Methods for controlling and optimizing fracture toughness of low-Mg content high-strength aluminum alloys in laser additive manufacturing

Abstract

A method for controlling and optimizing the fracture toughness of low-Mg-content high-strength aluminum alloys using laser additive manufacturing was developed. The mass percentages of each element in the prepared Al-Mg-Mn-Sc-Zr alloy were: Mg: 1.1%–2.2%, Mn: 2.1%–2.2%, Sc: 0.7%–0.8%, Zr: 0.4%–0.5%, with total impurities not exceeding 0.1%, and the balance being Al. The fracture toughness value K of the alloy was... IC ≥37.5 MPa∙m 1 / 2 Furthermore, as the Mg content decreases within the range of 1.1% to 2.2%, the fracture toughness value K of the alloy decreases. IC The trend is upward. Therefore, this invention reveals the quantitative correlation between Mg content and fracture toughness in the alloy within the low Mg content range, finding that reducing Mg content significantly improves fracture toughness within this range, providing a novel approach for toughness control of high-strength aluminum alloys.

Description

Technical Field

[0001] This invention relates to a method for controlling and optimizing the fracture toughness of high-strength aluminum alloys with low Mg content in laser additive manufacturing, belonging to the technical field of special processing in laser additive manufacturing. Background Technology

[0002] Additive manufacturing technology, with its core advantages of "layer-by-layer stacking and near-net-shape forming," has broken through the manufacturing limitations of traditional processing for complex structures. It occupies a key position in lightweight manufacturing in strategic fields such as aerospace, high-end equipment, and new energy, enabling high-precision and rapid manufacturing of complex parts while significantly reducing material waste and shortening development cycles. Aluminum alloys, due to their low density, high specific strength, excellent corrosion resistance, and formability, have become key structural materials in these fields. Among them, Al-Mg-Mn-Sc-Zr alloys, with their fine-grain strengthening and solid solution strengthening effects introduced by Mn, Sc, and Zr elements, exhibit excellent mechanical properties during additive manufacturing and are widely expected to be used in manufacturing critical components that withstand complex loads. However, current research on laser additive manufacturing of Al-Mg-Mn-Sc-Zr alloys focuses primarily on macroscopic optimization of the overall composition ratio or the influence of single elements on strength and plasticity, neglecting fracture toughness (KIC), a core indicator related to the component's resistance to crack propagation. Current research on the performance regulation of Al-Mg-Mn-Sc-Zr alloys faces significant limitations in its focus on Mg. Firstly, high Mg content in the alloy can lead to the formation of coarse second-phase precipitates and grain boundary segregation during rapid solidification in additive manufacturing. This intensifies internal stress concentration, causing not only forming defects such as porosity and cracks but also a significant decrease in fracture toughness. Conversely, high-strength aluminum with low Mg content not only improves formability but also reduces dust during forming, facilitating the formation of large components. Secondly, most studies simply classify Mg as a "strengthening element" to enhance alloy strength, failing to systematically analyze the subtle variations in Mg content within the low Mg content range or delve into the intrinsic relationship between these variations and the alloy's fracture toughness. This limits the application of additively manufactured Al-Mg-Mn-Sc-Zr alloys.

[0003] Therefore, how to analyze the correlation between Mg content and KIC value in additive manufacturing Al-Mg-Mn-Sc-Zr alloys, guide industrial production, and help overcome fracture resistance bottlenecks is a hot research topic in the independent and controllable development of high-end manufacturing materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the technical problems of difficult and unclear mechanism in the control of fracture toughness of Al-Mg-Mn-Sc-Zr alloy in the prior art, and to provide a method for controlling and optimizing the fracture toughness of high-strength aluminum alloy with low Mg content in laser additive manufacturing. This provides a replicable and scalable technical path for the high-performance application of additive manufacturing technology in the field of high-end equipment, and further releases the design potential of lightweight and structurally complex designs.

[0005] To achieve the above-mentioned technical objectives, the present invention will adopt the following technical solution:

[0006] A laser additive manufacturing method for a low-Mg content high-strength aluminum alloy, wherein the mass percentages of each element are: Mg: 1.1%–2.2%, Mn: 2.1%–2.2%, Sc: 0.7%–0.8%, Zr: 0.4%–0.5%, the total impurity content not exceeding 0.1%, and the balance being Al; the fracture toughness value of the alloy is... Furthermore, as the Mg content decreases within the range of 1.1% to 2.2%, the fracture toughness value K of the alloy decreases. IC It shows an upward trend.

[0007] Preferably, when the Mg content is 1.1%, the fracture toughness value of the alloy is... And the microstructure characteristics satisfy: the depth of the dimples at the fracture surface is dimple density is , The average size of the precipitated phase was 2.02 nm, and the precipitation density was [missing value]. .

[0008] Another technical objective of this invention is to provide a method for controlling and optimizing the fracture toughness of low-Mg-content high-strength aluminum alloys produced by laser additive manufacturing as described above, comprising the following steps:

[0009] Step S1: Fix the content of Mn, Sc and Zr elements, and prepare at least four Al-Mg-Mn-Sc-Zr alloy samples with different Mg element contents by laser additive manufacturing within the range of 1.1% to 2.2% by mass percentage;

[0010] Step S2: Perform fracture toughness tests on each alloy sample to obtain the fracture toughness value K for each alloy sample. IC ;

[0011] Step S3: Perform microstructure characterization on each alloy sample to obtain microstructure characteristic parameters, including fracture dimple characteristic parameters and... Precipitated phase characteristic parameters; fracture dimple characteristic parameters include fracture dimple depth and fracture dimple density; The characteristic parameters of the precipitated phase include Average size of precipitated phase and Precipitation density of the precipitated phase;

[0012] Step S4: Establish Mg elemental content, microstructure characteristic parameters, and fracture toughness value K. IC The quantitative correlation model determined that within the low Mg content range of 1.1% to 2.2% by mass percentage, as the Mg element content decreased, The average size of the precipitated phase increases, the precipitation density decreases, the dimple depth of the fracture surface increases, and the density increases, resulting in a higher fracture toughness value K of the alloy. IC The corresponding relationship of increase.

[0013] Preferably, the contents of at least four different Mg elements mentioned in step S1 include 2.2%, 1.8%, 1.5%, and 1.1%, corresponding to fracture toughness values ​​K. IC They are respectively , , and .

[0014] Preferably, the alloy sample in step S1 is prepared into powder by gas atomization and then laser additive manufacturing. The process parameters of the gas atomization method are: atomization temperature 820-850℃, atomization pressure 2.0-2.5 MPa, and metal liquid flow rate 2.0 kg / min.

[0015] Preferably, the powder prepared by the gas atomization method is selected with a particle size of [missing value] after sieving. The powder was subjected to passivation treatment in an oxygen-containing atmosphere at room temperature for 24 hours to form an oxide film on the powder surface.

[0016] Preferably, the established quantitative correlation model uses Mg elemental content and the microstructure characteristic parameters as independent variables, and fracture toughness value K as the independent variable. IC For the multiple regression equation established with the dependent variable as the dependent variable, and when establishing the quantitative correlation model, at least one of the fracture dimple characteristic parameters, namely fracture dimple depth and fracture dimple density, should be considered. The characteristic parameters of the precipitated phase should at least be considered. Average size of precipitated phase and One of the precipitation densities of the precipitated phase; the quantitative correlation model can predict the fracture toughness value K of the alloy based on the input Mg content and microstructure characteristic parameters. IC , represented as:

[0017] ;

[0018] In the above formula: KIC represents the fracture toughness value; β0 is the regression constant term, and β1 is the partial regression coefficient of Mg content; β2 represents the Mg content, with a mass percentage ranging from 1.1% to 2.2%; h represents the characteristic parameter of the fracture dimples; β3 represents the partial regression coefficient of the characteristic parameter of the precipitates; and d represents the characteristic parameter of the precipitates.

