Electrochemically corrosion resistant Ti-6al-4v alloy with direct current pulse and preparation method thereof

Abstract

The application discloses a kind of electrochemical corrosion resistant Ti-6Al-4V alloy with direct current pulse and a preparation method thereof.The method comprises the following steps: cutting hot working state Ti-6Al-4V alloy plate into electrochemical corrosion samples, mechanically grinding, ultrasonic cleaning and constant temperature drying, connecting direct current pulse through power supply, accurately controlling the action time of electric pulse by relay, changing a series of electric pulse action time and current density, obtaining electrochemical corrosion resistant Ti-6Al-4V alloy under different direct current pulse conditions, and obtaining the corrosion resistance of Ti-6Al-4V electrochemical corrosion test piece.The application performs direct current pulse treatment on Ti-6Al-4V alloy sample, significantly improves the electrochemical corrosion performance of the alloy, and is simple and convenient to operate.The direct current pulse makes the passive film formed on the surface of the electric pulse Ti-6Al-4V alloy sample have more ideal electrochemical corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of corrosion-resistant titanium alloys, and particularly relates to a Ti-6Al-4V alloy resistant to electrochemical corrosion using direct current pulses and its preparation method. Background Technology

[0002] Ti-6Al-4V (TC4) duplex titanium alloy, due to its superior mechanical properties, stable physicochemical properties, excellent biocompatibility, and good corrosion resistance, is now widely used in biomedicine, commonly as a biorepair material in areas such as dental implants, vascular stents, and artificial orthopedic joints. Because the human body fluid environment is complex and often contains Cl... - Na + PO3 3- Even with electrolytes and organic substances such as proteins and phospholipids, titanium alloys still inevitably face problems such as ion precipitation, localized corrosion, and wear. This leads to corrosion products spreading to surrounding human tissues, causing physiological harm and a series of other issues. Therefore, further optimizing and improving the corrosion resistance and biocompatibility of Ti-6Al-4V titanium alloys has clear and far-reaching practical significance. Currently, researchers have developed a series of surface treatment technologies to specifically optimize the electrochemical properties of titanium alloys. For example, patent CN103233260 A proposes a micro-arc oxidation technology to prepare a fouling-resistant and damage-resistant ceramic film on the surface of Ti-6Al-4V alloys. Compared with the titanium alloy substrate, this technology significantly optimizes electrochemical corrosion performance, hardness, and wear resistance. Patent CN201010173044.6 obtains a cast titanium alloy with significantly improved mechanical properties, corrosion resistance, and wear resistance by incorporating indium into the titanium matrix through solid solution treatment, making it suitable for the design and production of high-precision, small-volume implants.

[0003] Currently, DC pulse-assisted forming or deformation technology has achieved microstructure control and mechanical property optimization in various metallic material systems. DC pulse technology typically offers advantages such as simple equipment operation, short preparation cycles, and low energy consumption, and can usually significantly optimize the comprehensive mechanical properties of titanium alloys in a short time. However, the specific mechanisms by which DC pulse technology modulates electrochemical corrosion performance remain unclear. Summary of the Invention

[0004] To address the practical problems in the prior art, such as the need for further improvement in the electrochemical corrosion performance of Ti-6Al-4V alloy materials and the high risk of damage caused by corrosion products, the main objective of this invention is to provide a Ti-6Al-4V alloy resistant to electrochemical corrosion using DC pulses and its preparation method, thereby achieving significant optimization of the electrochemical corrosion performance of Ti-6Al-4V alloy in NaCl electrolyte environment in a short time and with high efficiency.

[0005] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows, including the following steps:

[0006] Step S1: First, several electrochemical corrosion samples were obtained by wire cutting of the Ti-6Al-4V alloy raw material. The Ti-6Al-4V alloy raw material used was a commercially available hot-worked Ti-6Al-4V alloy round bar with a diameter of 30 mm and a length of 200 mm. Then, multiple electrochemical corrosion samples were obtained by wire cutting along the axial length of the alloy round bar. The dimensions of the electrochemical corrosion samples were 13 mm in length, 4 mm in width, and 1.5 mm in thickness.

