LOW TEMPERATURE IRRADIATIONS OF SOME Fe-B METALLIC GLASSES

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LOW TEMPERATURE IRRADIATIONS OF SOME

Fe-B METALLIC GLASSES

A. Audouard, J. Jousset, J. Dural

To cite this version:

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LOW TEMPERATURE IRRXDIATICNS

OF

SOME Fe-B METFLLIC GLASSES

A . Audouard, J.C. J o u s s e t and J . ~ u r a l *

Centre drEtudes NuclIaires de Saclay, I n s t i t u t National des Sciences e t Techniques NucZlaires, Laboratoire de MItaZlurgie

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B.P. N06

-

91190 Cif s u r Y v e t t e , France.

*

Centre drEtudes NucZdaires de Fontenay a m Roses, Section dlEtudes des Solides Irradids

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B. P. N06, 92260 Fontenay a m Roses, France.

1

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I n t r o d u c t i o n _{For t h e f i s s i o n fragment i r r a d i a t i o n s t h e} The first i r r a d i a t i o n s o f m r p h o u s

m e t a l l i c a l l o y s have been performed i n t h e e a r l y s e v e n t i e s by D. LESUEUR (1). H e had s h t h a t f o r Pd80Si20:i/U 235 f i s s i o n f r a p e n t 20 K i r r a d i a t i o n s induced a n amorphous s t a t e d i f f e r e n t f r o m t h e one obtained by s p l a t c o o l i n g .

i i / t h e r e was a competition between damage and m e a l a l l along t h e i r r a d i a t i o n . Me i n t e r p r e - t a t e d t h i s competition as being due t o t h e two d i f f e r e n t ways o f energy d e p o s i t i o n o f a f i s s i o n fragment i n a metal, e l e c t r o n i c i n t e r a c t i o n s which l e a d t o t h e m 1 e f f e c t s ( s o c a l l e d "thermal spike") and atomic c o l l i s i o n s ("cascades").

~ r r a h i a t i o n experiments of m r p h o u s m e t a l l i c a l l o y s have a t l e a s t two g o a l s :

i / d i s t i n g u i s h between t h e s e t h e m 1 and c o l l i s i o n e f f e c t s : i i / u n d e r s t a n d t h e microscopic n a t u r e of t h e dannge and consequently g e t a n i d e a of t h e s h o r t range o r d e r o f t h e m r p h o u s m e t a l l i c a l l o y s .

For t h e s e r e a s o n s , we have i r r a d i a t e d a-FeB a l l o y s a t 20 K with : i / h i g h doses o f 2.5 MeV e l e c t r o n s which, i n c r y s t a l l i n e m e t a l s , induce i n d i v i d u a l displacements o f atoms, ii/ f i s s i o n neu-.

t r o n s

w h i c h i n d u c e t h e ' ' ~ ( n , a ) n u c l e a r

re-

a c t i o n . T h e 6 MeV i n d u c e d a p a r t i c l e s l e a d t o a c o l l e c t i v e d a m a g e , i i i / U 235 f i s s i o n F r a g m e n t s w h i c h h a v e , a s p r e v i o u s l y s a i d ,

samples were e l e c t r o l y t i c a l l y thinned a t t h i c k - n e s s e s f r o m 6 p m t o 14prn.U 235 was deposited on both s i d e s of t h e samples by evaporation o f U02 enriched t o 95 % i n t h e 235 i s o t o p e

.

1 4 k m was t h e m x k t h i c h e s s s i n c e t h e range of U 235 f i s s i o n f r a p n t s is around 7 p m i n i r o n . These coated samples, a s w e l l a s t h e E i s s i o n n e u t r o n s samples, were i r r a d i a t e d i n t h e Vinka f a c i l i t y ( 2 )

of t h e r e a c t o r T r i t o n o f Fontenay aux Roses. The e l e c t r o n i r r a d i a t i o n were p e r f o m d a l s o a t Fontenay aux Roses i n t h e Vinkac f a c i l i t y o f t h e V a n d e Graaf accelerector ( 3 ) .

3

-

R e s u l t s

3.1. D m g e production

E l e c t r o n and n e u t r o n i r r a d i a t i o n s :

Figures 1 and 2 show d m g e production curves f o r both a l l o y s d u r i n g e l e c t r o n and f i s s i o n neutron i r r a d i a t i o n s ( 6 MeV a p a r t i c l e s ) r e s p e c - t i v e 1 y . A r a d i a t i o n darrage i s c l e a r e l y seen i n both c a s e s . A s a t u r a t i o n e f f e c t appears i n t h e c a s e o f e l e c t r o n i r r a d i a t i o n and t h e s a t u r a t i o n i s complete in t h e c a s e o f neutron i r r a d i a t i o n . The e l e c t r i c a l r e s i s t i v i t y i n c r e a s e a t s a t u r a t i o n i s

APs

= 6 , s

?

