JP2003096527A - Titanium alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a titanium alloy which has excellent corrosion resistance, and high hardness, and is easily subjected to forming at a low temperature even when a sample has large dimensions. SOLUTION: The titanium alloy has a composition containing Cu and Au, and containing at least one element X (Zr, Hf, Nb, Ta) which enters into solid solution in titanium at a total rate, has an amorphous structure, and has the property of metallic glass. Alternatively, the titanium alloy contains Cu, Au and Ni, has an amorphous structure, and has the property of metallic glass.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a titanium alloy having good corrosion resistance, high surface hardness, easy molding at low temperature, and characteristics of metallic glass and a large shape. .

[0002]

2. Description of the Related Art In recent years, titanium and titanium alloys have excellent corrosion resistance, are lightweight, have a low specific gravity, and are unlikely to cause metal allergies even when they come into contact with the skin.
It is widely used in various fields such as ornaments such as bracelets and earrings, spectacles, golf clubs, tableware, automobile parts and building materials.

However, since titanium has poor workability and is difficult to work in cold, a high temperature atmosphere at 700 ° C. or higher was required. However, when the processing is performed at a high temperature in the atmosphere, a thick oxide layer is formed on the surface, and it is necessary to remove the oxide layer in a later step, which causes a problem that the number of steps is further increased and becomes complicated.

Further, there is a problem in that surface scratches are likely to occur and the underlying material cannot be sufficiently protected. It is considered that this is because the hardness of the titanium material itself is insufficient, and further improvement in hardness has been desired.

A titanium-based metallic glass having excellent mechanical strength and corrosion resistance and having a glass transition temperature is disclosed in JP-A-07-252.
561. Metallic glass refers to a material that is structurally amorphous and that has a glass transition temperature before the crystallization onset temperature. Therefore, this metallic glass has high corrosion resistance, high strength, and high hardness, which are peculiar to amorphous, and the viscosity of the metallic glass material decreases in the supercooled liquid region in the temperature range above the glass transition temperature and below the crystallization start temperature. Has the property of

A desired product shape can be obtained by subjecting this metallic glass material to mechanical forming processing such as press molding, extrusion and rolling in the supercooled liquid region. The product after molding is characterized by excellent corrosion resistance and high hardness. However, the processing temperature and processing time must be strictly controlled, and depending on the molding conditions, crystallization progresses, an amorphous structure cannot be obtained, and the characteristics peculiar to amorphous are lost.

The conventional titanium-based metallic glass material is unlikely to have an amorphous structure having such characteristics. This is because the critical cooling rate for obtaining the amorphous structure has a large value in the conventional titanium-based metallic glass material. If the amorphous structure cannot be obtained, a solid solution and an intermetallic compound are generated, and the characteristics of the metallic glass cannot be obtained.

In particular, when the shape is large, it is difficult to obtain the cooling rate necessary for obtaining the amorphous structure, so that there is a problem that the glass does not become a metallic glass and the characteristics possessed by the metallic glass cannot be obtained.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems by providing a titanium alloy having the characteristics of metallic glass, being easy to mold at low temperature and having a large shape. is there.

[0010]

In order to achieve the above object, the titanium alloy of the present invention adopts the constitution described below.

At least one element X (Zr, Hf, Nb, Ta) containing Cu and Au, which is a solid solution in titanium, is contained, has an amorphous structure, and has characteristics of metallic glass. Titanium alloy. Or the above titanium alloy is N
A titanium alloy containing i. Or Cu, Au, Ni
A titanium alloy that contains, has an amorphous structure, and has the characteristics of metallic glass. When the chemical composition of the titanium alloy is TiaXbCucAue (where X is Zr,
At least one element selected from Hf, Nb, and Ta. ), 35 at% ≤ a + b ≤ 55 at% 5 at% ≤ b ≤ 20 at% 45 at% ≤ c + e ≤ 65 at% 0.2 at% ≤ e ≤ 8 at%. Titanium alloy chemical composition
XbCucNidAue (where X is Zr,
At least one element selected from Hf, Nb, and Ta. ), 35 at% ≤ a ≤ 55 at% 5 at% ≤ b ≤ 20 at% 45 at% ≤ c + d + e ≤ 65 at% 5 at% ≤ d ≤ 10 at% 0.2 at% ≤ e ≤ 8 at%. Titanium alloy chemical composition
When CucNidAue is used, it is preferable that 35 at% ≦ a ≦ 55 at% 45 at% ≦ c + d + e ≦ 65 at% 5 at% ≦ d ≦ 10 at% 0.2 at% ≦ e ≦ 8 at%.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Metallic glass is an alloy composed of an amorphous material having a glass transition temperature. Amorphous alloy has a structure with no grain boundaries,
Has excellent corrosion resistance. In addition, it has a characteristic of high hardness, and exhibits mechanical properties superior to existing crystalline alloys.

