JP2002285268A - Titanium alloy and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a titanium alloy having high strength and high ductility. SOLUTION: The alloy has a composition containing, by atom, 15 to 30% of the group Va elements, 1.5 to 6% oxygen (O) and/or nitrogen (N), and the balance titanium (Ti) with inevitable impurities. The high strength and high ductility titanium alloy can be obtained by reversing the conventional concept, i.e., by incorporating large quantities of O and N therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a titanium alloy and a method for producing the same. More specifically, the present invention relates to a high-strength titanium alloy that can be used for various products and a method for producing the same.

[0002]

2. Description of the Related Art Titanium alloys have been used in the fields of aviation, military, space, deep sea exploration, and chemical plants because of their excellent specific strength and corrosion resistance. Recently, attention has been focused on titanium alloys having a low Young's modulus (for example, β alloys), and the fields of use of titanium alloys are expanding. For example, titanium alloys having a low Young's modulus are being used for biocompatible articles (for example, artificial bones and the like), accessories (for example, frames for glasses), sports equipment (for example, golf clubs), springs, and the like. The following publications can be cited as prior arts that have disclosed such a low Young's modulus titanium alloy.

[0003] JP-A-10-501719, JP-A-6-233811 and JP-A-6-73475.
Publications These publications disclose similar titanium alloys. For example, Japanese Patent Publication No. 10-501719 discloses a titanium alloy.
"A total of about 10 to 20 wt% or about 35 to 50 wt% of a metal selected from the group consisting of (i) Ti and (ii) Nb and Ta, (iii) acts as a β stabilizer and Sufficient Zr to reduce the rate of β-structure transformation
And a dental device formed at least in part of such an alloy and having low modulus and corrosion resistance. Is disclosed. And the disclosed titanium alloy has relatively high strength and low Young's modulus. However, the Young's modulus is 7
As for a titanium alloy having a tensile strength of 5 MPa or less and a tensile strength of 700 MPa or more, only Ti-13Nb-13Zr is disclosed. In addition, the claims include "a metal selected from the group consisting of Nb and Ta in a total amount of about 35 to 50 w
t% ", but no specific embodiment corresponding thereto is disclosed. Moreover, O, which is an essential component of the present invention, is not disclosed at all. By the way,
Ti-13Nb-13Zr (wt%) is Ti-7.7Nb-7.8Zr in terms of at%. Further, according to the publication, the titanium alloy disclosed therein is a titanium alloy having a homogeneous structure of α-based martensite (hexagonal close-packed), having a structure different from that of β-titanium alloy, and an ordinary β alloy. -It is described that titanium alloys are easily strain hardened and difficult to process. As described later, the titanium alloy according to the present invention is a β-titanium alloy, and does not cause work hardening unlike a normal β-titanium alloy described in that publication. Therefore, the titanium alloy disclosed in the publication is completely different from the titanium alloy according to the present invention, as well as having a different structure from the β-titanium alloy.

Japanese Patent Application Laid-Open No. 8-299428 discloses that “2.5 to 13 wt% of Zr and 20 to
It consists essentially of 40 wt% of Nb, 4.5 to 25 wt% of Ta and the remaining amount of Ti, the total amount of Nb and Ta is 35 to 52 wt%, and the ratio of Nb / Ta is 2 to 13
And the relative proportions of Ti, Zr, Ta and Nb are determined to have an elastic modulus lower than about 65 GPa,
A medical device formed of an isotropic biocompatible titanium alloy having a Young's modulus of 65 GPa or less. Is disclosed. However, this publication only discloses Young's modulus,
There is no disclosure of strength, workability, and the like. Also,
"The total amount of C, N and O is less than 0.5 wt%.
Contains at least one interstitial element selected from the group consisting of: "
It becomes about 2.0% or less. Further, it is considered that it is difficult to obtain a titanium alloy having high strength and high elastic deformability as in the present invention by the manufacturing method disclosed in the publication.

[0005] Japanese Unexamined Patent Publication No. 10-219375 discloses that "Nb and Ta are combined in a total amount of 20 to 60 wt.
%, With the balance being Ti and unavoidable impurities. And "a titanium alloy to which at least one of Mo of 10 wt% or less, Zr of 5 wt% or less, or Sn of 5 wt% or less is added." However, this publication does not disclose O, which is an essential component of the present invention. In addition, the titanium alloy disclosed therein having high strength (for example, 1200 MPa class)
The Young's modulus is also increasing (for example, about 115 GPa). Therefore, the titanium alloy is not high in strength, low in Young's modulus and high in elasticity as in the present invention.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances. That is, an object of the present invention is to provide a titanium alloy having a high strength and a high elastic deformability, which has not existed conventionally. It is another object of the present invention to provide a manufacturing method suitable for manufacturing the titanium alloy.

