Modified aluminum alloy for network connecting hardware and preparation method thereof

Abstract

The application discloses a modified aluminum alloy for network connection fittings and a preparation method thereof. The modified aluminum alloy is prepared from the following raw materials in mass fraction: 95.7-99.2% of aluminum alloy powder, 0.5-2% of titanium hydride powder, 0.2-2% of rare earth metal powder and 0.1-0.3% of carbon fiber coated with a SiC coating on the surface by PVD. The preparation method comprises the following steps: mixing the aluminum alloy powder, the titanium hydride powder and the rare earth metal powder to obtain a mixture, ball-milling the mixture under the protection of inert gas, drying the mixture, mixing the mixture with the carbon fiber coated with the SiC coating on the surface by PVD under the protection of an argon atmosphere to obtain a secondary mixture, and sintering and hot forging the secondary mixture to obtain the modified aluminum alloy for network connection fittings. The modified aluminum alloy for network connection fittings has excellent tensile strength and toughness, and no obvious intergranular corrosion, and can be well applied to network connection fittings.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, specifically relating to a modified aluminum alloy for power distribution network connection fittings and its preparation method. Background Technology

[0002] The power distribution network is a crucial public infrastructure for national economic and social development. Currently, most power distribution network connection fittings are made of ferrous materials, which presents several problems: First, the alternating magnetic field of the transmitted current during operation causes energy losses such as hysteresis and eddy currents. Second, the hot-dip galvanizing process for corrosion protection is highly polluting and energy-intensive. Aluminum alloys possess excellent properties such as lightweight, high strength, corrosion resistance, non-ferromagnetism, and low energy loss, making them a good alternative to ferrous materials for power distribution network connection fittings. However, the tensile strength of ferrous materials such as Q235 used in power distribution network connection fittings is no less than 350 MPa, and the elongation after fracture is no less than 10%. Traditional aluminum alloys cannot meet these performance requirements. For example, 2-series and 7-series high-strength aluminum alloys exhibit significant intergranular corrosion (which will develop into exfoliation failure), and even the corrosion-resistant 6-series aluminum alloys, such as 6061 aluminum alloy, have a tensile strength of only 310 MPa, lower than the 350 MPa of Q235. Therefore, traditional aluminum alloys cannot be used in power distribution network connection fittings. While existing novel aluminum alloy materials, such as the Al-Si-Cu-Mg wrought aluminum alloy disclosed in CN111893354A, can meet the tensile strength requirements, their elongation after fracture is only 5% to 7%, failing to meet the requirement that the elongation after fracture of connecting hardware materials should not be less than 10%. The same applies to the corrosion-resistant carbon fiber aluminum alloy composite material disclosed in CN114672746A. Furthermore, the method for preparing silicon-coated carbon nanotubes disclosed in CN111455208A is practically infeasible because the bonding force during ball milling is weak, failing to form a coating. During subsequent preparation, the carbon nanotubes directly contact Al, forming a brittle aluminum carbide phase, which will lose toughness and easily lead to fatigue failure. Therefore, it does not meet the requirement of "5.2 The metal materials used to manufacture hardware should meet the service life" mentioned in GBT23142008 General Technical Conditions for Power Fittings. Moreover, carbon nanotubes will break during ball milling, failing to effectively improve strength. Therefore, materials prepared by this method cannot actually meet the requirements for decades of long-term operation and strength. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a modified aluminum alloy for power distribution network connection fittings with high strength (tensile strength not less than 370MPa), good toughness (elongation after fracture not less than 10%) and no obvious intergranular corrosion, and a method for preparing the same.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0005] A modified aluminum alloy for power distribution network connection fittings is made from the following raw materials in the indicated mass fractions: 95.7%–99.2% aluminum alloy powder, 0.5%–2% titanium hydride powder, 0.2%–2% rare earth metal powder, and 0.1%–0.3% carbon fiber with a PVD-coated SiC layer.

[0006] The modified aluminum alloy used for the above-mentioned power distribution network connection fittings preferably contains the following components by mass fraction: 94% to 99.2% aluminum, 0.4% to 2% magnesium, 0.2% to 2% copper, and 0.2% to 2% silicon.

[0007] In the modified aluminum alloy used for the above-mentioned power distribution network connection fittings, preferably, the particle size of the titanium hydride powder is 2μm to 5μm.

[0008] Preferably, in the modified aluminum alloy used for the above-mentioned power distribution network connection fittings, the aspect ratio of the carbon fiber with the PVD-coated SiC coating is 20:1, and the thickness of the SiC coating is 2μm to 3μm.

