WO2015030131A1

WO2015030131A1 - Zirconium alloy for organism, method for manufacturing said alloy, and medical tool for organism incorporating zirconium alloy for organism

Info

Publication number: WO2015030131A1
Application number: PCT/JP2014/072622
Authority: WO
Inventors: 茜津野; 勇太田中; 塙　隆夫; 川崎　亮; 野村　直之
Original assignee: 株式会社Ihi; 国立大学法人東京医科歯科大学; 国立大学法人東北大学
Priority date: 2013-08-30
Filing date: 2014-08-28
Publication date: 2015-03-05
Also published as: JPWO2015030131A1; JP6160699B2

Abstract

　A zirconium alloy for an organism, the alloy containing Zr as a main ingredient and 12% to less than 20% of Ta (percentages expressed in terms of mass), the constituent phase comprising martensite including orthorhombic crystals of martensite.

Description

Biomedical zirconium alloy, method for producing the same, and biomedical device using the biomedical zirconium alloy

The present invention relates to a biomedical zirconium alloy, a production method thereof, and a biomedical device using the biomedical zirconium alloy.

Metal materials are used in many medical devices mainly because of their mechanical reliability. Among them, implant materials such as artificial hip joints, artificial knee joints, bone plates, and artificial tooth roots are pure materials with excellent hard tissue compatibility. Ti and Ti alloys are used. However, these metal materials are considered to have the following problems at the time of image diagnosis using a magnetic resonance diagnosis (MRI) apparatus.

If MRI is performed with a metal material placed in the body, an image defect called artifact occurs around the member, making it difficult to evaluate and confirm the bone fusion of the member. The cause of the artifact is a mismatch between the magnetic susceptibility of the implant material and the negative magnetic susceptibility of the living tissue. As a solution to this problem, the use of a metal material having a low magnetic susceptibility or a negative magnetic susceptibility has been proposed. Can be mentioned. Since a diamagnetic metal material (eg, a gold alloy) having a negative magnetic susceptibility has difficulty in strength, the present inventors have attempted to lower the magnetic susceptibility with a paramagnetic metal material.

Zirconium (Zr) is inferior in mechanical strength to Ti, but has lower cytotoxicity and magnetic susceptibility than Ti. Therefore, the present inventors have proposed a low magnetic susceptibility alloy for living body mainly composed of Zr. In recent years, when a Ti alloy is applied as a material for a bone anchor, a problem has been reported in which the bone anchor adheres to the bone and is difficult to remove after bone fusion. Zr-based alloys have the property of not forming calcium phosphate, the main component of bone, on the surface of the material, thus eliminating the above problems.

The elastic modulus of Ti-based alloy (about 100 to 200 GPa) is much larger than that of cortical bone (about 20 GPa). This elastic modulus gap causes overload shielding (stress shielding) to the bone, resulting in bone atrophy. Therefore, if a low-elasticity Zr alloy that is as close to cortical bone as possible can be developed, it can be provided as a material for a bone anchor that can be easily removed and stress shielding is less likely to occur.

There is a possibility that the magnetic susceptibility and elastic modulus of the Zr-based alloy may change greatly by controlling the alloying elements and the constituent phases. In this regard, several proposals have been made in the past.
For example, in Patent Document 1, among the main transition metals of Groups 4 to 6 in the periodic element periodic table, Zr is a main component, and the main component other than Zr is used as a subcomponent having a lower content than the main component. A biomaterial is described that contains 0.5 to 15% by mass of at least one transition metal (Ti, V, Cr, Nb, Mo, Hf, Ta, W).
For example, Patent Document 2 describes a biological zirconium alloy containing Zr as a main component and containing Nb in a range of more than 15 mass% and 25 mass% or less.
For example, Patent Document 3 includes Ti 25 to 50% by mass, Zr 25 to 60% by mass, Nb 5 to 30% by mass and Ta 5 to 40% by mass, and the mass ratio of Zr to Ti is 0.5 to 0.5%. A Ti—Zr-based alloy having a mass ratio of Nb to Ta of 0.125 to 1.5 is described.

JP 2010-75413 A JP 2012-66017 A Japanese Patent Laid-Open No. 2001-3127

In the medical field, the magnetic field of MRI is increasing for high-resolution imaging, and further low magnetic susceptibility alloys are required in the future. Conventional biomedical zirconium alloys represented by those described in Patent Document 1 or 2 have room for improvement in elastic modulus.

