1. The ternary refractory medium-entropy alloy is characterized in that the medium-entropy alloy component is Ti_aV_bHf_cWherein a, b and c respectively represent the mol percentage of the corresponding elements, a is 30-60 at%, b is 5-35 at% and c is 30-35 at%.

2. The ternary refractory entropy alloy as claimed in claim 1, wherein the entropy alloy is Ti₆₀V₈Hf₃₂、Ti₅₃V₁₅Hf₃₂、Ti₄₉V₁₉Hf₃₂、Ti₄₁V₂₇Hf₃₂、Ti₃₃V₃₃Hf₃₃One kind of (1).

3. A method of producing a ternary refractory entropy alloy as claimed in claim 1 or 2, characterized in that it comprises the following steps:

smelting: placing the raw materials in a vacuum arc melting furnace, controlling the current to be 150-280A under the inert atmosphere condition, carrying out multiple melting for 3-6 min each time, then carrying out intermission for 3-6 min, turning over, carrying out next melting, and casting the alloy melt into a mold after the melting is finished to obtain an as-cast alloy ingot;

suction casting: and placing the as-cast alloy ingot on a casting mold, smelting the alloy ingot, performing suction casting when the alloy ingot is completely liquid and has good fluidity, cooling, and removing the mold to obtain a rectangular suction-cast alloy ingot, namely the ternary refractory mid-entropy alloy.

4. A method of producing a ternary refractory entropy alloy as claimed in claim 3, wherein at least 5 heats are applied.

5. The preparation method of the ternary refractory medium-entropy alloy as claimed in claim 4, wherein in the first smelting process, the current is controlled to be 150-180A; in the second smelting and the subsequent multiple smelting processes, the current is controlled to be 260-280A.

6. The method for preparing the ternary refractory entropy alloy as claimed in claim 3, wherein the raw materials are cleaned by vibration with ethanol, dried and then placed in a vacuum arc melting furnace, and the metal with the lowest melting point is placed on the bottom layer and the metal with the highest melting point is placed on the surface layer.

7. The method for preparing the ternary refractory entropy alloy as claimed in claim 3, wherein after the raw materials are placed in a vacuum arc melting furnace, the oxygen is discharged from the furnace chamber by repeatedly vacuumizing and filling inert gas for a plurality of times, and then the melting operation is carried out; wherein the vacuum is pumped to 2 × 10^-3Pa, and introducing argon into the furnace chamber to-0.05 MPa.

8. The method for preparing the ternary refractory entropy alloy as claimed in claim 3, wherein in the process of suction casting, the current is controlled to be 150-200A for low-temperature preheating after the alloy ingot in the cast state is ignited, and after the whole ingot is heated, the current is increased to be 300-400A, so that the ingot is melted.

Background

In recent years, the high/medium entropy alloy breaks through the traditional alloy design concept of single principal element component design, and is a novel multi-principal element metal material mainly designed by configuration entropy, and the excellent physical and chemical properties attract wide attention. Unlike conventional alloys, the medium entropy alloy is a result of the combined action of a plurality of principal elements, rather than a single element, and is prone to form a solid solution phase, such as a simple Body Centered Cubic (BCC) or Face Centered Cubic (FCC) phase. The refractory high-medium entropy alloy (the melting point is more than 2123K) mainly comprises metal elements of IVB (Ti, Zr, Hf), VB (V, Nb, Ta) and VIB (Cr, Mo and W), and is mainly based on metal elements of a body-centered cubic (BCC) structure, so that the refractory medium-entropy alloy is mostly a single-phase BCC solid solution phase or a BCC solid solution phase. In the general definition, the entropy alloy is an alloy containing more than 5 constituent elements or the mixed entropy is more than or equal to-1.6R. The refractory entropy alloy has the advantages of high melting point, high hardness, corrosion resistance, excellent high-temperature strength and the like, the application temperature of the alloy is as high as 1373-1593K, the alloy is much higher than that of the traditional high-temperature alloy such as Inconel 718 alloy and the like, and the alloy has lower elastic modulus and specific modulus compared with nickel-based high-temperature alloy and stainless steel, and has potential application prospects in the fields of aerospace (turbines and engine blades), nuclear industry, biomedicine and the like.

The glide systems of BCC refractory alloys at room temperature are much less than those of the medium entropy alloys of the FCC structure, and generally exhibit significant brittleness at room temperature or higher. Therefore, the BCC refractory alloy has the first problems of low room temperature or high temperature plasticity, difficult meeting of the tensile property with the requirement of engineering materials and poor processability.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a ternary refractory intermediate entropy alloy and a preparation method thereof. The alloy has a simple body-centered cubic structure, has good room-temperature tensile plasticity and strength, makes up for the defects of the prior art, meets the requirements of high-performance metal structural materials, and provides new component selection for the BCC medium-entropy alloy, so that the alloy has great application potential.