[0009] In the modified aluminum alloy used for the above-mentioned power distribution network connection fittings, preferably, the rare earth metal powder includes one or more of cerium powder, yttrium powder, and lanthanum powder, and the particle size of the rare earth metal powder is 2μm to 5μm.

[0010] Preferably, the modified aluminum alloy used in the above-mentioned power distribution network connection hardware has a mesh size of 425-625 mesh.

[0011] As a general technical concept, the present invention also provides a method for preparing the above-mentioned modified aluminum alloy for power distribution network connection fittings, comprising the following steps:

[0012] (1) Prepare raw materials: Mix aluminum alloy powder, titanium hydride powder and rare earth metal powder in proportion to obtain a mixture;

[0013] (2) Ball milling: The mixture obtained above is ball milled under inert gas protection;

[0014] (3) Drying: Dry the mixture obtained from ball milling;

[0015] (4) Secondary mixing: The dried mixture and the carbon fiber with PVD coating SiC on the surface are mixed twice under the protection of argon atmosphere to obtain a secondary mixture.

[0016] (5) Sintering: The secondary mixture obtained above is subjected to rapid hot pressing sintering at a heating rate of 50℃ / min~100℃ / min. First, the temperature is raised to 500℃~550℃ at 2MPa~5MPa and sintered for 20min~30min. Then, the temperature is raised to 600℃~680℃ at 30MPa~50MPa and sintered for 20min~25min to obtain the masterbatch.

[0017] (6) Hot forging: The masterbatch is heated to 500℃~550℃ in the mold and hot forged. After annealing, the modified aluminum alloy for power distribution connection hardware is obtained.

[0018] In the above-mentioned method for preparing modified aluminum alloy for power distribution network connection fittings, preferably, in step (2), the ball-to-material mass ratio of the ball mill is 4 to 8:1, and the ball milling time is 36 to 64 hours; the ball milling is a wet ball milling, the wet ball milling medium is anhydrous ethanol, and the grinding balls are cemented carbide balls; the wet ball milling adopts a planetary ball milling or a drum ball milling, the rotation speed of the planetary ball milling is 200 to 300 rpm, and the rotation speed of the drum ball milling is 60 to 100 rpm.

[0019] In the above-mentioned method for preparing modified aluminum alloy for power distribution network connection fittings, preferably, in step (3), the drying is carried out in a vacuum drying oven, first by nitrogen purging, and then by vacuum drying, the drying temperature is 50℃~70℃, and the drying pressure is 5000Pa~10000Pa.

[0020] In the above-mentioned method for preparing modified aluminum alloy for power distribution network connection fittings, preferably, in step (4), the secondary mixing is carried out in a V-type mixer or a three-dimensional mixer, and the secondary mixing time is 24h to 36h.

[0021] In the above-mentioned method for preparing modified aluminum alloy for power distribution network connection fittings, preferably, in step (6), the annealing temperature is 150℃~200℃ and the annealing time is 6h~12h.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] 1. The modified aluminum alloy for power distribution network connection fittings of the present invention uses aluminum alloy powder composed of aluminum, magnesium, copper, and silicon, titanium hydride powder, rare earth metal powder, and carbon fiber with PVD coating of SiC as raw materials for synergistic effect: First, the SiC coating can protect the carbon fiber from violent reaction with aluminum to generate a large amount of brittle aluminum carbide phase while bonding with the matrix. At the same time, the SiC coating itself contains C through PVD coating, resulting in strong bonding with carbon fiber after coating. Second, by adding titanium hydride, on the one hand, titanium oxidation is prevented, and on the other hand, the reducing gas generated during sintering can reduce powder oxidation to a certain extent, increasing activity. Moreover, the addition of titanium can form titanium-aluminum intermetallic compounds, which disperse and strengthen the aluminum matrix. Third, the addition of rare earth metals can adsorb oxygen during ball milling and sintering crystal boundaries, purify the grain boundaries, promote sintering, and disperse and strengthen the aluminum alloy matrix. Fourth, after high-energy ball milling and mixing of aluminum, magnesium, copper, and silicon alloy powder, titanium hydride powder, and rare earth metal powder in an inert gas, dry mixing is carried out with carbon fiber with PVD coating of SiC, which can avoid the carbon fiber being broken by ball milling, thus preventing the strength from being improved. The modified aluminum alloy of the present invention has both excellent tensile strength and elongation after fracture, meeting the performance requirements of tensile strength not less than 370MPa and elongation after fracture not less than 10%, and can be well applied in power distribution network connection fittings.

