Method for preparing low-oxygen titanium alloy sheet from titanium alloy powder through multi-element sequence control

Abstract

The invention discloses a method for preparing a low-oxygen titanium alloy sheet from titanium alloy powder in a multi-element sequence control manner, which comprises the following steps: S1, granulation: mixing and granulating titanium alloy powder and an adhesive; s2, powder rolling is conducted, specifically, the powder particle raw materials are rolled, and a titanium alloy plate blank is obtained; s3, degreasing and dehydrogenation treatment; s4, oxygen control treatment, wherein the oxygen content in the titanium alloy sheet blank is controlled; and S5, sintering is conducted, specifically, the titanium alloy sheet blank is sintered at high temperature and used for closing internal pores of the material and densifying the blank. According to the process route, titanium hydride powder is creatively added into an adhesive for granulation, then powder rolling is carried out, and a thin plate or a coil is formed preliminarily. And then through a series of precise control procedures such as vacuum degreasing, dehydrogenation, oxygen control and sintering, impurities are effectively removed, the oxygen content and the hydrogen content are precisely controlled, the structure and performance of the thin plate are further optimized through hot rolling and cold rolling, and the problems that energy consumption is high and impurities are introduced after multiple times of rolling are successfully solved.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy, and particularly relates to a method for preparing a low-oxygen titanium alloy thin plate by multi-element controlled sequence preparation of titanium alloy powder. Background Art

[0002] Titanium alloys exhibit extremely important application values in many high-end fields such as aerospace, electronic devices, and medical devices due to their advantages of low density, high strength, and good corrosion resistance. Currently, the traditional methods for preparing titanium alloy thin plates mainly include the casting-rolling process and the powder metallurgy process. Powder metallurgy technology is one of the most economical titanium alloy preparation processes at present, which can greatly improve the material utilization rate, and the prepared titanium alloy has uniform and fine grains and good performance. However, due to the high activity and high melting point of titanium alloys, it is difficult to densify powder titanium alloys. Usually, it is necessary to combine expensive spherical pre-alloyed powders with high-cost forming processes such as hot isostatic pressing to achieve, which is contrary to the purpose of reducing costs in powder metallurgy. In the prior art, for example, a method for preparing a high-density fine-grained titanium alloy by powder rolling disclosed in CN110238401A. This patent mentions improving the density and refining the grains through powder rolling combined with subsequent treatments. It uses the cold isostatic pressing process to make a bulk titanium alloy billet, and then performs rolling. It can roll out a high-density and grain-refined titanium alloy by means of powder metallurgy, but it still needs to perform the traditional multiple rolling methods, that is, first form a titanium alloy ingot, and then obtain a thin plate with the required thickness through multiple rolling processes. For example, first form an ingot, and then perform repeated hot rolling and continuous rolling. If a 1-mm thin plate needs to be rolled, about 10 to 20 times of repeated rolling may be required. However, this method of rolling thin plates from a titanium alloy ingot billet has many drawbacks. On the one hand, the melting process requires extremely high temperatures and a large amount of energy input, which not only results in huge energy consumption, but also easily causes the titanium alloy to react with the furnace environment at high temperatures, introducing impurity elements such as oxygen and nitrogen, thereby affecting the quality of the thin plate. On the other hand, when rolling thin plates with a thickness of millimeters or even thinner, the requirements for equipment accuracy and process control are extremely high, the processing difficulty is large, the yield is low, and the production cost is high. The powder metallurgy process has, to a certain extent, improved some problems of the melting-casting and rolling process. It can increase the material utilization rate, and the microstructure of the prepared titanium alloy is relatively uniform. However, this process also faces challenges. Since titanium alloy powder itself has high activity, it is extremely easy to react with oxygen, water vapor, etc. in the surrounding environment during conventional pressing and sintering processes, resulting in powder oxidation and affecting the performance of the final product. Moreover, to obtain dense titanium alloy thin sheets, complex and expensive subsequent treatment processes such as hot isostatic pressing are often required, which goes against the original intention of powder metallurgy to reduce costs. At the same time, there are limitations in the thickness control of thin sheets prepared by traditional powder metallurgy, and it is difficult to stably produce ultra-thin products with a thickness of less than millimeters. In view of the above, it is necessary to propose a method for preparing low-oxygen titanium alloy thin sheets by multi-element controlled sequencing of titanium alloy powder to solve the above problems. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects existing in the prior art and provide a method for preparing low-oxygen titanium alloy thin sheets by multi-element controlled sequencing of titanium alloy powder.

