Multi-stage regulation and control aluminum-lithium-magnesium-zinc system additive manufacturing alloy

Abstract

The invention relates to the technical field of metal material preparation, in particular to a multi-stage regulation and control aluminum-lithium-magnesium-zinc system additive manufacturing alloy which is prepared through the following steps that vacuum induction smelting is conducted, specifically, weighed raw materials are smelted under the oxygen partial pressure smaller than or equal to 10 <-3 > Pa, and 0.1-0.3% O2 / Ar mixed gas is introduced for 3-8 min before pouring; homogenizing treatment is conducted, specifically, the temperature is increased to 300 + / -5 DEG C and kept for 1-3 h, then the temperature is increased to 470 + / -5 DEG C and kept for 10-14 h, and argon protection is conducted in the whole process; thermomechanical processing is conducted, multi-directional forging is conducted firstly, the total deformation is 55%-65%, and the temperature is gradually reduced to 250 + / -5 DEG C from 350 + / -5 DEG C; then hot rolling is conducted to obtain a plate with the thickness being 6 mm, the pass deformation is 12-18%, then cold rolling is conducted to obtain the plate with the thickness being 2 mm, and the total deformation is 60-70%; wherein the raw materials comprise the following components in percentage by weight: 9.0 to 10 percent of Li, 3.5 to 5 percent of Al, 1.0 to 2.5 percent of Zn, 0.2 to 0.6 percent of Sc, 0.4 to 0.8 percent of Zr, 0.3 to 0.7 percent of Mn and the balance of Mg and inevitable impurities; wherein the molar ratio of Sc to Zr is (1: 1.4)-(1: 1.6). According to the technical scheme, the molar ratio of Sc to Zr is strictly controlled to range from 1: 1.4 to 1: 1.6, and balance of high strength and good plasticity is achieved.

Description

Technical Field

[0001] This invention relates to the field of metal material preparation technology, specifically to a multi-level controlled aluminum-lithium-magnesium-zinc additive manufacturing alloy. Background Technology

[0002] Aluminum-lithium-magnesium-zinc alloys, due to their low density, high specific strength, and excellent overall performance, show broad application prospects in aerospace, transportation, and high-end equipment manufacturing. Traditional magnesium-lithium based alloys typically improve strength by adding alloying elements (such as Al and Zn) and employing thermomechanical treatment; however, the balance between strength and plasticity, as well as corrosion resistance, still falls short of increasingly demanding application requirements. Especially for advanced forming processes such as additive manufacturing, materials must simultaneously possess good formability, high thermal stability, and resistance to environmental corrosion. Summary of the Invention

[0003] To address the problems in related technologies, this application provides a multi-level controlled aluminum-lithium-magnesium-zinc additive manufacturing alloy.

[0004] This disclosure provides a multi-level controlled aluminum-lithium-magnesium-zinc additive manufacturing alloy, which is prepared through the following steps: Vacuum induction melting involves melting the weighed raw materials under an oxygen partial pressure of ≤10-3Pa, and then introducing a 0.1-0.3% O2 / Ar mixture for 3–8 min before casting. Homogenization treatment: first heat to 300±5℃ and hold for 1-3 hours, then heat to 470±5℃ and hold for 10-14 hours, with argon gas protection throughout the process; Thermomechanical processing begins with multi-directional forging, with a total deformation of 55-65%, and the temperature is gradually reduced from 350±5℃ to 250±5℃; then it is hot-rolled to 6 mm plate with a deformation of 12-18% per pass, and then cold-rolled to 2 mm with a total deformation of 60-70%; The raw materials, by weight percentage, comprise: Li 9.0-10%, Al 3.5-5%, Zn 1.0-2.5%, Sc 0.2-0.6%, Zr 0.4-0.8%, Mn 0.3-0.7%, with the balance being Mg and unavoidable impurities; wherein the molar ratio of Sc to Zr is 1:1.4-1:1.6.