[0019] Another technical objective of this invention is to provide a method for preparing low-Mg-content high-strength aluminum alloys by laser additive manufacturing as described above, comprising the following steps:

[0020] Step A: Prepare alloy powder according to the alloy composition ratio, and use gas atomization method for preparation. The atomization temperature is 820-850℃, and the atomization pressure is... Metal liquid flow rate ;

[0021] Step B: The alloy powder is sieved to select alloy powder with a particle size of 15-53 μm, and then passivated in an oxygen-containing atmosphere at room temperature for 24 hours.

[0022] Step C: The powder processed in step B is printed into shape using laser additive manufacturing equipment to obtain an Al-Mg-Mn-Sc-Zr alloy sample;

[0023] The alloy composition in step A is as follows: Mg: 1.1%–2.2%, Mn: 2.1%–2.2%, Sc: 0.7%–0.8%, Zr: 0.4%–0.5%, the total impurity content does not exceed 0.1%, and the balance is Al.

[0024] Preferably, the alloy sample printed in step C has a density ≥99.98%, the width and depth of the molten pool decrease as the Mg content decreases, and the molten pool size dispersion decreases.

[0025] Preferably, the powder processed in step B has a loose packing density of The tap density is Sphericity greater than 90%, powder .

[0026] Based on the above-mentioned technical objectives, the present invention has the following advantages compared with the prior art:

[0027] 1. This invention systematically reveals the quantitative correlation between Mg content and fracture toughness KIC value in Al-Mg-Mn-Sc-Zr alloys within the low Mg content range (1.1% to 2.2%). It finds that reducing Mg content within this range can significantly improve the fracture toughness of the alloy, providing a new approach for the toughness control of high-strength aluminum alloys.

[0028] 2. This invention establishes a "Mg content-microstructure-K" model. ICThe correlation model of "value" clarifies that the decrease in Mg content leads to an increase in the average size of Al3(Sc,Zr) precipitates (from 1.34 nm to 2.02 nm) and a decrease in precipitation density (from 1.34 nm to 2.02 nm). Down to At the same time, the depth of the fracture dimples increases (from 3-4 μm to 7-8 μm) and the density increases (from 3-5 dimples / m²). Increase to 12-15 / The microscopic mechanism of the alloy provides a theoretical basis for the precise control of alloy properties.

[0029] 3. The fracture toughness value K of the Al-Mg-Mn-Sc-Zr alloy provided by this invention. IC All reached The above shows the fracture toughness value K when the Mg content is 1.1%. IC Gundam It represents a significant improvement over existing alloys of the same type.

[0030] 4. The alloy powder prepared by the gas atomization method of this invention has high sphericity (>90%), good flowability, and low bulk density. tap density Due to its excellent properties, the density of the alloy sample after laser additive manufacturing reaches over 99.98%, ensuring the stability and reliability of the material properties.

[0031] 5. Based on the quantitative correlation between "composition-structure-property", this invention realizes the transformation of performance control of additive manufacturing aluminum alloys from "experience-based trial and error" to "precise controllability", providing a replicable and scalable technical path for the urgent needs of aerospace and other fields for high fracture toughness materials. Attached Figure Description

[0032] Figure 1 The image shows the morphology of the prepared Al-Mg-Mn-Sc-Zr powder.

[0033] Figure 2 Load-displacement curves for fracture toughness testing of Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0034] Figure 3 SEM images of the fracture surface region of Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0035] Figure 4 SEM images of the transition region from pre-crack to fracture surface in Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0036] Figure 5EDS images of the transition region from pre-crack to fracture surface in Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0037] Figure 6 TEM images of Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0038] Figure 7 The images show the inverse Fourier transforms of Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0039] Figure 8 Pore ​​distribution diagrams of Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0040] Figure 9 The image shows the molten pool characteristics of Al-Mg-Mn-Sc-Zr alloys with four different Mg contents.

[0041] Figure 10 A comparison of the fracture toughness of four Al-Mg-Mn-Sc-Zr alloys with different Mg contents.

[0042] Figure 11 The images show the pore distribution, molten pool morphology, and fracture toughness of Al-Mg-Mn-Sc-Zr alloy specimens with high Mg content.

[0043] Figure 12 The images show the pore distribution, molten pool morphology, and fracture toughness of Al-Mg-Mn-Sc-Zr alloy specimens with low Mg content. Detailed Implementation

[0044] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specifically stated, the relative arrangement, expressions, and values ​​of components and steps set forth in these embodiments do not limit the scope of the present invention. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0045] Example 1

[0046] This embodiment uses an Al-Mg system as the base. The elements are calculated by mass percentage as follows: Mg: 2.2%, Mn: 2.1-2.2%, Sc: 0.7-0.8%, Zr: 0.4-0.5%, the total impurity content does not exceed 0.1%, and the balance is Al.

[0047] This invention uses gas atomization to prepare powder, with the following parameters: atomization temperature 820-850 ℃ and atomization pressure 2.0-2.5 MPa.

[0048] After atomization, the powder is sieved to select particles with a size between 15 and 53 μm. Then, a passivation treatment is performed by placing the powder in an atmosphere containing a small amount of oxygen at room temperature for 24 hours, allowing a thin oxide film to form on the powder surface, improving its oxidation resistance and storage stability. The resulting powder meets the requirements for laser additive manufacturing.

[0049] The processed powder has good flowability and a bulk density of up to [value missing]. The tap density can reach The Al-Mg-Mn-Sc-Zr alloy powder exhibits regular spherical shapes with a sphericity greater than 90%. Powder D 10 (μm): 22.140, D 50 (μm): 38.012, D 90 (μm): 64.294. Powder morphology as follows: Figure 1 As shown.

[0050] Using the aforementioned powder as raw material, Al-Mg-Mn-Sc-Zr alloy samples were obtained by laser additive manufacturing equipment. The samples were then processed according to the national standard GB / T 4161-2007, "Plane Strain Fracture Toughness K of Metallic Materials". IC The test method requires fracture toughness testing, and the load-displacement curve of the obtained alloy specimen is as follows: Figure 2 As shown in the figure. The test results show that the peak load of the alloy sample is stable at 22-23 kN. This load value corresponds to the maximum external force that the material can withstand during the crack initiation stage, marking the critical state of the material transitioning from elastic deformation to plastic deformation and reaching its bearing limit. Simultaneously, the displacement corresponding to the peak load is 0.8-0.9 mm. This displacement parameter reflects the material's basic ability to absorb energy through plastic deformation before reaching its maximum bearing capacity, indicating that the matrix possesses certain plastic flow characteristics. Furthermore, the curve shows a steep downward trend after the peak load. This morphological feature corresponds to the crack propagation process after initiation, indicating that the material can still transfer load through its own structural response during the crack propagation stage, enabling the alloy sample to achieve a fracture toughness value of [value missing]. .

