A method for in-situ solution and step aging of laser additive manufacturing

Abstract

The application discloses a kind of laser additive manufacturing in-situ solution and grading aging method, belong to metal additive manufacturing and heat treatment technical field.The application constructs main and vice laser time multiplexing dual optical path processing system, and three core procedures of laser additive manufacturing formation, in-situ solution, grading aging are integrated in the same equipment cavity and are continuously completed;Through the scanning of vice laser after layer forming, infrared temperature measurement, PID temperature control, the solution treatment of the formed region is completed synchronously, and then the two-stage in-situ heat treatment of homogenization spot pre-aging and Gaussian spot high-peak aging is completed in sequence.The application relieves the pain points of long offline heat treatment process flow, easy deformation of component, grain easy coarsening and significant performance anisotropy of traditional additive manufacturing, realizes the precise control of microstructure of metal component throughout the process and the synergistic improvement of high plasticity, greatly shortens the production cycle and reduces the manufacturing cost, and can be widely applied to the preparation of metal components in the fields of aerospace, automobile and rail transit.

Description

Technical Field

[0001] This invention belongs to the field of metal additive manufacturing and heat treatment technology, specifically relating to a method for in-situ solid solution and graded aging in laser additive manufacturing. Background Technology

[0002] Laser additive manufacturing technology (also known as metal 3D printing), with selective laser melting (SLM) and laser directed energy deposition (LDED) as its core mainstream processes, has become one of the core technologies for manufacturing high-end metal components in aerospace, automotive, mold, medical device and other fields due to its core advantages such as moldless free forming, integrated preparation of complex structures and high material utilization.

[0003] However, laser additive manufacturing is essentially a non-equilibrium thermodynamic cycle process of rapid melting and solidification. The formed components generally suffer from three inherent technical bottlenecks: First, the coarse columnar crystals and strong crystallographic texture formed during the forming process result in significant anisotropy in the mechanical properties of the components. The transverse properties of most alloys are more than 20% lower than their longitudinal properties, which seriously restricts the service reliability of the components. Second, the high residual stress generated during the cyclic heating and cooling process can easily cause warping and cracking of complex thin-walled components, which greatly reduces the dimensional accuracy and yield of the components. Third, the segregation of alloying elements and uneven distribution of the second phase caused by non-equilibrium solidification prevent the precipitation strengthening potential of heat-treatable alloys from being fully utilized, making it difficult to achieve forging-level mechanical properties.

[0004] The current industry standard solution is a separate process of additive manufacturing forming, offline solution treatment, and aging. After printing, the component is removed from the forming cavity and placed in a heat treatment furnace for subsequent solution and aging treatments. However, this process has inherent drawbacks: First, it is lengthy, energy-intensive, and costly. Traditional solution treatment followed by aging typically requires tens of hours, and the processes of component transfer, secondary clamping, and subsequent straightening further increase manufacturing costs, making it unsuitable for large-scale production. Second, complex thin-walled components are prone to irreversible deformation during multiple heating and cooling cycles in offline heat treatment, resulting in severe loss of dimensional accuracy and even direct scrapping of the component. Third, traditional furnace solution treatment involves prolonged high-temperature heating, which can cause excessive coarsening of the matrix grains, leading to a significant decrease in material plasticity and toughness, making it impossible to achieve a synergistic improvement in strength and plasticity. Fourth, large integral components require extremely precise furnace dimensions, resulting in large equipment investment, and the temperature uniformity within the furnace is difficult to guarantee, easily causing significant differences in microstructure and properties in different parts of the component.

[0005] To address the aforementioned issues, the industry has gradually conducted research on heat treatment technology for laser additive manufacturing. However, existing publicly available technologies still have significant shortcomings: First, most existing heat treatment schemes involve interlayer stress relief at a single temperature, without incorporating the precipitation strengthening mechanism of heat-treatable alloys. This makes it impossible to achieve full-process microstructure control of solution treatment and graded aging, resulting in low precision in controlling the precipitation of strengthening phases and limited performance improvement. Second, the few schemes that achieve in-situ solution treatment mostly employ interlayer laser remelting processes, requiring multiple repeated scans of the formed layer, which severely reduces production efficiency, significantly extends the printing cycle, and diminishes the value for industrial applications. Third, existing technologies struggle to form uniform supersaturated solid solutions, leading to a substantial reduction in subsequent aging strengthening effects.

