As-cast light high-strength high-temperature high-entropy alloy and preparation method thereof

Abstract

The invention relates to an as-cast light high-strength high-temperature high-entropy alloy and a preparation method thereof. The high-temperature high-entropy alloy is composed of Ti, Al, Nb, V and Sc elements, and the alloy comprises Ti (2.9-3.1) Al (1.9-2.1) Nb (0.8-1.2) V (1.9-2.1) Scx, wherein 0.1 < = x < = 0.3. Meanwhile, the invention provides a method for preparing the high-temperature high-entropy alloy through smelting. The preparation method of the light high-strength high-temperature high-entropy alloy is simple, meanwhile, the structure is uniform, casting defects are few, and the light high-strength high-temperature high-entropy alloy is suitable for application and popularization.

Description

Technical Field

[0001] The invention relates to a cast lightweight high-strength high-temperature high-entropy alloy and a preparation method thereof, belonging to the technical field of metallurgy. Background Art

[0002] With the further development of the aerospace industry, engine parts will face more stringent service conditions, namely higher operating temperatures, greater impact loads, and longer service life. Currently commonly used high-temperature titanium alloys have a "thermal barrier temperature". Once the operating temperature exceeds 600°C, the titanium alloy will lose most of its high-temperature strength and fracture toughness. In addition, titanium alloys also have a contradictory relationship between strength and toughness similar to traditional alloys. In addition, the composition design and thermomechanical treatment process of high-temperature titanium alloys are relatively complicated, which has led to a bottleneck in the development of high-temperature and high-strength titanium alloys.

[0003] Currently, the academic and engineering communities are looking for a new type of high-temperature alloy that can meet the increasingly harsh high-temperature service environment. High-entropy alloys are regarded as materials with great potential due to their excellent comprehensive properties. In addition, each principal element in a high-entropy alloy will have a greater dominant effect on the overall performance and organization of the alloy, greatly expanding the system scope of metal material alloy design and allowing more room for regulation of alloy composition. Perhaps, the development and design of a high-entropy alloy system with a density close to that of titanium alloys, a higher service temperature, better specific strength, plasticity and toughness, and better processing capabilities can effectively promote the development of the aerospace industry.

[0004] The new high-entropy alloy with refractory metal elements such as Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, and W with a melting point higher than 1650°C as the main components has better high-temperature mechanical properties than traditional high-temperature alloys and has great application potential at high temperatures.

[0005] The invention patent application No. 202210497849.9 specifically discloses a high-strength, lightweight, refractory high-entropy alloy and a preparation method thereof. The composition expression of the alloy is MoNbVTa 0.5 Al x , wherein 0<x<1, and the ratio in the composition expression is a relative atomic ratio. The preparation method uses pure metal elements of Mo, Nb, V, Ta, and Al as raw materials, and weighs and proportions each metal raw material according to the alloy composition; uses Al and V raw materials to prepare Al-V pre-alloyed ingots by vacuum arc melting, and uses Mo, Nb and Ta raw materials to prepare Mo-Nb-Ta pre-alloyed ingots by vacuum arc melting; the Al-V pre-alloyed ingot and the Mo-Nb-Ta pre-alloyed ingot are mixed and vacuum arc melted to prepare Mo-Nb-V-Ta-Al alloy ingots.

[0006] Most refractory high entropy alloys have too high a density because of the addition of high melting point heavy elements. Although the above alloys have added a small amount of light element Al, their density is still 8g / cm 3 In addition, the room temperature compression plasticity of refractory high entropy alloys is generally poor, and the processing ability is also poor.

[0007] By increasing the proportion of lightweight elements such as Ti and Al, the density of high-entropy alloys can be greatly reduced. Invention patent application No. 202210193405.6 provides a lightweight, high-strength high-entropy alloy with a high aluminum content and a preparation method thereof. The high-entropy alloy is based on low-density Al, Mg, and Ti elements, and then adds Cr, V and non-metallic elements Si with relatively low density and high strength properties. A high-entropy alloy with a density close to that of an aluminum alloy and excellent mechanical properties such as high hardness and wear resistance was prepared by using a horizontal low-speed ball milling powder mixing + high-energy ball milling + discharge plasma sintering process.

