An ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures

Abstract

The present application discloses an ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure, which relates to the field of metal material processing technology. The method comprises installing a metal material sample and an ultrasonic rolling strengthening device on a lathe and setting ultrasonic rolling processing parameters; starting the lathe to perform step-by-step ultrasonic rolling processing on the surface of the metal material sample to obtain a metal material sample having a gradient nano-lamellar structure; observing the axial cross-section of the gradient nano-lamellar structure using a microscope to obtain a microstructure image, determining the strain rate of the gradient nano-lamellar structure, and determining whether the strain rate exceeds a preset strain rate threshold; if so, reprocessing the gradient nano-lamellar structure to obtain a prepared gradient nano-lamellar structure; if not, adjusting the corresponding ultrasonic rolling processing parameters until the strain rate of the gradient nano-lamellar structure exceeds the preset strain rate threshold. The present application improves the fatigue performance of the gradient nano-lamellar structure.

Description

Technical Field

[0001] The present application relates to the technical field of metal material processing, and in particular to an ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure. Background Art

[0002] The rapid development of strategic emerging industries such as new-generation renewable energy and high-end equipment manufacturing has created a more pressing need for improved performance in metal materials. The primary failure modes of metal materials in various service applications include corrosion, wear, and fatigue, with fatigue being the most common. Fatigue failure occurs when components are subjected to alternating loads such as heat and force, leading to the accumulation of damage and eventual sudden fracture. Therefore, improving the fatigue resistance of metal materials has become a key research priority.

[0003] In engineering, fatigue failure of components often begins on the material surface. This is because defects or crack-like conditions on the component surface create significant stress concentrations. Under cyclic loading, cracks tend to initiate from these defects, leading to fatigue failure. Therefore, various surface enhancement processes are often used in engineering to improve the surface quality and fatigue resistance of components.

[0004] Currently, common surface strengthening methods include shot peening, laser shock peening, and ultrasonic rolling. Ultrasonic rolling involves more complex process parameters. Compared with traditional rolling, the ultrasonic impact energy of ultrasonic rolling is higher, which can cause severe plastic deformation in the strengthened area and easily lead to surface roughness. Summary of the Invention

[0005] The purpose of this application is to provide an ultrasonic rolling composite strengthening method, device, equipment, medium and product for preparing gradient nano-lamellar structures, so as to solve the problem that ultrasonic rolling surface strengthening to prepare gradient nano-lamellar structures is prone to surface defects, thereby affecting fatigue performance.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] The present application provides an ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure, the ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure comprising:

[0008] The current metal material sample and the ultrasonic rolling strengthening device are respectively installed on a CNC lathe, and the ultrasonic rolling processing parameters are set; the ultrasonic rolling processing parameters include the static pressure of the ultrasonic rolling strengthening device, the feed speed of the CNC lathe, and the rotation speed of the CNC lathe;

[0009] Start the ultrasonic generator, adjust the frequency of the ultrasonic generator to a preset frequency, and adjust the amplitude of the ultrasonic generator to a preset amplitude;

[0010] Starting a CNC lathe to perform a step-by-step ultrasonic rolling process on the surface of the current metal material sample, and lubricating and cooling the surface of the current metal material sample during the step-by-step ultrasonic rolling process, thereby obtaining a metal material sample with a gradient nano-lamellar structure;

[0011] The axial cross section of the gradient nano-lamellar structure is observed using an optical microscope to obtain a microstructure image of the axial cross section of the gradient nano-lamellar structure;

[0012] determining a strain rate of the gradient nano-lamellar structure based on a microstructure image of an axial cross-section of the gradient nano-lamellar structure, and judging whether the strain rate of the gradient nano-lamellar structure is greater than or equal to a preset strain rate threshold;

[0013] If so, the gradient nano-lamellar structure is subjected to surface reprocessing to obtain a prepared gradient nano-lamellar structure;

[0014] If not, the corresponding ultrasonic rolling processing parameters are adjusted until the strain rate of the gradient nano-lamellar structure is greater than or equal to the preset strain rate threshold, and the gradient nano-lamellar structure is surface-processed to obtain the prepared gradient nano-lamellar structure.

[0015] Optionally, the preset frequency is 20 kHz, and the preset amplitude is 16 μm.

