An Al-Bi-Ni immiscible alloy and its preparation method

Abstract

The present invention relates to an Al-Bi-Ni immiscible alloy and a preparation method thereof, belonging to the technical field of non-ferrous metal alloys. An Al-Bi-Ni immiscible alloy, by mass percentage, consists of the following components: 3-20% of Bi, 0.1-2% of Ni, and the balance being Al. In the preparation method of the Al-Bi immiscible alloy of the present invention, by combining the action of a 0.2-1T horizontal steady magnetic field with the action of the compound formed by adding the third component Ni, an Al-Bi immiscible alloy with fine and dispersed Bi-rich phases is prepared, and the soft Bi-rich phases are dispersed in the Al matrix. In the method of the present invention, the combination of the action of the horizontal steady magnetic field and the Al-Ni compound can hinder the sinking movement of the Bi-rich droplets and inhibit macrosegregation. In the method of the present invention, when the third component Ni is added to the Al-Bi immiscible alloy, the Al-Ni compound formed during solidification promotes the nucleation of the Bi-rich droplets, refines the Bi-rich particles, and improves the hardness of the alloy.

Description

Technical Field

[0001] The present invention relates to an Al-Bi-Ni immiscible alloy and a preparation method thereof, belonging to the technical field of non-ferrous metal alloys. Background Art

[0002] The characteristic of immiscible alloys is that liquid-liquid separation occurs during solidification, causing severe macrosegregation, so it is not easy to be prepared by casting methods. There is a liquid-liquid immiscibility range in the binary phase diagram of immiscible alloys. When a homogeneous melt passes through the immiscibility range during solidification, the single-phase melt decomposes into two immiscible liquid phases, and a liquid-liquid separation reaction occurs. First, a small amount of liquid phase nuclei are formed, and then through the combined action of diffusion growth, Ostwald ripening, Marangoni motion, Brownian motion, etc., the second-phase liquid droplets coarsen and float or sink under the action of gravity, causing macrosegregation. Due to their special physical and chemical properties, immiscible alloys have great application potential in superconducting materials, electronic packaging materials, semiconductors, self-lubricating bearing materials, etc. Among them, the Al-Bi immiscible alloy has a hard Al matrix, and soft Bi-rich dispersed phases are distributed in the matrix, with self-lubricating properties. The homogeneous Al-Bi alloy has good thermal conductivity and wear resistance, and has application prospects in automotive bearing materials due to its rich resources and low cost.

[0003] Immiscible alloys are extremely prone to segregation during solidification. In order to disperse the Bi-rich phase in the Al matrix, the requirements for production equipment are greatly increased. Therefore, suppressing the segregation of the Bi-rich phase and preparing a homogeneous immiscible alloy are the keys to producing high-quality automotive bearing materials.

[0004] At present, research shows that applying an external magnetic field during solidification can refine alloy particles and make them evenly distributed, suppressing segregation. The invention patent 20211263542.4 discloses a method for regulating the solidification structure of immiscible alloys by a strong magnetic field, and obtains Cu after solidification treatment by a strong magnetic field 50 Co 50The alloy transforms from a segregated core-shell structure into a homogeneous structure. Invention Patent 202111387322.2 discloses a method for preparing a homogeneous immiscible alloy by subjecting a melt to combined treatment with a strong magnetic field and overheating, obtaining a method of changing the melt structure by a strong magnetic field to make the melt composition uniform, increasing the nucleation supercooling degree, and suppressing segregation. Invention Patent 200710047493.4 discloses a method and device for preparing a monotectic alloy material without segregation, obtaining a method of suppressing the segregation of the second phase of the alloy by the combined action of a steady magnetic field and an alternating current, and obtaining an immiscible alloy with a dispersed distribution of the second phase, thereby improving the performance of the alloy. In the above patents, the method of using a strong magnet as the generating device for the applied magnetic field requires the use of a superconducting magnet or a large water-cooled resistive magnet, which has high requirements for industrial production equipment and is not conducive to application in industrial production. For the method of the combined action of a magnetic field and an alternating current, the electromagnetic force varies greatly at different positions in the melt and is not easy to control in production.

