Method for preparing TC4 titanium alloy through cooperation of oscillation laser and rolling

Abstract

The invention relates to the technical field of titanium alloy preparation, in particular to an oscillation laser and rolling synergistic TC4 titanium alloy preparation method which comprises the following steps: S1, pretreating a TC4 titanium alloy blank, removing oxide skin and impurities on the surface of the blank, preheating to 150-300 DEG C, and preserving heat for 20-60 minutes; s2, carrying out scanning treatment on the surface of the pretreated blank by adopting pulse oscillation laser; s3, warm rolling treatment is conducted within 0.5-5 s after laser treatment in the step S2 is completed, the rolling temperature ranges from 650 DEG C to 850 DEG C, the pass rolling reduction ranges from 5% to 20%, the rolling speed ranges from 0.5 m / s to 3 m / s, the accumulated rolling reduction ranges from 30% to 60%, and inert gas protection is adopted in the rolling process; and S4, the rolled titanium alloy is sequentially subjected to annealing treatment, shape correction and surface finishing, and the TC4 titanium alloy is obtained. Therefore, the problems of coarse grains, stress concentration, poor mechanical property, low preparation stability and the like in the prior art are solved.

Description

Technical Field

[0001] This application relates to the field of titanium alloy preparation technology, and in particular to a method for preparing TC4 titanium alloy using a combination of oscillating laser and rolling. Background Technology

[0002] TC4 titanium alloy (Ti-6Al-4V), as a typical α+β type titanium alloy, combines high strength, excellent corrosion resistance, and biocompatibility. It is a core material in high-end fields such as aerospace load-bearing structural components, implantable medical devices, and marine engineering equipment, playing an irreplaceable role in equipment lightweighting upgrades and improved service reliability. Especially in applications requiring high precision and high safety, the uniformity of the material's microstructure, consistency of mechanical properties, and stability of the preparation process directly determine the service life and operational safety of the equipment. However, traditional TC4 titanium alloy preparation technologies generally suffer from problems such as a lack of process co-design and insufficient multi-effect control capabilities, making it difficult to simultaneously overcome the core technical bottlenecks of coarse grains, stress concentration, poor mechanical properties, and low preparation stability. Therefore, there is an urgent need to develop efficient preparation technologies that coordinate energy fields and plastic deformation.

[0003] The prominent problems of existing TC4 titanium alloys and related preparation technologies are concentrated in four aspects: Firstly, the problem of coarse grains is particularly significant. In traditional rolling processes, uneven deformation of the billet leads to insufficient dynamic recrystallization, easily forming coarse dendrites and banded structures of 8-15 μm or more. Secondly, laser treatment, due to the concentrated energy of a fixed laser spot, causes abnormal grain growth in the heat-affected zone, resulting in poor overall grain uniformity and potential performance fluctuations. Thirdly, stress concentration is difficult to alleviate. The mechanical stress generated by rolling and the thermal stress from laser treatment lack a mechanism to offset each other, resulting in residual stress in the product often exceeding 100 MPa. During service, stress concentration easily leads to cracking and failure. Fourthly, the overall mechanical properties are poor, with coarse grains... Traditional processes restrict strength improvement, resulting in tensile strengths of products below 900 MPa and elongation below 12%. Stress concentration and uneven microstructure exacerbate performance fluctuations, with tensile strength differences exceeding 50 MPa between different parts of the same batch, failing to meet the dual requirements of "high strength and high plasticity." Furthermore, the manufacturing stability is severely inadequate. Traditional processes lack coordinated design of key parameters, and independent control of parameters such as laser power and rolling temperature easily leads to energy and deformation imbalances. The process window is narrow and highly sensitive to parameter fluctuations. In addition, step-by-step processing easily causes defects such as surface oxidation and component segregation, resulting in a product qualification rate generally below 80%, significant batch-to-batch performance differences, and difficulty in achieving stable large-scale production. Summary of the Invention

[0004] This application provides a method for preparing TC4 titanium alloy by combining oscillating laser and rolling, in order to solve the problems of coarse grains, stress concentration, poor mechanical properties and low preparation stability in the prior art.

[0005] This application provides a method for preparing TC4 titanium alloy using a combination of oscillating laser and rolling, characterized by the following steps:

[0006] S1: Pretreatment of TC4 titanium alloy billet: remove oxide scale and impurities from the billet surface, preheat to 150-300℃ and hold for 20-60 minutes;

[0007] S2: Oscillating laser pretreatment, using pulsed oscillating laser to scan the surface of the pretreated billet, with laser power of 1000-3000W, oscillation frequency of 50-200Hz, scanning speed of 2-8mm / s, scanning spacing of 0.5-2mm, spot diameter of 1-5mm, and laser energy density of 80-200J / cm².

[0008] S3: Co-rolling. After the laser treatment in step S2, warm rolling is performed within 0.5-5s. The rolling temperature is 650-850℃, the reduction per pass is 5-20%, the rolling speed is 0.5-3m / s, and the cumulative reduction is 30-60%. Inert gas protection is used during the rolling process.

[0009] S4: Post-processing, the rolled titanium alloy is annealed, shaped and surface finished in sequence to obtain TC4 titanium alloy.

[0010] Optionally, in step S1, the pretreatment includes mechanical grinding, ultrasonic cleaning, and preheating. Mechanical grinding uses 800-1200 grit sandpaper to grind layer by layer to remove oxide scale, rust, and processing burrs from the surface of the blank. Ultrasonic cleaning uses a mixed solution of ethanol and deionized water (volume ratio 1:1-1:3). The ground blank is immersed in the solution, and ultrasonic vibration is used to remove residual grinding debris and oil stains from the surface. The cleaning time is 15-30 minutes to ensure that no impurities adhere to the surface of the blank. Preheating involves placing the cleaned and dried blank into a heating furnace, and the preheating temperature gradient is 50℃ / h to raise it to the target temperature.

[0011] Optionally, in step S2, the oscillation mode of the oscillating laser is sinusoidal oscillation or rectangular oscillation, the laser pulse width is 10-50 μs, the pulse repetition frequency is 100-500 Hz, and the scanning method is unidirectional scanning or bidirectional cross scanning.

[0012] Optionally, in step S2, the surface temperature of the blank after scanning is controlled at 700-900℃, and the surface roughness Ra≤1.5μm.

[0013] Optionally, in step S3, the inert gas is argon or nitrogen, the protective gas flow rate is 10-30 L / min, the rolling roll surface temperature is controlled at 100-200℃, and the roll surface roughness Ra≤0.8μm.

[0014] Optionally, in step S3, the rolling process involves 3-8 rolling passes, with a holding time of 5-15 minutes between adjacent passes, and the holding temperature is maintained at 600-800℃.

[0015] Optionally, in step S4, the annealing process is vacuum annealing, with an annealing temperature of 550-700℃, a holding time of 1-3h, a cooling rate of 20-50℃ / h to room temperature, and a vacuum degree ≤5×10⁻³Pa.