[0007] Step S2: The electrochemically corroded sample obtained in step S1 is subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain an initial alloy sample for DC pulse treatment.

[0008] Step S3: Then place the initial alloy sample from step S2 on the test bench and connect the two ends of the initial alloy sample to the two copper plate electrodes in the power supply system, respectively.

[0009] The power supply is an ISB-300A inverter welding power supply, and the current density and DC pulse processing time are controlled by an external CNC panel on the power supply.

[0010] Step S4: Turn on the power supply and perform DC pulse treatment on the initial alloy sample. Then, perform mechanical grinding, ultrasonic cleaning and constant temperature drying on the initial alloy sample after DC pulse treatment to finally obtain the electrochemical corrosion resistant Ti-6Al-4V alloy.

[0011] Step S5: All electrochemical tests are performed using a standard three-electrode system. Add an electrolyte solution with a concentration of 0.9 wt.% NaCl to the electrolytic cell of the standard three-electrode system until the electrolyte surface is tangent to the lower surface of the platinum electrode holder, ensuring that the electrochemically resistant Ti-6Al-4V alloy sample to be tested is completely immersed in the electrolyte solution. Place the assembled electrolytic cell on a constant-temperature stage, ensuring the electrolyte temperature remains at 37°C throughout the test. After the test, obtain the average values ​​of the electrochemical impedance, corrosion current, and corrosion potential of the alloy sample to ensure data reliability.

[0012] In step S3, a conductive copper block is placed between the copper plate electrode and the end of the initial alloy sample. The conductive copper block is used to conduct electricity to the initial alloy sample.

[0013] In step S4, the specific method for processing the initial state alloy sample with DC pulse is as follows: start the power supply and input an instantaneous DC pulse with a specific current density into the initial state alloy sample.

[0014] In step S4, the current density of the instantaneous DC pulse is 130 A / mm². 2 ~150A / mm 2 .

[0015] In step S4, the processing time for the instantaneous DC pulse is 35ms to 80ms.

[0016] In step S4, the current density of the instantaneous DC pulse is 140 A / mm. 2 The processing time for instantaneous DC pulses is 70ms.

[0017] In step S4, the application rate of the instantaneous DC pulse is greater than 11.4 K / ms.

[0018] An induction coil device is installed at the input cable of the power supply. The induction coil device is used to measure the instantaneous current value released by the power supply and ensure that the error range between the actual current value measured by the induction coil device and the target current value is ±5A. A thermistor infrared thermometer is set at the center of the initial alloy sample. The thermistor infrared thermometer is used to measure the temperature rise of the initial alloy sample during the DC pulse treatment process.

[0019] In step S1, the chemical composition of the Ti-6Al-4V alloy raw material mainly includes: Ti, Al, V, Fe, C, and N; the mass percentage content of aluminum (Al) is 5.5% to 6.8%, the mass percentage content of vanadium (V) is 3.5% to 4.5%, the mass percentage content of iron (Fe) is 0.3% to 0.4%, the mass percentage content of carbon (C) is 0.1% to 0.2%, and the mass percentage content of nitrogen (N) is 0.05% to 0.1%.

[0020] The electrochemical corrosion resistant Ti-6Al-4V alloy of the present invention was prepared by the above preparation method.

[0021] This invention employs a transient DC pulse, which differs significantly in principle from pulses with longer durations. By using a brief millisecond pulse at a rate of at least 11.4 K / ms for rapid heating, the pulse linearly raises the temperature from room temperature (25°C) to 882°C within 75 ms. This instantaneous energy surge triggers a rearrangement of atoms within the material, inducing vanadium diffusion from grain boundaries into the grain. The movement of dislocations within the material releases and regulates residual compressive stress in the crystal, thus suppressing localized pitting corrosion during electrochemical etching. Furthermore, after pulse treatment, the passivation film on the sample surface is denser and thicker, effectively preventing contact between the electrolyte and the Ti substrate and reducing the corrosion rate. The increased open-circuit potential / corrosion potential / charge transfer resistance results in a higher voltage required for Cl- ion corrosion of the Ti alloy substrate in the electrolyte, significantly improving electrochemical corrosion performance.

