Aluminum-nickel alloy for manufacturing heat conducting part such as heat exchanger

Abstract

To provide an aluminum alloy suitable for additive manufacturing of a lightweight highly thermally conductive component for an aircraft, such as a heat exchanger.SOLUTION: The present invention relates to an alloy consisting of aluminum, nickel, scandium and optionally one, two or more further metals. In a first step, the powder of aluminum alloy according to the invention is produced by additive manufacturing (AM technology), such as laser melting in the Laser Powder Bed Fusion (L-PBF; Laser Powder Bed Fusion) process. Larger grains can grow epitaxially along a build direction thereby increasing the mobility of phonons and electrons along the build direction. With this, a higher thermal conductivity can be achieved. In a second step, a preliminary part is hardened by precipitation of secondary phases at 250°C to 400°C to form a hardened part. 3D printed lightweight parts with high thermal conductivity are obtained.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aluminum alloy. The present invention further relates to a method of additive manufacturing (AM) using the aluminum alloy, and to a manufactured part (or portion), preferably a heat transfer part (or portion), such as a heat exchanger for an aircraft.

[0002] It should be noted that throughout this disclosure, the expression "wt. %" means "percent by weight." [Background technology]

[0003] DE 10 2007 018 123 B4 discloses an aluminum-scandium (AlSc) alloy suitable for rapid prototyping processes, the mass fraction of scandium being 0.4% by weight or more.

[0004] EP 2 646 587 B1 discloses an aluminum-scandium-calcium (AlScCa) alloy, which is able to combine a lightweight structure due to low density with improved tensile strength.

[0005] German patent application 10 2020 131 823.5, which was unpublished at the filing date and does not constitute prior art according to Article 54(2) or (3) of the European Patent Convention (EPC), discloses an aluminum-scandium-titanium (AlScTi) alloy that has been modified for rapid heating and cooling, as demonstrated in additive manufacturing processes such as laser powder bed fusion (L-PBF). Summary of the Invention [Problem to be solved by the invention]

[0006] It is an object of the present invention to provide improved alloys having improved thermal and / or strength properties.

[0007] This object is achieved by the subject matter of the independent claims. Preferred embodiments are the subject matter of the dependent claims. [Means for solving the problem]

[0008] The present invention provides an aluminum (Al) alloy, Nickel (Ni) in a proportion of 0.1% to 5.5% by weight; The balance is Al and unavoidable impurities totaling less than 0.5 wt. %; Optionally, scandium (Sc) in a proportion of 0.1% to 3.0% by weight; optionally, at least one first additional alloying element suitable for complementing or substituting Sc, wherein the individual proportion of each first additional alloying element does not exceed 2.0 wt.% and the total proportion of the first additional alloying element does not exceed 3.0 wt.%; optionally at least one second additional alloying element selected from the group consisting of vanadium (V), niobium (Nb), chromium (Cr), molybdenum (Mo), silicon (Si), iron (Fe), and cobalt (Co), wherein the individual proportion of each second additional alloying element does not exceed 3.0 wt.%, preferably does not exceed 2.0 wt.%, and the total proportion of the second additional alloying elements does not exceed 3.0 wt.%; optionally, at least one third additional alloying element selected from the group consisting of magnesium (Mg), manganese (Mn), and calcium (Ca), wherein the individual proportion of each third additional alloying element does not exceed 2.0% by weight and the total proportion of the third additional alloying elements does not exceed 3.0% by weight. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferably, the proportion of Ni is 0.3 wt% to 5.5 wt%, more preferably 0.5 wt% to 5.5 wt%, more preferably 0.6 wt% to 5.5 wt%, more preferably 1.0 wt% to 5.5 wt%, more preferably 1.0 wt% to 5.5 wt%, more preferably greater than 2.0 wt% to 5.5 wt%, more preferably 2.1 wt% to 5.5 wt%, more preferably 2.5 wt% to 5.5 wt%, more preferably greater than 2.5 wt% to 5.5 wt%, more preferably 2.6 wt% to 5.5 wt%, more preferably 2.6 wt% to 5.0 wt%, and more preferably 2.6 wt% to 4.0 wt%.

