Conductive heat-resistant aluminum alloy and preparation method and application thereof

Abstract

The present application relates to the technical field of metal materials, in particular to a conductive heat-resistant aluminum alloy, a preparation method and application thereof, and overcomes the problems of insufficient performance improvement of single element addition, insufficient thermal stability of composite addition, conflict of heat treatment process and difficulty in balancing conductivity and strength in the prior art, and provides a preparation method of a conductive heat-resistant Al-Mg-Si-Sc-Zr-Hf-Sn alloy, improves the microstructure stability of the dispersion phase in a wide temperature range of 250-350 DEG C, avoids high-temperature degradation of the Zr shell layer, optimizes the precipitation of the beta '' phase and the dispersion phase, and simultaneously improves the conductivity and strength, and provides a preparation method with a wide process window and suitable for industrialization.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, and in particular to a conductive and heat-resistant aluminum alloy, its preparation method, and its application. Background Technology

[0002] Al-Mg-Si (6xxx series) aluminum alloys are widely used in structural components with high requirements for electrical and thermal conductivity, such as automotive conductive components, power electronic heat dissipation substrates, and rail transit conductive rails, due to their moderate strength, good electrical conductivity, and formability. With the development of new energy vehicles, 5G communications, and power semiconductor modules towards higher power density and higher integration, the operating temperature of components is constantly rising (IGBT modules can reach above 250℃ for extended periods), and the requirements for conductivity are becoming increasingly stringent (≥57% IACS). Traditional 6xxx series alloys are strengthened through the precipitation of the β″ phase (Mg5Si6), which can meet the strength requirements. However, under long-term service at temperatures above 150℃, the β″ phase coarsens rapidly, causing a sharp decrease in strength, which cannot meet the reliability requirements in a wider temperature range (250-350℃).

[0003] To improve heat resistance, the industry uses microalloying elements such as Sc and Zr to form Al3Sc or Al3(Sc,Zr) dispersed phases to pin grain boundaries and inhibit recrystallization. However, this system still suffers from bottlenecks such as insufficient high-temperature stability. Therefore, developing new aluminum alloys with excellent electrical conductivity, outstanding strength, and a wide heat resistance range has become an urgent need in this field.

[0004] The closest existing technology to this invention is the method of adding Sc and Zr to form a double-layer structure of Al3Sc core-Al3Zr shell dispersed phase. In Al-Mg-Si alloy, Sc and Zr are added. The nascent Al3(Sc,Zr) composite phase can significantly refine the grains. Then, through an appropriate homogenization heat treatment process, the precipitation of fine and dispersed secondary L12 structure Al3(Sc,Zr) composite phase is promoted. This phase is coherent with the aluminum matrix and can effectively pin dislocations and grain boundaries. It can increase the recrystallization temperature to 330-340℃, while improving the room temperature strength, hardness, ductility and toughness of the material, as well as the high temperature performance of the alloy.

[0005] There have been a few reports on Hf as a microalloying element in aluminum alloys, but these are mainly focused on Al-Si-Cu superalloys, where it forms the Al3Hf phase, which has anti-coarsening properties. However, some studies have found that after solution treatment at 470℃ for 1 h, the primary L12 structure Al3Hf in the 7075 alloy changes, transforming into D0. 22The presence of acicular phases indicates that this phase has poor resistance to coarsening (Effect of T6 heat treatment on microstructure and mechanical properties of Hf-modified Al7075 alloy fabricated by laser powder bed fusion[J]. MaterialsCharacterization, 2025.). Some scholars have also compared the effects of adding Zr and Hf in Al-Mg-Si alloys. Adding Hf alone did not significantly change the hardness, while adding Zr alone did not improve the hardness as much as adding Zr-Hf composite. In the Zr-Hf composite alloy, a large number of Al3(Zr,Hf) composite particles precipitated in the matrix, which significantly improved the alloy hardness. However, despite this, after long-term annealing at 500℃, the strength retention of the alloy with Zr added alone was better than that of the alloy with Zr-Hf composite. The authors believe that the Zr-Hf composite phase has poor stability and is prone to change at high temperatures, resulting in poor heat resistance of the material (V Wessely, U Töpfer, I Basu, et al. Dispersoid evolution in Al-Zn-Mg alloys by combined addition of Hf and Zr: A mechanistic approach[J]. Materials and Design, 2024,247: 113366.).

