KR102301075B1 - Co-Ni-Cr-Fe HIGH ENTROPY ALLOY AND METHOD FOR MANUFACTURING THE SAME - Google Patents

Abstract

The present invention relates to a metal alloy that can be used as a component material for electromagnetic, chemical, shipbuilding, machinery, etc. or a component material used in extreme environments. It relates to a non-uniform composition high entropy alloy with improved mechanical properties by simultaneously increasing strength and ductility by increasing the work hardening rate by preventing the movement of the alloy and a method for manufacturing the same.

Description

Co-Ni-Cr-Fe-based high entropy alloy and method for manufacturing the same

The present invention relates to a Co-Ni-Cr-Fe-based high entropy alloy with a non-uniform composition exhibiting high mechanical properties by distributing twins or a second phase in an alloy matrix, and more particularly, twin boundary by twins or a second phase The present invention relates to a non-uniform composition Co-Ni-Cr-Fe-based high entropy alloy with improved mechanical properties by simultaneously increasing strength and ductility by increasing the work hardening rate by interfering with the movement of dislocations and a method for manufacturing the same.

In order to meet the complex functional needs that cannot be solved with a single metal, new types of materials called high entropy alloys as a new alloy system are being developed in various ways.

The high-entropy alloy has a large increase in configuration entropy by mixing of several elements rather than formation of a compound by reduction of free energy through formation of an intermetallic compound, thereby reducing the total free energy, and the metal between the multi-component alloy elements. It does not form an inter-compound or amorphous alloy, but means an alloy in which a solid solution in which several alloying elements are mixed is formed.

The high-entropy alloy became known through Non-Patent Document 1. _{In the Non-Patent Document 1, the multi-element alloy Fe 20} Cr ₂₀ Mn ₂₀ Ni ₂₀ Co ₂₀ prepared with the expectation that an amorphous alloy or complex intermetallic compound will be formed is formed as a crystalline FCC (Face Centered Cubic) solid solution, contrary to expectations. It is an alloy that has aroused interest. The high entropy alloy has a unique characteristic of forming a single phase even though the alloy elements of 4 to 5 or more elements are mixed in a similar ratio compared to the existing alloys in which other alloying elements are added to 60 to 90 wt% of the main alloying element, which It is found in alloys with large arrangement entropy due to mixing.

As prior art related to high entropy alloy, there are Patent Documents 1 and 2. The patent document 1 contains 5 or more types of metal components including V, Nb, Ta, Mo, Ti, etc. each element with a deviation of ±15 atomic% or less as a multi-type metal component, and all added elements act as main elements Disclosed is a high-entropy alloy that implements high hardness and high modulus composed of a single-phase solid solution having a face-centered cubic and/or body-centered cubic structure as an alloy system. However, in Patent Document 1 as described above, several kinds of expensive and heavy alloying elements are added, and there is a difficulty in the manufacturing process due to the melting point difference between the added alloying elements.

On the other hand, Patent Document 2 relates to a high entropy alloy that implements a high hardness manufactured through a powder metallurgy process of a ceramic phase (typically tungsten carbide) and a multi-component high entropy alloy powder, and has a face-centered cubic and/or body-centered cubic structure. It is a technology that realizes excellent mechanical properties by being composed of a single-phase solid solution of However, as in Patent Document 2, when an alloy is manufactured using a ceramic material, there is a problem in that manufacturing is difficult because a high-temperature process is required.

As in Patent Literature 1 and Patent Literature 2, high entropy alloys using metal or ceramic alloy elements are attracting attention as new materials in the metal field because they have excellent mechanical properties. Recently, various studies have been conducted as it is known that it exhibits excellent properties in extreme environmental properties such as high-temperature mechanical properties and low-temperature mechanical properties. Since it is at the level of manufacturing and evaluating mechanical properties and physical properties, research on alloy development to obtain more improved mechanical properties based on high entropy alloys is insufficient.

In addition, when the change in structure and mechanical properties due to the increase in entropy is applied to a non-uniform composition rather than an equal composition, new properties are likely to be induced or existing properties will be further improved. Studies and inventions to improve characteristics by applying

US Patent Publication US 2013/0108502 A1 US Patent Publication US 2009/0074604 A1

Matreial Science and Engineering A, Volumes 375-377, July 2004, page 213-218. Matreial Science and Engineering A, Volumes 711, January 2018, page 492-497.

