KR102096311B1 - Preparation method of body-centered cubic high-entropy alloy powder and the powder thereof - Google Patents

Abstract

An embodiment of the present invention comprises the steps of forming an ingot by dissolving the body-centered cubic structure high-entropy alloy material by a vacuum arc remelting method; Heat-treating the ingot in a hydrogen atmosphere to coarsely pulverize by lattice expansion to form a coarse pulverized material; Milling the coarse pulverized material to form a fine pulverized material; And forming a body-centered cubic structure high-entropy alloy powder by vacuum-treating the finely pulverized material to remove hydrogen, thereby providing a method for manufacturing a body-centered cubic structure high-entropy alloy powder, and milling time. It is possible to shorten and solve the problem of powder contamination caused by iron component inflow and oxidation from milling media, but has the effect of producing a body-centered cubic structure high-entropy alloy powder having excellent mechanical strength at high temperatures.

Description

Method of manufacturing a body-centered cubic structure high-entropy alloy powder and powder produced by the method {Preparation method of body-centered cubic high-entropy alloy powder and the powder thereof}

The present invention relates to a method for manufacturing a body-centered cubic structure high-entropy alloy powder and a powder produced by the method, and more specifically, to heat the ingot of the body-centered cubic structure high-entropy alloy material in a hydrogen atmosphere to hydrogen embrittlement of metals. It relates to a manufacturing method that facilitates the grinding process by coarse pulverization.

As shown in FIG. 1, traditionally, the common alloy 100 is composed of main elements 101 such as iron, copper, aluminum, magnesium, and titanium, and various small amounts of alloying elements 102. Typically, in the case of conventional multi-element alloys, as the number and amount of alloying elements 102 increases, an intermetallic compound that weakens the mechanical properties of the material is formed.

High-entropy alloy (HEA) is composed of a number of major elements of similar proportions that cannot be specified as the main element, so that no intermetallic compound is formed due to the high composition entropy, and the face-centered cubic structure or body-centered cubic Forms a single-phase structure. The composition and structural specificity of these high-entropy alloys are high strength and toughness due to severe lattice distortion, high temperature strength, structural stability, superior to superalloy such as Inconel, low creep resistance, low diffusion rate, good weldability, and strain hardening ability. It is known that this exhibits a large and high strain sensitivity of the flow stress. At room temperature, the general corrosion resistance of high-entropy alloys, represented by Cantor alloys, is superior to 304S stainless steel. Due to these outstanding properties, high-entropy alloys are spotlighted as promising multi-functional materials and next-generation structural materials.

Figure 2 shows the structure of the high-entropy alloy 200. The five elements make up the alloy, and the fractions of the constituent elements are similar, so the main element cannot be identified. It also shows a very distorted grid.

High-entropy alloys are divided into face-centered cubic (FCC) and body-centered cubic (BCC) series according to single-phase formation. The typical face-centered cubic high-entropy alloy is Fe-Co-Cr-Mn-Ni, and the face-centered cubic high-entropy alloy has low lamination defect energy and shows high strength and ductility at cryogenic temperatures. The body-centered cubic structure high-entropy alloy is mixed with elements such as W, Mo, Ti, which have a higher melting point than the face-centered cubic structure high-entropy alloy, and is excellent in mechanical strength at high temperatures, and is used in space, aviation parts, gas turbines, etc.

A representative method of manufacturing a high-entropy alloy is mechanical alloying (MA). Mechanical alloying refers to a process in which the powder is formed by impact of a hard ball or the like. The principle of mechanical alloying is that alloying progresses as the ball and material collide as the container rotates, and the process of hardening, flattening, cold bonding, and cracking is repeated. The mechanical alloying process has many advantages. It is possible to process at a temperature of room temperature or lower, and it is possible to manufacture materials that cannot be produced by a casting method due to a large melting point difference. In addition, problems such as segregation of the casting method can be minimized.

