Preparation method of high-strength anti-deformation aluminum alloy gearbox valve plate

Abstract

The invention relates to the technical field of metal matrix composite material forming, and discloses a preparation method of a high-strength anti-deformation aluminum alloy gearbox valve plate, which comprises the following steps: smelting an aluminum alloy raw material containing titanium nitride particles; the mixed melt is cooled to a semi-solid state interval with the solid phase rate being 20-50%, and slurry is prepared; the semi-solid slurry is injected into a mold, and 15-30 kHz mechanical pulse vibration is applied to assist forming during mold filling or pressure maintaining; and carrying out two-stage low-temperature aging treatment without high-temperature solid solution and quenching steps on the formed part. According to the method, the problem of contradiction between high strength and high dimensional precision caused by traditional T6 heat treatment is solved by combining low-temperature aging heat treatment with the self-limiting anchoring effect of the dispersed TiN particles. And meanwhile, through the synergistic effect of semi-solid forming and a pulse energy field, the internal density and wear resistance of the casting are improved. The gearbox valve plate prepared by the method has high strength, high dimensional stability, high density and excellent wear resistance.

Description

Technical Field

[0001] This invention relates to the field of metal matrix composite molding technology, specifically to a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate. Background Technology

[0002] Currently, aluminum alloy transmission valve plates are a core component of the hydraulic control system for automotive automatic transmissions and dual-clutch transmissions. The valve plate is a high-precision component with complex and intricate hydraulic oil passage grooves integrated inside. During operation, the spool valve reciprocates at high speed within the oil passage, achieving gear shifting. Therefore, the valve plate must possess extremely high dimensional accuracy, sufficient mechanical strength, and excellent wear resistance.

[0003] Regarding the aforementioned issues, existing aluminum alloy valve plate manufacturing processes typically employ high-pressure casting. The materials used are mostly die-cast aluminum alloys such as A380 or ADC12. After casting, the part generally undergoes T6 heat treatment to improve its mechanical properties. The T6 process includes a high-temperature solution treatment step, where the casting is heated to above 500°C. Subsequently, it undergoes rapid water quenching. Finally, artificial aging treatment is applied to precipitate strengthening phases.

[0004] However, existing technologies face challenges in manufacturing high-precision valve plates. T6 heat treatment is a major cause of valve plate deformation. Its high-temperature solution treatment and intense water quenching introduce significant thermal stress. The complex and thin-walled valve plate structure, coupled with the intense cooling during quenching, leads to stress concentration. These residual stresses, upon subsequent release, cause warping and deformation of the parts, compromising the accuracy of the hydraulic circuit. This creates a sharp conflict between strength and dimensional stability. While T6 treatment achieves high strength, it sacrifices dimensional accuracy. Using lower-temperature treatments like T5 to reduce deformation lowers the material's yield strength, failing to meet the durability requirements of high-pressure hydraulic conditions. Furthermore, traditional high-pressure casting processes are prone to air entrapment and shrinkage defects during mold filling, reducing the valve plate's density. The wear resistance of conventional aluminum alloy substrates is also insufficient to withstand the long-term friction of the spool valve.

[0005] Therefore, the present invention provides a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate, which solves the problem that it is difficult to simultaneously achieve high strength and high dimensional stability in existing aluminum alloy gearbox valve plate preparation processes.

[0007] To achieve the above objectives, the present invention provides a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate, comprising the following steps: S1. Material preparation and smelting: The raw materials containing aluminum alloy and 0.5-1.5 wt% surface-modified titanium nitride particles are smelted to obtain a mixed melt; S2. Semi-solid slurry preparation: The mixed melt is cooled to a semi-solid range with a solid content of 20-50% and stirred to obtain a semi-solid slurry; S3. Pulse energy field assisted forming: The semi-solid slurry is injected into the valve plate mold cavity, and a mechanical pulse vibration with a frequency of 15-30kHz is applied during the filling or holding process to form the valve plate part under pressure. S4. Low-temperature strain aging heat treatment: The valve plate part is subjected to a two-stage low-temperature aging treatment, which does not include solution treatment and quenching steps at temperatures above 500°C.

[0008] By adopting the above technical solution, this invention establishes a synergistic preparation path combining functional phase composites, semi-solid forming, pulsed energy field assistance, and low-temperature heat treatment. Its technical mechanism is mainly reflected in: First, step S4 employs a two-stage low-temperature strain aging heat treatment, avoiding the high-temperature (e.g., above 500℃) solution treatment and rapid water quenching steps in the traditional T6 heat treatment process. This fundamentally reduces the macroscopic residual stress introduced by severe thermal shock and uneven phase transformation, which is the core of controlling valve plate deformation. Simultaneously, the dispersed TiN particles introduced in step S1 play a crucial microscopic anchoring role during the low-temperature aging process in step S4, effectively pinning dislocations and grain boundaries, and suppressing size redistribution within the matrix caused by precipitation phase transformation and residual stress release. This self-limiting mechanism of TiN particles, combined with the low-stress field of low-temperature aging, synergistically ensures the dimensional stability of the valve plate.