[0016] Optionally, the surface of the current metal material sample is subjected to a step-by-step ultrasonic rolling process, specifically including:

[0017] The surface of the current metal material sample is subjected to step-by-step ultrasonic rolling processing using a first preset static pressure threshold and a second preset static pressure threshold in sequence; wherein the second preset static pressure threshold is greater than the first preset static pressure threshold.

[0018] Optionally, the surface of the current metal material sample is subjected to multiple step-by-step ultrasonic rolling processes.

[0019] Optionally, the number of step-by-step ultrasonic rolling processes is 4.

[0020] Optionally, the preset strain rate threshold is 10 3 s -1 .

[0021] Optionally, determining the strain rate of the gradient nano-lamellar structure based on the microstructure image of the axial cross-section of the gradient nano-lamellar structure specifically includes:

[0022] Based on the microstructure image of the axial cross section of the gradient nanolamellar structure, the rheological curve is drawn;

[0023] Based on the rheological curve, fitting to obtain first operating condition parameters and second operating condition parameters;

[0024] Determining a relationship between a rheological displacement field and a depth of a gradient nanolamellar structure based on the first operating condition parameter and the second operating condition parameter;

[0025] Based on the relationship between the rheological displacement field and depth of the gradient nanolamellar structure, the shear displacement field of the gradient nanolamellar structure is determined;

[0026] The strain rate of the gradient nanolamellar structure is determined based on the shear displacement field of the gradient nanolamellar structure.

[0027] Optionally, the relationship between the rheological displacement field and depth of the gradient nanolamellar structure is expressed as follows:

[0028] y(x)=y s exp(-kx);

[0029] Wherein, x is the depth of any point on the rheological curve of the gradient nano-lamellar structure; y is the rheological displacement of any point on the rheological curve of the gradient nano-lamellar structure; y s is the first operating condition parameter; k is the second operating condition parameter;

[0030] The expression of the shear displacement field of the gradient nanolamellar structure is:

[0031] γ(x)=y s kexp(kx);

[0032] Where γ(x) is the shear displacement field of the gradient nanosheet structure;

[0033] The expression of the strain rate of the gradient nanolamellar structure is:

[0034]

[0035] in, is the strain rate of the gradient nanolamellar structure; R is the diameter of the metal material sample; v1 is the rotation speed of the CNC lathe.

[0036] Optionally, the surface reprocessing methods for the gradient nano-lamellar structure at the moment include tumbling, vibrating and tumbling.

[0037] Optionally, tapping oil is used as a lubricating medium and a cooling medium to lubricate and cool the surface of the current metal material sample during the step-by-step ultrasonic rolling process.

[0038] Optionally, the metal material sample is one of titanium, nickel, copper, iron, and aluminum, or an alloy formed by several of them.

[0039] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0040] The present application discloses an ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure. The method comprises the following steps: ultrasonic rolling is performed on the surface of a metal material sample to obtain a metal material sample having a gradient nano-lamellar structure, and an optical microscope is used to obtain a microstructure image of the axial cross-section of the gradient nano-lamellar structure. Based on the microstructure image of the axial cross-section of the gradient nano-lamellar structure, the strain rate of the gradient nano-lamellar structure is determined to determine whether the strain rate meets the requirements. If not, the corresponding ultrasonic rolling processing parameters are changed, and the metal material sample having the gradient nano-lamellar structure is ultrasonically rolled again until the strain rate meets the requirements. The gradient nano-lamellar structure is then surface-reprocessed to obtain a prepared gradient nano-lamellar structure. The gradient nano-lamellar structure obtained when the strain rate meets the requirements has good fatigue performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1 A schematic flow chart of an ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure provided in one embodiment of the present application;

[0043] Figure 2 A schematic diagram of sampling a metal material sample provided in one embodiment of the present application;

[0044] Figure 3 This is a microstructure image of the axial cross-section of an industrial pure titanium rod sample provided in one embodiment of the present application;

[0045] Figure 4 A schematic diagram of a transmission electron microscope photograph of an industrial pure titanium rod sample after ultrasonic rolling processing provided in one embodiment of the present application;

[0046] Figure 5 Another schematic diagram of a transmission electron microscope photograph of an industrial pure titanium rod sample after ultrasonic rolling provided in one embodiment of the present application;