The present invention aims to solve the above problems.
That is, an object of the present invention is to provide a biomedical zirconium alloy having a low elastic modulus, a production method thereof, and a biomedical device using the biomedical zirconium alloy.

The inventor has intensively studied to solve the above-mentioned problems, and has completed the present invention.
The present invention includes the following (1) to (13).
(1) A biological zirconium alloy containing Zr as a main component, containing Ta in a range of 12% by mass or more and less than 20% by mass, and the constituent phase comprising martensite including orthorhombic martensite.
(2) The biomedical zirconium alloy according to (1), wherein Ta is contained in a range of 12% by mass or more and less than 20% by mass, and the balance is made of Zr and inevitable impurities.
(3) The biomedical zirconium alloy according to (2), which contains Ta in a range of 15% by mass or more and less than 20% by mass.
(4) The biomedical zirconium alloy according to (3), which contains Ta in a range of 15% by mass to 18% by mass.
(5) The biomedical zirconium alloy according to (4), which contains Ta in a range of more than 15% by mass and 18% by mass or less.
(6) The biological zirconium alloy according to any one of (1) to (5), wherein the constituent phase is composed of orthorhombic martensite and hexagonal martensite.
(7) The biomedical zirconium alloy according to any one of (1) to (5), obtained by heat treatment in the range of 1100 to 1500 ° C. and then cooling at a cooling rate of 200 ° C./min or more. .
(8) A metal molded body containing Zr as a main component and containing Ta in a range of 12% by mass to less than 20% by mass is heat-treated in a range of 1100 to 1500 ° C., and then cooled at a cooling rate of 200 ° C./min or more. Zirconium alloy for living body obtained as above.
(9) A biomedical instrument using the biomedical zirconium alloy according to (1) above.
(10) A metal molded body containing Zr as a main component and containing Ta in a range of 12% by mass to less than 20% by mass is heat-treated in a range of 1100 to 1500 ° C., and then cooled at a cooling rate of 200 ° C./min or more. The manufacturing method of the zirconium alloy for biological bodies provided with the process to do.
(11) The method for producing a zirconium alloy for living body according to (10), wherein the heat treatment time is 0.1 hour or more and 5 hours or less.
(12) The method for producing a zirconium alloy for living body according to (11), wherein the heat treatment time is 0.1 hour or more and 2 hours or less.
(13) The method for producing a zirconium alloy for living body according to (12), wherein the heat treatment time is 0.1 hour or more and 1 hour or less.

According to the present invention, it is possible to provide a biomedical zirconium alloy having both a low magnetic susceptibility and a low elastic modulus, a method for producing the same, and a biomedical device using the biomedical zirconium alloy.

It is a graph which shows the measurement result of the relationship between Ta content rate and an elasticity modulus. It is a graph which shows the measurement result of the relationship between Ta content rate and magnetic susceptibility in a heat-treated material and as-cast material. 3 is a metallographic photograph of a Zr-15 mass% Ta alloy (as cast) by a scanning electron microscope. 3 is a metallographic photograph of a Zr-15 mass% Ta alloy (heat treated material) by a scanning electron microscope. It is a metallographic photograph of a Zr-18 mass% Ta alloy (as cast) by a scanning electron microscope. 3 is a metallographic photograph of a Zr-18 mass% Ta alloy (heat treated material) by a scanning electron microscope. It is a metallographic photograph of a Zr-20 mass% Ta alloy (as cast) by a scanning electron microscope. 3 is a metallographic photograph of a Zr-20 mass% Ta alloy (heat treated material) by a scanning electron microscope. 3 is a graph showing X-ray diffraction results of an as-cast material and a heat-treated material in a Zr-15 mass% Ta alloy, a Zr-18 mass% Ta alloy, and a Zr-20 mass% Ta alloy. It is a figure which shows the test piece shape of a tension test. It is a stress-strain diagram of each alloy. It is a figure which shows the structure of a bone fixing device.

The present invention will be described.
In the present invention, a metal molded body containing Zr as a main component and containing Ta in a range of 12% by mass or more and less than 20% by mass is heat-treated in a range of 1100 to 1500 ° C., and then at a cooling rate of 200 ° C./min or more. It is a biological zirconium alloy obtained by cooling.
Such a biomedical zirconium alloy is hereinafter also referred to as “the alloy of the present invention”.

Each component of the alloy of the present invention will be described.
In the alloy of the present invention, the C content and the S content are values obtained by measurement by a high-frequency combustion-infrared absorption method, the Si content is a value obtained by measurement by a silicon dioxide weight method, and the O content is Is the value obtained by measuring by infrared absorption method, N content is the value obtained by measuring by thermal conductivity method, and the content of other components is the value obtained by measuring by ICP-AES method. .

