Process for improving strength and plasticity of 6-series aluminum alloys

Abstract

The present application relates to a kind of process methods for improving the strength and plasticity of 6 series aluminum alloy, belong to non-ferrous metal technical field, in view of the problem that conventional aging process is difficult to consider strength and plasticity, the present application is handled to the 6 series aluminum alloy extrusion material with specific mass percentage, such as Mg0.90wt%, Si0.71wt%, Cu0.72wt% etc.. Aging process is as follows: the extrusion material is heated from room temperature to 120-140 DEG C at 2-8 DEG C / h, and is kept for 1-20h, then heated to 160-195 DEG C at 4-10 DEG C / h, and is kept for 0.1-20h. This method matches aging parameters according to quenching stop time, induces a large number of nucleation center to produce matrix by slow heating, makes matrix precipitate dispersion distribution and radius ≤1.2nm precursor strengthening phase. The present application effectively overcomes room temperature stop effect, the yield strength of alloy prepared is ≥360MPa and plasticity is ≥15%, realizes the synchronous promotion of strength and plasticity.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metals technology, specifically, it relates to a process method for improving the strength and plasticity of 6-series aluminum alloys. Background Technology

[0002] 6-series aluminum alloys are typically Al-Mg-Si or Al-Mg-Si-Cu alloys. Due to their low density, high specific strength, excellent machinability, and good corrosion resistance, they are widely used in transportation, building profiles, and aerospace industries. These alloys are heat-treatable aluminum alloys, and the improvement in their macroscopic mechanical properties mainly depends on the evolution of precipitated phases within the matrix during the heat treatment process. Typically, 6-series aluminum alloys form a supersaturated solid solution after solution quenching. During subsequent aging, the supersaturated solid solution decomposes, successively precipitating solute atom clusters, GP zones, transition phases such as Mg2Si or Al5Cu2Mg8Si6 precursors, and equilibrium phases.

[0003] In industrial production, 6-series aluminum alloy extrusions often cannot be immediately placed in an aging furnace after quenching, but must be left to stand at room temperature for a period of time, resulting in an unavoidable room temperature standing effect. During this period, supersaturated vacancies in the matrix facilitate the segregation of solute atoms Mg and Si, forming solute atom clusters of a certain size. Current conventional artificial aging processes mostly employ single-stage rapid heating aging, such as directly heating to 175 to 185°C and holding for 8 to 10 hours, or conventional rapid two-stage aging, such as heating to 125°C at a rate greater than 20°C / h, holding, and then heating to 175°C at an even higher rate. These conventional high-heat-rate processes have a specific microscopic phase transformation obstacle: due to the excessively rapid heating, the matrix lacks sufficient thermodynamic buffer time, and the atom clusters of varying sizes formed during the room temperature standing stage are prone to uneven re-dissolution when rapidly subjected to thermal shock. The remaining dominant atomic clusters rapidly absorb free atoms in the subsequent high-temperature stage, resulting in coarsening of the final precipitated strengthening phase particles, and their distribution in the matrix exhibits a state of local aggregation and overall sparseness.

[0004] The coherent relationship between coarse precipitate particles and the aluminum matrix is ​​disrupted. Dislocations easily accumulate at the phase interface during material deformation under stress, leading to micro-stress concentration and becoming the direct initiation source of microcracks. This microscopic evolution directly causes a precipitous drop in macroscopic plasticity when the material reaches high strength. Adjusting conventional aging temperatures and times only allows for trade-offs in a single dimension: sacrificing plasticity for increased yield strength, or sacrificing strength to retain the material's ductility. Controlling the phase transformation kinetics after solution quenching, eliminating the interference of room temperature storage effects, and thus stabilizing the radius of the strengthening phase particles at the extremely small nanoscale level are specific technical problems that urgently need to be solved to achieve a balance between high strength and high plasticity in 6-series aluminum alloys. Summary of the Invention

[0005] The purpose of this invention is to provide a process method to improve the strength and plasticity of 6-series aluminum alloys. This method solves the technical problem in the prior art where 6-series aluminum alloys, after extrusion quenching, generate natural aging atomic clusters due to the room temperature resting effect, resulting in coarse and uneven precipitation of strengthening phases during subsequent conventional rapid heating aging, thus making it difficult to achieve both high yield strength and high plasticity.

[0006] The objective of this invention can be achieved through the following technical solutions: A process for improving the strength and plasticity of 6-series aluminum alloys includes providing 6-series aluminum alloy extrusions and subjecting the extrusions to aging treatment. The chemical composition and mass percentage of the 6-series aluminum alloy extrusion are as follows: Mg 0.90wt%, Si 0.71wt%, Cu 0.72wt%, Mn 0.10wt%, Ti 0.01wt%, Fe 0.10wt%, with the balance being Al and unavoidable impurities; The aging process is as follows: the 6-series aluminum alloy extrusion is heated from room temperature to 120 to 140°C at a rate of 2 to 8°C / h and held for 1 to 20 hours, and then heated to 160 to 195°C at a rate of 4 to 10°C / h and held for 0.1 to 20 hours. After the aging treatment, a diffusely distributed Mg2Si precursor strengthening phase is precipitated in the 6-series aluminum alloy matrix, and the radius of the Mg2Si precursor strengthening phase is ≤1.2nm.

[0007] Furthermore, when the standing time of the extruded material after extrusion quenching is ≤12h, the aging treatment process is as follows: heating from room temperature to 120 to 130℃ at a rate of 2 to 8℃ / h and holding for 1 to 10h, and then heating to 160 to 175℃ at a rate of 4 to 10℃ / h and holding for 0.1 to 10h.

[0008] Furthermore, when the extruded material has been left to stand for more than 12 hours after extrusion quenching, the aging process is as follows: the temperature is increased from room temperature to 131 to 140°C at a rate of 2 to 8°C / h and held for 10.1 to 20 hours, and then the temperature is increased to 176 to 195°C at a rate of 4 to 10°C / h and held for 10.1 to 20 hours.

[0009] Furthermore, prior to the aging treatment, the process includes extruding and quenching the 6-series aluminum alloy and then cooling it to room temperature.

[0010] Furthermore, during the process of heating from room temperature to 120 to 140°C at a rate of 2 to 8°C / h and holding at that temperature for 1 to 20 hours, nucleation particles for precipitating the Mg2Si precursor strengthening phase are generated inside the 6-series aluminum alloy matrix.

[0011] Furthermore, during the process stage of heating to 160 to 195°C at a rate of 4 to 10°C / h and holding at that temperature for 0.1 to 20h, the Mg2Si precursor strengthening phase precipitates based on the nucleation particles.

[0012] Furthermore, the radius of the Mg2Si precursor reinforcing phase is 0.85 to 0.99 nm.

[0013] Furthermore, the volume fraction of the Mg2Si precursor reinforcing phase is ≥0.3%.

[0014] Furthermore, the yield strength of the obtained 6-series aluminum alloy is ≥360MPa.

[0015] Furthermore, the plasticity of the obtained 6-series aluminum alloy is ≥15%.