However, mechanical alloying was used as a method of manufacturing a high-entropy alloy mainly in a face-centered cubic high-entropy alloy having a relatively low melting point, and a body-centered cubic structure high-entropy alloy having a relatively high melting point and high mechanical strength through mechanical alloying. There is a problem that requires a long process to manufacture. In addition, during the long-time process, a contamination problem of a high-entropy alloy powder finally generated due to oxidation or inflow of iron components from a milling vessel and a milling media occurred.

The technical problem to be achieved by the present invention is to solve the above-mentioned problems, shorten the milling time in the manufacture of the body-centered cubic high-entropy alloy powder and due to the iron component inflow and oxidation from the milling media. It is to provide a method for manufacturing a high-entropy alloy powder of a body-centered cubic structure having excellent mechanical strength at high temperatures while being able to solve the problem of powder contamination occurring.

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

In order to achieve the above technical problem, an embodiment of the present invention comprises the steps of dissolving a body-centered cubic high-entropy alloy material by a vacuum arc remelting method to form an ingot; Heat-treating the ingot in a hydrogen atmosphere to coarsely pulverize by lattice expansion to form a coarse pulverized material; Milling the coarse pulverized material to form a fine pulverized material; And removing the hydrogen by vacuum heat-treating the finely pulverized material to form a high-entropy alloy powder having a body-centered cubic structure.

In one embodiment of the present invention, the body-centered cubic structure high-entropy alloy material may include four or more selected from W, Ta, Mo, Nb, Cr, V, Ti, Hf and Zr.

In one embodiment of the present invention, the body-centered cubic structure high-entropy alloy material may further include one or more selected from Mn, Fe, Co, Ni, Cu and Al.

In one embodiment of the present invention, heat treatment in the hydrogen atmosphere may be performed under the condition of 100% hydrogen.

In one embodiment of the invention, the heat treatment in the hydrogen atmosphere may be performed at a heat treatment temperature of 450 to 1200 ℃.

In one embodiment of the present invention, the heat treatment in the hydrogen atmosphere may be maintained for 90 minutes to 150 minutes by reaching the heat treatment temperature at a heating rate of 3 to 7 ℃ / min.

In one embodiment of the present invention, the dew point of hydrogen during heat treatment in the hydrogen atmosphere may be less than -20 ° C.

In one embodiment of the present invention, when the ingot (ingot) and coarse pulverized by Cu Kα X-ray diffraction analysis, the angle of 110 peaks of the coarse pulverized material may be shifted to the left by 0.1 degrees or more compared to the ingot. have.

In one embodiment of the present invention, the milling (milling) is a horizontal mill (Horizontal mill), Attrition mill (Atrrition mill), planetary mill (Planetary mill) and a hammer mill (hammer-mill) selected from any one It can be done by one.

In one embodiment of the present invention, the milling can be performed for 20 to 60 minutes.

In order to achieve the above technical problem, another embodiment of the present invention provides a body-centered cubic structure high-entropy alloy powder prepared by the above manufacturing method.

According to an embodiment of the present invention, in the production of the body-centered cubic structure high-entropy alloy powder, it is possible to shorten the milling time and solve the problem of powder contamination caused by iron component inflow and oxidation from the milling media. It is possible to provide a method for manufacturing a body-centered cubic structure high-entropy alloy powder having excellent mechanical strength at high temperatures.

It should be understood that the effects of the present invention are not limited to the above-described effects, and include all effects that can be deduced from the configuration of the invention described in the detailed description or claims of the present invention.

1 is a structural diagram showing the structure of a general alloy.
2 is a structural diagram showing the structure of a high-entropy alloy.
3 is a schematic diagram of a method for manufacturing a body-centered cubic structure high-entropy alloy powder according to an embodiment of the present invention.
4 is a comparative picture of ingots and coarse pulverized before and after hydrogen heat treatment according to an embodiment of the present invention.
5 is a photograph of testing the Vickers hardness of the ingot and the coarsely pulverized material according to an embodiment of the present invention.
6 is a graph comparing 110 peaks in Cu Kα X-ray diffraction analysis of an ingot and a coarsely pulverized product according to an embodiment of the present invention.

