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A STUDY OF THE DEFORMATION DEPENDENCE OF THE BORDONI PEAK IN POLYCRYSTALLINE
6N ALUMINIUM
R. Hassan, D. Niblett
To cite this version:
R. Hassan, D. Niblett. A STUDY OF THE DEFORMATION DEPENDENCE OF THE BORDONI
PEAK IN POLYCRYSTALLINE 6N ALUMINIUM. Journal de Physique Colloques, 1983, 44 (C9),
pp.C9-659-C9-664. �10.1051/jphyscol:1983999�. �jpa-00223449�
JOURNAL DE PHYSIQUE
Colloque C9, suppi6ment au n012, Tome 44, d k e r n b r e 1983 page C9-659
A STUDY OF THE DEFORMATION DEPENDENCE OF
THE
BORDONI PEAK I N POLYCRYSTALLINE 6N ALUMINIUMR.A.R. Hassan and D.H. Niblett
Physics Laboratory, fie University, Canterbury, Kent, U.K.
R6sum6
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Nous presentons des m e s u r e d u f r o t t e m e n t i n t 6 r i e u r d'aluminium p o l y - c r y s t a l l i n de p u r e t 6 6N, dans l a gamme de tempgrature comprise e n t r e 80 e t 260K, h des fr6quences d ' e n v i r o n 23kHz. Nous avons 6 t u d i 6 l a hauteur e t l a tempgrature du p i c de Bordoni pour l e s v i b r a t i o n s l o n g i t u d i n a l e s des Bchanti- l l o n s c y l i n d r i q u e s apres p l u s i e u r s extensions h l a temp6rature ambiante.Nous avons B t u d i 6 6galement l e s e f f e t s du r e c u l t h l a temperature ambiante apres l a d6formation. La comparaison de nos r e s d l t a t s avec ceux obtenus par d ' a u t r e s auteurs nous montre que l e p i c de Bordoni e s t beaucoup p l u s import- a n t e t se p r o d u i t h une temp6rature nettement p l u s 6lev6e pour un aluminium de p u r e t 6 6N que pour des g c h a n t i l l o n s moins purs.
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 6N p u r i t y p o l y c r y s t a l l i n e aluminium has been measured i n t h e temperature range from 80 t o 260K a t a frequency o f about 23kHz. The h e i g h t and temperature o f t h e Bordoni peak were s t u d i e d f o r l o n g i t u d i n a l v i b r a t i o n s o f c y l i n d r i c a l rods a f t e r v a r i o u s amounts o f exten- s i o n a t room temperature, and t h e e f f e c t s o f annealing a t room temperature were a l s o i n v e s t i g a t e d . The r e s u l t s a r e compared w i t h measurements on a l u - minium r e p o r t e d by o t h e r authors, and i n d i c a t e t h a t t h e Bordoni peak i s much l a r g e r and occurs a t an a p p r e c i a b l y h i g h e r temperature f o r 6N aluminium than f o r specimens o f lower p u r i t y .1. INTRODUCTION
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 deformation 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 deformation i n t h e r e g i o n o f 7% /1/ o r has an approximately c o n s t a n t v a l u e f o r deformations g r e a t e r than about 2% /2/. However, Boch /I/ has shown t h a t f o r aluminium t h e Bordoni peak h e i g h t continues t o increase up t o a s t r a i n o f 30%, w h i l e VBlkl e t a l . /3/ found a s i m i l a r r e s u l t f o r deformations up t o 6%. As these two i n v e s t i g a t i o n s were made on aluminium o f 4N5 and 5N p u r i t y r e s p e c t i v e l y , and Sack /4/ and Mayadas / 5 / have shown t h a t t h e Bordoni peak i n aluminium i s v e r y sensi t i v e t o t h e i m p u r i t y content, we 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 of t h e deformation dependence o f t h e Bordoni peak i n p o l y c r y s t a l l i n e aluminium o f 6N p u r i t y .
