Precise forming process of high-performance dissimilar metal powder

Abstract

The invention relates to the technical field of metal powder processing, and discloses a high-performance dissimilar metal powder precision forming process which comprises the following steps: filling powder into a mold cavity, applying vibration disturbance, monitoring the change rate of a phase lag angle, judging that the powder is dense when the change rate is lower than an offset threshold value, outputting a pressing mode switching signal, an induction heating device is used for applying transient thermal load to induce cracks of an oxide film on the surfaces of particles, the pressure load is applied, the side wall is adjusted to generate shear displacement to peel off the oxide film, and metallurgical bonding is achieved through fresh metal surface contact. An interface is activated through thermal expansion mismatch and mechanical friction synergistically, a high-density uniform green body is obtained at low temperature, generation of brittle intermetallic compounds is inhibited, and the fatigue resistance of a formed part is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of metal powder processing technology, and in particular relates to a precision forming process for high-performance heterogeneous metal powders. Background Technology

[0002] Precision forming technology for high-performance heterogeneous metal powders is a key step in the preparation of composite functional parts. Metal powder processing methods typically involve applying pressure within a mold to mechanically interlock powder particles to form a green body with initial strength. This load-driven densification method gradually reveals its technical costs when dealing with heterogeneous systems that mix high-hardness refractory metals with high-ductility matrix metals. Due to the mechanical mismatch between particles, bridging effects are easily induced in the early stages of compaction. Hard component particles spontaneously build a mechanical support network and generate microscopic voids. The mainstream approach in the industry is to increase the total pressure to eliminate voids. While this can increase the overall density, it leads to excessive shearing and interfacial tearing in the ductile matrix, resulting in residual stress centers within the material. Although mechanical disturbance can disrupt bridging, the energy transfer deep within the particles is constrained by the damping gradient, leading to uneven kinetic energy distribution and particle gradation segregation within the green body.

[0003] Improved approaches that linearly increase load or extend vibration time cannot identify the physical transition nodes from fluid rearrangement to steady-state compaction within the particle system, making it difficult to resolve the contradiction of uneven microstructure distribution. Existing methods, while meeting the geometric accuracy of parts, often fail to simultaneously ensure the atomic-level bonding quality of heterogeneous interfaces. In addition to hardware limitations such as stress distribution imbalance, the dynamic sensing and interface activation mechanisms during the molding process also have shortcomings. For example, Chinese invention patent CN1074698C discloses a metal powder injection molding process that introduces a binder into the mixture to improve powder flowability and relies on subsequent high-temperature sintering for densification. This type of process is an open-loop control based on overall experience, which makes it difficult to accurately capture the physical transition nodes from fluid rearrangement to steady-state compaction within the powder system. The lengthy debinding and high-temperature sintering procedures can easily induce grain coarsening and the formation of brittle phases at the interface. For heterogeneous systems, this approach cannot specifically peel off the passivated oxide film on the particle surface, and the components only form microscopic mechanical interlocking rather than deep metallurgical bonding. The interface strength and fatigue resistance of the parts are difficult to meet the standards of high-end industrial applications.

[0004] Therefore, the technical problem to be solved by this invention is how to accurately capture the topologically densest packing point by characterizing the impedance evolution of the particle system in real time, and to achieve diffusion connection of heterogeneous components in coordination with the interface activation mechanism. Summary of the Invention

[0005] This invention provides a precision forming process for high-performance heterogeneous metal powders, characterized by comprising the following steps: Step S1: Fill the mold cavity with heterogeneous metal powder containing hard particulate phase and tough matrix phase, and drive the vibrator to apply vibration to the mold cavity, so that the heterogeneous metal powder will rearrange. Step S2: Monitor the phase lag angle between the input current of the frequency converter excitation source and the mechanical response of the vibrator, and calculate the rate of change of the phase lag angle over time. Step S3: When the absolute value of the phase hysteresis angle changes continuously below the preset offset threshold, it is determined that the heterogeneous metal powder has reached a dense filling state, and a pressing mode switching signal is output. Step S4: In response to the pressing mode switching signal, a transient thermal load is applied to the heterogeneous metal powder in the mold cavity using an induction heating device, causing brittle cracks to form on the oxide film on the particle surface of the heterogeneous metal powder. Step S5: Start the pressurizing mechanism to apply pressure load to the heterogeneous metal powder, and simultaneously adjust the sidewall of the mold cavity to generate shear displacement to peel off the oxide film on the particle surface, so that the exposed fresh metal surface undergoes atomic diffusion and metallurgical bonding under the action of pressure load to obtain green blank.

