U.S. patent application number 17/433972 was filed with the patent office on 2022-05-26 for shaped parts having uniform mechanical properties, comprising solid metallic glass.
The applicant listed for this patent is HERAEUS AMLOY TECHNOLOGIES GMBH. Invention is credited to Ralf Busch, Eugen Milke, Martin Schlott, Moritz Stolpe.
Application Number | 20220161312 17/433972 |
Document ID | / |
Family ID | |
Filed Date | 2022-05-26 |
United States Patent
Application |
20220161312 |
Kind Code |
A1 |
Stolpe; Moritz ; et
al. |
May 26, 2022 |
SHAPED PARTS HAVING UNIFORM MECHANICAL PROPERTIES, COMPRISING SOLID
METALLIC GLASS
Abstract
The invention relates to a method for producing a shaped part
comprising a solid metallic glass. According to the method, a
preform is shaped below the glass transition temperature and is
then heated to a temperature above the glass transition
temperature.
Inventors: |
Stolpe; Moritz; (Hanau,
DE) ; Schlott; Martin; (Hanau, DE) ; Milke;
Eugen; (Karlstein, DE) ; Busch; Ralf;
(Saarbrucken, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HERAEUS AMLOY TECHNOLOGIES GMBH |
Hanau |
|
DE |
|
|
Appl. No.: |
17/433972 |
Filed: |
February 24, 2020 |
PCT Filed: |
February 24, 2020 |
PCT NO: |
PCT/EP2020/054719 |
371 Date: |
August 25, 2021 |
International
Class: |
B21J 1/06 20060101
B21J001/06; B21J 1/00 20060101 B21J001/00; C22C 45/10 20060101
C22C045/10 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 12, 2019 |
EP |
19162224.0 |
Claims
1) A method for the production of a shaped part comprising a bulk
metallic glass, characterized by the following steps: a. providing
a preform comprising a bulk metallic glass, b. repeated plastic
deformation of the preform comprising a bulk metallic glass in
several steps with a deformation .DELTA.d, wherein the temperature
T.sub.1 of the preform is below the glass transition temperature of
the bulk metallic glass, and c. heating the preform to a
temperature T.sub.2 above the glass transition temperature and
below the crystallization temperature to obtain a shaped part
comprising a bulk metallic glass, wherein the plastic deformation
in step b) takes place in such a way that the deformation .DELTA.d
increases with an increasing number of steps.
2) The method according to claim 1, wherein the deformation
.DELTA.d per deformation step is at least 1 .mu.m, particularly at
least 5 .mu.m and at most 100 .mu.m, particularly at most 50
.mu.m.
3) The method according to claim 1, wherein the shaped part is
heated in step c) in such a way that the flexural strength of the
shaped part is not more than 15% below the value for the preform in
step a).
4) The method according to claim 1, wherein the shaped part is
plastically deformed in step b) in at least two and at most 300
steps.
5) The method according to claim 1, the heating in step c) taking
place with the application of a pressure in the range from 1 to 600
MPa to the shaped part.
6) The method according to claim 1, wherein the pressure is applied
between two plane-parallel surfaces.
7) The method according to claim 1, wherein the bulk metallic
glass, by weight, has zirconium or copper as its main
component.
8) The method according to claim 1, wherein the preform is formed
after step b) and before step c).
9) The method according to claim 1, wherein the forming is carried
out by hammering, deep drawing, or bending.
10) The method according to claim 1, wherein the repeated plastic
deformation takes place with the aid of at least one roller.
11) The method according to claim 1, wherein the repeated plastic
deformation takes place in each deformation step in the same
direction or in alternating directions, particularly in directions
orthogonal to one another.
12) (canceled)
13) (canceled)
14) A shaped part comprising a bulk metallic glass, wherein the
shaped part has a diameter of at least 200 .mu.m in at least one
dimension, characterized in that the bulk metallic glass has a
flexural strength of at most 15% which is below the flexural
strength of the cast alloy.
15) The shaped part according to claim 14, wherein the shaped part
has a diameter in at least two dimensions in the range of at least
200 .mu.m.
