A method for repairing cracks in aluminum alloy test pieces using a pointed thin sheet anode

Abstract

A method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode, belonging to the field of aluminum alloy specimen repair, includes: (1) determining the crack repair requirements based on the service environment of the aluminum alloy specimen, and determining the required solder according to the repair requirements; (2) ultrasonically cleaning the inside of the crack; (3) ultrasonically repairing the crack to be repaired; first, the specimen is placed on a heating platform for heating. After heating to the specified temperature, the solder is placed inside the crack. After the solder is completely melted, the pointed thin-film acoustic electrode is inserted into the solder, and the ultrasonic treatment is turned on for repair; (4) after the repair is completed, the microstructure and properties of the weld are tested. This repair method is highly operable. The repair process under ultrasonic action can be carried out directly in an atmospheric environment without the need for protective gas or special environment, reducing repair costs and adapting to various complex shapes, small widths, and large depths of cracks.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy specimen repair, specifically relating to a method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode. Background Technology

[0002] Lightweighting is a major trend in modern manufacturing, leading to the increasing use of lightweight aluminum alloy specimens. However, aluminum alloy specimens often exhibit defects such as fatigue cracks and corrosion cracks during use; in particular, if the aluminum alloy specimen has welded joints, the welded areas are particularly prone to defects. Directly replacing defective specimens would result in unnecessary waste and significantly increase manufacturing costs. Therefore, it is necessary to repair crack defects.

[0003] Currently, there are many methods for repairing crack defects, and the methods employed are diverse. Patent 202022744633.7 discloses a laser cladding device for easy crack repair. This device automates the operation of the laser cladding body, allowing it to move accordingly, and can be remotely controlled, facilitating operator use. Patent 202122443007.9 discloses a crack-filling welding device for gathering and transportation pipelines. Through the cooperation of the mounting block and mounting groove, the welding torch placement plate and welding torch can move around the outer wall of the pipeline. Operators can use the welding torch to complete the crack-filling welding work by moving the mounting block, reducing the workload and labor intensity of operators and improving work efficiency. Patent 202110795589.9 discloses an epoxy-encapsulated electronic component capable of in-situ crack repair and non-destructive disassembly. The main component of this method is epoxy potting compound, which is composed of epoxy resin, epoxy curing agent, epoxy diluent, inorganic filler, and catalyst. Capable of repairing cracks below 150℃ and disassembling below 100℃, its encapsulated electronic components enable in-situ crack repair and non-destructive disassembly. Patent 201710123487.6 discloses a method for in-situ repair of defects in thermoplastic composite materials using ultrasonic thermal in-situ. It utilizes the driving force generated by ultrasound to drive fluid outside the gap to fill it, thereby filling the local delamination area of ​​the composite material with homogeneous resin material, achieving the repair of delamination defects. This repair process can reduce the repair temperature, avoid problems such as overheating and oxidation of the material, and improve repair efficiency. Patent 202111306009.1 discloses a laser cladding method for repairing surface cracks in shaft parts, specifically for cracks with a depth not exceeding 500 micrometers. The method involves repairing cracks in shaft parts with a crack depth not exceeding 100 micrometers using pulsed current discharge, and repairing shaft parts with crack depths between 100 and 500 micrometers using laser cladding, applying ultrasonic vibration to the cladding layer during the cladding process. Patent 201610956707.9 discloses a three-dimensional brazing repair material and its preparation method for hot-end components of an engine. This method uses specialized vacuum sintering fixtures, and the repair material preparation method is simple and low-cost. The resulting repair material meets the requirements for three-dimensional repair of hot-end components of aero-engines, and also meets the requirements for repairing cracks with a width exceeding 1 mm. Patent 201710508805.0 discloses a brazing repair method for turbine guide vanes cracks. The general steps of this method are: removing the crack at the crack in the turbine guide vane, setting a bevel, laying a bottom layer of nickel-based alloy powder within the bevel, placing a mixed brazing filler metal on the bottom layer of nickel-based alloy powder, and performing vacuum brazing. The joint repaired by this method can guarantee stable structure and strength.Patent 202011131928.5 discloses a method for repairing cast iron parts by argon arc brazing. This method uses argon arc welding as the heat source, and the damaged area of ​​the part to be repaired needs to be removed and cleaned before repair. This method can achieve crack-free and efficient repair of cast iron parts, with good mechanical properties and machinability in the repaired area. Because a high-energy-density argon arc is used as the brazing heat source, the deformation of the repaired part is minimal.