[0006] Existing literature reports (M Baruah, A Borah. Structure-property correlation of Al-Mg-Si alloys micro-alloyed with Sn[J]. International Journal of Metalcasting, 2022, 16:924–944.) that adding trace amounts of Sn (0.08wt%) to Al-Mg-Si alloys can form the Mg2(Si, Sn) phase, improving the alloy's strength, hardness, and elongation. Other studies have found (Ultrafast artificial aging of Al-Mg-Sialloys[J]. Scripta Materialia, 2016, 112:248-151.) that the mechanism by which trace amounts of Sn effectively improve the T6 hardness and strength of Al-Mg-Si alloys is that Sn atoms have high binding energy to vacancies, which can capture quenching vacancies, inhibit natural aging, and simultaneously act as nucleation sites to promote uniform nucleation of the β” phase in the early stages of artificial aging. However, the composite effect of Sn with Sc, Zr, and Hf has not been addressed in existing technologies.

[0007] The addition of a single Sc, Zr, or Hf has limited effect on improving the strength, toughness, and thermal stability of materials at room temperature. Once a single-component dispersed phase fails at high temperatures, the internal core has no subsequent protection, the entire dispersed phase structure collapses, and the heat resistance suffers irreversible loss.

[0008] Although the addition of Sc-Zr composites can form core-shell particles, after prolonged thermal exposure at temperatures above 350°C, Zr diffuses into the core, gradually diluting and degrading the shell. This causes the Al3Sc core to lose its protection and rapidly coarsen, resulting in a sharp decrease in pinning force. After high-temperature annealing following the addition of Zr-Hf composites, diffusion occurs due to the high enthalpy of Al3Hf and the poor stability of Hf atoms, leading to decreased thermal stability of the composite phase and the inability to maintain the alloy's high-temperature strength for extended periods.

[0009] The β” phase requires a relatively low temperature (≤180℃) and a long time to precipitate in order to maintain its fine dispersion, while the dispersed Al3(Sc,Zr) phase requires a higher temperature (about 300℃) to promote the full diffusion of Zr and form a complete shell. In the traditional two-stage aging process, the high-temperature stage will cause the β” phase to over-age and coarsen, reducing conductivity; the single-stage compromise results in insufficient aging of both phases, leading to insufficient strength or conductivity.

[0010] Traditional Al-Mg-Si alloys typically use Zr and Ti for grain refinement, but introducing too many Zr and Ti atoms can lead to a significant loss in conductivity. Excess Mg atoms also impair the conductivity of the material. This results in current technologies achieving a conductivity of only 56.5-56.8% IACS when the tensile strength is ≥220 MPa, failing to break through the 57% IACS threshold and making it difficult to meet the requirements of next-generation high-voltage connectors and heat dissipation substrates. Summary of the Invention

[0011] Therefore, the technical problem to be solved by this invention is to overcome the problems of insufficient performance improvement from single-element addition, insufficient thermal stability of composite addition, conflict of heat treatment processes, and difficulty in balancing conductivity and strength in the prior art. Thus, it provides a method for preparing conductive and heat-resistant Al-Mg-Si-Sc-Zr-Hf-Sn alloy, which improves the microstructure stability of the dispersed phase in a wide temperature range of 250-350℃ and avoids high-temperature degradation of the Zr shell; at the same time, it optimizes the precipitation of β” phase and dispersed phase, so as to synergistically improve conductivity and strength; and provides a preparation method with a wide process window and suitable for industrialization.

