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THE SPECIAL TECHNOLOGY OF AMORPHOUS MATERIALS
PRODUCTION
V.S.Tsepelev, B.A.Baum, G.V.Tjagunov, V.I.Ladjanov, K.Y.Shmakova, A.N.Vloh
Institut of Liquid Metal Physics, Urals State Technical University,
19 Mira str., Yekaterinburg, 620002, Russia
ABSTRACT
The physical properties of liquid alloy Finemet type has been investigated. The
melting regimes of alloy has been proposed on the base of liquid metal properties
analysis. The first regime is the heating to the temperature below tc and further
amorphisation. The second regime is the heating to the temperature above tc, then
amorphisation by the first regime. The third regime is the heating to the temperature
above tc. The amorphisation temperature is below then by the first regime. The
physical characteristics of amorphous and nanocrystalline ribbons were tabulated. The
best service properties of ribbons were obtained by the third regime.
It has been established by the x-ray difraction and magnetometry that
nanocrystalline layer of boron and silicon solid solutions in -Fe is formed on the
specimen surface during amorphisation. The polyterms of magnetic anisotropy
effective field (Ha) have nonmonotonic type. The physical motive of such Ha
behaviour is the competition of main processes: the quenching stress relaxation, the
composition of nanocrystalline phase changing, surface and body crystallisation.
Such melt preparing leads to account of plane nanocrystalline phase on the
surface change in a nonannealed specimens.The means of Ha is changed and its
polyterm extremum position is moved out on temperature scale. The elimination of
plane nanocrystals from specimen surface by the chemical etching tends to double
decreasing of anisotropy effective field.
1. INTRODUCTION
The preparation technology of a commercial melt of specific chemical
composition can have many variants. For a given set of production conditions, the
optimal variant can be selected out of them only on a scientific basis by taking into
accoun the formation of the structure and properties of the liquid multicomponent
system during the course of melting. In a well prepared melt, there must not be any
traces of prehistory and it must be in equilibrium, i.e., under the given conditions, it
must have the maximum amount of homogeneity possible. The microinhomogeneity
existing in such a melt is determined only by the differences in the interaction
energies of particles (1).
The question arises then as to what model concepts can adequately describe the
structure of a melt, which has the aforementioned features, and is it correct to consider
the interrelationship found in the experiments between liquid and solid states of the
same real substance? In our opinion, the most complete answer to the problem is the
quasichemical model of the microinhomogeneous structure of liquids, which is result
of development of the views of Stuart, Frenkel, and Eyring (2).
The model essentially consists of the following. The melt is composed of
extended regions (cybotaxes or clusters), the atomic arrangement inside which is
distinguished by a certain order (short-range). Owing to relatively strong thermal
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motion of the particles, the clusters do not have any clear boundaries. The
predominant atomic coordination is continuously replased by other arrangements as
the distance from the core of the cluster increases. For the same reason, the lifetime of
the clusters is limited and depends on the energy of the chemical bonds in them as
well as temperature.
2. EXPERIMENTAL PROCEDURES
The main advantage of complex is the ability of simultaneous stadyng of
structure, electron and kinetic characteristics of liquid and solidifyed metals in the
wide temperature interval up to 1900°C. Obtaining absolute values of phisicochemical
properties of metal melts. The most of the units work in the automatic regimes, it
improve the results reliability. Metrological attestation of complex's unit is carried
out. Unique of the complex is in absence of analogies in the world practice.
Measurements of the strength f were carried out at 27 and -196oC with the
extension rate 1.5 x 10-4 s-1 using a deformation machine with a rigidity of 25 kN/mm.
Each experimental point of the strength was obtained by averaging the results of
measurements on five samples. The spread in values f was 3-5%. Samples for
measurements of the anisotropy of f were cut out from a "wide" ribbon at angles 
of 0, 22.5, 45, 67.5 and 90° to the ribbons length axis. Their width and gauge length
were 5-6 mm and 15-20 mm, respectively. Fracture toughness K1C was measured
under uniaxial tension of samples with a transversal crack made beforehand on the
axis of the sample. The failure surfaces of the samples were studied by means of a
JSM-T20 scanning electron microscope, surfaces of the samples were studied using
an optical microscope. The kinematic viscosity of melts was measured by the method
of damping of torsional vibrations of the crucible with the melt suspended on elastic
fibre (3).
