CN113957369B - Method for regulating and controlling high-entropy alloy structure and performance by using magnetic field - Google Patents
Method for regulating and controlling high-entropy alloy structure and performance by using magnetic field Download PDFInfo
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- CN113957369B CN113957369B CN202111266040.7A CN202111266040A CN113957369B CN 113957369 B CN113957369 B CN 113957369B CN 202111266040 A CN202111266040 A CN 202111266040A CN 113957369 B CN113957369 B CN 113957369B
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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
Technical Field
The invention belongs to the technical field of high-entropy alloy material treatment, and particularly relates to a method for regulating and controlling the structure and performance of a high-entropy alloy by using a magnetic field.
Background
Different from the traditional alloy design concept, the high-entropy alloy is promoted to form solid solution structures such as body-centered cubic (FCC), face-centered cubic (BCC) and close-packed Hexagonal (HCP) by the high mixing entropy of the high-entropy alloy. There are two forms of definition of the high-entropy alloy, and the high-entropy alloy is defined as an alloy containing five or more major elements each in the range of 5 to 35 atomic% on the basis of the composition, and further, if other elements are contained, these minor elements should not exceed 5 atomic%; the high-entropy alloy is defined as an alloy with a metamorphic entropy exceeding 1.5R in any state when the mixed entropy is taken as the basis. The high-entropy alloy has excellent performance, so that the high-entropy alloy becomes one of hot spots in the field of metal material research, and has wide industrial application prospects and research values.
Among the hot high-entropy alloys studied at present, the AlxCoCrFeNi high-entropy alloy is a typical good carrier for studying composition-structure-performance. With the increase of Al content, the alloy is changed into a FCC + BCC two-phase structure (x is more than or equal to 0.5 and less than or equal to 0.8) from a single-phase FCC structure (x is less than or equal to 0.4) and then changed into a single-phase BCC structure (x is more than or equal to 1.0). Meanwhile, the single-phase FCC structure alloy has better plasticity, and when x is 1.0, the single-phase BCC structure alloy has better magnetic performance in the system (Kao YF, Chen S K, Chen T J, et al, electric, magnetic, and Hall properties of AlxCoCrFeNi high-entry alloys [ J ]. Journal of alloys and composites, 2011,509: 1607-. At present, the mechanical properties of FCC single-phase CoCrFeNi high-entropy alloy are improved by homogenization, hot forging, annealing and subsequent twisting processes (Huo W, Fang. F, Zhou H, Xie Z, et al. Remarkable strip th of CoCrFeNi high-entry alloy with high temperature and improved temperature [ J ]. Scripta material, 2017,141: 125-. Furthermore, the students can regulate the structure and magnetic properties of BCC single-phase alloy after remelting or 1400K homogenization for 50 hours (Uport S, Bykov V, Pryanechnikov S, et al. Effect of synthesis route on structure and properties of AlCoCrFeNi high-entry alloy [ J ]. Intermetallics,201783: 1-8.); in the invention patent of AlCoCrFeNi high entropy alloy tissue regulation and control (publication No. CN104593707A) of northwest industry university, deep supercooling rapid solidification is used to change the tissue morphology. Although the effect of improving the structure and the performance of the high-entropy alloy can be achieved by the method, the experimental period is long, the process is complex, a high-strength material with obviously refined structure and a functional material with magnetic anisotropy are not easy to obtain, and the method for quickly and simply improving the structure and the performance is urgent to find.
Disclosure of Invention
In order to overcome the defects of long experimental period and more operation steps in the prior art, the invention provides a method for regulating and controlling the structure and the performance of a high-entropy alloy by using a magnetic field.
The strong magnetic field can generate magnetic energy, Lorentz force, magnetic force and the like to the material, and the alloy has strong regulation and control potential. The magnetic field treatment has the characteristics of no contact and high purity, so that melt stirring can be effectively realized, the tissue and phase distribution is more uniform, and the performance is more excellent. At present, the strong magnetic field is successfully applied to the treatment process of the orientation structure of various materials (such as steel, high-temperature alloy, aluminum alloy, titanium alloy and the like), some new phenomena are gradually discovered, and the performance of the materials is improved.
