High-iron-content aluminum alloy welding wire and preparation method and application thereof

Abstract

The application discloses a high-iron-content aluminum alloy welding wire and a preparation method and application thereof. The high-iron-content aluminum alloy welding wire comprises the following components in percentage by mass: Si: 0.8-1.6%, Fe: 1.5-3.8%, Zr: 0.05-0.25%, Ni: 0.5-1.8%, Mn: 0.2-0.8%, Sc: 0.01-0.12%, inevitable impurities: ≤0.15%, and the balance of Al; wherein the mass ratio of Ni to Fe is (0.4-0.6):1. Through component design, a dual-phase composite second-phase system composed of a hard skeleton phase and a soft buffer phase is actively constructed in a weld, based on a'skeleton-buffer' dual-phase composite second-phase synergistic strengthening and toughening mechanism, the complementary and synergistic effect of the two phases on mechanical properties is utilized, and the strength, toughness and crack resistance of a welded joint are simultaneously improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy welding materials technology, specifically to a high-iron-content aluminum alloy welding wire, its preparation method, and its application. Background Technology

[0002] With the rapid development of lightweight equipment manufacturing industries such as new energy vehicles, power battery trays, and rail transit equipment, aluminum alloys have become a core material due to their advantages such as high specific strength, corrosion resistance, and ease of forming. Recycled aluminum, with its wide availability of raw materials, low energy consumption, and low overall cost, is widely used in the large-scale production of aluminum alloy extruded profiles and castings. However, iron elements are difficult to remove effectively during the recycling and remelting process of recycled aluminum, with the iron content in the base material generally reaching 0.7-1.8%. During welding, iron elements in the base material migrate into the molten pool, easily forming brittle iron phases such as β-AlFeSi, Al3Fe, and Al6Fe upon solidification. The presence of these phases significantly reduces the plasticity and ductility of the weld, increases the probability of brittle fracture, and induces coarse weld structure and compositional segregation. In high-speed welding processes such as laser welding and laser-arc hybrid welding, these phases are more likely to cause defects such as cracks and porosity, leading to large fluctuations in weld joint strength, reduced overall welding reliability, and failure to meet the performance requirements of lightweight equipment.

[0003] Existing technologies employ methods to suppress or transform harmful brittle iron phases in the molten pool to address welding problems in high-iron-content aluminum alloys. These methods include adding elements such as Mn and Cr to promote the transformation of the β-AlFeSi phase to the α-Al(Fe,Mn,Si) phase, or adding elements such as Nb and Ti to alter the precipitation sequence and refine the morphology of the iron phase. However, under the high-speed cooling of modern welding processes, these existing iron phase control methods suffer from rapid solidification of the molten pool, leading to insufficient element diffusion and phase transformation, unstable control effects, and an inability to achieve a synergistic improvement in the strength and toughness of the weld joint. Furthermore, the composition systems of existing commercial welding wires (such as ER4043 and ER5356) are designed for conventional low-iron aluminum alloys and are not optimized for the high-iron-content welding environment, lacking effective control over the migration of iron elements in the molten pool. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem that brittle iron phases are easily formed in the weld seam when welding recycled aluminum base material with high iron content, and it is difficult to improve the strength and toughness in a synergistic way. The invention provides a high iron content aluminum alloy welding wire, its preparation method and application. The welding wire is suitable for laser welding, argon arc welding and laser-arc hybrid welding processes. It abandons the traditional idea of ​​"eliminating harmful phases" and actively constructs a two-phase composite second phase system composed of hard skeleton phase and soft buffer phase in the weld seam through composition design. Based on the "skeleton-buffer" two-phase composite second phase synergistic strengthening and toughening mechanism, the complementary and synergistic effect of the two phases in mechanical properties is utilized to simultaneously achieve a significant improvement in the strength and toughness of the weld joint.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution:

[0006] The first aspect of this invention provides a high-iron-content aluminum alloy welding wire, comprising the following components by mass percentage:

[0007] Si: 0.8-1.6%, Fe: 1.5-3.8%, Zr: 0.05-0.25%, Ni: 0.5-1.8%, Mn: 0.2-0.8%, Sc: 0.01-0.12%, unavoidable impurities ≤0.15%, balance Al; wherein the mass ratio of Ni to Fe is (0.4-0.6):1.

[0008] The design principles and synergistic effects of the elements in this invention are as follows:

[0009] (1) Zr and Sc: Both are highly efficient grain refiners and precipitation strengthening elements. During the rapid solidification of the weld pool, they preferentially form the thermally stable Al3(Sc,Zr) phase, which constructs a nanoscale hard skeleton phase for the weld after solidification. This phase has the characteristics of high hardness and high elastic modulus. As a rigid skeleton in the weld, it can provide basic high strength for the welded joint through significant Orowan strengthening effect and grain boundary pinning effect. Limiting the content of Zr and Sc can avoid excessive aggregation and coarsening of phase particles and ensure the strengthening effect.

