Highly conductive heat-resistant aluminum alloy and method for manufacturing the same

Abstract

The application discloses a kind of high-conductivity heat-resistant aluminum alloy, comprising: based on the total mass of the aluminum alloy, in terms of mass percentage, the aluminum alloy comprises: B: 0.2~0.5%, Sc: 0~0.3 %, Er: 0.2%~0.5%, graphene / graphite / carbon nanotube: 0.1%~3%, Zr: 0.1%~0.25 %, the balance is industrial pure aluminum and inevitable impurities therein, single impurity element≤0.05%, total amount of impurities≤0.25%. The alloy obtained by the method of the application has greatly improved electrical conductivity, and the mechanical properties are also further improved compared with industrial pure aluminum.

Description

Technical Field

[0001] This invention relates to the field of high electrical conductivity and heat resistance aluminum alloy technology, and particularly to a high electrical conductivity and heat resistance aluminum alloy and its preparation method. Background Technology

[0002] With the gradual improvement of my country's power transmission network in the east and west, and the rapid development of industries such as new energy vehicles and 5G communications, people are paying increasing attention to the miniaturization, lightweighting, and integration of conductive materials. Therefore, the requirements for the comprehensive performance of materials are becoming increasingly stringent, demanding not only excellent mechanical properties but also good electrical conductivity and heat resistance. Because aluminum alloys have low density, good electrical conductivity, and aluminum is the most abundant metallic element on Earth, with smelting costs much lower than precious metals such as copper, they are widely used in the power and electrical engineering industry, automotive, and aerospace fields.

[0003] Alloying is a crucial method for strengthening aluminum alloys, and the addition of elements such as Mg, Si, and Cu during alloying can significantly improve their mechanical properties. However, according to Masison's Law and practical observations in production and daily life, there is an inverse correlation between alloy strength and conductivity. In recent years, many new energy vehicles have increasingly used aluminum alloys with excellent conductivity in their battery casings, power transmission cables, and motor rotors. However, the conductivity and heat resistance of these materials must yield to strength, leading to frequent incidents of spontaneous combustion in new energy vehicles and cable fires under poor service conditions during long-distance power transmission. Therefore, overcoming the trade-off between the strength and conductivity of aluminum alloys, and balancing their mechanical, formability, and heat resistance while ensuring conductivity, is a pressing issue.

[0004] Existing heat-resistant and conductive aluminum alloys typically exhibit conductivity above 57% IACS at room temperature. However, this significantly sacrifices their tensile strength, which is generally 100-120 MPa, with service temperatures below 280℃ and elongation between 1.5% and 2%. This does not meet current requirements. To address these technical issues, researchers both domestically and internationally have conducted extensive research in the fields of aluminum-based composite materials and microalloyed aluminum alloys in recent years. For example, patent document CN201910577786.6 discloses a method for preparing graphene-reinforced aluminum-based composite materials through in-situ synthesis. This method prepares graphene through in-situ reaction, resulting in aluminum-based composite materials with improved conductivity and tensile strength compared to pure aluminum. However, this patent primarily focuses on the uniform dispersion of graphene and does not involve boronizing purification treatment or the introduction of microalloying elements such as Zr, Sc, and Er for synergistic strengthening. Patent document CN202410306064 discloses a graphene / aluminum composite conductor and its preparation method. This method synergistically improves conductivity through the physical combination of graphene and aluminum, achieving a conductivity of 67% IACS after directional alignment treatment. However, the graphene content in this patent is as high as 1%~10%, and the aluminum alloy matrix is ​​not systematically alloyed, leaving room for improvement in its mechanical properties. Furthermore, the preparation process involved in this method is complex, hindering large-scale industrial production. In addition, academic research has shown that while adding graphene to aluminum alloys can simultaneously improve strength and conductivity, the increase in conductivity is limited by graphene agglomeration and interfacial reaction issues.

[0005] Regarding microalloyed aluminum alloys, patent document CN106834814A discloses a high-conductivity, heat-resistant, and corrosion-resistant aluminum alloy wire, whose components include elements such as Er, Sc, Zr, and Si. Through the synergistic effect of process and composition, the conductivity reaches over 61.8% IACS and the tensile strength reaches over 180 MPa. However, it does not introduce carbon materials such as graphene for composite strengthening. Research literature shows that adding Er to Al-Zr-Sc alloys can promote the precipitation of Zr and Sc, forming an Al3(Er,Sc,Zr) phase with a core-double-shell structure, thereby improving the aging response rate and conductivity of the alloy. However, the conductivity of such alloys is generally difficult to exceed the theoretical conductivity limit of pure aluminum, and excessive addition of Sc will lead to a significant increase in cost. Another patent document, CN202311537476.4, discloses a heat-resistant aluminum alloy conductor material. By using Er, Sc, and Zr in combination with a three-stage aging heat treatment, an Al3(Sc,Zr,Er) precipitate with a double core-shell structure is obtained, exhibiting excellent overall performance. However, this method also does not involve the composite addition of carbon materials, and further improvement in its conductivity is limited by lattice distortion caused by solid solution atoms. Furthermore, the three-stage aging process not only significantly increases production costs but also reduces production efficiency.

