An l12 phase strengthened fcc-type multi-component alloy and a method of making the same

Abstract

The application discloses an L12 phase reinforced FCC type multi-component alloy and a preparation method thereof, and belongs to the field of high-entropy alloys and preparation technologies thereof.The L12 phase reinforced FCC type multi-component alloy comprises the following components in percentage of atoms: 42-45% of Ni, 21-24% of Co, 7-10% of Fe, 9-12% of Al, 10-13% of Ti and 1-3% of B.The application uses high-purity pure metals as raw materials, and through simple thermal mechanical treatment, a structure of "fine crystal + annealing twin crystal + L12 phase" is constructed, so that the toughening of the FCC type high-entropy alloy is realized, the room temperature yield strength of the alloy reaches 1063 MPa, the room temperature tensile strength reaches 1696 MPa, and the fracture elongation reaches 25.9%.

Description

Technical Field

[0001] This invention relates to the field of high-entropy alloys and their preparation technology, and in particular to an L12 phase-strengthened FCC-type multi-component alloy and its preparation method. Background Technology

[0002] In recent years, high-entropy alloys have attracted widespread attention due to their unique structural characteristics and excellent properties, particularly their superior strength-ductility combination, excellent corrosion resistance, and radiation resistance. Among them, face-centered cubic (FCC) high-entropy alloys have garnered significant attention due to their ease of processing and excellent ductility and toughness, with potential applications including engines, molds and tools, biomedical materials, and electromagnetic materials. However, the strength of these materials is typically low, limiting their widespread use as structural materials. Therefore, obtaining FCC-type high-entropy alloys that combine excellent strength and good ductility has become a pressing technical problem to be solved in this field. Summary of the Invention

[0003] The purpose of this invention is to provide an L12 phase-strengthened FCC-type multi-component alloy and its preparation method, thereby solving the problems existing in the prior art. The alloy of this invention is a high-entropy alloy with a "fine grain + annealed twin + L12 phase" microstructure, exhibiting excellent strength and good plasticity.

[0004] To achieve the above objectives, the present invention provides the following solution:

[0005] One of the technical solutions of the present invention is an L12 phase reinforced FCC type multi-component alloy, which, by atomic percentage, comprises the following components: Ni 42-45%, Co 21-24%, Fe 7-10%, Al 9-12%, Ti 10-13%, and B 1-3%.

[0006] Furthermore, the L12-phase-strengthened FCC-type multi-component alloy has an L12-structure strengthening phase and an FCC matrix phase.

[0007] This invention uses Ni, Co, and Fe as the alloying elements to form the FCC matrix. The resulting NiCoFe matrix exhibits good solid solubility for Al and Ti, enabling stable FCC matrix formation. Secondly, Ni and Co can form a stable L12 phase with Al and Ti, enhancing the alloy's strength and thermal stability. The introduction of Fe helps improve the alloy's plasticity while also suppressing the formation of brittle phases. Al and Ti are the main elements forming the L12 phase; they combine with Ni and Co to generate a Ni3(Al,Ti) type L12 phase with excellent mechanical properties. Furthermore, the addition of Al and Ti also improves the alloy's oxidation resistance and high-temperature performance.

[0008] The B element in this invention improves the overall performance of the alloy by suppressing grain boundary embrittlement. Omitting or replacing the B element will lead to a significant decrease in the tensile strength, elongation and creep resistance of the alloy.

[0009] The second technical solution of the present invention: a method for preparing the above-mentioned L12 phase strengthened FCC type multi-component alloy, comprising the following steps:

[0010] Take elemental metals Ni, Co, Fe, Al, and Ti, ultrasonically clean them in alcohol, weigh them according to atomic percentage, then mix the elemental metals with B powder, melt them multiple times, and then cast them to obtain an alloy ingot.

[0011] The alloy ingot was subjected to solution treatment, deep cryogenic rolling, and recrystallization treatment in sequence to obtain the L12 phase-strengthened FCC type multi-component alloy.

[0012] Furthermore, the raw material is a high-purity metal with a purity of not less than 99.99 wt.%.

