Powder material with high thermal conductivity

Abstract

The invention relates to the field of metallurgy and more specifically to an aluminum alloy based powder material for producing parts by additive techniques including selective laser melting. It is proposed an aluminum powder material containing silicon, iron, magnesium, zirconium, with the condition Si ≥ Mg*6.5 + Fe*5. The technical result is an increase in the strength and thermal conductivity properties of aluminum alloys for producing parts by powder techniques including additive techniques, while maintaining the strength properties corresponding to medium strength aluminum alloys.

Description

Technical Field

[0001] This invention relates to metallurgy, and more particularly to aluminum alloy powder materials for producing components by additive manufacturing technology. Background Technology

[0002] Additive manufacturing is increasingly used to produce parts from metal powder materials. Selective laser melting (SLM) is the most widely used additive manufacturing technology for producing metal parts. The key advantages of additive manufacturing over traditional aluminum alloy production technologies are: shorter production times, the ability to produce shaped parts with minimal machining allowances, the ability to produce parts with improved weight efficiency using topology optimization and biomimetic design methods, and the ability to ensure a higher range of properties compared to currently used alloys using novel material compositions.

[0003] This has attracted the interest of companies specializing in advanced products for the aerospace and automotive industries. To ensure competitiveness and cost-effectiveness, components and structural elements used in these fields are subject to stringent requirements regarding their weight efficiency. Heat exchangers are among the most critical devices used to ensure the operation of products in the aerospace and automotive industries; their efficiency is determined by the energy conversion efficiency factor. This energy conversion efficiency factor can be increased by increasing design complexity to ensure a larger heat transfer area and by using materials with high thermal conductivity. Currently, copper is the primary material of choice for heat exchangers due to its high thermal conductivity coefficient of 400 W / m*K. However, copper has a high density, 8.9 g / cm³. 3 This cannot meet the stringent weight efficiency requirements of highly competitive products. Using a material with a weight of 2.7 g / cm³... 3 With its high density and 200 W / m*K thermal conductivity, aluminum alloys, along with additive manufacturing technology that allows for the production of complex structures with an increased number of heat exchange zones, can reduce the weight of heat exchangers in aerospace and motor vehicles by 10 times compared to copper.

[0004] AlSi10Mg alloy is currently the most widely used aluminum alloy in SLM technology; it contains 9-11 wt% silicon and 0.20-0.60 wt% magnesium (see Process optimization and microstructural analysis for selective laser melting of AlSi10Mg. K. Kempen, L. Thijs, E. Yasa, M. Badrossamay, W. Verheecke, JP. Kruth. Solid Freeform Fabrication Symposium Conference, Vol. 22, Pages. 484-495, 2011).

[0005] This material is a medium-strength aluminum alloy with good castability and low susceptibility to hot cracking (tensile strength: 320 MPa, yield strength: 210 MPa), making it suitable for SLM processes. However, with high silicon content, the thermal conductivity of this alloy decreases to 160 W / m*K.

[0006] For heat exchanger components designed to dissipate heat from the heat transfer medium and operate in a temperature range up to 200°C, materials with high thermal conductivity are required, while the strength characteristics of the material should match those of medium-strength aluminum alloys.

[0007] Aluminum alloys are known (JP2008308760A, published on December 25, 2008) and contain the following components (wt%):

[0008] Silicon: 0.3 to 1.2;

[0009] Iron: 0.7 to 2.0;

[0010] Manganese: 0.2 to 0.8;

[0011] Zinc: 0.1 to 1.0;

[0012] Scandium: 0.0001 to 1.0;

[0013] Copper: 0.05 to 0.8;

[0014] Magnesium: 0.01 to 0.05;

[0015] Zirconium: 0.001 to 0.3;

[0016] Titanium: 0.01 to 0.25;

[0017] Chromium: 0.01 to 0.1;

[0018] Vanadium: 0.01 to 0.1;

[0019] Aluminum: Balance.

[0020] The alloy achieves sufficient strength, particularly through solid solution strengthening with the addition of various elements. However, the large number of elements in the solid solution leads to a significant reduction in thermal conductivity to 160 W / m*K.