Amorphous means an amorphous state in which the constituent elements of the alloy are irregularly arranged, and is generally obtained by quenching from a liquid state and solidifying before it transits to a stable crystalline state. it can.

All of the titanium alloys of the present invention are made of Ti, C
The elements composed of u, Au, Ni and X are
This is because it is an effective element for obtaining metallic glass. Especially A
The addition of u is an element that does not require a large cooling rate to obtain the metallic glass, that is, contributes greatly to the improvement of the glass forming ability. In particular, if the shape is large, it becomes difficult to obtain the cooling rate necessary for obtaining the amorphous structure, but since the addition of Au lowers the critical cooling rate,
It becomes possible to obtain a large-sized metallic glass. In particular, A
When the content of u is 0.2% or more and 8% or less, it is easy to obtain a large-sized metallic glass. On the other hand, if the Au content exceeds 8%, the cost of the material increases, which is also a problem.

The titanium alloy of the present invention contains Ti and the element X (Zr, Hf, Nb, Ta), which is a solid solution at all, because it has an effect of improving the glass forming ability.
It is considered that the reason for this is that metallic glass is generally composed of several elements having different atomic sizes. It is considered that when several kinds of elements having different atomic sizes are melted and cooled, the diffusion distance that each atom can move becomes short, which makes it difficult to generate crystals. In addition, it is considered that since it is a solid solution at all rates, it becomes difficult to generate crystals.

Similarly, Ni is also an element effective in improving the glass forming ability, and in particular, the Ni content is 5% or more, 1
If it is 0% or less, a large-sized metallic glass is likely to be obtained. This is because if it deviates from this range, the glass forming ability is lowered, and it becomes impossible to obtain metallic glass, and as a result, it becomes impossible to have the characteristics of metallic glass shown above.

The metallic glass of the present invention is a supercooled liquid region in which the metal obtained by the first near net shape process and the near net shape process for performing a molding process close to the product shape is in the range from the glass transition temperature to the crystallization temperature. It can be obtained by the second processing step.

The near net shape method as used herein refers to a casting method such as die casting or vacuum casting in which molten metal is molded in a mold close to a cooled product shape.

Further, the metallic glass of the present invention can be processed by utilizing viscous flow in the temperature range from the glass transition temperature Tg to the crystallization temperature Tx. The reason why the glass transition temperature is equal to or higher than Tg is that the viscosity is lowered to cause deformation due to press molding or the like. The reason why the crystallization temperature is equal to or lower than Tx is that the structure changes from amorphous to crystal when the crystallization temperature is exceeded. , Because deformation will not occur.

Further, the metallic glass of the present invention comprises a first melting step for obtaining a molten metal, a second step for moving the molten metal obtained in the melting step into a cooling die, and a forging step performed by the cooling die. It can also be obtained by the third forging step.

In general, ordinary metal solidifies at the same time as it flows into the cooling mold, but the alloy of the present invention has a large degree of supercooling and maintains a molten state until it solidifies for a certain time. . Therefore, a certain amount of time can be taken from performing the second step to the third step of the present invention, so that the above method can be realized.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) A first embodiment of the present invention will be described with reference to FIG. The composition of the alloy used in this example is Ti ₃₅ Zr ₁₀ Cu ₄₂ Ni ₈ Au ₅ alloy (composition is at%
, And the case used for the watch exterior was manufactured. Also, as the first near net shape process,
The vacuum casting device 2 was used. For the case production, a secondary molding die having an outer diameter of 40 mm, a width of 5 mm and a height of 6 mm was used.

