Composition optimization method of high strength and toughness aluminum lithium alloy for additive manufacturing with rare earth synergistic refinement
By synthesizing (Ce, Zr)Al3 nanocomposite phase in situ during additive manufacturing as a nucleation core, the problem of coarse grain structure in aluminum-lithium alloys during additive manufacturing was solved, and equiaxed grain structure of high-strength and tough aluminum-lithium alloys was achieved, improving the mechanical properties and plasticity of the material.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HENAN UNIV OF SCI & TECH
- Filing Date
- 2026-05-09
- Publication Date
- 2026-07-10
Smart Images
Figure CN122164895B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of metal material processing technology, specifically to a method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing using rare earth synergistic refinement. Background Technology
[0002] Due to its excellent properties such as low density, high specific strength, and high specific stiffness, aluminum-lithium alloys have irreplaceable application prospects in lightweight fields such as aerospace and rail transportation. Additive manufacturing technology, especially laser selective melting and electron beam melting, is used. However, the rapid solidification of the molten pool easily forms coarse columnar and equiaxed crystal structures, accompanied by obvious grain orientation. This leads to anisotropy of mechanical properties of components, low fatigue resistance, and susceptibility to hot cracking, which seriously restricts its application as a main load-bearing structure.
[0003] To refine the grain structure of additively manufactured metals, grain refiners such as zirconium (Zr) and scandium (Sc) are typically added to alloy powders. Zr can form a stable ZrAl phase, which can serve as an effective nucleation core for α-Al. However, under the extreme thermal cycling conditions of additive manufacturing, adding Zr alone often faces problems such as limited refining efficiency and the potential agglomeration or coarsening of the formed ZrAl phase. Rare earth element cerium (Ce) has also been attempted to improve the casting structure of aluminum alloys due to its unique metamorphic properties. However, its solid solubility in aluminum is extremely low, and traditional addition methods easily form coarse and brittle Ce-rich phases, which not only do not help with refining but also break the matrix and damage the plasticity of the material.
[0004] In the existing technology, research on adding Ce and Zr in combination to obtain synergistic effects is mostly found in the traditional casting field, and it is mostly in the form of pre-alloying or intermediate alloying. In the additive manufacturing process, after repeated melting and solidification, the nucleation potential of the pre-alloyed refining elements will be difficult to continuously provide nucleation particles under rapid solidification conditions due to the dissolution of particles. Summary of the Invention
[0005] This invention addresses the technical problems existing in the prior art by providing a method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing through rare earth synergistic refinement.
[0006] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing with rare earth synergistic refinement, comprising the following steps:
[0007] S1: Obtain aluminum-lithium alloy matrix powder, and obtain CeH2 powder as cerium source and ZrH2 powder as zirconium source as reaction precursors respectively;
[0008] S2: The CeH2 powder, ZrH2 powder and aluminum-lithium alloy matrix powder are uniformly mixed to form a composite powder raw material;
[0009] S3: In the electron beam additive manufacturing process, the ultra-high temperature and ultra-high cooling rate environment provided by the molten pool formed on the composite powder raw material by high energy beam scanning causes CeH2 and ZrH2 to decompose into highly active Ce atoms and Zr atoms, and promotes the two to undergo an in-situ synthesis reaction with molten aluminum to generate (Ce,Zr)Al3 nanocomposite phase.
[0010] S4: Based on the rapid solidification process of the molten pool, the dispersed (Ce, Zr)Al3 nanocomposite phase is used as a heterogeneous nucleation point to trigger the explosive nucleation and confined growth of α-Al grains, ultimately obtaining aluminum-lithium alloy components with equiaxed crystal structure.
[0011] Preferably, the aluminum-lithium alloy matrix powder uses aluminum as a solvent and contains 1.5%-3.5% lithium, 2.0%-4.0% copper, and 0.5%-1.5% magnesium by mass, and the particle size distribution range of the matrix powder is 15-53 micrometers.
[0012] Preferably, the atomic ratio of Ce to Zr is controlled between 1:2 and 2:1, and the total mass of Ce and Zr elements accounts for 0.3% of the composite powder raw material.
