Powdery material having high thermal conductivity

Abstract

The present invention relates to the field of metallurgy, and in particular to a powder material based on aluminum alloys used to manufacture parts using additive techniques including selective laser alloying. * 6.5+Fe * 5. The technical result is an increase in the strength and thermal conductivity properties of aluminum alloys for the manufacture of parts using powder technology with additives, while maintaining strength properties corresponding to medium strength aluminum alloys.

Description

Technical Field

[0001] The present invention relates to aluminum alloy powder materials used for producing parts by additional techniques, particularly in metallurgy.

[0002] Additive manufacturing is increasingly being used to produce parts from metal powder materials. Selective laser melting (SLM) is the most widely used additive technique for producing metal parts. The important advantages of additive techniques over conventional aluminum alloy production techniques are as follows: shorter time to produce the final product, the ability to produce shaped parts with minimal machining allowances, the ability to use topology optimization and biotonic design methods to produce parts with improved weight efficiency, and the ability to use new material compositions that ensure a higher set of properties compared to currently used continuous alloys.

[0003] This has attracted the attention of companies specializing in the production of advanced products for the aerospace and automotive industries. To ensure competitiveness and cost-effectiveness, the parts and structural elements used in these fields are subject to strict requirements regarding their weight efficiency. Heat exchangers are one of the most important devices used to ensure the operation of products in the aerospace and automotive industries. Their efficiency is determined by the energy conversion efficiency coefficient. This coefficient can be increased by increasing the complexity of the design to ensure the presence of more heat transfer areas and by using materials with high thermal conductivity. Currently, copper is the main material selected for heat exchangers because it has one of the highest thermal conductivity coefficients of 400 W / m * K. However, the high density of copper, 8.9 g / cm 3 does not meet the strict weight efficiency requirements for highly competitive products. The density of 2.7 g / cm 3 and the thermal conductivity of 200 W / m *The use of aluminum alloys with the thermal conductivity of K, and the use of additional technologies enabling the production of complex structures with an increased number of heat exchange areas, can reduce the weight of heat exchangers in aerospace and automotive vehicles by up to 10 times compared to copper.

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

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

[0006] For heat exchanger components designed to dissipate heat from a heat transfer medium operating at temperatures in the range up to 200 °C, materials with a higher thermal conductivity coefficient are required, while the strength properties of the material should match those of medium - strength aluminum alloys.

[0007] Aluminum alloys containing the following components (by weight%) are known (Published Application No. 2008308760(A), published on December 25, 2008): 0.3 - 1.2 silicon; 0.7 - 2.0 iron; 0.2 - 0.8 manganese; 0.1 - 1.0 zinc; 0.0001 to 1.0 of scandium; 0.05 to 0.8 of copper; 0.01 to 0.05 of magnesium; 0.001 to 0.3 of zirconium; 0.01 to 0.25 of titanium; 0.01 to 0.1 of chromium; 0.01 to 0.1 of vanadium; The balance is aluminum.

[0008] The sufficient strength of this alloy is achieved, inter alia, by solid solution hardening due to the addition of various elements. However, if there are a large number of elements in the solid solution, the thermal conductivity coefficient is significantly reduced to 160 W / m * K.

[0009] An aluminum-manganese alloy containing the following components (by weight %) is known (Published Application No. 2004176091(A), published on June 24, 2004): 2.0 to 3.0 of manganese; 0.8 to 1.5 of silicon; 0.05 to 0.4 of iron; 0.1 to 3.0 of zinc; 0.01 to 1.0 of nickel; 0.01 to 0.3 of zirconium; 0.01 to 0.30 of titanium; 0.001 to 0.2 of indium; 0.01 to 0.5 of tin; The balance is aluminum.

[0010] This alloy is designed to be used in automotive heat exchangers and has good thermal conductivity. However, the main drawback of this alloy is its insufficient high-strength characteristics (σ b = 145 MPa), and therefore it cannot be regarded as a heat exchanger material for the aerospace industry. In addition, since this alloy contains zinc with a high vapor pressure, this alloy is partially lost in the SLM process, and as a result, its strength characteristics are reduced.

[0011] An aluminum-iron alloy containing the following components (by weight %) is known (Patent No. 5301750 (B1), published on September 25, 2013): 0.00 - 2.30 copper; 1.20 - 2.60 iron; 0.00 - 1.50 silicon.

[0012] The advantage of this alloy is that it has a high thermal conductivity while maintaining the strength characteristics of medium-strength aluminum alloys. The main disadvantage of this alloy is that due to the wide solidification range of the alloying elements in this content, the workability is low when producing products using the SLM method. In addition, the high iron and copper content of the alloy has an adverse effect on the corrosion resistance of the material, significantly reducing the service life of parts manufactured from this alloy in a corrosive environment.