Hereinafter, the present invention will be described with reference to the accompanying drawings. However, the present invention may be implemented in various different forms, and thus is not limited to the embodiments described herein. In addition, in order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and like reference numerals are assigned to similar parts throughout the specification.

Throughout the specification, when a part is "connected (connected, contacted, coupled)" to another part, this is not only when it is "directly connected", but also "indirectly" with another member in between. "It also includes the case where it is. Also, when a part is said to “include” a certain component, this means that other components may be further provided instead of excluding the other component unless otherwise stated.

The terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “include” or “have” are intended to indicate that a feature, number, step, operation, component, part, or combination thereof described in the specification exists, and that one or more other features are present. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, a method for manufacturing a high-entropy alloy powder with a body-centered cubic structure will be described.

3 schematically shows an embodiment of the present invention. The present invention is a step of forming an ingot (ingot) by dissolving the body-centered cubic structure high-entropy alloy material by a vacuum arc re-dissolution method (S100); Heat-treating the ingot in a hydrogen atmosphere to coarsely pulverize by lattice expansion (S200); Forming a fine pulverized material by milling the coarse pulverized material (S300); And forming a body-centered cubic structure high-entropy alloy powder by removing the hydrogen by vacuum heat-treating the finely pulverized material (S400).

The body-centered cubic structure high-entropy alloy material includes four or more selected from W, Ta, Mo, Nb, Cr, V, Ti, Hf, and Zr. The metal element has a high melting point, excellent mechanical strength, and forms a high-entropy alloy with a body-centered cubic structure when producing an alloy with a similar fraction. Since a single metal also has high strength, it is not easy to process by milling. Therefore, a method of shortening the milling time is required to proceed with mechanical alloying.

The alloy material may be prepared in the form of an alloy of two or more elements or a single metal, or a mixture thereof. For example, if the constituent elements of the desired body-centered cubic structure high-entropy alloy are W, Ta, Nb, V, Ti, each of the above elements can be prepared in the form of a single metal, and the W-Ta alloy and Nb-V-Ti It may be prepared in the form of an alloy, or may be prepared in a single metal form of each of W-Ta alloy and Nb, V, Ti.

In addition, the body-centered cubic high-entropy alloy material may further include at least one selected from Mn, Fe, Co, Ni, Cu, and Al.

The vacuum arc remelting method (VAR) used in the step S100 is casting the first refined metal in a thin electrode form, generating arcs in a water-cooled mold in a vacuum, and sequentially melting from the tip of the electrode rod It means the method of dripping in. Since it undergoes a process such as degassing during dropping, it has the advantage of increasing the refining degree, and is used for melting high-strength metals such as high melting points. In the present invention, since the metal having a high melting point is mainly dissolved for manufacturing a body-centered cubic structure high-entropy alloy powder, an ingot is formed using a vacuum arc remelting method.

When an ingot is formed, in step S200, it is heat treated in a hydrogen atmosphere. Heat treatment in a hydrogen atmosphere may be performed under conditions of 100% hydrogen. After placing an ingot inside the furnace for heat treatment, hydrogen can be injected and heated externally to heat treatment. The type of furnace may be an induction heating type, a gas heating type, a mixing type, and the like, and is not limited as long as it has a structure capable of heating by injecting and sealing ingots and hydrogen.

When heat treated in a hydrogen atmosphere, ingots receive hydrogen and diffuse into it. The amount of hydrogen diffused increases as the heat treatment progresses, and the brittleness of the ingot is increased by hydrogen. This is due to the expansion of the metal lattice inside the ingot by hydrogen, and when the expansion becomes severe, the ingot eventually becomes coarsely crushed and split into pieces. The greater the amount of hydrogen, the greater the degree of embrittlement, and in the present invention, the purpose is to increase the brittleness, so heat treatment is performed under the condition of 100% hydrogen.