[0010] Preferably, the proportion of Sc is 0.1 wt % to 1.5 wt %, more preferably 0.1 wt % to 1.0 wt %, more preferably 0.1 wt % to 0.8 wt %, more preferably 0.1 wt % to 0.7 wt %, more preferably 0.1 wt % to 0.7 wt %, 0.1 wt % to 0.60 wt %, more preferably 0.1 wt % to less than 0.55 wt %, and more preferably 0.1 wt % to 0.50 wt %.

[0011] Preferably, the first additional alloying element is selected from the group consisting of zirconium (Zr), tantalum (Ta), hafnium (Hf), yttrium (Y), and erbium (Er).

[0012] Preferably, the individual proportion of each first additional alloying element is 0.1 wt.% to 1.0 wt.%, more preferably 0.1 wt.% to 0.7 wt.%, more preferably 0.1 wt.% to 0.60 wt.%, more preferably 0.1-0.55 wt.%, more preferably 0.1 wt.% to 0.50 wt.%.

[0013] Preferably, Zr is selected, the individual proportion of Zr being less than 0.3% by weight, more preferably less than 0.2% by weight.

[0014] Preferably, the alloy does not contain Zr. Preferably, the alloy does not contain Ti. Preferably, the alloy does not contain Mg. Preferably, the alloy does not contain Ca.

[0015] Preferably, the alloy is made of Al, Ni, Sc, and Ca, with the proportion of Ca being 0.5% to 5% by weight.

[0016] Preferably, the alloy is made of Al, Ni, Sc, and Cr, with the proportion of Cr being 0.2% to 3% by weight, preferably 0.5% to 2.7% by weight.

[0017] Preferably, the alloy is made of Al, Ni, Sc, and Zr, and the proportion of Zr is 0.1% to 0.5% by weight, preferably 0.1% to 0.2% by weight.

[0018] Preferably, the alloy is made of Al, Ni, Sc, Zr, and Ca, with the Zr content being 0.1% to 0.5% by weight, preferably 0.1% to 0.2% by weight, and the Ca content being 0.5% to 5% by weight.

[0019] Preferably, the alloy consists of Al, Ni, Sc, Zr, and Cr, with the Zr content being 0.1 to 0.5% by weight, preferably 0.1 to 0.2% by weight, and the Cr content being 0.2 to 3% by weight, preferably 0.5 to 2.7% by weight.

[0020] The present invention provides an additive manufacturing method for manufacturing a spare part, preferably a thermally conductive spare part such as a spare heat exchanger, the method comprising the following steps a) to c): a) Forming a powder layer from a powder layer comprising or consisting of a metal powder made from the preferred alloys described above. b) The powder bed and / or powder layer is heated globally to a temperature of 200°C to below the melting point of the metal powder, preferably between 200°C and 400°C, while the powder layer is locally melted, followed immediately by solidification. c) If the preliminary part is not finished, add another layer of powder on top of the previous layer of powder and repeat steps b) and c) until the preliminary part is finished.

[0021] Preferably, the powder bed comprises a build plate made of a monocrystalline material having a lattice constant that allows epitaxial growth, and in step a) the first powder layer is deposited on the build plate. Preferably, the monocrystalline material is an aluminum alloy.

[0022] Preferably, the build plate is made from the preferred alloy described above. Preferably, the build plate is a single crystal. Preferably, the single crystal is <100> The direction is oriented so that it is parallel to the direction in which the powder layer is built up.

[0023] Preferably, in step b), the overall heating of the powder bed is achieved by heating the build plate.

[0024] Preferably, the method further comprises: d) After the preliminary part is finished, it is heated to a temperature of 200°C to 450°C, preferably 210°C to 300°C, more preferably 225°C to 275°C, to convert the preliminary part into a hardened part by precipitation hardening.