[0012] To solve the above-mentioned technical problems, the present invention provides a method for preparing a conductive and heat-resistant aluminum alloy, comprising the following steps: S11: Aluminum ingots (99.99%) are first melted at 720-750℃. After the aluminum ingots are completely melted, magnesium ingots (99.9%), aluminum-silicon (Al-20Si) alloy, aluminum-scandium (Al-2Sc) alloy, aluminum-zirconium (Al-10Zr) alloy, aluminum-hafnium (Al-5Hf) alloy, and aluminum-tin (Al-50Sn) alloy are added sequentially for a second melting process. After complete melting, the mixture is thoroughly stirred and kept at the temperature for 20-30 minutes. The process is carried out to ensure sufficient diffusion of alloying elements, ultimately yielding a liquid aluminum alloy. By weight percentage, the liquid aluminum alloy comprises 0.20%-0.38% Mg, 0.40%-0.65% Si, 0.06%-0.15% Sc, 0.04%-0.10% Zr, 0.03%-0.08% Hf, 0.01%-0.05% Sn, with the balance being Al and unavoidable impurities, not exceeding 0.06% Fe, and not exceeding 0. The composition is 0.02% Cu, no more than 0.03% Cr, and no more than 0.03% Mn; wherein the mass ratio of Mg to Si is 0.5 to 0.8, the mass ratio of the sum of Sc, Zr, and Hf to Zr is no less than 3.0, and the mass ratio of Hf to the sum of Sc and Zr is 0.15 to 0.50, i.e., Mg / Si = 0.5 to 0.8, (Sc+Zr+Hf) / Zr is no less than 3.0, and Hf / (Sc+Zr) = 0.15 to 0.50; S12: The aluminum alloy liquid is refined with hexachloroethane (C2Cl6) at 720-730℃. After refining, it is allowed to stand for 10-20 min, and then semi-continuous casting is carried out. The casting speed is 2-3 t / h, the cooling water temperature is 20-30℃, the billet temperature is 410-460℃, and the aluminum alloy ingot is obtained after complete solidification. S13: The aluminum alloy ingot is subjected to a three-stage homogenization heat treatment; the three-stage homogenization heat treatment method is as follows: holding at 280-320℃ for 8-12 h, holding at 380-420℃ for 8-12 h, and finally holding at 540-560℃ for 6-10 h. S14: The aluminum alloy ingot after the three-stage homogenization heat treatment in step S13 is subjected to hot extrusion, solution treatment and aging treatment in sequence to obtain the conductive and heat-resistant aluminum alloy.

[0013] Preferably, the intermediate alloy is an aluminum-silicon (Al-20Si) alloy, an aluminum-scandium (Al-2Sc) alloy, an aluminum-zirconium (Al-10Zr) alloy, an aluminum-hafnium (Al-5Hf) alloy, and an aluminum-tin (Al-50Sn) alloy.

[0014] Preferably, in step S11, the secondary melting method is as follows: add an aluminum-scandium (Al-2Sc) alloy and hold at 735-745℃ for 10-15 min, then add an aluminum-silicon (Al-20Si) and aluminum-zirconium (Al-10Zr) alloy and hold at 730-740℃ for 10-15 min, then add an aluminum-hafnium (Al-5Hf) alloy and hold at 725-735℃ for 10-15 min, and finally add a magnesium ingot (99.9%) and an aluminum-tin (Al-50Sn) alloy and hold at 720-730℃ for 15-30 min.

[0015] Preferably, the aluminum alloy liquid comprises 0.25%-0.35% Mg, 0.45%-0.58% Si, 0.08%-0.12% Sc, 0.05%-0.08% Zr, 0.04%-0.06% Hf, and 0.02%-0.04% Sn, with the balance being Al and unavoidable impurities, wherein Fe≤0.04%, Cu≤0.015%, Cr≤0.015%, and Mn≤0.015%.

[0016] Preferably, in step S12, the casting method is semi-continuous casting, and the temperature of the semi-continuous casting is 710-730℃. This temperature range can suppress abnormal grain growth, obtain a relatively uniform as-cast structure, reduce element segregation, lay the microstructure foundation for the uniform nucleation of β” precipitates during subsequent aging, reduce performance fluctuations during subsequent processing and heat treatment, and ensure the alloy's electrical conductivity and heat resistance.

[0017] Preferably, by weight percentage, the total amount of unavoidable impurities in the aluminum alloy ingot is no more than 0.1%, and the amount of a single element is no more than 0.03%. Controlling the impurity content can reduce the formation of harmful second phases by impurity elements, reduce the segregation of impurities at grain boundaries, and mitigate damage to electrical conductivity. At the same time, reducing the non-uniform precipitation induced by impurities is beneficial to the uniform dispersion of β” nano-precipitates, improving the stability of the alloy's aging structure, avoiding the deterioration of plasticity and heat resistance caused by impurities, and ensuring the stable and controllable electrical conductivity and heat resistance of the alloy.

[0018] Preferably, in step S13, the three-stage homogenization heat treatment method is as follows: holding at 300℃ for 10 h, holding at 400℃ for 10 h, and finally holding at 550℃ for 8 h.

