KR102301567B1 - Titanium alloy with low elastic modulus and high yield strength - Google Patents

Abstract

The present invention relates to a titanium alloy that can greatly improve the yield strength and at the same time maintain a low modulus of elasticity below 95 GPa compared to the conventional titanium alloy, thereby improving durability and greatly expanding the use conditions when applied to products.
The titanium alloy according to the present invention includes, by weight%, Nb: 37 to 41%, Zr: 5 to 8%, Al: 0.05 to 1.5%, the remaining Ti and unavoidable impurities.

Description

Titanium alloy with low modulus of elasticity and high yield strength {TITANIUM ALLOY WITH LOW ELASTIC MODULUS AND HIGH YIELD STRENGTH}

The present invention relates to a titanium alloy having a low modulus of elasticity and high yield strength, and more particularly, it is possible to maintain a low modulus of elasticity below 95 GPa while significantly improving the yield strength compared to the prior art, and when used in medical articles, etc. It relates to a titanium alloy that can improve durability and greatly expand the conditions of use.

In the case of iron or iron alloy, which is currently widely used industrially, as problems such as an increase in carbon dioxide in the atmosphere and low corrosion resistance rise, a lightweight metal is attracting attention. Representative lightweight metals include titanium, aluminum, magnesium, etc. .

Among them, titanium exhibits superior corrosion resistance and specific strength compared to other metals, and has high stability at high temperatures, so it is widely used not only for industry but also as aerospace materials. In particular, it has a low modulus of elasticity compared to other metal materials and has excellent biocompatibility, so it is in the spotlight as a biomaterial.

Among the titanium alloys, Ti-6Al-4V alloy, the most commercialized alloy, is used in various fields such as aerospace materials and industry due to its excellent properties, and has been used as a biomaterial for medical purposes.

However, due to the toxicity of vanadium (V) contained in the Ti-6Al-4V alloy and the Alzheimer's causation of aluminum (Al) that the incidence of Alzheimer's disease increases if Al accumulates in the body for a long period of time, the use of Ti-6Al-4V material is discouraged. It has gradually decreased, and new alloys are being developed to replace them.

Therefore, when designing a titanium alloy for biomaterials, elements such as V, Cu, Cr, Ni, and Al, which are known to be harmful to the human body, are not used or it is necessary to implement desired properties while minimizing the amount used to a level harmless to the human body.

In relation to the titanium alloy for biomaterials harmless to the human body, a ternary alloy consisting only of Ti, Nb and Zr disclosed in the patent literature has been developed, and this alloy has an elastic modulus of 50 GPa or less and the elastic modulus of bones constituting the human body ( It is expected that the stress shielding effect can be significantly reduced as there is no significant difference from about 30 GPa).

However, the ternary alloy has excellent biocompatibility and has a very low modulus of elasticity, but has a low yield strength compared to pure titanium or other titanium alloys developed in the past, so that the use area is considerably limited.

Republic of Korea Patent Publication No. 2009-0123762

The present invention is to solve the problems of the prior art described above, it has a low elastic modulus and high yield strength to improve mechanical properties, and at the same time to provide a titanium alloy with substantially no harmfulness to the human body and excellent biocompatibility make it a task to be solved.

In order to solve the above problems, the present invention, in wt%, Nb: 37 to 41%, Zr: 5 to 8%, Al: 0.05 to 1.5%, the remaining Ti and unavoidable impurities, including a titanium alloy containing the titanium alloy is provided.

Titanium alloy according to the present invention, while remarkably improving the yield strength compared to the conventional Ti-Nb-Zr ternary alloy, maintains the elastic modulus as low as 45 ~ 95 GPa level, as well as the elongation of 10% or more, so that the workability is It is excellent and has excellent biocompatibility, and there is an advantage in that the use area can be greatly expanded to not only for the living body, but also for sports/leisure and industrial use compared to the conventionally developed titanium alloy.

