WO2023168874A1 - Special high-strength aluminum alloy for slm and slm forming method therefor - Google Patents

Abstract

The present invention relates to the technical field of special materials for aluminum alloy additive manufacturing, and provides a special high-strength aluminum alloy for SLM and an SLM forming method therefor. According to the special high-strength aluminum alloy for SLM provided by the present invention, the cracking tendency of the alloy is greatly reduced under the synergistic effect of elements Si and Ti, and meanwhile, a double-reinforced relative Al-Cu-Mg series alloy is introduced under the synergistic effect of the elements Si and Ti for remarkable reinforcement, such that the special high-strength aluminum alloy is more suitable for an SLM process, and the material system for aluminum alloy additive manufacturing is enriched. Experimental results show that the yield strength of the high-strength aluminum alloy prepared from the special high-strength aluminum alloy for SLM, provided by the present invention, subjected to SLM forming can reach 465-481 MPa, the tensile strength can reach 539-543 MPa, the elongation can reach 9.7-12.1%, the density can reach 99.99%, and no defect such as cracks exists.

Description

A high-strength aluminum alloy special for SLM and its SLM forming method

This application requires the priority of the Chinese patent application submitted to the China Patent Office on March 8, 2022, with the application number 2022102180041 and the invention title "A high-strength aluminum alloy for SLM and its SLM forming method", and its entire content has been approved This reference is incorporated into this application.

Technical field

The present invention relates to the technical field of special materials for additive manufacturing of aluminum alloys, and in particular to a high-strength aluminum alloy special for SLM and its SLM forming method.

Background technique

Laser additive technology (LAM) mainly includes laser three-dimensional forming (LSF) technology characterized by synchronous powder feeding and selective laser melting (SLM) technology based on powder bed forming. During the SLM forming process, since the laser beam spot size is small, about 100 μm, the cooling rate of the molten pool can reach 10 ⁴ to 10 ⁶ ℃/s, and the rapid melt melt process in the molten pool can be significantly refined. Solidify the structure and improve the solid solution strengthening effect of the matrix to achieve rapid manufacturing of high-performance metal components. However, due to the low melting point, high laser reflectivity, wide solidification interval, and poor powder fluidity of most aluminum alloys, when preparing aluminum alloys through the SLM process, especially when preparing high-strength aluminum alloys, there is still a narrow process window and low forming efficiency. , easy to crack and difficult to control process parameters and a series of problems. Therefore, it is necessary to develop an aluminum alloy raw material powder dedicated for the SLM process.

At present, most of the aluminum alloy systems used for SLM forming are derived from existing aluminum alloy raw materials used in traditional casting and welding. Traditional high-strength aluminum alloys generally have high thermal cracking sensitivity due to their high degree of alloying. Therefore, the design of high-strength aluminum alloys for SLM usually first considers how to avoid the problem of hot cracking of aluminum alloys during SLM preparation, and then considers how to achieve strength and toughness of aluminum alloys. There are two common ideas. One is to reduce the solidification temperature range of the alloy through alloying design, reduce the tendency of hot cracking, and at the same time achieve precipitation strengthening through the precipitation of self-strengthening phases in high-strength aluminum alloys; the second method is to introduce the third The two-phase particles refine the grains and improve the strength of the alloy.

