A laser additive manufacturing method for aluminum / titanium alloy gradient structure

Abstract

The present invention discloses a laser additive manufacturing method for an aluminum / titanium alloy gradient structure, belonging to the field of laser additive manufacturing technology. The steps of the laser additive manufacturing method include: using TiNbVZr or TiNbV high-entropy alloy powder to prepare a high-entropy alloy transition layer on the surface of the titanium alloy through a laser additive manufacturing process, and then preparing an aluminum alloy layer on the surface of the high-entropy alloy transition layer through a laser additive manufacturing process. The present invention combines the optimization of the high-entropy alloy intermediate transition layer of two preferred compositions with laser additive manufacturing technology to prepare a high-performance aluminum / titanium alloy gradient structure, which can effectively solve the current problems of aluminum / titanium alloy interface cracking and low bonding strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser additive manufacturing, and in particular relates to a laser additive manufacturing method for an aluminum / titanium alloy gradient structure. Background Art

[0002] A gradient structure refers to the combination of two or more metal alloys with different chemical compositions and mechanical properties through a reasonable gradient transition, which is used to meet the service temperature and mechanical property requirements of different parts of the component under complex service conditions under actual application conditions, and to achieve the effects of reducing costs, reducing weight or improving performance by combining different materials. For example, the aluminum alloy / titanium gradient structure material used in the honeycomb sandwich of a certain type of wing connects the titanium alloy skin and the aluminum alloy internal skeleton together, which can not only reduce the weight of the structure but also improve the overall strength of the structure, ensuring a high vibration resistance limit and stability. The manufacturing principle of laser additive manufacturing technology, which is point-by-point and layer-by-layer forming, also provides a feasible way to prepare aluminum alloy / titanium alloy gradient structures.

[0003] However, the huge differences in the physical and chemical properties of titanium and aluminum make the preparation of aluminum / titanium gradient structure materials extremely difficult. In terms of physical properties, titanium and aluminum have huge differences in melting point, density, linear expansion coefficient, etc., which easily generate large residual stresses in the bonding area between the two, causing deformation and even cracking; in terms of chemical properties, titanium and aluminum are relatively active and easily produce intermetallic compounds, which makes it easy for defects such as cracks and holes to appear in the bonding area, seriously reducing the mechanical properties of the interface. Therefore, it is impossible to directly form aluminum alloys and titanium alloys into gradient materials using laser additive manufacturing technology. The current preparation method of aluminum alloy / titanium alloy gradient structures is mainly brazing, but the bonding strength is only about 10-30MPa.

[0004] As a new type of alloy, high-entropy alloys (HEAs) break away from the traditional alloying strategy of using a single element as the primary component in alloy material design. Instead, they employ an alloy system composed of three to five primary elements in equimolar or near-equimolar ratios. Each element is present in a high concentration in the HEAs and has a significant impact on the alloy's properties. Their high system mixing entropy enables superior properties that differ from those of traditional alloys. Leveraging HEAs' high mixing entropy, slow diffusion rates due to hysteretic diffusion, and high stability, HEAs favor the formation of solid solutions of Al and Ti rather than precipitation of intermetallic compounds, mitigating the physical property differences between aluminum and titanium alloys. This makes HEAs a promising candidate for intermediate transition layers in aluminum / titanium gradient structures. While HEAs have been reported as intermediate transition layers in aluminum / titanium gradient structures, further exploration of HEAs systems is needed to achieve optimal results when simultaneously dissolving high concentrations of Al and Ti. Summary of the Invention

[0005] The present invention aims to provide a laser additive manufacturing method for aluminum / titanium alloy gradient structures. By combining the optimization of the intermediate transition layer of two high-entropy alloys with laser additive manufacturing technology, a high-performance aluminum / titanium alloy gradient structure is produced, effectively addressing the current issues of aluminum / titanium alloy interface cracking and low bonding strength.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for manufacturing an aluminum / titanium alloy gradient structure by laser additive manufacturing, comprising the following steps:

[0008] A high entropy alloy transition layer is prepared on the surface of a titanium alloy using TiNbVZr or TiNbV high entropy alloy powder through a laser additive manufacturing process, and then an aluminum alloy layer is prepared on the surface of the high entropy alloy transition layer through a laser additive manufacturing process.

[0009] Preferably, the atomic ratio of Ti, Nb, V and Zr in the TiNbVZr high entropy alloy powder is 1:0.5-2:0.5-2:0.5-2, and the powder particle size range is 53-250 μm; the atomic ratio of Ti, Nb and V in the TiNbV high entropy alloy powder is 1:0.5-2:0.5-2, and the powder particle size range is 53-250 μm.

