HIGH TEMPERATURE INTERNAL FRICTION AND DISLOCATION MOTION IN POLY AND SINGLE CRYSTALS OF F.C.C. METALS

(1)

HAL Id: jpa-00221108

https://hal.archives-ouvertes.fr/jpa-00221108

Submitted on 1 Jan 1981

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of

sci-entific research documents, whether they are

pub-lished or not. The documents may come from

teaching and research institutions in France or

abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est

destinée au dépôt et à la diffusion de documents

scientifiques de niveau recherche, publiés ou non,

émanant des établissements d’enseignement et de

recherche français ou étrangers, des laboratoires

publics ou privés.

HIGH TEMPERATURE INTERNAL FRICTION AND

DISLOCATION MOTION IN POLY AND SINGLE

CRYSTALS OF F.C.C. METALS

A. Rivière, J. Amirault, J. Woirgard

To cite this version:

(2)

JOURNAL DE PHYSIQUE

CoZZoque C S , supple'ment au nolO, Tome 4 2 , octobre 1981 page C5-439

HIGH TEMPERATURE INTERNAL FRICTION AND DISLOCATION MOTION

I N POLY AND

SINGLE

CRYSTALS

O F

FtCnC

I

METALS

A. RiviPre, J.P. Amirault and J . Woirgard

E.U. S.M. A. - Laboratoire de Me'canique e t de Physique des Matgriam, E. R.A. C.N.R.S. n o 123, 86034 P o i t i e r s Cedex, France

Abstract. - High temperature i n t e r n a l friction experiments were performed on different poly a n d single c r y s t a l s of four (Al, Ag, Cu, N i )

FCC metals i n t h e Hz frequency r a n g e .

Damping s p e c t r a e x h i b i t s r e l a x a t i o n p e a k s even for v i b r a t i o n amplitude corresponding to s t r a i n s a s low a s 2.5 1 0 - ~ . For h i g h e r s t r e s s levels (corresponding to s t r a i n s r a n g i n g between 2.5 10-7 a n d

5

1 0 - ~ ) damping proved to be very s e n s i t i v e to the s t r a i n amplitude. In t h e 0.4

- 0.5 TM temperature r a n g e , one peak h a v e been

found associated with a n a.ctivation e n e r g y of about 1 ev.

This peak is not p r e s e n t on s t r o n g l y cold-worked specimens a n d a p p e a r a f t e r a n n e a l i n g - a t medium temperature. He d i s a p p e a r s a f t e r high temperature a n n e a l i n g whereas new p e a k s a p p e a r a t 0.6 - 0.7 TM associated to a l a r g e a c t i v a t i o n energy.

The importance of the microstructural s t a t e a n d s p e c i a l l y of the dislocation network, a s r e g a r d s t h e presence of i n t e r n a l friction maxima, was confirmed by t h e f a c t t h a t same peak behaviour was observed on single a n d poly c r y s t a l s .

Introduction. - The high temperature i n t e r n a l spectrum of CFC metals i s re- solved i n t o s e v e r a l maxima superimposed on to a background i n c r e a s i n g ex- ponentially with t h e temperature ( 1 ) to ( 5 ) . Some of these maxima a r e not t r u e r e l a x a t i o n p e a k s but a r e dependent of t h e experimental conditions. The- refore a continuous v a r i a t i o n of the temperature c a n introduce a s show i n fi- g u r e ( 1 ) t r a n s i t o r y effects g i v i n g r i s e to i n t e r n a l friction maximum ( 6 ) .

Damping h a s a l s o been observed to be s e n s i t i v e to t h e maximal s t r a i n amplitude ( f i g u r e 2 ) even a t very low s t r a i n amplitudes ( 7 ) .

So, a n a c c u r a t e determination of t h e r e l a x a t i o n parameters would requi- r e t h a t measurements a r e c a r r i e d o u t a t c o n s t a n t temperature a n d a s low a s possible s t r a i n amplitudes.

Experimental method.- Most of t h e r e s u l t s described i n t h i s report were ob- t a i n e d from i n t e r n a l friction measurements, i n f l e x u r e , a t low frequencies ( * 1 Hz) under secondary vacuum o r sometimes a p a r t i a l p r e s s u r e of high

(3)

C5-440 JOURNAL DE PHYSIQUE

p u r i t y argon ( 8 ) . Other experiments were c a r r i e d out i n torsion with a c l a s - s i c a l pendulum a n d with a v a r i a b l e frequency pendulum ( 9 ) .

Experiments were c a r r i e d for s t r a i n amplitudes r a n g i n g between 2 1 0 - ~

6

a n d 8 10-

,

a f t e r s t a b i l i z a t i o n of four hours a t t h e measurement temperature. Thanks to these methods, it h a s been possible to s e p a r a t e s e v e r a l r e l a x a t i o n p e a k s a n d l a r g e amplitude effects.

Results.

