CN106493363B

CN106493363B - Titanium sintered compact and ornament

Info

Publication number: CN106493363B
Application number: CN201610806098.9A
Authority: CN
Inventors: 川崎琢; 中村英文
Original assignee: Seiko Epson Corp
Current assignee: Seiko Epson Corp
Priority date: 2015-09-07
Filing date: 2016-09-06
Publication date: 2021-05-07
Anticipated expiration: 2036-09-06
Also published as: EP3138433B1; US20170067137A1; CN106493363A; EP3138433A1

Abstract

The invention provides a titanium sintered body and a decorative article which can maintain good mirror surface property for a long time. The titanium sintered body (1) is characterized by comprising: as the alpha phase (2) and the beta phase (3) having the crystal structure, the average particle diameter of the alpha phase (2) is 3 to 30 μm in cross section, and the area ratio of the alpha phase (2) in cross section is 70 to 99.8%. The titanium sintered body (1) preferably has an average aspect ratio of the α phase (2) in the cross section of 1 to 3. The titanium sintered body (1) preferably contains titanium as a main component and includes an α -phase stabilizing element and a β -phase stabilizing element.

Description

Titanium sintered compact and ornament

Technical Field

The invention relates to a titanium sintered body and a decorative article.

Background

Since titanium alloys are excellent in mechanical strength and corrosion resistance, they are used in the fields of aircrafts, space development, chemical plants, and the like. In addition, recently, titanium alloys have been used for exterior parts of watches, ornaments such as eyeglass frames, sporting goods such as golf clubs, springs, and the like, by effectively utilizing characteristics such as biocompatibility and low young's modulus.

In such applications, the use of powder metallurgy enables easy production of a titanium sintered body having a shape close to the final shape. This can eliminate secondary processing, reduce the amount of processing, and enable efficient component production.

However, the titanium sintered body produced by the powder metallurgy method easily reflects the characteristics of the raw material powder, and it is difficult to improve the surface smoothness. Therefore, the specularity of the titanium sintered body is easily reduced, which is a technical problem in appearance.

In contrast, attempts have been made to improve the specularity of the titanium sintered body produced by the powder metallurgy method.

For example, patent document 1 discloses a decorative titanium alloy having the following characteristics: after powder compacting, a mixed powder is formed, wherein the mixed powder comprises 0.1-1.0 wt% of iron powder and 0.1-4.0 wt% of molybdenum powder, and the balance of the mixed powder is titanium powder, and then sintering is performed at 1200-1350 ℃. The obtained titanium alloy has a two-phase structure of α + β, and the mirror surface properties required for exterior parts of watches and the like are obtained.

However, the titanium alloy described in patent document 1 is inferior in aging resistance because it contains iron in addition to titanium. Therefore, when exposed to a severe environment for a long period of time, the surface is deteriorated, and as a result, the specularity is reduced.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 8-92674

Disclosure of Invention

The invention aims to provide a titanium sintered body and a decoration article which can maintain good mirror surface property for a long time.

The above object is achieved by the present invention described below.

The titanium sintered body of the present invention is characterized by comprising:

alpha phase and beta phase as crystalline structures,

the average particle diameter of the alpha phase in the cross section is 3-30 μm,

the area ratio of the alpha phase in the cross section is 70% to 99.8%.

Thus, a titanium sintered body capable of maintaining good mirror-surface properties for a long period of time was obtained.

In the titanium sintered body of the present invention, it is preferable that the average aspect ratio of the α phase in the cross section is 1 to 3.

Thus, since anisotropy is less likely to occur in the amount of polishing when the titanium sintered body is polished, irregularities are less likely to occur on the polished surface. Therefore, the smoothness of the polished surface can be further improved, and a titanium sintered body excellent in mirror surface properties in particular can be obtained.

In the titanium sintered body of the present invention, it is preferable that a peak of a reflection intensity based on the β -phase plane orientation (110) is 3% or more and 60% or less of a peak of a reflection intensity based on the α -phase plane orientation (100) in an X-ray diffraction spectrum obtained by an X-ray diffraction method.

Thus, the characteristics of the α phase and the characteristics of the β phase are not buried and not made significant. As a result, a titanium sintered body capable of maintaining high mirror surface properties for a long period of time is obtained.

In the titanium sintered body of the present invention, it is preferable that the titanium sintered body contains titanium as a main component and includes an α -phase stabilizing element and a β -phase stabilizing element.

Thus, even if the manufacturing conditions and the use conditions of the titanium sintered body vary, the alpha phase and the beta phase, which are crystal structures, can be contained together, and thus a material having excellent aging resistance can be formed. As a result, the titanium sintered body has both the characteristics of the α phase and the β phase, and particularly has excellent mechanical characteristics.

In the titanium sintered body of the present invention, the relative density of the titanium sintered body is preferably 99% or more.

This shows particularly good mirror-surface properties when the surface of the titanium sintered body is polished.

The decorative article of the present invention preferably comprises the titanium sintered body of the present invention.

This maintains good specularity for a long period of time, and as a result, a decorative article which can maintain excellent appearance and beauty for a long period of time is obtained.

Drawings

Fig. 1 is an electron microscopic image showing an embodiment of the titanium sintered body of the present invention.

Fig. 2 is a diagram schematically depicting a portion of the electron micrograph shown in fig. 1.

Fig. 3 is a perspective view showing a wristwatch case to which an embodiment of a decoration of the present invention is applied.

Fig. 4 is a partially sectional perspective view showing a bezel of an embodiment of a decorative article to which the present invention is applied.

Fig. 5 is an X-ray diffraction spectrum obtained for the titanium sintered body of example 1.

Fig. 6 is an electron micrograph of a cross section of the titanium sintered body of comparative example 2.

FIG. 7 is an electron microscopic image of a cross section of the titanium melt material of reference example 1.

Description of the symbols

1. A titanium sintered body; 2. an alpha phase; 3. a beta phase; 11. a watch case; 12. a table frame; 112. a housing main body; 114. a belt mounting portion.

Detailed Description

Hereinafter, the titanium sintered body and the decorative article of the present invention will be described in detail based on preferred embodiments shown in the drawings.

Titanium sintered compact

First, an embodiment of the titanium sintered body of the present invention will be explained.

Fig. 1 is an electron microscopic image showing an embodiment of the titanium sintered body of the present invention, and fig. 2 is a view schematically depicting a part of the electron microscopic image shown in fig. 1. Fig. 1 is a cross-sectional view of the titanium sintered body, and a dark band extending to the left and right at the upper end of fig. 1 is an area outside the titanium sintered body.

The titanium sintered body of the present embodiment is produced by, for example, a powder metallurgy method. That is, the titanium sintered body is configured by sintering particles of a titanium alloy powder.

More specifically, as shown in fig. 2, the titanium sintered body 1 includes an α phase 2 and a β phase 3 as crystal structures. Here, the α phase 2 means a region (titanium α phase) in which the crystal structure constituting the α phase is mainly a hexagonal closest packing (hcp) structure. On the other hand, the β phase 3 means a region (titanium β phase) in which the crystal structure constituting the β phase is mainly a body-centered cubic lattice (bcc) structure. In fig. 1, the α phase 2 appears as a relatively light-colored region, and the β phase 3 appears as a relatively dark-colored region.

