WO2017164602A1 - Cr-fe-mn-ni-v-based high-entropy alloy - Google Patents

Abstract

The present invention relates to a high-entropy alloy especially having excellent low-temperature tensile strength and elongation by means of having configured, through thermodynamic calculations, an alloy composition region having a FCC single-phase microstructure at 700°C or higher, and enabling the FCC single-phase microstructure at room temperature and at an ultra-low temperature. The high-entropy alloy, according to the present invention, comprises: Cr: 3-18 at%; Fe: 3-60 at%; Mn: 3-40 at%; Ni: 20-80 at%; V: 3-12 at%; and inevitable impurities, wherein the ratio of the V content to the Ni content (V/Ni) is 0.5 or less.

Description

CR-FE-MN-NI-V series high entropy alloy

The present invention relates to a high entropy alloy designed using a thermodynamic calculation of a computer simulation technique. Through the thermodynamic calculation, an alloy composition region having a microstructure of a face centered cubic (FCC) single phase is set up to 700 ° C. or more. In particular, the present invention relates to a Cr-Fe-Mn-Ni-V-based high entropy alloy having excellent low-temperature tensile strength and elongation by allowing FCC single-phase microstructure at room temperature and cryogenic temperature after rapid heat treatment at 700 ° C or higher. .

High Entropy Alloy (HEA) alloy is a five-element or more multi-element alloy system. Despite being a high alloy system, the high entropy alloy has a high mixed entropy, so that no intermetallic compound is formed and the ductility is excellent. Body Centered Cubic (BCC) is a new concept of new material consisting of a single phase.

When alloying five or more elements in a similar proportion without a main element, a single phase was obtained in 2004 under the name of High Entropy Alloy (HEA). .

The reasons for this particular atomic arrangement and its nature are not clear, but the excellent chemical and mechanical properties of these structures have been reported, and FCC single-phase CoCrFeMnNi high entropy alloys exhibit nano yield twins at low temperatures resulting in high yield and It has a tensile strength and is reported to have the highest toughness compared to the materials reported so far.

High entropy alloys having a face-centered cubic lattice (FCC) structure not only have excellent fracture toughness at cryogenic temperatures, but also have excellent corrosion resistance, high mechanical strength, and high mechanical properties.

On the other hand, Republic of Korea Patent Publication No. 2016-0014130 is a high entropy alloy that can be used as a heat-resistant material Ti _{16 . 6} Zr _{16 . 6} Hf _{16 . 6} Ni _{16 . 6} Cu _{16 .} High entropy alloys such as ₆ Co ₁₇ , Ti _16.6 Zr _16.6 Hf _16.6 Ni _16.6 Cu _16.6 Nb ₁₇ have been proposed, and Japanese Laid-Open Patent Publication No. 2002-173732 discloses Cu-Ti-V-Fe-Ni-Zr as the main element. High entropy alloys with high hardness and corrosion resistance are proposed.

As described above, various high entropy alloys are being developed, and in order to expand an application area of the high entropy alloy, development of high entropy alloys having various characteristics is required.

The present invention is to solve the problem to provide a Cr-Fe-Mn-Ni-V-based high entropy alloy having a FCC single-phase structure at room temperature and cryogenic temperature and having low temperature tensile strength and low temperature stretching characteristics can be used for cryogenic applications It is a task.

In order to solve the above problems, the present invention, Cr: 3 to 18 atomic%, Fe: 3 to 60 atomic%, Mn: 3 to 40 atomic%, Ni: 20 to 80 atomic%, V: 3 to 12 atomic% It is to provide a high entropy alloy, containing unavoidable impurities, the ratio of the V content to the Ni content (V / Ni) is 0.5 or less.

The alloy having such a composition consists of a single phase of the FCC structure without formation of an intermediate phase, and exhibits better tensile strength and elongation at cryogenic temperature (77K) than at room temperature (298K).