[0013] An aluminum-magnesium-silicon alloy containing the following components (by weight %) is known (Russian Patent No. 2014110911 (A), published on September 27, 2015): 1.0 - 4.0 silicon; 1.7 - 8.0 magnesium; 0.1 - 0.5 scandium; 0.3 - 0.6 cobalt; 0.2 - 1.2 titanium / zirconium; 0.4 iron (maximum); The balance is aluminum.

[0014] This alloy has high mechanical properties due to solid solution hardening and precipitation hardening. The main disadvantage of this alloy is its high magnesium content, which can cause changes in the chemical composition of the molten material compared to the original powder due to slag in the SLM process, thus impairing the alloy workability during SLM. In addition, this alloy has low castability, which increases the possibility of defects during the SLM process due to thermal stresses that cause hot cracks during melting. This alloy also contains scandium, which is an expensive alloying element, reducing the economic viability of the alloy.

[0015] An aluminum-silicon-copper alloy containing the following components (by weight %) is known (German Patent No. 112004001160 (B4), published on January 10, 2008): 11.25 to 11.75 silicon; 0.35 to 0.65 iron; 1.75 to 2.75 copper; 0.15 to 0.3 magnesium; 0.42 to 1.2 manganese; Up to 0.5 zinc; Up to 0.2 titanium; 0.01 to 0.03 strontium.

[0016] The manganese / iron ratio is 1.2 / 1.75.

[0017] The mechanical properties of this alloy are equal to those of a medium-strength aluminum alloy (310 MPa). Since there is more than 1% by weight of copper in this alloy, this alloy tends to cause pitting corrosion. In addition, the overall high alloying characteristics of this alloy result in a significant decrease in its thermal conductivity.

[0018] An aluminum-magnesium-silicon alloy containing the following components (by weight %) is known (European Patent No. 1167560 (A1), published on January 2, 2002): 1.0 to 2.6 magnesium; 0.5 to 2.0 silicon; 0.5 iron (maximum); 1.0 copper (maximum); 0.30 zinc (maximum); 0.20 titanium (maximum); 0.003 beryllium (maximum).

[0019] This 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 hardening.

[0020] An aluminum-silicon-copper alloy containing the following components (by weight %) is known (U.S. Patent No. 8,758,529 (B2), published on June 24, 2014): 0.5 to 14 silicon; 0.25 to 2.0 copper; 0.1 to 3.0 nickel; 0.1 to 1.0 iron; 0.1 to 2.0 zinc; 0.1 to 1.0 magnesium; 0 to 1.0 silver; 0 to 0.2 strontium; 0 to 1.0 manganese; 0 to 0.5 calcium; 0 to 0.5 germanium; 0 to 0.5 tin; 0 to 0.5 cobalt; 0 to 0.2 titanium; 0 to 0.1 boron; 0 to 0.3 cadmium; 0 to 0.3 chromium; 0 to 0.5 indium; And at least one of the following elements: 0 to 0.1 scandium; 0.1 to 0.2 zirconium; 0.25 to 0.5 yttrium.

[0021] This alloy has high mechanical properties ensured by two hardening types: solid solution hardening and precipitation hardening. However, the drawback of this alloy is its low thermal conductivity due to the high alloying characteristics of the solid solution and the numerous phases released during heat treatment. The high copper content in this alloy makes the material prone to pitting corrosion, which is another major drawback of this alloy.

[0022] The aluminum-based alloy (U.S. Patent Application Publication No. 20050106410 (A1), published on May 19, 2005) is the closest to what is claimed and contains the following elements (by weight %): 0.1 to 1.5 silicon; 0.1 to 0.6 iron; Copper from 0.0 to 1.0; Magnesium from 0.0 to 0.4; Manganese from 0.7 to 1.8; Zinc from 0.1 to 3.0; Titanium from 0.0 to 0.3; Zirconium from 0.0 to 0.3; The balance is aluminum.

[0023] The disadvantages of this alloy are its low mechanical properties (ultimate tensile strength: 204 MPa, yield strength: 190 MPa). Another disadvantage of this alloy is its zinc content, since zinc is prone to loss during SLM due to its high vapor pressure. The manganese content in the presence of magnesium and iron can lead to the formation of plate-like Al 6 (Mn, Fe) phases, which significantly reduce the thermal conductivity. Another disadvantage is the presence of copper in the alloy composition, which increases the alloy crystallization interval and leads to hot cracks during the SLM process.

