JP2022093280A - Non-magnetic member and method for manufacturing the same - Google Patents

Abstract

To provide a non-magnetic member which can achieve both high specific resistance and high intensity.SOLUTION: A non-magnetic member used in an alternating magnetic field is a non-magnetic member having a titanium alloy containing an α phase stabilization element having an Al equivalent of 5.5-11 and a β phase stabilization element having a Mo equivalent of 6-17 in a mass ratio to the whole alloy. The β phase stabilization element contains Fe and Mn. The titanium alloy can have such a composite tissue that a hexagonal closest lattice structure tissue (hcp tissue) is distributed in an island manner in a body-centered cubic lattice structure tissue (bcc tissue). The hcp tissue is, for example, 30-70 vol.% with respect to the whole composite tissue. The non-magnetic member can achieve both high specific resistance and high strength, and accordingly can be used in various electromagnetic members, and can reduce eddy current loss.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a non-magnetic member or the like used in an alternating magnetic field.

There are various types of devices that use electromagnetics (simply referred to as "electromagnetic devices"), such as motors (including motors and generators), actuators, etc., and in many cases, alternating magnetic fields are used. Such electromagnetic devices are used. In order to save energy, it is required to reduce the high frequency loss when used in an alternating magnetic field. Especially for (ultra) high-speed motors, etc., it is proportional to the square of the rotation speed (frequency of the alternating magnetic field). It is strongly required to reduce the eddy current loss that becomes large. For example, in the rotor core and the stator core of a motor, an electromagnetic steel plate coated with an insulating layer is laminated in order to suppress the eddy current generated in the direction orthogonal to the alternating magnetic field. It is often composed of.

However, some members (referred to as "electromagnetic members") used in an alternating magnetic field are difficult to adopt such a configuration. In this case, it is necessary to construct the electromagnetic member with a material having a high electrical resistivity (simply referred to as "specific resistance") to reduce the eddy current loss.

The electromagnetic member arranged in the magnetic circuit is not limited to a magnetic material, but may be a non-magnetic material. Further, the electromagnetic member may be required to satisfy not only electrical characteristics (for example, specific resistance) and magnetic characteristics (for example, magnetic permeability) but also predetermined mechanical characteristics (rigidity, strength, ductility, etc.). A description relating to such an electromagnetic member is found in the following patent documents.

JP 2001-339886 Japanese Patent Application Laid-Open No. 2008-2953 JP-A-2020-43746 JP-A-5-5142 Patent No. 3712614 (WO2000 / 005425) JP-A-2005-320618 Special Table 2005-524774 (WO2003 / 095690) US Pat. No. 4,731,115

Patent Documents 1 and 2 describe a protective tube (sleeve) made of carbon fiber reinforced plastic (CFRP) as an example of an electromagnetic member made of a non-magnetic material (referred to as "non-magnetic member"). The protective tube is fitted on the outer peripheral side of a cylindrical permanent magnet provided on the outer peripheral side of the rotor shaft (rotating shaft) of the motor. The protective tube prevents damage to the permanent magnets, which are subject to large centrifugal forces at high speeds. However, when the number of revolutions is further increased, the mechanical properties of the protective tube made of CFRP are not always sufficient.

Patent Document 3 proposes a non-magnetic member made of a titanium-based composite material. The titanium-based composite material is formed by dispersing reinforcing particles made of TiCy (0 <y <1) in which a part of C is deleted in a matrix made of Ti-6% Al-4% V or the like. This non-magnetic member has high resistivity, high strength and high rigidity.

Incidentally, although Patent Documents 4 to 8 also describe titanium alloys or titanium-based composite materials, there is no specific description regarding electromagnetic members and their specific resistances.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a non-magnetic member or the like using a titanium alloy different from the conventional one.

As a result of diligent research to solve this problem, the present inventor has succeeded in obtaining a titanium alloy having a composition different from the conventional one and exhibiting high resistivity and high strength. By developing this result, the present invention described below was completed.

