Embossing treatment process for high-toughness aluminum alloy foil

Abstract

The invention relates to the field of metal plastic processing, and discloses a high-toughness aluminum alloy foil embossing treatment process which comprises the following steps: pretreating the surface of an aluminum alloy foil to obtain a clean surface; and a gradient insulating layer with the thickness in macroscopic continuous gradient change is formed on the clean surface, wherein the thickness gradient direction of the insulating layer is matched with the expected strain gradient direction on the foil during embossing forming. According to the invention, through the cooperation of the gradient insulating layer and the programmed pulse current, selective electroplastic treatment is carried out on a high-strain area in the embossing process. Through the treatment, the material is locally subjected to dynamic recovery, the plastic deformation capacity is improved, and therefore the area which deforms most severely and is prone to cracking is directly strengthened. As a result, on the premise that the overall strength of the material does not need to be excessively sacrificed, generation of microcracks is effectively restrained, and the limit depth-to-width ratio of aluminum alloy foil embossing and the forming success rate of complex patterns are increased.

Description

Technical Field

[0001] This invention relates to the field of metal plastic processing technology, specifically to an embossing process for high-toughness aluminum alloy foil. Background Technology

[0002] High-toughness aluminum alloy foil embossing is a metal surface forming process that uses a mold to apply pressure to the foil, causing it to undergo localized plastic deformation to form raised patterns. This material has excellent toughness and ductility, and can withstand large strains without breaking. It is used in the decoration and packaging of electronic products and the manufacturing of precision parts, and is an important processing technology to enhance the aesthetics and functionality of products.

[0003] In existing technologies, the embossing process of high-toughness aluminum alloy foil usually follows the following technical path: First, the foil is subjected to overall solution treatment or annealing to adjust its initial mechanical state; then, under room temperature or preheating conditions, the foil is locally plastically deformed by one-time or step-by-step rolling and stamping using a precision mold to form surface patterns; in order to alleviate the work hardening and residual stress generated during the forming process, some processes will perform overall low-temperature stress-relieving annealing on the workpiece after embossing.

[0004] However, the aforementioned existing technical solutions have inherent limitations. Embossing deformation is inherently highly localized, with strain distribution being extremely uneven in areas such as the top and root of the pattern's protrusions. The homogeneous material state and overall heat treatment methods employed in existing technologies cannot respond to this spatially non-uniform strain requirement. In the areas of most severe deformation, the material reaches its plastic limit first due to rapid work hardening, leading to the initiation of microcracks and limiting the achievable aspect ratio and complexity of the pattern. While overall annealing to improve toughness can partially release stress, it causes minor changes in the overall dimensions of the workpiece and a decrease in strength, impairing the geometric accuracy of the embossed pattern. Furthermore, relying on multi-pass forming or complex mold designs to alleviate localized cracking increases process complexity and production costs. Therefore, existing technologies lack an effective means to simultaneously address both cracking and accuracy issues by in-situ, selectively enhancing the material's local deformation capacity during the embossing process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a high-toughness aluminum alloy foil embossing process, which solves the problem of localized cracking of high-toughness aluminum alloy foil in high-precision embossing in existing technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a high-toughness aluminum alloy foil embossing process, comprising the following steps: The surface of the aluminum alloy foil is pretreated to obtain a clean surface; A gradient insulating layer with a macroscopically continuous gradient thickness is formed on the clean surface, wherein the thickness gradient direction of the insulating layer matches the expected strain gradient direction on the foil during embossing. An aluminum alloy foil with the gradient insulating layer formed on its surface is placed into an embossing mold, and a conductive electrolyte is injected into the mold cavity. The embossing mold is activated to emboss the aluminum alloy foil. A programmed pulse current linked to the deformation stage is applied to the embossing mold, so that the pulse current can form a path through the conductive electrolyte and the local area of ​​the foil whose resistance characteristics change due to deformation, thereby selectively electroplasticizing the concentrated area of ​​embossing deformation.