[0006] Therefore, developing a laser additive manufacturing in-situ solid solution and graded aging method with a short process flow, small component deformation, high precision in microstructure control, strong equipment adaptability, and the ability to achieve synergistic improvement in strength and plasticity has become a core technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for in-situ solid solution and graded aging in laser additive manufacturing. This method solves the problems of long process, large component deformation, easy grain coarsening, and poor performance uniformity in traditional additive manufacturing and solid solution aging separate processes. At the same time, it overcomes the core defects of existing in-situ heat treatment technology, such as low efficiency, inability to achieve full-process precipitate phase control, and poor equipment adaptability.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: a method for in-situ solid solution and graded aging in laser additive manufacturing, comprising the following steps:

[0009] Step 1: Model and path preprocessing. Construct a 3D model of the part to be formed, add supports and slice the model, set the layer thickness, and plan the forming scan path, in-situ solution scan path, pre-aging scan path and peak aging scan path respectively.

[0010] Step 2: Pre-treatment of substrate and cavity. After surface deoxidation and cleaning of the substrate, it is preheated to the target temperature. The preheated substrate is fixed in the forming cavity of the laser additive manufacturing equipment. The forming cavity is replaced with inert gas to control the oxygen content in the cavity to ≤100ppm and the metal composition to ≤50ppm when titanium is present.

[0011] Step 3: Simultaneous in-situ solution treatment during additive forming. A dual-path processing mode with time-division multiplexing of the main and auxiliary lasers is employed. The main laser melts metal powder layer by layer along the forming scanning path to complete single-layer or multi-layer component forming. Selective laser melting (SLM) uses a powder-spreading method, while laser-directed energy deposition (LDED) uses a coaxial powder feeding method. After every n layers of forming and printing, powder spreading and feeding are paused. The auxiliary laser then performs a full-coverage scanning and heating of the formed area along the in-situ solution scanning path. Real-time infrared temperature measurement and PID closed-loop control stabilize the temperature of the formed area within the solution temperature range of the target material and maintain this temperature for a set duration. After the holding period, the substrate cooling system is instantly triggered to achieve rapid quenching of the formed area, allowing alloying elements to fully dissolve in the matrix to form a uniform supersaturated solid solution. This cycle of powder spreading, main laser forming, and auxiliary laser in-situ solution treatment is repeated until the overall component forming and solution treatment are completed.

[0012] Step 4, First-level in-situ pre-aging treatment: After the overall forming and solution treatment of the component are completed, the inert protective atmosphere is kept unchanged in the same forming cavity. The auxiliary laser is adjusted to a homogenization spot mode and matching process parameters. The entire component is scanned and heated according to the pre-aging scanning path. The overall temperature of the component is stabilized in the pre-aging temperature range through closed-loop temperature control and the temperature is held for a set time to complete the pre-aging treatment. High-density, diffusely distributed precipitated phase nuclei are precipitated in the matrix.

[0013] Step 5, second-level in-situ peak aging treatment: After the pre-aging treatment is completed, the auxiliary laser is directly adjusted to Gaussian spot mode and matched process parameters in the same forming cavity. The entire component is scanned and heated according to the peak aging scanning path. The overall temperature of the component is stabilized in the peak aging temperature range through closed-loop temperature control and the temperature is held for the set time to complete the peak aging treatment. This allows the strengthening phase to be uniformly dispersed and precipitated and grow to the target size, achieving coordinated control of the component's strength and plasticity.

[0014] Step 6, Controlled Cooling and Post-processing: After the peak aging process is completed, the component is cooled to room temperature at a set cooling rate. The cavity is opened and the component is removed. After removing the substrate and support and cleaning the surface, the finished component is obtained.