<< Non-magnetic member >>
(1) The present invention is a non-magnetic member used in an alternating magnetic field, and has an α-phase stabilizing element having an Al equivalent of 5.5 to 11 and a Mo equivalent of 6 to 17 in terms of mass ratio to the entire alloy. It is a non-magnetic member including a titanium alloy containing a β-phase stabilizing element, and the β-phase stabilizing element contains Fe and Mn.

(2) The non-magnetic member (electromagnetic member) of the present invention comprises a titanium alloy exhibiting high specific resistance and high strength. Therefore, even when used in an alternating magnetic field in a high frequency (for example, high rotation speed) region, the eddy current loss generated in the non-magnetic member can be reduced. Further, even when a large force (centrifugal force, inertial force, etc.) can be applied by high-speed motion (rotation, reciprocating motion, etc.), the non-magnetic member can be made thinner, lighter, smaller, and the like.

The reason why the titanium alloy according to the present invention exhibits high specific resistance and high strength is not always clear. At present, it is considered that the α-phase stabilizing element having a high Al equivalent and the β-phase stabilizing element having a high Mo equivalent act synergistically to obtain a titanium alloy having both specific resistance and strength at a high level. In particular, it is considered that Fe, which is a magnetic element, dissolves in Ti to improve the specific resistance of the non-magnetic titanium alloy. Further, it is considered that the strength of the titanium alloy is remarkably improved by containing Mn on the premise that the Al equivalent and the Mo equivalent are within a predetermined range.

"Production method"
The present invention can also be grasped as a method for manufacturing the above-mentioned non-magnetic member or titanium alloy. For example, when the titanium alloy is made of a sintered material, the non-magnetic member is obtained from a sintering step of obtaining a sintered body from powder and a processing step of forming the sintered body into a desired shape according to the non-magnetic member. .. Further, the titanium alloy made of the sintered material can always exhibit excellent high resistivity and high strength even if no special heat treatment (for example, solution treatment or aging treatment) is applied after the processing step. Of course, the titanium alloy according to the present invention is not limited to the sintered material, but may be a molten material.

"others"
(1) The α-phase stabilizing element referred to in the present specification is an alloy element that raises the allotropic transformation temperature (about 885 ° C.) of pure titanium and expands the α-phase region. The β-phase stabilizing element is an alloy element that lowers its allotropic transformation temperature and expands the β-phase region. In other words, the α phase stabilizing element is an element that appears in the Al equivalent calculation formula, and the β phase stabilizing element is an element that appears in the Mo equivalent calculation formula. As long as it is an alloy element that affects the allotropic transformation temperature or equivalent, even an alloy element (Sn, Zr, etc.) generally regarded as a neutral element (total rate solid-soluble element) is α-phase stable in the present specification. Treat as a chemical element or β-phase stabilizing element. Of course, the titanium alloy according to the present invention may further contain a neutral element that does not affect the allotropic transformation temperature or the equivalent (an alloy element that does not affect the allotropic transformation temperature).

The degree of "non-magnetic" (permeability) as used herein may be within a range that does not short-circuit the magnetic circuit of the electromagnetic device. In this specification, an electromagnetic member having a non-magnetic titanium alloy and used in an alternating magnetic field is referred to as a non-magnetic member. The non-magnetic member does not have to be a titanium alloy as a whole, and the non-magnetic member does not necessarily have to be a non-magnetic member as a whole. In short, the non-magnetic member of the present invention may have at least a part made of a titanium alloy.

(2) Unless otherwise specified, "x to y" in the present specification includes a lower limit value x and an upper limit value y. A range such as "a to b" may be newly established with any numerical value included in the various numerical values or numerical ranges described in the present specification as a new lower limit value or upper limit value. Further, "x to yμΩm" as used herein means xμΩm to yμΩm. The same applies to other unit systems (MPa, GPa, etc.).

It is a microstructure photograph (SEM image) of the titanium alloy of the sample 2. It is an enlarged photograph (SEM image) of the tissue. It is a microstructure photograph (SEM image) of the titanium alloy of the sample 3. It is explanatory drawing which shows the measuring method of specific resistance.

