ANELASTIC BEHAVIOR OF COLD ROLLED 304 L STAINLESS STEEL

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ANELASTIC BEHAVIOR OF COLD ROLLED 304 L

STAINLESS STEEL

J . Quiroga, A. de Salva, M. Mondino, A. Lamagna, J.a . Caro

To cite this version:

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JOURNAL DE PHYSIQUE

Colloque C10, supplbment au n012, Tome 46, dbcembre 1985 page C10-661

ANELASTIC BEHAVIOR OF COLD ROLLED 304 L STAINLESS STEEL

J. QUIROGA, A. GHILARDUCCI DE SALVA,M. MONDINO*, A. LAMAGNA AND

J.A. CAR0

Centro ~ t d m i c o Bariloche, 8400 S. C. de Bariloche, Rio Negro,

Argentina

+ Centro ~thrnico Constituyentes, Av. de 10s Constituyentes y

Gral. Paz, 1427 Buenos Aires, Argentina

~esum;

-

Des mesures de f r o t t e m e n t i n t k r i e u r

>

basse frGquence (1Hz e t 30,Hz)

--

s u r 1 T c i e r i n o x y d a b l e 304 L nous permet d ' i d e n t i f i e r deux p i c ~ b i e n separes a s s o c i d s

2

l a phase y deformde e t aux phases m a r t e n s i t i q u e s ( E e t a ' ) i q d u i t e s

p a r d d f o r m a t i o n . Des mesures $ h a u t e fr6quence o n t 6 t d f a i t e s

2

f i n d ' e t u d i e r l ' a c t i v a t i o n t h e r m i q u e des p i c s .

A b s t r a c t

-

I n t e r n a l f r i c t i o n a t l o w frequency ( 1 Hz) on 304 L SS a l l o w s i d e n t i f i c a t i o n o f w e l l separated peaks a s s o c i a t e d w i t h t h e deformed y phase and t o t h e low t e m p e r a t u r e s t r a i n induced m a r t e n s i t i c phases E and a ' .

Measurements a t h i g h frequency were a l s o made i n o r d e r t o s t u d y whether t h e s e peaks a r e t h e r m a l l y a c t i v a t e d o r not.

I

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INTRODUCTION

It i s w e l l known t h a t i n 304 L s t a i n l e s s - s t e e l two m a r t e n s i t i c phases can be induced by c o l d - w o r k i n g (CW). They a r e E (h.c.p.) and a ' (b.c.t.). Because of t h e t e c h n o l o g i c a l i m p l i c a t i o n s o f t h e presence o f a ' and E, m a i n l y concerned w i t h

hydrogen b e h a v i o r /1/2/, i t i s o f g r e a t i n t e r e s t t o know t h e r e l a t i o n s h i p between t h e degree o f d e f o r m a t i o n and t h e volume f r a c t i o n of E and a ' .

Complete d e t e r m i n a t i o n o f volume f r a c t i o n o f a ' phase as a f u n c t i o n o f t e m p e r a t u r e and degree o f CW has been r e p o r t e d by S. Hecker e t a l . /3/ by means o f magnetic p e r m e a b i l i t y measurements and TEM o b s e r v a t i o n s . They compare t h e i r r e s u l t s w i t h t h o s e o f L.E. Murr e t a l . /4/.

P r e v i o u s work by P.L. Mangonon and G. Thomas /5,6/, u s i n g TEM, magnetic p e r m e a b i l i t y and XR d i f f r a c t i o n , determined t h e m i c r o s t r u c t u r a l mechanism r e s p o n s i b l e f o r t h e f o r m a t i o n o f a ' and E phases a f t e r d e f o r m a t i o n a t l i q u i d

n i t r o g & t e m p e r a t u r e (LN) as w e l l as t h e i r volume f r a c t i o n .

Concerning t h e i n t e r n a l f r i c t i o n ( I F ) t e c h n i q u e r e c e n t works by N. I g a t a e t a l . /7,8/ a n a l y z e t h e s p e c t r a o f SS 304 L a t d i f f e r e n t l e v e l s o f CW a t room t e m p e r a t u r e (RT) and LN temperature. The s p e c t r a o b t a i n e d a f t e r CW a t RT - o n l y y phase- show t h r e e peaks: PI, P2 and P3 whose h e i g h t s i n c r e a s e w i t h t h e degree o f CW. The a c t i v a t i o n e n e r g i e s and frequency f a c t o r s were deFermined. On t h e o t h e r hand, t h e s p e c t r a o b t a i n e d a f t e r CW a t LN t e m p e r a t u r e -y, a and E phases p r e s e n t - show an

e n l a r g e d P3 paek. T h i s enlargement i s due t o t h e presence o f a n o t h e r peak p r o b a b l y due t o t h e a ' phase. T h i s o v e r l a p does n o t a l l o w f o r q u a n t i t a t i v e c o n c l u s i o n s

r e l a t i n g t h e peaks t o t h e amount o f phases present.