[0019] In the three-stage homogenization heat treatment process, the first stage involves rapid diffusion of Sc, which preferentially nucleates Al3Sc. The second stage involves slower diffusion of Zr and Hf, which encapsulate the Al3Sc phase to form a shell structure, inhibiting Al3Sc coarsening and ultimately forming the stable Al3(Sc,Zr,Hf) phase. In the third stage, the Mg- and Si-rich dendrites formed during solidification undergo complete re-dissolution. The low-temperature stage completes the nucleation and growth of the stable Al3(Sc,Zr,Hf) phase, while the high-temperature stage eliminates Mg and Si atomic segregation and removes the damage to strength and toughness caused by dendrites.

[0020] Preferably, in step S14, the hot extrusion method is as follows: extrusion is performed at 450-485℃ and a speed of 0.5-2.5 m / min, the extrusion ratio is 25-50, and the extrusion outlet temperature is 475-495℃.

[0021] Further, in step S14, the hot extrusion method is as follows: extrusion is performed at 460-475℃ and a speed of 0.8-2 m / min, the extrusion ratio is 35-45, and the extrusion outlet temperature is 480-490℃.

[0022] Preferably, in step S14, the solution treatment method is as follows: after holding at 525-540℃ for 3-5 hours, cool to room temperature (20-30℃) at a rate of not less than 80℃ / s.

[0023] Further, in step S14, the solution treatment method is as follows: after holding at 535℃ for 4 hours, cool to room temperature at a rate of not less than 100℃ / s. This allows the MgSi phase precipitated during the homogenization heat treatment cooling process and the extrusion process to be fully dissolved again, obtaining a supersaturated solid solution, which prepares for the precipitation during the aging stage.

[0024] Preferably, in step S14, the aging treatment method is as follows: keep at 150-170℃ for 12-20 h and then cool to room temperature (20-30℃).

[0025] Further, in step S14, the aging treatment method is as follows: heat treatment at 160℃ for 16 h followed by air cooling to room temperature. The aging treatment allows the Mg and Si atoms dissolved in the matrix to fully desolve and precipitate. Furthermore, the addition of Sn atoms captures vacancies, creating natural sites for the nucleation of the β” phase, and to some extent reduces the solid solubility of Mg and Si elements, accelerating the desolvation rate and nucleation quantity of the β” phase, while inhibiting the coarsening of the β” phase. The process flow diagram is as follows: Figure 2 As shown.

[0026] The present invention also provides a conductive and heat-resistant aluminum alloy prepared by the above preparation method.

[0027] The present invention also provides an automotive conductive component, which is prepared using the above-mentioned conductive and heat-resistant aluminum alloy.

[0028] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: The composition system of this invention adopts a quaternary composite microalloying system of Sc-Zr-Hf-Sn, especially the introduction of Hf and the addition of Sn, and the ratio of the three (Sc, Zr, Hf) to Zr (Sc+Zr+Hf) / Zr is not less than 3.0 and Hf / (Sc+Zr) = 0.15 to 0.50. At the same time, the Mg content is reduced to improve the conductivity of the alloy.

[0029] In this invention, the core-shell structure of the dispersed phase, consisting of an Al3Sc core and an Al3ZrHf outer shell, increases the thermal stability of the core. The Al3ZrHf outer shell inhibits the coarsening of the Al3Sc phase under high-temperature conditions such as homogenization heat treatment and solution treatment, and has a stronger pinning effect on grain boundaries and dislocation migration. Simultaneously, it ensures the thermal stability of the material over a wide temperature range, maintaining its integrity even after 350℃ / 100 h. A stepwise temperature control method is employed: the first stage (280-320℃ / (8-12)h, preferential nucleation of Al3Sc); the second stage (380-420℃ / (8-12)h, Zr and Hf atoms encapsulating the Al3Sc phase to form a shell structure); and the third stage (540-560℃ / (6-10)h, full dissolution of Mg-rich and Si dendrites formed during solidification). This method optimizes the stable core-shell structure of the dispersed phase.

[0030] In this invention, the mold exit temperature is 475-495℃, combined with an extrusion ratio ≥35 (strain energy ≥3.5).