The new high entropy alloys provided by the present invention have high tensile strength and elongation at cryogenic temperatures rather than at room temperature, and thus have high utility as structural materials used in extreme environments such as cryogenic environments.

In the high entropy alloy according to the present invention, reinforcing effects can be easily obtained by adding vanadium (V) different from elements having different nearest interatomic distances. In addition, by controlling the content of the other four elements according to the vanadium (V) content, it suppresses the generation of sigma phase and implements FCC single-phase structure to perform conventional high entropy without performing strictly controlled heat treatment process Compared with the alloy, mechanical properties more than equivalent can be obtained.

1 is a phase at 700 ° C. according to the molar fractions of iron (Fe), manganese (Mn) and nickel (Ni) of an alloy comprising 15 atomic% chromium (Cr) and 10 atomic% vanadium (V). Equilibrium information is shown.

FIG. 2 shows a change in equilibrium with temperature for an alloy having a composition marked with a star in FIG. 1.

FIG. 3 shows the phase at 700 ° C. according to the molar fractions of iron (Fe), manganese (Mn) and nickel (Ni) of an alloy comprising 10 atomic percent chromium (Cr) and 10 atomic percent vanadium (V). Equilibrium information is shown.

FIG. 4 illustrates a change in equilibrium with temperature of an alloy having a composition indicated by a star (★) in FIG.

FIG. 5 shows the phase at 700 ° C. according to the remaining mole fractions of chromium (Cr), nickel (Ni) and vanadium (V) of an alloy comprising 30 atomic% iron (Fe) and 20 atomic% manganese (Mn). Equilibrium information is shown.

FIG. 6 illustrates a change in equilibrium with temperature of an alloy having a composition indicated by a star (★) in FIG. 5.

FIG. 7 shows a binary alloy based state diagram composed of two elements of five elements of chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), and vanadium (V).

8 is an EBSD inverse pole figure (IPF) map photograph of a high entropy alloy sheet prepared according to Examples 1 and 3 of the present invention.

9 is an X-ray diffraction analysis of the high entropy alloy sheet prepared according to Examples 1 and 3 of the present invention.

FIG. 10 is an EBSD phase map photograph of a high entropy alloy sheet prepared according to Examples 1 and 3 of the present invention. FIG.

Figure 11 shows the results of room temperature (298K) tensile test of the high entropy alloy prepared according to Examples 1 and 3 of the present invention.

12 shows the cryogenic (77K) tensile test results of the high entropy alloy prepared according to Examples 1 and 3 of the present invention.

Figure 13 shows the cryogenic (77K) tensile test results of the high entropy alloy prepared according to Example 2 of the present invention.

Hereinafter, the configuration and operation of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

1 shows an alloy comprising 15 atomic% chromium (Cr) and 10 atomic% vanadium (V) at 700 ° C. according to the remaining iron (Fe), manganese (Mn) and nickel (Ni) mole fractions. Phase equilibrium information is shown.

Regions 1 and 2 in FIG. 1 represent regions for maintaining the FCC single phase at 700 ° C. or lower, and regions for maintaining two-phase or three-phase equilibrium are indicated in the remaining regions. Alloys having a composition belonging to region 2 of FIG. 1 maintain the FCC single phase from melting temperature up to 700 ° C. to 500 ° C. FIG. The composition at the two-phase equilibrium region and the boundary maintains the FCC single phase up to 700 ° C.

The line between the zone 1 and zone 2 is a line representing the boundary between the FCC single-phase zone and the two-phase equilibrium zone calculated at 500 ° C. Alloys having a composition belonging to zone 1 of FIG. Maintain FCC single phase. The composition located at the boundaries of zones 1 and 2 computationally maintains the FCC single phase up to 500 ° C.

1 means that 15 atomic% chromium (Cr), 10 atomic% vanadium (V) and 0 to 48 atomic% iron (Fe), 0 to 25 atomic% manganese (Mn), 27 All five-membered and lower alloys containing ~ 75 atomic percent nickel (Ni) maintain the FCC single phase from the melting temperature up to 700 ° C.

