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INFLUENCE OF REMAINING IMPURITY
CONCENTRATION ON THE INTERNAL FRICTION
AFTER CYCLIC DEFORMATION IN PURE
ALUMINIUM
F. Baudraz, B. Tirbonod, R. Gotthardt
To cite this version:
JOURNAL DE PHYSIQUE
CoZZoque C5, suppZe'ment au nOIO, I'ome 42, octobre 1981 page C5-229
INFLUENCE OF REMAINING IMPURITY CONCENTRATION ON T H E INTERNAL FRICTION
AFTER CYCLIC DEFORMATION IN P U R E ALUMINIUM
P*
F. ~audraz*, B. Tirbonod and R. Gotthardt
I n s t i t u t de Ge'nie Atomique, Swiss Federal I n s t i t u t e o f TeehoZogy, EeubZens,
CH-1 015 Lausanne, Srsitzer Zand
A b s t r a c t
.-
The c h a r a c t e r i s t i c i n t e r n a l f r i c t i o n peak o f low temperature (78K) c y c l i c deformation i n Aluminium has been s t u d i e d .The peak can be explained by an i n t e r a c t i o n d i s l o c a t i o n - d i s l o c a t i o n l o o p (1)
.
The h e i g h t o f t h i s peak depends on the type and the c o n c e n t r a t i o n o f impur-i t i e s and i t s e v o l u t i o n w i t h annealing temperature can be understood by supposing a d i f f u s i o n mechanism o f d i s l o c a t i o n loops and i m p u r i t i e s .
1. I n t r o d u c t i o n . - The d e f e c t s created by cold-working a r e n o t o f t h e same nature and c o n c e n t r a t i o n a f t e r a one way o r a c y c l i c deformation. As transmission e l e c t r o n microscopy observations revealed, t h e l a t t e r treatment creates a very dense arrange- ment o f d i s l o c a t i o n s and a h i g h number o f small d i s l o c a t i o n loops.
I n Aluminium t h e i n t e r n a l f r i c t i o n spectrum measured a t 1 Hz r e v e a l s two peaks between 80K and 300K, f i g u r e 1: The Bordoni peak B P , a t ~ 9 0 K , and the peak PF a t
% 250K, c h a r a c t e r i s t i c o f a c y c l i c deformation ( f a t i g u e peak) (1,2).
15 a-'
.
loO AI 5N f(H2)Fatigued WOO cycles. 78K
I
F i g . 1: I n t e r n a l o f temperature.
f r i c t i o n as a f u n c t i o n
2. Experiments
.-
I n o r d e r t o study t h e i n f l u e n c e o f t h e i m p u r i t i e s on t h e i n t e r n a l f r i c t i o n spectrum a f t e r c y c l i c deformation, Aluminium samples o f d i f f e r e n t o r i g i n s and d i f f e r e n t i m p u r i t y concentrations have been measured ( t a b l e 1 ) . The measurements have been c a r r i e d o u t i n an i n v e r t e d t o r s i o n pendulum w i t h a frequency o f 1 Hz f o r1
m
i n diameter samples and 2,4 Hz f o r 2.5 mm i n diameter samples r e s p e c t i v e l y .3. Results.- 3.1.
influence-of-I~puritIe~.-
On t h e f i g u r e s 2 and 3 t h e e v o l u t i o n o f t h e peak h e i g h t s o f B , and PF and o f t h e peak temperature o f PF as a f u n c t i o n o f"NOW a t M i n i p e r S.A., CH-1095 L u t r y , S w i t z e r l a n d X *
Now a t Swiss Federal I n s t i t u t e f o r Reactor Research, CH-5303 Wirenlingen, Switzerland
( 5 - 2 3 0 JOURNAL DE PHYSIQUE
Fig. 2: Peak h e i g h t s
Qg'
andQ
;
;
,
2
frequency f and PF
-
peak temper- a t u r e T as a f u n c t i o n o f anneal- i n g temperature TA i n A1 511 l.F i g . 3: Peak h e i g h t s and peak temperature T(PF) as a f u n c t i o n o f annealing temperature TA i n
AT 5N 2.
annealing temperature i s shown f o r t h e samples A1 5N 1 and A1 5N 2 (about 10 ppm i m p u r i t y c o n c e n t r a t i o n ) .