I n t h i s work we s t u d y t h e peaks o b t a i n e d a f t e r c o l d r o l l i n g -CR- a t LN temperatures. The l o w v i b r a t i o n f r e q u e n c i e s a l l o w us t o s e p a r a t e t h e e f f e c t s a r i s i n g f r o m d i f f e r e n t phases, r e n d e r i n g i t p o s s i b l e t o r e l a t e t h e peak h e i g h t s t o t h e amount o f phases p r e s e n t i n each sample.

EXPERIMENTAL PROCEDURE

11

-

-The I.F. was measured a t f r e q u e n c i e s o f 1 Hz and 30 Hz u s i n g two t o r s i o n

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C10-662 JOURNAL DE PHYSIQUE

pendula and a t 40 kHz u s i n g l o n g i t u d i n a l e x c i t a t i o n . H e a t i n g r a t e o f 1.2"K/minute i n t h e temperature rang of 100°K t o 550°K, t o g e t h e r w i t h d e f o r m a t i o n a m p l i t u d e s always s m a l l e r t h a n i n t o r s i o n and _{i n t h e l o n g i t u d i n a l mode c h a r a c t e r i z e} t h e r e l e v a n t parameters i n a l l t h e runs.

The samples were made o u t of SS 304 L whose chemical c o m p o s i t i o n i s as f o l l o w s :

C Cr Ni

Mn

Si P S

Mo

N 0 Fe

0.026 18 11 1.5 0.42 0.018 0.010 0.07 0.0301 0.01 t h e r e s t

A f t e r quenching f r o m 1300°K t h e samples were g i v e n v a r i o u s amounts o f

d e f o r m a t i o n by s o l d - r o l l i n g near 80°K. The samples f o r 1 Hz and 30 Hz were p l a t e s o f 75x 4 x 1 mm and f o r 40 kHz r o d s 3 mm i n diameter and 60 mm i n l e n g t h .

I 1 1

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EXPERIMENTAL RESULTS

Figt?i-.-aa~Tio~TTl?i-~F

r e s u l t s a t 1 Hz d u r i n g f i r s t h e a t i n g f o r specimens w i t h 3. 9. 15 and 50 oer c e n t o f CR a t 80°K. The c u r v e f o r t h e non deformed m a t e r i a l i s aisorshown f o r cbmparison. The spectrum f o r t h e 3% deformed samples shows two maxima a t about 270°K and 360°K; t h e h e i g h t o f t h e s e maxima i n c r e a s e s w i t h

d e f o r m a t i o n o n l y up t o 15% o f CR and t h e n decreases. A1 so t h e l o c a t i o n o f t h e peaks changes: t h e 270°K peak s h i f t s towards low temperature w h i l e t h e 360°K peak s h i f t s t o h i g h e r temperatures.

The r e s u l t s f o r f r e q u e n c i e s around 30 Hz and f i r s t h e a t i n g a r e p r e s e n t e d i n Fig. 1.b f o r d e f o r m a t i o n of 3, 9, 15 and 50% o f CR a t 80°K. I n t e r e s t i n g e v o l u t i o n o f t h e s p e c t r a i s observed. Samples w i t h 3, 9 and 15% o f

CR

show a b r o a d peak, presumably composed by t h r e e peaks, w h i l e a t h i g h e r d e f o r m a t i o n s (we o n l y show t h e curve c o r r e s p o n d i n g t o 50%) t h e spectrum e v o l v e s t o show two w e l l d e f i n e d peaks a t 230°K and 380°K a t 50% o f

CR.

This r e s u l t i s q u a l i t a t i v e l y s i m i l a r t o t h a t observed a t 1 Hz.

A f i r s t h e a t i n g of samples v i b r a t i n g i n t h e 40 kHz range i s shown i n Fig. 1.c. I n t h i s case t h e spectrum i s composed o f a small peak around 200°K and a wide peak a t around 400°K. Here a g a i n t h e peak h e i g h t s i n c r e a s e w i t h

CR

a t 80 K up t o 10% and t h e n decrease f o r h i g h e r d e f o r m a t i o n . The wide peak i s p r o b a b l y composed o f t h e two h i g h e r t e m p e r a t u r e peaks observed a t 1 Hz and 30 Hz, s i n c e t h a t o f 360°K seems t o be n o t t h e r m a l l y a c t i v a t e d .

