Method of electron beam hybrid ultrasonic vibration welding of dissimilar metals

Abstract

The application is a method for electron beam composite ultrasonic vibration welding of dissimilar metals, in particular a method for electron beam composite ultrasonic vibration welding of Ti-6Al-4V and T2 pure copper. The specific steps of the method are as follows: first, the welding parts are pretreated before welding; then the workpiece, three-axis slide rail are put into the welding chamber; then the ultrasonic device is assembled and the distance between the ultrasonic rolling head ball and the electron beam and the pressure between the workpiece to be welded are adjusted; then the ultrasonic parameters and the electron beam welding parameters are set. Finally, the welding chamber is vacuumized and double electron beam welding is carried out, the front electron beam is on the copper side, the rear electron beam is on the titanium side, and the two welds are adjacent but not overlapping. The welding feature of the application is that, aiming at the problems of coarse weld grain, large residual stress after welding and the like existing in the process of electron beam welding of dissimilar metals, the ultrasonic rolling head ball is used to vibrate the welding material, the acoustic streaming and cavitation effect are generated on the welding pool, so as to refine the grain, discharge the pores and eliminate the welding residual stress, and then the mechanical properties of the welded joint are improved.

Description

Technical Field

[0001] The present invention relates to the field of welding dissimilar metals with relatively large differences in physical and chemical properties, and is a method for welding dissimilar metals using electron beam composite ultrasonic vibration. Background Art

[0002] Dissimilar metal components, as composite components that combine the excellent properties and advantages of different metals, have attracted widespread attention and application in various industrial fields in recent years due to their low cost, high efficiency, and simple process. They meet the requirements of modern industry for multifunctional and multi-layered materials, as well as high quality and low cost. At the same time, due to their characteristics of combining the properties of multiple metals, they generally have high mechanical properties while also ensuring excellent physical properties such as corrosion resistance and high conductivity, significantly improving the overall value of industrial products and saving production costs. Welding, as a highly efficient, low-cost process that can achieve good dissimilar metal connections, has received special attention, and the field of dissimilar metal welding has gradually become a research hotspot.

[0003] In recent years, titanium and its alloys have become a popular welding structural material and additive material, mainly due to their low density, high strength and other excellent properties. They still occupy an important application position in aerospace, automotive structural weight reduction, shipbuilding and other fields, especially when combined with other metals to achieve the effect of weight reduction. Copper and its alloys have excellent electrical and thermal conductivity, ductility and corrosion resistance. As one of the earliest metals discovered and used by humans, they are widely used in various fields. The disadvantages of these two metals are high cost and many welding defects. However, titanium-copper welded structures can maintain the high strength and toughness characteristics of titanium itself, while taking into account the excellent physical properties of copper. They have great application value in various fields with multiple performance requirements. Compared with traditional titanium steel structures, they have higher specific strength and environmental friendliness. Therefore, they can be widely used in ships, aerospace, and even automation.

[0004] At present, a common problem in the field of dissimilar metal welding is that due to the large difference in physical and chemical properties between the two metals, high residual stress and deformation caused by the large difference in thermal expansion coefficient, alloy element loss, and large differences in wettability or fluidity make it impossible to achieve sufficient mixing of liquid metals, resulting in cracks and unfused parts, and residual gas cannot be discharged to form pores. Among them, thicker intermetallic compounds will form between most dissimilar metals. These intermetallic compounds usually grow in the form of columnar crystals to form needle-shaped or ribbon-shaped intermetallic compounds, and their grain boundary strength is low. Therefore, the intermetallic compound layer will cause the mechanical properties of the weld joint to deteriorate seriously.

