Double laser-electric arc composite additive manufacturing method for heat-resistant rare earth magnesium alloy structural member

Abstract

The invention discloses a double laser-electric arc composite additive manufacturing method for a heat-resistant rare earth magnesium alloy structural part, and aims to solve the problem of'size bimodal distribution 'of an eutectic phase caused by cooling rate difference during high-speed electric arc additive manufacturing of a rare earth magnesium alloy. A dual-wavelength laser beam which is coaxially integrated and has synergistic functions is creatively compounded with a cold metal transition electric arc. Wherein the straight-out blue laser is used for carrying out wide-area pre-melting on a processing area, so that the reflection loss of subsequent red laser is reduced, the stirring effect of the red laser is improved, and element burning loss is inhibited; and the coaxial oscillation type red laser performs high-frequency stirring on the arc molten pool. Through the synergistic effect of the blue light laser stabilizing thermal gradient and the red light laser homogenizing solute field in the molten pool, the problem that the eutectic phase size difference between the interlayer remelting area and the single-layer center area is large is effectively solved, the eutectic phase in the structural part is evenly and dispersively distributed on the whole, and the mechanical property uniformity of the structural part at the room temperature and the high temperature is remarkably improved.

Description

Dual-laser-arc composite additive manufacturing method for heat-resistant rare-earth magnesium alloy structural components Technical Field

[0001] This invention belongs to the field of metal additive manufacturing technology, specifically relating to a laser-arc composite additive manufacturing method for heat-resistant rare earth magnesium alloy structural parts, and particularly to a method that utilizes a coaxial dual-wavelength laser in conjunction with an electric arc heat source to actively control the thermal history of the molten pool and the solute field, thereby achieving a uniform distribution of eutectic phase inside the component. Background Technology

[0002] Rare earth magnesium alloys, such as WE43 (Mg-Y-Nd-Zr series), exhibit great application potential in aerospace, high-end equipment, and other fields with stringent requirements for lightweighting and high-temperature performance due to their high specific strength, excellent heat resistance, and damping characteristics. Arc-wire additive manufacturing technology, with its high deposition efficiency, low cost, and applicability to the manufacture of large components, has become a highly promising process for forming such alloy components.

[0003] However, when fabricating rare-earth magnesium alloy structural parts using conventional high-speed electric arc additive manufacturing processes, a long-standing core challenge arises: severe microstructure inhomogeneity caused by the inherent characteristics of the solidification process. Under high-speed deposition conditions, the thermal cycle of the molten pool exhibits significant periodic fluctuations, resulting in substantial differences in cooling rates between different regions of the molten pool (such as the interlayer remelting zone and the central region of monolayer deposition). For alloys like WE43, which rely on the precipitation of rare-earth elements (Y, Nd) to form eutectic phases of intermetallic compounds dominated by Mg-RE (such as Mg-Y, Mg-Nd) for strengthening, this non-uniform thermal history directly leads to the non-uniform precipitation of the eutectic phase.

[0004] The typical defective microstructure is as follows: in the central region of the layer where the cooling rate is relatively slow, the eutectic phase has sufficient time to nucleate, grow, and aggregate, forming a coarse, continuous, or even network-like distribution, leading to increased brittleness in this region; while in the interlayer remelting zone where the cooling rate is extremely fast, the eutectic phase is forced to precipitate rapidly in a fine, dispersed but poorly distributed manner. This periodic "coarse-fine alternation" eutectic phase distribution pattern at the microscale is the fundamental reason why additively manufactured components exhibit significant anisotropy in mechanical properties, unstable high-temperature performance, and potential failure risks at the macroscopic level.

[0005] In existing technologies, laser-arc composite heat sources have been introduced to attempt to improve the additive manufacturing process. However, most existing solutions use a single-wavelength laser, or, although they use composite lasers, they do not incorporate refined synergistic design to address the solidification characteristics of rare-earth magnesium alloys. For example, using a single oscillating laser primarily acts on the molten pool to stir the molten pool to eliminate porosity or refine the matrix grains, but its highly concentrated energy may lead to increased localized burn-off of magnesium and rare-earth elements, and its effect on mitigating the overall temperature gradient of the molten pool is limited, making it difficult to fundamentally solve the problem of uniform nucleation and growth of the eutectic phase across the entire three-dimensional spatial scale of the component.