Among them, regarding the alloying design scheme, Maria et al. studied the effect of adding less than 4wt.% Si on the hot cracking behavior of 7075 aluminum alloy SLM forming and found that as the Si content increased, the number of cracks in the alloy prepared by SLM significantly decreased. , the density has been significantly improved. The addition of Si forms a low-melting-point eutectic phase, which backfills the interdendritic areas during the final stage of solidification to reduce the cracking tendency of the alloy. However, when Si is added, the strength of both the deposited sample and the heat-treated sample is lower than that of the traditional 7075-T6 aluminum alloy. The main reason is that a large amount of Zn element is burned during the SLM process, and the amount of burnt reaches 33%, resulting in a decrease in the content of the strengthening phase eta (MgZn ₂ ). Zhang, Nie et al. all found that the addition of Zr can broaden the process window for SLM preparation of Al-4.24Cu-1.97Mg alloy and effectively improve the mechanical properties of the alloy. They found that when the Zr content was 2wt.%, the tensile strength was the highest, close to 500MPa, but the elongation was less than 5%. As the Zr content continued to increase, the tensile strength of the alloy began to decrease, and the elongation increased to 6%, showing obvious strength. Plastic mismatch. Zhang, Tan et al. introduced 1.5wt.%Ti and 1wt.%Ti elements into Al-2.25Cu-1.8Mg and Al-3.7Cu-1.21Mg alloys respectively to obtain a fully equiaxed SLM microstructure. Through thermodynamic calculations, Zhang et al. found that the introduction of Ti element can eliminate cracks in Al-Cu-Mg alloys by refining the grains. At the same time, Tan et al. found that nano-S phase (Al ₂ CuMg) precipitated in the Al-3.7Cu-1.21Mg-1Ti alloy after T6 heat treatment, and obtained a yield strength of 288MPa, a tensile strength of 432MPa, and an elongation of 10 % of the sample, and eliminates the anisotropy of mechanical properties. However, even if hot cracks are eliminated, the strength of the alloy still fails to exceed 500MPa. It can be seen that the above alloying design cannot obtain an aluminum alloy with both high strength and no thermal cracking.

For the solution of introducing second phase particles to refine the grains and effectively reduce the tendency of alloy cracking, Zhou et al. simultaneously added 4wt.% Si and 2wt.% into the SLM formed Al-5.43Zn-2.65Mg-1.40Cu aluminum alloy. TiB ₂ particles prepared crack-free Al-Zn-Mg-Cu+Si+TiB ₂ specimens. Although the tensile strength of the sample reached 500MPa after T6 heat treatment, its elongation was less than 5%, which may be related to the agglomeration of _TiB particles. Therefore, the method of directly introducing the reinforcing phase from the outside can easily lead to particle agglomeration, thereby inducing crack nucleation during the stress process, thereby reducing the mechanical properties of the material and worsening the mechanical properties of the aluminum alloy.

Therefore, there is an urgent need to provide a high-strength aluminum alloy dedicated to SLM, which can effectively suppress the cracking problem of the aluminum alloy during the SLM forming process and also achieve high strength.

Contents of the invention

The object of the present invention is to provide a high-strength aluminum alloy special for SLM and a SLM forming method thereof. The high-strength aluminum alloy special for SLM provided by the present invention can be suitable for the SLM forming process, will not crack during the forming process, and has high strength.

In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

The invention provides a high-strength aluminum alloy special for SLM, which includes the following components in terms of mass percentage: Cu 4.1~4.4%, Mg 2.9~3.2%, Si 1.9~2.2%, Ti 0.6~0.9% and the balance Al.

Preferably, it includes the following components in terms of mass percentage: Cu 4.1~4.3%, Mg 2.9~3.1%, Si 2.0~2.1%, Ti 0.6~0.8% and the balance Al.

Preferably, it includes the following components in terms of mass percentage: Cu 4.2%, Mg 3.0%, Si 2.0~2.1%, Ti 0.7% and the balance Al.

Preferably, the SLM-specific high-strength aluminum alloy is a spherical powder prepared by an atomic gas atomization method.

Preferably, the particle size of the spherical powder is 5 to 80 μm.

Preferably, the bulk density of the spherical powder is 1.35-1.45g/cm ³ .

The present invention provides a SLM forming method for SLM-specific high-strength aluminum alloy described in the above technical solution, including:

After using a computer to draw the three-dimensional model required for SLM forming, SLM-specific high-strength aluminum alloy is used as raw material, and SLM forming is performed on the surface of the substrate to obtain a high-strength aluminum alloy;

The laser power for SLM forming is 280-340W, and the laser scanning rate for SLM forming is 100-1000mm/s.

Preferably, the SLM-specific high-strength aluminum alloy is dried before use.

Preferably, the drying atmosphere is vacuum; the drying temperature is 100-150°C; and the drying heat preservation time is 3-5 hours.

Preferably, the laser scanning pitch of the SLM forming is 80-120 μm.

Preferably, the thickness of each layer of powder during SLM forming is 25 to 35 μm.