[0016] The beneficial effects of this invention are: 1. This invention employs a specific chemical ratio, combined with a two-stage slow heating process of 2 to 8℃ / h and 4 to 10℃ / h, to construct a quasi-static thermodynamic phase transformation environment. This process generates high-density stable nucleation particles within the alloy during the extremely slow heating process, limiting the growth space of the strengthening phase in the high-temperature stage. This ensures that the radius of the dispersed Mg2Si precursor strengthening phase is strictly controlled within the range of ≤1.2nm. The refinement of the microstructure effectively avoids local stress concentration during deformation, resulting in a product with a yield strength ≥360MPa and a plasticity ≥15%, solving the problem of a sharp drop in plasticity caused by strength improvement in conventional processes.

[0017] 2. The process of this invention matches corresponding aging parameters with a quenching dwell time of 12 hours as the boundary. When the dwell time is ≤12 hours, a lower first-stage target temperature (120 to 130°C) is used to gently induce nucleation; when the dwell time is >12 hours, the first-stage target temperature is increased (131 to 140°C) and a long-term holding time of 10.1 to 20 hours is performed to fully reorganize the undesirable naturally aged atomic clusters. This scheme eliminates the steric hindrance interference of room temperature storage effect on the artificial precipitation process, ensuring that extruded materials from different batches have highly consistent mechanical properties. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a transmission electron microscope image of the microstructure of 6-series aluminum alloy obtained in Example 1 of the present invention; Figure 2 This is a transmission electron microscope image of the microstructure of 6-series aluminum alloy obtained in Comparative Example 1 of this invention. Figure 3 A process flow chart for improving the strength and plasticity of 6-series aluminum alloys provided by the present invention; Figure 4 This is a temperature-time curve of the two-stage slow heating aging process of the present invention. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] A process for improving the strength and plasticity of 6-series aluminum alloys includes providing 6-series aluminum alloy extrusions and aging the extrusions. The chemical composition and mass percentage of the 6-series aluminum alloy extrusions are: Mg 0.90wt%, Si 0.71wt%, Cu 0.72wt%, Mn 0.10wt%, Ti 0.01wt%, Fe 0.10wt%, with the balance being Al and unavoidable impurities. The aging process involves heating the 6-series aluminum alloy extrusions from room temperature to 120-140℃ at a rate of 2-8℃ / h and holding for 1-20h, then heating to 160-195℃ at a rate of 4-10℃ / h and holding for 0.1-20h. After the aging treatment, a diffusely distributed [precipitate / effect] is formed in the 6-series aluminum alloy matrix. The precursor strengthening phase, the The radius of the precursor strengthening phase is ≤1.2 nm. The 6-series aluminum alloy belongs to the Al-Mg-Si-Cu alloy system. By controlling the proportions of elements such as Mg, Si, and Cu, and combining a segmented slow-heating aging process, fine strengthening phases with a certain volume fraction precipitate within the alloy, improving the yield strength and maintaining elongation. This process addresses the room-temperature storage effect that occurs in 6-series aluminum alloys after extrusion quenching. The initial slow-heating process induces the formation of precipitation nuclei in the matrix, laying the microscopic foundation for the dispersed precipitation of the strengthening phase in the subsequent high-temperature stage.

[0022] As attached Figure 3 As shown, in the preparation stage of the basic materials, the process of obtaining the 6-series aluminum alloy extrusion involves smelting, casting, homogenization treatment, heating, and extrusion quenching. During the smelting process, industrial pure aluminum with a purity of 99.7% or higher is used as the matrix, combined with Al-Si master alloys, Al-Cu master alloys, Al-Mn master alloys, and Al-Ti master alloys, and magnesium metal with a purity of 99.9% or higher is added. The smelting temperature is controlled between 720 and 760°C, and refining is performed using refining agents to remove hydrogen and inclusions from the melt. After settling and filtration, the melt is cast into aluminum alloy round ingots using a semi-continuous casting method. The ingots require homogenization treatment at 540-560℃ for 12-15 hours to eliminate dendritic segregation generated during casting, dissolve the non-equilibrium eutectic phase into the matrix, and uniformly precipitate Mn-containing dispersed phase particles. The homogenized ingots are then cooled to room temperature for later use. In the extrusion process, the ingots are heated to 480-520℃, the extrusion barrel temperature is set to 420-460℃, and the extrusion ratio is controlled within the range of 10-50. After exiting the extrusion die, the extruded product undergoes online quenching using mist quenching or water quenching media, maintaining the temperature of the extruded material at the die at no less than 500℃ and cooling it to below 60℃ during quenching. This online quenching process forms a supersaturated solid solution within the alloy, retaining supersaturated vacancies and solute atoms, providing a driving force for subsequent aging precipitation. Unavoidable impurity elements include Zn, Cr, and V, with the content of any single impurity not exceeding 0.05wt% and the total impurity content not exceeding 0.15wt%. Controlling impurity content aims to reduce the formation of coarse intermetallic compounds, preventing these phases from becoming crack initiators under stress and ensuring the material's ductility. The aforementioned material preparation processes ensure the substrate possesses chemical homogeneity, fine grain structure, and supersaturation, reducing the strength fluctuations common in 6-series aluminum alloys.

[0023] The quenching and resting time refers to the period from the moment the extruded material completes online quenching and cooling to room temperature until the moment it enters the aging furnace and begins heating. 6-series aluminum alloys exhibit room temperature resting sensitivity, i.e., natural aging in the T1 state. During room temperature resting, solute atoms Mg and Si agglomerate with the assistance of supersaturated vacancies, forming solute atom clusters. These clusters undergo re-dissolution or coarsening during conventional rapid heating aging, resulting in a reduction in the number and an increase in the size of the strengthening phase formed by artificial aging. The process differentiates between resting times exceeding 12 hours, employing a slow heating path and utilizing a controlled thermodynamic process to treat these atom clusters. Achieving slow heating rates of 2 to 8°C / h and 4 to 10°C / h requires an aging furnace with programmed temperature control. This equipment uses a PID closed-loop control system with a temperature control accuracy set to ±1°C, and the furnace airflow circulation system maintains temperature fluctuations at various points within the set range. During the initial heating process from room temperature to 120-140°C, the slow temperature increase allows solute atoms time to rearrange in the matrix, inducing the formation of thermally stable GP regions or precursor nuclei and preventing agglomeration of atomic clusters due to crossing unstable temperature zones. This step transforms the atomic clusters generated during room temperature storage into nucleation particles, addressing the phenomenon of reduced performance consistency caused by differences in storage time, as shown in the attached diagram. Figure 4 The figure shows a schematic diagram of the temperature-time curves for a two-stage slow-heating aging process. The solid line represents process path 1, which corresponds to a short-term quenching and resting time of ≤12h for extruded materials, while the dashed line represents process path 2, which corresponds to a long-term quenching and resting time >12h. Both paths include a complete thermodynamic cycle of slow heating to the first holding plateau to induce nucleation, and then heating again to the second holding plateau to promote the dispersion and precipitation of the strengthening phase.

