A method for laser twin-wire additive manufacturing of aluminum / magnesium bimetallic material based on dynamic heat input

Abstract

The application discloses a kind of based on dynamic heat input's laser double-wire additive manufacturing aluminum / magnesium bimetallic material method, it is related to metal material additive manufacturing technical field.The method includes the following steps: using aluminum alloy welding wire and magnesium alloy welding wire as deposition material, aluminum alloy and magnesium alloy are sequentially deposited on the surface of substrate by double-wire feeding mechanism, and aluminum / magnesium bimetallic material is obtained;Aluminum alloy deposition process and magnesium alloy deposition process are independently carried out layering dynamic heat input parameter control respectively;The heat input parameter includes laser power and wire feeding speed.The application uses the manufacturing process of "double-wire independent feeding+dynamic heat input control", wherein, double-wire independent feeding can improve manufacturing efficiency;Dynamic heat input control can inhibit the concentrated generation of interface brittle intermetallic compound from the process level, and improve interface bonding strength.The aluminum / magnesium bimetallic material prepared by the method of the application 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 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 respectively, so as to spatially allocate material properties on demand and realize the manufacturing of functionally graded materials or composite structures, which is difficult to achieve by traditional manufacturing methods. However, due to the significant differences in 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 rapid and high-quality preparation of aluminum / magnesium bimetallic material by laser wire additive manufacturing is the focus of research for technicians in this field 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 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 high-quality and high-efficiency near-net shaping of aluminum / magnesium bimetallic material, 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 scheme:

[0008] 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:

[0009] Aluminum alloy welding wire and magnesium alloy welding wire are used as deposition materials, and aluminum alloy and magnesium alloy are deposited in turn (aluminum alloy is deposited first and then magnesium alloy) on the surface of the substrate by a double-wire feeding mechanism to obtain aluminum / magnesium bimetallic material;

[0010] 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);

[0011] The heat input parameters include laser power and wire feeding speed.

[0012] The application adopts the 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 the need to replace welding wire in a single-wire system, and improving manufacturing efficiency; the dynamic heat input control refers to designing heat input parameters (power + wire feeding speed) in layers according to the differences in thermal physical properties of aluminum alloy and magnesium alloy, realizing on-demand control of aluminum alloy side and on-demand control of oxidation of magnesium alloy side, and inhibiting the concentrated generation of interface brittle intermetallic compounds (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. The method of the application is simple in process, and can improve the manufacturing efficiency while improving the comprehensive performance of the product.

[0013] Further, during the aluminum alloy deposition process, the layered dynamic heat input parameter control includes:

[0014] The bottom layer: the laser power is 1.5-1.7 kW, and the wire feeding speed is 2.0-2.5 m / min;

[0015] The transition layer: the laser power is 2.0-2.2 kW, and the wire feeding speed is 3.0-3.5 m / min;

[0016] The upper layer: the laser power is 2.6-2.8 kW, and the wire feeding speed is 4.0-4.5 m / min.

[0017] 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 tight 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.

[0018] 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.

[0019] Further, during the magnesium alloy deposition process, the layered dynamic heat input parameter control includes:

[0020] Before deposition: a laser power of 0.3-0.5 kW is used to preheat the interface;

[0021] The bottom layer: the laser power is 1.6-1.8 kW, and the wire feeding speed is 2.5-3.0 m / min;

[0022] The transition layer: the laser power is 1.8-2.0 kW, and the wire feeding speed is 3.0-3.5 m / min;

[0023] The upper layer: the laser power is 1.7-1.9 kW, and the wire feeding speed is 2.8-3.2 m / min.

[0024] During the deposition of the magnesium alloy, the interface is preheated at a low power (0.3-0.5 kW) before deposition; the bottom layer (combined with the aluminum alloy layer) is deposited at a low power (1.6-1.8 kW) + a medium speed (2.5-3.0 m / min), so that the magnesium alloy wire and the surface of the deposited aluminum alloy layer are melted and solidified at a relatively fast speed, the liquid coexistence time of aluminum / magnesium is shortened, and the excessive growth of brittle phases (such as Al3Mg2) is inhibited; the transition layer (i.e., the main layer) is deposited at a medium power (1.8-2.0 kW) + a medium speed (3.0-3.5 m / min), so as to control the temperature of the molten pool under the premise of ensuring the deposition efficiency and the interlayer bonding; the upper layer is deposited at a low power (1.7-1.9 kW) + a medium speed (2.8-3.2 m / min), so as to avoid more serious heat accumulation and help reduce the burning loss of the magnesium alloy.

