Cutter-oriented high-strength and high-hardness Ti-V-Fe-Ta-W series refractory high-entropy alloy

Abstract

The invention discloses a high-strength and high-hardness Ti-V-Fe-Ta-W series refractory high-entropy alloy for a cutter. The component of the Ti-V-Fe-Ta-W series refractory high-entropy alloy is (TiVFe < 0.2 > Ta < 0.8 >) < 95 > W5 or (TiVFe < 0.7 > Ta) < 90 > W10. The refractory high-entropy alloy has the characteristics of high strength, high hardness, high melting point, low activation and the like, and has great application potential in the fields of cutting tools and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials and preparation thereof, and in particular relates to a high-strength and high-hardness Ti-V-Fe-Ta-W series refractory high-entropy alloy for cutting tools. Background Art

[0002] The concept of high entropy alloy was first proposed in 2004. Different from traditional alloys, high entropy alloys are usually composed of at least five elements, and the content of each element is 5%-35% (atomic percentage). Thanks to the unique elemental composition of high entropy alloys, it has four core effects: high entropy effect, hysteresis diffusion effect, lattice distortion effect and cocktail effect, which improves the strength, hardness, corrosion resistance, thermal stability and radiation resistance of metal materials to an unprecedented level. Therefore, it has great application potential. At the same time, it has a profound impact on the research and development of metal materials and the application of structural materials. It is precisely because of the unique elemental composition of high entropy alloys that the design and performance regulation of high entropy alloys have great space, but also great challenges. It is a common method to adjust the type and content of the main element to regulate the type and proportion of the phase. For example, by changing the element content to achieve second phase strengthening and precipitate strengthening, etc., to meet the performance requirements of high entropy alloys.

[0003] With the continuous development of the aviation industry, the performance requirements for high-temperature alloys are increasing. The performance of nickel-based high-temperature alloys seems to have reached its limit. Therefore, the demand for a new generation of high-temperature materials with excellent performance is becoming more and more urgent. Refractory high-entropy alloys were first proposed in 2010. They are basically composed of refractory elements, so they have a high melting point and exhibit excellent mechanical properties and good thermal stability in high-temperature environments. The excellent performance of refractory high-entropy alloys in high-temperature environments gives them great application potential. They are considered to be candidate materials for the next generation of high-temperature alloys. In addition, they also have great application potential in the fields of nuclear reactors, cutting tools, etc.

[0004] At present, the components of high entropy alloys used in cutting tools are basically non-refractory elements, which means that the alloy system has a low melting point and poor adaptability in high temperature environments. Refractory high entropy alloys are basically composed of refractory elements, which have high melting points, good thermal stability and high temperature softening resistance. During the cutting process, the tool has to withstand severe loads such as high temperature and high pressure. In comparison, refractory high entropy alloys have higher application potential in cutting tools.

[0005] Therefore, it is of great significance to develop refractory high entropy alloys with high strength, high hardness and high melting point characteristics for cutting tools. Summary of the invention

[0006] The present invention discloses a high-strength and high-hardness Ti-V-Fe-Ta-W refractory high-entropy alloy for cutting tools, which aims to regulate the performance of the alloy by adjusting the contents of strengthening components Fe and W elements to meet different performance requirements: when the Fe and W contents are low, the alloy has excellent plasticity; when the Fe and W contents are high, the alloy has high strength and high hardness.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] The invention discloses a high-strength and high-hardness Ti-V-Fe-Ta-W refractory high-entropy alloy for cutting tools. The screening principle of the components is as follows: according to the cocktail effect of the high-entropy alloy, in order to obtain the characteristics of high strength, high hardness, low activation and high melting point, the main component of the alloy is selected from a refractory element range A (including Ti, V, Cr, Zr, Nb, Mo, W, Ta, Hf) and a low activation element range B (including Fe, Ti, Cr, V, Ta, Zr, W); in order to obtain a larger lattice distortion to improve its mechanical properties, a selection design is made from a large atomic radius element range C (such as Ti, Zr, Hf, etc.) and a small atomic radius element range D (such as Fe, Cr, V, Ni, Co, etc.). According to the above alloy main element selection conditions, the present invention provides a high-strength and high-hardness Ti-V-Fe-Ta-W refractory high-entropy alloy for cutting tools, with Ti, V and Ta as basic components and Fe and W as strengthening components, so that the alloy has the characteristics of high strength, high hardness, low activation and high melting point. The specific composition is (TiVFe 0.2 Ta 0.8 ) 95 W5 or (TiVFe 0.7 Ta) 90 W 10 .

