Method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material based on dynamic heat input

Abstract

The invention discloses a method for laser double-wire additive manufacturing of an aluminum / magnesium bimetallic material based on dynamic heat input, and relates to the technical field of metal material additive manufacturing. The method comprises the following steps that an aluminum alloy welding wire and a magnesium alloy welding wire are adopted as deposition materials, aluminum alloy and magnesium alloy are sequentially deposited on the surface of a base plate through double wire feeding mechanisms, and the aluminum / magnesium bimetallic material is obtained; layered dynamic heat input parameter control is independently carried out in the aluminum alloy deposition process and the magnesium alloy deposition process; the heat input parameters comprise laser power and wire feeding speed. The manufacturing process of double-wire independent feeding and dynamic heat input control is adopted, and the manufacturing efficiency can be improved through double-wire independent feeding; dynamic heat input control can inhibit centralized generation of brittle intermetallic compounds on the interface from the process level, and the interface bonding strength is improved. The aluminum / magnesium bimetallic material prepared by the method disclosed by the invention has good interface bonding strength and excellent comprehensive mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal material additive manufacturing, in particular to a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input. BACKGROUND

[0002] With the increasing demand for lightweight structures in the fields of aerospace, rail transportation and high-end equipment manufacturing, dissimilar metal composite structures have become a research hotspot because they can achieve the complementary advantages of material properties. Among them, aluminum / magnesium bimetallic materials combine the high specific strength, good corrosion resistance of aluminum alloys and the low density, excellent damping and shock absorption performance of magnesium alloys, and are considered as a promising lightweight solution.

[0003] Currently, the main manufacturing processes for aluminum / magnesium bimetallic materials include explosive composite method, rolling composite method and casting composite method, etc. However, these traditional methods have different degrees of drawbacks such as long manufacturing time, complex manufacturing process, low material utilization rate, poor overall performance of the product, environmental pollution, etc.

[0004] Double-metal fusion welding is a simpler and easier-to-operate manufacturing process compared to the above manufacturing processes, and has a more promising application prospect in the field of aluminum / magnesium bimetallic material manufacturing. However, there are significant differences in the physical and chemical properties of aluminum alloys and magnesium alloys, and their direct fusion welding still faces severe scientific challenges. The core difficulty lies in the fact that a large number of hard and brittle intermetallic compounds (IMCs) are easily generated between the two, mainly Al3Mg2 and Al 12 Mg 17 . These intermetallic compounds have complex crystal structures, high hardness and extremely poor ductility, and act as stress concentration points in the welded joint, which can severely deteriorate the mechanical properties, leading to a sharp decline in joint strength and plasticity. In addition, the differences in physical parameters such as melting point, linear expansion coefficient and oxide film properties between aluminum alloys and magnesium alloys easily lead to defects such as thermal stress, cracks, pores and element burning during welding, making it extremely difficult to obtain a high-quality aluminum / magnesium metallurgical bonding interface. Moreover, double-metal fusion welding cannot achieve near-net shaping of aluminum / magnesium bimetallic material components, and cannot meet the preparation of complex structure components. Therefore, developing an advanced manufacturing technology that can achieve near-net shaping of aluminum / magnesium bimetallic material components is of great significance for improving design freedom, shortening manufacturing cycle and optimizing component performance.

[0005] Laser wire additive manufacturing (WAAM) is a technology that uses laser as heat source and metal wire as raw material to realize three-dimensional solid component forming through layer-by-layer cladding accumulation. It can effectively avoid the problems existing in traditional manufacturing methods, and is particularly suitable for rapid manufacturing of medium and large metal components. The core advantage of applying WAAM technology to the manufacturing of aluminum / magnesium bimetallic material components is that it can realize the controllable distribution of composition and structure. That is, by planning the deposition path and wire feeding strategy, aluminum alloy and magnesium alloy can be deposited at different parts of the component, so as to spatially allocate material properties on demand and realize the manufacturing of functionally graded materials or composite structures, which is difficult for traditional manufacturing methods to achieve. However, due to the significant difference between the physical and chemical properties of aluminum alloy and magnesium alloy, there are still problems such as poor interface bonding performance and the need to further improve the preparation efficiency when using laser wire additive manufacturing process to prepare aluminum / magnesium bimetallic material. How to realize the rapid and high-quality preparation of aluminum / magnesium bimetallic material through laser wire additive manufacturing is the focus of research for those skilled in the art at this stage. SUMMARY

[0006] The purpose of the present application is to provide a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material based on dynamic heat input, to solve the problems of low manufacturing efficiency, poor product performance and complex process of aluminum / magnesium bimetallic material in the prior art. The method of the present application can realize the rapid manufacturing of aluminum / magnesium bimetallic material. By independently regulating the heat input parameters on the aluminum and magnesium sides, the method of the present application effectively suppresses the concentrated generation of brittle intermetallic compounds at the interface, realizes the near-net forming of aluminum / magnesium bimetallic material with high quality and high efficiency, and the prepared aluminum / magnesium bimetallic material component has good interface bonding strength and comprehensive mechanical properties.

