High-strength plastic six-element FeNiCoCrAlV high-entropy alloy and preparation method thereof

Abstract

The application provides a high-strength and high-plasticity six-element FeNiCoCrAlV high-entropy alloy and a preparation method thereof, and relates to the technical field of high-entropy alloys.The high-strength and high-plasticity six-element FeNiCoCrAlV high-entropy alloy provided by the application comprises the following elements with atomic percentages: Fe 40-42%, Ni 18-22%, Co 18-22%, Cr 8-12%, Al 4-6%, V 3-5%, and the atomic percentages of Ni and Co are equal.The high-entropy alloy provided by the application is a six-element non-equal-atomic-ratio single-phase high-entropy alloy;Al and V are added in the CoCrFeNi high-entropy alloy, the solid solution strengthening effect is increased, and the alloy still has an FCC structure, which enables the alloy to be rolled at room temperature with a large deformation, and further refines the grain size of the alloy, improves the strength of the alloy, so that the high-entropy alloy has high strength and high plasticity, and has excellent strength and plasticity matching.

Description

Technical Field

[0001] This invention relates to the field of high-entropy alloy technology, and in particular to a high-strength, high-ductility hexa-eight-membered FeNiCoCrAlV high-entropy alloy and its preparation method. Background Technology

[0002] The concept of high-entropy alloys (HEAs) was first proposed in 2004, providing a new design philosophy for alloys and facilitating the customization of alloy properties for specific applications. HEAs are typically composed of five or more elements in equiatomic or near-equiatomic ratios, with each element comprising between 5% and 35% of the total atomic mass; they are also known as multi-principal element alloys or complex compositional alloys. In recent years, the concept of HEAs has further evolved, no longer adhering to the traditional near-equiatomic ratio alloy design principle. Pradeep in Germany proposed the concept of non-equiatomic ratio HEAs, greatly expanding the development possibilities for HEAs. HEAs are typically composed of solid solution phases, exhibiting face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) crystal structures or mixtures thereof. HEAs possess many excellent properties, such as high strength, high plasticity, high wear resistance, excellent corrosion resistance, good high-temperature resistance and oxidation resistance, and excellent radiation resistance.

[0003] Generally, high-entropy alloys with a face-centered cubic (FCC) structure tend to exhibit excellent plasticity and work hardening ability at room temperature. However, the yield strength of these alloys is too low (<200 MPa), limiting their use in engineering applications. To date, researchers have taken many measures to improve the yield strength of FCC-phase high-entropy alloys in order to obtain high-entropy alloys that combine high strength and high plasticity. For example, Otto et al. improved the strength of FeCrNiCoMn high-entropy alloys by grain refinement; when the grain size was reduced from 144 μm to 4.4 μm, the room-temperature yield strength of the high-entropy alloy increased from 200 MPa to 350 MPa. Although the yield strength of FCC-phase high-entropy alloys has been improved, it is still low and cannot meet the requirements of engineering applications for high-strength and high-plasticity materials. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a high-strength, high-ductility hexa-membered FeNiCoCrAlV high-entropy alloy and its preparation method. The high-strength, high-ductility hexa-membered FeNiCoCrAlV high-entropy alloy provided by this invention has a good balance between strength and ductility.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy comprising the following atomic percentages of elements: Fe 40-42%, Ni 18-22%, Co 18-22%, Cr 8-12%, Al 4-6%, V 3-5%, with Ni and Co having equal atomic percentages.

[0007] Preferably, it includes the following elements in atomic percentage: Fe 41-42%, Ni 19-21%, Co 19-21%, Cr 9-11%, Al 4.5-5.5%, and V 3-4%.

[0008] This invention provides a method for preparing the high-strength, high-ductility hexa-eighth-membered FeNiCoCrAlV high-entropy alloy described above, comprising the following steps:

[0009] Fe, Ni, Co, Cr, Al and V are mixed according to the elemental ratio of the high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy and then vacuum arc-melted to obtain a high-entropy alloy ingot.

[0010] The high-entropy alloy ingot is subjected to homogenization treatment and hot rolling in sequence to obtain a hot-rolled plate;

[0011] The hot-rolled plate is subjected to solution treatment and cold rolling in sequence to obtain a cold-rolled plate;

[0012] The cold-rolled sheet is annealed to obtain the high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy.

