A TiAl-Ti2AlNb dissimilar metal welding material and its low-temperature and highly efficient diffusion welding connection method

Abstract

The present invention discloses a TiAl-Ti2AlNb dissimilar metal welding material and a low-temperature and highly efficient diffusion welding connection method thereof, belonging to the field of dissimilar metal welding. In this method, the base metals to be welded are assembled in a conductive mold. Under vacuum conditions, a pulsed high current is passed through and pressure is applied. After rapid heating, short-time heat preservation and cooling, the welding is completed. The present invention proposes suitable welding parameters, which can achieve good control over the pulsed high current diffusion welding process of TiAl alloy and Ti2AlNb alloy. Under the conditions that the diffusion time and temperature are significantly less than those of conventional diffusion welding, a defect-free joint structure similar to that of the base metal is obtained, and the room-temperature shear performance of the welded joint of this material reaches 60% to 90% of that of the base metal.

Description

Technical Field

[0001] The present invention belongs to the field of dissimilar metal material welding, and particularly relates to a low-temperature and high-efficiency diffusion welding connection method for TiAl-Ti2AlNb dissimilar materials. Technical Background

[0002] Titanium aluminide intermetallic compounds are emerging lightweight high-temperature structural materials in the aerospace field, with low density, high elastic modulus and high specific strength at high temperature, and excellent flame retardancy, oxidation resistance and creep resistance at high temperature. Among titanium aluminide intermetallic compounds, TiAl alloy and Ti2AlNb alloy are the two most representative materials, each with unique properties. TiAl alloy has attracted much attention for its low density (3.7~3.9 g / cm 3 ) and high specific strength at high temperature, and its working temperature can reach 760°C to 850°C, but its room temperature plasticity and workability are poor; although the density of Ti2AlNb alloy (5.0~5.8 g / cm 3 ) is higher than that of TiAl alloy and its working temperature is between 650°C and 750°C, its plasticity is significantly improved compared with TiAl, and the elongation rate can reach up to 13% at most. Connecting TiAl alloy and Ti2AlNb alloy by welding technology can make full use of the advantages of the two materials to replace traditional nickel-based superalloys to manufacture some key components in aeroengines, effectively reducing the weight of the components. For example, using TiAl alloy to manufacture low-pressure turbine blades with higher service temperature and smaller size, and Ti2AlNb alloy to manufacture low-pressure turbine disks with slightly lower service temperature and larger size. However, due to problems such as post-weld cold cracks and difficulty in deformation at high temperature in the dissimilar metal connection of TiAl and Ti2AlNb alloys, there are great difficulties in welding by conventional methods such as fusion welding and friction welding. Solving their welding problems is the key to promoting the application of TiAl alloy and Ti2AlNb alloy.