Preferably, the interlayer rotation angle of each layer of powder during SLM forming is 65 to 70°.

Preferably, the substrate is an aluminum substrate.

Preferably, the substrate is preheated before use, and the preheating temperature is 120°C to 180°C.

The invention provides a special high-strength aluminum alloy for SLM, which includes the following components in terms of mass percentage: Cu 4.1-4.4%, Mg 2.9-3.2%, Si 1.9-2.2%, Ti 0.6-0.9% and the balance Al. The high-strength aluminum alloy for SLM provided by the present invention can form a low-melting-point eutectic phase under the action of Si by simultaneously introducing Si and Ti elements on the basis of Al-Cu-Mg alloy, and backfills dendrites in the final stage of solidification. space, thereby reducing the cracking tendency of the alloy; at the same time, the metastable D0 ₂₂ -Al ₃ Ti phase is formed under the action of Ti, which can serve as an effective heterogeneous nucleation core and promote the formation of equiaxed crystals, which is beneficial to crystallization. Grain refinement further improves the alloy's resistance to hot cracking and effectively increases the strength of the aluminum alloy, making up for the shortcomings of adding the Si element alone. Therefore, the SLM-specific high-strength aluminum alloy provided by the present invention not only greatly reduces the cracking tendency of the alloy under the synergistic effect of Si and Ti elements, but also introduces a double strengthening phase Al-Cu-Mg under the synergistic effect of Si and Ti elements. The series alloy has been significantly strengthened, making it more suitable for SLM processes and enriching the material system of additive manufacturing aluminum alloys. Experimental results show that the yield strength of the high-strength aluminum alloy prepared by the SLM-specific high-strength aluminum alloy provided by the present invention after SLM molding can reach 465-481MPa, the tensile strength can reach 539-543MPa, and the elongation can reach 9.7-12.1%. , the density can reach 99.99% without any defects such as cracks.

Description of the drawings

Figure 1 is a powder particle size distribution diagram of the SLM-specific high-strength aluminum alloy used in Examples 1 to 12 of the present invention;

Figure 2 is a scanning electron microscope image of the powder of the SLM-specific high-strength aluminum alloy used in Examples 1 to 12 of the present invention;

Figure 3 is a cross-sectional light microscope view of high-strength aluminum alloys prepared under different SLM forming parameters in Examples 1 to 12 of the present invention;

Figure 4 is an XRD pattern of the powder of the SLM-specific high-strength aluminum alloy used in Example 9 of the present invention and an XRD pattern of a high-strength aluminum alloy sample prepared by the SLM molding method;

Figure 5 is the microstructure of the powder of the SLM-specific high-strength aluminum alloy used in Example 9 of the present invention;

Figure 6 is the microstructure of the high-strength aluminum alloy sample prepared by the SLM forming method in Example 9 of the present invention;

Figure 7 is an EBSD scanning image of a high-strength aluminum alloy sample prepared by the SLM forming method in Example 9 of the present invention;

Figure 8 is the stress-strain curve obtained by the room temperature tensile test of the high-strength aluminum alloy sample prepared by the SLM forming method in Example 9 of the present invention;

Figure 9 is a cross-sectional light microscope image of 12 groups of aluminum alloy samples prepared in Comparative Examples 1 to 12 of the present invention without Ti;

Figure 10 is a cross-sectional light microscope image of 12 groups of aluminum alloy samples prepared in Comparative Examples 13 to 24 of the present invention without Ti and Si;

Figure 11 is a stress-strain curve obtained by conducting tensile tests three times at room temperature on the aluminum alloy prepared in Comparative Example 3 of the present invention;

Figure 12 is a stress-strain curve obtained by conducting tensile tests three times at room temperature on the aluminum alloy prepared in Comparative Example 13 of the present invention.

Detailed ways

The invention provides a high-strength aluminum alloy special for SLM, which includes the following components in terms of mass percentage: Cu 4.1~4.4%, Mg 2.9~3.2%, Si 1.9~2.2%, Ti 0.6~0.9% and the balance Al.

