Arc additive multi-axial loading forming method for large and complex magnesium alloy components

Abstract

The present application relates to the technical field of metal additive manufacturing, and discloses an arc additive-multiple loading forming method for large complex magnesium alloy components. In view of the problems of many defects, poor performance, low forming precision and the like in the manufacturing of large complex magnesium alloy components by traditional processes, the present application divides the core and contour forming area, formulates an additive-loading collaborative strategy, builds an integrated system integrating arc additive, multiple loading, real-time monitoring and central control, applies multiple local loading to the cladding layer during the additive process, dynamically adjusts the process parameters in combination with closed-loop control, and obtains high-performance components after post-processing. The present application converts the arc deposition state organization into a deposition composite state organization, and is suitable for the manufacturing of large special-shaped magnesium alloy components in the fields of aerospace and rail transportation.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, specifically to a method for the synergistic forming of large and complex magnesium alloy components by arc additive manufacturing and multi-directional loading, applicable to the integrated manufacturing of large, irregular, and high-performance magnesium alloy load-bearing components in aerospace, rail transportation and other fields. Background Technology

[0002] Magnesium alloys, as the lightest engineering metal materials, possess high specific strength, high specific stiffness, and excellent electromagnetic shielding properties, giving them irreplaceable advantages in lightweight equipment manufacturing. Traditional manufacturing methods for large and complex magnesium alloy components (such as aircraft engine casings and high-speed rail bogie frames) often employ integrated casting and forging processes. However, these methods suffer from high mold costs, long forming cycles, and difficulties in accurately realizing complex structures, and are prone to defects such as shrinkage cavities, cracks, and uneven microstructure.

[0003] Wafer-Arc Additive Manufacturing (WAAM) technology, with its high deposition efficiency, high material utilization, and good forming flexibility, has become the preferred technology for manufacturing large metal components. However, magnesium alloys have low melting points, high thermal conductivity, and strong chemical reactivity, making them prone to problems such as hot cracking, porosity, and residual stress concentration during WAAM. In existing technologies, a single additive process cannot simultaneously achieve both forming accuracy and mechanical properties of the component, while traditional unidirectional loading strengthening methods can easily lead to instability and deformation of large components, failing to meet the forming requirements of complex structures. Therefore, there is an urgent need to develop a synergistic control technology to achieve precise matching between the additive process and plastic deformation, solving the dual challenges of forming quality and performance of large and complex magnesium alloy components. Summary of the Invention

[0004] This invention provides an arc additive manufacturing-multi-directional loading forming method for large and complex magnesium alloy components. This method optimizes the temperature and stress fields through arc additive manufacturing and multi-directional loading, reduces defects, refines the microstructure, and achieves high-precision, high-performance integrated forming of large and complex magnesium alloy components, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An arc additive manufacturing-multi-directional loading forming method for large and complex magnesium alloy components is disclosed. This method utilizes arc additive manufacturing and multi-directional loading synergistic control technology to form large and complex magnesium alloy components in a regional and time-sequence manner. The specific steps include: S1 Digital Model Processing and Collaborative Strategy Formulation Based on the three-dimensional design model of large and complex magnesium alloy components, UG or ANSYS software is used for layer slicing to divide the core forming area and the contour forming area according to the structural characteristics of the components. By analyzing the heat accumulation law and stress distribution characteristics in the additive manufacturing process through numerical simulation, a collaborative strategy of layered additive manufacturing path and multi-directional loading is formulated. S2 Integrated System Setup An integrated system for electric arc additive manufacturing and multi-directional loading was constructed, comprising four core modules: electric arc additive manufacturing module, multi-directional loading module, real-time monitoring module, and central control unit. S3 Pretreatment and Initial Shaping The substrate is subjected to three-stage pretreatment: First, the surface oxide scale and oil are removed by mechanical sanding with sandpaper; then, it is ultrasonically cleaned with anhydrous ethanol for 15 minutes; finally, it is preheated in a heating furnace at a temperature of 150-250℃ for a holding time of ≥30 minutes. During the forming process, the substrate temperature is maintained at 80-150℃ to reduce the thermal stress between the substrate and the molten pool. Initial forming: The magnesium alloy welding wire is loaded into the automatic wire feeder, and the arc additive manufacturing module is started through the central control unit. The first layer of cladding is formed according to the layered additive manufacturing path, and the core forming area is formed first. S4 Additive Manufacturing - Loading Collaborative Operation When the height of the first cladding layer reaches the set threshold, the central control unit automatically switches to collaborative mode and starts the multi-directional loading module. According to the preset collaborative strategy, the loading actuator moves to the target position along the planned path. Data is fed back by pressure sensors and laser displacement sensors to accurately apply multi-directional local loading. The loading accuracy is controlled within ±0.05MPa and the displacement accuracy is ≤±0.02mm. After loading is completed, the load is unloaded, and the arc additive module continues to perform the next cladding layer, repeating the above additive-loading cycle until all operations in the core forming area are completed. Then, the forming parameters of the contour forming area are switched to repeat the additive-loading cycle. S5 Real-time Monitoring and Parameter Adjustment During the forming process, the real-time monitoring module continuously collects data and transmits it to the central control unit. Based on infrared temperature measurement, displacement monitoring, and stress-strain data, the central control unit adjusts the welding parameters and loading strategy in real time through the PID algorithm, forming a closed loop of "monitoring-feedback-adjustment". S6 Post-processing After all the forming is completed, the components are subjected to stress release treatment in the furnace. After stress release, post-processing is carried out. The machining allowance is removed by milling and grinding, and finally a large and complex magnesium alloy component that meets the design requirements is obtained.

