A reinforced and toughened Ti-6Al-4V alloy based on direct current pulse and a preparation method thereof

Abstract

The application discloses a kind of based on DC pulse's enhanced toughening Ti-6Al-4V alloy and preparation method thereof.Method includes that hot working state Ti-6Al-4V alloy plate is cut into tensile specimen, after mechanical grinding, ultrasonic cleaning, constant temperature drying, by power connection DC pulse processing, by relay accurately control electric pulse action duration, by changing a series of electric pulse action duration and current density, obtain the enhanced toughening Ti-6Al-4V alloy under different DC pulse conditions, and obtain the comprehensive mechanical properties of Ti-6Al-4V tensile specimen.By the efficient DC pulse processing method provided by the application, the extremely short power cycle of microsecond level, and simple and convenient operation, significantly improve the yield strength, tensile strength and elongation of Ti-6Al-4V alloy.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium alloy strengthening, and particularly relates to a strengthening and toughening Ti-6Al-4V alloy based on direct current pulse and a preparation method thereof. BACKGROUND

[0002] Ti-6Al-4V (TC4) dual-phase titanium alloy has been a research focus in extreme technical fields such as aerospace, deep space exploration, national defense and military industry, high-voltage power transmission and marine transportation due to its characteristics of light weight, high strength and excellent corrosion resistance, and has a profound development prospect and strategic significance. At present, difficult-to-deform metal materials represented by titanium alloy still have objective problems such as poor plasticity and toughness, serious residual stress and unsatisfactory processing quality in the room temperature plastic processing. Therefore, relevant researchers have tried to explore the combination of mechanical alloying method or heat treatment process to solve the above problems. However, the alloying elements of the above process have high cost, the heat treatment process is relatively complicated, the performance is unstable, and the production cycle is long. Therefore, it is very urgent to design a titanium alloy performance optimization technology with high efficiency and low energy consumption.

[0003] At present, power-assisted forming or deformation technology has been practically applied to a variety of metal material systems, and has achieved a certain degree of microstructure control and performance optimization. For example, patent CN202011050214.1 adopts an electric pulse-assisted hot stamping forming method, fully utilizes the electric stress relaxation advantage caused by pulse current, and prepares a hot stamping titanium alloy part with less springback and excellent comprehensive mechanical properties, which provides inspiration for solving the contradiction between part size precision and mechanical properties. Patent CN102896193B adopts an electric current-assisted hot spinning preparation technology, that is, the joule heat generated by the current passing through the pipe blank is used for continuous heat preservation of the pipe material, and then combined with the pressure generated by the pressing device to effectively improve the spinning forming efficiency. In addition, patent CN118789154A also proposes an electric pulse repair process, which adjusts the pulse voltage of electric pulse heating to a certain extent to heal the cracks and holes in the Ti-6Al-4V alloy.

[0004] Although the above-mentioned related power-on process optimizes the mechanical properties of Ti-6Al-4V alloy to different degrees, the electric auxiliary equipment or design is complicated, and the forming effect is seriously dependent on the equipment. Or the process control parameters of pulse current are numerous, and it is difficult to realize accurate control. Or the power-on duration is long, and the temperature is high, which causes high energy consumption of equipment and raw materials. Therefore, the electric treatment process cycle still needs to be further shortened, the electric pulse treatment process needs to be simplified, the product preparation cost needs to be reduced, and the utilization efficiency of materials needs to be improved. SUMMARY

[0005] To address the problems existing in the background technology, the strength and toughness of Ti-6Al-4V alloy materials are still insufficient for large-scale, high-volume production applications. Traditional thermo-mechanical treatment techniques and existing electro-assisted preparation techniques still suffer from problems such as cumbersome cycles, complex processes, unstable performance, excessively high preparation costs, and unsatisfactory mechanical properties. The purpose of this invention is to provide a reinforced and toughened Ti-6Al-4V alloy based on DC pulse and its preparation method.

