U.S. patent application number 11/995842 was filed with the patent office on 2008-12-04 for method for producing a copper alloy having a high damping capacity.
Invention is credited to Agniezka Mielczarek, Werner Riehemann, Babette Tonn, Soenke Vogelgesang, Hennadiy Zak.
Application Number | 20080298999 11/995842 |
Document ID | / |
Family ID | 37309676 |
Filed Date | 2008-12-04 |
United States Patent
Application |
20080298999 |
Kind Code |
A1 |
Zak; Hennadiy ; et
al. |
December 4, 2008 |
Method for Producing a Copper Alloy Having a High Damping
Capacity
Abstract
The invention relates to a copper alloy which is used for
mechanically stressed components which, during operation, are
subjected to vibrations and/or impacts to produce the same, and
have particularly good mechanical damping properties. The
composition of said copper alloy depends upon the utilisation
temperature or working temperature of the component. Said copper
alloy consists of 2-12 wt.-% manganese, 5-14 wt.-% aluminum and
individually or in total 0-18 wt.-% of one or several elements,
nickel, iron, cobalt, zinc, silicon, vanadium, niobium, molybdenum,
chromium, tungsten, beryllium, lithium, yttrium, cerium, scandium,
calcium, titanium, phosphorous, zirconium, boron, nitrogen, carbon,
whereby each element does not contain more that 6% and 100 wt.-%
copper. The alloy is obtained by adapting the martensite-austenitic
conversation temperatures or the associated intervals
M.sub.S-M.sub.F and/or A.sub.S-A.sub.F to a predetermined
utilisation temperature or working temperature of the component by
varying the weight proportion of the above-mentioned alloy
component during melting thereof. The damping can reach above
70%.
Inventors: |
Zak; Hennadiy;
(Clausthal-Zellerfeld, DE) ; Vogelgesang; Soenke;
(Bremen, DE) ; Mielczarek; Agniezka;
(Clausthal-Zellerfeld, DE) ; Tonn; Babette;
(Clausthal-Zellerfeld, DE) ; Riehemann; Werner;
(Clausthal-Zellerfeld, DE) |
Correspondence
Address: |
WHITHAM, CURTIS & CHRISTOFFERSON & COOK, P.C.
11491 SUNSET HILLS ROAD, SUITE 340
RESTON
VA
20190
US
|
Family ID: |
37309676 |
Appl. No.: |
11/995842 |
Filed: |
July 27, 2006 |
PCT Filed: |
July 27, 2006 |
PCT NO: |
PCT/DE2006/001305 |
371 Date: |
July 8, 2008 |
Current U.S.
Class: |
420/479 ;
148/509; 148/511; 420/478; 420/480; 420/486; 420/489 |
Current CPC
Class: |
C22C 9/05 20130101; C22C
9/01 20130101 |
Class at
Publication: |
420/479 ;
148/511; 148/509; 420/480; 420/478; 420/486; 420/489 |
International
Class: |
C22C 9/01 20060101
C22C009/01; C22F 1/08 20060101 C22F001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 27, 2005 |
DE |
10 2005 035 709.1 |
Claims
1. A process for producing a Copper alloy having specifically
improved mechanical damping for mechanically stressed components,
which comprises, as constituents of the alloy, from 2 to 12% by
weight of manganese, from 5 to 14% by weight of aluminum and,
individually or together, from 0 to 18 by weight of one or more of
the elements nickel, iron, cobalt, zinc, silicon, vanadium,
niobium, molybdenum, chromium, tungsten, beryllium lithium,
yttrium, cerium, scandium, calcium, titanium, phosphorus,
zirconium, boron, nitrogen, carbon, but each element in an amount
of not more than 6%, and copper to 100% by weight, characterized in
that a) a composition for the alloy is selected and the
constituents are melted in a Customary way at a suitable
temperature, b) during this melting, at least one of the
marten-sjtjc and austenitic transformation temperatures M.sub.S,
M.sub.F, A.sub.S and A.sub.F is determined on a sample taken from
the melt, C) these transformation temperatures are increased or
reduced on the basis of a predetermined use or working temperature
of the component by targeted addition of at least one constituent
of the alloy and thus matched to the use or working temperature, d)
the new transformation temperatures and, if appropriate, ranges are
checked by means of a further sample and e) the alloy is cast into
the desired mold.