<Zr>
The alloy of the present invention contains Zr as a main component. “Main component” means a content of 30% by mass or more. The alloy of the present invention preferably contains 40 mass% or more of Zr, more preferably contains 50 mass% or more, more preferably contains 60 mass% or more, and more preferably contains 65 mass% or more. In such a case, the alloy of the present invention having a lower magnetic susceptibility and elastic modulus can be obtained.
Hereinafter, unless otherwise specified, the “main component” is used in the meaning as described above.

Zr has a lower magnetic susceptibility than Ti. Since the alloy of the present invention is mainly composed of Zr, the magnetic susceptibility is low, and artifacts during MRI diagnosis are suppressed.

The alloy of the present invention preferably contains Zr as a main component, contains Ta in a specific range, and the other consists of inevitable impurities. Inevitable impurities mean components that may be mixed from raw materials, manufacturing processes, etc. without intentional addition.
In the alloy of the present invention, B, C, N, O, Na, Mg, Si, P, S, K, Ca, Mn, and the like are impurity components. The lower the content, the better.

<Ta>
The alloy of the present invention contains Ta in the range of 12 mass% or more and less than 20 mass%.
Assuming that a specific heat treatment is performed, an alloy having a high elastic modulus is obtained when Zr is the main component and Ta is contained in an amount of 20% by mass or more, but less than 20% by mass (preferably about 18% by mass or less). The inventors have found that an alloy having a very low elastic modulus can be obtained. That is, the present inventors have found that there is a critical condition for the elastic modulus.
When the elastic modulus is low, for example, when the alloy of the present invention is used as a bone fixture, the load is easily transmitted to the bone tissue, and the bone resorption is suppressed.

The Ta content in the alloy of the present invention is preferably 13% by mass or more, more preferably 14% by mass or more, and further preferably 15% by mass or more. The Ta content is more preferably greater than 15% by mass. Further, the Ta content is more preferably 19% by mass or less, and further preferably 18% by mass or less. This is because a biological zirconium alloy having a lower elastic modulus can be obtained.
Thus, for example, the Ta content is preferably 15% by mass or more and less than 20% by mass, more preferably 15% by mass or more and 18% by mass or less, and more than 15% by mass and 18% by mass or less. More preferably it is.

As described above, the alloy of the present invention is obtained by subjecting a metal molded body containing Zr as a main component and Ta in a range of 12 mass% to less than 20 mass% to specific heat treatment and cooling.

The metal compact is preferably obtained by melting and casting the raw material.
For example, by using a melting raw material of Zr 99.5% by mass and Ta 99.5% by mass, melting the alloy in an Ar atmosphere by a non-consumable electrode type arc melting method, and casting using a desired mold, metal forming You can get a body.

The metal compact can also be obtained by powder metallurgy.
For example, after mixing metal powder and a binder and shape | molding in a desired shape, a degreasing process and sintering can be given and a metal molded object can be obtained. Specifically, for example, a metal material powder having an average particle diameter of about 1 to 30 μm is used, and this and a binder are kneaded to obtain a kneaded product, and the obtained kneaded product is injected into a mold by an injection molding machine. The resulting product can be degreased at about 100 to 750 ° C. in the atmosphere to obtain a molded body. The obtained product is sintered at a sintering temperature of 1000 to 1500 ° C. to obtain a metal molded body made of the sintered body.

