A method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy

Abstract

The present application relates to the technical field of aluminum alloy heat treatment, and discloses a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy, which comprises the following steps: preparing RDAM 7075 aluminum alloy blanks by using aluminum alloy rods and plate materials of the same grade on a rotary stirring deposition additive manufacturing system; performing solid solution treatment on the blanks; performing room temperature cold rolling pre-deformation on the solid solution state blanks along the deposition direction to obtain cold rolling state blanks; and performing low-temperature short-time artificial aging treatment on the cold rolling state blanks to obtain final RDAM aluminum alloy components. By introducing cold rolling pre-deformation between solid solution and aging, the present application realizes the comprehensive improvement of the mechanical properties of the alloy; at the same time, the deformation-aging synergistic effect optimizes the heat treatment conditions, reduces the heating temperature and holding time, effectively reduces the energy consumption and shortens the cycle; and the present process does not need to modify the existing equipment or add heterogeneous phases, has high compatibility, avoids interface defects, and has large-scale industrialization potential.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy heat treatment technology, specifically to a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy. Background Technology

[0002] 7075 aluminum alloy, as a representative of Al-Zn-Mg-Cu series high-strength aluminum alloys, possesses high specific strength and fatigue resistance, and is widely used in main load-bearing components in aerospace and new energy vehicle fields. Traditional forging and cutting processes are difficult to meet the manufacturing requirements of integrated complex structures, while existing mainstream liquid phase additive manufacturing technologies (such as laser powder bed melting and directional energy deposition) are difficult to produce qualified components when processing this alloy due to the material's high sensitivity to hot cracking and the tendency for elemental loss.

[0003] Rotary stirring deposition (RDAM), as a solid-state additive manufacturing technology, effectively avoids the defects generated during liquid-solid phase transformation. This technology primarily relies on plastic deformation and frictional heat to achieve layer-by-layer metallurgical bonding, and can be used to prepare aluminum alloy components with fine grains and uniform composition. However, the deposited RDAM7075 aluminum alloy undergoes repeated thermal cycling during the forming process, leading to coarsening of the η' / η phase and S phase within it, and simultaneously causing widening of the non-precipitated grain boundaries. This microstructural evolution results in deposited components having lower strength than the forged base material, exhibiting significant differences in mechanical properties between the construction and deposition directions, and a clear hardness gradient between layers, affecting the practical engineering applications of the components.

[0004] To improve the overall performance of RDAM aluminum alloys, existing treatment methods mainly include heterojunction, ceramic particle doping, and low-temperature heat control during the process. However, these methods generally face problems such as complex processes, increased manufacturing costs, and the potential introduction of new defects, making large-scale engineering applications difficult. Furthermore, while the conventional T6 heat treatment process (i.e., solution treatment at 470-480℃ for 1-2 hours, followed by aging at 120-125℃ for 24-36 hours) can improve the strength of RDAM7075 aluminum alloys to some extent, its practical application still has limitations. Specifically, the conventional T6 process not only has a long heat treatment cycle and high energy consumption, but it also easily leads to abnormal grain growth during the process and cannot effectively eliminate the original anisotropy and interlayer hardness gradient of the deposited component.

[0005] Studies have shown that introducing cold rolling pre-deformation can utilize internal crystal defects in metals to regulate precipitation behavior. However, for the specific RDAM7075 aluminum alloy system, there is currently a lack of composite control schemes that combine wide-range cold deformation with low-temperature short-time aging, as well as a lack of relevant process methods to utilize defects introduced by cold rolling to accelerate precipitation kinetics, thereby reducing heat treatment parameters and shortening the production cycle. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy, which solves the problems of insufficient strength, significant mechanical anisotropy, large interlayer property gradient, high energy consumption and long cycle of traditional T6 heat treatment in existing technologies.

[0007] To achieve the above objectives, the present invention provides a method for improving the deformation-aging composite treatment of RDAM7075 aluminum alloy, employing the following technical solution: Using Al7075-T6 aluminum alloy rods as raw materials and sheet metal of the same grade as substrates, RDAM7075 aluminum alloy billets were prepared on a rotary stirring deposition additive manufacturing system. The RDAM7075 aluminum alloy billet was subjected to solution treatment to obtain a solution-treated billet. The solution-treated billet is subjected to room temperature cold rolling pre-deformation along the deposition direction to obtain a cold-rolled billet; The cold-rolled billet is subjected to low-temperature short-time artificial aging treatment to obtain the final RDAM aluminum alloy component.