The general c h a r a c t e r i s t i c s o f peak PF i n A1 5N samples a r e t h e f o l l o w i n g (3) (4) :
-
t h e peak appears a f t e r room temperature annealing-
i t s h e i g h t i s maximum a f t e r annealing a t 380K-
t h e peak temperature increases w i t h annealing temperature-
when t h e peak h e i g h t o f PF i s i n c r e a s i n g , t h e one o f B q i s decreasing.F i g . 5: Peak h e i g h t s as a f u n c t i o n o f annealing temperature TA i n A1 6N 2. o-~-O Oi Tp(; , , 5&
j
On f i g u r e s 4 and 5 t h e corresponding250 o-~H r e s u l t s are shown f o r t h e A1 6N 1 and A1
TA (K)
230 6N 2 samples (about 1 ppm i m p u r i t y
300
-
t h e r e i s no P peak a f t e r room t e m p e r a t u r e a n n e a l i n gF
-
t h e peak h e i g h t o f PF i s maximum a f t e r a n n e a l i n g a t 420K-
t h e peak h e i g h t o f PF i s s m a l l and t h e one o fB,
i s b i g compared w i t h t h o s e o f t h e A1 5N samples.Some o f t h e r e s u l t s o b t a i n e d w i t h A1 5M 3 samples ( 1 5 ppm S i ) a r e shown on f i g u r e 6 (5). I n t h e case o f t h i s t y p e o f Aluminium t h e maximum peak h e i g h t i s a1 r e a d y o b t a i n e d a f t e r one anneal i ng be1 ow 340K.
3.2.
~ ~ ~ c ~ y g ~ - ~ j ~ y g ~ ~ g p j ~ ~ ~ - _ o ~ _ s ~ ~ ~ ~ ~ j ~ ~ _ ~ . -
I n o r d e r t o have supplementary i n f o r m a t i o n s on t h e mechanism r e s p o n s i b l e f o r t h e peak PF, s i m i l a r t r e a t e d specimenhad been observed i n a t r a n s m i s s i o n e l e c t r o n microscope ( 6 ) . I t appeared t h a t a s m a l l p a r t o f t h e d i s l o c a t i o n l o o p s , c r e a t e d b y t h e f a t i g u e t r e a t m e n t , i s h i g h l y m o b i l e above 240K. I n an impure Aluminium (e.g. 99.98%) no peak P i s measured, b u t a l s o no
F
m o b i l e l o o p s can be d e t e c t e d . The l o o p s a r e m o b i l e o v e r more o r l e s s l o n g p e r i o d s o f t i m e depending on t h e c o n c e n t r a t i o n and on t h e element o f i m p u r i t y r e m a i n i n g i n t h e m e t a l . I n Aluminium samples w i t h a t o t a l i m p u r i t y c o n c e n t r a t i o n o f a5N and 1 ppm S i t h e l o o p s remain m o b i l e d u r i n g s e v e r a l months whereas i n a sample w i t h 15 ppm S i (A1 5N 3) t h e l o o p s become immobile a f t e r a few days.
I n s i t u d e f o r m a t i o n experiments w i t h f a t i g u e d specimen r e v e a l e d a s t r o n g i n t e r - a c t i o n between l o n g d i s l o c a t i o n s and s m a l l d i s l o c a t i o n l o o p s . I n t h e t e m p e r a t u r e domain o f t h e P maximum d e p i n n i n g as w e l l as d r a g g i n g processes have been observed
F (5)
.
T , ; 290K : l0 mvl 6 0 - TR = 336K : 30mm TR ; 350K : 30 min 100 ZOO 300 0.'.
