Additive manufacturing aluminum alloy with high formability, high strength and heat resistance

Abstract

The invention provides a high-formability, high-strength and heat-resistant additive manufacturing aluminum alloy, and relates to the field of aluminum alloy additive manufacturing. The aluminum alloy is prepared from, by mass, 4.5%-6.5% of Zn, 1.5%-3.0% of Mg, 1.0%-2.0% of Cu, 1.0%-3.0% of Ti, 1.0%-3.0% of Nb, 0.15%-0.3% of Cr, 0.1%-1.0% of Fe, 0.05%-0.5% of Si, 0.05%-0.5% of Mn and the balance aluminum. Compared with the addition of elemental Ti / Ni / Nb / Ta elements or particles, by adding the alloy powder containing Ti and Nb at the same time, more precipitated phases can be separated out in the additive-manufactured aluminum alloy, and a stronger solid solution strengthening effect is generated, so that the strength of the additive-manufactured aluminum alloy can be greatly improved, the strength of the additive-manufactured aluminum alloy can be compared favorably with the strength of aluminum alloys such as 7075 / 7050 / 2024 and the like which are cast and forged traditionally, and the additive-manufactured aluminum alloy can be widely applied to the field of aluminum alloy casting and forging. In addition, the high-temperature performance of the alloy is more excellent.

Description

Technical Field

[0001] The present invention relates to the field of aluminum alloy additive manufacturing, and in particular to an aluminum alloy for additive manufacturing with high formability, high strength and heat resistance. Background Art

[0002] High-strength aluminum alloys are widely used in aviation, aerospace, automobile and other fields due to their low density, high specific strength and other performance characteristics. Additive manufacturing can produce arbitrarily complex parts and components due to its excellent near-net forming ability, and is expected to promote the application of high-strength aluminum alloys in many fields. However, the molten pool formed by metal additive manufacturing often has a steep thermal gradient and an ultra-fast cooling rate, which makes it easy to form coarse columnar crystals and huge internal stresses inside the material during the solidification process. This makes materials such as high-temperature alloys, intermetallic compounds and high-strength aluminum alloys (such as 7075, 7050 and 2024) prone to crack formation during the additive manufacturing process, showing extremely low formability. The presence of columnar crystals also leads to severe anisotropy of mechanical properties and performance instability in the material.

[0003] Adding single elements or particles such as Zr, Sc, Ti, Ni, Ta, and Nb to high-strength aluminum alloys such as 7075 can promote the formation of Al3X precipitation phase (X=Zr / Sc / Ti / Ni / Ta / Nb) in the solidification process of the alloy. This type of precipitation phase has a high lattice matching degree with the α-Al matrix, and can act as a strong nucleating agent to promote the nucleation of grains during the solidification process, which helps to promote the transformation of columnar crystals to equiaxed crystals and the refinement of grains, and effectively inhibit the cracking problem of additively manufactured high-strength aluminum alloys. However, the strength of 7075 or 2024 modified by single Ti / Ni / Ta / Nb elements or particles after additive manufacturing is low, and the yield strength and tensile strength are lower than those of 7075 or 2024 aluminum alloys prepared by traditional casting and forging processes, which greatly limits the application of such additively manufactured aluminum alloys. In addition, due to their high melting points, elements such as Ta and Nb can only be added to high-strength aluminum alloys in the form of ultrafine particles (particle size of several hundred nanometers to 1-2 microns), and special powder mixing equipment, such as horizontal ball mills and electrostatic assembly methods, are required to add them to aluminum alloys, which is costly. If Ta or Nb is added by pre-alloying + atomization, such as Ta / Nb being added to aluminum alloys as a single metal block, it will lead to problems such as difficulty in smelting and difficulty in accurately controlling the alloy composition.

