WO2024085348A1

WO2024085348A1 - Titanium alloy and manufacturing method therefor

Info

Publication number: WO2024085348A1
Application number: PCT/KR2023/009396
Authority: WO
Inventors: 이동근
Original assignee: 순천대학교 산학협력단
Priority date: 2022-10-21
Filing date: 2023-07-04
Publication date: 2024-04-25
Also published as: KR20240056276A

Abstract

The present invention relates to a titanium alloy that can be manufactured at low cost while possessing excellent mechanical properties and can be used in defense, aviation, space, biomaterials, etc. The titanium alloy according to the present invention comprises 2.0 wt% (inclusive) to 10.0 wt% (exclusive) of molybdenum (Mo), 0.5 wt% to 6.5 wt% (both inclusive) of iron (Fe), with the balance being titanium (Ti) and inevitable impurities.

Description

Titanium alloy and its manufacturing method

The present invention relates to a titanium alloy that has excellent mechanical properties, can be manufactured at low cost, and can be used in defense, aviation, space, biomaterials, etc., and a method for manufacturing the same.

Titanium and titanium alloys have high specific strength and excellent corrosion resistance, and are widely used in many fields such as national defense, aviation, space, and biomaterials. In particular, titanium alloy has a lower elastic modulus and higher specific strength than stainless steel, cobalt alloy, and alumina, so it is widely used as a biomaterial.

Meanwhile, pure titanium has low hardness and relatively low mechanical properties such as tensile strength, making it difficult to use as a biomaterial, so it is mainly used by alloying.

However, it has been reported that aluminum (Al) added to Ti-6Al-4V, a commercial titanium alloy, can cause Alzheimer's-type dementia, and vanadium (V) can cause serious complications and allergies due to the release of toxic ions.

Therefore, to replace it, there is a need to develop a biocompatible β titanium alloy. In this case, biofriendly β stabilizing elements include niobium (Nb), zirconium (Zr), tantalum (Ta), and molybdenum (Mo). there is.

Utilizing the above β stabilizing elements, many β titanium such as Ti-3Zr-5Fe, Ti-14Mn, Ti-10Fe-10Ta, Ti-27Nb-7Fe-8Cr, Ti-33Cr-3Fe-4Cr and Ti-7.5Mo alloy was developed. This β titanium alloy has superior heat treatment characteristics compared to α+β titanium alloy and has a BCC structure, so it can secure excellent formability. In addition, it has a low elastic modulus, so it is used not only in biomaterials but also in various fields.

However, the β stabilizing elements niobium (Nb), zirconium (Zr), and tantalum (Ta) are a major factor limiting the application of β titanium alloys because their high density and melting point inevitably leads to an increase in process costs, resulting in low price competitiveness. It is becoming.

Accordingly, research is underway to replace expensive alloy elements such as niobium (Nb), zirconium (Zr), and tantalum (Ta) with low-cost elements such as iron (Fe), molybdenum (Mo), and manganese (Mn). However, there is a problem in that it is difficult to realize physical properties sufficient to replace titanium alloy with expensive alloy elements added.

One purpose of the present invention is to use only low-cost alloy elements such as molybdenum (Mo) and iron (Fe) instead of expensive alloy elements such as niobium (Nb), zirconium (Zr), and tantalum (Ta), while providing excellent quality. The aim is to provide a titanium alloy with mechanical properties.

Another object of the present invention is to provide a method for manufacturing a titanium alloy having excellent mechanical properties while using only low-cost alloy elements such as molybdenum (Mo) and iron (Fe).

One aspect of the present invention for achieving the above object includes molybdenum (Mo) in an amount of 2.0% by weight or more and 10.0% by weight or less, iron (Fe) in an amount of 0.5% by weight or more and 6.5% by weight or less, and the remaining titanium and inevitable impurities. Provides a titanium alloy consisting of.

Another aspect of the present invention for achieving the above other object is that molybdenum (Mo) is 2.0% by weight or more and 10.0% by weight or less, iron (Fe) is 0.5% by weight or more and 6.5% by weight or less, the remaining titanium (Ti) and inevitable impurities. A method for manufacturing a titanium alloy consisting of, comprising the steps of melting raw materials to make a molten metal of the alloy composition, casting the molten metal to make an ingot, and forming the ingot into a molded product of a predetermined shape. A method for manufacturing titanium alloy is provided.