0 , ~ I J l c m and 4,7 f 0,3@cm for a-Feg0 B20 and a-Fe78M02B20 r e s p e c t i v e l y .

t h e t w o e f f e c t s , t h e r m a l s p i k e s a n d c o l l i - s i o n c a s c a d e s . 2

-

E x p e r i m e n t a l p r o c e d u r e s .

-

T h e s a n p l e s

_-E

w e r e M e t g l a s a s p r o v i d e d b y A l l i e d C h e m i c a l .

3

Two t y p e s o f a l l o y s w e r e i r r a d i a t e d : a - F e p & p

5

a n d a-Fe7$o 2B 20

.

T h e y w h e r e r i b b o n s , 40 pm t h i c k . T h e d a m a g e a n d t h e a n n e a l i n g s w e r e f o l - l o w e d b y m e a n s o f t h e m e a s u r e o f t h e elec- t r i c a l r e s i s t i v i t y of t h e s a m p l e s

a t

20 K

w i t h t h e u s u a l f o u r w i r e s p o t e n t i o m e t r i c Fig.1 - Darrage production curves o f e l e c t m n i r r a - d i a t e d amor?hous Fe-R samples

a

p is t h e i r r a d i a f . io n

m e t h o d . _{induced i n c ~ a s e}_{of t h e e l e c + r i c a l m s i ~ + i v i t y .}

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JOURNAL DE PHYSIQUE

-

3

1 0 - ~ ~ x d o s e ( 6 MeV a

.

crn ₎

Fig. 2 - Damage production

curves

o f f a s t neutron i r r a d i a t e d m r p h o u s Fe-B samples.

AP

is t h e i r r a d i a t i o n induced i n c r e a s e o f t h e e l e c t r i c a l r e s i s t i v i t y .

F i s s i o n fragment i r r a d i a t i o n s :

F i g w e 3 shows d m g e production curves o f a-Fe78M~2B20 w i t h d i f f e r e n t t h i c h e s s e s . The r e s u l t s , a s it i s t h e c a s e f o r a-Fe

80 B20 can be s m r i z e d a s follows :

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A t low doses, t h e r e s i s t i v i t y i n c r e a s e s very quickly. The t h i n n e r t h e sample, t h e h i g h e r t h e i n c r e a s e r a t e d

( b P

d

(eft

)

-

The curves e x h i b i t a mximum. The lower t h e t h i c h e s s , t h e lower t h e dose a t which t h e maximm occurs.

- At high doses, t h e r e s i s t i v i t y i n c r e a s e s l i n e a r l y with t h e d o s e . ~ h i s could be d u e t o a s p u t t e - r i n g e f f e c t a s it was pointed o u t by

LESUEUR

(1).

If we assume t h a t t h e s a t m a t i o n o f t h e i r r a d i a t i o n e f f e c t is complete, i . e . t h e r e i s no mre i n c r e a s e o f

p

,

we can deduce from t h e s l o p e o f t h e curve t h e s p u t t e r i n g r a t e . W e found few thousands a t o m p e r f i s s i o n fragment, in good accordance with LESUEUR's r e s u l t s . So, t h e t h i n n e r t h e sample, t h e lower t h e r e s i s t i v i t y a t s a t u r a t i o n . More, t h e r e s i s t i v i t y becomes s m l l e r t h a n b e f o r e i r r a d i a t i o n f o r t h e two t h i n n e s t samples.

The main part of t h e s e f e a t u r e s were a l r e a d y observed by LESUEUR (1) in t h e c a s e o f t h e f i s s i o n f r a m n t i r r a d i a t i o n o f c-Pd80Si20 and a-Pd S i

80 20

Fig. 3a

Fig. 3b

Fig.3

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Damge production c w v e s of f i s s i o n f r a p e n t i r r a d i a t e d a-Fe7b Mo2 B2,, a l l o y . Fig.3a : low doses

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Fig. 4

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A ~ l e a l i n g curves f o r t h e a-Fe78M~2B20 a l l o y .

A R o i s

t h e i r r a d i a t i b n induced Increase of e l e c t p i c a 1 resistance.

A

R

i s what m i n s a f t e r an annealing a t a temperature T.

,

and

V

r e f e r s t o electron, . n e u t r o n a n d f i s s i o n fragment i r r a d i a t i o n respectively. F i w 4 shows t h e a n n e z l i n ~ derivative - -

-

dY

b~

crwes[m(m.)

,

T]

f o r t h e a-Fe78E(02B20 a l l o y . For t h e t h r e e types of i r r a d i a t i o n , low temperature recovery stages occur. These stages are l e s s defi- ned than i n t h e mre usual c r y s t a l i r r a d i a t i o n case.

A f t e r an annealing up t o r o o m temperature, a c e r t a i n munt of t h e induced

bPo

has not recovered : about 0,6

AQ,

and 0,2

AQo

f o r n e u t r o n and e l e c t r o n i r r a d i a t i o n r e s p e c t i v e l y .

The i r r a d i a t i o n e f f e c t was a l s o characte- r i z e d by t h e influence of t h e damage on t h e curves

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T,

.