In terms of mass percentage, the SLM-specific high-strength aluminum alloy provided by the present invention includes Cu 4.1 to 4.4%, preferably 4.1 to 4.3%, and more preferably 4.2%. In the present invention, by adding Cu and controlling its content within the above range, it can be combined with other alloying elements to form a nano-precipitated phase to improve the strength of the aluminum alloy.

In terms of mass percentage, the SLM-specific high-strength aluminum alloy provided by the present invention includes Mg 2.9-3.2%, preferably 2.9-3.1%, and more preferably 3.0%. By adding Mg and controlling its content within the above range, the present invention can precipitate fine S phase (i.e. Al ₂ CuMg) in the aluminum alloy, and combine it with the Q phase (Al-Cu-Mg-Si), β' -Cu phase precipitates simultaneously to achieve synergistic strengthening, further improving the strength of aluminum alloys.

In terms of mass percentage, the SLM-specific high-strength aluminum alloy provided by the present invention includes Si 1.9 to 2.2%, preferably 2.0 to 2.1%. By adding Si and controlling its content within the above range, the present invention can form a low-melting-point eutectic phase under the action of Si and backfill the dendrite gaps in the final stage of solidification, thereby reducing the cracking tendency of the alloy.

In terms of mass percentage, the SLM-specific high-strength aluminum alloy provided by the present invention includes Ti 0.6-0.9%, preferably 0.6-0.8%, and more preferably 0.7%. By adding Ti and controlling its content within the above range, the present invention can form a metastable D0 ₂₂ -Al ₃ Ti phase under the action of Ti, which can serve as an effective heterogeneous nucleation core and promote the formation of equiaxed crystals. It is formed, which is conducive to grain refinement, further improves the alloy's resistance to hot cracking and effectively increases the strength of the aluminum alloy, making up for the shortcomings of adding the Si element alone.

In terms of mass percentage, the SLM-specific high-strength aluminum alloy provided by the present invention includes a balance of Al.

In the present invention, the SLM-specific high-strength aluminum alloy is preferably a spherical powder prepared by an atomic gas atomization method. The present invention has no special requirements for the atomic gas atomization method, and it is sufficient to adopt the atomic gas atomization method well known to those skilled in the art. The present invention selects SLM-specific high-strength aluminum alloy to prepare spherical powder through atomic gas atomization method, which can ensure that the alloy powder has excellent fluidity, which is more conducive to rapid heating and full melting of the alloy powder, and improves the forming efficiency and forming quality.

In the present invention, the particle size of the spherical powder is preferably 5 to 80 μm, more preferably 15 to 53 μm, and most preferably 20 to 50 μm. In the present invention, the bulk density of the spherical powder is preferably 1.35 to 1.45g/cm ³ , more preferably 1.38 to 1.42g/cm ³ , and most preferably 1.40g/cm ³ . By controlling the particle size and bulk density of the spherical powder within the above range, the present invention can ensure that the alloy powder has excellent fluidity, which is more conducive to rapid heating and full melting of the alloy powder, and improves the forming efficiency and forming quality.

The SLM-specific high-strength aluminum alloy provided by the present invention further adds Si and Ti elements based on the Al-Cu-Mg series alloy, which can not only greatly reduce the cracking tendency of the alloy under the synergistic effect of Si and Ti elements, but also The synergistic effect of Si and Ti elements introduces double strengthening, which significantly strengthens the Al-Cu-Mg alloy, making it more suitable for the SLM process and enriching the material system of additive manufacturing aluminum alloys.

The present invention also provides a method for SLM forming of the SLM-specific high-strength aluminum alloy described in the above technical solution, including:

After using a computer to draw the three-dimensional model required for SLM forming, SLM-specific high-strength aluminum alloy is used as raw material, and SLM forming is performed on the surface of the substrate to obtain a high-strength aluminum alloy;

The laser power for SLM forming is 280-340W, and the laser scanning rate for SLM forming is 100-1000mm/s.

The present invention uses a computer to draw the three-dimensional model required for SLM forming, and then uses SLM-specific high-strength aluminum alloy as raw material to perform SLM forming on the surface of the substrate to obtain a high-strength aluminum alloy. By using SLM-specific high-strength aluminum alloy as raw material and combining it with the SLM forming process, the invention utilizes the technical characteristics of rapid solidification of SLM technology to greatly refine the alloy microstructure, reduce the cracking tendency of the alloy, and broaden the SLM of the aluminum alloy. The processing technology window greatly improves the SLM preparation efficiency and alloy strength of aluminum alloys.

