A method of diffusion bonding assisted by a dynamic phase coupling electromagnetic field device

Abstract

The application discloses a kind of by dynamic phase coupling electromagnetic field device auxiliary vacuum diffusion welding method, belong to metal material solid-phase welding technical field.The method aims at solving the problems, such as grain coarsening, joint performance decline and heterogeneous material welding uneven caused by high temperature and long time heating in traditional diffusion welding process.The core scheme includes: (1) surface treatment, clamping positioning and vacuum pretreatment are carried out to the workpiece to be welded;(2) double-band nested induction coil structure is used, and pulse current module is loaded cooperatively, three-module electromagnetic field is realized by FPGA chip dynamic phase coupling, and periodic oscillation electromagnetic pressure field is formed;(3) based on convolution neural network model, parameters are real-time regulated during welding process, and interface diffusion behavior is optimized.The application realizes deep cooperation of pulse joule heat and induction eddy current heat through dynamic phase coupling mechanism, significantly reduces welding temperature and shortens welding time, is especially suitable for high-quality connection of copper alloy, molybdenum alloy and other heterogeneous materials, the joint tensile strength is improved, and the structure is uniform, corrosion resistance is excellent.

Description

[0001] manual Technical Field

[0002] This invention relates to a welding method for metallic materials, specifically a method for diffusion welding assisted by a dynamic phase-coupled electromagnetic field device, belonging to the field of advanced manufacturing technology. Background Technology

[0003] Diffusion welding is a solid-state welding method that achieves bonding between two or more materials by allowing atoms to diffuse into each other under high temperature and pressure. Diffusion welding offers advantages such as applicability to joining similar or dissimilar metals and non-metals, high joint strength, and excellent joint performance. However, traditional diffusion welding processes typically require high temperatures and long durations, which can lead to grain growth and oxidation, thus affecting the mechanical properties and processing efficiency of the joint. During diffusion welding, surface atoms overcome energy barriers through thermal activation, migrating across the interface. The diffusion rate follows the Arrhenius equation and is exponentially related to temperature. Traditional processes rely on high temperatures and prolonged holding times to drive atomic diffusion, but these thermodynamic conditions easily induce grain boundary migration, grain coarsening, and thickening of the interfacial oxide layer, resulting in decreased joint toughness and fluctuations in interfacial bonding strength. Furthermore, the high temperature and high pressure environment places stringent requirements on the heat resistance of equipment and consumes significant energy, limiting its application in precision components or heat-sensitive materials.

[0004] In the prior art, patent document CN119973330B discloses a method and apparatus for preparing complex hollow structures using pulsed DC and induction eddy current cyclic loading assisted diffusion connection. This method improves heating efficiency and temperature uniformity through the cyclical combination of pulsed DC heating and induction eddy current heating. However, this method has the following limitations: the pulsed DC and induction eddy current use simple frequency synchronization settings and lack a dynamic phase coupling mechanism, resulting in insufficient electromagnetic field interaction. Especially for dissimilar materials (such as materials with large differences in electrical and thermal conductivity), it is prone to interfacial stress concentration and uneven diffusion problems. In addition, the heating method of this patent does not finely divide the heat source, and cannot achieve the decoupling and synergy between precise energy concentration in the interfacial micro-region and uniform heating of the entire workpiece. For welding high-melting-point or dissimilar materials, such as copper alloys and molybdenum alloys, it is difficult to ensure that the interface reaches the optimal diffusion temperature while avoiding overheating of the substrate. Its embodiments are mainly concentrated on common materials such as magnesium alloys and steel, and lack adaptability to complex material combinations.