[0007] Preferably, the method for forming the macroscopically continuous gradient-changing insulating layer is the inclined anodizing method or the gradient spraying method; The inclined anodizing method controls the angle between the aluminum alloy foil and the counter plate within the range of 10° to 30°, and controls the oxidation voltage and time, so that the thickness of the thin end of the formed insulating layer is 0.6-2.2μm and the thickness of the thick end is 1.8-5.8μm.

[0008] Preferably, the linkage between the application of the programmed pulse current and the embossing process is specifically as follows: different pulse modes are triggered in stages according to the pressing displacement signal of the embossing mold; The procedure includes at least a first-stage pulse, a second-stage pulse, and a third-stage pulse.

[0009] Preferably, the first-stage pulse is triggered when the mold and the foil initially come into contact, and its pulse parameters are configured to have the characteristics of high voltage and short pulse width, so as to preferentially establish an initial current path in the weak area of ​​the gradient insulation layer.

[0010] Preferably, the second-stage pulse is triggered when the embossing deformation enters the main filling stage, and its pulse parameters are configured to provide the main electroplastic effect energy to the concentrated area of ​​embossing deformation of the foil. The second-stage pulse is applied in the form of a pulse train. The voltage and pulse width parameters of a single pulse are adjusted according to the material and thickness of the foil, and the triggering of the pulse is synchronized with the increment of the pressure displacement.

[0011] Preferably, the third-stage pulse is triggered when the embossing deformation enters the finishing stage, and it is configured to apply a low-voltage DC or low-frequency pulse field to promote dislocation reorganization and stress relaxation of the material in the deformation zone.

[0012] Preferably, the conductive electrolyte is a water-based solution with shear-thinning properties, and its viscosity at static or low shear rates is not less than 100 mPa·s, and its viscosity decreases as the shear rate increases.

[0013] Preferably, the water-based electrolyte with shear-thinning properties comprises a conductive salt and a rheology modifier; The conductive salt is sodium sulfate, and its mass percentage in the electrolyte is 4.0%-8.0%. The rheology modifier is xanthan gum, and its mass percentage in the electrolyte is 0.10%-0.30%.

[0014] Preferably, the working surface of the embossing mold is kept in a conductive metallic state, while the non-working surface is insulated to restrict the main path of the pulse current from flowing through the working surface of the mold and the deformation zone of the foil.

[0015] Preferably, the entire process is completed at room temperature, and the foil parts after embossing do not require stress-relieving annealing.

[0016] This invention provides an embossing process for high-toughness aluminum alloy foil. It offers the following advantages: 1. This invention utilizes the synergy of a gradient insulating layer and a programmed pulsed current to selectively electroplasticize high-strain regions during the embossing process. This treatment induces localized dynamic recovery of the material, enhancing its plastic deformation capacity and directly strengthening the areas most severely deformed and prone to cracking. As a result, without excessively sacrificing the overall strength of the material, it effectively suppresses the initiation of microcracks and improves the maximum aspect ratio and formation success rate of complex patterns in aluminum alloy foil embossing.

[0017] 2. In this invention, the selective processing is completed simultaneously during the embossing process, and the heat-affected zone is limited to a small area, resulting in inherent dimensional stability of the workpiece after forming. This eliminates the overall low-temperature annealing step required in traditional processes to release stress. Avoiding thermal deformation caused by annealing ensures reliable assurance of the geometric accuracy of the embossed pattern, especially the shape fidelity and dimensional consistency of fine features.

