Method for controlling thermal cracking tendency of laser additive manufacturing 6061 high thermal conductivity aluminum alloy

Abstract

The application discloses a method for controlling thermal cracking tendency of 6061 high-thermal-conductivity aluminum alloy for aerospace by laser additive manufacturing. The method comprises the following steps: firstly, the heat transfer behavior of the laser additive manufacturing 6061 alloy in the lap scanning process is calculated to obtain the temperature gradient of the micro-melting pool and meso-melting channel at different positions in the solidification process; then, the influence of the temperature gradient evolution law on the thermal stress of the laser additive manufacturing 6061 alloy is obtained through a thermal-mechanical coupling interface; then, the 6061 alloy samples are printed under different parameters; the model accuracy is verified by comparing the lap pool topography; the cracking influence mechanism is obtained by comparing the thermal cracking distribution law and the key position of the formation; the mapping relationship among the laser additive manufacturing process of the 6061 alloy for aerospace, the thermal stress and the cracking tendency is established; finally, the theoretical model for controlling the forming thermal cracking tendency is obtained, so that the laser additive manufacturing process parameter optimization screening and the forming quality optimization of the 6061 high-thermal-conductivity aluminum alloy for aerospace are realized.

Description

Technical Field

[0001] This invention relates to the fields of laser additive manufacturing and finite element physical simulation calculation, and more specifically, to a method for controlling the thermal cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing. Background Technology

[0002] 6061 aluminum alloy, characterized by high thermal conductivity, moderate strength, and low density, is widely used in the manufacture of key heat dissipation components in aerospace, rail transportation, and other fields. Currently, laser additive manufacturing technology has attracted widespread attention to meet the demands of applications for high-efficiency, customized, and high-precision manufacturing of complex shapes such as heat dissipation channels and grilles. This technology, through layer-by-layer powder deposition, laser scanning path planning, and high-energy laser rapid melting-solidification processes, can achieve automated and rapid manufacturing of complex shapes. Therefore, the use of laser additive manufacturing of 6061 thermally conductive aluminum alloy is one of the current research hotspots in the heat dissipation structure manufacturing industry (E. Cakmak, MN Gussev, TR Watkins, DJ Arregui-Mena, KATerrani, Addit. Manuf. 2021, 48, 102401). However, in the actual laser additive manufacturing process, 6061 thermally conductive aluminum alloy will develop severe thermal cracking, which is one of the key industry challenges limiting its application.

[0003] The high thermal cracking tendency of 6061 aluminum alloy stems from the material's inherent properties and the characteristics of laser additive manufacturing (SZUddin, LE Murr, CA Terrazas, P. Morton, DA Roberson, RB Wicker, Addit. Manuf. 2018, 22, 405-415). Due to the low content of functional elements in thermally conductive aluminum alloys, the primary phase during solidification is α-Al. Under the high cooling rate of laser additive manufacturing, Al grains grow rapidly in columnar and dendritic forms, forming residual liquid films between grains in the later stages of solidification, which crack during solidification shrinkage. Simultaneously, the rapid melting-solidification process of laser additive manufacturing creates a high temperature gradient, resulting in significant differences in expansion and contraction at different locations within the alloy, leading to severe thermal stress. When this thermal stress exceeds the alloy's ultimate strength at high temperatures, crack initiation and propagation occur. Crack defects are critical to the alloy's service performance; under applied stress, they propagate rapidly, causing alloy components to fail.