[0008] By adopting the above technical solution, this invention introduces a cold rolling pre-deformation process between solution treatment and aging treatment. Utilizing the synergistic coupling effect of the physical defects introduced by deformation and the subsequent thermodynamic precipitation kinetics, the microstructure of the alloy is improved and its macroscopic mechanical properties are enhanced. The specific mechanism and reaction process are as follows: Solution treatment promotes the re-dissolution of the coarse second phase aggregated in the additive manufacturing deposited structure into the matrix. Rapid water quenching and cooling suppress the precipitation of solute atoms, forming a supersaturated solid solution of zinc, magnesium, and copper solute atoms and vacancies within the matrix. The phase transformation process at this stage is characterized by the coarse second phase dissolving in the matrix to form a supersaturated solid solution.

[0009] Room temperature cold rolling pre-deformation of solution-solidified billets results in good plasticity due to the alloy being in a supersaturated solution state. The plastic deformation generates a high-density dislocation network within the matrix grains. These dislocations not only produce an initial work hardening effect but also alter the distribution of the internal stress field in the matrix.

[0010] In the subsequent artificial aging process, high-density dislocations act as non-uniform nucleation sites, reducing the nucleation barrier of the precipitated phase. Meanwhile, dislocations, acting as rapid diffusion channels for solute atoms, accelerate the enrichment of zinc and magnesium atoms. The precipitation reaction sequence of conventional 7075 aluminum alloy is as follows: supersaturated solid solution reacts to form solute atom clusters, which then evolve into GP zones, subsequently transforming into the metastable η′ phase, and finally growing into the equilibrium η phase. Introducing high-density dislocations shifts the nucleation sites from grain boundaries and subgrain boundaries to intragranular dislocation lines, promoting the dense and uniform precipitation of numerous GP zones and η′ strengthening phases along these dislocation lines. This inhibits the broadening of the non-precipitated zone and blocks the transformation of the η′ phase into the coarse equilibrium phase.

[0011] Further theoretical calculations and quantitative characterization show that the deformation-aging coupling mechanism of this invention is mainly reflected in the following aspects: After solution treatment, 5% to 30% of the cold deformation introduces dislocations and vacancies into the matrix, and aging treatment does not completely achieve dislocation recovery. Experimental results show that dislocation strengthening contributes 116.2 MPa to 145.6 MPa to the strength of RDAM 7075 aluminum alloy, an increase of 4.3% to 30.7% compared to the conventional T6 state. This increase in strengthening can offset the decrease in fine-grain strengthening caused by the increase in grain size during heat treatment.

[0012] Dislocations and vacancies within the matrix provide heterogeneous nucleation sites for the strengthening phase, increasing the nucleation rate of the precipitated phase by 2 to 3 times. Simultaneously, these defects constitute rapid diffusion channels for solute atoms, increasing the diffusion coefficient by 1 to 2 orders of magnitude compared to the undeformed state. Through these structural changes, the precipitation activation energy of the η phase is reduced from approximately 120 kJ / mol in the conventional T6 state to 80-90 kJ / mol.

[0013] Due to the decrease in precipitation activation energy, precipitation can be completed in the material under treatment conditions of 110-120℃. Calculations show that the contribution of precipitation to the relative alloy strength reaches 125-140 MPa, which is 39.3% to 56.1% higher than the conventional T6 state's 89.7 MPa. Precipitation strengthening is the main reason for the improvement in the overall strength of the material by this composite treatment method.

[0014] Furthermore, the high-density dislocation network formed within the matrix effectively pins the grain boundaries of the precipitates, hindering their growth and avoiding the coarsening problem that easily occurs under conventional high-temperature aging. Simultaneously, since the intense plastic deformation generated during RDAM deposition causes some of the coarse second phases to break down and dissolve, this invention eliminates the need for the high-temperature, long-duration solution treatment of the conventional T6 process. The low-temperature solution treatment at 450-475℃ ensures sufficient solute dissolution while effectively suppressing grain growth.