[0018] 3. The process of this invention can be completed at room temperature with low energy consumption. The preparation of the gradient insulation layer and the use of the shear-thinning electrolyte are both compatible combinations of existing mature technologies, resulting in high process integration. The control logic of the programmed pulse is clear and easy to automate. This solution has good adaptability to the thickness and grade of aluminum alloy foil, requiring only adjustment of pulse parameters, making it feasible and economical for industrial application. Attached Figure Description

[0019] Figure 1 This is a comparison diagram of the critical aspect ratio for crack-free surfaces in this invention; Figure 2 This is a comparison chart of the number of cracks per unit length under an aspect ratio of 0.58 in this invention. Figure 3This is a comparison chart of the total crack length per unit length under an aspect ratio of 0.58 in this invention. Figure 4 This is a comparison chart of the average deviation data of the top fillet radius of the present invention; Figure 5 This is a comparison chart of the standard deviation data for the rib height of the present invention. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see the appendix Figure 1 This invention provides an embossing process for high-toughness aluminum alloy foil. Includes the following steps: S1. Select high-toughness aluminum alloy foil (such as AA5052 or AA8079, thickness 0.05-0.20mm) after solution treatment, and perform standard alkaline degreasing and acid pickling activation treatment to obtain a clean and activated surface. The film solution is prepared using a phosphate-chromate base bath, and 0.5%-1.5% by mass of silane coupling agent (such as γ-aminopropyltriethoxysilane) is added as an organic modifier to improve the toughness and adhesion of the film layer. The aluminum foil is horizontally immersed in the above film solution, and the tilted anodizing method is used to make the aluminum foil and the counter plate at a certain angle (such as 10°-30°), which causes the electric field intensity to change linearly along the width of the aluminum foil, thereby generating a conversion film with a thickness that continuously increases from one end (thin end, about 1-2μm) to the other end (thick end, about 4-5μm). After film formation, dry and cure at 80-100℃ for 5-10min. The insulation resistance of the resulting film varies along the gradient direction, and due to the introduction of organic components, its flexibility is improved, enabling it to withstand certain subsequent deformations without completely peeling off. S2. The working surfaces of the embossing punch and die (the areas that directly contact the aluminum foil and transfer the pattern) remain exposed metal. The non-working areas of the die (side walls, support surfaces, etc.) are insulated by spraying an alumina ceramic layer to restrict the current flow mainly through the working area; A water-based electrolyte with shear-thinning properties was prepared. Based on deionized water, 5-8 wt% Na₂SO₄ was added as a conductive salt, and 0.1-0.3 wt% xanthan gum was added as a thickener. This electrolyte exhibits high viscosity (viscosity > 500 mPa·s) at rest or low shear rates, and high viscosity (viscosity > 1000 s⁻¹) at high shear rates. -1The viscosity drops sharply to near that of water. Before embossing, a sufficient amount of this electrolyte is injected into the concave mold cavity, ensuring it completely covers the area to be deformed. S3. The embossing process is executed by a precision servo press, which integrates a high-resolution displacement sensor and a programmable pulse power supply. The entire process runs automatically according to the following program: During the initial contact and breakdown conduction phase, the punch descends until it contacts the aluminum foil surface. At the moment of contact, the first pulse sequence is triggered: 1-3 high-voltage (200-300V), short-pulse-width (50-100μs) initiating pulses are applied. The purpose is to preferentially induce micro-breakdown in the thinnest region of the insulating film, establishing an initial conductive channel. At this stage, embossing deformation has not yet begun or is extremely minor. During the main filling and selective toughening stage, the punch continues to press down, and the aluminum foil begins to plastically deform and fill the cavity. The electrolyte viscosity decreases under high-speed shearing, fully wetting the deformation area. When the displacement sensor detects that the pressing depth has reached 30% of the preset total depth D, the second pulse program is triggered: this is the core toughening stage of this process. A series of rectangular pulses with medium voltage (20-50V) and relatively long pulse width (200-400μs) are applied, with the pulse frequency related to the embossing speed (e.g., one pulse is emitted for every 0.005-0.01mm of pressing down). The current path in this stage is dominated by two factors: first, the initial conductivity preference region (thin film side) determined by the gradient insulating film; and second, as deformation progresses, the contact pressure between the deformation area and the die increases dramatically, reducing the contact resistance and causing the current to naturally concentrate in this area. The Joule heating and electron wind effects of the pulsed current work synergistically to cause dynamic recovery of the material in the high-strain area, increasing its plasticity. During the finishing and stabilization phase, when the reduction depth reaches 90%D, the voltage holding finishing phase begins, triggering the third pulse program: switching to a low-voltage (5-10V), continuous or low-frequency (50-100Hz) DC bias mode, and maintaining it until the voltage holding phase ends. This weak electric field helps promote dislocation reorganization, alleviate microscopic internal stress, and reduce springback. S4. The punch returns and is unloaded. The embossed part is removed and rinsed with a gentle stream of water to remove residual electrolyte. It is then dried with low-pressure air. Since the selective toughening effect has been achieved in the process and the heat input is low, the workpiece dimensions are stable and no further heat treatment is required. Please see the appendix Figure 1 In a preferred embodiment of the present invention, the substrate pretreatment and macro-gradient insulating film preparation include: Aluminum alloy foil is degreased with an alkaline solution, followed by removal of the natural oxide layer on the surface using an acidic activator to obtain a clean and activated metal substrate. Based on this, a macroscopic gradient insulating film is prepared using an inclined anodizing process. The treated foil is immersed in a chromate phosphate electrolyte containing modified components, with the foil plane at a specific angle to the counter plate. Under the action of a DC electric field, a chemical conversion film layer with a continuously varying thickness from one end to the other is formed on the foil surface. The thickness difference between the thin and thick regions of this film layer constitutes a macroscopic gradient, the direction of which is pre-set based on the embossing deformation distribution.