[0024] When the quenching and holding time of the extruded material undergoing aging treatment is ≤12h, the matrix is ​​in the initial stage of natural aging. At this stage, a strategy is adopted to raise the temperature from room temperature to 120-130℃ at a rate of 2-8℃ / h and hold for 1-10h. Gradient heating rates of 2℃ / h, 5℃ / h, and 8℃ / h are all within the protection range. Slow heating within this temperature range allows Mg and Si atoms to combine, forming dispersed nucleation centers. The subsequent second-stage heating rate is set at 4-10℃ / h, with a target temperature of 160-175℃ and a holding time of 0.1-10h. The purpose of this second-stage heating is to allow the cores formed in the first stage to grow... Precursor phase. If the storage time is >12h, the degree of natural aging inside the material deepens, and the atomic cluster size increases. The process is adjusted to heat from room temperature to 131-140℃ at a rate of 2-8℃ / h, and extend the holding time to 10.1-20h. The higher end temperature of the first stage and the longer holding time cause the existing natural aging products to recombine or be covered by new nucleation processes. The second stage heats to 176-195℃ and holds for 10.1-20h, using the corresponding thermal activation energy to promote the precipitation of the strengthening phase and compensate for the loss of matrix solutes caused by long storage. Throughout the aging cycle, the temperature control system executes the set gradient. The above process steps lock the radius of the precipitated strengthening phase below 1.2nm, addressing the performance degradation caused by thermal history sensitivity, and achieving the technical indicators of yield strength ≥360MPa and plasticity ≥15%.

[0025] A process for improving the strength and plasticity of 6-series aluminum alloys includes providing 6-series aluminum alloy extrusions and subjecting the extrusions to an aging treatment. The chemical composition and mass percentage of the 6-series aluminum alloy extrusions are: Mg 0.90 wt%, Si 0.71 wt%, Cu 0.72 wt%, Mn 0.10 wt%, Ti 0.01 wt%, Fe 0.10 wt%, with the balance being Al and unavoidable impurities. The aging treatment involves heating the 6-series aluminum alloy extrusions from room temperature to 120-140°C at a rate of 2-8°C / h and holding at that temperature for 1-20 hours, then further heating to 160-195°C at a rate of 4-10°C / h and holding at that temperature for 0.1-20 hours. After the aging treatment, a diffusely distributed [precipitate / effect] is formed in the 6-series aluminum alloy matrix. The precursor strengthening phase, the The radius of the precursor strengthening phase is less than or equal to 1.2 nm. The process method involves constructing aging parameter gradients for different quenching and resting times, as shown in the attached figure. Figure 4 As shown, when the quenching and holding time of the extruded material under aging treatment is ≤12h, the matrix is ​​in the initial stage of natural aging. At this time, a strategy of heating from room temperature to 120-130℃ at a rate of 2-8℃ / h and holding for 1-10h is adopted to precisely control the synergistic effect of the heating rate, target temperature, and holding time, thereby adjusting the solute atom migration and precipitation kinetics within the aluminum alloy matrix. Based on two states—holding time less than or equal to 12h and holding time greater than 12h—a process route covering the extreme endpoint values ​​and the optimal intermediate values ​​is set to verify the control capability of specific heat treatment parameters in overcoming the room temperature holding effect and microscopic phase evolution. Example 1

[0026] A 6-series aluminum alloy extrusion with the stated chemical composition and mass percentages was prepared. The preparation process included melting, casting, homogenization, heating, and extrusion forming. The extruded material was immediately subjected to online quenching at the die and cooled to room temperature. The quenching time was controlled to be less than or equal to 12 hours, during which time the alloy matrix was in the early stages of natural aging, and large-scale undesirable segregation of Mg and Si atoms in the supersaturated solid solution had not yet occurred. The extruded material was then placed in a high-precision programmable temperature-controlled aging furnace for aging treatment. Using extremely low-speed parameters, the furnace was slowly heated from room temperature to 120°C at a rate of 2°C / h and held at this temperature for 1 hour. After the first stage of holding, the furnace was further heated to 175°C at a rate of 4°C / h and held at this temperature for 0.1 hours. After the treatment, the extruded material was removed and cooled. In this process, the extremely slow heating rate of 2℃ / h, combined with a relatively low target temperature of 120℃, provides an extremely stable thermodynamic environment for solute atoms within the matrix, promoting the steady aggregation of solute atoms into high-density nucleation particles without disrupting the existing micro-cluster structure. Due to the extremely short holding time, a short holding time of 1 hour is sufficient to complete nucleation preparation. The second stage involves heating to 175℃ at a rate of 4℃ / h and holding for only 0.1 hours, utilizing a short-duration high-temperature energy pulse to excite the precipitation of the strengthening phase. This parameter combination solves the technical problem of balancing the nucleation driving force and subsequent growth control in short-term held-state aluminum alloys during the early stages of aging, suppressing excessive growth of the strengthening phase in the high-temperature stage. The resulting technical effect is the precipitation of a large number of fine, dispersed nuclei in the matrix. The precursor reinforcing phase has a radius strictly controlled at 0.85 nm and a volume fraction of 0.43%. The macroscopic mechanical properties are characterized by a yield strength of 368 MPa, a tensile strength of 385 MPa, and a plasticity of 17.6%, achieving a simultaneous improvement in high yield strength and high elongation of the material. Example 2

[0027] 6-series aluminum alloy extrusions were prepared using the same melting and extrusion quenching process. The quenching dwell time of the extrusions was controlled to be less than or equal to 12 hours. The extrusions were then fed into an aging furnace and processed using the upper limit parameter combination within the short dwell time range. The aging furnace was heated from room temperature to 130°C at a rate of 8°C / h, and the holding time was extended to 10 hours. Subsequently, the aging furnace was heated to 160°C at a rate of 10°C / h and held at this temperature for 10 hours, followed by cooling. The heating rate of 8°C / h is higher than that in Example 1, allowing for a faster transition from room temperature to 130°C. To compensate for insufficient nucleation time that might result from the rapid heating, a holding period of up to 10 hours was set to provide a sufficient reaction window for solute atoms to accumulate a large number of nucleation particles. The second stage involves heating to a lower temperature of 160℃ at a rate of 10℃ / h. This lower second-stage temperature inhibits rapid long-distance atomic diffusion, necessitating a long holding time of 10 hours to ensure sufficient growth of the strengthening phase and achieve the required volume fraction. This parameter combination solves the technical problem of insufficient or uneven phase precipitation that easily occurs when using higher heating rates. The resulting technical effect is to promote the precipitation of phases with a radius of 0.89 nm within the alloy. The precursor reinforcing phase has a volume fraction of 0.38%. The material's yield strength is 365 MPa, tensile strength is 381 MPa, and plasticity is 15.5%, proving that the upper limit of the process parameters can still meet the design requirements for high strength and plasticity under short-term storage conditions. Example 3

[0028] Obtain 6-series aluminum alloy extrusions that have undergone online quenching and cooling to room temperature. The quenching dwell time is controlled to be less than or equal to 12 hours. The extrusions are then placed in an aging furnace and treated using a moderate parameter gradient. The aging furnace is heated from room temperature to 125°C at a rate of 6°C / h and held for 6 hours. Immediately afterwards, the furnace is heated to 168°C at a rate of 6°C / h and held for 7 hours, followed by cooling. The moderate heating rate of 6°C / h strikes a balance between production efficiency and microstructure control. Holding at 125°C for 6 hours induces the formation of numerous fine and highly thermally stable precipitates. The second stage, holding at 168°C for 7 hours, provides a gentle thermal activation energy that allows the strengthening phase to grow stably attached to the primary nuclei, effectively avoiding phase grain coarsening caused by the Oswald ripening effect. This parameter combination solves the problem of product quality fluctuations caused by an excessively narrow parameter control window in industrial mass production. The resulting technical effect is the formation of a highly uniformly distributed... The precursor-reinforced phase has a precipitate radius of 0.88 nm and a stable volume fraction of 0.37%. The extruded material ultimately exhibits a yield strength of 363 MPa, a tensile strength of 389 MPa, and a plasticity of 16.6%, demonstrating the excellent stability of this median process route in maintaining mechanical properties. Example 4

