CN113957369B - Method for regulating and controlling high-entropy alloy structure and performance by using magnetic field - Google Patents

Abstract

The invention discloses a method for regulating and controlling the structure and performance of a high-entropy alloy by using a magnetic field, which comprises the following steps: placing the high-entropy alloy block prepared by smelting in a quartz glass tube, and paving B in the quartz glass tube₂O₃The purifying agent completely coats the high-entropy alloy block; will be provided with B₂O₃And (3) placing the sample-carrying quartz glass tube of the purifying agent and the high-entropy alloy block in a uniform strong magnetic field of the excitation coil, heating, preserving heat and cooling the sample-carrying quartz glass tube, and finally quenching to obtain the high-entropy alloy melt coated with the purifying agent. According to the invention, the high-entropy alloy is coated by using the coating agent in an atmospheric environment, a strong magnetic field is acted on the treatment process, the alloy structure obtained after the CoCrFeNi high-entropy alloy is subjected to magnetic field treatment is refined compared with that obtained under the condition of no magnetic field, and the mechanical property is more excellent; meanwhile, after the AlCoCrFeNi high-entropy alloy is subjected to magnetic field treatment, the obtained alloy structure is uniformly distributed and generates orientation, so that the magnetic orientation is more excellent.

Description

A method for controlling the microstructure and properties of high-entropy alloys by using a magnetic field

technical field

The invention belongs to the technical field of high-entropy alloy material processing, and in particular relates to a method for regulating the microstructure and properties of high-entropy alloys by utilizing a magnetic field.

Background technique

Different from traditional alloy design concepts, high-entropy alloys form solid solution structures such as body-centered cubic (FCC), face-centered cubic (BCC), and hexagonal close-packed (HCP) due to their high mixing entropy. There are two forms regarding the definition of high-entropy alloys. Based on composition, high-entropy alloys are defined as alloys containing five or more main elements, each in the range of 5 to 35 atomic percent, and if If other elements are contained, the atomic percentage of these minor elements shall not exceed 5%; based on the entropy of mixing, high-entropy alloys are defined as alloys whose configuration entropy exceeds 1.5R in any state. The excellent properties of high-entropy alloys make it one of the hot spots in the field of metal materials research, with broad industrial application prospects and research value.

Among the hot high-entropy alloys currently studied, AlxCoCrFeNi high-entropy alloy is a typical good carrier for studying composition-structure-property. With the increase of Al content, the alloy transforms from single-phase FCC structure (x≤0.4) to FCC+BCC dual-phase structure (0.5≤x≤0.8), and then into single-phase BCC structure (x≥1.0). At the same time, the high-entropy alloy with single-phase FCC structure has better plasticity, and the alloy with single-phase BCC structure has better magnetic properties in this system when x=1.0 (Kao YF, Chen S K, Chen TJ, et al. Electrical, magnetic , and Hall properties of AlxCoCrFeNi high-entropyalloys [J]. Journal of Alloys and Compounds, 2011, 509:1607-1614.). At present, the mechanical properties of FCC single-phase CoCrFeNi high-entropy alloys have been improved by homogenization, hot forging, annealing and subsequent torsion processes (Huo W, Fang. F, Zhou H, Xie Z, et al. Remarkable strength of CoCrFeNi high-entropy alloys) alloywires at cryogenic and elevated temperatures [J]. Scripta Materialia, 2017, 141:125-128.). In addition, scholars can control the microstructure and magnetic properties of BCC single-phase alloy by remelting or homogenizing at 1400K for 50 hours (Uporov S, Bykov V, Pryanichnikov S, et al. Effect of synthesis route on structure and properties of AlCoCrFeNi high-entropy alloy[J] .Intermetallics, 201783:1-8.); the invention patent of Northwestern Polytechnical University "A method for regulating the structure of AlCoCrFeNi high-entropy alloy (Publication No. CN104593707A)" uses deep supercooling and rapid solidification to change the structure. Although the above methods can achieve the effect of improving the structure and properties of high-entropy alloys, the experimental period is often long and the process is complicated, and it is not easy to obtain high-strength materials with significantly refined structures and functional materials with magnetic anisotropy. The methods of its organization and performance are extremely urgent.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies in the prior art that the experiment period is long and the operation steps are many, the present invention proposes a method for regulating the microstructure and properties of a high-entropy alloy by using a magnetic field.

