Nb-rich high-entropy alloy and preparation method thereof

Abstract

The invention belongs to the technical field of metal materials and preparation thereof, and particularly provides a Nb-rich high-entropy alloy and a preparation method thereof. The atomic percent expression of the high-entropy alloy is NBaZrbTicVd, a is larger than or equal to 35 and smaller than or equal to 55 at%, b is larger than or equal to 15 and smaller than or equal to 22 at%, c is larger than or equal to 15 and smaller than or equal to 22 at%, d is larger than or equal to 15 and smaller than or equal to 26 at%, b = c = d, a + b + c + d = 100, the high-entropy alloy is composed of a single BCC phase, the microstructure is a typical dendritic structure, the tensile strength of the high-entropy alloy is 965-1079 MPa, and the elongation at break is 12.3%-27.6%. According to the method, the problem of poor room-temperature plasticity of the equal-atomic-ratio NbZrTiV high-entropy alloy is solved by increasing the content of the Nb element, collaborative optimization of room-temperature strength and plasticity is achieved, and the method is simple in process and suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal materials and its preparation, in particular to a Nb-rich high-entropy alloy and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for material performance in extreme high-temperature (>1000°C) service environments in modern industry, especially in the fields of aero-engines, gas turbines, nuclear energy systems, etc., it is an urgent need to develop new high-temperature alloys with higher temperature resistance, excellent high-temperature strength, and good oxidation resistance / creep resistance. High-entropy alloys (HEAs) have been an important breakthrough in the field of metal materials in recent years, breaking the traditional alloy design concept of single or two elements. It is usually composed of five or more main elements at an atomic ratio (or non-atomic ratio but with a high concentration of elements). Its core feature is the significant high-entropy effect, which tends to form simple solid solution structures (such as FCC, BCC, or HCP), rather than complex intermetallic compounds. This unique structure endows high-entropy alloys with a series of excellent performance potential, such as high strength, high hardness, good wear resistance, excellent corrosion resistance, and good high-temperature stability. Among them, refractory high-entropy alloys composed of high-melting-point elements often exhibit excellent high-temperature performance. For example, NbMoTaW and NbMoTaWV refractory high-entropy alloys still have a yield strength of 405 and 477 MPa at 1600°C. However, their room temperature deformation ability is poor, with a room temperature compression strain of only about 2%, and they do not have tensile deformation ability. This makes it difficult to prepare and process this series of refractory high-entropy alloys, which cannot meet the actual application requirements.

[0003] Therefore, it is necessary to provide a Nb-rich high-entropy alloy and a preparation method thereof, which breaks the design limit of equal atomic ratio of high-entropy alloys, has good room temperature mechanical properties, and greatly meets the preparation and processing requirements of alloys in actual application. SUMMARY

[0004] In order to break through the key room temperature mechanical property problem in the background art, the present application provides a Nb-rich high-entropy alloy and a preparation method thereof. Compared with traditional equal atomic ratio high-entropy alloys, the Nb-rich high-entropy alloy solves the problem of poor intrinsic room temperature deformation ability of this series of alloys, and reduces the manufacturing cost.

[0005] The technical scheme of the present application is as follows: The application discloses a high-strength plastic Nb-rich high-entropy alloy, and an atomic percentage expression of the high-entropy alloy is NbaZrbTicVd, wherein 35 <= a <= 55 at%, 15 <= b <= 22 at%, 15 <= c <= 22 at%, 15 <= d <= 26 at%, and b = c = d and a + b + c + d = 100 are met.

[0006] Further, the high-strength plastic Nb-rich high-entropy alloy has a phase composition of a single BCC phase.

[0007] As a preferred solution, the Nb-rich high-entropy alloy is Nb 35 (ZrTiV) 65 .

[0008] As a preferred solution, the Nb-rich high-entropy alloy is Nb 45 (ZrTiV) 55 .

[0009] As a preferred solution, the Nb-rich high-entropy alloy is Nb 55 (ZrTiV) 45 .

[0010] Further, the high-strength plastic Nb-rich high-entropy alloy has a room-temperature tensile strength of 965-1079 MPa and a fracture elongation of 12.3%-27.6%. The application further discloses a preparation method of the Nb-rich high-entropy alloy, and the preparation method comprises the following steps: 1) batching: atomic percentages in an alloy chemical formula are converted into mass percentages, and Nb, Zr, Ti and V metal elemental raw materials with a purity of not less than 99.9% are respectively taken and pretreated in petroleum ether and anhydrous ethanol in sequence; 2) smelting: the pretreated raw materials in step 1) are sequentially placed into a copper crucible according to melting points from low to high; vacuum is extracted to 5´10 -3 Pa or below, then high-purity argon gas with a purity of 99.95-99.99 wt.% is introduced as a protective gas, until the pressure in a furnace cavity reaches-0.08-0.03 MPa to stop the aeration, and smelting is performed; 3) copper mold casting: the smelted alloy is cast by using a water-cooled copper mold to obtain a cast high-entropy alloy sample with a required shape and size.

