Aluminum alloy for selective laser melting and method for manufacturing the same

Abstract

The application discloses a kind of aluminum alloy for selective laser melting forming and preparation method thereof, belong to aluminum alloy material and additive manufacturing technical field.The aluminum alloy of the present application comprises by mass percentage: Mg 3.8~5.2%, Zn 3.8~5.2%, Cu 0.5~1.0%, Ti 0.4~1.6%, C 0.1~0.4%, the balance is Al.Its preparation method includes: using Al-5Ti-1C intermediate alloy and other raw materials are melted into ingot, is atomized by vacuum, then it is printed by selective laser melting, finally it is solid solution and aging treatment.The application is introduced by Al-5Ti-1C intermediate alloy by component control and by submicron level TiC particle cooperates grain refinement, inhibits thermal crack, the yield strength of obtained alloy is greater than or equal to 480MPa, tensile strength is greater than or equal to 550MPa, elongation is greater than or equal to 10%, low in cost, suitable for additive manufacturing.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials and additive manufacturing technology, and in particular to an aluminum alloy for selective laser melting forming and its preparation method. Background Technology

[0002] Additive manufacturing (also known as 3D printing), especially selective laser melting (SLM) technology, has provided a new approach for the integrated manufacturing of complex structural metal parts. In the field of aluminum alloys, additive manufacturing materials are mainly divided into two categories: one is low-cost alloys represented by Al-Si and Al-Mg-Si systems, but the strength of their formed parts is generally low, with a yield strength usually below 300MPa, making it difficult to meet the requirements of load-bearing structural parts; the other is high-strength and high-toughness aluminum alloys containing high-cost alloying elements such as scandium (Sc) or erbium (Er), represented by Al-Mg-Mn-Sc-Zr and Al-Cu-Sc-Zr. Although they can achieve high strength, the high price of elements such as Sc and Er (usually with a content of more than 0.5%) leads to a sharp increase in material costs, which seriously limits the large-scale application of 3D printed high-strength aluminum alloys in the civilian industrial field.

[0003] Al-Zn-Mg-Cu alloys (such as 7075 alloy) are traditional high-strength and high-toughness wrought aluminum alloys with relatively low cost. However, their wide solidification range makes them highly susceptible to hot cracking during the rapid solidification process of SLM (Solid Melting Melting), hindering their direct application. Existing technologies attempt to improve their resistance to hot cracking by adding ceramic nanoparticles such as TiN and TiC and refining the grain size through mechanical mixing methods such as ball milling and ultrasonic vibration. However, this method has significant drawbacks: the nanoparticles are prone to agglomeration, severely impairing the alloy's plasticity; simultaneously, the mixing process is inefficient, making stable, mass production difficult.

[0004] Therefore, developing a low-cost aluminum alloy material with no tendency to thermal cracking, high strength and good plasticity for selective laser melting forming and its preparation method is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The main objective of this invention is to provide an aluminum alloy for selective laser melting forming and its preparation method, so as to solve the technical problems of insufficient strength of low-cost aluminum alloys and high cost of high-strength aluminum alloys in the prior art.

[0006] To achieve the above objectives, the present invention provides an aluminum alloy for selective laser melting forming, wherein the aluminum alloy comprises the following components by mass percentage: Mg 3.8%~5.2%, Zn 3.8%~5.2%, Cu 0.5%~1.0%, Ti 0.4%~1.6%, C 0.1%~0.4%, Fe ≤0.3%, Si ≤0.3%, with the balance being Al and unavoidable impurities.

[0007] In some embodiments of the present invention, the microstructure of the aluminum alloy is an equiaxed fine-grained structure.

[0008] In some embodiments of the present invention, the aluminum alloy has a yield strength ≥480MPa, a tensile strength ≥550MPa, and an elongation after fracture ≥10%.

[0009] This invention also provides a method for preparing aluminum alloys for selective laser melting forming, comprising the following steps: Ingot: According to the composition of the aluminum alloy described in claim 1, pure Mg, pure Zn, pure Cu, pure Al and Al-5Ti-1C master alloy are weighed as raw materials, the pure Al is melted under the first temperature condition, and then the pure Zn, pure Cu, pure Mg and Al-5Ti-1C master alloy are added in sequence, mixed and melted, allowed to stand, slag and gas are removed and then cast and solidified to obtain an ingot; Powdering: The ingot is powdered to obtain spherical powder; Printing: The spherical powder is printed using a selective laser melting process; Heat treatment: The printed workpiece is subjected to solution treatment and aging treatment to obtain aluminum alloy.