[0007]

The inventor of the present invention has conducted intensive research and repeated trial and error in order to solve this problem. As a result, in addition to a predetermined amount of the Va group element, the present inventors have found that oxygen in a range that is inconsistent with conventional technical knowledge. Alternatively, it has been newly found that a titanium alloy having high strength and high elastic deformability can be obtained by adding nitrogen, and the present invention has been completed. (Titanium alloy) That is, the titanium alloy of the present invention has a Va of 15 to 30 at% when the whole is 100 at%.
Group element and one or more of O and N in total of 1.5 to 6
at%, with the balance being Ti and unavoidable impurities.

Although the details of the mechanism of development are not clear, the inclusion of an appropriate amount of a Va group element and a large amount of O or N in an atomic ratio makes it possible to obtain a titanium alloy having remarkably high strength and high elastic deformability. Was. It is considered that such excellent characteristics are not obtained only by the Va group element, but are obtained by increasing the allowable amounts of O and N to an insane level according to the conventional technical knowledge. Note that oxygen and nitrogen have the same effect theoretically, and thus, in the present invention, oxygen will be described as a representative example. In the case of a conventional titanium alloy (for example, Ti-6Al-4V alloy), the upper limit of the O content was considered to be about 1.0 at%. And it was actually very difficult to control the amount of O within that range.
However, the titanium alloy of the present invention contains 1.5 at% or more of O, which is much higher than this. As a result, it has been newly found that not only the control of the O amount becomes easy, but also the excellent mechanical properties described above are exhibited.

As described above, the present invention has discovered for the first time that O and N are very effective additive elements when increasing the strength while suppressing an increase in the Young's modulus of a titanium alloy. It was completed by discovery. This discovery is groundbreaking in the titanium alloys industry and of great academic value. The titanium alloy of the present invention can be widely used for various products because of its excellent properties, and exerts great power in improving the functions of various products and expanding the degree of freedom in design. Here, O and N are 1.5 at% in total.
If it is less than 6%, a sufficiently high strength cannot be obtained, and if it exceeds 6 at%, the toughness and ductility of the titanium alloy are reduced. On the other hand, if the Va group element is less than 15 at%, sufficient elastic deformability cannot be achieved, and if it exceeds 30 at%, material segregation tends to occur,
It is not preferable because a sufficiently high strength cannot be achieved and a reduction in specific strength is caused.

(Method of Manufacturing Titanium Alloy) Although it is considered that the above titanium alloy can be manufactured by various manufacturing methods, the present inventor has also newly developed a manufacturing method suitable for the manufacturing. That is, the method for producing a titanium alloy according to the present invention uses T
15 to 30 at% when i and the whole are 100 at%
Mixing a raw material powder containing a total of 1.5 to 6 at% of O and / or N with a group Va element of formula (I), and forming the mixed powder obtained in the mixing step into a molded body having a predetermined shape Step, a sintering step of heating and sintering the molded body obtained in the molding step, and a hot working step of hot working and densifying the sintered body obtained in the sintering step, It is characterized by having.

By using the sintering method instead of the so-called melting method, a stable quality titanium alloy can be obtained by avoiding macroscopic segregation even when a large amount of a Va group element or O is contained. The melting of titanium does not require a lot of man-hours, costs, or special equipment. Since the molded body formed into a desired shape is sintered, the number of subsequent processing steps can be reduced. Then, by making the sintered body after the sintering step dense in the hot working step, it is possible to achieve both a sufficiently high strength and a low Young's modulus. Thus, according to the production method of the present invention, the above titanium alloy can be produced efficiently.

By the way, in the above-described titanium alloy and the method of manufacturing the same according to the present invention, the total amount of O and N is 2.0 to 2.0.
More preferably, it is 5.0 at%. Further, among the Va group elements, Nb and Ta are preferably 18 to 27 at% in total, and more preferably 20 to 25 at%. It is not clear why Nb and Ta are preferred among the Va group elements, but even if a large amount of oxygen is contained in the β phase containing Nb or Ta as a main constituent element, oxygen segregates at the grain boundaries and becomes brittle. It is presumed that some action different from the conventional embrittlement mechanism is working.

The composition range of each element is shown in the form of "x to y atomic%", which means that it includes the lower limit (x) and the upper limit (y) unless otherwise specified. This is the same when “x to y weight%” is displayed. Further, “high strength” in the present application means that the tensile elastic limit strength or the tensile strength is large. "High elastic deformability" means that the elongation of the test piece within the tensile elastic limit strength is large. Here, the "tensile elastic limit strength" refers to the stress applied when the permanent elongation reaches 0.2% in a tensile test in which loading and unloading of the test piece are gradually repeated. Say "Tensile strength" is a stress obtained by dividing the load immediately before the final fracture of the test piece by the cross-sectional area of the parallel portion of the test piece before the test in the tensile test. Further, the “titanium alloy” referred to in the present invention includes various forms, and includes materials (for example,
Not only ingots, slabs, billets, sintered bodies, rolled products, forged products, wires, plates, bars, etc., but also titanium alloy members processed from them (eg, intermediate processed products, final products, some of them) Etc.) (the same applies hereinafter).

