A method for manufacturing aluminum alloys and their composites using external ultrasonic vibration-assisted pulsed current arc wire feeding.

Abstract

This invention discloses a method for manufacturing aluminum alloys and their composite materials using an external ultrasonic vibration-assisted pulsed current arc wire feeding system, belonging to the technical field of arc additive manufacturing of aluminum alloys and aluminum alloy composite materials. This invention aims to solve the technical problems of coarse microstructure, numerous pores, and poor deposition quality in existing aluminum alloy arc additive manufacturing. The method involves: pre-treatment of the substrate and welding wire; placing an ultrasonic vibration head on the substrate; under a protective gas atmosphere, the ultrasonic device vibrates in the z-axis direction, while the arc wire feeding system deposits the welding wire layer by layer along a certain direction in the x-y plane; then sequentially performing solution treatment, water quenching, and aging treatment to complete the process. This application, by simultaneously applying current pulses and ultrasonic vibration during the printing process, creates a stirring effect on the molten pool, thereby promoting dendrite breakage, significantly refining the solidified grain structure, reducing defects such as pores, and improving the mechanical properties of the product. This invention is applicable to the processing of large-size thin-walled cylindrical parts.

Description

Technical Field

[0001] This invention belongs to the field of electric arc additive manufacturing technology for aluminum alloys and aluminum alloy composites. Specifically, it relates to a method for manufacturing aluminum alloys and their composites by external ultrasonic vibration-assisted pulsed current arc wire feeding, which is particularly suitable for processing large-size thin-walled cylindrical parts. Background Technology

[0002] Aluminum alloys and aluminum alloy composites possess excellent properties such as low density, high strength, good corrosion resistance, and good weldability, and are widely used in aerospace, electronics, and machinery industries. Large-size thin-walled cylindrical products have always been a manufacturing challenge in this field. Traditional methods, such as precision casting, plastic forming, welding, and joining, suffer from low manufacturing efficiency, long cycle times, and high costs. Therefore, high-efficiency, low-cost additive manufacturing technology has become a current research hotspot.

[0003] Arc-fed additive manufacturing technology uses an electric arc as a heat source and aluminum alloy or aluminum alloy composite wire with a diameter of millimeters (typically 1.2-1.5 mm) as an electrode. A robotic arm precisely moves the wire to manufacture complex shapes according to the required form. Due to the large heat input of the electric arc, the molten aluminum alloy remains in the high-temperature environment for a long time, and the solidification rate of the molten pool is slow. This can easily lead to problems such as coarse metal grains and poor product precision after solidification, thereby reducing the mechanical properties and forming accuracy of the product. Optimizing arc-fed additive manufacturing technology for aluminum alloys has become a key issue restricting the application of this technology. Summary of the Invention

[0004] This invention addresses the technical problems of coarse microstructure, numerous pores, and poor deposition quality in existing aluminum alloy arc additive manufacturing. It proposes a method for manufacturing aluminum alloys and their composites using ultrasonic vibration-assisted pulsed current arc wire feeding. This method employs ultrasonic vibration-assisted pulsed current arc additive manufacturing to improve the microstructure and properties of the additive aluminum alloy, refining the microstructure and reducing defects. Through heat treatment, high-performance arc additive aluminum alloy materials and their composites are obtained, enabling the production of large-size thin-walled cylindrical components. Taking 4-series aluminum-silicon alloys as an example, a dense, defect-free, and fine-structure aluminum-silicon alloy is prepared, improving its mechanical properties. This method is also applicable to other grades such as 2-series and 5-series aluminum alloys, as well as aluminum-based composites with added TiB2, SiC, and other ceramic phases.

[0005] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0006] The purpose of this invention is to provide a method for welding aluminum alloys and their composite materials using external ultrasonic vibration-assisted pulsed current arc wire feeding, characterized by comprising the following steps:

[0007] Step 1: Remove the oxide film from the substrate surface, then clean the substrate and solder wire with acetone, and vacuum dry.

