阅读说明：本技术 一种高强高韧CoFeNiTiV高熵合金及其制备方法 (High-strength high-toughness CoFeNiTiV high-entropy alloy and preparation method thereof ) 是由 乙姣姣 王璐 杨林 徐明沁 于 2020-06-17 设计创作，主要内容包括：本发明涉及一种高强高韧CoFeNiTiV高熵合金及其制备方法,包括如下原子百分比的金属单质：Co 18％～22％、Fe 18％～22％、Ni 18％～22％、Ti 18％～22％、V 22～26％；采用真空电弧熔炼法制备,所制得的CoFeNiTiV高熵合金具有BCC单相固溶体结构,屈服强度达到2430MPa以上,断裂伸长率达到18％以上,具有高强高韧性。(The invention relates to a high-strength high-toughness CoFeNiTiV high-entropy alloy and a preparation method thereof, wherein the high-strength high-toughness CoFeNiTiV high-entropy alloy comprises the following metal simple substances in atomic percentage: 18-22% of Co, 18-22% of Fe, 18-22% of Ni, 18-22% of Ti and 22-26% of V; the CoFeNiTiV high-entropy alloy prepared by adopting a vacuum arc melting method has a BCC single-phase solid solution structure, the yield strength reaches over 2430MPa, the elongation at break reaches over 18 percent, and the CoFeNiTiV high-entropy alloy has high strength and high toughness.)

1. The high-strength high-toughness CoFeNiTiV high-entropy alloy is characterized by comprising the following metal simple substances in atomic percentage: 18-22% of Co, 18-22% of Fe, 18-22% of Ni, 18-22% of Ti and 22-26% of V.

2. The high-strength high-toughness CoFeNiTiV high-entropy alloy is characterized by comprising the following metal elements in atomic percentage: 20% of Co, 19% of Fe, 20% of Ni, 20% of Ti and 21% of V.

3. The high-strength high-toughness CoFeNiTiV high-entropy alloy is characterized by comprising the following metal elements in atomic percentage: 21% of Co, 18% of Fe, 18% of Ni, 20% of Ti and 23% of V.

4. The high-strength high-toughness CoFeNiTiV high-entropy alloy is characterized by comprising the following metal elements in atomic percentage: 19% of Co, 19% of Fe, 18% of Ni, 20% of Ti and 24% of V.

5. The CoFeNiTiV high-entropy alloy with high strength and toughness as claimed in claim 1, wherein the purity of the elementary metal is 99.9 wt%.

6. The preparation method of the high-strength high-toughness CoFeNiTiV high-entropy alloy according to any one of claims 1 to 5, characterized by comprising the following steps:

(1) removing impurities and oxides on the surfaces of metal simple substances Co, Fe, Ni, Ti and V, and cleaning and drying for later use;

(2) firstly melting a metal titanium block in a non-consumable vacuum arc melting furnace under the protection of argon, then adding the metal simple substance according to the proportion, vacuumizing, and carrying out arc melting under the protection of argon, wherein the process of arc melting is accompanied with electromagnetic stirring, and cooling to obtain a button sample;

(3) and (3) repeating the electric arc melting for multiple times on the button sample, overturning the button sample before repeating the electric arc melting for each time, cooling and removing a surface oxide layer of the button sample after the electric arc melting for multiple times is finished, repeating the step (2), and cooling to obtain the high-strength high-toughness CoFeNiTiV high-entropy alloy.

7. The preparation method of the high-strength high-toughness CoFeNiTiV high-entropy alloy according to claim 6, wherein the impurities and oxides removed in the step (1) are ground by using a grinder or sand paper; the cleaning process adopts acetone as cleaning solvent to carry out oscillation cleaning for 5min in ultrasonic waves, and the power density of the ultrasonic waves is 0.8W/cm²And the frequency was 33 Hz.