FIG. 2 illustrates a change in equilibrium with temperature for an alloy having a composition indicated by a star (★) in FIG. 1. An alloy having a composition indicated by a star (★) has a boundary between regions 2 and a two-phase equilibrium region in FIG. 1. Because of the composition located at, it forms the FCC single phase region from the melting temperature to 700 ° C.

3 is an alloy containing 10 atomic% chromium (Cr) and 10 atomic% vanadium (V), according to the mole fractions of iron (Fe), manganese (Mn), and nickel (Ni), which are the remaining alloy components, Phase equilibrium information at 700 ° C is shown.

3 means 10 atomic% chromium (Cr) and 10 atomic% vanadium (V) and 0 to 56 atomic% iron (Fe), 0 to 41 atomic% manganese (Mn), 23 to 80 All five-membered and lower alloys containing atomic percent nickel (Ni) maintain the FCC single phase from the melting temperature up to 700 ° C.

4 shows a change in equilibrium with temperature of an alloy having a composition indicated by a star (★) in FIG.

5 is an alloy containing 30 atomic% iron (Fe) and 20 atomic% manganese (Mn), according to the mole fractions of chromium (Cr), nickel (Ni) and vanadium (V), which are the remaining alloy components, Phase equilibrium information at 700 ° C is shown.

5 means that 30 atomic% iron (Fe) and 20 atomic% manganese (Mn) and 0 to 18 atomic% chromium (Cr), 28 to 50 atomic% nickel (Ni), 0-18 All five-membered and lower alloys containing atomic percent vanadium (V) maintain the FCC single phase from the melting temperature up to 700 ° C.

6 shows a change in equilibrium with temperature of an alloy having a composition indicated by a star (★) in FIG.

FIG. 7 shows a binary alloy-based state diagram composed of two elements of five elements of chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), and vanadium (V).

In FIG. 7, the FCC single phase region and the sigma phase region which degrades mechanical properties are shown in dark color. Six binary alloy systems containing no vanadium (V) have a small sigma phase region and a wide FCC single phase region. On the other hand, the sigma phase is relatively widely distributed in four binary alloy systems including vanadium (V). In particular, in the case of the nickel (Ni) -vanadium (V) binary system, the sigma phase is distributed up to a high temperature at which the liquid phase is stable. However, the sigma phase in the nickel (Ni) -vanadium (V) alloy-based state diagram mainly appears in the section where the ratio (V / Ni) of the vanadium (V) content to the nickel (Ni) content is high. In the section where the ratio of vanadium (V) to V content is low, a wide FCC single phase section appears.

7 means that if the ratio of the V content to the Ni content (V / Ni) is lowered, it is possible to design a high entropy alloy consisting of FCC single phase.

From the thermodynamic information of FIGS. 1, 3, 5, and 7 as described above, the present inventors are high-entropy alloys composed of FCC single phase and excellent low temperature characteristics, Cr: 3-18 atomic%, Fe: 3-60 atomic %, Mn: 3 to 40 atomic%, Ni: 20 to 80 atomic%, V: 3 to 12 atomic%, and inevitable impurities, and the ratio of V content to Ni content (V / Ni) is 0.5 or less High entropy alloys were derived.

When the content of Cr is less than 3 atomic%, it adversely affects the properties of the alloy, such as corrosion resistance, and when the content of more than 18 atomic% increases the possibility of forming an intermediate phase, 3 to 18 atomic% is preferable, and the phase In view of the stability, mechanical properties and manufacturing cost of the more preferable content of Cr is 7 to 18 atomic%.

When the content of Fe is less than 3 atomic%, it becomes disadvantageous in terms of manufacturing cost, and when it exceeds 60 atomic%, the phase becomes unstable, so 3 to 60 atomic% is preferable, and phase stability In view of the mechanical properties and the more preferable content of Fe is 18 to 35 atomic%.