In the present invention, the SLM-specific high-strength aluminum alloy is preferably dried before use; the drying atmosphere is preferably vacuum; the drying temperature is preferably 100 to 150°C, more preferably 120 to 140°C; The drying heat preservation time is preferably 3 to 5 hours, more preferably 4 hours. By drying the raw materials in a vacuum environment, the present invention can not only remove the gas in the raw materials but also remove the moisture in the raw materials, which is more conducive to improving the compactness and strength of the high-strength aluminum alloy.

In the present invention, the substrate is preferably an aluminum substrate.

In the present invention, the substrate is preferably preheated before use, and the preheating temperature is preferably 120 to 180°C, more preferably 140 to 160°C, and most preferably 150°C. By preheating the substrate and controlling the preheating temperature within the above range, the present invention can reduce the thermal shock of the aluminum alloy bottom metal during initial printing and avoid the formation of cracks due to large temperature differences.

In the present invention, the thickness of each layer of powder during SLM molding is preferably 25 to 35 μm, more preferably 27 to 32 μm, and most preferably 29 to 30 μm. By controlling the thickness of each layer of powder during SLM forming to be within the above range, the present invention can closely combine the aluminum alloys between the layers, make the structure denser, effectively inhibit the formation and expansion of hot cracks, and thus be more conducive to obtaining high density. of high-strength aluminum alloy.

In the present invention, the interlayer rotation angle of each layer of powder during SLM molding is preferably 65 to 70°, more preferably 66 to 69°, and most preferably 67 to 68°. By controlling the interlayer rotation angle of each layer of powder during SLM forming to be within the above range, the present invention can closely combine the aluminum alloys between the layers, make the structure denser, effectively inhibit the formation and expansion of hot cracks, and thus be more conducive to obtaining High-density, high-strength aluminum alloy.

In the present invention, the laser power for SLM forming is 280-340W, preferably 290-340W, more preferably 320-340W, and most preferably 340W. By controlling the laser power for SLM forming within the above range, the present invention can ensure that the SLM-specific high-strength aluminum alloy raw material obtains appropriate heat input, avoids the high-energy laser beam from causing the burning of trace alloy elements in the raw material, and avoids the formation of higher interlayer Thermal stress, thereby ensuring that high-strength aluminum alloys have excellent strength and avoid cracking during aluminum alloy forming.

In the present invention, the laser scanning rate of the SLM forming is 100~1000mm/s, preferably 200~800mm/s, more preferably 300~700mm/s, most preferably 400~600mm/s. By controlling the laser scanning rate of SLM forming within the above range, the present invention can obtain appropriate melting rate and stacking rate of the high-strength aluminum alloy raw materials for SLM, ensure tight inter-layer bonding, and effectively suppress the formation of hot cracks.

In the present invention, the laser scanning pitch of the SLM forming is preferably 80 to 120 μm, more preferably 90 to 110 μm, and most preferably 100 μm. By controlling the laser scanning spacing of SLM forming within the above range, the present invention can obtain an appropriate cooling rate for the high-strength aluminum alloy during the forming process, avoid repeated heating between layers caused by laser beams overlapping at a high altitude, and thereby rapidly solidify the molten pool to obtain The structure with fine grains is more conducive to improving the strength of aluminum alloys.

The SLM forming method of SLM-specific high-strength aluminum alloy provided by the present invention can not only effectively suppress the problem of serious cracking tendency during the forming process, but also has high preparation efficiency and forming accuracy, expands the SLM processing window and simultaneously improves the strength of the aluminum alloy, reducing the It reduces the preparation cost of high-strength aluminum alloy and enables large-scale production.

The technical solutions in the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Example 1

The high-strength aluminum alloy for SLM provided in this embodiment is composed of the following components in terms of mass percentage: Cu 4.2%, Mg 3.04%, Si 2.1%, Ti 0.67% and the balance Al; the high-strength aluminum alloy for SLM is made of atomic gas. Spherical powder prepared by atomization method; the particle size of the spherical powder is 15-53 μm, and the bulk density of the spherical powder is 1.40g/cm ³ .

