Note: Descriptions are shown in the official language in which they were submitted.
6D~734
ZIRCONIUM-CONT~INING AMORPHOUS
METAL ALLOYS
.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to amorphous metal alloys, and,
more particularly, to high strength, low density compositions in
the beryllium~titanium-zirconium system.
2~ Description of the Prior Art
Investigations have demonstrated that it is possible to
obtain solid amorphous materials from certain metal alloy
compositions. An amorphous material substantially lacks any long
range order and is characterized by an X-ray di~fraction profile
in which intensity varies slowly with diffraction angle. Such
a profile is ~ualitatively similar to the diffraction profile
of a liquid or ordinary window glass. This is in contrast
to a crystalline material which produces a diffraction profile
in which intensity varies rapidly with diffraction angle.
These amorphous metals exist in a metastable state.
Upon heating to a sufficiently high temperature, they crystallize
with evolution of heat of crystallization, and the X-ray
diffraction profile changes from one having amorphous charac-
`I 20 teristics to one having crystalline characteristics.
Z Novel amorphous metal alloys have been disclosed
and claimed by H. S. Chen and D. E. Pol~ in U.S. Patent 3,856,513,
issued December 24, 1974. These amorphous alloys have the
formula MaYbZC where M is at least one metal selected from
the group of iron, nickel, cobalt, chromium and vanadium, Y
is at least on~ element selected from the group consisting of
phosphorus, boron and carbon, Z is at least one element selected
from the group consisting of aluminum, antimony, beryllium,
germanium, indium, tin and silicon, "a" ranges from about 60 to
90 atom percent, "b" ranges ~rom about 10 to 30 atom percent
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and "c" ranges from about 0.1 to 15 atom percent. Theseamorphous alloys have been found suitable for a wide variety of
applications, including ribbon, sheet, wire, powder, etc.
Amorphous alloys are also disclosed and claimed having the formula
TiXj, where T is at least one transition metal, X is at
least one element sele~ted from the group consisting of
aluminum, antimony, beryllium, boron, germanium, carbon, indium,
phosphorus, silicon and tin, "i" ranges from about 70 to 87 atom
percent and "j" ranges from about 13 to 30 atom percent. These
amorphous alloys have been found suitable for wire applications.
At the time these amorphous alloys were discovered,
they evidenced mechanical properties that were superior to then
known polycrystalline alloys. Such superior mechanical pro-
perties included ultimate tensile strengths of up to 350,000
psi, hardness values (DPH) of about 650 to 750 kg/mm2 and good
ductility. Nevertheless, new applications requiring improved
magnetic, physical and mechanical properties and higher
thermal stability have necessitated efforts to develop further
compositions. More specifically, there remains a need for
high strength, low density material suitable for structural
applications.
SUMM~RY OF THE INVENTION
In accordance with the invention, high strength,
low density amorphous metal alloys are formed from compositions
of the formula BeaTibZrcXd, wherein X is at least
one additional alloying element selected from the group
consisting of the transition metals listed in Groups IB to
VIIB and Group VII~, Rows 4, 5 and 6, of the Periodic Table
and of the metalloid elements phosphorus, boron, carbon,
aluminum, silicon, tin, germanium, indium and antimony; "a"
varies from 30 to 52 atom percent, "b" from 0 to 68 atom percent
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"c" varies from 0 to 70 atom percent, and "d" varies from 0 to lO
atom percent. Two species of alloy within this formula are
(I) those formed from compositions having about 48 to 68
atom percent titanium, about 32 to 52 atom percent beryllium,
with a maximum of up to about 10 atom percent of beryllium
replaced by at least one additional alloying element, selected
from the group consisting of transition metals listed in Groups
IB to VIIB and Group VIII, Rows 4, 5 and 6 of the Periodic
Table, and metalloid elements phosphorus, boron, carbon,
aluminum, silicon, tin, germanium, indium and antimony. Preferably,
amorphous titanium-beryllium base alloys are formed from compo-
sitions having about 50 to 61 atom percent titanium, about 37
to 41 atom percent beryllium and about 2 to 10 atom percent
of at least one element selected from the group consisting
of aluminum, boron, tantalum and zirconium. Also, preferred
are amorphous titanium-beryllium binary alloys formed from
; ` compositions having from about 58 to 68 atom pe~cent titanium
and from about 32 to 42 atom percent beryllium. The second
species (II) of compositions according to the invention are those
defined within an area on a ternary diagram, having as its
coordinates in atom percent Be, atom percent Ti and atom
percent Zr, the area being defined by a polygon having at its
corners the five points defined by
; (a) 30% Be, 0% Ti, 70% Zr
tb) 50% Be, 0% Ti, 50% Zr
(c) 50% Be, 40% Ti, lO~ Zr
(d) 42% Be, 56% Ti, 2% zr
(e) 36~ Be, 62% Ti, 2% Zr.