[0010] (2) Ni, Fe and Mn: The Fe element inherent in the recycled aluminum base material, along with the actively added Ni and Mn elements, are used as beneficial components for regulation. By controlling the mass ratio of Ni to Fe at 0.4-0.6 and adding an appropriate amount of Mn, the molten pool can be induced to generate a submicron-scale soft buffer phase, Al3(Ni,Fe) phase or (Fe,Mn,Ni)-Al intermetallic compound phase, in a temperature range slightly lower than the precipitation temperature of the skeleton phase during welding. This phase has moderate hardness and good plastic deformation ability. It can undergo coordinated deformation under stress, effectively relax local stress concentration, and passivate the microcrack tips, thereby significantly improving the hardness and tensile properties of the welded joint.

[0011] (3) Si: The content is controlled at 0.8-1.6%. Its main function is to ensure the fluidity and hot crack resistance of the weld pool, and at the same time promote the formation of an appropriate amount of Al-Si eutectic structure in the weld pool to achieve effective filling of dendrite gaps. This content range can fully meet the actual needs of the welding process, and can also avoid the formation of coarse primary silicon phase, preventing it from interfering with the toughening effect of the two-phase composite second phase system.

[0012] Preferably, the high-iron content aluminum alloy welding wire comprises, by mass percentage, the following components: Si: 0.8-1.6%, Fe: 1.5-3.8%, Zr: 0.05-0.25%, Ni: 0.5-1.8%, Mn: 0.2-0.8%, Sc: 0.04-0.10%, unavoidable impurities ≤0.15%, and the balance being Al.

[0013] A second aspect of this invention provides a method for preparing the high-iron-content aluminum alloy welding wire described in the first aspect, comprising the following steps:

[0014] S1. Heat the aluminum ingot to 760-800 ℃ to melt it, then add Al-Si master alloy and Al-Fe master alloy in sequence and stir to mix them evenly;

[0015] S2. Adjust the temperature of the aluminum alloy melt obtained in S1 to 750-760 ℃, and then subject the aluminum alloy melt to electromagnetic stirring and ultrasonic treatment in sequence.

[0016] S3. Heat the aluminum alloy melt treated in S2 to 760-780 ℃, and then add Al-Zr master alloy, Al-Ni master alloy, Al-Mn master alloy and Al-Sc master alloy in sequence and stir to mix.

[0017] S4. The aluminum alloy melt obtained in S3 is subjected to gas refining treatment, and then continuously cast at a cooling rate of not less than 35 ℃ / s to obtain a continuous casting wire billet.

[0018] S5. The continuously cast wire rod obtained in S4 is subjected to cold drawing deformation treatment, intermediate annealing treatment and secondary drawing treatment in sequence to obtain the high iron content aluminum alloy welding wire.

[0019] The preparation method provided by this invention (especially the composite dynamic melt treatment and rapid solidification continuous casting) can obtain a welding wire matrix microstructure with highly supersaturated and uniformly distributed solute elements. During the rapid solidification process of the weld pool, thanks to the precise component ratio and uniform pre-state microstructure in the welding wire, the weld pool follows a solidification path of "preferential precipitation of hard skeleton phases followed by filling of soft buffer phases," ultimately dynamically constructing the target two-phase composite microstructure in the weld. The welding wire preparation process provided by this invention ensures the stability and reliability of the weld microstructure formation.

[0020] Furthermore, in S2, the magnetic induction intensity of the electromagnetic stirring treatment is 0.5-1.5 T, and the time is 8-12 min.

[0021] Furthermore, in S2, the frequency of the ultrasonic treatment is 20-30 kHz, the power is 800-1200 W, and the time is 5-8 min.

[0022] Furthermore, in S4, the cooling rate is 35-60 °C / s.

[0023] Furthermore, in S4, the continuous casting starts at a temperature of 720-740 ℃ and the casting speed is 1.8-2.5 m / min.

[0024] Furthermore, in S4, the diameter of the continuous casting billet is 6.5-7.5 mm.

[0025] Furthermore, in S5, the total deformation amount of the cold drawing deformation treatment is 18-22%.

[0026] Furthermore, in S5, the intermediate annealing treatment is carried out at a temperature of 320-340°C for a time of 1.0-1.2 h.

[0027] Furthermore, in S5, the total deformation of the secondary drawing process is 40-48%.

[0028] Furthermore, in S5, the secondary drawing process further includes the steps of surface cleaning, fluoride activation, and drying of the aluminum alloy welding wire.

[0029] Furthermore, the specific method for activating the fluoride salt is as follows: activation in an NH4HF2 solution with a concentration of 0.01-0.02 wt% for 30-60 s.

[0030] The third aspect of this invention provides an application of the high-iron-content aluminum alloy welding wire described in the first aspect in the welding of recycled aluminum welding plates.