Therefore, the team of the application finds that the treatment process of directly acting a strong magnetic field on the high-entropy alloy has a plurality of obvious advantages compared with the traditional mode: 1) the experimental period is short, the whole treatment process is directly solidified under the glass coating, vacuum packaging and complex pre-treatment are not needed, meanwhile, the heat preservation time is short, and cyclic overheating or long-term aging is not needed; 2) the magnetic phase of the alloy is indirectly regulated and controlled through a magnetic field, so that the structure distribution of the alloy is more uniform; 3) the effect is obvious, the structure of the CoCrFeNi high-entropy alloy is refined and the mechanical property is improved after the magnetic field treatment; meanwhile, the AlCoCrFeNi high-entropy alloy generates orientation arrangement, and the magnetic anisotropy is enhanced, so that the structure and functional characteristics of the material are enhanced, and the material has a remarkable engineering application value; 4) compared with the prior vacuum packaging and high-intensity magnetic field solidification treatment process, heterogeneous nucleation on the tube wall in the alloy solidification process can be effectively avoided through cladding of molten glass. Meanwhile, the experimental procedures are reduced, so that the tissue is more uniform, and the effect of high-intensity magnetic field treatment is more obvious.
The invention is realized by the following technical scheme:
the method for regulating and controlling the structure and the performance of the high-entropy alloy by using the magnetic field comprises 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 B2O3The purifying agent completely coats the high-entropy alloy block;
will be provided with the B2O3The 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 more than 0 and less than or equal to 30T; heating, preserving heat and cooling the sample-carrying quartz glass tube, and finally quenching to obtain a high-entropy alloy melt coated with a purifying agent; wherein the heat preservation temperature is above the melting point of the high-entropy alloy block.
As a further explanation of the present invention, the magnetic field strength of the shim magnetic field is set to 6T.
As a further illustration of the invention, the heating rate is 1-200K/min, the heat preservation time is 2-60min, and the cooling rate is 1-500K/min.
As a further illustration of the invention, the heating rate is 40K/min, the holding time is 15min, and the cooling rate is 30K/min.
As a further explanation of the present invention, the quenching is carried out after the cooling treatment to 600 ℃ or higher.
As further illustration of the invention, the preparation process of the high-entropy alloy block is as follows:
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.
As a further explanation of the present invention, the smelting of the raw materials by using the vacuum induction smelting method comprises the following processes:
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.
As a further illustration of the invention, said B2O3The cleaning agent is pretreated powder or block B2O3。
As a further description of the invention, 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.
As a further illustration of the invention, the high-entropy alloy is a CoCrFeNi high-entropy alloy or an AlCoCrFeNi high-entropy alloy.
Compared with the prior art, the invention has the following beneficial technical effects:
after the magnetic field treatment is carried out on the existing high-entropy alloy, the performance of the alloy can be optimized under the condition of obviously improving the structure:
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. The method is simple and feasible, and opens up a new way for the functional application of the high-entropy alloy.
Drawings
FIG. 1 is a schematic diagram of the apparatus used in the high-entropy alloy high-intensity magnetic field treatment experiment of the present invention.
FIG. 2 is a picture of the texture of a CoCrFeNi high-entropy alloy sample in example 1 under no magnetic field and after 6T magnetic field treatment; in the figure: (a)0T, parallel to the magnetic field direction; (b)6T, parallel to the magnetic field direction; (c)0T, perpendicular to the magnetic field direction; (d)6T, perpendicular to the magnetic field direction.
FIG. 3 is a compressive stress-strain curve of CoCrFeNi high entropy alloy sample under different conditions in example 1, wherein the strain rate is 1X 10-3s-1。
FIG. 4 is a picture of the morphology of the AlCoCrFeNi high-entropy alloy sample in the absence of a magnetic field and after 6T magnetic field treatment 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 magnetic field direction; (d)6T, perpendicular to the magnetic field direction.
FIG. 5 is the hysteresis loops parallel and perpendicular to the magnetic field direction of AlCoCrFeNi high-entropy alloy samples after 6T magnetic field treatment in example 2.
FIG. 6 is a simplified flowchart of a method for controlling the structure and properties of a high-entropy alloy by using a magnetic field according to an embodiment of the present invention.