[0010] More preferably, the TiNbVZr high entropy alloy powder and the TiNbV high entropy alloy powder are dried at 120° C. for 2 hours before use.

[0011] Preferably, the titanium alloy is pretreated before laser additive manufacturing.

[0012] Preferably, the titanium alloy is an α-type, α+β-type or β-type titanium alloy, and the grades include but are not limited to TA2, TC4 or TC11.

[0013] Preferably, the height of the high entropy alloy transition layer is 1-4 mm.

[0014] Preferably, when preparing the high-entropy alloy transition layer, the process parameters of the laser additive manufacturing process are: laser beam diameter 3-6 mm, laser power 2-6 kW, scanning speed 500-1500 mm / min, single layer height 0.3-0.6 mm, overlap rate 30-50%, powder feeding rate 800-2000 g / h, and oxygen content less than 80 ppm.

[0015] Preferably, the particle size range of the aluminum alloy powder used in preparing the aluminum alloy layer is 53-250 μm.

[0016] More preferably, the material of the aluminum alloy powder includes but is not limited to ZL105A, AlSi10Mg, AlSi7Mg or 5A06 aluminum alloy.

[0017] More preferably, the aluminum alloy powder is dried at 120° C. for 2 hours before use.

[0018] Preferably, when preparing the aluminum alloy layer, the process parameters of the laser additive manufacturing process are: laser beam diameter 3-6 mm, laser power 2-6 kW, scanning speed 500-1500 mm / min, single layer height 0.3-0.6 mm, overlap rate 30-50%, powder feeding rate 500-1000 g / h, and oxygen content less than 80 ppm.

[0019] Preferably, an annealing step is further included after the aluminum alloy layer is prepared.

[0020] More preferably, the annealing treatment is performed at a temperature of 200-500° C., with a holding time of 1-6 hours, and air cooling or furnace cooling.

[0021] The beneficial technical effects of the present invention are as follows:

[0022] The laser additive manufacturing method for an aluminum alloy / titanium alloy gradient structure with an optimized high-entropy alloy transition layer of the present invention adopts TiNbV or TiNbVZr high-entropy alloy as an intermediate transition layer between aluminum and titanium alloys for the first time, thereby avoiding direct additive contact between the aluminum alloy and the titanium alloy. When TiNbV or TiNbVZr high-entropy alloy is used as a transition layer for additive connection between aluminum and titanium alloys, the diffusion rate of titanium atoms and aluminum atoms is reduced, the solid solubility in the alloy is increased, and the formation of TiAl-based brittle intermetallic compounds can be suppressed, thereby significantly improving the bonding strength at the aluminum alloy / titanium alloy interface.

[0023] Compared with traditional brazing and other methods that are more suitable for connecting regular plates, the present invention uses laser additive manufacturing to prepare aluminum alloy / titanium alloy gradient structures, which can give full play to the characteristics of laser additive manufacturing such as refinement and flexibility, greatly shorten the R&D cycle, reduce production costs, and fully meet the needs of high-performance integrated manufacturing of dissimilar metals.

[0024] The present invention uses TiNbV or TiNbVZr high entropy alloy as a transition layer for laser additive joining of aluminum and titanium alloys and achieves defect-free connection between the two. It can provide a new preparation idea for the connection of dissimilar metals such as titanium / steel, nickel / steel, and titanium / nickel, and can be promoted in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1Schematic diagram of the process for laser additive manufacturing of an optimized aluminum alloy / titanium alloy gradient structure for a high-entropy alloy transition layer in an embodiment of the present invention, wherein: 1 - laser cladding head; 2 - shielding gas input / output connector; 3 - powder feed nozzle; 4 - laser beam; 5 - laser additive manufacturing of a high-entropy alloy transition layer; 6 - titanium alloy substrate; 7 - laser additive manufacturing equipment workbench; 8 - laser additive manufacturing of an aluminum alloy layer.

[0026] Figure 2 This is a macroscopic physical image and a metallographic photograph of the bonding area of ​​the aluminum alloy / titanium alloy gradient structure specimen with optimized TiNbVZr high entropy alloy transition layer prepared in Example 1 of the present invention, wherein A is a macroscopic physical image and B is a metallographic photograph of the bonding area.