Relaxation peaks.- Four CFC p o l y c r y s t a l l i n e a n d monocrystalline metals (Al, A g , Cu, Ni) h a v e been s t u d i e d . All samples e x h i b i t r e l a x a t i o n peaks. The peak temperatures a r e plotted v e r s u s frequency i n figure ( 3 ) to ( 6 ) . In t a b l e /l/ to /4/ a r e reported the main c h a r a c t e r i s t i c s of the peaks.

Table l

-

Aluminium Table 2 - Silver

Table 3

-

Copper Table 4 - Nickel

The s u b s t a n t i a l differences a p p e a r i n g between those r e s u l t s a n d those obtained b y other a u t h o r s ( 1 ) to

( 5 )

c a n probably been explained by differences experimental conditions used i n t h i s work a n d i n the previous ones.

Peaks evolution

.-

The four studied metals e x h i b i t a low temperature peak located about 0.4 TM a t 1 Hz. This peak i s not present on a n polycrys- t a l l i n e cold rolled specimen b u t a p p e a r s ofter a n a n n e a l i n g above the re-

Tp/TM at 1 Hz

H p eV

Hp/HV T

c r y s t a l l i z a t i o n temperature. High temperature a n n e a l i n g makes i t d i s a p p e a r 0 . 4 0.95 0.47 3.10-l0 0.54 1.7L 0.85 2 . 1 0 ~ ~ ~

completly. This peak h a s been a l s o observed on monocrystalline samples ( a - luminium

5N,

nickel

4N5)

probably s l i g h t l y deformed d u r i n g the p r e p a r a t i o n .

(4)

It disappears also after high temperature annealings (650 K for aluminium, 1150 K for nickel). That disappearance of this f i r s t peak h a s been described elsewhere p a r t i c u l a r l y in the case of polycrystalline nickel (10).

A second peak h a s been found for silver (0.5 T M a t 1 Hz). It increa- ses after a medium temperature annealing and d i s a p p e a r s a f t e r a high temperature one. This peak i s very sensitive to the direction of the s t r a i n u- sed during measurements a s shown in figure ( 7 ) obtained i n flexion and torsion i n two s i l v e r specimens after the same cold-rolling and 1170 K annealing.

High temperature annealing gives rise to peaks located about 0.6 and 0.7 TM. These l a s t peaks have not been observed i n copper and nickel, probably because the annealing temperature was not high enough. The presence of two peaks i n aluminium i s shown in figure ( 8 ) r e l a t i v e to a sample elongated by creep a t 770 K before the i n t e r n a l friction measurements. Annealings just under the melting temperature make disappear successively the f i r s t and the second of these two peaks.

Amplitude effect. - The amplitude effect can be obtained by the difference between i n t e r n a l friction measurements performed a t two different s t r a i n amplitudes. This variation plotted versus temperature, exhibits some maxima (Figure 9 ) t h e temperature of which i s independent of the frequency measurement. On the other hand, the maxima heigth change with high temperature annealing. Any maxima can disappear and others increase ( f i g u r e 1 0 ) . During a n annealing, i t can be observed with the relaxation peak disappearance, a n amplitude effect increasing.

Discussion. - Several relaxation peaks have been found i n the i n t e r n a l friction spectra of four FCC metals, located between the room temperature and the melting point, for a vibration frequency of about 1 Hz.

The peaks associated with t h e poly and the single c r y s t a l s a r e identi- c a l a s r e g a r d s the location ( i n both temperature and frequency) and the behaviour during successive annealings.

In p a r t i c u l a r , the height of t h e peaks i s not directly connected with the size of the g r a i n s (which c a n eventually be a b s e n t ) , but r a t h e r with t h e previous thermomechanical treatments. Thus i t appears t h a t the geome- t r y of t h e dislocation arrangement have the most important influence and i t i s confirmed t h a t the g r a i n boundaries have only an indirect influence throughthe interactions with t h e dislocation network.

(5)

JOURNAL DE PHYSIQUE

i ) Free dislocations moving on l a r g e d i s t a n c e s i n s i d e the g r a i n s ( o r the s u b g r a i n s ) g i v e r i s e amplitude effects a n d not to t r u e r e l a x a t i o n ones; damping a r i s e s probably when t h e dislocations overcome localized b a r r i e r s ( a s the t r e e s of t h e forest for e x a m p l e ) .

i i ) Dislocations t r a p p e d i n polygonisation w a l l s c a n undergo r a t h e r l a r g e but slow displacements t h r o u g h , for example, mechanisms of t r i p l e no- des diffusion ( 1 4 ) ; i n t h a t c a s e v e r y h i g h temperature r e l a x a t i o n peaks ap- p e a r .

i i i ) When the i n t e r a c t i o n s between dislocations a r e strong enough to prevent a n y motion, a s f o r the dislocations belonging to c e l l s due to previous cold-working, no maximum c a n be detected.

i v ) The intermediate c a s e corresponds to the lower temperature peaks (0.4 T _M) a n d to dislocations undergoing medium interaction forces : for example non equilibrium dislocations belonging to c e l l s fragments p a r t i a l l y destroyed d u r i n g medium temperature a n n e a l i n g s .

