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Submitted on 1 Jan 1981
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AN ANOMALOUS INTERNAL FRICTION PEAK IN
Au3Cu
K. Iwasaki
To cite this version:
JOURNAL DE PHYSIQUE
CoZZoque C5, s u p p l h e n t au n O I O , Tome 4 2 , octobre 1981 page C5-951
AN ANOMALOUS INTERNAL FRICTION PEAK I N A u 3 C u K . Iwasaki
The I n s t i t u t e of PhysicaZ and ChemicaZ Research, Wakoshi, Saitama, 351, Japan
Abstract.
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An anomalous i n t e r n a l f r i c t i o n peak i s observed p r o m i n e n t l y when t h e specimens are quenched from 1073OK and subsequently deformed belowroom temperature. This peak i s anomalous i n the f o l l o w i n g p o i n t s . 1 ) A t t h e peak temperature t h e p e r i o d o f v i b r a t i o n r e v e a l s a step o f o p p o s i t e d i r e c t i o n t o t h a t associated w i t h t h e usual r e l a x a t i o n peak. 2) The peak temperature v a r i e s very w i d e l y . 3) The peak i s very sharp. The peak i s t e n t a t i v e l y i n t e r p r e t e d t o be due t o some k i n d o f o r d e r - d i s o r d e r t r a n s i t i o n which may occur l o c a l l y under the i n f l u e n c e o f d i s l o c a t i o n motion.
1. I n t r o d u c t i o n .
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I n t h e previous work') i n t e r n a l f r i c t i o n o f d i l u t e Cu-Au a l l o y s (0.021-
4.87 at.%Au) was s t u d i e d i n t h e low temperature range. I t w i l l be very i n t e r e s t i n g t o increase Au c o n c e n t r a t i o n f u r t h e r t o i n c l u d e ordered a l l o y s and t o measure i n t e r n a l f r i c t i o n i n the s i m i l a r way, Among the well-known ordered a l l o y s , Cu3Au, CuAu and Au3Cu, t h e l a s t one was chosen here because i t s low t r a n s i t i o n tem- p e r a t u r e ( T = 4 7 0 0 ~ ) ~ ) would ma!<e i t easy t o handle specimens i n s i t u i n t h e low temperature i n t e r n a l f r i c t i o n apparatus (maximum temperature i s about 3 3 0 " ~ ) ? ) For example, i f t h e specimens are quenched from h i g h temperature, even i n - s i t u o r d e r i n g i s p o s s i b l e w i t h t h e h e l p o f excess vacancies?) I n the present work t h e e f f e c t s of heat treatments and deformation were m a i n l y i n v e s t i g a t e d .2. Experimental Procedures.
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An a l l o y i n g o t o f n e a r l y s t o i c h i o m e t r i c composition (Au/Cu = 74.3/25.7) was made by m e l t i n g h i g h p u r i t y (99.999 %) Au and Cu t o g e t h e r i n vacuum T o r r ) . U i r e specimens o f 0.4 mm i n diameter were made by drawing w i t h i n t e r m e d i a t e annealing a t 873°K.Three d i f f e r e n t specimen c o n d i t i o n s were prepared by t h e f o l l o w i n g treatments. A ) Two-hour-annealing a t 1073°K and quenching i n t o i c e d water (designated as
"1073K X 2H WQ" i n t h i s paper) expecting t h e disordered s t a t e w i t h excess vacan- c i e s .
6)
Ordering treatment below Tc a f t e r t h e quenching ( f o r example, "1073KX
2H WQ+
373K X 10H") expecting t h e ordered s t a t e .C) No t r e a t m e n t ("As Drawn") expecting t h e disordered s t a t e w i t h many d i s l o c a t i o n s . The annealing a t 1073'K and t h e quenching were made w i t h the use o f vacuum-sealed t h i n q u a r t z tubes. The A and t h e B specimens were measured b o t h i n non-deformed
C5-952 JOURNAL DE PHYSIQUE
and i n deformed s t a t e s . The deformation was clone by t w i s t i n g , f o r example, a t room temperature by n % i n s i t u i n t h e i n t e r n a l f r i c t i o n apparatus ("n%RTH).
