Preparation method of aluminum alloy and product thereof

Abstract

The invention provides a preparation method of an aluminum alloy and a product thereof. According to the method, the anti-fatigue performance of the aluminum alloy is improved by adjusting the process sequence of multidirectional forging and pressing; the yield strength is improved through stabilizing treatment and differential temperature equal channel angular pressing; the uniformity of the anodic oxidation appearance of the aluminum alloy is improved by adding Cr and Mn elements; the corrosion resistance of the aluminum alloy material is improved through the dispersed phase pre-precipitation step; by reducing the viscosity of a molten aluminum alloy liquid phase, the pore generation rate of an aluminum alloy material during pulse laser welding is reduced.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, specifically to a method for preparing aluminum alloys and its products. Background Technology

[0002] Aluminum alloys are widely used in aerospace, automotive manufacturing, and electronics industries due to their excellent specific strength, good formability, and corrosion resistance. High-strength aluminum alloys, in particular, can achieve even higher mechanical properties through heat treatment methods such as solution treatment and aging, meeting modern industry's demands for lightweighting and structural performance. However, current aluminum alloy materials still have the following issues that require improvement.

[0003] Fatigue failure is one of the main failure modes of aluminum alloy structural components. Traditional high-strength aluminum alloy heat treatment processes (solution treatment + aging treatment) have a fundamental flaw: solution treatment requires heating above the recrystallization temperature, leading to recrystallization and abnormal grain coarsening, significantly reducing the material's fatigue strength. Even subsequent aging treatment cannot compensate for this microstructural defect, resulting in a decline in the overall fatigue performance of the final product, failing to meet the application requirements of high-end structural components. Existing technologies attempt to refine the grains by adding elements such as Zr and Sc and applying intense plastic deformation before solution treatment, but the subsequent high-temperature solution treatment process still damages the fine-grained structure, and may even lead to more severe grain coarsening due to uneven local strain; the problem remains unresolved.

[0004] Intense plastic deformation techniques such as equal channel angle extrusion are effective methods for preparing ultrafine-grained, ultra-high-strength aluminum alloys. However, for alloys containing Zn and Mg, such as 7xxx alloys, if equal channel angle extrusion is directly performed on the solution-quenched state, the metastable supersaturated solid solution will undergo dynamic precipitation during the deformation process. This dynamic precipitation is closely related to many parameters such as temperature and time, and the precipitated phases are difficult to control and unevenly distributed, leading to a decrease in the yield strength of the material and affecting its corrosion resistance.

[0005] Aluminum alloys often require anodizing to improve their corrosion resistance and aesthetics. However, improper control of the alloying process can lead to differences in oxide film thickness and morphology during anodizing, resulting in visible defects such as color differences, mottles, and streaks, which severely impact the product's commercial value.

[0006] During laser welding of aluminum alloys, various defects are prone to occur at the weld joint, with porosity being a common abnormality. In the rapid melting and solidification process of laser welding, gases generated within the molten pool (such as hydrogen, shielding gas, or metal vapor) that cannot escape in time will remain and form pores. These residual pores are not only difficult to eliminate under the remelting effect of subsequent pulsed lasers, but may also expand abnormally due to energy concentration, affecting the mechanical properties of the weld joint and impairing its airtightness and other sealing performance, ultimately affecting the reliability of the component. Summary of the Invention

[0007] To address the above problems, a first aspect of the present invention provides a method for preparing an aluminum alloy, comprising the following steps: Step S1, alloy smelting and casting: Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti and Al are smelted into a liquid phase, then poured, and then cooled and shaped in a water-cooled crystallizer to form billet A; the viscosity of the liquid phase after smelting is 0.0012 Pa·s to 0.0016 Pa·s; Step S2, Solution treatment: Billet A is solution treated and quenched to produce billet B; Step S3, pre-precipitation of dispersed phase: After heating the billet B, pre-precipitation of dispersed phase is carried out, and then the billet C is prepared by quenching. Step S4, multi-directional forging: billet C is forged into billet D through multi-directional forging; Step S5, Stabilization treatment: The billet D undergoes a two-stage stabilization treatment to produce billet E; Step S6, Differential Temperature Equal Channel Angle Extrusion: The billet E is extruded at equal channel angles using a die to form billet F; the temperature of the die is lower than the temperature of the billet E. Step S7, Aging treatment: Heat the billet F to perform aging treatment to produce billet G; Step S8, Anodizing treatment: After surface polishing, the billet G undergoes sulfuric acid anodizing treatment to produce finished aluminum alloy products.

