Methods for regulating the interfacial microstructure and properties of diffusion-bonded joints in TiAl / Ti2AlNb alloys

Abstract

This disclosure provides a method for controlling the interfacial microstructure and properties of TiAl / Ti2AlNb alloy diffusion-bonded joints, comprising: subjecting the TiAl / Ti2AlNb alloy diffusion-bonded joints to electro-pulse treatment and thermomechanical treatment respectively; wherein the electro-pulse parameters are: pulse voltage of 30~50V, pulse frequency of 120~180Hz, and pulse time of 10~30s; the thermomechanical treatment parameters are: deformation temperature of 1050℃~1150℃, holding time of 20~40min, and deformation controlled below 15%, wherein the deformation direction during the thermomechanical treatment is parallel to the alloy diffusion-bonded interface. This invention employs an integrated technology of post-weld electro-pulse and thermomechanical coupling treatment, which can eliminate the defect of equal brittleness at the interface of the TiAl / Ti2AlNb alloy joint, while simultaneously allowing for more complete microstructure evolution, a more uniform and finer diffusion layer microstructure, and ultimately resulting in better strength and toughness at the TiAl / Ti2AlNb alloy joint, yielding a bi-alloy material with excellent comprehensive mechanical properties.

Description

Technical Field

[0001] The embodiments of this disclosure relate to the field of interface microstructure control technology for dissimilar metal material bonding, specifically, to a method applicable to controlling the interface microstructure and properties of TiAl / Ti2AlNb alloy diffusion bonding joints. Background Technology

[0002] Currently, the high-temperature materials widely used in aerospace vehicle engines mainly include titanium-based alloys, nickel-based alloys, and cobalt-based alloys. Among them, nickel-based and cobalt-based high-temperature alloys have high densities, making it difficult to meet the lightweight requirements of aerospace materials. High-temperature titanium alloys, on the other hand, suffer from limitations in operating temperature and poor resistance to high-temperature oxidation and creep. Therefore, the design and development of lightweight high-temperature structural materials with excellent properties has always been a research hotspot for researchers both domestically and internationally.

[0003] TiAl alloys possess advantages such as low density, high melting point, high high-temperature specific strength, and good oxidation and creep resistance, making them promising for applications in lightweight high-temperature structural materials. However, TiAl exhibits poor room-temperature plasticity and fracture toughness, and its creep and oxidation resistance decrease sharply when service temperatures exceed 800℃. Adding Nb to TiAl alloys yields Ti2AlNb alloys, which improves both room-temperature plasticity and high-temperature performance; however, the addition of Nb increases the material density, hindering its lightweight nature. Integral bladed disks welded from TiAl alloy blades and Ti2AlNb alloy inner rings can improve the thrust-to-weight ratio and efficiency of aerospace engines while maintaining high-temperature reliability by reducing weight. However, the performance at the welded joint is poor. Although there are reports on methods for controlling the performance of TiAl-based alloy heterogeneous diffusion bonding joints, these generally employ a single method, making it difficult to effectively control the microstructure of the bonding interface and thus failing to significantly improve joint performance. Summary of the Invention

[0004] The embodiments described in this paper address the technical problems existing in the background art above and propose a method for controlling the interfacial microstructure and properties of TiAl / Ti2AlNb alloy diffusion bonding joints. The method mainly adopts an integrated technology of post-weld electrical pulse and thermomechanical coupling treatment. The two work together to control the interfacial microstructure of the welded joint, thereby improving the joint strength and plasticity at the same time, which has good application prospects.

[0005] According to the present disclosure, a method for controlling the interfacial microstructure and properties of diffusion-bonded joints in TiAl / Ti2AlNb alloys is provided, including:

[0006] The TiAl / Ti2AlNb alloy diffusion joints were subjected to electro-pulse treatment and thermo-mechanical treatment, respectively.

[0007] The electrical pulse parameters are as follows: pulse voltage is 30~50V, pulse frequency is 120~180Hz, and pulse time is 10~30s.

[0008] The thermomechanical treatment parameters are: deformation temperature of 1050℃~1150℃, holding time of 20~40min, and deformation amount controlled below 15%.