[0006] Preferably, the monitoring of the phase lag angle in step S2 includes extracting the phase of the AC current output by the frequency converter excitation source, comparing it with the signal phase fed back by the displacement sensor of the vibrator, and calculating the physical characteristic value reflecting the evolution of the internal mechanical damping of the heterogeneous metal powder.

[0007] Preferably, the output of the suppression mode switching signal in step S3 includes capturing the physical moment when the phase lag angle reaches a preset minimum stable value, locking the critical point for optimizing the pose of the heterogeneous metal powder particles, and stopping the application of vibration after outputting the suppression mode switching signal.

[0008] Preferably, the heating rate of the transient thermal load in step S4 is 500°C. / s to 1200 / s, by utilizing the mismatch in the thermal expansion coefficients between the hard particle phase and the tough matrix phase, a normal shear force is generated at the interface between the oxide film on the particle surface and the particle matrix.

[0009] Preferably, it also includes a real-time pressure compensation step, which involves acquiring the acoustic emission signal generated by grinding heterogeneous metal powder particles using a sensor and calculating the frequency coherence coefficient of the sound wave transmission. The compensation increment for the pressure load is determined according to the following formula. : ,in, This is the compensation increment for the pressure load. This is a preset material elastic rebound compensation pressure value, whose physical dimensions are consistent with the pressure load. For frequency coherence coefficients; based on compensation increments Adjust the loading rate of the pressure load to counteract the elastic rebound between particles.

[0010] Preferably, in step S5, the sidewall generates shear displacement, including controlling the mold ring of the mold cavity to generate axial reciprocating movement, and the mechanical displacement of the sidewall is 2μm to 10μm, so as to mechanically abrade the particles of the heterogeneous metal powder through the sidewall.

[0011] Preferably, before step S1, a mold damping calibration step is also included: when the mold cavity is in an unloaded state, the unloaded phase lag angle reference of the exciter is measured, and the unloaded phase lag angle reference is used as the initial reference point for calculating the real-time offset of the phase lag angle.

[0012] Preferably, the metallurgical bonding is carried out in a temperature-pressure coupling environment below the melting point of the ductile matrix phase. By controlling the direct contact between atoms on the fresh metal surfaces, the diffusion energy barrier is reduced, thereby suppressing the formation of brittle intermetallic compounds between heterogeneous components.

[0013] Preferably, the hardness gradient distribution of the heterogeneous metal powder is in the range of 150HV to 800HV, and the frequency range of the vibration applied in step S1 is in the range of 15kHz to 35kHz.

[0014] Preferably, after obtaining the green blank, the process further includes a controlled cooling step: cooling the green blank under a protective atmosphere at 10°C. / min to 30 The cooling rate is reduced to room temperature at a rate of / min, releasing the microscopic residual stress accumulated during the molding process through a controlled temperature drop process.

[0015] Compared with existing technologies, the precision forming process of high-performance heterogeneous metal powder of the present invention has the following advantages: 1. In the precision forming of metal powder, the mechanical impedance evolution law inside the powder system can be characterized in real time by monitoring the phase lag angle change between the excitation signal and the feedback signal of the actuator. Since the phase lag angle directly reflects the degree of friction and mechanical locking between particles, when the rate of change of the lag angle enters the preset stable range, it indicates that the powder particles have changed from an unstable mechanical bridging state to the densest packing state at the topological level. This rearrangement judgment mechanism based on physical impedance feedback can capture the critical point of particle pose optimization, avoid particle gravity segregation caused by blindly increasing vibration energy, and ensure the uniform distribution of density inside the heterogeneous powder green body.

[0016] 2. The formation of micro-brittle cracks in the oxide film on the particle surface is induced by thermal pulse impact, and the physical peeling of the oxide film is achieved by the relative displacement of particles guided by shear stress. This mechanism allows the fresh metal interface to come into direct contact under forming pressure, reducing the diffusion energy barrier between heterogeneous atoms. This interface activation path, which is jointly constructed by thermal mismatch stress and mechanical friction, enables heterogeneous components to achieve metallurgical-grade bonding at temperatures below the melting point of the matrix, thereby inhibiting grain coarsening and the formation of brittle intermetallic compounds caused by high-temperature sintering.