[0008] As a preferred technical solution, in step S1, the mass ratios of Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and Al are 0.6%–0.7%, 0.1%–0.2%, 0.2%–0.3%, 0.05%–0.1%, 1.1%–1.3%, 0.11%–0.13%, 0.08%–0.1%, and 0.01%–0.03%, respectively; the aluminum alloy billet A is cylindrical with a diameter of 50 mm and a length of 150 mm; the casting method is continuous casting; the melting temperature is 720℃–750℃, the melting time is 30 minutes–60 minutes, and the casting speed is 100 mm / minute–200 mm / minute.

[0009] As a preferred technical solution, in step S2, the solution treatment temperature is 535℃~545℃, and the time is 2 hours~3 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of the billet C after quenching is 50℃.

[0010] As a preferred technical solution, in step S3, the pre-precipitation temperature of the dispersed phase is 610℃~620℃, and the time is 2 hours~3 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of the billet C after quenching is 50℃.

[0011] As a preferred technical solution, the multi-directional forging temperature in step S4 is 225℃~235℃; the multi-directional forging includes 4 passes of deformation, each pass lasting 10 minutes to 20 minutes; the first pass is axial compression, forging the cylindrical billet C into a square billet, with an equivalent change of 0.8; the square billet is rotated 45° and forged in the new direction for the second pass, with the equivalent change accumulating to 1.6; the third and fourth passes repeat the above rotation and forging, with the cumulative equivalent change becoming 2.0; the forging rate is 5 mm / s, and the interval between passes is 30 seconds.

[0012] As a preferred technical solution, in step S5, the first stabilization temperature is 88℃~92℃ and the time is 8 hours~10 hours; the second stabilization temperature is 110℃~120℃ and the time is 40 hours~45 hours.

[0013] As a preferred technical solution, in step S6, the medium channel angle extrusion is performed in 4 passes with a turning angle of 90 degrees; the equivalent strain is accumulated to 4.0; the mold temperature is 20℃~30℃; and the billet temperature is 110℃~120℃.

[0014] As a preferred technical solution, the aging treatment temperature in step S7 is 178℃~182℃, the time is 5 hours~6 hours, and the heating rate is 5℃ / min.

[0015] As a preferred technical solution, in step S8, the electrolyte for sulfuric acid anodizing is sulfuric acid, the oxidation temperature is 18℃~22℃, the current density is 1.2 A / dm~1.8 A / dm², the current is direct current, and the voltage is 12 V~18 V; the oxidation time is 30 minutes~60 minutes; the concentration of the sulfuric acid is 180 g / L~200 g / L; an aluminum part is used as the anode, and a lead plate is used as the cathode.

[0016] In a second aspect, the present invention provides an aluminum alloy, said aluminum alloy being prepared by any of the preparation methods of the first aspect.

[0017] A third aspect of the present invention provides a method for improving the fatigue resistance of aluminum alloys, wherein the method employs any of the preparation methods described in the first aspect.

[0018] In a fourth aspect, the present invention provides a method for improving the yield strength of aluminum alloys, wherein the method employs any of the preparation methods described in the first aspect.

[0019] In a fifth aspect, the present invention provides a method for improving the uniformity of the appearance of anodized aluminum alloys, wherein the method employs any of the preparation methods of the first aspect.

[0020] In a sixth aspect, the present invention provides a method for improving the corrosion resistance of aluminum alloys, wherein the method employs any of the preparation methods described in the first aspect.

[0021] In a seventh aspect of the present invention, a method for reducing the porosity during pulsed laser welding of aluminum alloy materials is provided, wherein the method employs any of the preparation methods of the first aspect.

[0022] Through the above technical solutions, the present invention achieves the following technical effects: (1) By adjusting the process sequence of multi-directional forging, multi-directional forging is placed between the solution treatment and aging treatment steps, which improves the fatigue resistance of aluminum alloy.