[0025] The present invention provides a heat transfer component or heat exchanger, preferably for an aircraft, which comprises a part made from the preferred alloy described above or which is obtainable by the preferred method described above.

[0026] The present invention deals with improved manufacturing techniques for a particular newly developed Al alloy (Al-xNi-ySc; where x and y define the weight percentage of each alloying element) in the field of additive manufacturing, with particular focus on improved thermal properties in heat exchanger applications, while at the same time providing sufficient strength levels. Each alloy and manufacturing technique allows for lightweight structures for thermal applications, especially in future mobility scenarios such as zero-emission aircraft and urban air mobility aircraft.

[0027] Currently, additive manufacturing (AM) is a manufacturing technique aimed at suppressing epitaxial grain growth. This allows isotropic material properties to evolve from non-epitaxial microstructures. On the other hand, coarse grains, which essentially form quasi-monocrystalline materials with a low grain boundary density, are advantageous for better thermal properties. Grain boundaries typically pose obstacles to so-called phonons (lattice vibrations described as quasi-particles in the quantum mechanical approach). The present invention aims to reduce these obstacles to quasi-particles and improve the thermal conductivity of materials. Adjacent to grain boundaries, solid solution hardening and incoherent precipitates can cause scattering of phonons and electrons, thereby hindering their movement.

[0028] As a result, new alloys that can resolve this conflict of objectives are needed. The objective of this disclosure is to enable the emergence of quasi-single crystalline fractions and promote epitaxial grain growth along at least one direction, e.g., for heat exchanger applications, by combining the advantages of each with the design freedom of additive manufacturing (AM) processes.

[0029] High thermal conductivity is important for heat exchanger materials, especially for high-performance heat exchangers relevant for future mobility concepts. This material property can be strongly influenced by the material's microstructure, ultimately allowing for lighter constructions compared to conventional constructions made of, for example, copper.

[0030] The additive manufacturing (AM) processes envisaged in this application, such as Laser Powder Bed Fusion (L-PBF), are to some extent comparable and equivalent to the zone melting techniques for producing Si single crystals. Preferably, the substrate plate used is <100> It is a single crystal Al alloy to stimulate favorable crystal growth directions such as the .

[0031] The adapted Al alloy preferably contains only alloying elements that do not exhibit high constitutional supercooling during solidification (e.g., Al-1Ni-0.7Sc) to suppress grain refinement, which promotes exceptional grain growth along the production direction and allows for a high-strength alloy with a quasi-single crystal microstructure.

[0032] Global heating allows for directional solidification, supporting the creation of elongated quasicrystalline grains along the build direction. Contrary to conventional belief, the grain growth restriction factor (GRF) is used in the opposite way. In other words, according to the present invention, it is preferable to grow grains epitaxially along a specific direction. Therefore, elements with low GRF are preferred. Elements that function as grain refiners are used only to the extent necessary for other advantageous properties, and excessive grain refinement is avoided.

[0033] Additionally, elements that may contribute to the strength of the alloy due to solid solution hardening should be avoided.

[0034] The precipitation of primary, nano-sized coherent precipitates, such as Al3Ni and Al3Sc, should be avoided due to their grain-refining properties. Primary precipitates appear during solidification after initial heating.

[0035] Precipitation of secondary, nano-sized coherent precipitates, such as Al3Ni or Al3Sc, is preferred. Secondary precipitates are those that arise during heat treatment.

[0036] In general, Al-Ni alloys exhibit low GRF, which induces or at least enables epitaxial grain growth throughout the weld layer. Strength gains can be obtained due to the formation of coherent precipitates of Al3Ni, but the effect on electron or phonon mobility is relatively small. There is also little solid solubility. A small solidification temperature range is advantageous for avoiding hot cracking. Therefore, this alloy is particularly suitable for additive manufacturing (AM), which involves high heating and cooling rates associated with the process.

