Bcc single-phase light-weight high-entropy alloy and preparation method thereof

Abstract

The application discloses a BCC single-phase light high-entropy alloy and a preparation method thereof, in particular relates to a TiAlCrMg light high-entropy alloy material and a preparation method thereof. The application designs a light high-entropy alloy with high strength and high plasticity, which is composed of TiaAlbCrcMgd, wherein the atomic percentage of a is 55-80%, the atomic percentage of b is 10-20%, the atomic percentage of c is 5-15%, and the atomic percentage of d is 0-15%, wherein b > c >= d, and a + b + c + d = 100%. The density of the alloy is between 3.8-4.4 g / cm 3 The compression yield strength of the alloy at room temperature is about 1.15 GPa, the fracture strain is greater than 50%, the tensile yield strength at room temperature is about 1.02 GPa, and the fracture strain is about 5.5%. The light high-entropy alloy obtained by the application has high strength, high hardness and good plasticity, and higher specific strength and specific hardness than common light alloys, so that the light high-entropy alloy can replace the light alloy, especially the TC4 titanium alloy, and be used in the structural parts in the field of military armor protection materials and aerospace, so as to realize the target of weight reduction, strengthening and energy saving.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-entropy alloys, and relates to a BCC single-phase light high-entropy alloy and a preparation method thereof, in particular to a TiAlCrMg system light high-entropy alloy material and a preparation method thereof. BACKGROUND

[0002] High-entropy alloys refer to a kind of alloys with four or more metal elements as main elements (atomic mole ratio > 5). Compared with traditional alloys, the high-entropy alloys have high-entropy effects, can reduce the generation of intermetallic compounds of multi-main element alloys, have lattice distortion effects, can increase the strength of the alloys and reduce the thermal conductivity of the alloys, have slow diffusion effects, metal atoms are slow to diffuse in the alloys, and grains are not easy to grow, and finally have cocktail effects, different metal elements as main elements are added to form complex structures and unexpected properties. The four effects make the high-entropy alloys become a research hotspot in the field of metal science in the past decade. Light high-entropy alloys refer to high-entropy alloys with a density < 5 g / cm 3 , which generally have the advantages of high strength, low density, good corrosion resistance and the like, and have great application potential in the industrial field of energy saving, environmental protection, lightness and high efficiency.

[0003] Light alloys refer to a kind of low-density alloys represented by titanium alloys (4.5 g / cm 3 ), aluminum alloys (2.8 g / cm 3 ) and magnesium alloys (1.8 g / cm 3 ), which have the remarkable mechanical characteristics of high specific strength, high specific hardness and good plasticity, and are widely applied in the fields of military and civil structural parts. The most representative light alloy is titanium alloy TC4, which has a density of 4.51 g / cm 3 , a tensile yield strength of 920 MPa, an elongation of 12%, a compression yield strength of about 980 MPa, a hardness of about 330 HV, a specific strength of about 204 MPa*cm 3 / g, a specific hardness of about 73 HV*cm 3 / g, and has the typical characteristics of low density, high strength, high hardness and excellent plasticity, and is widely applied in the structural parts of aerospace vehicles and military armored protection parts. However, in the fields of aerospace and military armor, faster, higher and stronger are pursued, and all materials are required to reduce the mass and increase the reliability as much as possible. Under this background, the research on light high-entropy alloys is in demand, and the current research on light high-entropy alloys mainly focuses on light high-entropy alloys composed of Al, Mg as main elements and adding V, Mn, Ti and the like, which have a density of about 3 g / cm3-5 g / cm 3, compression strength is about 600-800MPa, with the characteristics of light weight and high strength, however, most of the current lightweight high-entropy alloys have a fatal defect, that is, lack of good plasticity, which leads to the inability to perform tensile test, which seriously limits the possibility of its application. For the application of the alloy, plasticity is as important as strength and hardness. In the patent: a high-strength and high-toughness lightweight high-entropy alloy and a preparation method thereof, the alloy is composed of Ti, Al, Cr and Mn; first, the density is relatively large, and the lightweight degree is insufficient; second, the plasticity is slightly poor, and the tensile property test is not performed, which indicates that the tensile property is poor and effective results cannot be obtained; third, the hardness is also low.

