A directional solidification high-entropy alloy FeCoNi(AlTi) 0.5

Abstract

The application belongs to the technical field of alloy preparation, and particularly relates to a directional solidification high-entropy alloy FeCoNi(AlTi) 0.5 . A preparation method thereof comprises the following steps: (1) cleaning each metal in the FeCoNi(AlTi) 0.5 alloy according to the mass ratio converted from the molar ratio of each metal in the alloy; (2) placing the cleaned metals in a smelting furnace cavity according to the melting points, vacuumizing, filling argon, and leading an arc; (3) smelting a mother alloy after leading the arc, placing the smelted mother alloy on a suction casting mold, heating the mother alloy, waiting for complete melting, and cooling to obtain a mother alloy rod; and (4) directional solidification of the mother alloy rod at a pulling speed of 5-100 microns per second, and then quickly pulling the mother alloy into a Ga-In-Sn cooling liquid. The yield strength of the alloy can reach 1020.91 MPa, the tensile strength can reach 1308.57 MPa, and the elongation can reach 15.67%.

Description

Technical Field

[0001] This invention belongs to the field of alloy preparation technology, specifically relating to a directionally solidified high-entropy alloy FeCoNi(AlTi). 0.5 . Background Technology

[0002] Traditional alloys typically use a single element as the main component, with performance improvements primarily achieved by adding small amounts of other alloying elements. According to Gibbs's phase rule, excessive addition of alloying elements can lead to the formation of intermetallic compounds. Once brittle compounds form, they severely impact the alloy's performance, causing deterioration. Therefore, in the design philosophy of traditional alloys, the number of alloying elements should be minimized when the alloy's performance meets application requirements.

[0003] However, the design concept of high-entropy alloys (HEAs) is completely different from that of traditional alloys. Since Yeh and Cantor first proposed the concept of HEAs in 2004, it has attracted widespread attention and research interest from scholars worldwide. HEAs contain at least five elements, each with a content ranging from 5% to 35% (at.%). Although the types and contents of elements in HEAs deviate from the Gibbs phase rule, they can suppress the formation of harmful intermetallic compounds. High-entropy alloys exhibit four major effects: the high-entropy effect, the lattice distortion effect, the hysteresis diffusion effect, and the "cocktail" effect. In terms of performance, high-entropy alloys have many advantages, including high strength, excellent fatigue and fracture resistance, thermal stability, wear resistance, corrosion resistance, and radiation resistance, as well as other novel physical properties. High-entropy alloys show great potential in engineering fields such as metallurgical materials, catalysts, aerospace materials, and nuclear materials.

[0004] Therefore, developing a high-entropy alloy is of great significance. Summary of the Invention

[0005] To achieve the above objectives, the present invention aims to provide a directionally solidified high-entropy alloy FeCoNi(AlTi). 0.5 This directionally solidified high-entropy alloy FeCoNi(AlTi) 0.5 It is an alloy that grows in a single direction using a directional solidification method, thus solving the problem of as-cast FeCoNi(AlTi) alloys. 0.5 High-entropy alloys have the problem of low strength; and the prepared alloys have good plasticity.

[0006] To achieve the above objectives, the present invention can adopt the following technical solutions:

[0007] This invention provides a directionally solidified high-entropy alloy FeCoNi(AlTi). 0.5 Its preparation method includes: (1) preparing FeCoNi(AlTi) 0.5The metals in the alloy are cleaned according to the mass ratio converted from the molar ratio of the metals in the alloy; (2) the cleaned metals are placed in a smelting furnace cavity according to the melting point, vacuumized, filled with argon, and arc struck; (3) the mother alloy is smelted after the arc is struck, the smelted mother alloy is placed on a suction casting mold, the mother alloy is heated, and the mother alloy is completely melted, and the mother alloy rod is prepared after being completely melted and cooled; (4) the mother alloy rod is directionally solidified, the pulling speed of directional solidification is 5-100 mu m / s, and then the mother alloy is quickly pulled into a Ga-In-Sn cooling liquid.

