A titanium alloy material, its preparation method and application

Abstract

This invention provides a titanium alloy material, its preparation method, and its applications, relating to the field of titanium alloy technology. Specifically, a titanium-niobium-oxygen alloy ingot containing α and β phases is rotary forged; the titanium alloy material is obtained by synergistic preparation with rotary forging using a design incorporating short-time solution treatment, short-time annealing, water quenching, and static settling. This invention, combining material innovation, develops a method for preparing titanium alloy materials by precisely controlling the parameters of rotary forging and heat treatment. The resulting titanium-niobium-oxygen alloy material simultaneously possesses low elastic modulus, high mechanical properties, and excellent fatigue performance. Furthermore, this alloy material also exhibits excellent biocompatibility, showing promising application prospects in medical materials.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy technology, and more specifically, to a titanium alloy material, its preparation method, and its application. Background Technology

[0002] One of the main challenges facing existing stainless steel and titanium alloy implants in orthopedic applications is their elastic modulus, which is far higher than the natural biomechanical properties of human bone. The elastic modulus of human bone is typically in the range of 10–30 GPa, while the elastic modulus of traditional medical stainless steel (such as 316L) exceeds 180 GPa, and that of titanium alloys (such as Ti-6Al-4V) is approximately 110 GPa. This significant difference in elastic modulus leads to an imbalance in the distribution of mechanical load between the implant and the bone, triggering a "stress shielding effect"—that is, the implant bears most of the stress load, while the stress stimulation received by the bone itself is significantly reduced. Over the long term, the bone, lacking necessary mechanical stimulation, undergoes bone resorption and osteoporosis, ultimately leading to implant loosening or displacement. This phenomenon is particularly pronounced after hip and knee replacement surgery.

[0003] Furthermore, high-elasticity materials may exacerbate fretting wear and interface failure risks under dynamic loads. Due to the mismatch between the elastic deformation capacity of the implant and the bone, excessively rigid implants can restrict bone fretting during physiological activities (such as walking or weight-bearing), leading to abnormal stress concentration at the bone-implant interface. This not only accelerates the dissolution of surrounding bone tissue but may also cause implant fatigue fracture. For example, the incidence of nonunion of surrounding bones is relatively high when using traditional titanium alloy screws for fixation in areas such as the clavicle or ankle joint. Meanwhile, while the torsional properties of stainless steel implants are advantageous for surgical manipulation due to their higher rigidity, long-term implantation makes them more prone to fibrous capsule formation, hindering osseointegration.

[0004] Regarding biocompatibility, although titanium alloys have a higher elastic modulus than stainless steel, they still cannot fully mimic the biomechanical environment of bone. Studies have shown that while titanium alloy implants can promote callus formation through micromotion, their excessive rigidity can still inhibit adaptive remodeling at the fracture site, prolonging the healing period. Stainless steel implants, due to their even higher elastic modulus, exhibit more pronounced immune responses and metal ion release issues, potentially accelerating local corrosion and increasing the risk of infection. Current research focuses on developing β-type titanium alloys with an elastic modulus close to that of bone, but existing mainstream clinical materials have not yet completely resolved the biomechanical adaptation challenges posed by high elastic modulus.

[0005] Furthermore, fatigue performance is a core technological barrier that low-modulus titanium alloy implants must overcome in orthopedic applications. Although the elastic modulus of titanium alloys can be reduced to 50-60 GPa through alloying design with β-phase stabilizing elements (such as Nb, Zr, Mo, etc.), which is close to the mechanical properties of human bones, the simultaneous improvement of fatigue strength remains a key challenge in current research and development.

[0006] Fatigue failure mechanisms under dynamic loads are more complex. Titanium alloy implants are subjected to millions of cyclic stresses during physiological activities (e.g., approximately 3.6 × 10⁻⁶ cycles per year for the hip joint). 6 Secondary load impacts, if fatigue strength is insufficient, can easily lead to the initiation and propagation of microcracks, ultimately causing implant fracture. Studies have found that dwell fatigue is particularly prominent in low-modulus titanium alloys, meaning that maintaining a load below the peak load of the yield stress (such as during the resting period of breathing or standing) accelerates crack formation through localized stress concentration and slip band activation, causing the fatigue life to plummet to less than 1 / 10 of that of conventional cyclic fatigue. Furthermore, traditional titanium alloy bone plates introduce microcracks due to plastic deformation caused by repeated bending. These microcracks propagate continuously during the long-term service of the bone plate due to cyclic stress from patient movement, ultimately leading to reduced fatigue performance and fracture before reaching the designed service life. In other words, microcracks caused by repeated bending reduce the high-cycle fatigue performance of titanium alloy bone plates.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The primary objective of this invention is to provide a method for preparing titanium alloy materials, specifically titanium-niobium-oxygen alloys, to address the shortcomings of conventional titanium alloy materials in simultaneously satisfying the requirements of low elastic modulus, high biocompatibility, and high fatigue resistance.

[0009] The second objective of this invention is to provide a titanium alloy material.

[0010] A third objective of this invention is to provide an application of the aforementioned titanium alloy material in medical materials, particularly in bone materials.

