Zirconium-titanium alloys containing transition metal elements

Abstract

Zirconium-titanium alloys containing at least one of the transition metal elements of iron, cobalt, nickel and copper are disclosed. The alloys consist essentially of about 1 to 64 atom percent titanium plus at least one element selected from the group consisting of about 15 to 27 atom percent iron, about 15 to 43 atom percent cobalt, about 15 to 42 atom percent nickel and about 35 to 68 atom percent copper, balance essentially zirconium plus incidental impurities, with the proviso that when iron is present, the maximum amount of titanium is about 25 atom percent, when cobalt is present, the maximum amount of titanium is about 54 atom percent and when nickel is present, the maximum amount of titanium is about 60 atom percent. The alloys in polycrystalline form are capable of being melted and rapidly quenched to the glassy state. Substantially totally glassy alloys of the invention evidence unusually high electrical resistivities of over 200 .mu..OMEGA.-cm.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to zirconium-base alloys, and, in particular, to zirconium-titanium alloys containing transition metal elements.

2. Description of the Prior Art

Materials having high electrical resistivity (over 200 .mu..OMEGA.-cm) and negative or zero temperature coefficients of resistivity are required for precision resistors, resistance thermometers and the like. High resistivity materials permit fabrication of smaller resistors. Negative temperature coefficients of resistivity provide larger resistance values at lower temperatures, thus increasing the sensitivity of low temperature resistance thermometers. Zero temperature coefficients of resistivity provide stability of resistance with temperature, which is required for useful precision resistors. Commonly available alloys such as Constantan (49 .mu..OMEGA.-cm) and Nichrome (100 .mu..OMEGA.-cm) are examples of materials generally employed in these applications.

A number of splat-quenched foils of binary alloys of zirconium and titanium with transition metal elements such as nickel, copper, cobalt and iron have been disclosed elsewhere; see, e.g., Vol. 4, Metallurgical Transactions, pp. 1785- 1790 (1973) (binary Zr-Ni alloys); Izvestia Akadameya Nauk SSSR, Metals, pp. 173-178 (1973) (binary Ti or Zr alloys with Fe, Ni or Cu); and Vol. 2, Scripta Metallurgica, pp. 357-359 (1968) (binary Zr-Ni, Zr-Cu, Zr-Co and Ti-Cu alloys). While metastable, noncrystalline single phase alloys are described in these references, no useful properties of these materials are disclosed or suggested.

SUMMARY OF THE INVENTION

In accordance with the invention, zirconium-titanium alloys which additionally contain transition metal elements are provided. The alloys consist essentially of about 1 to 64 atom percent titanium plus at least one element selected from the group consisting of about 15 to 27 atom percent iron, about 15 to 43 atom percent cobalt, about 15 to 42 atom percent nickel and about 35 to 68 atom percent copper, balance essentially zirconium plus incidental impurities, with the proviso that when iron is present, the maximum amount of titanium is about 25 atom percent, when cobalt is present, the maximum amount of titanium is about 54 atom percent and when nickel is present, the maximum amount of titanium is about 60 atom percent.

The alloys in polycrystalline form are capable of being melted and rapidly quenched to the glassy state in the form of ductile filaments. Further, such glassy alloys may be heat treated, if desired, to form a polycrystalline phase which remains ductile. Such polycrystalline phases are useful in promoting die life when stamping of complex shapes from ribbon, foil and the like is contemplated.

Substantially glassy alloys of the invention possess useful electrical properties, with resistivities of over 200 .mu..OMEGA.-cm, moderate densities and moderately high crystallization temperatures and hardness values.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1, on coordinates of atom percent, depicts the preferred glass-forming region in the zirconium-titanium-iron system;

FIG. 2, on coordinates of atom percent, depicts the preferred glass-forming region in the zirconium-titanium-cobalt system;

FIG. 3, on coordinates of atom percent, depicts the preferred glass-forming region in the zirconium-titanium-nickel system; and

FIG. 4, on coordinates of atom percent, depicts the preferred glass-forming region in the zirconium-titanium-copper system.