The alloys of the invention evidence specific strengths of
about 28 to 60 x 105 cm. Also, the alloys of this invention
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are at least 50% amorphous, and preferably substantially
amorphous, that is, at least 80~ amorphous; and most
preferably about 100% amorphous~ as determined by X-ray
diffraction.
The amorphous metal alloys are fabricated by a process
which comprises forming a melt of the desired composition and
quenching at a rate of about 105 to 106C./sec by castlng
molten alloy onto a chill wheel in an inert atmosphere or in a
partial vacuum.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a ternary phase diagr.am, in atom percent,
: of the Ti~Be-X, system of species (I) where X represents at least
one additional alloying element, depicting the glass-forming
range;
` ~IG. 2 is a binary phase diagram, in atom p~rcent, - --
of the Ti-Be system within species (I) depicting the glass-forming
range.
FIG. 3 is a ternary phase diagram in atom percent of
the Be-Ti-Zr system within species (II) depicting the glass-
forming region.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the invention, high strength, low
density amorphous metal alloys are formed from compositions
; of the formula BeaTibzrcxd~ wherein X is at least one
additional alloying element selected from the group consisting
of the transition metals listed in Groups IB to VIIB and Group
VIII, Rows 4, 5 and 6, of the Periodic Table and of the metalloid
elements phosphorus boron, carbon, alluminum, silicon, tin,
germanium, indium and antimony; "a" varies from 30 to 52 atom
30 percent, "b" from 0 to 68 atom percent, "c" varies from 0 to 70
atom percent, and "d" varies from 0 to 10 atom percent.
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The amorphous metal alloys in accordance with theinvention comprise about 30 to 52 atom percent beryllium, zero to
about 68 atom percent titanium and zero to about 70 atom percent
zirconium, with a maximum of up to about 10 atom percent of
one additional alloying element selected from the group consisting
of transition metal elements and metalloids. The transition
metal elements are those listed in Groups IB to VIIB and Group
~III, Rows 4, 5 and 6 of the Periodic Table. The metalloid
elements include phosphorus, boron, caebon, aluminum, silicon,
tin, germanium, indium and antimony. Examples of preferred
additional alloying elements include boron, aluminum, tantalum
and zirconium. In a preferred species, the amorphous metal
alloys have a composition consisting essentially of about 50
to 61 atom percent titanium, 37 to 41 atom percent beryllium
and about 2 to 10 atom percent of at least one element selected
from the group consisting of aluminum, boron, tantalum and
zirconium. The purity of all elements is that found in normal
commercial practice.
FIG. 1, which is a ternary composition phase diagram,
depicts the glass-forming region in accordance with this species.
This region, which is designated by the polygon a-b-c-d-a, en~
compasses glass-forming compositions having high strength, good
ductility and low density.
Specifically the amorphous metal alloys of the first
species have a binary composition consisting essentially of
about 58 to 68 atom percent titanium and about 32 to 42 atom
percent beryllium. Such preferred alloys evidence high strength
and low density, resulting in a high strength-to-weight ratio.
In FIGS. l and 2, the preferred range is depicted by the line
a-e. As a consequence of the high strength-to-weight ratio
realized for the binary system, it is preferred that any additional
alloying elemen~s added have a relatively low density in order
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to retain the favorable strength-to-weight ratio. A second
species (II) of alloys contemplated by the formula are defined
within an area on a ternary diagram having as its coordinates
in atom percent Be, atom percent Ti and atom percent Zr, the
area being defined by a polygon having at its corners the five
points defined by
(a) 30% Be, 0% Ti, 70% Zr
(b) 50% Be, 0% Ti, 50% Zr
(c) 50% Be, 40% Ti, 10% Zr
(d) 42% Be, 56~ Ti, 2% Zr
(e) 36% Be, 62~ Ti, 2% Zr.
FIG. 3, which is ternary composition phase diagram,
depicts the glass-forming region of species (II~ of the inventionO
This region, which is designated by the polygon a-b-c-d-e-a,
encompasses glass-forming compositions having high strength,
low density and good ductility.
Amorphous metal alloys evidencing substantial improve-
ments in strength-to-weight ratios are represented by the formula
Be40Ti60 xZrx, where "x" ranges from about 2 to 60 atom percent.
These alloys are depicted in the Figure by the line f-g and are
preferred.
For low values of "x", that is, from about 2 to about
10 atom percent, hardness values of about 630 to 720 kg/mm2
and densities of about 3.8 to 4.1 g/cm3 are realized. While
the hardness values are within the range of those of prior art
amorphous alloys, the densities are considerably lower, by a
factor of about 2. Since hardness is related to strength, it
is evident that for low values of "x", a substantial improvement
in the strength-to-weight ratio is realized. Accordingly, such
compositions are especially preferred.