[0010] In some embodiments of the present invention, the TiC particles in the Al-5Ti-1C master alloy are at the submicron level; The Al-5Ti-1C master alloy contains 1% C by mass and 5% Ti by mass.

[0011] In some embodiments of the present invention, the first temperature is 720°C-750°C; And / or, the particle size of the spherical powder is 15μm~53μm.

[0012] In some embodiments of the present invention, the powder preparation step employs a vacuum atomization process.

[0013] In some embodiments of the present invention, in the vacuum atomization process, the atomizing gas is at least one of argon and nitrogen, and the atomization pressure is 3MPa to 6MPa.

[0014] In some embodiments of the present invention, the printing parameters are: laser power 300W~330W, scanning speed 800mm / s~1200mm / s, layer thickness 0.02mm~0.04mm, and overlap 0.08mm~0.12mm.

[0015] In some embodiments of the present invention, the solution treatment temperature is 480℃~500℃, and the holding time is 2~3 hours; the aging treatment temperature is 120℃~150℃, and the holding time is 6~12 hours.

[0016] The beneficial effects that this invention can achieve are: This invention reduces the solidification range of the Al-Zn-Mg-Cu alloy system by precisely controlling the contents of Mg, Zn, and Cu, thereby significantly reducing its tendency to hot crack during selective laser melting and providing a basis for solving the cracking problem of high-strength aluminum alloys in additive manufacturing.

[0017] This invention uses an Al-5Ti-1C master alloy as the source for introducing TiC ceramic particles, replacing the existing method of mechanically incorporating nanoparticles. The in-situ self-generated TiC particles in the Al-5Ti-1C master alloy are small, reaching submicron size, and uniformly distributed without agglomeration. During selective laser melting, these TiC particles act as efficient nucleation sites, significantly refining the alloy grain size and forming a microstructure dominated by equiaxed fine grains. This further suppresses the generation of hot cracks and simultaneously improves the alloy's strength and plasticity.

[0018] Compared to Al-3Ti-0.2C or Al-5Ti-0.2C master alloys, the Al-5Ti-1C master alloy selected in this invention has a higher carbon content (Ti:C mass ratio of approximately 5:1), resulting in a greater number and better morphology of TiC particles formed internally, which can achieve better grain refinement under the ultrafast solidification conditions unique to additive manufacturing.

[0019] The aluminum alloy of this invention contains no expensive elements such as Sc and Er, and TiC is introduced through an intermediate alloy. The process is simple and easy to mass-produce, resulting in significantly lower material costs compared to additive manufacturing aluminum alloys containing Sc / Er. Furthermore, after optimized heat treatment, the aluminum alloy exhibits a yield strength ≥480MPa, tensile strength ≥550MPa, and elongation ≥10%, achieving an excellent balance between strength, plasticity, and cost. This makes it suitable for manufacturing lightweight structural components in civilian applications such as automotive and aerospace. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0021] Figure 1 A metallographic photograph of the Al-5Ti-1C master alloy used in this invention; Figure 2 This is a microscopic morphology diagram of TiC particles in the Al-5Ti-1C master alloy used in this invention; Figure 3 A metallographic photograph of the aluminum alloy in Embodiment 1 of the present invention; Figure 4 This is another metallographic photograph of the aluminum alloy in Embodiment 1 of the present invention; Figure 5 This is another metallographic photograph of the aluminum alloy in Embodiment 1 of the present invention; Figure 6 This is a metallographic photograph of the aluminum alloy in Comparative Example 1 of the present invention.

[0022] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0025] In this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this invention.

[0026] This invention provides an aluminum alloy for selective laser melting forming. The aluminum alloy comprises the following components by mass percentage: Mg 3.8%~5.2%, Zn 3.8%~5.2%, Cu 0.5%~1.0%, Ti 0.4%~1.6%, C 0.1%~0.4%, Fe≤0.3%, Si≤0.3%, with the balance being Al and unavoidable impurities.

[0027] Specifically, Mg can be 3.8%, 4.0%, 4.2%, 4.5%, 4.8%, 5.0%, 5.2%, etc.; Zn can be 3.8%, 4.0%, 4.2%, 4.5%, 4.8%, 5.0%, 5.2%, etc.; Cu can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc.; Ti can be 0.4%, 0.6%, 0.8%, 1.0%, 1.2%, 1.4%, 1.6%, etc.; C can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, etc.; Fe can be ≤0.3%, for example 0.3%, 0.2%, 0.1%, 0.05%, etc.; Si can be ≤0.3%, for example 0.3%, 0.2%, 0.1%, 0.05%, etc.

