Aluminum alloy conductive part and preparation method thereof

Abstract

The invention discloses a preparation method of an aluminum alloy conductive part. The aluminum alloy conductive part with high strength and high conductivity is prepared through continuous extrusion, online quenching, subzero treatment and aging treatment. The aluminum extrusion part is subjected to aging treatment after being subjected to subzero treatment, segregation of solute atoms and optimized distribution of precipitated phases after subzero treatment can reduce electron scattering centers, an electron conduction path is optimized, and the electric conductivity is improved; and more, finer and uniformly distributed aging phases can effectively hinder dislocation movement, so that the strength of the aluminum alloy is improved. During aging treatment, solute atoms in the supersaturated solid solution are separated out in the form of a precipitation phase, the concentration of the solute atoms in a matrix is reduced, the lattice distortion degree is reduced, and the electron scattering probability is reduced, so that the electric conductivity is improved; the formation of the precipitated phase makes the structure more refined and uniform, so that the strength and hardness of the aluminum alloy material are improved, and the prepared aluminum alloy conductive part has high strength and high conductivity.

Description

Technical Field

[0001] The present invention relates to the technical field of processing conductive parts for new energy electric vehicles, and more specifically, to an aluminum alloy conductive part and a preparation method thereof. Background Art

[0002] Conductive parts are components with a relatively large cost in the high-voltage connector harness of electric vehicles. The traditionally used conductor materials are mainly copper and copper alloys. Copper has good electrical and mechanical properties and is an ideal material for electrical conduction. Against the background of the development of charging power towards high-power charging, the current charging technology standard has increased the maximum allowable charging current to 800A, and it will further develop towards 1000A and higher in the future. Without adding cooling measures at the vehicle end, when the current increases, according to Joule's law (Q = I 2 Rt), it is necessary to reduce the conductor resistance to prevent the vehicle from experiencing problems such as thermal failure. An effective measure to reduce resistance is to increase the conductor cross-sectional area. Generally, the maximum current-carrying capacity of a 120mm 2 copper cable is 500A. To obtain a higher current-carrying capacity, the cross-sectional area of the cable needs to be larger than 120mm 2 This large size will cause problems such as overweight wire harness quality and too large bending radius. Therefore, based on the requirements of new energy vehicles for lightweight, cost control, and energy efficiency, aluminum alloy conductive parts are widely used due to their light weight, low cost, and good electrical conductivity.

[0003] Aluminum alloy conductive parts in new energy vehicles need to withstand various mechanical stresses during vehicle operation, such as vibration, impact, and tension. Improving the strength of aluminum alloy conductive parts can ensure that these components are not easily damaged during long-term use, thereby improving the safety and reliability of the entire vehicle.

[0004] In the prior art, the strength of aluminum alloy is usually improved by adding alloying elements. The higher the degree of alloying of aluminum alloy, the corresponding increase in the strength of aluminum alloy. However, the increase in the degree of alloying will also lead to a decrease in conductivity. Currently, the conductivity of aluminum alloy conductive parts in new energy vehicles is about 55% IACS. In the prior art, the strength of aluminum alloy conductive parts is also improved by continuous extrusion technology combined with heat treatment process. However, how to improve the conductivity while increasing the strength of aluminum alloy conductive parts has become a technical difficulty to be overcome in this field. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art, and provide an aluminum alloy conductive part and a preparation method thereof, so that the prepared aluminum alloy conductive part has high strength and high conductivity.

[0006] To achieve the above purpose, the technical solution of the present invention is as follows:

[0007] The present invention provides a preparation method of an aluminum alloy conductive part, including the following processes:

[0008] S1: Obtain an aluminum billet;

[0009] S2: Continuously extrude the aluminum billet to obtain an aluminum extrusion;

[0010] S3: Perform an on-line quenching treatment on the aluminum extrusion;

[0011] S4: Deep-cool the quenched aluminum extrusion with liquid nitrogen;

[0012] S5: Perform an aging treatment on the deep-cooled aluminum extrusion to obtain an aluminum alloy conductive part.

[0013] The present invention also provides an aluminum alloy conductive part, which is obtained by the preparation method of the above aluminum alloy conductive part.

