U.S. patent application number 11/661991 was filed with the patent office on 2008-08-14 for amorphous alloys on the base of zr and their use.
This patent application is currently assigned to Eidgenossische Technische Hochschule Zurich. Invention is credited to Kaifeng Jin, Jorg F. Loffler.
Application Number | 20080190521 11/661991 |
Document ID | / |
Family ID | 34932261 |
Filed Date | 2008-08-14 |
United States Patent
Application |
20080190521 |
Kind Code |
A1 |
Loffler; Jorg F. ; et
al. |
August 14, 2008 |
Amorphous Alloys on the Base of Zr and their Use
Abstract
An alloy is disclosed which contains at least four components.
The alloy has a bulk structure containing at least one amorphous
phase. The alloy composition follows an "80:20 scheme", i.e., the
alloy composition is
[(A.sub.xD.sub.100-x)a(E.sub.yG.sub.100-y).sub.100-a].sub.100-bZ.sub.b
with the number "a" being approximately 80. Preferably, component A
is Zr. The other components D, E, G and, optionally, Z are all
different from each other and different from component A. A
preferred system is Zr--Cu--Fe--Al. Further disclosed are Cu-free
systems of the type Zr--Fe--AI-Pd/Pt. Importantly, the alloy is
substantially free of nickel. This makes the alloy especially
suitable for medical applications. Methods of preparing such an
alloy, uses of the alloy and articles manufactured from the alloy
are also disclosed.
Inventors: |
Loffler; Jorg F.; (Zurich,
CH) ; Jin; Kaifeng; (Zurich, CH) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W., SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
Eidgenossische Technische
Hochschule Zurich
Zurich
CH
|
Family ID: |
34932261 |
Appl. No.: |
11/661991 |
Filed: |
September 5, 2005 |
PCT Filed: |
September 5, 2005 |
PCT NO: |
PCT/CH2005/000525 |
371 Date: |
September 25, 2007 |
Current U.S.
Class: |
148/538 ;
148/403 |
Current CPC
Class: |
C22C 45/10 20130101 |
Class at
Publication: |
148/538 ;
148/403 |
International
Class: |
C22C 45/10 20060101
C22C045/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 6, 2004 |
EP |
04405550.7 |
Claims
1-42. (canceled)
43. An alloy having a structure containing at least one amorphous
phase, the alloy being represented by the general formula
[(Zr.sub.xCu.sub.100-x).sub.a(E.sub.yG.sub.100-y).sub.100-a].sub.100-bZ.s-
ub.b, wherein a, b, x and y are real numbers signifying atomic
percentages with 70.ltoreq.a.ltoreq.90, x.gtoreq.50, y>0, and
0.ltoreq.b.ltoreq.6, wherein E is selected from the group
consisting of Fe and Co, wherein G and Z are components each
consisting of at least one element, wherein all elements in E, G
and Z are mutually different and different from Zr and Cu, and
wherein said alloy is substantially free of nickel, with the
proviso that, if E=Al, then G.noteq.Pd.
44. The alloy according to claim 43, wherein G is at least one
element selected from the group consisting of Al (aluminum) and the
metalloids.
45. The alloy according to claim 43, wherein E is Fe (iron) and G
is Al (aluminum).
46. The alloy according to claim 43, wherein
30.ltoreq.y.ltoreq.50.
47. The alloy according to claim 43, wherein
62.ltoreq.x.ltoreq.83.
48. The alloy according to claim 43, wherein the alloy is
essentially represented by the formula
(Zr.sub.xCu.sub.100-x).sub.80(Fe.sub.40Al.sub.60).sub.20 with
62.ltoreq.x.ltoreq.83.
49. The alloy according to claim 48, wherein x is substantially
selected from the numbers 62, 64, 66, 68, 72.5, 77, 79, 81 or
83.
50. An alloy substantially represented by one of the formulas
(Zr.sub.95Ti.sub.5).sub.72Cu.sub.13Fe.sub.13Al.sub.2,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.3Sn.sub.1,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Cr.sub.2,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Nb.sub.2,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Zn.sub.2,
(Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2).sub.98Mo.sub.2,
(Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2).sub.98P.sub.2,
(Zr.sub.95Hf.sub.5).sub.72Cu.sub.13Fe.sub.13Al.sub.2,
Zr.sub.70Cu.sub.11 Fe.sub.11Al.sub.8,
Zr.sub.71Cu.sub.11Fe.sub.10Al.sub.8,
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.90Al.sub.10,
Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2,
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Al.sub.2,
Zr.sub.73Cu.sub.13Fe.sub.13Al.sub.1,
Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2,
Zr.sub.71Cu.sub.13Fe.sub.13Al.sub.3,
Zr.sub.72Cu.sub.12Fe.sub.12Al.sub.4,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.4, Zr.sub.72Cu.sub.11
Fe.sub.11Al.sub.6, Zr.sub.72Cu.sub.11.5Fe.sub.11Al.sub.5.5,
Zr.sub.73Cu.sub.11Fe.sub.11Al.sub.5,
Zr.sub.71Cu.sub.11Fe.sub.11Al.sub.7,
Zr.sub.69Cu.sub.11Fe.sub.11Al.sub.9,
Zr.sub.70Cu.sub.10.5Fe.sub.100.5Al.sub.9,
Zr.sub.70Cu.sub.10Fe.sub.11Al.sub.9,
Zr.sub.70Cu.sub.11Fe.sub.10Al.sub.9,
Zr.sub.69Cu.sub.10Fe.sub.10Al.sub.11,
Zr.sub.69Cu.sub.10Fe.sub.11Al.sub.10,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Sn.sub.2,
Zr.sub.72Cu.sub.13Fe.sub.13Sn.sub.2,
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Sn.sub.2,
(Zr.sub.79Cu.sub.21).sub.80(Fe.sub.40Al.sub.60).sub.20, (Zr.sub.81
Cu.sub.19).sub.80(Fe.sub.40Al.sub.60).sub.20,
(Zr.sub.83Cu.sub.17).sub.80(Fe.sub.40Al.sub.60).sub.20,
(Zr.sub.66Cu.sub.34).sub.80(Fe.sub.40Al.sub.60).sub.20,
(Zr.sub.64Cu.sub.36).sub.80(Fe.sub.40Al.sub.60).sub.20, and
(Zr.sub.62Cu.sub.38).sub.80(Fe.sub.40Al.sub.60).sub.20.
51. An alloy having a structure containing at least one amorphous
phase, the alloy being represented by the general formula
[(Zr.sub.xFe.sub.100-x).sub.a(Al.sub.yG.sub.100-y).sub.100-a].sub.100-bZ.-
sub.b, wherein a, b, x and y are real numbers signifying atomic
percentages with 70.ltoreq.a.ltoreq.90, x.gtoreq.50, y>0, and
0.ltoreq.b.ltoreq.6, wherein G is at least one element selected
from the group consisting of Pt and Pd, wherein Z is a component
consisting of at least one element, wherein all elements in G and Z
are mutually different and different from Zr, Fe and Al, and
wherein said alloy is substantially free of copper and nickel.
52. The alloy according to claim 51, wherein G is Pd
(palladium).
53. The alloy according to claim 51, wherein the atomic percentages
of Fe and Al are substantially equal.
54. The alloy according to claim 51, wherein 68.ltoreq.x.ltoreq.89
and 73.ltoreq.a.ltoreq.87.
55. The alloy according to one claim 51, wherein
40.ltoreq.y.ltoreq.82.
56. The alloy according to claim 51, wherein 81.ltoreq.x.ltoreq.85,
80.ltoreq.a.ltoreq.83, and 65.ltoreq.y.ltoreq.80.
57. The alloy according to one of claims 43 and 51, wherein
0.ltoreq.b.ltoreq.2.
58. The alloy according to one of claims 43 and 51, wherein b>0,
and wherein Z is at least one element selected from the group
consisting of Ti, Hf, V, Nb, Y, Cr, Mo, Fe, Co, Sn, Zn, P, Pd, Ag,
Au and Pt.
59. The alloy according to one of claims 43 and 51, wherein
b=0.
60. An alloy having a structure containing at least one amorphous
phase, the alloy being substantially represented by the general
formula
Zr.sub.i(Fe.sub.50+.epsilon.Al.sub.50-.epsilon.).sub.jX.sub.k,
wherein X is one or more elements selected from the group
consisting of Pd and Pt, wherein i, j, k and .epsilon. are real
numbers signifying atomic percentages, and wherein
-10.ltoreq..epsilon..ltoreq.10, i.gtoreq.50, j.gtoreq.19,
k.gtoreq.0.5 and i+j+k=100.
61. The alloy according to claim 60, wherein X is Pd
(palladium).
62. The alloy according to claim 60, wherein
62.ltoreq.i.ltoreq.77.
63. The alloy according to claim 60, wherein
19.ltoreq.j.ltoreq.34.
64. The alloy according to claim 60, wherein
-2.ltoreq..epsilon..ltoreq.2.
65. The alloy according to claim 60, wherein .epsilon. is
substantially zero, 66.ltoreq.i.ltoreq.70, 25.ltoreq.j.ltoreq.29
and 4.ltoreq.k.ltoreq.7.
66. An alloy having the features of both claim 51 and claim 60.
67. An alloy substantially represented by one of the formulas
Zr.sub.67Fe.sub.13.2Al.sub.113.2Pd.sub.6.6,
Zr.sub.69.7Fe.sub.12.95Al.sub.12.95Pd.sub.4.4,
Zr.sub.66.7Fe.sub.14.45Al.sub.14.45Pd.sub.4.4,
Zr.sub.68.3Fe.sub.13.4Al.sub.113.4Pd.sub.4.9,
Zr.sub.65.4Fe.sub.14.85Al.sub.14.85Pd.sub.4.9,
Zr.sub.62.3Fe.sub.16.7Al.sub.16.7Pd.sub.4.3,
Zr.sub.59.2Fe.sub.18.3Al.sub.18.3Pd.sub.4.2,
Zr.sub.72Fe.sub.11.5A.sub.11.5Pd.sub.5,
Zr.sub.73.4Fe.sub.10.9Al.sub.10.9Pd.sub.4.8,
Zr.sub.75.2Fe.sub.10.2Al.sub.10.2Pd.sub.4.3,
Zr.sub.77Fe.sub.9.5Al.sub.9.5Pd.sub.4,
Zr.sub.67.9Fe.sub.11.8Al.sub.11.8Pd.sub.8.5.
Zr.sub.65Fe.sub.11.4Al.sub.11.4Pd.sub.12.2,
Zr.sub.62.5Fe.sub.10.75Al.sub.10.75Pd.sub.16,
Zr.sub.i(Fe.sub.50Al.sub.50).sub.30Pd.sub.70-i with
62.ltoreq.i.ltoreq.69.5, Zr.sub.69.5Fe.sub.15Al.sub.15Pd.sub.0.5,
Zr.sub.69Fe.sub.115Al.sub.15Pd.sub.0.5,
Zr.sub.68Fe.sub.15Al.sub.15Pd.sub.2,
Zr.sub.67Fe.sub.15Al.sub.15Pd.sub.3,
Zr.sub.66Fe.sub.15Al.sub.15Pd.sub.4,
Zr.sub.65Fe.sub.15Al.sub.15Pd.sub.5,
Zr.sub.64Fe.sub.115Al.sub.15Pd.sub.6,
Zr.sub.63Fe.sub.15Al.sub.15Pd.sub.7,
Zr.sub.62Fe.sub.15Al.sub.15Pd.sub.8,
Zr.sub.71Fe.sub.12Al.sub.12Pd.sub.5,
Zr.sub.69Fe.sub.12.85Al.sub.12.85Pd.sub.5.3,
Zr.sub.66.8Fe.sub.13.7Al.sub.13.7Pd.sub.5.8,
Zr.sub.65Fe.sub.14.5Al.sub.14.5Pd.sub.6,
Zr.sub.61.9Fe.sub.16.2Al.sub.16.2Pd.sub.5.7,
Zr.sub.50Fe.sub.12Al.sub.12Pd.sub.26,
Zr.sub.53.2Fe.sub.12.6Al.sub.12.6Pd.sub.21.6,
Zr.sub.57.6Fe.sub.13.95Al.sub.13.95Pd.sub.14.5, and
Zr.sub.60Fe.sub.14.3Al.sub.14.3Pd.sub.11.4.
