Aluminum materials for additive technology and products made from these materials

Abstract

The present invention relates to metallurgy, and in particular to aluminum-based alloys used in the production of powders for additive manufacturing, including laser additive manufacturing. [Solution] The aluminum powder alloy is composed of the following (unit: wt%): iron 0.3-1.5, cerium 0.35-2.6, titanium 0.15-0.4, at least one element from group A consisting of manganese, lanthanum, and yttrium 0.2-2.0 (total or individual), at least one element from group B consisting of zirconium, vanadium, chromium, hafnium, and scandium 0.6-1.5 (total or individual), and optionally: 3-60 ppm hydrogen and 1.5-4.5 ppm magnesium, and unavoidable impurities including aluminum and up to 0.2 ppm silicon, up to 0.05 ppm copper, and up to 0.05 ppm zinc.

Description

[Technical Field]

[0001] The present invention relates to metallurgy, and in particular to aluminum-based alloys used in the production of powders for component manufacturing using both conventional powder metallurgy techniques and additive manufacturing techniques, including laser additive manufacturing. [Background technology]

[0002] Aluminum materials are divided into alloys that can be hardened by solution treatment, quenching, and subsequent artificial or natural aging, and non-hardenable alloys. Age-hardenable alloys exhibit improved mechanical properties due to the precipitation of numerous nanoscale hardening particles during heat treatment. However, quenching precision parts manufactured by powder metallurgy or additive manufacturing techniques can result in distortion and defects. Therefore, alloys that do not require quenching are in demand. 3D printing and powder metallurgy can generally produce rapidly solidified alloys containing various elements at concentrations significantly above their equilibrium concentrations, resulting in high strength but low ductility. Some applications require materials with a high degree of plasticity. Laser additive manufacturing and similar 3D metal printing technologies essentially deposit metal layers on a substrate of the same metal. The challenge is to achieve both high ductility and strength in aluminum alloys.

[0003] A rapidly solidified aluminum alloy containing chromium is known (US Patent US5049211, Publication date: September 17, 1991). The alloy contains 1-7 wt% Cr and up to 6 wt% X, where X is selected from refractory metals (Nb, Mo, Hf, Ta, W). This alloy has high strength and excellent thermal stability. However, due to the high content of transition metals, it has low ductility and extremely low impact strength.

[0004] Patent EP2112241 (published September 21, 2011) describes an alloy strengthened by the L12 phase. The alloy composition is as follows: nickel: 4-25%, cerium: 2-25%, and at least one of the following elements: scandium (0.1-4%), erbium (0.1-20%), thulium (0.1-15%), ytterbium (0.1-25%), and lutetium (0.1-25%), and at least one of the following elements: gadolinium (2-30%), yttrium (2-30%), zirconium (0.5-5%), titanium (0.5-10%), hafnium (0.5-10%), niobium (0.5-5%), and iron (0.5-15%). The alloy is produced using rapid solidification technology and has high strength. However, due to its over-alloying, it is extremely difficult to manufacture the final product using any technique other than laser additive manufacturing or conventional powder metallurgy. Another drawback is that the alloy contains many rare and expensive elements.

[0005] A known aluminum alloy for additive technology (patent EP3406372, publication date: 1 January 2020) consists of the following components (in wt%): Cerium 2.0~10.0 Titanium 0.5~2.5 Nickel 0~3.0 Nitrogen 0~0.75 Others 0~0.05 The remainder is aluminum.

[0006] These alloys have high heat resistance and, depending on the type, high strength. However, the high number of eutectic forming elements reduces ductility and, as a result, fatigue life. Also, due to the high number of alloying elements, they are likely to have lower corrosion resistance than corrosion-resistant aluminum alloys.

[0007] Patent application US2021129270 (published May 6, 2021) presents an aluminum material for lamination technology having the following composition (wt%): Cerium 0~35 Nickel 1~35 Manganese 0~3 Iron 0-3 Magnesium 0-2 Zirconium 0~2 Silicon 0~1 Chromium 0~5 The remainder is aluminum.

