A heat treatment method and application of Ti2AlNb alloy diffusion welded structural parts

Abstract

The present invention relates to the field of aerospace vehicles, and more specifically, to a heat treatment method and application of a Ti2AlNb alloy diffusion-welded structural component. The method comprises: subjecting the Ti2AlNb alloy diffusion-welded structural component to a first vacuum heat treatment and a first gas quenching; subjecting the Ti2AlNb alloy diffusion-welded structural component that has undergone the first gas quenching to a second vacuum heat treatment and a second gas quenching; and subjecting the Ti2AlNb alloy diffusion-welded structural component that has undergone the second gas quenching to a heat preservation treatment and furnace cooling. This method can restore the performance of Ti2AlNb alloy diffusion-welded structural components that have undergone diffusion bonding, improve the tensile strength of the alloy material and welded joints at room temperature and 750°C, while ensuring that the room temperature and high temperature plasticity is not less than 6%, and that other comprehensive mechanical properties meet the use requirements, thereby improving the reliability of the Ti2AlNb alloy diffusion-welded structural component.

Description

Technical Field

[0001] The present invention relates to the field of aerospace vehicles, and in particular to a heat treatment method and application of a Ti2AlNb alloy diffusion-welded structural component. Background Art

[0002] With the design requirements of aerospace vehicles being faster, higher and lighter, aircraft and engines have put forward requirements for structural materials to be lighter and more resistant to high temperatures. Lightweight high-temperature materials and lightweight structural design have become the main development trends of structural materials. Ti2AlNb alloy has a low density (5.3g / cm 3 ), higher high temperature yield strength and creep resistance, good flame retardant properties, high specific modulus, low thermal expansion coefficient and non-magnetic properties. The long-term use temperature is 600-750℃, and the short-term use temperature can reach 800-1000℃. It has become one of the new lightweight and high-temperature resistant materials preferred in the aerospace field to replace nickel-based high-temperature alloys.

[0003] The structure is mainly based on lightweight design with thin walls and hollow cavities. However, due to the complex structure of components in the aerospace field, it is usually necessary to connect the same or dissimilar materials. As an intermetallic compound, Ti2AlNb has a long-range ordered atomic structure, and the atoms are bonded by a mixed bond with metallic bonds and covalent bonds. This bonding method makes it have excellent high-temperature performance while also having intrinsic brittleness. The reliability of the performance of the welded joint is a problem. At the same time, due to the structural characteristics of the hollow cavity and thin wall, deformation is prone to occur during welding. During the welding process, air can easily enter the cavity of the hollow structure, causing oxidation problems. This requires that the performance recovery heat treatment after welding requires vacuum. Therefore, achieving reliable connection of Ti2AlNb alloy hollow thin-walled structural parts themselves will become a key issue in the promotion and application of such materials.

[0004] The recent development of solid-phase diffusion bonding technology has effectively solved the problem of joining similar materials in Ti2AlNb alloys. Diffusion bonding, as a precise joining method, relies on localized plastic deformation of the material surface at high temperatures to create intimate contact between the contacting surfaces. Diffusion across the surface layer creates atomic-level bonding, forming a monolithic joint. This minimizes specimen deformation after welding, making it an effective method for joining similar hollow, thin-walled Ti2AlNb alloy components. However, due to the high Nb content in Ti2AlNb alloys, welding temperatures are relatively high, typically between 960°C and 1020°C, within the material's near-β phase region, to ensure interatomic diffusion at the contact interface. Furthermore, due to the hollow structure of the inner cavity, vacuum diffusion welding must be used to prevent oxidation at the weld interface and the hollow cavity. Furthermore, to minimize structural deformation, a sufficiently low cooling rate is required; furnace cooling is generally used in actual production. Due to the high temperature treatment and low cooling rate, the room temperature and elevated temperature strengths of the welded parent metal and joint are significantly lower than those of the pre-welded material. In particular, the tensile strength at a service temperature of 750°C falls far short of the design requirements.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] Aiming at the problem of performance degradation after welding of hollow Ti2AlNb alloy diffusion-welded structural parts used in aerospace aircraft components, the present invention provides a heat treatment method and application of Ti2AlNb alloy diffusion-welded structural parts. The heat treatment method can restore the performance of the structural parts after diffusion bonding, thereby improving the comprehensive mechanical properties of the Ti2AlNb alloy diffusion-welded structural parts.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0008] One aspect of the present invention relates to a heat treatment method for a Ti2AlNb alloy diffusion-welded structural component, comprising the following steps:

[0009] (a) performing a first vacuum heat treatment and a first gas quenching on a Ti2AlNb alloy diffusion-welded structure;

[0010] (b) subjecting the Ti2AlNb alloy diffusion-welded structure that has undergone the first gas quenching to a second vacuum heat treatment and a second gas quenching;

[0011] (c) subjecting the Ti2AlNb alloy diffusion-welded structure that has undergone the second gas quenching to a heat preservation treatment and a furnace cooling.