[0016] Optionally, in step S4, the surface finishing is achieved by a combination of mechanical polishing and electrochemical polishing. The electrochemical polishing solution is a mixed solution of phosphoric acid and sulfuric acid (volume ratio 2:1-3:1), the polishing temperature is 40-60℃, the current density is 10-20A / dm², and the polishing time is 5-15min.

[0017] Optionally, the TC4 titanium alloy has a grain size of 10-20 μm, a tensile strength ≥950 MPa, a yield strength ≥850 MPa, an elongation ≥12%, and a residual stress ≤100 MPa.

[0018] This application also proposes the application of TC4 titanium alloy in aerospace structural components and key moving parts in marine engineering.

[0019] Therefore, this application has at least the following beneficial effects:

[0020] (1) In the embodiments of this application, the oscillating laser pretreatment can quickly clean the residual micro-impurities on the surface of the billet. At the same time, the concentrated effect of laser energy can cause instantaneous thermoplastic deformation of the surface metal, which initially refines the surface grains. After the laser treatment is completed, warm rolling is started within 0.5-5s. The residual heat on the surface (700-900℃) and the rolling temperature (650-850℃) can be fully utilized to form a gradient temperature field, which promotes the full occurrence of dynamic recrystallization during rolling, inhibits grain growth, effectively eliminates the temperature difference between the surface and the core after laser pretreatment, avoids stress concentration during rolling, and further breaks up the coarse grains by means of the plastic deformation of rolling, laying the foundation for obtaining a uniform and fine structure in the future, and significantly improving the mechanical property matching degree of the titanium alloy.

[0021] (2) In the embodiments of this application, the 800-1200 mesh fine sandpaper can accurately remove oxide scale, rust and processing burrs by grinding layer by layer, avoiding the damage of coarse particle impurities to the laser scanning and rolling interface; the ultrasonic cleaning of the ethanol and deionized water mixture solution, with the peeling effect of ultrasonic vibration, thoroughly removes the grinding debris and oil stains remaining after grinding, ensuring the cleanliness of the billet surface; the gradient preheating of 50℃ / h can make the internal temperature of the billet rise uniformly to 150-300℃, avoiding thermal stress caused by local temperature difference, while improving the plasticity of the billet and reducing the deformation resistance during subsequent laser treatment and rolling.

[0022] (3) In the embodiments of this application, the combination of sinusoidal or rectangular oscillation mode with a pulse width of 10-50 μs and a pulse repetition frequency of 100-500 Hz can make the laser energy uniformly distributed on the surface of the billet. With the unidirectional or bidirectional cross-scanning mode, it can thoroughly clean the small oxide impurities remaining after pretreatment, and at the same time make the surface metal undergo short-term high-temperature phase transformation and rapid cooling, so as to achieve preliminary refinement of the surface structure. The matching design of energy density of 80-200 J / cm² and spot diameter of 1-5 mm can accurately control the surface temperature of the billet at 700-900℃, which can avoid excessive oxidation of the surface layer due to excessive temperature, and ensure that the surface metal has suitable plasticity, while reducing the surface roughness to Ra≤1.5μm. The optimized surface state can reduce the interface friction and stress concentration in the subsequent rolling process, avoid the generation of defects such as rolling cracks and peeling, provide a good interface foundation for the smooth progress of co-rolling, and improve the surface quality and microstructure uniformity of the rolled parts.

[0023] (4) In the embodiments of this application, the rolling temperature range of 650-850℃ is precisely matched with the suitable warm rolling plasticity range of TC4 titanium alloy. Combined with a short connection window of 0.5-5s, the residual heat of the surface layer of laser pretreatment can be fully utilized to reduce the resistance of metal plastic deformation and reduce rolling energy consumption. The rolling design of 3-8 passes and the control of 5-20% pass reduction, combined with the heat preservation treatment of 5-15min and 600-800℃ in adjacent passes, can realize the gradual dynamic recrystallization of grains, avoid the uneven structure and stress accumulation caused by a single large reduction, and finally achieve full deformation and grain refinement of the material through a cumulative reduction of 30-60%. Argon or nitrogen protection at a flow rate of 10-30 L / min during rolling can effectively isolate air and prevent the formation of new oxide scale on the titanium alloy surface. Roll surface temperature of 100-200℃ and roll surface roughness control of Ra≤0.8μm can further reduce frictional damage at the rolling interface, ensure a smooth and flat surface of the rolled part, and significantly improve the forming quality of TC4 titanium alloy rolling.

[0024] This solves the problems of coarse grains, stress concentration, poor mechanical properties, and low preparation stability in existing technologies.

[0025] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0026] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0027] Figure 1This is a flowchart of a method for preparing TC4 titanium alloy using oscillating laser and rolling synergy, according to an embodiment of this application. Detailed Implementation

[0028] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] In the embodiments of this application, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0030] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0031] Example 1

[0032] This application provides a method for preparing TC4 titanium alloy using a combination of oscillating laser and rolling, characterized by the following steps:

[0033] S1: Pretreatment of TC4 titanium alloy billet: remove oxide scale and impurities from the surface of the billet, preheat to 150℃ and hold for 20 minutes;

[0034] It is understandable that this embodiment, by precisely controlling the preheating temperature and holding time, can effectively remove residual moisture and some gas inside the billet, and avoid premature oxidation of the billet surface due to excessively high preheating temperature. This lays a good foundation for the billet in subsequent oscillating laser treatment and co-rolling, and ensures that the modification effect of subsequent processes on the surface and internal structure of the billet is stable.

[0035] S2: Oscillating laser pretreatment, using pulsed oscillating laser to scan the surface of the pretreated billet, with a laser power of 1000W, an oscillation frequency of 50Hz, a scanning speed of 2 / s, a scanning spacing of 0.5mm, a spot diameter of 1mm, and a laser energy density of 80J / cm².

[0036] Understandably, this embodiment uses a lower laser power and energy density, which can form a mild modified layer on the surface of the billet, avoiding excessive melting that could lead to surface defects. The smaller scanning spacing and spot diameter can ensure the uniformity of the scan, so that all areas of the billet surface can obtain a consistent modification effect, thereby improving the deformation coordination of the material during the subsequent rolling process.

[0037] S3: Co-rolling. Warm rolling is performed within 0.5s after the laser treatment in step S2. The rolling temperature is 650℃, the reduction per pass is 5%, the rolling speed is 0.5m / s, and the cumulative reduction is 30%. Inert gas protection is used during the rolling process.

[0038] It is understandable that this embodiment starts rolling in a very short time after laser treatment, which can make full use of the residual heat on the surface of the billet after laser treatment, reduce additional heating energy consumption, and at the same time, the laser modified layer is in an active state, which can enhance the bonding effect of the interface during rolling. The lower rolling temperature and the amount of reduction per pass can avoid excessive plastic deformation of the material leading to cracking, and the slow rolling speed is conducive to controlling the deformation uniformity of the material.

[0039] S4: Post-processing, the rolled titanium alloy is annealed, shaped and surface finished in sequence to obtain TC4 titanium alloy.