[0024] 2. In the preparation method of this invention, aluminum alloy powder composed of aluminum, magnesium, copper, and silicon, titanium hydride powder, and rare earth metal powder are subjected to high-energy ball milling in an inert gas. After ball milling and mixing, they are dry-mixed with carbon fibers coated with SiC by PVD to avoid the carbon fibers from being broken. The mixture is then subjected to rapid hot-pressing sintering in a sintering device. The sintering temperature and pressurization process are very important during sintering. Pressurization is applied after holding the titanium hydride at 500°C to decompose it into hydrogen gas to avoid the formation of porous materials. Finally, the temperature is raised to the final temperature for final sintering. Detailed Implementation

[0025] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0026] Example 1:

[0027] A modified aluminum alloy for power distribution network connection fittings of the present invention is made from the following raw materials in the indicated mass fractions: 98.4% aluminum alloy powder, 1% titanium hydride powder, 0.5% rare earth metal powder, and 0.1% carbon fiber with a PVD-coated SiC coating.

[0028] In this embodiment, the aluminum alloy contains the following components by mass fraction: 96% aluminum, 2% magnesium, 1% copper, and 1% silicon.

[0029] In this embodiment, the particle size of the titanium hydride powder is 2-5 μm.

[0030] In this embodiment, the aspect ratio of the carbon fiber with the PVD-coated SiC coating is 20:1, and the thickness of the SiC coating is 2μm.

[0031] In this embodiment, the rare earth metal powder is cerium powder with a particle size of 2-5 μm.

[0032] In this embodiment, the aluminum alloy powder has a mesh size of 500.

[0033] A method for preparing a modified aluminum alloy for power distribution network connection fittings according to this embodiment includes the following steps:

[0034] (1) Prepare raw materials: Mix aluminum alloy powder, titanium hydride powder and rare earth metal powder in the above proportions to obtain a mixture.

[0035] (2) Ball milling: The mixture obtained above is wet ball milled under the protection of inert gas (argon in this embodiment). The wet ball milling medium is anhydrous ethanol, the grinding balls are cemented carbide balls, the mass ratio of ball to material is 5:1, and the ball milling time is 48h.

[0036] (3) Drying: Place the ball milled mixture in a vacuum drying oven, first purge with nitrogen, then evacuate, maintain the pressure at 6000 Pa, dry at 50 °C for 12 h.

[0037] (4) Secondary mixing: The dried mixture is mixed with the PVD-coated SiC carbon fiber under argon atmosphere for 24 hours to obtain the secondary mixture.

[0038] (5) Sintering: The secondary mixture obtained above is subjected to rapid hot pressing sintering at a heating rate of 80℃ / min. First, it is heated to 520℃ at 3MPa and sintered for 25min, and then heated to 630℃ at 40MPa and sintered for 20min to obtain the masterbatch. This process has a fast heating rate, low temperature, fine grains and high strength.

[0039] (6) Hot forging: The masterbatch is heated to 530°C in the mold for hot forging, and then annealed at 150°C for 12 hours to obtain the modified aluminum alloy for power distribution connection fittings.

[0040] In this embodiment, in step (2), the wet ball mill can be a planetary ball mill or a drum ball mill. When using a planetary ball mill, the rotation speed of the planetary ball mill is 240 rpm. When mass production is carried out, considering the output of mass production, it is preferable to use a drum ball mill with a rotation speed of 80 rpm.

[0041] In this embodiment, in step (3), the secondary mixing can be carried out in a V-type mixer or a three-dimensional mixer.

[0042] Three modified aluminum alloy samples for power distribution network connection fittings were prepared using the method of this embodiment, and their mechanical strength was tested. The results are shown in Table 1. The intergranular corrosion test of the aluminum alloy samples obtained in this embodiment showed an intergranular corrosion level of 1, meaning no significant intergranular corrosion.

[0043] Table 1. Mechanical strength of the modified aluminum alloy samples for power distribution connection fittings prepared in Example 1.

[0044] sample tensile strength Elongation after fracture 1-1 393MPa 12％ 1-2 388MPa 15％ 1-3 383MPa 13％

[0045] Example 2

[0046] A modified aluminum alloy for power distribution network connection fittings of the present invention is basically the same as that in Example 1, except that the aluminum alloy contains the following components by mass fraction: 98% aluminum, 1% magnesium, 0.5% copper and 0.5% silicon.

[0047] Three modified aluminum alloy samples for power distribution network connection fittings were prepared using the method of this embodiment, and their mechanical strength was tested. The results are shown in Table 2.

