JP2006037150A - Ti BASED HIGH STRENGTH SUPERELASTIC ALLOY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop a material having a low Young's modulus and exhibiting a high elastic elongation threshold and high plastic elongation as well while having high tensile strength and hardness deviating from the past fundamental principles, i.e., a new alloy having high tensile strength and hardness, and further exhibiting high elastic elongation and plastic modulus. <P>SOLUTION: This invention is composed of a Ti based single phase solid solution consisting of a five componential system of M1 to M4 whose composition is represented by Ti<SB>100-x-y</SB>-M1<SB>x</SB>-(M2<SB>Y1</SB>-M3<SB>Y2</SB>-M4<SB>Y3</SB>) (all the numerical values are weight%); wherein, M1 is one kind of element selected from Nb, Zr, Ta and W; M2 is one kind of element selected from Al and Mo; M3 is one kind of element selected from Co, Cr, Ni and Fe; and M4 is one kind of element selected from Sn, Si, In and Ge. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to the development of a novel Ti-based high-strength superelastic alloy having high strength, superelasticity, low Young's modulus (superelasticity), and high cold workability.

  Generally, in crystalline metal materials, it is known that as the yield strength (σy), ultimate tensile strength (σu) and Vickers hardness (Hv) increase, the Young's modulus (E) increases accordingly. (Σy) to 0.02E (= The above expression means that the yield strength (σy) is about 1/50 of Young's modulus (E)), (Hv) to 0.06E (= The above expression has the relationship that Vickers hardness (Hv) means about 6/100 of Young's modulus (E).) In addition, the elastic elongation limit is usually low, 1.0% or less for metals, and if the crystalline metal material is subjected to elongation deformation beyond this, permanent plastic deformation occurs, and the crystalline material does not return to its original shape.

  In other words, if a large elastic elongation [= low Young's modulus (E)] is obtained in the conventional crystal material, naturally, the Vickers hardness (Hv) is low (= soft), the yield strength (σy) and the ultimate tensile strength (σu ) Decreases and yields or breaks with small tensile stress, conversely, increasing yield strength (σy) and ultimate tensile strength (σu) increases Vickers hardness (Hv) and Young's modulus ( E) also increases and the elastic elongation decreases.

  Therefore, a crystalline material (a crystalline material that is strong and easily stretched) that has a high Young's modulus (E), a large elastic elongation limit, and a large plastic elongation with high tensile strength and hardness has been developed. For example, conventional crystal materials have high yield strength (σy), ultimate tensile strength (σu), and Vickers hardness (Hv)), and are expected to be applied in a wide range of fields that take advantage of their new properties. However, the Young's modulus (E) increases as the bonding force of the constituent atoms of the crystalline metal material increases, and the basic principle of material strength is that the yield strength and hardness increase as the bonding force increases. Therefore, obtaining a material with high yield strength and hardness and low Young's modulus (E) is contrary to the basic principles of strength and elasticity of conventional crystal materials. The material was not found.

Therefore, in order to obtain a material having special physical properties that deviate from the principle of such a metal material, the inventors have conducted intensive research, and as a result, the material is contrary to the conventional technical common sense (i.e., the past). A material with high tensile strength and hardness that deviates from the basic principle, low Young's modulus, large elastic elongation limit and large plastic elongation, in other words, high tensile strength and hardness. A new alloy that also exhibits large elastic elongation and plastic elongation) was developed. (JP 2001-192755 A)
JP 2001-192755 A

  However, even in the case of the above-mentioned new alloy, higher performance is required in applications where the elastic deformation region is insufficient, for example, materials used for the face surface of the head of a golf club (especially a driver). In other words, the face surface of a golf club is required to have high tensile strength and hardness. On the other hand, when a golf ball is hit, the ball has a good ball holding at the time of impact, excellent directionality, and high repulsive force, that is, high elasticity. Deformation is required. In this respect, the new alloy developed by the inventors is insufficient and further improvement has been required.

  An object of the present invention is to further improve tensile strength and elastic deformation while maintaining or improving hardness as compared with conventional new alloys.

The Ti-based high-strength superelastic alloy according to claim 1,
Ti _100-xy -M1 _x- (M2 _Y1 -M3 _Y2 -M4 _Y3 ) (numerical values are all by weight), a Ti-based single-phase solid solution consisting of five components M1 to M4,
(a) M1 is one element selected from Nb, Zr, Ta, W,
M2 is one element selected from Al and Mo,
M3 is one element selected from Co, Cr, Ni and Fe,
M4 is one element selected from Sn, Si, In and Ge, and
12% by weight <X <30% by weight,
1 wt% <Yl <5 wt%,
1 wt% <Y2 <6 wt%,
1 wt% <Y3 <6 wt%,
(b) the ratio of atomic dimensions of the two components of Ti-Ml is 2.5% or more;
(c) The heat of mixing of the Ti-Ml constituent elements has a positive value, 0 or a slightly negative value, and the bonding properties between atoms are repelling each other,
The composition satisfies the following three conditions.