[0017] 3. During the pressure switching and temperature-pressure coupling stages, the stability of the internal mechanical network of the green blank is inverted in real time by capturing the acoustic emission signal generated by particle grinding and calculating the frequency coherence of the acoustic wave transmission. The loading rate of the main pressure is dynamically fine-tuned according to the convergence state of the acoustic nonlinear parameters, and the elastic rebound vector of the high modulus component is offset by pressure compensation. This closed-loop locking logic that senses physical quantities eliminates submicron-level microcracks caused by elastic mismatch between dissimilar metals and improves the fatigue resistance of the formed parts under complex alternating loads. Attached Figure Description

[0018] Figure 1 This is a flow chart of the precision molding process of phase lag feedback and thermo-mechanical synergy of the present invention; Figure 2 This is a closed-loop control principle diagram of the heterogeneous metal powder forming system integrating multi-dimensional sensing feedback according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0020] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, low, lateral, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly indicating the number of technical features indicated.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0022] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0023] This invention provides a precision forming process for high-performance heterogeneous metal powders. By performing time-sequential physical intervention on metal powders containing hard particle phases and a tough matrix phase, a manufacturing process is constructed from particle topological rearrangement and interfacial oxide film peeling to thermo-pressure coupled diffusion bonding. Through steps such as powder filling monitoring, induction heating activation, dynamic pressure compensation, and controlled cooling, the forming process is closed-loop controlled by capturing the mechanical damping evolution signal and acoustic emission coherence characteristics within the particle system. During the heterogeneous metal powder filling stage, the high-hardness particle phase and the tough matrix phase, due to mechanical properties... Energy mismatch can easily lead to bridging effects, resulting in uneven microstructure density. To address this technical problem, this process fills the mold cavity with heterogeneous metal powder with a hardness gradient distribution ranging from 150HV to 800HV. A vibrator is then activated to apply vibrations at a frequency of 15kHz to 35kHz to the mold cavity, inducing rearrangement displacement of the particles. During this process, the variable frequency excitation source acquires the output current phase in real time and compares it with the signal phase fed back by the displacement sensor of the vibrator. The physical characteristic value characterizing the evolution of internal mechanical damping of the heterogeneous metal powder, namely the phase hysteresis angle, is calculated. When the phase lag angle is detected The absolute rate of change remains below the preset offset threshold for 15 seconds. When the speed reaches rad / s, it is determined that the heterogeneous metal powder has reached a dense filling state. At this point, a pressing mode switching signal is output and vibration is stopped, thereby determining the critical point for particle pose optimization. Mold damping reference pre-calibration is then performed, and the exciter is driven to... to Frequency band sweep and data acquisition Phase features extracted from input current signal of each cycle Calculate the reference variance of the phase lag angle. Set offset threshold Among them, the correction factor Based on the calibration of the ratio of the inner surface area of ​​the mold cavity to the powder filling volume, the hysteresis phase change rate is collected in real time and compared. Bias, determining the time during which the bias enters the statistical envelope and remains stable. This locks in the local minimum potential energy of the powder system, shielding the zero-point drift caused by the inherent frequency difference of the mechanical structure and the assembly gap.

