High-entropy alloy nanocrystalline wire and preparation method thereof

Abstract

The invention discloses a high-entropy alloy nanocrystalline wire and a preparation method thereof.The length of the nanocrystalline wire is 5-10 mm. The preparation method comprises the steps that high-entropy alloy powder is prepared, a high-entropy alloy block is printed through selective laser melting, heat treatment is conducted on the high-entropy alloy block, the high-entropy alloy block subjected to heat treatment is cut into wires, and annealing is conducted to obtain the high-entropy alloy nanocrystalline wire. According to the method, three technical routes of selective laser melting, precipitation strengthening heat treatment and ultra-precision cutting are integrated, so that the defects of low efficiency, complexity, narrow application range and the like of a traditional nanocrystalline wire preparation method are overcome, and the efficiency, the performance, the cost, the process control and the like are remarkably improved; particularly, in preparation of nanocrystalline wires of hard and brittle materials such as high-entropy alloy, the invention provides a brand-new solution which is efficient, accurate and low in cost, and a solid foundation is laid for large-scale preparation, popularization and application of the high-performance nanocrystalline wires.

Description

Technical Field

[0001] The invention relates to a high entropy alloy nanocrystalline wire and also to a method for preparing the high entropy alloy nanocrystalline wire. Background Art

[0002] Nanocrystalline wires have attracted widespread attention in the field of materials science due to their extremely small grain size (usually less than 100 nanometers) and significant performance advantages. As a new type of functional material, nanocrystalline wires show significant superiority in mechanical, thermal, electrical and magnetic properties. For example, their high strength, high hardness and high thermal stability make them an ideal choice for advanced aerospace materials and precision structural parts; their excellent electrical and thermal conductivity give them an important position in the fields of microelectronic devices, sensors and wearable devices; in addition, the specific surface area and activity of nanocrystalline wires are significantly improved, and they have great application potential in the fields of energy storage and catalysis, such as lithium-ion battery electrodes, supercapacitors and high-efficiency catalyst carriers. Therefore, the development of preparation processes for high-performance nanocrystalline wire materials has become an important research direction in the field of materials science.

[0003] At present, the common preparation methods of nanocrystalline wires mainly include the following: Wire drawing method: Through mechanical processing, the bulk material or alloy is stretched into a nanoscale wire with a very small diameter. Although the wire drawing method is simple and suitable for large-scale production of metal nanocrystalline wires, it has high requirements for processing equipment and wire drawing dies, and it is difficult to achieve precise control. In addition, defects and stress concentration are easily introduced during the processing, resulting in a decrease in material performance. In addition, the wire drawing method is difficult to apply to the processing of hard and brittle materials, such as high entropy alloys and ceramic materials. Chemical vapor deposition (CVD) method: Through chemical reactions under a specific atmosphere and high temperature, materials are deposited on the surface of the substrate and gradually form nanocrystalline wires. The CVD method is suitable for the preparation of high-purity and high-uniformity nanocrystalline wires, such as semiconductor materials such as silicon and boron. However, its process has precise requirements for reaction conditions (such as temperature, atmosphere and chemical substances), high energy consumption and long preparation cycle. In addition, the CVD method still has the problem of limited output efficiency in batch preparation. Template method: The nanowire morphology is formed by injecting the material liquid into the template holes, and then the template is removed to obtain the nanocrystalline wire. This method can achieve the preparation of nanocrystalline wires with uniform size and is often used to prepare organic or metal polymer-based wires. However, the template method usually requires the use of expensive special nanotemplates, and the template removal process is complicated and may even lead to product loss, which limits its widespread application. Rapid solidification technology: The formation of nanocrystalline grain structure by solidifying liquid metal or alloy at an extremely fast cooling rate is an important method for processing nanocrystalline materials. Although this technology has the advantages of fast preparation speed and material organization refinement, its process complexity is relatively high, and the prepared material usually exhibits a nanostructure of refined particles, and it is difficult to directly obtain a complete nanocrystalline wire morphology.