[0009] Second, the preparation of the semi-solid slurry in step S2 is combined with the pulsed energy field-assisted molding in step S3. The semi-solid slurry (solidity 20-50%) has a low molding temperature and solidification shrinkage rate. The high-frequency mechanical pulse vibration applied during the filling and holding stages improves the rheology of the semi-solid slurry through acoustic flow and cavitation effects, which helps to break up the primary solid phase structure, promotes the uniform dispersion of TiN particles, and effectively eliminates microscopic air entrapment and shrinkage defects, ultimately obtaining a valve plate casting with high density and uniform structure.

[0010] Third, the TiN ceramic phase (0.5-1.5wt%) introduced in step S1 is uniformly distributed in the matrix, and its high hardness gives the valve plate surface excellent wear resistance.

[0011] In summary, this invention combines the self-limiting anchoring effect of TiN particles, the low-stress strengthening mechanism of low-temperature aging, and the high density control of semi-solid pulse field forming to synergistically regulate the microstructure, internal stress, and macroscopic density of the valve plate.

[0012] Preferably, in step S1, the surface-modified titanium nitride particles are prepared in advance by the following steps: adding titanium nitride powder to an alcohol-water mixture containing a silane coupling agent, stirring at 50-70°C, and then separating and drying.

[0013] More preferably, the silane coupling agent is γ-aminopropyltriethoxysilane.

[0014] By employing the above-mentioned technical solution, TiN particles are surface-treated using silane coupling agents. The mechanism involves, for example, γ-aminopropyltriethoxysilane, where the ethoxy group in its molecular structure undergoes hydrolysis in an alcohol-water solution to generate highly reactive silanol groups. These silanol groups then condense with hydroxyl groups formed on the surface of TiN particles due to slight oxidation or water adsorption, forming stable covalent bonds. Through this reaction, metalophilic aminopropyl groups are grafted onto the surface of the TiN particles, improving the wettability of the TiN ceramic phase with the aluminum alloy matrix, increasing the interfacial bonding strength between the two, and ensuring the stable existence of the TiN particles as a reinforcing phase within the matrix.

[0015] Preferably, in step S2, stirring is performed by applying an electromagnetic field with a frequency of 10-50Hz and a magnetic field strength of 0.05-0.2T.

[0016] By employing the above technical solution, electromagnetic stirring can apply periodically varying Lorentz forces to semi-solid slurries under non-contact conditions. This force generates strong forced convection and shearing in the melt, effectively breaking down nascent coarse dendrites and promoting their transformation into fine, rounded, near-spherical solid particles. This morphology reduces the apparent viscosity of the slurry and improves its rheological properties.

[0017] Preferably, in step S3, the amplitude of the mechanical pulse vibration is 1-5 micrometers.

[0018] By adopting the above technical solution, an amplitude range of 1-5 micrometers is a preferred energy input range. This amplitude can effectively transfer high-frequency mechanical energy to the semi-solid slurry, excite sufficient acoustic flow and cavitation effects, while avoiding fatigue damage to the mold and vibration actuator caused by excessive amplitude.

[0019] Preferably, in step S3, the valve plate mold is preheated to 150-250°C and pressure is maintained at 80-150 MPa.

[0020] By adopting the above technical solution, a mold temperature of 150-250℃ helps maintain the rheological properties of the semi-solid slurry during the filling process and prevents cold shut defects. A high holding pressure of 80-150MPa ensures that, in the final stage of solidification, the liquid phase can fully penetrate and fill the micropores caused by the shrinkage of the solid phase.

[0021] Preferably, in step S4, the two-stage low-temperature aging treatment includes a first aging stage and a second aging stage; the holding temperature of the first aging stage is 100-130℃, and the holding time is 6-10 hours; the holding temperature of the second aging stage is 150-180℃, and the holding time is 8-12 hours.

[0022] By employing the above technical solution, the two-stage aging process utilizes the kinetics of precipitation strengthening. The first aging stage (100-130℃) is at a lower temperature, primarily promoting the abundant and dispersed nucleation of the strengthening phase within the matrix. The subsequent second aging stage (150-180℃) is at a slightly higher temperature, providing a driving force for the uniform growth of these nuclei. Compared to single-stage aging, this strategy of nucleation followed by growth helps to form precipitates with higher dispersion and more uniform distribution, thereby maximizing the mechanical strength of the material.

[0023] Preferably, step S3 further includes localized forced cooling of the valve plate parts within the mold to achieve directional solidification.