[0028] In some embodiments, the microstructure of the aluminum alloy is dominated by equiaxed fine grains.

[0029] In some embodiments, the aluminum alloy has a yield strength ≥480MPa, a tensile strength ≥550MPa, and an elongation after fracture ≥10%.

[0030] This invention also provides a method for preparing a high-strength aluminum alloy for selective laser melting forming, comprising the following steps: Ingot: Weigh pure Mg, pure Zn, pure Cu, pure Al and Al-5Ti-1C master alloy as raw materials according to the above aluminum alloy composition. Melt pure Al under the first temperature condition, and then add pure Zn, pure Cu, pure Mg and Al-5Ti-1C master alloy in sequence. Mix and melt, let stand, remove slag and gas, and then pour and solidify to obtain an ingot. Powdering: Powdering ingots to obtain spherical powder; Printing: Spherical powder is printed using a selective laser melting process; Heat treatment: The printed workpiece is subjected to solution treatment and aging treatment to obtain aluminum alloy.

[0031] This invention reduces the solidification range of the Al-Zn-Mg-Cu alloy system by precisely controlling the contents of Mg, Zn, and Cu, thereby significantly reducing its tendency to hot crack during selective laser melting and providing a basis for solving the cracking problem of high-strength aluminum alloys in additive manufacturing.

[0032] This invention uses an Al-5Ti-1C master alloy as the source for introducing TiC ceramic particles, replacing the existing method of mechanically incorporating nanoparticles. The in-situ self-generated TiC particles in the Al-5Ti-1C master alloy are small, reaching submicron size, and uniformly distributed without agglomeration. During selective laser melting, these TiC particles act as efficient nucleation sites, significantly refining the alloy grain size and forming a microstructure dominated by equiaxed fine grains. This further suppresses the generation of hot cracks and simultaneously improves the alloy's strength and plasticity.

[0033] Compared to Al-3Ti-0.2C or Al-5Ti-0.2C master alloys, the Al-5Ti-1C master alloy selected in this invention has a higher carbon content (Ti:C mass ratio of approximately 5:1), resulting in a greater number and better morphology of TiC particles formed internally, which can achieve better grain refinement under the ultrafast solidification conditions unique to additive manufacturing.

[0034] In the ingot melting process, the Al-5Ti-1C master alloy is a key raw material. Unlike the Al-3Ti-0.2C or Al-5Ti-0.2C master alloys, the Al-5Ti-1C master alloy used in this invention has a C mass percentage of 1% and a Ti mass percentage of 5%. The TiC particles formed in situ inside the Al-5Ti-1C master alloy are submicron in size, with regular morphology and uniform distribution. These TiC particles are retained in the subsequent powder preparation and printing processes, and act as nucleation cores during selective laser melting, resulting in a better grain refinement effect and forming a microstructure dominated by equiaxed fine grains. This further suppresses the generation of hot cracks and simultaneously improves the strength and plasticity of the alloy.

[0035] In some embodiments, the first temperature is 720°C to 750°C, and may be 720°C, 725°C, 730°C, 735°C, 740°C, 745°C, 750°C, etc.

[0036] In some embodiments, the powder preparation step employs a vacuum atomization process.

[0037] In some embodiments, the atomizing gas is at least one of argon and nitrogen.

[0038] In some embodiments, the atomization pressure is 3MPa~6MPa, which can be 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5MPa, 5.5MPa, 6MPa, etc.

[0039] In some embodiments, the collected spherical powder particles have a diameter of 15 μm to 53 μm.

[0040] In some embodiments, the parameters for the printing step are: laser power 300W~330W, scanning speed 800mm / s~1200mm / s, layer thickness 0.02mm~0.04mm, and overlap 0.08mm~0.12mm.

[0041] For example, the laser power is 300W, 310W, 320W or 330W, the scanning speed is 800mm / s, 1000mm / s or 1200mm / s, the layer thickness is 0.02mm, 0.03mm or 0.04mm, and the overlap is 0.08mm, 0.1mm or 0.12mm.

[0042] In some embodiments, during the heat treatment step, the solution treatment temperature is 480°C to 500°C, and the temperature is maintained for 2 to 3 hours.

[0043] In some embodiments, the aging treatment temperature is 120℃~150℃, and the temperature is maintained for 6~12 hours.