Strong magnetic fields will generate magnetization energy, Lorentz force and magnetization force, etc., and have strong control potential for alloys. Magnetic field treatment has the characteristics of non-contact and high purity, which can effectively achieve melt stirring, make the structure and phase distribution more uniform, and have better performance. At present, strong magnetic fields have been successfully applied to the treatment process of oriented microstructure of various materials (such as steel, superalloy, aluminum alloy, titanium alloy, etc.), some new phenomena have been gradually discovered, and the performance of materials has also been improved.

Therefore, the application team found that the treatment process of directly acting on the high-entropy alloy with a strong magnetic field has many obvious advantages compared with the traditional method: 1) The experimental period is short, and the entire treatment process is directly solidified under the glass coating, without the need for Vacuum encapsulation and complex pretreatment, and short holding time, do not require cyclic overheating or long-term aging; 2) No contact, the magnetic phase of the alloy is indirectly controlled by a magnetic field, which can make the alloy's structure distribution more uniform; 3) The effect is obvious. After the magnetic field treatment, the structure of CoCrFeNi high-entropy alloy is refined and the mechanical properties are improved; at the same time, the AlCoCrFeNi high-entropy alloy produces orientation arrangement, and the magnetic anisotropy is enhanced, thereby enhancing the structural and functional properties of the material. 4) Compared with the previous vacuum packaging + strong magnetic field solidification treatment process, the coating of molten glass can effectively avoid the heterogeneous nucleation of the tube wall during the alloy solidification process. At the same time, the experimental procedures are reduced, the tissue is more uniform, and the effect of strong magnetic field treatment is more obvious.

The present invention is specifically realized through the following technical solutions:

Provided is a method for adjusting the microstructure and properties of a high-entropy alloy by using a magnetic field, including:

The high-entropy alloy ingot prepared by smelting is placed inside the quartz glass tube, and the bottom of the quartz glass tube and the top of the sample are covered with B ₂ O ₃ purifying agent, so that the B ₂ O ₃ purifying agent can make the high entropy alloy The entropy alloy block is completely covered;

Put the sample-carrying quartz glass tube containing the B ₂ O ₃ purifying agent and the high-entropy alloy block in the uniform magnetic field of the excitation coil, and the applied magnetic field strength is 0 < the magnetic field strength of the uniform magnetic field≤ 30T; heat-insulation-cooling treatment is performed on the sample-carrying quartz glass tube, and a high-entropy alloy melt coated with a scavenger is obtained after final quenching; wherein the temperature of the heat-retaining is equal to the melting point of the high-entropy alloy block. superior.

As a further description of the present invention, the magnetic field strength of the uniform magnetic field is set to 6T.

As a further description of the present invention, the heating rate is 1-200K/min, the holding time is 2-60min, and the cooling rate is 1-500K/min.

As a further description of the present invention, the heating rate is 40K/min, the holding time is 15min, and the cooling rate is 30K/min.

As a further description of the present invention, quenching is performed by cooling to 600°C or higher.

As a further description of the present invention, the preparation process of the high-entropy alloy ingot is as follows:

Using a multi-principal master alloy with a purity of 99.95% and a high-purity element with a purity of 99.99% as raw materials, and with the atomic ratio of the target components, the raw materials are smelted by a vacuum induction melting method to obtain a high-entropy alloy ingot. The high-entropy alloy ingot is cut into high-entropy alloy blocks.

As a further description of the present invention, the vacuum induction smelting method is used to smelt the raw materials, including the following process:

First put the raw materials into a vacuum induction melting furnace, vacuumize to below 10Pa, heat to 400°C for 4-6 hours to remove water vapor, then fill the furnace body with Ar gas, and repeat this cycle for three times, and finally the furnace body is quickly The temperature is raised to 1550° C., and the temperature is maintained for 15 minutes, followed by casting in a steel mold to obtain the high-entropy alloy ingot.

As a further description of the present invention, the B ₂ O ₃ purifying agent is pre-treated powdery and bulk B ₂ O ₃ .

As a further description of the present invention, the thickness of the B ₂ O ₃ purifying agent spread on the lower surface of the high-entropy alloy block is greater than the thickness of the B ₂ O ₃ purifying agent spread on the upper surface of the high-entropy alloy block thickness.

As a further description of the present invention, the high-entropy alloy is a CoCrFeNi high-entropy alloy or an AlCoCrFeNi high-entropy alloy.

Compared with the prior art, the present invention has the following beneficial technical effects:

After the present invention performs magnetic field treatment on the existing high-entropy alloy, its performance can be optimized under the condition that the structure is obviously improved:

In the present invention, the high-entropy alloy is coated with a coating agent in an atmospheric environment, and a strong magnetic field acts on the high-entropy alloy in the treatment process, and the alloy structure obtained after the magnetic field treatment of the CoCrFeNi high-entropy alloy is refined relative to the condition without a magnetic field. , the mechanical properties are more excellent; at the same time, the alloy structure obtained by magnetic field treatment of AlCoCrFeNi high-entropy alloy is uniformly distributed and has orientation, which makes the magnetic orientation more excellent. This method is simple and easy to implement, and opens a new avenue for functionalized applications of high-entropy alloys.