[0024] By employing the above technical solution, localized forced cooling establishes a controlled temperature gradient within the mold, aiming to control the solidification sequence of the valve plate. This method allows the solidification front to advance sequentially from a specific area of ​​the valve plate towards the core functional area or the final feeding channel, achieving sequential solidification. This ensures that in the final stage of solidification, the liquid phase or solid-liquid mixture can effectively feed the solidified areas, thereby reducing the tendency for internal defects such as shrinkage porosity and shrinkage cavities to occur in the core functional area of ​​the valve plate, and improving the overall density and structural integrity of the part.

[0025] Preferably, in step S1, after adding the surface-modified titanium nitride particles, the process further includes mechanical stirring at a speed of 500-800 rpm for 5-15 minutes.

[0026] By employing the above technical solution, high-temperature mechanical stirring is a means to achieve macroscopically uniform dispersion of TiN particles. Shear stirring at 500-800 rpm helps to initially deagglomerate the added TiN particle clusters, allowing them to be uniformly suspended throughout the aluminum alloy melt.

[0027] Preferably, in step S3, the semi-solid slurry is injected into the mold cavity at a piston speed of 0.05-0.5 m / s, and the holding time is 5-15 seconds.

[0028] By adopting the above technical solution, an injection speed of 0.05-0.5 m / s is matched with the high viscosity rheological properties of the semi-solid slurry. This speed range helps to achieve smooth laminar flow filling, avoiding turbulence and air entrapment that are prone to occur during high-speed filling. A holding time of 5-15 seconds ensures sufficient time to complete the final feeding of the casting.

[0029] This invention provides a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate. It has the following beneficial effects: 1. This invention employs a two-stage low-temperature strain aging heat treatment, avoiding the high-temperature solution treatment and rapid water quenching steps that cause warping in the traditional T6 process. At the same time, combined with the pinning, anchoring and self-limiting effects of the introduced dispersed TiN particles during the aging process, the release and redistribution of internal stress are synergistically suppressed, enabling the valve plate to maintain high dimensional accuracy while being strengthened, thus improving the dimensional stability of the valve plate and effectively suppressing heat treatment deformation.

[0030] 2. This invention forms a highly dispersed and uniformly distributed precipitated strengthening phase in the aluminum alloy matrix through two-stage low-temperature aging; combined with the dispersion strengthening effect of TiN particles, the valve plate still meets high standard requirements for tensile strength and yield strength even without high-temperature quenching, thus resolving the contradiction between strength and deformation and achieving excellent comprehensive mechanical properties under the premise of low deformation.

[0031] 3. This invention prepares a semi-solid slurry and applies a pulsed energy field to assist in forming. It utilizes the acoustic flow and cavitation effect of high-frequency vibration to improve the slurry flow and eliminate micro-defects, thereby obtaining a high-density casting. At the same time, the high-hardness TiN ceramic phase introduced is uniformly distributed in the matrix, which improves the wear resistance of the working surface of the valve plate and enhances the internal density and surface wear resistance of the valve plate. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0033] Preparation Examples 1-3: Preparation of Surface-Modified TiN Particles Preparation Example 1: This preparation example uses a TiN particle surface modification method with a low concentration of silane coupling agent and mild treatment conditions.

[0034] Preparation of silane coupling agent solution: Slowly add 0.5 parts (by weight) of γ-aminopropyltriethoxysilane to a mixed solvent consisting of 100 parts (by volume) of ethanol and 50 parts (by volume) of deionized water, and stir until homogeneous. Then, add glacial acetic acid dropwise to adjust the pH of the solution to 4.0.

[0035] TiN particle surface treatment: Weigh 100 parts (by weight) of titanium nitride (TiN) powder (99.8% purity) with an average particle size of 1.0 micrometers, and slowly add it to the prepared silane coupling agent solution, stirring to form a suspension. In a constant temperature water bath, maintain the temperature of the suspension at 50°C and mechanically stir at 300 rpm for 30 minutes.

[0036] Separation and Drying: After treatment, the suspension was centrifuged (3000 rpm, 10 minutes), and the supernatant was discarded. The resulting solid precipitate was washed repeatedly with anhydrous ethanol to remove unreacted coupling agent and byproducts. The washed TiN particles were dried in a vacuum oven at 80°C for 8 hours until the sample mass was constant. The final product was surface-modified TiN particles A.

[0037] Preparation Example 2: This preparation example aims to illustrate a method for surface modification of TiN particles using intermediate concentration silane coupling agents and conventional treatment conditions.

[0038] Preparation of silane coupling agent solution: Slowly add 1.2 parts (by weight) of γ-aminopropyltriethoxysilane to a mixed solvent consisting of 100 parts (by volume) of ethanol and 33 parts (by volume) of deionized water, and stir until homogeneous. Then, add glacial acetic acid dropwise to adjust the pH of the solution to 4.5.

