A pure titanium nanocrystal, its preparation method and application

Abstract

The present invention discloses a pure titanium nanocrystal and its preparation method and application. Using pure titanium as a raw material, forging is carried out to obtain a precursor blank; the precursor blank is heat-insulated at a temperature lower than T β for 1-2 h, and then rolling is carried out to obtain a pure titanium sheet; the pure titanium sheet is subjected to cyclic heat treatment, that is, a cyclic quenching-annealing process; the sheet after stable heat treatment is subjected to ultrasonic overlap welding treatment to obtain a pure titanium nanocrystal sheet. The present invention can achieve grain refinement and high strength of pure titanium metal, obtain a three-dimensional nanocrystal material with a certain thickness, and is used to prepare medical devices such as oral implants, abutments, and guided bone regeneration membranes.

Description

Technical Field

[0001] The present invention belongs to the field of medical devices, and particularly relates to a pure titanium nanocrystal and its preparation method and application. Background Art

[0002] Grain refinement is an effective means to improve the mechanical properties of metal materials. Currently, there are various methods for refining the grains of metals. One is to refine the grains through processing techniques, such as drawing method, equal-channel angular pressing method, etc.; the other is to refine the grains through composition improvement, such as adding nucleating agents to the metal to increase the amount of crystal nuclei formed per unit time, so that the grains grow simultaneously and hinder each other's growth to achieve the purpose of refinement. Patent CN202210584415.2 discloses a method for efficiently and low-costly preparing an industrial pure titanium billet for ultra-long fine-grained skew rolling piercing, which realizes the fragmentation of grains by using the process of single-pass blooming in the β phase region + one-pass large deformation rolling on a large-tonnage rolling mill, so that a fine-grained structure is formed in the product; however, this method can only achieve grain refinement in two dimensions, producing ultra-long fine grains, and the size in one dimension still cannot be refined, and three-dimensional fine grains cannot be made. Patent CN201410035189.8 provides a method for preparing a fine-grained TA15 titanium alloy thin plate for superplastic forming. After four passes of rolling, a fine-grained TA15 titanium alloy thin plate with a thickness of 0.6 mm to 2.5 mm for superplastic forming is obtained; however, its composition is Ti-6.5Al-2Zr-1Mo-1V, containing aluminum that cannot be metabolized by the human body and cannot be used in the biomedical field; in addition, the material with a thickness of 0.6 mm to 2.5 mm obtained by it cannot meet the size requirements of dental implants. Patent CN202210414071.0 relates to a method for refining the ferrite grain size in duplex stainless steel and duplex stainless steel, which is used to solve the problems of harsh preparation processes and large rolling deformation in the existing duplex stainless steel fine grain preparation; however, this method requires the assistance of alloying elements to achieve grain refinement and cannot meet the application scenario requirements for preparing implants based on pure titanium fine grains. The present invention mainly solves the following technical problems: 1. How to refine the grains of pure metals; 2. How to achieve high strength of materials; 3. How to prepare three-dimensional nanocrystalline materials with a certain thickness to meet the processing size requirements. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies existing in the prior art and provide a pure titanium nanocrystal and its preparation method and application, which can realize the grain refinement and high strength of pure titanium metal, obtain three-dimensional nanocrystalline materials with a certain thickness, and be used to prepare medical devices such as oral implants, abutments, and guided bone regeneration membranes.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A preparation method of a pure titanium nanocrystal, comprising the following steps:

[0006] (1) Using pure titanium as raw material, perform forging to obtain a precursor blank.

[0007] (2) Keep the precursor blank at a temperature 30 - 60 °C lower than T β for 1 - 2 h (T β is the β-phase transformation temperature of pure titanium), then perform rolling to obtain a pure titanium sheet.

[0008] (3) Perform cyclic heat treatment on the pure titanium sheet, that is, adopt the cyclic quenching - annealing process.

[0009] (4) Perform ultrasonic overlap welding on the sheet after heat treatment stabilization to obtain a pure titanium nanocrystalline sheet.