[0013] Preferably, the mixing process includes a pretreatment step, in which CeH2 and ZrH2 powders are premixed with a trace amount of process control agent, which is stearic acid or liquid paraffin, and the amount of process control agent is 0.1%-0.5% of the total mass of the precursor powder. Then, under the protection of inert gas, the pretreated precursor powder and aluminum-lithium alloy matrix powder are placed in a three-dimensional mixer and mixed at a speed of 20-40 rpm for 1-4 hours to ensure that the precursor powder is uniformly attached to the surface of the matrix powder to form a composite powder raw material.
[0014] Preferably, the high-energy beam is a laser beam, and the power density range of the laser beam is set to 1×10^4-1×10^6 W / cm. 2 The scanning speed is set to 600-1500 mm / s.
[0015] Preferably, the molten pool atmosphere is actively controlled. The additive manufacturing process should be carried out in a high-purity argon or nitrogen protective atmosphere. The oxygen content of the protective atmosphere should be less than 100 ppm. The hydrogen released by the decomposition of the precursor and the trace amounts of volatile substances that may be generated can be carried away from the reaction zone by the protective gas flow, thereby ensuring that the synthesis reaction of the composite nanophase is carried out in a clean melt environment and avoiding the generation of defects such as pores.
[0016] Preferably, under the action of a high-energy beam, the CeH2 and ZrH2 precursor powders absorb energy and decompose rapidly to generate highly active cerium atoms, zirconium atoms and hydrogen gas. Subsequently, the newly generated cerium atoms and zirconium atoms are mixed under the convection and diffusion of the molten pool. The atomic ratio of cerium to zirconium is specifically limited to 1:1.5 to 1.5:1.
[0017] Preferably, the rapid solidification process is achieved by synergistically controlling the following process parameters: preheating the substrate and stabilizing it within a temperature range of 150℃±50℃, controlling the interlayer cooling time after each layer is scanned within a range of 10 seconds to 60 seconds, and ensuring that the solidification cooling rate of the molten pool is not less than 1×10^5 K / s based on the laser process parameters, thereby forming α-Al crystal nuclei with (Ce, Zr)Al3 nanocomposite phase as the nucleation core.
[0018] Preferably, the microstructure of the component consists of α-Al equiaxed crystals formed by nucleation and growth of an in-situ synthesized (Ce, Zr)Al3 nanocomposite phase. The (Ce, Zr)Al3 nanocomposite phase is spherical or nearly spherical, with a particle size distribution between 20 nm and 100 nm, and is diffusely and uniformly distributed within the α-Al matrix. The average grain size of the α-Al equiaxed crystals is 1 μm to 3 μm. The total mass of cerium and zirconium elements present in the (Ce, Zr)Al3 nanocomposite phase in the form of coordination bonds accounts for 0.08% to 0.45% of the total mass of the component.
[0019] Preferably, the microstructure of the component consists of uniform ultrafine equiaxed crystals, with (Ce, Zr)Al3 composite nanophases of 20-100 nanometers in size dispersed inside the grains.
[0020] The beneficial effects of this invention are as follows: By using CeH2 and ZrH2 as precursors, this invention triggers their decomposition in the high-temperature environment of the additive manufacturing molten pool, and promotes the release of highly active Ce and Zr atoms to react in situ with molten aluminum to generate a (Ce,Zr)Al3 nanocomposite phase. This achieves the spatiotemporal synchronization of refined phase generation and solidification nucleation, avoiding the failure of the pre-alloyed phase during the remelting process. All Ce and Zr elements are dissolved in the target phase through coordination bonds, eliminating the risk of coarse and brittle phase formation and hydrogen-induced porosity. By controlling the atomic ratio of Ce to Zr between 1:1.5 and 1.5:1, the generated (Ce,Zr)Al3 phase has a lattice constant and interfacial energy that best match the α-Al matrix, enabling its heterogeneous nucleation efficiency to reach its peak. Attached Figure Description
[0021] Figure 1 This is a flowchart of the present invention;
[0022] Figure 2Optical microscope images of samples with different Ce / Zr molar ratios according to the present invention;
[0023] Figure 3 X-ray diffraction patterns of samples with different Ce / Zr molar ratios according to the present invention;
[0024] Figure 4 The EDS energy spectrum surface scan of the Ce / Zr=1:1.2 molar ratio sample of the present invention;
[0025] Figure 5 The EDS energy spectrum surface scan of the Ce / Zr=1:1.1 molar ratio sample of the present invention;
[0026] Figure 6 This is an EDS energy spectrum surface scan of the Ce / Zr=1:1 molar ratio sample of the present invention;
[0027] Figure 7 The images are scanning electron microscope images of samples with different Ce / Zr molar ratios according to the present invention. Detailed Implementation
[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0029] In the description of this application, the term "for example" is used to mean "used as an example, illustration, or description." Any embodiment described as "for example" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use the invention. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that the invention can be made without using these specific details. In other instances, well-known structures and processes will not be described in detail to avoid obscuring the description of the invention with unnecessary detail. Therefore, the invention is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.
