MEDICAL Au-Pt-Pd ALLOY

Abstract

The present invention relates to a medical Au-Pt-Pd alloy including Au, Pt,Pd, and inevitable impurities. The Au-Pt-Pd alloy has an alloy compositioninside a polygon (A1-A2-A3-A4) surrounded by straight lines connected at pointA1 (Au: 53 atom%, Pt: 4 atom%, and Pd: 43 atom%), point A2 (Au: 70 atom%,Pt: 4 atom%, and Pd: 26 atom%), point A3 (Au: 69.9 atom%, Pt: 30 atom%, and Pd: 0.1 atom%), and point A4 (Au: 49.9 atom%, Pt: 50 atom%, and Pd: 0.1 atom%) in a Au-Pt-Pd ternary state diagram. In a metal structure of the alloy, at least one of a Au-rich phase and a Pt-rich phase is distributed, and the total of the area ratio of the Au-rich phase and the area ratio of the Pt-rich phase is 1.5% or more and 25.4% or less.

Claims

1. A medical device comprising an Au-Pt-Pd alloy, wherein the medical device is one of a stent, a catheter, an embolization coil, an embolization clip, and a guide wire, the Au-Pt-Pd alloy has an alloy composition inside a polygon (A1-A2-A3-A4) surrounded by straight lines connected at point A1 (Au: 53 atom%, Pt: 4 atom%, and Pd: 43 atom%), point A2 (Au: 70 atom%, Pt: 4 atom%, and Pd: 26 atom%), point A3 (Au: 69.9 atom%, Pt: 30 atom%, and Pd: 0.1 atom%), point A4 (Au: 49.9 atom%, Pt: 50 atom%, and Pd: 0.1 atom%) in a Au-Pt-Pd ternary state diagram, and in a metal structure on any cross-section, with a composition of a mother phase Au-Pt-Pd alloy as a criterion, at least either of a Au-rich phase which is an alloy phase having a Au content higher by 4 atom% or more than that of the mother phase or a Pt-rich phase which is an alloy phase having a Pt content higher by 4 atom% or more than that of the mother phase is distributed, and a total of an area ratio of the Au-rich phase and an area ratio of the Pt-rich phase is 1.5% or more and 25.4% or less.

2. The medical device of claim 1, wherein the Au-Pt-Pd alloy has an alloy composition within the range inside a polygon (A1-A2-B3-B4) surrounded by straight lines connected at point A1 (Au: 53 atom%, Pt: 4 atom%, and Pd: 43 atom%), point A2 (Au: 70 atom%, Pt: 4 atom%, and Pd: 26 atom%), point B3 (Au: 70 atom%, Pt: 20 atom%, and Pd: 10 atom%), and point B4 (Au: 55 atom%, Pt: 35 atom%, and Pd: 10 atom%) in the Au-Pt-Pd ternary state diagram.

3. The medical device of claim 1, wherein the Au-Pt-Pd alloy has an alloy composition within the range inside a polygon (A1-C2-C3-C4) surrounded by straight lines connected at point A1 (Au: 53 atom%, Pt: 4 atom%, and Pd: 43 atom%), point C2 (Au: 60 atom%, Pt: 4 atom%, and Pd: 36 atom%), point C3(Au: 62 atom%, Pt: 12 atom%, and Pd: 26 atom%), and point C4 (Au: 54 atom%, Pt: 20 atom%, and Pd: 26 atom%) in the Au-Pt-Pd ternary state diagram.

4. The medical device of claim 1, wherein the Au-Pt-Pd alloy has a volume magnetic susceptibility of -32 ppm or more and 60 ppm or less and a Young’s modulus of 100 GPa or more.

5. The medical device of claim 2, wherein the Au-Pt-Pd alloy has a volume magnetic susceptibility of -32 ppm or more and 60 ppm or less and a Young’s modulus of 100 GPa or more.

6. The medical device of claim 3, wherein the Au-Pt-Pd alloy has a volume magnetic susceptibility of -32 ppm or more and 60 ppm or less and a Young’s modulus of 100 GPa or more.

