A rare earth doped Ti-Nb-Dy alloy and its preparation and processing method

Abstract

The present invention provides a rare earth-doped Ti-Nb-Dy titanium alloy and a preparation and processing method thereof, comprising weighing Ti, Nb, and Dy raw materials according to a composition ratio of 23 to 30% Nb, 0.1 to 5% Dy, and the balance Ti, smelting the raw materials into an alloy ingot in a vacuum melting furnace using a non-consumable vacuum arc melting process, and subjecting the alloy ingot to a solid solution treatment and processing to obtain a rare earth element Dy-doped Ti-Nb-Dy alloy. By doping the rare earth element Dy into the Ti-Nb alloy, the alloy contains Ti, Nb, and Dy elements. The rare earth element Dy has a high affinity for O atoms in the melt and can capture interstitial oxygen in the alloy matrix, reducing the oxygen content in the alloy matrix. After the alloy in a solid solution state is processed, more defects are introduced into the alloy, reducing the elastic modulus of the titanium alloy, while maintaining a high yield strength of the alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloys, and in particular to a rare earth-doped Ti-Nb-Dy alloy and a preparation and processing method thereof, and more particularly to a Ti-Nb-Dy alloy in the biomedical field having superelasticity, low elastic modulus, chemical stability, high corrosion resistance and good biocompatibility. Background Art

[0002] As a multifunctional material with high strength, low elastic modulus and good thermal stability, titanium alloy has been widely used in aerospace, automotive and marine, sports equipment and biomedicine fields. Due to the excellent comprehensive mechanical properties, good corrosion resistance and biocompatibility of titanium alloy itself, stainless steel and cobalt-based alloys that were once the main materials for human implants have been gradually replaced by titanium alloy. Studies have found that the elastic modulus of human bone is only about 30GPa. If the elastic modulus of the implant is higher than that of the surrounding bone tissue, a stress shielding effect will occur clinically, which will lead to implant failure and fracture, bone atrophy and even fracture. Therefore, the design and development of low modulus and high strength titanium alloys has always been a research hotspot in the field of biomedical devices.

[0003] The α+β titanium alloys Ti-6Al-4V and Ti-6Al-7Nb, which are widely used in clinical medicine, have elasticity that has dropped to about half of that of stainless steel and cobalt-based alloys, at approximately 110 GPa, which reduces the stress shielding effect to a certain extent. However, this system of alloys will wear and corrode due to long-term implantation in the human body, thereby releasing Al and V ions that are cytotoxic and neurotoxic. TiNi-based shape memory alloys have excellent functional properties such as superelasticity and shape memory effect, as well as comprehensive mechanical properties, but the Ni element in them can cause allergic reactions in some people and is carcinogenic. Therefore, since the mid-1990s, researchers have focused on developing biomedical titanium alloy materials that do not contain Ni.

[0004] At present, α+β and β-type titanium alloys with excellent biocompatibility have been developed one after another, including Ti-15Zr-4Nb-4Ta-0.2Pd, Ti-15Zr-4Nb-aTa-0.2Pd-(0.20~0.05)N, Ti-15Sn-4Nb-2Ta-0.2Pd and Ti-15Sn-4Nb-2Ta-0.2Pd-0.2O, as well as Ti-12Mo-Zr-2Fe, Ti-13Nb-13Zr, Ti-15Mo-2.5Nb-0.2Si, Ti-16Nb-9.5Hf and Ti-15Mo. The corrosion strength, fatigue strength and corrosion resistance of these alloys are better than those of Ti-6Al-4V, among which Ti-Nb titanium alloys are quite a few. Compared with α and α+β titanium alloys, metastable β titanium alloys have a lower elastic modulus and therefore have better human body mechanical compatibility.

[0005] In recent years, Ti-Nb-based metastable β-type titanium alloys have gradually become an important development direction for the next generation of biomedical titanium alloys. However, the low strength of Ti-Nb binary alloys has severely limited their widespread application. Currently, most research focuses on improving their strength by adding large amounts of solid solution elements. Metastable β-type titanium alloys such as Ti 24Nb 4Zr 7.9Sn, Ti 29Nb 13Ta 4.6Zr, Ti 25Nb 3Mo 3Zr 2Sn, and Ti 35N 5TaZr have been developed and are gradually being used in clinical practice. However, these alloys have certain shortcomings in large-scale commercial production. These alloys contain a large number of β-stabilizing elements (such as Ta and Mo) and / or neutral elements (such as Zr, Hf, and Sn), resulting in complex alloy compositions. Impurities are easily introduced during the preparation process, causing element segregation and other phenomena, which affect the alloy properties. In addition, titanium alloys are highly susceptible to oxygen absorption and oxidation during the preparation process. Oxygen atoms present as interstitial point defects significantly increase the elastic modulus of the metastable β-titanium alloy matrix and inhibit the thermoelastic martensitic transformation. Currently, the preparation and processing of low-oxygen titanium alloys is typically performed using ultra-high-purity raw metals and an ultra-high vacuum atmosphere, which is extremely costly. Summary of the Invention