[0006] Furthermore, the standard for dividing the core forming region and the contour forming region according to the structural characteristics of the component in S1 is as follows: The core forming area refers to the structural part of a component that bears the main load and has high requirements for the density of the microstructure, such as flanges, beams, and bases; The contour-forming area refers to the parts of a component, such as its external contour, assembly surfaces, and internal holes, which require high dimensional accuracy and surface quality. This division can be based on the component's finite element analysis results, load distribution diagrams, and functional areas in the design drawings.

[0007] Furthermore, the layered additive manufacturing path and multi-directional loading coordination strategy in S1 includes dynamic matching rules for loading timing, loading direction, loading force magnitude, and holding time, specifically: The loading time is selected when the single layer height reaches 3-8mm and the molten pool is in a semi-solid state with a temperature range of 400-550℃. At this time, the metal has good plasticity, which can effectively eliminate porosity and refine the grains. The loading direction is dynamically adjusted according to the local structure of the component. Symmetrical loading in the XY direction is used for planar areas; oblique loading (30-60° angle with the forming surface) is used for curved or irregular areas; and local loading in the Z direction is used for deep cavity structures. The loading force is dynamically matched according to the wall thickness of the component. When the wall thickness is 5-20mm, the loading force is 50-250MPa; when the wall thickness is 20-50mm, the loading force is 250-500MPa; the holding time is 2-10s to ensure sufficient plastic deformation.

[0008] Furthermore, the arc additive manufacturing module in S2 adopts a cold metal transfer welding (CMT) power supply, equipped with a six-axis robotic arm and an automatic wire feeder. The CMT power supply can achieve low heat input, reducing the risk of hot cracking in magnesium alloys. The automatic wire feeder adopts a dual-drive wheel structure, and the wire feeding accuracy is controlled within ±0.1m / min.

[0009] Furthermore, the multi-directional loading module in S2 is configured with three sets of independently movable loading actuators, capable of local loading in the X, Y, Z directions and oblique directions. Each set of mechanisms consists of a roller, a reversing turntable, a motion robotic arm, and a fixed base. The reversing turntable can rotate 360° to achieve continuous adjustment of the loading direction from 0 to 90°. It is also equipped with a pressure sensor and a displacement sensor, with loading accuracy controlled within ±0.05MPa and displacement accuracy ≤±0.02mm. The roller is made of silicon nitride ceramic material to avoid adhesion to the high-temperature magnesium alloy.

[0010] Furthermore, the real-time monitoring module in S2 includes: an integrated infrared thermometer (temperature range 200-1200℃, accuracy ±5℃), a laser displacement sensor (measurement range 0-500mm, accuracy ±0.01mm), and a stress strain gauge (measurement range 0-500MPa), with a data acquisition frequency ≥100Hz, to capture real-time feedback data on molten pool temperature, component deformation, and loading force.