[0004] Existing research has explored two approaches. First, by adding other functional elements or nucleating agents to refine the aluminum matrix grains, significant thermal stresses in laser additive manufacturing can be dispersed, while simultaneously suppressing the initiation and propagation of hot cracks. However, grain refinement and increased precipitates lead to increased electron scattering, resulting in decreased thermal conductivity of 6061 aluminum alloy (A. Mehta, L. Zhou, T. Huynh, S. Park, H. Hyer, ST. Song, YL. Bai, DD. Imholte, NEWoolstenhulme, DM. Wachs, Y. Sohn, Addit. Manuf. 2021, 41, 101966). Second, by optimizing laser additive manufacturing process parameters to control the intensity and uniformity of thermal stress distribution, the hot cracking tendency of the alloy can be improved without significantly reducing its thermal conductivity (J. Petrusa, T. Palcevski, W. Waldhauser, V. Petrovic-Filipovic, Rapid Prototyping J. 2025, 31, 386-399). However, the current optimization of process parameters is mainly carried out through traditional trial and error methods, which have high testing cycles and costs.

[0005] Finite element simulation provides an innovative and feasible approach for predicting the forming quality of alloys in laser additive manufacturing. By calculating the heat transfer process between the laser heat source and the material, the melting-solidification process can be simulated, which may indirectly reveal the influence mechanism of the hot cracking tendency of aluminum alloys. This is of great significance for guiding the optimization of laser additive manufacturing processes and improving the forming quality of 6061 aluminum alloys. Summary of the Invention

[0006] The purpose of this invention is to provide a method for controlling the hot cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing, so as to reveal the correlation between laser additive manufacturing process, temperature gradient and thermal stress, thereby guiding the optimization of process parameters, improving the hot cracking tendency of 6061 alloy and improving the forming quality.

[0007] According to one aspect of the present invention, a method for controlling the hot cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing is provided, comprising the following steps:

[0008] Step 1: Establish a Gaussian distribution laser heat source model and a powder bed / matrix physical model for laser additive manufacturing of 6061 high thermal conductivity aluminum alloy, and perform physical model mesh generation;

[0009] Step 2: Based on the model established in Step 1, set the laser additive manufacturing process parameters, material properties and heat transfer boundary conditions, and carry out transient heat transfer process calculations;

[0010] Step 3: Based on the temperature distribution data obtained in Step 3, perform mechanical field calculations for laser additive manufacturing of 6061 thermally conductive alloy as boundary conditions;

[0011] Step 4: Based on the results calculated in Step 2 and Step 3, extract the temperature gradient and thermal stress distribution data at different locations in the molten pool, molten channel, and substrate under different laser process parameters to establish the correlation between the two.

[0012] Step 5: Perform powder bed fusion printing based on the laser additive manufacturing process parameters set in Step 2, and verify the model by comparing the molten pool morphology;

[0013] Step 6: Based on the 6061 alloy sample obtained in Step 5, crack statistics are performed, and the crack initiation and propagation behavior is obtained by comparing with the results of Step 4.

[0014] Step 7: Based on the thermo-mechanical coupling calculation results of laser additive manufacturing of 6061 alloy, optimize and screen process parameters based on the principles of minimum and uniform thermal stress distribution.

[0015] Preferably, in step 1, the physical model of the laser heat source is a Gaussian heat source physical model, and the energy distribution satisfies the formula:

[0016] (1)

[0017] Formula (1) A is the laser absorption rate of the powder material, P is the laser power, R is the laser spot radius, (x, y, z) are the spatial coordinates of the laser spot, v is the laser scanning speed, and t is the laser spot movement time.

[0018] Preferably, the powder bed / matrix physical model in step 1 includes a 6061 alloy powder bed and a matrix. The length and width of the model are more than 5 times the size of the laser spot, and the thickness of the powder bed model is 20-50 μm. The model mesh is divided using a gradient meshing scheme, with the powder layer using a fine hexahedral mesh of 0.01-0.03 mm and the matrix using a coarse tetrahedral mesh of 0.03-0.3 mm.

[0019] Preferably, the laser process parameters in step 2 include laser power of 120-250 W, laser spot size of 50-150 μm, laser scanning speed of 100-450 mm / s, and scanning interval of 50-150 μm; the boundary conditions include one or more of the following: heat conduction, heat radiation, heat convection, and initial temperature of 25-200 ℃.

