INVESTIGATION OF THE DISTRIBUTION AND THE STATE OF SMALL AMOUNT OF RARE EARTH ELEMENTS IN PURE IRON BY THE METHOD OF INTERNAL FRICTION

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INVESTIGATION OF THE DISTRIBUTION AND

THE STATE OF SMALL AMOUNT OF RARE

EARTH ELEMENTS IN PURE IRON BY THE

METHOD OF INTERNAL FRICTION

Li Wern-Bin, Liu Zheng-Qun, Yang Quo-Ping, Li Cheng-Hsiu, Zhang Bin

To cite this version:

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JOURNAL DE PHYSIQUE

CoZZoque C5, suppze'ment au nO1O, Tome 4 2 , octobre 1981 page C5-463

I N V E S T I G A T I O N OF THE D I S T R I B U T I O N AND THE STATE OF SMALL AMOUNT OF RARE EARTH ELEMENTS I N PURE IRON BY THE METHOD OF INTERNAL F R I C T I O N

Li Wern-bin, Liu Zheng-qun, Yang Quo-ping, L i Cheng-hsiu and Zhang B i n

Beijing University o f Iron & SteeZ TechnoZogy

ABSTRACT.- Eleven k i n d s of pure i r o n specimens dopted with a s m a l l amount of r a r e e a r t h elements were used i n p r e s e n t research. In- t e r n a l f r i c t i o n s were measured with a t o r s i o n pendulum. Experi- mental r e s u l t s s h ~ w e d that t h e n i t r o g e n Snoek peak becomes broadened and t h e optimum i n t e r n a l f r i c t i o n s h i f t s t o a h i g h e r tem- p e r a t u r e . When t h e r a r e e a r t h elements a r e i n c r e a s e d t h e n i t r o g e n peak t e n d s t o s e p a r a t e i n t o two p a r t s . I n g e n e r a l , t h e h e i g h t of n i t r o g e n Snoek peak d e c r e a s e s with t h e i n c r e a s e of rase e a r t h c o n t e n t s .

On t h e b a s i s of t h e experimental r e s u l t s i t i s suggested t h a t the r a r e e a r t h elements i n t h e i n t e r i o r o f pure i r o n g r a i n s is i n a s t a t e o f s o l i d s o l u t i o n .

The high temperature i n t e r n a l f r i c t i o n s were measured i n two pure i r o n specimens c o n t a i n i n g d i f f e r e n t c o n t e n t of Lanthanum. Two i n t e r n a l f r i c t i o n peaks were o b t a i n e d i n each specimen. One i n t e r n a l f r i c t i o n peak around 550'C i s t h e g r a i n boundary peak of pure i r o n , while t h e o t h e r i n t e r n a l f r i c t i o n peak around 700°C i s a new one.

A f t e r t r e a t i n g one of t h e above two specimens i n t o very l a r g e g r a i n s i n specimen both t h e i n t e r n a l f r i c t i o n peaks of pure i r o n and new one were a l l o d i s a p p e a r e d . Only the pure i r o n g r a i n boundary peak around 500 C w a s observed i n t h e pure i r o n specimen c o n t a i n i n g no r a r e e a r t h elements. Therefore, t h e new i n t e r n a l f r i c t i o n peak may be a s s o c i a t e d with t h e g r a i n boundary which ad-

sorbed a small amount of r a r e e a r t h elements.

Based on t h e r e s u l t s p r e s e n t e d as above, i t may be concluded t h a t t h e r a r e e a r t h elements i n pure i r o n d i s t r i b u t e not only i n t h e i n t e r i o r o f g r a i n s i n a s t a t e of s o l i d s o l u t i o n , but a l s o se- g r e g a t e s l i g h t l y a t t h e g r a i n boundary a r e a i n a s t a t e of adsorp- t i o n .