[0005] The above-mentioned problems also exist in the field of titanium-copper dissimilar metal welding. The main solutions at present are to reduce atomic diffusion through solid-phase welding methods such as diffusion welding and friction welding, or to reduce or inhibit the formation of intermetallic compounds by adding a welding intermediate layer. However, such methods are expensive and have low welding efficiency. They are not suitable for rapid process production and do not solve problems such as cracks, pores, and large residual stresses. Experiments have shown that electron beam time-sharing dual-beam welding can achieve in-situ remelting of the intermetallic compound layer, thereby reducing the thickness of the intermetallic compound layer and improving the mechanical properties of the welded joint. Moreover, as a fusion welding method, it has lower welding costs and higher welding efficiency. However, this method has defects such as large grains in the intermetallic compound layer, a small amount of unfused metals and high residual stress. In order to solve these problems, this method adopts ultrasonic composite welding, which increases the nucleation undercooling inside the molten pool through the ultrasonic cavitation effect and acoustic streaming effect, breaks the intermetallic compounds and coarse dendrites, thereby increasing the number of nucleations and achieving the purpose of grain refinement; in addition, the introduction of ultrasonic waves can also effectively promote the diffusion and flow of liquid metal, thereby reducing the porosity and residual stress after welding, and since the liquid metal is more fluid, the phenomenon of unfused metals will also be greatly reduced; finally, ultrasound can also enhance the wetting and spreading ability of liquid metal on the surface of the base material, thereby improving the weld morphology and reducing the possibility of stress concentration after welding. Summary of the Invention

[0006] The present invention provides a method for electron beam composite ultrasonic vibration welding of dissimilar metals. This method overcomes the problems of coarse intermetallic compound layer grains, a small amount of unfused metals, and high residual stresses that often occur with dual-beam electron beam welding of dissimilar metals. This method achieves grain refinement, reduces porosity, and lowers residual stress, ultimately resolving the issue of low strength in welded Ti6Al4V and T2 pure copper dissimilar metal structures.

[0007] The ultrasonic composite time-sharing dual-beam electron beam welding method of the present invention is designed to enable the welding pool to effectively receive ultrasonic waves. First, it is necessary to ensure that there is sufficient pressure between the rolling head ball and the workpiece without damaging the workpiece to ensure the effective propagation of ultrasonic waves. Secondly, since ultrasonic waves will refract at the interface when entering from one medium to another different medium, the propagation direction of the ultrasonic waves inside the workpiece will change. Therefore, in order to ensure that the ultrasonic waves propagate parallel to the workpiece, it is necessary to adjust the angle between the ultrasonic device and the workpiece according to the material properties so that the ultrasonic energy can be effectively transmitted to the molten pool. In this way, ultrasonic waves can effectively promote the diffusion and flow of liquid metal, thereby giving pores more time to overflow, increasing the wetting and spreading ability of wood metal, and improving the weld morphology. Due to the high density of copper and the large attenuation of ultrasonic waves propagating inside it, the ultrasonic waves emitted from the copper side lose more energy when reaching the molten pool. Therefore, the ultrasonic rolling head ball on the copper side should be closer to the center of the electron beam spot. In order to enhance the effect of ultrasonic waves on the molten pool, the ultrasonic wavelength should be calculated according to the material properties so that the ultrasonic wave peak occurs at the center of the molten pool. When the welding pool receives ultrasonic waves of sufficient energy, the intermetallic compounds and coarse dendrites will be broken, the number of nucleations will increase, and the grain size will be refined, which will reduce the tendency to crack.

[0008] An electron beam composite ultrasonic vibration welding method, the specific steps are as follows:

[0009] Step 1: Pre-treat the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate before welding, including removing impurities, grinding and polishing, etc.

[0010] Step 2: Place the pre-treated workpiece to be welded in the middle of the workbench in the electron beam welding chamber, and use a cylindrical clamping device to apply a pressure of 5 to 10 kN on the four corners of the plate.

[0011] Step 3: Place two sets of movable three-axis slides on both sides of the workpiece to be welded. Use four sets of threaded connections to fix each set of slides to the bottom workbench.

