A high-low power laser dynamic coordination directional energy deposition method and system

Abstract

This invention belongs to the field of metal additive manufacturing and intelligent control technology, and discloses a method and system for directional energy deposition using dynamic coordination of high and low power lasers. This invention actively avoids deep-melting keyhole collapse, ensuring the molten pool remains in a stable, heat-limited, non-deep-melting state. By establishing a spatially asymmetric dynamic thermal field matrix, the auxiliary laser is shaped and deflected into a ring-shaped gradient thermal field surrounding the main molten pool. In the time dimension, a model predictive control (MPC) algorithm is used to fuse the molten pool morphology, temperature gradient, and spatter frequency for forward-looking closed-loop adjustment. This invention not only effectively reduces the solidification temperature gradient, eliminates internal residual stress and hot cracks, but also utilizes the local Marangoni effect to construct virtual supports to suppress gravity collapse in large-angle overhangs and thin-walled corner regions, inducing in-situ transformation of coarse columnar crystals into fine equiaxed crystals, significantly improving the forming accuracy and comprehensive mechanical properties of high-performance metal components.

Description

Technical Field

[0001] This invention belongs to the fields of metal additive manufacturing, intelligent heat source control and complex metal component forming technology. Specifically, it relates to a laser-directed energy deposition (L-DED) method and system with dynamic coordination of high and low power lasers, which is particularly suitable for in-situ defect control and metallurgical microstructure optimization of large-size complex structural parts of high-performance titanium alloys. Background Technology

[0002] In practical engineering applications, existing laser-directed energy deposition (L-DED) technology and equipment typically employ a single high-power continuous laser as the melting heat source. This single-point concentrated heat input mode has extremely significant physical limitations. Due to the highly focused laser energy, the temperature at the center of the main molten pool spikes instantaneously, while the edges and substrate remain relatively cold. This extreme spatial non-uniform heat distribution results in a very large temperature gradient (G) at the boundary of the liquid molten pool. Driven by such a high temperature gradient, the cooling rate of the liquid metal's transition to solidification is extremely rapid. For high-performance lightweight alloy materials such as Ti-6Al-4V, which exhibit strong anisotropy and thermal cracking sensitivity, the single continuous heat source deposition process is highly susceptible to inducing the following defects: 1. Solidification cracks and residual stress accumulation: Due to the intense thermal expansion and contraction and extremely high temperature gradient within the molten pool and its solid-liquid boundary micro-regions, strong downward tensile residual stress is formed within the deposited layer. When the stress value locally exceeds the yield limit of the material at that temperature, it will directly induce microscopic liquid film cracking or macroscopic solid-state cold cracking.

[0003] 2. Severe anisotropy in metallurgical structure: Under the coupled effect of extremely high temperature gradient G and solidification rate R, newly solidified grains tend to grow into long-distance epitaxial columnar crystals along the Z-axis direction away from the heat dissipation surface (i.e., perpendicular to the deposition layer interface). These coarse and unidirectional columnar crystals lead to severe anisotropy in the longitudinal and transverse mechanical properties of the components, greatly limiting the service reliability of the formed parts in aerospace main load-bearing components.

[0004] 3. Instability in extreme structural forming: When printing thin-walled panels, unsupported cantilevered structures, or complex geometries such as 90° sharp turns, conventional single-heat source systems cannot proactively adjust heat input when decelerating at corners or when the physical heat dissipation boundary changes abruptly, leading to excessive local heat accumulation. This can cause the surface tension at the molten pool edge to collapse, resulting in phenomena such as molten pool flow, thin-wall ablation and collapse, unstable edge fusion, and exponential bursts of spatter particles, severely deteriorating forming accuracy and surface quality.

[0005] In the field of additive manufacturing multi-beam or composite heat sources, although some existing technologies propose to improve processing performance by introducing auxiliary beams, existing multi-beam improvement schemes are mostly applied to the processing of high-reflectivity materials in deep penetration welding or selective laser melting (SLM). The core physical logic is to induce or maintain a stable "deep penetration keyhole" by having multiple beams overlap or be arranged at very close distances in space, and to force the material to improve the overall energy utilization rate of the laser by relying on multiple geometric reflections inside the keyhole.

[0006] Conversely, in liquid-directed energy deposition (L-DED) processes, if a deep keyhole is created in the molten pool due to excessive energy concentration, the unstable keyhole is prone to violent volumetric oscillations and collapse under the interference of a dense coaxial carrier gas powder flow with a certain mechanical impact. This can lead to the external protective gas or unmelted powder particles being directly entrained into the depths of the molten pool, leaving a large number of unstable pores and inclusions inside the formed part after solidification. Furthermore, existing multi-heat source composite schemes are basically simple superpositions with fixed spatial relative positions and static power ratios. Their auxiliary heat sources cannot perform asymmetric redistribution of spatial heat flow with the deflection of the laser beam's instantaneous motion vector, nor can they provide proactive feedback based on the evolution of the molten pool geometry and spatter intensity. Summary of the Invention

[0007] To address the shortcomings of the existing technology, the present invention aims to provide a method and system for directional energy deposition using dynamic coordination of high and low power lasers.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a method for directional energy deposition using dynamic coordination of high and low power lasers, as follows: S1. Based on the preset first process parameter package, a high-energy-density main laser is projected onto the metal powder fed into the predetermined deposition area of ​​the substrate to construct a heat transfer pool in a non-deep melting state, thereby realizing the melting of the metal powder and the deposition and shaping of the liquid metal body. S2. An auxiliary laser is projected around the heat transfer molten pool. The heat source of the auxiliary laser dynamically and asymmetrically distributes the energy density according to the motion vector of the instantaneous scanning path. A transient preheating zone is constructed in front of the scan, and a delayed cooling zone is constructed behind the scan, so as to realize the in-situ reconstruction of the temperature field gradient between the solidification front of the molten pool and the solid phase transition zone. S3. Online real-time acquisition of the instantaneous width of the heat transfer molten pool, the geometric features of the three-dimensional molten pool boundary morphology, and the transient fluctuation frequency of the edge of the liquid metal micro-region. At the same time, the number of splash particles ejected from the molten pool per unit time and the burst frequency are identified and counted through image edge segmentation to form transient morphology data. S4. The radiation intensity distribution of the in-situ captured molten pool and its surrounding heat-affected zone is converted into continuous temperature field control information, including the highest temperature at the center of the molten pool, the temperature gradient at the solid-liquid boundary of the molten pool, and the cooling slope of the tail solidification, after grayscale decoupling and real-time emissivity correction. S5. Based on the transient morphology data and temperature field control information, calculate the comprehensive index parameters of molten pool stability online in real time, and substitute the current state as the initial boundary condition into the built-in model prediction and control model to solve the molten pool instability probability and morphology deviation trend in the future prediction window in a rolling manner. S6. Based on the rolling optimization results of the model prediction control model, dynamically fine-tune the power ratio between the power corresponding to the central main light spot and the power corresponding to the auxiliary heat source.

[0009] As a further technical solution, in step S2, based on the change in the direction and angle of the instantaneous scanning motion vector, the asymmetric dynamic adjustment of the spot energy density is performed using the following spatial mapping matrix:

[0010] In the formula, Power allocation for the front preheating zone Power is allocated to the rear slow-cooling area. Power is allocated to the stable regions on both sides of the boundary; To assist the total output power of the laser; This is the real-time angle between the current scanning motion vector and the reference coordinate axis of the forming plane; This represents the accumulated deposition height of the current layer; , , This is the power-weighted adjustment coefficient for the corresponding region.

[0011] As a further technical solution, in step S5, the model predictive control model adopts an adaptive closed-loop algorithm for control. The adaptive closed-loop algorithm uses the main laser power, auxiliary laser power, scanning speed and powder feeding rate as control inputs, and the real-time maximum temperature of the molten pool, the instantaneous width of the molten pool and the height of the deposition layer as state variables. Based on the state variables collected at the current moment, it predicts the evolution of the molten pool state within a specific time step in the future through a preset system state space equation, and outputs dynamic correction instructions for the dual laser output parameters in advance.

