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Damping characteristics of ZnAl matrix composites
Scripta Metallurgica et Materialia, V01.30, No. 10, pp. 1321-1326, 1994 Copyright © 1994 Elsevier Science Ltd Printed in the USA. All rights reserved 0956-716X/94 $6.00 + 00
Pergamon
13dOdPING {}IARACTERISTICS OF Zn-AI MATRIX ~ S I T E S M i n g y u a n Gu, Zbel~gyang C h e n , Z h a n g m i n WaivE, Y a n p i n g 3 i n ,
3 i n Huang m~l G u o d i n g Z h a n g
S t a t e Key L a b o r a t o r y o t M e t a l M a t r i x C e e ~ s i t e Materials, S h a n g h a i 3 i a o Tong I l n i v e r s i t y , Shanghai 200030, P.R.C~lina
(Received November 15, 1993) (Revised February 2, 1994) 1 .. l n.t_r.oO_uct.~o!) Among h i g h d a m p i n g t ~ a t e r i a l s Zn-AI a l l o y s a r e c o n s i d e r f - d to be t h e m o s t e x c e l l e ~ l non f e r r o m a g n e t i c d a m p i n g a l l o , / s d u e to t h e i r a t t r a c l i v e properties s u c h a s low r a e ! l i n g p o i n t , low density, good w o r k a b i l i t y and h i R h d a m p i n g c a p a c i t y in a b r o a d t r e q u e n c y range (1,Z). The limitations to h i g h t e m p e r a t u r e u s e o l t h e s e a l l o y s a r e t h e i r poor h i g h t e m p e r a t u r e m e c h a n i c a l properties and dimensional instability. R e c e n t l y , v a r i o u s r e i n f o r c e m e n t s h a v e b e e n a d d e d to Zn AI a l l o y s to i m p r o v e t h e i r h i g h t e m p e r a t u r e p r o p e r t i c , s w h i l e to i n c r e a s e t h e i r s p e c i f i c s t r e n g t h , stillness, wear r e s i s t a n c e a n d to d e c r e a s e t h e r ~ { t e x p a n s i o n c o e | f i c i e n t (3,0,5). However,the e f t e c t s o l t h e s e r e i n l o r c e m e n t s on d;nnping b e h a v i o r o f Zn.--A[ a l t o y s a r e y e t t o be e l u c i d a t e d . The p r e s e n t p a p e r i s t o r e p o r t some new p h e n o m e n a t o u n d in p r e l i m i n a r y dampi|~g s t u d i e s o l l o n g g r a p h i t f . f i b e r , s h o r t g r a p h i t e f i b e r a n d s i l i c o n c a r b i d e w h i s k e r r e i n I o r c e d Zn-Ai a l l o y b a s e d c o m p o s i t e s . 2. EX _l:~er ~._m#.nts
The e x p e r i m e n t a l m a t e r i a l s used in t h i s work were [ a b r i c a t e d by vacuum p r e s s u r e i n f i l t r a t i o n t e c h n i q u e . They a r e : 1. ZAM, Zn-AI m a t r i x a l l o y , l t s chemical c~mkoosition was d e t e r m i n e d by e l e c t r o n e n e r g y d i s p e r s i v e s p e c t r o s c o p y . Data from f i v e s e p a r a t e p o i n t s g i v e t h a t : A [ : (23.37_+0.79} Wt%, Cu: (2.17_+0.11) Wtga a n d Zn: th(.' r e s t . 2. ZAW, ZAM r e i n f o r c e d w i t h 20 vol% SiC w h i s k e r . 3. Z/kS, 2AM r e i n f o r c e d w i t h 10 vol% s h o r t g r a p h i t e f i b e r a n d l0 vol% SiC p a r t i c l e . 8. ~kL, ZAM r e i n f o r c e d w i t h 60 vot% l o n g g r a p h i t e f i b e r . The f o u r k i n d s o f m a t e r i a l s were s u b j e c t e d to solid solubilization of 380°C/2~h atter fabrication. The 7_Aht, ZAW a n d 7,~S were t h e n e x t r u d e d u n d e r a n r e d u c t i o n r a t i o o f 12 a f t e r preheating at 260C for 0.5 hour. Specimens for damping tests were spark cut to the dimensions of ~0 m m x 4 mm x 1 mm w i t h t h e l o n g i t u d i n a l direction parallel to the extrusion or the tong fiber direction. Damping was m e a s u r e d u s i n g a f o r c e d - v i b r a t i o n pendulum in a multi-functional internal f r i c t i o n a p p a r a t u s . The i n t e r n a l f r i c t i o n O t i s c a l c u l a t e d f r o m Q - i : t a n ~ , w h e r e ~ i s the phase a n g l e by which s t r a i n lags s t r e s s d u r i n g the ~orced v i b r a t i o n . The s t r a i n a m p l i t u d e was f i x e d t o 1 x 10"j t h r o u g h o u t t h i s work. 3 , Re_su_!t__s__a~_.Oi s cus.sj 3.1 Dependency of
lnterna~l Friction
O-I a n d D y n a m i c M o d u l u s (; o n V i b r a t i o n
1321
Frequency f:
1322
Zn-AI MATRIX COMPOSITES
Vol. 30, No. 10