[0015] Ultimately, this invention improves the ultimate tensile strength and plasticity of aluminum alloy components through the synergistic effect of dislocation strengthening and fine dispersed phase strengthening; at the same time, by utilizing the dislocation accelerated diffusion mechanism, it reduces the activation energy required for aging, thereby reducing the heating temperature and shortening the holding time.

[0016] In a preferred embodiment, the total cumulative rolling strain of the room temperature cold rolling pre-deformation is 5%-15%; the heating temperature of the solution treatment is 460-470℃, and the holding time is 1.0-1.5h; The artificial aging treatment is carried out at a heating temperature of 115-120℃ and a holding time of 16-20h.

[0017] Preferably, the process parameters for preparing the RDAM7075 aluminum alloy billet are controlled as follows: the stirring head speed is 700-900 r / min, the table travel speed is 38-48 mm / min, and the raw material bar feeding speed is 8.5-10.0 mm / min.

[0018] By adopting the above technical solution, the appropriate material feed rate and thermomechanical coupling input are limited. The precise matching of rotational speed, travel rate, and feeding rate ensures that the raw materials achieve full mixing and dense packing in the plastic rheological state generated by frictional heat, avoiding grain coarsening caused by excessive heat input or interlayer incomplete welding defects caused by insufficient heat input, thus ensuring the density of the formed component.

[0019] Preferably, the solution treatment specifically involves placing the RDAM7075 aluminum alloy billet in a heat treatment furnace and holding it at 455–470°C for 1.0–2.0 hours. After the solution treatment is completed, the solution-treated billet is immediately cooled to room temperature using water quenching.

[0020] By adopting the above technical solution, the set temperature and time range can ensure the full dissolution of the eutectic structure and coarse second phase in the deposited microstructure, while avoiding local overheating or abnormal grain growth in the matrix. The water quenching operation fixes the solute distribution at high temperature, providing a single matrix phase with good plasticity for the subsequent cold rolling process, and maximizing the driving energy for the aging precipitation process.

[0021] Preferably, the total cumulative strain of the room temperature cold rolling pre-deformation is controlled to be 5% to 30%. The room temperature cold rolling pre-deformation adopts multi-pass rolling, and the reduction per pass does not exceed 3.0%.

[0022] By adopting the above technical solution, a critical dislocation density sufficient to alter precipitation kinetics is introduced into the matrix within the strain range of 5% to 30%, ensuring that the material does not undergo macroscopic cracking. The multi-pass, small-reduction rolling process allows strain to penetrate uniformly from the material surface to the core, alleviating localized residual stress concentration caused by single large strains, preventing microcrack initiation, and resulting in a more uniform dislocation network distribution.

[0023] Preferably, the artificial aging treatment specifically involves placing the cold-rolled billet in an aging furnace for heating. The heating temperature for the artificial aging treatment is 112–120°C, and the holding time is 16–24 hours. After the holding time is completed, the final RDAM aluminum alloy component is cooled to room temperature using air cooling.

[0024] By employing the above-mentioned technical solution, combined with the dislocation acceleration effect introduced by the previous deformation, the precipitation process can occur under relatively low thermodynamic conditions. Aging within this parameter range allows for precise control of the precipitation process at the stage of abundant metastable η′ phase formation, maintaining the semi-coherent interface relationship between the precipitated phase and the matrix, achieving peak strengthening effects, while simultaneously reducing energy consumption and improving production efficiency compared to conventional methods.

[0025] Preferably, the Al7075-T6 aluminum alloy rod has a diameter of 16mm.

[0026] By adopting the above technical solution, the physical specification diameter of the raw material rod is limited to 16mm, which can match the feeding channel and forming size of the rotary stirring deposition additive manufacturing system, which is beneficial to ensuring the continuity of material transportation and the stability of the deposition process.