[0005] According to embodiments of this disclosure, the raw materials, by weight percentage, comprise: Li 9.2-9.8%, Al 4.0-4.5%, Zn 1.5-2.0%, Sc 0.3-0.5%, Zr 0.5-0.7%, Mn 0.4-0.6%, with the balance being Mg and unavoidable impurities.

[0006] According to embodiments of this disclosure, the raw materials, by weight percentage, further comprise: Ti 0.2-0.4% and Y 0.1-0.3%, and the alloy contains TiO2 and Y2O3 composite nanoparticles.

[0007] According to embodiments of this disclosure, the composite nanoparticles have an average particle size ≤100nm, a particle spacing ≤300nm, and a volume fraction of 1.0-1.5%.

[0008] According to embodiments of this disclosure, the monthly degradation rate of the multi-level controlled aluminum-lithium-magnesium-zinc additive manufacturing alloy in Hank's solution at 37±2℃ is 0.15-0.20 mm, and the corrosion current density is ≤1.0μA / cm2.

[0009] According to an embodiment of this disclosure, the vacuum induction melting step uses water-cooled copper mold casting, and the cooling rate of the casting is 102-103 K / s.

[0010] According to embodiments of this disclosure, the heating rate in the homogenization process is ≤5℃ / min.

[0011] According to embodiments of this disclosure, in the thermomechanical processing step, the deformation directions of each pass of multi-directional forging are perpendicular to each other, and each pass is followed by a furnace heat treatment for 5-10 minutes.

[0012] According to embodiments of this disclosure, the method further includes an aging process step, located between the homogenization process step and the thermomechanical processing step, wherein the parameters of the aging process include a temperature of 120±2℃, a time of 24±2h, and an air cooling method.

[0013] According to embodiments of this disclosure, the method further includes a dual aging process, located between the homogenization process and the thermomechanical processing process. The dual aging process includes: first holding at 180±2℃ for 8 hours and then air cooling, and then holding at 120±2℃ for 16 hours and then air cooling.

[0014] The multi-level controlled aluminum-lithium-magnesium-zinc additive manufacturing alloy disclosed herein achieves a balance between high strength and good plasticity by strictly controlling the molar ratio of Sc to Zr between 1:1.4 and 1:1.6. The corrosion current density of the alloy is consistently below 1.2 μA / cm². 2 The slow monthly degradation rate indicates excellent corrosion resistance. The synergistic effect of Sc and Zr not only enhances the stability of the precipitated phase but also improves the surface passivation behavior. Throughout the preparation process, multi-level control methods such as argon protection, homogenization treatment, and stepped cooling rolling effectively avoided compositional segregation and microstructure inhomogeneity, ensuring the stability and repeatability of the alloy's properties.

[0015] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Detailed Implementation

[0016] The present invention is further illustrated below by way of examples, but it should be understood that these specific examples are not intended to limit the scope of the invention in any way. It should be noted that, unless otherwise specified, the raw materials used in the following examples are all commercially available.

[0017] Example 1: A multi-level controlled aluminum-lithium-magnesium-zinc alloy was prepared, comprising, by weight percentage: Li 9.0%, Al 3.5%, Zn 1.0%, Sc 0.2%, Zr 0.6%, Mn 0.3%, with the balance being Mg and impurities (total <0.1%). First, the weighed raw materials were placed in a vacuum induction melting furnace, and the melting was carried out at an oxygen partial pressure below 10... -3 Melting was carried out under a vacuum environment of Pa. After the raw materials were completely melted and refined, an argon-oxygen mixture containing 0.1% oxygen was introduced into the furnace for 5 minutes before casting. The alloy melt was then poured into a water-cooled copper mold, and the cooling rate was measured to be approximately 500 K / s. The resulting ingot was homogenized by heating it to 300°C at a rate of 5°C / min under argon protection and holding it for 1 hour, followed by heating it to 470°C and holding it for 10 hours. After homogenization, thermomechanical processing was performed directly. Multi-directional forging was first carried out, with an initial forging temperature of 350°C. After each forging pass, the billet was returned to the furnace and held for 5 minutes, with the forging direction of the next pass perpendicular to the previous pass. This process was repeated, and the temperature was gradually reduced to 250°C as forging progressed, resulting in a total deformation of 55%. The forged billet is then hot-rolled into a 6 mm thick plate, with the deformation amount controlled at 12% per pass. After that, it is cold-rolled to finally obtain a 2 mm thick plate with a total deformation amount of 60%.