[0007] To achieve the above purpose, the present application provides the following solutions: One of the technical solutions of the present application: a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material based on dynamic heat input, comprising the following steps: Aluminum alloy wire and magnesium alloy wire are used as deposition materials, and aluminum alloy and magnesium alloy are deposited in sequence (aluminum alloy is deposited first and then magnesium alloy) on the surface of the substrate through a double-wire feeding mechanism to obtain aluminum / magnesium bimetallic material; The layer-by-layer dynamic heat input parameter control is independently carried out during the aluminum alloy deposition process and the magnesium alloy deposition process (i.e. the heat input parameters on the aluminum alloy side and the magnesium alloy side are independently regulated, and the layer-by-layer dynamic heat input parameters are used on both the aluminum alloy side and the magnesium alloy side); The heat input parameters include laser power and wire feeding speed.

[0008] The application adopts a core technical route of "double-wire independent feeding + dynamic heat input control", wherein the double-wire independent feeding specifically refers to realizing accurate switching and feeding control of aluminum alloy welding wire and magnesium alloy welding wire through independent double-wire feeding mechanism, avoiding process interruption caused by replacement of welding wire in a single-wire system, and improving manufacturing efficiency; the dynamic heat input control refers to hierarchical design of heat input parameters (power + wire feeding speed) according to differences in thermal physical properties of aluminum alloy and magnesium alloy, realizing on-demand control combination of aluminum alloy side and on-demand control oxidation of magnesium alloy side, and inhibiting concentrated generation of interface brittle intermetallic compounds (IMCs) from the process level. The aluminum / magnesium bimetal material component prepared by the method of the application has good interface bonding strength and excellent comprehensive mechanical properties. The method of the application is simple in process, and can improve manufacturing efficiency while improving comprehensive performance of products.

[0009] Further, during the aluminum alloy deposition process, the hierarchical dynamic heat input parameter control includes: the bottom layer: the laser power is 1.5-1.7 kW, and the wire feeding speed is 2.0-2.5 m / min; the transition layer: the laser power is 2.0-2.2 kW, and the wire feeding speed is 3.0-3.5 m / min; the upper layer: the laser power is 2.6-2.8 kW, and the wire feeding speed is 4.0-4.5 m / min.

[0010] During the aluminum alloy deposition process, the bottom layer (combined with the substrate) adopts low power (1.5-1.7 kW) + slow speed (2.0-2.5 m / min) to ensure close combination with the substrate; the transition layer (i.e. the main layer) adopts medium power (2.0-2.2 kW) + medium speed (3.0-3.5 m / min) to smoothly improve efficiency and power, and avoid defects caused by parameter mutation; the upper layer adopts high power (2.6-2.8 kW) + fast speed (4.0-4.5 m / min) to improve efficiency under the premise of ensuring forming quality.

[0011] Further, the bottom layer is 20-30% of the total deposition layers (i.e. the total deposition thickness) of the aluminum alloy; the transition layer is 40-60% of the total deposition layers of the aluminum alloy; and the upper layer is 20-30% of the total deposition layers of the aluminum alloy.

[0012] Further, during the magnesium alloy deposition process, the hierarchical dynamic heat input parameter control includes: before deposition: 0.3-0.5 kW of laser power is used to preheat the interface; the bottom layer: the laser power is 1.6-1.8 kW, and the wire feeding speed is 2.5-3.0 m / min; the transition layer: the laser power is 1.8-2.0 kW, and the wire feeding speed is 3.0-3.5 m / min; Upper layer: laser power is 1.7-1.9kW, wire feeding speed is 2.8-3.2m / min.

