Al-Bi alloy and preparation method and application thereof

Abstract

The invention belongs to the technical field of aluminum alloy material design and preparation, and particularly relates to an Al-Bi alloy and a preparation method and application thereof. The aluminum alloy material comprises the following components in percentage by weight: 0.5%-3.5% of Bi, 0.02%-0.3% of Si, 0.05%-1% of Fe, less than or equal to 0.05% of impurities and the balance of aluminum, the content of the iron is greater than that of the silicon. The solid solubility of Bi in aluminum is extremely low and is as low as 1t at room temperature; in the solidification process, most Bi is separated out in a pure metal eutectic phase mode, the scattering effect of Bi on lattice electrons is small, and then it is guaranteed that the conductivity of the alloy is maintained at the high level; meanwhile, Bi can be used as a strengthening phase of an Al matrix, and through cold deformation, the hardness of the Al-Bi alloy is higher than that of pure Al, so that the Al-Bi alloy has high conductivity and high strength at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy material design and preparation, and particularly relates to an Al-Bi alloy, a preparation method thereof, and an application thereof. Background Art

[0002] With the rapid development of fields such as power transmission, new energy equipment, and electronic devices, the requirements for the performance of wire materials are increasing day by day. Traditional wire materials are mainly pure aluminum or aluminum alloys. Their light weight, high electrical conductivity, and low cost make them the first choice for power transmission. However, the tensile strength of pure aluminum is relatively low, usually <100 MPa, and it is prone to creep under high temperature or long-term stress, resulting in the risk of wire sagging or breaking, seriously restricting its application in high-voltage power transmission or complex working conditions.

[0003] To improve the strength of aluminum-based wires, precipitation strengthening is mainly achieved by adding alloying elements in the prior art. For example, 6xxx series aluminum-magnesium-silicon alloys (common grades include: 6061, 6063, 6082, etc.) generate Mg2Si precipitation phases through aging treatment, and the tensile strength can be increased to more than 300 MPa. However, the electrical conductivity of such alloys decreases significantly, usually less than 50% IACS (International Annealing Copper Standard, which also represents the international annealing copper standard), resulting in an increase in power transmission loss. At the same time, some high-strength aluminum alloys rely on complex heat treatment processes or nanoparticle doping technologies, resulting in a significant increase in production costs and making large-scale application difficult to achieve.

[0004] The Al-Bi alloy is a special aluminum alloy that contains two main elements, aluminum (Al) and bismuth (Bi). The element composition and content in the Al-Bi alloy directly affect the alloy performance. The Bi content in existing alloys is relatively high, usually >10%, and it is mainly used for wear-resistant materials; but due to the high Bi content, the segregation of Bi is serious during the casting process, and the electrical conductivity is reduced significantly, making it difficult to be used for the preparation of aluminum alloy wires. In addition, although the prior art discloses that the chemical composition and weight percentage are: Si: 0. {12}-0. {34}%, Fe: 0. {2}-0. {4}%, Cu: 0. {05}-0. {2}%, Mg: 0. {3}-0. {42}%, Bi: 0. {03}-0. {1}%, Sr: 0. {06}-0. {25}%, B: 0. {01}-0. {05}%, Mn+Ti+Cr+V≤0. {01}%, and the balance is Al. An aluminum alloy single wire is made through the process steps of smelting, degassing, casting, rolling, and wire drawing. However, this alloy uses Mg and Si as the main strengthening elements, that is, an aluminum-magnesium-silicon alloy, and the electrical conductivity is reduced significantly while the strength is improved. Summary of the Invention

[0005] To address the above problems, the present application designs the composition of the Al-Bi alloy reasonably, controls it within a range that is easy to cast and has little impact on electrical conductivity, aiming to prepare a high-strength and high-conductivity aluminum alloy wire material. Therefore, the objective of the present invention is to provide an Al-Bi alloy and its preparation method and application, so as to overcome the deficiencies of the prior art. The present application uses Bi as the main alloying and strengthening element, and improves the mechanical properties of the alloy while achieving high electrical conductivity by preparing the Al-Bi alloy conductive material, in order to reduce power transmission losses.

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

[0007] In the first aspect, the present invention provides an Al-Bi alloy, which is composed of the following components by weight percentage: Bi 0.5%-3.5%, Si 0.02%-0.3%, Fe 0.05%-1%, the total amount of impurities ≤0.05%, and the balance is aluminum; the content of iron is greater than that of silicon.

