A method for enhancing the toughness and strength of additively manufactured aluminum components based on continuous ultrafast composite laser.

Abstract

This invention discloses a method for improving the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser. To address the current problems of limited mechanical properties and difficulties in synergistic strengthening and toughness improvement of additively manufactured aluminum alloy components, a continuous / ultrafast composite laser additive manufacturing process is designed. By performing interlayer local ultrafast laser secondary processing in the continuous laser additive manufacturing process, spatially alternating grain refinement and grain coarsening regions are obtained. Based on local stress regulation and back stress effect, the strength and toughness of aluminum alloy metal components are synergistically improved.

Description

Technical Field

[0001] This invention belongs to the field of strengthening and toughening of metallic materials, specifically relating to a method for improving the strengthening and toughening properties of additively manufactured aluminum components based on continuous ultrafast composite laser. Background Technology

[0002] Metal laser additive manufacturing technology employs a "layer-by-layer melting and deposition" method to integrally form complex components. It possesses forming characteristics unconstrained by complex structures, resulting in higher material utilization, shorter production cycles, and the ability to achieve complex internal features. Selective laser melting (SLM) is one such metal laser additive manufacturing technology. It can form complex components based on layer-by-layer powder bed deposition and selective laser melting, showing broad application prospects in aerospace, automotive, and shipbuilding fields. However, current SLM-formed aluminum alloy components suffer from limited strength and toughness. On one hand, commonly used aluminum alloys in SLM are primarily Al-Si based, with a relatively simple strengthening mechanism, making it difficult to meet the high-performance requirements of aerospace. On the other hand, precipitation-strengthened aluminum alloys, represented by Al-Cu, Al-Mg-Si, and Al-Zn, primarily utilize in-situ nanoprecipitation as their strengthening mechanism, exhibiting high strength and toughness. However, due to intrinsic material factors, excessively high nanoprecipitate density leads to increased strength but decreased ductility, and vice versa. Currently, there is a lack of effective processing methods and strengthening mechanisms to reconcile the contradictory relationship between strength and ductility / toughness.

[0003] In addition, the selective laser melting forming process for aluminum alloys typically involves 10 5 -10 7 The ultra-high solidification rate of K / s leads to a significant increase in the temperature gradient during the non-equilibrium interaction between laser and powder. Consequently, residual stress and lattice distortion are significant within laser additively manufactured components. Excessive residual stress can affect service life and significantly reduce mechanical properties. Therefore, to overcome these technical bottlenecks, it is necessary to design additively manufactured aluminum alloy microstructures based on process innovation. Summary of the Invention

[0004] Purpose of the invention: The technical problem to be solved by the present invention is that the existing selective laser melting forming of aluminum alloy components has insufficient strength and toughness and excessive internal stress, resulting in limited service performance. By introducing a continuous ultrafast composite laser alternating forming process, the contradiction between strength and toughness and the problem of limited mechanical properties of laser additive manufacturing aluminum alloy components can be solved.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for improving the toughness and strength of additively manufactured aluminum components based on continuous ultrafast composite lasers includes the following steps:

[0007] (1) Optimize the stress distribution within the spatial micro-region to obtain an optimized stress concentration / stress release area distribution configuration;

[0008] (2) Based on the optimized configuration obtained in step (1), slice the three-dimensional stress distribution configuration for laser additive manufacturing into layers and import the slice information into the forming equipment;

[0009] (3) Preparation of metal laser additive manufacturing process, laying high-strength aluminum alloy powder layer by layer;

[0010] (4) Continuous laser selectively melts powder areas layer by layer based on component slice information;

[0011] (5) After the single-layer scanning is completed by continuous laser in step (4), based on the micro-area stress relief area slice information, ultrafast laser is used to selectively process the solidified area in a secondary micro-area process to complete the processing and shaping of the layer.

[0012] (6) Repeat steps (3) to (5) until a three-dimensional component is obtained.

[0013] Specifically, in step (1), based on finite element analysis software, the internal stress distribution design and its strengthening behavior under load are analyzed. The stress distribution design of the formed specimen is optimized to obtain a stress concentration / stress release region distribution configuration with optimized performance. The stress release region includes rectangular, elliptical, and layered micro-regions; wherein, the rectangular and elliptical stress release regions include the horizontal side length l of the stress release micro-region, the height d in the forming direction, the horizontal distance t and the vertical distance s between adjacent micro-regions; the layered micro-regions include the height d and the vertical distance s of the stress release region; 80μm≤l≤400μm, 100μm≤d≤600μm, 100μm≤t≤400μm, 100μm≤s≤600μm.