[0013] During the deposition of magnesium alloy, the interface is first preheated at low power (0.3-0.5kW) before deposition; the bottom layer (combined with the aluminum alloy layer) uses low power (1.6-1.8kW) + medium speed (2.5-3.0m / min), so that the magnesium alloy wire and the surface of the deposited aluminum alloy layer melt and solidify at a faster speed, shortening the liquid coexistence time of aluminum / magnesium, thereby inhibiting the excessive growth of brittle phases (such as Al3Mg2); the transition layer (i.e. the main layer) uses medium power (1.8-2.0kW) + medium speed (3.0-3.5m / min) to control the molten pool temperature under the premise of ensuring deposition efficiency and interlayer bonding; the upper layer uses low power (1.7-1.9kW) + medium speed (2.8-3.2m / min) to avoid more serious heat accumulation, which helps to reduce the burning loss of magnesium alloy.

[0014] Further, the bottom layer is 20-30% of the total number of deposited layers (i.e. the total deposition thickness) of magnesium alloy; the transition layer is 40-60% of the total number of deposited layers of magnesium alloy; the upper layer is 20-30% of the total number of deposited layers of magnesium alloy.

[0015] Further, the aluminum alloy wire is A6061 aluminum alloy wire, and the magnesium alloy wire is AZ31 magnesium alloy wire.

[0016] Further, the diameter of the A6061 aluminum alloy wire is 1.2mm.

[0017] Further, the A6061 aluminum alloy wire has a composition of Si 0.85%, Mg 0.57%, Cu 0.22%, Mn 0.11%, Cr 0.15%, Zn 0.19%, Ti 0.13%, and the balance of Al and unavoidable impurities, in terms of mass percentage.

[0018] Further, the diameter of the AZ31 magnesium alloy wire is 1.2mm.

[0019] Further, the AZ31 magnesium alloy wire has a composition of Al 3.26%, Zn 0.85%, Mn 0.41%, Fe 0.01%, Si 0.07%, and the balance of Mg and unavoidable impurities, in terms of mass percentage.

[0020] The A6061 aluminum alloy contains a low amount of Mg (0.57wt%), while the AZ31 contains a high amount of Al (3.26wt%), which helps to form a controllable diffusion layer, reduce brittle phases, and improve the metallurgical bonding strength. That is, the wire composition is complementary, which synergistically improves the interface performance.

[0021] Further, the aluminum alloy deposition process and the magnesium alloy deposition process both use argon as a protective gas, and the gas flow rate is 20 L / min.

[0022] Further, before sequentially depositing the aluminum alloy and the magnesium alloy on the substrate surface by the double-wire feeding mechanism, the method further comprises a step of preheating the substrate.

[0023] Further, the preheating specifically comprises: increasing the temperature of the substrate to 200℃ at a rate of 5℃ / min, and maintaining the temperature for 10 min.

[0024] Further, the aluminum alloy deposition process and the magnesium alloy deposition process both use argon as a protective gas, and the gas flow rate is 20 L / min.

[0025] Further, the aluminum alloy deposition process and the magnesium alloy deposition process both use argon as a protective gas, and the gas flow rate is 20 L / min.

[0026] Optionally, the method further comprises a step of mechanical polishing after the cooling is completed, and the mechanical polishing process uses argon as a protective gas, and the gas flow rate is 20 L / min.

[0027] Further, after the magnesium alloy deposition is completed, the method further comprises a step of maintaining argon protection until the temperature of the aluminum / magnesium bimetallic material decreases to room temperature.

[0028] The method further comprises the following specific steps: Step one, establishing a laser additive manufacturing system, the system comprising a double-wire feeding mechanism capable of feeding aluminum alloy welding wire and magnesium alloy welding wire respectively; Step two, performing parameter simulation and no-load trial operation; Step three, pre-treating the surface to be deposited of the substrate, the pre-treatment comprising mechanical polishing and acetone wiping; using a clamp to fix the pre-treated substrate on a welding platform, and preheating; Step four, using the aluminum alloy welding wire to deposit aluminum alloy on the substrate layer by layer according to the set aluminum alloy side process parameters, to form an aluminum alloy deposition layer; Step five, switching to the magnesium alloy welding wire to deposit magnesium alloy on the aluminum alloy deposition layer layer by layer according to the set magnesium alloy side process parameters, to form a magnesium alloy deposition layer, and finally forming an aluminum / magnesium bimetallic material; Wherein, the aluminum alloy side process parameters and the magnesium alloy side process parameters are independent of each other, to realize dynamic heat input control according to the characteristics of aluminum alloy and magnesium alloy materials.