FIG. 1 is a conceptual diagram showing the vacuum casting apparatus 2, in which a vacuum evacuation apparatus 4 for evacuating the inside of the vacuum casting apparatus 2, a heating mechanism 6 for melting metal, and a quartz tube 16 are moved up and down. The vacuum casting apparatus 2 is provided with an elevating mechanism 14 for supplying the molten metal into the mold, and has a jetting mechanism 8 for flowing molten metal into the mold, a sample outlet 10, a gas introduction line 12, and a mold 18 on the sample table 20. .

First, a Ti alloy ingot in which the above-described composition components are uniformly melted is prepared by an arc melting method, a high frequency melting method, or the like. From the sample take-out port 10, the Ti alloy in an amount necessary for producing a watch case from the obtained Ti alloy ingot is introduced into the quartz tube 16 in the vacuum casting apparatus 2. Further, a mold 18 in the shape of a watch case was placed on the sample table 20 as a mold.

Inside the vacuum casting apparatus 2, the sample outlet 10 is closed.
1 × 10 with the vacuum exhaust device 4. ^-3Vacuum up to about Pa
Exhaust. From the gas introduction line 12, add Ar and He
The inert gas is introduced, and the inside of the apparatus 2 is evacuated again.
After performing the above gas replacement several times, inert the vacuum exhaust system.
About 5000 Pa of gas was introduced. The heating mechanism 6
The sample in English 16 was melted. Once uniformly melted, rise
The descending mechanism 14 descends so that the injection port contacts the mold,
The molten metal material is poured into the mold 18 by the injection mechanism 8.
Mu. From the mold to the primary molded product 22 in the shape of a watch case
It was taken out and the casting molding was completed.

Next, the warm work forming will be described with reference to FIG. FIG. 2 is a conceptual diagram showing a warm work forming apparatus. A vacuum exhaust device 4 for exhausting the inside of the warm working device 24,
A heating mechanism 6 for heating the primary molded product 22 obtained by vacuum casting to a glass transition temperature region, a secondary molding die 28 arranged above and below the primary molded product 22, a pressing mechanism 26 for pressing, a gas introduction line. A warm work forming apparatus 24 having 12 is shown.

First, a near net shape primary molded product 22 having a shape of a watch case similar to the product obtained by vacuum casting is used for secondary molding installed on the sample stage 20 in the warm working device 24. It is installed on the mold 28. Next, the inside of the warm working device 24 is evacuated by the evacuation device 4. After evacuation, titanium and Ar, which is an inert gas species, are introduced through the gas introduction line 12 to perform gas replacement several times. The heating mechanism 6 heated the sample at a heating rate of about 20 K / sec to about 500 ° C. in the glass transition temperature range. The press mechanism 26 is used to mold the sample, and the upper and lower secondary molding dies 2 are used.
Molded into a product shape according to No. 8. After molding, it was cooled to room temperature and the sample was taken out from the sample outlet to obtain a secondary molded product (finished product).

(Embodiment 2) A second embodiment of the present invention will be described. The titanium alloy used was Ti ₃₅ Zr ₁₀ Cu ₄₂ Ni ₈
A band which is an Au ₅ alloy (composition is described in at%) and used for a watch exterior was manufactured. For the band production, a secondary molding die having an outer shape of 20 mm × 8 mm and a thickness of 3 mm was used.

FIG. 3 is a view showing the concept of the molten metal forging device 36. The sample melting portion for melting the sample, such as the melting electrode 34, the sample moving mechanism 30, and the melting sample table 32, and the secondary molding. A mold 28, a press mechanism 26, a processing mechanism portion for processing a sample, a gas introduction line 12,
A vacuum exhaust device 4 is provided.

A sample adjusted so as to have the alloy composition of the above composition is placed on the melting sample table 32. Melting electrode 3
In the sample melting section having No. 4, the alloy sample having the above composition is uniformly melted. Next, by the sample moving mechanism 30,
The molten state is conveyed to the secondary molding die 28. Using the pressing mechanism 26, molten metal forging is performed by pressing with band-shaped secondary molding dies 28 arranged above and below to obtain a molded product.

