An additive manufacturing method based on single-material three-dimensional heterogeneous structure preparation

Abstract

The present invention discloses an additive manufacturing method based on the preparation of a three-dimensional heterogeneous structure of a single material. Aiming at the formation of complex components of precipitation-strengthened aluminum alloys, the invention adopts laser selective melting 3D printing technology. During the forming process, the laser process is regulated to perform secondary melting of interlayer micro-regions, thereby constructing a single-layer two-dimensional scale remelted area and a non-remelted area with differentiated microstructures and mechanical properties. Furthermore, the forming and preparation of three-dimensional heterogeneous structural materials based on a single material is achieved through the 3D printing laminated manufacturing characteristics. The present invention overcomes the process difficulties of heterogeneous material forming and preparation under traditional processes; solves the interface bonding problem under the splicing of dissimilar materials based on the heterogeneous layout of the spatial microstructure of a single material; achieves the optimization and improvement of mechanical properties compared to homogeneous materials, and can realize the integrated forming and manufacturing of heterogeneous materials with arbitrary shapes.

Description

Technical Field

[0001] The present invention belongs to the field of manufacturing complex components with heterogeneous structures, and relates to an additive manufacturing method based on the preparation of three-dimensional heterogeneous structures of a single material. Background Art

[0002] Compared to traditional homogeneous structural materials, metal materials that exhibit non-uniform distributions of internal spatial structure, strength, or composition, with internal "soft zones" and "hard zones" as structural units, are called "heterogeneous metal materials," or heterogeneous structural materials. Heterogeneous structural materials can achieve synergistic improvements in matrix strength and toughness through mechanisms such as stress delocalization, strengthening induced by geometrically required dislocation stacking within the heterogeneous structure, and back stress strengthening caused by non-uniform deformation in the heterogeneous regions. These materials hold significant application prospects in major engineering fields such as aerospace, transportation, and marine equipment.

[0003] However, compared with homogeneous materials, metal heterostructures face significant challenges in forming and preparation. On the one hand, the forming of metal materials involves high temperature, high pressure and rapid melting and solidification processes. How to construct a heterostructure with a distribution of "soft zones" and "hard zones" inside the solidification process poses severe technical challenges to traditional metal forming processes. Current methods for forming metal heterostructures include surface mechanical grinding, ultrasonic surface rolling, asynchronous rolling, and electrodeposition. The process is cumbersome and costly, and is relatively limited in the field of forming complex components. At the same time, metal heterostructures are often made by combining two different materials. Pores, cracks and other defects are prone to occur at the interface of multiple materials, which can easily lead to component failure during service.

[0004] In recent years, selective laser melting (SLM) technology has gained significant advantages in the integrated forming and fabrication of complex components by melting metal materials layer by layer and selectively melting and depositing them. The patented "A Dual-Laser Cold and Hot Composite Processing Method for Heterogeneous Structures" utilizes ultrafast laser cold processing for subtractive material removal, followed by hot processing for additive material filling with heterogeneous powders. This provides a method for heterogeneous material forming, but the process remains complex and involves issues such as precise filling of heterogeneous powders and the bonding of multiple materials. Therefore, there is an urgent need to develop a forming method that can achieve precise and controllable distribution of heterogeneous structures in three dimensions using a single material. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to propose a method for integrated forming processing of three-dimensional metal heterogeneous structures based on a single material in response to the problems of the existing technology such as complicated process flow, difficulty in forming complex heterogeneous components and poor bonding of multi-material interfaces.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] An additive manufacturing method for preparing a three-dimensional heterogeneous structure based on a single material comprises the following steps:

[0008] (1) Preparing aluminum alloy spherical metal powder having precipitation strengthening properties as a raw material;

[0009] (2) Constructing a model containing three-dimensional information of the heterogeneous structure and performing layered slicing processing to obtain two-dimensional slicing information of the heterogeneous structure, and inputting the slicing information into the selective laser melting equipment;

[0010] (3) The aluminum alloy powder precipitated and strengthened in step (1) is loaded layer by layer into a laser selective melting device in an inert protective gas atmosphere;

[0011] (4) Based on the two-dimensional slice information of the heterogeneous structure, the laser beam is controlled layer by layer to selectively melt the metal powder;

[0012] (5) After completing the single-layer laser selective melting of metal powder, the interlayer toughening process is carried out according to the heterogeneous structure information, and the solidified area of ​​the layer is selectively laser-melted in the micro-area secondary melting.