Description of drawings

Fig. 1 is a schematic diagram of the device used in the high-entropy alloy strong magnetic field treatment experiment in the present invention.

Figure 2 is a picture of the microstructure of the CoCrFeNi high-entropy alloy sample without a magnetic field and after being treated with a 6T magnetic field in Example 1; in the figure: (a) 0T, parallel to the magnetic field direction; (b) 6T, parallel to the magnetic field direction ; (c) 0T, perpendicular to the direction of the magnetic field; (d) 6T, perpendicular to the direction of the magnetic field.

3 is a compressive stress-strain curve of a CoCrFeNi high-entropy alloy sample under different conditions in Example 1, wherein the strain rate is 1×10 ⁻³ s ⁻¹ .

Figure 4 is a picture of the microstructure of the AlCoCrFeNi high-entropy alloy sample without a magnetic field and after being treated with a 6T magnetic field in Example 2; in the figure: (a) 0T, parallel to the magnetic field direction; (b) 6T, parallel to the magnetic field direction ; (c) 0T, perpendicular to the direction of the magnetic field; (d) 6T, perpendicular to the direction of the magnetic field.

5 is the hysteresis loops of the AlCoCrFeNi high-entropy alloy sample parallel and perpendicular to the direction of the magnetic field after being treated with a 6T magnetic field in Example 2.

FIG. 6 is a schematic flowchart of a method for adjusting the microstructure and properties of a high-entropy alloy by using a magnetic field according to an embodiment of the present invention.

Figure 7 is a picture of the microstructure of the CoCrFeNi high-entropy alloy sample without a magnetic field and after being treated with a 10T magnetic field in Comparative Example 1; in the figure: (a) 0T, parallel to the magnetic field direction; (b) 10T, parallel to the magnetic field direction .

8 is a compressive stress-strain curve of CoCrFeNi high-entropy alloy samples under different conditions in Comparative Example 1, where the strain rate is 1×10 ^-3 s ^-1 .

Figure 9 is a picture of the microstructure of the AlCoCrFeNi high-entropy alloy sample without a magnetic field and after being treated with a 10T magnetic field in Comparative Example 2; in the figure: (a) 0T, parallel to the magnetic field direction; (b) 10T, parallel to the magnetic field direction .

Figure 10 is the hysteresis loops of the AlCoCrFeNi high-entropy alloy sample parallel and perpendicular to the magnetic field direction after being treated with a 10T magnetic field in Comparative Example 2.

In the figure: 1. Water cooler; 2. Compressor; 3. Excitation power supply; 4. Superconducting magnet; 5. Quartz tube; 6. Copper sleeve; 7. Copper end cap; 8. Insulation layer; 9. Water cooling layer; 10. Sample; 11. Heating body; 12. Tray; 13. Insulating refractory disc; 14. Thermocouple fixing plate; 15. Thermocouple; 16. Heating power source; 17. Eurotherm controller; 18. Computer; 19. Infrared probe; 20. Test tube clamp; 21. Balance.

Detailed ways

In order to more clearly understand the above objects, features and advantages of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments may be combined with each other under the condition of no conflict.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terms used herein in the description of the present invention are for the purpose of describing specific embodiments only, and are not intended to limit the present invention.

FIG. 6 is a schematic flowchart of a method for regulating the structure and properties of high-entropy alloys by using a magnetic field provided in an embodiment of the present invention. As shown in FIG. 6 , the present invention provides a method for regulating the microstructure and properties of high-entropy alloys by using a magnetic field, include:

Step 1: Place the high-entropy alloy ingot prepared by smelting inside the quartz glass tube, and coat the bottom of the quartz glass tube and the top of the sample with B ₂ O ₃ purifying agent, so that the B ₂ O ₃ purifying agent will the high-entropy alloy block is completely coated;

Step 2: Put the sample-carrying quartz glass tube containing the B ₂ O ₃ purifying agent and the high-entropy alloy block in the uniform magnetic field of the excitation coil, and the applied magnetic field strength is 0 < the uniform magnetic field. Magnetic field strength≤30T; heat-insulation-cooling treatment is performed on the sample-carrying quartz glass tube, and finally a high-entropy alloy melt coated with a purifying agent is obtained after quenching; wherein the temperature of the heat-retaining is the high-entropy alloy block above the melting point.

