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

Abstract

The present invention is an Au-Ni-Pd-Pt noble metal alloy obtained by adding a metal element [alpha] to a base alloy comprising Au, Ni, Pd, and Pt. In the present invention, the metal element [alpha] is at least one metal element selected from In, Sn, Mg, Al, and Ti. The noble metal alloy according to the present invention contains 4 at% to 24 at% (inclusive) of Au, 5 at% to 60 at% (inclusive) of Ni, 2.5 at% to 40 at% (inclusive) of Pd, 10 at% to 60 at% (inclusive) of Pt, 0.15 at% to 7.5 at% (inclusive) of a metal element alpha, and unavoidable impurities. The noble metal alloy of the present invention achieves high hardness by means of a modulated structure based on rotary joint decomposition and / or an ordered phase based on ordering, and can have a Vickers hardness of 500 Hv or more. The noble metal alloy of the present invention is a high-hardness noble metal alloy using a strengthening mechanism different from the currently common methods such as work hardening, precipitation hardening and the like.

Description

Technical Field

[0001] This invention relates to high-hardness noble metal alloys with Au, Pt, and Pd as essential constituent metals. More specifically, it relates to noble metal alloys with an Au-Ni-Pd-Pt alloy as a base alloy, in which a specified metallic element α is added, and high hardness is achieved through spinolysis and / or ordering. Background Technology

[0002] Precious metals such as Pt (platinum) and Au (gold) are metals with excellent chemical stability, corrosion resistance, and electrical properties such as conductivity. Therefore, precious metals and their alloys are used in various fields, including electrical / electronics and medicine. Examples of the use of precious metal alloys in the electrical / electronics field include probe needles on probe cards for testing semiconductor devices, brushes for motors, and electrical contacts (sliding contacts, switch contacts) for relays and switches. In recent years, their use in the medical field has attracted attention, with precious metal alloys being used as constituent materials for various medical devices. Examples of such medical devices include embolization coils, embolization clips, guidewires, stents, and catheters. These medical devices are implanted in direct contact with the human body, thus requiring biocompatibility and chemical stability. Furthermore, X-ray visibility is also considered in medical devices for use in surgeries and diagnostic procedures using X-rays. Precious metal alloys also exhibit good biocompatibility and X-ray visibility.

[0003] Furthermore, for precious metal alloys used in the aforementioned applications, there is a demand for improved mechanical properties such as hardness and strength. For example, probe needles require wear resistance due to prolonged and repeated contact with the target component. In particular, to cope with the high integration of various devices and the high performance of electric motors in recent years, there is a need to develop probe needles with higher hardness. In addition, regarding medical devices, for those that move and are implanted in pulsating, beating blood vessels, such as guidewires and embolization coils, mechanical properties such as hardness and elasticity are required to prevent malfunctions in their operation.

[0004] Since noble metal alloys are also metallic materials, their hardness can be increased using general strengthening mechanisms found in metallic materials. Specifically, to date, the hardness of noble metal alloys has been improved through a combination of work hardening (dislocation strengthening), solid solution strengthening, and precipitation hardening (dispersion strengthening). Examples of hardness improvement for noble metal alloys used as probe and contact materials include the Pt-Ni alloy described in Patent Document 1 and the Pt-W alloy in Patent Document 2, which achieved increased hardness through solid solution strengthening by alloying Ni and W into Pt, and work hardening by increasing the final workability. Furthermore, 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 added elements, high-hardness noble metal alloys were obtained through work hardening by adjusting the workability.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2005-233967

[0008] Patent Document 2: Description of Japanese Patent No. 6997354

[0009] Patent Document 3: Japanese Patent Application Publication No. 2012-242184

[0010] Patent Document 4: Japanese Patent No. 6372952 Specification Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] As mentioned above, various applications demand improved mechanical properties such as hardness in noble metal alloys. To meet this requirement, further strengthening through the aforementioned strengthening mechanisms is necessary. However, regarding solid solution strengthening and precipitation strengthening, although attempts have been made to optimize the selection and amount of added elements and manufacturing processes such as heat treatment, the resulting hardening is limited. For example, the hardness increase based on precipitation hardening in the noble metal alloys of Patent Documents 3 and 4 is approximately 150 Hv, indicating that sufficient hardness cannot be achieved through precipitation hardening alone. In practice, for these noble metal alloys, hardness is supplemented by work hardening concurrent with precipitation hardening.

[0013] Furthermore, there are concerns regarding the overuse of work hardening. While work hardening can be a useful strengthening method due to its large amount of hardening, it can also lead to material embrittlement. This embrittlement can be a major cause of wire breakage during drawing, secondary processing (pressing, winding, bending, etc.), and cracking or fracture during actual use. Since electrical materials such as probes, guidewires, and embolization coils are manufactured using fine wires, it is crucial to ensure the machinability of these wires during processing. Therefore, when considering the issues of material embrittlement and machinability, it must be acknowledged that the amount of hardening achieved through work hardening is also limited.

[0014] This invention was made based on the background described above, and provides a high-hardness noble metal alloy achieved by applying a strengthening mechanism different from currently used methods to noble metal alloys with Au, Pd, and Pt as essential constituent elements. In particular, this invention proposes a material strengthening mechanism based on a heat treatment-based process that does not rely on work hardening that causes embrittlement.

[0015] Methods for solving problems

[0016] To address the aforementioned problems, as an enhancement method different from those commonly used to date, the inventors focus on two phenomena: spindle decomposition and ordering.

