CN111893364B

CN111893364B - Multi-element doped reinforced toughened high-entropy alloy and preparation method thereof

Info

Publication number: CN111893364B
Application number: CN202010780987.9A
Authority: CN
Inventors: 刘文胜; 李松; 廖羽扬; 黄兰萍
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2020-08-06
Filing date: 2020-08-06
Publication date: 2022-03-25
Anticipated expiration: 2040-08-06
Also published as: CN111893364A

Abstract

The invention belongs to the field of high-entropy alloys, and particularly relates to a multi-element doped reinforced toughened high-entropy alloy and a preparation method thereof. The high-entropy alloy comprises Al, Co, Cr, Fe, Ni and M, and the atomic percentages of the elements are respectively as follows: 16 to 22 percent of Al, 16 to 22 percent of Co, 16 to 22 percent of Cr, 16 to 22 percent of Fe, 16 to 22 percent of Ni and 1 to 8 percent of M; omega of the high-entropy alloy is 1.1-1.5, and delta is 6.2-6.8; the M element is at least 2 selected from Zr, Ti and Hf. The preparation method comprises the following steps: putting high-purity metal into a vacuum arc melting furnace, and repeatedly melting for more than four times under the protection of inert atmosphere. The invention adopts the concept of multi-element doping, so that the strength and the toughness of the high-entropy alloy of the system are obviously improved, the density is also reduced, and the specific strength of the alloy is increased.

Description

Multi-element doped reinforced toughened high-entropy alloy and preparation method thereof

Technical Field

The invention belongs to the field of high-entropy alloys, and particularly relates to a multi-element doped reinforced toughened high-entropy alloy and a preparation method thereof.

Background

Researchers have been developing high strength, high toughness materials. High entropy alloys are a promising material with a variety of main elements and a simple solid solution structure, usually composed at equiatomic or near-equiatomic ratios. The component design and the interaction of various elements of the high-entropy alloy are always core problems in the field of the high-entropy alloy.

In previous studies, AlCoCrFeNi high entropy alloys have been extensively studied due to their excellent compressive strength and plastic strain. The proper amount of elements such as Ti, V, Mo, Nb, Zr and the like is added, so that the AlCoCrFeNi matrix alloy can be subjected to solid solution strengthening and precipitation strengthening, and certain excellent mechanical properties are generated. However, the AlCoCrFeNi high-entropy alloy is mainly doped by one element, and few reports about multi-element doping exist. The multi-element doped high-entropy alloy has wide development space and huge performance potential.

Disclosure of Invention

The invention aims to provide a multi-element doped reinforced and toughened high-entropy alloy and a preparation method thereof, and overcomes the defects of single element doping so as to achieve the purpose of simultaneously improving the strength and the toughness.

The invention tries to dope the high-entropy alloy by utilizing bimetallic elements such as Ti-Zr, Ti-Hf, Zr-Hf and the like for the first time; the obtained product has low density, excellent mechanical property and industrial application value. Meanwhile, the design idea adopted by the invention has certain foresight.

The technical scheme adopted by the invention is as follows:

the multi-element doped toughened high-entropy alloy comprises the following components in atomic percentage: 16 to 22 percent of Al, 16 to 22 percent of Co, 16 to 22 percent of Cr, 16 to 22 percent of Fe, 16 to 22 percent of Ni and 1 to 8 percent of M; the omega value of the high-entropy alloy is 1.1-1.5, and the delta value is 6.2-6.8; the M element is at least 2 selected from Zr, Ti and Hf;

wherein;

Ω＝T_mΔS_mix/|ΔH_mix|

wherein δ is an atomic size difference, c_iAnd r_iIs the atomic fraction and atomic radius, Δ H, of the ith element in the high entropy alloy_mixIs the enthalpy of mixing, Δ H, of the alloy_{ij mix}Is the mixed enthalpy of a binary system of the ith element and the jth element in the high-entropy alloy, T_mIs the melting point, Δ S, calculated as a percentage of each element_mixIs the entropy of mixing of the alloy.