[0027] This invention provides a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy. It has the following beneficial effects: 1. This invention achieves comprehensive improvement and directional control of the mechanical properties of RDAM7075 aluminum alloy by introducing a room temperature cold rolling pre-deformation process between solution treatment and artificial aging. By controlling the total cumulative strain of cold rolling, the ultimate tensile strength and elongation after fracture of the component in the deposition direction and construction direction are effectively improved, overcoming the problem of insufficient comprehensive mechanical properties of aluminum alloy components manufactured by conventional additive manufacturing.

[0028] 2. This invention optimizes and improves the conventional heat treatment conditions of aluminum alloys through the synergistic effect of deformation and aging combined treatment. Compared with the traditional conventional heat treatment process, it effectively reduces the heating temperature of solution treatment and aging, shortens the holding time, effectively reduces the overall energy consumption, and shortens the production cycle. While ensuring that the components have excellent mechanical properties, it improves production efficiency and reduces manufacturing costs.

[0029] 3. By adding a physical cold rolling process to the traditional heat treatment process, this invention ensures high compatibility and structural stability of the production process. It does not require modification of existing additive manufacturing equipment and heat treatment equipment, and no additional alloying elements or reinforcing particles are needed throughout the process. This avoids interface defects and performance fluctuations caused by the introduction of heterogeneous phases. The overall process is simple to operate and has the potential for large-scale industrial application. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the preparation process and orientation of the present invention, wherein (a) is a schematic diagram of the RDAM deposition process, (b) is a schematic diagram of the deposition sample, and (c) is a schematic diagram of the cold rolling orientation; Figure 2 Comparison of engineering stress-strain curves and Vickers hardness distribution of conventional RDAM7075-T6 specimen and RDAM7075-CR-T6 specimen along different directions (X, Z). Figure 3 The images show a comparison of the microstructures of conventionally heat-treated samples and the deformation-aging composite-treated samples of the present invention. In the images, (a) is a distribution diagram of the precipitates in the conventionally heat-treated sample, (b) is a distribution diagram of the precipitates in the deformation-aging composite-treated sample of the present invention, (c) is a pole figure of the conventionally heat-treated sample, and (d) is a pole figure of the deformation-aging composite-treated sample of the present invention. Detailed Implementation

[0031] 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.

[0032] Examples 1-4: Example 1: This embodiment provides a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy, including the following steps: Combination Figure 1As shown in (a), Al7075-T6 aluminum alloy rods with a diameter of 16 mm are used as raw materials, and the same grade of sheet metal is used as the substrate (labeled Substrate in the figure). The material is prepared using a rotary stirring deposition additive manufacturing system (e.g., RDAM-XL200). During the preparation process, the raw material rod passes through a hollow rotating stirring head (labeled Hollow rotationtool ω in the figure). The bottom of the stirring head has a shoulder (labeled Shoulder in the figure), and the material is stacked layer by layer on the substrate to form a deposited layer (labeled Deposited layer in the figure). The process parameters are controlled as follows: stirring head speed 700-900 r / min, table travel speed (i.e., Tool liner velocity Vt in the figure) 38-48 mm / min, and raw material rod feed rate (i.e., Bar feed rate F in the figure) 8.5-10.0 mm / min (preferably stirring head speed 800 r / min, table travel speed 43 mm / min, and raw material rod feed rate 9.3 mm / min), to obtain RDAM7075 aluminum alloy billet. The RDAM7075 aluminum alloy billet was subjected to solution treatment, specifically by placing it in a heat treatment furnace and holding it at 465℃ for 1.5 hours. After the holding period, it was immediately water-quenched to room temperature to obtain the solution-treated billet. Combination Figure 1 The spatial coordinate system shown in (b) and (c) illustrates the process of room temperature cold rolling pre-deformation of the solution-treated billet along the deposition direction (i.e., the X direction in the figure, corresponding to the rolling direction RD), controlling the total cumulative strain to 10%, using multi-pass rolling, with a single-pass reduction controlled at 2%. The rolling reduction direction is the construction direction (i.e., the Z direction in the figure, corresponding to the construction direction BD), while the transverse direction (i.e., the Y direction in the figure, corresponding to the transverse direction TD) is kept free-stretched to obtain the cold-rolled billet. The cold-rolled billet was subjected to low-temperature short-time artificial aging treatment, specifically by placing it in an aging furnace and holding it at 115℃ for 18 hours. After the holding period, it was air-cooled to room temperature to obtain the final RDAM aluminum alloy component (7075-CR-T6-1 state sample).