One or more components arbitrarily selected from the present specification may be added to the above-mentioned components of the present invention. The contents described in this specification correspond not only to non-magnetic members but also to manufacturing methods thereof and the like. It can also be a methodical component or a component related to an object. Which embodiment is the best depends on the target, required performance, and the like.

《Titanium alloy》
(1) Composition Titanium alloys are α-phase stabilizing elements having an Al equivalent of 5.5 to 11, 6 to 10, 7 to 9.5, and further to 8 to 9 (or even less), and a Mo equivalent of 6 to. It may contain 17, 6.5 to 15, 7 to 12, and further β-phase stabilizing elements of 8 to 11.5. If the Al equivalent is too small, the resistivity will be insufficient, and if it is too large, the elongation will be small. If the Mo equivalent is too small, the strength will be insufficient, and if it is too large, the elongation will be small.

Here, the Al equivalent ([Al "eq) and Mo equivalent ([Mo" eq)) are calculated as follows (Source: Light Metal Vol. 55, No. 2 (2005), PP.97-102).
[Al] eq = [Al] + [Zr] / 6 + [Sn] / 3 + 10 [O] + 16.4 [N] + 11.7 [C]
[Mo] eq = [Mo] + [Ta] / 5 + [Nb] /3.5+ [W] /2.5+[V]/1.5+1.25[Cr]
＋1.25 [Ni] ＋1.7 [Mn] ＋1.7 [Co] ＋2.5 [Fe]
However, in the present invention, unless otherwise specified, the Al equivalent is specified based on Al, Zr, and Sn, which are the main elements of the α phase stabilizing element ([Al] eq = [Al] + [Zr] / 6+). [Sn] / 3).

Unless otherwise specified, the composition ratio (concentration) referred to in the present specification is a mass ratio (mass%), and is simply indicated by "%". [] In the above calculation formula indicates the mass ratio (%) of each alloying element to the entire titanium alloy. In the case of a titanium-based composite material containing reinforcing particles (for example, TiC, TiB, etc.) in the titanium alloy (matrix), Al equivalent and Mo equivalent are calculated as the mass ratio to the entire matrix.

The α phase stabilizing element may be, for example, Zr, Sn (neutral element) or the like in addition to Al. A typical Al may be contained, for example, 7 to 10% or even 8 to 9% with respect to the entire titanium alloy (100% by mass).

The β-phase stabilizing element is, for example, Mo, V, Mn, Fe, or the like. A typical Mo may be contained, for example, 1 to 5%, further 1.5 to 4%, and V may be 4 to 8% or even 5 to 7% with respect to the entire titanium alloy.

In addition, Fe that contributes to the improvement of specific resistance is 0.5 to 3.5%, 0.9 to 3%, further 1 to 2.5%, and Mn that contributes to the improvement of strength is 0 with respect to the entire titanium alloy. .2 to 3%, 0.4 to 2.5% and even 0.5 to 1.5% may be contained.

Further, S may be contained in the entire titanium alloy in an amount of 0.1 to 1%, 0.2 to 0.7%, and further 0.3 to 0.5%, which contributes to the improvement of machinability and the like. .. Although S is not essential, if S is included, the machinability can be expected to be improved. However, if S is excessive, the titanium alloy may become brittle.

Titanium alloys contain impurities (eg, O, N, etc.) that are technically and economically difficult or unavoidable to remove. For example, O may be contained in an amount of 0.1 to 0.7% or even 0.2 to 0.5% with respect to the entire titanium alloy.

(2) Structure The metal structure of the titanium alloy (simply referred to as the “structure”) can change under the influence of the manufacturing process and heat treatment. The structure differs depending on, for example, the molten material or the sintered material, and the sintered material also differs depending on the presence or absence of heat treatment and the heat treatment conditions thereof. However, since the titanium alloy according to the present invention has a sufficiently large Al equivalent and Mo equivalent, apart from the specific form, the titanium alloy tends to have a metal structure in which α phase and β phase are mixed.