[0006] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows, including the following steps:

[0007] Step S1: First, wire cut the Ti-6Al-4V alloy raw material to obtain several tensile specimens;

[0008] 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. Multiple tensile specimens were then obtained by wire cutting along the axial length of the alloy round bar. The gauge length of the tensile specimens was 8 mm in length, 2 mm in width, and 1 mm in thickness.

[0009] Step S2: The tensile specimen obtained in step S1 is subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the initial state alloy sample for DC pulse processing.

[0010] 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.

[0011] 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.

[0012] 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 reinforced and toughened Ti-6Al-4V alloy.

[0013] The yield strength, tensile strength and elongation of the reinforced and toughened Ti-6Al-4V alloy can be tested using a tensile testing machine, and the hardness and elastic modulus of the reinforced and toughened Ti-6Al-4V alloy can be tested using a nanoindentation tester.

[0014] 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.

[0015] 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.

[0016] In step S4, the current density of the instantaneous DC pulse is 140 A / mm². 2 ~160A / mm 2 .

[0017] In step S4, the processing time for the instantaneous DC pulse is 40ms to 90ms.

[0018] In step S4, the current density of the instantaneous DC pulse is 140 A / mm². 2 The processing time for instantaneous DC pulses is 75ms.

[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 reinforced and toughened Ti-6Al-4V alloy of the present invention was prepared by the above-described preparation method.

[0021] This invention employs a transient DC pulse, which differs significantly in principle from electrical pulses with longer durations. This invention transforms the micron-sized β particles, rich in V and located in the intergranular spaces of the initial microstructure, into nano-sized β phase laths within the grains, achieving a strengthening effect. Simultaneously, the phase transformation during the electrical pulse process activates a certain number of c+a dislocations within the α' martensite laths, increasing the elongation of the titanium alloy. Furthermore, a small amount of tensile twins can be observed in the electrically pulsed samples.

[0022] This invention utilizes a DC pulse device to perform electrical pulse treatment on hot-worked Ti-6Al-4V alloy tensile specimens. By exploring the thermal and non-thermal effects involved in the instantaneous process, a series of parameters related to current density and pulse duration were investigated. This allows for the efficient and short-process preparation of high-strength, high-toughness Ti-6Al-4V alloys without complex thermo-mechanical treatments. Therefore, optimizing the comprehensive mechanical properties of commercially available hot-worked Ti-6Al-4V alloys through DC pulse treatment technology, significantly shortening the alloy preparation cycle and reducing energy consumption, has strong practical significance and application prospects.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention involves DC pulse treatment of commercially available hot-worked Ti-6Al-4V alloy. Under the action of a transient DC pulse, the yield strength, tensile strength, elongation, hardness, and elastic modulus of the Ti-6Al-4V tensile sample can be effectively improved.

[0025] 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, which synergistically achieves a significant improvement in the yield strength, tensile strength and elongation of Ti-6Al-4V alloy. Attached Figure Description

[0026] Figure 1 For Comparative Example 1, the engineering stress-engineering strain curves of commercially available hot-worked Ti-6Al-4V alloys after DC pulse treatment for 0-75ms in Examples 1-3;

[0027] Figure 2 For Comparative Example 1, the engineering stress-engineering strain curves of commercially available hot-worked Ti-6Al-4V alloys after DC pulse treatment for 75-90 ms in Examples 3-6;

[0028] Figure 3 The displacement-load curves of nanoindentation are shown for the initial state sample of Comparative Example 1 and the peak performance sample of Example 3.

[0029] Figure 4 For Comparative Example 1, Examples 7-8 used commercially available hot-worked Ti-6Al-4V alloys with a DC pulse current density of 140 A / mm². 2 150A / mm 2 and 160A / mm 2 The engineering stress-engineering strain curve. 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: DC pulse duration 40ms

[0032] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0033] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0034] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0035] (4) Conductive copper block material was placed at the gap between the tensile specimen and the power supply copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0036] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 280A to ensure that the average current density at the gauge length of the tensile specimen is 140A / mm. 2 ;

[0037] (6) Set the electrical pulse treatment time to 40ms (hereinafter referred to as 40ms sample), turn on the DC power supply, and after the DC electrical pulse treatment is completed, wait for the specimen to cool completely to room temperature before taking the sample off the fixture.

