LOW-FREQUENCY INTERNAL FRICTION OF As-CAST MANGANESE-COPPER ALLOYS

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LOW-FREQUENCY INTERNAL FRICTION OF As-CAST MANGANESE-COPPER ALLOYS

Wen Yiting, Xie Cunyi, Chen Hui

To cite this version:

Wen Yiting, Xie Cunyi, Chen Hui. LOW-FREQUENCY INTERNAL FRICTION OF As-CAST MANGANESE-COPPER ALLOYS. Journal de Physique Colloques, 1985, 46 (C10), pp.C10-413- C10-416. �10.1051/jphyscol:19851093�. �jpa-00225478�

JOURNAL DE PHYSIQUE

Colloque C10, suppldment a u n012, Tome 46, ddcembre 1985 page C10-413

LOW-FREQUENCY INTERNAL F R I C T I O N OF As-CAST MANGANESE-COPPER ALLOYS

WEN Y I T I N G , XIE CUNYI and CHEN HUI

Institute of Solid State Physics, Academia Sinica, Hefei, China

A b s t r a c t Low-frequency i n t e r n a l f r i c t i o n and e l a s t i c modulus were s t u d i e d f o r c a s t manganes-copper a l l o y s w i t h Mn-content from 60 t o 90%. T r a n s f o r m a t i o n peak and r e l a x a t i o n p e a k ( d u e t o t w i n b o u n d a r i e s ) were o b s e r v e d f o r a l l t h e c a s t a l l o y s i n t h e tempera- t u r e r a n g e from -150 t o 300'~. The r e s u l t s a r e compared w i t h t h o s e o f homogenized specimens.

I. I n t r o d u c t i o n Sugimoto e t a l . measured t h e i n t e r n a l f r i c t i o n and e l a s t i c modulus f o r Mn-Cu a l l o y s w i t h Cu-content o f 10 t o 45% /I-3/, They o b s e r v e d two i n t e r n a l - f r i c t i o n p e a k s f o r t h e a l l o y s h a v i n g a h i g h Mn-content:The l o w e r - t e m p e r a t u r e peak which i s t h e r e l a x a t i o n peak and t h e h i g h e r - t e m p e r a t u r e peak t h e p h a s e t r a n s f o r m a t i o n peak. They c o n s i - d e r e d t h a t t h e p h a s e t r a n s f o r m a t i o n i s a second o r d e r a n t i f e r r o m a g n e t i c t r a n s f o r m a t i o n which accompanies a s t r u c t u r e change from f c c t o f c t and t h e f o r m a t i o n o f (101) t w i n b o u n d a r i e s . The r e l a x a t i o n peak i s due t o t h e s t r e s s r e l a x a t i o n a c r o s s t w i n b o u n d a r i e s .

P r e v i o u s e x p e r i m e n t s were chiefly done f o r Mn-Cu a l l o y s h a v i n g h i g h Mn c o n t e n t s , a n d were s u b j e c t e d t o a homogenized t r e a t m e n t ( h i g h t e m p e r a t u r e annealing f o r v e r y l o n g t i m e t h e n quenchedinto water).The e x p e r i m e n t s were performed w i t h a c o u s t i c f r e q u e n c i e s . T h e r e h a s n o t been any r e p o r t o f r e s e a c h work on c a s t Mn-Cu a l l o y , e s p e c i a l l y on t h e a l l o y o f low Mn- c o n t e n t . We have s t u d i e d t h e c a s t Mn-Cu a l l o y s by u s i n g low-frequency methods and t h e r e s u l t s a r e canparedd w i t h t h o s e o f homogenized s p e c i - mens.

.- . . . -

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11. E x p e r i m e n t a l Methods The J i a o t o n n U n i v e r s i t y . T a b l e 1 The i m p u r i t y c o n t e n t i n t h e a l l o y s i s l e s s t h a n 0.03%.

The c a s t a l l o y s were c u t i n t o 6 0 x 4 ~ 1 mm s h e e t s and u s e d f o r low f r e q u e n c y mea- surements. The homogenized specimens were p r e p a r e d by a n n e a l i n g i n a vaccum t u b e f u r n a c e a t 8 5 0 ' ~ f o r 100h and t h e n quenched i n t o water.