[0029] 6-series aluminum alloy extrusions were prepared and subjected to online quenching and cooling. The quenching dwell time was controlled to be greater than 12 hours. Prolonged room temperature dwell inevitably led to natural aging within the alloy matrix, resulting in a certain number of large and unevenly distributed solute atom clusters. The extrusion was then placed in an aging furnace, and parameter combinations within a long holding range were used to address the long dwell time. The aging furnace was heated from room temperature to 131°C at a rate of 8°C / h and subjected to an extreme holding treatment for up to 20 hours. After this process, the aging furnace was heated to an extremely high target temperature of 195°C at a rate of 10°C / h, held for 10.1 hours, and then cooled. In the first stage, the 20-hour holding time combined with the 131°C temperature promoted the recombination of the undesirable atom clusters generated during the long room temperature dwell time, transforming them into high-density nucleation centers conducive to subsequent artificial aging and eliminating the negative historical record of natural aging. The second stage involves heating to 195℃, utilizing extremely high thermal activation energy to forcibly drive the strengthening phase to precipitate rapidly and lock into a state within a short period of 10.1 hours. This parameter combination solves the technical challenge of steric hindrance and solute consumption caused by naturally aged clusters resulting from long-term quenching and storage, which hinder the growth of artificially aged precipitates. The resulting technical effect is the successful overcoming of the room-temperature storage effect, allowing the precipitate to form in the matrix... The radius of the precursor reinforcing phase was limited to within 0.94 nm, with a volume fraction of 0.34%. The yield strength of the material jumped to 370 MPa, the tensile strength reached 391 MPa, and the plasticity remained at 15.3%, maintaining excellent comprehensive mechanical properties even after long-term storage. Example 5

[0030] The same process was used to obtain 6-series aluminum alloy extrusions, with the quenching and holding time controlled to be greater than 12 hours. The extrusions were placed in an aging furnace using a combination of extremely slow and extremely long process parameters. The aging furnace was heated from room temperature to 140°C at a slow rate of 2°C / h and held for 10.1 hours. Subsequently, the furnace was heated to 176°C at a rate of 4°C / h and held for an extremely long time of 20 hours before being removed and cooled. The extremely slow heating rate of 2°C / h, combined with the relatively high target temperature of 140°C in the first stage, provided an extremely mild dissolution and redistribution period for the stubborn atomic clusters formed during the long holding time. The 10.1-hour holding time allowed the matrix to regain a uniform solute distribution and complete a new round of fine nucleation. The second stage, heating to 176°C at 4°C / h and holding for 20 hours, ensured sufficient time for phase transformation and precipitation at the lower second-stage temperature, maximizing the volume fraction. This parameter combination solves the technical problem that conventional rapid heating aging methods struggle to reverse deep natural aging products, leading to incomplete phase precipitation. The resulting technical effect is the formation of a dense phase within the alloy. The precursor-reinforced phase network was controlled with a phase radius of 0.90 nm and a volume fraction of 0.35%. Test results showed a yield strength of 369 MPa, a tensile strength of 389 MPa, and a plasticity of 15.5%, demonstrating the high effectiveness of the synergistic treatment of long-term stored materials with extremely slow heating and extremely long heat preservation. Example 6

[0031] 6-series aluminum alloy extrusions were prepared, with the quenching and holding time controlled to be greater than 12 hours. The extrusions were then placed in an aging furnace and aged using median parameters under long-term holding conditions. The aging furnace was heated from room temperature to 135°C at a rate of 6°C / h and held for 13 hours. Next, the furnace was heated to 190°C at a rate of 7°C / h and held for 13 hours, followed by cooling. Under this process, the parameter settings in the first stage smoothly deconstructed the atomic segregation caused by room temperature holding, and the 13-hour holding reshaped the microscopic nucleation sites within the alloy. The second stage, heating to 190°C and holding for 13 hours, provided ample driving force to rapidly grow the strengthening phase to the ideal nanoscale size and then cease development. This combination of median parameters solved the problem of excessive energy consumption or excessively long control cycles during long-term holding. The resulting technical effect is the acquisition of a stable and dispersed microstructure. The precursor reinforcing phase has a radius of 0.96 nm and a volume fraction of 0.33%. The material exhibits a yield strength of 366 MPa, a tensile strength of 387 MPa, and a plasticity of 15.2%, demonstrating good batch-to-batch reproducibility of performance.

[0032] A process for improving the strength and plasticity of 6-series aluminum alloys includes providing 6-series aluminum alloy extrusions and subjecting the extrusions to an aging treatment. The chemical composition and mass percentage of the 6-series aluminum alloy extrusions are: Mg 0.90 wt%, Si 0.71 wt%, Cu 0.72 wt%, Mn 0.10 wt%, Ti 0.01 wt%, Fe 0.10 wt%, with the balance being Al and unavoidable impurities. The aging treatment involves heating the 6-series aluminum alloy extrusions from room temperature to 120-140°C at a rate of 2-8°C / h and holding at that temperature for 1-20 hours, then further heating to 160-195°C at a rate of 4-10°C / h and holding at that temperature for 0.1-20 hours. After the aging treatment, a diffusely distributed [precipitate / effect] is formed in the 6-series aluminum alloy matrix. The precursor strengthening phase, the The radius of the precursor strengthening phase is less than or equal to 1.2 nm. The process method sets aging parameter gradients for different quenching and holding times, controlling the synergistic effect of heating rate, target temperature, and holding time to adjust the solute atom migration and precipitation kinetics within the aluminum alloy matrix. Based on two states—holding times less than or equal to 12 h and holding times greater than 12 h—process routes covering endpoint and midpoint values ​​are established to illustrate the influence of heat treatment parameters on overcoming the room temperature holding effect and microscopic phase evolution. Example 1

[0033] A 6-series aluminum alloy extrusion with the stated chemical composition and mass percentages was prepared. The preparation process included melting, casting, homogenization, heating, and extrusion forming. The extruded material was then subjected to online quenching at the die and cooled to room temperature. The quenching time was controlled to be less than or equal to 12 hours, during which time the alloy matrix was in the early stages of natural aging, and Mg and Si atoms in the supersaturated solid solution had not undergone large-scale segregation. The extruded material was then placed in a temperature-controlled aging furnace for aging treatment. Using low-speed parameters, the furnace was heated from room temperature to 120°C at a rate of 2°C / h and held at this temperature for 1 hour. After the first stage of holding, the furnace was further heated to 175°C at a rate of 4°C / h and held at this temperature for 0.1 hours. After the treatment, the extruded material was removed and cooled. During this process, the heating rate of 2°C / h combined with the target temperature of 120°C provided a stable thermodynamic environment for the solute atoms in the matrix, promoting the aggregation of solute atoms into core particles while maintaining the existing micro-cluster structure. The nucleation preparation is completed in a short 1-hour holding process with a short dwell time. The second stage involves heating to 175℃ at a rate of 4℃ / h and holding for 0.1h, utilizing the energy input of a short period at a relatively high temperature to stimulate the precipitation of the strengthening phase. This parameter combination solves the technical problem of balancing the nucleation driving force and subsequent growth control in aluminum alloys with short dwell time during the early stages of aging, suppressing excessive growth of the strengthening phase in the high-temperature stage, as shown in the attached figure. Figure 1 As shown, the resulting technical effect is the precipitation of fine and dispersed precursor reinforcing phases in the matrix, with a radius controlled at 0.85 nm and a volume fraction of 0.43%. The macroscopic mechanical properties are characterized by a yield strength of 368 MPa, a tensile strength of 385 MPa, and a plasticity of 17.6%, achieving a simultaneous improvement in the material's yield strength and elongation.