1. Introduction.- The a p p l i c a t i o n s o f r a r e e a r t h elements t o i n d u s t r y o f i r o n and s t e e l a r e very e x t e n s i v e ( 1 . 2 ) . However t h e mechanism o f phy- s i c a l phenomena i s s t i l l i n ambiquity, e s p e c i a l l y t h e fundamental i d e a about t h e d i s t r i b u t i o n and t h e s t a t e of a s m a l l amount o f r a r e e a r t h elements i n i r o n and s t e e l are s t i l l i n argument.

I n t h e p a s t , q u i t e a number o f i n v e s t i g a t i o n s (3-6) had showed t h a t i n t e r n a r y n i t r o g e n - f e r r i t e a l l o y systems, because of t h e i n t e r a c - t i o n between s u b s t i t u t i o n a l and i n t e r s t i t i a l s o l u t e s , t h e n i t r o g e n Snoek peak becomes broader and t h e optimum temperature s h i f t s t o a h i g h e r tem- p e r a t u r e , sometimes t h e peak even t e n d s t o s e p a r a t e i n t o s e v e r a l compo- n e n t r e l ~ x a t i o n s . I n g e n e r a l , t h e h e i g h t of t h e peak d e c r e a s e s w i t h t h e i n c r e a s e of a l l o y i n g elements c o n t e n t s . These i n v e s t i g a t i o n s have g i v e n important i n f o r m a t i o n on t h e n a t u r e of s u b s t i t u t i o n a l and i n t e r - s t i t i a l s o l u t e s i n t e r a c t i o n i n t h e i n t e r i o r o f g r a i n .

A f t e r t h e i n t e r n a l f r i c t i o n peak of g r a i n boundary was first

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C5-464 JOURNAL DE PHYSIQUE

observed i n pure p o l y c r y s t a l by

K6

( I 1 , 1 2 ) , q u i t e a number of i n v e s t i - g a t i o n s i n t h i s f i e l d were followed (13-T5). Pearson and Rotherham ( 1 6 ) found t h a t f o r h i g h e r valency s o l u t e s c o n t e n t n e a r l y

15,

t h e o r i g i n a l g r a i n boundary peak f o r t h e FCC pure m e t a l s (PM peak! i a s u ~ p r e s s e d , and a new s o l i d s o l u t i o n peak (SS peak) t h e n appeprs a t h i g h e r temperzture. The a c t i v a t i o n e n e r g i e s f o r t h e SS peal: i n a l a r g e number of FCC m e t a l s o l u t i o n s a r e a l l g r e a t e r t h a n t h a t of c o r r e s p o n d i n g PM peak and n e a r v a l u e c h a r a c t e r e s t i c of s e l f - d i f f u s i o n f o r a l l o y mentioned (16-17). Barrand (1 8 ) h a s o b t a i n e d a PM and a SS peak i n BCC Fe-Cr a l l o y s , where t h e SS pe(8.k a g a i n showed a n a c t i v a t i o n e n e r g i e s a r e a l s o g r e a t e r t h a n t h a t of PM peak and c l o s e t o t h a t f o r i t s s e l f - d i f f u s i o n .

I n t h i s paper a t t e m p t i s made t o f i n d t h e dependence of t h e change of n i t r o g e n Snoek peak and g r a i n boundary peak i n pure i r o n c o n t a i n i n g a s m a l l amount of r a r c e a r t h elements. I n o r d e r t o s t u d y t h e d i s t r i b u t i o n and t h e s t a t e of a small amount a d d i t i o n s . Although few s t u d i e s had been examined, i t only d e a l t w i t h t h e e f f e c t of t h e s e a d d i t i o n s , but t h e d i s t r i b u t i o n and t h e s t a t e o f r a r e e a r t h e l e m e n t s i n i r o n a ~ d s t e e l r e l a t e d t o t h e change of n i t r o g e n Snoek peak and ob- s e r v a t i o n of SS g r a i n boundory peak were excluded from c o n s i d e r a t i o n (8-1 0 ) .