[0008] The present application has at least the following beneficial effects: the yield strength of the directionally solidified high-entropy alloy FeCoNi(AlTi) 0.5 of the present application can reach 1020.91 MPa, the tensile strength can reach 1308.57 MPa, and the elongation can reach 15.67%; and the preparation method is simple to operate, and high-strength high-entropy alloy materials can be obtained without cold rolling and heat treatment processes. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 FeCoNi(AlTi) 0.5 of the present application prepared in Example 1 has a pulling speed of 5 mu m / s, and the metallographic diagram of the directionally solidified high-entropy alloy is shown in the figure, wherein (a) is a solid-liquid interface structure diagram, and (b) is a steady-state structure diagram;

[0010] Figure 2 FeCoNi(AlTi) 0.5 of the present application prepared in Example 2 has a pulling speed of 15 mu m / s, and the metallographic diagram of the directionally solidified high-entropy alloy is shown in the figure, wherein (a) is a solid-liquid interface structure diagram, and (b) is a steady-state structure diagram;

[0011] Figure 3 FeCoNi(AlTi) 0.5 of the present application prepared in Example 3 has a pulling speed of 30 mu m / s, and the metallographic diagram of the directionally solidified high-entropy alloy is shown in the figure, wherein (a) is a solid-liquid interface structure diagram, and (b) is a steady-state structure diagram;

[0012] Figure 4 FeCoNi(AlTi) 0.5 of the present application prepared in Example 4 has a pulling speed of 50 mu m / s, and the metallographic diagram of the directionally solidified high-entropy alloy is shown in the figure, wherein (a) is a solid-liquid interface structure diagram, and (b) is a steady-state structure diagram;

[0013] Figure 5 FeCoNi(AlTi) 0.5 of the present application prepared in Example 5 has a pulling speed of 100 mu m / s, and the metallographic diagram of the directionally solidified high-entropy alloy is shown in the figure, wherein (a) is a solid-liquid interface structure diagram, and (b) is a steady-state structure diagram;

[0014] Figure 6 The directional solidified FeCoNi(AlTi) prepared in all examples 0.5 Room temperature engineering stress-strain curves of high-entropy alloys. Detailed Implementation

[0015] The embodiments described are provided to better illustrate the present invention, but are not intended to limit the scope of the invention to the embodiments described. Therefore, non-essential improvements and adjustments made to the embodiments by those skilled in the art based on the above description are still within the scope of protection of the present invention.

[0016] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. Singular expressions include plural expressions unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” “including,” are intended to indicate the presence of features, numbers, operations, components, parts, elements, materials, or combinations thereof. The terminology of the invention is disclosed in the specification and is not intended to exclude the possibility that one or more other features, numbers, operations, components, parts, elements, materials, or combinations thereof may be present or added. As used herein, “ / ” may be interpreted as “and” or “or,” depending on the context.

[0017] This invention provides a directionally solidified high-entropy alloy FeCoNi(AlTi). 0.5 Its preparation method includes: (1) preparing FeCoNi(AlTi) 0.5 (1) After converting the molar ratio of each metal in the alloy into a mass ratio, the metals are cleaned separately; (2) The cleaned metals are placed in the melting furnace according to their melting point, vacuum is drawn, argon is filled, and arc is ignited; (3) After arc ignition, the master alloy is melted, the melted master alloy is placed on the suction casting mold, the master alloy is heated, and after it is completely melted, it is cooled to obtain the master alloy rod; (4) The master alloy rod is directionally solidified, and the pulling speed of the directionally solidified is 5μm / s-100μm / s. Then the master alloy is quickly pulled into the Ga-In-Sn coolant.