[0004] Although the above methods have their own applications in the preparation of nanocrystalline wires, they all have limitations: such as insufficient particle size uniformity, limited material selection, high equipment cost or difficult process control. These problems limit the industrial promotion of high-performance nanocrystalline wires and also hinder their wide application in aerospace, electronic devices and energy storage systems. Therefore, it is particularly important to develop a preparation technology with high precision, high efficiency and low cost. Summary of the invention

[0005] Purpose of the invention: The purpose of the present invention is to provide a method for preparing high entropy alloy nanocrystalline wire based on the fusion of laser selective melting technology and ultra-precision cutting process and the prepared high entropy alloy nanocrystalline wire.

[0006] Technical solution: The present invention discloses a high entropy alloy nanocrystalline wire with a length of 5-10 mm and a diameter of 20-200 μm. The chemical composition of the high entropy alloy is as follows in atomic percentage: Fe: 28-30%; Co: 28-30%; Ni: 28-30%; Al: 6-8%; Ti: 6-8%.

[0007] The preparation method of the above-mentioned high entropy alloy nanocrystalline wire is to prepare high entropy alloy powder and print a high entropy alloy block by laser selective melting, heat treat the high entropy alloy block, cut the heat-treated high entropy alloy block into wires, and anneal to obtain the wires.

[0008] Wherein, the preparation method specifically comprises the following steps:

[0009] (1) Preparation of high entropy alloy powder and block forming: Preparation of high entropy alloy powder by gas atomization technology; Printing of high entropy alloy blocks by laser selective melting technology under dynamic argon protective atmosphere;

[0010] (2) Heat treatment: Heat treatment is performed on the high entropy alloy block to eliminate residual stress, optimize the microstructure, and remove the oxide layer on the surface of the block;

[0011] (3) Cutting plane preparation: The heat-treated high-entropy alloy block is clamped on an ultra-precision cutting machine to ensure that the cutting plane is parallel to the printing direction; a cubic boron nitride tool is used to cut the cutting plane multiple times until the plane is flat and completely perpendicular to the tool feed direction;

[0012] (4) Nanocrystalline wire cutting and forming: adjust the direction of the plane to be cut so that the printing direction is parallel to the cutting direction; control the tool feed speed and feed depth to cut the high entropy alloy block to obtain the nanocrystalline wire formed by cutting and extrusion;

[0013] (5) Vacuum annealing: The nanocrystalline wire is placed in a vacuum annealing furnace for low-temperature annealing to eliminate some residual stress.

[0014] Among them, in step (1), the printing parameters include: laser power of 150-210W, laser spot diameter of 60μm, layer thickness of 25-50μm, and scanning speed of 700-1200mm / s; more preferably, the laser power is 180W, the spot diameter is 60μm, the layer thickness is 30μm, and the scanning speed is 800mm / s.

[0015] Wherein, in step (2), the heat treatment is to keep the block at 680-980°C for 2-6 hours and then water cool it, and then keep the block at 300-400°C for 2-4 hours and then furnace cool it.

[0016] Among them, in step (3), the cutting parameters are: spindle speed 800-1200rpm, feed speed 0.8-1.5mm / min, cutting depth 1-3μm multiple cutting until the plane is defect-free, and the cutting environment is an oil mist environment.

[0017] Wherein, in step (4), the cutting has a cutting depth of 3 to 18 μm and a cutting speed of 30 to 70 mm / min.

[0018] Wherein, in step (5), the annealing temperature is 100-200° C., the annealing time is 1-3 hours, and the furnace is cooled after annealing.

[0019] Principle of the invention: Compared with the existing nanocrystalline wire preparation technologies (such as wire drawing, chemical vapor deposition, template method and rapid solidification technology, etc.), the preparation method of the high entropy alloy nanocrystalline wire of the present invention overcomes many limitations of traditional technologies by adopting the integrated process of "selective laser melting (SLM) + heat treatment + ultra-precision cutting", and realizes the preparation of nanocrystalline wire with high efficiency, precision and low cost and applicable to various material systems. Its advantages are mainly reflected in the following aspects:

[0020] (1) Significantly improved preparation efficiency: Traditional nanocrystalline wire preparation methods, such as wire drawing and template methods, are limited by process equipment and material properties, usually time-consuming and can only be applied to a single material system, lacking universality. The present invention combines laser selective melting (SLM) and ultra-precision cutting to directly prepare columnar crystal structure high entropy alloy blocks through SLM technology, and then process them into nanocrystalline wires in one step through ultra-precision cutting technology.