[0018] Example 2: The alloy composition of Example 2 is exactly the same as that of Example 1. The first part of its preparation process, including vacuum melting, introduction of 0.1% O2 / Ar gas, and water-cooled copper mold casting, is the same as in Example 1. However, after homogenization treatment, aging treatment is performed, and the alloy is placed in an aging furnace at 120°C and held for 24 hours, then air-cooled to room temperature. Then, the same thermomechanical processing as in Example 1 is performed.

[0019] Example 3: A multi-level controlled aluminum-lithium-magnesium-zinc alloy was prepared, comprising, by weight percentage: Li 10.0%, Al 5.0%, Zn 2.5%, Sc 0.6%, Zr 1.1%, Mn 0.7%, with the balance being Mg and impurities (total <0.1%). First, the weighed raw materials were placed in a vacuum induction melting furnace, and the melting was carried out at an oxygen partial pressure below 10... -3Melting was carried out under a vacuum environment of Pa. After the raw materials were completely melted and refined, an argon-oxygen mixture containing 0.3% oxygen was introduced into the furnace for 3 minutes before casting. The alloy melt was then poured into a water-cooled copper mold, and the cooling rate was measured to be approximately 1000 K / s. The resulting ingot was homogenized by heating it to 305°C at a rate of 3°C / min under argon protection and holding it for 3 hours, followed by heating it to 475°C and holding it for 14 hours. After homogenization, aging treatment was performed by placing the alloy in an aging furnace at 120°C and holding it for 24 hours, then air-cooling it to room temperature. Subsequently, thermomechanical processing was performed, starting with multi-directional forging. The forging temperature was 355°C. After each forging pass, the billet was returned to the furnace and held for 10 minutes, with the forging direction of the next pass perpendicular to the previous pass. This process was repeated, and the temperature was gradually reduced to 255°C as forging progressed, with the total deformation reaching 65%. The forged billet is then hot-rolled into a 6 mm thick plate, with the deformation amount controlled at 18% per pass. After that, it is cold-rolled to finally obtain a 2 mm thick plate with a total deformation amount of 70%.

[0020] Example 4: A multi-level controlled aluminum-lithium-magnesium-zinc alloy was prepared, comprising, by weight percentage: Li 9.2%, Al 4.0%, Zn 1.5%, Sc 0.3%, Zr 0.76%, Mn 0.4%, with the balance being Mg and impurities (total <0.1%). First, the weighed raw materials were placed in a vacuum induction melting furnace, and the melting was carried out at an oxygen partial pressure below 10... -3 Melting was carried out under a vacuum environment of Pa. After the raw materials were completely melted and refined, an argon-oxygen mixture containing 0.2% oxygen was introduced into the furnace for 8 minutes before casting. The alloy melt was then poured into a water-cooled copper mold, and the cooling rate was measured to be approximately 800 K / s. The resulting ingot was homogenized by heating it to 300°C at a rate of 4°C / min under argon protection and holding it for 2 hours, followed by heating it to 470°C and holding it for 12 hours. The aging treatment and thermomechanical processing parameters were consistent with those in Example 3.

[0021] Example 5: A multi-level controlled aluminum-lithium-magnesium-zinc alloy was prepared, comprising, by weight percentage: Li 9.8%, Al 4.5%, Zn 2.0%, Sc 0.5%, Zr 0.86%, Mn 0.6%, with the balance being Mg and impurities (total <0.1%). The melting, casting, and subsequent homogenization, aging, and thermomechanical processing parameters were consistent with those in Example 3.

