A method for preparing functionally gradient material

Abstract

The present invention relates to the technical field of functional gradient materials, and in particular to a method for preparing functional gradient materials. An embodiment of the present invention provides a method for preparing functional gradient materials, comprising: preparing metal particles of different particle sizes by adjusting the rotation speed of the rotating electrode in the plasma rotating electrode process; mixing the metal particles of different particle sizes with different amounts of ceramic powder to obtain multiple groups of mixed particles; wherein, in the multiple groups of mixed particles, the finer the particle size of the metal particles, the higher the proportion of the ceramic powder; performing a first hot pressing and sintering treatment on each group of the mixed particles to obtain multiple hot pressed layered bodies; stacking the multiple hot pressed layered bodies in the order of the ceramic content along the thickness direction, and performing a second hot pressing and sintering treatment to obtain the functional gradient material. An embodiment of the present invention provides a method for preparing a functional gradient material, which can provide a functional gradient material that takes into account both hardness and toughness.

Description

Technical Field

[0001] The present invention relates to the technical field of functional gradient materials, and in particular to a method for preparing a functional gradient material. Background Art

[0002] In the aerospace field, high material performance requirements are placed on materials, requiring both high hardness and good toughness. However, the properties of materials in nature are often relatively stable, and it is difficult to achieve both hardness and toughness.

[0003] Therefore, a functionally gradient material that can balance hardness and toughness is needed. Summary of the Invention

[0004] The embodiment of the present invention provides a method for preparing a functionally gradient material, which can provide a functionally gradient material having both hardness and toughness.

[0005] An embodiment of the present invention provides a method for preparing a functionally gradient material, comprising:

[0006] By adjusting the rotation speed of the rotating electrode in the plasma rotating electrode process, metal particles of different particle sizes can be prepared;

[0007] The metal particles of different particle sizes are mixed with different amounts of ceramic powder to obtain multiple groups of mixed particles; wherein, in the multiple groups of mixed particles, the finer the particle size of the metal particles, the higher the proportion of the ceramic powder;

[0008] performing a first hot pressing and sintering process on each group of the mixed particles to obtain a plurality of hot pressed layered bodies;

[0009] A plurality of the hot-pressed layered bodies are stacked in the order of ceramic content along the thickness direction, and subjected to a second hot-pressing sintering process to obtain the functional gradient material.

[0010] In a possible design, before the second hot pressing and sintering process, the plurality of hot pressed layered bodies are subjected to ultrasonic treatment and high-temperature hot air treatment.

[0011] In a possible design, the metal particles include titanium alloy, and the ceramic powder includes ceramic powder containing boron, carbon, and / or nitrogen.

[0012] In a possible design, the particle size of the ceramic powder is 5-10 μm.

[0013] In one possible design, the method of preparing metal particles of different sizes by adjusting the rotation speed of the rotating electrode in the plasma rotating electrode process includes:

[0014] Determine the different size ranges of metal particles;

[0015] According to the particle size range, the rotation speed of the rotating electrode in the plasma rotating electrode process is allocated between 8000 and 35000 rpm;

[0016] According to the rotating electrode speed, the current value in the plasma rotating electrode process is controlled within the range of 600~1200A; wherein, the current and the speed are inversely proportional;

[0017] Micron-sized metal particles with different particle sizes of 5 to 20 μm are obtained.

[0018] In a possible design, each group of the mixed particles is subjected to a first hot pressing and sintering process to obtain a plurality of hot pressed layered bodies, including:

[0019] A first hot pressing sintering treatment at different temperatures is performed on each group of the mixed particles; wherein, the higher the proportion of metal particles in the mixed particles, the higher the temperature of the first hot pressing sintering.

[0020] In a possible design, in the multiple groups of mixed particles, the volume fraction of ceramic powder is 1 to 8.

[0021] In one possible design, the plurality of hot-pressed laminates are stacked in the thickness direction in order of ceramic content, and subjected to a second hot-pressing sintering process to obtain the functionally gradient material, including:

[0022] stacking a plurality of the hot-pressed laminates in order of ceramic content along a thickness direction;

[0023] After a heat insulation layer is provided on one side of the hot-pressed layered body having the lowest ceramic content, a second hot-pressing sintering process is performed to obtain the functional gradient material.

[0024] In a possible design, the temperature of the first hot pressing sintering is 800-1200° C., and the pressure of the first hot pressing sintering is 80-120 MPa.