[0014] Implementing the embodiments of the present invention will have the following beneficial effects:

[0015] In the embodiments of the present invention, an aluminum alloy conductive part with high strength and high conductivity is prepared through continuous extrusion, on-line quenching, deep cooling, and aging treatment in sequence. After the aluminum extrusion is deep-cooled and then aged, the segregation of solute atoms and the optimized distribution of precipitation phases after deep cooling can reduce the electron scattering centers, optimize the electron conduction path, reduce the electron scattering probability, and improve the conductivity; more, finer, and uniformly distributed aging phases can effectively hinder the movement of dislocations, thereby further improving the strength of the aluminum alloy. During the aging treatment, the solute atoms in the supersaturated solid solution precipitate in the form of precipitation phases, the solute atom concentration in the matrix decreases, the lattice distortion degree decreases, and the electron scattering probability decreases, thereby improving the conductivity; the formation of precipitation phases makes the structure finer and more uniform, effectively hindering the movement of dislocations, thereby improving the strength and hardness of the aluminum alloy material, achieving the balance between conductivity and strength, and making the prepared aluminum alloy conductive part have high strength and high conductivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0017] Among them:

[0018] Figure 1 is a flowchart of a preparation method of an aluminum alloy conductive part provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0020] Referring to Figure 1 , the present invention discloses a preparation method of an aluminum alloy conductive part, including the following processes:

[0021] S1: Obtain an aluminum billet.

[0022] The aluminum alloy raw material is obtained as an aluminum billet after continuous casting and rolling, solution treatment and heat treatment. Further, the raw materials of the aluminum alloy include 1-series, 6-series, 8-series aluminum alloys, etc. The aluminum billet is a T4-state aluminum alloy, and the T4-state aluminum alloy has high yield strength and tensile strength, can withstand a large extrusion force during continuous extrusion, and is not prone to deformation or fracture, thus ensuring the stability of the extrusion process and the quality of the product.

[0023] S2: Continuously extrude the aluminum billet to obtain an aluminum extrusion.

[0024] During the continuous extrusion of the aluminum billet, on the one hand, the large plastic deformation makes the aluminum alloy grains refined and the grain boundary area increased. The refined grains and the increased grain boundaries can, through the synergistic effect with other microstructural changes in subsequent processing, reduce the electron scattering probability, thus laying a foundation for improving the conductivity. On the other hand, the large plastic deformation promotes the uniform distribution of alloying elements in the aluminum matrix, which is beneficial to the uniform formation of precipitates during subsequent aging treatment, and further improves the mechanical properties.

[0025] S3: Perform online quenching treatment on the aluminum extrusion.

[0026] During continuous extrusion, high temperature makes the alloying elements fully dissolve in the aluminum matrix. Online quenching can enable the solute atoms (such as copper, magnesium, silicon, etc.) dissolved in the aluminum alloy at high temperature to be retained in the matrix during rapid cooling, forming a supersaturated solid solution. The existence of the supersaturated solid solution provides a solute atom source for subsequent aging treatment, which is beneficial to the formation and uniform distribution of precipitates during the aging process, thereby further improving the properties of the material.

[0027] Furthermore, the aluminum extrusions need to be coiled and then aged. Therefore, the aluminum extrusions are coiled after quenching treatment, and then cryogenic treatment is carried out to facilitate the next aging treatment. Optionally, after the quenching treatment step of the aluminum extrusions, refractory paper is covered on the surface of the aluminum extrusions, and the aluminum alloy material covered with refractory paper is coiled; by covering refractory paper on the surface of the aluminum extrusions and coiling, the contact between the aluminum extrusions and air is effectively isolated, the occurrence of oxidation is reduced, and the surface of the aluminum extrusions is protected.

[0028] S4: Perform cryogenic treatment on the quenched aluminum extrusions.

[0029] Online quenching makes the aluminum alloy form a supersaturated solid solution. Cryogenic treatment causes the lattice points of the aluminum alloy to contract due to the sharp drop in temperature, increasing the supersaturation degree of alloying solute elements and vacancies in the unit geometric space, promoting the local segregation of different solute atoms, and increasing the quantity and uniformity of the precipitation of the aging phase. On the one hand, the segregation of solute atoms and the optimized distribution of precipitation phases after cryogenic treatment can reduce the electron scattering centers, optimize the electron conduction path, reduce the electron scattering probability, and increase the conductivity; on the other hand, more, finer and uniformly distributed aging phases can effectively hinder the movement of dislocations, thereby further increasing the strength of the aluminum alloy.

[0030] Furthermore, the interval time between quenching treatment and cryogenic treatment is not more than 24 h. When the interval time between quenching treatment and cryogenic treatment is greater than 24 h, the interval time is too long, the temperature of the aluminum alloy will gradually increase, atoms will gain more energy and start to diffuse, the grains have a tendency to grow, and the increase in grain size increases the electron scattering probability, which is not conducive to the increase in conductivity.

[0031] S5: Perform aging treatment on the cryogenically treated aluminum extrusions to obtain aluminum alloy conductive parts.

