A rare earth element Y-doped Ti-Nb-based titanium alloy and its preparation and processing method

Abstract

The present invention provides a rare earth element Y-doped Ti-Nb-based titanium alloy, wherein the alloy comprises 20-30% Nb, 0-5% Y, and the remainder is Ti and unavoidable impurity elements in terms of atomic percentage content. The present invention also provides a preparation method and a processing method of the above-mentioned low modulus and high strength Ti-Nb-Y alloy, wherein a non-consumable vacuum arc melting process is combined with a heat treatment to produce a solid solution alloy, and the solid solution alloy is processed to obtain a treated alloy. By doping the rare earth element Y into the Ti-Nb titanium alloy, the alloy comprises Ti, Nb and Y elements. The rare earth element Y has a high affinity for O atoms in the melt. The Y element can capture interstitial oxygen in the alloy matrix to form Y2O3, thereby reducing the oxygen content in the alloy matrix. The addition of the Y element refines the titanium alloy grains. After the solid solution alloy is processed, more defects are introduced into the alloy, which reduces the elastic modulus of the titanium alloy and improves the yield strength of the titanium alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloys, and in particular to a rare earth element Y-doped Ti-Nb-based alloy and a preparation and processing method thereof, and more particularly to a Ti-Nb-Y titanium alloy with superelasticity, low elastic modulus and good biocompatibility for use in the biomedical field. Background Art

[0002] Titanium alloys have high specific strength, specific stiffness, and low elastic modulus, and have received widespread attention and application in industries such as medicine, aviation, and sports. In addition to their excellent comprehensive mechanical properties, titanium alloys have good corrosion resistance and biocompatibility, and have gradually replaced stainless steel and cobalt-based alloys to become the main metal material currently used in human implants. The elastic modulus of human internal tissue is small, and the elastic modulus of human bone is only about 30GPa. If the modulus of the implant is higher than that of the surrounding bone tissue, a stress shielding effect will occur clinically, which can lead to implant failure and fracture, bone atrophy, and even fracture. Therefore, the design and development of low-modulus, 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 an elastic modulus of approximately 110 GPa, which is half that of stainless steel and cobalt-based alloys, reducing the stress shielding effect to a certain extent. However, this alloy system releases cytotoxic and neurotoxic Al and V ions due to wear and corrosion after long-term implantation in the human body. Ti-Ni shape memory alloys have excellent comprehensive mechanical properties and functional characteristics in the field of titanium alloys, but some people are allergic to the Ni element and may even develop cancer. Therefore, since the mid-1990s, researchers have been committed to developing low-modulus, high-strength titanium alloys with better biocompatibility.

[0004] A series of α+β titanium alloys with excellent biocompatibility have been developed, including Ti-15Zr-4Nb-4Ta-0.2Pd, Ti-15Zr-4Nb-aTa-0.2Pd, Ti-15Sn-4Nb-2Ta-0.2Pd, and Ti-15Sn-4Nb-2Ta-0.2Pd-0.2O. Five β-type titanium alloys have also been recommended for medical applications, including Ti-12Mo-Zr-2Fe, Ti-13Nb-13Zr, Ti-15Mo-2.5Nb-0.2Si, Ti-16Nb-9.5Hf, and Ti-15Mo. Compared to α+β and β-type titanium alloys, the metastable β-type has a lower elastic modulus and, therefore, better mechanical compatibility with the human body.

[0005] In recent years, Ti-Nb-based β-titanium alloys have gradually become an important research 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 3Mo3Zr 2Sn, and Ti 35Nb 5Ta Zr 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 present invention aims to provide a rare earth element Y-doped Ti-Nb-based alloy and its preparation and processing methods to address the complex alloy composition and high production costs of existing Ti-Nb-based biomedical alloys. The invention provides a novel metastable β-type titanium alloy with low modulus, high strength, superelasticity, and high biocompatibility. This alloy can be widely used in biomedical, aerospace, and sports equipment applications. To achieve this objective, the present invention provides a rare earth element Y-doped Ti-Nb-based titanium alloy comprising, by atomic percentage, 20-30% Nb, 0.1-5% Y, and the balance Ti and unavoidable impurity elements.