[0006] In summary, while aluminum-based composites made by simply adding carbon materials such as graphene in existing conventional casting technologies have high conductivity, their mechanical properties are insufficient. Aluminum alloys treated with microalloying alone have good strength, but their conductivity is limited by lattice distortion caused by the solid solution of alloying elements. Methods that synergistically add graphene with multiple microalloying elements and achieve uniform dispersion even with high graphene additions using traditional mechanical stirring casting are rarely reported. This invention addresses these technical challenges by synergistically adding graphene with elements such as B, Zr, Er, and Sc to industrial pure aluminum, combined with an optimized heat treatment process. Simultaneously, it utilizes boronizing treatment to purify the matrix, graphene to construct metal-nonmetal composite conductive channels, and Zr / Er / Sc to form a nanoscale reinforcing phase. This achieves technical effects that existing technologies have failed to reach, improving conductivity while simultaneously maintaining mechanical and heat resistance. Summary of the Invention

[0007] In view of this, the present invention provides a highly conductive and heat-resistant aluminum alloy and a method for preparing the same, so as to provide an aluminum alloy with good mechanical properties, electrical conductivity and heat resistance.

[0008] On one hand, the present invention provides a high electrical conductivity and heat resistance aluminum alloy, comprising: based on the total mass of the aluminum alloy, by mass percentage, the aluminum alloy comprises: B: 0.2%~0.5%, Sc: 0~0.3%, Er: 0.2%~0.5%, graphene / graphite / carbon nanotubes: 0.1%~3%, Zr: 0.1%~0.25%, with the balance being industrial pure aluminum and unavoidable impurities therein, wherein the individual impurity element is ≤0.05% and the total amount of impurities is ≤0.25%.

[0009] Preferably, the unavoidable impurities include one or more of Fe, Si, Ti, V, Cr, and Mn, wherein Fe ≤ 0.03% and Si ≤ 0.02%.

[0010] Preferably, the aluminum alloy is in a heat-treated state after solution treatment and aging treatment, and meets at least one of the following conditions: tensile strength ≥195MPa, yield strength ≥120MPa, elongation ≥6.5%, and electrical conductivity ≥61%IACS.

[0011] Preferably, the graphene is a single-layer graphene.

[0012] Secondly, the present invention also provides a method for preparing the aforementioned high electrical conductivity and heat-resistant aluminum alloy, comprising the following steps:

[0013] Industrial pure aluminum, raw materials containing B, and / or raw materials containing Sc, and / or raw materials containing Er, and / or raw materials containing Zr, and graphene / graphite / carbon nanotubes are heated and melted to obtain a homogeneous alloy melt;

[0014] The alloy melt is cast and cooled to obtain a cast aluminum alloy;

[0015] The cast aluminum alloy is subjected to solution treatment and aging treatment in sequence to obtain the finished aluminum alloy.

[0016] Preferably, industrial pure aluminum is heated and smelted, and raw materials containing B, and / or Sc, and / or Er, and / or Zr are added and heated to melt, to obtain a first alloy melt;

[0017] Graphene / graphite / carbon nanotubes are added to the first aluminum melt, and the mixture is stirred evenly by electric stirring under an argon-protected atmosphere to obtain the homogeneous alloy melt.

[0018] Preferably, the heating temperature for preparing the first alloy melt is 680-750°C, and the heating temperature for preparing the homogeneous alloy melt is 640-660°C.

[0019] Preferably, the solution treatment specifically involves holding the solution at 540-600℃ for 2-12 hours; the aging treatment involves holding the solution at 230-430℃ for 2-12 hours.

[0020] Preferably, in the preparation method of the high conductivity and heat resistance aluminum alloy, after solution treatment and aging treatment, the finished aluminum alloy has a tensile strength ≥195 MPa, a conductivity ≥61% IACS, and a strength residual rate ≥90% after holding at 280℃ for 100 hours.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention optimizes the multi-element microalloying design, utilizing the synergistic effects of boron, sc, ergon, zirconium, and carbon nanomaterials (graphene / graphite / carbon nanotubes), combined with suitable melting, casting, and heat treatment processes, to prepare an aluminum alloy possessing both high electrical conductivity and excellent heat resistance and mechanical properties. The alloy of this invention achieves a significant increase in electrical conductivity while simultaneously enhancing mechanical properties and thermal stability, effectively solving the technical challenge of traditional high-conductivity aluminum alloys where "conductivity, strength, and heat resistance are difficult to balance." Specifically:

[0023] 1. Highly efficient boriding purification, achieving a win-win situation of impurity removal and property preservation: This invention controls the boron content to 0.2~0.5%, which can efficiently remove impurity elements such as Ti, V, and Cr from industrial pure aluminum. B reacts with these impurities to form high-melting-point boride precipitates, significantly reducing the scattering effect of impurity atoms on electrons and improving the alloy's conductivity from the source. At the same time, limiting the B content within a reasonable range can avoid the formation of coarse boride phases due to excessive B, ensuring excellent impurity removal effect without compromising the alloy's plasticity and conductivity due to excessive second phase, thus achieving the dual effect of "highly efficient impurity removal + no performance loss".