The α phase 2 is relatively low in hardness and rich in ductility, and thus contributes to the realization of the titanium sintered body 1 having excellent strength and deformation resistance particularly at high temperatures. On the other hand, the β phase 3 is relatively high in hardness and easily undergoes plastic deformation, and therefore contributes to realization of the titanium sintered body 1 having excellent toughness as a whole.

In the cross section of the titanium sintered body 1, it is preferable that most of it is occupied by such α phase 2 and β phase 3. The occupancy ratio (area ratio) of the total of the α phase 2 and the β phase 3 is not particularly limited, but is preferably 95% or more, and more preferably 98% or more. In the titanium sintered body 1, the α phase 2 and the β phase 3 are dominant in characteristics, and thus reflect many advantages of titanium.

The total occupancy of the α phase 2 and the β phase 3 is determined as follows: for example, a cross section of the titanium sintered body 1 is observed by an electron microscope, an optical microscope, or the like, and a crystal phase is distinguished based on a difference in color appearance and a contrast depending on a crystal structure, and an area is measured.

The crystal structures other than the α phase 2 and the β phase 3 include, for example, the ω phase and the γ phase.

As described above, the titanium sintered body 1 includes the α phase 2 and the β phase 3, and the average particle diameter of the α phase 2 is 3 μm to 30 μm, and the occupancy (area ratio) of the α phase 2 is 70% to 99.8%.

The α phase 2 of the titanium sintered body 1 is fine, and the α phase 2 is dominant, so that the titanium sintered body has high strength and is rich in uniformity of polishing. Therefore, during polishing, unevenness due to the difference in hardness between the α phase 2 and the β phase 3 is less likely to occur, and the smoothness of the polished surface can be improved. In addition, the α phase 2, which is mainly present, is less likely to generate dislocations and is therefore less likely to be modified by polishing, and is also higher in corrosion resistance, and thus contributes to maintaining a smooth state after polishing for a long period of time. In other words, since the abrasion resistance is improved, the abrasion of the polishing surface can be suppressed, and the polishing surface can be maintained well for a long period of time. On the other hand, the β phase 3, which is present in a smaller amount than the α phase 2, is easily plastically deformed as described above, and thus the sliding of the α phases 2 is promoted. Therefore, even when a stress is applied during polishing, the stress can be relaxed in the β phase 3. As a result, it is possible to suppress the occurrence of defects such as a reduction in smoothness associated with residual stress. In other words, since the polishing property capable of performing good polishing is obtained, a polished surface having high specularity can be easily obtained.

If the average particle size of the α phase 2 is less than the lower limit, the particle size of the α phase 2 becomes too small, so that proper polishing is difficult, and the small-diameter α phase 2 easily affects light reflection, which may cause mirror surface property of the polished surface. In addition, since the occupancy rate of the α phase 2 cannot be sufficiently increased, there is a possibility that the mechanical strength of the titanium sintered body 1 cannot be sufficiently increased. On the other hand, if the average particle size of the α phase 2 exceeds the upper limit, the α phase 2 tends to have a needle-like shape. When the titanium sintered body 1 has a needle-like shape, the fatigue strength is liable to be lowered, and it is difficult to maintain high mirror surface property for a long period of time. Further, since the abrasion resistance is reduced, the polished surface is likely to be scratched, and it may be difficult to maintain the polished surface well for a long period of time. In addition, it is possible to reduce the mechanical strength mainly derived from the α phase 2.

When the area ratio of the α phase 2 is lower than the lower limit value, the area of the β phase 3 is increased accordingly. This increases the degree to which the β phase 3 contributes to light reflection, and reduces the specularity of the polished surface. On the other hand, if the area ratio occupied by the α phase 2 is higher than the upper limit value, the amount of the β phase 3 present is reduced accordingly. This impairs the function of the β -phase 3 for relaxing the stress generated between the α -phases 2, and therefore, there is a possibility that the smoothness of the polished surface is reduced along with the residual stress.

The average particle diameter of the α phase 2 is preferably 5 μm to 25 μm, and more preferably 7 μm to 20 μm.

The average particle diameter of the α phase 2 was measured as follows. First, a cross section of the titanium sintered body 1 was observed with an electron microscope, and 100 or more α phases 2 were randomly selected in the obtained observation image. Next, the area of the α -phase 2 selected in the observation image is calculated, and the diameter of a circle having the same area as the area is obtained. The circle thus obtained was regarded as the particle diameter (circle-equivalent diameter) of the α phase 2, and an average value for 100 or more α phases 2 was obtained. This average value is defined as the average particle size of the α phase 2.

The area ratio of the α phase 2 is preferably 75% to 99%, more preferably 80% to 98%.

The area ratio of the α phase 2 was measured as follows. First, the cross section of the titanium sintered body 1 was observed with an electron microscope, and the area of the obtained observation image was calculated. Next, the total area of the α -phase 2 appearing in the observation image is determined. Then, the sum of the areas of the obtained α phases 2 is divided by the area of the observation image. The solution is the area ratio occupied by the alpha phase 2.

On the other hand, when the α phase 2 has the area ratio as described above, the area ratio of the β phase 3 is smaller than that. Specifically, the area ratio of the β phase 3 is preferably about 0.2% to 30%, more preferably about 1% to 25%, and still more preferably about 2% to 20%. The β phase 3 is easily plastically deformed as described above, and thus, the sliding of the α phases 2 is promoted. Therefore, by making the β phase 3 exist at a ratio within the above range, it is possible to prevent a resistance at the time of polishing from increasing significantly when the titanium sintered body 1 is polished. As a result, the smoothness of the polished surface can be further improved, and the titanium sintered body 1 having high mirror surface property and excellent appearance can be obtained.

The constituent material of the titanium sintered body 1 is a titanium single body or a titanium-based alloy.

The titanium-based alloy is an alloy containing titanium as a main component, and contains elements other than titanium (Ti), such as carbon (C), nitrogen (N), oxygen (O), aluminum (Al), vanadium (V), niobium (Nb), zirconium (Zr), tantalum (Ta), molybdenum (Mo), chromium (Cr), manganese (Mn), cobalt (Co), iron (Fe), silicon (Si), gallium (Ga), tin (Sn), barium (Ba), nickel (Ni), and sulfur (S).

Among them, the titanium-based alloy of the present embodiment preferably contains an α -phase stabilizing element and a β -phase stabilizing element. Thus, the titanium sintered body 1 can have both the α phase 2 and the β phase 3 as crystal structures even if the manufacturing conditions and the use conditions thereof vary, and thus has excellent aging resistance. Therefore, the titanium sintered compact 1 has both the characteristics of the α phase 2 and the β phase 3, and is particularly excellent in mechanical properties.

Among these, examples of the α -phase stabilizing element include aluminum, gallium, tin, carbon, nitrogen, oxygen, and the like, and one or two or more of these elements are used in combination. On the other hand, examples of the β -phase stabilizing element include molybdenum, niobium, tantalum, vanadium, iron, and the like, and one or two or more of these elements are used in combination.

Specific compositions of titanium-based alloys are described in JIS H4600: 2012 titanium alloys of 60, 60E, 61 or 61F. Specifically, Ti-6Al-4V, Ti-6Al-4V ELI, Ti-3Al-2.5V, and the like are mentioned. Further, Ti-6Al-6V-2Sn, Ti-6Al-2Sn-4Zr-2Mo-0.08Si, Ti-6Al-2Sn-4Zr-6Mo and the like which are defined in the Aerospace Material Specification (AMS) are exemplified. Further, Ti-5Al-2.5Fe, Ti-6Al-7Nb and the like are given as the specifications stipulated by the International organization for standardization (ISO). Further, Ti-13Zr-13Ta, Ti-6Al-2Nb-1Ta, Ti-15Zr-4Nb-4Ta, Ti-5Al-3Mo-4Zr and the like are exemplified.

