THE INFLUENCE OF ATHERMAL TRANSFORMATION AND COLD-WORKING ON THE LOW TEMPERATURE (77 - 300) K INTERNAL FRICTION BEHAVIOUR OF Fe-Ni-C ALLOYS

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THE INFLUENCE OF ATHERMAL

TRANSFORMATION AND COLD-WORKING ON

THE LOW TEMPERATURE (77 - 300) K INTERNAL

FRICTION BEHAVIOUR OF Fe-Ni-C ALLOYS

C. Prioul, M. Carrard

To cite this version:

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JOURNAL DE PHYSIQUE

CoZZoque C5, suppzdment au n0Z0, Tome 42, octobre 1981

page

c5-1067

THE INFLUENCE O F ATHERMAL TRANSFORMATION AND COLD-WORKING ON THE LOW TEMPERATURE ( 7 7

-

3 0 0 )

K

I N T E R N A L F R I C T I O N BEHAVIOUR OF F e - N i - C ALLOYS

C. P r i o u l and M. C a r r a r d

Laboratoire Hydrogane e t MatBriam, EcoZe CentraZe des Arts e t Manufactures,

92290 Cha'tenay-MaZabry, France

A b s t r a c t . - M e a s u r e m e n t s p e r f o r m e d when r e h e a t i n g r e c e n t l y q u e n -

-

-c h e d Fe-Ni-C s t r u c t u r e s f r o m 7 7 t o 3 0 0 K i n d i c a t e t h a t i n t e r n a l f r i c t i o n b e h a v i o u r i s g r e a t l y i n f l u e n c e d b y i n t e r n a l s t r e s s e s . T h e e f f e c t o f c o l d - w o r k i n g a t 77

K

i s r e p o r t e d . T h e t w i n n i n g i n - d u c e d i n t h a t c a s e a n d t h e m a r t e n s i t i c t r a n s f o r m a t i o n t w i n n i n g a p p e a r t o h a v e c u m u l a t i v e c o n s e q u e n c e s o n t h e i n t e r n a l f r i c t i o n p l o t . A c o m p a r a t i v e s t u d y i s c o n d u c t e d o n d i f f e r e n t s t r u c t u r e s i n o r d e r t o c o n f i r m t h e s e o b s e r v a t i o n s . T h e r e s u l t s l e a d u s t o s u p g e s t a n e w a p p r o a c h f o r t h e p h y s i c a l i n t e r p r e t a t i o n o f t h e i n t e r n a l f r i c t i o n m e a s u r e m e n t s o n r e c e n t l y q u e n c h e d Fe-Ni-C s t r u c t u r e s i n t h e ( 7 7 - 3 0 0 ) K t e m p e r a - t u r e ' r a n g e . 1 . I n t r o d u c t i o n . - T h e f i r s t s t a g e o f r e h e a t i n g o f Fe-Ni-C a l l o y s f r o m 7 7 t o 3 0 0 K , a f t e r t h e a t h e r m a l m a r t e n s i t i c t r a n s f o r m a t i o n , h a s b e e n i n - t e r p r e t e d f r o m l o w f r e q u e n c y i n t e r n a l f r i c t i o n e x p e r i m e n t s i n t e r m s o f a n i s o t h e r m a l m a r t e n s i t i c t r a n s f o r m a t i o n ( P r i o u l a n d C a r r a r d , 1 9 7 9 ) w h i c h t a k e s p l a c e i n t h e ( 7 7 - 1 5 0 ) ~ t e m p e r a t u r e r a n g e ( c o r r e s p o n d i n g a n o m a - l y

@

i n F i g . ] ) . T h e i n t e r p r e t a t i o n o f t h e l a r g e i n c r e a s e o f t h e i n t e r n a l f r i c t i o n g i v i n g b i r t h t o t h e m a i n maximum ( c a l l e d