[0024] 2. Synergistic strengthening by rare earth and transition elements, overcoming the bottleneck of the trade-off between strength and conductivity: This invention controls the content of Sc to 0~0.3%, Er to 0.2%~0.5%, and Zr to 0.1%~0.25%, which synergistically precipitate nanoscale Al3(Sc,Zr,Er) dispersed strengthening phase in the aluminum matrix. This phase is coherent with the Al matrix and has excellent thermal stability, effectively pinning grain boundaries and dislocations, significantly improving the room temperature strength and high temperature heat resistance of the alloy, solving the problems of insufficient strength and easy softening at high temperatures in industrial pure aluminum. By strictly controlling the addition of each element at a low level, the increased electron scattering caused by excessive rare earth / transition elements is avoided, maximizing the preservation of the alloy's high electrical conductivity while achieving strengthening, thus overcoming the bottleneck of traditional aluminum alloys where "strength improvement inevitably sacrifices conductivity".

[0025] 3. Carbon nanomaterials construct a conductive network, achieving synergistic enhancement of conductivity and mechanical properties: This invention adds 0.1%~3% graphene / graphite / carbon nanotubes, utilizing the ultra-high conductivity and mechanical properties of carbon nanomaterials to form a continuous conductive network in the aluminum matrix, further improving the overall conductivity of the alloy. Simultaneously, carbon nanomaterials can act as heterogeneous nucleation cores, refining as-cast grains, enhancing grain boundary bonding, and simultaneously improving the alloy's strength, plasticity, and thermal stability. By controlling the addition amount within a reasonable range, the performance degradation caused by carbon nanomaterial agglomeration is effectively avoided, achieving a synergistic effect of "conductive enhancement + mechanical strengthening."

[0026] 4. Strictly limit impurity content to ensure alloy purity and service reliability: This invention strictly controls impurity elements, ensuring that the content of a single impurity element is ≤0.05% and the total amount of impurities is ≤0.25%. This minimizes the formation of coarse intermetallic compounds by impurity elements such as Fe and Si, avoiding the scattering of electrons by impurities and their cutting effect on grain boundaries. This ensures both the high electrical conductivity of the alloy and improves its plasticity and mechanical properties, providing a reliable foundation for the long-term stable service of the alloy.

[0027] 5. Adaptable smelting process, balancing microstructure uniformity and industrial production: This invention employs an adapted smelting process that ensures the uniform dispersion of microalloying elements such as B, Sc, Er, and Zr with carbon nanomaterials in molten aluminum, avoiding element segregation and carbon nanomaterial agglomeration. Simultaneously, reasonable smelting temperature control reduces the loss of alloying elements, ensuring compositional accuracy, resulting in a uniform alloy microstructure and stable performance, suitable for large-scale industrial production, achieving a balance between high performance and mass production. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The following are local SEM and EDS energy dispersive spectra after borylation treatment provided by this invention;

[0031] Figure 2 This is a schematic diagram of the structure of the multilayer graphene used in this invention;

[0032] Figure 3 This is a resistivity comparison diagram of different embodiments of the present invention and comparative samples. Detailed Implementation

[0033] The present invention will be further explained below with reference to specific implementation schemes, but this explanation does not limit the scope of the invention.

[0034] Because pure aluminum has a relatively pure matrix with few impurities, it exhibits good electrical conductivity, but poor mechanical and heat resistance. For example, pure aluminum with a purity of 99.99% has a tensile strength of less than 50 MPa. Adding elements can improve the mechanical and heat resistance of the alloy; for instance, pure aluminum with a purity of 99% can exceed 100 MPa in strength, but its electrical conductivity remains low. The addition of different elements, their concentrations, and their proportions all have varying effects on the mechanical, electrical, and heat resistance properties of aluminum alloys. Therefore, the rational selection of elements, their concentrations, and their proportions is crucial for developing aluminum alloys with excellent mechanical, electrical, and heat resistance properties.