In step 1, the preparation process of the high-entropy alloy ingot is as follows:

Using a multi-principal master alloy with a purity of 99.95% and a high-purity element with a purity of 99.99% as raw materials, and with the atomic ratio of the target components, the raw materials are smelted by a vacuum induction melting method to obtain a high-entropy alloy ingot. The high-entropy alloy ingot is cut into high-entropy alloy blocks.

In order to ensure the purity and cleanliness of the above-mentioned raw materials, before vacuum induction melting, the following cleaning pretreatment process is required: remove the wire cutting marks, and perform ultrasonic cleaning with acetone for 10min-20min to remove the dust and oil on the surface of the master alloy, and then Place in drying oven to dry.

The above-mentioned vacuum induction smelting method is used to smelt the raw materials, including the following process:

First put the raw materials into a vacuum induction melting furnace, vacuumize to below 10Pa, heat to 400°C for 4-6 hours to remove water vapor, then fill the furnace body with Ar gas, and repeat this cycle for three times, and finally the furnace body is quickly The temperature is raised to 1550° C., and the temperature is maintained for 15 minutes, followed by casting in a steel mold to obtain the high-entropy alloy ingot. The obtained high-entropy alloy ingot is preferably a large-volume high-entropy alloy ingot of 3-20 kg.

The B ₂ O ₃ purifying agent used in step 1 is preferably treated in the following manner before use: mash the pre-treated and hardened B ₂ O ₃ into powder and then place them in sample bags respectively.

In step 1, when using B ₂ O ₃ purifying agent to completely coat the high-entropy alloy block, the following method is specifically adopted: a layer of B 2 O 3 purifying agent is spread on the inner bottom of the quartz glass tube, and the high-entropy alloy to be regulated is coated with a layer of B ₂ O ₃ purifying agent. The block is placed inside the quartz glass tube, and B ₂ O ₃ scavenger is then spread on the quartz glass tube, so that the B ₂ O ₃ scavenger completely coats the high-entropy alloy block. The thickness of the B ₂ O ₃ scavenger covered on the lower surface of the high-entropy alloy block is greater than the thickness of the B ₂ O ₃ scavenger covered on the upper surface of the high-entropy alloy block.

In step 2, the magnetic field solidification process is specifically implemented by the excitation power supply and the heating power supply. First, the quartz glass tube containing the B ₂ O ₃ purifier and the high-entropy alloy block is placed in the uniform magnetic field of the excitation coil, and the excitation coil is heated by the excitation power supply. Power on the excitation to make it reach the required magnetic field strength at the maximum uniform magnetic field: 0T-30T. The high-entropy alloy block and the B ₂ O ₃ purifying agent in the quartz glass tube are heated, kept warm and cooled according to the set procedure through the heating power supply. After final quenching, a high-entropy alloy melt coated with a scavenger is obtained.

In step 2, the heating rate when heating the high-entropy alloy block and the B ₂ O ₃ purifying agent in the quartz glass tube is 1-200 K/min, and the heating temperature is above the melting point of the high-entropy alloy block, and the temperature is kept for 2 -60min, then cooled at a cooling rate of 1-500K/min, and quenched at a temperature above 600°C to obtain a high-entropy alloy melt coated with a purifying agent.

Further, the heating rate is preferably 40K/min, the holding time is preferably 15min, and the cooling rate is preferably 30K/min.

The technical solutions of the embodiments of the present invention are implemented by a magnetic field material processing device. The technical solution of the magnetic field material processing device is disclosed in the invention with the application number of 201910364023.3. As shown in Figure 1, the device includes a water cooler 1, a compressor 2, an excitation power supply 3, a superconducting magnet 4, a quartz tube 5, a copper jacket 6, a thermal insulation layer 8, a water cooling layer 9, a heating body 11, and a thermocouple fixing plate 14 and thermocouple 14. Wherein: the water cooler 1 is connected with the compressor 2; the compressor is connected with the input end and the output end of the liquid nitrogen cooling nozzle of the superconducting magnet. The excitation power supply 3 is connected to the superconducting magnet 4 .