[0004] Recently, some new additively manufactured aluminum alloys designed with Sc and Zr elements not only have high formability, but also show strength comparable to or even better than high-strength aluminum alloys prepared by traditional manufacturing methods. However, the cost of such additively manufactured high-strength aluminum alloys is very high, and the price of its powder is 3-4 times that of 7075 powder materials. Moreover, after additive manufacturing, such high-strength aluminum alloys are prone to form a heterogeneous structure of columnar crystals and equiaxed crystals, or coarse equiaxed crystals and fine equiaxed crystals, and their performance and quality stability are low. In addition, the strength of such Zr / Sc / Ti / Ni / Ta / Nb-modified additively manufactured aluminum alloys decreases rapidly at high temperatures, showing low heat resistance. Therefore, it is imperative to develop low-cost additively manufactured aluminum alloys with high formability and high strength over a wide temperature range. Summary of the invention

[0005] The present invention aims to address the problem that high-strength aluminum alloys such as 2xxx series and 7xxx series aluminum alloys are prone to forming cracks and coarse columnar crystals during laser additive manufacturing, as well as the problem that such alloys modified with single elements / particles have low strength after additive manufacturing. The present invention aims to design a new aluminum alloy that can form a completely equiaxed crystal structure after additive manufacturing and has high strength over a wide temperature range, while ensuring that the material price of the alloy is similar to that of existing 2xxx series and 7xxx series aluminum alloy powders.

[0006] The present invention provides an additively manufactured aluminum alloy with high formability, high strength and heat resistance, wherein the mass percentage of each element is: Zn 4.5-6.5%, Mg 1.5-3.0%, Cu 1.0-2.0%, Ti 1.0-3.0%, Nb 1.0-3.0%, Cr 0.15-0.3%, Fe 0.1-1.0%, Si 0.05-0.5%, Mn 0.05-0.5%, and the balance is aluminum.

[0007] Preferably, in the aluminum alloy, the mass percentage of Ti and Nb is 4.0-6.0% in total.

[0008] Preferably, during the preparation of the aluminum alloy, the two elements Ti and Nb are added to the aluminum alloy in the form of an alloy, rather than in the form of metal single particles or single elements. It can be added to the aluminum alloy powder in the form of an alloy powder containing Ti and Nb, or prepared in the form of a bulk Ti and Nb alloy with a bulk aluminum alloy metal smelting + atomization method. The added bulk alloy or alloy powder contains the two elements Ti and Nb to promote the solidification process to form high-melting point Al3 (Ti, Nb) particles, and utilizes its crystallographic properties that are highly matched with α-Al to promote nucleation and equiaxed grain refinement, and the formed precipitate phase can also play a strengthening role. And because such precipitate phases can maintain high stability at high temperatures, it helps to improve the heat resistance of aluminum alloys.

[0009] Preferably, in the added Ti and Nb-containing alloy (including alloy block and alloy powder, which will not be described in detail below), the atomic percentage of Ti is 52-54 at.%, the atomic percentage of Nb is 24-26 at.%, and the oxygen content is ≤1000ppm. The particle size of the alloy powder is 15-53 μm. Compared with the single-substance ultrafine nanoparticles of Ti and Nb, the alloy powder has a lower cost.

[0010] Preferably, the added Ti and Nb-containing alloy may also contain one or more of Zn, Mg, Cu, Cr, Fe, Si, Mn, and Al elements, which can also be dissolved into the matrix or promote the formation of more new precipitation phases, thereby further strengthening the prepared aluminum alloy.

[0011] The present invention also provides a method for preparing the aluminum alloy, firstly, by mixing powders, adding Ti and Nb alloy powders with similar particle sizes to aluminum alloy powders to prevent Nb / Ti from being added in the form of single-substance nanoparticles, which helps to keep the powder price low. Secondly, 7075 or 7050 aluminum alloy ingots are mixed with Ti and Nb alloy ingots in proportion, wherein the Ti and Nb alloys account for 4wt.% to 6wt.%, and then the metals are melted and fused by arc melting or electromagnetic induction melting to form new alloy ingots, and then the alloy ingots are melted and powdered by gas atomization / plasma atomization / rotating electrode method.

[0012] Furthermore, the aluminum alloy is prepared by the following method:

[0013] S1. preparing aluminum alloy powder;

[0014] S2. Use selective laser melting equipment, selective electron beam melting equipment or laser direct deposition equipment to melt and prepare samples.

