Method for efficiently forming nanocrystalline al2cu at al / cu bonding interface

Abstract

The application relates to a method for efficiently forming nanocrystalline Al2Cu at an Al / Cu bonding interface, and belongs to the technical field of heterogeneous metal connection and bonding. The copper substrate and the aluminum substrate are subjected to high-speed collision interface bonding through electromagnetic pulses, and process parameters are optimized, so that an ultrafine nanocrystalline Al2Cu transition layer is formed at the bonding interface, the bonding strength is improved, the connection toughness is increased, and the problems that the traditional Al / Cu heterogeneous metal bonding is prone to generating the brittle and hard intermetallic compound Al2Cu at the interface, thereby reducing the bonding strength and causing brittle fracture are solved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of dissimilar metal connection bonding, in particular to a method for efficiently forming nanocrystalline Al2Cu at an Al / Cu bonding interface. BACKGROUND

[0002] Lightweight technology is to improve energy efficiency, reduce weight and emission through material composition, structure and manufacturing process optimization, among which material lightweight technology is the most widely used and the most obvious effect, especially in the electrical manufacturing field, gradually forming the lightweight strategy of 'aluminum instead of copper, aluminum-copper combination'. The physical and chemical properties such as melting point (660 DEG C, 1083 DEG C respectively), resistivity, thermal conductivity, specific heat capacity and potential difference of aluminum and copper are quite different, and the traditional fusion welding technology is easy to produce serious segregation, stress gradient and a large number of brittle intermetallic compounds such as Al2Cu, Al4Cu9 and AlCu at the bonding interface, resulting in reduced bonding strength and brittle fracture.

[0003] Therefore, how to obtain aluminum-copper dissimilar metal interface bonding with high quality, high stability and long service life has become a research focus and technical difficulty.

[0004] The strength of nanocrystalline is higher than that of traditional materials, which can withstand greater pressure and tension, at the same time, nanocrystalline has better toughness and is not easy to break when subjected to impact or bending force, if nanocrystalline refinement structure can be formed at the aluminum-copper dissimilar metal bonding interface, the problems such as reduced strength and brittle fracture caused by traditional fusion welding technology can be significantly improved.

[0005] Electromagnetic pulse technology (EMPT) can realize ultra-fast connection (40-60 mu s) by driving high-speed collision between welding parts through electromagnetic force at normal temperature and pressure, overcome the segregation problem and limit the formation of most common undesirable compounds and metallurgical defects in most fusion welding technologies, and the whole process is environmentally friendly and efficient, and easy to realize automation.

[0006] At present, the electromagnetic pulse high-speed collision interface connection technology is not very widely used, and there are few reports on the preparation of nanocrystalline Al2Cu with excellent mechanical properties, therefore, the preparation of Al / Cu bonding interface with nanocrystalline faces challenges. SUMMARY

[0007] In view of this, the purpose of the application is to provide a method for efficiently forming nanocrystalline Al2Cu at an Al / Cu bonding interface, which adopts EMPT technology and optimizes process parameters to form an ultra-fine nanocrystalline Al2Cu transition layer at the bonding interface, thereby improving the bonding strength and increasing the connection toughness, so as to solve the problem of reduced bonding strength and brittle fracture caused by the generation of brittle and hard intermetallic compound Al2Cu at the bonding interface in traditional Al / Cu bonding.

[0008] The application realizes the technical solutions of the following aspects:

[0009] A method for efficiently forming nanocrystalline Al2Cu at an Al / Cu bonding interface, which comprises high-speed collision interface bonding of a copper substrate and an aluminum flyer plate through electromagnetic pulses.

[0010] Further, the electromagnetic force is optimized by comprehensively considering the electrical and magnetic properties of the workpiece, the structural characteristics of the coil, and the properties of the power supply, and the formula includes:

[0011] The Lorentz force received by the aluminum flyer plate is:

[0012] F = J e × B

[0013] Where J e is the induced eddy current density on the Al plate, and B is the magnetic induction intensity between the coil and the Al plate

[0014] The electromagnetic pressure is:

[0015]

[0016] Where s is the thickness of the flyer plate, d is the skin depth, and mu is the magnetic permeability of the material

[0017] The skin depth of the material is:

[0018]

[0019] Where omega is the current frequency in the coil, mu is the magnetic permeability of the material, and gamma is the electrical conductivity of the material

[0020] The corrected electromagnetic pressure is:

[0021]

[0022] Where I is the discharge current, d is the skin depth, h is the coil height, s is the coil thickness, W is the coil width, and mu is the magnetic permeability of the material.