[0013] Preferably, the vacuum arc melting is performed four times.

[0014] Preferably, the homogenization treatment is performed at a temperature of 1100–1200°C for 8–10 hours.

[0015] Preferably, the hot rolling temperature is 1100-1200℃, the hot rolling is a multi-pass rolling process, the reduction of each pass is 1mm, and the temperature is held for 2min after each pass. The total deformation of the hot rolling is 70-80%.

[0016] Preferably, the solution treatment temperature is 1100–1200°C, and the holding time is 20–30 min.

[0017] Preferably, the cold rolling temperature is room temperature, the cold rolling is a multi-pass rolling process, the reduction in each pass is 0.2 mm, and the total deformation of the cold rolling is 70-80%.

[0018] Preferably, the annealing temperature is 500–1000°C, and the holding time is 1 hour.

[0019] Preferably, the homogenization treatment, solution treatment and annealing treatment are all carried out in a vacuum tube furnace, and the heating rate of the vacuum tube furnace is 9°C / min.

[0020] This invention provides a high-strength, high-ductility hexa-element FeNiCoCrAlV high-entropy alloy, comprising the following atomic percentages: Fe 40-42%, Ni 18-22%, Co 18-22%, Cr 8-12%, Al 4-6%, and V 3-5%, with Ni and Co having equal atomic percentages. The high-entropy alloy provided by this invention is a hexa-element, non-equiatomic-ratio single-phase high-entropy alloy. By adding Al and V to the CoCrFeNi high-entropy alloy, the solid solution strengthening effect is increased while ensuring that the alloy still possesses the FCC structure. This is because the FCC structure has the most slip systems and excellent ductility, allowing the designed alloy to be rolled with large deformations at room temperature, thereby significantly refining the alloy's grain size and improving its strength. Therefore, the high-entropy alloy provided by this invention exhibits high strength and ductility, with an excellent balance between strength and ductility.

[0021] This invention provides a method for preparing the high-strength, high-ductility hexa-eighth-element FeNiCoCrAlV high-entropy alloy described above. This invention uses vacuum arc melting of elemental metals to obtain alloy ingots, and then controls the microstructure of the high-entropy alloy through rolling and heat treatment, regulating grain size and dislocation density to obtain a single-phase high-entropy alloy with excellent strength-ductility matching. The preparation method provided by this invention is simple and easy to operate.

[0022] The results of the examples show that the high-entropy alloy provided by the present invention has excellent strength-type matching. The high-entropy alloy after annealing at 800℃ has a yield strength of 364MPa and a plasticity (elongation at break) of 49.1%, and the high-entropy alloy after annealing at 700℃ has a yield strength of 866MPa and a plasticity of 14.9%. Attached Figure Description

[0023] Figure 1 The XRD patterns are of the high-entropy alloys prepared in Examples 1-3;

[0024] Figure 2 Microstructure of the high-entropy alloy prepared in Example 1;

[0025] Figure 3 Microstructure of the high-entropy alloy prepared in Example 2;

[0026] Figure 4 Microstructure of the high-entropy alloy prepared in Example 3;

[0027] Figure 5 The engineering stress-strain curves obtained by tensile testing of the high-entropy alloys prepared in Examples 1-3 are shown. Detailed Implementation

[0028] This invention provides a high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy comprising the following atomic percentages of elements: Fe 40-42%, Ni 18-22%, Co 18-22%, Cr 8-12%, Al 4-6%, V 3-5%, with Ni and Co having equal atomic percentages.

[0029] In this invention, the atomic percentage of Fe is preferably 41-42%, more preferably 41-41.5%; the atomic percentage of Ni is preferably 19-21%, more preferably 19-20%; the atomic percentage of Co is preferably 19-21%, more preferably 19-20%; the atomic percentage of Cr is preferably 9-11%, more preferably 9.5-10%; the atomic percentage of Al is preferably 4.5-5.5%, more preferably 4.5-5%; and the atomic percentage of V is preferably 3-4%, more preferably 3.5-4%.