The v a r i a t i o n s o f 0 -I and G w i t h v i b r a t i o n f r e q u e n c y f f o r the [our m a t e r i a l s a t 30~C i n t h e f r e q u e n c y r a n g e from 0.06 Hz t o lO Hz a r e shown in F i g . l and F i g . 2 , r e s p e c t i v e l y . 1"he 0 `l o f ?.AM, ZAW and ZAS d e c r e a s e s w i t h f when v i b r a t i o n f r e q u e n c y i s s m a l l , and t h e n g r a d u a l l y r e a c h e s a c o n s t a n t v a l u e . The c o r r e s p o n d i n g G i n c r e a s e s w i t h f m o n o t o n o u s l y . [ h e r e a s o n t h a t t h e v a r i a t i o n t e n d e n c y of Q-I and G with f f o r ZA~ and 7.~ i s s i m i l a r to t h a t f o r m a t r i x ~ i s p e r h a p s t h a t the a d d i t i o n o f r e i n f o r c e m e n t s to ZA~ and ZA5 i s r e l a t i v e l y s m a l l . On t h e c o n t r a r y , t h e Q[ and G a r e a l m o s t i n d e p e n d e n t on f f o r ZAL. T h i s v a r i a t i o n t e n d e n c y i s s i m i l a r t o t h a t of ~ r a p h i t e f i b e r (6) which has 60 vol% i n the ZAL C o m p o s i t e . T h i s i n d i c a t e s t h a t t h e damping n a t u r e o f t h e m a j o r i t y component i n t h e composite p l a y s a v e r y i m p o r t a n t r o l e in d e t e r m i n i n g t h e o v e r a l l damping characteristics of the composite,
160
~
140 120 100
13
0
....
l
0.I
•
.
,
. . . . .
t
,
13
.
i-
13
i
=
. . . .
1
i
10
4O
0.1
FIG. I
I
10
Frequen=y (Hz)
Frequency (Hz) V a r i a t i o n s o f Q-I w i t h f
FIC, 2
Variations
of G w i t h f
3.2 E f f e c t of Reinforcements on Q-I and C: I t c a n b e s e e n from F i g . 1 t h a t t h e QI v a l u e s f o r c o m p o s i t e s a r e lower t h a n t h a t f o r m a t r i x . The d e s c e n d i n g o r d e r o f ~ I f o r t h e f o u r m a t e r i a l s i s Z / ~ > ZAS > ZAW > ZAL. The r e a s o n of t h i s d e c r e a s e i s m a i n l y due t o t h e low damping c a p a c i t y of t h e r e i n f o r c e m e n t s and t h e i n t e r f a c e e f f e c t s . I t i s w e l l known t h a t t h e i n t e r n a l damping of a c o m p o s i t e m a t e r i a l a r i s e s m a i n l y from i n t r i n s i c damping of i t s components, t h e i n t e r f a c e e f f e c t between t h e m a t r i x and t h e r e i n f o r c e m e n t and t h e e f f e c t o f m i c r o s t r u c t u r a l change i n b o t h m a t r i x and r e i n f o r c e m e n t due t o t h e d i f f e r e n c e i n p h y s i c a l o r m e c h a n i c a l p r o p e r t i e s such as c o e f f i c i e n t o f t h e r m a l e x p a n s i o n and e l a s t i c modulus ( 7 , 8 ) . The c o n t r i b u t i o n of i n t r i n s i c damping of m a t r i x and r e i n f o r c e m e n t t o damping c a p a c i t y o f t h e c o m p o s i t e c o u l d be e s t i m a t e d on t h e b a s i s of t h e r u l e o f m i x t u r e s . T h a t i s t o say , t h e o v e r a l l c o n t r i b u t i o n o f i n t r i n s i c damping c e p a c i t y , ( Q l ) i n t r , would be p r o p o r t i o n a l t o t h e i n d i v i d u a l damping c a p a c i t i e s of t h e m a t r i x , 0~, and r e i n f o r c e m e n t , Or, m u l t i p l i e d by t h e i r r e s p e c t i v e volume f r a c t i o n s , Vm and Vr, as g i v e n by
(0 -1 ) ~ . = (O -=) =v.+ (0-*) .V.
A c o m p a r i s o n o f t h e c a l c u l a t e d (Ot)intr and t h e c o r r e s p o n d i n g e x p e r i m e n t a l r e s u l t s f o r c o m p o s i t e 1 m a t e r i a l s , (Q'I)oc, a r e g i v e n i n T a b l e 1, where (Q)SiC was t a k e n as 5xl0" ] (9) and (Ol)ga~hite as
1.3x10 "z (10) and the (Q-l)= and o - i were obtained from present experimental data at the f l a t area in FIB. 1. Inspection of Table I reveals t h a t the d i f f e r e n c e between (QI)z&! and i t s (Q-I)intr is small, which
V01.30, No. 10
Zn-A1 MATRIX COMPOSITES
I323
i n d i c a t e s t h a t i n t r i n s i c damping i s t h e d o m i n a n t component i n t h e t o t a l damping of the c o m p o s i t e and t h e damping c o n t r i b u t i o n from o t h e r mechanisms i n t h e c o m p o s i t e i s n e g l i g i b l e . (QI)~S i s TABLE 1. Comparison of t h e (Q-I)intr w i t h t h e C o r r e s p o n d i n g (Q-t)mc
Materials
(Q-l)mc x I00
(O-I)intt x 100
Z~
3.00
ZAW
2.50
I
2.52
ZAS
2.58
I
2.93
ZAL
1.98
I
1.1~
,
I
slightly larger than the corresponding (Q'I)intr " I t means t h a t damping mechanisms o t h e r t h a n intrinsic contribution are functioning. The f r a c t o g r a p h of ZAS in F i g . 3 d e m o n s t r a t e s weak interracial bonding between t h e m a t r i x and SiC w h i s k e r s . The i n t e r r a c i a l viscous slip in this c o m p o s i t e m i g h t be an i m p o r t a n t s o u r c e of damping.