[0031] Furthermore, the method for welding the recycled aluminum welded sheet is laser welding, argon arc welding, or laser-arc hybrid welding.

[0032] Furthermore, the mass fraction of Fe in the recycled aluminum welded sheet is 0.7-1.8%.

[0033] Furthermore, when the high-iron content aluminum alloy welding wire is used to weld recycled aluminum welding plates, the welded joint after solidification contains both a nanoscale hard framework phase and a submicron-scale soft buffer phase; wherein, the nanoscale hard framework phase is an Al3(Sc,Zr) phase, and the submicron-scale soft buffer phase is an Al3(Ni,Fe) phase or a (Fe,Mn,Ni)-Al intermetallic compound phase.

[0034] Under conditions of rapid solidification of the weld pool, a nanoscale hard framework phase precipitates first. This phase serves both as a heterogeneous nucleation core for the α-Al phase to refine grains and as dispersed strengthening particles to provide reinforcement. Subsequently, a submicron-scale soft buffer phase disperses and precipitates in the dendrite interstices and the gaps in the framework phase network. The two phases are spatially interspersed, forming a highly efficient synergistic effect in mechanical behavior—the hard framework phase, as the load-bearing main body, bears the main load and effectively hinders dislocation movement, providing high strength assurance for the welded joint; the soft buffer phase absorbs deformation energy and homogenizes local stress through its own micro-plastic deformation, endowing the welded joint with excellent toughness. This unique "reinforced concrete" type dual-phase composite microstructure achieves a synergistic improvement in the strength and toughness of high-iron content aluminum alloy welded joints, solving the technical problem of strength-toughness imbalance.

[0035] Furthermore, the average size of the nanoscale hard framework phase is 20-100 nm, the average size of the submicron-scale soft buffer phase is 0.2-1.0 μm, and the average size ratio of the nanoscale hard framework phase to the submicron-scale soft buffer phase is 1:(4-10).

[0036] The above-described technical solution of the present invention has the following beneficial effects:

[0037] 1. This invention abandons the traditional approach of "passive elimination" for welding aluminum alloys with high iron content. Instead of simply suppressing or transforming the harmful iron phase formed in the molten pool, it transforms the Fe element in the welding environment of aluminum alloys with high iron content into the core component of the beneficial soft buffer phase, turning the unfavorable factors in the welding process into favorable conditions for improving the performance of the welded joint, and realizing the high-value utilization of the Fe element.

[0038] 2. This invention achieves a balance between high strength and high toughness in high-iron content aluminum alloy welded joints through a two-phase composite structure design of hard skeleton phase and soft buffer phase. The tensile strength of the welded joint can reach more than 280 MPa, and the elongation after fracture is not less than 6%. This solves the technical problem of mutual restriction and performance imbalance between strength and toughness in high-iron content aluminum alloy welded joints in the prior art, and significantly improves the comprehensive mechanical properties of the welded joint.

[0039] 3. The high-iron content aluminum alloy welding wire of the present invention has excellent process adaptability and can be used in high-energy beam high-speed welding processes such as laser welding and laser-arc hybrid welding. It is highly compatible with the rapid solidification process of the weld pool. During the welding process, the flowability and solidification stability of the weld pool are good. The porosity of the weld after forming is less than 3%, the tendency of hot cracking is significantly reduced, and the welding forming quality and process stability are greatly improved.

[0040] 4. The preparation method of high-iron content aluminum alloy welding wire provided by the present invention is stable and reliable. Through the composite dynamic melt treatment process combining electromagnetic stirring and ultrasonic waves, and the forming process of controlled rapid continuous casting, it effectively solves the technical problem that high-performance intermetallic compound phases are difficult to uniformly disperse in aluminum-based melts. It can meet the requirements of industrial mass production and has good prospects for industrial application. Attached Figure Description

[0041] Figure 1 The images show scanning electron microscope (SEM) backscattered electron (BSE) images and X-ray diffraction (XRD) patterns of the welds after solidification of high-iron-content aluminum alloy welding wires in Examples 1, Comparative Examples 1, and 2, respectively; where (a) is Example 1, (b) is Comparative Example 1, (c) is Comparative Example 2, and (d) is the XRD pattern of the weld after solidification of high-iron-content aluminum alloy welding wires in Example 1.

[0042] Figure 2 These are stereomicroscopic images of the cross-section of the weld seam after solidification of high-iron-content aluminum alloy welding wires in Examples 1 and 3; where (a) is Example 1 and (b) is Comparative Example 3.

[0043] Figure 3 The images show the anodic coating near the weld fusion line after solidification of the high-iron content aluminum alloy welding wire in Example 1 and Comparative Example 3; where (a) is Example 1 and (b) is Comparative Example 3.

