Nano modified Al-Zn-Mg-Cu alloy welding wire and preparation method thereof

Abstract

The invention belongs to the field of metal materials and additive manufacturing materials, and relates to a nano-modified Al-Zn-Mg-Cu alloy welding wire and a preparation method thereof.The preparation method comprises the following steps that firstly, aluminum powder, magnesium powder, zinc powder, copper powder and ceramic nano-particle powder are evenly mixed, and raw material powder A is obtained; secondly, the raw material powder A is subjected to cold pressing forming, and an alloy blank B is obtained; thirdly, the alloy blank B is sintered in the protective atmosphere environment, and an alloy ingot C is obtained; fourthly, the alloy cast ingot C is subjected to two-stage homogenizing annealing, and an alloy cast ingot D is obtained; 5, the alloy cast ingot D is heated to the recrystallization temperature or above and then extruded, and an alloy bar E is obtained; sixthly, the alloy bar E is subjected to multi-pass hot rolling, and an alloy rod F is obtained; and seventhly, the alloy rod material F is subjected to multi-pass drawing annealing, and finally the nano-modified Al-Zn-Mg-Cu alloy welding wire is obtained.

Description

Technical Field

[0001] The present invention belongs to the field of metal materials and additive manufacturing materials, and relates to a nano-modified Al-Zn-Mg-Cu alloy welding wire and a preparation method thereof. Background Art

[0002] Al-Zn-Mg-Cu alloys, a typical representative of the 7XXX series of high-strength aluminum alloys, are heat-treatable aluminum alloys. This family of alloys offers numerous significant advantages and demonstrates enormous potential for application in numerous high-end applications. Their exceptional strength allows them to withstand significant loads, meeting the stringent material strength requirements of these sectors. Furthermore, they possess excellent ductility and toughness, allowing them to deform to a certain degree without immediate fracture when subjected to external forces, while maintaining structural integrity. Furthermore, they exhibit excellent fatigue resistance, maintaining stable performance under repeated loading conditions and extending the material's service life. Their excellent stress corrosion resistance is also a key feature of these alloys, enhancing their reliability and safety in complex and harsh environments. These exceptional properties have led to their widespread application in high-end sectors such as aerospace, defense, rail transportation, and new energy.

[0003] However, despite the excellent performance of Al-Zn-Mg-Cu alloys, they face many difficulties during the welding process. This series of alloys has the characteristic of fast thermal conductivity, and heat is transferred rapidly during the welding process, making it difficult to accurately control the temperature distribution in the welding area. At the same time, its wide solidification range makes the cooling rate of different parts during the solidification process vary greatly, which easily leads to stress concentration. In addition, the large expansion and contraction coefficient further aggravates the stress changes during welding, making the tendency of thermal cracking extremely serious. In the actual welding process, these characteristics lead to a series of problems in the joints. The softening phenomenon of the joint reduces the strength and load-bearing capacity of the joint; the uneven composition causes differences in the chemical composition of different parts of the joint, affecting the overall performance of the joint; the coarse structure destroys the microstructure of the material and reduces the plasticity and toughness of the material; and the extreme ease of thermal cracking directly threatens the quality and reliability of the welded joint, significantly increasing the difficulty of welding the material.

[0004] Therefore, how to effectively reduce and minimize the occurrence of hot cracks during the welding process of Al-Zn-Mg-Cu alloys, improve and optimize the microstructure uniformity of the joints, and enhance the mechanical properties of the joints has become a key issue in the current research field of high-strength aluminum alloy welding. Solving these problems is of great practical significance for promoting the application of this series of alloys in more fields and improving the quality and performance of related products. Summary of the Invention

[0005] In view of this, the object of the present invention is to provide a nano-modified Al-Zn-Mg-Cu alloy welding wire and a preparation method thereof, so as to solve the industry problems of easy cracking and low welding strength of 7XXX aluminum alloy welding.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a nano-modified Al-Zn-Mg-Cu alloy welding wire comprises the following steps:

[0008] Step 1: uniformly mixing aluminum powder, magnesium powder, zinc powder, copper powder and ceramic nanoparticle powder to obtain raw material powder A;

[0009] Step 2: cold pressing the raw material powder A to obtain the alloy body B;

[0010] Step 3: Sintering the alloy body B in a protective atmosphere to obtain an alloy ingot C;

[0011] Step 4: performing double-stage homogenization annealing on the alloy ingot C to obtain alloy ingot D;

[0012] Step 5: heating the alloy ingot D to above the recrystallization temperature and then extruding it to obtain the alloy rod E;

[0013] Step 6: hot-rolling the alloy bar E in multiple passes to obtain alloy rod F;

[0014] Step 7: The alloy rod material F is subjected to multiple drawing annealing processes to finally obtain a nano-modified Al-Zn-Mg-Cu alloy welding wire.

[0015] Furthermore, in step 1, the purity of the aluminum powder, magnesium powder, zinc powder, and copper powder is greater than 99%, and the average particle size is 15-200 μm;

[0016] The ceramic nanoparticle powder is selected from one or more combinations of oxide nanoparticles, carbide nanoparticles or boride nanoparticles, and has a particle size range of 1-500 nm;

[0017] The mass percentages of the components are: Mg 1.0-10.0%, Zn 3.0-10.0%, Cu 1.5-4.5%, ceramic nanoparticles 0.5-10%, and the balance is aluminum powder.

[0018] Furthermore, the oxide nanoparticles include Al2O3 or ZrO, the carbide nanoparticles include TiC, SiC, WC or VC, and the boride nanoparticles include TiB2.

[0019] Furthermore, in step 2, the diameter of the alloy blank B is in the range of 150 mm to 200 mm.

[0020] Furthermore, in step three, the protective atmosphere is argon or nitrogen, the sintering temperature is 480° C.-600° C., and the sintering time is 30 min-5 h.

[0021] Furthermore, in step 4, the parameters of the double-stage homogenization annealing are: the first-stage annealing temperature is 450-470° C., and the holding time is 20h-24h; the second-stage annealing temperature is 475-500° C., and the holding time is 8-12h.

[0022] Furthermore, in step five, the diameter of the alloy rod E is in the range of 30-40 mm, the extrusion ratio is in the range of 10-50, and the extrusion temperature is in the range of 400° C.-450° C.

[0023] Furthermore, in step six, the diameter of the alloy rod F is in the range of 5-6 mm, the number of hot rolling passes is 5-8, and the hot rolling temperature is 400° C.-450° C.

[0024] Furthermore, in step seven, the diameter of the nano-modified Al-Zn-Mg-Cu alloy welding wire is 1.2 mm to 2.4 mm, the drawing annealing passes are 5 to 8 times, and the annealing temperature is 300° C. to 400° C.;

[0025] After drawing and annealing, scraping, polishing and cleaning are performed to finally obtain nano-modified Al-Zn-Mg-Cu alloy welding wire.

[0026] A nano-modified Al-Zn-Mg-Cu alloy welding wire is prepared by adopting the preparation method.

[0027] The beneficial effects of the present invention are:

[0028] In the prior art, 7XXX series Al-Zn-Mg-Cu aluminum alloys are widely used in aerospace, rail transportation and other fields due to their high strength and excellent corrosion resistance. However, they are prone to problems such as thermal cracking, low joint strength, and uneven structure during welding, which limits their application in high-demand scenarios. The present invention proposes solutions to these problems through an innovative nano-modified welding wire preparation process. It adopts powder metallurgy combined with ceramic nanoparticle modification and multi-step process optimization to significantly improve the performance of the welding wire, providing a new technical path for the welding application of 7XXX aluminum alloys; it solves the industry pain points in the welding of 7XXX aluminum alloys, making its application in high-end fields such as aerospace, rail transportation, etc. more reliable and extensive.