[0005] Some academic articles have discussed how to use a steady magnetic field to reduce the macrosegregation in immiscible alloys; among them, Zhang Lin et al. (Journal of Northeastern University (Natural Science Edition), 2010, 31(06): 816-819) found that a horizontal steady magnetic field has a certain inhibitory effect on the Marangoni motion of the Bi-rich phase when studying the effect of a horizontal steady magnetic field on the distribution of the second phase in a Zn-10%Bi monotectic alloy; Yasuda Hideyuki (ISIJ Int, 2003, 43(46): 942-949) found that a strong magnetic field reduces the upward velocity of Cu-rich droplets and weakens the macrosegregation when studying the effect of a strong magnetic field on the solidification of a Cu-Pb monotectic alloy; Zhang Lin et al. (Acta Metallurgica Sinica. 2010, 46(04): 423-428) found that a strong magnetic field reduces the coarsening of the Cu-rich phase and the segregation degree of the specimen when studying the effect of a strong magnetic field on the migration behavior of Cu-rich particles in a Cu-80%Pb monotectic alloy; Wang Jiang et al. (Acta Physica Sinica, 2009, 58(02): 893-900) found that applying a longitudinal strong magnetic field alone has a certain improvement effect on the segregation of the alloy in the solidification experiment of a Zn-30wt%Bi monotectic alloy under the combined action of a strong magnetic field and an alternating current. In the above literature, the magnetic field acts on binary immiscible alloys and does not act synergistically with the compounds formed by the added elements proposed in this patent. Therefore, the influence on the motion of the second phase is limited, and it can only reduce the macrosegregation and cannot completely inhibit the sedimentation behavior of the second phase.

[0006] The addition of a third component can refine the second phase of the immiscible alloy and make it uniformly distributed, inhibit segregation, and further improve the alloy properties. Invention Patent 201711073537.0 discloses an Al-based immiscible alloy with needle-shaped reinforcing phases and its preparation method, obtaining that the addition of Ti generates rod-shaped in-situ formed Al3Ti phases, enhancing the hardness of the matrix and improving the wear resistance of the alloy; Invention Patent 201710026348.1 discloses a preparation method of an immiscible alloy with baseball composite structure particles, obtaining that the addition of rare earth metal Nd generates particles of intermetallic compound NdBi2 with a rod-shaped structure wrapped by a Bi-rich phase. The wettability between the rod-shaped NdBi2 and the Bi-rich phase is good, which can be used as heterogeneous nucleation sites for the Bi-rich phase, promoting the nucleation of the Bi-rich phase and making it disperse in the Al matrix, improving the self-lubricating performance of the alloy; Invention Patent 201911017746.2 discloses a method for preparing a homogeneous immiscible alloy by adding two components of B and Cu, obtaining rod-shaped AlB2 solid phases and network-shaped Al2Cu phases, which can inhibit segregation and obtain a homogeneous and wear-resistant immiscible alloy. Invention Patent 201710404159.3 discloses a bulk homogeneous Al-Bi immiscible alloy and its preparation method, obtaining that the addition of rare earth elements, rare earth metals or rare earth master alloys can effectively refine the particles and improve the alloy properties. In the above patents, only the method of adding a third component is adopted, which has the effect of reducing the macroscopic segregation of the alloy in small-sized ingots in practical applications. However, macroscopic segregation may still occur in immiscible alloys with larger ingot sizes, restricting the production and application of industrial large-sized alloy ingots. Summary of the Invention

[0007] Aiming at the problem in the prior art that the segregation that easily occurs during the solidification of the Al-Bi immiscible alloy cannot be completely solved, restricting its application value, the present invention proposes an Al-Bi-Ni immiscible alloy and its preparation method.