In the above description of the alloy composition, the components having a high concentration are described in order from the left, and the numbers before the elements are used to represent the concentrations of the elements in mass%. For example, Ti-6Al-4V means that 6 mass% of Al and 4 mass% of V are contained and the remainder is Ti and impurities. The impurities are elements that are inevitably mixed in at a predetermined ratio (for example, 0.40 mass% or less in total of the impurities) or elements that are intentionally added.

The ranges of the main components of the alloy composition described above are as follows.

The Ti-6Al-4V alloy contains 5.5 to 6.75 mass% of Al, 3.5 to 4.5 mass% of V, and the balance Ti and impurities. As the impurities, for example, the elements are allowed to be contained in a proportion of 0.4 mass% or less of Fe, 0.2 mass% or less of O, 0.05 mass% or less of N, 0.015 mass% or less of H, and 0.08 mass% or less of C. Further, it is permissible to include the other elements in a proportion of 0.10% by mass or less of the other elements and 0.40% by mass or less in total.

The Ti-6Al-4V ELI alloy contains 5.5 to 6.5 mass% of Al, 3.5 to 4.5 mass% of V, and the balance Ti and impurities. As the impurities, for example, the elements are allowed to be contained in a proportion of 0.25 mass% or less of Fe, 0.13 mass% or less of O, 0.03 mass% or less of N, 0.0125 mass% or less of H, and 0.08 mass% or less of C. Further, it is permissible to include the other elements in a proportion of 0.10% by mass or less of the other elements and 0.40% by mass or less in total.

The Ti-3Al-2.5V alloy is allowed to contain Al in an amount of 2.5 mass% to 3.5 mass%, V in an amount of 1.6 mass% to 3.4 mass%, S in an amount of 0.05 mass% to 0.20 mass% as necessary, and at least one of La, Ce, Pr, and Nd in a total amount of 0.05 mass% to 0.70 mass% as necessary, with the balance being Ti and impurities. As the impurities, for example, the elements are allowed to be contained in a proportion of 0.30 mass% or less of Fe, 0.25 mass% or less of O, 0.05 mass% or less of N, 0.015 mass% or less of H, and 0.10 mass% or less of C. Further, it is permissible to include other elements in a proportion of 0.40 mass% or less in total.

The Ti-5Al-2.5Fe alloy is allowed to contain Al in an amount of 4.5 to 5.5 mass%, Fe in an amount of 2 to 3 mass%, and the balance Ti and impurities. As the impurities, for example, it is permissible that the elements are contained in proportions such that O is 0.2 mass% or less, N is 0.05 mass% or less, H is 0.013 mass% or less, and C is 0.08 mass% or less, respectively. Further, it is permissible to include other elements in a proportion of 0.40 mass% or less in total.

The Ti-6Al-7Nb alloy contains 5.5 to 6.5 mass% of Al, 6.5 to 7.5 mass% of Nb, and the balance Ti and impurities. As the impurities, for example, the above elements are allowed to be contained in a proportion of 0.50 mass% or less of Ta, 0.25 mass% or less of Fe, 0.20 mass% or less of O, 0.05 mass% or less of N, 0.009 mass% or less of H, and 0.08 mass% or less of C, respectively. Further, it is permissible to include other elements in a proportion of 0.40 mass% or less in total. Further, since the Ti-6Al-7Nb alloy is particularly low in cytotoxicity compared with other alloy types, it is particularly useful when the titanium sintered body 1 is applied to a biocompatible application.

The components contained in the titanium sintered body 1 can be analyzed by a method based on a titanium-ICP emission-spectroscopy method defined in JIS H1632-1 (2014) -JIS H1632-3 (2014), for example.

The titanium sintered body 1 may contain particles containing titanium oxide as a main component (hereinafter, referred to as "titanium oxide particles" for brevity). It is considered that the titanium oxide particles are dispersed in the titanium sintered body 1 to share the stress applied to the metallic titanium as a matrix. Therefore, the inclusion of the titanium oxide particles improves the mechanical strength of the entire titanium sintered body 1. In addition, since titanium oxide is harder than metallic titanium, the wear resistance of the titanium sintered body 1 can be further improved by dispersing titanium oxide particles. This suppresses scratching of the polished surface, and therefore the polished surface can be maintained well for a long period of time.

The particles containing titanium oxide as a main component are particles that are analyzed by, for example, a fluorescent X-ray analysis method or an electron probe microanalyzer to analyze the composition of the particles to be analyzed so that the element contained at most is one of titanium and oxygen, and the next element contained in a large amount is the other.

The average particle diameter of the titanium oxide particles is not particularly limited, but is preferably 0.5 μm to 20 μm, more preferably 1 μm to 15 μm, and still more preferably 2 μm to 10 μm. When the average particle diameter of the titanium oxide particles is within the above range, the mechanical properties such as toughness and tensile strength of the titanium sintered body 1 are not significantly impaired, and the wear resistance can be improved. That is, if the average particle diameter of the titanium oxide particles is less than the lower limit, the content of the titanium oxide particles may reduce the share of stress by the titanium oxide particles. When the average particle diameter of the titanium oxide particles is larger than the upper limit, the titanium oxide particles may become starting points of cracks due to the content of the titanium oxide particles, and the mechanical strength may be lowered.

The crystal structure of the titanium oxide particles may be any of rutile type, anatase type, and brookite type, or a mixture of a plurality of types.

The average particle diameter of the titanium oxide particles was measured as follows. First, the cross section of the titanium sintered body 1 was observed by an electron microscope, and 100 or more titanium oxide particles were randomly selected in the obtained observation image. In this case, the presence or absence of titanium oxide particles can be determined by contrast of an image, surface analysis of oxygen, or the like. Next, the area of the titanium oxide particles selected on the observation image was calculated, and the diameter of a circle having the same area as the area was obtained. The circle thus obtained was regarded as the particle diameter (circle-equivalent diameter) of the titanium oxide particles, and the average value of 100 or more titanium oxide particles was obtained. The average value is the average particle diameter of the titanium oxide particles.

The shape of the α -phase 2 in the present embodiment is preferably not a needle shape, but an equirectangular shape or a shape based on the equirectangular shape. By having such a shape, as described above, a decrease in fatigue strength of the titanium sintered body 1 can be suppressed. As a result, the titanium sintered body 1 capable of maintaining the high mirror surface property for a long period of time was obtained.

Specifically, in the cross section of the titanium sintered body 1, the average aspect ratio of the α phase 2 is preferably 1 to 3, and more preferably 1 to 2.5. By setting the average aspect ratio of the α phase 2 within the above range, the reduction of the fatigue strength and the hardness of the titanium sintered body 1 is suppressed. Thus, the titanium sintered body 1 useful as a structural member was obtained. Further, by adjusting the average aspect ratio to fall within the above range, anisotropy is less likely to occur in the amount of polishing when the titanium sintered body 1 is polished, and therefore, unevenness is less likely to occur on the polished surface. As a result, the smoothness of the polished surface can be further improved, and the titanium sintered body 1 having excellent mirror surface properties in particular can be obtained. In other words, if anisotropy is likely to occur in the polishing amount, anisotropy may occur also in reflection of light, and specularity and aesthetic quality may be degraded.