[0039] TiN particle surface treatment: Weigh 100 parts (by weight) of titanium nitride (TiN) powder (99.5% purity) with an average particle size of 2.0 micrometers, and slowly add it to the prepared silane coupling agent solution, stirring to form a suspension. In a constant temperature water bath, maintain the temperature of the suspension at 60°C and mechanically stir at 400 rpm for 45 minutes.

[0040] Separation and Drying: After treatment, TiN particles were separated from the solution by filtration. The filter cake was washed multiple times with anhydrous ethanol. The washed TiN particles were then dried in a vacuum oven at 100°C for 6 hours until the sample mass was constant. The final product was surface-modified TiN particles B.

[0041] Preparation Example 3: This preparation example aims to illustrate a method for surface modification of TiN particles using a high concentration of silane coupling agent and under enhanced treatment conditions.

[0042] Preparation of silane coupling agent solution: Slowly add 2.0 parts (by weight) of γ-aminopropyltriethoxysilane (APTES, chemically pure) to a mixed solvent consisting of 100 parts (by volume) of ethanol and 100 parts (by volume) of deionized water, and stir until homogeneous. Then, add glacial acetic acid dropwise to adjust the pH of the solution to 5.0.

[0043] TiN particle surface treatment: Weigh 100 parts (by weight) of titanium nitride (TiN) powder (99.8% purity) with an average particle size of 3.0 micrometers, and slowly add it to the prepared silane coupling agent solution, stirring to form a suspension. In a constant temperature water bath, maintain the temperature of the suspension at 70°C and mechanically stir at 500 rpm for 60 minutes.

[0044] Separation and drying: After treatment, the suspension was centrifuged (3500 rpm, 15 minutes), and the supernatant was discarded. The resulting solid precipitate was washed multiple times with anhydrous ethanol. The washed TiN particles were dried in a vacuum oven at 120°C for 4 hours until the sample mass was constant. The final product was surface-modified TiN particles C.

[0045] Examples 1-3: Example 1: This embodiment provides a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate, specifically including the following steps: Material preparation and melting: 99.5 kg of 6061 aluminum alloy ingot was weighed and placed in a graphite crucible for heating and melting to 720°C. After refining and degassing the melt under argon protection, 0.5 kg of surface-modified TiN particles A prepared in Preparation Example 1 was added, and mechanical stirring (500 rpm) was started for 15 minutes to initially disperse the TiN particles evenly.

[0046] Semi-solid slurry preparation: The above-mentioned mixed melt is cooled at a rate of 5℃ / min. When the melt temperature reaches 580℃ (corresponding to a solid fraction of approximately 20%), the electromagnetic stirring system is started, and an alternating magnetic field with a frequency of 10Hz and a magnetic field strength of 0.05T is applied. The mixture is stirred continuously for 20 minutes to obtain a semi-solid slurry.

[0047] Pulse Energy Field Assisted Molding: The valve plate die-casting mold is preheated to 150℃. The prepared semi-solid slurry is transferred to the injection cylinder and injected into the mold cavity at a piston speed of 0.05 m / s. The final holding pressure is set to 80 MPa, and the holding time is 15 seconds. Within 2 seconds of the start of filling, the piezoelectric ceramic actuator integrated in the mold is activated to apply mechanical pulse vibration with a frequency of 15 kHz and an amplitude of 1 micrometer. At the same time, the local forced cooling system of the mold is activated to directionally solidify the core functional area of ​​the valve plate.

[0048] Low-temperature strain aging heat treatment: After demolding, the parts are allowed to cool naturally to room temperature in air. Then, the valve plate is placed in an aging furnace and held at 100°C for 10 hours. The furnace temperature is then increased to 150°C and held for another 12 hours. After the treatment, the parts are cooled in the furnace to obtain the final gearbox valve plate product.

[0049] Example 2: This embodiment provides a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate, specifically including the following steps: Material preparation and melting: 99.0 kg of 6061 aluminum alloy ingot was weighed and placed in a graphite crucible for heating and melting to 735°C. After refining and degassing the melt under argon protection, 1.0 kg of surface-modified TiN particles B prepared in Preparation Example 2 was added, and mechanical stirring (650 rpm) was started for 10 minutes to initially disperse the TiN particles evenly.

[0050] Semi-solid slurry preparation: The above-mentioned mixed melt was cooled at a rate of 3℃ / min. When the melt temperature reached 600℃ (corresponding to a solid fraction of approximately 35%), the electromagnetic stirring system was started, and an alternating magnetic field with a frequency of 30Hz and a magnetic field strength of 0.12T was applied. The mixture was stirred continuously for 12 minutes to obtain a semi-solid slurry.