[0011] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0012] A method for preparing a titanium alloy material includes: forging a titanium-niobium-oxygen alloy ingot containing α-phase and β-phase; and the preparation method includes one of the following steps (a) to (c):

[0013] (a) The titanium-niobium-oxygen alloy ingot is subjected to short-time solution treatment, and then rotated in several passes, with the short-time solution treatment performed once between each pass of the rotational forging, and titanium alloy material is obtained after the rotational forging.

[0014] (b) The titanium-niobium-oxygen alloy ingot is subjected to rotary forging in several passes, and then subjected to short-time annealing after rotary forging to obtain titanium alloy material;

[0015] (c) The titanium-niobium-oxygen alloy ingot is subjected to short-time solution treatment and then water quenched, and then rotated in several passes, with a static treatment between each pass of the rotational forging. After the rotational forging, a short-time annealing treatment is performed to obtain the titanium alloy material.

[0016] In some embodiments, the α phase accounts for 18 vt.% to 22 vt.% of the titanium-niobium-oxygen alloy ingot.

[0017] In some embodiments, the titanium-niobium-oxygen alloy ingot comprises the following elemental composition by mass percentage: Ti 82%~86%, Nb 15.4%~17.0%, O 0.35%~0.55%;

[0018] In some preferred embodiments, the impurity content of the titanium-niobium-oxygen alloy ingot is ≤0.3 wt.%.

[0019] In some embodiments, the titanium alloy material obtained in step (a) includes an α phase and a β phase, the titanium alloy material obtained in step (b) includes an α phase, an α' phase and a β phase, and the titanium alloy material obtained in step (c) includes an α phase, a β phase and a SIMα'' phase.

[0020] In some implementations, step (a) includes at least one of the following listed features:

[0021] The short-time solution treatment temperature is 880℃~920℃, and the duration is 8min~40min; and / or, the number of passes in the rotary forging is 2~8; and / or, the radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3mm~12mm; and / or, the axial feeding speed of the ingot material is 0.3m / min~0.8m / min, and the rotation frequency is 5rpm~15rpm.

[0022] In some implementations, step (b) includes at least one of the following listed features:

[0023] The number of passes in the rotary forging is 2 to 8; and / or, the radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3 mm to 12 mm; and / or, in the rotary forging, the axial feeding speed of the ingot material is 0.3 m / min to 0.8 m / min, and the rotation frequency is 5 rpm to 15 rpm; and / or, the temperature of the short-time annealing treatment is 400℃ to 700℃, and the duration is 8 min to 20 min.

[0024] In some implementations, step (c) includes at least one of the following listed features:

[0025] The short-time solution treatment temperature is 880℃~920℃, and the duration is 50min~75min; and / or, the number of passes in the rotary forging is 2~8; and / or, the radial clearance of the rotary forging hammer decreases with the increase of passes, and the decrease range is 3mm~12mm; and / or, the time for each settling treatment is independently 45min~75min; and / or, the short-time annealing temperature is 400℃~700℃, and the duration is 8min~20min.

[0026] A titanium alloy material, obtained based on the aforementioned preparation method. And, the use of the said titanium alloy material in medical materials.

[0027] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention combines material innovation and develops a method for preparing titanium alloy materials by precisely controlling the parameters of rotary forging and heat treatment. The resulting titanium alloy (titanium-niobium-oxygen alloy) material simultaneously possesses low elastic modulus, high mechanical properties, and excellent fatigue performance. Furthermore, this alloy material also exhibits excellent biocompatibility, showing promising application prospects in medical materials. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. In addition, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0029] This invention provides a method for preparing titanium alloy materials, which mainly includes: forging a titanium-niobium-oxygen alloy ingot containing α phase and β phase.

[0030] This invention primarily addresses the shortcomings of conventional titanium alloys, which lack low elastic modulus, high biocompatibility, and fatigue resistance. Good fatigue performance requires both high strength and high ductility. Achieving an ultrafine grain (UFG) structure through rotary forging enables the simultaneous attainment of both high strength and excellent ductility. Furthermore, the UFG structure can also lead to improvements in various mechanical properties.

[0031] Specifically, rotary forging is a precision forming process that integrates high-frequency pulse loading and multi-directional forging. In rotary forging, multiple hammer modules rotate at high speed around the bar and simultaneously perform radial high-frequency impacts, applying dozens of blows per second, or even thousands per minute. While the bar is continuously fed axially, it is locally compressed, and the material undergoes plastic flow point-by-point and layer-by-layer under near-triaxial compressive stress, achieving outer diameter reduction, length extension, and surface shaping. Because the deformation amount per stroke in rotary forging is extremely small and the metal flow distance is short, frictional resistance is low, and deformation is uniform, significantly suppressing crack initiation. The applicant's experiments have shown that, compared to other forging methods, rotary forging of titanium alloy bars can fully leverage their advantages in cold forming and high static pressure. Titanium alloys have low room temperature plasticity and a strong tendency for work hardening; traditional drawing and cold rolling processes easily produce surface cracks. In contrast, rotary forging, through high-frequency multi-directional forging, allows titanium alloys to achieve sufficient plastic deformation at room temperature, simultaneously improving strength and fatigue life.

[0032] Rotary forging processes for titanium metals such as pure titanium and TC4 have been extensively researched and applied in existing technologies. However, the development of rotary forging processes for titanium-niobium-oxygen alloys, a relatively novel low-modulus titanium alloy, presents unique engineering challenges and is difficult to achieve through conventional rotary forging methods. The specific reasons are as follows:

[0033] (i) Titanium-niobium-oxygen alloys have a complex phase transformation mechanism during rotary forging. It is necessary to accurately explore and control the processing parameters in order to obtain titanium-niobium-oxygen alloys with low elastic modulus, high mechanical properties and excellent fatigue properties.

