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THE DYNAMIC FRACTURE OF TWO PHASE ALLOYS WITH SECOND PHASE INCLUSIONS
S. Pytel, L. Wojnar
To cite this version:
S. Pytel, L. Wojnar. THE DYNAMIC FRACTURE OF TWO PHASE ALLOYS WITH SEC- OND PHASE INCLUSIONS. Journal de Physique Colloques, 1985, 46 (C5), pp.C5-251-C5-255.
�10.1051/jphyscol:1985533�. �jpa-00224764�
T H E D Y N A M I C FRACTURE O F TWO P H A S E A L L O Y S W I T H SECOND P H A S E I N C L U S I O N S
S. pytel* and L. Wojnar
I n s t i t u t e o f Material Science-M2, Cracow Technical U n i v e r s i t y , AZ.Planu 6-Zetniego 19A, Cracow, Poland
R6sum6: - T r o i s a c i e r s a m a t r i c e f e r r i t i q u e a v e c d e s s i l i c a t e s e t s u l f u r e s comme i n c l u s i o n s d e deuxisme p h a s e o n t Q t Q e x a m i n 8 s . O n a e f f e c t u g d e s e s s a i s p o u r comparer l e s phgnomsnes m i c r o s t r u c t u r a u x s e p r o d u i s a n t l o r s du p r o c e s s u s d e d 6 f o r m a t i o n dynamique. L ' i n t r o - d u c t i o n d u r a p p o r t d e c r o i s s a n c e d e s v i d e s v a p e r m i s l a d e s c r i p t i o n q u a n t i t a t i v e du p r o c e s s u s d e c r o i s s a n c e d e s v i d e s e t l ' e s t i m a t i o n d e l ' e f f e t d e v i t e s s e d e d g f o r m a t i o n .
A b s t r a c t : - T h r e e s t e e l s b a s e d on f e r r t i c m a t r i x w i t h s i l i c a t e s and s u l p h i d e s a s t h e s e c o n d p h a s e i n c l u s i o n s were examined. To compare t h e m i c r o s t r u c t u r a l phenomena o c c u r i n g d u r i n g s t a t i c and dynamic d e f o r m a t i o n p r o c e s s t h e t e n s i l e t e s t s were c a r r i e d o u t . I n t r o d u c e d v o i d g r o w t h r a t i o u a l l o w e d t h e v o i d growth p r o c e s s t o be d e s c r i b e d q u a n t i t a t i v e l y a n d t h e s t r a i n r a t e e f f e c t t o b e e s t i m a t e d .
I . - IKTRODUCTION
The p r e s e n c e o f t h e n o n - m e t a l l i c i n c l u s i o n s i n a low c a r b o n s t e e l c a u s e s a m a j o r c h a n g e on i t s d u c t i l i t y and a n i s o t r o p h y o f t h e mechani- c a l p r o p e r t i e s . T h i s phenomena i s w e l l e s t a b l i s h e d q u a l i t a t i v e l y , however q u a n t i t a t i v e r e l a t i o n s h i p between m i c r o s t r u c t u r e of s t e e l and i t s t o u g h n e s s i s s t i l l e l u s i v e f o r dynamic f r a c t u r e p a r t i c u l a r l y .