[0008] The present invention proposes to add an appropriate amount of Ni powder to the Al-Bi immiscible alloy during the smelting process to prepare a dispersion-distributed Bi-rich phase and an Al3Ni phase distributed in the Al dendrite gaps. The Ni powder reacts with the Al matrix in the melt to generate compounds such as Al3Ni2 and Al3Ni, which act as nucleation sites to promote the nucleation rate of the Bi-rich phase, thereby refining the size of the Bi-rich liquid droplets generated during solidification. At the same time, the Al-Ni compounds are dispersed in the melt, blocking the direct downward channel of the Bi-rich phase, and the externally applied horizontal steady magnetic field has a braking effect on the conductive melt and suspended matter, keeping the Al-Ni compounds dispersed. The combination of various effects makes it difficult for the Bi-rich liquid droplets to directly sink or move in the melt convection, thereby suppressing the macrosegregation of the Bi-rich liquid droplets and making the Bi-rich phase in the alloy ingot structure uniformly dispersed. In the later stage of solidification, part of the Ni element dissolved in the Al matrix and the Al-Ni compounds are transformed into Al3Ni and distributed in the Al dendrite gaps. The dispersion-distributed Bi-rich phase and Al3Ni compounds simultaneously improve the self-lubricating performance and hardness of the alloy.

[0009] An Al-Bi-Ni immiscible alloy, by mass percentage, consists of the following components: Bi 3-20%, Ni 0.1-2%, and the balance is Al.

[0010] Preferably, by mass percentage, the alloy consists of the following components: Bi 10-20%, Ni 1-2%, and the balance is Al.

[0011] Further preferably, by mass percentage, the alloy consists of the following components: Bi 15-20%, Ni 1.5-2%, and the balance is Al.

[0012] The solidification structure of the alloy obtained by the present invention has an Al matrix, a uniformly dispersed spherical Bi-rich phase, and Al3Ni compounds dispersed in the Al dendrite gaps.

[0013] Another object of the present invention is to provide a preparation method of the above Al-Bi-Ni immiscible alloy.

[0014] A preparation method of an Al-Bi-Ni immiscible alloy. Under the protection of an inert atmosphere, first heat the metal Al to complete melting, then add the metal Bi to the melt, keep it at a temperature of 1000°C - 1100°C for 3 - 10 minutes. After obtaining a completely miscible alloy melt, add Ni powder and continue to keep it warm for 1 minute to disperse the Ni powder under the action of electromagnetic stirring to obtain an Al-Bi-Ni alloy melt; inject the obtained Al-Bi-Ni alloy melt into a copper mold under the action of an externally applied horizontal steady magnetic field to obtain an Al-Bi-Ni alloy melt billet.

[0015] Preferably, using pure metal Al, pure metal Bi, and pure metal Ni powder as raw materials, under the protection of an inert atmosphere, first place the metal Al ingot in an intermediate frequency induction furnace for heating. When the temperature reaches 1000 °C, the metal Al is completely melted. Then add metal Bi to the melt, and then control the heating power of the intermediate frequency induction furnace. At a temperature of 1000 °C to 1100 °C, keep it warm for 3 to 10 minutes. After obtaining a completely miscible alloy melt, add Ni powder and continue to keep it warm for 1 minute to disperse the Ni powder under the action of electromagnetic stirring to obtain an Al-Bi-Ni alloy melt; turn off the induction power supply, and then inject the obtained Al-Bi-Ni alloy melt into a slab copper mold with an inner cavity thickness of 0.5 to 40 mm under the action of an externally applied horizontal steady magnetic field to obtain an Al-Bi-Ni alloy plate-shaped casting blank.

[0016] Further, the inert atmosphere is an argon atmosphere.

[0017] Further, the intensity of the externally applied horizontal steady magnetic field is 0.2 to 1 T, provided by a permanent magnet or a DC electromagnet.