[0023] Further, the copper substrate and the aluminum flyer plate are fixed by a tool, and the spacing error between the bonding area of the two plates is ensured to be ±0.05mm.

[0024] Further, the discharge voltage and the initial gap value are set by equal difference, if the bonding cannot be achieved, the parameters are supplemented by interpolation method, then the tensile lap shear test is carried out, the peak load and the fracture condition are compared by using the control variable method, and the reference voltage and the reference gap are determined.

[0025] Further, after the reference voltage and the reference gap are determined, three groups of constant-voltage variable-gap and three groups of constant-gap variable-voltage parameters are selected for research, and tensile lap shear tests are performed on the bonding samples of the selected process group, 5 samples for each process group, and the welded part with the highest tensile strength is selected for TEM analysis according to the tensile test results to investigate whether the nanocrystalline Al2Cu is formed at the bonding interface.

[0026] Further, the spacing distance of the bonding area of the copper substrate and the aluminum flyer plate on both sides is adjusted by the spacer block, the thickness tolerance of the spacer block on both sides is controlled within 0.01 mm, and the flatness and parallelism of the bonding area are both controlled within 0.01 mm.

[0027] Further, the size of the copper substrate and the aluminum flyer plate is 100mmX20mmX1mm, and the mutual lap is 60mm long.

[0028] Further, the discharge voltage range is 10-16kV and the initial gap value is 1-2mm.

[0029] Further, the reference voltage is 14kV and the gap value is 1mm.

[0030] The beneficial effects of the present application are:

[0031] The present application adopts the EMPT technology and optimizes the process parameters to form a superfine nanocrystalline Al2Cu transition layer at the bonding interface, which not only improves the bonding strength but also increases the connection toughness, solves the problem that the traditional Al / Cu combination is easy to generate brittle and hard intermetallic compound Al2Cu at the interface, which leads to the decrease of bonding strength and brittle fracture. The high-quality, high-stability and high-service-life aluminum-copper combination is possible, which also helps the substantial progress of lightweight technology. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 TEM sampling position of Al-Cu interface, transition layer morphology and EDS analysis

[0033] (a) Transition zone FIB sampling, (b) TEM sample, (c) transition layer morphology, (d) interface bright field image and EDS line scanning position, (e) transition layer TEM analysis position, (f-h) EDS area scanning results of figure d, (i) transition layer line scanning results of figure d;

[0034] Figure 2TEM analysis of region 1 (a) TEM bright field image of region 3 and surrounding area, (b) selected area electron diffraction (SAED) pattern of region A, (c) HRTEM of the lower left partial area of region A and FFT diffraction pattern of region B, (d) inverse FFT pattern of region B, (e) HRTEM of the lower right partial area of region A and FFT diffraction pattern of region C and inverse FFT pattern, (f) inverse FFT pattern of region D, (g) diffraction pattern corresponding to (b), (h) standard diffraction pattern of Al2Cu, (i) Al2Cu interplanar spacing comparison;

[0035] Figure 3 TEM analysis of region 2 (a) TEM bright field image of region 2 and surrounding area, (b) selected area electron diffraction (SAED) pattern of region A, (c) HRTEM of region A and Al2Cu characteristic plane analysis, (d) FFT diffraction pattern of (c), (e) FFT diffraction pattern of regions B, C, (f-g) inverse FFT diffraction pattern of regions B, C, (h) diffraction pattern corresponding to (b), (i)

[0036] Al2Cu interplanar spacing comparison, (j) atomic structure of body-centered tetragonal Al2Cu;

[0037] Figure 4 TEM analysis of region 3 (a) TEM bright field image of region 3 and surrounding area, (b) selected area electron diffraction (SAED) pattern of region A, (c) HRTEM of region A and Al2Cu characteristic plane analysis, (d) FFT diffraction pattern of (c), (e) inverse FFT diffraction pattern of region B, (f-g) lattice distortion and dislocation of (1 2 1) and (1 1 0) in (e) (h) diffraction pattern corresponding to (b), (i) Al2Cu interplanar spacing comparison;

[0038] Figure 5 Layout of the workpiece of the present embodiment;

[0039] Figure 6 Interface connection state diagram of the present embodiment. DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings of the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0041] Therefore, the following detailed description of the embodiments of the application provided in the drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of the application. All other embodiments obtained based on the embodiments of the application by one of ordinary skill in the art without creative work are within the scope of the protection of the application.