When the content of Mn is less than 3 atomic%, it is disadvantageous in terms of manufacturing cost, and if it is more than 40 atomic%, the phase becomes unstable, and it is disadvantageous due to oxide formation during the manufacturing process. Preferably, the Mn content is more preferably 10 to 25 atomic percent in terms of phase stability and mechanical properties.

When the content of Ni is less than 20 atomic%, the phase becomes unstable, and if it is more than 80 atomic%, it becomes disadvantageous in terms of manufacturing cost, so 20 to 80 atomic% is preferable, and the stability of the phase In terms of mechanical properties, more preferable Ni content is 25 to 45 atomic%.

When the content of V is less than 3 atomic%, it is difficult to obtain a reinforcing effect, and when the content of V is higher than 12 atomic%, the possibility of forming an intermediate phase is increased, and 3 to 12 atomic% is preferable, and the phase stability, mechanical properties and In view of the production cost, a more preferable content of V is 5 to 12 atomic%.

In addition, in order to stably implement a single-phase FCC structure, the ratio of the V content to the content of Ni (V / Ni) is preferably 0.5 or less.

It is preferable to maintain the composition range of the alloy because it is difficult to obtain a solid solution having an FCC single phase when it is out of each composition constituting the alloy.

In addition, in the high entropy alloy, since the Ni content exhibits optimum properties when it is 30 atomic% or more, the sum of the Fe and Mn contents is preferably 50 atomic% or less.

In addition, in terms of obtaining excellent physical properties and stable high entropy alloy, the composition of each component constituting the high entropy alloy is 7-18 atomic% Cr, 18-35 atomic% Fe, 10-25 atomic% Mn. , Ni: 25 to 45 atomic%, V: 5 to 12 atomic%, more preferably the ratio (V / Ni) of the V content to the content of Ni is 0.5 or less.

In addition, the high entropy alloy may have a tensile strength of 1000 MPa or more and an elongation of 30% or more at cryogenic temperatures (77 K).

In addition, the high entropy alloy may have a tensile strength of 1000 MPa or more and an elongation of 60% or more at cryogenic temperatures (77 K).

In addition, the high entropy alloy may have a tensile strength of 800 MPa or more and an elongation of 30% or more at room temperature (298 K).

Hereinafter, the present invention will be described in more detail based on the preferred embodiments of the present invention, but the present invention should not be construed as being limited to the preferred embodiments of the present invention.

EXAMPLE

High Entropy Alloy Manufacturing

Table 1 below shows three compositions selected for the alloy preparation of the regions calculated through the above-mentioned thermodynamic review.

Alloy No.	Ingot composition (atomic%)
	Cr	Fe	Mn	Ni	V
One	15	22	13	40	10
2	10	30	20	30	10
3	15	30	20	30	5

After preparing 99.9% or more of pure Cr, Fe, Mn, Ni, V to the composition of Table 1, the ingot was prepared by a known method by dissolving the alloy at 1500 ° C or more using an induction furnace.

Example 1

No. The alloy ingot was kept in the FCC single phase region for 2 hours at 1000 ° C. to homogenize the tissue, and then the homogenized ingot was pickled to remove surface impurities and oxide layer.

The pickled ingot was cold rolled at a reduction ratio of 75% to prepare a cold rolled sheet.

The cold rolled sheet was heat-treated (800 ° C., 2 hours) in the FCC single phase region to remove residual stress, completely recrystallized the crystal grains, and then cooled with water to prepare a high entropy alloy sheet.

Example 2

No. The ingot of the alloy 1 was homogenized by maintaining the ingot in the FCC single-phase region at 1100 ° C. for 6 hours, and then the homogenized ingot was pickled to remove impurities and oxide layers from the surface.

The pickled ingot was cold rolled at a reduction ratio of 75% to prepare a cold rolled sheet.