In expressing the mechanical properties of the titanium alloy of the present invention, a longitudinal elastic modulus (Young's modulus) is appropriately used.
At this time, a general Young's modulus may be used, but an average Young's modulus is used as appropriate. “Average Young's modulus” does not refer to the “average” of Young's modulus in a strict sense,
It means the Young's modulus representative of the titanium alloy of the present invention having high elasticity. Specifically, in the stress-strain diagram obtained by the above-mentioned tensile test, one-half of the tensile elastic limit strength was obtained.
The slope of the curve (the slope of the tangent) at the stress position corresponding to
The average Young's modulus was used (see FIG. 1).

[0015]

Next, the present invention will be described in more detail with reference to embodiments. A. Titanium alloy (1) Composition The titanium alloy of the present invention further has a total content of 100 at%.
And Zr is 15 at% or less and Hf is 10 at%.
% Or less and 30 at% or less of Sc are preferable. Z
r, Hf, and Sc are all elements that can improve the proof stress of the titanium alloy. If the sum of them exceeds 15 at%, material segregation is likely to occur, and improvement in strength and ductility cannot be expected, and the density of titanium alloy increases (decrease in specific strength), which is not preferable. By the way, when Zr or Hf is solely included in the titanium alloy, 1 to 10 at.
%, Further 5 to 10 at%, and in the case of Sc, 1 to 2
0 at%, and more preferably 5 to 10 at%.

It is preferable that the titanium alloy of the present invention further contains Sn at 13 at% or less when the whole is 100 at%. Sn is an element that can improve the strength of the titanium alloy and lower the Young's modulus. 13a
If the content exceeds t%, the ductility of the titanium alloy is reduced.
Not preferred.

The titanium alloy of the present invention further includes Cr, Mo, and Zr, Hf, Sc, and Sn as long as the high strength, low Young's modulus, and high elastic deformability can be maintained or improved. Mn, Fe, Co, Ni, Al,
A material containing C and B may be used. For example, Cr, Mn, and Fe
Is 30 at% or less, Mo is 20 at% or less,
It is preferable that each of Co and Ni is 13 at% or less. Further, Al is 0.5 to 12 at%, and C is 0.2 to 12 at%.
It is preferable that 5.0 at% and B be 0.2 to 6.0 at%. In addition, regarding these compositions, the same can be said for the raw material powder used in the production method of the present invention.

(2) Mechanical Properties The average Young's modulus and tensile elastic limit strength of the titanium alloy of the present invention will be described below in detail with reference to FIGS. 1A and 1B.
FIG. 1A is a diagram schematically showing a stress-strain diagram of a titanium alloy according to the present invention, and FIG. 1B is a diagram schematically showing a stress-strain diagram of a conventional titanium alloy (Ti-6Al-4V alloy). FIG. As shown in FIG. 1B, in the conventional metal material, the elongation linearly increases (between '-') in proportion to the increase in the tensile stress, and the Young's modulus is obtained by the slope of the straight line. When a tensile stress is applied beyond this elastic range (between '-'), the conventional metal material starts plastic deformation, and the elongation of the test piece does not return to 0 even when the stress is unloaded, and permanent elongation occurs. Usually, stress σ at which permanent elongation becomes 0.2%
p is referred to as 0.2% proof stress (JIS Z 224).
1). This 0.2% proof stress corresponds to a straight line ('-: tangent line at the rising portion) in the elastic deformation range of 0.1% on the stress-strain diagram.
The straight line ('-) and the stress that translated by 2% elongation
It is also the stress at the intersection (position) with the distortion curve. In the case of a conventional metal material, it is usually determined based on an empirical rule that “when the elongation exceeds about 0.2%, the elongation becomes permanent”.
It is considered that 2% proof stress ≒ tensile elastic limit strength. vice versa,
Within this 0.2% proof stress, the relationship between stress and strain is considered to be generally linear or elastic.

However, as can be seen from the stress-strain diagram of FIG. 1A, such a conventional concept does not apply to the titanium alloy of the present invention. Although the reason is not clear, in the case of the titanium alloy of the present invention, the stress-strain diagram does not become a straight line in the elastic deformation region, but becomes an upwardly convex curve ('-). Along elongation returns to zero, or along-'permanent elongation. Thus, in the titanium alloy of the present invention, the elastic deformation region ('-
Even in the case of (1), the stress and the strain do not have a linear relationship. When the stress increases, the strain rapidly increases. The same applies to the case of unloading. When the stress is not linearly related to the strain and the stress decreases, the strain rapidly decreases. It is considered that such a feature appears as the high elastic deformation ability of the titanium alloy of the present invention.