[0011] Furthermore, the central control unit in S2 adopts a PLC controller with a built-in PID algorithm to realize closed-loop linkage between additive parameters, loading strategy and monitoring data, with a response time of ≤0.1s, ensuring timely parameter adjustment.

[0012] Furthermore, the composition of the magnesium alloy welding wire used for initial forming in S3, by mass percentage, is: Al 5.5-7.0%, Zn 0.5-1.5%, Mn 0.2-0.5%, Zr 0.1-0.3%, with the balance being Mg and unavoidable impurities with a total content ≤0.15%. This composition design can improve the high-temperature strength and crack resistance of the magnesium alloy.

[0013] Furthermore, in S3, the initial forming parameters of the core forming area are set as follows: welding current 120-180A, arc voltage 18-24V, welding speed 3-8mm / s, and wire feeding speed 12.0-14.5m / min.

[0014] Furthermore, in S4, the forming parameters of the contour forming area are: welding current 80-120A, arc voltage 15-18V, welding speed 5-10mm / s, and wire feeding speed 12.0-14.5m / min, to reduce heat input and ensure the accuracy of contour dimensions.

[0015] Furthermore, in step S5, the parameter adjustment strategy is as follows: When the molten pool temperature exceeds 550℃, the welding current is automatically reduced by 5-10A. When the deformation of the component exceeds 0.3mm, adjust the loading direction and loading force, and increase the holding time by 2-3s; When the force feedback deviation exceeds ±0.5MPa, the position of the actuator is dynamically calibrated using a PID algorithm. Closed-loop control enables precise matching of additive manufacturing and loading, preventing defects from occurring.

[0016] Furthermore, in the stress relief treatment in S6, a stepped cooling method is adopted, starting from 180-220℃ and cooling down to room temperature at a rate of 10-20℃ / h, effectively releasing residual stress and ensuring that the residual stress of the component is ≤80MPa.

[0017] Furthermore, in the method, the maximum forming size of large and complex magnesium alloy components is ≤5000mm in length, ≤3000mm in width, and ≤2000mm in height. The component wall thickness ranges from 5 to 50mm. After forming, the dimensional accuracy of the component is ≤±0.5mm / m, the internal porosity is ≤0.8%, and the tensile strength is ≥280MPa.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention effectively suppresses defects such as hot cracks and porosity in magnesium alloys, refines grain structure, and improves the mechanical properties of components through the synergistic effect of electric arc additive manufacturing and multi-directional loading.

[0019] 2. The present invention adopts a partitioned forming strategy, with the parameters of the core and contour areas optimized separately, taking into account both load-bearing performance and forming accuracy.

[0020] 3. This invention achieves dynamic matching of additive manufacturing and loading processes through real-time monitoring and closed-loop control, thereby improving the stability and controllability of the forming process.

[0021] 4. The method of the present invention is applicable to the integrated manufacturing of large, irregular, and high-performance magnesium alloy components. It has high forming efficiency and high material utilization, and meets the stringent requirements for lightweight components in aerospace, rail transportation and other fields. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the equipment used in the arc additive manufacturing-multi-directional loading forming method for large and complex magnesium alloy components of the present invention. Figure 2 for Figure 1 A partial side view; In the diagram: 1-Arc additive manufacturing robotic arm; 2-Cold metal transition welding power source; 3-Automatic wire feeder; 4-Magnesium alloy welding wire; 5-Forming substrate; 6-Large and complex magnesium alloy component in formation; 7-Multi-directional loading actuator; 8-Infrared thermometer; 9-Laser displacement sensor; 10-Stress strain gauge; 11-Central control unit; 12-Data transmission line; 13-Fixed worktable.

