Lightweight high-entropy alloy and preparation method thereof

Abstract

The application discloses a light high-entropy alloy, and has a composition of TiaAlbCrcFed, wherein the alloy is composed of Ti, Al, Cr and Fe; a, b, c and d respectively represent the atomic percentages of the four elements of Ti, Al, Cr and Fe; a is 60-80%, b is 10-20%, c is 5-15%, and d is 1-10%; the sum of a, b, c and d is 100, wherein b>c>=d; and the alloy is a BCC solid solution single phase. Compared with a traditional light alloy TC4, the light high-entropy alloy has the advantages of basically unchanged density, 37% improved compressive yield strength, about 43% improved hardness, and good plastic deformation capacity, and has a simple preparation method and high forming efficiency in a casting process, and therefore has a wide application prospect in the fields of aerospace and military armor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-entropy alloys, in particular to a lightweight high-entropy alloy and a preparation method thereof. BACKGROUND

[0002] Lightweight alloys refer to a class of alloys represented by titanium alloys, magnesium alloys and aluminum alloys, with a density of less than 6 g / cm 3 . Due to its low density and certain strength, it has a specific strength comparable to general steel, and is widely used in various fields such as national defense and livelihood. High-entropy alloys refer to a class of alloys with four or more elements as main elements (molar ratio > 5%), which breaks the framework of traditional alloys in element composition, and has excellent properties such as high-entropy effect, lattice distortion effect, and delayed diffusion effect.

[0003] Lightweight high-entropy alloys refer to high-entropy alloys with a density of less than 6 g / cm 3 . Lightweight high-entropy alloys are a research hotspot in recent years. Some researches on high-temperature performance based on lattice distortion effect, some researches on chemical properties based on delayed diffusion effect, and most researches on new alloys with high strength and high hardness to replace some lightweight alloys. The current research on lightweight high-entropy alloys is focused on alloys composed of Mg, Al, and light elements such as V, Mn, and Ti. The density of these alloys is generally between 2 g / cm 3 and 4 g / cm 3 , the strength is about 300 MPa-800 MPa, and the specific strength is higher than that of titanium, aluminum, and magnesium alloys, which can reach 220-250 MPa*cm 3 / g. However, the compression strain of the above-mentioned lightweight high-entropy alloys is mostly between 10-30%, and too many intermetallic compounds result in poor plasticity, which seriously limits their application. In addition to the above research, some researchers have synthesized a class of high-entropy alloys with a density of 6 g / cm 3 -7 g / cm 3 based on Al, Co, Cr and other elements, and added Fe, Ni, Ti and other elements. The characteristics of these alloys are that the strength and hardness are close to alloy steel, the density is slightly lower than alloy steel, and they have a certain plasticity, so as to replace general steel structures and protective structures in the fields of aerospace and national defense. However, the problem is that the specific strength is not high enough, and the weight reduction advantage is not obvious. Based on the above research status, there is a need for a new type of high-entropy alloy with lower density, higher strength and hardness, and certain plasticity, so as to replace titanium alloys and alloy steels in a large number of scenarios. SUMMARY

[0004] The present application aims to solve the problems of low specific strength, low specific hardness and poor plasticity of the prior art lightweight high-entropy alloy, and provides a lightweight high-entropy alloy and a preparation method thereof.

[0005] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a lightweight high-entropy alloy, the alloy composition is TiaAlbCrcFed, the alloy is composed of Ti, Al, Cr and Fe, a, b, c and d respectively represent the atomic percentage of Ti, Al, Cr and Fe, a is 60-80%, b is 10-20%, c is 5-15%, d is 1-10%, the sum of a, b, c and d is 100, and b>c>=d; the alloy is a BCC solid solution single phase.

[0006] The present application simultaneously provides a preparation method of the above lightweight high-entropy alloy, comprising the following steps:

[0007] S1, according to the atomic percentage of Ti, Al, Cr and Fe, weighing the elemental Ti, Al, Cr and Fe metal particles;

[0008] S2, according to the order from low to high melting point, putting the Al, Fe, Ti and Cr metal particles into a vacuum melting furnace in turn for melting, completely melting and uniformly mixing, and then cooling after heat preservation to obtain an ingot;

[0009] S3, turning over the ingot for secondary melting, and cooling after heat preservation; repeating the secondary melting step 4 times to obtain the lightweight high-entropy alloy.

[0010] Preferably, in S1, the elemental Ti, Al, Cr and Fe metal particles are first ultrasonically rinsed with anhydrous ethanol before weighing.

[0011] Preferably, in S2, before melting, the vacuum melting furnace is first subjected to a gas washing operation: first vacuumize the furnace, and when the vacuum degree is <9.9*10 -4 Pa, stop filling argon with a purity of 99.9% when the pressure in the furnace reaches -0.5MPa; after standing for 10-20 minutes, repeat the gas washing operation once.

[0012] Preferably, the heat preservation time of the melting and secondary melting is 15s.