<Heat treatment>
The metal molded body obtained as described above is heat-treated in the range of 1100-1500 ° C.
Hereinafter, this temperature is also referred to as a heat treatment temperature.
The heat treatment temperature is preferably 1150 ° C. or higher. The heat treatment temperature is preferably 1300 ° C. or less, and more preferably 1250 ° C. or less. The heat treatment temperature is preferably about 1200 ° C. The heat treatment is preferably performed in a vacuum atmosphere or an inert gas atmosphere in order to prevent oxidation.
In the biomedical zirconium alloy of the present invention, a metal molded body containing Zr as a main component and containing Ta in a range of 12% by mass to less than 20% by mass is subjected to heat treatment (solution treatment, homogeneous treatment) in the range of 1100 ° C to 1500 ° C. In this heat treatment temperature range, the metal formed body becomes a single phase of β-Zr during the heat treatment.
This β-Zr causes martensitic transformation. For this reason, when the heat-treated metal molded body is quenched by water cooling or the like in order to cause martensite transformation, the constituent phase of the biological zirconium alloy is composed of martensite containing orthorhombic martensite. For example, the constituent phase of the biomedical zirconium alloy is composed of orthorhombic martensite and hexagonal martensite.
When this metal formed body is heat-treated at a heat treatment temperature lower than 1100 ° C., the metal formed body may be subjected to solid phase separation during the heat treatment to be in a two-phase coexistence state of β-Zr and β-Ta. is there. When this heat-treated metal compact is quenched with water or the like, β-Zr undergoes martensitic transformation, whereas β-Ta does not undergo martensitic transformation. β-Ta may be included. When β-Ta is contained in the constituent phase of the biological zirconium alloy, the ductility of the biological zirconium alloy may be lowered. Therefore, it is preferable that β-Ta is suppressed.
For these reasons, the heat treatment of the metal molded body is performed in the range of 1100 ° C. to 1500 ° C. If the heat treatment temperature exceeds 1500 ° C., the heat treatment temperature becomes high, and the productivity of the biomedical zirconium alloy may be reduced. Therefore, it is preferable that the heat treatment is performed within the range of the heat treatment temperature in order to improve the productivity of the biological zirconium alloy.

The time for heat-treating the metal molded body at such a heat treatment temperature is also referred to as heat treatment time below.
Although the heat treatment time is not particularly limited, it is preferably 0.1 hour or longer, and preferably 0.25 hour or longer. The heat treatment time is preferably 5 hours or less, preferably 2 hours or less, and more preferably 1 hour or less. The heat treatment time is preferably about 0.5 hours.
As described above, the heat treatment time can be further homogenized by performing the heat treatment for 0.1 hours or more and 5 hours or less. Note that if the heat treatment time exceeds 5 hours, the heat treatment time becomes longer, and the productivity of the biomedical zirconium alloy may be reduced. Therefore, it is preferable that the heat treatment is performed for 0.1 hour or more and 5 hours or less in order to improve the productivity of the biomedical zirconium alloy.
In addition, if the heat treatment time becomes longer, β-Ta may be formed in the constituent phase of the biological zirconium alloy. Therefore, in order to suppress the formation of β-Ta, the heat treatment time is about 0.1 hour. It is preferably 2 hours or less and more preferably 0.1 hours or more and 1 hour or less.

<Cooling>
After heat-treating the metal molded body at the heat treatment temperature as described above, it is cooled at a cooling rate of 200 ° C./min or more.
The cooling rate is preferably 200 ° C./min or more, and more preferably 300 ° C./min or more.
Thus, by rapidly cooling at a cooling rate of 200 ° C./min or more, it becomes possible to cause martensitic transformation in the metal molded body heat-treated at the heat treatment temperature in the range of 1100 to 1500 ° C. as described above. .

The cooling method is not particularly limited, but water cooling is preferable. Air cooling can also be applied.
By such a production method, the biological zirconium alloy of the present invention can be produced.

<Medical medical device>
A biomedical device can be obtained using the alloy of the present invention.
Such a biomedical device is also referred to as “the device of the present invention”.

The instrument of the present invention can be obtained by, for example, melting a raw material containing Zr and Ta, solidifying the raw material into a predetermined shape, and further performing a predetermined heat treatment and cooling. Furthermore, you may perform surface treatments, such as machining, such as cutting and grinding, and various blast processes, as needed.

Specific examples of biomedical devices include aneurysm treatment devices (clips, embolization coils, stent grafts, etc.), stents (blood vessels, bile ducts, pancreatic ducts, tracheas, esophagus, intestinal tracts, etc.), indwelling in the body Devices (hemostatic clips, prosthetic valves, etc.), medical instruments (MRI compatible surgical instruments, devices (endoscopes, etc.), etc.), bone fixation instruments (eg osteosynthesis plates, osteosynthesis nails, osteosynthesis screws, bone fixation) Plate, intramedullary nail, etc.).

Next, examples and comparative examples of the present invention will be described.
<Melting of Zr-Ta alloy>
An alloy was melted by a non-consumable electrode type arc melting method in an Ar atmosphere using melting raw materials of Zr 99.5 mass% and Ta 99.5 mass%. In order to prevent segregation of the alloy, melting was performed three times, and the ingot was inverted each time.
Thus, an ingot of a Zr—Ta alloy having six compositions (each 350 g, approximately 500 mm × 400 mm × 15 mm) was obtained. The target composition of Ta in the six alloys is 10 mass%, 13 mass%, 15 mass%, 18 mass%, 20 mass%, and 30 mass%, and the balance is Zr.