[0004] To achieve the above purpose, the technical solution of the present invention is as follows: A method for preparing low-oxygen titanium alloy thin sheets by multi-element controlled sequencing of titanium alloy powder, comprising the following steps. S1: Granulation, mixing titanium alloy powder with an adhesive for granulation to obtain powder particle raw materials wrapped by the adhesive; the composition of the adhesive includes 8 - 18Wt% of polyethyleneimine (PEI), 0.1 - 1Wt% of hydroxyethyl cellulose (HEC), 15 - 25Wt% of isopropanol, 25 - 35Wt% of ethylene glycol monobutyl ether, and the balance is water. During the granulation stage, the mass ratio of the added adhesive is controlled at 0.5 - 7%, the viscosity of the adhesive is 500 - 1000 cps, the granulation temperature is 25 - 35°C, and the particle size uniformity and strength of the powder particle raw materials are controlled.

[0005] S2: Powder rolling. The raw material of powder particles is rolled to obtain a billet of titanium alloy thin sheet or thin coil. The rolling speed is controlled at 0.5 - 6 m / min, and the rolling pressure is 50 - 150 MPa to ensure uniform rolling thickness. The initial rolling thickness is controlled at 1 - 3 mm. During actual processing, the powder particles can be rolled by a rolling mill to obtain a billet of titanium alloy thin sheet or thin coil. A special powder rolling mill is used, which has some special designs to adapt to the rolling of powder particles. The granulated powder particle raw material is evenly fed between the two rollers of the rolling mill. As the rollers rotate, the powder particles are gradually compacted under the pressure of the rollers. Since the surface of the rollers is smooth and has a certain pressure, the gaps between the powder particles gradually decrease, and the particles are extruded and deformed and approach each other. Under the continuous action of the rolling pressure, the bonding force between the powder particles gradually increases, and a continuous billet begins to form. By controlling parameters such as the rolling speed, rolling pressure, and the state of the initial powder particles, the rolling thickness can be ensured to be uniform, and the powder particles gradually form a billet of titanium alloy thin sheet or thin coil with a certain thickness, width, and length.

[0006] S3: Degreasing and dehydrogenation treatment. This step is used to remove the binder added in the granulation step from the billet. The vacuum degree reaches 10 -3 -10 -4 Pa, the degreasing temperature is 400 - 700 °C, and the degreasing time is 2 - 4 h. During actual use, the control of the degreasing time is based on the constant maintenance of the environmental vacuum degree. The number of titanium alloy thin sheets entering the furnace in different batches is different. During degreasing, a vacuum environment is established in the furnace. During the degreasing process, as the binder volatilizes, the vacuum degree in the furnace will decrease. Monitor the vacuum degree during the process. When the high vacuum degree in the furnace is maintained constantly for a certain time, it can be judged that the product degreasing is completed, thus ensuring complete degreasing. The dehydrogenation temperature is 750 - 900 °C, the heating rate is 5 - 10 °C / min, and the holding time is 1 - 2 h. Dehydrogenation and degreasing are carried out successively in the same furnace, and the basis for dehydrogenation judgment can be the same as the aforementioned degreasing judgment method to ensure sufficient dehydrogenation.

[0007] When using 150 MPa high-pressure rolling on titanium alloy powder, the powder particles can undergo plastic deformation and mutual extrusion, promoting an increase in the contact area between the particles, thereby forming a certain mechanical meshing and physical adsorption effect, preliminarily connecting the powders, and thus forming the thin sheet. During subsequent degreasing and dehydrogenation treatments, at a high temperature of 900 °C, although it has not reached the melting point of titanium alloy particles, at a high temperature of 900 °C, the atoms have high activity and diffusion will occur. The atoms on the surface of titanium alloy particles will diffuse with each other, causing metallurgical bonding between the particles and gradually forming connections. This connection is achieved through the diffusion and bonding of atoms, which helps to improve the density and mechanical properties of the material.

[0008] The degreasing is carried out in a vacuum or an inert gas atmosphere. In a vacuum environment, it effectively avoids the reaction of the material with oxygen in the air during the degreasing process and prevents oxidation. Using inert gases such as argon and nitrogen can also play a role in isolating oxygen, providing an oxygen-free environment for degreasing, and ensuring the degreasing effect and the purity of the material.

[0009] The dehydrogenation is carried out in a vacuum or a mixed atmosphere of hydrogen and inert gas. The vacuum environment is conducive to the diffusion of hydrogen atoms from the interior of the material to the surface and their escape. In the mixed atmosphere of hydrogen and inert gas, an appropriate hydrogen partial pressure can promote the dehydrogenation reaction, while the inert gas plays a role in dilution and protection to prevent excessive oxidation of the material.