[0012] As a further technical solution, the system objective optimization function J, which is solved in each rolling iteration of the predictive control adaptive closed-loop algorithm, is characterized as:

[0013]

[0014] In the formula, To predict the time-domain step size, To control the time-domain step size; and These represent the predicted maximum temperature and instantaneous width of the molten pool at the current k-th time, respectively, at the future k+j-th time. and These are the set reference target temperature and target width of the molten pool, respectively; and These are the control step adjustments for the main and auxiliary laser power, respectively. , This refers to the weighting coefficient for the state tracking deviation. , To control the input suppression weight coefficient.

[0015] As a further technical solution, in step S5, the method for calculating the comprehensive index parameter S of the molten pool stability is as follows:

[0016] In the formula, and These are the statistical average and standard deviation of the molten pool width collected within the current slip time window, respectively. and These represent the mean and standard deviation of the highest surface temperature of the molten pool collected within the same slip time window; This refers to the total number of splash particles counted per unit time. This is a preset critical splash quantity threshold limit; , , These are dimensionless weighting coefficients that are independent of each other.

[0017] Secondly, the present invention also provides a directional energy deposition system for dynamic coordination of high and low power lasers, comprising: A high-power laser module is configured to project a high-energy-density main laser onto metal powder fed into a predetermined deposition area of ​​the substrate according to a preset first process parameter package, thereby constructing a heat transfer pool in a non-deep melting state and realizing the melting of metal powder and the deposition and shaping of the liquid metal body. The low-power auxiliary laser module is configured to project an auxiliary laser around the heat transfer molten pool. The heat source of the auxiliary laser dynamically and asymmetrically distributes the energy density according to the motion vector of the instantaneous scanning path, constructing a transient preheating zone in front of the scan and a delayed cooling zone behind the scan, thereby realizing the in-situ reconstruction of the temperature field gradient between the solidification front of the molten pool and the solid phase transition zone. The molten pool visual monitoring module is configured to collect the instantaneous width of the heat transfer molten pool, the geometric features of the three-dimensional molten pool boundary morphology, and the transient fluctuation frequency of the edge of the liquid metal micro-region online in real time. At the same time, it identifies and counts the number and burst frequency of the splash particles ejected from the molten pool per unit time through image edge segmentation, forming transient morphology data. The infrared radiation temperature field acquisition and information decoupling module is configured to capture the radiation intensity distribution of the molten pool and its surrounding heat-affected zone in situ. After grayscale decoupling and real-time emissivity correction, it is converted into continuous temperature field control information, including the highest temperature at the center of the molten pool, the temperature gradient at the solid-liquid boundary of the molten pool, and the cooling slope of the solidification at the tail. The control module is configured to calculate the comprehensive index parameters of molten pool stability online in real time based on the transient topography data and temperature field control information, and to substitute the current state as the initial boundary condition into the built-in model prediction control model to continuously solve the probability of molten pool instability and the trend of topography deviation within the future prediction window. The dynamic power allocation module is configured to dynamically fine-tune the power ratio between the main laser and the auxiliary laser based on the rolling optimization results of the model prediction control model.

[0018] As a further technical solution, the low-power auxiliary laser module is equipped with a dynamic optical shaping element or a high-speed dual-axis galvanometer system. By linking with the system's instantaneous scanning motion vector v, the auxiliary laser beam is controlled to form a preheating region in front of the scanning direction, a slow cooling region in the rear of the scanning direction, and boundary stabilization regions on both sides of the scanning direction, thereby constructing a three-segment moving thermal field topology structure of "preheating zone - melting zone - slow cooling zone".

[0019] As a further technical solution, the low-power auxiliary laser module is used to periodically disturb the local thermal balance at the solid-liquid interface around the molten pool, thereby reducing the temperature field fluctuation at the edge of the molten pool and blocking the extension of coarse columnar crystals in situ.

[0020] Thirdly, the present invention also provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by the processor of the control module, implements the steps of the directional energy deposition method for dynamic coordination of high and low power lasers.

[0021] Fourthly, the present invention also provides a computer program product having a computer program stored thereon. The computer program product includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer performs the steps of the high- and low-power laser dynamic coordinated directional energy deposition method.

[0022] The beneficial effects of this invention are as follows: This invention actively avoids deep-melting keyhole collapse, ensuring the molten pool remains in a stable, heat-limited, non-deep-melting state. By constructing a synergistic heat input mechanism spatially enveloped by an asymmetric annular gradient thermal field, and introducing forward-looking adaptive closed-loop control using model predictive control (MPC) in time, it fundamentally reduces the solidification thermal gradient, eliminates residual stress, suppresses thermal stress cracking, and induces in-situ transformation of coarse columnar crystals to fine equiaxed crystals (CET), significantly improving the forming accuracy, metallurgical structure, and mechanical properties of complex structures.

[0023] This invention not only effectively reduces the solidification temperature gradient, eliminates internal residual stress and hot cracks, but also utilizes the local Marangoni effect to construct virtual supports to suppress gravity collapse in areas with large-angle overhangs and thin-walled corners, and induces in-situ transformation of coarse columnar crystals into fine equiaxed crystals, thus significantly improving the forming accuracy and comprehensive mechanical properties of high-performance metal components. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 A flowchart of a method for directional energy deposition using dynamic coordination of high and low power lasers disclosed in some embodiments of the present invention; Detailed Implementation It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. As described in the background section, there are shortcomings in the existing technology. In order to solve the above-mentioned technical problems, this invention proposes a method and system for directional energy deposition with dynamic coordination of high and low power lasers.

[0027] The directional energy deposition method for dynamic coordination of high and low power lasers proposed in this embodiment includes the following steps: S1: Initialization of the Coordinated Heat Source System A collaborative heat source system consisting of a high-power main laser and a low-power auxiliary laser is established. Through optical alignment and focal plane calibration, the ring or multiple ring-shaped light spots of the auxiliary laser are coaxially or symmetrically wrapped around the high-power main laser light spot. The coaxial powder feeding module and the vision and infrared monitoring module are aligned with the homogeneous matrix of the spatial coordinate system. S2: High-energy melting deposition using a main laser According to the preset first process parameter package, the high-power laser module is driven to project a high-energy-density central main spot onto the metal powder fed into the predetermined deposition area of ​​the substrate, thereby constructing a heat transfer pool in a non-deep melting state and realizing the melting of the metal powder and the deposition and shaping of the liquid metal body. S3: Spatiotemporal Reconstruction of the Annular Auxiliary Thermal Field The synchronously driven low-power auxiliary laser module outputs a ring or split multi-beam auxiliary heat source to act on the periphery of the heat transfer molten pool. According to the motion vector of the instantaneous scanning path, the energy density of different quadrants of the ring spot is dynamically and asymmetrically distributed. A transient preheating zone is constructed in front of the scan, and a delayed cooling zone is constructed behind the scan, so as to realize the in-situ reconstruction of the temperature field gradient between the solidification front of the molten pool and the solid phase transition zone. Specifically, the spatial distribution of energy density within the annular auxiliary spot projected by the low-power auxiliary laser module must undergo asymmetric transformation based on the scanning motion velocity vector v output in real time by the path control system. The homogeneous decoupling control matrix formula for the central controller to control the auxiliary laser to perform dynamic deflection and topological deformation in the spatial coordinate system is shown in the following formula (1): Formula (1) The meanings of the parameters in the above formula are as follows: : A continuous processing time variable, measured in seconds (s). It serves as the fundamental time variable in the entire formula, characterizing the entire processing deflection process as a dynamic process that evolves continuously with high frequency over time.