[0030] This invention adds Al and V to a CoCrFeNi high-entropy alloy, enhancing solid solution strengthening while maintaining the FCC structure. The FCC structure possesses the most slip systems and exhibits excellent plasticity, allowing the designed alloy to undergo large deformation rolling at room temperature. This significantly refines the grain size and improves the alloy's strength, resulting in a high-strength, high-plasticity high-entropy alloy. Furthermore, the high-entropy alloy provided by this invention has non-equiatomic ratios of elements, with a significantly increased Fe (1538℃) content and a decreased Cr (1907℃) content. This helps reduce raw material and smelting costs because Fe is cheaper and has a lower smelting temperature compared to Cr.

[0031] This invention provides a method for preparing the high-strength, high-ductility hexa-eighth-membered FeNiCoCrAlV high-entropy alloy described above, comprising the following steps:

[0032] Fe, Ni, Co, Cr, Al and V are mixed according to the elemental ratio of the high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy and then vacuum arc-melted to obtain a high-entropy alloy ingot.

[0033] The high-entropy alloy ingot is subjected to homogenization treatment and hot rolling in sequence to obtain a hot-rolled plate;

[0034] The hot-rolled plate is subjected to solution treatment and cold rolling in sequence to obtain a cold-rolled plate;

[0035] The cold-rolled sheet is annealed to obtain the high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy.

[0036] This invention involves mixing Fe, Ni, Co, Cr, Al, and V according to the elemental ratio of a high-strength, ductile, hexavalent FeNiCoCrAlV high-entropy alloy and then performing vacuum arc melting to obtain a high-entropy alloy ingot. In this invention, Fe, Ni, Co, Cr, Al, and V are the corresponding elemental metals, with each element preferably having a purity of 99.99% and a weighing error of less than ±0.1%. Preferably, the vacuum arc melting is performed under a high-purity argon atmosphere, and the vacuum arc melting is preferably performed four times to ensure the uniformity of the ingot composition.

[0037] After obtaining the high-entropy alloy ingot, the present invention sequentially performs homogenization treatment and hot rolling on the high-entropy alloy ingot to obtain a hot-rolled plate. In the present invention, the homogenization treatment temperature is preferably 1100-1200℃, more preferably 1150-1200℃, and the holding time is preferably 8-10h, more preferably 9-10h. The present invention ensures the uniformity of the chemical composition of the ingot through the homogenization treatment. In the present invention, the hot rolling temperature is preferably 1100-1200℃, the hot rolling is preferably multi-pass rolling, the reduction of each pass is preferably 1mm, wherein each pass is preferably held for 2min (at the hot rolling temperature), and the total deformation of the hot rolling is preferably 70-80%, more preferably 73%. In the present invention, the specific operation of the hot rolling is preferably as follows: the ingot obtained by the homogenization treatment is held at 1100-1200℃ for 40min, and then the multi-pass rolling is performed. The present invention refines the grains and improves the mechanical properties of the alloy through hot rolling.

[0038] After obtaining the hot-rolled plate, the present invention sequentially performs solution treatment and cold rolling on the hot-rolled plate to obtain a cold-rolled plate. In the present invention, the solution treatment temperature is preferably 1100–1200℃, more preferably 1100–1150℃, and the holding time is preferably 20–30 min, more preferably 25–30 min. The present invention improves the processability of the alloy through the solution treatment, facilitating the subsequent rolling process. In the present invention, the cold rolling temperature is preferably room temperature, the cold rolling is preferably a multi-pass rolling process, the reduction in each pass is preferably 0.2 mm, and the total deformation of the cold rolling is preferably 70–80%, more preferably 70–75%. The present invention further refines the grains and introduces a large number of dislocations into the high-entropy alloy through the cold rolling, thereby improving the mechanical properties of the alloy.

[0039] After obtaining the cold-rolled sheet, the present invention anneales the cold-rolled sheet to obtain the high-strength, high-ductility hexa-membered FeNiCoCrAlV high-entropy alloy. In the present invention, the annealing temperature is preferably 500–1000℃, more preferably 700–1000℃, and even more preferably 700–800℃, and the holding time is preferably 1 hour. In the present invention, during the annealing process, the high-entropy alloy undergoes recovery recrystallization, which refines the grains, reduces residual stress, and thus improves the mechanical properties of the alloy.

[0040] In this invention, the homogenization treatment, solution treatment and annealing treatment are preferably carried out in a vacuum tube furnace, and the heating rate of the vacuum tube furnace is preferably 9°C / min.