[0017] Spiral decomposition refers to a mode of phase separation in a material microstructure, a phenomenon that occurs independently of nucleation and growth processes applied to precipitation hardening, through a continuous increase in concentration fluctuations. The microstructure generated by spiral decomposition caused by these concentration fluctuations exhibits a very fine periodic structure, ranging from a few nm to tens of nm, known as a modulated structure. In the modulated structure exhibited in spiral decomposition, the concentration of solute atoms in the crystal varies periodically as a function of position, and the lattice constant also changes periodically. This generates a periodic internal stress field on the sliding surface, which interacts with dislocations. The strengthening mechanism based on spiral decomposition can be said to be similar to precipitation strengthening based on nucleation and growth, but the difference lies in that, instead of precipitates, the change in the lattice constant caused by concentration modulation hinders dislocation movement. Moreover, as mentioned above, spiral decomposition strengthening exhibits high hardening due to its fine modulated structure, and is therefore considered useful as a means of increasing material hardness without causing work hardening and resulting in material embrittlement.

[0018] On the other hand, ordering refers to the phenomenon of generating an ordered phase with a prescribed structure through the ordered arrangement of the constituent elements of an alloy. The ordered phase generated through ordering contributes to the high hardness of the alloy through the following factors: (i) an increase in the Burgers vector of dislocations; (ii) the possible formation of antiphase boundaries within the ordered phase; and (iii) the volume changes accompanying ordering, which deform the lattice inside and outside the ordered phase, thus suppressing dislocation motion. Ordering sometimes occurs in conjunction with the aforementioned spinolysis, and sometimes it occurs alone.

[0019] The phenomena and material microstructures exhibited by spinolysis and ordering are well-known. Furthermore, it is known that noble metal alloys possess compositions capable of spinolysis and ordering. Regarding spinolysis, Pt-Au alloys are known to be capable of spinolysis in noble metal alloys. Figure 1 The phase diagram of the Pt-Au system is shown. Thermodynamic calculations also reveal the regions of composition and temperature ranges where vortex decomposition can occur in Pt-Au alloys (chemical vortex curves).

[0020] On the other hand, regarding the ordering of noble metal alloys, Pt-Ni alloys are known to exhibit ordering. Ordering in Pt-Ni alloys is known to occur through solution treatment and aging heat treatment, and through aging heat treatment within the order-disorder phase transformation region, air cooling starting from the single-phase region, etc., resulting in ordering and hardening. In the ordering of these Pt-Ni alloys, L10-type or L12-type ordered phases can be generated. Furthermore, although not as known as Pt-Ni alloys, Au-Pd alloys are also indicated to have the potential to exhibit ordering. In the case of ordering in Au-Pd alloys, it is predicted that the same ordered phases as in Pt-Ni alloys will be generated and hardened.

[0021] However, while it is known that spinolysis and ordering can contribute to increased hardness in alloy materials, the resulting increase in hardness is not significant in known alloy systems. For example, in the aforementioned Pt-Au alloy, even with hardening through spinolysis, the maximum increase in hardness is only about 160 Hv, making it difficult to stably achieve a hardness above 500 Hv for noble metal alloys. Furthermore, the hardness of Pt-Ni alloys, which can exhibit ordering, is also unlikely to exceed 500 Hv.

[0022] Furthermore, while the phenomena and mechanisms of spinolysis and ordering are well-known, there are few specific applications, especially in noble metal alloys. Therefore, the inventors observed that there is much room for improvement in spinolysis and ordering as hardening and strengthening methods for noble metal alloys, and conducted further research. Moreover, improvements were conceived through the following two approaches.

[0023] The first approach to increasing the hardness of noble metal alloys, as obtained by the inventors, is the diversification of the composition of noble metal alloys. To maximize the hardening capacity resulting from the decomposition and ordering of nodal components in noble metal alloys, the inventors believed that compositional optimization within binary alloys (Pt-Au alloys, Pt-Ni alloys, Au-Pd alloys, etc.) was limited, and therefore, ternary or higher alloys should be applied. Furthermore, the inventors conducted in-depth research and found that, as a component of noble metal alloys, optimizing the composition of quaternary alloys of Au, Ni, Pd, and Pt, and performing appropriate heat treatment, can achieve an effective increase in hardness due to nodal decomposition and / or ordering.

[0024] Furthermore, a second approach to increasing the hardness of noble metal alloys involves using the aforementioned Au-Ni-Pd-Pt alloy as a base alloy and further adding other metallic elements to it. In this invention, this added element is referred to as metallic element α. Metallic element α is not an element that alters the material microstructure exhibited in the Au-Ni-Pd-Pt alloy based on spinolysis and / or ordering, but rather an element that imparts an additional increase in hardness to the base alloy strengthened through spinolysis and / or ordering. The mechanism of this additional hardness increase is not yet clear, but the inventors have envisioned several factors, such as the effect of metallic element α on the matrix.

[0025] Based on the two approaches described above, the inventors conducted a detailed study on the range of metallic element α that should be added to the Au-Ni-Pd-Pt alloy as the base alloy, and on the composition range of the Au-Ni-Pd-Pt alloy that becomes effective in achieving high hardness due to spinolysis and / or ordering when metallic element α is added, which led to the invention.

[0026] That is, the present invention is an Au-Ni-Pd-Pt noble metal alloy, which is formed by adding the metal element α to a basic alloy composed of Au, Ni, Pd and Pt. The metal element α is at least one of In, Sn, Mg, Al and Ti. The Au-Ni-Pd-Pt noble metal alloy contains 4 atomic% or more and 24 atomic% or less Au, 5 atomic% or more and 60 atomic% or less Ni, 2.5 atomic% or more and 40 atomic% or less Pd, 10 atomic% or more and 60 atomic% or less Pt, 0.15 atomic% or more and 7.5 atomic% or less metal element α and unavoidable impurities.

[0027] Moreover, as described above, the noble metal alloy of the present invention, composed of Au-Ni-Pd-Pt alloys, contains modulated structures and / or ordered phases based on spinolysis.

[0028] The Au-Ni-Pd-Pt noble metal alloy of the present invention achieves high hardness through spinolysis and / or ordering. The Vickers hardness of this high-hardness Au-Ni-Pd-Pt noble metal alloy reaches over 500 Hv.