[0015] Preferably, in S1, aluminum alloy powder and alloy powder containing Ti and Nb are mixed in an inert gas by a metal powder mixer to obtain aluminum alloy powder, the mixing speed is 25 to 35 rpm, and the mixing time is 1 to 3 hours. Further preferably, the particle size of the aluminum alloy powder and the alloy powder containing Ti and Nb are both 15 to 53 μm. The alloy powder containing Ti and Nb accounts for 4wt.% to 6wt.%, the atomic percentage of Ti in the alloy powder is 52 to 54 at.%, and the atomic percentage of Nb is 24 to 26 at.%.

[0016] Preferably, in S1, the metal raw materials are mixed in proportion, wherein Zn accounts for 5-5.5wt.%, Mg accounts for 2-2.5wt.%, Cu accounts for 1-1.5wt.%, Ti accounts for 2-2.5wt.%, Nb accounts for 2-2.5wt.%, Cr accounts for 0.2-0.5wt.%, Fe accounts for 0.1-0.5wt.%, Si accounts for 0.05wt.%, Mn accounts for 0.05-0.1wt.%, Ti and Nb are added in the form of alloy ingots, and other elements are added in the form of single or alloy ingots. Pre-alloyed rods are prepared by arc melting or electromagnetic induction melting and casting processes, and then aluminum alloy powder is prepared by inert gas atomization, plasma atomization or rotating electrode method.

[0017] Preferably, in S2, the parameters for melting and preparing samples by using a selective laser melting device or a selective electron beam melting device are: power 300 W, scanning rate 950 mm / s, line spacing 80 μm, and layer thickness 30 μm.

[0018] Preferably, in S2, the parameters for melting and sample preparation using laser direct deposition equipment are: power 1000 W, scanning speed 950 mm / min, and powder feeding rate 6 g / min.

[0019] In one embodiment of the present invention, a powder mixing method is used to prepare powder, comprising the following steps: using a metal powder mixer to mix aluminum alloy powder with equivalent particle size (15-53 μm) and Ti and Nb alloy powder in proportion in argon / nitrogen / helium, wherein the Ti and Nb alloy powder accounts for 4wt.%~6wt.%, the atomic percentage of Ti in the alloy powder is 52-54at.%, and the atomic percentage of Nb is 24-26at.%, the mixing speed is 25-35 rpm, and the mixing time is 1-3 hours.

[0020] Then, the mixed powder with a particle size of 15 to 53 μm was melted and sampled using a selective laser melting device or a selective electron beam melting device under the process conditions of 300 W power, 950 mm / s scanning rate, 80 μm line spacing, and 30 μm layer thickness. Alternatively, the mixed powder with a particle size of 53 to 105 μm was melted and sampled using a laser direct deposition device under the process conditions of 1000 W power, 950 mm / min scanning rate, and 6 g / min powder feeding rate.

[0021] The applicant has found that if a single Nb powder particle with a particle size comparable to that of the aluminum alloy powder is added, the Nb particles cannot be melted during the 3D printing process and can only be added in the form of nano Nb particles, which requires special powder mixing equipment such as a horizontal ball mill or an electrostatic assembly facility for mixing. However, nano Nb particles are expensive, and the strength of nano Nb particles added alone after printing is low. If an alloy powder containing Ti and Nb is added, it can be added in a particle size comparable to that of the aluminum alloy powder, and ordinary powder mixing equipment can be used, which can reduce production costs and obtain high strength and high heat resistance.

[0022] In another embodiment of the present invention, pre-alloying powder making is adopted, comprising the following steps: adding metal raw materials (proportionally, Zn accounts for 5-5.5wt.%, Mg accounts for 2-2.5wt.%, Cu accounts for 1-1.5wt.%, Ti accounts for 2-2.5wt.%, Nb accounts for 2-2.5wt.%, Cr accounts for 0.2-0.5wt.%, Fe accounts for 0.1-0.5wt.%, Si accounts for 0.05wt.%, Mn accounts for 0.05-0.1wt.%, Ti and Nb are added in the form of alloy ingots, and other elements are added in the form of single substance or alloy ingots. Pre-alloyed rods are prepared by arc melting or electromagnetic induction melting (melting temperature range 1500-2500°C) and casting, and then pre-alloyed powder is prepared by inert gas atomization method, plasma atomization method or rotating electrode method.