[0022] Example 6: A multi-level controlled aluminum-lithium-magnesium-zinc alloy was prepared, comprising, by weight percentage: Li 9.5%, Al 4.2%, Zn 1.8%, Sc 0.5%, Zr 0.86%, Mn 0.6%, Ti 0.2%, Y 0.1%, with the balance being Mg and impurities (total <0.1%). First, the weighed raw materials were placed in a vacuum induction melting furnace, and the melting was carried out at an oxygen partial pressure below 10... -3 Melting was carried out under a vacuum environment of Pa. After the raw materials were completely melted and refined, an argon-oxygen mixture containing 0.2% oxygen was introduced into the furnace for 6 minutes before casting. The alloy melt was then poured into a water-cooled copper mold, and the cooling rate was measured to be approximately 1000 K / s. The resulting ingot was homogenized by heating it to 300°C at a rate of 5°C / min under argon protection and holding it for 2 hours, followed by heating it to 470°C and holding it for 12 hours. After homogenization, a double aging treatment was performed: the alloy was first placed in an aging furnace at 180°C and held for 8 hours, then air-cooled to room temperature, and then placed in an aging furnace at 120°C and held for 16 hours before being air-cooled again. Thermomechanical processing followed, starting with multi-directional forging at an initial temperature of 350℃. After each forging pass, the billet was returned to the furnace for 8 minutes of holding, with the forging direction of the next pass perpendicular to the previous one. This process was repeated, with the temperature gradually reduced to 250℃ as forging progressed, resulting in a total deformation of 60%. The forged billet was then hot-rolled into a 6 mm thick sheet, with the deformation controlled at 15% per pass. Cold rolling continued to yield a 2 mm thick sheet, with a total deformation of 70%. Transmission electron microscopy revealed uniform distribution of TiO2 and Y2O3 composite nanoparticles in the alloy, with an average particle size of 85 nm, an interparticle spacing of 220 nm, and a volume fraction of 1.1%.

[0023] Example 7: A multi-level controlled aluminum-lithium-magnesium-zinc alloy was prepared, comprising, by weight percentage: Li 9.5%, Al 4.2%, Zn 1.8%, Sc 0.5%, Zr 0.86%, Mn 0.6%, Ti 0.4%, Y 0.3%, with the balance being Mg and impurities (total <0.1%). First, the weighed raw materials were placed in a vacuum induction melting furnace, and the melting was carried out at an oxygen partial pressure below 10... -3Melting was carried out under a vacuum environment of Pa. After the raw materials were completely melted and refined, an argon-oxygen mixture containing 0.25% oxygen was introduced into the furnace for 4 minutes before casting. The alloy melt was then poured into a water-cooled copper mold, and the cooling rate was measured to be approximately 1000 K / s. The resulting ingot was homogenized by heating it to 300°C at a rate of 4°C / min under argon protection and holding it for 1.5 hours, followed by heating it to 470°C and holding it for 13 hours. After homogenization, a double aging treatment was performed: the alloy was first placed in an aging furnace at 180°C and held for 8 hours, then air-cooled to room temperature, and then placed in an aging furnace at 120°C and held for 16 hours before being air-cooled again. Thermomechanical processing followed, starting with multi-directional forging at an initial temperature of 350℃. After each forging pass, the billet was returned to the furnace for 8 minutes of holding, with the forging direction of the next pass perpendicular to the previous one. This process was repeated, with the temperature gradually reduced to 250℃ as forging progressed, resulting in a total deformation of 62%. The forged billet was then hot-rolled into a 6 mm thick sheet, with the deformation controlled at 16% per pass. Cold rolling continued to yield a 2 mm thick sheet, with a total deformation of 70%. Transmission electron microscopy revealed uniform distribution of TiO2 and Y2O3 composite nanoparticles in the alloy, with an average particle size of 95 nm, an interparticle spacing of 180 nm, and a volume fraction of 1.4%.

[0024] Comparative Example 1: The alloy composition of Comparative Example 1 is: Li 9.0%, Al 3.5%, Zn 1.0%, Zr 0.4%, Mn 0.3%, with the balance being Mg and impurities (total <0.1%). This formulation does not contain Sc, therefore a specific molar ratio of Sc to Zr cannot be achieved. Its preparation process is exactly the same as in Example 3, including vacuum melting, introduction of 0.1% O2 / Ar gas, water-cooled copper mold casting, and the same homogenization, aging, and thermomechanical processing.