7. The medical device of claim 1, wherein the medical device is a stent.

8. The medical device of claim 1, wherein the medical device is a catheter.

9. The medical device of claim 1, wherein the medical device is an embolization coil.

10. The medical device of claim 1, wherein the medical device is an embolization clip.

11. The medical device of claim 1, wherein medical device is a guide wire.

12. The medical device of claim 2, wherein the medical device is a stent.

13. The medical device of claim 2, wherein the medical device is a catheter.

14. The medical device of claim 2, wherein the medical device is an embolization coil.

15. The medical device of claim 2, wherein the medical device is an embolization clip.

16. The medical device of claim 2, wherein the medical device is a guide wire.

17. The medical device of claim 3, wherein the medical device is a stent.

18. The medical device of claim 3, wherein the medical device is a catheter.

19. The medical device of claim 3, wherein the medical device is an embolization coil or an embolization clip.

20. The medical device of claim 3, wherein the medical device is a guide wire.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 is a ternary state diagram of a Au-Pt-Pd alloy, which also shows a composition range (A1-A2-A3-A4: good region) of the present inventive alloy.

[0046] FIG. 2 is a ternary state diagram of a Au-Pt-Pd alloy, which also shows the composition range (A1-A2-B3-B4: better region) of the present inventive alloy.

[0047] FIG. 3 is a ternary state diagram of a Au-Pt-Pd alloy, which also shows the composition range (A1-C2-C3-C4: best region) of the present inventive alloy.

[0048] FIG. 4 is a ternary state diagram showing a composition of a Au-Pt-Pd alloy produced in an embodiment.

[0049] FIG. 5 is a diagram showing a metal structure of an alloy of No. 7.

DESCRIPTION OF EMBODIMENTS

[0050] Hereinafter, an embodiment of the present invention will be described. In this embodiment, Au-Pt-Pd alloys of various compositions were produced, and evaluated for magnetic characteristics and mechanical characteristics.

[0051] For the Au-Pt-Pd alloys, raw metals of pure Au, pure Pt, and pure Pd with a purity of 99.99% were weighed to various compositions, and melted at a high frequency and cast into an alloy ingot (crucible: zirconia crucible, mold: water-cooled Cu mold, maximum power during melting: 2.5 kW). A mother alloy ingot of 7 mm (diameter) × 65 mm was produced by the melting and casting step.

[0052] Next, the mother alloy was subjected to homogenization treatment in which the alloy was heated in an Ar atmosphere at 1,100° C. for 1 hour. After the heating, the mother alloy was cooled with water.

[0053] The homogenization-treated mother alloy was subjected to plastic working and solution treatment. In the plastic working step, swaging was performed at ordinary temperature, and the ingot with a diameter of 7 mm was reduced in diameter to a diameter of 4 mm in increments of 0.5 to 1 mm. The processed mother alloy was heated in an Ar atmosphere at a temperature of 1,100° C. for 12 hours, and then rapidly cooled to perform solution treatment.

[0054] After the solution treatment and before age treatment, the mother alloy with a diameter of 4 mm was subjected to wire drawing at a working rate of 15% per pass until the diameter was 3 mm. In the age treatment, the mother alloy was heated in an Ar atmosphere at a temperature of 600° C. for 1 hour, and then rapidly cooled. By the above steps, a Au-Pt-Pd alloy wire material was produced. For some alloys (Nos. 16 and 17 in Table 1 below), the heat treatment temperature was 300° C.

[0055] For the Au-Pt-Pd alloys produced in this embodiment, cross-sections were observed by SEM to examine metal structures. In the structure observation, a sample obtained by cutting the wire material at any position was polished into a mirror surface state, and subjected to ion milling to make the surface state easily observable. The sample was then observed by SEM.

[0056] In observation of separate phases which are an Au-rich phase and a Pt-rich phase, the Au-rich phase and the Pt-rich phase were identified with respect to a matrix phase by SEM-EDX composition analysis (accelerating voltage: 15 kV). In addition, when there was a sample in which it was difficult to identify the Au-rich phase and the Pt-rich phase, a surface of the sample was observed by EPMA (accelerating voltage: 15 kV), and mapping was performed to identify the phases. The area ratios of the Au-rich phase and the Pt-rich phase were determined by image evaluation. For the image evaluation, the area ratios of the separate phases were calculated by use of the crystal grain evaluation tool: Grain Expert which is commercially available image analysis software (Leica Application Suite manufactured by Leica).

[0057] Further, the Au-Pt-Pd alloys produced in this embodiment were subjected to volume magnetic susceptibility measurement, processability evaluation, and mechanical property evaluation. For the volume magnetic susceptibility measurement, a sample of 3 mm (diameter) × 8 mm was prepared, and volume magnetic susceptibility (Xv) was measured at room temperature (25° C.) by use of a high-sensitivity small magnetic balance (MSB-AUTO).