[0005] This invention addresses the aforementioned problems by introducing a dynamic phase-coupled electromagnetic field device composed of three independent modules (pulsed current, high-frequency induction, and medium-frequency induction). A precisely positionable high-frequency inner rectangular coil achieves concentrated interface heating, while a medium-frequency outer spiral coil ensures overall temperature uniformity. An FPGA chip is used for precise dynamic phase closed-loop control. This solution achieves deep coupling of the thermo-mechanical fields, significantly improving the joint quality and efficiency of dissimilar material welding, and particularly solving the challenges of interface energy concentration and substrate heat-affected zone control. Compared to traditional single-heat-source diffusion welding, the dynamic phase-coupled electromagnetic field device achieves dynamic coupling through the Joule heating effect of the pulsed current and the eddy current heating and Lorentz force of the induction coil. The pulsed current generates a Joule heating effect inside the workpiece; its transient high-energy input can excite interface dislocation slip and lattice distortion, reducing the atomic diffusion activation energy. Simultaneously, it promotes dislocation mobility and accelerates interdiffusion of interface elements through the electroplastic effect. During welding, the pulsed current can reduce welding temperature, shorten diffusion time, and significantly improve the quality of the weld joint. The alternating magnetic field generated by the induction coil further induces eddy current heating and Lorentz force, achieving selective heating in localized micro-regions. Electromagnetic stirring breaks up the oxide film and cleans the interface. The electromagnetic coupling between these two forces creates a dynamic thermo-mechanical field, enabling the interface to achieve an equivalent diffusion driving force at a lower macroscopic temperature, inhibiting abnormal grain growth and reducing thermal stress accumulation. This process, through the combined effect of electromagnetic induction and pulsed current, excites localized heating within the material, thereby accelerating the diffusion process. Summary of the Invention

[0006] The main objective of this invention is to provide a method for diffusion welding assisted by a dynamic phase-coupled electromagnetic field device. By rationally setting parameters such as pulse current, pressure, and temperature, and especially by incorporating a three-module synergy (pulse current, high-frequency inner rectangular coil, and mid-frequency outer spiral coil) and a dynamic phase closed-loop coupling mechanism, high-quality welded joints can be obtained in a shorter time. This solves the problems of excessively high temperature, excessively long welding time, and poor joint quality in traditional diffusion welding processes, and optimizes the handling of dissimilar materials (such as copper alloys and molybdenum alloys). The technical solution of this invention is as follows:

[0007] (1) Structure of diffusion welding assisted by dynamic phase-coupled electromagnetic field device:

[0008] 1) Pulse Current Module (0-1 MHz): Pulse power supply, generating and regulating the pulse current passing through the workpiece. The current pulse can be set to different waveforms such as square wave and sine wave. The pulse current generates a Joule heating effect inside the workpiece, directly acting on the interface and reducing the atomic diffusion activation energy. The frequency range of the pulse current is 0-1 MHz, the pulse current intensity range is 50A~50000A, the pulse width range is 1ms~1000ms, and the duty cycle range is 1%~99%.

[0009] 2) High-frequency induction module (100-500 kHz): Employs an inner rectangular coil. This coil is mounted on a programmable multi-axis moving mechanism. By applying a high-frequency current, utilizing the skin effect and the field concentration characteristics of the rectangular coil, energy is highly concentrated within the extremely thin layer of the welding interface, achieving selective deep heating of the interface micro-region without affecting the substrate temperature. The power output range is 800W ~ 3000W.

[0010] 3) Medium-frequency induction module (1-100 kHz): Employs an outer spiral coil. This coil is fixedly installed. When a medium-frequency current is applied, it generates a widely penetrating electromagnetic field, achieving uniform preheating and heat preservation of the workpiece, and promoting uniform diffusion of elements through electromagnetic stirring. The power output range is 200W~1000W.

[0011] 4) Dynamic Phase Coupling Control System: This system is key to realizing the core innovation of this invention. Its hardware foundation is a high-speed, high-precision digital closed-loop control platform built with an FPGA chip as the core processor. The system includes the following modules:

[0012] a. Independent power drive units: The high-frequency induction module and the intermediate-frequency induction module are not driven by a single power supply, but are powered by two independent full-bridge inverters based on IGBTs or MOSFETs. This architecture is a prerequisite for achieving independent controllability of the amplitude, frequency, and phase of the current in each module.