[0008] Although the density of high-entropy alloys will be significantly reduced by significantly increasing the content of light elements, the room temperature plasticity will not necessarily be enhanced; at the same time, due to the reduction in the proportion of high-melting point heavy elements, the room temperature strength and high temperature strength of the alloy will be significantly reduced; furthermore, the above-mentioned preparation process is complicated and easily introduces impurities and defects. Summary of the invention

[0009] In order to solve the problems of insufficient strength at high temperatures, complex composition design and thermomechanical treatment processes of current titanium alloys used in aerospace, the purpose of the present invention is to provide a high-temperature high-entropy alloy and a preparation method thereof. The density of the alloy is equivalent to that of titanium alloy, and the room temperature and high temperature mechanical properties are better than those of titanium alloy.

[0010] To achieve the above object, the present invention provides a cast lightweight high-strength high-temperature high-entropy alloy, wherein the high-temperature high-entropy alloy is composed of Ti, Al, Nb, V and Sc elements, and the alloy composition is Ti (2.9-3.1) Al (1.9-2.1) Nb (0.8-1.2) V (1.9-2.1) Sc x ; where 0.1≤x≤0.3.

[0011] According to a specific embodiment of the present invention, preferably, the alloy composition of the high temperature high entropy alloy is Ti3Al2NbV2Sc 0.1 、Ti3Al2NbV2Sc 0.2 or Ti3Al2NbV2Sc 0.3 .

[0012] According to a specific embodiment of the present invention, preferably, the density of the high temperature high entropy alloy is lower than 5.6 g / cm 3 , more preferably 4.69-5.05 g / cm3 .

[0013] According to a specific embodiment of the present invention, preferably, the high temperature high entropy alloy has a compressive yield strength of 1302-1423 MPa in the cast state.

[0014] According to a specific embodiment of the present invention, preferably, the compression deformation of the high temperature high entropy alloy in the cast state is 13%-50%.

[0015] According to a specific embodiment of the present invention, preferably, the yield strength of the high temperature high entropy alloy at 600°C is 967-1061 MPa.

[0016] According to a specific embodiment of the present invention, preferably, the yield strength of the high temperature high entropy alloy at 800°C is 442-568 MPa.

[0017] The present invention also provides a method for preparing the above-mentioned cast lightweight and high-strength high-temperature high-entropy alloy, wherein the high-temperature high-entropy alloy is prepared by powder metallurgy or additive manufacturing.

[0018] According to a specific embodiment of the present invention, preferably, the preparation method comprises:

[0019] Place Ti, Al, Nb, V and Sc in a crucible in order from low to high melting points;

[0020] Under a protective atmosphere, smelting is performed. During smelting, the titanium ingot is first melted at a current of 80-120A to remove excess oxygen in the cavity, and then Ti, Al, Nb, V and Sc are melted at a current of 200-300A for 1-2 minutes to obtain an alloy ingot;

[0021] The alloy ingot is turned over and repeatedly melted, and then cooled to obtain a uniform, cast, lightweight, high-strength, high-temperature high-entropy alloy ingot.

[0022] According to a specific embodiment of the present invention, preferably, the argon protective atmosphere is obtained by the following method:

[0023] The melting chamber was evacuated, and when the vacuum reached 1-5 Pa, argon was backwashed to 2×10 4 -4×10 4 Pa and evacuate to 1-5Pa again. Repeat this process 3-4 times and evacuate to 3×10 -4 -5×10 -4 Pa, and then introduce argon protective gas to 3×10 4 -6×10 4 Pa.

[0024] According to a specific embodiment of the present invention, preferably, the purity of the Ti, Al, Nb, V and Sc materials is above 99.9 wt %.

[0025] According to a specific embodiment of the present invention, preferably, the equipment used for smelting is a non-consumable vacuum arc furnace, but other suitable equipment is not excluded.

[0026] According to a specific embodiment of the present invention, during the smelting process, the crucible is generally a water-cooled copper crucible.

