IN-SITU MEASUREMENTS IN METALLIC GLASSES BY SMALL-ANGLE SCATTERING OF X-RAYS

(1)

HAL Id: jpa-00220338

https://hal.archives-ouvertes.fr/jpa-00220338

Submitted on 1 Jan 1980

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

IN-SITU MEASUREMENTS IN METALLIC GLASSES BY SMALL-ANGLE SCATTERING OF X-RAYS

A. Flank, A. Naudon

To cite this version:

A. Flank, A. Naudon. IN-SITU MEASUREMENTS IN METALLIC GLASSES BY SMALL-ANGLE SCATTERING OF X-RAYS. Journal de Physique Colloques, 1980, 41 (C8), pp.C8-123-C8-126.

�10.1051/jphyscol:1980832�. �jpa-00220338�

(2)

JOURNAL DE PHYSIQUE CoZZoque 6 8 , suppZ6ment au n o 8, Tome 41, aouAt 1980, page

C8-123

I N - S I T U MEASUREMENTS I N M E T A L L I C G L A S S E S B Y SMALL-ANGLE S C A T T E R I N G OF X-RAYS

A.M. Flank and A . Naudon

L a b o r a t o i r e de Me'taZZurgie Physique, 40, avenue du Reoteur Pineau, 86022 P o i t i e r s , France.

INTRODUCTION

Up t o d a t e much e f f o r t has been devoted t o determine t h e s t r u c t u r e o f amorphous m a t e r i a l s by means of d i f f r a c t i o n t e c h n i q u e s which g i v e i n f o r - mations on t h e short-range o r d e r . Sometimes no d i f - f e r e n c e can be d e t e c t e d i n t h e s t r u c t u r e of a me- t a l l i c g l a s s , liquid-quenched o r s g u t t e r e d , b u t obvious d i f f e r e n c e s e x i s t i n t h e c r mechanical pro- p e r t i e s , namely b r i t t l e n e s s v e r s u s d u c t i l i t y ( 1 ) . Consequently, such d i f f e r e n c e s must b e l i n k e d t o another range o f o r d e r (middle-range o r d e r o r mean- range s t r u c t u r e ) . Such an o r d e r o r s t r u c t u r e i s r e l e v a n t t o s c a t t e r i n g t e c h n i q u e s i n t h e small- angles r e g i o n . This t e c h n i q u e provides a l s o ilifor- mation on i m p u r i t i e s ; p o l l u t i o n o f t h e samples such

a s o x i d a t i o n d u r i n g t h e i r h e a t i n g , f l u c t u a t i o n s i n composition o r d e n s i t y . S u r p r i s i n g l y , small- angle s c a t t e r i n g has n o t much been used i n t h e p a s t on amorphous m a t e r i a l s . So we chose t h i s t e c h - nique i n t h e p r e s e n t study.

Our i n v e s t i g a t i o n i n m e t a l l i c g l a s s i s twofold. F i r s t l y we a r e i n t e r e s t e d i n the2im s t r u c - t u r e a f t e r e l a b o r a t i o n , a s t r u c t u r e which depends on t h e i r way o f p r e p a r a t i o n and t h e i r nominal com- p o s i t i o n . Secondly, we have s t u d i e d " i n s i t u "

t h e i r e v o l u t i o n w i t h time and t e m p e r a t u r e when approaching t h e g l a s s t r a n s i t i o n temperature.

We s h a l l b e g i n w i t h some r e s u l t s on Cu-Zr a l l o y s p r e p a r e d by two d i f f e r e n t t e c h n i q u e s , i . e . r a p i d quenching from t h e l i q u i d s t a t e and s p u t t e - r i n g . These r e s u l t s w i l l show t h a t h i g h l y s i g n i f i - cant d i f f e r e n c e s appear on t h e s c a t t e r i n g p a t t e r n s . Then we s h a l l c o n t i n u e w i t h an i n v e s t i g a t i o n of t h e i n i t i a l s t a t e s of d i f f e r e n t compositions o f Cu-Ho,

Cu-Y and N i - Y amorphous a l l o y s p r e p a r e d by t h e s p u t t e r i n g t e c h n i q u e a l o n e , i n which s p a t i a l c o r r e -

l a t i o n s a r e o b s e r v e d . F i n a l l y , t h e e v o l u t i o n of Cu-Y a n d Ni-Y with t e m p e r a t u r e and time w i l l b e followed and analyzed.