[0013] b. Precise phase synchronization mechanism: The system uses a phase-locked loop circuit to strictly synchronize the operating frequencies of the two inverters with a unified, highly stable reference clock (or pulse current waveform), ensuring absolute frequency consistency and laying the foundation for precise control of the phase difference.

[0014] c. Closed-loop control with phase difference as the variable: The system sets the phase difference (ΔΦ) as the direct control target. High-precision current sensors monitor the current waveforms of each induction coil in real time, and the FPGA's internal logic quickly calculates the real-time deviation from the reference phase.

[0015] d. Dynamic Feedback and Real-Time Adjustment: The FPGA chip runs a high-speed control algorithm, comparing the real-time phase difference with the preset optimal value. If a deviation occurs, a control signal is immediately generated, and the phase is dynamically compensated at the millisecond level by adjusting the trigger timing of the inverter's PWM drive signal, thereby ensuring that the preset phase relationship (adjustable within ±15°) remains stable throughout the welding process. This closed-loop control makes the generated electromagnetic pressure field strength constant and controllable.

[0016] e. Intelligent adaptive capability: The phase difference setting value is not fixed. The host computer control system can dynamically optimize the phase difference setting value based on the output of the convolutional neural network model or based on feedback signals such as the temperature sensor of the welding area and the interface impedance, so as to adapt to the needs of different materials or welding stages and realize intelligent welding.

[0017] 5) Welding pressure device: Provides welding pressure through a mechanical or hydraulic system to ensure that the workpiece maintains a stable contact pressure during the welding process. The pressure can be constant or dynamically adjusted according to process requirements.

[0018] 6) Temperature Control System: This system includes a temperature sensor and a temperature control module for real-time monitoring of the welding area temperature. Based on the welding progress, the temperature control system can precisely adjust the power of the induction coil and the parameters of the pulse current to ensure that the welding temperature fluctuates within a reasonable range.

[0019] 7) Workpiece support platform: Used to support the welding workpiece. The platform has good electrical and thermal conductivity, which can prevent heat accumulation. In addition, the platform can be used in conjunction with a pressure device to ensure accurate positioning of the workpiece during the welding process.

[0020] 8) Data acquisition and control system: including high-precision sensors and control units, which collect data such as temperature, current, voltage, and displacement in real time during the welding process, and coordinate the control of pulse power supply, coil module and pressure device to achieve precise adjustment of the welding process.

[0021] (2) Process flow:

[0022] 1) Workpiece preparation: Clean and grind the surface of the workpiece to be welded to ensure that the contact surface is clean and free of oxide layer. For dissimilar materials (such as copper alloy and molybdenum alloy), add a gradient diffusion layer material (such as nickel-based interlayer) between the contact surfaces to reduce the interface barrier and improve diffusion.

[0023] 2) Clamping and positioning: Clamp the cleaned workpiece on the welding device, accurately align the area to be welded, apply initial pressure to ensure close contact of the workpiece, and adjust the relative position of the induction coil and the welding area.

[0024] 3) Vacuum treatment: The vacuum level in the vacuum chamber is evacuated to 1×10⁻³~4×10⁻³ Pa, and then high-purity argon gas is introduced to prevent oxidation.

[0025] 4) Preheating treatment: Preheat the workpiece to the set temperature, which is usually lower than the actual welding temperature. The preheating temperature is usually 200℃~400℃. The preheating time is 5min~20min to reduce thermal stress and improve the plasticity of the workpiece.