As an example, in a titanium alloy made of a sintered material, a structure of a hexagonal close-packed lattice is contained in a structure of a body centered cubic lattice (referred to as “bcc structure”). A complex structure in which (referred to as “hcp structure”) is distributed in an island shape is obtained (see FIG. 1A). The bcc structure mainly consists of the β phase, and the hcp structure mainly consists of the α phase. More specifically, the bcc structure is mainly composed of Ti, which is a basic element, and one or more of β-phase stabilizing elements (Mo, Fe, V, etc.). The hcp structure is mainly composed of Ti, which is a basic element, and one or more of α-phase stabilizing elements (Al, etc.). The bcc structure may contain one or more α-phase stabilizing elements. Similarly, the hcp structure may contain one or more β-phase stabilizing elements.

The hcp tissue occupies, for example, 30-70% by volume, 37-67% by volume, and even 43-60% by volume with respect to the entire composite tissue. Incidentally, the hcp structure is, for example, an aggregate of needle-shaped or granular ultrafine structures. Each hyperfine structure has, for example, a maximum length of 2 μm or less, further 1 μm or less, and an aspect ratio (maximum length / minimum length) of 3 to 20, further 5 to 10. The volume ratio, size, and aspect ratio of each structure (phase) can be obtained by analyzing (calculating) a two-dimensional optical micrograph (image) with analysis software: ImageJ (open source program).

The above-mentioned composite structure is a structure not found in conventional titanium alloys. However, the correlation between the structure of the titanium alloy and the characteristics of the titanium alloy (specific resistance, strength, etc.) is not clear at present.

(3) Characteristics Titanium alloys exhibit excellent electrical or mechanical characteristics. For example, it exhibits specific resistances of 2 to 5 μΩm, 2.1 μΩm to 4 μΩm, and further 2.2 μΩm to 3 μΩm. Such specific resistance is far higher than the specific resistance of pure Ti (about 0.4 μΩm) and the specific resistance of a typical titanium alloy (Ti-6% Al-4% V) (about 1.7 μΩm). Is big. Unless otherwise specified, the resistivity value referred to in the present specification can be obtained by measuring a sample (bulk material) of a predetermined size by the DC four-terminal method (see FIG. 3).

The titanium alloy can exhibit high strength of, for example, 1200 to 1700 MPa in tensile strength (breaking strength), further 1350 to 1650 MPa, further 1350 to 1550 MPa, and 0.2% proof stress of 1150 to 1600 MPa, further 1200 to 1500 MPa. Further, the titanium alloy can exhibit high rigidity of 115 to 135 GPa and further 120 to 130 GPa in Young's modulus, for example.

Further, the titanium alloy has an elongation of, for example, 0.2 to 2% and further 0.4 to 1.5%, and can be plastically processed into a non-magnetic member.

"Production method"
The titanium alloy (non-magnetic member) can be manufactured by, for example, a sintering method, a melting method, a (powder) additive manufacturing method (so-called 3D printer), or the like. As an example, a case where a titanium alloy is manufactured by a sintering method will be described below.

The sintering method is a method of heating a molded body of powder to obtain a sintered body. Post-processing can be reduced if the molded or sintered body is close to the form of the non-magnetic member (ie, near-net shape). Of course, the sintered body may be subjected to plastic working such as forging or pressing in a cold state or a hot state.

(1) Powder Usually, molding and sintering are performed using a mixed powder in which a plurality of kinds of raw material powders are mixed (weighed). As the raw material powder, in addition to a simple substance powder, an alloy powder, a compound powder and the like are used. As a simple substance powder, for example, there is a Ti source powder (pure Ti powder). Examples of the alloy powder include Al—V powder, Ti—Al powder, Fe—Mo powder (ferromolybdenum powder) and the like. Examples of the compound powder include Mn—S powder (manganese sulfide powder) and Fe—Mn powder (ferromanganese powder). Even powders of the same type having the same alloying elements have various composition ratios. An appropriate raw material powder may be selected according to the desired compounding composition. In any case, by using the alloy powder or the compound powder rather than the simple substance powder, the raw material cost can be reduced, and the structure can be made uniform and stabilized.

