JP2004107691A - High strength titanium alloy and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high strength titanium alloy, its production method and its formed body. <P>SOLUTION: In the method for producing a high strength titanium alloy in which low temperature forming is realized, both of 0.5 to 10 atomic% iron and 0.5 to 15 atomic% silicon are added to titanium, and non-equilibrium treatment is carried out. In the method for producing a high strength titanium alloy, both of 0.5 to 10 atomic% iron and 0.5 to 15 atomic% silicon are added to titanium, and one or more kinds of metals selected from niobium, chromium, vanadium and molybdenum are further added thereto, and non-equilibrium treatment is carried out. As for a compounding method, the powder of ceramic or metal, or a fiber is added in the above method for producing a high strength titanium alloy. In the method for producing a high strength titanium alloy, the above high strength titanium alloy is subjected to secondary working. The high strength titanium alloys and high strength titanium alloy members are produced by these methods. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high-strength titanium alloy and a method for producing the same. More specifically, a titanium alloy containing both 0.5 to 10 atomic% or less of iron and 0.5 to 15 atomic% of silicon is machined. The present invention relates to a high-strength titanium alloy having a structure of fine crystal grains produced by realizing pressure molding at a low temperature of 1000 ° C. or less by non-equilibrium by a dynamic alloying method, and a method for producing the same.
The high-strength titanium alloy according to the present invention can be formed at a low temperature by non-equilibrium treatment, and can synthesize a titanium alloy having a fine structure. And biological members.
[0002]
[Prior art]
In general, a high-strength titanium alloy can be produced by increasing the number of alloying elements, making the structure fine by a heat treatment utilizing phase transformation, or making the structure fine by a mechanical alloying method. These methods for high-strength titanium alloys have been introduced in prior literature (see Non-Patent Documents 1 to 3). Further, a powder metallurgical approach using the elementary powder mixing method and the like have been introduced in the prior literature (see Non-Patent Document 4).
[0003]
[Non-patent document 1]
Yoshinori Kawabe, Bulletin of the Japan Institute of Metals, Materia, Vol. 1 (1998), 17-21
[Non-patent document 2]
Sugimoto et al., Bulletin of the Japan Institute of Metals, Materia, Vol. 1 (1998), 27-30
[Non-Patent Document 3]
Masashi Maki, Bulletin of the Japan Institute of Metals, Materia, Vol. 1 (1998), 31-34
[Non-patent document 4]
Saito et al., Toyota Central R & D Review, 21-1 (1991), 44
[0004]
However, when the number of alloying elements is increased, there is a problem that the inherent lightness and corrosion resistance of titanium are reduced, and the titanium is not suitable for recycling. Further, the heat treatment utilizing the phase transformation can be applied only to a specific titanium alloy, and cannot always be used as a high-strength material. On the other hand, high-strength titanium alloys composed of non-toxic elements with few alloying elements have not yet been developed. There are also attempts to refine the structure by mechanical alloying. However, when the titanium content is large, there is a problem that powder adheres to a container or the like much and powder cannot be produced.
[0005]
[Problems to be solved by the invention]
Under these circumstances, the present inventors have conducted intensive studies in view of the above-mentioned prior art to solve those problems, and as a result, added a small amount of silicon and iron to titanium and performed a non-equilibrium treatment. As a result, it has been found that the crystal grains of the titanium alloy are fine and the strength can be increased, and the present invention has been completed.
[0006]
That is, the present invention has been made to produce a high-strength titanium alloy by adding a small amount of a less toxic element to titanium. The object of the present invention is to provide a high-strength titanium alloy by forming a titanium alloy at a low temperature by processing, thereby making the structure of the titanium alloy finer, and providing a high-strength titanium alloy obtained thereby. It is.
[0007]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems includes the following technical means.
(1) A titanium alloy containing both 0.5 to 10 atomic% of iron and 0.5 to 15 atomic% of silicon is subjected to non-equilibrium treatment by a mechanical alloying method and optionally solidified to form a titanium alloy A method for producing a high-strength titanium alloy, which is a powder or a compact thereof.
(2) The method for producing a high-strength titanium alloy according to the above (1), wherein the non-equilibrium-treated titanium alloy powder is pressure-formed at 1000 ° C. or lower.
(3) The method for producing a high-strength titanium alloy according to the above (2), wherein the non-equilibrium-treated titanium alloy powder is subjected to pressure molding while applying electric heating.
