Method for ultrasonic-assisted laser additive manufacturing of multi-scale structure coupling high-toughness aluminum alloy and application

Abstract

The invention discloses a method and application for ultrasonic-assisted laser additive manufacturing of a multi-scale structure coupling high-toughness aluminum alloy, and the method comprises the steps that high-Ni-content alloy steel powder is refined through high-energy ball milling, and then the refined alloy steel powder is dispersed and distributed in Al-Mg-Sc-Er-Zr alloy powder; an ultrasonic energy field is introduced to assist selective laser melting to form mixed powder, the ultrasonic energy field assists in generating nonlinear effects such as cavitation, acoustic streaming and heat effect, defects such as air holes and cracks are overcome to eliminate residual stress, and the Marlangoni effect is accelerated to increase the solidification speed; and finally, the high-strength and high-toughness aluminum alloy which has high density and is composed of micron-scale, submicron-scale and nano-scale multi-scale phase structures is prepared. The production cost is low, and the room-temperature tensile properties of the prepared high-strength and high-toughness aluminum alloy are as follows: the strength is greater than 850 MPa, and the fracture strain is greater than 6%.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy additive manufacturing technology, and specifically relates to the ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys and their applications. Background Technology

[0002] Advanced lightweight materials, represented by high-strength and high-toughness aluminum alloys, possess excellent specific strength and fatigue resistance, significantly reducing structural weight and improving economic efficiency. They also exhibit reliability and long service life in extreme environments (high and low temperatures), making them suitable as key load-bearing and functional integrated components in aerospace vehicles, new energy vehicles, and high-speed rail transportation. To improve the strength and toughness of aluminum alloys, conventional alloying elements such as copper (Cu), magnesium (Mg), silicon (Si), manganese (Mn), and titanium (Ti), as well as rare earth elements such as scandium (Sc), zirconium (Zr), erbium (Er), and yttrium (Y), are added to promote the precipitation of nanoparticle strengthening phases. Through multi-scale structural coupling strengthening strategies (such as nanoprecipitate grain refinement strengthening, pinning strengthening, dispersion strengthening, and solid solution strengthening), high-strength and high-toughness aluminum-based alloys are formed, significantly improving their specific strength, toughness, and work hardening ability.

[0003] However, improving the strength and toughness of the aforementioned multi-scale coupled aluminum alloys faces a series of challenges. These challenges stem primarily from two factors: firstly, the difficulty in identifying truly effective multi-element alloying elements to enhance the strength and toughness of aluminum alloys; and secondly, the limitations of existing preparation processes in ensuring the good integration of multi-element alloying elements with the aluminum matrix to form a robust multi-scale structure. Conventional casting methods for preparing high-strength and high-toughness aluminum alloys (such as the Al-Zn-Mg-Cu system) result in a wide solidification range for aluminum and elements like magnesium (Mg) and zinc (Zn), leading to deviations in equilibrium distribution coefficients, severe microsegregation, or coarse brittle eutectic structures. These limitations significantly restrict the alloy's microstructure uniformity, toughness, and subsequent processing performance. Conventional selective laser melting (SLM) technology has certain advantages in constructing bimodal grain structures (equiaxed crystals 1~5μm, columnar crystals 20~100μm) and generating nano-precipitates through in-situ heat treatment via ultra-high cooling rates. It can induce strong unidirectional heat flow through extremely high temperature gradients from the center to the edge of the melt pool, forcing dendrites to grow epitaxially along the heat flow direction (usually perpendicular to the melt pool boundary) to form coarse columnar crystals. However, the nucleation rate of equiaxed crystals is poor. This is because, on the one hand, the extremely fast cooling rate of the melt pool inhibits solute diffusion, resulting in a narrow supercooled zone that cannot meet the supercooling required for equiaxed crystal nucleation. On the other hand, there are few impurities / unmelted particles in the melt pool, and the nucleating agent is deactivated at high temperatures, resulting in a significant lack of heterogeneous nucleation sites for equiaxed crystals. Therefore, conventional SLM technology suffers from problems such as an imbalance in the size ratio of columnar crystals to equiaxed crystals, insufficient precipitation of precipitates, and poor microstructure uniformity. It cannot obtain good multi-scale structures and has a poor effect on improving the strength and toughness of aluminum alloys. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a method and application for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys. This high-strength and high-toughness aluminum alloy has broad application prospects in fields such as new energy vehicles, drones, aerospace, and humanoid robots.

[0005] The first objective of this invention is to provide a method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys.

[0006] The second objective of this invention is to provide a high-strength and high-toughness aluminum alloy with multi-scale structural coupling.

[0007] The third objective of this invention is to provide an application of a multi-scale structurally coupled high-strength and high-toughness aluminum alloy.