[0029] The core of the present invention is to introduce ceramic nanoparticles (such as Al2O3, TiC, etc.) through powder metallurgy technology, and combine it with processes such as cold pressing, sintering, two-stage homogenization annealing, extrusion, hot rolling and drawing annealing to prepare nano-modified Al-Zn-Mg-Cu alloy welding wire; the addition of nanoparticles refines the grain structure and improves the strength and toughness of the welding wire; the two-stage homogenization annealing optimizes the component distribution and reduces segregation; extrusion and hot rolling further improve the density and uniformity of the structure; these processes work synergistically to make the welding wire show a lower cracking tendency during welding, while the joint strength is increased, significantly improving the welding performance. When using nano-modified aluminum alloy welding wire to weld 7075 aluminum alloy plates, no cracking occurs during the welding process. After welding heat treatment, the weld strength reaches 569MPa and the elongation reaches 9.8%, which completely solves the major problem of 7XXX aluminum alloy welding being prone to cracking and low joint strength, which is traditionally believed.

[0030] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0032] Figure 1 This is a microscopic characterization of the nano-modified 7055 aluminum alloy welding wire (AA7055-TiB2 welding wire) prepared in Example 2, where Figure a is a metallographic image of the welding wire after anodic coating, and the black lines are nanoparticles, which are distributed in strips under extrusion and drawing. Figure b is a scanning electron microscope characterization of the welding wire, where the gray part is the aluminum matrix and the black part is the nanoparticles, which are distributed in strips under extrusion and drawing. DETAILED DESCRIPTION

[0033] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0034] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0035] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0036] Example 1: Preparation of Nano-modified 7075 Aluminum Alloy Welding Wire

[0037] This example describes a process for preparing nano-modified 7075 aluminum alloy welding wire using SiC ceramic nanoparticles as a modifier. The specific preparation steps are as follows:

[0038] Step 1: Mixing of raw material powders

[0039] Weigh the following raw materials:

[0040] 26790g of aluminum powder with a purity greater than 99% (average particle size 100μm),

[0041] 870g (mass percentage 2.9%) of magnesium powder with a purity greater than 99% (average particle size 100μm),

[0042] 1590g (5.3% by mass) of zinc powder with a purity greater than 99% (average particle size 100μm),

[0043] 450g (mass percentage 1.5%) of copper powder with a purity greater than 99% (average particle size 100μm),

[0044] 300 g (mass percentage 1%) of SiC ceramic nanoparticle powder with a particle size of 100 nm.

[0045] These powders were placed in a V-type mixer and mixed for 1 hour to ensure uniform distribution of the components to obtain raw material powder A.

[0046] Step 2: Cold pressing

[0047] Raw material powder A was poured into a circular mold with a diameter of 180 mm and cold-pressed using a hydraulic press. The pressing pressure was 200 MPa and the holding time was 1 minute, forming a cylindrical alloy blank B with a diameter of 180 mm.

[0048] Step 3: Sintering

[0049] Alloy blank B was placed in a pit furnace and sintered under a high-purity argon protective atmosphere at a temperature of 500°C for 90 minutes. After sintering, the blank was cooled to room temperature to obtain alloy ingot C.

[0050] Step 4: Double-stage homogenization annealing

[0051] The alloy ingot C is placed in a heat treatment furnace for double-stage homogenization annealing:

[0052] First stage: temperature 460℃, keep warm for 22 hours;

[0053] Second stage: temperature 480℃, keep warm for 10 hours. After annealing, alloy ingot D with uniform structure is obtained.

[0054] Step 5: Extrusion

[0055] Alloy ingot D was heated to 420°C and kept at this temperature for 30 minutes to make the temperature uniform. It was then hot extruded on a 3000-ton extruder with an extrusion ratio of 25 to obtain alloy rod E with a diameter of 30 mm.

[0056] Step 6: Hot rolling

[0057] The alloy bar E was heated to 420° C. and hot rolled in a hot rolling mill for 5 passes with a reduction of about 20% in each pass, ultimately obtaining an alloy rod F with a diameter of 5 mm.