FIG, 3
SF_~Ifractograph of ZAS
F[C. ~
S l ~ fractograph o f ZAL
The r e s u l t in T a b l e I a l s o shows t h a t the (0 -i)z~L i s l e s s t h a n t h e c o r r e s p o n d i n g (Q-!)intr. T h i s i s p r o b a b l y due t o the e f f e c t o£ mutual c o n s t r a i n t of K r a p h i t e f i b e r s and Zn-AI m a t r i x , Tile h i g h damping c a p a c i t y of g r a p h i t e i s b e l i e v e d 1o r e s u l t Ir(~n t h e a n i s o t r o p i c c r y s t a l s t r u c t u r e found in g r a p h i t e ( 7 ) . The s t r o n g i n - p l a n e c o v a l e n t b o n d i n g and weak van d e ; Waals t h r o u g h - p l a n e f o r c e s r e s u l t i n t h e easy d i s p l a c e m e n t of b a s a l p l a n e i n t h e in--plane d i r e c t i o n when s u b j e c t e d to s h e a r f o r c e s . Under c y c l i c l o a d i n g t h i s s l i d i n g i n d u c e s f r i c t i o n tosses atlributed l a r g e l y to t h e sweeping m o t i o n of d i s l o c a t i o n from pinning,, p o i n t s on t h e b a s a l p l a n e . The h i g h damping c a p a c i t y of the Zn-AI a l l o y presumably r e s u l t s irom v i s c o u s s l i p a l o n ~ the ~ r a i n b o u n d a r i e s and the o s c i l l a t i o n of d i s l o c a t i o n t i n e s ( 1 ) . The very s t r o n g i n t e r f a c i a l bonding which i s m a n i f e s t e d i n F i g . ~ imposes a s t t o n g c o n s t r a i n t
t o the sweepmg m o t i o n ot d i s t o c a l i o n s
in g r a p h i t e and t o v i s c o u s
g l i d i n g of g r a i n b o u n d a r i e s i n Zn-Al a l l o y . T h i s e f l e c t of t h e i n t e r f a c e d e c r e a s e s t h e damping c a p a c i t y of t h e c o m p o s i t e and t h e (Q-I)Z~L i s a c c o r d i n g l y l e s s than lhal of t h e corr~,sponding (0 1 }intr' 3.3 P e c u l i a r Dempirk~ Peak and Modulus .lc~p A distinct damping peak was found ill the f r e q u e n c y range of 4.5~6.5 14z f o r each m a t e r i a l when t h e t e s t i n t e r v a l i s as small as 0.05 ltz. "[he o c c u r r e n c e o f the damping peak is accompanied w i t h an a b r u p t change i n dynamic modulus. When the v i b r a t i o n ~requency sweeps a c r o s s the frequency of dampjn~ peak. the dynamic r~)dulus decreases f a s t to a minim~a~ and then itmlps to a maximum w i t h i n
1324
Zn-A1 MATRIX COMPOSITES
Vol 30, No. 10
a b o u t a 0 . 2 Hz range, and t h e n d e c r e a s e s f a s t t o t h e n o r m a l v a l u e . 5 t o 12, t h e f o l l o w i n g g e n e r a l f e a t u r e s can be seen:
:F
.... ;;1" ......... .............
Comparing the c u r v e s i n f i g u r e s
[ :
4.5
5
~5
O
8~
4.5
5
r~5
Frequm:y (Hz) O"1 v e r s u s
FIG. 5 0=6
.
.
.
8
6.5
FrequenW(Hz)
f for
ZAM
FIG. 6
G versus
f for 7.~
.
1,o[ 80
0.1 t - ' ' " ' ~ F ~
............ "'I
, p = , , , . , = = = o = = . o o = o = ~ =.,,.=,.~,.= o,, o o =.~
0
~
_
4.5
5
5.5
8
8.5
•
,
,
,
!
4.5
,
.
Q-I v e r s u s
0.18 .~.~...=% "~"~. 0,18
i
0.14 0.12
f for
ZAII/
FIG.
~ ,
.
.
.
6
6.5
8
G versus
f f o r ZAW
!, i'
,
i"8O
O.O4
75
-
4.5
.
~ ,~, ,,--=... . . . . .
OO8
~
.
115 1 110!
,,~
0.1
,
.
~(Hz)
O.O8
0
.
5.5
FmqLaw (Hz) FIG. 7
.
5
•
.
.
i
5
.
.
.
.
[
.
.
.
.
&6
i
.
.
.
.
.