[0021] Key improvements: SLM process efficiency: Directly forming high-performance columnar crystal block materials avoids the long processing cycle and complex process of traditional block materials. Ultra-precision cutting one-step processing: Compared with the multi-stage and complex traditional methods, the present invention can quickly realize the precise processing of nanocrystalline wires, and can simply control the length and diameter of nanocrystalline wires by cutting stroke and cutting depth, greatly shortening the preparation cycle and improving the overall efficiency by more than 5 times.

[0022] (2) Optimize the microstructure and significantly improve the performance of the wire: Through SLM technology, the high entropy alloy material naturally generates special columnar crystals and finer cellular structures; heat treatment further forms evenly distributed L21 precipitation phase particles and L12 precipitation phase particles in the columnar crystals. This multi-level organizational characteristic significantly improves the hardness, strength and plastic deformation capacity of the substrate, laying the foundation for subsequent cutting nano-sizing. Compared with the traditional wire drawing method that only forms nanocrystalline wires through mechanical stretching and plastic deformation, the present invention can obtain a more uniform nanocrystalline structure and stable performance through the combination of heat treatment + cutting nano-sizing.

[0023] Key improvements: Synergistic effect of precipitation strengthening + plastic deformation: Hard L21 phase particles accelerate lattice distortion during cutting, while superplastic deformation of cellular structure promotes nanocrystallization, resulting in ultrafine grain structure far superior to nanocrystalline wires produced by wire drawing and template methods. Wire performance is significantly improved: microhardness is increased by about 20% compared to wires prepared by conventional methods, and has a more uniform equiaxed nanostructure.

[0024] (3) Strong material applicability, breaking through the limitations of traditional technology: Traditional methods, such as wire drawing and template methods, are only applicable to metal or polymer materials with high plasticity, and are almost difficult to use for hard and brittle materials (such as high entropy alloys). The present invention adopts SLM manufacturing technology, through precise control of laser process parameters and heat treatment, to give the high entropy alloy block excellent plasticity and structural uniformity, and then uses ultra-precision cutting technology to achieve processing, easily breaking through the technical bottleneck of preparing nanocrystalline wires from traditional hard and brittle materials.

[0025] Key improvements: The present invention can be widely applied to various high-performance materials, especially hard and brittle materials that are difficult to process by traditional methods, such as high-entropy alloys, and expands the range of material systems for the preparation of nanocrystalline wires.

[0026] (4) Process costs are significantly reduced: Compared with the high energy consumption and expensive equipment of the CVD method, the present invention adopts an organic combination of laser selective melting and ultra-precision cutting, which greatly simplifies the preparation process, reduces energy consumption, and effectively avoids the dependence on harsh environmental conditions (such as high temperature and high atmosphere) in CVD preparation.

[0027] Key improvements: The popularity of high-performance SLM equipment has significantly reduced process costs. Combined with mature ultra-precision cutting technology, it has not only improved preparation efficiency but also lowered the production threshold. Using SLM to directly form complex grain structures avoids additional steps such as the use of wire drawing dies or templates, resulting in less material loss and more significant cost-effectiveness.

[0028] (5) The process is simple and highly controllable: Traditional technologies such as rapid solidification require high precision control of the cooling rate, which easily leads to process fluctuations and is difficult to achieve stable mass production. In contrast, the process of the present invention is highly integrated. From SLM block manufacturing, heat treatment to cutting processing, each link can be optimized by controlling laser parameters, heat treatment conditions and cutting parameters (such as cutting depth and speed), making the production of nanocrystalline wires more consistent and convenient for industrial promotion.

[0029] Key improvements: Better control over grain structure: Through SLM and optimized heat treatment process, the formation of columnar crystals and precipitated particles can be precisely controlled to ensure the uniformity and high performance of the final nanocrystalline wire. Flexible adjustment of cutting parameters: Parameters such as cutting speed and depth during processing can be quickly adjusted to match different materials, improving process flexibility.