[0008] The first objective of this invention can be achieved by adopting the following technical solution: A method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys, the method comprising: High-Ni content alloy steel powder is mechanically ball-milled to obtain fine alloy steel powder; the mass fraction of Ni in the high-Ni content alloy steel powder is greater than 10%, and the particle sizes of the high-Ni content alloy steel powder and the fine alloy steel powder are 15~53μm and 3~15μm, respectively; The alloy steel fine powder and Al-Mg-Sc-Er-Zr alloy powder are mechanically ball-milled to obtain a mixed powder; the vacuum-dried mixed powder is loaded into a powder supply hopper; the alloy steel fine powder and Al-Mg-Sc-Er-Zr alloy powder are in a mass ratio of 95~99:1~5. A three-dimensional model of the high-strength and high-toughness aluminum alloy component to be prepared is established and layered slicing is performed. A series of scanning trajectories for laser selective melting and forming are generated based on the slice contour information. Adjust the distance between the quartz lamp and the upper surface of the substrate to 80~120mm to ensure that the substrate can effectively absorb infrared radiation energy; extract the oxygen in the forming sealed chamber and introduce argon to reach the set oxygen content threshold and balance the pressure difference inside and outside the forming chamber. Turn on the ultrasonic generator and search for the resonant frequency of the ultrasonic vibration emission system in the range of 20.0~80.0kHz. Observe and select the resonant point that matches the optimal waveform characteristics during the SLM forming process on an ultrasonic oscilloscope. Use the laser beam of the composite ultrasonic energy field to print the composite powder on the preheated substrate in channels and layers according to the scanning trajectory until the forming size is met. The composite energy field of ultrasonic vibration coupled with high-energy laser beam induces supersaturated solute to precipitate in at least two of the following ways: decomposition precipitation, solid solution precipitation, and secondary precipitation, forming nano and submicron reinforcing phases. The printed aluminum alloy is heat-treated and then vacuum-cooled to eliminate the internal stress generated during the laser additive manufacturing process, further promoting the precipitation of a large number of dispersed strengthening phases, and finally obtaining a high-strength and high-toughness aluminum alloy with a bimodal structure coupled by columnar crystals with grain sizes of 2~5μm and equiaxed crystals with grain sizes of 100~500nm.

[0009] Furthermore, during the ultrasonic-assisted laser selective melting and forming process, the ultrasonic waves impact and stir the molten pool, causing cavitation and agitation, which is superimposed with the in-situ heat treatment of the ultrasonic field; during the rapid solidification process, supersaturated Fe, Ni and Co nanoparticles are induced to precipitate within columnar crystals and at the grain boundaries of equiaxed crystals, as well as a small amount of Co, Sc and Er nanoparticles are precipitated through overcrystallization.

[0010] Furthermore, the ultrasonic energy field can be used to improve the solidification and precipitation behavior of the molten pool during SLM, including: After the ultrasonic waves at the bottom of the forming platform act on the molten pool, the ultrasonic energy field generates instantaneous high-explosive shock waves through the cavitation effect, which can effectively eliminate porosity and inhibit the formation of cracks. By utilizing the ultrasonic waves generated on the side of the forming platform to laterally impact and transmit them to the surface of the molten pool, the Marangoni effect can be accelerated to increase the solidification rate. Under the combined energy field of ultrasound and laser, the precipitation of multi-scale phase particles can be induced. A large number of nanoparticles precipitated in the columnar crystal region of aluminum alloy are dispersed and distributed as strengthening phases. With the decomposition of the melt pool, the density of heterogeneous nucleation sites increases significantly, the fine-grained region expands, and the grain size is not coarsened due to the pinning restriction of the precipitates. The particles in the coarse-grained region tend to coarsen and form equiaxed grains, which greatly improves the equiaxed crystal nucleation rate. At the same time, the acoustic flow agitation homogenizes the melt temperature or solute field through strong convection, expands the compositional undercooling region and inhibits the epitaxial growth of columnar crystals. The ratio of grain size between the fine-grained region and the coarse-grained region in the bimodal structure increases significantly. It improves the temperature distribution and solute transport inside the melt pool, reduces heat accumulation and promotes uniform mixing, thereby inhibiting the formation of solidification defects.

[0011] Furthermore, the multi-scale phase particles include micron-sized particles. α -Al phase, submicron-sized Al6Fe, Al 13 Fe4, Al9FeNi, Al 13 Co4 and nano-sized Al3 (Er, Sc, Zr) and Mg2Si particles.

[0012] Furthermore, a continuous fiber laser is used, with the following process parameters: laser power of 200W~360W, scanning speed of 800~1000mm / s, overlap rate of 20~50%, layer thickness of 20~30μm, and coupling laser rotation angle of 67° during interlayer scanning.