[0020] Preferably, the transient heat transfer process in step 2 is calculated according to the following formula:

[0021] (2)

[0022] In formula (2), k is thermal conductivity, ρ is density, C is specific heat capacity, Q is laser heat source, T is temperature, t is heat transfer time, and (x, y, z) are three-dimensional spatial coordinates.

[0023] Preferably, in step 3, the thermal stress in the mechanical field calculation process obeys the VON MISES criterion:

[0024] (3)

[0025] In formula (3) , , There are three principal stresses in mutually perpendicular directions; the equivalent strain follows:

[0026] (4)

[0027] In formula (4) , , denoted as the three principal strains in mutually perpendicular directions; μ is the Poisson's ratio of the material.

[0028] Preferably, the characteristic locations of the molten pool, molten channel, and matrix in step 4 include the center, boundary, and interface location.

[0029] Preferably, the preferred range of process parameters for laser additive manufacturing in step 5 is as follows: laser power 140-220W, laser spot size 50-100 μm, laser scanning speed 150-400 mm / s, scanning interval 60-120 μm, and initial temperature 100-180 ℃; the molten pool morphology parameters include molten pool shape, melting width, and depth.

[0030] Preferably, the crack statistics results in step 6 include crack density, distribution location, and initiation-propagation path.

[0031] Preferably, in step 7, the optimized laser process parameters are: laser power 180 W, laser spot size 60 μm, laser scanning speed 380 mm / s, scanning interval 70 μm, and initial temperature 140 ℃.

[0032] During the simulation, mesh generation significantly impacts the model's computational efficiency. A gradient meshing scheme, employing a fine hexahedral mesh (0.01-0.03 mm) in the powder bed region and a coarse tetrahedral mesh (0.03-0.3 mm) in the matrix region, improves computational efficiency and convergence while maintaining accuracy. Furthermore, laser energy attenuation during actual printing leads to significant discrepancies between the simulated and actual molten pool morphologies, resulting in poor accuracy in thermal stress control and process parameter optimization. By comparing the error coefficients between the simulated and actual molten pool morphologies, the simulated laser process parameters (absorption rate, laser power, scanning speed, etc.) are corrected, thereby enhancing the accuracy of the simulation results.

[0033] The present invention provides a method for controlling the hot cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing. This method reveals the correlation between process parameters, temperature gradient, and thermal stress in the laser additive manufacturing of 6061 thermally conductive alloy, thereby elucidating the influence mechanism and evolution law of its hot cracking tendency. More importantly, based on the above mechanisms and laws, the thermal stress of 6061 alloy in laser additive manufacturing can be effectively controlled, thereby guiding the optimization and screening of process parameters to reduce the hot cracking sensitivity of alloy forming, improving forming quality, and reducing the trial-and-error costs of process verification.

[0034] Through the above technical solutions, the present invention can achieve the following technical effects:

[0035] 1) Obtain the correlation between process parameters, temperature gradient, and thermal stress in laser additive manufacturing of 6061 aluminum alloy;

[0036] 2) To reveal the influence mechanism of the hot cracking sensitivity of 6061 aluminum alloy in laser additive manufacturing and to obtain the evolution law of hot cracks;

[0037] 3) Based on the results of thermal stress simulation prediction, we can optimize the laser additive manufacturing process, thereby improving the accuracy and success rate of process experiments, which is beneficial to improving the thermal cracking tendency of laser-printed aluminum alloys and improving their forming quality;

[0038] 4) By precisely controlling the laser additive manufacturing process parameters, the hot cracking tendency of 6061 thermally conductive alloy can be improved and the forming quality can be enhanced. Attached Figure Description

[0039] Figure 1 This is a flowchart of a method for controlling the thermal cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing;

[0040] Figure 2 It is a physical model of the heat source and powder bed / matrix for laser additive manufacturing of 6061 high thermal conductivity aluminum alloy;

[0041] Figure 3These are the calculated results of the heat transfer temperature field and the temperature change curves under different process parameters;

[0042] Figure 4 This is a thermal stress distribution cloud map of 6061 high thermal conductivity aluminum alloy produced by laser additive manufacturing;

[0043] Figure 5 These are temperature gradient and stress distribution curves of 6061 high thermal conductivity aluminum alloy under different parameters produced by laser additive manufacturing.