2. The process as claimed in claim 1, Characterized in that the
steps c) and d) are repeated as often as necessary.
3. The process as claimed in claim 1, characterized in that
correction of the transformation temperatures is carried out during
melting by addition of copper or aluminum.
4. The process as claimed in claim 1, characterized in that the
transformation temperatures are set so that the temperatures in the
middle of the martensitic or austenitic range of the phase
transformation are very close to the predetermined use or working
temperature.
5. The process as claimed in claim 1, characterized in that the
alloy in the form of a Shaped part obtained initially by Casting or
forging and if appropriate forming is subjected to heat treatment
at temperatures of from 650.degree. C. to 950.degree. C. and
subsequent cooling or quenching in liquid or gaseous media, in
particular air, liquid nitrogen, water, a salt bath or oil.
6. The process as claimed in claim 5, characterized in that the
temperature of the quenching medium is above the M.sub.S
temperature of the alloy.
7. The process as claimed in claim 1, characterized in that the
alloy in the form of a shaped part obtained initially by casting or
forging and if appropriate forming is heat treated/aged at a
temperature of from 100 to 300.degree. c. for from about 5 to 120
minutes.
8. The process as claimed in claim 1, characterized in that the
alloy is subjected to one or more thermal cycles between the
austenitic state and the martensitic state and back.
9. The process as claimed in claim 1, characterized in that heat
treatment of the outer layer of a shaped part obtained from the
alloy by casting or forging and if appropriate forming is effected
by means of laser remelting of the outer zone.
10. The process as claimed in claim 1, characterized in that the
sample for quick monitoring of the transformation temperatures is
taken by means of a fused silica tube in which a subatmospheric
pressure is produced.
11. The process as claimed in claim 1, characterized in that the
transformation temperatures are determined on the sample by
calorimetry, dilatometry, measurement of the electrical
conductivity, optical microscopy or measurement of the acoustic
emission.
12. The process as claimed in claim 1, characterized in that the
damping behavior is additionally influenced by targeted alteration
of the grain size.
13. A copper alloy, in particular for mechanically stressed
components, having specifically improved mechanical damping, which
comprises, as constituents of the alloy, from >4 to 12% by
weight of manganese, from >10 to 14% by weight of aluminum, from
0.01 to 0.8% by weight of chromium and, individually or together,
from 0 to 18% by weight of one or more of the elements nickel,
iron, cobalt, zinc, silicon, vanadium, niobium, molybdenum,
chromium, tungsten, beryllium, lithium, yttrium, cerium, scandium,
calcium, titanium, phosphorus, zirconium boron, nitrogen, carbon,
but each element in an amount of not more than 6%, and copper to
100% by weight.
14. The copper alloy as claimed in claim 13, characterized in that
the alloy contains from 1 to 4% by weight of nickel.
15. The copper alloy as claimed in claim 13, characterized in that
the alloy contains from 11.6 to 12% by weight, preferably about
11.8% by weight, of aluminum.
16. The copper alloy as claimed in claim 13, characterized in that
the alloy contains from 8 to 10% by weight of manganese.
17. The copper alloy as claimed in claim 13, characterized in that
the alloy contains from 2 to 4% by weight of iron and/or from 0.001
to 0.05% by weight of boron.
18. The copper alloy as claimed in claim 13, characterized in that
the alloy contains from 0.01 to 1% by weight of cobalt.
19. The copper alloy as claimed in claim 13, characterized in that
the alloy contains from 0.01 to 0.3% by weight of rare earths.
20. The copper alloy as claimed in claim 13, characterized in that
the alloy contains from 2 to 6% by weight of zinc.
21. (canceled)
22. (canceled)
Description
[0001] The invention relates to a process for producing a copper
alloy which is particularly suitable for components which are
mechanically stressed, for example by vibration, shock or impact
and has alloy properties which are matched to the intended use of
the components, especially specifically improved or optimally set
mechanical damping. The invention further relates to such an alloy
having a particular composition and possible uses of the alloys
obtained by the process.
