Additive manufacturing of al-cu-sc alloy and high strength and toughness preparation method thereof

Abstract

The application discloses an additive manufacturing Al-Cu-Sc alloy and a high-strength and high-toughness preparation method thereof, and the Al-Cu-Sc alloy is formed through an additive manufacturing process and prepared through heat treatment, wherein the mass percentage of each element is as follows: Cu is 2.5-5%, Mg is less than or equal to 10%, Sc is 0.1-1.5%, Zr is less than or equal to 3%, Fe is less than or equal to 0.1%, Si is less than or equal to 0.1%, the total of other alloy elements is 0-1.5%, and the balance is Al; the heat treatment comprises high-temperature short-time heat preservation and water quenching treatment and aging treatment in sequence. The additive manufacturing technology is adopted to be combined with a specific heat treatment process, the mismatch problem of strength and toughness caused by a traditional heat treatment process is overcome, the work hardening capacity is improved while the yield strength and the tensile strength of the alloy are obviously improved, the synergic improvement of the strength and the fracture toughness of the alloy is realized, and the service stability and safety of the additive manufacturing Al-Cu-Sc alloy are ensured.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing alloy technology, and more specifically, relates to an additive manufacturing Al-Cu-Sc alloy and its high strength and toughness preparation method. Background Technology

[0002] Additive manufacturing of high-strength and high-toughness aluminum alloys is crucial for improving the service performance, lifespan, and reliability of modern aerospace equipment. Currently, Al-Si cast aluminum alloys widely used in additive manufacturing have relatively low mechanical strength (yield strength typically less than 300 MPa), while 2xxx and 7xxx series forged aluminum alloys are prone to hot cracking during LPBF (laser-by-brush) forming, making it difficult to meet the requirements of high-performance components in aerospace and other fields. Introducing Sc / Zr alloying elements into 2xxx and 7xxx series forged aluminum alloys can effectively construct dispersed nucleation sites, refine grains to suppress hot cracking, and successfully improve their strength. However, the increased proportion of fine-grained structures can easily lead to early strain localization, causing serious toughness losses such as non-uniform deformation, low strain hardening, and low uniform plasticity, severely affecting the service safety and stability of additively manufactured forged aluminum alloy components.

[0003] To address the issue of reduced toughness in additively manufactured Sc / Zr-containing forged aluminum alloys, researchers have attempted to modify the strength and toughness of aluminum alloys by optimizing laser process parameters and improving heat treatment regimes, thereby controlling the precipitated phases. However, most additively manufactured Sc / Zr-containing forged aluminum alloys treated by these methods require direct aging treatment or solution treatment followed by peak aging. While the yield strength increases, this is often accompanied by a significant decrease in fracture toughness. The mismatch between strength and toughness remains a challenging problem in the current additive manufacturing of Sc / Zr-containing forged aluminum alloys. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned shortcomings by providing an additive manufacturing method for Al-Cu-Sc alloys and a method for preparing high-strength and high-toughness alloys. This method significantly improves the yield strength of the alloys while effectively enhancing their work hardening ability, thereby achieving a synergistic improvement in the strength and fracture toughness of Al-Cu-Sc alloys.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0006] In a first aspect, the present invention provides an additive manufacturing Al-Cu-Sc alloy, wherein the mass percentage of each element in the Al-Cu-Sc alloy is: Cu 2.5~5%, Mg ≤10%, Sc 0.1~1.5%, Zr ≤3%, Fe≤0.1%, Si≤0.1%, the total of other alloying elements is 0~1.5%, and the balance is Al.

[0007] Furthermore, the other alloying elements include any one or more of Zn, Mn, Ni, Co, Fe, Ag, Cr, Li, V, Ti, Ca, and Er, which can be selected and added according to actual needs.

[0008] The Al-Cu-Sc alloy of the present invention is formed by additive manufacturing and then prepared by heat treatment, which includes high-temperature short-time holding, water quenching, and aging treatment.

[0009] In a second aspect, the present invention also provides a method for preparing high-strength and high-toughness Al-Cu-Sc alloys by additive manufacturing as described in the first aspect, comprising:

[0010] Al-Cu-Sc alloy samples were formed using additive manufacturing processes;

[0011] The Al-Cu-Sc alloy sample was subjected to high-temperature short-time holding and water quenching treatment; the high-temperature short-time holding temperature was 450℃~525℃, and the holding time was 0.1~5min.