[0044] Figure 4 The images show the anode coating on the center of the weld after solidification of the high-iron content aluminum alloy welding wire in Example 1 and Comparative Example 3; where (a) is Example 1 and (b) is Comparative Example 3.

[0045] Figure 5 The images are SEM images of the welds after solidification of aluminum alloy welding wires with high iron content in Example 1 and Comparative Example 4; where (a) is Example 1 and (b) is Comparative Example 4. Detailed Implementation

[0046] 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 this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used are commercially available.

[0049] The elemental composition and mass percentage of the high-iron-content A356 aluminum alloy cast from recycled aluminum in the following examples are as follows: Si: 7.0%, Fe: 1.00%, Mg: 0.3%, Cr: 0.01%, Mn: 0.1%, Zn: 0.1%, Ti: 0.1%, with the balance being Al and unavoidable impurities.

[0050] Example 1

[0051] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0052] Si: 1.2%, Fe: 2.5%, Zr: 0.15%, Ni: 1.2%, Mn: 0.5%, Sc: 0.08%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.48:1.

[0053] The preparation method of the high-iron-content aluminum alloy welding wire in Example 1 includes the following steps:

[0054] S1. Place the high-purity aluminum ingot in an induction furnace and heat it to 790 °C until it is completely melted. Then, add Al-12Si master alloy and Al-10Fe master alloy in sequence and stir mechanically for 10 min until the mixture is uniform.

[0055] S2. Adjust the temperature of the aluminum alloy melt obtained in S1 to 755 ℃, turn on the electromagnetic stirring device, and process it for 10 min under the condition of magnetic induction intensity of 1.0 T; then insert the ultrasonic amplitude transformer and ultrasonically process it for 6 min under the condition of frequency of 25 kHz and power of 1000 W.

[0056] S3. Heat the aluminum alloy melt treated in S2 to 775 ℃, and then add Al-5Zr master alloy, Al-20Ni master alloy, Al-10Mn master alloy and Al-2Sc master alloy in sequence. Stir at 200 rpm for 12 min until the alloy is completely melted and mixed evenly.

[0057] S4. High-purity Ar gas is introduced into the aluminum alloy melt obtained in S3 for refining treatment for 8 min. Then, the aluminum alloy melt is transferred to a continuous casting machine and continuously cast under the conditions of casting start temperature of 730 ℃, casting speed of 2.0 m / min and cooling rate of 40 ℃ / s to obtain a continuous casting wire billet with a diameter of 7 mm.

[0058] S5. The continuously cast wire rod obtained from S4 is cold-drawn to a deformation of 20%, then annealed at 330 °C for 1.1 h, and then drawn in multiple passes to a diameter of 1.2 mm. The total deformation of this drawing process is 45%. Finally, the welding wire is sequentially ultrasonically cleaned (frequency 35 kHz, power 400 W, time 5 min), activated in a 0.015 wt% NH4HF2 solution for 50 s, and hot-air dried (temperature 80 °C, time 8 min) to obtain a high-iron content aluminum alloy welding wire.

[0059] Example 2

[0060] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0061] Si: 0.8%, Fe: 1.5%, Zr: 0.05%, Ni: 0.6%, Mn: 0.2%, Sc: 0.01%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.48:1.

[0062] The preparation method of the high-iron content aluminum alloy welding wire in Example 2 is basically the same as that in Example 1.

[0063] Example 3

[0064] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0065] Si: 1.6%, Fe: 3.0%, Zr: 0.25%, Ni: 1.8%, Mn: 0.8%, Sc: 0.12%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.6:1.

[0066] The preparation method of the high-iron content aluminum alloy welding wire in Example 3 is basically the same as that in Example 1.

[0067] Comparative Example 1

[0068] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0069] Si: 1.2%, Fe: 2.5%, Ni: 1.5%, Mn: 0.5%, Sc: 0.05%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.75:1.

[0070] The preparation method of the high iron content aluminum alloy welding wire in Comparative Example 1 is basically the same as that in Example 1, except that Al-5Zr master alloy is not added in S3.

[0071] Comparative Example 2

[0072] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0073] Si: 1.5%, Fe: 3.0%, Zr: 0.22%, Ni: 0.8%, Mn: 0.7%, Sc: 0.10%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.27:1.

[0074] The preparation method of the high-iron content aluminum alloy welding wire in Comparative Example 2 is basically the same as that in Example 1.

[0075] Comparative Example 3

[0076] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0077] Si: 1.2%, Fe: 2.5%, Zr: 0.15%, Ni: 0.3%, Mn: 0.5%, Sc: 0.08%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.12:1.

[0078] The preparation method of the high-iron content aluminum alloy welding wire in Comparative Example 3 is basically the same as that in Example 1.

[0079] Comparative Example 4

[0080] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0081] Si: 1.2%, Fe: 2.5%, Zr: 0.15%, Ni: 5.0%, Mn: 0.5%, Sc: 0.08%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 2:1.