2. EXPERIMENTAL PROCEDURE
The specimens used were o f 99.9999% pure p o l y c r y s t a l l i n e aluminium, s u p p l i e d by Metal C r y s t a l s L i m i t e d i n t h e form o f c y l i n d r i c a l rods o f 6mm diameter and about lOcm long. They were annealed i n argon f o r one hour a t 350°C, and then subjected t o a s e r i e s o f deformations by l o n g i t u d i n a l extension a t room temperature i n a H o u n s f i e l d tensometer. The g r i p p e d ends were n o t removed a f t e r each deformation, b u t a small p o r t i o n was c u t o f f when t h e specimen had become t o o long t o f i t i n t h e i n t e r n a l f r i c t i o n apparatus. As i t i s w e l l known /6/ t h a t t h e h e i g h t o f t h e Bordoni peak i n aluminium decreases w i t h t i m e a t room temperature, t h e specimen was normally mounted and cooled t o 78K w i t h i n about t h r e e hours a f t e r each deformation.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1983999
C9-660 JOURNAL DE PHYSIQUE
The i n t e r n a l f r i c t i o n was measured i n t h e temperature range from 80 t o 260K a f t e r each deformation, u s i n g l o n g i t u d i n a l v i b r a t i o n s a t a frequency between 21 and 24kHz.
The measurement technique was s i m i l a r t o t h a t described by Brown and N i b l e t t /7/.
RESULTS
3.
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Measurements on t h e f i r s t specimen showed t h a t t h e h e i g h t o f t h e Bordoni peak was approximately c o n s t a n t (maximum Q-'* 11 x f o r extensions ranging from about 5% t o 44%. The peak appeared a t a temperature i n t h e range from 160 t o 175K, t h e lower values o c c u r r i n g f o r t h e h i g h e r deformations. As t h e peak was much l a r g e r , and occurred a t an a p p r e c i a b l y h i g h e r temperature, than t h a t observed by Boch /1/
f o r 4N5 aluminium, a more d e t a i l e d i n v e s t i g a t i o n o f t h e deformation dependence was c a r r i e d o u t on a second specimen.
The i n t e r n a l f r i c t i o n o f t h e second specimen was measured i n t h e annealed c o n d i t i o n and a f t e r each o f f i f t e e n successive deformations r a n g i n g up t o a t o t a l extension o f 35%, produced by a s t r e s s o f 41 N m r 2 . The s t r e s s - s t r a i n curve f o r t h i s specimen i s shown i n Fig.1, and t h e v a r i a t i o n o f t h e i n t e r n a l f r i c t i o n w i t h temperature a f t e r a s e l e c t i o n o f t h e deformations i s g i v e n i n Fig.2.
Table 1 l i s t s t h e peak height, t h e temperature o f t h e peak and t h e frequency ( a t t h e temperature o f t h e peak) a f t e r each stage o f deformation. I n e s t i m a t i n g t h e values o f t h e peak h e i g h t an approximate c o r r e c t i o n was made f o r t h e background damping o c c u r r i n g a t t h e temperature o f t h e peak, b u t no c o r r e c t i o n was made f o r t h e e f f e c t of t h e s u b s i d i a r y peak which occurs on t h e low temperature s i d e o f t h e Bordoni peak b u t i s n o t pronounced i n o u r measurements. On t h e few occasions when t h e specimen was l e f t a t room temperature f o r more than t h r e e hours a f t e r t h e deformation, an approximate c o r r e c t i o n t o t h e peak h e i g h t has been made t o a l l o w f o r t h e annealing of t h e peak a t room temperature. The c o r r e c t i o n t o be a p p l i e d was determined by measuring the h e i g h t o f t h e Bordoni peak f o r 6N aluminium specimens as a f u n c t i o n o f t h e t i m e a t room temperature a f t e r deformation: Fig.3 shows t h e r e s u l t s f o r two specimens a f t e r extensions o f 1.4% and 44%.