FIG. 7 is a picture of the texture of CoCrFeNi high-entropy alloy samples in comparative example 1 under no magnetic field and after 10T magnetic field treatment; in the figure: (a)0T, parallel to the magnetic field direction; (b)10T, parallel to the magnetic field direction.
FIG. 8 is a compressive stress-strain curve of CoCrFeNi high entropy alloy sample under different conditions in comparative example 1, wherein the strain rate is 1X 10-3s-1。
FIG. 9 is a photograph showing the morphology of the AlCoCrFeNi high-entropy alloy sample in comparative example 2 in the absence of a magnetic field and after being subjected to a 10T magnetic field; in the figure: (a)0T, parallel to the magnetic field direction; (b)10T, parallel to the magnetic field direction.
FIG. 10 is the hysteresis loop parallel and perpendicular to the magnetic field direction of the AlCoCrFeNi high-entropy alloy sample after the 10T magnetic field treatment in comparative example 2.
In the figure: 1. a water cooling machine; 2. a compressor; 3. an excitation power supply; 4. a superconducting magnet; 5. a quartz tube; 6. a copper sleeve; 7. a copper end cap; 8. a heat-insulating layer; 9. a water-cooling layer; 10. a sample; 11. a heating body; 12. a tray; 13. an insulating refractory disc; 14. a thermocouple fixing plate; 15. a thermocouple; 16. a heating power supply; 17. an continental controller; 18. a computer; 19. an infrared probe; 20. a test tube clamp; 21. a balance.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a detailed description of the present invention will be given below with reference to the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and features of the embodiments may be combined with each other without conflict.
Unless defined otherwise, 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 terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
Fig. 6 is a simplified flow chart of a method for regulating the structure and performance of a high-entropy alloy by using a magnetic field according to an embodiment of the present invention, and as shown in fig. 6, the present invention provides a method for regulating the structure and performance of a high-entropy alloy by using a magnetic field, including:
step 1: 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 B2O3The purifying agent completely coats the high-entropy alloy block;
and 2, step: will be provided with the B2O3The 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 more than 0 and less than or equal to 30T; heating, preserving heat and cooling the sample-carrying quartz glass tube, and finally quenching to obtain a high-entropy alloy melt coated with a purifying agent; wherein the temperature of the heat preservation is above the melting point of the high-entropy alloy block.
In the step 1, the preparation process of the high-entropy alloy block is as follows:
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.
In order to ensure the purity and cleanliness of the raw materials, the following cleaning pretreatment processes are carried out before vacuum induction melting: removing the line cutting mark, performing ultrasonic cleaning with acetone for 10min-20min, removing dust and oil stain on the surface of the intermediate alloy, and drying in a drying oven.
The raw materials are smelted by adopting a vacuum induction smelting method, and the 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. The high-entropy alloy ingot is preferably a large-volume high-entropy alloy ingot of 3-20 kg.
B used in step 12O3The scavenger is preferably treated before use in the following manner: hardening the pretreated B2O3Crushed into powder and then respectively placed in sample bags.
Use of B in step 12O3When the purifying agent is used for completely coating the high-entropy alloy block, the following method is specifically adopted: a layer B is laid on the inner bottom of the quartz glass tube2O3A purifying agent, namely placing the high-entropy alloy block to be regulated in a quartz glass tube, and paving B on the quartz glass tube2O3A purifying agent, the B2O3The purifying agent completely coats the high-entropy alloy block. The B is paved 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.
The magnetic field solidification process in the step 2 is implemented by an excitation power supply and a heating power supply, and B is firstly arranged2O3The purifying agent and the quartz glass tube of the high-entropy alloy block are placed in a uniform magnetic field of the excitation coil, and the excitation power supply is used for electrifying and exciting the excitation coil to ensure that the maximum uniform magnetic field reaches the required magnetic field intensity: 0T-30T. Heating the high-entropy alloy blocks and B in the quartz glass tube by a heating power supply according to a set program2O3Heating the purifying agent, preserving heat and cooling. Finally, the high-entropy alloy melt coated with the purifying agent is obtained after quenching.