In the case of the titanium alloy of the present invention, as can be seen from FIG. 1A, as the stress increases, the inclination of the tangent line on the stress-strain diagram decreases. As described above, since the stress and the strain do not change linearly in the elastic deformation region, it is not appropriate to define the Young's modulus of the titanium alloy of the present invention by the conventional method. Similarly, in the case of the titanium alloy of the present invention, since stress and strain do not change linearly, it is also appropriate to evaluate 0.2% proof stress (σp ′) ≒ tensile elastic limit strength by the same method as in the past. Absent. That is, in the 0.2% proof stress obtained by the conventional method, the value is significantly smaller than the original tensile elastic limit strength.
% Proof stress ≒ tensile elastic limit strength cannot be considered. Therefore, returning to the original definition, the tensile elastic limit strength (σe) of the titanium alloy of the present invention is obtained as described above (the position in FIG. 1A), and the above average Young's modulus is introduced as the Young's modulus. And

In FIGS. 1A and 1B, σt is the tensile strength, εe is the strain in the tensile elastic limit strength (σe) of the titanium alloy of the present invention, and εp is 0.2% of the conventional metal material. This is distortion in proof stress (σp). Thus, the titanium alloy of the present invention has a tensile elastic limit strength of 1100M.
Pa or more, 1200 MPa or more, 1300 MPa or more,
1400MPa or more, 1500MPa or more and 16
It can be 00 MPa or more. Further, while maintaining such high strength, the elastic deformability is 1.5% or more.
% Or more and 2.5% or more. And
Both can be combined appropriately. Further, the titanium alloy of the present invention has an elongation of 3% or more, 5% or more, 7% or more,
8% or more, 9% or more, 10% or more, 12% or more, 15%
The above can also be applied. In the specification of the present application, "elongation"
Means elongation at break after plastic deformation.

(3) Cold workability The titanium alloy of the present invention has excellent cold workability. Then, by performing the cold working, the mechanical properties of the titanium alloy are improved. That is, when cold working is performed on a titanium alloy, working elastic strain is given to the inside. The introduced processing elastic strain can promote further strengthening and high elasticity performance of the titanium alloy. In order to sufficiently introduce the working elastic strain into the constituent structure of the titanium alloy, the above-described appropriate amounts of the Va group element, O, and N are important. In particular,
It has been found that O and N play an important role in introducing the processing elastic strain. That is, in a titanium alloy to which a large amount of Va group element is solely added, it is difficult to sufficiently introduce working elastic strain into its constituent structure. By adding appropriate amounts of O and N to the titanium alloy in addition to the Va group element, it becomes possible to introduce sufficient working elastic strain into the titanium alloy, and by accumulating it, it is possible to further increase the strength and the high elastic deformation of the titanium alloy. It is possible to achieve compatibility with the activation.

Further, it has been found that the titanium alloy of the present invention does not cause work hardening to the extent that it can be said to be completely cold-worked. As described above, the titanium alloy of the present invention exhibits surprisingly cold workability that cannot be considered with conventional titanium alloys, and furthermore, the cold working does not cause work hardening, so that mechanical properties can be improved. Therefore, even if the details are not clear, it is clear that the titanium alloy of the present invention has a completely different structure from the conventional titanium alloy. And, in the titanium alloy of the present invention, the cold working rate is 10%, 30%.
%, 50%, 70%, 90%, and even 99%. By performing cold working, the (average) Young's modulus can be reduced to 90 GPa or less, 85 GPa or less, 80 GPa or less, or 75 GPa or less. Further, by performing cold working, the tensile elastic limit strength is set to 1110 MPa or more, 1200 MPa or more, 1300 MPa or more, 140
0 MPa or more, 1500 MPa or more, and 1600 M
It can be Pa or more. These can be appropriately combined. For example, a titanium alloy having a tensile elastic limit of 1100 MPa or more can be obtained by performing cold working at a cold working rate of 10% or more.

Here, the term "cold" means that the temperature is sufficiently lower than the recrystallization temperature (minimum temperature at which recrystallization occurs) of the titanium alloy. The recrystallization temperature varies depending on the composition, but is about 600 ° C., and the titanium alloy of the present invention
Usually, it is good to carry out cold working in the range of normal temperature to 300 ° C.
The cold working rate X% is defined by the following equation. X = (change amount of cross-sectional area before and after processing: S0−S) / (initial cross-sectional area before processing: S0) × 100%, (S0: cross-sectional area before cold working, S: break after cold working) area)

(4) Heat treatment characteristics The titanium alloy of the present invention is subjected to an aging treatment (heat treatment) at 200 ° C. to 500 ° C. for 10 minutes to 100 hours (this time is not limited if an appropriate time is selected). It is preferable to do so. If cold working is performed before aging treatment,
This is more preferable because the number of precipitation sites increases during aging and many fine precipitate phases are dispersed. When the titanium alloy of the present invention is subjected to aging treatment, a 2000 MPa class super-strong titanium alloy is obtained.

