Method and device for preparing gradient crystal structure of metal material through cryogenic electric treatment

Abstract

The invention relates to the technical field of material processing, in particular to a method and device for preparing a metal material gradient crystal structure through cryogenic electric treatment. The method for preparing the gradient crystal structure of the metal material through cryogenic electric treatment is based on a workpiece clamp. The workpiece clamp comprises a base, a conductive part and two conductive bands, the two conductive bands are distributed in a spaced mode and extend in the length direction of the base, an installation gap used for installing a metal material workpiece is formed between the conductive part and at least one conductive band, and when the metal material workpiece is installed in the installation gap, the metal material workpiece is clamped in the installation gap. The metal material workpiece, the conductive part and the two conductive bands jointly form a conductive loop; the method for preparing the metal material gradient crystal structure through cryogenic electric treatment comprises the steps that a metal material workpiece is installed in an installation gap of a workpiece clamp; and the metal material workpiece is electrified, and the workpiece clamp is soaked in liquid nitrogen for subzero treatment. The method has the effect of optimizing the microcosmic grain structure of the metal material so as to improve the mechanical property of the metal material.

Description

Technical Field

[0001] The present invention relates to the technical field of material processing, and more particularly, to a method and device for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing. Background Art

[0002] In the field of metal material science, the grain size and microstructure distribution of metal materials have a decisive influence on their properties. Refining grains can significantly improve the strength, toughness, plasticity, fatigue properties, etc. of materials. How to effectively refine grains to enhance the properties of metal materials is a long-term pursued goal.

[0003] Currently, common grain refinement methods include hot working, adding trace elements, severe plastic deformation, etc. However, these methods have certain limitations. During hot working, high temperatures may cause defects such as surface oxidation and decarburization of the material, affecting the material quality; although adding trace elements can refine grains to a certain extent, it may introduce impurities, change the chemical composition of the material, and affect its stability; the severe plastic deformation method is difficult to implement for some materials with complex shapes or large sizes, and it is easy to cause stress concentration inside the material. Therefore, traditional metal material treatment methods often have difficulty in forming a uniform and ideal gradient grain structure inside the material, thereby affecting the microstructure and mechanical properties of metal materials. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to prepare a gradient crystal structure of a metal material to improve the mechanical properties of the metal material.

[0005] To solve the above problems, as a first aspect, the present invention provides a method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing. The method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing is based on a workpiece fixture. The workpiece fixture includes a base, a conductive part, and two conductive bands. The two conductive bands are spaced apart and extend along the length direction of the base respectively. There is an installation gap for installing a metal material workpiece between the conductive part and at least one of the conductive bands. When the metal material workpiece is installed in the installation gap, the metal material workpiece, the conductive part, and the two conductive bands jointly form an electrical conduction loop;

[0006] The method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing includes:

[0007] Install the metal material workpiece in the installation gap of the workpiece fixture;

[0008] Apply electricity to the metal material workpiece and immerse the workpiece fixture in liquid nitrogen for cryogenic treatment.

[0009] Optionally, the position of the conductive part along the length direction of the base is adjustable.

[0010] Optionally, the workpiece fixture further includes a workpiece pressing plate for fixing the metal material workpiece to the conductive belt and the conductive part respectively.

[0011] Optionally, the workpiece fixture further includes an insulating baffle disposed in the installation gap.

[0012] Optionally, the conductive belt and the conductive part are made of pure copper, and the base and the insulating baffle are made of G10.

[0013] Optionally, the workpiece fixture further includes a hanging plate, and the position of the hanging plate along the length direction of the base is adjustable.

[0014] Optionally, an installation gap for installing the metal material workpiece is respectively provided between the conductive part and the two conductive belts.

[0015] Optionally, each conductive belt includes a plurality of conductive segments distributed at intervals along the length direction of the base, and an installation gap for accommodating the metal material workpiece is provided between every two conductive segments.

[0016] Optionally, energizing the metal material workpiece and immersing the workpiece fixture in liquid nitrogen for cryogenic treatment includes: determining the working current density when the metal material workpiece is energized based on the recrystallization temperature of the metal material workpiece.

[0017] As a second aspect, the present invention further provides a device for preparing a gradient crystal structure of a metal material by cryogenic electro-treatment. The device for preparing a gradient crystal structure of a metal material by cryogenic electro-treatment includes a liquid nitrogen container and the workpiece fixture as described above. The workpiece fixture can be immersed in the liquid nitrogen container to complete the method for preparing a gradient crystal structure of a metal material by cryogenic electro-treatment as described above.