The invention relates to a multi-element doped toughened high-entropy alloy, and as one of preferable schemes, the M element is composed of Zr and Ti.

The invention relates to a multi-element doped toughened high-entropy alloy, which is a preferred scheme, and comprises the following components in percentage by atom: ti is 4-6%, and Zr is 0.01-2%.

The invention relates to a multi-element doped toughened high-entropy alloy, which is a further preferable scheme, wherein the high-entropy alloy comprises the following components in atomic percentage: ti is 4.7-4.75%, Zr is 0.9-0.95%.

The invention relates to a multi-element doped toughened high-entropy alloy, which is a further preferable scheme, wherein the high-entropy alloy comprises the following elements in atomic ratio: al, Co, Fe, Ni, Ti, Zr, 20:20:20:20:20:5: 1.

The invention relates to a multi-element doped strengthening and toughening high-entropy alloy, and when the high-entropy alloy is AlCoCrFeNiTi_0.25Zr_0.05In the case of high-entropy alloy, the yield strength of room-temperature compression is 1926MPa, the breaking strength is 3046MPa, the compression ratio is 35 percent, and the specific strength is 276 MPa-cm³g^-1The Vickers hardness is 778 HV.

The invention relates to a multi-element doped toughened high-entropy alloy, which also comprises the scheme that the high-entropy alloy comprises Al, Co, Cr, Fe, Ni, Zr and Hf, wherein the atomic percentages of the elements are respectively 19-20% of Al, 19-20% of Co, 19-20% of Cr, 19-20% of Fe, 19-20% of Ni, 0.001-2% of Hf, preferably 0.001-1%, more preferably 0.95-1%, 0.001-2% of Zr, preferably 0.001-0.03%, and more preferably 0.01-0.02%.

The invention relates to a multi-element doped toughened high-entropy alloy, which is one of schemes, wherein the elements are calculated by atomic ratio: co, Fe, Ni, Hf, Zr, 100:100:100:100:100:5: 1. When the high-entropy alloy is AlCoCrFeNiHf_0.05Zr_0.01In the case of high-entropy alloy, the yield strength of room-temperature compression is 1410MPa, the breaking strength is 2657MPa, the compressibility is 33%, and the specific strength is 195MPa cm³g^-1The Vickers hardness is 666 HV.

The invention relates to a multi-element doped toughened high-entropy alloy, which also comprises the scheme that the high-entropy alloy comprises 17-21 atomic percent of Al, 17-21 atomic percent of Co, 17-21 atomic percent of Cr, 17-21 atomic percent of Fe, 17-21 atomic percent of Ni, 3-5 atomic percent of Ti, preferably 3-4 atomic percent of Ti, further preferably 3.8-3.82 atomic percent of Ti, and 0.001-2 atomic percent of Hf, preferably 0.95-0.96 atomic percent of Hf.

In the scheme designed by the invention, in the high-entropy alloy, the following components are calculated by atomic ratio: al, Co, Fe, Ni, Ti, Hf, 20:20:20:20:20:4: 1. When in useThe high-entropy alloy is AlCoCrFeNiTi_0.2Hf_0.05In the case of high-entropy alloy, the yield strength of room-temperature compression is 1539MPa, the breaking strength is 2262MPa, the compression ratio is 23 percent, and the specific strength is 217 MPa-cm³g^-1The Vickers hardness is 734 HV.