[0030] like Figure 1This embodiment provides a method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing through rare earth synergistic refinement. This method involves introducing cerium and zirconium as specific hydride precursors and triggering their decomposition and combination reactions in the high-temperature instantaneous thermal environment of the additive manufacturing molten pool. This results in the in-situ generation of a (Ce, Zr)Al3 nanocomposite phase that can serve as an efficient nucleation core for α-Al grains. The method includes the following specific steps:
[0031] S1: Obtain aluminum-lithium alloy matrix powder, and obtain CeH2 powder as cerium source and ZrH2 powder as zirconium source as reaction precursors respectively;
[0032] S2: The CeH2 powder, ZrH2 powder and aluminum-lithium alloy matrix powder are uniformly mixed to form a composite powder raw material;
[0033] S3: In the electron beam additive manufacturing process, the ultra-high temperature and ultra-high cooling rate environment provided by the molten pool formed on the composite powder raw material by high energy beam scanning causes CeH2 and ZrH2 to decompose into highly active Ce atoms and Zr atoms, and promotes the two to undergo an in-situ synthesis reaction with molten aluminum to generate (Ce,Zr)Al3 nanocomposite phase.
[0034] S4: Based on the rapid solidification process of the molten pool, the dispersed (Ce, Zr)Al3 nanocomposite phase is used as a heterogeneous nucleation point to trigger the explosive nucleation and restricted growth of α-Al grains, ultimately obtaining aluminum-lithium alloy components with ultrafine equiaxed crystal structure.
[0035] Furthermore, the aluminum-lithium alloy matrix powder uses aluminum as a solvent and contains 1.5%-3.5% lithium, 2.0%-4.0% copper, and 0.5%-1.5% magnesium by mass, with the remainder being aluminum and unavoidable impurities. The particle size distribution of the matrix powder ranges from 15 to 53 micrometers, exhibiting good flowability and high packing density to meet the requirements of additive manufacturing processes.
[0036] Furthermore, the atomic ratio of Ce to Zr should be strictly controlled between 1:2 and 2:1 to ensure that a suitable (Ce, Zr) intermetallic compound can be formed subsequently. The total mass of Ce and Zr elements should account for 0.1% to 0.5% of the composite powder raw material. This range can ensure a significant refining effect while avoiding the formation of coarse and brittle phases due to excessive addition.
[0037] Furthermore, the mixing process includes a pretreatment step, in which CeH2 and ZrH2 powders are premixed with a trace amount of process control agent, which is stearic acid or liquid paraffin, at a dosage of 0.1%-0.5% of the total mass of the precursor powder. Then, under inert gas protection, the pretreated precursor powder and aluminum-lithium alloy matrix powder are placed in a three-dimensional mixer and mixed at a speed of 20-40 rpm for 1-4 hours to ensure that the precursor powder is uniformly attached to the surface of the matrix powder, forming a composite powder raw material with uniform composition.
[0038] Furthermore, the high-energy beam is a laser beam, and the power density range of the laser beam is set to 1×10^4-1×10^6 W / cm². 2 The scanning speed is set to 600-1500 mm / s. This combination of parameters ensures that the molten pool obtains a maximum temperature of over 1500℃, a cooling rate of 10^3 to 10^6 K / s, and sufficient thermodynamic and kinetic conditions to drive the decomposition of precursors and the completion of inter-elemental reactions.