[0013] Furthermore, the mechanical ball milling of the high-Ni content alloy steel powder includes: High-Ni content alloy steel powder and grinding balls of different diameters were loaded into a ball milling jar at a ball-to-material ratio of 20:1, and the ball milling speed was 320 r / min. The ball milling was carried out for 20 h in a pure argon atmosphere by milling for 30 min and then pausing for 10 min. The process parameters for mechanical ball milling of alloy steel fine powder and Al-Mg-Sc-Er-Zr alloy powder are as follows: the ball-to-material ratio is set to 10~15:1, the ball milling speed is 120~240 r / min, and the ball milling is carried out for 10~16 h in a pure argon atmosphere by ball milling for 10~20 min and then pausing for 20 min.

[0014] Furthermore, the high Ni content alloy steel powder includes, but is not limited to, one of 18Ni250, 18Ni300, 18Ni350, 317 / 317L, 904L and 254SMO.

[0015] Furthermore, the Al-Mg-Sc-Er-Zr aluminum-based alloy powder has a particle size of 15μm~53μm, and by mass fraction, the contents of Mg, Er, Sc, Zr, Mn, Si, Fe, Ni and Co are 2~5%, 0.7~1.0%, 0.3~0.4%, 0.1~0.4%, 0.2~0.5%, 0.2~0.8%, 2.0~5.0%, 1.0~4.0% and 0.4~1.0%, respectively, with the remainder being Al and other impurities.

[0016] The second objective of this invention can be achieved by adopting the following technical solution: A multi-scale structurally coupled high-strength and high-toughness aluminum alloy was prepared based on the above-mentioned ultrasonic-assisted laser additive manufacturing method for multi-scale structurally coupled high-strength and high-toughness aluminum alloys.

[0017] The third objective of this invention can be achieved by adopting the following technical solution: Application of a multi-scale structurally coupled high-strength and high-toughness aluminum alloy: The multi-scale structurally coupled high-strength and high-toughness aluminum alloy prepared by the above-mentioned ultrasonic-assisted laser additive manufacturing method, or the above-mentioned multi-scale structurally coupled high-strength and high-toughness aluminum alloy, in the fields of new energy vehicles, drones, aerospace and humanoid robot technology.

[0018] The present invention has the following advantages over the prior art: This invention utilizes fine alloy steel powder and Al-Mg-Sc-Er-Zr alloy powder, and improves the solidification and precipitation behavior of the molten pool during the SLM process based on an ultrasonic energy field. On the one hand, it can efficiently induce the formation of multi-scale phase structures at the micron, submicron, and nanoscale. On the other hand, it can effectively improve the temperature distribution and solute transport within the molten pool, reduce heat accumulation, promote uniform mixing, ensure the uniformity of microstructure distribution, and suppress the formation of solidification defects (such as porosity and cracks). Among these, multi-element alloying of Fe, Ni, and Al is a prerequisite for achieving multi-scale structure formation in ultrasound-assisted laser additive manufacturing and a prerequisite for obtaining high-strength and high-toughness aluminum alloys. By refining the particle size of high-Ni content mold steel multi-element alloy powder through high-energy ball milling and using a low-energy ball milling mixing process, a mixed powder of high-Ni content alloy steel dispersed within the Al-Mg-Sc-Er-Zr alloy is obtained. This method has low preparation cost, simple powder preparation process, and strong operability, ensuring the uniformity and consistency of the composite powder composition used in ultrasound-assisted laser additive manufacturing as much as possible. The high-strength and high-toughness aluminum alloy based on ultrasound-assisted laser additive manufacturing has room temperature tensile properties of: strength greater than 850 MPa and fracture strain greater than 6%. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the molten pool cross-section of the ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys in Embodiments 1-3 of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be understood that the specific embodiments described are merely used to explain this application and are not intended to limit the scope of this application.

[0022] Example 1: The ultrasonic-assisted laser additive manufacturing method for multi-scale structural coupling high-strength and tough aluminum alloys provided in this embodiment specifically includes the following steps: (1) In this embodiment, the original purity of Al-Mg-Sc-Er-Zr powder and 18Ni300 powder is above 99.9%, and the average particle size is 15μm~53μm. First, the high Ni content alloy steel powder is mechanically ball-milled for 20h to granulate and obtain fine powder of high Ni content alloy steel with small particle size. Then, spherical Al-Mg-Sc-Er-Zr aluminum alloy powder with a mass ratio of 98wt.% and high Ni content alloy steel fine powder are further ball-milled for 10~16h to mix at room temperature to obtain mixed powder of high Ni content alloy steel dispersed in Al-Mg-Sc-Er-Zr alloy. Then, the mixed powder is placed in a dryer for vacuum drying for 2h and placed in a powder feeding tank.