Ingots with a target composition of Ta of 10% by mass and 13% by mass were obtained one by one. Two ingots having Ta target compositions of 15 mass%, 18 mass%, 20 mass% and 30 mass% were obtained.

And about each alloy, the elasticity modulus measurement was performed with casting.
Further, for ingots having a target composition of Ta of 15% by mass, 18% by mass, 20% by mass and 30% by mass, heat treatment at a heat treatment temperature of 1200 ° C. for 30 minutes, followed by water cooling The elastic modulus was measured.

<Elastic modulus measurement>
The elastic modulus of each alloy was measured by a free resonance method in the air and at room temperature using JE-RT (manufactured by Nippon Techno Plus). A sample obtained by cutting a round bar of φ3 mm × 25 mm from an ingot was used. Moreover, it measured twice about the sample of the same composition, and made those average values into the elasticity modulus in the alloy of each composition. The measurement results are shown in Table 1 and FIG. In addition, the literature value was used for the value of 0 mass% Ta in FIG.

As shown in Table 1 and FIG. 1, in the case of heat-treated 15% by mass Ta alloy and 18% by mass Ta alloy corresponding to the alloy of the present invention, the elastic modulus was extremely low.

In addition, the magnetic susceptibility of the heat-treated 15% by mass Ta alloy and 18% by mass Ta alloy is a value at which MRI imaging can be performed without any problem, and compared with Zr—Mo alloys and Zr—Nb alloys that are being developed in the same way. However, it is equivalent or low.
FIG. 2 is a graph showing the measurement results of the relationship between the Ta content and the magnetic susceptibility of the heat-treated material and the as-cast material. Regarding the measurement of magnetic susceptibility, the magnetic susceptibility of each alloy was measured by an Evans method in the atmosphere and at room temperature using a magnetic balance MSB-MKI (manufactured by Sherwood Scientific LTD). A sample obtained by cutting a round bar of φ3 mm × 25 mm from an ingot was used. Moreover, it measured twice about the sample of the same composition, and those average values were made into the magnetic susceptibility in the alloy of each composition. In addition, the literature value was used for the value of 0 mass% Ta in the graph of FIG. As for the heat-treated material, measurement was performed on a Zr-15 mass% Ta alloy, a Zr-20 mass% Ta alloy, and a Zr-30 mass% Ta alloy.
As shown in the graph of FIG. 2, the magnetic susceptibility of the heat-treated material was equivalent to the magnetic susceptibility of the as-cast material, and a low value was obtained. From this result, the effect of heat treatment on the magnetic susceptibility was hardly recognized.

<Organization>
The martensite found in the as-cast Zr alloy with relatively few additive elements is hexagonal α ', whereas the martensite found in the heat-treated materials of 15% Ta and 18% Ta alloy is orthorhombic. It can be inferred from the structural observation and X-ray diffraction peak that it is α ′, and it is presumed that this change in crystal structure contributes at least to a decrease in elastic modulus.

FIG. 3A is a metallographic photograph of a Zr-15 mass% Ta alloy (as cast) by a scanning electron microscope. FIG. 3B is a metallographic photograph of a Zr-15 mass% Ta alloy (heat treated material) obtained by a scanning electron microscope. FIG. 4A is a metallographic photograph of a Zr-18 mass% Ta alloy (as cast) by a scanning electron microscope. FIG. 4B is a metallographic photograph of a Zr-18 mass% Ta alloy (heat treated material) obtained by a scanning electron microscope. FIG. 5A is a metallographic photograph of a Zr-20 mass% Ta alloy (as cast) by a scanning electron microscope. FIG. 5B is a metallographic photograph of a Zr-20 mass% Ta alloy (heat treated material) obtained by a scanning electron microscope.

FIG. 6 is a graph showing X-ray diffraction results of the as-cast material and the heat-treated material in a Zr-15 mass% Ta alloy, a Zr-18 mass% Ta alloy, and a Zr-20 mass% Ta alloy. For X-ray diffraction measurement, the surface mechanically polished with water-resistant abrasive paper is used as the measurement surface, the acceleration voltage is 40 kV, the current is 30 mA (in the air, at room temperature), the measurement range (2θ) is 20 ° to 120 °, and the scanning speed is 1.2 °. Measurement was performed under the condition of / min. In addition, in each alloy of the graph of FIG. 6, the upper side represents the X-ray diffraction data of the heat-treated material, and the lower side represents the X-ray diffraction data of the material as cast.