[0024] Even when the powder reaches a densely packed state, the passivated oxide film on the particle surface still hinders direct diffusion between heterogeneous atoms. To address this obstacle, the system responds to the pressing mode switching signal and uses an induction heating device to apply a heating rate of 500°C to the heterogeneous metal powder within the mold cavity. / s to 1200 A transient thermal load of / s is applied, utilizing the mismatch in thermal expansion coefficients between the hard granular phase and the tough matrix phase, generating normal shear force at the interface between the oxide film on the particle surface and the particle matrix, causing brittle cracks in the oxide film. Simultaneously, a pressurizing mechanism is activated to apply pressure load to the dissimilar metal powder, driving the die ring in the mold cavity to reciprocate axially, causing 2... m to 10 The shear displacement m, through mechanical friction between the sidewalls and the heterogeneous metal powder particles, peels off the oxide film on the surface of the cracked particles, exposing the fresh metal surface. This surface then comes into direct contact with the metal under a temperature-pressure coupling environment below the melting point of the ductile matrix phase, achieving metallurgical bonding through atomic diffusion. As the pressure load increases to the forming pressure... During the grinding process, the difference in elastic modulus between heterogeneous components easily leads to elastic rebound. To suppress microcracks caused by rebound, acoustic emission signals generated by grinding heterogeneous metal powder particles are collected using sensors, and the frequency coherence coefficient of the sound wave during transmission through the particle network is calculated. According to the formula Determine the compensation increment for pressure load. ,in, This is the compensation increment for the pressure load. This is a preset material elastic rebound compensation pressure value, whose dimensions are consistent with the pressure load. For frequency coherence coefficients, based on compensation increments Adjusting the loading rate of the pressure load to counteract the elastic rebound vector of the high-modulus component ensures the stability of the internal mechanical network of the green body, and determining the proportional limit of the tough matrix phase. Using a linear regression model of heterogeneous mismatch coefficients The compensating pressure reference is calibrated, and the acoustic emission sensor captures the particle grinding signal sequence. ,according to The sampling point step size is divided into sliding windows, and a fast Fourier transform is performed. The normalized cross-correlation coefficient of adjacent windows within the main frequency bandwidth is extracted, and the frequency coherence coefficient is defined. Real-time calculation of compensation increment The pressure loading rate slope is dynamically adjusted and fed back to the hydraulic servo station to counteract the elastic recovery potential energy during the unloading of hard particles and eliminate submicron-level lamination defects caused by modulus mismatch of heterogeneous components. Uneven distribution of microscopic energy accumulated during the forming process easily generates residual stress. To address this issue, a controlled cooling step is performed after obtaining the green compact, where the green compact is cooled at 10°C under a protective atmosphere. / min to 30 The cooling rate is reduced to room temperature at a rate of / min, releasing the microscopic residual stress accumulated during the molding process through a controlled temperature drop process, thereby reducing the risk of deformation of the part during demolding.

[0025] Example 1: In preparing a heterogeneous metal wear-resistant ring with tungsten carbide as the hard particulate phase and cobalt-based alloy as the tough matrix phase, the tungsten carbide particles have a hardness of 800 HV and a volume percentage of 45%. The overlapping of the particles forms a bridging structure with mechanical deadlock characteristics, causing nonlinear attenuation of the pressing pressure transmission within the powder body, resulting in local density gradients and micropores. In this example, the process determined in the aforementioned specific implementation method is used to apply a high-frequency vibration excitation of 25 kHz to the mold cavity. The frequency conversion drive module synchronously collects the input current and calculates the phase lag angle. During this particle rearrangement stage, the phase lag angle The phase shifts as the kinetic energy absorption state of the powder system changes, and when the phase hysteresis angle is detected... The absolute rate of change remained stable for 15 seconds. When the speed is below rad / s, the powder system is determined to have reached the topological packing limit, and the output vibration excitation is stopped to provide a uniform initial particle spatial distribution for subsequent pressing and densification.

[0026] After obtaining densely packed powder, the induction heating device is driven at 800°C to target the passivation oxide layer present on the particle surface. A transient heating load is applied at a rate of / s, utilizing the difference in thermal expansion coefficients between the cobalt-based matrix phase and the tungsten carbide reinforcing phase to induce microscopic shear stress at the oxide film interface and cause brittle cracks in the oxide film. Secondly, the mold sidewall is adjusted to generate 5 The axial reciprocating motion of m utilizes the friction between the sidewall and powder particles to peel off the damaged oxide film, allowing the exposed fresh metal surface to directly contact the substrate under a temperature and pressure environment below the melting point of the cobalt-based matrix. By leveraging the synergistic effect of thermal mismatch stress and mechanical shear friction at the interface, the atomic diffusion activation energy is reduced, achieving interfacial metallurgical bonding without inducing grain coarsening. This is achieved as the pressure load increases from the initial stage to the forming pressure. During the process, in order to suppress the springback cracking of the green blank caused by the high elastic modulus of tungsten carbide particles, the sensor collects the acoustic emission signal generated by the grinding between particles and calculates the frequency coherence coefficient reflecting the coherence characteristics of the internal mechanical network. And according to the formula Determine the compensation increment for pressure load. ,in, This is the compensation increment for the pressure load. This is a preset material elastic rebound compensation pressure value, whose dimensions are consistent with the pressure load. The frequency coherence coefficient is determined by real-time adjustment of the pressure load compensation increment. To counteract the elastic recovery vector of the high-modulus component, the internal stress distribution of the green body is brought to a balanced state before unloading. The molded part is then placed in an argon protective atmosphere and heated to 20°C. Controlled cooling is performed at a rate of / min, and a constant temperature drop sequence is used to guide the dislocation rearrangement at the heterogeneous interface, dissipating the residual thermal stress accumulated during the forming process. The resulting heterogeneous metal forming part exhibits a metallurgical bond between the particles and the matrix, and the density deviation of each part is less than 0.5%.