I n t e r n a l f r i c t i o n
Q-I
and t h e p e r i o d o f v i b r a t i o n t were measured as f u n c t i o n s o f temperature w i t h a f u l l y automatic i n v e r t e d t o r s i o n pendulum?) The measurements were performed i n t h e h e a t i n g r u n a t a h e a t i n g r a t e o f about 0.8"K/min w i t h a sur- face shear s t r a i n o f 2 X i f n o t otherwise stated.3. Experimental Results.
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As an i n t e r e s t i n g i n t e r n a l f r i c t i o n peak was observed o n l y i n t h e specimens whichweredeformed a f t e r t h e quenching, d e t a i l e d experiments were c a r r i e d o u t m a i n l y on t h e A specimens. The peak behavior o f t h e A specimens i s shown f i r s t i n d e t a i l and then t h e r e s u l t s on t h e o t h e r specimens f o l l o w b r i e f l y .F i g u r e 1 shows an example o f t h e peak which appears when t h e quenched specimen i s deformed a t room temperature and subsequently annealed a t 373°K i n s i t u . I n t h i s case t h e specimen was k e p t a t 300°K f o r 50 hours a f t e r t h e quenching and t h e n de- formed. The peak, which i s very small i n t h e as-deformed c o n d i t i o n (6%RT), becomes l a r g e r a f t e r h e a t i n g up t o 373'K. The peak temperature and t h e h e i g h t change o n l y a l i t t l e d u r i n g the i s o t h e r m a l annealing a t 373OK. A t the peak temperature the p e r i o d of v i b r a t i o n t shows a s t e p which i s opposite i n d i r e c t i o n compared w i t h t h a t asso- c i a t e d w i t h t h e usual r e l a x a t i o n peak. N e i t h e r the e l e c t r i c a l r e s i s t i v i t y n o r t h e zero p o i n t o f the pendulum shows any p e c u l i a r change there.
When t h e specimen i s deformed soon a f t e r t h e quenching, t h e peak appears l a r g e already i n t h e as-deformed c o n d i t i o n as shown i n F i g . 2. Sometimes t h e peak appears i n a t w i n form accompanied by two corresponding steps i n t and t h e peak temperature moves l a r g e l y as i n t h i s case.
The peak appears sometimes i n a s i n g l e form and sometimes i n a t w i n form. The peak temperature movement i s sometimes small and sometimes l a r g e r e g a r d l e s s of t h e peak forms. Two extreme cases were shown i n F i g s . 1 and 2 f o r comparison's sake. The experimental condi t i ons domi n a t i ng these d i f f e r e n c e s
,
however, are n o t known a t t h e present stage.The e f f e c t s o f thermal c y c l i n g s a r e shown i n Fig. 3, where t h e h e a t i n g and t h e c o o l i n g runs were repeated i n t h e sequences i n d i c a t e d by t h e arrows. The peak tem- p e r a t u r e increases d u r i n g t h e repeated thermal c y c l i n g s w i t h a l i t t l e change i n the peak h e i g h t .
The i s o c h r o n a l annealing behavior i s shown i n F i g . 4. The peak remains s t a b l e a g a i n s t t h e annealing below Tc, w h i l e i t disappears when annealed around o r above Tc. Once t h e peak has disappeared, i t does n o t reappear even i f t h e specimen i s addi- t i onal l y deformed again.