[0023] (2) Using aluminum alloy as the substrate, clean the residual powder in the printing chamber and use anhydrous ethanol to clean the impurities on the substrate surface. Adjust the distance between the quartz lamp and the upper surface of the substrate to 100mm to ensure that the substrate can effectively absorb infrared radiation energy and preheat to 200°C; load the aluminum alloy composite powder into the powder supply chamber.

[0024] (3) A three-dimensional model is established based on the high-strength and tough aluminum alloy component to be prepared and layered slicing is performed. A series of two-dimensional scanning trajectories for laser selective melting and forming are generated based on the slice contour information.

[0025] (4) Adjust the substrate plane, extract the air from the printing chamber and fill it with argon to balance the pressure difference between the inside and outside, so that the oxygen content is less than 1000ppm; turn on the ultrasonic generator in advance and adjust the ultrasonic frequency to 40kHz so that the ultrasonic generator can stably emit the ultrasonic field.

[0026] (5) With ultrasonic field assistance, Al-Mg-Sc-Er-Zr aluminum-based composite powder is printed onto a preheated substrate in single-pass layer-by-layer printing. Each layer is printed using a stripe scanning strategy. After one layer is formed, the laser head is returned to the starting position of the current layer and the thickness of the current layer is increased along the Z-axis until the multi-scale structure coupled high-strength and tough aluminum alloy meets the dimensional requirements. The ultrasonic generator is turned off 3-5 minutes after the forming is completed.

[0027] The laser printing parameters are as follows: a continuous fiber laser is used, the focused spot diameter is 100μm, the laser power is 200W, the scanning speed is 800mm / s, the overlap rate is 20%, the layer thickness is 30μm, and the laser rotation angle during interlayer scanning is 67°.

[0028] The composite powder was formed by SLM, and the alloy exhibited a bimodal microstructure, consisting of an equiaxed fine-grained region at the molten pool boundary and a large number of columnar coarse-grained regions at the center of the molten pool. In the columnar coarse-grained regions, a large number of dispersed strengthening phases were randomly distributed at the grain boundaries; the strengthening phases were predominantly composed of Fe, Ni, and Co, with the remainder being Al, Mg, Sc, Er, Zr, etc.

[0029] The aluminum alloy nano-reinforcing phase exhibits a bimodal microstructure due to in-situ heat treatment, forming multi-scale phase coupling reinforcement, including columnar α-Al phases with sizes of 2–5 μm and equiaxed α-Al phases with sizes of 0.1–0.5 μm; among which, a large number of Al6Fe and Al6Fe phases with sizes of 10–50 nm exist at the equiaxed grain boundaries. 13 Fe4 and Al3(Er, Sc, Zr) nanoparticles, with 30~100nm granular Al3(Sc, Zr) dispersed reinforcing phases at the columnar crystal boundaries.

[0030] After ultrasonic field-assisted SLM forming, the nucleation sites increase and the fine-grained zone expands, accompanied by melt pool decomposition. The particles in the coarse-grained zone tend to coarsen and form equiaxed crystals.

[0031] (6) The substrate is removed by electrical discharge wire cutting to obtain a multi-scale structurally coupled high-strength and high-toughness aluminum alloy.

[0032] The relative density of the printed sample reached 99.7% when tested using Archimedes' displacement method.

[0033] (7) By heat-treating the above Al-Mg-Er-Zr composite aluminum alloy at 350 °C for 2 h and then vacuum cooling, the internal stress generated during the manufacturing process is eliminated, and the precipitation of a large number of dispersed strengthening phases is further promoted, and finally a multi-scale structural coupling high strength and toughness aluminum alloy is obtained.

[0034] Microstructural characterization and mechanical property analysis of multi-scale coupled high-strength and high-toughness aluminum alloys yielded the following conclusions: The microstructure of the multi-scale coupled high-strength and high-toughness aluminum alloy prepared in this embodiment is characterized by: approximately 40% equiaxed fine grains with a grain size of less than 1 μm and an average diameter of approximately 300 nm; and approximately 60% columnar coarse grains with an average grain size of 2.5 μm. Numerous 10–50 nm Al6Fe and Al atoms are present at the equiaxed grain boundaries. 13 Fe4, Al9FeNi, Al 13 The alloy contains nanoscale Co4 and Al3 (Er, Sc, Zr) particles; in addition to the above particles, there are also 30-100 nm granular Al3 (Sc, Zr) and Mg2Si dispersed strengthening phases within the columnar crystals. The abundant nanoscale precipitates enhance the alloy's strength through Orowan strengthening mechanism, dispersion strengthening, and pinning strengthening.