[0023] Then, the alloy powder with a particle size of 15 to 53 μm is melted and sampled using a selective laser melting device or a selective electron beam device under the process conditions of 300 W power, 950 mm / s scanning rate, 80 μm line spacing, and 30 μm layer thickness. Alternatively, the alloy powder with a particle size of 53 to 105 μm is melted and sampled using a laser direct deposition device under the process conditions of 1000 W power, 950 mm / min scanning rate, and 6 g / min powder feeding rate.

[0024] The applicant has found that, during the alloy smelting process, if Nb blocks are directly added, it is not easy to melt and needs to be smelted at a higher temperature, which easily leads to the volatilization of low melting point elements such as Zn, Mg, and Al, and the alloy composition is difficult to control. However, the alloy ingot containing Ti and Nb with lower melting points does not have the above problems, and the alloy composition is easy to control.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] In the prior art, Nb is added in the form of extremely expensive nanoparticles and requires special equipment (such as a horizontal ball mill or an electrostatic assembly method). Unlike the prior art, the present invention adds Ti and Nb alloy powders with a particle size comparable to that of the aluminum alloy powder and mixes them using ordinary powder mixing technology, which will ensure that the price of the synthesized powder is comparable to that of 2xxx series and 7xxx series aluminum alloy powders.

[0027] Compared with adding single Ti / Ni / Nb / Ta elements or particles, adding alloy powders containing both Ti and Nb can precipitate more precipitation phases in the additively manufactured aluminum alloy and produce a stronger solid solution strengthening effect, thus greatly improving the strength of the additively manufactured aluminum alloy, making it comparable to the strength of traditional cast and forged 7075 / 7050 / 2024 aluminum alloys. Compared with adding expensive Nb / Ta nanopowder particles or adding rare metals such as Sc / Zr, adding Ti and Nb alloy powder particles with a particle size comparable to that of aluminum alloy powder particles (lower in cost) or directly preparing new aluminum alloy powders through pre-alloying + gas atomization methods will make the synthesized powder cost much lower.

[0028] In addition, compared with aluminum alloys modified by adding single Ti / Ni / Nb / Ta / Sc / Zr elements or particles, aluminum alloys modified by adding Ti and Nb alloy powder particles have higher microstructural thermal stability and heat resistance. These new high-strength, heat-resistant and low-cost aluminum alloys that are expected to promote additive manufacturing have been widely used in aviation, aerospace, automobile and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 The scanning electron microscope (SEM) images of the aluminum alloy prepared in Example 1, wherein (a) is magnified 5000 times, and (b) is magnified 10000 times.

[0031] Figure 2 These are transmission electron microscope (TEM) images of the aluminum alloy prepared in Example 1, wherein (a) is a transmission electron microscope image of the grain structure and Al3(Ti,Nb) precipitate phase, (b) is a transmission electron microscope image of the MgZn2 precipitate phase and its diffraction pattern, (c) is a transmission electron microscope image of the strip-shaped Al7Cu2Fe precipitate phase, and (d) is an electron diffraction pattern of the strip-shaped Al7Cu2Fe precipitate phase.

[0032] Figure 3The figures are grain boundary test images of the aluminum alloy prepared in Example 1, wherein (a) is a transmission electron microscope image of a certain grain and grain boundary area for composition analysis, (b) is an energy spectrum surface scanning distribution image of Mg in the selected area, (c) is an energy spectrum surface scanning distribution image of Cu in the selected area, (d) is an energy spectrum surface scanning distribution image of Zn in the selected area, (e) is a transmission electron microscope image of the grain boundary precipitation phase, (f) is an electron diffraction pattern of the grain boundary precipitation phase MgCu2, (g) is an electron diffraction pattern of the grain boundary quasicrystal phase, and (h) is a high-resolution transmission electron image of the grain boundary quasicrystal phase and its Fourier transform pattern.

[0033] Figure 4 The tensile curves of the aluminum alloy prepared in Example 1 at room temperature and high temperature.

[0034] Figure 5 The mechanical properties of the aluminum alloy prepared in Example 1 (marked with an asterisk) are compared with those of other additively manufactured aluminum alloys or forged aluminum alloys, where (a) is the room temperature mechanical property and (b) is the high temperature mechanical property.

[0035] Figure 6 These are test pictures of the aluminum alloy prepared in Example 2, where (a) is a SEM picture, (b) is a TEM picture, and (c) is a room temperature tensile curve.