[0032] On the one hand, after online quenching treatment and cryogenic treatment, alloying elements are dissolved into the aluminum matrix to form a supersaturated solid solution. During the aging treatment process, solute atoms in the supersaturated solid solution preferentially nucleate and grow at defects such as vacancies, forming fine and dispersed precipitation strengthening phases. The formation of precipitation phases makes the structure more refined and uniform, effectively hindering the movement of dislocations, thereby increasing the strength and hardness of the aluminum alloy material. On the other hand, during aging treatment, solute atoms in the supersaturated solid solution precipitate in the form of precipitation phases, the solute atom concentration in the matrix decreases, the lattice distortion degree decreases, and the electron scattering probability decreases, thereby increasing the conductivity and achieving the balance of conductivity and strength.

[0033] Furthermore, the time interval between cryogenic treatment and aging treatment is 10 min to 24 h. If the transfer time is too short (less than 10 min), the material may not have enough time to smoothly transition from the cryogenic low-temperature state, resulting in uneven internal stress release, which may cause local instability of the microstructure and affect the subsequent aging treatment effect. If the transfer time is too long (more than 24 h), the material stays at room temperature for too long, and the atoms start to become active again, which may cause some relaxation of the favorable microstructure formed by cryogenic treatment. For example, the uniformity of the distribution of atomic clusters and precipitates deteriorates. Controlling the time interval between cryogenic treatment and aging treatment within 10 minutes to 24 h can enable the material to enter the aging treatment stage orderly while maintaining the stable microstructure after cryogenic treatment, which is beneficial to the further optimized growth of precipitates, reducing the electron scattering centers and improving the conductivity.

[0034] It can be understood that: First, after the aluminum extrusion parts in this embodiment are cryogenically treated and then aged. During cryogenic treatment, the temperature drops sharply, and the lattice points of the aluminum alloy contract strongly, further increasing the supersaturation degree of solute atoms and vacancies in the unit geometric space, forming atomic clusters with higher density, providing more nucleation sites for the formation of precipitates in the subsequent aging treatment, and being beneficial to the refinement and uniform distribution of precipitates. The segregation of solute atoms and the optimized distribution of precipitates after cryogenic treatment can reduce the electron scattering centers, optimize the electron conduction path, reduce the electron scattering probability, and increase the conductivity; more, finer and uniformly distributed aging phases can effectively hinder the movement of dislocations, thereby further increasing the strength of the aluminum alloy. During aging treatment, the solute atoms in the supersaturated solid solution precipitate in the form of precipitate phases, the solute atom concentration in the matrix decreases, the lattice distortion degree decreases, and the electron scattering probability decreases, thereby increasing the conductivity; the formation of precipitate phases makes the structure finer and more uniform, effectively hindering the movement of dislocations, thereby increasing the strength and hardness of the aluminum alloy material and achieving the balance of conductivity and strength.

[0035] Second, after continuous extrusion of the aluminum billet, online quenching treatment is carried out, and the process has a high degree of automation, realizing continuous production.

[0036] Third, through continuous extrusion, online quenching, cryogenic treatment and aging treatment of the aluminum billet, an aluminum alloy conductive part with high conductivity can be obtained, with short process and cost savings.

[0037] In a specific embodiment, the temperature of cryogenic treatment is -100 °C to -190 °C, the cooling rate of cryogenic treatment is 5 °C / min to 10 °C / min, and the cryogenic treatment time is 4 h to 16 h.

[0038] It should be noted that the temperature of cryogenic treatment affects the properties of aluminum alloys. A lower cryogenic temperature can promote significant microstructural changes inside the aluminum alloy. The contraction of the aluminum alloy lattice points is more intense, the supersaturation degree of solute atoms and vacancies increases, which is conducive to the precipitation and refinement of the aging phase. When the cryogenic treatment temperature is too low, there is a risk of increasing the brittleness of the material. Therefore, the cryogenic treatment temperature is -100°C to -190°C, which can improve the performance while maintaining good toughness.

[0039] The time of cryogenic treatment is directly related to the degree of evolution of the internal microstructure of the aluminum alloy. When the time of cryogenic treatment is too short, the induced microstructural changes are limited, and the effect of improving the performance is not obvious; cryogenic treatment can allow solute atoms to have enough time to migrate and aggregate, promoting the precipitation and uniform distribution of more aging phases. However, when the time of cryogenic treatment is too long, the cost increases. Therefore, the cryogenic treatment time is 4h to 16h, which can not only effectively improve the strength but also take into account the cost and internal stress control.

[0040] In another specific embodiment, the cryogenic treatment includes a primary cryogenic treatment and a secondary cryogenic treatment. The temperature of the primary cryogenic treatment is higher than that of the secondary cryogenic treatment. The aluminum extruded parts after quenching treatment are sequentially subjected to the primary cryogenic treatment and the secondary cryogenic treatment; the temperature of the primary cryogenic treatment is higher than that of the secondary cryogenic treatment, and the cooling rate of the primary cryogenic treatment is greater than that of the secondary cryogenic treatment.