[0014] Specifically, in step (1), the configuration features include the size, shape and boundary of the stress concentration region, and the size, shape and boundary of the stress release region; wherein, the stress concentration region corresponds to the powder region subjected to continuous laser, and the stress release region corresponds to the micro-region used for interlayer ultrafast laser treatment.

[0015] Specifically, in step (2), based on the configuration obtained in step (1), the layered slicing software is used to slice the model, obtain the 3D model slicing information, and import it into the selected area laser melting device.

[0016] Furthermore, the slicing information includes the continuous laser processing area and laser path, and the ultrafast laser interlayer processing area and laser path.

[0017] Specifically, in step (3), the high-strength aluminum alloy powder is aluminum alloy spherical powder, and its composition range is Mg content of 3-8 wt.%, Sc content of 0.05-1 wt.%, Zr content of 0.02-0.8 wt.%, Fe content of 0.01-0.2 wt.%, Si content of no more than 5 wt.%, with the balance being Al; the particle size of the aluminum alloy spherical powder is 15-45 μm.

[0018] Furthermore, in step (3), the oxygen content of the cavity where the high-strength aluminum alloy powder is laid is less than 100 ppm.

[0019] Furthermore, in step (3), the thickness of the single-layer high-strength aluminum alloy powder is 30-60 μm.

[0020] Specifically, in step (4), the continuous laser power is 150-450W, the scanning speed is 400-2000mm / s, and the spot diameter is 50-100μm.

[0021] Specifically, in step (5), the ultrafast laser power is 20-100W and the pulse width is 1-100ns.

[0022] Beneficial effects:

[0023] This invention adds a secondary melting and solidification process based on ultrafast lasers to the continuous laser-based layer-by-layer additive manufacturing process, resulting in a significant reduction in the local solidification temperature gradient and grain coarsening. This creates alternating grain refinement and coarsening zones, thereby achieving local stress relief and precise control of spatial stress distribution. During load-bearing, a new strengthening mechanism is employed through back stress effect and dislocation pile-up in coarse-grained regions, achieving a synergistic improvement in the strength and toughness of laser-added aluminum alloy components. Attached Figure Description

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0025] Figure 1 This is a flowchart of the method for improving the toughness and strength of additively manufactured aluminum components based on continuous ultrafast composite lasers, according to the present invention.

[0026] Figure 2 This is a schematic diagram of the stress distribution optimization design of the formed specimen based on rectangular micro-regions according to the present invention.

[0027] Figure 3 This is a schematic diagram of the stress distribution optimization design of the formed specimen based on the elliptical micro-region of the present invention.

[0028] Figure 4This is a schematic diagram of the stress distribution optimization design of the formed specimen based on layered micro-regions according to the present invention.

[0029] Figure 5 This is a schematic diagram of the continuous / ultrafast composite laser additive manufacturing process and the typical microstructure characteristics obtained as described in this invention.

[0030] Figure 6 SEM images of typical microstructure of aluminum alloy specimens formed using the process method of this invention.

[0031] Figure 7 The figures show the room temperature stress-strain curves for Examples 1 and 2 in the specific implementation scheme. Detailed Implementation

[0032] The present invention can be better understood from the following embodiments.

[0033] like Figure 1 As shown, the present invention provides a method for improving the toughness and strength of additively manufactured aluminum components based on continuous ultrafast composite laser, comprising the following steps:

[0034] Step 1: Spatial Local Stress Control Design for 3D Components: Optimize the stress distribution design of the formed specimen using finite element simulation software to obtain a stress concentration / stress release area distribution configuration with optimized performance.

[0035] The aforementioned configurational features include the size, shape, and boundaries of stress concentration regions, and the size, shape, and boundaries of stress relief regions. For example... Figure 2-4 As shown, the shapes of stress-relieving micro-regions can be mainly divided into rectangular, elliptical, and layered micro-regions. For the stress distribution design optimization of rectangular and elliptical micro-regions, the main structural parameters include the horizontal side length *l* of the stress-relieving micro-region, the height *d* in the forming direction, and the horizontal and vertical distances *t* between adjacent micro-regions. For the force distribution design optimization of layered micro-regions, the main structural parameters include the height *d* and vertical distance *s* of the stress-relieving region. The stress concentration region corresponds to the powder region subjected to continuous laser treatment, while the stress-relieving region is used for micro-regions subjected to interlayer ultrafast laser treatment.

