High-density high-strength high-entropy alloy and preparation method thereof

Abstract

According to the high-density high-strength high-entropy alloy and the preparation method, high-density tungsten powder and the high-entropy alloy with good plasticity are mixed in proportion, the tungsten-containing high-entropy alloy is prepared through a method of hot isostatic pressing after mechanical alloying, and the alloy density is remarkably improved by controlling the proportion of the tungsten powder; and the nearly-fully-dense high-entropy alloy is formed under the high-temperature and high-pressure action of hot isostatic pressing, so that the high-density and high-strength high-entropy alloy is prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation and high entropy alloy, and in particular to a high-density and high-strength high-entropy alloy and a preparation method thereof. Background Art

[0002] High entropy alloy is a new type of alloy material proposed in the 1990s. High entropy alloy has a series of excellent properties, including high hardness, high work hardening, high temperature softening resistance, corrosion resistance, high resistivity and other characteristics, which makes the potential application prospects of high entropy alloy very broad and has become one of the current research hotspots. High-density and high-strength high-entropy alloys are materials with important application prospects in the fields of nuclear industry, aerospace and high-pressure physics. The composition design optimization and preparation technology research and development have always been one of the research frontiers and hot issues in basic science and applied technology.

[0003] The existing high-entropy alloy system with high-density characteristics still has significant deficiencies in composition design, smelting preparation, etc. High-density and high-strength are mainly based on refractory metals (W, Ta, Mo, Hf, Nb, etc.) for composition modulation. However, the high melting point of refractory metals leads to high energy consumption, and the melting point temperature and density of each component are greatly different, making it difficult to form an alloy material with uniform structure. In addition, high-density and high-strength high-entropy alloys mainly rely on the thermal deformation method after smelting to improve performance, but there are still technical problems such as insufficient performance, difficulty in thermal deformation, easy forging cracking, and long process flow, difficulty in forming special-shaped parts, low density, uneven structure, unstable mechanical properties, etc. The development and application of alloy systems are greatly restricted. Summary of the invention

[0004] The present invention overcomes the shortcomings of the prior art and provides a method for preparing a high-entropy alloy with high density and high strength.

[0005] In order to achieve the above technical objectives, the technical solution provided by the present invention is:

[0006] A method for preparing a high-density, high-strength, high-entropy alloy comprises the following steps:

[0007] Step 1: Prepare a mixed powder of high entropy alloy pre-alloyed powder and tungsten powder;

[0008] Step 2: high-energy ball milling the mixed powder obtained in step 1 to obtain mixed powder A;

[0009] Step 3: cold isostatically pressing the mixed powder A in step 2 to obtain a molded blank;

[0010] Step 4: The formed blank in step 3 is subjected to vacuum heat degassing, hot isostatic pressing, dense alloying, and annealing to obtain a high-density, high-strength, high-entropy alloy.

[0011] Furthermore, in step 1, the mass ratio of the high entropy alloy pre-alloyed powder to the tungsten powder is 1:0.5-2.

[0012] Furthermore, in step 1, the high entropy alloy pre-alloy powder is AlFeCoCrNi 2.1 or AlFeCoCrNi or (CoCrNi) 82 Ti9Al9, including AlFeCoCrNi 2.1 The atomic ratio of each element is Al:Fe:Co:Cr:Ni=1:1:1:1:2.1, the atomic ratio of each element of AlFeCoCrNi is Al:Fe:Co:Cr:Ni=1:1:1:1:1, (CoCrNi) 82 The atomic ratio of each element in Ti9Al9 is (CoCrNi):Ti:Al=82:9:9 and the atomic ratio of each element in (CoCrNi) is Co:Cr:Ni=1:1:1.

[0013] Furthermore, the specific method of high-energy ball milling in step 2 includes firstly performing alloying by dry milling without a medium, and then performing homogenization by wet milling with ethanol accounting for 100% to 200% of the total mass of the powder as a medium.

[0014] Furthermore, in step 2, the ball milling uses a stainless steel tank and stainless steel balls, the ball-to-material ratio is 8:1-15:1, the ball milling time is 30h-40h, and the rotation speed is 250r / m-300r / m.

[0015] Furthermore, the step 2, after high-energy ball milling, also includes heating and evacuating the ball mill jar, heating it to 100° C., and keeping it warm for 10-15 hours to dry the powder.