2. Exgeriroental Methods.

-

I n t e r ~ a l f r i c t i o n measurements were c a r r i e d o u t i n K'f's pendulum p r e v i o u s l y d e s c r i b e d ( 5 , 1 1 , 12). The c h i e f specimens used i n t h e experiment were prepared f r o n pure i r o n , p u r i f i e d by e l e c t r o n bombardment and dopted w i t h a s m a l l amount of pure s i n g l e r a r e e a r t h e l e m e n t s i n d i f f e r e n t c o n t e n t s (1. pure i r o n c o n t a i n i n g no r a r e e a r t h , 2. 0.002 w t % La, 3. 0.009 we& La, 4. 0.06 W% La, 5. 0.006 W% Ce, 6. 0.28 wi$ Ce, 7. C.049 wt$ Y, 8. 0.28 W* Y ) . Another specf- meno were prepared from Armco i r o n c o n t a i n i n g a s m a l l amount of mixed r a r e e a r t h e l e t i e n t s (Armco i r o n . c o n t a i n i n g 0.035 Re, 0.1 6 W@, Re).

These two k i n d s of specimens were drawn t o w i r e s about 1 rnrn i n d i a m e t e r throqqh a s e r i e s of d i e s from c i x * c u l a r r o d s w i t h 8 m i n d i a - meter.

I n o r d e r t o remove carbon and n i t r o g e n c o n t a i n e d i n tlz specimens all t h e e l e v e n specimens were a n n e a l e d i n an atmosphere of wet hydrogen a t 720" C f o r 46 h r s and t h e n quenched i n t o water. L f t e r adding n i t r o - gen, e x c e p t specimen 4, a l l t h e speci.mens were t r e a t e d a t 580°C i n a m i x t u r e of d r y hydrogen and ammonia (1 NH3:1H2 by volume) f o r t h r e e hours. Homogenizatior, were c a r r i e d o u t by h e a t i n g i n an atmosphere of argon and t h e n quenched i n c016 w a t e r ( 5 , 6 ) .

Every experiment€' c u r v e s w a s r e p e a t e d f o r s e v e r a l t i m e s under t h e s a n e c o n d i t i o n u n t i l t h e same i n t e r n a l f r i c t i o n curve w a s o b t a l n e d a c c u r a t e l y .

3. Experimental. R e s u l t s and Discussior,.-

( I ) Changes of n i t r o g e n Snoek peal: by means of a d d i n g r a r e e a r t h e l e - ments

I n t e r n a l f r i c t i o n as a f u n c t i o n of temperature were measured f o r specimen 1,2,3. The v i b r a t i o n a l f r e q u e n c i e s used were 1 .l 2 Hz, 1 .l 5 Hz,

1.15 Hz f o r specinens 1,2,3, r e s p e c t i v e l y . A s e t of i n t e r n a l f r i c t i o n c u r v e s were o b t a i n e d as shown i n Fig.1. Experimental. r e s u l t s demons- t r a t e t h a t t h e n i t r o g e n Snoek peaks become broadened and t h e optimum i n t e r n a l f r i c t i o n s h i f t t o a h i g h e r temperature, When the Lanthanum a r e i n c r e a s e d t h e n i t r o g e n Snoek peak t e n d s t o s e p a r a t e i n t o two p a r t s . The h e i g h t of n i t r o g e n Snoek peak d e c r e a s e s f o r specimen 3 w i t h 0.009

wt$o of Lanthanum c o n t e n t s . Thowh t h e h e i g h t o f i n t e r n a l f r i c t i o n peak

of specimen 2 w i t h 0.002 W% of Lanthanum is i n appearance l a r g e r t h a n t h a t of specimen 1. It may be t h e o v e r a l l of two peaks.

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o f v i b r a t i o n l

.le

Hz was used f o r specimen

5

and 6. Excepting t h e n i - t r o g e n Snoek peaks broadening, s e p a r a t i n g and t h e optimum i n t e r n a l f r i - c t i o n s h i f t i n g t o t h e h i g h e r temperzture they a r e a l l s i m i l a r t o t h o s e mentioned above r e s u l t s . The h e i g h t of Snoek peaks d e c r e a s e d o b v i o u s l y w i t h an i n c r e a s e of Cerium c o n t e n t s .