[0018] Further, the wall thickness is greater than 50 mm, the inner cavity thickness is 0.5 to 40 mm, and the inner cavity height and width are not limited.

[0019] The beneficial effects of the present invention are as follows: The preparation method of the Al-Bi immiscible alloy described in the present invention combines the action of a 0.2 to 1 T horizontal steady magnetic field and the action of the compound formed by adding the third component Ni to prepare an Al-Bi immiscible alloy with fine and dispersed Bi-rich phases. The soft Bi-rich phases are dispersed in the Al matrix. In the method of the present invention, the combination of the horizontal steady magnetic field and the action of the Al-Ni compound can hinder the sinking movement of the Bi-rich droplets and inhibit macroscopic segregation. In the method of the present invention, adding the third component Ni to the Al-Bi immiscible alloy, the Al-Ni compound formed during solidification promotes the nucleation of Bi-rich droplets, refines the Bi-rich particles, and improves the hardness of the alloy.

[0020] The preparation method of the Al-based immiscible alloy provided by the present invention can solve the existing problems of macroscopic segregation, complex process, and high requirements for production equipment in immiscible alloys. The Al-Bi immiscible alloy prepared by the present invention has a uniform structure, good self-lubricating and wear-resistant properties, and can be used as a bearing material. Brief Description of the Drawings

[0021] Figure 1 It is the microstructure of the Al-3%Bi-0.1%Ni alloy prepared in Example 1 of the present invention under the conditions of a horizontal steady magnetic field of 1 T and an inner cavity thickness of 40 mm of the slab copper mold;

[0022] Figure 2Microstructure of the Al-10%Bi-1.5%Ni alloy prepared in Example 3 of the present invention under the conditions of a horizontal steady magnetic field of 0.6 T and an inner cavity thickness of 10 mm of the slab copper mold;

[0023] Figure 3 Microstructure of the Al-20%Bi-2%Ni alloy prepared in Example 5 of the present invention under the conditions of a horizontal steady magnetic field of 0.2 T and an inner cavity thickness of 0.5 mm of the slab copper mold;

[0024] Figure 4 Microstructure of the Al-10%Bi immiscible alloy prepared in Comparative Example 1 of the present invention. Detailed implementation manners

[0025] The following non-limiting examples can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way.

[0026] In the following examples, the test methods are conventional methods unless otherwise specified; the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0027] One of the detailed implementation manners:

[0028] A method for preparing an Al-Bi-Ni immiscible alloy with a uniformly dispersed Bi-rich phase, comprising the following steps:

[0029] Using pure metal Al, pure metal Bi, and pure metal Ni powder as raw materials, under the protection of an inert atmosphere, first place the metal Al ingot in an intermediate frequency induction furnace for heating. When the temperature reaches 1000 °C, the metal Al is completely melted. Then add metal Bi to the melt, and then control the heating power of the intermediate frequency induction furnace. At a temperature of 1000 °C to 1100 °C, keep warm for 3 to 10 minutes to obtain a completely miscible alloy melt. Add Ni powder and continue to keep warm for 1 minute to disperse the Ni powder under the action of electromagnetic stirring. Turn off the induction power supply, and then inject the alloy melt into a slab copper mold with an inner cavity thickness of 0.5 to 40 mm under the action of an externally applied horizontal steady magnetic field to obtain an Al-Bi-Ni alloy plate-shaped ingot.

[0030] Preferably, the mass of the metal Bi accounts for 3 to 20% of the total mass of all metal raw materials, more preferably 10 to 20%, and still more preferably 15 to 20%.

[0031] Preferably, the mass of the Ni powder accounts for 0.1 to 2% of the total mass of all metal raw materials, more preferably 1 to 2%, and still more preferably 1.5 to 2%.

[0032] Preferably, the magnetic induction intensity of the horizontal steady magnetic field is 0.2 to 1 T.