[0018] It should be noted that, generally, FeCoNi(AlTi) 0.5The FeCoNi system is selected as the base alloy, and the FeCoNi alloy is a face-centered cubic structure and has excellent plasticity but low strength. The directional solidification high-entropy alloy FeCoNi(AlTi)0.5 of the application dissolves a certain content of Al and Ti elements in the FeCoNi base alloy; on the one hand, the atomic radius of Al and Ti elements is large, and the lattice distortion effect is significant after being dissolved into the base body, thus the solid solution strengthening effect is achieved; on the other hand, the mixing enthalpy between Al and Ti elements and other component elements (Fe, Co, Ni, etc.) is negative, thus Al and Ti elements are beneficial to the formation of ordered nanoparticles (such as B2, L12 and L21 ordered phases) in the high-entropy alloy, and the alloy is further strengthened through the precipitation strengthening. In addition, the directional solidification technology is used to prepare the high-entropy alloy, and the casting high-entropy alloy with directional order columnar crystal structure is obtained by controlling the solidification parameters. Since the transverse grain boundaries of the alloy are limited, the stress on the transverse grain boundaries during the tensile deformation process is greatly reduced, and thus the strength of the alloy is improved.

[0019] In some specific embodiments, the pulling speed in the above step (4) is 30 μm / s. It should be noted that when the pulling speed is 30 μm / s, the yield strength of the prepared alloy is 1020.91 MPa, the tensile strength is 1308.57 MPa, and the elongation is 15.67%; the yield strength, tensile strength and elongation of the alloy prepared by other pulling speeds are higher.

[0020] In some specific embodiments, the purity of each metal raw material in the alloy in the above step (1) is 99.9 wt.% or higher.

[0021] In some specific embodiments, in the above step (3), the titanium ingot is first melted after the arc striking, and then the master alloy is heated and melted.

[0022] In some specific embodiments, in the above step (3), the master alloy needs to be repeatedly melted for 5 times, and each time after the melting, the alloy ingot is turned over with a shovel after solidification, so that the composition of the alloy ingot is uniform.

[0023] In some specific embodiments, in the above step (3), the titanium ingot is first melted after the arc striking, and then the master alloy is heated and melted. It should be noted that the purpose of first melting the titanium ingot after the arc striking is to absorb the residual oxygen in the sample chamber, so as to prevent the alloy from being oxidized when the pure metal is melted.

[0024] In some specific embodiments, in the above step (4), the pulling distance of the directional solidification is 60 mm.

[0025] In some specific embodiments, in the above step (3), the diameter of the master alloy rod after suction casting is 8 mm, and the length is 90 mm.

[0026] In some embodiments, in step (4) above, the mother alloy is drawn into the Ga-In-Sn cooling liquid at a drawing speed of 15000 μm / s.

[0027] In some embodiments, in step (3) above, the arc melting furnace used for striking the arc can be a WK-II type non-consumable high vacuum arc furnace. It should be noted that the arc melting furnace chamber needs to be filled with argon gas before striking the arc.

[0028] In some embodiments, in step (5) above, the directional solidification is performed using a directional solidification furnace, which can be heated by a carbon tube, cooled by cooling water on the outer wall, connected to a quenching pool at the bottom, and heated and directionally solidified under argon protection.

[0029] In some embodiments, the preparation method of the directionally solidified high-entropy alloy FeCoNi(AlTi) 0.5 may include the following steps:

[0030] (I) Sample preparation: The purity of the metal raw materials is selected to be more than 99.9 wt.%, the mass of each element required for the mother alloy is calculated according to the atomic molar ratio, the electronic balance is weighed to an accuracy of four decimal places (with a positive and negative error of not more than 10 mg), and then each metal element is prepared. Small pieces of metal need to be polished with sandpaper, a file or a hand grinder to remove surface oxides, and granular or flaky metals can be cleaned with the corresponding acid solution to remove the surface oxide layer (chromic acid solution: sulfuric acid-potassium dichromate solution; manganic acid solution: 5 vol.% hydrofluoric acid-20 vol.% nitric acid-75 vol.% water); after removing the surface oxides of each metal, the metal is cleaned with alcohol ultrasonic cleaning, dried at room temperature, and the surface impurities of the metal are removed.