[0033] Example 2: This embodiment provides a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy, including the following steps: Using 16mm diameter Al7075-T6 aluminum alloy rods as raw materials and sheet metal of the same grade as substrates, the process is carried out on a rotary stirring deposition additive manufacturing system (e.g., RDAM-XL200). The process parameters are controlled as follows: stirring head speed 700-900 r / min, table travel speed 38-48 mm / min, and raw material rod feed rate 8.5-10.0 mm / min (preferably stirring head speed 800 r / min, table travel speed 43 mm / min, and raw material rod feed rate 9.3 mm / min) to obtain RDAM7075 aluminum alloy billet. The RDAM7075 aluminum alloy billet was subjected to solution treatment, specifically by placing it in a heat treatment furnace and holding it at 460℃ for 1.0h. After the holding period, it was immediately water-quenched to room temperature to obtain the solution-treated billet. The solid solution billet was pre-deformed by room temperature cold rolling along the deposition direction, and the total cumulative strain was controlled to be 20%. Multi-pass rolling was adopted, and the single-pass reduction was controlled to be 2.5% to obtain the cold-rolled billet. The cold-rolled billet was subjected to low-temperature short-time artificial aging treatment, specifically by placing it in an aging furnace and holding it at 118°C for 16 hours. After the holding period, it was air-cooled to room temperature to obtain the final RDAM aluminum alloy component (7075-CR-T6-2 state sample).

[0034] Example 3: This embodiment provides a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy, including the following steps: Using 16mm diameter Al7075-T6 aluminum alloy rods as raw materials and sheet metal of the same grade as substrates, the process is carried out on a rotary stirring deposition additive manufacturing system (e.g., RDAM-XL200). The process parameters are controlled as follows: stirring head speed 700-900 r / min, table travel speed 38-48 mm / min, and raw material rod feed rate 8.5-10.0 mm / min (preferably stirring head speed 800 r / min, table travel speed 43 mm / min, and raw material rod feed rate 9.3 mm / min) to obtain RDAM7075 aluminum alloy billet. The RDAM7075 aluminum alloy billet was subjected to solution treatment, specifically by placing it in a heat treatment furnace and holding it at 470℃ for 2.0h. After the holding period, it was immediately water-quenched to room temperature to obtain the solution-treated billet. The solid solution billet was pre-deformed by room temperature cold rolling along the deposition direction, and the total cumulative strain was controlled at 5%. Multi-pass rolling was adopted, and the single-pass reduction was controlled at 1.5% to obtain the cold-rolled billet. The cold-rolled billet was subjected to low-temperature short-time artificial aging treatment, specifically by placing it in an aging furnace and holding it at 120°C for 24 hours. After the holding period, it was air-cooled to room temperature to obtain the final RDAM aluminum alloy component (7075-CR-T6-3 state sample).

[0035] Example 4: This embodiment provides a method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy, including the following steps: Using 16mm diameter Al7075-T6 aluminum alloy rods as raw materials and sheet metal of the same grade as substrates, the process is carried out on a rotary stirring deposition additive manufacturing system (e.g., RDAM-XL200). The process parameters are controlled as follows: stirring head speed 700-900 r / min, table travel speed 38-48 mm / min, and raw material rod feed rate 8.5-10.0 mm / min (preferably stirring head speed 800 r / min, table travel speed 43 mm / min, and raw material rod feed rate 9.3 mm / min) to obtain RDAM7075 aluminum alloy billet. The RDAM7075 aluminum alloy billet was subjected to solution treatment, specifically by placing it in a heat treatment furnace and holding it at 455℃ for 1.0h. After the holding period, it was immediately water-quenched to room temperature to obtain the solution-treated billet. The solid solution billet was pre-deformed by room temperature cold rolling along the deposition direction, and the total cumulative strain was controlled to be 30%. Multi-pass rolling was adopted, and the single-pass reduction was controlled to be 3% to obtain the cold-rolled billet. The cold-rolled billet was subjected to low-temperature short-time artificial aging treatment, specifically by placing it in an aging furnace and holding it at 112℃ for 20 hours. After the holding period, it was air-cooled to room temperature to obtain the final RDAM aluminum alloy component (7075-CR-T6-4 state sample).