[0016] Furthermore, in step 3, the pressure of cold isostatic pressing is 200 MPa-270 MPa, and the time is 240 s-360 s.

[0017] Furthermore, in step 4, the temperature of vacuum thermal degassing is 650° C.-800° C., and the thermal degassing time is 1 h-3 h.

[0018] Furthermore, in step 4, the hot isostatic pressing densification alloying temperature is 50°C-200°C lower than the melting point of the pre-alloyed powder, the pressure is 90MPa-110MPa, and the time is 1h-2h.

[0019] Furthermore, in step 4, the annealing temperature is 900°C-1000°C.

[0020] The present invention also provides a high-density, high-strength high-entropy alloy, which is a high-entropy alloy pre-alloyed powder and tungsten powder, the mass ratio of the high-entropy alloy pre-alloyed powder to the tungsten powder is 1:0.5-2, and the high-entropy alloy pre-alloyed powder is AlFeCoCrNi2.1 or AlFeCoCrNi or (CoCrNi) 82 Ti9Al9, including AlFeCoCrNi 2.1 The atomic ratio of each element is Al:Fe:Co:Cr:Ni=1:1:1:1:2.1, the atomic ratio of each element of AlFeCoCrNi is Al:Fe:Co:Cr:Ni=1:1:1:1:1, (CoCrNi) 82 The atomic ratio of each element in Ti9Al9 is (CoCrNi):Ti:Al=82:9:9 and the atomic ratio of each element in (CoCrNi) is Co:Cr:Ni=1:1:1.

[0021] The present invention has the following beneficial effects:

[0022] 1. The present invention adopts high-density tungsten powder and iron-based high-entropy alloy with good plasticity to mix evenly, and then forms a nearly fully dense high-entropy alloy through hot isostatic pressing at high temperature and high pressure. High-density high-entropy alloy can be obtained by regulating high-density tungsten.

[0023] 2. High melting point tungsten particles are added to the high entropy alloy with good plasticity, and are dissolved in the high entropy alloy to play a role of solid solution strengthening. At the same time, the tungsten particles that are not completely dissolved in the matrix play a role of dispersion strengthening and dislocation pinning, thereby obtaining a high-strength high entropy alloy.

[0024] 3. The melting points of high entropy alloy components are similar, so it is easy to form pre-alloyed powder with uniform composition. Pre-alloyed powder and high melting point tungsten powder are mechanically alloyed by high-energy ball milling to achieve uniform mixing of components and grain refinement. High-energy ball milled fine particles have high surface energy and distortion energy. By hot isostatic pressing at a temperature far below the melting point of tungsten, the growth of grains is hindered during the recrystallization process, and the grains are small, which plays a role in fine grain strengthening. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Compressive stress-strain curves for different examples. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] Example 1

[0029] A high-density, high-strength, high-entropy alloy having a mass ratio of W: (CoCrNi) 82 Al9Ti9=2:1, converted into atomic percentage, its composition is W:Co:Cr:Ni:Al:Ti=57.78:27.33:27.33:27.33:9:9.

[0030] In the first step, 15 μm-53 μm (CoCrNi) 82 Al9Ti9 high entropy alloy pre-alloyed powder and 3 micron-10 micron tungsten powder according to W: (CoCrNi) 82 A total of 300 g of Al9Ti9 was mixed in a mass ratio of 2:1, and 2.4 kg of stainless steel balls were weighed and loaded into a stainless steel ball mill.

[0031] The second step is to evacuate the stainless steel ball mill jar, seal it tightly, and then perform high-energy ball milling at a ball milling speed of 300 rpm for 30 hours.

[0032] Step 3: Open the ball mill cover in the argon glove box and pour in 600 g of alcohol. Evacuate the stainless steel ball mill, seal it tightly and perform high-energy ball milling. The ball milling speed is 200 rpm and the ball milling time is 12 hours.

[0033] The fourth step is to heat the ball mill and vacuum dry it at a temperature of 100° C. for 10 hours.

[0034] The fifth step is to subject the dry powder to cold isostatic pressing with a molding pressure of 200 MPa and a molding time of 6 minutes.