[0022] This invention, while ensuring a stable current density, precisely obtains the optimal duration of energization treatment by controlling the energization time of the titanium alloy sample. For example, a fixed current density of 140 A / mm² is selected. 2 Different pulse durations of 65ms and 70ms were selected for the electrical pulse treatment. Repeatable electrochemical corrosion tests were then performed on the electrochemical test samples prepared using the two sets of electrical pulse parameters.

[0023] This invention utilizes a DC pulse device to perform electro-pulse treatment on hot-worked Ti-6Al-4V alloy cuboid electrochemically corroded samples. Different pulse durations were explored, and a highly efficient, short-process preparation of excellent electrochemically resistant Ti-6Al-4V alloy was achieved without complex processes such as thermo-mechanical treatment. Therefore, optimizing the electrochemical performance of commercially available hot-worked Ti-6Al-4V alloy through DC pulse treatment significantly shortens the alloy preparation cycle and reduces energy consumption, demonstrating strong practical significance and application prospects. By constructing a simulated human body fluid environment at 37℃ with a 0.9 wt.% NaCl electrolyte and selecting appropriate DC pulse treatment parameters, a significant improvement in the electrochemical corrosion performance of titanium alloys was achieved, effectively avoiding physiological hazards caused by corrosion products.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention involves DC pulse treatment of commercially available hot-worked Ti-6Al-4V alloy to create an electrolyte environment, which can effectively improve the electrochemical corrosion resistance of Ti-6Al-4V electrochemical corrosion samples.

[0026] 2. The efficient DC pulse processing method provided by this invention has an extremely short energizing cycle of several microseconds and is easy and convenient to operate. The DC pulse makes the passivation film formed on the surface of the Ti-6Al-4V alloy sample with more ideal electrochemical corrosion resistance. Attached Figure Description

[0027] Figure 1 For Comparative Example 1, the open-circuit potential of the Ti-6Al-4V alloys in Examples 1-2 changes over time in 0.9 wt.% NaCl electrolyte at 37°C;

[0028] Figure 2 For Comparative Example 1, Tafel polarization curves of Ti-6Al-4V alloys in Examples 1-2 at 37°C in 0.9 wt.% NaCl electrolyte;

[0029] Figure 3 For Comparative Example 1, electrochemical impedance spectroscopy of Ti-6Al-4V alloys in Examples 1-2 at 37°C in 0.9 wt.% NaCl electrolyte. Detailed Implementation

[0030] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] Example 1

[0032] Commercially available hot-worked Ti-6Al-4V alloy was selected as the initial material for electrochemical corrosion performance testing. First, it underwent DC pulse treatment, followed by a detailed analysis of its electrochemical corrosion performance.

[0033] (1) First, a commercially available hot-worked Ti-6Al-4V alloy round bar with a diameter of 30 mm and a length of 200 mm was wire-cut to obtain multiple sets of cuboid electrochemical samples with lengths of 13 mm, widths of 4 mm and thicknesses of 1.5 mm.

[0034] (2) The rectangular electrochemical sample obtained in step (1) is subjected to mechanical grinding with sandpaper to 2000#, ultrasonic cleaning and constant temperature drying to obtain the initial state sample for electrochemical testing.

[0035] (3) Process the sample using a DC pulse device and place the initial sample on the external sample holder of the inverter welding power supply device;

[0036] (4) A conductive copper block was placed at the gap between the electrochemical sample and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly attached.

[0037] (5) After the electrochemical sample is installed, the input current of the inverter welding power supply is set to 840A to ensure that the average current density passing through the cross-section of the electrochemical sample is 140A / mm². 2 ;

[0038] (6) Set the electrical pulse processing duration to 65ms (hereinafter referred to as 140A / mm). 2 (Sample -65ms), connect the DC power supply. After the DC pulse processing is complete, wait for the specimen to cool completely to room temperature before removing the sample from the fixture;

[0039] (7) An induction coil device was installed on the outside of the power input cable, the instantaneous current value released by the power supply was measured, and the test current value of the induction coil was ensured to be within the range of 835 to 845A.