[0025] Further, the bottom layer accounts for 20-30% of the total number of deposited layers (i.e., the total deposition thickness) of the magnesium alloy; the transition layer accounts for 40-60% of the total number of deposited layers of the magnesium alloy; and the upper layer accounts for 20-30% of the total number of deposited layers of the magnesium alloy.

[0026] Further, the aluminum alloy wire is an A6061 aluminum alloy wire, and the magnesium alloy wire is an AZ31 magnesium alloy wire.

[0027] Further, the diameter of the A6061 aluminum alloy wire is 1.2 mm.

[0028] Further, the A6061 aluminum alloy wire comprises, by mass percentage: 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.

[0029] Further, the diameter of the AZ31 magnesium alloy wire is 1.2 mm.

[0030] Further, the AZ31 magnesium alloy wire comprises, by mass percentage: Al 3.26%, Zn 0.85%, Mn 0.41%, Fe 0.01%, Si 0.07%, and the balance of Mg and unavoidable impurities.

[0031] The Mg content in the A6061 aluminum alloy is low (0.57 wt%), and the Al content in the AZ31 is high (3.26 wt%), which helps to form a controllable diffusion layer, reduce brittle phases, and improve the metallurgical bonding strength. That is, the two wires are complementary and synergistically improve the interface performance.

[0032] Further, argon is used as a protective gas during the aluminum alloy deposition process and the magnesium alloy deposition process, and the gas flow rate is 20 L / min.

[0033] Further, before depositing the aluminum alloy and the magnesium alloy on the substrate surface by the double-wire feeding mechanism, the method further includes a step of preheating the substrate.

[0034] Further, the preheating specifically includes increasing the temperature of the substrate to 200°C at a rate of 5°C / min and maintaining the temperature for 10 min.

[0035] Further, the aluminum alloy deposition process and the magnesium alloy deposition process further include the following parameters: the distance between the wire end and the surface of the deposited layer is 15-20 mm; the laser walking path is unidirectional; the deposition height of each layer is 0.8-1.1 mm; and after each layer deposition is completed, cooling for 100-120 s.

[0036] Further, argon is used as a protective gas during the cooling process, and the gas flow rate is 20 L / min.

[0037] Optionally, the method further includes a mechanical polishing step after the cooling is completed, and argon is used as a protective gas during the mechanical polishing process, and the gas flow rate is 20 L / min.

[0038] Further, after the magnesium alloy deposition is completed, the method further includes a step of maintaining argon protection until the temperature of the aluminum / magnesium bimetallic material decreases to room temperature.

[0039] The method further includes the following specific steps:

[0040] Step one, establishing a laser additive manufacturing system, the system including a double-wire feeding mechanism capable of feeding aluminum alloy wire and magnesium alloy wire respectively;

[0041] Step two, performing parameter simulation and no-load trial operation;

[0042] Step three, pretreating the surface to be deposited of the substrate, the pretreatment including mechanical polishing and acetone wiping; using a clamp to fix the pretreated substrate on a welding platform and preheating;

[0043] Step four, using the aluminum alloy wire to deposit aluminum alloy on the substrate layer by layer according to the set aluminum alloy side process parameters, forming an aluminum alloy deposited layer;

[0044] Step five, switching to the magnesium alloy wire, depositing magnesium alloy on the aluminum alloy deposition layer according to the set magnesium alloy side process parameters, forming a magnesium alloy deposition layer, and finally forming an aluminum / magnesium bimetallic material;

[0045] The aluminum alloy side process parameters and the magnesium alloy side process parameters are independent of each other, so as to realize dynamic heat input control for the aluminum alloy and the magnesium alloy material characteristics.

[0046] Further, the laser additive manufacturing system further 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.