[0036] Figure 7 These are test images of the aluminum alloy of Comparative Example 1, where (a)-(c) are SEM images and (d) is a tensile curve. DETAILED DESCRIPTION

[0037] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] A metal powder mixer was used to mix aluminum alloy powder with comparable particle size (15-53 μm) and Ti and Nb alloy powder in proportion in argon / nitrogen / helium, wherein the Ti and Nb alloy powder accounted for 5 wt.%, the atomic percentage of Ti in the alloy powder was 53 at.%, and the atomic percentage of Nb was 25 at.%. The mixing speed was 28 rpm and the mixing time was 3 hours.

[0040] Then, a selective laser melting device is used to melt and sample the mixed powder with a particle size of 15 to 53 μm under the process conditions of 300 W power, 950 mm / s scanning rate, 80 μm line spacing, and 30 μm layer thickness to obtain the additively manufactured aluminum alloy.

[0041] Figure 1This is a SEM image of the aluminum alloy prepared in Example 1, used to observe its microstructure. The aluminum alloy is modified by alloy powder containing Ti and Nb to be 7075 alloy. (a) is magnified 5000 times, and (b) is magnified 10000 times. It can be seen that the prepared alloy is completely composed of fine equiaxed crystal structure, and the grain size is between several hundred nanometers and 1μm. The alloy is completely free of cracks.

[0042] Figure 2 The transmission electron microscope (TEM) images of the aluminum alloy prepared in Example 1 are used to observe the internal precipitation phase of its grains, wherein (a) is a transmission electron microscope image of the grain structure and Al3(Ti, Nb) precipitation phase, (b) is a transmission electron microscope image of the MgZn2 precipitation phase and its diffraction pattern, (c) is a transmission electron microscope image of the strip-shaped Al7Cu2Fe precipitation phase, and (d) is an electron diffraction pattern of the strip-shaped Al7Cu2Fe precipitation phase. It can be seen that there are many precipitation phases, including relatively coarse Al3(Ti, Nb) particles (playing a nucleation role), very fine MgZn2 precipitation phases, and strip-shaped Al7Cu2Fe precipitation phases.

[0043] Figure 3 The grain boundary test diagram of the aluminum alloy prepared in Example 1 is used to observe its grain boundary component segregation and precipitation phase, wherein (a) is a transmission electron microscope image of a certain grain and grain boundary area for component analysis, (b) is an energy spectrum surface scanning distribution diagram of Mg in the selected area, (c) is an energy spectrum surface scanning distribution diagram of Cu in the selected area, (d) is an energy spectrum surface scanning distribution diagram of Zn in the selected area, (e) is a transmission electron microscope image of the grain boundary precipitation phase, (f) is an electron diffraction pattern of the grain boundary precipitation phase MgCu2, (g) is an electron diffraction pattern of the grain boundary quasicrystalline phase, and (h) is a high-resolution transmission electron image of the grain boundary quasicrystalline phase and its Fourier transform pattern. Figure 3 (a)-(d) show that there is obvious component segregation at the alloy grain boundary, mainly Mg, Cu, and Zn segregation. Figure 3 (e)-(h) It can be seen that the component segregation at the grain boundary also promotes the formation of some precipitate phases, including MgCu2, Al2CuMg and some quasi-crystalline phases. The existence of these uniformly distributed precipitate phases can effectively hinder the movement of dislocations during the deformation of the alloy, thereby strengthening the alloy and promoting the alloy to obtain high strength. In addition, these precipitate phases such as Al3(Ti,Nb) have a high melting point (>1500°C) and can maintain high stability at high temperatures, which helps to improve the high temperature strength and heat resistance of the alloy.

[0044] Figure 4The tensile curves of the aluminum alloy prepared in Example 1 at room temperature and high temperature. It can be seen that the additively manufactured aluminum alloy has a yield strength of 470MPa at room temperature, which is comparable to the strength level of the forged 7075 aluminum alloy. At 200°C, the alloy still retains a yield strength of 375MPa; at 300°C, the additively manufactured aluminum alloy still has a yield strength of 275MPa. It can be seen that the alloy exhibits high strength in a wide temperature range.