[0012] Step 4, assemble the ultrasonic device; assemble the ultrasonic generator, rotating plate, fixed plate, and three-axis slide rail in sequence by tightening screws, wherein the rotating plate and fixed plate both use steel clamps; install a copper heat conducting strip on the clamp between the fixed plate and the slide rail; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator; the copper side rolling head ball is made of TC4 material and has a diameter of 8-10mm, and the titanium side rolling head ball is made of hardened steel and has a diameter of 6-8mm; according to Snell's law n1 sinθ i =n2 sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, θ i and θ tThe incident angle and refraction angle are respectively adjusted to adjust the incident angle of the ultrasonic device; the ultrasonic parameters are adjusted, the power of the ultrasonic generating device on the copper side is set to 180~220W, and the ultrasonic frequency is set to 8~12kHz; the power of the ultrasonic generating device on the titanium side is set to 120~180W, and the ultrasonic frequency is set to 12~18kHz.

[0013] Step 5: Adjust the distance between the rolling head ball and the center of the electron beam spot according to the formula Where λ is the wavelength, v is the speed of sound, and f is the frequency. Where E is the Young's modulus and ρ is the material density. Set the distance between the rolling ball and the center of the electron beam spot to an integer multiple of the wavelength. Adjust the pressure between the rolling ball at the bottom of the ultrasonic generator and the workpiece to 15-20 MPa.

[0014] Step 6: Evacuate the weld before welding, then turn on the electron beam gun for welding. The electron beam welding speed (v) is 8-12 mm / s. The front electron beam welding path is offset from the butt joint centerline by a distance of 1.5 mm toward the copper side. The welding power (P1) is 25-40 kW. The weld bead width is C1. The rear electron beam welding path is offset from the butt joint centerline by a distance of 3 mm toward the titanium side. The welding power (P2) is 15-30 kW. The weld bead width is C2. The two welds do not intersect. The distance difference (D) between the rear and front electron beams along the butt joint centerline is 8-12 mm.

[0015] Compared with the prior art, the present invention has the following significant advantages:

[0016] The present invention adopts ultrasonic vibration composite electron beam welding in the titanium-copper dissimilar metal welding process. On the one hand, it can generate a mechanical vibration effect in the molten pool, thereby promoting the diffusion of copper atoms and inhibiting the production of titanium-rich phase intermetallic compounds. On the other hand, the cavitation effect and the acoustic streaming effect will cause the nucleated crystals to move randomly in the molten pool and cannot grow fixedly, thereby reducing the size of the growing intermetallic compound grains, and ultimately reducing the influence of the intermetallic compound layer on the mechanical properties of the welded joint. At the same time, ultrasonic composite welding can also play a stirring role to reduce the porosity of the weld. In addition, ultrasound can enhance the wetting and spreading ability of liquid metal on the surface of the parent material, thereby improving the weld morphology and reducing the possibility of stress concentration after welding, thereby improving the tensile strength and other mechanical properties of the welded joint. Therefore, the electron beam composite ultrasonic vibration welding method of Ti6Al4V and T2 pure copper is expected to solve the shortcomings of low strength of titanium-copper dissimilar metal welding, promote the lightweight and multifunctional process in the industrial field, and take into account the concepts of green manufacturing and economic practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural diagram of electron beam composite ultrasonic vibration welding equipment.

[0018] Figure 2It is a schematic diagram of the weld formation of the workpiece to be welded.

[0019] 1. Workbench, 2. Movable three-axis slide, 3. Copper plate, 4. Titanium plate, 5. Ultrasonic transmitting device, 6. Power supply, 7. Deflection coil, 8. Focusing coil, 9. Anode, 10. Electron beam cathode, 11. Time-sharing dual-beam control system, 12. Ultrasonic device control system, 13. Rotating plate, 14. Fixed plate, 15. Titanium side weld, 16. Copper side weld, 17. Titanium side molten pool, 18. Copper side molten pool. DETAILED DESCRIPTION

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] An electron beam composite ultrasonic vibration welding method, the specific steps are as follows:

[0022] Step 1: Pre-treat the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate before welding, including removing impurities, grinding and polishing, etc.

[0023] Step 2: Place the pre-treated workpiece to be welded in the middle of the workbench in the electron beam welding chamber, and use a cylindrical clamping device to apply a pressure of 5 to 10 kN on the four corners of the plate.