I f t h e specimen which has t h e peak i s deformed a d d i t i o n a l l y , t h e peak does n o t disappear b u t grows as shown i n F i g . 5, where the t o t a l degree o f deformation i s
Tine s t r a i n ampl i tude dependences o f the peak p r o p e r t i e s are summarized i n Fig. 6 . The measurements i n the h e a t i n g runs were c a r r i e d o u t a t several s t r a i n ampli- tudes which were f i r s t increased (designated as " I n c r e a s i n g Amp1 i tude") and then decreased ("Decreasing Amplitude") step by step by a f a c t o r o f 2. The e f f e c t s o f
5
v i b r a t i o n a t t h e l a r g e s t amplitude ( 8 X 10- ) are seen as the d i f f e r e n c e between the i n c r e a s i n g and the decreasing amplitudes i n t h e peak temperature and t a t 150°K, the lower temperature s i d e o f t h e peak, w h i l e t a t 22Q0X, t h e h i g h e r temperature side, shows l i t t l e e f f e c t . The strange behavior o f the peak h e i g h t may be due t o the d i f - f i c u l t y i n t h e p r e c i s e peak h e i g h t d e t e r m i n a t i o n because o f i t s abnormal sharpness.
As shown i n Fig. 7 i f the specimen i s deformed a f t e r the o r d e r i n g treatment i n s i t u ( 3 7 3 ~ X IOH), no peak i s observed. This f i g u r e a l s o shows t h a t t h e r e appears no peak unless t h e specimen i s deformed before the o r d e r i n g (compare w i t h Figs. 1
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6 ) . The r e s u l t s on t h e as-drawn specimen are shown i n Fig. 8, where no peak i s ob- served. The isothermal annealing a t 373°K was extended t o 100 hours i n b o t h cases o f Figs. 7 and 8 t o have almost no change.As described above, t h e peak i s observed o n l y i n t h e quenched and subsequently deformed specimens and i t s anomalous c h a r a c t e r i s t i c s are summarized as f o l l o w s . 1) A t t h e peak temperature there appears a step i n t which i s opposite i n d i r e c t i o n
compared w i t h t h a t associated w i t h t h e r e l a x a t i o n peak.
2) The peak temperature v a r i e s l a r g e l y from specimen t o specimen and a l s o by anneal- i n g , by thermal c y c l i n g , by deformation degree and by v i b r a t i o n a t l a r g e s t r a i n ampl i tude
.
3) The peak i s very sharp.
4. Discussion.
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The unstable nature o f the peak suggests t h a t i t may be r e l a t e d w i t h some n o n - e q u i l i b r i u m o r meta-stable s t a t e . The i n t e r n a l s t r u c t u r e t o g i v e r i s e t o t h e peak i s supposed t o be formed i n the f o l l o w i n g way. When the quenched speci- men i s deformed, most o f the quenched-in vacancies may be swept by moving d i s l o c a - t i o n s and some o f them gather t o g e t h e r near t h e d i s l o c a t i o n s . A t t h e same time new excess vacancies may a l s o be produced, f o r example, by t h e non-conservative motion o f t h e jogs i n the screw d i s l o c a t i o n s . These vacancies are expected t o be concen- t r a t e d i n the v i c i n i t y o f the d i s l o c a t i o n s . Consequently t h e ordered regions are formed near t h e d i s l o c a t i o n s w i t h t h e h e l p o f the excess vacancies, o t h e r regions remaining disordered.When t h e specimen i s v i b r a t e d d u r i n g t h e i n t e r n a l f r i c t i o n measurement, the d i s l o c a t i o n s may b e g i n t o i n t e r a c t w i t h the ordered regions a t some temperature, which may depend on the c o n f i g u r a t i o n and t h e d i s t r i b u t i o n o f the ordered regions
and the d i s l o c a t i o n s . This i n t e r a c t i o n i s expected t o change the volume and/or the order degree o f t h e ordered regions. This process can be regarded as a k i n d of o r d e r - d i sorder t r a n s i t i o n which occurs l o c a l l y a t temperatures lower than Tc w i t h the h e l p o f d i s l o c a t i o n motion.
