Amorphous metal alloys and products thereof

A class of amorphous metal alloys is provided in which the alloys are rich in iron, nickel, cobalt, chromium and/or manganese. These alloys contain at least one element from each of three groups of elements and are low in metalloids compared to previously known liquid quenched amorphous alloys rich in iron, nickel, cobalt, chromium and/or manganese. The alloys can be readily formed in the amorphous state and are characterized by high hardness, high elastic limit and, for selected compositions, good corrosion resistance. Products made from these alloys include cutting tools, such as razor blades.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to amorphous metal alloys and products 
thereof and more particularly is directed towards a novel class of 
amorphous metal alloys rich in iron, nickel, cobalt, chromium and/or 
manganese and low in metalloids. 
2. Description of the Prior Art 
A solid amorphous metal is one in which the constituent atoms are arranged 
in a spatial pattern that exhibits no long range order, that is, it is 
non-crystalline. This lack of long range order is also a characteristic of 
liquids, but amorphous solids are distinguished from liquids by their high 
rigidity, which is comparable to that of crystalline bodies. Some metallic 
alloys, if cooled rapidly, can be formed into amorphous solids. Amorphous 
solids of this type are sometimes known as glassy metals. Solid amorphous 
metals may be obtained from certain alloy compositions, and an amorphous 
substance generally characterizes a non-crystalline or glassy substance. 
In distinguishing an amorphous substance from a crystalline substance, 
X-ray diffraction measurements are generally employed. 
Heretofore, a limited number of amorphous metal alloys have been prepared. 
An alloy can be produced in the amorphous state by rapidly quenching a 
molten alloy of a suitable composition or, alternatively, by a deposition 
technique or other suitable means. Suitably employed vapor deposition, 
sputtering, electro-deposition or chemical deposition can be used to 
produce the amorphous metal. 
Previously, amorphous metals quenched from melts which have been rich in 
iron, nickel, cobalt, chromium and/or manganese have generally either 
contained about 15 to 25 atomic percent of a metalloid (e.g. phosphorus, 
boron, carbon, silicon, etc.), generally referred to as transition 
metal-metalloid (TM-M) alloys, or more than about 30 percent of early 
transition metals (e.g. niobium or tantalum), generally referred to as 
inter-transition metal (TM-TM) alloys. 
It is an object of the present invention to provide a novel class of alloys 
and products made therefrom in which the alloys are rich in iron, nickel, 
cobalt, chromium and/or manganese and low in metalloids compared to 
previously known liquid-quenched amorphous alloys rich in iron, nickel, 
cobalt, chromium and/or manganese. 
SUMMARY OF THE INVENTION 
This invention features a class of amorphous metal compositions which are 
readily quenched to the amorphous state in which they display improved 
physical characteristics, the class of compositions being defined by the 
formula M.sub.a T.sub.b X.sub.c where M is any combination of elements 
from the group consisting of iron, nickel, cobalt, chromium and manganese; 
T is any combination of elements from the group consisting of zirconium, 
tantalum, niobium, molybdenum, tungsten, yttrium, titanium and vanadium; 
and X is any combination of elements in the group consisting of boron, 
silicon, phosphorus, carbon, germanium and arsenic where a ranges from 60 
to 87 atomic percent; b ranges from 3 to 30 atomic percent; and c ranges 
from 1 to 10 atomic percent. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The novel compositions of this invention can be made into amorphous metals 
by various quenching techniques to produce amorphous metal alloys 
displaying characteristics useful in production of products such as razor 
blades, high strength fibers, and other products where high hardness, high 
strength and corrosion resistance are desirable and in the production of 
products where soft magnetic properties are desirable. The group of alloys 
which is the subject of this invention is defined by the general formula 
M.sub.a T.sub.b X.sub.c where M is any combination of elements of the 
group consisting of iron, nickel, cobalt, chromium and manganese; T is any 
combination of elements in the group consisting of zirconium, tantalum, 
niobium, molybdenum, tungsten, yttrium, titanium and vanadium; an X is any 
combination of elements from the group consisting of boron, silicon, 
phosphorus, carbon, germanium and arsenic where a ranges from 60 to 87 
(preferably 70 to 85) atomic percent; b ranges from 3 to 30 (preferably 6 
to 20) atomic percent; and c ranges from 1 to 10 (preferably 5 to 10) 
atomic percent. The subscripts a, b and c represent atomic percent and, 
therefore, a + b + c =100 in any one case. 
