Electrolytic machining method and system for microstructure on surface of titanium alloy

Abstract

The invention provides a titanium alloy surface microstructure electrolytic machining method and system, and belongs to the technical field of electrolytic machining. In the electrolytic machining process of the titanium alloy, passivation and super-passivation behaviors are shown under different machining current densities, controllable machining of the microstructure on the surface of the titanium alloy is achieved by dynamically adjusting the current density of a machining area, and the method comprises the steps that the alpha / beta phase distribution rule of the titanium alloy is obtained through a metallographic analyzer; preparing a neutral salt solution containing aggressive chloride ions; simulating polarization characteristics of the titanium alloy by using an electrochemical workstation, obtaining a polarization curve, and extracting current density values of a passivation region and a super-passivation region from the curve; and electrolytic machining is conducted through the extracted current density value, the titanium alloy surface alpha / beta phase material corrosion process is regulated and controlled, and microstructures of different depths and shapes are prepared based on titanium alloy alpha / beta phase electrocorrosion differences. In-situ precision electrolytic machining of the microstructure can be achieved, and the preparation method is efficient and convenient.

Description

Technical Field

[0001] This invention relates to the field of electrochemical machining technology, and in particular to a method and system for in-situ electrochemical machining of microstructures on the surface of titanium alloys. Background Technology

[0002] Titanium alloys, due to their low density, high strength, excellent corrosion resistance / biocompatibility, and good high and low temperature performance, have wide applications in marine engineering, chemical equipment, and aerospace. In materials science and surface engineering, designing surface microstructures to endow materials with new macroscopic properties enables the creation of superhydrophobic / superhydrophilic surfaces. Hydrophobic surfaces achieve self-cleaning, while superhydrophilic surfaces are used for anti-fogging and efficient condensation. Rib-like microstructures can reduce fluid, water, or air resistance, and are applied to the inner walls of aircraft, ships, and pipelines. Internal microstructure design (such as lattice and porous structures) achieves lightweight, high strength, and high toughness, which can be used in aerospace and bioimplants. Creating micro-pits or textures on the surface can store lubricants and reduce wear, and is used in the manufacture of mill rolls for food processing.

[0003] Currently, common methods for fabricating metal microstructures include additive manufacturing, etching, laser processing, and nanoimprinting, all of which can achieve precision fabrication of complex three-dimensional micro / nano structures. However, these processes place stringent requirements on processing equipment and involve high initial investment costs. Electrolytic machining, based on the principle of electrochemical anodic dissolution, enables the controllable removal of materials at the atomic scale, offering a fundamental advantage in the fabrication of micro / nano-scale structures on the surfaces of difficult-to-machine materials such as titanium alloys.

[0004] The applicant's previous research focused on the surface quality control of titanium alloy electrolytic machining and has discovered the special differential dissolution phenomenon of titanium alloy. In electrolytic machining, titanium alloy is an easily passivated metal. Neutral chloride ion salt solution can promote the breakdown of the passivation film and form pitting pits. By taking advantage of the differences in the types and contents of α / β phase elements in titanium alloy materials, the applicant proposed to control the in-situ differential dissolution of titanium alloy surface materials by adjusting the current density, so as to achieve regular electrolytic machining of the pit and protrusion microstructure of titanium alloy interface. Summary of the Invention

[0005] The purpose of this invention is to provide a method and system for electrolytic machining of microstructures on the surface of titanium alloys. The method of this invention can realize in-situ electrolytic machining of microstructures on the surface of titanium alloys.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention proposes an electrolytic machining method and system for microstructures on the surface of titanium alloys, belonging to the field of electrolytic machining technology. During electrolytic machining, titanium alloys exhibit passivation and hyperpassivation behaviors under different machining current densities. This invention achieves controllable machining of microstructures on the surface of titanium alloys by dynamically adjusting the current density in the machining zone. The method includes: obtaining the distribution law of the α / β phases of the titanium alloy using a metallographic analyzer; preparing a neutral salt solution containing aggressive chloride ions; simulating the polarization characteristics of the titanium alloy using an electrochemical workstation and obtaining a polarization curve, extracting the current density values ​​of the passivation and hyperpassivation zones from the curve; performing electrolytic machining using the extracted current density values ​​to control the corrosion process of the α / β phase materials on the titanium alloy surface, and preparing microstructures of different depths and shapes based on the differences in electrochemical corrosion of the α / β phases of the titanium alloy. This invention enables in-situ precision electrolytic machining of microstructures, and the preparation method is efficient and convenient. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating the principle of electrolytic machining of microstructures on the surface of titanium alloys provided by the present invention;