[0009] As a further explanation of this disclosure, the deformation direction during the thermomechanical treatment is parallel to the alloy diffusion bonding interface.

[0010] As a further explanation of this disclosure, the deformation amount during the thermomechanical treatment is controlled at 9% to 15%.

[0011] As a further explanation of this disclosure, the depressurization rate in the thermomechanical treatment is 0.35~0.5 mm / s.

[0012] As a further explanation of this disclosure, the brittle phase at the interface of the TiAl / Ti2AlNb alloy diffusion joint can be completely eliminated after the electro-pulse treatment and thermomechanical treatment.

[0013] As a further explanation of this disclosure, the strength and toughness of the TiAl / Ti2AlNb alloy diffusion joint are improved after the electro-pulse treatment and thermomechanical treatment.

[0014] Compared with the prior art, the technical solution disclosed herein has the following beneficial technical effects:

[0015] This invention employs an integrated post-weld electro-pulse and thermomechanical coupling treatment technology, which can eliminate the equal brittleness defect at the interface of TiAl / Ti2AlNb alloy joints. At the same time, it allows for more complete microstructure evolution, a more uniform and finer diffusion layer structure, and ultimately improves the strength and toughness of the TiAl / Ti2AlNb alloy joint, resulting in a bi-alloy material with excellent comprehensive mechanical properties.

[0016] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings of the embodiments will be briefly described below. It should be understood that the drawings described below only relate to some embodiments of this disclosure and are not intended to limit this disclosure, wherein:

[0018] Figure 1The microstructure is a direct interface between TiAl alloy and Ti2AlNb alloy;

[0019] Figure 2 This is the microstructure of the TiAl / Ti2AlNb alloy bonding interface after electropulse and thermomechanical coupling treatment in Embodiment 1 of the present invention;

[0020] Figure 3 This is a roadmap of the electropulse and thermomechanical coupling processing technology of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are also within the scope of protection of this disclosure.

[0022] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0023] This disclosure addresses the problems of brittle phase formation and low joint performance at the TiAl / Ti2AlNb alloy bonding interface by selecting electro-pulse and thermomechanical coupling technology to strengthen and toughen the TiAl / Ti2AlNb bialloy bonding joint and control the microstructure of the joint interface.

[0024] like Figure 3 As shown, this disclosure provides a method for controlling the microstructure and properties of the diffusion-bonded joint interface in TiAl / Ti2AlNb alloys, comprising the following steps:

[0025] Step 1: Cut the TiAl / Ti2AlNb alloy diffusion joint into a suitable sample size, for example, a sample with a width of 3mm, a thickness of 3mm, and a length of 40mm.

[0026] Step 2: Set appropriate electrical pulse parameters: pulse voltage of 30~50V, pulse frequency of 120~180Hz, and pulse duration of 10~30s, and perform electrical pulse processing. The pulse voltage can be, for example, 30V, 35V, 40V, 45V, 50V, etc.; the pulse frequency can be, for example, 120Hz, 130Hz, 140Hz, 150Hz, 160Hz, 170Hz, 180Hz, etc.; and the pulse duration can be, for example, 10s, 15s, 20s, 25s, 30s, etc.

[0027] Step 3: Set appropriate thermomechanical treatment parameters: deformation temperature of 1050~1150℃, holding time of 20~40min, pressing rate of 0.35~0.5mm / s, and deformation amount controlled at 9%~15%. Perform thermomechanical treatment, with the deformation direction parallel to the alloy diffusion bonding interface. For example, the deformation temperature can be 1050℃, 1070℃, 1100℃, 1120℃, 1150℃, etc.; the holding time can be 20min, 25min, 30min, 35min, 40min, etc.; and the deformation amount can be 9%, 11%, 13%, 15%, etc.