  As an alloy element applicable to the present invention, Ti is used as a main constituent material, Zr, Nb, Ta, W as the main additive material (M1), Al as the second additive material (M2), Mo is Co, Cr, Ni, Fe as the third additive material (M3), Sn, Si, Ge, In, etc. as the fourth additive material (M4). These atomic radii are as follows.

Ti: 1.47 angstrom,
Zr: 1.62 angstrom,
Nb: 1.43 angstrom,
Ta: 1.43 angstrom,
W: 1.37 Angstroms,

  The calculation method of the atomic dimensional difference is described by taking Ti and Zr as an example, and is expressed by (radius of Zr−radius of Ti) ÷ Ti radius × 100. When the atomic radii of Ti and Zr are substituted into the above formula, (1.62-1.47) ÷ 1.62 × 100 = 9.2%. In the present invention, at least two constituent multi-elements, that is, Ti is used as a main constituent material, and the main additive material (M1) has a ratio of atomic ratios of Zr, Nb, Ta, and W of 2.5%. That is necessary.

  The heat of mixing of the constituent elements is generally a thermal change when 1 mol of A element and 1 mol of B element are mixed at the atomic level. The state where the heat of mixing is zero is a state where there is almost no heat absorption or heat dissipation when mixing, a state having a positive value is a state where heat is absorbed when mixing, and a state having a negative value is when mixing It is in a state of radiating heat. The heat of mixing of Ti and Zr (HmixKJ / mol) is 0, 1 for Ti and Ta, and 4 for Zr and Nb. In the present invention, at least two constituent multi-elements, that is, Ti is used as a main constituent material, and as the main additive material (M1), the mixed heat of Zr, Nb, Ta, W is a positive value or zero or slightly. Must have a negative value.

  Single-phase solid solution is a state in which alloy elements are uniformly dissolved and the whole alloy is composed of, for example, a single α phase, β phase, or γ phase. This is a state in which two or more phases are mixed together such as (α + β) phase or (α + β + γ) phase. In the present invention, it is a β phase single phase. The β-phase solid solution accompanied by the second precipitate means a case where some precipitates (for example, intermetallic compounds) are accompanied in the β-phase single phase.

  The state in which the bonds between atoms repel each other is a state in which a repulsive force acts between adjacent atoms when the atoms are brought closer to a certain limit.

  Ti, the main constituent element of this alloy, has a hexagonal close-packed structure at room temperature, and changes to a body-centered cubic structure at 882 ° C or higher. Can be cold worked.

  Nb, which is the main additive element of this alloy, takes a hexagonal close-packed lattice structure (α phase) at room temperature and changes to a body-centered cubic structure (β phase) at 862 ° C. or higher. Further, Nb produces a dense oxide film in the air and has excellent corrosion resistance. In particular, the corrosion resistance in high-temperature water is remarkably higher than that of other metals, and has the property that it hardly reacts even in molten alkali. Thus, since Zr has excellent corrosion resistance and acid resistance, it is used for various machine applications. The Young's modulus of pure Nb is 105 GPa.

  Nb, which is another main additive element of this alloy, exhibits ductility, its Young's modulus is 105 GPa, its hardness is similar to that of wrought iron, and is a metal softer than Ta, which is another constituent element. Therefore, by adding Nb, flexibility (low elasticity = low Young's modulus) can be imparted to the obtained alloy. Nb is a metal that forms an oxide film in the air and exhibits corrosion resistance, is insoluble in acids other than hydrofluoric acid, does not dissolve in alkaline aqueous solutions, and is a component of various alloys (for example, heat-resistant alloys). Widely used as an additive element. By using Nb as a constituent of the Ti—Nb alloy of the present invention, the corrosion resistance and acid resistance can be further improved in cooperation with Nb.

  When the Nb content X is less than 12% by weight, Ti α-phase precipitates in the alloy, which significantly impairs workability. Conversely, when X is greater than 30% by weight, no improvement in corrosion resistance is observed, and only the specific gravity increases. Ti does not change in air at normal temperature, and Nb forms a solid solution and increases the strength of the alloy.