[0024] Step 3: Place two sets of movable three-axis slides on both sides of the workpiece to be welded. Use four sets of threaded connections to fix each set of slides to the bottom workbench.

[0025] Step 4, assemble the ultrasonic device; assemble the ultrasonic generator, rotating plate, fixed plate, and three-axis slide rail in sequence by tightening screws, wherein the rotating plate and fixed plate both use steel clamps; install a copper heat conducting strip on the clamp between the fixed plate and the slide rail; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator; the copper side rolling head ball is made of TC4 material and has a diameter of 8-10mm, and the titanium side rolling head ball is made of hardened steel and has a diameter of 6-8mm; according to Snell's law n1 sinθ i =n2 sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, θ i and θ t The incident angle and refraction angle are respectively adjusted to adjust the incident angle of the ultrasonic device; the ultrasonic parameters are adjusted, the power of the ultrasonic generating device on the copper side is set to 180~220W, and the ultrasonic frequency is set to 8~12kHz; the power of the ultrasonic generating device on the titanium side is set to 120~180W, and the ultrasonic frequency is set to 12~18kHz.

[0026] Step 5: Adjust the distance between the rolling head ball and the center of the electron beam spot according to the formula Where λ is the wavelength, v is the speed of sound, and f is the frequency. Where E is the Young's modulus and ρ is the material density. Set the distance between the rolling ball and the center of the electron beam spot to an integer multiple of the wavelength. Adjust the pressure between the rolling ball at the bottom of the ultrasonic generator and the workpiece to 15-20 MPa.

[0027] Step 6: Evacuate the weld before welding, then turn on the electron beam gun for welding. The electron beam welding speed (v) is 8-12 mm / s. The front electron beam welding path is offset from the butt joint centerline by a distance of 1.5 mm toward the copper side. The welding power (P1) is 25-40 kW. The weld bead width is C1. The rear electron beam welding path is offset from the butt joint centerline by a distance of 3 mm toward the titanium side. The welding power (P2) is 15-30 kW. The weld bead width is C2. The two welds do not intersect. The distance difference (D) between the rear and front electron beams along the butt joint centerline is 8-12 mm.

[0028] Furthermore, in step 1, the pre-welding preparation step is that the Ti-6Al-4V titanium alloy plate and the T2 pure copper alloy plate are not grooved, the surface of the to-be-welded position and the adjacent 30 mm area are mechanically polished with a grinding wheel and a wire brush, and after the metallic luster is exposed, 240#, 400#, and 600# sandpapers are used for fine polishing, and finally, acetone is used to clean the surface oil; the mass percentage composition of the Ti-6Al-4V titanium alloy used in step 1 is as follows: Ti: 87.65-88.83%, Al: 5.51-6.75%, V: 3.51-4.5%, Fe: 0-0.3%, C: 0-0.08%; the mass percentage composition of the T2 pure copper is as follows: Cu: 99.9%, Fe: 0-0.05%, and Si: 0-0.05%.

[0029] Furthermore, in step 2, the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate are placed in a butt joint on a stainless steel pad with a circular hole groove to form a butt joint. The workpiece assembly gap is n: 0-0.1mm, and a cylindrical clamping device with a diameter of 10mm is used to apply a vertical pressure of 5 to 10kN to the four corners of the workpiece to make it tightly combined with the stainless steel pad.

[0030] Furthermore, in step 3, the movable three-axis slide rails are placed on both sides of the workpiece to be welded and kept parallel to the weld bead. Finally, four sets of threaded connections are used to fix the two sets of slide rails on the workbench.