[0013] Preferably, the time of the melting and secondary melting is 3min.

[0014] Preferably, during the melting and secondary melting, the melting current of the melting furnace is 25A and the melting voltage is 300V.

[0015] The present application has the following beneficial effects:

[0016] (I) The present application is based on Ti, and Al, Fe and Cr are added as main elements to form a lightweight high-entropy alloy TiaAlbCrcFed; the density of the alloy is between 4.3-4.8 g / cm 3 Through organization observation and mechanical property test, the organization is BCC phase, the compression yield strength at room temperature is 1.22-1.55 GPa, the fracture strain is greater than 32%, the hardness is 405-490 HV, the specific strength is 260-336 MPa*cm 3 / g, and the specific hardness is 87.3-106 HV*cm 3 / g; compared with the traditional lightweight alloy TC4, the compression yield strength of the lightweight high-entropy alloy of the present application is increased by 37%, the hardness is increased by about 43%, and the plastic deformation ability is still good, so the TiaAlbCrcFed lightweight high-entropy alloy of the present application has specific strength and specific hardness far exceeding general lightweight alloys, and has certain plasticity;

[0017] (II) The preparation method of the lightweight high-entropy alloy TiaAlbCrcFed in the present application is simple, the forming efficiency in the casting process is high, and it has wide application prospects in the fields of aerospace and military armor. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is the X-ray diffraction pattern of the lightweight high-entropy alloy Ti70Al15Cr10Fe5;

[0019] Figure 2 is the SEM microstructure diagram of the lightweight high-entropy alloy Ti70Al15Cr10Fe5;

[0020] Figure 3 is the room temperature quasi-static compression stress-strain curve of the lightweight high-entropy alloy Ti70Al15Cr10Fe5;

[0021] Figure 4 is the hardness test result of the lightweight high-entropy alloy Ti70Al15Cr10Fe5. DETAILED DESCRIPTION

[0022] The present application will be further described below in combination with the drawings and specific examples.

[0023] Example 1

[0024] 1. The alloy prepared in this example is Ti70Al15Cr10Fe5. According to the atomic mole ratio of Ti, Al, Cr and Fe in the alloy Ti70Al15Cr10Fe5, the corresponding mass of Ti, Al, Cr and Fe elemental metals is taken. According to the melting point of the raw materials from low to high, that is, in the order of Al, Fe, Ti and Cr, the four kinds of elemental metals are sequentially placed into the copper crucible of the non-consumable vacuum suspension melting furnace.

[0025] 2. Close the furnace door and perform gas washing operation on the vacuum melting furnace body: first, vacuumize the furnace, and when the vacuum degree is < 9.9*10 -4 Pa, inject argon with a purity of 99.9%; stop gas injection when the pressure in the furnace reaches -0.5 MPa; after standing for 10-20 minutes, perform the second vacuumization and gas washing operation.

[0026] 3. Set the melting current of the melting furnace to 25 A and the melting voltage to 300 V, start melting until the metal in the furnace is completely melted and uniformly mixed, cool after holding for 15 s to obtain an ingot; turn the ingot over for secondary melting, cool after holding for 15 s; repeat the secondary melting step 4 times, i.e. a total of 5 times of melting, and the melting time of each time is 3 min. After the melting is completed, cool the alloy and take out the ingot to obtain the lightweight high-entropy alloy Ti70Al15Cr10Fe5.

[0027] Cut the ingot for sampling. First, use the Archimedes drainage method to measure the density of the alloy, which is 4.61 g / cm 3 ; then perform XRD and SEM tests for observation, and the results are shown in Figure 1 and 2 respectively; at the same time, perform quasi-static compression and hardness tests, and the results are shown in Figure 3 and 4 respectively. The XRD test result shows that the Ti70Al15Cr10Fe5 lightweight high-entropy alloy is BCC single phase; in the SEM image, a large-size equiaxed BCC phase can be observed. The mechanical property test result shows that the compression yield strength of the Ti70Al15Cr10Fe5 lightweight high-entropy alloy is 1350 MPa, the compression strain is > 60%, and the hardness is about 450 HV. Through calculation, the specific strength of the alloy is about 292 MPa*cm 3 / g, and the specific hardness is about 97.5 HV*cm 3 / g.

[0028] Example 2

[0029] The alloy prepared in the embodiment is Ti60Al20Cr10Fe10, and the preparation method is consistent with that of the embodiment 1, except that the corresponding mass of Ti, Al, Cr and Fe metal elements is taken as raw materials according to the atomic molar ratio of Ti, Al, Cr and Fe in the alloy Ti60Al20Cr10Fe10.

[0030] The density of the Ti60Al20Cr10Fe10 lightweight high-entropy alloy prepared in the embodiment is tested by the Archimedes drainage method, and the density is 4.62 g / cm 3 Then, the quasi-static compression and hardness test are performed. The results show that the compression yield strength of the alloy is 1550 MPa, the compression strain is 34%, the hardness is about 490 HV, the specific strength of the alloy is about 336 MPa*cm 3 / g, and the specific hardness of the alloy is about 106 HV*cm 3 / g.