[0038] (7) The samples were mechanically ground, ultrasonically cleaned and dried at constant temperature in sequence to remove the surface oxide layer and impurities of the tensile specimens, and the reinforced and toughened Ti-6Al-4V alloy was obtained. Then, the mechanical properties of the samples were repeatedly tested for 40ms using a tensile testing machine.

[0039] Example 2: DC pulse duration 65ms

[0040] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0041] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0042] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0043] (4) Conductive copper block material was placed at the gap between the tensile specimen and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0044] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 280A to ensure that the average current density at the gauge length of the tensile specimen is 140A / mm. 2 ;

[0045] (6) Set the electrical pulse treatment duration to 65ms (hereinafter referred to as the 65ms sample) and turn on the DC power supply. After the DC electrical pulse treatment is completed, wait for the specimen to cool completely to room temperature before removing the sample from the fixture.

[0046] (7) Mechanical grinding, ultrasonic cleaning and constant temperature drying were performed in sequence to remove the surface oxide layer and impurities of the tensile specimen to obtain the reinforced and toughened Ti-6Al-4V alloy. Then, the mechanical properties of the 65ms sample were repeatedly tested using a tensile testing machine.

[0047] Example 3: DC pulse duration 75ms

[0048] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0049] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0050] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0051] (4) Conductive copper block material was placed at the gap between the tensile specimen and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0052] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 280A to ensure that the average current density at the gauge length of the tensile specimen is 140A / mm. 2 ;

[0053] (6) Set the electrical pulse treatment duration to 75ms (hereinafter referred to as the 75ms sample) and turn on the DC power supply. After the DC electrical pulse treatment is completed, wait for the specimen to cool completely to room temperature before removing the sample from the fixture.

[0054] (7) Mechanical grinding, ultrasonic cleaning and constant temperature drying were performed in sequence to remove the surface oxide layer and impurities of the tensile specimen to obtain the reinforced and toughened Ti-6Al-4V alloy. Then, the mechanical properties of the 75ms sample were repeatedly tested using a tensile testing machine.

[0055] Example 4: DC pulse duration 80ms

[0056] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0057] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0058] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0059] (4) Conductive copper block material was placed at the gap between the tensile specimen and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0060] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 280A to ensure that the average current density at the gauge length of the tensile specimen is 140A / mm. 2 ;

[0061] (6) Set the electrical pulse treatment duration to 80ms (hereinafter referred to as the 80ms sample) and turn on the DC power supply. After the DC electrical pulse treatment is completed, wait for the specimen to cool completely to room temperature before removing the sample from the fixture.

[0062] (7) Mechanical grinding, ultrasonic cleaning and constant temperature drying were performed in sequence to remove the surface oxide layer and impurities of the tensile specimen to obtain the reinforced and toughened Ti-6Al-4V alloy. Then, the mechanical properties of the 80ms sample were repeatedly tested using a tensile testing machine.

[0063] Example 5: DC pulse duration 85ms

[0064] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0065] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0066] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0067] (4) Conductive copper block material was placed at the gap between the tensile specimen and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0068] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 280A to ensure that the average current density at the gauge length of the tensile specimen is 140A / mm. 2 ;

[0069] (6) Set the electrical pulse treatment duration to 85ms (hereinafter referred to as the 85ms sample) and turn on the DC power supply. After the DC electrical pulse treatment is completed, wait for the specimen to cool completely to room temperature before removing the sample from the fixture.

[0070] (7) Mechanical grinding, ultrasonic cleaning and constant temperature drying were performed in sequence to remove the surface oxide layer and impurities of the tensile specimen to obtain the reinforced and toughened Ti-6Al-4V alloy. Then, the mechanical properties of the 85ms sample were repeatedly tested using a tensile testing machine.