68. The alloy according to one of claims 43, 51 and 60, wherein the
alloy has a structure comprising at least one amorphous phase and
at least one crystalline phase.
69. The alloy according to one of claims 43, 51 and 60, wherein
said at least one amorphous phase is obtainable by cooling from a
temperature above the melting point of the alloy to a temperature
below the glass-transition temperature of the amorphous phase at a
cooling rate of 1000 K/s or less.
70. A method of manufacturing an alloy, the method comprising:
preparing a melt of aliquots of all components of
(Zr.sub.xCu.sub.100-x).sub.a(E.sub.yG.sub.100-y).sub.100-a].sub.100-bZ.su-
b.b, and cooling the melt from a temperature above the melting
point of the alloy to a temperature below the glass-transition
temperature of the amorphous phase with a cooling rate of 1000 K/s
or less to obtain a solidified material, wherein a, b, x and y are
real numbers signifying atomic percentages with
70.ltoreq.a.ltoreq.90, x.gtoreq.50, y>0, and
0.ltoreq.b.ltoreq.6, wherein E is selected from the group
consisting of Fe and Co, wherein G and Z are components each
consisting of at least one element, wherein all elements in E, G
and Z are mutually different and different from Zr and Cu, and
wherein said alloy is substantially free of nickel, with the
proviso that, if E=Al, then G.noteq.Pd.
71. A method of manufacturing an alloy, the method comprising:
preparing a melt of aliquots of all components of
[(Zr.sub.xFe.sub.100-x).sub.a(Al.sub.yG.sub.100-y).sub.100-a].sub.100-bZ.-
sub.b, and cooling the melt from a temperature above the melting
point of the alloy to a temperature below the glass-transition
temperature of the amorphous phase with a cooling rate of 1000 K/s
or less to obtain a solidified material, wherein a, b, x and y are
real numbers signifying atomic percentages with
70.ltoreq.a.ltoreq.90, x.gtoreq.50, y>0, and
0.ltoreq.b.ltoreq.6, wherein G is at least one element selected
from the group consisting of Pt and Pd, wherein Z is a component
consisting of at least one element, wherein all elements in G and Z
are mutually different and different from Zr, Fe and Al, and
wherein said alloy is substantially free of copper and nickel.
72. A method of manufacturing an alloy, the method comprising:
preparing a melt of aliquots of all components of
Zr.sub.i(Fe.sub.50+.epsilon.Al.sub.50-.epsilon.).sub.jX.sub.k, and
cooling the melt from a temperature above the melting point of the
alloy to a temperature below the glass-transition temperature of
the amorphous phase with a cooling rate of 1000 K/s or less to
obtain a solidified material, wherein X is one or more elements
selected from the group consisting of Pd and Pt, wherein i, j, k
and .epsilon. are real numbers signifying atomic percentages, and
wherein -10.ltoreq..epsilon..ltoreq.10, i.gtoreq.50, j.gtoreq.19,
k.gtoreq.0.5 and i+j+k=100.
73. The method according to one of claims 70, 71 and 72, the method
comprising casting the melt into a mold, in particular into a
microstructured mold.
74. The method according to one of claims 70, 71 and 72, the method
comprising heat-treating the solidified material at a temperature
below the onset temperature of melting for a time period sufficient
for the formation of at least one crystalline phase.
75. The method according to one of claims 70, 71, and 72, the
method comprising a step of bringing the alloy into a superplastic
state and forming a microstructure in this state.
76. Use of an alloy according to one of claims 43, 51 and 60 for
manufacturing a product intended for being brought into prolonged
contact with a human or animal body.
77. An implant for implantation in the human or animal body
comprising an alloy according to one of claims 43, 51 and 60.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an alloy with the features
of the preamble of claim 1 or 19, to the use of such an alloy, and
to articles manufactured from such an alloy, in particular implants
such as endoprostheses.
BACKGROUND OF THE INVENTION
[0002] A number of alloys may be brought into a glassy state, i.e.,
an amorphous, non-crystalline structure, by splat cooling at very
high cooling rates, e.g., 10.sup.6 K/s. However, most of these
alloys cannot be cast into a bulk glassy structure at much lower
cooling rates achievable with casting.
[0003] In recent years, many bulk metallic glass-forming liquids
have been discovered for which cooling rates of less than 1000 K/s
are sufficient for vitrification. For the purposes of this
document, a "bulk metallic glass" is to be understood as an alloy
which develops an at least partially amorphous structure when
cooled from a temperature above the melting point to a temperature
below the glass-transition temperature of the amorphous phase with
a cooling rate of 1000 K/s or less, preferably with a cooling rate
of 100 K/s or less. Cooling rates in this range are typically
experienced in bulk casting operations.
[0004] Bulk metallic glasses generally have mechanical properties
that are superior to their crystalline counterparts. Due to the
absence of a dislocation mechanism for plastic deformation, they
often have a high yield strength and elastic limit. Furthermore,
many bulk metallic glasses show good fracture toughness, corrosion
resistance, and fatigue characteristics. For an overview of the
properties and areas of application of such materials see, for
example, Johnson W L, MRS Bull. 24, 42 (1999) and Loffler J F,
Intermetallics 11, 529 (2003). Reference is made explicitly to the
disclosure of these documents and the references cited therein for
teaching properties of glass-forming metallic alloys and methods
for the determination of such properties. Commercial applications
of bulk metallic glasses are described, e.g., in Buchanan O, MRS
Bull. 27, 850 (2002).
[0005] Currently, only Zr-based bulk metallic glasses (and some
Pt-based glasses for jewelry) have found their way into
applications. The following documents of the prior art deal with
Zr-based glass-forming alloys: [0006] U.S. Pat. No. 5,740,854
discloses an alloy of composition
Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5. [0007] U.S. Pat. No.
5,288,344 discloses alloys of general composition
Zr--Ti--Cu--Ni--Be. Specifically, the alloy
Zr.sub.41.2Ti.sub.13.8Cu.sub.12.5Ni.sub.10Be.sub.22.5, which has
become known under the trade name Vitreloy 1.TM. or Vit1.TM., and
Zr.sub.46.75Ti.sub.8.8Ni.sub.10Cu.sub.7.5 Be.sub.27.5, which is
known under the trade name Vitreloy 4.TM. or Vit4.TM., are
disclosed in that document. [0008] U.S. Pat. No. 5,737,975
discloses alloys of the general composition Zr--Cu--Ni--Al--Nb.
Specifically, an alloy of composition
Zr.sub.57Cu.sub.15.4Ni.sub.2.6Al.sub.10Nb.sub.5, which is known
under the trade name Vitreloy 106.TM. or as Vit106T, is disclosed
in this document. [0009] Lin X H, Johnson W L, Rhim W K, Mater.
Trans. JIM 38, 473 (1997)) discloses the alloy
Zr.sub.52.5Ti.sub.5Cu.sub.179Ni.sub.14.6Al.sub.10, also known as
Vit105.TM.. [0010] Loffler J F, Bossuyt S, Glade S C, Johnson W L,
Wagner W, Thiyagarajan P, Appl. Phys. Lett. 77, 525 (2000) and
Loffler J F, Johnson W L, Appl. Phys. Lett. 76, 3394 (2000)
describe comparative investigations of Vit1.TM., Vit105.TM. and
Vit106.TM..
[0011] Kundig A A, Loffler J F, Johnson W L, Uggowitzer P J,
Thiyagarajan P, Scr. mater. 44, 1269 (2001) describes alloys of the
general formula
Zr.sub.52.5Cu.sub.17.9Ni.sub.14.6Al.sub.10-xTi.sub.5+x, i.e., alloy
compositions which have been varied in the vicinity of the
composition of Vit105.TM.. [0012] Inoue A, Shibata T. and Zhang T.,
Mater. Trans. JIM 36, 1426 (1995) discloses alloys of composition
Zr.sub.65-xTi.sub.xAl.sub.10Cu.sub.15Ni.sub.10. [0013] Zhang T,
Inoue A, Mater. Trans. JIM 39, 1230 (1998) discloses alloys of
composition Zr.sub.70-x-yTi.sub.xAl.sub.yCu.sub.20Ni.sub.10. [0014]
Xing L Q, Ochin P, Harmelin M et al, Mat. Sci. Eng. A220, 155
(1996) discloses, inter alia, an alloy of composition
Zr.sub.57Cu.sub.20Al.sub.10Ni.sub.8Ti.sub.5, as well as other
Zr--Cu--Al--Ni--Ti alloys. [0015] Loffler J F, Thiyagarajan P,
Johnson W L, J. Appl. Cryst. 33, 500 (2000) describes
Zr--Ti--Cu--Ni--Be alloys whose (Zr, Ti) and (Cu, Be) contents were
varied between the compositions of Vit1.TM. and Vit4.TM.. [0016]
Inoue A, Zhang T, Nishiyama N, Ohba K, Masumoto T, Mater. Trans.
JIM 34, 1234 (1993) discloses an alloy of composition
Zr.sub.65Al.sub.7.5Cu.sub.17.5Ni.sub.10.
[0017] According to the following documents, the addition of Fe to
an Zr--Al--Ni--Cu alloy was believed not to improve or to even
decrease the glass-forming ability: [0018] Inoue A, Shibata T,
Zhang T, Mater. Trans. JIM 36, 1420 (1995). [0019] Eckert J, Kubler
A, Reger-Leonhard A et al, Mater. Trans. JIM 41, 1415 (2000).
[0020] Mattern N, Roth S, Kuhn U et al, Mater. Trans. JIM 42, 1509
(2001).
[0021] Due to their favorable mechanical properties, bulk metallic
glasses are interesting candidate materials for biomedical
applications. However, most known glass-forming alloys, especially
Zr-based alloys, contain a considerable proportion of nickel (Ni).
Exposure to nickel is known to possibly cause allergies. Therefore
these alloys are not well suited for medical applications, in which
the alloy can come into contact with body fluids, with the skin,
with tissue or other body parts. Specifically, these alloys may
cause allergic reactions because they tend to release small amounts
of nickel when they come into a prolonged contact with the body.
Copper (Cu) may also be problematic, albeit to a lesser extent.
[0022] Fan C, Inoue A, Mater. Trans. JIM 38, 1040 (1997) describes
the improvement of mechanical properties by precipitation of
nanoscale compound particles in Zr--Cu--Pd--Al amorphous alloys.
However, these alloys are not bulk metallic glasses; they are only
amorphous when using melt spinning or splat quenching.
SUMMARY OF THE INVENTION
[0023] It is therefore an object of the present invention to
provide an alloy which has good glass-forming ability and an
improved biocompatibility, in particular, an alloy which does not
release nickel in contact with body liquids.
[0024] This object is achieved by an alloy with the features of
claim 1.
[0025] It is another object of the present invention to provide an
alloy which has good glass-forming ability and an improved
biocompatibility, in particular, an alloy which is essentially free
of both copper and nickel.
[0026] This object is achieved by an alloy with the features of
claim 19.
[0027] Thus, an alloy is provided which contains at least four
components A, D, E and G. Optionally, a fifth component Z may be
present. The alloy preferably has a bulk structure containing at
least one amorphous phase, i.e., a volume fraction of at least 10%,
preferably at least 50% of the alloy is amorphous. In the context
of this document, a structure is considered to be fully amorphous
if the material having this structure does not exhibit significant
Bragg peaks in an X-ray diffraction pattern. Accordingly, the
volume fraction of the amorphous phase in a mixed-phase material
may be estimated by integrating the intensity of Bragg peaks and
comparing with the intensity of non-Bragg features.