[0008] The cerium and nickel in the alloy are sufficient to form at least one of the following intermetallic compounds: Al23Ni6Ce4, Al7Ni2Ce, Al20Mn2Ce, or Al3Ni.

[0009] This alloy is designed for high temperature use. It does not require quenching heat treatment, but its high alloying element content results in low ductility.

[0010] Another known aluminum alloy for additive manufacturing (U.S. Patent US2022168811, Publication Date: June 2, 2022) contains the following elements (wt%): Titanium 0.1~15.0 Scandium 0.1~3.0 Zirconium 0.1~3.0 The remainder is aluminum and unavoidable impurities.

[0011] In transition metals, the alloy is susceptible to precipitation hardening. Some embodiments of the present invention have poor manufacturability. According to the phase diagram, the alloy is in the region containing 100% intermetallic compounds and is substantially non-ductile. This leads to cracking.

[0012] Patent CN110791686 (published February 14, 2020) presents the prototype aluminum powder of the present invention. This patent proposes an aluminum powder alloy for additive manufacturing with an Al-XY composition, where X is one of the elements e·Co·Ni, and Y is one of the elements Sc·Ti·Zr. The atomic content of element X is 0.1-10%, and the atomic content of element Y is 0.1-5%. The remainder is aluminum. This material does not require quenching. Because the alloying element content varies greatly, some compositions have extremely low elongation, while others have significantly reduced corrosion resistance due to a high content of element X. Summary of the Invention

[0013] The objective and technical effect of the present invention is to create an aluminum alloy that can be used as a powder for the production of parts using additive manufacturing techniques. The alloy must have high strength (over 320 MPa) without quenching or artificial aging. It must also be highly manufacturable for 3D printing and highly corrosion resistant for use in a variety of corrosive environments.

[0014] To achieve this technical effect, a powder aluminum alloy is proposed, which consists of iron, cerium, at least one element from group A consisting of manganese, lanthanum, and yttrium, at least one element from group B consisting of zirconium, vanadium, chromium, hafnium, and scandium, optionally hydrogen and magnesium, and aluminum, and inevitable impurities including silicon, copper, and zinc, with such elements having the following concentrations in wt%: Iron 0.3~1.5 Cerium 0.35~2.6 Titanium 0.15~0.4 At least one element from group A consisting of manganese, lanthanum, and yttrium 0.2 to 2.0 (total or individual)

[0015] At least one element from group B consisting of zirconium, vanadium, chromium, hafnium, and scandium 0.6 to 1.5 (total or individually) any: Hydrogen 3-60 ppm Magnesium 1.5-4.5, and Aluminum and unavoidable impurities, with a compositional balance of silicon, copper and zinc, The silicon, copper and zinc contents are as follows: Silicon max 0.2 Copper max 0.05 Zinc max 0.05

[0016] The structure consists of an aluminum solid solution, a eutectic, and up to 10% nanoscale dispersoids of AlB-type phase, the dispersoids being formed by elements of the B group.

[0017] "Total or singly" means the content (quantity) of one or more elements (total) within a specified range.

[0018] The preferred contents (wt%) are as follows: iron: 0.3 to 1.0, cerium: 0.35 to 1.0, titanium: 0.15 to 0.25, at least one element from group A: 0.5 to 2.0, at least one element from group B: 0.6 to 0.8, and optionally magnesium: 2.0 to 4.0 wt%. [Brief explanation of the drawings]

[0019] [Figure 1] Cuboid samples produced by laser additive manufacturing. Typical cubes produced by 3D printing. A: Composition Y, B: Composition No. 3. [Figure 2] SEM image (SEM stands for scanning electron microscope) of the powder after atomization and screening. [Figure 3] Structures of samples with compositions 1, 2, 3, A, and B. Microstructures of Alloy No. 1 (A), Alloy No. 5 (B), and Alloy No. 6 (C). DETAILED DESCRIPTION OF THE INVENTION

[0020] A certain range of iron additions is necessary to form a eutectic, reducing the tendency for hot brittleness and hot cracking during rapid solidification. Below this range, a solid solution-like structure forms at high solidification rates. Iron increases the susceptibility of aluminum to pitting corrosion, so excessive iron content reduces corrosion resistance. According to the equilibrium phase diagram, the eutectic point for the aluminum-iron system is in the 1.8 wt% concentration region, but the proposed range is sufficient for eutectic formation.