[0010] In step (1), the forging temperature is 800 - 1200 °C, the forging time is 5 - 10 min, and the forging reduction is 4 - 5 mm.

[0011] In step (1), after forging, keep the forged blank in a furnace at 1100 - 1200 °C for 0.5 - 1 h, then take it out and air cool, and then grind the forged blank to remove surface cracks and folding defects to obtain a precursor blank.

[0012] In step (2), the rolling process conditions are: the reduction per pass is 0.9 - 1 mm, and the rolling speed of the roll is 5 - 10 m / s; after each pass of rolling, quickly reheat for 1 - 3 minutes and then perform the next pass of rolling. Roll continuously more than once to obtain a pure titanium sheet with a thickness of 0.5 - 1 mm. Preferably, the number of continuous rolling passes is 5 or more.

[0013] In step (3), for the cyclic quenching - annealing process, first quench the pure titanium sheet in cold water at room temperature, and the quenching liquid temperature is 10 - 30 °C; then perform annealing treatment, the annealing temperature is 680 - 750 °C, and the annealing time is 0.5 - 1 h; then repeat the quenching treatment, and anneal after quenching, and the annealing temperature is reduced by 60 - 100 °C on the original basis; repeat the cyclic quenching - annealing more than once until the material no longer curls, that is, reach the state of residual stress elimination.

[0014] In step (4), before ultrasonic overlap welding treatment, first grind the surface of the material with a grinding wheel to remove the oxide layer and expose the fresh metal surface.

[0015] In step (4), the ultrasonic overlap welding process is to bring the largest surfaces of two sheets into contact with each other, and after fixation, overlap welding is carried out. The fixed static pressure is 0.6 - 1 MPa, the vibration frequency is 50 - 80 kHz, the amplitude is 5 - 25 μm, and the welding time is controlled within 4 - 10 s. After the two sheets are welded together, new sheets are stacked one by one for welding. As the thickness increases, the vibration frequency gradually increases by 5 - 10 KHz, and the number of overlap welding layers is 8 - 16 layers.

[0016] In step (4), the pure titanium nanocrystalline sheet after overlap welding is ground to remove pits and defects, and the thickness of the sheet is controlled between 6 - 12 mm.

[0017] A pure titanium nanocrystal is prepared by the above method.

[0018] The application of the above pure titanium nanocrystal is for preparing medical devices such as oral implants, abutments, guided bone regeneration membranes, etc.

[0019] The principle of the present invention is as follows: (1) By adopting multi-pass rolling in combination with cyclic quenching-annealing process, the ultrafine grain refinement of the material is realized without introducing other alloying elements. Through multi-pass rolling below the recrystallization temperature of the material, the internal grains are initially broken, and then combined with the cyclic quenching-annealing process. This is because after quenching, the material curls due to the uneven stress distribution during rolling. At this time, eliminating the residual stress can not only cause dislocation pile-up inside the material to further refine the grains, but also play a role in releasing stress. After several annealing-quenching cycles, when the material no longer curls and becomes flat naturally, it can be considered that the residual stress is eliminated and the material properties are stable. (2) By adopting ultrasonic overlap welding technology, thin sheets are overlapped and welded together to obtain a fine-grained material with a certain thickness. The ultrasonic welding time is short, no flux, gas, or solder is required, and by selecting process parameters, the welding material is controlled not to melt, and the grains will not grow secondary or recrystallize. In addition, by oscillating the material with ultrasonic waves, it is more conducive to refining the internal grains. After layer-by-layer stacking and welding, the overall thickness of the material can reach 6 - 12 mm, and the minimum size can meet the size processing requirements of oral implants. (3) The purpose of fine grains is to improve the material strength. The pure titanium fine-grained material prepared by this method has its strength nearly doubled on the basis of a slight increase in elongation.