[0027] According to a specific embodiment of the present invention, during the smelting process, the protective atmosphere is generally argon.

[0028] According to a specific embodiment of the present invention, preferably, the preparation method further comprises the following steps: before smelting, the five raw materials of Ti, Al, Nb, V and Sc are polished to remove oxide scale, ultrasonically cleaned and air-dried.

[0029] The technical solution of the present invention has the following beneficial effects:

[0030] 1. The present invention develops a lightweight, high-strength, high-temperature, high-entropy alloy system with low density (close to the density of titanium alloy) and excellent mechanical properties by reasonably selecting alloy elements and regulating the proportion of light elements, which can effectively promote the development of the aerospace industry.

[0031] 2. Ti3Al2NbV2Sc of the present invention x A series of lightweight, high-strength, high-temperature high-entropy alloys with a density lower than 5.6 g / cm 3 , uniform composition; the compressive yield strength of the cast sample can reach 1302-1423MPa, and the maximum compression deformation can reach more than 50%, with extremely strong work hardening and uniform plastic deformation capabilities.

[0032] 3. The current Ti alloy (Ti600) used in aerospace has a room temperature yield strength of 1050MPa and a deformation of 11%; while its yield strength and deformation at 600°C are only 615MPa and 16%; above 600°C, its mechanical properties will deteriorate sharply, and there is currently no effective solution. x The series of lightweight, high-strength, high-temperature high-entropy alloys have high-temperature yield strengths of 967-1061MPa and 442-568MPa at 600℃ and 800℃, respectively. The room temperature and high-temperature mechanical properties are significantly higher than those of traditional Ti alloys.

[0033] 4. The preparation method of the lightweight, high-strength, high-temperature high-entropy alloy of the present invention is simple, and the structure is uniform and there are fewer casting defects, so it is suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Ti3Al2NbV2Sc 0.1 Engineering stress-strain curves of alloys.

[0035] Figure 2 Ti3Al2NbV2Sc 0.2 Engineering stress-strain curves of alloys.

[0036] Figure 3 Ti3Al2NbV2Sc 0.3 Engineering stress-strain curves of alloys. DETAILED DESCRIPTION

[0037] In order to have a clearer understanding of the technical features, purposes and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be construed as limiting the applicable scope of the present invention.

[0038] Example 1

[0039] This embodiment provides a cast lightweight high-strength high-temperature high-entropy alloy Ti3Al2NbV2Sc 0.1 , and its preparation method is:

[0040] Ingredients: Five raw materials (Ti, Al, Nb, V and Sc, with a purity of more than 99.9 wt%) were ground to remove oxide scale, ultrasonically cleaned and air-dried. 0.1 The molar ratio is weighed.

[0041] Melting (using vacuum arc melting furnace to prepare cast lightweight and high-strength high-temperature high-entropy alloy):

[0042] 1) placing Ti, Al, Nb, V and Sc in a water-cooled copper crucible inside a non-consumable vacuum arc furnace in order from low to high melting points;

[0043] 2) Evacuate the air, and when the vacuum reaches 5 Pa, backwash the argon gas to 2×10 4 Pa and evacuate to 5Pa again. Repeat this process 3 times and evacuate to 4×10 -4 Pa, and then introduce argon protective gas to 5×10 4 Pa;

[0044] 3) Turn on the smelting DC power switch to start smelting. During smelting, first melt the titanium ingot under the condition of 100A current to absorb the excess oxygen in the cavity, and then melt Ti, Al, Nb, V and Sc under the condition of 200A current for about 2 minutes to obtain an alloy ingot;

[0045] 4) The alloy ingot is turned over and smelted repeatedly for 4 times, and cooled to obtain a uniform cast, lightweight, high-strength, high-temperature high-entropy alloy ingot.

[0046] The lightweight, high-strength, high-temperature high-entropy alloy Ti3Al2NbV2Sc of this embodiment 0.1 The density is about 4.92g / cm 3 , the composition is uniform.