In addition, the titanium alloy according to the present invention reduces the stress shielding effect and has excellent usability as a substitute material for hard tissue for biomedical use.

1 is an optical microscope image of a titanium alloy prepared according to Example 2 of the present invention.
2 is an optical microscope image of a titanium alloy prepared according to a comparative example.
Figure 3 shows the tensile properties test results of the titanium alloy prepared according to Example 2 and Comparative Example of the present invention.
4 shows the results of measuring the number of cells after dispensing the cells in the titanium alloy prepared according to Example 2 and Comparative Example of the present invention, and culturing for 72 hours.
5 shows the results of measuring the absorbance after dispensing the cells in the titanium alloy prepared according to Example 2 and Comparative Example of the present invention and culturing for 72 hours.

Hereinafter, the present invention will be described in detail based on preferred examples of the present invention, but the present invention is not limited to the following examples.

Hereinafter, the configuration and operation of the embodiment of the present invention will be described with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, when a part "includes" a certain component, this means that other components may be further included, rather than excluding other components, unless otherwise stated.

Titanium alloy according to the present invention, by weight, Nb: 37 ~ 41%, Zr: 5 ~ 8%, Al: 0.05 ~ 1.5%, the remaining Ti and unavoidable impurities are characterized in that it contains.

The reason for limiting the composition range of each alloy element of the beta-type titanium alloy according to the present invention as described above is as follows.

Niobium (Nb): 37 to 41 wt%

Nb is a bio-friendly metal material that exhibits stability without showing harmful reactivity with fibers, corrosion products, and biological solutions in the human body. However, when added to titanium within the composition range, a beta phase is formed to lower the elastic modulus, and when it is out of the range, it is difficult to obtain low elastic properties, so it is preferable to be added in the above range, and 38 to 40% by weight. It is more preferable to be included.

Zirconium (Zr): 5 to 8 wt%

Zr is a metal with very high corrosion resistance in acid and base atmospheres and high temperature water. It produces an oxide film in air, shows strong corrosion resistance, and is a non-cytotoxic element. It is a biocompatible metal material. When added outside the above range, titanium Since the elastic modulus of the alloy is rapidly increased, it is preferable to be included in the above range, and it is more preferable to be included in 5 to 7% by weight.

Aluminum (Al): 0.05 to 1.5 wt%

When Al is added in the above range, the yield strength of the titanium alloy can be greatly improved while minimizing the decrease in the elastic modulus, and when the content is less than 0.05% by weight, the effect of improving the yield strength is not sufficient. In addition, when Al is added to the titanium alloy, it is an element that stabilizes the alpha phase that increases the modulus of elasticity, and if Al accumulates in the human body for a long period of time, the incidence of Alzheimer's disease may increase, so its content exceeds 1.5 wt% It is preferable not to add it, and more preferably, the content of Al is 0.3 to 1.0% by weight.

inevitable impurities

Inevitable impurities refer to components that may be unintentionally incorporated in the raw material or manufacturing process of the titanium alloy.

Specifically, since oxygen decreases the deformability of the titanium alloy and causes cracks when cold working of strength is performed and increases the deformation resistance, it is preferable to maintain it to be 0.4 wt% or less, and 0.25 wt% It is more preferable to keep it so that it may become below.

In addition, since hydrogen decreases the ductility and toughness of the titanium alloy, it is better to include less hydrogen, preferably at least 0.03% by weight or less, and more preferably 0.015% by weight or less.

In addition, since carbon also greatly reduces the deformability of the titanium alloy, it is better to include less carbon, preferably at least 0.15% by weight or less, and more preferably 0.1% by weight or less. In addition, since nitrogen also greatly reduces the deformability of the titanium alloy, it is better to include less nitrogen, preferably at least 0.1% by weight or less, and more preferably 0.05% by weight or less.

In addition, since iron serves to stabilize the beta phase of the titanium alloy and also causes cracks, at least 0.5 wt% or less is preferable, and 0.3 wt% or less is more preferable.