[0028] Preferably, the amorphous phase can be obtained by cooling
from a temperature above the melting point to a temperature below
the glass-transition temperature of the amorphous phase with a
cooling rate of 1000 K/s or less, i.e., preferably the alloy is a
bulk metallic glass. More preferably, the amorphous phase can be
obtained by cooling with a cooling rate of 100 K/s or less. This
enables the material to be formed by casting, in particular
copper-mold casting. In other words, preferably the alloy with at
least one amorphous phase can be obtained in a shape with
dimensions of at least 0.1 mm, preferably at least 0.5 mm, more
preferred at least 1 mm in any spatial direction. This is not
possible for alloys which adopt an amorphous structure only at
cooling rates as achievable by splat cooling or melt spinning.
[0029] Component A consists of at least one element selected from
the group consisting of Zr (zirconium), Hf (hafnium), Ti
(titanium), Nb (niobium), La (lanthanum), Pd (palladium) and Pt
(platinum). The other components D, E, G and, optionally, Z are all
different from each other and from component A. Each of these
components may consist of more than one element, as long as all
elements of all components are different. Preferably, however,
components D, E and G each consist of a single element. The alloy
composition follows an "80:20 scheme", i.e., the ratio of the
combined atomic content of components A and D to the combined
atomic content of components E and G is approximately 80 to 20,
within a band of plus or minus 10, preferably a band of plus or
minus 5, in particular a band of plus or minus 2.
[0030] Expressed as a chemical formula, the alloy composition
is
[(A.sub.xD.sub.100-x).sub.a(E.sub.yG.sub.100-y).sub.100-a].sub.100-bZ.su-
b.b,
where x, y, a and b are independent numbers selected from zero and
the positive real numbers and denote atomic percentages, with
70.ltoreq.a.ltoreq.90, preferably 75.ltoreq.a.ltoreq.85, more
preferred 78.ltoreq.a.ltoreq.82. The following example is meant to
illustrate the meaning of the term "atomic percentage": Before
multiplying indices outside and inside of brackets, the indices
inside the brackets should be divided by 100, e.g.,
(Zr.sub.72.5Cu.sub.27.5).sub.80(Fe.sub.40Al.sub.60).sub.20.dbd.Zr.sub.58C-
u.sub.22Fe.sub.8Al.sub.2. After all brackets have been removed,
each index indicates the number of atoms contributing to a formula
unit of the alloy. In the present example, 58 atoms of Zr would be
combined with 22 atoms of Cu, 8 atoms of Fe and 12 atoms of Al in
order to arrive at one formula unit. In other words, if a number is
an "atomic percentage", this means that the number, when divided by
100, indicates the stoichiometry in the sense as it is usually
understood in chemistry.
[0031] Component A is the main component of the alloy, in the sense
that x.gtoreq.50. In order to have a significant content of
component D, preferably x.ltoreq.95 and more preferably
x.ltoreq.90. Advantageously, the content of component G relative to
component E is not too small, preferably y.gtoreq.5, more preferred
y.gtoreq.10. On the other hand, the content should not be too
large. Preferably y.ltoreq.95, more preferred y.ltoreq.90. If a
fifth component Z is present at all, then it is present in a
comparatively small proportion only. In numbers,
0.ltoreq.b.ltoreq.6, preferably 0.ltoreq.b.ltoreq.4, more
preferably 0.ltoreq.b.ltoreq.2. The numbers x, y, a and b are
generally independent of each other.
[0032] Importantly, the alloy is substantially free of nickel. In
the context of this document, "substantially free of nickel" means
that the total nickel content of the alloy is less than 1 atomic
percent, preferably less than 0.1 atomic percent. It may even be
required that the nickel content is below 10 atomic ppm, e.g., in
medical applications. In particular, none of the components A, D,
E, G or Z should comprise nickel.
[0033] Preferably, components A and E are miscible in a wide
composition and temperature range. The term "wide composition and
temperature range" is to be understood as a range extending over a
temperature range of at least 600 K and over a range of
compositions spanning at least 60 at. % of either component in the
liquid state and below the liquidus temperature in the A-E phase
diagram. In the present example, a wide composition range would,
e.g., be the range from 20 at. % to 80 at. % of component A in the
binary mixture A-E.
[0034] More preferably, components A and E are capable of forming a
deep eutectic composition in the absence of other components. The
term "capable of forming a deep eutectic composition" is to be
understood as meaning that, if A and E are mixed in the melt in the
absence of other components, there is a composition for which A and
E are miscible down to the liquidus temperature, and the liquidus
temperature of the mixture for that composition has a local minimum
as a function of composition. In other words, when varying the
composition in a small vicinity of a deep eutectic, the liquidus
temperature is higher than at the composition of the deep eutectic
itself. Often, the liquidus temperature of the binary mixture at
the deep eutectic will additionally be lower than the melting point
of each of the components taken alone. As an example for a very
deep eutectic, for A=Zr, the melting temperature is
T.sub.m(Zr)=2128 K, for E=Fe, it is T.sub.m(Fe)=1811 K; an eutectic
occurs at 1201 K=0.66 T.sub.m(Fe); likewise, for T.sub.m(Au)=1337
K, T.sub.m(Si)=1687 K, and an eutectic is at 636 K=0.47
T.sub.m(Au).
[0035] Preferably, the components are chosen such that a deep
eutectic composition of the A-E mixture occurs at a composition
A.sub.a'E.sub.100-a' with 70.ltoreq.a'.ltoreq.90, preferably
75.ltoreq.a'.ltoreq.85. Then the number a is preferably chosen such
that the absolute value of the difference between a and a' is
smaller or equal to 10 (i.e., |a-a'|.ltoreq.10), preferably
|a-a'|.ltoreq.5.
[0036] Preferably, also components A and D are miscible over a wide
temperature and composition range. More preferably, they are
capable of forming a deep eutectic composition when mixed in a
binary mixture. If components A and D form a deep eutectic
composition at A.sub.x'D.sub.100-x', then x is preferably chosen
such that |x-x'|.ltoreq.10, more preferably |x-x'|.ltoreq.5.
[0037] Preferably, component G is miscible with component E over a
wide temperature and composition range, in particular if E is at
least one element selected from the group consisting of the
transition metals, in particular the group consisting of Fe and Co.
It is then preferred that G is capable of forming a deep eutectic
composition with component A.
[0038] More preferably, components G and E are capable of forming a
deep eutectic composition at E.sub.y'G.sub.100-y'. Then y is
preferably chosen such that |y-y'|.ltoreq.10, more preferably
|y-y'|.ltoreq.5. Alternatively or additionally, A and G are
preferably capable of forming a deep eutectic composition.
[0039] Preferably, the atomic Goldschmidt radius of each element in
component A is relatively large, at least 0.137 nm, preferably at
least 0.147 nm, more preferred at least 0.159 nm. In particular, if
the atomic Goldschmidt radius of each element in component A is at
least 0.159 nm, then preferably 70.ltoreq.a.ltoreq.90, if this
radius is at least 0.147 nm, then preferably 75.ltoreq.a.ltoreq.85,
and if this radius is at least 0.137 nm, then preferably
78.ltoreq.a.ltoreq.82. In particular, this means that for Zr-, Hf-,
and La-based alloys, preferably 70.ltoreq.a.ltoreq.90; for Ti- and
Nb-based alloys, preferably 75.ltoreq.a.ltoreq.85; and for Pt- and
Pd-based alloys, preferably 78.ltoreq.a.ltoreq.82.
[0040] The components A, D, E and G may have similar atomic radii
and atomic properties. However, it is preferred that the atomic
radius of each element in component E is smaller than the atomic
radius of each element in component A.
[0041] The atomic (Goldschmidt) radii of the elements can be found
tabulated in standard textbooks or in the 2004 Goodfellow Catalog,
available from Goodfellow Inc., Huntingdon, U.K. In particular, for
selected elements, reference is made to Table 1 below.
TABLE-US-00001 TABLE 1 Atomic Goldschmidt radii of selected
elements Element Ag Al As Au B Be C Ca Atomic radius 0.144 0.143
0.125 0.144 0.097 0.113 0.077 0.197 [nm] Element Cd Ce Co Cr Cu Fe
Ga Ge Atomic radius 0.152 0.182 0.125 0.128 0.128 0.128 0.135 0.139
[nm] Element In Ir Hf La Mo Mg Mn Nb Atomic radius 0.157 0.135
0.159 0.187 0.140 0.160 0.112 0.147 [nm] Element Nd Ni P Pb Pd Pt
Rh Rb Atomic radius 0.182 0.125 0.109 0.175 0.137 0.138 0.134 0.251
[nm] Element Se Si Ta Ti Sb Sn W V Atomic radius 0.116 0.117 0.147
0.147 0.161 0.158 0.141 0.136 [nm] Element Y Yb Zn Zr Atomic radius
[nm] 0.181 0.193 0.137 0.160
[0042] In general terms, component D is preferably at least one
element selected from the group consisting of Cu (copper), Be
(beryllium), Ag (silver) and Au (gold). Specifically, if component
A is at least one element selected from the group consisting of La
(lanthanum), Pd (palladium) and Pt (platinum), component D is
preferably Cu (copper). If A is at least one element selected from
the group consisting of Zr (zirconium), Hf (hafnium) and Ti
(titanium), then D is preferably Cu (copper) or Be (beryllium).
Both copper and beryllium have deep eutectics with Zr, Hf and
Ti.
[0043] In general terms, component E is preferably at least one
metal selected from the group consisting of the transition metals
except Ni (nickel); particularly Sc (scandium), Ti (titanium), V
(vanadium), Cr (chromium), Mn (manganese), Fe (iron), Co (cobalt),
Zn (zinc), Y (yttrium), Mo (molybdenum), Ta (tantalum), and W
(tungsten). A transition metal is defined as any of the thirty
chemical elements with atomic number 21 through 30, 39 through 48,
and 71 through 80. These metals are preferred because of their
tendency to form deep eutectics with component A and because of
their specific electronic properties. In particular, component E is
preferably at least one metal selected from Fe (iron) and Co
(cobalt). These metals have empirically been found to be
preferred.
[0044] Component G is preferably at least one element selected from
the group consisting of Al (aluminum), Zr (zirconium), P
(phosphorus), C (carbon), Ga (gallium), In (indium) and the
metalloids, particularly B (boron), Si (silicon), and Ge
(germanium). The known metalloids are B (boron), Si (silicon), Ge
(germanium), As (arsenic), Sb (antimony), Te (tellurium), and Po
(polonium). It is believed that the specific electronic properties
of these elements favorably influence the glass-forming ability.
Furthermore, the elements B, P, C, and Si have particularly small
atomic sizes (.ltoreq.0.117 nm), which contributes to a large size
difference between the components A and G. In particular, if
component E is Fe (iron), component G is preferably selected from
the group consisting of Al (aluminum), Zr (zirconium), P
(phosphorus), B (boron), Si (silicon) and C (carbon). More
preferred, if component E is Fe (iron), then component G is Al
(aluminum). Then y is advantageously chosen to be in the range from
about 30 to about 50, in particular approximately 40.
Alternatively, if component E is Co (cobalt), component G is
preferably at least one element selected from the group consisting
of Zr (zirconium), Al (aluminum), B (boron), Si (silicon), Ge
(germanium), Ga (gallium) and In (indium).
[0045] In a preferred embodiment, component A is Zr (zirconium) or
a mixture of Zr (zirconium) with either Hf (hafnium) or Ti
(titanium) or both wherein at least 80 atomic percent of component
A is Zr (zirconium). It is then preferred that component D is Cu
(copper). It has been found empirically that this combination leads
to alloys with superior glass-forming ability.
[0046] If component A is Zr and component D is Cu, it is preferred
that x is chosen between 62 and 83 (i.e., 62.ltoreq.x.ltoreq.83),
preferably 68.ltoreq.x.ltoreq.77, in particular that x is
approximately 72.5. If component A is Zr and component D is Cu, it
is further preferred that component E is Fe (iron) and component G
is Al (aluminum). Then y is advantageously chosen to be in the
range from about 30 to about 50, in particular approximately 40.