Table 1
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Parameters o f t h e Bordoni peak f o r p o l y c r y s t a l l i n e 6N aluminium.4. DISCUSSION
The v a r i a t i o n o f t h e h e i g h t o f t h e Bordoni peak w i t h s t r a i 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 Boch /1/ and V d l k l e t a1 /3/. Comparison o f t h e curves confirms t h a t t h e peak h e i g h t i s very s e n s i t i v e t o t h e i m p u r i t y content. Our maxi- mum Q-' values o f around a r e comparable t o those p r e v i o u s l y obtained f o r 6N aluminium by D e t e r r e e t a l . /8/ and Mayadas /5/, and a r e c o n s i d e r a b l y l a r g e r than those found f o r specimens o f lower p u r i t y .
Stress (~mm-2)
0 5.2 7.1 8.9 11 14 16 19 23 2 7 3 1 34 36 38 40 4 1
Peak temperature (K)
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196 190 188 182 180 176 174 174 163 159 160 160 159 160 158 S t r a i n
( % I
0 0.15 0.36 0.58 0.96 1.4 2.0 2.9 4.5 7.0 10.6 14 18 23 29 3 5
Frequency (kHz) 23.9 23.5 23.3 23.3 23.2 23.1 23.0 22.7 22.4 21.8 22.0 22.1 24.0 23.6 23.6 22.8 Peak h e i g h t
(9-1 x l o 3 ) 0.3 5.3 6.0 6.3 7.5 8.8 9.5 9.4 9.7 9.1 10.0 10.6 10.8 10.9 10.5 10.8
Fig.1
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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 6N aluminium.0 0 0
0 0
0 10 2 0 30
Strain (%)
Fig.2
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The i n t e r n a l f r i c t i o n of p o l y c r y s t a l l i n e 6N aluminium (T = temperature i n K ) .a
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annealed 1 hour a t 350°C;b
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extended 0.15%;c
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extended 0.58%;d
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extended 2.0%;e
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extended 10.6%;f
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extended 35%.JOURNAL DE PHYSIQUE
Fig.3
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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 6N aluminium w i t h t i m e ( t ) a t room tempera- t u r e a f t e r deformation.A
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extended 1.4%;x
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extended 44%.Fig.4
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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 aluminium w i t h s t r a i n .A
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Boch /1/ (4N5 p u r i t y ) ; x-
Vi5lkl e t a1./3/ (5N p u r i t y ) ; o-
This study (6N p u r i t y ) .10 2 0
Strain (%I
The peak grows r a p i d l y f o r extensions up t o about 2%, w h i l e t h e background damping decreases s t e a d i l y i n t h i s r e g i o n . F u r t h e r deformation has l i t t l e e f f e c t on t h e peak h e i g h t , t h e p o s s i b l e increase o c c u r r i n g as t h e s t r a i n i s increased t o 35% be- i n g comparable t o t h e u n c e r t a i n t y i n e s t i m a t i n g t h e peak h e i g h t . The s t r a i n depen- dence observed here f o r h i g h - p u r i t y aluminium i s very s i m i l a r t o t h a t u s u a l l y found f o r copper. The peak h e i g h t i s e i t h e r approximately c o n s t a n t f o r deformations g r e a t e r than 2%, as i n t h e measurements on p o l y c r y s t a l l i n e c o p p e r b y N i b l e t t and W i l ks /2/, o r increases s l i g h t l y w i t h i n c r e a s i n g deformation i n t h i s region, as ob- served by Farman and N i b l e t t /9/ f o r copper s i n g l e c r y s t a l s .
Boch /1/ found t h a t t h e Bordoni peak i n 4N5 aluminium occurred a t a temperature be- tween 140 and 145K f o r measurements a t a frequency o f 17kHz. As o u r frequency was o n l y s l i g h t l y h i g h e r than t h i s , one m i g h t expect t h a t t h e peak would be near 145K.
However, as shown i n Table 1, we found t h a t t h e peak occurred a t an a p p r e c i a b l y h i g h e r temperature than t h i s . This i s c o n s i s t e n t w i t h t h e work o f Sack /4/ and Mayadas /5/, who a l s o found t h a t t h e temperature o f t h e peak was h i g h e r f o r speci- mens o f h i g h e r p u r i t y . This temperature s h i f t i n aluminium i s much l a r g e r than, and
i n t h e o p p o s i t e d i r e c t i o n to, t h a t observed f o r g o l d doped w i t h copper by Bonjour and B e n o i t
/ l o / .