[0041] It can be understood that in the primary cryogenic treatment stage, the material starts to cool from room temperature, is kept warm after being reduced to the target temperature, and a faster cooling rate can avoid the premature occurrence of unnecessary reactions such as natural aging caused by too slow cooling. In the secondary cryogenic treatment stage, as the temperature decreases, the thermal conductivity of the material changes. Reducing the cooling rate helps to maintain the temperature uniformity inside the material, make the lattice contraction more uniform, and reduce the microdefects caused by non-uniform contraction. Through the two-stage cryogenic treatment, the cryogenic time can be reduced and the energy consumption can be lowered; the gradient cooling method can more precisely control the temperature change rate and the thermal stress distribution, provide relaxation and adjustment time for the internal stress of the material, reduce the residual stress generated by the rapid temperature change, and prevent the material from deforming and cracking during subsequent processing.

[0042] Specifically, the temperature of the primary cryogenic treatment is -50°C to -80°C, the cooling rate of the primary cryogenic treatment is 5°C / min to 15°C / min, and the treatment time of the primary cryogenic treatment is 1h to 8h;

[0043] The temperature of the secondary cryogenic treatment is -80°C to -150°C, the cooling rate of the secondary cryogenic treatment is 1°C / min to 5°C / min, and the treatment time of the secondary cryogenic treatment is 1h to 8h.

[0044] Furthermore, during the process of the temperature rising back to room temperature after cryogenic treatment, a three-stage heating treatment is adopted. In the stage of heating from the target cryogenic temperature to -100°C, the heating rate is controlled at 0.5°C / min to 1°C / min. When the temperature rises from the cryogenic temperature, the material is in a highly unstable state inside. Slowly heating can allow enough time for the lattice and precipitates to adjust, reducing the microstructural damage caused by rapid temperature changes. In the stage of heating from -100°C to -50°C, the heating rate is increased to 1°C / min to 2°C / min. At this time, the material has passed the most unstable low-temperature stage. Appropriately increasing the heating rate can improve production efficiency. In the stage of heating from -50°C to room temperature, the heating rate is 2°C / min to 5°C / min. When approaching room temperature, the release of thermal stress in the material is relatively easy. A faster heating rate helps to shorten the treatment cycle while ensuring that the material properties are not significantly affected.

[0045] In a specific embodiment, the temperature of the aging treatment is 180°C to 300°C, and the time of the aging treatment is 6h to 16h.

[0046] When the temperature of the aging treatment is too high, it will cause the precipitates to grow too fast, forming coarse precipitates. The coarse precipitates will become electron scattering centers, significantly reducing the conductivity. When the temperature of the aging treatment is too low, the diffusion rate of solute atoms is slow, and it is difficult to form effective precipitates. Moreover, due to the disordered distribution of solute atoms in the solid solution, the electron scattering may increase, resulting in a decrease in conductivity. Therefore, when the temperature of the aging treatment is selected as 180°C to 300°C, the microstructure of the aluminum alloy undergoes changes that are beneficial to improving the conductivity, which can promote the orderly diffusion and aggregation of solute atoms in the matrix to form specific precipitates, and at the same time will not cause excessive damage to the crystal structure of the matrix.

[0047] The length of the aging treatment time directly affects the growth degree and distribution state of the precipitates, and thus affects the conductivity and strength. The time of the aging treatment is 2h to 16h, which can give enough time for solute atoms to diffuse, aggregate and the precipitates to grow. When the time of the aging treatment is less than 2h, the time of the aging treatment is too short, resulting in unstable alloy properties. When the time of the aging treatment is greater than 16h, the time of the aging treatment is too long, and the coarsening phenomenon of the precipitates may occur, leading to a decrease in strength (over-aging) and a significant reduction in conductivity. The aging treatment time required for different compositions of aluminum alloys to achieve the best balance between conductivity and strength varies, and it is adjusted according to the specific alloy composition in actual production.

[0048] In a specific embodiment, the aluminum billet is continuously extruded after surface cleaning treatment.

[0049] Specifically, the aluminum billet is traction straightened and then cleaned by a cleaning device to remove the oxide scale and impurities on the surface of the aluminum billet, so that the surface roughness Sa of the aluminum billet is less than 1 μm, avoiding the influence of impurity attachment on the conductivity of the aluminum alloy conductive part.

[0050] In a specific embodiment, the aluminum billet is continuously extruded by a continuous extruder, and the outlet temperature of the continuous extruder is 380°C to 480°C.

