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DISLOCATION RELAXATION IN HIGH PURITY POLYCRYSTALLINE ALUMINUM AT MEGAHERTZ
FREQUENCIES
M. Zein
To cite this version:
M. Zein. DISLOCATION RELAXATION IN HIGH PURITY POLYCRYSTALLINE ALUMINUM
AT MEGAHERTZ FREQUENCIES. Journal de Physique Colloques, 1985, 46 (C10), pp.C10-297-
C10-300. �10.1051/jphyscol:19851066�. �jpa-00225450�
JOURNAL DE PHYSIQUE
Colloque C10, suppl6ment au n o 12, Tome 46, dOcembre 1985 page (210-297
DISLOCATION RELAXATION IN HIGH PURITY POLYCRYSTALLINE ALUMINUM AT MEGAHERTZ FREQUENCIES
M. Z E I N
P h y s i c s Department, U n i v e r s i t y C o l l e g e of B a h r a i n , PO Box 1082, B a h r a i n , A r a b i a n Gulf,
A b s t r a c t
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The i n t e r n a l f r i c t i o n o f cold-worked p o l y c r y s t a l l i n e aluminum has----
been measured i n t h e temperature range o f lOOK t o 290K, a t f r e q u e n c i e s o f 10 and SMHZ, u s i n g a c o n v e n t i o n a l u l t r a s o n i c p u l s e t e c h n i q u e w i t h a s i n g l e t r a n s d u c e r . Temperature, h e i g h t and shape o f t h e i n t e r n a l f r i c t i o n peak were s t u d i e d as a f u n c t i o n o f t h e magnitude o f s t r e s s used i n t h e p r i o r deformation. The r e s u l t s show a l a r g e decrease i n t h e peak t e m p e r a t u r e as t h e d e f o r m a t i o n i s i n c r e a s e d f o l l o w e d by a s l i g h t i n c r e a s e as t h e
d e f o r m a t i o n i s continued. An i n c r e a s e i n t h e h e i g h t o f t h e peak, and decrease i n t h e a c t i v a t i o n energy has been observed by i n c r e a s i n g t h e d e f o r m a t i o n .
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INTRODUCTION-
The i n t e r e s t o f t h e p r e s e n t work c e n t e r e d on t h e study o f t h e Bordoni peak i n p o l y c r y s t a l l i n e aluminum o f 5N p u r i t y as a f u n c t i o n o f p l a s t i c deformation, a t megahertz frequency. The peak i s c h a r a c t e r i z e d by i t s presence o n l y i n deformed samples and i t s s h i f t w i t h frequency which f o l l o w s a t h e r m a l l y a c t i v a t e d r e l a x a t i o n mechanism. The e a r l y work on p o l y c r y s t a l l i n e m a t e r i a l suggested t h a t , f o r a g i v e n metal a t a p a r t i c u l a r frequency, t h e Bordoni peak always o c c u r r e d a t t h e same temperature, a p a r t f r o m v a r i a t i o n s o f a few degrees due t o d i f f e r e n t amounts o f p r i o r d e f o r m a t i o n o r i m p u r i t y c o n t e n t . The measurements o f t h e Bordoni peak i n p o l y c r y s t a l l i n e copper as a f u n c t i o n o f t h e amount o f p l a s t i c d e f o r m a t i o n have shown t h a t t h e h e i g h t o f t h e peak has a maximum v a l u e f o r a d e f o r m a t i o n i n t h e r e g i o n o f 7% /I/. Or has an a p p r o x i m a t e l y c o n s t a n t v a l u e f o r d e f o r m a t i o n s g r e a t e r t h a n about 2% /2/. However Boch /1/ has shown t h a t f o r aluminum t h e Bordoni peak h e i g h t c o n t i n u e s t o i n c r e a s e up t o s t r a i n o f 30%, w h i l e V o l k l e t a l . /3/ found s i m i l a r r e s u l t s f o r deformations up t o 6%. Hassan and N i b l e t t /4/ have shown s i m i l a r r e s u l t s f o r 6N aluminum f o r a d e f o r m a t i o n up t o 35%. As t h e s e t h r e e i n v e s t i g a t i o n s have been made on aluminum o f 4N5, 5N and 6N p u r i t y r e s p e c t i v e l y , Sack / 5 / and Mayadas /6/ have shown t h a t t h e Bordoni peak i n aluminum i s v e r y s e n s i t i v e t o t h e i m p u r i t y c o n t e n t . A l l t h a t work has been done a t k i l o h e r t z f r e q u e n c i e s , so I decided t o c a r r y o u t a d e t a i l e d i n v e s t i g a t i o n a t megahertz f r e q u e n c i e s .