[0029] Further, the laser additive manufacturing system comprises a total power supply, a laser, a protective gas cylinder, a CNC (computer numerical control) port and a welding platform in addition to the double-wire feeding mechanism.

[0030] The application adopts a double-wire feeding mechanism combined with a dynamic heat input control additive manufacturing process to manufacture aluminum / magnesium bimetallic materials. Through the characteristics of directional energy deposition, the application has the potential to accurately deposit different materials in specific areas. Through dynamic heat input control, the application can effectively alleviate the residual stress caused by the huge difference in thermal physical properties of aluminum alloy and magnesium alloy, and inhibit the concentrated generation of brittle intermetallic compounds at the interface. In addition, the method has the characteristics of high deposition efficiency and relatively low cost, opening up a promising new path for low-cost and rapid manufacturing of large-size aluminum / magnesium bimetallic material components.

[0031] The application discloses the following technical effects: The application provides a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input. The method adopts a double-wire independent feeding + dynamic heat input control additive manufacturing process to manufacture aluminum / magnesium bimetallic materials. The double-wire independent feeding specifically refers to the precise switching and feeding control of aluminum alloy welding wire and magnesium alloy welding wire through an independent double-wire feeding mechanism, avoiding process interruption caused by the need to replace welding wire in a single-wire system, and improving manufacturing efficiency. The dynamic heat input control refers to the layered design of heat input parameters (power + wire feeding speed) according to the difference in thermal physical properties of aluminum alloy and magnesium alloy, realizing on-demand control of aluminum alloy side (aiming to ensure the metallurgical bonding quality of aluminum alloy deposition layer and substrate and interlayer, optimize the molten pool shape and solidification process, and provide a stable and high interface activity bonding surface for subsequent magnesium alloy deposition) and on-demand control of magnesium alloy side (aiming to realize good metallurgical bonding with the aluminum alloy layer, strictly control the molten pool temperature and liquid residence time, and maximize the inhibition of magnesium element evaporation, burning loss and severe oxidation caused by overheating), and inhibit the concentrated generation of interface brittle IMCs from the process level. The aluminum / magnesium bimetallic material component prepared by the method of the application has good interface bonding strength and excellent comprehensive mechanical properties.

[0032] The application provides a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input, which can realize active gradient transition of aluminum / magnesium components through layer-by-layer melting and alternating wire feeding. In the metallurgical bonding area, the element components of aluminum and magnesium are not suddenly changed, but the concentration of aluminum gradually decreases and the concentration of magnesium gradually increases from the aluminum alloy side to the magnesium alloy side, thereby inhibiting the excessive growth of brittle intermetallic compounds. The spatial positions of the aluminum alloy area and the magnesium alloy area are accurately set on a macro level, thereby avoiding the direct and sharp physical interface formed by mechanical pressing in traditional rolling or explosive compounding. Moreover, the diffusion can be controlled through dynamic heat input. Specifically, the power and wire feeding speed are designed layer by layer according to the thermal physical difference between the aluminum alloy side and the magnesium alloy side, so as to avoid insufficient bonding caused by low heat input and prevent high heat input from accelerating Al-Mg atomic interdiffusion. In addition, the double-wire feeding mechanism does not need to replace the welding wire in the middle, and compared with traditional rolling, explosive compounding and other methods or single-wire feeding method, the manufacturing cycle is shortened by more than 30%, and the deposition path can be flexibly adjusted through the CNC port, which is suitable for near-net forming of complex aluminum / magnesium bimetallic material components, and the dependence on molds in traditional rolling and casting processes can be eliminated. Large components with complex internal structures or special curved surfaces can be directly digitally and rapidly formed, high design freedom and manufacturing flexibility are realized, the preparation process of aluminum / magnesium bimetallic materials is simplified, and the manufacturing efficiency is improved. The full-process digitalization is more conducive to process optimization and monitoring, and is in line with the intelligent manufacturing trend, laying a foundation for on-demand manufacturing of high-performance components in the future. Moreover, the control logic of “double-wire independent feeding + dynamic heat input control” can be migrated to the additive manufacturing of other dissimilar metals (such as aluminum / copper and magnesium / steel), thereby providing a general technical framework for the preparation of dissimilar metal composite components.

