An amorphous alloy powder precision forming method based on multi-stage pressure gradient regulation

Abstract

The application discloses a kind of amorphous alloy powder precision forming methods based on multistage pressure gradient regulation, comprising the following steps: step 1: to be pressed amorphous alloy powder is placed in mould cavity;Step 2: first stage pressure P1 is applied to the amorphous powder in mould cavity, and the first stage pressure P1 is kept for the first preset time t1;Step 3: after the first preset time t1, the applied pressure is adjusted to second stage pressure P2, and the second stage pressure P2 is kept for the second preset time t2;Through the implementation of the application, the instantaneous breakage of particles and the initiation of microcracks caused by stress concentration in the initial pressurization stage are avoided, the generation and expansion of cracks are effectively inhibited, the cracking tendency of the compact is greatly reduced, the integrity of the formed product is improved, and has certain use value and popularization value.

Description

Technical Field

[0001] This invention relates to the field of powder metallurgy technology, and in particular to a method for precision forming of amorphous alloy powder based on multi-level pressure gradient control. Background Technology

[0002] Amorphous materials, due to their unique disordered atomic arrangement, typically exhibit excellent physical and chemical properties, such as high strength, high hardness, good wear resistance, and corrosion resistance. These unique properties make them promising for applications in aerospace, electronic devices, precision molds, and other fields.

[0003] However, these characteristics, especially high hardness and brittleness, also pose significant challenges to the compression molding of the powder. During the compression process, amorphous powder particles are difficult to plastically deform, and the contact between particles is mainly point contact, making it difficult to form a dense compact, and the green strength of the compact is low. This point contact state is due to the inability of particles to increase the contact area through plastic flow, resulting in high stress concentration.

[0004] When traditional single-pass rapid compression molding methods are applied to such hard and brittle amorphous powders, stress tends to concentrate at a few particle contact points due to the powder's poor deformability. When the local stress exceeds the material's fracture strength, microcracks form inside the compact. These microcracks easily propagate during pressure increases, pressure release, and subsequent demolding and handling, eventually developing into macroscopic cracks. Furthermore, the powder's inherent physical properties (such as poor particle size distribution, irregular shape, and rough surface) also make effective filling and densification difficult, further complicating molding and exacerbating cracking. These problems severely restrict the application of amorphous powders in components requiring precision molding and structural integrity.

[0005] Currently, advanced technologies such as isostatic pressing, hot pressing, and spark plasma sintering (SPS) are used for pressing some powder materials. However, hot pressing and SPS technologies typically require more complex forming conditions and involve high-temperature environments, which may cause amorphous materials to crystallize, thus losing their valuable amorphous properties and related excellent performance. Although cold isostatic pressing can be performed in stages at room temperature, avoiding the risk of crystallization and providing a more uniform pressure distribution, its effectiveness in solving the cracking problem caused by local stress concentration and deformation incompatibility in conventional uniaxial pressing molds for hard and brittle amorphous powders is still limited. Furthermore, it has drawbacks such as complex equipment, with equipment investment costs 3-5 times higher than conventional pressing equipment; low production efficiency, with a single forming cycle lengthening by more than 40%; difficulty in continuous production; and low batch capacity, resulting in high production costs and making it unsuitable for all applications.

[0006] Therefore, there is an urgent need to develop a simple, effective, and low-cost method for pressing amorphous powder to overcome the shortcomings of the existing technology, especially to effectively prevent compact cracking and improve molding quality under conventional uniaxial pressing conditions. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a precision forming method for amorphous alloy powder based on multi-level pressure gradient control. This method aims to solve the problems of poor forming effect and easy cracking of compacts caused by the high hardness, high brittleness, and difficulty in deformation of amorphous powder during pressing.

[0008] To achieve the above objectives, the present invention provides a method for densifying and pressing amorphous soft magnetic composite magnetic powder cores, comprising the following steps:

[0009] Step 1: Place the amorphous alloy powder to be pressed into the mold cavity;

[0010] Step 2: Apply a first-stage pressure P1 to the amorphous powder in the mold cavity, and maintain the pressure under the first-stage pressure P1 for a first preset time t1;

[0011] Step 3: After the first preset time t1, the applied pressure is adjusted to the second stage pressure P2, and the pressure is maintained at the second stage pressure P2 for a second preset time t2.