[0023] Figure 3 This is a timing diagram of single-layer additive manufacturing and loading in Embodiment 1 of the present invention, wherein T1-T3: additive manufacturing stage, T4-T5: loading stage, T6-T7: unloading and preparation stage for the next layer. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] A schematic diagram of the equipment used in the arc additive manufacturing-multi-directional loading forming method for large and complex magnesium alloy components of this invention is shown below. Figure 1-2As shown, the system includes an arc additive manufacturing robotic arm 1, a cold metal transfer welding power source 2, an automatic wire feeder 3, magnesium alloy welding wire 4, a forming substrate 5, a large and complex magnesium alloy component being formed 6, a multi-directional loading actuator 7, an infrared thermometer 8, a laser displacement sensor 9, a stress strain gauge 10, a central control unit 11, a data transmission line 12, and a fixed worktable 13; among which, The arc additive manufacturing robotic arm 1 is connected to the cold metal transition welding power source 2 via a cable. The automatic wire feeder 3 is fixed at the end of the robotic arm, and the magnesium alloy welding wire 4 is fed to the molten pool via the wire feeder. The multi-directional loading actuator 7 is arranged around the component and achieves multi-directional loading through the robotic arm and the reversing turntable. The infrared thermometer 8, the laser displacement sensor 9, and the stress strain gauge 10 are installed in appropriate positions to collect data in real time and transmit it to the central control unit 11 via the data transmission line 12. All equipment is installed on the fixed workbench 13 to ensure the rigidity of the system.

[0026] To achieve high-precision real-time monitoring of temperature, deformation, and stress state during the forming process, the infrared thermometer 8, laser displacement sensor 9, and stress strain gauge 10 are arranged in the equipment as follows: The infrared thermometer 8 is mounted on a fixed bracket near the welding torch at the end of the arc additive manufacturing robot arm 1, at a 45° angle to the welding torch axis, with its lens facing the molten pool area. The temperature measurement point covers the current cladding layer and a 5-10mm range along the rear edge of the molten pool, ensuring real-time capture of the molten pool temperature field distribution. Three sets of laser displacement sensors 9 are installed on the side of the reversing turntable of each multi-directional loading actuator 7, moving synchronously with the loading mechanism. Each set of sensors includes two probes: one vertically aligned with the component surface of the current loading area, and the other monitoring the edge contour of the loading area at a 30° angle, enabling comparative measurement of deformation before and after loading. The stress strain gauges 10 are arranged using a combination of pre-embedded and online bonding methods. Pre-embedded strain gauges: The strain gauges are arranged on the upper surface of the formed substrate 5 according to the grid of the component projection area. One high-temperature strain gauge is pre-attached at the center of each 100mm×100mm grid, and the signal line is led out along the bottom surface of the substrate. Online bonding strain gauges: After each layer is formed, a small automatic bonding device (not shown in the figure) is used to temporarily bond the strain gauges at key stress concentration points (such as the flange root and the intersection of reinforcing ribs). The strain gauges are automatically removed after the test is completed.

[0027] In the equipment used in the method of the present invention, the multi-directional loading module moves to the target position after each layer of additive manufacturing is completed according to the instructions of the central control unit. Closed-loop control is achieved through pressure sensors and displacement sensors to ensure that the loading force and direction are accurately executed.