(5-954 JOURNAL DE PHYSIQUE
d i s o r d e r t r a n s i t i o n under t h e i n f l u e n c e o f d i s l o c a t i o n motion. The opposite step i n t and the abnormal sharpness o f the peak are o f t e n observed i n the phase t r a n s i - t i o n 5 ) and then are n o t discussed f u r t h e r here. The l a r g e v a r i a t i o n o f t h e peak temperature and the peak shape are considered t o be due t o t h e d i f f e r e n c e i n the c o n f i g u r a t i o n and t h e d i s t r i b u t i o n o f the ordered regions and t h e d i s l o c a t i o n s , which are very d i f f i c u l t t o c o n t r o l e x p e r i m e n t a l l y .
The peak shown i n Fig. 1 i s s m a l l e r than t h a t i n Fig. 2. This may be due t o t h e d i f f e r e n c e i n t h e i n i t i a l o r d e r degree b e f o r e the deformation. The specimen used i n Fig. 1 i s estimated t o be a l i t t l e ordered because i t was k e p t a t 300°K f o r 50 hours a f t e r the quenching, w h i l e t h a t i n Fig. 2 i s almost completely disordered. Another specimen which was k e p t a t 300°K f o r 43 days a f t e r t h e quenching and then deformed showed no peak. This f a c t shows t h a t t h e o r d e r i n g i s p o s s i b l e a t tempera- t u r e s as low as 300°K i f t h e specimen i s quenched from h i g h temperature.
The specimen shown i n Fig. 7 was annealed a t 373°K f o r 10 hours a f t e r the quenching. This annealing i s thought t o be s u f f i c i e n t t o order t h e specimen?) The deformation o f several percent i s n o t h i g h enough t o change t h e order degree largely!) Consequently no c o n f i g u r a t i o n t o g i v e r i s e t o the peak i s expected t o be formed i n the B specimens.
Though t h e as-drawn specimens c o n t a i n many d i s l o c a t i o n s , o n l y very few vacan- c i e s e x i s t i n them. The vacancies produced by drawing a r e expected t o a n n i h i l a t e on the spot because t h e temperature r i s e d u r i n g the drawing i s known t o be as h i g h as 3 7 0 " ~ ? ) Consequently no peak i s observed i n t h e C specimens. The deformation tem- p e r a t u r e dependence o f the peak h e i g h t i s c o n s i s t e n t w i t h t h i s i n t e r p r e t a t i o n .
A t the peak temperature n e i t h e r t h e e l e c t r i c a l r e s i s t i v i t y n o r t h e zero p o i n t o f the pendulum shows any p e c u l i a r i t y t y p i c a l of t h e t r a n s i t i o n . This may be due t o t h e f a c t s t h a t t h e d i f f e r e n c e s i n the r e s i s t i v i t i e s and t h e l a t t i c e parameters be- tween t h e ordered and t h e disordered s t a t e s are very and t h a t t h e t r a n s i - t i o n i s very l o c a l i n t h e present case.
Though t h e mechanism given above could e x p l a i n t h e peak behavior r a t h e r w e l l , i t i s o n l y a t e n t a t i v e one and f u r t h e r experimental works o t h e r than i n t e r n a l f r i c - t i o n are h i g h l y desired.
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3
(1978) 1583. 2) B. W. Batterman; J. Appl. Phys.8
(1957) 556. 3) K. Iwasaki ; B u l l . Japan I n s t . Metals15
(1976) 43. 4) G. R. P l a t e r i n k ; P h i l . Mag.11
(1968) 327.5) A. S. Nowick and B. S. Berry; A n e l a s t i c R e l a x a t i o n i n C r y s t a l l i n e S o l i d s (Academic Press, New York, 1972) p. 463.
6 ) A. H. C o t t r e l l ; R e l a t i on o f P r o p e r t i e s t o M i c r o s t r u c t u r e (ASM, Cleaveland, 1954) p. 131.