[0035] In the sixth step, the cold isostatically formed blank is sealed in a stainless steel package for vacuum thermal degassing. The thermal degassing temperature is 650°C and the thermal degassing time is 3 hours.

[0036] In the seventh step, the package after heat degassing is subjected to hot isostatic pressing and densification alloying treatment, and the hot isostatic pressing temperature is 1100° C. and the time is 2 hours.

[0037] In the eighth step, the hot isostatic pressing package is vacuum annealed at a temperature of 900° C. for 1 hour.

[0038] The ninth step is to process and test the annealed samples.

[0039] The sample density was measured to be 12.4 g / cm 3 , the compressive strength is 2270MPa.

[0040] Example 2

[0041] A high-density, high-strength, high-entropy alloy, the mass ratio of the alloy is W:AlCoCrFeNi 2.1=2.03:1, converted into atomic ratio, its composition is W:Al:Co:Cr:Fe:Ni=3.5:1:1:1:2.1.

[0042] In the first step, 15 μm-53 μm AlCoCrFeNi 2.1 High entropy alloy pre-alloyed powder and 3 micron-10 micron tungsten powder according to W:AlCoCrFeNi 2.1 The mass ratio is 2.03:1, totaling 250g, and 3kg of stainless steel balls are weighed and loaded into a stainless steel ball mill.

[0043] In the second step, the stainless steel ball mill was evacuated, tightly sealed and then subjected to high-energy ball milling at a ball milling speed of 260 rpm for 35 hours.

[0044] Step 3: Open the ball mill cover in the argon glove box and pour in 500 g of alcohol. Evacuate the stainless steel ball mill, seal it tightly and perform high-energy ball milling. The ball milling speed is 180 rpm and the ball milling time is 15 hours.

[0045] The fourth step is to heat the ball mill and vacuum dry it at a temperature of 100° C. for 10 hours.

[0046] The fifth step is to subject the dry powder to cold isostatic pressing with a molding pressure of 270 MPa and a molding time of 4 minutes.

[0047] In the sixth step, the cold isostatically formed blank is sealed in a stainless steel package for vacuum thermal degassing. The thermal degassing temperature is 700°C and the thermal degassing time is 1 hour.

[0048] In the seventh step, the package after heat degassing is subjected to hot isostatic pressing and densification alloying treatment, and the hot isostatic pressing temperature is 1300° C. and the time is 1 hour.

[0049] In the eighth step, the hot isostatic pressing package is vacuum annealed at a temperature of 950° C. for 1 hour.

[0050] The ninth step is to process and test the annealed samples.

[0051] The sample density was measured to be 14.6 g / cm 3 , the compressive strength is 2734MPa.

[0052] Example 3

[0053] A high-density, high-strength, high-entropy alloy, the mass ratio of the alloy is W:AlCoCrFeNi 2.1 =0.73:1, converted into atomic ratio, its composition is W:Al:Co:Cr:Fe:Ni=3.5:1:1:1:1.

[0054] In the first step, in an argon glove box, 200 g of 15-53 μm AlCoCrFeNi high entropy alloy pre-alloyed powder and 3-10 μm tungsten powder were mixed at a W:AlCoCrFeNi mass ratio of 0.73:1, and 3 kg of stainless steel balls were weighed and loaded into a stainless steel ball mill.

[0055] In the second step, the stainless steel ball mill was evacuated, tightly sealed and then subjected to high-energy ball milling at a ball milling speed of 240 rpm for 40 hours.

[0056] Step 3: Open the ball mill cover in the argon glove box and pour in 400 g of alcohol. Evacuate the stainless steel ball mill, seal it tightly and perform high-energy ball milling. The ball milling speed is 160 rpm and the ball milling time is 15 hours.

[0057] The fourth step is to heat the ball mill and vacuum dry it at a temperature of 100° C. for 10 hours.

[0058] The fifth step is to subject the dry powder to cold isostatic pressing with a molding pressure of 250 MPa and a molding time of 5 minutes.

[0059] In the sixth step, the cold isostatically formed blank is sealed in a stainless steel package for vacuum thermal degassing. The thermal degassing temperature is 600°C and the thermal degassing time is 2 hours.

[0060] In the seventh step, the package after heat degassing is subjected to hot isostatic pressing and densification alloying treatment, and the hot isostatic pressing temperature is 1300° C. and the time is 1 hour.