The average aspect ratio of the α phase 2 was measured as follows. First, a cross section of the titanium sintered body 1 was observed with an electron microscope, and 100 or more α phases 2 were randomly selected in the obtained observation image. Next, the long axis of the selected α -phase 2 is determined on the observation image, and the axis longest in the direction orthogonal to the long axis is determined as the short axis. Next, the long axis/short axis is calculated as the aspect ratio. Then, the aspect ratios of 100 or more α phases 2 are averaged, and the average aspect ratio is set.

In the titanium sintered body 1 of the present embodiment, the particle diameter of the α phase 2 is relatively uniform. Therefore, the titanium sintered body 1 can have a uniform grain size in addition to a rectangular shape or a shape based on the rectangular shape, and can have improved fatigue strength and high mirror surface property over a long period of time.

When the measurement results of the particle diameters are plotted with the particle diameter of the α phase 2 as the horizontal axis of the plot area and the number of α phases 2 corresponding to the particle diameter as the vertical axis of the plot area, the particle size distribution of the α phase 2 is obtained. In this particle size distribution, the particle size at 16% of the total cumulative total of the numbers from the small diameter side is D16, and the particle size at 84% of the total cumulative total of the numbers from the small diameter side is D84. In this case, the standard deviation SD of the particle size distribution is determined by the following equation.

SD＝(D84-D16)/2

The standard deviation SD thus obtained is the reference for the distribution width of the particle size distribution. In the titanium sintered body 1 of the present embodiment, the standard deviation SD of the particle size distribution of the α phase 2 is preferably 5 or less, more preferably 3 or less, and still more preferably 2 or less. The titanium sintered body 1 having the standard deviation SD of the particle size distribution of the α phase 2 within the above range has a sufficiently narrow particle size distribution, and the particle size of the α phase 2 is sufficiently aligned. The titanium sintered body 1 has a high fatigue strength and can maintain high mirror surface properties for a long period of time.

The titanium sintered body 1 was used for crystal structure analysis by X-ray diffraction, and the obtained X-ray diffraction spectrum included a peak of reflection intensity due to the α phase and a peak of reflection intensity due to the β phase.

Here, the X-ray diffraction spectrum obtained particularly preferably includes a peak of the reflection intensity based on the plane orientation (100) of the titanium α phase and a peak of the reflection intensity based on the plane orientation (110) of the titanium β phase. In addition, the peak value (peak value) of the reflection intensity based on the plane orientation (110) of the titanium β phase is preferably 3% to 60%, more preferably 5% to 50%, and still more preferably 10% to 40% of the peak value (peak value) of the reflection intensity based on the plane orientation (100) of the titanium α phase. This prevents the characteristics of the α phase 2 and the characteristics of the β phase 3 from being buried and emphasized. As a result, the titanium sintered body 1 which can maintain particularly high mirror surface property for a long period of time is obtained.

In addition, 2 θ is located in the vicinity of 35.3 ° in the peak of the reflection intensity due to the plane orientation (100) of the titanium α phase. On the other hand, 2 θ is located in the vicinity of 39.5 ° in the peak of the reflection intensity based on the plane orientation (110) of the titanium β phase.

Further, as an X-ray source of the X-ray diffraction apparatus, Cu — K α rays were used, a tube voltage was set to 30kV, and a tube current was set to 20 mA.

The relative density of the titanium sintered compact 1 is preferably 99% or more, and more preferably 99.5% or more. By setting the relative density of the titanium sintered body 1 within the above range, a titanium sintered body 1 exhibiting particularly good mirror-surface properties when the surface is polished is obtained. That is, by adopting such a relative density, voids are less likely to be generated in the titanium sintered body 1. Therefore, the blocking of light reflection by the void can be suppressed.

Further, the relative density of the titanium sintered body 1 is set in accordance with JIS Z2501: 2000, the dry density of the sintered metal material measured based on the density test method of the sintered metal material.

The vickers Hardness (HV) of the titanium sintered body 1 is not particularly limited, but is preferably 300 or more, and more preferably 350 or more and 600 or less. The titanium sintered body 1 having such hardness is less likely to cause scratches and the like on the surface. Therefore, even when used as a constituent material of a decorative product or the like, for example, the titanium sintered body 1 can be obtained in which deterioration of the aesthetic appearance due to scratching or the like can be suppressed.

The vickers Hardness (HV) of the titanium sintered body 1 was measured at the surface of the titanium sintered body 1, and the measurement method was based on JIS Z2244: 2009 as defined in the specification. The test force of the tablet was set to 9.8N (1kgf), and the retention time of the test force was set to 15 seconds. Then, the average of the measurement results at 10 points was set as the vickers hardness of the surface.

The titanium sintered body 1 can be applied to various uses, is not particularly limited, and can be used as a constituent material of a decorative article.

Ornament (CN)

Next, an embodiment of the accessory of the present invention will be explained.

Examples of the decorative article of the present invention include watch cases (e.g., main body, back cover, and single-piece case in which main body and back cover are integrated), watch bands (including buckles, band-bracelet attaching and detaching mechanisms), watch cases (e.g., rotary watch cases), watch grips (e.g., screw-lock watch grips), buttons, glass edges, scale rings, dial plates, watch exterior parts such as pads, glasses (e.g., spectacle frame), pins, cuffs, rings, necklaces, bracelets, links, brooches, earrings, ear nails, clothing articles such as spoons, forks, chopsticks, knives, butter knives, bottle openers, lighters or their housings, sporting goods such as golf clubs, tags, panels, trophuses, and cases (e.g., mobile phones, smart phones, traffic signpost terminals, mobile computers, music players), A housing of a camera, a shaver, etc.), and the like. These ornaments all have excellent appearance aesthetics. By using the titanium sintered compact 1 as a constituent material of these ornaments, excellent mirror surface properties can be imparted to the surface of the ornaments. Thus, a decorative article capable of maintaining excellent appearance and beauty for a long period of time is obtained.

Fig. 3 is a perspective view showing a wristwatch case to which an embodiment of a decorative article of the present invention is applied, and fig. 4 is a partially sectional perspective view showing a bezel to which an embodiment of a decorative article of the present invention is applied.

The wristwatch case 11 shown in fig. 3 includes a case body 112, and a band attachment portion 114 provided to protrude from the case body 112 and to which a band is attached. The case 11 can be formed into a container together with a glass plate and a back cover, not shown. In the container, a pointer, a dial, and the like, not shown, are housed. Thus, the container protects the hand and the like from the external environment, and greatly affects the appearance of the timepiece.

The bezel 12 shown in fig. 4 is ring-shaped, and is fitted to the case so as to be rotatable relative to the case as required. When the bezel 12 is fitted to the wristwatch case, the bezel 12 is located on the outside of the wristwatch case, and therefore the bezel 12 may affect the appearance of the watch.

In addition, since the wristwatch case 11 and the bezel 12 are used in a state of being attached to a human body, scratching is often easily caused. Therefore, by using the titanium sintered compact 1 as a constituent material of such a decorative article, a decorative article having high mirror surface properties and excellent appearance and beauty can be obtained. In addition, the specularity can be maintained for a long period of time.

