KR20190140393A - Titanium alloy with low elastic modulus and high yield strength - Google Patents

Abstract

The present invention relates to a titanium alloy that can significantly improve yield strength and maintain a low modulus of elasticity of 95 GPa or less as compared to a conventional titanium alloy, thereby improving durability and greatly expanding use conditions when applied to a product. The titanium alloy according to the present invention includes, by wt%, 37 to 41% of Nb, 5 to 8% of Zr, 0.05 to 1.5% of Al, and the remaining amount of Ti and inevitable impurities.

Description

Titanium alloy with low modulus 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 a high yield strength. More particularly, the present invention can significantly improve the yield strength and maintain the modulus of elasticity of less than 95 GPa at the same time as compared with the prior art. The present invention relates to a titanium alloy capable of improving durability and greatly extending the conditions of use.

In the case of iron or iron alloy, which is widely used in the industry, light metals are attracting attention due to problems such as increase of carbon dioxide in the atmosphere and low corrosion resistance. Titanium, aluminum, magnesium, etc. are representative of lightweight metals. .

Titanium has excellent corrosion resistance and specific strength compared to other metals, and has high temperature stability and is widely used not only for industrial use but also for aerospace material. In particular, it has a low elastic modulus and excellent biocompatibility compared to other metal materials, so it is also attracting attention as a biomaterial.

Ti-6Al-4V alloy, which is the most commercialized among titanium alloys, has been used in various fields such as aerospace, industrial, etc., and has also been used as a biomaterial for medical use.

However, due to the toxicity of vanadium (V) in Ti-6Al-4V alloys and the Alzheimer's induction of aluminum (Al), which increases Alzheimer's incidence if Al accumulates in the body for a long time, the use of Ti-6Al-4V It has been gradually reduced and new alloy development is under way.

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, need not be used or have a desired physical property while minimizing the amount used to be harmless to the human body.

In connection with the titanium alloy for biomaterials, which is harmless to the human body, ternary alloys composed of only Ti, Nb and Zr disclosed in the patent literature have been developed, and the alloy has an elastic modulus of bone constituting the human body with an elastic modulus of 50 GPa or less. It is expected that the stress shielding effect can be remarkably reduced since it is not significantly different from about 30 GPa).

However, the ternary alloy has excellent biocompatibility and a very low elastic modulus, but has a lower yield strength than pure titanium or other titanium alloys previously developed, and thus has a problem in that the use area is considerably limited.

Republic of Korea Patent Publication No. 2009-0123762

The present invention is to solve the above-mentioned problems of the prior art, and has a low modulus of elasticity, high yield strength to improve the mechanical properties and at the same time provide a titanium alloy excellent in biocompatibility with substantially no harmful to human body. Let's solve the problem.

In order to solve the above problems, the present invention provides a titanium alloy containing, by weight%, Nb: 37 to 41%, Zr: 5 to 8%, Al: 0.05 to 1.5%, remaining Ti and unavoidable impurities.

Titanium alloy according to the present invention, while significantly improving the yield strength compared to the conventional Ti-Nb-Zr ternary alloy, while maintaining the elastic modulus low to 45 ~ 95GPa level, elongation is also 10% or more workability Excellent and excellent biocompatibility, there is an advantage that can greatly extend the area of use compared to the conventionally developed titanium alloys not only for living, sports / leisure, industrial, etc.

In addition, the titanium alloy according to the present invention reduces the stress shielding effect, it is excellent in utilization as a substitute material for biomedical hard tissue.

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 characteristics test results of the titanium alloy prepared according to Example 2 and Comparative Example of the present invention.
Figure 4 shows the results of measuring the number of cells after dispensing cells in the titanium alloy prepared according to Example 2 and Comparative Example of the present invention, and cultured for 72 hours.
Figure 5 shows the results of measuring the absorbance after dispensing cells in the titanium alloy prepared according to Example 2 and Comparative Example of the present invention, and cultured for 72 hours.

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

Hereinafter, the configuration and operation 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 known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted. In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

Titanium alloy according to the present invention, in weight percent, Nb: 37 to 41%, Zr: 5 to 8%, Al: 0.05 to 1.5%, characterized in that the remaining Ti and inevitable impurities.

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

Niobium (Nb): 37 to 41 wt%

Nb is a bio-friendly metal material that shows stability without showing harmful reactivity with fiber cells, corrosion products, biological solutions, etc. in the human body. It is very stable at room temperature and does not corrode in oxygen or strong acids. However, when added to the titanium in the composition range to form a beta phase to lower the modulus of elasticity, if out of the range, it is difficult to obtain low elastic properties, it is preferably added in the above range, 38 to 40% by weight More preferably included.

Zirconium (Zr): 5 to 8% by weight

Zr is a metal that is highly corrosion resistant in acid and base atmospheres and high temperature water. It forms an oxide film in the air and shows strong corrosion resistance. It is a bio-friendly metal material that is not cytotoxic. Since the modulus of elasticity of the alloy is sharply increased, it is preferable to be included in the above range, more preferably 5 to 7% by weight.

Aluminum (Al): 0.05 to 1.5% by weight

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

Inevitable impurities

Unavoidable impurity means a raw material of titanium alloy or a component that may be inadvertently incorporated in the manufacturing process.

Specifically, since oxygen lowers the deformability of the titanium alloy and causes cracking when cold working of strength, and increases deformation resistance, it is preferable to keep it at 0.4% by weight or less, and 0.25% by weight. It is more preferable to keep so that it becomes below.