_@

i n F i g . 1 ) r e m a i n s h o w e v e r u n d e f i n i t e u n t i l n o w . F o l l o w i n g m e a s u r e m e n t s r e a l i z e d a t 1 0 0 H z , C a r r a r d a n d o t h e r s ( 1 9 7 7 ) h a v e p r o p o s e d t h a t a s h o r t - r a n g e - d i s t a n c e r e a r r a n g e m e n t may a p p e a r i n t h e ( 1 5 0 - 2 2 0 ) K t e m p e r a t u r e r a n g e . T h e p u r p o s e o f t h i s p a p e r i s t o p o i n t o u t t h e d i s c r e p a n c y o b s e r v e d b e t w e e n t h i s l a s t i n t e r p r e t a t i o n a n d o u r p r e s e n t r e s u l t s o b t a i n e d i n t h e l o w f r e q u e n c y r a n g e ( a b o u t 1 H z ) . We w i l l t h u s b e l e d t o p r o p o s e a n e w a p p r o a c h t o t h i s p h e n o m e n o n . 2 . E x p e r i m e n t a l p r o c e d u r e . 2 . 1 . e t e r n a l f r i c t i o n a p p a r a t u s :

-

T h e e x p e r i m e n t s w e r e c a r r i e d o u t o n a n i n v e r t e d t o r s i o n p e n d u l u m . D a t a p r o c e s s i n g w a s r e a l i s e d o n l i n e b y a m i c r o - c o m p u t e r c o n n e c t e d t o a d i g i t a l p l o t t e r ( P r i o u l a n d o t h e r s , 1 9 8 1 ) . T h e d a t a s t o r a g e o n a t a p e - r e c o r d e r a l l o w s f o r a c o n v e n i e n t p l o t t i n g o f t h e d i f f e r e n t f i g u r e s p r e s e n t e d i n t h i s p a p e r .

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JOURNAL

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Cylindrical specimens (diameter 3 mm, useful length 5 0 mm) anchored by two threaded heads were set up at room temperature before in-situ cooling to 7 7

K.

The cooling and heating rates were 1.5 K/min

,

the strain amplitude was less than co = 5 x 1 0 - ~ and the test frequency w a s 1.5

Hz.

A one-hour maintenance of the sample was performed at 7 7 K in order to realise a quasi-equilibrium state, before reheating the structure back up to room temperature.

2.2. Material : - T h e Fe-Ni-C alloys were melted using a high frequency furnace. After high temperature forging, an austenitizing treatment ( 1 3 2 3 K , 2 hours followed by water quenching) was performed. This treatment led to an entirely austenitic structure at room temperature.

After machining the samples were electrolytically po- lished before being set i n the apparatus. After in-situ cooling to 7 7

K

and reheating to room temperature, a metallographic study revealed 8 5 % of acicular martensite and 15% of retained austenite.

Three different Fe-Ni-C alloys w e r e tested. The alloy noted A is a Fe-24% Ni-0.41% C(in weight),B is a Fe-27% Ni-0.17%and C isaFe-30% Ni-0.024X C

.

The Ns temperature w a s

225 K

for alloys A and B and 2 5 0 K for alloy

C.

3. Experimental results.

-

We have reported in Fig. 1 the typical in-

*

ternal friction and relative frequency plots versus temperature (cur-

ves

l ,

l'), when reheating the recently quenched structure of the A

alloy from

77

to 3 0 0 K.

On both sides of the main maximum

@

w e can notice two anomalies : @which has been associated with an isothermal martensitic transformation (Prioul and Carrard,l979), and

@)

which is not y e t completely understood.

This paper will be restricted to the study of the main maximum

@

.

The complete irreversibility of all the plot when reheating the structure for the second time is well known (see for example Fig.

3).

In order to specify this irreversible character of the

@

maximum, w e have performed the thermal cycle presented in Fig.l.The corresponding internal friction and frequency evolutions are also plot- ted in Fig.1. Heatings are represented on curves AiBi, A ~ B ; , isothermal maintenances are represented on curves B i C i , BiCi. As previously reported (Prioul and Carrard,l979) the

@

anomaly is irreversible in the

(77-150) K temperature range, thus the second heating up to 170 K

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C5- 1070 JOURNAL

DE

PHYSIQUE

cold-working at 7 7

K

o f the recently quenched structures. The evolutions observed w h e n reheating are presented in Fig. 3 a , b , c respec- tively for A ,

B ,

C alloys (first heating - curves l , l f , s e c o n d heating-

100 158 200 TEMPERATURE OO r s 3 !2 e 2

5

L L . 1 c: Z

...