8. The method for preparing the CoFeNiTiV high-entropy alloy with high strength and toughness according to claim 6, wherein the vacuum pumping in the step (2) is up to 2 × 10^-3Filling argon to 5Pa after Pa; the electric arc melting current is 50A-100A, and the time is 30 s-1 min.

9. The method for preparing the CoFeNiTiV high-entropy alloy with high strength and toughness according to claim 6, wherein the molten state is kept for 2-3 min in the process of repeating the arc melting for multiple times in the step (3); the number of times is 4.

Technical Field

The invention relates to the technical field of alloys, in particular to a high-strength high-toughness CoFeNiTiV high-entropy alloy and a preparation method thereof.

Background

High-entropy alloys (HEA) generally comprise 5 or more than 5 metals as main elements, and the mole fraction of each element is 5-35%, and have a simple solid solution phase structure. The high-entropy alloy has the characteristics of high-entropy effect in thermodynamics, large lattice distortion effect in structure, delayed diffusion effect in kinetics, cocktail effect in performance and the like, so that the high-entropy alloy presents a simple solid solution phase with an FCC or BCC crystal structure on a microstructure. The factor contributing to the formation of this texture is the high entropy of mixing that the multi-elemental alloy has. At the same time, the absolute value of the enthalpy of mixing between the alloy constituents cannot be too high, so as to avoid the formation of intermetallic compounds or the formation of separate multinomial coexisting structures. The performance of the high-entropy alloy is high strength, high hardness, high temperature resistance, oxidation resistance and the like, the comprehensive performance of the high-entropy alloy is obviously superior to that of the traditional unit metal material or conventional alloy, and the application field of the high-entropy alloy is widened.

The high-entropy alloy is mainly prepared by adopting a vacuum arc melting process, under vacuum, utilizing high temperature generated by arc discharge between an electrode and two electrodes of a crucible as a heat source to rapidly heat and melt a high-purity metal raw material, and then rapidly cooling a melt by adopting a water-cooling copper mold to solidify the melt into an ingot in the crucible. The electric arc melting temperature is higher, so that the alloy with higher melting point can be melted, and the good effect on removing a plurality of impurities and certain gases is achieved. However, the prepared alloy is easy to have the phenomena of dendrite segregation and uneven components, and has the problems of coarse grains and low plasticity.

To date, a large number of high entropy alloys of various compositions have been reported, more than 50% of which contain the following five high frequency element groups: AlCrFeNi, CoCrFeNi, AlCoFeNi, AlCoCrNi and AlCoCrFe, which indicates that the research in the field of high-entropy alloys is still in the initial stage. Among the alloy systems that have been reported, a true single phase solid solution structure is observed in only a few alloys, including Co-Fe-Ni-Ti-Al, Co-Fe-Ni-Ti-Cr, and Co-Fe-Ni-Ti-Cu.

Research shows that the element composition is a key factor in alloy design, the alloy components can be obviously changed by adjusting the composition of alloy elements so as to influence the mechanical property of the alloy, even if one element is adjusted, the multielement high-entropy alloy can cause great difference between the phase structure and the performance, and has unpredictability. The problem of how to adjust the alloy components to improve the contradiction between the strength and the toughness of the high-entropy alloy becomes one of the technical problems which are urgently needed to be solved in the field of the high-entropy alloy.

Disclosure of Invention

In order to solve the technical problem of contradiction between strength and toughness of the high-entropy alloy, a high-strength high-toughness CoFeNiTiV high-entropy alloy and a preparation method thereof are provided. The CoFeNiTiV high-entropy alloy prepared by the method has excellent strength and plasticity, and plays an important role in promoting the engineering application of CoFeNiTiV series alloys.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a high-strength high-toughness CoFeNiTiV high-entropy alloy comprises the following metal simple substances in atomic percentage: 18-22% of Co, 18-22% of Fe, 18-22% of Ni, 18-22% of Ti and 22-26% of V.

Further, the high-strength high-toughness CoFeNiTiV high-entropy alloy comprises the following metal simple substances in atomic percentage: 20% of Co, 19% of Fe, 20% of Ni, 20% of Ti and 21% of V.