[0044] Figure 6 This is a comparison of the simulated and actual molten pool morphology of 6061 high thermal conductivity aluminum alloy produced by laser additive manufacturing.

[0045] Figure 7 It is the surface crack morphology of 6061 high thermal conductivity aluminum alloy produced by laser additive manufacturing;

[0046] Figure 8 This describes the cross-sectional microstructure of 6061 high thermal conductivity aluminum alloy produced by laser additive manufacturing under different process parameters. Detailed Implementation

[0047] The present invention is described in further detail with reference to the following embodiments, but is not limited to the following embodiments.

[0048] A method for controlling the thermal cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing according to the present invention includes the following steps:

[0049] Step 1: Establish a Gaussian distribution laser heat source model and a powder bed / matrix physical model for laser additive manufacturing of 6061 high thermal conductivity aluminum alloy, and perform physical model division;

[0050] In a preferred embodiment, the laser heat source model in step 1 is a Gaussian heat source, and the energy distribution satisfies the formula:

[0051] (1)

[0052] Formula (1) A is the laser absorption rate of the powder material, P is the laser power, R is the laser spot radius, (x, y, z) are the spatial coordinates of the laser spot, v is the laser scanning speed, and t is the laser spot movement time.

[0053] In a preferred embodiment, the powder bed / matrix physical model in step 1 includes a 6061 alloy powder bed and a matrix. The length and width of the model are more than 5 times the size of the laser spot, and the thickness of the powder bed model is 20-50 μm. The model mesh is divided using a gradient meshing scheme, with the powder layer using a fine hexahedral mesh of 0.01-0.03 mm and the matrix using a coarse tetrahedral mesh of 0.03-0.3 mm.

[0054] Step 2: Based on the model established in Step 1, set the laser additive manufacturing process parameters, material properties and heat transfer boundary conditions, and carry out transient heat transfer process calculations;

[0055] In a preferred embodiment, the laser process parameters in step 2 include laser power of 120-250 W, laser spot size of 50-150 μm, laser scanning speed of 100-450 mm / s, and scanning interval of 50-150 μm; the boundary conditions include one or more of the following: heat conduction, heat radiation, heat convection, and initial temperature of 25-200 °C.

[0056] In a preferred embodiment, the transient heat transfer process in step 2 is calculated according to the following formula:

[0057] (2)

[0058] In formula (2), k is thermal conductivity, ρ is density, C is specific heat capacity, Q is laser heat source, T is temperature, t is heat transfer time, and (x, y, z) are spatial coordinates.

[0059] Step 3: Based on the temperature distribution data obtained in Step 3, perform mechanical field calculations for laser additive manufacturing of 6061 thermally conductive alloy as boundary conditions;

[0060] In a preferred embodiment, the thermal stress in the mechanical field calculation process of step 3 obeys the VON MISES criterion:

[0061] (3)

[0062] In formula (3) , , There are three principal stresses in mutually perpendicular directions; the equivalent strain follows:

[0063] (4)

[0064] In formula (4) , , denoted as the three principal strains in mutually perpendicular directions; μ is the Poisson's ratio of the material.

[0065] Step 4: Based on the results calculated in Step 2 and Step 3, extract the temperature gradient and thermal stress distribution data at different locations in the molten pool, molten channel, and substrate under different laser process parameters to establish the correlation between the two.

[0066] In a preferred embodiment, the characteristic locations of the molten pool, molten channel, and matrix in step 4 include the center, boundary, and interface location.

