃ with an elongation after fracture of 22%; and a creep life greater than 500 h under creep conditions of 800℃ and 100 MPa, with a minimum creep rate of 3.7 × 10⁻⁶. -8 s -1 .

[0108] Example 6

[0109] This embodiment provides a high Nb-TiAl-based composite material for powder metallurgy. The chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 45 at.%, Nb 8 at.%, B 1.3 at.%, Si 0.3 at.%, with the balance being Ti and unavoidable impurity elements.

[0110] A method for preparing high Nb-TiAl based composite materials for powder metallurgy, wherein the method for preparing high Nb-TiAl based composite materials for powder metallurgy is combined with Figure 1 The preparation steps include the following:

[0111] S1. Raw Material Weighing and Melting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder, or aluminum-boron master alloy according to the above chemical composition ratio. Then, use vacuum suspension melting to fully melt the raw materials according to the composition ratio to obtain the dimensional... Cylindrical master alloy ingot, 50mm × 600mm;

[0112] S2, Atomization powder production: The master alloy ingot obtained in S1 is atomized by plasma rotating electrode and then the powder is sieved to obtain pre-alloyed powder with a particle size range of less than 45μm required for powder metallurgy and an oxygen content of 624ppm.

[0113] S3. Powder Hot Pressing Sintering: The pre-alloyed powder of S2 is sintered by spark plasma sintering. The vacuum degree inside the spark plasma sintering furnace is 4.7 × 10⁻⁶. -3The sintering conditions were: Pa, sintering temperature: 1230℃, sintering pressure: 50MPa, sintering time: 30min, and cooling to room temperature in the furnace after sintering. The mold used was made of graphite. A cylindrical high-Nb-TiAl based composite preform measuring 45mm × 7mm;

[0114] The matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy prepared in this embodiment is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 20 μm. The matrix structure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

[0115] The high Nb-TiAl based composite material for powder metallurgy prepared in this embodiment has a density of 99.4%, a room temperature tensile strength of 761 MPa, and an elongation after fracture of 1.5%; a high temperature tensile strength of 623 MPa at 800℃ with an elongation after fracture of 3.5%; a high temperature tensile strength of 527 MPa at 900℃ with an elongation after fracture of 25.6%; and a creep life greater than 500 h under creep conditions of 800℃ and 100 MPa, with a minimum creep rate of 6.4 × 10⁻⁶. -8 s -1 .

[0116] The above-mentioned solution proposes a high Nb-TiAl based composite material for powder metallurgy and its preparation method, which can solve the problems of low room temperature plasticity, limited high temperature resistance, oxidation and microstructure stability of existing TiAl alloys, as well as the technical problems of existing TiAl alloys having a service temperature not exceeding 650℃ and being difficult to form.

[0117] This invention, through rational design of the TiAl alloy composition, powder metallurgy, high-temperature heat treatment + low-temperature heat treatment, introduces borides and silicides into the matrix to form a fine and uniform ceramic phase composite structure. This results in a composite material with a room temperature tensile strength of not less than 700 MPa, a yield strength of not less than 600 MPa, and an elongation after fracture of not less than 0.5%; a high-temperature tensile strength of not less than 600 MPa, a yield strength of not less than 500 MPa, and an elongation after fracture of not less than 1.5% at 800℃; a high-temperature tensile strength of not less than 500 MPa, a yield strength of not less than 400 MPa, and an elongation after fracture of not less than 10% at 900℃; and a creep life greater than 500 hours and a minimum creep rate less than 8 × 10⁻⁶ h under creep conditions of 800℃ and 100 MPa. -8 s -1 It is a high Nb-TiAl based composite material with excellent comprehensive performance at both room temperature and high temperature.

[0118] The high Nb-TiAl based composite material of the present invention meets the requirements of strength, creep resistance and oxidation resistance of hot end components at service temperatures of 650-800℃. It can be applied to rotor components such as engine turbine blades and turbocharger turbines of automobile engines, and has great application and promotion value.

[0119] In summary, compared with traditional TiAl-based composite material preparation methods, the method of this invention obtains high-Nb-TiAl-based composite materials for high-temperature service through composition design, pre-alloyed powder preparation, and powder metallurgy hot pressing sintering. The prepared composite material has excellent room temperature and high-temperature mechanical properties, further broadening the service temperature range of TiAl alloys. The composition design of this invention is controllable, the production equipment and process are simple, the production cost is low, and the efficiency is high, which is conducive to large-scale industrial production and application.

[0120] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0121] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0122] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0123] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-Nb-TiAl based composite material for powder metallurgy, characterized in that, The chemical composition of the high Nb-TiAl-based composite material for powder metallurgy, by atomic percentage, is: Al 44-49 at.%, Nb 1-10 at.%, B 0.6-1.4 at.%, Si 0.1-0.3 at.%, with the balance being Ti and unavoidable impurity elements.