[0058] For the processability, whether or not breakage occurred was evaluated in formation of a wire material with a diameter of 1 mm by subjecting a wire material (diameter: 3 mm) to wire drawing at a working rate of 10% per pass. For the mechanical properties, a sample with a diameter of 1 mm was set with a chuck-to-chuck distance of 100 mm in a tensile tester, and a tension test was conducted at a cross head speed of 1 mm/min to measure a Young’s modulus.

[0059] Table 1 shows the evaluation results of various Au-Pt-Pd alloys produced in this embodiment. In addition The compositions of the Au-Pt-Pd alloys produced in this embodiment are shown in a ternary state diagram of FIG. 4.

TABLE-US-00001 No. Composition (at%) Total area ratio of separate phases (%) Xv (ppm) Young’s modulus (GPa) Processability Au Pt Pd 1 Balance 13.5 28.5 1.9 -9 138 O 2 7 40 1.5 -2 137 O 3 10.2 34.4 10.2 -5 137 O 4 24 21 10.4 14 113 O 5 24.5 13.9 4.7 5 122 O 6 27.8 3.7 12.8 -10 106 O 7 25.3 7.2 22.5 -7 109 O 8 37.6 3.6 11.3 33 118 O 9 35.5 13.5 25.4 41 122 O 10 Balance 25.4 34.3 0.1 61 146 O 11 19.3 44.2 0.5 79 152 O 12 37.2 26 0.5 77 148 O 13 11.7 59.3 0.5 138 174 O 14 27.2 44.2 0.1 119 157 O 15 13.7 53.2 1.8 109 135 O 16 23.3 24.6 0.9 61 137 O 17 10.2 20.2 0.4 -34 117 O

[0060] It will be apparent from Table 1 that in a region surrounded by point A1 -point A2 -point A3 -point A4 (good region) in the ternary state diagram specified in the present application, the volume magnetic susceptibility of the Au-Pt-Pd alloy is within a range of -32 ppm or more and 60 ppm or less, and the Young’s modulus is 100 GPa or more (Nos. 1 to 9). FIG. 5 is a photograph showing a metal structure of the alloy of No. 7. Separate phases deposited in a layered form are observed in proximity to a crystal grain boundary of the mother phase.

[0061] Au-Pt-Pd alloys with an alloy composition range in a better region or a best region narrower than the good region exhibits a more preferred volume magnetic susceptibility and Young’s modulus (Nos. 1 to 5). The alloys of Nos. 1 to 3 have a particularly good volume magnetic susceptibility and Young’s modulus, and the alloy of No. 3 is an alloy which has a volume magnetic susceptibility of - 5 ppm, so as to be artifactless.

[0062] On the other hand, alloys with a composition outside the composition range specified in the present invention tend to have a low area ratio of separate phases (Au-rich phase and Pt-rich phase) and a volume magnetic susceptibility of more than 60 ppm (Nos. 11 to 14). In addition, when the composition is outside the composition range, the volume magnetic susceptibility is not appropriate even through a separate phase area ratio of 1.5% or more (No. 15). In the Au-Pt-Pd alloy covered by the present invention, it is first considered necessary to optimize the composition range.

[0063] Indeed, even alloys with a composition in the composition range specified in the present application have a small area ratio of the Au-rich phase and the Pt-rich phase due to insufficient precipitation of these phases if heat treatment conditions during production are not appropriate (Nos. 16 and 17). These alloys cannot exhibit minimum required volume magnetic susceptibility (-32 ppm or more and 60 ppm or less).

[0064] Any alloy composition (good region, better region, or best region) enables optimization of only magnetic properties or mechanical properties. For example, alloys in which only the magnetic susceptibility is an optimum value (-20 ppm or more and 0 ppm or less) can be produced even if the composition is within the good region that is the widest range (Nos. 6 and 7). These alloys have a relatively low Young’s modulus, and even such alloys are useful for applications in which the magnetic susceptibility is considered important. In use of the present inventive Au-Pt-Pd alloy, it may be preferable to consider both the alloy composition and the total area ratio of separate phases while giving a top priority to the required volume magnetic susceptibility and Young’s modulus.

Industrial Applicability

[0065] The present inventive medical Au-Pt-Pd alloy is suitable as a constituent material for medical equipment which is used in a magnetic field environment. The alloy of the present invention is capable of coping with the artifact problem, and has mechanical properties required for various kinds of medical equipment. The present invention can be expected to be applied to various kinds of medical equipment such as coils such as embolization coils, stents, catheters, and guide wires.