[0021] The addition of cerium also promotes the formation of eutectic phases. Cerium also has a much smaller effect on corrosion resistance than iron. Furthermore, cerium can form separate eutectic phases with aluminum, or partially form ternary phases with aluminum, iron, and other elements, including metastable phases. The cerium content is limited to maintain high ductility, which decreases with the formation of a large eutectic phase. Cerium misch metal can also be used as a substitute for cerium. The rare earth elements and iron contained in misch metal are also alloying elements and generally do not significantly change the properties of 3D printed products.

[0022] The specified amount of titanium creates a fine grain structure in the printed part. The formation of Al3Ti nano-disperse intermetallic compounds refines the part structure and further reduces susceptibility to hot cracking. Excessive titanium content leads to the formation of undesirable large intermetallic compounds. Titanium also significantly increases the melting point of the alloy, requiring overheating and increasing energy costs.

[0023] Elements selected from group A (manganese (Mn), lanthanum (La), and yttrium (Y)) are eutectic-forming additives (they undergo a eutectic transformation in the "aluminum corner" of the phase diagram). These elements improve manufacturability in 3D printing and contribute to further precipitation hardening. This is because their solubility in aluminum varies with temperature. At fast solidification rates, these elements tend to form anomalously supersaturated solid solutions. They precipitate from the solid solution, forming binary nanoscale phases, leading to hardening. Because the solubility of these elements is limited even during non-equilibrium solidification, their maximum total content must be limited to maintain high ductility to avoid cold cracking. To maintain high ductility, it is also desirable to ensure that the content of group A elements does not exceed the eutectic point shown in the equilibrium phase diagram. This is because high solidification rates can shift this point during both powder atomization and printing.

[0024] As shown in the two phase diagrams, the elements selected from group B (Zr (zirconium), V (vanadium), Cr (chromium), Hf (hafnium), and Sc (scandium)) are mostly peritectic (with the exception of scandium). Their solubility in aluminum varies, and rapid quenching from the liquid state tends to result in supersaturated solid solutions with a tendency for the maximum solubility to increase significantly. This is the case with gas atomization and 3D printing. As a result, nano-dispersed precipitates are formed during subsequent annealing. These precipitates exert a significant hardening effect without significantly reducing ductility. Because the formation of intermetallic compounds during solidification adversely affects ductility and fatigue life, it is very important to limit the maximum content of additives so as not to exceed the anomalous solubility limit. Experiments have shown that the maximum content of each element should be limited to 2–3 times the maximum solubility value in the phase diagram. It is desirable for alloys to contain both group A and group B elements, as this allows for a uniform distribution of various dispersed particles both within the grains and near the grain boundaries.

[0025] Oxygen in powders is generated during the atomization process. This has many positive effects. Another effect is reduced flammability due to the formation of a protective oxide film on the surface of each particle as the droplets solidify and oxidize. In horizontal spraying, adding small amounts of oxygen increases the surface tension, thereby improving powder sphericity. However, the oxygen content in powders should be limited to avoid the formation of large oxide inclusions, which can become solidification nuclei and gas condensates when the powder remelts during printing.

[0026] Hydrogen is a functional additive. On the one hand, it has a positive effect on solution hardening, which is related to the extremely small size of the hydrogen atom and its good mobility within the aluminum lattice. On the other hand, above a certain experimentally confirmed concentration, it causes a sharp increase in gas porosity, which reduces the performance of the printed part.