[0013] The raw materials have extremely high purity, which can avoid the introduction of other impurities and promote the alloy to exhibit better mechanical properties.

[0014] Furthermore, the melting is vacuum electromagnetic levitation melting, and the melting is performed 8 to 10 times; the mold used for casting has a size of 12mm×18mm×100mm.

[0015] Vacuum electromagnetic levitation melting can eliminate contamination of the melting material by air molecules and contamination of the melting material by the crucible material, thus obtaining the purest product.

[0016] Repeated melting can produce alloys with uniform composition.

[0017] Choosing a mold size of 12mm×18mm×100mm maximizes the contact between the alloy melt and the circulating water-cooled copper mold, avoiding inconsistent solidification rates caused by inconsistent conduction rates between the center and edge of the alloy ingot.

[0018] Furthermore, the cooling is achieved by using a circulating water-cooled copper mold.

[0019] Circulating water-cooled copper molds can increase the cooling rate of the molten metal during solidification, resulting in finer grains.

[0020] Furthermore, the heating rate of the solution treatment is 5℃ / min. After the sample is placed in the furnace, the temperature is raised to 1050℃ and then held for 12 hours. The environment is a flowing argon atmosphere, and the cooling method is air cooling.

[0021] Solution treatment at 1050℃ can promote alloy composition homogenization and reduce elemental segregation; argon gas is chemically inert, and using it as a protective gas can isolate the sample from air and prevent oxidation. Furthermore, a 12-hour solution treatment time can further improve the compositional homogenization of the as-cast alloy.

[0022] Furthermore, the low-temperature rolling process is a liquid nitrogen rolling process;

[0023] The liquid nitrogen rolling process includes: after each cold rolling pass, immersing in liquid nitrogen for 15 minutes (temperature reduced to the same temperature as liquid nitrogen, 77K); and performing an intermediate annealing process at reductions of 25%, 50%, and 75% until the total deformation reaches 90%.

[0024] Compared to traditional room temperature cold rolling, cryogenic treatment in a liquid nitrogen environment has a stronger grain refinement effect and can achieve similar plasticity, resulting in better mechanical properties of the alloy.

[0025] Furthermore, the heating rate of the intermediate annealing treatment is 5℃ / min. The sample is placed in the tube furnace after being heated to 1050℃ and held for 15min. The environment is a flowing argon atmosphere, and the cooling method is air cooling.

[0026] Intermediate annealing can effectively reduce the dislocation density in the alloy, reduce rolling stress and promote uniform deformation, improve the mobility of dislocations in the alloy sample, and allow the alloy sample to continue to deform.

[0027] Furthermore, the recrystallization process involves a heating rate of 5°C / min, raising the temperature to 1050°C before placing the sample in and holding it at that temperature for 30–90 min. The environment is filled with flowing argon gas, and the cooling method is air cooling.

[0028] Controlling the temperature and time of recrystallization treatment can cause recrystallization of cold-rolled elongated grains, and can control the degree of crystallization, ensuring that the degree of crystallization reaches 80-95%, while retaining a certain density of dislocations.

[0029] The third technical solution of the present invention: the application of the above-mentioned L12 phase reinforced FCC type multi-component alloy in the fields of construction, bridges, automobile manufacturing or aerospace.

[0030] The present invention discloses the following technical effects:

[0031] (1) The L12 phase reinforced FCC type multi-component alloy of the present invention has an L12 phase and an FCC matrix phase (obtained by the preparation method and element composition), has a certain density of geometrically necessary dislocations, and has excellent strength and ductility.