[0010] S4: Sintering. The titanium alloy thin slab blank is sintered at a high temperature to close the internal pores of the material and densify the blank. The sintering temperature is 1100 - 1300 °C, and the holding time is 2 - 5 h. Pulse current sintering can improve the density. Vacuum sintering can remove oxygen and other impurity gases in the furnace, avoid oxidation of the material at high temperature, and is conducive to the closure and densification of the internal pores of the material. When sintering in an inert gas, the gas purity should be high enough to prevent adverse effects of impurity gases on the sintering process.

[0011] During the above-mentioned degreasing, dehydrogenation, and sintering processes, oxygen control treatment is maintained to ensure that the oxygen content of the product is controlled at a low level. Under the strict control of the oxygen content environment, by controlling the environmental temperature and pressure and reducing the contact of the blank with oxygen, a vacuum environment can be established to control the oxygen content in the titanium alloy thin slab blank; it can also be in a high-purity inert gas atmosphere, such as transitioning from a vacuum environment to an inert gas atmosphere, and filling high-purity argon for protection in the vacuum environment, with the oxygen content controlled at 100 - 200 ppm or even lower. The above-mentioned processes need to be carried out in an environment with strict oxygen content control, such as an argon environment with a purity of more than 99.99%. Then, by precisely controlling parameters such as the flow rate, pressure, and environmental temperature of the inert gas, the contact between external oxygen and the material is reduced, thereby precisely controlling the oxygen content in the titanium alloy thin slab to ensure that the oxygen content is controlled at a low level.

[0012] Furthermore, the following steps are also included. S5: Hot rolling. It improves the tissue performance of the titanium alloy thin slab, enables the titanium alloy thin slab to undergo dynamic recrystallization at high temperature, the coarse grains are broken and refined, forming a fine and uniform equiaxed grain structure, and improving the strength, toughness, plasticity, and density of the titanium alloy; the heating temperature for hot rolling is 850 - 950 °C, and the reduction ratio is controlled at 30% - 40%. S7: Cold rolling, precisely controlling dimensions and surface quality. Through cold rolling, the thickness, width, and length of the titanium alloy thin sheet are precisely controlled to achieve high dimensional accuracy and surface flatness, making its surface smoother and flatter, with reduced roughness, meeting the requirements for the surface quality of titanium alloy thin sheets in different application fields. The surface roughness Ra of the roll is 0.05 - 0.1μm, the rolling speed is 1 - 3m / s, and the reduction rate is controlled at 10% - 20% each time. After cold rolling, the structure of the titanium alloy thin sheet is more uniform, and the degree of anisotropy is reduced. The mechanical properties in the rolling direction and perpendicular to the rolling direction are closer, improving the stability and consistency of the material properties, which is beneficial for subsequent processing and use.

[0013] Furthermore, the binder includes polyvinyl alcohol (PVA) or polyethylene glycol (PEG). Polyvinyl alcohol (PVA) has good bonding properties and can bond titanium alloy powder particles well together to form particles with a certain strength and shape. At the same time, it is relatively easy to remove during subsequent debinding treatment. Polyethylene glycol (PEG): It can adjust the viscosity and fluidity of the particles, making the granulation process more uniform, and the obtained particles have regular shapes and relatively uniform size distributions. Moreover, it can volatilize well when heated, facilitating the debinding treatment.

[0014] Acrylic resins can also be used, which can endow the particles with higher strength and stability, helping to maintain the integrity of the particles during subsequent processing. However, its debinding process may be relatively more complex, and appropriate debinding methods and conditions need to be selected.

[0015] The use of the binder helps to improve formability. Titanium alloy powder usually has a small particle size and a large specific surface area, and it is difficult to form directly during processing such as rolling. The binder can bond fine powder particles together to form larger particles, increasing the fluidity and formability of the powder, facilitating subsequent operations such as powder rolling, and can also well isolate the contact with oxygen, enabling the powder to better fill the space between the mold or roll to form a titanium alloy thin sheet blank with the required shape and size.

[0016] It can also improve the strength of the green body. During the powder rolling process, the green body needs to withstand certain pressure and friction. The binder can form a bonding bridge between the powder particles, improving the strength and toughness of the green body, preventing defects such as cracks and breakage in the green body during the rolling process, ensuring the integrity and stability of the green body, and being beneficial for the smooth progress of subsequent processing steps.

[0017] One of the main purposes of the degreasing treatment is to remove the binder added during granulation. During subsequent high-temperature treatments such as sintering, if the binder remains, it will decompose to produce gases, resulting in the formation of pores and defects inside the titanium alloy thin sheet, affecting its density and mechanical properties. Therefore, it is necessary to remove the binder completely through degreasing treatment. In the degreasing process of this process, heating is used to decompose, volatilize or pyrolyze the binder under certain temperature and atmosphere conditions. Due to different chemical structures and properties of different binders, the conditions such as temperature, time and atmosphere for degreasing also vary. If the degreasing is incomplete, the remaining binder will have an adverse effect during the sintering process, such as reducing the density of the material and affecting the diffusion of alloying elements.