[0034] The resulting technical effect lies in the precipitation of fine, dispersed particles in the matrix. The precursor reinforcing phase has a radius controlled at 0.85 nm and a volume fraction of 0.43%. The macroscopic mechanical properties are characterized by a yield strength of 368 MPa, a tensile strength of 385 MPa, and a plasticity of 17.6%, achieving a simultaneous improvement in the material's yield strength and elongation. Example 2

[0035] 6-series aluminum alloy extrusions were prepared using the same melting and extrusion quenching process. The quenching dwell time of the extrusions was controlled to be less than or equal to 12 hours. The extrusions were then fed into an aging furnace and processed using the upper limit parameter combination within the short dwell time range. The aging furnace was heated from room temperature to 130°C at a rate of 8°C / h, and the holding time was extended to 10 hours. Subsequently, the aging furnace was heated to 160°C at a rate of 10°C / h and held at this temperature for 10 hours, followed by cooling. The 8°C / h heating rate spanned the temperature range from room temperature to 130°C. To compensate for the difference in nucleation time caused by the heating, a 10-hour holding period was set to allow solute atoms a reaction window to complete the accumulation of nucleation particles. The second stage used a rate of 10°C / h to heat to 160°C. The corresponding second-stage temperature limited the long-distance diffusion of atoms, and the 10-hour holding period ensured the growth of the strengthening phase and the achievement of the set volume fraction. This parameter combination solved the technical problem of insufficient or uneven phase precipitation that occurred when using higher heating rates. The resulting technical effect is to induce the precipitation of particles with a radius of 0.89 nm inside the alloy. The precursor reinforcing phase has a volume fraction of 0.38%. The material's yield strength is 365 MPa, tensile strength is 381 MPa, and plasticity is 15.5%, indicating that the upper limit of the process parameters can meet the strength and plasticity requirements under short-term storage conditions. Example 3

[0036] Obtain 6-series aluminum alloy extrusions that have undergone online quenching and cooling to room temperature. The quenching dwell time is controlled to be less than or equal to 12 hours. The extrusions are placed in an aging furnace and treated using a moderate parameter gradient. The aging furnace is heated from room temperature to 125°C at a rate of 6°C / h and held for 6 hours. Then, the furnace is heated to 168°C at a rate of 6°C / h and held for 7 hours. After aging, the furnace is cooled. The 6°C / h heating rate balances production efficiency and microstructure control. Holding at 125°C for 6 hours induces the formation of fine and thermally stable precipitates. The second stage, holding at 168°C for 7 hours, allows the corresponding thermal activation energy to allow the strengthening phase to adhere to the primary nuclei for growth, avoiding phase grain coarsening caused by the Oswald ripening effect. This parameter combination solves the problem of product quality fluctuations caused by a narrow parameter control window in production. The resulting technical effect is the formation of a uniformly distributed... The precursor-reinforcing phase has a precipitate radius of 0.88 nm and a volume fraction of 0.37%. The extruded material exhibits a yield strength of 363 MPa, a tensile strength of 389 MPa, and a plasticity of 16.6%, demonstrating the stability of the median process route in terms of mechanical properties. Example 4

[0037] 6-series aluminum alloy extrusions were prepared and subjected to online quenching and cooling. The quenching dwell time was controlled to be greater than 12 hours. Room temperature dwell allowed for natural aging within the alloy matrix, producing large and unevenly distributed solute atom clusters. The extrusion was then placed in an aging furnace, with a long holding parameter combination employed to accommodate the extended dwell time. The aging furnace was heated from room temperature to 131°C at a rate of 8°C / h and held for 20 hours. After this step, the aging furnace was heated to the target temperature of 195°C at a rate of 10°C / h and held for 10.1 hours before cooling. The first stage, with its 20-hour holding time and 131°C temperature, facilitated the recombination of the atom clusters generated during the long room temperature dwell time, transforming them into nucleation sites for subsequent artificial aging and mitigating the effects of natural aging. In the second stage, the temperature was increased to 195°C, and the corresponding thermal activation energy was used to drive the precipitation and stabilization of the strengthening phase within 10.1 hours. This parameter combination solves the technical problem of steric hindrance and solute consumption caused by naturally aged clusters resulting from long-term quenching and storage, which hinder the growth of artificially aged precipitates. The resulting technical effect is to address the room-temperature storage effect and reduce the precipitation of naturally aged clusters in the matrix. The radius of the precursor reinforcing phase is limited to within 0.94 nm, and the volume fraction is 0.34%. The material achieves a yield strength of 370 MPa, a tensile strength of 391 MPa, and maintains a plasticity of 15.3%, retaining its mechanical properties even after prolonged storage. Example 5

[0038] The same process was used to obtain 6-series aluminum alloy extrusions, with the quenching and holding time controlled to be greater than 12 hours. The extrusions were placed in an aging furnace using a combination of slow and long-duration process parameters. The aging furnace was heated from room temperature to 140°C at a rate of 2°C / h and held for 10.1 hours. Then, the furnace was heated to 176°C at a rate of 4°C / h and held for 20 hours before cooling. The 2°C / h heating rate, combined with the initial target temperature of 140°C, provided sufficient time for the dissolution and redistribution of atomic clusters formed during the long holding period. The 10.1-hour holding period ensured a uniform solute distribution in the matrix and facilitated micro-nucleation. The second stage, heating to 176°C at 4°C / h and holding for 20 hours, ensured sufficient time for phase transformation and precipitation at the set second-stage temperature, increasing the volume fraction. This parameter combination solved the technical problem of incomplete phase precipitation caused by the inability to reverse natural aging products when using conventional heating aging. The resulting technical effect is the formation of dispersed... The precursor-reinforced phase had a phase radius controlled at 0.90 nm and a volume fraction of 0.35%. Test results showed a yield strength of 369 MPa, a tensile strength of 389 MPa, and a plasticity of 15.5%, indicating that the synergistic treatment of slow heating and long-term heat preservation for long-term storage materials is effective. Example 6

[0039] 6-series aluminum alloy extrusions were prepared, with the quenching and holding time controlled to be greater than 12 hours. The extrusions were then placed in an aging furnace and aged using median parameters under long-term holding conditions. The aging furnace was heated from room temperature to 135°C at a rate of 6°C / h and held for 13 hours. Then, the furnace was heated to 190°C at a rate of 7°C / h and held for 13 hours, followed by cooling. In this process, the first-stage parameter settings deconstruct atomic segregation caused by room temperature holding, while the 13-hour holding reshapes the nucleation sites within the alloy. The second stage, heating to 190°C and holding for 13 hours, provides the driving force to promote the growth of the strengthening phase to the set nanoscale level. This combination of median parameters solves the problem of excessive energy consumption or excessively long control cycles during long-term holding. The resulting technical effect is the acquisition of a stable and dispersed microstructure. The precursor reinforcing phase has a radius of 0.96 nm and a volume fraction of 0.33%. The material exhibits a yield strength of 366 MPa, a tensile strength of 387 MPa, and a plasticity of 15.2%, demonstrating batch-to-batch reproducibility of performance.