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EXPERIMENTAL PROCEDUREThe specimens used i n t h i s i n v e s t i g a t i o n were h i g h p u r i t y 5N aluminum p o l y c r y s t a l s , s u p p l i e d by MetalfResearch L i m i t e d , i n t h e f o r m o f c y l i n d e r s a p p r o x i m a t e l y 10mm l o n g and llmm i n diameter. They a r e g i v e n a successive amount o f d e f o r m a t i o n by
compression a l o n g t h e a x i s o f t h e c y l i n d e r i n a Monsanto tensometer a t room temperature. The u l t r a s o n i c a t t e n u a t i o n was measured d i r e c t l y a f t e r t h e
deformation. The measurement t e c h n i q u e was s i m i l a r t o t h a t d e s c r i b e d by Zein and N i b l e t t /9/. Measurements were made i n t h e t e m p e r a t u r e range f r o m 100 t o 290K, t h e t e m p e r a t u r e b e i n g measured w i t h t w o p l a t i n u m sensors p l a c e d c l o s e t o t h e specimen and connected t o a Lakeshore d i g i t a l thermometer and c o n t r o l l e r . The t e m p e r a t u r e was h e l d c o n s t a n t w h i l e each a t t e n u a t i o n measurement was made.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19851066
(30-298 JOURNAL DE PHYSIQUE
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RESULTSThe measurements were c a r r i e d o u t on two alumi num p o l y c r y s t a l 1 i ne specimens. The temperature dependence o f t h e u l t r a s o n i c a t t e n u a t i n were measured a f t e r each s e r i e s o f compressions f o r a s t r e s s ranging up t o 80N/mm-
B . F i g u r e 1 shows t h e s t r e s s - s t r a i n curve f o r one o f t h e specimens.
F i g (1) The s t r e s s - s t r a i n curve f o r p o l y c r y s t a l l i n e aluminum 5N.
The measurement showed t h a t t h e h e i g h t o f t h e Bordoni peak i s increased by
i n c r e a s i n g t h e deformation. The peak appeared a t temperatures i n t h e range from 186 t o 220K. The lower values occurred f o r l a r g e r deformations. The v a r i a t i o n o f t h e u l t r a s o n i c a t t e n u a t i o n w i t h temperature i s shown i n Figs. 2 and 3.
F i g ( 2 ) The u l t r a s o n i c a t t e n u a t i o n o f p o l y c r y s t a l l i ne 5N a1 uminum as a f u n c t i o n o f temperature.
( 0 ) 3.5Nmrn-'
(v)
5.9hm-'(X)
7Nmm-' (a) 9.5N11m-~F i g (3) The u l t r a s o n i c a t t e n u a t i o n o f p o l y c r y s t a l l i n e 5N aluminum as a f u n c t i o n of temperature.
35.7~mm-~
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047.6~mm-~Table 1 l i s t s t h e peak h e i g h t and t h e temperature o f t h e peak, a f t e r each stage o f deformation.
Table 1
Summary o f t h e R e s u l t s f o r 5N P o l y c r y s t a l l i n e Aluminum a t 10.2MHz
A few measurements were made a t 5.6MHz, i n o r d e r t o study t h e v a r i a t i o n o f t h e a c t i v a t i o n energy w i t h deformation.
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DISCUSSIONThe v a r i a t i o n of t h e Bordoni peak h e i g h t w i t h d e f o r m a t i o n i s shown i n Fig. 4 which a l s o includes' t h e r e s u l t s o f Hassan and N i b l e t t /4/,
F i g (4) V a r i a t i o n o f t h e Bordoni peak h e i g h t f o r aluminum w i t h s t r e s s .
(a)
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This s t u d y( 0 )
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Hassan and N i b l e t t / 4 / ,The comparison o f t h e curves shows t h a t t h e peak h e i g h t i s v e r y s e n s i t i v e t o t h e i m p u r i t y c o n t e n t . Our values a r e comparable as w e l l t o t h o s e p r e v i o u s l y o b t a i n e d f o r 5N aluminum by V o l k l
131,
and a r e l o w e r t h a n t h o s e found f o r specimen o f h i g h e r p u r i t y by Hassan and Ni b l e t t /4/, D e t e r r e e t a l . /7/, and Mayadas /5/. The peak grows r a p i d l y up t o a s t r e s s o f 35Nmm-,
and t h e n remains a p p r o x i m a t e l y c o n s t a n t f o r h i g h e r deformation. T h i s i s i n agreement w i t h t h e work done by Hassan and N i b l e t t /4/ and observed i n copper by Farman and N i b l e t t /8/. I a l s o found t h a t t h e t e m p e r a t u r e o f t h e Bordoni peak decreased about t h i r t y f i v e degrees as t h e d e f o r m a t i o n was increased. F i g u r e 5 shows t h e v a r i a t i o n o f t h e peak w i t h s t r e s s .I t s shape i s r a t h e r s i m i l a r t o t h a t found f o r aluminum by Hassan and N i b l e t t 141, and t h a t found f o r copper by N i b l e t t and Zein /9/, and Farman and N i b l e t t /8/, b u t t h e magnitude of t h e s h i f t i n t h e Bordoni peak i s g r e a t e r i n t h e case of aluminum.