[0051] During the continuous extrusion process, the aluminum alloy undergoes plastic deformation in the die. When the temperature is lower than 380°C, the temperature is too low, the plastic deformation ability of the aluminum alloy decreases, work hardening intensifies, and a greater extrusion force is required, which not only increases the equipment energy consumption but also may cause defects such as cracks in the material interior. When the temperature is higher than 480°C, the temperature is too high, the aluminum alloy may experience overheating, grain growth, resulting in a decrease in the strength and hardness of the material and loss of good comprehensive properties. Therefore, when the extrusion machine outlet temperature is 380°C to 480°C, it is within the appropriate hot working temperature range of the aluminum alloy, which can promote plastic deformation while effectively controlling the degree of work hardening. Within this temperature range, the thermal motion of atoms in the aluminum alloy is relatively active, and deformation mechanisms such as dislocation slip are more likely to occur, enabling the material to smoothly undergo plastic deformation, fill the die cavity, and obtain the required shape and size.

[0052] In a specific embodiment, the rotational speed of the extrusion wheel in the extruder is 10 rpm to 15 rpm.

[0053] When the rotational speed of the extrusion wheel is relatively low, the residence time of the aluminum alloy in the die is longer, the deformation is more sufficient, which is beneficial to grain refinement, but the production efficiency is low. As the rotational speed increases, the deformation rate accelerates, the temperature of the aluminum alloy increases significantly, which may cause grain growth, and at the same time, it will also increase the frictional heat between the aluminum alloy and the die, affecting the die life. Reasonably controlling the rotational speed of the extrusion wheel can optimize the performance of the outlet aluminum alloy on the premise of ensuring production efficiency. Therefore, setting the rotational speed of the extrusion wheel at 10 rpm to 15 rpm can not only enable the aluminum alloy to obtain a better grain refinement effect, improve strength and hardness, but also ensure a certain production efficiency.

[0054] Furthermore, optimizing the feeding speed of the aluminum billet can ensure uniform deformation of the aluminum alloy in the die, improving product quality and production efficiency. Controlling the feeding speed within the range of 2 m / min to 4 m / min can enable the aluminum alloy to deform smoothly in the die, which is beneficial to obtaining a uniform and fine grain structure and reducing internal defects. The feeding speed of the aluminum billet determines the amount of aluminum alloy entering the extrusion die per unit time. If the feeding speed is too fast, the deformation of the aluminum alloy in the die is uneven, prone to stress concentration, resulting in defects such as cracks in the interior of the outlet aluminum alloy, and at the same time, it will also affect the grain refinement effect. If the feeding speed is too slow, it will reduce production efficiency and increase production costs.

[0055] In a specific embodiment, the aluminum extruded part is subjected to on-line quenching treatment by a quenching device, and the quenching device is installed at the outlet of the continuous extruder. The time interval from when the aluminum extruded part leaves the outlet of the continuous extruder to when it enters the on-line quenching device is less than 10 s.

[0056] Optionally, the quenching device can be a water-based quenching device or an oil-based quenching device.

[0057] It can be understood that during the process from when the aluminum extruded part leaves the outlet of the continuous extruder to when it enters the on-line quenching device, the aluminum extruded part will have heat exchange with the air. If the time is too long, the temperature of the aluminum extruded part will drop, resulting in uneven cooling and affecting the quenching effect.

[0058] The time interval from when the aluminum extruded part leaves the outlet of the continuous extruder to when it enters the on-line quenching device is the transfer time of the quenching treatment, and the transfer time of the quenching treatment is less than 10 s. When the transfer time of the quenching treatment exceeds 10 s, the surface of the aluminum alloy product may have started to cool down. After entering the quenching medium, the difference in cooling rates between the surface and the interior increases, and quenching stress is likely to be generated, resulting in problems such as product deformation and uneven surface hardness, reducing the product quality.

[0059] In a specific embodiment, the time of the quenching treatment is 10 s to 60 s.

[0060] It should be noted that the specific time of the quenching treatment is adjusted according to the size, shape of the aluminum alloy conductive part and the cooling capacity of the quenching medium. The time of the quenching treatment is not specifically limited here. Exemplarily, for aluminum alloy products with smaller size and simple shape, the time of the quenching treatment can be between 10 s and 25 s; while for products with larger size and thicker thickness, the time of the quenching treatment can reach 30 s to 60 s to ensure that the entire cross-section can be sufficiently cooled.

[0061] The following are specific embodiments.

[0062] Embodiment 1:

[0063] S1: Select a 6061 aluminum alloy ingot that meets national standards as the aluminum blank. Its main chemical composition (mass fraction) is: Mg: 1.0%, Si: 0.6%, Cu: 0.2%, Fe: 0.5%, Mn: 0.1%, Zn: 0.2%, Ti: 0.1%, and the rest is Al. Clean the surface of the ingot to remove impurities such as oxide scale and oil stains to ensure the surface finish.

