阅读说明：本技术 一种耐腐蚀高熵合金的制备方法 (Preparation method of corrosion-resistant high-entropy alloy ) 是由 高卡 刘东岳 马天宇 孙德建 李贵忠 康佳臣 张米纳 高阳 樊磊 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种耐腐蚀高熵合金的制备方法,通过对高熵合金预合金粉体采用热压预烧结与振荡热压烧结组合的方式,以较低的温度实现了提高高熵合金的耐腐蚀性。在振荡热压烧结前采用传统的热压烧结进行预烧结,增大了样品的初始致密度,之后对样品施加循环振荡压力,在真空的条件下,借助烧结炉内的热场与力场的相互作用,使高熵合金材料的内部缺陷有效减少,抑制了孔隙、孔洞的出现,同时颗粒边界也随着温度的升高逐渐消融,从而使得组织薄弱处受腐蚀的风险大大减小。本发明的热压预烧结与振荡热压烧结组合的方式用于制备耐腐蚀高熵合金,大幅降低了烧结温度,具有绿色、节能的特点。(The invention discloses a preparation method of a corrosion-resistant high-entropy alloy, which improves the corrosion resistance of the high-entropy alloy at a lower temperature by adopting a mode of combining hot-pressing pre-sintering and oscillating hot-pressing sintering on high-entropy alloy pre-alloy powder. The method is characterized in that the traditional hot-pressing sintering is adopted for pre-sintering before the oscillating hot-pressing sintering, the initial density of a sample is increased, then the circulating oscillating pressure is applied to the sample, under the vacuum condition, the internal defects of the high-entropy alloy material are effectively reduced by means of the interaction of a thermal field and a force field in a sintering furnace, the occurrence of pores and holes is inhibited, and meanwhile, the particle boundaries are gradually ablated along with the rise of the temperature, so that the risk that the weak tissue part is corroded is greatly reduced. The mode of combining hot-pressing presintering and oscillating hot-pressing sintering is used for preparing the corrosion-resistant high-entropy alloy, greatly reduces the sintering temperature, and has the characteristics of greenness and energy conservation.)

1. The preparation method of the corrosion-resistant high-entropy alloy is characterized by comprising the following steps of:

(1) putting high-entropy alloy prealloy powder into a die, and performing prepressing molding;

(2) putting the die filled with the high-entropy alloy prealloy powder after the prepressing molding in the step (1) into a sintering furnace, and prepressing and loading the sampleVacuumizing, heating to a set temperature T₁Then entering a heat preservation state, and carrying out hot-pressing pre-sintering on the sample;

(3) continuously heating the sample after the hot-pressing pre-sintering in the step (2) to reach the set temperature T₂And boosting pressure, carrying out oscillation hot-pressing sintering, cooling after the completion, applying constant pressure to the sample in the cooling process, and obtaining a final product after the cooling is completed.

2. The preparation method of the corrosion-resistant high-entropy alloy according to claim 1, wherein the pressure rise rate in the step (3) is 2MPa/min, the median value of the oscillating hot-pressing pressure is 40-65 MPa, the amplitude is +/-1- +/-10 MPa, and the oscillating frequency is 1-5 Hz.

3. The method for preparing the corrosion-resistant high-entropy alloy according to claim 1, wherein the temperature rise rate in the step (3) is 8 ℃/min, and the set temperature T is₂The temperature is 1000-1100 ℃, and the heat preservation time is 0.5-1 h.

4. The method for preparing the corrosion-resistant high-entropy alloy according to claim 1, wherein the constant pressure applied in the cooling process in the step (3) is 40-65 MPa.

5. The method for preparing the corrosion-resistant high-entropy alloy according to claim 1, wherein the temperature rise rate in the step (2) is 8 ℃/min, and the set temperature T is₁The temperature is 500-700 ℃, and the heat preservation time is 0.25-0.5 h.

6. The preparation method of the corrosion-resistant high-entropy alloy according to claim 1, wherein the pressure applied by the hot-pressing and pre-sintering in the step (2) is 10-30 MPa; the pre-pressing loading pressure is 1.4MPa, and the loading rate is 1.4 MPa/min.

7. The method for preparing the corrosion-resistant high-entropy alloy according to claim 1, wherein the pressure for the pre-compaction forming in the step (1) is 7MPa, and the time is 15 min.

8. The preparation method of the corrosion-resistant high-entropy alloy of claim 1, wherein the high-entropy alloy pre-alloyed powder in the step (1) is AlCoCrNiFe, the atomic ratio of each element is 1:1:1:1:1, and the purity of each element is more than 99.6%.

Technical Field

The invention belongs to the technical field of powder metallurgy, and relates to a preparation method of a corrosion-resistant high-entropy alloy.

