On the deformation behavior of dual-phase steels
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Table I. Composition (Wt. Pct) o f the Steels, Balance F e
On the Deformation Behavior of Dual-Phase Steels
Code HT-1 HT-6
C
Mn
LUIS F. RAMOS, DAVID K. MATLOCK and GEORGE KRAUSS are Graduate Student Associate Professor, and AMAX Professor of Physical Metallurgy, respectively,Department of Metallurgical Engineering, Colorado School of Mines, Golden, CO 80401. Manuscript submitted May 3 0 , 1978. METALLURGICAL
TRANSACTIONS A
V
Ti
P
AI
N
Table II. Summary o f Heat Treatments*
Sample
Steel
Heat Treat. Temp., °C
A B C D
HT-1 HT-1 HT-1 HT-I HT-1 HT-6 HT-6 HT-6
745 780 800 820 840 745 780 800
E
F G H
Mart. Volume Fraction,Pet 6 10 15 25 35 15 25 35
Pet C in Martensite 0.64 0.42 0.30 0.24 0.15 0.64 0.42 0.30
samples were heat treated for 6 rain andicedbrine quenched. Constant grain size = 0.010 mm.
*All
p e r m i t v a r i a t i o n of e i t h e r M V F o r t h e p c t C i n the m a r t e n s i t e w h i l e t h e o t h e r p a r a m e t e r w a s h e l d cons t a n t . T h e m i c r o s t r u c t u r a l p a r a m e t e r s l i s t e d in T a b l e II w e r e p r e d i c t e d f r o m t h e p h a s e d i a g r a m a n d the volume fraction of s e c o n d p h a s e was confirmed with metallography. Tensile s p e c i m e n s with a red u c e d gage l e n g t h o f 3 1 . 2 5 m m a n d a c r o s s - s e c t i o n of 6.25 × 2 m m w e r e m a c h i n e d p r i o r t o h e a t t r e a t m e n t . All tensile t e s t s were p e r f o r m e d at r o o m t e m p e r a t u r e o n a n I n s t r o n a t a s t r a i n r a t e o f 6.7 × 1O"~ s -1" T h e o b s e r v e d s t r e s s - s t r a i n d a t a , a s s h o w n in Fig. 1, c h a n g e w i t h b o t h M V F a n d p c t C i n m a r t e n s i t e . Figures 2 a n d 3 show t h a t t h e standard tensile p r o p e r t i e s a r e a f u n c t i o n o f b o t h MVF a n d p c t C in m a r t e n s i t e . Also f r o m Fig. 1, it is a p p a r e n t in s p e c i m e n s with a constant MVF, that t h e initial s t r a i n hardening c h a r a c t e r i s t i c s d e p e n d o n t h e p e t C i n m a r t e n s i t e , i.e. the martensite strength a n d / o r morphology. I n g e n e r a l , t h e d e f o r m a t i o n b e h a v i o r of a m u l t i p h a s e m i c r o s t r u c t u r e i s c h a r a c t e r i z e d by t h e d e f o r m a t i o n of e a c h p h a s e p l u s t h e i n t e r a c t i o n b e t w e e n t h e p h a s e s . In dual-phase s t e e l s , t h e deformation behavior
35 % Mart. Vol. Fract. /~
BOO
C-Mn S~ SteeLs
0.30 % C 600
ENGINEE R~NG
STRESS (MPa)
~ 400
~"
V
6JI~4%C
"030%C
15 °l. M~rL VoL Fract.
110
210
ENGINEERfNG STRAIN (%)
Fig. 1--Engineering s t r e s s - s t r a i n c u r v e s o f F e - C - M n - S i s t e e l s with d u a l - p h a s e s t r u c t u r e . Martensite c a r b o n contents and m a r t e n s i t e v o l u m e fractions a s shown.
ISSN 0360-2133/79/0211-0259500.75/0 SOCIETY FOR METALS AND T H E METALLURGICAL SOCIETY OF A1ME
© 1979 AMERICAN
S
0.052 0.90
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