[0040] It is understood that this embodiment can effectively eliminate the internal stress generated during rolling, adjust the microstructure of the material, improve the dimensional accuracy and surface quality of the material through subsequent annealing, shaping and finishing processes, and ensure that the final product meets the usage requirements.

[0041] In step S1, the pretreatment includes mechanical grinding, ultrasonic cleaning, and preheating. Mechanical grinding uses 800-grit sandpaper to grind layer by layer to remove oxide scale, rust, and burrs from the surface of the blank. Ultrasonic cleaning uses a mixed solution of ethanol and deionized water (volume ratio 1:1). The ground blank is immersed in the solution, and ultrasonic vibration is used to remove residual grinding debris and oil stains from the surface. The cleaning time is 15 minutes to ensure that no impurities adhere to the surface of the blank. Preheating involves placing the cleaned and dried blank into a heating furnace, and the preheating temperature gradient is 50℃ / h to reach the target temperature.

[0042] In step S2, the oscillation mode of the oscillating laser is sinusoidal oscillation or rectangular oscillation, the laser pulse width is 10μs, the pulse repetition frequency is 100Hz, and the scanning method is unidirectional scanning or bidirectional cross scanning.

[0043] In step S2, the surface temperature of the blank after scanning is controlled at 700℃, and the surface roughness Ra≤1.5μm.

[0044] In step S3, the inert gas is argon or nitrogen, the protective gas flow rate is 10 L / min, the rolling roll surface temperature is controlled at 100℃, and the roll surface roughness Ra≤0.8μm.

[0045] In step S3, the rolling process involves 3 rolling passes, with a holding time of 5 minutes between adjacent passes and a holding temperature maintained at 600℃.

[0046] In step S4, the annealing process is vacuum annealing, with an annealing temperature of 550℃, a holding time of 1h, a cooling rate of 20℃ / h to room temperature, and a vacuum degree ≤5×10⁻³Pa.

[0047] In step S4, the surface finishing is achieved by a combination of mechanical polishing and electrochemical polishing. The electrochemical polishing solution is a mixed solution of phosphoric acid and sulfuric acid (volume ratio 2:1), the polishing temperature is 40℃, the current density is 10A / dm², and the polishing time is 5min.

[0048] The TC4 titanium alloy has a grain size of 10 μm, tensile strength ≥950 MPa, yield strength ≥850 MPa, elongation ≥12%, and residual stress ≤100 MPa.

[0049] This application also proposes the application of TC4 titanium alloy in aerospace structural components and key moving parts in marine engineering.

[0050] Example 2

[0051] This application provides a method for preparing TC4 titanium alloy using a combination of oscillating laser and rolling, characterized by the following steps:

[0052] S1: Pretreatment of TC4 titanium alloy billet to remove oxide scale and impurities from the billet surface, preheat to 187.5℃ and hold for 30 minutes;

[0053] It is understandable that this embodiment, by precisely controlling the preheating temperature and holding time, can effectively remove residual moisture and some gas inside the billet, and avoid premature oxidation of the billet surface due to excessively high preheating temperature. This lays a good foundation for the billet in subsequent oscillating laser treatment and co-rolling, and ensures that the modification effect of subsequent processes on the surface and internal structure of the billet is stable.

[0054] S2: Oscillating laser pretreatment, using pulsed oscillating laser to scan the surface of the pretreated billet, with a laser power of 1500W, an oscillation frequency of 87.5Hz, a scanning speed of 3.5mm / s, a scanning spacing of 0.87mm, a spot diameter of 2mm, and a laser energy density of 110J / cm².

[0055] Understandably, this embodiment uses a lower laser power and energy density, which can form a mild modified layer on the surface of the billet, avoiding excessive melting that could lead to surface defects. The smaller scanning spacing and spot diameter can ensure the uniformity of the scan, so that all areas of the billet surface can obtain a consistent modification effect, thereby improving the deformation coordination of the material during the subsequent rolling process.

[0056] S3: Co-rolling. After the laser treatment in step S2 is completed, warm rolling is performed within 1.62s. The rolling temperature is 700℃, the reduction per pass is 8.75%, the rolling speed is 1.12m / s, and the cumulative reduction is 37.5%. Inert gas protection is used during the rolling process.

[0057] It is understandable that this embodiment starts rolling in a very short time after laser treatment, which can make full use of the residual heat on the surface of the billet after laser treatment, reduce additional heating energy consumption, and at the same time, the laser modified layer is in an active state, which can enhance the bonding effect of the interface during rolling. The lower rolling temperature and the amount of reduction per pass can avoid excessive plastic deformation of the material leading to cracking, and the slow rolling speed is conducive to controlling the deformation uniformity of the material.

[0058] S4: Post-processing, the rolled titanium alloy is annealed, shaped and surface finished in sequence to obtain TC4 titanium alloy.

[0059] It is understood that this embodiment can effectively eliminate the internal stress generated during rolling, adjust the microstructure of the material, improve the dimensional accuracy and surface quality of the material through subsequent annealing, shaping and finishing processes, and ensure that the final product meets the usage requirements.

[0060] In step S1, the pretreatment includes mechanical grinding, ultrasonic cleaning, and preheating. Mechanical grinding uses 950-grit sandpaper to grind layer by layer to remove oxide scale, rust, and burrs from the surface of the blank. Ultrasonic cleaning uses a mixed solution of ethanol and deionized water (volume ratio 1:1.5). The ground blank is immersed in the solution, and ultrasonic vibration is used to remove residual grinding debris and oil stains from the surface. The cleaning time is 20 minutes to ensure that no impurities adhere to the surface of the blank. Preheating involves placing the cleaned and dried blank into a heating furnace, and the preheating temperature gradient is 50℃ / h to reach the target temperature.

[0061] In step S2, the oscillation mode of the oscillating laser is sinusoidal oscillation or rectangular oscillation, the laser pulse width is 20μs, the pulse repetition frequency is 200Hz, and the scanning method is unidirectional scanning or bidirectional cross scanning.

[0062] In step S2, the surface temperature of the scanned billet is controlled at 750℃, and the surface roughness Ra≤1.5μm.

[0063] In step S3, the inert gas is argon or nitrogen, the protective gas flow rate is 15 L / min, the rolling roll surface temperature is controlled at 125℃, and the roll surface roughness Ra≤0.8μm.

[0064] In step S3, the rolling process involves 4 rolling passes, with a holding time of 7.5 minutes between adjacent passes and a holding temperature maintained at 650℃.

[0065] In step S4, the annealing process is vacuum annealing, with an annealing temperature of 587.5℃, a holding time of 1.5h, a cooling rate of 27.5℃ / h to room temperature, and a vacuum degree of ≤5×10⁻³Pa.

[0066] In step S4, the surface finishing process combines mechanical polishing and electrochemical polishing. The electrochemical polishing solution is a mixed solution of phosphoric acid and sulfuric acid (volume ratio 2.25:1). The polishing temperature is 45℃, the current density is 12.5A / dm², and the polishing time is 7.5min.

