RECENT STRUCTURAL RESULTS WITH AMORPHOUS ALLOYS USING NEUTRON DIFFRACTION

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RECENT STRUCTURAL RESULTS WITH

AMORPHOUS ALLOYS USING NEUTRON

DIFFRACTION

S. Steeb, P. Lamparter

To cite this version:

JOURNAL DE PHYSIQUE

Colloque C8, supplCrnent a u n012, Tome 46, dCcernbre 1985 page C8-247

RECENT STRUCTURAL RESULTS W I T H ANORPHOUS ALLOYS U S I N G NEUTRON D I F F R A C T I O N

S. Steeb and P. Lamparter

Max-PZanck-Institut fiir MetaZZforschung, Institut fiir

Werkstoffwissenschaften, Seestr. 92, 7000 Stuttgart I , F.R.G.

Resume

-

Les f a c t e u r s de s t r u c t u r e p a r t i e l l e , l e s d i s t a n c e s atomiques, l e s nombres de c o o r d i n a t i o n o a r t i e l l e e t l e s parametres d ' o r d r e c o u r t e d i s t a n c e

o n t S t @ d s t e r m i n e s p o u r l e s a l l i a g e s amorphes Dy80 N i 2 0 e t N i 8 0 P20. Lesocor- r 6 i a t i o n s D

-

D o n t

e t @

egalement dsterminees dans un a l l i a g e amorphe Dy69 Ni d e u t e r e

a

10 % a t . E n f i n , des mesures de d i f f u s i o n aux p e t i t s angles u t ! t i s a n t l e c o n t r a s t e v a r i a b l e de Ni dans am

-

N i P20 o n t mis e n evidence 1 'e x i s t e n c e de deux 7hase de compositions d i f f e r e n f e s

.

A b s t r a c t

-

P a r t i a l s t r u c t u r e f a c t o r s and p a r t i a l p a i r c o r r e l a t i o n f u n c t i o n s as w e l l as a t o m i c d i s t a n c e s , p a r t i a l c o o r d i n a t i o n numbers and s h o r t range o r d e r parameters a r e p r e s e n t e d f o r t h e amorphous a l l o y s Dy80Ni20 and NiB0Pp0. Com- p a r i n g t o p a r t i a l f u n c t i o n s o b t a i n e d e a r l i e r w i t h NiglBlg _{- . . -} and Y67Ni33 we r e -

- -

-p o r t on s t r i k i n g s i m i l a r i t i e s between t h e -p a r t i a l -p a i r c o r r e l a t i o n f u n c t i o n s between t h o s e p a i r s which b e l o n g t o one and t h e same o f t h e f o l l o w i n g groups:

Group 1 : N i - P ( f r o m Ni80P20) ; Ni-B(Ni81Blg) ; N i -Dy(Dy69Ni31 ) ; ~ i - Y ( Y ~ ~ N ~ ~ ~ ) Group 2: P-P(Ni 80 P 20 ) ; E-B(Ni81Blg) ; N i - N i (Dy69Ni31) ; ~ i - ~ i ( Y ~ ~ N ~ ~ ~ ) Group 3: N i - ~ i ( N i ~ ~ p ~ ~ ) ; N ~ - N ~ ( N ~ ~ ~ B , ~ ) ; ~ y - ~ y ( ~ y ~ ~ ~ i ~ , ) ; Y - Y ( Y ~ ~ F ! ~ ~ ~ )

W i t h a-Dy69Ni31 c o n t a i n i n g 10a/o D we show t h a t i t w i l l be p o s s i b l e t o determine D-D c o r r e l a t i o n s by n e u t r o n d i f f r a c t i o n w i t h an a l l o y made f r o m z e r o - s c a t t e r i n g Dy and f r o m z e r o - s c a t t e r i n g N i .