The lower end of the quartz tube 5 is inserted into the heating body through the copper sleeve 6; the upper end of the thermocouple 15 is inserted into the heating body through the thermocouple fixing plate 14; There is a distance of 10 to 20 mm between the upper end faces of the thermocouple. The heating body is located in the heat insulating layer 8, and there is a distance of 10-20 mm between the outer circumferential surface of the heating body and the inner circumferential surface of the heat insulating layer. The thermal insulation layer is located in the water cooling layer 9, and the outer circumferential surface of the thermal insulation layer is attached to the inner peripheral surface of the water cooling layer; the thermal insulation layer and the water cooling layer have the same length. The water-cooling layer is located in the superconducting magnet 4, and the outer circumferential surface of the water-cooling layer is attached to the inner circumferential surface of the superconducting magnet; End fit. A copper end cap 7 is placed in the inner hole at the upper end of the thermal insulation layer.

A tray 12 is fixed below the superconducting magnet 4; an insulating and refractory disc 13 is placed in a slot on the upper surface of the tray 12; the center hole of the tray is in clearance fit with the outer circumferential surface of the heating body; the The insulating refractory disc is fixed on the outer circumferential surface of the heating body through clay. And make the flange on the upper end of the copper end cover fit with the end faces of the heat preservation layer and the water cooling layer. The copper sleeve is placed on the stop at the orifice of the central hole on the upper end face of the copper end cap. The infrared probe 19, the test tube clamp 20 and the balance 21 constitute a balance magnetic susceptibility measurement system. When measuring the magnetic susceptibility of the balance, remove the copper sleeve on the quartz tube, connect the top end of the test tube clamp to the balance through a hook, and connect the bottom end of the test tube clamp to the quartz tube through nylon bolts, so that the quartz The tube is free to float. The infrared probe and the balance are connected with the computer through the wire and the conversion interface.

The casing of the heating body is provided with a through groove, and the groove width of the through groove is 7 mm; the upper end of the through groove is a spiral groove, and the lower end is a vertical groove; the top notch of the spiral groove is separated from the heating body. The upper end face is 30mm; the notch of the vertical groove penetrates the lower end face of the heating body. The ratio of the axial vertical length of the spiral groove to the axial length of the vertical groove is 1:1.5. The helix angle of the helical grooves is 25°, and the vertical distance between the centers in the width direction of adjacent helical grooves is 40 mm. The outer diameter of the small outer diameter end of the copper sleeve 6 is the same as the inner diameter of the copper end cap; four radial threaded holes are evenly distributed on the large outer diameter end, and each of the threaded holes and the copper sleeve are connected. The central hole runs through; the diameter of the central hole of the copper sleeve is the same as the outer diameter of the quartz tube, and the two are gap-fitted. After the quartz tube is inserted into the central hole of the copper sleeve, bolts are inserted into each of the threaded holes to fasten the quartz tube. The thermocouple fixing plate 14 is a triangular plate with a thermocouple via hole in the geometric center of the thermocouple fixing plate, and screw holes for connecting with the tray at three corners of the thermocouple fixing plate.

The center of the tray 12 has a mounting hole for the heating body. There is an axially protruding ring on the upper surface of the tray, and the inner diameter of the ring is the same as the outer diameter of the insulating and refractory disc. Screw holes for fixing the superconducting magnets are evenly distributed on the outer edge of the tray surface; there are triangularly distributed screw holes on the tray surface for connecting the thermocouple fixing plate. The mass range of the balance in the balance magnetic susceptibility measuring system is 650g at most; the quartz tube can accommodate a sample of Ф30mm.

The position from the upper surface of the superconducting magnet 4 to the inner cavity of the superconducting magnet with a depth of 460 mm is the position of the uniform magnetic field, where the magnetic field gradient is 0, and the uniform magnetic field strength can reach a maximum of 10T. The position 330mm down from the upper surface of the superconducting magnet is the position with the largest magnetic field gradient, and the gradient magnetic field at this position can reach up to 300T ² /m.

The following two preferred embodiments are specifically described, wherein the high-entropy alloy in Example 1 is a CoCrFeNi high-entropy alloy; the high-entropy alloy in Example 2 is an AlCoCrFeNi high-entropy alloy.

Example 1:

The high-entropy alloy described in this embodiment is CoCrFeNi, and the used magnetic field strength is 6T.

The specific process of the method for adjusting the microstructure and mechanical properties of CoCrFeNi high-entropy alloys by magnetic field treatment described in this embodiment is as follows:

Step 1, alloy preparation:

The first step is to prepare alloy raw materials. Select FeCoCr master alloy, Ni block (purity 99.95%) and high-purity Co, Cr, Fe, Ni (purity 99.99%) as raw materials, the Co, Cr, Fe, Ni are solid elemental raw materials. The ingredients were prepared with the atomic ratio of Co:Cr:Fe:Ni=1:1:1:1:1, ultrasonically cleaned with acetone for 10 min, dried with a hair dryer, and put into a sample bag for use.