[0008] By controlling the content of Fe to be greater than that of Si, Fe, Si and Al combine to form the AlFeSi ternary phase, which serves as the strengthening component of the alloy and synergistically improves the strength with Bi. At the same time, the solid solubility of Fe and Si in aluminum is reduced, alleviating the impact on electrical conductivity.

[0009] In some other embodiments, it is composed of the following components by weight percentage: Bi 0.5%-3.0%, Si 0.02%-0.05%, Fe 0.06%-0.09%, the total amount of impurities ≤0.05%, and the balance is aluminum.

[0010] In some other embodiments, it is composed of the following components by weight percentage: Bi 3.0%, Si 0.05%, Fe 0.08%, the total amount of impurities ≤0.05%, and the balance is aluminum. The Al-Bi alloy within this range has both high electrical conductivity and mechanical properties.

[0011] In some other embodiments, the impurities are Mn, Cr, V and Ti, and the content of a single impurity ≤0.01%. Mn, Cr, V and Ti are the main impurity elements affecting electrical conductivity. Therefore, strict control is required, and the content of a single impurity and the total impurity content within this range have the least impact on the electrical conductivity of the alloy.

[0012] In some other embodiments, the solid solubility of Bi in aluminum in the Al-Bi alloy is <0.01wt% at room temperature. During the solidification process, Bi precipitates in the form of a pure metal phase, forming a dispersed particle distribution in the aluminum matrix.

[0013] In the second aspect, the present invention provides a preparation method for the Al-Bi alloy described in the first aspect, including the following steps:

[0014] Melt pure aluminum ingots, then add pure Bi, pure Si and Al-20Fe master alloy for smelting and melt insulation, then conduct melt refining. After degassing, slag removal and static heat preservation, an Al-Bi alloy is obtained by casting. This preparation method is simple to operate and can accurately control the ratio of raw materials.

[0015] In some other embodiments, the melting temperature of the pure aluminum ingot is 700°C - 800°C;

[0016] The melt insulation time is 5 min - 30 min;

[0017] The melt refining is carried out by using 0.55 - 0.65% of C2Cl6 for melt refining; C2Cl6 has significant advantages in dehydrogenation, impurity removal and grain refinement as a melt refining agent.

[0018] The static heat preservation time is 20 - 30 min;

[0019] Preferably, the melting temperature of the pure aluminum ingot is 750°C;

[0020] The melt insulation time is 20 min;

[0021] The melt refining is carried out by using 0.60% of C2Cl6 for melt refining;

[0022] The static heat preservation time is 30 min.

[0023] In some other embodiments, the purity of the pure aluminum ingot is ≥99.9%;

[0024] The purity of the pure Bi is ≥99.9%;

[0025] The purity of the pure Si is ≥99.9%;

[0026] The impurity content of the Al-20Fe is ≤0.1%.

[0027] Among them, Bi is the main strengthening element, and Si and Fe play an auxiliary strengthening role. As the strengthening components of the alloy, they cooperate with Bi to improve the strength, and at the same time reduce the solid solubility of Fe and Si in aluminum, reducing the impact on the electrical conductivity.

[0028] In the third aspect, the present invention provides the application of the Al-Bi alloy described in the first aspect in power transmission, new energy equipment and electronic devices.

[0029] In the fourth aspect, the present invention provides an aluminum alloy wire using the Al-Bi alloy described in the first aspect.

[0030] The beneficial effects of the present invention:

[0031] (1) The present invention creatively uses Bi as the main alloying element. Since the solid solubility of Bi in aluminum is extremely low, <0.01wt% at room temperature according to the phase diagram, most of the Bi precipitates in the form of a pure metal eutectic phase during solidification, which has a small scattering effect on lattice electrons, thereby ensuring that the conductivity of the alloy is maintained at a high level. At the same time, Bi can serve as a strengthening phase of the Al matrix. After cold deformation, the hardness of the Al-Bi alloy is higher than that of pure Al, so that the Al-Bi alloy achieves high strength while having high conductivity.

[0032] (2) Both Fe and Si in the present invention reduce electrical conductivity and contribute to alloy strength. To minimize their impact on electrical conductivity, the present invention controls Fe>Si, allowing them to combine with Al to form an AlFeSi ternary phase, which acts as a strengthening component of the alloy and synergistically improves strength with Bi. This also reduces the solid solubility of Fe and Si in aluminum, mitigating their impact on electrical conductivity. DETAILED DESCRIPTION

[0033] Those skilled in the art will appreciate that the following examples are intended to illustrate the present invention only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the examples were performed under conventional conditions or manufacturer's recommended conditions. Components used without manufacturer's indication are commercially available conventional products.