[0045] Figure 5 The mechanical properties of the aluminum alloy prepared in Example 1 (marked with an asterisk) are compared with those of other additively manufactured aluminum alloys or forged aluminum alloys, where (a) is the room temperature mechanical property and (b) is the high temperature mechanical property. Figure 5 (a) It can be seen that compared with the additively manufactured 7075 or 2024 aluminum alloy modified with single elements (such as Ti / Nb / Zr / Si / Er), the additively manufactured 7075 aluminum alloy modified with Ti and Nb alloy provided by the present invention exhibits high room temperature yield strength, and its yield strength is equivalent to that of the forged 7075 aluminum alloy. Figure 5 (b) It can be seen that the room temperature yield strength of the additively manufactured aluminum alloy provided by the present invention is slightly lower than that of some new additively manufactured aluminum alloys containing Sc and Zr, but its strength under high temperature conditions is much higher than these alloys. In fact, the high temperature strength of the additively manufactured aluminum alloy provided by the present invention is higher than that of most current additively manufactured aluminum alloys, and is also much higher than that of the forged 7075 aluminum alloy. It can be seen that the additively manufactured aluminum alloy provided by the present invention has excellent mechanical properties in a wide temperature range.

[0046] Example 2

[0047] The metal raw materials are mixed in proportion, wherein Zn accounts for 5.36wt.%, Mg accounts for 2.2wt.%, Cu accounts for 1.33wt.%, Ti accounts for 2.33wt.%, Nb accounts for 2.13wt.%, Cr accounts for 0.21wt.%, Fe accounts for 0.3wt.%, Si accounts for 0.05wt.%, Mn accounts for 0.08wt.%, and the balance is aluminum. Among them, Ti and Nb are added in the form of alloy ingots, accounting for 5wt.% of the total amount of added elements, and other elements are added in the form of 7075 alloy ingots. The above metal raw materials are arc melted at a melting temperature of 2500℃, cast to obtain pre-alloyed rods, and then aluminum alloy powder is obtained by inert gas atomization. Finally, the sample is prepared using a selective laser melting device, and the sample preparation parameters are: power 300W, scanning rate 950mm / s, line spacing 80μm, layer thickness 30μm.

[0048] Figure 6The test images of the aluminum alloy prepared in Example 2, wherein (a) is a SEM image of the aluminum alloy prepared in Example 2, with a magnification of 5000 times, for observing its microstructure. It can be seen that the aluminum alloy prepared in this example is composed of equiaxed crystals like the aluminum alloy prepared in Example 1, and the grain size is also between several hundred nanometers and 1 μm. The alloy is completely free of cracks.

[0049] (b) is a transmission electron microscope (TEM) image of the aluminum alloy prepared in Example 2, which is used to observe the internal precipitation phase of its grains. Like the aluminum alloy prepared in Example 1, the aluminum alloy prepared in this example also contains precipitation phases such as Al3(Ti, Nb), MgZn2 and Al7Cu2Fe.

[0050] (c) is the room temperature tensile curve of the aluminum alloy prepared in Example 2. It can be seen from the figure that the alloy also has a yield strength of 470 MPa at room temperature, which is equivalent to the strength of the aluminum alloy prepared in Example 1. It can be seen that the aluminum alloy prepared in Example 2 is consistent with that in Example 1 in terms of microstructure and mechanical properties, and both schemes can prepare high-strength aluminum alloys.

[0051] Comparative Example 1

[0052] Using a horizontal ball mill, aluminum alloy powder with a particle size of 15 to 53 μm and elemental Nb particles with a particle size of 100 nm to 2 μm were mixed in argon gas, with a steel ball: powder mass ratio of 5:1, a steel ball diameter of 5 mm, a horizontal ball mill shaft speed of 500 rpm, ball milling for 10 minutes, and the subsequent selective laser melting step was the same as in Example 1 to obtain an additively manufactured aluminum alloy.

[0053] Figure 7 The test images of the aluminum alloy of comparative example 1, where (a)-(c) are SEM images, indicating that Nb particles have been added / assembled to the surface of the 7075 aluminum alloy, and the white particles on the surface are nano Nb particles. (d) is the tensile curve of the aluminum alloy of comparative example 1, indicating that although the 7075-Nb alloy melted by selective laser has overcome the cracking problem, its tensile yield strength is too low (<290MPa), which is much lower than the strength level of the 7075 alloy prepared by traditional casting and forging (yield strength can reach 450MPa).