As the method for evaluating the titanium-based metallic glass produced in Examples 1 and 2 of the present invention, structural analysis and thermal analysis using differential thermal scanning analysis DSC were performed. In addition, a corrosion resistance test and hardness measurement were also performed.

The structural analysis is carried out by the diffraction angle 20 by X-ray diffraction.
It was measured in the range of -80 degrees. Corrosion resistance test was evaluated by the cass test, sodium chloride 50 g / L, cupric chloride 0.2
The degree of discoloration on the surface of the test product was examined when a mixed solution of 6 g / L and 2 mL / L of acetic acid was sprayed in an amount of about 1.5 cc / hr / 80 cm ² for about 72 hours in a tank adjusted to an atmosphere of about 35 ° C. . The hardness was measured by measuring the Vickers hardness of the surface of the material under a load of 25 gf. The differential scanning calorimetry analysis shows the results when measured from room temperature to 500 ° C. at a heating rate of 10 K / sec.

The TiZrCuNiAu alloys produced according to the first and second embodiments of the present invention were subjected to the XR of the θ-2θ method.
X ray diffraction was performed using D in the range of the diffraction angle of 20 ° to 80 °. As a result, as shown in FIG.
The rCuNiAu alloy showed a broad peak peculiar to amorphous, and structurally almost amorphous single-phase characteristics were obtained.

FIG. 5 shows TiZ which is the composition range of the present invention.
It is the figure which showed the evaluation result when the differential scanning calorimetry DSC of rCuNiAu type | system | group alloy was performed. In addition, the evaluation results of the TiZrCuNi-based alloy without addition of Au are also shown. As is clear from this figure, A in the composition range of the present invention
It can be seen that the alloy added with u has a wide supercooled region, that is, between the crystallization start temperature and the glass transition temperature. Empirically, the width of the supercooled region is considered to indicate the stability of the metallic glass, and the result shows that the composition range of the present invention results in a bulk metallic glass having a large shape.

As a result of hardness measurement, it was found that the Vickers hardness was 500 or more, and the corrosion resistance by the cass test showed good results without rusting. As a result, it was found that the characteristics of the metallic glass shown above can be obtained even in a large-sized sample such as a watch case and a band.

Next, Table 1 shows the results of evaluation and evaluation of the watch bands produced by the experiment of Example 2 for several different compositions of TiZrCuNiAu type alloys.

As for the large shape of the evaluation results, the sample having a single phase in the cross-section of the sample which was an amorphous single phase by the structural analysis of X-ray diffraction at a diffraction angle of 20 to 80 degrees was marked with ◯ and the others were marked with x.
Corrosion resistance test is a cass test, sodium chloride 50g
/ L, cupric chloride 0.26 g / L, acetic acid 2 mL / L mixed solution in a tank adjusted to an atmosphere of about 35 ° C for about 1.5 cc
/ Hr / 80 cm ² was sprayed with an amount of about 72 hours, and depending on the degree of discoloration on the surface of the test product, the sample having no discoloration and excellent was judged as pass (◯). Hardness measurement is a load of 2
H is the evaluation result of Vickers hardness when measured at 5 gf.
Those with a value of v300 or more were passed (◯).

All of a to f within the scope of the present invention were good results, and all evaluation results were acceptable. On the other hand, the ratio of elements consisting of Ti and X is 3
0%, and the ratio of elements consisting of Cu, Ni, Au is 7
In Comparative Example g in which 0% was obtained, the characteristics of the amorphous single phase were not obtained, and the corrosion resistance test was discolored, and the comprehensive evaluation was unacceptable. On the contrary, when the ratio of the element composed of Ti and X in Comparative Example h was out of the composition range of the present invention, it was also unacceptable. In addition, when the Ni content exceeded 10% as in Comparative Example i and when the added amount of Au was less than 0.2% as in Comparative Example j, the results were also unacceptable. The Ni content of 5% or more and 10% or less within the range of the present invention is effective for obtaining the metallic glass.