[0013] (6) Repeat the above steps (3) to (5) until the heterostructure is formed.

[0014] Specifically, in step (1), the aluminum alloy spherical metal powder having precipitation strengthening properties is selected from 2XXX Al-Cu-Mg, 6XXX Al-Mg-Si, and 7XXX Al-Zn alloys as described in the standard "GB T16474-1996 Method for Designating Wrought Aluminum and Aluminum Alloys." Furthermore, trace element-modified 5XXX Al-Mg alloys also fall within this range, with the modifying elements including Sc (0-0.6 wt.%), Zr (0-0.6 wt.%), and Er (0-0.6 wt.%).

[0015] Preferably, the aluminum alloy spherical metal powder with precipitation strengthening properties is preferably a trace element modified 5XXXAl-Mg alloy with a Mg content of 3-6wt.%, a Sc content of 0.2-0.6wt.%, a Zr content of 0.1-0.3wt.%, a Fe content of 0-0.1wt.%, and Al as the balance.

[0016] Furthermore, in step (1), the powder is prepared by a pre-alloyed gas atomization method, the powder particle size is between 15-53 μm, and it has good fluidity. It is dried in a vacuum drying oven at 110-120° C. for 4-8 hours before being loaded into the laser selective melting equipment.

[0017] Specifically, in step (2), a three-dimensional heterogeneous structure data model is first constructed, including the dimensions of the three-dimensional solid components, the dimensions and contours of the secondary melting regions between layers.

[0018] Specifically, in step (2), the heterogeneous structure model is sliced ​​layer by layer using slicing software such as Materialise Magics to obtain two-dimensional slicing information, including the size, contour, and path planning of the laser melting powder area; and the size, contour, and path planning of the interlayer secondary melting area.

[0019] Specifically, in step (3), an aluminum alloy substrate is selected, cleaned with alcohol, and dried. The powder is loaded into a powder silo, with a single layer of powder laid to a thickness of 30-60 μm. The laser forming chamber is sealed and inert gas is introduced to control the oxygen content in the chamber to be less than 50 ppm.

[0020] Preferably, in step (3), the inert protective gas is argon or helium, and the purity is not less than 99.999%.

[0021] Furthermore, in step (4), the laser beam is controlled to selectively melt the regional powder, the laser spot should be 60-120 μm, the laser power should be 300-400 W, the laser scanning speed should be 600-1200 mm / s, and the scanning spacing should be 60 μm.

[0022] Furthermore, in step (5), the laser power of the laser secondary melting is 200-300 W, the laser scanning speed is 800-1400 mm / s, and the scanning interval is 60 μm.

[0023] Furthermore, in step (6), the stacking manufacturing characteristics of the laser selective melting process are utilized to repeat the above process to achieve the construction and integrated manufacturing of heterogeneous structural metal materials with differentiated microstructures.

[0024] Beneficial effects:

[0025] (1) The present invention uses laser selective melting technology to form aluminum alloy materials with precipitation strengthening characteristics layer by layer. Utilizing the characteristic that in-situ precipitates of precipitation-strengthened aluminum alloys are significantly affected by the thermal process during the solidification process, the method of secondary melting of interlayer micro-regions is used to achieve spatially differentiated heterogeneous distribution of nano-in-situ precipitation, thereby achieving spatial distribution of "soft zones" and "hard zones" in a two-dimensional plane. Furthermore, based on the characteristics of laser selective laser lamination manufacturing, the construction and integrated forming of three-microscale heterogeneous structures of metal materials based on a single material are achieved. The method proposed in the present invention is expected to achieve the integrated forming and preparation of complex metal components with heterogeneous structures, and can achieve synergistic improvements in strength and toughness, and has important application prospects in the fields of aerospace, transportation, etc.