[0033] The application provides a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input. The preferred deposition sequence is to first deposit aluminum alloy and then deposit magnesium alloy. When laser acts on the substrate or the previous deposition layer, a molten pool is formed, at this time, metal wire (i.e., welding wire) is fed, the newly added metal wire and the surface part of the solidified base layer are partially melted to form a small molten pool. In this high-temperature liquid pool, aluminum and magnesium atoms undergo intense convection and interdiffusion, so that the aluminum alloy and the magnesium alloy are metallurgically bonded and form an aluminum / magnesium bimetallic material with a transition region. In addition, the use of aluminum alloy as the bottom metal can better transfer heat and prevent excessive grain size caused by excessive heat input, thereby better improving the bonding force of the interface and significantly improving the mechanical properties of the entire structure. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative effort.

[0035] Figure 1 Process schematic diagram of the method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material based on dynamic heat input according to the present application.

[0036] Figure 2 Microscopic morphology diagram of the aluminum / magnesium interface in the aluminum / magnesium bimetallic material thin-walled part prepared in Embodiment 1 of the present application.

[0037] Figure 3 Microhardness distribution diagram of the aluminum / magnesium bimetallic material thin-walled part prepared in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0038] The various illustrative embodiments of the present application will now be described in detail below. The detailed description is not intended to be limiting of the present application, but rather is an explanation of certain aspects, features, and embodiments of the present application.

[0039] It should be understood that the terms used in the present application merely describe particular embodiments and are not intended to limit the present application. In addition, for the numerical ranges in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intermediate value in the stated range, is also encompassed within the present application. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All publications mentioned in this specification are herein incorporated by reference to disclose and describe the methods and / or materials in connection with which the publications are cited. The citation of any reference in this specification is not intended as an admission that the reference is prior art, but rather that the reference is part of the technical knowledge in the art.

[0041] Many modifications and variations of this application specification can be made in the light of the above teachings without departing from the spirit or scope of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only. It is intended to cover all alternatives, modifications and equivalents.

[0042] As used herein, the terms “comprises”, “comprising”, “includes”, “including”, “has”, “having”, “contains” and “containing” are open-ended terms that mean includes but not limited to.

[0043] It should be noted that the parts not described in detail in the present application are the conventional operation means in the art, and are not the focus of the present application.

[0044] If it involves room temperature in the following examples and comparative examples of the present application, it specifically refers to 20-30℃.

[0045] The raw materials used in the following examples and comparative examples of the present application are all ordinary commercially available products, wherein the diameter of the A6061 aluminum alloy welding wire is 1.2mm, and the chemical composition consists of Si 0.85%, Mg 0.57%, Cu 0.22%, Mn 0.11%, Cr 0.15%, Zn 0.19%, Ti 0.13%, and the balance of Al and unavoidable impurities, in terms of mass percentage; the diameter of the AZ31 magnesium alloy welding wire is 1.2mm, and the chemical composition consists of Al 3.26%, Zn 0.85%, Mn 0.41%, Fe 0.01%, Si 0.07%, and the balance of Mg and unavoidable impurities, in terms of mass percentage.

[0046] Example 1 A method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material based on dynamic heat input (process schematic diagram as shown in Figure 1 The steps are as follows: Step one, system configuration: establish a laser additive manufacturing system, including a total power supply, a laser, a double-wire feeding mechanism, a protective gas cylinder, a CNC (computer numerical control) port and a welding platform. The laser is connected with the computer through the CNC port to realize accurate control of the moving path, speed and direction.

[0047] Step two, system debugging: perform parameter simulation and no-load trial operation to ensure system stability and path accuracy.

[0048] Step three, mechanically polish the aluminum substrate to be welded (aluminum alloy substrate with the same composition as the A6061 aluminum alloy welding wire) with a length of 200mm, a width of 200mm and a thickness of 20mm, with uniform polishing force until the surface oxidation skin is completely removed, and then wipe the aluminum substrate surface with acetone to ensure that the additive interface and molten pool environment are not contaminated. Put the pretreated (i.e. polished and wiped) aluminum substrate into the welding platform clamp, tighten it by hand, firmly fix the aluminum substrate on the welding platform, and ensure that the aluminum substrate is not loose; start the welding platform temperature control module, and raise the temperature of the aluminum substrate to 200℃ at a rate of 5℃ / min, and keep it for 10min to ensure uniform internal temperature of the aluminum substrate, avoiding local temperature difference leading to thermal stress. Perform simulation test, adjust the initial point of the additive deposition path, start the laser and return to the initial point.

