High-hardness Au-Ni-Pd-Pt noble metal alloy

Abstract

The present invention is an Au-Ni-Pd-Pt-based noble metal alloy which contains from 1.5 at% to 47 at% (inclusive) of Au, from 4 at% to 57 at% (inclusive) of Ni, from 1 at% to 43.5 at% (inclusive) of Pd, and from 6 at% to 58.5 at% (inclusive) of Pt, and which further contains from 0.003 at% to 8 at% (inclusive) of B. The noble metal alloy according to the invention achieves high hardness by means of a modulated structure based on amplitude-modulated decomposition and / or an ordered phase based on ordering. According to the present invention, in addition to the aforementioned high hardness, the ductility of the recrystallized structure is improved by adding B. In addition, the noble metal alloy of the present invention may optionally contain Cu, an added metal alpha (In, Sn, Sb), and an added metal beta (Al, Ti, Zr, Hf).

Description

TECHNICAL FIELD

[0001] The present application relates to a high-hardness noble metal alloy which takes Pt, Au, Pd as essential constituent elements as noble metals, and which takes into account workability. In detail, it relates to a high-hardness noble metal alloy of Au-Ni-Pd-Pt system which is high-hardened by spinodal decomposition and / or ordering, and which has improved ductility of recrystallized structure by solid solution treatment or the like, and which has improved workability. BACKGROUND

[0002] A noble metal such as Pt (platinum), Au (gold) is a metal which is excellent in chemical stability, corrosion resistance, and also has good electric properties such as electric conductivity. Therefore, the noble metal and its alloy are used in various fields such as the electric / electronic field, the medical field, and the like. As an example of use of the noble metal alloy in the electric / electronic field, a probe pin used in inspection of a semiconductor, a brush for a motor, an electric contact (sliding contact, switching contact) of a relay, a switch, and the like can be listed. In recent years, use in the medical field is attracting attention, and the noble metal alloy is used as a constituent material of various medical devices. As the medical device, various medical devices such as an embolism coil, an embolism clip, a guide wire, a stent, a catheter, and the like can be listed. These medical devices are instruments which are directly contacted with a human body and are buried in the inside of the human body, and thus are required to have biocompatibility, chemical stability. In addition, in the medical device, X-ray visibility which takes into account use in surgery and diagnosis using X-rays is also required. Such biocompatibility, X-ray visibility of the noble metal alloy is also good.

[0003] Further, for the noble metal alloy for the above-described various uses, improvement in mechanical properties such as hardness and strength is required. For example, a probe pin is required to have wear resistance because it is repeatedly contacted with an object member for a long time. In particular, in order to cope with high integration of various devices and high performance of a motor in recent years, development of a probe pin having higher hardness is required. In addition, with respect to a medical instrument, for an instrument such as a guide wire, an embolism coil which moves in a pulsating, beating blood vessel and is buried therein, mechanical properties such as hardness and elasticity are required so that its action does not become disordered.

[0004] As a method for increasing the hardness of a metal material containing a noble metal alloy, material strengthening methods such as work hardening (dislocation strengthening), solid solution strengthening, and precipitation strengthening (dispersion strengthening) are known, and they can be applied alone or in combination. As an example of increasing the hardness of a noble metal alloy applied to the above-mentioned probe needle, contact material, medical equipment, and the like, the Pt-Ni alloy described in Patent Document 1 and the Pt-W alloy of Patent Document 2 achieve an increase in hardness by solid solution strengthening of alloying Ni, W, or the like in Pt and work hardening by increasing the final processing rate. In addition, in Patent Document 3 (Ag-Pd-Cu alloy) and Patent Document 4 (Pt-Cr-Ni alloy), in addition to solid solution strengthening and precipitation hardening using an added element, work hardening by adjusting the processing rate is used to obtain a noble metal alloy with high hardness.

[0005] On the other hand, as a material strengthening method different from the above-mentioned known technology, the applicant of the present application has developed a noble metal alloy that is high in hardness by modulation decomposition and / or ordering (Patent Document 5).

[0006] Modulation decomposition refers to one way of phase separation in a material structure, and is a phenomenon that proceeds by continuous increase in concentration fluctuation. The material structure generated by modulation decomposition caused by this concentration fluctuation exhibits a very fine periodic structure of about several nm to about several tens of nm, which is called a modulated structure. In the modulated structure exhibited in modulation decomposition, the concentration of solute atoms in the crystal periodically varies as a function of position, and the lattice constant also periodically changes. As a result, a periodic internal stress field is generated on the slip plane, which interacts with dislocations. The strengthening mechanism based on modulation decomposition is similar to precipitation strengthening based on nucleation and growth, but differs in that, instead of precipitates, the internal stress field generated by concentration modulation acts as an obstacle to dislocation movement.

[0007] In addition, ordering refers to a phenomenon in which an ordered phase having a prescribed structure is generated by ordering of the arrangement of constituent elements of an alloy. The ordered phase generated by ordering contributes to high hardness of the alloy by the following factors: (i) increase in Burgers vector of dislocations; (ii) possibility of generation of antiphase boundaries within the ordered phase; (iii) volume change accompanying ordering deforms the lattice inside and outside the ordered phase and acts to inhibit dislocation movement. Ordering is sometimes exhibited in conjunction with the above-mentioned modulation decomposition, and sometimes occurs alone.

[0008] Amplitude modulation and ordering are phenomena that exhibit high hardness increases due to unique material structures such as modulated microstructures and ordered phases. In the aforementioned known material strengthening methods, such as solid solution strengthening and precipitation strengthening, there are limits to the extent of hardness increase. Compared to these conventional strengthening methods, amplitude modulation and ordering can expect higher hardening amounts. Furthermore, while work hardening can expect increased hardness due to increased workability, there are concerns about the embrittlement associated with hardening. Amplitude modulation and ordering are considered useful as means to increase hardness without causing material embrittlement.

[0009] Furthermore, the noble metal alloy proposed by the applicant of this application (Patent Document 5) is composed of Au-Ni-Pd-Pt alloys, which are quaternary or higher alloys, in order to effectively exhibit the strengthening effect based on amplitude modulation and ordering. While binary alloys such as Pt-Au alloys and Pt-Ni alloys are known to exhibit amplitude modulation and ordering, their hardening capacity is not particularly high. The amplitude modulation and ordering in these binary alloys do not exceed the level of conventional strengthening methods such as work hardening and precipitation strengthening. The Au-Ni-Pd-Pt alloy proposed by the applicant of this application, by diversifying the aforementioned binary alloys and optimizing the composition range of each constituent element, can effectively exert the strengthening effect based on amplitude modulation and / or ordering. Moreover, the amplitude modulation and ordering in this Au-Ni-Pd-Pt alloy are exhibited by solution treatment or the like, which transforms the alloy of appropriate composition into a supersaturated solid solution with a recrystallized structure, followed by aging treatment, thus achieving the desired hardness.

[0010] Existing technical documents

[0011] Patent documents

[0012] Patent Document 1: Japanese Patent Application Publication No. 2005-233967

[0013] Patent Document 2: Description of Japanese Patent No. 6997354

[0014] Patent Document 3: Japanese Patent Application Publication No. 2012-242184

[0015] Patent Document 4: Japanese Patent No. 6372952 Specification

[0016] Patent Document 5: International Publication No. WO2023 / 063156 Summary of the Invention

[0017] The problem that the invention aims to solve

[0018] When precious metal alloys are used in probe needles, sliding contacts, medical devices, etc., they need to be plastically processed to achieve the required shape and size for their application. Regarding the machinability of the Au-Ni-Pd-Pt alloys mentioned above by the applicant of this application, these precious metal alloys, even in their cast state or in the state of a two-phase separation structure produced during heat treatment at approximately 700°C to approximately 900°C, exhibit sufficient ductility and good machinability even at room temperature. Therefore, when processing these Au-Ni-Pd-Pt alloys into probe needles, sliding contacts, medical devices, etc., firstly, under the aforementioned machinability-friendly state (cast structure or two-phase separation structure), a primary processing step such as rolling and drawing is performed to produce a rough material such as wire. Then, it is envisioned that the rough material after the primary processing step is subjected to solution treatment, followed by secondary processing or finishing such as surface rolling, straightening, bending, and winding, and then aging treatment to harden it.