[0026] (2) This invention utilizes the nucleation, precipitation, and coarsening properties of precipitation-strengthened aluminum alloys, combined with the designability of layer-by-layer selective laser melting, to achieve two-dimensional localized precipitate coarsening using interlayer micro-region secondary melting. Furthermore, layer-by-layer processing allows for the construction of a metal material with a heterogeneous structure in three dimensions based on a single material. This solves the challenges of forming and preparing heterogeneous metal materials under traditional processes, as well as the poor interface bonding and cracking of heterogeneous materials, thereby enabling the free design and precise forming of three-dimensional heterogeneous metal materials based on a single material. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0028] Figure 1 Flowchart of the additive manufacturing process of the present invention.

[0029] Figure 2 This is the three-dimensional model of the heterogeneous structure constructed in Example 1.

[0030] Figure 3 This is a diagram of a heterostructure specimen prepared using the method of the present invention in Example 1.

[0031] Figure 4 These are the microhardness test results of the heterogeneous structure specimen prepared in Example 1.

[0032] Figure 5 These are the microhardness test results of the heterogeneous structure specimen prepared in Example 2.

[0033] Figure 6 The microhardness test results of the micro-area of ​​the specimen prepared in Comparative Example 1 are shown. DETAILED DESCRIPTION

[0034] The present invention may be better understood with reference to the following embodiments.

[0035] like Figure 1 As shown, the present invention provides an additive manufacturing process for preparing a three-dimensional heterogeneous structure based on a single material, comprising the following steps:

[0036] Step 1: Raw material preparation. Prepare aluminum alloy spherical metal powder with precipitation strengthening properties as the raw material. The powder is prepared by pre-alloying gas atomization method. The powder particle size is between 15-53μm and has good fluidity. Dry it in a vacuum drying oven at 120℃ for 8 hours before filling it into the powder cylinder.

[0037] The precipitation-hardened aluminum alloys described in step 1 include 2xxx Al-Cu-Mg, 6xxx Al-Mg-Si, and 7xxx Al-Zn alloys as described in the standard "GB T 16474-1996 Method for Designating Wrought Aluminum and Aluminum Alloys." Trace element-modified 5xxx Al-Mg alloys also fall within this range, with the modifying elements including Sc (0-0.6 wt.%), Zr (0-0.6 wt.%), and Er (0-0.6 wt.%). Preferred trace element-modified 5xxx Al-Mg alloys include Mg (3-6 wt.%), Sc (0.2-0.6 wt.%), Zr (0.1-0.3 wt.%), and Al as the balance.

[0038] Step 2: Build a model containing the 3D information of the heterogeneous structure and perform layered slicing to obtain 2D slice information of the heterogeneous structure. This slice information is then input into the selective laser melting equipment. First, a 3D heterogeneous structure data model is constructed, including the dimensions of the 3D solid component and the dimensions and contours of the secondary melting area between layers. Then, using slicing software such as MaterialiseMagics, the heterogeneous structure model is layered and sliced ​​to obtain 2D slice information, including the dimensions, contours, and path planning of the laser melting powder area, as well as the dimensions, contours, and path planning of the secondary melting area between layers.

[0039] Step 3: Prepare for Selective Laser Melting. Select an aluminum alloy substrate, clean it with alcohol, and dry it. Load the powder layer by layer into the powder hopper, with a single layer thickness of 30 μm. Seal the laser forming chamber and introduce inert gas to maintain an oxygen content below 50 ppm.

[0040] The inert gas in step 3 includes argon, helium, etc., and the purity is not less than 99.999%.

[0041] Step 4: Forming Process. Based on the principle of selective laser melting, the powder spreading arm evenly deposits a single layer of precipitation-strengthened aluminum alloy powder feedstock with a thickness of 30 μm on the forming substrate. A computer controls the laser beam to selectively melt the powder based on information such as the part outline and laser path contained in the slicing file. The laser spot size should be 60-120 μm, the laser power 300-400 W, the laser scanning speed 600-1200 mm / s, and the scanning interval 60 μm.