6
l=requ=~ (Hz) FIG. 9
q-I v e r s u s
f f o r ZAS
6.5
70
i
.
.
.
i
5
4.5
.
.
.
.
i
,
,
•
~5
.
i
8
F r e q u e n ~ (Hz) FIG.
10
G v e r s u s f f o r ZAS
.
.
.
.
8.5
Vol. 30 No. 10
Zn-A1 MATRIX COMPOSITES
i
1325
i" FIG.
11
Q-t v e r s u s I I o r ZAL
FIG.
12
G v e r s u s f f o r ZAL
(I) Damping peak and modulus jtmpoccur in all the matrix alloys and three composite materials within a narrow frequency range at 30°C and 95~C. At 150~C, no modulus jtmlp is shown in their modulus versus frequency curves for ZAM, ZAW and 7AS. Another interesting phenomenon is that instead of a damping peak there is a dan~ping valley at the frequency of the otherwise dan~oing peak in ZAS at 150°C. (2) The frequency of the damping peak, the height of dang)ing peak (difference between maximum and background in vertical scale) and the height of modulus jump (difference between maximum and minimtma in vertical scale) all decrease with temperature for each material when the experimental error is also taken into account (see Table 2). TABLE 2, P o s i t i o n s
Temperature
~
o f Damping Peak (Hz)
ZAW
ZAS
ZAL
30~C
5.282
5,485
5.233
5.643
95°C
5.233
5.485
5.161
5.696
150°C
5.069
5.383
5.135
5.696
(3) The frequency of damping peak, the heights of the da~.ing peak and modulus jump are vary from material to material. The frequency of the damaping peak of ZAL is the largest in the four materials, followed by ZAW, ZAM and ZAS. The height of the damping peak and the modulus jump of ZAW is the largest followed by ZAL, ZAM and ZAS at 30°C. At 95°C the heights of the damping peak of ZAM is larger than that of ZAL. When the temperature reaches to 150"C only ZAL has d i s t i n c t modulus juml) and the order of dam~ing peak height is the same as that at 30°C except that there is a deep dam~ing valley in ZAS instead of damping peak (see Table 3). The above features of the damping capacity and dynamic modulus have not been reported in the l i t e r a t u r e . The detailed mechanism which results in the features is not clear. However, because the features are present in all the matrix alloy and con%Dosites, i t must be related to some nature or process in the matrix alloy. The addition of the reinforcements to the matrix has neither brought about nor eliminated the phenomena. It only mK)difies the feature in some d e t a i l s . Fromthe distinguishing c h a r a c t e r i s t i c shape of the curves of the damping capacity and dynamicmodulus vs. frequency and the dependence of them on temperature, i t is speculated that this phenomenon is mainly related to some phase transformation processes occurring in the matrix alloy. However, more
1326
Zn-AI MATRIX COMPOSITES
Vol. 30, No. 10
work has to be conducted in this direction before an affirmative conclusion can be drawn. TABLE 3. Heights of Damping Peaks and Modulus Jumps i
Temperature
ZAM
7.AW
ZAS
ZAL
30°C
25.21 (18.4)
49.79 (53.3)
11.48 (13.8)
25.32 (20.8) 15.47 (10.7)
95"C
150"C
20.99
32.13
10.90
(14.1)
(31.0)
(20.3)
I .07 ( .... )
2.53
-11.16
( ....
)
( ....
)
8.39 (6.5)
Note: data without parentheses are heights of damping peak times tO0 and data in parentheses represents heights of modulus jump in GPa. The dashed line represents no distinct modulus jump.
4. Conclusions I. The damping capacity of ZAW, ZAS and ZAL is lower than that of ZAM. The intrinsic damping of matrix and reinforcements are the main source of the damping of the composites. Interface effect has different influences on the damping properties of different composites. 2. In the frequency range studied the damping capacity of ZAM, ZAW and ZAS decreases white the dynamic modulus increases with frequency. However, in the ZAL both are almost independent of vibration frequency. 3. Sharp damping peaks are found in all four materials at the frequencies around 5.5 Hz. At the corresponding frequency the dynamic modulus undergoes a sudden change. The position and height of the damping peak and modulus jump varied with material and temperature. The mechanism of the phenomenon needs to be further studied. References 1. 2. 3. 4. 5. 6. 7. 8. 9.
H.Masumoto, M.Hinai and S.Sawaya, Trans. 31M, 22(I0), 681(1983) and 32(I0), 957(1991). G.Gao and M.Gu, Functional Matls., 22(~), 209(1991). M.A.Detiis, 3.P.Keustermans and F.Delannay, Mater. Sci. Eng., A135, 253(1991). 3.S.Kim, 3.Kaneko and M.Sugamata, 3. 3apan Inst. Metals, 55(9), 986(1991). H.Zhu and S.Liu, Matls. Sci. Prog., 6(I), 88(1992). K.Nishiyama, M.Yamanaka, M.Omort and S.Umekawa, 3.Mat.Sci.Lett., 9, 526(1990). R.J.Perez,3.Zhang, M.N.Gungor and E.J.Lavernia, Met. Trans., 2/~A, 701(1993). R.D.Adams, Matls. Sci. Forums, I19-121, 3(1993). L.A.Lbrahim, F.A.Mohamed and E.J.Lavernia, 3. Mater. Sci., 26, I137(1991).