[0035] For mechanical property analysis, dog bone tensile test specimens were machined according to ASTM-E8M standards and tested on a Zwick / Roell Z100 testing machine. The tensile strength of the multi-scale structurally coupled high-strength and high-toughness aluminum alloy after appropriate heat treatment reached 750 MPa; this is significantly stronger than the room temperature tensile strength (430 MPa) of the Al-Mg-Sc-Er-Zr alloy without 18Ni300 reinforcement, and it also exhibits good plasticity, maintaining a difference of over 12%.

[0036] Example 2: The ultrasonic-assisted laser additive manufacturing method for multi-scale structural coupling high-strength and tough aluminum alloys provided in this embodiment specifically includes the following steps: (1) In this embodiment, the original purity of Al-Mg-Sc-Er-Zr powder and 18Ni300 powder is above 99.9%, and the average particle size is 15μm~53μm. First, the high Ni content alloy steel powder is mechanically ball-milled for 20h to obtain fine powder of high Ni content alloy steel with small particle size. Then, spherical Al-Mg-Sc-Er-Zr aluminum alloy powder with a mass ratio of 97wt.% and high Ni content alloy steel fine powder are further ball-milled for 10~16h and mixed at room temperature to obtain mixed powder of high Ni content alloy steel dispersed in Al-Mg-Sc-Er-Zr alloy. Then, the mixed powder is placed in a dryer for vacuum drying for 2h and placed in a powder feeding tank.

[0037] (2) Using aluminum alloy as the substrate, clean the residual powder in the printing chamber and use anhydrous ethanol to clean the impurities on the substrate surface. Adjust the distance between the quartz lamp and the upper surface of the substrate to 100 mm to ensure that the substrate can effectively absorb infrared radiation characteristics and preheat to 200°C; load the aluminum alloy composite powder into the powder supply chamber.

[0038] (3) A three-dimensional model is established based on the high-strength and tough aluminum alloy component to be prepared and layered slicing is performed. A series of two-dimensional scanning trajectories for laser selective melting and forming are generated based on the slice contour information.

[0039] (4) Adjust the substrate plane, extract the air from the printing chamber and fill it with argon to balance the pressure difference inside and outside, so that the oxygen content is less than 1000ppm; turn on the ultrasonic generator in advance and adjust the ultrasonic frequency to 60kHz so that the ultrasonic generator can stably emit the ultrasonic field.

[0040] (5) After coupling with ultrasonic field assistance, Al-Mg-Sc-Er-Zr aluminum-based composite powder is printed onto the preheated substrate in single-pass layer-by-layer printing. Each layer is printed using a stripe scanning strategy. After one layer is formed, the laser head is returned to the starting position of the current layer and the thickness of the current layer is increased along the Z-axis until the multi-scale structure coupled with the high-strength and tough aluminum alloy meets the dimensional requirements. The ultrasonic generator is turned off 3-5 minutes after the forming is completed.

[0041] The laser printing parameters are as follows: a continuous fiber laser is used, the focused spot diameter is 100μm, the laser power is 250W, the scanning speed is 900mm / s, the overlap rate is 20%, the layer thickness is 30μm, and the laser rotation angle during interlayer scanning is 67°.

[0042] (6) The substrate was removed by electrical discharge wire cutting to obtain a multi-scale structurally coupled high-strength and high-toughness aluminum alloy; in addition, the relative density of the printed sample was tested using the Archimedes water displacement method and found to reach 99.8%.

[0043] (7) By heat-treating the above Al-Mg-Er-Zr composite aluminum alloy at 300°C for 2 hours and then vacuum cooling, the internal stress generated during the manufacturing process is eliminated, and the precipitation of a large number of dispersed strengthening phases is further promoted, and finally a multi-scale structurally coupled high-strength and high-toughness aluminum alloy is obtained.

[0044] Microstructural characterization and mechanical property analysis of multi-scale coupled high-strength and high-toughness aluminum alloys yielded the following conclusions: The microstructure of the multi-scale coupled high-strength and high-toughness aluminum alloy prepared in this embodiment is characterized by: approximately 41% equiaxed fine grains with a grain size of less than 1 μm and an average diameter of approximately 290 nm; and columnar coarse grains with an average grain size of 2.4 μm; wherein a large number of Al6Fe and Al atoms of 10–50 nm are present at the equiaxed grain boundaries. 13 Fe4, Al9FeNi, Al 13 The alloy contains Co4 and Al3 (Er, Sc, Zr) nano-sized particles; in addition to the above particles, there are also 30-100 nm granular Al3 (Sc, Zr) and Mg2Si dispersed strengthening phases within the columnar crystals. The abundant nano-sized precipitates enhance the alloy's strength through Orowan strengthening mechanism, dispersion strengthening, and pinning strengthening. In terms of mechanical property analysis, dog bone tensile test specimens were machined according to ASTM-E8M standards and tested on a Zwick / Roell Z100 testing machine. Among them, the tensile strength of the multi-scale structurally coupled high-strength and tough aluminum alloy after corresponding heat treatment reached 850 MPa, which is significantly enhanced compared with the room temperature tensile strength (750 MPa) of the aluminum alloy in Example 1, while the plasticity is still maintained above 7%.