After the heat treatment (800 ℃, 2 hours) in the FCC single-phase region to remove the residual stress, completely recrystallized crystal grains and then cooled by water to prepare a high entropy alloy sheet.

That is, the high entropy alloy sheet manufactured according to Example 2 is different from the heat treatment conditions in the same composition as in Example 1.

Example 3

No. An ingot of two alloys was manufactured from a high entropy alloy sheet through the same production process as in Example 1.

No. 1 in Table 1 above. In the case of alloy 3, the ingot was made of a high entropy alloy sheet and the microstructure and mechanical properties thereof were not evaluated. However, as shown in FIG. 6, when quenched after heat treatment in an FCC single phase region (800 ° C. or higher), It can be seen that the composition capable of forming an FCC single phase at room temperature (298K) and cryogenic temperature (77K).

Microstructure

The microstructure of the high entropy alloy sheet prepared as described above was analyzed using a scanning electron microscope, an X-ray diffractometer and an EBSD.

FIG. 8 is an EBSD inverse pole figure (IPF) map photograph of a high entropy alloy sheet prepared according to Examples 1 and 2 of the present invention. FIG.

From this map, the grain size can be measured, and the two alloys (Examples 1 and 3) subjected to cold rolling and recrystallization heat treatment with a 75% reduction ratio have an average grain size of 5.4-7.4 μm. The crystalline phases were in polycrystalline form and their sizes were relatively uniform regardless of the alloy composition.

9 is an X-ray diffraction analysis of the high entropy alloy sheet prepared according to Examples 1 and 3 of the present invention. Both alloys show the same peak, and the analysis shows that both peaks correspond to the FCC structure.

FIG. 10 is an EBSD phase map photograph of a high entropy alloy sheet prepared according to Examples 1 and 3 of the present invention. FIG. The EBSD phase map displays each phase in a different color when two or more different phases are in the microstructure. As can be seen in FIG. 10, the alloys according to Example 1 and Example 3 are all the same. Shown in color, this means that the microstructure of these alloys consists of the FCC single phase and no second phase, such as a sigma phase, that degrades mechanical properties has been produced.

Evaluation of room temperature and cryogenic mechanical properties

The high entropy alloy sheet produced as described above was evaluated for tensile properties at room temperature (298K) through a tensile tester, Figure 11 and Table 2 shows the results.

	Room temperature (298K)
	YS (MPa)	UTS (MPa)	El. (%)
Example 1	460	815	45.2
Example 3	503	842	35.2

As shown in Table 2, the yield strength at room temperature (298K) of the high entropy alloy sheet according to Examples 1 and 3 of the present invention is 460 to 503 MPa, tensile strength is 815 to 842 MPa, and elongation is about 35 to 45% shows excellent tensile properties.

12 and 13 and Table 3 below show the results of evaluating the tensile properties at cryogenic temperatures (77K) through the cryogenic chamber and the tensile tester.

Claims (6)

1. Cr: 3-18 atomic%, Fe: 3-60 atomic%, Mn: 3-40 atomic%, Ni: 20-80 atomic%, V: 3-12 atomic% and inevitable impurities,

   A high entropy alloy, wherein the ratio of V content to Ni content (V / Ni) is 0.5 or less.
2. The method of claim 1,

   The high entropy alloy is a face centered cubic single phase high entropy alloy.
3. The method of claim 1,

   A high entropy alloy having a sum of Fe and Mn content of 50 atomic% or less.
4. The method according to any one of claims 1 to 3,

   The high entropy alloy has a high tensile strength of at least 1000 MPa and an elongation of at least 30% at cryogenic temperatures (77K).
5. The method according to any one of claims 1 to 3,

   The high entropy alloy has a high tensile strength of at least 1000 MPa and an elongation of at least 60% at cryogenic temperatures (77 K).
6. The method according to any one of claims 1 to 3,

   The high entropy alloy has a high tensile strength of 800 MPa or more at room temperature (298 K) and an elongation of at least 30%.

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