[0051] Pulse Energy Field Assisted Molding: The valve plate die-casting mold is preheated to 200℃. The prepared semi-solid slurry is transferred to the injection barrel and injected into the mold cavity at a piston speed of 0.25 m / s. The final holding pressure is set to 115 MPa, and the holding time is 10 seconds. Within 5 seconds of the start of filling, the piezoelectric ceramic actuator integrated in the mold is activated to apply mechanical pulse vibration with a frequency of 22 kHz and an amplitude of 3 micrometers. At the same time, the local forced cooling system of the mold is activated to directionally solidify the core functional area of ​​the valve plate.

[0052] Low-temperature strain aging heat treatment: After demolding, the parts are cooled to room temperature by air cooling. Then, the valve plate is placed in an aging furnace and first held at 115℃ for 8 hours, then the furnace temperature is raised to 165℃ and held for another 10 hours. After the treatment, it is cooled in the furnace to obtain the final gearbox valve plate product.

[0053] Example 3: This embodiment provides a method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate, specifically including the following steps: Material preparation and melting: 98.5 kg of 6061 aluminum alloy ingot was weighed and placed in a graphite crucible for heating and melting to 750°C. After refining and degassing the melt under argon protection, 1.5 kg of surface-modified TiN particles C prepared in Preparation Example 3 was added, and mechanical stirring (800 rpm) was started for 5 minutes to initially disperse the TiN particles evenly.

[0054] Semi-solid slurry preparation: The above-mentioned mixed melt is cooled at a rate of 1℃ / min. When the melt temperature reaches 620℃ (corresponding to a solid fraction of approximately 50%), the electromagnetic stirring system is started, and an alternating magnetic field with a frequency of 50Hz and a magnetic field strength of 0.2T is applied and stirred continuously for 5 minutes to obtain a semi-solid slurry.

[0055] Pulse Energy Field Assisted Molding: The valve plate die-casting mold is preheated to 250℃. The prepared semi-solid slurry is transferred to the injection cylinder and injected into the mold cavity at a piston speed of 0.5 m / s. The final holding pressure is set to 150 MPa, and the holding time is 5 seconds. Within 8 seconds of the start of filling, the piezoelectric ceramic actuator integrated in the mold is activated to apply mechanical pulse vibration with a frequency of 30 kHz and an amplitude of 5 micrometers. At the same time, the local forced cooling system of the mold is activated to directionally solidify the core functional area of ​​the valve plate.

[0056] Low-temperature strain aging heat treatment: After demolding, the parts are cooled to room temperature by air cooling. Then, the valve plate is placed in an aging furnace and first held at 130°C for 6 hours, then the furnace temperature is raised to 180°C and held for another 8 hours. After the treatment, it is cooled in the furnace to obtain the final gearbox valve plate product.

[0057] Comparative Examples 1-4: Comparative Example 1: This comparative example uses existing mainstream technology to prepare the gearbox valve plate. Its process steps are different from those of Example 2. Specifically, A380 aluminum alloy (without TiN) is used, and it is formed by traditional full-liquid high-pressure die casting. After forming, the valve plate is subjected to standard T6 heat treatment (solution at 510℃ for 1 hour, water quenching, and artificial aging at 175℃ for 5 hours).

[0058] Comparative Example 2: Compared with Example 2, the difference is that the low-temperature strain aging heat treatment step is not used, but instead replaced by the traditional T6 heat treatment (solution at 530°C for 1 hour, water quenching, and then artificial aging at 170°C for 6 hours). All other steps are the same.

[0059] Comparative Example 3: Compared with Example 2, the difference is that the surface-modified TiN particles B obtained in Example 2 were not added in the material preparation and melting steps; that is, pure 6061 aluminum alloy was used as the matrix material. All other aspects are the same.

[0060] Comparative Example 4: Compared with Example 2, the difference is that the micro-vibration actuator integrated in the mold is not activated in the pulsed energy field assisted molding step, that is, constant pressure filling and directional solidification are performed without applying high-frequency mechanical pulse vibration. All other aspects are the same.

[0061] Test Example 1-2: Test Example 1: Feasibility Verification of the Invention The purpose of this test is to verify the macroscopic properties of the aluminum alloy gearbox valve plate prepared by the methods of Examples 1, 2 and 3 of this invention, so as to prove the feasibility of the technical solution.

[0062] Experimental instructions The test samples were taken from the final valve plates prepared in Examples 1, 2, and 3, respectively. To ensure the representativeness of the test results, 5 samples were randomly selected from each group, and the average value of all test results was taken.

[0063] Basic mechanical property testing Sampling: In areas where the valve plate body has a uniform thickness and no complex oil passages, standard plate-shaped tensile specimens are cut using wire cutting. The sampling direction is parallel to the main filling direction of the semi-solid slurry.