The v a r i a t i o n with T of t h e e l e c t r i c a l r e s i s t i v i t y

p

qf t h e a l l o y was measured before i r r a d i a t i o n . After i r r a d i a t i o n , t h e same measurement was m d e between 20 K ( i r r a d i a t i o n temperature) and T (annealing temperature). Figure 5 and 6 show t h e s e curves f o r a-FemE and a-Fe78M~2B20 samples. It can be seen t h a t

$

decreases a f t e r i r r a d i a t i o n and t h a t t h e recovery e f f e c t of t h e annealings leads t o an increase of t o m r d s i t s p m i r r a - d i a t i o n value.

4

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Discussion

4.1. E l e c t r o n a n d n e u t r o n i r r a d i a t i o n s

.

I r r a d i a t i o n induces an important e f f e c t i n t h e s e Fe-B base amrphous alloys.

b p ,

induced increase is of t h e same order of mgnitude than i n c r y s t a l s i . e . few

p.&

cm.

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s t r u c t u r a l changes a s observed in the case of neutron i r r a d i a t e d a-Pd80Si20 (7) and helium ion i r r a d i a t e d a-Pd80Si20 (8).

dP

Fig.5

-(rn,

T)

N"" of a-Fe80B20sa"ple, before and a f t e r n e u t r o n i r r a d i a t i o n . f is t h e f r a c - t i o n r e s i s t i v i t y which have recovered a f t e r -the annealing a t t h e temperatme indicated on t h e curve.

Fig.6

-

(g,

T ) curves of a-Fe

Mo

B sample, before a n d a f t e r neutron aad!a?!?on. f i s t h e f r a c t i o n r e s i s t i v i t y which have recovered a f t e r t h e h e a l i n g a t t h e tempemture indicated on t h e curve.

The hypothesis of a p i n t defect creation i s supported by t h e occurence of low temperature recovery stages i n t h e annealing curves. A s t h e short range order degree is probably lower than i n a c r y s t a l , recovery peaks in f i g u r e 4 are m t h e r than in t h e case of a c r y s t a l . So, it seems possible t o a s s o c i a t e t o a defect a spectrum of migration energy (4) ( 5 ) .

The r a d i a t i o n m g e m y be interpreted i n

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JOURNAL DE PHYSIQUE

If we assume that the Mathiessen's rule is dP

valid, The

3

value is representative of the structural state of an alloy. Figures 5 and 6 show that

3

is very sensitive to the irradiation. This could mean that structural changes occur during

neutron irradiation i.e. 6 MeV a particles irradia-

tion. An alternate explanation is that the

~athiessen's rule is not valid for these neutron

irradiated alloys.

4.2. Fission frappent irradiations. In the case of fission fragment i m d i a - tions, production curves of figure 3 can only be explained by the existence of two processes (1)(4).

A

fission fragmnt losses its energy in two ways :

-

nuclear collisions which induce displacement cascades

in

the whole bulk of the irradiated sample and lead to the creation of pint de" ~ects and m y be to the nucleation of another structural state as it is the case in neutron irradiations. This process induces an increase of the electrical resistivity.

-

electivnic excitation which induce t h e m 1 spikes near the surface of the sample and leads to the annealing out of the pint defects and probably to the creation of another different structural state. This process lowers the electrical resistivity.

5 - Conclusion.

The results presented here show important d m g e effects

in

Fe-B type amorphous alloys irradiated at 20 K by 2,5 MeV electrons, ( 6 MeV cr p a r - t i c l e s ) n e u t r o n s a n d f i s s i o n f r a g m e n t s .

These effects are interpretated in terms of pint defects creation in the short range order of the mrphous structure and of induced structural changes in the mrphous state.

Further experiments are planned or in progress to support these assumptions. Aknowledgements

The authors are very grateful to

Dr.

C.

1 1

JANOT,

Dr.

D. LESUEUR, Dr. Y. QUERE for m y helpful discussions. Thanks

are

also due to

Mrs

K.

LORENZELLI f o r p r e p a r i n g t h e f i s s i o n

fragment experiment samples, to MM. J. ARDONCEAU and R. 3LOT for efficient experimental help.

References

(1) D. LESUELIR, Rad.Eff.24, - 101 (1975) and rapport CEA R 4502 (1973).

(2) R.R. CONTE and J. DURAL, Rev.Phys.Appl.,;?,l (1967).

(3)

J. D m ,

J. ARDONCEAU and J.C. JOUSSET to be published.

(4) A. AUWUARD, J.

D

W

and J.C. JOUSSET, Rad.Eff.Let.g, 9 (1979).

( 5 ) A. AUWUNU), J. BALOGH, J.

DURAL

and J.C. JOUSSET, to be published.

(6)

J.

HILIAIRET, E. BALANZAT, J. BIGOT and

H.

KUNZI,

this conf.

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K.

DOI,

T.

AYANO ar,d K.KAWAMUF.A, J. Non-Cryst So1.34,415 (1979). _-

(8)

T.

AYANO,

H.

OFNO,

K.

UTUMI,

K.

KAWAMURA and