For k and l within the range of the present invention, both were good results, and the evaluation results were all acceptable. On the other hand, when the proportion of the element consisting of Ti and X is less than the range of the present invention (Comparative Example m), is large (Comparative Example n), and the addition amount of Au is 0.1%, the result is unacceptable. It was

Similarly, for p within the range of the present invention, all were good results, and all evaluation results were acceptable. On the other hand, when the proportion of the element consisting of Ti and X was less than the range of the present invention (Comparative Example q) and was large (Comparative Example r), the result was unacceptable.

As described above, if the alloy composition and the composition range thereof are the present invention, an amorphous structure can be obtained even in a large shape such as a general watch case, and the corrosion resistance test and the hardness of the metallic glass are good. It was found that the characteristics of In particular, it is considered that the addition of 0.2 to 8 atomic percent of Au contributes to obtaining a stable metallic glass, and as a result, it is considered that the excellent corrosion resistance is exhibited. That is, the corrosion resistance test of the alloy of the present invention,
It is considered that the hardness is excellent because it does not have a grain boundary and exhibits a surface-passivated characteristic. For a composition in which the amount of Au added exceeds 8 atomic percent, the material cost may increase and the industrial application range is limited. Therefore, the composition is preferably within the range of the present invention.

On the other hand, the ratio of the elements consisting of Ti and X and C
It has been found that the ratios of u and Ni elements are greatly influenced, but within the range of the present invention, the favorable properties of metallic glass are exhibited as described above. Regarding the X element, the titanium alloy is originally characterized in that it is lightweight, and the specific gravity of the material itself increases as the amount of the X element added increases, so it is preferably within the range of the present invention. However, if the X element is not contained at all, it becomes difficult to obtain the characteristics of the metallic glass. Therefore, the range of 5% or more and 20% or less of the present invention is effective.

It has been found that the warm work forming in Example 1 of the present invention can be carried out at a low temperature as compared with the conventional hot forging because the work can be performed near the glass transition temperature of about 500 ° C. . In addition, this processing method has a feature that processing can be performed with extremely excellent transferability. That is, the metallic glass exhibits viscous flow in the glass transition temperature region, and the molding method utilizing the viscous flow also has a characteristic of high transferability that reflects finely formed irregularities. It is suitable as a processing method for decorative members such as the watch case and band created this time, and it has the effect that if it is necessary to form finely printed characters on the mold, it can be transferred as it is.

The metallic glass of the present invention is characterized in that, when it is cooled after being heated above its melting point, the cooling rate in a liquid state is slow, and even if it is actively cooled, it has a certain level. It becomes possible to maintain the liquid state for a time. It is because of this feature that the molten metal forging of Example 2 is possible. Since the metallic glass of the present invention tends to be in a more stable liquid state, a larger shaped metallic glass is obtained. Contribute to that.

In the first and second embodiments of the present invention, the chi
Ti as a tan metallic glass₃₅Zr _TenCu₄₂Ni₈Au_Five
The explanation was given using alloys, but there is no particular limitation.
Importantly, the amorphous phase, that is, metallic glass
Which is within the composition range of the present invention.
iaXbCucNidAue, where [a, b,
c, d, and e are atomic percentages 35 ≦ a + b ≦ 55, 5
≦ b ≦ 20, 45 ≦ c + d + e ≦ 65, 5 ≦ d ≦ 10,
0.2 ≦ e ≦ 8].

Further, in the first and second embodiments of the present invention, the explanation was made using the timepiece case and the band as the timepiece exterior material of the base material, but there is no particular limitation, and the timepiece bezel is used. Alternatively, the band may be created by the method of the first embodiment. Of course, by changing the mold,
Similar effects can be obtained by using titanium alloy accessories, various decorative materials such as rings, and sports equipment such as golf clubs.

Table 2 shows the evaluation results of the TiZrCuNi system to which several additives having different components were added. The sample used for the evaluation was produced by the quenching casting method in which the molten metal was poured into a cylindrical mold having a diameter of 5 mm and a length of 50 mm and quenched by using the vacuum casting apparatus shown in FIG. .