[0019] However, according to the inventors' research, the Au-Ni-Pd-Pt alloys described above by the applicant of this application exhibit poor ductility in the post-solution treated state. This reduction in ductility affects processing and may deteriorate machinability during secondary processing, etc.

[0020] In the Au-Ni-Pd-Pt alloys proposed by the applicant in this application, high hardness is achieved through amplitude-modulated decomposition and / or ordering via aging treatment. However, to maximize this effect, solution treatment prior to aging is a necessary step. Therefore, if the above processing technology is to be applied to the Au-Ni-Pd-Pt alloys proposed by the applicant in this application, the improvement of ductility after solution treatment is an important issue.

[0021] This invention was made based on the background described above, and provides a technique for improving the ductility of a high-hardness noble metal alloy composed of Au-Ni-Pd-Pt alloys, as proposed by the applicant of this application, while maintaining the hardness increased by amplitude modulation decomposition and / or ordering, and improving the ductility after solid solution treatment and other processes.

[0022] Methods for solving problems

[0023] The Au-Ni-Pd-Pt alloy system proposed by the applicant of this application (Patent Document 5) is a technique that, to date, has no precedent for actively utilizing the effects of amplitude modulation decomposition and / or ordering in noble metal alloys. Therefore, it can be said that the phenomenon of reduced ductility after solution treatment, as described above, is itself unknown. In order to solve the above-mentioned problem, the inventors have identified the factors contributing to the reduction in ductility in Au-Ni-Pd-Pt alloy systems after solution treatment.

[0024] As a result, the inventors discovered that Au-Ni-Pd-Pt alloys capable of amplitude-modulated decomposition and ordering exhibit grain boundary segregation of Au and / or Pd in ​​the recrystallized structure, which is a material structure generated through solution treatment. Furthermore, the inventors observed that this grain boundary segregation leads to grain boundary embrittlement in the recrystallized structure, which is a factor contributing to reduced ductility. It should be noted that this recrystallized structure is a material structure observed in the entirety or a portion of the Au-Ni-Pd-Pt alloy after solution treatment or similar processes.

[0025] When the decrease in ductility after solution treatment is due to grain boundary embrittlement caused by the segregation of Au and / or Pd in ​​the recrystallized structure, the prerequisite for countermeasures is to improve ductility within a range that does not hinder the hardening ability of amplitude modulation decomposition and ordering. That is, while the aim is to suppress the segregation of Au and Pd, changing the composition of Au, Pd, and other constituent elements to a range where amplitude modulation decomposition and ordering cannot produce the desired results is not a preferred approach. Therefore, the inventors explored elements that, for Au-Ni-Pd-Pt alloys, can strengthen grain boundaries without hindering amplitude modulation decomposition and ordering. The results showed that B (boron) satisfies the above conditions, leading to the present invention.

[0026] That is, the present invention is an Au-Ni-Pd-Pt noble metal alloy, which is an Au-Ni-Pd-Pt noble metal alloy containing more than 1.5 atomic% and less than 47 atomic% of Au, more than 4 atomic% and less than 57 atomic% of Ni, more than 1 atomic% and less than 43.5 atomic% of Pd and more than 6 atomic% and less than 58.5 atomic% of Pt, wherein it contains more than 0.003 atomic% and less than 8 atomic% of B.

[0027] The noble metal alloy of the present invention uses Au, Ni, Pd, Pt and B as essential constituent elements, and allows the inclusion of some additive elements, including Cu with a content greater than 0.1 atomic% and less than 27.5 atomic%.

[0028] Furthermore, the Au-Ni-Pd-Pt noble metal alloy of the present invention may contain 0.15 atomic% or more and 5 atomic% of metal element α and / or 0.05 atomic% or more and 5 atomic% of metal element β as optional additive elements. Here, metal element α is at least one of In, Sn, and Sb. In addition, metal element β is at least one of Al, Ti, Zr, and Hf.

[0029] Moreover, as described above, the Au-Ni-Pd-Pt noble metal alloy of the present invention contains modulated microstructure and / or ordered phase based on amplitude modulation decomposition.

[0030] The Au-Ni-Pd-Pt noble metal alloy of the present invention achieves high hardness through amplitude modulation decomposition and / or ordering. The Vickers hardness of this high-hardness Au-Ni-Pd-Pt noble metal alloy reaches over 500 Hv.

[0031] Invention Effects

[0032] As explained above, the Au-Ni-Pd-Pt noble metal alloy of the present invention improves the ductility of the recrystallized structure after solution treatment. The present invention can achieve high hardness by means of appropriate heat treatment, such as aging treatment, similar to that of the Au-Ni-Pd-Pt noble metals proposed by the applicant of this application, exhibiting a modulated structure based on amplitude decomposition and / or an ordered phase based on ordered phases. According to the present invention, even in the recrystallized structure state after solution treatment, workability in shapes corresponding to various applications can be ensured, and appropriate hardness can be obtained through subsequent aging treatment. Attached Figure Description

[0033] Figure 1 The figure shows the XRD results of the solution-treated and age-treated materials of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) of Example 4-2.

[0034] Figure 2 This is a STEM-EDS mapping image of a sample of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) from Example 4-2 that underwent aging treatment after solution treatment.

[0035] Figure 3 The electron diffraction pattern is for the sample of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) of Example 4-2, which underwent aging treatment after solution treatment.

[0036] Figure 4 This is a photograph showing the results of STEM-EDS analysis of the noble metal alloy (Au7.5-Ni41.25-Pd10-Pt41.25) of Comparative Example 2, representing the elemental distribution near the large-angle grain boundaries.

[0037] Figure 5 This is an Auger spectrum of the grain boundary fracture surface and the intragranular fracture surface of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) of Example 4-2 after impact fracture.

[0038] Figure 6This is a graph showing the results of room-temperature tensile tests of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) of Example 4-2 and the noble metal alloy (Au12.5-Ni37.5-Pd12.5-Pt37.5) of Comparative Example 4-1. Detailed implementation mode

[0039] The embodiments of the present invention will be described below. As described above, the noble metal alloy of the present invention is an Au-Ni-Pd-Pt alloy system alloy in which B is added as an additive element to the Au-Ni-Pd-Pt alloy. Hereinafter, the composition of the noble metal alloy of the present invention and the manufacturing method of the noble metal alloy of the present invention will be described.

[0040] (A) Composition of the noble metal alloy of the present invention

[0041] (A-1) Each constituent element and composition range of the noble metal alloy of the present invention

[0042] The noble metal alloy of the present invention contains Au, Ni, Pd, and Pt as essential constituent elements, and contains B as an essential additive element. In the following description, the essential constituent elements and constituent elements and their composition ranges are clarified. Moreover, optional additive elements (Cu, metal element α, and metal element β) that are allowed to be added in the noble metal alloy of the present invention in addition to B and their addition concentrations are also described.

[0043] (1) Essential constituent elements (Au, Ni, Pd, Pt)

[0044] By containing the above essential elements, the noble metal alloy of the present invention exhibits at least one of spinodal decomposition and ordering, and has a hardness equal to or higher than that of noble metal alloys based on conventional general strengthening mechanisms (solid solution strengthening, precipitation strengthening, work hardening).

[0045] As described in Patent Document 5 of the Au-Ni-Pd-Pt alloy system alloy proposed by the applicant who disclosed this application, periodic concentration fluctuations occur in the modulated structure formed by spinodal decomposition, and contribute to high hardness by forming an internal stress field around. The resistance (critical shear stress) of dislocation movement in this periodic internal stress field is represented by the following formula, and it is considered that lattice strain (ε), elastic coefficient (Y), and concentration modulation amplitude (A) are dominant factors (as a detailed reference, for example, "Introduction to Dislocation Theory" by Shoji Kato (published in August 1999, publisher: Shoeka Publishing House)).

[0046] [Mathematical formula 1]

[0047] τ: Critical shear stress

[0048] Y: Elasticity coefficient

[0049] A: Concentration modulated amplitude

[0050] ε: lattice strain

[0051] Moreover, according to the above formula, the constituent elements of a noble metal alloy that effectively demonstrates the material strengthening based on amplitude modulation decomposition preferably have the following three requirements: (1) the constituent elements include metals with high elastic coefficients; (2) the mixing enthalpy between constituent elements is high and the phase separation tendency is strong in the low temperature range; (3) the difference in lattice constants between constituent elements is large and the lattice strain (ε) is also large.