[0064] Test standard: Based on GB / T228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0065] Experimental steps: Use vernier calipers to accurately measure the width and thickness of the original gauge length of each tensile specimen, and calculate its original cross-sectional area.

[0066] The sample is clamped on the WDW-100 microcomputer-controlled electronic universal testing machine.

[0067] The specimen was subjected to a constant tensile rate of 2 mm / min until it fractured.

[0068] Record the maximum test force and the load during the yielding stage during the test, and measure the gauge length of the specimen after fracture.

[0069] The tensile strength, yield strength, and elongation after fracture of the material are calculated based on the recorded data.

[0070] Hardness test Sampling: Test points were selected directly on the flat main working surface of the valve plate. To eliminate the influence of accidental surface factors, 5 dispersed test points were selected on each valve plate sample, with a distance of more than 10 mm between the test points.

[0071] Test standard: Based on GB / T231.1-2018 "Metallic materials - Brinell hardness test - Part 1: Test method".

[0072] Experimental steps: Place the valve plate sample firmly on the test stage of the HBS-3000 digital display Brinell hardness tester.

[0073] A carbide ball indenter with a diameter of 2.5 mm was selected, and a test force of 612.9 N (62.5 kgf) was applied and the loading time was maintained for 15 seconds.

[0074] After the test force is removed, the average diameter of the indentation is measured using a reading microscope.

[0075] The Brinell hardness value (HBW) of the sample is calculated based on the indentation diameter.

[0076] Density and porosity testing Sampling: Cut a block sample with a size of approximately 10mm × 10mm × 5mm from the valve plate body.

[0077] Test standard: Measurement is performed using the drainage method based on Archimedes' principle.

[0078] Experimental steps: Using an electronic balance with an accuracy of 0.1 mg, weigh the mass of the dried sample in air. ).

[0079] The sample was immersed in deionized water, and its suspended mass in the water was measured. ).

[0080] According to the formula Calculate the actual density of the sample, where The density of water at the test temperature.

[0081] Calculate its theoretical density based on the alloy composition. ), through the formula relative density Calculate its relative density.

[0082] Experimental data: Table 1 Performance test data of valve plate samples prepared in Examples 1-3 Conclusion: As can be seen from the test data in Table 1, the gearbox valve plates prepared by the methods in Examples 1, 2 and 3 all exhibit excellent comprehensive performance.

[0083] First, the relative density of all sample examples reached over 99.6%. This high density result indicates that the semi-solid constant-pressure filling process combined with the assistance of a pulsed energy field can effectively suppress gas entrapment or shrinkage defects in the slurry during filling and solidification, thus ensuring the internal quality of the molded parts.

[0084] Secondly, all samples in the embodiments exhibited high strength and hardness. Data shows that, without traditional high-temperature solution quenching, low-temperature two-stage aging effectively strengthens the 6061 aluminum alloy matrix. With increasing TiN content and appropriately higher aging temperature, the strength and hardness of the material showed an upward trend, demonstrating a synergistic effect between the dispersed TiN particles and the precipitated strengthening phase.

[0085] Finally, the sample achieved high strength while maintaining a certain degree of plasticity. The comprehensive mechanical performance indicators demonstrate that the technical solution proposed in this invention is feasible and can stably produce valve plate components that meet high-performance requirements, providing a valid basis for subsequent comparative analysis with existing technologies.

[0086] Test Example 2: Performance Comparison Experimental description: The test samples were the final valve plates prepared in Example 2, Comparative Example 1, Comparative Example 2, Comparative Example 3, and Comparative Example 4. Five samples were randomly selected from each group, and the average value of all test results was taken.

[0087] Dimensional deformation test after heat treatment Test equipment: High-precision coordinate measuring machine, measurement accuracy ±1μm.

[0088] Test objective: To evaluate the macroscopic dimensional changes caused by different process schemes during their respective heat treatments (Examples 1, 2, and 3 are low-temperature aging; Comparative Examples 1 and 2 are T6 treatment).

[0089] Experimental steps: Place all samples (before heat treatment) on a CMM and let them stand for 4 hours in a constant temperature (20℃) environment.

[0090] Select the main plane (A surface) of the valve plate as the reference and measure its flatness (warping).

[0091] Select the center coordinates of the three key hydraulic valve holes (K1, K2, K3) on the valve plate as the position reference. Record all initial measurement data.

[0092] Each group of samples was subjected to the heat treatment process specified in its respective scheme (Example 2, Comparative Examples 1-4).

[0093] After heat treatment, all samples were left to stand again for 4 hours in the same constant temperature environment, and their final flatness and hole coordinates were measured at the same location using a CMM.