As an evaluation result, no crystalline peak was observed in the structural analysis, and the sample was in an amorphous single phase.
And As a result, it was found that the evaluation result of t, which is the composition range of the present invention, was good. In addition, s when nothing is added in the comparative example and Al, Co, and Ag of the other components are not good results. Especially, addition of Co and Ag decreases the amorphous forming ability, that is, compared with s where nothing is added. And showed a tendency to get worse.

As a result of the evaluation, the sample having a diameter of 5 mm was used to obtain a product such as a case, a band, or a golf club which is a watch exterior, and a large sample having a diameter of 5 mm or more. If a bulk-shaped metallic glass can be obtained, the range of application to relatively large products such as the above products will be expanded.

[0051]

[Table 1]

[0052]

[Table 2]

[0053]

The titanium alloy of the present invention contains the element X (Zr, Hf, N) which contains Cu and Au and is a solid solution in titanium.
It is a titanium alloy having at least one type of (b, Ta), an amorphous structure, and the characteristics of metallic glass. Alternatively, it is a titanium alloy containing Ni in the above titanium alloy. Alternatively, it is a titanium alloy containing Cu, Au, and Ni, having an amorphous structure, and having the characteristics of metallic glass. According to the above configuration, even if the sample has a large size, excellent corrosion resistance, high hardness, and easy molding at low temperature can be obtained.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing an apparatus for performing vacuum casting.

FIG. 2 is a conceptual diagram showing an apparatus for performing warm work forming.

FIG. 3 is a conceptual diagram showing an apparatus for performing molten metal forging.

FIG. 4 is a TiZ produced according to the first embodiment of the present invention.
2 shows the results of X-ray diffraction performed on a rCuNiAu alloy in a diffraction angle range of 20 ° to 80 °.

FIG. 5 is a comparison example of TiZrCuNiAu alloy and T which is a comparative example.
It is the figure which showed the evaluation result when the differential thermal scanning analysis of iZrCuNi type | system | group alloy is performed.

[Explanation of symbols]

2 vacuum casting equipment 4 vacuum exhaust device 6 heating mechanism 8 injection mechanism 10 Sample outlet 12 gas introduction line 14 Lifting mechanism 16 quartz tube 18 Primary Mold 20 sample table 22 Primary molded products 24 Warm processing equipment 26 Press mechanism 28 Secondary Mold 30 Sample moving mechanism 32 Melting sample table 34 Melting electrode 36 Molten Metal Forging Equipment

Continued front page    (72) Inventor Satoshi Atsushi             6-12 Tanashi-cho, Nishi-Tokyo, Tokyo             Chisun Watch Co., Ltd.

Claims (7)

[Claims] 1. A titanium alloy containing Cu and Au, containing at least one element which is a solid solution in titanium at all, has an amorphous structure, and has characteristics of metallic glass. 2. An element which is a solid solution in the titanium is Z
The titanium alloy according to claim 1, which is r, Hf, Nb, or Ta. 3. The titanium alloy according to claim 1, which contains Ni. 4. A titanium alloy containing Cu, Au and Ni, having an amorphous structure, and having the characteristics of metallic glass. 5. The chemical composition of the titanium alloy is TiaXb.
CucAue (where X is Zr, Hf, Nb
Alternatively, it is at least one element of Ta. ), 35 at% ≤ a + b ≤ 55 at% 5 at% ≤ b ≤ 20 at% 45 at% ≤ c + e ≤ 65 at% 0.2 at% ≤ e ≤ 8 at% Titanium according to claim 1 or 2, alloy. 6. The chemical composition of the titanium alloy is TiaXb.
CucNidAue (where X is Zr, H
At least one element selected from f, Nb, and Ta. ), 35 at% ≤ a ≤ 55 at% 5 at% ≤ b ≤ 20 at% 45 at% ≤ c + d + e ≤ 65 at% 5 at% ≤ d ≤ 10 at% 0.2 at% ≤ e ≤ 8 at%. The described titanium alloy. 7. The chemical composition of the titanium alloy is TiaCu.
When it is set to cNidAue, 35 at% ≦ a ≦ 55 at% 45 at% ≦ c + d + e ≦ 65 at% 5 at% ≦ d ≦ 10 at% 0.2 at% ≦ e ≦ 8 at% Titanium according to claim 4, characterized in that alloy.