[0041] To further illustrate the present invention, the high-strength, high-ductility hexa-eight-membered FeNiCoCrAlV high-entropy alloy and its preparation method provided by the present invention are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0042] Example 1

[0043] A high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy is composed of the following elements by atomic percentage: Fe 41%, Ni 20%, Co 20%, Cr 10%, Al 5%, V 4%, wherein the atomic percentages of Ni and Co are equal. The preparation method of the above-mentioned high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy is as follows:

[0044] (1) Prepare metallic elemental raw materials according to the designed composition of the target product FeNiCoCrAlV high-entropy alloy; the mass purity of the metallic elemental raw materials is 99.99%;

[0045] (2) The metal raw materials prepared in (1) are subjected to vacuum arc melting to obtain a FeNiCoCrAlV high-entropy alloy ingot with a mass of 2kg. Four melting processes are used to ensure the uniformity of the ingot composition.

[0046] (3) The FeNiCoCrAlV high-entropy alloy ingot obtained in (2) was homogenized by holding it at 1100℃ for 10h to ensure the uniformity of the chemical composition of the ingot. Then, the homogenized ingot was hot rolled at 1200℃ with a reduction of 1mm per pass. Each pass was held for 2min after rolling, and the total deformation was 73%. The obtained hot-rolled plate was solution-treated by holding it at 1100℃ for 30min, and then cold-rolled at room temperature with a reduction of 0.2mm per pass and a deformation of 70%.

[0047] (4) The cold-rolled sheet obtained in (3) is annealed at 1000℃ for 1h to obtain the FeNiCoCrAlV high-entropy alloy, denoted as A1000-1.

[0048] The sample after annealing in step (4) was wire-cut, and then the phase composition, microstructure and tensile properties were studied.

[0049] Example 2

[0050] A high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy has the same composition as in Example 1 and is prepared in a similar manner to Example 1. The difference is that the sample in Example 2 is prepared by annealing the cold-rolled sheet obtained in step (3) of Example 1 at 800°C for 1 hour. The rest is the same as in Example 1. The resulting high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy is denoted as A800-1.

[0051] Example 3

[0052] A high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy has the same composition as in Example 1 and is prepared in a similar manner to Example 1. The difference is that the sample in Example 3 is prepared by annealing the cold-rolled sheet obtained in step (3) of Example 1 at 700°C for 1 hour. The rest is the same as in Example 1. The resulting high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy is denoted as A700-1.

[0053] Phase composition analysis was performed on the high-entropy alloys prepared in Examples 1-3 using X-ray diffraction (XRD). Samples used for XRD analysis required mechanical grinding and polishing. The operating voltage and current were 40 kV and 200 mA, respectively. The X-ray source was CuKα (λ = 0.1542 nm) radiation, and the scanning angle 2θ ranged from 10 to 80°. Experimental results are as follows: Figure 1 As shown, by Figure 1 It can be seen that the high-entropy alloys obtained in Examples 1 to 3 are all FCC single-phase structures.

[0054] The high-entropy alloys prepared in Examples 1-3 were subjected to microstructural analysis. Microstructural observation was performed under EBSD. The samples were first mechanically ground, then mechanically polished, and finally electrolytically polished. The experimental results are as follows: Figures 2-4 As shown, by Figures 2-4 It can be seen that the high-entropy alloys in Examples 1 and 2 have equiaxed grains, while the sample in Example 3 is partially recrystallized and contains a large amount of banded structure introduced by cold deformation. The grain size of Example 2 (9 μm) is significantly smaller than that of Example 1 (40 μm).

[0055] The high-entropy alloys prepared in Examples 1-3 were subjected to uniaxial tensile tests using an Instron 3369 mechanical testing machine. The dimensions of the parallel portion of the tensile samples were 18 × 4 × 2 mm, the tensile rate was 0.6 mm / min, and each sample was tested three times. The tensile test results are as follows: Figure 5 As shown. By Figure 5 It can be seen that as the annealing temperature decreases, the strength of high-entropy alloys gradually increases, while the plasticity decreases accordingly. Specific mechanical property data are shown in Table 1.