[0023] (2) Adding a stabilization treatment before the equal channel angle extrusion step can improve the yield strength.

[0024] (3) Use differential temperature equal channel angle extrusion to improve yield strength.

[0025] (4) The uniformity of the anodized appearance of aluminum alloys can be improved by adding Cr and Mn elements.

[0026] (5) Adding a dispersed phase pre-precipitation step improves the corrosion resistance of aluminum alloy materials.

[0027] (6) By adjusting the mass ratio of titanium, the viscosity of the molten aluminum alloy liquid phase can be reduced, thereby reducing the porosity during pulsed laser welding of aluminum alloy materials. Detailed Implementation

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the applicant provides an explanation and analysis through specific embodiments and comparative examples.

[0029] Example 1

[0030] Step S1, Alloy Melting and Casting: Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and Al are melted into a liquid phase, then poured, and cooled and shaped in a water-cooled crystallizer to form billet A; the viscosity of the melted liquid phase is 0.0012 Pa·s; the mass ratios of Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and Al are 0.6%, 0.1%, 0.2%, 0.05%, 1.1%, 0.11%, 0.08%, and 0.01%, respectively; the aluminum alloy billet A is cylindrical with a diameter of 50 mm and a length of 150 mm; the casting method is continuous casting; the melting temperature is 720℃, the melting time is 30 minutes, and the casting speed is 100 mm / min; Step S2, solution treatment: billet A is solution treated and quenched to form billet B; the solution treatment temperature is 535℃ and the time is 2 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of billet C after quenching is 50℃. Step S3, Pre-precipitation of dispersed phase: After heating billet B, pre-precipitation of dispersed phase is carried out, and then quenched to form billet C; the pre-precipitation temperature of dispersed phase is 610℃, and the time is 2 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of billet C after quenching is 50℃. Step S4, Multi-directional forging: The billet C is multi-directionally forged to form billet D; the multi-directional forging temperature is 225℃; the multi-directional forging includes 4 passes of deformation, each pass lasting 10 minutes; the first pass is axial compression, forging the cylindrical billet C into a square billet, with an equivalent change of 0.8; the square billet is rotated 45° and forged in the new direction for the second pass, accumulating the equivalent change to 1.6; the third and fourth passes repeat the above rotation and forging, accumulating the equivalent change to 2.0; the forging rate is 5 mm / s, and the interval between passes is 30 seconds; Step S5, Stabilization Treatment: The billet D undergoes a two-stage stabilization treatment to produce billet E; the first stage stabilization temperature is 88℃ and the time is 8 hours; the second stage stabilization temperature is 110℃ and the time is 40 hours. Step S6, Differential Temperature Equal Channel Angle Extrusion: The billet E is extruded at an equal channel angle using a die to form billet F; the equal channel angle extrusion is performed in 4 passes with a 90-degree angle; the equivalent strain is accumulated to 4.0; the die temperature is lower than the billet E temperature; the die temperature is 20°C; the billet temperature is 110°C. Step S7, Aging treatment: The billet F is heated for aging treatment to produce billet G; the aging treatment temperature is 178℃, the time is 5 hours, and the heating rate is 5℃ / min. Step S8, Anodizing treatment: After surface polishing, the billet G is subjected to sulfuric acid anodizing treatment to produce aluminum alloy finished products; the electrolyte for sulfuric acid anodizing is sulfuric acid, the oxidation temperature is 18℃, the current density is 1.2 A / dm, the current is direct current, and the voltage is 12 V; the oxidation time is 30 minutes; the concentration of sulfuric acid is 180 g / L; the aluminum part is used as the anode, and the lead plate is used as the cathode.