[0012] The water-quenched Al-Cu-Sc alloy sample is subjected to one or two aging treatments; the aging treatment temperature is 125~200℃ and the holding time is 0.5~12h.

[0013] Furthermore, the additive manufacturing process includes laser powder bed melting, laser melting deposition, or electron beam selective melting.

[0014] Furthermore, the additive manufacturing process uses laser powder bed melting, with process parameters including: laser power 370W, scanning speed 1150mm / s, powder layer thickness 0.04mm, and scanning spacing 0.1mm.

[0015] Furthermore, the Al-Cu-Sc alloy sample formed by additive manufacturing process has a density of over 99.5%.

[0016] Furthermore, the process of high-temperature short-time heat preservation and water quenching includes:

[0017] The Al-Cu-Sc alloy sample was placed in a high-temperature salt bath furnace and heated to the set temperature. The temperature was held for a preset time, and then the sample was taken out and cooled to room temperature with water.

[0018] Furthermore, the timeliness processing procedure includes:

[0019] The water-quenched Al-Cu-Sc alloy sample was placed in a low-temperature oil bath furnace, heated to the set temperature, held for a preset time, and then removed and air-cooled to room temperature.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The Al-Cu-Sc alloy provided by this invention is formed using additive manufacturing technology and combined with a specific heat treatment process, achieving a synergistic improvement in mechanical properties, namely high strength and high toughness. Compared with conventional additive manufacturing alloys, this material maintains excellent fracture toughness while significantly improving yield strength and tensile strength, effectively solving the common problem of difficulty in achieving both strength and toughness in traditional processes. This characteristic gives it stronger damage tolerance and service reliability under complex load environments, making it particularly suitable for critical components in aerospace, energy, and other fields with stringent material performance requirements, providing a material basis for improving the long-term safety and stability of structural components.

[0022] The high-strength and high-toughness preparation method provided by this invention is a special heat treatment method for additively formed Al-Cu-Sc alloys that synergistically improves strength and toughness. By significantly reducing the formation of continuous precipitates at grain boundaries and inducing the synergistic precipitation of nano-Al2Cu phase and nano-Al3(Sc,Zr) phase, it can significantly overcome the strength and toughness mismatch problem caused by traditional direct aging or solution plus peak aging heat treatment processes. While significantly improving the yield strength and tensile strength of the alloy, it effectively improves its work hardening ability, realizes the synergistic improvement of alloy strength and fracture toughness, and ensures the service stability and safety of additively formed Al-Cu-Sc alloys. Attached Figure Description

[0023] Figure 1 This is a comparative diagram of the heat treatment process described in this invention and the heat treatment process in the prior art;

[0024] Figure 2 The images show the microstructures of laser additive manufacturing Al-Cu-Sc alloy samples obtained by heat treatment processes in Example 1 of the present invention and in the prior art; where (a) is the printed sample, (b) is the directly aged sample, (c) is the solution-treated and peak-aged sample, and (d) is the heat-treated sample of Example 1.

[0025] Figure 3 The stress-strain curves of the sample in Example 1 of this invention are compared with those of the Al-Cu-Sc alloy printed sample, the directly aged sample, and the solution-treated and peak-aged sample.

[0026] Figure 4 This invention provides a comparison of the ultimate tensile strength and fracture toughness of the sample from Example 1 of the present invention with Al-Cu-Sc alloy printed samples, directly aged samples, solid solution plus peak aging samples, and Al-Si alloys commonly used in laser additive manufacturing;

[0027] Figure 5The stress-strain curves of the sample in Example 2 of this invention are compared with those of the Al-Cu-Sc alloy printed sample, the directly aged sample, and the solution-treated and peak-aged sample.

[0028] Figure 6 This invention provides a comparison of the ultimate tensile strength and fracture toughness of the sample from Example 2 with Al-Cu-Sc alloy printed samples, directly aged samples, solid solution plus peak aging samples, and commonly used Al-Si alloys in laser additive manufacturing. Detailed Implementation

[0029] Preferred embodiments of the present invention will now be described in more detail with reference to the accompanying drawings and specific examples.