[0061] In the eighth step, the hot isostatic pressing package is vacuum annealed at a temperature of 900° C. for 1 hour.

[0062] The ninth step is to process and test the annealed samples.

[0063] The sample density is 9.2g / cm3 and the compressive strength is 2350MPa.

[0064] The compressive mechanical properties of the embodiments of the present invention are shown in Figure 1 In the examples, different high-density high-entropy alloys were obtained by the method of the present invention, all of which showed high compressive strength, providing a variety of optional preparation processes and materials for further research and development.

[0065] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0066] The above specific implementation methods are detailed descriptions of the present invention. It cannot be determined that the specific implementation methods of the present invention are limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions and substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing a high-density, high-strength, high-entropy alloy, characterized in that: The steps include: Step 1: Prepare a mixed powder of high entropy alloy pre-alloyed powder and tungsten powder; Step 2: high-energy ball milling the mixed powder obtained in step 1 to obtain mixed powder A; Step 3: cold isostatically pressing the mixed powder A in step 2 to obtain a molded blank; Step 4: The formed blank in step 3 is subjected to vacuum heat degassing, hot isostatic pressing, dense alloying, and annealing to obtain a high-density, high-strength, high-entropy alloy.

2. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: In the step 1, the mass ratio of the high entropy alloy pre-alloyed powder to the tungsten powder is 1:0.5-2.

3. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: In step 1, the high entropy alloy pre-alloy powder is AlFeCoCrNi 2.1 or AlFeCoCrNi or (CoCrNi) 82 Ti9Al9, including AlFeCoCrNi 2.1 The atomic ratio of each element is Al:Fe:Co:Cr:Ni=1:1:1:1:2.1, the atomic ratio of each element of AlFeCoCrNi is Al:Fe:Co:Cr:Ni=1:1:1:1:1, (CoCrNi) 82 The atomic ratio of each element in Ti9Al9 is (CoCrNi):Ti:Al=82:9:9 and the atomic ratio of each element in (CoCrNi) is Co:Cr:Ni=1:1:

1.

4. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: The specific method of high-energy ball milling in step 2 includes firstly performing alloying by dry milling without a medium, and then performing homogenization by wet milling using ethanol accounting for 100% to 200% of the total mass of the powder as a medium.

5. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: In the step 2, a stainless steel tank and stainless steel balls are used for ball milling, the ball-to-material ratio is 8:1-15:1, the ball milling time is 30h-40h, and the rotation speed is 250r / m-300r / m.

6. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: The step 2, after high-energy ball milling, also includes heating and evacuating the ball mill jar, heating it to 100° C., and keeping the temperature for 10-15 hours to dry the powder.

7. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: In the step 3, the pressure of cold isostatic pressing is 200MPa-270MPa, and the time is 240s-360s.

8. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: In the step 4, the temperature of vacuum thermal degassing is 650° C.-800° C., and the thermal degassing time is 1 h-3 h.

9. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: In the step 4, the hot isostatic pressing densification alloying temperature is 50° C.-200° C. lower than the melting point of the pre-alloyed powder, the pressure is 90 MPa-110 MPa, and the time is 1 h-2 h.

10. The method for preparing a high-density, high-strength, high-entropy alloy according to claim 1, characterized in that: In the step 4, the annealing temperature is 900°C-1000°C.

11. A high-density, high-strength, high-entropy alloy prepared by a method as described in any one of claims 1 to 10, characterized in that: The alloy is a high entropy alloy prealloy powder and a tungsten powder, wherein the mass ratio of the high entropy alloy prealloy powder to the tungsten powder is 1:0.5-2. The high entropy alloy prealloy powder is AlFeCoCrNi 2.1 or AlFeCoCrNi or (CoCrNi) 82 Ti9Al9, including AlFeCoCrNi 2.1 The atomic ratio of each element is Al:Fe:Co:Cr:Ni=1:1:1:1:2.1, the atomic ratio of each element of AlFeCoCrNi is Al:Fe:Co:Cr:Ni=1:1:1:1:1, (CoCrNi) 82 The atomic ratio of each element in Ti9Al9 is (CoCrNi):Ti:Al=82:9:9 and the atomic ratio of each element in (CoCrNi) is Co:Cr:Ni=1:1:1.

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