Preparation method of ultrafine-grain structure solid-solution oxygen reinforced Ti15Zr alloy

Abstract

The application provides a preparation method of a superfine-grain structure solid-solution oxygen-strengthened Ti15Zr alloy. The mechanical properties of the material are simultaneously improved through solid-solution oxygen atom strengthening and superfine-grain structure, on the basis of which, the comprehensive performance of the Ti-Zr alloy is further improved by eliminating the deformed structure and restoring the plasticity through a vacuum heat treatment process while retaining the fine-grain structure, so as to meet the safety of the Ti-Zr alloy in the service process of the human body.

Description

Technical Field

[0001] This invention belongs to the field of Ti-Zr alloys, specifically relating to a method for preparing an ultrafine-grained solid solution oxygen-reinforced Ti15Zr alloy. Background Technology

[0002] With the aging population and the development of medical technology, the demand for high-performance biomedical materials is increasing. The research and development of ultrafine-grained titanium-based materials has significant scientific importance and broad application prospects. Due to the excellent mechanical and biological properties of Ti-Zr alloys, research on Ti-Zr alloys has attracted widespread attention from researchers both domestically and internationally. In the 1990s, reference 1 developed a binary Ti-Zr alloy with a Zr content ranging from 5 to 25 wt.%. This alloy exhibits excellent mechanical strength and resistance to corrosion cracking, and shows good biocompatibility with both soft and hard human tissues. It can be used in components such as screws, plates, and nails for joint implants, dental implants, and facial prostheses. Currently, domestic and international research on medical Ti-Zr alloys mainly focuses on developing and preparing Ti-Zr alloy systems with higher mechanical properties. However, the strengthening mechanism of simple binary Ti-Zr alloys is mainly solid solution strengthening of Zr, and the degree of improvement in material strength is still very limited. Introducing other metallic elements increases the risk of metal particle release in medical titanium-based alloys compared to other multi-element systems. The design and development of novel titanium-based materials for medical implants requires improving the mechanical properties of the materials while ensuring their biocompatibility.

[0003] Therefore, strengthening Ti-Zr materials to improve their mechanical properties has received widespread attention in the development of medical implant materials. Literature reports that oxygen solid solution strengthening design can improve the strength, heat resistance, and corrosion resistance of titanium alloys within a certain range, while retaining their good plasticity, biocompatibility, and biocompatibility. However, although solid solution atoms can effectively improve the strength of Ti-Zr alloys, they still have a certain adverse effect on the plasticity of Ti-Zr alloys. Reference 2 points out that, as the oxygen content increases, the yield strength and tensile strength of Ti-Zr alloys significantly increase, but their ductility and fracture toughness significantly decrease. This phenomenon is because oxygen atoms occupy interstitial positions in the titanium and zirconium lattices, forming a strong solid solution strengthening effect, while inhibiting dislocation movement, thus increasing strength but reducing the material's plasticity. Reference 3 indicates that with increasing O content, the tensile strength, yield strength, and microhardness of Ti-3Zr-xO alloy samples increase, while plasticity decreases. When O ≥ 0.3 wt.%, the plasticity of the samples decreases significantly. Therefore, it is necessary to regulate the oxygen content and further control the microstructure of the Ti-Zr alloy reinforced with dissolved oxygen atoms in order to coordinate its strength and plasticity and achieve a synergistic improvement in the strength and plasticity of the Ti-Zr alloy.

[0004] Another effective way to improve the overall mechanical properties of medical titanium-based materials is to prepare titanium alloys with ultrafine grain structures through severe plastic deformation (SPD) processes. Ultrafine-grained titanium alloys obtained through SPD technology possess superior mechanical properties while maintaining the excellent corrosion resistance and biocompatibility of titanium alloys, and are therefore widely used to strengthen medical titanium alloy materials. Equal channel angular pressing (ECAP), as a type of SPD technology, has many advantages such as simple equipment and processes, a wide range of applicable materials, and high production efficiency. However, due to the limited movable slip system and poor machinability of titanium alloys, the process for preparing Ti-Zr alloys via ECAP is still under development.

[0005] In summary, while dissolved oxygen atoms can effectively improve the strength of Ti-Zr alloys, they still have a certain adverse effect on their plasticity. The process for preparing dissolved oxygen-controlled Ti-Zr alloys using large plastic deformation techniques is still under development. Based on the shortcomings of the above-mentioned ultrafine-grained Ti-Zr alloy preparation techniques, the applicant is committed to developing a method for preparing ultrafine-grained dissolved oxygen-reinforced Ti-15Zr-(0.3~0.6)O alloys. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an ultrafine-grained solid solution oxygen-reinforced Ti15Zr alloy.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for preparing an ultrafine-grained solid solution oxygen-reinforced Ti15Zr alloy includes the following steps:

[0009] (1) Material mixing

[0010] Ti-15Zr alloy powder and TiO2 powder are mixed in a certain proportion and then mixed using a powder mixer to ensure the uniformity of the powder.