[0027] Example 2: A cobalt-based powder system with 45% tungsten carbide particles was selected as the test subject. A molding system integrating an induction heating module and a high-frequency piezoelectric vibration module was used. The data acquisition resolution was 16 bits, the pressure sensor range was 0 MPa to 1000 MPa, and the measurement accuracy was 0.5%. A frequency converter driver was used to capture current signals in real time with a frequency range of 10 kHz to 50 kHz to monitor the evolution of internal damping of the powder and the phase hysteresis angle. The threshold setting balances the sufficiency of particle rearrangement with the economy of the molding cycle, when the phase lag angle... The rate of change remained stable for 15 seconds. When the potential energy is below rad / s, the potential energy inside the powder system reaches a local minimum, and mechanical disturbance destroys the bridging structure between particles.

[0028] In the comparative experiment, 10 groups of metal powders with the same initial ratio were divided into the present invention sample group, the partially missing control group, and the out-of-range control group. The present invention sample group underwent the vibration rearrangement, transient thermal load stripping, and pressure compensation process as described in the specific implementation method. The vibration rearrangement step was removed from control group A, the transient induction heating step was removed from control group B, and the out-of-range control group C had its heating rate set to 1500. / s, the out-of-range control group D set the mold sidewall shear displacement to 15. m, the microstructure of the heterogeneous interface was observed using a high-magnification scanning electron microscope, and the samples were tested using an ultrasonic fatigue testing machine. The fatigue strength under multiple cycles was tested by actively superimposing Gaussian white noise with a signal-to-noise ratio of 20dB into the test signal source to simulate vibration interference in industrial settings. The system used phase-locked logic to filter out environmental harmonics.

[0029] Table 1: Comparison of Process Performance of Precision Molding Technology for Heterogeneous Metal Powders

[0030] Referring to the data in Table 1, the sample group of this invention is superior to the control group in both relative density and fatigue strength. Control group A lacks the vibration rearrangement step, and the bridging effect inside the powder leads to a microscopic gradient in the green density. Control group B, without applying transient thermal load, cannot break the passivated oxide film on the particle surface, resulting in mechanical interlocking rather than metallurgical bonding between heterogeneous components. Control group C exceeds the range when the heating rate exceeds 1200°C. At a temperature of / s, an excessively high thermal stress gradient caused microcracks to initiate at the edges of tungsten carbide particles, resulting in a decrease in fatigue strength from 755.8 MPa to 620.4 MPa. This determined the 500... / s to 1200 The / s range is the working window to ensure oxide film rupture without damaging the particle matrix. The fatigue strength of sample group 2 of this invention is 57.3% higher than that of control group B, confirming the enhancing effect of direct contact between fresh metal surfaces under the synergistic effect of thermal mismatch stress and mechanical shear on interfacial strength; in the later stage of densification, the system calculates the frequency coherence coefficient of the acoustic emission signal in real time. The size increases with the closure of internal pores and the strengthening of the mechanical network in the green body, according to the formula... Determine the compensation increment for pressure load. ,in, This represents the compensation increment for the pressure load, expressed in MPa. The preset material elastic rebound compensation pressure value is 120MPa, which characterizes the equivalent elastic recovery potential energy of the cobalt matrix under molding pressure. The dimensionless frequency coherence coefficient reflects the continuity of sound wave transmission within the particle skeleton, and varies with... Increase, calculated Gradually decrease, when When it stabilizes above 0.95, The pressure approaches 0 MPa, indicating that the elastic rebound energy of the high-modulus tungsten carbide particles is offset by the external pressure load. This closed-loop compensation mechanism suppresses the delamination defects caused by heterogeneous modulus mismatch during unloading.

