Spray forming 7xxx series alloy powder by-product recycling and reusing method based on DED additive manufacturing and application of spray forming 7xxx series alloy powder by-product recycling and reusing method

Abstract

The invention discloses a recycling and reusing method for spray forming 7xxx series alloy powder by-products based on DED additive manufacturing and application of the recycling and reusing method, and belongs to the technical field of material preparation, and the recycling and reusing method comprises the steps of spray forming 7xxx series aluminum alloy powder by-product multi-stage screening, drying treatment, powder mixing, DED laser additive manufacturing and heat treatment. According to the method, the 7xxx series waste powder generated in the spray forming process is converted into the high-added-value powder used for additive manufacturing, the energy loss and production cost of aluminum powder preparation are reduced, environmental pollution caused by spray forming aluminum powder by-products is reduced, the tensile strength of the alloy block prepared through the method can reach 487 + / -23 MPa, the ductility reaches 5.8 + / -0.1%, and the service life of the alloy block is prolonged. The density of the alloy is at least 99.14%, and the peak hardness of the alloy after aging is at least 171 HV0.2.

Description

Technical Field

[0001] The present invention relates to a method for recycling and reusing the by-product powder of spray-formed 7xxx series alloys based on DED (directed energy deposition) additive manufacturing and its application, and particularly relates to a comprehensive utilization method for using the powder by-products generated during the spray-forming process for additive manufacturing, belonging to the technical field of material preparation. Background Art

[0002] 7xxx series aluminum alloys have the advantages of high specific strength, good machining performance, low density, etc., and are widely used in the fields of aerospace, automotive, and military as lightweight and high-strength materials. 7xxx series aluminum alloys usually contain high alloying elements such as Zn, Mg, Cu, etc. When preparing ingots of 7xxx series aluminum alloys by traditional casting methods, there are problems such as large internal stresses and element segregation, resulting in difficulties in preparing 7xxx series aluminum alloys with high Zn content. In recent years, the spray-forming technology has shown obvious advantages in ingots of 7xxx series aluminum alloys with high element content and large specifications. The spray-forming technology is a rapid solidification technology that uses high-pressure inert gases such as argon and nitrogen to atomize metal droplets into micron-sized fine droplets and deposit them into billets at high speed along the axis direction of the nozzle before the metal droplets are completely solidified. The ingots of 7xxx series prepared by this technical method have the advantages of high element content, fine grains, uniform structure, and no obvious macroscopic segregation, and it is a mainstream technology for preparing high-alloyed and large-sized materials. Therefore, the use of spray-forming to prepare high-performance 7xxx series aluminum alloys has attracted extensive attention in the fields of aerospace, automotive, and military.

[0003] During the preparation of 7xxx series aluminum alloy ingots by spray forming technology, although most of the gas-atomized metal droplets are deposited on the substrate to form ingots, some metal droplets are still deposited outside the substrate, forming micron-sized aluminum powder by-products, which account for about 20-30% of the raw material weight. The aluminum powder by-products not only reduce the material utilization rate and increase the production cost, but also easily pollute the environment during storage. When encountering a humid environment and reaching a certain concentration, they are extremely prone to explosion, posing a safety hazard. Therefore, during the preparation of 7xxx series aluminum alloy ingots by spray forming, the recycling and reuse of aluminum powder by-products are urgent problems to be solved. At present, the main method to solve the spray forming aluminum powder by-products is to recycle and reuse the aluminum powder by hot pressing sintering, cold isostatic pressing and other powder metallurgy methods to prepare ingots (CN 111922345 B, CN 113732288 A). However, in the industrial production process, additional equipment such as hot pressing sintering and cold isostatic pressing needs to be added, and on the basis of converting aluminum powder into aluminum ingots, further recycling and reuse are achieved through deformation processing technologies such as extrusion and forging. This increases the recycling cost of aluminum powder and greatly reduces the recycling value of aluminum powder. Therefore, it is urgent to seek a new process to directly utilize the spray formed 7xxx series aluminum powder by-products and improve the economic value of the aluminum powder by-products. This can not only solve the problem of storing 7xxx series aluminum powder faced by spray forming enterprises, but also obtain economic benefits.

