HAL Id: jpa-00225467
https://hal.archives-ouvertes.fr/jpa-00225467
Submitted on 1 Jan 1985
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 RELAXATION MECHANISMS IN Cu-Al SOLID SOLUTIONS
S. Belhas, A. Riviere, J. Woirgard, J. Vergnol, J. de Fouquet
To cite this version:
S. Belhas, A. Riviere, J. Woirgard, J. Vergnol, J. de Fouquet. HIGH TEMPERATURE RELAXATION MECHANISMS IN Cu-Al SOLID SOLUTIONS. Journal de Physique Colloques, 1985, 46 (C10), pp.C10-367-C10-370. �10.1051/jphyscol:19851082�. �jpa-00225467�
JOURNAL DE PHYSIQUE
Colloque C10, suppl6ment au n012, Tome 46, dbcembre 1985 , page C10-367
HIGH TEMPERATURE RELAXATION MECHANISMS I N CU-A1 SOLID SOLUTIONS
S. BELHAS, A. RIVIERE, J. WOIRGARD, J. VERGNOL* AND J. DE FOUQUET
Laboratoire de M6canique et Physique des Materiaux, UA
C N R S n0863, ENSMA, 86034 Poitiers Cedex, France
'~aboratoire de MBtallurgie physique, U A CNRS n o 131, Facult6 des Sciences, 86022 Poitiers, France
ABSTRACT
The high temperature damping of copper-a1 umini um sol id solutions has been investigated i n s i n g l e c r y s t a l s containing various aluminium c o n t e n t s : 3.1
-
5.4
-
7.3-
9.3 and 11 . j 4 a t % of Al. Measurements have been performed in a wide frequency range (10 Hz-
10 Hz) between room temperature and 1200 K.Two internal f r i c t i o n peaks have been observed i n s l i g h t l y strained specimens.
Both the relaxation strength and t h e activation energy have been found t o be s e n s i t i v e with t h e aluminium content. The r e s u l t s can be explained with a mechanism involving dislocation climb and independent gliding of Shockley p a r t i a l s i n widely s p l i t dislocations.
I
-
INTRODUCTIONHigh temperature relaxation e f f e c t s i n metals a r e commonlyassignedto mechanisms involving dislocation climb especially i n the case of single c r y s t a l s where no kind of grain boundary s l i d i n g can occur. Therefore the stacking f a u l t energy i s one of t h e most important parameters determining the p l a s t i c behavior, through t h e s p l i t t i n g of dislocations Cu-A1 sol id solutions can give valuable r e s u l t s since the composition dependence of r i s now well documented.
11- EXPERIMENTAL METHOD
The experimental method has been discussed elsewhere / I / . A variable frequency torsional pendulum was used a1 lowing isothermal internal f r i c t i o n measurements f o r vibration f r e uencies ranging between and 10 Hz a t maximum s t r a i n amplitudes between 5.10- and 10
2
-5. In t h a t s t r a i n amplitude range no c l e a r influence of t h e applied s t r e s s level could be detected.Single c r y s t a l s were spark-machined in the form of f l a t bars (50x5~1 mm ) parallel t o < l l l > directions. Specimens were1 prepared' from 5 N copper containing1 various amounts of aluminium: 3.1
-
5.4-
7.3-
9.3 and 11.4 a t %.I11
-
EXPERIMENTAL RESULTSNo c l e a r peaks were found i n specimens w i t h low aluminium contents (3.1 and 5.4 a t
%) i n t h e i n i t i a l s t a t e but a small peak appeared, superimposed onto an exponential low frequency background, a f t e r t h e specimens were submitted t o a 1 % flexure s t r a i n . Isothermal damping spectra obtained a t increasing temperatures on we1 1 s t a b i l i z e d s t a t e s are shown i n figure 1.
In specimens with l a r g e r aluminium contents (9.3 and 11.4 a t % ) a peak was detected in t h e i n i t i a l s t a t e which was s i g n i f i c a n t l y increased during subsequent s t r a i n i n g (1 % i n f l e x u r e ) . The peak was also s h i f t e d towards t h e high frequencies. This
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19851082
C10-368 JOURNAL DE PHYSIQUE
double e f f e c t i s c l e a r l y i l l u s t r a t e d i n f i g u r e 2 where t h e isothermal damping curves are replotted versus t h e measurement temperature. In f i g u r e 3 i t can be observed t h a t annealing a t very high temperatures increases t h e height of peak and does not modify i t s frequency location.
In f i g u r e 4 a r e plotted the v a r i a t i o n s of t h e value of t h e maximum damping with t h e annealing temperature i n t h e case of a specimen containing 11.4 a t % of Al. The apparently complex behavior Can be simply explained when t h e damping maximum i s analyzed in two elementary peaks : a "low" temperature peak Pi and a high temperature one P2
.
When t h e specimen i s f i r s t heated from A t o B ( f i g u r e 4 ) the amplitude of t h e Pi peak decreases and remains constant during cooling (from B t o C ) . During f u r t h e r heating t h e height of t h e Pi peak goes on decreasing (from B t o D ) and again remains s t a b l e during cooling (from D t o E). A higher temperature annealing (from D t o F) increases t h e height of P2 which a t t a i n s a roughly s t a b l e value (F t o C cooling).These r e s u l t s were obtained assuming a low frequency background obeying the r e l a t i o n l/wn,/l ,2,3,,4/.
The a c t i v a t i o n parameters of P1 and P2 are l i s t e d in Table 1.
Table 1
From t a b l e 1 i t appears t h a t P p i s a very high temperature peak since i t would be located a t t h e melting temperature Tm f o r a vibration frequency of 1 Hz; I t i s a l s o observed t h a t the a c t i v a t i o n energy of P1 i s higher than t h a t of P2 but t h a t , conversely, the limiting relaxation time ro i s much higher f o r P2
.