[0031] In this invention, the comprehensive performance indicators are: conductivity ≥57%IACS, tensile strength ≥220 MPa, elongation ≥14%, and strength retention ≥88% after heat exposure of 250-350℃ / 100 h. Attached Figure Description

[0032] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0033] Figure 1 These are transmission electron microscope (TEM) images of the morphology of the dispersed phase precipitated at different homogenization heat treatment stages in Embodiment 1 of the present invention, wherein (a) the morphology of the dispersed phase after the first two homogenization heat treatment stages; and (b) the morphology of the dispersed phase after the three-stage homogenization heat treatment. Figure 2 This is a schematic diagram of the process route of the present invention; Figure 3 These are optical microscope (OM) images of the microstructure after aging treatment in Embodiment 1 of the present invention, wherein (a) is a micrometer-scale second phase morphology image; and (b) is a grain morphology image. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0035] Example 1: Preparation method of conductive and heat-resistant aluminum alloy (1) The aluminum ingot (99.99%) is smelted at 730°C under normal atmospheric pressure until the aluminum ingot is completely melted; (2) During the second melting process, the temperature was raised to 740℃ and aluminum-scandium (Al-2Sc) alloy was added and held for 15 min; the temperature was lowered to 735℃ and aluminum-silicon (Al-20Si) and aluminum-zirconium (Al-10Zr) alloy were added and held for 10 min; the temperature was lowered to 730℃ and aluminum-hafnium (Al-5Hf) alloy was added and held for 10 min; the temperature was lowered to 725℃ and magnesium ingot (99.9%) and aluminum-tin (Al-50Sn) alloy were added and held for 20 min, and then stirred thoroughly; hexachloroethane (C2Cl6) was used for refining, and after refining, the slag was removed and the mixture was allowed to stand for 20 min to obtain aluminum alloy liquid; By weight percentage, the aluminum alloy liquid is controlled to contain 0.30% Mg, 0.55% Si, 0.10% Sc, 0.06% Zr, 0.05% Hf, and 0.03% Sn, with the balance being Al and unavoidable impurities, satisfying Fe≤0.04%, Cu≤0.015%, Cr≤0.015%, and Mn≤0.015%; the ratio is Mg / Si=0.545; (Sc+Zr+Hf) / Zr=3.50; Hf / (Sc+Zr)=0.312.

[0036] (3) The aluminum alloy liquid was semi-continuously cast at 720℃, the crystallizing wheel casting speed was 2.5 t / h, the cooling water temperature was 22-25℃, and the billet temperature was 420-440℃, to obtain an aluminum alloy ingot with a diameter of 150 mm. (4) The aluminum alloy ingot is subjected to a three-stage homogenization heat treatment. The three-stage homogenization heat treatment method is: 300℃ for 10 h, 400℃ for 10 h, and finally 550℃ for 8 h. (5) Hot extrusion is performed on the aluminum alloy ingot after three-stage homogenization heat treatment at 470℃ and 1.5 m / min. The extrusion ratio is 35:1, the exit temperature of the extrusion die is 485℃, and the finished product is a round aluminum rod with a diameter of Φ12.5 mm.

[0037] (6) The hot-extruded aluminum alloy is subjected to solution treatment, held at 535℃ for 4 h and then cooled to 25℃ at a rate of 120℃ / s.

[0038] (7) The aluminum alloy after solution treatment is subjected to aging treatment, held at 160℃ for 16 h and then cooled to 25℃ to obtain the final conductive and heat-resistant aluminum alloy (T6 state alloy).

[0039] The test results of the conductive and heat-resistant aluminum alloy in Example 1 are as follows: conductivity 57.4% IACS (using a double-arm bridge, referring to GB / T 3048.2-2007 Electrical properties test methods for wires and cables - Part 2: Resistivity test of metallic conductor materials), tensile strength 223 MPa, elongation 15.5% (using a universal testing machine, referring to GB / T 208.1-2021 Metallic materials - Tensile testing - Part 1: Room temperature test method); after heat exposure of 250℃ / 100 h, the tensile strength retention rate is 96.0%, 92.8% at 300℃ / 100 h, and 88.8% at 350℃ / 100 h (using a universal testing machine, referring to GB / T 208.1-2021 Metallic materials - Tensile testing - Part 1: Room temperature test method).

[0040] Example 2: Preparation method of conductive and heat-resistant aluminum alloy The method is the same as in Example 1, except that: by weight percentage, the aluminum alloy liquid is controlled to contain 0.28% Mg, 0.52% Si, 0.07% Sc, 0.05% Zr, 0.04% Hf, 0.025% Sn, with the balance being Al and unavoidable impurities, and Fe≤0.04%, Cu≤0.015%, Cr≤0.015%, Mn≤0.015%.