[0029] Invention Effects

[0030] As explained above, for the noble metal alloys of the present invention, instead of the solid solution strengthening, precipitation strengthening, and work hardening methods widely used to date, material strengthening is achieved through modulated microstructure based on spindle decomposition and / or based on ordered phases. According to the present invention, even without relying on work hardening (dislocation strengthening) which may lead to material embrittlement, high-hardness noble metal alloys can be obtained through previously unseen strengthening capabilities. Attached Figure Description

[0031] Figure 1 This is a diagram showing the state diagram of the Pt-Au system and the swirl curve of the Pt-Au alloy.

[0032] Figure 2 The graph shows the XRD results of the solid solution and aging materials of the noble metal alloy (Au12.5-Ni30.625-Pd25-Pt30.625-Sn1.25) as an example, B-5.

[0033] Figure 3 This is a STEM-EDS mapping image showing the modulation structure of the noble metal alloy (Au12.5-Ni30.625-Pd25-Pt30.625-Sn1.25) as an example, B-5.

[0034] Figure 4 The electron diffraction pattern shows the ordered phase (L12 structure) of the noble metal alloy (Au12.5-Ni30.625-Pd25-Pt30.625-Sn1.25) as an example B-5. Detailed Implementation

[0035] The embodiments of the present invention will be described below. As described above, the noble metal alloy of the present invention is composed of an Au-Ni-Pd-Pt alloy in which a specified metallic element α is added to an Au-Ni-Pd-Pt alloy as a base alloy. In the noble metal alloy of the present invention, as its hardening factor, it includes at least one of a modulated structure based on spinolysis and an ordered phase based on ordering. In the following description, in order to disclose (A) the structure of the noble metal alloy of the present invention, the following items will be described: (A-1) the various strengthening mechanisms (spinolysis and ordering) applied in the present invention; (A-2) the constituent metals of the noble metal alloy of the present invention and their composition ranges; (A-3) the material structure of the noble metal alloy of the present invention; and (A-4) the hardness of the noble metal alloy of the present invention. Furthermore, (B) the manufacturing method (heat treatment process) of the noble metal alloy of the present invention will also be described.

[0036] (A) The composition of the noble metal alloy of the present invention

[0037] (A-1) Strengthening mechanism of noble metal alloy in this invention

[0038] (1) Spin decomposition

[0039] As already explained, the structure formed by spinolysis is called a modulated structure. Periodic concentration variations are generated in the modulated structure, contributing to increased hardness by creating an internal stress field around it. The resistance to dislocation motion (critical shear stress) in this periodic internal stress field is expressed by the following formula, where lattice strain (ε), elastic coefficient (Y), and concentration modulation amplitude (A) are considered to be the governing factors (for detailed reference, see, for example, Masaharu Kato's *Introduction to Dislocation Theory* (published August 1999, by Shukabo)).

[0040] [Mathematical Expression 1]

[0041]

[0042] τ: Critical shear stress

[0043] Y: Elasticity coefficient

[0044] A: Concentration modulated amplitude

[0045] ε: lattice strain

[0046] In the study based on the formula in Equation 1 above, it is generally accepted that the elastic modulus is proportional to the Young's modulus of each constituent metal, and the lattice strain ε is proportional to the difference in lattice constants between the constituent metals. Furthermore, for the concentration modulation amplitude A in Equation 3, it is assumed that the larger the enthalpy of mixing between the metal elements, the larger the value. Regarding the lattice constants of Au, Ni, Pd, and Pt constituting the Au-Ni-Pd-Pt alloy, which is the basic alloy of this invention, the values ​​in Table 1 below are known. Furthermore, regarding the value of the enthalpy of mixing, the values ​​in Table 2 below are known (Reference: Akira Takeuchi, Akihisa Inoue, “Classification of Bulk Metallic Glasses by Atomic Size Difference, Heat of Mixing and Period of Constituent Elements and Its Application to Characterization of the Main Alloying Element”, Materials Transactions, vol46(2005), p2817-2829.).

[0047]

[0048]

[0049] Referring to Table 2, the enthalpy of mixing is positive in the combinations of Au-Pt, Au-Ni, and Pt-Pd. From their binary phase diagrams, it can be seen that Au-Pt and Au-Ni alloys, although they form a single phase at high temperatures, still possess very high enthalpy of mixing. The behavior of the noble metal alloys of this invention, including the spinolysis and significant hardening caused by the modulated structure, can be estimated based on the binary phase diagrams of each constituent metal, while also referring to the lattice constants in Table 1 and the enthalpy of mixing in Table 2, and considering mathematical formula 3. This will be explained in more detail later.

[0050] (2) Ordering (ordered phase)

[0051] As described above, the ordered phase generated through ordering contributes to the high hardness of the alloy through factors such as the Burgers vector of dislocations, the generation of antiphase boundaries within the ordered phase, and the lattice strain caused by the volume change accompanying ordering. Furthermore, the noble metal alloy of the present invention comprises both combinations of metals known as those constituting Pt-Ni alloys and Au-Pd alloys, which are combinations of metals that generate ordering.

[0052] The noble metal alloys of the present invention, like Pt-Ni and Au-Pd alloys, can also achieve high hardness due to the ordered phase generated through ordered behavior. The composition of the ordered phase in the present invention is not necessarily entirely clear, but it is considered to be a phase having the same or similar crystal structure as the ordered phases that can be generated in Pt-Ni or Au-Pd alloys. That is, it is a phase composed of Pt and Ni or a phase composed of Au and Pd, and it is a phase having an fcc structure and / or an fct structure. Furthermore, it is presumed that the ordered phase in the present invention is preferably a phase with an L10 type structure (PtNi, AuPd) or an L12 type structure (Pt3Ni, Ni3Pt, Au3Pd, Pd3Au), or a phase with a similar crystal structure.