[0021] An aluminum-manganese alloy (JP2004176091A, published on June 24, 2004) is known to contain the following components (wt%):

[0022] Manganese: 2.0 to 3.0;

[0023] Silicon: 0.8 to 1.5;

[0024] Iron: 0.05 to 0.4;

[0025] Zinc: 0.1 to 3.0;

[0026] Nickel: 0.01 to 1.0;

[0027] Zirconium: 0.01 to 0.3;

[0028] Titanium: 0.01 to 0.30;

[0029] Indium: 0.001 to 0.2;

[0030] Tin: 0.01 to 0.5;

[0031] Aluminum: Balance.

[0032] This alloy is designed for use in automotive heat exchangers and exhibits good thermal conductivity. However, its main drawback is its insufficient strength properties (σ). b =145MPa), therefore it cannot be considered a heat exchanger material for the aerospace industry. Furthermore, the alloy contains zinc, which has a high vapor pressure, so some of the alloy is lost during the SLM process, resulting in a decrease in its strength properties.

[0033] An aluminum-iron alloy (JP5301750B1, published on September 25, 2013) is known to contain the following components (wt%):

[0034] Copper: 0.00 to 2.30;

[0035] Iron: 1.20 to 2.60;

[0036] Silicon: 0.00 to 1.50;

[0037] The advantages of this alloy include its high thermal conductivity while maintaining the strength characteristics of a medium-strength aluminum alloy. The main disadvantage is its poor machinability when producing products using the SLM method, due to the wide solidification range of the alloying elements in this composition. Furthermore, the high iron and copper content negatively impacts the material's corrosion resistance, significantly reducing the service life of components made from this alloy in corrosive environments.

[0038] An aluminum-magnesium-silicon alloy (RU2014110911A, published on September 27, 2015) is known to contain the following components (wt%):

[0039] Silicon: 1.0 to 4.0;

[0040] Magnesium: 1.7 to 8.0;

[0041] Scandium: 0.1 to 0.5;

[0042] Cobalt: 0.3 to 0.6;

[0043] Titanium / Zirconium: 0.2 to 1.2;

[0044] Iron (maximum): 0.4;

[0045] Aluminum: Balance.

[0046] This alloy exhibits high mechanical properties due to solid solution and precipitation strengthening. Its main drawback is its high magnesium content, which impairs its machinability during the SLM process, as the chemical composition of the molten material changes compared to the original powder due to slag formation during SLM. Furthermore, the alloy has low castability, increasing the likelihood of defects caused by thermal stress during SLM, leading to hot cracking during melting. The alloy also contains scandium, an expensive alloying element, which reduces its economic viability.

[0047] An aluminum-silicon-copper alloy (DE112004001160B4, published on January 10, 2008) is known to contain the following components (wt%):

[0048] Silicon: 11.25 to 11.75;

[0049] Iron: 0.35 to 0.65;

[0050] Copper: 1.75 to 2.75;

[0051] Magnesium: 0.15 to 0.3;

[0052] Manganese: 0.42 to 1.2;

[0053] Zinc: Maximum 0.5;

[0054] Titanium: Maximum 0.2;

[0055] Strontium: 0.01 to 0.03;

[0056] The manganese / iron ratio is 1.2 / 1.75.

[0057] The mechanical properties of this alloy are comparable to those of a medium-strength aluminum alloy (310 MPa). However, due to the presence of more than 1 wt% copper, the alloy exhibits a tendency for pitting corrosion. Furthermore, the overall high alloying properties result in a significant reduction in its thermal conductivity.

[0058] An aluminum-magnesium-silicon alloy (EP1167560A1, published on January 2, 2002) is known to contain the following components (wt%):

[0059] Magnesium: 1.0 to 2.6;

[0060] Silicon: 0.5 to 2.0;

[0061] Iron (maximum): 0.5;

[0062] Copper (maximum): 1.0;

[0063] Zinc (maximum): 0.30;

[0064] Titanium (maximum): 0.20;

[0065] Beryllium (maximum): 0.003.

[0066] The alloy has low mechanical properties (tensile strength at casting: 230 MPa, yield strength: 140 MPa), which is due to insufficient alloying with elements that ensure dispersion strengthening.