[0058] Step 7: Drawing annealing

[0059] Alloy rod F was placed in a drawing mill and subjected to six drawing annealing passes. After each drawing pass, it was annealed at 330°C for one hour. This resulted in a nano-modified 7075 aluminum alloy welding wire with a diameter of 1.6 mm. The wire was then scraped, polished, and cleaned to remove surface oxides and impurities.

[0060] The nano-modified 7075 aluminum alloy welding wire (AA7075-SiC welding wire) prepared in this embodiment has a diameter of 1.6 mm, a fine metallographic structure, and SiC nanoparticles are evenly distributed in the aluminum alloy matrix without obvious agglomeration.

[0061] Welding test: 7075 aluminum alloy plates were welded using the TIG (argon arc welding) process using 1.6mm AA7075-SiC welding wire. No cracking occurred during the welding process. After the weld was subjected to T6 heat treatment, the weld strength reached 570MPa and the elongation reached 8%, solving the industry's problem of 7075 aluminum alloy welding being prone to cracking and low joint strength.

[0062] Example 2: Preparation of Nano-modified 7055 Aluminum Alloy Welding Wire

[0063] This example describes a process for preparing nano-modified 7055 aluminum alloy welding wire using TiB2 ceramic nanoparticles as a modifier. The specific preparation steps are as follows:

[0064] Step 1: Mixing of raw material powders

[0065] Weigh the following raw materials:

[0066] 25470g of aluminum powder with a purity greater than 99% (average particle size 150μm),

[0067] 690g (mass percentage 2.3%) of magnesium powder with a purity greater than 99% (average particle size 150μm),

[0068] 2520g (8.4% by mass) of zinc powder with a purity greater than 99% (average particle size 150μm),

[0069] 720g (mass percentage 2.4%) of copper powder with a purity greater than 99% (average particle size 150μm),

[0070] 600 g (mass percentage 2%) of TiB2 ceramic nanoparticle powder with a particle size of 50 nm.

[0071] These powders were placed in a V-type mixer and mixed for 1 hour to ensure uniform distribution of the components to obtain raw material powder A.

[0072] Step 2: Cold pressing

[0073] Raw material powder A was poured into a circular mold with a diameter of 150 mm and cold-pressed using a hydraulic press. The pressing pressure was 150 MPa and the holding time was 1 minute, forming a cylindrical alloy blank B with a diameter of 150 mm.

[0074] Step 3: Sintering: Alloy blank B is placed in a pit furnace and sintered under a high-purity argon atmosphere. The sintering temperature is 550°C and the sintering time is 120 minutes. After sintering, the blank is cooled to room temperature in the furnace to obtain alloy ingot C.

[0075] Step 4: Double-stage homogenization annealing

[0076] The alloy ingot C is placed in a heat treatment furnace for double-stage homogenization annealing:

[0077] Level 1: temperature 465℃, keep warm for 24 hours;

[0078] Second stage: temperature 490℃, keep warm for 12 hours. After annealing, alloy ingot D with uniform structure is obtained.

[0079] Step 5: Extrusion

[0080] Alloy ingot D was heated to 430°C and kept at this temperature for 30 minutes to make the temperature uniform. It was then hot extruded on a 3000-ton extruder with an extrusion ratio of 18 to obtain alloy rod E with a diameter of 35 mm.

[0081] Step 6: Hot rolling

[0082] The alloy bar E was heated to 425° C. and hot rolled in a hot rolling mill for 6 passes with a reduction of about 15% in each pass, ultimately obtaining an alloy rod F with a diameter of 5.5 mm.

[0083] Step 7: Drawing annealing

[0084] Alloy rod F was placed in a drawing mill and subjected to eight drawing annealing passes. After each drawing pass, it was annealed at 350°C for one hour. This resulted in a nano-modified 7055 aluminum alloy welding wire with a diameter of 1.2 mm. The wire was then scraped, polished, and cleaned to remove surface oxides and impurities.