[0024] The technical problem of the present invention is to develop an aluminum powder material with high thermal conductivity and mechanical properties corresponding to medium-strength aluminum alloys for producing parts of heat exchangers and radiators by additive techniques, while ensuring that there are no hot crack areas and large pores in the molten material.

[0025] The technical result is to increase the thermal conductivity characteristics of the aluminum alloy and improve the strength characteristics so that parts can be produced using additive production techniques.

[0026] This problem is solved and the result is achieved by proposing a new aluminum powder material containing elements in the following proportions (by weight): Silicon from 2.00 to 6.00; Iron from 0.10 to 0.50; Magnesium from 0.10 to 0.80; Zirconium from 0.10 to 0.40; Copper at most 0.02; Manganese at most 0.02; Titanium up to 0.02; The balance is aluminum and unavoidable impurities.

[0027] The following ratios are appropriate for the contents of silicon, magnesium and iron: Si ≧ Mg * 6.5 + Fe * 5.

[0028] The inventors also provide an article produced using an additional technique from the above-described aluminum powder material, which has an ultimate tensile strength exceeding 290 MPa and a tensile yield strength exceeding 210 MPa, an elongation exceeding 8% and a thermal conductivity exceeding 190 W / m * K.

[0029] It is possible to produce the powder using the following techniques: - Preparation of an aluminum-based melt with control of the required chemical composition; - Purifying the aluminum melt and superheating it to a temperature at least 100 °C higher than the liquidus temperature; - Gas atomization of the aluminum melt with a gas that is nitrogen, argon or a mixture thereof; - Separation of the required part of the powder.

[0030] The silicon content was selected based on the need for high castability of the material to ensure workability when producing the product using the SLM method and to ensure a sufficient level of thermal conductivity of the material.

[0031] The magnesium additive increases the alloy strength by forming the Mg 2 Si phase during heat treatment hardening.

[0032] The alloying of iron contributes to the formation of insoluble intermetallic compound inclusions based on aluminum, silicon and iron, which ensures additional hardening, increases the thermal stability of the alloy, and also contributes to the depletion of the aluminum matrix by alloying elements, which results in an increase in thermal conductivity.

[0033] Zirconium is formed by the decomposition of the supersaturated solid solution during heat treatment, resulting in the formation of finely dispersed Al. 3 It is introduced to form the Zr phase. Zirconium has a low diffusion coefficient in the aluminum matrix, which results in the formation of a nanoscale phase during high-temperature aging, which has little effect on the thermal conductivity due to its size. Since the phase is coherent with the aluminum matrix, a strong hardening effect can be achieved. The zirconium content is selected to avoid the formation of large intermetallic compounds in the fused material, which would result in a significant reduction in the hardening effect and thermal conductivity.

[0034] Experimentally, it was unexpectedly found that the ratio of iron, silicon and magnesium in the alloy Si ≥ Mg * 6.5+Fe * It has been shown that Ratio 5 ensures that there is an optimal combination of strength, ductility and thermal conductivity of the printed material. This ratio of alloying elements ensures that there is an optimal amount of hardening phase and an optimal composition of solid solution. Above the magnesium and iron content, the elongation and yield strength of the material decreases due to the excess iron and magnesium in solid solution, which also contributes to a decrease in the thermal conductivity of the material.

[0035] Example 1 below shows the alloy properties when this ratio is met. Example 2 shows the alloy properties when Si <Mg * 6.5+Fe * The results of the materials research in 5 are presented.

[0036] The proposed alloy has limited contents of manganese, copper and titanium. High temperature processing is required to form the manganese-based intermetallic phases.

[0037] High temperature treatment is Mg 2 Si and Al 3 It reduces the hardening effect caused by Zr growth and adversely affects the thermal conductivity and strength properties of the alloy.

[0038] Another drawback of manganese present in iron-containing aluminum alloys is the formation (during heat treatment) of a coarse non-spheroidal phase (MnFe)Al 6The formation of this has an adverse effect on the thermal conductivity.

[0039] The upper limits of the copper and titanium contents in the alloy are restricted to narrow the solidification range of the alloy. In addition, the titanium content is restricted so as not to significantly reduce the thermal conductivity of the alloy.

Brief Description of the Drawings

[0040]

Figure 1

Figure 2

Figure 3

[0041] The proposed invention will be described by the following examples.

[0042] Example 1 The alloy was prepared in the following order.

[0043] Aluminum was melted and heated to a temperature of 800 - 810 °C. Then it was alloyed with crystalline silicon. Iron was introduced at 720 - 740 °C as Fe80F20 tablets (80% Fe, 20% flux).