The present invention introduces the concept of forming a solid solution matrix by arrangement entropy of a high entropy alloy to a material having a non-uniform composition rather than a uniform composition, and by designing the types and contents of various alloying elements in the direction of increasing entropy, brittleness due to increase in entropy It has technical significance in providing a high-entropy alloy with excellent workability and mechanical properties by suppressing the formation of intermetallic compounds.

Accordingly, one aspect of the present invention is a non-uniform composition Co-Ni with improved mechanical properties by simultaneously increasing strength and ductility by increasing the work hardening rate by preventing the movement of dislocations by twin boundary or phase boundary by twin or second phase An object of the present invention is to provide a -Cr-Fe-based high entropy alloy and a method for manufacturing the same.

The problems to be solved by the present invention are not limited to the problems mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The present invention for achieving the above object,

In atomic%, the workability and work hardening performance of the composition including Co: more than 35% and 80% or less, Ni: more than 35% and 80% or less, Cr: more than 5% to 35% or less, and Fe: more than 4.6% to 5.0% or less It relates to an excellent non-uniform composition high entropy alloy.

The non-uniform composition entropy alloy is, C: 0.01 to 5.0%, N: 0.01 to 5.0%, B: 0.01 to 5.0%, Si: 0.01 to 10%, Cu: 0.01 to 10%, V: 0.01 to 10% and Al: at least one of 0.01 to 10% may be further included.

Also, the present invention

preparing a metal material satisfying the compositional component;

preparing an alloy by melting the prepared metal material;

Homogenizing heat treatment of the prepared alloy at a temperature range of 800 to 1250° C. for 1 to 48 hours;

cooling after the homogenization heat treatment; and

It relates to a method for manufacturing a non-uniform composition high entropy alloy comprising; processing the cooled alloy.

The metal material is C: 0.01 to 5.0%, N: 0.01 to 5.0%, B: 0.01 to 5.0%, Si: 0.01 to 10%, Cu: 0.01 to 10%, V: 0.01 to 10%, and Al: 0.01 to It may further include one or more of 10%.

In order to alloy the prepared metal material, one selected from casting, arc melting, powder metallurgy, thermal spray casting, thermal spray coating, spray coating, and 3D-printing may be used.

After the homogenization treatment, the cooled alloy may be processed using one of forging, extrusion, rolling, and drawing.

It may further comprise the step of heat-treating the processed alloy for 0.5 to 72 hours at a temperature range of 350 ~ 800 ℃.

According to the present invention having the above configuration, the mechanical properties and workability of the high entropy alloy can be improved by inducing strain twins by inhibiting dislocation movement or inducing expansion of partial twin dislocations by reacting with dislocations of alloying elements.

In addition, the non-uniform composition high-entropy alloy of the present invention has greatly improved mechanical properties, so it can be applied to offshore plants requiring excellent toughness and high strength at low temperatures, as well as structural materials in extreme environments, as well as nuclear pressure vessels, cladding tubes, and thermal power plants. It has the advantage of being able to use more diverse high-entropy alloys such as applications as high-temperature materials such as turbine blades for use.

1 shows a conceptual diagram of the design of a twin-organic alloy by the influence of the stacking fault energy and the alloy composition of the high entropy alloy of the present invention.
2 is a flowchart showing an example of the manufacturing method of the present invention.
3 is a photograph observing the microstructure of Inventive Example 1 among the Examples of the present invention.
4 is a photograph observing the microstructure of Inventive Example 2 among the Examples of the present invention.
5 is an XRD analysis graph of Inventive Examples 1 and 2 among the Examples of the present invention.
6 is a graph showing the mechanical properties of Inventive Examples 1 and 2 among the Examples of the present invention.

Hereinafter, the present invention will be described.

The inventors of the present invention have recently conducted research on the development of new materials exhibiting mechanical properties of high strength and high ductility. As a result, by introducing the concept of a non-uniform composition to a high-entropy alloy of uniform composition, and by designing the types and contents of various alloying elements in a direction in which entropy increases, the formation of brittle intermetallic compounds caused by an increase in entropy is suppressed to improve workability and It was confirmed that a high entropy alloy having excellent work hardening performance can be provided. In addition, the present invention was completed after recognizing that the twin boundary or phase boundary caused by the twin or the second phase in the alloy matrix increases the work hardening rate by interfering with the movement of dislocations, thereby achieving excellent strength and ductility.