[0007] The present invention also discloses a preparation and processing method of a rare earth element Y-doped Ti-Nb-based titanium alloy, comprising the following steps:

[0008] (1) The alloy comprises, in atomic percentage, 20-30% Nb, 0.1-5% Y, and the balance Ti, wherein Ti, Nb, and Y raw materials are weighed and melted into an alloy ingot in a vacuum melting furnace using a non-consumable vacuum arc melting process;

[0009] (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 Y-doped Ti-Nb-based superelastic low modulus titanium alloy;

[0010] (3) Processing the Ti-Nb-Y alloy obtained in step (2) to obtain a processed alloy.

[0011] Titanium alloys are prone to the introduction of interstitial oxygen atoms during melting and subsequent thermomechanical treatment, resulting in a high O content and a solid solution of O in the alloy matrix, which in turn increases the modulus. By doping the rare earth element Y into a Ti-Nb alloy, the alloy is made to contain Ti, Nb, and Y. The rare earth element Y has a high affinity for O atoms in the melt and can capture interstitial oxygen in the alloy matrix to form Y2O3, reducing the oxygen content in the alloy matrix. The addition of Y 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.

[0012] The atomic percentage content of Nb in the titanium alloy of the present invention is 20-30%, so as to ensure that the alloy achieves 2% superelasticity, an elastic modulus less than 53GPa and high damping performance under room temperature.

[0013] In one embodiment of the present invention, the atomic percentage content of Nb in the titanium alloy is 23-26%, preferably 25%.

[0014] In one embodiment of the present invention, the purity of Ti, Nb and Y in the alloy is not less than 99.9%.

[0015] In one embodiment of the present invention, the sum of the mass percentages of Nb and Y in the alloy is no more than 35%. The Y content in the titanium alloy of the present invention is 0.1 to 5 at%, and the total content of Nb and Y is no more than 35%, thereby controlling the interstitial O atom content in the matrix and obtaining better comprehensive mechanical properties.

[0016] In one embodiment of the present invention, the content of Y in the titanium alloy is 0.3 to 4 at %.

[0017] In one embodiment of the present invention, the content of Y in the titanium alloy is 0.5 to 3 at %, preferably 0.5 to 2 at %.

[0018] In one embodiment of the present invention, a method for preparing a rare earth element Y-doped Ti-Nb-based alloy includes vacuum melting and heat treatment steps. The vacuum melting process includes preparing an alloy ingot from weighed and balanced metal raw materials through non-consumable vacuum arc melting.

[0019] 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.

[0020] In one embodiment of the present invention, the quenching method includes water quenching or ice-salt water quenching.

[0021] 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.

[0022] In one embodiment of the present invention, the deformation rate is controlled to be greater than 80% during cold working.

[0023] In one embodiment of the present invention, the total deformation rate during processing is 80-99.9%, and the single deformation amount is 0.1-5%.

[0024] The present invention also provides a use of the Ti-Nb-based titanium alloy in biomedical equipment, aerospace equipment, and sports equipment.

[0025] 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.

[0026] Beneficial effects of the present invention:

[0027] 1. By doping the rare earth element Y into the Ti-Nb titanium alloy, the alloy contains Ti, Nb and Y elements. The rare earth element Y has a high affinity for O atoms in the melt. The Y element can capture the interstitial oxygen in the alloy matrix to form Y2O3, thereby reducing the oxygen content in the alloy matrix. The addition of the Y element can not only refine the titanium alloy grains, but also reduce the elastic modulus of the titanium alloy, increase the plasticity of the alloy, and at the same time maintain a high strength of the alloy.

[0028] 2. The Ti-Nb-Y alloy of the present invention is produced using 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-Y alloy of the present invention is as low as 38 GPa, and the yield strength is as high as 665 MPa.

[0029] 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

[0030] Figure 1 This is a backscattered contrast-scanning electron microscope photograph of a Ti-25Nb-0.5Y alloy solid solution sample of the present invention;

[0031] Figure 2This is a backscattered contrast-scanning electron microscope photograph of the Ti-25Nb-2Y alloy solid solution sample of the present invention;

[0032] Figure 3 is the tensile curve of the Ti-25Nb-0.5Y alloy of the present invention after cold rolling;

[0033] Figure 4 is the superelastic tensile curve of the Ti-25Nb-0.5Y alloy of the present invention after cold rolling;

[0034] Figure 5 is the tensile curve of the Ti-25Nb-2Y alloy of the present invention after cold rolling;

[0035] Figure 6 This is the superelastic tensile curve of the Ti-25Nb-2Y alloy of the present invention after cold rolling. DETAILED DESCRIPTION

[0036] 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.