[0047] The present application adopts a double-wire feeding mechanism combined with a dynamic heat input control additive manufacturing process to manufacture an aluminum / magnesium bimetallic material. Through the characteristics of directional energy deposition, it has the potential to accurately deposit different materials in specific areas; through dynamic heat input control, it can effectively relieve 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, this method has the characteristics of high deposition efficiency and relatively low cost, opening up a promising new path for the low-cost and rapid manufacturing of large-size aluminum / magnesium bimetallic material components.

[0048] The present application discloses the following technical effects:

[0049] The present application provides a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material based on dynamic heat input, which adopts a double-wire independent feeding + dynamic heat input control additive manufacturing process to manufacture aluminum / magnesium bimetallic material. The double-wire independent feeding specifically refers to the precise switching and feeding control of aluminum alloy wire and magnesium alloy wire through independent double-wire feeding mechanism, avoiding process interruption caused by the need to replace the wire in the single-wire system, and improving the 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 aluminum alloy side on-demand control combination (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 the subsequent deposition of magnesium alloy), magnesium alloy side on-demand control oxidation (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 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 present application has good interface bonding strength and excellent comprehensive mechanical properties.

[0050] 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.

[0051] The application provides a method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input, and the preferred deposition sequence is that the aluminum alloy is deposited first and then the magnesium alloy is deposited. When the laser acts on the substrate or the previous deposition layer, a molten pool is formed, at this time, the 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 an aluminum / magnesium bimetallic material with a transition region is formed. In addition, the aluminum alloy as the bottom metal can better transfer heat and prevent excessive grain size caused by excessive heat input, so that the bonding force of the interface can be better improved, thereby significantly improving the mechanical properties of the entire structure. BRIEF DESCRIPTION OF DRAWINGS

[0052] 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.

[0053] 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.

[0054] 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.

[0055] Figure 3 Microhardness distribution diagram of the aluminum / magnesium bimetallic material thin-walled part prepared in Embodiment 1 of the present application. DETAILED DESCRIPTION

[0056] 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.

[0057] 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 within any stated range or within any stated intermediate value, as well as any other stated value or intermediate value within 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.

[0058] 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.

[0059] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the present application. Other implementations of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the present application. The specification and examples are illustrative only.

[0060] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or the like are open-ended terms that are intended to mean including but not limited to.

[0061] It should be noted that the present application does not describe in detail the conventional operation means in the art, and is not the focus of the present application.

[0062] In the following examples and comparative examples of the present application, if it refers to room temperature, it specifically refers to 20-30℃.

[0063] In the following examples and comparative examples of the present application, each raw material used is a common commercially available product, 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.

[0064] Example 1

[0065] 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:

[0066] 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.

[0067] Step two, system debugging: perform parameter simulation and no-load trial operation to ensure system stability and path accuracy.

[0068] Step three, the length of 200 mm, 200 mm wide, 20 mm thick to be welded aluminum substrate (the same composition of A6061 aluminum alloy wire aluminum alloy substrate) mechanical polishing, polishing force evenly, until the surface of the oxide scale is completely removed, and using acetone to wipe the aluminum substrate surface oil, to ensure that the interface and the molten pool environment without pollution. The pretreatment (i.e. polishing, wiping) after the aluminum substrate into the welding platform fixture, fasten by hand knob, firmly fixed on the aluminum substrate on the welding platform, to ensure that the aluminum substrate no loose; start the welding platform temperature control module, the aluminum substrate temperature to 200℃ at a rate of 5℃ / min, 10 min to ensure uniform temperature inside the aluminum substrate, to avoid local temperature difference caused by thermal stress. Simulation test, adjust the initial point of the deposition path, start the laser and return to the initial point.