[0051] The SEM fracture morphology of the alloy sample is as follows: Figure 3-4 As shown, the fracture surface exhibits certain ductile fracture characteristics, with numerous irregular polygonal dimples. These dimples are typical products formed during the fracture process through matrix plastic deformation, micropore nucleation, and polymerization. The depth of a single dimple is approximately 3-4 μm, indicating that the matrix possesses a certain degree of plastic flow capability. The dimple density is [not specified]. This indicates the presence of matrix plastic deformation and micropore coalescence mechanisms during fracture. Simultaneously, some relatively rough and irregular areas were observed on the fracture surface, possibly due to insufficient resistance during crack propagation, affecting further energy dissipation and resulting in the alloy's fracture toughness reaching a certain level. .

[0052] EDS elemental surface scan of alloy samples Figure 5 As shown, Mg in the alloy sample exists in a solid solution state within the Al matrix, while exhibiting a localized enrichment trend at grain boundaries. This distribution pattern is spontaneously formed during alloy solidification and heat treatment based on the energy difference between the grain boundaries and the matrix region, consistent with the basic laws of element migration and enrichment in alloys. More importantly, EDS analysis clearly shows that Mn, Sc, and Zr maintain good synergistic distribution characteristics, with the three elements jointly constituting a significant portion of the alloy within the matrix. and Composite reinforcing phase. Among them, The phase can effectively hinder dislocation movement through the Orowan mechanism, significantly improving the matrix's resistance to plastic deformation; while If they are in harmony, then they will be together. The synergistic effect on grain boundaries helps to pin them, inhibiting excessive grain growth during preparation and maintaining the stability of the grain structure, thus enabling the alloy sample to achieve a high fracture toughness value. .

[0053] TEM images of alloy samples as follows Figure 6-7 As shown, Mn elements exhibit a cooperative distribution with Sc and Zr elements, thus forming... and Composite reinforcing phase. Among them, The precipitated phase exhibits excellent strengthening properties, with an average size of only 1.34 nm. This small size provides favorable conditions for hindering dislocation movement through the Orowan mechanism; simultaneously, The precipitated density is relatively high, reaching High-density precipitates can pin displacements at more sites, significantly improving the matrix's resistance to deformation. Furthermore, The dense distribution of precipitates can synergistically enhance the grain boundary pinning effect, effectively stabilize the grain structure, and improve the fracture toughness of the alloy. )achieve .

[0054] Example 2:

[0055] This embodiment uses an Al-Mg system as the base. The elements are calculated by mass percentage as follows: Mg: 1.8%, Mn: 2.1-2.2%, Sc: 0.7-0.8%, Zr: 0.4-0.5%, the total impurity content does not exceed 0.1%, and the balance is Al.

[0056] This invention uses gas atomization to prepare powder, with the following parameters: atomization temperature 820-850 ℃ and atomization pressure 2.0-2.5 MPa.

[0057] After atomization, the powder is sieved to select particles with a size between 15 and 53 μm. Then, a passivation treatment is performed by placing the powder in an atmosphere containing a small amount of oxygen at room temperature for 24 hours, allowing a thin oxide film to form on the powder surface, improving its oxidation resistance and storage stability. The resulting powder meets the requirements for laser additive manufacturing.

[0058] The processed powder has good flowability and a bulk density of up to [value missing]. The tap density can reach ,Should The alloy powder is in the form of regular spheres, with a sphericity greater than 90%. Powder D 10 (μm): 22.140, D 50 (μm): 38.012, D 90 (μm): 64.294. Powder morphology as follows: Figure 1 As shown.

[0059] Using the aforementioned powder as raw material, alloy samples printed by laser additive manufacturing equipment meet the national standard GB_T4161-2007 "Plane strain fracture toughness K of metallic materials". IC The test method requires that the formed Al-Mg-Mn-Sc-Zr alloy samples be observed and tested.

[0060] Observe the load-displacement curve of the fracture toughness test, such as Figure 2As shown, the peak load of the alloy specimen increased to 23-24 kN. This load value means that the material needs to withstand greater external force to reach its bearing limit during the crack initiation stage, indicating a significant enhancement in its initial crack resistance and a higher critical load for the transition from elastic deformation to plastic deformation. Simultaneously, the displacement corresponding to the peak load increased to 0.7-0.8 mm. This displacement parameter reflects the material's stronger ability to absorb energy through plastic deformation before reaching its maximum bearing capacity, indicating superior matrix plastic flow characteristics and the ability to store more energy before fracture to resist crack initiation. Furthermore, the curve shows a steep downward trend after the peak load, a characteristic corresponding to the crack propagation process after initiation. This indicates that the material can still transfer load through its own structural response during crack propagation, resulting in the alloy achieving high fracture toughness. .

[0061] SEM fracture morphology as follows Figure 3-4 As shown, the overall ductile fracture characteristics of the fracture surface are significantly enhanced, with numerous irregular polygonal dimples. These dimples are typical products formed during the fracture process through matrix plastic deformation, micropore nucleation, and polymerization. The depth of individual dimples increases to 5-6 μm, indicating a significant enhancement in the plastic flow capacity of the matrix, which provides more space for dimple development. Simultaneously, the dimple density increases to [missing information]. This confirms that the matrix undergoes more complete plastic deformation during fracture, significantly increasing the energy consumed by micropore polymerization. Furthermore, the relatively rough and irregular areas at the fracture surface decrease, resulting in more effective resistance to crack propagation and improved energy dissipation efficiency, thus enhancing the alloy's fracture toughness. .

[0062] EDS elemental surface scan of alloy samples Figure 5 As shown, although Mg remains dissolved in the Al matrix in this alloy sample, the grain boundary enrichment trend is significantly weakened, with only trace enrichment in local grain boundary regions. This optimized distribution stems from the fact that the driving force for element migration along grain boundaries decreases with the reduction of Mg content, which is more in line with the ideal state of uniform solid solution of alloying elements and effectively avoids the weakening of grain boundary bonding caused by high Mg concentration. Crucially, the synergistic distribution of Mn with Sc and Zr is more compact, and the three elements form a more cohesive distribution within the matrix. and Composite reinforcing phase. Among them, The phase has a stronger resistance to dislocation movement through the Orowan mechanism, further enhancing the matrix's resistance to plastic deformation; The phase then forms a more stable strengthening layer at the grain boundaries, synergistically The phase enhances the grain boundary pinning effect, more effectively inhibits grain growth, and makes the grain structure more uniform and stable, resulting in a high fracture toughness of the alloy. .

[0063] TEM images of alloy samples Figure 6-7As shown, Mn elements exhibit a cooperative distribution with Sc and Zr elements, thus forming... and Composite reinforced phase. The average size of the precipitated phase increased to The ability of the enhanced phase to impede dislocation movement is strengthened; its precipitation density is reduced to The distribution uniformity is significantly improved, allowing for the formation of a more continuous dislocation hindering network within the matrix; simultaneously, The precipitated phases not only exhibited a further increased distribution density but also a more rational aggregation state in the grain boundary regions, resulting in enhanced synergistic strengthening effects. This effectively improved the grain boundaries' resistance to crack propagation, leading to a higher fracture toughness in the alloy. .

[0064] Example 3:

[0065] This embodiment uses Al-Mg as the basic system. The elements are calculated by mass percentage, including: Mg: 1.5%, the existing optimized element content range: Mn: 2.1-2.2%, Sc: 0.7-0.8%, Zr: 0.4-0.5%, the total impurity content does not exceed 0.1%, and the balance is Al.

[0066] This invention uses gas atomization to prepare powder, with the following parameters: atomization temperature 820-850 ℃ and atomization pressure 2.0-2.5 MPa.