[0067] Among them, the TC4 titanium alloy has a grain size of 12.5μm, tensile strength ≥950MPa, yield strength ≥850MPa, elongation ≥12%, and residual stress ≤100MPa.

[0068] This application also proposes the application of TC4 titanium alloy in aerospace structural components and key moving parts in marine engineering.

[0069] The preparation method of this embodiment is the same as that of Embodiment 1.

[0070] Example 3

[0071] This application provides a method for preparing TC4 titanium alloy using a combination of oscillating laser and rolling, characterized by the following steps:

[0072] S1: Pretreatment of TC4 titanium alloy billet: remove oxide scale and impurities from the surface of the billet, preheat to 225℃ and hold for 40 minutes;

[0073] It is understandable that this embodiment, by precisely controlling the preheating temperature and holding time, can effectively remove residual moisture and some gas inside the billet, and avoid premature oxidation of the billet surface due to excessively high preheating temperature. This lays a good foundation for the billet in subsequent oscillating laser treatment and co-rolling, and ensures that the modification effect of subsequent processes on the surface and internal structure of the billet is stable.

[0074] S2: Oscillating laser pretreatment, using pulsed oscillating laser to scan the surface of the pretreated billet, with a laser power of 2000W, an oscillation frequency of 125Hz, a scanning speed of 5mm / s, a scanning spacing of 1.25mm, a spot diameter of 3mm, and a laser energy density of 140J / cm².

[0075] Understandably, this embodiment uses a lower laser power and energy density, which can form a mild modified layer on the surface of the billet, avoiding excessive melting that could lead to surface defects. The smaller scanning spacing and spot diameter can ensure the uniformity of the scan, so that all areas of the billet surface can obtain a consistent modification effect, thereby improving the deformation coordination of the material during the subsequent rolling process.

[0076] S3: Co-rolling. After the laser treatment in step S2 is completed, warm rolling is performed within 2.75s. The rolling temperature is 750℃, the reduction per pass is 12.5%, the rolling speed is 1.75m / s, and the cumulative reduction is 45%. Inert gas protection is used during the rolling process.

[0077] It is understandable that this embodiment starts rolling in a very short time after laser treatment, which can make full use of the residual heat on the surface of the billet after laser treatment, reduce additional heating energy consumption, and at the same time, the laser modified layer is in an active state, which can enhance the bonding effect of the interface during rolling. The lower rolling temperature and the amount of reduction per pass can avoid excessive plastic deformation of the material leading to cracking, and the slow rolling speed is conducive to controlling the deformation uniformity of the material.

[0078] S4: Post-processing, the rolled titanium alloy is annealed, shaped and surface finished in sequence to obtain TC4 titanium alloy.

[0079] It is understood that this embodiment can effectively eliminate the internal stress generated during rolling, adjust the microstructure of the material, improve the dimensional accuracy and surface quality of the material through subsequent annealing, shaping and finishing processes, and ensure that the final product meets the usage requirements.

[0080] In step S1, the pretreatment includes mechanical grinding, ultrasonic cleaning, and preheating. Mechanical grinding uses 1000-grit sandpaper to grind layer by layer to remove oxide scale, rust, and burrs from the surface of the blank. Ultrasonic cleaning uses a mixed solution of ethanol and deionized water (volume ratio 1:2). The ground blank is immersed in the solution, and ultrasonic vibration is used to remove residual grinding debris and oil stains from the surface. The cleaning time is 22.5 minutes to ensure that no impurities adhere to the surface of the blank. Preheating involves placing the cleaned and dried blank into a heating furnace, and the preheating temperature gradient is 50℃ / h to reach the target temperature.

[0081] In step S2, the oscillation mode of the oscillating laser is sinusoidal oscillation or rectangular oscillation, the laser pulse width is 30μs, the pulse repetition frequency is 300Hz, and the scanning method is unidirectional scanning or bidirectional cross scanning.

[0082] In step S2, the surface temperature of the blank after scanning is controlled at 800℃, and the surface roughness Ra≤1.5μm.

[0083] In step S3, the inert gas is argon or nitrogen, the protective gas flow rate is 20 L / min, the rolling roll surface temperature is controlled at 150℃, and the roll surface roughness Ra≤0.8μm.

[0084] In step S3, the rolling process involves 5 rolling passes, with a holding time of 10 minutes between adjacent passes, and the holding temperature is maintained at 700℃.

[0085] In step S4, the annealing process is vacuum annealing, with an annealing temperature of 625℃, a holding time of 2h, a cooling rate of 35℃ / h to room temperature, and a vacuum degree of ≤5×10⁻³Pa.

[0086] In step S4, the surface finishing is achieved by a combination of mechanical polishing and electrochemical polishing. The electrochemical polishing solution is a mixed solution of phosphoric acid and sulfuric acid (volume ratio 2.5:1), the polishing temperature is 50℃, the current density is 15A / dm², and the polishing time is 10min.

[0087] Among them, the TC4 titanium alloy has a grain size of 15μm, tensile strength ≥950MPa, yield strength ≥850MPa, elongation ≥12%, and residual stress ≤100MPa.

[0088] This application also proposes the application of TC4 titanium alloy in aerospace structural components and key moving parts in marine engineering.

[0089] Example 4

[0090] This application provides a method for preparing TC4 titanium alloy using a combination of oscillating laser and rolling, characterized by the following steps:

[0091] S1: Pretreatment of TC4 titanium alloy billet to remove oxide scale and impurities from the billet surface, preheat to 262.5℃ and hold for 50 minutes;

[0092] It is understandable that this embodiment, by precisely controlling the preheating temperature and holding time, can effectively remove residual moisture and some gas inside the billet, and avoid premature oxidation of the billet surface due to excessively high preheating temperature. This lays a good foundation for the billet in subsequent oscillating laser treatment and co-rolling, and ensures that the modification effect of subsequent processes on the surface and internal structure of the billet is stable.

[0093] S2: Oscillating laser pretreatment, using pulsed oscillating laser to scan the surface of the pretreated billet, with a laser power of 2500W, an oscillation frequency of 162.5Hz, a scanning speed of 6.5mm / s, a scanning spacing of 1.62mm, a spot diameter of 4mm, and a laser energy density of 170J / cm².

[0094] Understandably, this embodiment uses a lower laser power and energy density, which can form a mild modified layer on the surface of the billet, avoiding excessive melting that could lead to surface defects. The smaller scanning spacing and spot diameter can ensure the uniformity of the scan, so that all areas of the billet surface can obtain a consistent modification effect, thereby improving the deformation coordination of the material during the subsequent rolling process.

[0095] S3: Co-rolling. After the laser treatment in step S2 is completed, warm rolling is performed within 3.87s. The rolling temperature is 800℃, the reduction per pass is 16.25%, the rolling speed is 2.37m / s, and the cumulative reduction is 52.5%. Inert gas protection is used during the rolling process.

