Heat treatment method of high-strength and high-plasticity Ti-Nb-O titanium alloy

Abstract

The invention discloses a heat treatment method of a high-strength and high-plasticity Ti-Nb-O titanium alloy, the titanium alloy comprises three elements of Ti, Nb and O, and the components comprise 13-22 wt% of Nb, 0.3-0.9 wt% of O and the balance Ti and inevitable impurities; through the design of a solid solution and aging heat treatment scheme, Nb and O elements in the structure are reasonably distributed in an alpha phase and a beta phase, finally, the alloy structure is controlled to contain the alpha phase and the beta phase, and a large number of nanometer martensite domains exist in the beta phase; the tensile strength of the alloy can reach 1100 MPa or above, the ductility is larger than 15%, and the elasticity modulus is smaller than 65 GPa. The high-strength and high-plasticity Ti-Nb-O titanium alloy has the characteristics of high strength, high plasticity, low elastic modulus, excellent biocompatibility and the like, is simple in component, reduces the preparation difficulty and cost, has important theoretical significance and engineering value, and is suitable for manufacturing biological implantation medical devices.

Description

Technical Field

[0001] The invention relates to a heat treatment method for a high-strength and high-plasticity Ti-Nb-O titanium alloy, belonging to the technical field of titanium alloy material preparation. Background Art

[0002] Titanium alloys have been widely used in aerospace, biomedicine and other fields due to their low density, high specific strength, excellent corrosion resistance and biocompatibility. Among the many titanium alloy grades, TC4 is currently the most widely used titanium alloy material, which is used to make aerospace structural parts and biomedical devices. However, since TC4 titanium alloy contains Al and V elements that are toxic to the human body, and its elastic modulus is much higher than that of human bones, it is easy to cause the "stress shielding" effect and lead to implant failure. Therefore, medical titanium alloy materials with non-toxicity and good mechanical compatibility have always been the key development direction of advanced titanium alloy materials. Oxygen is a very beneficial element for the human body, and it can produce a significant solid solution strengthening effect on titanium alloys; but in engineering titanium alloys, since oxygen can easily cause a significant reduction in the plasticity of the alloy, it is usually considered an impurity element and its content needs to be strictly controlled.

[0003] In 2003, Toyota Research Center of Japan developed a β single-phase titanium alloy (GUM METAL) with active addition of high oxygen content, but the alloy needs to be prepared by powder metallurgy and contains a large amount of Nb, Ta and other elements, which greatly increases the preparation cost. National invention patent CN109628796 B discloses a high-strength and high-elasticity titanium alloy, in which the Nb content is 6-18wt%, the O content is 0.1-0.5wt%, and the balance is Ti. Through solution treatment and 300-400℃ aging treatment, the alloy obtains α+β two-phase structure with an elastic modulus of 60-80GPa, but compared with TC4 alloy, the strength of Ti-Nb-O alloy is lower and it shows plastic processing softening phenomenon. Although the strength of the alloy can be improved by adding elements such as Fe, Zr, Sn, etc., the addition of more types of alloying elements brings risks to the safety of clinical application. Summary of the invention

[0004] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a heat treatment method for a high-strength and high-plasticity Ti-Nb-O titanium alloy. The alloy includes Ti, Nb and O elements. Through the design of the heat treatment process, a stable α+β two-phase structure is obtained, so that the two-phase alloy has excellent comprehensive properties such as high strength, high plasticity and low elastic modulus at a higher oxygen content. The elastic modulus of the alloy is less than 65GPa and the tensile strength can reach more than 1100MPa.

[0005] The technical solution of the present invention is as follows:

[0006] A heat treatment method for a high-strength and high-plasticity Ti-Nb-O titanium alloy, wherein a stable α+β two-phase structure is obtained by designing alloy element components and combining a heat treatment method, wherein the alloy element components include 13-22wt% Nb, 0.3-0.9wt% O and the remainder Ti; the heat treatment method is specifically as follows:

[0007] Solution treatment: After the heating furnace is heated to 760-900°C (preferably 760-850°C), the billet is placed in the heating furnace for 0.5-1h, taken out and water-cooled to room temperature; or furnace-cooled to 530-660°C at 5-15°C / min.