[0071] Example 6: DC pulse duration 90ms

[0072] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0073] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0074] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0075] (4) Conductive copper block material was placed at the gap between the tensile specimen and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0076] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 280A to ensure that the average current density at the gauge length of the tensile specimen is 140A / mm.2 ;

[0077] (6) Set the electrical pulse treatment duration to 90ms (hereinafter referred to as the 90ms sample) and turn on the DC power supply. After the DC electrical pulse treatment is completed, wait for the specimen to cool completely to room temperature before removing the sample from the fixture.

[0078] (7) Mechanical grinding, ultrasonic cleaning and constant temperature drying were performed in sequence to remove the surface oxide layer and impurities of the tensile specimen to obtain the reinforced and toughened Ti-6Al-4V alloy. Then, the mechanical properties of the 90ms sample were repeatedly tested using a tensile testing machine.

[0079] Example 7, current density 150A / mm 2

[0080] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0081] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0082] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0083] (4) Conductive copper block material was placed at the gap between the tensile specimen and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0084] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 300A to ensure that the current density at the gauge length of the tensile test piece is 150A / mm. 2 ;

[0085] (6) Set the electrical pulse processing duration to 75ms (hereinafter referred to as 75ms-150A / mm). 2 (Sample), connect the DC power supply. After the DC pulse treatment is completed, wait for the specimen to cool completely to room temperature, then remove the sample from the fixture.

[0086] (7) Mechanical grinding, ultrasonic cleaning, and constant temperature drying were performed sequentially to remove the surface oxide layer and impurities of the tensile specimen, resulting in a reinforced and toughened Ti-6Al-4V alloy. Subsequently, the tensile testing machine was used to repeatedly test the 75ms-150A / mm range. 2 Mechanical properties of the sample.

[0087] Example 8, current density 160A / mm 2

[0088] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0089] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for mechanical testing of the initial state sample;

[0090] (3) Subsequently, the tensile specimen after step (2) with a smooth and defect-free surface is placed on the specimen clamp outside the welding power supply equipment.

[0091] (4) Conductive copper block material was placed at the gap between the tensile specimen and the copper plate electrode and fixed with fastening bolts to ensure that the three are tightly fitted together.

[0092] (5) After the tensile specimen is installed, set the input current of the inverter welding power supply to 320A to ensure that the current density at the gauge length of the tensile test piece is 160A / mm. 2 ;

[0093] (6) Set the electrical pulse processing duration to 75ms (hereinafter referred to as 75ms-160A / mm). 2 (Sample), connect the DC power supply. After the DC pulse treatment is completed, wait for the specimen to cool completely to room temperature, then remove the sample from the fixture.

[0094] (7) Mechanical grinding, ultrasonic cleaning, and constant temperature drying were performed sequentially to remove the surface oxide layer and impurities of the tensile specimen, resulting in a reinforced and toughened Ti-6Al-4V alloy. Subsequently, the tensile testing machine was used to repeatedly test the 75ms-160A / mm range. 2 Mechanical properties of the sample.

[0095] Comparative Example 1

[0096] Commercially available hot-worked Ti-6Al-4V alloy was selected as the initial material, and its mechanical properties were directly analyzed:

[0097] (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 tensile specimens. The length, width, and thickness of the tensile specimens at the gauge length were 8 mm, 2 mm, and 1 mm, respectively;

[0098] (2) The tensile specimens obtained in step (1) are subjected to mechanical grinding, ultrasonic cleaning and constant temperature drying in sequence to obtain the raw materials for the mechanical testing of the initial state samples. The initial yield strength, tensile strength and elongation are directly tested using a tensile testing machine. The initial state samples are set as the reference group and are not subjected to any DC pulse treatment;

[0099] (3) The mechanical properties of the initial tensile specimen should be tested repeatedly at least three times to ensure the reliability of the performance.