[0004] In addition, in the metal spray forming process, about 20-30% of the atomized powder (i.e., the above-mentioned micron-sized aluminum powder by-products) is often generated. After testing, such powder has the following characteristics:

[0005] 1. Morphology defects: The sphericity ≤ 0.88 (the requirement for commercial additive powder > 0.9), and there are a large number of abnormal particles.

[0006] 2. Poor fluidity: The Hall flow rate ≥ 60.3 s / 50 g (the standard value < 25 s / 50 g),

[0007] Powder of this quality is generally recycled by hot pressing sintering, cold isostatic pressing, melting and casting, forging methods. However, hot pressing sintering, cold isostatic pressing, melting and casting, forging, etc. have problems such as complex required equipment, complex processes, and high recycling costs. Due to large defects, poor sphericity, poor fluidity of this powder, and high Zn and Mg content in the powder, the additive prepared from this powder has defects such as cracks and pores, resulting in the inability to perform additive manufacturing with this powder. Therefore, the powder generated during the spray forming process is not suitable for additive manufacturing. Summary of the Invention

[0008] The technical problem to be solved by the present invention is that for the first time, the present invention provides a method for recycling the by-product of 7xxx aluminum powder during the spray forming process by using laser directed energy deposition (DED) additive manufacturing. This method uses the by-product of 7xxx series aluminum powder generated during the spray forming process as the high-value aluminum powder raw material for DED additive manufacturing, and is used for the DED additive manufacturing of 7xxx series aluminum alloy materials and components. Through this method, both the direct utilization of the 7xxx series powder by-products can be realized, and the cost of 7xxx series aluminum powder for DED additive manufacturing can be significantly reduced. This method has a simple process and high economic benefits, and at the same time meets the requirements for the recycling of 7xxx aluminum powder by-products in spray forming and the low cost of 7xxx series aluminum powder for DED additive manufacturing.

[0009] Meanwhile, the present invention provides an application of a method for recycling the by-product of 7xxx series alloy powder in spray forming based on DED (laser directed energy deposition) additive manufacturing in additive manufacturing.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0011] The method for recycling the by-product of 7xxx series alloy powder in spray forming based on DED additive manufacturing includes screening and drying the powder by-products, and then using laser directed energy deposition to prepare a block.

[0012] The additive manufacturing of the powder by-products is carried out by using a laser directed energy deposition printer for forming, and its process parameters are determined by the orthogonal experiment method.

[0013] The powder by-products are aluminum alloy powder by-products generated during the spray forming of 7xxx series aluminum alloy formed blanks; the process of using the 7xxx series aluminum alloy powder by-products to prepare a block is as follows:

[0014] S1. Screening treatment: Use a vibrating sieve powder machine to screen the spray formed 7xxx series aluminum alloy powder, and obtain aluminum alloy powder with a particle size range of 53 - 150 μm. This powder is spray formed Al-Zn-Mg-Cu powder.

[0015] For the screened aluminum alloy with a particle size of 53 - 150 μm, as a whole, the sphericity is low and there are many irregular powders, the sphericity ≤ 0.88, and the Hall flow rate ≥ 60.3 s / 50 g, with poor fluidity.

[0016] S2. Drying treatment: Dry the spray formed Al-Zn-Mg-Cu powder obtained in S1 in a vacuum drying oven to remove gas and water. The specific process is a heating temperature of 80 - 150 °C and a holding time of 4 - 10 h.

[0017] S3. Powder mixing: Add the spray-formed Al-Zn-Mg-Cu powder after drying and nano-Ti powder with a particle size range of 5 - 100 nm (stored in vacuum before opening) into a planetary powder mixer (Integrity) / ball mill at a certain mass fraction ratio to prepare Ti / Al-Zn-Mg-Cu composite powder. The mixing time is at least 2 h to ensure uniform powder mixing.

[0018] The addition amount of nano-Ti powder is 0.5 - 3.5 wt% of the spray-formed Al-Zn-Mg-Cu powder after drying.

[0019] S4. Additive manufacturing: Put the Ti / Al-Zn-Mg-Cu composite powder obtained in S3 into the powder supply cylinder of a DED printer, turn on the DED printer, and print an aluminum alloy block. The laser power is 1500 - 2400 W, the laser scanning speed is 6 - 12 mm / s, the powder mass flow rate is 4 - 5 g / min, and the overlap rate is 40 - 80%.