[0067] After atomization, the powder is sieved to select particles with a size between 15 and 53 μm. Then, a passivation treatment is performed by placing the powder in an atmosphere containing a small amount of oxygen at room temperature for 24 hours, allowing a thin oxide film to form on the powder surface, improving its oxidation resistance and storage stability. The resulting powder meets the requirements for laser additive manufacturing.

[0068] The processed powder has good flowability and a bulk density of up to [value missing]. The tap density can reach ,Should The alloy powder is in the form of regular spheres, with a sphericity greater than 90%. , , Powder morphology as follows Figure 1 As shown.

[0069] Using the aforementioned powder as raw material, alloy samples printed by laser additive manufacturing equipment meet the national standard GB_T4161-2007 "Plane strain fracture toughness K of metallic materials". IC The test method requires that the formed Al-Mg-Mn-Sc-Zr alloy samples be observed and tested.

[0070] Observe the load-displacement curve of the fracture toughness test, such as Figure 2 As shown, the peak load of the alloy sample further increased to 24-26 kN. This load value indicates that the material needs to withstand greater external force to reach its load-bearing limit during the crack initiation stage, demonstrating a significant enhancement in initial crack resistance and a higher critical load for the transition from elastic deformation to plastic deformation, laying the foundation for improved fracture toughness. Simultaneously, the displacement corresponding to the peak load decreased to 0.7-0.75 mm. This displacement parameter reflects the material's stronger ability to absorb energy through plastic deformation before reaching its maximum load-bearing capacity, indicating superior matrix plastic flow characteristics and the ability to store more energy before fracture to resist crack initiation and propagation. Furthermore, the curve shows a steep downward trend after the peak load, a characteristic corresponding to the crack propagation process after initiation. This indicates that the material can still transfer load through its own structural response during crack propagation, resulting in improved fracture toughness of the alloy. .

[0071] SEM fracture morphology as follows Figure 3-4 As shown, the overall ductile fracture characteristics of the fracture surface are further enhanced, with numerous irregular polygonal dimples. These dimples are typical products formed during the fracture process through matrix plastic deformation, micropore nucleation, and polymerization. The depth of a single dimple is increased to 6-7 μm, indicating that the matrix plastic flow capacity is further enhanced, providing more space for dimple development. At the same time, the dimple density increases to 9-11 dimples per square meter. This confirms that the matrix undergoes more complete plastic deformation during fracture, significantly increasing the energy consumed by micropore polymerization. Furthermore, the relatively rough and irregular areas at the fracture surface are further reduced, resulting in more effective resistance to crack propagation and further improved energy dissipation efficiency, thus enhancing the alloy's fracture toughness. .

[0072] EDS elemental surface scan of alloy samples Figure 5 As shown, Mg in the alloy sample achieves a more uniform solid solution in the Al matrix, and the grain boundary enrichment trend is further weakened, with trace enrichment only occurring at a very few grain boundaries. This optimized distribution stems from the fact that the driving force for element migration along grain boundaries is significantly reduced after the Mg content is further decreased, making it closer to the ideal state of uniform solid solution of alloying elements. This avoids the potential weakening of grain boundary bonding due to excessively high Mg concentration, laying the foundation for improved grain boundary crack resistance. Crucially, the synergistic distribution precision of Mn, Sc, and Zr elements is significantly improved, and the three elements form a more uniform solid solution in the matrix. and Composite reinforcing phase. Among them, The phase has a stronger resistance to dislocation movement through the Orowan mechanism, further enhancing the matrix's resistance to plastic deformation; The phase then forms a denser reinforcing layer at the grain boundaries, working synergistically. Enhancing grain boundary pinning effect more effectively inhibits grain growth, resulting in a more uniform and stable grain structure, thus improving the fracture toughness of the alloy. .

[0073] TEM images of alloy samples Figure 6-7 As shown, Mn elements exhibit a cooperative distribution with Sc and Zr elements, thus forming... and Composite reinforced phase. The average size of the precipitated phase further increased to 1.96 nm, and the ability of the strengthening phase to impede dislocation movement was further enhanced; its precipitation density decreased to The uniformity of distribution is further improved, enabling the formation of a more continuous dislocation hindering network in the matrix; simultaneously, The precipitated phases not only exhibit a further increased distribution density but also a more rational aggregation state in the grain boundary regions, resulting in a further enhanced synergistic strengthening effect. This effectively improves the grain boundaries' resistance to crack propagation, leading to a higher fracture toughness in the alloy. .

[0074] Example 4:

[0075] This embodiment uses Al-Mg as the basic system. The elements are calculated by mass percentage as follows: Mg: 1.1%, Mn: 2.1-2.2%, Sc: 0.7-0.8%, Zr: 0.4-0.5%, the total impurity content does not exceed 0.1%, and the balance is Al.

[0076] This invention uses gas atomization to prepare powder, with the following parameters: atomization temperature 820-850 ℃ and atomization pressure 2.0-2.5 MPa.

[0077] After atomization, the powder is sieved, and particles within a certain size are selected. The powder is then subjected to a passivation treatment by placing it in an atmosphere containing a small amount of oxygen at room temperature for 24 hours to form a thin oxide film on the powder surface, thereby improving the powder's oxidation resistance and storage stability. The resulting powder meets the requirements of laser additive manufacturing.

[0078] The processed powder has good flowability and a bulk density of up to [value missing]. The tap density can reach ,Should The alloy powder is in the form of regular spheres, with a sphericity greater than 90%. Powder D 10 (μm): 22.140, D 50 (μm): 38.012, D 90 (μm): 64.294. Powder morphology as follows: Figure 1 As shown.

[0079] Using the aforementioned powder as raw material, alloy samples printed by laser additive manufacturing equipment meet the national standard GB_T4161-2007 "Plane strain fracture toughness K of metallic materials". IC The test method requires that the formed Al-Mg-Mn-Sc-Zr alloy samples be observed and tested.

[0080] Observe the load-displacement curve of the fracture toughness test, such as Figure 2 As shown, the peak load of the alloy sample further increased to 26-28 kN. This load value indicates that the material needs to withstand greater external force to reach its load-bearing limit during the crack initiation stage, significantly enhancing its initial crack resistance. The critical load for the transition from elastic deformation to plastic deformation is also higher, laying a solid foundation for improved fracture toughness. Simultaneously, the displacement corresponding to the peak load decreased to 0.6-0.7 mm. This displacement parameter reflects the material's stronger ability to absorb energy through plastic deformation before reaching its maximum load-bearing capacity, indicating superior matrix plastic flow characteristics and the ability to store more energy before fracture to resist crack initiation and propagation. Furthermore, the curve shows a steep downward trend after the peak load, a characteristic corresponding to the crack propagation process after initiation. This indicates that the material can still transfer load through its own structural response during crack propagation, enabling the alloy to achieve its fracture toughness target. .

[0081] SEM fracture morphology as follows Figure 3-4 As shown, the overall ductile fracture characteristics of the fracture surface are further enhanced, with numerous irregular polygonal dimples on the surface. These dimples are typical products formed during the fracture process through matrix plastic deformation, micropore nucleation, and polymerization. The depth of a single dimple is increased to [missing information]. This indicates that the matrix's plastic flow capacity is further enhanced, providing more space for dimple development, while the dimple density increases to [missing information]. This confirms that the matrix undergoes more complete plastic deformation during fracture, significantly increasing the energy consumed by micropore polymerization. Furthermore, the relatively rough and irregular areas at the fracture surface are further reduced, resulting in more effective resistance to crack propagation and further improved energy dissipation efficiency, thus enhancing the alloy's fracture toughness. .