[0064] S2: Use a CONFORM continuous extruder, set the extrusion wheel speed to 12 rpm, the die outlet temperature to 400 °C, and the blank feeding speed to 3 m / min.

[0065] Feed the 6061 aluminum alloy ingot into a continuous extruder. Under the action of the extrusion wheel and the die, the aluminum alloy undergoes plastic deformation to obtain an aluminum alloy extruded part, which is an aluminum alloy rod with a diameter of 20 mm. During the extrusion process, parameters such as extrusion pressure and temperature are monitored in real time through an on-line monitoring system to ensure process stability.

[0066] S3: The aluminum alloy extruded part quickly enters an on-line quenching device for on-line quenching treatment within 5 s. Select water as the quenching medium, and control the temperature of the quenching medium at 20 °C through a circulating cooling system to ensure good fluidity and cooling performance of the quenching medium. The quenching treatment time is controlled at 20 s to ensure uniform cooling of the whole material and form a supersaturated solid solution state.

[0067] S4: The quenched aluminum alloy extruded part is immediately subjected to cryogenic treatment. Use a liquid nitrogen cryogenic equipment, the cryogenic treatment temperature is -150 °C, the cooling rate is 8 °C / min, and the cryogenic treatment time is 12 h.

[0068] S5: After cryogenic treatment, the aluminum alloy material is slowly heated to room temperature in the air, and then aging treatment is carried out to obtain a 6061 aluminum alloy conductive part. Select an air-circulating heating furnace for aging treatment, heat the heating furnace to 160 °C, and set the aging time to 12 h.

[0069] Example 2:

[0070] S1: Select a 1060 aluminum alloy ingot as the aluminum billet. Its main chemical composition (mass fraction) is: Al: 99.6%, Si: 0.1%, Fe: 0.12%, Cu: 0.05%, Mn: 0.03%, Mg: 0.03%, Zn: 0.04%, Ti: 0.03%. Clean the surface of the ingot to remove impurities such as oxide scale and oil stains to ensure surface finish.

[0071] S2: Use a CONFORM continuous extruder, set the rotation speed of the extrusion wheel to 10 rpm, the die outlet temperature to 380 °C, and the billet feeding speed to 2.5 m / min.

[0072] Feed the 1060 aluminum alloy ingot into a continuous extruder. Under the action of the extrusion wheel and the die, the aluminum alloy undergoes plastic deformation to obtain an aluminum alloy extruded part, which is an aluminum alloy rod with a diameter of 20 mm. During the extrusion process, parameters such as extrusion pressure and temperature are monitored in real time through an on-line monitoring system to ensure process stability.

[0073] S3: The aluminum alloy extruded part rapidly enters the on-line quenching device for on-line quenching treatment within 3 s. A water-based polymer quenching agent is selected as the quenching medium, and the temperature of the quenching medium is controlled at 20 °C through a circulating cooling system to ensure good fluidity and cooling performance of the quenching medium. The quenching treatment time is controlled at 20 s to ensure uniform cooling of the whole material and form a supersaturated solid solution state.

[0074] S4: The quenched aluminum alloy extruded part is immediately subjected to cryogenic treatment. A liquid nitrogen cryogenic equipment is used, the cryogenic treatment temperature is -150 °C, the cooling rate is 8 °C / min, and the cryogenic treatment time is 12 h.

[0075] S5: After cryogenic treatment, the aluminum alloy material is slowly heated to room temperature in the air, and then aging treatment is carried out to obtain a 6061 aluminum alloy conductive part. An air-circulation heating furnace is selected for aging treatment, the heating furnace is heated to 160 °C, and the set aging time is 12 h.

[0076] Example 3:

[0077] The difference between Example 3 and Example 1 is that the cryogenic treatment includes a primary cryogenic treatment and a secondary cryogenic treatment. The quenched aluminum alloy material is first subjected to the primary cryogenic treatment and then the secondary cryogenic treatment. The primary cryogenic treatment temperature is -80 °C, the cooling rate is 15 °C / min, and the cryogenic treatment time is 4 h. The secondary cryogenic treatment temperature is -150 °C, the cooling rate is 5 °C / min, and the cryogenic treatment time is 4 h.

[0078] Comparative Example 1:

[0079] The difference between Comparative Example 1 and Example 1 is that aging treatment is directly carried out after quenching treatment, and cryogenic treatment is not carried out before aging treatment. A 6061 aluminum alloy ingot is selected, and through continuous extrusion, quenching treatment and aging treatment in sequence, a 6061 aluminum alloy conductive part is obtained.