Further, the heating rate is preferably 40K/min, the holding time is preferably 15min, and the cooling rate is preferably 30K/min.
The technical scheme of each embodiment of the invention is implemented by a magnetic field material processing device. The technical scheme of the magnetic field material processing device is disclosed in the invention with the application number of 201910364023.3. As shown in fig. 1, the device comprises a water cooling machine 1, a compressor 2, an excitation power supply 3, a superconducting magnet 4, a quartz tube 5, a copper sleeve 6, a heat insulation layer 8, a water cooling layer 9, a heating body 11, a thermocouple fixing plate 14 and a 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 a liquid nitrogen cooling pipe orifice of the superconducting magnet. The excitation power supply 3 is connected to the superconducting magnet 4.
The lower end of the quartz tube 5 penetrates through the copper sleeve 6 and is arranged in the heating body; the upper end of the thermocouple 15 penetrates through the thermocouple fixing plate 14 and is arranged in the heating body; and a distance of 10-20 mm is formed between the lower end face of the quartz tube and the upper end face of the thermocouple. The heating body is positioned in the heat preservation layer 8, and a distance of 10-20 mm is formed between the outer circumferential surface of the heating body and the inner circumferential surface of the heat preservation layer. The heat-insulating layer is positioned in the water-cooling layer 9, and the outer circumferential surface of the heat-insulating layer is attached to the inner circumferential surface of the water-cooling layer; the heat-insulating layer and the water-cooling layer are the same in length. The water-cooling layer is positioned 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; the lower end face of the positioning boss at the upper end of the water cooling layer is attached to the upper end face of the superconducting magnet. A copper end cover 7 is arranged in an inner hole at the upper end of the heat-insulating layer.
A tray 12 is fixed below the superconducting magnet 4; the insulating fireproof disc 13 is arranged in a clamping groove on the upper surface of the tray 12; the central hole of the tray is in clearance fit with the outer circumferential surface of the heating body; the insulating fire-resistant disc is fixedly connected to the outer circumferential surface of the heating body through clay. And the flange at the upper end of the copper end cover is attached to the end faces of the heat-insulating layer and the water-cooling layer. The copper sleeve is arranged on the spigot at the hole of the central hole on the upper end surface of the copper end cover. The infrared probe 19, the test tube clamp 20 and the balance 21 form a balance magnetic susceptibility measuring system. When the balance magnetic susceptibility is measured, the copper sleeve on the quartz tube is removed, the top end of the test tube clamp is connected with the balance through the hook, and the bottom end of the test tube clamp is connected with the quartz tube through the nylon bolt, so that the quartz tube is freely suspended. The infrared probe and the balance are connected with a computer through a lead and a conversion interface.
A through groove is formed in the shell of the heating body, and the width of the through groove is 7 mm; the upper end of the through groove is a spiral groove, and the lower end of the through groove is a vertical groove; the distance between the notch at the top end of the spiral groove and the upper end surface of the heating body is 30 mm; the notch of the vertical groove penetrates through 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 spiral angle of the spiral groove is 25 degrees, and the vertical distance between the center distances of the adjacent spiral grooves in the width direction is 40 mm. The outer diameter of the small outer diameter end of the copper bush 6 is the same as the inner diameter of the copper end cover; four radial threaded holes are uniformly distributed on the large outer diameter end, and each threaded hole is communicated with the central hole of the copper sleeve; the aperture of the central hole of the copper sleeve is the same as the outer diameter of the quartz tube, and the copper sleeve and the quartz tube are in clearance fit. After the quartz tube is arranged in the central hole of the copper sleeve, bolts are arranged in the threaded holes to fasten the quartz tube. The thermocouple fixing plate 14 is a triangular plate, a thermocouple through hole is formed in the geometric center of the thermocouple fixing plate, and screw holes for connecting the tray are formed in three corners of the thermocouple fixing plate.
The center of the tray 12 is provided with a mounting hole of a heating body. The upper surface of the tray is provided with an axially protruding ring, and the inner diameter of the ring is the same as the outer diameter of the insulating refractory disc. Screw holes for fixedly connecting with the superconducting magnet are uniformly distributed on the outer edge of the tray surface; the tray surface is provided with screw holes distributed in a triangular shape and used for connecting the thermocouple fixing plate. The mass measuring range of the balance in the balance magnetic susceptibility measuring system is 650g at most; the quartz tube can accommodate a specimen of phi 30 mm.