With a-Ni80P20 we r e p o r t f o r t h e f i r s t t i m e on t h e e v a l u a t i o n o f p a r t i a l s t r u c t u r e f a c t o r s i n t h e s m a l l Q-Region which show t h a t a-NigoP20 c o n s i s t s o f two phases namely a m a t r i x a c e r t a i n cNi/cD-ratio and r e g i o n s w i t h diame- t e r s o f 158, and a d i f f e r e n t ~ , \ ~ / c ~ - r a t i o .

I

-

INTRODUCTION

The p r e s e n t paper i s concerned w i t h s t r u c t u r a l work performed r e c e n t l y w i t h i n t h i ' s l a b o r a t o r y by n e u t r o n d i f f r a c t i o n u s i n g t h e method o f i s o t o p i c s u b s t i t u t i o n . Thus p a r t i a l s t r u c t u r e f a c t o r s and p a r t i a l c o r r e l a t i o n f u n c t i o n s were o b t a i n e d w i t h t h e f o l l o w i n g amorphous a l l o y s : i ) Dy69Ni31(+10a/o D) h i g h Q-Region i i ) NigOPeO h i g h Q-Region i i i ) Ni80P20 s m a l l Q-Region

C8-248 JOURNAL

DE

PHYSIQUE

I 1

-

AMORPHOUS Dy6qNi31(+10a/o D); HIGH Q-REGION; /I/

The t o t a l s t r u c t u r e f a c t o r according t o Faber Ziman f o r a t e r n a r y system c o n t a i n i n g t h e t h r e e atomic species 1,2, and 3 can be w r i t t e n as

2 2

c3b3 S ( Q )

+

2 c l c 2 b l b 2

+z

33 < b>L S12 w i t h

<b> = clbl+c2b2+c3b3. ( 2 )

From ( 1 ) i t f o l l o w s t h a t the c o n t r i b u t i o n S 3 ( Q ) from deuterium (element 3) w i t h i n the amorphous a l l o y formed by t h e elements

$

and 2 can be measured d i r e c t j v b.v one s c a t t e r i n g experiment if

bl = b2 = 0. ( 3 )

Equations ( 1 ) and (3) then y i e l d sF.z.

(Q) = S33(Q).

( 4 )

Four m e l t spun amorphous a l l o y s were p u t i n t o V-containers and a t room temperature d i f f r a c t i o n experiments were performed w i t h t h e instrument D4B a t t h e h i g h f l u x r e a c - t o r o f ILL, Grenoble, u s i n g neutrons w i t h a wavelength of 0.78. At t h e same time t h e background s c a t t e r i n g , t h e c r u c i b l e s c a t t e r i n g , and the Cd-rod s c a t t e r i n g were measured.

The i s o t o p i c composition of t h e f o u r specimens was as f o l l o w s : i) natNi n a t

31 DY69 ; n a t = n a t u r a l i s o t o p i c abundance, ii) n a t

.

0

Nlgl DY ; OOy = zero coherent s c a t t e r i n g m i x t u r e o f and 1 6 2 ~ y ,

0 n a t

i i i ) N i 3 ? Dy69 ;

ON^

= zero coherent s c a t t e r i n g m i x t u r e o f 6 0 ~ i and 6 2 ~ i ,

i V ) o ~ i 3 1 0 ~ y 6 9

+

10a/o D; t h e deuterium was loaded under h i g h pres- sure.

According t o eqn. ( I ) , specimen i i ) should y i e l d S

,

specimen i i i ) should y i e l d S D ~ D ~

,

and these two p a r t i a l s t o g e t h e r w i t h speci#J%ii) should y i e l d SNiDy

.

Fig. 1 shows the p a r t i a l Faber Ziman s t r u c t u r e f a c t o r s o f t h e amorphous a l l o y Dy Ni These can be compared t o those obtained w i t h Y67Ni33 by /2/ and show p r o - nofi4ced1similari ty.

F i g . 1

-

a-Dy N i (+lOa/o D). P a r t i a l F i g . 2

-

a-Dy N i

.

P a r t i a l r a d i a l ~ i m a n s t r u c t u F 8 f i l l t o r s . d i s t r i b u t i o n $8nc?.!ons.