[0031] Example 2

[0032] Step S1, Alloy Melting and Casting: Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and Al are melted into a liquid phase, then poured, and cooled and shaped in a water-cooled crystallizer to form billet A; the viscosity of the liquid phase after melting is 0.0014 Pa·s; the mass ratios of Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and Al are 0.65%, 0.15%, 0.25%, 0.07%, 1.2%, 0.12%, 0.09%, and 0.02%, respectively; the aluminum alloy billet A is cylindrical with a diameter of 50 mm and a length of 150 mm; the casting method is continuous casting; the melting temperature is 730℃, the melting time is 40 minutes, and the casting speed is 150 mm / min; Step S2, solution treatment: billet A is solution treated and quenched to form billet B; the solution treatment temperature is 540℃ and the time is 2.5 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of billet C after quenching is 50℃. Step S3, pre-precipitation of dispersed phase: After heating the billet B, pre-precipitation of dispersed phase is carried out, and then quenched to form billet C; the pre-precipitation temperature of dispersed phase is 615℃, and the time is 2.5 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of billet C after quenching is 50℃. Step S4, multi-directional forging: billet C is multi-directionally forged to form billet D; the multi-directional forging temperature is 230℃; the multi-directional forging includes 4 passes of deformation, each pass lasting 15 minutes; the first pass is axial compression, forging the cylindrical billet C into a square billet, with an equivalent strain of 0.8; the square billet is rotated 45° and forged in the new direction for the second pass, accumulating the equivalent strain to 1.6; the third and fourth passes repeat the above rotation and forging, accumulating the equivalent strain to 2.0; the forging rate is 5 mm / s, and the interval between passes is 30 seconds; Step S5, Stabilization Treatment: The billet D undergoes a two-stage stabilization treatment to produce billet E; the first stage stabilization temperature is 90℃ and the time is 9 hours; the second stage stabilization temperature is 115℃ and the time is 42 hours. Step S6, Differential Temperature Equal Channel Angle Extrusion: The billet E is extruded at an equal channel angle using a die to form billet F; the equal channel angle extrusion is performed in 4 passes with a 90-degree angle; the equivalent strain is accumulated to 4.0; the die temperature is lower than the billet E temperature; the die temperature is 25°C; the billet temperature is 115°C; Step S7, Aging treatment: The billet F is heated for aging treatment to produce billet G; the aging treatment temperature is 180℃, the time is 5.5 hours, and the heating rate is 5℃ / min; Step S8, Anodizing treatment: After surface polishing, the billet G is subjected to sulfuric acid anodizing treatment to produce aluminum alloy finished products; the electrolyte for sulfuric acid anodizing is sulfuric acid, the oxidation temperature is 20℃, the current density is 1.5 A / dm², the current is direct current, and the voltage is 15 V; the oxidation time is 40 minutes; the concentration of sulfuric acid is 190 g / L; the aluminum part is used as the anode, and the lead plate is used as the cathode.

[0033] Example 3

[0034] Step S1, Alloy Melting and Casting: Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and Al are melted into a liquid phase, then poured, and cooled and shaped in a water-cooled crystallizer to form billet A; the viscosity of the liquid phase after melting is 0.0016 Pa·s; the mass ratios of Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and Al are 0.7%, 0.2%, 0.3%, 0.1%, 1.3%, 0.13%, 0.1%, and 0.03%, respectively; the aluminum alloy billet A is cylindrical with a diameter of 50 mm and a length of 150 mm; the casting method is continuous casting; the melting temperature is 750℃, the melting time is 60 minutes, and the casting speed is 200 mm / min; Step S2, solution treatment: billet A is solution treated and quenched to form billet B; the solution treatment temperature is 545℃ and the time is 3 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of billet C after quenching is 50℃. Step S3, Pre-precipitation of dispersed phase: After heating billet B, pre-precipitation of dispersed phase is carried out, and then quenched to form billet C; the pre-precipitation temperature of dispersed phase is 620℃, and the time is 3 hours; the quenching medium is water, the water temperature is 50℃, and the quenching cooling rate is 30℃ / second; the temperature of billet C after quenching is 50℃. Step S4, multi-directional forging: billet C is multi-directionally forged to form billet D; the multi-directional forging temperature is 235℃; the multi-directional forging includes 4 passes of deformation, each pass lasting 20 minutes; the first pass is axial compression, forging the cylindrical billet C into a square billet, with an equivalent change of 0.8; the square billet is rotated 45° and forged in the new direction for the second pass, accumulating the equivalent change to 1.6; the third and fourth passes repeat the above rotation and forging, accumulating the equivalent change to 2.0; the forging rate is 5 mm / s, and the interval between passes is 30 seconds; Step S5, Stabilization Treatment: The billet D undergoes a two-stage stabilization treatment to produce billet E; the first stage stabilization temperature is 92℃ and the time is 10 hours; the second stage stabilization temperature is 120℃ and the time is 45 hours. Step S6, Differential Temperature Equal Channel Angle Extrusion: The billet E is extruded at an equal channel angle using a die to form billet F; the equal channel angle extrusion is performed in 4 passes with a 90-degree angle; the equivalent strain is accumulated to 4.0; the die temperature is lower than the billet E temperature; the die temperature is 30°C; the billet temperature is 120°C; Step S7, Aging treatment: The billet F is heated for aging treatment to produce billet G; the aging treatment temperature is 182℃, the time is 6 hours, and the heating rate is 5℃ / min. Step S8, Anodizing treatment: After surface polishing, the billet G is subjected to sulfuric acid anodizing treatment to produce aluminum alloy finished products; the electrolyte for sulfuric acid anodizing is sulfuric acid, the oxidation temperature is 22℃, the current density is 1.8 A / dm², the current is direct current, and the voltage is 18 V; the oxidation time is 60 minutes; the concentration of sulfuric acid is 200 g / L; the aluminum part is used as the anode, and the lead plate is used as the cathode.