[0027] It is very important to limit certain unavoidable impurities. Even trace amounts can adversely affect the manufacturability and performance of the material. Silicon, in particular, can increase hot cracking by reacting with aluminum and iron, resulting in the formation of a three-phase rather than a two-phase. Silicon also adversely affects the supersaturation of solid solutions of transition metals, such as scandium, with aluminum. Even small amounts of copper increase the tendency to hot cracking; therefore, its content should be limited. Higher copper contents have less effect on casting properties and further promote solid-solution hardening. However, copper has a significant negative effect on overall corrosion resistance. Therefore, this element is not recommended as an additive. Zinc is also undesirable because it evaporates easily. Heating and remelting aluminum powder results in partial zinc loss, resulting in the introduction of contaminants and increased porosity in printed parts. In addition, significant zinc content is required to benefit strength, which further increases the specific gravity.

[0028] This alloy can be alloyed with magnesium within the specified range to achieve additional hardening of 30 to 100 MPa without reducing corrosion resistance or significantly decreasing ductility. This is because the magnesium is embedded in the aluminum matrix lattice, enhancing the strength of the solid solution. It is desirable to limit the magnesium content to avoid significant powder contamination during printing. It is noteworthy that even without the optional magnesium addition, this alloy offers a unique combination of strength, relative elongation, and corrosion resistance.

[0029] This alloy can be used to make powders for various 3D metal printing techniques.

[0030] Examples of applications of the invention are given below. [Example]

[0031] The alloy is prepared as follows: A8 grade aluminum (99.8% purity) was melted by heating to at least 800°C. Then Fe80F20 and element A (as a double aluminum compound) were added.

[0032] The melt was heated to 850°C and held for 45 minutes. Titanium and metallic cerium were then added. After deslag, flux (2 kg / t) was sprinkled on the surface of the melt.

[0033] The metal was heated to a temperature at least 20°C above the equilibrium liquidus temperature and held for 30 minutes. The melt was stirred every 15 minutes.

[0034] The slag was removed from the surface of the melt and samples were taken for chemical composition analysis.

[0035] After a quick analysis, the chemical composition was adjusted to meet specifications.

[0036] The melt was then sprayed from a nozzle to produce spherical powder, which was classified into particle sizes ranging from 20 to 63 μm.

[0037] The atomizing gas used was a nitrogen-oxygen mixed gas (oxygen content 3 vol%).

[0038] Table 1 shows the chemical composition of the resulting powder. [Table 1] X and Y are elements added to the prototype alloy.

[0039] Using this powder, samples were fabricated by laser additive manufacturing on an EOS M290 printer (https: / / www.eos.info / en / additive-manufacturing / 3d-printing-metal / eos-metal-systems / eos-m-290). The laser power was 270 W, the hatch distance was varied, and the printing speed ranged from 400 to 1,500 mm / s.

[0040] To assess the quality of the samples, the microstructure was investigated. Microsections were prepared using standard methods. The unetched surfaces were analyzed with an inverted metallurgical microscope. For the microstructural study, cubes of 10x10x10 mm were printed. The criteria for selecting the optimal printing parameters were the absence of cracks and minimal porosity.

[0041] Cylinders with a diameter of 12 mm and a height of 90 mm were printed in the XY plane using the optimized printing parameters. After printing, the parts were removed and subjected to heat treatment (annealing). Cylindrical samples were cut from the printed parts for tensile testing according to GOST 1497. The results are shown in Table 2.

[0042] [Table 2]

[0043] Comparing the values ​​in Table 2, the alloying limitations, optimal selection of alloying elements, and their contents result in high relative elongation values ​​and satisfactory strength. All tested alloys are suitable for 3D printing and do not require quenching. It should be noted that Alloy Y (Table 2) is not suitable for 3D printing due to its strong over-alloying. Figure 1 shows cube samples with and without cracks.