(4) The method for producing a high-strength titanium alloy according to (1), wherein a titanium alloy containing at least one of niobium, chromium, vanadium, and molybdenum is non-equilibrium-treated by a mechanical alloying method.
(5) The method for producing a high-strength titanium alloy according to the above (4), wherein the non-equilibrium-treated titanium alloy powder is pressed at 1000 ° C. or lower.
(6) The method for producing a high-strength titanium alloy according to the above (5), wherein the non-equilibrium-treated titanium alloy powder is subjected to pressure molding while being electrically heated.
(7) The titanium alloy produced by the method according to the above (1) or (4) is made into a powder, and a ceramic or metal powder or a fiber is added thereto, and is subjected to pressure molding at 1000 ° C. or less. Method for producing a high-strength titanium alloy.
(8) The method for producing a high-strength titanium alloy according to the above (7), wherein the high-strength titanium alloy is subjected to pressure molding while applying electric current.
(9) A high-strength titanium alloy having fine crystal grains of 10 μm or less, produced by the method according to any one of (1) to (8).
(10) A high-strength titanium alloy member obtained by forming the high-strength titanium alloy according to (9) by secondary processing such as rolling, forging, or deep drawing.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in more detail.
The titanium alloy used in the present invention may be a powder or a pre-melted alloy. Non-equilibrium treatment of titanium alloys is generally performed by a rapid solidification method, a sputtering method, or the like.However, these methods are more preferable methods because there is a concern that oxygen and nitrogen are contaminated from a melting atmosphere during melting. is not. Non-equilibrium treatment of titanium alloys can be achieved by using a metal powder that constitutes the alloy as a starting material, by non-equilibrium by mechanical alloying, or by turning a pre-alloyed titanium alloy into a powder by machining such as a lathe. A mechanical alloying treatment such as a method of non-equilibrium by gliding is used as a preferable method. These non-equilibrium techniques are described in "Pulse-Current Sintering of Amorphous Titanium Powder Synthesized by Mechanical Alloying", Kobayashi et al .: Journal of the Japan Institute of Metals, Vol. 66 (2002) 155-158, and "solidification molding of Ti-35at% Fe-5at% Si-5at% B alloy powder produced by mechanical gliding", Kobayashi et al .: Journal of the Japan Institute of Metals, Vol. 64 (2000) 723-726.
[0009]
However, the non-equilibrium treatment is easily affected by the alloy composition of the titanium alloy, and in the present invention, contains both 0.5 atomic% to 10 atomic% of iron and 0.5 atomic% to 15 atomic% of silicon. Is necessary and important. In the case of a titanium alloy containing only iron, non-equilibrium treatment is difficult, long treatment is required, and contamination during treatment becomes a problem. An alloy containing only silicon can perform non-equilibrium treatment, but cannot exhibit high strength. Further, if these elements are added in less than 0.5 atomic%, it is difficult to disperse uniformly, and if iron is added in more than 10 atomic% or silicon is added in more than 15 atomic%, a hard and brittle intermetallic compound (TiFe) is added. , Ti ₅ Si _3, etc.), and both cannot exhibit high strength.
[0010]
The non-equilibrium-treated titanium alloy is generally in the form of a powder and has high hardness even in a powder state, but is difficult to use as an industrial material. In the present invention, the non-equilibrium-treated titanium alloy can be formed into a bulk by heating while applying pressure. In this case, particularly when the powder subjected to the non-equilibrium treatment is molded at a temperature or higher at which the powder transitions to an equilibrium state, excellent moldability can be obtained. As a heating mechanism, an electric furnace, a high-frequency furnace, or the like can be used, but it is preferable to perform heating in a vacuum in order to suppress oxidation and nitridation of titanium. This heating mechanism can be easily realized by using a commercially available electric heating device. A compact formed at a temperature slightly higher than the temperature at which the state transitions to the equilibrium state has fine crystal grains of 10 μm or less, and becomes a high-strength titanium alloy bulk material. Further, if heating is performed even after reaching the equilibrium state, the crystal grains become coarse and the strength is significantly reduced. Therefore, the heating temperature at the time of molding needs to be 1000 ° C. or lower, and it is necessary to perform molding at a temperature lower than the sintering temperature of the conventional titanium alloy powder.