[0080] Comparative Example 2:

[0081] The difference between Comparative Example 2 and Example 2 is that cryogenic treatment is directly carried out after continuous extrusion, and quenching treatment is not carried out before cryogenic treatment. A 6061 aluminum alloy ingot is selected, and through continuous extrusion, cryogenic treatment and aging treatment in sequence, a 6061 aluminum alloy conductive part is obtained.

[0082] Comparative Example 3:

[0083] The difference between Comparative Example 3 and Example 1 is that aging treatment is carried out first and then cryogenic treatment after continuous extrusion. A 6061 aluminum alloy ingot is selected, and through continuous extrusion, aging treatment and cryogenic treatment in sequence, a 6061 aluminum alloy conductive part is obtained.

[0084] Comparative Example 4:

[0085] The difference between Comparative Example 4 and Example 1 is that after continuous extrusion, cold deformation is carried out first and then cryogenic treatment. A 6061 aluminum alloy ingot is selected and successively subjected to continuous extrusion, cold deformation, cryogenic treatment and aging treatment to obtain a 6061 aluminum alloy electrical conductor.

[0086] Performance testing:

[0087] After the aluminum alloy electrical conductors in Examples 1-3 and Comparative Examples 1-4 were processed, a tensile test was carried out in accordance with the standard of GB / T 228.1-2010; the conductivity was tested by the four-probe method. The test results are shown in the following table.

[0088] Table of conductivity and tensile strength of aluminum alloy electrical conductors in Examples 1-3 and Comparative Examples 1-4

[0089]

[0090]

[0091] Result description:

[0092] Example 1

[0093] Conductivity: After continuous extrusion, online quenching, cryogenic treatment and aging treatment, the conductivity reaches 60.3% IACS. During continuous extrusion, grain refinement and uniform distribution of alloying elements lay the foundation for subsequent processing; online quenching forms a supersaturated solid solution, cryogenic treatment further increases the supersaturation of solute atoms and promotes atomic segregation, and when aging treatment is carried out, solute atoms precipitate to form precipitate phases, reducing lattice distortion and electron scattering, and jointly acting to improve the conductivity.

[0094] Tensile strength: The tensile strength is 320.2 MPa. Continuous extrusion refines grains and promotes uniform distribution of alloying elements to enhance the matrix strength; the supersaturated solid solution formed by online quenching precipitates strengthening phases after aging treatment, and cryogenic treatment optimizes the microstructure to make the strengthening phases more effectively hinder the movement of dislocations, comprehensively improving the tensile strength.

[0095] Example 2

[0096] Conductivity: The conductivity of the 1060 aluminum alloy in this example after treatment is 62.1% IACS. The 1060 aluminum alloy itself has high purity and few impurities, and processes such as continuous extrusion further optimize the microstructure, reduce the electron scattering centers, and improve the conductivity.

[0097] Tensile strength: The tensile strength is 110.5 MPa. The 1060 aluminum alloy contains few alloying elements and has relatively low strength, but after being processed by processes such as continuous extrusion, grain refinement and a certain degree of solid solution strengthening slightly increase its strength.

[0098] Example 3

[0099] Conductivity: The conductivity of the 6061 aluminum alloy treated by gradient cryogenic treatment reaches 61.2% IACS. Through the control of different temperature stages, gradient cryogenic treatment can more precisely regulate the microstructure, promote the segregation of solute atoms and the uniform distribution of precipitation phases. Compared with sequential cryogenic treatment, the conductivity is improved.

[0100] Tensile strength: The tensile strength is 300.8 MPa. Gradient cryogenic treatment optimizes the microstructure, makes the distribution of aging precipitation phases more reasonable, effectively hinders the movement of dislocations, and improves the strength.

[0101] Comparative Example 1

[0102] Conductivity: The conductivity is only 45.2% IACS. Due to the lack of cryogenic treatment steps, the supersaturation of solute atoms before aging is relatively low, resulting in a relatively small number, large size and non-uniform distribution of precipitation phases during aging. The coarse precipitation phases become electron scattering centers. Compared with Example 1, the conductivity of Comparative Example 1 drops significantly.

[0103] Tensile strength: The tensile strength is 260.1 MPa. The formed precipitation phases cannot effectively hinder the movement of dislocations, resulting in the strength of the material being lower than that of Example 1.

[0104] Comparative Example 2

[0105] Conductivity: The conductivity is only 48.0% IACS. Due to the lack of online quenching, a supersaturated solid solution cannot be formed after extrusion. Although cryogenic treatment can shrink the lattice, the initial solid solution degree of solute atoms is low. During aging, the number of precipitation phases is small, the size is large and the distribution is uneven, resulting in an increase in electron scattering centers and a decrease in conductivity.