[0002] Metallic materials or alloys having a high damping capacity
are known in principle and are also referred to as HIDAMETs (HIgh
DAmping METals).
[0003] A high mechanical damping capacity is desirable, for
example, for reduction of vibrations and for noise damping. Such
alloys are therefore particularly suitable for producing ships'
propellers and pump housings and for use in vibrating machines and
for preventing malfunctions caused by vibration in the case of
various precision apparatuses and electronic instruments. In
addition, the alloys have not only a high wear resistance but are
suitable for use in various tools which are subjected to vibrations
and/or impacts during operation, for example punches or dies in the
shaping of sheetmetal or in lathes and milling machines.
[0004] Many HIDAMETs which can be used for noise damping and for
absorption of vibrations are known. However, the fields of use of
most of these materials, in particular magnesium and magnesium
alloys, are seriously restricted by their unsatisfactory mechanical
and corrosion properties.
[0005] HIDAMETs which display martensitic phase transformations are
of particular importance in the prior art for achieving good
damping properties. Alloys which display martensitic phase
transformations have a different arrangement of atoms in the solid
state at high temperatures than at low temperatures. The
hightemperature phase is referred to as "austenite" and the
low-temperature phase is referred to as "martensite". The
transformation of austenite into martensite occurs on cooling the
material from the austenitic state and commences at the martensite
start temperature M.sub.S. The martensitic transformation is
concluded on reaching the martensite finish temperature M.sub.F.
The transformation of martensite into austenite takes place on
heating the material from the martensitic state, commences at the
austenite start temperature A.sub.S and is concluded on reaching
the austenite finish temperature A.sub.F. In general, the damping
in the martensite range (T<M.sub.F) is higher because of the
very much higher defect density than in the austenite range
(T>A.sub.F).
[0006] The best-known alloys of the type mentioned are Ni--Ti
alloys ("Nitinol"), Cu--Zn--Al alloys ("Proteus") and Mn--Cu alloys
("Sonoston"). However, these three types of alloys have
disadvantages which substantially restrict their possible
applications. Ni--Ti alloys have to be produced in a complicated
fashion under reduced pressure and are also very expensive because
of the participating alloying elements. Compared to Nitinol,
Cu--Zn--Al alloys are significantly cheaper. The limited corrosion
resistance and the tendency to display brittle fracture are
significant disadvantages of these alloys. In addition, they are
extraordinarily prone to aging both in the austenitic state and in
the martensitic state. The widely used Mn--Cu alloys were developed
specifically for producing ships' propellers. Due to the relatively
wide solidification range of about 130.degree. C., these alloys
display a strong tendency to hot crack formation. In addition,
aging effects also occur here, so that the damping effect is
significantly reduced after storage for about 1000 hours at room
temperature.
[0007] The patent text U.S. Pat. No. 3,868,279 discloses
high-damping Cu--Mn--Al alloys and a possible way of improving
their damping properties by means of heat treatment. These ternary
alloys comprise 32-42% by weight of Mn, from 2-4% by weight of Al
and Cu as balance, with the Mn content preferably being 40% and the
Al content preferably being 2-3%. These alloys are cold rolled and
subjected to heat treatment at temperatures in the range from
649.degree. C. to 760.degree. C., quenched in water, subsequently
aged at from 204.degree. C. to 482.degree. C. for from 1.5 to 24
hours and cooled in air. A significant improvement in the damping
properties combined with reduced brittleness compared to the
previously known Heusler alloys is described.
[0008] An industrially interesting alternative to the
above-described HIDAMETs are Cu--Al--Mn shape memory alloys. These
materials, too, display a thermoelastic martensitic transformation.
The U.S. Pat. No. 4,146,392 describes Cu--Al--Mn shape memory
alloys which comprise copper as main constituent and from 4.6 to
13% by weight of manganese and from 8.6 to 12.8% by weight of
aluminum as alloying constituents and have a good resistance to
aging. These are alloys whose austenite-martensite transformation
takes place at temperatures below 0.degree. C. and whose shape
memory effect is exploited to produce, for example, pipe connection
elements.