[0040] (8) The sample is mechanically ground with sandpaper to 2000#, ultrasonically cleaned and dried at constant temperature in sequence to remove the surface oxide layer and impurities of the electrochemical sample, and obtains the electrochemical corrosion resistant Ti-6Al-4V alloy, thus completing the sample preparation for electrochemical testing.

[0041] (9) All electrochemical tests were performed using a standard three-electrode system powered by a Princeton 3000A-DX electrochemical workstation. (10×10 mm) 2 A platinum sheet electrode was used as the counter electrode; a saturated calomel electrode (SCE) was used as the reference electrode; a defect-free initial state sample was loaded onto the platinum sheet electrode holder, exposing 10 × 4 mm. 2 As a working electrode;

[0042] (10) Assemble the three electrodes in the C001 sealed electrolytic cell, and add an electrolyte solution with a concentration of 0.9 wt.% NaCl to the electrolytic cell with a dropper until the electrolyte surface is tangent to the lower surface of the platinum electrode clip, ensuring that the test sample is completely immersed in the electrolyte solution.

[0043] (11) Place the installed electrolytic cell on the constant temperature stage and ensure that the temperature of the electrolyte is 37°C throughout the test.

[0044] (12) First, the open circuit potential test was performed. The open circuit potential was read after the working electrode was placed in the electrolyte and recorded continuously for 40,000 seconds. After the test potential stabilized, the open circuit potential value was read.

[0045] (13) Subsequently, at an open-circuit potential, in the range of 0.1 to 10 5Electrochemical impedance spectroscopy was acquired using a 10mV AC signal as the amplitude within the Hz frequency range, and the measurement results were read using Versa.Studio v2.66.2 software;

[0046] (14) At the open circuit potential, the initial potential of the Tafel polarization curve test was set to -0.25V vs OC, the termination potential was set to 0.25V vs OC, and the scan rate was set to 0.1666mV / s;

[0047] (15) Repeat the above tests, read and calculate the average values ​​of open circuit potential, electrochemical impedance, corrosion current and corrosion potential to ensure the reliability of the data.

[0048] Example 2

[0049] Commercially available hot-worked Ti-6Al-4V alloy was selected as the initial material for electrochemical corrosion performance testing. First, it underwent DC pulse treatment, followed by a detailed analysis of its electrochemical corrosion performance.

[0050] (1) First, a commercially available hot-worked Ti-6Al-4V alloy round bar with a diameter of 30 mm and a length of 200 mm was wire-cut to obtain multiple sets of cuboid electrochemical samples with lengths of 13 mm, widths of 4 mm and thicknesses of 1.5 mm.

[0051] (2) The rectangular electrochemical sample obtained in step (1) is subjected to mechanical grinding with sandpaper to 2000#, ultrasonic cleaning and constant temperature drying to obtain the initial state sample for electrochemical testing.

[0052] (3) Process the sample using a DC pulse device and place the initial sample on the external sample holder of the inverter welding power supply device;

[0053] (4) A conductive copper block was placed at the gap between the electrochemical sample and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly attached.

[0054] (5) After the electrochemical sample is installed, the input current of the inverter welding power supply is set to 840A to ensure that the average current density passing through the cross-section of the electrochemical sample is 140A / mm². 2 ;

[0055] (6) Set the electrical pulse processing duration to 70ms (hereinafter referred to as 140A / mm). 2 (70ms sample), connect the DC power supply. After the DC pulse processing is completed, wait for the specimen to cool completely to room temperature before removing the sample from the fixture;

[0056] (7) An induction coil device was installed on the outside of the power input cable, the instantaneous current value released by the power supply was measured, and the test current value of the induction coil was ensured to be within the range of 835 to 845A.

[0057] (8) The sample is mechanically ground with sandpaper to 2000#, ultrasonically cleaned and dried at constant temperature in sequence to remove the surface oxide layer and impurities of the electrochemical sample, and obtains the electrochemical corrosion resistant Ti-6Al-4V alloy, thus completing the sample preparation for electrochemical testing.