[0012] The heat treatment method for Ti2AlNb alloy diffusion-welded structural components can restore the performance of Ti2AlNb alloy diffusion-welded structural components after diffusion bonding, improve the tensile strength of the alloy material and the welded joint at room temperature and 750°C, while ensuring that the room temperature and high temperature plasticity is not less than 6%, and that other comprehensive mechanical properties meet the use requirements, thereby improving the reliability of the Ti2AlNb alloy diffusion-welded structural components.

[0013] Another aspect of the present invention also relates to a method for preparing a Ti2AlNb alloy diffusion-welded structural component, including a heat treatment method for the Ti2AlNb alloy diffusion-welded structural component.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The heat treatment method for Ti2AlNb alloy diffusion-welded structural parts provided by the present invention can restore the performance of Ti2AlNb alloy diffusion-welded structural parts after diffusion bonding through a three-step vacuum annealing heat treatment, thereby improving the tensile strength of the alloy material and the welded joint at room temperature and 750°C, while ensuring that the room temperature and high temperature plasticity is not less than 6%, and other comprehensive mechanical properties meet the use requirements, thereby improving the reliability of the Ti2AlNb alloy diffusion-welded structural parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 This is the initial microstructure of the Ti2AlNb alloy diffusion-welded structural component;

[0018] Figure 2 This is the microstructure of the Ti2AlNb alloy diffusion-welded structural component after heat treatment. DETAILED DESCRIPTION

[0019] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0020] One aspect of the present invention relates to a heat treatment method for a Ti2AlNb alloy diffusion-welded structural component, comprising the following steps:

[0021] (a) performing a first vacuum heat treatment and a first gas quenching on a Ti2AlNb alloy diffusion-welded structure;

[0022] (b) subjecting the Ti2AlNb alloy diffusion-welded structure that has undergone the first gas quenching to a second vacuum heat treatment and a second gas quenching;

[0023] (c) subjecting the Ti2AlNb alloy diffusion-welded structure that has undergone the second gas quenching to a heat preservation treatment and a furnace cooling.

[0024] The heat treatment method for Ti2AlNb alloy diffusion-welded structural components can restore the performance of Ti2AlNb alloy diffusion-welded structural components after diffusion bonding through a three-step vacuum annealing heat treatment, thereby improving the tensile strength of the alloy material and the welded joint at room temperature and 750°C, while ensuring that the room temperature and high temperature plasticity is not less than 6%, and that other comprehensive mechanical properties meet the requirements for use, thereby improving the reliability of the Ti2AlNb alloy diffusion-welded structural components.

[0025] The Ti2AlNb alloy diffusion-welded structure is subjected to a first vacuum heat treatment and a first gas quenching to ensure the shape and quantity of the primary strips. The Ti2AlNb alloy diffusion-welded structure, which has undergone the first gas quenching, is subjected to a second vacuum heat treatment and a second gas quenching to ensure the shape and quantity of the secondary strips.

[0026] Furthermore, the vacuum degree of the first vacuum heat treatment is less than 1×10 -1 Pa.

[0027] Furthermore, the temperature of the first vacuum heat treatment is 940°C to 960°C, including but not limited to any one of 940°C, 945°C, 950°C, 955°C, or 960°C, or a range of values ​​therebetween. If the temperature of the first vacuum heat treatment is too high, the plasticity of the structural component will be reduced; if the temperature is too low, the strength of the structural component will be reduced.

[0028] Furthermore, the time of the first vacuum heat treatment is 0.5 to 1.5 h, including but not limited to any one of 0.5 h, 0.7 h, 0.9 h, 1.1 h, 1.3 h or 1.5 h, or a range between any two of them.

[0029] Furthermore, the heating rate of the first vacuum heat treatment is 2 to 4°C / min, including but not limited to any one of 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min or 4°C / min or a range between any two of them.

[0030] Furthermore, the pressure of the first gas quench is 0.5 to 1 bar, including but not limited to any one of 0.5 bar, 0.6 bar, 0.7 bar, 0.8 bar, 0.9 bar, or 1 bar, or any range therebetween. Limiting the gas quench pressure to a certain range allows for reasonable control of the cooling rate of the gas quench.