The second step is alloy melting. First, the furnace body is preheated, then the raw materials are put into the crucible of the vacuum induction melting furnace, heated to 400 °C in a vacuum below 10Pa for 4 hours, and the melting chamber is filled with argon to make the furnace pressure reach 0.05MPa. Close the argon-filling valve, and repeat this cycle for three times. Under this argon condition, the furnace body is rapidly heated to 1550°C, and poured in a steel mold after holding for 15 minutes. Finally, 8kg of CoCrFeNi bulk high-entropy alloy ingot was obtained.

Step 2, purifier preparation and sample placement. The pretreated plate-shaped B ₂ O ₃ was mashed into powder and lump and placed in a sample bag. A layer of B ₂ O ₃ purifying agent is spread on the inner bottom of a quartz glass tube with an outer diameter of 18mm and an inner diameter of 15mm, and a CoCrFeNi high-entropy alloy block of Ф12mm×10mm is placed inside the quartz glass tube, and is then covered on the quartz glass tube. Purifying agent, so that the CoCrFeNi high-entropy alloy block is completely covered by the purifying agent, and finally the quartz glass tube containing the purifying agent and the CoCrFeNi high-entropy alloy block is placed in the uniform magnetic field of the excitation coil.

Step 3: Strong magnetic field solidification: The magnetic field solidification process is specifically implemented by the excitation power supply and the heating power supply. First, the quartz glass tube containing the purifying agent and the CoCrFeNi high-entropy alloy block is placed in the uniform magnetic field of the excitation coil, and the excitation power is applied to the excitation power. The coil is energized and excited to achieve the required magnetic field strength (0T and 6T) at the maximum uniform magnetic field. Through the heating power supply, the CoCrFeNi high-entropy alloy block and the purifying agent in the quartz glass tube are heated, kept warm, cooled and cooled according to the set procedure. Heating at a heating rate of 40K/min above the melting point of the CoCrFeNi high-entropy alloy block, ie, 1470°C. After holding for 15 minutes, it was cooled at a cooling rate of 30 K/min, and then quenched at 900 °C to obtain a CoCrFeNi high-entropy alloy melt coated with a purifying agent.

Using wire cutting, the magnetic field treated CoCrFeNi high-entropy alloy sample was cut into 1mm thin slices along the direction parallel to the magnetic field to observe the microstructure. At the same time, a Ф3mm×6mm cylinder was cut out. The testing machine was used for room temperature compressive performance testing with a strain rate of 1×10 ^-3 s ^-1 . The test results are:

The microstructures of CoCrFeNi high-entropy alloys treated with and without magnetic field are shown in Fig. 2, and the grains in the direction parallel to and perpendicular to the magnetic field were obtained with a 6T magnetic field (Fig. 2b, d) compared with no magnetic field (Fig. 2a, c). According to statistics, the grain size decreased from 42 μm without magnetic field to 3.6 μm after applying 6T magnetic field.

Figure 3 shows the compressive stress-strain curves of CoCrFeNi high-entropy alloys under different conditions. Compared with the no-magnetic field condition, the compressive yield strength in the direction parallel to the magnetic field increased from 315MPa to 546MPa, and increased by 400MPa relative to the as-cast state. In the present invention, a strong magnetic field acts on the solidification process of the CoCrFeNi high-entropy alloy, so that the structure of the alloy is refined and the mechanical properties are more excellent than those under the condition of no magnetic field.

Comparative Example 1: Step 2 of Example 1 was replaced with vacuum packaging: the CoCrFeNi high-entropy alloy block of Ф12mm×10mm was put into a quartz glass tube for vacuum packaging, and the vacuum degree was 8×10 ^-3 Pa; The quartz glass tube of the scavenger and the CoCrFeNi high-entropy alloy ingot is replaced by a quartz glass tube with a vacuum-sealed CoCrFeNi high-entropy alloy ingot; The required magnetic field strengths (0T and 10T) are achieved at the maximum uniform magnetic field; the rest of the steps and the setting of process parameters are the same as those in Example 1.

Figure 7 is a picture of the microstructure of the CoCrFeNi high-entropy alloy sample without a magnetic field and after being treated with a 10T magnetic field in Comparative Example 1; in the figure: (a) 0T, parallel to the magnetic field direction; (b) 10T, parallel to the magnetic field direction ; The results show that the application of a magnetic field in the process of vacuum packaging has no significant changes to its tissue.