[0028] The dynamic coordinate deflection of the geometric energy center of the low-power auxiliary laser at time t, relative to the center of the main laser's optical axis along the X-axis of the processing plane (XY plane), is expressed in millimeters (mm). This variable is directly mapped to the instantaneous control voltage or current digital signal that controls the deflection angle of the drive motor of the X-axis deflection galvanometer in the auxiliary laser module.

[0029] The dynamic coordinate deflection of the geometric energy center of the low-power auxiliary laser at time t, relative to the center of the main laser's optical axis along the Y-axis of the processing plane (XY plane), is expressed in millimeters (mm). This variable is directly mapped to the instantaneous control voltage or current digital signal that controls the deflection angle of the drive motor of the Y-axis deflection galvanometer in the auxiliary laser module.

[0030] θ(t): At the current time t, the real-time angle (heading angle) between the instantaneous scanning motion velocity vector v of the forming head and the reference X-axis of the forming plane (XY plane), in radians (rad). This value is intercepted and read in real time by the central controller 107 from the trajectory interpolator of the scanning path control system 109 at a frequency of ≥200Hz during the processing. Its control function is to drive the rotation transformation matrix in the formula, so that the entire auxiliary spot follows the curve motion of the printing trajectory, such as turning and circling, and rotates synchronously at the same angle in real time.

[0031] fs: The fundamental scanning frequency of the auxiliary laser, measured in Hertz (Hz), is used to construct a closed ring, elliptical, or saddle-shaped topology in space by scanning the space through a biaxial galvanometer. In this invention, the preferred range is 200Hz-1000Hz. This frequency is much higher than the thermal time constant of heat conduction and solidification in the molten metal pool, thus the auxiliary laser does not macroscopically appear as a discrete point heat source, but rather as an equivalently continuous and stable ring-shaped auxiliary gradient thermal field around the molten pool.

[0032] ampx: The reference scanning amplitude gain of the auxiliary laser biaxial galvanometer system in the X-axis direction of the processing plane, in millimeters (mm). This constant variable determines the geometrical macroscopic span (such as the major axis radius of an ellipse) of the constructed basic annular auxiliary thermal field in the X-direction.

[0033] ampy: The reference scanning amplitude gain of the auxiliary laser biaxial galvanometer system in the Y-axis direction of the processing plane, in millimeters (mm). This constant variable determines the geometric macroscopic span (such as the minor axis radius of an ellipse) of the constructed basic annular auxiliary thermal field in the Y direction.

[0034] gx: Spatial asymmetric distortion correction and morphology adjustment coefficient, which is a dimensionless constant or a control variable rewritten in real time by the control module. Its control function is to multiply it by the sin(2πfst) term during trajectory flow, artificially scaling the amplitude of the basic sine waveform, thereby stretching or distorting the perfect circular ring spot into an asymmetric saddle shape.

[0035] gy: Spatial asymmetric distortion correction and morphology adjustment coefficient, which is a dimensionless constant or control variable. Its control effect is that during trajectory flow, it is multiplied by the cos(2πfst) term, and together with g_x, it performs asymmetric redistribution of the local energy flux density of the light spot in the longitudinal direction of the processing plane.

[0036] L(t): At time t, the dynamic spatial displacement (translation scalar) of the overall energy centroid of the low-power auxiliary laser ring thermal field relative to the geometric center of the high-power main laser optical axis, in millimeters (mm). The core control function of this variable is to introduce a time-decoupled thermal input mechanism in the spatiotemporal dimension: by making... L(t)>0, forcibly pulls the energy center of gravity of the auxiliary spot along the front or back of the scanning direction, thereby accurately separating the preheating zone at the forefront of the movement and the slow cooling annealing zone dragged behind the molten pool in the space.

[0037] Specifically, the asymmetric dynamic adjustment of the spot energy density is achieved through the following spatial mapping matrix, as shown in formula (2): Formula (2) In the formula, Power allocation for the front preheating zone Power is allocated to the rear slow-cooling area. Power is allocated to the stable regions on both sides of the boundary; To assist the total output power of the laser; This is the real-time angle between the current scanning motion vector and the reference coordinate axis of the forming plane; This represents the accumulated deposition height of the current layer; , , This is the power-weighted adjustment coefficient for the corresponding region.

[0038] S4: Multidimensional transient topography visual in-situ capture The molten pool visual monitoring module is used to collect the instantaneous width of the heat transfer molten pool, the geometric features of the three-dimensional molten pool boundary morphology, and the transient fluctuation frequency of the edge of the liquid metal micro-region online in real time. At the same time, the number of splash particles ejected from the molten pool per unit time and the burst frequency are identified and counted through image edge segmentation. S5: Decoupling of Infrared Radiation Temperature Field Information The infrared temperature acquisition module captures the radiation intensity distribution of the molten pool and its surrounding heat-affected zone in situ. After grayscale decoupling and real-time emissivity correction, it is converted into continuous temperature field control information, including the highest temperature at the center of the molten pool, the temperature gradient at the solid-liquid boundary of the molten pool, and the cooling slope of the solidification at the tail. S6: Evaluation of Molten Pool Stability and Derivation of MPC Model The control module calculates the comprehensive index parameters of molten pool stability online in real time based on the transient morphology data and temperature field control information input in steps S4 and S5, and substitutes the current state as the initial boundary condition into the built-in model predictive control (MPC) model to solve the molten pool instability probability and morphology deviation trend in the future prediction window. Furthermore, the model predictive control model employs an adaptive closed-loop algorithm for control. The adaptive closed-loop algorithm uses the main laser power, auxiliary laser power, scanning speed, and powder feeding rate as control inputs, and the real-time maximum temperature of the molten pool, the instantaneous width of the molten pool, and the deposition layer height as state variables. Based on the state variables collected at the current moment, it predicts the evolution of the molten pool state within a specific time step in the future through a preset system state space equation, and outputs dynamic correction instructions for the dual laser output parameters in advance.

[0039] Specifically, the mathematical formulas in the adaptive closed-loop model of model predictive control (MPC) are as follows. In order to prevent the deep melting keyhole from collapsing or the gravity flow from burning down in complex and special structural areas, the control module deeply integrates a forward-looking model predictive control (MPC) algorithm.

[0040] 1. Discrete State-Space Prediction Equations The discretized state-space matrix equations established within the central controller for forward prediction of the dynamic evolution trend of the molten pool within several sampling steps are shown in equations (3) and (4): X(k+1)=A·X(k)+B·U(k)+d(k) Formula (3) Y(k)=C·X(k) Formula (4) Where: k: discrete sampling period time step variable (i.e., discrete time base), dimensionless. In this system, the time span corresponding to each k is equal to the hardware sampling period of the control system. t (preferred setting is) t=5ms).

[0041] X(k): At the current sampling time k, the system state vector characterizing the dynamic properties of the directional energy deposition molten pool and its morphology metallurgical properties is represented as a 3×1 column matrix, consisting of three components with definite physical meaning and units, namely X(k)=[T(k),W(k),Hz(k)] T : T(k): At time k, the real-time highest temperature value of the central region of the molten pool surface, which is collected in situ by the infrared temperature detection system 105 and transmitted to the controller, in degrees Celsius (°C).

[0042] W(k): At time k, the instantaneous width of the geometric contour of the molten pool extracted by the visual inspection system 104 through digital image edge segmentation, in millimeters (mm).

[0043] Hz(k): At time k, the actual accumulated deposition height of the current layer and historical stacked layers in the Z-axis direction perpendicular to the processing plane, in millimeters (mm).

[0044] U(k): At the current sampling time k, the external control input vector that the system directly applies to the actuator is represented as a 3×1 column matrix, which consists of three core control components, i.e., U(k) = [P main (k),P aux (k),F(k)] T : P main (k): The dynamic power value of the main melting laser output by the high-power laser module at time k, in watts (W).

