ANELASTIC BEHAVIOUR OF SOME SIX COMPONENT METALLIC GLASSES

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ANELASTIC BEHAVIOUR OF SOME SIX COMPONENT METALLIC GLASSES

S. Kiss, G. Posgay, Cs. Kopasz, F. Kedves, I. Harangozó

To cite this version:

S. Kiss, G. Posgay, Cs. Kopasz, F. Kedves, I. Harangozó. ANELASTIC BEHAVIOUR OF SOME SIX COMPONENT METALLIC GLASSES. Journal de Physique Colloques, 1983, 44 (C9), pp.C9- 127-C9-131. �10.1051/jphyscol:1983914�. �jpa-00223360�

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JOURNAL DE PHYSIQUE

Colloque C9, supplbment au n012, Tome 44, dCcembre 1983 page C9-127

A N E L A S T I C BEHAVIOUR OF SOME S I X COMPONENT M E T A L L I C GLASSES

S . K i s s , G . Posgay, Cs. ~ o ~ a s z ' , F . J . Kedves and 1.2. Harango26

I n s t i t u t e f o r Appbied P h y s i c s , K o s s u t h L. U n i v e r s i t y , Debrecen, P.O. Box 2, H- 4 0 10, Hungary

' ~ s e p e Z Metab Works, CsepeZ 1 , P.O. Box 4 9 , H-1757, Hungary

Abstract

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Internal friction, dynamic elastic modulus and microhardness were measured on FeCoNiCrBSi amorphous alloys. Vartous modulus increases were found in the strcutural relaxation range below the crystallization temperature.

The three crystallization steps up to 700'C marked by modulus increase and damping decrease depend on the composition and the previous heat treatments. This effect diminished markedly after heat treatments at a temperature 30-40'~ below the crystallization point, No definiterelaxation peak was found. The microhardness i-nvestigations confirmed the results inferred from themo- dulus measurements. The stability of the amorphous system increases with increasing Cr and Si content.

1, Emerimental

The measurements were made using a torsion pendulum having a light svringing part with low inertial momentum in the frequency range 0.1 to 1 Hz, In order to avoid energy consume of the measuring system optical detection using a Sefrm type light following galvanometer was applied, The spectra were measured between room temperature and

800'~ viith a heating rate of 3-4 deg/min, The deformation amplitude during the measurements was less than 10'4. In course of a measurement the smallest axial load arose from the pendulum of 30 g mass.

Excess load could be put onto the swinging pendulum in vacuum without opening the system using up to 5 discs of 170 g each. This load corresponds to a stress of 100

-

¹⁵⁰

n/mrn2

maximally for common specimen sizes,

The metallic glasses were prepared by melt spinning method. The specimens were 1.5 mm wide, 0.04 mm thick and 20-30 mm long stsips.

The composition of the four sets of samples in at% were the folloviing:

Sign Pe Co Hi Cr B Si

1 7 51 19 1 14 8

2 7 51 18 2 14 ⁸

3 7 51 16 4 14 8

4 7 53 15 5 15 5

2. Results and discussion

The internal friction of the as received samples /Pig.l, 3/ near room temperature was about 15.10'4 which value is higher than the common value for crystalline materials. The background between about 100 and 400°c is approximately exponential, In some cases a decrease in the slope of the increasing curve occurs at about 300°C. Taking into account the run of the modulus curve this effect in damping can- not be a relaxation eak but it could result from the weak AE effect

m d magnetomechanica? damping. The Curie temperatures of these 871&t- ly magnetistrictiv alloys are near 300°C.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983914

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JOURNAL DE _{PHY SlQUE}

Pig, 1

Internal friction and modulus spec- of the as produced alloy M02

It can be concluded studying the behaviour of the relative modulus that the common decrease can be found up to 200-2500C in general which is cbmacterfstic of a stabile materFal or of ones having only slight changes in the stru dure within the given range [l]

.

At hi&er temperatures the modulus increased almost in all cases up to about 360-380~~. The amount of increase is very different. For a group of specimens the modulus at 350°C falls vrithin 25% of the value measured at room temperature. For another group the increase of the modulus is much more higher, at 350'~ it is20-30% of the value measured at room temperature.

In the range above 400°C on the spectra of the four different amorphous alloys there are three characteristic mAma.Between 410 and 460°C there are generally peaks /200-450/ x 10'4 high vdth a half width of 20-30% follov~ed by an increase in the modulus of about 10%. These values for alloy 4 are smaller. Comparing alloys 1-3 an increase of the peak temperature can be observed /41C, 450, 460°c/.

According to our previous work [2] and to the DSC, electric resisti- vity and TEE measurements

p]

on the same materials this effect could be ascribed to a partial crystallisation in the alloy when fcc Ni and hcp Co crystallizes from the amorphous material, This W h a s no relaxation character;it arises, indeed, from the decrease of background crystallization* I*Teasuring the room temperature microhardness of the specimens taken out of the furnace during the continuous heating period we found characteristic changes in the same temperature re-nge as before /Fig,2/ [4, 53,

A peak of similar character but much higher /1000-1500/ x 10'4 with half width of 20°C, i.e, a very sharp peak, was found in the range 530

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540°C in the four different alloys. The modulus increase was significant and proportional to the peak height. In the case of

alloys 2 and 3 the 1500 x 10'4 high peak is accompanied by a 50% increase in the modulus. This behzviour of the internal friction and dynamic modulus, furthermore the characteristics of the DSC curves can'be attributed to a second step of crystallization, The peak found is a pseudopeak caused by a decrease of the background.