[0044] The preparation method of this invention introduces TiC particles into alloy powder through chemical metallurgy, rather than mechanical mixing, fundamentally avoiding the problem of nanoparticle agglomeration and ensuring the stability of batch preparation and the maintenance of alloy plasticity. Simultaneously, by optimizing the printing and heat treatment processes, the reinforcing phases of the alloy (such as MgZn2) are fully precipitated, achieving an optimal balance between strength and plasticity.

[0045] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0046] Example 1 This embodiment provides an aluminum alloy for selective laser melting forming. The composition of the aluminum alloy by mass percentage is: Mg 5.2%, Zn 4.0%, Cu 1.0%, Ti 1.2%, C 0.3%, Fe ≤0.3%, Si ≤0.3%, with the balance being Al.

[0047] The preparation method is as follows: Ingot preparation: According to the above composition, take pure Mg, pure Zn, pure Cu, pure Al, and Al-5Ti-1C master alloy (the mass percentage of Ti in Al-5Ti-1C master alloy is 5%, and the mass percentage of C is 1%). Add pure Al to a crucible and heat to 740℃ to melt. Then, add pure Zn, pure Cu, pure Mg, and Al-5Ti-1C master alloy in sequence, stir until completely melted, let stand, remove slag and degas, and pour into a mold at 740℃ to solidify, obtaining an ingot.

[0048] Powder preparation: The above-mentioned ingots are powdered using a vacuum atomization process. The atomizing gas is high-purity argon, the atomization pressure is 4.5 MPa, and spherical powder with a particle size range of 15~53 μm is collected.

[0049] Printing: Selective laser melting equipment is used for printing. The process parameters are: laser power 320W, scanning speed 1000mm / s, powder layer thickness 0.03mm, and overlap (scanning distance) 0.1mm.

[0050] Heat treatment: After printing, solution treatment is performed at 490℃ for 2 hours. After solution treatment, water quenching is performed, followed by aging treatment at 130℃ for 8 hours. After heat treatment, the aluminum alloy is cooled to room temperature.

[0051] Example 2 In this embodiment, the same Al-5Ti-1C master alloy and preparation process as in Example 1 were used to prepare the aluminum alloy. The composition of the obtained aluminum alloy by mass percentage is: Mg 3.9%, Zn 5.0%, Cu 1.0%, Ti 0.8%, C 0.2%, Fe ≤0.3%, Si ≤0.3%, with the balance being Al.

[0052] Example 3 In this embodiment, the same Al-5Ti-1C master alloy and preparation process as in Example 1 were used to prepare the aluminum alloy. The composition of the obtained aluminum alloy by mass percentage is: Mg 4.5%, Zn 4.1%, Cu 0.8%, Ti 1.6%, C 0.4%, Fe ≤0.3%, Si ≤0.3%, with the balance being Al.

[0053] Comparative Example 1 Comparative Example 1: An aluminum alloy was prepared using the same method as in Example 1, but without adding Al-5Ti-1C master alloy during ingot melting. The composition of the resulting aluminum alloy by mass percentage was: Mg 4.6%, Zn 4.1%, Cu 0.9%, with the balance being Al, and it contained no Ti or C.

[0054] Comparative Example 2 Comparative Example 2 prepared an aluminum alloy according to the preparation method of Example 1, but Al-5Ti-0.2C intermediate alloy was used instead of Al-5Ti-1C intermediate during the preparation process. The composition of the obtained aluminum alloy by mass percentage was Mg 5.2%, Zn 4.0%, Cu 1.1%, Ti 1.2%, C 0.05%, Fe ≤0.3%, Si ≤0.3%, and the balance was Al.

[0055] Comparative Example 3 Comparative Example 3 prepared an aluminum alloy using the same method as in Example 1, but the composition of the prepared aluminum alloy by mass percentage was: Mg 4.8%, Zn 4.3%, Cu 0.9%, Ti 2.4%, C 0.6%, Fe ≤0.3%, Si ≤0.3%, with the balance being Al.

[0056] Performance testing 1. Morphological observation The Al-5Ti-1C master alloy was observed using a metallographic microscope and a scanning electron microscope. The results are shown in the figure. Figure 1 and Figure 2 .in Figure 1 Metallographic photograph, Figure 2 This image shows the microstructure of TiC particles under a scanning electron microscope. Figure 1 It can be seen that a large number of fine granular phases are dispersed in the Al-5Ti-1C master alloy; Figure 2 It can be seen that these TiC particles are submicron in size, with regular shape, uniform distribution, and no aggregation.