I n t e r n a l f r i c t i o n mea- s u r e m e n t s were performed by u s i n g a forced v i b r a t i o n pendulum w i t h wide f r e q u e n c y r a n g e which was b u i l t by o u r l a b o r a t a r y . It measures d i - r e c t l y t h e a n g l e o f p h a s e l a g 9 between t h e a p p l i e d s t r e s s and t h e s t r a i n

an

Mn-Cu a l l o y s were s u p p l i e d by Shanghai shows t h e main c o m p o s i t i o n o f t h e s e a110

T a b l e 1. Composition and some r e l e v a n t p a r - m e t e r s o f Mn-Cu a l l o y s

Mn Cu A 1 E 1 Tc

specimen ( wt96) (eV) ( l / s ) (OC) MC6-1 60 40 0 0.57 2 . 1 ~ 1 0 " 110

~ c 6 - 2 60 39 1 0 . 6 0 5 . 7 ~ 1 0 " 113

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19851093

C10-414 JOURNAL DE PHYSIQUE

Specimens f o r m e t a l l o g r a p h i c o b s e r v a t i o n were p r e p a r e d by mechanical and e l e c t r o l y t i c a l p o l i s h i n g , a n d t h e n by e t c h i n g . The e t c h i n g a g e n t c o n s i s t s o f one p a r t o f 85% HsP04 and g l y c e r i n e s a n d two p a r t s o f a l c o - hol. E l e c t r o l y t i c a l p o l i s h i n g agent consists o f one p a r t o f e t c h i n g a g e n t and one p a r t o f water. The specimens were examined w i t h a micro- s c o p e u s i n g p o l a r i z e d l i g h t .

111. E x p e r i m e n t a l R e s u l t s Two i n t e r n a l - f r i c t i o n p e a k s were o b s e r v e d i n t h e t e m p e r a t u r e r a n g e o f from -150 t o 300°c f o r a l l t h e c a s t s p e c i - mens. Fig.1 shows t h e t y p i c a l c u r v e s

o f i n t e r n a l f r i c t i o n and s h e a r mo- d u l u s o f t h e specimen MC9-4 v e r s u s t h e t e m p e r a t u r e o f measurement. The

c u r v e s o f a l l t h e o t h e r c a s t s p e c i - -

mens a r e s i m i l a r t o t h o s e shown i n

.-

Fig.1. The modulus c u r v e a p p e a r s t o

b e anomalous i n t h e t e m p e r a t u r e _R r a n g e o f t h e h i g h e r - t e m p e r a t u r e i n -

t e r n a l - f r i c t i o n peak, and t h e c u r v e d o e s n ' t s h i f t w i t h a change o f f r e -

quency. T h e r e i s a d i f f e r e n c e o f Fig. 1

-

c o o l i n g measurements. The lower-

t e m p e r a t u r e peak s h i f t s toward h i g h f = ~ . l ~ z , A ~ = l x l ~ - ~ .

t e m p e r a t u r e s w i t h a change o f frequency,and t h e peak h e i g h t i s indepen- d e n t o f t h e s t r a i n a m p l i t u d e when t h e s t r a i n a m p l i t u d e i s l e s s t h a n l x 1 0 ' ~ , s o t h i s peak i s a r e l a x a t i o n i n t e r n a l - f r i c t i o n peak. I n Fig.2 a r e shown t h e i n t e r n a l - f r i c t i o n c u r v e s ( a ) f o r c a s t specimens and ( b ) f o r homogenized specimens. T h e r e a r e two i n t e r n a l - f r i c t i o n p e a k s f o r homogenized specimen MC9-l+,but t h e h e i g h t o f t h e r e l a x a t i o n peak i s

1

( b )

1 1 0 1

Fig. 2

-

.

(b) Homogenized specimens, f=ZHz,Ac =5x10'~.

l o w e r t h a n t h a t o f t h e c a s t specimen MC9-1. For t h e homogenized s p e c i - men MC6-13ksno i n t e r n a l - f r i c t i o n peak was o b s e r v e d i n t h e t e m p e r a t u r e r a n g e measured and t h e r e i s no anomalous change o f t h e modulus curve.

Whereas two pronounced i n t e r n a l - f r i c t i o n p e a k s were o b s e r v e d f o r t h e c a s t specimen MC6-1.