[0054] Therefore, if the elemental Nb / Ta is added to the aluminum alloy in the form of nanoparticles through special equipment such as a horizontal ball mill or electrostatic assembly equipment, the powder cost and manufacturing cost will be high, and the yield strength cannot meet the requirements of high-strength application scenarios.

[0055] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A high-formability, high-strength and heat-resistant additively manufactured aluminum alloy, characterized in that: The mass percentage of each element in the aluminum alloy is: Zn 4.5-6.5%, Mg 1.5-3.0%, Cu 1.0-2.0%, Ti 1.0-3.0%, Nb 1.0-3.0%, Cr0.15-0.3%, Fe 0.1-1.0%, Si 0.05-0.5%, Mn 0.05-0.5%, and the balance is aluminum.

2. The high-formability, high-strength and heat-resistant additively manufactured aluminum alloy according to claim 1, characterized in that: In the aluminum alloy, the mass percentage of Ti and Nb is 4.0-6.0% in total.

3. The high-formability, high-strength and heat-resistant additively manufactured aluminum alloy according to claim 2, characterized in that: During the preparation of the aluminum alloy, the two elements Ti and Nb are added to the aluminum alloy in the form of an alloy, rather than being added in the form of metal single particles or a single element.

4. The high-formability, high-strength and heat-resistant additively manufactured aluminum alloy according to claim 3, characterized in that: In the added Ti- and Nb-containing alloy, the atomic percentage of Ti is 52 to 54 at.%, the atomic percentage of Nb is 24 to 26 at.%, and the oxygen content is ≤1000 ppm.

5. The high-formability, high-strength and heat-resistant additively manufactured aluminum alloy according to claim 4, characterized in that: The Ti and Nb-containing alloy is added in the form of alloy powder or alloy block, and preferably the particle size of the alloy powder is 15-53 μm.

6. The high-formability, high-strength and heat-resistant additively manufactured aluminum alloy according to any one of claims 3 to 5, characterized in that: The added Ti and Nb-containing alloy also contains one or more of the elements Zn, Mg, Cu, Cr, Fe, Si, Mn, and Al.

7. The method for preparing the aluminum alloy according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. preparing aluminum alloy powder; S2. Use selective laser melting equipment, selective electron beam melting equipment or laser direct deposition equipment to melt and prepare samples.

8. The method for preparing the aluminum alloy according to claim 7, characterized in that: In S1, aluminum alloy powder and Ti and Nb alloy powder are mixed in an inert gas by a metal powder mixer to obtain aluminum alloy powder, the mixing speed is 25 to 35 rpm, and the mixing time is 1 to 3 hours; And / or, the particle sizes of the aluminum alloy powder and the alloy powder containing Ti and Nb are both 15 to 53 μm.

9. The method for preparing the aluminum alloy according to claim 7, characterized in that: In S1, the metal raw materials are mixed in proportion, wherein Zn accounts for 5-5.5wt.%, Mg accounts for 2-2.5wt.%, Cu accounts for 1-1.5wt.%, Ti accounts for 2-2.5wt.%, Nb accounts for 2-2.5wt.%, Cr accounts for 0.2-0.5wt.%, Fe accounts for 0.1-0.5wt.%, Si accounts for 0.05wt.%, Mn accounts for 0.05-0.1wt.%, Ti and Nb are added in the form of alloy ingots, and other elements are added in the form of simple or alloy ingots. Pre-alloyed rods are prepared by arc melting or electromagnetic induction melting and casting processes, and then aluminum alloy powder is prepared by inert gas atomization, plasma atomization or rotating electrode method.

10. The method for preparing the aluminum alloy according to claim 7, characterized in that: In S2, the parameters for melting and preparing samples using a selective laser melting device or a selective electron beam melting device are: power 300 W, scanning rate 950 mm / s, line spacing 80 μm, and layer thickness 30 μm; And / or, in S2, the parameters of melting and sample preparation using laser direct deposition equipment are: power 1000 W, scanning speed 950 mm / min, powder feeding rate 6 g / min.

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