[0045] Example 3: The ultrasonic-assisted laser additive manufacturing method for multi-scale structural coupling high-strength and tough aluminum alloys provided in this embodiment specifically includes the following steps: (1) In this embodiment, the original purity of Al-Mg-Sc-Er-Zr powder and 18Ni300 powder is above 99.9%, and the average particle size is 15μm~53μm. First, the high Ni content alloy steel powder is mechanically ball-milled for 20h to obtain fine powder of high Ni content alloy steel with small particle size. Then, spherical Al-Mg-Sc-Er-Zr aluminum alloy powder with a mass ratio of 96wt.% and high Ni content alloy steel fine powder are further ball-milled for 10~16h and mixed at room temperature to obtain mixed powder of high Ni content alloy steel dispersed in Al-Mg-Sc-Er-Zr alloy. Then, the mixed powder is placed in a dryer for vacuum drying for 2h and placed in a powder feeding tank.

[0046] (2) Using aluminum alloy as the substrate, clean the residual powder in the printing chamber and use anhydrous ethanol to clean the impurities on the substrate surface. Adjust the distance between the quartz lamp and the upper surface of the substrate to 100 mm to ensure that the substrate can effectively absorb infrared radiation characteristics and preheat to 200°C; load the aluminum alloy composite powder into the powder supply chamber.

[0047] (3) A three-dimensional model is established based on the high-strength and tough aluminum alloy component to be prepared and layered slicing is performed. A series of two-dimensional scanning trajectories for laser selective melting and forming are generated based on the slice contour information.

[0048] (4) Adjust the substrate plane, extract the air from the printing chamber and fill it with argon to balance the pressure difference between the inside and outside, so that the oxygen content is less than 1000ppm; turn on the ultrasonic generator in advance and adjust the ultrasonic frequency to 80kHz so that the ultrasonic generator can stably emit the ultrasonic field.

[0049] (5) After coupling with ultrasonic field assistance, Al-Mg-Sc-Er-Zr aluminum-based composite powder is printed onto the preheated substrate in single-pass layer-by-layer printing. Each layer is printed using a stripe scanning strategy. After one layer is formed, the laser head is returned to the starting position of the current layer and the thickness of the current layer is increased along the Z-axis until the multi-scale structure coupled with the high-strength and tough aluminum alloy meets the dimensional requirements. The ultrasonic generator is turned off 3-5 minutes after the forming is completed.

[0050] The laser printing parameters are as follows: a continuous fiber laser is used, the focused spot diameter is 100μm, the laser power is 300W, the scanning speed is 1000mm / s, the overlap rate is 20%, the layer thickness is 30μm, and the laser rotation angle during interlayer scanning is 67°.

[0051] (6) The substrate was removed by electrical discharge wire cutting to obtain a multi-scale structurally coupled high-strength and high-toughness aluminum alloy; in addition, the relative density of the printed sample was tested using the Archimedes water displacement method and found to reach 99.7%.

[0052] (7) By heat-treating the above Al-Mg-Er-Zr composite aluminum alloy at 250°C for 2 hours and then vacuum cooling, the internal stress generated during the manufacturing process is eliminated, and the precipitation of a large number of dispersed strengthening phases is further promoted, and finally a multi-scale structural coupling high strength and toughness aluminum alloy is obtained.

[0053] Microstructural characterization and mechanical property analysis of multi-scale coupled high-strength and high-toughness aluminum alloys yielded the following conclusions: The microstructure of the multi-scale coupled high-strength and high-toughness aluminum alloy prepared in this embodiment is characterized by: approximately 40% equiaxed fine grains with a grain size of less than 1 μm and an average diameter of approximately 305 nm; and columnar coarse grains with an average grain size of 2.6 μm; wherein a large number of Al6Fe and Al atoms of 10–50 nm are present at the equiaxed grain boundaries. 13 Fe4, Al9FeNi, Al 13 The alloy contains Co4 and Al3 (Er, Sc, Zr) nano-sized particles. In addition to these particles, the columnar crystals also contain 30-100 nm granular Al3 (Sc, Zr) and Mg2Si dispersed strengthening phases. These abundant nano-sized precipitates enhance the alloy's strength through Orowan strengthening, dispersion strengthening, and pinning strengthening mechanisms.