[0008] Aging treatment: After the heating furnace is heated to 550-650° C., the billet is placed in the heating furnace for 1-3 hours, and then taken out and water-cooled to room temperature.

[0009] Preferably, the blank used for the heat treatment of the present invention is a two-phase hot-rolled Ti—Nb—O titanium alloy plate or a Ti—Nb—O titanium alloy rod.

[0010] Preferably, the method for preparing the blank of the present invention is as follows:

[0011] (1) According to the composition ratio of 13-22wt% Nb, 0.3-0.9wt% O, and the balance Ti, the titanium sponge and Nb particles of the titanium alloy are ultrasonically cleaned and pickled to remove surface impurities, and then mixed with TiO2 powder, and smelted in a vacuum consumable melting furnace to prepare a titanium alloy ingot.

[0012] (2) The titanium alloy ingot prepared in step S1 is homogenized at 1000-1100° C. for more than 2 h, and then hot forged, rolled or wire drawn at 650-750° C. (α+β two-phase region) to obtain a Ti-Nb-O titanium alloy plate or bar with a deformation of 75-90%.

[0013] Preferably, the residual β phase of the Ti—Nb—O titanium alloy structure of the present invention contains a large number of nanodomains and has the characteristics of high strength and low elastic modulus.

[0014] Another object of the present invention is to provide an application of the Ti-Nb-O titanium alloy prepared by the method in the preparation of biological implant medical devices, such as artificial knee joints, hip joints, femoral stems, caval bones, medullary bones, screws and tooth roots.

[0015] The Ti-Nb-O titanium alloy prepared by the method of the present invention has a tensile strength of more than 1100 MPa, an elongation of more than 15%, and an elastic modulus of less than 65 GPa; the titanium alloy has the characteristics of high strength, high plasticity, low elastic modulus and excellent biocompatibility, and is suitable for making biological implantable medical devices.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The present invention makes the Nb and O elements in the microstructure reasonably distributed in the α and β phases through the design of Nb and O components and the control of heat treatment process, so that the β phase has the characteristics of high strength and low elastic modulus.

[0018] (2) The high-strength and high-plasticity titanium alloy of the present invention does not contain toxic elements. According to the room temperature tensile performance test, the elastic modulus of the alloy is less than 65 GPa, and the tensile strength can reach more than 1100 MPa.

[0019] (3) The present invention adopts an alloy composition with simple ingredients, which avoids the introduction of impurities during the preparation process. At the same time, a lower Nb content is used to reduce the smelting difficulty and preparation cost, which has important theoretical significance and engineering value. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. The features and advantages of the present invention will be more clearly understood by referring to the drawings. The drawings are schematic and should not be construed as limiting the present invention in any way. For those skilled in the art, other drawings can be obtained based on these drawings without creative work; among them:

[0021] Figure 1 This is the tensile curve of the heat-treated titanium alloy plate in Example 1 of the present invention.

[0022] Figure 2 This is the XRD spectrum of the titanium alloy plate of Example 1 of the present invention.

[0023] Figure 3 This is the microstructure diagram of the titanium alloy plate of Example 1 of the present invention.

[0024] Figure 4 This is the tensile curve of the heat-treated titanium alloy plate in Example 2 of the present invention.

[0025] Figure 5 This is a microstructure diagram of the heat-treated titanium alloy plate of Example 2 of the present invention.

[0026] Figure 6 This is the tensile curve of the heat-treated titanium alloy bar of Example 3 of the present invention.

[0027] Figure 7 This is the microstructure diagram of the heat-treated titanium alloy rod of Example 3 of the present invention.

[0028] Figure 8 These are macroscopic morphology diagrams of Examples 1 and 3 of the present invention.

[0029] Fig. 9 The microstructure diagram, tensile property curve and XRD spectrum of comparative example 1 of the present invention are shown.