[0052] In addition, regarding the performance of ordering, Pt and Ni, as well as Au and Pd, are metal combinations that can contribute to the generation of ordered phases based on ordering.

[0053] Au, Ni, Pd, and Pt, which are essential constituent elements of the noble metal alloy of the present invention, are combinations of metals that can possess these requirements. By setting the composition range as described later, the strengthening ability based on amplitude modulation decomposition is effectively exerted. The specific functions and composition ranges of these essential constituent elements are explained below.

[0054] Au

[0055] Au is an essential element for exhibiting amplitude modulated decomposition in the alloy system of this invention. Amplitude modulated decomposition is not observed when the Au concentration is too low or too high; there is a specific Au concentration range required for its occurrence. Outside of this optimal range, normal nucleation and growth are easily induced, resulting in an inadequate increase in hardness. Furthermore, Au is a metal capable of forming ordered phases with Pd, and thus contributes to the increase in hardness based on this ordering.

[0056] The Au-Ni-Pd-Pt alloy of the present invention has an Au concentration of 1.5 atomic% or more and 47 atomic% or less. The Au concentration is preferably 4 atomic% or more and 30 atomic% or less, more preferably 6 atomic% or more and 24 atomic% or less, and even more preferably 7 atomic% or more and 20 atomic% or less.

[0057] Ni

[0058] Ni, as a noble metal alloy, exhibits a strengthening effect during amplitude-dependent decomposition. Ni has a higher elastic modulus than Au, Pt, and Pd. Furthermore, Ni has a smaller lattice constant than Au, Pt, and Pd, thus having a greater effect on increasing lattice strain ε. Therefore, according to Equation 1 above, Ni has the effect of increasing the strengthening ability based on amplitude-dependent decomposition. In addition, Ni is a metal capable of forming ordered phases with Pt, and also contributes to the increase in hardness based on ordering.

[0059] Furthermore, Ni belongs to the same group as Pt and Pd, and has a similar electronic structure. Therefore, it is possible to form alloys with minimal impairment to the corrosion resistance and oxidation resistance of precious metals. This also has the secondary effect of reducing the overall price of precious metal alloys.

[0060] The Ni concentration of the Au-Ni-Pd-Pt alloy of the present invention is 4 atomic% or more and 57 atomic% or less. The Ni concentration is preferably 10 atomic% or more and 52.5 atomic% or less, more preferably 12.5 atomic% or more and 50 atomic% or less, and even more preferably 15 atomic% or more and 47.5 atomic% or less.

[0061] Pd

[0062] Pd expands the solid solution limits of the constituent elements in noble metal alloys, broadens the concentration range at which noble metal alloys exhibit amplitude-dependent decomposition, and promotes amplitude-dependent decomposition. Through these effects, Pd increases the hardening amount based on amplitude-dependent decomposition. Furthermore, Au, being a metal capable of forming ordered phases with Pd, also contributes to the increase in hardness based on ordering. However, with excessive addition of Pd, the amplitude-dependent decomposition temperature decreases excessively, thus tending to inhibit amplitude-dependent decomposition. Moreover, excessive addition of Pd tends to suppress ordering, leading to a decrease in the overall hardening amount of the alloy system. Therefore, to optimize the hardening amount of noble metal alloys, there exists an optimal concentration range for Pd as described above.

[0063] Regarding the Pd concentration of the Au-Ni-Pd-Pt alloy of the present invention, the Pd concentration is 1 atomic% or more and 43.5 atomic% or less. The Pd concentration is preferably 3 atomic% or more and 37.5 atomic% or less, more preferably 4 atomic% or more and 32.5 atomic% or less, and even more preferably 5 atomic% or more and 27.5 atomic% or less.

[0064] Pt

[0065] Pt is also an essential element for amplitude modulation decomposition in the alloy system of this invention. Amplitude modulation decomposition does not occur when the Pt concentration is too low or too high; there is a range of Pt concentrations required for its occurrence. Furthermore, Pt can form an ordered phase with Ni, which contributes to increased hardness. Additionally, due to its relatively high elastic modulus, Pt is expected to increase the hardening amount of the alloy when amplitude modulation decomposition occurs.

[0066] The Au-Ni-Pd-Pt alloy of the present invention has a Pt concentration of 6 atomic% or more and 58.5 atomic% or less. The Pt concentration is preferably 12.5 atomic% or more and 52.5 atomic% or less, more preferably 15 atomic% or more and 50 atomic% or less, and even more preferably 17.5 atomic% or more and 47.5 atomic% or less.

[0067] (2) Required element (B)

[0068] In the Au-Ni-Pd-Pt alloy of the present invention, B, as an essential additive element, is an element that exhibits grain boundary strengthening of noble metal alloys by preventing grain boundary segregation in recrystallized structures generated due to solid solution treatment, etc. Thus, it suppresses the reduction in ductility or embrittlement caused by Au and Pd grain boundary segregation that can occur at sites where recrystallization occurs in the noble metal alloy after solid solution treatment, and imparts appropriate workability to the noble metal alloy containing recrystallized structures.

[0069] In the noble metal alloy of the present invention, the concentration of boron (B) is 0.003 atomic% or more and 8 atomic% or less. When the concentration is less than 0.003 atomic%, the segregation of recrystallized structures towards grain boundaries is insufficient, and the aforementioned grain boundary strengthening effect cannot be fully achieved. Furthermore, when the concentration exceeds 8 atomic%, a tendency for reduced ductility occurs not only in the recrystallized structure but also in the cast structure and two-phase structure, which is therefore undesirable. It should be noted that the concentration of B is preferably set to 0.0075 atomic% or more. Additionally, the concentration of B can be appropriately set to 0.01 atomic% or more and 4 atomic% or less, greater than 0.1 atomic% or less and 3 atomic% or less, or 0.2 atomic% or more and 2.5 atomic% or less, while considering the overall alloy composition of the Au-Ni-Pd-Pt alloy.

[0070] (3) Optional addition of elements (Cu, α metal, β metal)

[0071] The Au-Ni-Pd-Pt alloy of the present invention uses a noble metal alloy composed of the aforementioned essential constituent elements as a base alloy, which may contain optional additive elements. Examples of optional additive elements include Cu, metallic element α, and metallic element β.

[0072] Cu

[0073] Cu (Cu) expands the concentration range for representing amplitude decomposition by increasing the solid solution limits among the constituent elements of noble metal alloys. In this respect, Cu has a similar effect to Pd and can therefore be used as an additive element. However, even though it shares some similarities with Pd, Cu is an optional additive element, not a necessary constituent element like Pd. This is because, while Cu expands the concentration range for representing amplitude decomposition, it does not increase the amount of hardening based on amplitude decomposition. It should be noted that, in addition to the aforementioned effects, Cu, as an optional additive element, also improves machinability. Furthermore, as a less expensive metal compared to noble metals, it has the secondary effect of reducing the overall price of noble metal alloys.

[0074] When Cu is added as an optional additive element to achieve the above-mentioned effects, its concentration is preferably set to be greater than 0.1 atomic% and less than 27.5 atomic%. Excessive Cu addition may lead to a decrease in the amplitude modulation decomposition temperature and inhibit ordering, resulting in a decrease in the overall hardening amount of the alloy system. Furthermore, excessive Cu addition can also reduce the corrosion resistance of the alloy. More preferably, the Cu concentration when adding Cu is set to be greater than 2.5 atomic% and less than 22.5 atomic%, and particularly preferably greater than 5 atomic% and less than 18.5 atomic%.

[0075] metal element α, metal element β

[0076] The Au-Ni-Pd-Pt alloy of the present invention, in addition to the essential constituent elements and Cu as described above, may also contain metal elements α and β as optional additive elements. Metal elements α and β have the effect of increasing the hardness of the aged noble metal alloy. The reason for increasing the hardness of the noble metal alloy by adding metal elements α and β is not yet clear, but the inventors have observed that it is related to the increase in the strength of the alloy matrix due to the increase in lattice strain, the grain refinement of the aged alloy, and the formation of precipitates containing the additive elements. It should be noted that even the addition of metal elements α and β does not hinder the formation of a material structure containing modulated structures and / or ordered phases. Metal elements α and β may be included, or both.