Method for producing titanium sintered body

Next, a method for producing the titanium sintered body 1 will be explained.

The method for producing the titanium sintered body 1 includes [1] a step of obtaining a kneaded product by kneading a titanium alloy powder and an organic binder, [2] a step of forming the kneaded product by a powder metallurgy method to obtain a compact, [3] a step of degreasing the compact to obtain a degreased body, [4] a step of firing the degreased body to obtain a sintered body, and [5] a step of subjecting the sintered body to a hot isostatic pressing treatment (HIP treatment). Hereinafter, the respective steps will be described in order.

[1] Kneading step

First, a titanium single powder or a titanium alloy powder (hereinafter, referred to as "titanium alloy powder" as an abbreviation) which is a raw material of the titanium sintered body 1 is kneaded together with an organic binder to obtain a kneaded product.

The average particle diameter of the titanium alloy powder is not particularly limited, but is preferably 1 μm to 50 μm, and more preferably 5 μm to 40 μm.

The titanium alloy powder may be a powder (pre-alloyed powder) composed of particles of a single alloy composition, or a mixed powder (pre-mixed powder) obtained by mixing a plurality of particles having different compositions. In the case of the premixed powder, each particle may be a particle containing only one kind of element, or may be a particle containing a plurality of kinds of elements, as long as the premixed powder as a whole satisfies the above-described composition ratio.

The content of the organic binder in the kneaded mixture is appropriately set according to molding conditions, a shape to be molded, and the like, and is preferably about 2% by mass or more and 20% by mass or less, and more preferably about 5% by mass or more and 10% by mass or less of the whole kneaded mixture. By setting the content of the organic binder within the above range, the kneaded product has good fluidity. This improves the filling property of the kneaded material during molding, and a sintered body having a shape closer to the final intended shape (near-net shape) is obtained.

Examples of the organic binder include polyolefins such as polyethylene, polypropylene and ethylene-vinyl acetate copolymers, acrylic resins such as polymethyl methacrylate and polybutyl methacrylate, styrene resins such as polystyrene, polyesters such as polyvinyl chloride, polyvinylidene chloride, polyamide, polyethylene terephthalate and polybutylene terephthalate, polyethers, polyvinyl alcohol, polyvinylpyrrolidone and copolymers thereof, and various organic binders such as various hair waxes, paraffin waxes, higher fatty acids (e.g., stearic acid), higher alcohols, higher fatty acid esters and higher fatty acid amides, and one or more of these organic binders can be used in combination.

In addition, a plasticizer may be added to the kneaded product as needed. Examples of the plasticizer include phthalate esters (e.g., DOP, DEP, DBP), oxalic acid esters, trimellitic acid esters, and sebacic acid esters, and one or two or more of these plasticizers can be used in combination.

In addition to the titanium alloy powder, the organic binder and the plasticizer, various additives such as a lubricant, an antioxidant, a degreasing accelerator and a surfactant may be added to the kneaded mixture as necessary.

The kneading conditions vary depending on various conditions such as the alloy composition of the titanium alloy powder to be used, the particle size, the composition of the organic binder, and the blending amount of these substances, and can be, for example, a kneading temperature of about 50 ℃ to 200 ℃ and a kneading time of about 15 minutes to 210 minutes.

The kneaded mixture is made into particles (small pieces) as needed. The particle size of the particles is, for example, about 1mm to 15 mm.

Further, a granulated powder may be produced instead of the kneaded product according to a molding method described later.

[2] Shaping step

Then, the kneaded product is molded to produce a molded body.

The Molding method is not particularly limited, and examples thereof include various Molding methods such as powder compaction (compression Molding), Metal powder Injection Molding (MIM), and extrusion Molding. Among them, the metal powder injection molding method is preferably used from the viewpoint of being able to produce a near-net-shape sintered body.

The molding conditions in the case of the powder compaction method vary depending on various conditions such as the composition and particle size of the titanium alloy powder used, the composition of the organic binder, and the amount of these components to be blended, but the molding pressure is preferably 200MPa to 1000MPa (2 t/cm)²Above 10t/cm²Below) about.

The molding conditions in the case of titanium alloy powder are still different depending on various conditions, but it is preferable that the material temperature be about 80 ℃ to 210 ℃ inclusive and the injection pressure be about 50MPa to 500MPa (0.5 t/cm)²Above 5t/cm²Below) about.

The molding conditions in the case of the extrusion molding method are still different depending on various conditions, but it is preferable that the material temperature be about 80 ℃ to 210 ℃ inclusive and the extrusion pressure be about 50MPa to 500MPa inclusive (0.5 t/cm)²Above 5t/cm²Below) about.

The molded body obtained in this way is in a state in which the organic binder is uniformly distributed in the gaps between the particles of the titanium alloy powder.

The shape and size of the molded body to be produced are determined in consideration of the shrinkage of the molded body in the degreasing step and the firing step described below.

Further, if necessary, the molded body may be subjected to machining such as cutting, polishing, or cutting. Since the molded body has a relatively low hardness and a relatively high plasticity, the molded body can be prevented from being deformed and can be easily machined. By such machining, the titanium sintered body 1 having high final dimensional accuracy can be obtained more easily.

[3] Degreasing step

Next, the obtained molded body was subjected to degreasing treatment (binder removal treatment) to obtain a degreased body.

Specifically, the organic binder is decomposed by heating the molded body, and at least a part of the organic binder is removed from the molded body, thereby completing the degreasing treatment.

Examples of the degreasing treatment include a method of heating the molded body, a method of exposing the molded body to a gas that decomposes the binder, and the like.

In the case of using the method of heating the molded article, the heating conditions of the molded article are slightly different depending on the composition and the amount of the organic binder, but the temperature is preferably 100 ℃ to 750 ℃ and 0.1 hour to 20 hours, and more preferably 150 ℃ to 600 ℃ and 0.5 hour to 15 hours. This makes it possible to sufficiently degrease the molded body without sintering the molded body. As a result, it is possible to reliably prevent a large amount of organic binder component from remaining in the degreased body.

The environment when the molded body is heated is not particularly limited, and examples thereof include a reducing gas environment such as hydrogen gas, an inert gas environment such as nitrogen gas and argon gas, an oxidizing gas environment such as the atmosphere, and a reduced-pressure environment obtained by reducing the pressure of these environments.

On the other hand, examples of the gas for decomposing the binder include ozone and the like.

In addition, such a degreasing step is performed in a plurality of steps (steps) under different degreasing conditions, and thus the organic binder in the molded body can be removed more quickly and without remaining the molded body.

Further, if necessary, the degreased body may be subjected to machining such as cutting, polishing, or cutting. Since the degreased body has a relatively low hardness and a relatively high plasticity, the shape of the degreased body can be prevented from being broken, and the mechanical processing can be easily performed. By such machining, the titanium sintered body 1 having high final dimensional accuracy can be obtained more easily.

[4] Firing Process

Next, the degreased body obtained is fired in a firing furnace to obtain a sintered body. That is, diffusion occurs at the interface between the particles of the titanium alloy powder, and sintering is completed. As a result, the titanium sintered body 1 was obtained.

The firing temperature varies depending on the composition, particle size, and the like of the titanium alloy powder, and is, for example, about 900 ℃ to 1400 ℃. Preferably, the temperature is 1050 ℃ to 1300 ℃.

The firing time is set to 0.2 hours to 20 hours, preferably 1 hour to 6 hours.

