KR20170109158A

KR20170109158A - High entropy alloy having interstitial solid solution hardening and method for manufacturing the same

Info

Publication number: KR20170109158A
Application number: KR1020160032683A
Authority: KR
Inventors: 홍순익; 송재숙; 김형섭
Original assignee: 충남대학교산학협력단
Priority date: 2016-03-18
Filing date: 2016-03-18
Publication date: 2017-09-28
Also published as: KR101783242B1

Abstract

TECHNICAL FIELD The present invention relates to a metal alloy which can be used for parts materials of electromagnetic, chemical, shipbuilding, machinery and the like and for parts used in extreme environments, and more particularly to a high entropy alloy.

Description

TECHNICAL FIELD [0001] The present invention relates to a high entropy alloy and a method of manufacturing the same,

Along with the breakthrough of industrial technology level, a new type of material called High Entropy Alloy has been recently developed as a new alloy system in order to meet the multi functional requirement that can not be solved by a single metal. Have been proposed and developed.

The entropy alloys are formed by the formation of intermetallic compounds to increase the entropy of configuration due to the mixing of various elements rather than the formation of compounds by reduction of free energy, thereby reducing the total free energy, Means an alloy in which a solid solution in which various alloying elements are mixed is formed instead of forming an intermediate compound or an amorphous alloy.

The above-mentioned high entropy alloy is known through Non-Patent Document 1. In the above Non-Patent Document 1, a multi-element alloy Fe ₂₀ Cr ₂₀ Mn ₂₀ Ni ₂₀ Co ₂₀ which is anticipated to form an amorphous alloy or a complex intermetallic compound is formed into a crystal of FCC (Face Centered Cubic) solid solution unexpectedly It is an alloy that has attracted interest. The above-mentioned entropy alloys have a unique characteristic of being single-phase, even though alloying elements of 4 to 5-member system or more are mixed at a similar ratio, compared with the case where other alloying elements are added to main alloying elements of 60 to 90 wt% Arrangement entropy due to mixing is found in large alloys.

The high entropy alloy is an alloying system containing at least four metal components having an atomic concentration of between 5 and 35 at.% And all the alloying elements added serve as the main element. Due to the similar atomic fraction in the alloy, Entropy is induced and a simple structure solid solution stable at high temperature instead of an intermetallic compound or an intermediate compound is formed.

Patent literatures 1 and 2 are prior art related to high entropy alloys. Patent Document 1 discloses a method of manufacturing a semiconductor device which comprises a plurality of metal components and at least five kinds of metal components, each of which includes V, Nb, Ta, Mo, Ti, etc. in a deviation of ± 15 atomic% or less, And a high entropy alloy which is composed of a single phase solid solution of a face-centered cubic and / or a body-centered cubic structure, which realizes a hardness and a high modulus. However, the above-mentioned Patent Document 1 has various kinds of expensive heavy alloying elements added, and there is a difficulty in the manufacturing process due to the difference in melting point between the added alloying elements.

On the other hand, Patent Document 2 relates to a high entropy alloy which realizes a high hardness produced by a powder metallurgy process in a ceramic phase (typically tungsten carbide) and a multi-component giant alloys powder, and has a face centered cubic and / Of single-phase solid solution. However, as in the case of Patent Document 2, there is a problem that it is difficult to manufacture an alloy using a ceramic material because a high-temperature process is required.

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

Matreial Science and Engineering, Volumes 375-377, July 2004, pages 213-218.

An aspect of the present invention is to provide a high entropy alloy, and more particularly, to provide a high entropy alloy capable of securing excellent strength and ductility by using an invasive solid solution and a method of manufacturing the same.

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

An embodiment of the present invention is a steel sheet comprising, by weight%, Fe: more than 5% to 35%, Cu: more than 5% to less than 35%, Ni: more than 5% to less than 35% And 35% or less,

0.05 to 0.5% of C, and 0.05 to 0.5% of N. The present invention provides an interstitial solid solution strengthening entropy alloy containing at least one of C: 0.05 to 0.5% and N: 0.05 to 0.5%.

Another aspect of the present invention is a steel sheet comprising, by weight%, Fe: more than 5% and not more than 35%, Cu: not less than 5% and not more than 35%, Ni: not less than 5% and not more than 35%, Mn: And Co: more than 5% and not more than 35%; and a metal material containing at least one of C: 0.05 to 0.5% and N: 0.05 to 0.5%;

Melting the prepared metal component to produce an alloy;

Subjecting the produced alloy to a homogenization heat treatment; And

And a step of cooling after the homogenization heat treatment and a step of cooling after the homogenization heat treatment.