[0020] S5. Heat treatment: First, perform solution treatment on the printed aluminum alloy block in S4. The solution temperature is 475 - 490 °C, and the solution time is 1 - 4 h. Then, perform aging treatment. The aging temperature is 100 - 140 °C, and the aging time is 11 - 24 h.

[0021] Preferably, the spray-formed Al-Zn-Mg-Cu powder is a by-product of 7055 aluminum alloy powder.

[0022] Preferably, multi-pass samples are prepared on a DED printer with a laser power of 1800 W - 2100 W, a scanning speed of 10 - 12 mm / s, a powder mass flow rate of 4.62 g / min, and an overlap rate of 60% - 70%.

[0023] Preferably, bulk samples are prepared on a DED printer with a laser power of 2100 W, a scanning speed of 12 mm / s, a powder mass flow rate of 4.62 g / min, and an overlap rate of 65%.

[0024] Preferably, the DED printer is a raycham LMD8060 DED printer.

[0025] During printing, high-purity inert gas is fed into the forming chamber of the DED printer, which is one of argon, nitrogen, and helium, and the gas purity is ≥99.995%.

[0026] The composition and weight percentage of the 7xxx series aluminum alloy powder are as follows: Zn 5 - 13 wt.%, Mg 0.5 - 3 wt.%, Cu 0.5 - 3 wt.%, Zr 0.05 - 0.4 wt.%, Fe 0.1 - 0.5 wt.%, Cr 0 - 0.3 wt.%, Mn 0.1 - 0.5 wt.%, Ti 0 - 0.2 wt.%, Si 0.05 - 0.5 wt.%, and the balance is Al element.

[0027] The additive manufactured by the method for recycling and reusing the by - product of the spray - formed 7xxx series alloy powder based on DED additive manufacturing of the present invention has a tensile strength of 487 ± 23 MPa, an elongation of 5.8 ± 0.1%, a relative density of at least 99.14%, and a peak hardness of at least 171 HV. 0.2 。

[0028] The application of the additive of the present invention in 7xxx series aluminum alloy components in the fields of aerospace, automotive, and military.

[0029] An additive, prepared by the method of the present invention, and the precipitation phase of the additive is η′ phase.

[0030] The present invention has the following beneficial effects:

[0031] The present invention realizes the comprehensive utilization of the by - product of the spray - formed powder, solves the problems faced by enterprises, and obtains economic benefits.

[0032] The process of the present invention is simple, flexible, and economical in application, with high utilization rate of raw materials, low equipment requirements, and few processes.

[0033] The alloy material produced by the method of the present invention has a maximum tensile strength of 487 ± 23 MPa and an elongation of 5.8 ± 0.1%. The relative density of the alloy is at least 99.14%, without crack defects, and further eliminates irregular pores. The peak hardness of the alloy is at least 171 HV. 0.2 。

[0034] The present invention provides a method for recycling and reusing the by-products of spray-formed 7xxx series alloy powders based on DED additive manufacturing and its application, including multi-stage screening, drying treatment, powder mixing, DED laser additive manufacturing, and heat treatment of the by-products of spray-formed 7xxx series aluminum alloy powders; the powder by-products mainly come from the additional powder by-products generated during the preparation of spray-formed 7xxx series aluminum alloy formed blanks; the DED additive manufacturing uses the method of coaxial powder feeding by laser directed energy deposition to prepare alloys from spray-formed 7xxx series aluminum alloy powders, thereby realizing the recycling and reusing of the powder by-products. The method of the present invention transforms the 7xxx series waste powders generated during the spray-forming process into powders with high added value for additive manufacturing, which not only reduces the energy consumption and production cost of aluminum powder preparation, but also reduces the environmental pollution of the spray-formed aluminum powder by-products. The tensile strength of the alloy block prepared by this method can reach 487±23 MPa, and the elongation rate can reach 5.8±0.1%. The performance is equivalent to that of the laser directed energy deposition additive manufacturing of 7055 aluminum alloy using gas atomization powder making. The alloy density obtained by the present invention is at least 99.14%, and the peak hardness after alloy aging is at least 171 HV 0.2 。 Description of the Drawings

[0035] Figure 1 is the morphology of the spray powder of the present invention (particle size after screening is 53-150 μm);

[0036] Figure 2 is the metallographic diagram of the alloy under the same parameters of the present invention;