-

6

.~

5 4

.

-3

-

3 .. . f i 100 150 208 TEMPERATURE (K)

a)alloy

A

strained 2.5% b)alloy B strained 5 % cjalloy C strainCd 7.5%

at 7 7

K

at 7 7 K at 7 7

K.

Fig. 3 : Influence of cold-working at 7 7 K curves(l,lf) first heating after cold-working curves(2,2') second heating after cold-working curves(3,3') uncold-worked specimen.

curves 2,2') in c o m p a r i s o n w i t h uncold-worked specimens (curves 3,3'). According to previous s t u d i e s (Carrard and others,1973) the intensity of the

@

maximum i s strongly dependent o n c a r b o n content. I n the c a s e of alloy C (0,024% .C) t h e

_@

maximum is considerably reduced.In apurer Fe-Ni alloy (0,004%C i n weight) Hoang (1975) mentioned n o

@

maximum w h e n reheating the recently quenched structure. F o r each a l l o y , the l o w temperature cold-working induced an important increase in the intensity of the

@

maximum. I t must be noted that in spite of a m o r e important cold-working for lower carbon alloys, the influence i s comparatively smaller i n the c a s e of alloy C. T h i s o b s e r v a t i o n c a n be related t o the density of d e f e c t s generated by cold-working,in h i g h or low carbon Fe-Ni-C alloys.

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C5-1072 JOURNAL DE PHYSIQUE

dislocations. From this point of view the influence of carbon content must be related to the density of dislocations created during the athermal martensitic transformation, this density being probably considerably larger in high carbon Fe-Ni-C alloys. Thus, the

@

maximum should be considered as the result of two antagonpstic effects :

-

the first one is due to the increase of the dislocation mobility with temperature. The mechanism of this relaxation phenomenon might be simi- lar to the one previously proposed in order to explain the screw dislocation peak in pure cubic metals ( y peak according to Chamber's classification, (1966)).

-

the second effect which becomes effective for temperatures higher than 190

K

is related to dislocation pinning by carbon and induces the decrease in the internal friction and the correlative increase in mo- dulus.

Nevertheless, a short range distance carbon rearrangement could be considered in order to explain the small irreversible compo- nent observed in the (77-190) K temperature range.

References.

CARRARD, M.,

L.

HYSPECKA, J . PLUSQUELLEC, P. AZOU, and

P.

BASTIEN (1973). C.R. Acad. Sc. (Paris), 277C, 445-450.

CARRAPD,

M.,

J . PLUSQUELLEC, P. AZOU, and P. BASTIEN (1977).

Proceedings of the Sixth International Conference on Internal Friction and Ultrasonic Attenuation in Solids, University of Tokyo Press, 689-693.

CHAMBERS, R.H. (1966)."Physical Acoustics" (Ed. Pason Acad. Press New York), 3A, chap. 4.

DECHAMPS, Y . , L.M. BROWN (1979). Acta Met., 27, 1281-1291. HOANG,

G.K.

(19751. Thesis ( ~ a n c ~ ) .

PBIOUL, C.,N. CABRASD

(1979).

Proceedings of the Third European Con- ference on Internal Friction and Ultrasonic Attenuation in Solids, University of Manchester (Pergamon Press!, 287-291.

PRIOUL, C.,M. PASQBET, C. CARRASD, J . PLUSQUELLEC, and P. AZOU (1981). Hemoires Scientifiques Pev. Vet., To be published.

PRIOUL,C., H. CARFARD, L. HYSPECKA, J. PLUSQUELLEC, and P. AZOU

(1980). Proceedings of the international conference on Hiph S t r e n ~ t h Martensitic Steels, Ostrava (Tchecoslovaquie). Sept. 1980.