[0045] P aux (k): The dynamic total power value of the auxiliary laser output by the low-power auxiliary laser module at time k, in watts (W).

[0046] F(k): The dynamic powder feeding rate of the coaxial powder feeding system at time k, in grams per minute (g / min).

[0047] d(k): At time k, the unpredictable external random thermal resistance and heat transfer disturbance vector of the system are represented by a 3×1 column matrix. It is used to characterize the nonlinear thermal disturbance caused by abrupt changes at the matrix edge, deterioration of interlayer heat dissipation conditions, and local fluctuations in powder flow.

[0048] A: The system state transition matrix is ​​represented as a 3×3 two-dimensional constant array. Its internal coefficients were determined by the previous identification of the heat and mass transfer system of the additive manufacturing molten pool and the experimental thermodynamic fitting data, which profoundly characterizes the inherent physical laws of heat conduction, heat diffusion and the self-evolution of the molten pool volume over time.

[0049] B: The system control input matrix is ​​represented as a 3×3 two-dimensional constant array. Its internal coefficients quantitatively characterize the physical sensitivity and heat transfer coupling coefficient of the effect on the maximum temperature of the molten pool, the width of the molten pool, and the height of the deposited layer at the next moment when the main laser power, auxiliary laser power, or powder feeding rate undergoes a unit step change.

[0050] C: Output observation matrix, represented as a diagonal matrix. Its control function is to map the internally hidden state vector X(k) into a system observation output vector Y(k) that can be directly read by external sensing devices.

[0051] Y(k): The system observation output vector, which is usually numerically equivalent to the dataset directly measured by vision and infrared hardware.

[0052] 2. Parametric equations for the comprehensive index of molten pool stability based on multi-feature fusion In order to quantitatively assess whether the molten pool is about to experience keyhole collapse, spatter runaway, or gravity collapse, the control module calculates the dimensionless comprehensive index parameter S(k) of the molten pool stability in real time, and its mathematical expression is shown in formula (5): Formula (5) S(k): The dimensionless comprehensive stability index parameter of the molten pool calculated at the current sampling time k. This value is a real number between 0 and infinity. When S(k) ≤ 1.0, the molten pool is determined to be in a steady-state flow state completely dominated by the heat transfer mechanism; when S(k) > 1.0, pathological instability has occurred inside or at the edge of the molten pool, and the system will forcibly activate the abnormal closed-loop suppression protection.

[0053] sigmaW(k): The statistical standard deviation of the molten pool width continuously captured by the vision inspection system 104 within a sliding time window (preferably spanning Δtau_window = 50ms, i.e., including the most recent 10 sampling history points) traced back from the current k-th time, in millimeters (mm). This metric is extremely sensitive in detecting whether the edges of the molten pool's three-phase lines are experiencing high-frequency, violent oscillations or excessive lateral flow.

[0054] W: The statistical average baseline value of the expected geometric width of the molten pool preset for the current layer thickness in process database 106, in millimeters (mm). As the denominator, it serves to perform dimensionless normalization of the molten pool width fluctuation.

[0055] T(k): The statistical standard deviation of the highest temperature field on the surface of the molten pool, measured by the infrared temperature detection system 105, within the same sliding time window traced back from the current k-th time, in degrees Celsius. This index quantitatively characterizes whether there are drastic unsteady temperature fluctuations caused by localized heat accumulation inside the molten pool.

[0056] T: The statistical average baseline value of the highest surface temperature of the gold molten pool preset in process database 106, in degrees Celsius. As the denominator, it serves to perform dimensionless normalization of the temperature field fluctuations.

[0057] N splash (k): At the current k-th moment, the system extracts and identifies the total number of splash particles ejected outward from the edge of the liquid molten pool in situ within a unit time (e.g., 1 second) through high-speed digital image processing, in units of individual particles.

[0058] N th The maximum safety threshold for the number of critical splashes preset for the entire system, in units of individual splashes, is preferably set to 50 in this invention for the manufacture of titanium alloys.

[0059] ω1: Dimensionless weighting coefficient for the morphological fluctuation term. In this invention, it is preferably limited to a real constant of 0.3.

[0060] ω2: Dimensionless weighting coefficient for the temperature fluctuation term. In this invention, it is preferably limited to a real constant of 0.3.

[0061] ω3: Dimensionless weighting coefficient for the intensity of the splash burst. In this invention, it is preferably limited to a real constant of 0.4. The sum of the three values ​​satisfies ω1 + ω2 + ω3 = 1.0.

[0062] 3. Objective Functional Equation for Rolling Optimization in MPC Quadratic Programming In each sampling period k, the central controller uses its built-in optimization solver to solve online for the future control input increment sequence that minimizes the objective functional J. The objective functional expression is shown in the following formula (6): Formula (6) J: The objective functional value of discrete rolling optimization, which is a dimensionless scalar value of the comprehensive cost. By solving mathematically to make J approach its minimum value, it can be guaranteed that the processing process perfectly approximates the desired stable state on a macroscopic level.

[0063] ΔU: The core optimization variable to be solved in the entire formula, representing the dynamic step adjustment increment matrix of the future control input vector. That is, ΔU(k) ​​= U(k) - U(k-1), specifically including the main laser power increment ΔP. main , Auxiliary laser power increment ΔP aux And the increase in powder delivery rate ΔF.

[0064] Np: The prediction time step of the MPC algorithm, which is a dimensionless integer constant. In this system, Np is preferably set to 15, which means that the control module can proactively predict the morphology and temperature evolution trend of the melt pool over a period of 15 × 5 ms = 75 ms at the current k-th time.

[0065] Nc: The control time-domain step size of the MPC algorithm, which is a dimensionless integer constant and must satisfy Nc≤Np. In this system, N_c=4 is preferably set. Its physical meaning is that only the first 4 sampling steps in the future are used as the adjustment range of the control weight, so as to significantly reduce the matrix operation of online quadratic programming.

[0066] j: Index variable (counter) for loop iteration in the prediction and control time domains, a dimensionless integer.

[0067] Y(k+j|k): Based on the system state observed at the current k-th time, output the prediction vector for the melt pool observation at the future forward prediction time k+j.

[0068] Yref The desired gold output vector constant preset in the process parameter database 106 is determined by the optimal target temperature T_target and the optimal target width W. target The control target benchmark is formed.

[0069] : The diagonal quadratic norm of the weighted matrix. Here, Q is the diagonal matrix of state tracking error weights, represented as a 2×2 positive definite matrix. The magnitude of each diagonal element quantitatively adjusts the degree of penalty imposed by the control module on tracking deviations.

[0070] : The diagonal quadratic norm of the weighted matrix. Here, R is the diagonal matrix penalized for the rate of change of the control input, represented as a 3×3 positive definite matrix. Its diagonal elements prevent potentially severe power oscillations in the actuator.

[0071] Large-coefficient relaxation factor or overlimit penalty constant coefficient, dimensionless, which is set to a very large positive real number in the system software (e.g., =10 5 ).

[0072] max(0,S(k)-S max ) 2 : Nonlinear hard-constrained boundary operator. Where S max The critical threshold constant representing the upper limit of safety and stability of the entire system (set as a constant of 1.0 in this invention) is used. The control logic of this operator is as follows: as long as the current molten pool stability index S(k) is within the safe steady-state region of 1.0, the output value of the entire operator is 0, and the hard penalty term at the end of the formula is completely invalidated; once the current or predicted future state causes S(k)>1.0, this term instantly triggers a huge penalty cost, forcing the system to make reverse fine adjustments at the microsecond level, forcibly extinguishing any molten pool instability state that may cause defects at the physical initiation stage.