[0009] DE 2055755 discloses a process for producing articles
composed of copper-based alloys which are able to change their
shape when the temperature changes. The alloys proposed for this
purpose comprise copper and aluminum together with, for example, an
additional element from the group consisting of zinc, silicon,
manganese and iron.
[0010] Despite the very advantageous combination of mechanical
properties and martensitic transformation temperatures which can be
achieved, the use of Cu--Al--Mn shape memory alloys for noise- and
vibration-damping materials has hitherto not been considered, since
the mechanical damping properties have hitherto not been able to be
set in a targeted fashion and sometimes even fluctuated greatly
from batch to batch.
[0011] It was therefore an object of the invention to provide
high-strength and corrosion-resistant HIDAMETs having a high
damping capacity which can be reliably set in the temperature range
critical for the planned use and a process for producing them.
[0012] The object of the invention is achieved by a process for
producing a copper alloy having specifically improved mechanical
damping, in particular for mechanically stressed components, which
is characterized by the following steps: [0013] a) a composition
for the alloy is selected and the constituents are melted in a
customary way at a suitable temperature, [0014] b) during this
melting, at least one of the martensitic and austenitic
transformation temperatures M.sub.S, M.sub.F, A.sub.S and A.sub.F
is determined on a sample taken from the melt, [0015] c) these
transformation temperatures are increased or reduced on the basis
of a predetermined use or working temperature of the component by
targeted addition of at least one constituent of the alloy and thus
matched to the use or working temperature, [0016] d) the new
transformation temperatures and, if appropriate, ranges are checked
by means of a further sample and [0017] e) the alloy is cast into
the desired mold.
[0018] Steps c) and d) can be repeated as often as necessary until
the desired matching of the transformation temperatures or ranges
has been achieved.
[0019] The composition of the alloy is selected from among the
constituents: [0020] from 2 to 12% by weight of manganese, [0021]
from 5 to 14% by weight of aluminum and, [0022] individually or
together, [0023] from 0 to 18% by weight of one or more of the
elements nickel, iron, cobalt, zinc, silicon, vanadium, niobium,
molybdenum, chromium, tungsten, beryllium, lithium, yttriium,
cerium, scandium, calcium, titanium, phosphorus, zirconium, boron,
nitrogen, carbon, [0024] but each element in an amount of not more
than 6%, and [0025] copper to 100% by weight.
[0026] The alloys obtained by the process of the invention are
otherwise produced by conventional melting and casting processes.
The alloy can be used not only as a casting alloy but also as a
forging alloy. The alloy can be shaped cold or hot. The alloys
described here are particularly advantageous for all applications
in which a high mechanical damping capacity is important, i.e. in
particular for mechanically stressed components, instruments or
housings which are subjected to vibrations, impacts or shocks.
[0027] The alloys differ from Sonoston in their considerably higher
aluminum contents and significantly lower manganese contents. The
high aluminum content improves the strength of the material
according to the invention and at the same time increases its
resistance to abrasion, erosion and cavitation. The reduced
manganese concentration has a positive effect on the casting
properties of the alloy because it reduces the solidification
range. Dense, oxide-free and hot-crackfree castings can thus be
produced without quality problems even for piece weights of several
tons.
[0028] To obtain the properties which are optimal for a desired
use, the proportions of the components of the alloy are usually
varied, e.g. as described in more detail below. It has been found
that the mechanical damping capacity which frequently alters
greatly when the composition is varied can be optimized by means of
a targeted fine tuning of the contents of the individual components
of the alloy and set to higher values than if only the martensitic
range were to be preferred for more readily reproducible damping
properties, as is otherwise customary in the prior art.