[0003] At present, the solid-state diffusion welding technology is a popular method for joining TiAl and Ti2AlNb alloys. Due to the characteristics of small deformation and similar joint microstructure to the base metal, high-strength joints can be obtained. Therefore, the diffusion welding connection technology of TiAl alloy and Ti2AlNb alloy has attracted the research of scholars at home and abroad. The literature "Difiusion Bonding of DissimilarIntermetallic Alloys Based on Ti2AlNb and TiAl, Jianying Zou, Yuyou Cui, RuiYang.: Journal of Marine Science and Technology, 2009, 25(06):P. 819-824." used diffusion welding to join TiAl alloy and Ti2AlNb alloy, and obtained the highest shear strength of 259.8 MPa at the welding parameters of 1000°C / 20MPa / 60min. The research shows that the welding temperature needs to be maintained above 1000°C. When the temperature is lower than 1000°C, the weld microstructure will form brittle AlNb2 tissue; the welding time must reach 60min, but too long welding time will also form a B2-rich zone on the Ti2AlNb alloy side, and the AlNb2 tissue and the B2-rich zone will reduce the joint strength. The literature "Microstructureevolution and mechanical properties of diffusion bonding high Nb containingTiAl alloy to Ti2AlNb alloy, Zhu Lei, Li Jinshan, Tang Bin, Liu Yan, ZhangMengqi, Li Lei, Kou Hongchao.: Vacuum, 2019, 164: P.140-148" also obtained similar results, and the joint strength was the highest at the welding parameters of 1000 °C / 20 MPa / 90 min. On this basis, in order to reduce the formation of brittle phases at the diffusion interface, some researchers further added an interlayer during the welding process. The Beijing Institute of Aeronautical Materials, AECC, proposed a diffusion welding method with a Ti-Nb alloy as the interlayer in the invention with the publication number of "CN114131295A". This interlayer can control the formation of brittle tissue in the connection joint, reduce the residue of the alloy interlayer, reduce the brittleness tendency of the joint, and obtain a weld microstructure similar to the base metal; at the same time, it can reduce the diffusion welding connection temperature to a certain extent. The welding implementation process is: temperature 960°C, welding pressure 5-25MPa, welding time 0.5-1h.However, in the above diffusion welding technology, whether it is the direct connection of TiAl alloy and Ti2AlNb alloy or the method of applying an interlayer, the welding time required is relatively long and the temperature is high, resulting in low production efficiency and increased cost of the welded parts. In addition, since the welding temperature exceeds the safe working temperature of the two base materials and is exposed to high temperature conditions for a long time, it has a non-negligible damage to the mechanical properties of the base materials themselves, which is not conducive to obtaining high-temperature resistant components that meet the requirements of aero-engines in terms of mechanical properties. Summary of the Invention

[0004] In view of the above problems, based on the need to shorten the welding time and reduce the welding temperature for the diffusion welding of TiAl alloy and Ti2AlNb alloy, the present invention provides a method for pulsed high-current diffusion welding. A square-wave pulsed current is passed during the welding process of the welded parts to promote the welding of the welded parts. The pulsed current in this welding method can accelerate the diffusion of elements, thereby achieving the purpose of low-temperature and rapid welding. In addition, the welding heat source comes from the Joule heat of the welded parts themselves, and the highest temperature zone is at the connection interface. Therefore, this method also has the characteristic of non-isothermal temperature, which can reduce the high-temperature damage to the base materials during the welding process and achieve high-efficiency and high-quality connection of the welded parts.

[0005] To prepare a welded joint of TiAl-Ti2AlNb high-strength dissimilar materials. The purpose of the present invention is to provide a low-temperature and high-efficiency diffusion welding connection method for TiAl-Ti2AlNb dissimilar metals.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] (1) Surface treatment of the welding surfaces of TiAl and Ti2AlNb specimens. The surfaces of the specimens are polished successively with 360#, 600#, 1200#, and 2000# SiC water sandpapers. After removing the oxide layer and significant scratches on the specimen surfaces, mechanical polishing is carried out with 1.5# diamond grinding paste until the surfaces to be welded present a mirror surface, and then ultrasonic cleaning is carried out with acetone and absolute ethanol for 5 - 10 min successively. Store them in absolute ethanol for standby before welding.

[0008] (2) Assembly of the welded parts. The polished surfaces of the workpieces to be welded are fitted together and placed into an assembly mold. The assembly mold is made of high-strength graphite to make it have a conductive function. The graphite mold applies pressure to the welding surface, and 0.2 - 0.4 mm graphite paper is placed to increase the conductive area between the mold and the welded parts. When assembling the welded parts, it is required that the temperature measurement holes and the welding interface are at the same height so as to directly detect the temperature of the welding interface.

[0009] (3) Pulsed high-current diffusion welding connection. The assembled workpieces to be welded according to the requirements are placed into a pulsed high-current welding device. The pulsed high-current welding in this technical solution is realized through a spark plasma welding device. After completing the heating program, the pulsed current is disconnected and cooled to room temperature with the furnace.