According to the present invention, an alloy element is added to a high-entropy alloy to form an intrusion-type solid solution, thereby strengthening a matrix and realizing excellent strength and ductility. This makes it possible to utilize a wide variety of high entropy alloys.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photograph of microstructure of Inventive Example 1 of the present invention. FIG.
2 is an XRD analysis graph of Inventive Example 1 of the present invention.

The inventors of the present invention have studied a method for improving mechanical / physical properties such as strength and ductility of a high entropy alloy. As a result, in a high entropy alloy in which one metal component exhibits partial employment or employment relationship with other metallic components, carbon (C) and nitrogen (N), which are structural strengthening and stabilizing elements, are added to the periodic structure matrix To increase the mixing entropy to achieve high strength and high ductility, leading to the present invention.

Hereinafter, the inventive entropy alloy will be described in detail. First, the composition of the inventive entropy alloy will be described in detail.

The present inventive high entropy alloy contains Fe: more than 5% to 35%, Cu: more than 5% to 35%, Ni: more than 5% to less than 35%, Mn: more than 5% to less than 35% % Or more and 35% or less, and contains at least one of C: 0.05-0.5% and N: 0.05-0.5%.

The Fe, Cu, Ni, Mn, and Co elements constitute a high entropy alloy, and are four-cycle transition element groups.

The entropy alloy of the present invention is Fe-Cu-Ni-Mn-Co, Fe-Cu-Ni-Co, Fe-Cu-Ni-Mn or Fe-Cu- (C) and nitrogen (N).

The alloy elements of Fe, Cu, Ni, Mn and Co do not form precipitates such as carbides or nitrides even when a small amount of carbon (C) to nitrogen (N) is added and increase the known mixing entropy To form an intrusion solid solution. On the other hand, in the present invention, Cr is not added, because Cr bonds with C or N to form a precipitate such as carbide or nitride. On the other hand, Mn alone tends to form carbides or nitrides by bonding with C or N. However, when the mixed entropy increases, solid solution forms, which is an element that can be added. The reason why the content of Fe, Cu, Ni, Mn, and Co is not less than 5% and not more than 35% is to induce a change in entropy in a homogeneous composition maximizing entropy as possible, It is for this reason.

The entropy alloy of the present invention adds carbon (C) and / or nitrogen (N) capable of strengthening or stabilizing single-phase FCC (face center cubic) to BCC (body center cubic) structures. A solid solution base in which an intrusion type solid solution strengthening effect is added through the addition of C or N is formed on a substitutional solid solution base formed by some or all of the main alloy elements Fe, Cu, Ni, Mn and Co. The addition of C or N forms an intrinsic solid solution and stabilizes the solid solution by contributing to the increase of configurational entropy of the high entropy alloy matrix formed by Fe, Cu, Ni, Mn and Co. However, if the cooling rate during casting is high or if the post-casting heat treatment is not sufficient, the alloying element combination may be formed in another separated phase and entropy solid solution base.

The content of C and N is preferably 0.05 to 0.5%. If the contents of C and N are less than 0.05%, they do not contribute to the increase of entropy. If the contents of C and N are more than 0.5%, it may exceed the solubility limit and precipitate like carbonitride may be formed.

In addition to the above-mentioned elements, the entropy alloy of the present invention may further include at least one of Mo and W in an amount of 3% or less. When Mo or W is added in an amount of 3% or less, it is solidified in a single phase of face-centered cubic (FCC) to body-centered cubic (BCC) structure composed of the intrusion-type solid solution without forming any additional compound to improve strength. If Mo or W exceeds 3%, reduction of free energy due to formation of carbide or nitride becomes higher than increase of entropy, and there is a possibility that precipitates and the like are formed.

Hereinafter, the method for producing the entropy alloy of the present invention will be described in detail. In the present invention, it is preferable that at least Fe: more than 5% and not more than 35%, Cu: more than 5%, not more than 35%, Ni: more than 5% to less than 35%, Mn: more than 5% to less than 35%, and Co: And 35% or less. A metal material containing at least one of C: 0.05-0.5% and N: 0.05-0.5% is prepared, and the metal material is melted, homogenized and heat-treated and cooled , And processing can be added to the thus-prepared high entropy alloy.

The melting process is for alloying the produced metal material, and the method of the present invention is not particularly limited, and the melting process is generally performed in the technical field of the present invention. For example, by casting, arc melting, powder metallurgy or the like.

Next, the produced alloy is homogenized and heat-treated. The homogenization is a process for inducing diffusion and is preferably carried out at a temperature of 600 to 1200 ° C for 1 to 48 hours.