[0035] The strengthening mechanisms of aluminum alloys mainly include solid solution strengthening and age hardening. Solid solution strengthening involves adding alloying elements to the aluminum matrix to form a solid solution, causing lattice distortion and hindering dislocation movement, thus achieving solid solution strengthening and increasing the alloy's strength. Age hardening refers to the process where the alloying elements have a certain solid concentration in the aluminum alloy, which decreases sharply with decreasing temperature. After the aluminum alloy is heated to a certain temperature and quenched (i.e., after solid solution treatment), a supersaturated aluminum-based solid solution can be obtained. After age hardening, certain nano- and intermetallic compounds are adsorbed from the supersaturated aluminum-based solid solution, which has a strengthening effect on the alloy.

[0036] Pure aluminum (99.99%) has a very high electrical conductivity, approximately 63% IACS (International Standard for Annealed Copper) at 20°C, corresponding to a resistivity of 2.65 × 10⁻⁶. -8Ω·m, generally speaking, the addition of any alloying element will reduce the conductivity. For example, the conductivity of an aluminum alloy with 1% magnesium added (such as type 5056) drops sharply to 28% IACS. Similarly, the addition of other elements will also reduce the conductivity. The above phenomenon can be explained by classical electronic theory because the size of the solute atoms is different from that of aluminum atoms. When added to aluminum, they form solid solutions or second phases with aluminum. Whether forming interstitial solid solutions or substitutional solid solutions, they will cause lattice distortion, reduce the mean free path of electrons, and hinder the free movement of electrons, thereby reducing the conductivity of the aluminum alloy.

[0037] For high-conductivity and heat-resistant aluminum alloys, it is necessary to consider both the mechanical properties of the alloy and its electrical conductivity and heat resistance. Adding any metallic element will decrease the alloy's electrical conductivity, thus posing a challenge to determining the appropriate metallic element content. Therefore, this invention focuses on the addition of non-metallic elements and improvements to the casting process to achieve a more perfect balance between the alloy's electrical conductivity, heat resistance, and mechanical properties.

[0038] In summary, the present invention provides a high electrical conductivity and heat resistance aluminum alloy, comprising, based on the total mass of the aluminum alloy, by mass percentage: B: 0.2%~0.5%, Sc: 0~0.3%, Er: 0.2%~0.5%, graphene / graphite / carbon nanotubes: 0.1%~3%, Zr: 0.1%~0.25%, with the balance being industrial pure aluminum and unavoidable impurities therein, wherein the individual impurity element is ≤0.05% and the total impurity is ≤0.25%.

[0039] Among them, the raw material aluminum element can be one or more of electrolytic aluminum ingots, remelted aluminum ingots or cast aluminum alloy ingots, or it can be a mixture of recycled materials or recovered waste from the factory and Al ingots.

[0040] Raw material B can be made of aluminum-boron master alloy. When aluminum-boron master alloy is used as raw material B, aluminum ingots can be melted and laid into the bottom of the furnace for melting during preparation, and then aluminum-boron master alloy can be added.

[0041] The raw material Sc can be an aluminum-scandium master alloy;

[0042] The raw material Er can be an aluminum-erbium master alloy;

[0043] The raw material Zr can be an aluminum-zirconium master alloy;

[0044] The raw materials for graphene, graphite, or carbon nanotubes are selected from at least one of single-layer graphene, multi-layer graphene, nanoscale graphene, and micrometer-scale graphene.

[0045] Preferably, the graphene is single-layer graphene. For example... Figure 2As can be seen, the special three-dimensional structure of sheet graphene makes it difficult for free electrons to move freely between layers due to the large van der Waals forces between the layers. Therefore, this invention uses monolayer graphene. For the monolayer two-dimensional structure of graphene, the sp2 hybrid orbitals cause the different chemical bonds formed to perform different tasks, mainly forming σ bonds to maintain strength, and the remaining electron forming a delocalized π bond to contribute to conductivity.

[0046] Zr, Er, and Sc in the above composition are all important strengthening elements of aluminum alloys. Adding a very small amount of these elements can play a very good strengthening role. Moreover, the addition of these trace elements has little effect on the electrical conductivity of the alloy, and can be compensated for by the addition of graphene later. By reasonably controlling the content of these elements, the mechanical properties of the alloy can be improved without significantly reducing the electrical conductivity, thus maintaining the original electrical conductivity.

[0047] Alloying elements often form various eutectic phases in alloys. The morphology of these eutectic phases plays different roles in the mechanical properties and strength of the alloy. Zr has a much larger atomic radius than Al, therefore Zr can cause severe lattice distortion in the Al matrix, and the conductivity of the alloy decreases with increasing Zr content. During aluminum alloy smelting, most rare earth elements, such as Er and Sc, play a role in degassing, impurity removal, and purifying the molten aluminum. Furthermore, during the aging process of aluminum alloys, they improve the distribution of impurities such as Fe and Si, thereby increasing the electrical conductivity of the aluminum alloy.