[0029] For the targeted improvement of the mechanical damping, the
martensite-austenite transformation temperatures or the associated
ranges M.sub.S to M.sub.F and/or A.sub.S to A.sub.F are matched to
a predetermined use or working temperature which will occur in the
intended use of the alloy in a "component". A high internal
friction is also set as a result. The term "component" is intended
to cover all conceivable practical use possibilities and include
both individual parts and more complex multipart components,
housings, machines and the like. Both the use temperature and the
working temperature can be average temperatures, i.e. means of a
working range or use range. If appropriate, both transformation
temperature ranges, viz. the martensitic range and the austenitic
range, can be used for matching to one relatively large working
temperature range or two different working temperature ranges.
Matching is achieved by variation of the proportions by weight of
the abovementioned constituents of the alloy during melting of the
alloy.
[0030] The properties of the alloy obtained by the process can be
specifically matched to the respective intended use by means of the
elements nickel, iron, cobalt, zinc, silicon, vanadium, niobium,
molybdenum, chromium, tungsten, beryllium, lithium, yttrium,
cerium, scandium, calcium, titanium, phosphorus, zirconium, boron,
nitrogen, carbon. Thus, for example, an addition of nickel or
silicon increases the corrosion resistance and strength properties.
The elements iron, vanadium, niobium, molybdenum, chromium,
tungsten, yttrium, cerium, scandium, calcium, titanium, zirconium,
boron are of importance for achieving a fine-grade structure.
Nitrogen and carbon together with transition elements improve the
mechanical properties of the alloy obtained according to the
invention. The aging resistance of the alloy both in the austenitic
state and the martensitic state is increased by addition of cobalt.
Beryllium and phosphorus protect the melt against oxidation. In
addition, various combinations of the alloying elements enable a
more or less strong influence to be exerted on the transformation
temperatures of the alloy of the invention in order to optimally
match the requirement profile for a specific application.
[0031] The alloy therefore preferably contains from 1 to 4% by
weight of nickel. A preferred embodiment of the alloy contains from
11.6 to 12% by weight, preferably about 11.8% by weight, of
aluminum. Furthermore, manganese contents in the range from 8 to
10% by weight in the alloy are preferred. The alloy can also
preferably contain from 0.01 to 1% by weight of cobalt.
[0032] The microstructure of the cast alloy has relatively large
cast grains and the grains are preferably made finer in order to
achieve the optimal mechanical properties. Boron additions in the
range from 0.001 to 0.05% by weight and/or chromium additions in
the range from 0.01 to 0.8% by weight and/or iron additions of from
2 to 4% by weight are particularly effective for this purpose. In
addition, grain refinement can also be effected by addition of rare
earths in an amount of up to 0.3% by weight.
[0033] The alloy can also contain from 2 to 6% of zinc.
[0034] The alloys preferably have M.sub.S temperatures of
>0.degree. C., without the invention being restricted
thereto.
[0035] The invention gives a significant improvement in the damping
properties since optimal setting of these properties while at the
same time maintaining other desired properties has been made
possible for the first time by the invention. The process of the
invention enables the transformation temperatures in the material
to be matched to the respective use conditions so that the specific
damping capacity of the alloys of the invention at the intended use
temperature is up to 80% and more.
[0036] The invention also encompasses a copper alloy which has a
particular composition and comprises, as constituents of the
alloy,
more than 4% by weight of manganese, more than 10% by weight of
aluminum, from 0.01 to 0.8% by weight of chromium and, individually
or together, from 0 to 18% by weight of one or more of the elements
nickel, iron, cobalt, zinc, silicon, vanadium, niobium, molybdenum,
chromium, tungsten, beryllium, lithium, yttrium, cerium, scandium,
calcium, titanium, phosphorus, zirconium, boron, nitrogen, carbon,
but each element in an amount of not more than 6%, and copper to
100% by weight.
[0037] This novel alloy for mechanically stressed components can
additionally have the further specifications as indicated above and
can likewise be obtained by matching the martensite-austenite
transformation temperatures or the associated ranges M.sub.S to
M.sub.F and/or A.sub.S to A.sub.F to a predetermined use or working
temperature of the component, as described above.