[0053] (A-2) The constituent metals and composition range of the noble metal alloy of the present invention

[0054] The noble metal alloy of the present invention is formed by using an Au-Ni-Pd-Pt alloy of a specified composition as a base alloy and adding metallic element α to the base alloy. Hereinafter, the constituent metals and composition range of the base alloy, as well as the range and concentration of the element α, will be described.

[0055] (1) The constituent metals of the basic alloy (Au-Ni-Pd-Pt alloy)

[0056] The base alloy used as the basis for this invention is an Au-Ni-Pd-Pt quaternary alloy. The base alloy exhibits at least one of the strengthening mechanisms applied in this invention: spindle decomposition and ordering, ensuring the basic material structure and strength. That is, the base alloy itself also exhibits high hardness, possessing a hardness equal to or greater than that of noble metal alloys based on conventional strengthening mechanisms (solid solution strengthening, precipitation strengthening, work hardening).

[0057] The base alloys consist of metallic elements (Au, Ni, Pd, Pt) that effectively exhibit spinolysis and / or ordering. Regarding the ability to exhibit spinolysis, referring to the binary state diagrams related to each constituent metal of the base alloy, the Au-Ni, Au-Pt, and Pt-Pd alloys are two-phase separation types. Furthermore, as shown in Table 2 above, there are many combinations of elements with positive enthalpy of mixing among Au, Ni, Pd, and Pt. Therefore, the Au-Ni-Pd-Pt alloys are considered to have high enthalpy of mixing and a strong tendency for phase separation in the low-temperature range. Thus, the Au-Ni-Pd-Pt quaternary alloys are considered to have a high probability of exhibiting spinolysis, resulting in a large concentration amplitude (A). Additionally, since Pt and Ni have relatively high Young's moduli, their elastic modulus (Y) is also considered to be high. Furthermore, the large difference in lattice constants between Ni and Au, Pt, and Pd suggests that their lattice strain (ε) is also large. Considering these factors and mathematical formula 3, it is believed that the constituent metals of the base alloy in this invention are a preferred combination in terms of achieving performance in splice decomposition and achieving high hardness based on splice decomposition.

[0058] Furthermore, regarding the possibility of exhibiting ordering, as mentioned above, Pt and Ni, as well as Au and Pd, are combinations of metals that can contribute to the formation of ordered phases based on ordering. Moreover, the specific roles of each metal constituting the base alloy are explained below.

[0059] Au

[0060] Au is an element essential for exhibiting spinolysis in the alloy system of this invention. Spinolysis is not observed at excessively low or high Au concentrations; there exists a specific Au concentration range required for its manifestation. 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, thus contributing to an increase in hardness based on this ordered phase.

[0061] Ni

[0062] Ni, as a base alloy, exhibits a strengthening effect based on spinolysis. Ni has a higher Young's modulus than Au, Pt, and Pd. Furthermore, referring to Table 1 above, the large difference in lattice constants between Ni and Au, Pt, and Pd increases the lattice strain ε. Therefore, according to Equation 3 above, Ni has the effect of increasing the strengthening ability based on spinolysis. In addition, Ni is a metal capable of forming ordered phases with Pt, and also contributes to the increase in hardness based on ordering.

[0063] 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 inherent in precious metals. This also has the secondary effect of reducing the overall price of precious metal alloys.

[0064] Pd

[0065] Pd expands the solid solution limits of the elements constituting the base alloy, broadens the concentration range at which the base alloy exhibits spinolysis, and promotes spinolysis. Through these effects, Pd increases the hardening amount based on spinolysis. Furthermore, Au, being a metal capable of forming ordered phases with Pd, also contributes to increased hardness based on ordering. However, excessive Pd addition leads to an excessively low spinolysis temperature, thus potentially hindering spinolysis. Moreover, excessive Pd addition tends to suppress ordering, resulting in 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.

[0066] Pt

[0067] Pt is an essential element for spinolysis in the alloy system of this invention. Spinolysis is not exhibited when the Pt concentration is too low or too high; there is a range of Pt concentrations required for its manifestation. Furthermore, Pt can form an ordered phase with Ni, which contributes to increased hardness. Additionally, Pt has a relatively high Young's modulus of 169.9 GPa. As can be seen from Equation 3 above, Pt can be expected to be a metal that increases the hardening amount of the alloy when spinolysis is manifested.

[0068] (2) Metallic elements as metallic element α

[0069] This invention relates to a noble metal alloy formed by adding the metallic element α to the Au-Ni-Pd-Pt alloy with the aforementioned composition as the base alloy. The metallic element α has the effect of increasing the hardness of the aged heat-treated noble metal alloy without altering the microstructure of the base alloy. Specifically, the base alloy has a microstructure comprising a modulated structure based on spinolysis and / or an ordered phase based on ordering, and the metallic element α is not an additive element that affects these microstructures. While the reason for the increase in hardness of the noble metal alloy through the addition of the metallic element α is not yet clear, the inventors have observed that the increase in the strength of the alloy matrix due to the increase in lattice strain is one of the main reasons.

[0070] Metal element α is In, Sn, Mg, Al, or Ti. According to the inventors' research, an increase in hardness was confirmed in Au-Ni-Pd-Pt alloys using these metal elements. At least one metal from the above-mentioned group of metal elements is added as metal element α.

[0071] (3) The composition of the noble metal alloy of the present invention

[0072] Regarding the composition ranges of each constituent metal in the noble metal alloy of the present invention, for Au, Ni, Pd, and Pt, Au is set to 4 atomic% or more and 24 atomic% or less, Ni is set to 5 atomic% or more and 60 atomic% or less, Pd is set to 2.5 atomic% or more and 40 atomic% or less, and Pt is set to 10 atomic% or more and 60 atomic% or less. These composition ranges are concentration ranges specified to exhibit effective spinolysis and ordering for increasing hardness.