Hereinafter, the non-uniform composition high entropy alloy of the present invention will be described in detail.

The non-uniform composition high entropy alloy of the present invention, in atomic%, Co: more than 35% 80% or less, Ni: more than 35% 80% or less, Cr: more than 5% 35% or less, and Fe: more than 4.6% and 5.0% or less is composed, including

The Co, Ni, Fe, and Cr are elements constituting a high entropy alloy, and are a group of four-period transition elements, and are elements suitable for forming a solid solution and the like due to small differences in atomic radii. The Ni is an element that promotes a face-centered cubic (FCC) solid solution, Co improves the microstructure, and Cr improves corrosion resistance. The reason why the content of Co and Ni among the elements is greater than 35% and less than or equal to 80% is to maximize entropy as much as possible, so that the components of Co and Ni are higher than other elemental elements so that the matrix has the characteristics of a single phase. Specifically, the reason why the Ni content is more than 35% and less than 80% is to maximize entropy, but to make the matrix have the characteristics of FCC, and the reason why the Co content is more than 35% and less than 80% maximizes entropy, but This is to optimize refinement and induction of phase transformation.

And the reason that the Cr content is more than 5% and less than 35% is to maximize entropy but to optimize corrosion resistance, and the reason why the Fe content is more than 4.6% and less than 5.0% is to maximize entropy, but the matrix has FCC characteristics. am.

As described above, the present invention is characterized in that it provides a Co-Ni-Cr-Fe-based high-entropy alloy designed so that the Cr and Fe contents do not exceed the Co or Ni contents, respectively.

The non-uniform composition high entropy alloy of the present invention, C: 0.01 to 5.0%, N: 0.01 to 5.0%, B: 0.01 to 5.0%, Si: 0.01 to 10%, Cu: 0.01 to 10%, V: 0.01 to 10% and Al: may further include one or more of 0.01 to 10%.

The C, N, and B are interstitial elements, and Si, Cu, V, and Al are substitution-type elements, which react with dislocations or twin partial dislocations to induce twin or phase transformations, so that twin boundaries or phase boundaries interfere with the movement of dislocations. It serves to increase the curing rate.

The content of C, N and B is 0.01 to 5%, respectively, when these elements are too small, less than 0.01%, the reaction stress with dislocation is too small, and when it exceeds 5%, lattice distortion is severe and solid solution This is because it embrittles the matrix beyond the limit and reduces the efficiency of the reaction with dislocations.

On the other hand, Si, Cu, V and Al have a large difference in atomic radius compared to Fe, Cr, Ni and Co, which are the main elements constituting the matrix of a high entropy alloy, and a large difference in valence, etc. By interfering with the bonding of partial dislocations, twins or phase transformations are induced, and thus twin boundaries or phase boundaries impede the movement of dislocations, thereby increasing the work hardening rate. If the content of Si, Cu, V and Al is less than 0.01%, respectively, the segregation and reaction effect with dislocations is too small, whereas if it exceeds 10%, lattice distortion is severe and embrittles the matrix beyond the solid solution limit, The reaction efficiency with

1 shows a conceptual diagram of a twin organic alloy design by the influence of the stacking fault energy and the alloy composition of the non-uniform composition high entropy alloy of the present invention.

As shown in Fig. 1, wavy slip is exhibited in the high stacking fault energy region, and as the atomic size difference x alloy composition % value increases, alloying elements react with dislocations to inhibit dislocation movement or induce expansion of partial twin dislocations and deform induce twins. Accordingly, the wavy slip region changes to the planar slip region and the TWIP region even for materials with low stacking fault energy as well as high stacking fault energy. In a high entropy alloy with a lower stacking fault energy as described above, the twin boundary or phase boundary due to twin and phase transformation interferes with the movement of dislocations, thereby increasing the work hardening rate, thereby exhibiting superior strength and ductility compared to high entropy alloys.

Next, a method for producing a non-uniform composition high entropy alloy of the present invention will be described in detail.