[0006] Therefore, developing a new method that can synergistically control heat input and molten pool flow to achieve uniform distribution of eutectic phase in rare earth magnesium alloy additive manufacturing components is of urgent industrial demand and significant scientific value. Summary of the Invention

[0007] (I) Purpose of the Invention The purpose of this invention is to overcome the shortcomings of existing single laser modes or simple composite lasers in controlling the uniformity of solidification structure of heat-resistant rare earth magnesium alloys, and to provide a dual laser-arc composite additive manufacturing method for heat-resistant rare earth magnesium alloy structural parts. This method fundamentally bridges the differences in thermal history between layers and within layers by synergistic differentiation of dual-wavelength coaxial lasers, thereby achieving uniform distribution of eutectic phase in high-speed additive manufacturing of rare earth magnesium alloy structural parts, and thus enabling the manufacture of rare earth magnesium alloy structural parts with highly uniform microstructure and excellent comprehensive performance.

[0008] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: a dual-laser-arc composite additive manufacturing method for heat-resistant rare-earth magnesium alloy structural parts, comprising the following steps: S1, preparation and preheating: providing magnesium alloy wire containing rare-earth elements and preheating the substrate to 80℃~120℃; S2, layer-by-layer composite deposition: performing layer-by-layer deposition on the preheated substrate at a deposition rate of 10~20mm / s under a protective atmosphere; the deposition process of each layer is completed by a synergistic cold metal transition arc, a first laser beam and a second laser beam, wherein: (a) the first laser beam is used to pre-melt the solid surface in the current processing area, the first laser beam being a direct-output blue laser with a wavelength of 400~480nm and a power of 500~100 (a) Using the cold metal transition arc to melt the fed magnesium alloy wire in the area pre-melted by the first laser beam, forming the main molten pool for additive manufacturing; (b) Using the second laser beam to oscillate and stir the main molten pool, the second laser beam is a red laser with a wavelength of 1000~1080nm, a power of 800~1500W, and a spot diameter of 0.3~0.5mm. It is output coaxially with the first laser beam through an optical system and oscillates in a two-dimensional plane in the main molten pool at a frequency of 200~300Hz and an amplitude of 1.0~3.0mm; S3, Cooling: After deposition, it is cooled to room temperature in a protective atmosphere to obtain a magnesium alloy structural part with a uniform eutectic phase distribution.

[0009] Furthermore, in step S2, during the layer-by-layer deposition process, the interlayer temperature is controlled to be maintained at 80°C to 120°C.

[0010] Furthermore, the trajectory of the two-dimensional plane oscillation is circular or figure-eight shaped.

[0011] Furthermore, the coaxial laser beam formed by the first laser beam and the second laser beam is angled at 15° to 45° with the axis of the cold metal transition arc welding gun and points to the current processing area.

[0012] Furthermore, the protective atmosphere is argon gas with a purity greater than 99.99%, and its gas flow rate is 15~30L / min.

[0013] Furthermore, on the longitudinal section of the magnesium alloy structural component, the average size of the eutectic phase is less than 5 μm, and the coefficient of variation of the size distribution is less than 15%.

[0014] Furthermore, the room temperature yield strength anisotropy coefficient of the magnesium alloy structural component is less than 1.10 in both the deposition direction and the direction perpendicular to the deposition direction.

[0015] Furthermore, at a high temperature of 250°C, the ratio of the creep strength in the deposition direction to that perpendicular to the deposition direction of the magnesium alloy structural component is greater than 0.95.

[0016] Furthermore, the magnesium alloy wire is WE43 magnesium alloy wire, and the eutectic phase in the resulting magnesium alloy structural component is β-Mg. 12 (Nd,Y)5 phase.