16) The shaped part according to claim 14, the bulk metallic glass
contain-ing zirconium as its main component by weight.
Description
INTRODUCTION
[0001] The present invention relates to a method for producing a
shaped part comprising a bulk metallic glass and a shaped part
produced according to the method and its use. Metallic glasses have
been the subject of extensive research since they were discovered
about 50 years ago at the California Institute of Technology. Over
the years, it has been possible to continuously improve the
processability and properties of this class of materials. While the
first metallic glasses were still simple, binary alloys (made up of
two components), the production of which required cooling rates in
the range of 10.sup.6 Kelvin per second (K/s), more recent, more
complex alloys can already be transferred into the glassy state at
significantly lower cooling rates in the range of a few K/s. This
has a significant influence on process management and the
components that can be implemented. The cooling rate at which the
melt does no longer crystallize and solidifies in the glassy state
is referred to as the critical cooling rate. It is a
system-specific variable that is heavily dependent on the
composition of the melt and also defines the maximum component
thicknesses that can be achieved. If you consider that the thermal
energy stored in the melt must be discharged through the system
sufficiently fast, it becomes clear that only components with a
small thickness can be manufactured from systems with high critical
cooling rates. In the beginning, metallic glasses were therefore
mostly produced using the melt spinning process. The melt is
stripped onto a rotating copper wheel and solidifies like a glass
in the form of thin strips or films with thicknesses in the range
of a few hundredths to tenths of a millimeter. With the development
of new, complex alloys having significantly lower critical cooling
rates, other manufacturing processes can increasingly be used.
Today's solid glass-forming metallic alloys can be converted into
the glassy state by pouring a melt into cooled copper molds. The
implementable component thicknesses are alloy-specific in the range
from a few millimeters to centimeters. Such alloys are called bulk
metallic glasses (BMG). A large number of such alloy systems are
known today. The subdivision of bulk metallic glasses is usually
based on their composition, wherein the alloy element with the
highest weight percentage is referred to as the base element. The
existing systems include, for example, precious metal-based alloys
such as gold, platinum, and palladium-based bulk metallic glasses,
early transition metal-based alloys such as titanium or
zirconium-based bulk metallic glasses, late transition metal-based
systems based on copper, nickel, or iron, but also systems based on
rare earths, such as neodymium or terbium. Bulk metallic glasses
typically have the following properties compared to classic
crystalline metals: [0002] higher specific strength, which enables
thinner wall thicknesses, for example, [0003] higher hardness,
which means that the surfaces can be particularly
scratch-resistant, [0004] much higher elastic extensibility and
resilience, [0005] thermoplastic moldability, and [0006] higher
corrosion resistance.
[0007] There are various methods of manufacturing shaped parts from
bulk metallic glass. The melt spinning process as described in U.S.
Pat. No. 4,116,682 A is suitable for producing thin metal strips
having a thickness of approximately 100 .mu.m.
[0008] Due to the high cooling rates that can be achieved, alloys
that have comparatively high critical cooling rates can also be
processed amorphously in this way. For the production of cast parts
with dimensions in the range of a few millimeters, special alloys
have been developed that have lower critical cooling rates and
still solidify amorphously, at casting thicknesses in the range of
a few millimeters. Such alloys are described in US 20150307975 A1,
for example.
[0009] The prior art has certain disadvantages. Although thin
structures with a high degree of homogeneity can be produced using
melt spinning, thicker shaped parts with a diameter of more than
150 .mu.m are not easily accessible. Thicker shaped parts can be
produced by melt casting than by melt spinning, but these shaped
parts often have highly fluctuating mechanical properties.
[0010] Furthermore, shaped parts with a thickness of less than 500
.mu.m are often difficult to manufacture using casting processes,
since the viscosity of the melt increases rapidly during
casting.
[0011] Shaped parts made from bulk metallic glass using casting
processes often show a high degree of heterogeneity in terms of
mechanical properties, such as flexural strength. This makes the
use of shaped parts made of bulk metallic glass difficult or
impossible in precision applications, for example in precision
engineering.
[0012] Furthermore, shaped parts often have defects in the form of
tiny gas inclusions, which have a negative impact on the mechanical
properties.