[0037] Figure 3 is the aging hardness curve of the present invention;

[0038] Figure 4 is the strengthening phase of the heat-treated alloy of the present invention. Detailed Embodiments

[0039] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0040] Example 1

[0041] A method for recycling and reusing the by-products of spray-formed 7xxx series alloy powders based on DED additive manufacturing includes the following steps:

[0042] S1. Screening treatment: Using a vibrating sieving machine to screen the spray-formed 7xxx series aluminum alloy powder to obtain aluminum alloy powder with a particle size range of 53-150 μm. This powder is spray-formed Al-Zn-Mg-Cu powder;

[0043] Such as Figure 1As shown, the sieved aluminum alloy with a particle size of 53 - 150 μm has a low sphericity and many irregularly shaped powders overall, with a sphericity of 0.88 and a Hall flow rate of 60.3 s / 50 g, showing poor fluidity.

[0044] S2. Drying treatment: The spray-formed Al-Zn-Mg-Cu powder obtained in S1 is dried in a vacuum drying oven to remove gas and water. The specific process is a heating temperature of 100 °C and a holding time of 6 h.

[0045] S3. Powder mixing: The dried spray-formed Al-Zn-Mg-Cu powder and nano-Ti powder with a particle size range of 5 - 100 nm (vacuum-preserved before opening) are added to a planetary mixer (Integrity) at a certain mass fraction ratio to prepare Ti / Al-Zn-Mg-Cu composite powder. The mixing time is 2 h to ensure uniform powder mixing.

[0046] The addition amount of nano-Ti powder is 1.8 wt% of the dried spray-formed Al-Zn-Mg-Cu powder.

[0047] S4. Additive manufacturing: The Ti / Al-Zn-Mg-Cu composite powder obtained in S3 is placed in the powder supply cylinder of a DED printer, and the DED printer is started to print an aluminum alloy block. The printing parameters are: laser power 2100 W, scanning speed 720 mm / min, powder mass flow rate 4.62 g / min, and overlap rate 65%.

[0048] S5. Heat treatment: The printed aluminum alloy block in S4 is first solution-treated at a solution temperature of 490 °C for 1 h; then aged at an aging temperature of 120 °C for 24 h.

[0049] The composition and weight percentage of the 7xxx series aluminum alloy powder are: Zn 10 wt.%, Mg 2 wt.%, Cu 1 wt.%, Zr 0.2 wt.%, Fe 0.3 wt.%, Cr 0.2 wt.%, Mn 0.3 wt.%, Si 0.3 wt.%, and the balance is Al element.

[0050] Application of a method for recycling and reusing by-products of spray-formed 7xxx series alloy powder based on DED (directed energy deposition) additive manufacturing in this embodiment in additive manufacturing.

[0051] An additive body prepared by using a method for recycling and reusing by-products of spray-formed 7xxx series alloy powder based on DED (directed energy deposition) additive manufacturing in this embodiment.

[0052] Application of the additive body in this embodiment in 7xxx series aluminum alloy components in the fields of aerospace, automotive, and military.

[0053] An additive body obtained by the method of this embodiment.

[0054] In this embodiment, nano-Ti is added. As can be seen from the metallographic diagram (as Figure 2 shown in b), the defects are significantly reduced, and basically there are some regular small holes. Generally speaking, holes are inevitably generated in the additive manufacturing process due to the volatilization of Zn and Mg and the entrainment of inert gas. However, in this embodiment, through the addition of nano-Ti, the irregular holes are further eliminated, and the alloy density is significantly increased to 99.14%.

[0055] The mechanical properties of the Al-Zn-Mg-Cu+Ti alloy in this embodiment are as follows: the tensile strength and elongation reach 487 MPa and 5.8% respectively. It is basically comparable to the properties of cast aluminum alloys, that is, the alloy in this embodiment combines the effects of a high Zn content and properties comparable to those of forged aluminum alloys. The reason for the analysis is as Figure 4 shown in a, the precipitation phase formed in the T6 heat-treated Al-Zn-Mg-Cu alloy (Comparative Example 2) is the η phase with a hexagonal C14 structure. In contrast, as Figure 4 shown in b, the precipitation phase formed in the T6 heat-treated Al-Zn-Mg-Cu-Ti alloy (this embodiment) is the typical η′ phase, and the η′ phase structure is composed of an orthorhombic unit (O-unit) and a rhombic unit (R-unit). This result confirms that the addition of Ti can inhibit the transformation of η′ phase to its equilibrium phase (η phase), thereby having a beneficial effect on the mechanical properties of the alloy. The peak hardness of the Al-Zn-Mg-Cu+Ti alloy is increased to 171 HV after 24 h of aging 0.2 .