[0073] Furthermore, the system objective optimization function J, which is solved in each rolling iteration of the predictive control adaptive closed-loop algorithm, is represented by formula (7): Formula (7) In the formula, To predict the time-domain step size, To control the time-domain step size; and These represent the predicted maximum temperature and instantaneous width of the molten pool at the current k-th time, respectively, at the future k+j-th time. and These are the set reference target temperature and target width of the molten pool, respectively; and These are the control step adjustments for the main and auxiliary laser power, respectively. , This refers to the weighting coefficient for the state tracking deviation. , To control the input suppression weight coefficient.

[0074] Furthermore, the method for calculating the comprehensive index parameter S of the molten pool stability is as follows: Formula (8) In the formula, and These are the statistical average and standard deviation of the molten pool width collected within the current slip time window, respectively. and These represent the mean and standard deviation of the highest surface temperature of the molten pool collected within the same slip time window; This refers to the total number of splash particles counted per unit time. This is a preset critical splash quantity threshold limit; , , These are dimensionless weighting coefficients that are independent of each other.

[0075] S7: Hot Input Dual Laser Proportional Dynamic Closed-Loop Mapping The control module and dynamic power allocation module output joint control commands for the high-power laser module drive current and the low-power auxiliary laser module modulation signal in real time within microseconds based on the rolling optimization results of the MPC model, and dynamically fine-tune the instantaneous output ratio of the main laser power and the auxiliary laser power. S8: Dynamic gradient thermal field adaptive stabilization forming The system maintains a closed-loop flow of the above steps during the full-path scanning process, and adaptively reconstructs the dynamic gradient thermal input field in thin-walled, abrupt corner, and large-angle overhang regions to achieve stable additive manufacturing with defect suppression and microstructure refinement.

[0076] The above method actively avoids and eliminates the formation of deep-melting keyholes, ensuring that the entire processing remains in a stable "non-deep-melting heat transfer pool" state. By constructing a synergistic heat input mechanism spatially enveloped by an asymmetric annular gradient thermal field, and introducing model predictive control (MPC) with forward-looking adaptive closed-loop regulation in time, the solidification thermal gradient is fundamentally reduced, residual stress is eliminated, and thermal stress cracking is suppressed. Furthermore, it induces in-situ transformation of coarse columnar crystals to fine equiaxed crystals (CET), significantly improving the forming accuracy, metallurgical structure, and mechanical properties of complex structures.

[0077] Furthermore, this embodiment proposes a directional energy deposition system with dynamic coordination of high and low power lasers, such as... Figure 1As shown, the overall hardware connection topology and electrical signal interaction architecture of the high- and low-power laser dynamic coordinated directional energy deposition system proposed in this invention are as follows: High-power laser module: Its core hardware includes a continuous fiber laser with a maximum output power of 3000W and a working center wavelength of 1064nm. This laser is connected to the main focusing probe inside the directional energy deposition head via a flexible transmission fiber. It is used to project a central main spot with a diameter of 1.5mm-2.5mm and a high-energy-density Gaussian or parallel distribution onto the geometric center of the deposition area. The core function of this system is to provide a pure heat transfer and melting heat source, enabling the metal powder delivered by the powder feeding channel to rapidly melt on the substrate surface.

[0078] Low-power auxiliary laser module: Its core hardware includes a near-infrared semiconductor laser with a maximum output power of 500W and a working center wavelength of 980nm. The optical output end of this laser integrates a high-speed dual-axis deflection mirror system (consisting of a set of mutually perpendicular X-axis and Y-axis coated mirrors and a matching high-speed galvanometer drive motor) or a variable diffraction optical element (DOE). This auxiliary thermal input system is connected to the analog / digital output port of the central controller 107 via signal lines, receiving microsecond-level voltage deflection signals to dynamically shape and deflect the auxiliary laser into a continuous ring, saddle, elliptical, or multi-beam auxiliary spot composed of multiple discrete sub-spots tightly surrounding each other.

[0079] For the deposition manufacturing optimization of Ti-6Al-4V titanium alloy material, the main laser power output of the high-power laser module ranges from 1000W to 4000W, and the total auxiliary laser power output of the low-power auxiliary laser module ranges from 100W to 1000W. The instantaneous power distribution ratio P_aux / P_main between the two is continuously adjusted in real time between 0.05 and 0.35 according to the geometric characteristics of the deposition area.

[0080] The coaxial powder feeding system includes a high-precision dual-cylinder scraper or rotary powder feeder, using high-purity argon as the powder carrier gas. It connects via multiple powder feeding hoses to four coaxial powder feeding nozzles or a fully enclosed annular coaxial powder feeding nozzle symmetrically distributed around the main optical axis. The feeder's motor driver is connected to the central controller 107 via an industrial bus (such as CANopen or Modbus) to ensure that the spatial convergence center of the metal powder precisely coincides with the optical axis center of the high-power main laser.

[0081] The molten pool vision inspection system includes a high-speed CMOS industrial camera arranged either off-axis or coaxially, with a maximum sampling frequency ≥200Hz. A narrow-band heavy-duty filter with a center cutoff wavelength of 850nm and a bandwidth of ±10nm is installed in the front-end assembly of the camera's imaging lens. The physical function of this filter is to completely shield the strong reflected stray light generated by the 1064nm main laser and the 980nm auxiliary laser on the liquid metal surface, enabling the high-speed industrial camera to capture the two-dimensional light and dark geometric boundary contours of the molten pool in a high-temperature incandescent state in situ. The high-speed camera uploads the digital images to the central controller in real time via a high-speed image transmission bus such as GigEVision or CameraLink.

[0082] The infrared temperature detection system includes a high-resolution long-wave infrared thermal imager (response wavelength range of 8-14 micrometers) or a dual-color full-band radiation thermometer, coaxially or off-axis focused on the main laser's point of action. This infrared detection system is used for real-time in-situ scanning of the infrared radiation intensity inside the molten pool, the solid-liquid contact three-phase interface of the molten pool, and the surrounding heat-affected zone (HAZ). Its internal processor performs real-time grayscale decoupling and emissivity correction, thereby generating a real-time digital two-dimensional temperature field distribution matrix, which is then transmitted to the central controller in real-time via an Ethernet bus.

[0083] Process parameter base database: Built into the non-volatile memory of the central controller or the industrial control computer connected to it, it pre-stores basic process parameter packages (including main laser power reference value, auxiliary laser power reference value, scanning speed reference value and basic powder feeding rate) for different metal materials (such as Ti-6Al-4V titanium alloy, stainless steel, nickel-based high temperature alloy) under different geometric wall thicknesses and different heat dissipation tilt angles.

[0084] Central Controller: The main control brain of the entire system, employing a high-performance multi-core industrial microprocessor (such as an advanced DSP and FPGA co-architecture, or an embedded real-time operating system RTOS). The central controller connects to the vision inspection system and the infrared detection system through high-speed input / output interfaces, reads the two-dimensional transient characteristic data of the molten pool, runs the dynamic spatial flow matrix and MPC model predictive control algorithm on the board, and outputs deflection commands and power adjustment signals to the actuators at high speed.

[0085] Dynamic power distribution module: Composed of a high-frequency digital switching power supply driver module, a high-speed serial control bus (such as EtherCAT), and actuators. This system can respond to the optimized adjustment voltage or PWM duty cycle signal output by the central controller within microseconds (≤10µs) to quickly change the pump drive current of the main and auxiliary lasers, thereby achieving high-speed fine-tuning of laser power.

[0086] Scanning path control system: This includes a multi-axis linkage CNC numerical control system or a 6-axis high-precision industrial robot. The system is connected to the central controller 107 via a numerical control bus and is used to precisely manipulate the deposition head relative to the substrate to complete spatial vector movement along a predetermined three-dimensional slicing path.

[0087] The main laser beam output by the high-power laser module is positioned in the central region of the molten pool, and the auxiliary laser beam output by the low-power auxiliary laser module is arranged in a ring or split multi-beam ring distribution structure around the main laser beam in space, thereby creating a spatial gradient thermal field around the main molten pool.