[0025] In a possible design, the temperature of the second hot pressing sintering process is 950-1100° C., and the pressure is 100-150 MPa.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] In the present invention, metal particles of varying particle sizes are first prepared by controlling the rotational speed of a plasma rotating electrode. The faster the rotational speed, the smaller the metal particle size, the faster the cooling rate, and the smaller the crystal size. Conversely, the slower the rotational speed, the larger the metal particle size, the slower the cooling rate, and the larger the crystal size. The smaller the crystal size, the higher the hardness, and the larger the crystal size, the better the toughness. In summary, by controlling the electrode rotational speed, it is possible to produce small metal particles with small particle size and small crystal size, and large metal particles with large particle size and large crystal size. Metal particles of different particle sizes are mixed with ceramic powders of different volumes. The smaller the metal particle size, the higher the proportion of ceramic powder in the mixed particles, resulting in multiple groups of mixed particles. Within these multiple groups of mixed particles, the smaller the metal particle size, the higher the proportion of ceramic powder in the mixed particles. The addition of ceramic powder can improve the material's ablation resistance. Furthermore, during sintering, it can react at the boundaries of the metal grains, generating a ceramic body that fills and distributes at the boundaries of the metal grains, increasing the hardness of the material itself. A higher proportion of ceramic powder results in a more significant increase in hardness. Conversely, a lower proportion of ceramic powder results in relatively higher toughness. Each group of mixed particles undergoes a first hot-pressing sintering process to produce multiple hot-pressed laminates. These laminates are then stacked along the thickness direction in order of ceramic content and subjected to a second hot-pressing sintering process to produce a functionally graded material. The resulting material exhibits varying ceramic content and crystal sizes along the thickness direction. One side has smaller crystals, a higher ceramic content, and higher hardness, while the other side has larger crystals, a lower ceramic content, or even no ceramic, and better toughness. The middle section exhibits a gradient of hardness and toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 This is a flow chart of a method for preparing a functional gradient material provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] In the description of the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "plurality" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] In the description of this specification, it should be understood that the directional terms such as "upper" and "lower" described in the embodiments of the present invention are described from the perspectives shown in the accompanying drawings and should not be understood as limiting the embodiments of the present invention. In addition, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" of another element, it can not only be directly connected "upper" or "lower" of the other element, but also indirectly connected "upper" or "lower" of the other element through an intermediate element.

[0033] Please refer to Figure 1 , an embodiment of the present invention provides a method for preparing a functionally gradient material, comprising:

[0034] By adjusting the rotation speed of the rotating electrode in the plasma rotating electrode process, metal particles of different particle sizes can be prepared;

[0035] Mixing metal particles of different particle sizes with different amounts of ceramic powder to obtain multiple groups of mixed particles; wherein, in the multiple groups of mixed particles, the finer the particle size of the metal particles, the higher the proportion of the ceramic powder;

[0036] performing a first hot pressing and sintering process on each group of mixed particles to obtain a plurality of hot pressed layered bodies;

[0037] Multiple hot-pressed layered bodies are stacked in the order of ceramic content along the thickness direction, and subjected to a second hot-pressing sintering process to obtain a functional gradient material.

[0038] In the present invention, metal particles of varying particle sizes are first prepared by controlling the rotational speed of a plasma rotating electrode. The faster the rotational speed, the smaller the metal particle size, the faster the cooling rate, and the smaller the crystal size. Conversely, the slower the rotational speed, the larger the metal particle size, the slower the cooling rate, and the larger the crystal size. The smaller the crystal size, the higher the hardness, and the larger the crystal size, the better the toughness. In summary, by controlling the electrode rotational speed, it is possible to produce small metal particles with small particle size and small crystal size, and large metal particles with large particle size and large crystal size. Metal particles of different particle sizes are mixed with ceramic powders of different volumes. The smaller the metal particle size, the higher the proportion of ceramic powder in the mixed particles, resulting in multiple groups of mixed particles. Within these multiple groups of mixed particles, the smaller the metal particle size, the higher the proportion of ceramic powder in the mixed particles. The addition of ceramic powder can improve the material's ablation resistance. Furthermore, during sintering, it can react at the boundaries of the metal grains, generating a ceramic body that fills and distributes at the boundaries of the metal grains, increasing the hardness of the material itself. A higher proportion of ceramic powder results in a more significant increase in hardness. Conversely, a lower proportion of ceramic powder results in relatively higher toughness. Each group of mixed particles undergoes a first hot-pressing sintering process to produce multiple hot-pressed laminates. These laminates are then stacked along the thickness direction in order of ceramic content and subjected to a second hot-pressing sintering process to produce a functionally graded material. The resulting material exhibits varying ceramic content and crystal sizes along the thickness direction. One side has smaller crystals, a higher ceramic content, and higher hardness, while the other side has larger crystals, a lower ceramic content, or even no ceramic, and better toughness. The middle section exhibits a gradient of hardness and toughness.