[0020] Compared with the prior art, the present invention has the following advantages and effects:

[0021] (1) The present invention realizes the fine grain strengthening of pure metals. In the existing technologies for making fine grains of materials, there has been no report on pure metals. The present invention selects pure titanium metal as the base material to achieve the elementalization of the material. The fewer the types of alloys introduced into the material, the higher the safety of the material made into an implant. The difficulty in refining the grains inside pure metals lies in the absence of alloying elements for assisting nucleation, and it is difficult to accumulate dislocations, making it hard to form fine grains or even ultrafine grains. The present invention refines the grains of the material to the nanoscale through a multi-pass rolling and cyclic heat treatment process flow, thereby greatly improving the mechanical properties of the material.

[0022] (2) The present invention uses a cyclic heat treatment method to release the residual stress inside the thin plate, making the material flatten naturally and avoiding the risks of warping and cracking during subsequent overlay welding.

[0023] (3) The present invention uses an ultrasonic overlay welding method to laminate thin materials to thicken the material. There are fewer defects inside the material, and it can still maintain a fine grain state with improved strength. The grain refinement of the present invention has multiple dimensions. Compared with the prior art that can only prepare single-oriented fine grain rods, this material can achieve three-dimensional nanoscale grain refinement.

[0024] (4) The material prepared by the present invention has strong properties. Compared with ordinary pure titanium, the tensile strength of pure titanium after fine grain treatment can reach more than 1200 MPa, meeting the requirements of small size and high strength in the preparation of implants. Description of the Drawings

[0025] Figure 1 Effect diagram of the cyclic heat treatment process.

[0026] Figure 2 Microscopic morphology and grain size of different materials.

[0027] Figure 3 Histogram of Rockwell hardness distribution of different materials.

[0028] Figure 4 Histogram of tensile strength distribution of different materials.

[0029] Figure 5 Histogram of elongation distribution of different materials.

[0030] Figure 6 Contact angle data diagram of different materials. Detailed Description of the Invention

[0031] For the convenience of understanding the present invention, the present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention. However, the present invention is not limited in any form. It should be noted that for those skilled in the art, without departing from the concept of the present invention, the present invention can also be made with several deformations and improvements, and these all belong to the protection scope of the present invention.

[0032] Example 1. Forging the precursor blank

[0033] Using industrial pure titanium TA4 with a diameter of 10 mm as the raw material, the material is forged at 800 °C. A 3500T press is used, the forging time is 10 min, and the forging reduction is 4 mm, to obtain a long strip-shaped material with an approximately rectangular cross-section, and the cross-sectional dimensions are 12 mm in length and 6 mm in width.

[0034] After forging, it is taken out and air-cooled after being kept warm at 1100 °C in the furnace for 1 h. The forged blank is ground with a grinding wheel to remove the surface cracks and folding defects, to obtain the precursor blank.

[0035] Example 2. Forging the precursor blank

[0036] Using industrial pure titanium TA4 with a diameter of 10 mm as the raw material, the material is forged at 1000 °C. A 3500T press is used, the forging time is 8 min, and the forging reduction is 4.5 mm, to obtain a long strip-shaped material with an approximately rectangular cross-section, and the cross-sectional dimensions are 13 mm in length and 5.5 mm in width.

[0037] After forging, it is taken out and air-cooled after being kept warm at 1150 °C in the furnace for 40 min. The rolled forged blank is ground with a grinding wheel to remove the surface cracks and folding defects, to obtain the precursor blank.

[0038] Example 3. Forging the precursor blank

[0039] Using industrial pure titanium TA4 with a diameter of 10 mm as the raw material, the material is forged at 1200 °C. A 3500T press is used, the forging time is 5 min, and the forging reduction is 5 mm, to obtain a long strip-shaped material with an approximately rectangular cross-section, and the cross-sectional dimensions are 15 mm in length and 5 mm in width.

[0040] After forging, it is taken out and air-cooled after being kept warm at 1200 °C in the furnace for 0.8 h. The rolled forged blank is ground with a grinding wheel to remove the surface cracks and folding defects, to obtain the precursor blank.