[0018] The process control of the above process flow also includes: Pre-treatment before granulation: Screen the powder to remove coarse particles and impurities to ensure uniform powder particle size. After powder rolling: Increase flatness detection and perform preliminary leveling on uneven places. After vacuum degreasing: Perform weight detection to judge whether the degreasing is complete. After dehydrogenation: Use a gas analyzer to detect the degree of dehydrogenation. After sintering: Perform hardness and density detection to judge the sintering quality. After hot rolling: Perform metallographic structure analysis and adjust the subsequent cold rolling process parameters. After cold rolling: Perform surface quality detection, including roughness, glossiness, etc.

[0019] Furthermore, it also includes a laser shock peening treatment step. By irradiating the surface of the titanium alloy thin sheet with a high-energy density laser beam, the surface thin layer of the titanium alloy thin sheet is rapidly vaporized and ionized to form a plasma. The plasma rapidly expands to generate a high-pressure shock wave, causing plastic deformation on the material surface to form a strengthened layer, improving the surface hardness and fatigue resistance of the titanium alloy thin sheet.

[0020] Furthermore, it also includes material pre-treatment. For the titanium alloy thin sheet after hot rolling and cold rolling, first perform surface cleaning treatment to remove impurities such as oil stains and dust on the surface to ensure the consistency of the laser shock peening effect. The ultrasonic cleaning method can be used. Place the thin sheet in an aqueous solution containing an appropriate amount of cleaning agent, set the ultrasonic frequency to 40 kHz, and the cleaning time to 15 minutes. Then perform double annealing heat treatment. Place the thin sheet in a vacuum furnace, heat it to 950 °C, hold it for 1.5 hours, then rapidly cool it to 550 °C with argon and hold it for 4 hours, and finally cool it to room temperature and take it out. This step can eliminate the residual stress generated during the cold rolling process, adjust the internal organizational structure of the material, and lay a good foundation for the subsequent laser shock peening. Laser shock peening stage: A layer of absorption layer, such as black paint, is evenly coated on the surface of the cleaned thin plate, with the thickness controlled at 0.1 - 0.2 mm. The thin plate coated with the absorption layer is clamped on a special manipulator, and the thin plate is remotely controlled to enter the initial position of the laser shock path. The laser used is a high-energy pulsed laser with a wavelength of 1064 nm, a pulse width of 20 ns, and an energy density of 3 J / cm². The laser is turned on to accurately focus the light spot on the shock area of the thin plate surface. At the same time, the waterway system is turned on, and the position of the water outlet is adjusted so that the ejected water forms a uniform constraint layer on the thin plate surface, with the water layer thickness of about 2 mm. The pre-designed shock path simulation program is imported, and the laser shock peening treatment is started. The laser energy beam impacts the absorption layer through the water constraint layer, causing the absorption layer to instantly vaporize and generate a large number of high-energy particles. These particles act on the thin plate surface to generate a shock pressure wave, forming residual compressive stress and realizing surface modification.

[0021] Furthermore, it also includes an ion implantation modification step. The cold-rolled titanium alloy thin plate is subjected to strict surface degreasing treatment. The thin plate is immersed in an organic solvent (acetone can be used) and ultrasonically cleaned for 20 minutes to remove surface oil stains. Then pickling is carried out using a mixed solution of 5% hydrofluoric acid and 15% nitric acid for 5 minutes to remove the surface oxide layer and impurities, exposing the fresh metal surface and improving the effect and uniformity of ion implantation. After pickling, it is rinsed clean with deionized water and dried in an oven at 100°C for 10 minutes. Ion implantation stage: The pretreated thin plate is placed in the vacuum chamber of the ion implantation equipment, and the vacuum is pumped down to below 10 -6 Pa. Nitrogen ions (N⁺) are selected as the implanted ions, the ion energy is accelerated to 80 keV, and the implantation dose is 5×10 17 ions / cm². During the implantation process, the temperature of the vacuum chamber is controlled at about 150°C to reduce the lattice damage generated during implantation and promote the diffusion and solid solution of ions inside the material. By precisely controlling the scanning method and time, the ions are ensured to be uniformly implanted on the thin plate surface. Post-treatment stage: After ion implantation, the thin plate is subjected to low-temperature annealing treatment. It is heated to 300°C in a vacuum environment, held for 1 hour, and then cooled with the furnace. This step helps to eliminate the residual stress generated during implantation, stabilize the new structure formed by the implanted ions and the matrix, and further improve the wear resistance, corrosion resistance, surface hardness and other properties of the material.