The alloys of interest are rich in iron, nickel, cobalt, chromium and/or 
manganese. These five metals make up from 60 to 87 atomic percent of the 
preferred alloys. The generalized composition of the alloys describes a 
compositional range which includes alloys which can be formed readily in 
the amorphous state, i.e., such amorphous alloys can be formed by rapid 
quenching of the corresponding melt. 
Previously, amorphous metals prepared by quenching of the melt which have 
contained &gt; 70 at % of Fe, Ni, Co, Cr and/or Mn have generally contained 
about 15 to 25 atomic percent of a metalloid, e.g. phosphorus, boron, 
carbon or silicon. Examples of such alloys are Fe.sub.75 P.sub.15 
C.sub.10, Fe.sub.80 B.sub.20 and Fe.sub.40 Ni.sub.40 P.sub.14 B.sub.6. 
These alloys generally are referred to as transition metal-metalloid 
(TM-M) alloys. Examples of another type of related amorphous alloys 
prepared from the liquid are Ni.sub.60 Nb.sub.40 and Ni.sub.50 Ta.sub.50 ; 
for this type of alloy, the early transition metal (i.e. niobium or 
tantalum for these examples) is present with compositions greater than 
about 35 atomic percent. These alloys are generally referred to as 
inter-transition metal (TM-TM) alloys. 
The class of alloys of this invention is unique in that the class includes, 
for example, alloys containing 85 atomic percent iron but less than 10 
atomic percent metalloid. Further, alloys of this class such as Fe.sub.84 
Zr.sub.8 B.sub.8 cannot be obtained by mixing compositions typical of 
previously known TM-M and TM-TM amorphous alloys. 
The alloys of interest in the following examples were prepared by melting 
together the properly proportioned elements. The metal was prepared in the 
amorphous state, i.e. as a metallic glass, by being rapidly quenched from 
the liquid. Quenching was accomplished using a process similar to either 
the arc-melting piston-and-anvil technique as described by M. Ohring and 
A. Haldipur, Rev. Sci. Instrum. 42, 530 (1971) or the melt spinning 
technique as described by R. Pond and R. Maddin, Trans. Met. Soc. AIME 
245, 2475 (1969). Alloys were judged to be amorphous on the basis of X-ray 
diffraction patterns.

EXAMPLE I 
The alloy Fe.sub.84 Zr.sub.8 B.sub.8 was prepared from the proper elements 
which were first melted and then quenched to the amorphous state using the 
arc-melting piston-and-anvil technique. Using X-ray diffraction 
techniques, the solid metal alloy was established to be amorphous. 
EXAMPLE II 
The alloy Ni.sub.40 Fe.sub.23 Cr.sub.13 Ti.sub.16 B.sub.8 was prepared by 
mixing together the appropriate constituents and melting them to a liquid 
form. The liquid was then rapidly quenched to the amorphous state using 
the arc-melting piston-and-anvil technique. 
EXAMPLE III 
The alloy Ni.sub.36 Co.sub.28 Cr.sub.12 Ti.sub.16 B.sub.8 was prepared and 
quenched in accordance with the procedures of Example I and produced a 
solid amorphous metal alloy useful as razor blade material. 
EXAMPLE IV 
The alloy Fe.sub.76 Ti.sub.16 B.sub.8 was prepared and quenched following 
the procedures set forth in Example I and the resulting solid alloy proved 
to be in the amorphous state. 
EXAMPLE V 
The alloy Ni.sub.39 Co.sub.32 Cr.sub.12 Zr.sub.8 B.sub.6 Si.sub.3 may be 
prepared, melted and quenched following the procedures in Example I and 
result in an amorphous metal alloy. 
EXAMPLE VI 
The alloy Ni.sub.38 Co.sub.30 Cr.sub.12 Zr.sub.8 Ta.sub.4 P.sub.8 may be 
prepared, melted and quenched following the procedures in Example I and 
result in an amorphous metal alloy. 