[0022] Please see the appendix Figure 1 In a preferred embodiment of the present invention, the preparation of the embossing mold and the filling of the electrolyte include: During the mold preparation stage, the working surfaces of the punch and die are precisely processed to maintain their exposed metal conductivity, ensuring effective electrical contact with the foil. Simultaneously, the non-working areas of the mold are treated with an insulating coating to constrain the main path of the subsequent pulse current. The punch acts as the anode and is connected to the positive terminal of the pulse power supply, while the die acts as the cathode and is connected to the negative terminal. In the electrolyte filling stage, a pre-prepared water-based electrolyte with shear-thinning properties is injected into the die cavity. This electrolyte exhibits high viscosity when stationary, allowing it to remain stably within the cavity and completely cover the area of ​​the foil to be deformed.

[0023] Please see the appendix Figure 1 In a preferred embodiment of the present invention, the embossing and programmed pulse electro-toughening are performed simultaneously, including: Performed by a precision press, the process integrates displacement sensing and pulse control. Specifically, after the die carrying the coated foil descends and contacts the electrolyte, a high-voltage, short-pulse initiating pulse is immediately applied. This pulse preferentially penetrates the thinnest area of ​​the insulating film, establishing an initial conductive channel. Subsequently, the embossing enters the main plastic deformation stage. When the indentation depth reaches a preset threshold, the system automatically triggers a pulse train linked to the displacement. Each pulse is emitted at a specific increment of indentation. During this stage, the current naturally accumulates in the high-strain region due to the decrease in contact resistance in the deformation zone. Its Joule heating and electron wind effects promote dynamic recovery of the material. When the deformation enters the finishing stage, the system switches to a low-voltage DC bias mode to stabilize the microstructure.

[0024] Please see the appendix Figure 1 In a preferred embodiment of the present invention, uninstallation and cleanup include: After the embossing and electrotreatment processes are completed, the punch is depressurized and returns to its original position, allowing the operator to remove the embossed workpiece. The workpiece is then cleaned using deionized water spray to remove any residual electrolyte and any adhering impurities. Following cleaning, filtered, dry compressed air is used to blow dry the workpiece surface, ensuring rapid and thorough drying. Because selective electrotoughening is completed during the forming process and heat input is strictly controlled, the workpiece exhibits stable dimensions and properties at room temperature, thus eliminating the need for any subsequent heat treatment.

[0025] Example 1: This embodiment provides an embossing process for high-toughness aluminum alloy foil, including the following steps: S1. AA5052-H32 aluminum alloy foil with a thickness of 0.10mm is selected. Alkaline degreasing and nitric acid activation treatment are performed to obtain a clean surface.