[0040] A process for improving the strength and plasticity of 6-series aluminum alloys includes providing 6-series aluminum alloy extrusions and subjecting the extrusions to an aging treatment. The chemical composition and mass percentage of the 6-series aluminum alloy extrusions are: Mg 0.90 wt%, Si 0.71 wt%, Cu 0.72 wt%, Mn 0.10 wt%, Ti 0.01 wt%, Fe 0.10 wt%, with the balance being Al and unavoidable impurities. The aging treatment involves heating the 6-series aluminum alloy extrusions from room temperature to 120-140°C at a rate of 2-8°C / h and holding at that temperature for 1-20 hours, then further heating to 160-195°C at a rate of 4-10°C / h and holding at that temperature for 0.1-20 hours. After the aging treatment, a diffusely distributed [precipitate / effect] is formed in the 6-series aluminum alloy matrix. The precursor strengthening phase, the The radius of the precursor strengthening phase is less than or equal to 1.2 nm. Multiple comparative examples were set to verify the correspondence between the boundary significance of the process parameter settings and the technical effects. All comparative examples used the same 6-series aluminum alloy chemical composition as the examples, with specific mass percentages corresponding to the aforementioned limited proportions, and values ​​retained to two decimal places. Maintaining consistent chemical composition eliminated the possibility of fluctuations in the material's basic composition interfering with the final mechanical properties. Subsequent differences in microstructure and macroscopic mechanical properties were attributed to changes in the thermodynamic parameters of the aging treatment, establishing a logical correlation between performance evolution and the established heat treatment method.

[0041] Comparative Example 1 A 6-series aluminum alloy extrusion with the aforementioned chemical composition and mass percentages was prepared. In the material preparation stage, industrial pure aluminum and various intermediate alloys were smelted and proportioned, and aluminum alloy round ingots were formed through semi-continuous casting. Homogenization treatment was performed at 540-560℃, followed by cooling. The ingots were heated to the set temperature and then formed in an extruder. The extruded products were ejected from the die and subjected to online water quenching to room temperature. The quenching dwell time was controlled to be greater than 12 hours, allowing the matrix to undergo natural aging. This comparative example verified the effect of the upper limit setting of the heating rate; the aging heating rate was set at 12℃ / h, exceeding the limit by 10℃ / h. The extruded material was placed in a programmable temperature-controlled aging furnace, which directly heated from room temperature to 175℃ at a rate of 12℃ / h, and held for 8 hours. The 12℃ / h heating rate shortened the residence period of the alloy matrix in the low-temperature range. Solute atoms Mg and Si lacked a time window for short-distance diffusion and ordered rearrangement within the aluminum matrix. During the room temperature storage period, naturally aged atomic clusters formed in the matrix underwent uneven re-dissolution under the corresponding thermodynamic energies. Some larger clusters absorbed surrounding free solute atoms and coarsened, failing to form densely distributed and uniformly sized precipitate nuclei within the matrix. During the isothermal holding period at 175℃, The precursor-enhanced phase grows relying on a relatively small number of large cores. The phase precipitation kinetics are altered, as shown in the attached figure. Figure 2 As shown, the precipitated precursor reinforcing phase exhibits a sparse distribution and relatively large monomer size. Microstructural characterization data shows that the average radius of the reinforcing phase reaches 1.7 nm, exceeding the process limit of less than or equal to 1.2 nm, and the phase volume fraction decreases to 0.21%. According to the dislocation strengthening mechanism, the larger precipitated phase expands the phase spacing between adjacent particles, weakening the matrix's resistance to dislocation slip. During stress deformation, dislocations bypass the coarse particles through a bypass mechanism, causing local stress concentration at the particle-matrix phase interface, becoming the source of microcrack initiation. The test results of macroscopic mechanical properties show that the yield strength of the extruded material decreases to 348 MPa, the tensile strength is 369 MPa, and the plasticity decreases to 10.1%. The deviation of the heating rate alters the synergistic mechanism of nucleation and growth, failing to achieve the target of improving the material's strength and plasticity, verifying the necessity of setting an upper limit for the heating rate.

[0042] Comparative Example 2 6-series aluminum alloy extrusions were prepared using the same composition and preparation procedures as described above. After extrusion molding and online quenching and cooling, the quenching dwell time was controlled to be less than or equal to 12 hours. This comparative example uses a single-stage aging process, omitting the first-stage low-temperature nucleation and holding process in the specified process. The extrusions were loaded into an aging furnace, and the furnace was heated from room temperature to 175°C at a rate of 12°C / h. At this target temperature, a single-stage isothermal holding treatment was performed for 8 hours. This process places the alloy, after a short dwell time, in a corresponding thermally activated energy environment. The process lacks the induction and plateau holding within the 120-140°C temperature range, allowing supersaturated solute atoms within the matrix to acquire kinetic energy and enter a long-distance diffusion state. The small clusters generated in the early stages of natural aging undergo re-dissolution at the corresponding temperature, reducing the number of effective particles that remain and reach the critical nucleation size. The precipitation process transforms into a coarsening process for some dominant phase particles. The temperature environment promotes the aggregation of free Mg and Si atoms towards the growth points, resulting in a lower overall precipitation density of the strengthening phase. Microstructure testing and statistical analysis showed that the precipitates in the matrix The precursor strengthening phase has a radius of 2.1 nm and a corresponding volume fraction of 0.28%. The increased size of the precipitated phase particles alters the coherent relationship with the aluminum matrix, leading to a decrease in the strengthening effect generated by the coherent distortion strain field. Under tensile stress, the material's resistance to deformation decreases, and interfacial stress concentration easily leads to fracture failure. Mechanical property tests show that the sample has a yield strength of 353 MPa, a tensile strength of 374 MPa, and a plasticity index reflecting ductility of 12.6%. The single-stage aging process failed to construct a fine and dispersed strengthening phase network within the matrix, resulting in the material's mechanical properties not meeting expectations, highlighting the role of the two-stage temperature gradient setting in controlling the alloy's microstructure.

[0043] Comparative Example 3 6-series aluminum alloy extrusions were obtained using the same chemical proportions and pretreatment process as in the examples. After online quenching, the extruded products were kept at room temperature for at least 12 hours. This comparative example employed a two-stage aging process with heating parameters exceeding the defined slow range. The prepared extrusions were placed in a programmed aging furnace, and the equipment was controlled to heat from room temperature to 120°C at a rate of 20°C / h, holding for 1 hour. After the first stage of holding, the equipment was controlled to heat to 175°C at a rate of 30°C / h, holding for 8 hours. The heating rates of 20°C / h and 30°C / h induced changes in the phase transformation thermodynamic response in this specific alloy system. The faster heating rate created a temperature gradient inside and outside the material, altering the thermal equilibrium within the crystal lattice. During the first stage of heating, the dwell time of the temperature window suitable for solute atom nucleation was shortened, and the solute atoms failed to complete the structural transformation into nuclei within this time. The 1-hour holding time could not compensate for the deviation in the initial nucleation time window. In the second stage, the temperature is increased to 175℃ at a rate of 30℃ / h, causing secondary dissolution of some unstable nuclei. The remaining cores then grow under the corresponding thermal energy. Microscopic structure analysis images show that... The precursor reinforcing phase is aggregated within the matrix, with uneven particle radius distribution; the statistical average radius is 1.9 nm, and the overall volume fraction is 0.31%. The macroscopic properties of the material are affected by changes in microstructure, with a yield strength of 369 MPa and a plasticity index decreasing to 7.9%. Phase particles formed by rapid heating are difficult to coordinate with matrix deformation under stress, easily becoming initiation sources for microcracks, which connect and induce fracture in the early stages of tensile strain. These comparative results verify the effectiveness of the designed slow heating logic in controlling the material's microstructure and preserving its ductility.