[0015] As a preferred technical solution of the present invention, in step one, the layer thickness is set to 20μm~100μm for SLM and 50μm~500μm for LDED; the forming scanning path uses strip or island scanning for SLM and unidirectional scanning, reciprocating scanning, or spiral scanning for LDED, with the deflection angle between adjacent scanning paths being 60°~90°, which can effectively reduce forming texture and improve the uniformity of the structure; the in-situ solid solution scanning path has a deflection angle of 90° with the same layer forming scanning path, and the deflection angle of adjacent solid solution layer scanning paths is consistent with that of the forming layer, ensuring that there are no dead angles in heating and that the temperature field is uniform; the pre-aging and peak aging scanning paths use reciprocating or spiral full-coverage scanning, with an overlap rate of ≥30% between adjacent scanning passes, to avoid uneven local temperature of the component.

[0016] As a preferred embodiment of the present invention, in step two, the preheating temperature of the substrate is set according to the target material: the preheating temperature of aluminum alloy is 80℃~150℃, the preheating temperature of titanium alloy is 200℃~300℃, the preheating temperature of nickel-based alloy is 300℃~400℃, and the preheating temperature of martensitic aging steel is 150℃~250℃; the inert gas is argon with a purity ≥99.999%, and the final oxygen content in the cavity is ≤100ppm to avoid oxidation and burn-off of alloy elements at high temperatures and ensure the metallurgical quality of the component.

[0017] Additionally, in step two, if the metal material used for additive manufacturing contains titanium, the final oxygen content in the cavity should be ≤50ppm.

[0018] In a preferred embodiment of the present invention, in step three, the value of n is 1~10, where n is 1~10 for SLM process and 1~5 for LDED process. This value is flexibly adjusted according to the hardenability of the target material and the wall thickness of the component, ensuring that the formed area completes solution treatment before cooling to the martensitic transformation temperature, maximizing the solution treatment effect. The main laser is a single-mode fiber laser with a center wavelength of 1064nm. The forming process parameters are as follows: SLM: laser power 100W~400W, scanning speed 500mm / s~2000mm / s, scanning spacing 50μm~150μm, focused spot diameter 50μm~200μm; LDED: laser power 1000W~6000W, scanning speed 300mm / s~1500mm / s, powder feeding rate 5g / min~60g / min, scanning spacing 1mm~5mm, focused spot diameter 1mm~6mm. This ensures that the component forming density is ≥99.5%.

[0019] As a preferred embodiment of the present invention, in step three, the process parameters for the secondary laser in-situ solidification are as follows: SLM: laser power 50W~300W, scanning speed 200mm / s~1000mm / s, scanning spacing 100μm~300μm, focused spot diameter 100μm~500μm; LDED: laser power 300W~1500W, scanning speed 100mm / s~800mm / s, scanning spacing 1mm~3mm. The focused spot diameter is 500μm~2000μm; the solid solution temperature range and holding time are set according to the target material, the holding time is 10s~120s, and the temperature control accuracy is ±10℃, to ensure that the second phase is fully dissolved and to avoid coarsening of matrix grains; the rapid quenching cooling rate is ≥50℃ / s, and the quenching termination temperature is ≤100℃, to suppress the premature precipitation of the second phase by rapid cooling, forming a uniform supersaturated solid solution, laying the foundation for subsequent aging strengthening.

[0020] In a preferred embodiment of the present invention, in step four, the diameter of the secondary laser homogenizing spot for the pre-aging treatment is 1mm~5mm for SLM and 1mm~10mm for LDED; the pre-aging process parameters are as follows: SLM: laser power 20W~200W, scanning speed 50mm / s~500mm / s, scanning spacing 0.5mm~2mm; LDED: laser power 100W~800W, scanning speed 50mm / s~400mm / s, scanning spacing 1mm~5mm; the pre-aging temperature range and holding time are set according to the target material, and the temperature control accuracy is ±10℃. By homogenizing the spot, uniform low-temperature heating of the entire component is achieved, forming a high-density GP region or metastable phase in the matrix, providing a large number of nucleation sites for subsequent aging precipitation, effectively refining the precipitated phase, and avoiding the problems of coarse and unevenly distributed precipitated phases caused by a single aging process.

[0021] In a preferred embodiment of the present invention, in step five, the diameter of the secondary laser Gaussian spot for the peak aging treatment is 1mm~5mm for SLM and 1mm~10mm for LDED; the peak aging process parameters are as follows: for SLM, laser power 50W~300W, scanning speed 50mm / s~400mm / s, scanning spacing 0.5mm~2mm; for LDED, laser power 200W~1000W, scanning speed 50mm / s~300mm / s, scanning spacing 1mm~5mm; the peak aging temperature range and holding time are set according to the target material, and the temperature control accuracy is ±10℃. Precise temperature control and heating are achieved through the Gaussian spot, allowing the strengthening phase to precipitate uniformly and grow to its optimal size, thus achieving the best match between the strength and plasticity of the component.