From the observation of the metal structure and the X-ray diffraction results, it was found that the constituent phases of the Zr-15 mass% Ta alloy (as cast) and the Zr-18 mass% Ta alloy (as cast) consisted of hexagonal martensite. . On the other hand, the constituent phases of the Zr-15 mass% Ta alloy (heat treated material) and the Zr-18 mass% Ta alloy (heat treated material) consist of orthorhombic martensite and hexagonal martensite. It was found to be composed of martensite including crystal martensite.
The constituent phase of the Zr-20 mass% Ta alloy (heat treatment material) is composed of a β-Zr phase and an ω phase, and neither hexagonal martensite nor orthorhombic martensite was observed.
From this result, it is inferred that the formation of orthorhombic martensite in the Zr-15 mass% Ta alloy (heat treated material) and the Zr-18 mass% Ta alloy (heat treated material) contributes to the decrease in the elastic modulus. .
For Zr-15 mass% Ta alloy (heat treated material), Zr-18 mass% Ta alloy (heat treated material) and Zr-20 mass% Ta alloy (heat treated material), β-Ta was detected from the X-ray diffraction results. In other words, the formation of β-Ta was suppressed.

<Tensile properties>
Next, the tensile properties will be described. A Zr-15 mass% Ta alloy (heat treated material), a Zr-18 mass% Ta alloy (heat treated material) and a Zr-20 mass% Ta alloy (heat treated material) were used as test pieces for the tensile test. The tensile test was performed in the air at room temperature in accordance with JIS Z2241. FIG. 7 is a diagram showing the shape of a test piece in a tensile test.

FIG. 8 is a stress-strain diagram of each alloy. Table 2 shows the tensile test results of each alloy. The fracture toughness values shown in Table 2 are the work required for the material to break, and can be expressed as integrated values of the stress-strain diagram shown in FIG. Moreover, a large fracture toughness value means that the material does not break easily even if the elastic limit is exceeded.

Zr-15 mass% Ta alloy (heat treated material) and Zr-18 mass% Ta alloy (heat treated material) have higher tensile strength, elongation and fracture toughness values than Zr-20 mass% Ta alloy (heat treated material). The result was obtained. For the Zr-15 mass% Ta alloy (heat treated material) and the Zr-18 mass% Ta alloy (heat treated material), fracture toughness values equal to or higher than those of maraging steel and Ti-6Al-4V alloy were obtained.

Thus, Zr such as Zr-15 mass% Ta alloy (heat treated material) and Zr-18 mass% Ta alloy (heat treated material) is the main component, and Ta is contained in the range of 12 mass% to less than 20 mass%. The biomedical zirconium alloy whose constituent phase is composed of martensite including orthorhombic martensite has a low magnetic susceptibility and elastic modulus, and thus can be applied to biomedical devices such as bone fixation devices. FIG. 9 is a diagram illustrating a configuration of the bone fixation device 10. The bone fixation device 10 includes an osteosynthesis plate 10a for fixing the bone 12 and an osteosynthesis screw 10b.

The biological zirconium alloy of the present invention has a low magnetic susceptibility and elastic modulus, and thus is useful for biological medical instruments such as bone anchors.

Claims

Zr is the main component, Ta is contained in the range of 12 mass% or more and less than 20 mass%,
A zirconium alloy for living body, wherein the constituent phase is composed of martensite including orthorhombic martensite.
2. The biological zirconium alloy according to claim 1, wherein Ta is contained in a range of 12% by mass or more and less than 20% by mass, and the balance is made of Zr and inevitable impurities.
The biological zirconium alloy according to claim 2, comprising Ta in a range of 15% by mass or more and less than 20% by mass.
The biomedical zirconium alloy according to claim 3, containing Ta in a range of 15 mass% or more and 18 mass% or less.
The biological zirconium alloy according to any one of claims 1 to 4, wherein the constituent phase is composed of orthorhombic martensite and hexagonal martensite.
The biomedical zirconium alloy according to any one of claims 1 to 4, obtained by heat treatment in the range of 1100 to 1500 ° C and then cooling at a cooling rate of 200 ° C / min or more.
A medical device for living body using the zirconium alloy for living body according to claim 1.
A step of heat-treating a metal molded body containing Zr as a main component and containing Ta in a range of 12% by mass or more and less than 20% by mass in a range of 1100 to 1500 ° C., and then cooling at a cooling rate of 200 ° C./min or more. A method for producing a biological zirconium alloy.