[0037] Example 1

[0038] Three pure metal raw materials, Ti, Nb, and Y, 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 solution-treated alloy ingot samples 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 95%.

[0039] The microstructure of the solid solution Ti-25Nb-0.5Y alloy sample is as follows: Figure 1 As shown, the average grain size is 100 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. Y element Y2O3 oxide particles are uniformly distributed at the grain boundaries and within the grains, and are also relatively similar in size (1-3 μm).

[0040] Example 2

[0041] Three pure metal raw materials, Ti, Nb, and Y, 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 a protective atmosphere at 1000°C for 24 hours, followed by quenching in ice-salt water. The solution-treated alloy ingot samples 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%.

[0042] The microstructure of the solid solution Ti-25Nb-2Y alloy sample is as follows: Figure 2 As shown, the average grain size is 80 μm. Compared with the sample in Example 1, the Y2O3 particle size and volume fraction in the sample have increased significantly, but the density change is not obvious. The Y2O3 particles are evenly distributed at the grain boundaries and within the grains, and the size is relatively close (4 to 10 μm).

[0043] Tensile properties testing

[0044] The titanium alloy plates prepared in Examples 1 and 2 were cut into 20×4×1 mm samples and the samples were cut into 20×4×1 mm samples. -4 s -1 The 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 stress-strain curve. The elastic modulus was calculated from the linear elastic deformation section of the curve. The tensile curves were as follows: Figure 3 and Figure 5 In the hyperelastic measurement, the sample is loaded until plastic yield and then unloaded. The total strain recovered during the unloading process is taken as the hyperelastic strain. The results are shown in Figure 4 and Figure 6 .

[0045] from Figure 3 The results show that the alloy Ti-25Nb-0.5Y in Example 1 exhibits good tensile properties, with an elastic modulus of 38 GPa, close to the modulus of human bones, and a yield strength of 665 MPa.

[0046] from Figure 4 The results show that the alloy Ti-25Nb-0.5Y in Example 1 exhibits good superelasticity, and its superelastic strain reaches 2.0%.

[0047] from Figure 5The results show that the alloy Ti-25Nb-2Y in Example 2 also exhibits good tensile properties, with an elastic modulus of 52 GPa and a yield strength of 669 MPa. Although its elastic modulus is higher than that of the alloy in Example 1, its yield strength is also increased. Figure 6 The results show that the alloy Ti-25Nb-2Y in Example 2 exhibits a certain degree of superelasticity, with a superelastic strain of 1.1%, in which linear elasticity is dominant.

Claims

1. A low modulus superelastic Ti-Nb-Y alloy for biomedical devices, characterized in that: Calculated by atomic percentage, the alloy comprises 20-30% Nb, 0.5% Y, and the remainder Ti and unavoidable impurity elements. The alloy is prepared by non-consumable vacuum arc melting a metal raw material into an alloy ingot, followed by heat treatment and cold working. The heat treatment process comprises solution treatment at 800-1200° C. in an argon environment for 1-40 hours, followed by quenching. The total deformation rate during the cold working is 80-99.9%, and the single deformation is 0.1-5%.

2. The Ti-Nb-Y alloy according to claim 1, wherein The purity of Ti, Nb and Y in the alloy is not less than 99.9%.

3. A method for preparing a Ti-Nb-Y alloy according to claim 1 or 2, comprising the steps of vacuum melting, heat treatment and cold working, wherein: The vacuum melting process includes preparing alloy ingots from weighed and counterweighted metal raw materials through non-consumable vacuum arc melting. The heat treatment process includes solution treatment at 800-1200°C in an argon environment for 1-40 hours, followed by quenching. The cold working includes at least one of cold rolling, cold wire drawing, cold rotary forging, or cold heading deformation. The total deformation rate during cold working is 80-99.9%, and the single deformation amount is 0.1-5%.

4. The preparation method according to claim 3, characterized in that The quenching method includes water quenching or ice-salt water quenching.

5. Use of the Ti-Nb-Y alloy according to claim 1 or 2 in biomedical equipment, aerospace equipment, and sports equipment.

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