[0025] Comparative Example 2: The alloy composition of Comparative Example 2 is: Li 9.0%, Al 3.5%, Zn 1.0%, Sc 0.2%, Zr 0.29%, Mn 0.3%, with the balance being Mg and impurities (total <0.1%). Its preparation process is exactly the same as that of Example 3, including vacuum melting, introduction of 0.1% O2 / Ar gas, water-cooled copper mold casting, and the same homogenization, aging, and thermomechanical processing.

[0026] Comparative Example 3: The alloy composition of Comparative Example 3 is: Li 9.5%, Al 4.2%, Zn 1.8%, Sc 0.5%, Zr 0.86%, Mn 0.6%, Ti 0.2%, with the balance being Mg and impurities (total <0.1%). Its preparation process is exactly the same as that of Example 6, including vacuum melting, introduction of 0.2% O2 / Ar gas, water-cooled copper mold casting, the same homogenization, double aging, and thermomechanical processing.

[0027] Comparative Example 4: The alloy composition of Comparative Example 4 is exactly the same as that of Example 6, containing 0.2% Ti and 0.1% Y. The first part of its preparation process, including vacuum melting, introduction of argon-oxygen mixed gas, water-cooled copper mold casting, and homogenization treatment, is the same as that of Example 6. However, after homogenization treatment, only a single aging treatment is performed, that is, the alloy is placed in an aging furnace at 180°C and held for 8 hours, then air-cooled to room temperature, and then subjected to the same thermomechanical processing as in Example 6.

[0028] Performance Testing Methods: To evaluate the alloy's performance, performance tests were conducted on the 2mm thick plates obtained in the examples and comparative examples. The corrosion resistance of the alloy in a simulated body fluid environment was tested using an electrochemical workstation. A standard three-electrode system was used, with the alloy sample under test as the working electrode and an exposure area of ​​1cm². 2 The reference electrode was a saturated calomel electrode, the auxiliary electrode was a platinum electrode, and the electrolyte was a Hank's solution at a constant temperature of 37°C. Corrosion current density was measured using potentiodynamic polarization curves, with each sample tested three times and the average value taken. The degradation rate was assessed using the immersion weight loss method. Samples were immersed in Hank's solution at 37°C, removed, cleaned, dried, and weighed every 7 days for 28 days. The monthly degradation rate was calculated based on the weight loss, and the result was the average of three parallel samples. Mechanical properties were obtained by tensile testing at room temperature using a universal testing machine, with a tensile rate of 1 mm / min.

[0029] The test results of Examples 1-5 and Comparative Examples 1-2 are shown in Table 1 below:

[0030] Results Analysis: By strictly controlling the molar ratio of Sc to Zr between 1:1.4 and 1:1.6, and in conjunction with other components and multi-level process control, the embodiments of this invention successfully obtained alloys with excellent comprehensive properties. Their corrosion current densities are all below 1.2 μA / cm². 2The Al3(Sc, Zr) strengthening phase in Comparative Example 1, due to the complete absence of Sc, could not form, resulting in significant deterioration of its mechanical properties and corrosion resistance, highlighting the crucial role of Sc. Although Comparative Example 2 added Sc, its molar ratio to Zr was only 1:1, far below the required lower limit. This meant that Sc could not be fully utilized to form a coherent nano-strengthening phase. While its performance was better than Comparative Example 1, it was significantly inferior to all other examples, indicating that controlling the molar ratio of Sc to Zr within a specific range is crucial to maximizing its synergistic strengthening effect.