[0010] Specific welding parameters in step (3):

[0011] Vacuum degree: 9×10 -2 Pa~5×10 -2 Pa,

[0012] Welding temperature: 750°C to 950°C,

[0013] Welding time: 3 min to 20 min,

[0014] Welding pressure: 5 MPa to 15 MPa

[0015] Pulse current: 1500 A to 2500 A,

[0016] Voltage: 3 V to 5 V,

[0017] Pulse ratio (ON / OFF): 12 / 2 to 6.

[0018] Preferred parameters are: welding temperature 900°C, welding time 10 min, welding pressure 10 MPa, pulse On / Off = 12 / 2, welding pressure 10 MPa, pulse current 1800 A, voltage 3.0 - 3.5 V.

[0019] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0020] The present invention proposes a method for joining TiAl alloy and Ti2AlNb alloy by pulsed high - current diffusion welding. This method is simple to operate and does not require skilled operators and special die - sleeve technology.

[0021] Compared with fusion welding, brazing, and conventional hot - press diffusion welding, the pulsed high - current diffusion welding proposed by the present invention does not require overall heating. The heat source mainly comes from the joule heat generated by the interface resistance between the diffusion interfaces and the resistance of the base material itself. The temperature of the diffusion interface is the highest, and the rest of the base material is lower than the diffusion interface. Therefore, the mechanical properties are less affected by heat.

[0022] The present invention can conveniently adjust the current pulse parameters by adjusting the current ON / OFF ratio, and can produce special effects: electro - plastic effect and electric - field - assisted diffusion effect. Among them, the electric field formed by the pulsed high - current has an electro - plastic effect, which can improve the plasticity of the welded part and reduce the welding pressure required. The electric - field - assisted diffusion effect can significantly accelerate element diffusion, reduce the welding temperature and time required. Compared with conventional hot - press diffusion welding, the welding temperature is reduced by more than 100°C, the welding time required is shortened by 50% - 90% or more, the energy consumption is only 1 / 5 - 1 / 3 of that of conventional hot - press diffusion welding, and the welding efficiency is high and the cost is low.

[0023] The electric field formed by pulsed high current can clean the oxides and adsorbed gases at the diffusion interface, purify the welding surface, activate the diffusion interface, and reduce the impurities in the welded joint. The welding time is fast, the joint forming mechanism is special, the brittle structure of the joint is reduced, the grains of the joint are fine, and the TiAl alloy and Ti2AlNb alloy can be directly welded, with a shear strength of up to 258 MPa.

[0024] Pulsed high current diffusion welding has a wide range of applications and can weld most difficult-to-weld metal materials and non-metal materials. The welding parameters have strong applicability, and the welding parameters provided by the present invention are applicable to diffusion welding with intermediate layers such as Ti and Nb added. Brief Description of the Drawings

[0025] Figure 1 Schematic diagram of the pulsed high current diffusion welding process;

[0026] Figure 2 Schematic diagram of the pulsed current during the pulsed high current diffusion welding process;

[0027] Figure 3 It is the interfacial microstructure of the pulsed high current diffusion welded joint under the conditions of a temperature of 900 °C, a welding time of 10 min, a welding pressure of 10 MPa, and ON / OFF = 12 / 2 for the TiAl-Ti2AlNb alloy. Detailed Description of the Invention

[0028] Example 1

[0029] Step 1: Surface treatment of the specimen for welding. The surface of the specimen was polished successively with 360#, 600#, 1200#, and 2000# SiC water sandpapers. After removing the oxide layer and significant scratches on the surface of the specimen, mechanical polishing was carried out with 1.5# diamond spray polishing agent until the surface to be welded showed a mirror finish. Then, it was ultrasonically cleaned with acetone and absolute ethanol for 5 - 10 min in sequence. It was stored in absolute ethanol for standby before welding.