[0085] As attached Figure 1 As shown in FIG, the metallographic image shows the microstructural characteristics of the welding wire. The nano-modified 7055 aluminum alloy welding wire (AA7055-TiB2 welding wire) prepared in this embodiment has a diameter of 1.2 mm, a fine metallographic structure, and TiB2 nanoparticles are evenly distributed in the aluminum alloy matrix without obvious agglomeration.

[0086] Welding test: 7055 aluminum alloy plates were welded using a 1.2mm AA7075-TiB2 welding wire using the MIG (Metal Inert Gas) process. No cracking occurred during the welding process. After the weld was subjected to T6 heat treatment, the weld strength reached 569MPa and the elongation reached 9.8%, solving the industry's problem of 7055 aluminum alloy welding being prone to cracking and having low joint strength.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a nano-modified Al-Zn-Mg-Cu alloy welding wire, characterized in that: The following steps are involved: Step 1: uniformly mixing aluminum powder, magnesium powder, zinc powder, copper powder and ceramic nanoparticle powder to obtain raw material powder A; Step 2: cold pressing the raw material powder A to obtain the alloy body B; Step 3: Sintering the alloy body B in a protective atmosphere to obtain an alloy ingot C; Step 4: performing double-stage homogenization annealing on the alloy ingot C to obtain alloy ingot D; Step 5: heating the alloy ingot D to above the recrystallization temperature and then extruding it to obtain the alloy rod E; Step 6: hot-rolling the alloy bar E in multiple passes to obtain alloy rod F; Step 7: The alloy rod material F is subjected to multiple drawing annealing processes to finally obtain a nano-modified Al-Zn-Mg-Cu alloy welding wire.

2. The preparation method according to claim 1, characterized in that In step 1, the purity of the aluminum powder, magnesium powder, zinc powder, and copper powder is greater than 99%, and the average particle size is 15-200 μm; The ceramic nanoparticle powder is selected from one or more combinations of oxide nanoparticles, carbide nanoparticles or boride nanoparticles, and has a particle size range of 1-500 nm; The mass percentages of the components are: Mg 1.0-10.0%, Zn 3.0-10.0%, Cu 1.5-4.5%, ceramic nanoparticles 0.5-10%, and the balance is aluminum powder.

3. The preparation method according to claim 2, characterized in that The oxide nanoparticles include Al2O3 or ZrO, the carbide nanoparticles include TiC, SiC, WC or VC, and the boride nanoparticles include TiB2.

4. The preparation method according to claim 1, characterized in that In step 2, the diameter of the alloy body B is in the range of 150 mm to 200 mm.

5. The preparation method according to claim 1, characterized in that In step three, the protective atmosphere is argon or nitrogen, the sintering temperature is 480° C.-600° C., and the sintering time is 30 min-5 h.

6. The preparation method according to claim 1, characterized in that In step 4, the parameters of the double-stage homogenization annealing are: the first-stage annealing temperature is 450-470° C., and the holding time is 20 h-24 h; the second-stage annealing temperature is 475-500° C., and the holding time is 8-12 h.

7. The preparation method according to claim 1, characterized in that In step 5, the diameter of the alloy rod E is in the range of 30-40 mm, the extrusion ratio is in the range of 10-50, and the extrusion temperature is in the range of 400° C.-450° C.

8. The preparation method according to claim 1, characterized in that In step six, the diameter of the alloy rod F is in the range of 5-6 mm, the number of hot rolling passes is 5-8, and the hot rolling temperature is 400° C.-450° C.

9. The preparation method according to claim 1, characterized in that In step 7, the diameter of the nano-modified Al-Zn-Mg-Cu alloy welding wire is 1.2 mm to 2.4 mm, the drawing annealing passes are 5 to 8 times, and the annealing temperature is 300° C. to 400° C.; After drawing and annealing, scraping, polishing and cleaning are performed to finally obtain nano-modified Al-Zn-Mg-Cu alloy welding wire.

10. A nano-modified Al-Zn-Mg-Cu alloy welding wire, characterized in that: The nano-modified Al-Zn-Mg-Cu alloy welding wire is prepared by the preparation method according to any one of claims 1 to 9.

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