[0041] The test results of the conductive and heat-resistant aluminum alloy in Example 2 are as follows: conductivity 57.8% IACS, tensile strength 220MPa, elongation 17%, and strength retention rate 88.0% after heat exposure of 350℃ / 100 h.

[0042] Example 3: Preparation method of conductive and heat-resistant aluminum alloy The method is the same as in Example 1, except that: by weight percentage, the aluminum alloy liquid is controlled to contain 0.32% Mg, 0.58% Si, 0.12% Sc, 0.08% Zr, 0.07% Hf, 0.035% Sn, with the balance being Al and unavoidable impurities, and Fe≤0.04%, Cu≤0.015%, Cr≤0.015%, Mn≤0.015%.

[0043] The test results of the conductive and heat-resistant aluminum alloy in Example 3 are as follows: conductivity 57.0% IACS, tensile strength 228MPa, elongation 15%, and strength retention rate 88.2% after heat exposure of 350℃ / 100h.

[0044] Comparative Example 1: Preparation method of general aluminum alloy The method is the same as in Example 1, except that the aluminum alloy liquid does not contain Hf and Sn.

[0045] The test results of the aluminum alloy in Comparative Example 1 were as follows: conductivity 56.8% IACS, tensile strength 200 MPa, elongation 20.5%, dispersion phase coarsening after heat exposure of 350℃ / 100 h, strength retention rate of only 82.2%, and low amount of β” phase precipitation and coarsening during aging.

[0046] Comparative Example 2: Preparation Method of General Aluminum Alloys The method is the same as in Example 1, except that the aluminum alloy liquid does not contain Sn.

[0047] The test results of the aluminum alloy in Comparative Example 2 were as follows: conductivity 56.5% IACS, tensile strength 198 MPa, elongation 19%, heat exposure at 350℃ / 100 h retention rate 89.0%, and low amount of β” phase precipitation with coarsening.

[0048] Comparative Example 3: Preparation Method of General Aluminum Alloys The method is the same as in Example 1, except that the aluminum alloy liquid does not contain Hf.

[0049] The test results of the aluminum alloy in Comparative Example 3 were as follows: conductivity 57.0% IACS, tensile strength 210 MPa, elongation 14.5%, and after heat exposure of 350℃ / 100 h, the dispersed phase was significantly coarsened, with a retention rate of only 81.0%.

[0050] Comparative Example 4: Preparation Methods of Common Aluminum Alloys The method is the same as in Example 1, except that: by weight percentage, Sc is 0.10%, Zr is 0.10%, and Hf is 0.02% in the aluminum alloy liquid, and Hf / (Sc+Zr)=0.10 is calculated.

[0051] The test results of the aluminum alloy in Comparative Example 4 were as follows: conductivity 56.9% IACS, tensile strength 218 MPa, elongation 15%, and after heat exposure of 350℃ / 100 h, the dispersed phase was coarsened compared with Example 1, and the strength retention rate was 84.5%.

[0052] Comparative Example 5: Preparation Method of General Aluminum Alloys The method is the same as in Example 1, except that the homogenization heat treatment is a single-stage 550℃ / 8 h.

[0053] The test results of the aluminum alloy in Comparative Example 5 were as follows: conductivity 57.2% IACS, tensile strength 208 MPa, elongation 17%. The number of secondary dispersed phases after homogenization heat treatment was significantly lower than that of the three-stage homogenization heat treatment sample. Only a small number of large-sized dispersed phases were found in the matrix. The strength retention rate after heat exposure of 350℃ / 100 h was 75.0%.

[0054] Effect evaluation: The data in Table 1 show that the difference between Example 1 and Comparative Example 3 lies in the strength retention rate under heat exposure, indicating that Hf can effectively suppress the coarsening of the dispersed phase during the high-temperature homogenization stage and the heat exposure process, thus improving the material's heat resistance. The difference between Example 1 and Comparative Example 2 indicates that Sn mainly plays a role during the aging stage, promoting the nucleation and precipitation of the MgSi phase, increasing the precipitation density of the nano-precipitated phase and suppressing coarsening, thereby improving the material's strength and increasing its conductivity. The significant difference in heat resistance between the materials in Example 1 and Comparative Example 5 suggests that although the alloy composition is similar, the three-stage homogenization heat treatment more effectively promotes the formation of a heat-resistant dispersed phase within the matrix, while a simple single-stage high-temperature homogenization heat treatment is not conducive to the diffusion of Sc, Zr, and Hf elements to form a fine Al3X phase.