[0004] It can be seen that laser cladding is currently one of the commonly used methods for crack repair, but this method has certain shortcomings. First, laser cladding equipment is expensive, which greatly increases the repair cost. Second, aluminum alloy specimens reflect laser light to some extent, resulting in poor repair effects. Third, laser cladding has a limited repair thickness and cannot effectively repair deep cracks. Another commonly used method is vacuum brazing repair, but this method also has some shortcomings. First, the experimental conditions for vacuum brazing are harsh and cannot be carried out in an atmospheric environment. Second, vacuum furnaces are often limited in size, making it impossible to place large aluminum alloy specimens inside for repair. Third, the temperature of vacuum brazing is generally high, which can easily cause significant softening of the specimen. In addition, many methods require grinding and planing away the original crack location before repair, a time-consuming and labor-intensive process. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a method for repairing crack defects using a pointed thin-film ultrasonic electrode. The advantages of this method are: 1. The ultrasonic soldering iron (ultrasonic generator) is simple to operate and significantly lower in cost than laser cladding and vacuum brazing methods; 2. This method is not limited by the repair environment and can be performed directly in an atmospheric environment; 3. The repair temperature is low, resulting in minimal specimen deformation and low softening of the base material; 4. It is not limited by the crack shape and can repair small cracks; 5. It is not limited by the crack depth and can repair cracks of any depth; 6. It is not limited by the shape of the aluminum alloy specimen, making it highly applicable.

[0006] To achieve rapid and efficient repair of cracks in aluminum alloy specimens, this invention utilizes a special pointed thin-film acoustic electrode. The pointed thin-film acoustic electrode has an extremely small tip size, allowing it to penetrate deep into the crack defect. Figure 1 .

[0007] The tip-shaped acoustic electrode of this invention is made of TC4 titanium alloy and is divided into upper and lower parts. The upper part (also known as the clamping area, used to connect the ultrasonic generator) is cylindrical with a diameter of 18-20 mm and a height of 30-80 mm. The lower part (also known as the tip part) is pointed with a height of 30-100 mm and a thickness of 0.1 mm-0.5 mm at its tip. The θ angle of the tip is 1-20°.

[0008] A method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode, comprising the following steps:

[0009] (1) Determine the crack repair requirements based on the service environment of the aluminum alloy specimen, and determine the required solder according to the repair requirements;

[0010] (2) Perform ultrasonic cleaning on the inside of the crack;

[0011] (3) Perform ultrasonic repair on the crack to be repaired; First, place the specimen on a heating platform and heat it. When it reaches the specified temperature, place the solder in the crack. When the solder is completely melted, insert the tip thin-plate acoustic electrode into the solder and turn on the ultrasonic to repair it.

[0012] (4) After the repair is completed, the microstructure and properties of the weld are tested.

[0013] In step (1), aluminum alloy specimens under different usage environments have different requirements for the repair process. For example, specimens used for sealing have requirements for airtightness after repair; load-bearing specimens have requirements for strength and hardness after repair; and precision specimens have requirements for deformation after repair.

[0014] Specifically, if the aluminum alloy specimen has strict requirements for deformation, a low-temperature solder, such as Sn-based solder, should be selected during the repair process; if the specimen has requirements for airtightness, a solder with high miscibility with aluminum and a similar coefficient of thermal expansion should be selected, such as Zn-based solder; if the specimen has requirements for strength after repair, a high-strength Al-Si solder or Al-based solder (such as Al-Si-Cu solder) with higher operating temperature should be selected.