[0018] The present invention adopts liquid nitrogen cryogenic electro-treatment for the metal material workpiece. Specifically, the metal material workpiece can be installed in the workpiece fixture. By energizing one of the conductive belts, which serves as the current input end, and the other conductive belt serves as the current output end, the current forms a conductive loop in sequence along the conductive belt - conductive part - conductive belt to achieve current treatment. The current can promote atomic diffusion, reduce the resistance of dislocation movement, and achieve dynamic recrystallization, thereby refining the grains. At the same time, the liquid nitrogen cryogenic treatment can utilize the extremely low temperature environment to reduce retained austenite, and further inhibit dislocation movement and grain boundary migration, providing favorable conditions for grain refinement. Therefore, the embodiment of the present invention combines ultra-low temperature and current to treat the metal material workpiece, achieving the effect of preparing a gradient crystal structure of the metal material to improve the mechanical properties of the metal material. Description of the Drawings

[0019] Figure 1is a schematic diagram of the three-dimensional structure of a workpiece fixture in an exemplary embodiment of the present invention;

[0020] Figure 2 is a top view of a workpiece fixture in an exemplary embodiment of the present invention;

[0021] Figure 3 For the Figure 2 The cross-sectional view obtained by cutting along the cutting line;

[0022] Figure 4 for Figure 3 A magnified schematic diagram of area A in the middle;

[0023] Figure 5 A schematic structural diagram of a workpiece fixture in an exemplary embodiment of the present invention when mounting a metal workpiece;

[0024] Figure 6 A schematic structural diagram of a workpiece fixture in an exemplary embodiment of the present invention extending into a liquid nitrogen container;

[0025] Figure 7 The Al that has been subjected to deep cooling and electrical treatment in Example 1 of the present invention 0.1 Grain size distribution of CoCrFeNi high entropy alloy workpiece;

[0026] Figure 8 Al in Example 1 of the present invention 0.1 Grain distribution diagram of fine grain and coarse grain regions in CoCrFeNi high entropy alloy workpiece;

[0027] Figure 9 The Al that has been subjected to deep cooling and electrical treatment in Example 1 of the present invention 0.1 Engineering stress-strain curves of CoCrFeNi high-entropy alloy workpiece and its torsion state and original casting state;

[0028] Figure 10 Schematic diagram of a portion of the structure of a workpiece fixture in Example 2 of the present invention;

[0029] Figure 11 This is a partial structural diagram of the workpiece fixture in Example 3 of the present invention.

[0030] Explanation of the accompanying reference numerals: 1. workpiece fixture; 11. base; 111. groove; 112. fixing hole; 12. conductive part; 13. conductive belt; 131. conductive segment; 14. installation gap; 15. conductive belt pressure plate; 16. conductive part pressure plate; 17. workpiece pressure plate; 18. insulating baffle; 19. hanging plate; 2. metal workpiece; 3. liquid nitrogen container. DETAILED DESCRIPTION

[0031] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides a detailed description of specific embodiments of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by those skilled in the technical field to which this application belongs; the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application;

[0033] The term "including" and its variants used herein are open-ended, that is, "including but not limited to"; the term "based on" is "at least partially based on"; the term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one additional embodiment"; the term "some embodiments" means "at least some embodiments"; the term "optionally" means "optional embodiment". The relevant definitions of other terms will be given in the following description. It should be noted that the concepts of "first", "second", etc. mentioned in the present invention are used to distinguish different objects, rather than to describe a specific order or primary-secondary relationship. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, unless otherwise stated, the meaning of "a plurality" is two or more.

[0034] An embodiment of the present invention provides a method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing. The method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing is based on a workpiece fixture 1. Among them, the workpiece fixture 1 includes a base 11, a conductive part 12, and two conductive bands 13. The two conductive bands 13 are spaced apart and extend along the length direction of the base 11 respectively. There is an installation gap 14 for accommodating the metal material workpiece 2 between the conductive part 12 and at least one conductive band 13. When the metal material workpiece 2 is installed in the installation gap 14, the metal material workpiece 2, the conductive part 12, and the two conductive bands 13 jointly form an electrical conduction loop.