Heat treatment in a hydrogen atmosphere may be performed at a heat treatment temperature of 450 to 1200 ° C. At temperatures below 450 ° C, hydrogen embrittlement is not sufficiently induced, so it is not preferable. At temperatures above 1200 ° C, hydrogen embrittlement and crushing efficiency are lowered compared to the energy input. The ingot (ingot) in which hydrogen embrittlement is induced within the above range is coarsely pulverized to increase the grinding efficiency in the subsequent S300 process.

The temperature rise up to the heat treatment temperature may be made at a heating rate of 3 to 7 ° C / min. When heating at a rate of less than 3 ° C / min, the heat treatment time is too long, which is undesirable, and when it exceeds a temperature of 7 ° C / min, it is not preferable because the process efficiency compared to the energy input to the heating decreases.

When the heat treatment temperature is reached, heat treatment may be performed by maintaining the temperature for 90 minutes to 150 minutes. The time of less than 90 minutes is not preferable because the heat treatment is not sufficiently performed, so that hydrogen embrittlement may not be sufficient, and the time exceeding 150 minutes may increase the process time and decrease the efficiency of hydrogen embrittlement compared to the energy input to heating. This is not preferred.

When heat treatment in the hydrogen atmosphere, the dew point of hydrogen may be less than -20 ° C. Hydrogen reacts with oxygen to generate water vapor. The high dew point of hydrogen means that the concentration of oxygen in the reactor or the concentration of oxygen contained in the reactant is high. When the concentration of oxygen increases and the dew point of hydrogen increases, contamination of the ingot to be heat treated is caused. Oxygen acts as an impurity in the body-centered cubic high-entropy alloy, which weakens the properties of the alloy, so it is preferable that the concentration is not increased. For example, when the dew point of hydrogen is less than -20 ° C in a 100% hydrogen reactor condition, if the concentration of oxygen contained in the ingot before heat treatment is 0.13 wt%, the oxygen concentration contained in the crude pulverized material after heat treatment is 0.15 wt% It may be: At dew points above -20 ° C, the oxygen concentration can increase significantly, which is not desirable.

4 is a photograph showing the shape of the ingot and the coarsely pulverized before and after hydrogen heat treatment. It can be seen that after heat treatment in a hydrogen atmosphere, hydrogen embrittlement is induced and the ingot is coarsely crushed by lattice expansion.

When Cu Kα X-ray diffraction analysis of the ingot and coarse pulverized material, the angle of 110 peaks of the coarse pulverized material may be shifted to the left by 0.1 degrees or more compared to the ingot. In Miller Indices, which indicate a crystal plane or a lattice plane, 110 becomes a plane parallel to the z axis and diagonally crosses the x and y axes, and 110 in the X-ray diffraction analysis shifted the angle of the peak to the left. This means that the diffraction has been reduced. This is because the lattice of the ingot is inflated and the distance between the lattices increases, and eventually the angle of 110 peaks is shifted to the left, and it can be accepted that the lattice of the ingot is sufficiently expanded. When the 110 peak shifts to less than 0.1, it is not preferable because the lattice of the ingot is sufficiently expanded and coarsely pulverized by hydrogen embrittlement.

In step S300, the coarsely pulverized material is milled to generate finely pulverized material. Milling may be performed by any one selected from a horizontal mill, an attrition mill, a planetary mill, and a hammer-mill. Mechanical alloying proceeds by milling.

The milling time is preferably 20 to 60 minutes. When the milling is performed in less than 20 minutes, mechanical alloying is not sufficiently progressed, which is not preferable. If the milling is performed for more than 60 minutes, contamination by the milling media may occur. Do not.

Contamination may be caused by a zirconia ball (ZrO ₂ ball) mainly used as a milling media. It appears that unwanted zirconia (ZrO ₂ ) is introduced into the alloy when it is milled for a long time, and is known to decrease elongation in high-entropy alloys.

The present invention can reduce the milling (milling) time while manufacturing a high-entropy alloy powder of a body-centered cubic structure having a high strength and difficult to be milled, thereby avoiding contamination by the milling media.

In step S400, the finely pulverized material formed by milling is vacuum-heated to remove hydrogen, thereby forming a body-centered cubic structure high-entropy alloy powder. The final manufactured body-centered cubic structure high-entropy alloy preferably has low hydrogen embrittlement to maintain mechanical properties such as high temperature strength and structural stability, and thus removes hydrogen by vacuum heat treatment.