The curve SDD shows t h e r e s u l t o f a s c a t t e r i n g experiment o b t a i n e d w i t h o ~ y 6 g o ~ i 3 ,

+

10a/o deuterium, i .e. an a l l o y which c o n s i s t e d o f z e r o s c a t t e r i n g Dy and z e r o s c a t -

t e r i n g N i and which was charged w i t h 10a/o deuterium. It i s i n t e r e s t i n g t o no e l t h a t

a

t h e D-D d i s t a n c e w i t h i n a D molecule s h o u l d show s t r u c t u r a l f e a t u r e s near 10

.

Anyhow, by t h i s experiment $e show t h a t i n near f u t u r e i t i s p o s s i b l e t o e v a l u a t e t h e d i s t r i b u t i o n o f d e u t e r i u m w i t h i n amorphous a l l o y s i f you p e r f o r m a d i f f r a c t i o n exper- iment w i t h a b i n a r y a l l o y whose b o t h components a r e z e r o s c a t t e r e r s a t t h e same t i m e . F i g . 2 shows t h e r a d i a l d i s t r i b u t i o n f u n c t i o n s c a l c u l a t e d f r o m t h e Sii i n F i g . 1. The v e r y s m a l l f i r s t peak i n GNiNi shows t h a t c o n t a c t o f N i - N i atoms d o e s n ' t e x i s t v e r y o f t e n . The r a t h e r l a r g e d i f f e r e n c e 0.56 o f t h e e l e c t r o - n e g a t i v i t i e s o f N i and Dy a p p a r e n t l y l e a d s t o p r e f e r e n c e o f Ni-Dy c o n t a c t s . T h i s i s expressed i n a r a t h e r s t r o n g f i r s t GNiDv maximum. I n so f a r , t h e r e e x i s t s a s t r i k i n g s i m i l a r i t y t o Ni33Y67, too. F r o r , ~ t h e ~ ~ ? s t h e p a r t i a l

c o o r d i n a t i o n n u m b e r s Z N i N i = 3 . 2 , Z

=14.7,and Z

.

= I 1.0 were o b t a i n e d y i e l d i n g a r e l a t i v e C a r g i l l -Spaepen s h o r ? ~ & n g e o r d e r p a r a - m&&# i-

.

=1.3%. Thus t h e chemical s h o r t range o r d e r i s about 25% o f t h a t ob-

t a i n e d YADY2rehr Ni,,Y,,.

--

_",

The p a r t i a l c o o r d i n a t i o n numbers f o r amorphous N i 1Dy63 as w e l l as t h e r e l a t i v e Car- g i l l - S p a e p e n chemical s h o r t range o r d e r f o r d i f f e r e n t a l l o y s a r e p r e s e n t e d i n Table 1. A l l o y N i j l 0 ~ 6 9 N i 3 1 0 ~ 6 9

ZNINi

=

3.2 Cu33Y67 Z D ~ D ~

=

1L.7

Ni3gY67

Z N i ~ y

=

11.0 N i g l B i g

Table 1. P a r t i a l c o o r d i n a t i o n numbers and s h o r t range o r d e r parameters.

C8-250 JOURNAL DE PHYSIQUE

111

-

AMORPHOUS NigOPpO ; HIGH Q-REGION; /5/

The experimental procedure was the same as w i t h D Y ~ ~ N ~ ~ , . The i s o t o p i c composition o f t h e t h r e e specimens was:

i i ) 6 2 ~ i 8 0 ~ 2 0

According t o eqn.

( I ) ,

specimen i i i ) should y i e l d Spp and t o g e t h e r w i t h t h e r e s u l t s of specimen i ) and i i ) one o b t a i n s SNiNi and SNip.

The Bhatia Thornton p a r t i a l s t r u c t u r e f a c t o r s SNN(Q), SCC(Q), and SNC(Q) a r e p l o t t e d i n Fig. 3 and t h e i r F o u r i e r transforms i n Fig.4.

m G7

'0

i

i

6

8 i o

ii

i~

R

[ A ]

Fig. 3

-

Amorphous Ni P

.