[0044] Comparison table of parameters and performance between comparative examples and embodiments: A process for improving the strength and plasticity of 6-series aluminum alloys includes providing 6-series aluminum alloy extrusions and subjecting the extrusions to an aging treatment. The chemical composition and mass percentage of the 6-series aluminum alloy extrusions are: Mg 0.90 wt%, Si 0.71 wt%, Cu 0.72 wt%, Mn 0.10 wt%, Ti 0.01 wt%, Fe 0.10 wt%, with the balance being Al and unavoidable impurities. The aging treatment involves heating the 6-series aluminum alloy extrusions from room temperature to 120-140°C at a rate of 2-8°C / h and holding at that temperature for 1-20 hours, then further heating to 160-195°C at a rate of 4-10°C / h and holding at that temperature for 0.1-20 hours. After the aging treatment, a diffusely distributed [precipitate / effect] is formed in the 6-series aluminum alloy matrix. The precursor strengthening phase, the The radius of the precursor reinforcing phase is less than or equal to 1.2 nm. A rigorous performance testing method and data characterization system are established to verify the control results of the process parameters on the macroscopic mechanical properties and microscopic phase evolution of the extruded material. This characterization system covers macroscopic tensile fracture testing and atomic-scale microstructure statistics, establishing a correspondence between thermodynamic parameter inputs and material performance outputs, and defining the measurement and calculation standards for microstructural characteristics.

[0045] The evaluation of the macroscopic mechanical properties of metallic materials involves standardized testing procedures. Tensile testing is performed according to the national standard GB / T228.1 Metallic materials, tensile testing—Part 1: Room temperature test method. Tensile specimens are taken from aging-treated 6-series aluminum alloy extrusions. The sampling direction is parallel to the extrusion direction of the aluminum alloy, avoiding the unstable deformation zones at the head and tail of the extrusion. A longitudinal specimen blank is taken from the middle section of the extrusion. The blank is machined into a standard-proportion circular or rectangular cross-section dog-bone-shaped tensile specimen, ensuring that the gauge length and the square root of the original cross-sectional area meet the standard's specified ratio. The surface roughness parameter Ra of the working part of the gauge length section of the specimen is machined to less than 0.8 micrometers, and precision turning and ultra-fine sandpaper mechanical polishing are used to completely remove any machining marks and micro-pits. A smooth surface condition avoids stress concentration caused by surface geometric defects during tensile testing, preventing premature brittle fracture of the specimen before reaching the intrinsic plastic limit of the material, and ensuring that the plasticity measurement data accurately reflects the deformation coordination ability of the 6-series aluminum alloy matrix. The testing equipment used was a microcomputer-controlled electronic universal testing machine equipped with an extensometer. The relative error of the force sensor readings in the loading system of the testing machine was calibrated to within ±1%, and the accuracy class of the extensometer was required to reach 0.5. The testing environment was set at room temperature of 25 degrees Celsius. The specimen clamping required that the center lines of the upper and lower clamps of the testing machine coincide with the longitudinal axis of the specimen to eliminate the additional bending moment stress caused by eccentricity. During the elastic stage of tensile loading, a stress rate control mode was used, with the loading rate set between 10 MPa per second and 30 MPa per second. After the material deformation entered the yield stage and the plastic deformation stage, the control system of the testing machine seamlessly switched to the strain rate control mode, maintaining the tensile strain rate between 0.00025 s / s and 0.0025 s / s until the specimen fractured. The extensometer tracked and recorded the dynamic elongation of the specimen's gauge length in real time, and the testing machine synchronously acquired the tensile load values ​​of the loading system. The processing system plotted the engineering stress and engineering strain curves based on the original cross-sectional area and original gauge length of the specimen.

[0046] Key mechanical data are extracted from the stress-strain curves generated by the tests. A parallel line with an intercept of 0.2% on the strain axis is plotted on the curve, parallel to the linear elastic segment. The stress value corresponding to the intersection of this parallel line and the stress-strain curve is recorded as the specified non-proportional elongation strength, i.e., the yield strength data point of the material. The two ends of the fractured specimen are tightly joined at the fracture point, and the gauge length after fracture is measured using vernier calipers. The elongation after fracture is calculated based on the original gauge length as the plasticity data point of the material. Standardized mechanical property testing methods shield the test results from the interference of specimen geometry preparation and loading rate fluctuations, and solve the problem of data distortion caused by non-standard operation during macroscopic performance verification. The resulting technical effect is to establish the objectivity of measuring macroscopic performance indicators such as yield strength greater than or equal to 360 MPa and plasticity greater than or equal to 15%, and to provide a mechanical evaluation benchmark for verifying the improvement of the macroscopic load-bearing capacity of aluminum alloys by the two-stage slow heating aging process.

[0047] Quantitative characterization of microscopic phase characteristics requires electron-optical instruments with atomic-level resolution. Measurement The radius and volume fraction of the precursor reinforcing phase were observed and data acquired using a high-resolution transmission electron microscope (TEM). The accelerating voltage of the TEM was set to 200 kV or 300 kV, and the point resolution of the instrument needed to be better than 0.2 nm to meet the optical requirements for clear imaging of extremely fine precipitates with a size of 1.2 nm or less. The core of the characterization process was to prepare a thin film sample that could be penetrated by a high-energy electron beam without altering the original microscopic thermodynamic state of the material. A 0.5 mm thick metal sheet was cut from the region at the clamping end of the tensile specimen where no plastic deformation occurred. The sheet was mechanically thinned stepwise to 50 to 70 μm using silicon carbide wet sandpaper. Sufficient water-based coolant was applied during the mechanical grinding process to remove the heat generated by friction and prevent local temperature rise that could lead to secondary precipitation, coarsening, or re-dissolution of the nanoscale reinforcing phase inside the matrix. The thinned metal sheet was then stamped into a standard TEM sample disc with a diameter of 3 mm. A dual-jet electrolytic polishing instrument was used to perform the final thinning of the sample disc until a central perforation was achieved. The electrolyte was prepared as a mixture of 30% concentrated nitric acid and 70% methanol by volume. The polishing process was conducted under strictly controlled low-temperature conditions, using liquid nitrogen to maintain the electrolyte temperature between -25°C and -30°C, with the operating voltage set between 15V and 20V. This low-temperature environment suppressed the impact of anodic dissolution heat generation on the thermal stability of the strengthening phase during electropolishing, prevented preferential corrosion of the interface between the strengthening phase and the aluminum matrix by the electrolyte, and ensured the observed... strong precursor The phase morphology fully reflects the true microscopic results of the low-temperature induction process at 2 to 8 degrees Celsius per hour and the high-temperature precipitation process at 4 to 10 degrees Celsius per hour. When a light-transmitting micropore appears in the center of the sample, the photoelectric sensing system of the dual-jet instrument immediately cuts off the power and triggers a deionized water rinsing program to wash away the corrosive electrolyte remaining on the metal surface. The sample is then dehydrated multiple times with anhydrous ethanol and dried with cold air.