[0030] Fig.10 This is the tensile property curve of comparative example 3 of the present invention. DETAILED DESCRIPTION

[0031] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other; the following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0033] Example 1

[0034] Preparation of Ti-18Nb-0.8O titanium alloy sheet + heat treatment process

[0035] (1) According to the composition ratio of 18wt% Nb, 0.8wt% O, and the balance Ti, the titanium sponge and Nb particles of the titanium alloy are ultrasonically cleaned to remove surface oxides and impurities, and then mixed with TiO2 powder, and smelted in a vacuum consumable melting furnace to prepare a titanium alloy ingot.

[0036] (2) The Ti—Nb—O alloy ingot was homogenized at 1100° C. for 2 h, then hot forged at 750° C., and then rolled at 750° C. with a deformation of 75% to obtain a rolled Ti—Nb—O titanium alloy plate.

[0037] (3) The rolled alloy plate was solution treated at 830°C for 0.5 h and furnace cooled to 600°C at 10°C / min to obtain a solid solution Ti-Nb-O titanium alloy plate.

[0038] (4) The alloy after the solid solution treatment is aged at 600°C for 2 hours and water-cooled to room temperature to obtain an aged Ti-Nb-O titanium alloy plate.

[0039] The typical tensile curve of the Ti-18Nb-0.8O titanium alloy prepared in this embodiment after heat treatment process 1 is as follows: Figure 1As shown in the figure, both the solid solution and aged alloys have good strength-plasticity matching and low elastic modulus. The tensile strength of the solid solution alloy is 996MPa, the elongation is 13.5%, and the elastic modulus is 58GPa; the tensile strength of the aged alloy is 1257MPa, the elongation is 15.6%, and the elastic modulus is 63GPa; the microstructure of the alloy after heat treatment process 1 is mainly α+β two-phase (see Figure 2 As shown in Figure 2, after solution treatment, part of the α phase dissolves back into the matrix, and after aging, needle-shaped α phase precipitates in the remaining β phase, showing a bimodal distribution. It is worth noting that due to the low stability of β, there are a large number of nano-martensite domains in the remaining β phase region, which to a certain extent inhibits the long-range ordered conventional martensite phase transformation, making it have the characteristics of high strength and low elastic modulus (see Figure 2). Figure 3 shown).

[0040] Example 2

[0041] Preparation of Ti-13Nb-0.9O titanium alloy sheet + heat treatment process

[0042] (1) According to the composition ratio of 13wt% Nb, 0.9wt% O, and the balance Ti, the titanium sponge and Nb particles of the titanium alloy are ultrasonically cleaned to remove surface oxides and impurities, and then mixed with TiO2 powder, and smelted in a vacuum consumable melting furnace to prepare a titanium alloy ingot.

[0043] (2) The Ti—Nb—O alloy ingot was homogenized at 1100° C. for 2 h, then hot forged at 750° C., and then rolled at 750° C. with a deformation of 75% to obtain a rolled Ti—Nb—O titanium alloy plate.

[0044] (3) The rolled alloy plate is solution treated at 760° C. for 1 h, and then water-cooled to room temperature to obtain a solid solution Ti—Nb—O titanium alloy plate.

[0045] (4) The alloy after the solid solution treatment is aged at 650°C for 1 h and water-cooled to room temperature to obtain an aged Ti-Nb-O titanium alloy plate.

[0046] The typical tensile curve of the Ti-13Nb-0.9O titanium alloy prepared in this embodiment after heat treatment process 2 is as follows: Figure 4 As shown in Figure 2, the tensile strength of the solid solution alloy is 927MPa, the elongation is 22.8%, and the elastic modulus is 70GPa; the tensile strength of the aged alloy is 1100MPa, the elongation is 19.4%, and the elastic modulus is 61GPa. The alloy is still an α+β two-phase structure after heat treatment. After treatment at a lower solid solution temperature (see Figure 5As shown in the figure, the α phase is different from the solid solution structure of Example 1, and is not completely dissolved back into the β group, retaining the short rod shape of the rolled state. After aging, the α phase grows in a certain direction.