[0041] Example 4. Rolling pure titanium sheets

[0042] The prepared precursor blank is kept warm at a temperature lower than T β by 30 °C for 1 h (T βis the β-phase transformation temperature of commercially pure titanium. Then, it enters the rolling machine. The reduction per pass is controlled at 0.9 mm, and the rolling speed of the rolls is 5 m / s. After each pass of rolling, it is quickly reheated for 1 minute and then the next pass of rolling is carried out. Rolling is carried out continuously five times. A pure titanium sheet with a thickness of 1 mm is obtained.

[0043] Example 5: Rolling of pure titanium sheet

[0044] The prepared precursor billet is kept at a temperature below T β for 1.5 h at 45 °C (T β is the β-phase transformation temperature of commercially pure titanium). Then, it enters the rolling machine. The reduction per pass is controlled at 0.95 mm, and the rolling speed of the rolls is 8 m / s. After each pass of rolling, it is quickly reheated for 2 minutes and then the next pass of rolling is carried out. Rolling is carried out continuously five times. A pure titanium sheet with a thickness of 0.75 mm is obtained.

[0045] Example 6: Rolling of pure titanium sheet

[0046] The prepared precursor billet is kept at a temperature below T β for 2 h at 60 °C (T β is the β-phase transformation temperature of commercially pure titanium). Then, it enters the rolling machine. The reduction per pass is controlled at 1 mm, and the rolling speed of the rolls is 10 m / s. After each pass of rolling, it is quickly reheated for 3 minutes and then the next pass of rolling is carried out. Rolling is carried out continuously five times. A pure titanium sheet with a thickness of 0.5 mm is obtained.

[0047] Example 7: Cyclic heat treatment

[0048] The rolled pure titanium sheet is quenched in cold water at room temperature, and the temperature of the quenching liquid is 10 °C. After quenching, the material may curl due to uneven stress distribution during rolling. At this time, annealing treatment is carried out to eliminate the residual stress. The annealing temperature is 680 °C, and the annealing time is 0.5 h. Then, the quenching treatment is repeated, and after quenching, annealing is carried out. The annealing temperature is reduced by 100 °C on the original basis. After several annealing-quenching cycles, when the material no longer undergoes curling changes, it can be considered that the residual stress is eliminated and the material properties are stable.

[0049] Example 8: Cyclic heat treatment

[0050] The rolled pure titanium sheet is quenched in cold water at room temperature, and the temperature of the quenching liquid is 20 °C. After quenching, the material may curl due to uneven stress distribution during rolling. At this time, annealing treatment is carried out to eliminate the residual stress. The annealing temperature is 700 °C, and the annealing time is 40 min. Then, the quenching treatment is repeated, and after quenching, annealing is carried out. The annealing temperature is reduced by 80 °C on the original basis. After several annealing-quenching cycles, when the material no longer undergoes curling changes, it can be considered that the residual stress is eliminated and the material properties are stable.

[0051] Example 9: Cyclic heat treatment

[0052] The rolled pure titanium sheet is quenched in normal-temperature cold water, and the temperature of the quenching liquid is 30°C. After quenching, the material may curl due to uneven stress distribution during rolling. At this time, annealing treatment is carried out to eliminate the residual stress. The annealing temperature is 750°C, and the annealing time is 1h. Then, the quenching treatment is repeated, and after quenching, annealing is performed. The annealing temperature is reduced by 60°C on the original basis. After several annealing-quenching cycles, when the material no longer undergoes curling changes, it can be considered that the residual stress is eliminated and the material properties are stable.

[0053] Figure 1 For a group of comparative examples, in order to show the effect of the cyclic heat treatment process, Figure a is a pure titanium plate just after rolling, and it can be seen that there is warping due to uneven stress; Figure b is a plate processed by the cyclic heat treatment method, and the internal stress has been eliminated, and it is relatively flat, suitable for the next process.