P a r t i a l Bhatia F i g . 4

-

Amorphous Ni P : P a r t i d l den- Thornton s t r u c t u r e fa@?o?!?.sNN(~), S C C ( ~ ) , s i t y - and

concentratiBR-Z8rrelation

and SNC(Q). f u n c t i o n s GNN(R), GCC(R), and GNC(R).

The s e r i e s o f a l t e r n a t i n g p o s i t i v e and negative peaks o f G (R) c l e a r l y shows how t h e atomic s t r u c t u r e i n t h e Ni P g l a s s i s governed by c&mical o r d e r i n g e f f e c t s . The short-range parameter, acc8Pd8!Ig t o Warren and Cowley, may be c a l c u l a t e d from:

Ru RU

2

a

= RGCC(R)dR/

j

(RGNN(R)+ 4riR po)dR ( 5 )

R1 R1

where t h e i n t e g r a t i o n l i m i t s R1= 2.0

8

and

R .

= 2.88

8

bound t h e f i r s t c o o r d i : ~ a t i o n s h e l l defined by t h e p r i n c i p a l peak o f G ~ ~ ( R ! which covers t h e R range o f t h e f i r s t negative Ni-P- and t h e f i r s t p o s i t i v e Ni-Ni-peak o f G (R). As a r e s u l t we o b t a i n

a=

-0.20. The maximum p o s s i b l e value o f

la1

i s given by Eke r a t i o o f t h e concentrations a,,,a:: = cP/cNi = 0.25.

Table 2 shows a c o m p i l a t i o n o f s t r u c t u r a l data obtained w i t h t h e Faber-Ziman p a r ' l i a l s . Table 2: S t r u c t u r a l parameters o f amorphous Ni P

.

R..= distance, zij= number o f j atoms around a c e n t r a l i atom, 6ij= w i d t h o f c88riiPnat1~n sphere.

The s h o t t range order parameter according t o t h e d e f i n i t i o n given by C a r g i l l I11 and Spaepen can be c a l c u l a t e d from t h e p a r t i a l zi. i n Table 1 and we o b t a i n rl

.

=+0.13 which i s w i t h i n t h e accuracy of p a r t i a l z ; ; t h d maximum p o s s i b l e value, thug-&roving

'

J

t h e complete chemical o r d e r i n g i n t h e NiR0PZ0 glass. - . -.

Fig. 5 shows a c o m p i l a t i o n o f G ~ ~ ( R ) c o r r e l a t i o n f u n c t i o n s , where E means t h e smaller

atom i n t h e m e t a l l i c glasses NigoPz0 / 5 / , NiglB19, Ni64B36 /6/, Y67Ni33 /2/, D Y ~ ~ N ~ ~ ~ , and T i Ni /7/, r e s p e c t i v e l y . Hereby R/Rm i s normalized t o t h e p o s i t i o n Rm o f t h e

largesfope% i n G (R). Keeping i n mind t h a t these examples a r e chosen from q u i t e d i f f e r e n t groups

6k

metal1 i c glasses we observe e x c i t i n g s i m i l a r i t i e s : t h e peak a t R/Rm = 1 i s t h e main maximum o f a double peak s t r u c t u r e , and t h e preceding peak a t R/Rm = 0.5....0.65 which r e f l e c t s d i r e c t E-E c o n t a c t i s q u i t e small o r even n o t p r e - sent a t a l l . T h i s suggests t h a t t h e u n l i k e l y h o o d f o r c l o s e c o n t a c t between t h e smal- l e r component i s , more o r l e s s pronounced, a general f e a t u r e i n t h e s h o r t range o r - d e r i n g which goes through a l l t h e d i f f e r e n t types o f m e t a l l i c glasses.

Fig. 5

-

P a r t i a l p a i r c o r r e l a t i o n f u n c t i o n GBB o f t h e Ni-P-, Ni-B-, Y-Ni-, Dy-Ni-, and Ti-Ni-systems, where B i s t h e smaller atomic species.