[0082] EDS elemental surface scan of alloy samples Figure 5 As shown, Mg in the alloy sample achieves a more uniform solid solution in the Al matrix, and the grain boundary enrichment trend is further weakened. This optimized distribution stems from the fact that the driving force for element migration along the grain boundaries is further reduced after the Mg content is further decreased, which is closer to the ideal state of uniform solid solution of alloying elements. This avoids the potential weakening of grain boundary bonding due to excessive Mg concentration, laying a solid foundation for improving grain boundary crack resistance. Crucially, the synergistic distribution precision of Mn, Sc, and Zr elements is further improved, and the three elements form a more uniform solid solution in the matrix. and Composite reinforcing phase. Among them, The phase has a stronger resistance to dislocation movement through the Orowan mechanism, further enhancing the matrix's resistance to plastic deformation; The phase then forms a denser reinforcing layer at the grain boundaries, working synergistically. Enhancing grain boundary pinning effect more effectively inhibits grain growth, resulting in a more uniform and stable grain structure, thus improving the fracture toughness of the alloy. .

[0083] TEM images of alloy samples Figure 6-7 As shown, Mn elements exhibit a cooperative distribution with Sc and Zr elements, thus forming... and Composite reinforced phase. The average size of the precipitated phase further increased to 2.02 nm, and the ability of the strengthening phase to impede dislocation movement was further enhanced; its precipitation density decreased to The uniformity of distribution is further improved, enabling the formation of a more continuous dislocation hindering network in the matrix; simultaneously, The precipitated phases not only exhibit a further increased distribution density but also a more rational aggregation state in the grain boundary regions, resulting in a further enhanced synergistic strengthening effect. This effectively improves the grain boundaries' resistance to crack propagation, leading to a higher fracture toughness in the alloy. .

[0084] The results of comparing four Al-Mg-Mn-Sc-Zr alloys with different Mg contents in Examples 1-4 are as follows:

[0085] 1. Comparison of fracture toughness:

[0086] As shown in Table 1 and Figure 10 As shown, as the Mg content decreases from 2.2% to 1.1%, the fracture toughness value of the alloy decreases. from Gradually improve to The Mg content shows a significant upward trend. That is, in the low Mg content range, when the Mg content decreases within a certain range, the fracture toughness of the alloy can be significantly improved.

[0087] Table 1 Mg content ~ K IC

[0088]

[0089] 2. Load-displacement curve characteristics ( Figure 2 ):

[0090] Observe the fracture toughness load-displacement curves of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents. Figure 2It was found that as the Mg content decreased, the curve shape exhibited a characteristic of "increased peak load and decreased displacement". For the alloy sample with a Mg content of 2.2%, its fracture toughness load-displacement curve showed a peak load of 22-23 kN, corresponding to a displacement of 0.8-0.9 mm. Furthermore, the curve showed a steep downward trend after the peak, indicating rapid crack propagation after initiation, weak plastic deformation capacity of the material, and limited energy absorption, resulting in a low fracture toughness value (K0). IC )achieve As the Mg content decreases, the peak load of the curve increases, the displacement decreases, the crack propagation rate slows down, and the material's crack resistance gradually improves, resulting in a significant increase in the alloy's fracture toughness. When the Mg content drops to 1.1%, the peak load reaches 26-28 kN, and the displacement is 0.6-0.7 mm. No significant abrupt change in energy dissipation occurs throughout the loading process, indicating that this Mg-content material possesses excellent energy absorption capabilities during both crack initiation and propagation stages, leading to a significant improvement in the Kc of the alloy sample. IC Value reached .

[0091] Therefore, comparing the load-displacement curves of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents, it was found that as the Mg content decreased, the load-displacement curves of the alloy fracture toughness test showed a characteristic of increasing peak load and decreasing corresponding displacement. This indicates that after crack initiation, the propagation rate slows down, and during the stress process, from crack initiation to propagation, the material's plastic deformation capacity gradually increases, its energy absorption capacity continuously improves, and its crack resistance gradually improves, ultimately achieving a significant improvement in the alloy's fracture toughness.

[0092] In summary, the Al-Mg-Mn-Sc-Zr alloy sample of this invention exhibits the characteristic of "increased peak load and decreased displacement" as the Mg content decreases in the low Mg content range (1.1% to 2.2%), indicating that the crack propagation rate slows down after crack initiation and the material's crack resistance is enhanced.

[0093] 3. Evolution of fracture morphology ( Figure 3-4 ):

[0094] Observe the SEM fracture morphology of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents ( Figure 3-4 It was found that for the alloy sample with a Mg content of 2.2%, the fracture surface exhibited uniform ductile fracture characteristics, with numerous irregular polygonal dimples on the fracture surface, and the depth of a single dimple was within [missing information]. This is the result of micropore nucleation, growth, and aggregation, indicating that the matrix undergoes plastic deformation during fracture, consuming some energy and thus affecting the alloy's fracture toughness value. )achieve As the Mg content decreases, the depth of dimples on the fracture surface continuously increases, and the dimple distribution becomes more uniform. Only a small number of shallow, flat dimples remain in localized areas at the grain boundaries, indicating a reduction in grain boundary embrittlement. Crack propagation requires overcoming more resistance to plastic deformation of the matrix, resulting in a significant improvement in the alloy's fracture toughness. When the Mg content decreases to 1.1%, the depth of a single dimple increases to 7-8 μm, and the dimple density reaches [value missing]. The inner wall of the dimples contains a large number of fine second-phase particles (50-80 nm in size), with no obvious cleavage planes. During micropore growth and aggregation, the pinning effect of strengthening dislocations must be continuously overcome, consuming a large amount of fracture energy, resulting in the alloy sample... Value reached .

[0095] Therefore, by comparing the SEM fracture morphology images of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents, it can be found that the ductile fracture characteristics of the alloy fracture surface become more pronounced as the Mg content decreases. The depth of dimples in the fracture surface increases and their distribution becomes more uniform, the number of shallow flat dimples remaining locally at grain boundaries decreases, the degree of grain boundary embrittlement weakens, and crack propagation needs to overcome greater resistance to plastic deformation of the matrix. At the same time, the fine second-phase particles attached to the inner wall of the dimples can continuously consume a large amount of fracture energy by pinning dislocations during micropore growth and aggregation. These changes ultimately lead to a significant improvement in the fracture toughness of the alloy.

[0096] In summary, the Al-Mg-Mn-Sc-Zr alloy samples described in this invention exhibit increasingly pronounced ductile fracture characteristics in the low Mg content range (1.1%–2.2%), with the Mg content decreasing from 3–4 μm to 7–8 μm and the dimple density increasing from 3–5 dimples / 100 μm² to 12–15 dimples / 100 μm².

[0097] 4. Element distribution characteristics ( Figure 5 ):

[0098] Observe the EDS elemental composition of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents. Figure 5 It was found that when the Mg content was 2.2%, Mg showed a local tendency to accumulate at grain boundaries, while Mn, Sc, and Zr were distributed synergistically, forming... and The composite strengthening phase can both hinder dislocation movement through the Orowan mechanism to improve the matrix's resistance to deformation and pin grain boundaries to inhibit grain growth, thereby increasing the alloy's fracture toughness. )achieve .