[0047] Example 3

[0048] Preparation of Ti-22Nb-0.3O titanium alloy rod

[0049] (1) According to the composition ratio of 22wt% Nb, 0.3wt% O, and the balance Ti, the titanium sponge and Nb particles of the titanium alloy are ultrasonically cleaned to remove surface oxides and impurities, and then mixed with TiO2 powder, and smelted in a vacuum consumable melting furnace to prepare a titanium alloy ingot.

[0050] (2) The Ti-Nb-O alloy ingot was homogenized at 1100°C for 2 h, then hot forged at 750°C, and then drawn into a ф5 mm Ti-Nb-O titanium alloy rod.

[0051] (3) The drawn alloy rod is solution treated at 850°C for 0.5 h and water-cooled to room temperature to obtain a solid solution Ti-Nb-O titanium alloy rod.

[0052] (4) The alloy after the solid solution treatment is aged at 550°C for 3 hours and water-cooled to room temperature to obtain an aged Ti-Nb-O titanium alloy rod.

[0053] The typical tensile curve of the Ti-22Nb-0.3O titanium alloy prepared in this embodiment after heat treatment is as follows: Figure 6 As shown, the tensile strength of the solid solution alloy is 991MPa, the elongation is 13.7%, and the elastic modulus is 65GPa; the tensile strength of the aged alloy is 1109MPa, the elongation is 15.3%, and the elastic modulus is 60GPa; the alloy is a uniform α+β two-phase structure after heat treatment (see Figure 7 shown).

[0054] Through Example 1, Example 2 and Example 3, it is shown that the high-strength and high-plasticity Ti-Nb-O titanium alloy of the present invention has a simple composition, reduces the manufacturing cost and the risk of alloying elements to the safety of clinical application. After the heat treatment process is designed, the strength and plasticity of the alloy can be improved at the same time, and the special nano-domain structure in the remaining β phase gives it a lower elastic modulus property, so that the alloy still has high strength (tensile strength of more than 1100MPa), high plasticity (elongation greater than 15%), and low elastic modulus (elastic modulus less than 65GPa) excellent comprehensive performance under high oxygen content.

[0055] Comparative Example 1

[0056] (1) The method and conditions described in this embodiment are the same as those in Embodiment 1, except that the solution treatment condition is 1000°C for 1 h, that is, the solution treatment is performed above the phase transformation point, and the solution treatment is then cooled to room temperature to obtain a 1000°C solid solution Ti-Nb-O titanium alloy plate.

[0057] (2) The alloy after the solid solution treatment is aged at 600°C for 2 h and water-cooled to room temperature to obtain a 600°C aged Ti-Nb-O titanium alloy plate.

[0058] The tensile properties and microstructure of the Ti-18Nb-0.8O titanium alloy prepared in this example after heat treatment are shown in Figure 2. Fig. 9 As shown, the tensile strength of the 1000℃ solid solution alloy is 997MPa, the elongation is 8.3%, and the elastic modulus is 56GPa; the tensile strength of the 600℃ aged alloy is 1044MPa, brittle fracture after yielding, and the elastic modulus is 78GPa; the 1000℃ solid solution treatment exceeding the phase transition point causes all the α phases to transform into β phases, and in the subsequent rapid cooling process, a martensitic phase transition occurs, that is, the solid solution state structure is mainly composed of needle-shaped martensite phase and β matrix; after aging at 600℃, the structure is α lamellar structure, which has a greater impact on plasticity; compared with the dual-state structure obtained by the heat treatment process of Example 1, after the solid solution treatment conditions are set to 1000℃ exceeding the phase transition point temperature, the alloy has a large number of needle-shaped martensite phases or α lamellars, which have a greater impact on plasticity.

[0059] Comparative Example 2

[0060] The method and conditions described in this embodiment are the same as those in Example 1, except that: instead of performing solid solution treatment, the hot-rolled Ti-Nb-O alloy plate is directly subjected to aging treatment at 600°C for 2h and water-cooled to room temperature to obtain a directly aged Ti-Nb-O titanium alloy plate.