[0009] Figure 2 This invention relates to the α / β phase structure of titanium alloy;

[0010] Figure 3 This invention relates to the current density distribution in the passivation and superpassivation regions of titanium alloy polarization characteristics.

[0011] Figure 4 This is a schematic diagram of the microstructure electrolytic machining test system of the present invention;

[0012] Figure 5 This is the metallographic structure of the titanium alloy TC4 of this invention;

[0013] Figure 6 This is the polarization curve of the titanium alloy TC4 of the present invention in a 10% sodium chloride solution;

[0014] Figure 7 This is the microstructure of the TC4 titanium alloy surface electrolytically processed according to the present invention; Detailed Implementation

[0015] This invention provides a method and system for electrolytic machining of microstructures on the surface of titanium alloys, the machining principle of which is as follows: Figure 1 As shown, it includes the following steps:

[0016] First, titanium alloy samples were prepared, ground, and etched. Then, the distribution of the α / β phases in the titanium alloy was obtained using a metallographic microscope, including the shape, size, and proportion of the phases. Figure 2 As shown.

[0017] A neutral salt solution containing aggressive chloride ions was prepared using deionized water and analytical grade solid sodium chloride particles, and used as an electrolyte solution for microstructure electrolytic processing.

[0018] In a neutral chloride salt solution, the polarization characteristics of titanium alloy were simulated using an electrochemical workstation, and polarization curves were obtained. The current density values ​​in the passivation and hyperpassivation regions were extracted from these curves. Figure 3 As shown. The selected superpassivation current density value can be obtained through electrolytic machining of the microstructure.

[0019] Energy dispersive X-ray spectroscopy (EDS) was used to characterize the types and contents of elements in the α / β phase of titanium alloy materials.

[0020] The formula for calculating the electrochemical dissolution rate of metals is as follows:

[0021] v=ηωi (1)

[0022] Where η is the electrochemical dissolution efficiency, ω is the metal electrochemical volume equivalent, and i is the processing current density.

[0023] The electrochemical dissolution efficiency η is obtained using the gravimetric method, and the calculation formula is as follows:

[0024]

[0025] Among them, M 实际 The actual mass removed during the electrochemical dissolution process is obtained from the difference in the mass of material removed before and after the experiment, M. 理论 This is for theoretical calculations of material removal mass.

[0026] ω is the metal electrochemical volume equivalent, calculated using the following formula:

[0027]

[0028] Where ρ is the metal density, F is the Faraday constant, and n j It is the valence, A j It is the relative atomic mass, a j It is the percentage content of elements.

[0029] Conduct experimental research on microstructure electrolytic machining, experimental setup such as Figure 4 As shown, the system includes a motion platform, a programmable power supply, an electrolyte circulation and filtration system, and a data logger. The workpiece and tool are connected to the positive and negative terminals of the programmable power supply, respectively. The electrolyte in the machining area is kept at a constant temperature and is updated and flows in real time. The electrolyte flows in a high-speed jet manner, and the current changes during the machining process can be characterized by the data logger. For planar workpieces, a flat tool electrode can be used for machining, in which case the tool moves linearly; for workpieces with rotating arc surfaces, an arc-shaped tool electrode can be used for electrolytic machining, in which case the workpiece rotates.

[0030] Based on the above steps, the present invention can realize in-situ precision electrolytic processing of microstructures, and the preparation method is efficient and convenient.