[0067] Step 5: Perform powder bed fusion printing based on the laser additive manufacturing process parameters set in Step 2, and verify the model by comparing the molten pool morphology;

[0068] In a preferred embodiment, the preferred range of process parameters for laser additive manufacturing in step 5 is as follows: laser power 140-220 W, laser spot size 50-100 μm, laser scanning speed 150-400 mm / s, scanning interval 60-120 μm, and initial temperature 100-180 ℃; the molten pool morphology parameters include molten pool shape, melting width, and depth.

[0069] Step 6: Based on the 6061 alloy sample obtained in Step 5, crack statistics are performed, and the crack initiation and propagation behavior is obtained by comparing with the results of Step 4.

[0070] In a preferred embodiment, the crack statistics in step 6 include crack density, distribution location, and initiation-propagation path.

[0071] Step 7: Based on the thermo-mechanical coupling calculation results of laser additive manufacturing of 6061 alloy, optimize and screen process parameters based on the principles of minimum and uniform thermal stress distribution.

[0072] In a preferred embodiment, the optimized laser process parameters in step 7 are: laser power 180 W, laser spot size 60 μm, laser scanning speed 380 mm / s, scanning interval 70 μm, and initial temperature 140 ℃.

[0073] According to another aspect of the present invention, the present invention provides a method for controlling the hot cracking tendency of 6061 thermally conductive alloy obtained by laser additive manufacturing using any of the above technical solutions, which can obtain the correlation between laser process parameters, temperature gradient and thermal stress, and reveal the influence mechanism and evolution law of hot cracking tendency.

[0074] In a preferred embodiment, the process parameters for laser additive manufacturing of 6061 thermally conductive alloy can be optimized, and the thermal stress intensity and distribution uniformity of the alloy during the manufacturing process can be controlled, thereby reducing the hot cracking sensitivity of 6061 alloy in laser additive manufacturing, improving the forming quality, and improving the accuracy of process verification while reducing verification costs.

[0075] Example 1

[0076] A method for controlling the thermal cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing, the specific implementation steps of which are as follows:

[0077] Step 1: Establish the laser heat source model and powder bed / matrix physical model for laser additive manufacturing of 6061 thermally conductive alloy, and perform physical model mesh generation. The energy distribution of the laser heat source model satisfies the formula:

[0078] (1)

[0079] Formula (1) A is the laser absorptivity of the powder material, P is the laser power, R is the laser spot radius, (x, y, z) are the spatial coordinates of the laser spot, v is the laser scanning speed, and t is the laser spot movement time. Figure 2 As shown, the energy density distribution of the laser heat source follows a Gaussian distribution. The powder bed is assumed to be a thin, integral model with a thickness of 20-50 μm, and it is mechanically assembled with the substrate model. The length and width of the powder bed / substrate model are more than 5 times the size of the laser spot. The model mesh is generated using a gradient meshing scheme, with the powder layer using a fine hexahedral mesh of 0.01-0.03 mm and the substrate using a coarser tetrahedral mesh of 0.03-0.3 mm.

[0080] Step 2: Based on the model established in Step 1, set the laser additive manufacturing process parameters, material properties, and heat transfer boundary conditions, and conduct transient heat transfer analysis.

[0081] Thermal process calculation. Laser process parameters include laser power (120-250 W), laser spot size (50-150 μm), laser scanning speed (100-450 mm / s), and scanning interval (50-150 μm). Boundary conditions include heat conduction, heat radiation, heat convection, and an initial temperature of 140 ℃. The transient heat transfer process calculation follows the formula below:

[0082] (2)

[0083] In formula (2), k is thermal conductivity, ρ is density, C is specific heat capacity, Q is laser heat source, T is temperature, t is heat transfer time, and (x, y, z) are spatial coordinates. The calculated heat transfer temperature distribution is as follows: Figure 3 As shown, the temperature gradually decreases with increasing distance from the center of the molten pool, but the temperature gradient first increases and then decreases; the rate of temperature change is faster the further away from the molten pool. Meanwhile, when the scanning speed remains constant at 380 mm / s, the maximum temperature of the molten pool increases with increasing laser power, its rate of change slows down, and the distance between adjacent isotherms increases.