[0037] It is preferred to use Sc or its complements or substitutes to increase the alloy strength through precipitation hardening of nano-sized precipitates. [Example]

[0038] A) Manufacturing method of aluminum alloy <Example 1: Production of powder aluminum alloy> In an inert crucible, 0.5 wt. % Ni and 99.5 wt. % Al are melted. The melt may be homogenized before further processing.

[0039] The first part of the melt is poured into another inert crucible where it cools and solidifies. During cooling, a primary AlNi phase precipitates. The resulting material is ground to a powder suitable for selective laser melting in a powder bed.

[0040] A second portion of the melt is poured onto a rotating, water-cooled copper roll in a melt-spinning process. The melt is cooled at a rate of 1,000,000 K / s to form a strip. This ribbon is then cut into short flakes.

[0041] The alloy material resulting from either or both cooling processes is pulverized into a powder that can be used for selective laser melting in a powder bed.

[0042] Example 2: Preparation of powder aluminum alloys with different nickel contents The above process is repeated while increasing the Ni percentage to 0.6, 1.0, 2.1, 2.6, 3.0, 4.0, 5.0, and 5.45 wt%, respectively, and decreasing the Al percentage accordingly, preferably close to but less than 5.5 wt%, and decreasing the Al percentage accordingly.

[0043] Example 3: Production of powder aluminum alloy containing scandium as an additive element The process of Examples 1 or 2 is repeated by adding 0.6 wt%, 0.7 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, and 1.5 wt% additional Sc to the crucible, respectively, while keeping Ni constant and decreasing the percentage of Al accordingly.

[0044] Example 4: Preparation of powder aluminum alloys containing additional elements to complement or replace scandium The process of Examples 1, 2, or 3 is repeated by adding 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, and 0.5 wt% additional Zr to the crucible, respectively, while keeping the Ni content constant and, if applicable, the Sc content constant, and decreasing the proportion of Al as Zr increases. Typically, Ti can be added instead of or in addition to Zr. However, due to its grain-refining properties, it is preferred that the alloy be Ti-free.

[0045] Example 5: Production of powder aluminum alloy containing magnesium and / or calcium as additional elements The process of Examples 1, 2, 3, or 4 is repeated by adding 0.5 wt%, 1.0 wt%, 2.4 wt%, and 5.0 wt% additional Ca or Mg to the crucible, respectively, while keeping the Ni content constant and, if applicable, the Sc and Zr contents constant, and decreasing the proportion of Al as the Ca or Mg content increases.

[0046] Example 6: Production of powder aluminum alloys with various metal additions The process of Examples 1, 2, 3, 4, or 5 is repeated by adding to the crucible additional V, Nb, Cr, Mo, Si, Fe, Co, Ta, Hf, Y, or Er at 0.5 wt%, 1.4 wt%, 1.7 wt%, and 2.0 wt%, respectively, with the Ni content held constant, and the Sc and Zr contents, if applicable, held constant, and the Al percentage reduced accordingly.

[0047] B) Manufacturing methods for heat conducting parts and other components In either case, aluminum alloy powder from one of Examples 1-6 above is added to a system for additive manufacturing by selective laser melting (AM) to form a powder bed. The powder bed includes a build plate made of an aluminum alloy or a single crystal of aluminum from one of Examples 1-6 above. The single crystal is <100> The orientation is such that the direction is formed layer by layer.

[0048] The powder bed, specifically the build plate, is heated to a temperature of from 200°C to below the melting point of the metal powder, preferably from 200°C to 400°C.

[0049] The laser beam moves over the powder bed according to digital information, which may describe a heat exchanger or other heat transfer component, as the powder bed, including the build plate, is lowered in stages to apply a new layer of powder.

[0050] The alloy forms elongated quasicrystalline grains aligned in the build direction, i.e., perpendicular to the powder layer. The spot-molten aluminum alloy cools so quickly that the scandium, zirconium, and / or titanium are completely, substantially, or predominantly frozen in solid solution. This occurs regardless of the other composition of the aluminum alloy and regardless of whether the powder is produced by normal cooling or rapid cooling, e.g., at rates of 1,000,000 K / sec. After the scanning process is complete, the preliminary part (or section) is removed from the powder bed.