In the firing step, the firing temperature and the firing environment described later may be changed in the middle.

The atmosphere during firing is not particularly limited, but when preventing significant oxidation of the metal powder, it is preferable to use a reducing gas atmosphere such as hydrogen, an inert gas atmosphere such as argon, or a reduced pressure atmosphere obtained by reducing the pressure of these atmospheres.

When the titanium sintered body 1 is produced from a titanium alloy powder, both the α phase 2 and the β phase 3 may be formed depending on the firing conditions and the like. In particular, when the titanium alloy powder contains the β -phase stabilizing element, the β -phase 3 can be formed more reliably.

On the other hand, by optimizing various production conditions, the ratio of the α phase 2 in the titanium sintered body 1, that is, the area ratio of the α phase 2 in the cross section of the titanium sintered body 1 can be adjusted. For example, since the proportion of β phase 3 increases as the firing temperature increases, the firing temperature may be adjusted so that the proportion of β phase 3 falls within the target range, and the firing time may be set in consideration of the enlargement of the crystal structure due to an excessively long firing time.

Thus, for example, in the case of producing the titanium sintered body 1 using a titanium alloy powder containing almost no β -phase 3, the firing temperature is adjusted so that the area ratio of the α -phase 2 falls within the above range, and the firing time is set so that insufficient sintering or excessive sintering is not caused by the adjustment of the firing temperature, because the higher the firing temperature is, the higher the proportion of the β -phase 3 is, depending on the composition of the titanium alloy powder.

When the average particle size of the α phase 2 is within the above range, the shape of the α phase 2 tends to be close to an equirectangular shape as the area ratio of the α phase 2 increases. This is because, by decreasing the proportion of the β phase 3, the probability that the α phases 2 are adjacent to each other increases, and the α phases 2 interfere with each other, thereby inhibiting anisotropic particle growth.

[5] HIP Process

Further, the sintered body thus obtained may be subjected to HIP treatment (hot isostatic pressing treatment) or the like. This enables further densification of the sintered body, thereby obtaining a decorative article having more excellent mechanical properties.

The conditions for the HIP treatment are, for example, 850 ℃ to 1200 ℃ and 1 hour to 10 hours.

The pressurizing force is preferably 50MPa or more, and more preferably 100MPa or more and 500MPa or less.

The obtained sintered body may be further subjected to annealing treatment, solution treatment, aging treatment, hot working treatment, cold working treatment, or the like as necessary.

Further, the obtained titanium sintered body 1 may be subjected to a polishing treatment as needed. The polishing treatment is not particularly limited, and examples thereof include electrolytic polishing, semi-polishing, dry polishing, chemical polishing, barrel polishing, and sand blasting. By performing these polishing treatments, the surface of the titanium sintered body 1 can be further given a metallic luster, and the mirror surface properties can be improved.

The titanium sintered body and the decorative article of the present invention have been described above based on preferred embodiments, but the present invention is not limited thereto.

For example, the use of the titanium sintered body is not limited to a decorative article, and various structural members and the like are also possible. Examples of the structural members include automobile members, bicycle members, railway vehicle members, ship members, aircraft members, transportation equipment members such as space transportation equipment (e.g., rockets) members, personal computer members, electronic equipment members such as mobile phone terminal members, electric equipment members such as refrigerators, washing machines and heating and cooling machines, machine members such as machine tools and semiconductor manufacturing apparatuses, equipment members such as nuclear power plants, thermal power plants, hydroelectric power plants, oil refineries and chemical system apparatuses, medical equipment such as surgical instruments, artificial bones, artificial joints, artificial teeth, artificial tooth roots and orthodontic members.

Further, the titanium sintered body has high biocompatibility, and thus can be used as an artificial bone or a dental metal member in particular. The dental metal member is not particularly limited as long as it is a metal member that is temporarily or semi-permanently left in the oral cavity, and examples thereof include metal frames such as an inlay, a crown, a bridge, a metal abutment, an artificial tooth, an implant, an abutment, a jig, and a screw.

Examples

Next, specific embodiments of the present invention will be explained.

1. Production of titanium sintered body

(example 1)

< 1 > first, a Ti-6Al-4V alloy powder having an average particle diameter of 23 μm produced by a gas atomization method was prepared.

Next, a mixture of polypropylene and hair wax (organic binder) was prepared so that the mass ratio of the raw material powder to the organic binder was 9: 1 to obtain a composition for producing a titanium sintered body.

Next, the obtained composition for producing a titanium sintered body was kneaded by a kneader to obtain a composite. The composite is then processed into particles.

< 2 > Next, the obtained particles were molded under the molding conditions shown below to produce a molded article.

< Forming Condition >

A forming method: metal powder injection molding method

Material temperature: 150 ℃ C

Injection pressure: 11MPa (110 kgf/cm)²)

< 3 > Next, the obtained molded body was degreased under the following degreasing conditions to obtain a degreased body.

< degreasing Condition >

Degreasing temperature: 520 ℃ C

Degreasing time: 5 hours

Degreasing environment: nitrogen atmosphere

< 4 > Next, the obtained degreased body was fired under the firing conditions shown below. Thus, a sintered body was produced.

< firing Condition >

Firing temperature: 1100 deg.C

Firing time: 5 hours

Firing environment: argon environment

Ambient pressure: atmospheric pressure (100kPa)

< 5 > Next, the obtained sintered body was subjected to HIP treatment under the treatment conditions shown below. Thus, a rod-shaped titanium sintered body having a diameter of 5mm × a length of 100mm was obtained.

< HIP treatment Condition >

Treatment temperature: 900 deg.C

Processing time: 3 hours

The treatment pressure: 1480kgf/cm²(145MPa)

< 6 > the obtained titanium sintered body was cut, and the cut section was subjected to half-grinding treatment.

Then, the polished surface was observed with an electron microscope to determine the average particle diameter of the α phase, the area ratio occupied by the α phase and the β phase, and the average aspect ratio of the α phase. The results are shown in table 1.

(examples 2 to 6)

A titanium sintered body was obtained in the same manner as in example 1, except that the production conditions were changed so that the average particle diameter of the α phase, the area ratios of the α phase and the β phase, and the average aspect ratio of the α phase were changed to values shown in table 1, respectively.

Comparative examples 1 to 3

(reference example 1)

First, a Ti-6Al-4V alloy melting material is prepared.

Next, the obtained molten material was cut, and a half-grinding treatment was performed on the cut surface.

Then, the polished surface was observed with an electron microscope to determine the average particle diameter of the α phase, the area ratio of the α phase and the β phase, and the average aspect ratio of the α phase. The results are shown in table 1.

(example 7)

A titanium sintered body was obtained in the same manner as in example 1 except that a Ti-3Al-2.5V alloy powder having an average particle diameter of 23 μm was used instead of the Ti-6Al-4V alloy powder.

Then, the obtained titanium sintered body was cut, and the cut section was subjected to half-grinding treatment.

Then, the polished surface was observed with an electron microscope to determine the average particle diameter of the α phase, the area ratio occupied by the α phase and the β phase, and the average aspect ratio of the α phase. The results are shown in Table 2.

(examples 8 to 12)

A titanium sintered body was obtained in the same manner as in example 7, except that the production conditions were changed so that the average particle diameter of the α phase, the area ratios of the α phase and the β phase, and the average aspect ratio of the α phase were set to values shown in table 2, respectively.