Background

At present, trace elements are generally introduced into alloy materials to improve the physical and chemical properties of the alloy, and the alloy materials have better properties than single metal materials in certain special properties, such as strength and hardness improvement, excellent corrosion resistance and high-temperature softening property. However, with the addition of trace elements, intermetallic compounds with complex structures or equivalent brittleness often appear in alloy systems, which reduces the shaping and toughness of the materials and has adverse effects on the application of the alloy materials. High-entropy alloy has come into play, and as a metal material which is hot in recent years, the high-entropy alloy has the performances of high corrosion resistance, high temperature resistance, oxidation resistance, high strength, high hardness and the like. Particularly, with the development of scientific technology and the requirement of practical engineering application in recent years, the corrosion resistance of the high-entropy alloy is receiving more and more attention due to the advantages of high entropy value, relatively simple structure and the like.

The preparation method of the high-entropy alloy mainly adopts a vacuum melting method and a powder metallurgy method, but the vacuum melting method causes phenomena of uneven stress distribution, component segregation, shrinkage cavity, gaps and the like in the alloy due to the phenomena of thermal expansion and condensation in the casting process, so that the performance of the high-entropy alloy is seriously influenced, and particularly the corrosion resistance of the high-entropy alloy is further hindered after the influence on the phase of the cast alloy is generated. Although the powder metallurgy technology can reduce the sintering temperature and avoid the generation of defects of tissues, the densification degree is low, the formed phases are complex, the improvement of the compactness of the high-entropy alloy is not facilitated, and the preparation of the corrosion-resistant high-entropy alloy is influenced to a certain extent. Therefore, in order to overcome the above existing problems, it is necessary to introduce a new technical solution for improving the performance of the high-entropy alloy.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a preparation method of a corrosion-resistant high-entropy alloy, which has the characteristics of low sintering temperature and good corrosion resistance of the obtained high-entropy alloy.

The purpose of the invention is realized by adopting the following technical scheme:

a preparation method of a corrosion-resistant high-entropy alloy comprises the following steps:

(1) putting high-entropy alloy prealloy powder into a die, and performing prepressing molding;

(2) putting the die filled with the high-entropy alloy prealloy powder after the prepressing forming in the step (1) into a sintering furnace, prepressing, loading and vacuumizing a sample, and heating to a set temperature T₁Then entering a heat preservation state, and carrying out hot-pressing pre-sintering on the sample;

(3) continuously heating the sample after the hot-pressing pre-sintering in the step (2) to reach the set temperature T₂And (4) boosting pressure, performing oscillation hot-pressing sintering, cooling after the completion, applying constant pressure to the sample in the cooling process, and obtaining a final product after the cooling is completed.

Further, the pressure increasing rate in the step (3) is 2MPa/min, the median value of the oscillating hot-pressing pressure is 40-65 MPa, the amplitude is +/-1- +/-10 MPa, and the oscillating frequency is 1-5 Hz.

Further, the heating rate in the step (3) is 8 ℃/min, and the temperature T is set₂The temperature is 1000-1100 ℃, and the heat preservation time is 0.5-1 h.

Further, the constant pressure applied in the cooling process in the step (3) is 40-65 MPa.

Further, the heating rate in the step (2) is 8 ℃/min, and the temperature T is set₁The temperature is 500-700 ℃, and the heat preservation time is 0.25-0.5 h.

Further, the pressure applied by the hot-pressing pre-sintering in the step (2) is 10-30 MPa; the pre-pressing loading pressure is 1.4MPa, and the loading rate is 1.4 MPa/min.

Further, the pressure of the pre-pressing forming in the step (1) is 7MPa, and the time is 15 min.

Further, the high-entropy alloy prealloying powder in the step (1) is AlCoCrNiFe, the ratio of elements is 1:1:1:1:1, and the purity of each element is more than 99.6%.

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

the invention provides a preparation method of a corrosion-resistant high-entropy alloy, which improves the corrosion resistance of the high-entropy alloy at a lower temperature by adopting a mode of combining hot-pressing pre-sintering and oscillating hot-pressing sintering on high-entropy alloy pre-alloy powder. The method is characterized in that the traditional hot-pressing sintering is adopted for pre-sintering before the oscillating hot-pressing sintering, the initial density of a sample is increased, then the circulating oscillating pressure is applied to the sample, under the vacuum condition, the internal defects of the high-entropy alloy material are effectively reduced by means of the interaction of a thermal field and a force field in a sintering furnace, the occurrence of pores and holes is inhibited, and meanwhile, the particle boundaries are gradually ablated along with the rise of the temperature, so that the risk that the weak tissue part is corroded is greatly reduced. The mode of combining hot-pressing presintering and oscillating hot-pressing sintering is used for preparing the corrosion-resistant high-entropy alloy, so that the sintering temperature is greatly reduced, the energy consumption in the preparation process is reduced, abnormal growth of crystal grains caused by high-temperature sintering is effectively avoided, and the corrosion resistance of the alloy is improved.

Drawings

FIG. 1 is an SEM image of electrochemical corrosion of samples obtained in example 1 and comparative example 1 of the present invention, wherein FIGS. 1a to 1c correspond to the temperature of 1100 ℃ to 1000 ℃ in the oscillatory thermal compression sintering of example 1 and the sample obtained in comparative example 1, respectively;

FIG. 2 is a potentiodynamic polarization curve of samples obtained in example 1 of the present invention and comparative example 1.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

Example 1

A preparation method of a corrosion-resistant high-entropy alloy comprises the following steps:

(1) loading AlCoCrNiFe high-entropy alloy prealloy powder into a graphite grinding tool coated with boron nitride powder, then performing pre-pressing forming, and pressing for 15min under the condition that the pressure of a cold press is 7 MPa; pressing into cylindrical sheet with diameter of 10mm and thickness of 5 mm. The atomic ratio of each element in the AlCoCrNiFe high-entropy alloy prealloying powder is 1:1:1:1:1, and the purity of each element is more than 99.6%.