[0031] Furthermore, the first gas quenching is terminated when the Ti2AlNb alloy diffusion-welded structural component is cooled to a furnace temperature below 100°C (for example, but not limited to, any one of 99°C, 90°C, 80°C, 70°C, 60°C, 50°C, 40°C, 30°C, or 20°C, or a range therebetween). Terminating the first gas quenching at a furnace temperature below 100°C minimizes residual stress in the structural component and prevents deformation or cracking.

[0032] Furthermore, the vacuum degree of the second vacuum heat treatment is less than 1×10 -1 Pa.

[0033] Furthermore, the temperature of the second vacuum heat treatment is 780-800°C, including but not limited to any one of 780°C, 785°C, 790°C, 795°C, or 800°C, or a range between any two of them. The temperature of the second vacuum heat treatment is the aging temperature. If the temperature is too high, the strength will be reduced, and if the temperature is too low, the plasticity will be insufficient.

[0034] Furthermore, the time of the second vacuum heat treatment is 6 to 10 hours, including but not limited to any one of 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, or a range between any two of them.

[0035] Furthermore, the heating rate of the second vacuum heat treatment is 2 to 4°C / min, including but not limited to any one of 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min or 4°C / min or a range between any two of them.

[0036] Furthermore, the second gas quenching pressure is 0.5 to 1 bar, including but not limited to any one of 0.5 bar, 0.6 bar, 0.7 bar, 0.8 bar, 0.9 bar, or 1 bar, or any range therebetween. Limiting the gas quenching pressure to a certain range allows for reasonable control of the gas quenching cooling rate.

[0037] Furthermore, the second gas quenching is terminated when the Ti2AlNb alloy diffusion-welded structure is cooled to a furnace temperature below 400°C (for example, but not limited to, any one of 399°C, 350°C, 300°C, 250°C, 200°C, 150°C, or 100°C, or a range therebetween). Terminating the second gas quenching at a furnace temperature below 400°C can release some residual stress.

[0038] Furthermore, the holding treatment temperature is 350°C to 400°C, including but not limited to any one of 350°C, 360°C, 370°C, 380°C, 390°C, or 400°C, or any range therebetween. If the holding treatment temperature is too high, the microstructure transformation may be affected; if the temperature is too low, the stress relief effect may be insignificant.

[0039] Furthermore, the heat preservation treatment time is 6 to 10 hours, including but not limited to any one of 6 hours, 7 hours, 8 hours, 9 hours or 10 hours or a range between any two of them.

[0040] Furthermore, the Ti2AlNb alloy diffusion-welded structural component is cooled to a furnace temperature below 100°C (for example, but not limited to, any one of 99°C, 90°C, 80°C, 70°C, 60°C, 50°C, 40°C, 30°C, or 20°C, or a range therebetween), whereupon furnace cooling is terminated. Terminating furnace cooling at a temperature below 100°C minimizes residual stress in the structural component, preventing deformation or cracking.

[0041] The main purpose of heat preservation treatment and furnace cooling is to eliminate the residual stress during high temperature gas quenching.

[0042] Furthermore, the Ti2AlNb alloy diffusion-welded structural component includes but is not limited to: a Ti2AlNb alloy hollow structure diffusion-welded structural component.

[0043] Furthermore, the Ti2AlNb alloy diffusion-welded structure is placed on a flat ceramic sheet for the first and second vacuum heat treatments. The ceramic sheet is used to prevent the metal from reacting with the steel base and to provide a flat surface for the workpiece to ensure uniform stress distribution.

[0044] The diffusion-welded structural part mentioned in the present invention refers to a welded structural part obtained by diffusion-bonding two Ti2AlNb alloy parts of the same composition using a vacuum diffusion bonding process and then cooling them in a vacuum furnace.

[0045] Gas quenching as mentioned in the present invention is a metal heat treatment process, which refers to the process of heating a metal material such as steel to a certain temperature and then rapidly cooling it using high-pressure gas.

[0046] The furnace cooling mentioned in the present invention refers to a method in which the material or workpiece is heated and kept warm in a heat treatment furnace, and then the furnace power is cut off to allow the material or workpiece to cool along with the furnace.

[0047] The present invention adopts a vacuum heat treatment furnace with a gas quenching function to perform performance recovery heat treatment on the structural parts after diffusion bonding.

[0048] Another aspect of the present invention also relates to a method for preparing a Ti2AlNb alloy diffusion-welded structural component, including a heat treatment method for the Ti2AlNb alloy diffusion-welded structural component.