[0082] The preparation method of the high-iron content aluminum alloy welding wire in Comparative Example 4 is basically the same as that in Example 1.

[0083] Comparative Example 5

[0084] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0085] Si: 1.2%, Fe: 2.5%, Zr: 0.15%, Mn: 0.5%, Sc: 0.08%, unavoidable impurities: 0.15%, balance Al.

[0086] The preparation method of the high-iron content aluminum alloy welding wire of Comparative Example 5 is basically the same as that of Example 1, except that Al-20Ni master alloy is not added in S3.

[0087] Comparative Example 6

[0088] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0089] Si: 1.2%, Fe: 2.5%, Ni: 1.2%, Mn: 0.5%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.48:1.

[0090] The preparation method of the high iron content aluminum alloy welding wire in Comparative Example 6 is basically the same as that in Example 1, except that Al-5Zr master alloy and Al-2Sc master alloy were not added in S3.

[0091] Comparative Example 7

[0092] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0093] Si: 1.2%, Fe: 2.5%, Ti: 0.15%, Ni: 1.2%, Mn: 0.5%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.48:1.

[0094] The preparation method of the high-iron content aluminum alloy welding wire of Comparative Example 7 is basically the same as that of Example 1, except that: in S3, Al-5Zr master alloy and Al-2Sc master alloy were not added, but Al-Ti master alloy was added.

[0095] Comparative Example 8

[0096] A high-iron-content aluminum alloy welding wire, by weight percentage, comprises the following components:

[0097] Si: 1.2%, Fe: 2.5%, Zr: 0.15%, Ni: 1.2%, Mn: 0.5%, Sc: 0.08%, unavoidable impurities: 0.15%, balance Al; wherein the mass ratio of Ni to Fe is 0.48:1.

[0098] The preparation method of the high-iron content aluminum alloy welding wire of Comparative Example 8 is basically the same as that of Example 1, except that the cooling rate in S4 is 20 ℃ / s.

[0099] Comparison Example

[0100] Commercially available ER4043 welding wire, by weight percentage, includes the following composition: Si: 5%, Fe < 0.8%, with the balance being Al.

[0101] Test Example 1

[0102] Laser-arc hybrid welding was performed on A356 aluminum alloy base material using high-iron content aluminum alloy welding wires from Examples 1, 1, and 2, respectively. The welding process parameters were as follows: laser power 2.8 kW, welding speed 50 mm / s, wire feed speed 4.2 m / min, arc voltage 22 V, welding current 120 A; shielding gas was argon with a flow rate of 15 L / min; oscillation frequency 100 Hz, oscillation amplitude 1.5 mm.

[0103] Figure 1 The images show scanning electron microscope (SEM) backscattered electron (BSE) images of the weld seams after solidification of high-iron content aluminum alloy welding wires in Examples 1, 1, and 2, and the X-ray diffraction (XRD) pattern of Example 1; where (a) is Example 1, (b) is Comparative Example 1, (c) is Comparative Example 2, and (d) is the XRD pattern of the weld seam after solidification of high-iron content aluminum alloy welding wires in Example 1. Figure 1 As shown in Figure (a), the weld seam formed after solidification of the high-iron content aluminum alloy welding wire in Example 1 exhibits a dual-phase composite microstructure, clearly distinguishable in two characteristic phases: a nanoscale hard framework phase, consisting of fine, high-brightness dispersed particles, confirmed by XRD analysis to be an Al3(Sc,Zr) phase rich in Zr and Sc, with a size of approximately 20-50 nm, uniformly dispersed within the α-Al matrix; and a submicron-scale soft buffer phase, existing in slightly larger, lower-contrast blocky or short rod-shaped morphology, with a size of approximately 0.2-0.8 μm, confirmed by XRD analysis to be a (Fe,Mn,Ni)-Al intermetallic compound phase or an Al3(Ni,Fe) phase rich in Ni, Fe, and Mn. This phase also exhibits a dispersed distribution, interspersed with the hard framework phase, without forming a continuous brittle phase network. Figure 1 As can be seen in (b), in Comparative Example 1, the (Fe,Mn,Ni)-Al intermetallic compound phase can still precipitate in the weld after solidification of the high-iron content aluminum alloy welding wire. The second phase exists as slender strips, with a more uneven distribution, and does not form the characteristic submicron-sized blocky / short rod-shaped soft buffer phase of Example 1. Simultaneously, due to the lack of sufficient Ni, Fe elements combine more with Si elements, forming Al3(Ni,Fe) phases with larger sizes and uncontrollable morphology and distribution, or Fe-containing impurities of unknown composition, making it impossible to construct a stable two-phase composite structure. Figure 1 As shown in Figure (c), the second phase composition of the weld after solidification of the high-iron content aluminum alloy welding wire in Comparative Example 2 is relatively simple, mainly consisting of coarse plate-like or needle-like β-AlFeSi phase and eutectic silicon phase, with almost no nanoscale hard skeleton phase and characteristic blocky buffer phase observed.