After the homogenization heat treatment, cooling is performed. Since the cooling method is not particularly limited, it can be performed by a method of air cooling or furnace cooling. During the cooling process, elements of C or N are dissolved. That is, a solid entropy solid solution having an intrusion-type solid strengthening effect added by the addition of C or N is formed in a substitutional solid solution base formed of a part or all of Fe, Cu, Ni, Mn and Co, Alloy.

Further processing can be performed on the high entropy alloy produced by the above method. In the present invention, the above-described working method is not particularly limited, and can be applied to any ordinary working method in the technical field of the present invention. Examples thereof include hot working, rolling, drawing, and room temperature processing.

Hereinafter, embodiments of the present invention will be described in detail. The following examples are for the purpose of understanding the present invention and are not intended to limit the present invention.

(Example)

First, the high entropy alloys of Comparative Examples 1 to 3 and Inventive Examples 1 to 6 were produced as shown in Table 1 below.

A metal material having the composition (% by weight) shown in the following Table 1 was prepared and subjected to arc melting in a vacuum atmosphere to prepare an alloy. Thereafter, homogenization heat treatment was performed at 1050 ° C for 24 hours and then cooled.

On the other hand, the thus-prepared high entropy alloy was rolled at room temperature to produce a sheet having a thickness of 1 mm.

The tensile test was carried out on the hyperentrophic alloys prepared as described above, and their mechanical properties were evaluated.

division alloy Microstructure Tensile Strength (MPa) Yield strength (MPa) Elongation (%) Comparative Example 1 Co ₂₀ Cr ₂₀ Fe ₂₀ Mn ₂₂ Ni ₁₈ Solid solution phase 620 480 40 Comparative Example 2 Fe ₂₅ Ni ₂₅ Co ₂₅ Cr ₂₅ Solid solution phase 1000 870 35 Comparative Example 3 Fe ₂₀ Mn ₂₀ Ni ₂₀ Co ₂₀ Cr ₂₀ Solid solution phase 760 640 17 Inventory 1 _{Fe 20 Cu 20 Ni 20 Mn 19} .85 Co 20 C 0 .15 Solid solution phase 1150 935 26 Inventory 2 _{Fe 20 Cu 20 Ni 20 Mn 19} .85 Co 20 N 0 .15 Solid solution phase 1195 913 24 Inventory 3 _{Fe 25 Cu 25 Ni 24 .85 Co} 25 C 0 .15 Solid solution phase 1025 945 28 Honorable 4 _{Fe 25 Cu 25 Ni 24 .85 Mn} 25 N 0 .15 Solid solution phase 1050 945 23 Inventory 5 _{Fe 25 Cu 25 Ni 25 Mn 22} .85 Mo 2 C 0 .15 Solid solution phase 1130 963 21 Inventory 6 _{Fe 25 Cu 25 Ni 25 Mn 22} .85 Mo 2 N 0 .15 Solid solution phase 1160 965 20

As shown in Table 1, in the case of Inventive Examples 1 to 6 satisfying the composition of the present invention and having a matrix containing an invasive solid solution or a substituted solid solution and having a filament structure, both the high strength and the excellent elongation .

Figure 1 is a picture of observing the microstructure of the alloy and the entropy of the invention example 1 of _{Fe 20 Cu 20 Ni 20 Mn 19} .85 Co 20 C 0 .15. As shown in FIG. 1, it can be confirmed that a high entropy alloy of a single-phase face-centered cubic (FCC) structure is formed by adding C as an interstitial-type solid element.

2 is a graph showing the results of XRD analysis of Inventive Example 1. FIG. Referring to FIG. 5, it can be confirmed that the inventive example 1 is a single-phase structure having a base structure of a face-centered cubic structure.

Claims

Fe: more than 5% to 35% or less, Cu: more than 5% to 35% or less, Ni: more than 5% to less than 35%, Mn: more than 5% to less than 35%, and Co: more than 5% to less than 35% Group includes at least four selected from the group,
C: 0.05 to 0.5% and N: 0.05 to 0.5%.

The method according to claim 1,
Wherein said high entropy alloy further comprises at least one of Mo and W in an amount of 3% or less.

Ni: more than 5% to 35% or less, Mn: more than 5% to 35% or less, and Co: more than 5% to less than 35% Preparing a metallic material containing at least two selected from the group consisting of C: 0.05 to 0.5% and N: 0.05 to 0.5%;
Melting the prepared metal component to produce an alloy;
Subjecting the produced alloy to a homogenization heat treatment; And
After the homogenization heat treatment, cooling
Wherein the interstitial solid solution strengthening entropy alloy is prepared by a method comprising the steps of:

The method of claim 3,
Wherein the metal material additionally comprises at least 3% of at least one of Mo and W. < RTI ID = 0.0 > 18. < / RTI >

The method of claim 3,
Wherein said melting is performed by any one of casting, arc melting, and powder metallurgy.