The alloy according to an embodiment of the present invention uses relatively inexpensive alloy elements such as molybdenum (Mo) and iron (Fe) instead of expensive alloy elements such as niobium (Nb), zirconium (Zr), and tantalum (Ta). By providing β titanium alloy with excellent mechanical properties while using alloy elements, the application range of β titanium alloy can be expanded.

Additionally, the alloy manufacturing method according to an embodiment of the present invention can manufacture β titanium alloy at low cost.

Figure 1 is a scanning microscope tissue photograph of an ingot manufactured according to an embodiment of the present invention.

Figure 2 is a graph showing the correlation between the tensile strength and Vickers hardness of cast ingots of Examples 1 to 6.

Figure 3 is a graph showing the correlation between elongation and Vickers hardness of cast ingots of Examples 1 to 6.

Figure 4 is a graph showing changes in Vickers hardness, elongation, and tensile strength in response to changes in iron (Fe) content in a cast ingot when the molybdenum (Mo) content is fixed at 5% by weight.

Figure 5 is a graph showing changes in hardness, elongation, and tensile strength in response to changes in molybdenum (Mo) content in a cast ingot when the iron (Fe) content is fixed at 2% by weight.

Figure 6 is a graph showing the correlation between tensile strength and Vickers hardness of Examples 7 to 12 of hollow rolled specimens.

Figure 7 is a graph showing the correlation between elongation and Vickers hardness of Examples 7 to 12 of cavity-rolled specimens.

Figure 8 is a graph showing the change in hardness, elongation, and tensile strength in response to the change in iron (Fe) content when the molybdenum (Mo) content in a die-rolled specimen was fixed at 5% by weight.

Figure 9 is a graph showing changes in hardness, elongation, and tensile strength in response to changes in molybdenum (Mo) content when the iron (Fe) content was fixed at 2% by weight in a die-rolled specimen.

Hereinafter, in describing the present invention, if a detailed description of a related known function or configuration is judged to unnecessarily obscure the gist of the present invention, the detailed description will be omitted. In addition, when a part is said to 'include' a certain component, this does not mean that other components are excluded, but that it can further include other components, unless specifically stated to the contrary.

The alloy according to the present invention is characterized by being composed of molybdenum (Mo) at least 2.0% by weight and less than 10.0% by weight, iron (Fe) at least 0.5% by weight and less than 6.5% by weight, and the remainder being titanium (Ti) and inevitable impurities.

The reason for limiting the composition range of alloy elements in the alloy according to the present invention as described above is as follows.

Molybdenum (Mo)

When added to titanium (Ti), molybdenum (Mo) not only improves corrosion resistance, lowers the elastic modulus, and increases strength, but is also non-toxic to living organisms, making it an element that can greatly improve so-called "biocompatibility." am.

In the alloy according to the present invention, when the molybdenum (Mo) content is less than 2.0% by weight, the effect of adding molybdenum (Mo) is not sufficient, and the molybdenum (Mo) content is 2.0% by weight ~ 10.0% by weight or less is preferable.

The content of molybdenum (Mo) is more preferably 3.0% by weight to 9.5% by weight, more preferably 3.2% by weight to 7.0% by weight, and most preferably 4.5% by weight to 6.0% by weight.

Iron (Fe)

Iron (Fe) is a very inexpensive alloy element and is not allergenic or toxic to the human body, so it not only has excellent "human compatibility", but also plays a role in stabilizing the beta (β) phase when added to titanium (Ti). and gives a strengthening effect.

In the alloy according to the present invention, when the content of iron (Fe) is less than 0.5% by weight, the effect of adding iron (Fe) is not sufficient, and when it is added at more than 6.5% by weight, adverse effects such as cracking in the alloy occur. Since negative effects occur, the iron (Fe) content is preferably 0.5% by weight to 6.5% by weight.

The content of iron (Fe) is more preferably 1.0% by weight to 5.5% by weight, more preferably 1.5% by weight to 4.5% by weight, and most preferably 1.5% by weight to 2.5% by weight.

unavoidable impurities

Unavoidable impurities refer to components that may be unintentionally mixed into the raw materials of titanium (Ti) alloy or during the manufacturing process.

Specifically, oxygen (O) reduces the deformability of titanium (Ti) alloy, causes cracks to occur during high-strength cold working, and increases deformation resistance, so it is recommended to keep it at 0.4% by weight or less. It is preferable, and it is more preferable to keep it at 0.25% by weight or less.