[0038] In the case of existing HIDAMETs displaying martensitic
phase transformations, it has been stated in the prior art that
maximum damping occurs when the material is cooled from the
austenitic state to close to the M.sub.S temperature and when the
material is heated from the martensitic state to the region of the
A.sub.S temperature. These damping maxima are not utilized in
industry since the transformation temperatures of the material are
difficult to reproduce using the existing processes. Apparently
small changes in the chemical composition caused by oxidation or
burning of the alloying elements result in shifts in the
transformation temperatures which can be more than 100.degree. C.
For this reason, it has hitherto not been possible to set the
M.sub.S or A.sub.S temperature reproducibly to within
.+-.10.degree. C. even by very precise formulation of the charge
and carrying out melting with great care. Attainment of the damping
maximum is therefore deliberately dispensed with in favor of
smaller but more reproducible damping values in the purely
martensitic state in the production of conventional HIDAMETs.
[0039] This disadvantage is overcome by the invention.
[0040] Experiments carried out by the inventor show that addition
of copper increases the transformation temperatures. Additions of
other alloying elements reduce the transformation temperatures. A
particularly strong effect on the martensitic transformation
temperatures can be achieved by addition of aluminum and manganese.
In a preferred embodiment, correction of the transformation
temperatures is therefore achieved during melting by addition of
copper or aluminum. Due to the high melting point of manganese and
the high affinity for oxygen, addition of aluminum is preferred
over addition of manganese for reducing the transformation
temperatures.
[0041] In the case of the alloy of the invention, the maximum
values for the specific damping capacity occur when the alloy is
cooled from the austenitic state to a temperature in the range from
M.sub.S to M.sub.F and when the alloy is heated from the
martensitic state to a temperature in the range from A.sub.S to
A.sub.F.
[0042] The temperature in the middle of the martensitic or
austenitic range of the phase transformation should therefore be
very close to the use temperature of components composed of the
alloy of the invention. The invention therefore makes it possible
to produce alloys for specific predetermined use or working
temperatures or temperature ranges, which are then particularly
suitable for particular applications and components.
[0043] The precise setting of the transformation temperatures is
carried out using a sample which is taken during the melting
process and allows express monitoring of the transformation
temperatures for the liquid alloy. As sample for express
monitoring, preference is given to using a cast wire which is drawn
from the melt with the aid of a fused silica tube in which a
subatmospheric pressure is generated. The transformation
temperatures can be determined on this sample either in the cast
state or after heat treatment, depending on the intended use, by
means of known experimental methods for detecting phase
transformations.
[0044] The transformation temperature of the sample is preferably
determined by calorimetry, dilatometry, measurement of the
electrical conductivity, optical microscopy or measurement of the
acoustic emission.
[0045] Based on the results of the examination of the express
sample, a direct correction of the chemical composition of the melt
is made, preferably by means of copper or aluminum as described
above. The process of the invention thus makes it possible to set
the transformation temperatures in the material so that the alloy
achieves the maximum possible damping capacity at the desired use
temperature. Efficient matching of the material to the respective
use conditions is therefore basically ensured.
[0046] The martensitic transformation can also be induced in a
defined temperature range by means of externally applied stresses.
In this case, the transformation temperatures in the material
increase linearly with the stress. This increase in the
transformation temperatures has to be taken into account in the
production of components from the alloy of the invention if
mechanical stresses are to be expected there.
[0047] In addition to the abovementioned influencing factors, the
damping maximum is also influenced to a considerable extent by the
microstructure of the alloy, with larger grains leading to better
damping properties. The grain size of the alloy can be set by means
of suitable alloying measures so that an optimal compromise between
the damping capacity and the mechanical properties is achieved for
each specific application.
[0048] It has also been found that an improvement in the damping
properties can be achieved by means of heat treatment. Heating at
temperatures of from 650.degree. C. to 950.degree. C. with
subsequent cooling or quenching in liquid or gaseous media, e.g.
air, liquid nitrogen, water, a salt bath or oil, has been found to
be particularly effective. The temperature of the quenching medium
should preferably be above the M.sub.S temperature in order to
avoid uncontrollable shifts in the transformation temperatures in
the material. The aging sensitivity of the transformation
temperatures can, according to the invention, be reduced by means
of additional heat treatment of the quenched alloy at a temperature
of from 150.degree. C. to 250.degree. C. The duration of such a
heat treatment is advantageously from 5 to 120 minutes.