[0022] As a preferred technical solution of the present invention, in steps three, four and five, a coaxial infrared high temperature instrument is used to collect temperature data of the component processing area in real time and transmit it to the equipment control system at a sampling frequency of 1kHz. The output power and scanning speed of the auxiliary laser are adjusted in real time through PID closed-loop regulation to achieve precise closed-loop control of the temperature of the processing area and ensure the uniformity of the overall structure and performance of the component.

[0023] As a preferred technical solution of the present invention, the target material is a heat-treatable metal material, including any one of aluminum alloy, titanium alloy, nickel-based alloy, and maraging steel; the laser additive manufacturing equipment is a selective laser melting (SLM) equipment or a laser directional energy deposition (LDED) equipment, which does not require major modifications to the main structure of the equipment, but only requires the addition of a standardized auxiliary laser and temperature measurement module, which has strong adaptability and is easy to scale up.

[0024] As a preferred technical solution of the present invention, in step six, the cooling rate of the controllable cooling is 2℃ / min to 15℃ / min. During the cooling process, the inert protective atmosphere inside the cavity remains unchanged until the component temperature drops to room temperature, so as to avoid oxidation and deformation of the component during the cooling process.

[0025] Compared with the prior art, the present invention has the following significant advantages:

[0026] This invention integrates the entire process, resulting in significant advantages in production efficiency and cost. For the first time, it integrates three core processes—additive manufacturing, solution quenching, and two-stage aging—into a single equipment cavity and under the same protective atmosphere for continuous completion. This eliminates the need for component transfer, secondary clamping, and additional heat treatment equipment, completely removing the lengthy offline heat treatment process. This shortens the production cycle, reduces energy consumption and manufacturing costs of high-end metal components, and is particularly suitable for the large-scale production of large and complex integral components.

[0027] This invention completes the forming and heat treatment entirely within the same cavity, avoiding irreversible deformation of components caused by multiple heating and cooling cycles in traditional offline heat treatment. At the same time, through a layer-by-layer, zoned in-situ solution treatment process, residual stress generated during the forming process is released step by step, resulting in better reduction of residual stress and deformation, significantly improved dimensional accuracy, and increased yield.

[0028] This invention achieves full solid solution of alloying elements while effectively suppressing matrix grain coarsening, breaking up the coarse columnar crystals formed during additive manufacturing, significantly eliminating performance anisotropy, and reducing the difference in mechanical properties between the transverse and longitudinal directions of the component.

[0029] This invention achieves precise temperature control throughout the entire heat treatment process through infrared temperature measurement and PID closed-loop control, keeping the overall temperature uniformity of the component within a small range, ensuring the consistency of the microstructure and performance of different parts of the component, and significantly enhancing its service reliability. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0031] Figure 1 This is a process flow diagram of the in-situ solid solution and graded aging method for laser additive manufacturing described in this invention. Detailed Implementation

[0032] The present invention will be described in detail below through embodiments. It should be understood that the embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Example

[0033] This embodiment provides a method for in-situ solid solution treatment and graded aging of 7075 aluminum alloy by selective laser melting, used to prepare complex thin-walled radome components for aerospace applications. The specific steps are as follows:

[0034] 1. Model and path preprocessing: A 3D model of the 7075 aluminum alloy radome component was constructed using UGNX software and imported into MaterialiseMagics software for lightweight support addition and slicing layer processing, with the layer thickness set to 30μm; the planned forming scanning path adopted strip scanning, with the scanning paths of adjacent layers deflected by 67°; the in-situ solid solution scanning path deflected by 90° from the same layer forming scanning path, and the deflection angle of adjacent solid solution layers was consistent with that of the forming layer; the pre-aging and peak aging scanning paths adopted reciprocating full-coverage scanning, with an overlap rate of 35% between adjacent channels.