[0031] Furthermore, in step 4, the ultrasonic device assembly steps are as follows:

[0032] 4.1. Connect the ultrasonic generator to the fixed plate. A cylindrical boss with a radius of 12mm and a height of 8mm is provided on the contact surface between the rotating plate and the fixed plate, and a graduated dial is provided on the upper half. A countersunk hole with a radius of 10mm and a depth of 10mm is provided in the center of the fixed plate, so that the two can fit together. Furthermore, a 1 / 2 countersunk annular groove is provided on the other side of the rotating plate, the non-contact surface, and corresponding threaded holes are provided on both horizontal sides of the fixed plate. According to the formula n1 sinθ i =n2 sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, θ i and θ t are the incident angle and refraction angle, respectively. Adjust the inclination angle of the ultrasonic device on the copper side to 46±2° and the inclination angle of the ultrasonic device on the titanium side to 66±2° to ensure that the ultrasonic wave propagates parallel to the inside of the workpiece. Finally, use two fastening screws to fix the fixed plate and the rotating plate.

[0033] 4.2. Considering that the working environment of the ultrasonic system is a high-temperature vacuum environment, the rotating plate and the fixed plate are both made of steel fixtures. Copper heat-conducting strips are installed on the fixtures between the fixed plate and the slide rail to ensure heat dissipation.

[0034] 4.3. In order to isolate the high heat of the electron beam from the splashing impact on the ultrasonic device, a double-layer aluminum sheet is installed between the electron beam device and the ultrasonic device;

[0035] 4.4, Due to the different hardness of the two materials, the diameter of the copper side rolling ball is set to 10mm, and the diameter of the titanium side rolling ball is set to 8mm;

[0036] 4.5. The power of the ultrasonic generator on the copper side is set to 180-220W, and the ultrasonic frequency is set to 8-12kHz; the power of the ultrasonic generator on the titanium side is set to 120-180W, and the ultrasonic frequency is set to 12-18kHz;

[0037] Furthermore, in step 5, according to the Young's modulus, density and working temperature of the two different materials, the copper side rolling header ball is set to be 40 mm away from the center of the electron beam spot and the line connecting the two points is perpendicular to the welding direction, and the titanium side rolling header ball is set to be 70 mm away from the center of the electron beam spot and the line connecting the two points is perpendicular to the welding direction; according to the different hardness and elastic modulus of the two materials, the pressure between the rolling header ball and the workpiece to be welded is adjusted, and the clamping force between the copper side rolling header ball and the workpiece is set to 15 MPa, and the clamping force between the titanium side rolling header ball and the workpiece is set to 20 MPa.

[0038] Furthermore, in step 6, the welding area is vacuumed to 2.0×10 -2 -4.0×10 -2Pa, in order to reduce the deformation of the base material during welding, a defocused electron beam is used to preheat the environment and the base material. The parameters are: electron beam current 15-20mA, electron beam focus diameter 3-4mm, preheating speed 20-30mm / s; the set welding parameters are electron beam acceleration voltage: 60-150kV, welding height: 250-300mm, focusing current: 650-750mA.

[0039] Furthermore, in step 6, the signal power supply of the ultrasonic generating device is connected to the power supply of the welding equipment. During the electron beam composite ultrasonic vibration welding process, the ultrasonic composite welding equipment will be turned on and off as the welding starts and ends, ensuring that the ultrasonic composite welding acts on the entire welding process.

[0040] Furthermore, the power distribution of the electron beam in step 6 is achieved by adjusting the duty cycle of the deflection current, which satisfies: 2≤(P1*V1 / P2*D)≤2.5; and the current frequency in the deflection coil forming the time-sharing dual electron beam is 15 kHz.

[0041] Furthermore, in step 6, in order to suppress the growth of intermetallic compounds at the interface, the electron beam on the copper side first scans 10 mm, and then the electron beam on the titanium side starts scanning, so that the metal is remelted in situ at the interface.

[0042] The present invention provides specific embodiments as follows

[0043] Example 1

[0044] In this embodiment, the electron beam composite ultrasonic vibration welding method for Ti6Al4V and T2 pure copper is carried out in the following steps:

[0045] Step 1: Prepare Ti6Al4V titanium alloy plates and T2 pure copper plate samples with specifications of 300mm*100mm*4mm, and mechanically polish the surface of the welding position and the adjacent 30mm area with a grinding wheel and a wire brush. After the metallic luster is exposed, use 240#, 400#, and 600# sandpaper to finely polish to remove the oxide layer on the surface to be welded. Finally, use acetone to clean the surface oil.