[0049] In the case of large and solid castings composed of the
alloy of the invention which cannot be subjected to heat treatment
and quenching, a martensitic microstructure can, according to a
further aspect of the invention, be produced in the outer layer by
laser remelting. Here, the outer layer takes on the damping role
without the entire component having to be subjected to costly heat
treatment. In the production of such castings, the transformation
temperatures of the alloy are set during melting by means of
express monitoring so that, taking into account the cooling
conditions during laser remelting, the transformation temperatures
in the outer layer correspond to the use temperature of the
component.
[0050] The alloys obtained by the process of the invention can be
used particularly advantageously for reducing vibrations and for
noise damping on mechanically stressed components, especially for
ships, propellers, machine housings, in particular pump housings,
generator housings, vibrating machines, precision apparatuses,
electronic instruments, tools which are subjected to vibrations
and/or impacts during operation or produce these, in particular for
punches, dies, machine hammers, lathe tools and milling tools.
[0051] The invention is illustrated below with the aid of an
example.
EXAMPLE
[0052] Noise-damping compressor housings or various hydraulic
components can be produced using an alloy which displays its
maximum damping properties at a temperature of about 120.degree.
C.
[0053] For this purpose, the following alloy was produced in air in
an induction furnace: [0054] Basic composition: [0055] 84% by
weight of copper [0056] 12% by weight of aluminum [0057] 4% by
weight of manganese
Express Sampling:
[0058] For the express monitoring of the transformation
temperatures, the following method was developed: A cast wire
having a length of from 10 to 150 mm (preferably from 15 to 100 mm)
and a cross-sectional area of from 0.2 to 7 mm.sup.2, preferably
from 0.7 to 3.2 mm.sup.2, serves as sample. This is drawn from the
melt by means of a fused silica tube in which a subatmospheric
pressure is produced. Known detection methods can be applied
directly and very quickly to this sample. In a preferred method
used here, too, the acoustic emission is monitored over a
temperature profile.
[0059] The first sample for the express monitoring of the
transformation temperatures on the melt having the basic
composition gave A.sub.F=100.degree. C.; A.sub.S=52.degree. C.;
M.sub.S=68.degree. C. and M.sub.F=15.degree. C.
[0060] The transformation temperatures of this melt were corrected
to higher values by addition of copper. Values determined on the
subsequent express sample were A.sub.F=145.degree. C.,
A.sub.S=74.degree. C.; M.sub.S=102.degree. C. and
M.sub.F=43.degree. C. These transformation temperatures are
well-suited to achieving maximum damping values at 120.degree. C.
The melt was cast into an ingot mold which had been preheated to
300.degree. C. Specimens for damping measurements were cut from the
castings obtained. The damping behavior was characterized by means
of the specific damping capacity. The internal friction was
measured at a flexural vibration frequency of 0.1 Hz with a
constant heating rate and cooling rate (1 K/s). The 2980 DTMA V1.7B
instrument from TA Instruments was used for these purposes. The
internal friction is measured as the phase angle between mechanical
stress and strain. The damping behavior was characterized by means
of a specific damping capacity given by the formula
spec. damping capacity=2.pi. tan .phi..
[0061] The damping behavior of the alloy produced in this way is
shown in FIG. 1.
[0062] FIG. 1: Development of the specific damping capacity of the
alloy from the example, recorded for one heating and cooling
cycle
[0063] FIG. 1 shows a curve recorded for the above-described
example. The specific damping capacity in % is plotted against the
temperature in 0.degree. C. The temperatures were raised from below
zero to 200.degree. C. and brought back again in a heating and
cooling cycle. As can be seen, significantly higher damping is
achieved in the austenitic range than in the martensitic range for
the illustrative alloy, so that the restriction to martensitic
structures which is frequently applied in the prior art has to lead
to significant disadvantages in terms of the alloy properties.
[0064] The illustrative alloy attains its maximum damping
properties at a temperature of 120.degree. C. and thus successfully
achieves the object set. The damping which can be achieved is above
70%.
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