[0044] The typical content of the peritectic binary phase of Y element (excluding scandium) is up to 10%, which gives it high strength. [Example]

[0045] The aluminum alloy was prepared from the same materials as in Example 1. Before atomization, carnallite flux was sprinkled on the surface of the melt. After the flux completely covered the metal surface, magnesium was added to the melt. After the magnesium had melted, the melt was thoroughly stirred, the slag removed, and the temperature was raised to at least 40°C above the liquidus temperature. The melt was atomized using an argon-oxygen mixture containing 0.3 vol% oxygen. This resulted in spherical powders, as shown in Figure 2. Their chemical compositions are shown in Table 3. The oxygen content of all powders in the table varied between 0.01 and 0.3 wt% depending on the oxygen content of the atomizing gas. The hydrogen content ranged from 3 to 60 ppm.

[0046] [Table 3]

[0047] The powder was sorted into sizes D50 = 35 μm and D50 = 100 μm. Cylindrical samples for tensile testing were printed using the D50 = 35 μm (particle size 15-45 μm). Tensile tests were performed at room temperature in accordance with GOST 1497 after annealing to relieve stress and precipitate dispersed particles. The test results are shown in Table 4, which also lists the porosity. Figure 3 shows a typical microstructure of the sample.

[0048] [Table 4]

[0049] The addition of magnesium has a positive effect on strength and has little to no significant effect on relative elongation. However, high magnesium concentrations significantly reduce the quality of printed parts. This is related to the high tendency of magnesium vapor to evaporate from the liquid melt. This leads to the formation of large amounts of impurities in the powder that is released when the laser beam hits the powder layer. Therefore, the magnesium content must also be limited. [Example]

[0050] Castings (see Table 5 for chemical composition) were processed in an induction furnace using A85-grade aluminum as alloy or commercial-purity metal and charge. The samples were placed in an atomizer, melted, and heated to a temperature at least 25°C above the equilibrium liquidus temperature and atomized with a nitrogen stream. The resulting powder was sorted to isolate particles with diameters between 20 and 63 μm, and cubes were printed on an EOS M290 SLM machine. Printing parameters were selected from Example 1. The cubes were cut in half along the XZ plane and polished for microstructural study and defect identification. Sections were observed under a bright-field inverted metallographic microscope without etching. Table 5 summarizes the results of porosity and hot crack detection, with hydrogen levels ranging from 10 to 50 ppm.

[0051] [Table 5]

[0052] Depending on the alloying elements, high impurity contents can have undesirable effects and reduce manufacturability. Hot cracking can be suppressed by appropriate selection of printing parameters (e.g., reducing the scan speed), but excessive impurities are undesirable. Another negative effect is increased porosity due to a high content of burnt particles contaminating the top powder layer. [Example]

[0053] Alloy No. 3 (Example 3) was made from grade A7 aluminum and additives AlTi5, AlY10, AlZr10, and AlCr10. The iron and manganese were of commercial purity. Cerium was replaced by misch metal. The aluminum was melted at 830°C, and all additives except misch metal were added. After melting, the melt was stirred and settled at 870°C for at least 30 minutes. Flux and misch metal were then added. The melt temperature was raised to 950°C, the slag was removed, samples were taken for chemical composition analysis, and atomization began. A nitrogen-oxygen gas mixture (oxygen content 2 vol%) was used for atomization. Atomization produced metal powder containing 0.075 wt% oxygen. Powders with particle sizes ranging from 15 to 63 μm were poured into an EOS M290 machine to print various parts and test samples. The samples were annealed at temperatures between 350 and 420°C in a forced convection furnace. The tensile strength and corrosion resistance of the samples were tested by immersion in a 1N NaCl aqueous solution containing 0.3% H2O2 for 45 days. The corrosion rate was estimated by measuring the weight of the samples before and after the test. The results are shown in Table 6.

[0054] This alloy has high strength and ductility. Its corrosion resistance is close to that of 6XXX grade aluminum alloys. Printed parts can be used in a variety of applications, including aerospace, automotive, and mechanical engineering.