[0017] (III) Principle Explanation The core principle of this invention lies in its comprehensive heat source system—a clearly defined and spatiotemporally coordinated system of "blue light pre-melting foundation, red light focusing and strong stirring, and electric arc main body forming"—that addresses the thermodynamic and kinetic problems leading to eutectic phase inhomogeneity from the very source of the solidification process. This principle can be understood from the following three levels: First, this invention is not simply a superposition of heat sources, but rather a precise functional positioning and coordinated design of the cold metal transition arc, the direct-emission blue laser, and the coaxial oscillating red laser. The cold metal transition arc, as the main forming heat source, is responsible for efficiently melting the wire and forming a stable main molten pool to achieve material addition. The direct-emission blue laser, as a pre-melting and thermal control source, utilizes its wide beam (2~3mm) for large-scale pre-melting. Its core function is to pre-input a gently distributed heat, actively suppressing the rapid cooling trend of the molten pool (especially the interlayer remelting zone). Coaxial oscillating red laser, acting as a source of strong stirring and solute homogenization, utilizes its small spot size (0.3~0.5mm) and high-frequency oscillation to implement high-intensity forced convection stirring of the molten pool. Secondly, this division of labor directly addresses the two root causes of microstructure inhomogeneity in high-speed additive manufacturing of rare-earth magnesium alloys: one is the significant difference in cooling rates between and within layers (thermodynamic inhomogeneity), which leads to coarse eutectic phases in areas of slow cooling and fine phases in areas of excessively fast cooling; the other is the macroscopic segregation of solutes (rare earth elements) during solidification (kinetic inhomogeneity), which results in a rapid eutectic phase distribution. Blue laser pre-melting directly bridges the thermodynamic differences by increasing the heat base of the remelting zone and slowing its cooling, providing similar growth time windows for the eutectic phase in various locations. Red laser strong stirring, on the other hand, eradicates kinetic inhomogeneity by violently disturbing the molten pool and breaking up solute-rich areas, creating uniform compositional conditions for the homogeneous nucleation of the eutectic phase. Thirdly, the synergy of these three components not only has a clear division of labor but also produces a multiplier effect. The liquid layer formed by blue light pre-melting significantly reduces the high reflectivity of the solid metal to the red laser, allowing the energy of the red laser to be converted into the kinetic energy of the molten pool more efficiently, thus "amplifying" its stirring effect. This reduces the red laser power required to achieve the same or even better stirring intensity. Combined with the reduction in the overall heat input peak by blue light pre-melting, this suppresses the burn-off of magnesium and rare earth elements. Ultimately, through the synergy of "blue light homogenizing field to control cooling rate and red light homogenizing field to control distribution," this invention achieves unified and precise control over both the thermodynamic conditions of solidification and the solute transport kinetics, thereby obtaining a uniform eutectic phase structure with consistent size and diffuse distribution in the three-dimensional space of the component.

[0018] (iv) Beneficial Effects Compared with the prior art, the present invention has the following significant advantages: (1) The present invention creatively proposes a functional synergy strategy of "direct blue light pre-melting" and "coaxial oscillating red light strong stirring". Blue light pre-melting not only creates a low-reflection and high-efficiency working environment for red laser, reducing its required power and amplifying its flow stirring effect, but also effectively suppresses the burning loss of magnesium alloy elements by reducing the overall heat input peak. In the optimized energy environment, the red laser converts its energy into the kinetic energy of the molten pool to the maximum extent, realizing the ultrafine and homogenization of the eutectic phase. This synergy is functionally complementary and has a multiplied effect.

[0019] (2) This invention works synergistically from two fundamental sources: solidification thermodynamics and kinetics. The blue laser, through its wide-spot pre-melting, smooths the temperature gradient between the remelted zone and the central region within the layer, solving the problem of "coarse phase" caused by differences in cooling rates; the red laser, through high-intensity stirring, homogenizes the solute field within the molten pool, breaking up solute enrichment and solving the problem of "uneven distribution" of the eutectic phase. The synergy of these two technologies fundamentally bridges the differences in thermal history and compositional field between different regions.