[0099] As the Mg content decreases, the grains become finer and the number of grain boundaries increases, making crack propagation paths more tortuous and requiring more energy. Furthermore, the enrichment of Mn at grain boundaries gradually diminishes, and with the decrease in Mg content, it further exerts a "grain boundary purification" effect, effectively inhibiting Mg diffusion to grain boundaries and preventing weakening of grain boundary bonding. Synergistic strengthening of grain boundaries reduces the risk of crack propagation along grains, resulting in a significant improvement in the fracture toughness of the alloy.

[0100] When the Mg content is reduced to 1.1%, Mg is uniformly dissolved in the matrix without local enrichment or grain boundary segregation, and the synergistic distribution of Mn, Sc, and Zr reaches its optimal level. and The composite strengthening phase is uniformly and densely distributed, while the slight enrichment of Mn at the grain boundaries plays a significant role, resulting in a substantial increase in grain boundary strength. Crack propagation requires continuous penetration through numerous fine grains and overcoming the resistance of the composite strengthening phase, leading to a significant increase in energy consumption and impacting the alloy sample. Value reached .

[0101] Therefore, by comparing the EDS images of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents, it can be found that as the Mg content decreases, its solid solution homogeneity in the matrix increases, the grain boundary enrichment phenomenon gradually disappears, and the "grain boundary purification" effect of Mn is more complete, effectively preventing the weakening of grain boundary bonding. At the same time, the finer grains make the crack propagation path more tortuous, the distribution of composite strengthening phases is better, and crack propagation needs to overcome more resistance and consume more energy, ultimately achieving a significant improvement in the fracture toughness of the alloy.

[0102] In summary, in the Al-Mg-Mn-Sc-Zr alloy sample described in this invention, within the low Mg content range (1.1%–2.2%), the enrichment of Mg elements at grain boundaries gradually disappears as the Mg content decreases, and the "grain boundary purification" effect of Mn elements becomes more pronounced. and The composite reinforced phase has a better distribution.

[0103] 5. Evolution of precipitated phases ( Figure 6-7 ):

[0104] Comparing the TEM images of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents, as follows: Figure 6-7 As shown, the findings are as follows:

[0105] 5.1. Mn elements are distributed in conjunction with Sc and Zr elements to form... and Composite strengthening phase. When the Mg content is 2.2%, The precipitated phase has a small size, with an average size of only 1.34 nm, and a high precipitation density, reaching [value missing]. ; The dense distribution of precipitates synergistically enhances the grain boundary pinning effect to stabilize the grain structure, thereby improving the fracture toughness of the alloy. )achieve As the Mg content decreases, The average size of the precipitated phase increases, the precipitation density decreases, and the ability of the strengthening phase to hinder dislocation movement continuously increases; simultaneously... The distribution at grain boundaries is also more uniform and dense, resulting in a more significant synergistic effect of the strengthening phases. This not only reduces crack initiation but also increases the resistance to crack propagation, leading to a significant improvement in the alloy's fracture toughness. When the Mg content is reduced to 1.1%, The average size of the precipitated phase increased to 2.02 nm, and the precipitation density decreased to ; The distribution reached its optimal state. Furthermore, coarse, irregular precipitates were significantly reduced, and the synergistic effect between precipitates was fully optimized, resulting in excellent strengthening effects on the matrix and grain boundaries. Energy consumption was significantly increased, leading to improved performance of the alloy sample. Value reached .

[0106] 5.2, with The element content decreased. The precipitates are more uniform and refined, with an increased average size and decreased density, which effectively hinders dislocation movement and reduces crack initiation. The Al6Mn strengthening phases are more densely distributed, synergistically enhancing grain boundary pinning to stabilize the grain structure. At the same time, the reduction of coarse and irregular precipitates lowers the probability of crack formation and propagation, and the optimized synergistic effect between precipitates further strengthens the matrix and grain boundaries, requiring more energy to fracture, ultimately resulting in a significant improvement in the alloy's fracture toughness.

[0107] In short, the Al-Mg-Mn-Sc-Zr alloy sample described in this invention, in the low Mg content range (1.1%–2.2%), shows that as the Mg content decreases, The average size of the precipitated phase increased from 1.34 nm to 2.02 nm, and the precipitation density increased from... Down to This enhances the ability of the phase to impede dislocation motion.

[0108] 6. Forming properties ( Figure 8-9 ):

[0109] Observe the pore distribution diagrams of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents. Figure 8 It was found that the density of the four alloy samples did not vary much, all reaching over 99.98%, and the pores were mostly near-circular pores with a size of less than 10 μm, indicating that they have good formability.

[0110] Observe the molten pool characteristics of Al-Mg-Mn-Sc-Zr alloy samples with four different Mg contents. Figure 9 It was found that as the Mg content decreased, the width and depth of the molten pool of the alloy sample decreased, and the width-to-depth ratio decreased, indicating that the size of the molten pool tended to be smaller and the dispersion of the molten pool size also decreased, showing more stable forming performance and achieving a significant improvement in the fracture toughness of the alloy.

[0111] In short, as the Mg content decreases, the width and depth of the molten pool decrease, the molten pool size dispersion decreases, and the forming performance becomes more stable.

[0112] In summary, this invention confirms that in the low Mg content range (1.1%–2.2%), the fracture toughness of the obtained Al-Mg-Mn-Sc-Zr alloy samples significantly increases with decreasing Mg content. Figure 10 Its microscopic mechanism is closely related to the evolution of precipitates, grain boundary strengthening and fracture morphology optimization.

[0113] Comparative Example 1: Mg content was 3.6%.

[0114] This comparative example uses an Al-Mg system as the base. The elements are calculated by mass percentage, including: Mg: 3.6%, Mn: 2.1-2.2%, Sc: 0.7-0.8%, Zr: 0.4-0.5%, with the total impurity content not exceeding 0.1%, and the balance being Al.

[0115] This invention uses gas atomization to prepare powder, with the following parameters: atomization temperature 820-850 ℃ and atomization pressure 2.0-2.5 MPa.

[0116] After atomization, the powder is sieved, and particles within a certain size are selected. The powder is then subjected to a passivation treatment by placing it in an atmosphere containing a small amount of oxygen at room temperature for 24 hours to form a thin oxide film on the powder surface, thereby improving the powder's oxidation resistance and storage stability. The resulting powder meets the requirements of laser additive manufacturing.

[0117] The processed powder has good flowability and a bulk density of up to [value missing]. The tap density can reach The Al-Mg-Mn-Sc-Zr alloy powder exhibits regular spherical shapes with a sphericity greater than 90%. Powder D 10 (μm): 22.140, D 50 (μm): 38.012, D 90 (μm): 64.294. Powder morphology as follows: Figure 1 As shown.

[0118] Using the aforementioned powder as raw material, alloy samples printed by laser additive manufacturing equipment meet the national standard GB_T4161-2007 "Plane strain fracture toughness K of metallic materials". IC The test method requires that the formed Al-Mg-Mn-Sc-Zr alloy samples be observed and tested.

[0119] Observe the porosity distribution, melt pool morphology, and fracture failure characteristics of the sample with a Mg content of 3.6%, such as... Figure 11 As shown. Analysis of its pore distribution characteristics revealed a significant increase in the number of pores in the sample, with highly irregular pore morphology, some exhibiting a narrow or dendritic distribution, and the size generally exceeding [a certain value]. In some areas, even pore clusters form. These irregular, large-sized pores primarily stem from the increased melt viscosity and decreased fluidity due to high Mg content, making it difficult for gas to escape. Simultaneously, the volatilization of Mg during rapid solidification exacerbates pore formation. Furthermore, the presence of these coarse pores severely disrupts the matrix continuity, becoming a preferential pathway for crack initiation and propagation. This directly leads to a decrease in material density to below 99.5%, significantly deteriorating mechanical properties and resulting in a low fracture toughness value for the alloy, only reaching [value missing]. .