[0009] The method for preparing the refractory high entropy alloy of the present invention is carried out according to the following steps:

[0010] Step 1: Determine the required mass of Ti, V, Fe, Ta and W metal raw materials according to the atomic percentage of each component in the alloy; grind the metal raw materials to remove the surface oxide layer, weigh them accurately, and then ultrasonically clean and dry them; the specific method is:

[0011] The theoretical density of the alloy (g / cm) is calculated based on the atomic percentage and density of each component in the alloy system. 3 ), the total mass of the alloy (g) can be taken between 4ρ and 5ρ depending on the situation, and then the required mass of Ti, V, Fe, Ta and W can be obtained based on the total mass of the alloy and the atomic percentage of each component.

[0012] According to the calculated mass of each component, take Ti, V, Fe, Ta and W metal raw materials and leave a certain amount of surplus (such as 0.5g to 1g surplus), and then perform rough grinding, first use a file to remove the oxide layer on the metal surface and then grind each component to the required mass as much as possible. The rough-ground metal raw materials are further accurately proportioned through fine grinding to achieve the required mass (mass accuracy to 0.001g), and then the metal raw materials are ultrasonically cleaned in alcohol, and then taken out and blown dry.

[0013] Step 2: Put the metal raw materials into the copper mold crucible of the vacuum arc melting furnace, evacuate the furnace chamber, and then fill it with argon as a protective gas and for arc initiation.

[0014] Step 3, the tungsten needle strikes the arc. After the arc is struck, the titanium ingot is first melted to consume the remaining oxygen in the furnace chamber. After the melting of the titanium ingot is completed, the current is lowered and the tungsten needle is moved to the metal raw material. Then the current is increased to melt the metal raw material, and the alloy is melted multiple times. After each melting, it is turned over to ensure that its composition is uniform. After the melting is completed, the Ti-V-Fe-Ta-W refractory high entropy alloy is obtained.

[0015] Preferably, in step 1, the purity of the Ti, V, Fe, Ta and W metal raw materials used is not less than 99.95%.

[0016] Preferably, in step 2, the furnace is first evacuated to 5 Pa using a mechanical pump, and then the molecular pump is turned on to evacuate to 8×10 -4 Pa, and then fill with argon until the pressure in the furnace chamber is -0.05MPa.

[0017] Preferably, in step 3: the arc striking current is 20A; when melting titanium ingots, the current is adjusted to 180A and melted for 2 to 3 minutes; when melting metal raw materials, the current is adjusted to 250A to 280A, each melting is 4 to 6 minutes, and the melting is repeated 12 times. After each melting, the alloy ingot is turned over with a spoon in the furnace chamber.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. The refractory high entropy alloy composed of five components of Ti, V, Fe, Ta and W in the present invention has the characteristics of high strength, high hardness, low activation, high melting point, excellent performance, and great application potential in the fields of nuclear reactors and cutting tools. The two specific components of the alloy selected by the present invention have their own characteristics and can meet different performance requirements: when the Fe and W contents are low, the alloy has excellent plasticity (greater than 50%); when the Fe and W contents are high, the alloy has high strength (2200MPa) and high hardness (778HV).

[0020] 2. The preparation method of the present invention is simple and easy to operate, and the alloy composition is uniform, which is mainly BCC phase and a small amount of Laves phase, and has the potential to be used as a high-temperature structural material. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The TiVFe 0.2 Ta 0.8 ) 95 Room temperature compressive stress-strain curve of W5 alloy.

[0022] Figure 2 The TiVFe 0.2 Ta 0.8 ) 95 XRD pattern of W5 alloy.