[0015] In step (2), when the crack depth is large (the crack depth is greater than or equal to 1 / 2 of the specimen thickness), the amplitude is selected as 20-100μm and the ultrasonic time is greater than or equal to 20s to ensure that the oxide film inside the crack is removed more thoroughly; when the crack width and depth are small (the crack depth is less than 1 / 2 of the specimen thickness), the amplitude is selected as 10-50μm and the ultrasonic time is less than 20s.

[0016] In step (3), the frequency of the ultrasound is 15-60kHz, the amplitude is 10-30μm, the power is 300-2000W, the ultrasound time is 1-100s, and the heating temperature is 200-700℃.

[0017] Step (4) specifically includes: performing microstructural testing on the repaired weld to observe the removal of the oxide film from the cracks and the presence of porosity in the weld; testing the hardness and strength of the weld to observe whether its strength meets the repair requirements; and performing X-ray testing on the weld to observe the internal repair effect without damaging the weld. If the hardness or strength of the repaired weld does not meet the requirements, the specimen can be heat-treated to improve its strength. Alternatively, the repaired weld area can be melted down, and a new material can be selected for repair.

[0018] The mechanism of this invention is as follows:

[0019] Without ultrasonic treatment, liquid solder is difficult to fill to the crack tip due to its surface tension. Applying ultrasound can significantly increase the sound pressure level inside the liquid solder, effectively solving the problem of difficult crack tip filling. For complex-shaped cracks, the thin-film acoustic electrode at the tip can more easily penetrate into the defect. The closer the thin-film acoustic electrode is to the crack wall, the stronger the acoustic cavitation effect near the crack, resulting in better removal of the surface oxide film. Furthermore, strong acoustic cavitation can accelerate element diffusion between the solder and the substrate, facilitating high-quality repair. After crack repair, element diffusion can occur at the crack tip, and the solder dissolves the base material, eliminating stress concentration at the crack tip.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The pointed thin-film acoustic electrode is inexpensive, small in size, and easy to carry and operate. The complete repair device is highly adaptable to different structures, making it convenient for repairing various types of complex structural components, and can also adapt to various complex operating environments.

[0022] 2. The tip of the thin-film acoustic electrode is small in size and thickness, which can adapt to cracks of various complex shapes, narrow widths and deep depths.

[0023] 3. During the repair process, because the liquid solder is located inside the narrow gap structure of the crack, this narrow gap structure causes extremely strong acoustic cavitation within the solder. The high acoustic pressure within the solder can overcome the large surface tension at the crack tip, which is beneficial for the solder to fill the crack tip. In addition, when extremely strong acoustic cavitation occurs in the liquid solder, it can complete the removal of the oxide film inside the crack in a very short time, thereby greatly shortening the repair time.

[0024] 4. High efficiency of ultrasonic cleaning inside cracks. Similar to the previous principle, when using solvents such as alcohol and acetone to ultrasonically clean impurities inside cracks, the narrow gap structure allows for extremely strong acoustic cavitation within the alcohol / acetone, which can greatly improve cleaning efficiency.

[0025] 5. This repair method is highly operable. The repair process under ultrasonic action can be carried out directly in an atmospheric environment without the need for protective gas or special environment, thus reducing repair costs. Attached Figure Description

[0026] Figure 1 This invention is a thin-film acoustic electrode with a pointed tip;

[0027] Figure 2 Schematic diagram of ultrasonic cleaning cracks;

[0028] Figure 3 Diagram of the repair process;

[0029] Figure 4 Image showing the effect of oxide film removal after repair;

[0030] Figure 5 Overall restoration effect diagram;

[0031] Figure 6 Diagram showing the repair results.

[0032] In the figure: 1-tipped thin acoustic electrode, 2-crack, 3-sample, 4-cavitation bubble in alcohol, 5-alcohol, 6-cavitation bubble in solder, 7-solder, 8-heating stage, 9-atmospheric environment. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Example 1

[0035] A method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode

[0036] The material used for the tip-shaped thin acoustic electrode is TC4 titanium alloy. It is divided into upper and lower parts. The upper part (also known as the clamping area, used to connect the ultrasonic generator) is cylindrical with a diameter of 20mm and a height of 30mm. The lower part (also known as the tip part) is pointed with a height of 35mm. The thickness at the tip is 0.1mm and the θ angle at the tip is 3°.