[0013] It was an object of the present invention to provide a
method which solves at least one of the aforementioned
problems.
[0014] A preferred object of the present invention was to provide a
method which allows producing shaped parts comprising a bulk
metallic glass, wherein the shaped parts have defined and
homogeneous mechanical properties.
[0015] It was an object of the present invention to provide a
method which allows producing shaped parts comprising a bulk
metallic glass and which have a reduced number of defects, such as
air inclusions, compared to cast molded parts.
[0016] Furthermore, it was an object of the invention to provide an
improved method which allows producing shaped parts comprising a
bulk metallic glass in fewer work steps.
[0017] Another preferred object of the invention was to provide a
method with which shaped parts can be produced from bulk metallic
glasses with a diameter of 600 .mu.m or less, particularly 400
.mu.m or less, by means of the casting process.
[0018] A contribution to achieving at least one of the objects
mentioned is made by the subject matter of the independent
claims.
[0019] A first aspect of the invention relates to a method for
producing a shaped part comprising a bulk metallic glass,
characterized by the following steps: [0020] a) providing a preform
comprising a bulk metallic glass, [0021] b) repeated plastic
deformation of the preform comprising a bulk metallic glass in
several steps with a deformation .DELTA.d, wherein the temperature
T.sub.1 of the preform is below the glass transition temperature of
the bulk metallic glass, and [0022] c) heating the preform to a
temperature T.sub.2 above the glass transition temperature and
below the crystallization temperature to obtain a shaped part
comprising a bulk metallic glass, [0023] wherein the plastic
deformation in step b) takes place in such a way that the
deformation .DELTA.d increases with an increasing number of
steps.
[0024] Optionally, further steps can be carried out before, during
or after the steps mentioned, as long as the specified sequence of
steps a)-c) is adhered to.
[0025] The method according to the invention provides a production
route for shaped parts having a bulk metallic glass. According to
the invention, the shape of the shaped part is not restricted any
further. In one possible embodiment, the shaped part can be
selected from the group consisting of strips, cuboids, wires, rods,
or sheets.
[0026] The method according to the invention is particularly
suitable for the production of shaped parts, particularly sheets
and strips with a thickness of 100-600 .mu.m, particularly 200
.mu.m-500 .mu.m. Such shaped parts are typically too thick to be
produced by melt spinning and too thin to be produced by injection
molding.
[0027] Furthermore, with the process parameters remaining the same,
multiple shaped parts with homogeneous mechanical properties can be
obtained using the method according to the invention, based on the
relative standard deviation over several components. The relative
standard deviation of the strength in the case of multiple shaped
parts produced according to the invention is preferably not greater
than 10% and particularly not greater than 5%.
[0028] In one aspect, the invention relates to a method for
producing a shaped part. The shaped part according to the invention
comprises a bulk metallic glass or consists thereof. Bulk metallic
glasses are alloys that have a metallic binding character and at
the same time an amorphous, i.e. non-crystalline, phase. In the
context of the invention, an alloy can be referred to as bulk
metallic glass if the respective alloy can be brought into the
glassy state in a body with dimensions of 1 mm.times.1 mm.times.1
mm at a suitable cooling rate.
[0029] The bulk metallic glasses can be based on different
elements. In this context, "based" means that the element mentioned
in each case represents the largest proportion in relation to the
weight of the alloy. Typical components, which can preferably also
form the basis of the alloy, can be selected from: [0030] A. metals
from groups IA and IIA of the periodic table, such as magnesium
(Mg), calcium (Ca), [0031] B. metals from groups IIIA and IVA, such
as aluminum (Al) or gallium (Ga), [0032] C. early transition metals
from groups IVB to VIIIB, such as titanium (Ti), zirconium (Zr),
hafnium (Hf), niobium (Nb), tantalum (Ta), chromium (Cr),
molybdenum (Mo), manganese (Mn), [0033] D. late transition metals
from groups VIIIB, IB, IIB, such as iron (Fe), cobalt (Co), nickel
(Ni), copper (Cu), palladium (Pd), platinum (Pt), gold (Au), silver
(Ag), zinc (Zn), [0034] E. rare earth metals such as scandium (Sc),
yttrium (Y), terbium (Tb), lanthanum (La), cerium (Ce), neodymium
Nd) or gadolinium (Gd), [0035] F. non-metals such as boron, carbon,
phosphorus, silicon, germanium, sulfur.