[0039] Furthermore, the atmosphere of the molten pool is actively controlled. The additive manufacturing process should be carried out in a high-purity argon or nitrogen protective atmosphere with an oxygen content of less than 100 ppm. The hydrogen released by the decomposition of the precursor and the trace amounts of volatile substances that may be generated can be carried away from the reaction zone by the protective gas flow, thereby ensuring that the synthesis reaction of the composite nanophase is carried out in a clean melt environment and avoiding the generation of defects such as pores.
[0040] Furthermore, the in-situ synthesis reaction is a multi-stage continuous process. Its core lies in controlling the reaction of cerium and zirconium at a specific stoichiometric ratio to generate a composite phase with optimal nucleation efficiency. First, under the action of a high-energy beam, the CeH2 and ZrH2 precursor powders absorb energy and rapidly decompose, generating highly reactive cerium atoms, zirconium atoms, and hydrogen gas. Subsequently, the newly formed cerium and zirconium atoms mix under the convection and diffusion of the molten pool. To achieve minimal lattice mismatch between the generated phase and the α-Al matrix, the mixing ratio of cerium and zirconium atoms needs to be controlled so that they can co-enter (Ce, In the crystal structure of the (Ce,Zr)Al3 intermetallic compound, based on the crystallographic characteristics and atomic occupancy rules of the ternary compound, the atomic ratio of cerium to zirconium is specifically limited to 1:1.5 to 1.5:1. Within this ratio range, the generated (Ce,Zr)Al3 composite nanophase has a lattice constant and interfacial energy closest to α-Al, and its effectiveness as a heterogeneous nucleation core reaches its peak, most effectively promoting heterogeneous nucleation during the solidification process of the molten pool.
[0041] Furthermore, the rapid solidification process is achieved by synergistically controlling the following process parameters: preheating the substrate and stabilizing it within the temperature range of 150℃±50℃, controlling the interlayer cooling time after each layer scan within the range of 10 seconds to 60 seconds, and ensuring that the solidification cooling rate of the molten pool is not less than 1×10^5 K / s based on the laser process parameters. The combined effect of the above parameters enables the uniform formation of α-Al crystal nuclei with (Ce, Zr)Al3 nanocomposite phase as the nucleation core in the molten pool.
[0042] Furthermore, the microstructure of the component consists of α-Al equiaxed crystals formed by nucleation and growth of an in-situ synthesized (Ce, Zr)Al3 nanocomposite phase. The (Ce, Zr)Al3 nanocomposite phase is spherical or nearly spherical, with a particle size distribution between 20 nm and 100 nm, and is diffusely and uniformly distributed within the α-Al matrix. The average grain size of the α-Al equiaxed crystals is 1 μm to 3 μm. The total mass of cerium and zirconium elements present in the (Ce, Zr)Al3 nanocomposite phase in the form of coordination bonds accounts for 0.08% to 0.45% of the total mass of the component.
[0043] Furthermore, the microstructure of the component consists of uniform ultrafine equiaxed crystals, with (Ce, Zr)Al3 composite nanophases of 20-100 nanometers in size dispersed within the grains.
[0044] Example 1
[0045] This invention provides a method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing through rare earth synergistic refinement, comprising the following steps:
[0046] S1: Prepare an aluminum-lithium alloy matrix powder with the following chemical composition by mass percentage: lithium 2.8%, copper 3.2%, magnesium 1.0%, with the balance being aluminum and unavoidable trace impurities. This matrix powder is prepared by aerosol method, with a particle size distribution of 20-45 micrometers. Simultaneously, prepare CeH2 powder and ZrH2 powder as reaction precursors, both with a purity higher than 99.5% and an average particle size of approximately 5 micrometers. In this embodiment, the atomic ratio of Ce to Zr is 1:1, and the total addition amount is 0.3% of the alloy mass.
[0047] S2: The measured CeH2 and ZrH2 powders and stearic acid (0.3% of their total mass) were placed together in a small mixing tank as a process control agent and premixed for 10 minutes to ensure that the stearic acid was uniformly coated on the surface of the precursor powder. Then, in an argon-protected glove box, the pretreated precursor powder and all the aluminum-lithium alloy matrix powder were fed into a three-dimensional oscillating mixer. The mixer speed was set to 30 rpm and the mixing was continued for 3 hours. After the mixing was completed, a composite powder raw material with uniform composition was obtained, in which CeH2 and ZrH2 powders were uniformly attached to the surface of the larger matrix powder particles.