[0069] Step four, aluminum alloy side deposition: aluminum alloy side using hierarchical dynamic heat input parameters, as follows:

[0070] The bottom layer (combined with the aluminum substrate layer, accounting for 20% of the total number of deposition layers (i.e. total deposition thickness) on this side): laser power is 1.7kW, to ensure full fusion with the aluminum substrate; wire feed speed is 2.0m / min, to extend the residence time of the molten pool;

[0071] Transition layer (main layer, accounting for 60% of the total number of deposition layers on this side): laser power is 2.1kW, to improve efficiency and power smoothly; wire feed speed is 3.3m / min, to avoid defects;

[0072] Upper layer (near the interface, accounting for 20% of the total number of deposition layers on this side): laser power is 2.7kW, to balance efficiency and forming quality; wire feed speed is 4.3m / min, to reduce grain coarsening;

[0073] According to the above hierarchical dynamic heat input parameter settings for aluminum alloy side deposition, the laser and A6061 aluminum alloy wire between 45°, the distance between the end of the wire and the surface of the aluminum substrate is 20mm (the distance between the end of the wire and the surface of the last deposition layer is 20mm during deposition), start the laser power, at the same time, open the double wire feed mechanism to send A6061 aluminum alloy wire, according to the preset path (one-way walking path) layer by layer deposition, each layer deposition height is 1.1mm; after each deposition, the interlayer cooling program is automatically triggered, and the cooling time is 110s. After cooling, the deposition surface is mechanically polished to remove surface dirt and oxides (mechanical polishing time is about 5s). During the deposition, cooling and mechanical polishing process, argon is continuously protected, and the argon flow is set to 20L / min. A total of 10 layers are deposited, and the aluminum layer surface is free of cracks, pores and other defects after deposition.

[0074] 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 layering dynamic heat input parameters are adjusted synchronously as follows:

[0075] Interfacial preheating: laser power is 0.4 kW, no wire feeding is performed for one pass, and the interfacial stress is avoided;

[0076] Bottom layer (combined with the aluminum alloy side, accounting for 20% of the total number of deposition layers on this side): the laser power is 1.8 kW, which ensures that the AZ31 magnesium alloy welding wire and the aluminum alloy side surface are quickly melted and quickly solidified; the wire feeding speed is 2.9 m / min, which avoids excessive fusion to cause excessive generation of intermetallic compounds (IMCs);

[0077] Transition layer (main layer, accounting for 60% of the total number of deposition layers on this side): the laser power is 2.0 kW, and the wire feeding speed is 3.0 m / min, which ensures the deposition efficiency and controls the molten pool temperature;

[0078] Upper layer (top of the magnesium alloy side, accounting for 20% of the total number of deposition layers on this side): the laser power is 1.9 kW, which avoids heat accumulation and reduces magnesium alloy oxidation loss; the wire feeding speed is 3.2 m / min, which improves the density of the magnesium alloy layer.

[0079] After confirming that the double-wire switching is completed, the laser and the AZ31 magnesium alloy welding wire are adjusted to be at an angle of 45°, the distance between the welding wire end and the surface of the aluminum alloy deposition layer is 20 mm, the laser is restarted, and the deposition is restarted layer by layer according to the same path as the aluminum alloy side, and the deposition height of each layer is 1.1 mm; after each layer is deposited, the same 110 s of cooling is performed, after the cooling is completed, the deposition surface is mechanically polished to remove surface dirt and oxides (the mechanical polishing time is about 5 s), the argon protection is continuously performed during the deposition, cooling and mechanical polishing processes, the argon flow rate is set to 20 L / min, and a total of 10 layers are deposited to obtain an aluminum / magnesium bimetallic material thin-walled component, which has a smooth surface and 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 for oxidation; then the aluminum / magnesium bimetallic material thin-walled component is taken out, and no subsequent machining is required to meet the near-net-shape forming requirement.

[0080] 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 results are as follows: Figure 2As shown, 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 IMC aggregation in the transition zone. The reason for the formation of the transition zone is the atomic diffusion behavior between aluminum and magnesium, and its core role is to realize the effective metallurgical bonding of aluminum and magnesium, and to act as a stress buffer layer by controlling the brittle IMCs at the interface to relieve the thermal stress generated by 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 double wires effectively inhibits the excessive generation of IMCs, and the interface is well bonded.