[0022] The advantages and beneficial effects of the present invention are as follows: A method for preparing a low-oxygen titanium alloy thin plate by multi-element controlled sequence of titanium alloy powder in the present invention aims at the deficiencies of the prior art. This process route innovatively uses titanium hydride powder (or titanium alloy powder), granulates it by adding a binder, and then performs powder rolling to initially form a thin plate or coil. Subsequently, through a series of precisely controlled processes such as vacuum degreasing, dehydrogenation, oxygen control, and sintering, impurities are effectively removed, and the oxygen content and hydrogen content are precisely controlled, laying a good foundation for subsequent processing. Finally, the structure and properties of the thin plate are further optimized through hot rolling and cold rolling, successfully solving the problems of high energy consumption, impurity introduction, high cost, and difficulty in preparing ultra-thin specification thin plates in the traditional process, and is expected to bring a new solution with higher efficiency, lower cost, and higher quality for the production of titanium alloy thin plates. Specific Embodiments

[0023] The following combines examples to further describe the specific embodiments of the present invention. The following examples are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0024] Example 1: In this example, Ti-6Al-4V titanium alloy powder is used as the raw material with a purity of 99.5%. The binder has a composition of 8-18Wt% of polyethyleneimine (PEI), 0.1-1Wt% of hydroxyethyl cellulose (HEC), 15-25Wt% of isopropanol, 25-35Wt% of ethylene glycol monobutyl ether, and the remaining amount is water. Its viscosity is within the experimental requirements.

[0025] The specific implementation is as follows: S1 Granulation: During the granulation stage, the mass ratio of the added binder is controlled at 5%. The binder viscosity is 750 cps, and the granulation temperature is 30°C.

[0026] S2 Powder rolling: The rolling speed is 1 m / min, the rolling pressure is 100 MPa, and the initial rolling thickness is 2 mm.

[0027] S3 Degreasing and dehydrogenation treatment: The vacuum degree is 10 -3 Pa, the degreasing temperature is 600°C, the degreasing time is 3 h; the dehydrogenation temperature is 850°C, the heating rate is 7°C / min, and the holding time is 1.5 h.

[0028] S4 Oxygen control treatment: The oxygen content is controlled at 150 ppm.

[0029] S5 Sintering: The sintering temperature is 1250°C, and the holding time is 4 h.

[0030] S6 Hot rolling: The heating temperature is 900°C, and the reduction ratio is 35%.

[0031] S7 Cold Rolling: The surface roughness Ra of the roll is 0.07 μm, the rolling speed is 2 m / s, and the reduction rate is 15% each time.

[0032] Example 2: The raw materials used in this example are the same as those in the previous example.

[0033] The specific implementation is as follows: S1 Granulation: The mass fraction of the binder is 5%, the viscosity of the binder is 500 cps, and the granulation temperature is 25°C.

[0034] S2 Powder Rolling: The rolling speed is 3 m / min, the rolling pressure is 50 MPa, and the initial rolling thickness is 1 mm.

[0035] S3 Degreasing and Dehydrogenation Treatment: The vacuum degree is 10 -4 Pa, the degreasing temperature is 500°C, the degreasing time is 4 h; the dehydrogenation temperature is 800°C, the heating rate is 5°C / min, and the holding time is 2 h.

[0036] S4 Oxygen Control Treatment: The oxygen content is controlled at 100 ppm.

[0037] S5 Sintering: The sintering temperature is 1200°C, and the holding time is 5 h.

[0038] S6 Hot Rolling: The heating temperature is 850°C, and the reduction rate is 30%.

[0039] S7 Cold Rolling: The surface roughness Ra of the roll is 0.05 μm, the rolling speed is 1 m / s, and the reduction rate is 10% each time.

[0040] Example 3: The raw materials used in this example are the same as those in the previous example.

[0041] The specific implementation is as follows: S1 Granulation: The mass fraction of the binder is 5%, the viscosity of the binder is 1000 cps, and the granulation temperature is 35°C.

[0042] S2 Powder Rolling: The rolling speed is 1 m / min, the rolling pressure is 150 MPa, and the initial rolling thickness is 3 mm.

[0043] S3 Degreasing and Dehydrogenation Treatment: The vacuum degree is 10 -3 Pa, the degreasing temperature is 400°C, the degreasing time is 2 h; the dehydrogenation temperature is 900°C, the heating rate is 10°C / min, and the holding time is 1 h.

[0044] S4 Oxygen Control Treatment: The oxygen content is controlled at 200 ppm.

[0045] S5 Sintering: The sintering temperature is 1300 °C and the holding time is 3 h.

[0046] S6 Hot rolling: The heating temperature is 950 °C and the reduction ratio is 40%.