[0120] Analysis of the molten pool morphology revealed a significant increase in both width and depth, blurred boundaries, and an expanded heat-affected zone, indicating excessive heat input and poor molten pool stability during laser additive manufacturing. The high Mg content lowered the alloy's liquidus temperature, increasing overheating and leading to flow instability, significant melt splashing, and incomplete fusion defects. Furthermore, the molten pool exhibited extreme dimensional dispersion, a high aspect ratio, poor overlap between adjacent melt channels, and localized microcracks. This unstable behavior not only reduced forming accuracy but also introduced residual stress concentration at the molten pool boundaries, further promoting hot crack formation and resulting in a low fracture toughness value for the alloy. .

[0121] Analysis of the fracture morphology revealed typical brittle fracture characteristics. The fracture surface exhibited very few and shallow dimples, with smooth cleavage planes and river patterns visible in localized areas—typical morphologies of cleavage fracture. This indicates that the crack propagated rapidly transgranularly with almost no plastic deformation. More importantly, intergranular fracture morphology was observed in multiple locations: the grain outlines were clearly defined and prominent, exhibiting a "candy-like" fracture surface, indicating that the crack primarily propagated along grain boundaries. The grain boundaries themselves had extremely weak bonding forces, failing to effectively hinder crack propagation. No obvious traces of plastic deformation (such as tear ridges or dimple bands) were observed on the overall fracture surface, indicating that the material absorbed almost no energy before fracture, and the crack rapidly penetrated the entire cross-section once it initiated. This brittle fracture characteristic directly resulted in low fracture toughness, only reaching [value missing]. .

[0122] Comparative Example 2: Mg content was 0.8%.

[0123] This comparative example uses an Al-Mg system as the base. The elements are calculated by mass percentage, including: Mg: 0.8%, Mn: 2.1-2.2%, Sc: 0.7-0.8%, Zr: 0.4-0.5%, with the total impurity content not exceeding 0.1%, and the balance being Al.

[0124] This invention uses gas atomization to prepare powder, with the following parameters: atomization temperature 820-850 ℃ and atomization pressure 2.0-2.5 MPa.

[0125] After atomization, the powder is sieved, and particles within a certain size are selected. The powder is then subjected to a passivation treatment by placing it in an atmosphere containing a small amount of oxygen at room temperature for 24 hours to form a thin oxide film on the powder surface, thereby improving the powder's oxidation resistance and storage stability. The resulting powder meets the requirements of laser additive manufacturing.

[0126] The processed powder has good flowability and a bulk density of up to [value missing]. The tap density can reach The Al-Mg-Mn-Sc-Zr alloy powder exhibits regular spherical shapes with a sphericity greater than 90%. Powder D 10 (μm): 22.140, D 50 (μm): 38.012, D 90 (μm): 64.294. Powder morphology as follows: Figure 1 As shown.

[0127] Using the aforementioned powder as raw material, alloy samples printed by laser additive manufacturing equipment meet the national standard GB_T4161-2007 "Plane strain fracture toughness K of metallic materials". IC The test method requires that the formed Al-Mg-Mn-Sc-Zr alloy samples be observed and tested.

[0128] Observe the porosity distribution, melt pool morphology, and fracture failure characteristics of the sample with a Mg content of 0.8%, such as... Figure 12 As shown. Analysis of its pore distribution characteristics revealed a significant decrease in the number of pores, but a small number of relatively large spherical pores still existed, with a diameter of approximately... The pores are relatively scattered. These spherical pores usually originate from inert gases such as argon that were not completely released during powder preparation or printing, or from the decomposition of the oxide film on the powder surface in the molten pool. The presence of localized pores weakens the effective load-bearing cross section of the material. Moreover, the pore size is relatively large and the distribution is random. During subsequent stress, these pores will become stress concentration points, easily inducing early cracks. This deteriorates the mechanical properties of the sample, resulting in a low fracture toughness value for the alloy, only reaching [value missing]. .

[0129] Analysis of the molten pool morphology revealed that the width and depth of the molten pool were further reduced, the molten pool boundary was clear, and the heat-affected zone was narrow, indicating good heat input control. However, due to the excessively low Mg content, the surface tension of the melt increased and the wettability decreased, resulting in poor overlap between molten pools. Multiple incompletely fused gaps were visible at the junctions of the melt channels, and interlayer delamination defects appeared locally. These unfused areas were distributed linearly, weakening the bonding strength between layers. Although the dispersion of the molten pool size was reduced, the continuity of the molten pool was interrupted in some areas, forming tiny pores or gaps. Moreover, the Mg deficiency altered the melt kinetics, introducing new forming defects. These defects are prone to inducing delamination cracks under stress, impairing the overall mechanical properties and resulting in a low fracture toughness value for the alloy, only reaching [value missing]. .

[0130] Analysis of its fracture morphology revealed a small number of shallow dimples in the partial area, with relatively small dimple sizes (approximately [diameter missing]). The shallow depth of the cleavage surface indicates the presence of a certain microporous aggregation mechanism, but the degree of plastic deformation is limited. Meanwhile, the fracture surface exhibits a large distribution of flat cleavage plateaus and sharp tear ridges: the cleavage plateaus are smooth and flat, with clear convergence directions of the river-like patterns, indicating that the crack rapidly penetrates the grains via cleavage; the tear ridges indicate that brief plastic tearing occurred in localized areas, but quickly transitioned to brittle propagation. Grain outlines are faintly visible in some areas, showing intergranular fracture traces, indicating insufficient grain boundary strength, which failed to effectively deflect or hinder the crack. Overall, the low dimple coverage and high proportion of cleavage planes on the fracture surface indicate limited absorption of plastic deformation energy during fracture, resulting in a fracture toughness of only [insert value here]. .

[0131] Based on the data provided in Examples 1 to 4 above, this invention establishes the relationship between Mg elemental content, microstructure characteristic parameters, and fracture toughness value K. IC A quantitative correlation model was used to determine the relationship between Mg content and mass percentage in the low Mg content range of 1.1%–2.2%. The average size of the precipitated phase increases, the precipitation density decreases, the dimple depth of the fracture surface increases, and the density increases, resulting in a higher fracture toughness value K of the alloy. IC The corresponding relationship of increase.

[0132] Furthermore, the established quantitative correlation model uses Mg elemental content and the aforementioned microstructure characteristic parameters as independent variables, and fracture toughness value K as the variable. IC For the multiple regression equation established with the dependent variable as the dependent variable, and when establishing the quantitative correlation model, at least one of the fracture dimple characteristic parameters, namely fracture dimple depth and fracture dimple density, should be considered. The characteristic parameters of the precipitated phase should at least be considered. Average size of precipitated phase and One of the precipitation densities of the precipitated phase; the quantitative correlation model can predict the fracture toughness value K of the alloy based on the input Mg content and microstructure characteristic parameters. IC , represented as:

[0133] ;

[0134] In the above formula: This represents the fracture toughness value; β0 is the regression constant term, and β1 is the partial regression coefficient of Mg content; β2 represents the Mg content, with a mass percentage ranging from 1.1% to 2.2%; h represents the characteristic parameter of the fracture dimples; β3 represents the partial regression coefficient of the characteristic parameter of the precipitates; and d represents the characteristic parameter of the precipitates.