[0020] (3) Through the above-mentioned synergistic regulation, the method of the present invention can effectively reduce the size difference of the eutectic phase between the interlayer remelting zone and the single-layer deposition center zone, so that the eutectic phase on the longitudinal section of the component can achieve a uniform and dispersed distribution, specifically manifested as an average size of less than 5 μm and a coefficient of variation of the size distribution of less than 15%. This directly brings excellent uniformity of mechanical properties, with the yield strength anisotropy coefficient between the deposition direction and the perpendicular deposition direction at room temperature being less than 1.10, and the creep strength ratio at 250℃ being greater than 0.95. At the same time, due to the reduction in red laser power requirements and the effective control of overall heat input, additional engineering benefits such as energy saving, reduction of precious rare earth element burn-off, and improvement of laser lifespan are also generated. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the dual-wavelength coaxial laser-cold metal transition arc composite additive manufacturing system used in this invention.

[0022] Figure 2 shows the metallographic structure of the longitudinal section of the WE43 alloy obtained in Comparative Example 1 (traditional high-speed CMT arc additive manufacturing), which shows the “coarse-fine alternating” distribution of the eutectic phase.

[0023] Figure 3 is a metallographic diagram of the longitudinal section of the WE43 alloy obtained in Example 1 of the present invention, showing that the eutectic phase is uniformly dispersed. Detailed Implementation

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

[0025] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0026] This invention provides a dual-laser-arc composite additive manufacturing method for heat-resistant rare-earth magnesium alloy structural components. Its core lies in employing coaxially integrated and functionally synergistic blue and red lasers, combined with a cold metal transition arc to form a composite heat source, controlling the molten pool through step-by-step synergistic action. The specific method is described in detail below: S1, Preparation and Preheating: Provide magnesium alloy wire containing rare-earth elements; pre-treat the substrate (e.g., polishing, cleaning) and fix it on the worktable; preheat the entire substrate to a temperature range of 80℃~120℃ to reduce thermal stress and improve the wettability of the initial deposited layer; S2, Layer-by-Layer Composite Deposition: Deposit layer by layer on the preheated substrate at a deposition rate of 10~20 mm / s under a protective atmosphere such as pure argon (flow rate 15~30 L / min). The deposition process of each layer is completed synergistically by the cold metal transition arc, the first laser beam (blue light), and the second laser beam (red light). Its core collaborative mechanism is as follows: (a) A first laser beam is used to pre-melt the solid surface (substrate or previous deposited layer surface) in the current processing area. The first laser beam is a direct-output blue laser with a wavelength of 400-480nm, using a flat-top spot with a spot diameter of 2-3mm and an output power of 500-1000W, and does not perform scanning oscillation. Its function is to preheat the processing area to a melting or semi-melting state over a wide area before or simultaneously with the electric arc heat source, forming a large-area preheated molten pool or softened layer. This approach has three key benefits: First, it significantly reduces the high reflection loss when the subsequent red laser acts on the solid metal, thereby reducing the power requirement of the red laser while achieving the same molten pool penetration and stirring effect, thus saving energy and reducing the system load; Second, the liquid metal layer formed by pre-melting greatly enhances the energy absorption and heat conduction efficiency of the red laser, converting the energy of the red laser more effectively into the kinetic energy of the molten pool flow, thereby "amplifying" its stirring effect; Third, the wide-range blue laser pre-melting reduces the dependence on the high-intensity arc heat required to maintain the molten pool, which helps to reduce the overall heat input peak and effectively suppress the volatilization and burning loss of magnesium and rare earth elements; (b) Using a cold metal transition arc as the main heat source, the continuously fed magnesium alloy wire is melted in the area pre-melted by the first laser beam to form the main molten pool of additive manufacturing, completing the main addition and forming of materials; (c) A second laser beam is used to perform high-intensity oscillation stirring on the main molten pool formed by the cold metal transition arc. The second laser beam is a red laser with a wavelength of 1000-1080nm, a spot diameter of 0.3-0.5mm, and an output power of 800-1500W. This laser beam is guided by a mirror and galvanometer system to ensure strict coaxial output with the first laser beam (blue light). The red laser operates within the molten pool region pre-melted by the blue light, performing high-frequency two-dimensional planar oscillations (frequency 200-300Hz, amplitude 1.0-3.0mm, trajectory in simple patterns such as circles or figures-eights).Its main function is to utilize its high focused energy density and mechanical oscillation effect to generate strong forced convection and stirring in the molten pool, thereby breaking up the already grown eutectic phase prototype, dispersing the solute (especially rare earth elements Y and Nd) enrichment areas, promoting the uniform diffusion of solute in the molten pool, and creating conditions for subsequent uniform nucleation; the coaxial dual laser beams and CMT arc work together precisely in time and space to form a composite heat source division system of "blue light pre-melting foundation, red light focusing strong stirring, and arc main body forming", realizing precise and integrated control of the molten pool temperature field, flow field and solidification process; S3, cooling: after all the deposition layers are completed, the component is slowly cooled to room temperature in a protective atmosphere (such as continuing to pass argon gas) to obtain a magnesium alloy structural component with uniform eutectic phase distribution.