[0036] Preferred combinations of elements contained in bulk
metallic glasses are selected from: [0037] late transition metals
and non-metals, wherein the late transition metal are the base,
such as Ni--P, Pd--Si, Au--Si--Ge, Pd--Ni--Cu--P,
Fe--Cr--Mo--P--C--B, [0038] early and late transition metals,
wherein both metals can represent the base, such as Zr--Cu, Zr--Ni,
Ti--Ni, Zr--Cu--Ni--Al, Zr--Ti--Cu--Ni--Be, [0039] metals from
group B with rare earth metals, wherein the metal B represents the
base, such as Al--La, Al--Ce, Al--La--Ni--Co, La--(Al/Ga)--Cu--Ni,
[0040] metals from group A with late transition metals, wherein the
metal A is the base, such as Mg--Cu, Ca--Mg--Zn, Ca--Mg--Cu.
[0041] Other particularly preferred examples of alloys that form
bulk metallic glasses are selected from the group consisting of
Ni--Nb--Sn, Co--Fe--Ta--B, Ca--Mg--Ag--Cu, Co--Fe--B--Si Nb,
Fe--Ga--(Cr, Mo) (P, C, B), Ti--Ni--Cu--Sn, Fe--Co--Ln--B, Co--(Al,
Ga)--(P, B, Si), Fe--B--Si--Nb and Ni--(Nb, Ta)--Zr--Ti. In one
embodiment of the invention, alloys based on copper and/or
zirconium are preferred. Particularly, the bulk metallic glass can
be a Zr--Cu--Al--Nb alloy. In addition to zirconium, this
Zr--Cu--Al--Nb alloy preferably also contains 23.5-24.5% by weight
copper, 3.5-4.0% by weight aluminum and 1.5-2.0% by weight niobium,
the proportions by weight adding up to 100% by weight. The latter
alloy is commercially available under the name AMZ4.RTM. from
Heraeus Deutschland GmbH. In another particularly preferred
embodiment, the bulk metallic glass can contain the elements
zirconium, titanium, copper, nickel and aluminum. Particularly
suitable bulk metallic glasses for the production of shaped parts
have the composition
Zr.sub.52.5Ti.sub.5Cu.sub.17.9Ni.sub.14.6Al.sub.10 and
Zr.sub.59.3Cu.sub.28.8Al.sub.10.4Nb.sub.1.5, wherein the indices
specify at-% of the respective elements in the alloy. Another
preferred group of alloys can contain the elements Zr, Al, Ni, Cu
and Pd, particularly Zr.sub.60Al.sub.10Ni.sub.10Cu.sub.15Pd.sub.5
(indices in at.-%). Another preferred group of alloys contains at
least 85 wt-% Pt as well as Cu and phosphorus, wherein the alloy
may also contain Co and/or nickel, for example
Pt.sub.57.5Cu.sub.14.5Ni.sub.5P.sub.23 (indices in at.-%).
[0042] In step a) of the method according to the invention, a
preform comprising a bulk metallic glass is provided. The preform
preferably consists of a bulk metallic glass. In a preferred
embodiment, the preform is made with a bulk metallic glass using a
casting process, particularly injection molding or suction
casting.
[0043] For example, the starting components of the solid
glass-forming alloy can be melted in an arc under vacuum until a
homogeneous alloy is created to produce this preform comprising a
bulk metallic glass. The alloy obtained can be processed into a
preform comprising a bulk metallic glass by suction or injection
molding, for example. The casting process preferably takes place in
an argon atmosphere. The preform comprising a bulk metallic glass
is preferably a strip, a cuboid, a wire, a rod, or a sheet metal.
The preform preferably has a solid diameter (that is to say without
cavities or recesses) of at least 1 mm in the smallest
dimension.