[0104] The above results indicate that only when the mass ratio of Ni to Fe is controlled within a suitable range can Fe and Ni atoms form a stable substitutional solid solution in the Al3(Ni,Fe) lattice, namely, the (Fe,Mn,Ni)-Al intermetallic compound phase or the Al3(Ni,Fe) composite phase. The crystal structure of this phase is intermediate between Al3Fe and Al3Ni. Compared to single phases, its hardness and modulus are optimized, and its interfacial compatibility and deformation coordination are superior to those of single Al3Fe or Al3Ni phases. Adding an appropriate amount of Mn (0.2-0.8%) can further dissolve into this phase, stabilizing the lattice and inhibiting the precipitation of harmful β-AlFeSi phase.

[0105] Test Example 2

[0106] Laser-arc hybrid welding was performed on A356 aluminum alloy base material using high-iron content aluminum alloy welding wires from Examples 1 and 3-4, respectively. The welding process parameters were as follows: laser power 2.5 kW, welding speed 45 mm / s, wire feed speed 4.2 m / min, arc voltage 22 V, welding current 120 A; shielding gas was argon, flow rate 15 L / min; oscillation frequency 100 Hz, oscillation amplitude 1.5 mm.

[0107] Figure 2 These are stereomicroscopic images of the cross-sections of the weld seams after solidification of high-iron-content aluminum alloy welding wires used in Examples 1 and 3 (Comparative Example 3); where (a) is Example 1 and (b) is Comparative Example 3. Figure 2 As shown in Figure (a), the weld formed after solidification of the high-iron content aluminum alloy welding wire in Example 1 is continuous, flat, and uniform. The fusion line has a smooth arc or a typical wine glass-shaped profile. The transition between the weld zone (WM) and the A356 aluminum alloy base material is smooth, without welding defects such as depressions, undercut, or humps. The weld width is uniform. This indicates that the molten pool has excellent fluidity during welding, the liquid metal fully wets and spreads on the base material, and the solidification process is stable and orderly. Figure 2 As shown in Figure (b), the weld fusion line of the high-iron content aluminum alloy welding wire in Comparative Example 3 exhibits a distinct serrated or irregular wavy shape after solidification. In regions DB1 and DB2, the fusion line shows localized concavity or convexity, and the weld width is significantly uneven. This morphology reflects poor molten pool fluidity and stability, with irregular growth characteristics at the solidification front. Furthermore, software analysis shows that the porosity of Example 1 is significantly lower than that of Comparative Example 3, decreasing to 1.97%, while the porosity of Comparative Example 3 is 9.23%.

[0108] The macroscopic forming quality of the weld directly depends on the fluidity, surface tension, and solidification behavior of the molten metal in the weld pool. In Example 1, an appropriate amount of Ni promotes the formation of a low-melting-point, highly ductile (Fe,Mn,Ni)-Al composite buffer phase in the later stages of solidification. This phase, distributed between dendrites, acts like a "liquid adhesive," effectively filling dendrite gaps, compensating for solidification shrinkage, and optimizing the overall rheological properties of the weld pool, thus resulting in a smooth and regular fusion line. In contrast, Comparative Example 3, due to insufficient Ni content, struggles to form a sufficient amount of effective composite buffer phase. The fluidity of the weld pool decreases and its shrinkage compensation capacity is insufficient in the later stages of solidification, and local solidification shrinkage cannot be adequately compensated, ultimately resulting in an irregular fusion line morphology. Such macroscopic forming defects easily become sources of microscopic stress concentration, reducing the mechanical properties and crack resistance of the joint.

[0109] Figure 3 These are images of the anodic coating near the weld fusion line after solidification of high-iron content aluminum alloy welding wires in Examples 1 and 3; where (a) is Example 1 and (b) is Comparative Example 3. Figure 3 As shown in (a), the weld seam after solidification of the high-iron content aluminum alloy welding wire in Example 1 exhibits a uniform, fine equiaxed grain structure with a narrow grain size distribution and clear, straight grain boundaries. Figure 4 As shown, at higher magnifications, the average grain size of the weld seam changes significantly after introducing a nanoscale Al3(Sc,Zr) hard framework phase and a submicron-scale (Fe,Mn,Ni)-Al soft buffer. This microstructure indicates that a large number of effective nucleation sites were formed in the weld pool during solidification, grain growth in all directions was effectively suppressed, and a large compositional undercooling zone was formed within the weld pool. Figure 3 As shown in Figure (b), the uniformity of the grain structure of the weld after solidification of the high-iron content aluminum alloy welding wire in Comparative Example 3 was significantly reduced, with large differences in grain size, the presence of some relatively coarse grains, more tortuous grain boundary morphology, and in some local areas, a mixture of fine equiaxed grains and columnar grains growing along a specific direction. This phenomenon reflects the non-uniformity of the nucleation process during the solidification of the molten pool, or a more intense competition mechanism for grain growth.