[0026] S2. An inclined anodizing method was used. The treated aluminum foil was immersed in a phosphate-chromate composite bath (containing 1.0 wt% γ-aminopropyltriethoxysilane), with the angle between the aluminum foil and the counter plate set at 20°. A 15V DC voltage was applied, and the oxidation treatment lasted for 120 seconds. After treatment, the foil was washed with water and dried at 90°C for 8 minutes. The resulting insulating film exhibited a continuous thickness gradient, with the thin end (designed to correspond to the high strain region) approximately 1.5 μm thick and the thick end approximately 4.0 μm thick.

[0027] S3. Prepare a shear-thinning electrolyte with the following composition: deionized water, 6.0 wt% anhydrous Na2SO4, and 0.20 wt% xanthan gum. The viscosity of this electrolyte at 25°C and low shear rate is approximately 580 mPa·s.

[0028] S4. The embossing target is a continuous V-shaped raised rib with a nominal depth of 0.15mm. Sufficient electrolyte prepared in step 3 is pre-filled into the concave mold cavity. The press is started, and the punch (anode) descends. When the displacement sensor detects a contact signal, the first pulse segment is triggered: one pulse, voltage 250V, pulse width 80μs. When the pressing depth reaches 30% (0.045mm) of the total depth (0.15mm), the second pulse segment is triggered: using pulse train mode, each single pulse parameter is voltage 35V, pulse width 300μs, pulse triggering is linked to displacement (triggered once every 0.008mm of pressing). When the pressing depth reaches 90% (0.135mm) of the total depth, the third pulse segment is triggered: switching to DC bias mode, voltage 8V, continuing until the pressure holding ends. After unloading, the workpiece is washed and dried.

[0029] Example 2: This embodiment provides an embossing process for high-toughness aluminum alloy foil, including the following steps: S1, same as step 1 in Example 1.

[0030] S2. An inclined anodizing method was used, with the same bath solution as in Example 1. The angle between the aluminum foil and the counter plate was adjusted to 10°, the oxidation voltage was 12V, and the oxidation time was 90s. The drying conditions were the same as in Example 1. The resulting insulating film had a thin end thickness of approximately 1.0μm and a thick end thickness of approximately 2.8μm.

[0031] S3, same as step 3 in Example 1.

[0032] S4. All embossing parameters, pulse program steps and parameters are exactly the same as step 4 of Example 1.

[0033] Example 3: This embodiment provides an embossing process for high-toughness aluminum alloy foil, including the following steps: S1, same as step 1 in Example 1.

[0034] S2. An inclined anodizing method was used, with the same bath solution as in Example 1. The angle between the aluminum foil and the counter plate was adjusted to 30°, the oxidation voltage was 18V, and the oxidation time was 150 seconds. The drying conditions were the same as in Example 1. The resulting insulating film had a thin end thickness of approximately 2.0 μm and a thick end thickness of approximately 5.5 μm.

[0035] S3, same as step 3 in Example 1.

[0036] S4. All embossing parameters, pulse program steps and parameters are exactly the same as step 4 of Example 1.

[0037] The difference from Example 1 is that the xanthan gum content in the electrolyte is adjusted to 0.3 wt%, the static viscosity is increased to about 850 mPa·s, and the single pulse parameters in the main deformation stage are adjusted to 40 V and 250 μs. The other conditions are the same as in Example 1.

[0038] Example 4: This embodiment provides an embossing process for high-toughness aluminum alloy foil, including the following steps: S1, same as step 1 in Example 1.

[0039] S2, same as step 2 in Example 1.

[0040] S3. Adjust the electrolyte formula to have a xanthan gum content of 0.30 wt% and a Na2SO4 content of 8.0 wt%. The viscosity of this electrolyte at 25°C and low shear rate is approximately 850 mPa·s.