[0067] An aluminum-silicon-copper alloy (US8758529B2, published on June 24, 2014) is known to contain the following components (wt%):

[0068] Silicon: 0.5 to 14;

[0069] Copper: 0.25 to 2.0;

[0070] Nickel: 0.1 to 3.0;

[0071] Iron: 0.1 to 1.0;

[0072] Zinc: 0.1 to 2.0;

[0073] Magnesium: 0.1 to 1.0;

[0074] Silver: 0 to 1.0;

[0075] Strontium: 0 to 0.2;

[0076] Manganese: 0 to 1.0;

[0077] Calcium: 0 to 0.5;

[0078] Germanium: 0 to 0.5;

[0079] Tin: 0 to 0.5;

[0080] Cobalt: 0 to 0.5;

[0081] Titanium: 0 to 0.2;

[0082] Boron: 0 to 0.1;

[0083] Cadmium: 0 to 0.3;

[0084] Chromium: 0 to 0.3;

[0085] Indium: 0 to 0.5;

[0086] and at least one of the following elements:

[0087] Scandium: 0 to 0.1;

[0088] Zirconium: 0.1 to 0.2;

[0089] Yttrium: 0.25 to 0.5.

[0090] This alloy possesses high mechanical properties, ensured by two types of strengthening: solid solution and precipitation strengthening. However, a drawback of this alloy is its low thermal conductivity, due to the highly alloyed nature of the solid solution and the large amount of phase released during heat treatment. The high copper content in this alloy is another major disadvantage, as it makes the material susceptible to pitting corrosion.

[0091] The aluminum-based alloy (US20050106410A1, published on May 19, 2005) is the closest to the claimed aluminum-based alloy; it contains the following elements (wt%):

[0092] Silicon: 0.1 to 1.5;

[0093] Iron: 0.1 to 0.6;

[0094] Copper: 0.0 to 1.0;

[0095] Magnesium: 0.0 to 0.4;

[0096] Manganese: 0.7 to 1.8;

[0097] Zinc: 0.1 to 3.0;

[0098] Titanium: 0.0 to 0.3;

[0099] Zirconium: 0.0 to 0.3;

[0100] Aluminum: Balance.

[0101] The disadvantages of this alloy are its low mechanical properties (ultimate tensile strength: 204 MPa, yield strength: 190 MPa). Another disadvantage is its zinc content, as zinc is easily lost during the SLM process due to its high vapor pressure. The manganese content, in the presence of magnesium and iron, can lead to the formation of plate-like Al6(Mn,Fe) phases, which significantly reduces thermal conductivity. Another disadvantage is the presence of copper in the alloy composition, which increases the alloy's crystallization intervals and leads to hot cracking during the SLM process. Summary of the Invention

[0102] The technical problem of this invention is to develop an aluminum powder material with high thermal conductivity and mechanical properties corresponding to medium-strength aluminum alloys for the production of heat exchanger and radiator components by additive manufacturing technology, while ensuring that there are no hot cracks and macropores in the molten material.

[0103] The technical effect is to increase the thermal conductivity and strength properties of aluminum alloys, enabling the production of parts using additive manufacturing technology.

[0104] This problem was solved and results were obtained by proposing a new aluminum powder material containing the following elements in the following proportions (wt%):

[0105] Silicon: 2.00 to 6.00;

[0106] Iron: 0.10 to 0.50;

[0107] Magnesium: 0.10 to 0.80;

[0108] Zirconium: 0.10 to 0.40;

[0109] Copper: Maximum 0.02;

[0110] Manganese: Maximum 0.02;

[0111] Titanium (maximum): 0.02;

[0112] Aluminum and unavoidable impurities: Balance.

[0113] The following ratio of silicon, magnesium, and iron content will be appropriate: Si ≥ Mg*6.5 + Fe*5.

[0114] We also provide articles produced from the above-mentioned aluminum powder materials using additive manufacturing technology, which have an ultimate tensile strength of over 290 MPa and a tensile yield strength of over 210 MPa, an elongation of over 8%, and a thermal conductivity of over 190 W / m*K.