[0110] The core difference in the aforementioned structures lies in the regulatory effect of Ni. In Example 1, the addition of an appropriate amount of Ni promoted the formation of the (Fe,Mn,Ni)-Al composite buffer phase at the end of solidification, altering the composition and properties of the remaining liquid phase. The Ni-rich liquid phase formed between dendrites, not only existing as a second phase but also expanding the compositional undercooling zone of the molten pool. Through solute redistribution, it effectively hindered the continuous epitaxial growth of α-Al dendrites, thus strongly promoting the equiaxed transformation of grains. In contrast, Comparative Example 3, due to insufficient Ni content, could not form a sufficient amount of composite buffer phase, and the inhibitory effect on grain growth and the promoting effect on equiaxed transformation were significantly weakened. Although some nucleation sites still existed, the grains were more likely to preferentially grow along the heat flow direction during growth, ultimately leading to increased grain size inhomogeneity and even a tendency for local columnar crystals. This inhomogeneous grain structure is the root cause of fluctuations in weld mechanical properties and weak structural links.

[0111] Figure 5 The images show SEM images of the welds after solidification of aluminum alloy welding wires with high iron content in Example 1 and Comparative Example 4. In Example 1, the second phase is diffusely distributed, uniform and fine, with no element segregation or excessive precipitation. In Comparative Example 4, due to the excessive Ni element, although a framework phase can still be formed, the second phase is significantly coarsened, and continuous / semi-continuous Ni-rich brittle phases precipitate at the grain boundaries. This structure degrades the joint's load-bearing and deformation capacity, leading to a decrease in mechanical properties.

[0112] Test Example 3

[0113] Laser-arc hybrid welding was performed on A356 aluminum alloy base material using high-iron content aluminum alloy welding wires from Examples 1-3, Comparative Examples 1-8, and the ER4043 welding wire from the control example. The welding process parameters were as follows: laser power 2.5 kW, welding speed 45 mm / s, wire feed speed 4.2 m / min, arc voltage 22 V, welding current 120 A; shielding gas was argon, flow rate 15 L / min; oscillation frequency 100 Hz, oscillation amplitude 1.5 mm. The mechanical properties of the welded joints, including yield strength, tensile strength, elongation after fracture, and Vickers hardness, were tested using the following methods:

[0114] (1) Yield strength, tensile strength and elongation after fracture: The welded joint was processed into standard dog-bone shaped tensile specimens using a DK7745 CNC EDM machine. The gauge length of the specimen was 32 mm, the thickness was 2 mm, and the width was 6 mm. Tensile tests were performed at room temperature using a DNS-300 universal testing machine, and the tensile strain rate was 1×10⁻⁶. -3 s -1 Each group of samples was tested in parallel three times.

[0115] (2) Average hardness: The Wilson VH1102 automatic Vickers hardness tester was used for testing. The test load was 0.98 N and the holding time was 15 s. The test points were evenly distributed along the cross-section of the welded joint, with an adjacent indentation spacing of 0.2 mm. The average value was taken as the average hardness.

[0116] The test results are shown in Table 1:

[0117] Table 1

[0118]

[0119] As shown in Table 1, the welded joint obtained using the high-iron content aluminum alloy welding wire of Example 1 has a tensile strength close to 300 MPa, while the elongation after fracture reaches 6.5%, achieving a synergistic match between high strength and high toughness. The welding wire prepared in Example 2 can still form an effective dual-phase composite structure after welding, with a tensile strength of 282 MPa and an elongation after fracture of 6.1%, and its comprehensive mechanical properties are significantly better than those of Comparative Example 8 (insufficient cooling rate) and the control example (commercially available welding wire). The welded joint obtained in Comparative Example 2 has significantly reduced toughness, indicating that the soft buffer phase is the key to ensuring the toughness of the welded joint.

[0120] The strength of the welded joint obtained in Comparative Example 3 was significantly reduced, proving that the hard skeleton phase is the main load-bearing and strengthening phase of the weld. The properties of the welded joint obtained in Comparative Example 4 were all slightly lower than those in Example 1, indicating that excessive Ni content would disrupt the strength-toughness balance. In Comparative Example 4, excessive Fe, Si, and Ni content easily promoted the precipitation of coarse intermetallic compounds such as β-AlFeSi and Al3Ni within the grains and at grain boundaries, often in a non-uniform distribution as blocky, needle-like, or skeletal shapes, with some phases reaching several micrometers in size. Simultaneously, excessive Ni easily promoted the formation of complex brittle (Fe,Ni)-Si phases, further deteriorating the joint toughness.