Alloys of this composition, specifically, the alloy compositions in
the vicinity of Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12, have been
found by the inventors to belong to the best glass formers known to
date.
[0047] If a fifth component Z is present, this component is
preferably at least one element selected from the group consisting
of Ti, Nb, Hf. Alternatively, component Z may preferably be at
least one element selected from the group consisting of the
transition metals, or component Z may preferably be at least one
element selected from the group consisting of Be (beryllium), Y
(yttrium), Pd (palladium), Ag (silver), Pt (platinum), and Sn
(tin). In general terms, component Z is preferably capable of
forming a deep eutectic composition with component A.
[0048] The alloy may have a structure comprising at least one
amorphous phase and at least one crystalline phase. The volume
fraction of the amorphous phase preferably is at least 10%. The
amorphous and crystalline phases should not be macroscopically
separated. Such a structure can be generated by different means. In
one approach, a composite comprising crystals embedded in an
amorphous matrix is produced by subjecting the alloy to heat
treatment at a temperature above the glass transition temperature.
For details, see the description of the preferred embodiments
below. In another approach, the alloy is subjected to electric
currents, as described, e.g., in (Holland T B, Loffler J F, Munir Z
A, J. Appl. Phys. 95, 2896 (2004)), who describe the
crystallization of metallic glasses under the influence of high
density DC currents. In still another approach, the alloy
composition in the melt is chosen to be initially outside the
glass-forming region. During cooling, crystals start forming in the
melt. This alters the composition of the mixture remaining in the
melt, which is shifted into the glass-forming region. Upon further
cooling, a glassy matrix with embedded crystals is formed. For
details, see (Hays C C, Kim C P, Johnson W L, Phys Rev. Lett. 84,
2901 (2000)). In yet another approach, development of crystals in
the amorphous matrix is fostered by a suitable choice of the fifth
component Z. Suitable components Z are preferably at least one
element selected from the group consisting of Ti, Nb, Ta, or at
least one element selected from the group consisting of the
transition metals, or at least one element selected from the group
consisting of Be and Pd. For details, see, e.g., (He G, Eckert J,
Loser W, Schultz L, Nature Materials 2, 33 (2003)).
[0049] In a preferred embodiment, A is Zr (zirconium) and D is
selected from the group consisting of Cu (copper) and Fe
(iron).
[0050] Specifically, it is preferred that A is Zr (zirconium), D is
Cu (copper), and E is selected from the group consisting of Fe
(iron) and Co (cobalt). Then G is preferably at least one element
selected from the group consisting of Al (aluminum) and the
metalloids. A particularly preferred system is the Zr--Cu--Fe--Al
system, i.e., A is Zr (zirconium), D is Cu (copper), E is Fe (iron)
and G is Al (aluminum). It has been found that alloys of this
composition, when following the 80:20 concept, have favorable
glass-forming properties.
[0051] If A is Zr (zirconium) and D is Cu (copper), it is preferred
that the ratio of these is chosen according to
62.ltoreq.x.ltoreq.83. If E is Fe (iron) and F is Al (aluminum), it
is preferred that their ratio is chosen according to
30.ltoreq.y.ltoreq.50. The combination of these ranges, together
with the general 80:20 concept, defines a region of quaternary
compounds with exceptionally good glass-forming properties.
[0052] In particular, the alloy may substantially be represented by
the formula
(Zr.sub.xCu.sub.100-x).sub.80(Fe.sub.40Al.sub.60).sub.20 with
62.ltoreq.x.ltoreq.83, in particular, with x=62, 64, 66, 68, 72.5,
77, 79, 81 or 83, or by one of the formulas
(Zr.sub.95Ti.sub.5).sub.72Cu.sub.13Fe.sub.13Al.sub.2,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.3Sn.sub.1,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Cr.sub.2,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Nb.sub.2,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Zn.sub.2,
(Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2).sub.98Mo.sub.2,
(Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2).sub.98P.sub.2,
(Z.sub.95Hf.sub.5).sub.72Cu.sub.13Fe.sub.13Al.sub.2,
Zr.sub.70Cu.sub.11Fe.sub.11Al.sub.8,
Zr.sub.71Cu.sub.11Fe.sub.10Al.sub.8,
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.90Al.sub.10,
Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2,
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Al.sub.2,
Zr.sub.73Cu.sub.13Fe.sub.13Al.sub.1,
Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2,
Zr.sub.71Cu.sub.13Fe.sub.13Al.sub.3,
Zr.sub.72Cu.sub.12Fe.sub.12Al.sub.4,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.4,
Zr.sub.72Cu.sub.11Fe.sub.11Al.sub.6,
Zr.sub.72Cu.sub.11.5Fe.sub.11Al.sub.5.5,
Zr.sub.73Cu.sub.11Fe.sub.11Al.sub.5,
Zr.sub.71Cu.sub.11Fe.sub.11Al.sub.7,
Zr.sub.69Cu.sub.11Fe.sub.11Al.sub.9,
Zr.sub.70Cu.sub.10.5Fe.sub.10.5Al.sub.9,
Zr.sub.70Cu.sub.10Fe.sub.11Al.sub.9,
Zr.sub.70Cu.sub.11Fe.sub.10Al.sub.9,
Zr.sub.69Cu.sub.10Fe.sub.10Al.sub.11,
Zr.sub.69Cu.sub.10Fe.sub.11Al.sub.10,
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Sn.sub.2,
Zr.sub.72Cu.sub.13Fe.sub.13Sn.sub.2,
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Sn.sub.2,
(Zr.sub.79Cu.sub.21).sub.80(Fe.sub.40Al.sub.60).sub.20,
(Zr.sub.81Cu.sub.19).sub.80(Fe.sub.40Al.sub.60).sub.20,
(Zr.sub.83Cu.sub.17).sub.80(Fe.sub.40Al.sub.60).sub.20,
(Zr.sub.66Cu.sub.34).sub.80(Fe.sub.40Al.sub.60).sub.20,
(Zr.sub.64Cu.sub.36).sub.80(Fe.sub.40Al.sub.60).sub.20, and
(Zr.sub.62Cu.sub.38).sub.80(Fe.sub.40Al.sub.60).sub.20.
[0053] Another system having excellent glass-forming properties if
following the 80:20 concept is the Zr--Fe--Al--(Pd/Pt) system. This
system has the additional advantage that it is free of copper. In
other words, preferably A is Zr (zirconium), D is Fe (iron), E is
Al (aluminum), and G is one or both elements selected from Pd
(palladium) and Pt (platinum). Specifically, excellent glass
formers have been found if G is palladium, while a slightly
improved biocompatibility may result by partially or fully
replacing Pd by Pt. In this connection, it is to be noted that Pd
and Pt are known to occupy the same group of the periodic system of
elements, and have a similar (outer-shell) electronic structure,
almost the same Goldschmidt radius and a similar chemical
behaviour. It is therefore to be expected that Pd may be replaced
by Pt without dramatic changes in the glass-forming properties of
the alloys. In these systems, it has been found to be advantageous
if the atomic percentages of Fe and Al are substantially equal. A
range of good glass formers was found for 68.ltoreq.x.ltoreq.89 and
73.ltoreq.a.ltoreq.87. Particularly good results were achieved for
81.ltoreq.x.ltoreq.85, 80.ltoreq.a.ltoreq.83, and
65.ltoreq.y.ltoreq.80, in particular if G was Pd. The ratio of Al
to Pd/Pt is favourably chosen according to
40.ltoreq.y.ltoreq.82.
[0054] Generally, it is preferred that only small amounts of
additional elements are present, i.e., 0.ltoreq.b.ltoreq.2. In
particular, it is preferred that b=0, i.e., that there are
substantially at most trace amounts of additional elements present.
If such elements are present, i.e., if b>0, then Z is preferably
at least one element selected from the group consisting of Ti, Hf,
V, Nb, Y, Cr, Mo, Fe, Co, Sn, Zn, P, Pd, Ag, Au and Pt.
[0055] Expressed in another way, Zr--Fe--Al--Pd/Pt system has been
found to have good glass-forming properties if conforming to the
general formula
Zr.sub.i(Fe.sub.50+.epsilon.Al.sub.50-.epsilon.).sub.jX.sub.k
wherein X is one or both elements selected from Pd and Pt, a, b, c
and .epsilon. are zero or real positive numbers signifying atomic
percentages, and .epsilon..ltoreq.10, i.gtoreq.50, j.gtoreq.19,
k.gtoreq.0.5 and i+j+k=100. Excellent glass-forming abilities were
achieved in examples where X was Pd, while a slightly improved
biocompatibility may be expected by partially or fully replacing Pd
by Pt, which has very similar properties as Pd. Preferred ranges
are (independently or in combination) 62.ltoreq.i.ltoreq.77,
19.ltoreq.j.ltoreq.34, and .epsilon..ltoreq.2. Preferably,
.epsilon. is substantially zero, i.e., the atomic percentages of Fe
and Al are approximately equal. For the best glass formers which
have been found in this system, .epsilon. is substantially zero,
66.ltoreq.i.ltoreq.70, 25.ltoreq.j.ltoreq.29 and
4.ltoreq.k.ltoreq.7. The best glass formers of this system also
conform to the 80:20 concept as described above.
[0056] In particular, alloys being substantially represented by one
of the following formulas were found to be good glass formers: An
alloy represented by one of the formulas
Zr.sub.67Fe.sub.13.2Al.sub.13.2Pd.sub.6.6,
Zr.sub.69.7Fe.sub.12.95Al.sub.12.95Pd.sub.4.4,
Zr.sub.66.7Fe.sub.14.45Al.sub.1445Pd.sub.4.4,
Zr.sub.68.3Fe.sub.13.4Al.sub.13.4Pd.sub.4.9,
Zr.sub.65.4Fe.sub.14.85Al.sub.14.85Pd.sub.4.9,
Zr.sub.62.3Fe.sub.16.7Al.sub.16.7Pd.sub.4.3,
Zr.sub.59.2Fe.sub.18.3Al.sub.18.3Pd.sub.4.2,
Zr.sub.72Fe.sub.11.5Al.sub.1.5Pd.sub.5,
Zr.sub.73.4Fe.sub.10.9Al.sub.10.9Pd.sub.4.8,
Zr.sub.75.2Fe.sub.10.2Al.sub.10.2Pd.sub.4.3,
Zr.sub.77Fe.sub.9.5Al.sub.9.5Pd.sub.4,
Zr.sub.67.9Fe.sub.11.8Al.sub.1.8Pd.sub.8.5,
Zr.sub.65Fe.sub.11.4Al.sub.11.4Pd.sub.12.2,
Zr.sub.62.5Fe.sub.10.75Al.sub.10.75Pd.sub.16,
[0057] by the formula
Zr.sub.i(Fe.sub.50Al.sub.50).sub.30Pd.sub.70-i with
62.ltoreq.i.ltoreq.69.5, in particular by one of the formulas
Zr.sub.69.5Fe.sub.15Al.sub.15Pd.sub.0.5,
Zr.sub.69Fe.sub.15Al.sub.15Pd.sub.0.5,
Zr.sub.68Fe.sub.15Al.sub.15Pd.sub.2,
Zr.sub.67Fe.sub.15Al.sub.5Pd.sub.3,
Zr.sub.66Fe.sub.15Al.sub.15Pd.sub.4,
Zr.sub.65Fe.sub.15Al.sub.15Pd.sub.5,
Zr.sub.64Fe.sub.15Al.sub.15Pd.sub.6,
Zr.sub.63Fe.sub.15Al.sub.15Pd.sub.7,
Zr.sub.62Fe.sub.15Al.sub.15Pd.sub.8, or by one of the formulas
Zr.sub.71Fe.sub.12Al.sub.12Pd.sub.5,
Zr.sub.69Fe.sub.12.85Al.sub.12.85Pd.sub.5.3,
Zr.sub.66.8Fe.sub.13.7Al.sub.13.7Pd.sub.5.8,
Zr.sub.65Fe.sub.14.5Al.sub.14.5Pd.sub.6,
Zr.sub.61.9Fe.sub.16.2Al.sub.16.2Pd.sub.5.7,
Zr.sub.50Fe.sub.12Al.sub.12Pd.sub.26,
Zr.sub.53.2Fe.sub.12.6Al.sub.12.6Pd.sub.21.6,
Zr.sub.57.6Fe.sub.13.95Al.sub.13.95Pd.sub.14.5,
Zr.sub.60Fe.sub.14.3A.sub.14.3Pd.sub.11.4.