[0077] The metallic element α is at least one of In, Sn, and Sb. According to the inventors' research, the increased hardness of the noble metal alloy of the present invention has been confirmed using these metallic elements. The addition of metallic element α is preferably of one or more of In, Sn, and Sb. Furthermore, the composition range of at least one of In, Sn, and Sb as metallic element α is 0.15 atomic% or more and 5 atomic% or less. When the addition amount is less than 0.15 atomic%, it is difficult to contribute to the increase of the hardness of the noble metal alloy; when it exceeds 5 atomic%, the decrease in workability becomes significant. The composition range of metallic element α is preferably 0.3 atomic% or more and 3 atomic% or less, more preferably 0.5 atomic% or more and 1.5 atomic% or less.

[0078] The metallic element β is at least one of Ti, Zr, Hf, and Al. According to the inventors' research, the grain refinement and increased hardness of the noble metal alloy of the present invention have been confirmed using these metallic elements. The addition of metallic element β is preferably of one or more of Ti, Zr, Hf, and Al. Furthermore, the composition range of at least one of Ti, Zr, Hf, and Al as metallic element β is 0.05 atomic% or more and 5 atomic% or less. When the addition amount is less than 0.05 atomic%, it is difficult to contribute to the grain refinement and increased hardness of the noble metal alloy; when it exceeds 5 atomic%, the decrease in processability becomes significant. Additionally, the composition range of metallic element β is preferably greater than 0.1 atomic% and less than 3 atomic%, more preferably 0.15 atomic% or more and less than 1.5 atomic%.

[0079] The noble metal alloy of the present invention comprises Au, Ni, Pd, Pt, and B as essential elements within the aforementioned composition range, and preferably is a noble metal alloy composed of Au, Ni, Pd, Pt, and B within the aforementioned range. However, the noble metal alloy of the present invention may contain optional unavoidable impurities. Unavoidable impurities refer to impurities in the raw materials or unavoidable components contained due to manufacturing processes, etc. Specifically, unavoidable impurities include Rh, Ir, Fe, Y, Zn, Co, Si, Cu, Th, H, rare earth elements, etc. These unavoidable impurities are introduced from raw materials and melting and casting equipment, etc. The content of these unavoidable impurities is preferably within a range that does not impair the characteristics of the noble metal alloy of the present invention, preferably less than 0.05 atomic% for each element, preferably less than 0.5 atomic% in total, and particularly preferably less than 0.1 atomic%. It should be noted that when the noble metal alloy contains the aforementioned unavoidable impurities, it is difficult to clearly distinguish whether they are unavoidably present components or actively added components. In this invention, as long as the component does not significantly alter the properties of the precious metal alloy, it is considered an unavoidable impurity regardless of its intended inclusion. The same definition of unavoidable impurities applies when the alloy contains Cu, α, and β, which are added elements as described above.

[0080] The amplitude-modulated decomposition and ordering of the noble metal alloy of the present invention are manifested in the solution treatment process of rapidly cooling a solid solution alloy within the above-mentioned composition range after holding it at a high temperature, followed by an aging treatment. The noble metal alloy of the present invention exhibits a wide range of regions where complete solid solution is achieved at high temperatures, while maintaining a solubility gap at low temperatures. Therefore, it is considered that a noble metal alloy within the above-mentioned composition range can form a supersaturated solid solution by rapidly cooling it after solution treatment at a high temperature, and then undergo amplitude-modulated decomposition and ordering through subsequent aging treatment. It should be noted that the CALPHAD method (Calculation of Phase Diagrams Method) is also effective for the thermodynamic behavior (phase transformation point, phase equilibrium, solid solution limit, melting point, etc.) related to the noble metal alloy of the present invention. Calculations using the CALPHAD method preferably utilize commercially available thermodynamic calculation software (e.g., Thermo-Calc and noble metal alloy databases (e.g., TCNOBL1)).

[0081] (A-2) Material structure of the noble metal alloy of the present invention

[0082] The noble metal alloy of the present invention achieves increased hardness through amplitude modulation decomposition and / or ordering. Therefore, the microstructure of the noble metal alloy of the present invention may include a fine modulation structure based on amplitude modulation decomposition and / or an ordered phase based on ordering.

[0083] In the noble metal alloy of the present invention, the modulated microstructure generated by amplitude modulation decomposition is a material microstructure whose composition changes with a modulation period of about a few nm to tens of nm. Specifically, the modulated microstructure in the present invention consists of two regions: a region with relatively high Au and Pd concentrations (a region with relatively low Pt and Ni concentrations) and a region with relatively low Au and Pd concentrations (a region with relatively high Pt and Ni concentrations).

[0084] Furthermore, the composition and structure of the ordered phase in this invention may not be entirely clear. However, it is believed that phases with crystal structures that are the same as or similar to those that can be generated in Pt-Ni alloys or Au-Pd alloys, which are known as noble metal alloys capable of producing ordered phases, are also produced in the noble metal alloys of this invention. Therefore, it is presumed that the ordered phase in this invention has an L10 type structure or an L12 type structure, or a crystal structure similar to them.

[0085] The microstructure of the noble metal alloy of the present invention can be confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction patterns of TEM, scanning transmission electron microscopy (STEM), TEM / STEM-EDS mapping images, TEM / STEM-EELS mapping images, three-dimensional atomic probes, etc.

[0086] The modulation structure of the noble metal alloy of the present invention can be confirmed by one or both of diffraction and elemental analysis (elemental mapping).

[0087] As a diffraction method, there are methods for confirming X-ray diffraction patterns based on X-ray diffraction (XRD) or electron beam diffraction patterns based on TEM. When confirming using diffraction, in the case of a modulated structure, broad peaks known as so-called side peaks (companion peaks) or fringes are observed on the sides (preferably both sides) of at least one of the main peak and ordered reflection peaks. The presence or absence of these side peaks indicates whether a modulated structure based on amplitude modulation decomposition is present. For example, in the diffraction pattern obtained by X-ray diffraction, the crystal structure of the matrix of the noble metal alloy of the present invention is a face-centered cubic (fcc) structure, therefore the Miller indices {111} plane, {200} plane, {220} plane, {311} plane, etc., appear as main peaks. For at least one of the above main peaks, an amplitude modulation decomposition structure appears on both sides or one side. It should be noted that this is because when the side peak only appears on one side of the main peak, it is difficult to separate it from the main peak.

[0088] On the other hand, as a confirmation method using elemental mapping, methods such as using STEM-EDS / EELS and three-dimensional atom probes to visually confirm the concentration of atoms can be listed.

[0089] Furthermore, the confirmation of ordered phases generally involves using X-ray diffraction patterns or TEM electron diffraction patterns to determine the presence or absence of ordered reflection peaks. For example, in the observation of ordered reflection peaks in X-ray diffraction patterns, when using CuKα rays as the X-ray source for θ-2θ measurements, ordered reflection peaks appear around 2θ = 22.5–27.5° and around 30°–35°. Additionally, in the case of electron diffraction patterns, diffraction spots of 100, 110, and 120° appear that are not present in the fcc structure.

[0090] (A-3) Hardness of the noble metal alloy of the present invention

[0091] The noble metal alloy of the present invention has the above-mentioned composition range and is hardened through amplitude modulation decomposition and / or ordering. The noble metal alloy of the present invention can stably exhibit a hardness of 500 Hv or higher on a Vickers hardness scale. Preferably, the Vickers hardness of the noble metal alloy of the present invention is 540 Hv or higher, more preferably 590 Hv or higher, and even more preferably 640 Hv or higher. The noble metal alloy of the present invention can be produced as a high-hardness noble metal alloy with the above-mentioned Vickers hardness through heat treatment alone, without any work hardening, i.e., without material embrittlement caused by dislocation strain.

[0092] It should be noted that the upper limit of the hardness of the precious metal alloy of the present invention should not be particularly limited, but the upper limit is preferably 850 Hv or less. If it exceeds 850 Hv, fracture or breakage may occur during use. Furthermore, the Vickers hardness described above is the value at room temperature. Vickers hardness can be measured using a known Vickers hardness tester. The testing load is preferably set to 0.025 kgf or more and 0.5 kgf or less, more preferably 0.075 kgf.