DETAILED DESCRIPTION OF THE INVENTION

In substantially totally glassy form, the alloys of the invention find use in a number of applications, especially including electrical applications, because of their uniquely high electrical resistivities of over 200 .mu..OMEGA.-cm and negative or zero temperature coefficients of resistivity. These high electrical resistivities render such glassy alloys suitable for use in various applications such as elements for resistance thermometers, precision resistors and the like.

When formed in the crystalline state by well-known metallurgical methods, the compositions of the invention would be of little utility, since the crystalline compositions are observed to be hard, brittle and almost invariably multiphase, and cannot be formed or shaped. Consequently, these compositions cannot be rolled forged, etc. to form ribbon, wire, sheet and the like. On the other hand, such crystalline compositions may be used as precursor material for advantageously fabricating filaments of glassy alloys, employing well-known rapid quenching techniques. Such glassy alloys are substantially homogeneous, single phase and ductile. Further, such glassy alloys may be heat treated, if desired, to form a polycrystalline phase which remains ductile. The heat treatment is typically carried out at temperatures at or above that temperature at which devitrification occurs, called the crystallization temperature. The polycrystalline form permits stamping of complex piece parts from ribbon, foil and the like without the rapid degradation of stamping dies which otherwise occurs with the glassy phase.

As used herein, the term "filament" includes any slender body whose transverse dimensions are much smaller than its length, examples of which include ribbon, wire, strip, sheet and the like of regular or irregular cross-section.

The alloys of the invention consist essentially of about 1 to 64 atom percent titanium plus at least one element selected from the group consisting of about 15 to 27 atom percent iron, about 15 to 43 atom percent cobalt, about 15 to 42 atom percent nickel and about 35 to 68 atom percent copper, balance essentially zirconium plus incidental impurities, with the proviso that when iron is present, the maximum amount of titanium is about 25 atom percent, when cobalt is present, the maximum amount of titanium is about 54 atom percent and when nickel is present, the maximum amount of titanium is about 60 atom percent.

In weight percent, the composition ranges of the alloys of the invention may be expressed as follows:

______________________________________Ti 0.6-16 Ti 0.6-41 Ti 0.6-53 Ti 0.6-57Fe 19-10 Co 33-12 Ni 38-12 Cu 72-27Zr bal. Zr bal. Zr bal. Zr bal.______________________________________

The purity of all compositions is that commonly found in normal commercial practice. However, addition of minor amounts of other elements that do not appreciably alter the basic character of the alloys may also be made.

Preferably, the alloys of the invention are primarily glassy, but may include a minor amount of crystalline material. However, since an increasing degree of glassiness results in an increasing degree of ductility, together with exceptionally high electrical resistivity values, it is most preferred that the alloys of the invention be substantially totally glassy.

The term "glassy", as used herein, means a state of matter in which the component atoms are arranged in a disorderly array; that is, there is no long range order. Such a glassy material gives rise to broad, diffuse diffraction peaks when subjected to electromagnetic radiation in the X-ray region (about 0.01 to 50 A wavelength). This is in contrast to crystalline material, in which the component atoms are arranged in an orderly array, giving rise to sharp diffraction peaks.

The thermal stability of a glassy alloy is an important property in certain applications. Thermal stability is characterized by the time-temperature transformation behavior of an alloy, and may be determined in part by DTA (differential thermal analysis). Glassy alloys with similar crystallization behavior as observed by DTA may exhibit different embrittlement behavior upon exposure to the same heat treatment cycle. By DTA measurement, crystallization temperatures T.sub.c can be accurately determined by heating a glassy alloy (at about 20.degree. to 50.degree. C./min) and noting whether excess heat is evolved over a limited temperature range (crystallization temperature) or whether excess heat is absorbed over a particular temperature range (glass transition temperature). In general, the glass transition temperature is near the lowest, or first, crystallization temperature T.sub.cl and, as is conventional, is the temperature at which the viscosity ranges from about 10.sup.13 to 10.sup.14 poise.