In addition, the titanium alloy according to the present invention, the microstructure may preferably include a substantially equiaxed structure (equiaxed structure).

In addition, the elastic modulus of the titanium alloy according to the present invention may be 95 GPa or less, preferably 60 ~ 75 GPa.

In addition, the yield strength of the titanium alloy according to the present invention may be 500 MPa or more, preferably 600 MPa or more, and may be 600 to 1100 MPa depending on whether a post-treatment process such as cold working or post-heat treatment is performed.

In addition, in order to further improve the strength of the titanium alloy according to the present invention, heat treatment may be performed at a temperature of 300 to 500° C. for 1 to 50 hours.

In addition, the elongation of the titanium alloy according to the present invention is preferably 10% or more, more preferably 20 to 30%. However, the elongation may be 4% or more depending on whether a post-treatment process is applied.

In addition, the titanium alloy according to the present invention may be manufactured as a medical article or a sports/leisure article, and its use is not necessarily limited to a medical article or a sports/leisure article.

[Example]

As an embodiment of the present invention, for comparison with the alloy compositions of Examples 1 to 5 having the composition shown in Table 1 below, and the Examples of the present invention, the Nb and Zr contents are the same as in Example 2 and Comparative Example in which Al is not added The alloy composition according to the method was prepared by dissolving it using a vacuum arc remelting method (VAR). At this time, impurities such as oxygen (O), nitrogen (N), carbon (C), iron (Fe), hydrogen (H) in all alloys was set to be less than 1.0% by weight.

alloy Composition (wt%) Nb Zr Al Ti Example 1 38.3 6.2 0.72 Bal. Example 2 39 6 0.45 Bal. Example 3 39.7 6.6 0.89 Bal. Example 4 38.5 5.4 0.36 Bal. Example 5 38.5 5.4 0.36 Bal. comparative example 39 6 - Bal.

The titanium alloy composition remelted in a vacuum arc with the composition shown in Table 1 was cast into an ingot. Then, the cast ingot was forged and processed into a square or rod shape. A titanium alloy manufactured in a square or rod shape having a diameter of 16 mm to 20 mm and a length of 500 mm or more was heated to 810° C., and then through 3 to 5 passes of ball rolling. , was prepared with a 12mm diameter bar.

In addition, the alloys according to Examples 1 to 4 and Comparative Examples did not perform a separate post-treatment process after the ball rolling, and the alloy according to Example 5 was added after the alloy having the same composition as that of Example 4 was ball-rolled. A post-treatment process such as aging treatment was performed at 400° C. for 32 hours.

microstructure

The manufactured alloy rod was cut into a cross section perpendicular to the longitudinal direction and a cross section parallel to the longitudinal direction, and then macro-polished up to 2400 with sandpaper, and then micro-polishing was performed using diamond paste. After performing such mechanical polishing, the microstructure was observed using an optical microscope by etching with a _{Kroll etchant (H 2} O 100 ml + HNO _{3 5 ml + HF 3 ml).}

1 is an optical microscope image of a titanium alloy prepared according to Example 2 of the present invention, and FIG. 2 is an optical microscope image of a titanium alloy prepared according to Comparative Example.

As can be seen in FIG. 1 , the microstructure of the titanium alloy according to Example 2 of the present invention containing a small amount of Al was confirmed to consist of a beta (β) phase single-phase structure consisting of equiaxed crystals having an average size of several hundred μm.

In contrast, as shown in Figure 2, in the case of the comparative example not containing Al, the same beta-phase single-phase structure is formed, but unlike the example of the present invention (conformally rolling a 16 mm diameter bar or square material to a 12 mm diameter), A 20mm-diameter bar was processed into a 12mm-diameter bar through ball rolling, and the reduction ratio was relatively high, resulting in a marble-like microstructure.

In addition, although not shown in the drawings, Examples 1 and 3 to 5 also showed a microstructure similar to that of Example 2.

mechanical properties

In Examples 1 to 4, hardness was measured without additional heat treatment on the ball-rolled material, and in Example 5, hardness was measured after performing post-heat treatment, and the results are shown in Table 2 below.