[0093] The shape and form of the precious metal alloy of the present invention are not particularly limited. For the aforementioned medical devices, probe needles, etc., the present invention can generally be used in the form of a suitably processed bulk alloy. In the present invention, the ductility for processing into shapes and sizes suitable for these applications is improved. In addition, the present invention can also be formed in a layered or film-like form on a suitable substrate or base material.

[0094] (B) The method for manufacturing the noble metal alloy of the present invention

[0095] Next, a method for manufacturing the precious metal alloy of the present invention will be described. As described above, the precious metal alloy of the present invention can be provided in various shapes and forms. In the following description, a detailed method for manufacturing a bulk precious metal alloy, which is a frequently used form, will be provided, while methods for manufacturing layered and film-like precious metal alloys will also be mentioned.

[0096] In this invention, high hardness is achieved by optimizing the selection and composition range of the constituent elements (essential constituent elements (Au, Ni, Pd, Pt, B) and optional added metallic elements (Cu, metallic elements α, β) of the noble metal alloy, and by performing amplitude modulation decomposition and / or ordering. Furthermore, the noble metal alloy of this invention is manufactured by performing appropriate heat treatment processes on the basis of producing and preparing alloy blocks (ingots) with the aforementioned composition range. Appropriate heat treatment processes refer to heat treatment processes based on a combination of solution treatment and aging treatment, through which amplitude modulation decomposition and / or ordering are performed, thereby achieving high hardness and resulting in the noble metal alloy of this invention.

[0097] The following description, along with the explanation of each heat treatment step including solution treatment and aging treatment, will also describe the method for manufacturing the precious metal alloy of the present invention. It should be noted that, unless otherwise specified, the heating temperatures, etc., in the various heat treatments described below refer to the temperatures of the precious metal alloy being treated.

[0098] (B-1) Preparation process (production of precious metal alloys)

[0099] First, a precious metal alloy ingot, which serves as a precursor to the precious metal alloy of the present invention, is prepared. The precursor precious metal alloy ingot can be manufactured using a conventional melting and casting method. The alloy ingot is manufactured by appropriately weighing the aforementioned Au, Ni, Pd, Pt, B, and optional elements Cu, α, and β, and then melting and casting them to achieve the above composition. Alternatively, a precious metal alloy (Au-Ni-Pd-Pt alloy), a binary alloy Au-Pd alloy, or a Pt-Ni alloy (containing Cu, α, and β), can be appropriately combined as a master alloy and melted. The melting and casting of the precious metal alloy can be performed using known methods such as arc melting, high-frequency melting, vacuum melting, continuous casting, and liquid quenching.

[0100] Precious metal alloys can also be prepared using methods other than melting and casting, such as powder metallurgy. In powder metallurgy, by sintering precious metal alloy powder with the above-described composition (e.g., precious metal alloy powder produced by atomization), an alloy ingot suitable for heat treatment can be obtained. Alternatively, near-net-shape ingots can be manufactured using the precious metal alloy powder with the above-described composition through known metal powder injection molding or additive manufacturing methods. Furthermore, a precious metal alloy layer with the above-described composition can be formed on any base material using known alloy forming methods such as plating, sputtering, and spraying.

[0101] (B-2) Solution treatment

[0102] For the noble metal alloy prepared as described above, a supersaturated solid solution is formed through solution treatment. Solution treatment is a process in which the noble metal alloy is heated to a high temperature to create a structure with increased solid solution concentration, and then rapidly cooled to form a supersaturated solid solution. When the melting point (solid line) of the noble metal alloy is set as Tm (°C), the heating temperature for solution treatment is preferably set to a temperature above (Tm-500°C) and below Tm. Below (Tm-500°C), the solid solubility of each element is low, insufficient to form a supersaturated solid solution; above Tm, melting begins near the grain boundaries, which is therefore undesirable. The holding time during heating is preferably in the range of 0.0001 hours or more and 168 hours. Less than 0.0001 hours results in insufficient formation of a supersaturated solid solution, and even heating for more than 168 hours will not significantly affect the formation of the supersaturated solid solution; therefore, this is undesirable from a productivity perspective. It should be noted that in this invention, melting point refers to the solid line temperature.

[0103] Furthermore, during cooling from the solution treatment temperature, rapid cooling is required, i.e., quenching to a level that prevents excessive grain boundary reactions from occurring within the high-temperature range. This is because if grain boundary reactions occur within the high-temperature range, the grain boundaries are strengthened, increasing ductility, but the hardness after aging heat treatment is sometimes insufficient. Specifically, it is preferable to set the cooling rate to 10°C / s or more, more preferably 50°C / s or more, and even more preferably 150°C / s or more. On the other hand, from the viewpoint of preventing quenching cracks, dimensional changes, deformation, etc., a slow cooling rate is preferable. Therefore, from the viewpoint of improving the hardness of noble metal alloys, in the low-temperature range where grain boundary reactions do not occur and excessive decomposition and / or ordering does not occur, it is not necessary to set the aforementioned cooling rate, referred to as quenching, is required. For example, regarding the cooling rate in the temperature range below 250°C, quenching is not necessary. Therefore, in order to suppress or mitigate the occurrence of quenching cracks, for example, air cooling can be performed in the temperature range below 200°C after quenching to 200°C. It should be noted that the endpoint of cooling in the solution treatment here is preferably set to room temperature.

[0104] (B-3) Timeliness Processing

[0105] The amplitude-modulated decomposition and ordering of the noble metal alloy of the present invention are carried out by aging the supersaturated solid solution formed by solid solution treatment in a temperature range below the amplitude-modulated decomposition temperature and the order-disorder phase transition temperature.

[0106] As for the aging treatment conditions for noble metal alloys with supersaturated solid solutions, the heating temperature is preferably 250°C or higher and 800°C or lower. Below 250°C, phase transformation or ordering is difficult to achieve. Furthermore, above 800°C, material softening due to grain boundary reactions is significant. The heating temperature is more preferably 350°C or higher and 650°C or lower. Additionally, the aging treatment heating time is preferably set to 0.001 hours or higher and 168 hours or lower. Less than 0.001 hours results in insufficient phase transformation and fluctuations in hardness; treatments exceeding 168 hours lead to poor productivity and increased manufacturing costs. There are no particular restrictions on the cooling method after the aging treatment. The high-hardness noble metal alloy of the present invention can be obtained by undergoing this aging treatment.

[0107] (B-4) Other heat treatment processes

[0108] In the manufacture of the precious metal alloy of the present invention, the above-mentioned solution treatment and aging treatment are essential steps, but other heat treatment steps may also be included. Examples of such other heat treatment steps include homogenization treatment, two-phase treatment, and intermediate annealing. However, these other heat treatments do not affect the process of amplitude modulation decomposition and ordering. Therefore, these heat treatments are optional steps.

[0109] Homogenization treatment is performed on precious metal alloys prepared by melting and casting in order to form a metallic structure with a uniform distribution of elemental concentrations. Homogenization treatment involves heating the precious metal alloy at a high temperature below its melting point for an extended period (preferably 0.1 hours or more and 72 hours or less).

[0110] The two-phase treatment is a process that forms a two-phase microstructure with the best workability in the alloy system of the present invention. It is a heat treatment performed to facilitate warm and cold working. The heating temperature for the two-phase treatment is 700°C or higher and 900°C or lower, more preferably 750°C or higher and 850°C or lower. The heating time is 0.1 hours or higher and 10 hours or lower, more preferably 0.2 hours or higher and 2 hours or lower.

[0111] Intermediate annealing is a heat treatment performed on ingots of precious metal alloys, etc., in conjunction with warm working, cold working, and other processes described later to accumulate strain. Intermediate annealing is a treatment used to restore the workability of a material after its strength has been reduced. The heating temperature for intermediate annealing is 700°C or higher and 900°C or lower, more preferably 750°C or higher and 850°C or lower. The heating time is 0.1 hours or higher and 10 hours or lower, more preferably 0.2 hours or higher and 2 hours or lower.

[0112] (B-5) Processing steps of the precious metal alloy of the present invention

[0113] The precious metal alloy of the present invention can be processed into various shapes corresponding to its intended use by undergoing at least one processing step before aging treatment. Examples of such processing steps include hot working, warm working, cold working, surface rolling, straightening, winding, and bending. Hot working can eliminate defects such as solidification structure damage and voids in the prepared precious metal alloy ingot. Warm working and cold working, in addition to changing the overall shape of the alloy, also have the significance of controlling the grain shape. It should be noted that, in the case of multiple warm working and cold working processes, the aforementioned intermediate annealing can be performed between processing passes.