[0033] Preferably, the inert atmosphere is composed of an inert gas, which is argon.

[0034] In the present invention, a homogeneous immiscible alloy is prepared by adding a third component Ni, and an Al-Bi immiscible alloy with fine and dispersed Bi-rich phases distributed on the Al matrix is obtained.

[0035] A horizontal magnetic field is applied to the side of the slab during solidification, suppressing melt convection. Combined with the hindering effect of the Al-Ni compound, the sinking movement of Bi-rich droplets is suppressed, and the macrosegregation of the Bi-rich phase is eliminated.

[0036] Example 1

[0037] An Al-3%Bi-0.1%Ni immiscible alloy and its preparation method are as follows:

[0038] Using pure metal Al, pure metal Bi, and pure metal Ni powder as raw materials, the content of each element is weighed by weight percentage as follows: Al is 96.9%, Bi is 3%, and Ni is 0.1%.

[0039] Under the protection of an inert atmosphere, through vacuum induction melting, first place the metal Al ingot in a medium-frequency induction furnace for heating. When the temperature reaches 1000 °C, the metal Al is completely melted. Then add metal Bi to the melt, and then control the heating power of the medium-frequency induction furnace. At a temperature of 1000 °C, hold for 10 min to obtain a completely miscible alloy melt. Add Ni powder and continue to hold for 1 min to disperse the Ni powder under the action of electromagnetic stirring. Turn off the induction power supply, and then inject the alloy melt into a slab copper mold with an inner cavity thickness of 40 mm under the action of an externally applied horizontal steady magnetic field of 1 T to obtain an Al-3%Bi-0.1%Ni alloy plate-shaped ingot.

[0040] The preparation method of this example prepares an Al-Bi immiscible alloy with dispersed Bi-rich phases. As Figure 1 shown, the black in the figure is the Al matrix, the white spherical droplets are the Bi-rich phases, and the gray Al3Ni phases. Melt convection is suppressed, the collision and coalescence of Bi-rich phase droplets are hindered, Stokes motion and Marangoni motion are suppressed, the strength of the matrix is enhanced, and the hardness of the Al-Bi immiscible alloy is increased. The preparation method of this example prepares an Al-3%Bi-0.1%Ni immiscible alloy with dispersed Bi-rich phases. Its Vickers hardness is 33.3 HV.

[0041] Example 2

[0042] The method is the same as that in Example 1, and the differences are as follows:

[0043] (1) The content of each element is by weight percentage: Al is 94%, Bi is 5%, and Ni is 1%.

[0044] (2) The magnetic induction intensity of the horizontal steady magnetic field is 0.8 T.

[0045] (3) The thickness of the inner cavity of the copper mold is 20 mm.

[0046] The Al-5%Bi-1%Ni immiscible alloy with a dispersed Bi-rich phase is prepared by the preparation method of this embodiment. Its Vickers hardness is 35.28 HV.

[0047] Example 3

[0048] The method is the same as that of Example 1, the differences are as follows:

[0049] (1) The content of each element by weight percentage is: Al is 88.5%, Bi is 10%, and Ni is 1.5%.

[0050] (2) The magnetic induction intensity of the horizontal steady magnetic field is 0.6 T.

[0051] (3) The thickness of the inner cavity of the copper mold is 10 mm.

[0052] The Al-10%Bi-1.5%Ni immiscible alloy with a dispersed Bi-rich phase is prepared by the preparation method of this embodiment, as Figure 2 shown. Its Vickers hardness is 36.8 HV.

[0053] Example 4

[0054] The method is the same as that of Example 1, the differences are as follows:

[0055] (1) The content of each element by weight percentage is: Al is 83%, Bi is 15%, and Ni is 2%.

[0056] (2) The magnetic induction intensity of the horizontal steady magnetic field is 0.4 T.