At present time the fundamental properties and structural changes investigations
of the Fe-C-Si, Fe-B, Ni-B, Co-B alloys cany out on the units of the complex. The
composition and melt technology this alloys are improved.
It may be additionally carry out the investigations of the amorphous alloys on
the iron, nickel and cobalt base and wide range of alumin alloys.
3. EXPERIMENTAL RESULTS AND DISCUSSION
Investigations of physical properties of liquid alloys based on iron, nickel and
cobalt that are designated for producing amorphous materials deserve to be paid
special attention. This is related, on the one hand, to the high crystallization rates and
retention of the structural features of the liquid metal in the solid state and, on the
other hahd, to the substantial effect of the kinematic viscosity and surface properties
on the production technology of amorphous ribbons.
The reason of anomaly forming on the properties polyterms may be follows.
Alloys for amorphization have as a rule the eutectic composition or close to it. The
phases that forming eutectic are bordered in the solid state. After melting the liquid
metal inherites their local structure. The physical properties polyterms anomalys are
determined by the intensive destruction of this microregions where internal
interatomic interaction in the region is stronger than outside. Upon heating to the
critical temperature (or tan) the energy of the thermal motion of the particles in the
melt becomes comparable to the bond-breaking energy of the strongest interatomic
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interaction in the nonequilibrium atomic clusters. The heat motion destroys clusters,
the melt loses its heredity.
The destruction of strong microregions leads to significant melt overcooling
during solidification, that increases its glassforming ability and gives the possibility to
stabilize production technology and to get the more amorphous straps.
So, the kinematik viscosity (Fig.l) of nanocristalline magnetic alloy Finemet
type, has been studied (4). The first regime is heating to the temperature belove t C,
and fumer amorphisation. The second regime is heating to the temperature above tC,
then amorphisation by the first regime. The third regime is heating to the temperature
above tC, then overcooling and further amorphisation. The physical characteristics of
amorphous ribbons were tabulated. The best service properties of ribbons were
obtained by the third regime.
Fig. 1. The politerm of kinematic viscosity of the amorphous solder Finemet type:
 - heating; o - cooling; tC - critical temperature. The numbers about the curves are the
termal diagrams of three regims
Quantitative study of the melt thermal treatment influence on mechanical
properties of metallic glass ribbons (MGRs) had begun in the early 1990s (5). It had
648
turned out that the ductile shear failure stress f and the fracture toughness K1C of the
MGRs obtained after the melt heating above the melt critical temperature tC are higher
than those obtained from the melts that were not heated above tC. The critical
temperatures tC were determined from the measurements of the temperature
dependence of the melt kinematic viscosity under heating and cooling.
Results are clear from the Table 1 and Fig. 2 where f values are indicated for
the Fe73.5Nb3Cu1Si13.5B9 metallic glass obtained from the melt after its different
thermal treatments.
Table 1
Dependence of strength of the Fe73.5Nb3Cu1Si13.5B9 ribbons on the thermal treatment
of the melt before quenching
f (GPa)
Termal treatment
Regime 1
Regime 2
27oC
1.43
1.10
-196oC
1.13
0.97
Fig. 2. The polar of strength diagrams  f () / f (0о) of the Fe73.5Nb3Cu1Si13.5B9
ribbons 1 - regime 1, 2 - regime 2
It is well known that the temperature of the beginning crystallization of the
amorphous alloys increases with the growth of heating rate. For the comparision of
the regimes the annealing in the temperature region from 250 to 600°C during 1 hour.
The minimal DC coercive force (HC) 1,04-1,20 A/m is reached after annealing at 500520°C in comparision with nonannealed spesimens that have HC = 28,8-36,0 A/m.
The rapid crystallization during 2,5,10 second at 620°C made by the method of Physic
Metal Institute of Urals departament of Russian Academy of Science gives the
opportunity to reach the values HC = 1,20 A/m. Holding time after annealing (to 10
days and in the initial state to 1 year) and melting regime does not influence on HC.