  Ti, Nb, Zr, Ta, and W form a dense oxide film on the alloy surface, do not change in air at room temperature, and have excellent strength and corrosion resistance. Ti, Zr and Nb are all materials excellent in human compatibility, and when used as a member that comes into contact with the human body, they exhibit an excellent action that does not cause allergies to the human body. Ta is an element having properties similar to those of Nb.

From the above, Ti alloys are excellent in corrosion resistance by forming a dense oxide film of TiO _{2 on} the surface in the atmosphere, light and strong specific strength (quotient obtained by dividing tensile strength by specific gravity) Material. In general, Ti-based alloys have a hard and brittle α phase at room temperature, and are difficult to machine such as rolling, forging, or cutting. It becomes a β phase single phase and can be easily machined at room temperature (in other words, room temperature plastic workability). In addition, the elastic deformation region is greatly expanded and exhibits a large elongation. Also, after 80% cold rolling and age hardening, the tensile strength is greatly improved and the Young's modulus is slightly higher than the Young's modulus during the solution treatment. The value is significantly lower than that of the alloy.

  “Claim 2” is characterized in that “β-phase solid solution is accompanied by the second precipitate” with respect to the metallographic structure of the Ti-based alloy according to claim 1, and “Claim 3” is claimed in Claim 1. The other metal structure of the described Ti-based alloy is characterized in that “aging precipitates based on age hardening treatment are precipitated in the β-phase solid solution”. As a result, fine precipitates are precipitated in the matrix, and high strength, high hardness, and high elasticity can be achieved by using the pinning action of dislocations by countless fine aging precipitates dispersed and precipitated in the alloy. In addition, since it has a low Young's modulus (high elastic deformation rate), when processed into the face surface of an driver head or an iron head, the grip and repulsive force of the golf ball are greatly improved, and the flight distance is greatly increased. Not only will it grow, it will also improve its direction. In addition, the mechanical properties are improved by the addition of metals shown in M3 and M4, but the human affinity is slightly lowered. However, its toxicity is mitigated by a dense oxide film of metal such as Ti or M1, and it can be applied to a material that requires high workability, high strength, high elasticity and the like such as a spectacle frame.

“Claim 4” relates to the conditions for establishing the Ti alloy according to claim 1 from another viewpoint. “At least one of the three conditions according to claim 1 is satisfied and the solvent metal is The Young's modulus is 80% or less of the Young's modulus of the solute metal "
“Claim 5” relates to the fulfillment condition as viewed from still another aspect of claim 1, satisfies at least one of the three conditions described in “Claim 1”, and yield strength αy (MPa ) / Young's modulus E (MPa) is 0.015 or more.

  “Claim 6” relates to the conditions established from another viewpoint according to claim 1. “At least one of the three conditions according to claim 1 is satisfied, and the hardness Hv (DPN) / The Young's modulus E (MPa) is 0.05 or more ".

  “Claim 7” is characterized in that the degree of workability of the Ti-based high-strength superelastic alloy “is cold-worked with a cross-section reduction rate of 50% or more”. In the case of [original thickness before rolling (t0) −thickness after rolling (t1)] ÷ original thickness before rolling (t0), this needs to be 50% or more. . As a result, a large amount of dislocations are generated inside the alloy and entangled with each other, making it difficult to move and contributing to strength improvement. The strength can be greatly improved by combining aging treatment and cold working.

  “Claim 8” is a specific example of the Ti-based high-strength superelastic alloy of the present invention, and is characterized in that “M1 is Nb, M2 is Al or Mo, M3 is Cr, and M4 is Sn”.

  According to the alloy of the present invention, the composition (a) satisfies the conditions (b) and (c), so that the tensile strength and hardness deviate from the basic principles of metallurgy in the past, and the Young A material that has a significantly low rate, a large elastic elongation limit (substantial improvement in resilience) and a large plastic elongation (substantially capable of plastic working), in other words, high tensile strength and hardness. We were able to develop a new alloy that exhibits large elastic and plastic elongation.

  Also, by applying aging treatment or significant cold working, the entanglement of dislocations can be dramatically increased, or fine aging precipitates can be dispersed and precipitated in the alloy to achieve the pinning action of dislocations. It was possible to achieve a significant improvement in strength.