The invention relates to a preparation method of multi-element doped toughened high-entropy alloy; the method comprises the following specific steps:

(1) removing oxide layers on the surfaces of Al, Co, Cr, Fe, Ni and M metal raw materials with the purity of not less than 99.99% by using SiC sand paper, then putting the materials into an ultrasonic cleaner, cleaning the materials by using alcohol, taking the materials out, and naturally drying the materials in the air;

(2) weighing and proportioning according to designed atomic percentage;

(3) sequentially putting the raw materials into a copper crucible of a vacuum arc melting furnace in the order of low melting point to high melting point of the metal, wherein the vacuum degree is at least 2.5 multiplied by 10^-3Introducing high-purity argon in a Pa environment;

(4) firstly, smelting pure titanium, and absorbing residual oxygen in a furnace chamber; then, smelting the alloy, keeping the arc time at 20-30 seconds, simultaneously performing electromagnetic stirring, turning the alloy over after the alloy is cooled, and repeating the process for more than 4 times; and (5) obtaining a product.

In general, compared with the AlCrFeCoNi high-entropy alloy doped with a single element, the technical scheme of the invention has the following advantages and positive effects:

(1) the invention provides a multi-element doped reinforced and toughened high-entropy alloy, which utilizes the characteristic that the atomic sizes of Ti, Zr and Hf are larger to improve the atomic size difference delta, obviously increase the lattice distortion energy and generate stronger solid solution strengthening effect; secondly, the enthalpy of mixing Ti, Zr and Hf with other elements is a large negative value, and can increase | Delta H remarkably_mixAnd the omega is reduced, so that the possibility of generating nano precipitates in the high-entropy alloy is increased.

(2) The Ti, Zr and Hf used in the invention belong to the same main group element and have similar physical properties, thereby avoiding the generation of complex microstructures such as intermetallic compounds and the like, and simultaneously avoiding the occurrence of the condition that the product is difficult to process and analyze.

(3) The invention carries out multi-element doping in the AlCrFeCoNi high-entropy alloy to respectively obtain the Ti-Zr, Hf-Zr and Ti-Hf doped high-entropy alloy, and further preferably the Ti-Zr doped high-entropy alloy, the strength and toughness of the alloy are obviously improved compared with the AlCrFeCoNi alloy, the specific strength of the alloy is not less than 276MPa cm³g^-1Density not greater than 6.99cm³g^-1The compressive yield strength is not lower than 1926MPa, the compressive fracture strength is not lower than 3045MPa, and the Vickers hardness is not lower than 728 HV.

In the optimized scheme, a proper amount of Ti and Zr is added, so that the density of the high-entropy alloy is reduced, but the comprehensive performance of the product is remarkably improved, and necessary conditions are provided for the environment-friendly, energy-saving and controllable batch production of the product.

Drawings

FIG. 1 is a diagram of criteria for phase formation for high entropy alloys based on Ω and δ, which typically satisfy Ω >1.1 and δ < 6.6% for solid solution formation.

FIG. 2 is a Scanning Electron Microscope (SEM) morphology of the AlCoCrFeNiM high-entropy alloy.

FIG. 3 is a room temperature compressive stress-strain curve of the AlCoCrFeNiM high entropy alloy of the invention.

FIG. 4 is a graph comparing the compressive yield strength and the compression ratio of the AlCoCrFeNiM high-entropy alloy of the invention and other high-entropy alloys.

FIG. 5 is a Vickers hardness test result diagram of the AlCoCrFeNiM high-entropy alloy of the invention.

Detailed Description

The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments, and it should be noted that the embodiments described herein are only for explaining the present invention and are not limited to the present invention. Further modifications to these embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention.

In the following examples and comparative examples:

a vacuum arc melting furnace: a DHSD-400 type vacuum arc melting furnace manufactured by shanghai alling instruments and equipments ltd.

Microscopic morphology: the high-entropy alloy prepared by the invention is subjected to microscopic morphology observation and element analysis by using a Quanta 250FEG type scanning electron microscope and an energy spectrometer assembled by the scanning electron microscope, which are produced by FEI company in America.

Room temperature compression mechanical property test: compression testing was carried out at room temperature using a universal tester model 3369, Instron USA, with a strain rate of 10^-3s^-1The test sample is 2X 4mm³The rectangular shape of (a) compresses the sample.