[0049] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0050] Example 1

[0051] The heat treatment method of the Ti2AlNb alloy diffusion-welded structural component provided in this embodiment includes the following steps:

[0052] The first step of solution annealing heat treatment: the Ti2AlNb alloy diffusion welded structure is placed in a vacuum heat treatment furnace for the first vacuum heat treatment. The Ti2AlNb alloy diffusion welded structure is placed on a flat ceramic sheet and vacuum is started. The vacuum degree reaches 1×10 -1 Pa or less; apply electric heating, and the workpiece heats up along with the furnace, with the heating rate controlled at 3°C / min, heating to 945°C, and holding for 1 hour; after the holding period, perform the first gas quenching at a pressure of 1 bar, with a cooling rate of 50°C / min, and cool to below 100°C before being removed from the furnace;

[0053] The second step is aging annealing heat treatment: the Ti2AlNb alloy diffusion welding structure is placed in a vacuum heat treatment furnace for the second vacuum heat treatment. The Ti2AlNb alloy diffusion welding structure is placed on a flat ceramic sheet and the vacuum degree reaches 1×10 -1 Start electric heating below Pa, control the heating rate at 3℃ / min, heat to 780℃, and keep it warm for 6 hours; after the end of the heat preservation, perform the second gas quenching at a pressure of 1 bar, maintain the cooling rate at about 50℃ / min, and cool it to below 400℃;

[0054] The third step is stress relief annealing heat treatment: keep the temperature at 400℃ for 6 hours, cool the furnace to below 100℃ and take it out of the furnace.

[0055] Figure 1 This is the initial microstructure of the Ti2AlNb alloy diffusion-welded structural component in this embodiment without heat treatment. Figure 2 This is the organizational morphology of the embodiment after heat treatment to restore performance. Figure 1 and Figure 2 It can be seen that the microstructure of the Ti2AlNb alloy diffusion-welded structural component changes before and after the heat treatment. The microstructure obtained by the three-step heat treatment in this embodiment is a double-lath microstructure composed of α2+O+B2 phases. The size of the primary lath is 5-8 μm, and the size of the secondary lath is about 0.5 μm. Figure 2 .

[0056] Example 2

[0057] The heat treatment method of the Ti2AlNb alloy diffusion-welded structural component provided in this embodiment includes the following steps:

[0058] The first step of solution annealing heat treatment: the Ti2AlNb alloy diffusion welded structure is placed in a vacuum heat treatment furnace for the first vacuum heat treatment. The Ti2AlNb alloy diffusion welded structure is placed on a flat ceramic sheet and vacuum is started. The vacuum degree reaches 1×10 -1 Pa or less; apply electric heating, and the workpiece heats up along with the furnace, with the heating rate controlled at 2°C / min, heating to 940°C and keeping warm for 0.5h; after the end of the holding period, perform the first gas quenching at a pressure of 0.5bar, and cool to below 100°C before being taken out of the furnace;

[0059] The second step is aging annealing heat treatment: the Ti2AlNb alloy diffusion welding structure is placed in a vacuum heat treatment furnace for the second vacuum heat treatment. The Ti2AlNb alloy diffusion welding structure is placed on a flat ceramic sheet and the vacuum degree reaches 1×10 -1 Start electric heating below Pa, control the heating rate at 2℃ / min, heat to 780℃, and keep it warm for 10 hours; after the end of the heat preservation, perform the second gas quenching at a pressure of 0.5 bar and cool to below 400℃;

[0060] The third step is stress relief annealing heat treatment: keep the temperature at 350℃ for 10 hours, cool the furnace to below 100℃ and take it out of the furnace.

[0061] Example 3

[0062] The heat treatment method of the Ti2AlNb alloy diffusion-welded structural component provided in this embodiment includes the following steps:

[0063] The first step of solution annealing heat treatment: the Ti2AlNb alloy diffusion welded structure is placed in a vacuum heat treatment furnace for the first vacuum heat treatment. The Ti2AlNb alloy diffusion welded structure is placed on a flat ceramic sheet and vacuum is started. The vacuum degree reaches 1×10 -1 Pa or less; apply electric heating, and the workpiece heats up along with the furnace, with the heating rate controlled at 4°C / min, heating to 960°C and keeping warm for 1.5 hours; after the end of the holding period, perform the first gas quenching at a pressure of 0.8 bar, and cool to below 100°C before being taken out of the furnace;

[0064] The second step is aging annealing heat treatment: the Ti2AlNb alloy diffusion welding structure is placed in a vacuum heat treatment furnace for the second vacuum heat treatment. The Ti2AlNb alloy diffusion welding structure is placed on a flat ceramic sheet and the vacuum degree reaches 1×10 -1 Start electric heating below Pa, control the heating rate at 4℃ / min, heat to 800℃, and keep it warm for 6h; after the end of the heat preservation, perform the second gas quenching at a pressure of 0.8bar and cool to below 400℃;

[0065] The third step is stress relief annealing heat treatment: keep the temperature at 380℃ for 8 hours, cool the furnace to below 100℃ and take it out of the furnace.