EXAMPLE VII 
In this example a ribbon of an amorphous metal alloy was formed by melt 
spinning techniques from a composition of Ni.sub.38 Co.sub.30 Cr.sub.12 
Zr.sub.8 W.sub.4 B.sub.8. The amorphous ribbon formed in this example was 
approximately 30.mu.m thick, displayed a very high hardness (DPH = 943 
Kg/mm.sup.2) and had in addition a high elastic limit and excellent 
corrosion resistance. The excellent corrosion resistance was attributed in 
part to compositional homogeneity and the lack of grain boundaries. The 
amorphous alloy in ribbon form provides superior razor blade material and 
may have one or more edges sharpened. 
EXAMPLE VIII 
An amorphous ribbon was formed by the melt-spinning techniques, as set 
forth in Example VII, from an alloy composition Fe.sub.84 Zr.sub.8 
B.sub.8. The amorphous ribbon alloy produced by this example displayed 
good bending ductility and high hardness. 
While many amorphous metals have been available heretofore, the group of 
alloys of this invention is compositionally distinct from those previously 
reported. Previous amorphous metals containing high concentrations of the 
M elements can be described as falling into two categories: (1) those in 
which M was alloyed primarily with elements such as those labelled T 
(above) or rare earths, where these added elements typically comprised 30 
to 60 atomic percent (e.g., Ni.sub.60 Nb.sub.40); and (2) those in which M 
was alloyed primarily with elements such as those labelled X above, where 
these added elements typically comprised 15 to 25 atomic percent (e.g., 
Fe.sub.75 P.sub.15 C.sub.10 and Ni.sub.50 Fe.sub.30 P.sub.14 B.sub.6). 
While various amounts of X elements may have been added to previous alloys 
of Type (1) or various amounts of elements T may have been added to 
previous alloys of Type (2), the amounts of elements T and X were not 
adjusted simultaneously to produce amorphous metals where both the T and X 
elements were present in amounts as low as those obtained in the present 
case, e.g., M.sub.84 Zr.sub.8 B.sub.8. Such alloys as a group are distinct 
from previous alloys. It is noted that an alloy such as M.sub.84 Zr.sub.8 
B.sub.8 cannot be produced by mixing amorphous metals of the compositional 
types previously produced from the melt. 
It is also noted that the addition of small amounts of certain other 
elements (e.g., aluminum) to the compositions described above does not 
produce significantly different alloys. 
These amorphous (non-crystalline) metallic alloys are produced by a rapid 
quenching of the corresponding liquid at rates on the order of 10.sup.5 
.degree. C/sec. so as to retain the metastable amorphous solids. 
Any preparation technique which imposes a sufficiently high cooling rate 
upon the liquid can be used to produce these materials. Typically, the 
high quench rate is achieved by spreading the liquid metal as a thin layer 
on a colder substrate of high thermal conductivity such as copper. The 
thermal conductivity of the liquid being cooled and of potential 
substrates (or fluid quench media) require that at least one dimension of 
the quenched material be small so as to achieve the required cooling rate 
via conductance of the heat from the liquid metal. Another example of 
processes which can be used to produce such quench rates is described by 
Chen and Miller, Rev. Sci. Instrum. 41, 1237 (1970). Such processes are 
generally used to produce ribbon shaped material having thicknesses on the 
order of 0.0005 to 0.0050 inch. 
Such materials have potential commercial applications dependent on their 
mechanical and magnetic properties. These materials are relatively strong 
and hard; they display tensile strengths on the order of 300,000 to 
500,000 psi; diamond pyramid hardnesses on the order of 700 to 1,100 
Kg/mm.sup.2 are obtained. 
Such properties make filaments of these alloys suitable for use as high 
strength fibers. In addition, the good corrosion resistance of selected 
compositions within the more general range described above, combined with 
their very high elastic limit and the ductility evidenced in their ability 
to sustain a permanent deformation upon severe bending, make these 
materials desirable for use as razor blades. Further, some of these 
alloys, e.g., iron rich alloys, are soft ferromagnets which may find 
applications where high permeability and low loss ferromagnetic metal is 
required as, for example, those applications now employing Permalloy.