[0051] The preliminary component (or part) is heated to a temperature in the range of 200°C to 450°C, preferably in the range of 210°C to 300°C, and more preferably in the range of 225°C to 275°C, at which point precipitation of various AlX phases (X = Ni, Sc, Zr, or non-stoichiometric mixtures of any individual element) occurs. The precipitation of these phases increases the strength of the component (or part) but has only a relatively small effect on electron and phonon transport.

[0052] The present invention relates to an alloy consisting of aluminum, nickel, and scandium, or consisting of these metals and, optionally, one, two, or more additional metals. This aluminum alloy is suitable for additive manufacturing (AM) production of lightweight, highly thermally conductive aircraft components, such as heat exchangers. In a first step, powder of the aluminum alloy according to the present invention is produced by an additive manufacturing method, such as laser melting in a laser powder bed fusion (L-PBF) process. Large grains can grow epitaxially along the build direction, increasing the phonon and electron mobility along the build direction. This can lead to higher thermal conductivity. In a second step, the preliminary part is hardened by precipitating secondary phases at 250°C to 400°C to form a hardened part. A 3D-printed lightweight part with high thermal conductivity is obtained.

Claims

1. An aluminum (Al) alloy, i) nickel (Ni) in a proportion of 0.1% to 5.5% by weight; ii) the balance Al; and iii) unavoidable impurities totaling less than 0.5 wt. %; or An aluminum (Al) alloy comprising the above i) to iii) and at least one selected from the following iv) to vii): iv) Scandium (Sc) in a proportion of 0.1% to 3.0% by weight. v) At least one first additional alloying element suitable for supplementing or substituting for Sc, wherein the individual proportion of each first additional alloying element does not exceed 2.0 wt.% and the total proportion of the first additional alloying elements does not exceed 3.0 wt.%. vi) at least one second additional alloying element selected from the group consisting of vanadium (V), niobium (Nb), chromium (Cr), molybdenum (Mo), silicon (Si), iron (Fe), and cobalt (Co), wherein the individual proportion of each second additional alloying element does not exceed 3.0 wt.%, preferably does not exceed 2.0 wt.%, and the total proportion of the second additional alloying elements does not exceed 3.0 wt.%. vii) at least one third additional alloying element selected from the group consisting of magnesium (Mg), manganese (Mn), and calcium (Ca), wherein the individual proportion of each third additional alloying element does not exceed 2.0 wt.% and the total proportion of the third additional alloying elements does not exceed 3.0 wt.%.

2. 2. The aluminum (Al) alloy of claim 1, wherein the Ni percentage is 0.3 wt% to 5.5 wt%, 0.5 wt% to 5.5 wt%, 0.6 wt% to 5.5 wt%, 1.0 wt% to 5.5 wt%, greater than 2.0 wt% to 5.5 wt%, 2.1 wt% to 5.5 wt%, 2.5 wt% to 5.5 wt%, greater than 2.5 wt% to 5.5 wt%, 2.6 wt% to 5.5 wt%, 2.6 wt% to 5.0 wt%, or 2.6 wt% to 4.0 wt%.

3. 2. The aluminum (Al) alloy of claim 1, wherein the proportion of Sc is 0.1 wt% to 1.5 wt%, 0.1 wt% to 1.0 wt%, 0.1 wt% to 0.8 wt%, 0.1 wt% to 0.7 wt%, 0.1 wt% to 0.60 wt%, 0.1 wt% to less than 0.55 wt%, or 0.1 wt% to 0.50 wt%.