The SLM forming method of the SLM-specific high-strength aluminum alloy specifically includes the following steps:

After using a computer to draw the three-dimensional model required for SLM molding, SLM-specific high-strength aluminum alloy is used as raw material, and SLM molding is performed on the surface of the substrate to obtain a high-strength aluminum alloy;

Among them, the laser power of the SLM molding is 280W, the laser scanning rate is 100mm/s, the laser scanning spacing is 100μm, the thickness of each layer of powder molding during SLM molding is 30μm, and the interlayer rotation angle of each layer of powder molding is 67°. ; The substrate is an aluminum substrate and is preheated before use. The preheating temperature is 150°C; the SLM-specific high-strength aluminum alloy is dried in a vacuum atmosphere before use. The drying temperature is 120°C and the drying holding time is 4h. .

Example 2

The laser scanning rate of SLM forming in Example 1 was replaced with 200 mm/s, and the other technical features were the same as Example 1.

Example 3

The laser scanning rate of SLM forming in Example 1 is replaced with 400 mm/s, and the other technical features are the same as Example 1.

Example 4

The laser scanning rate of SLM forming in Example 1 is replaced with 600 mm/s, and the other technical features are the same as Example 1.

Example 5

The laser scanning rate of SLM forming in Example 1 is replaced with 800 mm/s, and the other technical features are the same as Example 1.

Example 6

The laser scanning rate of SLM forming in Example 1 is replaced with 1000 mm/s, and the other technical features are the same as Example 1.

Example 7

The laser power of SLM shaping in Example 1 is replaced with 340W, and the other technical features are the same as Example 1.

Example 8

The laser power of SLM forming in Example 1 was replaced with 340W, the laser scanning rate was replaced with 200mm/s, and the other technical features were the same as Example 1.

Example 9

The laser power of SLM forming in Example 1 was replaced with 340W, the laser scanning rate was replaced with 400mm/s, and the other technical features were the same as Example 1.

Example 10

The laser power of SLM forming in Example 1 was replaced with 340W, the laser scanning rate was replaced with 600mm/s, and the other technical features were the same as Example 1.

Example 11

The laser power of SLM forming in Example 1 was replaced with 340W, the laser scanning rate was replaced with 800mm/s, and the other technical features were the same as Example 1.

Example 12

The laser power of SLM forming in Example 1 was replaced with 340W, the laser scanning rate was replaced with 1000mm/s, and the other technical features were the same as Example 1.

Comparative example 1

Respectively replace the components of the SLM-specific high-strength aluminum alloy in Example 1 with the following components (by mass percentage): Cu 4.3%, Mg 3.16%, Si 1.96% and the balance Al, and replace the components in Example 1 The laser power of SLM molding was replaced with 260W. The other technical features were the same as those in Example 1. An Al-Cu-Mg-Si alloy without Ti was prepared.

Comparative Examples 2 to 6

The laser scanning rate of SLM molding in Comparative Example 1 was replaced with 200mm/s, 300mm/s, 400mm/s, 600mm/s, and 800mm/s. The other technical features are the same as Comparative Example 1. After replacing the above parameters, The plans are sequentially used as comparative examples 2 to 6.

Comparative Examples 7 to 12

The laser power of SLM molding in Examples 1 to 6 was replaced with 280W respectively. The other technical features were the same as those in Comparative Examples 1 to 6 respectively. The solutions after replacing the above parameters were used as Comparative Examples 7 to 12.

Comparative example 13

The components of the SLM-specific high-strength aluminum alloy in Example 1 are replaced with the following components (by mass percentage): Cu 4.34%, Mg 2.96% and the balance Al. The remaining technical characteristics are the same as Example 1, and the preparation does not contain Al-Cu-Mg alloy of Si and Ti.

Comparative Examples 14~18

The laser scanning rate of SLM molding in Comparative Example 13 was replaced with 200mm/s, 300mm/s, 400mm/s, 600mm/s, and 800mm/s. The other technical features are the same as Comparative Example 13. After replacing the above parameters, The plans are sequentially used as comparative examples 14 to 18.