[0036] Comparative Example 1: This comparative example provides a conventional heat treatment method for RDAM7075 aluminum alloy, including the following steps: The same batch of RDAM7075 aluminum alloy billets were prepared using the same process parameters as in Example 1; The RDAM7075 aluminum alloy billet was subjected to conventional T6 solution treatment, specifically by placing it in a heat treatment furnace and holding it at 475℃ for 2 hours. After the holding period, it was immediately water-quenched to room temperature to obtain the solution-treated billet. Without cold rolling pre-deformation treatment, the solution-treated billet was directly placed in an aging furnace for conventional artificial aging treatment, specifically, it was held at 121℃ for 24 hours, and then air-cooled to room temperature after the holding period to obtain the final 7075-T6 state sample.

[0037] Test method: To verify the technical effect of the present invention, the samples prepared in Examples 1-4 and Comparative Example 1 were subjected to microstructure observation and room temperature mechanical property testing. The specific testing standards and methods are as follows: Room temperature tensile test: Standard tensile specimens were prepared according to GB / T228.1-2021 "Metallic materials, tensile testing—Part 1: Test at room temperature". A quasi-static room temperature tensile test was performed on a universal testing machine at a tensile rate of 2 mm / min. Figure 1 The spatial coordinate systems shown in (b) and (c) are used for sampling and testing along the depositional travel direction (X-direction / RD-direction) and the formation direction (Z-direction / BD-direction), respectively.

[0038] Hardness distribution test: The hardness distribution characteristics of the sample along the construction direction (Z direction) were tested using a Vickers hardness tester. The load was set to 200g and the holding time was 15s.

[0039] Microstructure characterization: Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electron backscatter diffraction (EBSD) techniques were used to observe and analyze the precipitate size, volume fraction, and grain orientation (pole diagram) of the samples.

[0040] Test results: The mechanical properties and hardness test results of each embodiment and comparative example are shown in Table 1 below: Table 1. Mechanical properties and hardness test results of the examples and comparative examples Notes: The 7075-T6 state sample in the table was prepared in Comparative Example 1; the 7075-CR-T6-1, 7075-CR-T6-2, 7075-CR-T6-3, and 7075-CR-T6-4 state samples were prepared in Examples 1, 2, 3, and 4 above, respectively. In the table, the hyphens and spaces in the longitudinal hardness fluctuation (HV) column indicate that the data is not applicable or does not need to be repeated.

[0041] Results Analysis and Technical Effects: Based on the test data and microstructure observation results in Table 1, the deformation-aging coupling treatment method of this invention achieves the following technical effects compared with the existing conventional T6 process: Simultaneous improvement of strength and plasticity: As shown in Table 1, after introducing cold rolling pre-deformation, the tensile strength of Examples 1-4 is higher than that of Comparative Example 1. When the cold rolling strain is in the range of 5%-15% (such as Examples 1 and 3), the tensile strength in the deposition direction increases to 467-476 MPa, and the elongation after fracture increases from 11.0% in Comparative Example 1 to 12.5%-12.8%. Figure 2A comparison of the stress-strain curves in (a) and (b) shows that the curve of the specimen (CR-T6) of this invention is generally above that of the conventional T6 specimen, proving that this invention improves the problem of the inverted strength and toughness of traditional high-strength aluminum alloys through the synergistic strengthening of dislocations / substructures and fine precipitates. When the deformation reaches 30% (as in Example 4), its ultimate tensile strength reaches 509.64 MPa, which is significantly better than that of traditional additive components.

[0042] Effective elimination of anisotropy and interlayer hardness gradient: Comparative Example 1 (conventional T6) exhibits performance differences in the deposition and formation directions, with longitudinal hardness fluctuations along the formation direction reaching ±14.7 HV, indicating interlayer softening. After treatment using Examples 1-4 of this invention, the tensile strength and elongation at fracture in the formation direction are improved, and the longitudinal hardness fluctuation is reduced to within the range of ±2.2 to ±3.1 HV. Figure 2 As shown in Vickers hardness distribution diagrams (c) and (d), the conventional T6 sample exhibits a sawtooth-like fluctuation in the Z direction, while the hardness distribution curve of the sample (CR-T6) in this embodiment tends to be flatter. This confirms that cold rolling pre-deformation effectively eliminates the interlayer microstructure differences caused by repeated thermal cycling during RDAM deposition through uniform plastic deformation, thus achieving homogenization of component performance.