[0023] Figure 3 The TiVFe 0.7 Ta) 90 W 10 SEM image of the alloy microstructure.

[0024] Figure 4 The TiVFe 0.7 Ta) 90 W 10 Room temperature compressive stress-strain curves of the alloy.

[0025] Figure 5 The TiVFe 0.7 Ta) 90 W 10 XRD patterns of the alloys.

[0026] Figure 6 The TiVFe 0.7 Ta) 90 W 10 SEM image of the alloy microstructure.

[0027] Figure 7 The figure is a hardness variation trend diagram of the Ti-V-Fe-Ta-W refractory high entropy alloy obtained in each embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. The following content is only an example and explanation of the concept of the present invention. The technicians in the relevant technical field make various modifications or supplements to the specific implementation cases described or replace them with similar methods. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the protection scope of the present invention.

[0029] Example 1

[0030] The refractory high entropy alloy composition of this embodiment is (TiVFe 0.2 Ta 0.8 ) 95 W5, wherein the atomic percentages of Ti, V, Fe, Ta and W are 31.667 at.%, 31.667 at.%, 6.333 at.%, 25.333 at.% and 5 at.%, respectively, is prepared as follows:

[0031] Step 1: Calculate the theoretical density of the alloy (g / cm) according to the atomic percentage and density of each component in the alloy system. 3 ) is 9.268 g / cm 3 , the total mass of the alloy (g) is taken as 42.2g. According to the total mass of the alloy and the atomic percentage of each component, the required masses of Ti, V, Fe, Ta and W are 7.12g, 7.575g, 1.661g, 21.526g and 4.317g respectively.

[0032] According to the calculated mass of each component, take Ti, V, Fe, Ta and W metal raw materials and leave 0.5g~1g surplus to compensate for the mass lost by grinding the surface, and then perform rough grinding, first use a file to remove the oxide layer on the metal surface and then grind each component to the required mass as much as possible.

[0033] The metal surface is polished with a diamond file, and a high-precision balance is used to weigh it after each polishing, and finally the required mass is reached (the mass is accurate to 0.001g). Then the metal raw materials with the completed proportion are put into alcohol for ultrasonic cleaning, and then taken out and blown dry.

[0034] Step 2: Place the metal raw materials into the copper crucible of the vacuum arc melting furnace. The metal raw materials are arranged from high to low according to their melting points, so that the high melting point metal is closer to the tungsten needle and is heated more fully. First, use a mechanical pump to evacuate the furnace chamber to 5Pa, and then turn on the molecular pump to evacuate to 8×10 -4 Pa, and then fill with argon until the pressure in the furnace chamber reaches -0.05MPa.

[0035] Step 3, tungsten needle arc, first adjust the melting current to 20A, then use the tungsten needle to contact the copper column to complete the arc, after the arc is struck, first melt the titanium ingot, at this time adjust the current to 180A and melt for 2 to 3 minutes to consume the remaining oxygen in the furnace chamber. Then lower the current and move the tungsten needle to the metal raw material, increase the melting current to 250A and melt for 4 to 6 minutes, turn off the melting power supply and adjust the current to 0. After the alloy ingot cools for 3 to 5 minutes, use a spoon to flip it over and lean it against the side wall of the copper mold crucible, so that the low-melting-point metal will melt first and flow to the bottom of the crucible next time, and then melt the exposed high-melting-point metal to make the alloy mix more evenly. Then repeat the above process, and repeat the melting 10 times to ensure that the alloy composition is uniform. In the last two times, place the alloy flat in the copper mold crucible for melting, and finally obtain a button-like (TiVFe 0.2 Ta 0.8 ) 95 W5 alloy.

[0036] The TiVFe 0.2 Ta 0.8 ) 95 W5 alloy was tested for mechanical properties and microstructure characterization:

[0037] Figure 1 The TiVFe 0.2 Ta 0.8 ) 95 The room temperature compressive stress-strain curve of W5 refractory high entropy alloy. 0.2 Ta 0.8 ) 95 The average Vickers hardness of W5 alloy is 482HV1.0, the average strength at room temperature is 1207.44MPa, the plasticity exceeds 50%, and the theoretical density is 9.268g / cm 3 , the theoretical melting point is 2439 K. The alloy has excellent plasticity, high strength and hardness, high melting point and other characteristics.