[0031] Example 3: This example combines Figures 1 to 2 The precision forming process of a high-performance heterogeneous metal powder is described, such as... Figure 1As shown, the process begins with step S1, where dissimilar metal powder containing hard granular phase and tough matrix phase is filled into the mold cavity. The exciter is driven to apply vibration to the mold cavity, causing the dissimilar metal powder to rearrange. Step S2 monitors the phase lag angle between the input current of the frequency conversion excitation source and the mechanical response of the exciter, and calculates the rate of change of the phase lag angle over time. Based on this, step S3 is executed. When the absolute value of the phase lag angle changes continuously below the preset offset threshold, it is determined that the dissimilar metal powder has reached a dense filling state, and a pressing mode switching signal is output. Immediately following the pressing mode switching signal, step S4 is executed, where an induction heating device is used to apply a transient thermal load to the dissimilar metal powder in the mold cavity, causing brittle cracks to form on the oxide film on the particle surface of the dissimilar metal powder. Finally, step S5 is executed, where a pressurizing mechanism is activated to apply a pressure load to the dissimilar metal powder, and the sidewall of the mold cavity is simultaneously adjusted to generate shear displacement to peel off the oxide film on the particle surface. Under the action of the pressure load, the exposed fresh metal surface undergoes atomic diffusion and achieves metallurgical bonding to obtain a green blank.

[0032] like Figure 2 As shown, the system is centered on a central control and data processing workstation, which integrates a phase lag angle analysis module, an acoustic emission signal calculation module, and a pressure closed-loop compensation module. These modules are used to calculate the phase difference between current and displacement, the frequency coherence coefficient, and the rebound compensation increment, respectively. The workstation controls the frequency converter excitation source through output drive signals to drive the piezoelectric vibrator to generate high-frequency vibration output. It adjusts the induction heating power supply through power control to drive the induction coil to apply transient thermal load control. It controls the hydraulic servo station through pressure commands to perform pressure loading and compensation on the heterogeneous metal powder in the precision mold cavity. It controls the mold ring drive mechanism through displacement commands to generate shear displacement on the sidewall. In the closed-loop feedback link, the displacement sensor collects the state of the piezoelectric vibrator and transmits the displacement feedback signal to the phase lag angle analysis module. The acoustic emission sensor captures the acoustic emission signal in the precision mold cavity and transmits it to the acoustic emission signal calculation module, thus forming a perception and control closed loop across physical quantities.

[0033] Example 4: In the process of manufacturing tungsten carbide reinforced cobalt-based alloy sleeves with large aspect ratios, the mechanical friction generated by the mold cavity sidewalls on the powder system introduces non-stationary damping components, interfering with the system's response to phase lag angle. Identification of evolution patterns; To address this technical challenge, this embodiment initiates a mold damping reference self-calibration process before powder filling, applying a 25kHz excitation signal to the unloaded mold using a vibrator, and acquiring the phase hysteresis angle in real time via a frequency converter driver. The original data and its standard deviation were calculated. This sets the offset threshold to , Satisfy the formula This allows us to utilize statistical envelope intervals to shield measurement noise caused by differences in mold hardware features.

[0034] After the powder enters the thermo-pressure coupling stage, the sensor captures the acoustic emission signal sequence generated by the grinding between particles. The data processing unit processes the sequence in steps of 1024 sampling points. The system divides the signal into continuous sliding windows and performs a Fast Fourier Transform on the time-domain signal within each window. The frequency coherence coefficient is extracted by calculating the normalized cross-correlation coefficient between two adjacent windows within the main frequency bandwidth. When the frequency coherence coefficient As the porosity of the green body increases from 0.65 to 0.95, the pressure load compensation increment... The calculation logic is activated, and the pressure load compensation increment is increased. The calculation formula is as follows: ,in, This represents the pressure load compensation increment, in MPa. The elastic rebound compensation pressure value for the material is taken as 120 MPa in this embodiment. This value is obtained through the formula... Calibration, among which The preset heterogeneity mismatch coefficient, The proportional limit of the tough matrix phase is expressed in MPa. is the frequency coherence coefficient.