[0055] [Table 6]

[0056] Pursuant to the disclosed claims, legal protection is sought for a powder aluminum alloy containing iron and cerium, at least one element from group A consisting of manganese, lanthanum, and yttrium, at least one element from group B consisting of zirconium, vanadium, chromium, hafnium, and scandium, and optionally hydrogen and magnesium, as well as aluminum and unavoidable impurities including silicon, copper, and zinc, in the following concentrations (by weight): Iron 0.3~1.5 Cerium 0.35~2.6 Titanium 0.15~0.4 At least one element from group A consisting of manganese, lanthanum, and yttrium 0.2 to 2.0 (total or individual) At least one element from group B consisting of zirconium, vanadium, chromium, hafnium, and scandium 0.6 to 1.5 (total or individually) any: Hydrogen 3-60 ppm Magnesium 1.5-4.5, and Aluminum and unavoidable impurities, with a compositional balance of silicon, copper and zinc, The silicon, copper and zinc contents are as follows: Silicon max 0.2 Copper max 0.05 Zinc max 0.05

[0057] The structure consists of an aluminum solid solution, a eutectic, and up to 10% nanoscale dispersoids of AlB-type phase, the dispersoids being formed by elements of the B group.

[0058] A preferred embodiment is an alloy containing 0.3-1.0 wt% iron, 0.35-1.0 wt% cerium, 0.15-0.25 wt% titanium, 0.5-2.0 wt% of at least one element from group A, 0.6-0.8 wt% of at least one element from group B, and optionally 2.0-4.0 wt% magnesium. The aluminum alloy powder is produced by gas atomization using nitrogen, argon, or a mixture of these gases with oxygen. Therefore, the powder further contains 0.01-0.3 wt% oxygen. The average particle size of the powder is generally 20-100 μm. Parts made from the powder are produced by layer-by-layer technology and have a strength of at least 320 MPa after annealing.

[0059] The proposed aluminum alloy can be used as powder to fabricate parts using additive manufacturing, has high strength without quenching or artificial aging, is suitable for 3D printing, and exhibits high corrosion resistance for use in harsh environments.

Claims

1. 1. An aluminum powder alloy consisting of iron, cerium, at least one element from group A consisting of manganese, lanthanum, and yttrium, at least one element from group B consisting of zirconium, vanadium, chromium, hafnium, and scandium, optionally hydrogen and magnesium, and aluminum, with inevitable impurities including silicon, copper, and zinc, said elements having the following concentrations in wt%: Iron 0.3 to 1.5 Cerium 0.35 to 2.6 Titanium 0.15 to 0.4 At least one element from group A consisting of manganese, lanthanum, and yttrium 0.2 to 2.0 (total or individually) At least one element from group B consisting of zirconium, vanadium, chromium, hafnium, and scandium 0.6 to 1.5 (total or individual) any: Hydrogen 3 to 60 ppm Magnesium 1.5 to 4.5, and Includes compositional balance of silicon, copper, and zinc Aluminum and unavoidable impurities, The silicon, copper and zinc contents are as follows: Silicon max 0.2 Copper max 0.05 Zinc max 0.05 The structure consists of an aluminum solid solution, a eutectic, and up to 10% nanoscale dispersed particles of an AlB-type phase, the dispersed particles being formed by elements of the B group.

2. 10. The aluminum alloy of claim 1, comprising: Iron 0.3 to 1.0 wt% Cerium 0.35 to 1.0 wt% Titanium 0.15 to 0.25 wt% At least one element from group A: 0.5 to 2.0 wt% At least one element from group B: 0.6 to 0.8 wt% Optionally, magnesium 2.0 to 4.0 wt%

3. 3. The aluminum alloy of claim 2, containing manganese as an element of group A and zirconium and vanadium as elements of group B.

4. A powder produced from the aluminum alloy according to any one of claims 1 to 3, produced by gas atomization using nitrogen or argon, or a mixture of these gases with oxygen, and further containing 0.01 to 0.3 wt% oxygen.

5. The powder of claim 4, wherein the average particle size of the powder is 20 to 100 μm.

6. 10. A part manufactured from an aluminum alloy powder using layer-by-layer technology, said part being manufactured from the powder according to claim 4, and further having a strength of 320 MPa or more after annealing.

Images