阅读说明：本技术 一种氧掺杂纳米晶难熔金属高熵合金及其制备方法 (Oxygen-doped nanocrystalline refractory metal high-entropy alloy and preparation method thereof ) 是由 李延超 梁静 李来平 林小辉 高选乔 张新 于 2020-06-16 设计创作，主要内容包括：本发明公开了一种氧掺杂纳米晶难熔金属高熵合金的制备方法,该氧掺杂纳米晶难熔金属高熵合金的化学式为TiZrNbMoRe<Sub>X</Sub>,其中,X为0.1、0.2、0.3或0.4,该方法包括以下步骤：一、称取原料粉末在无惰性气体保护下高能球磨得到高熵合金粉末；二、将高熵合金粉末进行放电等离子烧结,随炉冷却后得到氧掺杂纳米晶难熔金属高熵合金；本发明还公开了上述方法制备的氧掺杂纳米晶难熔金属高熵合金。本发明通过无惰性气体保护下高能球磨并控制高能球磨工艺参数,得到纳米尺寸的高熵合金粉末并引入氧,从而经烧结后得到的氧掺杂纳米晶难熔金属高熵合金晶粒尺寸小,成分均匀,致密性良好,强度高,塑性好。(The invention discloses a preparation method of an oxygen-doped nanocrystalline refractory metal high-entropy alloy, wherein the chemical formula of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is TiZrNbMoRe X Wherein X is 0.1, 0.2, 0.3 or 0.4, comprising the steps of: weighing raw material powder, and carrying out high-energy ball milling under the protection of no inert gas to obtain high-entropy alloy powder; secondly, performing discharge plasma sintering on the high-entropy alloy powder, and cooling along with the furnace to obtain the oxygen-doped nanocrystalline refractory metal high-entropy alloy; the invention also discloses the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared by the method. According to the invention, through high-energy ball milling without inert gas protection and control of high-energy ball milling process parameters, high-entropy alloy powder with a nano size is obtained, and oxygen is introduced, so that the oxygen-doped nanocrystalline refractory metal high-entropy alloy obtained after sintering has small crystal grain size, uniform components, good compactness, high strength and good plasticity.)

1. The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is characterized in that the chemical formula of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is TiZrNbMoRe_XWherein X is 0.1, 0.2, 0.3 or 0.4, comprising the steps of:

step one, according to TiZrNbMoRe_XRespectively weighing Ti powder, Zr powder, Nb powder, Mo powder and Re powder according to the molar ratio of the elements in the alloy, and carrying out mechanical alloying treatment by high-energy ball milling under the protection of no inert gas to obtain high-entropy alloy powder; the high-energy ball milling is carried out by adopting a planetary high-energy ball mill, the rotating speed of the high-energy ball milling is 300-350 rpm, the ball milling time is 30-40 h, and the ball-material ratio is (10-15): 1;

secondly, filling the high-entropy alloy powder obtained in the first step into a graphite die for spark plasma sintering, and cooling along with the furnace to obtain the oxygen-doped nanocrystalline refractory metal high-entropy alloy; the spark plasma sintering process comprises the following steps: under the pressure condition of 30MPa to 60MPa, the temperature is firstly increased to 1200 ℃ at the speed of 20 ℃/min, then is increased to 1400 ℃ to 1700 ℃ at the speed of 5 ℃/min, and is kept for 10min to 20 min.

2. The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy according to claim 1, wherein in the first step, the mass purities of the Ti powder, the Zr powder, the Nb powder, the Mo powder and the Re powder are not less than 99.9%, and the particle sizes of the Ti powder, the Zr powder, the Nb powder, the Mo powder and the Re powder are 200-400 meshes.

3. The method for preparing the oxygen-doped nanocrystalline refractory metal high-entropy alloy according to claim 1, wherein a ball-milling pot adopted by the high-energy ball-milling in the first step is an agate pot, and a grinding ball is a tungsten carbide ball.

4. The method for preparing the oxygen-doped nanocrystalline refractory metal high-entropy alloy according to claim 1, wherein absolute ethyl alcohol is added as a control agent in the high-energy ball milling process in the step one.

5. The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy according to claim 1, characterized in that the high-energy ball-milled powder obtained after the high-energy ball milling in the step one is sequentially subjected to absolute ethyl alcohol ultrasonic cleaning for 30min and acetone ultrasonic cleaning for 30min, and then is placed in a 50 ℃ oven to be dried, so that the high-entropy alloy powder is obtained.

6. The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy according to claim 1, characterized in that in the second step, graphite paper is laid around and above and below the interior of a graphite mold, and then the high-entropy alloy powder is filled into the graphite mold.

7. An oxygen-doped nanocrystalline refractory metal high entropy alloy prepared by the method of any one of claims 1 to 6.

Technical Field

The invention belongs to the technical field of powder metallurgy, and particularly relates to an oxygen-doped nanocrystalline refractory metal high-entropy alloy and a preparation method thereof.