[0035] 2. Substrate and cavity pretreatment: 6061 aluminum alloy is selected as the forming substrate. The oxide scale is removed by polishing the surface of the substrate step by step with 800# and 1200# sandpaper. The substrate is ultrasonically cleaned in anhydrous ethanol for 15 minutes. After removal, it is dried with high-purity nitrogen. The substrate is preheated to 120°C and fixed in the forming cavity of the SLM equipment. The cavity is replaced with high-purity argon gas until the oxygen content in the cavity drops below 30ppm.

[0036] 3. Additive forming with simultaneous in-situ solution treatment: A dual-path processing mode with time-division multiplexing of main and auxiliary lasers is adopted. The main laser is a single-mode fiber laser with a center wavelength of 1064nm. The forming process parameters are: laser power 280W, scanning speed 1200mm / s, scanning spacing 80μm, and focused spot diameter 80μm. 7075 aluminum alloy powder is melted and atomized layer by layer to complete the component forming. The powder particle size range is 15μm~53μm. After every 3 layers of forming and printing, the powder laying process is paused, and the auxiliary laser is used to perform in-situ solution scanning on the formed area. The auxiliary laser process parameters are: laser power 150W. The scanning speed is 600 mm / s, the scanning spacing is 150 μm, and the focused spot diameter is 200 μm. The temperature of the formed area is monitored in real time by a coaxial infrared pyrometer and transmitted to the control system at a sampling frequency of 1 kHz. The PID closed-loop control stabilizes the temperature at 475℃~485℃ for 60s. After the holding time is completed, the substrate water cooling system is triggered instantly to achieve rapid quenching of the formed area. The cooling rate is ≥80℃ / s and the quenching termination temperature is ≤80℃, forming a uniform supersaturated solid solution. The cycle of powder spreading, main laser forming, and secondary laser in-situ solidification is repeated until the overall forming and solidification treatment of the component are completed.

[0037] 4. First-stage in-situ pre-aging treatment: After the overall forming and solution treatment of the component are completed, the argon protective atmosphere is kept constant in the same forming cavity. The auxiliary laser is adjusted to a 3mm diameter homogenization spot mode. The process parameters are: laser power 80W, scanning speed 200mm / s, scanning interval 1mm. The entire component is scanned and heated. The overall temperature of the component is stabilized at 105℃~115℃ through closed-loop temperature control and the holding time is 2h to complete the pre-aging treatment. High-density GP region nucleation cores are precipitated in the matrix.

[0038] 5. Second-stage in-situ peak aging treatment: After the pre-aging treatment is completed, the auxiliary laser is directly adjusted to a 3mm diameter Gaussian spot mode in the same forming cavity. The process parameters are: laser power 120W, scanning speed 150mm / s, scanning spacing 1mm; the overall temperature of the component is stabilized at 135℃~145℃ through closed-loop temperature control, and the holding time is 8h to complete the peak aging treatment, so that the η' strengthening phase is uniformly dispersed and precipitated and grows to the optimal size.

[0039] 6. Controlled cooling and post-processing: After the peak aging process is completed, the component is cooled to room temperature with the furnace at a cooling rate of 5℃ / min, and the argon protective atmosphere in the cavity is maintained throughout the process; the cavity is opened and the component is taken out, the substrate and support are removed by wire cutting, and the surface powder and oxide layer are cleaned by sandblasting to obtain the finished 7075 aluminum alloy radome component. Example

[0040] This embodiment provides a method for in-situ solution treatment and graded aging of TC4 titanium alloy by laser-directed energy deposition (EDA) for fabricating aero-engine suspension structural components. The specific steps are as follows:

[0041] 1. Model and path preprocessing: A 3D model of the TC4 titanium alloy hanging structure was constructed using SolidWorks, and sliced ​​and layered processing was performed, with a layer thickness of 80μm. The planned forming scanning path adopted unidirectional scanning, with adjacent scanning paths deflected by 90°. The in-situ solution scanning path was orthogonal to the forming scanning path of the same layer. The pre-aging and peak aging scanning paths adopted spiral full-coverage scanning, with an overlap rate of 40% between adjacent passes.

[0042] 2. Pretreatment of substrate and cavity: TC4 titanium alloy hot-rolled substrate is selected. After grinding to remove the surface oxide scale, it is ultrasonically cleaned in anhydrous ethanol for 15 minutes, dried, preheated to 250℃, and fixed in the forming cavity of the LDED equipment. High-purity argon gas is circulated and replaced to control the oxygen content in the cavity to ≤50ppm.