[0031] The test results of Examples 6-7 and Comparative Examples 3-4 are shown in Table 2 below:

[0032] Results Analysis: The mechanical properties of Examples 6 and 7, including tensile strength and yield strength, are significantly higher than those of Comparative Examples 3 and 4, while the elongation remains at a good level. Simultaneously, their corrosion current density is also significantly lower, exhibiting superior corrosion resistance. Comparative Example 3, lacking the addition of Y, lacks hard oxide nanoparticles as a reinforcing phase, resulting in the lowest strength. This demonstrates the crucial role of introducing composite nanoparticles in improving strength. Although Comparative Example 4 generated nanoparticles, the lack of a dual aging treatment step prevented further strengthening of the matrix through single aging precipitation. Its strength is higher than Comparative Example 3 but significantly lower than Example 6, indicating that dual aging treatment is essential for fully utilizing the nucleation sites provided by nanoparticles and achieving multi-level precipitation strengthening.

[0033] The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features disclosed in this disclosure that have similar functions.

Claims

1. A multi-level controlled aluminum-lithium-magnesium-zinc additive manufacturing alloy, characterized in that, It is prepared through the following steps: Vacuum induction melting involves weighing raw materials at a temperature of ≤10°C. -3 Smelting under an oxygen partial pressure of Pa, and purging with a 0.1-0.3% O2 / Ar mixture for 3–8 min before casting; Homogenization treatment: first heat to 300±5℃ and hold for 1-3 hours, then heat to 470±5℃ and hold for 10-14 hours, with argon gas protection throughout the process; Thermomechanical processing begins with multi-directional forging, with a total deformation of 55-65%, and the temperature is gradually reduced from 350±5℃ to 250±5℃; then it is hot-rolled to 6 mm plate with a deformation of 12-18% per pass, and then cold-rolled to 2 mm with a total deformation of 60-70%; The raw materials, by weight percentage, comprise: Li 9.0-10%, Al 3.5-5%, Zn 1.0-2.5%, Sc 0.2-0.6%, Zr 0.4-0.8%, Mn 0.3-0.7%, with the balance being Mg and unavoidable impurities; wherein the molar ratio of Sc to Zr is 1:1.4-1:1.

6.

2. The alloy according to claim 1, characterized in that, The raw materials, by weight percentage, comprise: Li 9.2-9.8%, Al 4.0-4.5%, Zn 1.5-2.0%, Sc 0.3-0.5%, Zr 0.5-0.7%, Mn 0.4-0.6%, with the balance being Mg and unavoidable impurities.

3. The alloy according to claim 2, characterized in that, The raw materials, by weight percentage, also contain: Ti 0.2-0.4% and Y 0.1-0.3%, and the alloy contains TiO2 and Y2O3 composite nanoparticles.

4. The alloy according to claim 3, characterized in that, The composite nanoparticles have an average particle size ≤100nm, a particle spacing ≤300nm, and a volume fraction of 1.0-1.5%.

5. The alloy according to claim 1, characterized in that, The multi-level regulated aluminum-lithium-magnesium-zinc additive manufacturing alloy exhibits a monthly degradation rate of 0.15-0.20 mm in Hank's solution at 37±2℃, with a corrosion current density ≤1.0 μA / cm². 2 .

6. The alloy according to claim 1, characterized in that, The vacuum induction melting step uses a water-cooled copper mold for casting, and the cooling rate of the casting is 10. 2 -10 3 K / s.

7. The alloy according to claim 1, characterized in that, The heating rate in the homogenization process is ≤5℃ / min.

8. The alloy according to claim 1, characterized in that, In the thermomechanical processing steps, the deformation directions of each pass of multi-directional forging are perpendicular to each other, and each pass is followed by a furnace heat treatment for 5-10 minutes.

9. The alloy according to claim 1, characterized in that, Also includes: The aging treatment step is located between the homogenization treatment step and the thermomechanical processing step. The parameters of the aging treatment include a temperature of 120±2℃, a time of 24±2h, and air cooling.

10. The alloy according to claim 3, characterized in that, Also includes: dual The aging process is located between the homogenization process and the thermomechanical processing process. The dual aging process includes: first, holding at 180±2℃ for 8 hours and then air cooling, and then holding at 120±2℃ for 16 hours and then air cooling.

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