On the resistance of TRIP steel to hydrogen embrittlement
- PDF / 1,289,904 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 63 Downloads / 207 Views
I
I
L
I000
SO0 --
Y =20,000 Erg/crn 2
IO0
~
50
150.2
I
I 0 "E
I
IO0
CRACK LENGTH, MICRONS
Fig. 4--Values of f r a c t u r e s t r e s s calculated for v a r i o u s c r a c k lengths over an o r d e r of magnitude v a r i a t i o n in s u r face e n e r g y (calculation is for a t o m i c a l l y s h a r p crack). for applied stresses approaching half the yield stress, the stress concentrations always approach the yield stress. Under most conditions, one would expect c/p v a l u e s of at l e a s t 2, a n d s t r e s s e s a p p r o a c h i n g y i e l d s t r e s s at one h a l f t h e f r a c t u r e s t r e s s . It m u s t b e n o t e d , of c o u r s e , t h a t t h e s t r o n g e s t c r y s t a l s s h o u l d show yielding or at least microstrain, even without t h e a i d of s t r e s s c o n c e n t r a t i o n s .
On the Resistance of TRIP Steel to Hydrogen Embrittlement R . A . M c C O Y , W. W. G E R B E R I C H , AND V. F . Z A C K A Y TRIP steels (TRansformation Induced Plasticity), r e c e n t l y d e v e l o p e d b y Z a c k a y et al.,1,2 d e m o n s t r a t e a u s e f u l c o m b i n a t i o n of h i g h s t r e n g t h , h i g h d u c t i l i t y , a n d g o o d f r a c t u r e t o u g h n e s s . B y a c a r e f u l b a l a n c e of c o m position and thermomechanical treatment, TRIP steel is metastable austenite at room temperature. The temperature below which strain-induced martensite c a n f o r m ( M D) i s s l i g h t l y a b o v e r o o m t e m p e r a t u r e , whereas the temperature below which martensite can f o r m s p o n t a n e o u s l y u p o n c o o l i n g (Ms ) i s w e l l b e l o w room temperature. T h e h i g h y i e l d s t r e n g t h of t h e a u s t e n i t e i s p r o d u c e d b y a c o m b i n a t i o n of s o l i d s o l u t i o n strengthening, precipitation strengthening, and work hardening. The high ductility and toughness result from t h e a u s t e n i t e to m a r t e n s i t e t r a n s f o r m a t i o n o c c u r r i n g d u r i n g p l a s t i c d e f o r m a t i o n a t r e g i o n s of p o t e n t i a l n e c k i n g a s i n u n i a x i a l b e h a v i o r o r a t a c r a c k t i p a s in crack propagation behavior. Hydrogen embrittlement is an especially serious problem to high-strength martensitic steels because R. A. McCOY, W. W. GERBERICH, and V. F. ZACKAY are Graduate Student, Lecturer, and Professor, respectively. Inorganic Materials Research Division, Lawrence Radiation Laboratory, Department of Materials Science and Engineering, College of Engineering, University of California, Berkeley, Calif. Manuscript submitted October 16, 1969. METALLURGlCALTRANSACTIONS
It i s t h e r e f o r e c o n c l u d e d t h a t b o t h d i r e c t a n d i n d i rect evidence support the view that plastic deformat i o n a c c o m p a n i e s f r a c t u r e i n s a p p h i r e a n d r u b y at room temperature. Thus, microslip can occur and can t h e r e f o r e b e t r e a t e d b y i t s e l f to u n d e r s t a n d t h e m e c h a n i c a l p r o
Data Loading...