Since these c e l l s a r e mostly destroyed by climb, the different behaviour observed, a f t e r a n n e a l i n g s , on aluminium o r nickel a n d on s i l v e r c a n b e simply e x p l a i n e d .

- I n the h i g h s t a c k i n g f a u l t metals (Al, N i ) where climbing occurs e a s i l y , t h e c e l l s a r e completly destroyed a f t e r moderate temperature annea- l i n g s ( < 0.7 T M ) a n d the low temperature peak d i s a p p e a r r a p i d l y .

- Conversely i n the low s t a c k i n g f a u l t metals ( A g ) , v e r y high tempe- r a t u r e a n n e a l i n g s ( > 0.9 T

_M

) h a v e been proved necessary to destroy completly t h e cell walls a n d c a n c e l the peak.

A s r e g a r d t h e elementary mechanism responsible for t h e motion of t h e dislocations, we h a v e the feeling t h a t i t i s s t i l l prematured to v e n t u r e pre- c i s e assumptions, because of t h e l a c k of sufficently precise v a l u e s of the a c t i v a t i o n parameters. It seems u s l i k e l y t h a t such a c c u r a t e v a l u e s c a n be obtain only by mean of isothermal experiments performed on well s t a b i l i z e d specimens with v a r i a b l e frequency pendulum.

References

l - J . Woirgard, ThGse Docteur

es

Sciences, Poitiers, (1974).

2 - 0.1. Datsko a n d V.A. Pavlov, Relaxation Phenomena i n Metals a n d Al- l o y s , p. 174, New-York, (1963).

3 - J.N. Cordea a n d J . W . S p r e t n a k , Trans. Met. Soc. AIME, 236, 1685,(1966)

4 - T.M. Williams a n d G.M. Leak, Acta Met. 15, 1111, (1967).

5

- J.T.A. Roberts a n d P. B a r r a n d , Met. Sci. J . , 3, 97, (1969). 6 - Y.A. Bertin, These Docteur 6 s Sciences, Poitiers, (1979).

(6)

8

- J. Woirgard a n d Coll., Rev. Phys. Appl.

6,

355, (1971).

9

- J . Woirgard a n d Coll., Rev. Sci. Instrum.

48, 1322, (1977)

10-

J.T.A. Roberts a n d P. B a r r a n d , J . I n s t . Met.

96, 172, (1968).

11- C. Bonneti, E. E v a n g e l i s t a , P . Gondi a n d R . Tognato, I1 Nuovo Cimento

33,

408 (1976).

12-

C. Esnouf, M. Gabbay a n d G , Fantozzi, J . Phys. Lett. 38, L 401,

(1977)

13

- A . Rivi6re a n d Coll., Proc. ICIFUAS, Tokyo,

(1977)

14-

J . F r i e d e l , J . Phys. Lett.,

5,

L

61, (1978).

FIG.1- Damping spectra obtained on a p o l y c r y s t a l o f 3N aluminium annealed i n s i t u a t 670 K.

a) a f t e r the specimen has been h o l d f o r fowr hours _FIG.2 _-_{I n f l u e n c e of the s t r a i n amplitude on a} a t the measurement temperature. p o l y c r y s t a l o f 3N aluminium.

b) On a continnously heated specimen (60 K/h) a) annealed a t 890 K- b) annealed a t 980 K.

(7)

JOURNAL DE PHYSIQUE

FIG.5 - Temperature peaks versus logarithm o f the FIG.6 - Temperature peaks versus logarithm of the frequency f o r p o l y c r y s t a l l i n e 4N copper. frequency f o r 4N5 n i c k e l .

FIG.7 - I n t e r n a l f r i c t i o n p l o t t e d versus tempera- FIG.8 - I n t e r n a l f r i c t i o n measured f o r d i f f e r e n t t u r e f o r a p o l y c r i s t a l l i n e 5 N sukver soe- s t r a i n amplitudes on a p o l y c r y s t a l l i n e cimen c o l d - r o l l e d (50%) and annealed a t sample o f 3N aluminium elongated by creep 1170 K. a t 770 K.

FIG.10 - Difference between i n t e r n a l f r i c t i o n l e v e l s FIG.9 - 5N p o l y c r y s t a l l i n e s i l v e r specimen annealed

a t 1170 K : d i f f e r e n c e between i n t e r n a l measured on a p o l y c r y s t a l l i n e 3N aluminium a t two s t r a i n amplitudes E = 4 . 1 0 - ~ a n d f r i c t i o n measurements performed a t two s t r a i n

E = 8 10- 7. amplitudes : s = 5.10-~ and c = 10- 6.