[0042] It should be noted that similar reference numbers and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0043] In the above description of the application, it should be noted that the terms "one side", "the other side" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the application is usually placed, and are only for the convenience of describing the application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the application. In addition, the terms "first", "second" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0044] In addition, the terms "same" and the like do not mean that the parts must be absolutely the same, but there can be slight differences. The term "vertical" only means that the positional relationship between the parts is more vertical than "parallel", and does not mean that the structure must be completely vertical, but can be slightly inclined.

[0045] The application provides a method for efficiently forming nanocrystalline Al2Cu at an Al / Cu bonding interface, which specifically comprises the following steps:

[0046] 1. Selecting an electromagnetic pulse device;

[0047] 2. Considering the size of the workpiece and the electromagnetic force according to the electrical and magnetic properties of the device, the structural characteristics of the coil and the power supply properties;

[0048] 3. Determining the reference voltage and the reference gap;

[0049] 4. Determining the connecting piece with the highest tensile strength;

[0050] 5. TEM analysis of the connecting piece with the highest tensile strength.

[0051] An embodiment is listed as follows:

[0052] The interface connection adopts a PUSR-70 type electromagnetic pulse device, which is composed of a power supply cabinet, a control cabinet, a working platform and a control terminal, the threshold voltage is 25kV, the maximum energy storage is 70kJ, and an "E" shaped flat electromagnetic coil 6 is adopted, such as Figure 6The high-strength copper alloy coil is wrapped with high-pressure resistant insulating tape; the coil gap is filled with insulating blocks to insulate and reduce deformation, and spacers are arranged between the plates to adjust the initial gap; the positioning accuracy of the base plate and the flying plate is ensured by the fixing tool of bolts and steel plates.

[0053] During the interface bonding process, the Lorentz force acting on the aluminum flying plate is shown in formula 1-1:

[0054] F = J e × B (1-1)

[0055] In the formula, J e is the induced eddy current density on the Al plate, B is the magnetic induction intensity between the coil and the Al plate, and the Lorentz force is converted into electromagnetic pressure, as shown in formula 1-21:

[0056]

[0057] Where s is the thickness of the flying plate, d is the skin depth, and μ is the magnetic permeability of the material. Electromagnetic force is a key factor to realize high-speed collision interface metallurgical bonding, and different materials have different yield strengths and deformation properties,

[0058] which results in different electromagnetic pressures required for interface bonding, and different magnetic permeability and electrical conductivity of materials, different skin depths and shielding effect of magnetic field (i.e. magnetic field utilization rate). The skin depth is the depth at which the current density in a conductor decreases to l / e (e is a natural number, e = 2.71828183) of the current density on the cross-sectional surface of the conductor. When the material thickness is equal to the skin depth, 86% of the electromagnetic field is shielded; when the material thickness is equal to 2 times the skin depth, 98% of the magnetic field is shielded. The better the magnetic field shielding effect, the lower the magnetic leakage rate, and the higher the magnetic field utilization rate. The skin depth of the material is shown in formula 1-3:

[0059]

[0060] In the formula, ω is the current frequency in the coil, μ is the magnetic permeability of the material, and γ is the electrical conductivity of the material. Based on formula 1-2, the skin effect and proximity effect of the current are considered, and the single-sided bonding analysis model is improved, and its formula is shown in 1-4:

[0061]

[0062] In the formula, P c is the workpiece pressure limit, σ Y is the fluid stress, and l is the workpiece length. Assuming P c << electromagnetic pressure P, the magnetic field strength (Hg) and the electromagnetic pressure (P) can be calculated by formulas 1-5 and 1-6.

[0063]

[0064]

[0065] where I is the discharge current, d is the skin depth, h is the coil height, s is the coil thickness, and W is the coil width. Equation 1-6 takes into account the skin effect of the current, but still uses the discharge current in the coil, while the actual electromagnetic pressure is the interaction of the induced eddy current (I e ) and the magnetic field, therefore, equation 1-6 can be modified as:

[0066]

[0067] In summary, the electrical and magnetic properties of the workpiece, the structural design of the coil, and the properties of the power source, etc. comprehensively determine the size and distribution of the electromagnetic force.

[0068] According to the above analysis and multiple experiments, the aluminum flyer plate 1 and the copper substrate 2 of the embodiment are taken as the same size, which are rectangular blocks of 100X20mm, and the thicknesses are both 1mm. At the same time, the same thickness of the pad 4 is arranged on the left and right sides of the bonding area 3, so that the bonding area between the aluminum flyer plate and the copper substrate is kept at a relatively stable distance, as shown in Figure 5 .