[0047] Figure 6 Schematic diagram of SN fatigue curves of industrial pure titanium rod specimens under different surface strengthening methods provided in one embodiment of the present application. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0049] Ultrasonic rolling strengthening technology combines the advantages of static rolling and ultrasonic impact. It uses ultrasonic vibration to generate a huge impact while making the working ball roll on the surface, so that it can effectively introduce residual compressive stress, form a surface gradient layer, and reduce the surface roughness as much as possible. In addition, this technology also has the advantages of simple operation, low installation and maintenance costs, and good process controllability. High strain rate and large static pressure are the formation conditions for preparing gradient nano-lamellar structures, and they will also lead to more surface defects. These factors affect the fatigue performance of the material after surface strengthening, and surface reprocessing methods are needed to improve the fatigue performance of the material after surface strengthening. In response to the problem that ultrasonic rolling surface strengthening is prone to surface defects that affect fatigue performance in the preparation of gradient nano-lamellar structures, this application proposes an ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures to enhance the surface strengthening effect of the material and further improve the fatigue performance of the material.

[0050] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0051] In an exemplary embodiment, Figure 1 As shown, a method for preparing a gradient nano-lamellar structure by ultrasonic rolling composite strengthening is provided, comprising the following steps S1 to S7.

[0052] Step S1: Install the current metal material sample and the ultrasonic rolling strengthening device on a CNC lathe, and set the ultrasonic rolling processing parameters, including the static pressure of the ultrasonic rolling strengthening device, the feed speed of the CNC lathe, and the rotation speed of the CNC lathe.

[0053] Specifically, the metal sample is mounted on the rotatable spindle of a CNC lathe, and a working ball is mounted on the feed shaft of the CNC lathe. The working ball of the ultrasonic rolling device is aligned with the metal sample, and ultrasonic waves are converted into mechanical vibrations by the working ball. The rotation of the spindle and the movement of the feed shaft form a gradient nano-lamellar structure on the metal sample. Preferably, the working ball is a YG6 tungsten steel ball, and the metal sample is a rod-shaped sample.

[0054] Step S2: Start the ultrasonic generator and adjust its frequency and amplitude to a preset frequency and amplitude. The purpose of ultrasound is to ensure a smooth surface. A higher frequency improves the surface quality. However, too high a frequency can cause the ultrasonic mechanical vibration of the working ball to be unstable.

[0055] As an optional implementation, the preset frequency is 20 kHz, and the preset amplitude is 16 μm.

[0056] In step S3, the CNC lathe is activated to perform a step-by-step ultrasonic rolling process on the surface of the metal sample. During this process, the surface of the metal sample is continuously lubricated and cooled, thereby producing a metal sample with a gradient nanolamellar structure. The specific operating principle is that under certain static pressure and feed speed conditions, a machining head applies mechanical vibrations at ultrasonic frequencies to the surface of the metal sample, causing plastic deformation of the material surface.

[0057] As an optional implementation, the surface of the current metal material sample is subjected to step-by-step ultrasonic rolling processing, specifically including:

[0058] The surface of the current metal material sample is subjected to step-by-step ultrasonic rolling processing using a first preset static pressure threshold and a second preset static pressure threshold in sequence; wherein the second preset static pressure threshold is greater than the first preset static pressure threshold.

[0059] The step-by-step ultrasonic rolling process involves first rolling the metal sample surface with a relatively low static pressure (equal to a first preset static pressure threshold), and then applying a target static pressure (equal to a second preset static pressure threshold) to the metal sample surface for ultrasonic rolling. By first rolling the metal sample surface with a relatively low static pressure to achieve a hardened surface, and then applying a higher static pressure for ultrasonic rolling, the process avoids applying too much load all at once, which could cause surface defects in the material.

[0060] As an optional embodiment, the surface of the metal material sample is subjected to multiple, step-by-step ultrasonic rolling processes; preferably, the number of such step-by-step ultrasonic rolling processes is four. The number of rolling processes is one of the most important parameters for ensuring surface smoothness. Too few rolling processes will prevent the formation of a gradient nanolamellar structure, while too many will lead to excessive accumulated plasticity and surface defects such as cracks. Experimental verification shows that when the number of step-by-step ultrasonic rolling processes is four, the gradient nanolamellar structure produced in this embodiment exhibits optimal fatigue performance, thickness, and other parameters.