The position from the upper surface of the superconducting magnet 4 to the 460mm deep hole of the inner cavity of the superconducting magnet is the position of a uniform magnetic field, the gradient of the magnetic field at the position is 0, and the strength of the uniform magnetic field can reach 10T at most. The position 330mm down from the upper surface of the superconducting magnet is the position with the maximum magnetic field gradient, and the gradient magnetic field at the position can reach 300T at most2/m。
Two preferable examples are specifically described below, wherein the high-entropy alloy in example 1 is a CoCrFeNi high-entropy alloy; the high-entropy alloy in the embodiment 2 is AlCoCrFeNi high-entropy alloy.
Example 1:
the high-entropy alloy described in this embodiment is CoCrFeNi, and the magnetic field strength used is 6T.
The method for regulating and controlling the structure and the mechanical property of the CoCrFeNi high-entropy alloy by utilizing the magnetic field treatment comprises the following specific processes:
step one, preparing an alloy:
firstly, preparing alloy raw materials. Selecting FeCoCr intermediate alloy, Ni blocks (with the purity of 99.95%) and high-purity Co, Cr, Fe and Ni (with the purity of 99.99%) as raw materials, wherein the Co, Cr, Fe and Ni are solid elementary raw materials. The materials are mixed according to the atomic ratio of Co, Cr, Fe and Ni being 1:1:1:1:1, ultrasonic cleaning is carried out for 10min by acetone, then drying is carried out by a blower, and the mixture is put into a sample bag for standby.
And secondly, smelting the alloy. Preheating a furnace body, then putting the raw materials into a crucible of a vacuum induction melting furnace, heating to 400 ℃ in vacuum below 10Pa, preserving heat for 4 hours, filling argon into the melting chamber, closing an argon filling valve after the pressure in the furnace reaches 0.05MPa, circulating the steps for three times, quickly heating the furnace body to 1550 ℃ under the argon condition, preserving heat for 15 minutes, and then pouring in a steel die. Finally obtaining 8kg of CoCrFeNi large-volume high-entropy alloy cast ingot.
And step two, preparing a purifying agent and placing a sample. Pre-treated plate-shaped B2O3Crushed into powder and blocks and then placed in a sample bag. A layer B is laid on the inner bottom of the quartz glass tube with the outer diameter of 18mm and the inner diameter of 15mm2O3The purifying agent is characterized in that a CoCrFeNi high-entropy alloy block with the diameter of 12mm multiplied by 10mm is placed in a quartz glass tube, the purifying agent is paved on the quartz glass tube, the CoCrFeNi high-entropy alloy block is completely coated by the purifying agent, and finally the quartz glass tube filled with the purifying agent and the CoCrFeNi high-entropy alloy block is placed in a uniform strong magnetic field of an excitation coil.
Step three, high-intensity magnetic field solidification: the magnetic field solidification process is implemented by an excitation power supply and a heating power supply, a quartz glass tube filled with a purifying agent and a CoCrFeNi high-entropy alloy block is placed in a uniform magnetic field of an excitation coil, and the excitation coil is electrified and excited by the excitation power supply, so that the maximum uniform magnetic field reaches the required magnetic field intensity (0T and 6T). Heating the CoCrFeNi high-entropy alloy block and the purifying agent in the quartz glass tube by a heating power supply according to a set program, preserving heat, cooling and cooling. Heating to a temperature above the melting point of the CoCrFeNi high-entropy alloy block at a heating rate of 40K/min, namely 1470 ℃. And cooling at a cooling speed of 30K/min after heat preservation for 15min, and quenching at 900 ℃ to obtain the CoCrFeNi high-entropy alloy melt coated with the purifying agent.