[0028] The flowchart of the method described in this invention is as follows: Figure 3 As shown, it includes T1-T3: additive manufacturing stage, T4-T5: loading stage, and T6-T7: unloading and preparation stage for the next layer, specifically including the following steps: S1 Digital Model Processing and Collaborative Strategy Formulation Based on the three-dimensional design model of large and complex magnesium alloy components, UG or ANSYS software is used for layer slicing to divide the core forming area and the contour forming area according to the structural characteristics of the components. By analyzing the heat accumulation law and stress distribution characteristics in the additive manufacturing process through numerical simulation, a collaborative strategy of layered additive manufacturing path and multi-directional loading is formulated. S2 Integrated System Setup An integrated system for electric arc additive manufacturing and multi-directional loading was constructed, comprising four core modules: electric arc additive manufacturing module, multi-directional loading module, real-time monitoring module, and central control unit. S3 Pretreatment and Initial Shaping The substrate is subjected to three-stage pretreatment: First, the surface oxide scale and oil are removed by mechanical sanding with sandpaper; then, it is ultrasonically cleaned with anhydrous ethanol for 15 minutes; finally, it is preheated in a heating furnace at a temperature of 150-250℃ for a holding time of ≥30 minutes. During the forming process, the substrate temperature is maintained at 80-150℃ to reduce the thermal stress between the substrate and the molten pool. Initial forming: The magnesium alloy welding wire is loaded into the automatic wire feeder, and the arc additive manufacturing module is started through the central control unit. The first layer of cladding is formed according to the layered additive manufacturing path, and the core forming area is formed first. S4 Additive Manufacturing - Loading Collaborative Operation When the height of the first cladding layer reaches the set threshold, the central control unit automatically switches to collaborative mode and starts the multi-directional loading module. According to the preset collaborative strategy, the loading actuator moves to the target position along the planned path. Data is fed back by pressure sensors and laser displacement sensors to accurately apply multi-directional local loading. The loading accuracy is controlled within ±0.05MPa and the displacement accuracy is ≤±0.02mm. After loading is completed, the load is unloaded, and the arc additive module continues to perform the next cladding layer, repeating the above additive-loading cycle until all operations in the core forming area are completed. Then, the forming parameters of the contour forming area are switched to repeat the additive-loading cycle. S5 Real-time Monitoring and Parameter Adjustment During the forming process, the real-time monitoring module continuously collects data and transmits it to the central control unit. Based on infrared temperature measurement, displacement monitoring, and stress-strain data, the central control unit adjusts the welding parameters and loading strategy in real time through the PID algorithm, forming a closed loop of "monitoring-feedback-adjustment". S6 Post-processing After all the forming is completed, the components are subjected to stress release treatment in the furnace. After stress release, post-processing is carried out. The machining allowance is removed by milling and grinding, and finally a large and complex magnesium alloy component that meets the design requirements is obtained.

[0029] Example 1: Forming of a large magnesium alloy engine casing Component parameters: Annular thin-walled casing, total length 1800mm, maximum outer diameter 800mm, wall thickness 15-35mm (35mm for flange part, 15mm for cylinder part), magnesium alloy welding wire composition: Al 6.2wt%, Zn 1.0wt%, Mn 0.35wt%, Zr 0.2wt%, balance Mg, total impurity content 0.12wt%.

[0030] S1 model processing and collaboration strategy: UG NX 2023 software is used for layered slicing with a slice thickness of 5mm. The core forming area (flange and main body of cylinder) adopts a spiral additive path, while the contour forming area (casing end face and inner hole surface) adopts a circumferential path. The loading timing is set when the layer height reaches 5mm and the molten pool temperature is 480-520℃. For the flange part (wall thickness 35mm), symmetrical loading in the X direction and auxiliary loading in the Z direction are used, with a loading force of 300MPa and a holding time of 5-6s. For the cylinder part (wall thickness 15mm), 30° oblique loading is used, with a loading force of 100MPa and a holding time of 3-4s.

[0031] S2-S4 System Parameter Settings: Core forming area: cold metal transition welding power supply, welding current 155-165A, arc voltage 20.5-21.5V, welding speed 5.2-5.8mm / s, wire feed speed 13.2-13.8m / min, shielding gas is Ar+2% He mixed gas, flow rate 25-28L / min; Contour forming area: Welding current 95-105A, arc voltage 16.2-16.8V, welding speed 7.3-7.7mm / s, wire feed speed 12.3-12.7m / min, shielding gas flow rate 30L / min; Substrate pretreatment: AZ31B magnesium alloy substrate (size 2000mm×2000mm×50mm) was selected, mechanically polished to a surface roughness Ra≤1.6μm, ultrasonically cleaned with anhydrous ethanol for 15min (power 300W, frequency 40kHz), preheated to 200℃, held for 0min, and the substrate temperature was maintained at 100-120℃ by infrared thermometry during the forming process.

[0032] S5 forming process control: The infrared thermometer monitors the temperature of the molten pool in real time. When the temperature exceeds 550°C, the welding current is automatically reduced by 8A, and when the temperature is below 480°C, the welding current is increased by 5A. A laser displacement sensor monitors the roundness of the casing. When the deformation reaches 0.3 mm, the X-axis loading force increases by 2 MPa and the holding time is extended by 1 second. The stress strain gauge provides real-time feedback on the stress at the flange location. When the stress exceeds 120MPa, the additive manufacturing process is paused, and the loading state is maintained for 3 seconds before resuming.