The first purpose of the invention is to provide a ternary refractory medium-entropy alloy, wherein the medium-entropy alloy component is Ti_aV_bHf_cWherein a, b and c respectively represent the mol percentage of the corresponding elements, a is 30-60 at%, b is 5-35 at% and c is 30-35 at%.

Preferably, the medium entropy alloy is Ti₆₀V₈Hf₃₂、Ti₅₃V₁₅Hf₃₂、Ti₄₉V₁₉Hf₃₂、Ti₄₁V₂₇Hf₃₂、Ti₃₃V₃₃Hf₃₃One kind of (1).

The second purpose of the invention is to provide a preparation method of the ternary refractory medium-entropy alloy, which comprises the following steps:

smelting: placing the raw materials in a vacuum arc melting furnace, controlling the current to be 150-280A under the inert atmosphere condition, carrying out multiple melting for 3-6 min each time, then carrying out intermission for 3-6 min, turning over, carrying out next melting, and casting the alloy melt into a mold after the melting is finished to obtain an as-cast alloy ingot;

suction casting: and placing the as-cast alloy ingot on a casting mold, smelting the alloy ingot, performing suction casting when the alloy ingot is completely liquid and has good fluidity, cooling, and removing the mold to obtain a rectangular suction-cast alloy ingot, namely the ternary refractory mid-entropy alloy.

Preferably, at least 5 smelts are carried out.

More preferably, in the primary smelting process, the current is controlled to be 150-180A; in the second smelting and the subsequent multiple smelting processes, the current is controlled to be 260-280A.

Preferably, the raw materials are cleaned by vibration with ethanol, dried and then placed in a vacuum arc melting furnace, and the metal with the lowest melting point is placed on the bottom layer and the metal with the highest melting point is placed on the surface layer.

Preferably, after the raw materials are placed in a vacuum arc melting furnace, the oxygen is discharged from the furnace chamber by repeatedly vacuumizing and filling inert gas for a plurality of times, and then the melting operation is carried out; wherein the vacuum is pumped to 2 × 10^-3Pa, and introducing argon into the furnace chamber to-0.05 MPa.

Preferably, in the process of suction casting, the current is controlled to be 150-.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a ternary infusible medium-entropy alloy and a preparation method thereof. The alloy has a simple body-centered cubic structure, has good room-temperature tensile plasticity and strength, makes up for the defects of the prior art, meets the requirements of high-performance metal structural materials, and provides new component selection for the BCC medium-entropy alloy, so that the alloy has great application potential.

The room temperature plasticity of the ternary infusible medium entropy alloy provided by the invention basically reaches 10% or above, wherein Ti₄₁V₂₇Hf₃₂The room temperature plasticity is about 22 percent, the tensile strength can reach 1181MPa, the yield strength can reach 1106MPa, and the excellent combination of the strength and the plasticity is realized. The Ti/V ratio of the TiVHf system alloy with the best comprehensive strength and hardness is 5/2-3/2, and through alloy design and experimental verification, the TiVHf system intermediate entropy alloy with unified strong plasticity is obtained.

The medium-entropy alloy has high melting point of the constituent elements, alloy smelting is carried out by a non-consumable vacuum arc smelting process, and the ternary TiVHf medium-entropy alloy material with uniform components and excellent mechanical properties is prepared by regulating and controlling the smelting frequency and the smelting current.

The ternary refractory entropy alloy provided by the invention has potential application prospects in the fields of aerospace, nuclear industry, biomedicine and the like.

Drawings

FIG. 1 is a flow chart of a preparation process of the ternary refractory medium entropy alloy provided by the invention.

FIG. 2 is a structure diagram of the medium entropy alloy provided in examples 1 to 5.

FIG. 3 is a XRD spectrum of the medium entropy alloy provided in examples 1-5;

FIG. 4 is a graph showing the grain distribution and size of EBSD (IPF plot) of the medium entropy alloys provided in examples 1-5; a quantitative statistical graph of grain size distribution; the grain size is shown by the variation trend of V content.

FIG. 5 is a tensile stress-strain curve of the medium entropy alloy provided in examples 1-5.

Detailed Description

The present invention is described in detail below with reference to the attached drawings and specific embodiments so that those skilled in the art can better understand the present invention and can implement the present invention, but the present invention is not limited by the examples.

The invention provides a ternary infusible medium-entropy alloy, wherein the medium-entropy alloy component is Ti_aV_bHf_cWherein a, b and c respectively represent the mol percentage of the corresponding elements, a is 30-60 at%, b is 5-35 at% and c is 30-35 at%. .

The raw materials used in the following examples are all metal raw materials with a purity of not less than 99.95%.