[0004] Therefore, in order to solve the problems of poor plasticity and low tensile elongation of the current lightweight high-entropy alloy, and to further improve the specific strength of the alloy, a lightweight high-entropy alloy containing Ti as the base element and Al, Cr and Mg as the main elements is invented, so as to realize a lightweight high-entropy alloy with a density lower than that of TC4 titanium alloy, a yield strength and a hardness higher than those of TC4 titanium alloy, and a plasticity basically consistent with that of TC4 titanium alloy. SUMMARY

[0005] In view of the above-mentioned deficiencies, the present application mainly aims to solve the problems of poor plasticity and insufficient specific strength of the lightweight high-entropy alloy. First, the plasticity of the alloy is one of the main mechanical property indexes of the alloy, which is as important as the yield strength and the hardness. The plasticity of the structural alloy commonly used in the general aviation and military fields is good, and the main tensile elongation index is about 10%-20%, and the compression fracture strain is >50%. However, most of the current lightweight high-entropy alloys have poor plasticity, and the compression fracture strain is generally 30%-40%, and the tensile elongation is basically below 1%, and most of them do not perform tensile test due to the low elongation. Second, among the commonly used lightweight alloys, the specific strength of AZ31 magnesium alloy is about 134MPa*cm 3 / g; the specific strength of 7075 aluminum alloy is about 176MPa*cm 3 / g, the specific hardness is about 56HV*cm 3 / g; the specific strength of TC4 titanium alloy is about 210MPa*cm 3 / g, and the specific hardness is about 71HV*cm 3 / g. Due to the limitation of the traditional alloy design concept, it is difficult to greatly improve the mechanical properties of the above-mentioned alloys.

[0006] In combination with the above two reasons, the present application is to solve the problem of poor plasticity of the lightweight high-entropy alloy, and to improve the specific strength and specific hardness, so as to realize the breakthrough of the mechanical properties on the basis of the original alloy.

[0007] The present application discloses a BCC single-phase lightweight high-entropy alloy, which is composed of TiaAlbCrcMgd, wherein:

[0008] a is 55-80% by atomic percentage,

[0009] b is 10-20% by atomic percentage,

[0010] c is 5-15% by atomic percentage,

[0011] d is 0-15% by atomic percentage,

[0012] b > c >= d, a + b + c + d = 100%.

[0013] Further, the BCC single-phase light-weight high-entropy alloy is Ti 69 Al 15 Cr 10 Mg6.

[0014] The application further discloses a preparation method of the TiaAlbCrcMgd light-weight high-entropy alloy material, comprising the following steps:

[0015] (1) according to atomic percentage, weighing elemental Ti, Al, Cr and Mg metal particles;

[0016] (2) the weighed materials are put into a non-consumable vacuum induction melting furnace for melting, Mg, Al, Cr and Ti metal elements are sequentially put in according to melting point from low to high, and after complete melting, heat preservation and cooling are carried out.

[0017] (3) the ingot is repeatedly melted for multiple times by turning over, and then heat preservation and cooling are carried out.

[0018] (4) the ingot is cast in a water-cooled copper crucible and cooled by water to obtain an ingot.

[0019] Further, the elemental substances in step (1) further comprise ultrasonic flushing with anhydrous ethanol before weighing.

[0020] Further, the vacuum melting furnace in step (2) is provided with a 20 DEG C cooling device, and the cooling device adopts a water cooling mode.

[0021] Further, before melting in step (2), a gas washing operation is carried out on the vacuum melting furnace body: first, vacuumizing the furnace, after the vacuum degree is less than 9.9*10 -4 Pa, argon with a purity of 99.9% is injected, and the injection is stopped when the pressure in the furnace reaches-0.5MPa; after standing for 10-20 minutes, a second vacuumizing and gas washing operation is carried out.

[0022] Further, the voltage of the vacuum melting in step (2) is set to 300V, and the current is 25A.

[0023] Further, the heat preservation time in step (2) is 15s.

[0024] Further, the smelting times in step (3) are 5 times.

[0025] Further, the magnetic stirring is started when smelting to the third and fourth times, so that the high-entropy alloy master alloy ingot is more uniform.

[0026] Further, the hardness of the light high-entropy alloy can be adjusted by adjusting the content of Al, the plasticity of the light high-entropy alloy can be adjusted by adjusting the content of Cr, and the yield strength and density of the light high-entropy alloy can be adjusted by adjusting the content of Mg.

[0027] The application further discloses a TiaAlbCrcMgd light high-entropy alloy material prepared by any one of the preparation methods.