In addition, since hydrogen (H) reduces the ductility and toughness of titanium (Ti) alloy, the less it contains, the better. It is preferable to include 0.03% by weight or less, and more preferably 0.015% by weight or less.

In addition, since carbon (C) greatly reduces the deformability of titanium (Ti) alloy, the less it is included, the better. 0.15% by weight or less is preferable, and 0.1% by weight or less is more preferable.

In addition, since nitrogen (N) greatly reduces the deformability of titanium (Ti) alloy, the less it contains, the better. 0.1% by weight or less is preferable, and 0.05% by weight or less is more preferable.

In addition, the titanium (Ti) alloy according to the present invention, in its microstructure, can be basically composed of a β phase consisting of a body centered cubic structure (BCC) and a small amount of an α phase having a hexagonal close-packed structure (HCP), and can be post-processed. Alternatively, the α' phase, α" phase, ω phase, etc. may be additionally formed by heat treatment. The β phase, which constitutes the basic structure, may have an area fraction of at least 90% as observed in the cross-sectional structure.

In addition, the tensile strength of the titanium (Ti) alloy according to the present invention may be 900 MPa or more, preferably 1000 MPa or more, and may be 1000 to 1300 MPa depending on whether a post-treatment process such as cold working or post-heat treatment is performed.

Additionally, the elongation of the titanium (Ti) alloy according to the present invention may be 1% or more, preferably 2% or more, more preferably 3% or more, and most preferably 4% or more.

In addition, the titanium (Ti) alloy according to the present invention can be manufactured into medical articles or sports/leisure articles, and its use is not necessarily limited to medical articles or sports/leisure articles.

In addition, the method for producing an alloy according to the present invention consists of 2.0% by weight or more and 10.0% by weight or less of molybdenum (Mo), 0.5% by weight or more and 6.5% by weight or less of iron (Fe), and the remaining titanium (Ti) and inevitable impurities. A method for manufacturing a titanium alloy, comprising the steps of melting raw materials to make a molten metal of the alloy composition, casting the molten metal to make an ingot, and forming the ingot into a molded product of a predetermined shape. do.

In the method of manufacturing the alloy, the process of melting the raw material may preferably be performed by a vacuum arc remelting method (VAR).

In the method of manufacturing the alloy, the heat treatment process for the melt-manufactured product is preferably performed in the range of 750°C to 950°C for 30 minutes to 4 hours.

In the method of manufacturing the alloy, the swaging process may be performed in 1 to 10 passes at room temperature or below 500°C.

[Example]

As an example of the present invention, a composition having the composition shown in Table 1 below was prepared by dissolving using the vacuum arc re-dissolution (VAR) method. At this time, impurities such as oxygen (O), nitrogen (N), carbon (C), and hydrogen (H) in all alloys were kept to less than 0.65% by weight.

[Table 1]

An ingot was made by casting a titanium (Ti) alloy composition re-melted in a vacuum arc with the composition shown in Table 1 above. Titanium (Ti) alloy manufactured into a rod shape with a diameter of 16 mm to 20 mm and a length of 500 mm or more was maintained at 850°C for 1 hour and subjected to furnace cooling, followed by 3 to 8 passes of form rolling ( It was manufactured into a bar with a diameter of 12 mm through swaging.

microstructure

The manufactured alloy ingot was cut into a cross section perpendicular to the longitudinal direction and a cross section parallel to the longitudinal direction, macro polished with sandpaper no. 2400, and then micro polished using diamond paste. After performing this mechanical polishing, it was etched with Kroll etchant (100 ml of H ₂ O + 5 ml of HNO ₃ + 3 ml of HF), and the microstructure was observed using a scanning electron microscope (SEM). It has a cast structure as shown in Figure 1, and titanium alloy has a β phase as its basic structure and includes a small amount of α phase, α' phase, α" phase, or ω phase.

mechanical properties

Table 2 below shows the Vickers hardness, elongation, and tensile strength test results for the cast ingots.

[Table 2]

As shown in Table 2, the tensile strength of Examples 1 to 6 in the ingot state was 900 to 1050 MPa, the elongation was 0 to 4%, and the Vickers hardness was 300 to 430 Hv.