[0012] Step 4: After the second preset time t2, adjust the applied pressure to the final target pressure P. f Under the final target pressure P f The pressing process is completed to obtain a pressed and shaped object.

[0013] Preferably, in step 2, the first-stage pressure P1 is the final target pressure P. f The first preset ratio, and the first preset ratio satisfies the following relationship: 5% ≤ First stage pressure P1 / Final target pressure P f ≤30%.

[0014] Preferably, in step 2, the first preset time t1 is 0.5 seconds to 10 seconds.

[0015] Preferably, in step 3, the pressure P2 in the second stage is higher than the pressure P1 in the first stage.

[0016] Preferably, the second-stage pressure P2 is the final target pressure P. f The second preset ratio, and the second preset ratio satisfies the following relationship: 30% < second stage pressure P2 / final target pressure P f ≤70%.

[0017] Preferably, in step 3, the second preset time t2 is 0.5 seconds to 10 seconds.

[0018] Preferably, the second-stage pressure P2 and the final target pressure P are applied. f In addition, there are at least one staged pressurization and pressure holding steps, with the pressure of each subsequent step being higher than that of the previous step but lower than the final target pressure P. f .

[0019] Preferably, the final target pressure P f The range is from 600MPa to 2500MPa.

[0020] The substantial effects of this invention:

[0021] 1. In this invention, by applying pressure in stages and coordinating with intermediate holding times, the response characteristics of the material at different pressure stages are utilized. In the initial, lower pressure stage, the hard and brittle amorphous powder particles undergo preliminary packing adjustment and a small amount of elastic deformation. Crucially, the holding time in this stage allows the particles to slide and rotate as necessary to seek a more stable packing position and release localized high stress caused by uneven initial packing. This avoids immediate particle breakage and microcrack initiation due to excessively rapid stress concentration in the initial pressurization stage. The subsequent intermediate pressure stage and its holding time, after initial stabilization... Further pressure is applied to the granular system to promote a more compact packing of particles, which may be accompanied by some minor plastic deformation or controlled micro-fragmentation to fill the pores. The pressure holding at this stage is equally important, as it allows the internal stress generated under higher pressure to relax and redistribute to a certain extent. Since the stress peak is effectively weakened, the initiation and propagation of cracks are effectively suppressed. When the full pressure is finally applied, the powder is already in a relatively uniform and pre-compacted state, which can better withstand the final high-pressure impact, thereby significantly reducing the cracking tendency of the compact and improving the integrity of the molded product.

[0022] 2. In this invention, the gradual pressurization process, especially the combination of holding time, facilitates the expulsion of gas between powder particles and reduces the formation of closed pores. At the same time, the particles have more time to rearrange, gradually transitioning from initially unstable point contact to more stable limited surface contact, increasing the effective bonding area between particles. This not only results in a higher and more uniform compact density but also correspondingly improves the green strength of the compact, laying a good foundation for subsequent possible sintering or other processing steps. Higher green strength also means that the compact is less prone to damage during demolding, handling, and subsequent processing.

[0023] 3. In this invention, by controlling the pressurization process, it can be achieved on conventional hydraulic presses or mechanical presses by modifying the control system or operating procedures, without the need to purchase complex and expensive special equipment. Therefore, this method has low equipment modification costs, is easy to operate, and is easy to realize industrial production. It has good economic benefits and broad application prospects, and is especially suitable for cost-sensitive or high-output applications. It has certain use value and promotion value. Attached Figure Description

[0024] Figure 1 This is a pressure-time diagram of the amorphous powder segmented pressure molding method in Example 1. Detailed Implementation

[0025] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments.

[0026] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0027] Example 1:

[0028] This embodiment is basically the same as Embodiment 1, except that this embodiment provides a method for pressing and molding iron-based amorphous powder. The Fe-Si-B-Cr amorphous powder used is prepared by water atomization, and the average particle size D of the iron-based amorphous powder is... 50 It has a diameter of 15μm and exhibits high hardness and significant brittleness.

[0029] The compression steps are as follows:

[0030] Step 1: Powder preparation and mold loading: 2 grams of amorphous powder granulation powder are evenly loaded into a cemented carbide steel mold cavity with an inner diameter of 12 mm and an outer diameter of 7 mm. The loading amount is calculated and determined based on the target compact thickness (e.g., 4.7 mm) and the desired density.