[0034] To address the problem in the prior art that lattice distortion generated during the strengthening of aluminum wire alloys can improve strength but exacerbate electron scattering, leading to a significant decrease in conductivity, the present invention provides an Al-Bi alloy. The solid solubility of Bi in aluminum is extremely low. During solidification, most of the Bi precipitates in the form of a pure metal phase, forming dispersed particles distributed in the aluminum matrix, achieving dispersion strengthening. The scattering effect of the alloy on the lattice electrons is relatively small, thereby ensuring that its conductivity is maintained at a high level.

[0035] Example 1

[0036] The invention discloses a preparation method of an Al-Bi alloy. The invention uses pure Al, pure Bi, pure Si and an Al-20Fe master alloy as raw materials, and mixes the raw materials according to a target alloy composition of Al-0.5Bi-0.05Si-0.08Fe (the target alloy composition, in weight percentage, consists of the following components: Bi 0.5%, Si 0.05%, Fe 0.08%, total impurity amount ≤0.05%, and the balance being aluminum). An industrial pure aluminum ingot is melted and heated to 750°C, pure Bi, pure Si and the Al-20Fe master alloy are added, fully stirred and kept warm for 20 minutes, melt refined with 0.6% C2Cl6, degassed and deslagging, and kept warm for 30 minutes. The melt is then poured into an iron mold and cast into a shape.

[0037] The Al-Bi alloy is cold-rolled with a cold rolling deformation of 50% to increase the matrix dislocation density and produce dislocation strengthening.

[0038] Example 2

[0039] A preparation method of an Al-Bi alloy uses pure Al, pure Bi, pure Si, and an Al-20Fe master alloy as raw materials. The raw material ratio is based on the target alloy composition Al-3Bi-0.05Si-0.08Fe (the target alloy composition, by weight percentage, consists of the following components: Bi 3%, Si 0.05%, Fe 0.08%, the total amount of impurities ≤ 0.05%, and the balance is aluminum).

[0040] The industrial pure aluminum ingot is melted and heated to 750 °C, pure Bi, pure Si, and the Al-20Fe master alloy are added, stirred thoroughly and held for 20 min, 0.6% of C2Cl6 is used for melt refining, degassing and slag removal, statically held for 30 min, and then the melt is poured into an iron mold and cast into shape.

[0041] The Al-Bi alloy is cold-rolled with a cold rolling deformation of 50% to increase the matrix dislocation density and produce dislocation strengthening.

[0042] Example 3

[0043] A preparation method of an Al-Bi alloy uses pure Al, pure Bi, pure Si, and an Al-20Fe master alloy as raw materials. The raw material ratio is based on the target alloy composition Al-3.5Bi-0.05Si-0.08Fe (the target alloy composition, by weight percentage, consists of the following components: Bi 3.5%, Si 0.05%, Fe 0.08%, the total amount of impurities ≤ 0.05%, and the balance is aluminum).

[0044] The industrial pure aluminum ingot is melted and heated to 750 °C, pure Bi, pure Si, and the Al-20Fe master alloy are added, stirred thoroughly and held for 20 min, 0.6% of C2Cl6 is used for melt refining, degassing and slag removal, statically held for 30 min, and then the melt is poured into an iron mold and cast into shape.

[0045] The Al-Bi alloy is cold-rolled with a cold rolling deformation of 50% to increase the matrix dislocation density and produce dislocation strengthening.

[0046] Example 4

[0047] A preparation method of Al-Bi alloy uses pure Al, pure Bi, pure Si and Al-20Fe master alloy as raw materials, and performs raw material proportioning according to the target alloy composition Al-1Bi-0.05Si-0.08Fe (the target alloy composition, by weight percentage, consists of the following components: Bi 1%, Si 0.05%, Fe 0.08%, the total amount of impurities ≤ 0.05%, and the balance is aluminum).

[0048] Melt and heat the industrial pure aluminum ingot to 750 °C, add pure Bi, pure Si and Al-20Fe master alloy, stir well and keep warm for 20 min, use 0.6% of C2Cl6 for melt refining, degas and remove slag, stand and keep warm for 30 min, and then pour the melt into an iron mold and cast it into shape.