B. Production method of titanium alloy (1) Raw material powder The raw material powder is composed of Ti and 15 to 30 at% Va group element when the whole is 100 at%, for a total of 1.5 to 6 a.
and at least one of t% of O and N. This raw material powder may be a mixed powder obtained by mixing elementary powders or an alloy powder having a desired composition. Compositions other than Ti, Va group elements and O and N are as described above. As the raw material powder, for example, sponge powder, hydrodehydrogenated powder, hydrogenated powder, atomized powder and the like can be used. The particle shape and particle size (particle size distribution) of the powder are not particularly limited, and a commercially available powder can be used. However, it is preferable that the average particle size be 100 μm or less, and more preferably 45 μm (# 325) or less, since a dense sintered body can be obtained.

In addition, the raw material powder has a high oxygen content and a high nitrogen content.
It is preferable that the mixed powder is obtained by a mixing step of mixing the i powder and the alloy element powder containing the Va group element. By using the high oxygen Ti powder, it becomes easy to control the amounts of O and N, and it becomes easy to contain a large amount of O and N in the titanium alloy. For example, high oxygen Ti powder is obtained by an oxidation step of heat treating Ti powder in an oxidizing atmosphere. The mixing step can be performed using a V-type mixer, a ball mill, a vibration mill, a high energy ball mill (for example, an attritor), or the like.

(2) Forming Step The forming step can be performed using, for example, die forming, CIP forming (cold isostatic press forming), RIP forming (rubber isostatic press forming), or the like. However, it is preferable that this molding step be a step of CIP molding the raw material powder, since a dense molded body can be obtained relatively easily. The shape of the molded body may be the final shape of the product, a billet shape, or the like.

(3) Sintering Step The sintering of the compact is preferably performed in a vacuum or an atmosphere of an inert gas. The sintering temperature is preferably lower than the melting point of the alloy and in a temperature range in which the component elements are sufficiently diffused. For example, the temperature range is 1200 ° C. to 1600 ° C., and further 1200 to 1500 ° C.
C. is preferred. The sintering time is preferably 2 to 18 hours, more preferably 4 to 16 hours.

(4) Hot Working Step By performing hot working, the pores and the like of the sintered alloy can be reduced and the structure can be densified. The hot working process is
For example, it can be performed by hot forging, hot swaging, hot extrusion or the like. The hot working may be performed in any atmosphere such as the air or an inert gas. In terms of equipment management, it is economical and preferable to carry out in air. The hot working in the manufacturing method of the present invention is performed for densification of the sintered body, but may be performed together with product molding.

(5) Cold Working Step As described above, the titanium alloy according to the present invention has excellent cold workability, and the mechanical properties thereof are improved by cold working. Things. Therefore, it is preferable that the manufacturing method of the present invention further includes a cold working step of performing cold working after the hot working step. This cold working step can be performed by cold forging, cold swaging, die drawing, drawing or the like. Further, the cold working may be performed also as product forming. In the manufacturing method of the present invention, heat treatment is not necessarily required, but heat treatment may be appropriately performed as long as high strength, low Young's modulus, and high elastic deformability can be maintained.

C. Uses of Titanium Alloy Since the titanium alloy of the present invention has high strength and high elastic deformability, it can be widely used for products matching the characteristics. In addition, since the titanium alloy of the present invention is used for a cold-worked product because it has excellent cold workability, work cracks and the like are significantly reduced, and the yield is improved. In addition, conventional titanium alloys can be formed by cold forging, etc., according to the titanium alloy of the present invention, even for products that require cutting in shape. But it is very effective. For example, the titanium alloy of the present invention is used for industrial machinery, automobiles, motorcycles, bicycles, home appliances, aerospace equipment,
It can be used for ships, accessories, sports and leisure equipment, biological products, medical equipment, toys, etc.

Taking the (coil) spring of an automobile as an example, the titanium alloy of the present invention has a Young's modulus of 1/3 to 1/5 of a conventional spring steel and an elastic deformation capacity of 5%.
Since it is twice or more, the number of turns can be reduced from 1/3 to 1/5. Furthermore, since the titanium alloy of the present invention has a specific gravity of only about 70% of steel used for a normal spring, a significant reduction in weight can be realized. In addition, when an eyeglass frame is taken as an accessory, for example, the titanium alloy of the present invention has a lower Young's modulus than a conventional titanium alloy, so that the vine and the like are easily bent and fit well on the face. Excellent shape recovery. Furthermore, since it is high in strength and excellent in cold workability, it can be easily formed from a thin wire into an eyeglass frame or the like, and the yield can be improved. In addition, according to the spectacle frame from the thin wire material, the fit, the lightness, and the wearing feeling of the spectacles are further improved.

Further, a golf club will be described as an example of a sports / regular article. For example, when the shaft of a golf club is made of the titanium alloy of the present invention, the shaft is easily bent and the elasticity transmitted to the golf ball is increased. Energy can be increased and the flight distance of the golf ball can be expected to be improved. Further, when the head of the golf club, particularly the face portion, is made of the titanium alloy of the present invention, the natural frequency of the head is significantly reduced as compared with the conventional titanium alloy due to its low Young's modulus and thinning due to high strength. According to the golf club having the head, it is expected that the flight distance of the golf ball can be considerably extended. The theory regarding the golf club is described in, for example, Japanese Patent Publication No. 7-9807.
No. 7 and International Publication WO98 / 46312.