[0031] Step 2: Segmented pressurization and pressure holding (refer to...) Figure 1 This demonstrates the process of applying pressure in stages over time, including an initial pressure stage, an intermediate pressure stage, and a final pressure stage, as well as the holding time for each stage, intuitively illustrating the core technical features of the invention.

[0032] Step 2.1: Initial pressurization and pressure holding: Apply pressure to the cavity of the cemented carbide steel mold using a servo press, so that the powder is subjected to pressure that reaches 5% of the final target pressure (set to 1800 MPa), i.e., 90 MPa, and hold the pressure at this 90 MPa pressure for 10 seconds.

[0033] Step 2.2: Intermediate pressurization and pressure holding: Subsequently, the pressure is steadily increased from 90 MPa to 40% of the final target pressure, i.e., 720 MPa, and held at this 720 MPa pressure for 5 seconds.

[0034] Step 2.3: Final pressurization: Finally, the pressure is steadily increased from 720 MPa to the final target pressure of 1800 MPa. After reaching 1800 MPa, the pressure is held for 2 seconds to ensure that the pressure is evenly transmitted, and then the pressure is released.

[0035] Step 3: Demolding and Inspection: After depressurization, the pressed blank is ejected from the mold. The macroscopic integrity of the blank is observed, and any defects such as cracks or missing corners are checked. At the same time, the density and hardness of the blank can be measured.

[0036] Using the method of this embodiment, the obtained amorphous iron-based powder compact has a smooth surface, no obvious cracks, and a complete shape. The density can reach 82% of the theoretical density, indicating good molding effect. In this embodiment, the initial 5% pressure and 10-second holding pressure mainly serve to overcome the initial frictional resistance between powder particles and promote initial sliding and a small amount of rearrangement. The pressure at this stage is relatively low, but sufficient to allow the particle system to form a relatively stable initial skeleton. The holding pressure time gives the particles enough time to complete this adjustment, avoiding immediate brittle fracture of particles due to excessive initial impact. The key to this stage is to establish initial soft contact between particles, laying the foundation for the subsequent densification process and reducing stress concentration sources in the subsequent high-pressure stage.

[0037] The subsequent application of 40% pressure (720 MPa) and a 5-second holding pressure further compresses the powder based on the already initially stabilized particle skeleton, forcing the particles to pack more tightly and increasing the contact area and coordination number between particles. Since the particles have already undergone preliminary rearrangement, the stress distribution caused by the increased pressure at this stage is more uniform. The holding pressure process helps to redistribute and relax the stress between particles, reducing new crack initiations caused by excessive local stress, or closing existing micropores.

[0038] Finally, pressurizing to 1800 MPa completes the main densification process. Due to the effective pretreatment in the first two stages, the powder now possesses good pressure resistance and a relatively uniform internal structure, enabling it to withstand the final high pressure without easily causing catastrophic cracking. The above process guides material behavior by precisely controlling the pressurization path, thereby achieving the desired molding effect.

[0039] Example 2:

[0040] This embodiment is basically the same as Embodiment 1, except that this embodiment provides a method for pressing and molding iron-based amorphous powder. The Fe-Si-B-Nb-Cr amorphous powder used is prepared by water atomization, and the average particle size D is... 50 It has a diameter of 12.8 μm and exhibits high hardness and significant brittleness.

[0041] The compression steps are as follows:

[0042] Step 1: Powder preparation and mold loading: Evenly load 2 grams of the above-mentioned amorphous powder granulation powder into a cemented carbide steel mold cavity with an inner diameter of 12 mm and an outer diameter of 7 mm.

[0043] Step 2: Segmented pressurization and pressure holding:

[0044] Step 2.1: Initial pressurization and holding pressure: Apply pressure to the mold through the press so that the powder is subjected to 20% of the final target pressure (set to 2500 MPa), i.e., 500 MPa, and hold the pressure at this 500 MPa pressure for 3 seconds.

[0045] Step 2.2: Intermediate pressurization and pressure holding: Subsequently, the pressure is steadily increased from 500 MPa to 60% of the final target pressure, i.e., 1500 MPa. This 1500 MPa pressure is held for 3 seconds.