Background

The High Entropy Alloy (HEAS) is a novel multi-component alloy, which is composed of 5 or more than 5 metal elements with equal atom ratio or near equal atom ratio, and the molar ratio of each metal element is 5-35%. Despite the high number of alloying elements, simple solid solution phases such as Face Centered Cubic (FCC), Body Centered Cubic (BCC), and even Hexagonal Close Packed (HCP) phases can be present due to their high configuration entropy. Since Yeh et al first defined HEAs, high entropy alloys have attracted considerable interest in their unique compositions, microstructures, and excellent properties, such as high strength, moderate ductility, thermal stability, corrosion and wear resistance. Particularly, the high-entropy alloy mainly comprises BCC phase which mainly comprises refractory metal elements such as tungsten (W), molybdenum (Mo), tantalum (Ta), vanadium (V), niobium (Nb) and the like. Senkov for the first time at 2010 suggests that refractory metal high entropy alloys have better strength and hardness than nickel based alloys at high temperature stages (1200 ℃ C. to 1600 ℃ C.). High entropy alloys are receiving attention as promising materials for future high temperature applications.

At present, refractory metals are mainly prepared by an electric arc melting method, but the melting process is complex, the melting point of each element needs to be reached before melting, the temperature requirement is higher, and the structural defects of larger grain size, reduced structure performance and the like are caused; in addition, internal stress is generated in the smelting process, so that structural defects such as component segregation, shrinkage cavity and the like are caused, and the performance of the high-entropy alloy is not improved.

Disclosure of Invention

The technical problem to be solved by the present invention is to provide a method for preparing an oxygen-doped nanocrystalline refractory metal high-entropy alloy, aiming at the defects of the prior art. According to the method, a small amount of oxides are generated in the high-entropy alloy powder by introducing air through high-energy ball milling, the improvement of the strength of the high-entropy alloy is facilitated, meanwhile, the high-energy ball milling process parameters are controlled to obtain the high-entropy alloy powder with the nanometer size, and the nanocrystalline is facilitated to be obtained through sintering, so that the prepared oxygen-doped nanocrystalline refractory metal high-entropy alloy is small in grain size, uniform in components, good in compactness, high in strength and good in plasticity.

In order to solve the technical problems, the invention adopts the technical scheme that: the preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is characterized in that the chemical formula of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is TiZrNbMoRe_XWherein X is 0.1, 0.2, 0.3 or 0.4, comprising the steps of:

step one, according to TiZrNbMoRe_XRespectively weighing Ti powder, Zr powder, Nb powder, Mo powder and Re powder according to the molar ratio of the elements in the alloy, and carrying out mechanical alloying treatment by high-energy ball milling under the protection of no inert gas to obtain high-entropy alloy powder; the high-energy ball milling is carried out by adopting a planetary high-energy ball mill, the rotating speed of the high-energy ball milling is 300-350 rpm, the ball milling time is 30-40 h, and the ball-material ratio is (10-15): 1;

secondly, filling the high-entropy alloy powder obtained in the first step into a graphite die for spark plasma sintering, and cooling along with the furnace to obtain the oxygen-doped nanocrystalline refractory metal high-entropy alloy; the spark plasma sintering process comprises the following steps: under the pressure condition of 30MPa to 60MPa, the temperature is firstly increased to 1200 ℃ at the speed of 20 ℃/min, then is increased to 1400 ℃ to 1700 ℃ at the speed of 5 ℃/min, and is kept for 10min to 20 min.

The invention selects the powder corresponding to the high-melting-point metal elements Ti, Zr, Nb, Mo and Re as the raw material, firstly carries out high-energy ball milling under the protection of inert gas to carry out mechanical alloying to prepare high-entropy alloy powder, and then carries out spark plasma sintering. The invention firstly introduces air through high-energy ball milling to generate a small amount of oxide ZrO in high-entropy alloy powder₂The second phase particles are beneficial to improving the strength of the high-entropy alloy, and simultaneously, the high-energy ball milling process parameters are controlled to obtain the high-entropy alloy powder with nanometer size, so that the nanocrystalline is obtained through sintering, and the oxygen-doped nanocrystalline refractory metal high-entropy alloy disclosed by the invention is small in grain size, uniform in components, good in compactness, high in strength and good in plasticity.

The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is characterized in that in the step one, the mass purities of the Ti powder, the Zr powder, the Nb powder, the Mo powder and the Re powder are not less than 99.9%, and the particle sizes of the Ti powder, the Zr powder, the Nb powder, the Mo powder and the Re powder are 200-400 meshes. The quality purity of the optimized raw material powder avoids the introduction of excessive impurity elements, and the quality of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is improved; the optimized particle size is beneficial to improving the ball milling efficiency and promoting the formation of the nano-sized high-entropy alloy powder.