In addition, according to the titanium alloy of the present invention, it is possible to improve the feel of a golf club due to its excellent properties, and it is possible to significantly increase the degree of freedom in designing a golf club. In the medical field, the titanium of the present invention is used for artificial bones, artificial joints, artificial grafts, bone fasteners, and the like, and functional members (catheter, forceps, valves, etc.) of medical instruments. Alloys are available. For example, when the artificial bone is made of the titanium alloy of the present invention, the artificial bone has a low Young's modulus close to human bone, is balanced with human bone, is excellent in biocompatibility, and has a sufficiently high strength as bone. . Further, the titanium alloy of the present invention is suitable for a vibration damping material. E = ρV2 (E: Young's modulus, ρ: Material density,
This is because, as can be seen from the relational expression of (V: sound speed transmitted through the material), the sound speed transmitted through the material can be reduced by lowering the Young's modulus.

In addition, the titanium alloy of the present invention is, for example,
Materials (wires, bars, squares, plates, foils, fibers, fabrics, etc.), mobile goods (watches (watches), Vallettas (hair ornaments),
Necklaces, bracelets, earrings, earrings, rings, tie pins, brooches, cufflinks, belts with buckles, lighters, fountain pen nibs, fountain pen clips, key chains, keys, ballpoint pens, mechanical pencils, etc., mobile information terminals (mobile phones) , Portable recorders, mobile PC cases, etc.), engine valve springs, suspension springs, bumpers, gaskets, diaphragms, bellows, hoses, hose bands, tweezers, fishing rods, fishing hooks, sewing needles, sewing needles,
Injection needles, spikes, metal brushes, chairs, sofas, beds, clutches, bats, various wires, various binders, paper clips, cushioning materials, various metal seals, expanders, trampolines, various health exercise equipment, wheelchairs, nursing equipment , Rehabilitation equipment, brassier, corset, camera body, shutter parts, blackout curtains, curtains, blinds, balloons, airships, tents, various membranes, helmets, fishnets, tea strainers, umbrellas, fire clothes, bulletproof vests, fuel tanks, and other containers It can be used for various products in various fields such as tire linings, tire reinforcements, bicycle chassis, bolts, rulers, various torsion bars, springs, and power transmission belts (such as CVT hoops).

[0037]

Next, the present invention will be described more specifically with reference to examples. (First Embodiment) A titanium alloy according to a first embodiment was manufactured by using the manufacturing method of the present invention. In this embodiment, the sample No. 1-1 to 1-10. In these samples, only the O amount was changed while keeping the ratio of the Va group element constant.
That is, Ti-20.2Nb-3.4Ta-3.4Zr
-XO (at%: x is a variable). This embodiment is a case where the cold working step according to the present invention is not performed after the hot working step. First, commercially available hydrogenated / dehydrogenated Ti powder (-# 325) and Nb powder (-#
325), Ta powder (-# 325) and Zr powder (-# 3
25) was prepared. Nb powder, Ta powder and Zr powder correspond to the alloy element powder in the present invention.

Next, the Ti powder was heat-treated in the atmosphere to produce a high oxygen Ti powder containing a predetermined amount of O (oxidation step). The heat treatment conditions at this time are 200 ° C. and 40 ° C.
Heating in air at 0 ° C. for 30 minutes to 128 hours. This high oxygen Ti powder, Nb powder, Ta powder and Zr powder are blended and mixed so as to have the composition ratio (at%) and the oxygen ratio (at%) shown in Table 1 to obtain a desired mixed powder. (Mixing step). This mixed powder is pressure 4 ton / c
and CIP molding (cold isostatic pressing) in m ^2, φ40 × 8
A 0 mm cylindrical shaped body was obtained (forming step). The obtained molded body was heated at 1300 ° C. in a vacuum of 1 × 10 −5 torr.
× 16 hours of heating and sintering to obtain a sintered body (sintering step). This sintered body was hot forged in the atmosphere at 700 to 1150 ° C. (hot working step) to obtain a round bar of φ10 mm.
For each sample obtained in this way, various measurements described below were performed,
The results are shown in Table 1.

(Second Embodiment) In this embodiment, each sample of the first embodiment is further subjected to cold working at a cold working rate of 90%.
Sample No. 2-1 to 2-10. Therefore, the composition ratios of Nb, Ta and Zr are as described above. Further, in the case of the present embodiment, steps before the hot working step are the same as those in the first embodiment, and therefore, the steps after the hot working step will be described. The round bar having a diameter of 10 mm after the hot working step was subjected to cold swaging by a cold swaging machine (a cold working step) to produce a round bar having a diameter of 4 mm. Various measurements described later were performed on each of the samples thus obtained, and the results are shown in Table 2.