When Yttrium nnd mixed r a r e e a r t h i n s t e a d of Lanthanum o r Cerium i n specimens, t h e n i t r o g e n Snoek peaks were o b t a i n e d as shown i n Fig.3. and Fig.4. The r e s u l t s a r e a l l similar t o t h a t a s shown i n Fig.?. and Fig.2. I n o r d e r t o a v c i d t h e e f f e c t of n i t r o g e n p r e c i p i t a t i o n , t h e

t r e a t m e n t of specimen and measurement of i n t e r n a l f r i c t i o n were k e p t i n same procedure as mentioned above.

Based on t h e above e x p e r i m e n t a l r e s u l t s , i t may be concluded t h a t t h e n i t r o g e n Snoek peak becomes broadener, s h i f t s t h e optinlum i n t e r n a l f r i c t i o n t o h i g h e r temperature and d e c r e a s e s t h e h e i g h t of t h e i n t e r n a l f r i c t i o n peak by adding a small amount of r a r e e a r t h elements i n pure i r o n specimen a r e g e n e r a l r u l e s .

E v i d e n t l y , t h e s e broadener peaks can n o t be i n t e r p r e t e d i n terrcs of a s i n g l e r e l a . x a t i o n time and consequently a number of r e l a x a t i o n pro- c e s s e s a r e assumed t o c o n t r i b u t e t o t h e o v e r a l l damping.

Therefore, i t may be suggested t h a t r a r e e a r t h elements i n pure i r o n d i s t r i b u t e i n t h e i n t e r i o r o f t h e g r a i n , and p r e s e n t i n a s t a t e of s u b s t i t u t i o n a l s o l i d s o l u t i o n s . These phenomena a r e s i m i l a r t o t h o s e of o t h e r s u b s t i t u t i o n a l a l l o y e l e m e n t s c o n t a i n i n g i n pure i r o n as pre- v i o u s l y r e p o r t e d (4-7). When t h e Fe-Re specimen i s n i t r i d e d under s u i - t a b l e c o n d i t i o n s , t h e solute-atom p a i r s and c l u s t e r s a r e proiruced i n t h e i n t e r i o r of g r a i n s by t h e i n t e r a c t i o n between t h e s u b s t i t u t i o n a l s o l u t e atom of r a r e e a r t h and i n t e r s t i t i a l s o l u t e atom o f n i t r o g e n . The n i t r o g e n Snoek peak and i n t e r a c t i o n peak: were c a r r i e d o u t due t o s t r e s s - i n d u c e d o r d e r i n g of n i t r o g e n atoms and r o t a t i n g of atomic p a i r s and c l u s t e r s forming v a r i o u s component r e l a x a t i o n s . The bro-aderling of Snoek peak by Re a d d i t i o n i n pure i r o n can be i n t e r p r e t e d consequently by the s u p e r p o s i t i o n of t h e s e v a r i o u s component r e l a x a t i o n s .

( 2 ) Observation of new i n t e r n a l f r i c t i o n peak

The h i g h tempereture i n t e r n a l f r i c t i o n of specimen 4 (0.06 w v o L a ) a f t e r removing t h e carbon and n i t r o g e n w a s measured. I n o r d e r t o avoid o x i d a t i o n thn specimen was k e p t i n t h e atmosphere 02 argon from b e g i n i n g t o end on t h e measurement. Two i n t e r n a l f r i c t i o n peaks were observed as shown i n r'ig.5. The curve 1 w i t h i n t h e f i g u r e was o b t a i n e d by the o r i g i n a l . d a t a . The curve 2 d e n o t i - . g t h e h i g h temperbture background may be considered as a n e a r l y e x p o n e n t i d f u n c t i o n of I / T whei-e T i s t h e aF- s o l u t e tempereture. T h i s curve was o b t a i n e d from t h e r e l a t i o n (19-21)

Q-'