Comparative Examples 19~24

The laser power of the SLM molding in Examples 13 to 18 was replaced with 300W respectively. The other technical features were the same as those in Comparative Examples 13 to 18. The solutions after replacing the above parameters were used as Comparative Examples 19 to 24.

Performance Testing

The powder of the SLM-specific high-strength aluminum alloy used in Examples 1 to 12 of the present invention was subjected to a particle size distribution test, and the obtained particle size distribution test chart is shown in 1. It can be seen from Figure 1 that the powder of the SLM-specific high-strength aluminum alloy used in the present invention is mainly D ₁₀ =21.5 μm, D ₅₀ =33.1 μm, and D ₉₀ =50.9 μm.

The powder morphology of the SLM-specific high-strength aluminum alloy used in Examples 1 to 12 of the present invention was observed using a scanning electron microscope, and the obtained scanning electron microscope picture is shown in Figure 2. It can be seen from Figure 2 that the particle size of the powder of the SLM-specific high-strength aluminum alloy used in Examples 1 to 12 of the present invention is relatively uniform, and most of the powder morphology is uniformly spherical.

The cross-sectional morphology of the high-strength aluminum alloys prepared in Examples 1 to 12 of the present invention under different SLM forming parameters was observed using an OLYMPUS LEXT ols4000 optical microscope, and the obtained cross-sectional light microscope image is shown in Figure 3. It can be seen from Figure 3 that under different parameters of the SLM forming process, no crack defects appear, and only extremely tiny pores and trace amounts of aggregated precipitation phases exist.

The powder of the SLM-specific high-strength aluminum alloy used in Example 9 of the present invention and the high-strength aluminum alloy sample prepared by the SLM forming method were tested for metallographic composition using an X-ray diffractometer. The obtained XRD pattern is shown in Figure 4. It can be seen from Figure 4 that the powder of the SLM-specific high-strength aluminum alloy used in Example 9 of the present invention and the high-strength aluminum alloy sample prepared by the SLM forming method are composed of α-Al phase, Al ₂ CuMg phase, Al ₂ Cu phase and Mg ₂ Si phase composition.

The powder of the SLM-specific high-strength aluminum alloy used in Example 9 of the present invention was subjected to microstructure observation using a Tescan MIRA 3 XMU scanning electron microscope, and the obtained microstructure diagram is shown in Figure 5. It can be seen from Figure 5 that the powder of the SLM-specific high-strength aluminum alloy used in Embodiment 9 of the present invention has good sphericity and contains small-sized satellite powder.

The high-strength aluminum alloy sample prepared by the SLM forming method in Example 9 of the present invention was subjected to microstructure observation using a Tescan MIRA 3 XMU scanning electron microscope. The obtained microstructure diagram is shown in Figure 6. It can be seen from Figure 6 that the high-strength aluminum alloy prepared by the SLM forming method in Example 9 of the present invention exhibits a non-uniform structure with fine grains and no defects.

The high-strength aluminum alloy sample prepared by the SLM forming method in Example 9 of the present invention was subjected to EBSD testing using the electron backscatter diffraction probe equipped with the Tescan MIRA 3 XMU electron microscope. The obtained EBSD scanning image is shown in Figure 7. It can be seen from Figure 7 that fine-grained areas and coarse-grained areas are alternately distributed along the deposition direction. The grain orientation in the fine-grained area is random and the grains are small. The coarse-grained area shows a certain texture and the grain size is larger than the grains in the fine-grained area. size.

The high-strength aluminum alloy sample prepared by the SLM forming method in Example 9 of the present invention was subjected to tensile testing three times at room temperature, and the obtained stress-strain curve is shown in Figure 8. It can be seen from Figure 8 that the yield strength of the high-strength aluminum alloy sample prepared by the SLM forming method of the SLM-specific high-strength aluminum alloy provided by the present invention can reach 465-481MPa, the tensile strength can reach 539-543MPa, and the elongation can reach 9.8～12.3%.