[0043] Thermodynamic kinetic acceleration and microstructure optimization: Microscopic observations show that, compared to Comparative Example 1 (average precipitate size 90.38 nm, volume fraction 3.29%), the average size of the η-phase (MgZn2) within the matrix of the sample in this embodiment is refined to 55-70 nm, and the volume fraction increases to 6.8%-8.5%. Figure 3 As can be seen from the precipitate distribution and EDS surface scan comparison of (a) and (b) of the present invention, the sample ( Figure 3 b) The precipitates within the matrix are finer and more diffusely distributed; At the same time, combined Figure 3 A comparison of the EBSD pole figures in (c) and (d) shows that cold deformation alters the grain orientation and introduces numerous substructures. The high-density dislocations and vacancies generated by cold rolling act as short-circuit diffusion channels and preferential nucleation sites, reducing the precipitation activation energy from approximately 120 kJ / mol to 80-90 kJ / mol. This allows the present invention to obtain fine, dispersed precipitates superior to those obtained by conventional high-temperature long-term aging treatments at lower temperatures (110-120 °C) and within shorter timeframes (12-24 h), while suppressing the coarsening of the precipitates.

[0044] Reduced energy consumption and shortened cycle time: Comparative examples and Comparative Example 1 show that the solution treatment temperature of this invention is reduced by 5-20℃, the holding time is shortened by 0.5-1.0h, the aging temperature is reduced by 3-9℃, and the holding time is shortened by 0-8h. The overall energy consumption of heat treatment in this invention is reduced by more than 30%, the production cycle is shortened by 30%-50%, and high strength and toughness can be achieved without adding external reinforcing particles, demonstrating promising prospects for industrial applications.

Claims

1. A method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy, characterized in that, include: Using Al7075-T6 aluminum alloy rods as raw materials and sheet metal of the same grade as substrates, RDAM7075 aluminum alloy billets were prepared on a rotary stirring deposition additive manufacturing system. The RDAM7075 aluminum alloy billet was subjected to solution treatment to obtain a solution-treated billet. The solution-treated billet is subjected to room temperature cold rolling pre-deformation along the deposition direction to obtain a cold-rolled billet; The cold-rolled billet is subjected to low-temperature short-time artificial aging treatment to obtain the final RDAM aluminum alloy component.

2. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 1, characterized in that, The process parameters for preparing the RDAM7075 aluminum alloy billet are controlled as follows: the stirring head speed is 700-900 r / min, the table travel speed is 38-48 mm / min, and the raw material bar feeding speed is 8.5-10.0 mm / min.

3. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 1, characterized in that, The solution treatment specifically involves placing the RDAM7075 aluminum alloy billet in a heat treatment furnace and holding it at 455–470°C for 1.0–2.0 hours.

4. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 1, characterized in that, After the solution treatment is completed, the solution-treated billet is immediately cooled to room temperature by water quenching.

5. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 1, characterized in that, The total cumulative strain of the room temperature cold rolling pre-deformation is controlled to be 5% to 30%.

6. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 5, characterized in that, The room temperature cold rolling pre-deformation adopts multi-pass rolling, and the reduction per pass does not exceed 3.0%.

7. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 1, characterized in that, The artificial aging process specifically involves placing the cold-rolled billet in an aging furnace for heating.

8. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 7, characterized in that, The artificial aging treatment is performed at a heating temperature of 112–120°C and a holding time of 16–24 hours.

9. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 8, characterized in that, After the artificial aging treatment is completed, the final RDAM aluminum alloy component is cooled to room temperature using air cooling.

10. The method for improving the deformation-aging composite treatment of RDAM 7075 aluminum alloy according to claim 1, characterized in that, The diameter of the Al7075-T6 aluminum alloy rod is 16mm.

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