[0027] It should be noted that during the entire layer-by-layer deposition process in step S2, the interlayer temperature (i.e., the temperature of the component surface before the next layer begins deposition) after each deposition layer is completed must be controlled to be maintained between 80°C and 120°C.

[0028] In implementing the technical solution of this invention, a dual-wavelength coaxial laser-cold metal transition arc composite additive manufacturing system, as shown in Figure 1, needs to be constructed. The core optical components and optical path design for achieving coaxial laser output in this system are as follows: As shown in Figure 1 (schematic diagram, some components not shown), the system includes a first laser generator and a second laser generator. The first laser generator outputs a blue laser beam with a wavelength of 400-480nm. After collimation, this beam is transmitted along the optical axis (O) in a direct output mode, characterized by not passing through a scanning galvanometer, and having a fixed spot pattern and position. To achieve coaxiality, a red laser beam with a wavelength of 1000-1080nm output from the second laser generator is first guided to a two-dimensional scanning galvanometer system. The core function of this galvanometer system is to drive the reflecting mirror to perform high-frequency deflection, thereby causing the red laser beam to oscillate and scan in the XY plane according to a preset trajectory (such as a circle or a figure-eight shape). The oscillating red laser beam, after being reflected by the galvanometer, is guided to a beam splitter / combiner. This beam combiner features a special coating design tailored to the wavelength characteristics of blue and red light, resulting in high transmittance for blue laser light and high reflectivity for red laser light. Therefore, the direct blue laser beam passes through the beam combiner with almost no loss, while the oscillating red laser beam, reflected by the galvanometer, is reflected back by the beam combiner. The two beams converge at the beam combiner and propagate along the same output optical axis (O), achieving strictly spatial coaxial output. This coaxially output composite laser beam is then processed by a shared focusing or collimating lens and precisely pointed towards the molten pool region at a specific angle (e.g., 15-45°) with the CMT welding torch. This design ensures a high degree of spatial overlap between the blue pre-melting area and the red oscillating stirring area, providing the hardware foundation for precise spatiotemporal coordination of "pre-melting" and "intense stirring."

[0029] The technical solution of the present invention will be further described below with reference to specific embodiments and comparative examples.

[0030] Example 1 This example illustrates the manufacturing method of a thin-walled wall sample with dimensions of 10mm (width) × 200mm (length) × 80mm (height). The specific manufacturing method is as follows: Step 1: Preparing raw materials before deposition: WE43 magnesium alloy wire with a diameter of 1.2mm is selected as the deposition material; Substrate treatment: AZ31 magnesium alloy plate with a thickness of 6mm is used as the substrate. First, the surface of the substrate is polished with sandpaper to remove the oxide layer. Then, it is ultrasonically cleaned with anhydrous ethanol to remove oil stains. After cleaning, it is dried and firmly fixed on the CNC worktable; Preheating: Using a resistance heating plate installed on the tooling, the fixed substrate is preheated to 100℃±5℃. Preheating helps to reduce the thermal stress during subsequent deposition and improves the wetting and spreading behavior of the first molten pool on the substrate.