[0034] For low-elastic-modulus β-titanium alloys such as titanium-niobium-oxygen and Ti-40Nb, on the one hand, rotary forging can lead to the formation of stress-induced α'' martensite; this phase transformation helps to reduce the elastic modulus, but its precise formation ratio has a significant impact on the final mechanical properties and requires fine control. On the other hand, during deformation or rapid cooling, metastable ω phases may form; the precipitation of these ω phases usually leads to material embrittlement and increases the elastic modulus.

[0035] (ii) In low-elastic-modulus titanium alloy raw materials, rotary forging will also result in nanoscale phase separation (spinoclonus decomposition), forming niobium-rich and titanium-rich regions. This phenomenon may also lead to an increase in elastic modulus and hardness. The interaction of the aforementioned complex phase transformations, such as α'' and ω phase separation, makes the final mechanical properties of β titanium alloys after rotary forging highly sensitive to process parameters. Therefore, precisely controlling processing parameters to manage the proportion and morphology of these phases, thereby avoiding embrittlement and achieving specific performance targets, is both necessary and challenging in the rotary forging design of titanium-niobium-oxygen alloys.

[0036] (III) While rotary forging refines the grain size, it can also lead to a significant decrease in plasticity and fatigue properties. For example, the β-titanium alloy Ti-13Nb-13Zr, which has a low elastic modulus (approximately 80 GPa), exhibits significantly refined grain size and reduced plasticity after ECAP-Conform combined with rotary forging. This is mainly due to the extreme grain refinement generating numerous grain boundaries, which severely hinder dislocation slip. Furthermore, when machining pure titanium, rotary forging also results in lower tensile ductility and work hardening capacity, leading to extremely high fatigue notch sensitivity, i.e., 100% complete notch sensitivity.

[0037] While post-annealing can improve ductility and reduce notch sensitivity, this typically comes at the cost of strength. For example, the α- and β-phase titanium alloy Ti-54M exhibits 100% fatigue notch sensitivity after rotary forging and air cooling at 800°C, a result of its extremely low work hardening capacity. Although post-treatment with furnace cooling at 940°C can reduce notch sensitivity to 42% and improve work hardening capacity, this improvement comes at the expense of fatigue strength. This highlights the necessity of making engineering trade-offs between strength and fatigue notch sensitivity.

[0038] In summary, compared to pure titanium or α-phase-dominated titanium alloys, the main engineering challenge of rotary-forged β-titanium alloys lies in their inherently complex phase transformation behavior, such as the formation of SIMα'' and ω phases, as well as phase separation. These phase transformations have a direct and complex impact on the final mechanical properties, requiring more precise process control to balance properties such as strength, plasticity, elastic modulus, and brittleness. Furthermore, similar to all materials processed using severe plastic deformation techniques, the reduction in plasticity and increased fatigue notch sensitivity resulting from grain refinement are common challenges faced by β-titanium alloys during rotary forging.

[0039] In a preferred embodiment, the α phase accounts for 18 vt.% to 22 vt.% of the titanium-niobium-oxygen alloy ingot. Further, testing revealed that the β phase in the titanium-niobium-oxygen alloy ingot is mixed and co-doped with the α', α'', and ω phases. Although the volume percentage of the aforementioned mixed phases cannot be precisely measured, it can be confirmed that the α', α'', and ω phases also play a crucial role in the mechanical properties of the material and cannot be simply confused with the β phase. In some embodiments, the α', α'', and ω phases typically account for a very low percentage in the initial state of the titanium-niobium-oxygen alloy ingot. Therefore, based on the fundamental principles of the dual-phase structure of titanium alloys, the β phase percentage can be considered to be 75 vt.% to 82 vt.%. In some optional embodiments, the β phase percentage is 78 vt.% to 82 vt.%.

[0040] In a preferred embodiment, the titanium-niobium-oxygen alloy ingot comprises the following elemental composition by mass percentage: Ti 82%~86%, Nb 15.4%~17.0%, O 0.35%~0.55%; and impurities ≤0.3%. In some optional embodiments, the mass percentage of the main elemental composition in the titanium-niobium-oxygen alloy ingot includes, but is not limited to: Ti 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%; Nb 15.4%, 15.5%, 15.6%, 15.8%, 16.0%, 16.2%, 16.5%, 16.8%, 17.0%; O 0.35%, 0.36%, 0.38%, 0.40%, 0.42%, 0.45%, 0.48%, 0.50%, 0.52%, 0.55%; the above values ​​can be any one of the listed values ​​or any range of two of them.

[0041] In a more preferred embodiment, the impurities include the following elemental composition by mass percentage: Fe≤0.26%, N≤0.05%, H≤0.01%, C≤0.1%.

[0042] In a preferred embodiment, the titanium-niobium-oxygen alloy ingot is rod-shaped, and the diameter of the rod is 40mm to 60mm, including but not limited to any one or any two of the following values: 40, 42, 45, 48, 50, 52, 55, 58, and 60 (mm).