[0036] Based on the aforementioned micro-region structural types and parameters, and considering the application scenario, material physical properties were used as input. Stress-strain simulation analysis software was employed to perform deformation and failure analysis of the overall structure under load constraints for different structural parameters, obtaining optimized structural parameter values. Combining the laser additive manufacturing process constraint forming limit and previous optimization experimental results, the optimization ranges are as follows: 80μm≤l≤400μm, 100μm≤d≤600μm, 100μm≤t≤400μm, 100μm≤s≤600μm.

[0037] Step 2: Layered Slicing of Stress-Alternating Structures for 3D Printing: Based on the configuration obtained in Step 1, layered slicing software such as Magics is used to slice the structure, obtain the 3D model slicing information, and import it into a selected area laser melting equipment. The slicing information includes the continuous laser processing area and laser path, and the ultrafast laser interlayer processing area and laser path.

[0038] Step 3, Continuous / Ultrafast Composite Laser Additive Manufacturing Process: After single-layer powder placement, the first step is to perform a continuous laser selective melting process based on the slice information. Further, based on the slice information, an interlayer continuous laser micro-area stress relief process is carried out, thereby completing the processing of the single-layer specimen. This process is repeated until the three-dimensional specimen is completed. Figure 5 ).

[0039] Example 1 (Comparative Example)

[0040] Example 1 shows a typical selective laser melting process for forming aluminum alloy specimens. The specific steps are as follows:

[0041] (1) Use layer slicing software to slice the model into layers, obtain slicing information and import it into the selected area laser melting equipment.

[0042] (2) Selective laser melting equipment was used to form aluminum alloy specimens. The aluminum alloy composition was as follows: Mg content was 4.2%, Sc content was 0.4%, Zr content was 0.2%, Fe content was 0.1%, and the balance was Al. The above powder particle size was 15-45μm. Before printing, the powder was dried in a vacuum drying oven at 120℃ for 6h.

[0043] The process parameters for forming the continuous laser processing area in step (2) are: laser power 400W, laser scanning speed 1000mm / s, spot diameter 70μm, layer thickness 30μm, and scanning spacing 60μm.

[0044] (3) The formed specimen was separated from the substrate by wire cutting, and its room temperature mechanical properties were tested according to standards. The tensile strength of Example 1 was 301.4 MPa, and the elongation was 19.8%.

[0045] Example 2

[0046] The method for enhancing the strength and toughness of additively manufactured aluminum components using continuous ultrafast composite lasers differs from the conventional selective laser melting forming process in Example 1 in that: before step (1), the macroscopic stress distribution is optimized using Abaqus simulation software. The stress distribution configuration used in Example 2 is an elliptical micro-region, where l = 200 μm, d = 300 μm, t = 200 μm, and s = 400 μm. Layered slicing is then performed based on this model.

[0047] In step (3), an interlayer ultrafast laser power micro-region stress relief process is added. The ultrafast laser interlayer processing area (stress relief micro-region) has a laser power of 50W, a pulse width of 50ns, a pulse wavelength of 1064nm, and a scanning spacing of 70μm.

[0048] The process parameters for forming the continuous laser processing area are: laser power 400W, laser scanning speed 1000mm / s, spot diameter 70μm, layer thickness 30μm, and scanning spacing 60μm.

[0049] The cross-section of the formed specimen was ground and polished, and the results were observed using a scanning electron microscope. Figure 6 As shown, the specimen formed using the continuous ultrafast composite laser additive manufacturing process described in this invention exhibits a grain refinement region in the continuous laser irradiation area, which has high residual stress due to the high temperature gradient during solidification. A "stress release zone" is formed in the interlayer ultrafast laser irradiation region, where grain coarsening occurs and the residual stress is significantly reduced due to the lower solidification temperature from the secondary processing.

[0050] The aluminum alloy specimen formed using the method of this invention, which enhances the strength and toughness of additively manufactured aluminum components using continuous ultrafast composite laser technology, exhibits a room temperature tensile strength of 412.3 MPa and an elongation of 22.1%. Figure 7 Compared with Example 1, the strength and elongation are synergistically improved, that is, the process method proposed in this invention enables the component to achieve a good strengthening and toughening effect.