[0035] The system adjusts the output pressure of the hydraulic actuator in real time based on the calculation results, and uses pressure load to compensate for the increment. To counteract the elastic recovery tendency of the hard granular phase at the moment of stress unloading, the frequency coherence coefficient... With a stability above 0.98, a continuous mechanical network is established inside the green blank. Due to the real-time judgment threshold compensation of mold friction during the pressing process and the correction of pressure increment using acoustic feedback, the final heterogeneous metal sleeve part has an axial relative density deviation of less than 0.3% under the condition of a length-to-diameter ratio of 5:1. The axial elastic expansion rate after demolding of the green blank is stable below 0.15%, which meets the manufacturing requirements of high-precision heterogeneous components for dimensional stability.

[0036] Example 5: The work hardening rate and proportional limit of different batches of tough matrix phase raw materials When fluctuations exist, the system determines the heterogeneous mismatch coefficient. The values ​​were determined by parameter calibration based on quasi-static compression tests before the molding process began. A standard specimen of the tough matrix phase with a diameter of 10 mm and a height of 15 mm was selected, and the stress-strain curve was measured under the condition of a displacement control rate of 0.5 mm / min to obtain the proportional limit. Powder consisting solely of a tough matrix phase was pressed within a mold cavity, and the elastic recovery displacement after unloading was recorded. ,according to and The heterogeneity mismatch coefficient is calculated from the mapping relationship. ,in The calculation uses a linear regression model, and the results are used to determine the pressure load compensation increment under different mix proportions. .

[0037] In the scenario of powder molding of hard particulate phases with multiple particle size distributions, the system locks the frequency coherence coefficient. Calculate the required frequency range During the pre-compression stage, a 500ms background sound emission signal was collected, and the power spectral density estimation method was used to identify the characteristic frequency bands of energy transmission in the particle network. The center frequency of the characteristic frequency band was then determined. Set as the cross-correlation calculation benchmark, monitor the moment when the output power of the induction heating device reaches the preset stable value. and in After a 50ms delay, the axial reciprocating movement of the mold ring is triggered. The delay time is used to induce brittle cracks in the oxide film on the particle surface, so that the mechanical friction peeling action acts on the physically weakened interface, realizing the synergy between particle pose rearrangement and interface activation in the timing logic.

[0038] Example 6: In a scenario where a precision forming process is deployed on an industrial pressing machine with different stiffnesses, the system performs pre-calibration to determine a quantization benchmark for a preset offset threshold. The mold under no-load conditions is selected as the calibration object, and the exciter is driven to perform a frequency sweep within the 15kHz to 35kHz frequency band. The input current signal for 100 cycles is acquired through a frequency converter driver, and phase characteristics are extracted to determine the inherent damping distribution characteristics of the mold, and the phase lag angle is calculated. The baseline variance under this distribution characteristic Preset offset threshold Through formula It is confirmed that, among them, For the preset offset threshold, The correction factor is determined based on the ratio of the inner surface area of ​​the mold cavity to the filling volume of the dissimilar metal powder. In a mold cavity with an inner surface area of ​​5000 mm², And the filling volume is 20000mm² Under the working conditions, Select 3.2. As the baseline variance, this pre-calibration procedure extracts the phase lag angle. The fluctuation envelope determined the range of zero-point drift caused by the inherent frequency difference of the mechanical structure and the assembly gap.

[0039] When processing batches of tungsten carbide particles with different initial oxidation degrees, the system determines the transient thermal load curve based on the complex impedance change law of the heterogeneous metal powder in the initial stage of induction heating, selects a current excitation with a frequency of 1MHz to pass through the induction coil, and extracts the equivalent resistance of the powder system. ,use The positive correlation between the temperature rise rate and the oxide film thickness determines the numerical value of the heating rate. When the real part of the complex impedance exhibits a nonlinear step change with increasing temperature, it indicates that cracks have formed in the oxide film on the particle surface. The system synchronously commands the mold ring to initiate axial reciprocating movement, resulting in shear displacement on the sidewall. Through formula Calculate, where, This refers to the mechanical shear displacement generated by the cavity sidewall, in units of... m, The preset displacement conversion coefficient, whose physical meaning is the reference displacement compensation amount under unit phase ratio evolution, is expressed in μm, and is selected as 5.5 in this embodiment. m, This represents the maximum phase lag angle monitored during the molding process. To monitor the phase hysteresis angle value in real time, this logic triggers a physical peeling action within the time window of oxide film embrittlement, increasing the relative density of the powder system from 65.4% at the beginning of pressing to over 99.2% before demolding.