[0030] Step 2: Assembly of the welded parts. The polished surfaces of the workpieces to be welded were fitted together and placed into the assembly mold. The assembly mold was made of high-strength graphite to make it have a conductive function. The graphite mold applied pressure to the welding surface, and 0.2 - 0.4 mm graphite paper was placed to increase the conductive area between the mold and the welded parts. When assembling the welded parts, according to Figure 1 the shown assembly schematic diagram, it was required that the temperature measurement hole and the welding interface were at the same height so as to directly detect the temperature of the welding interface.

[0031] Step 3: Connection by pulsed high current diffusion welding. The assembled workpieces to be welded according to the requirements were placed into the pulsed high current welding equipment. The pulsed high current welding in this technical solution was realized through a spark plasma welding device, and the welding parameters were: vacuum degree 9×10 -2 Pa - 5×10 -2Pa, the welding temperature is 750 °C, the welding time is 20 min, the welding pressure is 15 MPa, the pulse ratio (ON / OFF) = 12 / 4, the voltage is 3.0 - 3.5 V, the pulse current is 1500 A, and the pulse current waveform is as Figure 2 shown. Before the temperature is 50 °C lower than the target welding temperature, the heating rate is 100 °C / min, and then it reaches the target temperature at a heating rate of 25 °C / min. After the heating program is completed, the pulse current is disconnected and cooled to room temperature in the furnace.

[0032] For the strength of the diffusion welding joint of TiAl-Ti2AlNb dissimilar metals with low temperature and high efficiency in this example, according to the room temperature shear test, the obtained shear strength is 178.2 MPa; it reaches 60.5% of the base metal;

[0033] Example 2

[0034] Step 1: Surface treatment of the specimen for welding. The surface of the specimen is polished successively with 360#, 600#, 1200#, and 2000# SiC sandpapers. After eliminating the oxide layer and significant scratches on the specimen surface, mechanical polishing is carried out with 1.5# diamond spray until the surface to be welded presents a mirror surface, and then ultrasonic cleaning is carried out with acetone and absolute ethanol for 5 - 10 min. It is placed in absolute ethanol for storage and standby before welding.

[0035] Step 2: Assembly of the welded parts. The polished surfaces of the workpieces to be welded are fitted together and placed in an assembly mold. The assembly mold is made of high-strength graphite to make it have a conductive function. A 0.2 - 0.4 mm graphite paper is placed on the pressure-applying surface of the graphite mold to the welding machine to increase the conductive area between the mold and the welded parts. When assembling the welded parts, according to the Figure 1 shown assembly schematic diagram, it is required that the temperature measurement hole and the welding interface are at the same height so as to directly detect the temperature of the welding interface.

[0036] Step 3: Diffusion welding connection with pulsed high current. The workpieces to be welded assembled as required are placed in a pulsed high current welding equipment. The pulsed high current welding in this technical solution is realized through a spark plasma welding device, and the welding parameters are: the vacuum degree is 9×10 -2 Pa - 5×10 -2 Pa, the welding temperature is 850 °C, the welding time is 15 min, the welding pressure is 15 MPa, the pulse ratio (ON / OFF) = 12 / 4, the voltage is 3.0 - 3.5 V, the pulse current is 1700 A, and the pulse current waveform is as Figure 2 shown. Before the temperature is 50 °C lower than the target welding temperature, the heating rate is 100 °C / min, and then it reaches the target temperature at a heating rate of 25 °C / min. After the heating program is completed, the pulse current is disconnected and cooled to room temperature in the furnace.

[0037] The strength of the diffusion welding joint of TiAl-Ti2AlNb dissimilar metals with high efficiency at low temperature in this embodiment, tested according to the room-temperature shear test, the obtained shear strength is 201.7 MPa, reaching 68.6% of the base metal.