[0084] Step 3: Based on the temperature distribution data obtained in Step 3, perform mechanical field calculations for laser additive manufacturing of 6061 thermally conductive alloy as boundary conditions. During the mechanical field calculation process, the thermal stress follows the Von Mises criterion.

[0085] (3)

[0086] In formula (3) , , There are three principal stresses in mutually perpendicular directions; the equivalent strain follows:

[0087] (4)

[0088] In formula (4) , , Let μ be the three principal strains in mutually perpendicular directions; μ be the Poisson's ratio of the material. Figure 4 As shown, due to the uneven temperature distribution, significant residual stress is formed in the powder bed / matrix model. With increasing distance from the laser scanning position, the stress exhibits a fluctuating trend of first increasing, then decreasing, and then increasing again, similar to the variation pattern of the temperature gradient. Simultaneously, the thermal stress reaches its maximum value at the interface between the powder bed and the matrix, as well as at the edge regions of the powder bed and matrix model.

[0089] Step 4: Based on the results calculated in Steps 2 and 3, extract the temperature gradient and thermal stress distribution data at different locations in the molten pool, melt channel, and substrate under different laser process parameters to establish the correlation between the two; for example... Figure 5 As shown, temperature gradient and thermal stress data were extracted along the perpendicular forming direction, and their trends were similar. By comparing their distribution patterns and their variation with process parameters, it can be seen that the thermal stress is greatest in the region near the molten pool and at the powder bed-matrix interface; at the same time, due to the faster temperature change rate at low power, the thermal stress in the solidified area is relatively large.

[0090] Step 5: Perform powder bed fusion printing based on the laser additive manufacturing process parameters set in Step 2, and verify the model by comparing the molten pool morphology; such as Figure 6 As shown, when the laser spot size is 80 μm, the laser scanning speed is 380 mm / s, the laser scanning interval is 180 μm, and the initial temperature is 140 ℃, the matching degree of the melting width and depth of the simulated and printed melt pools is high at a laser power of 200 W, with an error of less than 15%.

[0091] Step 6: Based on the crack statistics of the 6061 alloy samples obtained in Step 5, the crack initiation and propagation behavior patterns are obtained by comparing the results with those in Step 4; for example... Figure 7 As shown, crack defects in the printed 6061 alloy mainly appear at the edge of the molten pool and in the interface area between the molten powder layer and the substrate.

[0092] Step 7: Based on the thermo-mechanical coupling calculation results of laser additive manufacturing of 6061 alloy, optimize and screen process parameters based on the principles of minimum and uniform thermal stress distribution. For example... Figure 5As shown, by comparing the stress intensity and distribution uniformity under different laser powers, it can be seen that the thermal stress intensity is lower and the distribution uniformity is better at 200 W laser power. Although reducing the power can reduce the laser heat input and the molten pool temperature, its temperature change rate and temperature gradient are higher, leading to unevenly distributed and stronger thermal stress. Figure 8 It can be seen that as the laser power increases, the number and length of cracks gradually decrease, showing a good match with the simulation results of the model. Therefore, based on the model and actual results, crack sensitivity prediction and parameter optimization can be performed. The optimized process parameters are: laser power 180 W, laser spot size 60 μm, laser scanning speed 380 mm / s, scanning interval 70 μm, and initial temperature 140 ℃.

[0093] The results of the examples show that the rapid temperature change rate caused by uneven heat transfer during the laser additive manufacturing of 6061 aluminum alloy leads to high-intensity thermal stress concentration, resulting in a severe tendency for hot cracking in the alloy. The prediction model proposed in this patent can obtain the variation law of thermal stress distribution and intensity, thereby enabling the design and optimization of process parameters to obtain optimized parameters with lower hot cracking sensitivity and improve the forming quality of 6061 aluminum alloy.

