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INTERNAL FRICTION STUDIES ON STRUCTURAL RELAXATION AND CRYSTALLIZATION IN
Co75Si10B15 METALLIC GLASS
T. Poloczek, G. Haneczok, J. Moro_
To cite this version:
T. Poloczek, G. Haneczok, J. Moro_. INTERNAL FRICTION STUDIES ON STRUCTURAL RE-
LAXATION AND CRYSTALLIZATION IN Co75Si10B15 METALLIC GLASS. Journal de Physique
Colloques, 1983, 44 (C9), pp.C9-115-C9-120. �10.1051/jphyscol:1983912�. �jpa-00223356�
INTERNAL F R I C T I O N S T U D I E S ON S T R U C T U R A L RELAXATION A N D CRYSTALLIZATION I N
c ~ ~
M E T A L L I C GLASS*~ s ~ ~ ~ B ~ ~
T. Poloczek, G. Haneczok and J.W. Moroii
I n s t i t u t e of the Physics and Chemistry o f Metals, S i l e s i a n University, Bankowa 2 2, 40-00 7 Katowice, Poland
~ k s u m g
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On a 6tudig le frottement interne /FI/ et le module de torsion en fonction de tempkrature dans l'alliage a m o r ~ h e C O ~ ~ S Sur la courbe ~ ~ ~ B ~ ~FI . on a trouvg les maximums li6s A la cristallisation du cobalt et la pr6cipitation de ces compos6s intermgtalliques avec le bore et le silicium. Sur la courbe G/T/ on a d6montr6 l'existance d'un processus de relaxa- tion structurale. On a 6valu6 1'Qnergie de ce processus: 0,48eV.Abstract
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Internal friction /IF/ and shear modulus as functio-ns of temperature were investigated for C O ~ ~ metallic S ~ ~ ~ B ~ ~
-
glass. On the IF curves were found maxima associated with the crystallisation of cobalt and also with the precipitation of intermetallic compounds of cobalt with boron and silicon.
A structural relaxation process was ascertained on the G/T/
curve. The energy of this process was estimated and found to be 0.48 eV.
I
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INTRODUCTIONIn glassy alloys three types of phenomena can occur which could influ- ence the form of the internal friction curves Q-~/T/ and also the cur- ves f 2 /T/ a G/T/ where G is the dynamic shear modulus [l]: 1. peaks on the Q-~/T/ curve associated with relaxation processes of migratio- nal type, 2. variations in Q-~/T/ and f /T/ caused by structural rela- 2
xation, 3. maxima on Q - ~ / T / and extrema on f 2 /T/ due to crystallisa- tion and the precipitation of crystalline intermetallic phases. From study of accessible literature it would appear that no investigations have as yet been undertaken on cobalt-based alloys. Hence studies were conducted on IF and shear modulus in Co 75Si10B15 glassy alloy.
I1
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SAMPLES AND PROCEDURESamples of the tested alloy were in the from of ribbons of dimensions 50x3.5x0.04 mm3 produced by the traditional melt-spinning method at the Institute of Materials Engineering of khe Warsaw Polytechnical University.
IF was determined using a K& type inverted pendulum, as described in
*
This research was supported by the Polish Academy of Sciences.Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983912
C9-116 JOURNAL DE PHYSIQUE
detail in [2]
,
in vacuum / l ~ - ~ t o r r ~ Measurements were performed using a linear heating rate of 2.5 K/min. in a temperature range from 300 to 1000 K. Vibrations frequency varied from 0.3-
0.6 Hz. Vibrations amplitude, calculated as described in [3],
was about 3x10-~. Lateral vibrations of the vibrating system which disturb the IF measurements were eliminated, as described in 133, by applying an external tensile stress to the sample. In this case the stress applied was 0.8 kg/mm 2.
Curves Q-~/T/ and G/T/ were determined for several samples in the as- -quenched state. Further curves Q - l / ~ / and G/T/ were determined for a sample raised to increasingly high temperatures, the sample being coo- led to room temperature after each measurement. These measurements were made on a sample, which had initially been in the as-quenched state.
Additionally, X-ray examinations were made of the as-quenched samples and also for these samples heated to temperatures chosen on basis ofthe form of the Q-~/T/ curve obtained. X-ray tests showed that the as-quen- ched samples were not in a crystalline state.
111
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RESULTSThe IF curve Q-~/T/ and the shear modulus curve f 2 /T/ for as-quenched samples are shown on Fig.1. On the Q - ~ / T / curve a sharp maximum B may be distinguished at temperature 783 K. On the low temperature side of peak B, which begins from about 400 K, may be seen a clear inflexion A at about 740 K. The right side of peak B exhibits a rapid drop on which, at a temperature of about 810 K, may be observed an inflexion C.
After reaching a minimum at 850 K the curve rises to 950 K and at this temperature begins the plateau D which extends to 980 K, that is the highest measurement temperature.
The distinctive features of the shear modulus versus temperature curve correspond temperature-wise to the characteristic points B
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D on Q-~/T/, i.e. peak B corresponds to minimum B' on the f 2 / ~ / curve, in- flexion C corresponds to inflexion C ' and plateau D to the small in- flexion D r . The inflexion A on Q-'/T/ has no corresponding element on2 2
f /T/. On the f /T/ curve, after a slight drop in interval up to 430K, there is a distinct rise in shear modulus due to which there appears a wide maximum close to 550 K.
The second measurement shows that all the special points distinguished have disappeared, both on the Q - ~ / T / and f 2 /T/ curves. There is only a high temperature IF background and a fall in value of shear modulus with increasing temperature.
/f=0.53 Hz at peak B/: l-measure- ever hiaher temperatures; sample ment for samples in as-quenched cooled to room temperature after state, 2-second measurement. every measurement.