Small-angle s c a t t e r i n g of X-rays i s a s u i - t a b l e t e c h n i q u e when emphasis i n a s t u d y i s p u t on mean-range o r d e r o r mean-range s t r u c t u r e [domains

0

of some t e n A o r l e s s ) i n s m a l l and t h i c k samples.

But i n an amorphous m a t e r i a l it i s a l s o worthwhile t o g e t i n f o r m a t i o n on h e t e r o g e n e i t i e s and v a r i a - t i o n s i n f i r s t atomic d i s t a n c e s . This i s t h e reason why a s p e c i f i c camera h a s been r e a l i z e d f o r X-ray s c a t t e r i n g measurements between t h e a n g u l a r c r i g i n a n d q = 4TSin0 X - 6.25

W1

i n c l u d i n g t h e small-angles r e g i o n and t h e f i r s t d i f f r a c t i o n h a l o c h a r a c t e r i s t i c of an amorphous m a t e r i a l . The hea- t i n g of t h e sample i s c a r r i e d o u t " i n s i t u " w i t h a s m a l l e l e c t r i c a l f u r n a c e on t h e ax& o f t h e X-ray beam and i n t h e middle of t h e vacuum chamber ( u p t o t o r r . ) The camera works i n punctual c o l l i - n a t i o n , t h i s means t h a t i n t e n s i t i e s a r e lower in t h e small-angle r e g i o n t h a n w i t h l i n e a r collima- t i o n g e n e r a l l y used by workers i n t h i s f i e l d . This i s t h e reason why o u r camera i s adapted f o r an a l i - gnment on t h e very powerful beam given by t h e syn- c h r o t r o n r a d i a t i o n o f L . u . R . E . ~ a t Orsay. F u r t n e r - more t h e s c a t t e r e d i n t e n s i t i e s a r e recorded by means o f a p o s i t i o n - s e n s i t i v e p r o p o r t i o n a l c o u n t e r . The h i g h s e n s i t i v i t y of t h i s t e c h n i q u e a l l o w s

" i n s i t u " measurements when h e a t i n g t h e sample and p r o v i d e s i n a s h o r t time i n f o r m a t i o n s concerning t h e

3

r e g i o n s i n d i - a t e d on f i g u r e 1 . The c o u n t e r can b e r o t a t e d around an a x i s c e n t e r e d on t h e sample.

*

L a b o r a t o i r e U t i l i s a n t l e Rayonnement Electroma- gnCtique.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980832

(3)

JOURNAL DE PHYSIQUE

F i g . 1 : Scheme of t h e S.A.S. s e t up.

S.A.S. RESULTS ON Cu-Zr

We s t u d i e d amorphous Cu

66

Z r 3 4 a l l o y prepa- r e d by two d i f f e r e n t t e c h n i q u e s , i . e . s p u t t e r i n g and r a p i d quenching from t h e melt ( m e l t s p i n n i n g ) . We used c a l o r i m e t r i c measurements and t h e s c a t t e - r i n g of X-rays. Our r e s u l t s a r e t o appear soon ( 3 ) , b u t , a s t h i s a l l o y behaves d i f f e r e n t l y from t h e o t h e r s s t u d i e d i n t h i s p a p e r , it i s i n t e r e s t i n g t o g i v e h e r e some r e s u l t s o b t z i n e d with X-rays only, a s shown on f i g u r e 2 where d i f f e r e n c e s occur

i n t h e t h r e e a n g u l a r r e g i o n s .

Fig.2 : S c a t t e r e d i n t e n s i t i e s of t h e two Cu 66 Z r 3 4 a l l o y s j u s t prepared by s p u t t e r i n g o r quench from t h e l i q u i d s t a t e .

F i r s t of a l l t h e liquid-quenched a l l o y h a s a very s m a l l s c a t t e r e d i n t e n s i t y n e a r t h e a n g u l a r o r i g i n , i n o p p o s i t i o n t o t h e s p u t t e r e d a l l o y where i t s s c a t t e r i n g i n c r e a s e s very s t r o n g l y and c o r r e s - ponds t o l a r g e d e f e c t s . The d i f f e r e n c e s a r e a l s o important f o r t h e f i r s t d i f f r a c t i o n h a l o , concerning i t s angular p o s i t i o n , amplitude and width.

At l e a s t i n t h e ~ d d l e a n g u l a r r e g i o n t h e s c a t t e - r e d i n t e n s i t y i s

4

o r

5

t i m e s h i g h e r f o r t h e s o u t - t e r e d a l l o y t h a n f o r t h e o t h e r .