Third Embodiment A titanium alloy according to a third embodiment was manufactured by using the manufacturing method of the present invention. In this embodiment, the sample No. 3-1 to 3-10.
In these samples, only the O amount was changed while keeping the ratio of the Va group element constant. That is, Ti-8.9Nb-11.4T
a-5.3Zr-2.7V-xO (at%: x is a variable)
And This embodiment is a case where the cold working step according to the present invention is not performed after the hot working step. First, commercially available hydrogenated / dehydrogenated Ti powder (-# 3
25), Nb powder (-# 325) and Ta powder (-# 32
5), Zr powder (-# 325), V powder (-# 325)
And prepared. Nb powder, Ta powder, Zr powder and V
The powder corresponds to the alloy element powder in the present invention.

Next, the Ti powder was heat-treated in the air to produce a high oxygen Ti powder containing a predetermined amount of O (oxidation step). The heat treatment conditions at this time are 200 ° C. and 40 ° C.
Heating in air at 0 ° C. for 30 minutes to 128 hours. This high oxygen Ti powder, Nb powder, Ta powder and Zr powder are blended and mixed so as to have the composition ratio (at%) and the oxygen ratio (at%) shown in Table 1 to obtain a desired mixed powder. (Mixing step). This mixed powder is pressure 4 ton / c
and CIP molding (cold isostatic pressing) in m ^2, φ40 × 8
A 0 mm cylindrical shaped body was obtained (forming step). The obtained molded body was heated at 1300 ° C. in a vacuum of 1 × 10 −5 torr.
× 16 hours of heating and sintering to obtain a sintered body (sintering step). This sintered body was hot forged in the atmosphere at 700 to 1150 ° C. (hot working step) to obtain a round bar of φ10 mm.
For each sample obtained in this way, various measurements described below were performed,
The results are shown in Table 3.

(Fourth Embodiment) In this embodiment, each sample of the third embodiment is further subjected to cold working at a cold working rate of 90%. 4-1 to 4-10. Therefore,
The composition ratios of Nb, Ta, Zr and V are as described above. Further, in the case of this embodiment, each step before the hot working step is the same as that of the third embodiment, and the cold working step is the same as that of the second embodiment. Various measurements described below were performed on each of the obtained samples, and the results are shown in Table 4.

(Fifth Embodiment) In this embodiment, the sample No. 2 of the second embodiment is used. Sample No. 2-5 was aged at 400 ° C. for 12 hours. 5-5. Various measurements described later were performed on this sample, and the results are shown in Table 5.

(Measurement of Each Sample) The Young's modulus was measured by using a strain gauge method. The tensile properties were determined from a load-strain diagram by performing a tensile test using an Instron (manufacturer) testing machine.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

[0049]

[Table 5] (Evaluation of each test material) Strength and Young's modulus Any of the titanium alloys of the present invention has a tensile strength of 1000MP.
a or more. In particular, it is understood that the strength is further enhanced by performing cold working. In addition, any of the titanium alloys has a low Young's modulus of 90 GPa or less, and it can be seen that the Young's modulus can be further reduced by performing cold working. Drawing and Elongation The titanium alloy of the present invention has a drawing of at least about 10%. In addition, each of the titanium alloys has an elongation exceeding 5%, and high elongation is obtained, which indicates that each sample of the examples has high ductility. Elastic deformability The titanium alloy of the present invention, when subjected to cold working, has an elastic deformability of more than 2%, indicating that a high elastic deformability is obtained.

(Regarding Oxygen Content) Taking a cold-worked titanium alloy (Example 2) as an example, the effect of oxygen content on mechanical properties is summarized below. Although the Young's modulus is increased by about 75 GPa at the maximum from 58 GPa, the influence of the oxygen amount on the Young's modulus is slow, indicating a low value as a titanium alloy. On the other hand, the strength improvement is remarkable,
A material exhibiting 700 MPa was obtained. As for the ductility, it can be seen that the drawn material has a drawn value of about 10% even when the material is a high acid material.
The elongation does not decrease at all even if the oxygen content increases by 4.5 at%,
The value is close to 10%. As a result, the elastic deformability is
Even if the amount of oxygen increases, it hardly changes, indicating that it has a high elastic deformability of 2% or more.

An ordinary titanium alloy has an oxygen content of 0.7 at
% Or less, and at most 1.0 at% or less. This is because, when the amount of oxygen increases, although strength is improved, elongation is reduced. Especially for high strength materials
It is common sense that oxygen management is rather strict. Nevertheless, in the case of the titanium alloy of the present invention, high ductility was obtained even when the oxygen content was increased. That is, the ductility of the titanium alloy did not decrease. This phenomenon is considered to be unique for a titanium alloy. The change in Young's modulus is slow as described above, which is 2% even in the 1700 MPa class.
This is considered to be the reason that the high elastic deformation ability was obtained.