[0011] (2) Cold isostatic pressing

[0012] The mixed powder is loaded into a flexible mold and placed in a cold isostatic press for pressurization within a certain pressure range for 20 to 40 minutes to form a high-density preform.

[0013] (3) Vacuum sintering

[0014] The cold isostatically pressed preforms are placed in a vacuum sintering furnace, and sintered at a vacuum degree of 10. -4 Pa, sintering at a certain temperature for a certain time, this process ensures the material's density and uniform microstructure.

[0015] (4) Rolling process

[0016] The sintered material is rolled at room temperature using a rolling mill, with a reduction rate of 10-15% and a rolling speed of 0.5-1 m / s.

[0017] (5) ECAP processing

[0018] After rolling, the material undergoes multiple passes of equal-channel angular extrusion at a certain angle and extrusion speed in the ECAP die system.

[0019] (6) Annealing treatment

[0020] The material treated with ECAP was annealed in a vacuum annealing furnace. Finally, by annealing at a certain temperature for a certain time, a Ti-15Zr-(0.3~0.6)O alloy with an ultrafine grain structure was obtained. The purpose of the annealing treatment is to eliminate the deformed structure and restore its plasticity while retaining the fine grain structure, thereby further improving the comprehensive performance of the Ti-Zr alloy.

[0021] Furthermore, in step (1), Ti-15Zr alloy powder and TiO2 powder are mixed in a mass ratio of 99.6:0.4.

[0022] Furthermore, in step (2), the pressure of the cold isostatic press is set to 300 MPa.

[0023] Furthermore, in step (3), the vacuum sintering temperature is 1200 ℃ and the sintering time is 4 h.

[0024] Furthermore, in step (5), the extrusion angle is 120° and the extrusion speed is 0.3 mm / s, and two extrusion processes are performed.

[0025] Furthermore, in step (5), equal channel corner extrusion is performed in the ECAP mold system. First, the surface of the titanium zirconium oxide rod is wrapped. In order to reduce the wear of the material on the mold during the deformation process, the channel corner position adopts a concentric arc transition design and is lubricated with molybdenum disulfide lubricant to avoid stress concentration and prevent cracking.

[0026] Furthermore, in step (6), the annealing temperature is 600 °C and the annealing time is 1 h.

[0027] Furthermore, the composition of the Ti-15Zr-(0.3~0.6)O alloy by mass percentage is: C≤0.08%, O0.3%-0.6%, N≤0.03%, H≤0.02%, Fe≤0.30%, Zr 14%-16%, with the balance being Ti.

[0028] Compared with existing technologies, the ultrafine-grained solid-solution oxygen-reinforced Ti15Zr alloy prepared by this invention has excellent mechanical and biological properties, and can be widely used in the biomedical field, possessing the following beneficial effects:

[0029] (1) Excellent performance: Solid solution oxygen atom strengthening and ultrafine grain structure simultaneously improve the mechanical properties of the material. On this basis, the vacuum heat treatment process can eliminate the deformed structure and restore its plasticity while retaining the fine grain structure, further improving the comprehensive performance of Ti-Zr alloy.

[0030] (2) Safety: The ultrafine-grained solid solution oxygen-reinforced Ti15Zr alloy prepared by this method has excellent biocompatibility and mechanical properties, which meets the safety requirements of implants during human service.

[0031] (3) Low process requirements: The surface of the titanium zirconium oxide rod is wrapped to reduce the wear of the material on the mold during the deformation process. The corner of the channel adopts a concentric arc transition design and through lubrication, stress concentration is avoided and cracking is prevented. Room temperature ECAP deformation is achieved. It is easy to produce in large quantities. Attached Figure Description

[0032] Figure 1The preparation process of an ultrafine-grained solid solution oxygen-reinforced Ti15Zr alloy;

[0033] Figure 2 The elemental content of the Ti-15Zr-(0.3~0.6)O alloy in the present invention patent scheme;

[0034] Figure 3 The microstructure of the rolled Ti-15Zr-(0.3~0.6)O alloy;

[0035] Figure 4 The stress-strain curves of the rolled Ti-15Zr-(0.3~0.6)O alloy are shown.

[0036] Figure 5 The ECAP process flow in the present invention patent solution;

[0037] Figure 6 The microstructure of Ti-15Zr-(0.3~0.6)O alloy after ECAP deformation;

[0038] Figure 7 The stress-strain curves of Ti-15Zr-(0.3~0.6)O alloy after ECAP deformation are shown.