[0115] The following technologies can be used to produce powder:

[0116] - Prepare aluminum-based melts by controlling the desired chemical composition;

[0117] - Refine the aluminum melt and superheat it to at least 100°C above the liquidus temperature;

[0118] - Atomize the molten aluminum with nitrogen, argon, or a mixture thereof;

[0119] - Separate the required powder fractions.

[0120] The choice of silicon content is based on the need for high castability of the material to ensure machinability when manufacturing products using the SLM method and to ensure sufficient thermal conductivity of the material.

[0121] Magnesium additives improve alloy strength by forming the Mg2Si phase during heat treatment strengthening.

[0122] Ferroalloying helps to form insoluble intermetallic inclusions based on aluminum, silicon, and iron, which ensures additional strengthening and improves the thermal stability of the alloy, and also helps to consume the aluminum matrix by alloying elements, which results in an increase in thermal conductivity.

[0123] During heat treatment, zirconium is introduced to form a finely dispersed Al3Zr phase during the decomposition of the supersaturated solid solution. Zirconium has a low diffusion coefficient in the aluminum matrix, which leads to the formation of nanoscale phases during high-temperature aging and has little effect on thermal conductivity due to their size. Since this phase bonds to the aluminum matrix, a strong strengthening effect can be achieved. The zirconium content is selected to avoid the formation of large intermetallic compounds in the molten material, which would result in a significant reduction in the strengthening effect and thermal conductivity.

[0124] Experiments unexpectedly showed that the ratio of iron, silicon, and magnesium in the alloy Si≥Mg*6.5+Fe*5 ensures an optimal combination of the strength, ductility, and thermal conductivity of the printed material. This ratio of alloying elements ensures an optimal amount of strengthening phases and an optimal solid solution composition. If the magnesium and iron contents are too high, due to the excessive iron and magnesium in the solid solution, the material has a lower elongation rate and yield strength, which also contributes to a reduction in the thermal conductivity of the material.

[0125] Example 1 below shows the alloy properties when this ratio is met; Example 2 presents the research results of the material under Si<Mg*6.5+Fe*5.

[0126] The proposed alloy has a limited content of manganese, copper, and titanium. High-temperature treatment is required to form manganese-based intermetallic phases.

[0127] High-temperature treatment will reduce the strengthening effect of Mg2Si and Al3Zr due to their growth, which will adversely affect the thermal conductivity and strength characteristics of the alloy.

[0128] Another disadvantage of the presence of manganese in the iron-containing aluminum alloy is the formation of rough non-spherical phases (MnFe)Al6 (during heat treatment), which has a negative impact on thermal conductivity.

[0129] The upper limits of the copper and titanium contents in the alloy are restricted to narrow the solidification range of the alloy. Additionally, the titanium content is restricted so as not to significantly reduce the thermal conductivity of the alloy. Description of the Drawings

[0130] Figure 1 : Powder particles of compositions 2, 3, 4, and 6 of the proposed alloy obtained by atomizing the melt into an air stream in Example 1 of the present invention.

[0131] Figure 2 : Selective laser melting process and the appearance of the fused sample.

[0132] Figure 3: Structural images of sample compositions 2, 3, 4 and 6 from Example 1 of the Invention. Detailed Implementation

[0133] The invention is explained through the following examples.

[0134] Example 1

[0135] The alloy is prepared in the following order:

[0136] Aluminum is melted and heated to a temperature of 800-810°C. It is then alloyed with crystalline silicon. Iron is introduced at 720-740°C in the form of Fe80F20 tablets (80% Fe, 20% flux).

[0137] The melt is then heated to 780°C. Al15Zr master alloy is added, and the mixture is held at this temperature for 1 hour, stirring every 15 to 20 minutes.

[0138] After soaking, the slag is removed. After removing the slag, carnallite flux is loaded onto the surface of the melt at a rate of 2 kg / t. After the flux melts, magnesium is injected below the flux layer.

[0139] After magnesium is injected, soak for 60 minutes, stirring every 15 minutes.

[0140] After soaking, the slag is removed from the surface of the melt and samples are taken to control the chemical composition.

