VISCOSITIES OF Fe-C, Fe-P AND Fe-P-C EUTECTIC LIQUID ALLOYS BY A CAPILLARY METHOD UNDER REDUCED PRESSURE

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VISCOSITIES OF Fe-C, Fe-P AND Fe-P-C EUTECTIC

LIQUID ALLOYS BY A CAPILLARY METHOD

UNDER REDUCED PRESSURE

Y. Nishi, H. Watanabe, K. Suzuki, T. Masumoto

To cite this version:

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JOURNAL DE PHYSIQUE CoZZoque C8, suppZ6ment au n08, Tome 41, aoiit 1980, page C8-359

VISCOSITIES OF Fe-C, Fe-P AND Fe-P-C EUTECTIC LIQUID ALLOYS BY A CAPILLARY METHOD UNDER REDUCED PRESSURE

*

Y . Nishi, H. Watanabe, K. ~ u z u k i * and T . Masumoto

Department of Materials Science, Faculty of Engineering, Tokai University, 1117 Kitakaname Hiratsuka 259-12, Japm.

*!The Research I n s t i t u t e for Iron, Steel and Other Metals, Tohoku University, 2 Katahira Sendai 980, Japan.

INTRODUCTION

Based on the kinetic and thermo- dynamic points of view, the viscosity is an atomic scale measure of the thermal motion and structure of materials in the liquid state. Therefore, the viscosity has been known to be one of the most sensitive factors controlling the glass forming ability of metallic liquids.

In this study, viscosities and densities of Fe-C, Fe-P and Fe-C-P liquid alloys around their eutectic compositions are measured as a function of temperature and then the glass forming ability of these liquid alloys is discussed in terms of the critical cooling rate associated with experimental viscosities.

EXPERIMENTAJ!

Nine different kinds of samples as shown in Table 1 were prepared by melting electrolytic iron, reagent-grade carbon and phosphorus in an Ar induction furnace. The chemical composition of the samples was analysed to be identified before and after the viscosity measurement.

The viscosity was measured by the reduced pressure capillary qethod, in

whichthe apparatus used is shown as a schematic diagram in Fig.1. If a liquid flows through a capillary in reduced pressure atmosphere under the laminar flow condition, its viscosity is calculated from Hagen-Poiseuille's equation as follows

11 = C1(poH

-

ph)t

-

c2pt-l

,

(1 where 0 is the viscosity, C1 and C are the constants proper to the apparatus,

P o and p are the densities of mercury and the sample, H is the difference between the heights of Hg columns in the manometer, h is the effective mean height of the column of the sample and t is the flow time of the liquid sample.

The calibration of the viscometer was carried out using Hg(0 and 305 K ) , ~ g ( 1 3 2 3 and 1423 K) 2nd a standard organic liquid JS 50(305 K) to determine the values of C1

and C 2 in eq. (1). Quartz capillaries of 3

-

5

X m in diameter and 0.8

-

1.0

x

10-I m in length were heated up to the experimental temperature in a silicon carbide furnace. The atmosphere gas _- filling the viscometer is an Ar-5at$H2 mixture gas, which is chosen to prevent oxidation of liquid samples during the measurement.

Uncertainties in the pressure and time measurements in the present work are less than atmospheres- and 10-I seconds respectively. The density was measured using the maximum bubble pressure technique simultaneously together with the viscosity measurement.

Fig.1 Schematic diagram of t h e apparatus f o r v i s c o s i t y measurment using c a p i l l a r y method under

reduced pressure.

-

RESULT

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JOURNAL DE PHYSIQUE C8-360

Experimental results of viscosities result is not in agreement with D r a g o m i r * ~ for the nine liquid alloys are summarized /1/ observation that the viscosity of Fe-P in terms of the Arrhenius and Vogel- liquid alloys reaches a maximum at the Fulcher relations together with the eutectic composition.

temperature dependence of densities in Table. 1.

Table 1. Experigental viscosities (17: mPa.s) and densities ( p : 10

.

g.n~-~) of Fe-C, Fe-P and Fe-C-P liquid alloys

Fig.2 shows the Arrhenius relation of viscosities,i.e. log q

-

T-l plots for the nine liquid alloys, from which the

activation energy for viscous flow is calcu.lated using the least squares fitting.