[0061] The tensile strength of the Ti-18Nb-0.8O titanium alloy prepared in this embodiment is 1140MPa and the elongation is 2.3%. Due to the high plate texture strength caused by rolling, the elastic modulus of the rolled alloy is very high and the plasticity is poor. Without solution treatment, the hot-rolled plate is directly subjected to aging treatment at 600°C, and the tensile strength of the alloy is 860MPa, the elongation is 12%, and the elastic modulus is 73GPa.

[0062] Comparative Example 3

[0063] The method and conditions described in this embodiment are the same as those in Example 1, except that the composition of the Ti-Nb-O titanium alloy is Ti-8Nb-0.28O, the rolled plate is solution treated at 830°C for 0.5h to obtain a solid solution Ti-8Nb-0.28O titanium alloy plate, and the solid solution plate is aged at 600°C for 2h to obtain an aged Ti-8Nb-0.28O titanium alloy plate.

[0064] The tensile strength of the Ti-8Nb-0.28O solid solution alloy prepared in this embodiment is 742MPa, the elongation is 13.5%, and the elastic modulus is 66GPa; the tensile strength of the aged alloy is 874MPa, the yield elongation is 10.3%, and the elastic modulus is 82GPa. By comparing Example 1 in the present invention, it can be seen that the strength and plasticity of the titanium alloy with lower Nb and O contents are reduced by using the same heat treatment conditions. Among them, there is a double yield phenomenon in the tensile curve of the solid solution alloy, indicating that the reduction in Nb content reduces the stability of the β matrix, and the stress induces a certain martensite phase after yielding, resulting in low yield strength. There is no obvious work hardening effect after aging, and the necking is more serious. By comparison, it is explained that the design of the alloy element composition in the Ti-Nb-O titanium alloy involved in the present invention needs to be combined with a specific heat treatment process method to achieve high strength and high plasticity together.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heat treatment method for high-strength and high-plasticity Ti-Nb-O titanium alloy, characterized in that: A stable α+β two-phase structure is obtained by designing alloy element components and combining a heat treatment method, wherein the alloy element components include 13-22wt% Nb, 0.3-0.9wt% O and the balance Ti; The heat treatment method is as follows: Solution treatment: After the heating furnace is heated to 760-900°C, the billet is placed in the heating furnace for 0.5-1h, and then taken out and water-cooled to room temperature; Aging treatment: After the heating furnace is heated to 550-650° C., the billet is placed in the heating furnace for 1-3 hours, and then taken out and water-cooled to room temperature.

2. The heat treatment method of the high-strength and high-plasticity Ti-Nb-O titanium alloy according to claim 1, characterized in that: The blank used for heat treatment is a two-phase hot-rolled Ti-Nb-O titanium alloy plate or a Ti-Nb-O titanium alloy rod.

3. The heat treatment method of the high-strength and high-plasticity Ti-Nb-O titanium alloy according to claim 1, characterized in that: During the solution process, the cooling method is replaced by furnace cooling to 530-660°C at 5-15°C / min.

4. The heat treatment method of the high-strength and high-plasticity Ti-Nb-O titanium alloy according to claim 2, characterized in that: The preparation method of the blank is as follows: (1) According to the composition ratio of 13-22wt% Nb, 0.3-0.9wt% O, and the balance Ti, the titanium sponge and Nb particles of the titanium alloy are washed to remove surface oxides and impurities, mixed with TiO2 powder, and smelted in a vacuum consumable melting furnace to prepare a titanium alloy ingot; (2) The titanium alloy ingot prepared in step S1 is homogenized at 1000-1100° C. for more than 2 h, and then hot forged, rolled or wire drawn at 650-750° C. to obtain a Ti-Nb-O titanium alloy plate or bar with a deformation of 75-90%.

5. The heat treatment method of the high-strength and high-plasticity Ti-Nb-O titanium alloy according to claim 1, characterized in that: The remaining β phase of the Ti-Nb-O titanium alloy structure contains a large number of nano-martensite domains.

6. Use of the Ti-Nb-O titanium alloy prepared by the method according to any one of claims 1 to 5 in the preparation of biological implantable medical devices.

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