Our i n t e r p r e t a t i o n of t h e s e d i f f e r e n c e s i s based on t h e f a c t t h a t t h e s p u t t e r i n g t e c h n i q u e , when p r o j e c t i n g t h e atoms on a t a r g e t , b u i l d a d i f f e r e n t sample from t h e one o b t a i n e d by melt spinning which has a memory o f t h e l i q u i d s t a t e . Thus t h e s p u t t e r e d a l l o y r e t a i n s Argon atoms which c r e a t e v o i d s f i l l e d w i t h Argon and d e n s i t y f l u c - t u a t i o n s . Furthermore, t h e macroscopic d e n s i t i e s o f t h e two a l l o y s a r e d i f f e r e n t . These o b s e r v a t i o n s l e a d us t o t h e conclusion t h a t t h e sqlat-quenched a l l o y i s a more homogeneous m a t e r i a l t h a n t h e sput- t e r e d one.

During h e a t i n g , t h e y behave a l s o d i f f e r e n t l y , t h e c r y s t a l l i s a t i o n temperature being h i g h e r f o r t h e s p u t t e r e d a l l o y . But d u r i n g t h e h e a t i n g , some o x i d a t i o n o c c u r s (even i n a vacuum of 10

-6

T o r r ) n e a r t h e g l a s s t r a n s i t i o n t e m p e r a t u r e l o c a - t e d a t 476OC f o r t h e liquid-quenched a l l o y and 532OC f o r t h e s p u t t e r e d one. This i s t h e reason why we choose o t h e r a l l o y s i n which t h e s t r u c t u - r a l e v o l u t i o n s occur a t lower t e m p e r a t k e s and a r e d i f f e r e n t from t h o s e observed w i t h t h e Cu-Zr system a s shown on f i g u r e 2 , where d i f f e -

r e n c e s occur i n t h e t h r e e a n g u l a r r e g i o n s .

INITIAL STATES OF Cu-KO, Cu-Y and N i - Y ALLOYS.

These amochous a l l o y s have been p r e p a r e d by s ~ u t t e r i n g method which makes it p o s s i b l e t o o b t a i n a l a r g e r range i n composition t h a n t h e quench from t h e l i q u i d s t a t e . The t h i c k n e s s of t h e samples i s sometimes d i f f e r e n t , b u t t h e accu- mulation t i m e s vary a c c o r d i n g l y .

The recorded i n t e n s i t i e s '9f t h r e e amorphous Cu-Ho a l l o y s a r e shown on f i g u r e 3.

I .

0 5 1 . " 15 .O 45 z e -

F i g . 3 : Sca-ttered i n t e n s i t i e s o f Cu-Ho a l l o y s . Concerning t h e a n g u l a r p o s i t i o n o f t h e d i f f r a c t i o n h a l o , we n o t e a c l a s s i c a l r e s u l t : the h i g h e r t h e composftion i n l a r g e Ho atoms, t h e more important t h e s h i f t towards t h e primary beam.

But t h e new f a c t w i t h t h i s amoqhous system i s t h e presence o f a small-angle s c a t t e r i n g r i n g .

(4)

There a r e two e x p l a n a t i o n s f o r such a r i n g i n a S.A.S. p a t t e r n : t h e d e p l e t e d s h e l l model ( 4 ) and t h e i n t e r f e r e n c e e f f e c t which can be l i n k e d w i t h s p i n o d a l decomposition ( 5 ) a s it o c c u r s i n pre- p r e c i p i t a t e d Al-Zn a l l o y s f o r example ( 6 ) . The f i r s C model seems u n l i k e l y f o r u s because an embryo must e x i s t o r be c r e a t e d and an important d i f f u s i o n i s needed t o b u i l d t h e c o n c e n t r a t i o n g r a d i e n t . On t h e c o n t r a r y , f l u c t u a t i o n s i n compo- s i t i o n , l i n k e d w i t h f l u c t u a t i o n s i n d e n s i t y can form s m a l l domains e n r i c h e d i n e l e c t r o n s , w h i l e o t h e r domains a r e impoverished, and consequently account f o r t h e observed S.A.S. p a t t e r n . I f t h e second model i s r e t a i n e d , t h e a n g u l a r p o s i t i o n o f

0

t h e r i n g i n d i c a t e s a s p a t i a l c o r r e l a t i o n o f " . 2 5 A between domains.