For higher values of "x", the hardness remains substan-
tially unchanged, while the density increases to about 5.4 g/cm3,
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~Gi473~
still well below that of prior art amorphous alloys. Thus,
high strength to-weight ratios are retained for the entire range
of compositions.
The specific strength of amorphous metal alloys is cal-
culated by dividiny the hardness value (in kg/mm2) by both a
dimensionless factor of about 3.~ and the density (in g/cm3).
The basis for the dimensionless factor is given in Scripta
Metallurgica, Vol. 9, pp. 431-436 (1975). The high strength-to-
weight properties of alloys in accordance with the invention may
then be compared with those of other prior art amorphous metal
alloys. For example, Pd80Si20 has a specific strength
(in units of 105 cm) of 1501 and Ti50Cu50 has a specific
strength of 29.6. In contrast, one of the typical preferred
alloys of this invention, Be40Ti50Zr10, has a speci~ic
strength of 54.8, considerably higher than that of prior art
amorphous metal alloys.
In general, the amorphous metal alloys of the invention
evidence specific strengths of about 28 to 60 x 105 cm.
Illustration of alloys of the invention evidencing high specific
strengths are those represented by the formula given above,
Be40Ti60 xZrx. Alloys within the scope of the invention
evidencing lower density and the same or higher hardness values
have correspondingly higher specific strengths.
Typical amorphous metal alloys of the invention
evidencing good strength-to-weight ratios and exceptional ease
of glass-forming behavior are represented by the formula
BeyZr10O y, where "y" ranges from about 30 to 50 atom percent.
These compositions are depicted in FIG. 3 by the line a-b and
are also preferred.
The amorphous metal alloys are formed by cooling a
melt of the desired composition at a rate of about 105
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to 106C./sec. The purity of all compositions is that found
in normal commercial practice. A variety of techniques are
available, as is now well-known in the art, for fabricating
splat-quenched foils and rapid-quenched continuous ribbon, wire,
sheet, powder, etc. Typically, a particular composition is
selected, powders or granules of the requisite elements in
the desired portions are melted and homogenized, and the molten
alloy i5 rapidly quenched on a chill surface, such as a
rotating cylinder. Due to the highly reactive nature of those
compositions, it is preferred that the alloys be fabricated
in an inert atmosphere or in a partial vacuum.
While amorphous metal alloys are defined earlier
as being at least 50~ amorphous, a higher degree of amorphousness
yields a higher degree of ductility. Accordingly, amorphous
metal alloys that are substantially amorphous, that is, at least
80~ amorphous are preferred. Even more preferred are totally
amorphous alloys.
Because of the strength of these alloys, based on the
hardness data, and their low density, these alloys a~e useful in
applications re~uiring high strength-to-weight ratio such as
structural materials in aerospace applications and as fibers in
composite materials.
Further, the amorphous metal alloys in accordance with
the invention evidence crystallization temperatures of over
400C. Thus, they are suitable in applications involving moderate
temperatures up to about 400~C.
EXAMPLE 1
~ n arc splat unit for melting and liquid quenching
high temperature reactive alloys was used. The unit, which
was a conventional arc-melting button furnace modified to
provide "hammer and anvil" splat quenching of alloys under
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inert atmosphere, included a vacuum chamber connected with a
pumping system. The quenching was accomplished by providing a
flat-surfaced water-cooled copper hearth on the floor of the
chamber and a pneumatically driven copper-block hammer positioned
above the molten alloy. As is conventional, arc-melting was
accomplished by negatively biasing a copper shaft provided with
a nonconsumable tungsten tip inserted through the top of the
chamber and by positively biasing the bottom of the chamber. All
alloys were prepared directly by repeated arc-melting of con-
stituent elements. A single alloy button (about 200 mg) wasremelted and then "impact-quenched" into a foil about 0.004
inch thick by the hammer situated just above the molten pool.
The cooling rate attained by this technique was about 105
to 106C/s~c.
The impact-quenched foil directly beneath the hammer
may have suffered plastic deformation after solidification.
~ However, portions of the foil formed from the melt spread away
`~ from the hammer were undeformed and, hence, suitable for hardness
and other ~elated tests. Hardness was measured by the diamond
pyramid technique, using a Vickers-type indenter consisting of
a diamond in the form of a square-based pyramid with an included
angle of 136 between opposite faces.
Various compositions were prepared using the ar;c-
splatting apparatus described above. A nonreactive atmosphere
of argon was employed. Amorphousness was determined by X-ray
diffraction. Beryllium-rich compositions, such as Ti40Be60
and Ti50Be50, formed an amorphous alloy only at very extreme
quench rates (much g~eater than about 106C./sec). The eutectic
composition, Ti63Be37, and a hyper-eutectic composition,
Ti60Be40, easily formed totally amorphous alloys in the
quench rate range of about 105 to 106C/sec.