[0058] Preferably, the alloy has a structure comprising at least
one amorphous phase and at least one crystalline phase. The at
least one amorphous phase is preferably obtainable by cooling from
a temperature above the melting point of the alloy to a temperature
below the glass-transition temperature of the amorphous phase at a
cooling rate of 1000 K/s or less, i.e., the alloy is preferably a
bulk metallic glass.
[0059] The present invention is further directed at a method of
manufacture of the inventive alloys. The method comprises [0060]
preparing a melt of aliquots of A, D, E, G, and optionally Z, and
[0061] cooling the melt from a temperature above the melting point
to a temperature below the glass-transition temperature of the
amorphous phase with a cooling rate of 1000 K/s or less to obtain a
solidified material. Preferably, the method comprises casting of
the melt into a mold, in particular, a copper mold.
[0062] Alternatively, the inventive alloys may be produced by
mechanical alloying, as described, e.g., in (Eckert J, Mater. Sci.
Eng. A 226-228, 364 (1997): Mechanical alloying of highly
processable glassy alloys). Mechanical alloying means mechanical
processing of the alloy or its constituents in the solid state,
without passing through the liquid state. In particular, by
mechanical alloying of, e.g., a crystalline powder, an amorphous
metallic alloy may be obtained. Suitable mechanical alloying
methods include, but are not restricted to, ball milling. For
details, explicit reference is made to the teachings of the
above-mentioned Eckert paper.
[0063] The method may additionally comprise a step of processing
the alloy above the glass transition temperature, e.g., for
obtaining a mixed-phase material. In particular, the method may
comprise a step of heat-treating the solidified material for a few
minutes up to 15 hours at a temperature below the first
crystallization temperature or for a few seconds up to 2 hours at a
temperature above the first crystallization temperature. The first
crystallization temperature is the temperature of the first
exothermic feature in a DTA scan of the amorphous alloy when the
temperature is raised from the glass transition temperature. Heat
treatment at relatively low temperatures results in slow kinetics,
which is believed to lead to the formation of small crystals. For
details, see the description of the preferred embodiments
below.
[0064] For obtaining material with specific surface properties, the
alloy may be subjected to a microstructuring process as described,
e.g., in (Kundig A A, Cucinelli M, Uggowitzer P J, Dommann A,
Microelectr. Eng. 67, 405 (2003): Preparation of high aspect ratio
surface microstructures out of a Zr-based bulk metallic glass) or
in the patent application PCT/CH 2004/000401. The content of these
documents is incorporated herein by reference in its entirety.
Microstructuring may be achieved by casting the liquid alloy into a
mold having itself a microstructured surface. For details,
reference is made to the teachings of the above-mentioned Kundig et
al. paper and to PCT/CH 2004/000401. In a different embodiment, an
already solidified alloy is brought into a superplastic state, i.e,
into a state in which it can be easily shaped, by heating the alloy
to a temperature above the glass-transition temperature, and is
pressed onto a microstructured matrix. For details, reference is
made to PCT/CH 2004/000401. In an advantageous embodiment, the
microstructured mold resp. matrix is a silicon wafer which has been
structured by etching, as it is well known in the art. In yet
another embodiment, the liquid alloy is drawn into a system of
capillaries by the capillary effect and rapidly solidified within
the capillaries. For details, reference is made to the teachings of
the application PCT/CH 2004/000401.
[0065] The invention is also directed at the use of an inventive
alloy for the manufacture of an article destined to be brought into
contact with the human or animal body. In particular, the invention
is directed at the use of such an alloy for the manufacture of a
surgical instrument, a jewelry item, in particular a watch case, or
a prosthesis, in particular an endoprosthesis, specifically, a
so-called stent. A stent is an endoprosthesis for insertion into a
blood vessel, lining the inner surface of the vessel. Stents are
used in particular for ensuring sufficient blood flow through the
vessel, or for stabilizing the blood vessel to prevent aneurisms.
Other implants for which the inventive alloys can be used are in
the field of osteosynthesis, e.g., hip implants, artificial knees,
etc. The present invention is also directed at an endoprosthesis,
in particular a stent, manufactured from an inventive alloy.
[0066] The inventive alloys are particularly suited for such
biomedical applications due to their good biocompatibility, high
strength and high elasticity. In particular, the inventive alloys
of general composition Zr--Cu--Fe--Al or Zr--Fe--Al--Pd are well
suited for these purposes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] The invention will be described in more detail in connection
with an exemplary embodiment illustrated in the drawings, in
which
[0068] FIG. 1 shows a strongly simplified, schematic phase diagram
of a binary Zr--Fe alloy;
[0069] FIG. 2 shows a strongly simplified, schematic phase diagram
of a binary Cu--Zr alloy;
[0070] FIG. 3 shows a strongly simplified, schematic phase diagram
of a binary Fe--Al alloy together with the .epsilon.-phase;
[0071] FIG. 4 shows XRD patterns of as-cast 1 mm.times.1 cm.sup.2
alloys of composition Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12,
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12, and
Zr.sub.61.6Cu.sub.18.4Fe.sub.8Al.sub.12;
[0072] FIG. 5 shows SANS intensity data of as-cast 1 mm.times.1
cm.sup.2 alloys of composition
Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12,
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12, and
Zr.sub.61.6Cu.sub.184Fe.sub.8Al.sub.12 (wave number Q=4.pi. sin
.theta./.lamda., with .theta.=half the scattering angle and
.lamda.=wavelength of neutrons);
[0073] FIG. 6 shows DTA scans on samples of composition
Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12,
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12,
Zr.sub.61.6Cu.sub.18.4Fe.sub.8Al.sub.12, and
Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5, performed with a heating
rate of 20 K/min (T.sub.g=glass transition, T.sub.x1=first
crystallization temperature);
[0074] FIG. 7 shows a DTA scan of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12, performed with a heating rate
of 20 K/min;
[0075] FIG. 8 shows a photograph of cast samples of composition
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 together with a ruler
illustrating their actual size;
[0076] FIG. 9 shows XRD patterns of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 cast to cylindrical rods of
diameters 5, 7 and 8 mm, and to a plate of 1 mm thickness
(inset);
[0077] FIG. 10 shows DTA scans of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 cast to cylindrical rods of
diameters 5, 7 and 8 mm (heating rate 20 K/min);
[0078] FIG. 11 shows XRD patterns of
Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12 cast to a cone with outer
diameter 6 mm;
[0079] FIG. 12 shows a DTA scan of
Zr.sub.61.6Cu.sub.18.4Fe.sub.8Al.sub.12, performed with a heating
rate of 20 K/min;
[0080] FIG. 13 shows a SEM image showing the fracture surface of
glassy Zr.sub.61.6Cu.sub.18.4Fe.sub.8Al.sub.12;
[0081] FIG. 14 shows a room-temperature tensile stress-strain curve
of an as-cast cylindrical Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12
sample with a diameter of 5 mm;
[0082] FIG. 15 shows XRD patterns of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 in the as-prepared state and
after annealing for several hours at different temperatures;
[0083] FIG. 16 shows an XRD pattern (72 hours scan) of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 after annealing at 708 K for 12
h. The indexing shows an icosahedral phase with a lattice constant
of 4.76 .ANG.;
[0084] FIG. 17 shows DTA scans of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 in the as-prepared state and
after annealing for several hours at different temperatures, as
indicated in the figure (heating rate 20 K/min);
[0085] FIG. 18 shows SANS intensity data of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 obtained from in-situ SANS
measurements performed at a temperature of 708 K at different
times, as indicated in the figure;
[0086] FIG. 19 shows the time evolution of the particle size, (D,
of Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 using the Guinier
approximation;
[0087] FIG. 20 shows a pseudoternary mixing diagram;
[0088] FIG. 21 shows a DTA scan of the alloy
Zr.sub.68.3(Fe.sub.0.5Al.sub.0.5).sub.26.8Pd.sub.4.9 cast to a
thickness of 1 mm; and
[0089] FIG. 22 shows an X-ray diffraction pattern of the alloy
Zr.sub.68.3(Fe.sub.0.5Al.sub.0.5).sub.26.8Pd.sub.4.9 cast to a
thickness of 1 mm.
DETAILED DESCRIPTION OF THE INVENTION
[0090] Before describing specific examples of inventive alloys and
their characterization, the concept which led to the development of
the inventive alloys shall be described and exemplified.
[0091] Many binary alloys which form metallic glasses when
splat-cooled have the composition A.sub.80X.sub.20, where the
atomic radius of A is significantly larger than that of X. The good
glass-forming ability of such alloys with large size ratio has been
explained by topological effects. In the present invention, this
"80-20 concept" has been generalized to quaternary or
higher-component alloys and has been successfully applied for
developing Ni-free bulk metallic glasses. It has surprisingly been
found that alloys with exceptionally good glass-forming ability
result when following the principles laid down in claim 1. While it
is generally believed in the art that the presence of nickel
improves the glass-forming abilities of an alloy, making nickel an
essential component of many quaternary bulk glass-forming alloys,
and especially of Zr-based alloys, it has been found by the
inventors that nickel can be dispensed with by following the
principles of the present invention, while still alloys with
excellent glass-forming abilities are obtained.
[0092] While the invention is not limited to the particular
compositions described hereafter, the underlying principles of the
invention will in the following be exemplified for an alloy with
general composition Zr--Cu--Fe--Al. Of the four components present
in such an alloy, Zr is the element with the largest atomic size
(r=0.160 nm). With Fe (r=0.128 nm), it forms a deep eutectic
composition near 20 atomic percent (at. %) Fe. This is illustrated
in FIG. 1, which shows, in a highly schematic manner, part of the
phase diagram of a binary Zr--Fe alloy. The transitions between the
various solid phases have been omitted from the diagram for
clarity, such that the diagram shows only the expected liquidus
line, i.e., the liquidus temperature as a function of composition
(S=solid, L=liquid). A deep eutectic feature at 24 at. % Fe is
clearly visible. This deep eutectic can be qualitatively explained
by topological considerations.
[0093] Also Zr and Cu have eutectic compositions, one of which
occurs at 72.5% Zr, as illustrated in FIG. 2. This diagram shows,
again in a highly schematic fashion, the liquidus line. At various
compositions between 38.2 at. % and 72.5 at. %, several other
eutectics are expected.
[0094] The fourth component in the above-mentioned general
composition is Al. FIG. 3 shows, again in a highly schematic
fashion, part of the phase diagram of a binary Al--Fe alloy.
Several solid-solid transitions have been included in this diagram.
In particular, a high-temperature phase, the so-called
.epsilon.-phase 301, is present around the composition
Al.sub.6Fe.sub.4. This phase prevents a deep eutectic to be present
at around 60 at. % in the Al--Fe phase diagram, which would
otherwise be expected by extrapolation, as indicated by the dotted
line in FIG. 3. However, since the eutectics of Zr.sub.76Fe.sub.24
and Zr.sub.72.5Cu.sub.27.5 are already below 1000.degree. C., it is
likely that the high-temperature .epsilon.-phase, which spans a
temperature range between 1102 and 1232.degree. C., will not form
any more in the quaternary alloy.
[0095] These considerations led to the development of the
composition
(Zr.sub.72.5Cu.sub.27.5).sub.80(Fe.sub.40Al.sub.60).sub.20 as a
starting point for further investigations as detailed below. It was
found that this alloy, even without any further refinement of the
composition, exhibits excellent glass-forming ability. In addition,
the composition of the alloy was varied, and it was found that the
alloy retained its good glass-forming properties in a rather wide
range of compositions.