[0035] Comparative Example 1

[0036] The multi-directional forging step is placed before the solution treatment step, and the other steps and parameters are the same as in Example 1.

[0037] Comparative Example 2

[0038] The multi-directional forging step is placed after the aging treatment step, and the other steps and parameters are the same as in Example 1.

[0039] Test Example 1: Fatigue Life Test

[0040] Referring to ASTM E466, "Standard Test Method for Force-Controlled Constant Amplitude Axial Fatigue Testing of Metallic Materials", fatigue life tests were conducted at a stress level of 150 MPa.

[0041] The experimental results are shown in the table below. By adjusting the process sequence of multi-directional forging, placing it between the solution treatment and aging treatment steps, the fatigue resistance of the aluminum alloy was improved. The applicant speculates that forging before solution treatment refines the grains, but during the subsequent high-temperature solution treatment, the grains recrystallize and grow, resulting in coarse grains in the final product. Coarse grains and grain boundaries become preferential initiation points and propagation channels for fatigue cracks, reducing fatigue life. Placing forging after solution treatment avoids the damage to the fine-grained structure caused by subsequent high-temperature processes, allowing the ultrafine grains obtained by multi-directional forging to be retained in the final product. After aging treatment, brittle strengthening phases have precipitated in the material, and the matrix plasticity has decreased. Forging deformation at this time will induce microcracks, leading to premature fracture. Forging in a soft, supersaturated solid solution state provides good plasticity and a low risk of cracking. The strengthening phases precipitated during subsequent aging treatment are uniformly distributed on the fine-grained matrix, effectively inhibiting crack initiation and propagation.

[0042] Table 1: Detection results of Example 1

[0043] Comparative Example 3

[0044] The stabilization process in step S5 was not performed; the other steps and parameters were the same as in Example 1.

[0045] Comparative Example 4

[0046] During the differential temperature equal channel angle extrusion in step S6, the heating control mold temperature is consistent with the billet temperature, and other steps and parameters are consistent with those in Example 1.

[0047] Test Example 2: Yield Strength Test

[0048] The yield strength was determined in accordance with ASTM E8, "Standard Test Method for Tensile Testing of Metallic Materials".

[0049] The experimental results are shown in the table below. Stabilization treatment prior to the equal channel angle extrusion step can improve the yield strength. The applicant hypothesizes that the stabilization treatment creates a stable and uniform microstructure foundation for subsequent intense plastic deformation. Through a two-stage stabilization process, solute atoms in the unstable supersaturated solid solution are transformed into fine, uniform, and thermodynamically stable transition precipitates, improving material homogeneity and stability, suppressing local stress concentration, and increasing yield strength.