Cutting a 1mm slice of a CoCrFeNi high-entropy alloy sample subjected to magnetic field treatment along a direction parallel to a magnetic field by using linear cutting for observing a microstructure, simultaneously cutting a cylinder with the diameter of 3mm multiplied by 6mm, and carrying out room temperature compression performance test by adopting a CMT5025 electronic universal mechanical testing machine produced by American national standards, wherein the strain rate is 1 multiplied by 10-3s-1. The test results are as follows:
the microstructure of the CoCrFeNi high-entropy alloy after being processed by the non-magnetic field and the magnetic field is shown in figure 2, the grains are thinned in the directions parallel to and perpendicular to the magnetic field when the 6T magnetic field (figure 2b, d) is applied relative to the non-magnetic field (figure 2a, c), and the grain size is statistically reduced from 42 mu m of the non-magnetic field to 3.6 mu m after the 6T magnetic field is applied.
FIG. 3 is a compressive stress-strain curve of the CoCrFeNi high-entropy alloy under different conditions, the compressive yield strength of the applied 6T magnetic field in a direction parallel to the magnetic field is improved from 315MPa to 546MPa relative to the non-magnetic field, and the compressive yield strength is improved by 400MPa relative to an as-cast state. According to the 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 compared with that of the alloy under the condition of no magnetic field, and the mechanical property is more excellent.
Comparative example 1: step two of example 1 was replaced with vacuum packaging: placing CoCrFeNi high-entropy alloy block with the diameter of 12mm multiplied by 10mm into a quartz glass tube for vacuum packaging, wherein the vacuum degree is 8 multiplied by 10-3Pa; replacing the quartz glass tube filled with the purifying agent and the CoCrFeNi high-entropy alloy block in the third step with the quartz glass tube vacuum-packaged with the CoCrFeNi high-entropy alloy block; replacing the magnetic field intensity (0T and 6T) required by the maximum uniform magnetic field with the magnetic field intensity (0T and 10T) required by the maximum uniform magnetic field; the rest of the steps and the setting of the process parameters are the same as in example 1.
FIG. 7 is a picture of the structure morphology of CoCrFeNi high-entropy alloy samples in comparative example 1 under no magnetic field and after 10T magnetic field treatment; in the figure: (a)0T, parallel to the magnetic field direction; (b)10T, parallel to the magnetic field direction; the results demonstrate that the magnetic field applied during the vacuum encapsulation process has no significant change to the structure.
FIG. 8 is a compressive stress-strain curve of CoCrFeNi high entropy alloy sample under different conditions in comparative example 1, wherein the strain rate is 1X 10-3s-1. The yield strength is 137MPa under the condition of no magnetic field, and the yield strength is 121MPa after the magnetic field of 10T is applied.
Example 2:
the high-entropy alloy in the embodiment is AlCoCrFeNi, and the adopted magnetic field intensity is 6T.
The method for regulating the AlCoCrFeNi high-entropy alloy structure and the magnetic property by using the magnetic field treatment comprises the following specific processes:
step one, preparing an alloy:
firstly, preparing alloy raw materials. Selecting FeCoCr, Ni2Al intermediate alloy (with the purity of 99.95%) and high-purity Al, Co, Cr, Fe and Ni (with the purity of 99.99%) are used as raw materials, and the Al, Co, Cr, Fe and Ni are solid simple substance raw materials. The raw materials are mixed according to the atomic ratio of Al, Co, Cr, Fe and Ni of 1:1:1:1, polished mechanically to remove linear cutting marks, cleaned ultrasonically by acetone for 10min and then placed in a drying box for drying.
And secondly, smelting the alloy. Preheating a furnace body, then putting the raw materials into a crucible of a vacuum induction melting furnace, heating to 400 ℃ in vacuum below 10Pa, preserving heat for 4 hours, filling argon into the melting chamber, closing an argon filling valve after the pressure in the furnace reaches 0.05MPa, circulating the steps for three times, quickly heating the furnace body to 1550 ℃ under the argon condition, preserving heat for 15 minutes, and then pouring in a steel die. Finally obtaining 7kg of AlCoCrFeNi large-volume high-entropy alloy cast ingot.