[0038] Figure 2 The TiVFe 0.2 Ta 0.8 ) 95 XRD pattern of W5 refractory high entropy alloy. The alloy is mainly composed of BCC phase and contains a small amount of Laves phase.

[0039] Figure 3 The TiVFe 0.2 Ta 0.8 ) 95 SEM image of the microstructure of W5 refractory high entropy alloy.

[0040] Example 2

[0041] The refractory high entropy alloy composition of this embodiment is (TiVFe 0.7 Ta) 90 W 10 , wherein the atomic percentages of Ti, V, Fe, Ta and W are 24.324at.%, 24.324at.%, 17.027at.%, 24.324at.% and 10%, respectively, and the preparation steps are the same as those in Example 1, except that: during the preparation, the masses of Ti, V, Fe, Ta and W required are 5.148g, 5.477g, 4.204g, 19.455g and 8.127g, respectively; during smelting, the smelting current of the high entropy alloy is increased to 280A.

[0042] The TiVFe 0.2 Ta 0.8 ) 95 W5 alloy was tested for mechanical properties and microstructure characterization:

[0043] Figure 4 The TiVFe 0.7 Ta) 90 W 10 Room temperature compressive stress-strain curve of refractory high entropy alloy. 0.7 Ta) 90 W 10 The average Vickers hardness of the alloy is 778HV1.0, the average strength at room temperature is 2241MPa, and the theoretical density is 10.177g / cm 3 , the theoretical melting point is 2481 K. Compared with Example 1, the strength and hardness of the alloy in this embodiment are significantly improved.

[0044] Figure 5 The TiVFe 0.7 Ta) 90 W 10 XRD pattern of refractory high entropy alloy. The alloy is mainly composed of BCC phase and contains a small amount of Laves phase.

[0045] Figure 6 The TiVFe 0.7 Ta) 90 W 10 SEM image of the microstructure of refractory high entropy alloy.

[0046] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-strength and high-hardness Ti-V-Fe-Ta-W refractory high-entropy alloy for cutting tools, characterized in that: The composition of the refractory high entropy alloy is (TiVFe 0.2 Ta 0.8 ) 95 W5 or (TiVFe 0.7 Ta) 90 W 10 .

2. A method for preparing the refractory high entropy alloy according to claim 1, characterized in that: Proceed as follows: Step 1: Determine the required mass of Ti, V, Fe, Ta and W metal raw materials according to the atomic percentage of each component in the alloy; grind the metal raw materials to remove the surface oxide layer, weigh them accurately, and then ultrasonically clean and dry them; Step 2, placing each metal raw material into a copper mold crucible of a vacuum arc melting furnace, evacuating the furnace chamber, and then filling it with argon as a protective gas and for arc initiation; Step 3, tungsten needle strikes the arc, after striking the arc, first melt the titanium ingot to consume the remaining oxygen in the furnace chamber, then melt the metal raw materials, and melt the alloy multiple times, turning it over after each melting to ensure its uniform composition; after the melting is completed, the Ti-V-Fe-Ta-W series refractory high entropy alloy is obtained.

3. The preparation method according to claim 2, characterized in that: In step 1, the purity of the Ti, V, Fe, Ta and W metal raw materials used is not less than 99.95%.

4. The preparation method according to claim 2, characterized in that: In step 2, the furnace was first evacuated to 5 Pa using a mechanical pump, and then the molecular pump was turned on to evacuate to 8 × 10 -4 Pa, and then fill with argon until the pressure in the furnace chamber is -0.05MPa.

5. The preparation method according to claim 2, characterized in that: In step 3, the arc striking current is 20A. When melting the titanium ingot, the current is adjusted to 180A and melted for 2 to 3 minutes.

6. The preparation method according to claim 2 or 5, characterized in that: In step 3, when smelting the metal raw material, the current is adjusted to 250A-280A, each smelting is 4-6 minutes, and the smelting is repeated 12 times.

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