[0043] Titanium-niobium-oxygen (Ti-Nb-O) alloys exhibit significant advantages in low elastic modulus and biocompatibility, making them an important research direction in the field of orthopedic implant materials. By introducing niobium and oxygen elements and combining them with β-phase stabilization design, the elastic modulus can be reduced to below 60 GPa, significantly better than traditional titanium alloys (such as Ti-6Al-4V at 110 GPa). For example, the elastic modulus of Ti-38Nb-0.5O alloy is only 52 GPa, close to the mechanical properties of human cancellous bone (10~40 GPa), thus effectively mitigating the "stress shielding" effect and reducing the risk of bone resorption and implant loosening. The addition of oxygen not only enhances the alloy strength through solid solution strengthening but also refines the grains and inhibits the precipitation of harmful phases, achieving synergistic optimization of low modulus (<60 GPa) and high strength (yield strength up to 1141 MPa).

[0044] In terms of biocompatibility, the titanium-niobium-oxygen alloy, with non-toxic Ti, Nb, and O as its main components, avoids elements such as Al and V found in traditional alloys that may cause neurotoxicity. In vitro experiments have shown that this alloy does not inhibit the adhesion and proliferation of bone marrow mesenchymal stem cells, with a cell survival rate exceeding 90%, and does not induce a significant inflammatory response. The porous titanium-niobium-oxygen alloy (elastic modulus 2.23 GPa at 70% porosity) promotes calcium and phosphorus deposition and osteoid tissue ingrowth by mimicking the three-dimensional interconnected pores (pore size 200–500 μm) of cancellous bone, significantly enhancing the mechanical locking and biological bonding at the bone-implant interface. Furthermore, surface nano-sizing further activates osteoblast differentiation, accelerating the bone healing process.

[0045] The mechanical properties of titanium-niobium-oxygen alloys also lie in their superelasticity and fatigue resistance. For example, the Ti-38Nb-0.5O alloy exhibits a superelastic strain of 2.2%, enabling it to adapt to periodic deformations under dynamic loading environments (such as joint movement), while the dispersed precipitation of the nanoscale ω phase significantly improves fatigue life. Through powder metallurgy or additive manufacturing techniques, this alloy can also achieve porous gradient structure designs, maintaining excellent compressive strength while reducing modulus. These properties make it an ideal implant material that combines biomechanical adaptability, long-term stability, and osseointegration potential, offering new possibilities for personalized medicine and the manufacture of complex implants.

[0046] In this invention, the preparation method includes one of the following steps (a) to (c):

[0047] (a) The titanium-niobium-oxygen alloy ingot is subjected to short-time solution treatment, and then rotated in several passes, with the short-time solution treatment performed once between each pass of the rotational forging, and the titanium alloy material is obtained after the rotational forging.

[0048] (b) The titanium-niobium-oxygen alloy ingot is subjected to rotary forging in several passes, and then subjected to short-time annealing after rotary forging to obtain titanium alloy material.

[0049] In this step, cold forging can further refine the grain size to the submicron level compared to hot forging. At the same time, by inducing or retaining specific metastable phases (such as α' phase) or promoting phase transformation (such as β→α''), α' or α'' phase can be obtained by forging. Thus, cold forging can effectively reduce the elastic modulus of the material. The effect of short-time annealing is to retain the α' or α'' phase.

[0050] (c) The titanium-niobium-oxygen alloy ingot is subjected to short-time solution treatment and then water quenched, and then rotated in several passes, with a static treatment between each pass of the rotational forging. After the rotational forging, a short-time annealing treatment is performed to obtain the titanium alloy material.

[0051] In this step, heat treatment followed by water quenching yields the initial α' martensite structure. Then, a cold forging process preserves the specific metastable α' phase. Simultaneously, the induced β phase transforms into stress-induced martensite (orthorhombic system), forming β and SIMα'' phases. The elastic modulus of this combination is lower than that of the initial α and β phases. Furthermore, in this step, a settling period is required during the cold forging interval to prevent the internal temperature rise of the bar during the forging process from causing the α' martensite to decompose.

[0052] In summary, for the purposes of this invention, the titanium alloy material obtained in step (a) includes α and β phases, the titanium alloy material obtained in step (b) includes α, α', and β phases, and the titanium alloy material obtained in step (c) includes α, β, and SIMα'' phases.

[0053] Furthermore, for step (a), the following preferred features exist:

[0054] In a preferred embodiment, the temperature of any one of the short-time solution treatments is 880°C to 920°C, and the duration is 8 min to 40 min. It is worth noting that there are at least two short-time solution treatments in step (a), and the temperature and time of each short-time solution treatment do not necessarily have to be the same. Those skilled in the art can independently select the values ​​within the above-mentioned range.

[0055] In a preferred embodiment, the number of passes in the rotary forging is 2 to 8.

[0056] In a preferred embodiment, the radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3mm to 12mm.

[0057] In a more preferred embodiment, the radial clearance of the hammer head is 32mm to 48mm in the first pass of rotary forging.

[0058] In a preferred embodiment, during the rotary forging, the frequency of the radial high-frequency impact of the hammer head is 10Hz~18Hz, and the energy of a single impact is 12J~24J.

[0059] In a preferred embodiment, the axial feeding speed of the ingot material in the rotary forging is 0.3 m / min to 0.8 m / min, and the rotation frequency is 5 rpm to 15 rpm; in some more preferred embodiments, the number of hammer blows per revolution of the ingot material is 60 to 120.