[0026] 5) Dynamic Phase-Coupled Electromagnetic Field Loading Step: While applying a constant or variable initial welding pressure (pressure range 5MPa~20MPa), the dynamic phase-coupled electromagnetic field device is activated, and the output is synchronously provided by a multi-band coupled power supply system. The high-frequency inner coil is controlled by the moving mechanism to precisely scan and heat the interface; the medium-frequency outer coil provides uniform background heating; the FPGA chip executes the dynamic phase coupling step to form a periodic oscillating electromagnetic pressure field (0.5-3MPa), which promotes atomic diffusion and oxide film breakage at the interface.

[0027] 6) Maintenance and Control Steps: During the welding process, the temperature, current, voltage, and pressure changes in the welding area are monitored in real time. Based on the real-time monitoring data, the pulse current parameters and the power output of the induction coil are dynamically adjusted through a convolutional neural network model to ensure the stability of the welding process and the quality of the joint. Especially for heterogeneous materials, the model is adaptively optimized based on differences in thermal expansion coefficients and element diffusion gradients.

[0028] 7) Cooling and unloading: After welding is completed, turn off the pulse current and induction coil, gradually reduce the welding temperature and slowly unload the pressure. Remove the workpiece after it has cooled to room temperature.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] This invention utilizes a three-module (pulse current, high-frequency induction, and medium-frequency induction) dynamic phase-coupled electromagnetic field device to assist diffusion welding, achieving for the first time the decoupling and synergy between concentrated interface heating and uniform overall heating. A movable high-frequency inner rectangular coil precisely focuses energy onto the interface, significantly reducing thermal damage to the substrate; a fixed medium-frequency outer spiral coil ensures process stability. Combined with dynamic phase closed-loop control, it significantly improves the joint strength and efficiency of dissimilar material welding, while reducing welding temperature and time. The dual-coil design (outer spiral coil and inner rectangular coil) achieves synergistic surface and depth heating, and the phase coupling mechanism enhances electromagnetic field uniformity, especially for dissimilar materials (such as copper alloys and molybdenum alloys), effectively reducing interface stress, improving diffusion uniformity, and minimizing welding defects. The real-time monitoring system precisely controls temperature, current, and pressure, ensuring the stability and consistency of welding quality. Attached Figure Description

[0031] Figure 1 A schematic diagram of a dynamic phase-coupled electromagnetic field device for assisted diffusion welding. Detailed Implementation

[0032] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments.

[0033] Example 1

[0034] (1) Experimental materials and equipment:

[0035] Experimental material: copper alloy (C11000) plate, 3 mm thick.

[0036] Welding apparatus: The dynamic phase-coupled electromagnetic field device of the present invention is used for diffusion welding.

[0037] Process parameter settings: Dynamic phase-coupled electromagnetic field loading: Pulse current module: 15kHz, 120A. High-frequency induction module: 400kHz, 1500W, providing centralized heating through precise tracking of the interface via a moving mechanism. Medium-frequency induction module: 50kHz, 400W, providing a uniform background temperature field. Phase difference: -5°.

[0038] (2) Welding process:

[0039] Workpiece preparation: Clean the surface of the copper alloy plate to remove the oxide layer and impurities, ensuring that the welding surface is clean.

[0040] Clamping and positioning: Accurately align the two plates, clamp them on the workpiece support platform, and apply an initial pressure of 10MPa.

[0041] Vacuum treatment: The vacuum level in the vacuum chamber is evacuated to 1×10⁻³~4×10⁻³ Pa, and then high-purity argon gas is introduced.

[0042] Preheating treatment: The welding area is preheated to 200°C for 15 minutes using a temperature control system to reduce thermal stress.

[0043] Dynamic phase-coupled electromagnetic field loading: Apply pulsed current and electromagnetic field of induction coil while maintaining a pressure of 10 MPa, and complete diffusion welding in 25 minutes.

[0044] Cooling and unloading: After welding is completed, gradually reduce the temperature to room temperature and slowly unload the pressure to remove the welded parts.

[0045] (3) Welding results:

[0046] Welding temperature: The peak temperature during actual welding is approximately 720℃.

[0047] Welding time: The total welding time is 40 minutes.