[0031] Step 2, Layer-by-layer composite deposition. This step is the core of implementing the present invention. Under a specific system configuration, through precisely set parameters and processes, the synergistic deposition of dual-wavelength laser and electric arc is achieved: (1) First, the system is configured and set up. The electric arc system uses a Fronius CMT Advanced 4000R cold metal transfer welding machine, equipped with its dedicated welding torch and wire feeding mechanism. The laser system consists of two lasers and a matching optical system: one is a direct-output semiconductor blue laser (wavelength 450nm), and the other is a fiber red laser (wavelength 1064nm) in conjunction with a two-dimensional scanning galvanometer system. Through precise optical design (including reflectors, beam combiners, etc.), it is ensured that the red laser, after being oscillated and reflected by the galvanometer, is strictly coaxial with the direct-output blue laser in space, and is finally output through a shared collimating lens. The coaxial laser output head and the CMT welding torch are fixed by a custom fixture, so that the axes of the two are at a 20° angle and point to the deposition position together. The entire deposition process is carried out in a sealed chamber, which is integrated with a CNC three-axis motion platform. The protective gas is high-purity argon (purity ≥ 99.99%). (2) Subsequently, the process parameters are preset and the path is planned. The specific settings are as follows: turn on the argon gas source, replace the oxygen content in the chamber to less than 50ppm, set the gas flow rate to 25L / min, and maintain this flow rate throughout the deposition process. Set the CMT welding mode, the process parameters are current 149A and wire feeding speed 12m / min. Turn on the blue laser, set the output power to 700W, the spot diameter to 2.5mm (flat top spot mode), the beam is straight out, and no scanning oscillation is performed. Turn on the red laser, set the output power to 800W; through the galvanometer control system, set the beam to perform circular trajectory oscillation, the oscillation frequency to 250Hz, and the oscillation amplitude (circular diameter) to 2.0mm. After passing through the optical system, it is output coaxially with the blue light, and the measured spot diameter acting on the workpiece surface is about 0.3mm. In the motion control system, the deposition speed is set to 15 mm / s, and a single-pass multi-layer deposition is carried out using a "bow" shaped reciprocating scanning path to form a thin wall; in order to disperse thermal stress, the scanning direction between adjacent deposition layers is rotated by 180°; (3) After all presets are completed, the program is started to execute collaborative deposition. The welding torch and laser head move collaboratively according to the set path and speed. At each instantaneous position, the blue laser first (or synchronously) pre-melts the solid surface of the substrate or the deposited layer; then, the CMT arc is stably started in the area of ​​blue pre-melting, melting the continuously fed WE43 wire to form the main molten pool; at the same time, the coaxial red laser beam performs high-frequency circular oscillation in the main molten pool to achieve strong stirring. This is the collaborative process of "blue pre-melting foundation, red focusing strong stirring, and arc main body forming"; throughout the deposition process, process monitoring and interlayer temperature control are implemented. The surface temperature of the component is monitored in real time using a non-contact infrared thermometer.By controlling the interval between the completion of each deposition layer and the start of the next deposition layer (i.e., the cooling time), the interlayer temperature (i.e., the substrate temperature at the starting point of the next layer) is strictly maintained within the range of 100℃±10℃.

[0032] Step 3: Post-Deposition Cooling. After all 200 deposition layers are completed, first shut off all heat sources, including the CMT arc, blue and red lasers, while maintaining the argon atmosphere in the protective chamber (flow rate maintained at 25 L / min). Allow the component to cool naturally to room temperature (approximately 25°C) under argon protection. After cooling, turn off the gas supply, remove the component, and you will obtain the desired WE43 magnesium alloy thin-walled wall additive manufacturing sample.

[0033] Comparative Example 1, as a comparison, used the exact same WE43 filament, substrate preheating temperature (100°C), deposition rate (15 mm / s), path, and interlayer temperature control, but employed only a cold metal transition arc for additive manufacturing without any laser assistance. The protective atmosphere was also argon (25 L / min). Thin-walled wall samples of the same size were prepared.