4. the alloy consists of Al, Ni, and Sc; The proportion of Ni is 0.3% to 5.5% by weight and the proportion of Sc is 0.1% to 1.5% by weight, or The proportion of Ni is 0.6% to 5.5% by weight and the proportion of Sc is 0.1% to 0.7% by weight, or The proportion of Ni is 1.0 wt% to 5.5 wt% and the proportion of Sc is 0.1 wt% to 0.7 wt%, or 3. The aluminum (Al) alloy according to claim 2, wherein the proportion of Ni is greater than 2.0 wt.% and up to 5.5 wt.% and the proportion of Sc is 0.1 wt.% to 0.7 wt.%.

5. 5. An aluminum (Al) alloy according to any one of claims 1 to 4, wherein the first additional alloying element is selected from the group consisting of zirconium (Zr), tantalum (Ta), hafnium (Hf), yttrium (Y), and erbium (Er).

6. 5. An aluminum (Al) alloy according to any one of claims 1 to 4, wherein the individual proportion of each first additional alloying element is 0.1 wt.% to 1.0 wt.%, 0.1 wt.% to 0.7 wt.%, 0.1 wt.% to 0.60 wt.%, 0.1 wt.% to 0.55 wt.%, or 0.1 wt.% to 0.50 wt.%.

7. 6. The aluminum (Al) alloy of claim 5, wherein Zr is selected and the individual proportion of Zr is less than 0.3 wt.%.

8. The aluminum (Al) alloy according to any one of claims 1 to 4, which does not contain Zr, Ti, Mg, and / or Ca.

9. consisting of Al, Ni, Sc, and Ca, with the proportion of Ca being 0.5% by weight to 5% by weight, or consisting of Al, Ni, Sc, and Cr, with the Cr content being 0.2 wt % to 3 wt %, or 0.5 wt % to 2.7 wt %, or consisting of Al, Ni, Sc, and Zr, with the proportion of Zr being 0.1 wt % to 1 wt %, or 0.1 wt % to 0.5 wt %, more preferably 0.1 wt % to 0.2 wt %, or consisting of Al, Ni, Sc, Zr, and Ca, wherein the Zr content is 0.1% to 0.5% by weight, or 0.1% to 0.2% by weight, and the Ca content is 0.5% to 5% by weight, or The aluminum (Al) alloy according to any one of claims 1 to 4, consisting of Al, Ni, Sc, Zr, and Cr, wherein the Zr ratio is 0.1 wt% to 0.5 wt%, or 0.1 wt% to 0.2 wt%, and the Cr ratio is 0.2 wt% to 3 wt%, or 0.5 wt% to 2.7 wt%.

10. An additive manufacturing method for producing a spare heat exchanger, a spare heat transfer part, or other spare part, comprising: a) forming a powder bed comprising or consisting of a metal powder made of an alloy according to any one of claims 1 to 4; b) heating the powder bed and / or powder layer generally to a temperature of 200°C to below the melting point of the metal powder, preferably from 200°C to 400°C, while locally melting the powder layer and immediately solidifying it; c) if the preliminary part is not finished, adding another layer of powder on top of the previous layer of powder and repeating steps b) and c) until the preliminary part is finished.

11. 11. The additive manufacturing method of claim 10, wherein the powder bed comprises a build plate made of a single crystal material having a lattice constant that allows epitaxial growth, and in step a) a first layer of powder is deposited on the build plate.

12. 12. The additive manufacturing method of claim 11, wherein the build plate is made from an alloy according to any one of claims 1 to 4.

13. 11. The additive manufacturing method of claim 10, wherein in step b), globally heating the powder bed is performed by heating the build plate.

14. d) after finishing the preliminary part, heating the preliminary part to a temperature of 200°C to 450°C, preferably 210°C to 300°C, more preferably 225°C to 275°C to transform the preliminary part into a hardened part by precipitation hardening.

15. A heat transfer component or heat exchanger for an aircraft or other device, comprising: A heat transfer component or heat exchanger, the heat transfer component or heat exchanger comprising a part made from an alloy according to any one of claims 1 to 4.

16. A method for manufacturing a heat conduction part or heat exchanger for an aircraft or other purpose, which is obtained by the additive manufacturing method described in claim 10.