P r e v i o u s r e s e a r c h c o n c e r n i n g f r a c t u r e o f a l l o y s composed o f a p l a s t i c m a t r i x w i t h t h e h a r d s e c o n d p h a s e i n c l u s i o n s showed t h a t d u r i n g d e f o r m a t i o n p r o c e s s one c a n n o t i c e t h r e e c h a r a c t e r i s t i c s t a g e s a s f o l l o w s C l ] :
I . - n u c l e a t i o n o f m i c r o - c r a c k s i n s i d e p a r t i c l e s on v o i d f o r m a t i o n a t t h e p a r t i c l e s - m a t r i x boundary
11. - l o c a l c r a c k ( o r v o i d ) g r o w t h w i t h o u t f a i l u r e of m a t r i x between n e i g h b o u r p a r t i c l e s
111. - m i c r o - c r a c k c o a l e s c e n c e a s a r e s u l t t h e l o s s o f m a t r i x c o h e s i o n l e a d i n g t o t h e t o t a l f a i l u r e o f a specimen
I n t r o d u c i n g t h e v o i d g r o w t h r a t i o - U d e f i n e d f o r a c o l l e c t i o n of p a r t i c l e s a s f o l l o w s C21
where : d s - e l e m e n t a r y i n c r e a s e o f t h e mean t r u e s t r a i n o f v o i d d$ - e l e m e n t a r y i n c r e a s e o f t h e mean t r u e s t r a i n o f specimen one c a n d e s c r i b e q u a n t i t a t i v e l y t h e n u c l e a t i o n and v o i d growth p r o c e s s d u r i n g d e f o r m a t i o n o f s t e e l . T h e r e a r e some p r o p o s i t i o n s d e s c r i b i n g t h e r a t i o u [ 3 , 4 ] . T h e s e f u n c t i o n s a f t e r b e i n g p u t i n t o r e l a t i o n (1) a n d i n t e g r a t i o n g i v e t h e v o i d g r o w t h r e l a t i o n s h i p a s e = F ( u ) . I n o u r p a p e r w e assume t h a t u = ~ = c o n s t a n d t h e n f i n a l l y
& = K . U ( 2 )
University of Pittsburgh, Metallurgical Engineering Department, 848 Benedum Hall, Pittsburgh, PA. 15261, U.S.A.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1985533
C5 -25 2 JOURNAL DE PHYSIQUE
11. - EXPERIMENTAL METHODS
As m a t e r i a l s f o r i n v e s t i g a t i o n s t h r e e low c a r b o n s t e e l s ( a b o u t 0,1%C) were u s e d ( d e s i g n a t e d i n t h i s r e p o r t by A , B a n d C). M a t e r i a l s A a n d B h a v e b e e n i n v e s t i g a t e d i n t h e a s - c a s t c o n d i t i o n s w h i l e s t e e l C h a s b e e n h o t r o l l e d a t two d i f f e r e n t t e m p e r a t u r e s (1100K a n d 1500K).
T h i s s t e e l was marked i n o u r p a p e r a s Cl a n d C 2 r e s p e c t i v e l y . A l l s t e e l s h a d a two p h a s e s t r u c t u r e composed o f a f e r r i t i c m a t r i x ( w i t h t r a c e q u a n t i t y o f p e a r l i t e ) a n d n o n - m e t a l l i c i n c l u s i o n s which were i n d e n t i f i e d a s f o l l o w s :
A - g l o b u l a r MnS(type I ) , B - e u t e c t i c MnS ( t y p e I I ) , C - g l o b u l a r ( F e , Mn) - s i l i c a t e s , C 2 - e l o n g a t e d ( S e , Mn) - S i l i c a t e s
F l a t , o n e s i d e p o l i s h e d specimens underwent s t a t i c t e n s i l e t e s t s u s i n g t h e a u x i l i a r y equipment mounted o n t h e t a b l e o f a m e t a l l o - g r a p h i c y i c r o s c p e [ 5 1 . During s t a t i c t e n s i l e t e s t
~ 2 . 1 0 - s e c
.-'
t h e l o a d - d i s p l a c e m e n t c u r v e s were r e c o r d e d . The'S s t e e l C2 ( w i t h e l o n g a t e d s i l i c a t e s ) was t e s t e d i n t h e two d i r e c t i o n s , p a r a l l e l a n d p e r p e n d i c u l a r t o t h e r o l l i n g d i r e c t i o n o f s t e e l . I n a d d j t i ~ n ~ u s i n g a s p e c i a l e x p l o s i v e d e v i c e C61 t h e dynamic t e n s i l e t e s t s ( Y d z 1 0 s e c . - l ) were c a r r i e d o u t . During s t a t i c t e n s i l e t e s t s t h e i n c r e a s e o f a n a v e r a g e v o i d s i z e was measured a n d t h e r a t i o
U f o r t h i r t y randomly c h o s e n i n c l u s i o n s was c a l c u l a t e d . These r e s u l t s a r e shown i n F i g . 1. I n t h e c a s e o f t h e dynamic l o a d e d s a m p l e s t h e c o n t i n u o u s measurements were i m p o s s i b l e and t h e r e f o r e a n e s t i m a t i o n o f v o i d s i z e were made a f t e r r u p t u r e o f m a t e r i a l o n l y ( i n v i c i n i t y o f f r a c t u r e s u r f a c e ) . The v o i d growth r a t i o u was e s t i m a t e d on t h e b a s i s o f t h e s e measurements a n d t h e mean v a l u e o f u a n d i t s s t a n d a r d d e v i a t i o n a r e shown i n T a b l e 1 f o r a l l s t e e l s t e s t e d .