As complementary i n f o r m a t i o n , Fig. 1.d shows r e s u l t s a t 30 Hz d u r i n g a second h e a t i n g , a f t e r a s h o r t a n n e a l i n g a t 550°K, consequence o f t h e f i r s t h e a t i n g . The h i g h e s t temperature peak i s u n s t a b l e and anneals-out a t 550°K, w h i l e t h a t o f 280°K i s s t a b l e and i n c r e a s e s w i t h t h e amount o f CR up t o 15%, t h e n decreases

s i g n i f i c a n t l y t o become v e r y s m a l l a t 50% o f CR. I V

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DISCUSSION

C a l l i n g LT, I T and HT o u r peaks c o r r e s p o n d i n g t o low, i n t e r m e d i a t e and h i g h temperature r e s p e c t i v e l y , i t appears e v i d e n t t h a t our I T peak corresponds t o t h e P3 peak o f I g a t a e t a l . /7,8/. The s t r o n g e s t evidence a r i s e s f r o m t h e A r r h e n i u s p l o t , Fig. 2 where our I T peak a t 3 f r e q u e n c i e s i s shown t o g e t h e r w i t h t h e o b s e r v a t i o n s o f I g a t a e t a l . The e v o l u t i o n w i t h r o l l i n g a t 80°K shows, up t o 15%, t h e same

dependence as found by I g a t a e t a l . c o l d - w o r k i n g a t room temperature, b u t f o r h i g h e r d e f o r m a t i o n t h e peak l o w e r s u n t i l i t disappears a t 25% o f CR a t 80°K. T h i s i s i n agreement w i t h t h e phase-diagram o f Hecher e t a l . ( 3 ) which i n d i c a t e s t h a t f o r CW a t 80°K g r e a t e r t h a n 20%, more t h a n 80% o f Y phase has t r a n s f o r m e d i n t o a ' ,

Second h e a t i n g s show t h a t t h i s peak i s s t a b l e below 550°K. We cdnclude t h a t i t i s a cold-work peak i n t o t h e y-phase.

The HT peak shows t h r e e main c h a r a c t e r i s t i c s : i t appears o n l y a f t e r CR a t low temperature, i t i s n o t t h e r m a l l y a c t i v a t e d and i t s dependence w i t h t h e amount o f CR f o l l o w s c l o s e l y t h a t o f t h e E phase, a c c o r d i n g t o t h e phase diagram o f r e f . 6 and o u r f i g . 3. It o n l y suggests t h a t t h i s peak c o u l d be a s s o c i a t e d t o b o t h E o r a '

phase: a l t h o u g h t h e volume f r a c t i o n o f a' i n c r e a s e s w i t h CR w h i l e t h e HT peak s a t u r a t e s , one c o u l d s t i l l t h i n k o f a s a t u r a t i n g mechanism i n a ' f o r t h i s HT peak.

Another p o s s i b i l i t y i t t h a t t h i s peak has c o n t r i b u t i o n s o f both, y , a ' and o phases, s i m u l t a n e o u s l y . It i s suggested b y t h e s h i f t o f t h e temperature o f t h e maximum f o r l a r g e amounts o f CK, as can be seen i n f i g s . 1.a and 1.b. The

e x p l a n a t i o n i n t h i s case would be t h a t E disappears f o r CR l a r g e r t h a n 20%. Second

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P.L. Mangonon and G. Thomas /5/ have shown t h a t a n n e a l i p g a t 473OK ( l 1 l 2 h s ) i n c r e a s e a' and y , d e c r e a s i n g E , and a n n e a l i n g a t 673OK (1 h s ) l e t s a' s t a b l e b u t

E disappears. I n our case f i r s t h e a t i n g r e p r e s e n t s a s h o r t a n n e a l i n g a t t h e

i n t e r m e d i a t e te-mperature of 550°K;. t h e r e f o r e , we c o u l d suppose t h a t b o t h and a'

a r e p r e s e n t and t h a t t h e HT peak i s s e n s i t i v e t o t h e r e c o v e r y o f t h e deformed m i c r o s t r u c t u r e . This peak c e r t a i n l y corresponds t o t h a t observed by I g a t a e t a l .