[0011] Further, the preparation method of the Nb-rich high-entropy alloy smelts the alloy more than four times by using suspension smelting, arc smelting or electron beam smelting.

[0012] Further, the preparation method of the Nb-rich high-entropy alloy smelts a titanium ingot before smelting to absorb residual air in the furnace cavity, and a smelting current is increased to 400-450 A at most.

[0013] Furthermore, in the above-mentioned method for preparing Nb-rich high-entropy alloys, 8×12×60mm alloys are used during casting. 3 The copper mold was evacuated to a vacuum level of 3.5 × 10⁻⁶ m³ before casting. -3 After Pa, high-purity argon gas is introduced to 400 mbar.

[0014] Compared with the prior art, the advantages of the present invention are as follows: 1. This invention breaks through the traditional design concept of equal atomic ratio in high-entropy alloys by increasing the Nb content, thus significantly reducing the cost of the alloy.

[0015] 2. The Nb-rich high-entropy alloy of the present invention has a single BCC phase, exhibiting good phase stability.

[0016] 3. The Nb-rich high-entropy alloy of the present invention has good room temperature deformation capability, with a maximum room temperature tensile strength of 1079 MPa and a maximum elongation at break of 27.6%.

[0017] 4. The Nb-rich high-entropy alloy described in this invention is easy to process and deform, and has broad application prospects in the fields of aerospace and high-end equipment manufacturing. Attached Figure Description

[0018] Figure 1 Nb prepared in Example 1 35 (ZrTiV) 65 Microstructure of high-entropy alloys; Figure 2 Nb prepared in Example 2 45 (ZrTiV) 55 Microstructure of high-entropy alloys; Figure 3 Nb prepared in Example 3 55 (ZrTiV) 45 Microstructure of high-entropy alloys; Figure 4 XRD patterns of Nb-rich high-entropy alloys prepared for the example; Figure 5 The diagram shows the engineering stress-engineering strain curves of the Nb-rich high-entropy alloy prepared for the example under room temperature tensile stress. Detailed Implementation

[0019] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] In a specific implementation, the raw materials are elemental Nb, Zr, Ti and V metals with a purity of 99.9%.

[0021] Example 1

[0022] This embodiment provides an Nb-rich Nb 35 (ZrTiV) 65 The specific steps for preparing high-entropy alloys are as follows: Step 1) Batching: Convert the atomic percentage in the alloy chemical formula to the mass percentage, Nb:Zr:Ti:V=44.1:26.8:14.1:15.0, weigh each raw material separately, and ultrasonically clean them in petroleum ether and anhydrous ethanol respectively. Step 2) Melting: Place the pretreated raw materials from Step 1) into the copper crucible in order of increasing melting point; then evacuate the electric arc melting furnace until the vacuum reaches 3.5 × 10⁻⁶. -3 After Pa, high-purity argon gas with a purity of 99.99 wt.% is introduced as a protective gas until the pressure inside the furnace reaches -0.08 MPa and then the gas introduction is stopped. The furnace chamber of the electric arc melting furnace contains multiple water-cooled copper crucibles. Before melting the raw materials, the electric arc gun is first aimed at the crucible containing titanium ingots to melt the titanium ingots and absorb the residual air in the furnace chamber. When melting the raw materials, the current is slowly increased, up to a maximum of 400A. After all the raw materials are melted to form an alloy ingot, the ingot is cooled and flipped over. It is then melted again and the magnetic stirring is turned on. The melting is repeated 4 times to obtain the final alloy casting ingot. Step 3) Copper mold casting: Place the smelted alloy ingot in the copper crucible of the casting system, with an 8×12×60mm mold underneath. 3 Copper molds; the furnace cavity is evacuated to 3.5 x 10⁻⁶. -3 After Pa, high-purity argon gas is introduced to 400 mbar; during melting, the current is slowly increased to 450 A. When the ingot is completely liquid, the copper crucible is turned over so that it flows into the copper mold.

[0023] See Figure 1 It can be seen that the as-cast Nb of the embodiments of the present invention 35 (ZrTiV) 65 High-entropy alloys consist of dendrites and interdendritic spaces. See also Figure 4 The XRD patterns show that the as-cast Nb of the embodiments of the present invention 35 (ZrTiV) 65 High-entropy alloys consist of a single BCC phase without the formation of other phases. Nb, as a BCC phase stabilizing element, can stabilize the single-phase BCC structure and suppress the formation of a second phase by increasing its content. (See Table 1 and...) Figure 5 The room temperature tensile stress-strain curve shows that the tensile strength is 1079 MPa and the elongation at break is 12.3%.

[0024] Example 2

[0025] The difference from Example 1 is that the Nb-rich high-entropy alloy in this example is composed of Nb. 45 (ZrTiV)55 .