[0038] Example 3

[0039] Step 1: Surface treatment of the specimen for welding. The surface of the specimen is polished successively with 360#, 600#, 1200#, and 2000# SiC sandpapers. After eliminating the oxide layer and significant scratches on the specimen surface, mechanical polishing is carried out with 1.5# diamond spray until the surface to be welded presents a mirror surface, and then ultrasonic cleaning is performed with acetone and absolute ethanol for 5 - 10 min successively. It is stored in absolute ethanol for standby before welding.

[0040] Step 2: Assembly of the welded parts. The polished surfaces of the workpieces to be welded are fitted together and placed into the assembly mold. The assembly mold is made of high-strength graphite to make it have the function of conducting electricity. A 0.2 - 0.4 mm graphite paper is placed on the pressure-applying surface of the graphite mold for the welding machine to increase the conductive area between the mold and the welded parts. When assembling the welded parts, according to Figure 1 the shown assembly schematic diagram, it is required that the temperature measurement hole and the welding interface are at the same height so as to directly detect the temperature of the welding interface.

[0041] Step 3: Diffusion welding connection with pulsed high current. The assembled workpieces to be welded according to the requirements are placed into the pulsed high-current welding equipment. The pulsed high-current welding in this technical solution is realized through a spark plasma welding device, and the welding parameters are: vacuum degree 9×10 -2 Pa - 5×10 -2 Pa, welding temperature is 900 °C, welding time is 10 min, welding pressure is 10 MPa, pulse ratio (ON / OFF) = 12 / 4, voltage is 3.0 - 3.5 V, pulsed current is 1800 A, and the pulsed current waveform is as Figure 2 shown. Before reaching 50 °C below the target welding temperature, the heating rate is 100 °C / min, and then it reaches the target temperature at a heating rate of 25 °C / min. After completing the heating program, the pulsed current is disconnected, and it is cooled to room temperature with the furnace.

[0042] The strength of the diffusion welding joint of TiAl-Ti2AlNb dissimilar metals with high efficiency at low temperature in this embodiment, tested according to the room-temperature shear test, the obtained shear strength is 237.4 MPa, reaching 80.7% of the base metal.

[0043] Example 4

[0044] Step 1: Surface treatment of the specimen for welding. The surface of the specimen was polished successively with 360#, 600#, 1200#, and 2000# SiC sandpapers. After removing the oxide layer and obvious scratches on the specimen surface, mechanical polishing was carried out with 1.5# diamond spray. After the surface to be welded showed a mirror surface, ultrasonic cleaning was carried out with acetone and absolute ethanol for 5 - 10 min in sequence. It was stored in absolute ethanol for standby before welding.

[0045] Step 2: Assembly of the welded parts. The polished surfaces of the workpieces to be welded were fitted together and placed into the assembly die. The assembly die was made of high-strength graphite to make it have the function of conducting electricity. A 0.2 - 0.4 mm graphite paper was placed on the pressure surface of the graphite die against the welding machine to increase the conductive area between the die and the welded parts. When assembling the welded parts, according to Figure 1 the shown assembly schematic diagram, it was required that the temperature measurement hole and the welding interface were at the same height so as to directly detect the temperature of the welding interface.

[0046] Step 3: Diffusion welding connection with pulsed high current. The assembled workpieces to be welded as required were placed into the pulsed high current welding equipment. The pulsed high current welding in this technical solution was realized through a spark plasma welding device. The welding parameters were: vacuum degree 9×10 -2 Pa - 5×10 -2 Pa, welding temperature 900°C, welding time 10 min, welding pressure 10 MPa, pulse ratio (ON / OFF) = 12 / 2, voltage 3.0 - 3.5 V, pulsed current 1800 A, and the pulsed current waveform was as shown in Figure 2 the figure. Before reaching 50°C lower than the target welding temperature, the heating rate was 100°C / min, and then it reached the target temperature at a heating rate of 25°C / min. After completing the heating program, the pulsed current was disconnected and it was cooled to room temperature with the furnace. The strength of the diffusion welding connection joint of a TiAl - Ti2AlNb dissimilar metal with low temperature and high efficiency in this embodiment, Figure 3 as shown in the figure, was the joint interface morphology under this parameter. The interface structure was uniform and there were no welding defects. According to the room temperature shear test, the obtained shear strength was 252.1 MPa, reaching 85.7% of the base metal;