~ i ~ : b : S c a t t e r e d i n t e n s i t i e s o f Cu-Y a l l o y s . The s p e c t r a concerning two compositions o f t h e amorphous Cu-Y system, prepared by a n o t h e r s p u t t e r i n g a p p a r a t u s , a r e shown on f i g u r e

4.

There i s a l s o a s p a t i a l c o r r e l a t i o n between d e n s i t y f l u c -

0

t u a t i o n s with a wavelenght o f % 20 A i n t h e s e f r e s h l y - p r e p a r e d samples. The i n t e n s i t y which in- c r e a s e s n e a r t h e primary beam could be due t o a small degree o f o x i d a t i o n o f t h e s e samples.

Other experiments upon amorphous N i - Y a l l o y s p r e p a r e d by a n o t h e r again s p u t t e r i n g d e v i c e were c a r r i e d o u t . T h e i r s c a t t e r i n g c u r v e s , most o f t h e t i m e , d i s p l a y a l s o a r i n g .

So, t h e S.A.S. p a t t e r n o f m e t a l l i c g l a s s e s , corresponding t o t h r e e systems, each p r e p a r e d w i t h a d i f f e r e n t s p u t t e r i n g a p p a r a t u s , do p r e s e n t s i m i - l a r i t i e s : a r i n g . Emphasis has been made on t h e i n i t i a l s t a t e o f t h e s e a l l o y s because it w i l l c e r t a i n l y p l a y a major p a r t d u r i n g t h e i r e v o l u t i o n w i t h t e m p e r a t u r e and t i m e .

EVOLUTION WITH TEMPERATURE AND TIME

We s t a r t w i t h t h e amorphous C U ~ ~ - Y ~ ~ a l l o y ( f i g u r e 5 ) .

F i g . 5.: S c a t t e r e d i n t e n s i t i e s of C U ~ ~ - Y ~ ~ During t h e h e a t i n g , t h e r e i s a g r a d u a l evo- l u t i o n of t h e r i n g which amplitude i n c r e a s e s and

a n g u l a r ~ o s i t i o n s h i f t s towards t h e primary beam.

Such a behaviour i s i n f u l l y agreement w i t h Laagert s t h e o r y of s p i n o d a l mechanism ( 7 ) . F i n a l - l y a t 2 4 0 ' ~ appears a f . c . c . t r a n s i t i o n a l phase

0

with parameter a = 5,15 A. The c r y s t a l l o g r a p h i c systems of copper oxide o r Y203 does n o t appear.

A more i n t e r e s t i n g ax~orphous system i s N i - Y because we have 6 d i f f e r e n t compositions r a n g i n g from 5 t o 33 a t .

%

Y.They a l l c r y s t a l l i z e i n t h e N i Y phase which i s a Hauke phase

( 8 ) ,

b u t

5

t h e i r S.A.S. c u r v e s evolue d i f f e r e n t l y . F i g u r e 6 shows what happens with t h e composition Y N i

-

2 7 '

F i g .

6

: S c a t t e r e d i n t e n s i t i e s of Y N i 2

7

There i s a weak e v o l u t i o n of t h e r i n g up t o 315OC and a two hours a g i n g a t t h i s t e m p e r a t u r e l e a d s t o c r y s t a l l i z a t i o n , w h i l e it o c c u r s a t 370°C a f t e r a r a p i d h e a t i n g . It does n o t appear nor h y d r i d e s nor o x i d e s i n t h e d i f f r a c t i o n r e g i o n .

A small-angle i n t e g r a t e d i n t e n s i t y Q can b e measured :

00

w i t h 6 = and a cut-off a t s 0.1 O-1 A

.

(5)

JOURNAL DE PHYSIQUE

I n a two-phase system, t h i s i n t e g r a t e d i n t e n s i t y Qo can a l s o be w r i t t e n :

Qo = c ( 1 - c ) Ap 2 V

;rl?erec i s t h e volume f r a c t i o n of t h e d i f f r a c t i n g

~ a r t i c l e s , Ap t h e d i f f e r e n c e between t h e i r e l e c - t r o n i c d e n s i t y and t h e medium where t h e y a r e ;