[0050] Isothermal equal channel angular extrusion (ESEE) can improve yield strength. Heated billets ensure good plasticity under the intense shear deformation of EEE, preventing cracking. Simultaneously, the low-temperature die rapidly quenches the billet as it passes through the deformation zone, effectively suppressing dislocation dynamic recovery and recrystallization. This freezes and accumulates a higher dislocation density and finer subgrain boundaries within the material than in conventional EEE, providing optimal nucleation sites for strengthening phases during subsequent aging treatment. This promotes the formation of finer, more dispersed nanoprecipitates. Through this synergistic effect of dislocation strengthening, grain refinement strengthening, and precipitation strengthening, the yield strength of the aluminum alloy is improved.

[0051] Table 2: Detection results of detection example 2

[0052] Comparative Example 5

[0053] In step S1, no Cr was added, and the other steps and parameters were the same as in Example 1.

[0054] Comparative Example 6

[0055] In step S1, Mn was not added, and the other steps and parameters were the same as in Example 1.

[0056] Comparative Example 7

[0057] The pre-precipitation of the dispersed phase in step S3 was not performed; the other steps and parameters were the same as in Example 1.

[0058] Example 3: Assessment of the number and distribution of dispersed phase particles

[0059] The number and distribution of dispersed particles were measured using transmission electron microscopy.

[0060] 1. Sample preparation: The sample to be tested is evenly divided into 10 equal parts along the elongation direction, and each part is cut into a thin film sample with a thickness of 400 nm for observation by transmission electron microscopy.

[0061] 2. Image Acquisition: Observe the sample at a magnification of 50,000x, focusing on dispersed particles with a size between 10nm and 300nm. These dispersed particles are typically intermetallic compounds composed of elements such as Al, Mn, and Cr.

[0062] 3. Image Analysis and Counting: Count the dispersed particles with sizes between 10nm and 300nm in three fields of view, each field of view being 3μm. 2 Calculate the unit area (1μm) 2 The number of dispersed particles within a 10-part sample is calculated by taking the average number of dispersed particles in each part; the average number of dispersed particles in 10 parts is the total number of dispersed particles in the sample.

[0063] 4. Distribution evaluation: The ratio of the standard deviation to the mean of the number of dispersed particles in 10 equal parts is the coefficient of variation. The coefficient of variation is used to evaluate the uniformity of the dispersed particle distribution.

[0064] Example 4: Appearance evaluation of anodized surface

[0065] The evaluators observed the surface appearance of the samples after anodizing. The appearance was mainly divided into two categories: (1) The sample has a uniform color, with no visible color difference, spots, stripes or irregular patterns, and the surface presents a consistent overall visual effect. (2) The sample surface is mottled, spots appear in some areas, or the oxide film fails to form evenly.

[0066] Test Example 5: Corrosion Resistance Evaluation

[0067] Refer to JIS H8681-2 "Test methods for corrosion resistance of anodic oxide films of aluminum and aluminum alloys - Part 2: KAS test" to evaluate the corrosion resistance of the material.

[0068] The experimental results are shown in the table below. Cr and Mn elements can improve the uniformity of the anodized appearance of aluminum alloys. The applicant speculates that the synergistic effect of Cr and Mn elements increases the density of nanoscale dispersed phases in the aluminum alloy; during solution treatment and equal-channel extrusion, the dispersed phases can strongly pin grain boundaries, effectively inhibiting abnormal grain growth and recrystallization, thereby obtaining a uniform and consistent ultrafine-grained microstructure throughout the billet. Comparative Examples 5 and 6, due to the lack of Cr or Mn respectively, could not form a sufficient number of dispersed phases, resulting in insufficient grain boundary pinning effect. In subsequent heat treatment, local grain coarsening easily occurs, forming a mixed structure of coarse and fine grains, leading to differences in the growth rate and morphology of the surface oxide film during anodizing, manifesting as a mottled and uneven appearance.

[0069] The dispersed phase pre-precipitation step can improve the corrosion resistance of aluminum alloy materials. By performing "dispersed phase pre-precipitation" treatment on the billet, elements such as Cr and Mn in the alloy are actively and controlled to pre-precipitate in the form of coarse and stable intermetallic compounds, thereby reducing the non-uniformity of their dynamic precipitation during subsequent processing, improving the uniformity of dispersed phase precipitation, and enhancing the corrosion resistance of the material.