[0060] Furthermore, for step (b), the following preferred features exist:

[0061] In a preferred embodiment, the number of passes in the rotary forging is 2 to 8.

[0062] In a preferred embodiment, the radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3mm to 12mm.

[0063] In a more preferred embodiment, the radial clearance of the hammer head is 32mm to 48mm in the first pass of rotary forging.

[0064] In a preferred embodiment, during the rotary forging, the frequency of the radial high-frequency impact of the hammer head is 18Hz~32Hz, and the energy of a single impact is 12J~24J.

[0065] In a preferred embodiment, the axial feeding speed of the ingot material in the rotary forging is 0.3 m / min to 0.8 m / min, and the rotation frequency is 5 rpm to 15 rpm; in some more preferred embodiments, the number of hammer blows per revolution of the ingot material is 60 to 120.

[0066] In a preferred embodiment, the temperature of the short-time annealing treatment is 400℃~700℃, and the duration is 8min~20min.

[0067] Furthermore, step (c) has the following preferred features:

[0068] In a preferred embodiment, the temperature of the short-time solution treatment is 880℃~920℃, and the duration is 50min~75min.

[0069] In a preferred embodiment, the time interval between the short-time solution treatment and the water quenching is ≤2 min, and in some embodiments it is 1 min to 2 min; it is understood that the water quenching is performed after the short-time solution treatment or immediately.

[0070] In a preferred embodiment, the number of passes in the rotary forging is 2 to 8.

[0071] In a preferred embodiment, the radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3mm to 12mm.

[0072] In a more preferred embodiment, the radial clearance of the hammer head is 32mm to 48mm in the first pass of rotary forging.

[0073] In a preferred embodiment, during the rotary forging, the frequency of the radial high-frequency impact of the hammer head is 18Hz~32Hz, and the energy of a single impact is 12J~24J.

[0074] In a preferred embodiment, the axial feeding speed of the ingot material in the rotary forging is 0.3 m / min to 0.8 m / min, and the rotation frequency is 5 rpm to 15 rpm; in some more preferred embodiments, the number of hammer blows per revolution of the ingot material is 60 to 120.

[0075] In a preferred embodiment, the settling time for each settling process is independently 45 min to 75 min, and the settling process is carried out at 20°C to 30°C.

[0076] In a preferred embodiment, the temperature of the short-time annealing treatment is 400℃~700℃, and the duration is 8min~20min.

[0077] Example: Preparation of titanium-niobium-oxygen alloy ingots

[0078] Titanium-niobium-oxygen alloy ingots were obtained by electron beam melting (EBM) under a protective argon atmosphere. 29.4 kg of pure Ti-45Nb alloy, 49.4 kg of sponge titanium, and 1.2 kg of TiO2 powder were used as raw materials, and a total of 80 kg of alloy ingots were obtained by melting.

[0079] Wherein: 1) The sponge titanium is grade 0 sponge titanium; 2) In the Ti-45Nb alloy, excluding Ti, the mass content of Nb element is 45%, and the impurity elements are Fe < 0.3%, Si < 0.2%, O < 0.3%, and N < 0.1%; 3) The dry mass of TiO2 powder is > 98 wt.%, and the mass content of impurities is Fe2O3 < 0.05%, Na2O < 0.02%, and SiO2 < 0.05%.

[0080] The above raw materials were mixed and pressed into electrodes, and 80 kg of Φ50 mm rod-shaped ingots (Ti 83.62%, Nb 15.80%, O 0.58%, trace impurity elements are not included in this mass percentage) were obtained by vacuum arc remelting. This rod-shaped ingot was used as the raw material for the initial titanium-niobium-oxygen alloy in all the following embodiments.

[0081] Example 1

[0082] The ingot is subjected to a short-term solution treatment, held at 900°C for 30 minutes; immediately after the solution treatment, rotary forging begins; the mold is a four-hammer integral cemented carbide cavity; the rotary forging process is carried out in five passes, with the radial clearance of the hammers in each pass set by the hydraulic servo system to 45, 40, 35, 30, and 25 mm respectively; between each pass, the bar is removed and held at 900°C for 30 minutes; after the rotary forging machine is started, the hammers are driven at a frequency of 12Hz to perform radial high-frequency impacts, with a single impact energy of 18J; simultaneously, the ingot is axially fed at a constant linear velocity of 0.5m / min under the drive of the servo motor, and maintains a rotational motion of 8rpm, so that the material forms a spiral multi-directional compression in the cavity, with 90 hammer blows per revolution; after the five passes of rotary forging are completed, it is air-cooled to room temperature to obtain the titanium alloy material of this embodiment.

[0083] This embodiment employs a process of "short-time solution treatment + alternating multi-pass rotary forging". The initial ingot has an α-β dual-phase structure. After a short-time solution treatment at 900℃, the α phase partially dissolves to form a supersaturated β phase. Subsequently, each pass of rotary forging introduces high-density dislocations and strain-induced α'' martensite, while significantly refining the grain size. The solution treatment between passes (900℃, 30 min) plays a dynamic recovery role, partially recrystallizing the β phase and controlling the precipitation size of the α phase, ultimately forming a uniform structure dominated by fine-grained α and β phases, containing a small amount of metastable α'' phase. This structure, while ensuring strength (yield strength 820 MPa) and plasticity (elongation 22%), reduces the elastic modulus to 84 GPa and improves fatigue performance by suppressing crack propagation through grain refinement.