The average particle size (median diameter: D50) of each powder is, for example, preferably 1 to 20 μm and further preferably 3 to 15 μm. The mixed powder is prepared using a V-type mixer, a ball mill, a vibration mill, or the like (mixing step).

(2) Molding process The mixed powder is molded into a mold, CIP (Cold Isostatic Pressing) molding, RIP (Rubber Isostatic Pressing) molding, etc. to obtain the desired shape. It becomes a molded body. The shape of the molded body may be a shape close to the final member (non-magnetic member), or may be a billet shape (intermediate material shape) or the like when processing is performed after the sintering process. The molding pressure can be adjusted as appropriate, but for example, it may be 200 to 600 MPa, more preferably 300 to 400 MPa.

(3) Sintering step The molded product becomes a sintered body by heating in vacuum or in an inert gas. The sintering temperature may be, for example, 1150 ° C to 1400 ° C, more preferably 1200 to 1350 ° C. The sintering time may be, for example, 3 to 25 hours or even 10 to 20 hours. With an appropriate sintering temperature and sintering time, a titanium alloy with high characteristics can be efficiently obtained. The above-mentioned molding step and sintering step may be performed at the same time by HIP (Hot Isostatic Pressing) molding.

(4) Cooling step Cooling after the sintering step may be, for example, furnace cooling or forced cooling (introduction of an inert gas, etc.) at 0.1 to 10 ° C./s. The structure and properties of the titanium alloy may be adjusted by controlling the cooling rate.

(5) Processing step The sintered body may be made into a non-magnetic member as it is, or may be made into a non-magnetic member by plastic working, cutting or the like. The plastic working may be cold working or hot working. By hot working, it is possible to suppress cracking and the like and obtain a non-magnetic member with a good yield. Cooling after hot working may be furnace cooling, but air cooling is also sufficient.

The titanium alloy according to the present invention can exhibit a desired structure and characteristics without being subjected to heat treatment such as solution treatment and aging treatment. Such a non-heat-treated titanium alloy contributes to a reduction in the manufacturing cost of the non-magnetic member.

<< Non-magnetic member / electric device >>
Since the non-magnetic member of the present invention has high resistivity, high strength, and low magnetic permeability, it is suitable as an electromagnetic member used in an alternating magnetic field. The specific use thereof is not limited, but it can be used, for example, as a protective member (protective tube, protective case) of a permanent magnet (field source) incorporated in an electric motor (electromagnetic device, electric device) (described above). See JP-A-2020-43746). As an example of such an electric motor, there is a centrifugal compressor that requires high rotation. Such compressors are used, for example, in engine superchargers and fuel cell air compressors.

Various samples (sintered titanium alloys) having different component compositions were produced, and their electrical properties (specific resistance) and mechanical properties (tensile strength, 0.2% proof stress, Young's modulus, elongation) were evaluated. The present invention will be described in more detail below with reference to such specific examples.

<< Production of sample >>
(1) Raw material powder As the Ti powder, a commercially available hydrogenated dehydrogenated powder (manufactured by Toho Tech Co., Ltd.) classified by a sieve (# 350, average particle size 75 μm) was used.

As the alloy powder as the alloy element source, one or more of the following powders were used.
(a) Al-40% V powder (average particle size: 9 μm / manufactured by Kinsei Matek Co., Ltd.)
(b) Ti-36% Al powder (average particle size: 9 μm / manufactured by Daido Steel Co., Ltd.)
(c) Fe-60% Mo powder (average particle size: 45 μm / manufactured by Taiyo Koko Co., Ltd.)
(d) MnS powder (average particle size: 9 μm / manufactured by Fukuda Metal Co., Ltd.)
(e) Fe-78% Mn powder (average particle size: 10 μm / manufactured by Fukuda Metal Co., Ltd.)

Unless otherwise specified, the composition shown in this example is the mass ratio (mass%) of each raw material powder or mixed powder to the whole, and is simply indicated by "%". The average particle size of each powder was determined by a laser diffraction / scattering type particle size distribution measuring device (MT3300EX / manufactured by Nikkiso Co., Ltd.). In addition, each powder may contain a small amount of oxygen (impurities) inevitably adsorbed or bonded to the particle surface.