[0008] Step 2: Place the ultrasonic vibrating head on the substrate. Under the protective gas, the ultrasonic equipment vibrates in the z-axis direction, while the arc wire feed stacks the welding wire layer by layer in a certain direction on the xy plane.

[0009] Step 3: Then proceed with solution treatment, water quenching, and aging treatment in sequence to complete the process.

[0010] Further specifying, the material of the welding wire is 4-series aluminum-silicon alloy, 2-series aluminum alloy, 5-series aluminum alloy, or aluminum-based composite material with added ceramic phase, wherein the ceramic phase is one or more of TiB2, SiC, and TiC.

[0011] Further specifying, in step one, vacuum drying is performed at 100℃-150℃ for 6h-10h.

[0012] Further specifying, in step one, the diameter of the welding wire is 1.2 mm.

[0013] To further specify, in step two, the diameter of the ultrasonic vibrating head is 55mm.

[0014] Further specifying, in step two, the protective gas is Ar + 20 vol% CO2 (i.e., CO2 accounts for 20% of the total volume of Ar and CO2 gas), and the gas flow rate is 10 L / min - 20 L / min.

[0015] Further specifying the process parameters for step two: welding torch speed 30mm / min-50mm / min, maximum pulse voltage 21V-22V, pulse time 2.0ms-3.2ms, maximum pulse current 235A-238A, SKS base current 26A-32A, base current time 3.0ms-3.2ms; arc initiation current 80A-90A, arc termination current 60A-70A, welding current 110A-135A, welding speed 350mm / min-500mm / min, wire feed speed 5m / min-9m / min, substrate temperature 100℃-200℃, and interlayer welding interval 45s-90s. Within this range, the optimal heat input during welding is 240-350J / mm, resulting in the best deposition morphology.

[0016] Further specifying, in step three, the solution treatment is carried out at 500℃-520℃ for 4h-6h.

[0017] Further specifying, in step three, the aging treatment is carried out at 180℃-200℃ for 4h-8h.

[0018] Further specifying, the welding wire of the present invention is a 4047 aluminum alloy wire, which can be prepared by the following operation: homogenizing a 4047 aluminum alloy ingot at a temperature of 450-480℃ for 6-8 hours, then extruding the ingot into a bar with a diameter of 10mm, performing multiple cold drawing operations, and performing an intermediate annealing operation for every 0.4mm reduction in diameter at a temperature of 400-460℃ for 2-8 hours, finally drawing it into an aluminum-silicon alloy welding wire with a diameter of 1.2mm; wherein, the 4047 aluminum alloy ingot contains 11.0%-13.0% Si, 0.8%-1.0% Fe, 0.2%-0.3% Cu, 0.05%-0.1% Mg, 0.05%-0.1% Mn, 0.1%-0.2% Zn, with the balance being Al.

[0019] Any of the above methods can be used to process large-sized thin-walled cylindrical parts.

[0020] This application applies current pulses and ultrasonic vibrations simultaneously during the printing process to create a stirring effect on the molten pool, thereby promoting dendrite breakage, significantly refining the grain structure after solidification, reducing defects such as porosity, and improving the mechanical properties of the product.

[0021] In arc wire feeding printing, the current-voltage waveform can be mainly divided into pulse mode and constant current mode, corresponding to pulsed arc and non-pulsed arc respectively. Pulse mode can achieve three droplet transmission methods: one droplet per pulse, one droplet per multiple pulses, or multiple droplets per pulse. The current-voltage waveform needs to be adjusted to achieve one droplet transmission per pulse (i.e., one droplet per pulse) to reduce droplet splashing, ensure manufacturing process stability, and improve product forming quality. At the same arc power, pulse mode has higher manufacturing efficiency than constant current mode, and it also has a stirring effect on the molten pool, which can refine the microstructure and reduce porosity.