T a b l e l'. Value o f r a t i o U f o r s t a t i c a l l y and d y n a m i c a l l y l o a d e d s a m p l e s
\I - symLol o f p d r a l l e l d i i e c t i o n , i - Symbol d f d i r e &
t i o n I n a d d i t i o n a l l t e s t e d s p e c i m e n s were c a u t i o u s l y examined w i t h t h e u s e o f SEM a n d some examples o f c r a c k s o r v o i d s i n t h e v i c i n i t y o f n o n - m e t a l l i c i n c l u s i o n s d i f f e r e n t s h a p e and t y p e a r e g i v e n - F i g . 2 .
Symbol o f s t e e l
111. - DISCUSSION AND CONCLUSIONS
A 2,7-0,63 +
36-0,82 +
s t r a i n r a t e - l
[ s e c I
D e t a i l e d m i c r o s c o p i c o b s e r v a t i o n s showed t h a t d u r i n g s t a t i c t e n s i l e t e s t s t h e v o i d n u c l e a t i o n s t a r t e d i n t h e v i c i n i t y o f s u l p h i d e s I a n d I1 t y p e (mat. A a n d B) and a l s o compact s i l i c a t e s ( m a t . Cl) a t a t r u e s t r a i n q~-0.0018-0.05 ( e a l i e r f o r l a r g e r p a r t i c l e s ) . I n c r e a s e o f sample l o a d i n g c a u s e d growth o f t h e s e v o i d s which became a n
e l i p s o i d a l s h a p e - F i g . 2 a , b . For m a t e r i a l C 2 v o i d n u c l e a t i o n i n t h e p e r p e n d i c u l a r d i r e c t i o n a p p e a r e d e a r l i e r a n d s t r a i n s i n t h e r a n g e of q ~ ~ 0 , 0 1 2 + 0 , 0 0 1 5 were l a r g e enough t o o b s e r v e some t r a c e s o f d i s c o n - t i n u i t i e s on t h e i n t e r p h a s e b o u n d a r i e s which n e x t became more w i d e r -
F i g . 2c. A f t e r l o a d i n g t h e s p e c i m e n s i n t h e p a r a l l e l d i r e c t i o n (mat. UC2) o n e c a n n o t l c e t h e change o f t h e n u c l e a t i o n and growth mechanism o f d i s c o n t i n u i t i e s i n t h e e n v i r o n m e n t o f n o n - m e t a l l i c
2. 10-3 1 0 3
B 5,5-1,32 +
6,O-1,48 +
C 1 2 , l - 0 , 2 3 +
390-0,37 +
f l c 2 1,03-0,12 +
1 , l - 0 , 2 7 +
I C 2 3,87+0,29
+ .-
4,91-0,63
i n c l u s i o n s . The p r e v a i l i n g mechanism was c r a c k a p p e a r a n c e and growth i n s i d e t h e p a r t i c l e s when t h e t r u e s t r a i n s of specimens were above 1 J ~ z 0 . 0 1 t 0 . 0 5 - F i g . 2d.