[0048] S3: The composite powder raw material is filled into the forming chamber of the laser selective melting equipment. The forming substrate is preheated to 150°C. The forming process is carried out under the protection of high-purity argon gas with an oxygen content of less than 50 ppm. The laser process parameters are set as follows: laser power of 350W, scanning speed of 1000 mm / s, spot diameter of 80μm, and powder layer thickness of 30μm. Under these parameters, the laser power density is approximately 7×10⁻⁶. 4 W / cm 2 During laser scanning, the powder melts to form a tiny molten pool. The highest temperature at the center of the molten pool exceeds 1600℃. Under the high-temperature environment of the molten pool, CeH2 and ZrH2 rapidly decompose, releasing highly reactive Ce atoms, Zr atoms, and hydrogen gas. The hydrogen gas is carried away by the protective gas, while Ce and Zr atoms rapidly diffuse and mix under the strong convection of the molten pool. Subsequently, the atoms react with the surrounding molten aluminum, combining in a 1:1 atomic ratio to form (CeH2O). 0.5 Zr 0.5 Al3 nanocomposite phase;
[0049] S4: The molten pool is rapidly cooled after the laser is removed. After each layer is scanned, the interlayer cooling time is set to 30 seconds. Under this cooling rate, the dispersed (Ce) 0.5 Zr 0.5 The Al3 nanocomposite phase becomes the heterogeneous nucleation core, triggering explosive nucleation of the α-Al melt, and the crystal nuclei eventually form fine equiaxed crystals.
[0050] Example 2
[0051] This invention provides a method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing through rare earth synergistic refinement, comprising the following steps:
[0052] S1: Prepare an aluminum-lithium alloy matrix powder with the following chemical composition by mass percentage: lithium 2.8%, copper 3.2%, magnesium 1.0%, with the balance being aluminum and unavoidable trace impurities. This matrix powder is prepared by aerosol method, with a particle size distribution of 20-45 micrometers. Simultaneously, prepare CeH2 powder and ZrH2 powder as reaction precursors, both with a purity higher than 99.5% and an average particle size of approximately 5 micrometers. In this embodiment, the atomic ratio of Ce to Zr is 1:1.2 (i.e., the Zr ratio is slightly higher), and the total addition amount is 0.3% of the alloy mass.
[0053] S2: The measured CeH2 and ZrH2 powders and stearic acid (0.3% of their total mass) were placed together in a small mixing tank and premixed for 10 minutes. Then, in an argon-protected glove box, the pretreated precursor powder and all the aluminum-lithium alloy matrix powder were fed into a three-dimensional oscillating mixer. The mixer speed was set to 30 rpm and the mixture was continuously mixed for 3 hours. After the mixing was completed, a composite powder raw material with uniform composition was obtained.
[0054] S3: The composite powder raw material is filled into the forming chamber of the laser selective melting equipment. The forming substrate is preheated to 150°C. The forming process is carried out under the protection of high-purity argon gas with an oxygen content of less than 50 ppm. The laser power of the laser process is set to 350W, the scanning speed is 1000 mm / s, the spot diameter is 80μm, and the powder layer thickness is 30μm. After the laser scanning forms the molten pool, CeH2 and ZrH2 decompose. Since the initial powder has a slightly higher proportion of Zr atoms, after atomic diffusion and mixing in the molten pool, the ratio of Ce to Zr atoms participating in the reaction approaches 1:1.2.
[0055] S4: The molten pool is rapidly cooled after the laser is removed. After each layer is scanned, the interlayer cooling time is set to 30 seconds, generating (Ce... 0.45 Zr 0.55 Al3 nanocomposite phase (size approximately 25-70 nm) serves as an efficient nucleation core, promoting the equiaxed crystallization of α-Al, ultimately resulting in a uniform ultrafine equiaxed crystal structure in the final component.