[0031] (II) Alloy melting: When preparing the sample, first place pure metals with a purity of more than 99.9% on the sample groove of the water-cooled copper mold in the melting furnace chamber according to the melting point, close the furnace door, vacuumize the sample chamber, first use a mechanical pump to pump to below 5 Pa, then use a molecular pump to pump to below 9 x 10 -4 Pa, fill with argon, repeat three times, and then fill with argon as a protective gas and an arc striking gas. After striking the arc, first melt the titanium ingot to absorb the residual oxygen in the furnace, then heat and melt the mother alloy. In order to ensure the uniformity of the composition, the mother alloy needs to be repeatedly melted for 5 times. Place the melted mother alloy on the suction casting mold, heat the mother alloy, open the suction valve when it is completely melted, connect the copper mold cavity to the vacuum pump, and use the pressure difference between the furnace chamber and the copper mold to quickly suck the alloy melt into the water-cooled copper mold to obtain an alloy rod with a diameter of 8 mm and a length of about 90 mm. Grind the surface oxide layer of the suction-cast mother alloy rod with sandpaper, clean it with alcohol ultrasonic cleaning, and then store it with alcohol. Then, directional solidification experiments are performed.

[0032] (III) Directional Solidification: The alloy rod prepared in step (II) is placed inside a corundum tube with an inner diameter of 8 mm and fixed to the front end of the pull rod with high-temperature adhesive to ensure the stability of the sample during the pulling process. Then, the sample and the quenching pool are slowly pushed into the directional solidification furnace cavity simultaneously and then fixed with bolts. The inert gas device valve is opened to fill the furnace with argon gas, and the temperature control power supply is turned on to slowly heat at a heating rate of 10℃ / min. After the furnace cavity temperature reaches the set temperature (1550℃), it is held for 40 min. Then, the servo motor is turned on to conduct directional solidification experiments at different pulling speeds. The pulling distance is set to 60 mm, and then the sample is rapidly pulled into the Ga-In-Sn coolant at a speed of 15000 μm / s for quenching, preserving the microstructure at the solid / liquid interface of the alloy under stable directional solidification growth.

[0033] To better understand the present invention, specific examples are provided below to further illustrate the content of the present invention, but the content of the present invention is not limited to the examples below.

[0034] In this embodiment of the invention, the directional solidification equipment used was manufactured by Shanghai University.

[0035] Example 1

[0036] (1) Sample preparation

[0037] The selected metal raw materials all have a purity of 99.9% (wt.%) or higher, and the master alloy FeCoNi(AlTi) is selected based on the atomic molar ratio. 0.5 The required mass of each element is calculated, and the electronic balance is weighed to four decimal places with a precision of plus or minus 10 mg. Then, the metal elements are prepared. Small pieces of metal need to be polished with sandpaper, files or hand grinders to remove the surface oxides. Particles or flakes of metal can be cleaned with appropriate pickling solutions to remove the surface oxide layer (chromic acid pickling solution: sulfuric acid-potassium dichromate solution; manganese acid pickling solution: 5 vol.% hydrofluoric acid-20 vol.% nitric acid-75 vol.% water). After removing the surface oxides of each metal, ultrasonic cleaning with alcohol is performed and the metal is dried at room temperature to remove impurities from the metal surface.