[0035] The method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing includes:

[0036] Step S1: Install the metal material workpiece 2 in the installation gap 14 of the workpiece fixture 1;

[0037] Step S2: Energize the metal material workpiece 2 and immerse the workpiece fixture 1 in liquid nitrogen for cryogenic treatment.

[0038] In the embodiment of the present invention, the metal material workpiece 2 is subjected to liquid nitrogen cryogenic-electrical treatment. Specifically, the metal material workpiece 2 can be installed in the workpiece fixture 1. By energizing one of the conductive bands 13, which serves as the current input end, and the other conductive band 13 serves as the current output end, the current forms a conductive loop in sequence along the conductive band 13 - the conductive part 12 - the conductive band 13 to achieve current treatment. The current can promote atomic diffusion, reduce the resistance of dislocation movement, and achieve dynamic recrystallization, thereby refining the grains. At the same time, the liquid nitrogen cryogenic treatment can utilize the extremely low-temperature environment to reduce retained austenite, and then inhibit dislocation movement and grain boundary migration, providing favorable conditions for grain refinement. And in the embodiment of the present invention, the workpiece fixture 1 can be directly inserted into the liquid nitrogen container 3, so that the area where the metal material workpiece 2 is located in the workpiece fixture 1 is completely immersed in liquid nitrogen, which is convenient for making full use of liquid nitrogen. Therefore, the embodiment of the present invention combines ultra-low temperature and current to process the metal material workpiece 2, which can optimize the microstructure of the metal material to improve the mechanical properties of the metal material.

[0039] It should be noted that the method for preparing the gradient crystal structure of the metal material by cryogenic-electrical treatment in the embodiment of the present invention can be applied to processing pure metals such as copper and aluminum, or steel materials such as low-carbon steel and stainless steel, as well as titanium alloys, magnesium alloys, and high-entropy alloy materials.

[0040] Figure 1 It is a schematic structural diagram of the workpiece fixture 1 in an exemplary embodiment of the present invention. As Figure 1 can be seen, in an exemplary embodiment, the workpiece fixture 1 is overall slender, which is more conducive to being inserted into the liquid nitrogen container 3 for liquid nitrogen cryogenic treatment. Among them, the base 11 is provided with channels 111 on both the upper and lower sides. Each channel 111 extends along the length direction of the base 11 and penetrates through the two ends of the base 11, making the side of the base 11 in an "H" shape. The two conductive bands 13 are respectively embedded in the upper and lower channels 111, and each conductive band 13 is fixed to the base 11 through at least one conductive band pressing plate 15.

[0041] As Figure 1 shown, exemplarily, the number of the conductive band pressing plates 15 can be multiple, and the multiple conductive band pressing plates 15 are spaced along the length direction of the base 11. Each conductive band 13 is located between the corresponding conductive band pressing plate 15 and the base 11. Correspondingly, a plurality of fixing holes 112 can be opened along the length direction on the base 11, and each conductive band pressing plate 15 can be connected to one of the fixing holes 112 through fasteners such as bolts, so as to press and fix the conductive band 13 between the conductive band pressing plate 15 and the base 11.

[0042] Referring to Figure 2 and Figure 3 shown, in some alternative embodiments, the position of the conductive part 12 along the length direction of the base 11 is adjustable.

[0043] Specifically, as Figure 3 and Figure 4 shown, as an example, there is an installation gap 14 between the conductive part 12 and the end of one of the conductive strips 13, and it abuts against the other conductive strip 13 or is connected by bolts. Refer to Figure 5 shown, when the metal material workpiece 2 is installed at the installation gap 14, both ends of the metal material workpiece 2 are respectively connected to the conductive part 12 and one of the conductive strips 13. The conductive part 12 is slidably connected to the base 11, so that the length of the installation gap 14 between the conductive part 12 and the conductive strip 13 can be adjusted to adapt to metal material workpieces 2 of different length dimensions. Further, the conductive part 12 is fixed to the base 11 by at least one conductive part pressing plate 16, that is, the conductive part pressing plate 16 can also be connected to one of the fixing holes 112 by fasteners such as bolts, so as to press and fix the conductive part 12 between the conductive part pressing plate 16 and the base 11.