2. The high Nb-TiAl based composite material for powder metallurgy according to claim 1, characterized in that, The matrix microstructure of the high Nb-TiAl-based composite material for powder metallurgy is mainly composed of γ-TiAl phase and α2-Ti3Al phase. The matrix grains are fine, with a size of 5-80 μm. The matrix microstructure contains a large number of borides with a size of 0.05-50 μm and a small amount of silicides with a size of 10-500 nm. A large number of silicides will precipitate from the matrix during long-term service at high temperature.

3. The high Nb-TiAl based composite material for powder metallurgy according to claim 1, characterized in that, The high Nb-TiAl based composite material for powder metallurgy has a room temperature tensile strength of not less than 700 MPa, a yield strength of not less than 600 MPa, and an elongation after fracture of not less than 0.5%; a high temperature tensile strength of not less than 600 MPa, a yield strength of not less than 500 MPa, and an elongation after fracture of not less than 1.5%; a high temperature tensile strength of not less than 500 MPa, a yield strength of not less than 400 MPa, and an elongation after fracture of not less than 10%; and under creep conditions of 800℃ and 100 MPa, a creep life greater than 500 h and a minimum creep rate less than 8 × 10⁻⁶. -8 s -1 .

4. A method for preparing a high Nb-TiAl based composite material for powder metallurgy as described in claim 1, characterized in that, The preparation method of the high Nb-TiAl based composite material for powder metallurgy includes the following preparation steps: S1. Raw material weighing and smelting: Weigh the sponge titanium, high-purity aluminum, aluminum-niobium master alloy, aluminum-silicon master alloy, boron powder or aluminum-boron master alloy according to the above chemical composition ratio, and then use vacuum suspension smelting to fully smelt the raw materials of the above composition ratio to obtain the master alloy ingot. S2, Atomization powder production: The master alloy ingot obtained in S1 is subjected to plasma rotating electrode atomization powder production or gas atomization powder production, and then the powder is sieved to obtain pre-alloyed powder with the required particle size for powder metallurgy. S3. Powder hot pressing sintering: The pre-alloyed powder of S2 is hot pressed and sintered to obtain a high Nb-TiAl based composite material blank with the required shape and size. S4. High-temperature heat treatment / low-temperature heat treatment: High-temperature heat treatment is performed on the high Nb-TiAl matrix composite billet of S3 to regulate the matrix microstructure, or low-temperature heat treatment is performed to relieve stress and regulate the precipitation of the reinforcing phase, so as to obtain high Nb-TiAl matrix composites with different matrix microstructures.

5. The method for preparing high Nb-TiAl based composite materials for powder metallurgy according to claim 4, characterized in that, S1 is a master alloy ingot of a certain size. 50- Cylindrical blanks of 60mm × 300-600mm.

6. The method for preparing high Nb-TiAl based composite materials for powder metallurgy according to claim 4, characterized in that, The pre-alloyed powder obtained by sieving in S2 has a particle size of 5-300μm and an oxygen content of less than 800ppm.

7. The method for preparing high Nb-TiAl based composite materials for powder metallurgy according to claim 4, characterized in that, S3 includes any one of the following powder metallurgy hot pressing sintering methods: hot isostatic pressing, induction hot pressing sintering, spark plasma sintering, and other hot pressing sintering methods; the vacuum degree inside the sintering equipment or forming mold is less than 1×10⁻⁶. -2 Pa or argon inert gas protection.

8. The method for preparing high Nb-TiAl based composite materials for powder metallurgy according to claim 7, characterized in that, The sintering temperature for S3 medium-temperature isostatic pressing is 1000-1400℃, the sintering pressure is 100-300MPa, and the sintering time is 0.5-6h; the sintering temperature for induction hot pressing and discharge plasma sintering is 1000-1450℃, the sintering pressure is 30-100MPa, and the sintering time is 10-120min.

9. The method for preparing high Nb-TiAl based composite materials for powder metallurgy according to claim 7, characterized in that, The S3 medium-temperature isostatic pressing mold is made of stainless steel; the induction hot pressing sintering and spark plasma sintering molds are made of graphite or carbon fiber.

10. The method for preparing high Nb-TiAl based composite materials for powder metallurgy according to claim 4, characterized in that, The S4 high-temperature heat treatment and low-temperature heat treatment are carried out under vacuum or argon atmosphere protection; the high-temperature heat treatment temperature is 1250-1425℃ and the high-temperature heat treatment time is 0.5-72h; the low-temperature heat treatment temperature is 700-900℃ and the low-temperature heat treatment time is 2-24h; the cooling method includes at least one of furnace cooling, air cooling, water cooling and oil cooling.

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