[0038] (2) Alloy smelting

[0039] The alloy was mainly prepared using a WK-type non-consumable vacuum melting furnace. During sample preparation, the pure metals were first placed in sample slots on a water-cooled copper mold within the furnace chamber according to their melting points. The furnace door was then closed, and the sample chamber was evacuated. First, a mechanical pump was used to evacuate the sample chamber to below 5 Pa, followed by a molecular pump to 9 × 10⁻⁶ Pa. -4After that, argon is filled in, and the process is repeated three times, and then argon is filled in as a protective gas and an arc striking gas. After striking the arc, the titanium ingot is first smelted to absorb the residual oxygen in the furnace, and then the master alloy is heated and melted. In order to ensure the uniformity of the composition, the master alloy needs to be repeatedly smelted 5 times. The smelted master alloy is placed on the suction casting mold, the master alloy is heated, and when it is completely melted, the suction casting valve is opened, the cavity of the copper mold is connected with the vacuum pump, and the pressure difference between the furnace cavity and the copper mold is used to quickly suck the alloy melt into the water-cooled copper mold, so as to obtain an alloy rod with a diameter of 8 mm and a length of about 90 mm. The surface oxide layer of the suction-cast master alloy rod is removed by sandpaper grinding, and then the alloy rod is stored in alcohol after alcohol ultrasonic cleaning, and then directional solidification is carried out.

[0040] (3) Directional solidification

[0041] Before directional solidification, the sample is placed in a corundum tube with an inner diameter of 8 mm, and is fixed at the front end of the pull rod with high-temperature glue to ensure the stability of the sample during the pulling movement. Then the sample and the quenching pool are slowly pushed into the directional solidification furnace cavity at the same time, and then are fixed by bolts. The inert protective gas device valve is opened, argon fills the furnace, the temperature control power supply is turned on, and the temperature is slowly raised at a rate of 10 ℃ / min. After the furnace cavity temperature reaches the set temperature, it is kept for 40 min, and then the directional solidification experiment is carried out at a pulling speed of 5 μm / s by opening the servo motor. The sample pulling distance is set to 60 mm, and then the sample is quickly pulled into the Ga-In-Sn cooling liquid at a speed of 15000 μm / s for quenching. The microstructure morphology at the alloy solid / liquid interface during stable growth in directional solidification is reserved.

[0042] As shown in Figure 1 , when the directional solidification pulling speed is 5 μm / s, the grains mainly grow in the form of elimination competition, the growth speed component of the crystal in the horizontal direction is large, and the cellular dendrite is easy to grow to the two sides to form side branches, which promotes the increase of the dendrite spacing. At the same time, it can be seen that the tip of the cellular dendrite is in the form of an arc, and many small bumps and pits can be observed at the tip, which indicates that the anisotropy of crystal growth begins to appear, and indicates that the solidification structure has the tendency to form dendrites.

[0043] In addition, the yield strength, tensile strength and elongation of the prepared alloy are tested, and the results are shown in Figure 6 . The yield strength of the prepared alloy is 809.42 MPa, the tensile strength is 985.56 MPa, and the elongation is 6.63%.

[0044] Example 2

[0045] The steps of the embodiment of the present application and example 1 are basically the same, except that the directional solidification pulling speed is selected to be 15 μm / s. The microstructure morphology of the prepared alloy is shown in Figure 2As shown in the figure, when the pulling speed is 15 μm / s, the alloy still maintains the cellular dendrite morphology, the two sides of the cellular dendrite appear obvious secondary dendrites, and the whole grain growth direction is inclined to the left with an angle of 3° to the pulling direction.

[0046] In addition, the yield strength, tensile strength and elongation of the prepared alloy are tested, and the results are as follows Figure 6 As shown in the figure, the yield strength of the alloy is 941.52 MPa, the tensile strength is 1096.77 MPa, and the elongation is 9.25%.

[0047] Example 3

[0048] The steps of the embodiment of the application and example 1 are basically the same, except that the directional solidification pulling speed is selected to be 30 μm / s; and the microstructure morphology of the prepared alloy is as shown in the figure Figure 3 As shown in the figure, when the pulling speed is increased to 30 μm / s, the crystal growth has anisotropy, the interface vacancy between the primary dendrites is occupied by developed secondary dendrites, and the grain growth competes in the form of dendrite tip splitting.

[0049] In addition, the yield strength, tensile strength and elongation of the prepared alloy are tested, and the results are as follows Figure 6 As shown in the figure, the yield strength of the alloy is 1020.91 MPa, the tensile strength is 1308.57 MPa, and the elongation is 15.67%.