A common feature of the behaviour ?or all four alloys that another generally very high /lo00 x 10' or higher/ peak appears at about 640-650°C but with a wider half :vi,dth /40-600C/ eccompanied by various modulus increase, The peak temperatures for alloys 2 and 3 are also here a bit higher at about 650°C. Similarly to the previous

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t Alloy No 2 ^__o

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OH- --%,p

J-a-G-5 .I5

,125 Alloy N' 1

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⁺ ^- ^O ^L ¹ ⁴

0 100 200 300 -KO SOoTf'Cj

_B"'

^lo'

Pig.2

-

Bicrohardnesses measured at room temperature after the heating up to the marked temperature,

peaks these are also not of relaxation character but could be the result of a third step in crystallization. Here /FeNic~/~ B phases of cementite type are formed and the whole alloy becomes crystalline

w

?..

LJJ A heat treatment at 300 or 375OC for 1 hr before the measurements caused an alongation of the decreasing range of the modulus and also the increase of the damping was lower. This can be under- stood since the structural relaxation which causes an increase in the modulus before crystallization [6, 71, already proceeded during the previous heat treatment. In such cases the structural relaxation in- dicated by a modulus increase during measurement begins always above the temperature of the previous heat treatment,

Stopping the temperature increase well below the first peak an isotherm increase of modulus and decrease of damping caused by structural relaxation was also observed in accordance 6 t h results already knovm earlier for other materials [2].

The effect of isothemal heat treatments for 0.5

-

1 hr /inter- rupting heating during the measurements/ ~vas studied near /20

-

^50°C

below/ the peaks indicating crystallization /Fig.4,5/. A heat treatment 50

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600C below the peak /e.g. 350°C/50 min for alloy 1/ had no effect on the peak height after having continued heating, But af-

ter a heat treatment at 375OC for 50 rnin the peak height decreased to the half of its original value. Stopping heating up at higher temperatures, e.g. at 381, or 391°C an increase of 1% in the mo8ulus was found which value corresponds 'to that measured at the peak temperature. After these last two isotherm heat treatments, .continu- ing heating up, the peak attributed to the first crystallization step did not appear. Similar results were found for the other saaples too, i.e, the heat treatment 40°C below the peak temperature or nearer caused the above phenomenon. The curves measured during the isotherm heat treatments /Pig.G/ show a two step form; the process seems to gain a new impulse after 20-30 min. This can be interpreted in a way that if there is enough time the crystallization starts or it is completed at lower temperatures too, but a time of incubation is also needed. Ue can conclude from the separation of the cooling and heating curves after having an isothermal anneal, that the procesqonce stacted during the anneal proceeds at loser temperatures too /Fig. 5/,

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C9-130 JOURNAL DE PHYSIQUE

Pig.3

-

⁵

The e f f e c t o f i s o - thermal h e a t t r e a t - ments during heat-

ing up / a l l o y 1/.

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Fig. 6

Internal friction and modulus

changes of alloy 1 during the isothermal treatments,

Similar results were found for the effect of the isothemal anneal below the second and third crystallization peak. In these cases, hovrever, not only a decrease of the peak height and of the modulus increase was observed but the peak \??as also shifted to lovrer

temperatures by 5

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10'~ too, The incubation effect for crystallization has been found in the case of the second peak but there vms no incubation before peak three /Pig. 6/.

Since the higher the stability the higher the crystallization temperature we can conclude from the results received for samples 1

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³that a small Cr content increases the stability because the crystallization temperature lied higher. Comparing the peak temperatures of ello-;e 3 and 4 te g&a similar conclusion in the case of Si too.

This work was sponsored by Csepel Netal Works.

References

[I] IIUTITIPGTOIT H.B., The Elastic Constants of Crystals, Academic Press, ITevr York, London /l958/,

[2) KISS S,, POSGAY G., M M E G O Z ~ I.Z,, KEDVES F. J., J. Physique Colloque C5 Supple'ment au ITolO,

42

^/1981/C5-529, [3] FOGAMSSY E., C Z I R ~ Y A,, private communication

[4] CHAFTG J., IiADD.IT F,, ROSEIT I!;., IUIJRABIAli R., Scripta Met. 16 /l982/ 'Ib73,

IS]

^HI^Lm\nRAl\m^F;. ^G.

,

KOSTEE U., TERSTZXGmI G., Conference on I~Ietallic Glasses: Science and Technology, Bu- dapest 1980. Proceedings

2

_- /1980/ 383,

161 KITRSUEBOVIE A,

,

SCOTT Ii?. G.

,

^GIRT^E,

,

^{CAHN R.}^17,

,

^Scripta Ftfet. 14 /1980/ 1307.

[7] BOTIB K., XEUH.4USER H., Scripta 1:Iet.

16

/1982/ 1053/.