0' 11. AI 6N.cold worked at 78Kb A1 6N, irradloted and cdd worked at 7% All onneoled for M m n ot 390K
F i g . 6: I n t e r n a l f r i c t i o n as a F i g . 7: I n t e r n a l f r i c t i o n as a f u n c t i o n o f t e m p e r a t u r e a f t e r f u n c t i o n o f t e m p e r a t u r e i n A1 6N 2
d i f f e r e n t a n n e a l i n g t r e a t m e n t s deformed a t 78K ( a ) , w i t h a p r e c e d i n g i n A1 5N 3 (15 ppm S i ) . n - i r r a d i a t i o n a t 78K ( b ) .
4. D i s c u s s i o n . - The i n t e r p r e t a t i o n o f t h e f a t i g u e - p e a k PF by an i n t e r a c t i o n between d i s l o c a t i o n s and d i s l o c a t i o n l o o p s has been c o n f i r m e d by t h e appearance of such a peak when d i s l o c a t i o n s and l o o p s were c r e a t e d s e p a r a t e l y (7)
.
C5-232 JOURNAL
DE
PHYSIQUEpeak a t 260K, which behaves as PF, can b e a t t r i b u t e d t o t h e presence o f d i s l o c a t i o n l o o p s observed by T r a n s m i s s i o n E l e c t r o n Microscopy i n s i d e s i m i l a r l y t r e a t e d specimens.
A c c o r d i n g t o t h e e l e c t r o n mi croscopy o b s e r v a t i o n and t h e r e s u l t s a f t e r n- i r r a d i a t i o n , an i n t e r a c t i o n d i s l o c a t i o n s w i t h d i s l o c a t i o n l o o p s i s proposed as t h e r e s p o n s i b l e mechanism f o r t h e peak PF. The assumed model i s based on a d r a g g i n g o f t h e loops p e r p e n d i c u l a r t o t h e d i s l o c a t i o n l i n e (1,4,7). I f A i s t h e t o t a l d e n s i t y o f d i s l o c a t i o n s ,
N,
andN I
t h e number o f loops and i m p u r i t i e s , r e s p e c t i v e l y , a t t h e d i s l o c a t i o n s p e r u n i t y o f l e n g t h , and L, t h e i n i t i a l l e n g t h o f a d i s l o c a t i o n segment, t h e n t h e h e i g h t o f peak PF i s g i v e n b y :( g 2
=
0 . 1 : o r i e n t a t i o n f a c t o r )A g e n e r a l e x p r e s s i o n t o d e s c r i b e t h e number o f d e f e c t s which have m i g r a t e d t o t h e d i s l o c a t i o n s i s g i v e n b y (8):
With Ki: f a c t o r depending on t h e c o n c e n t r a t i o n and t y p e o f d e f e c t s ; Di : d i f f u s i o n c o e f f i c i e n t o f d e f e c t i;
t : a n n e a l i n g time; mi : a c o n s t a n t ( < 1 ) .
A l t h o u g h t h e d i f f u s i o n o f t h e l o o p s i s n o t i s o t r o p i c , i t i s s t i l l r e a s o n a b l e t o assume t h a t i t can be d e s c r i b e d b y e q u a t i o n ( 2 ) ( i n d e x i = 1 f o r t h e loops; i = 2 f o r t h e i m p u r i t i e s ) .
The c o e f f i c i e n t s C. = K
-
D mi, mi and t h e a c t i v a t i o n e n e r g i e s Ei f o r t h eI i o i
d i f f u s i o n c o e f f i c i e n t s have been d e t e r m i n e d f r o m i s o t h e r m a l a n n e a l i n g experiments w i t h A1 5N 2 samples (7)
.