[0028] The application has the following beneficial effects:

[0029] Compared with the prior art, the light high-entropy alloy is formed by adding Al, Mg and Cr as main elements to Ti, and the density of the light high-entropy alloy is 3.9 g / cm 3 -4.4 g / cm 3 Through observation of the structure and mechanical property testing, the structure is BCC phase, the tensile yield strength is 1.02 GPa, the tensile elongation is about 5.5%, the compressive yield strength is about 1.15 GPa, the compressive strain is greater than 50%, and the hardness is about 410 HV. Compared with the traditional light alloy TC4, the density of the TiaAlbCrcMgd light high-entropy alloy is reduced by about 7%, the tensile yield strength is increased by about 11%, the compressive yield strength is increased by 15%, the hardness is increased by about 24%, and the plastic deformation capacity is still good. The TiaAlbCrcMgd light high-entropy alloy has a plasticity and tensile yield strength far exceeding general light high-entropy alloys, the material design method is simple, the preparation process is economical and efficient, the forming efficiency is high in the casting process, and the TiaAlbCrcMgd light high-entropy alloy has a wide application prospect in the fields of aerospace and military armor. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is an SEM microstructure diagram of a Ti69Al15Cr10Mg6 alloy;

[0031] Figure 2 is an X-ray diffraction diagram of a Ti69Al15Cr10Mg6 alloy;

[0032] Figure 3 is a room temperature quasi-static tensile stress-strain curve of a Ti69Al15Cr10Mg6 alloy;

[0033] Figure 4is the room temperature quasi-static compression stress-strain curve of Ti69Al15Cr10Mg6 alloy. DETAILED DESCRIPTION

[0034] The application will be further described below in conjunction with the accompanying drawings and examples.

[0035] Example 1

[0036] A BCC single-phase light-weight high-entropy alloy, which is Ti 69 Al 15 Cr 10 Mg6 alloy, under as-cast condition, the alloy is single-phase BCC structure, as shown in Figure 2 .

[0037] A preparation method of a BCC single-phase Ti 69 Al 15 Cr 10 Mg6 light-weight high-entropy alloy, the specific steps are as follows:

[0038] (1) Select Ti, Al, Cr and Mg four elements, and according to the atomic mole ratio, take the corresponding mass of Ti, Al, Cr and Mg metal elements. According to the melting point of the raw materials from high to low, that is, in the order of Mg, Al, Ti and Cr, the metal elements are sequentially put into the copper crucible of the non-consumable vacuum induction melting furnace.

[0039] (2) Close the furnace door, and then pump the non-consumable vacuum induction melting furnace to a vacuum state, and then introduce high-purity argon gas with a purity of 99.99% as a protective gas.

[0040] (3) Repeat the melting of Ti 69 Al 15 Cr 10 Mg6 alloy for 5 times, the melting current is 25A, the melting voltage is 300V, and the melting time is 3min each time. After the melting is completed, the alloy is cooled and the ingot is taken out.

[0041] (4) The ingot is cut for sampling. First, the Archimedes drainage method is used to measure the density of the alloy, which is 4.21g / cm 3 , and then XRD and SEM tests are performed for observation, and the results are shown in Figure 1 and 2 respectively; at the same time, quasi-static tension, quasi-static compression and hardness tests are performed, and the results are shown in Figure 3 and 4 respectively. The XRD test result shows that the Ti 69 Al 15 Cr 10 Mg6 light-weight 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 Ti69 Al 15 Cr 10 Mg6 lightweight high-entropy alloy has a tensile yield strength of 1020 MPa, a fracture strain of 5.5%, a compressive yield strength of 1150 MPa, a compressive strain of >50%, and a hardness of 410 HV.

[0042] Example 2

[0043] A BCC single-phase lightweight high-entropy alloy has a composition of Ti 65 Al 20 Cr 10 Mg5 alloy, under as-cast conditions, has a single-phase BCC structure.

[0044] A BCC single-phase Ti 65 Al 20 Cr 10 The preparation method of the Mg5 lightweight high-entropy alloy includes the following specific steps:

[0045] (1) Four elements of Ti, Al, Cr, and Mg are selected, and the corresponding masses of Ti, Al, Cr, and Mg elemental substances are weighed according to the atomic molar ratio. According to the melting points of the raw materials from high to low, that is, in the order of Mg, Al, Ti, and Cr, the metal elements are sequentially placed into the copper crucible of a non-consumable vacuum induction melting furnace.

[0046] (2) The furnace door is closed, and the consumable vacuum arc melting furnace is pumped to a vacuum state, and then high-purity argon gas with a purity of 99.99% is introduced as a protective gas.

[0047] (3) The Ti 65 Al 20 Cr 10 Mg5 alloy is repeatedly melted for 5 times, the melting current is 25 A, the melting voltage is 300 V, and the melting time is 3 min each time. After the melting is completed, the alloy is cooled and the ingot is taken out.

[0048] The density of the Ti 65 Al 20 Cr 10 Mg5 lightweight high-entropy alloy is tested by the Archimedes drainage method, and the density is measured to be 4.31 g / cm 3 , and then the alloy is subjected to quasi-static tensile and compressive tests and hardness tests. The results show that the alloy has a tensile yield strength of 1120 MPa, an elongation of 0.9%, a compressive yield strength of 1250 MPa, a compressive strain of >50%, and a hardness of 430 HV.