[0106] Tensile strength: The tensile strength is 280.0 MPa. Due to the failure to form a good supersaturated solid solution and an optimized precipitation phase structure, the strengthening effect is poor, the hindrance to dislocation movement is insufficient, and the strength is lower than that of Example 1.

[0107] Comparative Example 3

[0108] Conductivity: The conductivity is 50.1% IACS. Cryogenic treatment is carried out after aging. At this time, a certain precipitation phase structure has been formed during aging. The cryogenic treatment has limited adjustment to the microstructure and cannot promote the formation of more favorable microstructures at the appropriate stage like in Example 1. There are more electron scattering centers, and the conductivity improvement is not as good as that of Example 1.

[0109] Tensile strength: The tensile strength is 280.3 MPa. Cryogenic treatment after aging has limited influence on the formed precipitation phases and microstructure, and cannot effectively optimize the distribution of strengthening phases and hinder the movement of dislocations. The tensile strength is lower than that of Example 1.

[0110] Comparative Example 4

[0111] Conductivity: The conductivity is 55.3% IACS. Although cold deformation after continuous extrusion refines the grains, it introduces inhomogeneity, affecting the subsequent cryogenic treatment and aging effects, resulting in a less uniform and stable microstructure than in Example 1. The complex electron scattering path leads to a lower conductivity than in Example 1.

[0112] Tensile strength: The tensile strength is 310.6 MPa. Cold deformation introduces residual stress and an inhomogeneous structure, resulting in a lower tensile strength than in Example 1.

[0113] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent shall be subject to the appended claims.

Claims

1. A method for preparing an aluminum alloy conductive part, characterized in that: The process includes: S1: Obtain aluminum billet; S2: continuously extruding the aluminum billet to obtain an aluminum extrusion; S3: performing online quenching treatment on the aluminum extrusion; S4: subjecting the aluminum extrusion after quenching to cryogenic treatment by liquid nitrogen; S5: performing aging treatment on the aluminum extrusion after deep cryogenic treatment to obtain an aluminum alloy conductive part.

2. The method for preparing an aluminum alloy conductive part according to claim 1, characterized in that: The temperature of the cryogenic treatment is -80°C to -190°C, the cooling rate of the cryogenic treatment is 5°C / min to 10°C / min, and the cryogenic treatment time is 4h to 16h; The interval between the quenching treatment and the cryogenic treatment is no more than 24 hours.

3. The method for preparing an aluminum alloy conductive part according to claim 1, characterized in that: The cryogenic treatment includes primary cryogenic treatment and secondary cryogenic treatment, and the aluminum extrusion after quenching treatment is subjected to the primary cryogenic treatment and the secondary cryogenic treatment in sequence; the temperature of the primary cryogenic treatment is higher than the temperature of the secondary cryogenic treatment, and the cooling rate of the primary cryogenic treatment is greater than the cooling rate of the secondary cryogenic treatment.

4. The method for preparing an aluminum alloy conductive part according to claim 3, characterized in that: The temperature of the first cryogenic treatment is -50°C to -80°C, and the temperature of the second cryogenic treatment is -80°C to -150°C; The cooling rate of the primary cryogenic treatment is 5°C / min to 15°C / min, and the cooling rate of the secondary cryogenic treatment is 1°C / min to 5°C / min.

5. The method for preparing an aluminum alloy conductive part according to claim 3, characterized in that: The processing time of the primary cryogenic treatment is 1 hour to 8 hours, and the processing time of the secondary cryogenic treatment is 1 hour to 8 hours.

6. The method for preparing an aluminum alloy conductive part according to claim 1, characterized in that: The temperature of the aging treatment is 180°C to 300°C, and the time of the aging treatment is 2h to 16h; The interval time between the deep cryogenic treatment and the aging treatment is 10 minutes to 24 hours.

7. The method for preparing an aluminum alloy conductive member according to claim 1, characterized in that: The aluminum billet is continuously extruded through a continuous extruder, and the outlet temperature of the continuous extruder is 350° C. to 480° C.

8. The method for preparing an aluminum alloy conductive member according to claim 1, characterized in that: The quenching treatment time is 10s to 60s; the transfer time of the quenching treatment is less than 10s.

9. The method for preparing an aluminum alloy conductive member according to claim 1, characterized in that: The raw materials of the aluminum billet material include one or more of 1 series, 6 series, and 8 series aluminum alloys.

10. An aluminum alloy conductive part, wherein the aluminum alloy conductive part is prepared by the method for preparing an aluminum alloy conductive part according to any one of claims 1 to 9.

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