The glassy alloys of the invention are formed by cooling a melt of the desired composition at a rate of at least about 10.sup.5 .degree. C./sec. A variety of techniques are available, as is well-known in the art, for fabricating splat-quenched foils and rapid-quenched substantially continuous filaments. Typically, a particular composition is selected, powders or granules of the requisite elements in the desired proportions are melted and homogenized, and the molten alloy is rapidly quenched on a chill surface, such as a rapidly rotating cylinder. Alternatively, polycrystalline alloys of the desired composition may be employed as precursor material. Due to the highly reactive nature of these compositions, it is preferred that the alloys be fabricated in an inert atmosphere or in a partial vacuum.

While splat-quenched foils are useful in limited applications, commercial applications typically require homogeneous, ductile materials. Rapidly-quenched filaments are substantially homogeneous, single phase and ductile and evidence substantially uniform thickness, width, composition and degree of glassiness and are accordingly preferred.

Preferred alloys of the invention and their glass-forming ranges are as follows:

Zirconium-Titanium-Iron System

Compositions of the invention in the zirconium-titanium-iron system consist essentially of about 1 to 25 atom percent (about 0.6-16 wt%) titanium, about 27 to 15 atom percent (about 19-10 wt%) iron and the balance essentially zirconium plus incidental impurities. Substantially totally glassy compositions are obtained in the region shown in FIG. 1 bounded by the polygon a-b-c-d-e-a having at its corners the points defined by

(a) 77 Zr - 1 Ti - 22 Fe

(b) 72 Zr - 1 Ti - 27 Fe

(c) 55 Zr - 25 Ti - 20 Fe

(d) 60 Zr - 25 Ti - 15 Fe

(e) 74 Zr - 11 Ti - 15 Fe.

Zirconium-Titanium-Cobalt System

Compositions of the invention in the zirconium-titanium-cobalt system consist essentially of about 1 to 54 atom percent (about 0.6-41 wt%) titanium, about 43 to 15 atom percent (about 33-12 wt%) cobalt and the balance essentially zirconium plus incidental impurities. Substantially totally glassy compositions are obtained in the region shown in FIG. 2 bounded by the polygon a-b-c-d-e-f-a having at its corners the points defined by

(a) 64 Zr - 1 Ti - 35 Co

(b) 56 Zr - 1 Ti - 43 Co

(c) 31 Zr - 40 Ti - 29 Co

(d) 31 Zr - 54 Ti - 15 Co

(e) 55 Zr - 30 Ti - 15 Co

(f) 63 Zr - 14 Ti - 23 Co.

Zirconium-Titanium-Nickel System

Compositions of the invention in the zirconium-titanium-nickel system consist essentially of about 1 to 60 atom percent (about 0.6-53 wt%) titanium, about 42 to 15 atom percent (about 38-12 wt%) nickel and the balance essentially zirconium plus incidental impurities. Substantially totally glassy compositions are obtained in the region shown in FIG. 3 bounded by the polygon a-b-c-d-e-a having at its corners the points defined by

(a) 71 Zr - 1 Ti - 28 Ni

(b) 57 Zr - 1 Ti - 42 Ni

(c) 5 Zr - 60 Ti - 35 Ni

(d) 21 Zr - 60 Ti - 19 Ni

(e) 55 Zr - 30 Ti - 15 Ni.

Zirconium-Titanium-Copper System

Compositions of the invention in the zirconium-titanium-copper system consist essentially of about 1 to 64 atom percent (about 0.6-57 wt%) titanium, about 68 to 35 atom percent (about 72-27 wt%) copper and the balance essentially zirconium plus incidental impurities. Substantially totally glassy compositions are obtained in the region shown in FIG. 4 bounded by the polygon a-b-c-d-a having at its corners the points defined by

(a) 64 Zr - 1 Ti - 35 Cu

(b) 31 Zr - 1 Ti - 68 Cu

(c) 1 Zr - 32 Ti - 67 Cu

(d) 1 Zr - 64 Ti - 35 Cu.