Copper shows o n l y a small s h i f t /11/ i n t h e same d i r e c t i o n as t h a t observed here, b u t the range o f p u r i t y used extended o n l y t o 5N and i t i s p o s s i b l e t h a t 6N copper m i g h t show a comparable s h i f t t o t h a t f o r 6N aluminium.We a l s o found t h a t the temperature o f t h e Bordoni peak decreased by about t h i r t y de- grees as t h e deformation was increased. Fig.5 shows t h e v a r i a t i o n o f t h e peak tem- p e r a t u r e 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 copper by N i b l e t t and Zein /12/ and by Farman and N i b l e t t /9/, b u t t h e magnitude o f t h e s h i f t i s g r e a t e r i n t h e case o f 6N aluminium. The peak temperature remains e s s e n t i a l l y constant f o r stresses g r e a t e r than about 30 Nmm-2 o r s t r a i n s g r e a t e r than about 10%.
Fig.5
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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 6N aluminium w i t h p r i o r s t r e s s .3 0"
0 1 0 2 0 30 40
Stress (Nmm-'1
The l a r g e dependence o f t h e peak temperature on b o t h t h e p u r i t y and t h e deformation makes i t v e r y d i f f i c u l t t o determine an accurate v a l u e f o r t h e a c t i v a t i o n energy o f t h e Bordoni peak i n aluminium. Most o f t h e previous measurements have used e i t h e r aluminium o f lower p u r i t y o r small deformations i n t h e range where the peak tempera- t u r e v a r i e s w i t h deformation. Mayadas /5/ found t h e peak a t 150K f o r 6N aluminium compressed by 7%, using a frequency o f about 4kHz. U n f o r t u n a t e l y t h i s frequency i s t o o c l o s e t o t h a t used here t o enable us t o determine t h e a c t i v a t i o n energy p r e c i s e - l y . Measurements o f t h e Bordoni peak temperature a t frequencies i n t h e r e g i o n o f 1 Hz o r 10 Mhz f o r 6N aluminium deformed by about 10% o r more would be u s e f u l t o compare w i t h t h e value o f about 159K obtained here f o r about 23kHz.
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 r e - viewed by Fantozzi e t a l . /13/, 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 l a r g e r peak i n t h e p u r e r aluminium i s due t o t h e l o n g e r l o o p l e n g t h s o c c u r r i n g when fewer i m p u r i t i e s a r e present, and Engelke /14/ has shown t h a t t h e existence o f these l o n g e r loops causes t h e peak t o s h i f t t o a h i g h e r temperature, as observed i n t h i s study. High 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, b u t t h e s i t u a t i o n i s then complicated by t h e increase i n t h e i n t e r n a l s t r e s s /15/. 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 loop l e n g t h d i s t r i b u t i o n s vary w i t h t h e p r i o r s t r e s s o r s t r a i n .
REFERENCES
1. BOCH, P . , Thesis, P o i t i e r s (1968).
2. NIBLETT, D.H. and WILKS, J., Adv.Phys., 9 (1960) 1.
3. VOLKL, J., WEINLANDER, W. and CARSTEN, JT, Phys.Stat.So1
., 10
(1965) 739.4. SACK, H.S., Acta Met. 10 (1962) 455.
5. MAYADAS, A.F., T h e s i s , T o r n e l l (1966).
6. BAXTER, W.J. and WILKS, J., Acta Met. 11 (1963) 979.
7. BROWN, G.R. and NIBLETT, D.H., J.Phys.EAppl.Phys.6 (1973) 809.
8. DETERRE Ph., ESNOUF, C., FANTOZZI, G., PEGUIN, P., PEREZ, J., RITCHIE, I., VANONI, F. and VINCENT, A., Acta Met. 27 (1979) 1779.
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C9-664 JOURNAL DE PHYSIQUE