[0081] A Jinan Huafeng HJ-20 micro Vickers hardness tester is used, the test load is 100g, the pressure holding time is 15s, and every 50μm 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 1 hardness value, and a total of 30 points are tested; the hardness distribution graph is as shown in Figure 3 As shown, it can be seen that the hardness of the aluminum alloy side (i.e. the aluminum matrix) is stable at 65-85HV, the hardness of the magnesium alloy side (i.e. the magnesium matrix) is stable at 60-90HV, and the hardness of the interface transition zone is 210-280HV, 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 area, indicating that the interface is tightly bonded, and there are no inclusions, porosity and other defects, which is consistent with the SEM observation results.

[0082] In this embodiment, by standardizing the operation and accurately controlling the parameters, an aluminum / magnesium bimetallic material thin-walled component with good interface bonding and stable performance is successfully prepared, and the feasibility of the "double-wire dynamic heat input" method is verified.

[0083] Comparative Example 1

[0084] A method for laser double-wire additive manufacturing of aluminum / magnesium bimetallic material, the steps are as follows:

[0085] Step one, system configuration: establish a laser additive manufacturing system, including total power supply, laser, double-wire feeding mechanism, protection 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.

[0086] Step two, system debugging: parameter simulation and no-load trial operation are carried out to ensure system stability and accurate path.

[0087] Step 3: Mechanically grind the aluminum substrate (with the same composition as A6061 aluminum alloy welding wire) to be welded, measuring 200mm in length, 200mm in width, and 20mm in thickness, using uniform grinding pressure until the surface oxide scale is completely removed. Wipe the surface of the aluminum substrate with acetone to ensure the additive interface and molten pool environment are free of contamination. Place the pre-treated (grinded and wiped) aluminum substrate into the welding platform fixture and manually tighten the knobs to firmly fix the aluminum substrate on the welding platform, ensuring it is not loose. Activate the welding platform temperature control module to raise the aluminum substrate temperature to 200℃ at a rate of 5℃ / min, and hold at this temperature for 10 minutes to ensure uniform internal temperature of the aluminum substrate and avoid thermal stress caused by localized temperature differences. Conduct a simulation test, adjust the initial point of the additive deposition path, start the laser, and return to the initial point.

[0088] Step 4: Aluminum alloy side deposition, as detailed below:

[0089] The laser power was 2.1kW, and the wire feeding speed was 3.3m / min. The laser and the A6061 aluminum alloy welding wire were at a 45° angle, and the distance between the end of the welding wire and the surface of the aluminum substrate was 20mm (the distance between the end of the welding wire and the surface of the previous deposition layer was 20mm during the deposition process). The laser power was turned on, and the dual wire feeding mechanism was turned on to feed the A6061 aluminum alloy welding wire. The wire was deposited layer by layer according to the preset path (unidirectional travel path), and the deposition height of each layer was 1.1mm. After each layer was deposited, the interlayer cooling program was automatically triggered, and the layer was cooled for 110s. After cooling, the deposition surface was mechanically polished with a steel rubber to remove surface dirt and oxides (mechanical polishing time was about 5s). Argon gas was continuously protected during deposition, cooling and mechanical polishing. The argon gas flow rate was set to 20L / min. A total of 10 layers were deposited. After deposition, the surface morphology of the aluminum layer was uneven and there were macroscopic defects.

[0090] 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:

[0091] The laser power is 2.0kW and the wire feeding speed is 3.0m / min.

[0092] 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.

[0093] The comparative example prepares the aluminum / magnesium bimetallic thin-walled part by fixed power and wire feeding speed, the sample has large macroscopic defects, the thin-walled part is broken due to uneven heat input in the additive process, and cannot be formed. The feasibility of the "double-wire dynamic heat input" method of the application is verified again.

[0094] The above-described embodiments are only used to describe the preferred modes of the present application, and do not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

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; 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, wire feeding speed is 4.0-4.5m / min; 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.

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, The aluminum alloy welding wire is A6061 aluminum alloy welding wire, and the magnesium alloy welding wire is AZ31 magnesium alloy welding wire.

3. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 2, 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.

4. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 2, 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.

5. 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.

6. 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.

7. The method for laser dual-wire additive manufacturing of aluminum / magnesium bimetallic materials based on dynamic heat input as described in claim 6, 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.

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, 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.

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