[0006] The purpose of the present invention is to provide a rare earth-doped Ti-Nb-Dy alloy and its preparation and processing methods to solve the problems of complex alloy composition and high production cost in existing Ti-Nb-based biomedical alloys, thereby obtaining a new metastable β-type titanium alloy with low modulus, high strength, superelasticity and good biocompatibility. This alloy can be widely used in biomedical and aerospace equipment. To achieve the above objectives, the present invention discloses a rare earth-doped Ti-Nb-Dy alloy preparation and processing method, which is characterized by comprising the following steps:

[0007] (1) Weighing Ti, Nb, and Dy raw materials in a composition ratio of 23 to 30 atomic percent Nb, 0.1 to 5 atomic percent Dy, and the balance Ti, and melting the raw materials into an alloy ingot in a vacuum melting furnace using a non-consumable vacuum arc melting process;

[0008] (2) subjecting the alloy ingot prepared in step (1) to a solid solution treatment under an argon protective atmosphere to obtain a rare earth element Dy-doped Ti-Nb-Dy superelastic low modulus titanium alloy;

[0009] (3) Processing the Ti-Nb-Dy alloy obtained in step (2) to obtain a processed alloy.

[0010] Titanium alloys are prone to the introduction of interstitial oxygen atoms during smelting and subsequent thermomechanical treatment, resulting in a high oxygen content and a solid solution of oxygen in the alloy matrix, which in turn increases the modulus. By doping the rare earth element Dy into a Ti-Nb alloy, the alloy is made to contain Ti, Nb, and Dy elements. The rare earth element Dy has a high affinity for O atoms in the melt and can capture interstitial oxygen from the alloy matrix, reducing the oxygen content in the alloy matrix. The addition of Dy not only refines the titanium alloy grains but also reduces the elastic modulus of the titanium alloy, increasing the alloy's plasticity while maintaining a high strength. The Nb content in the titanium alloy of the present invention is 23-30%, ensuring that the alloy has superelasticity of 2%, an elastic modulus of less than 41 GPa, and high damping properties at room temperature.

[0011] In one embodiment of the present invention, the purity of Ti, Nb and Dy in the raw materials is not less than 99.9%.

[0012] In one embodiment of the present invention, the percentage of Nb atoms in the alloy is 23-26%, preferably 25%.

[0013] In one embodiment of the present invention, the percentage of Dy atoms in the alloy is 0.3-4%, preferably 0.5-4%.

[0014] In one embodiment of the present invention, the sum of the atomic percentages of Nb and Dy in the alloy is not higher than 35%. The total content of Nb and Dy is not higher than 35%, thereby controlling the oxygen content while ensuring the alloy properties and achieving better strengthening effect.

[0015] In one embodiment of the present invention, the heat treatment process is solution treatment at 800-1200° C. in an argon environment for 1-40 hours, followed by quenching.

[0016] In one embodiment of the present invention, the cooling method includes water quenching or ice-salt water quenching.

[0017] In one embodiment of the present invention, the processing is cold processing, and the cold processing includes at least one of cold rolling, cold wire drawing, cold rotary forging or cold heading deformation.

[0018] In one embodiment of the present invention, the deformation rate during cold working is greater than 80%.

[0019] In one embodiment of the present invention, the total deformation rate after processing is 80-99%, and the single deformation amount is 0.1-4%.

[0020] The present invention also discloses a Ti-Nb-Dy alloy obtained according to the above preparation and processing methods.

[0021] The object of the present invention is to provide a use of the above-mentioned Ti-Nb-Dy alloy in biomedical equipment, aerospace equipment, and sports equipment.

[0022] In one embodiment of the present invention, the use includes the use of Ti-Nb-based titanium alloy in biomedical human implants, and the biomedical human implants include artificial knee joints, hip joints, femoral stems, cervical vertebrae, medullary bones, screws and tooth roots.

[0023] Beneficial effects of the present invention:

[0024] 1. By doping the rare earth element Dy into the Ti-Nb alloy, the alloy contains Ti, Nb and Dy elements. The rare earth element Dy has a high affinity for O atoms in the melt. The Dy element can capture the interstitial oxygen in the alloy matrix and reduce the oxygen content in the alloy matrix. The addition of the Dy element can not only refine the titanium alloy grains, but also reduce the elastic modulus of the titanium alloy while maintaining a high strength of the alloy.