[0056] Example 3
[0057] This invention provides a method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing through rare earth synergistic refinement, comprising the following steps:
[0058] S1: Prepare an aluminum-lithium alloy matrix powder with the following chemical composition by mass percentage: lithium 2.8%, copper 3.2%, magnesium 1.0%, with the balance being aluminum and unavoidable trace impurities. This matrix powder is prepared by aerosol method, with a particle size distribution of 20-45 micrometers. Simultaneously, prepare CeH2 powder and ZrH2 powder as reaction precursors, both with a purity higher than 99.5% and an average particle size of approximately 5 micrometers. In this embodiment, the atomic ratio of Ce to Zr is 1.1:1 (i.e., Ce has a slightly higher proportion), and the total addition amount is 0.3% of the alloy mass.
[0059] S2: The measured CeH2 and ZrH2 powders and stearic acid (0.3% of their total mass) were placed together in a small mixing tank and premixed for 10 minutes. Then, in an argon-protected glove box, the pretreated precursor powder and all the aluminum-lithium alloy matrix powder were fed into a three-dimensional oscillating mixer. The mixer speed was set to 30 rpm and the mixture was continuously mixed for 3 hours. After the mixing was completed, a composite powder raw material with uniform composition was obtained.
[0060] S3: The composite powder raw material is filled into the forming chamber of the laser selective melting equipment. The forming substrate is preheated to 150°C. The forming process is carried out under the protection of high-purity argon gas with an oxygen content of less than 50 ppm. The laser power of the laser process is set to 350W, the scanning speed is 1000 mm / s, the spot diameter is 80μm, and the powder layer thickness is 30μm. After the laser scanning forms the molten pool, CeH2 and ZrH2 decompose. Since there is a large initial supply of Ce atoms, the ratio of Ce to Zr atoms participating in the reaction is about 1.1:1.
[0061] S4: The molten pool cools rapidly after the laser is removed, with a cooling rate as high as approximately 1×10⁻⁶. 6 K / s, after each layer scan is completed, the interlayer cooling time is set to 30 seconds, and the diffuse distribution (Ce) 0.52 Zr 0.48 The Al3 nanophase (approximately 20-80 nm in size) effectively promotes the nucleation of α-Al, resulting in a uniform, ultrafine equiaxed crystal structure in the final component.
[0062] The following table can be derived from Examples 1-3:
[0063] Table 1:
[0064]
[0065] As shown in Table 1:
[0066] Examples 1-3, while maintaining completely consistent core process parameters, successfully prepared ultrafine equiaxed crystal structures by changing only the atomic ratio of Ce to Zr. Example 1, using a symmetrical ratio, produced (Ce... 0.5 Zr 0.5 Al3 phase may have the highest structural symmetry. In Example 2, the proportion of Zr-rich phase generated a composite phase with a slightly higher Zr content. Zr diffuses slowly in Al, which may slightly affect the uniform distribution of nucleation particles. In Example 3, the proportion of Ce-rich phase may enhance the convection of the molten pool and promote the dispersed distribution of the composite nanophase.
[0067] In this invention, by finely adjusting the ratio of Ce to Zr, the composition and distribution of the composite phase can be precisely controlled, thereby achieving directional fine-tuning of the final grain size.
[0068] Experimental Example
[0069] To verify the effect of the Ce / Zr atomic ratio on the microstructure and mechanical properties of the aluminum-lithium alloy in this invention, three composite powder raw materials with Ce / Zr molar ratios were prepared, and aluminum-lithium alloy samples were prepared using the same laser selective melting process parameters. The three ratios were: Sample A: Ce / Zr = 1:1.2, Sample B: Ce / Zr = 1.1:1, and Sample C: Ce / Zr = 1:1. Subsequently, the samples were characterized by optical microscopy, X-ray diffraction, energy dispersive spectroscopy, and scanning electron microscopy.
[0070] like Figure 2 As shown, sample A: Ce / Zr = 1: 1.2, with coarse grains and a continuous network distribution of grain boundary phases at low magnification, indicating that the relatively insufficient Ce content leads to a weak driving force for grain boundary purification and grain refinement.
[0071] Sample C:Ce / Zr=1:1, with an overdeveloped grain boundary phase, forming a continuous network structure that severely disrupts the matrix. Under 20μm magnification, a large number of dendritic or acicular second phases are visible distributed along the grain boundaries, inducing significant stress concentration and grain boundary brittleness.