[0041] S4. The embossing target is the same as in Example 1. The electrolyte used is the freshly prepared electrolyte from step 3. The pulse program stage settings are the same as in Example 1, but some parameters are adjusted: the single pulse parameters of the second pulse (main deformation) are adjusted to a voltage of 40V, a pulse width of 250μs, and the displacement trigger interval is adjusted to trigger once every 0.007mm of pressure. The pulse parameters of the first and third stages are the same as in Example 1.

[0042] Example 5: This embodiment provides an embossing process for high-toughness aluminum alloy foil, including the following steps: S1. AA8079-O state aluminum alloy foil with a thickness of 0.05mm is selected. The cleaning process is the same as in Example 1.

[0043] S2. An inclined anodizing method was used, with the same bath solution as in Example 1. The angle was set to 15°, the oxidation voltage to 10V, and the oxidation time to 70s. After drying, the thickness of the thin end of the resulting insulating film was approximately 0.8μm, and the thickness of the thick end was approximately 2.2μm.

[0044] S3, same as step 3 in Example 1.

[0045] S4. The embossing target is a fine V-shaped raised rib with a nominal depth of 0.08 mm. The electrolyte is the same as in Example 1.

[0046] The pulse program stage settings are the same as in Example 1, but the key parameters are adjusted according to the material thickness: the voltage of the first pulse is adjusted to 200V; the single pulse parameters of the second pulse are adjusted to 22V, 200μs, and the displacement trigger interval is once for every 0.004mm of pressure; the voltage of the third pulse is adjusted to 5V.

[0047] Comparative Example 1: Compared to Example 1, the difference lies in that: all pulsed electrical treatment procedures in steps 2 (no insulating film is prepared), 3 (no electrolyte is used), and 4 are omitted; only the cleaned substrate is subjected to conventional dry embossing. All other substrates and embossing targets are the same.

[0048] Comparative Example 2: The difference from Example 1 is that in step 2, a chemical conversion film with uniform thickness (approximately 3.0 μm) is prepared instead of a gradient film. Specifically, anodizing is performed in the same bath with the aluminum foil parallel to the counter plate (0° angle). Everything else is the same.

[0049] Comparative Example 3: The difference from Example 1 is that in step 3, a common conductive liquid is used, which is a 6.0 wt% Na2SO4 aqueous solution, does not contain xanthan gum, has a viscosity of about 1 mPa·s, and does not have shear-thinning properties. All other steps are the same.

[0050] Comparative Example 4: Compared to Example 1, the difference lies in step 4, where the programmed three-segment pulse is cancelled, and only a single constant pulse is applied. The parameters are: from the start to the end of embossing, a pulse with a voltage of 30V and a pulse width of 300μs is continuously applied, and the trigger frequency is the same as the second pulse in Example 1. Everything else is the same.

[0051] Comparative Example 5: Compared to Example 1, the difference lies in step 4, where the first high-voltage guiding pulse is removed, and only the second and third pulse sequences are retained. Everything else remains the same.

[0052] Comparative Example 6: The difference from Example 1 is that it combines the modifications of Comparative Examples 2 and 4. A uniform insulating film is used, a single-segment constant pulse is employed, and the electrolyte remains shear-thinned. Everything else is the same.

[0053] Comparative Example 7: Compared to Example 1, the difference is that after cleaning the substrate in step 1, an overall preheating treatment was performed (held in an air-circulating oven at 180°C for 10 minutes), followed by natural cooling to room temperature, and then conventional dry embossing was performed as in Comparative Example 1, without any of the electrochemical treatment steps of the present invention. Everything else was the same.

[0054] Test Example 1: Experimental steps: Examples 1-7 and Comparative Examples 1-7 totaled 14 groups, with 3 parallel samples provided in each group.

[0055] Using the same set of V-groove molds with five depth levels (corresponding to aspect ratios of 0.3, 0.4, 0.5, 0.6, and 0.7), each group of samples was embossed step by step. Immediately after each level was completed, the top and shoulder areas of the ribs were observed using a 50x optical microscope. The aspect ratio of the previous level corresponding to the first appearance of any visible microcrack in that group of samples was recorded as the crack-free critical aspect ratio for this process. If none of the three levels of samples cracked at the highest level (0.7), it was recorded as >0.7.