10. 3.Zhang, R.3.Perez, M.gupta and E.J.Lavernia, Scripta Metall., 28, 91(1991).
Pergamon
13dOdPING {}IARACTERISTICS OF Zn-AI MATRIX ~ S I T E S M i n g y u a n Gu, Zbel~gyang C h e n , Z h a n g m i n WaivE, Y a n p i n g 3 i n ,
3 i n Huang m~l G u o d i n g Z h a n g
S t a t e Key L a b o r a t o r y o t M e t a l M a t r i x C e e ~ s i t e Materials, S h a n g h a i 3 i a o Tong I l n i v e r s i t y , Shanghai 200030, P.R.C~lina
(Received November 15, 1993) (Revised February 2, 1994) 1 .. l n.t_r.oO_uct.~o!) Among h i g h d a m p i n g t ~ a t e r i a l s Zn-AI a l l o y s a r e c o n s i d e r f - d to be t h e m o s t e x c e l l e ~ l non f e r r o m a g n e t i c d a m p i n g a l l o , / s d u e to t h e i r a t t r a c l i v e properties s u c h a s low r a e ! l i n g p o i n t , low density, good w o r k a b i l i t y and h i R h d a m p i n g c a p a c i t y in a b r o a d t r e q u e n c y range (1,Z). The limitations to h i g h t e m p e r a t u r e u s e o l t h e s e a l l o y s a r e t h e i r poor h i g h t e m p e r a t u r e m e c h a n i c a l properties and dimensional instability. R e c e n t l y , v a r i o u s r e i n f o r c e m e n t s h a v e b e e n a d d e d to Zn AI a l l o y s to i m p r o v e t h e i r h i g h t e m p e r a t u r e p r o p e r t i c , s w h i l e to i n c r e a s e t h e i r s p e c i f i c s t r e n g t h , stillness, wear r e s i s t a n c e a n d to d e c r e a s e t h e r ~ { t e x p a n s i o n c o e | f i c i e n t (3,0,5). However,the e f t e c t s o l t h e s e r e i n l o r c e m e n t s on d;nnping b e h a v i o r o f Zn.--A[ a l t o y s a r e y e t t o be e l u c i d a t e d . The p r e s e n t p a p e r i s t o r e p o r t some new p h e n o m e n a t o u n d in p r e l i m i n a r y dampi|~g s t u d i e s o l l o n g g r a p h i t f . f i b e r , s h o r t g r a p h i t e f i b e r a n d s i l i c o n c a r b i d e w h i s k e r r e i n I o r c e d Zn-Ai a l l o y b a s e d c o m p o s i t e s . 2. EX _l:~er ~._m#.nts
The e x p e r i m e n t a l m a t e r i a l s used in t h i s work were [ a b r i c a t e d by vacuum p r e s s u r e i n f i l t r a t i o n t e c h n i q u e . They a r e : 1. ZAM, Zn-AI m a t r i x a l l o y , l t s chemical c~mkoosition was d e t e r m i n e d by e l e c t r o n e n e r g y d i s p e r s i v e s p e c t r o s c o p y . Data from f i v e s e p a r a t e p o i n t s g i v e t h a t : A [ : (23.37_+0.79} Wt%, Cu: (2.17_+0.11) Wtga a n d Zn: th(.' r e s t . 2. ZAW, ZAM r e i n f o r c e d w i t h 20 vol% SiC w h i s k e r . 3. Z/kS, 2AM r e i n f o r c e d w i t h 10 vol% s h o r t g r a p h i t e f i b e r a n d l0 vol% SiC p a r t i c l e . 8. ~kL, ZAM r e i n f o r c e d w i t h 60 vot% l o n g g r a p h i t e f i b e r . The f o u r k i n d s o f m a t e r i a l s were s u b j e c t e d to solid solubilization of 380°C/2~h atter fabrication. The 7_Aht, ZAW a n d 7,~S were t h e n e x t r u d e d u n d e r a n r e d u c t i o n r a t i o o f 12 a f t e r preheating at 260C for 0.5 hour. Specimens for damping tests were spark cut to the dimensions of ~0 m m x 4 mm x 1 mm w i t h t h e l o n g i t u d i n a l direction parallel to the extrusion or the tong fiber direction. Damping was m e a s u r e d u s i n g a f o r c e d - v i b r a t i o n pendulum in a multi-functional internal f r i c t i o n a p p a r a t u s . The i n t e r n a l f r i c t i o n O t i s c a l c u l a t e d f r o m Q - i : t a n ~ , w h e r e ~ i s the phase a n g l e by which s t r a i n lags s t r e s s d u r i n g the ~orced v i b r a t i o n . The s t r a i n a m p l i t u d e was f i x e d t o 1 x 10"j t h r o u g h o u t t h i s work. 3 , Re_su_!t__s__a~_.Oi s cus.sj 3.1 Dependency of
lnterna~l Friction
O-I a n d D y n a m i c M o d u l u s (; o n V i b r a t i o n
1321
Frequency f:
1322
Zn-AI MATRIX COMPOSITES
Vol. 30, No. 10
The v a r i a t i o n s o f 0 -I and G w i t h v i b r a t i o n f r e q u e n c y f f o r the [our m a t e r i a l s a t 30~C i n t h e f r e q u e n c y r a n g e from 0.06 Hz t o lO Hz a r e shown in F i g . l and F i g . 2 , r e s p e c t i v e l y . 1"he 0 `l o f ?.AM, ZAW and ZAS d e c r e a s e s w i t h f when v i b r a t i o n f r e q u e n c y i s s m a l l , and t h e n g r a d u a l l y r e a c h e s a c o n s t a n t v a l u e . The c o r r e s p o n d i n g G i n c r e a s e s w i t h f m o n o t o n o u s l y . [ h e r e a s o n t h a t t h e v a r i a t i o n t e n d e n c y of Q-I and G with f f o r ZA~ and 7.~ i s s i m i l a r to t h a t f o r m a t r i x ~ i s p e r h a p s t h a t the a d d i t i o n o f r e i n f o r c e m e n t s to ZA~ and ZA5 i s r e l a t i v e l y s m a l l . On t h e c o n t r a r y , t h e Q[ and G a r e a l m o s t i n d e p e n d e n t on f f o r ZAL. T h i s v a r i a t i o n t e n d e n c y i s s i m i l a r t o t h a t of ~ r a p h i t e f i b e r (6) which has 60 vol% i n the ZAL C o m p o s i t e . T h i s i n d i c a t e s t h a t t h e damping n a t u r e o f t h e m a j o r i t y component i n t h e composite p l a y s a v e r y i m p o r t a n t r o l e in d e t e r m i n i n g t h e o v e r a l l damping characteristics of the composite,
160
~
140 120 100
13
0
....