[0022] In arc additive manufacturing, applying ultrasonic vibration to the substrate transmits this vibration into the molten pool, effectively stirring the molten pool. Ultrasonic vibration accelerates convective motion from the solid-liquid interface to the center of the molten pool, which helps increase the cooling rate of the melt. The liquid phase maintains convective motion, and the melt solidifies rapidly along the temperature gradient, which not only refines grains and reduces defects but also improves the microstructure and material properties. Therefore, combining ultrasonic vibration with pulsed arc mode can further refine the microstructure of aluminum alloys, reduce defects, and improve performance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention uses an ultrasonic vibration-assisted current pulse arc additive manufacturing method to prepare aluminum alloy materials and their composite materials, thereby refining the microstructure of the aluminum alloy and reducing defects. Finally, through heat treatment, high-performance arc additive aluminum alloy materials and their composite materials are obtained.

[0025] To further understand the features and technical content of this invention, please refer to the following detailed description and accompanying drawings. However, the accompanying drawings are for reference and illustration only and are not intended to limit the invention. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the ultrasonic vibration-assisted current pulse device in Example 1;

[0027] Figure 2 Image of the microstructure of the ultrasonic vibration-assisted current pulse arc additive aluminum alloy in Example 1;

[0028] Figure 3 The tensile stress-strain curve of the aluminum alloy material in Example 1;

[0029] Figure 4 The image shows the XRD curve of the aluminum alloy in Example 1. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, while not limiting the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0031] Example 1: The preparation method of ultrasonic vibration-assisted current pulse arc additive aluminum alloy and its composite material in this example is carried out according to the following steps:

[0032] Step 1: Pre-treatment of the substrate and 4047 aluminum alloy welding wire: A 350×350mm 1060 pure aluminum substrate was selected as the arc additive manufacturing substrate to prevent the introduction of other elements at high temperatures. The aluminum alloy welding wire was ER4047 with a diameter of 1.2mm. The aluminum alloy substrate was ground using a louvered angle grinder to remove the surface oxide film. Then, acetone was used to clean the substrate and welding wire surfaces to remove any residual oil. Finally, the welding wire and substrate were placed in a vacuum drying oven at 120℃ for 8 hours. After drying, they were ready for subsequent arc additive manufacturing.

[0033] Step 2: Place the ultrasonic vibrating head on the substrate. Under the protective gas, the ultrasonic equipment vibrates in the z-axis direction, while the arc wire feed stacks the welding wire layer by layer in a certain direction on the xy plane.

[0034] Step 3: Then proceed with solution treatment, water quenching, and aging treatment in sequence to complete the process.

[0035] In this embodiment, the ultrasonic system consists of an ultrasonic transducer, an amplitude transformer, and an ultrasonic vibrating head. The ultrasonic transducer converts the input electrical power into ultrasonic waves, which are then transmitted. The amplitude transformer is mainly used to change the resonant frequency of the vibration system. Finally, the ultrasonic waves are transmitted to the substrate through the ultrasonic vibrating head, which has a diameter of 55 mm. The ultrasonic vibration device has a power of 1000 W, an output frequency of 30 kHz, and an amplitude of 100 μm. The ultrasonic device is fixed to the substrate surface using a clamp, and the ultrasonic vibration is transmitted to the molten pool through the substrate. Applying ultrasonic vibration during gas metal arc welding accelerates the convective motion of the molten pool metal from the solid-liquid interface to the center of the molten pool, which helps to increase the cooling rate of the melt. This not only helps to refine the grains and reduce defects, but also breaks the growing dendrites and large grains, and blocks the growth of columnar crystals.