[0034] Performance testing and result analysis: The samples obtained in Example 1 and Comparative Example 1 were tested and analyzed as follows.

[0035] (1) Microstructure analysis: The longitudinal sections (planes parallel to the deposition direction) of the two samples were cut to prepare metallographic samples. After etching, the morphology and distribution of the eutectic phase were observed using an optical microscope and a scanning electron microscope.

[0036] Comparative Example 1 uses a conventional high-speed CMT arc additive manufacturing process to prepare WE43 magnesium alloy components. The metallographic structure of its longitudinal section is shown in Figure 2. As can be seen from the macroscopic metallographic image at x100x in Figure 2, the component structure exhibits obvious layered alternation characteristics. The interlayer remelting zone and the central zone within the layer form a clear boundary of light and dark differences, which intuitively reflects the microstructural partitioning phenomenon caused by the periodic fluctuations of the molten pool thermal cycle under the conventional process. Combined with the microscopic metallographic image at x500x, it can be further observed that the central zone within the layer has a slower cooling rate, allowing the eutectic phase to grow sufficiently, forming a coarse, continuous, and network-like morphology. In contrast, the interlayer remelting zone cools extremely quickly, forcing the eutectic phase to precipitate rapidly, exhibiting a fine, dispersed but well-distributed state. The above characteristics are completely consistent with the "coarse-fine alternating" bimodal distribution pattern of the eutectic phase described in the background art.

[0037] The metallographic structure of the longitudinal section of the WE43 magnesium alloy component prepared in Example 1 is shown in Figure 3. As can be seen from the macroscopic metallographic image at x100x in Figure 3, there are no obvious traces of layered alternation in the longitudinal section of the component. The overall microstructure exhibits a uniform grayscale distribution, and the boundary between the interlayer remelting zone and the intralayer central zone is completely eliminated, directly demonstrating the technical effect of consistent microstructure. The microscopic metallographic image at x500x shows that the eutectic phase is uniformly and diffusely distributed, without coarse network structures or local fine agglomerations. Its regular morphology and uniform distribution density fully demonstrate the synergistic effect of "blue light pre-melting to smooth the thermal gradient and red light strong stirring to homogenize the solute field." This contrasts sharply with the microstructure defects of the traditional process shown in Figure 2, proving that the technical solution of this invention can fundamentally solve the problem of uneven eutectic phase distribution. Image analysis shows that the average size of the eutectic phase in this component is 3.5 μm, with a size variation coefficient of only 11%, satisfying the β-Mg... 12 The technical requirements are that the average size of the (Nd,Y)5 eutectic phase is less than 5 μm and the coefficient of variation is less than 15%.

[0038] (2) Room temperature mechanical property test: Samples were taken from the deposition direction and perpendicular to the deposition direction of the two types of specimens, and room temperature tensile tests were conducted to determine the yield strength. The anisotropy coefficient is the ratio of the maximum and minimum yield strength in the deposition direction and perpendicular to the deposition direction.

[0039] Example 1: Yield strength in the deposition direction is 209 MPa, yield strength in the vertical direction is 205 MPa, and anisotropy coefficient is 1.02.

[0040] Comparative Example 1: Yield strength in the deposition direction is 215 MPa, yield strength in the vertical direction is 185 MPa, and anisotropy coefficient is 1.16.

[0041] This indicates that the method of the present invention effectively reduces the direction dependence of performance by homogenizing the tissue.

[0042] (3) High-temperature creep performance evaluation: Referring to the national standard GB / T 2039 "Metallic Materials - Uniaxial Tensile Creep Test Method", the WE43 magnesium alloy specimens prepared in Example 1 were subjected to creep strength tests at 250℃. During the test, standard tensile specimens were cut from the deposition direction (Z-direction) and perpendicular to the deposition direction (X-direction) of the component, respectively. The test was conducted at a constant test temperature and constant tensile stress (set according to the typical yield strength of the material at that temperature). The time to fracture of the specimen was recorded or the residual strength after a specified time (e.g., 100 hours) was measured. Due to the severe inhomogeneity of the microstructure of the specimen in Comparative Example 1, its high-temperature performance dispersion was large and unstable, and it did not have effective comparability. Therefore, quantitative comparative tests were not conducted on it.