(2) Mixing Step Each raw material powder was weighed and blended so as to have the overall composition (Al equivalent, Mo equivalent) shown in Table 1 (excluding samples C4 and C5). Each compounded powder was mixed in a V-type mixer for 1 hour to obtain a mixed powder for each sample.

(3) Molding Step Each mixed powder was put into a vinyl chloride tube (PVC) and CIP molded to obtain a round bar-shaped molded product (φ16 mm × 150 mm). The molding pressure at this time was 4 t / cm ² (392 MPa).

(4) Sintering step Each molded product was heated (1300 ° C. × 16 hours) in vacuum (1 × 10 ^-5 torr) and sintered. The rate of temperature rise to reach the sintering temperature was about 5 ° C./min, and the cooling rate after the lapse of the sintering time was 10 ° C./s.

(5) Processing step Further, the sintered body of each sample was hot-processed (forged) in the air atmosphere. The heating temperature was 1200 ° C. and the processing rate was 56%. The processing rate referred to here was calculated by the cross-sectional reduction rate (Aw / Ao). Aw is the cross-sectional area after processing, and Ao is the cross-sectional area before processing.

The sintered body (processed product) after hot working was air-cooled in an air atmosphere to lower the temperature, and no heat treatment was performed after the air cooling. Various measurements and observations were performed using each test material (billet) thus obtained.

(6) Laminated lumber (comparative example)
For the samples C4 and C5 shown in Table 1, a commercially available molten material (manufactured by Daido Steel Co., Ltd.) was used as a test material as it was.

"measurement"
(1) Electrical characteristics (specific resistance)
The specific resistance of each sample was determined as shown in FIG. Specifically, first, electrodes were formed on a prism (3.014 mm (t) × 3.014 mm (w) × 20 mm) manufactured from each test material as follows. The central portion of each prism (between the voltage electrodes (L): 10 mm) is masked with masking tape. Wrap the terminal wire (silver wire: φ0.20 mm) around the masked both end portions and the two outer portions thereof (see FIG. 3). Silver paste (Dotite D-550 manufactured by Fujikura Kasei Co., Ltd.) is applied to the portion around which each terminal wire is wound and both end faces of the prism. The prism after application is heated in the air at 100 ° C. for 12 hours to dry. In this way, a test piece provided with a current electrode and a voltage electrode was prepared.

For each test piece, the voltage value (V) and current value (I) measured by the DC four-terminal method in the room temperature range and the cross-sectional shape (S = t × w) of the test piece (square column) are used for each sample. The specific resistance (electric resistivity) was calculated (see equation (1) in FIG. 3). The specific resistance (measured value) of each sample thus obtained is also shown in Table 1.

(2) Mechanical properties (Young's modulus, tensile strength, elongation)
A tensile test was performed using an autograph (AUTOGRAPH AG-1 50kN manufactured by Shimadzu Corporation) using a round bar tensile test piece (parallel part diameter: φ2.4 mm, gauge length: 14 mm) manufactured from the test material. ..

The tensile test was performed at room temperature in the air at a strain rate of 5 × 10 ^-4 / s. Based on the load-stress-strain relationship calculated from the load-stroke diagram obtained from the load cell and video extensometer in this tensile test, the mechanical properties of each sample were determined (see JIS Z 2241: 2011). The results are also shown in Table 1. The tensile strength was calculated based on the load at break and the initial shape of the test piece. Elongation is the strain of the test piece at break.

"observation"
(1) The structure of the test material before the tensile test was observed with an SEM (Scanning Electron Microscope). As an example, observation images (SEM images) relating to sample 2 are shown in FIGS. 1A and 1B. Moreover, the SEM image which concerns on a sample 3 is shown in FIG. Both FIGS. 1B and 2 show an enlarged island-like structure.

(2) The SEM image obtained by observing the structure before the tensile test was image-analyzed with ImageJ to determine the abundance ratio of the island-like structure for each sample. The results are also shown in Table 1.