[0028] Because brittle phases exist at the diffusion bonding interface of dissimilar brittle intermetallic compounds, this invention first eliminates the brittle intermetallic compounds in the interface reaction layer through electro-pulse treatment, thereby increasing the thickness of the diffusion layer and regulating the matrix structure while controlling the interface, preparing for subsequent micro-deformation. Furthermore, during the electro-pulse treatment, based on the resistance characteristics at the diffusion bonding interface of dissimilar brittle intermetallic compounds, this invention rationally sets the electro-pulse treatment parameters to achieve optimal results. After the electro-pulse treatment, thermomechanical treatment is applied. Unlike known thermomechanical treatment methods, because the brittle phases of the diffusion bonding joint have been eliminated through the aforementioned electro-pulse treatment, this invention selects a lower temperature, a larger deformation amount, and a faster deformation rate for the thermomechanical treatment. This micro-deformation of the bialloy joint promotes the precipitation of uniformly dispersed precipitates at the bonding interface, while simultaneously causing interface recrystallization, thereby strengthening the interface and improving the joint performance. Simultaneously, its elongation is increased, resulting in superior performance of the TiAl and Ti2AlNb alloy diffusion bonding joints, yielding a bialloy material with excellent overall performance.

[0029] The following is an explanation with reference to specific embodiments: Example 1

[0030] A method for controlling the interfacial microstructure and properties of diffusion-bonded joints in TiAl / Ti2AlNb alloys is provided, comprising the following steps:

[0031] Step 1: Cut the diffusion-bonded TiAl / Ti2AlNb alloy block into samples with a width of 3 mm, a thickness of 3 mm, and a length of 40 mm.

[0032] Step 2: Perform electrical pulse treatment on the sample. Under the parameters of pulse voltage of 40V, frequency of 150Hz and time of 20s, connect and fix the two ends of the sample to the pulse power supply for electrical pulse treatment.

[0033] Step 3: Perform thermomechanical treatment on the sample. Place the sample in a box furnace and heat it to 1100℃ at a uniform rate (5℃ / min). Hold the temperature for 30 minutes. Then, quickly transfer the sample from the box furnace to a 630T superplastic molding machine for thermomechanical deformation. The pressing rate is 0.45mm / s and the deformation amount is 12%. During the thermomechanical treatment, the deformation direction is parallel to the alloy diffusion bonding interface.

[0034] Performance and organization testing:

[0035] After the treated specimens were cut into tensile specimens, their surfaces were mechanically polished with sandpaper of 80#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence before tensile testing was performed.

[0036] The interface was wire-cut into blocks of appropriate size, which were then mounted, mechanically ground and polished, and the interface structure was observed using a scanning electron microscope. Example 2

[0037] A method for controlling the interfacial microstructure and properties of diffusion-bonded joints in TiAl / Ti2AlNb alloys is provided, comprising the following steps:

[0038] Step 1: Cut the diffusion-bonded TiAl / Ti2AlNb alloy block into samples with a width of 3 mm, a thickness of 3 mm, and a length of 40 mm.

[0039] Step 2: Perform electrical pulse treatment on the sample. Under the parameters of pulse voltage of 30V, frequency of 180Hz and time of 30s, connect and fix the two ends of the sample to the pulse power supply for electrical pulse treatment.

[0040] Step 3: Perform thermomechanical treatment on the sample. Place the sample in a box furnace and heat it to 1050℃ at a uniform rate (5℃ / min). Hold the temperature for 40 minutes. Then, quickly transfer the sample from the box furnace to a 630T superplastic forming machine for thermomechanical deformation. The pressing rate is 0.35mm / s and the deformation amount is 15%. During the thermomechanical treatment, the deformation direction is parallel to the alloy diffusion bonding interface.

[0041] Performance and organization testing:

[0042] After the treated specimens were cut into tensile specimens, their surfaces were mechanically polished with sandpaper of 80#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence before tensile testing was performed.

[0043] The interface was wire-cut into blocks of appropriate size, which were then mounted, mechanically ground and polished, and the interface structure was observed using a scanning electron microscope. Example 3

[0044] A method for controlling the interfacial microstructure and properties of diffusion-bonded joints in TiAl / Ti2AlNb alloys is provided, comprising the following steps:

[0045] Step 1: Cut the diffusion-bonded TiAl / Ti2AlNb alloy block into samples with a width of 3 mm, a thickness of 3 mm, and a length of 40 mm.