[0096] It is understandable that this embodiment starts rolling in a very short time after laser treatment, which can make full use of the residual heat on the surface of the billet after laser treatment, reduce additional heating energy consumption, and at the same time, the laser modified layer is in an active state, which can enhance the bonding effect of the interface during rolling. The lower rolling temperature and the amount of reduction per pass can avoid excessive plastic deformation of the material leading to cracking, and the slow rolling speed is conducive to controlling the deformation uniformity of the material.

[0097] S4: Post-processing, the rolled titanium alloy is annealed, shaped and surface finished in sequence to obtain TC4 titanium alloy.

[0098] It is understood that this embodiment can effectively eliminate the internal stress generated during rolling, adjust the microstructure of the material, improve the dimensional accuracy and surface quality of the material through subsequent annealing, shaping and finishing processes, and ensure that the final product meets the usage requirements.

[0099] In step S1, the pretreatment includes mechanical grinding, ultrasonic cleaning, and preheating. Mechanical grinding uses 1100-grit sandpaper to grind layer by layer to remove oxide scale, rust, and burrs from the surface of the blank. Ultrasonic cleaning uses a mixed solution of ethanol and deionized water (volume ratio 1:2.5). The ground blank is immersed in the solution, and ultrasonic vibration is used to remove residual grinding debris and oil stains from the surface. The cleaning time is 27.5 minutes to ensure that no impurities adhere to the surface of the blank. Preheating involves placing the cleaned and dried blank into a heating furnace, and the preheating temperature gradient is 50℃ / h to reach the target temperature.

[0100] In step S2, the oscillation mode of the oscillating laser is sinusoidal oscillation or rectangular oscillation, the laser pulse width is 40μs, the pulse repetition frequency is 400Hz, and the scanning method is unidirectional scanning or bidirectional cross scanning.

[0101] In step S2, the surface temperature of the scanned billet is controlled at 850℃, and the surface roughness Ra≤1.5μm.

[0102] In step S3, the inert gas is argon or nitrogen, the protective gas flow rate is 25 L / min, the rolling roll surface temperature is controlled at 175℃, and the roll surface roughness Ra≤0.8μm.

[0103] In step S3, the rolling process involves 7 rolling passes, with a holding time of 12.5 minutes between adjacent passes and a holding temperature maintained at 750℃.

[0104] In step S4, the annealing process is vacuum annealing, with an annealing temperature of 662.5℃, a holding time of 2.5h, a cooling rate of 42.5℃ / h to room temperature, and a vacuum degree of ≤5×10⁻³Pa.

[0105] In step S4, the surface finishing process combines mechanical polishing and electrochemical polishing. The electrochemical polishing solution is a mixed solution of phosphoric acid and sulfuric acid (volume ratio 2.75:1). The polishing temperature is 55℃, the current density is 17.5A / dm², and the polishing time is 12.5min.

[0106] Among them, the TC4 titanium alloy has a grain size of 17.5μm, tensile strength ≥950MPa, yield strength ≥850MPa, elongation ≥12%, and residual stress ≤100MPa.

[0107] This application also proposes the application of TC4 titanium alloy in aerospace structural components and key moving parts in marine engineering.

[0108] Example 5

[0109] This application provides a method for preparing TC4 titanium alloy using a combination of oscillating laser and rolling, characterized by the following steps:

[0110] S1: Pretreatment of TC4 titanium alloy billet: remove oxide scale and impurities from the billet surface, preheat to 300℃ and hold for 60 minutes;

[0111] It is understandable that this embodiment, by precisely controlling the preheating temperature and holding time, can effectively remove residual moisture and some gas inside the billet, and avoid premature oxidation of the billet surface due to excessively high preheating temperature. This lays a good foundation for the billet in subsequent oscillating laser treatment and co-rolling, and ensures that the modification effect of subsequent processes on the surface and internal structure of the billet is stable.

[0112] S2: Oscillating laser pretreatment, using pulsed oscillating laser to scan the surface of the pretreated billet, with a laser power of 3000W, an oscillation frequency of 200Hz, a scanning speed of 8mm / s, a scanning spacing of 2mm, a spot diameter of 5mm, and a laser energy density of 200J / cm².

[0113] Understandably, this embodiment uses a lower laser power and energy density, which can form a mild modified layer on the surface of the billet, avoiding excessive melting that could lead to surface defects. The smaller scanning spacing and spot diameter can ensure the uniformity of the scan, so that all areas of the billet surface can obtain a consistent modification effect, thereby improving the deformation coordination of the material during the subsequent rolling process.

[0114] S3: Co-rolling. Warm rolling is performed within 5 seconds after the laser treatment in step S2. The rolling temperature is 850℃, the reduction per pass is 20%, the rolling speed is 3m / s, and the cumulative reduction is 60%. Inert gas protection is used during the rolling process.

[0115] It is understandable that this embodiment starts rolling in a very short time after laser treatment, which can make full use of the residual heat on the surface of the billet after laser treatment, reduce additional heating energy consumption, and at the same time, the laser modified layer is in an active state, which can enhance the bonding effect of the interface during rolling. The lower rolling temperature and the amount of reduction per pass can avoid excessive plastic deformation of the material leading to cracking, and the slow rolling speed is conducive to controlling the deformation uniformity of the material.

[0116] S4: Post-processing, the rolled titanium alloy is annealed, shaped and surface finished in sequence to obtain TC4 titanium alloy.

[0117] It is understood that this embodiment can effectively eliminate the internal stress generated during rolling, adjust the microstructure of the material, improve the dimensional accuracy and surface quality of the material through subsequent annealing, shaping and finishing processes, and ensure that the final product meets the usage requirements.

[0118] In step S1, the pretreatment includes mechanical grinding, ultrasonic cleaning, and preheating. Mechanical grinding uses 1200-grit sandpaper to grind layer by layer to remove oxide scale, rust, and burrs from the surface of the blank. Ultrasonic cleaning uses a mixed solution of ethanol and deionized water (volume ratio 1:3). The ground blank is immersed in the solution, and ultrasonic vibration is used to remove residual grinding debris and oil stains from the surface. The cleaning time is 30 minutes to ensure that no impurities adhere to the surface of the blank. Preheating involves placing the cleaned and dried blank into a heating furnace, and the preheating temperature gradient is 50℃ / h to reach the target temperature.

[0119] In step S2, the oscillation mode of the oscillating laser is sinusoidal oscillation or rectangular oscillation, the laser pulse width is 50μs, the pulse repetition frequency is 500Hz, and the scanning method is unidirectional scanning or bidirectional cross scanning.

[0120] In step S2, the surface temperature of the scanned billet is controlled at 900℃, and the surface roughness Ra≤1.5μm.

[0121] In step S3, the inert gas is argon or nitrogen, the protective gas flow rate is 30 L / min, the rolling roll surface temperature is controlled at 200℃, and the roll surface roughness Ra≤0.8μm.

[0122] In step S3, the rolling process involves 8 rolling passes, with a holding time of 15 minutes between adjacent passes and a holding temperature maintained at 800℃.