[0025] 2. The Ti-Nb-Dy alloy of the present invention is produced by a non-consumable vacuum arc melting process, and is subjected to heat treatment and cold working to obtain alloy plates. After the solid solution alloy is cold worked, more defects are introduced into the alloy, thereby greatly reducing the elastic modulus of the alloy and increasing the yield strength. The elastic modulus of the Ti-Nb-Dy alloy of the present invention is as low as 35.9 GPa, and the yield strength is as high as 680 MPa.

[0026] 3. The alloy obtained using the method of the present invention has low modulus, high strength, superelasticity, shape memory, damping properties, corrosion resistance, and high biocompatibility. The modulus of the titanium alloy obtained by the present invention is similar to that of human bone and can be used as bone transplants or medical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a backscattered contrast-scanning electron microscope photograph of a Ti-25Nb-0.5Dy alloy solid solution sample of the present invention;

[0028] Figure 2 This is a backscattered contrast-scanning electron microscope photograph of the Ti-25Nb-2Dy alloy solid solution sample of the present invention;

[0029] Figure 3 This is a backscattered contrast-scanning electron microscope photograph of a Ti-25Nb-4Dy alloy solid solution sample of the present invention;

[0030] Figure 4 is the tensile curve of the Ti-25Nb-0.5Dy alloy of the present invention after cold rolling;

[0031] Figure 5is the superelastic tensile curve of the Ti-25Nb-0.5Dy alloy of the present invention after cold rolling;

[0032] Figure 6 is the tensile curve of the Ti-25Nb-2Dy alloy of the present invention after cold rolling;

[0033] Figure 7 is the superelastic tensile curve of the Ti-25Nb-2Dy alloy of the present invention after cold rolling;

[0034] Figure 8 This is the tensile curve of the Ti-25Nb-4Dy alloy of the present invention after cold rolling. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below based on embodiments in conjunction with the accompanying drawings. The embodiments are merely for explaining the present invention and do not constitute a limitation to the present invention.

[0036] Example 1

[0037] Three pure metal raw materials, Ti, Nb, and Dy, with a purity of no less than 99.9% and a content ratio of 74.5%, 25%, and 0.5%, respectively, were melted in a non-consumable vacuum arc furnace. To ensure uniform alloy composition, the ingots were flipped and repeatedly melted ten times to produce alloy ingots. After sandpaper grinding and polishing, the samples were solution treated in an argon atmosphere at 1000°C for 24 hours, followed by quenching in ice-salt water. The alloy ingot samples after solution treatment were cold rolled. The deformation was 0.5% per cold rolling until the total deformation was less than 80%; after the total deformation exceeded 80%, the deformation was 0.25% per cold rolling. The cold-rolled samples were in the form of plates with a total deformation of approximately 95%.

[0038] The microstructure of the solid solution Ti-25Nb-0.5Dy alloy sample is as follows: Figure 1 As shown, the average grain size is 60 μm. Compared to the grain size of a solid solution Ti-25Nb sample (~2 mm) obtained under the same preparation and heat treatment conditions, the grain refinement is significant. Dy exists as Dy2O3 oxide particles both at the grain boundaries and within the grains. The Dy2O3 at the grain boundaries is larger (~1 μm), while the Dy2O3 within the grains is much smaller, predominantly on the nanoscale (~100 nm).

[0039] Example 2

[0040] Three pure metal raw materials, Ti, Nb, and Dy, with a purity of no less than 99.9% and a content ratio of 73%, 25%, and 2%, respectively, were melted in a non-consumable vacuum arc furnace. To ensure uniform alloy composition, the ingots were flipped and repeatedly melted ten times to produce alloy ingots. After sandpaper grinding and polishing, the samples were solution treated in an argon atmosphere at 1000°C for 24 hours, followed by quenching in ice-salt water. The solution-treated alloy ingot samples were cold rolled. Each cold rolling deformation was 0.5% before the total deformation fell below 80%, and 0.25% after the total deformation exceeded 80%. The cold-rolled samples were in the form of plates with a total deformation of approximately 95%.

[0041] The microstructure of the solid solution Ti-25Nb-2Dy alloy sample is as follows: Figure 2 As shown in the figure, the average grain size is 35 μm. Compared with the sample in Example 1, the particle size, density and volume fraction of Dy2O3 in the sample have increased significantly. The size of Dy2O3 at the grain boundary has not changed much (~2 μm), while the size of Dy2O3 within the crystal has increased significantly, mainly to the submicron scale (~0.5 μm).