[0072] Sample B: Ce / Zr = 1.1:1 exhibits fine grains, uniform distribution, and clear grain boundary outlines at scales of 100 μm, 50 μm, and 20 μm. It has no continuous network brittle phase or needle-like harmful phase, and only a small amount of uniformly distributed fine grain boundary strengthening phase.
[0073] The above results indicate that a Ce / Zr ratio of 1.1:1 can achieve better grain refinement and microstructure uniformity.
[0074] like Figure 3 As shown, the three groups of samples have the same phase system, mainly composed of Al matrix phase and (Ce, Zr)Al3 intermetallic compound phase, which proves that the method successfully achieved the in-situ synthesis of (Ce, Zr)Al3 phase;
[0075] The intensity of the second phase diffraction peak in sample A is slightly higher than that in sample B, indicating that the excess Zr leads to a higher amount of second phase precipitation.
[0076] The diffraction peak intensity of the (Ce, Zr)Al3 phase in sample C was significantly higher, and some peaks were broadened, indicating that the second phase was over-precipitated and agglomerated.
[0077] The matrix diffraction peaks of sample B are sharp and symmetrical, and the intensity of the second phase diffraction peaks is moderate and highly matched with the matrix, indicating that the amount of second phase formation is reasonable, the crystallinity is high, and there is no tendency for phase aggregation or coarsening. XRD analysis confirms that the 1.1:1 ratio can achieve the best balance between the content of the second phase and the crystallinity, thus providing the highest density of effective heterogeneous nucleation cores for α-Al.
[0078] like Figure 4-6As shown, the distribution of Ce and Zr elements in the sample was characterized by EDS surface scanning. Figure 4 In sample A, Zr exhibits a higher degree of localized aggregation, while Ce is relatively uniformly distributed; however, the overall uniformity is still lower than that of sample B. Figure 6 In sample C, Ce and Zr elements exhibit large-area continuous segregation, forming distinct rare-earth-rich and zirconium-rich bands with clear boundaries from the matrix. Figure 5 Ce and Zr elements are distributed in a diffuse dotted pattern without obvious blocky agglomeration. The element interfaces are smoothly transitioned, and the overall composition is uniformly distributed without any enriched or depleted areas. EDS results show that the 1.1:1 ratio can effectively suppress element segregation and ensure that the (Ce, Zr)Al3 nanocomposite phase is diffusely and uniformly distributed in the matrix.
[0079] like Figure 7 As shown, sample C has a relatively large grain size and continuous grain boundaries, but the fine grain strengthening effect is weak. Sample A has extremely poor uniformity, with a large number of needle-like or rod-like coarse second phases. The grain boundaries are cut or even cracked by the needle-like phases, and there are obvious problems of porosity and insufficient density.
[0080] Sample B is uniform overall, with only a very small number of isolated inclusions. The grain boundaries are continuous and complete, the grain size is uniform and small, and there are a suitable amount of fine precipitates at the grain boundaries. It achieves the systematic effect of fine grain strengthening, grain boundary strengthening and dispersion strengthening. The particle size distribution of the (Ce,Zr)Al3 nanocomposite phase observed by SEM is between 20-100nm, and it is spherical or nearly spherical.
[0081] The experimental results show that the Ce / Zr molar ratio of 1.1:1 is significantly better than the 1:1.2 and 1:1 ratios in terms of grain size, microstructure uniformity, second phase content and distribution, elemental uniformity and density.
[0082] It should be noted that the descriptions of each embodiment in the above embodiments have different focuses. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.
[0083] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.
[0084] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.
Claims
1. A method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing with rare earth synergistic refinement, characterized in that, Includes the following steps: S1: Obtain aluminum-lithium alloy matrix powder, and obtain CeH2 powder as cerium source and ZrH2 powder as zirconium source as reaction precursors respectively; S2: The CeH2 powder, ZrH2 powder and aluminum-lithium alloy matrix powder are uniformly mixed to form a composite powder raw material; S3: In the electron beam additive manufacturing process, the ultra-high temperature and ultra-high cooling rate environment provided by the molten pool formed on the composite powder raw material by high energy beam scanning causes CeH2 and ZrH2 to decompose into highly active Ce atoms and Zr atoms, and promotes the two to undergo an in-situ synthesis reaction with molten aluminum to generate (Ce,Zr)Al3 nanocomposite phase. S4: Based on the rapid solidification process of the molten pool, the dispersed (Ce, Zr)Al3 nanocomposite phase is used as a heterogeneous nucleation point to trigger the nucleation and confined growth of α-Al grains, and finally obtains aluminum-lithium alloy components with equiaxed crystal structure. The atomic ratio of Ce to Zr is controlled between 1:2 and 2:1, and the total mass of Ce and Zr elements accounts for 0.3% to 0.5% of the composite powder raw material.
2. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloy for additive manufacturing through rare earth synergistic refinement according to claim 1, characterized in that, The aluminum-lithium alloy matrix powder uses aluminum as a solvent and contains 1.5%-3.5% lithium, 2.0%-4.0% copper, and 0.5%-1.5% magnesium by mass. The particle size distribution of the matrix powder ranges from 15 to 53 micrometers.
3. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloy for additive manufacturing with rare earth synergistic refinement according to claim 1, characterized in that, The mixing process includes a pretreatment step, in which CeH2 and ZrH2 powders are premixed with a trace amount of process control agent, which is stearic acid or liquid paraffin, at a dosage of 0.1%-0.5% of the total mass of the precursor powder. Then, under inert gas protection, the pretreated precursor powder and aluminum-lithium alloy matrix powder are placed in a three-dimensional mixer and mixed at a speed of 20-40 rpm for 1-4 hours to ensure that the precursor powder is uniformly attached to the surface of the matrix powder to form a composite powder raw material.
4. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloys for additive manufacturing through rare earth synergistic refinement according to claim 1, characterized in that, The high-energy beam is a laser beam, and the scanning speed is set to 600-1500 mm / s.
5. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloy for additive manufacturing with rare earth synergistic refinement according to claim 1, characterized in that, Active control of the molten pool atmosphere is required. The additive manufacturing process should be carried out in a high-purity argon or nitrogen protective atmosphere. The oxygen content of the protective atmosphere should be less than 100 ppm. Hydrogen released from the decomposition of the precursor and trace amounts of volatile substances that may be generated can be carried away from the reaction zone by the protective gas flow.
6. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloy for additive manufacturing with rare earth synergistic refinement according to claim 1, characterized in that, Under the action of a high-energy beam, CeH2 and ZrH2 precursor powders absorb energy and decompose rapidly to generate highly active cerium atoms, zirconium atoms and hydrogen gas. Subsequently, the newly generated cerium atoms and zirconium atoms are mixed under the convection and diffusion of the molten pool. The atomic ratio of cerium to zirconium is specifically limited to 1:1.5 to 1.5:
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7. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloy for additive manufacturing with rare earth synergistic refinement according to claim 1, characterized in that, The rapid solidification process is achieved through coordinated control of the following process parameters: preheating the substrate and stabilizing it within a temperature range of 150℃±50℃; controlling the interlayer cooling time after each layer scan within the range of 10 to 60 seconds; and ensuring that the solidification and cooling rate of the molten pool is not less than 1×10⁻⁶ based on the laser process parameters. 5 K / s, forming α-Al crystal nuclei with (Ce, Zr)Al3 nanocomposite phase as the nucleation core.
8. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloy for additive manufacturing with rare earth synergistic refinement according to claim 1, characterized in that, The microstructure of the component consists of α-Al equiaxed crystals formed by nucleation and growth of an in-situ synthesized (Ce, Zr)Al3 nanocomposite phase. The (Ce, Zr)Al3 nanocomposite phase is spherical or nearly spherical, with a particle size distribution between 20 nm and 100 nm, and is diffusely and uniformly distributed within the α-Al matrix. The average grain size of the α-Al equiaxed crystals is 1 μm to 3 μm. The total mass of cerium and zirconium elements present in the (Ce, Zr)Al3 nanocomposite phase in the form of coordination bonds accounts for 0.08% to 0.45% of the total mass of the component.
9. The method for optimizing the composition of high-strength and high-toughness aluminum-lithium alloy for additive manufacturing with rare earth synergistic refinement according to claim 1, characterized in that, The microstructure of the component consists of uniform ultrafine equiaxed crystals, with (Ce, Zr)Al3 composite nanophases of 20-100 nanometers in size dispersed inside the grains.