[0114] The improved ductility of the recrystallized structure of the noble metal alloy of the present invention is particularly evident when performing warm working, cold working, surface rolling, straightening, winding, and bending on the solution-treated noble metal alloy. After solution treatment (before aging), it is envisioned that the noble metal alloy be processed into a final shape or a shape similar to that intended for its application. The noble metal alloy of the present invention exhibits improved ductility due to grain boundary strengthening caused by grain boundary segregation of boron (B) as an additive element, allowing for processing without defects even in the recrystallized structure state after solution treatment. It should be noted that processing after aging treatment (after hardening) is not excluded for the noble metal alloy of the present invention. Even the high-hardness noble metal alloy after aging treatment can be processed. Furthermore, after aging treatment, grinding / laundering, cutting, electrical discharge machining, pressing, bending, straightening, and other finishing processes can be performed. Moreover, the amplitude-modulated decomposition and ordering exhibited in the noble metal alloy of the present invention are reversible, thus allowing for repeated solution treatment and aging treatments. Processing can also be carried out through a combination of multiple solution treatments and aging treatments.

[0115] (B-6) Other methods for manufacturing the precious metal alloy of the present invention

[0116] In the manufacturing method described above, the noble metal alloy of the present invention is obtained by performing solution treatment and aging treatment on an alloy ingot that has undergone melt casting. In the present invention, solution treatment is the main heat treatment step; however, even without solution treatment, it is sometimes possible to prepare a noble metal alloy with a microstructure equivalent to a supersaturated solid solution with a recrystallized structure. In this case, by aging the noble metal alloy, the noble metal alloy of the present invention can be manufactured. Furthermore, the addition of B in the present invention contributes to improving the ductility of the noble metal alloy in the recrystallized or supersaturated solid solution microstructure before aging treatment.

[0117] Examples of processes for obtaining a solid solution state of noble metals without solution treatment include liquid quenching for molten noble metal alloys, and rapid heating and cooling processes or rapid solidification processes using lasers for bulk metals. Additionally, noble metal alloys that approximate a supersaturated solid solution state can sometimes be manufactured using various film-forming processes such as welding, sputtering, plating, and spraying. Noble metal alloys manufactured through these processes can be used to produce the noble metal alloys of this invention by performing aging treatment without solution treatment. These processes are useful for manufacturing near-net-shape noble metal alloys and layered or film-like noble metal alloys such as high-hardness coatings. It should be noted that even without such solution treatment, the preferred conditions for aging treatment are the same as described above.

[0118] Example

[0119] The following describes specific embodiments of the present invention. In this embodiment, various Au-Ni-Pd-Pt noble metal alloys are manufactured by changing the composition of Au, Ni, Pd, Pt, B, Cu, metal element α, and metal element β. Then, for the manufactured noble metal alloys, the ductility in the state after solution treatment (recrystallized microstructure) is evaluated, and the hardness after aging treatment is measured. The manufacturing process and evaluation method of the noble metal alloys in each embodiment are described below.

[0120] [Manufacturing of precious metal alloys]

[0121] High-purity raw materials of Au, Ni, Pd, Pt, B, Cu, and the metallic elements α and β were weighed and mixed in a specified manner. The mixture was then placed in an alumina crucible and evacuated, followed by high-frequency melting under a reduced-pressure argon atmosphere. The resulting ingot was then cast in a copper mold (11 mm in diameter and 70 mm in length). The ingot was then homogenized. The homogenization process, taking into account the composition and melting point of the precious metal alloy, involved heating at a temperature between 800°C and 1225°C under a vacuum atmosphere (less than 5 × 10⁻⁶ ppm). -2 The process was carried out at a temperature of 16 Pa. The heating time for homogenization was set to 16 hours.

[0122] After homogenization treatment, the ingot (11 mm in diameter) was subjected to a two-phase treatment (800°C, 60 minutes, vacuum atmosphere), then cold-worked to a diameter of 6 mm by die forging, and finally cold-worked to a square diameter of 2.5 mm by die rolling. In these processing steps, the processing rate for each pass was set to 10-15%, and intermediate annealing (800°C, 60 minutes, vacuum atmosphere) was performed within a total processing rate of 30-50%. Next, wire drawing was performed using a wire drawing machine with a processing rate of 10-20% per pass until a diameter of 0.6 mm was achieved. In this wire drawing process, intermediate annealing was performed within a total processing rate of 30-60%. Through the above processing steps, the precious metal alloys of each embodiment and comparative example were processed into wires with a diameter of 0.6 mm. These wires were used as samples for evaluating the ductility and hardness of the recrystallized state.

[0123] [Solution treatment]

[0124] Then, the wire samples of each embodiment were subjected to solution treatment. The solution treatment was as follows: in a vacuum atmosphere, the heating temperature was set to 925°C to 1225°C, the heating time was set to 1 minute to 5 minutes, and after heating, the sample was placed in a water cooling bath (20±5°C) within 3 seconds to cool to room temperature.

[0125] [Time-sensitive processing]

[0126] After solution treatment, each wire sample underwent a bending test for ductility evaluation, followed by aging treatment. The method for the bending test will be described later. The aging treatment was performed as follows: the heating temperature was set between 450°C and 600°C, and the samples were heated and held at each aging treatment temperature for 1 hour, followed by water cooling to room temperature. Then, for the aged sample pieces, in order to remove the oxide layer, residual stress on the surface caused by thermal strain, and to prepare samples for hardness testing, the sample pieces were embedded in resin and subjected to coarse grinding (#500, #800, #1200) and mirror grinding using 1μm and 1 / 4μm diamond suspensions.

[0127] It should be noted that, in this embodiment, while manufacturing the Au-Ni-Pd-Pt noble metal alloy used as an example, a comparative example was also manufactured with an Au-Ni-Pd-Pt alloy having a composition similar to that of the noble metal alloys of each example but without the addition of B. Additionally, a comparative example was also manufactured with an Au-Ni-Pd-Pt noble metal alloy having a composition similar to that of the examples but with C (carbon) added instead of B. Furthermore, as a comparative example related to grain boundary strengthening effects based on grain boundary segregation, an Au-Ni-Pd-Pt noble metal alloy with added Ag and Zr was manufactured.

[0128] [Research on Material Microstructure Based on XRD Analysis]

[0129] Furthermore, XRD analysis was performed on each noble metal alloy after aging treatment to confirm the amplitude modulation decomposition and the formation of ordered phases. The XRD analysis conditions used for each research item are described below. XRD analysis was performed on noble metal alloys after solution treatment (solution-treated materials) and noble metal alloys after aging treatment following solution treatment (aging-treated materials). The results can be compared to confirm the amplitude modulation decomposition and ordering based on aging treatment. It should be noted that, regarding the samples used for XRD analysis, in order to improve the S / N ratio of the ordered reflection peaks with low diffraction intensity, the casting... A 30mm × L100mm precious metal alloy undergoes the same homogenization and two-phase treatment as described above (800℃, 60 minutes), followed by cold forging. After 22 mm, the same solution treatment (holding time of 10 minutes) and aging treatment as described above are performed to prepare samples for XRD analysis. Then, XRD analysis is performed on the solution-treated samples (solution-treated material) and the aging-treated samples (aging-treated material). Resin embedding and grinding of the analytical samples are carried out using the same method as described above.

[0130] [Common conditions]

[0131] Sample size: 22mm×2mmt

[0132] • XRD apparatus: Rigaku Manufacturing's SmartLab

[0133] • Target: Cu anode

[0134] • Optical systems and detectors: Concentrated optical systems, semiconductor detectors (HyPix-3000)

[0135] Voltage and current: 40kV, 30mA

[0136] • Length-limiting slit: 10mm

[0137] (a) Confirmation of amplitude modulation decomposition (sideband peaks)

[0138] • 2θ scan range: 20°~130°

[0139] ·2θ step size (°): 0.0012

[0140] • 2θ scan rate (° / min): 6

[0141] (b) Confirmation of the ordered phase (ordered peaks)

[0142] 2θ scan range: 20°~38°

[0143] 2θ step size (°): 0.0132

[0144] 2θ scan rate (° / min): 1.3

[0145] In XRD-based amplitude modulation decomposition studies, for the XRD diffraction patterns obtained under the above conditions, the presence of one or more side peaks (approximately ±0.5 to 3° in 2θ angle) on either side of the main peak in the {111}, {200}, {220}, and {311} planes is used for evaluation. The presence of one or more side peaks is considered as amplitude modulation decomposition occurring, while the absence of any side peaks is considered as not occurring.