[0054] For mechanical property analysis, dog bone tensile test specimens were machined according to ASTM-E8M standards and tested on a Zwick / Roell Z100 testing machine. The tensile strength of the multi-scale structurally coupled high-strength and high-toughness aluminum alloy after appropriate heat treatment reached 860 MPa; its plasticity was 6.1%.

[0055] The room temperature tensile strength (850 MPa) of the aluminum alloy in Example 2 is not significantly increased, but its plasticity is reduced.

[0056] The molten pool cross-sections in Examples 1-3 can be referenced. Figure 1 Due to ultrasonic shock oscillation, porosity and cracks are reduced, while the Marangoni flow velocity is increased. The alloy exhibits a bimodal microstructure, with equiaxed grains at the melt pool boundary and strengthening phases precipitated at the grain boundaries. A large number of columnar grains exist in the center of the melt pool, with submicron and nanoscale strengthening phases dispersed within the grains.

[0057] Replacing the 18Ni300 powder in Examples 1-3 with 18Ni250, 18Ni350, 317 / 317L, 904L, or 254SMO yields largely the same phenomena and conclusions, so they will not be repeated here.

[0058] In summary, this invention introduces multi-element alloy powders such as high-Ni content alloy steel and titanium alloys into the SLM process, which is beneficial for promoting the precipitation of multi-element nano-precipitates in the bimodal grain structure of aluminum alloys. Based on ultrasonic energy field assistance, the synergistic mechanism of ultrasonic cavitation effect and acoustic flow significantly accelerates solute diffusion and suppresses microsegregation, thereby refining grains and improving the uniformity of nano-precipitate distribution. This effectively inhibits particle coarsening, adjusts the size ratio of columnar to equiaxed crystals, and improves microstructure uniformity. Through dispersion strengthening and grain refinement, it effectively enhances the strength and toughness of aluminum alloys, overcoming the problems of low density and uneven precipitate distribution leading to insufficient strength and poor toughness in existing aluminum alloys. This invention has low production costs, allows for effective control of the mass ratio and distribution of the reinforcing phase in high-Ni content alloy steel, and the microstructure of aluminum alloys, resulting in aluminum alloys with high strength and high toughness.

[0059] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the scope of protection of the present invention.

Claims

1. A method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys, characterized in that, The method includes: High-Ni content alloy steel powder is mechanically ball-milled to obtain fine alloy steel powder; the mass fraction of Ni in the high-Ni content alloy steel powder is greater than 10%, and the particle sizes of the high-Ni content alloy steel powder and the fine alloy steel powder are 15~53μm and 3~15μm, respectively; The alloy steel fine powder and Al-Mg-Sc-Er-Zr alloy powder are mechanically ball-milled to obtain a mixed powder; the vacuum-dried mixed powder is loaded into a powder supply hopper; the alloy steel fine powder and Al-Mg-Sc-Er-Zr alloy powder are in a mass ratio of 95~99:1~5. A three-dimensional model of the high-strength and high-toughness aluminum alloy component to be prepared is established and layered slicing is performed. A series of scanning trajectories for laser selective melting and forming are generated based on the slice contour information. Adjust the distance between the quartz lamp and the upper surface of the substrate to 80~120mm to ensure that the substrate can effectively absorb infrared radiation energy; extract the oxygen in the forming sealed chamber and introduce argon to reach the set oxygen content threshold and balance the pressure difference inside and outside the forming chamber. Turn on the ultrasonic generator and adjust the frequency to stably emit ultrasonic waves; use the laser beam of the composite ultrasonic energy field to print the composite powder on the preheated substrate in channels and layers according to the scanning trajectory until the forming size is met; the composite energy field of ultrasonic vibration coupled with high-energy laser beam induces supersaturated solute to precipitate in at least two of the following ways: decomposition precipitation, solid solution precipitation and secondary precipitation, to form nano and submicron reinforcing phases. The printed aluminum alloy is heat-treated and then vacuum-cooled to eliminate the internal stress generated during the laser additive manufacturing process, further promoting the precipitation of a large number of dispersed strengthening phases, and finally obtaining a high-strength and high-toughness aluminum alloy with a bimodal structure coupled by columnar crystals with grain sizes of 2~5μm and equiaxed crystals with grain sizes of 100~500nm.

2. The method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys according to claim 1, characterized in that, During the ultrasonic-assisted laser selective melting and forming process, the ultrasonic waves impact and stir the molten pool, causing cavitation and agitation, which is superimposed with the in-situ heat treatment of the ultrasonic field. During the rapid solidification process, supersaturated Fe, Ni and Co nanoparticles are induced to precipitate in columnar crystals and at the grain boundaries of equiaxed crystals, and a small amount of Co, Sc and Er nanoparticles are precipitated in over-permacrystalline crystals.