EXAMPLES

Example 1

Continuous ribbons of several compositions of glassy alloys of the invention were fabricated in vacuum employing quartz crucibles and extruding molten material onto a rapidly rotating copper chill wheel (surface speed about 3000 to 6000 ft/min) by over-pressure of argon. A partial pressure of about 200 .mu.m of Hg was employed. A cooling rate of at least about 10.sup.5 .degree. C./sec was attained. The degree of glassiness was determined by X-ray diffraction. From this, the limit of the glass-forming region in each system were established.

In addition, a number of physical properties of specific compositions were measured. Hardness was measured by the diamond pyramid technique, using a Vickers-type indenter consisting of a diamond in the form of a square-base pyramid with an included angle of 136.degree. between opposite faces. Loads of 100 g were applied. Crystallization temperature was measured by differential thermal analysis at a scan rate of about 20.degree. C./min. Electrical resistivity was measured at room temperature by a conventional four-probe method.

The following values of hardness in kg/mm.sup.2, density in g/cm.sup.3, crystallization temperature in .degree. K. and electrical resistivity in .mu..OMEGA.-cm, listed in Table I below, were measured for a number of compositions within the scope of the invention.

TABLE I______________________________________ Crystal-Composition lization Electrical(atom Hardness Density Temp. Resistivitypercent) (kg/mm.sup.2) (g/cm.sup.3) (.degree. K.) (.mu..OMEGA.-cm)______________________________________Zr.sub.60 Ti.sub.20 Fe.sub.20 492 6.40 645 256Zr.sub.55 Ti.sub.20 Co.sub.25 473 6.56 655 286Zr.sub.35 Ti.sub.30 Ni.sub.35 569 6.52 790 277Zr.sub.35 Ti.sub.20 Cu.sub.45 623 6.87 712 326______________________________________

EXAMPLE 2

Continuous ribbons of several compositions of glassy alloys in the zirconium-titanium-iron system were fabricated as in Example 1. Hardness values in kg/mm.sup.2 (50 g load) and density in g/cm.sup.3 are listed in Table II.

TABLE II______________________________________Composition(atom percent) Hardness DensityZr Ti Fe (kg/mm.sup.2) (g/cm.sup.3)______________________________________75 5 20 460 6.6470 5 25 475 6.7865 10 25 496 6.8455 20 25 -- 6.54______________________________________

EXAMPLE 3

Continuous ribbons of several compositions of glassy alloys in the zirconium-titanium-cobalt system were fabricated as in Example 1. Hardness values in kg/mm.sup.2 (50 g load) and density in g/cm.sup.3 are listed in Table III.

TABLE III______________________________________Composition(atom percent) Hardness DensityZr Ti Co (kg/mm.sup.2) (g/cm.sup.3)______________________________________80 5 15 549 6.7070 5 25 437 6.9460 5 35 494 7.0755 5 40 -- 7.2270 10 20 429 6.6865 10 25 460 6.7660 10 30 441 6.8955 10 35 480 6.9650 10 40 -- 7.1770 15 15 -- 6.5860 20 20 401 6.5650 20 30 471 6.6845 20 35 527 6.7540 20 40 575 6.9255 30 15 -- 6.2250 30 20 449 6.3345 30 25 475 6.3940 30 30 527 6.5635 30 35 581 6.5930 30 40 613 6.7335 35 30 539 6.4240 40 20 -- 6.1635 40 25 506 6.2325 40 35 -- 6.3830 45 25 557 6.1135 50 15 -- 5.9225 50 25 532 6.04______________________________________

EXAMPLE 4

Continuous ribbons of several compositions of glassy alloys in the zirconium-titanium-nickel system were fabricated as in Example 1. Hardness values in kg/mm.sup.2 (50 g load) and density in g/cm.sup.3 are listed in Table IV.