Psalter Hardness
(Hv) Example 1 190 Example 2 176 Example 3 197 Example 4 180 Example 5 325 comparative example 182

As can be seen in Table 2, the hardness of the titanium alloys according to the embodiment of the present invention exhibited a level similar to the hardness of the titanium alloy according to the comparative example. That is, the hardness characteristics of the titanium alloy according to the embodiment of the present invention exhibited characteristics similar to those of the comparative example. In addition, in Examples 1 to 4, without separate heat treatment for the ball-rolled material, Example 5 was post-heat treatment After carrying out, the tensile properties were evaluated, and the results are shown in Table 3 below.

Psalter yield strength
(MPa) tensile strength
(MPa) elongation
(%) modulus of elasticity
(GPa) Example 1 618 635 22 63 Example 2 600 616 21 60 Example 3 623 650 20 67 Example 4 524 608 24 48 Example 5 1094 1153 4.7 94 comparative example 500 600 21.3 45

As can be seen in Table 3 and FIG. 3, the alloys according to Examples 1 to 4 of the present invention in which a small amount of Al, an alpha-phase stabilizing element, was added to the alloy composition according to the comparative example, compared with the comparative example, the tensile strength It can be seen that the level is similar or slightly increased, but the yield strength is remarkably improved. In the alloy according to Example 5, the elongation is much lowered by the additional post-heat treatment process, but it can be seen that the tensile strength and the yield strength are sharply increased to almost double. In addition, in terms of modulus of elasticity, the In the titanium alloy according to the embodiment, although Al, an alpha-phase stabilizing element that increases the modulus of elasticity, was added, the modulus of elasticity did not significantly increase.

That is, Al added to the example of the present invention improves the yield strength to a level close to the tensile strength, and has almost no loss in hardness and elongation, and the elastic modulus is not significantly higher than that of the comparative example, and is as good as 50 to 60 GPa. Since it represents the level, it is advantageous to increase the extensibility to products requiring durability and strength, compared to the titanium alloy according to the comparative example. Durability, strength, elongation, and modulus of elasticity can be additionally controlled by the post-heat treatment process.

biocompatibility

When the cells were dispensed on the specimen, the more the cells proliferated, the more biocompatibility could be judged.

In this test, 1.223×10 ⁵ cells were seeded on the specimen. When the cells are dispensed on the specimen, the recovery rate is not 100% because not all cells are attached to the specimen. Also, considering the doubling time of MG-63 cells, it is estimated that only about 25-30% of the total cells initially adhered to the specimen and proliferated.

As a result of culturing cells for 72 hours and direct counting, assuming that the initial adhesion rate is the same, as shown in FIG. 4 , the cell proliferation rate of the titanium alloy according to Example 2 of the present invention is Ti-6Al-4V It was superior to the alloy and showed a result similar to the cell proliferation rate of the titanium alloy according to the comparative example reported to have a biocompatibility similar to that of CP Ti.

In addition, as confirmed in FIG. 5 , the results of measuring the absorbance also showed the same tendency as the results of measuring the number of cells.

From this, it can be seen that the titanium alloy according to the embodiment of the present invention is similar to the titanium alloy according to the comparative example having biocompatibility similar to CP Ti, and thus the biocompatibility of the titanium alloy according to the present invention is very excellent.

Claims (7)

By weight%, Nb: 37 to 41%, Zr: 5 to 8%, Al: 0.3 to 1.0%, as a titanium alloy containing the remainder Ti and unavoidable impurities,
The elastic modulus of the titanium alloy is 45 ~ 95 GPa,
The yield strength of the titanium alloy is 600 MPa or more,
The elongation of the titanium alloy is 20% or more, a titanium alloy. delete delete delete delete A medical article made of the titanium alloy according to claim 1 . A sports/leisure article made of the titanium alloy according to claim 1 .

Images