I V -AMORPHOUS NigoPz0 ; SMALL Q-REGION ; /8/

JOURNAL

DE

PHYSIQUE

According to these curves the medium range structure consists of

0.9 0.7- -0.5-

2

V) 0.3- SNN(OLLQ~;

i)

Small regions (15

8

diameter) which differ frqm the surroundinq matri?

only by the ccncentration (because SCC rises with smaller

Q)

but not by the den-

sity, because SNN remains constant.

ii) Large regions

( -

1000

8

diameter) which differ from the surrounding ma-

trix by the concentration

@

by the densitv.

In /8/ we presented a method. which allowed the determination of the concentration

of the regions of kind

i)

and the ratio of Nickel to Phosphorus within these regions

as well as within the matrix.

Introducing the following concentrations in atomic fractions

:

-

Concentration of regions within the specimen

:;

-=

I-cR

=

Concentration of the matrix

cNiR: Concentration of Ni-atoms within the regions

Concentration of Ni-atoms within the specimen

N

i

he evaluation finally leads to eqn. (6):

2

Ni)

2 =

cNi cp

.

5.14*10-~

(6)

2~

P,

cR(l-cR)(cNiR

-

c c

This is the analytical form for the plot cNiR(cR) shown in Fig.

7.

It should be noted that it is not possible to determine from diffraction experiments

that point on this curve which represents the specimen under consideration. If we

assume the regions to have the same c

.

/c -ratio as the first crystallization pro-

duct Ni3P,

i

.e. cNiR/cpR

=

3,

then weNdBtaPR as a result:

Atomic concentration of regions within the specimen cR

=

43.8 a/o.

Concentration ratio within the regions cNiq/cpR== 3.

Concentration ratio within the matrix cNiM cpM 5.2.

o

a04 0.0.8 012 0.16 020

oz

028

a

[A-'1

CR

-

Amorphous Ni OP20: Partial

Fig.7

-

Amorphous Ni OP20. Concentration

k%&

Thornton struc&ure factors

r

o

f

Nickel withia regions versus con-

This means a disproportion of the original ratio cNi/cp

=

4. Anyhow we should

learn from this experiment that this amorphous alloy is not uniform, but heteroge-

neous.

it should be noted that the term "regions1'

as used in this paper does not mean

well defined particles which then would be separated by a sharp interface from the

matrix. Furthermore there are no features in :he scattering functions which indicate

any distance correlation between the "regions

.

These "regions" rather should be de-

scribed as uncorrelated fluctuations in the amorphous structure where the system pro-

bably adjusts the short range order locally to that prevailing in the first crystal-

lisation product, i.e. Ni3P in the case of a-Nig0P2,,.

Acknowledgement

Thanks are due to ILL, Grenoble and to GKSS-research centre, Geesthacht, for alloca-

tion of beam time.

REFERENCES

/I/ Wildermuth, A., Lamparter, P. and Steeb, S.,

Z.

Naturforschung 40a (1985) 191.

/2/

Maret, M., Chieux

,

P., Hicter, P., Atzmon,

M.,

and Johnson,

W.L.,

Rapidly

Quenched Metals, Eds. Steeb, S. and Warlimont, H., Elsevier Science Publishers B.V.

Amsterdam (1985).

/3/ Wildermuth, A., Thesiswork, University of Stutt art (1985).

/4/ Wright, A.C. et al., J. Phys.

F:

Met. Phys.

71984) L201 and Proceedings of

the present conference.

/5/ Lamparter, P., and Steeb, S., Rapidly Quenched Metals, Eds. Steeb, S.,

War1 imont, H., Elsevier Science Publishers

B.V.

Amsterdam (1985) 459.

/6/

Cowlam, N., Guoan, W., Gardner, P.P. and Davies,

H.A.,

Liquid and Amorphous Me-

tals V, Eds. Wagner, C.N.J.,

Johnson,

W.L.,

North Holland (1984) 337.

/7/ Fukunaga, T., Watanabe,

N.,

and Suzuki,

K.,

LAM 5.