[0032] (2) This invention uses high-purity pure metal as raw material and performs simple thermomechanical treatment to construct a structure of "fine grain + annealed twin + L12 phase" to achieve the toughening of FCC type high-entropy alloy, so that the room temperature yield strength of the alloy reaches 1063MPa, the room temperature tensile strength reaches 1696MPa, and the fracture elongation reaches 25.9%. The strength of the alloy is improved and it has excellent strength-plasticity matching. It can be applied to structural materials with high requirements, such as buildings, bridges, automobiles, aerospace, etc., and has a wide range of applications. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a microstructure diagram of the alloy ingot obtained by vacuum electromagnetic levitation melting in step (1) of Embodiment 2 of the present invention. Among them, (a) is a macrostructure SEM image, (b) is a single grain SEM image, (c) is a SEM image of the L12 particles at the grain center, (d) is a TEM image of the L12 particles, (e) to (h) are high-resolution images and FFT images of the FCC phase and the L12 phase, and (i) is an inverse pole figure;

[0035] Figure 2 The images show the IPF diagrams, grain boundary and twin boundary distribution diagrams, and geometrically necessary dislocation density diagrams of the L12 phase-strengthened FCC-type multi-component alloys prepared using different recrystallization times in Examples 1-3 of this invention. Specifically, (a) to (c) are the IPF diagrams of the alloys prepared in Examples 1-3, (d) to (f) are the grain boundary and twin boundary distribution diagrams of the alloys prepared in Examples 1-3, and (g) to (i) are the geometrically necessary dislocation density diagrams of the alloys prepared in Examples 1-3.

[0036] Figure 3 The graphs show the uniaxial tensile test results of the L12 phase-reinforced FCC-type multi-component alloys prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0037] Figure 4 The mechanical properties of the L12 phase-reinforced FCC-type multi-component alloy prepared in Example 2 of this invention are compared with the strength and ductility of other high-entropy alloys with dual-phase structures. Among them, (a) is a comparison of elongation and yield strength with other alloys, (b) is a comparison of elongation and tensile strength with other alloys, and (c) is a comparison of yield strength and tensile strength with other alloys. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] Example 1

[0044] A method for preparing L12 phase-strengthened FCC-type multi-component alloy:

[0045] (1) The L12 phase-strengthened FCC type multi-component alloy has the following composition by atomic percentage (at.%): 43.9% Ni, 22.4% Co, 8.8% Fe, 10.7% Al, 11.7% Ti, and 2.5% B.

[0046] Metallic elements Ni, Co, Fe, Al, and Ti were ultrasonically cleaned in alcohol. Then, according to atomic percentage (accurate to 0.001 g), the metallic elements (all raw materials are high-purity metal particles, purity not less than 99.99 wt.%, particle size 3 mm) and B powder were weighed and mixed, then placed in a vacuum electromagnetic levitation melting furnace for vacuum electromagnetic levitation melting. During the melting process, a vacuum was first drawn to a negative pressure (10 Pa), and then the molecular pump was turned on to evacuate the vacuum to 5 × 10⁻⁶ Pa. -3 Pa, high-purity argon gas is introduced to 75000 Pa, the melting power is controlled at 130kW, the molten pool is always in a suspended state under the action of electromagnetic force during the melting process, the melting is repeated 8 times (each melting time is 5min) and then poured into a water-cooled copper mold (size is 12mm×18mm×100mm), and then formed by circulating water cooling (10min) to obtain alloy ingot.

[0047] (2) The alloy ingot prepared in step (1) is placed in a vacuum tube furnace and heated to 1050°C at a heating rate of 5°C / min under flowing argon atmosphere. It is then held for 12 hours (solution treatment for 12 hours) and air-cooled to obtain a homogenized sample.

[0048] (3) The homogenized sample prepared in step (2) is subjected to liquid nitrogen rolling treatment (after 10 passes of rolling to reduce the amount by 25%, then after 11 passes of rolling to reduce the amount by 50%, then after 18 passes of rolling to reduce the amount by 75%, and then after 22 passes of rolling to reduce the amount by 90%). After each pass of cold rolling treatment, the sample is immersed in liquid nitrogen (the temperature is reduced to the same as the liquid nitrogen temperature, 77K). When the reduction amount is 25%, 50% and 75%, an intermediate annealing treatment is performed (the tube furnace is heated to 1050℃ at a heating rate of 5℃ / min, and the sample with a reduction amount of 25%, 50% or 75% is placed in the tube furnace and kept at the temperature for 15min. The environment is flowing argon gas and the cooling method is air cooling) until the total deformation amount reaches 90%.