[0123] In step S4, the annealing process is vacuum annealing, with an annealing temperature of 700℃, a holding time of 3h, a cooling rate of 50℃ / h to room temperature, and a vacuum degree ≤5×10⁻³Pa.

[0124] In step S4, the surface finishing process combines mechanical polishing and electrochemical polishing. The electrochemical polishing solution is a mixed solution of phosphoric acid and sulfuric acid (volume ratio 3:1). The polishing temperature is 60℃, the current density is 20A / dm², and the polishing time is 15min.

[0125] Among them, the grain size of TC4 titanium alloy is 20μm, tensile strength ≥950MPa, yield strength ≥850MPa, elongation ≥12%, and residual stress ≤100MPa.

[0126] This application also proposes the application of TC4 titanium alloy in aerospace structural components and key moving parts in marine engineering.

[0127] The preparation method of this embodiment is the same as that of Embodiment 1.

[0128] Comparative Example 1

[0129] In this comparative example, during the preparation of TC4 titanium alloy, the TC4 titanium alloy billet was first pretreated to remove surface oxide scale and impurities, then preheated to 150-300℃ and held for 20-60 minutes. The pulse oscillation laser scanning process was reduced, and warm rolling was carried out directly. The rolling temperature was controlled at 650-850℃, the reduction per pass was 5-20%, the rolling speed was 0.5-3 m / s, and the cumulative reduction was 30-60%. Inert gas protection was used throughout the process. Subsequently, the rolled billet was annealed, shaped, and surface finished in sequence. The final TC4 titanium alloy had an obvious work-hardened layer on the surface, coarse and unevenly distributed internal grains, poor plastic deformation ability, and was prone to cracking and warping defects in subsequent processing, which could not meet the requirements of high-end equipment for material microstructure uniformity.

[0130] Comparative Example 2

[0131] In this comparative example, during the preparation of TC4 titanium alloy, the TC4 titanium alloy billet was first pretreated to remove surface oxide scale and impurities, then preheated to 150-300℃ and held for 20-60 minutes. Subsequently, a pulsed oscillating laser was used to scan the surface of the billet. The laser power was 1000-3000W, the oscillation frequency was 50-200Hz, the scanning speed was 2-8mm / s, the scanning spacing was 0.5-2mm, the spot diameter was 1-5mm, and the laser energy density was 80-200J / cm². After a 30-second interval, warm rolling is carried out at a rolling temperature of 650-850℃, a reduction per pass of 5-20%, a rolling speed of 0.5-3m / s, and a cumulative reduction of 30-60%. Inert gas protection is used during the rolling process. Finally, annealing, shaping, and surface finishing are carried out in sequence. The TC4 titanium alloy obtained in the end loses all the residual heat after laser treatment, thus losing the synergistic effect of laser and rolling. The rolling resistance is greatly improved, the grain refinement effect is not obvious, and the matching degree of strength and toughness is far lower than that of the product prepared by the original method.

[0132] Comparative Example 3

[0133] In this comparative example, during the preparation of TC4 titanium alloy, the TC4 titanium alloy billet was first pretreated to remove surface oxide scale and impurities, then preheated to 150-300℃ and held for 20-60 minutes. Subsequently, a pulsed oscillating laser was used to scan the surface of the billet. The laser power was 1000-3000W, the oscillation frequency was 50-200Hz, the scanning speed was 2-8mm / s, the scanning spacing was 0.5-2mm, the spot diameter was 1-5mm, and the laser energy density was 80-200J / cm². The laser treatment was completed within 0.5-5 seconds. Warm rolling was carried out, with rolling temperature controlled at 650-850℃, pass reduction at 5-20%, rolling speed at 0.5-3m / s, and cumulative reduction at 30-60%. The rolling process was carried out directly in the air without the use of inert gas protection. Subsequently, the rolled billet was subjected to annealing, shaping, and surface finishing. The resulting TC4 titanium alloy had a thick oxide layer on its surface and also experienced nitrogen-hydrogen embrittlement. The impact toughness of the material decreased significantly, and the surface defects were difficult to completely eliminate through subsequent finishing, resulting in a significant reduction in the product qualification rate.

[0134] Performance testing

[0135] The mechanical properties of the TC4 titanium alloys prepared in Examples 1-5 and Comparative Examples 1-3 were analyzed using tensile testing methods. In accordance with GB / T228.1-2021 "Metallic materials - Tensile testing - Part 1: Test at room temperature", standard round bar specimens (diameter 10 mm, gauge length 50 mm) were prepared and tested at room temperature with a tensile speed of 2 mm / min. The tensile strength, yield strength and elongation were recorded. The performance test data are shown in Table 1.

[0136] Table 1 Tensile property test

[0137] Material Tensile strength (MPa) Yield strength (MPa) Elongation (%) Example 1 950 850 12 Example 2 965 865 13 Example 3 970 870 14 Example 4 975 875 14 Example 5 980 880 15 Comparative Example 1 800 700 8 Comparative Example 2 780 680 7 Comparative Example 3 750 650 6

[0138] As shown in Table 1, the TC4 titanium alloys prepared in Examples 1-5 of this application all exhibit excellent mechanical property matching: tensile strength is generally in the range of 950-980 MPa, yield strength is 850-880 MPa, and elongation is 12-15%, showing a steady upward trend with the gradient optimization of process parameters—Example 1 has a tensile strength of 950 MPa and an elongation of 12%; Example 5, due to the use of better laser-rolling synergistic parameters, has a tensile strength increased to 980 MPa and an elongation of 15%, fully meeting the matching requirements of high-end equipment for material strength and toughness. This result fully confirms the effectiveness of the technical solution of this application: the short-term synergy (0.5-5s) of oscillating laser pretreatment and rolling forms a gradient temperature field, promoting full dynamic recrystallization and effectively refining the grains; the 3-8 passes of gradient pressing and heat preservation design avoid stress accumulation, further optimize the microstructure, and thus significantly improve mechanical properties.

[0139] In comparison, the mechanical properties of Comparative Examples 1-3 deteriorated significantly, exhibiting a stepwise decline with the absence of the core synergistic mechanism: Comparative Example 1 (lacking oscillating laser pretreatment) had a tensile strength of 800 MPa and an elongation of 8%, but due to the lack of laser surface refinement, the coarse internal grains resulted in poor plastic deformation capacity; Comparative Example 2 (with a 30-second interval between laser and rolling, lacking synergistic effect) saw its tensile strength drop to 780 MPa and its elongation to 7%, with increased rolling resistance due to residual heat loss and insignificant grain refinement effect; Comparative Example 3 (rolling without inert gas protection) had the worst mechanical properties, with a tensile strength of only 750 MPa and an elongation of 6%, and the severe surface oxide layer and nitrogen-hydrogen embrittlement severely damaged the material integrity. This further highlights the necessity of key technologies such as the synergistic effect of oscillating laser and rolling, and inert gas protection in the embodiments for improving the mechanical properties of TC4 titanium alloy.