[0046] Among them, the mass percentage composition of the Ti-6Al-4V titanium alloy used is: Ti: 87.65~88.83%, Al: 5.51~6.75%, V: 3.51~4.5%, Fe: 0~0.3%, C: 0~0.08%; the mass percentage composition of T2 pure copper is: Cu: 99.9%, Fe: 0~0.05%, Si: 0~0.05%.

[0047] Step 2: Assemble the ungrooved Ti6Al4V titanium alloy plate and the T2 pure copper plate to form a butt joint. The workpiece assembly gap is n: 0.1mm. Place the sample plate on a stainless steel pad with multiple circular heat dissipation holes. Use four cylindrical clamping devices with a diameter of 10mm to place them in the holes of the stainless steel pad to make the weldment tightly combined with the stainless steel pad.

[0048] Step 3: Place the movable three-axis slide rails on both sides of the workpiece to be welded and keep them parallel to the weld bead. Finally, use four sets of threaded connections to fix the two sets of slide rails on the workbench.

[0049] Step 4: Adjust the angles between the copper side and titanium side ultrasonic generators and the workpiece to be welded to 45° and 65° respectively, and use two fastening screws to fix the fixed plate and the rotating plate; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator to prevent splashing; install a copper heat conducting strip between the fixed plate and the slide rail; set the diameter of the copper side rolling head ball to 10mm and the diameter of the titanium side rolling head ball to 8mm; set the power of the copper side ultrasonic generator to 200W and the ultrasonic frequency to 10kHz; set the power of the titanium side ultrasonic generator to 150W and the ultrasonic frequency to 15kHz;

[0050] Step 5: Set the copper-side rolling ball to a distance of 40 mm from the center of the electron beam spot, with the line connecting the two points perpendicular to the welding direction. Set the titanium-side rolling ball to a distance of 70 mm from the center of the electron beam spot, with the line connecting the two points perpendicular to the welding direction. Set the clamping force between the copper-side rolling ball and the workpiece to 15 MPa, and the titanium-side rolling ball to 20 MPa.

[0051] Step 6: Vacuum the welding area to 2.0×10 -2 -4.0×10 -2 Pa, in order to reduce the deformation of the base material during welding, a defocused electron beam is used to preheat the environment and the base material. The parameters are: electron beam current 15mA, electron beam focus diameter 3.5mm, and preheating speed 25mm / s.

[0052] Modify the parameters of the electron beam emission equipment and compile the electron beam welding work path. The set welding parameters are electron beam acceleration voltage: 80kV, welding height: 270mm, focusing current: 700mA; welding speed v1: 10mm / s, beam rise and fall time 1s.

[0053] Plan the distribution and beam current of the dual electron beams. Start the deflection coils and pass a high-frequency current through them at a controlled frequency of 20 kHz, forming a time-sharing dual electron beam. Adjust the electron beam focus so that the two electron beams form a front-to-back dual beam with their spot centers 10 mm apart along the weld. Simultaneously, the front electron beam is offset to the copper plate, with the spot center offset from the butt joint centerline by a distance a1 of 1.5 mm. The rear electron beam is offset to the titanium plate, with a distance a2 of 3 mm from the centerline. Adjust the duty cycle to achieve an output power of 30,000 W for the front electron beam and 15,000 W for the rear electron beam.

[0054] Start the servo enable of the vacuum chamber motion system, move the electron beam emitting device to the starting vertical welding surface position, start the welding program and the power supply of the ultrasonic generator, and after the rear beam forms a complete molten pool, move in a direction parallel to the center line of the butt joint to complete the welding. After completing two offset welds, turn off the equipment and the power supply of the ultrasonic generator to complete the entire welding.

[0055] After the surface of the present invention is cleaned, tensile testing and microscopic joint interface observation are performed, and the weld is well formed, and the intermetallic compound layer is partially remelted, and the thickness of the layer is reduced.