3. The method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys according to claim 1, characterized in that, Utilizing ultrasonic energy fields to improve the solidification and precipitation behavior of the molten pool during SLM, including: After the ultrasonic waves at the bottom of the forming platform act on the molten pool, the ultrasonic energy field generates instantaneous high-explosive shock waves through the cavitation effect, which can effectively eliminate porosity and inhibit the formation of cracks. By utilizing the ultrasonic waves generated on the side of the forming platform to impact the molten pool laterally and transmit them to the surface of the molten pool, the Marangoni effect can be accelerated to increase the solidification rate. Under the combined energy field of ultrasound and laser, the precipitation of multi-scale phase particles can be induced. A large number of nanoparticles precipitated in the columnar crystal region of aluminum alloy are dispersed and distributed as strengthening phases. With the decomposition of the melt pool, the density of heterogeneous nucleation sites increases significantly, the fine-grained region expands, and the grain size is not coarsened due to the pinning restriction of the precipitates. The particles in the coarse-grained region tend to coarsen and form equiaxed grains, which greatly improves the equiaxed crystal nucleation rate. At the same time, the acoustic flow agitation homogenizes the melt temperature or solute field through strong convection, expands the compositional undercooling region and inhibits the epitaxial growth of columnar crystals. The ratio of grain size between the fine-grained region and the coarse-grained region in the bimodal structure increases significantly. It improves the temperature distribution and solute transport inside the melt pool, reduces heat accumulation and promotes uniform mixing, thereby inhibiting the formation of solidification defects.

4. The method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys according to claim 3, characterized in that, The multi-scale phase particles include micron-sized particles. α -Al phase, submicron-sized Al6Fe, Al 13 Fe4, Al9FeNi, Al 13 Co4 and nano-sized Al3 (Er, Sc, Zr) and Mg2Si particles.

5. The method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys according to claim 1, characterized in that, A continuous fiber laser is used, and the process parameters are as follows: laser power is 200W~360W, scanning speed is 800~1000mm / s, overlap rate is 20~50%, layer thickness is 20~30μm, and the coupling laser rotation angle during interlayer scanning is 67°.

6. The method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys according to claim 1, characterized in that, The mechanical ball milling of high-Ni content alloy steel powder includes: High-Ni content alloy steel powder and grinding balls of different diameters were loaded into a ball milling jar at a ball-to-material ratio of 20:1, and the ball milling speed was 320 r / min. The ball milling was carried out for 20 h in a pure argon atmosphere by milling for 30 min and then pausing for 10 min. The process parameters for mechanical ball milling of alloy steel fine powder and Al-Mg-Sc-Er-Zr alloy powder are as follows: the ball-to-material ratio is set to 10~15:1, the ball milling speed is 120~240 r / min, and the ball milling is carried out for 10~16 h in a pure argon atmosphere by ball milling for 10~20 min and then pausing for 20 min.

7. The method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys according to any one of claims 1 to 6, characterized in that, The high Ni content alloy steel powder includes, but is not limited to, one of 18Ni250, 18Ni300, 18Ni350, 317 / 317L, 904L and 254SMO.

8. The method for ultrasonic-assisted laser additive manufacturing of multi-scale structurally coupled high-strength and high-toughness aluminum alloys according to any one of claims 1 to 6, characterized in that, The Al-Mg-Sc-Er-Zr aluminum-based alloy powder has a particle size of 15μm~53μm. By mass fraction, the contents of Mg, Er, Sc, Zr, Mn, Si, Fe, Ni and Co are 2~5%, 0.7~1.0%, 0.3~0.4%, 0.1~0.4%, 0.2~0.5%, 0.2~0.8%, 2.0~5.0%, 1.0~4.0% and 0.4~1.0%, respectively, with the remainder being Al and impurities.

9. A multi-scale structurally coupled high-strength and high-toughness aluminum alloy, characterized in that, The high-strength and high-toughness aluminum alloy was prepared based on the ultrasonic-assisted laser additive manufacturing method for multi-scale structural coupling as described in any one of claims 1 to 8.

10. An application of a multi-scale structurally coupled high-strength and high-toughness aluminum alloy, characterized in that, Applications of multi-scale structurally coupled high-strength and high-toughness aluminum alloys prepared by the ultrasonic-assisted laser additive manufacturing method according to any one of claims 1 to 8, or the multi-scale structurally coupled high-strength and high-toughness aluminum alloy according to claim 9, in the fields of new energy vehicles, drones, aerospace, and humanoid robots.

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