[0058] (9) All electrochemical tests were performed using a standard three-electrode system powered by a Princeton 3000A-DX electrochemical workstation. (10×10 mm) 2 A platinum sheet electrode was used as the counter electrode; a saturated calomel electrode (SCE) was used as the reference electrode; a defect-free initial state sample was loaded onto the platinum sheet electrode holder, exposing 10 × 4 mm. 2 As a working electrode;

[0059] (10) Assemble the three electrodes in the C001 sealed electrolytic cell, and add an electrolyte solution with a concentration of 0.9 wt.% NaCl to the electrolytic cell with a dropper until the electrolyte surface is tangent to the lower surface of the platinum electrode clip, ensuring that the test sample is completely immersed in the electrolyte solution.

[0060] (11) Place the installed electrolytic cell on the constant temperature stage and ensure that the temperature of the electrolyte is 37°C throughout the test.

[0061] (12) First, the open circuit potential test was performed. The open circuit potential was read after the working electrode was placed in the electrolyte and recorded continuously for 40,000 seconds. After the test potential stabilized, the open circuit potential value was read.

[0062] (13) Subsequently, at an open-circuit potential, in the range of 0.1 to 10 5 Electrochemical impedance spectroscopy was acquired using a 10mV AC signal as the amplitude within the Hz frequency range, and the measurement results were read using Versa.Studio v2.66.2 software;

[0063] (14) At the open circuit potential, the initial potential of the Tafel polarization curve test was set to -0.25V vs OC, the termination potential was set to 0.25V vs OC, and the scan rate was set to 0.1666mV / s;

[0064] (15) Repeat the above tests, read and calculate the average values ​​of open circuit potential, electrochemical impedance, corrosion current and corrosion potential to ensure the reliability of the data.

[0065] Comparative Example 1

[0066] Commercially available hot-worked Ti-6Al-4V alloy was selected as the initial material for electrochemical corrosion performance testing, and its electrochemical corrosion performance was analyzed in detail:

[0067] (1) First, a commercially available hot-worked Ti-6Al-4V alloy round bar with a diameter of 30 mm and a length of 200 mm was wire-cut to obtain multiple sets of cuboid samples with lengths, widths and thicknesses of 13 mm, 4 mm and 1.5 mm, respectively.

[0068] (2) The cuboid sample obtained in step (1) was mechanically ground with sandpaper to 2000#, ultrasonically cleaned, and dried at a constant temperature to obtain the initial sample for electrochemical testing. The initial sample was set as the reference group and was not subjected to any DC pulse treatment;

[0069] (3) All electrochemical tests were performed using a standard three-electrode system powered by a Princeton 3000A-DX electrochemical workstation. (At a 10×10 mm...) 2 A platinum sheet electrode was used as the counter electrode; a saturated calomel electrode (SCE) was used as the reference electrode; a defect-free initial state sample was loaded onto the platinum sheet electrode holder, exposing 10 × 4 mm. 2 As a working electrode;

[0070] (4) Assemble the three electrodes in the C001 sealed electrolytic cell, and add an electrolyte solution with a concentration of 0.9 wt.% NaCl to the electrolytic cell with a dropper until the electrolyte surface is tangent to the lower surface of the platinum electrode clip, ensuring that the test sample is completely immersed in the electrolyte solution.

[0071] (5) Place the installed electrolytic cell on the constant temperature stage and ensure that the temperature of the electrolyte is 37°C throughout the test.

[0072] (6) First, the open circuit potential test is performed. The open circuit potential is read from the moment the working electrode is placed in the electrolyte and is continuously recorded for 40,000 seconds. After the test potential stabilizes, the open circuit potential value is read.

[0073] (7) Subsequently, at an open-circuit potential, in the range of 0.1 to 10 5 Electrochemical impedance spectroscopy was acquired using a 10mV AC signal as the amplitude within the Hz frequency range, and the measurement results were read using Versa.Studio v2.66.2 software;

[0074] (8) At the open circuit potential, the initial potential of the Tafel polarization curve test is set to -0.25V vs OC, the termination potential is 0.25V vs OC, and the scan rate is set to 0.1666mV / s;

[0075] (9) Repeat the above tests, read and calculate the average values ​​of open circuit potential, electrochemical impedance, corrosion current and corrosion potential to ensure the reliability of the data.