[0141] Spherical powders are prepared by atomizing the melt through a nozzle. A nitrogen-oxygen mixture is used as the atomizing gas, wherein the oxygen content in the mixture does not exceed 0.8 vol%.

[0142] The resulting pulverized volume was subjected to pneumatic separation and sieving to separate the target fraction of 20-63μm.

[0143] As a result, a powder with the chemical composition shown in Table 1 was obtained.

[0144] Table 1

[0145]

[0146]

[0147] The resulting powder was used to prepare samples via SLM. An EOS M290 SLM printer was used for sample preparation. Samples were prepared by varying the laser power from 220-350W and the scanning speed from 450-1000 mm / s.

[0148] The quality of the obtained samples was determined using qualitative and quantitative metallography. These polished samples were produced using standard techniques; the microstructure of the uncoated surfaces was analyzed using an inverted metallographic microscope.

[0149] To determine the strength and thermal conductivity properties, a sample blank was melted. The molten sample blank was processed according to GOST 1497-84. Thermal conductivity was determined using a laser flash method with an LFA 467 apparatus. Tensile tests were performed according to GOST 1497-84.

[0150] The samples were analyzed after aging at 300℃ for 1 hour. The results are listed in Table 2.

[0151] Table 2

[0152]

[0153] The material is characterized by a 23% increase in thermal conductivity and a 41% increase in tensile strength compared to the prototype.

[0154] Compared to the prototype, the aluminum powder material with the proposed chemical composition exhibits increased thermal conductivity, tensile strength, and yield strength.

[0155] Example 2

[0156] The aluminum alloy powders with the chemical compositions shown in Table 3 were prepared using the method described in Example 1. The proportions of silicon, iron, and magnesium in the alloys varied.

[0157] Table 3

[0158]

[0159] To prepare the samples, an EOS M290 SLM unit was used. Molten samples (cylinders 80 mm long and 12 mm in diameter) were machined for tensile testing according to GOST 1497-84, and for thermal conductivity testing. Thermal conductivity was measured on the circular samples using a laser flash method with an LFA 467 apparatus. Tensile testing was performed according to GOST 1497-84. The samples were analyzed after aging at 300°C for 45 minutes.

[0160] Table 4 shows the results of tensile tests and thermal conductivity analyses of the samples after heat treatment, based on the chemical composition according to GOST 1497-84 and the samples in Table 3.

[0161] Table 4

[0162]

[0163] Therefore, compared with the prototype, the aluminum powder material with the proposed chemical composition has increased thermal conductivity, tensile strength and yield strength.

[0164] The formation of Mg2Si and Al3Zr dispersoids and multi-component inclusions based on iron, aluminum, and silicon improves the strength characteristics of the alloy. Heat treatment (aging treatment), by reducing the solid solution concentration and forming small, rounded inclusions, increases the thermal conductivity. However, when Si < Mg*6.5 + Fe*5, due to the high Mg and Fe content in the aluminum matrix, the characteristics are lower compared to alloys with the chemical composition shown in Table 1 and equivalent to Si ≥ Mg*6.5 + Fe*5.

[0165] Therefore, the present invention provides improved strength and thermal conductivity characteristics for an aluminum alloy used to produce components using additive techniques while maintaining high elongation.

Claims

1. An aluminum powder material for producing parts using additive manufacturing technology, said parts having improved strength and thermal conductivity properties while maintaining high elongation, said aluminum powder material comprising silicon, iron, magnesium, and zirconium, having the following component proportions (wt%): Silicon: 2.00 to 5.00; Iron: 0.10 to 0.50; Magnesium: 0.10 to 0.80; Zirconium: 0.10 to 0.40; Copper: Maximum 0.02; Manganese: Maximum 0.02; Titanium: Maximum 0.02; Aluminum and unavoidable impurities: Balance. The proportions of silicon, iron, and magnesium in the alloy meet the condition that Si ≥ Mg * 6.5 + Fe * 5.

2. The aluminum powder material according to claim 1, having a tensile strength exceeding 290 MPa, a yield strength exceeding 210 MPa, an elongation exceeding 8%, and a thermal conductivity exceeding 190 W / m*K.

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