[0073] Furthermore, the aforementioned compositional ranges of Au, Ni, Pd, and Pt are concentration ranges from which an increase in hardness is expected due to the addition of the metallic element α. That is, if only from the viewpoint of exhibiting spinolysis and / or ordering, an expanded compositional range can be set relative to the aforementioned range. However, within this expanded compositional range, an increase in hardness due to the addition of the metallic element α is sometimes not observed. The compositional ranges of Au, Ni, Pd, and Pt in this invention are ranges from which a definite increase in hardness is expected through both spinolysis and / or ordering and the effect of adding the metallic element α.

[0074] Furthermore, the composition of at least one of the metallic element α, In, Sn, Mg, Al, and Ti, must be between 0.15 atomic% and 7.5 atomic%. Addition amounts less than 0.15 atomic% are unlikely to contribute to increasing the hardness of the base alloy. Additionally, even if the addition amount of metallic element α exceeds 7.5 atomic%, the effect on increasing hardness is not significant; on the contrary, there is a tendency for decreased ductility.

[0075] Spiral decomposition and ordering are exhibited in the solution treatment and aging heat treatment processes of solid solution alloys within the above-mentioned composition range, which involve rapid cooling. The noble metal alloy of the present invention exhibits a wide range of regions where complete solid solution exists at high temperatures, while simultaneously possessing solubility gaps at low temperatures. Therefore, it is believed that a noble metal alloy containing metallic element α added to a base alloy having the above-mentioned composition range, through rapid cooling following solution treatment at high temperatures, forms a supersaturated solid solution, which can then undergo spiral decomposition and ordering through subsequent aging heat treatment. It should be noted that the CALPHAD method (Calculation of Phase Diagrams) is also effective for assessing 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 (Itochu Techno-Solutions Co., Ltd.)) and a noble metal alloy database (e.g., TCNOB1 (Itochu Techno-Solutions Co., Ltd.)).

[0076] The noble metal alloy of the present invention comprises Au, Ni, Pd, Pt, metallic element α, and unavoidable impurities within the above-mentioned composition range, and preferably is a noble metal alloy composed of Au, Ni, Pd, Pt, metallic element α, and unavoidable impurities within the above-mentioned composition range. Unavoidable impurities refer to impurities in the raw materials or unavoidable components contained due to manufacturing processes, etc. Examples of unavoidable impurities include: Ag, Rh, Ir, Ru, Fe, Sc, Y, Zn, Re, Mo, Cr, Nb, Ta, V, W, 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 properties of the noble metal alloy of the present invention, preferably 0.1 atomic% or less for each element, preferably 0.5 atomic% or less in total, and particularly preferably 0.1 atomic% or less in total. It should be noted that when precious metal alloys contain the aforementioned unavoidable impurities, it is difficult to clearly distinguish whether they are unavoidably present or intentionally added components. In this invention, as long as the component does not alter the properties of the precious metal alloy, it is considered an unavoidable impurity regardless of the intention behind its inclusion.

[0077] (A-3) Material structure of the noble metal alloy of the present invention

[0078] The noble metal alloys of the present invention achieve increased hardness through spinolysis and / or ordering. Therefore, the microstructure of the noble metal alloys of the present invention can comprise fine modulated structures based on spinolysis and / or ordered phases based on ordering. Modulated structures are material structures in which compositional changes occur within nanoscale modulation cycles. These material structures can be confirmed using X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction patterns of TEM, scanning transmission electron microscopy (STEM), and STEM-EDS mapping images.

[0079] In X-ray diffraction patterns obtained using X-ray diffraction (XRD) or electron beam diffraction patterns obtained using TEM, broad peaks known as so-called side peaks (companion peaks) are observed on at least one side (preferably both sides) of the main peak. The presence or absence of these side peaks indicates whether a spinolysis structure is present. The matrix of the noble metal alloy of the present invention has a face-centered cubic (fcc) crystal structure; therefore, the Miller indices {111}, {200}, {220}, and {311} planes appear as main peaks. For at least one of these main peaks, a spinolysis structure appears on either side or one side. It should be noted that if a side peak appears only on one side of the main peak, it is considered difficult to separate it from the main peak.

[0080] Furthermore, regarding the identification of ordered phases using X-ray diffraction patterns or electron diffraction patterns, this can be confirmed by observing 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 measurement, ordered reflection peaks appear around 2θ = 30° to 35°.

[0081] It should be noted that the modulated microstructure in the noble metal alloy of the present invention tends to consist 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). Furthermore, the ordered phase generated in the noble metal alloy of the present invention comprises at least one of an L10-type structure or an L12-type structure, particularly tending to comprise an ordered phase with an L12-type structure.

[0082] (A-4) Hardness of the noble metal alloy of the present invention

[0083] The noble metal alloy of the present invention achieves hardening based on spindle decomposition and / or ordering by having the above-described composition range. The noble metal alloy of the present invention can stably exhibit a hardness of 500 Hv or higher on a Vickers hardness scale. Furthermore, the addition of the metallic element α is expected to further increase the hardness, exhibiting a Vickers hardness of 550 Hv or higher, or 600 Hv or higher. The noble metal alloy of the present invention can be produced with the above-described high Vickers hardness through heat treatment alone, without utilizing work hardening, i.e., without causing material embrittlement due to dislocation strain.

[0084] 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 the upper limit exceeds 850 Hv, fracture or breakage may occur during use. Furthermore, the Vickers hardness described above is a value at room temperature. Vickers hardness can be measured using a known Vickers hardness tester. The testing load is preferably set to 0.05 kgf or more and 0.5 kgf or less, more preferably 0.2 kgf.

[0085] 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. Alternatively, the present invention can also be formed in a layered or film-like manner on a suitable substrate or base plate.

[0086] (B) The method for manufacturing the noble metal alloy of the present invention

[0087] 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.