[0026] See Figure 2 It can be seen that the as-cast Nb of the embodiments of the present invention 45 (ZrTiV) 55 High-entropy alloys consist of dendrites and interdendritic spaces. See also Figure 4 The XRD patterns show that the as-cast Nb of the embodiments of the present invention 45 (ZrTiV) 55 The high-entropy alloy consists of a single BCC phase, with no other phases formed. See Table 1 and... Figure 5 The room temperature tensile stress-strain curve shows that the tensile strength is 1062 MPa and the elongation at break is 22.7%.

[0027] Example 3

[0028] The difference from Example 1 is that the Nb-rich high-entropy alloy in this example is composed of Nb. 55 (ZrTiV) 45 .

[0029] See Figure 3 It can be seen that the as-cast Nb of the embodiments of the present invention 55 (ZrTiV) 45 High-entropy alloys consist of dendrites and interdendritic spaces. See also Figure 4 The XRD patterns show that the as-cast Nb of the embodiments of the present invention 55 (ZrTiV) 45 The high-entropy alloy consists of a single BCC phase, with no other phases formed. See Table 1 and... Figure 5 The room temperature tensile stress-strain curve shows that the tensile strength is 965 MPa and the elongation at break is 27.6%.

[0030] Comparative Example 1 The difference from Examples 1-3 is that the alloy composition in this example is Nb. 25 Zr 25 Ti 25 V 25 The alloy components are in equal atomic ratio, and the Nb content is the same as that of the other components.

[0031] As shown in Table 1, non-Nb-rich Nb 25 Zr 25 Ti 25 V 25 The room temperature plasticity of high-entropy alloys is only 7%. As an element with a low ductile-brittle transition temperature, increasing its content helps to obtain better room temperature plasticity. On the other hand, as a high-melting-point element, increasing its content can result in finer dendritic structures and grain sizes, which also contributes to better room temperature plasticity.

[0032] Table 1. Tensile strength and elongation of as-cast Nb-rich high-entropy alloys Alloy Tensile strength / MPa Elongation / % Nb 35 (ZrTiV) 65 ]]> 1079 12.3 Nb 45 (ZrTiV) 55 ]]> 1062 22.7 Nb 55 (ZrTiV) 45 ]]> 965 27.6 Nb 25 Zr 25 Ti 25 V 25 ]]> 1171 7 The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A Nb-rich high-entropy alloy, characterized in that, The atomic percentage expression for this high-entropy alloy is: Nb a Zr b Ti c V d , where 35≤a≤55 at%, 15≤b≤22 at%, 15≤c≤22 at%, 15≤d≤26 at%, and satisfy b=c=d, and a+b+c+d=100.

2. The Nb-rich high-entropy alloy according to claim 1, characterized in that, The phase composition of the Nb-rich high-entropy alloy is a single BCC phase.

3. The Nb-rich high-entropy alloy according to claim 1 or 2, characterized in that, The high-entropy alloy has the composition of Nb. 35 (ZrTiV) 65 、Nb 45 (ZrTiV) 55 or Nb 55 (ZrTiV) 45 Any one of them.

4. The Nb-rich high-entropy alloy according to any one of claims 1-3, characterized in that, The high-entropy alloy has a room temperature tensile strength of 965-1079 MPa and a fracture elongation of 12.3%-27.6%.

5. A method for preparing the Nb-rich high-entropy alloy according to any one of claims 1-4, characterized in that, Includes the following steps: 1) Batching: Convert the atomic percentage in the alloy chemical formula to the mass percentage, weigh out the Nb, Zr, Ti and V metal elemental raw materials with a purity of not less than 99.9%, and pretreat them in petroleum ether and anhydrous ethanol in sequence; 2) Melting: Place the pretreated raw materials from step 1) into the copper crucible in order of increasing melting point; evacuate to 5×10⁻⁶. - 3 Below Pa, high-purity argon gas with a purity of 99.95~99.99 wt.% is introduced as a protective gas until the pressure inside the furnace reaches -0.08~0.03 MPa, at which point the gas introduction is stopped and smelting is carried out. 3) Copper mold casting: The smelted alloy is cast using a water-cooled copper mold to obtain a cast high-entropy alloy sample of the required shape and size.

6. The method for preparing the Nb-rich high-entropy alloy according to claim 5, characterized in that, The smelting process employs suspension smelting, electric arc smelting, or electron beam smelting, with each alloy being smelted more than four times.

7. The method for preparing the Nb-rich high-entropy alloy according to any one of claims 5 or 6, characterized in that, Before smelting, the titanium ingots are smelted to absorb residual air in the furnace cavity, and the smelting current is increased to a maximum of 400-450A.

8. The method for preparing the Nb-rich high-entropy alloy according to claim 7, characterized in that, Use 8×12×60mm for casting 3 The copper mold was evacuated to a vacuum level of 3.5 × 10⁻⁶ m³ before casting. -3 After Pa, high-purity argon gas is introduced to 400 mbar.

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