The cross-sectional morphology of 24 groups of aluminum alloy samples prepared in Comparative Examples 1 to 12 and Comparative Examples 13 to 24 of the present invention under different alloy compositions were observed using an OLYMPUS LEXT ols4000 optical microscope. The obtained cross-sectional light microscopy images are shown in Figure 9 and Figure 9, respectively. Shown in 10. It can be seen from Figures 9 to 10 that when the Ti element was not introduced, when the laser scanning rate reached 600mm/s, thermal cracks appeared along the deposition direction. If the scanning speed continued to be increased to 800mm/s, the thermal cracking became more serious and almost traversed the entire test. Sample. When Si and Ti elements are not introduced, when the laser scanning rate reaches 400mm/s, thermal cracks appear on the sample. When the laser increases the scanning speed to 600mm/s, the thermal cracking becomes more serious.

Each group of the aluminum alloys prepared in Comparative Example 3 and Comparative Example 13 of the present invention with different alloy compositions were subjected to tensile testing at room temperature three times, and the obtained stress-strain curves are shown in Figures 11 to 12 respectively. It can be seen from Figures 11 to 12 that the introduction of Si increases the yield strength of the alloy from 234.7±9.6MPa to 327.9±6.0MPa, the yield strength and tensile strength from 281.1±8.2MPa to 418.7±12.2MPa, and the elongation from 2.5± 0.1% improvement to 4.0±0.7%.

In summary, it can be seen that the SLM-specific high-strength aluminum alloy provided by the present invention not only greatly reduces the cracking tendency of the alloy under the synergistic effect of Si and Ti elements, but also introduces double strengthening relative to Al-Cu under the synergistic effect of Si and Ti elements. -Mg series alloy is significantly strengthened; and by controlling the process parameters of SLM forming, the present invention can further ensure that the prepared high-strength aluminum alloy has high strength and effectively suppresses hot cracks and other defects.

The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the scope of the claims of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be practiced in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (14)

1. A high-strength aluminum alloy special for SLM, including the following components in terms of mass percentage: Cu 4.1~4.4%, Mg 2.9~3.2%, Si 1.9~2.2%, Ti 0.6~0.9% and the balance Al.
2. The high-strength aluminum alloy for SLM as claimed in claim 1, characterized in that it includes the following components in terms of mass percentage: Cu4.1~4.3%, Mg 2.9~3.1%, Si 2.0~2.1%, Ti 0.6~0.8% and the balance Al.
3. The high-strength aluminum alloy for SLM as claimed in claim 2, characterized in that it includes the following components in terms of mass percentage: Cu4.2%, Mg 3.0%, Si 2.0~2.1%, Ti 0.7% and the balance Al.
4. The high-strength aluminum alloy for SLM according to any one of claims 1 to 3, characterized in that the high-strength aluminum alloy for SLM is a spherical powder prepared by an atomic gas atomization method.
5. The high-strength aluminum alloy for SLM according to claim 4, wherein the particle size of the spherical powder is 5 to 80 μm.
6. The high-strength aluminum alloy for SLM according to claim 4, wherein the bulk density of the spherical powder is 1.35-1.45g/ ^cm3 .
7. A method for SLM forming of SLM-specific high-strength aluminum alloy according to any one of claims 1 to 6, including:

   After using a computer to draw the three-dimensional model required for SLM forming, SLM-specific high-strength aluminum alloy is used as raw material, and SLM forming is performed on the surface of the substrate to obtain a high-strength aluminum alloy;

   The laser power for SLM forming is 280-340W, and the laser scanning rate for SLM forming is 100-1000mm/s.
8. The method of claim 7, wherein the SLM-specific high-strength aluminum alloy is dried before use.
9. The method of claim 8, wherein the drying atmosphere is vacuum; the drying temperature is 100-150°C; and the drying heat preservation time is 3-5 hours.
10. The method of claim 7, wherein the laser scanning pitch of the SLM forming is 80 to 120 μm.
11. The method of claim 7, wherein the thickness of each layer of powder during SLM forming is 25 to 35 μm.
12. The method according to claim 7 or 11, characterized in that the interlayer rotation angle of each layer of powder during SLM forming is 65 to 70°.
13. The method of claim 7, wherein the substrate is an aluminum substrate.
14. The method of claim 7, wherein the substrate is preheated before use, and the preheating temperature is 120 to 180°C.

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