= A exp (-U/KT),

Where t h e parameters A & U a r e t a k e n frorn e x p e r j m e n t a l d a t a . The curves 3 a r e t h e i n t e r n a l f r i c t i o n as a f u n c t i o n of 1/T a f t e r s u b t r a c t i o n of t h e background a s curve 2 from curve 1 , two i n t e r n a l f r i c t i o n peaks appear v e r y c l e a r l y . One i n t e r n a l f r i c t i o n peak around 570°C w i t h t h e frequency 0.73 Hz may be the g r a i n boundary peak of puxe i r o n ( i . e . FM peak), i t s a c t i v i a t i o n energy deducing from t h e s h i f t of t h e peak tern- p e r a t u x e w i t h frequency is 2.68 ev. The o t h e r i n t e r n a l f r i c t i o n peak around 7 0 7 ' ~ w i t h t h e frequency of v i b r a t i o n 0.04 Ilz is a ncri one. i t s a c t i v i a t i o n energy determined e x p e r i n l e n t a l l y i s 3.68 ev.

When t h e i n t e r n a l f r i c t i o n of a pure i r o n specimen c o n t a i n i n g no r a r e e a r t h e l e m e n t s w a s measured. Only one i n t e r n a l f r i c t i o n peak was observed a t n e a r l y 476'C with frequency 0.37 &, as shown i n Fig.6. I t i s e v i d e n t l y t h e g r a i n boundary peak of pure i r o n ( i . e . PM peak). The p r e v i o u s specimen 4 thoroughly annealed i n t h e atmosphere of argon a t 1000' C f o r e i g h t hours, i t s grairr became v e r y l a r g e , t h e n t h e i n t e r n a l f r i c t i o n was measured, t h e above two i n t e r n a l f r i c t i o n peaks d i s a p p e a r e d completely as shown i n Pig.7.

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CS-466 JOURNAL DE PHYSIQUE

i r o n c o n t a i n i n g r a r e e a r t h elements may be a s s o c i a t e d with t h e g r a i n boundary and concerned with t h e s e g r e g a t i o n o f r a r e e a r t h a t t h e g r a i n boundary area, And s o t h e new i n t e r n a l f f r c t i o n peak is a g r a i n boundary peak i.e. a s o l i d s o l u t i o n peak (SS peak) a p p e a r s as i n o t h e r s u b s t i t u - t i o n a l a l l o y s (18, 21 ).

The i n t e r n a l f r i c t i o n of'specimen 3 (pure i r o n c o n t a i n i n g 0.009 W% La), w a s measured i n same procedure under same c o n d i t i o n s as above,

A s i m i l a r r e s u l t s was obtained, as expressed i n Fig.8. Two i n t e r n a l f r i c t i o n peaks were observed a l s o . One of them a p p e a r s a t n e a r l y 5 4 6 ' ~ with frequency 0.93 Nz and a c t i v a t i o n energy 2.5 ev. I t i s t h e i n t e r n a l f r i c t i o n peak of g r p i n boundary i n pure i r o n ( i . e . PM peak), Another peak a p p e a r s a t 689 C with frequency 0.79 Hz, and a c t i v a t i o n energy 3.9

ev. It m a y be t h e s o l i d s o l u t i o n peak (i.e. SS peak) concerned w i t h

r a r e e a r t h .

Based on t h e r e s u l t presented as above, i t may be concluded t h a t t h e r a r e e a r t h elements i n pure i r o n d i s t r i b u t e n o t only i n t h e i n t e r i o r of g r a i n s i n a s t a t e of s o l u t i o n , b u t a l s o s e g r e g a t e s l i g h t l y a t t h e g r a i n boundary a r e a i n a s t a t e of a d s o r p t i o n .

F i n a l l y , the a u t h o r s wish t o e x p r e s s t h e i r deep g r a t i t u d e t o p r o f e s s o r T.S.K$ f o r many h e l p f u l d i s c u s s i o n s and d i r e c t i o n s i n t h i s work.

4. References.

-

1 . S t u d i e s of A p p l i c a t i o n s of Rare E a r t h t o I r o n and S t e e l . B e i j i n g I n s t i t u t e of I r o n and S t e e l Technology, 1978.