[0069] In order to ensure the bonding quality, the interval distance of the bonding area needs to be constant, and the error is as small as possible, and the parallelism is controlled within 0.05mm. In order to achieve this goal, in the embodiment, the thickness tolerance of the two side pads is controlled within 0.01mm, and the flatness and parallelism of the bonding area are both controlled within 0.01mm. Before operation, the actual situation of the distance between the two is detected.

[0070] In order to realize the flatness and parallelism, and ensure the bonding effect, the aluminum flyer plate is formed with a boss 5 in the middle area of the lap joint section in the embodiment, which is higher than the plane of the plate body, as shown in Figure 5 , 6 The top surface of the boss is the bonding area, which is higher than the plane of the plate body, and is also convenient for processing, and the flatness and parallelism are convenient to control. At the same time, the length of the bonding area can be selected according to the actual situation of the electromagnetic pulse equipment parameters and workpiece parameters.

[0071] The discharge voltage and the initial gap are important process parameters affecting the bonding quality. According to the rated power and use characteristics of the equipment, the discharge voltage U=10kV, 12kV, 14kV, 16kV and the initial gap g=1mm, 1.2mm, 1.5mm, 1.7mm, 2.0mm are arranged and combined to carry out Al-Cu dissimilar metal electromagnetic pulse lap joint interface bonding, that is, one value of the discharge voltage is tested with any initial gap, and then another discharge voltage is tested with all initial gaps, until all values of the two parameters are combined.

[0072] If the above voltage and gap combination cannot achieve interface bonding, interpolation method is used to supplement reasonable process parameters for retesting until success.

[0073] When the bonding is completed, the tensile lap shear test is performed on the bonded sample.

[0074] The peak load and fracture (matrix fracture or weld fracture) are compared by using the control variable method to determine the reference voltage and gap. In this embodiment, when the bonding region length is about 12 mm, the reference voltage U = 14 kV and the gap g = 1 mm are determined.

[0075] Then, a plurality of tests are performed with the reference voltage and gap, including three groups of constant voltage variable gap tests and three groups of constant gap variable voltage tests.

[0076] Five samples are prepared for tensile test for any one group, and the connector with the highest tensile strength is selected for TEM analysis to investigate whether the nano-crystalline Al2Cu is formed at the bonding interface.

[0077] The TEM analysis of the connector selected in this embodiment is described in detail as follows:

[0078] Since the physical and chemical properties on both sides of the Al-Cu dissimilar metal bonding interface are different, the traditional TEM sample preparation method cannot obtain effective Al-Cu interface samples. Therefore, the focused ion beam cutting (Focused Ion beam, FIB) technology is used for slicing, and the sampling position is the transition layer interface, as shown in Figure 1 a, a Pt plating layer is deposited at the selected position to mark and protect, and after slicing, the sample thickness is about 50 nm, and the final TEM sample is shown in Figure 1 b. Figure 1 c, d show that the Al-Cu interface forms a relatively uniform transition layer with a thickness of about 1.3 μm, and EDS surface scanning Figure 1 f, g, h) shows that the left side of the transition layer is Al and the right side is Cu, and the line scanning Figure 1 i) result shows that the transition layer contains Al and Cu elements and forms intermetallic compounds. Figure 1 c is the upper region of the transition layer Figure 1 in the red rectangular frame region in b), regions 1, 2 and 3 are the characteristic morphologies of the transition layer, i.e. black area, uniform transition area and long strip-shaped characteristic area, which will be analyzed one by one below.

[0079] Figure 2 a is the TEM bright field image of region 3 and the surrounding area, and the selected area electron diffraction (SAED) of region A is shown in Figure 2As shown in b, its electron diffraction pattern is a nanocrystalline diffraction ring, and the calibration result is Al2Cu phase. The diffraction pattern ring was converted using Gatan Digital Micrograph software, as shown in Figure b. Figure 2 As shown in Figure g. By comparing with the standard diffraction patterns of three Al₂Cu crystal structures, it was found that the structure is a body-centered tetragonal structure, but the corresponding peak intensities differ, as shown in the figure. Figure 2 As shown in h, the measured interplanar spacing is compared with the standard interplanar spacing of body-centered tetragonal Al₂Cu, and the error is within the allowable range. Figure 2 As shown in i. Furthermore, HRTEM observation and analysis of the lower left region of region A revealed that region B exhibits a certain degree of disordered arrangement. FFT transformation of this region revealed a halo-like appearance, as shown in... Figure 2 As shown in c, the inverse FFT transform of region B is as follows: Figure 2 As shown in d, the atoms are arranged with "short-range order and long-range disorder," indicating that region B is an amorphous phase. Simultaneously, HRTEM observation of the lower right region of region A also shows a similar phenomenon. FFT and inverse FFT transformations indicate that region C is also an amorphous phase. Figure 2 As shown in d, Figure 2 d represents the inverse FFT transform of region D, indicating the presence of numerous dislocations. Therefore, region 1 is primarily composed of nanocrystalline Al₂Cu phase, with localized amorphous phases.