[0036] In this embodiment, the current pulse mode arc additive welding parameters are as follows: The welding power supply can be mainly divided into pulse mode and constant current mode based on the current waveform diagram of the process. This process primarily uses the microMIG pulse mode for welding experiments. First, the welding torch speed is set to 48 mm / min. Then, the pulse parameters are set: maximum pulse voltage 22V, pulse time 2.4ms, maximum pulse current 238A, SKS base current 26A, and base current time 3.0ms. The pulse mode consists of two stages: the first stage is the pulse stage, where the welding wire is rapidly melted by the pulse current; the second stage is the short-circuit stage, where the current drops to the SKS base current, and the molten pool temperature rapidly diffuses without heat input. During the pulse process, it is important to pay attention to the coordination between the pulse voltage, current, and welding speed. Increasing the pulse voltage and current will lead to increased heat input, causing the welding wire to melt too quickly, which has a significant impact on the weld morphology. Compared to the ordinary pulse process, this process appropriately optimizes and reduces the pulse current and voltage and adjusts the pulse time to better achieve a smooth, continuous transition. The basic parameters are: arc starting current 80A, arc ending current 60A, welding current 122A, welding speed 390mm / min, and wire feed speed 9.0m / min. Finally, to avoid a large temperature gradient between the molten pool and the substrate and to reduce porosity, the substrate temperature is set to 100℃. The welding interval between layers is 60s, which is beneficial for cooling of a single layer. During the welding process, a protective gas of Ar + 20 vol% CO2 is introduced at a flow rate of 20L / min. Based on these process parameters, 4047 aluminum alloy material was prepared.

[0037] V. Heat treatment of 4047 aluminum alloy: The obtained 4047 aluminum alloy material was solution treated at 500℃ in a muffle furnace for 5 hours, then water quenched and aged at 200℃ in a constant temperature drying oven for 6 hours.

[0038] This embodiment uses ultrasonic vibration-assisted current pulse arc additive manufacturing technology to prepare 4047 aluminum alloy material. From the perspectives of process parameters, arc, and weld bead control, based on the comprehensive control of welding heat input, weld morphology, and deposition size, the problems of coarse microstructure and poor deposition quality in the aluminum alloy printing process are solved, and relatively excellent mechanical properties are obtained.

[0039] A schematic diagram of an ultrasonic vibration-assisted current pulse arc additive manufacturing device is shown below. Figure 1 As shown. The power supply system for arc additive remanufacturing consists of an SKS LSQ5 welding power supply and a Power Feeder PF5 wire feeder from Sakai Welding Equipment (Shanghai) Co., Ltd. The microMIG pulse mode was primarily used for welding experiments. The Power Feeder PF5 wire feeder has a mechanical pull-out function, and when paired with the welding power supply, the wire feeding speed can be rapidly adjusted in real time according to the welding current, achieving digital control of wire feeding speed and droplet transfer. The instrument consists of a Yaskawa MOTOMAN-AR2010 industrial robot, a teach pendant programmer, a YRC1000 control cabinet, a positioner, and an ultrasonic system. This robot has six degrees of freedom, each axis has a servo motor, and the repeatability accuracy error is within ±0.08mm, ensuring the accuracy of path planning during the arc additive remanufacturing process. The ultrasonic equipment vibrates in the z-axis direction, which is transmitted to the molten pool through the substrate. The welding torch accumulates layer by layer in a certain direction on the xy plane, ultimately obtaining arc additive 4047 aluminum alloy material.

[0040] Metallographic images of 4047 aluminum alloy produced by ultrasonic vibration-assisted pulsed current arc additive manufacturing. Figure 2 As shown, in conventional casting and arc additive manufacturing of aluminum-silicon alloys, the molten pool and its interlayer bonding are subjected to thermal field effects, resulting in microstructure growth, mostly coarse columnar crystals. In contrast, the alloy microstructure prepared using ultrasonic vibration-assisted current pulse technology exhibits mostly fine grains, with a small number of columnar crystals, an average grain size of 10.8 μm, uniform microstructure, and fewer defects. In the literature "Influence of Ultrasonic Vibration on the Microstructure and Properties of Aluminum Alloys in CMT Arc Additive Manufacturing," ultrasonic vibration alone at an amplitude of 25 μm resulted in an average grain size of 15.4 μm. In the literature "Microstructure and Tensile Properties of 4043 Aluminum Alloy Thin-Walled Parts Manufactured by Cold Metal Transition and Pulsed Arc Additive Manufacturing," pulsed arc alone resulted in an average grain size of 20-30 μm, with a large number of coarse columnar crystals present in the microstructure.