2. Odd B. Michelsen, Analysis and A p p l i c a t i o n of Rare E a r t h Naterials. Noto Advanced Study I n s t i t u t e K j e l l e r Norway, 23rd-29th August 1972, 3. D i j s k t r a , L.J., Trans. AIME, 197 (1953) 69.

4. F a s t , J.D., P h i l i p s Research Reports 8 (1953) 1 . 5. K$ Ting-sui, S c i e n t i a l S i n i c a , 4 (1 955) 263.

6. Pope, M. e t al., ICIFUACS-5 Springer-Verlag, B e r l i n (1975) 266. 7. Swartz, J.C., Trans. AIME 245 (1969) 1083.

8. Sagues, A.A. and Gibala, R., S c r i p t a Met. 5 (1 971 ) 689.

9. Sagues, A.A. and Gibala, R., ICIFUACS-5, Springer-Verlag, B e r l i n , 1 (1975) 189.

10. You Miao, Acta Physica S i n i c a 23, (1 974) 293, l . K , S . , Phys.Rev. 71, (1947) 533.

12. K&, T.S., Phys.Rev. 72 (1947) 41.

13. Leak, C.M., Proc. Phy. Soc. 78 (1961) 1521. 14. Ratherhani e t al., Trans. AIME, 206 (1956) 381. 1 5. Weinig, S. ?. e t al., Trans. A I F E , 207 (1 956) 32. 16. Pearson, S. e t al., Trans. AIME, 206 (1956) 894.

17. Schnitzel,R.H., Met.Soc. Conf. (Reactive Metals) (1959) 245-263. 18. Barrand,P. Acta Met., 14 (1966) 1249.

19. Sch0ech.G. e t al., Acta Met. 12 (1964) 1460.

20, Wang Yen-ning e t al., Acta Physica S i n i c a 22 ( 1 966) 647.

21, Woirgard J. e t al., ICIFUACS-5 Springer-Verlag,Berlin, 1 (1 975)392. 22. Smith C .C. e t al., ICIFUACS-5 Springer-Verlag, B e r l i n , 1 ( 1975) 387. 23. Chadwick C.A. e t al., Grain Boundary S t r u c t u r e and P r o p e r t i e s ,

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T e m p e r a t u r e ( C )

F

70 I 50 1 I d I

L

_iI ₃ , L _c ₄ 1oon1T

Fig. 1 . T h e Snoek peaks of nitrogen in p u r e i r o n containing v a r i o u s a m o u n t of lanthanum: ( X ) p u r e iron, f = 1.12 Hz. ( A ) 0.002 w t % L a , f = 1 . 1 5 Hz. (0) 0.009 w t % L a , f = 1 . l 3 Hz. T e m p e r a t u r e ( " C ) & 'P 1 I I0 _t 30 I

1

OM-

-

I

S?

c! 0 nw- .- U U .4 h C

-

_m S. m:- A

-

A M! T e m p e r a t u r e ("C ) l 10 I 30 t m l

-

- - lOOO/T

Fig. 2 . T h e Snoek p e a k s of nitrogen in p u r e iron containing v a r i o u s a m o n n t of cerium: ( X ) p u r e i r o n , f = l . 12 Hz. ( A ) 0.006 w t % c e , f = 1.18 Hz. (0) 0 . 1 8 wt% C e , f = 1.18 Hz. T e m p e r a t u r e ( .C f 1 o o o / T lOOO/T

Fig. 3. T h e Snoek p e a k s of nitrogen

Fig. 4 . T h e Snoek p e a k s of nitrogen

i n p u r e i r o n containing v a r i o u s a m o u n t _{in A r m c o iron containing v a r i o u s a m o n u t}

of y t t r i u m : _{of mixed r a r e earth:}

( X ) p u r e iron, f = I . 12 Hz.

( X ) A r m c o iron, f = 1.27 Hz. ( A ) 0.049 w t % Y, f = 1:2U Hz. _{( A )}_0.035_{w t %}_{Re, f = 1 . 2 3}_Hz.

(7)

JOURNAL DE PHYSIQUE

T e m p e r a t u r e ( 'C ) T e m p e r a t u r e ( @ )