I n t h a t way t h e f o l l o w i n g v a l u e s have been o b t a i n e d :Assuming an a n n e a l i n g t i m e o f 30 m i n , t h e e v o l u t i o n o f t h e peak h e i g h t o f PF can be c a l c u l a t e d . The r e s u l t s shown on f i g u r e 8 a r e i n good agreement w i t h t h e measurements shown on f i g u r e s 2 and 3.
s e l f (0.43 eV)
.
The i n f l u e n c e o f the i m p u r i t i e s can be double. On t h e one hand i m p u r i t i e s can be n u c l e i f o r t h e f o r m a t i o n o f secondary d e f e c t (here d i s l o c a t i o n loops (g)), so t h a t i n a p u r e r metal l e s s loops are created. I n o r d e r t o see i f t h i s simple assumpt- i o n already describes the e v o l u t i o n o f t h e peak h e i g h t of PF i n A1 6N samples, i t was supposed t h a t t h e d e n s i t y o f t h e e f f e c t i v e i m p u r i t i e s i s 10 times s m a l l e r than i n the A1 5N 2 samples (e.g. S i atomes, see t a b l e 1 ) . Using otherwise the same
numerical values as those r e c e i v e d f o r A1 5N 2, t h e peak h e i g h t o f PF can be c a l c u l a t - ed a t t h e d i f f e r e n t annealing temperatures. Again t h e r e s u l t s ( f i g u r e 9) a r e i n good agreement w i t h the measurements ( f i g u r e s 5 and 6 ) . I n p a r t i c u l a r the s h i f t of the maximum peak h e i g h t t o h i g h e r temperatures i s p r e d i c t e d .
F i g . 8: E v o l u t i o n o f t h e peak h e i g h t PF as a f u n c t i o n o f annealing tefiperature. Calcul- a t i o n based on parameters determined by isothermal annealing experiments i n A1 5N 2 ( f o r d e t a i l s , see t e x t ) . F i g . 9 : E v o l u t i o n o f the peak h e i g h t PF as on f i g u r e 8, b u t i n A1 6N 2. For c a l c u l a t i o n same parameters have been used, except a 10 times s m a l l e r c o n c e n t r a t i o n o f i m p u r i t i e s .
JOURNAL DE PHYSIQUE
References
(1) B.Tirbonod, R.Gotthardt, B . V i t t o z , Proc. 6 t h I n t . Conf. on I n t e r n a l F r i c t i o n and U1 t r a s o n i c A t t e n u a t i o n i n S o l i d s , ed. by R.R.Hasiguti
,
p.579,U n i v e r s i t y o f Tokyo Press (1977)
(21 B.Tirbonod, B . V i t t o z , S c r i p t a Yet.
-
9, 1033 (1975)(3) B.Tirbonod, Ph.D. Thesis, Swiss Federal I n s t i t u t e o f Technology, Lausanne (1978)
(4) F.Baudraz, Ph .D. Thesis, Swiss Federal I n s t i t u t e o f Technology, Lausanne (1980) (5) J . M . B e r t e l e t t i , Graduate Thesis, Swiss Federal I n s t i t u t e o f Technology,
Lausanne ( 1981 )
(6) R.Gotthardt, Proc. 6 t h Eur. Congress on E l e c t r o n Microscopy, ed. by D.G.Brandon, Vol . I , p.512, Tal I n t e r n a t i o n a l Pub1 i s h i n g Company, Jerusalem (1976)
(7) F.Baudraz, R.Gotthardt, Proc. 3 r d Eur. Conf. on I n t e r n a l F r i c t i o n and U1 t r a s o n i c A t t e n u a t i o n i n S o l i d s , ed, by C.C.Smith, p.67, Pergamon Press (1980)
(8) A.Seeger, Proc. 5 t h I n t . Conf. on I n t e r n a l F r i c t i o n and U l t r a s o n i c A t t e n u a t i o n i n S o l i d s , ed. by D.Lenz and K.Liicke, p.232, Springer Verlag, B e r l i n -
Heidelberg (1975)
(9) Y.Shimomura, S.Kuwabara, Jour. Phys. Soc. o f Japan