[0096] This shows that the "80-20 concept" can be successfully
generalized to quaternary alloys. The concept is believed to be
generally applicable and not to be restricted to the particular
Zr--Cu--Fe--Al system described above. In particular, the same
considerations may be applied to alloys which are based on Ti, Hf,
Nb, La, Pd or Pt as a main component. Instead of Cu, other elements
having a deep eutectic with the main component may be employed.
Particularly good candidates are Be, Ag and Au. The Fe component
may be replaced by one or more of the transition metals except Ni,
e.g. by Co. The Al component may be replaced by, e.g., Zr or one or
more of the metalloids.
[0097] In the following, examples of the manufacture and
characterization of inventive alloys will be given.
EXAMPLE 1
Preparation and Characterization of Amorphous
(Zr.sub.xCu.sub.100-x).sub.80(Fe.sub.40Al.sub.60).sub.20
Samples
[0098] Several Zr-based Ni-free alloys with composition
(Zr.sub.xCu.sub.100-x).sub.80(Fe.sub.40Al.sub.60).sub.20 were
prepared, where x=60, 62, 64, 66, 68, 72.5, 77, 79, 81, 83 and 85.
Ingots were prepared by arc melting the constituents (purity
>99.9%) in a titanium-gettered argon atmosphere (99.9999%
purity). Using an induction-heating coil, the ingots were remelted
in a quartz tube (vacuum .apprxeq.10.sup.-5 mbar) and injection
cast into a copper mold with high-purity argon. Samples were cast
into plates with a thickness of 0.5 mm, width of 5 mm and length of
10 mm. To determine the critical casting thickness, some samples
were additionally or alternatively cast into various rod- and
cone-like shapes with diameters ranging up to 10 mm. Furthermore,
several samples were made with a thickness of 1 mm and cross
section 1 cm.times.4 cm. The samples were then, where appropriate,
cut into various pieces of length 1 cm and investigated by X-ray
diffraction (XRD), small-angle neutron scattering (SANS),
differential thermal analysis (DTA) and/or hardness measurements.
XRD was performed with a Scintag XDS-2000x-ray diffractometer,
using a collimated monochromatic Cu K.sub..alpha. x-ray source. The
thermo-physical properties were investigated with a Netzsch Proteus
C550 DTA and SANS was performed at Paul Scherrer Institute,
Switzerland, using a wavelength of .lamda.=6 .ANG. and
sample-detector distances of 1.8 m, 6 m, and 20 m.
[0099] FIG. 4 shows XRD patterns of as-cast alloys of composition
Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12,
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12, and
Zr.sub.61.6Cu.sub.184Fe.sub.8Al.sub.2, i.e.,
(Zr.sub.xCu.sub.100-x).sub.80(Fe.sub.40Al.sub.60).sub.20 with x=68,
72.5, and 77. All samples show a typical XRD pattern of an
amorphous structure without any Bragg peaks. The amorphicity is
also confirmed by SANS. As can be seen in FIG. 5, the same samples
do not show any small-angle scattering over a wide Q-range, giving
evidence for a homogeneous, amorphous structure.
[0100] The DTA scans in FIG. 6, performed with a heating rate of 20
K/min, reveal for all three alloys a clear glass transition,
followed by an extended undercooled liquid region and an exothermic
crystallization peak. For comparison, the Ni-bearing alloy
Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5 was also investigated by
DTA. This result is also shown in FIG. 6 for comparison.
Additionally, the DTA scan in FIG. 7, which was performed over an
extended temperature range, shows the endothermic melting peak of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12.
[0101] Table 2 gives the characteristic values extracted from DTA
scans like those of FIGS. 6 and 7. The glass transition
temperatures T.sub.g were extracted from the onset of the
endothermic events in FIG. 6 (arrows pointing up) and the first
crystallization temperatures T.sub.x1 were obtained from the onset
of the exothermic peaks (arrows pointing down). The onset of
melting T.sub.m and the offset of melting T.sub.l were obtained
from scans like that in FIG. 7. The new Ni-free alloys show an
undercooled liquid region .DELTA.T.sub.x=T.sub.x1-T.sub.g of 78 to
86 K and a reduced glass transition temperature T.sub.g/T.sub.l
between 0.56 and 0.57. Table 2 lists the ratios of T.sub.g/T.sub.m
also, since in many publications this ratio has been used as the
reduced glass transition temperature. The value of T.sub.g/T.sub.m
is 0.59 to 0.62 for the new Ni-free alloys and thus significantly
larger than that of Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5.
TABLE-US-00002 TABLE 2 Glass transition temperature T.sub.g, first
crystallization temperature T.sub.x1, undercooled liquid region
.DELTA.T.sub.x = T.sub.x1 - T.sub.g, liquidus temperature (offset
of melting) T.sub.l, reduced glass transition temperature
T.sub.g/T.sub.l, onset of melting T.sub.m, and ratio
T.sub.g/T.sub.m for three Ni-free alloys and for the Ni-bearing
alloy Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5, obtained by DTA
using a heating rate of 20 K/min. Alloy T.sub.g (K) T.sub.x1 (K)
.DELTA.T.sub.x (K) T.sub.l (K) T.sub.g/T.sub.l T.sub.m (K)
T.sub.g/T.sub.m
(Zr.sub.68Cu.sub.32).sub.80(Fe.sub.40Al.sub.60).sub.20 =
Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12 687 773 86 1234 0.556 1098
0.62 (Zr.sub.72.5Cu.sub.27.5).sub.80(Fe.sub.40Al.sub.60).sub.20 =
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 677 761 86 1192 0.568 1130 0.60
(Zr.sub.77Cu.sub.23).sub.80(Fe.sub.40Al.sub.60).sub.20 =
Zr.sub.61.6Cu.sub.18.4Fe.sub.8Al.sub.12 670 743 78 1189 0.563 1133
0.59 Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5 630 742 112 1165 0.540
1098 0.573
[0102] Table 3 shows the Vickers hardness HV of the Ni-free alloys
that was measured with a load of 500 g. From these measurements,
one obtains an estimated yield strength of 1.56 to 1.68 GPa, using
the scaling relation .sigma..sub.y=3 HV. Indeed, detailed tensile
tests show a yield strength of .sigma..sub.y=1.71 GPa and an
elastic limit of 2.25% for the alloy
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12.
TABLE-US-00003 TABLE 3 Vickers hardness HV (measured with a load of
500 g) and estimated yield strength .sigma..sub.y of the Ni-free
alloys. Alloy HV (kg/mm.sup.2) .sigma..sub.y (GPa)
Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12 563 1.68
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 542 1.62
Zr.sub.61.6Cu.sub.18.4Fe.sub.8Al.sub.12 521 1.56
[0103] Detailed casting experiments were performed on these Ni-free
alloys, and these were compared with the critical casting
thicknesses of Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5 and
Zr.sub.52.5Ti.sub.5Cu.sub.17.9Ni.sub.14.6Al.sub.10 (Vit105.TM.)
under equal experimental conditions. The alloy
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 (x=72.5) could be cast into a
fully amorphous state up to a rod-diameter of 7 mm. FIG. 8 shows
some examples of such cast samples. These examples prove that
indeed articles to be used in real-life applications can be
manufactured from the inventive alloys. The wedge-shaped sample is
fully amorphous up to a diameter of 7 mm.
[0104] FIG. 9 shows X-ray diffraction patterns of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 cast to cylindrical rods of
diameters 5, 7 and 8 mm, and to a plate of 1 mm thickness (inset).
No Bragg peaks are apparent either in the 5 mm rod sample or in the
1 mm plate, while only very weak Bragg peaks seem to arise in the 7
mm rod sample. In contrast, a clear crystalline component is
present in the 8 mm rod sample, as apparent from the strong Bragg
peaks from that sample.
[0105] These findings are consistent with the DTA scans shown in
FIG. 10, which were performed on the 5 mm, 7 mm and 8 mm rod
samples. Clear exothermic crystallization peaks are visible for the
5 mm and 7 mm samples, while no such peak is observed for the 8 mm
sample.
[0106] Likewise, the alloys with x=68, 77 could be cast in rod
shape with a diameter of at least 5 mm with an amorphous
structure.
[0107] FIG. 11 shows XRD patterns of
Zr.sub.54.4Cu.sub.256Fe.sub.8Al.sub.12 (x=68) cast to a cone with a
maximum outer diameter of 6 mm. The XRD scans were performed on 0.5
mm thick plates cut perpendicularly to the longitudinal axis of the
cone. The average diameter of the corresponding plates is given in
the figure. The XRD patterns of the plates with diameters of 5 mm
or less show typical amorphous structures, while the plate with 6
mm diameter appears to show some Bragg peaks indicating a small
volume fraction of crystals in the amorphous matrix. This is
perfectly consistent with the findings for rods with uniform
diameter.
[0108] FIG. 12 shows a DTA scan of
Zr.sub.616Cu.sub.184Fe.sub.8Al.sub.2 (x=77) performed with a
heating rate of 20 K/min. Clear glass-transition, crystallization
and melting features are observed. FIG. 13 shows a SEM image,
showing the fracture surface of glassy
Zr.sub.61.6Cu.sub.184Fe.sub.8A.sub.12 (x=77) which is typical for
an amorphous glass. These findings demonstrate that also
Zr.sub.61.6Cu.sub.184Fe.sub.8Al.sub.12 (x=77) is an excellent bulk
metallic glass-former.
[0109] In summary, of the three alloys with x=68, 72.5 and 77, the
alloy Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 (x=72.5) has the greatest
glass-forming ability, comparable to that of Vit105.TM., followed
by Zr.sub.61.6Cu.sub.184Fe.sub.8Al.sub.12 and
Zr.sub.54.4Cu.sub.25.6Fe.sub.8Al.sub.12, followed by the prior-art
alloy Zr.sub.65Al.sub.7.5Ni.sub.10Cu.sub.17.5. These experimental
results agree well with the Turnbull theory (D. Turnbull, Contemp.
Phys. 10, 473 (1969), F. Spaepen and D. Turnbull, Proc. Sec. Int.
Conf. on Rapidly Quenched Metals (Cambridge, Mass.: M.I.T. Press,
1976), pp. 205-229), which predicts that the best glass-forming
ability is obtained for the alloy with the highest ratio of
T.sub.g/T.sub.l (see Table 2).
[0110] FIG. 14 shows the tensile stress-strain curves of an as-cast
cylindrical Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 (x=72.5) sample
with a diameter of 5 mm. Hooke's law is well fulfilled for strain
up to 2.25%. The excellent elasticity and high tensile strength as
visible from this diagram are just one example of the excellent
mechanical properties of the inventive alloys.
[0111] The alloys with x=60, 62, 64, 66, 79, 81, 83 and 85 were
also investigated by selected similar methods. It was found that
the alloys with x between 62 and 81 were amorphous when cast to a
thickness of 0.5 mm, the alloy with x=60 was crystalline, the alloy
with x=83 was partially amorphous, and the alloy with x=85 was
crystalline when cast to a thickness of 0.5 mm.
[0112] It is apparent from this example that the composition of the
material can be varied within rather broad limits without losing
the good glass-forming properties. Specifically, it may be expected
that a variation in the composition with respect to the other
constituent elements, in particular a moderate variation of the
numbers a and y, will not alter the glass-forming ability
dramatically. Furthermore, it is expected that addition of a small
amount of an additional component will not negatively affect the
glass-forming ability or even possibly improve the glass-forming
ability of the inventive materials, while possibly improving
certain desired properties.
EXAMPLE 2
Preparation of Mixed-Phase Samples
[0113] Samples with a mixed-phase structure were prepared as
follows: Fully amorphous samples of
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 were prepared as in Example 1.