[0049] Step four, aluminum alloy side deposition: the aluminum alloy side uses a layered dynamic heat input parameter, as follows: Bottom layer (bonding layer with aluminum substrate, accounting for 20% of the total number of deposited layers on this side (i.e., total deposition thickness)): laser power is 1.7 kW, ensuring full fusion with the aluminum substrate; wire feeding speed is 2.0 m / min, extending the molten pool residence time; Transition layer (main layer, accounting for 60% of the total number of deposited layers on this side): laser power is 2.1 kW, smoothly improving efficiency and power; wire feeding speed is 3.3 m / min, avoiding defects; Upper layer (near the interface, accounting for 20% of the total number of deposited layers on this side): laser power is 2.7 kW, balancing efficiency and forming quality; wire feeding speed is 4.3 m / min, reducing grain coarsening; According to the above layered dynamic heat input parameter setting, the aluminum alloy side is deposited, the laser and A6061 aluminum alloy welding wire are at an angle of 45°, the distance between the welding wire end and the surface of the aluminum substrate is 20 mm (the distance between the welding wire end and the surface of the previous deposition layer is 20 mm during the deposition process), the laser power is started, and the double wire feeding mechanism is turned on to feed the A6061 aluminum alloy welding wire, and the deposition is carried out layer by layer according to the preset path (one-way walking path), with a deposition height of 1.1 mm for each layer. After each layer is deposited, the interlayer cooling program is automatically triggered, and the cooling lasts for 110 s. After cooling, the deposition surface is mechanically polished to remove surface dirt and oxides (the mechanical polishing time is about 5 s). During the deposition, cooling and mechanical polishing processes, argon gas is continuously protected, with a flow rate of 20 L / min. A total of 10 layers are deposited, and the aluminum layer surface is free of cracks, pores and other defects after deposition.

[0050] Step five, magnesium alloy side deposition: after the aluminum alloy side deposition is completed, the argon protection is not interrupted, the double wire switching (from A6061 aluminum alloy welding wire to AZ31 magnesium alloy welding wire) is triggered through the CNC system, and the layered dynamic heat input parameters are adjusted as follows: Interface preheating: laser power is 0.4 kW, no wire feeding, and air walking is performed once to avoid interface stress; Bottom layer (bonding with aluminum alloy side, accounting for 20% of the total number of deposited layers on this side): laser power is 1.8 kW, ensuring rapid melting and solidification of AZ31 magnesium alloy welding wire and the surface of the aluminum alloy side; wire feeding speed is 2.9 m / min, avoiding excessive fusion leading to excessive generation of intermetallic compounds (IMCs); Transition layer (main layer, accounting for 60% of the total number of deposited layers on this side): laser power is 2.0 kW, wire feeding speed is 3.0 m / min, ensuring deposition efficiency and controlling molten pool temperature; The upper layer (the top of the magnesium alloy side, accounting for 20% of the total deposition layer of the side): the laser power is 1.9 kW, avoiding heat accumulation and reducing oxidation and burning loss of the magnesium alloy; the wire feeding speed is 3.2 m / min, improving the density of the magnesium alloy layer.

[0051] After confirming the completion of the double-wire switching, the laser is adjusted to be 45° with the AZ31 magnesium alloy welding wire, the distance between the end of the welding wire and the surface of the aluminum alloy deposition layer is 20 mm, the laser is restarted, and the deposition is performed layer by layer along the same path as the aluminum alloy side, and the deposition height of each layer is 1.1 mm; after depositing each layer, the same cooling is performed for 110 s, after the cooling is completed, the deposition surface is mechanically polished by using a steel to remove surface dirt and oxides (the mechanical polishing time is about 5 s), and the argon gas is continuously protected during the deposition, the cooling and the mechanical polishing, and the argon gas flow is set to be 20 L / min; 10 layers are deposited in total, and an aluminum / magnesium bimetallic material thin-walled component is obtained, the surface of the component is flat, and there are no obvious defects such as oxidation discoloration and cracks. After the deposition is completed, the argon protection is maintained until the temperature of the component decreases to room temperature, so that the high-temperature component is prevented from being exposed to the air to be oxidized; then the aluminum / magnesium bimetallic material thin-walled component is taken out, and no subsequent machining is required to meet the near-net forming requirement.