A method for manufacturing a non-uniform composition high entropy alloy of the present invention, comprising the steps of: preparing a metal material satisfying the composition; preparing an alloy by melting the prepared metal material; and homogenizing heat treatment for 1 to 48 hours at a temperature range of 800 to 1250° C. for the prepared alloy.

2 is a flowchart showing an example of the manufacturing method of the present invention.

As shown in FIG. 2 , after preparing a metal material satisfying the above composition, it is melted to prepare an alloy.

The melting process is for alloying the manufactured metal material, and the method is not particularly limited in the present invention, and the method is generally performed in the technical field to which the present invention belongs.

That is, in the present invention, in order to alloy the prepared metal material, one method selected from casting, arc melting, powder metallurgy, thermal spray casting, thermal spray coating, spray coating, and 3D-printing may be used without limitation.

Next, in the present invention, the pre-fabricated alloy is subjected to a primary homogenization heat treatment in a temperature range of 800 to 1250° C. for 1 to 48 hours. Since various elements are mixed in a non-uniform composition high entropy alloy, homogenization heat treatment is performed to induce sufficient diffusion. The homogenization heat treatment is preferably maintained at a temperature range of 850 to 1250° C. for 1 to 48 hours. If the homogenization heat treatment temperature is less than 850 ℃, it takes a lot of time for the alloying elements to be uniformly dissolved in the alloy matrix, and if it exceeds 1250 ℃, it may cause a problem that some alloying elements cause partial melting.

And after cooling the alloy subjected to the first crack heat treatment in the present invention, it is processed.

Since the cooling method is not particularly limited in the present invention, the cooling method may be performed by water cooling, oil cooling, air cooling, or the like. Through the cooling process, some metal components that are not dissolved in the matrix in the microstructure are uniformly distributed.

In the present invention, the alloy cooled after the homogenization treatment may be processed using one of forging, extrusion, rolling, drawing, and the like.

Furthermore, in the present invention, heat treatment of the processed alloy in a temperature range of 350 to 800° C. for 0.5 to 72 hours; may further include.

And, after the processing, a heat treatment may be performed to create a microstructure in which twin crystals and phase transformation precipitates of various shapes by phase transformation exist simultaneously in a single-phase solid solution matrix structure. This heat treatment is a process for evenly precipitating phase transformation precipitates of various shapes by twins and phase transformation on a matrix, and is maintained at a temperature range of 350 to 850° C. for 0.5 to 72 hours and then cooled. If the secondary heat treatment temperature is less than 350 ℃, it is difficult to precipitate the alloying elements in the matrix, and if it exceeds 850 ℃, the alloying elements that have been deposited in the matrix are re-dissolved into the alloy matrix. Meanwhile, at this time, the cooling may be performed in the same manner as above, such as water cooling, oil cooling, air cooling, furnace cooling, or the like.

Hereinafter, embodiments of the present invention will be described in detail.

(Example)

First, a non-uniform composition high-entropy alloy having a composition component as shown in Table 1 was prepared.

Specifically, an alloy was prepared by preparing a metal material having the composition (at%) shown in Table 1 below, and arc melting it in a vacuum atmosphere. Thereafter, the homogenization heat treatment was performed at 1200° C. for 6 hours, followed by cooling.

Thereafter, each cooled alloy was rolled and heat treated at 850° C. for 1 hour to prepare a final alloy product.

On the other hand, for the non-uniform composition high entropy alloy prepared as described above, a 1 mm thick plate was made, a tensile test was performed, and the mechanical properties were evaluated, and the results are listed together in Table 1.

division alloy tensile strength
(MPa) yield strength
(MPa) elongation
(%) Comparative Example 1 Co ₂₀ Cr ₂₀ Fe ₂₀ Mn ₂₀ Ni ₂₀ 496 336 68 Comparative Example 2 Co ₂₅ Ni ₂₅ Fe ₂₅ Mn ₂₅ 784 532 60 Invention Example 1 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe ₅ 790 385 75 Invention Example 2 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.7 C _0.3 910 650 60 Invention example 3 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.7 N _0.3 810 564 75 Invention Example 4 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.7 B _0.3 805 560 70 Invention Example 5 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.6 C _0.2 N _0.2 880 600 65 Invention example 6 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.7 Al _0.3 875 540 58 Invention Example 7 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.7 V _0.3 900 643 55 Invention Example 8 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.7 Cu _0.3 860 585 59 Invention Example 9 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.7 Si _0.3 855 534 50 Invention example 10 Co ₄₀ Ni ₄₀ Cr ₁₅ Fe _4.6 V _0.2 C _0.2 925 660 53