[0049] Cold-roll the Al-Bi alloy, and the cold-rolling deformation is 50% to increase the matrix dislocation density and generate dislocation strengthening.

[0050] Comparative Example 1

[0051] Use pure Al, pure Si and Al-20Fe master alloy as raw materials, and perform raw material proportioning according to the target alloy composition Al-0.05Si-0.08Fe (the target alloy composition, by weight percentage, consists of the following components: Si 0.05%, Fe 0.08%, the total amount of impurities ≤ 0.05%, and the balance is aluminum).

[0052] Melt and heat the pure aluminum ingot to 750 °C, add pure Si and Al-20Fe master alloy, stir well and keep warm for 20 min, use 0.6% of C2Cl6 for melt refining, degas and remove slag, stand and keep warm for 30 min, and then pour the melt into an iron mold and cast it into shape.

[0053] Cold-roll the alloy, and the cold-rolling deformation is 50% to increase the matrix dislocation density and generate dislocation strengthening.

[0054] Comparative Example 2

[0055] A preparation method of Al-Bi alloy uses pure Al, pure Bi, pure Si and Al-20Fe master alloy as raw materials, and performs raw material proportioning according to the target alloy composition Al-10Bi-0.05Si-0.08Fe (the target alloy composition, by weight percentage, consists of the following components: Bi 10%, Si 0.05%, Fe 0.08%, the total amount of impurities ≤ 0.05%, and the balance is aluminum).

[0056] The industrial pure aluminum ingot is melted and heated to 750 °C, pure Bi, pure Si and Al-20Fe master alloy are added, stirred thoroughly and held for 20 min, the melt is refined with 0.6% C2Cl6 for degassing and slag removal, then held statically for 30 min, and then the melt is poured into an iron mold for casting and forming.

[0057] The Al-Bi alloy is cold-rolled with a cold rolling deformation of 50% to increase the matrix dislocation density and produce dislocation strengthening.

[0058] Comparative Example 3

[0059] A preparation method of an Al-Bi alloy uses pure Al, pure Bi, pure Si and Al-20Fe master alloy as raw materials, and the raw material ratio is carried out according to the target alloy composition Al-0.1Bi-0.05Si-0.08Fe (the target alloy composition, by weight percentage, consists of the following components: Bi 0.1%, Si 0.05%, Fe 0.08%, the total amount of impurities ≤ 0.05%, and the balance is aluminum).

[0060] The industrial pure aluminum ingot is melted and heated to 750 °C, pure Bi, pure Si and Al-20Fe master alloy are added, stirred thoroughly and held for 20 min, the melt is refined with 0.6% C2Cl6 for degassing and slag removal, then held statically for 30 min, and then the melt is poured into an iron mold for casting and forming.

[0061] The Al-Bi alloy is cold-rolled with a cold rolling deformation of 50% to increase the matrix dislocation density and produce dislocation strengthening.

[0062] Comparative Example 4

[0063] A preparation method of an Al-Bi alloy uses pure Al, pure Bi, pure Si, pure Ce and Al-20Fe master alloy as raw materials, and the raw material ratio is carried out according to the target alloy composition Al-0.1Bi-0.05Si-3.0Ce-0.08Fe (the target alloy composition, by weight percentage, consists of the following components: Bi 0.1%, Si 0.05%, Ce 3.0%, Fe 0.08%, the total amount of impurities ≤ 0.05%, and the balance is aluminum).

[0064] The industrial pure aluminum ingot is melted and heated to 750 °C, pure Bi, pure Si, pure Ce and Al-20Fe master alloy are added, stirred thoroughly and held for 20 min, the melt is refined with 0.6% C2Cl6 for degassing and slag removal, then held statically for 30 min, and then the melt is poured into an iron mold for casting and forming.

[0065] The Al-Bi alloy is cold-rolled with a cold rolling deformation of 50% to increase the matrix dislocation density and produce dislocation strengthening.

[0066] Performance Test

[0067] 1. Mechanical Property Test

[0068] The above-prepared alloy was subjected to mechanical property tests. Among them, the micro-Vickers hardness test was carried out with reference to the standard of GB / T4340.1-2024; the test of tensile mechanical properties (tensile strength and elongation) was carried out with reference to the standard of GB / T228.1-2021, and the test results are shown in Table 1.