[0048] Adding elements with high melting points and low diffusion rates, such as Zr and Sc, can increase the recrystallization temperature of the matrix, slow down the diffusion process of the solid solution, and improve its heat resistance. Adding trace amounts of Zr can refine the grains, improve the as-cast microstructure, and enhance the overall mechanical and heat resistance properties of the alloy. After aging treatment, Zr can induce the precipitation of an L12-type Al3Zr second phase within the microstructure. These fine and dispersed second-phase particles have excellent strengthening effects. Furthermore, Zr has a very low diffusion rate in the Al matrix, only 1.2 × 10⁻⁶ at 400℃. -20 m 2 Therefore, Al3Zr particles have good resistance to coarsening in a temperature range of around 400℃, allowing the alloy to maintain relatively good performance at high temperatures. However, the addition of Zr will cause lattice distortion in the Al matrix, and the conductivity of the alloy will decrease significantly with the increase of Zr content. For example, in Al-Zr-Y alloys, the conductivity decreases by 4.1% IACS for every 0.1 wt.% increase in Zr content.

[0049] Generally, adding rare earth elements can form easily segregating compounds around grain boundaries, increasing grain boundary strength, filling grain boundary vacancies, hindering atomic diffusion, and improving the alloy's thermal stability. It can also purify grain boundaries, allowing fusible impurities to transfer from the grain boundaries to the grain interior. Adding Er to Al-4Si alloys resulted in the formation of ErSi2 and Al3Er phases. Al3Er is coherent with the Al matrix, exhibiting an FCC structure, reducing lattice distortion. Therefore, with increasing Er content, the alloy's conductivity decreased slightly and then stabilized, while the alloy hardness continuously increased. Furthermore, heat treatment further enhances the conductivity of Er-added alloys. T6 heat treatment of Al-4Si-1Er resulted in alloys with excellent mechanical and electrical properties. Adding Er to the Al-Zr-Sc alloy promotes the precipitation of Zr and Sc elements, significantly improving the aging response rate of the alloy. The two-stage aging process forms the L12-type core-shell Al3(Sc,Zr) phase and the core-double-shell Al3(Er,Sc,Zr) phase, giving the alloy good mechanical and heat resistance properties.

[0050] Boron can form borate impurities with trace impurities such as Ti, V, Cr, and Mn in aluminum. These impurities then sink to the bottom of the furnace and are removed along with the slag, thus purifying the Al matrix and reducing the negative impact of impurities on the conductivity of aluminum conductors.

[0051] Figure 1 The images show the SEM and EDS spectra of a portion of the material after boronizing treatment according to this invention. As can be seen from the figures, after boronizing treatment, manually selected areas were analyzed (as shown in Figure (a)), yielding the distribution maps of Al, Zr, Sc, and B elements. These atomic percentages can be converted to mass fractions. Although some loss occurred during the smelting process, the results roughly match the composition of alloy #1. Furthermore, through automatic scanning analysis (as shown in Figure (b)), only C and O elements were detected. The approximately 0.3% impurity elements (such as Mn, Ti, V, Cr, Fe, etc.) originally present in industrial pure aluminum were removed after boronizing treatment and were not detected in the energy spectrum. This is also the reason why alloy #5 (Example 5) has the lowest resistivity, indicating a good boronizing effect and providing theoretical and experimental basis for further development of conductive aluminum alloys containing the synergistic effect of B and graphene. In addition, this invention provides a method for preparing the above-mentioned high-conductivity and heat-resistant aluminum alloy, the method comprising the following steps:

[0052] 1) Material preparation: Prepare raw materials according to the proportions;

[0053] 2) Heating and melting: The aluminum ingots are put into the furnace and heated and stirred.

[0054] Next, add the other raw materials except graphene to the aluminum melt until it melts. Finally, add the graphene. At this time, use an electric stirrer to stir it thoroughly in the furnace under the protection of argon gas to make the graphene uniform and obtain a uniform alloy melt. Take a spectral sample to determine the chemical composition to ensure that the chemical composition is qualified.

[0055] In step 2), when other raw materials besides graphene are added to the aluminum melt and heated to melt, the temperature of the alloy melt is 680-750℃, and the appropriate stirring temperature of the molten metal after adding graphene is 640-660℃.

[0056] 3) Casting: After the casting is demolded, it is cooled to obtain the as-cast state.

[0057] The heat-treated aluminum alloy after solution treatment and aging in the as-cast state.

[0058] Specifically, the solution treatment involves holding the solution at 500-600℃ for 2-12 hours.

[0059] The aging treatment involves holding the temperature at 230-430℃ for 2-12 hours.

[0060] The present invention will be further explained and described below with reference to specific embodiments, but it is not intended to limit the scope of protection of the present invention.