Example 1

A ternary refractory medium-entropy alloy with the chemical formula of Ti₆₀V₈Hf₃₂Abbreviated as V₈(ii) a Wherein, the proportion of each element is mole percentage.

Ti₆₀V₈Hf₃₂The preparation method of the ternary refractory medium entropy alloy is shown in figure 1 and comprises the following steps:

s1, preparing materials: vibrating and cleaning a high-purity (more than or equal to 99.95%) metal raw material by using alcohol, and drying for later use; the dosage of the raw materials is Ti according to the mole percentage of each element₆₀V₈Hf₃₂Weighing, specifically weighing 19.17gTi, 2.72gV and 38.11gV by using an analytical balance, sequentially putting the weighed materials into a water-cooled metal crucible, putting the metal with the lowest melting point on the bottom layer, and putting the metal with the highest melting point on the surface layer;

s2, vacuumizing: charging the raw materials into a non-consumable vacuum arc melting furnace and then closingThe furnace door carries out vacuum-pumping treatment on the sample chamber: first, the mechanical pump is turned on, and when the vacuum degree is less than 5X 10⁰Opening the molecular pump after Pa until the maximum frequency of the molecular pump reaches 450HZ and the vacuum degree is less than or equal to 2 multiplied by 10^-3Pa, closing the molecular pump, introducing high-purity argon to the sample chamber to achieve-0.05 MPa, and repeating the processes of vacuumizing and filling argon for 2 times to fully remove oxygen in the furnace body;

s3, smelting: smelting a pure titanium ingot for 5min to absorb residual oxygen, then repeatedly smelting the raw materials for 5 times, wherein each smelting time is 5min, and then carrying out next smelting after 5min of intermission;

the first smelting uses low current 160A to carry out low-temperature smelting so as to reduce the volatilization loss of volatile elements; stopping arc striking after the mixture is fully mixed, turning the cast ingot by 180 degrees by using a deflector rod after the cast ingot is cooled, and then turning the cast ingot by the turning operation after each time of smelting is finished so as to ensure the smelting uniformity;

the current is controlled to be 270A for high-temperature smelting from the second smelting to the fifth smelting, and the electromagnetic stirring function is used, the current is 1.5A, the fluidity of the alloy is enhanced, and the components are uniform;

s4, suction casting: placing a circular cast ingot smelted in a copper crucible on a casting mold, conducting low-temperature preheating by using a small current 180A after arc striking, waiting for the cast ingot to become red, increasing the current to 380A instantly after the whole is uniformly heated so as to melt the cast ingot, and simultaneously clicking a suction casting button to suction cast liquid alloy into a rectangular mold with the size of 60 multiplied by 10 multiplied by 8mm so as to prevent casting defects caused by over-rapid solidification; cooling and removing the mould to obtain a rectangular suction casting alloy ingot, namely ternary Ti₆₀V₈Hf₃₂A refractory mid-entropy alloy.

Example 2

A ternary refractory medium-entropy alloy with the chemical formula of Ti₅₃V₁₅Hf₃₂Abbreviated as V₁₅(ii) a Wherein, the proportion of each element is mole percentage.

The preparation method of the medium entropy alloy is the same as that of the embodiment 1, except that the raw materials are used according to the molar percentage of Ti₅₃V₁₅Hf₃₂And weighing.

Example 3

A ternary refractory medium-entropy alloy with the chemical formula of Ti₄₉V₁₉Hf₃₂Abbreviated as V₁₉(ii) a Wherein, the proportion of each element is mole percentage.

The preparation method of the medium entropy alloy is the same as that of the embodiment 1, except that the raw materials are used according to the molar percentage of Ti₄₉V₁₉Hf₃₂And weighing.

Example 4

A ternary refractory medium-entropy alloy with the chemical formula of Ti₄₁V₂₇Hf₃₂Abbreviated as V₂₇(ii) a Wherein, the proportion of each element is mole percentage.

The preparation method of the medium entropy alloy is the same as that of the embodiment 1, except that the raw materials are used according to the molar percentage of Ti₄₁V₂₇Hf₃₂And weighing.

Example 5

A ternary refractory medium-entropy alloy with the chemical formula of Ti₃₃V₃₃Hf₃₃Abbreviated as V₃₃(ii) a Wherein, the proportion of each element is mole percentage.

The preparation method of the medium entropy alloy is the same as that of the embodiment 1, except that the raw materials are used according to the molar percentage of Ti₃₃V₃₃Hf₃₃And weighing.

In order to illustrate various properties of the ternary refractory entropy alloy provided by the invention, the ternary refractory entropy alloy provided by the embodiments 1-5 is subjected to related property analysis. See Table 1 and FIGS. 2-5.