[0146] Furthermore, in the study of ordered phases based on XRD, the presence or absence of ordered reflection peaks generated around 2θ = 30° to 35° is used for judgment. Specifically, a phase with an ordered peak intensity higher than the background in that region is evaluated as having an ordered phase, while a phase with a peak intensity below the same level as the background is evaluated as having no ordered phase.

[0147] As an example of the results of the XRD analysis performed in this embodiment, Figure 1 The XRD diffraction patterns of the solution-treated and age-treated materials of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) of Example 4-2 are shown. Figure 1 (a) shows the XRD diffraction pattern used to confirm the amplitude modulation decomposition. Figure 1 (b) Shows the XRD diffraction pattern used to confirm the ordered phase. (Refer to...) Figure 1 (a) In this noble metal alloy, for the peaks near 2θ = 40°–42° corresponding to the {111} plane and the peaks near 2θ = 46.5°–48.5° corresponding to the {200} plane, clear peaks that can be identified as sideband peaks were confirmed on both sides of them. This indicates that the noble metal alloy exhibits amplitude modulation decomposition. Furthermore, referring to… Figure 1 (b) In the region around 2θ = 31.5° to 34°, a peak significantly higher than the background (ordered reflection peak) was observed. This indicates that the noble metal alloy also exhibits ordering.

[0148] [Research on Material Microstructure Based on TEM / STEM Analysis]

[0149] To confirm the amplitude modulation decomposition and ordering characteristics of the noble metal alloy manufactured in this embodiment, TEM / STEM analysis was performed. In the TEM / STEM analysis, samples that underwent aging treatment after solution treatment (…) After resin embedding and grinding (0.6 mm), samples for TEM / STEM analysis were prepared using focused ion beam (FIB) and TEM / STEM analysis was performed.

[0150] Figure 2 The results of STEM-EDS mapping measurements of the constituent elements (Au, Ni, Pd, Pt) of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) in Example 4-2 are shown (Pt, Au, Pd: L line, Ni: K line). It should be noted that the electron incident direction is parallel to the

[001] direction. Figure 2 It is evident that the microstructure of the noble metal alloy in this embodiment exhibits a modulated structure comprising two regions: one with relatively high Au and Pd concentrations, and the other with relatively low Au and Pd concentrations. These regions are alternately connected. The modulated structure lacks a defined interface, suggesting that it is caused by amplitude modulation decomposition. Furthermore, a comparison between the mapping image and the electron diffraction pattern confirms a modulated structure in the <010> direction.

[0151] in addition, Figure 3 This is the electron beam diffraction pattern (001 zone axis incident) of the noble metal alloy from Example 4-2 obtained by TEM analysis. Figure 3 It was observed that in this noble metal alloy, in addition to the basic reflection based on the fcc structure, diffraction spots based on the ordered phase were also confirmed. Based on the location, intensity, and plane spacing, the diffraction spots of the ordered phase are hypothesized to be an L12 structure as the structure of the ordered phase. Furthermore, fringes were observed at the reciprocal lattice points at 010 and 100 in the <010> and <100> directions, respectively, suggesting the presence of a modulation structure in the <010> direction. This result is consistent with the mapping measurements based on STEM-EDS.

[0152] The same results were obtained from TEM / STEM analyses of other noble metal alloys. Therefore, it can be confirmed that, in determining amplitude modulation decomposition and ordering, elemental analysis (composition mapping) and electron diffraction are also useful, in addition to XRD analysis (diffraction).

[0153] [Confirmation of segregation in noble metal alloys after solution treatment]

[0154] Figure 4 The results of STEM-EDS analysis near the large-angle grain boundaries of the noble metal alloy (Au7.5-Ni41.25-Pd10-Pt41.25) of Comparative Example 2 after solution treatment are shown. Figure 4In the photograph, the central part is a large-angle grain boundary, but the concentrations of Pt and Ni are lower near the grain boundaries, while the concentrations of Au and Pd are higher near the grain boundaries. This confirms that the Au-Ni-Pd-Pt noble metal alloy of this embodiment has a tendency to segregate Au and Pd near the grain boundaries through solid solution treatment.

[0155] Next, for the noble metal alloy of the embodiment with added B, the presence or absence of B segregation towards the grain boundaries was confirmed. In this embodiment, AES analysis (Auger electron spectrometry) was performed to detect B as a light element. The AES apparatus used was a PHI-700 model manufactured by ULVAC-PHI. In this embodiment, the noble metal alloy sample was subjected to impact fracture under ultra-high vacuum within the apparatus, and the fracture surface was observed. AES analysis was performed on the grain boundary fracture surface and the intra-grain fracture surface. It should be noted that in the preparation of the sample provided for AES analysis, the casting... The 11mm precious metal alloy undergoes the same homogenization and two-phase treatments as described above, followed by cold forging. 6 mm. Then, while performing intermediate annealing, the material was cold-rolled to 3.75 mm square, followed by solution treatment (1175°C, 10 minutes), and the resulting material was used as an evaluation sample. The temperature and time of this solution treatment were designed to intentionally coarsen the grains and facilitate the formation of grain boundary fractures. Furthermore, impact tests were conducted at approximately -100°C. Thus, both grain boundary fractures and intragranular fractures were obtained on the fracture surface after impact fracture, and their Auger spectra were measured.

[0156] As an example of the AES analysis results for the noble metal alloy in the embodiment, in Figure 5 Auger spectra of the grain boundary fracture surface and the intragranular fracture surface of the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) of Example 4-2 are shown. Comparing the spectra of the grain boundary fracture surface and the intragranular fracture surface, a peak was only identified at around 185 eV at the grain boundary fracture surface. This peak near 185 eV is considered to originate from B, thus indicating that B segregates at the grain boundaries of the recrystallized structure. This confirms that B added to the noble metal alloy has a tendency to segregate at grain boundaries.

[0157] [Evaluation of the ductility of recrystallized structures]

[0158] The ductility of the solution-treated wire was evaluated. The ductility evaluation test is as follows: A 0.6mm wire sample was subjected to a bending test (bending radius 1mm, 180° bend), and the bending angle until breakage was measured. The bending test was performed on the same sample 5 times, and the average bending angle was used as the bending value for evaluation. It should be noted that for samples that do not break even when bent to 180°, the bending value is set to 180°.

[0159] [Hardness Measurement After Aging Treatment]

[0160] In the hardness measurement of the aged wire samples, a measuring device (HM-210 manufactured by Mitutoyo Co., Ltd.) was used, the test load was set to 0.075 kgf, and the measurement was performed at room temperature. The measurement results are shown in Table 1. In the hardness measurement, 15 points were randomly measured for each sample, and the average value was taken as the hardness value. Regarding the measurement location in each sample, multiple grains were selected, and the measurement was performed near the non-grain boundary reaction area of ​​each grain, preferably near the center of the grain. It should be noted that the hardness measurement results shown below record the aging temperature and hardness at which the highest hardness was obtained among multiple set aging temperatures in the range of 450°C to 600°C. However, for the noble metal alloy of the example, the minimum hardness also showed to be above 500 Hv.

[0161] Tables 1 to 4 show the composition, ductility evaluation results, and hardness measurement results of the noble metal alloys manufactured in the examples and comparative examples according to this embodiment. These tables also show the presence or absence of the modulated microstructure (sideband peaks) and ordered phase (ordered peaks) based on the aforementioned XRD analysis. Furthermore, the alloy compositions listed in Tables 1 to 4 are analytical values ​​obtained from wire samples of each example. The alloy composition analysis was performed using ICP-OES analysis, and for samples with an expected B concentration of trace amounts (less than 0.05 atomic%), ICP-MS analysis was used in combination. It should be noted that in these tables, in this embodiment, to confirm the effects of the addition of the essential element B, the optional element Cu, and the metal elements α and β, noble metal alloys with similar concentrations of the essential metal elements (Au, Ni, Pd, Pt) were grouped and distinguished as examples and comparative examples.