[0044] It should be noted that the workpiece fixture 1 in the embodiment of the present invention can be applicable to processing metal material workpieces 2 of different shapes. Such as strip plates, "T"-shaped plates or rectangular blocks. Specifically, when processing a "T"-shaped workpiece, the vertical plate of the "T"-shaped workpiece can be inserted into the installation gap 14 between the conductive part 12 and the conductive strip 13. When processing a rectangular block, the rectangular block can be integrally embedded in the installation gap 14.

[0045] In some alternative embodiments, the workpiece fixture 1 further includes a workpiece pressing plate 17, and the workpiece pressing plate 17 is used to respectively fix the metal material workpiece 2 to the conductive strip 13 and the conductive part 12.

[0046] Specifically, as an example, refer to Figure 3 and Figure 4 shown, the number of workpiece pressing plates 17 can be two. The two workpiece pressing plates 17 are respectively located at the two ends of the metal material workpiece 2, and are used to respectively fix the metal material workpiece 2 to the conductive part 12 and one of the conductive strips 13. Optionally, the workpiece pressing plate 17 can be connected to the metal material workpiece 2, the conductive part 12 or the conductive strip 13 by bolts.

[0047] In some alternative embodiments, there are respectively installation gaps 14 for accommodating the metal material workpiece 2 between the conductive part 12 and the two conductive strips 13.

[0048] As an example, the conductive part 12 can be located at the same end of the two conductive strips 13. There is an installation gap 14 between the conductive part 12 and each conductive strip 13. When the conductive part 12 moves along the length direction of the base 11, the length of the installation gap 14 between the conductive part 12 and each conductive strip 13 can be adjusted simultaneously. Thus, the workpiece fixture 1 can install two metal material workpieces 2 at the same time, achieving the purpose of processing multiple workpieces simultaneously.

[0049] It should be understood that in some alternative embodiments, each conductive strip 13 may include a plurality of conductive segments 131 that are spaced apart along the length of the base 11. There is an installation gap 14 for accommodating the metal material workpiece 2 between every two conductive segments 131. When the metal material workpiece 2 is installed in the installation gap 14 of this part, its two ends can be respectively connected to the conductive segments 131. By adopting the above solution, the number of workpieces that can be processed simultaneously by the workpiece fixture 1 can be further increased, and the workpiece processing efficiency can be further improved.

[0050] In some alternative embodiments, referring to Figure 4 as shown, the workpiece fixture 1 further includes an insulating baffle 18, and the insulating baffle 18 is disposed in the installation gap 14 between the conductive part 12 and each conductive strip 13.

[0051] It should be understood that when no workpiece is installed on the workpiece fixture 1, an insulating baffle 18 can be inserted into each installation gap 14, which can be used to prevent a short circuit from forming between the conductive strip 13 and the conductive part 12.

[0052] In some alternative embodiments, referring to Figure 3 as shown, the workpiece fixture 1 further includes a hanging plate 19, and the position of the hanging plate 19 along the length direction of the base 11 is adjustable.

[0053] Specifically, as Figure 6 shown, the length of the hanging plate 19 extends beyond the base 11 and can be used to support and fix the base 11. When the workpiece fixture 1 is inserted into the liquid nitrogen container 3, the hanging plate can be used for limiting. Similarly, the hanging plate 19 can also be connected to one of the fixing holes 112 on the base 11, so that the length of the workpiece fixture 1 inserted into the liquid nitrogen container 3 can be adjusted to adapt to liquid nitrogen containers 3 of different sizes, ensuring that the metal material workpiece 2 is fully immersed in liquid nitrogen.

[0054] In some alternative embodiments, in the workpiece fixture 1, the conductive strips 13, the conductive parts 12, and the workpiece pressing plates 17 are all made of pure copper, and the base 11, the insulating baffles 18, the hanging plates 19, and the conductive strip pressing plates 15 are made of G10.

[0055] In the workpiece fixture 1 in the embodiments of the present invention, different structures adopt different materials. Among them, the conductive strips 13 and the conductive parts 12 are made of conductive materials and are used to transmit current; the base 11, the insulating baffles 18, the hanging plates 19, and the conductive strip pressing plates 15 have an insulating function and can effectively prevent the phenomenon of short circuit between the upper and lower conductive strips 13.

[0056] In some alternative embodiments, in step S2 of the method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing, the working current density when the metal material workpiece 2 is energized is determined based on the recrystallization temperature of the metal material workpiece 2.