[0057] (3) The thickness of the inner cavity of the copper mold is 5 mm.

[0058] The Al-15%Bi-2%Ni immiscible alloy with a dispersed Bi-rich phase is prepared by the preparation method of this embodiment. Its Vickers hardness is 37.84 HV.

[0059] Example 5

[0060] The method is the same as that of Example 1, the differences are as follows:

[0061] (1) The content of each element by weight percentage is: Al is 78%, Bi is 20%, and Ni is 2%.

[0062] (2) The magnetic induction intensity of the horizontal steady magnetic field is 0.2 T.

[0063] (3) The thickness of the inner cavity of the copper mold is 0.5 mm.

[0064] The preparation method of this example prepares an immiscible Al-20% Bi-2% Ni alloy with a dispersed Bi-rich phase, as Figure 3 shown. Its Vickers hardness is 38.62 HV.

[0065] Comparative Example 1

[0066] The method is the same as that of Example 3, except that:

[0067] The content of each element by weight percentage is: Al is 90%, Bi is 10%. Ni is not added. No magnetic field is applied during the casting process.

[0068] The preparation method of this example prepares an immiscible Al-10% Bi alloy with a dispersed Bi-rich phase, as Figure 4 shown. Its Vickers hardness is 27.43 HV.

Claims

1. An Al-Bi-Ni immiscible alloy, characterized in that, The alloy is composed of the following components by mass percentage: Bi 3-20%, Ni 0.1-2%, and the balance is Al. The solidified structure of the alloy has an Al matrix, spherical Bi-rich phases uniformly and dispersedly distributed, and Al3Ni compounds dispersed in the interstices of Al dendrites.

2. The immiscible alloy according to claim 1, characterized in that, The alloy is composed of the following components by mass percentage: Bi 10-20%, Ni 1-2%, and the balance is Al.

3. A preparation method of an Al-Bi-Ni immiscible alloy, characterized in that, Under the protection of an inert atmosphere, first heat metal Al to complete melting, then add metal Bi to the melt, keep it at a temperature of 1000°C to 1100°C for 3 to 10 minutes. After obtaining a completely miscible alloy melt, add Ni powder and continue to keep it warm for 1 minute to disperse the Ni powder under the action of electromagnetic stirring to obtain an Al-Bi-Ni alloy melt; inject the obtained Al-Bi-Ni alloy melt into a copper mold under the action of an externally applied horizontal steady magnetic field to obtain an Al-Bi-Ni alloy melt ingot.

4. The method according to claim 3, characterized in that, Using pure metal Al, pure metal Bi, and pure metal Ni powder as raw materials, under the protection of an inert atmosphere, first place the metal Al ingot in an intermediate frequency induction furnace for heating. When the temperature reaches 1000°C, the metal Al is completely melted. Then add metal Bi to the melt, and then control the heating power of the intermediate frequency induction furnace. Keep it at a temperature of 1000°C to 1100°C for 3 to 10 minutes. After obtaining a completely miscible alloy melt, add Ni powder and continue to keep it warm for 1 minute to disperse the Ni powder under the action of electromagnetic stirring to obtain an Al-Bi-Ni alloy melt; turn off the induction power supply, and then inject the obtained Al-Bi-Ni alloy melt into a slab copper mold with an inner cavity thickness of 0.5 to 40 mm under the action of an externally applied horizontal steady magnetic field to obtain an Al-Bi-Ni alloy slab ingot.

5. The method according to claim 3 or 4, characterized in that, The inert atmosphere is an argon atmosphere.

6. The method according to claim 3 or 4, characterized in that, The intensity of the externally applied horizontal steady magnetic field is 0.2 to 1 T, provided by a permanent magnet or a DC electromagnet.

7. According to the method described in claim 4, the slab copper mold: has a wall thickness greater than 50 mm, an inner cavity thickness of 0.5 to 40 mm, and the height and width of the inner cavity are not limited.

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