[0031] The following detailed description of the electrolytic machining method and system for microstructures on the surface of titanium alloys provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention. Example 1

[0032] The selected workpiece material is titanium alloy TC4, the electrolyte is 10% sodium chloride solution, the processing voltage is 10V, the test temperature is 30℃, the outer dimensions of the anode workpiece blank are 5mm×5mm, the metallographic analyzer model is BX51, and the electrochemical workstation model is AMEL2551.

[0033] The main elements of titanium alloy TC4 are Ti, Al, and V, with percentage contents of 90%, 6%, and 4%, respectively, and electrochemical volume equivalents of 0.0017 cm³. 3 A -1 min -1 0.0021cm 3 A -1 min -1 and 0.0013cm 3 A -1 min -1 .

[0034] The metallographic structure of titanium alloy TC4 is as follows Figure 5 As shown, the volume fraction ratio of the α / β phases is approximately 3:2, with Al being the α-phase stabilizer and V being the β-phase stabilizer.

[0035] The polarization curve of titanium alloy TC4 in 10% sodium chloride solution is as follows: Figure 6 As shown, the superpassivation current density range is 0.28 A / cm². -2 -1.35Acm -2 The microstructure electrolytic machining current density selected in the experiment was 0.80 Acm. -2 The processing time is 30 seconds. The processed microstructures are as follows: Figure 7 As shown, the height difference between the pit and the protrusion is approximately 39 μm.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method and system for electrolytic machining of microstructures on the surface of titanium alloys, characterized in that, Includes the following steps: The distribution pattern of α / β phases in titanium alloys was obtained using a metallographic analyzer. Prepare a neutral salt solution containing aggressive chloride ions; The polarization characteristics of titanium alloy were simulated using an electrochemical workstation, and polarization curves were obtained. The current density values ​​of the passivation region and the superpassivation region were extracted from the curves. Electrochemical machining is performed using extracted current density values ​​to control the corrosion process of the α / β phase materials on the titanium alloy surface, and microstructures of different depths and shapes are prepared based on the differences in electrochemical corrosion between the α / β phases of the titanium alloy. In this invention, the titanium alloy workpiece is connected to the positive terminal of a programmable power supply, and the tool is connected to the negative terminal. This invention enables in-situ precision electrochemical machining of microstructures, and the preparation method is efficient and convenient.

2. The method according to claim 1, characterized in that, The material can be any titanium alloy, and the workpiece can be manufactured by any processing technology, such as forging, casting, and extrusion.

3. The method according to claim 1, characterized in that, The metallographic analyzer can obtain the distribution pattern of α / β phases in titanium alloys.

4. The method according to claim 1, characterized in that, The polarization curve test of the titanium alloy material was performed using the prepared chloride ion neutral salt solution as the electrolyte. The test voltage range was 0-12 volts. The passivation and super-passivation ranges of the titanium alloy were to be characterized. The anodic dissolution of the titanium alloy was divided into three stages: passivation, pitting (microstructure processing) and uniform dissolution (polishing). The breakdown voltage, electrochemical corrosion and polishing current density of the titanium alloy were recorded.

5. The method according to claim 1, characterized in that, The titanium alloy has different elemental compositions in the α / β phases. The actual electrochemical volume equivalent of different elements can be obtained by weighing, and then the dissolution rate of the titanium alloy α / β phases under different current densities can be obtained. Based on the difference in the dissolution rate of different elements, the height of the microstructure (pits / protrusions) can be controlled.

6. The method according to claim 1, characterized in that, In the electrolytic machining process, the workpiece and tool are connected to the positive and negative terminals of a programmable power supply, respectively. The electrolyte in the machining area is in a state of real-time updating and flow. The surface material removal depth is less than 500μm. During machining, the gap between the workpiece and the tool is constant, with the machining gap selectable range being 0.2mm-10mm. The electrolyte can be recycled through a filtration system. The temperature is controlled by a constant temperature device, and the electrolyte temperature can be selected within the range of 15℃-45℃.

7. The method according to claim 1, characterized in that, The workpiece geometry can be planar or cylindrical.

8. The method according to claim 1, characterized in that, This invention enables in-situ precision electrolytic machining of microstructures, and the preparation method is efficient and convenient.

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