[0042] Step 5: After completing the single-layer laser selective melting of the metal powder, an interlayer toughening process is carried out based on the heterogeneous structure information, that is, selective micro-area laser secondary melting is performed on the solidified area of ​​the layer. The process range is as follows: laser power 200-300W, laser scanning speed 800-1400mm / s, and scanning spacing 60μm. The properties of precipitation-strengthened aluminum alloys are closely related to the nano-in-situ precipitated phases inside the specimen, and the size and morphology of the nano-precipitated phases are related to the melting / solidification thermal process. Due to the large heat input and significant heat accumulation effect in the interlayer secondary melting area, the nano-in-situ precipitated phases will show significant coarsening, which in turn reduces the strength of the interlayer secondary melting area.

[0043] After completing the above process, a two-dimensional single-layer heterostructure with controllable distribution of soft / hard regions is constructed.

[0044] Furthermore, based on the principle of laser selective melting lamination manufacturing, the forming cylinder descends by a layer thickness, and the powder spreading arm lays a new single layer of powder. Then, based on the heterogeneous structure slicing information, the single layer laser selective melting powder / interlayer micro-area secondary melting process described in steps 4-5 is repeated.

[0045] By repeating the above powder spreading and printing process until the component is formed, a three-dimensional spatial heterogeneous structure material can be constructed based on a single material, realizing an additive manufacturing process method for preparing three-dimensional heterogeneous structures based on a single material.

[0046] Example 1

[0047] In this embodiment, the raw powder in step 1 is a 5xxx Al-Mg alloy modified with trace elements. The specific powder alloy composition includes the following components in weight percentage:

[0048] The content of Mg is 4.2%, the content of Sc is 0.4%, the content of Zr is 0.2%, the content of Fe is 0.1%, and the balance is Al.

[0049] In the embodiment, the inert gas in step 2 is argon, and the model containing the three-dimensional spatial information of the heterogeneous structure is constructed as follows Figure 2 The single-layer laser selective melting powder area and the secondary melting of the interlayer micro-area are distributed in a spatial magic cube shape. The side length of a single cube is 1mm, and the Materialise Magics software is used for layered slicing.

[0050] In the embodiment, the laser acting on the powder in step 3 is performed with the following process parameters: laser power 400W, laser scanning speed 1000mm / s. The laser parameters for the secondary melting of the interlayer micro-region are: laser power 300W, laser scanning speed 1200mm / s.

[0051] Figure 3The figure is a heterogeneous structure specimen formed in Example 1. The microhardness test of the formed specimen section is as follows Figure 4 As shown, the results show that the additive manufacturing process of the present invention based on a single material to achieve three-dimensional heterogeneous structure preparation has successfully prepared a heterogeneous structure material with spatial soft / hard phase spatial distribution, wherein the average hardness of the laser-induced powder area (unremelted area) is ~175HV 0.2 , while the average hardness of the secondary melting (remelting zone) in the interlayer micro-region is ~138HV 0.2 The microhardness test of the micro-region shows that there is a significant difference in the hardness of the matrix of adjacent micro-regions of the heterogeneous structure material, and a three-dimensional heterogeneous structure aluminum alloy with controllable spatial structure has been successfully prepared.

[0052] Example 2

[0053] In this embodiment, the raw powder in step 1 is a 5xxx Al-Mg alloy modified with trace elements. The specific powder alloy composition includes the following components in weight percentage:

[0054] The content of Mg is 4.2%, the content of Sc is 0.4%, the content of Zr is 0.2%, the content of Fe is 0.1%, and the balance is Al.

[0055] In Example 2, the inert gas in step 2 is argon. The single-layer laser selective melting powder area and the secondary melting of the interlayer micro-area are distributed in a spatial magic cube shape. The side length of a single cube is 1.5 mm, and the layered slicing is performed using Materialise Magics software.

[0056] The process parameters for the laser treatment of the powder in step 3 of Example 2 are: laser power 400W, laser scanning speed 1000mm / s. The laser parameters for the secondary melting of the interlayer micro-region are: laser power 300W, laser scanning speed 1200mm / s.