8 is the compressive stress-strain curve of the CoCrFeNi high-entropy alloy sample under different conditions in Comparative Example 1, where the strain rate is 1×10 ^-3 s ^-1 . The yield strength under the condition of no magnetic field is 137MPa, and the yield strength after applying a 10T magnetic field is 121MPa. The results show that the application of a magnetic field in the process of vacuum packaging has no significant change in its mechanical properties.

Example 2:

The high-entropy alloy described in this embodiment is AlCoCrFeNi, and the used magnetic field strength is 6T.

The specific process of the method for adjusting the microstructure and magnetic properties of AlCoCrFeNi high-entropy alloys by magnetic field treatment described in this embodiment is as follows:

Step 1, alloy preparation:

The first step is to prepare alloy raw materials. Select FeCoCr, Ni ₂ Al master alloy (purity 99.95%) and high-purity Al, Co, Cr, Fe, Ni (purity 99.99%) as raw materials, the Al, Co, Cr, Fe, Ni are solid elemental raw materials . Al:Co:Cr:Fe:Ni=1:1:1:1:1 atomic ratio of ingredients, mechanical grinding to remove line cutting marks, ultrasonic cleaning with acetone for 10min, and drying in a drying oven.

The second step is alloy melting. First, the furnace body is preheated, then the raw materials are put into the crucible of the vacuum induction melting furnace, heated to 400 °C in a vacuum below 10Pa for 4 hours, and the melting chamber is filled with argon to make the furnace pressure reach 0.05MPa. Close the argon-filling valve, and repeat this cycle for three times. Under this argon condition, the furnace body is rapidly heated to 1550°C, and poured in a steel mold after holding for 15 minutes. Finally, 7kg of AlCoCrFeNi bulk high-entropy alloy ingot was obtained.

Step 2, purifier preparation and sample placement. The pretreated plate-shaped B ₂ O ₃ was mashed into powder and lump and placed in a sample bag. A layer of B ₂ O ₃ purifying agent is spread on the inner bottom of a quartz glass tube with an outer diameter of 18mm and an inner diameter of 15mm, and an AlCoCrFeNi high-entropy alloy block of Ф12mm×10mm is placed inside the quartz glass tube, and is then covered on the quartz glass tube. Purifying agent, so that the purifying agent completely coats the AlCoCrFeNi high-entropy alloy block, and finally the quartz glass tube containing the purifying agent and the AlCoCrFeNi high-entropy alloy block is placed in the uniform magnetic field of the excitation coil.

The third step is solidification with a strong magnetic field. The magnetic field solidification process is specifically implemented by the excitation power supply and the heating power supply. First, the quartz glass tube containing the purifying agent and the AlCoCrFeNi high-entropy alloy block is placed in the uniform magnetic field of the excitation coil, and the excitation coil is energized and excited through the excitation power supply to make it maximum The desired magnetic field strength (0T and 6T) is achieved at a uniform magnetic field. Through the heating power supply, the AlCoCrFeNi high-entropy alloy block and the purifying agent in the quartz glass tube are heated, kept warm, cooled and cooled according to the set procedure. Heating at a heating rate of 40K/min above the melting point of the AlCoCrFeNi high-entropy alloy block, that is, 1420°C. After holding for 15 minutes, it was cooled at a cooling rate of 30 K/min, and then quenched at 900 °C to obtain an AlCoCrFeNi high-entropy alloy melt coated with a purifying agent.

Using wire cutting, the magnetic field-treated AlCoCrFeNi high-entropy alloy samples were cut into 1mm thin slices along the direction parallel to the magnetic field for observing the microstructure, and a Ф3mm×3mm cylinder was cut for magnetic property testing. The test results are:

The microstructures of AlCoCrFeNi high-entropy alloys treated with no magnetic field and 6T magnetic field are shown in Fig. 4. Compared with no magnetic field (Fig. 4a), the oriented structure perpendicular to the magnetic field direction appears in the direction parallel to the magnetic field (Fig. 4b). , however, no oriented organization appeared in both the applied 6T magnetic field (Fig. 4d) and no magnetic field (Fig. 4c) conditions perpendicular to the magnetic field direction.

Figure 5 shows the magnetization curves of the AlCoCrFeNi high-entropy alloy sample parallel and perpendicular to the magnetic field direction after being treated with a 6T magnetic field. Due to the formation of oriented microstructure, the treated sample shows obvious magnetic anisotropy, and the saturation parallel to the magnetic field direction The magnetization rate is significantly higher than the saturation magnetization rate perpendicular to the direction of the magnetic field, which improves the functional properties of AlCoCrFeNi high-entropy alloys.