[0052] The IT-800 scanning electron microscope (SEM) is used to observe the micro-morphology of the aluminum / magnesium interface of the aluminum / magnesium bimetallic material thin-walled component prepared in this embodiment, and the result is shown in Figure 2 As shown in the figure, in the aluminum / magnesium bimetallic material thin-walled component, there is an aluminum / magnesium transition zone with obvious boundary between the aluminum alloy side and the magnesium alloy side, and there is no obvious brittle IMCs aggregation in the transition zone. The reason for the formation of the transition zone is the atomic diffusion behavior between aluminum and magnesium, the core function of which is to realize the effective metallurgical bonding of the two metals, and to serve as a stress buffer layer by controlling the brittle IMCs at the interface to relieve the thermal stress generated due to the difference in physical properties of the two metals, and to improve the bonding strength and stability of the interface. It is proved that the dynamic heat input of the double-wire effectively inhibits the excessive generation of IMCs, and the interface is well combined.

[0053] The Ji'nan Huafeng HJ-20 micro Vickers hardness tester is used to test the hardness, the load is 100 g, the pressure maintaining time is 15 s, and every 50 μm along the thickness direction (from the aluminum alloy side to the magnesium alloy side) of the aluminum / magnesium bimetallic material thin-walled component prepared in this embodiment is tested for one hardness value, and a total of 30 points are tested; the hardness distribution diagram is shown in Figure 3 As shown in the figure, the hardness of the aluminum alloy side (i.e. the aluminum matrix) is stable at 65-85 HV, the hardness of the magnesium alloy side (i.e. the magnesium matrix) is stable at 60-90 HV, and the hardness of the interface transition zone is 210-280 HV, which is higher than that of the matrix, proving that the Al-Mg intermetallic compound is a brittle hard phase, but the hardness gradient of the transition zone is smooth, avoiding stress concentration; and there is no sudden drop in hardness in the interface region, indicating that the interface is tightly combined, and there are no defects such as inclusions and porosity, which is consistent with the SEM observation result.

[0054] The embodiment successfully prepared thin-walled aluminum / magnesium bimetallic material components with good interface bonding and stable performance through standardized operation and precise parameter control, and verified the feasibility of the "double-wire dynamic heat input" method.

[0055] Comparative Example 1 A method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material, the steps are as follows: Step one, system configuration: establish a laser additive manufacturing system, including total power supply, laser, double wire feeding mechanism, protective gas cylinder, CNC (computer numerical control) port and welding platform. The laser is connected with the computer through the CNC port to realize accurate control of the moving path, speed and direction.

[0056] Step two, system debugging: parameter simulation and no-load trial operation are carried out to ensure system stability and path accuracy.

[0057] Step three, the aluminum substrate to be welded (aluminum alloy substrate with the same composition as A6061 aluminum alloy welding wire) with a length of 200 mm, a width of 200 mm and a thickness of 20 mm is mechanically polished, the polishing force is uniform, until the surface oxide skin is completely removed, and the aluminum substrate surface is wiped with acetone to ensure that the additive interface and the molten pool environment are not contaminated. Put the pretreated (i.e. polished and wiped) aluminum substrate into the welding platform clamp, tighten it by hand, firmly fix the aluminum substrate on the welding platform, and ensure that the aluminum substrate is not loose; start the welding platform temperature control module, and raise the temperature of the aluminum substrate to 200℃ at a rate of 5℃ / min, and keep it for 10 min to ensure uniform internal temperature of the aluminum substrate, avoiding local temperature difference leading to thermal stress. Perform simulation test, adjust the initial point of additive deposition path, start the laser and return to the initial point.

[0058] Step four, aluminum alloy side deposition, specifically as follows: The laser power is 2.1 kW, the wire feeding speed is 3.3 m / min; the laser and A6061 aluminum alloy welding wire are at an angle of 45°, the distance between the welding wire end and the surface of the aluminum substrate is 20 mm (the distance between the welding wire end and the surface of the previous deposition layer is 20 mm during the deposition process), the laser power is started, and the double wire feeding mechanism is started to feed A6061 aluminum alloy welding wire, and the deposition is carried out layer by layer according to the preset path (one-way walking path), and the deposition height of each layer is 1.1 mm; after each layer is deposited, the interlayer cooling program is automatically triggered, and the deposition stays for 110 s for cooling; after cooling, the deposition surface is mechanically polished to remove surface dirt and oxides (the mechanical polishing time is about 5 s); during the deposition, cooling and mechanical polishing process, argon gas is continuously protected, and the argon gas flow is set to 20 L / min; a total of 10 layers are deposited, and after the deposition is completed, the aluminum layer surface is uneven and has macroscopic defects.