The composition dependence of the activation energies i s shown in f i g u r e 5. I t i s observed t h a t f o r both1 peaks the energy i s minimum f o r an aluminium content between 5.4. and 7.3. A similar r e s u l t had been previously reported i n t h e case of polycrystals /5/.
The relaxation strength i s shown i n figure 6 , f o r the case of P and f o r t h e same annealing conditions. I t increases with the aluminium content, 6 h i l e t h e peak i s s h i f t e d towards high frequencies.
I V
-
DISCUSSIONFor t h e thermally activated motion of dislocation segments, the 1 imi t i ng re1 axation time i s of t h e form /6/ :
a kT a 2
a being a c o e f f i c i e n t o f t h e order o f 1/6 f o r pure climb /6/, vo t h e Debye frequency,Rthe mean l e n g t h o f t h e moving segments and h t h e distance covered d u r i n g one a c t i v a t i o n event. It leads t o 9, values r a n g i n g between 1 and 1 0 p f o r t h e P2 peak and between 0.05
-
0 . 5 ~ f o r t h e Pi peak. Thus Pi can correspond t o t h e motion o f s h o r t tangled segments belonging t o c e l l s formed d u r i n g s t r a i n i n g and P2 t o f r e e d i s l o c a t i o n s remaining a f t e r d e s t r u c t i o n o f t h e c e l l s d u r i n g h i g h temperature anneal i ngs.The observed minimum i n t h e a c t i v a t i o n energy o f t h e peaks seems t o i n d i c a t e t h a t a t l e a s t two elementary mechanisms are involved, t h e slowest one c o n t r o l i n g t h e deformation : f o r example d i f f u s i o n enhanced d i s l o c a t i o n c l i m b and independent g l i d e o f Shockley p a r t i a l s i n w i d e l y s p l i t d i s l o c a t i o n s .
I n a l l o y s w i t h a low aliminium content, corresponding t o a h i g h s t a c k i n g f a u l t energy, deformation i s c o n t r o l e d by t h e g l i d e o f p a r t i a l s which s t r o n g l y i n t e r a c t and i n t h e h i g h l y concentrated a l l o y s deformation i s c o n t r o l l e d by c l i m b i n g of w i d e l y s p l i t d i s l o c a t i o n s .
V
-
REFERENCES/1/ WOIRGARD, J., SARAZIN, Y. and CHAUMET, H.
Rev. Scient. Instrum. 48,1977, 1322.
/2/ WOIRGARD, J., Nuovo. Cimento, 338, 1976, 424.
/3/ WOIRGARD, J. and de FOUQUET, J., Proc. V I t h ICIFUAS, Tokyo, 1977, 743.
/4/ GERLAND, M., These 3eme c y c l e 1979.
/5/ GABORIAUD, R.J., WOIRGARD, J., GERLAND, M. and RIVIERE, A., P h i l . Mag. A.43, 1981, 363.
/6/ FRIDEL, J., D i s l o c a t i o n s , Pergamon Press.
/7/ KONG, Q.P., LI., G.Y. and, KE, T.S., J. de Phys. Colloque C5, 1981, 265.
/8/ YRAVALS, D i s l o c a t i o n s e t deformation p l a s t i q u e (1979).
/9/ GALLAGHER, P.C.J., M e t a l l . Trans. 1, 1970, 2429.
/ l o / RIVIERE, A. BELHAS, S. and WOIRGARD, J.,
ECIFUAS-4, Villeurbanne, J. de physique, 44, PC9, 1983, 747.
F i g u r e 1 - I n t e r n a l f r i c t i o n F i g u r e 2
-
I n f l u e n c e o f t h e p r e - s t r a i n 1 % i n measurments a f t e r i n Cu 11.4 % a t A l .successive annea- o ( a ) and c ( b ) p r e - s t r a i n e d specimen l i n g s on h e a t i n g * ( a ) and o ( b ) i n i t i a l s t a t e . i n Cu 3.1 % a t A l .
p r e - s t r a i n e d 1 % i n f l e x u r e .
JOURNAL DE PHYSIQUE
F i g u r e 3 - I n f l u e n c e o f t h e annealing F i g u r e 4 - V a r i a t i o n o f t h e a c t i v a t i o n temperature i n p r e - s t r a i n e d energy w i t h aluminium content
Cu 9.3 % a t A l . i n copper.
Specimen annealed a t : ( + ) 1178 K and ( m ) 1070 K.
LOO
0-3
'-5
-
-
-9: -
- -
I I I I I >
HpW)
F i g u r e 5 - V a r i a t i o n o f t h e maximum damping w i t h t h e annea- l i n g temperature i n Cu 11.4 % a t A l . p r e - s t r a i n e d 1 % i n f l e x u r e .
10.' 10-3 10.~ KT1 1 10 NlHd
"$1
T~=1O2O1K ' ' ' 'I
31 52. 23 93 11.4 at%Al
d,i o4
200-
100-
F i g u r e 6 - I n t e r n a l f r i c t i o n measured a t 1020 K a f t e r annealing a t 1160 K i n p r e - s t r a i n e d specimens 1 % i n f l e x u r e ( a ) Cu 3.1 % a t A l .
( 0 1 Cu 9.3 % a t A l . ( O ) CU 11.4 % a t A l .
- 4 -3 -2 -1 0 1loqN
I I I I I 3
TM :1020K ,++\
1
7' t
f
t
w +
#.-*A \'\ i 2- 1
I I I I I ,
- 6 - 3 -2 1 0 I o g N