And step two, preparing a purifying agent and placing a sample. Pre-treated plate-shaped B2O3Crushed into powder and blocks and then placed in a sample bag. A layer B is laid on the inner bottom of the quartz glass tube with the outer diameter of 18mm and the inner diameter of 15mm2O3The purifying agent is prepared by placing AlCoCrFeNi high-entropy alloy block with the diameter of 12mm multiplied by 10mm in a quartz glass tube, paving the purifying agent on the quartz glass tube, completely coating the AlCoCrFeNi high-entropy alloy block by the purifying agent, and finally placing the quartz glass tube filled with the purifying agent and the AlCoCrFeNi high-entropy alloy block in a uniform magnetic field of an excitation coil.
And step three, solidifying by a strong magnetic field. The magnetic field solidification process is implemented by an excitation power supply and a heating power supply, a quartz glass tube filled with a purifying agent and an AlCoCrFeNi high-entropy alloy block is placed in a uniform magnetic field of an excitation coil, and the excitation coil is electrified and excited by the excitation power supply, so that the maximum uniform magnetic field reaches the required magnetic field intensity (0T and 6T). Heating the AlCoCrFeNi high-entropy alloy block and the purifying agent in the quartz glass tube by a heating power supply according to a set program, preserving heat, cooling and cooling. Heating to a temperature above the melting point of the AlCoCrFeNi high-entropy alloy block at a heating rate of 40K/min, namely 1420 ℃. And cooling at a cooling speed of 30K/min after heat preservation for 15min, and quenching at 900 ℃ to obtain the AlCoCrFeNi high-entropy alloy melt coated with the purifying agent.
A1 mm slice of the AlCoCrFeNi high-entropy alloy sample subjected to magnetic field treatment is cut along a direction parallel to a magnetic field by using linear cutting to observe a microstructure, and a cylinder with phi 3mm multiplied by 3mm is cut for magnetic property test. The test results are as follows:
the microstructure of the AlCoCrFeNi high-entropy alloy after being treated by the non-magnetic field and the 6T magnetic field is shown in FIG. 4, an orientation structure which is perpendicular to the magnetic field direction appears in the direction parallel to the magnetic field direction (FIG. 4b) when the 6T magnetic field is applied relative to the non-magnetic field (FIG. 4a), but the orientation structure does not appear under the conditions that the 6T magnetic field is applied (FIG. 4d) and the non-magnetic field (FIG. 4c) is perpendicular to the magnetic field direction.
Fig. 5 is a magnetization curve of the AlCoCrFeNi high-entropy alloy sample parallel to and perpendicular to the magnetic field direction after 6T magnetic field treatment, the treated sample shows more obvious magnetic anisotropy due to the generation of orientation structure, the saturation magnetization rate parallel to the magnetic field direction is obviously higher than that perpendicular to the magnetic field direction, and the functional characteristics of the AlCoCrFeNi high-entropy alloy are improved.
Comparative example 2: step two of example 2 was replaced with vacuum packaging: putting the AlCoCrFeNi high-entropy alloy block with the diameter of 12mm multiplied by 10mm into a quartz glass tube for vacuum packaging, wherein the vacuum degree is 8 multiplied by 10-3Pa; replacing the quartz glass tube filled with the purifying agent and the AlCoCrFeNi high-entropy alloy block in the third step with a quartz glass tube vacuum-packaged with the AlCoCrFeNi high-entropy alloy block; replacing the magnetic field intensity (0T and 6T) required by the maximum uniform magnetic field with the magnetic field intensity (0T and 10T) required by the maximum uniform magnetic field; the rest of the steps and the setting of the process parameters are the same as in example 2.
FIG. 9 is a photograph of the morphology of the AlCoCrFeNi high-entropy alloy sample in comparative example 2 in the absence of a magnetic field and after treatment with a 10T magnetic field; in the figure: (a)0T, parallel to the magnetic field direction; (b)10T, parallel to the magnetic field direction. The results demonstrate that the magnetic field applied during the vacuum encapsulation process has no significant change to the structure.
FIG. 10 shows the hysteresis loops parallel and perpendicular to the magnetic field direction of AlCoCrFeNi high-entropy alloy samples prepared by the vacuum packaging +10T strong magnetic field treatment process in comparative example 2. It shows no magnetic orientation in the axial and radial directions.
Finally, it should be noted that the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the same, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solutions of the present invention 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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