Comparative examples 4 to 6

(reference example 2)

First, a Ti-3Al-2.5V melting material was prepared.

Next, the polished surface was observed with an electron microscope, and the average particle diameter of the α phase, the area ratio occupied by the α phase and the β phase, and the average aspect ratio of the α phase were obtained. The results are shown in Table 2.

(example 13)

A titanium sintered body was obtained in the same manner as in example 1, except that a Ti-6Al-7Nb alloy powder having an average particle size of 25 μm was used in place of the Ti-6Al-4V alloy powder. Then, the obtained titanium sintered body was cut, and the cut section was subjected to half-grinding treatment.

Next, the polished surface was observed with an electron microscope, and the average particle diameter of the α phase, the area ratio occupied by the α phase and the β phase, and the average aspect ratio of the α phase were obtained. The results are shown in Table 3.

(examples 14 to 18)

A titanium sintered body was obtained in the same manner as in example 13, except that the production conditions were changed so that the average particle diameter of the α phase, the area ratios of the α phase and the β phase, and the average aspect ratio of the α phase were changed to values shown in table 3, respectively.

Comparative examples 7 to 9

(reference example 3)

First, a Ti-6Al-7Nb melting material was prepared.

Next, the obtained molten material was cut, and the cut section was subjected to half-grinding treatment.

2. Evaluation of titanium sintered body

2.1 specularity

First, the polished surface of the titanium sintered compact (titanium smelted material) of each example, each comparative example, and each reference example was visually observed. Then, the mirror surface of the polished surface was evaluated with reference to the following evaluation criteria. The evaluation results are shown in tables 1 to 3.

< evaluation criterion of mirror surface Property of polished surface >

A: the mirror surface of the abrasive surface was very specular (the appearance was particularly good)

B: the mirror surface of the abrasive surface was slightly higher (slightly good appearance)

C: the mirror surface of the abrasive surface was slightly inferior (slightly off-spec in appearance)

D: the mirror surface of the abrasive surface was very low (disqualified appearance)

2.2 relative Density

Next, with respect to the titanium sintered bodies (titanium melting materials) of the examples, comparative examples, and reference examples, the titanium sintered bodies were prepared in accordance with JIS Z2501: 2000 to calculate the relative density. The calculation results are shown in tables 1 to 3.

2.3 Vickers hardness

Next, with respect to the polished surfaces of the titanium sintered bodies (titanium smelted materials) of the examples, comparative examples, and reference examples, the surface hardness was measured in accordance with JIS Z2244: 2009, vickers hardness was measured by the method specified in. The measurement results are shown in tables 1 to 3.

2.4 analysis of crystal Structure by X-ray diffraction method

Next, the crystal structure of the titanium sintered body of example 1 was analyzed by X-ray diffraction under the following measurement conditions.

< measurement conditions for crystal structure analysis by X-ray diffraction method >

X-ray source: Cu-K alpha ray

Tube voltage: 30kV

Tube current: 20mA

The obtained X-ray diffraction spectrum is shown in fig. 5. As is clear from fig. 5, the X-ray diffraction spectrum obtained for the titanium sintered body of example 1 includes a peak based on the reflection intensity of the α phase (α -Ti) and a peak based on the reflection intensity of the β phase (β -Ti). On the other hand, when the peak value of the reflection intensity due to the α -Ti of the plane orientation (100) having the 2 θ in the vicinity of 35.3 ° is taken as a reference, the ratio (peak ratio) of the peak value of the reflection intensity due to the β -Ti of the plane orientation (110) having the 2 θ in the vicinity of 39.5 ° to the reference is calculated. The same calculation was also performed for the titanium sintered bodies (titanium-smelted materials) of examples 2 to 18, comparative examples 1 to 9, and reference examples 1 to 3. The calculation results of the peak ratio are shown in tables 1 to 3.

2.5 abrasion resistance

Next, the titanium sintered compacts of examples and comparative examples, the titanium smelted materials of reference examples, and the like were evaluated for wear resistance of the surfaces thereof. Specifically, first, the surfaces of the titanium sintered body and the titanium smelting material are subjected to a half-polishing treatment. Next, a wear test based on a wear test method performed by a fine ceramic ball-and-disc method specified in JIS R1613 (2010) was performed on the polished surface, and the amount of wear of the disc-shaped sample was measured. The measurement conditions are as follows.

< measurement Condition for specific abrasion loss >

Material of the spherical sample: high-carbon chromium bearing steel (SUJ2)

Size of the spherical sample: diameter of 6mm

Material of disc-shaped sample: sintered bodies of examples and comparative examples and melting materials of reference examples

Size of disc-shaped sample: diameter of 35mm and thickness of 5mm

The size of the load: 10N

Sliding speed: 0.1m/s

Sliding circle diameter: 30mm

Sliding distance: 50m

Then, the wear amount obtained for the titanium smelted material of reference example 1 was set to 1, and the relative values of the wear amounts obtained for the titanium sintered bodies of each example and each comparative example shown in table 1 were calculated.

Similarly, the wear loss obtained for the titanium smelted material of reference example 2 was set to 1, and the relative values of the wear losses obtained for the titanium sintered bodies of the respective examples and comparative examples shown in table 2 were calculated.

Similarly, the wear loss obtained for the titanium smelted material of reference example 3 was assumed to be 1, and the relative values of the wear losses obtained for the titanium sintered bodies of the respective examples and comparative examples shown in table 3 were calculated.

Next, the calculated relative values were evaluated with reference to the following evaluation criteria. The evaluation results are shown in tables 1 to 3.

< evaluation reference of abrasion loss >

A: the amount of wear is very small (relative value less than 0.5)

B: small abrasion loss (relative value of 0.5 or more but less than 0.75)

C: slightly less wear (relative value of 0.75 or more but less than 1)

D: slightly more wear (relative value of 1 or more but less than 1.25)

E: large amount of wear (relative value of 1.25 or more but less than 1.5)

F: much wear (relative value of 1.5 or more)

2.6 tensile Strength

Next, the tensile strength of the titanium sintered compact of each example and each comparative example, the titanium smelted material of each reference example, and the like was measured. The tensile strength was measured in accordance with the tensile test method for metal materials specified in JIS Z2241 (2011).

Then, the tensile strength obtained for the titanium smelted material of reference example 1 was set to 1, and the relative values of the tensile strengths obtained for the titanium sintered bodies of the respective examples and comparative examples shown in table 1 were calculated.

Similarly, the tensile strength obtained for the titanium smelted material of reference example 2 was set to 1, and the relative values of the tensile strengths obtained for the titanium sintered bodies of the respective examples and comparative examples shown in table 2 were calculated.

Similarly, the tensile strength obtained for the titanium smelted material of reference example 3 was set to 1, and the relative values of the tensile strengths obtained for the titanium sintered bodies of the respective examples and comparative examples shown in table 3 were calculated.

Next, the obtained relative values were evaluated with reference to the following evaluation criteria. The evaluation results are shown in tables 1 to 3. In addition to the above test specimens, the tensile strength was evaluated for the sintered SUS316L, the casting material and sintered body of ASTM F75 (Co-28% Cr-6% Mo alloy), and the sintered α -Ti body as reference examples a to d (table 1). In addition, for reference example d, except that, the same evaluation as the above 2.1 to 2.3 and 2.5 was carried out.