The XRD phase identification test is carried out, the working voltage and current of an X-ray diffractometer are 40KV and 40mA respectively, an X-ray source is a Cu Ka (lambda is 0.1542nm) ray, the scanning speed is 5 DEG/min, the scanning step length is 0.02 DEG/step, and the scanning range is 20-100 DEG; tissue characterization was performed by BSE (backscattered electron)/EBSD (electron backscattered diffraction technique), and the samples were electropolished before measurement. And (3) testing the hardness by adopting a micro Vickers hardness tester, polishing the upper surface and the lower surface of the sample to be flat and keeping the upper surface and the lower surface parallel before measurement, and polishing the measurement surface. And testing the tensile mechanical property of the alloy by using a 48 x 10mm plate-shaped sample in an electronic universal material testing machine, analyzing and comparing to obtain the alloy components with the optimal performance, and determining the alloying action of Ti/V in the TiVHf alloy.

FIG. 2 is a structure diagram of the medium entropy alloy and the corresponding Vickers hardness of the alloy provided in examples 1-5, and it can be seen from FIG. 2 that Ti₆₀V₈Hf₃₂，Ti₅₃V₁₅Hf₃₂，Ti₄₉V₁₉Hf₃₂，Ti₄₁V₂₇Hf₃₂，Ti₃₃V₃₃Hf₃₃The hardness values of (A) are 300.3HV, 277.2HV,307.5HV, 321.9HV and 345.7HV respectively. The hardness value of the TiVHf alloy shows a trend of decreasing firstly and then increasing along with the increase of the content of V, and V has larger mismatch volume in the TiVHf alloy, so that the lattice distortion is increased, and the hardness is improved. Ti₄₁V₂₇Hf₃₂A micro intergranular precipitated phase, Ti, appears₃₃V₃₃Hf₃₃There are a large number of intergranular precipitates, and the structure of the remaining components is a solid solution phase, which indicates that Ti improves the compatibility of the constituent elements and suppresses the precipitation of the compound phase.

FIG. 3 is the XRD spectrum of the medium entropy alloy provided in examples 1-5, and it can be seen from FIG. 3 that most of the medium entropy alloys in TiVHf system are single-phase BCC structure, and the asymmetric peak may be caused by grain boundary and intragranular component segregation, or BCC₂Precipitated phases of the structure; as the V content increases, the diffraction peak of the BCC phase shifts rightward as a whole due to the lattice distortion, and the value of the lattice constant a becomes smaller.

FIG. 4 is a graph showing the grain distribution and size distribution of EBSDs (IPF plots) of the medium entropy alloys provided in examples 1-5 (plot a); quantitative statistical graph of grain size distribution (graph b); a variation trend graph (graph c) of the grain size with the V content; as can be seen from fig. 4, the EBSD (IPF map) of the TiVHf alloy exhibits grain distribution and grain size, with specific values in table 1. Wherein Ti₅₃V₁₅Hf₃₂Has a maximum grain size of about an average64.9 μm, Ti₄₁V₂₇Hf₃₂Has a minimum grain size, and has an average value of about 28.7 μm. The different compositions of the alloy have different solidification capacities during the casting process, and the growth speeds of the crystal grains are different, so that the difference of the sizes of the crystal grains is caused.

Table 1 is a summary of the average grain size and yield strength values for the ternary refractory entropy alloys provided in examples 1-5

FIG. 5 is a tensile stress-strain curve of the medium entropy alloy provided in examples 1-5. As can be seen from FIG. 5, room temperature plasticity of TiVHf alloy substantially reaches 10% or more, wherein Ti₄₁V₂₇Hf₃₂The room temperature plasticity is about 22 percent, the tensile strength can reach 1181MPa, the yield strength can reach 1106MPa, and the excellent combination of the strength and the plasticity is realized. The Ti/V ratio of the TiVHf system alloy with the best comprehensive strength and hardness is 5/2-3/2, and through alloy design and experimental verification, the TiVHf system intermediate entropy alloy with unified strong plasticity is obtained.

In conclusion, the invention provides a ternary refractory medium-entropy alloy and a preparation method thereof. The alloy has a simple body-centered cubic structure, has good room-temperature tensile plasticity and strength, makes up for the defects of the prior art, meets the requirements of high-performance metal structural materials, and provides new component selection for the BCC medium-entropy alloy, so that the alloy has great application potential.

The medium-entropy alloy has high melting point of the constituent elements, alloy smelting is carried out by a non-consumable vacuum arc smelting process, and the ternary TiVHf medium-entropy alloy material with uniform components and excellent mechanical properties is prepared by regulating and controlling the smelting frequency and the smelting current.

The ternary refractory entropy alloy provided by the invention has potential application prospects in the fields of aerospace, nuclear industry, biomedicine and the like.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.