The present invention also provides a body-centered cubic high-entropy alloy powder prepared by the above-described method. The body-centered cubic structure high-entropy alloy powder according to the present invention has excellent mechanical strength at high temperatures and can be used in aerospace materials, aviation materials, gas turbines, and the like.

Hereinafter, the present invention will be described in more detail through manufacturing examples and experimental examples.

<Production Example 1>

W, Ta, Nb, V, and Ti were each prepared from a single metal having the same mole number. The mixture was mixed and re-dissolved in a vacuum arc to form an ingot. The ingot was put into an induction furnace, hydrogen was injected, and then heated to 600 ° C at a rate of 5 ° C / min, and then maintained for 2 hours. The oxygen concentration of the initial ingot was 0.13 wt%, and the dew point of the injected hydrogen was -30 ° C. Thereafter, the coarse pulverized material formed by cooling the induction heating furnace was taken out, placed in a hammer mill having a medium of 5 mmФ cemented carbide, and ground at 150 rpm for 60 minutes to form a fine pulverized material. The pulverized material was vacuum heat-treated to remove hydrogen to prepare a body-centered cubic high-entropy alloy powder.

<Production Examples 2-9>

A body-centered cubic structure high-entropy alloy powder was prepared in the same manner as in Preparation Example 1, except that the hydrogen heat treatment temperatures were changed to 450 ° C, 500 ° C, 700 ° C, 800 ° C, 900 ° C, 1000 ° C, 1100 ° C, and 1200 ° C, respectively. It was prepared.

<Production Examples 10 to 14>

A body-centered cubic high-entropy alloy powder was prepared in the same manner as in Preparation Example 1, except that the dew point of hydrogen was changed to -40 ° C, -50 ° C, -60 ° C, -70 ° C, and -80 ° C, respectively.

<Comparative Examples 1 to 2>

A body-centered cubic structure high-entropy alloy powder was prepared in the same manner as in Preparation Example 1, except that the hydrogen heat treatment temperature was changed to 350 ° C and 400 ° C, respectively.

<Comparative Examples 3 to 7>

A body-centered cubic structure high-entropy alloy powder was prepared in the same manner as in Preparation Example 1, except that the dew point of hydrogen was changed to -20 ° C, -10 ° C, 0 ° C, 10 ° C, and 20 ° C, respectively.

<Experimental Example 1>

The ingot (inot) before and after the hydrogen heat treatment during the preparation of Preparation Example 1, and the Vickers hardness at 2.0 kgf were measured, respectively, and are shown in FIG. 5. The average strength of the ingot before the hydrogen heat treatment was 747.8 HV, but it can be seen that the crude pulverized material after the hydrogen heat treatment under the same measurement conditions did not withstand the load due to lattice expansion by hydrogen embrittlement and cracks occurred.

<Experimental Example 2>

During the preparations of Preparation Examples 1 to 9 and Comparative Examples 1 to 2, ingots and coarse pulverized products before and after the heat treatment of hydrogen were analyzed by Cu Kα X-ray diffraction, and the peak shift amounts of 110 are shown in Table 1 below. In Production Examples 1 to 9, 110 peaks shifted by 0.11 to 0.20, but in Comparative Examples 1 and 2, 110 peaks shifted by less than 0.10. 6 is a graph showing the shift of 110 peaks in Preparation Example 1.