/8/ as a h i d d e n c o n t r i b u t i o n t o h i s P3 peak i n samples deformed a t LN temperature. He a l s o observed s e l f - a n n e a l i n g a f t e r t w o hours and a h a l f a t 573OK.

F i n a l l y , t h e e v o l u t i o n o f t h e background versus amount o f CR, f i g . 3 i s

i n t e r e s t i n g . Previous r e s u l t s /8/ i n deformed y phase show a low background a t h i g h t e m p e r a t u r e b u t o u r r e s u l t s on deformed y , a' and E phase show a background

i n c r e a s i n g w i t h CR, i n t h e same way t h a t t h e peak a s s o c i a t e d w i t h t h e s e phases i ncreases.

V

-

_-

CONCLUSIONS

_{- -}

_{- - - -}

The I F s p e c t r a a t low f r e q u e n c i e s show t w o w e l l d i f f e r e n t i a t e d peaks, one c l e a r l y a s s o c i a t e d w i t h deformed y-phase and t h e o t h e r w i t h t h e l o w t e m p e r a t u r e s t r a i n induced m a r t e n s i t i c phases.

The i n t e r p r e t a t i o n o f t h e HT peak as a a ' peak supported by t h e r e c e n t o b s e r v a t i o n by K.P. Staudhammer e t a l .

191.

They conclude t h a t t h e morphology o f t b e a' phase changes w i t h d e f o r m a t i o n o v e r 20% o f s t r a i n due t o t h e coalescence o f

a embryos, g o i n g f r o m m i c r o - s h e a r band i n t e r s e c t i o n t o i r r e g u l a r b l o c k arrangements. The s a t u r a t i o n o f o u r HT peak c o u l d b e due t o t h i s phenomenon.

Complementary s t u d i e s a r e b e i n g pursued t o b e t t e r understand t h e s p e c i f i c r o l e of a' and E phases i n t h e appearance o f t h e HT peak.

t2

--r

OD/. 0 100 150 200 250 306 350 LOO L50 500 5 9 TEMPERATURE

rK]

a

8 - 7 7 -

I-

6 -

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V 5 -

'

1 0 I I I I I I I

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100 150 200 250 300 350 LOO L50 500 5% TEMPERATURE PK] " - 10 9 7 6 - 5 4 - 3 2 I t ,' \ , ,,.-,.. \, ,* ,... I' i l

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1,' - <rT,--:z-..-..- : / \ '\. F i g . 1: I F s p e c t r a o f samples w i t h d i f f e r e n t amounts o f c o l d r o l l i n g a t 80°K. a

,

b ) and c ) : f i r s t h e a t i n g a t 1 Hz, 30 Hz and 40 k Hz r e s p e c t i v e l y ; d l : second h e a t i n g a t 30 Hz. FIRST HEATING AT 30 Hz 15'/,,, (b) ,

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0 - 1 1 1 I I l l I 100 150 200 250 300 350 LOO L50 500 550 1 ...-7.-

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TEMPERATURE P K ]

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JOURNAL

D E PHYSIQUE

PER C E N T O F C.R

Fig. 2

-

Arrhenius p l o t f o r t h e I T peak; t t i i s work: closed c i r c l e s ; I g a t a r e s u l t s ( 8 ) : open c i r c l e s .

3 I n t e r n a l f r i c t i o n background a t Ei8'OK and maxima o f the peaks as a f u n c t i o n o f the amount o f c o l d r o l l i n g a t 80°K.

REFERENCES

( 1 ) N. Igata, H.B. Chen and K. Miyahara, S c r i

.

Met. 16, 169 (1982). ( 2 ) J.P. H i r t h . Met. Transac. A 11, 861 (1980!

-

( 3 ) S.S. Hecker, M.G. Stout, K.Y.Staudhammer and J.L. Smith.

Met.

Transac. A

13,

619 (1982).

(4)

L.E. Murr, K.P. Staudhammer and S.S. Hecker. Met. Transact. A

13,

627

(1982).

( 5 ) P.L. Mangonon and G. Thomas. Met. Transac. A 1, 1577 (1970).

(6)

P.L. Mangonon and G. Thomas. Met. Transac. A . 7 , 1587 (1970).

( 7 ) N. Igata, H.B. Chem., K. l ~ l y a h a r a and T. Wa, J. de Physique (Proc. o f ICIFUAS-7, J u l y 1981, Lausanne, Switzerland, E d i t e d by W. Benoit and G. Gremaud)

,

C5-193 (1982).