The samples were subjected to heat treatment (annealing) at various
temperatures for 12 hours. XRD patterns and DTA scans were recorded
for the heat-treated samples. FIG. 15 shows XRD patterns of the
samples in the as-prepared state (bottom trace) and after
annealing. The XRD patterns show typical amorphous structures up to
an annealing temperature of 683 K. At higher annealing
temperatures, however, clear Bragg peaks arising from an
icosahedral phase (I.P.) can be observed. At still higher
temperatures, peaks which are typical for a Zr.sub.2Fe structure
are observed. FIG. 16 shows the XRD pattern of the sample annealed
at 708 K for 12 hours in more detail. The indexing indicates the
presence of an icosahedral phase with a lattice constant of 0.476
nm. FIG. 17 shows DTA scans of the same samples as in FIG. 15,
which are consistent with the development of a structure with both
glassy and crystalline components.
[0114] In order to better characterize the structure after
annealing, in-situ small-angle neutron scattering (SANS)
experiments were performed during annealing at a temperature of 708
K of a Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 sample which was
initially fully amorphous. The results are shown in FIG. 18, for
total annealing times as indicated. The results show that
crystalline regions develop in the initially fully amorphous
sample, with typical sizes on the order of only nanometers. These
data were analyzed by applying the Guinier approximation. FIG. 19
shows the time evolution of the particle size, (D, in this
approximation. This clearly demonstrates the emergence of
nanocrystals within the glassy matrix. It is believed that the
generation of such nanocrystals is fostered by keeping the
annealing temperature only slightly above the laboratory glass
transition temperature, in particular, in a range between 0 and 150
K above the laboratory glass transition temperature. The laboratory
glass transition temperature is to be understood as the glass
transition temperature as determined by DSC (differential scanning
calorimetry) with a typical heating rate of 20 K/min. Higher
annealing temperatures often lead to the precipitation of larger
crystals; for example in the range of 0.1-20 .mu.m.
[0115] Such mixed-phase materials exhibit somewhat different
mechanical properties than a fully glassy material. In particular,
ductility is often improved, which can be rationalized by the fact
that shear bands which develop as a result of shear forces during
forming and which might lead to breaking of the material are
disrupted by the crystals. These properties may be particularly
beneficial in applications where the material must be shaped or
deformed during manufacture of the end product.
EXAMPLE 3
Variations of Composition
[0116] Samples in a widely varying range of compositions were
prepared and investigated. The compositions of the following Tables
proved to be at least partially amorphous when cast to a plate with
thickness of 1 mm (Table 4), 0.5 mm (table 5), or 0.2 mm (Table
6):
TABLE-US-00004 TABLE 4 Alloys having a partially or fully amorphous
structure when cast to a thickness of 1 mm.
(Zr.sub.95Ti.sub.5).sub.72Cu.sub.13Fe.sub.13Al.sub.2
Zr.sub.72Cu.sub.12Fe.sub.12Al.sub.4
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.3Sn.sub.1
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.4
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Cr.sub.2
Zr.sub.72Cu.sub.11Fe.sub.11Al.sub.6
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Nb.sub.2
Zr.sub.72Cu.sub.11.5Fe.sub.11Al.sub.5.5
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Zn.sub.2
Zr.sub.73Cu.sub.11Fe.sub.11Al.sub.5
(Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2).sub.98Mo.sub.2
Zr.sub.71Cu.sub.11Fe.sub.11Al.sub.7
(Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2).sub.98P.sub.2
Zr.sub.69Cu.sub.11Fe.sub.11Al.sub.9
(Zr.sub.95Hf.sub.5).sub.72Cu.sub.13Fe.sub.13Al.sub.2
Zr.sub.70Cu.sub.10.5Fe.sub.10.5Al.sub.9
Zr.sub.70Cu.sub.11Fe.sub.11Al.sub.8
Zr.sub.70Cu.sub.10Fe.sub.11Al.sub.9
Zr.sub.71Cu.sub.11Fe.sub.10Al.sub.8
Zr.sub.70Cu.sub.11Fe.sub.10Al.sub.9
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.90Al.sub.10
Zr.sub.69Cu.sub.10Fe.sub.10Al.sub.11
Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2
Zr.sub.69Cu.sub.10Fe.sub.11Al.sub.10
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Al.sub.2
Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Sn.sub.2
Zr.sub.73Cu.sub.13Fe.sub.13Al.sub.1
Zr.sub.72Cu.sub.13Fe.sub.13Sn.sub.2
Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Sn.sub.2
Zr.sub.71Cu.sub.13Fe.sub.13Al.sub.3
TABLE-US-00005 TABLE 5 Alloys with a partially or fully amorphous
structure when cast to a thickness of 0.5 mm.
(Zr.sub.79Cu.sub.21).sub.80(Fe.sub.40Al.sub.60).sub.20
(Zr.sub.66Cu.sub.34).sub.80(Fe.sub.40Al.sub.60).sub.20
(Zr.sub.81Cu.sub.19).sub.80(Fe.sub.40Al.sub.60).sub.20
(Zr.sub.64Cu.sub.36).sub.80(Fe.sub.40Al.sub.60).sub.20
(Zr.sub.83Cu.sub.17).sub.80(Fe.sub.40Al.sub.60).sub.20
(Zr.sub.62Cu.sub.38).sub.80(Fe.sub.40Al.sub.60).sub.20
TABLE-US-00006 TABLE 6 Alloys with a partially or fully amorphous
structure when cast to a thickness of 0.2 mm.
Zr.sub.72Cu.sub.13Fe.sub.13Al.sub.2
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Ge.sub.2
Zr.sub.72Cu.sub.13Fe.sub.13Sn.sub.2
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Sn.sub.2
[0117] For comparison, the alloys in Table 7, while being binary,
ternary or Ni-containing alloys, were also investigated and
developed an at least partially amorphous structure when cast to a
thickness of 0.2 mm.
TABLE-US-00007 TABLE 7 Comparative listing of other alloys with a
partially or fully amorphous structure when cast to a thickness of
0.2 mm. Zr.sub.70Cu.sub.13Fe.sub.13Al.sub.2Ni.sub.2
Zr.sub.76Fe.sub.20Al.sub.4
Zr.sub.70Cu.sub.6.5Fe.sub.13Al.sub.2Ni.sub.6.5
Zr.sub.70Fe.sub.27Nb.sub.3
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.98Ni.sub.2
Zr.sub.68Fe.sub.27Nb.sub.5
(Zr.sub.74Cu.sub.13Fe.sub.13).sub.96Ni.sub.4
Zr.sub.66Fe.sub.28Nb.sub.6 Zr.sub.76Fe.sub.24
Zr.sub.68Fe.sub.25Nb.sub.7 Zr.sub.75Fe.sub.23Sn.sub.2
Zr.sub.75Fe.sub.24Ni.sub.1 Zr.sub.70Fe.sub.28Nb.sub.2
Zr.sub.75.5Fe.sub.23.5Ge.sub.1 Zr.sub.76Fe.sub.22Sn.sub.2
Zr.sub.70Fe.sub.28Nb.sub.1Sn.sub.1 Zr.sub.76Fe.sub.23Sn.sub.1
Zr.sub.75.5Fe.sub.23.5Si.sub.1 Zr.sub.75Fe.sub.24Sn.sub.1
Zr.sub.77Fe.sub.23 Zr.sub.74Fe.sub.24Sn.sub.2
Zr.sub.69Fe.sub.30Nb.sub.1 Zr.sub.73.72Fe.sub.23.28Sn.sub.3
Zr.sub.68Fe.sub.31Nb.sub.1 Zr.sub.73Fe.sub.24Sn.sub.3
Zr.sub.75Fe.sub.25 Zr.sub.76Fe.sub.21Sn.sub.3
Zr.sub.68Fe.sub.26Nb.sub.6 Zr.sub.69Fe.sub.29Nb.sub.1Sn.sub.1
Zr.sub.69Fe.sub.27Nb.sub.4 Zr.sub.75.5Fe.sub.23.5Al.sub.1
Zr.sub.68Fe.sub.28Nb.sub.4 Zr.sub.76Fe.sub.23Al.sub.1
Zr.sub.71Fe.sub.26Nb.sub.3 Zr.sub.72Fe.sub.28
Zr.sub.70Fe.sub.28Nb.sub.2 Zr.sub.74Fe.sub.26
Zr.sub.70Fe.sub.26Nb.sub.4 Zr.sub.70Fe.sub.29Nb.sub.1
Zr.sub.74Fe.sub.13Cu.sub.13 Zr.sub.72Fe.sub.27Nb.sub.1
Zr.sub.71Fe.sub.16Cu.sub.13 Zr.sub.74Fe.sub.25Nb.sub.1
Zr.sub.74Fe.sub.13Cu.sub.13 Zr.sub.73Fe.sub.25Nb.sub.2
Zr.sub.76Fe.sub.23Cu.sub.1 Zr.sub.76Ni.sub.24
Zr.sub.76Fe.sub.12Cu.sub.12 Zr.sub.60Fe.sub.20Ni.sub.20
Zr.sub.73.5Fe.sub.21.5Cu.sub.5 Zr.sub.75.5Fe.sub.23.5Si.sub.1
Zr.sub.72Fe.sub.14Cu.sub.14 Zr.sub.76Fe.sub.16Al.sub.8
[0118] Specifically, this list shows that also ternary, nickel-free
alloys can be reasonably good glass-formers, especially if composed
according to the "80:20 scheme". Specifically, the list shows that
ternary alloys of composition
(Zr.sub.xD.sub.100-x).sub.aFe.sub.100-a, where the number a is in
the range from about 70 to about 90, in particular approximately
80, are good glass formers. Here D is advantageously Cu, Nb, Al or
Sn.
[0119] The alloys in Table 8 have also been prepared and were found
to be fully amorphous when subjected to splat cooling to a
thickness of 20 micrometers at high cooling rates of approximately
10.sup.6 K/s. These alloys may be regarded as candidate materials
for bulk metallic glasses, while casting experiments will be
necessary to verify which of these are indeed bulk metallic
glasses.
TABLE-US-00008 TABLE 8 Alloys having a fully amorphous structure
when splat-cooled. All numbers are atomic percentages.
Zr.sub.58Cu.sub.22Fe.sub.18Al.sub.2
(Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12).sub.98Nb.sub.2
Zr.sub.58Cu.sub.22Fe.sub.16Al.sub.4
(Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12).sub.98Ta.sub.2
Zr.sub.58Cu.sub.22Fe.sub.14Al.sub.6
(Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12).sub.98Cr.sub.2
Zr.sub.58Cu.sub.22Fe.sub.12Al.sub.8
(Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12).sub.98Co.sub.2
Zr.sub.58Cu.sub.22Fe.sub.10Al.sub.10
(Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12).sub.98Mo.sub.2
Zr.sub.58Cu.sub.22Fe.sub.6Al.sub.14
(Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12).sub.98Sn.sub.2
Zr.sub.58Cu.sub.22Fe.sub.4Al.sub.16
Zr.sub.58Cu.sub.22Fe.sub.6Al.sub.12Nb.sub.2
Zr.sub.58Cu.sub.22Fe.sub.2Al.sub.18
(Zr.sub.72.5Cu.sub.27.5).sub.76Fe.sub.8Al.sub.12Nb.sub.4
Zr.sub.62.4Co.sub.17.6Fe.sub.8Al.sub.12
Zr.sub.58Cu.sub.22Fe.sub.4Al.sub.12Nb.sub.4
Zr.sub.65Al.sub.15Fe.sub.15Nb.sub.5
Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.10Nb.sub.2
Zr.sub.58Cu.sub.22Co.sub.8Al.sub.12
(Zr.sub.72.5Cu.sub.27.5).sub.78Fe.sub.8Al.sub.12Co.sub.2
Zr.sub.68Al.sub.15Fe.sub.15Nb.sub.2
(Zr.sub.72.5Cu.sub.27.5).sub.78Fe.sub.8Al.sub.12Cr.sub.2
(Zr.sub.72.5Cu.sub.27.5).sub.78Fe.sub.8Al.sub.12Nb.sub.2
(Zr.sub.72.5Cu.sub.27.5).sub.78Fe.sub.8Al.sub.12Ta.sub.2
(Zr.sub.72.5Cu.sub.27.5).sub.78Fe.sub.8Al.sub.12Sn.sub.2
(Zr.sub.72.5Cu.sub.27.5).sub.78Fe.sub.8Al.sub.12Mo.sub.2
(Zr.sub.72.5Cu.sub.27.5).sub.80Fe.sub.6Al.sub.12Nb.sub.2
(Zr.sub.72.5Cu.sub.27.5).sub.76Fe.sub.8Al.sub.12Sn.sub.4
[0120] Also the ternary and binary alloys in Table 9 were found to
be fully amorphous when splat-cooled. These are listed for
comparative purposes.