[0057] Specifically, an infrared camera can be used to observe the maximum temperature of the workpiece under different current densities, and the current density corresponding to the maximum temperature that can reach the recrystallization temperature is determined as the working current density of the workpiece. Then, the workpiece is energized according to the working current density. While energizing, the entire workpiece fixture 1 is immersed in liquid nitrogen. When the energization time reaches the preset duration, the workpiece fixture 1 is immediately taken out of the liquid nitrogen, and at the same time, the power supply is cut off, that is, the energization and the cryogenic treatment with liquid nitrogen are carried out simultaneously. And in actual experiments, the energization time can be adjusted to prepare gradient crystal structures with different depths and different grain sizes.

[0058] By performing synchronous energization and liquid nitrogen cryogenic treatment on the metal material workpiece 2, it is beneficial to maximize the thermoelectric synergy effect. First of all, it can dynamically suppress Joule heat. Synchronous liquid nitrogen cooling is an instant response to the Joule heat generated by energization. By suppressing the temperature rise through real-time cooling, the material is always in a low-temperature state, avoiding local high temperatures caused by "no cooling during the energization stage" in the alternate treatment, thereby preventing grain coarsening and oxidation. In addition, by suppressing heat diffusion in a low-temperature environment, the electric pulse energy is forced to be more concentrated on dislocation movement rather than thermal vibration, strengthening the driving effect of the electron wind force on dislocations.

[0059] Another embodiment of the present invention provides a device for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing. The device includes a liquid nitrogen container 3 and the workpiece fixture 1 as described above. The workpiece fixture 1 can be immersed in the liquid nitrogen container 3 to complete the method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing as described above. Refer to Figure 6 As shown, when the workpiece fixture 1 is extended into the liquid nitrogen container 3, the end of the workpiece fixture 1 far from the hanging plate 19 extends downward into the liquid nitrogen container 3, and the hanging plate 19 is clamped at the opening of the liquid nitrogen container 3, so that the metal material workpiece 2 is completely immersed in liquid nitrogen. Specifically, the liquid nitrogen container 3 can be a liquid nitrogen tank.

[0060] The present invention will be described in detail below through specific embodiments:

[0061] Example 1

[0062] Refer to Figures 1 to 5As shown in the figure, the workpiece fixture 1 of this embodiment includes a base 11, a conductive part 12, two conductive bands 13, a workpiece pressing plate 17, a conductive part pressing plate 16, a conductive band pressing plate 15, an insulating baffle 18 and a hanging plate 19. The two conductive bands 13 are spaced apart and extend along the length direction of the base 11 respectively. There is an installation gap 14 for accommodating the metal material workpiece 2 between the conductive part 12 and one of the conductive bands 13, and it is connected to the other conductive band 13 by bolts. When the metal material workpiece 2 is installed at the installation gap 14, both ends of the metal material workpiece 2 are connected to the conductive part 12 and one of the conductive bands 13 respectively. The positions and connection relationships of other structures in this embodiment will not be elaborated.

[0063] This embodiment processes Al 0.1 CoCrFeNi high-entropy alloy workpieces, and its processing method includes:

[0064] Step S1: Install the Al 0.1 CoCrFeNi high-entropy alloy workpiece in the installation gap 14 of the workpiece fixture 1 so that the Al 0.1 CoCrFeNi high-entropy alloy workpiece, the conductive part 12 and the two conductive bands 13 together form an electrical conduction loop.

[0065] Step S2: While energizing the Al 0.1 CoCrFeNi high-entropy alloy workpiece, immerse the workpiece fixture 1 in liquid nitrogen. Among them, the current density during energization is determined by the recrystallization temperature of the metal material workpiece 2, and the energization time is 30 s.

[0066] Figure 7 This is the grain size distribution diagram of the Al 0.1 CoCrFeNi high-entropy alloy workpiece after cryogenic-electrical treatment in this embodiment. Figure 8 This is the grain distribution state diagram of the fine-grained region and the coarse-grained region in the Al 0.1 CoCrFeNi high-entropy alloy workpiece of this embodiment. Among them, the average particle size in the fine-grained region is 6.5 μm, and the average particle size in the coarse-grained region is 16.39 μm. The results show that the Al 0.1 CoCrFeNi high-entropy alloy workpiece in this embodiment can induce the internal grains to present a gradient state after cryogenic-electrical treatment.