[0056] Table 1. Mechanical property data of the high-entropy alloys prepared in Examples 1-3

[0057] sample Yield strength / MPa Tensile strength / MPa Elongation at break / % A1000-1 208 603 57.8 A800-1 364 718 49.1 A700-1 866 1004 14.9

[0058] Table 1 shows that the high-entropy alloys prepared in Examples 2 and 3 exhibit higher strength, with yield strengths increasing from 208 MPa in Example 1 to 364 MPa and 866 MPa, respectively. The high-entropy alloy of Example 2 has a tensile strength of 718 MPa and a plasticity of 49.1%, while the high-entropy alloy of Example 3 has a tensile strength of 1004 MPa and a plasticity of 14.9%. The significant increase in strength in Example 3 compared to Example 1 is attributed to the interfaces such as dislocation cells introduced by cold deformation, which significantly refines the microstructure of the high-entropy alloy. These findings demonstrate that the high-entropy alloys prepared in Examples 2 and 3 possess excellent strength-plasticity matching.

[0059] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy, composed of the following elements in atomic percentage: The composition is: Fe 40-42%, Ni 18-22%, Co 18-22%, Cr 8-12%, Al 4-6%, V 3-5%, with Ni and Co having equal atomic percentages. The preparation method of the high-strength, high-ductility, hexa-membered FeNiCoCrAlV high-entropy alloy includes the following steps: Fe, Ni, Co, Cr, Al and V are mixed according to the elemental ratio of the high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy and then vacuum arc-melted to obtain a high-entropy alloy ingot. The high-entropy alloy ingot is subjected to homogenization treatment and hot rolling in sequence to obtain a hot-rolled plate; The hot-rolled plate is subjected to solution treatment and cold rolling in sequence to obtain a cold-rolled plate; The cold-rolled sheet is annealed to obtain the high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy. The homogenization treatment is carried out at a temperature of 1100~1200℃ for 8~10 hours. The hot rolling temperature is 1100~1200℃, the hot rolling is a multi-pass rolling process, the reduction of each pass is 1mm, and the temperature is held for 2min after each pass. The total deformation of the hot rolling is 70~80%. The solution treatment temperature is 1100~1200℃, and the holding time is 20~30min; The cold rolling temperature is room temperature, the cold rolling is a multi-pass rolling process, the reduction in each pass is 0.2 mm, and the total deformation of the cold rolling is 70~80%. The annealing process is performed at a temperature of 700-800℃ for 1 hour.

2. The high-strength, high-ductility hexa-eighth-membered FeNiCoCrAlV high-entropy alloy according to claim 1, characterized in that, Elements with the following atomic percentages Composition: Fe 41~42%, Ni 19~21%, Co 19~21%, Cr 9~11%, Al 4.5~5.5%, V 3~4%.

3. The method for preparing the high-strength, high-ductility hexa-eighth-membered FeNiCoCrAlV high-entropy alloy according to claim 1 or 2, characterized in that, Includes the following steps: Fe, Ni, Co, Cr, Al and V are mixed according to the elemental ratio of the high-strength and ductile hexa-element FeNiCoCrAlV high-entropy alloy and then vacuum arc-melted to obtain a high-entropy alloy ingot. The high-entropy alloy ingot is subjected to homogenization treatment and hot rolling in sequence to obtain a hot-rolled plate; The hot-rolled plate is subjected to solution treatment and cold rolling in sequence to obtain a cold-rolled plate; The cold-rolled sheet is annealed to obtain the high-strength, high-ductility, hexa-element FeNiCoCrAlV high-entropy alloy. The homogenization treatment is carried out at a temperature of 1100~1200℃ for 8~10 hours. The hot rolling temperature is 1100~1200℃, the hot rolling is a multi-pass rolling process, the reduction of each pass is 1mm, and the temperature is held for 2min after each pass. The total deformation of the hot rolling is 70~80%. The solution treatment temperature is 1100~1200℃, and the holding time is 20~30min; The cold rolling temperature is room temperature, the cold rolling is a multi-pass rolling process, the reduction in each pass is 0.2 mm, and the total deformation of the cold rolling is 70~80%. The annealing process is performed at a temperature of 700-800℃ for 1 hour.

4. The preparation method according to claim 3, characterized in that, The vacuum arc melting process is performed four times.

5. The preparation method according to claim 3, characterized in that, The homogenization treatment, solution treatment, and annealing treatment are all carried out in a vacuum tube furnace, and the heating rate of the vacuum tube furnace is 9°C / min.

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