[0047] Example 5

[0048] Step 1: Surface treatment of the specimen for welding. The surface of the specimen was polished successively with 360#, 600#, 1200#, and 2000# SiC sandpapers. After removing the oxide layer and obvious scratches on the specimen surface, mechanical polishing was carried out with 1.5# diamond spray polishing agent. After the surface to be welded showed a mirror surface, ultrasonic cleaning was carried out with acetone and absolute ethanol for 5 - 10 min in sequence. It was stored in absolute ethanol for standby before welding.

[0049] Step 2: Weldment assembly. Fit the polished surfaces of the workpieces to be welded and place them in the assembly mold. The assembly mold is made of high-strength graphite to endow it with electrical conductivity. Place 0.2 - 0.4 mm graphite paper on the pressure surface of the graphite mold against the welding machine to increase the electrical conductivity area between the mold and the weldment. When assembling the weldment, follow Figure 1 the assembly schematic diagram shown, and require that the temperature measurement hole and the welding interface be at the same height for directly detecting the temperature of the welding interface.

[0050] Step 3: Pulse high-current diffusion welding connection. Place the assembled workpieces to be welded as required into the pulse high-current welding equipment. The pulse high-current welding in this technical solution is realized through a spark plasma welding device, and the welding parameters are: vacuum degree 9×10 -2 Pa - 5×10 -2 Pa, welding temperature 900 °C, welding time 5 min, pulse ratio (ON / OFF) = 12 / 4, voltage 3.0 - 3.5 V, pulse current 1800 A, and the pulse current waveform is as Figure 2 shown. Before reaching 50 °C below the target welding temperature, the heating rate is 100 °C / min, and then reach the target temperature at a heating rate of 25 °C / min. After completing the heating program, disconnect the pulse current and cool with the furnace to room temperature.

[0051] For the strength of the diffusion welding joint of TiAl-Ti2AlNb dissimilar metals with low temperature and high efficiency in this embodiment, according to the room-temperature shear test, the obtained shear strength is 213.6; reaching 72.7% of the base metal;

[0052] Example 6

[0053] Step 1: Surface treatment of the specimen for welding. Grind the surface of the specimen successively with 360#, 600#, 1200#, and 2000# SiC water sandpapers. After removing the oxide layer and obvious scratches on the specimen surface, perform mechanical polishing with 1.5# diamond spray polishing agent. After the surface to be welded presents a mirror surface, ultrasonically clean it with acetone and absolute ethanol for 5 - 10 min successively. Store it in absolute ethanol before welding for standby

[0054] Step 2: Weldment assembly. Fit the polished surfaces of the workpieces to be welded and place them in the assembly mold. The assembly mold is made of high-strength graphite to endow it with electrical conductivity. Place 0.2 - 0.4 mm graphite paper on the pressure surface of the graphite mold against the welding machine to increase the electrical conductivity area between the mold and the weldment. When assembling the weldment, follow Figure 1 the assembly schematic diagram shown, and require that the temperature measurement hole and the welding interface be at the same height for directly detecting the temperature of the welding interface.

[0055] Step 3: Diffusion welding connection with pulsed high current. Place the workpieces to be welded assembled as required into the pulsed high current welding equipment. The pulsed high current welding in this technical solution is realized through a spark plasma welding device. The welding parameters are as follows: vacuum degree 9×10 -2 Pa~5×10 -2 Pa, welding temperature 950°C, welding time 10 min, welding pressure 5 MPa, pulse ratio (ON / OFF) = 12 / 4, voltage 3.5 V, pulsed current 2000 A, and the pulsed current waveform is as shown in Figure 2 . Before reaching 50°C below the target welding temperature, the heating rate is 100°C / min, and then it reaches the target temperature at a heating rate of 25°C / min. After completing the heating program, disconnect the pulsed current and cool it in the furnace to room temperature.

