Reply to comments on “stress induced diffusion of oxygen in alpha zirconium”

Scripta METALLURGICA

Vol. 5 , pp. 977-980, 1971 Printed in the United States

Pergamon Press, Inc.

R E P L Y TO C O M M E N T S ON " S T R E S S I N D U C E D D I F F U S I O N O F O X Y G E N IN A L P H A

K.M.

ZIRCONIUM"

Browne

Central Research Laboratory John Lysaght (Australia) Limited Newcastle, N.S.W. Australia.

(Received September 20, 1971)

Mishra ly reported

a n d A s u n d i (1) h a v e e x p r e s s e d

(Z) i n z i r c o n i u m - o x y g e n

stitutional impurities, relaxation

the belief that the internal friction peak recent-

a l l o y s c o n t a i n i n g Z.4% Hf, 0.1% F e a n d 0.1% T i a s s u b -

i s d u e to a T i - O p a i r r e l a x a t i o n

which I suggested.

rather

than either Hf-O or O-O pair

That their conclusion is based on errors

of b o t h i n t e r p r e t a -

tion and logic will be evident in the following. The fact that Mishra

a n d A s u n d i f a i l e d to d e t e c t a p e a k i n h i g h p u r i t y z i r c o n i u m

t a i n i n g 80 p p m o x y g e n a n d m o r e

t h a n 265 p p m s u b s t i t u t i o n a l

t h e r e is no O - O p e a k a s t h e y c l a i m , to c a u s e a p e a k to o c c u r .

observe a t . %.

n o r d o e s it p r o v e t h a t a s u b s t i t u t i o n a l

m a y b e t o o l o w to r e s o l v e

atom is necessary

atom peak.

Mishra

either an oxygen-oxygen

and Asundi themselves

internal friction peaks even when the substitutional Since their high purity zirconium

ity the absence

con-

does not prove that

T h e only c o n c l u s i o n w h i c h c a n be d r a w n f r o m t h i s o b s e r v a t i o n

that the oxygen concentration oxygen-substitutional

impurities

contained more

of a p e a k i n t h i s m a t e r i a l

is

peak or an

s t a t e that it i s p o s s i b l e

concentration

to

is a s low a s 0.03

t h a n 0.03 at. % s u b s t i t u t i o n a l

impur-

could only mean that insufficient oxygen was pres-

e n t f o r a p e a k to b e r e s o l v e d . Since the oxygen-substitutional the oxygen and substitutional

atom peak height is proportional

atom concentrations

to t h e s q u a r e of t h e o x y g e n c o n c e n t r a t i o n , oxygen concentrations

higher temperatures

while the O-O peak height is proportional

it i s p o s s i b l e

that at low substitutional

an O-O peak could be significant.

d e t e c t e d two p e a k s in t h e i r a l l o y s ,

the first occurring

than the second.

Mishra

and Asundi have,

It i s d i f f i c u l t to d e v i s e a r e l a x a t i o n

to a c c o u n t f o r t h i s a n d a m o r e

low oxygen concentrations

t h e p e a k i s d u e to r e l a x a t i o n O-O pairs may form

will occur about twice as rapidly as the former 977

- high in f a c t ,

at l o w e r o x y g e n c o n c e n t r a t i o n s

which they have suggested

while at high concentrations

to t h e p r o d u c t of

realistic

and

m o d e l of t h e t y p e

m o d e l is a s f o l l o w s .

of o x y g e n - s u b s t i t u t i o n a l

At

atom pairs,

g i v i n g r i s e to a s e c o n d r e l a x a t i o n

which

s i n c e e i t h e r of t h e t w o a t o m s m a y j u m p .

978

R E P L Y TO C O M M E N T S ON " S T R E S S I N D U C E D D I F F U S I O N OF 0 IN A L P H A Zr"

Vol.

S, No.

Ii

T h e associated internal friction peak will therefore occur at a lower temperature than the oxygen-substitutional a t o m relaxation.

It s e e m s probable therefore that M i s h r a and Asundi

have themselves detected O - O pair relaxation similar to that found by Miller and B r o w n e in titanium alloys (3). M i s h r a and Asundi also reject the H f - O pair relaxation as an explanation for the peak which I reported because they m e a s u r e d a peak in Z r - H f alloys at 5 7 0 ° C for a frequency of 1.3 hertz w h e r e a s the reported peak would occur at 4 5 Z ° C for the s a m e ~ibration frequency. Since the latter is closer to the temperature at which they observed a peak in Z r - T i alloys (430°C at 1.3 hertz) they proposed that a T i-O pair relaxation w a s responsible for the peak. T he apparent difference in the temperature ascribed to the H f - O peak m a y be resolved by reference to the w o r k of Gacougnolle, Sarrazin and de Fouquet (4) w h o have recently carried out a c o m p r e h e n s i v e study of the internal friction of Z r - H f - O alloys, of which I w a s u n a w a r e at the time of publication of m y previous paper. Gacougnolle et alia m e a s u r e d grain boundary peaks in zirconium containing various a m o u n t s of hafnium, and found that the temperature of the peak varied f r o m 570 ° to 540°C as the hafnium content increased.

T h e s e w o r k e r s also m e a s u r e d a smaller peak at a tem-

perature of about 4Z0°C, the height of which varied linearly with both oxygen and hafnium concentrations, the latter h o w e v e r only at low concentrations. to be at least partially attributable to H f - O pair relaxation.

This peak certainly appears

It is apparent then, that the

internal friction peak attributed to H f - O pairs by M i s h r a and Asundi has been confused with the grain b o u n d a r y peak, and that the H f - O peak does, in fact, occur at a m u c h lower temperature. It should also be mentioned here that the w o r k of Gacougnolle et alia indicates that a finite peak would occur in an alloy containing zero hafnium and 2 at. ~0 oxygen, which also suggests the presence of an O - O

relaxation in these alloys.

However,

it is also possible

that other substitutional a t o m s w e r e present in concentrations large enough to cause oxygensubstitutional relaxation. In conclusion, the internal friction peak which I reported in zirconium-oxygen alloys containing Z.4% Hf is attributed to H f - O or O - O

relaxation as before since the high tempera-

ture peak which M i s h r a and Asundi ascribed to H f - O relaxation should be interpreted as a grain boundary peak. ibility of an O - O

Furthermore,

the w o r k of M i s h r a and Asundi does not refute the poss-

relaxation but on the contrary, provides further evidence for its existence.

Vol.

S, No.

ii

REPLY TO COMMENTS ON "STRESS INDUCED D I F F U S I O N OF O IN ALPHA Zr"

979

REFERENCES I.

S. Mishra and M . K .

Z. K . M .

Asundi, Scripta Met., this issue.

Browne, Scripta Met., 5, 519, (1971).

3.

D.R. Miller and K. M. Browne, p.401, P e r g a m o n (1970).

"The Science, Technology and Application of Titanium",

4.

J.L. Gacougnolle, S. Sarrazinand J. de Fouquet, C.R. Acad. Sc. Paris, Z70, 158,(1970).