l
0.I
•
.
,
. . . . .
t
,
13
.
i-
13
i
=
. . . .
1
i
10
4O
0.1
FIG. I
I
10
Frequen=y (Hz)
Frequency (Hz) V a r i a t i o n s o f Q-I w i t h f
FIC, 2
Variations
of G w i t h f
3.2 E f f e c t of Reinforcements on Q-I and C: I t c a n b e s e e n from F i g . 1 t h a t t h e QI v a l u e s f o r c o m p o s i t e s a r e lower t h a n t h a t f o r m a t r i x . The d e s c e n d i n g o r d e r o f ~ I f o r t h e f o u r m a t e r i a l s i s Z / ~ > ZAS > ZAW > ZAL. The r e a s o n of t h i s d e c r e a s e i s m a i n l y due t o t h e low damping c a p a c i t y of t h e r e i n f o r c e m e n t s and t h e i n t e r f a c e e f f e c t s . I t i s w e l l known t h a t t h e i n t e r n a l damping of a c o m p o s i t e m a t e r i a l a r i s e s m a i n l y from i n t r i n s i c damping of i t s components, t h e i n t e r f a c e e f f e c t between t h e m a t r i x and t h e r e i n f o r c e m e n t and t h e e f f e c t o f m i c r o s t r u c t u r a l change i n b o t h m a t r i x and r e i n f o r c e m e n t due t o t h e d i f f e r e n c e i n p h y s i c a l o r m e c h a n i c a l p r o p e r t i e s such as c o e f f i c i e n t o f t h e r m a l e x p a n s i o n and e l a s t i c modulus ( 7 , 8 ) . The c o n t r i b u t i o n of i n t r i n s i c damping of m a t r i x and r e i n f o r c e m e n t t o damping c a p a c i t y o f t h e c o m p o s i t e c o u l d be e s t i m a t e d on t h e b a s i s of t h e r u l e o f m i x t u r e s . T h a t i s t o say , t h e o v e r a l l c o n t r i b u t i o n o f i n t r i n s i c damping c e p a c i t y , ( Q l ) i n t r , would be p r o p o r t i o n a l t o t h e i n d i v i d u a l damping c a p a c i t i e s of t h e m a t r i x , 0~, and r e i n f o r c e m e n t , Or, m u l t i p l i e d by t h e i r r e s p e c t i v e volume f r a c t i o n s , Vm and Vr, as g i v e n by
(0 -1 ) ~ . = (O -=) =v.+ (0-*) .V.
A c o m p a r i s o n o f t h e c a l c u l a t e d (Ot)intr and t h e c o r r e s p o n d i n g e x p e r i m e n t a l r e s u l t s f o r c o m p o s i t e 1 m a t e r i a l s , (Q'I)oc, a r e g i v e n i n T a b l e 1, where (Q)SiC was t a k e n as 5xl0" ] (9) and (Ol)ga~hite as
1.3x10 "z (10) and the (Q-l)= and o - i were obtained from present experimental data at the f l a t area in FIB. 1. Inspection of Table I reveals t h a t the d i f f e r e n c e between (QI)z&! and i t s (Q-I)intr is small, which
V01.30, No. 10
Zn-A1 MATRIX COMPOSITES
I323
i n d i c a t e s t h a t i n t r i n s i c damping i s t h e d o m i n a n t component i n t h e t o t a l damping of the c o m p o s i t e and t h e damping c o n t r i b u t i o n from o t h e r mechanisms i n t h e c o m p o s i t e i s n e g l i g i b l e . (QI)~S i s TABLE 1. Comparison of t h e (Q-I)intr w i t h t h e C o r r e s p o n d i n g (Q-t)mc
Materials
(Q-l)mc x I00
(O-I)intt x 100
Z~
3.00
ZAW
2.50
I
2.52
ZAS
2.58
I
2.93
ZAL
1.98
I
1.1~
,
I
slightly larger than the corresponding (Q'I)intr " I t means t h a t damping mechanisms o t h e r t h a n intrinsic contribution are functioning. The f r a c t o g r a p h of ZAS in F i g . 3 d e m o n s t r a t e s weak interracial bonding between t h e m a t r i x and SiC w h i s k e r s . The i n t e r r a c i a l viscous slip in this c o m p o s i t e m i g h t be an i m p o r t a n t s o u r c e of damping.