[0047] S7 Cold rolling: The surface roughness Ra of the roll is 0.1 μm, the rolling speed is 3 m / s, and the reduction ratio is 20% each time.

[0048] Comparative example: The prior art cited in the background art is adopted to form a massive titanium alloy blank by powder pressing, and then rolling is carried out. During the rolling process, there is no strict control of oxygen, dehydrogenation and other precise parameter controls, and titanium alloy thin plates are obtained after several rollings.

[0049] The titanium alloy thin plates of each embodiment are tested for performance by the following various methods, specifically as follows: Hardness test: A Vickers hardness tester is used, the loading load is 1 kgf, the loading time is 15 s, and 10 points are measured at different positions on the surface of the thin plate and the average value is taken.

[0050] Tensile property test: An electronic universal material testing machine is used, the tensile rate is 1 mm / min, tensile specimens are made according to the standard, and the yield strength, tensile strength and elongation are tested.

[0051] Apparent density test: The density of the thin plate is measured by the Archimedes drainage method, and the apparent density is calculated by comparing with the theoretical density.

[0052] Oxygen content analysis: An oxygen and nitrogen analyzer is used to determine the oxygen content in the thin plate.

[0053] Performance comparison table of each embodiment

[0054] The hardness of Examples 1 - 3 is significantly higher than that of the control example, indicating that this process route effectively improves the hardness of the material through fine parameter control. Due to the higher sintering temperature and larger reduction ratio in Example 3, the hardness is relatively higher.

[0055] The embodiments under this process route are superior to the control example in terms of yield strength, tensile strength and elongation. The comprehensive performance of Example 1 is relatively balanced, reflecting the optimization of tensile properties by a suitable parameter combination. The apparent density of Examples 1 - 3 is significantly higher than that of the control example. In Example 3, the internal pores are effectively closed through a higher sintering temperature and pressure, and the apparent density is the highest. The oxygen control treatment effect of this process route is obvious, and the oxygen content of Examples 1 - 3 is much lower than that of the control example. In Example 2, the oxygen content is controlled at the lowest level through a strict oxygen control environment.

[0056] Further improve the process Example 4: In this example, Ti-6Al-4V titanium alloy powder is selected as the raw material with a purity of 99.5%. The viscosity of the binder is within the experimental requirements. Specifically: S1 Granulation: The mass fraction of the binder is 5%, the viscosity of the binder is 750 cps, and the granulation temperature is 30°C.

[0057] S2 Powder rolling: The rolling speed is 1 m / min, the rolling pressure is 150 MPa, and the initial rolling thickness is 2 mm.

[0058] S3 Degreasing and dehydrogenation treatment: The vacuum degree is 10 -3 Pa, the degreasing temperature is 600°C, and the degreasing time is 3 h; the dehydrogenation temperature is 850°C, the heating rate is 7°C / min, and the holding time is 1.5 h.

[0059] Oxygen control treatment: The oxygen content is controlled at 150 ppm.

[0060] S4 Sintering: The sintering temperature is 1250°C, and the holding time is 4 h.

[0061] S5 Hot rolling: The heating temperature is 900°C, and the reduction ratio is 35%.

[0062] S6 Cold rolling: The surface roughness Ra of the roll is 0.07 μm, the rolling speed is 2 m / s, and the reduction ratio is 15% each time.

[0063] S7 Laser shock peening: Material pretreatment: Ultrasonic cleaning is adopted with an ultrasonic frequency of 40 kHz and a cleaning time of 15 minutes. Subsequently, double annealing treatment is carried out. First, it is heated to 950°C, held for 1.5 hours, rapidly cooled to 550°C with argon, held for 4 hours, and then air-cooled to room temperature.

[0064] Laser shock peening treatment: The energy density of the laser beam is 3 J / cm², the pulse width is 20 ns, a black paint with a thickness of 0.15 mm is coated as the absorption layer, and the thickness of the water confinement layer is 2 mm.

[0065] The performance of the titanium alloy thin plate in this example is tested, and the results show that its Vickers hardness reaches 380, and the fatigue life reaches 4×10 6After the first cycle; after laser shock peening treatment, the surface hardness is significantly improved. Due to the high laser energy density and long pulse width, the hardness improvement is obvious, indicating that laser shock peening can effectively improve the surface hardness. And the fatigue life is much higher than that of the comparative example; showing the excellent effect of the improved process in improving the fatigue resistance performance, and the surface strengthening layer formed by laser shock peening effectively hinders the initiation and propagation of fatigue cracks.

[0066] Example 5: S1 Granulation: The mass fraction of the binder is 5%, the viscosity of the binder is 600 cps, and the granulation temperature is 28°C.

[0067] S2 Powder rolling: The rolling speed is 0.8 m / min, the rolling pressure is 130 MPa, and the initial rolling thickness is 1.5 mm.