[0031] Embodiment 3

[0032] The alloy prepared in the embodiment is Ti70Al10Cr15Fe5, and the preparation method is consistent with that of the embodiment 1, except that the corresponding mass of Ti, Al, Cr and Fe metal elements is taken as raw materials according to the atomic molar ratio of Ti, Al, Cr and Fe in the alloy Ti70Al10Cr15Fe5.

[0033] The density of the Ti70Al10Cr15Fe5 lightweight high-entropy alloy is tested by the Archimedes drainage method, and the density is 4.81 g / cm 3 Then, the quasi-static compression and hardness test are performed. The results show that the compression yield strength of the alloy is 1250 MPa, the compression strain is >60%, the hardness is about 420 HV, the specific strength of the alloy is about 260 MPa*cm 3 / g, and the specific hardness of the alloy is about 87.3 HV*cm 3 / g.

[0034] Embodiment 4

[0035] The alloy prepared in the embodiment is Ti79Al15Cr5Fe1, and the preparation method is consistent with that of the embodiment 1, except that the corresponding mass of Ti, Al, Cr and Fe metal elements is taken as raw materials according to the atomic molar ratio of Ti, Al, Cr and Fe in the alloy Ti79Al15Cr5Fe1.

[0036] The density of the Ti79Al15Cr5Fe1 lightweight high-entropy alloy is tested by the Archimedes drainage method, and the density is 4.42 g / cm3 Then, the alloy is subjected to quasi-static compression and hardness test. The results show that the compression yield strength of the alloy is 1220 MPa, the compression strain is 32%, the hardness is 405 HV. Through calculation, the specific strength of the alloy is about 276 MPa*cm 3 / g, and the specific hardness is about 91.6 HV*cm 3 / g.

[0037] In conclusion, the density of the light-weight high-entropy alloy in the application is between 4.3-4.8 g / cm 3 , the compression yield strength at room temperature is between 1.22-1.55 GPa, the fracture strain is greater than 32%, the hardness is between 405-490 HV, the specific strength is between 260-336 MPa*cm 3 / g, and the specific hardness is between 87.3-106 HV*cm 3 / g. Compared with the traditional light-weight alloy TC4, the density of the light-weight high-entropy alloy in the application basically remains unchanged, the compression yield strength is increased by 37%, the hardness is increased by about 43%, and the alloy still maintains good plastic deformation ability.

[0038] The specification and drawings of the application are considered to be illustrative rather than restrictive, and based on the application, those skilled in the art can make some substitutions and modifications to some technical features according to the disclosed technical content without creative labor, which are all within the protection scope of the application.

Claims

1. A lightweight high-entropy alloy, characterized in that, The alloy composition is TiaAlbCrcFed, which is composed of four elements: Ti, Al, Cr, and Fe. a, b, c, and d represent the atomic percentages of Ti, Al, Cr, and Fe, respectively. a is 60-80%, b is 10-20%, c is 5-15%, and d is 1-10%. The sum of a, b, c, and d is 100, where b > c ≥ d. The alloy is a single-phase BCC solid solution. The preparation method of the lightweight high-entropy alloy includes the following steps: S1. Weigh out elemental Ti, Al, Cr, and Fe metal particles according to the atomic percentages of the four elements Ti, Al, Cr, and Fe. S2. According to the order of melting point from low to high, Al, Fe, Ti and Cr metal particles are put into a vacuum melting furnace in sequence for melting. After they are completely melted and mixed evenly, they are kept at the temperature and then cooled to obtain an ingot. S3. Turn the ingot over and remelt it, then keep it warm and cool it. Repeat the remelting process 4 times to obtain a lightweight high-entropy alloy.

2. The lightweight high-entropy alloy according to claim 1, characterized in that, In step S1, the elemental Ti, Al, Cr, and Fe metal particles are ultrasonically rinsed with anhydrous ethanol before weighing.

3. The lightweight high-entropy alloy according to claim 1, characterized in that, In step S2, the vacuum melting furnace is first cleaned before smelting: the furnace is first evacuated until the vacuum degree is <9.9*10. -4 After Pa, purging with 99.9% pure argon gas is initiated. When the pressure inside the furnace reaches -0.5 MPa, the purging is stopped. After standing for 10-20 minutes, the purging operation is repeated once.

4. The lightweight high-entropy alloy according to claim 1, characterized in that, The holding time for both the smelting and secondary smelting is 15 seconds.

5. The lightweight high-entropy alloy according to claim 1, characterized in that, The melting and secondary melting times are both 3 minutes.

6. The lightweight high-entropy alloy according to claim 1, characterized in that, During the smelting and secondary smelting, the smelting current in the smelting furnace is 25A and the smelting voltage is 300V.

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