[0011]
For molding the powder, a graphite mold or a cemented carbide mold generally used for electric current sintering can be used. In the method of the present invention, no reaction with graphite or reaction with cemented carbide is observed in the sintered alloy. This is realized because the sintering temperature is 1000 ° C. or lower, which is lower than the sintering temperature of a general titanium alloy. The pressing force at the time of molding is not particularly specified. For example, when a graphite mold is used, about 40 MPa can be applied, and when a cemented carbide mold is used, about 400 MPa can be applied. The mechanism for generating the pressing force is not particularly limited, but generally, hydraulic pressure, pneumatic pressure, mechanical pressurization, or the like can be used. The heating atmosphere is not particularly limited, but a vacuum atmosphere is preferable in order to reduce the amount of oxygen and nitrogen contained in the molded body and improve mechanical properties.
[0012]
When one or more of niobium, chromium, vanadium, and molybdenum are included in the non-equilibrium treatment of the titanium alloy, β-type titanium is included in the bulk-formed titanium alloy. Since β-type titanium is excellent in ductility, the strength of the molded body can be further increased. The method of adding these additional elements is not particularly limited, but a method of adding them at the time of alloy preparation or a method of adding them in the form of metal powder at the time of mechanical alloying treatment can be used. Further, although the amounts of these additional elements are not particularly specified, β-type titanium increases in the molded body when the amount is large, and α-type titanium increases when the amount is small. When it is desired to increase the hardness of the compact, it is preferable to increase the amount of α-type titanium. In addition, even if these additional elements are present, almost no change is recognized in the sintering process and the like.
[0013]
Ceramic or metal fibers or powder can be added to the non-equilibrated titanium powder. Thereby, the strength of the molded body can be further improved. Further, the addition thereof can improve the poor thermal conductivity inherent in the titanium alloy. The method of adding these is not particularly specified, but a commonly used mixing method can be used. However, when the fibers are added, there is a possibility that the fibers are crushed at the time of mixing. Therefore, a mixing method having lower energy than the mechanical alloying treatment is preferable. For example, a wet mixing method or a mixing method using an automatic grinder can be used.
[0014]
A mixture of ceramics and metal added to non-equilibrated titanium powder can be formed into a bulk by the same process as non-equilibrated titanium powder. The amount of the added ceramic or metal is not particularly limited, but generally, it is preferable to add 30% by volume or less. If it is added in an amount of 30% by volume or more, uniform dispersion is difficult, and the strength of the molded body may decrease. For the sintering of the mixture, a method of heating while applying pressure can be used, and the sintering temperature can be set to 1000 ° C. or lower. For this reason, even if it becomes a composite material, there is almost no reaction between the titanium alloy serving as the matrix and the added metal or ceramics, and the composite material can exhibit high strength. Note that, as the metal material dispersed in the titanium alloy, for example, tungsten, molybdenum, a silicide intermetallic compound, or the like is preferable, and as the ceramic, for example, carbide ceramics, oxide ceramics, carbon, sulfide ceramics, or the like is preferable. is there.
[0015]
When the non-equilibrium-treated titanium powder is heated and pressurized and solidified into a bulk, the powder rapidly densifies at a temperature slightly higher than the equilibrium temperature. This compact has fine crystal grains and can exhibit high strength. Utilizing this denseness and high strength, secondary processing such as rolling, forging, and deep drawing can be easily performed. In the rolling and forging of titanium alloys, the technology of heating to a high temperature to control the atmosphere (reduce oxygen) or controlling the alloying elements to mix α-type and β-type titanium and perform secondary processing It's being used. In the present invention, an appropriate secondary processing technique can be used. In the alloy of the present invention, since the crystal grains of the titanium alloy are fine, large heating is not required and secondary processing can be easily performed. Further, the alloy of the present invention is produced by a powder metallurgy technique. However, since the compact is dense, cracks due to secondary processing do not occur. The high-strength titanium alloy produced by the method of the present invention is useful, for example, as a material such as a micromachine member, a biocompatible member, and the like.
[0016]
【Example】
Next, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples.
Example 1
Starting from titanium powder (99.5% by mass titanium), iron powder (atomized iron powder, 99.8% by mass iron) and silicon powder (99.9% by mass silicon) as starting materials, mechanical alloying was performed for 400 hours by a planetary ball mill. By the ing treatment, 20 g of a Ti-2at% Fe-10at% Si alloy powder was synthesized. 0.5 g of the obtained powder was filled in a cemented carbide mold having an outer diameter of 20 mm, an inner diameter of 6 mm, and a height of 20 mm, and a pulsed current was applied while pressurizing at 200 MPa to perform solidification molding. The solidification molding was performed by heating to 600 ° C. in a vacuum of about 10 Pa.