As shown in Table 1, in the case of Inventive Examples 1 to 10, in which the composition of the present invention is satisfied, twin crystals and phase transformation precipitates of various shapes due to phase transformation exist simultaneously in the single-phase solid solution matrix structure, superior strength and ductility compared to Comparative Examples It can be seen that a balance can be obtained. In particular, in comparison with Comparative Examples 1 and 2, the high entropy alloy of unequal composition in the inventive example of the present invention exhibits the movement of dislocations in the twin boundary or phase boundary due to twin or phase transformation in the matrix when deformed in the single-phase solid solution matrix structure. It can be confirmed that by increasing the work hardening rate by interfering, superior strength and ductility can be secured compared to high-entropy alloys of uniform composition.

3 is a photograph observing the microstructure of Inventive Example 1, and it can be confirmed that many dislocations are formed in the matrix as shown in FIG. 3a, and many twins are formed in the matrix as shown in FIG. 3b. can confirm.

4 is a photograph of the microstructure of Example 2 of the present invention, and as shown in FIG. 4, it is a microstructure showing the presence of a second phase in the matrix.

5 is a graph showing the XRD analysis results of Inventive Examples 1 and 2 above. As shown in FIG. 5 , it can be seen that Inventive Examples 1 and 2 have a matrix structure of a single-phase face-centered cubic structure.

Meanwhile, FIG. 6 is a graph showing the results of evaluating the mechanical properties of Inventive Examples 1 and 2 above. As shown in Figure 6, compared to Inventive Example 1, Inventive Example 2 in which carbon (C) was added to distribute the second phase in the matrix exhibited higher strength, and the elongation was the alloy of Inventive Example 1 in which twin crystals were formed in the matrix. This shows that the alloy of Inventive Example 2 is larger than that of the alloy. That is, it can be seen that both Inventive Example 1 and Inventive Example 2 exhibit superior properties in both strength and elongation compared to the alloy of Comparative Example.

The present invention is not limited to the above embodiments and examples, but may be manufactured in various different forms, and those of ordinary skill in the art to which the present invention pertains can use other methods without changing the technical spirit or essential features of the present invention. It will be understood that it may be embodied in specific forms. Therefore, it should be understood that the embodiments and embodiments described above are illustrative in all respects and not restrictive.

Claims (7)

delete delete Preparing a metallic material comprising, in atomic%, Co: more than 35% and 40% or less, Ni: more than 35% and 40% or less, Cr: more than 5% to 15% or less, and Fe: 4.6% or more to 5.0% or less;
preparing an alloy by melting the prepared metal material;
First homogenizing heat treatment for 1 to 48 hours in a temperature range of 800 to 1250 ℃ the prepared alloy;
cooling after the homogenization heat treatment; and
Processing the cooled alloy; Method for producing a non-uniform composition high entropy alloy excellent in workability and work hardening performance comprising a.
According to claim 3, wherein the metal material, C: 0.01 to 5.0%, N: 0.01 to 5.0%, B: 0.01 to 5.0%, Si: 0.01 to 10%, Cu: 0.01 to 10%, V: 0.01 to 10% and Al: A method for producing a non-uniform composition high entropy alloy excellent in workability and work hardening performance, characterized in that it further comprises at least one of 0.01 to 10%.
[4] The processability and processing according to claim 3, wherein one selected from casting, arc melting, powder metallurgy, thermal spray casting, thermal spray coating, spray coating, and 3D-printing is used to alloy the prepared metal material. A method for producing a non-uniform composition high entropy alloy with excellent hardening performance.
The method of claim 3, wherein the alloy cooled after the homogenization treatment is processed using one of forging, extrusion, rolling, and drawing methods. .
[Claim 4] The method of claim 3, further comprising heat-treating the processed alloy at a temperature of 350-800° C. for 0.5-72 hours.

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