[0044] The critical casting thickness should not be exceeded, such
that the preform comprising a bulk metallic glass solidifies
amorphously during casting. The melts of optimized alloys have
critical casting thicknesses of one millimeter or more, such that
at a sufficient cooling rate, e.g. in a copper mold with optional
water cooling, completely amorphous preforms comprising a bulk
metallic glass can be obtained. A person skilled in the art knows
how preforms comprising a bulk metallic glass can be produced by
means of a casting processes.
[0045] The preform comprising a bulk metallic glass obtained
preferably has a weight proportion of bulk metallic glass that is
at least 95%, particularly at least 98%. Particularly preferably,
the preform comprising a bulk metallic glass is completely
amorphous, measured by means of XRD due to the absence of
crystalline signals in the diffractogram.
[0046] In step b), the preform comprising a bulk metallic glass is
repeatedly plastically deformed, wherein the temperature T.sub.1 is
below the glass transition temperature of the bulk metallic glass.
Particularly, the temperature T.sub.1 during the deformation is at
least 15% below the glass transition temperature, measured in
.degree. C. According to the invention, the plastic deformation
takes place in multiple deformation steps, each with a deformation
.DELTA.d (.DELTA.d=d before the deformation step-d after the
deformation step). The diameter d of the preform is measured along
the deformation direction in the respective deformation step.
According to the invention, the plastic deformation in step b)
takes place in such a way that the deformation .DELTA.d of the
preform made of bulk metallic glass increases with an increasing
number of steps. In an optional embodiment, the deformation
.DELTA.d, after it has increased, can decrease again with an
increasing number of steps For example, the deformation .DELTA.d
can increase from 5 .mu.m to 50 .mu.m and then decrease again to 5
.mu.m or 10 .mu.m. By means of processes in which the deformation
.DELTA.d first increases and then decreases again, particularly
thin shaped parts with a diameter of less than 300 .mu.m can be
produced efficiently and homogeneously.
[0047] Deformation steps can be saved if the deformation .DELTA.d
increases with increasing deformation steps, which can make the
method according to the invention more cost-effective than
conventional methods in which the deformation .DELTA.d is kept
constant. The deformation .DELTA.d is preferably at least 1 .mu.m,
particularly at least 5 .mu.m and very particularly preferably at
least 10 .mu.m. At most, the deformation .DELTA.d can be a maximum
of 100 .mu.m, particularly a maximum of 50 .mu.m, per deformation
step. The change in the deformation .DELTA.d with an increasing
number of steps can preferably take place continuously or in
step-by-step. In this context, continuous means that the
deformation .DELTA.d changes with each further deformation step.
Step-by-step means here that multiple deformation steps with the
same deformation .DELTA.d are carried out before one or more
deformation steps with the next larger deformation .DELTA.d take
place. The increase in deformation .DELTA.d with increasing
deformation steps can increase linearly, e.g. in steps of 5 .mu.m
(.DELTA.d 5 .mu.m.fwdarw..DELTA.d 10 .mu.m.fwdarw..DELTA.d 15
.mu.m.fwdarw. . . . ) or increase further with increasing
deformation steps, e.g. .DELTA.d 5 .mu.m.fwdarw..DELTA.d 10
.mu.m.fwdarw..DELTA.d 20 .mu.m.fwdarw..DELTA.d 50 .mu.m, . . .
.
[0048] In the example of a preform made of bulk metallic glass in
the form of a cast strip with a thickness of 3 mm, the deformation
.DELTA.d can start at 5 .mu.m in the first step and end with a
deformation .DELTA.d of 50 .mu.m in the last step of the
deformation, with the final thickness of the strip is about 500
.mu.m. In this example, the reduction in thickness can preferably
take place in 50-150 steps.
[0049] The degree of deformation per deformation step is preferably
in the range of 0.1-0.5% of the diameter d, wherein the degree of
deformation is calculated by: (1-(d after the deformation step/d
before the deformation step)). The summed degree of deformation
.DELTA.d.sub.total of the preform over all deformation steps can
preferably be up to 90%, the summed degree of deformation
.DELTA.d.sub.total being calculated by: (.DELTA.d.sub.total=1-(d
after deformation/d before deformation)).