[0061] The aluminum ingots used in the following examples are Al99.70 as specified in the national standard GB / T1196-2008 "Aluminum Ingots for Remelting", with an aluminum content of not less than 99.70 wt%. Alternatively, pre-alloyed cast aluminum alloy ingots commonly used in the casting industry can be used, such as the aluminum ingots specified in the national standard GB / T8733-2016 "Cast Aluminum Alloy Ingots". The aluminum alloy scrap can be remelted aluminum ingots or bulk scrap such as automotive chips and aluminum shavings. All raw materials are purchased from the market.

[0062] Currently, the heat resistance temperature of most heat-resistant aluminum alloy conductors is between 150 and 200℃, while those between 210 and 250℃ are not yet widely available, and ultra-heat-resistant aluminum alloy conductors with a heat resistance temperature reaching 280℃ are extremely rare. According to national standards, the heat resistance of conductors is evaluated using the residual strength rate. The conductor is held at a certain temperature for a period of time, then returned to room temperature and stretched. Its tensile strength is measured, and the ratio of the tensile strength after heating to that before heating, multiplied by 100%, is the residual strength rate at that temperature. The highest temperature corresponding to a residual strength rate of 90% is used as the performance index of the conductor's heat resistance.

[0063] Example 1

[0064] A highly conductive and heat-resistant aluminum alloy is prepared by the following method:

[0065] 1) Material preparation: Prepare raw materials according to the proportions;

[0066] 2) Heating and Melting: Aluminum ingots are placed in a furnace and heated and stirred. Then, all raw materials except graphene are added to the molten aluminum until it melts. Finally, graphene is added, and at this point, an electric stirrer is used to thoroughly stir the mixture in an argon-protected atmosphere to ensure the graphene is uniformly mixed, resulting in a homogeneous alloy melt. Optical and spectral samples are taken to determine the chemical composition, ensuring it meets the required standards. Throughout this process, the melt temperature is controlled at 640-750℃.

[0067] In step 2), the temperature of the alloy melt during the heating and melting process is 680-750℃. The suitable stirring temperature for the molten metal after adding graphene is 640-660℃.

[0068] 3) Casting: After the casting is demolded, it is cooled to obtain the finished product.

[0069] The obtained as-cast aluminum alloy products were subjected to room temperature tensile properties testing, electrical conductivity testing, and heat resistance testing. The test results are shown in Table 1.

[0070] Example 2-10

[0071] The alloy products in Examples 2-10 have different compositions from those in Example 1. Except for the differences described below, the preparation methods are the same as those in Example 1.

[0072] Performance Testing: The yield strength, tensile strength, elongation, and electrical conductivity of the conductive aluminum alloy materials prepared in Examples 1-10 above were tested, as well as the tensile strength, yield strength, and elongation after heat exposure. Yield strength, tensile strength, and elongation were obtained according to the GB / T228.1-2010 testing standard; electrical conductivity was measured using a digital eddy current conductivity meter manufactured by Xiamen Tianyan Instrument Co., Ltd., model Sigma2008A. The test results are shown in Table 1.

[0073] Comparative Example 1 (without graphene)

[0074] This comparative example illustrates the effect of graphene addition on the conductivity and mechanical properties of the alloy.

[0075] Aluminum alloys without graphene were prepared using the same method as in Example 2, with the following specific steps:

[0076] Materials: By mass percentage, Zr: 0.1%, Sc: 0.05%, B: 0.2%, Er: 0.2%, with the balance being industrial pure aluminum and unavoidable impurities (individual impurity element ≤0.05%, total impurities ≤0.25%); the only difference from Example 2 is that graphene is not added.

[0077] Heating and melting: Aluminum ingots are put into the furnace and heated to 680-750℃ for melting and stirring. Raw materials containing B, Sc, Er, and Zr are added and heated to melt, resulting in the first alloy melt. Subsequently, the melt temperature is reduced to 640-660℃ and stirred electrically under an argon protective atmosphere to obtain a homogeneous alloy melt.

[0078] Casting: The alloy molten material is poured into the mold and cooled to obtain the as-cast aluminum alloy.

[0079] The performance of the above-mentioned cast aluminum alloy was tested using the same methods as in the previous example. The results showed that the tensile strength was 223.4 MPa, the yield strength was 168.3 MPa, the elongation was 6.1%, and the electrical conductivity was 57.8% IACS.

[0080] Compared to Example 2 (with 1% graphene added, as-cast tensile strength 157.7 MPa, conductivity 63.4% IACS), Comparative Example 1 showed a tensile strength approximately 41.7% higher, while conductivity decreased by approximately 8.8%. This result indicates that the addition of graphene can significantly improve the conductivity of the alloy by forming a metal-nonmetal composite conductive network, but it also weakens the as-cast strength to some extent. This may be related to the uniformity of graphene dispersion in the aluminum matrix, the interfacial bonding state, and the introduced micro-defects. Therefore, in practical applications, the amount of graphene added needs to be reasonably controlled to achieve the optimal balance between conductivity and mechanical properties.