[0162]

[0163] In studying the results shown in Tables 1 to 4, as a prerequisite for confirmation, it was confirmed that the Au-Ni-Pd-Pt alloys of each embodiment and comparative example, except for alloys that could not be solution treated due to cracks generated during processing, all exhibited amplitude decomposition and / or ordering, displaying a hardness of 500 Hv or higher. Therefore, it can be said that the Au-Ni-Pd-Pt alloys targeted by the applicant of this application have the potential to be suitable as high-hardness noble metal alloys.

[0164] Therefore, the effect of boron (B), an essential additive element for improving the ductility of recrystallized structures after solution treatment and the subject of this invention, was investigated. As shown in the table, the bending angle of the Au-Ni-Pd-Pt alloys in each embodiment with added boron was significantly increased compared to the comparative examples without added boron. This is evident, for example, by referring to Examples 1, 2, 3-1 to 3-5, 4-1 to 4-4 in Table 1 and their corresponding comparative examples. The same applies when comparing combinations of examples and comparative examples in each table. Therefore, it can be said that the addition of boron confirms the effect of improving the ductility of the recrystallized structure after solution treatment.

[0165] However, the results in Table 1 confirm that the addition of B to Au-Ni-Pd-Pt alloys should also be within the specified range. When the amount of B added is too small (0.001 atomic%), no effect on improving ductility was observed (Comparative Example 3). In addition, if too much B is added, the ductility of the originally well-processable two-phase structure decreases, and cracks are generated during processing (Comparative Examples 11-2).

[0166] Based on the research results regarding the addition of B described above, it is believed that in the Au-Ni-Pd-Pt alloy of the present invention, the addition of B causes grain boundary segregation and changes the grain boundary structure, resulting in increased grain boundary strength, thereby suppressing grain boundary embrittlement and improving the ductility of the recrystallized structure.

[0167] Regarding the effect of B, an essential additive element in the Au-Ni-Pd-Pt alloys of the present invention, the effects of additive elements other than B were investigated, and the results are shown in Comparative Examples 4-2 (additive element: C), 4-3 (additive element: C), 4-4 (additive element: Zr), and 4-5 (additive element: Ag) (see Table 1). When evaluating the Au-Ni-Pd-Pt alloys of these comparative examples, no improvement in ductility was observed in the recrystallized structure when C and Zr were added (Comparative Examples 4-2 and 4-4). Furthermore, increasing the C concentration significantly increased grain boundary embrittlement, causing grain boundary cracks even in a two-phase structure, making it difficult to process (Comparative Example 4-3). Moreover, adding Ag, an element with a strong tendency for grain boundary segregation, was also attempted, but grain boundary embrittlement became significant, causing grain boundary cracks even in a two-phase structure, making it difficult to process (Comparative Examples 3-5).

[0168] The effect of adding boron to Au-Ni-Pd-Pt alloys in the recrystallized state on improving ductility was also confirmed by room temperature tensile tests. Figure 6 The results of room-temperature tensile tests are shown for the noble metal alloy (Au12.5-Ni37.325-Pd12.5-Pt37.325-B0.35) of Example 4-2 and the noble metal alloy (Au12.5-Ni37.5-Pd12.5-Pt37.5) of Comparative Example 4-1. The room-temperature tensile tests were conducted on the solution-treated samples ( (0.6mm × L50mm) under the conditions of a chuck spacing of 25mm and a crosshead speed of 10mm / minute. From Figure 6 As confirmed, by adding B, a significant increase in elongation value and a significant improvement in ductility were observed.

[0169] Next, the effects of Cu, α, and β as optional additive elements were investigated. Table 3 shows the results for noble metal alloys with Cu added to the Au-Ni-Pd-Pt alloy system. Table 3 confirms that the Au-Ni-Pd-Pt alloys with Cu also exhibit amplitude modulation decomposition and ordering. These noble metal alloys showed good hardness of over 500 Hv after aging treatment.

[0170] Furthermore, the effect of adding B was also confirmed in Au-Ni-Pd-Pt alloys with Cu. In the comparative examples of noble metal alloys without B, the bending properties were poor and grain boundary embrittlement occurred. It was confirmed that by adding B as in the examples, the bending properties could be improved and grain boundary embrittlement could be suppressed.

[0171] Table 4 shows the effects of adding metallic elements α (In, Sn, Sb) and β (Ti, Zr, Hf, Al). First, it was confirmed that none of these added elements hindered the modulated decomposition and ordering of the Au-Ni-Pd-Pt alloy system. Furthermore, regardless of the addition of β, an increase in hardness was observed by adding at least one of these added elements. This hardness increase sometimes exceeded 100 Hv depending on the composition of the noble metal alloy.

[0172] Furthermore, in Au-Ni-Pd-Pt alloys with added metallic elements α and β, the effect of adding β in improving ductility was also confirmed. In addition, based on the comparison between Examples 24 and 26 in Table 3, in Au-Ni-Pd-Pt alloys containing Cu as an optional additive element, metallic elements α and β are also effective in increasing hardness. The addition of metallic elements α and β can be done by adding only one, both, or multiple metallic elements.

[0173] Industrial availability

[0174] As explained above, this invention is based on high-hardness noble metal alloys with amplitude modulation decomposition and / or ordering, thereby improving the ductility of recrystallized structures produced through solution treatment, etc. In this invention, for grain boundary embrittlement caused by grain boundary segregation of Au and Pd after solution treatment, it is believed that by adding B, B undergoes grain boundary segregation, thereby changing the grain boundary structure, resulting in increased grain boundary strength, and thus suppressing grain boundary embrittlement.

[0175] The precious metal alloy of the present invention is expected to be used in various applications such as electrical / electronic materials requiring high hardness and high wear resistance, such as probe needles and electrical contacts, medical devices, and high-hardness coated components. In these applications, post-treatment processing, such as solution treatment, is often necessary. The precious metal alloy of the present invention exhibits good ductility after heat treatment, such as solution treatment, thus effectively meeting the requirements of these applications. Furthermore, the precious metal alloy of the present invention can be manufactured by aging treatment of precious metal alloys obtained using additive manufacturing technology, metal powder injection molding technology, rapid cooling solidification technology, laser heating technology, welding technology, sputtering / spraying / plating, and other coating technologies, enabling its application in the aforementioned various applications.

Claims

1. An Au-Ni-Pd-Pt noble metal alloy, comprising 1.5 atomic% or more and 47 atomic% or less Au, 4 atomic% or more and 57 atomic% or less Ni, 1 atomic% or more and 43.5 atomic% or less Pd, and 6 atomic% or more and 58.5 atomic% or less Pt, wherein... It contains more than 0.003 atomic% and less than 8 atomic% of B.

2. The Au-Ni-Pd-Pt noble metal alloy according to claim 1, further comprising Cu at a concentration greater than 0.1 atomic% and less than 27.5 atomic% 3. The Au-Ni-Pd-Pt noble metal alloy according to claim 1 or claim 2, further comprising 0.15 atomic% and 5 atomic% of a metallic element α, wherein the metallic element α is at least one of In, Sn, and Sb.

4. The Au-Ni-Pd-Pt noble metal alloy according to claim 1 or claim 2, further comprising 0.05 atomic% and 5 atomic% of a metallic element β, wherein the metallic element β is at least one of Al, Ti, Zr, and Hf.

5. The Au-Ni-Pd-Pt noble metal alloy according to claim 3, further comprising 0.05 atomic% and 5 atomic% of a metallic element β, wherein the metallic element β is at least one of Al, Ti, Zr, and Hf.

6. The Au-Ni-Pd-Pt noble metal alloy according to claim 1 or claim 2, wherein, The material microstructure includes modulation microstructure based on amplitude modulation decomposition.

7. The Au-Ni-Pd-Pt noble metal alloy according to claim 1 or claim 2, wherein, The material contains an ordered phase.

8. The Au-Ni-Pd-Pt noble metal alloy according to claim 6, wherein, The material contains an ordered phase.

9. The Au-Ni-Pd-Pt noble metal alloy according to claim 1 or claim 2, wherein the Vickers hardness is above 500 Hv.

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