The typical temperature dependences of kinematic viscosity (), electrical
resistivity (), magnetic sucsecibility (), surface tension () and density (d) of the
melt containing high amount of element - amorphizator is shoun on Fig. 3. It is
founded that the special critical temperatures named t are determined on the base of
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such data. The heating above t leads to more homogenous melt state and, as a rule to
forming the physical properties hysteresis (2). The overcooling value t is measured
for this equilibrium melt. The presence of hysteresis is indicated the differencies
between the initial and finished melt state and wishes to each the tC during melting.
Some times the melt may be heated only to the anomaly temperatures tan. The melt
holding time at the maximal heating temperature is experimentally determined during
the investigation of the time dependence of properties changes at this temperature.
Fig. 3. The typical politerms of physical properties of amorphous alloys: t - a value
of overcooling; tan - the temperature of anomalies; th - the temperature of hysteresis;
tC - the critical temperature
It has been established by the x-ray difraction and magnetometry that
nanocrystalline layer of boron and silicon solid solutions in -Fe is formed on the
specimen surface during amorphisation. The polyterms of magnetic anisotropy
effective field (Ha) have nonmonotonic type. The physical motive of such Ha
behaviour is the competition of main processes: the quenching stress relaxation, the
composition of nanocrystalline phase changing, surface and body crystallisation.
650
Such melt preparing leads to account of plane nanocrystalline phase on the
surface change in a nonannealed specimens.The means of Ha is changed and its
polyterm extremum position is moved out on temperature scale. The elimination of
plane nanocrystals from specimen surface by the chemical etching tends to double
decreasing of anisotropy effective field.
In cooperation with GAMMAMET Research & Production Enterprise soft
magnetic alloy has been developed on a basis of GM 411 alloy which has found a
wide application in the field of magnetic core materials for high frequency
transformers, current transformers and measuring transformers.
4. CONCLUSION
An analysis of polytherms of properties in the crystal-liquid phase-transition
region shows that melting in metallic melts is not accompanied by a substantial
restructuring of their electronic structure or interatomic inteaction. While heating the
melt, discontinuous structural changes can take place in them.
While studying questions of the interrelationships between the properties and
structure of real iron-based melts, which differ in terms of their complex ratios of the
localized and collectivizedvalence electrons, whith properties and structures of the
corresponding solid substances, the quasichemical model seems to be the most
satisfactory among the models or the ingomogeneous structural state of the melt. The
usefulness of the latter is caused by its retention of information regarding the real
bond between liquid and solid states and consists of the possibility of predicting the
results of physicochemical effects affecting the melts and the properties of the final
solid product.
Regularities of low temperature mechanical properties of metallic glass ribbons
are determined both by their atomic structure and by peculiarities of their macroscopic
stressed state and macroscopic defects (inclusions, surface caverns etc). The
properties that find their explanation on the basis of knowledge of peculiarities of
clusterous atomic structure of metallic glasses are considered in this review. It turned
out that the theory of polycluster amorphous solids (5) is a satisfactory basis for
understanding mechanical properties of metallic glasses that enables the extension of
the 'structure-properties' conception to amorphous state of solids.
In all technologies investigated, the preparation of a melt toward amorphization
by its temperature-time treatment leads not only to improvement but also to
stabilization of the structure and properties of the metal from melt to melt.
AKNOWLEDGEMENTS
The work has been made thanks to finansial help of Russian Ministry of science
on the "Unical units for investigation of structure and physical properties of metal
melts. Melt. Registration number 06-02".
REFERENCES
1. Baum B.A: Metallic Liquids. Moscow, Sciens, 1979.
2. Baum B.A., Khasin G.A., Tyagunov G.V. et al.: Liquid Steel.
Metallurgiya, 1984.
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Moscow,
3. Egorov D.V., Tsepelev V.S., Tjagunov G.V., Pastuchov S.V: 'The automated
system of determinations of the kinematic viscosity of melts'. Industrial laboratory.
Diagnostics of materials 1998 (11) 46-48.
4. Tsepelev V.S., Baum B.A., Tjagunov G.V., Kulechov B.M:'The new technology of
melt preparing to amorphization'.14nd Int Scient Conference, Poland, Zakopane,1995.
5. Tabachnikova E.D., Bengus V.Z., Egorov D.V., Tsepelev V.S., Ocelik V:
'Mechanical properties of amorphous alloys ribbons prepared by rapid quenching of
the melt after different thermal treatments before quenching'. 9th Int Conf
Proceedings, Bratislava, Elsevier, 1997.
652
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