[0049] Example 3

[0050] A BCC single-phase lightweight high-entropy alloy has a composition of Ti 55 Al20 Cr 15 Mg 10 The alloy is single-phase BCC structure under as-cast condition.

[0051] A BCC single-phase Ti 55 Al 20 Cr 15 Mg 10 The preparation method of the lightweight high-entropy alloy comprises the following specific steps:

[0052] (1) Ti, Al, Cr and Mg are selected, and the corresponding mass of Ti, Al, Cr and Mg elemental substances is weighed according to the atomic molar ratio. According to the melting point of the raw materials from high to low, that is, in the order of Mg, Al, Ti and Cr, the metal elements are sequentially placed into the copper crucible of a non-consumable vacuum induction melting furnace.

[0053] (2) The furnace door is closed, the consumable vacuum arc melting furnace is pumped to a vacuum state, and then high-purity argon gas with a purity of 99.99% is introduced as a protective gas.

[0054] (3) Ti 55 Al 20 Cr 15 Mg 10 is repeatedly melted for 5 times, the melting current is 25 A, the melting voltage is 300 V, and the melting time is 3 min each time. After the melting is completed, the alloy is cooled and the ingot is taken out.

[0055] The Archimedes drainage method is used to test the density of the Ti 55 Al 20 Cr 15 Mg 10 lightweight high-entropy alloy, and the density of the alloy is 4.12 g / cm 3 , and then the quasi-static compression and hardness test are carried out. The results show that the compression yield strength of the alloy is 1450 MPa, the compression strain is 35%, and the hardness is 460 HV.

[0056] Example 4

[0057] A BCC single-phase lightweight high-entropy alloy comprises Ti 70 Al 10 Cr5Mg 15 The alloy is single-phase BCC structure under as-cast condition.

[0058] A BCC single-phase Ti 70 Al 10 Cr5Mg 15 The preparation method of the lightweight high-entropy alloy comprises the following specific steps:

[0059] (1) Select Ti, Al, Cr, Mg four elements, according to the atomic mole ratio, the corresponding mass of Ti, Al, Cr, Mg metal elements is taken. According to the melting point of raw materials from high to low, that is, the order of Mg, Al, Ti, Cr, the metal elements are put into the copper crucible of the non-consumable vacuum induction melting furnace in turn.

[0060] (2) Close the furnace door, and then the consumable vacuum arc melting furnace is pumped to the vacuum state, and then high-purity argon with a purity of 99.99% is introduced as a protective gas.

[0061] (3) Ti 70 Al 10 Cr5Mg 15 alloy is repeatedly melted for 5 times, the melting current is 25A, the melting voltage is 300V, and the melting time is 3min each time. After the melting is finished, the alloy is cooled, and the ingot is taken out.

[0062] The Archimedes drainage method is used to test the density of the Ti 70 Al 10 Cr5Mg 15 lightweight high-entropy alloy, and the density is 3.95g / cm 3 , then the quasi-static compression and hardness test are carried out. The results show that the compression yield strength of the alloy is 1120MPa, the compression strain is 32%, and the hardness is 375HV.

[0063] The above is the description of the preferred embodiments of the present application. It should be noted that the present application is not limited to the above embodiments, and any modification, equivalent replacement or improvement of the present application can be included in the protection scope of the present application, as long as the requirements of the claims, the summary of the invention and the drawings are met.

Claims

1. A method for preparing a BCC single-phase lightweight high-entropy alloy, comprising: (1) Weigh each element: weigh the elemental Ti, Al, Cr, and Mg in atomic percentage; (2) Melting to prepare high entropy alloy: the weighed raw materials are placed in a non-consumable vacuum induction melting furnace, the vacuum degree is adjusted, argon protective gas is filled in for washing, the melting is repeated for a preset number of times, and the temperature is kept and cooled to obtain a BCC single-phase lightweight high entropy alloy; Among them: The chemical composition of the BCC single-phase lightweight high entropy alloy is: Ti a Al b Cr c Mg d ; The atomic percentage of a is 50-80%; The atomic percentage of b is 10-20%; The atomic percentage of c is 5-15%; The atomic percentage of d is 6-15%; As mentioned above, b>c≥d, a+b+c+d=100%.

2. The preparation method according to claim 1, wherein: The purity of the argon gas in step (2) is 99.99 wt%.

3. The preparation method according to claim 1, wherein: The preset number of smelting times in step (2) is 5 times.

4. The preparation method according to claim 3, wherein: When the smelting reaches the third and fourth times, magnetic stirring is turned on.

5. The preparation method according to claim 1, wherein: The holding time in step (2) is 15s.

6. The preparation method according to claim 1, wherein: The smelting voltage in step (2) is 300V and the current is 25A.

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