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OBSERVATIONS OF AMORPHOUS ALLOY CHARACTERISTICS USING THE SCANNING
MICROSCOPE
J. Fléchon, F. Machizaud, F. Kuhnast, G. Mbemba, A. Obaida, A. Kohler
To cite this version:
J. Fléchon, F. Machizaud, F. Kuhnast, G. Mbemba, A. Obaida, et al.. OBSERVATIONS OF
AMORPHOUS ALLOY CHARACTERISTICS USING THE SCANNING MICROSCOPE. Journal
de Physique Colloques, 1984, 45 (C2), pp.C2-679-C2-682. �10.1051/jphyscol:19842157�. �jpa-00223829�
J O U R N A L D E PHYSIQUE
Colloque C2, supplkment
au
n02, Tome 45,f6vrier
1984 page C2-679OBSERVATIONS OF AMORPHOUS ALLOY CHARACTERISTICS USING THE SCANNING MICROSCOPE
J . FlGchon, F. Machizaud, F.A. Kuhnast, G. Mbemba, A . Obaida and A. Kohlerr
Laboratoire de Physique des D6po"ts Me'tazziques, Universite' de Nancy
I ,B.P. 239,
54506 Vandoeuvre Cedex, Frame
*service C m u n de MicroanaZyse, k b o r a t o i r e de Chimie Miniraze, UniversitL de Nancy
I , B.P. 239,54506 Vandoeuvre Ceder, Frame
RQsum6 - Les a l l i a g e s amorphes o b t e n u s p a r methode 6 l e c t r o l y t i q u e s o n t deposbs s u r une f e u i l l e d e c u i v r e 5 l a t e m p e r a t u r e a m b i a n t e .
Comme l e s v e r r e s d ' o x y d e , c e s v e r r e s m C t a l l i q u e s s o n t d e s m a t e r i a u x d e s o r - donn6s 5 1 ' B c h e l l e m o l 6 c u l a i r e . Mais l e s o b s e r v a t i o n s a u microscope B b a l a y a g e r 6 v S l e n t un m&me comportement 5 l'examen d e s s u r f a c e s d e f r a c t u r e .
Abstract
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Amorphous a l l o y s o b t a i n e d by e l e c t r o l y t i c a l methods a r e d e p o s i t e d on a c o p p e r l e a f a t ambient t e m p e r a t u r e .I n commun w i t h t h e o x i d e g l a s s e s , t h e s e m e t a l l i c g l a s s e s a r e d i s o r d o n n e d m a t e r i a l s on t h e m o l e c u l a r s c a l e . But o b s e r v a t i o n s w i t h a s c a n n i n g microscope r e v e a l t h e same b e h a v i o u r i f we examine t h e f r a c t u r e s u r f a c e s .
While t h e c r y s t a l l i n e s t a t e i s c h a r a c t e r i z e d by l o n g r a n g e o r d e r , t h e amorphous s t a t e i s d i f f e r e n t b e c a u s e t h i s o r d e r i s a b s e n t a l t h o u g h a c e r t a i n l o c a l a t o m i c a r r a n g e m e n t r e m a i n s and even a c e r t a i n o r d e r i n g among them a t medium d i s t a n c e .
The m e t a l l i c g l a s s e s a r e amorphous a l l o y s which c a n b e o b t a i n e d t h r o u g h v e r y d i f f e r e n t methods ( I ) , (21, ( 3 )
...
We have chosen o n l y t h e l i q u i d p h a s e o x i d a t i o n - r e d u c t i o n o f n i c k e l o r c o b a l t - s a l t s by sodium hypophosphide and by e l e c t r o l y s i s o f t h e same s o l u t i o n .The f i r s t p r o c e d u r e l e a d s t o a l l o y f i l m s , t h e t h i c k n e s s o f which c a n v a r y from a few hundred t o s e v e r a l t h o u s a n d Angstr8ms d e p o s i t e d on i n s u l a t i n g g l a s s o r p l a s t i c . and powders; t h e second t e c h n i q u e r e s u l t s i n l a y e r s whose t h i c k n e s s v a r i e s from one t o one hundred microns on t h e c o p p e r f o i l forming t h e c a t h o d o f an e l e c t r o l y t i c b a t h , two p l a t i n u m anods b e i n g s y m e t r i c a l l y s i t u a t e d w i t h r e s p e c t t o t h e p l a n e o f t h e r e c e p t o r .
We p r o p o s e comparing t h e b e h a v i o u r o f e l e c t r o l y t i c Nip and COP l a y e r s . The a m o r p h i s a t i o n o f t h e s e two t y p e s of m a t e r i a l i s c h a r a c t e r i z e d by X Ray d i f f r a c - t i o n .