<Experimental Example 3>

The body fractions of the high-entropy alloy powders of the body-centered cubic structures of Preparation Examples 1 to 9 and Comparative Examples 1 to 2 were observed for powder fractions of 75 µm or less, and are shown in Table 1 below. The powder fraction of 75 um or less in Preparation Examples 1 to 9 is 75% or more, and the crushing efficiency is excellent, but the powder fraction of 75 um or less in Comparative Examples 1 to 2 is less than 20%, indicating that the crushing efficiency is low.

division Hydrogen heat treatment temperature (℃) 110 peak shift Powder fraction below 75um (%) Comparative Example 1 350 0.04 15 Comparative Example 2 400 0.05 16 Preparation Example 2 450 0.11 75 Preparation Example 3 500 0.15 79 Preparation Example 1 600 0.19 82 Preparation Example 4 700 0.18 80 Preparation Example 5 800 0.20 85 Preparation Example 6 900 0.19 80 Preparation Example 7 1000 0.18 81 Preparation Example 8 1100 0.19 83 Preparation Example 9 1200 0.19 80

<Experimental Example 4>

The hydrogen dew point of the preparation examples 1, 10 to 14 and comparative examples 3 to 7, the initial ingot oxygen concentration, and the oxygen concentration of the crude pulverized material after hydrogen heat treatment are shown in Table 2 below. In Production Examples 1 and 10 to 14, the change in oxygen concentration was not large, but in Comparative Examples 3 to 7, it was found that the increase in oxygen concentration was large.

division Hydrogen dew point (℃) Initial ingot oxygen concentration (wt%) Oxygen concentration of crude pulverized material after heat treatment of hydrogen (wt%) Preparation Example 14 -80 0.13 0.13 Preparation Example 13 -70 0.13 0.13 Preparation Example 12 -60 0.13 0.13 Preparation Example 11 -50 0.13 0.13 Preparation Example 10 -40 0.13 0.14 Preparation Example 1 -30 0.13 0.15 Comparative Example 3 -20 0.13 0.23 Comparative Example 4 -10 0.13 0.27 Comparative Example 5 0 0.13 0.38 Comparative Example 6 10 0.13 0.45 Comparative Example 7 20 0.13 0.55

The above description of the present invention is for illustration only, and those skilled in the art to which the present invention pertains can understand that it can be easily modified to other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be interpreted to be included in the scope of the present invention.

100: ordinary alloy
101: main element 102: alloy element
200: high entropy alloy
201: the first major element 202: the second major element
203: 3rd main element 204: 4th main element
205: 5th main element

Claims (11)

Dissolving the body-centered cubic structure high-entropy alloy material by a vacuum arc remelting method to form an ingot;
Heat-treating the ingot in a hydrogen atmosphere to coarsely pulverize by lattice expansion to form a coarse pulverized material;
Milling the coarse pulverized material to form a fine pulverized material; And
And removing hydrogen by vacuum heat-treating the finely pulverized material to form a high-entropy alloy powder with a body-centered cubic structure.
Heat treatment in the hydrogen atmosphere, hydrogen 100%, the dew point of the hydrogen at a temperature of -30 ℃ or less, at a heating rate of 3 to 7 ℃ / min, heated to a heat treatment temperature of 450 to 1100 ℃ 90 minutes to 150 minutes By performing to maintain the temperature during,
When the ingot (ingot) and coarse pulverized were analyzed by Cu Kα X-ray diffraction, the angle of 110 peaks of the coarse pulverized material was shifted to the left by 0.1 degrees or more compared to the ingot,
A method of manufacturing a body-centered cubic structure high-entropy alloy powder, wherein the crude powder has an oxygen concentration of 0.15 wt% or less and more than 0 wt%. According to claim 1,
The body-centered cubic structure high-entropy alloy material is W, Ta, Mo, Nb, Cr, V, Ti, Hf and Zr, the body-centered cubic structure high-entropy alloy powder manufacturing method characterized in that it comprises at least four. According to claim 2,
The body-centered cubic structure high-entropy alloy material further comprises one or more selected from Mn, Fe, Co, Ni, Cu and Al. delete delete delete delete delete According to claim 1,
The milling is performed by any one selected from a horizontal mill, an attrition mill, a planetary mill, and a hammer-mill. Body-centered cubic structure high-entropy alloy powder manufacturing method. According to claim 1,
The milling (milling) is a body-centered cubic structure high-entropy alloy powder manufacturing method characterized in that is performed for 20 to 60 minutes. A body-centered cubic structure high-entropy alloy powder prepared by the method of claim 1.

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