[0027] Figure 3 The macroscopic physical image and metallographic photograph of the bonding area of ​​the aluminum alloy / titanium alloy gradient structure specimen with optimized TiNbV high entropy alloy transition layer prepared in Example 2 of the present invention, wherein A is the macroscopic physical image and B is the metallographic photograph of the bonding area.

[0028] Figure 4 These are the macroscopic physical image and the metallographic photograph of the bonding area of ​​the aluminum alloy / titanium alloy gradient structure specimen prepared in Comparative Example 1 of the present invention, wherein A is the macroscopic physical image and B is the metallographic photograph of the bonding area.

[0029] Figure 5 This is a macroscopic physical image and a metallographic photograph of the bonding area of ​​the aluminum alloy / titanium alloy gradient structure specimen containing a CoCrFeMnNi high-entropy alloy transition layer prepared in Comparative Example 2 of the present invention, wherein A is a macroscopic physical image and B is a metallographic photograph of the bonding area.

[0030] Figure 6 These are the macroscopic physical image and metallographic photograph of the bonding area of ​​the aluminum alloy / titanium alloy gradient structure specimen containing the CoCrFeNi high entropy alloy transition layer prepared in Comparative Example 3 of the present invention, wherein A is the macroscopic physical image and B is the metallographic photograph of the bonding area. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0032] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

[0034] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0035] The schematic diagram of the process of laser additive manufacturing of the aluminum alloy / titanium alloy gradient structure with optimized high entropy alloy transition layer in the embodiment of the present invention is shown in FIG. Figure 1 , among which, 1-laser cladding head; 2-shielding gas input / output connector; 3-powder feeding nozzle; 4-laser beam; 5-laser additive manufacturing high entropy alloy transition layer; 6-titanium alloy substrate; 7-laser additive manufacturing equipment workbench; 8-laser additive manufacturing aluminum alloy layer.

[0036] The aluminum alloy / titanium alloy gradient structure test pieces of the embodiment of the present invention and the comparative example are all manufactured by laser additive manufacturing method, using LMD-V type laser forming manufacturing system (part of the structure in the system is shown in FIG. Figure 1 ), the specific operation of the system is: first, the titanium alloy substrate 6 is fixed on the workbench 7 of the laser additive manufacturing system, when the powder feeding nozzle 3 feeds high entropy alloy powder, the laser beam 4 is turned on through the laser cladding head 1, so that the high entropy alloy powder is deposited on the titanium alloy substrate, when the high entropy alloy intermediate transition layer is formed to 1-4mm, the light beam 4 is closed, the powder feeding nozzle 3 feeds aluminum alloy powder, and then the laser beam 4 is turned on to deposit the aluminum alloy part, and the specific forming height can be adjusted according to the use requirements of the component. During the above whole process, inert gas is fed in real time through the protective gas input / output connector 2, and the oxygen content is always kept below 80ppm until the preparation of the gradient structure material is completed (in comparative example 1, if high entropy alloy powder is not used, the step of feeding high entropy alloy powder can be omitted).

[0037] Example 1

[0038] Laser additive manufacturing of aluminum alloy / titanium alloy gradient structure specimens with optimized TiNbVZr high entropy alloy transition layer:

[0039] S1. Prepare titanium alloy substrate, high entropy alloy and aluminum alloy powder: the titanium alloy substrate is TC11 titanium alloy substrate (nominal chemical composition Ti-6.5Al-3.5Mo-1.5Zr-0.3Si), with an outer dimension of 150mm*120mm*40mm, the high entropy alloy powder composition is TiNbVZr (equiatomic ratio), the particle size is 75-250μm, the aluminum alloy grade is ZL105A (Al-5Si-1Cu-Mg), and the particle size is 75-250μm.

[0040] S2. Processing of the titanium alloy substrate, high-entropy alloy, and aluminum alloy powders: The titanium alloy substrate was sanded with sandpaper until a metallic luster was revealed to remove the surface oxide layer. The substrate was then wiped with alcohol to remove surface oil and dirt, and dried. The two powders used for molding were dried in a vacuum oven at 120°C for 2 hours to remove moisture and improve powder fluidity during the molding process.

[0041] S3. Write the laser additive manufacturing process file and import it into the control system of the equipment: the files for the high entropy alloy transition layer and the additive manufacturing aluminum alloy area are written separately, and the corresponding process parameters are set to facilitate switching and adjustment during the molding process. The process parameters for depositing the high entropy alloy transition layer are: laser beam diameter of 6mm, scanning speed of 1000mm / min, single layer lifting height of 0.5mm, laser power of 3.5KW, powder delivery rate of the powder feeder of 1000g / h, and overlap rate of 40%. The process parameters for depositing the aluminum alloy area are: laser beam diameter of 6mm, scanning speed of 1000mm / min, single layer lifting height of 0.5mm, laser power of 3KW, powder delivery rate of the powder feeder of 700g / h, and overlap rate of 40%.