  The alloy of the present invention is a ternary alloy containing Ti as a main component as described above, and its metal structure exhibits a β phase at room temperature, and thus exhibits excellent plastic workability at room temperature. In addition, the five-component alloy of the present invention has high strength, high elasticity / low Young's modulus (that is, superelasticity), high ductility (high elongation, for example, at least about 6% even when the area reduction is 90% [conventional] In the example, the maximum is about 3%]), which is particularly effective when used for parts that require suppleness. For example, when hitting a golf ball or hitting a golf ball, it looks like rubber. In addition to being easy to catch the golf ball in contact with the golf ball and having excellent directionality, the golf ball exhibits a large repulsive force upon impact and can greatly increase the flight distance of the golf ball. Moreover, since Ti and the main additive elements Nb and / or Zr have good corrosion resistance and excellent biocompatibility, even if a human body inhibiting material is slightly added to the second and third additive materials, It is suitable for a member used for a portion that does not elute and contacts the human body. For example, it is applied to uses such as “glasses frame”, “watch band”, and “spring wire”. In particular, non-toxicity, high strength and high elasticity of the alloy of the present invention are effective for “golf face”, “spring wire”, “glasses frame”, and “watch band”.

  Hereinafter, Ti-18Nb-2Al-4Sn-4Cr alloy and Ti-18Nb-2Mo-4Sn-4Cr alloy, which are one of the high-strength superelastic alloys according to the present invention, will be described in detail as typical examples. All the figures are weight percent. This example alloy is composed of an element group five-component system belonging to a group number adjacent or close to each other in the periodic table of elements. The ratio of atomic size of Nb of M1 group to Ti is 2.5% or more, and the heat of mixing of Ti and Nb (HmixKJ / mol) is +2. As a result of examining X-ray diffractometry of ingots made of these alloys in an arc melting furnace, it was confirmed that they were β-phase single-phase body-centered cubes. Depending on the amount added, the second precipitate is accompanied.

  These were compared with conventional crystal alloys (for example, pure Ti, Ti-6Al-4V, etc.). FIG. 1 is an image of an elastic deformation region in which the vertical axis indicates tensile stress (MPa) and the horizontal axis indicates elongation (%). Pure Ti (dense hexagonal structure = hcp phase) is the elastic deformation region (the elastic elongation is the hatched portion). (Approx. 0.02% to 0.5%) is negligible, yielding starts at about 290 MPa, and then enters the plastic deformation region and eventually breaks. Ti-6Al-4V (a hexagonal close-packed structure + mixed phase of body-centered cubic structure = hcp + bcc phase), one of the conventional new metals according to the inventors' invention, is significantly larger than this, and starts yielding at about 770 MPa. It exhibits an elastic elongation of about 1%, and then enters the plastic deformation region and eventually breaks. The elastic elongation is more than twice that of pure Ti. On the other hand, Ti-18Nb-2Al-4Sn-4Cr alloy and Ti-18Nb-2Mo-4Sn-4Cr alloy started yielding at about 975 MPa and showed elastic elongation of about 2.5%. Enters and eventually breaks. The elastic elongation varies greatly depending on the degree of processing, and thus cannot be uniquely indicated, but generally exhibits the above-described tendency.

  Table 1 compares various conventional Ti alloys (ratio 1 to 5) as comparative examples with the present invention alloys (1 to 2).

  According to Table 1, the tensile strength after age hardening belongs to a higher class than conventional metals, but the Young's modulus is greatly reduced. In other words, an unprecedented low Young's modulus was achieved while maintaining high tensile strength.

  Moreover, the low elastic modulus, which is a characteristic of the mechanical properties of the material of the present invention, is realized by the ability of the atoms to move reversibly with low stress due to the fact that the constituent elements do not have an attractive interaction with each other or are weak. The large elastic elongation characteristic of the mechanical properties of the material of the present invention is that reversible atomic transfer can occur up to a high strain range due to the diversity of transfer sites due to many kinds of elements that do not interact. It is presumed that this is due to the fact that the increase in flow stress is difficult to occur.

  By producing a solid solution single phase composed of components that satisfy the above three conditions and work hardening it as necessary, low elasticity, high elastic elongation, and high plastic elongation can be obtained along with high strength and high hardness. Since Ti-based alloys have high corrosion resistance and high cold workability, sports equipment materials (especially face materials for golf clubs), spring materials, frame materials, medical and biomaterials, toys It is expected to be applied to a wide range of fields such as materials, acoustic materials, decorative materials, shock-absorbing materials, and aerospace materials.

  Next, the place where the head material of the golf club is formed using this material will be described. The Ti-18Nb-2Al-4Sn-4Cr alloy and Ti-18Nb-2Mo-4Sn-4Cr alloy melted as described above are used as blocks or plates having a certain thickness, and this is further subjected to cold forging with a die. To a predetermined shape. Thereafter, this member is subjected to a solution treatment to dissolve all precipitates in the mother phase, and then heated to, for example, 250 to 500 ° C. to precipitate the solid solution components as fine aging precipitates in the mother phase. Strengthen the mother phase. The cooling method in the age hardening treatment is performed by air cooling or furnace cooling. In this way, the preferred mechanical properties for the material for this application were revealed.