[0094] Calculate the change in flatness (i.e., the increase in warping) and the maximum offset of the center coordinates of the key hole before and after heat treatment.

[0095] Final mechanical performance comparison test Test standard: Based on GB / T228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0096] Experimental procedure: Tensile specimens were cut from the final heat-treated samples of each group and their tensile strength and yield strength were tested.

[0097] Wear resistance comparison test Testing equipment: MFT-5000 pin-disc friction and wear testing machine.

[0098] Test objective: To evaluate the surface wear resistance of different material schemes (with and without TiN).

[0099] Experimental steps: Pin samples with a diameter of 4 mm and a length of 12 mm were cut from the main working surface of each valve plate. The disc samples were made of GCr15 steel and surface hardened to HRC60.

[0100] The test was conducted at room temperature (25°C), relative humidity of 50%, and under dry friction conditions.

[0101] The test load was set at 10N, the linear velocity corresponding to the pin specimen rotation speed was 0.1m / s, and the total wear stroke was 500m.

[0102] After the test, the mass loss of the pin sample before and after wear was measured using an electronic balance with an accuracy of 0.1 mg.

[0103] The volumetric wear rate is calculated based on mass loss and material density.

[0104] Density Comparison Test Test standard: Archimedes' principle of drainage method is adopted.

[0105] Experimental procedure: Take samples from the final samples of each group and test their relative compactness.

[0106] Experimental data: Test equipment: High-precision coordinate measuring machine, measurement accuracy ±1μm.

[0107] Test objective: To evaluate the macroscopic dimensional changes caused by different process schemes during their respective heat treatment processes.

[0108] Experimental steps: Place all samples (before heat treatment) on a CMM and let them stand for 4 hours in a constant temperature (20℃) environment.

[0109] Select the main plane (A surface) of the valve plate as the reference and measure its flatness (warping).

[0110] Select the center coordinates of the three key hydraulic valve holes (K1, K2, K3) on the valve plate as the position reference. Record all initial measurement data.

[0111] Each group of samples was subjected to the heat treatment process specified in its respective scheme (Example 2, Comparative Examples 1-4).

[0112] After heat treatment, all samples were left to stand again for 4 hours in the same constant temperature environment, and their final flatness and hole coordinates were measured at the same location using a CMM.

[0113] Calculate the change in flatness (i.e., the increase in warping) and the maximum offset of the center coordinates of the key hole before and after heat treatment.

[0114] Final mechanical performance comparison test Test standard: Based on GB / T228.1-2010 "Metallic materials - Tensile testing - Part 1: Test method at room temperature".

[0115] Experimental procedure: Tensile specimens were cut from the final heat-treated samples of each group and their tensile strength and yield strength were tested.

[0116] Wear resistance comparison test Testing equipment: MFT-5000 pin-disc friction and wear testing machine.

[0117] Test objective: To evaluate the surface wear resistance of different material schemes (with and without TiN).

[0118] Experimental steps: Pin samples with a diameter of 4 mm and a length of 12 mm were cut from the main working surface of each valve plate. The disc samples were made of GCr15 steel and surface hardened to HRC60.

[0119] The test was conducted at room temperature (25°C), relative humidity of 50%, and under dry friction conditions.

[0120] The test load was set at 10N, the linear velocity corresponding to the pin specimen rotation speed was 0.1m / s, and the total wear stroke was 500m.

[0121] After the test, the mass loss of the pin sample before and after wear was measured using an electronic balance with an accuracy of 0.1 mg.

[0122] The volumetric wear rate is calculated based on mass loss and material density.

[0123] Density Comparison Test Test standard: Archimedes' principle of drainage method is adopted.

[0124] Experimental procedure: Take samples from the final samples of each group and test their relative compactness.

[0125] Experimental data: Table 2 Performance comparison data between Example 2 and Comparative Examples 1-4 Conclusion: The data comparison in Table 2 clearly reveals the synergistic advantages of the technical solution of this invention: Dimensional stability analysis (deformation control): Compared with Comparative Example 1 (145.8 μm) and Comparative Example 2 (160.3 μm), the dimensional deformation of Example 2 was reduced by more than 87%. The data indicates that the high-temperature solution treatment and rapid water quenching involved in the traditional T6 process (Comparative Examples 1 and 2) are the root cause of the severe warping and deformation of the valve plate.

[0126] Comparing Example 2 (18.3 μm) and Comparative Example 3 (48.7 μm), under the same low-temperature aging process, Example 2, containing TiN particles, exhibited lower deformation than Comparative Example 3, which did not contain TiN. This data confirms the technical mechanism, namely, that the dispersed TiN particles effectively pinnify and anchor the matrix during low-temperature aging, suppressing the release and redistribution of internal stress, thereby achieving a self-limiting deformation-resistant function.