[0052]

The titanium alloy of the present invention does not become brittle despite the fact that it contains an unusually large amount of O and N in addition to an appropriate amount of the Va group element. It hardly causes work hardening even when cold worked, and has high strength, low Young's modulus, high elastic deformability and high ductility. Therefore, the titanium alloy of the present invention can be widely used for various products according to its properties and has excellent cold workability, so that it can be easily applied to various products. And according to the manufacturing method of the present invention, such a titanium alloy can be easily obtained.

[Brief description of the drawings]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining tensile elastic limit strength and average Young's modulus, FIG. 1A is a view schematically showing a stress-strain diagram of a titanium alloy according to the present invention, and FIG. FIG. 3 is a diagram schematically showing a stress-strain diagram of a titanium alloy.

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 673 C22F 1/00 673 675 675 683 683 683 685 685Z 691 691B (72) Inventor Taku Saito Aichi 41 Toyota Chuo R & D Center, Nagakute-cho, Aichi-gun, No. 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Fang Jong-han F-term in Toyota Central Research Laboratories, 41-41, Nagakute-cho, Aichi-gun (Reference) 4K018 AA06 BC01 CA23 FA02

Claims (19)

[Claims] A total of 100 atomic% (at%) of 15 to 30 at% of a Va group element and one or more of oxygen (O) and nitrogen (N) in a total of 1.5 atomic% (at%). A titanium alloy containing up to 6 at%, with the balance being titanium (Ti) and unavoidable impurities. 2. The titanium alloy according to claim 1, wherein the total of niobium (Nb) and tantalum (Ta) of the group Va element is 18 to 27 at%. 3. The titanium alloy according to claim 2, wherein the total amount of Nb and Ta in the Va group element is 20 to 25 at%. Further, when the whole is 100 at%, it contains at least one metal element among zirconium (Zr), hafnium (Hf) and scandium (Sc), Zr is 15 at% or less, Hf Is 10at% or less, S
4. The titanium alloy according to claim 1, wherein c is 30 at% or less. 5. The titanium alloy according to claim 1, further comprising tin (Sn) of 13 at% or less, when the whole is 100 at%. 6. When the total is 100 at%, one of chromium (Cr), molybdenum (Mo), manganese (Mn), iron (Fe), cobalt (Co) and nickel (Ni) is selected. Containing more than one kind of metal element, Cr
, Mn, and Fe are each 30 at% or less, and Mo is 20 at%.
The titanium alloy according to any one of claims 1 to 5, wherein at% or less, and each of Co and Ni is 13 at% or less. 7. The titanium alloy according to claim 1, further comprising 0.5 to 12 at% of aluminum (Al) when the whole is 100 at%. 8. The method according to claim 1, further comprising 0.2 to 5.0 at% of carbon (C) when the whole is 100 at%.
7. The titanium alloy according to any one of 7. 9. The method according to claim 1, further comprising boron (B) in an amount of 0.2 to 6.0 at% when the whole is 100 at%.
A titanium alloy according to any one of claims 1 to 8. 10. The tensile elastic limit strength is 1100 MPa or more after cold working at a cold working rate of 10% or more.
10. The titanium alloy according to any one of claims 9 to 9. 11. The method according to claim 1, wherein the elongation is 3% or more.
The titanium alloy according to any one of claims 10 to 10. 12. The titanium alloy according to claim 1, wherein the titanium alloy is subjected to aging treatment at 200 ° C. to 500 ° C. to increase strength. 13. Ti and 15 to 30 at% of the Va group element when the total is 100 at% and 1.5 to 6 at% in total.
% Of O and / or N and a mixing step of mixing the raw material powder, a molding step of molding the mixed powder obtained in the mixing step into a molded article having a predetermined shape, and a molded article obtained in the molding step A sintering step of heating and sintering, and a hot working step of hot working and densifying the sintered body obtained in the sintering step. . 14. The raw material powder as a whole is 100
when at%, 1 out of Zr, Hf and Sc
At least 15 at%, Hf
The method for producing a titanium alloy according to claim 13, wherein is not more than 10 at% and Sc is not more than 30 at%. 15. The raw material powder further comprises Sn, Cr,
15. The composition according to claim 13, comprising at least one element selected from the group consisting of Mo, Mn, Fe, Co, Ni, C and B.
3. The method for producing a titanium alloy according to item 1. 16. The method for producing a titanium alloy according to claim 13, further comprising a cold working step of performing cold working after said hot working step. 17. The method for producing a titanium alloy according to claim 13, wherein said mixing step is a step of mixing the high oxygen Ti powder and the alloy element powder containing the Va group element. 18. The method for producing a titanium alloy according to claim 17, wherein said high oxygen Ti powder is a powder obtained by an oxidation step of heat-treating the Ti powder in an oxidizing atmosphere. 19. The method according to claim 13, wherein said forming step is a step of cold isostatic pressing (CIP) forming said raw material powder.