[0046] Step 2.3: Final pressurization: Finally, steadily increase the pressure from 1500 MPa to the final target pressure of 2500 MPa. After reaching 2500 MPa, hold the pressure for 1 second, and then release the pressure.

[0047] Step 3: Demolding and Inspection: After releasing the pressure, eject the pressed blank from the mold. Observe the macroscopic integrity of the blank, checking for defects such as cracks and missing corners. At the same time, the density and hardness of the blank can be measured.

[0048] Using the method of this embodiment, the obtained amorphous iron-based powder compact has a smooth surface, no obvious cracks, complete shape, and a density that can reach 85% of the theoretical density, resulting in good molding performance. In this embodiment, the three stages of pressing serve the same purpose as in Example 1, guiding material behavior through precise control of the pressurization path to achieve the desired molding effect.

[0049] Example 3:

[0050] This embodiment is basically the same as Embodiment 1, except that it provides a method for pressing and molding iron-based amorphous powder. The Fe-Si-B-Nb-Cr amorphous powder used is prepared by water atomization, with an average particle size D.50 It has a diameter of 11.6 μm and exhibits high hardness and significant brittleness.

[0051] The compression steps are as follows:

[0052] Step 1. Powder preparation and mold loading: Evenly load 2 grams of the above-mentioned amorphous powder granulation powder into a cemented carbide steel mold cavity with an inner diameter of 12 mm and an outer diameter of 7 mm.

[0053] Step 2. Segmented pressurization and pressure holding:

[0054] Step 2.1: Initial pressurization and holding pressure: Apply pressure to the mold using a press so that the powder is subjected to 30% of the final target pressure (set to 600 MPa), i.e., 180 MPa, and hold the pressure at this 180 MPa pressure for 5 seconds.

[0055] Step 2.2: Intermediate pressurization and pressure holding: Subsequently, the pressure is steadily increased from 180 MPa to 70% of the final target pressure, i.e., 420 MPa, and held at this 420 MPa pressure for 10 seconds.

[0056] Step 2.3: Final pressurization: Finally, the pressure is steadily increased from 420 MPa to the final target pressure of 600 MPa. After reaching 600 MPa, the pressure is held for 5 seconds to ensure that the pressure is evenly transmitted, and then the pressure is released.

[0057] Step 3. Demolding and Inspection: After releasing the pressure, eject the pressed blank from the mold. Observe the macroscopic integrity of the blank and check for defects such as cracks and missing corners. At the same time, the density and hardness of the blank can be measured.

[0058] Using the method of this embodiment, the obtained Fe-Si-B-Nb-Cr powder compact has a smooth surface, no obvious cracks, complete shape, and a density that can reach about 78% of the theoretical density, resulting in good molding effect.

[0059] Example 4:

[0060] The precision forming method for amorphous alloy powder in this embodiment is not limited to two intermediate pressurization and holding stages. As needed, more (e.g., three or four in total) segmented pressurization and holding steps can be set, with the pressure of each subsequent step being higher than that of the previous step, to achieve final densification in a smoother and more refined manner, which is more advantageous for particularly sensitive or extremely brittle amorphous powder systems.

[0061] This embodiment uses the following four-segment pressing sequence to press Fe-Si-B-Cr amorphous powder:

[0062] Phase 1: Apply 20% of the final target pressure and hold for 2 seconds;

[0063] Second stage: Increase the pressure to 40% of the final target pressure and hold the pressure for 2 seconds;

[0064] Third stage: Increase the pressure to 75% of the final target pressure and hold the pressure for 2 seconds;

[0065] Fourth stage: Increase the pressure to the final target pressure (2000 MPa) and hold the pressure for 2 seconds.

[0066] This more refined pressure step can further reduce the pressure increment ratio at each step, thereby more effectively controlling stress accumulation and release and minimizing the risk of cracking. Using the method of this embodiment, the obtained amorphous Fe-Si-B-Cr powder compact has a smooth surface, no obvious cracks, intact shape, and a density that reaches 84.5% of the theoretical density, exhibiting excellent molding performance.

[0067] The method of this invention is applicable to various types of amorphous powders, including but not limited to iron-based amorphous powders, cobalt-based amorphous powders, nickel-based amorphous powders, zirconium-based amorphous alloy powders, and other metal or alloy-based amorphous powders. Furthermore, this method may also be applicable to certain ceramic powders with similar high hardness and brittleness properties, provided they face similar cracking problems due to high hardness and brittleness during cold pressing.