[0056] Example 2

[0057] A method for recycling by-products of spray-formed 7xxx series alloy powders based on DED additive manufacturing, comprising the following steps:

[0058] S1. Screening treatment: Using a vibrating sieve powder machine to screen the spray-formed 7xxx series aluminum alloy powder to obtain aluminum alloy powder with a particle size range of 53 - 150 μm, and this powder is spray-formed Al-Zn-Mg-Cu powder;

[0059] The 53 - 150 μm aluminum alloy after screening has a low sphericity and many irregular powders on the whole, with a sphericity of 0.78 and a Hall flow rate of 70 s / 50 g, and poor fluidity;

[0060] S2. Drying treatment: Drying the spray-formed Al-Zn-Mg-Cu powder obtained in S1 in a vacuum drying oven to remove gas and water, and the specific process is a heating temperature of 80 °C and a holding time of 4 h;

[0061] S3. Powder mixing: The spray-formed Al-Zn-Mg-Cu powder after drying and the nano-Ti powder with a particle size range of 5 - 100 nm (vacuum-preserved before opening) are added to a planetary powder mixer (Integrity) at a certain mass fraction ratio to prepare the Ti / Al-Zn-Mg-Cu composite powder. The mixing time is 4 h to ensure uniform powder mixing.

[0062] The addition amount of the nano-Ti powder is 0.5 wt% of the spray-formed Al-Zn-Mg-Cu powder after drying.

[0063] S4. Additive manufacturing: The Ti / Al-Zn-Mg-Cu composite powder obtained in S3 is placed in the powder supply cylinder of a DED printer. The DED printer is turned on to print an aluminum alloy block. The laser power is 1500 W, the laser scanning speed is 6 mm / s, the powder mass flow rate is 4 g / min, and the overlap rate is 40%.

[0064] S5. Heat treatment: The printed aluminum alloy block in S4 is first solution-treated at a solution temperature of 475°C for 4 h; then aged at an aging temperature of 100°C for 11 h.

[0065] The composition and weight percentage of the 7xxx series aluminum alloy powder are: Zn 5 wt.%, Mg 0.5 wt.%, Cu 0.5 wt.%, Zr 0.05 wt.%, Fe 0.1 wt.%, Mn 0.1 wt.%, Ti 0.2 wt.%, Si 0.05 wt.%, and the balance is Al element.

[0066] Application of a method for recycling by-products of spray-formed 7xxx series alloy powder based on DED (directed energy deposition) additive manufacturing in additive manufacturing in this embodiment.

[0067] An additive body prepared by using the method for recycling by-products of spray-formed 7xxx series alloy powder based on DED (directed energy deposition) additive manufacturing in this embodiment.

[0068] Application of the additive body in this embodiment in 7xxx series aluminum alloy components in the fields of aerospace, automotive, and military.

[0069] An additive body prepared by the method of this embodiment.

[0070] The mechanical properties of the Al-Zn-Mg-Cu+Ti alloy in this embodiment are as follows: the tensile strength and elongation rate reach 464 MPa and 5.7% respectively. The density of the Al-Zn-Mg-Cu+Ti alloy is significantly increased to 99.25%, and the peak hardness after alloy aging is increased to 180 HV. 0.2 .

[0071] Example 3

[0072] A method for recycling by-products of spray-formed 7xxx series alloy powder based on DED additive manufacturing includes the following steps:

[0073] S1. Screening treatment: Using a vibrating sieving machine to screen the spray-formed 7xxx series aluminum alloy powder, and obtaining aluminum alloy powder with a particle size range of 53 - 150 μm. This powder is spray-formed Al-Zn-Mg-Cu powder;

[0074] For the screened aluminum alloy with a particle size of 53 - 150 μm, the sphericity is low as a whole and there are many irregular-shaped powders. The sphericity is 0.80, the Hall flow rate is 65 s / 50 g, and the fluidity is poor;