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734
The Ti63Be37 composition exhibited two crystal-
lization peaks of about 460C~ and~545C., as determined by
differential thermal analysis (DTA; scan rate 20C/min), a
hardness of about 450 to 550 DPH, as measured by the diamond
pyramid technique and a density of 3.83 g/cm3.
The Ti60Be40 composition exhibited a crystallization
peak of 423C, as determined by DTA; a hardness of 630 DPH and a
density of 3.76 g/cm3.
Other amorphous metal alloys of titanium and beryllium
1~ with one or more additional alloying elements of aluminum,
boron, tantalum, and zirconium were prepared by the procedure
described above. The compositions, their observed crystallization
temperatures (Tc), ha~dness values (DPH) and densities ~ (g~cm )
are listed in Table I below.
:
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TABLE I
Composition, atom percent Value, ~,
Be Ti Al B Ta Zr _c ~ C DPH g/cm
58 2 !_ _ _ 417 674 3.80
58 - 2 - - 403 640 3.85
. ! 40 50 - 10 - _ 362 880 3.55
- - 5 - 407 810 4.28
- - 10 - 475 818 4.69
54 3 - 3 - 437 650 3.90
56 2 2 - - 455 578 3.56
58 - - - 2 419 720 3.84
- - - 10 412,437 718 4.10
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Because of the strength of these alloys, based on the
hardness data, and their low density, these alloys are useful
in applications requiring high strength-to-weight ratios, such
as structural applications in aerospace and as fibers in composite
materials.
EXAMPLE 2
; An arc-splat unit for melting and liquid quenching
high temperature reactive alloys was used. The unit, which was
a conventional arc-melting button furnace modified to provide
"hammer and anvil" splat quenching of alloys under inert
atmosphere, included a vacuum chamber connected with a pumping
system. The quenching was accomplished by providing a flat-
surfaced water-cooled copper hearth on the floor of the chamber
and a pneumatically driven copper-block hammer positioned above
the molten alloy. As is conventional, arc-melting was accomplished
by negatively biasing a copper shaft provided with a nonconsumable
tungsten tip inserted through the top of the chamber and by
positively biasing the bottom of the chamber. All alloys were
prepared directly by repeated arc-melting of constituent elements.
A single alloy button (about 200 mg) was remelted and then
"impact-quenched" into a foil about 0.004 inch thick by the
hammer situated just above the molten pool. The cooling rate
attained by this technique was about 105 to 105C/sec.
~- Hardness (DPH) was measured by the diamond pyramid
technique, using a Vickers-type indenter consisting of a diamond
in the form of a square-based pyramid with an included angle of
136 between opposite faces. A 50 g load was applied.
Crystallization temperature was measured by differential
thermal analysis (DTA) at a scan rate of about 20C/min.
Typically, the amorphous metal alloys evidenced crystallization
temperatures ranging from about 412 to 455C.
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Various alloys were prepared using the arc-splatting
apparatus described above. A nonreactive atmosphere of argon
was employed. Amorphousness was determined by X-ray diffraction.
The compositions, their observed hardness values and
densities and calculated specific strengths are listed in
Table II below.
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TABLE II
Composition,
Atom Percent Hardness,Density, Specific Strength,
Be Ti Zr Al B kg/mm2 g/cm3 cm (calculated)
- 70 - - 495 5.42 28.5 x 105
- 65 - - 549 5.41 31.7
- 60 - - 572 5.40 33.2
- 55 - - 616 5.40 35.6
- 50 - - 693 5.07 42.7
- 5~ 2 - - 5.34
~ 58 - 2 - 5.39
- 58 1 1 ~ 5-40
58 2 - - 720 3.84 58.6
56 4 - - 722 3.92 57.6
40 54` 6 - - 713 3.98 56.0
40 52 8 - - 668 4.~7 51.4
40 50 10 - - 718 - 4.10 54.8
40 45 15 - - 667 4.37 47.7
40 40 20 - - 65g 4.50 45.8
, .
40 30 30 - - 657 4.73 43.5
40 20 40 - - ~50 4.95 41.0
40 10 50 - - 637 5.21 38.2
:
40 5 55 - - 625 5.36 36.4
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Serial No. 238,547, Allied Chemical Corporation, File 7000-1096Ca
In addition, ribbons o several compositions were
fabricated in vacuum employing quartz crucibles and extruding
molten material onto a quench wheel by overpressure of argon.
A partial vacuum of about 200 ~m ofHg was employed. Con-
tinuous ribbons of Be40Ti54Zr6'Be40Ti52 8' 40 50 10
and Be40Zr60 were produced by this technique.
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