[0084] Example 2

[0085] The ingot is subjected to short-term solution treatment and held at 900°C for 10 minutes; immediately after the solution treatment, rotary forging begins; the mold is a four-hammer integral cemented carbide cavity; the rotary forging is carried out in two passes, and the radial clearance of the hammers in each pass is set to 35 mm and 25 mm respectively by the hydraulic servo system, which is greater than the deformation between each pass in Example 1; as the deformation (area reduction rate) increases, the grain size will decrease, thereby forming an ultrafine grain (UFG) structure. Between each pass, the bar stock is removed and held at 900°C for 10 minutes to maintain the forging temperature while inhibiting further grain coarsening. After the forging machine is started, the hammer is driven at a frequency of 12Hz to perform radial high-frequency impact, with a single impact energy of 18J. At the same time, the ingot is fed axially at a constant linear speed of 0.5m / min under the drive of a servo motor and maintains a rotational motion of 8rpm, so that the material forms a spiral multi-directional compression in the cavity, with 90 hammer blows per revolution. After the two passes of forging are completed, the material is air-cooled to room temperature to obtain the titanium alloy material of this embodiment.

[0086] This process also employs alternating solution treatment and rotary forging, but with fewer passes (two passes) and a larger deformation per pass. Short-term solution treatment (900℃, 10 min) initially stabilizes the β phase, followed by large-deformation rotary forging to forcefully break down the α phase and induce the β phase to transform into stress-induced α'' martensite, forming an ultrafine-grained (UFG) structure. Inter-pass solution treatment suppresses grain coarsening and regulates dislocation density, resulting in a final microstructure with a fine-grained α and β matrix and a higher proportion of the α'' phase than in Example 1. This structure achieves higher strength (yield strength 903 MPa) and lower modulus (78 GPa), but with a slight decrease in plasticity (elongation 19%), demonstrating the regulatory effect of deformation on microstructure refinement and phase transformation.

[0087] Example 3

[0088] The ingot is fed into a rotary forging machine at room temperature. The mold is a four-hammer integral cemented carbide cavity. The rotary forging process is carried out in five passes. The radial clearance of the hammers in each pass is set to 45, 40, 35, 30, and 25 mm by the hydraulic servo system. After the rotary forging machine is started, the frequency of the high-frequency impact is 24 Hz, and the energy of a single impact is 18 J. At the same time, the ingot is axially fed at a constant linear velocity of 0.5 m / min under the drive of the servo motor and maintains a rotational motion of 8 rpm, so that the material forms a spiral multi-directional compression in the cavity. After the rotary forging is completed, it is air-cooled to room temperature. Then it is annealed at 550°C for a short time for 10 minutes, and then air-cooled to room temperature to obtain the titanium alloy material of this embodiment.

[0089] This embodiment directly processes the ingot using a combination of cold rotary forging and short-time annealing. Room temperature multi-pass rotary forging (five passes) introduces severe plastic deformation into the α-β dual-phase matrix. A large portion of the β phase transforms into stress-induced α'' martensite, while the α phase is broken up and partially transformed into α' martensite, forming an ultrafine-grained structure with high dislocation density. Subsequent short-time annealing at 550℃ promotes partial recrystallization and releases internal stress, but retains the metastable α'' and α' phases. The final microstructure is dominated by a mixture of α, α', β, and α'' phases. The high α'' phase content significantly reduces the elastic modulus to 65 GPa, while the high strength (tensile strength 1083 MPa) and uniform fine-grained structure provide excellent fatigue resistance (no failure under high loads).

[0090] Example 4

[0091] The ingot is fed into a rotary forging machine at room temperature. The mold is a four-hammer integral cemented carbide cavity. The rotary forging process is carried out in two passes. In this embodiment, the rotary forging passes are fewer, the deformation per pass is greater, the work hardening effect is better, and the strength is also higher. The radial clearance of the hammers in each pass is set to 35 mm and 25 mm respectively by the hydraulic servo system. After the rotary forging machine is started, the frequency of the high-frequency impact is 24 Hz, and the energy of a single impact is still 18 J. At the same time, the ingot is still axially fed at a constant linear velocity of 0.5 m / min under the drive of the servo motor, and maintains a rotational motion of 8 rpm, so that the material forms a spiral multi-directional compression in the cavity. After the rotary forging is completed, it is air-cooled to room temperature. Then it is annealed at 550°C for a short time for 10 minutes, and then air-cooled to room temperature to obtain the titanium alloy material of this embodiment.

[0092] This pass employs the same cold forging and annealing process as Example 3, but the number of forging passes is reduced to two, further increasing the deformation per pass. Intense cold deformation induces a complete transformation of the β phase into α'' martensite, while simultaneously refining the grains to the submicron level with extremely high dislocation density. Short-time annealing (550℃) partially restores plasticity while retaining the metastable phase, but due to the excessively high grain boundary density, plasticity is significantly reduced (elongation 6%). The final microstructure is dominated by the α'' phase, containing small amounts of α and β phases, achieving an extremely low elastic modulus (64 GPa) and the highest strength (yield strength 1152 MPa), but a trade-off between strength and plasticity is necessary.