[0075] S2. Drying treatment: Drying the spray-formed Al-Zn-Mg-Cu powder obtained in S1 in a vacuum drying oven to remove gas and water. The specific process is a heating temperature of 150 °C and a holding time of 10 h;

[0076] S3. Powder mixing: Adding the dried spray-formed Al-Zn-Mg-Cu powder and nano-Ti powder (vacuum-preserved before opening) to a ball mill at a certain mass fraction ratio to prepare Ti / Al-Zn-Mg-Cu composite powder. The mixing time is 7 h to ensure uniform powder mixing;

[0077] The addition amount of nano-Ti powder is 3.5 wt% of the dried spray-formed Al-Zn-Mg-Cu powder;

[0078] S4. Additive manufacturing: Putting the Ti / Al-Zn-Mg-Cu composite powder obtained in S3 into the powder supply cylinder of a DED printer, turning on the DED printer, and printing an aluminum alloy block. Among them, the laser power is 2400 W, the laser scanning speed is 10 mm / s, the powder mass flow rate is 5 g / min, and the overlapping rate is 80%;

[0079] S5. Heat treatment: Firstly, performing solution treatment on the printed aluminum alloy block in S4. The solution temperature is 485 °C and the solution time is 2 h; then performing aging treatment. The aging temperature is 140 °C and the aging time is 20 h.

[0080] The composition and weight percentage of the 7xxx series aluminum alloy powder are: Zn 13 wt.%, Mg 3 wt.%, Cu 3 wt.%, Zr 0.4 wt.%, Fe 0.5 wt.%, Cr 0.3 wt.%, Mn 0.5 wt.%, Ti 0.1 wt.%, Si 0.5 wt.%, and the balance is Al element.

[0081] Application of a method for recycling by - product powders of spray - formed 7xxx series alloys based on DED (Directed Energy Deposition) additive manufacturing in additive manufacturing in this embodiment.

[0082] An additive body prepared by using a method for recycling by - product powders of spray - formed 7xxx series alloys based on DED (Directed Energy Deposition) additive manufacturing in this embodiment.

[0083] Application of the additive body in this embodiment in 7xxx series aluminum alloy components in the fields of aerospace, automotive, and military.

[0084] An additive body, prepared by the method of this embodiment.

[0085] The mechanical properties of the Al - Zn - Mg - Cu + Ti alloy in this embodiment are as follows: the tensile strength and elongation reach 510 MPa and 5.9% respectively. The relative density of the Al - Zn - Mg - Cu + Ti alloy is significantly increased to 99.54%, and the peak hardness of the alloy after aging is increased to 189 HV. 0.2 。

[0086] Example 4

[0087] The difference between this example and Example 1 is only: printing parameters: laser power of 1800 W, scanning speed of 11 mm / s, and overlapping rate of 60%.

[0088] The mechanical properties of the Al - Zn - Mg - Cu + Ti alloy in this example are as follows: the tensile strength and elongation reach 479 MPa and 5.8% respectively. The relative density of the Al - Zn - Mg - Cu + Ti alloy is significantly increased to 99.33%, and the peak hardness of the alloy after aging is increased to 172 HV. 0.2 。

[0089] Example 5

[0090] The difference between this example and Example 1 is only: overlapping rate of 70%.

[0091] The mechanical properties of the Al - Zn - Mg - Cu + Ti alloy in this example are as follows: the tensile strength and elongation reach 499 MPa and 5.8% respectively. The relative density of the Al - Zn - Mg - Cu + Ti alloy is significantly increased to 99.48%, and the peak hardness of the alloy after aging is increased to 175 HV. 0.2 。

[0092] Comparative Example 1

[0093] The difference between this comparative example and Example 1 is only: no nano - Ti powder is added, and the heat treatment operation of S5 is not carried out.

[0094] For the spray-formed Al-Zn-Mg-Cu powder, through a wide range of orthogonal tests, appropriate printing parameters were screened out (printing parameters: laser power 2100W, scanning speed 720mm / min, powder mass flow rate 4.62g / min, overlap rate 65%). The metallographic diagram of the printed aluminum alloy block obtained (as shown in Figure 2 Figure a) still shows many irregular pores. The tensile strength of the alloy is 272MPa, and the elongation is only 2.8%. After parameter optimization of the Al-Zn-Mg-Cu alloy, crack defects are eliminated, and there are high-density and irregularly shaped pores. The alloy density is only 97.57%.