[0055] The T6 alloy obtained in Example 1 has the following microstructure characteristics: large-sized MgSi phases within the grains are fully dissolved, with only a small amount of extruded and broken Fe-rich phase remaining; the grains tend to be flattened and elongated fibrous structures; the degree of recrystallization is low; and the microstructure characteristics are as follows: Figure 3 As shown, the core-shell structure of Al3Sc core and Al3ZrHf shell exhibits uniform and fine dispersion of the dispersed phase and β” phase.

[0056] Table 1. Experimental test data for the examples and comparative examples

[0057] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a conductive and heat-resistant aluminum alloy, characterized in that, Includes the following steps: S11: After a primary smelting of aluminum ingots at 720-750℃, magnesium ingots and a master alloy are added for a secondary smelting to obtain a liquid aluminum alloy; by weight percentage, the liquid aluminum alloy comprises 0.20%-0.38% Mg, 0.40%-0.65% Si, 0.06%-0.15% Sc, 0.04%-0.10% Zr, 0.03%-0.08% Hf, and 0.01%- The composition consists of 0.05% Sn, no more than 0.06% Fe, no more than 0.02% Cu, no more than 0.03% Cr, and no more than 0.03% Mn, with the balance being Al and unavoidable impurities; wherein the mass ratio of Mg to Si is 0.5 to 0.8, the mass ratio of the sum of Sc, Zr, and Hf to Zr is not less than 3.0, and the mass ratio of Hf to the sum of Sc and Zr is 0.15 to 0.

50. S12: The aluminum alloy liquid is refined and semi-continuously cast at 720-730℃ to obtain an aluminum alloy ingot; S13: The aluminum alloy ingot is subjected to a three-stage homogenization heat treatment; the three-stage homogenization heat treatment method is as follows: holding at 280-320℃ for 8-12 h, holding at 380-420℃ for 8-12 h, and finally holding at 540-560℃ for 6-10 h. S14: The aluminum alloy ingot after the three-stage homogenization heat treatment in step S13 is subjected to hot extrusion, solution treatment and aging treatment in sequence to obtain the conductive and heat-resistant aluminum alloy.

2. The preparation method according to claim 1, characterized in that: The intermediate alloys include aluminum-silicon alloys, aluminum-scandium alloys, aluminum-zirconium alloys, aluminum-hafnium alloys, and aluminum-tin alloys.

3. The preparation method according to claim 2, characterized in that: In step S11, the secondary melting method is as follows: add aluminum-scandium alloy and hold at 735-745℃ for 10-15 min, then add aluminum-silicon alloy and aluminum-zirconium alloy and hold at 730-740℃ for 10-15 min, then add aluminum-hafnium alloy and hold at 725-735℃ for 10-15 min, and finally add magnesium ingot and aluminum-tin alloy and hold at 720-730℃ for 15-30 min.

4. The preparation method according to claim 1, characterized in that: In step S12, the casting method is semi-continuous casting, the casting temperature is 710-730℃, the casting speed is 2-3t / h, the cooling water temperature is 20-30℃, and the billet temperature is 410-460℃.

5. The preparation method according to claim 1, characterized in that: By weight percentage, the total amount of unavoidable impurities in the aluminum alloy billet is no more than 0.1%, and the mass of any single element among the unavoidable impurities is no more than 0.03%.

6. The preparation method according to claim 1, characterized in that: In step S14, the hot extrusion method is as follows: extrusion is performed at 450-485℃ and a speed of 0.5-2.5 m / min, with an extrusion ratio of 25-50 and an extrusion outlet temperature of 475-495℃.

7. The preparation method according to claim 1, characterized in that: In step S14, the solution treatment method is as follows: after holding at 525-540℃ for 3-5 hours, cool to room temperature at a rate of not less than 80℃ / s.

8. The preparation method according to claim 1, characterized in that: In step S14, the aging treatment method is as follows: keep at 150-170℃ for 12-20 h and then cool to room temperature.

9. A conductive and heat-resistant aluminum alloy prepared by the preparation method according to any one of claims 1-8.

10. A conductive component for automobiles, characterized in that, It is prepared using the conductive and heat-resistant aluminum alloy described in claim 9.

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