[0039] It should be noted that the large-size metal particles may be mixed with a small amount of ceramic powder or may not be mixed with ceramic powder. The above-mentioned different amounts of ceramic powder include 0-content ceramic powder.

[0040] In some embodiments of the present invention, before the second hot pressing and sintering process, the plurality of hot pressed layered bodies are subjected to ultrasonic treatment and high-temperature hot air treatment.

[0041] In this embodiment, before the second hot pressing sintering process, in order to ensure bonding strength and product quality, multiple hot pressed layered bodies are ultrasonically treated to disperse particles, stains or dust that may exist on their surfaces, and then high-temperature hot air is used to remove the dispersed particles, stains or dust.

[0042] In some embodiments of the present invention, the metal particles include titanium alloy, and the ceramic powder includes ceramic powder containing boron, carbon, and / or nitrogen.

[0043] In this embodiment, the titanium alloy has the characteristics of high temperature resistance, excellent mechanical properties and light weight, and is suitable for the aerospace field.

[0044] In this embodiment, ceramic powder containing boron, carbon and / or nitrogen elements can react with titanium to obtain a ceramic body with increased hardness.

[0045] In some embodiments of the present invention, the particle size of the ceramic powder is 5-10 μm.

[0046] In this embodiment, the particle size of the ceramic powder is within the range of 5 to 10 μm, which can better mix and encapsulate the metal particles, increase the contact surface between the metal particles and the ceramic powder, and increase the efficiency of the combination or reaction.

[0047] In some embodiments of the present invention, metal particles of different particle sizes are prepared by adjusting the rotation speed of the rotating electrode in the plasma rotating electrode process, including:

[0048] Determine the different size ranges of metal particles;

[0049] The rotation speed of the rotating electrode in the plasma rotating electrode process is allocated between 8000 and 35000 rpm according to the particle size range;

[0050] According to the rotating electrode speed, the current value in the plasma rotating electrode process is controlled within the range of 600~1200A; wherein, the current and the speed are inversely proportional;

[0051] Micron-sized metal particles with different particle sizes of 5 to 20 μm are obtained.

[0052] In this embodiment, the rotational speed can be controlled to 8,000-10,000 rpm, 18,000-20,000 rpm, and 30,000-35,000 rpm, corresponding to 1,000-1,200 A, 800-1,000 A, and 600-800 A, respectively. The higher the current, the higher the electrode temperature and the higher the degree of melting of the metal material. The higher the degree of melting, the larger the particles ejected. Furthermore, the slower the rotational speed, the larger the particles ejected by centrifugal force. Therefore, a low rotational speed combined with a high current can produce large-sized metal particles, while a high rotational speed combined with a low current can produce small-sized metal particles.

[0053] Of course, you can also set more different speeds between 8000 and 35000 rpm according to your needs to obtain metal particles of more different particle sizes. The current can also be adaptively adjusted according to different speeds.

[0054] In some embodiments of the present invention, each group of mixed particles is subjected to a first hot pressing and sintering process to obtain a plurality of hot pressed layered bodies, including:

[0055] Each group of mixed particles is subjected to a first hot pressing sintering treatment at different temperatures; wherein, the higher the proportion of metal particles in the mixed particles, the higher the temperature of the first hot pressing sintering.

[0056] In the present application, the temperature of the first hot pressing sintering treatment affects the degree of recrystallization of the metal. The higher the temperature, the better the degree of recrystallization and the larger the resulting grains. When the temperature is low, the degree of metal recrystallization is low or no recrystallization occurs. Therefore, by controlling the temperature of the first hot pressing sintering treatment at a higher temperature, the mixed particles of large metal grains can be sintered and the grains can be further enlarged; by controlling the first sintering temperature at a lower temperature, the mixed particles are only combined and compacted with each other, and no or little recrystallization occurs, so that after the mixed particles of small metal grains are sintered, the grains remain at a smaller level.

[0057] In some embodiments of the present invention, the volume fraction of the ceramic powder in the multiple groups of mixed particles is 1-8.

[0058] In some embodiments of the present invention, a plurality of hot-pressed laminates are stacked in the thickness direction in order of ceramic content and subjected to a second hot-pressing sintering process to obtain a functionally gradient material, comprising:

[0059] stacking a plurality of hot-pressed laminates in order of ceramic content along a thickness direction;

[0060] After a heat-insulating layer is provided on one side of the hot-pressed laminate having the lowest ceramic content, a second hot-pressing sintering process is performed to obtain a functionally gradient material.