[0081] Comparative Example 2 (excluding B)

[0082] This comparative example illustrates the effect of boronizing purification treatment of element B on the conductivity of the alloy.

[0083] Aluminum alloys without B were prepared using the same method as in Example 1, with the following specific steps:

[0084] Materials: By mass percentage, Zr: 0.1%, Sc: 0.05%, Er: 0.2%, graphene: 0.5%, with the balance being industrial pure aluminum and unavoidable impurities (individual impurity element ≤ 0.05%, total impurities ≤ 0.25%); the only difference from Example 1 is that element B is not added.

[0085] Heating and melting: The preparation process is exactly the same as in Example 1, including melting temperature, graphene addition method, argon-protected stirring and casting cooling.

[0086] Casting: to obtain cast aluminum alloy.

[0087] The performance of the above-mentioned cast aluminum alloy was tested using the same methods as in the previous example. The results showed that the tensile strength was 155 MPa, the yield strength was 103.5 MPa, the elongation was 6.2%, and the electrical conductivity was 56.9% IACS.

[0088] Compared to Example 1 (with 0.2% B added, tensile strength 161.6 MPa, conductivity 63.5% IACS), Comparative Example 2 showed a decrease in conductivity of approximately 11.6% and a slight decrease in tensile strength. This is because B reacts with impurities such as Ti, V, Cr, and Mn in industrially pure aluminum to form high-melting-point boride precipitates. Slag removal effectively removes these impurity atoms, reducing their scattering effect on electrons. Without B, impurity elements remain in the aluminum matrix, leading to increased lattice distortion and a significant decrease in conductivity. Therefore, the addition of B is one of the key factors in achieving high conductivity in the alloy. The alloy composition and the properties of the prepared castings are shown in Table 1.

[0089] Table 1: Chemical composition (wt%), mechanical properties and electrical conductivity of the alloy

[0090]

[0091] Note: Z represents the alloy in the as-cast state; R represents the alloy in the heat-treated state; UTS represents tensile strength in MPa; YS represents yield strength in MPa; EI represents elongation in %; and electrical conductivity in %IACS.

[0092] For ease of analysis, some of the examples in Table 1 are numbered as samples 1# to 5#, where:

[0093] Sample #1 corresponds to Example 1 (cast state, B content 0.2%); Sample #2 corresponds to Example 2 (cast state, B content 0.2%).

[0094] Sample #3 corresponds to Example 3 (cast state, B content 0.3%); Sample #4 corresponds to Example 4 (cast state, graphene content 2%); Sample #5 corresponds to Example 5 (cast state, graphene content 3%).

[0095] Based on the resistivity test results of the above samples, such as Figure 3As shown, the analysis is as follows: the resistivity of different alloys shows significant differences. Among them, the alloy in Example 6 has the lowest electrical conductivity at room temperature, which is in line with expectations. From the perspective of matrix composition, the alloy in Example 6 did not use too much graphene and was not heat-treated for strengthening compared to other alloys. Although the relatively small amount of boron plays a role in purifying the matrix, the purification effect is significantly less than that of other examples. During the borylation process, B mainly exists in the form of Al2B and reacts with transition metal elements in the matrix (such as Mn, Ti, V, Cr, Fe, etc.) to form multi-component borides, which reduces the solid solution content of these elements in the aluminum matrix, thereby improving the conductivity of the alloy, i.e., increasing the electrical conductivity.

[0096] Combined with SEM and EDS analysis results, it can be seen that after boronizing treatment, the original impurity elements in industrial pure aluminum (such as Mn, Ti, V, Cr, Fe, etc.) all form compounds with B and are removed by slag removal during the smelting process, significantly improving the purity of the matrix. According to Masison's rule, the resistivity caused by lattice distortion is significantly reduced, therefore, alloy #5 (Example 5) exhibits the lowest resistivity.

[0097] After heat treatment, the electrical conductivity of the alloys in Examples 2 and 3 increased by 5.5% and 0.9%, respectively, showing a slight improvement, and their strength also underwent a qualitative change. This is because solution treatment allows the alloying elements to fully dissolve into the aluminum matrix, forming a supersaturated solid solution after quenching. Subsequent aging treatment precipitates fine, dispersed strengthening phases, reducing the concentration of solid-solution atoms in the matrix, weakening electron scattering, and increasing conductivity. Although a small amount of fine, dispersed phases still exist in the matrix, their electron-blocking effect is far less than that of coarse phases or solid-solution atoms, thereby enabling aging strengthening and improving the alloy strength. Furthermore, heat treatment significantly reduces the dislocation density in the alloy, further reducing electron scattering and improving electrical conductivity.