[0033] S6 post-treatment: Stress relief is performed in the furnace, the temperature is raised to 200℃ and held for 2 hours, and then cooled to room temperature at a rate of 15℃ / h; 5mm machining allowance is removed by five-axis milling, and the inner hole surface is honed to a roughness Ra≤0.8μm.

[0034] Forming results: The casing dimensional accuracy is ±0.25mm / m, the roundness error is ≤0.3mm, the internal porosity is 0.5%, the tensile strength of the flange is 302MPa, the yield strength is 185MPa, and the elongation is 13.2%, the tensile strength of the cylinder is 295MPa, the yield strength is 180MPa, the elongation is 12.8%, and the residual stress is 62MPa, which meets the requirements of the HB 7718-2022 standard for aero-engine casings.

[0035] Example 2: Forming of Magnesium Alloy Frame for High-Speed ​​Railway Bogies Component parameters: Bogie H-frame, 2500mm long, 1200mm wide, 800mm high, wall thickness 20-40mm (40mm for crossbeams, 20mm for longitudinal beams), including 3 hollow windows (300mm×250mm) and 6 reinforcing ribs (15mm×20mm cross-section). The magnesium alloy welding wire used has the same composition as in Example 1.

[0036] S1 digital model processing and collaborative strategy: The slices were cut using ANSYS Additive software with a slice thickness of 6mm. The core of the crossbeams / longitudinal beams used a bidirectional staggered additive path, the stiffeners used a Z-axis layered path, and the periphery of the hollowed-out windows used a circumferential path. The loading timing is 6mm in height and 450-500℃ in the molten pool. The reinforcing rib area is loaded in the Z direction with a loading force of 100MPa and a holding time of 7-8s. The area around the hollowed-out window is locally loaded in the Y direction with a loading force of 150MPa and a holding time of 4-5s. The crossbeam is symmetrically loaded in the XY direction with a loading force of 300MPa and a holding time of 6s.

[0037] S2-S4 System Parameter Settings: Core forming area: welding current 165-175A, arc voltage 21-22V, welding speed 4.3-4.7mm / s, wire feed speed 13.5-14.0m / min, shielding gas is Ar+2% He mixed gas, shielding gas flow rate 27-30L / min; Contour forming area: welding current 105-115A, arc voltage 16.5-17V, welding speed 6.3-6.7mm / s, wire feed speed 12.5-13.0m / min, shielding gas flow rate 32L / min; Substrate pretreatment: The substrate used is the same as in Example 1. The preheating temperature is 220℃, and the temperature is maintained for 50 minutes. During the forming process, the substrate temperature is maintained at 110-130℃.

[0038] S5 forming process control: To address the issue of deformation in hollowed-out windows, the loading actuator adopts a loading sequence of "periphery first, then center"; When forming the stiffener, the Z-axis loading force is applied in two stages (first 15MPa preload for 2s, then increased to 28MPa and held for 6s) to avoid stress concentration.

[0039] S6 post-processing: stress release temperature 210℃, heat preservation for 2.5h, cooling rate 5℃ / h; use a gantry milling machine to remove 6mm machining allowance, and the surface roughness of key assembly surfaces Ra≤1.2μm.

[0040] Forming results: The component dimensional accuracy is ±0.35mm / m, the internal porosity is 0.65%, the tensile strength of the crossbeam is 292MPa, the yield strength is 178MPa, the elongation is 11.5%, and the residual stress is 70MPa, which meets the technical requirements of TB / T 3554-2023 for high-speed railway bogie components.

[0041] Example 3: Forming of a large magnesium alloy radar bracket Component parameters: Frame-type radar bracket, 3000mm long, 800mm wide, 1500mm high, wall thickness 5-25mm (25mm for the base, 5mm for the support arm), containing multiple complex curved surfaces (radius of curvature R150-R300mm). The magnesium alloy welding wire used has the same composition as described in Example 1.