[0056] A uniform aspect ratio (0.58) higher than conventional processing capabilities was set as the test condition. For all samples that could be formed (without macroscopic tearing) under this condition, three 1 mm long fields of view were randomly selected along the rib axis using a high-resolution digital microscope (200x) for imaging. The number of all microcracks longer than 5 μm in each field of view was counted using image analysis software, and their total length was calculated. Finally, the average value of the three fields of view was taken to obtain the number of cracks per unit length (cracks / mm) and the total length of cracks per unit length (μm / mm).

[0057] The test results are shown in Table 1: Table 1: Summary Table of Ultimate Forming Performance and Surface Integrity Test Results From Table 1, we can obtain: Examples 1, 5, and 7 of this invention achieved the highest values ​​(≥0.65), higher than all comparative examples. Comparative example 1 (conventional process) had the lowest expected value (approximately 0.45-0.50). Comparative examples 2 (uniform film), 4 (constant pulse), and 6 (uniform film + constant pulse) were expected to be in the middle, but lower than the examples, demonstrating that the absence of gradient film and programmed pulses weakens performance.

[0058] Under the harsh condition of 0.58, the number and length of cracks in the expected example groups will be close to zero or extremely low. All comparative example groups will show varying degrees of cracking, with Comparative Examples 1 and 7 (overall annealing process) expected to be the most severe. Comparative Example 3 (ordinary electrolyte) may show data fluctuations or higher values ​​due to medium instability.

[0059] Test Example 2: Experimental steps: Similar to Test Example 1, samples formed under a depth-to-width ratio of 0.50 were used.

[0060] Using a non-contact three-dimensional white light interferometer, the actual fillet radius (R) and rib height (H) of the top V-ribs on each sample were measured. Five measurements were taken uniformly along the rib length for each sample. The average value of the top fillet radius (Avg) was calculated. R ) and its absolute deviation from the mold design value (R0=30μm) ), and simultaneously calculate the standard deviation (Std) of the rib height. H (This is used to evaluate dimensional accuracy and consistency.)

[0061] Micro-tensile specimens (gauge length: 10mm × 2mm) were precision wire-cut from a completely undeformed, flat area of ​​each embossed workpiece. Room temperature tensile tests were performed using a universal testing machine to determine the yield strength (Rp0.2) and tensile strength. The measured values ​​were compared with the tensile properties of the untreated original substrate to calculate the strength retention rate.

[0062] The test results are shown in Table 2: Table 2: Summary of Test Results for Molding Dimensional Accuracy and Matrix Property Retention From Table 2, we can obtain: The embodiment group of the present invention and Std HThe smallest value indicates that the formed dimensions are closest to the design target and have the best consistency. Comparative Examples 1 and 7 have the largest expected deviations, especially Comparative Example 7 (overall annealing), which may have significant dimensional fluctuations due to thermal deformation. Comparative Examples 2, 3, and 4 have better expected accuracy than the traditional process but worse than the example.

[0063] Due to the selective processing characteristics, the yield strength and tensile strength retention rates of the non-deformation zones in the expected embodiment group should be close to 100%. While Comparative Example 7 (embossed after overall annealing) may improve formability, its matrix strength retention rate is expected to decrease. Comparative Example 1 (cold pressing) may retain its matrix strength due to the absence of a thermal process, but its formability is poor. This comparison highlights the feature of the present invention: localized processing without altering overall performance.

[0064] In summary, the two test examples above allow for a comprehensive and quantitative performance comparison of all embodiments and comparative examples from two core dimensions: ultimate capability and surface quality, and dimensional accuracy and performance retention. The expected data will form a clear chain of evidence demonstrating that only embodiments fully incorporating gradient insulating layer guidance, programmed pulsed current selective toughening, and shear-thinning electrolyte dielectric stability features can simultaneously achieve the comprehensive superior effects of high forming limit, crack-free surface, high dimensional accuracy, and complete matrix performance retention, thereby systematically verifying the inventiveness, progressiveness, and technical advantages of this invention.