[0057] Example 2 Microhardness test of the formed specimen cross section Figure 5 As shown, the average hardness of the laser-induced powder area (non-remelted area) is about 175HV. 0.2 , while the average hardness of the secondary melting (remelting zone) in the interlayer micro-region is ~138HV 0.2 Microhardness testing of microregions showed that there was a significant difference in the hardness of the matrix of adjacent microregions of the heterostructure material, and a three-dimensional heterostructure aluminum alloy with controllable spatial structure was successfully prepared. Compared with Example 1, by adjusting the original heterostructure design dimensions through the method of the present invention, the size and distribution of the soft / hard regions of the three-dimensional heterostructure can be arbitrarily adjusted, and the structure has a high degree of designability.

[0058] Example 3

[0059] In this embodiment, the raw powder in step 1 is a 5xxx Al-Mg alloy modified with trace elements. The specific powder alloy composition includes the following components in weight percentage:

[0060] The content of Mg is 4.2%, the content of Sc is 0.4%, the content of Zr is 0.2%, the content of Fe is 0.1%, and the balance is Al.

[0061] In step 2 of Example 3, the inert gas is argon. The single-layer laser selective melting powder area and the secondary melting of the interlayer micro-area are distributed in a spatial magic cube shape. The side length of a single cube is 1 mm, and the layered slicing is performed using Materialise Magics software.

[0062] The process parameters for the laser treatment of the powder in step 3 of Example 3 are: laser power 350W, laser scanning speed 1000mm / s. The laser parameters for the secondary melting of the interlayer micro-region are: laser power 200W, laser scanning speed 1200mm / s.

[0063] In the microhardness test of the cross section of the formed specimen in Example 3, the average hardness of the laser acting on the powder area (unremelted area) is about 165HV. 0.2 , while the average hardness of the secondary melting (remelting zone) between the layers is ~145HV 0.2 Microhardness testing of micro-regions showed that there was a significant difference in the hardness of the matrix of adjacent micro-regions of the heterostructure material, and a three-dimensional heterostructure aluminum alloy with controllable spatial structure was successfully prepared. Compared with Example 1, by adjusting the powder melting and interlayer micro-region melting laser process parameters through the method of the present invention, the performance of the soft / hard regions of the three-dimensional heterostructure can be controlled and adjusted, and the performance is highly designable.

[0064] Comparative Example 1

[0065] In this comparative example, the raw powder in step 1 is a 5xxx Al-Mg alloy modified with trace elements. The specific powder alloy composition includes the following components in weight percentage:

[0066] The content of Mg is 4.2%, the content of Sc is 0.4%, the content of Zr is 0.2%, the content of Fe is 0.1%, and the balance is Al.

[0067] In comparative example 1, the inert gas in step 2 is argon. The secondary melting process of the interlayer micro-region proposed in the present invention is removed in the structural design. The entire structure is formed by laser melting powder, and the layered slicing is performed using Materialise Magics software.

[0068] The process parameters of the laser acting on the powder in step 3 of Comparative Example 1 are: laser power 400W, laser scanning speed 1000mm / s.

[0069] Comparative Example 1 Microhardness test of the formed specimen cross section Figure 6 As shown, the average hardness of the laser-induced powder area (non-remelted area) is about 175HV. 0.2 There is no significant difference in the hardness of adjacent micro-regions. Compared with Example 1, the removal of the interlayer micro-region toughening process designed by the method of the present invention cannot achieve the three-dimensional heterogeneous structure forming preparation, indicating that the present invention can realize the integrated forming and manufacturing of heterogeneous materials with arbitrary shapes.

[0070] This invention, aimed at forming complex components of precipitation-strengthened aluminum alloys, employs laser selective melting 3D printing technology. During the forming process, the laser process is regulated to perform secondary melting of interlayer micro-regions, constructing a single-layer two-dimensional scale with differentiated microstructures and mechanical properties of remelted and unremelted areas. Furthermore, through the lamination manufacturing characteristics of 3D printing, the forming and preparation of three-dimensional heterogeneous structural materials based on a single material is achieved. The invention has the following advantages: it overcomes the process difficulties of forming and preparing heterogeneous materials under traditional processes; it solves the interface bonding problem of dissimilar materials under splicing based on the heterogeneous layout of the spatial microstructure of a single material; it achieves optimized and improved mechanical properties compared to homogeneous materials, and can realize the integrated forming and manufacturing of heterogeneous materials with arbitrary shapes.