[0050] Forming is preferably carried out by rolling. Optionally,
two or more rollers can be used for forming. In another preferred
embodiment, the forming, particularly rolling, takes place in such
a way that the shaped part is deformed with a force which is in the
range of serration in the stress-strain diagram. The serration in
the stress-strain diagram is to be understood as a curve in which,
with increasing strain, there is a sudden drop in stress, and this
process is repeated multiple times before the specimen breaks.
[0051] In a preferred embodiment of the invention, the preform
comprising a bulk metallic glass is either deformed in the same
direction or in different directions in each deformation step. If
the preform comprising a bulk metallic glass is deformed in
different directions, the deformation directions of successive
deformation steps can be parallel or perpendicular to one another.
A particularly homogeneous material can be obtained by a vertical
orientation of successive deformation steps.
[0052] The number of deformation steps, particularly rolling steps,
is not restricted any further according to the invention. In a
preferred embodiment, the shaped part is deformed in at least two
deformation steps, particularly in at least ten deformation steps
and specifically preferably in at least 30 deformation steps, and
particularly in at least 50 deformation steps. The preform
comprising a bulk metallic glass is particularly preferably
deformed in a maximum of 300 deformation steps, particularly a
maximum of 200 deformation steps and specifically preferably in a
maximum of 150 or a maximum of 100 deformation steps.
[0053] Forming can optionally take place after step b). Forming can
preferably be selected from bending, hammering, and deep
drawing.
[0054] In step c) of the method according to the invention, the
preform comprising a bulk metallic glass is heated to a temperature
T.sub.2 above the glass transition temperature and below the
crystallization temperature to obtain a shaped part comprising a
bulk metallic glass. The shaped part preferably consists of a bulk
metallic glass. In another preferred embodiment, the shaped part
contains both amorphous bulk metallic glass and at least one
crystalline phase. Such mixtures of amorphous and crystalline
phases are also called bulk metallic glass composites (BMGC).
[0055] The heating in step c) is preferably carried out below the
extrapolated initial crystallization temperature (according to DIN
EN ISO 11357-3:2018-07). The shaped part produced by the method can
have mechanical properties, particularly strengths, such as
flexural strength, which are similar to those of the preform before
the deformation. The preform comprising a bulk metallic glass is
preferably heated in step c) such that the bending strength of the
shaped part obtained corresponds to the initial value of the
bending strength of the preform comprising a bulk metallic glass in
step a). The flexural strength after step c) is preferably at most
15%, particularly at most 10% lower than the flexural strength of
the cast preform. In the context of the invention, the flexural
strength according to DIN EN ISO 7438:2016-07 can be determined in
a bending test. In a preferred embodiment, the preform comprosing a
bulk metallic glass is heated for a period of 0.1 to 3000 s,
particularly 5 to 300 s. In a particularly preferred embodiment,
the heating is terminated before the crystallization temperature in
the TTT-diagram of the alloy is achieved for the respective heating
rate.
[0056] The preform comprising a bulk metallic glass is preferably
heated to a temperature T.sub.2 which fulfills the following
condition:
T.sub.G<T.sub.2<T.sub.G+(60/100)*(T.sub.X-T.sub.G),
particularly the condition
T.sub.G<T.sub.2<T.sub.G+(30/100)*(T.sub.X-T.sub.G). In this
case, T.sub.G is the glass transition temperature and T.sub.X is
the crystallization temperature. Under these conditions,
particularly advantageous mechanical properties of the finished
shaped part can be obtained.
[0057] In a preferred embodiment, the heating in step c) takes
place while applying additional pressure to the shaped part. This
can lead to particularly small piece-to-piece deviations in the
mechanical properties of the resulting components. The pressure
applied to the shaped part is preferably from 1 to 600 MPa,
particularly from 5 to 300 MPa and very particularly preferably
from 10 to 150 MPa.
[0058] In a particularly preferred embodiment of the invention, the
heating in step c) takes place as thermoplastic forming (TPF). TPF
can change the overall dimensions of the shaped part, for example
the thickness of a sheet metal, or, alternatively, structures can
be embossed into the shaped part, that is, the preform is locally
deformed. Alternatively, the surface of the shaped part can be
changed using TPF. Heating is preferably carried out in a heatable
press.