[0068] S3 Degreasing and dehydrogenation treatment: The vacuum degree is 10 -4 Pa, the degreasing temperature is 500°C, the degreasing time is 3.5 h; the dehydrogenation temperature is 820°C, the heating rate is 6°C / min, and the holding time is 1.8 h.

[0069] Oxygen control treatment: The oxygen content is controlled at 120 ppm.

[0070] S4 Sintering: The sintering temperature is 1220°C, and the holding time is 4.5 h.

[0071] S5 Hot rolling: The heating temperature is 880°C, and the reduction ratio is 32%.

[0072] S6 Cold rolling: The surface roughness Ra of the roll is 0.06 μm, the rolling speed is 1.5 m / s, and the reduction ratio is 12% each time.

[0073] S7 Ion implantation modification step: Pretreatment stage: The surface is degreased by ultrasonic cleaning with acetone for 20 minutes, pickled with a mixed solution of 5% hydrofluoric acid and 15% nitric acid for 5 minutes, rinsed with deionized water and dried in an oven at 110°C for 10 minutes.

[0074] Ion implantation modification: Select nitrogen ion (N⁺) implantation, the ion energy is 80 keV, the implantation dose is 5×10 17 ions / cm², the temperature of the vacuum chamber is 150°C, and the low-temperature annealing is held in a vacuum environment at 300°C for 1 hour and then cooled with the furnace.

[0075] The same performance tests are also carried out on the titanium alloy thin plate of this example, as follows: Wear resistance test: Using a ball-disk friction and wear testing machine, the counter material is a Si3N4 ceramic ball with a diameter of 6 mm, the applied load is 5 N, the friction speed is 0.2 m / s, the test duration is 30 minutes, and the measured wear volume is 0.8×10 -3 mm³; Combining with the strengthened layer formed by ion implantation, the wear volume is the lowest, indicating that the improved process has greatly improved the wear resistance.

[0076] Corrosion resistance test: Potentiodynamic polarization tests were carried out through an electrochemical workstation. The test solution is 3.5% NaCl solution, the scanning rate is 0.01 V / s, and the measured corrosion potential is -0.15 V and the corrosion current density is 8×10 -8 A / cm²; The corrosion resistance of this embodiment is good, indicating that ion implantation modification changes the surface chemical composition and structure, effectively improving the corrosion resistance.

[0077] The performance tests fully confirm that the improved process of adding ion implantation modification and related pretreatment steps on the basis of the original process has significant advantages. In terms of wear resistance, corrosion resistance, surface hardness optimization, etc., the embodiments under the improved process perform excellently. Different combinations of process parameters have different degrees of influence on the performance, and can be flexibly adjusted according to actual application requirements.

[0078] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a low-oxygen titanium alloy thin plate by multi-element controlled sequence using titanium alloy powder, characterized in that, It includes the following steps, S1: Granulation, mixing titanium alloy powder with a binder for granulation to obtain powder particle raw materials wrapped by the binder; S2: Powder rolling, rolling the powder particle raw materials to obtain a sheet blank of titanium alloy thin sheet or thin coil; S3: Debinding and dehydrogenation treatment, this step is used to remove the binder added in the granulation step from the sheet blank; S4: Sintering, sintering the titanium alloy thin sheet blank at high temperature to close the internal pores of the material and densify the blank.

2. The method for preparing a low-oxygen titanium alloy thin sheet by multi-element controlled sequence preparation of titanium alloy powder according to claim 1, characterized in that, It also includes the following steps, S5: Hot rolling, improving the tissue performance of the titanium alloy thin sheet, causing dynamic recrystallization of the titanium alloy thin sheet at high temperature, breaking and refining the coarse grains to form a fine and uniform equiaxed grain structure, and improving the strength, toughness, plasticity and density of the titanium alloy; the heating temperature of hot rolling is 850 - 950 °C, and the reduction rate is controlled at 30% - 40%; S6: Cold rolling, precisely controlling the dimensions and surface quality, precisely controlling the thickness, width and length of the titanium alloy thin sheet through cold rolling to make it reach a high dimensional accuracy and surface flatness; the surface roughness Ra of the roll is 0.05 - 0.1 μm, the rolling speed is 1 - 3 m / s, and the reduction rate is controlled at 10% - 20% each time.

3. A method for preparing a low-oxygen titanium alloy thin plate by multi-element controlled sequence preparation of titanium alloy powder according to claim 1, characterized in that, The composition of the binder includes 8 - 18 Wt% of polyethyleneimine (PEI), 0.1 - 1 Wt% of hydroxyethyl cellulose (HEC), 15 - 25 Wt% of isopropanol, 25 - 35 Wt% of ethylene glycol monobutyl ether, and the balance is water.