[0095] Comparative Example 2

[0096] The difference between this comparative example and Example 1 is only that no nano-Ti powder was added, and the heat treatment operation of S5 was carried out.

[0097] After optimized heat treatment (490°C / 1h + 120°C / 24h), the tensile strength of the Al-Zn-Mg-Cu alloy is 350MPa, and the elongation is 1.9%.

[0098] As shown in Figure 4 Figure a, it is the strengthening phase of the heat-treated alloy. In the Al-Zn-Mg-Cu alloy under T6 heat treatment, the precipitation phase is the η phase with a hexagonal C14 structure, and its measured lattice parameters are a = 0.511nm and c = 0.863nm. This structure is composed of alternating close-packed rhombic units (R-units) and 180° rotated R' units (R'-units).

[0099] Comparative Example 3

[0100] The difference between this comparative example and Comparative Example 2 is only that the heat treatment (490°C / 1h + 120°C / 24h) in Comparative Example 2 was replaced with heat treatment (470°C / 1h + 120°C / 24h).

[0101] Study on the age hardening behavior of the Al-Zn-Mg-Cu alloy at different solution temperatures (470°C and 490°C):

[0102] The solution temperature has a significant effect on the age hardening behavior of the alloy. As shown in Figure 3 Figure a, for the Al-Zn-Mg-Cu alloy, when the solution temperature is 490°C, its age hardening value is significantly higher than that when the solution temperature is 470°C. The Al-Zn-Mg-Cu alloy reaches the peak hardness after aging treatment at 120°C for 24 hours. The peak hardness of the Al-Zn-Mg-Cu alloy increases to 149HV after 24h aging 0.2 , and the hardness tends to be stable in the later stage of aging.

[0103] Comparative Example 4

[0104] The only difference between this comparative example and Example 1 is that the heat treatment in Example 1 (490°C / 1h+120°C / 24h) is replaced by heat treatment (470°C / 1h+120°C / 24h).

[0105] The aging hardening behavior of Al-Zn-Mg-Cu+Ti alloy at different solution temperatures (470℃ and 490℃) was studied:

[0106] The solution temperature has a significant effect on the age hardening behavior of the alloy. Figure 3 As shown in Figure b, for Al-Zn-Mg-Cu+Ti alloy, when the solution temperature is 490°C, its aging hardness value is significantly higher than the hardness value when the solution temperature is 470°C. Al-Zn-Mg-Cu+Ti alloy reached a peak hardness of 171HV after solution treatment at 490°C and aging treatment at 120°C for 24 hours. 0.2 , and the hardness tends to be stable in the later stage of aging. After Al-Zn-Mg-Cu+Ti alloy is solid-solution treated at 470℃ and aged at 120℃ for 24 hours, the peak hardness is 155HV 0.2 Because the alloy precipitation phase of this comparative example is η phase, the solid solution temperature of 470℃ cannot inhibit the transformation of η′ phase to its equilibrium phase (η phase), so that the hardness of the alloy decreases, and the tensile strength and elongation reach 421MPa and 3.5% respectively.

[0107] Comparative Example 5

[0108] The difference between this comparative example and Example 1 is only that:

[0109] The addition amount of nano-Ti powder is 0.4wt%.

[0110] In this comparative example, the amount of nano-Ti powder added is too little, and the final alloy precipitation phase is η phase. The tensile strength of the Al-Zn-Mg-Cu+0.4%Ti alloy is 357MPa, the elongation is 2.0%, the alloy density is only 97.89%, and the peak hardness after aging is 155HV 0.2 .

[0111] Comparative Example 6

[0112] The difference between this comparative example and Example 1 is only that:

[0113] The addition amount of nano-Ti powder is 3.8wt%.

[0114] In this comparative example, the addition amount of nano-Ti powder is excessive. The precipitation phase of the final alloy is also the η phase. The tensile strength of the Al-Zn-Mg-Cu + 3.8% Ti alloy is 365 MPa, the elongation is 2.5%, the alloy density is 98.09%, and the peak hardness after aging is 153 HV 0.2 .