[0042] S4. Fix the prepared titanium alloy substrate on the machine tool workbench, introduce inert gas Ar gas to maintain the oxygen content in the entire molding environment below 80ppm, and adjust the angle of the powder feeding nozzle so that the delivered powder and the laser beam converge at the same point on the substrate.

[0043] S5. Select the process parameter file for forming a high-entropy alloy transition layer in the control system, turn on the laser, and form a TiNbVZr high-entropy alloy transition layer region on the TC11 titanium alloy substrate with a height of 2 mm.

[0044] S6. Switch the process parameter file of the aluminum alloy forming area in the control system, and form and prepare ZL105A aluminum alloy on the TiNbVZr high entropy alloy transition layer with a height of 20 mm.

[0045] S7. After the preparation is completed and cooled to room temperature, an aluminum alloy / titanium alloy gradient structure with an optimized TiNbVZr high entropy alloy transition layer is obtained, and a stress relief annealing heat treatment of 500°C / 6h / AC is performed. The specimen is cooled in the furnace to obtain an aluminum alloy / titanium alloy gradient structure specimen with an optimized TiNbVZr high entropy alloy transition layer.

[0046] The macroscopic physical picture of the aluminum alloy / titanium alloy gradient structure specimen with optimized TiNbVZr high entropy alloy transition layer prepared in Example 1 and the metallographic photograph of the bonding area are shown in Figure 2 , where A is the macroscopic physical picture and B is the metallographic photograph of the bonding area.

[0047] Figure 2 It shows that the aluminum alloy / titanium alloy gradient structure in the specimen has achieved good bonding both macroscopically and microscopically, with no defects such as cracks, holes, and unfused components found.

[0048] Example 2

[0049] Laser additive manufacturing of aluminum alloy / titanium alloy gradient structure specimens with optimized TiNbV high entropy alloy transition layer:

[0050] Compared with Example 1, the only difference is that the equiatomic ratio TiNbV high entropy alloy powder (powder particle size is 75-250μm) is used to replace the equiatomic ratio TiNbVZr high entropy alloy powder to prepare an aluminum alloy / titanium alloy gradient structure specimen with optimized TiNbV high entropy alloy transition layer.

[0051] The macroscopic physical picture of the aluminum alloy / titanium alloy gradient structure specimen with optimized TiNbV high entropy alloy transition layer prepared in Example 2 and the metallographic photograph of the bonding area are shown in Figure 3 , where A is the macroscopic physical picture and B is the metallographic photograph of the bonding area.

[0052] Figure 3 It shows that the aluminum alloy / titanium alloy gradient structure in the specimen has achieved good bonding both macroscopically and microscopically, with no defects such as cracks, holes, and unfused components found.

[0053] Comparative Example 1

[0054] Laser additive manufacturing of aluminum alloy / titanium alloy gradient structure specimens:

[0055] Compared with Example 1, the only difference is that the preparation of the high entropy alloy transition layer is omitted, and an aluminum alloy / titanium alloy gradient structure specimen is prepared.

[0056] The macroscopic physical picture of the aluminum alloy / titanium alloy gradient structure specimen prepared in comparative example 1 and the metallographic photograph of the bonding area are shown in Figure 4 , where A is the macroscopic physical picture and B is the metallographic photograph of the bonding area.

[0057] Figure 4 It shows that due to the huge differences in the physical and chemical properties of aluminum and titanium, there are obvious defects such as cracks and holes in the bonding area.

[0058] Comparative Example 2

[0059] Laser additive manufacturing of aluminum alloy / titanium alloy gradient structure specimens containing CoCrFeMnNi high entropy alloy transition layer:

[0060] Compared with Example 1, the only difference is that the equiatomic ratio TiNbVZr high entropy alloy powder is replaced by equiatomic ratio CoCrFeMnNi high entropy alloy powder (powder particle size is 75-250μm) to prepare an aluminum alloy / titanium alloy gradient structure specimen containing a CoCrFeMnNi high entropy alloy transition layer.