(3) X-ray diffraction The structure before the tensile test was subjected to X-ray diffraction analysis (XRD / Cu-Kα). As a result, it was found that the island-like tissue is a hexagonal close-packed hcp tissue, and the base tissue surrounding it is a body-centered cubic lattice-structured bcc tissue.

"evaluation"
(1) Characteristics As is clear from Table 1, the titanium alloys of Samples 1 to 5 containing Fe and Mn had high specific resistance and high strength while both Al equivalent and Mo equivalent were in a predetermined range.

Further, the titanium alloy containing no S, such as sample 5, had high specific resistance, high strength and high ductility even without heat treatment. Specifically, the titanium alloy exhibited a tensile strength of 1600 MPa or more and an elongation of 1% or more, and had both strength and elongation, which are generally contradictory, at a higher level.

On the other hand, the samples C1 and C2 having a small Mo equivalent had insufficient strength. Further, the samples C4 and C5 having a small Al equivalent had at least insufficient specific resistance. Further, the sample C3 had an Al equivalent and a Mo equivalent within a predetermined range and had a high resistivity, but the strength (particularly 0.2% proof stress) was insufficient because it did not contain Mn.

(2) Structure As is clear from FIGS. 1A and 1, in Samples 1 to 5, many island-like hcp tissues (simply referred to as “island-like tissues”) form a complex structure surrounded by bcc structures. I found out that there was. It was also found that the island-like structure consisted of a collection of needle-like or fibrous (ultra) microstructures, as can be seen from FIGS. 1B and 2. It was also found from the SEM image that each microstructure had a maximum length of 2 μm or less and an aspect ratio of 5 or more.

It was confirmed by actual processing that all the titanium alloys of Samples 1 to 4 were superior to the titanium alloys of Samples C1 to C5 in machinability.

From the above, the Al equivalent and Mo equivalent are both within a predetermined range, and the titanium alloy containing Fe and Mn has high resistivity and high strength, and is suitable for a non-magnetic member (non-magnetic member). It turned out that there was. It was also found that such a titanium alloy has a peculiar structure in which the hcp structure (island-like structure) in which fine structures are aggregated is dispersed in the bcc structure.

Claims (10)

A non-magnetic member used in an alternating magnetic field,
A titanium alloy containing an α-phase stabilizing element having an Al equivalent of 5.5 to 11 and a β-phase stabilizing element having a Mo equivalent of 6 to 17 in terms of mass ratio to the entire alloy is provided.
A non-magnetic member containing Fe and Mn as the β-phase stabilizing element. The non-magnetic member according to claim 1, wherein Mn is contained in an amount of 0.2 to 3% by mass with respect to the entire titanium alloy. The non-magnetic member according to claim 1 or 2, wherein the titanium alloy contains 0.1 to 1% of S in terms of mass ratio to the whole. The titanium alloy is composed of a composite structure in which a hexagonal close-packed structure (referred to as "hcp structure") is distributed in an island shape in a body-centered cubic lattice structure (referred to as "bcc structure"). The non-magnetic member according to any one of 3. The non-magnetic member according to claim 4, wherein the hcp structure is 30 to 70% by volume based on the entire composite structure. The non-magnetic member according to any one of claims 1 to 5, wherein the titanium alloy has a specific resistance of 2 μΩm or more. The non-magnetic member according to any one of claims 1 to 6, wherein the titanium alloy has a 0.2% proof stress of 1150 MPa or more. The non-magnetic member according to any one of claims 1 to 7, wherein the titanium alloy is made of a sintered material. The method for manufacturing a non-magnetic member according to claim 8.
The sintering process to obtain a sintered body from powder, and
The sintered body is provided with a processing step of forming a desired shape according to the non-magnetic member.
A method for manufacturing a non-magnetic member to obtain the titanium alloy without at least solution treatment after the processing step. The method for producing a non-magnetic member according to claim 9, wherein the powder contains at least ferromolybdenum powder and manganese sulfide powder.

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