Further, the high-strength high-toughness CoFeNiTiV high-entropy alloy comprises the following metal simple substances in atomic percentage: 21% of Co, 18% of Fe, 18% of Ni, 20% of Ti and 23% of V.

Further, the high-strength high-toughness CoFeNiTiV high-entropy alloy comprises the following metal simple substances in atomic percentage: 19% of Co, 19% of Fe, 18% of Ni, 20% of Ti and 24% of V.

Further, the purity of the metal simple substance is 99.9 wt%.

The invention also provides a preparation method of the high-strength high-toughness CoFeNiTiV high-entropy alloy, which comprises the following steps:

(1) removing impurities and oxides on the surfaces of metal simple substances Co, Fe, Ni, Ti and V, and cleaning and drying for later use;

(2) firstly melting a metal titanium block in a non-consumable vacuum arc melting furnace under the protection of argon gas, allowing titanium to adsorb oxygen remaining in a protective atmosphere so as to reduce oxidation behavior during high-entropy alloy melting, then adding the metal simple substance according to a ratio, vacuumizing, and carrying out arc melting under the protection of argon gas, wherein electromagnetic stirring is accompanied in the process of arc melting, and a button sample is obtained after cooling; if the oxygen content in the argon protective atmosphere is too high in the smelting process, the alloy generates oxide scales, the oxide scales are crushed and enter the alloy in the smelting process, oxide inclusions are introduced into the alloy, or the condition of difficult mixing and melting is caused;

(3) and (3) repeating the electric arc melting for multiple times on the button sample, overturning the button sample before repeating the electric arc melting for each time, cooling and removing a surface oxide layer of the button sample after the electric arc melting for multiple times is finished, repeating the step (2), and cooling to obtain the high-strength high-toughness CoFeNiTiV high-entropy alloy.

Further, removing the impurities and the oxides in the step (1) and polishing the impurities and the oxides by using a grinder or sand paper; the cleaning process adopts acetone as cleaning solvent to carry out oscillation cleaning for 5min in ultrasonic waves, and the power density of the ultrasonic waves is 0.8W/cm²And the frequency was 33 Hz.

Further, the vacuum pumping in the step (2) reaches 2 × 10^-3Filling argon to 5Pa after Pa; the electric arc melting current is 50A-100A, and the time is 30 s-1 min.

Further, in the step (3), the melting state needs to be kept for 2-3 min in the process of repeating the arc melting for multiple times; the number of times is 4.

The beneficial technical effects are as follows:

the CoFeNiTiV high-entropy alloy is obtained by vacuum arc melting, has a BCC single-phase solid solution structure, does not have the phenomena of segregation, uneven components and thick grains by vacuum arc melting, has excellent toughness, has compressive yield strength exceeding that of a series of reported alloys, has yield strength of over 2430MPa, has elongation at break of over 18 percent, and has high strength and high toughness.

Drawings

FIG. 1 shows Co obtained in example 3₁₉Fe₁₉Ni₁₈Ti₂₀V₂₄XRD patterns of the high-entropy alloy, the CoFeNiTiCr high-entropy alloy of comparative example 1, the CoFeNiTiAl high-entropy alloy of comparative example 2 and the CoFeNiTiCu high-entropy alloy of comparative example 3.

FIG. 2 shows Co obtained in example 3₁₉Fe₁₉Ni₁₈Ti₂₀V₂₄Compression performance of the high entropy alloy and the CoFeNiTiCr high entropy alloy of comparative example 1 are compared.

In the above figures, -AC represents the as-cast high entropy alloy.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Unless specifically stated otherwise, the numerical values set forth in these examples do not limit the scope of the invention. Techniques, methods known to those of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate. In all examples shown and discussed herein, any particular value should be construed as merely illustrative, and not limiting. Thus, other examples of the exemplary embodiments may have different values.