[0051] This invention optimizes the stress distribution design of the formed specimen and uses a continuous ultrafast composite laser additive manufacturing process. It employs an interlayer micro-region stress relief method to obtain a specimen with alternating stress concentration and stress release regions. It introduces new strengthening mechanisms such as back stress strengthening and dislocation pile-up strengthening to achieve a synergistic improvement in the strength and toughness of laser additive manufactured metal components.

[0052] This invention uses ultrafast lasers for the stress relief process in interlayer micro-regions. Ultrafast lasers have the advantages of small spot size, high controllability of micro-region size, and small interlayer heat-affected zone, which are significant advantages over continuous lasers in micro-region size control.

[0053] This invention provides a method for enhancing the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for improving the toughness and strength of additively manufactured aluminum components based on continuous ultrafast composite laser, characterized in that, Includes the following steps: (1) Optimize the stress distribution within the micro-region to obtain an optimized stress concentration and stress release area distribution configuration; (2) Based on the optimized configuration obtained in step (1), slice the three-dimensional stress distribution configuration for laser additive manufacturing into layers and import the slice information into the forming equipment; (3) Preparation for metal laser additive manufacturing process: layer by layer high-strength aluminum alloy powder is laid; (4) Continuous laser selectively melts powder areas layer by layer according to the component slice information; (5) After the single-layer scanning is completed by continuous laser in step (4), the solidified area is selectively processed by ultrafast laser according to the micro-area stress relief area slice information to complete the processing and shaping of the layer. (6) Repeat steps (3) to (5) until a three-dimensional component is obtained; In step (3), the high-strength aluminum alloy powder is aluminum alloy spherical powder, and its composition range is Mg content of 3-8 wt.%, Sc content of 0.05-1 wt.%, Zr content of 0.02-0.8 wt.%, Fe content of 0.01-0.2 wt.%, Si content of no more than 5 wt.%, with the balance being Al; the particle size of the aluminum alloy spherical powder is 15-45 μm; In step (1), based on finite element analysis software, the internal stress distribution design and its strengthening behavior under load are analyzed. The stress distribution design of the formed specimen is optimized to obtain the stress concentration and stress release area distribution configuration with optimized performance. The stress release area includes rectangular, elliptical and layered micro-regions. Among them, the rectangular stress release area includes the horizontal side length of the stress release micro-region. l Height in forming direction d Horizontal distance between adjacent micro-intervals t and vertical distance s ; Elliptical stress relief region, including the horizontal major axis of the stress relief micro-region l The short axis of the forming direction d Horizontal distance between adjacent micro-intervals t and vertical distance s； Layered micro-regions include stress relief zones. d and vertical distance s; 80μm≤l≤400μm 100μm≤d≤600μm, 100μm≤t≤400μm, 100μm≤s≤600μm; In step (1), the configuration features include the size, shape and boundary of the stress concentration region, and the size, shape and boundary of the stress release region; wherein, the stress concentration region corresponds to the powder region subjected to continuous laser, and the stress release region corresponds to the micro-region subjected to interlayer ultrafast laser.

2. The method for improving the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser as described in claim 1, characterized in that, In step (2), based on the configuration obtained in step (1), the layer slicing software is used to slice the model, obtain the 3D model slicing information, and import it into the selected area laser melting device.

3. The method for improving the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser as described in claim 1, characterized in that, The slicing information includes the continuous laser processing area and laser path, and the ultrafast laser interlayer processing area and laser path.

4. The method for improving the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser as described in claim 1, characterized in that, In step (3), the oxygen content of the cavity where the high-strength aluminum alloy powder is laid is less than 100 ppm.

5. The method for improving the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser as described in claim 1, characterized in that, In step (3), the thickness of the single-layer high-strength aluminum alloy powder is 30-60 μm.

6. The method for improving the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser as described in claim 1, characterized in that, In step (4), the continuous laser power is 150-450 W, the scanning speed is 400-2000 mm / s, and the spot diameter is 50-100 μm.

7. The method for improving the strength and toughness of additively manufactured aluminum components based on continuous ultrafast composite laser according to claim 1, characterized in that, In step (5), the ultrafast laser power is 20-100 W and the pulse width is 1-100 ns.

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