For c a s t s p e c i m e n s , t h e peak t e m p e r a t u r e o f t h e t r a n s f o r m a t i o n peak i n c r e a s e s a s t h e Mn-content i n c r e a s e s . The t r a n s f o r m a t i o n t e m p e r a t u r e Tc f o r t h e specimens i s shown i n T a b l e 1,and i s d i f f e r e n t from t h a t o f t h e homogenized specimens. According t o ~ a c o n / & / , t h e t r a n s f o r m a t i o n t e m p e r a t u r e f o r homogenized specimens d e c r e a s e s r a p i d l y a s t h e Mn-con- t e n t d e c r e a s e s . When t h e Mn-content i s 70%,the t r a n s f o r m a t i o n tempera- t u r e s h o u l d c l o s e t o a b s o l u t e z e r o degree. Howeversfor t h e c a s t s p e c i - men i n which t h e Mn-content i s a b o u t 60%,the t r a n s f o r m a t i o n s t i l l a p p e a r s from 100 t o 1 1 0 ~ ~ ( s e e T a b l e 1 ) .

Fig.3 shows t h e ~ n t e r n a l - f r i c t i o n c u r v e s o f 80%Mn a l l o y s t o which a v e r y s m a l l amount o f aluminium was added. A s Al-content i n c r e a s e s , t h e

r e l a x a t i o n peak h e i g h t becomes somewhat l o w e r s a n d t h e t r a n s f o r m a t i o n

peak moves t o l o w e r t e m p e r a t u r e . S i m i l a r c h a n g e s h a v e been o b s e r v e d f o r o t h e r Mn-Cu-A1 a l l o y s .

Fig.4 shows t h e m e t a l l o g r a p h o f a b i n a r y Mn-Cu a l l o y . A t room tempe- r a t u r e when t h e specimen i s i n i t s low t e m p e r a t u r e phase, a l o t o f t w i n s t r u c t u r e s were o b s e r v e d i n specimens MC9-1 and MC8-1. The amount o f t w i n s t r u c t u r e i n s p e c i - men MC9-1 i s more t h a n t h a t i n spe- cimen MC8-1. A few Mn-rich a r e a s were o b s e r v e d i n t h e 70% and 60% Mn

s p e c i m e n s , a n d t h e r e a r e more in t h e F i g 0 3

-

former. o f c a s t Mn-Cu-A16alloys.

F=O. ~ H z , AE =7xlO-

.

.'

Fig.4

-

Fig.5 shows t h e i n t e r n a l - f r i c t i o n and modulus c u r v e s o f specimen MC9-1 measured w i t h t h r e e f r e q u e n c i e s . It i s s e e n t h e higher-tempera- t u r e peak d o e s n ' t s h i f t a s t h e f r e q u e n c y changes. The a c t i v a t i o n ener- gy E o f t h e r e l a x a t i o n peak was d e t e r m i n e d by u s i n g t h e l e a s t - s q u a r e s f i t method t o t h e peak d a t a a t va-

r i o u s f r e q u e n c i e s . I t changes w i - t h i n t h e r a n g e o f 0.50 t o 0.63 eV ( s e e T a b l e l ) , a n d does n o t change a p p r e c i a b l y w i t h t h e change o f Mn- c o n t e n t . When aluminium i s added, t h e a c t i v a t i o n e n e r g y i n c r e a s e s s l i g h t 1 y.

E x p e r i m e n t s showed t h a t t h e h e i g h t ^&$C o f t h e t r a n s f o r m a t i o n peak depends on t h e r a t e o f tem- p e r a t u r e change T and t h e f r e q u e n c y

f. The mgre T and t h e l e s s f i s t h e h i g h e r Qm is. According t o r e s 9 i t s o f o u r e x p e r i m e n t , t h e h e i g h t Qm s t i l l depends on f r e q u e n c y f a t ?=o.

T h i s shows t h a t t h e h e i g h t Q; dogs n o t v a r v l i n e a l v w i t h t h e r a t i o T/f a s was s t a t e d

i n

'

Fig.5

-

3=0.

t h e t e m p e r a t u r e a t which t h e modu- l u s i s minimum) a r e shown i n T a b l e 1.