[0037] The specific operating steps include:

[0038] (1) This aluminum alloy specimen is mainly used under high-temperature conditions. After repair, the specimen will withstand a temperature range from room temperature to 400℃. Furthermore, the repaired specimen must have good sealing properties and be leak-free. Based on the above repair requirements, the required solder is Al5Si27Cu.

[0039] (2) Perform ultrasonic cleaning on the crack to be repaired; first, pour acetone into the crack, then insert the pointed thin-film acoustic electrode into the acetone, turn on the ultrasound, the frequency of the ultrasound is 27.6kHz, the amplitude is 10μm, the power is 300W, and the cleaning time is 5min to complete the cleaning of the inside of the crack. Figure 2 As shown;

[0040] (3) Ultrasonic repair of the crack to be repaired: The specimen was placed on a heating platform and heated to 530℃. After reaching the specified heating temperature, Al5Si27Cu ​​solder was placed inside the crack. After the solder was completely melted, a pointed thin-film ultrasonic electrode was inserted into the Al5Si27Cu ​​solder, and the ultrasonic treatment was started. The ultrasonic frequency was 27.6kHz, the amplitude was 10μm, the power was 300W, and the ultrasonic time was 2s. The entire repair process was carried out in an atmospheric environment. Figure 3 As shown;

[0041] (4) After repair, the specimen was removed from the heating platform and cooled to room temperature. Microstructure testing, hardness testing, and X-ray testing were then performed on the repaired specimen. The effect of oxide film removal after repair is shown in the image below. Figure 4 As shown, the overall repair effect is as follows: Figure 5 As shown.

[0042] Example 2

[0043] A method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode is described. The operation method is the same as in Example 1, except that the repair solder used in step (1) of Example 2 is Zn5Al, the heating temperature set in step (3) is 420℃, and the remaining steps and process parameters are the same as in Example 1.

[0044] Example 3

[0045] A method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode is described. The operation method is the same as in Example 1, except that the repair solder used in step (1) of Example 3 is Al12Si; the heating temperature set in step (3) is 620℃, and the remaining steps are the same as in Example 1.

[0046] Example 4

[0047] A method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode is described. The operation method is the same as in Example 1, except that the heating temperature set in step (3) of Example 4 is 550°C. The remaining steps are the same as in Example 1, and the repair result is as follows: Figure 6 As shown.

[0048] The above technical solutions illustrate the technical concept of the present invention, but should not be construed as limiting the scope of protection of the present invention. Any modifications or alterations made to the above technical solutions based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for repairing crack defects in aluminum alloy specimens using a pointed thin-film acoustic electrode, characterized in that, Includes the following steps: (1) Determine the crack repair requirements based on the service environment of the aluminum alloy specimen, and determine the required solder according to the repair requirements; (2) Perform ultrasonic cleaning on the inside of the crack; When the crack depth is greater than or equal to 1 / 2 of the specimen thickness, the amplitude should be 20-100 µm and the ultrasonic time should be greater than or equal to 20 s; when the crack depth is less than 1 / 2 of the specimen thickness, the amplitude should be 10-50 µm and the ultrasonic time should be less than 20 s. (3) Perform ultrasonic repair on the crack to be repaired; First, the specimen is placed on a heating platform and heated. Once the specified temperature is reached, solder is placed inside the crack. After the solder has completely melted, a pointed thin-film acoustic electrode is inserted into the solder, and ultrasonic testing is initiated for repair. The pointed thin-film acoustic electrode is made of TC4 titanium alloy and consists of two parts: an upper cylindrical part with a diameter of 18-20 mm and a height of 30-80 mm, and a lower pointed part with a height of 30-100 mm and a thickness of 0.1 mm-0.5 mm at its tip, with a θ angle of 1-20°. The ultrasonic frequency is 15-60 kHz, the amplitude is 10-30 µm, the power is 300-2000 W, the ultrasonic time is 1-100 s, and the heating temperature is 200-700 °C. (4) After the repair is completed, the structure and properties of the weld are tested.

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