TABLE-US-00009 TABLE 9 Ternary and binary alloys having a fully
amorphous structure when splat-cooled. Zr.sub.60Fe.sub.15Al.sub.15
Zr.sub.58Cu.sub.22Fe.sub.20 Zr.sub.75Fe.sub.23Sn.sub.2
Zr.sub.58Cu.sub.22Al.sub.20 Zr.sub.70Fe.sub.28Nb.sub.2
Nb.sub.60Co.sub.40
[0121] The wide range of alloys according to the present invention
which were investigated in these experiments clearly demonstrate
that wide variations of composition are possible without losing the
glass-forming properties of the alloys.
EXAMPLE 4
Biocompatibility Tests
[0122] As an example of the newly developed Ni-free alloys, the
cytotoxicity of the alloy Zr.sub.58Cu.sub.22Fe.sub.8Al.sub.12 was
determined. The effect of surface modification by passivation in
diluted nitric acid was also investigated.
[0123] Surface analysis using XPS showed that a natural oxide
layer, composed almost exclusively of zirconium oxide, forms on the
surface on this glass and that it has a thickness of 7-8 nm. This
layer protects mouse fibroblasts used in the study from the toxic
metals, especially Cu, present in the bulk, allowing for good cell
growth on the alloy. The results of indirect tests demonstrate that
this layer is stable in PBS (phosphate-buffered solution) for many
weeks, and that no toxic effects due to high ion concentrations
diffusing into the medium occur.
[0124] The thickness of the zirconia layer is only slightly
increased by passivation with nitric acid. However, this treatment
clearly improves the quality of the surface layer, which leads to
increased corrosion resistance and lower diffusion of bulk elements
into the medium, and thus to improved biocompatibility. After this
passivation treatment, the alloy shows cell growth comparable to
that on polystyrene, which is used here as a negative control.
[0125] In conclusion, the cytotoxic properties of the metallic
glasses of the present invention are very promising and thus
indicate a very good biocompatibility.
EXAMPLE 5
Cu- and Ni-Free Alloys
[0126] As Cu may nevertheless be problematic in many medical
applications, a search for Cu-free alloys was conducted. Starting
from the Zr--Cu--Fe--Al bulk metallic glasses of the previous
examples, Pd (palladium) was found to be promising in replacing Cu
in such alloys. For a systematic search for bulk metallic glasses,
alloys belonging to the pseudoternary
Zr--(Fe.sub.0.5Al.sub.0.5)--Pd system were screened. Initially, the
amount of Pd was varied between 0% and approximately 22% in a
pseudotemary Zr--(Fe.sub.0.5A.sub.0.5)--Pd system along the
(Fe.sub.0.5Al.sub.0.5).sub.30 line, while choosing the ratio of the
sums of the atomic percentages of Zr and Fe on the one hand and Al
and Pd on the other hand roughly according to the 80:20 concept. In
this manner, a number of initial alloy compositions with favorable
glass-forming properties were identified. The composition was then
varied around these initial compositions in an iterative manner
within the range of pseudoternary Zr--(Fe.sub.0.5Al.sub.0.5)--Pd
compositions.
[0127] The following tables summarize the results found in these
investigations.
TABLE-US-00010 TABLE 10 Cu-free Zr--Fe--Al--Pd alloys having a
partially or fully amorphous structure when cast to a thickness of
3 mm Zr.sub.67Fe.sub.13.2Al.sub.13.2Pd.sub.6.6
Zr.sub.69.7Fe.sub.12.95Al.sub.12.95Pd.sub.4.4
Zr.sub.66.7Fe.sub.14.45Al.sub.14.45Pd.sub.4.4
TABLE-US-00011 TABLE 11 Cu-free Zr--Fe--Al--Pd alloys having a
partially or fully amorphous structure when cast to a thickness of
1 mm Zr.sub.68.3Fe.sub.13.4Al.sub.13.4Pd.sub.4.9
Zr.sub.65.4Fe.sub.14.85Al.sub.14.85Pd.sub.4.9
Zr.sub.62.3Fe.sub.16.7Al.sub.16.7Pd.sub.4.3
Zr.sub.59.2Fe.sub.18.3Al.sub.18.3Pd.sub.4.2
Zr.sub.72Fe.sub.11.5Al.sub.11.5Pd.sub.5
Zr.sub.73.4Fe.sub.10.9Al.sub.10.9Pd.sub.4.8
Zr.sub.75.2Fe.sub.10.2Al.sub.10.2Pd.sub.4.3
Zr.sub.77Fe.sub.9.5Al.sub.9.5Pd.sub.4Zr.sub.67.9
Fe.sub.11.8Al.sub.11.8Pd.sub.8.5
Zr.sub.65Fe.sub.11.4Al.sub.11.4Pd.sub.12.2
Zr.sub.62.5Fe.sub.10.75Al.sub.10.75Pd.sub.16
TABLE-US-00012 TABLE 12 Cu-free Zr--Fe--Al--Pd alloys having a
partially or fully amorphous structure when cast to a thickness of
0.5 mm Zr.sub.69.5Fe.sub.15Al.sub.15Pd.sub.0.5
Zr.sub.69Fe.sub.15Al.sub.15Pd.sub.1
Zr.sub.68Fe.sub.15Al.sub.15Pd.sub.2
Zr.sub.67Fe.sub.15Al.sub.15Pd.sub.3
Zr.sub.66Fe.sub.15Al.sub.15Pd.sub.4
Zr.sub.65Fe.sub.15Al.sub.15Pd.sub.5
Zr.sub.64Fe.sub.15Al.sub.15Pd.sub.6
Zr.sub.63Fe.sub.15Al.sub.15Pd.sub.7
Zr.sub.62Fe.sub.15Al.sub.15Pd.sub.8
Zr.sub.71Fe.sub.12Al.sub.12Pd.sub.5
Zr.sub.69Fe.sub.12.85Al.sub.12.85Pd.sub.5.3
Zr.sub.66.8Fe.sub.13.7Al.sub.13.7Pd.sub.5.8
Zr.sub.65Fe.sub.14.5Al.sub.14.5Pd.sub.6
Zr.sub.61.9Fe.sub.16.2Al.sub.16.2Pd.sub.5.7
Zr.sub.50Fe.sub.12Al.sub.12Pd.sub.26
Zr.sub.53.2Fe.sub.12.6Al.sub.12.6Pd.sub.21.6
Zr.sub.57.6Fe.sub.13.95Al.sub.13.95Pd.sub.14.5
Zr.sub.60Fe.sub.14.3Al.sub.14.3Pd.sub.11.4
[0128] The examples of Tables 10, 11 and 12 are indicated by black
squares in the pseudotemary mixing diagram of FIG. 20. From this
diagram, it may be appreciated that alloys containing at least 50
at.-% Zr, at least 0.5 at.-% Pd and at least 19 at.-% of a mixture
of Fe and Al in approximately equal atomic proportions are expected
to be good glass formers. This is even more true for alloys of this
type containing at least approximately 59 at.-% of Zr, up to
approximately 36 at.-% of the Fe--Al mixture and/or at least
approximately 4 at.-% Pd. In particular, all alloys in the
trapezoidal area indicated in FIG. 20 may reasonably be expected to
be good glass formers. Small variations of the relative proportions
between Fe and Al within a few percent, say, between 60:40 and
40:60 or better between 55:45 and 45:55, are not expected to
strongly affect the glass-forming ability.
[0129] Notably, all alloys in Tables 10 and 11 and most of the
alloys in Table 12 correspond to the 80:20 principle in the
following sense: The ratio of the sum of the atomic percentages of
Zr and Fe to the sum of the atomic percentages of Al and Pd is
approximately 80:20. In the examples of Tables 10 and 11, the ratio
of the atomic content of Zr+Fe to that of Al+Pd varies between
approximately 73:27 and approximately 87:13. The 80:20 principle is
fulfilled to an excellent degree for the alloys in Table 10, i.e.,
for those alloy compositions which have been found to have the
highest critical casting thickness. There, the corresponding ratio
varies between approximately 80:20 and approximately 83:17.
[0130] Concerning the variations within the Zr--Fe subsystem, in
the preferred compositions of Tables 10 and 11, the ratio of the
atomic percentage of Zr to the atomic percentage of Fe is in the
range between approximately 76:24 and approximately 89:11. It
appears that this is a preferred range. In particular, in the
examples of Table 10, this ratio varies between approximately 81:19
and approximately 85:15. In contrast, the ratio between Al and Pd
may apparently vary in a wider range without detrimental effects on
the glass-forming ability of the alloy. In the examples of Tables
10 and 11, the ratio of the atomic percentage of Al to the atomic
percentage of Pd varies between approximately 40:60 and
approximately 82:18. In particular, in the examples of Table 10,
this ratio varies between approximately 65:35 and approximately
78:22.
[0131] An even improved biocompatibility may be achieved by
replacing Pd partly or fully by Pt (platinum) in the above
examples. Pt (platinum) has very similar properties as Pd, such as
outer electronic structure, in consequence, similar chemical
properties, and almost the same Goldschmidt radius. Therefore, a
partial or full replacement of Pd by Pt will not strongly alter the
mechanical properties of the alloy or its glass-forming
ability.
[0132] As an example of measurements performed on the Cu-free
alloys, FIG. 21 shows a DTA scan and FIG. 22 shows an X-ray
diffraction pattern, using a CoK.sub..alpha. X-ray source, of the
alloy Zr.sub.68.3(Fe.sub.0.5Al.sub.0.5).sub.26.8Pd.sub.4.9 cast to
a thickness of 1 mm. The DTA scan exhibits a clear glass transition
and a second crystallization event, while the X-ray diffraction
pattern exhibits the broad hump indicative of an amorphous
material.
[0133] Also the following Cu-free alloys were found to be at least
partially amorphous when cast to a thickness of 0.5 mm:
Zr.sub.69Fe.sub.15Al.sub.15Y.sub.1,
Zr.sub.68.5Fe.sub.15Al.sub.15Y.sub.1.5.
[0134] In these examples, Pd has been replaced by Y (yttrium).
[0135] A further example of an alloy found to be at least partially
amorphous when cast to a thickness to 0.2 mm is
Zr.sub.70Fe.sub.28Nb.sub.1Sn.sub.1.
[0136] It is to be understood that the above examples are only
provided for illustrative purposes and that the invention is in no
way limited to these examples.
LIST OF ABBREVIATIONS, SYMBOLS AND REFERENCE SIGNS
[0137] at. % atomic percent [0138] XRD X-ray diffraction [0139] SEM
scanning electron microscopy [0140] SANS small-angle neutron
scattering [0141] DTA differential thermal analysis [0142] DSC
differential scanning calorimetry [0143] T.sub.g glass transition
temperature [0144] T.sub.x1 first crystallization temperature
[0145] .DELTA.T.sub.x undercooled liquid region [0146] T.sub.l
offset of melting (liquidus temperature) [0147] T.sub.m onset of
melting [0148] T temperature [0149] .sigma..sub.y yield strength
[0150] HV Vickers hardness [0151] S solid [0152] L liquid [0153]
2.theta. scattering angle [0154] Int intensity [0155] a.u.
arbitrary units [0156] Q wave number [0157] S(Q) scattering
intensity [0158] q heat transfer [0159] cps counts per second
[0160] .sigma. tensile stress [0161] .epsilon. strain [0162] I.P.
icosahedral phase [0163] ann. annealed [0164] .PHI. particle
size
* * * * *