[0041] Tensile properties of 4047 aluminum alloy, etc. Figure 3As shown, its tensile strength is between 180-210 MPa, its yield strength is between 100-110 MPa, and its elongation is 3.6%-3.8%. The reference "Influence of Additional Water Cooling on the Microstructure and Mechanical Properties of 4047 Aluminum Alloy Components Manufactured by Arc Additive Manufacturing" indicates that the strength is 30-50 MPa higher than that of the material, resulting in an aluminum-silicon alloy with better mechanical properties.

[0042] XRD phase analysis of 4047 aluminum alloy as follows Figure 4 As shown in the figure, the main phases are Al and Si phases, with very little precipitate content and almost no precipitate peaks. At the same time, no impurities from the welding process are introduced into the material.

[0043] Table 1 shows the statistics of density and porosity of the printed 4047 aluminum alloy in this embodiment.

[0044] Table 1. Statistics on density and porosity of printed 4047 aluminum alloy

[0045] Number of trials M1 / g M2 / g Density / % Porosity / % 1 1.6117 0.9799 95.9 4.1 2 1.6102 0.9805 96.1 3.8 3 1.6111 0.9774 95.6 4.4

[0046] Table 1 shows the density and porosity of the samples tested using the Archimedes displacement method. The calculation formula is as follows: Where ρ s ρ is the actual density of the sample. w Let M1 be the density of water, M2 be the mass of the dried sample, and M3 be the mass of the sample when it is fully submerged and free of air bubbles. Dividing the actual density by the standard density gives the sample density. The porosity is calculated using the following formula: Where ρ st This refers to the standard density of aluminum alloy. (The standard density of 4047 aluminum alloy is 2.66 g / cm³.) 3 The density was 95-96%, the porosity was 3.8-4.4%, the porosity was low, and the density was high.

[0047] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for manufacturing aluminum alloys and their composite materials using external ultrasonic vibration-assisted pulsed current arc wire feeding, characterized in that, Includes the following steps: Step 1: Remove the oxide film from the substrate surface, then clean the substrate and solder wire with acetone, and vacuum dry. Step 2: Place the ultrasonic vibrating head on the substrate. Under the protective gas, the ultrasonic equipment vibrates in the z-axis direction, while the arc wire feed stacks the welding wire layer by layer in a certain direction on the xy plane. Step 3: Then, proceed with solution treatment, water quenching, and aging treatment in sequence to complete the process; The welding wire is made of 4-series aluminum-silicon alloy, 2-series aluminum alloy, 5-series aluminum alloy, or aluminum-based composite material with added ceramic phase, wherein the ceramic phase is one or more of TiB2, SiC, and TiC. The protective gas is Ar + 20 vol% CO2, meaning that CO2 accounts for 20% of the total volume of Ar and CO2, and the gas flow rate is 10 L / min - 20 L / min. Step 2 process parameters: welding torch speed 30mm / min-50mm / min, maximum pulse voltage 21V-22V, pulse time 2.0ms-3.2ms, maximum pulse current 235A-238A, base current 26A-32A, base current time 3.0ms-3.2ms; arc starting current 80A-90A, arc ending current 60A-70A, welding current 110A-135A, welding speed 350mm / min-500mm / min, wire feed speed 5 m / min-9 m / min, substrate temperature 100℃-200℃, welding interval between layers 45 s-90 s; Solution treatment at 500℃-520℃ for 4-6 hours; Aging treatment at 180℃-200℃ for 4-8 hours.

2. The method according to claim 1, characterized in that, Vacuum dry at 100℃-150℃ for 6-10 hours.

3. The method according to claim 1, characterized in that, The diameter of the welding wire is 1.2mm.

4. The method according to claim 1, characterized in that, The diameter of the ultrasonic vibrating head is 55mm.

5. A method according to any one of claims 1-4 for processing large-size thin-walled cylindrical parts.

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