< evaluation Standard of tensile Strength >

A: very high tensile strength (relative value of 1.09 or more)

B: high tensile strength (relative value of 1.06 or more but less than 1.09)

C: slightly greater tensile strength (relative value of 1.3 or more but less than 1.06)

D: slightly lower tensile strength (relative value of 1 or more but less than 1.03)

E: small tensile strength (relative value of 0.97 or more but less than 1)

F: very little tensile strength (relative value less than 0.97)

2.7 nominal Strain at Break (Break extension)

Next, the fracture elongation was measured for the titanium sintered bodies of examples and comparative examples, the titanium smelted materials of reference examples, and the like. The elongation at break was measured based on the tensile test method for metal materials specified in JIS Z2241 (2011).

Next, the obtained elongation at break was evaluated with reference to the following evaluation criteria. The evaluation results are shown in tables 1 to 3. In addition to the above-mentioned test specimens, the samples were evaluated for tensile elongation at break in reference examples a to d (Table 1) for a sintered SUS316L, a casting material and a sintered body in ASTM F75 (Co-28% Cr-6% Mo alloy), and an α -Ti sintered body.

< evaluation criterion of fracture elongation >

A: very large breaking extension (more than 0.15)

B: large breaking extension (more than 0.125 but less than 0.15)

C: slightly greater elongation at break (more than 0.10 but less than 0.125)

D: slightly smaller elongation at break (more than 0.075 but less than 0.10)

E: small breaking extension (more than 0.050 but less than 0.075)

F: the breaking extension is very small (less than 0.050)

2.8 cytotoxicity assays

Next, cytotoxicity tests were performed on test bodies made of the titanium sintered compacts of examples and comparative examples, the titanium smelted materials of reference examples, and the like. Furthermore, the cytotoxicity test was carried out according to ISO 10993-5: the cytotoxicity test as defined in 2009 was performed as a standard. Specifically, the ratio of the number of colonies of cells directly seeded on the test body to the number of colonies of the control group (colony formation rate [% ]) was determined by the colony formation method based on the direct contact method, assuming that the average value of the number of colonies of the control group is 100%. Further, the test conditions are as follows.

Cell lines: v97 cell

Culture medium: MEM10 Medium

Negative control material (negative control): high density polyethylene film

Positive control material (positive control): 0.1% polyurethane film containing zinc diethyldithiocarbamate

Control group (control): colony number of cells directly seeded onto the culture medium

Next, the obtained colony formation rates were classified with reference to the following evaluation criteria, and thereby the cytotoxicity of each test body was evaluated. The evaluation results are shown in tables 1 to 3. In addition to the above-mentioned test specimens, reference examples a, c, and d (Table 1) were evaluated for a sintered SUS316L, a sintered ASTM F75 (Co-28% Cr-6% Mo alloy), and an α -Ti sintered body in cytotoxicity tests.

< criterion for evaluation of cytotoxicity >

A: the colony forming rate is more than 90 percent

B: the colony forming rate is more than 80 percent but less than 90 percent

C: the colony forming rate is less than 80 percent

[ Table 1]

[ Table 2]

[ Table 3]

As is clear from tables 1 to 3, the polished surface of the titanium sintered body of each example has high mirror surface property. Further, since the relative density and the vickers hardness were high, respectively, it is considered that the titanium sintered body of each example can maintain the high mirror surface property for a long period of time.

The titanium sintered bodies of the examples are considered to be equivalent to or more than the titanium-melted material in terms of the properties such as mirror surface property, density, and hardness. Thus, according to the present invention, a titanium sintered body having characteristics of near-net shape and excellent characteristics can be obtained.

Further, an electron micrograph of a cross section of the titanium sintered body of comparative example 2 is shown in fig. 6. As is clear from fig. 6, the titanium sintered body of comparative example 2 has a slender α -phase shape, i.e., a shape having a large anisotropy.

In addition, an electron micrograph of a cross section of the titanium-melted material of reference example 1 is shown in fig. 7. As is clear from fig. 7, the titanium smelted material of reference example 1 has a shape in which the α phase has a relatively small grain size but a large anisotropy.

Claims

1. A titanium sintered body, comprising:

titanium oxide particles, and a titanium alpha phase and a titanium beta phase as a crystal structure,

the titanium alpha phase has an average particle diameter of 3 to 30 μm in cross section,

the area ratio of the titanium alpha phase in the cross section is 80% to 98% inclusive and the area ratio of the titanium beta phase is 2% to 20% inclusive,

the titanium oxide particles have an average particle diameter of 0.5 to 20 μm,

the average particle diameter of the titanium alpha phase is determined by: first, a cross section of the titanium sintered body is observed with an electron microscope, 100 or more titanium α phases are randomly selected in an obtained observation image, then, the area of each titanium α phase selected in the observation image is calculated, the diameter of a circle having the same area as the area is obtained, the diameter of the circle thus obtained is regarded as the particle diameter of the titanium α phase, the average value of the particle diameters of the 100 or more titanium α phases is obtained, the average value is regarded as the average particle diameter of the titanium α phase,

the area ratio occupied by the titanium alpha phase is determined by: first, the cross section of the titanium sintered body is observed by an electron microscope, the area of the obtained observation image is calculated, then the total of the areas of the titanium alpha phase appearing in the observation image is obtained, then the obtained total of the areas of the titanium alpha phase is divided by the area of the observation image, the area ratio of the titanium beta phase is solved as the area ratio of the titanium alpha phase, the area ratio of the titanium beta phase is measured in the same manner as the area ratio of the titanium alpha phase,

the average particle diameter of the titanium oxide particles is measured by: first, a cross section of the titanium sintered body is observed with an electron microscope, 100 or more titanium oxide particles are randomly selected in an obtained observation image, then, the area of each titanium oxide particle selected in the observation image is calculated, the diameter of a circle having the same area as the area is obtained, the diameter of the circle thus obtained is regarded as the particle diameter of the titanium oxide particles, the average value of the particle diameters of 100 or more titanium oxide particles is obtained, and the average value is defined as the average particle diameter of the titanium oxide particles.

2. The titanium sintered body as set forth in claim 1,

the titanium alpha phase has an average aspect ratio of 1 to 3 in cross section,

the average aspect ratio of the titanium alpha phase is determined by: first, a cross section of the titanium sintered body is observed with an electron microscope, 100 or more titanium α phases are randomly selected in an obtained observation image, then a long axis of each selected titanium α phase is determined on the observation image, a longest axis in a direction orthogonal to the long axis is further determined as a short axis, then a ratio of the long axis to the short axis is calculated as an aspect ratio, and then an average value of the aspect ratios for the 100 or more titanium α phases is obtained and the average value is set as the average aspect ratio of the titanium α phases.

3. The titanium sintered body as set forth in claim 1 or 2,

in an X-ray diffraction pattern obtained by an X-ray diffraction method, the peak of the reflection intensity based on the plane orientation (110) of the titanium beta phase is 3% to 60% of the peak of the reflection intensity based on the plane orientation (100) of the titanium alpha phase.

4. The titanium sintered body as set forth in claim 1 or 2,

the titanium sintered body contains titanium as a main component and contains a titanium alpha phase stabilizing element and a titanium beta phase stabilizing element.

5. The titanium sintered body as set forth in claim 1 or 2,

the titanium sintered body has a relative density of 99% or more.

6. An ornament, comprising:

the titanium sintered body as set forth in any one of claims 1 to 5.