[0093] Example 5

[0094] The ingot was subjected to a short-term solution treatment at 900°C for 60 minutes. After solution treatment, water quenching was immediately initiated, followed by rotary forging. The mold was a four-hammer integral cemented carbide cavity. Rotary forging was carried out in five passes, with the radial clearance of the hammers in each pass set by the hydraulic servo system to 45, 40, 35, 30, and 25 mm respectively. After the rotary forging machine was started, the high-frequency impact frequency was 24 Hz, and the single impact energy remained at 18 J. Simultaneously, the ingot was fed axially at a constant linear velocity of 0.5 m / min under the drive of the servo motor, maintaining a rotational motion of 8 rpm, causing the material to undergo helical multi-directional compression within the cavity. No annealing was performed between passes, and the ingot was allowed to stand for 1 hour between passes. After rotary forging, the ingot was briefly annealed at 550°C for 10 minutes, followed by air cooling to room temperature to obtain the titanium alloy material of this embodiment.

[0095] This embodiment employs a multi-stage process of solution treatment, water quenching, rotary forging, static cooling, and annealing to control the microstructure. First, a 900℃ solution treatment completely dissolves the α phase, forming a uniform β phase. Rapid water quenching inhibits the precipitation of the ω phase, resulting in metastable α' martensite. Subsequently, multiple passes of rotary forging further induce the β phase to transform into stress-induced α'' martensite within the α' matrix. A static cooling treatment (1 hour at room temperature) between passes prevents temperature rise from causing α' phase decomposition. Finally, short-time annealing stabilizes the α'' phase and reduces internal stress, forming a mixed microstructure dominated by α, β, and α'' phases, with the α'' phase having the highest proportion. This minimizes the elastic modulus (58 GPa) while maintaining high strength (tensile strength 1072 MPa) and good fatigue performance.

[0096] Comparative Example 1

[0097] This comparative example provides a TC4 material from Carpenter (USA) Corporation.

[0098] The original ingot material is heated near the β phase transformation temperature of 950℃ and held for 280 minutes to ensure uniform temperature. The forging process often adopts multi-fire deformation, first upsetting and drawing to refine the grains. The deformation amount of each fire is controlled at 30%, and the final forging temperature is not lower than 820℃ to avoid cracks.

[0099] Comparative Example 2

[0100] This comparative example provides a TC4 material from Carpenter (USA) Corporation.

[0101] The process employs isothermal forging, with the die temperature maintained at 900℃. The forging is achieved through three stages of progressively lowering and holding pressure. The first stage involves lowering the pressure at a rate of 0.2 mm / s, with a 20 mm under-pressure, and holding for 60 seconds. The second stage involves lowering the pressure at a rate of 0.15 mm / s, with a 20 mm under-pressure, and holding for 60 seconds. The third stage involves lowering the pressure at a rate of 0.1 mm / s, with a 20 mm under-pressure, and holding for 60 seconds. Finally, reverse upsetting and chamfering are used to ensure uniform microstructure. After forging, the material is air-cooled to below 300℃, followed by annealing at 780℃ for 60 minutes to optimize mechanical properties.

[0102] Comparative Example 3

[0103] A self-made titanium-niobium oxide material is prepared using a traditional forging process, the method of which includes:

[0104] First, the titanium-niobium-oxygen ingots undergo high-temperature homogenization pretreatment, and are then heated to 1150℃ in the furnace and held for 2 hours before the first forging process, which involves three forging passes and three drawing passes. The second forging temperature is 950℃, and the third forging temperature is 850℃. Part of the forging is forged into square billets, and the other part is forged into round billets.

[0105] The surfaces of the square and round billets were ground clean and smooth. The billets were then subjected to multiple rolling passes under an argon atmosphere at 750℃, with the deformation in each pass controlled between 15% and 25%. The total deformation during the rolling process was 85%. Each pass was annealed for 5 minutes before rolling, and after hot working, the billets were quenched to room temperature to obtain a 6.5mm thick sheet.

[0106] The round billet was drawn in multiple passes under the protection of argon atmosphere at 750℃. The deformation of each pass was controlled between 10% and 20%, and the total deformation of the drawing process was 85%. The billet was annealed for 5 minutes before each rolling pass and quenched to room temperature after hot working to finally obtain a bar with a diameter of 15mm.

[0107] Then, the titanium niobium oxide rods and plates were subjected to solution treatment, aged at 600°C for 120 minutes in an argon atmosphere, and then water-cooled to room temperature to obtain the corresponding rods and plates.

[0108] Experimental Example 1

[0109] The approximately 1 mm thick oxide layer formed on the surface of the materials in each embodiment was removed by machining, and then mechanical properties were evaluated and recorded in Table 1. For the bars and plates of Comparative Example 3, the average performance of both is provided.

[0110] Table 1

[0111]

[0112] Experimental Example 2

[0113] According to the standard "ISO10993-5:2009 Biochemical evaluation of medical devices - Part 5: In vitro cytotoxicity tests", in vitro cytotoxicity tests were conducted on the alloy material of Example 1 based on the experimental methods described in the standard. Blank control, positive control (0.1% ZDEC polyurethane film), negative control (high-density polyethylene film), and 100% / 75% / 50% / 25% sample extracts were prepared accordingly. The absorbance and cell viability of each sample are recorded in Table 2.