[0039] Figure 8 The microstructure of Ti-15Zr-(0.3~0.6)O alloy after vacuum annealing;

[0040] Figure 9 The stress-strain curves of Ti-15Zr-(0.3~0.6)O alloy after vacuum annealing are shown. Detailed Implementation

[0041] To make the above-mentioned features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail. Unless otherwise specified, the methods of the present invention are conventional methods in the art.

[0042] Example 1

[0043] A preparation process for an ultrafine-grained solid solution oxygen-reinforced Ti15Zr alloy includes the following steps:

[0044] (1) Material mixing

[0045] Ti-15Zr alloy powder and TiO2 powder were mixed at a mass ratio of 99.6:0.4 and mixed using a powder mixer to ensure the uniformity of the powder.

[0046] (2) Cold isostatic pressing

[0047] The mixed powder is loaded into a flexible mold and placed in a cold isostatic press and pressurized at 300 MPa for 30 minutes to form a high-density preform.

[0048] (3) Vacuum sintering

[0049] The cold isostatically pressed preforms are placed in a vacuum sintering furnace, and sintered at a vacuum degree of 10. -4 Pa, sintered at 1200 ℃ for 4 h;

[0050] (4) Rolling process

[0051] The sintered material was rolled at room temperature using a rolling mill, with a reduction rate of 15% and a rolling speed of 1 m / s.

[0052] (5) ECAP processing

[0053] After rolling, the material undergoes two passes of equal-channel angular extrusion in the ECAP die system at an extrusion angle of 120° and an extrusion speed of 0.3 mm / s.

[0054] (6) Annealing treatment

[0055] The ECAP-treated material was annealed in a vacuum annealing furnace at 600 °C for 1 h to obtain a Ti-15Zr-(0.3~0.6)O alloy with an ultrafine grain structure. Its composition, by mass percentage, was: C 0.03%, O 0.38%, N 0.01%, H 0.01%, Fe 0.15%, Zr 14.9%, with the balance being Ti. Figure 2 As shown.

[0056] Existing Ti-Zr alloys lack sufficient strength, and dissolved oxygen strengthening can negatively impact ductility. The process for preparing ultrafine-grained Ti-Zr alloys via ECAP is still under development. This invention simultaneously improves the mechanical properties of the material through dissolved oxygen atom strengthening and ultrafine grain structure formation. Furthermore, a vacuum heat treatment process is used to eliminate deformed structures while preserving the fine-grained structure, restoring its ductility and further improving the overall performance of the Ti-Zr alloy to meet safety requirements during human service.

[0057] like Figure 1As shown, the present invention patent proposes a preparation process for an ultrafine-grained solid solution oxygen-reinforced Ti-15Zr alloy: First, Ti-15Zr alloy powder and TiO2 powder are mixed in a certain proportion. The oxygen content of the Ti-Zr-O material is designed to be 0.30~0.60 wt.%. A powder mixer is used to ensure uniform powder mixing. Then, the mixed powder is placed into a flexible mold and subjected to pressure treatment in a cold isostatic press within a certain pressure range for 20~40 minutes to form a high-density preform. Next, the cold isostatically pressed preform is placed in a vacuum sintering furnace at a vacuum degree of 10... -4 Pa, sintering at a certain temperature for different times, this process ensures the density and uniform microstructure of the material; the sintered material is rolled at room temperature by rolling equipment with a reduction rate of 10~15% and a rolling speed of 0.5~1m / s; then, multi-pass equal channel corner extrusion is carried out under certain angle and extrusion speed conditions, and finally, Ti-15Zr-(0.3~0.6)O alloy with ultrafine grain structure is obtained by annealing at a certain temperature for different times.

[0058] This invention patent solution uses a cold isostatic pressing + vacuum sintering method to directly obtain Ti-15Zr-(0.3~0.6)O material. For example... Figure 2 As shown, in a preferred embodiment of the present invention, Ti-15Zr alloy powder and TiO2 powder are mixed at a mass ratio of 99.6:0.4. The mixed powder is then placed into a flexible mold and subjected to pressure treatment in a cold isostatic press at a pressure of 300 MPa for 30 min. The cold-isostatically pressed preform is then placed in a vacuum sintering furnace at a vacuum degree of 10... -4 Sintering was carried out at 1200 ℃ for 4 h under the conditions of Pa.

[0059] This invention patent solution involves rolling the sintered material at room temperature using a rolling mill to further improve the material's density and microstructure uniformity. In a preferred embodiment of this invention patent solution, the reduction rate is set to 15%, the rolling speed is 1 m / s, and the microstructure of the material is as follows: Figure 3 The stress-strain curve is as follows Figure 4 As shown.

[0060] like Figure 5As shown in the patented solution of this invention, the rolled material undergoes equal-channel corner extrusion in the ECAP die system. First, the surface of the titanium-zirconium oxide bar is sheathed. To reduce wear on the die during deformation, a concentric arc transition design is used at the corner positions of the channels, and lubrication is employed to avoid stress concentration and prevent cracking. In a preferred embodiment of the patented solution of this invention, a two-pass material with a 120° extrusion angle and an extrusion speed of 0.3 mm / s is selected. The microstructure is as follows: Figure 6 The stress-strain curve is as follows Figure 7 As shown.