1.3 I

Fig.2 Arrhenius plotting of experimental

viscosities of Fe-C, Fe-P and Fe-C-P liquid alloys

The values of the activation energy thus obtained are listed in Table 1. It is interesting to note that the activation energy for viscous flow in Fe-P liquid alloys deceases monotonically with increasing P content as shown in Fig.3. However, the absolute value of isothermal viscosities of Fe-P liquid alloys

increases with increasing P content. This

Fig.3 Activation energies of viscous flow in Fe-P liquid alloys.

Isothermal molar volumes of Fe-P, Fe- C and Fe-C-P liquid alloys at 1400 and 1600 K calculated from experimental

densities are illustrated as a function of metalloid atom content in Fig.4.

-

0 5 '10 15 20 25

P.C. ( a t % )

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The molar volume o f Fe-C l i q u i d a l l o y s i s 1.3

-

much s m a l l e r t h a n t h a t of p u r e l i q u i d i r o n

,

w h i l e t h e t h e r m a l e x p a n s i o n o f Fe-C

-

l i q u i d a l l o y s between 1400 and 1600 K i s m l a r g e r t h a n t h a t of p u r e l i q u i d i r o n .

..

1-2-

Both o f t h e molar volume and t h e r m a l _C

e x p a n s i o n o f Fe-P l i q u i d a l l o y s d e c r e a s e s

-

/

w i t h i n c r e a s i n g P c o n t e n t . The d e n s i t y of Fe-15.5~

Fe-C-P l i q u i d a l l o y i n d i c a t e s t h e t

1.1

i n t e r m e d i a t e b e h a v i o r between Fe-C and Fe-

4

P l i q u i d a l l o y s .

/.

DISCUSSION _1.0.

1 I I I I We d e f i n e a p p r o x i m a t e l y t h e dynamic 10 20 30 f r e e volume AVf(T) c o n t r i b u t i n g t o t h e ~ A V ~ (T)N,(RT)

I-'

v i s c o u s f l o w i n t h e l i q u i d a l l o y a s

f o l l o w s

A V ~ (TI = V1(T)

-

Vam(RT), ( 2 )

where V1(T) and Vam(RT) a r e t h e molar volumes o f t h e a l l o y i n t h e l i q u i d s t a t e a t T K and i n t h e amorphous s t a t e a t room t e m p e r a t u r e [8]

,

r e s p e c t i v e l y - According t o t h e p i o n e e r e d works by ~ a t s c h i n s k i / 2 / and Macleod/3/, t h e r e l a t i o n s - b e t w e e n l o g 0 and {Avf(T)/V _am(RT ) r l f o r Fe-P l i q u i d a l l o y s a r e p l o t t e d i n F i g 5 . T h i s f i g u r e shows t h a t t h e v i s c o s i t y o f Fe-P l i q u i d a l l o y s i n c r e a s e s w i t h i n c r e a s i n g P c o n t e n t , i f t h e dynamic f r e e volume i s k e p t c o n s t a n t . When Fe-P l i q u i d a l l o y s have a same v a l u e of t h e v i s c o s i t y , t h e dynamic f r e e volume i n c r e a s e s w i t h i n c r e a s i n g P c o n t e n t . The c h a r a c t e r i s t i c b e h a v i o r of t h e v i s c o s i t y of Fe-P l i q u i d a l l o y s mentioned above c a n be i n t e r p r e t e d i n t e r m s o f t h e c l u s t e r model/4/, which d e s c r i b e s t h a t Fe and P atoms s t r o n g l y i n t e r a c t t o form m o l e c u l e - l i k e c l u s t e r s even i n Fe-P l i q u i d a l l o y s . Namely, w i t h i n c r e a s i n g P c o n t e n t

, t h e c o n c e n t r a t i o n o f c l u s t e r s i n c r e a s e s i n Fe-P l i q u i d a l l o y s and t h e weak i n t e r a c t i o n between c l u s t e r s becomes a predominant f a c t o r d o m i n a t i n g t h e v i s c o u s f l o w . T h e r e f o r e , Fe-P l i q u i d a l l o y s w i t h h i g h P c o n t e n t show t h e h i g h v i s c o s i t y v a l u e accompanied w i t h t h e l a r g e dynamic f r e e volume and low a c t i v a t i o n e n e r g y o f t h e v i s c o u s f l o w , compared w i t h Fe-P l i q u i d a l l o y s w i t h low P c o n t e n t .