[0067] Figure 9 This is the engineering stress-strain curve diagram of the Al 0.1 CoCrFeNi high-entropy alloy workpiece after cryogenic-electrical treatment in this embodiment, its torsional state and as-cast state. As can be seen from Figure 9 it, the Al 0.1The CoCrFeNi high-entropy alloy workpiece, compared with the nanocrystalline state prepared by high-pressure torsion, has a slightly decreased strength, but its plasticity is greatly improved. Compared with the original as-cast structure, its strength is significantly improved.

[0068] Example 2

[0069] The difference between this example and Example 1 is that, referring to Figure 10 As shown, in the workpiece fixture 1, the conductive part 12 can be located at the same end of the two conductive bands 13. There is an installation gap 14 between the conductive part 12 and each conductive band 13. When the conductive part 12 moves along the length direction of the base 11, the length of the installation gap 14 between the conductive part 12 and each conductive band 13 can be adjusted simultaneously. Thus, the workpiece fixture 1 can install two metal material workpieces 2 at the same time, achieving the purpose of processing multiple workpieces simultaneously.

[0070] Example 3

[0071] The difference between this example and Example 1 is that, referring to Figure 11 As shown, in the workpiece fixture 1, each conductive band 13 includes a plurality of conductive segments 131 distributed at intervals along the length direction of the base 11. There is an installation gap 14 for accommodating the metal material workpiece 2 between every two conductive segments 131. When the metal material workpiece 2 is installed in the installation gap 14 of this part, its two ends can be respectively connected to the conductive segments 131. By adopting the above scheme, the number of workpieces that can be processed simultaneously by the workpiece fixture 1 can be further increased, and the workpiece processing efficiency can be further improved.

[0072] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will all fall within the protection scope of the present invention.

Claims

1. A method for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing, characterized in that, The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing is based on a workpiece fixture (1); The workpiece fixture (1) includes a base (11), a conductive part (12) and two conductive bands (13). The two conductive bands (13) are spaced apart and extend respectively along the length direction of the base (11). There is an installation gap (14) for installing a metallic material workpiece (2) between the conductive part (12) and at least one of the conductive bands (13). When the metallic material workpiece (2) is installed in the installation gap (14), the metallic material workpiece (2), the conductive part (12) and the two conductive bands (13) together form an electrical conduction loop; The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing includes: Install the metallic material workpiece (2) in the installation gap (14) of the workpiece fixture (1); Apply an electric current to the metallic material workpiece (2) and soak the workpiece fixture (1) in liquid nitrogen for cryogenic treatment.

2. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 1, characterized in that, The position of the conductive part (12) along the length direction of the base (11) is adjustable.

3. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 1, characterized in that, The workpiece fixture (1) further includes a workpiece pressing plate (17), and the workpiece pressing plate (17) is used to fix the metallic material workpiece (2) to the conductive band (13) and the conductive part (12) respectively.

4. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 1, wherein The workpiece fixture (1) further includes an insulating baffle (18), and the insulating baffle (18) is arranged in the installation gap (14).

5. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 4, wherein The materials of the conductive band (13) and the conductive part (12) are pure copper, and the materials of the base (11) and the insulating baffle (18) are G10.

6. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 1, wherein The workpiece fixture (1) further includes a hanging plate (19), and the position of the hanging plate (19) along the length direction of the base (11) is adjustable.

7. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 1, characterized in that, There are respectively installation gaps (14) for installing a metallic material workpiece (2) between the conductive part (12) and the two conductive bands (13).

8. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 1, wherein Each conductive band (13) includes a plurality of conductive segments (131) spaced apart along the length direction of the base (11), and there is an installation gap (14) for accommodating the metallic material workpiece (2) between every two conductive segments (131).

9. The method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to claim 1, wherein The step of applying an electric current to the metallic material workpiece (2) and soaking the workpiece fixture (1) in liquid nitrogen for cryogenic treatment includes: Determine the working current density when the metallic material workpiece (2) is energized based on the recrystallization temperature of the metallic material workpiece (2).

10. An apparatus for preparing a gradient crystal structure of a metal material by cryogenic electroprocessing, characterized in that, The device for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing includes a liquid nitrogen container (3) and the workpiece fixture (1) according to any one of claims 1-9. The workpiece fixture (1) can be immersed in the liquid nitrogen container (3) to complete the method for preparing a gradient crystal structure of a metallic material by cryogenic electroprocessing according to any one of claims 1-9.

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