[0040] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A precision forming process of high performance heterogeneous metal powder, characterized in that, The method comprises the following steps: Step S1, filling a heterogeneous metal powder containing hard particle phase and ductile matrix phase into a mold cavity, and driving a vibrator to apply vibration to the mold cavity to rearrange the heterogeneous metal powder; Step S2, monitoring the phase lag angle between the input current of the variable frequency excitation source and the mechanical response of the vibrator, and calculating the rate of change of the phase lag angle with time; Step S3, when the absolute value of the rate of change of the phase lag angle continues to be lower than a preset offset threshold, determining that the heterogeneous metal powder reaches a dense filling state, and outputting a pressing mode switching signal; Step S4, in response to the pressing mode switching signal, applying a transient thermal load to the heterogeneous metal powder in the mold cavity using an induction heating device to cause brittle cracks in the surface oxide film of the particles of the heterogeneous metal powder; Step S5, starting a pressurizing mechanism to apply a pressure load to the heterogeneous metal powder, and synchronously adjusting the side wall of the mold cavity to produce a shear displacement to peel off the surface oxide film, so that the exposed fresh metal surface atomically diffuses under the action of the pressure load and realizes metallurgical bonding to obtain a green body.

2. A precision forming process of high performance heterogeneous metal powder as claimed in claim 1 wherein, In step S2, the monitoring of the phase lag angle comprises extracting the phase of the alternating current output by the variable frequency excitation source, and comparing it with the phase of the signal fed back by the displacement sensor of the vibrator to calculate a physical characteristic value reflecting the evolution of the internal mechanical damping of the heterogeneous metal powder.

3. A precision forming process of high performance heterogeneous metal powder as claimed in claim 1 wherein, In step S3, the output of the pressing mode switching signal comprises capturing the physical time when the phase lag angle reaches a preset minimum stable value, locking the critical point of the particle pose optimization of the heterogeneous metal powder, and stopping applying vibration after outputting the pressing mode switching signal.

4. A precision forming process of high performance heterogeneous metal powder as claimed in claim 1 wherein, The temperature rising rate of the transient thermal load in step S4 is 500 / s to 1200 / s, a normal shear force is generated at the interface between the surface oxide film of the particle and the matrix of the particle by the mismatch of the thermal expansion coefficients of the hard particle phase and the ductile matrix phase.

5. A precision forming process of high performance heterogeneous metal powder as claimed in claim 1 wherein, The real-time pressure compensation step comprises collecting the acoustic emission signals generated by the heterogeneous metal powder particle grinding through the sensor and calculating the frequency coherence coefficient of the acoustic wave transmission , and determining the compensation increment of the pressure load according to the following formula : , wherein is the compensation increment of the pressure load, is the preset material elastic rebound compensation pressure value, which has the same physical dimension as the pressure load, is the frequency coherence coefficient; and adjusting the loading rate of the pressure load based on the compensation increment.

6. A precision forming process of high performance heterogeneous metal powder as claimed in claim 1 wherein, In step S5, the shear displacement of the side wall comprises controlling the mold ring of the mold cavity to produce axial reciprocating movement, and the mechanical displacement amount of the side wall is 2μm to 10μm, which mechanically rubs and peels off the particles of the heterogeneous metal powder through the side wall.

7. A precision forming process of high performance heterogeneous metal powder as claimed in claim 1 wherein, Before step S1, there is also a mold damping calibration step: in the empty state of the mold cavity, the no-load phase lag angle reference of the vibrator is determined, and the no-load phase lag angle reference is taken as the initial reference point for calculating the real-time offset of the phase lag angle.

8. A precision forming process of high performance dissimilar metal powder as claimed in claim 1 wherein, Metallurgical bonding is carried out in a temperature and pressure coupling environment below the melting point of the ductile matrix phase, and the direct contact between metal fresh surfaces is controlled to reduce the diffusion energy barrier.

9. A precision forming process of high performance dissimilar metal powder as claimed in claim 1 wherein, The hardness gradient distribution range of the heterogeneous metal powder is 150HV to 800HV, and the frequency range of the vibration applied in step S1 is 15kHz to 35kHz.

10. A precision forming process of high performance dissimilar metal powder as claimed in claim 1 wherein, After the green body is obtained, a controlled cooling step is also included: the green body is brought to room temperature at a cooling rate of 10 / min to 30 / min under a protective atmosphere, using a controlled temperature drop process to release the micro residual stresses accumulated during the forming process.

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