[0061] Step S4: observing the axial cross section of the gradient nano-lamellar structure using an optical microscope to obtain a microstructure image of the axial cross section of the gradient nano-lamellar structure.

[0062] Specifically, after the surface of the current metal material sample is subjected to step-by-step ultrasonic rolling processing, a gradient nano-lamellar structure is obtained, and an inverted Zeiss optical microscope is used to observe the depth direction axial section of the gradient nano-lamellar structure. First, the sampling position of the metallographic sample is the axial section sampling. The sampling diagram of the current metal material sample is as follows Figure 2 As shown. Sampling is carried out by wire cutting, that is, the metal material sample with gradient nano-lamellar structure is wire-cut to obtain the observation section. During cutting, in order to reduce the influence of high temperature on the structure and residual stress during wire cutting, a small current is used for cutting; then, the observation section is polished with 400 mesh, 800 mesh, 1200 mesh, 2000 mesh and 4000 mesh sandpaper in turn, and polished with a homemade alumina suspension; secondly, the polished observation section is corroded, and the metallographic etching solution is HF: HNO3: H2O = 1:2:17 solution, and the corrosion time is 20 seconds; finally, it is rinsed with alcohol, blown dry, and the observation section of the gradient nano-lamellar structure is observed under an optical microscope at a suitable magnification, and the following can be obtained. Figure 3 Microstructure image of the axial cross-section of the gradient nanolamellar structure shown.

[0063] Step S5: determining the strain rate of the gradient nano-lamellar structure based on the microstructure image of the axial cross-section of the gradient nano-lamellar structure, and judging whether the strain rate of the gradient nano-lamellar structure is greater than or equal to a preset strain rate threshold.

[0064] As an optional embodiment, in step S5, the strain rate of the gradient nano-lamellar structure is determined based on the microstructure image of the axial cross-section of the gradient nano-lamellar structure, specifically including:

[0065] Step S51 : drawing a rheological curve based on the microstructure image of the axial cross section of the gradient nano-lamellar structure.

[0066] Step S52: fitting the first operating condition parameter and the second operating condition parameter based on the rheological curve.

[0067] Step S53: Based on the first operating condition parameter and the second operating condition parameter, determine the relationship between the rheological displacement field and the depth of the gradient nano-lamellar structure. The relationship between the rheological displacement field and the depth of the gradient nano-lamellar structure is expressed as:

[0068] y(x)=y s exp(-kx)(1)

[0069] Wherein, x is the depth of any point on the rheological curve of the gradient nano-lamellar structure; y is the rheological displacement of any point on the rheological curve of the gradient nano-lamellar structure; y sis the first working condition parameter; k is the second working condition parameter. Among them, a point on the surface of the microstructure image of the axial cross-section of the gradient nano-lamellar structure is selected as the origin, the tangent direction along the surface is set as the y-axis, and the direction pointing to the center of the circle is set as the x-axis. An xy coordinate system is established, and the coordinates of the points on the rheological curve are obtained based on this coordinate system. The parameter y is obtained by fitting the coordinates (x and y values) of multiple points on the rheological curve. s and k.

[0070] Step S54: determining the shear displacement field of the gradient nano-lamellar structure based on the relationship between the rheological displacement field and the depth of the gradient nano-lamellar structure. The shear displacement field of the gradient nano-lamellar structure is expressed as:

[0071]

[0072] Where γ(x) is the shear displacement field of the gradient nanosheet structure.

[0073] Step S55: determining the strain rate of the gradient nano-lamellar structure based on the shear displacement field of the gradient nano-lamellar structure. The strain rate of the gradient nano-lamellar structure is expressed as:

[0074]

[0075] in, is the strain rate of the gradient nanolamellar structure; R is the diameter of the metal material sample; v1 is the rotation speed of the CNC lathe.

[0076] According to formula (3), when the diameter R of the metal specimen is constant, the CNC lathe speed v1 and the parameter k directly affect the strain rate. The parameter k is determined by the static pressure and the CNC lathe feed rate. Therefore, the specific static pressure, CNC lathe speed, and CNC lathe feed rate of the ultrasonic rolling process in this embodiment are determined by the ultrasonic rolling material.