Claims

1. A method for controlling the thermal cracking tendency of 6061 high thermal conductivity aluminum alloy in laser additive manufacturing, characterized in that, Includes the following steps: Step 1: Establish a Gaussian distribution laser heat source model and a powder bed / matrix physical model for laser additive manufacturing of 6061 thermally conductive alloy, and perform physical model mesh generation; Step 2: Based on the model established in Step 1, set the laser additive manufacturing process parameters, material properties and heat transfer boundary conditions, and carry out transient heat transfer process calculations; Step 3: Based on the temperature distribution data obtained in Step 3, perform mechanical field calculations for laser additive manufacturing of 6061 thermally conductive alloy as boundary conditions; Step 4: Based on the results calculated in Step 2 and Step 3, extract the temperature gradient and thermal stress distribution data at different locations in the molten pool, molten channel, and substrate under different laser process parameters to establish the correlation between the two. Step 5: Perform powder bed fusion printing based on the laser additive manufacturing process parameters set in Step 2, and verify the model by comparing the molten pool morphology; Step 6: Based on the 6061 alloy sample obtained in Step 5, crack statistics are performed, and the crack initiation and propagation behavior is obtained by comparing with the results of Step 4. Step 7: Based on the thermo-mechanical coupling calculation results of laser additive manufacturing of 6061 alloy, optimize and screen process parameters based on the principles of minimum and uniform thermal stress distribution.

2. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, In step 1, the physical model of the laser heat source is a Gaussian heat source physical model, and the energy distribution satisfies the formula: (1) Formula (1) A is the laser absorption rate of the powder material, P is the laser power, R is the laser spot radius, (x, y, z) are the spatial coordinates of the laser spot, v is the laser scanning speed, and t is the laser spot movement time.

3. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, In step 1, the powder bed / matrix physical model includes a 6061 alloy powder bed and a matrix. The length and width of the model are more than 5 times the size of the laser spot, and the thickness of the powder bed model is 20-50 μm. The model mesh is divided using a gradient meshing scheme, with the powder layer using a fine hexahedral mesh of 0.01-0.03 mm and the matrix using a coarse tetrahedral mesh of 0.03-0.3 mm.

4. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, The laser process parameters in step 2 include laser power of 120-250 W, laser spot size of 50-150 μm, laser scanning speed of 100-450 mm / s, and scanning interval of 50-150 μm; the boundary conditions include one or more of the following: heat conduction, heat radiation, heat convection, and initial temperature of 25-200 ℃.

5. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, The calculation of the transient heat transfer process in step 2 follows the formula below: （2） In formula (2), k is thermal conductivity, ρ is density, C is specific heat capacity, Q is laser heat source, T is temperature, t is heat transfer time, and (x, y, z) are three-dimensional spatial coordinates.

6. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, In step 3, the thermal stress in the mechanical field calculation process obeys the VON MISES criterion: （3） In formula (3) , , There are three principal stresses in mutually perpendicular directions; the equivalent strain follows: (4) In formula (4) , , denoted as the three principal strains in mutually perpendicular directions; μ is the Poisson's ratio of the material.

7. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, The characteristic locations of the molten pool, molten channel, and matrix in step 4 include the center, boundary, and interface location.

8. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, The preferred range of process parameters for laser additive manufacturing in step 5 is as follows: laser power 140-220 W, laser spot size 50-100 μm, laser scanning speed 150-400 mm / s, scanning interval 60-120 μm, and initial temperature 100-180℃; the molten pool morphology parameters include molten pool shape, melting width, and depth.

9. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, The crack statistics in step 6 include crack density, distribution location, and initiation-propagation path.

10. The method for controlling the hot cracking tendency of laser additive manufacturing of 6061 high thermal conductivity aluminum alloy according to claim 1, characterized in that, The optimized laser process parameters in step 7 are: laser power 180 W, laser spot size 60 μm, laser scanning speed 380 mm / s, scanning interval 70 μm, and initial temperature 140 ℃.

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