[0098] For the alloys of Examples 4 and 5, although more thorough boronizing treatment was performed, the conductivity exhibited a recurring trend due to the addition of more graphene. The mechanism lies in the fact that the graphene, after mechanical stirring, was uniformly dispersed in the aluminum alloy matrix, constructing a metal-nonmetal composite conductive structure. The conductivity mechanism of graphene differs from that of metals, originating from its unique two-dimensional honeycomb lattice structure and electronic band characteristics, primarily relying on the delocalization of π electrons and its zero-bandgap half-metallic properties. In graphene, carbon atoms form three σ bonds through sp² hybridization to maintain structural stability, while the remaining electron forms a delocalized π bond, contributing to conductivity. Graphene, as a hard particle dispersed in the matrix, provides more channels for electron migration, promoting electron transport and thus improving the alloy's conductivity. However, the sudden increase in graphene content led to the reappearance of some drawbacks in the dispersion of graphene in the melt, resulting in some stress concentration in the alloy's mechanical properties and a certain degree of decrease in tensile properties, as confirmed by tensile test results. The electrical conductivity and mechanical properties of an alloy are inherently interdependent, so a reasonable balance must be achieved between the two in material design.

[0099] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0100] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A high-conductivity heat-resistant aluminum alloy, characterized by comprising, include: Based on the total mass of the aluminum alloy, the aluminum alloy comprises, by mass percentage: B: 0.2%~0.5%, Sc: 0~0.3%, Er: 0.2%~0.5%, Graphene / Graphite / Carbon Nanotubes: 0.1%~3%, Zr: 0.1%~0.25%, the balance is industrial pure aluminum and unavoidable impurities, with individual impurity elements ≤0.05% and total impurities ≤0.25%.

2. The high-conductivity heat-resistant aluminum alloy as claimed in claim 1, wherein The mass percentages of Sc, Er, and Zr satisfy the following: Sc:Er:Zr = (0~0.3) : (0.2~0.5) : (0.1~0.25), and the total amount of Sc, Er, and Zr does not exceed 0.8%.

3. The high electrical conductivity and heat-resistant aluminum alloy as described in claim 1, characterized in that, The unavoidable impurities include one or more of Fe, Si, Ti, V, Cr, and Mn, wherein Fe ≤ 0.03% and Si ≤ 0.02%.

4. The high electrical conductivity and heat-resistant aluminum alloy as described in claim 1, characterized in that, The aluminum alloy is in a heat-treated state after solution treatment and aging treatment, and meets at least one of the following conditions: tensile strength ≥196MPa, yield strength ≥105MPa, elongation ≥6.5%, and electrical conductivity ≥62%IACS.

5. The high electrical conductivity and heat-resistant aluminum alloy as described in claim 1, characterized in that, The graphene is a single-layer graphene.

6. The method for preparing the high electrical conductivity and heat resistance aluminum alloy according to any one of claims 1-5, characterized in that, Includes the following steps: Industrial pure aluminum, raw materials containing B, and / or raw materials containing Sc, and / or raw materials containing Er, and / or raw materials containing Zr, and graphene / graphite / carbon nanotubes are heated and melted to obtain a homogeneous alloy melt; The alloy melt is cast and cooled to obtain a cast aluminum alloy; The cast aluminum alloy is subjected to solution treatment and aging treatment in sequence to obtain the finished aluminum alloy.

7. The method for preparing the high electrical conductivity and heat resistance aluminum alloy according to claim 6, characterized in that, Industrial pure aluminum is heated and smelted, and raw materials containing B, and / or Sc, and / or Er, and / or Zr are added and heated to melt, to obtain a first alloy melt; Graphene / graphite / carbon nanotubes are added to the first aluminum melt, and the mixture is stirred evenly by electric stirring under an argon-protected atmosphere to obtain the homogeneous alloy melt.

8. The method for preparing the high electrical conductivity and heat-resistant aluminum alloy according to claim 6, characterized in that, The heating temperature for preparing the first alloy melt is 680-750℃, and the heating temperature for preparing the homogeneous alloy melt is 640-660℃.

9. The method for preparing the high electrical conductivity and heat-resistant aluminum alloy according to claim 6, characterized in that, The solution treatment specifically involves holding the solution at 540-600℃ for 2-12 hours; the aging treatment involves holding the solution at 230-430℃ for 2-12 hours.

10. The method for preparing the high electrical conductivity and heat-resistant aluminum alloy according to claim 6, characterized in that, The method for preparing the high conductivity and heat resistance aluminum alloy is characterized in that, after solution treatment and aging treatment, the finished aluminum alloy has a cast tensile strength ≥120 MPa and a conductivity ≥61% IACS, a heat-treated tensile strength greater than 195 MPa and a conductivity ≥62% IACS, and a strength residual rate ≥90% after holding at 280℃ for 100 hours.

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