[0048] The prepared metal thin film sample was mounted into the double-tilt stage of the transmission electron microscope. The alpha and beta angles of the stage were adjusted, and using Kikuchi line navigation, the zone axis of the aluminum alloy substrate was precisely aligned along a specific crystal orientation. (6-series aluminum alloys) The precursor strengthening phase typically precipitates in needle-like or rod-like shapes along specific crystal orientations of the aluminum matrix. Observation along a specific zone axis allows for the acquisition of a two-dimensional projection image of the cross-section of this needle-like phase, eliminating the magnification error caused by the tilted placement of phase particles. High-contrast microscopic images can be obtained by switching to dark-field imaging mode of the transmission electron microscope or by using a high-angle annular dark-field scanning transmission mode. Under specific imaging modes... A significant difference in atomic number contrast or diffraction contrast exists between the precursor strengthening phase and the aluminum matrix, and the boundary contours of the nanoscale phase particles are clearly visible on the dark substrate. To ensure the representativeness and accuracy of the statistical data, the statistical processing method for the microscopic data employs a multi-field random sampling principle. At least 10 non-overlapping observation fields are randomly selected at the edge of the thin region penetrated by the electron beam in each sample, with the physical area of ​​each field of view set to be no less than 200 nm by 200 nm. Professional image analysis software is used to extract and process the geometric dimensions of the precipitated phases within each field of view.

[0049] Image processing software uses a grayscale thresholding algorithm to identify and delineate each [image segment]. The outline boundary of the precursor strengthening phase cross-section is used to calculate the area of ​​the pixels enclosed by the closed outline and convert it into the actual physical area. The cross-section of the needle-like strengthening phase is equivalent to a standard circular cross-section, and its equivalent circular radius is calculated by applying the inverse operation rules of the circle area formula. Statistical processing specifications require that the total number of effective phase particles measured in all randomly selected fields of view must not be less than 500, and outlier data points with blurred boundaries or overlapping with other particles that cannot be separated are removed. The arithmetic mean of the equivalent circular radii of these 500 or more particles is calculated, and this average value is used as the characterization of the strengthening phase of the material. The test radius data was obtained. The volume fraction of the strengthening phase was measured using stereoscopic principles combined with local sample thickness measurements for three-dimensional calculation. The actual metal sample thickness in the microscopic region of each observation field was measured using convergent-beam electron diffraction (CBED) or electron energy loss spectroscopy (EEDS). The matrix volume corresponding to that field of view was obtained by multiplying the two-dimensional projected area of ​​the field of view by the measured thickness value. The total volume occupied by the precipitated phase was calculated by multiplying the sum of the cross-sectional areas of all strengthening phases within the field of view by the estimated average length of the needle-like phases along the observation direction. The total volume of the precipitated phases was then divided by the matrix volume value to obtain the volume of the precipitated phases within that microscopic field of view. The volume fraction ratio of the precursor reinforcing phase. The volume fractions from all 10 independent fields of view are summarized and a weighted average is calculated as a test index for evaluating the micro-precipitation density of this batch of materials. A data processing method combining random sampling procedures, massive particle extraction analysis, and three-dimensional spatial phase conversion overlay eliminates local data distortion caused by deliberately seeking micro-enrichment regions, solving the technical challenge of accurately quantifying nanoscale reinforcing phases. The resulting technical effect is to establish the reinforcing phase in process control. The objectivity of the determination of microscale indicators such as radius less than or equal to 1.2 nanometers and volume fraction greater than or equal to 0.3% provides a measurement standard for verifying the evolution of microstructure with heat treatment parameters.

[0050] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A process for improving the strength and plasticity of 6-series aluminum alloys, characterized in that, This includes providing 6-series aluminum alloy extrusions and aging the extrusions; The chemical composition and mass percentage of the 6-series aluminum alloy extrusion are as follows: Mg 0.90wt%, Si 0.71wt%, Cu 0.72wt%, Mn 0.10wt%, Ti 0.01wt%, Fe 0.10wt%, with the balance being Al and unavoidable impurities; The aging process is as follows: the 6-series aluminum alloy extrusion is heated from room temperature to 120 to 140°C at a rate of 2 to 8°C / h and held for 1 to 20 hours, and then heated to 160 to 195°C at a rate of 4 to 10°C / h and held for 0.1 to 20 hours. After the aging treatment, the 6-series aluminum alloy matrix precipitates in a diffusely distributed manner. The precursor strengthening phase, the The radius of the precursor strengthening phase is ≤1.2nm.

2. The process for improving the strength and plasticity of 6-series aluminum alloys according to claim 1, characterized in that, When the extruded material is left to stand for ≤12h after extrusion quenching, the aging process is as follows: heat from room temperature to 120 to 130℃ at a rate of 2 to 8℃ / h and hold for 1 to 10h, then heat to 160 to 175℃ at a rate of 4 to 10℃ / h and hold for 0.1 to 10h.

3. The process for improving the strength and plasticity of 6-series aluminum alloys according to claim 1, characterized in that, When the extruded material is left to stand for more than 12 hours after extrusion quenching, the aging process is as follows: the temperature is increased from room temperature to 131 to 140°C at a rate of 2 to 8°C / h and held for 10.1 to 20 hours, and then the temperature is increased to 176 to 195°C at a rate of 4 to 10°C / h and held for 10.1 to 20 hours.

4. The process for improving the strength and plasticity of 6-series aluminum alloys according to claim 1, characterized in that, Prior to the aging treatment, the process also includes the step of extruding and quenching the 6-series aluminum alloy and cooling it to room temperature.

5. The process for improving the strength and plasticity of 6-series aluminum alloys according to claim 1, characterized in that, During the process of heating from room temperature to 120 to 140°C at a rate of 2 to 8°C / h and holding at that temperature for 1 to 20 hours, the 6-series aluminum alloy matrix generates a process for precipitating the [specific material]. Nucleation particles of the precursor strengthening phase.

6. The process for improving the strength and plasticity of 6-series aluminum alloys according to claim 5, characterized in that, During the process stage of heating to 160 to 195°C at a rate of 4 to 10°C / h and holding at that temperature for 0.1 to 20 hours, the The precursor-enhanced phase precipitates based on the nucleation particles.

7. The process method for improving the strength and plasticity of 6-series aluminum alloys according to claim 1, characterized in that, The The radius of the precursor strengthening phase is 0.85 to 0.99 nm.

8. The process for improving the strength and plasticity of 6-series aluminum alloys according to claim 1, characterized in that, The The volume fraction of the precursor reinforcing phase is ≥0.3%.

9. The process for improving the strength and plasticity of 6-series aluminum alloys according to claim 1, characterized in that, The yield strength of the obtained 6-series aluminum alloy is ≥360MPa.

10. A process for improving the strength and plasticity of 6-series aluminum alloys according to claim 9, characterized in that, The resulting 6-series aluminum alloy has a plasticity of ≥15%.

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