[0077] As an optional implementation, in step S5, the preset strain rate threshold is 10 3 s -1 .

[0078] Specifically, the preparation of gradient nano-lamellar structures is related to the strain rate in the processing process. Only high strain rate and high static pressure can produce thick and uniform gradient nano-lamellar structures.

[0079] Step S6: If yes, the gradient nano-lamellar structure is subjected to surface reprocessing to obtain a prepared gradient nano-lamellar structure.

[0080] If not, in step S7, the corresponding ultrasonic rolling parameters are adjusted until the strain rate of the gradient nanolamellar structure is greater than or equal to the preset strain rate threshold. The gradient nanolamellar structure is then surface-processed to obtain the prepared gradient nanolamellar structure. In other words, the metal sample with the gradient nanolamellar structure is used as the current metal sample, and the process returns to step S3, "Starting the CNC lathe and performing step-by-step ultrasonic rolling on the surface of the current metal sample," until the strain rate of the gradient nanolamellar structure is greater than or equal to the preset strain rate threshold.

[0081] As an optional implementation, the surface reprocessing methods for the gradient nano-lamellar structure at the moment include tumbling, vibrating and tumbling.

[0082] As an optional implementation, tapping oil is used as both a lubricant and a coolant to continuously lubricate and cool the metal sample surface during the step-by-step ultrasonic rolling process. Compared to lubricants like diesel and engine oil, tapping oil offers stronger lubrication and extreme pressure and anti-wear properties. Its outstanding cooling properties and excellent penetration properties effectively improve the surface roughness of metal samples.

[0083] As an optional implementation, the metal material sample is one of titanium, nickel, copper, iron, and aluminum, or an alloy formed by several of them.

[0084] The ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures in the present application will be further explained below by taking the application of the ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures in the present application to industrial pure titanium as an example.

[0085] Commercially pure titanium (CP-Ti) has the advantages of non-toxicity, low density, high specific strength, strong corrosion resistance and excellent biocompatibility. It has been widely used in aerospace, petrochemical, transportation and biomedicine. However, commercially pure titanium is a difficult-to-deform material, its strength is lower than that of titanium alloy, and its fatigue resistance is poor, which to a certain extent limits its in-depth application in the field of materials. Therefore, the ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structure in this application is used to optimize the fatigue resistance of commercially pure titanium. The specific steps are as follows:

[0086] 1) Install the industrial pure titanium sample and the ultrasonic rolling device on a CNC lathe respectively, and set the ultrasonic rolling processing parameters. Specifically, the industrial pure titanium sample is installed at the output end of the rotation system of the CNC lathe, and the ultrasonic rolling device is installed at the clamping end of the automatic feeding system of the CNC lathe, and the working ball is aligned with the sample. The industrial pure titanium sample is installed on the rotatable main shaft of the CNC lathe, so that the rotation of the main shaft drives the rotation of the sample, and the working ball is installed on the axially feedable feed shaft of the CNC lathe, so that the axial feeding of the working ball is driven by the movement of the feed shaft. Preferably, before the industrial pure titanium sample is installed on the main shaft, the surface to be processed of the industrial pure titanium sample is subjected to a precision turning process.

[0087] 2) Start the ultrasonic generator and adjust its frequency to 20kHz and its amplitude to 16μm. This converts the ultrasonic waves into ultrasonic-frequency mechanical vibrations of the working ball, which in turn applies a gradient of radial static pressure to the industrial pure titanium specimen. Specifically, adjusting the amplitude and frequency of the ultrasonic generator changes the amplitude and frequency of the working ball's vibrations. Preferably, the working ball is a YG6 tungsten steel ball and is replaced regularly to ensure the stability of the rolling process.

[0088] 3) Starting a CNC lathe to perform step-by-step ultrasonic rolling processing on the surface of the industrial pure titanium sample, and continuously lubricating and cooling the surface of the industrial pure titanium sample during the step-by-step ultrasonic rolling processing, thereby obtaining an industrial pure titanium sample with a gradient nano-lamellar structure.