IV. D i s c u s s i o n s

IV-1. F o r l o w e r Mn-content,the i n t e r n a l - f r i c t i o n c u r v e s o f t h e c a s t specimens a r e c o m p l e t e l y d i f f e r e n t from t h o s e o f t h e homogenized s p e c i - mkns. T h i s i s due- t o t h e e f f e c t o f c o m p o s i t i o n a l f l u c t u a t i o n . ~ e c a b s e

C10-416 JOURNAL DE PHYSIQUE

o f t h e e x i s t e n c e o f some s m a l l Mn-rich a r e a s i n t h e c a s t s p e c i m e n s , t h e t r a n s f o r m a t i o n t e m p e r a t u r e f o r t h o s e a r e a s i s r a i s e d t o around room t e m p e r a t u r e , s o t h a t t h e t r a n s f o r m a t i o n peak and t h e r e l a x a t i o n peak can be o b s e r v e d i n t h e experiments. However,for homogenized specimen MC6-1, t h e t r a n s f o r m a t i o n t e m p e r a t u r e i s c l o s e t o a b s o l u t e z e r o degree,so t h e specimen i s always c o n s i s t e d o f t h e h i g h t e m p e r a t u r e phase and b o t h t h e t r a n s f o r m a t i o n and t h e r e l a x a t i o n peak can n o t be observed, For h i g h e r Mn-content,the i n t e r n a l - f r i c t i o n c u r v e o f t h e c a s t specimens i s s i m i l a r

t o t h a t o f t h e homogenized specimens. T h e i r t r a n s f o r m a t i o n peak and r e l a x a t i o n peak a p p e a r a t t h e same temperature. T h i s shows t h a t t h e i n t e r n a l s t r u c t u r e i n t h e s e two specimens i s s i m i l a r .

IV-2. Measurements on t h e t ~ a n s f o r m a t i o n peak show t h a t : ( 1 ) When t h e r a t e o f t e m p e r a t u r e change T i n c r , e a s e s , t h e peak h e i g h t in( i n c r e a s e s . ( 2 ) When frequency f increases,Qm d e c r e a s e s . (3) I n h e a t i n g and c o o l i n g measurements,there i s s m a l l t h e r m a l - h y s t e r e s i s . A l l o f t h e s e b e h a v i o r s a r e i n a c c o r d a n c e w i t h t h e c h a r a c t e r i s t i c s o f t h e r m o e l a s t i c m a r t e n s i t i c t r a n s f o r m a t i o n . Meanwhile,a l o t o f t w i n s t r u c t u r e s were o b s e r v e d i n specimens MC9-1 and MC8-1. The e v i d e n c e s g i v e n above i l l u s t r a t e t h a t t h e phase t r a n s f o r m a t i o n i n t h e c a s t Mn-Cu a l l o y s (60-90%Mn) i s marten- s i t i c t r a n s f o r m a t i o n .

IV-3. F o r a l l t h e c a s t Mn-Cu s p e c i m e n s , t h e r e l a x a t i o n peak t e m p e r a t u r e , t h e a c t i v a t i o n e n e r g y E and t h e frequency f a c t o r 1/To change o n l y w i t h i n a s m a l l r a n g e ( s e e P a b l e 1 ). The 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 peak determined by Sugimoto & Mori f o r homogenized specimen MnaaCutt i s 0.52 eV/2/. T h i s i s v e r y c l o s e t o t h e v a l u e we determined

f o r o u r c a s t specimens. T h e r e f o r e , w h e t h e r t h e c a s t specimen i s o f h i g h o r low Mn-contentsthe r e l a x a t i o n peak i s due t o t h e s t r e s s r e l a x a t i o n a c r o s s t h e t w i n boundaries. However,as t h e Mn-content i n t h e specimens i s d i f f e r e n t , t h e amount o f t h e t w i n s t r u c t u r e s formed i s d i f f e r e n t . Consequently,when Mn-content d e c r e a s e s t h e amount of t h e twin s t r u c t u r e a l s o d e c r e a s e s , s o t h e h e i g h t o f r e l a x a t i o n peak becomes lower.

Acknowled~ements T h i s work w a s done under t h e d i r e c t i o n o f P r o f e s s o r T. S. K6. Thanks a r e due t o M r . Sheng Zongyi f o r s u p p l y i n g t h e Mn-Cu and Mn-Cu-A1 a l l o y s and many h e l p f u l d i s c u s s i o n s . We a r e g r a t e f u l t o M r . Wang L i t i a n and Y i Huchun f o r t h e i r h e l p i n e x p e r i m e n t a l work.

R e f e r e n c e s

1 Sugimoto K. and Mori T. and Shiode Sci. J., 103( 1973).

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/3/ Sugimoto K,,J. d e Physque,gsC5-971

/4/ Bacon G. E., Proc. Roy. Soc.,A,&J.,223(1957).