[0050] Example 4

[0051] The steps of the embodiment of the application and example 1 are basically the same, except that the directional solidification pulling speed is selected to be 50 μm / s; and the microstructure morphology of the prepared alloy is as shown in the figure Figure 4 As shown in the figure, when the pulling speed is further increased to 50 μm / s, the grain growth also competes in the form of dendrite tip splitting, the primary axis of the dendrite is slender, the secondary dendrite axis grows competitively, and has anisotropy. The left grain of the solid-liquid interface has a larger angle with the heat flow direction, and the right grain is parallel to the heat flow direction.

[0052] In addition, the yield strength, tensile strength and elongation of the prepared alloy are tested, and the results are as follows Figure 6 As shown in the figure, the yield strength of the alloy is 963.74 MPa, the tensile strength is 1124.79 MPa, and the elongation is 10.23%.

[0053] Example 5

[0054] The steps of the embodiment of the application and example 1 are basically the same, except that the directional solidification pulling speed is selected to be 100 μm / s; and the microstructure morphology of the prepared alloy is as shown in the figure Figure 5As shown, when the pulling rate increases to 100 μm / s, tip splitting phenomenon occurs at both ends of the grain growth, and tertiary dendrites are formed on the secondary dendrite axis. Compared with the pulling rate of 50 μm / s, the primary dendrite axis is more slender, and the dendrites are smaller.

[0055] In addition, the yield strength, tensile strength and elongation of the prepared alloy are tested, and the results are shown in Table 1. Figure 6 As shown, the yield strength of the alloy is 959.56 MPa, the tensile strength is 1097.62 MPa, and the elongation is 8.02%.

[0056] Finally, it should be pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the technical solutions of the present application, and they should be covered in the scope of the claims of the present application.

Claims

1. A directionally solidified high-entropy alloy FeCoNi(AlTi) 0.5 characterized in that, The preparation method comprises the following steps: (1) cleaning each metal according to the molar ratio of each metal in the alloy; (2) placing the cleaned metals in a smelting furnace cavity according to the melting point, vacuumizing, filling argon, and leading an arc; (3) smelting a mother alloy after leading the arc, placing the smelted mother alloy on a suction casting mold, heating the mother alloy, and cooling the mother alloy after complete melting to obtain a mother alloy rod; and (4) directionally solidifying the mother alloy rod at a pulling speed of 30 μm / s, and then quickly pulling the mother alloy into a Ga-In-Sn cooling liquid. 0.5 The preparation method comprises the following steps: (1) cleaning each metal according to the molar ratio of each metal in the alloy; (2) placing the cleaned metals in a smelting furnace cavity according to the melting point, vacuumizing, filling argon, and leading an arc; (3) smelting a mother alloy after leading the arc, placing the smelted mother alloy on a suction casting mold, heating the mother alloy, and cooling the mother alloy after complete melting to obtain a mother alloy rod; and (4) directionally solidifying the mother alloy rod at a pulling speed of 30 μm / s, and then quickly pulling the mother alloy into a Ga-In-Sn cooling liquid. In step (1), the purity of each metal raw material in the alloy is more than 99.9wt.%; In step (3), the titanium ingot is first smelted after the arc is ignited, and then the master alloy is melted and heated; In step (4), the directional solidification sample drawing distance is 60mm; In step (4), the master alloy is drawn into the Ga-In-Sn cooling liquid at a drawing speed of 15000μm / s.

2. The directionally solidified high-entropy alloy FeCoNi(AlTi) of claim 1. 0.5 characterized in that In step (3), the master alloy needs to be repeatedly smelted for 5 times.

3. The directionally solidified high-entropy alloy FeCoNi(AlTi) according to claim 1 or 2 0.5 characterized in that In step (3), the diameter of the master alloy rod after suction casting is 8mm, and the length is 90mm.

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