In addition, since hydrogen deteriorates the ductility and toughness of a titanium alloy, it is better to contain less, it is preferable to contain at least 0.03 weight% or less, and it is more preferable to contain it at 0.015 weight% or less.

Moreover, since carbon also greatly reduces the deformation ability of a titanium alloy, it is so preferable that it contains less, at least 0.15 weight% or less is preferable, and 0.1 weight% or less is more preferable. Moreover, since nitrogen also greatly reduces the deformation ability of a titanium alloy, it is so preferable that it contains less, at least 0.1 weight% or less is preferable, and 0.05 weight% or less is more preferable.

In addition, iron serves to stabilize the beta phase of the titanium alloy and may cause cracking, so at least 0.5% by weight or less is preferable, and 0.3% by weight or less is more preferable.

In addition, the titanium alloy according to the present invention, the microstructure can be made preferably comprising a substantially equiaxed structure.

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

In addition, the yield strength of the titanium alloy according to the present invention may be 500MPa or more, preferably 600MPa or more, and may be 600 to 1100MPa 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 for 1 to 50 hours at a temperature of 300 ~ 500 ℃.

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 the post-treatment process is applied.

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

EXAMPLE

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

alloy Composition (% by weight) 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.

Titanium alloy composition was vacuum-dissolved in the composition of Table 1 was cast in an ingot (ingot). The cast ingot was then forged and processed into squares or rods. Titanium alloys made of squares or rods having a diameter of 16 mm to 20 mm and a length of 500 mm or more were heated to 810 ° C., and then subjected to 3 to 5 passes of roll rolling. , 12 mm diameter rod was prepared.

In addition, the alloys according to Examples 1 to 4 and Comparative Examples did not perform a separate post-treatment process after the co-rolling, and the alloy according to Example 5 was added after co-rolling the alloy having the same composition as in Example 4. The post-treatment process such as aging treatment for 32 hours at 400 ℃.

Microstructure

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

1 is an optical microscope image of a titanium alloy prepared according to Example 2 of the present invention, Figure 2 is an optical microscope image of a titanium alloy prepared according to the comparative example.

As confirmed 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 be composed of a beta (β) phase single phase structure composed of equiaxed crystals having an average size of several hundred μm.

On the other hand, as shown in Figure 2, in the case of the comparative example does not contain Al, it is made of the same beta-phase single-phase structure, unlike the embodiment of the present invention (16mm diameter bar or square material 12mm in diameter rolled), A 20mm diameter bar was processed into a 12mm diameter bar through ball rolling to show a microstructure similar to marbling due to its relatively high reduction ratio.

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

Mechanical properties

Examples 1 to 4 measured the hardness of the rolled material without a separate heat treatment, and Example 5 measured the hardness after performing the 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 confirmed in Table 2, the hardness of the titanium alloys according to the embodiment of the present invention showed a level similar to the hardness of the titanium alloy according to the comparative example. In other words, the hardness characteristics of the titanium alloy according to the embodiment of the present invention showed similar characteristics to those of the comparative example. In addition, Examples 1 to 4 without post-heat treatment of the ball-rolled material, Example 5 was subjected to the post-heat treatment After performing the tensile properties were evaluated, the results are shown in Table 3 below.

Psalter Yield strength
(MPa) The 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 confirmed 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, which is an alpha-phase stabilizing element, were added to the alloy composition according to the comparative example, compared with the comparative example, tensile strength Is similar or slightly elevated, but yield strength is remarkably improved. In the alloy according to Example 5, although the elongation is much lowered by the additional post-heat treatment process, it can be seen that the tensile strength and the yield strength have increased rapidly to almost two times. Further, in view of the elastic modulus, In the titanium alloy according to the embodiment, the modulus of elasticity did not increase significantly even though Al, which is an alpha-phase stabilizing element that increases the modulus of elasticity, was added.

That is, Al added to the embodiment of the present invention improves the yield strength to a level close to the tensile strength, there is almost no loss in hardness and elongation, the elastic modulus is not significantly higher than the comparative example, good about 50 ~ 60GPa Because of the level, compared to the titanium alloy according to the comparative example, it is advantageous to increase the expandability to the product requiring durability and strength. By the post-heat treatment process, durability and strength, elongation and elastic modulus can be additionally controlled.

Biocompatibility

When the cells were dispensed on the specimen, the more proliferation can be determined to be suitable for the living body, the biocompatibility was determined through the test on the cell proliferation rate.

1.223 × 10 ⁵ cells were dispensed onto the specimens in this test. When cells were dispensed onto the specimens, the recovery was not 100% because not all cells adhered to the specimens. In addition, considering the doubling time of MG-63 cells, it is estimated that only about 25-30% of all cells initially proliferated by attaching to the specimen.

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

In addition, as confirmed in FIG. 5, the result of measuring absorbance also showed the same tendency as the result of cell number measurement.

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

Claims (7)

Titanium alloy, comprising, by weight, Nb: 37-41%, Zr: 5-8%, Al: 0.05-1.5%, remaining Ti and inevitable impurities. The method of claim 1,
The content of Al is 0.3 ~ 1.0%, titanium alloy. The method of claim 1,
Modulus of elasticity of the titanium alloy is 45 ~ 95GPa, titanium alloy. The method of claim 1,
Yield strength of the titanium alloy is 500MPa or more, titanium alloy. The method of claim 1,
Elongation of the titanium alloy is 4% or more, titanium alloy. A medical article made of the titanium alloy according to any one of claims 1 to 5. An article for sports / leisure made of the titanium alloy according to any one of claims 1 to 5.

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