  Fig. 2 shows the change in cold work and mechanical properties of the two types of metal according to the present invention (both metals are almost the same), and the horizontal axis shows the work degree (area reduction rate:%) from the left. In the upper (b), the left vertical axis is the tensile strength (MPa), the right vertical axis is the Young's modulus (GPa), the lower (b) is the left vertical axis is the hardness (Hv), and the right vertical axis is until the fracture. The growth (%) was taken. In the arrows shown in the line graph, in the upper (A), the right arrow indicates the Young's modulus, the left arrow indicates the tensile strength, and in the lower (B), the right arrow indicates the extension, and the left arrow indicates the hardness.

  Fig. 3 shows the annealing of the two types of metal according to the present invention (rolling rate 80%), showing the change in annealing temperature and mechanical properties (both metals are almost the same). (B), the left vertical axis is the tensile strength (MPa), the right vertical axis is the Young's modulus (GPa), and the lower (b) is the hardness ( Hv), and the right vertical axis represents the elongation (%) to break. Further, in the arrows shown in the line graph, in the upper (A), the right arrow indicates the Young's modulus, the left arrow indicates the tensile strength, in the lower (B), the right arrow indicates the hardness, and the left arrow indicates the elongation. According to these, low Young's modulus is realized while maintaining high hardness and high strength. In addition, the elongation at break shows a large value because of its low Young's modulus. Therefore, the golf face surface made of the material of the present invention has a good hit feeling when hitting the golf ball, and it easily touches the golf ball like a rubber to catch the golf ball and has excellent directionality. In addition to being a thing, it shows a large repulsive force at the time of impact and can greatly increase the flight distance of the golf ball.

  As described above, the alloy of the present invention is a Ti-based alloy and has many excellent features such as high corrosion resistance, high cold workability, high biocompatibility, and superelasticity. Expected to be applied to a wide range of fields such as equipment materials (golf faces), spring materials, frame materials, medical / biomaterials, toy materials, acoustic materials, decorative materials, shock absorbing materials, aerospace materials, etc. The

Comparison graph of elastic deformation region between the conventional example and the present invention The graph which shows the change regarding the processing rate of the mechanical property of this invention The graph which shows the change regarding the annealing temperature of the mechanical property of this invention

Claims (8)

Ti _100-XY -M1 _x- (M2 _Y1 -M3 _Y2 -M4 _Y3 ) (numerical values are all by weight), and a Ti-based single-phase solid solution consisting of five component systems of M1 to M4,
(a) M1 is one element selected from Nb, Zr, Ta, W,
M2 is one element selected from Al and Mo,
M3 is one element selected from Co, Cr, Ni and Fe,
M4 is one element selected from Sn, Si, In and Ge, and
12% by weight <X <30% by weight,
1 wt% <Yl <5 wt%,
1 wt% <Y2 <6 wt%,
1 wt% <Y3 <6 wt%,
(b) the ratio of atomic dimensions of the two components of Ti-Ml is 2.5% or more;
(c) The heat of mixing of the Ti-Ml constituent elements has a positive value, 0 or a slightly negative value, and the bonding properties between atoms are repelling each other,
A Ti-based high-strength superelastic alloy characterized in that the composition satisfies the following three conditions.   2. The Ti-based high-strength superelastic alloy according to claim 1, wherein the Ti-based single-phase solid solution is a β-phase solid solution, and the β-phase solid solution is accompanied by a second precipitate.   The Ti-based high-strength superelastic alloy according to claim 1, wherein the Ti-based single-phase solid solution is a β-phase solid solution, and an aging precipitate based on an age hardening treatment is precipitated in the β-phase solid solution.   A Ti-based high-strength superelasticity characterized in that at least one of the three conditions according to claim 1 is satisfied and the Young's modulus of the solvent metal is 80% or less of the Young's modulus of the solute metal alloy.   A Ti-based high strength characterized in that at least one of the three conditions according to claim 1 is satisfied and the yield strength σy (MPa) / Young's modulus E (MPa) is 0.015 or more. Super elastic alloy.   A Ti-based high-strength super-characteristic material characterized by satisfying at least one of the three conditions according to claim 1 and having a hardness Hv (DPN) / Young's modulus E (MPa) of 0.05 or more Elastic alloy. The Ti-based high-strength superelastic alloy according to any one of claims 1 to 6, wherein the Ti-based high-strength superelastic alloy is cold-worked at a cross-section reduction rate of 50% or more. The Ti-based high-strength superelastic alloy according to any one of claims 1 to 7, wherein M1 is Nb, M2 is Al or Mo, M3 is Cr, and M4 is Sn.