[0048] Table 2. Mechanical strength of the modified aluminum alloy samples for power distribution connection fittings prepared in Example 2.

[0049]

[0050]

[0051] In summary, this invention uses aluminum-magnesium-copper-silicon alloy powder, titanium hydride powder, rare earth metal powder, and carbon fibers with PVD-coated SiC as raw materials. Coating the carbon fiber surface with SiC avoids the formation of a brittle aluminum carbide phase due to the violent reaction between C and Al, which would reduce mechanical properties. The SiC coating has strong adhesion to the carbon fiber and allows for control over the degree of reaction with the Al matrix. The addition of titanium hydride prevents titanium oxidation and generates reducing gases during sintering, which can reduce powder oxidation to a certain extent and increase activity. The addition of titanium hydride can form titanium-aluminum intermetallic compounds, which disperse and strengthen the aluminum matrix. Rare earth metals are used to adsorb oxygen during ball milling and at the grain boundaries, purifying the grain boundaries and promoting sintering and dispersed distribution to strengthen the aluminum alloy matrix. The modified aluminum alloy of this invention exhibits excellent tensile strength and elongation after fracture, meeting the performance requirements of power distribution network connection fittings.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A modified aluminum alloy for power distribution network connection fittings, characterized in that, It is made from the following raw materials in the indicated mass fractions: 95.7%–99.2% aluminum alloy powder, 0.5%–2% titanium hydride powder, 0.2%–2% rare earth metal powder, and 0.1%–0.3% carbon fiber with a PVD-coated SiC layer. Aluminum alloys contain the following components by mass fraction: aluminum 94%–99.2%, magnesium 0.4%–2%, copper 0.2%–2%, and silicon 0.2%–2%. The particle size of the titanium hydride powder is 2μm to 5μm; The aspect ratio of the carbon fiber with the PVD-coated SiC coating is 20:1, and the thickness of the SiC coating is 2μm to 3μm. The rare earth metal powder includes one or more of cerium powder, yttrium powder, and lanthanum powder, and the particle size of the rare earth metal powder is 2μm to 5μm.

2. The modified aluminum alloy for power distribution network connection fittings according to claim 1, characterized in that, The aluminum alloy powder has a mesh size of 425 to 625 mesh.

3. A method for preparing a modified aluminum alloy for power distribution network connection fittings as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Prepare raw materials: Mix aluminum alloy powder, titanium hydride powder and rare earth metal powder in proportion to obtain a mixture; (2) Ball milling: The resulting mixture is ball milled under inert gas protection; (3) Drying: The mixture obtained from ball milling is dried; (4) Secondary mixing: The dried mixture and the carbon fiber with PVD coating on the surface of SiC are mixed in a secondary mixture under the protection of argon atmosphere to obtain a secondary mixture; (5) Sintering: The secondary mixture obtained above is subjected to rapid hot pressing sintering at a heating rate of 50℃ / min~100℃ / min. First, the temperature is raised to 500℃~550℃ at 2MPa~5MPa and sintered for 20min~30min. Then, the temperature is raised to 600℃~680℃ at 30MPa~50MPa and sintered for 20min~25min to obtain the masterbatch. (6) Hot forging: The masterbatch is heated to 500℃~550℃ in the mold and hot forged. After annealing, the modified aluminum alloy for power distribution connection hardware is obtained.

4. The method for preparing the modified aluminum alloy for power distribution network connection fittings according to claim 3, characterized in that, In step (2), the ball-to-material mass ratio of the ball mill is 4 to 8:1, and the milling time is 36 to 64 hours. The ball mill is a wet ball mill, the wet ball milling medium is anhydrous ethanol, and the grinding balls are cemented carbide balls. The wet ball mill is a planetary ball mill or a drum ball mill. The rotation speed of the planetary ball mill is 200 to 300 rpm, and the rotation speed of the drum ball mill is 60 to 100 rpm.

5. The method for preparing the modified aluminum alloy for power distribution network connection fittings according to claim 3 or 4, characterized in that, In step (3), the drying is carried out in a vacuum drying oven. First, nitrogen is purged, and then vacuum is drawn for drying. The drying temperature is 50℃~70℃, and the drying pressure is 5000Pa~10000Pa. In step (4), the secondary mixing is carried out in a V-type mixer or a three-dimensional mixer, and the secondary mixing time is 24h to 36h.

6. The method for preparing the modified aluminum alloy for power distribution network connection fittings according to claim 3 or 4, characterized in that, In step (6), the annealing temperature is 150℃~200℃ and the annealing time is 6h~12h.

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