[0068] Comparative Example 1:

[0069] The same iron-based amorphous Fe-Si-B-Cr powder and the same mold were used as in Example 1. The difference was that a conventional single-pressurization method was used: the pressure was applied directly and rapidly from 0 to the final target pressure of 1800 MPa, and held at 1800 MPa for 3 seconds.

[0070] Comparative Example 2:

[0071] The same iron-based amorphous Fe-Si-B-Nb-Cr powder and the same mold were used as in Example 3. The difference was that a conventional single-stage pressurization method was used: the pressure was applied directly and rapidly from 0 to the final target pressure of 600 MPa, and held at 600 MPa for 3 seconds.

[0072] Ten pressed samples were prepared for each of Examples 1-4 and Comparative Examples 1-2, and the results are recorded in Table 1 below.

[0073] Table 1: Comparison of the amorphous powder pressing effect between the method of the present invention and the traditional method.

[0074]

[0075] As can be seen from the comparison results in Table 1, the segmented pressure molding method of this invention significantly improves the cracking problem of amorphous powder compacts, greatly increases the molding success rate, and yields compacts with better appearance quality and higher density. This fully demonstrates the effectiveness and superiority of the technical solution of this invention. Providing these specific parameters and comparative data is to meet the requirements of patent law regarding the sufficiency of disclosure, enabling those skilled in the art to understand and reproduce this invention, while also clearly demonstrating the significant progress of this invention compared to the prior art. The selected parameters, such as final pressure, powder type, and particle size, are all designed to create a practical and operable scenario that highlights the effects of the invention.

[0076] Through the above technical solution, the present invention cleverly utilizes the principle of time for space, that is, by holding pressure at a specific pressure stage, the hard and brittle amorphous powder particles are given enough time to adjust their position and disperse stress, thereby avoiding the destructive consequences of traditional rapid one-time pressurization and realizing the effective and high-quality molding of amorphous powder.

[0077] Those skilled in the art should understand that this invention is not limited to the specific embodiments described above. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. For example, the pressure values ​​and holding times at each stage can be optimized and adjusted according to the specific type of amorphous powder, particle size, mold design, and performance requirements of the final product. The rates of pressurization and depressurization can also be controlled as process parameters.

[0078] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0079] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for precision forming of amorphous alloy powder based on multi-level pressure gradient control, characterized in that, Includes the following steps: Step 1: Place the amorphous alloy powder to be pressed into the mold cavity; Step 2: Apply a first-stage pressure P1 to the amorphous powder in the mold cavity, and maintain the pressure under the first-stage pressure P1 for a first preset time t1; Step 3: After the first preset time t1, the applied pressure is adjusted to the second stage pressure P2, and the pressure is maintained at the second stage pressure P2 for a second preset time t2. Step 4: After the second preset time t2, adjust the applied pressure to the final target pressure P. f Under the final target pressure P f The pressing process is completed to obtain a pressed and shaped object. Wherein, the first stage pressure P1 is the final target pressure P f The first preset ratio, and the first preset ratio satisfies the following relationship: 5% ≤ First stage pressure P1 / Final target pressure P f ≤30%; The second stage pressure P2 is the final target pressure P. f The second preset ratio, and the second preset ratio satisfies the following relationship: 30% < second stage pressure P2 / final target pressure P f ≤70%; The final target pressure P f The range is from 600MPa to 2500MPa.

2. The method for precision forming of amorphous alloy powder based on multi-level pressure gradient control according to claim 1, characterized in that, In step 2, the first preset time t1 is 0.5 seconds to 10 seconds.

3. The method for precision forming of amorphous alloy powder based on multi-level pressure gradient control according to claim 1, characterized in that, In step 3, the second preset time t2 is 0.5 seconds to 10 seconds.

4. The method for precision forming of amorphous alloy powder based on multi-level pressure gradient control according to claim 1, characterized in that, Applying the second-stage pressure P2 and the final target pressure P f In addition, there are at least one staged pressurization and pressure holding steps, with the pressure of each subsequent step being higher than that of the previous step but lower than the final target pressure P. f .

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