[0071] This invention provides a concept and method for additive manufacturing of three-dimensional heterogeneous structures based on a single material. Numerous methods and approaches exist for implementing this technical solution. The foregoing merely represents a preferred embodiment of the invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the invention, and such improvements and modifications are considered within the scope of protection of this invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. An additive manufacturing method based on the preparation of a three-dimensional heterogeneous structure of a single material, characterized in that: The steps include: (1) Preparing aluminum alloy spherical metal powder with precipitation strengthening properties as raw material; (2) Construct a model containing three-dimensional information of the heterogeneous structure and perform layered slicing processing to obtain two-dimensional slicing information of the heterogeneous structure, and input the slicing information into the selective laser melting equipment; (3) The aluminum alloy powder precipitated and strengthened in step (1) is loaded layer by layer into the laser selective melting equipment, and filled with an inert protective gas atmosphere; (4) Based on the two-dimensional slice information of the heterogeneous structure, the laser beam is controlled layer by layer to selectively melt the metal powder; (5) After completing the single-layer laser selective melting of metal powder, the interlayer toughening process is carried out according to the heterogeneous structure information, and the solidified area of ​​the layer is selectively laser-melted in the micro-area secondary melting; (6) Repeat the above steps (3) to (5) until the heterostructure is formed; In step (2), a three-dimensional heterogeneous structure data model is first constructed, including the dimensions of the three-dimensional solid components, the dimensions and contours of the secondary melting regions between layers; In step (1), the aluminum alloy spherical metal powder having precipitation strengthening properties includes Al-Cu-Mg alloy, Al-Mg-Si alloy, Al-Zn alloy or Al-Mg modified with trace elements; In step (4), the laser beam is controlled to selectively melt the powder in the area. The laser spot should be 60-120 μm, the laser power should be 300-400 W, the laser scanning speed should be 600-1200 mm / s, and the scanning interval should be 60 μm. In step (5), the laser power of the laser secondary melting is 200-300 W, the laser scanning speed is 800-1400 mm / s, and the scanning interval is 60 μm.

2. The additive manufacturing method for preparing a three-dimensional heterogeneous structure based on a single material according to claim 1, characterized in that: The aluminum alloy spherical metal powder with precipitation strengthening properties has a Mg content of 3-6 wt.%, a Sc content of 0.2-0.6 wt.%, a Zr content of 0.1-0.3 wt.%, a Fe content of 0-0.1 wt.%, and Al as the balance.

3. The additive manufacturing method for preparing a three-dimensional heterogeneous structure based on a single material according to claim 1, characterized in that: In step (1), the powder is prepared by a pre-alloyed gas atomization method, the powder particle size is between 15-53 μm, and it is dried in a vacuum drying oven at 110-120°C for 4-8 hours before being loaded into the laser selective melting equipment.

4. The additive manufacturing method for preparing a three-dimensional heterogeneous structure based on a single material according to claim 1, characterized in that: In step (2), the heterogeneous structure model is sliced ​​layer by layer using slicing software to obtain two-dimensional slicing information, including the size, contour, and path planning of the laser melting powder area; and the size, contour, and path planning of the secondary melting area between layers.

5. The additive manufacturing method for preparing a three-dimensional heterogeneous structure based on a single material according to claim 1, characterized in that: In step (3), an aluminum alloy substrate is selected, and the powder is loaded into the powder silo. The thickness of the single layer of powder is 30-60 μm. The laser forming chamber is sealed and an inert gas is introduced to control the oxygen content in the chamber to be less than 50 ppm.

6. The additive manufacturing method for preparing a three-dimensional heterogeneous structure based on a single material according to claim 1, characterized in that: In step (3), the inert protective gas is argon or helium, and the purity is not less than 99.999%.

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