[0089] Specifically, under given process parameters, the industrial pure titanium sample on the CNC lathe is rotated, and the vibrating working ball is pressed into the surface of the industrial pure titanium sample with radial static pressure. At the same time, the working ball is fed along the axial direction of the industrial pure titanium sample, so that the working ball and the industrial pure titanium sample roll relative to each other, thereby forming a nanoscale or submicron lamellar structure on the industrial pure titanium sample.

[0090] Preferably, the static pressure of the ultrasonic rolling device is 800N, the feed speed of the CNC lathe is 10mm / min, and the rotation speed of the CNC lathe is greater than 700rpm.

[0091] 4) The axial cross section of the gradient nano-lamellar structure is observed using an optical microscope to obtain a microstructure image of the axial cross section of the gradient nano-lamellar structure.

[0092] 5) Based on the microstructure image of the axial cross-section of the gradient nano-lamellar structure, determining the strain rate of the gradient nano-lamellar structure, and judging whether the strain rate of the gradient nano-lamellar structure is greater than or equal to a preset strain rate threshold.

[0093] The preparation conditions of gradient nanosheet structures are directly related to the strain rate in the processing technology. The strain rate is greater than 103 s -1 , a higher strain rate can be ensured by increasing the rotation speed of the CNC lathe.

[0094] The strain rate under this working condition is verified by contradiction. The relationship between the gradient structure rheological displacement field and depth is calculated using formula (1), where y s and k are the first working condition parameters and the second working condition parameters when the static pressure of the ultrasonic rolling device is 800N and the feed speed of the CNC lathe is 10mm / min, respectively. Figure 3 Take 10 rheological curves to fit and get y s and k are 1350 μm and 0.016 μm-1 respectively.

[0095] The shear displacement field can be obtained by formula (2):

[0096]

[0097] The shear strain rate can be calculated using formula (3):

[0098]

[0099] According to formula (3), it is calculated that when the diameter of the industrial pure titanium sample is R = 4000 μm and the rotation speed v1 = 700 rpm, the strain rate on the surface of the industrial pure titanium sample is about 3×10 3 s -1 , which is close to the strain rate estimated for preparing gradient nano-lamellar structures in nickel. Therefore, the lathe speed for ultrasonic rolling of industrial pure titanium samples should be greater than 700 rpm. Figure 4 and Figure 5 It can be observed from the transmission electron microscope photos in that a thick and uniform lamellar structure is generated on the surface of the industrial pure titanium rod sample after ultrasonic rolling processing, which proves that the ultrasonic rolling composite strengthening method used in this application to prepare gradient nano-lamellar structure can effectively modify the ultrasonic rolling processing parameters.

[0100] 6) determining that the strain rate of the gradient nano-lamellar structure is greater than or equal to a preset strain rate threshold, performing surface reprocessing on the gradient nano-lamellar structure to obtain a prepared gradient nano-lamellar structure; the surface reprocessing method includes grinding and polishing such as tumbling, vibrating, and tumbling.

[0101] 7) Furthermore, fatigue life tests were conducted to assess the fatigue life of the gradient nanolamellar structure. These tests were conducted on a fatigue testing platform. Specifically, fatigue tests were performed on unreinforced industrial pure titanium specimens, ultrasonically rolled reinforced industrial pure titanium specimens, and industrial pure titanium specimens treated using the ultrasonic rolling composite strengthening method used in this application to prepare gradient nanolamellar structures. The fatigue tests were stress-controlled, with the maximum stress selected being between 169 MPa and 234 MPa. Fatigue tests were performed in descending order of stress values.

[0102] According to the fatigue test results, Figure 6 As shown, the fatigue life of industrial pure titanium samples treated with the ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures in this application was significantly improved. Verification shows that the ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures in this application is simple to operate and can significantly improve the fatigue resistance of metal material samples.

[0103] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, stored data, displayed data, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of relevant data must comply with relevant regulations.

[0104] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM may be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0105] The databases involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processors involved in the various embodiments provided herein may include, but are not limited to, general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic units, data processing logic units based on quantum computing, and the like.