[0030] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The present invention overcomes the shortcomings of traditional methods for preparing nanocrystalline wires, such as inefficiency, complexity, and narrow application range, by integrating three technical routes: laser selective melting, precipitation strengthening heat treatment, and ultra-precision cutting, and achieves significant improvements in efficiency, performance, cost, and process control; (2) The preparation method of the present invention produces nanocrystalline wires of hard and brittle materials such as high entropy alloys, laying a solid foundation for the large-scale preparation and promotion and application of high-performance nanocrystalline wires. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The microstructure of high entropy alloy nanocrystalline wire is shown as nanocrystalline structure and nanocrystalline diffraction rings;

[0032] Figure 2 This is a local micrograph of the high entropy alloy nanocrystalline wire prepared in Example 1;

[0033] Figure 3 Figure 1 is the microstructure of laser selective melting high entropy alloy, where Figures a and b are the microstructures perpendicular to the printing direction, and Figure b is a local enlarged view showing the distribution of precipitated phase particles; Figures c and d are the microstructures parallel to the printing direction, where d is a local enlarged view showing the distribution of precipitated phase particles, and BD is the printing direction;

[0034] Figure 4 Figure 1. Ultra-precision cutting of high entropy alloy by laser selective melting;

[0035] Figure 5 EBSD-IPF image of the microstructure of high entropy alloy nanocrystalline wire;

[0036] Figure 6The cutting results of the unheat-treated samples, where a is the microstructure before cutting, b is the wire morphology after cutting, c is the EBSD-IPF image of the microstructure showing columnar crystals, and d is the TEM image;

[0037] Figure 7 This is the microstructure surface of the high entropy alloy wire prepared in Example 2. DETAILED DESCRIPTION

[0038] The technical scheme of the present invention is further described below in conjunction with the examples. The test materials used in the examples can all be purchased through conventional channels.

[0039] Example 1

[0040] The method for preparing the high entropy alloy nanocrystalline wire comprises the following steps:

[0041] (1) Preparation of high entropy alloy powder and block forming: High entropy alloy powder Fe was prepared by gas atomization technology 29.3 Co 28.7 Ni 28.6 Al 6.8 Ti 6.6 (at.%); SLM technology was used to print high-entropy alloy blocks under a dynamic argon protective atmosphere to ensure that the oxygen content was less than 100 ppm; the printing parameters included: laser power of 180 W, spot diameter of 60 μm, layer thickness of 30 μm, and scanning speed of 800 mm / s.

[0042] (2) Heat treatment: The high entropy alloy block is heat treated to eliminate residual stress and optimize the microstructure; the block is kept at 780°C for 4 hours and then water-cooled; then the block is kept at 350°C for 4 hours and furnace-cooled to remove the oxide layer on the surface of the block. The microstructure of the high entropy alloy block after heat treatment is as follows: Figure 3 , where Figures a and b are microstructures perpendicular to the printing direction, and Figure b is a local enlarged view showing the distribution of precipitated phase particles; Figures c and d are microstructures parallel to the printing direction, and Figure d is a local enlarged view showing the distribution of precipitated phase particles;

[0043] (3) Cutting plane preparation: The heat-treated high-entropy alloy block is clamped on an ultra-precision cutting machine to ensure that the cutting plane is parallel to the printing direction; a cubic boron nitride (CBN) tool is used to cut the cutting plane multiple times until the plane is flat and completely perpendicular to the tool feed direction; the cutting parameters are: spindle speed, 1000 rpm, feed speed 1 mm / min, cutting depth 2 μm, multiple cutting until the plane is defect-free, and the cutting environment is an oil mist environment.

[0044] (4) Nanocrystalline wire cutting and forming: adjust the direction of the plane to be cut so that the printing direction is parallel to the cutting direction; control the tool feed speed and feed depth to cut the high entropy alloy block to obtain nanocrystalline wire formed by cutting and extrusion; the length range of the nanocrystalline wire is 5 mm, the cutting depth is 9 μm, and the cutting speed is 50 mm / min. Figure 4 Ultra-precision cutting of laser selective melting high-entropy alloy block. The cutting direction is parallel to the printing direction.