[0088] In this invention, high hardness is achieved by decomposing and / or ordering the constituent metals (Au, Ni, Pd, Pt, and α-metallic element) of the noble metal alloy based on the selection of their composition range and the optimization of their composition range. Furthermore, the noble metal alloy of this invention is manufactured by performing appropriate heat treatment processes on an alloy block (ingot) within the aforementioned composition range. Appropriate heat treatment processes refer to heat treatment processes based on a combination of solution treatment and aging heat treatment, through which decomposition and / or ordering of the constituent metals are carried out, thereby achieving high hardness. Moreover, the method for manufacturing the noble metal alloy of this invention is a method of achieving material hardening through heat treatment without relying on work hardening.

[0089] Hereinafter, the manufacturing method of the precious metal alloy of the present invention will be described along with the description of each heat treatment process. Furthermore, processing methods that can be performed during or after the manufacturing of the precious metal alloy of the present invention will also be described. It should be noted that, in the present invention, unless otherwise specified, the heating temperatures, etc., in the various heat treatments described below refer to the temperatures of the precious metal alloy to be treated.

[0090] (B-1) Preparation process (production of precious metal alloys)

[0091] 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 and adjusting the composition of the aforementioned Au, Ni, Pd, Pt, and metallic element α, followed by melting and casting. Alternatively, alloys such as Au-Ni-Pd-Pt alloys, binary alloys (Au-Pd alloys, Pt-Ni alloys, etc.), 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, and continuous casting.

[0092] 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 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 sputtering and spraying.

[0093] (B-2) Solution treatment

[0094] For the noble metal alloy prepared by the above method, a supersaturated solid solution is formed by solution treatment. Solution treatment involves heating the noble metal alloy at a high temperature to form a single-phase or similar single-phase solid solution structure, followed by rapid cooling 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. Below 0.0001 hours, the formation of the supersaturated solid solution becomes insufficient, and even heating for more than 168 hours will not significantly affect the formation of the supersaturated solid solution; therefore, it is undesirable from a productivity perspective. It should be noted that in this invention, melting point refers to the solid line temperature.

[0095] Furthermore, during cooling from the solution treatment temperature, rapid cooling is required, i.e., quenching to a level that prevents excessive grain boundary reactions 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. 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 spinnervation 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 300°C, quenching is not necessary. Therefore, in order to suppress or mitigate the occurrence of quenching cracks, for example, quenching to 200°C followed by air cooling in the temperature range below 200°C can be performed. It should be noted that the endpoint of cooling in the solution treatment here is preferably set to room temperature.

[0096] (B-3) Aging Heat Treatment

[0097] The spinolysis and ordering of the noble metal alloy of the present invention are achieved by aging the supersaturated solid solution formed above in a temperature range below the spinolysis temperature and the order-disorder phase transition temperature.

[0098] As for the conditions for aging heat treatment of supersaturated solid solutions, the heating temperature is set to be 300°C or higher and 700°C or lower. Below 300°C, phase transformation is difficult to occur. Furthermore, above 700°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 heating time for aging heat treatment 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; treatment times exceeding 168 hours lead to poor productivity and increased manufacturing costs. There are no particular restrictions on the cooling method after the aging heat treatment.

[0099] (B-4) Other heat treatment processes

[0100] The noble metal alloy of the present invention is manufactured by the above-described solution treatment and aging heat treatment, but other heat treatment processes may be included in the manufacturing process. Examples of such other heat treatment processes include homogenization treatment, two-phase treatment, and intermediate annealing. However, these other heat treatment processes do not affect the decomposition and ordering of the swirl. Therefore, these heat treatments are optional processes.

[0101] 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).

[0102] 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.

[0103] 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 materials that have reduced strength. 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.

[0104] (B-5) Processing steps of the precious metal alloy of the present invention

[0105] 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.

[0106] In particular, the warm working, cold working, surface rolling, straightening, winding, and bending processes following solution treatment are useful as processing steps for the precious metal alloys of this invention. This is because solution-treated precious metal alloys have improved ductility. Moreover, the solution-treated (before aging) precious metal alloys can be processed into a final shape corresponding to or close to its intended use through the aforementioned processing methods.

[0107] However, in the precious metal alloy of the present invention, post-aging (after hardening) processing is not excluded. Even the high-hardness precious metal alloy after aging can be processed. Furthermore, the aged precious metal alloy can also undergo final adjustments such as grinding / laundering, cutting, electrical discharge machining, pressing, bending, and straightening. Moreover, the knot decomposition and ordering exhibited in the precious metal alloy of the present invention are reversible, therefore solution treatment and aging treatment can be repeatedly performed. Processing can also be performed between combinations of multiple solution treatments and aging treatments.

[0108] (B-6) Other methods for manufacturing the precious metal alloy of the present invention

[0109] 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 melting casting. In the present invention, solution treatment is an important heat treatment step; however, even without performing solution treatment, it is sometimes possible to prepare a noble metal alloy with a microstructure equivalent to that of a solution-based solid solution. In such cases, by performing aging treatment on this noble metal alloy, the noble metal alloy of the present invention can be manufactured.

[0110] Examples of processes for obtaining a solid solution state of a noble metal alloy 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 alloy of the present invention by aging 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 when aging heat treatment is performed without these solution treatments, the preferred conditions are the same as described above.

[0111] Example

[0112] The following describes specific embodiments, or examples, of the present invention. In this embodiment, various Au-Ni-Pd-Pt noble metal alloys were manufactured by changing the composition of Au, Ni, Pd, Pt, and the metallic element α, and their hardness was measured. In this embodiment, In, Sn, Mg, Al, and Ti were added as the metallic element α.

[0113] [Manufacturing of precious metal alloys]

[0114] High-purity raw materials of Au, Ni, Pd, Pt, and α-metallic elements (In, Sn, Mg, Al, Ti) are weighed and mixed in a manner that forms a specified composition. The mixture is then melted and cast into an alloy ingot using an electric arc in an inert gas atmosphere. Test pieces (5mm × 5mm × 3mm) are then cut from the alloy ingot.