[0115] It can be seen that in the present invention, too much or too little addition amount of nano-Ti powder, as well as whether the solution temperature is appropriate, will affect the mechanical properties of the alloy. Only the combination of the addition amount of nano-Ti powder and the heat treatment process in a specific ratio in the present invention can realize the efficient reuse of waste powder and additive manufacturing of the material.

[0116] It should be understood that, in order to streamline the present disclosure and assist in understanding one or more of the various inventive aspects, in the foregoing description of the exemplary embodiments of the present invention, the various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected by the claims, the inventive aspects lie in less than all of the features of the foregoing disclosed embodiments. Thus, the claims following the detailed description are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate embodiment of the present invention.

[0117] Although the present invention has been described in terms of a limited number of embodiments, those skilled in the art in this technical field will appreciate, from the foregoing description, that other embodiments can be contemplated within the scope of the invention thus described. In addition, it should be noted that the language used in this specification has been principally selected for readability and instructional purposes and not for the purpose of explaining or limiting the subject matter of the present invention. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure of the present invention is illustrative, not restrictive, and the scope of the present invention is defined by the appended claims.

[0118] The above are only the preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for recycling byproducts of spray-formed 7xxx alloy powders based on DED additive manufacturing, characterized in that: The following steps are involved: S1. Screening treatment: Screening treatment is performed on the spray-formed 7xxx series aluminum alloy powder to obtain an aluminum alloy powder with a particle size range of 53 to 150 μm, and the powder is a spray-formed Al-Zn-Mg-Cu powder; S2, drying treatment: drying the spray-formed Al-Zn-Mg-Cu powder obtained in S1; S3, powder mixing: adding the dried spray-formed Al-Zn-Mg-Cu powder and the nano-Ti powder with a particle size range of 5-100 nm into a powder mixer / ball mill at a certain mass fraction ratio to prepare Ti / Al-Zn-Mg-Cu composite powder; The amount of nano-Ti powder added is 0.5-3.5wt% of the spray-formed Al-Zn-Mg-Cu powder after drying; S4, Additive Manufacturing: Printing aluminum alloy blocks, laser power of 1500-2400W, laser scanning speed of 6-12mm / s, powder mass flow rate of 4-5g / min, overlap rate of 40-80%; S5, heat treatment: The aluminum alloy block printed in S4 is first subjected to solution treatment at a solution temperature of 475-490°C and a solution time of 1-4h; then subjected to aging treatment at an aging temperature of 100-140°C and an aging time of 11-24h.

2. The method according to claim 1, characterized in that In S1, the aluminum alloy with a size of 53 to 150 μm after screening has a sphericity of ≤0.88 and a Hall flow rate of ≥60.3 s / 50 g.

3. The method according to claim 1, characterized in that In S2, the drying is vacuum drying, the heating temperature is 80 to 150° C., and the heat preservation time is 4 to 10 hours.

4. The method according to claim 1, characterized in that: In S3, the nano-Ti powder is stored in a vacuum before opening; the mixing time is at least 2 h to ensure that the powder is mixed evenly.

5. The method according to claim 1, characterized in that In S4, the printing parameters are: 1800W~2100W laser power, 10~12mm / s scanning speed, 4.62g / min powder mass flow rate, 60%~70% overlap rate.

6. The method according to claim 1, characterized in that In S4, printing parameters were: 2100 W laser power, 12 mm / s scanning speed, 4.62 g / min powder mass flow rate, and 65% overlap rate.

7. The method according to claim 1, characterized in that The composition and weight percentage of the spray-formed 7xxx series aluminum alloy powder are: Zn 5~13wt.%, Mg 0.5~3wt.%, Cu 0.5~3wt.%, Zr 0.05~0.4wt.%, Fe 0.1~0.5wt.%, Cr 0~0.3wt.%, Mn 0.1~0.5wt.%, Ti 0~0.2wt.%, Si 0.05~0.5wt.%, and the rest is Al element.

8. The additive body obtained by the method according to any one of claims 1 to 7, characterized in that: The tensile strength is 487±23MPa, the elongation is 5.8±0.1%, the density is at least 99.14%, and the peak hardness is at least 171HV 0.2 .

9. Use of the additive body according to claim 8 in 7xxx series aluminum alloy components in the fields of aerospace, automobile and military industry.

10. An additive body, characterized in that: The additive body is prepared by the method according to any one of claims 1 to 7, wherein the precipitated phase of the additive body is η′ phase.

Images