[0056] The tensile strength of the joint is 249 MPa, and the elongation is 27.6%, which is as strong as the parent metal. The fracture occurs in the heat-affected zone on the copper side, showing obvious ductile fracture.

Claims

1. A method for electron beam composite ultrasonic vibration welding of dissimilar metals, characterized in that: The specific steps are as follows: Step 1: Pre-treating the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate before welding, including removing impurities and grinding and polishing; Step 2: Place the pre-treated workpiece to be welded in the middle of the workbench in the electron beam welding chamber, and use a cylindrical clamping device to apply pressure to the four corners of the plate; Step 3: Place two sets of movable three-axis slides on both sides of the workpiece to be welded. Use four sets of threaded connections to fix each set of slides to the bottom workbench. Step 4, assemble the ultrasonic device; assemble the ultrasonic generator, rotating plate, fixed plate, and three-axis slide rail in sequence by tightening screws, wherein the rotating plate and fixed plate use steel clamps; install a copper heat conducting strip on the clamp between the fixed plate and the slide rail; place a double-layer aluminum sheet near the ultrasonic end of the electron beam generator; the copper side rolling head ball is made of TC4 material and has a diameter of 8-10mm, and the titanium side rolling head ball is made of hardened steel and has a diameter of 6-8mm; according to Snell's law n1sinθ i =n2sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, θ i and θ t Adjust the incident angle of the ultrasonic device for the incident angle and the refraction angle respectively; adjust the ultrasonic parameters, set the power of the ultrasonic generator on the copper side to 180-220W, and the ultrasonic frequency to 8-12kHz; set the power of the ultrasonic generator on the titanium side to 120-180W, and the ultrasonic frequency to 12-18kHz; Step 5: Adjust the distance between the rolling head and the electron beam according to the formula Where λ is the wavelength, v is the speed of sound, and f is the frequency. Where E is Young's modulus, ρ is material density, and the spacing is set to an integer multiple of the wavelength; adjust the pressing force between the rolling head ball at the bottom of the ultrasonic generator and the workpiece to 15-20MPa; Step 6: Vacuum before welding, then turn on the electron beam gun for welding, the electron beam welding speed V1: 8-12 mm / s, the front electron beam welding trajectory is a distance a1: 1.5 mm from the butt center line to the copper side, the welding power P1: 25-40 KW, and the weld width is recorded as C1; the rear electron beam welding trajectory is a distance a2: 3 mm from the butt center line to the titanium side, the welding power P2: 15-30 KW, and the weld width is recorded as C2, wherein the two welds do not cross, and the distance difference D between the rear electron beam and the front electron beam along the butt center line direction is 8-12 mm.

2. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 1, the pre-welding preparation step is that the Ti-6Al-4V titanium alloy plate and the T2 pure copper alloy plate are not grooved, the surface of the to-be-welded position and the adjacent 30 mm area are mechanically polished with a grinding wheel and a wire brush, and after the metallic luster is exposed, 240#, 400#, and 600# sandpapers are used for fine polishing, and finally acetone is used to clean the surface oil; the mass percentage composition of the Ti-6Al-4V titanium alloy used in step 1 is as follows: Ti: 87.65-88.83%, Al: 5.51-6.75%, V: 3.51-4.5%, Fe: 0-0.3%, C: 0-0.08%; the mass percentage composition of the T2 pure copper is as follows: Cu: 99.9%, Fe: 0-0.05%, and Si: 0-0.05%.

3. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 2, the Ti-6Al-4V titanium alloy plate and the T2 pure copper plate are placed in a butt joint on a stainless steel backing plate with a circular hole groove to form a butt joint. The workpiece assembly gap is n: 0~0.1mm, and a cylindrical clamping device with a diameter of 10mm is used to apply a vertical pressure of 5~10kN to the four corners of the workpiece to make it tightly combined with the stainless steel backing plate.

4. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 3, the movable three-axis slide rails are placed on both sides of the workpiece to be welded and kept parallel to the weld bead. Finally, the two sets of slide rails are fixed to the workbench using four sets of threaded connections.

5. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 4, the ultrasonic device assembly steps are as follows: Step 4.1: Connect the ultrasonic generator to the fixed plate. A cylindrical boss with a radius of 12mm and a height of 8mm is provided on the contact surface between the rotating plate and the fixed plate, and a dial is provided on the upper half. A countersunk hole with a radius of 10mm and a depth of 10mm is provided in the center of the fixed plate, so that the two can fit together. In addition, a 1 / 2 countersunk annular groove is provided on the other side of the rotating plate, i.e., the non-contact surface, and corresponding threaded holes are provided on both horizontal sides of the fixed plate. According to the formula n1sinθ i =n2sinθ t , where n1 and n2 are the refractive indices of the rolling head and the workpiece, respectively, θ i and θ t are the incident angle and refraction angle, respectively. Adjust the inclination angle of the ultrasonic device on the copper side to 46±2° and the inclination angle of the ultrasonic device on the titanium side to 66±2° to ensure that the ultrasonic wave propagates parallel to the inside of the workpiece. Finally, use two fastening screws to fix the fixed plate and the rotating plate. In step 4.2, given that the ultrasonic system operates in a high-temperature vacuum environment, steel fixtures are used for the rotating plate and the fixed plate. Copper heat-conducting strips are installed on the fixtures between the fixed plate and the slide rail to ensure heat dissipation. Step 4.3: To isolate the ultrasonic device from the splashing impact of the electron beam, a double-layer aluminum sheet is placed between the electron beam device and the ultrasonic device; In step 4.4, due to the different hardness of the two materials, the diameter of the copper side rolling ball is set to 10 mm, and the diameter of the titanium side rolling ball is set to 8 mm; In step 4.5, the power of the ultrasonic generator on the copper side is set to 180-220 W, and the ultrasonic frequency is set to 8-12 kHz; the power of the ultrasonic generator on the titanium side is set to 120-180 W, and the ultrasonic frequency is set to 12-18 kHz.

6. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 5, according to the Young's modulus, density and working temperature of the two different materials, the copper side rolling header ball is set to be 40 mm away from the center of the copper side electron beam spot and the line connecting the two points is perpendicular to the welding direction, and the titanium side rolling header ball is set to be 70 mm away from the center of the titanium side electron beam spot and the line connecting the two points is perpendicular to the welding direction; in step 5, according to the different hardness and elastic modulus of the two materials, the pressure between the rolling header ball and the workpiece to be welded is adjusted, and the clamping force between the copper side rolling header ball and the workpiece is set to 15 MPa, and the clamping force between the titanium side rolling header ball and the workpiece is set to 20 MPa.

7. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, the welding area is vacuumed to 2.0×10 -2 -4.0×10 -2 Pa, in order to reduce the deformation of the base material during welding, a defocused electron beam is used to preheat the environment and the base material. The parameters are: electron beam current 15-20 mA, electron beam focus diameter 3-4 mm, and preheating speed 20-30 mm / s. In step 6, the welding parameters set are electron beam acceleration voltage: 60-150 kV, welding height: 250-300 mm, and focusing current: 650-750 mA.

8. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, the signal power supply of the ultrasonic generating device is connected to the power supply of the welding equipment. During the electron beam composite ultrasonic vibration welding process, the ultrasonic composite welding equipment will be turned on and off as the welding starts and ends, ensuring that the ultrasonic composite welding acts on the entire welding process.

9. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, the power distribution of the electron beam is achieved by adjusting the duty cycle of the deflection current, which satisfies: 2≤(P1*V1 / P2*D)≤2.5; in step 6, the current frequency in the deflection coil forming the time-sharing dual electron beam is 15kHz.

10. The method for electron beam composite ultrasonic vibration welding of dissimilar metals according to claim 1, characterized in that: In step 6, in order to suppress the growth of intermetallic compounds at the interface, the electron beam on the copper side first scans 10 mm, and then the electron beam on the titanium side starts scanning, causing the metal to be remelted in situ at the interface.

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