[0070] Table 3: Detection results of test cases 3, 4, and 5

[0071] Comparative Example 8

[0072] In step S1, the liquid phase viscosity of the molten aluminum alloy was adjusted to 0.0006 Pa·s by adding Ti, corresponding to a Ti mass ratio of 0.001%. Other steps and parameters were the same as in Example 1.

[0073] Comparative Example 9

[0074] In step S1, the liquid phase viscosity of the molten aluminum alloy is adjusted to 0.0025 Pa·s by adding Ti, and the corresponding mass ratio of Ti is 0.1%. Other steps and parameters are the same as in Example 1.

[0075] Example 6: Measurement of porosity at the weld.

[0076] The porosity at the weld was measured using transmission electron microscopy.

[0077] 1. Sample preparation: After the prepared sample is welded using pulsed laser welding, the sample containing the complete weld cross-section is cut perpendicular to the welding direction for observation by transmission electron microscopy.

[0078] 2. Image acquisition: Observe the pores in the sample with a size between 1μm and 10μm at a magnification of 500x.

[0079] 3. Image Analysis and Counting: Statistically count pores with sizes between 1μm and 10μm in the field of view, with each field of view being 1mm. 2 Calculate each field of view (1mm) 2 The porosity is calculated by analyzing the pore area within the three fields of view and taking the average value as the porosity formation rate.

[0080] The experimental results are shown in the table below. By adjusting the mass ratio of titanium, the viscosity of the molten aluminum alloy liquid phase can be reduced, thereby decreasing the porosity during pulsed laser welding of aluminum alloy materials. Adjusting the mass ratio of titanium controls the viscosity of the molten aluminum alloy liquid phase, regulating the fluidity of the molten pool during pulsed laser welding, allowing bubbles generated during welding to escape quickly, thus reducing the pore area formed at the weld and decreasing the porosity. Comparative Example 9, due to its high Ti content, has a high liquid phase viscosity; excessive viscosity makes the molten pool viscous, slowing the escape of welding bubbles, ultimately leading to solidification and the formation of pores, resulting in an increased porosity.

[0081] Table 4: Detection results of test case 6

Claims

1. A method for preparing an aluminum alloy, characterized in that, Includes the following steps: Step S1, alloy smelting and casting: Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti and Al are smelted into a liquid phase, then poured, and then cooled and shaped in a water-cooled crystallizer to form billet A; the viscosity of the liquid phase after smelting is 0.0012 Pa·s to 0.0016 Pa·s; Step S2, Solution treatment: Billet A is solution treated and quenched to produce billet B; Step S3, pre-precipitation of dispersed phase: After heating the billet B, pre-precipitation of dispersed phase is carried out, and then the billet C is prepared by quenching. Step S4, multi-directional forging: billet C is forged into billet D through multi-directional forging; Step S5, Stabilization treatment: The billet D undergoes a two-stage stabilization treatment to produce billet E; Step S6, Differential Temperature Equal Channel Angle Extrusion: The billet E is extruded at equal channel angles using a die to form billet F; the temperature of the die is lower than the temperature of the billet E. Step S7, Aging treatment: Heat the billet F to perform aging treatment to produce billet G; Step S8, Anodizing treatment: After surface polishing, the billet G undergoes sulfuric acid anodizing treatment to produce finished aluminum alloy products.

2. An aluminum alloy, characterized in that, The aluminum alloy is prepared by the preparation method described in claim 1.

3. A method for improving the fatigue resistance of aluminum alloys, characterized in that, The aluminum alloy is prepared using the preparation method described in claim 1.

4. A method for improving the yield strength of aluminum alloys, characterized in that, The aluminum alloy is prepared using the preparation method described in claim 1.

5. A method for improving the uniformity of the appearance of anodized aluminum alloys, characterized in that, The aluminum alloy is prepared using the preparation method described in claim 1.

6. A method for improving the corrosion resistance of aluminum alloys, characterized in that, The aluminum alloy is prepared using the preparation method described in claim 1.

7. A method for reducing the porosity of welded parts in aluminum alloys, characterized in that, The aluminum alloy is prepared using the preparation method described in claim 1.

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