[0045] (5) Vacuum annealing: The obtained nanocrystalline wire is placed in a vacuum annealing furnace for low temperature annealing to eliminate some residual stress; the annealing temperature is 150°C and the annealing time is 2 hours. After annealing, the high entropy alloy nanocrystalline wire is obtained by cooling in the furnace. Its microstructure is as follows: Figure 1 As shown, the microstructure Figure 2 As shown. Among them, Picture 1 is a microscopic image of the high entropy alloy nanocrystalline wire collected by a transmission electron microscope, showing a nanocrystalline structure, and the illustration in the upper left corner is the corresponding nanocrystalline diffraction ring; Picture 2 is a local microscopic image of the high entropy alloy nanocrystalline wire prepared in this embodiment, and the picture shows that the high entropy alloy nanocrystalline wire has a smooth surface, uniform texture, and good surface quality; Figure 5 This is the EBSD-IPF image of the microstructure of high entropy alloy nanocrystalline wire, showing the nanocrystalline structure produced by cutting, extrusion and deformation.

[0046] Example 2

[0047] Compared with Example 1, the cutting depth is adjusted to 12 μm. The method for preparing the high entropy alloy wire of the present invention comprises the following steps:

[0048] (1) Preparation of high entropy alloy powder and block forming: High entropy alloy powder Fe was prepared by gas atomization technology 29.3 Co 28.7 Ni 28.6 Al 6.8 Ti 6.6 (at.%); SLM technology was used to print high-entropy alloy blocks under a dynamic argon protective atmosphere to ensure that the oxygen content was less than 100 ppm; the printing parameters included: laser power of 180 W, spot diameter of 60 μm, layer thickness of 30 μm, and scanning speed of 800 mm / s.

[0049] (2) Heat Treatment The high-entropy alloy block is heat treated to eliminate residual stress and optimize the microstructure; the block is kept at 780°C for 4 hours and then water-cooled; the block is then kept at 350°C for 4 hours and furnace-cooled to remove the oxide layer on the surface of the block.

[0050] (3) Cutting plane preparation: The heat-treated high-entropy alloy block is clamped on an ultra-precision cutting machine to ensure that the cutting plane is parallel to the printing direction; a cubic boron nitride (CBN) tool is used to cut the cutting plane multiple times until the plane is flat and completely perpendicular to the tool feed direction; the cutting parameters are: spindle speed, 1000 rpm, feed speed 1 mm / min, cutting depth 2 μm, multiple cutting until the plane is defect-free, and the cutting environment is an oil mist environment.

[0051] (4) Wire cutting and forming: adjust the direction of the plane to be cut so that the printing direction is parallel to the cutting direction; control the tool feed speed and feed depth to cut the high entropy alloy block to obtain the cut extruded wire; the wire length range is 5 mm, the cutting depth is 12 μm, and the cutting speed is 50 mm / min.

[0052] (5) Vacuum annealing: The obtained wire is placed in a vacuum annealing furnace for low temperature annealing to eliminate some residual stress; the annealing temperature is 150°C and the annealing time is 2 hours. After annealing, the high entropy alloy wire is obtained by cooling in the furnace. The microstructure surface is as follows: Figure 7 ,The pictures show that the surface roughness of the wire increases when the cutting depth increases.

[0053] Comparative Example 1

[0054] Compared with the embodiment, the method for preparing a high entropy alloy wire obtained by ultra-precision cutting of a high entropy alloy printed block in Comparative Example 1 without heat treatment comprises the following steps:

[0055] (1) Preparation of high entropy alloy powder and block forming: High entropy alloy powder Fe was prepared by gas atomization technology 29.3 Co 28.7 Ni 28.6 Al 6.8 Ti 6.6 (at.%); SLM technology was used to print high-entropy alloy blocks under a dynamic argon protective atmosphere to ensure that the oxygen content was less than 100 ppm; the printing parameters included: laser power of 180 W, spot diameter of 60 μm, layer thickness of 30 μm, and scanning speed of 800 mm / s.

[0056] (2) Cutting plane preparation: The printed high-entropy alloy block is clamped on an ultra-precision cutting machine to ensure that the cutting plane is parallel to the printing direction; a cubic boron nitride (CBN) tool is used to cut the cutting plane multiple times until the plane is flat and completely perpendicular to the tool feed direction; the cutting parameters are: spindle speed, 1000 rpm, feed speed 1 mm / min, cutting depth 2 μm, multiple cutting until the plane is defect-free, and the cutting environment is an oil mist environment.