4. A method for preparing a low-oxygen titanium alloy sheet by multi-element controlled sequence preparation of titanium alloy powder according to claim 1, characterized in that, In the powder rolling stage, the rolling speed is controlled at 0.5 - 6 m / min, the rolling pressure is controlled at 50 - 150 MPa, ensuring uniform rolling thickness, and the initial rolling thickness is controlled at 1 - 3 mm.

5. A method for preparing a low-oxygen titanium alloy sheet by multi-element controlled sequence preparation of titanium alloy powder according to claim 1, characterized in that, For the degreasing and dehydrogenation treatment, the environmental vacuum degree is controlled to reach 10 -3 - 10 -4 Pa, the degreasing temperature is 400 - 700 °C, and the control of the degreasing time is based on the constant maintenance of the environmental vacuum degree; During dehydrogenation treatment, the dehydrogenation temperature is controlled at 750 - 900 °C, the heating rate is 5 - 10 °C / min, and the holding time is controlled based on the constant maintenance of the environmental vacuum degree to dehydrogenate the blank sufficiently.

6. The method for preparing a low-oxygen titanium alloy thin sheet by multi-element controlled sequence of titanium alloy powder according to claim 1, characterized in that, In the oxygen control treatment stage, high-purity argon is filled for protection in a vacuum environment, and the oxygen content is controlled at 100 - 200 ppm; In the sintering stage, the sintering temperature is 1100 - 1300 °C, and the holding time is 2 - 5 h.

7. A method for preparing a low-oxygen titanium alloy sheet by multi-element controlled sequence preparation of titanium alloy powder according to claim 2, characterized in that, It also includes a laser shock peening treatment step. By irradiating the surface of the titanium alloy thin sheet with a laser beam of high energy density, the surface thin layer of the titanium alloy thin sheet is rapidly vaporized and ionized to form a plasma, and the plasma rapidly expands to generate a high-pressure shock wave, causing plastic deformation on the material surface to form a strengthening layer, improving the surface hardness and fatigue resistance of the titanium alloy thin sheet.

8. A method for preparing a low-oxygen titanium alloy sheet by multi-element controlled sequence preparation of titanium alloy powder according to claim 7, characterized in that, It also includes material pretreatment, performing surface cleaning treatment on the titanium alloy thin sheet to remove surface impurities and improve the consistency of the laser shock peening effect; using ultrasonic cleaning and then performing double annealing heat treatment to eliminate the residual stress generated during cold rolling and adjust the internal organizational structure of the material; A layer of absorption layer is evenly coated on the surface of the cleaned thin plate and then enters the laser for laser shock peening treatment. Control the waterway system to make the ejected water form a uniform constraint layer on the surface of the thin plate. When performing laser shock peening treatment, the energy density of the laser beam is 1 - 10 J / cm², and the pulse width is 10 - 50 ns. The laser energy beam impacts the absorption layer through the water constraint layer, causing the absorption layer to instantly vaporize and generate a large number of high-energy particles. The high-energy particles form a shock wave on the surface of the thin plate, and the stress on the surface of the thin plate is surface-modified by using the shock wave.

9. A method for preparing a low-oxygen titanium alloy sheet by multi-element controlled sequence of titanium alloy powder according to claim 2, characterized in that, It also includes an ion implantation modification step. In a high-vacuum environment, specific ions are accelerated to a higher energy and then implanted into the surface of the titanium alloy thin plate to change the chemical composition, crystal structure, and residual stress state of the material surface, and improve the wear resistance, corrosion resistance, and other properties of the material.

10. A method for preparing a low-oxygen titanium alloy sheet by multi-element controlled sequence of titanium alloy powder according to claim 9, characterized in that, It also includes a pretreatment stage, including surface degreasing treatment. The thin plate is soaked in an organic solvent and ultrasonically cleaned for 20 minutes to remove the surface oil stain, and then pickled to remove the surface oxide layer and impurities. After pickling, it is rinsed with deionized water and dried. The thin plate is placed in the vacuum chamber of the ion implantation equipment, and the vacuum is pumped down to below 10 -6 Pa; nitrogen ions (N⁺) are selected as the implanted ions, the ion energy is accelerated to 80 keV, and the implantation dose is 5×10 17 ions / cm²; during the implantation process, the temperature of the vacuum chamber is controlled at about 150 °C to reduce the lattice damage generated during the implantation process and promote the diffusion and solid solution of ions inside the material; after the ion implantation is completed, the thin plate is subjected to a low-temperature annealing treatment, heated to 300 °C in a vacuum environment, held for 1 hour, and then cooled with the furnace to eliminate the residual stress generated during the implantation process.

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