[0046] Step 2: Perform electrical pulse treatment on the sample. Under the parameters of pulse voltage of 50V, frequency of 120Hz and time of 10s, connect and fix the two ends of the sample to the pulse power supply for electrical pulse treatment.

[0047] Step 3: Perform thermomechanical treatment on the sample. Place the sample in a box furnace and heat it to 1150℃ at a uniform rate (5℃ / min). Hold the temperature for 20 minutes. Then, quickly transfer the sample from the box furnace to a 630T superplastic molding machine for thermomechanical deformation. The pressing rate is 0.5mm / s and the deformation amount is 9%. During the thermomechanical treatment, the deformation direction is parallel to the alloy diffusion bonding interface.

[0048] Performance and organization testing:

[0049] After the treated specimens were cut into tensile specimens, their surfaces were mechanically polished with sandpaper of 80#, 400#, 600#, 800#, 1000#, 1500#, and 2000# in sequence before tensile testing was performed.

[0050] The interface was wire-cut into blocks of appropriate size, which were then mounted, mechanically ground and polished, and the interface structure was observed using a scanning electron microscope.

[0051] Figure 1 The microstructure is a direct interface between TiAl alloy and Ti2AlNb alloy; Figure 2The image shows the microstructure of the TiAl / Ti2AlNb alloy interface after electropulse and thermomechanical coupling treatment in Embodiment 1 of this invention. As can be seen from the image, the white equiaxed brittle precipitates at the interface have completely disappeared, the diffusion layer thickness has significantly increased, and uniformly dispersed precipitates have formed along the diffusion layer, indicating recrystallization at the interface. Simultaneously, the matrix microstructure of both the TiAl and Ti2AlNb alloys shows a phase transformation of the α2 phase and the elimination of the β phase. This demonstrates that electropulse and thermomechanical coupling treatment can regulate both the TiAl / Ti2AlNb alloy interface and the matrix microstructure, thereby strengthening the interface and effectively improving the strength and toughness of the joint.

[0052] Table 1 below shows the tensile strength and elongation data of the TiAl / Ti2AlNb alloy direct connection joint and the TiAl / Ti2AlNb alloy sample after electro-pulse and thermomechanical coupling treatment in Example 1 of the present invention. As can be seen from the table, after the electro-pulse and thermomechanical coupling treatment provided by the present invention, the tensile strength and elongation of the TiAl / Ti2AlNb alloy connection joint are simultaneously improved, thereby effectively improving the strength and toughness of the connection joint.

[0053] Table 1. Tensile strength and elongation data of the original joined specimens and the specimens after coupling treatment.

[0054]

[0055] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for regulating the interface structure and performance of a TiAl / Ti2AlNb alloy diffusion bonded joint, characterized in that, include: The TiAl / Ti2AlNb alloy diffusion joints were subjected to electro-pulse treatment and thermo-mechanical treatment, respectively. The electrical pulse parameters are as follows: pulse voltage is 30~50V, pulse frequency is 120~180Hz, and pulse time is 10~30s. The thermomechanical treatment parameters are: deformation temperature of 1050℃~1150℃, holding time of 20~40min, and deformation amount controlled below 15%.

2. The method according to claim 1, characterized in that, In the thermomechanical treatment, the deformation direction is parallel to the alloy diffusion bonding interface.

3. The method according to claim 1, characterized in that, The deformation during the thermomechanical treatment is controlled within 9% to 15%.

4. The method according to claim 1, characterized in that, The downward pressure rate during the thermomechanical treatment is 0.35~0.5 mm / s.

5. The method according to claim 1, characterized in that, After the electro-pulse treatment and thermomechanical treatment, the brittle phase at the interface of the diffusion joint of the TiAl / Ti2AlNb alloy can be completely eliminated.

6. The method according to claim 1, characterized in that, After the electro-pulse treatment and thermomechanical treatment, the strength and toughness of the TiAl / Ti2AlNb alloy diffusion joint are improved.

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