[0061] In this embodiment, after a thermal insulation layer is provided on one side of the hot-pressed layered body having the lowest ceramic content, the temperature rises slowly during the second hot-pressing sintering. However, as time passes, it can still reach a temperature (900°C) at which the titanium crystals can be transformed from a close-packed hexagonal structure to a body-centered cubic structure. As the second hot-pressing sintering ends, the temperature begins to gradually decrease. However, due to the presence of the thermal insulation layer, the cooling rate of the portion with a low ceramic content is slow. The cooling rate is related to the content of body-centered cubic structure crystals. The slower the cooling rate, the lower the content of body-centered cubic structure crystals, and the stronger the toughness of the material. The faster the cooling rate, the higher the content of body-centered cubic structure crystals, and the stronger the hardness of the material.

[0062] It should be noted that although the second hot-pressing sintering treatment also causes recrystallization, the size relationship between the larger and smaller crystals remains unchanged after both undergo recrystallization. Furthermore, the ceramic phase distributed at the boundaries of the smaller crystals within the hot-pressed layered structure limits the extent of recrystallization. Therefore, only a portion of the crystals within the hot-pressed layered structure undergo recrystallization, with minimal impact on the overall changes in the crystal grain size.

[0063] In some embodiments of the present invention, the temperature of the first hot pressing sintering is 800-1200° C., and the pressure of the first hot pressing sintering is 80-120 MPa.

[0064] In some embodiments of the present invention, the temperature of the second hot pressing sintering process is 950-1100° C., and the pressure is 100-150 MPa.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a functionally gradient material, characterized in that: include: By adjusting the rotation speed of the rotating electrode in the plasma rotating electrode process, metal particles of different particle sizes can be prepared; The metal particles of different particle sizes are mixed with different amounts of ceramic powder to obtain multiple groups of mixed particles; wherein, in the multiple groups of mixed particles, the finer the particle size of the metal particles, the higher the proportion of the ceramic powder; performing a first hot pressing and sintering process on each group of the mixed particles to obtain a plurality of hot pressed layered bodies; stacking a plurality of the hot-pressed layered bodies in order of ceramic content along a thickness direction, and performing a second hot-pressing sintering process to obtain the functionally gradient material; Before the second hot pressing and sintering process, the plurality of hot pressed layered bodies are subjected to ultrasonic treatment and high temperature hot air treatment; The first hot pressing and sintering process is performed on each group of the mixed particles to obtain a plurality of hot pressed layered bodies, including: performing a first hot pressing sintering process at different temperatures on each group of the mixed particles; wherein the higher the proportion of metal particles in the mixed particles, the higher the temperature of the first hot pressing sintering; The method of stacking a plurality of the hot-pressed laminates in order of ceramic content along the thickness direction and performing a second hot-pressing sintering process to obtain the functionally gradient material comprises: stacking a plurality of the hot-pressed laminates in order of ceramic content along a thickness direction; After providing a heat-insulating layer on one side of the hot-pressed layered body having the lowest ceramic content, a second hot-pressing sintering process is performed to obtain the functionally gradient material; The temperature of the first hot pressing sintering is 800-1200° C., and the pressure of the first hot pressing sintering is 80-120 MPa; The temperature of the second hot pressing sintering process is 950-1100° C., and the pressure is 100-150 MPa.

2. The preparation method according to claim 1, characterized in that The metal particles include titanium alloy, and the ceramic powder includes ceramic powder containing boron, carbon and / or nitrogen elements.

3. The preparation method according to claim 1, characterized in that The particle size of the ceramic powder is 5-10 μm.

4. The preparation method according to claim 1, characterized in that The method of preparing metal particles of different particle sizes by adjusting the rotation speed of the rotating electrode in the plasma rotating electrode process includes: Determine the different size ranges of metal particles; According to the particle size range, the rotation speed of the rotating electrode in the plasma rotating electrode process is allocated between 8000 and 35000 rpm; According to the rotating electrode speed, the current value in the plasma rotating electrode process is controlled within the range of 600~1200A; wherein, the current and the speed are inversely proportional; Micron-sized metal particles with different particle sizes of 5 to 20 μm are obtained.

5. The preparation method according to claim 1, characterized in that In the plurality of groups of mixed particles, the volume fraction of the ceramic powder is 1 to 8.

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