[0088] Furthermore, the low-power auxiliary laser module is equipped with a dynamic optical shaping element or a high-speed dual-axis galvanometer system. By linking with the system's instantaneous scanning motion vector v, it controls the auxiliary laser beam to form a preheating region in front of the scanning direction, a slow cooling region in the rear of the scanning direction, and boundary stabilization regions on both sides of the scanning direction, thereby constructing a three-segment moving thermal field topology structure of "preheating zone - melting zone - slow cooling zone".

[0089] Furthermore, the control module runs an adaptive closed-loop algorithm based on model predictive control (MPC). The adaptive closed-loop algorithm uses the main laser power P_main, the auxiliary laser power P_aux, the scanning speed v, and the powder feeding rate F as control inputs, and the real-time maximum molten pool temperature T, the instantaneous width of the molten pool W, and the deposition layer height H as state variables. Based on the state variables collected at the current moment, the control module predicts the evolution of the molten pool state within a specific time step in the future through a preset system state space equation, and outputs dynamic correction instructions for the dual laser output parameters in advance.

[0090] Furthermore, the low-power auxiliary laser module adopts an externally modulated pulse output mode or an internally controlled frequency amplitude modulation pulse mode, with a pulse output frequency range of 10Hz to 500Hz and a base power to peak power ratio of 0.1 to 0.5, in order to periodically disturb the local thermal balance at the solid-liquid interface around the molten pool, thereby reducing the temperature field fluctuation at the edge of the molten pool and blocking the extension of coarse columnar crystals in situ.

[0091] Specific application examples of extreme structures for high-performance metallic materials are as follows: Example 1: Adaptive shape and performance control implementation in areas with narrow, thin-walled stiffeners and sharp 90° turns. This embodiment is used to form and manufacture a Ti-6Al-4V titanium alloy aircraft fuselage reinforcing rib plate component with a continuous variable cross section, a wall thickness of only 2.0 mm, and a high cross density of 90 sharp corners.

[0092] Initial process parameter package configuration: Spherical vacuum atomized Ti-6Al-4V titanium alloy powder (particle size normally distributed between 45 μm and 105 μm) was selected. The central controller called the basic database and issued initialization process parameter commands: the main continuous laser power reference value of the high-power laser module was set to P. main-0 =1500W (circular Gaussian spot, focal plane spot diameter 2.0mm); the dual-axis galvanometer operation formula (1) controlled by the low-power auxiliary laser module 2, fundamental scanning frequency f s Set to 400Hz, amplitude gain parameter amp x =1.5mm, amp y =0.75mm, distortion coefficient g x =1.2,g y =0.8. This parameter configuration will set the power to P. aux_0 An auxiliary laser of 260W is spatially shaped and deflected into an asymmetric elliptical ring spot with a major axis of 3.6mm and a minor axis of 1.2mm. The initial power ratio P of the two laser beams is... aux_0 / P main_0 Precisely locked at 0.173. The baseline scanning travel speed v0 = 12 mm / s, and the baseline coaxial powder feeding rate F0 = 9.5 g / min. The forming chamber is filled with high-purity argon gas, maintaining a residual oxygen concentration ≤40 ppm.

[0093] Spatiotemporal adaptive control operation process: During the scanning of the straight, narrow, thin-walled section of the rib, the central controller 107 keeps the displacement scalar in the deflection formula (1) at ΔL = 1.2 mm. At this time, the overall energy center of gravity of the ring-assisted laser is forward-biased along the direction of robot travel. At this time, the real-time temperature gradient G at the liquid-solidification boundary at the edge of the molten pool, measured by the infrared and vision systems, remains at 2.4 × 10⁻⁶ mm. 4 The lower level of K / m, compared to 1.2 × 10⁻⁶ for a single laser system. 5 K / m decreased by nearly an order of magnitude.

[0094] When the robot maneuvered its head to a sharp 90° turn, its speed dropped from 12 mm / s to 4.5 mm / s in an instant due to the robot's mechanical deceleration interpolation. Local heat accumulated explosively at the sharp turn. The infrared temperature monitoring system 105 immediately detected that the highest temperature T(k) of the molten pool suddenly rose to 1820℃ (the expected gold target temperature T_target=1670℃, temperature deviation ΔT=-150℃). At the same time, the vision system 104 processed that the molten pool collapsed and flowed laterally due to the sudden decrease in surface tension caused by overheating (instantaneous width W(k)=2.5mm, process reference width W_target=2.0mm, width deviation ΔW=-0.5mm). At this time, due to the simultaneous exceedance of the morphology variance and temperature variance, the dimensionless molten pool stability index parameter S(k) calculated in real time by formula (5) soared to 1.18 (exceeding the safety critical limit S_max=1.0).

[0095] The MPC quadratic programming solver in the central controller performs rolling optimization of formula (6), and the end penalty term of the objective functional J is activated. Within 5ms after receiving the instability precursor data, the central controller 107 sends a multi-variable linkage fine-tuning command to the actuator through the control bus: the command dynamic power distribution system 108 quickly reduces the main continuous laser power P_main from 1500W to 1120W (attenuation of 25.3%), actively reducing the overall heat input inside the overheated molten pool and preventing the thin-walled corner edge from being melted through and flowing; at the same time, in order to compensate for the tendency of rapid cooling cracks at the solidification front caused by the decrease in main continuous laser power, the command low-power auxiliary laser module 2 increases its total output power P_aux from 260W to 340W against the trend, and starts the deflection matrix formula (1) to instantly perform centrifugal translation of the energy center of the saddle-shaped auxiliary spot to the outer edge of the arc of the corner; the powder feeding system simultaneously reduces the instantaneous powder feeding rate F to 6.5g / min.

[0096] Application effect: Through this precise decoupling and fine-tuning, the morphological geometric error of the thin-walled corner region was dramatically reduced from ±0.85 mm in traditional single-laser DED to within ±0.12 mm, completely eliminating corner ablation and collapse defects. Electron backscatter diffraction (EBSD) microstructure analysis of the entire micro-area showed that, due to the gentle thermal management of the solidification path by the slow cooling zone at the auxiliary laser tail, the temperature gradient at the liquid-solid solidification front was precisely controlled, successfully triggering the transformation from columnar to equiaxed crystals (CET) in situ within the formed part. The coarse, elongated β-columnar crystals that penetrate dozens of deposition layers during traditional single-laser manufacturing completely disappeared. Without adding any external nucleating agents, an ultrafine needle-like α+β equiaxed crystal structure with uniform distribution throughout the entire area and no obvious orientational anisotropy was obtained, with an average grain size of only 6.8 micrometers. The tensile strength of the component along the vertical stacking direction (Z-axis) reaches 1025MPa, and the elongation after fracture is 13.5%; the tensile strength along the scanning plane direction (XY plane) is 1040MPa, and the elongation after fracture is 14.0%. The anisotropic strength difference is only 1.4%, and the comprehensive mechanical behavior is close to that of forgings of the same material.

[0097] Example 2: Implementation of stable closed-loop net forming of a hollow casing with a 45° large-angle suspension and no support. This embodiment is used to directly form a large-angle suspended thin-walled unsupported structure with an outward tilt angle of up to 45° on the surface of a hollow casing under extremely complex spatial conditions without adding any external physical tooling or printing any external metal or graphite physical support.

[0098] Initial process parameter package configuration: Spherical Ti-6Al-4V titanium alloy powder was selected. The central controller 107 issued the initial process command: main continuous laser power reference value P. main_0 =1800W (circular flat-top beam, 2.5mm in diameter). The low-power auxiliary laser module 2 switches to a finely controlled external frequency-modulated pulse output mode, setting its initial average power P. aux_0 =360W, pulse modulation output frequency set to 150Hz, pulse duty cycle set to 35%. Based on these pulse parameters (duty cycle = pulse width / pulse period), the peak power output of the auxiliary laser is physically equal to P. peak =P average The duty cycle is 360 / 0.35 = 1028W, and the base power is physically equal to P_base = 0W. The auxiliary spot is shaped into an asymmetric semi-annular saddle-shaped structure by an optical shaper, symmetrically covering the side of the molten pool facing the suspended outer edge. The reference scanning speed is v = 15mm / s, and the reference coaxial powder feeding rate is F = 12.5g / min.