'a i s t h e mean atomic volume. We can determine c by t h e i r number and t h e i r s i z e , t h a t i s t o s a y b y t h e S.A.S. geak and t h e r a d i u s of g i r a t i o n given by t h e G u i n i e r p l o t . Consequently, a v a l u e o f Ap i s deduced. But i n amorphou? m a t e r i a l s , where f l u c t u a - t i o n s i n composition could c e r t a i n l y be l i n k e d w i t h d e n s i t y f l u c t u a t i o n s , such a value i s n o t s o meaningful t h a n with Guinier-Preston zones i n a l u - minum a l l o y s o r small oxide p a r t i c l e s i n i n t e r n a l - l y o x i d i z e d a l l o y s ( 9 ) . Nevertheless a v a l u e o f about 15 $ can be e s t i m a t e d . Furthermore t h e i n t e - g r a t e d i n t e n s i t y i s v e r y weak f o r Y N i 4 , more i m - p o r t a n t f o r Y N i and much more f o r Y N i and t h i s

2 7 3

i s an argument f o r t h e e x i s t e n c e of a m e t a s t a b l e m i s c i b i l i t y gap. But i t s boundaries a r e d i f f i c u l t t o determine because t h e i n i t i a l s t a t e s of t h e amorphous a l l o y s a r e n o t i d e n t i c a l and p r i n c i p a l l y do n o t d i s p l a y a f l a t S.A.S. curve proving t h a t t h e y a r e i n a r e a l l y homogeneous s t a t e .

CONCLUSION

Here a r e p r i l i m i n a r y s t u d i e s upon some metal- l i c g l a s s e s which d i s p l a y a r i n g i n t h e small-an- g l e s c a t t e r i n g p a t t e r n . The s i z e and t h i c k n e s s of t h e samples imply a p u n c t u a l X-ray c o l l i m a t i o n and consequently t h e i n t e n s i t i e s a r e weak, s o i s t h e accuracy. This i s t h e reason why experiments a r e planed with t h e synchrotron r a d i a t i o n .

Emphasis h a s been made i n t h i s s t u d y on t h e i n i t i a l s t a t e of t h e a l l o y s because t h e i r evolu- t i o n d u r i n g a h e a t i n g depends on it. Rare a r e t h e s p u t t e r e d amorphous a l l o y s having a f l a t S.A.S.

curve. When a r i n g a p p e a r s , it i s l i n k e d i n o u r opinion w i t h c o r r e l a t e d f l u c t u a t i o n s i n e l e c t r o n d e n s i t y . They a r e a s s o c i a t e d with f l u c t u a t i o n s i n composition, t h e n t h e y c r e a t e p a r t i c l e s which a r e a t r a n s i t i o n a l s t a t e towards t h e e q u i l i b r i u m p r e c i p i t a t e s a s f o r t h e N i - Y system where t h e c r y s t a l l i s a t i o n s t a t e i s always Y N i

5'

It i s n o t d o u b t f u l 1 t h a t some p h y s i c a l pro- p e r t i e s of such a l l o y s should be d i f f e r e n t accor- d i n g t o t h e i r middle range s t r u c t u r e which apTears on t h e small-angle s c a t t e r i n g p a t t e r n , w h i l e t h e i r d i f f r a c t i o n h a l o remains smooth.

ACKNOWLEDGEMENTS

The a u t h o r s a r e i n d e b t e d t o D r s . Boucher ( s a c l a y ) , R e b o u i l l a t reno noble) and Sadoc ( Orsay) f o r p r o v i d i n g t h e samples.

BIBLIOGRAPHY

( 1 ) P. DUWEZ. Rapidly quenched m e t a l s 111, v o l . 2 , Metals S o c i e t y (1978) p. 465.

( 2 ) A.B. BATHIA and D.E. THORNTON. Phys. Rev. B2 ( 1978) 3004.

( 3 ) A.M. FLANK, M. HARMELIN, M. JAULIN and A. NAUDON. To appear i n Rev. Phys. Appl.

( 4 ) C.B. WALKER and A. GUINIER. Acta Met., 1, 568 ( 1953).

( 5 ) K.B. RUNDMAN and J.E. HILLIARD. Acta Met., 15, 1025 ( 1 9 6 7 ) .

(6)

J. MIMAULT, J . DELAFOND, A. JUNQUA, A. NAUDON and J . GRILHE. P h i l . Mag. B, 38, 255 ( 1 9 7 8 ) . ( 7 ) J . S . LANGER. Phys. Rev. A , 1 1 , 1417 ( 1 9 7 5 ) . ( 8 ) J . F . SADOC and A. LIENARD. Rapidly quenched

m e t a l s 111, v o l . 2 , The Metals S o c i e t y (1978) p. 405.

( 9 ) J. ALLAIN, A. NAUDON, J. CAISSO. Acta Met., 27, 545 (1979).