FIG, 3
SF_~Ifractograph of ZAS
F[C. ~
S l ~ fractograph o f ZAL
The r e s u l t in T a b l e I a l s o shows t h a t the (0 -i)z~L i s l e s s t h a n t h e c o r r e s p o n d i n g (Q-!)intr. T h i s i s p r o b a b l y due t o the e f f e c t o£ mutual c o n s t r a i n t of K r a p h i t e f i b e r s and Zn-AI m a t r i x , Tile h i g h damping c a p a c i t y of g r a p h i t e i s b e l i e v e d 1o r e s u l t Ir(~n t h e a n i s o t r o p i c c r y s t a l s t r u c t u r e found in g r a p h i t e ( 7 ) . The s t r o n g i n - p l a n e c o v a l e n t b o n d i n g and weak van d e ; Waals t h r o u g h - p l a n e f o r c e s r e s u l t i n t h e easy d i s p l a c e m e n t of b a s a l p l a n e i n t h e in--plane d i r e c t i o n when s u b j e c t e d to s h e a r f o r c e s . Under c y c l i c l o a d i n g t h i s s l i d i n g i n d u c e s f r i c t i o n tosses atlributed l a r g e l y to t h e sweeping m o t i o n of d i s l o c a t i o n from pinning,, p o i n t s on t h e b a s a l p l a n e . The h i g h damping c a p a c i t y of the Zn-AI a l l o y presumably r e s u l t s irom v i s c o u s s l i p a l o n ~ the ~ r a i n b o u n d a r i e s and the o s c i l l a t i o n of d i s l o c a t i o n t i n e s ( 1 ) . The very s t r o n g i n t e r f a c i a l bonding which i s m a n i f e s t e d i n F i g . ~ imposes a s t t o n g c o n s t r a i n t
t o the sweepmg m o t i o n ot d i s t o c a l i o n s
in g r a p h i t e and t o v i s c o u s
g l i d i n g of g r a i n b o u n d a r i e s i n Zn-Al a l l o y . T h i s e f l e c t of t h e i n t e r f a c e d e c r e a s e s t h e damping c a p a c i t y of t h e c o m p o s i t e and t h e (Q-I)Z~L i s a c c o r d i n g l y l e s s than lhal of t h e corr~,sponding (0 1 }intr' 3.3 P e c u l i a r Dempirk~ Peak and Modulus .lc~p A distinct damping peak was found ill the f r e q u e n c y range of 4.5~6.5 14z f o r each m a t e r i a l when t h e t e s t i n t e r v a l i s as small as 0.05 ltz. "[he o c c u r r e n c e o f the damping peak is accompanied w i t h an a b r u p t change i n dynamic modulus. When the v i b r a t i o n ~requency sweeps a c r o s s the frequency of dampjn~ peak. the dynamic r~)dulus decreases f a s t to a minim~a~ and then itmlps to a maximum w i t h i n
1324
Zn-A1 MATRIX COMPOSITES
Vol 30, No. 10
a b o u t a 0 . 2 Hz range, and t h e n d e c r e a s e s f a s t t o t h e n o r m a l v a l u e . 5 t o 12, t h e f o l l o w i n g g e n e r a l f e a t u r e s can be seen:
:F
.... ;;1" ......... .............
Comparing the c u r v e s i n f i g u r e s
[ :
4.5
5
~5
O
8~
4.5
5
r~5
Frequm:y (Hz) O"1 v e r s u s
FIG. 5 0=6
.
.
.
8
6.5
FrequenW(Hz)
f for
ZAM
FIG. 6
G versus
f for 7.~
.
1,o[ 80
0.1 t - ' ' " ' ~ F ~
............ "'I
, p = , , , . , = = = o = = . o o = o = ~ =.,,.=,.~,.= o,, o o =.~
0
~
_
4.5
5
5.5
8
8.5
•
,
,
,
!
4.5
,
.
Q-I v e r s u s
0.18 .~.~...=% "~"~. 0,18
i
0.14 0.12
f for
ZAII/
FIG.
~ ,
.
.
.
6
6.5
8
G versus
f f o r ZAW
!, i'
,
i"8O
O.O4
75
-
4.5
.
~ ,~, ,,--=... . . . . .
OO8
~
.
115 1 110!
,,~
0.1
,
.
~(Hz)
O.O8
0
.
5.5
FmqLaw (Hz) FIG. 7
.
5
•
.
.
i
5
.
.
.
.
[
.
.
.
.
&6
i
.
.
.
.
.
6
l=requ=~ (Hz) FIG. 9
q-I v e r s u s
f f o r ZAS
6.5
70
i
.
.
.
i
5
4.5
.
.
.