[0061] In this invention patent scheme, the material treated with ECAP is annealed in a vacuum annealing furnace. In a preferred embodiment of this invention patent scheme, the material after two passes of ECAP deformation is selected, the annealing temperature is set to 600 °C, and the time is 1 hour. The microstructure is as follows. Figure 8 The stress-strain curve is as follows Figure 9 As shown, the purpose of annealing is to eliminate residual stress introduced during the ECAP process and retain the ultrafine grain structure, thereby further improving the overall performance of the Ti-Zr alloy.

[0062] Figure 3 The metallographic microstructure of the invention preparation process up to (4) rolling process, wherein the average grain size is 2μm (the grains are relatively fine). Figure 4 The stress-strain curves from the invention's preparation process to the rolling process (4) are shown, with a tensile strength of 917 MPa, a yield strength of 859 MPa, and an elongation of 9.39%. Figure 5 The process of ECAP treatment is shown in the first picture, which is a copper cladding Ti-15Zr-(0.3~0.6)O. The second picture is the material being put into the mold. The third picture is the extrusion through a press. The fourth picture is the end of the extrusion. Figure 6 The metallographic microstructure of the invention preparation process up to (5) ECAP treatment step, wherein the grain size is 760nm (ultrafine grain structure ≤1μm). Figure 7 The stress-strain curves from the invention preparation process to the (5) ECAP treatment step are shown, where the tensile strength is 1080MPa, the yield strength is 932MPa, and the elongation is 8.59%. Figure 8 The metallographic microstructure of the invention preparation process up to the (6) annealing treatment step, wherein the grain size is 880nm (ultrafine grain structure ≤1μm). Figure 9 The stress-strain curve of the invention preparation process up to the annealing step (6) is shown. The tensile strength is 996 MPa, the yield strength is 945 MPa, the elongation is 13.1%, and the maximum strength-ductility product is (strength * elongation).

[0063] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

[0064] [1] Steinemann S. Binary titanium-zirconium alloy for surgical implants and a suitable manufacturing process: US Patent 8, 168, 012[P].2012-5-1.

[0065] [2] Fukuo M, Kariya S, Umeda J, et al.Strengthening mechanisms ofpowder metallurgy extruded CP titanium materials with zirconium and oxygensolid solution via decomposition of ZrO2 additives insintering[J]. MaterialsTransactions, 2019, 60(9): 1881-1889.

[0066] [3] Fei Yang, Wang Tao, Miao Runjie, et al. Effect of trace oxygen content on microstructure and mechanical properties of Ti-3Zr alloy [J]. Rare Metals & Hard Alloys, 2019, 6.

Claims

1. A method for preparing an ultrafine-grained solid solution oxygen-reinforced Ti15Zr alloy, characterized in that, Includes the following steps: (1) Material mixing Ti-15Zr alloy powder and TiO2 powder were mixed at a mass ratio of 99.6:0.4 and a powder mixer was used to ensure the uniformity of the powder. (2) Cold isostatic pressing The mixed powder is loaded into a flexible mold and placed in a cold isostatic press at 300 MPa for 20-40 minutes to form a high-density preform. (3) Vacuum sintering The cold isostatically pressed preforms are placed in a vacuum sintering furnace, and sintered at a vacuum degree of 10. -4 Pa, sintered at 1200 ℃ for 4 h; (4) Rolling process The sintered material is rolled at room temperature using a rolling mill, with a reduction rate of 10-15% and a rolling speed of 0.5-1 m / s. (5) ECAP processing After rolling, the material undergoes two passes of equal-channel angular extrusion in the ECAP die system at an extrusion angle of 120° and an extrusion speed of 0.3 mm / s. (6) Annealing treatment The material treated with ECAP was annealed in a vacuum annealing furnace at 600 °C for 1 h to obtain a Ti-15Zr-(0.3~0.6)O alloy with an ultrafine grain structure. In step (5), equal channel corner extrusion is performed in the ECAP mold system. First, the surface of the titanium zirconium oxide rod obtained in step (4) is wrapped. In order to reduce the wear of the material on the mold during the deformation process, the channel corner position adopts a concentric arc transition design and is lubricated with molybdenum disulfide lubricant to avoid stress concentration and prevent cracking.

2. The method according to claim 1, characterized in that, The composition of Ti-15Zr-(0.3~0.6)O alloy by mass percentage is: C≤0.08%, O 0.3%-0.6%, N≤0.03%, H≤0.02%, Fe≤0.30%, Zr 14%-16%, with the balance being Ti.

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