[0066] Comparative Example 1

[0067] The only difference between this comparative example and Example 1 is that the temperature of the first vacuum heat treatment is 1000°C.

[0068] Comparative Example 2

[0069] The only difference between this comparative example and Example 1 is that the pressure of the first gas quenching is 1.5 bar.

[0070] Comparative Example 3

[0071] The only difference between this comparative example and Example 1 is that the temperature of the second vacuum heat treatment is 850°C.

[0072] Comparative Example 4

[0073] The only difference between this comparative example and Example 1 is that the pressure of the second gas quenching is 1.5 bar.

[0074] Experimental example

[0075] The properties of Ti2AlNb alloy diffusion welded structural parts before welding, after welding and after performance recovery heat treatment are shown in Tables 1 and 2.

[0076] Table 1 Tensile properties of Ti2AlNb alloy diffusion welded structural parts before and after welding

[0077]

[0078] Table 2 Comparison of tensile properties of Ti2AlNb alloy diffusion welded structural parts before performance recovery heat treatment

[0079]

[0080] The heat treatment method for Ti2AlNb alloy diffusion-welded structural components provided by the present invention utilizes a three-step vacuum annealing heat treatment process to address the issue of post-weld tensile strength degradation in diffusion-welded structural components with hollow cavities. This method restores the performance of the welded structural components to 90% of the material standard before welding (room temperature tensile strength ≥900 MPa, yield strength ≥760 MPa, room temperature plasticity ≥6%; 750°C room temperature tensile strength ≥540 MPa, yield strength ≥405 MPa, room temperature plasticity ≥9%). This method effectively increases the tensile strength margin of Ti2AlNb alloy diffusion-welded structural components and improves component reliability. The method is simple to operate, has a short process, and offers high stability, making it suitable for industrial production.

[0081] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A heat treatment method for Ti2AlNb alloy diffusion welded structural parts, characterized in that: The following steps are involved: (a) performing a first vacuum heat treatment and a first gas quenching on a Ti2AlNb alloy diffusion-welded structure; The temperature of the first vacuum heat treatment is 940-960°C; The time of the first vacuum heat treatment is 0.5 to 1.5 hours; The pressure of the first gas quenching is 0.5~1 bar; The Ti2AlNb alloy diffusion-welded structural component is cooled to a furnace temperature below 100° C. to terminate the first gas quenching; (b) subjecting the Ti2AlNb alloy diffusion-welded structure that has undergone the first gas quenching to a second vacuum heat treatment and a second gas quenching; The temperature of the second vacuum heat treatment is 780-800°C; The second vacuum heat treatment time is 6 to 10 hours; The pressure of the second gas quenching is 0.5~1 bar; The Ti2AlNb alloy diffusion-welded structural component is cooled to a furnace temperature below 400° C. to terminate the second gas quenching; (c) subjecting the Ti2AlNb alloy diffusion-welded structural component after the second gas quenching to a heat preservation treatment and furnace cooling; The temperature of the heat preservation treatment is 350-400°C; The heat preservation treatment time is 6 to 10 hours.

2. The heat treatment method of the Ti2AlNb alloy diffusion-welded structural component according to claim 1, characterized in that: The vacuum degree of the first vacuum heat treatment is less than 1×10 -1 Pa; And / or, the heating rate of the first vacuum heat treatment is 2-4°C / min.

3. The heat treatment method of the Ti2AlNb alloy diffusion-welded structural component according to claim 1, characterized in that: The vacuum degree of the second vacuum heat treatment is less than 1×10 -1 Pa; And / or, the heating rate of the second vacuum heat treatment is 2-4°C / min.

4. The heat treatment method of the Ti2AlNb alloy diffusion-welded structural component according to claim 1, characterized in that: The Ti2AlNb alloy diffusion-welded structural component is cooled to a furnace temperature below 100° C., and the furnace cooling is terminated.

5. A method for preparing a Ti2AlNb alloy diffusion-welded structural component, characterized in that: A heat treatment method for a Ti2AlNb alloy diffusion-welded structural component comprising the method described in any one of claims 1 to 4.

Images