[0061] Macroscopic physical image and metallographic photograph of the bonding area of ​​the aluminum alloy / titanium alloy gradient structure specimen containing the CoCrFeMnNi high entropy alloy transition layer prepared in Comparative Example 2 of the present invention Figure 5 , where A is the macroscopic physical picture and B is the metallographic photograph of the bonding area.

[0062] Figure 5 It shows that obvious cracks appear in the bonding area of ​​the high entropy alloy transition layer of the aluminum alloy / titanium alloy gradient structure specimen with the addition of CoCrFeMnNi high entropy alloy transition layer.

[0063] Comparative Example 3

[0064] Laser additive manufacturing of aluminum alloy / titanium alloy gradient structure specimens containing CoCrFeNi high entropy alloy transition layer:

[0065] Compared with Example 1, the only difference is that the equiatomic ratio TiNbVZr high entropy alloy powder is replaced by equiatomic ratio CoCrFeNi high entropy alloy powder (powder particle size is 75-250μm) to prepare an aluminum alloy / titanium alloy gradient structure specimen containing a CoCrFeNi high entropy alloy transition layer.

[0066] The macroscopic physical picture of the aluminum alloy / titanium alloy gradient structure specimen containing the CoCrFeNi high entropy alloy transition layer prepared in comparative example 3 and the metallographic photograph of the bonding area are shown in Figure 6 , where A is the macroscopic physical picture and B is the metallographic photograph of the bonding area.

[0067] Figure 6 It shows that obvious cracks appear in the bonding area of ​​the high entropy alloy transition layer of the aluminum alloy / titanium alloy gradient structure specimen with the addition of CoCrFeNi high entropy alloy transition layer.

[0068] Since the specimens prepared in Comparative Examples 1-3 all had obvious cracks in the bonding area, the tensile properties could not be tested.

[0069] The tensile properties of the test pieces prepared in Example 1-2 were tested, and the test results are shown in Table 1.

[0070] Table 1 Tensile properties of aluminum alloy / titanium alloy gradient structure specimens with optimized high entropy alloy transition layer

[0071]

[0072] The results in Table 1 show that the aluminum / titanium gradient structure material prepared by the present invention fully meets the needs of integrated manufacturing of aluminum and titanium dissimilar metals, and provides a new preparation idea for the connection of other high-performance dissimilar metals.

[0073] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for manufacturing an aluminum / titanium alloy gradient structure by laser additive manufacturing, characterized in that: The following steps are involved: Using TiNbVZr or TiNbV high entropy alloy powder to prepare a high entropy alloy transition layer on the surface of the titanium alloy by a laser additive manufacturing process, and then preparing an aluminum alloy layer on the surface of the high entropy alloy transition layer by a laser additive manufacturing process; The atomic ratio of Ti, Nb, V and Zr in the TiNbVZr high entropy alloy powder is 1:0.5-2:0.5-2:0.5-2, and the powder particle size range is 53-250 μm; the atomic ratio of Ti, Nb and V in the TiNbV high entropy alloy powder is 1:0.5-2:0.5-2, and the powder particle size range is 53-250 μm.

2. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 1, characterized in that: The titanium alloy is pretreated before laser additive manufacturing.

3. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 1, characterized in that: The titanium alloy is an α-type, α+β-type or β-type titanium alloy.

4. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 1, characterized in that: The height of the high entropy alloy transition layer is 1-4 mm.

5. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 1, characterized in that: When preparing the high-entropy alloy transition layer, the process parameters of the laser additive manufacturing process are: laser beam diameter 3-6 mm, laser power 2-6 kW, scanning speed 500-1500 mm / min, single layer height 0.3-0.6 mm, overlap rate 30-50%, powder feeding rate 800-2000 g / h, and oxygen content less than 80 ppm.

6. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 1, characterized in that: The particle size range of the aluminum alloy powder used in preparing the aluminum alloy layer is 53-250 μm.

7. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 1, characterized in that: When preparing the aluminum alloy layer, the process parameters of the laser additive manufacturing process are: laser beam diameter 3-6 mm, laser power 2-6 kW, scanning speed 500-1500 mm / min, single layer height 0.3-0.6 mm, overlap rate 30-50%, powder feeding rate 500-1000 g / h, and oxygen content less than 80 ppm.

8. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 1, characterized in that: After the aluminum alloy layer is prepared, an annealing step is also included.

9. The laser additive manufacturing method for aluminum / titanium alloy gradient structure according to claim 8, characterized in that: The annealing treatment is carried out at a temperature of 200-500° C., with a holding time of 1-6 hours, and is performed by air cooling or furnace cooling.

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