.
i
,
,
•
~5
.
i
8
F r e q u e n ~ (Hz) FIG.
10
G v e r s u s f f o r ZAS
.
.
.
.
8.5
Vol. 30 No. 10
Zn-A1 MATRIX COMPOSITES
i
1325
i" FIG.
11
Q-t v e r s u s I I o r ZAL
FIG.
12
G v e r s u s f f o r ZAL
(I) Damping peak and modulus jtmpoccur in all the matrix alloys and three composite materials within a narrow frequency range at 30°C and 95~C. At 150~C, no modulus jtmlp is shown in their modulus versus frequency curves for ZAM, ZAW and 7AS. Another interesting phenomenon is that instead of a damping peak there is a dan~ping valley at the frequency of the otherwise dan~oing peak in ZAS at 150°C. (2) The frequency of the damping peak, the height of dang)ing peak (difference between maximum and background in vertical scale) and the height of modulus jump (difference between maximum and minimtma in vertical scale) all decrease with temperature for each material when the experimental error is also taken into account (see Table 2). TABLE 2, P o s i t i o n s
Temperature
~
o f Damping Peak (Hz)
ZAW
ZAS
ZAL
30~C
5.282
5,485
5.233
5.643
95°C
5.233
5.485
5.161
5.696
150°C
5.069
5.383
5.135
5.696
(3) The frequency of damping peak, the heights of the da~.ing peak and modulus jump are vary from material to material. The frequency of the damaping peak of ZAL is the largest in the four materials, followed by ZAW, ZAM and ZAS. The height of the damping peak and the modulus jump of ZAW is the largest followed by ZAL, ZAM and ZAS at 30°C. At 95°C the heights of the damping peak of ZAM is larger than that of ZAL. When the temperature reaches to 150"C only ZAL has d i s t i n c t modulus juml) and the order of dam~ing peak height is the same as that at 30°C except that there is a deep dam~ing valley in ZAS instead of damping peak (see Table 3). The above features of the damping capacity and dynamic modulus have not been reported in the l i t e r a t u r e . The detailed mechanism which results in the features is not clear. However, because the features are present in all the matrix alloy and con%Dosites, i t must be related to some nature or process in the matrix alloy. The addition of the reinforcements to the matrix has neither brought about nor eliminated the phenomena. It only mK)difies the feature in some d e t a i l s . Fromthe distinguishing c h a r a c t e r i s t i c shape of the curves of the damping capacity and dynamicmodulus vs. frequency and the dependence of them on temperature, i t is speculated that this phenomenon is mainly related to some phase transformation processes occurring in the matrix alloy. However, more
1326
Zn-AI MATRIX COMPOSITES
Vol. 30, No. 10
work has to be conducted in this direction before an affirmative conclusion can be drawn. TABLE 3. Heights of Damping Peaks and Modulus Jumps i
Temperature
ZAM
7.AW
ZAS
ZAL
30°C
25.21 (18.4)
49.79 (53.3)
11.48 (13.8)
25.32 (20.8) 15.47 (10.7)
95"C
150"C
20.99
32.13
10.90
(14.1)
(31.0)
(20.3)
I .07 ( .... )
2.53
-11.16
( ....
)
( ....
)
8.39 (6.5)
Note: data without parentheses are heights of damping peak times tO0 and data in parentheses represents heights of modulus jump in GPa. The dashed line represents no distinct modulus jump.
4. Conclusions I. The damping capacity of ZAW, ZAS and ZAL is lower than that of ZAM. The intrinsic damping of matrix and reinforcements are the main source of the damping of the composites. Interface effect has different influences on the damping properties of different composites. 2. In the frequency range studied the damping capacity of ZAM, ZAW and ZAS decreases white the dynamic modulus increases with frequency. However, in the ZAL both are almost independent of vibration frequency. 3. Sharp damping peaks are found in all four materials at the frequencies around 5.5 Hz. At the corresponding frequency the dynamic modulus undergoes a sudden change. The position and height of the damping peak and modulus jump varied with material and temperature. The mechanism of the phenomenon needs to be further studied. References 1. 2. 3. 4. 5. 6. 7. 8. 9.
H.Masumoto, M.Hinai and S.Sawaya, Trans. 31M, 22(I0), 681(1983) and 32(I0), 957(1991). G.Gao and M.Gu, Functional Matls., 22(~), 209(1991). M.A.Detiis, 3.P.Keustermans and F.Delannay, Mater. Sci. Eng., A135, 253(1991). 3.S.Kim, 3.Kaneko and M.Sugamata, 3. 3apan Inst. Metals, 55(9), 986(1991). H.Zhu and S.Liu, Matls. Sci. Prog., 6(I), 88(1992). K.Nishiyama, M.Yamanaka, M.Omort and S.Umekawa, 3.Mat.Sci.Lett., 9, 526(1990). R.J.Perez,3.Zhang, M.N.Gungor and E.J.Lavernia, Met. Trans., 2/~A, 701(1993). R.D.Adams, Matls. Sci. Forums, I19-121, 3(1993). L.A.Lbrahim, F.A.Mohamed and E.J.Lavernia, 3. Mater. Sci., 26, I137(1991).
10. 3.Zhang, R.3.Perez, M.gupta and E.J.Lavernia, Scripta Metall., 28, 91(1991).