[0047] The prepared Ti3Al2NbV2Sc 0.1 The alloy was tested for room temperature and high temperature mechanical properties:

[0048] The compression tests were carried out on an Instron 5980 testing machine at room temperature, 600°C and 800°C. The strain rate was set at 10 -3 ·s -1 ; The maximum strain is set to 80%; The sample is For cylinders, ensure that all surfaces are clean and flat before testing.

[0049] Test results see Figure 1 The compressive yield strength of the cast sample of this embodiment can reach 1348MPa, and the compressive deformation can reach more than 50%, which has extremely strong work hardening and uniform plastic deformation capabilities. At the same time, the high temperature yield strength of the alloy at 600℃ and 800℃ can reach 967MPa and 442MPa respectively, and the room temperature and high temperature mechanical properties are significantly higher than those of traditional Ti alloys.

[0050] Example 2

[0051] This embodiment provides a cast lightweight high-strength high-temperature high-entropy alloy Ti3Al2NbV2Sc 0.2 , and its preparation method is:

[0052] Ingredients: Five raw materials (Ti, Al, Nb, V and Sc, with a purity of more than 99.9 wt%) were ground to remove oxide scale, ultrasonically cleaned and air-dried. 0.2 The molar ratio is weighed.

[0053] Melting (using vacuum arc melting furnace to prepare cast lightweight and high-strength high-temperature high-entropy alloy):

[0054] 1) placing Ti, Al, Nb, V and Sc in a water-cooled copper crucible inside a non-consumable vacuum arc furnace in order from low to high melting points;

[0055] 2) Evacuate the air, and when the vacuum reaches 5 Pa, backwash the argon gas to 3×10 4 Pa and evacuate to 1Pa again. Repeat this process 3 times and evacuate to 3×10 -4 Pa, and then introduce argon protective gas to 4×10 4 Pa;

[0056] 3) Turn on the smelting DC power switch to start smelting. During smelting, first melt the titanium ingot under the condition of 80A current to absorb the excess oxygen in the cavity, and then melt Ti, Al, Nb, V and Sc under the condition of 260A current for about 1.5 minutes to obtain an alloy ingot;

[0057] 4) The alloy ingot is turned over and smelted repeatedly for 6 times, and cooled to obtain a uniform cast lightweight, high-strength, high-temperature high-entropy alloy ingot.

[0058] The lightweight, high-strength, high-temperature high-entropy alloy Ti3Al2NbV2Sc of this embodiment 0.2 The density is about 4.89g / cm 3 , the composition is uniform.

[0059] The Ti3Al2NbV2Sc prepared in this embodiment is subjected to the same method as in Example 1. 0.2 The room temperature and high temperature mechanical properties of the alloy were tested. The test results are shown in Figure 2 The compressive yield strength of the cast sample of this embodiment can reach 1302MPa, and the compressive deformation can reach 35%, which has extremely strong work hardening and uniform plastic deformation capabilities. At the same time, the high temperature yield strength of the alloy at 600℃ and 800℃ can reach 1025MPa and 547MPa respectively, and the room temperature and high temperature mechanical properties are significantly higher than those of traditional Ti alloys.

[0060] Example 3

[0061] This embodiment provides a cast lightweight high-strength high-temperature high-entropy alloy Ti3Al2NbV2Sc 0.3 , and its preparation method is:

[0062] Ingredients: Five raw materials (Ti, Al, Nb, V and Sc, with a purity of more than 99.9 wt%) were ground to remove oxide scale, ultrasonically cleaned and air-dried. 0.3 The molar ratio is weighed.

[0063] Melting (using vacuum arc melting furnace to prepare cast lightweight and high-strength high-temperature high-entropy alloy):

[0064] 1) placing Ti, Al, Nb, V and Sc in a water-cooled copper crucible inside a non-consumable vacuum arc furnace in order from low to high melting points;

[0065] 2) Evacuate the air, and when the vacuum reaches 1Pa, backwash the argon gas to 4×10 4 Pa and evacuate to 3Pa again. Repeat this process 4 times and evacuate to 5×10 -4 Pa, and then introduce argon protective gas to 6×10 4 Pa;

[0066] 3) Turn on the smelting DC power switch to start smelting. During smelting, first melt the titanium ingot under the condition of 120A current to absorb the excess oxygen in the cavity, and then melt Ti, Al, Nb, V and Sc under the condition of 300A current for about 1 minute to obtain an alloy ingot;

[0067] 4) The alloy ingot is turned over and smelted repeatedly for 5 times, and cooled to obtain a uniform cast lightweight, high-strength, high-temperature high-entropy alloy ingot.