[0115] [Heat treatment process (solution treatment)]

[0116] The prepared test pieces were subjected to solution treatment and aging heat treatment. In the solution treatment, the test pieces were heated at a temperature of 1050℃~1250℃ and held for 16 hours, and then water-cooled until they reached room temperature.

[0117] [Heat treatment process (aging heat treatment)]

[0118] Regarding the heating temperature in the aging heat treatment, temperatures ranging from 450℃ to 600℃ were set at 25℃ intervals. The solution-treated test pieces were heated and held at each aging heat treatment temperature for 1 hour, and then water-cooled to room temperature. Then, for the aging heat-treated test 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 test pieces were embedded in resin and subjected to coarse grinding (#500, #800, #1200) and mirror grinding using 1μm and 1 / 4μm diamond suspensions. Through these operations, samples with various compositions were prepared.

[0119] In this embodiment, as an example, an Au-Ni-Pd-Pt noble metal alloy composed of Au, Ni, Pd, Pt, and metallic element α (In, Sn, Mg, Al, Ti) is manufactured.

[0120] Furthermore, as a reference example, an Au-Ni-Pd-Pt alloy with a composition similar to the noble metal alloys of each embodiment was manufactured without the addition of metallic element α. Furthermore, as a comparative example, an Au-Ni-Pd-Pt alloy outside the compositional range of the present invention was manufactured; and as a conventional example, Au-Pt alloys and Pt-Ni alloys, which are noble metal alloys capable of exhibiting spinolysis or ordering, were manufactured. For these reference examples, comparative examples, and conventional examples, the same solution treatment and aging heat treatment as described above were performed, and samples were prepared in the same manner as in the above embodiments.

[0121] [Hardness Measurement]

[0122] Hardness tests were performed on samples of each of the aforementioned precious metal alloys. For the hardness tests, a testing apparatus (Mitutoyo HM-210 manufactured by Mitutoyo Co., Ltd.) was used, the test load was set to 0.2 kgf, and the tests were conducted at room temperature. The results are shown in Table 1. For the hardness tests, 15 points were randomly measured on each sample, and the average value was taken as the hardness value. Regarding the measurement locations for each sample, multiple grains were selected, and measurements were performed on the non-grain boundary portions of each grain, preferably near the center of the grain. It should be noted that the hardness test results shown below (Tables 3 and 4) record the aging heat treatment temperature and hardness at which the highest hardness was obtained from multiple set aging heat treatment temperatures within the range of 450°C to 600°C. However, for the precious metal alloys of the examples, even the lowest hardness showed a value of 520 Hv or higher.

[0123] [Research on Material Microstructure Based on XRD Analysis]

[0124] In addition, for each noble metal alloy, XRD analysis was performed to confirm (a) swirl decomposition and (b) the formation of ordered phases. The analytical conditions, such as sample size, for each XRD-based study are described below. XRD analysis of solution-treated noble metal alloys (solution-treated materials) and age-treated noble metal alloys (age-treated materials) allows for comparison of results and confirmation of swirl decomposition and ordering based on age-treated materials.

[0125] [Common conditions]

[0126] Sample size: φ22mm×2mm

[0127] • XRD apparatus: Rigaku Manufacturing's SmartLab

[0128] • Target: Cu anode

[0129] • Optical systems and detectors: Concentrated optical systems, semiconductor detectors (HyPix-3000)

[0130] Current and voltage: 40kV, 30mA

[0131] • Length-limiting slit: 10mm

[0132] (a) Confirmation of spinolysis (sideband peaks)

[0133] • 2θ scan range: 20°~130°

[0134] ·2θ step size (°): 0.0012

[0135] • 2θ scan rate (° / min): 6

[0136] (b) Confirmation of the ordered phase (ordered peaks)

[0137] 2θ scan range: 20°~38°

[0138] 2θ step size (°): 0.0132

[0139] 2θ scan rate (° / min): 1.3

[0140] In XRD-based spinolysis studies, for the XRD diffraction patterns obtained under the above conditions, the determination is based on whether one or more side peaks appear on one or both sides of the main peak (approximately ±0.5 to 3° in terms of 2θ angle) for the Miller index {111}, {200}, {220}, and {311} planes. The presence of one or more side peaks is considered as spinolysis occurring, while the absence of any side peaks is considered as not occurring.

[0141] 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.

[0142] As an example of the results of the XRD analysis performed in this embodiment, Figure 2 The XRD diffraction pattern of alloy B-5 (Au12.5-Ni30.625-Pd25-Pt30.625-Sn1.25) of the embodiment is shown. Figure 2 (a) shows the XRD diffraction pattern used to confirm the spinolysis. Figure 2 (b) Shows the XRD diffraction pattern used to confirm the ordered phase. (Refer to...) Figure 2 (a) In this noble metal alloy, for the peaks near 2θ = 40°–41° corresponding to the {111} plane and the peaks near 2θ = 46.5°–47.5° corresponding to the {200} plane, clear peaks that can be identified as sideband peaks were confirmed on both sides. Furthermore, for the peaks corresponding to other crystal planes, broad peaks that can be identified as sideband peaks were also confirmed on both sides or one side. Therefore, it is inferred that this noble metal alloy exhibits spinolysis. Additionally, refer to… Figure 2 (b) In the region around 2θ = 30° to 35°, peaks significantly higher than the background (ordered peaks) were observed. This suggests that the noble metal alloy also exhibits ordering.

[0143] For the B-5 noble metal alloy, TEM / STEM analysis was performed. The TEM / STEM analysis apparatus used was an atomic resolution electron microscope (JEM-ARM300F GRAND ARM, NEC Corporation) (accelerating voltage 300kV). It should be noted that, prior to TEM / STEM analysis, the same heat treatment process (solution treatment and aging heat treatment) and resin embedding and grinding were performed as described above, and then the sample for TEM / STEM analysis was prepared using focused ion beam (FIB).