The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is characterized in that in the first step, a ball-milling tank adopted by the high-energy ball milling is an agate tank, and a milling ball is a tungsten carbide ball. The optimized tungsten carbide ball has high hardness, is beneficial to high-energy ball milling, avoids using a stainless steel tank to introduce iron impurities, and improves the quality purity of the high-entropy alloy powder.

The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is characterized in that absolute ethyl alcohol is added as a control agent in the high-energy ball milling process in the step one. The absolute ethyl alcohol is used as a control agent, so that the temperature in the ball milling process is effectively reduced, the welding and burning phenomena caused by overhigh local temperature in the high-energy ball milling process are avoided, the oxygen content and the oxide content in the high-entropy alloy powder are overhigh and impurities are generated due to serious oxidation, and the later sintering process is not facilitated, so that the performance of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is influenced.

The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is characterized in that high-energy ball-milled powder obtained after the high-energy ball milling in the step one is sequentially subjected to absolute ethyl alcohol ultrasonic cleaning for 30min and acetone ultrasonic cleaning for 30min, and then the high-energy ball-milled powder is placed in a 50 ℃ oven to be dried, so that the high-entropy alloy powder is obtained. The optimized cleaning process effectively removes carbon on the surface of the high-energy ball-milling powder, so that the high-energy ball-milling powder is fully dispersed, and later-stage sintering is facilitated; the preferred drying process effectively removes residual ethanol and acetone from the cleaning process.

The preparation method of the oxygen-doped nanocrystalline refractory metal high-entropy alloy is characterized in that in the second step, graphite paper is laid on the periphery and the upper and lower parts in the graphite die, and then high-entropy alloy powder is filled into the graphite die. The arrangement is beneficial to smooth demoulding of the green body after subsequent sintering.

In addition, the invention also provides the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared by the method.

Compared with the prior art, the invention has the following advantages:

1. according to the invention, air is introduced through high-energy ball milling to generate a small amount of oxides in the high-entropy alloy powder, so that the improvement of the strength of the high-entropy alloy is facilitated, and meanwhile, the high-energy ball milling process parameters are controlled to obtain the high-entropy alloy powder with nanometer size, so that the nanocrystalline is facilitated to be obtained through sintering, and therefore, the prepared oxygen-doped nanocrystalline refractory metal high-entropy alloy has the advantages of small grain size, uniform components, good compactness, high strength and good plasticity.

2. The oxygen atoms are introduced through the high-energy ball milling treatment under the protection of inert gas, so that the strength and the plasticity of the oxygen-doped nanocrystalline refractory metal high-entropy alloy are improved simultaneously.

3. According to the invention, the rhenium element is introduced to form a rhenium effect, so that the strength and the shape of the oxygen-doped nanocrystalline refractory metal high-entropy alloy are improved.

4. The preparation method is simple, only needs one-time sintering, has short sintering time, obviously reduces energy consumption and equipment loss, and has good application prospect.

The technical solution of the present invention is further described in detail by the accompanying drawings and examples.

Drawings

FIG. 1 is an XRD pattern of the high energy ball milled powder at 5h, 10h, 20h and 30h in example 1 of the present invention.

FIG. 2a is an SEM image (500X) of high energy ball milled powder of example 1 of the present invention when the powder is high energy ball milled for 40 h.

FIG. 2b is an SEM image (1000X) of the high energy ball milled powder of example 1 of the present invention when the powder is high energy ball milled for 40 h.

FIG. 2c is an SEM image (2000X) of high energy ball milled powder of example 1 of the present invention after 40h high energy ball milling.

FIG. 2d is an SEM image (5000X) of the high energy ball milled powder at 40h in example 1 of the present invention.

FIG. 3a is an SEM image (2000X) of an oxygen-doped nanocrystalline refractory metal high entropy alloy prepared according to example 1 of the present invention.

FIG. 3b is an SEM image (10000X) of the oxygen-doped nanocrystalline refractory metal high entropy alloy prepared by example 1 of the present invention.

Fig. 4a is a microstructure crystal phase diagram of the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 4b is a microstructure phase diagram of the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention after corrosion.

Fig. 5 is an XRD pattern of the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 6a is a scanning view of Nb element in the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 6b is a surface scanning diagram of Zr element in the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 6c is a scanning view of the Mo element in the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 6d is a scanning view of the surface of Ti element in the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 6e is a surface scanning diagram of the Re element in the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 6f is a scanning image of the O element in the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

Fig. 7 is a room temperature compression curve diagram of the oxygen-doped nanocrystalline refractory metal high-entropy alloy prepared in example 1 of the present invention.

FIG. 8 is a room temperature compression plot of a refractory metal high entropy alloy prepared according to comparative example 1 of the present invention.

Fig. 9 is an XRD pattern of the refractory metal high-entropy alloy prepared in comparative example 2 of the present invention.

Detailed Description