[0121] Comparative Example 5, without the addition of Ni, could not form a characteristic buffer phase, and the elongation after fracture of the welded joint was only 4.5%, significantly lower than the 6.5% of Example 1. Although the strength reduction was limited, the strength and toughness were seriously unbalanced.

[0122] Both Comparative Example 6 (excluding Zr and Sc) and Comparative Example 7 (using Ti instead of Zr and Sc) showed a significant decrease in strength and hardness, with tensile strength of only 270-275 MPa and hardness of 85-90 HV. This indicates that the Al3(Sc,Zr) nanophase is the core reinforcing phase in this system, and its strengthening effect is significantly better than that of the traditional Al3Ti phase.

[0123] The high-iron content aluminum alloy welding wire of Comparative Example 8 had the same composition as that of Example 1, except that the continuous casting cooling rate was reduced. Its yield strength, tensile strength, elongation after fracture, and hardness all decreased significantly. This result demonstrates that rapid solidification conditions of at least 35 °C / s are necessary process conditions for suppressing second-phase coarsening, locking in the nano / submicron dual-phase composite structure, and ensuring the strengthening and toughening effect of the welding wire.

[0124] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art should understand that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A high-iron-content aluminum alloy welding wire for welding recycled aluminum plates, characterized in that, By weight percentage, it includes the following components: Si: 0.8-1.6%, Fe: 1.5-3.8%, Zr: 0.05-0.25%, Ni: 0.5-1.8%, Mn: 0.2-0.8%, Sc: 0.01-0.12%, unavoidable impurities ≤0.15%, balance Al; wherein the mass ratio of Ni to Fe is (0.4-0.6):1; The mass fraction of Fe in the recycled aluminum welded sheet is 0.7-1.8%; The high-iron-content aluminum alloy welding wire is prepared by the following method: S1. Heat the aluminum ingot to 760-800 ℃ to melt it, then add Al-Si master alloy and Al-Fe master alloy in sequence and stir to mix them evenly; S2. Adjust the temperature of the aluminum alloy melt obtained in S1 to 750-760 ℃, and then subject the aluminum alloy melt to electromagnetic stirring and ultrasonic treatment in sequence. S3. Heat the aluminum alloy melt treated in S2 to 760-780 ℃, and then add Al-Zr master alloy, Al-Ni master alloy, Al-Mn master alloy and Al-Sc master alloy in sequence and stir to mix well. S4. The aluminum alloy melt obtained in S3 is subjected to gas refining treatment, and then continuously cast at a cooling rate of not less than 35 ℃ / s to obtain a continuous casting wire billet. S5. The continuously cast wire rod obtained in S4 is subjected to cold drawing deformation treatment, intermediate annealing treatment and secondary drawing treatment in sequence to obtain the high iron content aluminum alloy welding wire.

2. The high-iron-content aluminum alloy welding wire according to claim 1, characterized in that, In S2, the magnetic induction intensity of the electromagnetic stirring treatment is 0.5-1.5 T, and the time is 8-12 min; the frequency of the ultrasonic treatment is 20-30 kHz, the power is 800-1200 W, and the time is 5-8 min.

3. The high-iron-content aluminum alloy welding wire according to claim 1, characterized in that, In S4, the cooling rate is 35-60 °C / s.

4. The high-iron-content aluminum alloy welding wire according to claim 1, characterized in that, In S4, the continuous casting starts at a temperature of 720-740 ℃ and the casting speed is 1.8-2.5 m / min.

5. The high-iron-content aluminum alloy welding wire according to claim 1, characterized in that, In S5, the total deformation amount of the cold drawing deformation treatment is 18-22%; the temperature of the intermediate annealing treatment is 320-340℃ and the time is 1.0-1.2 h; the total deformation amount of the secondary drawing treatment is 40-48%.

6. The high-iron-content aluminum alloy welding wire according to claim 1, characterized in that, In S5, the secondary drawing process further includes the steps of surface cleaning, fluoride activation and drying of the aluminum alloy welding wire.

7. The application of the high-iron content aluminum alloy welding wire according to any one of claims 1-6 in the welding of recycled aluminum welded plates.

8. The application according to claim 7, characterized in that, When the high-iron content aluminum alloy welding wire is used to weld recycled aluminum welding plates, the weld joint after solidification contains both a nanoscale hard framework phase and a submicron-scale soft buffer phase; wherein, the nanoscale hard framework phase is an Al3(Sc,Zr) phase, and the submicron-scale soft buffer phase is an Al3(Ni,Fe) phase or a (Fe,Mn,Ni)-Al intermetallic compound phase.

9. The application according to claim 8, characterized in that, The average size of the nanoscale hard framework phase is 20-100 nm, the average size of the submicron-scale soft buffer phase is 0.2-1.0 μm, and the average size ratio of the nanoscale hard framework phase to the submicron-scale soft buffer phase is 1:(4-10).

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