[0042] S1 Digital Model Processing and Collaboration Strategy: HyperMesh software is used for digital model processing, with a slice thickness of 4mm. Adaptive slicing paths are used for curved areas, and grid paths are used for planar areas. The loading timing is as follows: layer height 4mm, molten pool temperature 420-480℃. Curved areas are loaded at a 45° oblique angle (loading force 250MPa, holding for 5-6s). Planar areas are loaded symmetrically in the XY direction with a loading force of 250MPa and a holding for 3-4s. The base is loaded with a three-dimensional composite load in the X+Y+Z directions, with a total loading force of 300MPa and a holding for 7s.

[0043] S2-S4 System Parameter Settings: Core forming area: welding current 135-145A, arc voltage 18.5-19.5V, welding speed 6.5-7.5mm / s, wire feed speed 12.8-13.3m / min, shielding gas is Ar+2% He mixed gas, shielding gas flow rate 24-26L / min; Contour forming area: Welding current 85-95A, arc voltage 15.5-16.2V, welding speed 8.5-9.5mm / s, wire feed speed 12.0-12.5m / min, shielding gas flow rate 28L / min; Substrate pretreatment: The substrate used is the same as in Example 1. The preheating temperature is 180°C and the temperature is held for 35 minutes. During the forming process, the substrate temperature is maintained at 90-110°C.

[0044] S5 forming process control: During the forming of curved surfaces, the loading actuator adjusts the roll angle in real time through the reversing turntable to maintain a 45° angle with the tangent direction of the curved surface; When loading the support arm (thin-walled 5mm), a "small force multiple times" strategy is adopted (loading force 8MPa, holding for 3s, repeating twice) to avoid instability and deformation.

[0045] S6 post-processing: stress release temperature 190℃, heat preservation for 2h, cooling rate 12℃ / h; use a five-axis machining center to remove 4mm machining allowance, and polish the curved surface to achieve a roughness Ra≤1.0μm.

[0046] Forming results: The component has a dimensional accuracy of ±0.3mm / m, an internal porosity of 0.55%, a tensile strength of 298MPa at the base, a tensile strength of 288MPa at the support arm, an elongation of 12.2%, and a residual stress of 65MPa, meeting the requirements for lightweight and load-bearing capacity of aerospace radar components.

[0047] The system and method described in this invention are not only applicable to magnesium alloys, but can also be extended to additive manufacturing of large components made of lightweight, high-strength metals such as aluminum alloys and titanium alloys.

[0048] The above are merely preferred embodiments of the present invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these should also be considered within the scope of protection of the present invention. These will not affect the effectiveness of the implementation of the present invention or the practicality of the patent.

Claims

1. A method for arc additive manufacturing-multi-directional loading forming of large and complex magnesium alloy components, characterized in that, This method utilizes arc additive manufacturing and multi-directional loading synergistic control technology to form large and complex magnesium alloy components in a regional and temporal manner, specifically including the following steps: S1 Digital Model Processing and Collaborative Strategy Formulation Based on the three-dimensional model of a large and complex magnesium alloy component, layered slicing is performed, and the core forming area and contour forming area are divided according to the structural characteristics of the component. The heat accumulation law and stress distribution characteristics during the additive manufacturing process are analyzed through numerical simulation, and a layered additive manufacturing path and multi-directional loading collaborative strategy are formulated. S2 Integrated System Setup An integrated system for electric arc additive manufacturing and multi-directional loading was constructed, comprising four core modules: electric arc additive manufacturing module, multi-directional loading module, real-time monitoring module, and central control unit. S3 Pretreatment and Initial Shaping Pre-process the substrate and begin initial forming: Load the magnesium alloy welding wire into the automatic wire feeder, start the arc additive module through the central control unit, and perform the first layer cladding forming according to the layered additive path, first forming the core forming area; S4 Additive Manufacturing - Loading Collaborative Operation When the height of the first cladding layer reaches the set threshold, the central control unit automatically switches to collaborative mode and starts the multi-directional loading module. According to the preset collaborative strategy, the loading actuator moves to the target position along the planned path. Data is fed back through pressure sensors and laser displacement sensors to accurately apply multi-directional local loading. After loading is completed, the module is unloaded and continues to perform the next cladding layer, repeating the above additive-loading cycle until all operations in the core forming area are completed. Then, the module switches to the forming parameters of the contour forming area and repeats the additive-loading cycle. S5 Real-time Monitoring and Parameter Adjustment During the forming process, the real-time monitoring module continuously collects data and transmits it to the central control unit. Based on infrared temperature measurement, displacement monitoring, and stress-strain data, the central control unit adjusts the welding parameters and loading strategy in real time through the PID algorithm, forming a closed loop of "monitoring-feedback-adjustment". S6 Post-processing After all the forming is completed, the components are subjected to stress release treatment in the furnace. After stress release, post-processing is carried out. The machining allowance is removed by milling and grinding, and finally a large and complex magnesium alloy component that meets the design requirements is obtained.