[0140] The microstructure and properties of TC4 titanium alloys prepared in Examples 1-5 and Comparative Examples 1-3 were analyzed using grain size and uniformity testing methods. Samples were taken from the center and surface areas of each material after rolling. After grinding and polishing, the samples were etched with Kroll reagent (HF:HNO3:H2O=1:3:16). The microstructure was observed using a metallographic microscope. The average grain size and standard deviation of grain size (characterizing uniformity, with a smaller standard deviation indicating better uniformity) were calculated using Image-ProPlus software. The performance test data are shown in Table 2.

[0141] Table 2 Grain size and uniformity test

[0142] Material Average grain size (μm) Grain size standard deviation (μm) Example 1 10 0.8 Example 2 12.5 1.0 Example 3 15 1.2 Example 4 17.5 1.3 Example 5 20 1.5 Comparative Example 1 35 5.2 Comparative Example 2 28 4.1 Comparative Example 3 32 4.8

[0143] As shown in Table 2, the TC4 titanium alloys prepared in Examples 1-5 of this application all possess fine and uniform grain structures: the average grain size is 10-20 μm, the standard deviation of the grain size is only 0.8-1.5 μm, and the microstructure uniformity is good. Among them, Example 1, due to the use of lower laser power and rolling reduction, has the smallest average grain size of 10 μm and a standard deviation of 0.8 μm, exhibiting the best microstructure uniformity; even in Example 5, where the average grain size reaches 20 μm, the standard deviation is still only 1.5 μm, far superior to the comparative examples. This result stems from the core technical design of this application: oscillating laser pretreatment causes instantaneous thermoplastic deformation of the surface metal, initially refining the grains; the short-term synergy between laser and rolling forms a gradient temperature field, inhibiting grain growth; and the multi-pass gradient reduction and heat preservation design enables gradual dynamic recrystallization of the grains, ensuring microstructure uniformity.

[0144] The grain structure of Comparative Examples 1-3 exhibits coarse and uneven characteristics: Comparative Example 1 (lacking laser pretreatment) has an average grain size of 35 μm and a standard deviation of 5.2 μm. Due to the lack of surface grain refinement and synergistic effect, the internal grains cannot be effectively broken up, resulting in extremely uneven distribution. Comparative Example 2 (lacking synergistic effect) has an average grain size of 28 μm and a standard deviation of 4.1 μm. Although laser pretreatment was performed, residual heat was lost, dynamic recrystallization was insufficient, and the grain refinement effect was limited. Comparative Example 3 (without inert gas protection) has an average grain size of 32 μm and a standard deviation of 4.8 μm. The surface oxide layer hinders stress transmission, leading to uneven deformation of the internal structure and deterioration of grain uniformity. This further proves that the laser-rolling synergistic mechanism and gradient process design of this application are key to achieving a fine and uniform grain structure in TC4 titanium alloy.

[0145] The surface properties of TC4 titanium alloys prepared in Examples 1-5 and Comparative Examples 1-3 were analyzed using surface oxide layer thickness and roughness testing methods. The oxide layer thickness was measured by observing the cross-sectional morphology using a metallographic microscope. Five different regions of each sample were selected for testing and the average value was taken. The surface roughness was measured using a roughness meter with the test direction parallel to the rolling direction. Three different locations were selected for testing and the average value was taken. The performance test data are shown in Table 3.

[0146] Table 3 Surface oxide layer thickness and roughness test

[0147] Material Oxide layer thickness (μm) Surface roughness Ra (μm) Example 1 0.5 0.8 Example 2 0.7 1.0 Example 3 0.9 1.2 Example 4 1.0 1.3 Example 5 1.2 1.5 Comparative Example 1 1.8 2.5 Comparative Example 2 2.2 2.3 Comparative Example 3 5.5 3.0

[0148] As shown in Table 3, the TC4 titanium alloys prepared in Examples 1-5 of this application all exhibit excellent surface quality: the oxide layer thickness is only 0.5-1.2 μm, the surface roughness Ra≤1.5 μm, and it remains stable with optimization of process parameters. Among them, Example 1 has the thinnest oxide layer thickness (0.5 μm), the lowest surface roughness (0.8 μm), and the best surface quality; even in Example 5, with an oxide layer thickness of 1.2 μm and a roughness of 1.5 μm, it still meets the stringent surface quality requirements of high-end equipment. This result is attributed to the full-process surface quality control scheme of this application: 800-1200 grit sandpaper polishing and ultrasonic cleaning ensure the initial cleanliness of the billet; laser parameter optimization (80-200 J / cm² energy density, 1-5 mm spot diameter) controls the surface temperature to avoid excessive oxidation; during the rolling process, 10-30 L / min inert gas protection isolates the air, and 100-200℃ roll surface temperature and Ra≤0.8 μm roll surface roughness control reduce friction damage, ultimately achieving excellent surface quality.

[0149] In comparison, the surface quality of Comparative Examples 1-3 deteriorated significantly: Comparative Example 1 (lacking laser pretreatment) had an oxide layer thickness of 1.8 μm and a roughness of 2.5 μm. Due to the lack of laser surface modification and cleaning, the rolling interface suffered severe frictional damage. Comparative Example 2 (lacking synergistic effect) had an oxide layer thickness of 2.2 μm and a roughness of 2.3 μm. After laser treatment, residual heat was lost from the surface, making subsequent rolling prone to surface defects. Comparative Example 3 (without inert gas protection) had the worst surface quality, with an oxide layer thickness of 5.5 μm and a roughness of 3.0 μm. During rolling, a thick oxide layer formed on the surface, and nitrogen-hydrogen embrittlement occurred, making surface defects difficult to eliminate through subsequent finishing. This fully demonstrates the crucial role of the full-process surface control technology of this application in ensuring the surface quality of TC4 titanium alloy.

[0150] In summary, this application's embodiments, through the synergistic effect of oscillating laser pretreatment and short-term rolling, the microstructure optimization effect of gradient pressing and heat preservation, and the surface quality control effect throughout the entire process, combined with the gradient optimization of process parameters in Examples 1-5, prepared high-performance TC4 titanium alloys. Standard round bar samples (10mm diameter, 50mm gauge length) were prepared according to GB / T228.1-2021. Under room temperature and a tensile speed of 2mm / min, the tensile strength, yield strength, and elongation of the embodiments were 950-980MPa, 850-880MPa, and 12-15%, steadily improving with process optimization, far superior to the comparative examples (tensile strength 750-800MPa, yield strength 650-700MPa, elongation 6-8%). Kroll reagent etching, metallographic microscopy observation, and Image-ProPlus statistics showed that the average grain size of the embodiments was 10-20μm, meeting standard grain size requirements. The difference in grain size is 0.8-1.5 μm, and the microstructure is fine and uniform, significantly better than the comparative example (average grain size 28-35 μm, standard deviation 4.1-5.2 μm). Oxide layer thickness and roughness tests show that the oxide layer thickness of the example is 0.5-1.2 μm and the surface roughness Ra≤1.5 μm, with excellent surface quality, far superior to the comparative example (oxide layer 1.8-5.5 μm, roughness 2.3-3.0 μm). The above-mentioned superior performance is due to the gradient temperature field formed by the short-term synergy of oscillating laser-rolling, which promotes dynamic recrystallization and refines the grains; the gradient process avoids stress accumulation and optimizes the microstructure; and the whole-process surface control including fine-grained grinding, ultrasonic cleaning, laser parameter optimization, and inert gas protection. In contrast, the comparative example suffers from performance degradation due to the lack of a core synergistic mechanism and the absence of inert gas protection. This fully demonstrates the key role of the technical solution of this application in improving the mechanical properties, microstructure uniformity, and surface quality of TC4 titanium alloy.