[0057] The aluminum alloy obtained in Example 1 was observed using a metallographic microscope, and images were taken at scale bars of 100 μm, 50 μm, and 400 μm. Figure 3 , Figure 4 and Figure 5 . Figures 3 to 5 All studies showed that the aluminum alloy of Example 1 had a dense microstructure, no hot cracks, and equiaxed fine grains.

[0058] The aluminum alloy obtained in Comparative Example 1 was observed using a metallographic microscope, and metallographic photographs were taken at a scale bar of 400 μm. Figure 6 Numerous microcracks are visible, and the grains are coarse and columnar.

[0059] 2. Mechanical property testing According to GB / T 228.1-2010 standard, the yield strength, tensile strength and elongation after fracture of the aluminum alloys in the above embodiments and comparative examples were tested, and the results are shown in Table 1.

[0060] Table 1

[0061] As can be seen from Table 1, Examples 1 to 3 all achieved an excellent combination of properties, including yield strength ≥483MPa, tensile strength ≥555MPa, and elongation ≥10%, and the printed parts were free of thermal cracks.

[0062] Comparative Example 1, without the addition of TiC, had an elongation of only 5.4%. Figure 6 The presence of numerous cracks indicates that adjusting the composition alone is insufficient to suppress cracking.

[0063] Comparative Example 2 used an Al-5Ti-0.2C master alloy with insufficient C content, and its elongation (4.8%) was significantly lower than that of Example 1 (12.5%).

[0064] In Comparative Example 3, the Ti and C content exceeded the scope of this invention. Although the strength was comparable to that of Example 3, the elongation dropped sharply to 1.3%, indicating that excessive TiC particles severely impaired plasticity.

[0065] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. An aluminum alloy for selective laser melting forming, characterized in that, The aluminum alloy comprises the following components by mass percentage: Mg 3.8%~5.2%, Zn 3.8%~5.2%, Cu 0.5%~1.0%, Ti 0.4%~1.6%, C 0.1%~0.4%, Fe≤0.3%, Si≤0.3%, with the balance being Al and unavoidable impurities.

2. The aluminum alloy for selective laser melting forming according to claim 1, characterized in that, The microstructure of the aluminum alloy is an equiaxed fine-grained structure.

3. The aluminum alloy for selective laser melting forming according to claim 1, characterized in that, The aluminum alloy has a yield strength ≥480MPa, a tensile strength ≥550MPa, and an elongation after fracture ≥10%.

4. A method for preparing an aluminum alloy for selective laser melting forming, characterized in that, Includes the following steps: Ingot: Pure Mg, pure Zn, pure Cu, pure Al and Al-5Ti-1C master alloy are weighed as raw materials according to the composition of the aluminum alloy according to any one of claims 1 to 3. The pure Al is melted under a first temperature condition, and then the pure Zn, pure Cu, pure Mg and Al-5Ti-1C master alloy are added in sequence, mixed and melted, allowed to stand, slag and gas are removed and then cast and solidified to obtain an ingot; Powdering: The ingot is powdered to obtain spherical powder; Printing: The spherical powder is printed using a selective laser melting process; Heat treatment: The printed workpiece is subjected to solution treatment and aging treatment to obtain aluminum alloy.

5. The method for preparing aluminum alloy for selective laser melting forming according to claim 4, characterized in that, The TiC particles in the Al-5Ti-1C master alloy are at the submicron level; The Al-5Ti-1C master alloy contains 1% C by mass and 5% Ti by mass.

6. The method for preparing aluminum alloy for selective laser melting forming according to claim 4, characterized in that, The first temperature is 720℃-750℃; And / or, the particle size of the spherical powder is 15μm~53μm.

7. The method for preparing aluminum alloy for selective laser melting forming according to claim 4, characterized in that, The powder preparation step employs a vacuum atomization process.

8. The method for preparing aluminum alloy for selective laser melting forming according to claim 7, characterized in that, In the vacuum atomization process, the atomizing gas is at least one of argon and nitrogen, and the atomization pressure is 3MPa~6MPa.

9. The method for preparing aluminum alloy for selective laser melting forming according to claim 4, characterized in that, The printing parameters are: laser power 300W~330W, scanning speed 800mm / s~1200mm / s, layer thickness 0.02mm~0.04mm, and overlap 0.08mm~0.12mm.

10. The method for preparing aluminum alloy for selective laser melting forming according to claim 4, characterized in that, The solution treatment temperature is 480℃~500℃, and the holding time is 2~3 hours; the aging treatment temperature is 120℃~150℃, and the holding time is 6~12 hours.

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