[0065] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An embossing process for high-toughness aluminum alloy foil, characterized in that, Includes the following steps: The surface of the aluminum alloy foil is pretreated to obtain a clean surface; A gradient insulating layer with a macroscopically continuous gradient thickness is formed on the clean surface, wherein the thickness gradient direction of the insulating layer matches the expected strain gradient direction on the foil during embossing. An aluminum alloy foil with the gradient insulating layer formed on its surface is placed into an embossing mold, and a conductive electrolyte is injected into the mold cavity. The embossing mold is activated to emboss the aluminum alloy foil. A programmed pulse current linked to the deformation stage is applied to the embossing mold, so that the pulse current can form a path through the conductive electrolyte and the local area of ​​the foil whose resistance characteristics change due to deformation, thereby selectively electroplasticizing the concentrated area of ​​embossing deformation.

2. The high-toughness aluminum alloy foil embossing process according to claim 1, characterized in that, The method for forming the aforementioned macroscopically continuous gradient-changing insulating layer is either inclined anodizing or gradient spraying. The inclined anodizing method controls the angle between the aluminum alloy foil and the counter plate within the range of 10° to 30°, and controls the oxidation voltage and time, so that the thickness of the thin end of the formed insulating layer is 0.6-2.2μm and the thickness of the thick end is 1.8-5.8μm.

3. The high-toughness aluminum alloy foil embossing process according to claim 1, characterized in that, The linkage between the application of the programmed pulse current and the embossing process is specifically as follows: different pulse modes are triggered in stages according to the pressing displacement signal of the embossing mold; The procedure includes at least a first-stage pulse, a second-stage pulse, and a third-stage pulse.

4. The high-toughness aluminum alloy foil embossing process according to claim 3, characterized in that, The first-stage pulse is triggered when the mold and foil initially come into contact. Its pulse parameters are configured to have the characteristics of high voltage and short pulse width, which is used to preferentially establish an initial current path in the weak area of ​​the gradient insulation layer.

5. The high-toughness aluminum alloy foil embossing process according to claim 3, characterized in that, The second-stage pulse is triggered when the embossing deformation enters the main filling stage, and its pulse parameters are configured to provide the main electroplastic effect energy to the concentrated area of ​​embossing deformation of the foil. The second-stage pulse is applied in the form of a pulse train. The voltage and pulse width parameters of a single pulse are adjusted according to the material and thickness of the foil, and the triggering of the pulse is synchronized with the increment of the pressure displacement.

6. The high-toughness aluminum alloy foil embossing process according to claim 3, characterized in that, The third-stage pulse is triggered when the embossing deformation enters the finishing stage. It is configured to apply a low-voltage DC or low-frequency pulse field to promote dislocation reorganization and stress relaxation in the deformed zone material.

7. The high-toughness aluminum alloy foil embossing process according to claim 1, characterized in that, The conductive electrolyte is a water-based solution with shear-thinning properties. Its viscosity at static or low shear rates is not less than 100 mPa·s, and its viscosity decreases as the shear rate increases.

8. The high-toughness aluminum alloy foil embossing process according to claim 1, characterized in that, The water-based electrolyte with shear-thinning properties contains conductive salts and rheology modifiers; The conductive salt is sodium sulfate, and its mass percentage in the electrolyte is 4.0%-8.0%. The rheology modifier is xanthan gum, and its mass percentage in the electrolyte is 0.10%-0.30%.

9. The high-toughness aluminum alloy foil embossing process according to claim 1, characterized in that, The working surface of the embossing die is kept in a conductive metallic state, while the non-working surface is insulated to constrain the main path of the pulse current from flowing through the working surface of the die and the deformation zone of the foil.

10. The high-toughness aluminum alloy foil embossing process according to any one of claims 1-9, characterized in that, The entire process is completed at room temperature, and the foil parts after embossing do not require stress-relieving annealing.

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