[0080] Figure 3 a is the bright-field TEM image of region 2 and its surrounding area, and the selected area electron diffraction (SAED) image of region A is as follows: Figure 3 As shown in b, its electron diffraction pattern is a nanocrystalline diffraction ring, and the calibration result is Al2Cu phase. The diffraction pattern ring was converted using Gatan Digital Micrograph software, as shown in Figure b. Figure 3 As shown in h, with Figure 2 Similarly, the spectral lines match the standard diffraction lines of Al₂Cu, but there are differences in the corresponding peak intensities. Furthermore, comparing the measured interplanar spacing with the standard interplanar spacing of body-centered tetragonal Al₂Cu, the error is within the acceptable range. Figure 3 As shown in i; Figure 3 j shows the atomic structure of body-centered tetragonal Al₂Cu. Furthermore, high-resolution transmission electron microscopy (HRTEM) observation and analysis were performed on region A, such as... Figure 3 c is the HRTEM lattice fringe image of region A, clearly showing a complex polycrystalline system with crisscrossing lattices. Fast Fourier Transform (FFT) analysis was performed on this region, as shown... Figure 3 As shown in d, the nanocrystalline diffraction rings in the figure were calibrated, and the results showed that they were still Al2Cu phase, consistent with... Figure 3The results are consistent with b, further indicating that it is a nanocrystalline polycrystalline Al2Cu phase, with characteristic crystal planes (1 1 0), (1 1 2), (3 1 0) and (1 2 1) as shown. Figure 3 As shown in c. It is noteworthy that, in addition to the polylattice fringes of the Al₂Cu phase, disordered atomic arrangements form in local regions. The FFT diffraction images of regions B and C are as follows: Figure 3 As shown in c, the diffraction result is a "halo," and the inverse FFT image is as follows. Figure 3 As shown in f and g, the atoms are arranged in a disordered manner. Therefore, region 2 contains a large number of nanocrystalline Al2Cu phases, with local regions accompanied by amorphous phases with disordered atomic arrangement.

[0081] Figure 4 a is the bright-field TEM image of region 3 and its surrounding area, and the selected area electron diffraction (SAED) image of region A is as follows. Figure 4 As shown in b, its electron diffraction pattern still shows a nanocrystalline diffraction ring, and the calibration result is Al2Cu phase. The diffraction pattern ring was then subjected to ring integral conversion using Gatan Digital Micrograph software, as shown below. Figure 4 As shown in h, with Figure 2 Similar to g and 3h, the spectral lines match the standard diffraction lines of Al₂Cu, but there are differences in the corresponding peak intensities. Furthermore, comparing the measured interplanar spacing with the standard interplanar spacing of body-centered tetragonal Al₂Cu, the error is within the acceptable range. Figure 4 As shown in i.

[0082] In addition, HRTEM observation was performed on region A, such as Figure 4 As shown in Figure c, a complex polycrystalline system with crisscrossing surfaces is presented. Fast Fourier Transform (FFT) analysis is performed on this region, as shown... Figure 4 As shown in d, the nanocrystalline diffraction rings in the figure were calibrated, and the result was Al2Cu, consistent with the figure. Figure 4 The results are consistent with b, further indicating that it is a nano-polycrystalline Al2Cu phase.

[0083] Observation of the (1 2 1) and (1 1 0) crystal planes in region B, after inverse FFT transformation, yielded clear striped phases, such as... Figure 4 As shown in f and g, there are obvious lattice distortions and dislocations in local regions of the crystal plane, such as Figure 4 e is the inverse FFT transform image of region B, indicating that disordered atomic structures are interspersed at the junction of crystal planes (1 2 1) and (1 1 0), acting like "locks" to bind and smoothly transition the crystal planes. Therefore, region 5 also contains a nanocrystalline polycrystalline Al2Cu phase, locally accompanied by disordered atomic arrangement. In addition, when studying the growth behavior of Al2Cu, Gao Ka also summarized previous studies, indicating that Al2Cu is often in the form of lamellar or dendritic structures.