Comparative Example 2: Step 2 of Example 2 was replaced with vacuum packaging: the AlCoCrFeNi high-entropy alloy block of Ф12mm×10mm was put into a quartz glass tube for vacuum packaging, and the vacuum degree was 8×10 ^-3 Pa; The quartz glass tube of the scavenger and the AlCoCrFeNi high-entropy alloy ingot is replaced by a quartz glass tube with a vacuum-sealed AlCoCrFeNi high-entropy alloy ingot; and the required magnetic field strength (0T and 6T) at the maximum uniform magnetic field is replaced by a The required magnetic field strength (0T and 10T) is achieved at the maximum uniform magnetic field; the rest of the steps and the setting of process parameters are the same as those in Example 2.

Figure 9 is a picture of the microstructure of the AlCoCrFeNi high-entropy alloy sample without a magnetic field and after being treated with a 10T magnetic field in Comparative Example 2; in the figure: (a) 0T, parallel to the magnetic field direction; (b) 10T, parallel to the magnetic field direction . The results show that the application of magnetic field in the process of vacuum encapsulation has no obvious change to its tissue.

Figure 10 shows the hysteresis loops of the AlCoCrFeNi high-entropy alloy sample prepared by the vacuum packaging + 10T strong magnetic field treatment process in Comparative Example 2, parallel to and perpendicular to the direction of the magnetic field. It exhibits no magnetic orientation in the axial and radial directions.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be Modifications or equivalent substitutions can be made without departing from the spirit and scope of the technical solutions of the present invention.

Claims (8)

1. A method for regulating and controlling the structure and the performance of a high-entropy alloy by using a magnetic field is characterized by comprising the following steps:

placing the high-entropy alloy block prepared by smelting in a quartz glass tube, and paving B on the bottom of the quartz glass tube and the top of a sample₂O₃A purifying agent, the purifying agent₂O₃The purifying agent completely coats the high-entropy alloy block;

will be provided with the B₂O₃A purifying agent and the sample-carrying quartz glass tube of the high-entropy alloy block are placed in a uniform magnetic field of the excitation coil, and the applied magnetic field intensity is 6T; and heating, preserving heat and cooling the sample-carrying quartz glass tube, wherein the temperature of the heat preservation is higher than the melting point of the high-entropy alloy block, and finally quenching to obtain the high-entropy alloy melt coated with the purifying agent.

2. The method for regulating and controlling the structure and the performance of the high-entropy alloy by using the magnetic field as claimed in claim 1, wherein the heating rate is 40K/min, the heat preservation time is 15min, and the cooling rate is 30K/min.

3. The method for regulating and controlling the structure and the performance of the high-entropy alloy by using the magnetic field as claimed in claim 1, wherein the high-entropy alloy is quenched by cooling to a temperature of 600 ℃ or higher.

4. The method for regulating and controlling the structure and the performance of the high-entropy alloy by using the magnetic field as claimed in claim 1, wherein the high-entropy alloy block is prepared by the following steps:

the method comprises the steps of taking a multi-principal-element intermediate alloy with the purity of 99.95% and a high-purity simple substance with the purity of 99.99% as raw materials, mixing the raw materials according to the atomic ratio of target components, smelting the raw materials by adopting a vacuum induction smelting method to obtain a high-entropy alloy ingot, and then cutting the high-entropy alloy ingot into high-entropy alloy blocks.

5. The method for regulating and controlling the structure and the performance of the high-entropy alloy by using the magnetic field as claimed in claim 4, wherein the smelting of the raw materials by using a vacuum induction smelting method comprises the following steps:

firstly, putting the raw materials into a vacuum induction melting furnace, vacuumizing to below 10Pa, heating to 400 ℃, preserving heat for 4-6 hours to remove water vapor, then filling the furnace body with Ar gas, circulating for three times, finally, quickly heating the furnace body to 1550 ℃, preserving heat for 15 minutes, and then pouring in a steel die to obtain the high-entropy alloy ingot.

6. A method for regulating and controlling high-entropy alloy structure and performance by using magnetic field according to claim 1, wherein B is₂O₃The cleaning agent is pretreated powder or block B₂O₃。

7. A method for regulating and controlling high-entropy alloy structure and performance by using a magnetic field according to claim 1, wherein the B is laid on the lower surface of the high-entropy alloy block₂O₃The purifying agent has a thickness larger than that of the B paved on the upper surface of the high-entropy alloy block₂O₃The thickness of the scavenger.

8. The method for regulating and controlling the structure and the performance of the high-entropy alloy by using the magnetic field according to claim 1, wherein the high-entropy alloy is CoCrFeNi high-entropy alloy or AlCoCrFeNi high-entropy alloy.

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