[0054] Example 10: Preparation of pure titanium nanocrystalline sheet by ultrasonic overlap welding

[0055] Using a metal ultrasonic welding machine, the surface of the pure titanium sheet is polished smoothly to remove the oxide layer and expose the fresh metal surface. The largest surfaces of the two sheets are brought into contact with each other, and after fixing, overlap welding is carried out. The fixed static pressure is 0.6MPa, the vibration frequency is 80kHz, the amplitude is 5μm, and the welding time is controlled within 10s. After the two sheets are welded together, new sheets are stacked one by one for welding. As the thickness increases, the vibration frequency gradually increases by 5KHz, and the number of overlap welding layers is 16. The completed pure titanium nanocrystalline sheet is ground to remove pits and defects, and the thickness of the titanium plate is controlled at 12mm.

[0056] Example 11: Preparation of pure titanium nanocrystalline sheet by ultrasonic overlap welding

[0057] Using a metal ultrasonic welding machine, the surface of the pure titanium sheet is polished smoothly to remove the oxide layer and expose the fresh metal surface. The largest surfaces of the two sheets are brought into contact with each other, and after fixing, overlap welding is carried out. The fixed static pressure is 0.8MPa, the vibration frequency is 75kHz, the amplitude is 15μm, and the welding time is controlled within 6s. After the two sheets are welded together, new sheets are stacked one by one for welding. As the thickness increases, the vibration frequency gradually increases by 8KHz, and the number of overlap welding layers is 14. The completed pure titanium nanocrystalline sheet is ground to remove pits and defects, and the thickness of the titanium plate is controlled at 9mm.

[0058] Example 12: Preparation of pure titanium nanocrystalline sheet by ultrasonic overlap welding

[0059] Using a metal ultrasonic welding machine, the surface of the pure titanium sheet was polished smoothly to remove the oxide layer and expose the fresh metal surface. The largest surfaces of the two sheets were brought into contact with each other, and after being fixed, they were overlapped and welded. The fixed static pressure was 1 MPa, the vibration frequency was 50 kHz, the amplitude was 25 μm, and the welding time was controlled at 4 s. After the two sheets were welded together, new sheets were successively stacked and welded. As the thickness increased, the vibration frequency gradually increased by 10 KHz, and the number of stacked welding layers was 8. The pure titanium nanocrystalline sheet after stacked welding was ground to remove pits and defects, and the thickness of the titanium plate was controlled at 6 mm.

[0060] Test Example 1: Measurement of the Grain Size of the Material

[0061] The grain size of the pure titanium nanocrystalline thin sheet prepared by the present invention was observed, measured and statistically analyzed by using a transmission electron microscope and a metallographic microscope. The commercially available industrial pure titanium TA4 was used as the control group. The experimental groups were the pure titanium nanocrystalline sheets prepared in Examples 10, 11, and 12, numbered A, B, and C respectively, and the industrial pure titanium in the control group was numbered D. The grain morphologies of the four materials are as Figure 2 shown. The grain sizes after test and statistics are shown in the following table:

[0062] Material Number A B C D Size (nm) 120±8 80±5 100±6 21000±2000

[0063] It can be seen that compared with the micron-sized grain size of the industrial pure titanium in the control group, the grain size of the pure titanium nanocrystals prepared by the present invention is significantly refined in three dimensions, and no elongated grains can be found, meeting the nanoscale requirements.

[0064] Test Example 2: Mechanical Property Test

[0065] The hardness, tensile strength and elongation of the materials were tested, and the results are as Figure 3 , 4 , 5 shown. Analyzing Figure 3 's hardness test results, compared with the industrial pure titanium control group, the HRC hardness of the pure titanium nanocrystalline sheets prepared by the methods described in Examples 10, 11, and 12 remained at about 70 (68 - 75), while the control group was only about 35. Analyzing Figure 4 's tensile strength results, compared with the industrial pure titanium control group, the tensile strength of the pure titanium nanocrystalline sheets prepared by the methods described in Examples 10, 11, and 12 all reached above 1200 MPa, much higher than 680 MPa of the control group. Analyzing Figure 5 's elongation test results, compared with the industrial pure titanium control group, the plasticity of the pure titanium nanocrystalline sheets prepared by the methods described in Examples 10, 11, and 12 was improved, remaining above 17%. In summary, it shows that for the materials processed by the method of the present invention, the hardness, strength, and plasticity indexes have been greatly improved.

