High-tensile, malleable molded bodies of titanium alloys

Abstract

The object of the invention is to create high-tensile molded bodies that are made of titanium alloys and are malleable at room temperature and that, compared with the metallic glasses, have macroscopic plasticity and work hardening, without other properties, such as breaking resistance, elastic elongation or corrosion behavior being thus greatly impaired. The molded bodies according to the invention are characterized in that they are made of a material that in its composition conforms to the formula Tia E1b E2c E3d E4e, where E1 comprises one or more elements of the group containing the elements Ta, Nb, Mo, Cr, W, Zr, V, Hf and Y, E2 comprises one or more elements of the group containing the elements Cu, Au, Ag, Pd and Pt, E3 comprises one or more elements of the group containing the elements Ni, Co, Fe, Zn, Mn and E4 comprises one or more elements of the group containing the elements Sn, Al, Ga, Si, P, C, B, Pb and Sb, where a=100−(b+c+d+e), b=0 to 20, c=5 to 30, d=5 to 30, e=1 to 15 (a, b, c, d, e in atomic %). The molded bodies have a homogenous microstructure, mainly comprising a glassy or nanocrystalline matrix with ductile dendritic body-centered cubic phase embedded therein. A third phase with low volumetric proportion can be present. Such molded bodies can be used as high-stress components, e.g., in the aircraft industry, space aviation and the automobile industry, but also for medical technical equipment and implants in the medical field.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to high-tensile molded bodies that are made of titanium alloys and are malleable at room temperature. Such molded bodies can be used as high-stress components, e.g., in the aircraft industry, space aviation and the automobile industry, but also for medical technical equipment and implants in the medical field, where high demands are made on the mechanical load-bearing capacity, corrosion resistance and surface stressing, in particular with complicated molded components.

2. Discussion of Background Information

It is known that certain multi-component metal materials can be converted into a metastable glassy state by rapid solidification (metallic glasses), in order to obtain advantageous (e.g., soft-magnetic, mechanical, catalytic) properties. Due to the necessary cool-down rate of the melt, these materials can usually only be produced with small measurements in at least one dimension, e.g., thin bands or powder. They are therefore not suitable as a solid construction material (see, e.g., T. Masumoto, Mater. Sci. Eng. A179/180 (1994) 8-16).

Certain composition ranges of multi-component alloys are known in which such metallic glasses can also be produced through casting processes in a solid form, e.g., with measurements>1 mm. Such alloys are, e.g., Pd—Cu—Si, Pd₄₀Ni₄₀P₂₀, Zr—Cu—Ni—Al, La—Al—Ni—Cu (see, e.g., T. Masumoto, Mater. Sci. Eng. A179/180 (1994) 8-16 and W. L. Johnson in Mater. Sci. Forum Vol. 225-227, pp. 35-50, Transtec Publications 1996, Switzerland). In particular metallic glasses are known with compositions of the chemical formulas Ti₅₀Ni₂₅Cu₂₅, Ti—Be—Zr, Ti—Ni—Cu—Al and Ti—Zr—Ni—Cu, which can be produced>1 mm (A. Inoue et al., Mater. Lett. 19,131 (1994), K. Amiya et al., Mater. Sci. Eng. A179/A180,692 (1994), L. E. Tanner et al., Scr. Met. 11, 1727 (1977), and D. V. Louzguine et al., J. Mater. Res. 14, 4426 (1999)).

Also known are metallic glass molded bodies>1 mm in all their dimensions in certain composition ranges of the quaternary Ti—Cu—Ni—Sn alloys (T. Zhang and A. Inoue, Mater. Trans., JIM 39, 1001 (1998)).

A composition for a multi-component beryllium-containing alloy with the chemical formula (Zr_100-a-bTi_aNb_b)₇₅ (Be_xCu_yNi_z)₂₅ is known. The coefficients a, b thereby signify the element proportions in atomic % where a=18.34; b=6.66 and the coefficients x, y, z signify the ratio proportions in atomic % where x:y:z=9:5:4. This alloy is diphase, it has a high-tensile, brittle, glassy matrix and a ductile, malleable dendritic body-centered cubic phase. A considerable improvement of the mechanical properties at room temperature thus occurs, particularly in the area of macroscopic elongation (C. C. Hays, C. P. Kim and W. L. Johnson, Phys. Rev. Lett. 84, 13, p. 2901-2904, (2000)).

Until now it has been impossible to produce diphase titanium alloys with a high-tensile glassy matrix and ductile, malleable, dendritic body-centered cubic phase embedded therein.

SUMMARY OF THE INVENTION

The object of the invention is to create high-tensile molded bodies that are malleable at room temperature and made of titanium alloys and that, compared with the referenced metallic glasses, have macroscopic plasticity and work hardening with forming processes at room temperature, without other properties such as strength, elastic elongation or corrosion behavior being thus greatly impaired.