[0057] (4) Wire cutting and forming: adjust the direction of the plane to be cut so that the printing direction is parallel to the cutting direction; control the tool feed speed and feed depth to cut the high entropy alloy block to obtain the cut extruded wire; the wire length range is 5 mm, the cutting depth is 9 μm, and the cutting speed is 50 mm / min.

[0058] (5) Vacuum annealing: The obtained wire is placed in a vacuum annealing furnace for low-temperature annealing to eliminate some residual stress; the annealing temperature is 150°C, the annealing time is 2 hours, and the wire is cooled in the furnace after annealing. The microstructure is as follows Figure 6 As shown, Figure a is the microstructure of the printed high-entropy alloy block without heat treatment; Figure b is the high-entropy alloy wire obtained by cutting the high-entropy alloy block without heat treatment, and the wire is easy to break; Figure c is the EBSD-IPF image of the microstructure of the high-entropy alloy wire obtained by cutting the high-entropy alloy block without heat treatment, showing columnar grains; Figure d is the TEM image of the microstructure of the high-entropy alloy wire obtained by cutting the high-entropy alloy block without heat treatment, showing that the original grains are transformed into columnar grains after cutting, extrusion and deformation.

Claims

1. A high entropy alloy nanocrystalline wire, characterized in that: The nanocrystalline wire has a length of 5-10 mm and a diameter of 20-200 μm. The chemical composition of the high entropy alloy is as follows in terms of atomic percentage: Fe: 28-30%; Co: 28-30%; Ni: 28-30%; Al: 6-8%; Ti: 6-8%.

2. A method for preparing the high entropy alloy nanocrystalline wire according to claim 1, characterized in that: The preparation method comprises the following steps: preparing high entropy alloy powder, printing a high entropy alloy block by laser selective melting, heat treating the high entropy alloy block, cutting the heat-treated high entropy alloy block into wires, and annealing the wires to obtain the obtained product.

3. The preparation method according to claim 2, characterized in that: The following steps are involved: (1) Preparation of high entropy alloy powder and block forming: Preparation of high entropy alloy powder by gas atomization technology; Printing of high entropy alloy blocks by laser selective melting technology under dynamic argon protective atmosphere; (2) Heat treatment: Heat treatment is performed on the high entropy alloy block to eliminate residual stress, optimize the microstructure, and remove the oxide layer on the surface of the block; (3) Cutting plane preparation: The heat-treated high-entropy alloy block is clamped on an ultra-precision cutting machine to ensure that the cutting plane is parallel to the printing direction; Use a cubic boron nitride tool to cut the surface to be cut multiple times until the surface is flat and completely perpendicular to the tool feed direction; (4) Nanocrystalline wire cutting and forming: adjust the direction of the plane to be cut so that the printing direction of the plane to be cut is parallel to the cutting direction; control the tool feed speed and feed depth to cut the high entropy alloy block to obtain the nanocrystalline wire formed by cutting and extrusion; (5) Vacuum annealing: The nanocrystalline wire is placed in a vacuum annealing furnace for low-temperature annealing to eliminate some residual stress.

4. The preparation method according to claim 2, characterized in that: In step (1), the printing parameters include: laser power of 150-210 W, laser spot diameter of 60 μm, layer thickness of 25-50 μm, and scanning speed of 700-1200 mm / s.

5. The preparation method according to claim 1, characterized in that: In step (2), the heat treatment is to keep the block at 680-980°C for 2-6 hours and then water cool it, and then keep the block at 300-400°C for 2-4 hours and then furnace cool it.

6. The preparation method according to claim 1, characterized in that: In step (3), the cutting parameters are: spindle speed 800-1200 rpm, feed speed 0.8-1.5 mm / min, cutting depth 1-3 μm, multiple cutting until the plane is defect-free, and the cutting environment is an oil mist environment.

7. The preparation method according to claim 1, characterized in that: In step (4), the cutting has a cutting depth of 3 to 18 μm and a cutting speed of 30 to 70 mm / min.

8. The preparation method according to claim 1, characterized in that: In step (5), the annealing temperature is 100-200° C., the annealing time is 1-3 hours, and the furnace is cooled after annealing.

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