(2) Placing the graphite die which is pre-pressed and formed in the step (1) and is provided with AlCoCrNiFe high-entropy alloy pre-alloyed powder into a furnace cavity of a sintering furnace, aligning a die base with a workbench, adjusting a pressure head in the furnace cavity to move downwards, and performing pre-pressing loading at the loading speed of 1.4MPa/min and the pressure of 1.4 MPa; and stopping the descending process when the pressure head reaches the upper end cover and the die does not crack under the target pressure value. After the descending program is stopped, a mechanical pump is started to vacuumize the furnace chamber, the temperature is raised to 500 ℃ at the speed of 8 ℃/min after the target vacuum degree is reached to 15Pa, the temperature is preserved for 0.25h, a constant pressure value of 20MPa is applied while the temperature is preserved, and the sample is subjected to hot-pressing pre-sintering.

(3) And (3) continuing heating the sample after the hot-pressing pre-sintering in the step (2), wherein the heating rate is 8 ℃/min, after the temperature is increased to 1100 ℃, applying oscillation pressure to the sample at the pressure rise of 2MPa/min until the heat preservation is finished, and the heat preservation time is 1 h. Wherein the median value of the fixed oscillation hot-pressing circulation pressure is 60MPa, the amplitude is +/-5 MPa, and the oscillation frequency is 1 Hz. After the oscillating procedure is finished, the sample is cooled along with the furnace, constant pressure is kept applied to the sample in the cooling process, the pressure value is the median value of the oscillating pressure and is 60MPa, the oscillating frequency is 0Hz until the sample is cooled to the room temperature, the furnace door is opened by breaking vacuum, meanwhile, the upper pressure head moves upwards through control parameters in software, the pressure of the upper pressure head is removed, and the graphite mold is taken out to obtain a final product (recorded as example 1-1100 ℃).

The set temperature in step (3) was adjusted to 1000 ℃ to give the corresponding product (noted as example 1-1000 ℃).

Comparative example 1

Comparative example 1 differs from example 1 in that: the set temperature in step (2) in example 1 was adjusted from 500 ℃ to 1100 ℃ and the constant pressure was adjusted from 20MPa to 65 MPa; step (3) omits the oscillating hot pressing sintering process, the pressure applied in the cooling process is 65MPa, and the rest is the same as the embodiment 1.

Experimental example 1

The samples obtained in the example 1 and the comparative example 1 are subjected to electrochemical corrosion performance comparison test in 3.5 wt% NaCl solution at room temperature of 25 ℃, the potential sweeping interval is-2V to 1V, and the potential scanning speed is 0.001V/s. Then, the sample after electrochemical corrosion is subjected to microscopic morphology characterization, and as a result, as shown in fig. 1, the corrosion range of the sample prepared by the mode of combining hot-pressing pre-sintering and oscillatory hot-pressing sintering is different, and when the temperature is 1100 and 1000 ℃ (fig. 1a and 1b), the sample shows obvious interdendritic corrosion, the grain boundary is corroded, no obvious grain boundary is separated out, a corrosion-resistant phase is left in the grain, and the corrosion resistance of the high-entropy alloy is enhanced.

FIG. 1c shows that the high-entropy alloy of comparative example 1 is prepared only by conventional hot-pressing sintering (i.e. only hot-pressing pre-sintering according to the present invention), and the grain boundary is clear, and the corrosion resistance effect is not obvious, and compared with the sample obtained by the combination of the hot-pressing pre-sintering and the oscillating hot-pressing sintering of FIG. 1b, the grain boundary is gradually ablated, the intra-granular corrosion resistance phase is exposed, and the corrosion resistance performance can be improved.

TABLE 1

Group of	Icorr/(A*cm-2)	Ecorr/V
			Examples 1-1100 deg.C	6.8993×10-6	-0.792
Examples 1-1000 deg.C	8.0380×10-6	-0.996
			Comparative example 1	9.7322×10-6	-1.001

FIG. 2 and Table 1 show the comparison of electrochemical corrosion resistance of the high-entropy alloy prepared by the invention. In the embodiment 1 of the invention, the high-entropy alloy corrosion current 6.8993X 10 is prepared by combining hot-pressing pre-sintering and oscillating hot-pressing sintering^-6～8.0380×10^-6A/cm²The corrosion potential is-0.792-0.996V, the high-entropy alloy shows obvious passivation composition, and the corrosion resistance is better. Compared with the corrosion resistance of the embodiment 1-1000 ℃, the corrosion resistance of the comparative example 1 is poorer, and the mode of combining the hot-pressing pre-sintering and the oscillating hot-pressing sintering is beneficial to reducing the sintering temperature of the alloy and improving the corrosion resistance.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.