[0049] (4) After heating the tube furnace to 1050°C at a heating rate of 5°C / min in a flowing argon atmosphere, the sample obtained in step (3) was placed in the tube furnace and kept at the temperature for 30 min (recrystallization treatment for 30 min), and then air-cooled to obtain the L12 phase strengthened FCC type multi-component alloy (a face-centered cubic high-entropy alloy with a "fine grain + annealed twin + L12 phase" structure).

[0050] The geometrically required dislocation density of the alloy prepared in this embodiment is 3.37 × 10⁻⁶. 14 m -2The average grain size is 7.97 μm, and the volume fraction of annealed twins is 17.1%. This structure gives the alloy both high yield strength and good ductility. Testing showed that the alloy prepared in this example has a tensile strength of 1732 MPa, a yield strength of 1104 MPa, and an elongation at break of 20.8%.

[0051] Example 2

[0052] Same as Example 1, except that the recrystallization treatment time in step (4) is 45 min.

[0053] The alloy prepared in this embodiment has an FCC+L12 two-phase structure with a geometrically required dislocation density of 1.13 × 10⁻⁶. 14 m -2 The average grain size is 8.27 μm, and the volume fraction of annealed twins is 26.6%. This structure gives the alloy both high yield strength and good elongation. Testing showed that the alloy prepared in this example has a tensile strength of 1696 MPa, a yield strength of 1063 MPa, and an elongation at break of 25.9%.

[0054] Example 3

[0055] Same as Example 1, except that the recrystallization treatment time in step (4) is 90 min.

[0056] The alloy prepared in this embodiment has an FCC+L12 two-phase structure with a geometrically required dislocation density of 0.34 × 10⁻⁶. 14 m -2 The average grain size is 8.96 μm, and the volume fraction of annealed twins is 20.6%. This structure gives the alloy high tensile strength and good elongation. Testing showed that the alloy prepared in this example has a tensile strength of 1425 MPa, a yield strength of 982 MPa, and an elongation at break of 13.8%.

[0057] Comparative Example 1

[0058] Same as Example 2, except that B is not added.

[0059] The L12 phase-strengthened FCC-type multi-component alloy has the following composition by atomic percentage (at.%): 46.4% Ni, 22.4% Co, 8.8% Fe, 10.7% Al and 11.7% Ti.

[0060] The alloy prepared in this embodiment has a tensile strength of 1274 MPa, a yield strength of 933 MPa, and an elongation at break of 5.3%, as tested.

[0061] Figure 1This is a microstructure diagram of the alloy ingot prepared by vacuum electromagnetic levitation melting in step (1) of Embodiment 2 of the present invention. Among them, (a) is a macrostructure SEM image, (b) is a single grain SEM image, (c) is a SEM image of the L12 particles at the grain center, (d) is a TEM image of the L12 particles, (e) to (h) are high-resolution images and FFT images of the FCC phase and the L12 phase, and (i) is an inverse pole figure.

[0062] from Figure 1 As can be seen from the data, nanoscale ellipsoidal precipitates exist in the grains of the alloy ingot. TEM observation revealed that the alloy has an FCC matrix, and the ellipsoidal precipitates are the L12 phase. The corresponding EBSD image shows that the average grain size of the alloy ingot is 69.71 μm.

[0063] Figure 2 The figures show the IPF diagrams, grain boundary and twin boundary distribution diagrams, and geometrically necessary dislocation density diagrams of the L12 phase-strengthened FCC-type multi-component alloys prepared by different recrystallization times in Examples 1-3 of this invention. Specifically, (a) to (c) are the IPF diagrams of the alloys prepared in Examples 1-3, (d) to (f) are the grain boundary and twin boundary distribution diagrams of the alloys prepared in Examples 1-3, and (g) to (i) are the geometrically necessary dislocation density diagrams of the alloys prepared in Examples 1-3.

[0064] from Figure 2 As can be seen, with the increase of annealing time (recrystallization treatment time) after rolling (30-90 min), the grains gradually grow, and the volume fraction of twin boundaries first increases and then decreases, reaching a peak of 26.6% at 45 min. At the same time, with the extension of annealing time, the density of geometrically necessary dislocations gradually decreases, and the sample is almost completely recrystallized at 90 min.