TABLE IV______________________________________Composition(atom percent) Hardness DensityZr Ti Ni (kg/mm.sup.2) (g/cm.sup.3)______________________________________60 5 35 512 7.0355 5 40 593 7.1870 10 20 401 6.6760 10 30 540 6.8355 10 35 529 6.9450 10 40 530 7.0460 20 20 438 6.4850 20 30 513 6.7040 20 40 584 6.8345 25 30 540 6.8745 30 25 483 6.3925 35 40 815 6.8825 40 35 593 6.3515 45 40 655 6.33 17.5 47.5 35 637 6.1810 55 35 701 5.96 5 55 40 726 6.12 5 60 35 633 5.91______________________________________

EXAMPLE 5

Continuous ribbons of several compositions of glassy alloys in the zirconium-titanium-copper system were fabricated as in Example 1. Hardness values in kg/mm.sup.2 and density in g/cm.sup.3 are listed in Table V below.

TABLE V______________________________________Composition(atom percent) Hardness DensityZr Ti Cu (kg/mm.sup.2) (g/cm.sup.3)______________________________________60 5 35 52 6.9455 5 40 626 7.1030 5 65 655 7.7140 10 50 557; 670 7.29; 7.2430 10 60 666; 743 7.5425 10 65 726; 693 7.64; 7.4945 15 40 549 6.9230 15 55 719 7.3025 15 60 603 7.4315 20 65 681 7.3440 25 35 560; 524 6.59; 6.6525 25 50 613 6.8630 30 40 566 6.6915 30 55 590 7.0210 30 60 704; 673 7.07; 7.05 5 30 65 651 7.1420 35 45 581; 603 6.60; 6.5925 40 35 546 6.3410 40 50 673; 640 6.57; 6.5315 50 35 557 6.0410 50 40 620; 584 6.19; 6.18 5 60 35 549 5.87______________________________________

Claims

1. A process for preparing a zirconium-base alloy comprising the steps of:

a. cooling a melt of alloy consisting essentially of a composition selected from the group consisting of

(i) zirconium, titanium and iron which, when plotted on a ternary composition diagram in atom percent Zr, atom percent Ti and atom percent Fe, is represented by a polygon having at its corners the points defined by

(1) 77 Zr - 1 Ti - 22 Fe

(2) 72 Zr - 1 Ti - 27 Fe

(3) 55 Zr - 25 Ti - 20 Fe

(4) 60 Zr - 25 Ti - 15 Fe

(5) 74 Zr - 11 Ti - 15 Fe;

(ii) zirconium, titanium and cobalt which, when plotted on a ternary composition diagram in atom percent Zr, atom percent Ti and atom percent Co, is represented by a polygon having at its corners the points defined by

(1) 64 Zr - 1 Ti - 35 Co

(2) 56 Zr - 1 Ti - 43 Co

(3) 31 Zr - 40 Ti - 29 Co

(4) 31 Zr - 54 Ti - 15 Co

(5) 55 Zr - 30 Ti - 15 Co

(6) 63 Zr - 14 Ti - 23 Co;

(iii) zirconium, titanium and nickel which, when plotted on a ternary composition diagram in atom percent Zr, atom percent Ti and atom percent Ni, is represented by a polygon having at its corners the points defined by

(1) 71 Zr - 1 Ti - 28 Ni

(2) 57 Zr - 1 Ti - 42 Ni

(3) 5 Zr - 60 Ti - 35 Ni

(4) 21 Zr - 60 Ti - 19 Ni

(5) 55 Zr - 30 Ti - 15 Ni; and

(iv) zirconium, titanium and copper which, when plotted on a ternary composition diagram in atom percent Zr, atom percent Ti and atom percent Cu, is represented by a polygon having at its corners the points defined by

(1) 64 Zr - 1 Ti - 35 Cu

(2) 31 Zr - 1 Ti - 68 Cu

(3) 1 Zr - 32 Ti - 67 Cu

(4) 1 Zr - 64 Ti - 35 Cu, said cooling step being conducted at a cooling rate of at least about 105.degree. C./sec to thereby produce a substantially glassy phase of said alloy; and

b. heating said substantially glassy alloy at a temperature at or above its crystallization temperature to cause said alloy to form a polycrystalline phase.

2. A process as recited in claim 1, wherein each of said cooling and heating steps is conducted in an inert atmosphere.

3. A process as recited in claim 1, wherein each of said cooling and heating steps is conducted in a partial vacuum.