[0069] It can be seen from the test results that with the increase of Bi content, the hardness and strength of the prepared alloy are significantly improved. When the Bi content is 3% (Example 2), the hardness can reach 39.7HV and the tensile strength reaches 127.7MPa. This shows that Bi is an effective strengthening phase, which can promote the generation of dislocations in the Al matrix during the cold rolling process, thereby improving the strength of the Al matrix.

[0070] 2. Electrical Conductivity

[0071] The above-prepared alloy was subjected to electrical conductivity tests, and the test was carried out with reference to the standard of GB / T 12966-2022. The test results are shown in Table 1.

[0072] It can be seen from the test results that with the increase of Bi content, the electrical conductivity of the prepared alloy decreases very little, or even does not decrease. When the Bi content is 3% (Example 2), the electrical conductivity is 61.4% IACS, while the electrical conductivity of pure Al without Bi (Comparative Example 1) is 60.6% IACS, slightly lower than that of the alloy containing 3% Bi (Example 2). This shows that the addition of Bi element has minimal damage to the electrical conductivity of the Al matrix.

[0073] The performances of the examples and comparative examples of this application are shown in Table 1.

[0074] Table 1 Performances of Examples and Comparative Examples

[0075] Serial number Hardness / HV Tensile strength / MPa Elongation / % Conductivity / % IACS Example 1 27.4 92.6 18.4 60.1 Example 2 39.7 127.7 12.2 61.4 Example 3 40.2 130.2 10.7 58.3 Example 4 27.9 95.6 15.2 59.7 Comparative example 1 26.3 84.0 24.3 60.6 Comparative example 2 46.8 158.3 5.2 55.6 Comparative example 3 26.6 87.4 22.7 58.1 Comparative example 4 42.1 147.1 6.8 52.1

[0076] It can be known from the comparison of the results of the mechanical properties and electrical conductivity of the implementation cases and comparative examples that after adding Bi, the hardness of the alloy is significantly improved, while the electrical conductivity hardly decreases. This shows that the goal of high strength and high electrical conductivity can be achieved by introducing Bi element.

[0077] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An Al-Bi alloy, characterized in that, By weight percentage, it consists of the following components: Bi 0.5% - 3.5%, Si 0.02% - 0.3%, Fe 0.05% - 1%, total impurities ≤ 0.05%, and the balance is aluminum; The content of the iron is greater than that of the silicon.

2. The Al-Bi alloy according to claim 1, characterized in that, By weight percentage, it consists of the following components: Bi 0.5% - 3.0%, Si 0.02% - 0.05%, Fe 0.06% - 0.09%, total impurities ≤ 0.05%, and the balance is aluminum.

3. The Al-Bi alloy according to claim 1, characterized in that, By weight percentage, it consists of the following components: Bi 3.0%, Si 0.05%, Fe 0.08%, total impurities ≤ 0.05%, and the balance is aluminum.

4. The Al-Bi alloy according to claim 1, characterized in that, The impurities are Mn, Cr, V, and Ti, and the content of a single impurity ≤ 0.01%.

5. The Al-Bi alloy according to claim 1, characterized in that, In the Al - Bi alloy, the solid solubility of Bi in aluminum is < 0.01 wt% at room temperature. During the solidification process, Bi precipitates in the form of a pure metal phase, forming a dispersed particle distribution in the aluminum matrix.

6. A method for preparing an Al-Bi alloy according to any one of claims 1-5, characterized in that, It includes the following steps: Melting pure aluminum ingots, then adding pure Bi, pure Si, and Al - 20Fe master alloy for smelting and melt holding, then performing melt refining. After degassing and slag removal and static heat preservation, the Al - Bi alloy is obtained by casting.

7. The method for preparing the Al - Bi alloy according to claim 6, wherein The melting temperature of the pure aluminum ingot is 700°C - 800°C; The melt holding time is 5 min - 30 min; The melt refining is to perform melt refining with 0.55% - 0.65% of C2Cl6; The static heat preservation time is 20 - 30 min.

8. The method for preparing the Al - Bi alloy according to claim 6, wherein The purity of the pure aluminum ingot is ≥ 99.9%; The purity of the pure Bi is ≥ 99.9%; The purity of the pure Si is ≥ 99.9%; The impurity content of the Al - 20Fe is ≤ 0.1%.

9. The application of the Al - Bi alloy according to any one of claims 1 - 5 in power transmission, new energy equipment, and electronic devices.

10. An aluminum alloy wire, characterized in that, Using the Al - Bi alloy according to any one of claims 1 - 5.