[0017]
The powder obtained by mechanical alloying was in an amorphous state, and was a powder that crystallized at about 560 ° C. (863K) as shown in FIG. 1 as a result of thermal analysis by DSC. Heating this powder to 600 ° C., slightly above the crystallization (equilibration) temperature, resulted in a shrinkage curve as shown in FIG. Large shrinkage was observed near the crystallization temperature, and densification proceeded rapidly.
[0018]
FIG. 3 shows the result of X-ray diffraction of the obtained molded body, and it is a composite material in which α-type titanium and Ti ₅ Si ₃ intermetallic compound are slightly mixed. The crystal grain size of this compact was as fine as about 100 nm, and its compressive strength showed a high value exceeding 1.5 GPa.
[0019]
Example 2
Starting from titanium powder (99.5 mass% titanium), iron powder (atomized iron powder, 99.85 mass% iron), silicon powder (99.9 mass% silicon) and niobium powder (98 mass% niobium), 20 g of a Ti-2at% Fe-10at% Si-2at% Nb alloy powder was produced by a mechanical alloying treatment using a planetary ball mill. 0.5 g of the obtained powder was filled in a cemented carbide mold having an outer diameter of 20 mm, an inner diameter of 6 mm, and a height of 20 mm, and a pulsed current was applied while pressurizing at 200 MPa to perform solidification molding. The solidification molding was performed by heating to 550 ° C. in a vacuum of about 10 Pa.
[0020]
The powder obtained by mechanical alloying was in an amorphous state, and was a powder that crystallized at about 460 ° C. (738K) as shown in FIG. 4 showing the results of thermal analysis by DSC. When this powder was heated to 550 ° C., which was higher than the crystallization (equilibrium) temperature, large shrinkage was observed and densification proceeded rapidly.
[0021]
The X-ray diffraction result of the obtained molded body is shown in FIG. 5, and it is a composite material in which α-type titanium, β-type titanium, and a slight amount of Ti ₅ Si ₃ intermetallic compound are mixed. The crystal grain size of this compact was as fine as about 200 nm, and its compressive strength showed a high value exceeding 1.2 GPa.
[0022]
Example 3
100 g of a Ti-10 at% Fe-5 at% Si-5 at% B alloy synthesized by the cold crucible levitation melting method is pulverized by a mechanical grinding method, and 3 g of the powder is graphite having an outer diameter of 30 mm, an inner diameter of 10 mm, and a height of 30 mm. And pressurized at 30 MPa to apply a pulsed current to perform solidification molding. The solidification molding was performed by heating to 700 ° C. in a vacuum of about 10 Pa.
[0023]
The powder obtained by mechanical grinding was in a non-equilibrium state including an amorphous phase, and crystallized at about 400 ° C. (673 K). When this powder was heated to 700 ° C., which was higher than the crystallization (equilibration) temperature, densification proceeded with large shrinkage.
[0024]
The obtained molded body was composed of α-type titanium, a Ti—Si intermetallic compound, TiB 2, and the like, and had a compressive strength of about 1 GPa. The crystal grain size of the compact was submicron.
[0025]
Example 4
Starting from titanium powder (99.5% by mass titanium), iron powder (atomized iron powder, 99.8% by mass iron) and silicon powder (99.9% by mass silicon) as starting materials, mechanical alloying was performed for 400 hours by a planetary ball mill. By the ing treatment, 20 g of a Ti-2at% Fe-10at% Si alloy powder was synthesized. To 0.5 g of the obtained powder, 0.07 g of yttrium oxide powder (particle size of about 1 μm) was mixed in a mortar, and the mixture was filled into a cemented carbide mold having an outer diameter of 20 mm, an inner diameter of 6 mm, and a height of 20 mm, A pulse-shaped current was applied while pressurizing at 200 MPa to perform solidification molding. The solidification molding was performed by heating to 600 ° C. in a vacuum of about 10 Pa.
[0026]
The powder obtained by mechanical alloying was in an amorphous state and crystallized at about 560 ° C. (863K). When this powder was heated to 600 ° C., which was slightly higher than the crystallization (equilibration) temperature, large shrinkage was observed near the crystallization temperature, and densification proceeded rapidly.
[0027]
The obtained compact is a composite material in which the added yttrium oxide particles are uniformly dispersed in a matrix containing α-type titanium and a slight amount of Ti ₅ Si ₃ intermetallic compound. The crystal grain size of this compact was as fine as about 100 nm, and its compressive strength showed a high value exceeding 1.0 GPa.