Vickers hardness test: vickers hardness testing was performed using a Vickers hardness tester model HV-1000Z from Jinan peak tester, Inc., with a load of 200g (1.96N) and a loading time of 15s, with each sample being measured at least 8 times in different zones, the maximum and minimum values being rejected, the mean and standard deviation being calculated and expressed in error bars.

The embodiment of the multi-element doped strengthening and toughening high-entropy alloy provided by the invention is explained in detail as follows:

comparative example 1

The method comprises the following steps: removing oxide layers on the surfaces of Al, Co, Cr, Fe and Ni metal raw materials with the purity of not less than 99.99% by using SiC sand paper, then putting the raw materials into an ultrasonic cleaning instrument, cleaning the raw materials by using alcohol, taking the raw materials out, and naturally drying the raw materials in the air;

step two: calculating and weighing pure metal raw materials with the total mass of (30 +/-0.1) g according to the atomic ratio of Al to Co to Cr to Fe to Ni being 1:1:1: 1;

step three: sequentially placing the raw materials into a copper crucible of a vacuum arc melting furnace in the order of low melting point to high melting point of the metal, wherein the vacuum degree is at least 2.5 multiplied by 10^-3Introducing high-purity argon in a Pa environment;

step four: firstly, smelting pure titanium, and absorbing residual oxygen in a furnace chamber; and then smelting the alloy, keeping the arc time at 20-30 seconds, simultaneously performing electromagnetic stirring, turning the alloy after the alloy is cooled, and repeating the process for more than 4 times to obtain the AlCoCrFeNi high-entropy alloy.

As can be seen from the SEM image of FIG. 2, the AlCoCrFeNi high entropy alloy is a coarse equiaxed structure with a grain size of about 100E150 μm. As can be seen from FIGS. 3, 4 and 5, the room-temperature compressive yield strength, fracture strength and specific strength of the AlCoCrFeNi high-entropy alloy were 1316MPa, 2432MPa, 32% and 32% respectively³g^-1The Vickers hardness was 651 HV.

Example 1

The method comprises the following steps: removing oxide layers on the surfaces of Al, Co, Cr, Fe, Ni, Ti and Zr metal raw materials with the purity of not less than 99.99% by using SiC sand paper, then putting the materials into an ultrasonic cleaning instrument, cleaning the materials by using alcohol, taking the materials out, and naturally drying the materials in the air;

step two: calculating and weighing pure metal raw materials with the total mass of (30 +/-0.1) g according to the atomic ratio of Al to Co to Cr to Fe to Ni to Ti to Zr of 20 to 5 to 1;

step four: firstly, smelting pure titanium, and absorbing residual oxygen in a furnace chamber; then smelting the alloy, keeping the arc time at 20-30 seconds, simultaneously performing electromagnetic stirring, turning the alloy over after the alloy is cooled, and repeating the process for more than 4 times to obtain AlCoCrFeNiTi_0.25Zr_0.05High entropy alloy.

Because AlCoCrFeNiTi_0.25Zr_0.05As is clear from fig. 1, the high-entropy alloy may form intermetallic compounds (precipitates) in the alloy, as δ being 6.7% and Ω being 1.27. From the SEM image of FIG. 2, it can be seen that AlCoCrFeNiTi_0.25Zr_0.05The crystal grains of the high-entropy alloy are obviously refined, the size of the crystal grains is about 20-30 mu m, and precipitates rich in Ti and Zr are generated among the crystal grains. As can be seen from FIGS. 3, 4 and 5, AlCoCrFeNiTi_0.25Zr_0.05The yield strength of the high-entropy alloy compressed at room temperature is 1926MPa, the breaking strength is 3046MPa, the compression ratio is 35 percent, and the specific strength is 276 MPa-cm³g^-1The Vickers hardness is 778 HV.