[0048] Connector quality:

[0049] Tensile strength: The tensile strength of the welded joint reaches 250 MPa.

[0050] Microstructure: The microstructure of the joint area is uniform, without obvious cracks or pores, and the grains are fine and dense.

[0051] Corrosion resistance: After 48 hours of salt spray testing, no significant corrosion was observed at the joint, indicating good corrosion resistance.

[0052] Example 2

[0053] (1) Experimental materials and equipment:

[0054] Experimental materials: copper alloy (C11000) plate and molybdenum alloy (Mo-1) plate, both with a thickness of 3 mm.

[0055] Welding apparatus: The dynamic phase-coupled electromagnetic field device of the present invention is used for diffusion welding.

[0056] Process parameter settings: Dynamic phase-coupled electromagnetic field loading: Pulse current module: 20kHz, 150A. High-frequency induction module (inner rectangular coil, movable): 250 kHz, 500W, providing scanning-type concentrated heating of the weld. Medium-frequency induction module (outer spiral coil, fixed): 15 kHz, 2000W, providing overall heating. Phase difference: +10°; Add a nickel-based gradient diffusion layer at the interface.

[0057] (2) Welding process:

[0058] Workpiece preparation: The surfaces of copper alloy and molybdenum alloy plates are mechanically ground and cleaned to ensure that the welding surfaces are free of contamination.

[0059] Clamping and positioning: Accurately align the copper alloy and molybdenum alloy plates, clamp them on the workpiece support platform, and apply an initial pressure of 10 MPa.

[0060] Vacuum treatment: The vacuum level in the vacuum chamber is evacuated to 1×10⁻³~4×10⁻³ Pa, and then high-purity argon gas is introduced.

[0061] Preheating treatment: The welding area is preheated to 300°C for 15 minutes using a temperature control system to improve the plasticity of the material.

[0062] Dynamic phase-coupled electromagnetic field loading: Apply pulsed current and electromagnetic field of induction coil while maintaining a pressure of 8 MPa, and complete diffusion welding in 55 minutes.

[0063] Cooling and unloading: After welding is completed, gradually reduce the temperature to room temperature and slowly unload the pressure to remove the welded parts.

[0064] (3) Welding results:

[0065] Welding temperature: The peak temperature during the actual welding process is approximately 810 ℃.

[0066] Welding time: The total welding time is 70 minutes.

[0067] Connector quality:

[0068] Tensile strength: The tensile strength of the welded joint reaches 120 MPa.

[0069] Microstructure: The grains in the joint area are fine and uniform, and no significant precipitates or cracks were found.

[0070] Corrosion resistance: After 48 hours of salt spray testing, no obvious corrosion spots were found at the joint, demonstrating good corrosion resistance.

[0071] Comparative Example 1

[0072] (1) Experimental materials and equipment:

[0073] Experimental material: copper alloy (C11000) plate, 3 mm thick.

[0074] Welding apparatus: Traditional diffusion welding apparatus.

[0075] Process parameter settings: Welding pressure: 10 MPa; Preheating temperature: 200℃; Holding time: 15 min.

[0076] (2) Welding process:

[0077] Workpiece preparation: Clean the surface of the magnesium alloy sheet, remove the oxide layer and impurities, and ensure that the welding surface is clean.

[0078] Clamping and positioning: Accurately align the two plates, clamp them on the workpiece support platform, and apply an initial pressure of 10MPa.

[0079] Vacuum treatment: The vacuum level in the vacuum chamber is evacuated to 1×10⁻³~4×10⁻³ Pa, and then high-purity argon gas is introduced.

[0080] Preheating treatment: The welding area is preheated to 200°C for 15 minutes using a temperature control system to reduce thermal stress.

[0081] Diffusion welding: Maintain a pressure of 10 MPa and complete diffusion welding in 60 minutes.

[0082] Cooling and unloading: After welding is completed, gradually reduce the temperature to room temperature and slowly unload the pressure to remove the welded parts.