[0100] Tensile deformation tests were conducted at room temperature on Ti-6Al-4V alloy samples subjected to DC pulse treatment in Examples 1-3 and the initial state sample in Comparative Example 1, with a strain rate of 10 rpm. -3 / s, equipped with a video extensometer to calculate strain in real time, the resulting engineering stress-strain curve is as follows: Figure 1 As shown. Tensile deformation tests were conducted at room temperature on the Ti-6Al-4V alloy samples from Examples 3-6 treated with DC pulses and the initial state sample from Comparative Example 1, with a tensile strain rate of 10. -3 / s, equipped with a video extensometer to calculate strain in real time, the resulting engineering stress-strain curve is as follows: Figure 2 As shown. 75ms-140A / mm for the optimal combination of strength and toughness. 2 Nanoindentation tests were performed on the electrically pulsed sample and the initial state sample, and the load-displacement curves of the indenter extrusion process are shown below. Figure 3 As shown.

[0101] Figure 1 The images show the engineering stress-strain curves of the Ti-6Al-4V alloy samples subjected to DC pulse treatment in Examples 1-3 and the initial state sample of Comparative Example 1. Figure 1It can be seen that, without DC pulse treatment (0 ms), the strain hardening phenomenon of the initial sample is not obvious after the elastic deformation stage. At this time, the yield strength of the initial sample is 871.3 MPa, the tensile strength is 947.6 MPa, and the elongation is 13.5%. When the DC pulse treatment time is 40 ms, the strain hardening phenomenon of the 40 ms sample is slightly enhanced, and the yield strength and tensile strength increase slightly to 881.6 MPa and 968.3 MPa, respectively, but the elongation decreases slightly to 12.2%. When the pulse duration is further increased to 65 ms, the plastic deformation process of the sample shows continuous strain hardening behavior, achieving a simultaneous increase in tensile strength (1060.9 MPa) and elongation (15.8%), but its yield strength (860.4 MPa) is slightly lower than that of the 40 ms sample. When the electric pulse duration was 75 ms, the yield strength and tensile strength of the Ti-6Al-4V alloy sample significantly increased to 1066.0 MPa and 1215.4 MPa, respectively, while the elongation was 15.5%, an increase of 14.8% compared to the initial sample. Therefore, it can be inferred that when the current density is 140 A / mm², the yield strength and tensile strength of the Ti-6Al-4V alloy sample are significantly increased. 2 When the DC pulse treatment time is 75ms, the yield strength, tensile strength and elongation of Ti-6Al-4V alloy are significantly optimized.

[0102] Figure 2 The figures show the engineering stress-strain curves of the Ti-6Al-4V alloy samples treated with DC electric pulses in Examples 3-6 and the initial state sample of Comparative Example 1. When the DC electric pulse time increased to 80 ms, the yield strength, tensile strength, and elongation of the Ti-6Al-4V alloy simultaneously decreased to 1048.0 MPa, 1141.5 MPa, and 14.3%, respectively. When the DC electric pulse time was further increased to 85 ms, the Ti-6Al-4V alloy exhibited significant embrittlement, with yield strength, tensile strength, and elongation at 1105.1 MPa, 1223.9 MPa, and 10.2%, respectively. When the electric pulse treatment time was selected as 90 ms, the elongation of the Ti-6Al-4V alloy was only 3.9%. In summary, it can be inferred that when the DC electric pulse treatment time is too long, the Ti-6Al-4V alloy gradually becomes embrittled, and both its strength and toughness decrease significantly.

[0103] Figure 3This document presents the displacement-load curves of nanoindentation for the DC pulse (75 ms) sample and the initial sample in Example 3. A KLA G200X nanoindenter equipped with a Berkovich diamond indenter was used in this study. The indenter depth into the sample surface was uniformly set to 1000 nm, and the minimum spacing between two adjacent indentations was set to 80 μm to avoid interference from testing errors and obtain reliable test values. When the indenter depth reached 1000 nm, the required loads for the two samples were 72.0 mN and 94.8 mN, respectively. This indicates that at the same indentation depth, the DC pulse (75 ms) sample requires a higher load, with average hardness and elastic modulus of 4.7 GPa and 128.3 GPa, respectively, representing increases of 38.2% and 13.3% in hardness (3.4 GPa) and elastic modulus (113.2 GPa) compared to the initial sample.