[0135] When the characteristic parameter h of the fracture dimple is selected as the dimple depth, and the characteristic parameter of the precipitate is selected as the average size of the precipitate, β0 = 30.2, β1 = −0.85, β2 = 1.02, and β3 = 2.15. The coefficient of determination R² of the quantitative correlation model is approximately 0.99, indicating that the model has extremely high fitting accuracy.

[0136] The quantitative correlation model constructed in this invention enables targeted performance design for additively manufactured Al-Mg-Mn-Sc-Zr alloys: for load-bearing components in the aerospace field requiring high strength and high fracture toughness, the contents of Mn, Sc, and Zr can be fixed, and the optimal Mg content range can be quickly determined through this quantitative correlation model, maximizing the fracture toughness value K of the alloy while ensuring strength. IC This approach guides industrial production and promotes the application of alloys in aerospace and other fields, helping to overcome fracture resistance bottlenecks and supporting the independent control of high-end manufacturing materials. This design concept, centered on quantitative correlation, shifts the performance control of additive manufacturing aluminum alloys from "trial and error" to "precise control," meeting the diverse performance requirements of the aerospace field and providing a replicable and scalable technical path for the high-performance application of additive manufacturing technology in high-end equipment, further unleashing the design potential for lightweighting and structural complexity.

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser additive manufacturing method for high-strength aluminum alloys with low Mg content, characterized in that, The mass percentages of each element in the alloy are as follows: Mg: 1.1%–2.2%, Mn: 2.1%–2.2%, Sc: 0.7%–0.8%, Zr: 0.4%–0.5%, with total impurities not exceeding 0.1% and the balance being Al; the fracture toughness value of the alloy is... Furthermore, as the Mg content decreases within the range of 1.1% to 2.2%, the fracture toughness value K of the alloy decreases. IC It shows an upward trend.

2. The laser additive manufacturing of low-Mg content high-strength aluminum alloy according to claim 1, characterized in that, When the Mg content is 1.1%, the fracture toughness value K of the alloy is... IC for Furthermore, the microstructure characteristics satisfy the following: the depth of the dimples on the fracture surface is 7–8 μm, and the dimple density is [missing information]. , The average size of the precipitated phase was 2.02 nm, and the precipitation density was [missing value]. .

3. A method for controlling and optimizing the fracture toughness of laser additive manufacturing of low-Mg content high-strength aluminum alloys as described in claim 1 or 2, characterized in that, Includes the following steps: Step S1: Fix the content of Mn, Sc and Zr elements, and prepare at least four Al-Mg-Mn-Sc-Zr alloy samples with different Mg element contents by laser additive manufacturing within the range of 1.1% to 2.2% by mass percentage; Step S2: Perform fracture toughness tests on each alloy sample to obtain the fracture toughness value K for each alloy sample. IC ; Step S3: Perform microstructure characterization on each alloy sample to obtain microstructure characteristic parameters, including fracture dimple characteristic parameters and... Precipitated phase characteristic parameters; fracture dimple characteristic parameters include fracture dimple depth and fracture dimple density; The characteristic parameters of the precipitated phase include Average size of precipitated phase and Precipitation density of the precipitated phase; Step S4: Establish Mg elemental content, microstructure characteristic parameters, and fracture toughness value K. IC The quantitative correlation model determined that within the low Mg content range of 1.1% to 2.2% by mass percentage, as the Mg element content decreased, The average size of the precipitated phase increases, the precipitation density decreases, the dimple depth of the fracture surface increases, and the density increases, resulting in a higher fracture toughness value K of the alloy. IC The corresponding relationship of increase.

4. The method for controlling and optimizing the fracture toughness of laser additive manufacturing of low-Mg content high-strength aluminum alloys according to claim 3, characterized in that, The at least four different Mg element contents mentioned in step S1 include 2.2%, 1.8%, 1.5%, and 1.1%, corresponding to fracture toughness values ​​K. IC They are respectively , , and .

5. The method for controlling and optimizing the fracture toughness of laser additive manufacturing of low-Mg content high-strength aluminum alloys according to claim 4, characterized in that, The alloy sample described in step S1 is prepared into powder by gas atomization and then laser additive manufacturing. The process parameters of the gas atomization method are: atomization temperature 820~850℃, atomization pressure 2.0~2.5 MPa, and metal liquid flow rate 2.0 kg / min.

6. The method for controlling and optimizing the fracture toughness of laser additive manufacturing of low-Mg content high-strength aluminum alloys according to claim 5, characterized in that, The powder prepared by the gas atomization method is sieved to select powder with a particle size of 15-53 μm, and then placed in an oxygen-containing atmosphere at room temperature for 24 hours for passivation treatment to form an oxide film on the powder surface.

7. The method for controlling and optimizing the fracture toughness of laser additive manufacturing of low-Mg content high-strength aluminum alloys according to claim 3, characterized in that, The established quantitative correlation model uses Mg elemental content and the aforementioned microstructure characteristic parameters as independent variables, and fracture toughness value K as the variable. IC For the multiple regression equation established with the dependent variable as the dependent variable, and when establishing the quantitative correlation model, at least one of the fracture dimple characteristic parameters, namely fracture dimple depth and fracture dimple density, should be considered. The characteristic parameters of the precipitated phases should at least consider the average size of the Al3(Sc,Zr) precipitates and One of the precipitation densities of the precipitated phase; the quantitative correlation model can predict the fracture toughness value K of the alloy based on the input Mg content and microstructure characteristic parameters. IC , represented as: ； In the above formula: KIC represents the fracture toughness value; β0 is the regression constant term, β1 is the partial regression coefficient of Mg content; C Mg β2 represents the Mg content, with a mass percentage ranging from 1.1% to 2.2%; h represents the characteristic parameter of the fracture dimples; β3 represents the partial regression coefficient of the characteristic parameter of the precipitates; and d represents the characteristic parameter of the precipitates.

8. A method for preparing a low-Mg-content, high-strength aluminum alloy by laser additive manufacturing as described in claim 1 or 2, characterized in that, Includes the following steps: Step A: Prepare alloy powder according to the alloy composition ratio and use gas atomization method to prepare it. The atomization temperature is 820-850℃, the atomization pressure is 2.0-2.5 MPa, and the metal liquid flow rate is 2.0 kg / min. Step B: The alloy powder is sieved to select alloy powder with a particle size of 15-53 μm, and then passivated in an oxygen-containing atmosphere at room temperature for 24 hours. Step C: The powder processed in step B is printed into shape using laser additive manufacturing equipment to obtain an Al-Mg-Mn-Sc-Zr alloy sample; The alloy composition in step A is as follows: Mg: 1.1%–2.2%, Mn: 2.1%–2.2%, Sc: 0.7%–0.8%, Zr: 0.4%–0.5%, the total impurity content does not exceed 0.1%, and the balance is Al.

9. The method for preparing low-Mg content high-strength aluminum alloy by laser additive manufacturing according to claim 8, characterized in that, The alloy sample printed in step C has a density ≥99.98%, and the width and depth of the molten pool decrease as the Mg content decreases, resulting in a decrease in the molten pool size dispersion.

10. The method for preparing low-Mg-content high-strength aluminum alloy by laser additive manufacturing according to claim 8, characterized in that, The powder processed in step B has a loose packing density of The tap density is Sphericity greater than 90%, powder , , .

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