[0042] Example 3

[0043] Three pure metal raw materials, Ti, Nb, and Dy, with a purity of no less than 99.9% and a content ratio of 71%, 25%, and 4%, respectively, were melted in a non-consumable vacuum arc furnace. To ensure uniform alloy composition, the ingots were flipped and repeatedly melted ten times to produce alloy ingots. After sandpaper grinding and polishing, the samples were solution treated in an argon atmosphere at 1000°C for 24 hours, followed by quenching in ice-salt water. The solution-treated alloy ingot samples were cold rolled. Each cold rolling deformation was 0.5% until the total deformation fell below 80%, and 0.25% after the total deformation exceeded 80%. The cold-rolled samples were in the form of plates with a total deformation of approximately 95%.

[0044] The microstructure of the solid solution Ti-25Nb-4Dy alloy sample is as follows: Figure 3 As shown in the figure, the average grain size is 30 μm. Compared with the sample in Example 2, the particle size, density and volume fraction of Dy2O3 in the sample have increased significantly. The Dy2O3 at the grain boundaries are connected into line segments, while the size of Dy2O3 inside the crystals is significantly increased, mainly in the micron scale (~2 μm).

[0045] Tensile properties testing

[0046] The titanium alloy plates prepared in Examples 1, 2 and 3 were cut into 20×4×1 mm samples and -4 s -1The tensile test was carried out at a strain rate of . To ensure the accuracy of the tensile elastic modulus and superelastic strain measurement, an extensometer was used to record the strain value. The elastic modulus was calculated from the linear elastic deformation section of the stress-strain curve. The tensile curves were as follows: Figure 4 、 Figure 6 and Figure 8 When measuring superelasticity, the titanium alloy plate samples prepared in Examples 1 and 2 were loaded and unloaded before plastic yield. The total strain recovered during the unloading process was taken as the superelastic strain. The results are shown in Figure 5 and Figure 7 .

[0047] from Figure 4 The results show that the alloy Ti-25Nb-0.5Dy in Example 1 exhibits good tensile properties, with an elastic modulus of 35.9 GPa and a yield strength of 678 MPa.

[0048] from Figure 5 The results show that the alloy Ti-25Nb-0.5Dy in Example 1 exhibits good superelasticity, and its superelastic strain reaches 2.1%.

[0049] from Figure 6 The results show that the alloy Ti-25Nb-2Dy in Example 2 also exhibits good tensile properties, with an elastic modulus of 40.8 GPa and a yield strength of 683 MPa.

[0050] from Figure 7 The results show that the alloy Ti-25Nb-2Dy in Example 2 exhibits good superelasticity, and its superelastic strain reaches 2%.

[0051] from Figure 8 The results show that the alloy Ti-25Nb-4Dy in Example 3 also exhibits good tensile properties, with an elastic modulus of 41.6 GPa and a yield strength of 686 MPa.

Claims

1. A method for preparing a low modulus superelastic Ti-Nb-Dy alloy for biomedical devices, characterized in that: The following steps are involved: (1) According to the composition ratio of 23-30% atomic percentage of Nb, 0.5-2% of Dy, and the balance of Ti, weigh Ti, Nb, and Dy raw materials, and use a non-consumable vacuum arc melting process to melt the raw materials into an alloy ingot in a vacuum melting furnace, wherein the sum of the atomic percentages of Nb and Dy is not higher than 31%; (2) subjecting the alloy ingot prepared in step (1) to solid solution treatment in an argon protective atmosphere and quenching to obtain a Ti-Nb-Dy alloy doped with the rare earth element Dy; (3) cold working the Ti-Nb-Dy alloy obtained in step (2) to obtain a processed alloy; the cold working comprises at least one of cold rolling, cold wire drawing, cold rotary forging or cold heading deformation, the total deformation rate after the cold working is 80-99%, and the single deformation amount is 0.1-4%.

2. The method for preparing the Ti-Nb-Dy alloy according to claim 1, wherein: The purity of Ti, Nb and Dy in the raw materials is not less than 99.9%.

3. The method for preparing the Ti-Nb-Dy alloy according to claim 1, wherein: The solution treatment is carried out at 800-1200° C. in an argon environment for 1-40 hours.

4. The method for preparing the Ti-Nb-Dy alloy according to claim 1, wherein: The quenching method includes water quenching or ice-salt water quenching.

5. The Ti-Nb-Dy alloy obtained by the preparation method according to any one of claims 1 to 4.

6. Use of the Ti-Nb-Dy alloy according to claim 5 in biomedical equipment, aerospace equipment, and sports equipment.

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