[0104] Figure 4 Example 7-8 DC pulse processing 75ms-140A / mm 2 75ms-150A / mm 2 and 75ms-160A / mm 2 The engineering stress-strain curve. When the electric pulse duration is set to 75ms, the current density of the Ti-6Al-4V alloy is increased from 140A / mm². 2 Increased to 150A / mm 2 and 160A / mm 2 At this time, the yield strength and tensile strength showed almost no further change with increasing tensile time, while the elongation decreased to 14.2% and 10.0%, respectively. The results indicate that further increasing the current density significantly reduces the ductility and toughness of the Ti-6Al-4V alloy.

[0105] The yield strength, tensile strength and elongation of the initial Ti-6Al-4V alloy sample prepared in Comparative Example 1 and the DC pulse samples obtained in Examples 1-6 were compared at room temperature. The results are shown in Table 1.

[0106] Table 1 Summary of mechanical properties for different electrical pulse processing times

[0107]

[0108]

[0109] The yield strength, tensile strength and elongation of the initial Ti-6Al-4V alloy sample prepared in Comparative Example 1 and the DC pulse samples obtained in Examples 7-8 were compared at room temperature. The results are shown in Table 2.

[0110] Table 2 Summary of mechanical properties at different electric pulse current densities

[0111]

[0112] As shown in Table 1, when maintaining a constant current density, the tensile strength and elongation of the DC pulsed Ti-6Al-4V alloy samples obtained in Examples 1-6 all showed a trend of first increasing and then decreasing with the continuous increase of the DC pulse duration. When a current density of 140 A / mm² was selected... 2 When the processing time was 75 ms, the strength and toughness of the Ti-6Al-4V alloy were significantly optimized compared to the initial state, with yield strength, tensile strength, and elongation of 1066.0 MPa, 1215.4 MPa, and 15.5%, respectively. Table 2 shows that when the DC pulse duration is kept constant, the electric pulse maintains a continuous strengthening effect on the Ti-6Al-4V alloy with increasing current density, but the toughness continuously decreases.

[0113] As can be seen from the above embodiments and comparative examples, the yield strength, tensile strength, and elongation of the commercially available hot-worked Ti-6Al-4V alloy treated with DC pulses provided by this invention are significantly improved simultaneously. Current density: 140 A / mm² 2 The average hardness and elastic modulus of the sample with an electrical pulse duration of 75 ms increased by 38.2% and 13.3% respectively compared with the initial state.

[0114] 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 production of enhanced toughened Ti-6AI-4V alloy based on direct current pulse, characterized by, The method comprises the following steps: Step S1, first, a Ti-6Al-4V alloy raw material is linearly cut to obtain a plurality of tensile samples; Step S2, the tensile 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 reinforced and toughened Ti-6Al-4V alloy is prepared; The current density of the transient direct current pulse in the step S4 is 140 A / mm 2 160 A / mm 2 The direct current pulse processing time of the transient direct current pulse is 40 ms to 90 ms.

2. A method of preparing a reinforced and toughened Ti-6AI-4V alloy based on direct current pulse as claimed in claim 1, wherein: 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 for preparing a reinforced and toughened Ti-6Al-4V alloy based on a direct current pulse according to claim 1, characterized in that: In step S4, the specific method for treating the initial state alloy sample by direct current pulse is as follows: the power supply is started, and a transient direct current pulse with a specific current density is input into the initial state alloy sample.

4. A method of preparing a reinforced and toughened Ti-6AI-4V alloy based on direct current pulse as claimed in claim 1, wherein the said method comprises the steps of: 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 75 ms.

5. The method for preparing a reinforced and toughened Ti-6Al-4V alloy based on a direct current pulse according to claim 1, characterized in that: 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%.

6. A reinforced and toughened Ti-6Al-4V alloy based on direct current pulse, characterized in that: The reinforced and toughened Ti-6Al-4V alloy is prepared by the preparation method of any one of claims 1-5.

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