[0030] In the following description, certain specific details are set forth for the purpose of illustrating various disclosed embodiments in order to provide a thorough understanding of the various disclosed embodiments. However, those skilled in the art will recognize that embodiments may be practiced without one or more of these specific details. In other instances, well-known apparatuses, structures, and techniques associated with this application may not have been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0031] Unless the context requires otherwise, throughout the specification and claims, the word “comprising” and its variations, such as “including” and “having”, shall be understood to have an open, inclusive meaning, that is, to be interpreted as “including, but not limited to”.

[0032] like Figure 1 As shown, traditional additive manufacturing of aluminum alloys mostly requires direct aging treatment or solution treatment followed by peak aging heat treatment. While the yield strength is improved, the fracture toughness of the material is often significantly reduced, resulting in a mismatch between strength and toughness. This invention first utilizes additive manufacturing processes (including but not limited to laser powder bed melting, laser melting deposition, and electron beam selective melting) to form Al-Cu-Sc alloy components. The formed components are placed in a high-temperature salt bath furnace, with the heating temperature set at 450-525 ℃ and the holding time at 0.1-5 min, followed by water cooling to room temperature. Subsequently, the components are placed in a low-temperature oil bath furnace for one or two aging treatments, with the low-temperature aging treatment set at a heating temperature of 125-200 ℃ and a holding time at 0.5-12 h, followed by air cooling to room temperature. For specific method steps, please refer to the following embodiments.

[0033] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0034] Example 1: This example provides an additive manufacturing method for an Al-Cu-Sc alloy and its high-strength and toughness preparation method. The chemical composition is 5 wt% Cu, 0.92 wt% Mg, 0.7 wt% Sc, 0.38 wt% Zr, 0.06 wt% Fe, 0.02 wt% Si, with the balance being Al. The preparation method specifically includes the following steps:

[0035] S1: The Al-Cu-Sc alloy sample was formed using laser powder bed melting process. The laser power was set to 370W, the scanning speed to 1150mm / s, the powder layer thickness to 0.04mm, and the scanning interval to 0.1mm, ensuring that the density of the formed sample reached more than 99.5%.

[0036] S2: Place the sample in a high-temperature salt bath furnace, heat it to 515℃ and hold it for 1 minute, then remove the sample and cool it to room temperature with water.

[0037] S3: Place the sample in a low-temperature oil bath furnace, heat it to 125°C and hold it for 12 hours. Then take out the sample and air cool it to room temperature to obtain the heat-treated sample.

[0038] The heat-treated sample was subjected to room temperature tensile testing, and its yield strength was measured to be 446.6 MPa, tensile strength to be 518.1 MPa, and elongation after fracture to be 13.8%.

[0039] The fracture toughness of the heat-treated samples was tested, and its K value was measured. JIC The value is 26.4 MPa·m 1 / 2 .

[0040] This invention utilizes SEM characterization to observe and analyze the microstructure morphology of laser additively manufactured Al-Cu-Sc alloy samples in the printed state (i.e., without heat treatment), direct-aged state, solution-treated and peak-aged state, and the novel heat-treated state sample in Example 1. Figure 2 As shown in the figure, compared with the printed state and the direct aging state, the continuous grain boundary precipitates in the novel heat-treated sample of this embodiment are significantly reduced, while avoiding the formation of coarse rod-shaped precipitates in the solid solution plus peak aging sample, thus transforming them into spherical precipitates that are more conducive to improving the fracture toughness of the alloy. In addition, the novel heat-treated sample contains both nano-Al2Cu phase and nano-Al3(Sc,Zr) phase, providing microstructure protection for the synergistic improvement of the alloy's strength and toughness.

[0041] Example 2: This example provides an additive manufacturing method for an Al-Cu-Sc alloy and its high-strength and toughness preparation method. The chemical composition is 5 wt% Cu, 0.92 wt% Mg, 0.7 wt% Sc, 0.38 wt% Zr, 0.06 wt% Fe, 0.02 wt% Si, with the balance being Al. The preparation method specifically includes the following steps:

[0042] S1: The Al-Cu-Sc alloy sample was formed using laser powder bed melting process. The laser power was set to 370W, the scanning speed to 1150mm / s, the powder layer thickness to 0.04mm, and the scanning interval to 0.1mm, ensuring that the density of the formed sample reached more than 99.5%.