[0083] (3) Welding results:

[0084] Welding temperature: The peak temperature during actual welding is approximately 830℃.

[0085] Welding time: The total welding time is 75 minutes.

[0086] Connector quality:

[0087] Tensile strength: The tensile strength of the welded joint is 200 MPa.

[0088] Microstructure: Microcracks exist in the grains in the joint area.

[0089] Corrosion resistance: After a 48-hour salt spray test, slight corrosion was observed after 24 hours.

[0090] Comparative Example 2

[0091] (1) Experimental materials and equipment:

[0092] Experimental materials: Copper alloy (C11000) plate and molybdenum alloy (Mo-1) plate, both with a thickness of 3 mm.

[0093] Welding apparatus: Traditional diffusion welding apparatus.

[0094] Process parameter settings: Welding pressure: 8 MPa; Preheating temperature: 300℃; Holding time: 15 min.

[0095] (2) Welding process:

[0096] Workpiece preparation: The surfaces of copper alloy (C11000) plates and molybdenum alloy (Mo-1) plates are mechanically ground and cleaned to ensure that the welding surfaces are free of contamination.

[0097] Clamping and positioning: Accurately align the copper alloy (C11000) plate and the molybdenum alloy (Mo-1) plate, clamp them on the workpiece support platform, and apply an initial pressure of 10MPa.

[0098] Vacuum treatment: The vacuum level in the vacuum chamber is evacuated to 1×10⁻³~4×10⁻³ Pa, and then high-purity argon gas is introduced.

[0099] Preheating treatment: The welding area is preheated to 300°C for 15 minutes using a temperature control system to improve the plasticity of the material.

[0100] Diffusion welding: Maintain a pressure of 8 MPa and complete diffusion welding in 105 minutes.

[0101] Cooling and unloading: After welding is completed, gradually reduce the temperature to room temperature and slowly unload the pressure to remove the welded parts.

[0102] (3) Welding results:

[0103] Welding temperature: The peak temperature during the actual welding process is approximately 920℃.

[0104] Welding time: The total welding time is 120 minutes.

[0105] Connector quality:

[0106] Tensile strength: The tensile strength of the welded joint is 90 MPa.

[0107] Microstructure: The grains in the joint area are relatively uniform, but microcracks are present.

[0108] Corrosion resistance: After a 48-hour salt spray test, corrosion spots appeared after 24 hours, indicating that the joint has moderate corrosion resistance.

[0109] Table 1: Comparison of results between the above embodiments and comparative examples:

[0110] Maximum welding temperature Welding time Joint tensile strength Microstructure and corrosion resistance evaluation Example 1 720℃ 40min 250MPa The joint area exhibits a uniform microstructure with no obvious cracks or pores, and the grains are fine and dense. It also demonstrates good corrosion resistance. Example 2 810℃ 70min 120MPa The joint area exhibits fine and uniform grains, with no significant precipitates or cracks observed. It demonstrates good corrosion resistance. Comparative Example 1 830℃ 75min 200MPa Microcracks exist in the grains at the joint area. Corrosion resistance is moderate. Comparative Example 2 920℃ 120min 90MPa The grain size in the joint area is relatively uniform, but microcracks are present. The joint exhibits moderate corrosion resistance.