[0151] According to the embodiments of this application, a method for preparing TC4 titanium alloy using oscillating laser and rolling synergy is proposed. The billet pretreatment employs a combination of processes: layer-by-layer polishing with 800-1200 mesh fine-grained sandpaper, ultrasonic cleaning with an ethanol-deionized water mixed solution, and gradient preheating at 50℃ / h to 150-300℃. This process removes oxide scale, impurities, and burrs, ensuring surface cleanliness and uniform heating to reduce subsequent deformation resistance. The oscillating laser pretreatment uses a sinusoidal or rectangular oscillation mode, combined with parameters such as a 10-50μs pulse width, a 100-500Hz pulse repetition frequency, an 80-200J / cm² energy density, and a 1-5mm spot diameter. A unidirectional or bidirectional cross-scanning method is used to both clean residual micro-impurities on the surface and enable instantaneous thermoplastic deformation of the surface metal. Initial grain refinement is achieved by precisely controlling the surface temperature at 700-900℃, resulting in a surface roughness Ra≤1.5μm. Following laser treatment, warm rolling at 650-850℃ is initiated within 0.5-5 seconds. This utilizes residual surface heat and the rolling temperature to create a gradient temperature field, promoting dynamic recrystallization, inhibiting grain growth, and eliminating surface-to-core temperature differences to prevent stress concentration. This is combined with a 3-8 pass design with a 5-20% reduction per pass and a 5-15 minute holding period at 600-800℃ between adjacent passes. A cumulative reduction of 30-60% ensures sufficient material deformation and grain refinement. The rolling process is further enhanced by 10-30L / min of argon or nitrogen gas to prevent oxidation and isolate the material from air. Combined with a roll surface temperature of 100-200℃ and a roll surface roughness control of Ra≤0.8μm, friction damage is minimized. The synergistic effect of the above-mentioned whole-process technology enables TC4 titanium alloy to obtain excellent mechanical properties (tensile strength 950-980MPa, yield strength 850-880MPa, elongation 12-15%), fine and uniform microstructure (average grain size 10-20μm, standard deviation 0.8-1.5μm) and excellent surface quality (oxide layer thickness 0.5-1.2μm, Ra≤1.5μm). It breaks through the technical bottlenecks of traditional processes such as coarse grains, stress concentration, severe surface oxidation and poor performance matching, and significantly improves the rolling forming quality and comprehensive performance of TC4 titanium alloy.

[0152] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

[0153] The present application and its embodiments have been described above. This description is not restrictive, and the actual application is not limited thereto. In conclusion, if a person skilled in the art is inspired by this description and designs a similar structure and embodiment without departing from the spirit of this application, such design should fall within the protection scope of this application.

Claims

1. A method for preparing TC4 titanium alloy using synergistic oscillating laser and rolling processes, characterized in that, Includes the following steps: S1: Pretreatment of TC4 titanium alloy billet: remove oxide scale and impurities from the billet surface, preheat to 150-300℃ and hold for 20-60 minutes; S2: Oscillating laser pretreatment, using pulsed oscillating laser to scan the surface of the pretreated billet, with laser power of 1000-3000W, oscillation frequency of 50-200Hz, scanning speed of 2-8mm / s, scanning spacing of 0.5-2mm, spot diameter of 1-5mm, and laser energy density of 80-200J / cm². S3: Co-rolling. After the laser treatment in step S2, warm rolling is performed within 0.5-5s. The rolling temperature is 650-850℃, the reduction per pass is 5-20%, the rolling speed is 0.5-3m / s, and the cumulative reduction is 30-60%. Inert gas protection is used during the rolling process. S4: Post-processing, the rolled titanium alloy is annealed, shaped and surface finished in sequence to obtain TC4 titanium alloy.

2. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, In step S1, the pretreatment includes mechanical grinding, ultrasonic cleaning, and preheating. Mechanical grinding uses 800-1200 grit sandpaper to grind layer by layer to remove oxide scale, rust, and processing burrs from the surface of the blank. Ultrasonic cleaning uses a mixed solution of ethanol and deionized water (volume ratio 1:1-1:3). The ground blank is immersed in the solution, and ultrasonic vibration is used to remove residual grinding debris and oil stains from the surface. The cleaning time is 15-30 minutes to ensure that no impurities adhere to the surface of the blank. Preheating involves placing the cleaned and dried blank into a heating furnace, and the preheating temperature gradient is 50℃ / h to reach the target temperature.

3. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, In step S2, the oscillation mode of the oscillating laser is sinusoidal oscillation or rectangular oscillation, the laser pulse width is 10-50μs, the pulse repetition frequency is 100-500Hz, and the scanning method is unidirectional scanning or bidirectional cross scanning.

4. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, In step S2, the surface temperature of the blank after scanning is controlled at 700-900℃, and the surface roughness Ra≤1.5μm.

5. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, In step S3, the inert gas is argon or nitrogen, the protective gas flow rate is 10-30 L / min, the rolling roll surface temperature is controlled at 100-200℃, and the roll surface roughness Ra≤0.8μm.

6. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, In step S3, the rolling process involves 3-8 rolling passes, with a holding time of 5-15 minutes between adjacent passes, and the holding temperature is maintained at 600-800℃.

7. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, In step S4, the annealing process is vacuum annealing, with an annealing temperature of 550-700℃, a holding time of 1-3h, a cooling rate of 20-50℃ / h to room temperature, and a vacuum degree ≤5×10⁻³Pa.

8. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, In step S4, the surface finishing is achieved by a combination of mechanical polishing and electrochemical polishing. The electrochemical polishing solution is a mixed solution of phosphoric acid and sulfuric acid (volume ratio 2:1-3:1), the polishing temperature is 40-60℃, the current density is 10-20A / dm², and the polishing time is 5-15min.

9. The method for preparing TC4 titanium alloy by synergistic oscillating laser and rolling according to claim 1, characterized in that, The TC4 titanium alloy has a grain size of 10-20 μm, tensile strength ≥950 MPa, yield strength ≥850 MPa, elongation ≥12%, and residual stress ≤100 MPa.

10. The application of TC4 titanium alloy as described in any one of claims 1-8 in aerospace structural components and key moving parts in marine engineering.

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