[0043] 3. Synchronous In-situ Solution Treatment in Additive Molding: A dual-path processing mode with time-division multiplexing of main and auxiliary lasers is adopted. The main laser forming process parameters are: laser power 1200W, scanning speed 800mm / s, powder feeding rate 15g / min, and focused spot diameter 2mm. After every 5 layers of forming and printing, the powder feeding and powder spreading process is paused, and the auxiliary laser is used to perform in-situ solution scanning on the formed area. The process parameters are: laser power 600W, scanning speed 500mm / s, scanning interval 2mm, and focused spot diameter 3mm. The temperature is stabilized at 920℃~940℃ by coaxial infrared temperature measurement and PID closed-loop control, and the holding time is 90s. After the holding time is completed, the substrate water cooling system is triggered instantaneously, with a cooling rate ≥60℃ / s and a quenching termination temperature ≤100℃, completing the solution treatment. The above cycle is repeated until the overall forming and solution treatment of the component are completed.

[0044] 4. First-stage in-situ pre-aging treatment: After the component is formed and solution treated, the protective atmosphere is kept constant in the same cavity. The auxiliary laser is adjusted to a 5mm diameter homogenization spot mode. The process parameters are: laser power 300W, scanning speed 300mm / s, scanning spacing 2.5mm; the closed-loop control temperature is kept stable at 450℃~470℃, and the holding time is 2h to complete the pre-aging treatment.

[0045] 5. Second-stage in-situ peak aging treatment: After pre-aging, the auxiliary laser is directly adjusted to a 5mm diameter Gaussian spot mode. The process parameters are: laser power 400W, scanning speed 250mm / s, scanning spacing 2.5mm; the closed-loop control temperature is stabilized at 520℃~540℃, and the holding time is 4h to complete the peak aging treatment.

[0046] 6. Controlled cooling and post-processing: After the aging treatment is completed, the component is cooled to room temperature at a controlled cooling rate of 10℃ / min. After the component is removed, the substrate and support are removed by wire cutting to obtain the finished TC4 titanium alloy hanging structure component. Example

[0047] This embodiment provides a method for selective laser melting in-situ solution treatment and graded aging of IN718 nickel-based superalloy, used to prepare centrifugal impeller components for aero-engines. The specific steps are as follows:

[0048] 1. Model and path preprocessing: A 3D model of the IN718 alloy centrifugal impeller was constructed, and support was added and sliced ​​for layering. The layer thickness was set to 40μm. The forming scanning path was planned using island scanning, with adjacent islands deflected by 30° and adjacent two-layer scanning paths deflected by 67°. The in-situ solution scanning path was orthogonal to the same-layer forming scanning path. The pre-aging and peak aging scanning paths adopted reciprocating full-coverage scanning, with an overlap rate of 30% between adjacent passes.

[0049] 2. Substrate and cavity pretreatment: 316L stainless steel substrate is selected, polished and cleaned, preheated to 350℃, fixed in the forming cavity of SLM equipment, and high-purity argon gas is circulated and replaced to control the oxygen content in the cavity to ≤20ppm.

[0050] 3. Synchronous in-situ solution treatment during additive manufacturing: The main laser forming process parameters are: laser power 320W, scanning speed 1000mm / s, scanning spacing 100μm, and focused spot diameter 100μm. After every two layers of forming and printing, the powder laying process is paused, and the secondary laser is used to perform in-situ solution scanning on the formed area. The process parameters are: laser power 200W, scanning speed 400mm / s, scanning spacing 200μm, and focused spot diameter 200μm. The closed-loop control temperature is kept stable at 970℃~990℃, and the holding time is 120s. After the holding time is completed, the substrate water cooling system is triggered instantaneously, with a cooling rate ≥100℃ / s and a quenching termination temperature ≤80℃, completing the solution treatment. The cycle is repeated until the overall forming and solution treatment of the component are completed.