The d i f f r a c t i o n p a t t e r n s from amorphous a l l o y s c o n t a i n o n l y a B e r i e s o f b r o a d maxima i n c o n t r a s t t o t h e s h a r p l i n e s o b s e r v e d from c r y s t a l l i n e m a t e r i a l s . T h i s is t h e e x p e r i m e n t a l p r i n c i p a l c r i t e r i o n o f t h e amorphous m a t e r i a l . I t l e a d s a f t e r c o r r e c t i o n s and F o u r i e r t r a n s f o r m s t o t h e R . D . F . where we can o b s e r v e l o c a l and medium r a n g e o r d e r .
The term m e t a l l i c g l a s s e s i s u s e d t o c h a r a c t e r i z e t h e d i s o r d e r e d m a t e r i a l
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19842157
C2-680 JOURNAL DE PHYSIQUE
from the oxide glasses.
While the behaviour of these glasses is analogous from a structural point ofview,the scanning microscope should, fcr similar magnifications, give micro- graphs with the same aspect. Thus, we have examined across their thichness, samples of an ordinary leaf of glass 100 microns thick and of COP and Nip amor- phous layers, about 40 microns thick, obtained at ambient temperature and not annealed. The views 1 to 3 reveal analogous fracture surfaces which show lines of stress normal or slightly oblique to the surface. They are the domains which have undergone plastic deformation before breaking. There l'esults a certain porosity.
These materials, treated by fracture, appear liquid like with a high vis- cosity. 0;; the edge, the transverse strain of the rupture has led to strained filiform zoneo of unequal importance which were stretched by the traction.
It was of interest to anneal the alloy samples so as to examine their evolu- tion after the phase-transition. The fracture surfaces appear more or 1-ess smooth according to the alloy and the composition.(view 4)
The comparison carried out using the scanning electron microscope reveals analogous behaviour of these metallic glasses in a certain range of observations.
It is naturally possible to extend the comparison by examining these substances with other investigation methods : for example, X-Ray diffraction, electrical resistivity, temperature coefficient of resistivity, density evolution.
In all cases, the micrographs concern the amorphous substance obtained at ambient temperature. It is then compared with that of the same material annealed under vacuum at 450°C. For example, these comparisons concern the interference function of the Nip and COP, the distribution function which corresponds to it in direct space. fig (1)
The analogy between these diagrams is very high. This is explained by the nature of the components : the same me-tallvPc1 and transition metals belon ing to the same group. The nearest neighbsurs distances are approximatly 2 , 5
f
inboth Nip as COP. fie ( 2 )
After the annealing the diagrams are clearly typical of a polycrystalline state in which the phosphides (Ni P and Co P) and metals (Co and Ni) show their
3 2
characteristic reflections : however, for a phosphorous content lower than the eutectic composition E, it is first the metal which crystallizes when the tempe- rature is increased, the phosphides appearing only at the higher temperatures.
The opposite is true for the substances situated. further than E on the phase diagram. fie (3)
Using X-rays, an evolution is also observed under the same treatment condi- tions ( 4 ) . , { 5 ) , ( 6 ) : this implies : stabilization step by step through temperature changes maintaining the amorphous state, then after the phase transition, by a progressive increasing of the conductivity associated with ordering of the substance without the X radiations can detect important modifications in the arnorphous state. The resistivity is sensitive to changes in the chemical bonding.
DTA also allows following this process but the energy phenomena involved are generally small. The most sensitive parameter of these latent modifications of the disordered structure semms to be the magnetization. (7)
Bibliography
(1) A.K.SINHA, B.C.GIESSEil, D.E.POLK, Treatise on Solid State Chemistry, Vo1.3, 1976, p.1
(2) R.E.MARINGER, C.E.MORLEY, E.W.COLLINS, ?roc. Scc. Int. Conf. on Rapidly Quentch Metals, 1976, Vol. 23, p.87
(3) R.POND, R-MADDIN, Trans. Met. Soc. AIIdE, Vol. 245, 1969, p. 2475 (4) G.MBEMBA, Th6se 3' cycle, Nancy 1981
(5) F-MACHIZAUD, Th6se Nancy 1373
/
( 6 ) A..OBAIDA, thGse 3O cycle , Nancy (1983)
(7) J.FLECHON, these Nancy (1960)
oxide glass
JOURNAL DE PHYSIQUE
F i g u r e 1
I n t e r f e r e n c e f u n c t i o n
F i g u r e 2
R e p a r t i t i o n f u n c t i o n
f i g u r e 3 : X-rays d i f f r a c t i o n p a t t e r n s (ACoKa)