[0044] Next, the melt was heated to 780 °C. After adding the Al15Zr master alloy, it was incubated for 1 hour with stirring every 15 - 20 minutes.

[0045] After immersion, the slag was removed. After removing the slag, carnallite flux was charged onto the surface of the melt at a rate of 2 kg / t. After the flux melted, magnesium was injected under the flux layer.

[0046] Following the magnesium injection, it was immersed for 60 minutes with stirring every 15 minutes.

[0047] After immersion, the slag was removed from the melt surface and samples were taken to control the chemical composition.

[0048] The spherical powder was produced by spraying the melt through an ejector nozzle. A nitrogen-oxygen mixture was used as the spray gas, and the oxygen content in the mixture was 0.8 vol% or less.

[0049] The obtained crushed volume was subjected to gas dynamic separation and sieving to separate the target fraction of 20 - 63 μm.

[0050] As a result, powders with the chemical compositions shown in Table 1 were produced.

[0051]

Table 1

[0052] Using the obtained powder, samples were fabricated by SLM. To fabricate the samples, an EOS M290 SLM printer was used. The samples were produced by varying the laser power in the range of 220 - 350 W and the scanning speed in the range of 450 - 1000 mm / s.

[0053] The quality of the obtained samples was determined by qualitative and quantitative metallography. These polished samples were analyzed with an inverted metallurgical microscope on the uncoated surface using standard techniques for the microstructure.

[0054] To determine the strength and thermal conductivity characteristics, the sample blanks were melted. The melted sample blanks were machined according to GOST 1497 - 84. The thermal conductivity was determined using the laser flash method with an LFA 467 apparatus. The tensile tests were carried out according to GOST 1497 - 84.

[0055] After aging at 300 °C for 1 hour, the samples were analyzed. The results are shown in Table 2.

[0056]

Table 2

[0057] This material is characterized in that, compared with the prototype, its thermal conductivity increases by 23% and its tensile strength increases by 41%.

[0058] The aluminum powder material with the proposed chemical composition has increased thermal conductivity, tensile strength and yield strength compared with the prototype.

[0059] Example 2 Aluminum alloy powders with the chemical compositions shown in Table 3 were prepared using the process described in Example 1. These alloys had different ratios of silicon, iron and magnesium.

[0060] [Table 3]

[0061] To fabricate the samples, an EOS M290 SLM unit was used. The as-fused samples (cylinders 80 mm in length and 12 mm in diameter) were machined into samples for tensile tests according to GOST 1497-84 and for thermal conductivity tests. The thermal conductivity was determined for circular samples using the laser flash method with an LFA 467 apparatus. The tensile tests were carried out according to GOST 1497-84. The samples were analyzed after aging at 300 °C for 45 minutes.

[0062] Table 4 shows the results of tensile tests according to GOST 1497-84 for samples with the chemical compositions according to Table 3 after heat treatment, and the results of thermal conductivity analysis before and after heat treatment.

[0063] [Table 4]

[0064] Therefore, the aluminum powder material having the proposed chemical composition has increased thermal conductivity, tensile strength, and yield strength compared to the prototype.

[0065] Mg 2 Si and Al 3 The formation of Zr dispersoids and multi-component inclusions based on iron, aluminum, and silicon improved the strength characteristics of the alloy. Heat treatment (aging) by reducing the solid solution concentration with the formation of small round inclusions enabled an increase in thermal conductivity. However, Si < Mg * 6.5 + Fe * At 5, Si ≧ Mg * 6.5 + Fe * Compared to the alloy having the chemical composition shown in Table 1 corresponding to 5, the properties are low because of the high Mg and Fe contents present in the aluminum matrix.

[0066] Therefore, the present invention proposed provides improved strength and thermal conductivity characteristics of an aluminum alloy for producing parts using additional techniques while maintaining high elongation.

Claims

1. An aluminum powder material for additive manufacturing of a product having improved strength and thermal conductivity characteristics while maintaining high elongation, with the following composition ratios (by weight): 2.00 to 5.00 silicon; 0.10 to 0.50 iron; 0.10 to 0.80 magnesium; 0.10 to 0.40 zirconium; Up to 0.02 copper; Up to 0.02 manganese; Up to 0.02 titanium; The balance being aluminum and inevitable impurities, containing silicon, iron, magnesium and zirconium, wherein the ratios of silicon, iron and magnesium in the alloy correspond to the condition Si ≥ Mg * 6.5 + Fe * 5, an aluminum powder material.

2. A product additively manufactured using the aluminum powder material according to Claim 1, the product 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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