[0144] Figure 3 The results of STEM-EDS mapping measurements of each constituent element (Au, Ni, Pd, Pt, Sn) are presented (Pt, Au, Pd, Sn: L-line, Ni: K-line). Figure 3It 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. This modulated structure lacks a clear interface, suggesting that it is caused by spinolysis. Furthermore, regarding the distribution of Sn, no precipitates were observed, indicating that it preferentially dissolves in the regions with relatively high Au and Pd concentrations. Based on these results, it can be concluded that Sn does not significantly affect the microstructure (modulated structure, ordering) of the noble metal alloy.

[0145] and, Figure 4 This is the electron beam diffraction pattern of alloy B-5 from the embodiment, obtained through TEM analysis (<001> zone axis incident conditions). Figure 4 As can be seen, in the noble metal alloy B-5 of this embodiment, in addition to the basic reflection based on the fcc structure, diffraction spots based on the ordered phase were also identified. Based on the location, intensity, and surface spacing, the diffraction spots of the ordered phase are presumed to be an L12 structure.

[0146] The results of hardness testing of the noble metal alloys manufactured in this embodiment, including the examples, reference examples, comparative examples, and existing examples, are shown in Tables 3 and 4. These tables also show the presence or absence of modulated microstructure (sideband peaks) and ordered phase (ordered peaks) based on XRD analysis. It should be noted that in these tables, in this embodiment, to confirm the effect of adding metal element α, noble metal alloys with similar compositions of the base alloys (concentrations of each element in Au, Ni, Pd, and Pt) are grouped, and each group is numbered with letters (A to I) and a serial number.

[0147]

[0148]

[0149] As shown in Tables 3 and 4, the noble metal alloys (alloys belonging to groups A to I) of the embodiments and reference examples, whose composition range is set within the scope of this invention, all exhibited spinolysis. Furthermore, regarding ordering, the formation of ordered phases was confirmed in all but a few cases. Regarding the ordered phase, similar to the results for alloy B-5 above, an L12 structure phase was identified. Moreover, these noble metal alloys of the embodiments and reference examples all exhibited hardness exceeding 500 Hv. The hardness of these noble metal alloys is higher than that of Au-Pt alloys (alloy X-1) and Pt-Ni alloys (alloy Y-1), which are capable of spinolysis and / or ordering. It is believed that by diversifying the alloy composition, the increase in hardness based on spinolysis and / or ordering is appropriately utilized.

[0150] Furthermore, regarding the noble metal alloys in groups A through I, when comparing the hardness of the studied examples and the reference examples for each group, it was confirmed that the examples in which metal element α was added to the Au-Ni-Pd-Pt alloy showed a significant increase in hardness compared to the reference examples without metal element α. The increase in hardness due to metal element α depends on the alloy composition, but it is at least 15 Hv or higher, and depending on the composition, a hardness increase of over 100 Hv was observed. Based on this comparison result, it was confirmed that the Au-Ni-Pd-Pt alloy, as the base alloy, is itself a high-hardness noble metal alloy, but further increases in hardness are possible by adding metal element α.

[0151] Furthermore, as in comparative examples alloys S-1 and S-2, although they are Au-Ni-Pd-Pt alloys, depending on the compositional ranges of Au, Ni, Pd, and Pt, sometimes nodal decomposition and ordering are not observed. These noble metal alloys exhibit hardness less than 500 Hv, indicating that setting the compositional range of the base alloy is fundamentally important.

[0152] It should be noted that the comparative examples, alloys S-3 and S-4, are noble metal alloys whose alloy composition (Au concentration) deviates from the scope of this invention. They were used to confirm the effect of hardness increase resulting from the presence or absence of the metal element α. These noble metal alloys all exhibited spinolysis and ordering, displaying a hardness of 500 Hv or higher. However, when compared, the hardness increase resulting from the addition of the metal element α was less than 10 Hv (6 Hv), which can be said to be almost negligible. This confirms that even outside the compositional scope of this invention, spinolysis and / or ordering can sometimes occur, but to maximize the hardness increase through the addition of the metal element α, it is preferable to apply the compositional scope defined in this invention.

[0153] Industrial availability

[0154] As explained above, the present invention relates to a noble metal alloy having a novel composition and range of components capable of exhibiting high hardness based on spindle decomposition and / or ordering. According to the present invention, high-hardness alloy materials can be obtained even without relying on work hardening (dislocation strengthening). Therefore, high hardness can be achieved without concern for the embrittlement associated with work hardening.

[0155] The precious metal alloy of this invention is expected to be used in various applications such as electrical / electronic materials requiring high hardness and high wear resistance, medical devices, and high-hardness coated components. The precious metal alloy of this invention can be manufactured by aging heat treatment of precious metal alloys obtained using techniques such as melt casting and solution treatment, additive manufacturing, rapid cooling and solidification, and coating techniques such as sputtering / spraying / plating, and can be applied to the aforementioned applications.

Claims

1. An Au-Ni-Pd-Pt noble metal alloy, which is an Au-Ni-Pd-Pt noble metal alloy formed by adding the metallic element α to a basic alloy composed of Au, Ni, Pd, and Pt, wherein, The metallic element α is at least one of the following metallic elements: In, Sn, Mg, Al, and Ti. The Au-Ni-Pd-Pt series noble metal alloy contains 4 atomic% or more and 24 atomic% of Au, 5 atomic% or more and 60 atomic% of Ni, 2.5 atomic% or more and 40 atomic% of Pd, 10 atomic% or more and 60 atomic% of Pt, 0.15 atomic% or more and 7.5 atomic% of metallic element α, and unavoidable impurities.

2. The Au-Ni-Pd-Pt noble metal alloy according to claim 1, wherein, The material microstructure includes a modulated microstructure based on spinolysis.

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

4. The Au-Ni-Pd-Pt noble metal alloy according to claim 1 has a Vickers hardness of 500 Hv or higher.

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