[0043] S2: Place the sample in a high-temperature salt bath furnace, heat it to 515℃ and hold it for 1 minute, then remove the sample and cool it to room temperature with water.

[0044] S3: Place the sample in a low-temperature oil bath furnace, heat it to 150°C and keep it at that temperature for 1 hour, then remove the sample and air cool it to room temperature;

[0045] S4: The sample was then placed back into a low-temperature oil bath furnace and heated to 125°C for 12 hours. The sample was then removed and air-cooled to room temperature to obtain the heat-treated sample.

[0046] The heat-treated sample was subjected to room temperature tensile testing, and its yield strength was measured to be 479.6 MPa, tensile strength to be 542.1 MPa, and elongation after fracture to be 14.3%.

[0047] The fracture toughness of the heat-treated samples was tested, and its K value was measured. JIC The value is 24.1 MPa·m 1 / 2 .

[0048] Stress-strain curves of heat-treated samples from Examples 1 and 2 of this invention compared with those of Al-Cu-Sc alloy printed samples, directly aged samples, and solution-treated samples with peak aging. Figure 3 and Figure 5 As shown, the ultimate tensile strength-fracture toughness of the above samples is compared with that of commonly used Al-Si alloys in laser additive manufacturing. Figure 4 and Figure 6 As shown, AlSi10Mg undergoes T6 heat treatment. T5 and T6 are common heat treatment codes for aluminum alloys. T5 heat treatment refers to direct artificial aging after forming, while T6 refers to solution quenching followed by artificial aging after forming. Figures 3 to 6As can be seen, the ultimate tensile strength of the laser additive manufacturing printed Al-Cu-Sc alloy is higher than that of the directly aged and solution-treated peak-aged alloys. The printed and solution-treated peak-aged alloys exhibit excellent fracture toughness, but both have low yield strengths. The directly aged alloy has excellent yield strength, but its fracture toughness is only 15.7 MPa·m. 1 / 2 The novel heat-treated states obtained in the various embodiments of this invention exhibit excellent comprehensive mechanical properties. Their yield strength is 20-50 MPa higher than that of the directly aged state, but the fracture toughness of each embodiment is 23-68% higher than that of the directly aged state, reaching approximately 24.1-26.4 MPa·m. 1 / 2 This demonstrates that the laser additive manufacturing Al-Cu-Sc alloy exhibits excellent comprehensive strength and toughness after undergoing the novel heat treatment provided by this invention.

[0049] Comparative Example 1

[0050] This comparative example provides an additive manufacturing method for an Al-Cu-Sc alloy, the chemical composition of which is 5 wt% Cu, 0.92 wt% Mg, 0.7 wt% Sc, 0.38 wt% Zr, 0.06 wt% Fe, 0.02 wt% Si, with the balance being Al. The preparation method specifically includes the following steps:

[0051] S1: The Al-Cu-Sc alloy sample was formed using laser powder bed melting process. The laser power was set to 370W, the scanning speed to 1150mm / s, the powder layer thickness to 0.04mm, and the scanning interval to 0.1mm, ensuring that the density of the formed sample reached more than 99.5%.

[0052] S2: Place the sample in a high-temperature salt bath furnace, heat it to 300℃ and keep it at that temperature for 5 hours, then take out the sample and cool it to room temperature with water.

[0053] The heat-treated sample was subjected to room temperature tensile testing, and its yield strength was measured to be 422.5 MPa, tensile strength to be 448.3 MPa, and elongation after fracture to be 12.4%.

[0054] The fracture toughness of the heat-treated sample was tested, and its KJIC value was measured to be 15.7 MPa·m. 1 / 2 .

[0055] Comparative Example 2

[0056] This comparative example provides an additive manufacturing method for an Al-Cu-Sc alloy, the chemical composition of which is 5 wt% Cu, 0.92 wt% Mg, 0.7 wt% Sc, 0.38 wt% Zr, 0.06 wt% Fe, 0.02 wt% Si, with the balance being Al. The preparation method specifically includes the following steps:

[0057] S1: The Al-Cu-Sc alloy sample was formed using laser powder bed melting process. The laser power was set to 370W, the scanning speed to 1150mm / s, the powder layer thickness to 0.04mm, and the scanning interval to 0.1mm, ensuring that the density of the formed sample reached more than 99.5%.