[0111] In summary, the dynamic phase-coupled electromagnetic field-assisted diffusion welding method of this invention achieves precise control of the thermo-mechanical field through the collaborative design of a three-module system: a pulse current module, a high-frequency induction module (an inner rectangular coil with a movable mechanism), and a medium-frequency induction module (an outer spiral coil). Its innovation lies in combining the movable, concentrated heating of the high-frequency inner rectangular coil with the overall uniform heating of the medium-frequency outer spiral coil, achieving precise and efficient excitation of the diffusion behavior at the welding interface. Simultaneously, it effectively suppresses thermal damage to the workpiece substrate and deeply synergizes with the Joule heating effect of the pulse current, forming a new highly efficient diffusion welding mode characterized by interface dominance and overall synergy. This method introduces for the first time an FPGA-based dynamic phase closed-loop coupling control strategy, ensuring the precise stability of the phase relationship between the three electromagnetic fields, generating an optimal periodic oscillating electromagnetic pressure field, and significantly enhancing interface activation and atomic migration efficiency. Combined with real-time adaptive control using a convolutional neural network model, it greatly improves the stability of the process and the consistency of joint quality. As shown in the examples and comparative results, compared with traditional diffusion welding and other existing technologies, the present invention significantly reduces the peak welding temperature, shortens the welding time, improves the joint strength, and enhances the microstructure and corrosion resistance, making it particularly suitable for high-quality joining of dissimilar materials. This method successfully solves the core problems of traditional diffusion welding, such as grain coarsening, performance degradation, and uneven welding of dissimilar materials caused by high-temperature, long-term heating. It has broad application prospects and practical value in advanced manufacturing fields such as aerospace and precision electronics.

Claims

1. A method for diffusion welding assisted by a dynamic phase-coupled electromagnetic field device, characterized in that, Includes the following steps: (1) Surface treatment steps: Clean and grind the contact surfaces of two or more metal workpieces to remove oxide layers, dirt and impurities to ensure that the welding surface is clean and flat. Adding a gradient diffusion layer between the contact surfaces of dissimilar materials can improve the diffusion welding quality of the joint.

2. (2) Clamping and positioning steps: Accurately align the surface-treated workpiece and clamp it on the workpiece support platform; apply initial pressure (5-20 MPa) through the welding pressure device to keep the workpiece in close contact, and compensate for deformation in real time through the displacement sensor.

3. (3) Vacuum treatment steps: Evacuate the vacuum chamber to 1×10⁻³~4×10⁻³Pa, and then introduce high-purity argon gas.

4. (4) Preheating treatment steps: Use a temperature control system to raise the temperature of the welding area to the preset preheating temperature, which is usually 200℃~400℃; maintain the preheating temperature for 5min~20min to reduce thermal stress and improve the plasticity of the workpiece.

5. (5) Dynamic phase coupling control system loading steps: While applying a constant or variable initial welding pressure (pressure range 5~20 MPa), start the dynamic phase coupling electromagnetic field device. The device mainly consists of a high frequency induction module (100-500kHz), a medium frequency induction module (1-100 kHz), and a pulse current module (0-1MHz), which are synchronously output through a multi-band coupling power supply system.

6. (6) Maintenance and control steps: During the welding process, monitor the temperature, current, voltage and pressure changes in the welding area in real time; based on the real-time monitoring data, dynamically adjust the pulse current parameters and the power output of the induction coil through the convolutional neural network model to ensure the stability of the welding process and the joint quality.

7. (7) Cooling and unloading steps: After welding is completed, gradually reduce the temperature of the welding area to room temperature; slowly reduce the welding pressure, and unload the workpiece after the joint has cooled down sufficiently.

8. The method according to claim 1, characterized in that, The induction coil adopts a dual-band nested structure, including a high-frequency induction module (100-500 kHz) and a medium-frequency induction module (1-100 kHz). The coil is arranged around the welding area to generate a uniform alternating electromagnetic field.

9. High-frequency induction module (100-500 kHz): Employing an inner rectangular coil, this module is supplied with a high-frequency current of 100~500 kHz, with a power output range of 800W~3000W. It generates a highly concentrated alternating electromagnetic field, enabling selective deep heating of the welding interface. The high-frequency induction module is mounted on a programmable multi-axis movable mechanism, which allows for real-time and precise adjustment of the relative position between the coil and the welding interface. This enables dynamic scanning and positioning heating of complex welds or specific areas, ensuring that energy is precisely concentrated on the interface without overheating the workpiece substrate.