Example 2

The method comprises the following steps: removing oxide layers on the surfaces of Al, Co, Cr, Fe, Ni, Hf and Zr metal raw materials with the purity of not less than 99.99% by using SiC sand paper, then putting the materials into an ultrasonic cleaner, cleaning the materials by using alcohol, taking the materials out, and naturally drying the materials in the air;

step two: calculating and weighing pure metal raw materials with the total mass of (30 +/-0.1) g according to the atomic ratio of Al to Co to Cr to Fe to Ni to Hf to Zr to 100 to 5 to 1;

step four: firstly, smelting pure titanium, and absorbing residual oxygen in a furnace chamber; then smelting the alloy, keeping the arc time at 20-30 seconds, simultaneously performing electromagnetic stirring, turning the alloy over after the alloy is cooled, and repeating the operation for more than 4 times to obtain AlCoCrFeNiHf_0.05Zr_0.01High entropy alloy.

Due to AlCoCrFeNiHf_0.05Zr_0.01As is clear from fig. 1, the high-entropy alloy may form intermetallic compounds (precipitates) in the alloy, as δ being 6.3% and Ω being 1.45. From the SEM image of FIG. 2, it can be seen that AlCoCrFeNiHf_0.05Zr_0.01The crystal grains of the high-entropy alloy are obviously refined, the size of the crystal grains is about 15-20 mu m, and precipitates rich in Hf and Zr are generated among the crystal grains. As can be seen from FIGS. 3, 4 and 5, AlCoCrFeNiHf_0.05Zr_0.01The yield strength of the high-entropy alloy in room-temperature compression is 1410MPa, the breaking strength is 2657MPa, the compression ratio is 33 percent, and the specific strength is 195 MPa-cm³g^-1The Vickers hardness is 666 HV.

Example 3

The method comprises the following steps: removing oxide layers on the surfaces of Al, Co, Cr, Fe, Ni, Ti and Hf metal raw materials with the purity of not less than 99.99% by using SiC sand paper, then putting the materials into an ultrasonic cleaner, cleaning the materials by using alcohol, taking the materials out, and naturally drying the materials in the air;

step two: calculating and weighing pure metal raw materials with the total mass of (30 +/-0.1) g according to the atomic ratio of Al to Co to Cr to Fe to Ni to Ti to Hf of 20 to 4 to 1;

step three: the raw materials are sequentially put into a copper crucible of a vacuum arc melting furnace according to the sequence from low to high of the melting point of the metal, and the vacuum degree is at least 2.5×10^-3Introducing high-purity argon in a Pa environment;

step four: firstly, smelting pure titanium, and absorbing residual oxygen in a furnace chamber; then smelting the alloy, keeping the arc time at 20-30 seconds, simultaneously performing electromagnetic stirring, turning the alloy over after the alloy is cooled, and repeating the process for more than 4 times to obtain AlCoCrFeNiTi_0.2Hf_0.05High entropy alloy.

Because AlCoCrFeNiTi_0.2Hf_0.05As is clear from fig. 1, the high-entropy alloy may form intermetallic compounds (precipitates) in the alloy, as δ being 6.6% and Ω being 1.32. From the SEM image of FIG. 2, it can be seen that AlCoCrFeNiTi_0.2Hf_0.05The crystal grains of the high-entropy alloy are obviously refined, the size of the crystal grains is about 15-25 mu m, and precipitates rich in Ti and Hf are generated among the crystal grains. As can be seen from FIGS. 3, 4 and 5, AlCoCrFeNiTi_0.2Hf_0.05The yield strength of the high-entropy alloy in room-temperature compression is 1539MPa, the breaking strength is 2262MPa, the compression ratio is 23 percent, and the specific strength is 217 MPa-cm³g^-1The Vickers hardness is 734 HV.

The preferred AlCoCrFeNiTi is adopted in the above embodiment_0.25Zr_0.05High entropy alloy. Compared with the method of independently adding one of Ti and Zr, the method of the invention selects Ti and Zr as doping elements, and has the advantages that: can improve the strength and the toughness at the same time.