[0099] Spatiotemporal dynamic collaborative control operation process: When depositing to the 32nd layer of the overhanging unsupported front, the thermal resistance inside the molten pool changes abruptly due to the lack of heat conduction and dissipation from the solid substrate on one side. Without closed-loop control, the liquid metal will experience severe downward drooping under the combined force of gravity and the impact force of the coaxial high-pressure carrier gas, leaving a large amount of slag and inclusions on the casing surface.

[0100] At this point, the system's molten pool visual inspection system, in situ and in real-time, captured a severe distortion in the aspect ratio of the molten pool, causing a sharp increase in the geometric variance of the molten pool width within the calculated continuous slip time window. =0.22mm. Simultaneously, the two-dimensional matrix of the digital temperature field scanned by the infrared temperature acquisition module 105 showed a large area of ​​asymmetric overheating at the outer edge of the molten pool, and the calculated statistical standard deviation of the temperature field soared to... =52℃. The image recognition module statistically analyzes the frequency N of splashes per unit time online and in situ. splash The number of cases surged to 145 (preset safety threshold limit N). th =50). The central controller 107 onboard operating stability formula (5) quickly calculates the current molten pool stability index parameter as S(k)=0.3×(0.22 / 2.5)+0.3×(52 / 1650)+0.4×(145 / 50)=1.196. It is determined that the hard constraint boundary has been broken, and the molten pool is about to undergo macroscopic gravitational flow and collapse.

[0101] Within 4ms of receiving the out-of-limit signal, the MPC adaptive optimization solver running in the control module proactively outputs the optimal joint adjustment matrix for quadratic programming: instructing the dynamic power allocation system 108 to rapidly increase the main continuous laser power P main By reducing the absolute volume and mass of the liquid metal in the molten pool by 18% (instantly reducing it from 1800W to 1476W), the absolute hydrodynamic driving force of gravity collapse is reduced from the physical source. At the same time, the control module outputs a pulse frequency control amplitude modulation signal, which steps up the pulse output frequency of the low-power auxiliary laser module 2 from 150Hz to 350Hz, and forcibly increases its modulation peak power to 1200W, increasing the auxiliary pulse duty cycle to 50%. Meanwhile, the driving galvanometer rotation formula (1) rapidly compresses the energy center of the high-frequency pulse semi-circular saddle-shaped spot towards the outermost boundary line of the overhanging region.

[0102] Application effect: The high-frequency pulsed laser generates high-frequency micro-amplitude temperature field oscillations at the outer edge of the suspended molten pool, cleverly utilizing the non-uniform instantaneous thermal expansion of the micro-regions at the liquid metal boundary to excite a reverse transient thermal stress field within the liquid metal. This thermal stress field, combined with a localized strong surface tension gradient (Marangoni Effect), constructs a virtual "thermal tension air support wall" in physical space, perfectly counteracting the downward flow tendency imposed by the powder carrier gas and gravity. The unstable suspended molten pool completely recovers equilibrium within 0.18s, and S(k) falls back to the steady-state region of 0.45. The final 45° large-angle outward-expanding suspended wall panel has a smooth and dense surface with a surface roughness Ra≤7 micrometers and no localized flow or slag. Industrial CT flaw detection revealed no unfused inclusions or unstable pores caused by molten pool fluctuations, and the overall internal metallurgical density reached an extremely high level of 99.9%.

[0103] Example 3: Implementation of "Time Dislocation" Crack-Resistant Forming of Gradient-Cast Crack-Sensitive Hard Alloy on Matrix Surface This embodiment is used to directly and directionally deposit a Stellite6 cobalt-based hard wear-resistant alloy layer on the surface of a common 316L austenitic stainless steel substrate. This layer is extremely sensitive to hot cracking and is prone to large-area macroscopic cold cracking due to huge differences in the coefficient of linear expansion.

[0104] Timing adaptive control operation process: The main continuous laser power is set to P main =2000W, the maximum total output power of the low-power auxiliary laser is set to P. aux_max =450W. The head travel speed v=10mm / s, and the reference powder feeding rate F=15g / min. The central controller 107 performs the following three-stage time-series dynamic control on the time misalignment translation scalar in formula (1) during processing: 1. First stage (preheating stage): Before the main continuous laser axis reaches the preset deposition point A on the processing plane, the path control system 109 moves first. The displacement in the instruction formula (1) of the central controller 107 is ΔL=+4.0mm (the positive sign indicates that it moves forward along the direction of movement). At this time, the low-power auxiliary laser (102) is activated first, and its large-area annular spot's gravity energy density end acts on point A Δt1=ΔL / v=4.0mm / 10mm / s=0.4s earlier than the main laser. The auxiliary laser, with a maximum power of 450W, smoothly preheats the local 316L stainless steel substrate from room temperature to 500℃ in situ before the metal powder flow arrives, thermally activating the substrate surface and reducing subsequent thermal shock.

[0105] 2. Second Stage (Main Melting and Deposition Stage): The main continuous laser then enters the A-point region, which has been thermally activated by the auxiliary laser. At this point, the metal powder smoothly forms a liquid pool in a pure heat transfer mode in an environment with an already elevated temperature (without any signs of deep melting keyholes). The dilution rate is precisely locked within an optimal chemical range of 6.5%, completely avoiding the macroscopic hardness decline caused by excessive dilution of the cobalt-based coating by the iron (Fe) element in the matrix.

[0106] 3. Third Stage (Post-Slow Cooling Annealing Stage): After the main continuous laser leaves the area at point A, the control system switches the offset translation amount to ΔL = -8.0mm (the negative sign indicates that the laser moves away from the direction of motion). The ring-shaped spot of the auxiliary laser spatially switches to a long-tail dragging mode, maintaining a slow cooling zone with a delay of Δt2 = |ΔL| / v = 8.0mm / 10mm / s = 0.8s, lagging behind the main laser. The auxiliary laser continuously covers the solidified metal surface with a moderate annealing power of 180W, controlling the continuous solid-state phase transformation cooling rate in the solid-state phase transformation region of the material to be strictly below 45℃ / s.

[0107] Application effect: By decoupling and controlling the timing of the pre-heating transient process and the post-heating in-situ annealing, the evolution of the elasto-plastic thermal stress field inside the deposited layer was completely altered. Full-size dye penetrant testing (PT) and residual stress blind-hole metallographic analysis showed that the macroscopic stress state at the interface between the deposited layer and the stainless steel substrate was completely reversed from the extremely high tensile stress (+450MPa, highly prone to cracking) of traditional single-laser DED to a safe micro-compressive stress state (-80MPa) or a neutral stress-free state. The macroscopic cold cracking rate and defect rate inside the entire cobalt-based hard wear-resistant coating were 0, the interlayer metallurgical bonding was extremely excellent, and the overall wear-resistant life achieved a leap of more than 35% compared to conventional single-laser components.

[0108] This invention provides a computer-readable storage medium storing a computer program thereon, which, when executed, implements a directional energy deposition method for dynamic coordination of high and low power lasers as described in any embodiment of this invention.

[0109] This invention provides a computer program product, which includes a computer program stored on a non-transitory computer-readable storage medium. The computer program includes program instructions, wherein when the program instructions are executed by a computer, the computer performs a directional energy deposition method for dynamic coordination of high and low power lasers as described in any embodiment of this invention.