[0028]
Example 5
Starting from titanium powder (99.5% by mass titanium), iron powder (atomized iron powder, 99.8% by mass iron) and silicon powder (99.9% by mass silicon) as starting materials, mechanical alloying was performed for 400 hours by a planetary ball mill. By the ing treatment, 20 g of a Ti-2at% Fe-10at% Si alloy powder was synthesized. 0.5 g of the obtained powder was filled in a cemented carbide mold having an outer diameter of 20 mm, an inner diameter of 6 mm, and a height of 20 mm, and a pulsed current was applied while pressurizing at 200 MPa to perform solidification molding. The solidification molding was performed by heating to 600 ° C. in a vacuum of about 10 Pa.
[0029]
The powder obtained by mechanical alloying was in an amorphous state and crystallized at about 560 ° C. (863K). When this powder was heated to 600 ° C., which was slightly higher than the crystallization (equilibrium) temperature, large shrinkage was observed near the crystallization temperature, and densification proceeded. The obtained molded body was a composite material in which α-type titanium and Ti5 Si3 intermetallic compound were slightly mixed.
[0030]
The compact having a diameter of 6 mm and a thickness of 3 mm was subjected to 80% rolling at room temperature by a rolling machine. No large cracks were observed in the rolled material, and molding could be performed. The obtained molded body had a compressive strength exceeding 1.2 GPa.
[0031]
【The invention's effect】
As described in detail above, the present invention relates to a high-strength titanium alloy having a fine grain structure and a method for producing the same. According to the present invention, fine processing can be performed using the high-strength titanium alloy of the present invention. It is possible to produce and provide the required lightweight and minute members. The present invention realizes solidification molding at a low temperature by once non-equilibrium treatment of a titanium alloy, and produces and supplies a titanium alloy member with much less energy than solidification molding of a titanium alloy by conventional powder metallurgy. can do. Further, in order to improve the strength of the titanium alloy, generally, many of the added elements are harmful to the human body, but in the present invention, the crystal grain size of the titanium alloy is reduced. High strength is achieved, and alloy components added for non-equilibrium treatment do not include those that are toxic to the human body. Therefore, the high-strength titanium alloy of the present invention can be used as a biocompatible member, and can be applied to implant materials and the like.
[Brief description of the drawings]
FIG. 1 shows the results of thermal analysis by DSC of Example 1.
FIG. 2 shows a shrinkage curve in electric current sintering of Example 1.
FIG. 3 shows an X-ray diffraction result of the molded article obtained in Example 1.
FIG. 4 shows a result of a thermal analysis by DSC of Example 2.
FIG. 5 shows the results of X-ray diffraction of the molded product obtained in Example 2.

Claims (10)

A titanium alloy containing both 0.5 to 10 atomic% of iron and 0.5 to 15 atomic% of silicon is subjected to non-equilibrium treatment by a mechanical alloying method and optionally solidified to form a titanium alloy powder or a titanium alloy powder thereof. A method for producing a high-strength titanium alloy, which is formed into a compact. The method for producing a high-strength titanium alloy according to claim 1, wherein the non-equilibrium-treated titanium alloy powder is subjected to pressure molding at 1000 ° C or lower. The method for producing a high-strength titanium alloy according to claim 2, wherein the non-equilibrium-treated titanium alloy powder is subjected to pressure molding while applying electric heating. The method for producing a high-strength titanium alloy according to claim 1, wherein a titanium alloy containing at least one of niobium, chromium, vanadium, and molybdenum is non-equilibrium-treated by a mechanical alloying method. The method for producing a high-strength titanium alloy according to claim 4, wherein the non-equilibrium-treated titanium alloy powder is pressed at 1000 ° C or lower. The method for producing a high-strength titanium alloy according to claim 5, wherein the non-equilibrium-treated titanium alloy powder is subjected to pressure molding while applying electric current and heating. A high-strength titanium alloy, comprising: forming a powder of the titanium alloy produced by the method according to claim 1, adding a powder or fiber of ceramics or metal, and press-forming at 1000 ° C. or less. Manufacturing method. The method for producing a high-strength titanium alloy according to claim 7, wherein the titanium alloy is pressure-formed while being electrically heated. A high-strength titanium alloy having fine crystal grains of 10 μm or less, produced by the method according to claim 1. A high-strength titanium alloy member obtained by forming the high-strength titanium alloy according to claim 9 by secondary processing such as rolling, forging, or deep drawing.

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