[0076] Electrochemical corrosion tests were conducted on the Ti-6Al-4V alloy samples treated with DC pulses in Examples 1-2 and the initial state sample in Comparative Example 1, under a constant temperature of 37°C and a 0.9 wt.% NaCl electrolyte environment. The curves showing the change of open circuit potential over time are shown below. Figure 1 As shown. Tafel polarization tests were conducted on the Ti-6Al-4V alloy samples from Examples 1-2 treated with DC pulses and the initial sample from Comparative Example 1, in a 0.9 wt.% NaCl electrolyte environment at 37°C. The obtained Tafel polarization curves are shown below. Figure 2 As shown, the corrosion potential and average corrosion current of different samples were calculated respectively. For the Ti-6Al-4V alloy samples treated with DC pulses in Examples 1-2 and the initial state sample of Comparative Example 1, the electrochemical impedance spectroscopy analysis curves were obtained under a constant temperature of 37℃ and a 0.9 wt.% NaCl electrolyte environment, as shown in the figure. Figure 3 As shown.

[0077] Figure 1 The curves show the change in open-circuit potential over time in 0.9 wt.% NaCl solution for the Ti-6Al-4V alloy samples of Examples 1 and 2 treated with DC pulses, and the initial state of the sample in Comparative Example 1. Figure 1 It can be seen that after the initial sample enters the electrolyte, the potential shifts in the positive direction, indicating the formation of a protective passivation film on the working electrode surface. As the test time increases, the open-circuit potential continues to increase, stabilizing at 0.21V in the final stage of the test and remaining at this value until the test ends. 140A / mm 2 The initial potential of the sample (Example 1) was almost the same as that of Comparative Example 1 after 65 ms. Subsequently, its open circuit potential showed a continuous increasing trend. After the sample was immersed for 40,000 s, the reading was 140 A / mm. 2 The open-circuit voltage of the sample at -65ms was 0.25V. Furthermore, the A / mm... 2 The initial potential (0.17V) of the sample in Example 2 (70ms) was significantly higher than that of Comparative Example 1 and Example 1. As the test continued, the open-circuit voltage dropped from 0.33V to 0.29V near the middle of the test time. Subsequently, the open-circuit potential increased again, with the highest open-circuit potential read at 0.34V. Potential fluctuations were observed on the open-circuit potential curve of Example 2, indicating that the passivation film was simultaneously growing and dissolving on the sample surface, and the passivation film product was still unstable at this time. Throughout the complete test, the open-circuit potential of Example 2 was significantly higher than that of Example 1 and Comparative Example 1, indicating that when the DC pulse density was 140A / mm...2 When the electrical pulse duration is 70ms, the open circuit potential of Ti-6Al-4V alloy is significantly increased, with an increase of 61.9% compared with Comparative Example 1.

[0078] Figure 2 Tafel polarization curves of Ti-6Al-4V alloys in 0.9 wt.% NaCl solution at 37°C for Comparative Example 1, Example 1, and Example 2. Figure 2 The ordinate of the graph represents the logarithm of the current density. Both the cathodic and anodic branches of the Tafel curve are used to determine the corrosion current (Icorr) and corrosion potential (Ecorr) of the Ti-6Al-4V alloy. Generally, a higher corrosion potential (Ecorr) and a lower corrosion current (Icorr) indicate better corrosion resistance of the material. Figure 2 As shown, the initial corrosion potential of the sample was 143.70 mV, and the corrosion current was 1021.91 pA. The current density of the applied DC pulse treatment was 140 A / mm². 2 At this point, the corrosion potential of the sample at 65ms was 155.37mV, and the corrosion current was 738.89pA. Further extending the pulse duration to 70ms, the corrosion potential increased to 210.73mV, while the corrosion current decreased to 2.79pA, indicating that the electrochemical corrosion performance of the Ti-6Al-4V alloy sample was significantly improved by DC pulse treatment.