[0110] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0111] In the several embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the shown or discussed mutual couplings, direct couplings, or communication connections may be indirect couplings or communication connections through some interfaces, apparatuses, or units, and may be electrical, mechanical, or other forms. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units, i.e., they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0112] Furthermore, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0113] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes: USB flash drive, portable hard drive, read-only memory (ROM). Various media that can store program code, such as only memory, random access memory (RAM), magnetic disks or optical disks.

[0114] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for directional energy deposition using dynamic coordination of high and low power lasers, characterized in that, as follows: S1. Based on the preset first process parameter package, a high-energy-density main laser is projected onto the metal powder fed into the predetermined deposition area of ​​the substrate to construct a heat transfer pool in a non-deep melting state, thereby realizing the melting of the metal powder and the deposition and shaping of the liquid metal body. S2. An auxiliary laser is projected around the heat transfer molten pool. The heat source of the auxiliary laser dynamically and asymmetrically distributes energy density according to the motion vector of the instantaneous scanning path. A transient preheating zone is constructed in front of the scan, and a delayed cooling zone is constructed behind the scan, so as to realize the in-situ reconstruction of the temperature field gradient between the solidification front of the molten pool and the solid phase transition zone. S3. Online real-time acquisition of the instantaneous width of the heat transfer molten pool, the geometric features of the three-dimensional molten pool boundary morphology, and the transient fluctuation frequency of the edge of the liquid metal micro-region. At the same time, the number of splash particles ejected from the molten pool per unit time and the burst frequency are identified and counted through image edge segmentation to form transient morphology data. S4. The radiation intensity distribution of the in-situ captured molten pool and its surrounding heat-affected zone is converted into continuous temperature field control information, including the highest temperature at the center of the molten pool, the temperature gradient at the solid-liquid boundary of the molten pool, and the cooling slope of the tail solidification, after grayscale decoupling and real-time emissivity correction. S5. Based on the transient morphology data and temperature field control information, calculate the comprehensive index parameters of molten pool stability online in real time, and substitute the current state as the initial boundary condition into the built-in model prediction and control model to solve the molten pool instability probability and morphology deviation trend in the future prediction window in a rolling manner. S6. Based on the rolling optimization results of the model prediction control model, dynamically fine-tune the power ratio between the power corresponding to the central main light spot and the power corresponding to the auxiliary heat source.

2. The directional energy deposition method for dynamic coordination of high and low power lasers as described in claim 1, characterized in that, In step S2, based on the change in the direction angle of the instantaneous scanning motion vector, the asymmetric dynamic adjustment of the spot energy density is performed using the following spatial mapping matrix: In the formula, Power allocation for the front preheating zone Power is allocated to the rear slow-cooling area. Power is allocated to the stable regions on both sides of the boundary; To assist the total output power of the laser; This is the real-time angle between the current scanning motion vector and the reference coordinate axis of the forming plane; This represents the accumulated deposition height of the current layer; , , This is the power-weighted adjustment coefficient for the corresponding region.

3. The method for directional energy deposition with dynamic coordination of high and low power lasers according to claim 1, characterized in that: In step S5, the model predictive control model is controlled by an adaptive closed-loop algorithm. The adaptive closed-loop algorithm uses the main laser power, auxiliary laser power, scanning speed and powder feeding rate as control inputs, and the real-time maximum temperature of the molten pool, the instantaneous width of the molten pool and the height of the deposition layer as state variables. Based on the state variables collected at the current moment, it predicts the evolution of the molten pool state within a specific time step in the future through a preset system state space equation, and outputs dynamic correction instructions for the dual laser output parameters in advance.

4. The method for directional energy deposition with dynamic coordination of high and low power lasers according to claim 3, characterized in that: The system objective optimization function J, which is solved in each rolling iteration of the adaptive closed-loop algorithm, is characterized as: In the formula, To predict the time-domain step size, To control the time-domain step size; and These represent the predicted maximum temperature and instantaneous width of the molten pool at the current k-th time, respectively, at the future k+j-th time. and These are the set reference target temperature and target width of the molten pool, respectively; and These are the control step adjustments for the main and auxiliary laser power, respectively; , This refers to the weighting coefficient for the state tracking deviation. , To control the input suppression weight coefficient.

5. The method for directional energy deposition with dynamic coordination of high and low power lasers according to claim 1, characterized in that: In step S5, the method for calculating the comprehensive index parameter S of molten pool stability is as follows: In the formula, and These are the statistical average and standard deviation of the molten pool width collected within the current slip time window, respectively. and These represent the mean and standard deviation of the highest surface temperature of the molten pool collected within the same slip time window; This refers to the total number of splash particles counted per unit time. This is a preset critical splash quantity threshold limit; , , These are dimensionless weighting coefficients that are independent of each other.

6. A directional energy deposition system for dynamic coordination of high and low power lasers, characterized in that: include: A high-power laser module is configured to project a high-energy-density main laser onto metal powder fed into a predetermined deposition area of ​​the substrate according to a preset first process parameter package, thereby constructing a heat transfer pool in a non-deep melting state and realizing the melting of metal powder and the deposition and shaping of the liquid metal body. The low-power auxiliary laser module is configured to project an auxiliary laser around the heat transfer molten pool. The heat source of the auxiliary laser dynamically and asymmetrically distributes the energy density according to the motion vector of the instantaneous scanning path, constructing a transient preheating zone in front of the scan and a delayed cooling zone behind the scan, thereby realizing the in-situ reconstruction of the temperature field gradient between the solidification front of the molten pool and the solid phase transition zone. The molten pool visual monitoring module is configured to collect the instantaneous width of the heat transfer molten pool, the geometric features of the three-dimensional molten pool boundary morphology, and the transient fluctuation frequency of the edge of the liquid metal micro-region online in real time. At the same time, it identifies and counts the number and burst frequency of the splash particles ejected from the molten pool per unit time through image edge segmentation, forming transient morphology data. The infrared radiation temperature field acquisition and information decoupling module is configured to capture the radiation intensity distribution of the molten pool and its surrounding heat-affected zone in situ. After grayscale decoupling and real-time emissivity correction, it is converted into continuous temperature field control information, including the highest temperature at the center of the molten pool, the temperature gradient at the solid-liquid boundary of the molten pool, and the cooling slope of the solidification at the tail. The control module is configured to calculate the comprehensive index parameters of molten pool stability online in real time based on the transient topography data and temperature field control information, and to substitute the current state as the initial boundary condition into the built-in model prediction control model to continuously solve the probability of molten pool instability and the trend of topography deviation within the future prediction window. The dynamic power allocation module is configured to dynamically fine-tune the power ratio between the main laser and the auxiliary laser based on the rolling optimization results of the model prediction control model.

7. The directional energy deposition system with dynamic coordination of high and low power lasers as described in claim 6, characterized in that: The low-power auxiliary laser module is equipped with a dynamic optical shaping element or a high-speed dual-axis galvanometer system. By linking with the system's instantaneous scanning motion vector v, it controls the auxiliary laser beam to form a preheating region in front of the scanning direction, a slow cooling region in the rear of the scanning direction, and boundary stabilization regions on both sides of the scanning direction, thereby constructing a three-segment moving thermal field topology structure of "preheating zone - melting zone - slow cooling zone".

8. The directional energy deposition system with dynamic coordination of high and low power lasers as described in claim 6, characterized in that: The low-power auxiliary laser module is used to periodically disturb the local thermal balance at the solid-liquid interface around the molten pool, thereby reducing temperature field fluctuations at the edge of the molten pool and blocking the elongation of coarse columnar crystals in situ.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor of the control module, it implements the steps of the directional energy deposition method for dynamic coordination of high and low power lasers as described in any one of claims 1 to 5.

10. A computer program product having a computer program stored thereon, characterized in that, The computer program product includes a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, wherein when the program instructions are executed by a computer, the computer performs the steps of the high- and low-power laser dynamic coordinated directional energy deposition method according to any one of claims 1 to 5.

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