This l a r g e s h i f t i s comparable t o t h a t found i n n i c k e l by Venkatesan and Beshers 1101.
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F i g (5) V a r i a t i o n o f t h e Bordoni peak temperature f o r p o l y - c r y s t a l l i n e 5N aluminum w i t h p r i o r s t r e s s .
This l a r g e s h i f t can be a t t r i b u t e d t o t h e h i g h e r s t a c k i n g f a u l t energy i n aluminum and n i c k e l . I n view o f t h e v a r i a t i o n i n t h e temperature o f t h e Bordoni peak w i t h p r i o r s t r e s s i t i s important t o compare r e s u l t s a t d i f f e r e n t frequencies o n l y on a s i m i l a r l y s t r e s s e d a1 umi num when a t t e m p t i n g t o determi ne t h e a c t i v a t i o n energy o f t h e r e l a x a t i o n process. A comparison o f t h e present r e s u l t s w i t h those a t k i l o h e r t z frequencies f o r specimens subjected t o s i m i l a r stresses shows t h a t t h e a c t i v a t i o n energy f o r t h e Bordoni peak i n 5N aluminum i s approximately 0.186ev f o r l i g h t deformation and decreases w i t h i n c r e a s i n g s t r e s s , reaching 0.165ev f o r i n t e r m e d i a t e stresses and 0.152ev f o r heavy deformation. The v a r i o u s t h e o r e t i c a l i n t e r p r e t a t i o n s o f t h e Bordoni peak have r e c e n t l y been reviewed by Fantozzi e t a l . /11/, and i t i s g e n e r a l l y agreed t h a t t h e double k i n k generation model gives t h e most s a t i s f a c t o r y explanation. The h i g h e r peak temperature observed i n t h e l i g h t l y deformed specimen i s b e l i e v e d t o be due t o l o n g e r d i s l o c a t i o n loops o c c u r r i n g a t t h i s deformation (Engelke 1121). Higher p l a s t i c deformation causes a r e d u c t i o n i n t h e l o o p l e n g t h w i t h a consequent r e d u c t i o n o f t h e temperature o f t h e peak. The s l i g h t increase i n t h e peak temperature a t h i g h e r deformation i s a t t r i b u t e d t o a r e d u c t i o n i n t h e i n t e r n a l s t r e s s caused by t h e f o r m a t i o n o f a c e l l s t r u c t u r e i n which a m a j o r i t y of d i s l o c a t i o n a r e located. An i n t e r p r e t a t i o n o f how t h e h e i g h t o f t h e Bordoni peak v a r i e s w i t h p l a s t i c deformation r e q u i r e s a knowledge o f how t h e d i s l o c a t i o n d e n s i t y and t h e i n t e r n a l s t r e s s and l o o p l e n g t h d i s t r i b u t i o n s vary w i t h p r i o r s t r e s s o r s t r a i n .
REFERENCES
/I/ Bock , R ~ + t t e s i s , P o i t i e r s (1968).
/2/ N i b l e t t , D. H. and Wilks, J., Adv. Phys. 9 (1960) 1.
/3/ V o l k l , J., Weinlonder, W. and Carsten, J., Phys. S t a t . Sol., 10 (1965) 7739.
/4/ Hassan, R.A.R. and Ni b l e t t
,
D. H., J. de. Phys. Col loque 44 (1983) C9-659.Fourth European Conference 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 Sol i d s (1983).
/5/ Sack, H. S., Acta Met. 10 (1962) 455.
/6/ Mayadas, A. F., Thesis, C o r n e l l (1966).
/7/ Deterre, Ph., Esnouf, C., Fantozzi, G., Pegin, P., Perez, J., R i t c h i e , I., Vanoni
,
F. and Vincent, A., Acta Met. 27 (1979) 1779./8/ Farman, H. and N i b l e t t , D. H., 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. Smith, C-C) (1980) 7.
/9/ N i b l e t t , D. H. and Zein, M., J. Phys. F. Metal Physics 10 (1980) 773.
/ l o /
Venkatesan, P. S. and Beshers, D. N., J. Appl. Phys. 4 1 (1970) 42./11/ Fantozzi, G., Esnouf, C., Benoit, W . and R i t c h i e , I . G., Prog. i n Mat. Sci., 27 (1982) 311.
/12/ Engelke, H., Phys. S t a t . Sol., 36 (1969) 231, 345.