[0066] Test Example 3: Contact Angle Test

[0067] The wettability of the material surface was contacted with deionized water, and the contact angle was detected by a contact angle measuring instrument.

[0068] Figure 6 It was a contact angle experiment using deionized water. The left and right contact angles were listed in the figure respectively. It can be seen from the results that there was no significant difference in the contact angle data between the experimental group and the control group, and both were less than 60°. This indicated that the surface was a hydrophilic surface, and the hydrophilicity did not change significantly before and after treatment, which was suitable for subsequent surface treatment or direct implantation. The angles on the left and right sides were basically symmetrically distributed along the central axis, indicating that the material surface was flat and smooth, and the data quality was high.

[0069] The above are only the embodiments of the present invention, but the implementation manners of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention are equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing pure titanium nanocrystals, characterized in that It includes the following steps: (1) Using pure titanium as the raw material, forging to obtain a precursor blank; (2) Keep the precursor blank at a temperature 30 - 60 °C lower than T β for heat preservation for 1 - 2 h, and then perform rolling to obtain a pure titanium sheet; (3) Subjecting the pure titanium sheet to cyclic heat treatment, i.e., adopting a cyclic quenching-annealing process; the cyclic quenching-annealing process is to first quench the pure titanium sheet in cold water at room temperature, with the quenching liquid temperature being 10-30°C; then perform annealing treatment, with the annealing temperature being 680-750°C and the annealing time being 0.5-1 h; then repeat the quenching treatment, followed by annealing, and the annealing temperature is reduced by 60-100°C on the original basis; the cyclic quenching-annealing is repeated more than once until the residual stress is eliminated; (4) Subjecting the sheet after heat treatment stabilization to ultrasonic overlap welding to obtain a pure titanium nanocrystalline sheet; the ultrasonic overlap welding is to bring the largest surfaces of the two sheets into contact with each other, fix them and then perform overlap welding, with the fixed static pressure being 0.6-1 MPa, the vibration frequency being 50-80 kHz, the amplitude being 5-25 μm, and the welding time being controlled within 4-10 s; after the two sheets are welded together, new sheets are successively stacked and welded, and as the thickness increases, the vibration frequency gradually increases by 5-10 KHz, and the number of overlap welding layers is 8-16 layers.

2. The preparation method of pure titanium nanocrystals according to claim 1, characterized in that: In step (1), the forging temperature is 800-1200°C, the forging time is 5-10 min, and the forging reduction is 4-5 mm.

3. The preparation method of pure titanium nanocrystals according to claim 1, wherein: In step (1), after forging, the forged blank is kept in a furnace at 1100-1200°C for 0.5-1 h, then taken out and air-cooled, and then the forged blank is ground to remove the surface cracks and folding defects to obtain the precursor blank.

4. The preparation method of pure titanium nanocrystals according to claim 1, characterized in that: In step (2), the rolling process conditions are: the reduction per pass is 0.9-1 mm, and the rolling speed of the rolling mill rolls is 5-10 m / s; after each pass of rolling, it is quickly reheated for 1-3 minutes and then the next pass of rolling is carried out, and continuous rolling is performed more than once to obtain a pure titanium sheet with a thickness of 0.5-1 mm.

5. The preparation method of pure titanium nanocrystals according to claim 1, characterized in that: In step (4), before the ultrasonic overlap welding treatment, the surface of the material is first ground with a grinding wheel to remove the oxide layer and expose the fresh metal surface.

6. The preparation method of pure titanium nanocrystals according to claim 1, characterized in that: In step (4), the pure titanium nanocrystalline sheet after overlap welding is ground to control the sheet thickness between 6-12 mm.

7. A pure titanium nanocrystal, characterized in that: It is prepared by using the method described in any one of claims 1-6.

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