[0056] The strength of the diffusion welding connection joint of TiAl-Ti2AlNb dissimilar metals with low temperature and high efficiency in this embodiment, according to the room temperature shear test, the obtained shear strength is 258.2 MPa; reaching 87.8% of the base metal.

Claims

1. A method for low-temperature and high-efficiency diffusion welding of TiAl-Ti2AlNb dissimilar metals, characterized in that, The above connection method can be used to prepare a TiAl-Ti2AlNb dissimilar metal welding material. Under vacuum conditions, a pulsed high current is passed through and pressure is applied, and it is welded after rapid heating, short-time heat preservation, and cooling. It includes the following steps: (1) Surface treatment of the welding surfaces of the TiAl and Ti2AlNb specimens. The surfaces of the specimens are polished successively with 360#, 600#, 1200#, and 2000# SiC water sandpapers. After eliminating the oxide layer and significant scratches on the specimen surfaces, mechanical polishing is carried out with 1.5# diamond spray polishing agent until the surfaces to be welded present a mirror surface, and then ultrasonic cleaning is carried out successively with acetone and absolute ethanol. Before welding, it is placed in absolute ethanol for storage and standby. (2) Assembly of the welded parts: The polished surfaces of the workpieces to be welded are fitted together and placed into an assembly mold. The assembly mold is made of high-strength graphite to make it have a conductive function. Graphite paper is placed between the pressure-applying surfaces of the graphite mold and the welded parts to increase the conductive area between the mold and the welded parts. When assembling the welded parts, it is required that the temperature measurement hole and the welding interface are at the same height to directly detect the temperature of the welding interface. (3) Diffusion welding connection with pulsed high current: The workpieces to be welded assembled as required are placed into a pulsed high current welding device. The pulsed high current welding is realized through a spark plasma welding device. After completing the heating process, the pulsed current is disconnected, and it is cooled to room temperature in the furnace. Specific welding parameters in step (3): Vacuum degree: 9×10 -2 Pa to 5×10 -2 Pa, welding temperature: 750°C to 950°C, welding time: 3 min to 20 min, welding pressure 5 - 15 MPa, pulse current: 1500 A to 2500 A, voltage: 3 V to 5 V, pulse ratio (ON / OFF): 12 / 2 to 6.

2. The method for low-temperature and high-efficiency diffusion welding of TiAl-Ti2AlNb dissimilar metals according to claim 1, characterized in that: In step (1), the welding raw materials are TiAl and Ti2AlNb bulk materials respectively.

3. The method for low-temperature and high-efficiency diffusion welding of TiAl-Ti2AlNb dissimilar metals according to claim 1, characterized in that: In step (1), the ultrasonic cleaning time is 5 - 10 min.

4. The method for low-temperature and high-efficiency diffusion welding of TiAl-Ti2AlNb dissimilar metals according to claim 1, characterized in that: In step (2), the thickness of the graphite paper placed is 0.2 - 0.4 mm.

5. The method for low-temperature and high-efficiency diffusion welding of TiAl-Ti2AlNb dissimilar metals according to claim 1, characterized in that: The specific welding parameters in step (3) are: welding temperature 900 °C, welding time 10 min, welding pressure 10 MPa, pulse On / Off = 12 / 2, welding pressure 10 MPa, pulsed current 1800 A, voltage 3.0 - 3.5 V.

6. A TiAl-Ti2AlNb dissimilar metal welding material prepared by the connection method according to any one of claims 1 to 5.

7. The TiAl-Ti2AlNb dissimilar metal welding material according to claim 6, characterized in that, The above material is welded by a TiAl bulk and a Ti2AlNb bulk material.

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