[0106] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. An ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure, characterized in that: The ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure comprises: The current metal material sample and the ultrasonic rolling strengthening device are respectively installed on a CNC lathe, and the ultrasonic rolling processing parameters are set; the ultrasonic rolling processing parameters include the static pressure of the ultrasonic rolling strengthening device, the feed speed of the CNC lathe, and the rotation speed of the CNC lathe; Start the ultrasonic generator, adjust the frequency of the ultrasonic generator to a preset frequency, and adjust the amplitude of the ultrasonic generator to a preset amplitude; Starting a CNC lathe to perform ultrasonic rolling processing on the surface of the current metal material sample step by step, and lubricating and cooling the surface of the current metal material sample during the ultrasonic rolling processing, thereby obtaining a metal material sample with a gradient nano-lamellar structure; The axial cross section of the gradient nano-lamellar structure is observed using an optical microscope to obtain a microstructure image of the axial cross section of the gradient nano-lamellar structure; determining a strain rate of the gradient nano-lamellar structure based on a microstructure image of an axial cross-section of the gradient nano-lamellar structure, and judging whether the strain rate of the gradient nano-lamellar structure is greater than or equal to a preset strain rate threshold; If so, the gradient nano-lamellar structure is subjected to surface reprocessing to obtain a prepared gradient nano-lamellar structure; If not, adjusting the corresponding ultrasonic rolling processing parameters until the strain rate of the gradient nano-lamellar structure is greater than or equal to the preset strain rate threshold, and performing surface reprocessing on the gradient nano-lamellar structure to obtain the prepared gradient nano-lamellar structure; The surface of the current metal material sample is subjected to step-by-step ultrasonic rolling processing, specifically including: The surface of the current metal material sample is subjected to step-by-step ultrasonic rolling processing using a first preset static pressure threshold and a second preset static pressure threshold in sequence; wherein the second preset static pressure threshold is greater than the first preset static pressure threshold.

2. The ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure according to claim 1, characterized in that: The preset frequency is 20 kHz, and the preset amplitude is 16 μm.

3. The ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure according to claim 2, characterized in that: The surface of the current metal material sample is subjected to multiple step-by-step ultrasonic rolling processes, and the number of step-by-step ultrasonic rolling processes is 4.

4. The ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure according to claim 1, characterized in that: The preset strain rate threshold is 10 3 s -1 .

5. The ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures according to claim 1, characterized in that: Based on the microstructure image of the axial cross-section of the gradient nanolamellar structure, the strain rate of the gradient nanolamellar structure is determined, specifically including: Based on the microstructure image of the axial cross section of the gradient nanolamellar structure, the rheological curve is drawn; Based on the rheological curve, fitting to obtain first operating condition parameters and second operating condition parameters; Determining a relationship between a rheological displacement field and a depth of a gradient nanolamellar structure based on the first operating condition parameter and the second operating condition parameter; Based on the relationship between the rheological displacement field and depth of the gradient nanolamellar structure, the shear displacement field of the gradient nanolamellar structure is determined; The strain rate of the gradient nanolamellar structure is determined based on the shear displacement field of the gradient nanolamellar structure.

6. The ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure according to claim 5, characterized in that: The relationship between the rheological displacement field and depth of the gradient nanolamellar structure is expressed as follows: ； Wherein, x is the depth of any point on the rheological curve of the gradient nano-lamellar structure; y is the rheological displacement of any point on the rheological curve of the gradient nano-lamellar structure; y s is the first operating condition parameter; k is the second operating condition parameter; The expression of the shear displacement field of the gradient nanolamellar structure is: ； in, is the shear displacement field of the gradient nanolamellar structure; The expression of the strain rate of the gradient nanolamellar structure is: ； in, is the strain rate of the gradient nanolamellar structure; is the diameter of the current metal material sample; is the rotation speed of the CNC lathe.

7. The ultrasonic rolling composite strengthening method for preparing a gradient nano-lamellar structure according to claim 1, characterized in that: Methods for surface reprocessing of gradient nanolamellar structures include tumbling, vibrating and tumbling.

8. The ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures according to claim 1, characterized in that: Tapping oil is used as a lubricating medium and a cooling medium to lubricate and cool the surface of the current metal material sample during the step-by-step ultrasonic rolling process.

9. The ultrasonic rolling composite strengthening method for preparing gradient nano-lamellar structures according to claim 1, characterized in that: The metal material sample is one of titanium, nickel, copper, iron, and aluminum, or an alloy formed by several of them.

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