[0127] The low-temperature strain aging combined with the TiN self-limiting mechanism of this invention is the key to achieving high dimensional stability of the valve plate.

[0128] Compared with Comparative Example 1 (145.8 μm) and Comparative Example 2 (160.3 μm), the dimensional deformation of Example 2 was reduced by more than 87%. The data shows that the high-temperature solution treatment and rapid water quenching involved in the conventional T6 process (Comparative Examples 1 and 2) are the root causes of the severe warping and deformation of the valve plate.

[0129] Comparing Example 2 (18.3 μm) and Comparative Example 3 (48.7 μm), under the same low-temperature aging process, Example 2, containing TiN particles, exhibited lower deformation than Comparative Example 3, which did not contain TiN. This data confirms the technical mechanism, namely, that the dispersed TiN particles effectively pinnify and anchor the matrix during low-temperature aging, suppressing the release and redistribution of internal stress, thereby achieving a self-limiting deformation-resistant function.

[0130] The low-temperature strain aging combined with the TiN self-limiting mechanism of this invention is the key to achieving high dimensional stability of the valve plate.

[0131] Mechanical properties and wear resistance analysis: Compared with Example 2 (331.7MPa) and Comparative Example 1 (295.2MPa), the present invention achieves low deformation while having better mechanical strength than traditional A380 die castings.

[0132] Comparing Example 2 (volume wear rate 4.7) with Comparative Example 1 (21.3) and Comparative Example 3 (18.5), the data show that the introduction of TiN particles significantly improves the wear resistance of the valve plate matrix itself, avoiding dependence on subsequent surface strengthening treatment.

[0133] Internal density analysis: Comparing Example 2 (relative density 99.85%) and Comparative Example 4 (99.45%), under similar conditions, Example 2, which received pulsed energy field assistance, achieved a higher density. This demonstrates that a pulsed energy field helps optimize flow, eliminate trace gases and defects during the semi-solid slurry filling process, thereby improving the internal quality of the casting.

[0134] Example 2 also showed a significant advantage in density compared to Comparative Example 1 (99.12%), which was produced by conventional high-pressure die casting.

[0135] In summary, the present invention fundamentally solves the problem of the contradiction between high strength and high dimensional accuracy in traditional processes through the synergistic effects of semi-solid forming, pulsed energy field assistance, TiN functional phase addition, and low-temperature strain aging, while endowing the material with excellent wear resistance and internal density.

Claims

1. A method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate, characterized in that, Includes the following steps: S1. Material preparation and smelting: The raw materials containing aluminum alloy and 0.5-1.5 wt% surface-modified titanium nitride particles are smelted to obtain a mixed melt; S2. Semi-solid slurry preparation: The mixed melt is cooled to a semi-solid range with a solid content of 20-50% and stirred to obtain a semi-solid slurry; S3. Pulse energy field assisted forming: The semi-solid slurry is injected into the valve plate mold cavity, and a mechanical pulse vibration with a frequency of 15-30kHz is applied during the filling or holding process to form the valve plate part under pressure. S4. Low-temperature strain aging heat treatment: The valve plate part is subjected to a two-stage low-temperature aging treatment, which does not include solution treatment and quenching steps at temperatures above 500°C.

2. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, In step S1, the surface-modified titanium nitride particles are prepared in advance through the following steps: Titanium nitride powder was added to an alcohol-water mixture containing a silane coupling agent and stirred at 50-70°C, followed by separation and drying.

3. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 2, characterized in that, The silane coupling agent is γ-aminopropyltriethoxysilane.

4. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, In step S2, stirring is performed by applying an electromagnetic field with a frequency of 10-50Hz and a magnetic field strength of 0.05-0.2T.

5. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, In step S3, the amplitude of the mechanical pulse vibration is 1-5 micrometers.

6. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, In step S3, the valve plate mold is preheated to 150-250℃ and pressure is maintained at 80-150MPa.

7. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, In step S4, the two-stage low-temperature aging treatment includes a first aging stage and a second aging stage; The heat preservation temperature for the first aging stage is 100-130℃, and the heat preservation time is 6-10 hours; The second aging stage has a holding temperature of 150-180℃ and a holding time of 8-12 hours.

8. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, Step S3 also includes localized forced cooling of the valve plate parts inside the mold to achieve directional solidification.

9. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, In step S1, after adding the surface-modified titanium nitride particles, the process further includes mechanical stirring at a speed of 500-800 rpm for 5-15 minutes.

10. The method for preparing a high-strength, deformation-resistant aluminum alloy gearbox valve plate according to claim 1, characterized in that, In step S3, the semi-solid slurry is injected into the mold cavity at a piston speed of 0.05-0.5 m / s, and the holding time is 5-15 seconds.

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