[0058] S2: Place the sample in a high-temperature salt bath furnace, heat it to 525℃ and keep it at that temperature for 2 hours, then take out the sample and cool it to room temperature with water.

[0059] S3: Place the sample in a low-temperature oil bath furnace, heat it to 185℃ and hold it for 12 hours, then take out the sample and air cool it to room temperature to obtain the heat-treated sample.

[0060] The heat-treated sample was subjected to room temperature tensile testing, and its yield strength was measured to be 292.9 MPa, tensile strength to be 378.1 MPa, and elongation after fracture to be 10.5%.

[0061] The fracture toughness of the heat-treated samples was tested, and its K value was measured. JIC The value is 24 MPa·m 1 / 2 .

[0062] The microstructure analysis of the comparative samples revealed that the grain boundary precipitates in the laser additive Al-Cu-Sc alloy were severely coarsened and continuously distributed after direct aging treatment, while coarse rod-shaped precipitates appeared after solution treatment followed by peak aging. These microstructure characteristics can serve as stress concentration points during tensile and fracture tests, leading to a significant loss in the alloy's fracture toughness. Furthermore, due to the difference in precipitation temperature, neither direct aging nor solution treatment followed by peak aging could achieve the synergistic precipitation distribution of nano-Al2Cu and nano-Al3(Sc,Zr) phases, thus weakening the alloy's strengthening effect and resulting in a mismatch between the alloy's strength and toughness.

[0063] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and principles of the described embodiments, and these modifications and variations should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength and high-toughness Al-Cu-Sc alloys through additive manufacturing, characterized in that, The mass percentage of each element in the Al-Cu-Sc alloy is as follows: Cu 2.5~5%, Mg ≤10%, Sc 0.1~1.5%, Zr ≤3%, Fe≤0.1%, Si≤0.1%, and the total of other alloying elements is 0~1.5%, with the balance being Al; The preparation method includes: Al-Cu-Sc alloy samples were formed using additive manufacturing processes; The Al-Cu-Sc alloy sample was subjected to high-temperature short-time holding and water quenching treatment; the high-temperature short-time holding temperature was 450℃~525℃, and the holding time was 0.1~5min. The water-quenched Al-Cu-Sc alloy sample is subjected to one or two aging treatments; the aging treatment temperature is 125~200℃ and the holding time is 0.5~12h.

2. The method for preparing high-strength and high-toughness Al-Cu-Sc alloy by additive manufacturing according to claim 1, characterized in that, The other alloying elements include any one or more of Zn, Mn, Ni, Co, Fe, Ag, Cr, Li, V, Ti, Ca, and Er.

3. The method for preparing high-strength and high-toughness Al-Cu-Sc alloy by additive manufacturing according to claim 1, characterized in that, The additive manufacturing process includes laser powder bed melting, laser melting deposition, or electron beam selective melting.

4. The method for preparing high-strength and high-toughness Al-Cu-Sc alloy by additive manufacturing according to claim 3, characterized in that, The additive manufacturing process uses laser powder bed melting, and the process parameters include: laser power 370W, scanning speed 1150mm / s, powder layer thickness 0.04mm, and scanning spacing 0.1mm.

5. The method for preparing high-strength and high-toughness Al-Cu-Sc alloy by additive manufacturing according to claim 1, characterized in that, The Al-Cu-Sc alloy sample formed by additive manufacturing process has a density of over 99.5%.

6. The method for preparing high-strength and high-toughness Al-Cu-Sc alloy by additive manufacturing according to claim 1, characterized in that, The process of high-temperature short-time heat preservation and water quenching includes: The Al-Cu-Sc alloy sample was placed in a high-temperature salt bath furnace and heated to the set temperature. The temperature was held for a preset time, and then the sample was taken out and cooled to room temperature with water.

7. The method for preparing high-strength and high-toughness Al-Cu-Sc alloy by additive manufacturing according to claim 1, characterized in that, The timeliness processing procedure includes: The water-quenched Al-Cu-Sc alloy sample was placed in a low-temperature oil bath furnace, heated to the set temperature, held for a preset time, and then removed and air-cooled to room temperature.

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