Fig. 5 Relations between l o g r( and { A V ~ ( T ) / V ~ ( R T

)I

-

The c r i t i c a l c o o l i n g r a t e n e c e s s a r y t o r e a l i z e t h e amorphous s t a t e by m e l t - quenching can be c a l c u l a t e d from t h e time- t e m p e r a t u r e - t r a n s f o r m a t i o n (TTT) c u r v e u s i n g Uhlman/5/'s k i n e t i c a n a l y s i s . The TTT c u r v e i n v o l v e s t h e h e a t of f u s i o n , l i q u i d u s t e m p e r a t u r e and v i s c o s i t y a s v e r y i m p o r t a n t f a c t o r s d o m i n a t i n g t h e g l a s s f o r m a t i o n from t h e u n d e r c o o l e d l i q u i d . l o g t ( t : s )

Fig.6 TPT curves f o r Fe-17.3atgC and Fe-13at%P- 7 a t % ~ e u t e c t i c l i q u i d a l l o y s . The dotted l i n e (q)

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C8-362 JOURNAL DE PHYSIQUE

Fig.6 shows the TTT curves of Fe-17.3 at%C and Fe-13at%P-Tat%C eutectic liquid alloys calculated by Uhlman's method using the experimental Vogel-Fulcher relations between the viscosity and temperature as shown in Table 1. The delay or crystallization for Fe-13at%P-7at%C alloy is about 60 times longer than that for Fe-17.3at%C alloy. The dotted line (n) shows TTT curve for Fe-17.3at%C alloy which is calculated by use of viscosity of Fe-13at% P-7at%C alloy. The dotted line (Tm) shows TTT curve for Fe-17.3at%C alloy which is calculated by use of melting point of Fe- 13at%P-7at%C alloy. These results show that the delay of crystallization, which is corresponds to glass formability, is dependent on melting point and viscosity. The critical cooling rate Rcis defined as

1

R, = ( Tm- Tn) t; 9 ( 3 )

where Tm is the melting point, and Tnand tn are the temperature and time at the nose point in the TTT curve.

The calculated Rc are summarized in Table 2 together with the experimental Rc 6 There are intimate relations between the viscosity and critical cooling rate for metal-metalloid liquid alloys as shown in F i ~ . 7 .

Table 2 Melting point (Tm), g l a s s t r a n s i t i o n temperature ( T g ) , v i s c o s i t y a t melting p o i n t ('I,), nose temperature (T,), nose time ( t n ) , v i s c o s i t y a t nose point (17 ), c a l c u l a t e d c r i t i c a l cooling r a t e

(RE)

and exBerimental c r i t i c a l cooling r a t e

. .

E 5 -

3 -

o Experimental';

-.

,

-

Calculated Fe17.5P ' 0

i i

3 k i ,

i'

log Rc (Re : W S ) CONCLUSIVE REMARKS

The viscosity and density of Fe-C, Fe -P and Fe-P-C liquid alloys around their eutectic compositions were measured as a function of temperature and composition. Based on the examination of a correlation between experimental viscosities and dynamic free volumes, the formation of molecule-like clusters may be considered to provide a predominant contribution to the viscous flow in Fe-P liquid alloys. The critical cooling rate of these liquid alloys was obtained from the TTT curves calculated by Uhlman's kinetic analysis using experimental viscosities. It was confirmed that there is an intimate

relation between the critical cooling rate and viscosity for metal-metalloid liquid alloys.

ACKNOWLEDGEMENT

The autnors wLsh to thank

Prof.

T. Matsumae, Prof. E. Yajima and Prof. T. Yokobori for their continuous encouragements and Mr. A. Yoshihiro of Tokai University for his useful helps during this study.

REFERENCES

(1) 1.Dragomi.r : The Properties of Liqui,d Metals (edited by S. Takeuchi, Taylor and Francis,London,l973) p507.

(2) A.J.Batschinski : Z. Phisik. Chem.,@ (19131,644.

(3) R.B.Macleod : Trans, Faraday Soc.,lg (1923) , 6 .

(4) J.J.Gilman : Phil. Mag.B.,3(1978), 577.

(5)

D.R.Uhlmann : J. Non-Cryst. Solids.,I (1972),337.

(6)

Y.Nishi, K.Suzuki and T.Masumoto : 4th. Inter. Conf. on Liquid and Amorphous Metals., (1980).

(7) J.F. Elliott, M. Gleiser : Thermo- chemistry for steel making.,

1

(19601, Addison-Wesley.

( 8 ) K. Shirakawa : private communication.