Measurements carried out at various values of frequency f show that temperature of peak B does not vary with f but the height of this peak decreases with increasing f.
Measurements of Q - ~ / T / and f /T/ carried out at ever higher temperatu- 2 res caused changes in the form of both curves /Fig.2/. The low tempe- rature branch of Q-~/T/ shifts towards higher temperatures after each consecutive measurement until maximum B occurs which does not disa- ppear even after measurement at 765 K. Measurement to temperature above peak B, to 804 K, causes its disappearance, as may clearly be seen on the Q-~/T/ curve determined to 854 K. The temperature of occur- rence of maximum B does not chanqe, relative to results obtained in continuous measurement /Fig.l/. However, a second small maximum occur- red at 810 K , hence corresponding to the inflexion C on Fig.1. During the following measurement up to 920 K neither peak B nor peak C appear.
The form of the f /T/ curves shows that durinq consecutive measuremen- 2
C9-118 JOURNAL DE PHYSIQUE
ts the values of shear modulus increase. As the peak B disappears, the minimum B' also disappears /Fig.2/. The minimum C' on the f /T/ curve, 2 which appeard at 810 K, corresponds to the maximum C occurring at this same temperature. After heating to 920 K this minimum also disappears.
IV
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DISCUSSIONThe temperature of inflexion A on Q-'/T/ agrees very well with the Curie temperature determined for this ferromagnetic alloy, i.e.T =740K.
C
Hence it may be presumed that the observed effect is associated with a magnetic phase change taking place in the tested glass. A similar effect was observed for a Fe-P-C ferromagnetic glass as reported in
141.
Measurements performed at various values of pendulum vibration freque- ncy showed that results are in agreement with those obtained in simi- lar investigations carried out for other metallic glasses [3,5,6]
.
The temperatures of peaks B and C and also of the plakeau remain un- changed while the height of peak B decreases with rise in measurement frequency. The behavior of peaks B and C considered in conjunction with the X-ray tests indicate that peak B is associated with the appe- arance of crystalline cobalt in the amorphous matrix. Peak C is asso- ciated with the precipitation of the compound COB and plateau D should most probably be associated with the precipitation of crystalline Co2Si.
Measurements of curves Q-l/~/ and f /T/ 2 carried out at ever higher temperatures revealed interesting changes in their forms /Fig.2/. Most importantly, peak C was distinguished from the high maximum B. With continuous measurement C appeared only as an inflexion on the curve /Fig. l/
.
The shifting of curve Q-'/T/ towards higher temperatures, at temperatures lower than crystallization temperature, is evidence of the permanent changes taking place already in the glassy phase. These changes are also to be observed in the form of the f /T/ curves. 2 A similar result was obtained in [4].In the continuous measurements carried out for as-quenched samples only one crystalization peak was obtained, but when measurements were carried out to ever higher temperatures a second phase change peak appeared. Similar results were reported in [4] for an Feg0Pl3C7 alloy Hence using the IF method it may be confirmed that passing to the equilibrium crystalline state during heating usually takes place in a multi-stage process via metastable intermediate states.
Fig. 3 shows the value f2, determined at temperature 300 K, as a func- tion of prior heating temperature of the tested sample. On this curve
which the previous curve was 300 400 500 600 700 800 determined.
four temperature intervals may be distinguished, i.e. I /300-430 K/
where the value of the modulus is constant, I1 /430-500 K/ where modu- lus value rises, I11 /500-650 K/ where the modulus value is again con- stant and IV /from 650 K/ where the modulus value shows a steady in- crease up to crystallization temperature. Hence it may be seen that structural changes above 430 K take place in two stages, between which /in the interval 500-650 K/ G remains virtually unchanged. It is also noteworthy that the secend temperature interval is identical with the temperature interval of rising G on Fiq.1, i.e. I1 430-510 K /Fig.3/, rising f2
-
430-520 K /Fig.l/.In order to verify if the changes in modulus value are related to ther- mal activation, for interval I1 the following equation was taken:
f2
-
:fa
2 = A exp /-
-
/fo k T
where Q is an effective activation energy and fo is vibration frequen- cy in interval I. The energy value was estimated at P=O.S eV.
This low activation energy obtained for process 11, plus the slight growth in value of modulus /about 3.5%/ associated with this process, undoubtedly indicate that it is associated with structural relaxation.
A similar results was obtained in [7] for Fe40Ni40B20 metallic glass, i-e. Q=0.6 eV. In [l] it was stated that the increase in modulus value during structural relaxation is of the order of a few percent /e.g.7%/.
Finally it may be added that at temperatures higher than 300 K no peaks due to migrational relaxation processes were found.
The authors wish to express their thanks to Dr Andrzej CaZka of the Institute of Materials Engineering, Warsaw Polytechnical University, for the samples supplied.
C9-120 JOURNAL DE PHYSIQUE
REFERENCES
1. CHEN H.S.,Rept.PrOgr.Phys. %/1980/355.
2. PIETRZYK J.,BRAWUSKI J.,Pomiary Automatyka Kontrola,No 9,/1976/325.
/in Polish/.
3. POLOCZEK T.,CIE~LAK L.,MoRo~~ J.W.,Paper to be presented at this conference.
4. SOSHIRODA T.,KOIWA M.,MASUMOTO T.,J.Non-Cryst-Solids 2/1976/173.
5. MO CHI-ME1,SHUI JIAPENG,HE YIZHEN,J.Physique %/1981/C5-523.
6. ZOLOTUKHIN I.V.,KALININ YU.E.,Fiz and Chim.Obrab.Materiallov No 2, /1982/80 /in Russian/.
7. KAMEL R.,GOBRAN N.K.,SALEH S.,HANNA B.F.,J.Physique %/1981/C5-505.