Figure 2 shows the correlation of tensile strength with Vickers hardness of cast ingots of Examples 1 to 6, and Figure 3 shows the correlation of elongation with Vickers hardness of cast ingots of Examples 1 to 6. . Figure 4 shows the change in Vickers hardness, elongation, and tensile strength with respect to the change in iron (Fe) content in the cast ingot when the molybdenum (Mo) content is fixed at 5% by weight, and Figure 5 shows In the cast ingot, the change in hardness, elongation, and tensile strength in response to the change in molybdenum (Mo) content is shown when the iron (Fe) content is fixed at 2% by weight.

Considering the tensile strength (UTS) and elongation (%), it is preferable that the molybdenum (Mo) content is in the range of 3.2 wt% to 7.0 wt%, and the iron (Fe) content is 1.5 to 4.5 wt. It can be seen that it is desirable to be included in the range of.

Table 3 below shows the Vickers hardness, elongation, and tensile strength test results for products that have completed the shape rolling process.

[Table 3]

As shown in Table 3, the tensile strength of Examples 7 to 12, which went through the forging process and the hollow rolling process, was 750 to 1300 MPa, the elongation was 0 to 6%, and the Vickers hardness was 300 to 400 Hv, and the tensile strength and elongation were at the level of 300 to 400 Hv. From the side, it can be seen that it is improved compared to Examples 1 to 6, which are in the ingot state.

Figure 6 shows the correlation of tensile strength with Vickers hardness of Examples 7 to 12 of the die-rolled specimens, and Figure 7 shows the correlation of elongation with the Vickers hardness of Examples 7 to 12 of the die-rolled specimens. It is shown. Figure 8 shows the change in hardness, elongation, and tensile strength in response to the change in iron (Fe) content when the molybdenum (Mo) content is fixed at 5% by weight in a shape-rolled specimen, and Figure 9 shows In a die-rolled specimen, the change in hardness, elongation, and tensile strength in response to the change in molybdenum (Mo) content is shown when the iron (Fe) content is fixed at 2% by weight.

In the case of co-rolled Examples 7 to 12, in terms of tensile strength (UTS) and elongation (%) compared to the ingot state, the molybdenum (Mo) content was 3.2% by weight to 7.0% by weight, and the iron (Fe) content was 1.5%. It can be seen that the composition range that simultaneously satisfies ~ 4.5 weight shows significant improvement compared to the composition range that does not.

Claims

Molybdenum (Mo) 2.0% by weight ~ 10.0% by weight,

Iron (Fe) 0.5% by weight ~ 6.5% by weight,

Titanium alloy consisting of the remaining titanium (Ti) and inevitable impurities.
According to claim 1,

A titanium alloy in which the content of molybdenum (Mo) is 3.0% by weight to 9.5% by weight.
According to claim 1,

A titanium alloy in which the content of molybdenum (Mo) is 3.2% by weight to 7.0% by weight.
According to claim 1,

A titanium alloy wherein the iron (Fe) content is 1.0% by weight to 5.5% by weight.
According to claim 1,

A titanium alloy wherein the iron (Fe) content is 1.5% by weight to 4.5% by weight.
The method according to any one of claims 1 to 5,

The titanium alloy has a tensile strength of 900 MPa or more and an elongation of 1% or more.
The method according to any one of claims 1 to 5,

The titanium alloy has a tensile strength of 1100 MPa or more and an elongation of 4% or more.
The method according to any one of claims 1 to 5,

The microstructure of the titanium alloy includes a basic structure consisting of a β phase and a small amount of α phase, α' phase, α" phase, or ω phase.
A method for producing a titanium alloy consisting of molybdenum (Mo) 2.0% by weight and 10.0% by weight, iron (Fe) 0.5% by weight and 6.5% by weight, the remainder titanium (Ti) and inevitable impurities,

melting raw materials to produce molten metal of the alloy composition;

Making an ingot by casting the molten metal,

heat treating the ingot at high temperature;

A method of producing a titanium alloy, comprising the step of ball rolling the heat-treated material into a molded product of a predetermined shape.
According to clause 9,

A method of manufacturing a titanium alloy in which the process of dissolving the raw material is performed by a vacuum arc remelting method (VAR).
According to clause 9,

A method of manufacturing a titanium alloy, wherein the heat treatment process is performed at 750°C to 950°C for 30 minutes to 4 hours.
According to clause 9,

A method of manufacturing a titanium alloy in which the form rolling is performed in 1 to 10 passes at room temperature or below 500°C.