10. Medium-frequency induction module (1-100 kHz): It adopts an outer spiral coil, through which a medium-frequency current of 1~100 kHz is applied, and the power output range is 200W~1000W. It generates a widely distributed alternating electromagnetic field to achieve uniform heating and electromagnetic stirring of the welding area, providing a stable and uniform thermodynamic background for interface diffusion.

11. The method according to claim 1, characterized in that, The pulse power supply module includes a power supply device with an adjustable output waveform, which can be selected as a square wave, a sine wave, or a composite waveform of a sine wave superimposed on a square wave. The pulse current module (0-1 MHz) applies pulse current to the welding area according to preset pulse parameters; the frequency range of the pulse current is 0-1 MHz, the pulse current intensity range is 50A~50000A, the pulse width range is 1ms~1000ms, and the duty cycle range is 1%~99%.

12. The method according to claim 1, characterized in that, The dynamic phase coupling control system performs high-precision dynamic phase synchronization and adjustment on the outputs of the above three modules through a digital control system based on an FPGA chip. Specific implementation methods include: (1) Independent power drive: The high-frequency induction module and the medium-frequency induction module are driven by two independent IGBT / MOSFET full-bridge or half-bridge inverter power supplies. Each inverter can independently control the amplitude, frequency and phase of its output current.

13. (2) Phase reference synchronization: The output waveform of the pulse current module or a high-stability master clock signal is used as the reference phase. The operating frequency of the two induction module inverters is strictly synchronized with the reference through the phase-locked loop circuit.

14. (3) Phase difference closed-loop control: The phase difference (ΔΦ) is used as a direct control variable. The system collects the current signals of the high-frequency and medium-frequency sensing modules in real time through the current sensor, compares them with the reference phase, and calculates the real-time phase difference.

15. (4) Dynamic feedback adjustment: The FPGA chip compares the preset optimized phase difference target value (adjustment range is ±15°) with the calculated real-time phase difference, generates a correction signal through the PID algorithm, and dynamically adjusts the PWM trigger pulse timing of one or two inverters to eliminate the deviation, so that the electromagnetic fields of the three modules are formed and stabilized on the preset phase relationship, thereby generating a periodic oscillating electromagnetic pressure field with controllable intensity.

16. (5) Adaptive optimization: The target value of the phase difference can be adaptively optimized according to the real-time working conditions (such as temperature uniformity and interface reaction state) fed back by temperature and impedance sensors during the welding process, so as to achieve the best welding effect.

17. The method according to claim 1, characterized in that, The temperature control system includes at least one temperature sensor installed near the welding area to enable real-time temperature monitoring and feedback adjustment.

18. The method according to claim 1, characterized in that, The data acquisition and control system includes a PLC controller and related software algorithms, which are used to process sensor data in real time and control the operation of the dynamic phase-coupled electromagnetic field device. The input parameters of the convolutional neural network model include: interface impedance signal, thermal expansion coefficient difference, and element diffusion concentration gradient.

19. The method according to claim 1, characterized in that, The workpiece support platform is made of a high thermal conductivity material to promote uniform heating and rapid cooling of the welding area.

20. The method according to claim 1, characterized in that, The welded workpiece includes combinations of similar and dissimilar materials between metals, such as copper alloys, molybdenum alloys, titanium alloys, aluminum alloys, stainless steel, etc.

21. The method according to claim 1, characterized in that, The process parameters can be dynamically optimized and adjusted according to the electrical conductivity, thermal conductivity and diffusion characteristics of the workpiece material to achieve the best welding quality and efficiency.

22. Claim 1 above is an independent claim of the present invention, covering the basic steps and apparatus composition of the method of diffusion welding assisted by dynamic phase-coupled electromagnetic field. Claims 2 to 9 are dependent claims, which further define and refine the features of the method of the present invention in terms of specific parameters, device structure and application fields, so as to ensure the comprehensiveness and specificity of patent protection.

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