[0114] Table 2

[0115]

[0116] Table 2 shows that the relative viability of L929 fibroblasts under 100% concentration sample extract reached 100.2±1.3%, while the cell viability under 50% sample extract showed an increase of 104.1±2.1%, indicating that the experimental sample extract had no potential cytotoxicity to L929 cells. In contrast, the cell viability of commercial Ti-6Al-4V alloy under the same extraction conditions (100% concentration sample extract) was only 98±1.8%, and the potential dissolution risk of Al and V elements may inhibit cell metabolic activity. The examples demonstrated excellent biocompatibility.

[0117] Experimental Example 3

[0118] The alloy strips obtained in the above embodiments or comparative examples were processed into 8-hole locking plates, and the 8-hole locking plates were subjected to a four-point bending fatigue test. The test method was carried out in accordance with ASTM - F382-17 Standard Specification and Test Method for Metallic Bone Plates – 2014. The test results are shown in Table 3.

[0119] Table 3

[0120]

[0121] It is worth noting that, as can be seen from the comparison between Comparative Example 3 and the various embodiments, the process path provided by the present invention has better engineering feasibility, efficiency, and controllability. Although the present invention does not achieve a significant improvement in absolute performance compared to the traditional process of Comparative Example 3, the traditional process of Comparative Example 3 requires a complex, multi-stage thermomechanical treatment process, including high-temperature homogenization pretreatment, multi-fire forging, intermediate annealing, rolling / drawing, and final solution treatment. Although the existing process can achieve a lower elastic modulus and higher strength, its process is cumbersome, energy-intensive, and has a long production cycle. It also relies on the precise coordination of multiple heating and deformation processes, which leads to problems such as difficulty in yield control, high cost, and difficulty in ensuring microstructure uniformity in actual large-scale production.

[0122] Furthermore, taking Example 3, which exhibits similar performance in Table 1, as an example, it achieves similar overall performance using only a simple process route of "room temperature rotary forging and short-time annealing," requiring only a 10-minute short-time annealing at 550°C as heat treatment, without the need for complex high-temperature pretreatment and multiple intermediate heat treatments. This sufficiently demonstrates that the present invention, through efficient and continuous deformation method of rotary forging, combined with a refined short-time heat treatment design, can achieve material performance levels comparable to traditional complex processes under conditions of shorter process flow, lower energy consumption, and simpler equipment, achieving the beneficial effects of similar performance but significantly simplified process and significantly reduced cost.

[0123] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a titanium alloy material, characterized in that, include: Titanium-niobium oxide alloy ingots containing α and β phases were rotary forged, with the α phase accounting for 18 VT.% to 22 VT.%. The titanium-niobium-oxygen alloy ingot comprises the following elemental composition by mass percentage: Ti 82%~84%, Nb 15.4%~17.0%, O 0.35%~0.55%; The preparation method includes one of the following steps (a) to (c): (a) The titanium-niobium-oxygen alloy ingot is subjected to short-time solution treatment, and then rotated in several passes, with the short-time solution treatment performed once between each pass of the rotational forging, and titanium alloy material is obtained after the rotational forging. (b) The titanium-niobium-oxygen alloy ingot is subjected to rotary forging in several passes, and then subjected to short-time annealing after rotary forging to obtain titanium alloy material; the duration of the short-time annealing is 8 min to 20 min. (c) The titanium-niobium-oxygen alloy ingot is subjected to short-time solution treatment and then water quenched, and then rotated in several passes, with a static treatment between each pass of the rotational forging. After the rotational forging, a short-time annealing treatment is performed to obtain the titanium alloy material. Step (a) includes the following features (A) to (D): (A) The temperature of the short-time solution treatment is 880℃~920℃, and the duration is 8min~40min; (B) The number of passes in the rotary forging is 2 to 8; (C) The radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3mm~12mm; (D) The axial feeding speed of the ingot material is 0.3m / min~0.8m / min, and the rotation frequency is 5rpm~15rpm; Step (c) includes the following features (I) to (V): (I) The temperature of the short-time solution treatment is 880℃~920℃, and the duration is 50min~75min; (II) The number of passes in the rotary forging is 2 to 8; (III) The radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3mm~12mm; (IV) The settling time for each settling process is independently 45 min to 75 min; (V) The temperature of the short-time annealing treatment is 400℃~700℃.

2. The preparation method according to claim 1, characterized in that, The impurity content of the titanium-niobium-oxygen alloy ingot is ≤0.3wt.%.

3. The preparation method according to claim 1, characterized in that, The titanium alloy material obtained in step (a) includes an α phase and a β phase; the titanium alloy material obtained in step (b) includes an α phase, an α' phase, and a β phase; and the titanium alloy material obtained in step (c) includes an α phase, a β phase, and a SIMα'' phase.

4. The preparation method according to claim 1, characterized in that, Step (b) includes at least one of the following features (1) to (4): (1) The number of passes in the rotary forging is 2 to 8; (2) The radial clearance of the hammer head in the rotary forging decreases with the increase of the number of passes, and the decrease range is 3mm~12mm; (3) In the rotary forging, the axial feeding speed of the ingot material is 0.3m / min~0.8m / min, and the rotation frequency is 5rpm~15rpm; (4) The temperature of the short-time annealing treatment is 400℃~700℃ and the duration is 8min~20min.

5. The titanium alloy material obtained by the preparation method according to any one of claims 1 to 4.

6. The use of the titanium alloy material as described in claim 5 in medical materials.

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