[0051] 4. First-stage in-situ pre-aging treatment: Maintain the protective atmosphere within the same cavity, adjust the auxiliary laser to a 4mm diameter homogenization spot mode, and set the process parameters as follows: laser power 150W, scanning speed 200mm / s, scanning spacing 1.5mm; keep the closed-loop temperature stable at 720℃~740℃, and maintain the temperature for 2 hours to complete the pre-aging treatment.

[0052] 5. Second stage in-situ peak aging treatment: Adjust the auxiliary laser to a 4mm diameter Gaussian spot mode. The process parameters are: laser power 200W, scanning speed 150mm / s, scanning spacing 1.5mm; the closed-loop control temperature is stabilized at 770℃~790℃, and the holding time is 6h to complete the peak aging treatment.

[0053] 6. Controlled cooling and post-processing: After aging, the component is cooled to room temperature at a rate of 8℃ / min. The component is then removed, the substrate and support are removed, and the IN718 alloy centrifugal impeller is obtained.

[0054] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, alterations, equivalent substitutions, improvements, etc., made under the present invention should be included within the protection scope of the present invention.

Claims

1. A method for in-situ solid solution and graded aging in laser additive manufacturing, characterized in that, Includes the following steps: Step 1: Model and path preprocessing. Construct a 3D model of the part to be formed, add supports and slice the model, set the layer thickness, and plan the forming scan path, in-situ solution scan path, pre-aging scan path and peak aging scan path respectively. Step 2: Pre-treatment of substrate and cavity. After surface deoxidation and cleaning of the substrate, it is preheated to the target temperature. The preheated substrate is fixed in the forming cavity of the laser additive manufacturing equipment. The forming cavity is replaced with inert gas to control the oxygen content in the cavity to ≤100ppm and the metal composition to ≤50ppm when titanium is present. Step 3: Simultaneous in-situ solution treatment during additive forming. A dual-path processing mode with time-division multiplexing of the main and auxiliary lasers is employed. The main laser melts metal powder layer by layer along the forming scanning path to complete single-layer or multi-layer component forming. Selective laser melting (SLM) uses a powder-spreading method, while laser-directed energy deposition (LDED) uses a coaxial powder feeding method. After every n layers of forming and printing, powder spreading and feeding are paused. The auxiliary laser then performs a full-coverage scanning and heating of the formed area along the in-situ solution scanning path. Real-time infrared temperature measurement and PID closed-loop control stabilize the temperature of the formed area within the solution temperature range of the target material and maintain this temperature for a set duration. After the holding period, the substrate cooling system is instantly triggered to achieve rapid quenching of the formed area, allowing alloying elements to fully dissolve in the matrix to form a uniform supersaturated solid solution. This cycle of powder spreading, main laser forming, and auxiliary laser in-situ solution treatment is repeated until the overall component forming and solution treatment are completed. Step 4, First-level in-situ pre-aging treatment: After the overall forming and solution treatment of the component are completed, the inert protective atmosphere is kept unchanged in the same forming cavity. The auxiliary laser is adjusted to a homogenization spot mode and matching process parameters. The entire component is scanned and heated according to the pre-aging scanning path. The overall temperature of the component is stabilized in the pre-aging temperature range through closed-loop temperature control and the temperature is held for a set time to complete the pre-aging treatment. High-density, diffusely distributed precipitated phase nuclei are precipitated in the matrix. Step 5, second-level in-situ peak aging treatment: After the pre-aging treatment is completed, the auxiliary laser is directly adjusted to Gaussian spot mode and matched process parameters in the same forming cavity. The entire component is scanned and heated according to the peak aging scanning path. The overall temperature of the component is stabilized in the peak aging temperature range through closed-loop temperature control and the temperature is held for the set time to complete the peak aging treatment. This allows the strengthening phase to be uniformly dispersed and precipitated and grow to the target size, achieving coordinated control of the component's strength and plasticity. Step 6, Controlled Cooling and Post-processing: After the peak aging process is completed, the component is cooled to room temperature at a set cooling rate. The cavity is opened and the component is removed. After removing the substrate and support and cleaning the surface, the finished component is obtained.