[0059] Preferably, the preform comprising a bulk metallic glass can
be pressurized or thermoplastically shaped between two
plane-parallel surfaces, whereby flat shaped parts can be obtained.
Flat means with a thickness variation in the range of at most 20%
around the mean value, e.g. +/-200 .mu.m with an average thickness
of 1 mm or +/-30 .mu.m with an average thickness of 150 .mu.m.
[0060] In one possible embodiment of the invention, the component
obtained after step c) can be used for technical applications
directly and without further treatment.
[0061] For example, the method according to the invention can be
used to produce a shaped part comprising a bulk metallic glass,
wherein the shaped part has a diameter of at least 200 .mu.m in at
least one dimension. The shaped part comprising a bulk metallic
glass can preferably have a flexural strength (in N/mm.sup.2) which
at most is 15% below the flexural strength of the cast alloy. The
shaped part preferably has a diameter of at least 200 .mu.m in at
least two dimensions. In one possible embodiment of the invention,
the shaped part has a thickness not greater than 600 .mu.m,
particularly not greater than 400 .mu.m. The bulk metallic glass of
the shaped part which has these properties is preferably selected
from Zr.sub.52.5Ti.sub.5Cu.sub.17.9Ni.sub.14.6Al.sub.10 and
Zr.sub.59.30Cu.sub.28.8Al.sub.10.4Nb.sub.1.5, wherein the indices
indicate at-% of the respective elements in the alloy.
[0062] Optionally, step c) can then be followed by one or more
aftertreatment steps for the shaped part comprising a bulk metallic
glass. The aftertreatment steps can be selected, for example, from
laser cutting, water jet cutting, milling, drilling, grinding,
polishing and sandblasting.
[0063] The process according to the invention can be used to
produce shaped parts for a wide variety of applications. The use of
the method is particularly advantageous wherever shaped parts are
required that have high geometric precision and isotropic
mechanical properties and can be produced with little
piece-to-piece deviation.
[0064] The use of the method according to the invention for the
production of precision mechanical components, such as springs,
gears, etc., is particularly preferred. For example, such
components can be used for the manufacture of watches.
[0065] FIG. 1 graphically represents a possible embodiment of the
invention. The process steps are described from left to right.
First, a preform made of solid metal glass is produced using a
casting process (A). The preform produced is then deformed to a
temperature T.sub.1 below the glass formation temperature by means
of cold rolling (B). The preform is then heated to a temperature
T.sub.2 above the glass transition temperature and below the
crystallization temperature with the application of pressure (C).
This is optionally followed by a polishing step (D) and optionally
cutting the shaped part to a specific shape (E).
MEASUREMENT METHODS
[0066] DSC Measurement
[0067] The DSC measurements in the context of the invention are
carried out in accordance with DIN EN ISO 11357-1:2017-02 and DIN
EN ISO 11357-3:2018-07. The sample to be measured in the form of a
thin disc or film (approx. 80-100 mg) is placed in the measuring
device (NETZSCH DSC 404F1, NETZSCH GmbH, Germany). The heating rate
is 20.0 K/min. Al.sub.2O.sub.3 is used as the crucible material.
The heat flow is measured against an empty reference crucible, such
that only the thermal behavior of the sample is measured.
[0068] The measurement method is carried out according to the
following steps: [0069] a) The sample to be measured is heated at
the above-mentioned heating rate to a temperature just below the
melting temperature (T=0.75*Tm), and the heat flow measured. The
measurement is completed when no more heat flow in connection with
phase transitions can be measured. Particularly, the measurement is
ended when an exothermic signal in connection with the
crystallization process is completely detected. In the examples
contained herein, measurements are performed from room temperature
to about 600.degree. C., for example. [0070] b) The sample is
allowed to cool to room temperature. [0071] c) The sample is again
heated to the same temperature at the same heating rate as in step
a), and the heat flow is measured. [0072] d) The measurement from
step c) is subtracted from the measurement from step a), which
reveals the measurement difference. The enthalpy of
crystallization, if any, can be determined from the difference
measurement by forming an integral.