On t h e b a s i s o f q u a n t i t a t i v e i n v e s t i g a t i o n s o f t h e v o i d growth p r o c e s s which were made d u r i n g s t a t i c l o a d i n g o f samples it h a s been r e v e a l e d t h a t t h e v a l u e o f r a t i o u s t r o n g l y depends on t h e
shape and o r i e n t a t i o n o f n o n - m e t a l l i c i n c l u s i o n s ( s e e T a b l e 1 ) . Only i n S t e e l B (composed o f f e r r t i c m a t r i x and e u t e c t i c MnS i n c l u s i o n s ) was t h e phenomenon o f v o i d c o a l e s c e n c e by s h e a r f r a c t u r e - F i g . 2e o r m a t r i x r u p t u r e - F i g . 2f between n e i g h b o u r p a r t i c l e s o b s e r v e d d u r i n g
s t a b l e e l o n g a t i o n o f t h e specimens. T h i s was p r o b a b l y c a u s e d by t h e s h o r t i n t e r - p a r t i c l e d i s t a n c e s and d i s t r i b u t i o n o f n o n - m e t t a l i c i n - c l u s i o n s a l o n g t h e g r a i n b o u n d a r i e s .
A l l s t e e l s t e s t e d were c h a r a c t e r i z e d by a n i n c r e a s i n g r a t i o
U d u r i n g dynamic l o a d i n g (mat. A and 1 C 2 p a r t i c u l a r l y ) . Based on t h e s e r e s u l t s i t h a s been con l u d e d t h a t an i n c r e a s e o f t h e s t r a i n r a t e from S
'! ~ 2 . 1 0 - 3 s e c - l t o i - 1 0 s e c - l c a u s e d more i n t e n s i v e v o i d growth i n v ? c i n i t y of n o n - m e t a l l i c i n c l u s i o n s . T h e r e f o r e i t h a s s u g g e s t e d t h a t d u r i n g dynamic l o a d i n g t h e s t e e l s a t t a i n b e t t e r c o n d i t i o n s n e c e s s a r y f o r v o i d c o a l e s c e n c e a t l o w e r s t r a i n ( w i t h s m a l l e r n e c k i n g o f s p e c i - mens). Anyway, t a k i n g i n t o c o n s i d e r a t i o n t h a t o u r e x p e r i m e n t a l p r o c e d u r e was based on s u r f a c e measurements o n l y , t h e s e r e s u l t s c a n n o t be f u l l y a p p l i c a b l e f o r d e s c r i b i n g i n t e r n a l - s t r u c t u r e changes
C5 -25 4 JOURNAL DE PHYSIQUE
Fig. 2 Examples of the void growth in vicinity of particles a - silica-te, b - sulphides type 11, c - silicate (perpendicular direction) d - silicate (parallel direction) ; examples of coalescence of voids: e - shear fracture of matrix between sulphides type 11, f - rupture of matrix between sulphides type 11.
a p p l i c a b l e f o r d e s c r i b i n g f r a c t u r e o f two-phase a l l o y s which depend on i n t e r n a l s t r u c t u r e c h a n g e s m a i n l y . However t h i s s h o r t r e p o r t i s a n a t t e m p t t o e x p l a i n some m e t a l l u r g i c a l a s p e c t o f t h i s p r o c e s s and t h e r e f o r e f u t h e r r e s e a r c h i n c l u d i n g a n a t u r e and s t e r e o l o g y o f t h e s e c o n d - p h a s e p a r t i c l e s i s n e c e s s a r y .
I V . REFERENCES
1. Broek, D . , Eng. F r a c t . Mech., 5 ( 1 9 7 3 ) 55.
2 . P y t e l , S . , Rudnik, S . , A r c h i v . H u t n . , 24 ( 1 9 7 9 ) 58.
3 . G u r l a n d , J . , P l a t e a u , J . , T r a n s . ASM, 56 ( 1 9 6 3 ) 442.
4 . B e l l o t , J . , G a n t o i s , M . , T r a n s J . S . J . , 18 ( 1 9 7 8 ) 546 5. P y t e l , S . , Wojnar, L . , P r o c . 1 1 t h Conf. o n ~ h y s . M e t . ,
Czestochowa P o l a n d ( 1 9 8 3 ) 8 1 .
6 . K i e t k u c k i , H . , The E x p l o s i v e T e n s i l e D e v i c e , T e c h n i c a l U n i v e r s i t y o f Cracow, P o l a n d , n o t p u b l i s h e d .