2. The method according to claim 1, characterized in that, The layered additive manufacturing path and multi-directional loading coordination strategy in S1 includes dynamic matching rules for loading timing, loading direction, loading force magnitude, and holding time, specifically: The loading time is selected when the single layer height reaches 3-8mm and the molten pool is in a semi-solid state with a temperature range of 400-550℃. At this time, the metal has good plasticity, which can effectively eliminate porosity and refine the grains. The loading direction is dynamically adjusted according to the local structure of the component. Symmetrical loading in the XY direction is used for planar areas; oblique loading (30-60° angle with the forming surface) is used for curved or irregular areas; and local loading in the Z direction is used for deep cavity structures. The loading force is dynamically matched according to the wall thickness of the component. When the wall thickness is 5-20mm, the loading force is 50-250MPa; when the wall thickness is 20-50mm, the loading force is 250-500MPa; the holding time is 2-10s to ensure sufficient plastic deformation.

3. The method according to claim 1, characterized in that, The multi-directional loading module in S2 is configured with three sets of independently movable loading actuators, which can realize local loading in the X, Y, Z directions and oblique directions; the loading accuracy is controlled within ±0.05MPa and the displacement accuracy is ≤±0.02mm.

4. The method according to claim 1, characterized in that, The real-time monitoring module in S2 includes an integrated infrared thermometer, a laser displacement sensor, and a stress strain gauge, with a data acquisition frequency ≥100Hz, and real-time capture of molten pool temperature, component deformation, and loading force feedback data.

5. The method according to claim 1, characterized in that, The magnesium alloy welding wire used for initial forming in S3 has the following composition by mass percentage: Al 5.5-7.0%, Zn 0.5-1.5%, Mn 0.2-0.5%, Zr 0.1-0.3%, with the balance being Mg and unavoidable impurities with a total content ≤0.15%.

6. The method according to claim 1, characterized in that, The pretreatment process of the substrate in S3 is as follows: First, the surface oxide scale and oil stains are removed by mechanical sanding with sandpaper; then, it is ultrasonically cleaned with anhydrous ethanol for 15 minutes; finally, it is preheated in a heating furnace at a preheating temperature of 150-250℃ and a holding time of ≥30 minutes. During the forming process, the substrate temperature is maintained at 80-150℃ to reduce the thermal stress between the substrate and the molten pool.

7. The method according to claim 1, characterized in that, In S3, the initial forming parameters of the core forming area are set as follows: welding current 120-180A, arc voltage 18-24V, welding speed 3-8mm / s, and wire feeding speed 12.0-14.5m / min.

8. The method according to claim 1, characterized in that, In S4, the forming parameters of the contour forming area are: welding current 80-120A, arc voltage 15-18V, welding speed 5-10mm / s, wire feeding speed 12.0-14.5m / min, to reduce heat input and ensure the accuracy of contour dimensions.

9. The method according to claim 1, characterized in that, In S5, the parameter adjustment strategy is as follows: When the molten pool temperature exceeds 550℃, the welding current is automatically reduced by 5-10A. When the deformation of the component exceeds 0.3mm, adjust the loading direction and loading force, and increase the holding time by 2-3s; When the force feedback deviation exceeds ±0.5MPa, the position of the actuator is dynamically calibrated using a PID algorithm. Closed-loop control enables precise matching of additive manufacturing and loading, preventing defects from occurring.

10. The method according to claim 1, characterized in that, The stress relief treatment in S6 adopts a stepped cooling method, starting from 180-220℃ and cooling down to room temperature at a rate of 10-20℃ / h, effectively releasing residual stress and ensuring that the residual stress of the component is ≤80MPa.

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