[0079] Figure 3 The electrochemical impedance spectroscopy spectra of Ti-6Al-4V alloys in Comparative Example 1, Example 1, and Example 2 in 0.9 wt.% NaCl solution at 37°C are shown. Figure 3 The horizontal and vertical axes represent the real and imaginary parts of the capacitive arc radius, respectively. By applying small-amplitude sinusoidal interference signals of different frequencies to the system, the equivalent circuit in the electrochemical corrosion process was inferred, thereby obtaining information on the electrode interface structure and kinetics. For Examples 1, 2, and Comparative Example 1, capacitive arc curves with different radii were observed in the Nyquist plots of the three groups of samples. The larger the radius of the capacitive arc, the higher the impedance value of its passivation film. Compared with the initial sample, as the pulse duration increased from 65 ms to 70 ms, the capacitive arc radius increased significantly, indicating that 140 A / mm 2 The passivation film formed on the sample surface in -70ms exhibits better corrosion resistance.

[0080] As can be seen from the above embodiments and comparative examples, the open-circuit potential, corrosion potential, and electrochemical impedance of the commercially available hot-worked Ti-6Al-4V alloy treated with DC pulses provided by this invention are all significantly improved. When a constant current density of 140 A / mm² is set... 2When the pulse duration was extended from 65ms to 70ms, the open circuit potential and corrosion potential of the sample increased by 61.9% and 35.6%, respectively.

[0081] 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 for the preparation of an electrochemically corrosion resistant Ti-6Al-4V alloy with direct current pulses, characterized in that, The method comprises the following steps: Step S1, a first Ti-6Al-4V alloy raw material is linearly cut to obtain a plurality of electrochemical corrosion samples; Step S2, the electrochemical corrosion samples obtained in step S1 are sequentially subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying to obtain initial state alloy samples for direct current pulse treatment; Step S3, then the initial state alloy samples of step S2 are placed on a test bench, and the two ends of the initial state alloy samples are respectively connected to two copper plate electrodes in a power supply system; Step S4, the power supply is started, the initial state alloy samples are subjected to direct current pulse treatment, and the initial state alloy samples after direct current pulse treatment are sequentially subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying, and finally the electrochemical corrosion resistant Ti-6Al-4V alloy is prepared; The current density of the transient direct current pulse in the step S4 is 130 A / mm 2 150 A / mm 2 The direct current pulse processing time of the transient direct current pulse is 35 ms to 80 ms.

2. The method of claim 1, wherein the method is characterized by: In step S3, a conductive copper block is arranged between the copper plate electrode and the end of the initial state alloy sample, and the conductive copper block is used for conducting electricity to the initial state alloy sample.

3. The method of claim 1, wherein the method is characterized by: In step S4, the specific method for treating the initial state alloy sample with direct current pulse is to start the power supply and input a transient direct current pulse with a specific current density into the initial state alloy sample.

4. The method of claim 1, wherein the method is characterized by: The current density of the transient direct current pulse in the step S4 is 140 A / mm 2 The direct current pulse processing time of the transient direct current pulse is 70 ms.

5. The method of claim 1, wherein the method is characterized by: In step S4, the application rate of the transient direct current pulse is greater than 11.4 K / ms.

6. The method of claim 1, wherein the method is characterized by: The inductive coil device is installed at the input cable of the power supply, and is used to measure the current released by the power supply; a thermosensitive infrared temperature detector is arranged at the center position of the initial state alloy sample, and is used to measure the temperature rise of the initial state alloy sample during the direct current pulse treatment.

7. The method of claim 1, wherein the method is characterized by: In step S1, the chemical composition of the Ti-6Al-4V alloy raw material mainly comprises Ti, Al, V, Fe, C and N; the mass percentage content of the Al element is 5.5%-6.8%, the mass percentage content of the V element is 3.5%-4.5%, the mass percentage content of the Fe element is 0.3%-0.4%, the mass percentage content of the C element is 0.1%-0.2%, and the mass percentage content of the N element is 0.05%-0.1%.

8. An electrochemical corrosion resistant Ti-6Al-4V alloy treated by a direct current pulse, characterized in that: The electrochemical corrosion resistant Ti-6Al-4V alloy is prepared by the method of any one of claims 1-7.

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