In summary, the present invention is only an embodiment of the present invention. The protection scope of the present invention is not limited thereto, and any modification and modification that can be made by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention.

Table 1 shows mechanical properties at room temperature of the AlCoCrFeNiM high-entropy alloys obtained in examples and comparative examples.

TABLE 1

	Comparative example 1	Example 1	Example 2	Example 3
					Density (g/cm)³)	7.114	6.985	7.234	7.074
Yield strength (MPa)	1316	1926	1410	1539
					Tensile strength (MPa)	2432	3046	2657	2262
Specific strength (MPa. cm)³g^-1)	185	276	195	217
					Compression ratio (%)	32	35	33	23
Vickers Hardness (HV)	651	778	666	734

Claims

1. A multi-element doped toughened high-entropy alloy is characterized in that: the high-entropy alloy comprises Al, Co, Cr, Fe, Ni and M, and the atomic percentages of the elements are respectively as follows: 16% -22% of Al, 16% -22% of Co, 16% -22% of Cr, 16% -22% of Fe and 16% -22% of Ni; the omega value of the high-entropy alloy is 1.1-1.5, and the delta value is 6.2-6.8; the M is composed of Zr and Ti; in the high-entropy alloy, the following components are calculated in atomic percentage: 4-6% of Ti and 0.01-2% of Zr;

or

The high-entropy alloy comprises Al, Co, Cr, Fe, Ni, Zr and Hf, wherein the atomic percentages of the elements are respectively 19% -20% of Al, 19% -20% of Co, 19% -20% of Cr, 19% -20% of Fe, 19% -20% of Ni, 0.001% -1% of Hf and 0.001% -0.2% of Zr; the omega value of the high-entropy alloy is 1.1-1.5, and the delta value is 6.2-6.8;

or

The high-entropy alloy consists of Al, Co, Cr, Fe, Ni, Ti and Hf, wherein the atomic percentages of the elements are respectively 17% -21% of Al, 17% -21% of Co, 17% -21% of Cr, 17% -21% of Fe, 17% -21% of Ni, 3% -5% of Ti and 0.001% -2% of Hf; the omega value of the high-entropy alloy is 1.1-1.5, and the delta value is 6.2-6.8;

wherein;

wherein δ is an atomic size difference, c_iAnd r_iIs the atomic fraction and atomic radius of the ith element in the high-entropy alloy_mixIs the mixed enthalpy of the alloy, Δ H_{ij mix}Is the mixed enthalpy of a binary system of the ith element and the jth element in the high-entropy alloy, T_mIs the melting point S calculated by the percentage of each element_mixIs the entropy of mixing of the alloy.

2. The multi-element doped toughened high entropy alloy of claim 1, wherein: in the high-entropy alloy, the following components are calculated in atomic percentage: ti is 4.7-4.75%, and Zr is 0.9-0.95%.

3. A multi-element doped toughened high entropy alloy as claimed in claim 2, wherein: in the high-entropy alloy, the atomic ratio: co, Cr, Fe, Ni, Ti, Zr =20:20:20:20:20:5: 1.

4. A multi-element doped toughened high entropy alloy as claimed in claim 3, wherein: the high-entropy alloy is AlCoCrFeNiTi_0.25Zr_0.05In the case of high-entropy alloy, the yield strength of room-temperature compression is 1926MPa, the breaking strength is 3046MPa, the compression ratio is 35 percent, and the specific strength is 276 MPa-cm³g^-1The Vickers hardness is 778 HV.

5. A method of producing the multi-element doped toughened high entropy alloy of any one of claims 1 to 4, characterized in that: the method comprises the following specific steps:

(2) weighing and proportioning according to designed atomic percentage;

(3) sequentially placing the raw materials into a copper crucible of a vacuum arc melting furnace in the order of low melting point to high melting point of the metal, wherein the vacuum degree is at least 2.5 multiplied by 10^-3Introducing high-purity argon in a Pa environment;