[0073] Glass Transition Temperature
[0074] In the context of the present invention, the glass
transition temperature is measured according to ASTM E1365-03 as
follows.
[0075] The sample to be examined is placed in a crucible in a DSC
device (NETZSCH DSC 404F1, NETZSCH GmbH, Germany). The system is
heated and cooled according to the following scheme, and the
respective heat flow is measured in steps a) and c). [0076] a)
heating to a temperature of 0.75*Tm at a heating rate of 20 K/min.
[0077] b) cooling to room temperature [0078] c) heating to the same
temperature as in step a) at the same heating rate [0079] d)
cooling to room temperature
[0080] As a result of the experiment, the enthalpy is obtained as a
function of the temperature for the sample. In step a), the
amorphous sample is crystallized. In step c), the thermal behavior
of the already completely crystallized sample is recorded.
[0081] In order to determine the glass transition temperature, the
measurement from step c) is subtracted from the measurement from
step a). The resulting curve includes an endothermic transition at
a lower temperature and an exothermic signal at a higher
temperature. The signal at a higher temperature corresponds to the
crystallization process. The endothermic signal corresponds to the
glass transition. In order to determine the glass transition
temperature, a tangent line to the baseline is determined before
the glass transition range (by linear fitting). A second tangent is
determined at the turning point (corresponding to the peak value of
the first derivative over time) of the glass transition range. The
temperature value at the intersection of the two tangents indicates
the glass transition temperature (T.sub.f according to AST
1356-03).
[0082] Crystallization Temperature
[0083] The crystallization temperature was determined by means of
DSC in accordance with the DIN EN ISO standard 11357-3:2018-07.
This standard is designed for polymers, but can be used analogously
for metallic glasses. In the context of the invention, the
crystallization temperature corresponds to the peak crystallization
temperature T.sub.p,c as used in the standard mentioned herein. The
heating rate was 20 K/min.
EXAMPLES
[0084] The alloy (Zr.sub.59.30Cu.sub.28.8Al.sub.10.4Nb.sub.1.5) was
produced by melting the elements in a vacuum arc. A preform was
made from the alloy produced by means of suction casting by pouring
the homogeneous, liquid melt of the alloy into a copper casting
mold. The copper mold was kept at room temperature. The casting
obtained in the form of a tape had the dimensions
3.times.15.times.40 mm.
[0085] The cast part obtained in the form of a strip was rolled in
a rolling mill at room temperature with increasing deformation
steps to a thickness of 0.5 mm. The deformation steps started with
a thickness reduction of 5 .mu.m, and the rolling ended at a
deformation .DELTA.d of 50 .mu.m per deformation steps after 70
rolling processes.
[0086] The cold-rolled strip was then heated using a heated press
below the crystallization temperature in the TTT diagram of the
alloy for 60 seconds to achieve the desired flexural strength of
approximately 2250 N/mm.sup.2 adjust.
[0087] According to the example described, 50 shaped parts were
produced. For the components obtained, the stress-strain behavior
was measured using a 3-point bending test (in accordance with DIN
EN ISO 7438:2016-07). The results of the measurements are
summarized in Table 1.
TABLE-US-00001 TABLE 1 Flexural strength Standard deviation
[N/mm.sup.2] [N/mm.sup.2] (Number of (average) measured parts) Cast
2447 282 (10) Cast and rolled 1682 224 (6) Cast, rolled, TPF 2261
84 (10)
[0088] Table 1 summarizes the measured flexural strengths of the
manufactured parts for different stages of manufacture and gives
the standard deviation of the flexural strength over several parts
for each processing step. It can be seen that shaped parts can be
obtained using the method of the invention (3.sup.rd row), which
parts have an average flexural strength of 2261 N/mm.sup.2 which is
close to the initial value of the cast preform of 2447 N/mm.sup.2
while the homogeneity of the components (expressed by the lower
standard deviation) has increased by a factor of 3.4 compared to
the cast parts (row 1).
* * * * *