[0068] The lightweight, high-strength, high-temperature high-entropy alloy Ti3Al2NbV2Sc of this embodiment 0.3 The density is about 4.85g / cm 3 , the composition is uniform.

[0069] The Ti3Al2NbV2Sc prepared in this embodiment is subjected to the same method as in Example 1. 0.3 The room temperature and high temperature mechanical properties of the alloy were tested. The test results are shown in Figure 3 The compressive yield strength of the cast sample of this embodiment can reach 1423MPa, and the compressive deformation can reach 13%, which has extremely strong work hardening and uniform plastic deformation capabilities. At the same time, the high temperature yield strength of the alloy at 600℃ and 800℃ can reach 1061MPa and 568MPa respectively, and the room temperature and high temperature mechanical properties are significantly higher than those of traditional Ti alloys.

[0070] The above embodiments are only preferred implementation modes of the present invention and are only used to explain the present invention rather than to limit the present invention. Any changes, substitutions, modifications, etc. made by those skilled in the art without departing from the spirit of the present invention should fall within the scope of protection of the present invention.

Claims

1. A cast lightweight, high-strength, high-temperature, high-entropy alloy, wherein: The high temperature high entropy alloy is composed of Ti, Al, Nb, V and Sc elements. The alloy composition is Ti (2.9-3.1) Al (1.9-2.1) Nb (0.8-1.2) V (1.9-2.1) Sc x ; where 0.1≤x≤0.

3.

2. The high temperature high entropy alloy according to claim 1, wherein: The alloy composition of the high temperature high entropy alloy is Ti3Al2NbV2Sc 0.1 、Ti3Al2NbV2Sc 0.2 or Ti3Al2NbV2Sc 0.3 .

3. The high temperature high entropy alloy according to claim 1, wherein: The density of this high-temperature high-entropy alloy is less than 5.6 g / cm 3 , preferably 4.69-5.05g / cm 3 .

4. The high temperature high entropy alloy according to claim 1, wherein: The compressive yield strength of the high-temperature high-entropy alloy in the cast state is 1302-1423 MPa.

5. The high temperature high entropy alloy according to claim 1, wherein: The compression deformation of the high-temperature high-entropy alloy in the cast state is 13%-50%.

6. The high temperature high entropy alloy according to claim 1, wherein: The yield strength of this high-temperature high-entropy alloy at 600°C is 967-1061MPa.

7. The high temperature high entropy alloy according to claim 1, wherein: The yield strength of this high-temperature high-entropy alloy at 800°C is 442-568MPa.

8. The method for preparing the as-cast lightweight, high-strength, high-temperature high-entropy alloy according to any one of claims 1 to 7, wherein: The high-temperature high-entropy alloy is prepared by smelting.

9. The preparation method according to claim 8, wherein: The preparation method comprises: Place Ti, Al, Nb, V and Sc in a crucible in order from low to high melting points; Under a protective atmosphere, smelting is performed. During smelting, the titanium ingot is first melted at a current of 80-120A to remove excess oxygen in the cavity, and then Ti, Al, Nb, V and Sc are melted at a current of 200-300A for 1-2 minutes to obtain an alloy ingot; The alloy ingot is turned over and repeatedly melted, and then cooled to obtain a uniform, cast, lightweight, high-strength, high-temperature high-entropy alloy ingot.

10. The preparation method according to claim 9, wherein: The protective atmosphere is obtained by: The melting chamber was evacuated, and when the vacuum reached 1-5 Pa, argon was backwashed to 2×10 4 -4×10 4 Pa and evacuate to 1-5Pa again. Repeat this process 3-4 times and evacuate to 3×10 -4 -5×10 -4 Pa, and then introduce argon protective gas to 3×10 4 -6×10 4 Pa.

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