[0043] Test results show that the ratio of the creep strength of the sample in Example 1 to that perpendicular to the deposition direction is greater than 0.95, which fully demonstrates that the components manufactured by the method of the present invention can still maintain excellent uniformity of mechanical properties under high-temperature service conditions.

[0044] The above embodiments and comparative examples fully demonstrate that the "coaxial dual-wavelength laser-arc composite additive manufacturing method" provided by this invention, through the synergistic mechanism of "blue light pre-melting" and "red light intense stirring," can fundamentally solve the problem of uneven eutectic phase distribution in high-speed arc additive manufacturing of rare-earth magnesium alloys. This method not only achieves three-dimensional homogenization of the microstructure and significantly reduces the anisotropy of the mechanical properties of the components, but also has additional advantages in energy saving and consumption reduction. It is of great significance for promoting the additive manufacturing application of high-performance rare-earth magnesium alloy structural components in key fields.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention in any way. All equivalent transformations or modifications made in accordance with the essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A dual-laser-arc composite additive manufacturing method for heat-resistant rare-earth magnesium alloy structural components, characterized in that, Includes the following steps: S1. Preparation and preheating: Provide magnesium alloy wire containing rare earth elements and preheat the substrate to 80℃~120℃; S2. Layer-by-layer composite deposition: Deposit layer by layer on the preheated substrate at a deposition rate of 10~20mm / s under a protective atmosphere. The deposition process of each layer is completed by a synergistic cold metal transition arc, a first laser beam, and a second laser beam, wherein: (a) the first laser beam is used to pre-melt the solid surface in the current processing area, and the first laser beam has a wavelength of 400~480 nm. (a) A direct-output blue laser with a wavelength of nm, a power of 500~1000W, and a spot diameter of 2~3mm is used, and no scanning is performed; (b) The magnesium alloy wire fed in is melted in the area pre-melted by the first laser beam using the cold metal transition arc to form the main molten pool for additive manufacturing; (c) The main molten pool is oscillated and stirred using the second laser beam, which is a red laser with a wavelength of 1000~1080nm, a power of 800~1500W, and a spot diameter of 0.3~0.5mm. It is output coaxially with the first laser beam through an optical system and oscillates in a two-dimensional plane in the main molten pool at a frequency of 200~300Hz and an amplitude of 1.0~3.0mm; S3, Cooling: After deposition, it is cooled to room temperature in a protective atmosphere to obtain a magnesium alloy structural part with a uniform eutectic phase distribution.

2. The method according to claim 1, characterized in that, In step S2, during the layer-by-layer deposition process, the interlayer temperature is controlled to be maintained at 80°C to 120°C.

3. The method according to claim 1, characterized in that, The trajectory of the two-dimensional plane oscillation is circular or figure-eight shaped.

4. The method according to claim 1, characterized in that, The coaxial laser beam formed by the first laser beam and the second laser beam is angled at 15° to 45° with the axis of the cold metal transition arc welding gun and points to the current processing area.

5. The method according to claim 1, characterized in that, The protective atmosphere is argon gas with a purity greater than 99.99%, and its gas flow rate is 15~30L / min.

6. The method according to claim 1, characterized in that, On the longitudinal section of the magnesium alloy structural component, the average size of the eutectic phase is less than 5 μm, and the coefficient of variation of the size distribution is less than 15%.

7. The method according to claim 1, characterized in that, The room temperature yield strength anisotropy coefficient of the magnesium alloy structural component is less than 1.10 in both the deposition direction and the direction perpendicular to the deposition direction.

8. The method according to claim 1, characterized in that, The ratio of the creep strength in the deposition direction to that perpendicular to the deposition direction of the magnesium alloy structural component is greater than 0.95 at a high temperature of 250°C.

9. The method according to claim 1, characterized in that, The magnesium alloy wire is WE43 magnesium alloy wire, and the eutectic phase in the resulting magnesium alloy structural component is β-Mg. 12 (Nd,Y)5 phase.

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