[0084] Finally, it is to be explained that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the present application, and all of them should be covered in the scope of the claims of the present application.

Claims

1. A method for efficiently forming nanocrystalline Al2Cu at an Al / Cu bonding interface, characterized by: The copper substrate and aluminum flyer plate are subjected to electromagnetic pulse high-speed collision bonding, and specifically comprises the following technical features: (1) Electromagnetic pressure design: comprehensively consider the electrical and magnetic properties of the workpiece to be welded, the structural characteristics of the coil and the properties of the power supply, and control the electromagnetic force by using a modified electromagnetic pressure formula, wherein the modified electromagnetic pressure formula is: where I is the discharge current, d is the skin depth, h is the coil height, s is the coil thickness, W is the coil width, μ is the permeability of the material, I e is the induced eddy current, d f is the thickness of the E-coil side arm; (2) Tool control: the copper substrate and aluminum flyer plate are fixed by a tool, and the interval distance of the bonding area on both sides is adjusted by a spacer, wherein the thickness tolerance of the spacer is ≤0.01 mm, the flatness and parallelism of the bonding area are both ≤0.01 mm, and the interval distance error of the bonding area section between the two plates is ±0.05 mm; (3) Electromagnetic pulse high-speed collision process parameters: the discharge voltage range is 10-16 kV, and the initial gap value is 1-2 mm, and the efficient bonding is realized by taking the reference voltage of 14 kV and the reference gap of 1 mm as the core parameters; (4) Target product structure: a transition layer of ultra-fine nanocrystalline Al2Cu with a thickness of about 1.3 μm is formed at the bonding interface, the transition layer is locally accompanied by amorphous phase, and no coarse-grained Al2Cu is generated.

2. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface with high efficiency according to claim 1, characterized in that: Comprehensively consider the electrical and magnetic properties of the workpiece to be welded, the structural characteristics of the coil and the properties of the power supply to optimize the design of the electromagnetic force, and the formula includes: The Lorentz force received by the aluminum flyer plate is: F = J e x B Among them, J e Let B be the induced eddy current density on the Al plate, and B be the magnetic induction intensity between the coil and the Al plate. The electromagnetic pressure is: Wherein, s is the thickness of the flyer plate, d is the skin depth, and μ is the magnetic permeability of the material; The skin depth of the material is: In the formula, ω is the current frequency in the coil, μ is the magnetic permeability of the material, and γ is the electrical conductivity of the material.

3. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface with high efficiency according to claim 2, characterized in that: The copper substrate and aluminum flyer plate are fixed by a tool, and the interval distance error of the bonding area section between the two plates is ±0.05 mm.

4. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface with high efficiency according to claim 3, characterized in that: The discharge voltage and initial gap value are set by equal difference, if the bonding interface cannot be formed, the interpolation method is used to supplement the parameters, then the tensile lap shear test is carried out, the peak load and fracture condition are compared by using the control variable method, and the reference voltage and reference gap are determined.

5. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface with high efficiency according to claim 4, characterized in that: After the reference voltage and reference gap are determined, three groups of constant voltage variable gap and three groups of constant gap variable voltage parameters are selected for research, the bonding samples of the selected process group are subjected to tensile lap shear test, 5 samples are selected for each group, the tensile strength of the highest tensile strength of the welding piece is selected according to the tensile test result, and TEM analysis is carried out to investigate whether the nanocrystalline Al2Cu is formed at the bonding interface.

6. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface with high efficiency according to claim 3, characterized in that: The interval distance of the bonding area on both sides of the copper substrate and aluminum flyer plate is adjusted by spacers, the thickness tolerance of the spacers on both sides is controlled within 0.01 mm, and the flatness and parallelism of the bonding area are both controlled within 0.01 mm.

7. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface efficiently according to any one of claims 1-6, characterized in that The size of the copper substrate and aluminum flyer plate is 100 mmX20 mmX1 mm, and the mutual lap length is 60 mm.

8. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface with high efficiency according to claim 7, characterized in that The discharge voltage range is 10-16 kV and the initial gap value is 1-2 mm.

9. The method for forming nanocrystalline Al2Cu at Al / Cu bonding interface with high efficiency according to claim 8, characterized in that The reference voltage is 14 kV and the gap value is 1 mm.

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