2. The method according to claim 1, characterized in that, In step one, the layer thickness is set to 20μm~100μm for SLM and 50μm~500μm for LDED; the forming scanning path uses strip or island scanning for SLM and unidirectional, reciprocating, or spiral scanning for LDED, with the deflection angle between adjacent scanning paths being 60°~90°; the in-situ solution scanning path deflects 90° from the forming scanning path of the same layer, and the deflection angle of the scanning path of adjacent solution layers is consistent with that of the forming layer; the pre-aging and peak aging scanning paths use reciprocating or spiral full-coverage scanning, with an overlap rate of ≥30% between adjacent scanning passes.

3. The method according to claim 1, characterized in that, In step two, the preheating temperature of the substrate is set according to the target material: the preheating temperature of Al-Zn-Mg-Cu and Al-Cu-Mg aluminum alloys is 80℃~150℃, the preheating temperature of TC4 and TC18 titanium alloys is 200℃~300℃, the preheating temperature of nickel-based alloys is 300℃~400℃, and the preheating temperature of martensitic aging steel is 150℃~250℃; the inert gas is high-purity argon with a purity ≥99.999%, and the final oxygen content in the cavity is ≤50ppm.

4. The method according to claim 1, characterized in that, In step three, the value of n is 1~10, where n is 1~10 for SLM process and 1~5 for LDED process; the main laser is a single-mode fiber laser with a center wavelength of 1064nm; the forming process parameters are as follows: SLM: laser power 100W~400W, scanning speed 500mm / s~2000mm / s, scanning spacing 50μm~150μm, focused spot diameter 50μm~200μm; LDED: laser power 1000W~6000W, scanning speed 300mm / s~1500mm / s, powder feeding rate 5g / min~60g / min, scanning spacing 1mm~5mm, focused spot diameter 1mm~6mm.

5. The method according to claim 1, characterized in that, In step three, the process parameters for the secondary laser in-situ solid solution are as follows: SLM: laser power 50W~300W, scanning speed 200mm / s~1000mm / s, scanning spacing 100μm~300μm, focused spot diameter 100μm~500μm; LDED: laser power 300W~1500W, scanning speed 100mm / s~800mm / s, scanning spacing 1mm~3mm, focused spot diameter 500μm~2000μm; the solid solution temperature range and holding time are set according to the target material, the holding time is 10s~120s, and the temperature control accuracy is ±10℃; the cooling rate of the rapid quenching is ≥50℃ / s, and the quenching termination temperature is ≤100℃.

6. The method according to claim 1, characterized in that, In step four, the diameter of the secondary laser homogenization spot for the pre-aging treatment is 1mm~5mm for SLM and 1mm~10mm for LDED; the pre-aging process parameters are as follows: SLM: laser power 20W~200W, scanning speed 50mm / s~500mm / s, scanning spacing 0.5mm~2mm; LDED: laser power 100W~800W, scanning speed 50mm / s~400mm / s, scanning spacing 1mm~5mm; the pre-aging temperature range and holding time are set according to the target material, and the temperature control accuracy is ±10℃.

7. The method according to claim 1, characterized in that, In step five, the diameter of the secondary laser Gaussian spot for the peak aging treatment is 1mm~5mm for SLM and 1mm~10mm for LDED; the peak aging process parameters are as follows: for SLM, laser power 50W~300W, scanning speed 50mm / s~400mm / s, scanning spacing 0.5mm~2mm; for LDED, laser power 200W~1000W, scanning speed 50mm / s~300mm / s, scanning spacing 1mm~5mm; the peak aging temperature range and holding time are set according to the target material, and the temperature control accuracy is ±10℃.

8. The method according to claim 1, characterized in that, In steps three, four, and five, a coaxial infrared pyrometer is used to collect temperature data of the component processing area in real time. The data is transmitted to the equipment control system at a sampling frequency of 1kHz. The output power and scanning speed of the auxiliary laser are adjusted in real time through PID closed-loop regulation to achieve precise closed-loop control of the temperature of the processing area.

9. The method according to claim 1, characterized in that, The target material is a heat-treatable metal material, including any one of aluminum alloy, titanium alloy, nickel-based alloy, and maraging steel; the laser additive manufacturing equipment is a selective laser melting (SLM) device or a laser-directed energy deposition (LDED) device.

10. The method according to claim 1, characterized in that, In step six, the controllable cooling rate is 2℃ / min to 15℃ / min. During the cooling process, the inert protective atmosphere inside the cavity remains unchanged until the component temperature drops to room temperature.

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