[0065] Figure 3 The graphs show the uniaxial tensile test results of the L12 phase-reinforced FCC-type multi-component alloys prepared in Examples 1-3 and Comparative Example 1 of this invention.

[0066] Figure 3 Re-30 is the alloy prepared in Example 1, Re-45 is the alloy prepared in Example 2, Re-90 is the alloy prepared in Example 3, Homogenized is the homogenized alloy obtained by solution treatment in step (2) of Example 1, and Re-45 (B-free) is the alloy prepared in Comparative Example 1 without adding B element.

[0067] from Figure 3As can be seen, the strength and plasticity of the alloy prepared by this invention first increase and then decrease with recrystallization time. The mechanical properties are optimal in Example 2, with yield strength and tensile strength increased by 14.9% and 63.07% respectively compared to the homogenized alloy, and the elongation at break significantly improved. Furthermore, the mechanical properties of the alloys prepared in Examples 1-3 are all far superior to those of the homogenized sample. In addition, comparing the mechanical properties of Example 2 and Comparative Example 1 with and without the addition of B, it can be found that B significantly improves the elongation at break of the alloy.

[0068] Figure 4 The mechanical properties of the L12-phase reinforced FCC-type multi-component alloy prepared in Example 2 of this invention are compared with those of other high-entropy alloys with dual-phase structures (other high-entropy alloys in L12-phase reinforced FCC structures). Among them, (a) is a comparison of elongation and yield strength with other alloys, (b) is a comparison of elongation and tensile strength with other alloys, and (c) is a comparison of yield strength and tensile strength with other alloys.

[0069] from Figure 4 As can be seen from the above, the mechanical properties of the L12 phase-strengthened FCC-type multi-component alloy prepared in Example 2 of the present invention are superior to those of other L12 phase-strengthened FCC high-entropy alloys.

[0070] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method of making an L12 phase strengthened FCC-type multi-component alloy, characterized in that, The method comprises the following steps: Taking metallic elements of Ni, Co, Fe, Al and Ti, cleaning them in alcohol by ultrasonic, weighing them according to atomic percentage, then mixing the metallic elements with B powder, pouring after multiple melting, and obtaining alloy ingot; Solid solution treatment, cryogenic rolling treatment and recrystallization treatment are sequentially performed on the alloy ingot to obtain the L12 phase strengthened FCC type multi-component alloy; The mold size used in the pouring is 12mm x 18mm x 100mm; cooling forming is performed after the pouring; Copper mold cooling is used for cooling; The cryogenic rolling treatment is liquid nitrogen rolling treatment; the method of the liquid nitrogen rolling treatment comprises: after each pass of rolling treatment, soaking for 15min to 77K under liquid nitrogen; Once intermediate annealing treatment is performed at a reduction of 25%, 50% and 75% until the total deformation reaches 90%; the heating rate of the intermediate annealing treatment is 5℃ / min, the sample is placed after heating to 1050℃, and the sample is kept for 15min in a flowing argon environment, and the cooling mode is air cooling; The heating rate of the recrystallization treatment is 5℃ / min, the sample is placed after heating to 1050℃, and the sample is kept for 30-90min in a flowing argon environment, and the cooling mode is air cooling; The L12 phase strengthened FCC type multi-component alloy has a chemical composition of Ni 42-45%, Co 21-24%, Fe 7-10%, Al 9-12%, Ti 10-13% and B 1-3% according to atomic percentage. The L12 phase strengthened FCC type multi-component alloy has L12 structure strengthening phase and FCC matrix phase.

2. The production method according to claim 1, characterized by, The melting is vacuum electromagnetic levitation melting, and the number of melting is 8-10 times.

3. The method of claim 1, wherein, The heating rate of the solid solution treatment is 5℃ / min, the sample is kept for 12h after heating to 1050℃, and the cooling mode is air cooling.

4. Application of the L12 phase strengthened FCC type multi-component alloy prepared by the preparation method of claim 1 in the fields of building, bridge, automobile manufacturing or aerospace.

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