This object is attained with the high-tensile molded bodies described in the claims.

The molded bodies according to the invention are characterized in that they are made of a material that in its composition conforms to the formula Ti_aE1_bE2_cE3_dE4_e where

E1 comprises one or more elements of the group containing the elements Ta, Nb, Mo, Cr, W, Zr, V, Hf and Y,

E2 comprises one or more elements of the group containing the elements Cu, Au, Ag, Pd and Pt,

E3 comprises one or more elements of the group containing the elements Ni, Co, Fe, Zn, Mn and

E4 comprises one or more elements of the group containing the elements Sn, Al, Ga, Si, P, C, B, Pb and Sb

where

a=100−(b+c+d+e)

b=0 to 20

c=5 to 30

d=5 to 30

e=1 to 15

(a, b, c, d, e in atomic %)

and with possibly low additives and impurities due to manufacture.

The molded bodies thereby have a structure with a homogenous microstructure, mainly comprising a glassy or nanocrystalline matrix with ductile dendritic body-centered cubic phase embedded therein. The occurrence of a third phase with low volumetric proportion of a maximum of 10% is possible.

To achieve particularly advantageous properties, the material should conform to the composition Ti_aCu_cNi_dSn_e, where a=45-55, c=20-25, d=15-25 and e=5-10 (proportions in atomic %).

According to the invention, the volumetric proportion of the formed dendritic body-centered cubic phase in the matrix is 20 to 90%, preferably 50 to 70%. The length of the primary dendrite axes is in the range of 1-100 μm and the radius of the primary dendrites is 0.2-2 μm.

To produce the molded bodies, the finished cast part is produced by casting the titanium alloy melt in a copper mold.

The analysis of the dendritic body-centered cubic phase in the glassy or nanocrystalline matrix and the determination of the size and volumetric proportion of the dendritic deposits can take place via x-ray diffraction, scanning electron microscopy or transmission electron microscopy.

The invention is explained in more detail below on the basis of examples.

EXAMPLE 1

An alloy with the composition Ti₅₀Cu₂₃Ni₂₀Sn₇ (figures in atomic %) is cast in a cylindrical copper mold with an internal diameter of 3 mm. The molded body obtained comprises a partially glassy, partially nanocrystalline matrix and ductile body-centered cubic phase embedded therein. The volumetric proportion of the dendritic phase is estimated at 50%. A breaking elongation of 7.5% with a breaking resistance of 2010 Mpa is thus achieved. The elastic elongation at the technical yield point (0.2% yield strength) is 2.5% with a strength of 1190 MPa. The modulus of elasticity is 85.8 GPa.

EXAMPLE 2

An alloy with the composition Ti₆₀Ta₁₀Cu₁₄Ni₁₂Sn₄ (figures in atomic %) is cast in a cylindrical copper mold with an internal diameter of 3 mm. The molded body obtained comprises a partially glassy, partially nanocrystalline matrix and ductile body-centered cubic phase embedded therein. The volumetric proportion of the dendritic phase is estimated at 50%. A breaking elongation of 3.0% with a breaking resistance of 2200 MPa is thus achieved. The elastic elongation at the technical yield point (0.2% yield strength) is 1.0% with a strength of 1900 MPa. The modulus of elasticity is 95.5 GPa.

Claims

1. High-tensile molded body malleable at room temperature and made of titanium alloy, wherein the molded body is made of a material composed of a composition which conforms to the formula

2. The molded body according to claim 1, wherein the material has a composition with b=0-15, c=20-25, d=15-25 and e=5-10 (atomic %).

3. The molded body according to claim 1, wherein a volumetric proportion of the formed dendritic body-centered cubic phase in the matrix is 20-90%.

4. The molded body according to claim 1, wherein a length of the primary dendrite axes is in the range of 1-100 μm and a radius of the primary dendrites is 0.2-2 μm.

5. The molded body according to claim 3, wherein the volumetric proportion of the formed dendritic body-centered cubic phase in the matrix is 50-70%.

6. The molded body according to claim 1, wherein the material conforms to the composition

7. A method of forming a high-tensile molded body malleable at room temperature and made of titanium alloy, comprising casting a titanium alloy melt in a copper mold, the titanium alloy comprising a composition which conforms to the formula

8. The method according to claim 7, wherein the material has a composition with b=0-15, c=20-25, d=15-25 and e=5-10 (atomic %).

9. The method according to claim 7, wherein a volumetric proportion of the formed dendritic body-centered cubic phase in the matrix is 20-90%.

10. The method according to claim 7, wherein a length of primary dendrite axes is in the range of 1-100 μm and a radius of the primary dendrites is 0.2-2 μm.

11. The method according to claim 9, wherein the volumetric proportion of the formed dendritic body-centered cubic phase in the matrix is 50-70%.

12. The molded body according to claim 7, wherein the material conforms to the composition