[0059] Step 5, Magnesium Alloy Side Deposition: After the aluminum alloy side deposition is completed, without interrupting the argon gas protection, trigger the dual-wire switching (from A6061 aluminum alloy welding wire to AZ31 magnesium alloy welding wire) via the CNC system, and simultaneously adjust the deposition parameters as follows: The laser power is 2.0kW and the wire feeding speed is 3.0m / min.

[0060] After confirming that the dual-wire switching is complete, adjust the laser to be at a 45° angle with the AZ31 magnesium alloy welding wire, and the distance between the end of the welding wire and the surface of the aluminum alloy deposition layer is 20mm. Restart the laser and deposit layer by layer along the same path as the aluminum alloy side. When depositing the second layer, warping and cracks appear at the interface. After the third layer is deposited, the sample falls off during mechanical polishing.

[0061] This comparative example fabricated aluminum / magnesium bimetallic thin-walled parts using fixed power and wire feed speed. The samples exhibited large macroscopic defects, and the thin-walled parts fractured during the additive manufacturing process due to uneven heat input, rendering them unusable. This further verifies the feasibility of the "dual-wire dynamic heat input" method of this invention.

[0062] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input, characterized in that, Includes the following steps: Aluminum alloy welding wire and magnesium alloy welding wire are used as deposition materials. Aluminum alloy and magnesium alloy are sequentially deposited on the substrate surface through a dual wire feeding mechanism to obtain aluminum / magnesium bimetallic material. The dynamic thermal input parameters for layering are controlled independently during the aluminum alloy deposition process and the magnesium alloy deposition process, respectively. The thermal input parameters include laser power and wire feed speed.

2. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 1, characterized in that, During aluminum alloy deposition, the control of layered dynamic thermal input parameters includes: Bottom layer: Laser power is 1.5-1.7kW, wire feeding speed is 2.0-2.5m / min; Transition layer: Laser power is 2.0-2.2kW, and wire feeding speed is 3.0-3.5m / min; Upper layer: Laser power is 2.6-2.8kW, and wire feeding speed is 4.0-4.5m / min.

3. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 1, characterized in that, During magnesium alloy deposition, the control of layered dynamic heat input parameters includes: Before deposition: the interface is preheated using a laser power of 0.3-0.5kW; Bottom layer: Laser power is 1.6-1.8kW, wire feeding speed is 2.5-3.0m / min; Transition layer: Laser power is 1.8-2.0kW, and wire feeding speed is 3.0-3.5m / min; Upper layer: Laser power is 1.7-1.9kW, and wire feeding speed is 2.8-3.2m / min.

4. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 1, characterized in that, The aluminum alloy welding wire is A6061 aluminum alloy welding wire, and the magnesium alloy welding wire is AZ31 magnesium alloy welding wire.

5. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 4, characterized in that, The diameter of the A6061 aluminum alloy welding wire is 1.2 mm; And / or, by mass percentage, the composition of the A6061 aluminum alloy welding wire is: Si 0.85%, Mg 0.57%, Cu 0.22%, Mn 0.11%, Cr 0.15%, Zn 0.19%, Ti 0.13%, with the balance being Al and unavoidable impurities.

6. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 4, characterized in that, The diameter of the AZ31 magnesium alloy welding wire is 1.2 mm; And / or, by mass percentage, the composition of the AZ31 magnesium alloy welding wire is: Al 3.26%, Zn 0.85%, Mn 0.41%, Fe 0.01%, Si 0.07%, with the balance being Mg and unavoidable impurities.

7. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 1, characterized in that, Argon was used as the protective gas throughout the aluminum alloy deposition process and the magnesium alloy deposition process, with a gas flow rate of 20 L / min.

8. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 1, characterized in that, Before sequentially depositing aluminum alloy and magnesium alloy on the substrate surface using a dual wire feeding mechanism, the process also includes a step of preheating the substrate.

9. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 8, characterized in that, The preheating process specifically involves raising the substrate temperature to 200°C at a rate of 5°C / min and holding it at that temperature for 10 minutes.

10. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 1, characterized in that, The following parameters are also included in the aluminum alloy deposition process and the magnesium alloy deposition process: the distance between the end of the welding wire and the surface of the deposition layer is 15-20mm; the laser travel path is unidirectional; the deposition height of each layer is 0.8-1.1mm; and after each layer is deposited, it is cooled for 100-120s.

Images