The effect of temperature and microstructure on the creep damage found in low alloy ferritic steels
- PDF / 3,658,125 Bytes
- 7 Pages / 613 x 788.28 pts Page_size
- 71 Downloads / 192 Views
IT is
well d o c u m e n t e d in the l i t e r a t u r e that for m a t e r i a l s which a r e d e f o r m e d at s t e a d i l y i n c r e a s i n g t e m p e r a t u r e s , t h e r e is f r e q u e n t l y found to be a change in f r a c t u r e mode f r o m t r a n s g r a n u l a r to i n t e r g r a n u l a r on d e f o r m i n g within and above a c r i t i c a l t e m p e r a t u r e r a n g e . The p h e n o m e n o n of g r a i n b o u n d a r y s l i d i n g ~ (gbs) is c l o s e l y r e l a t e d to this o c c u r r e n c e of i n t e r g r a n u l a r f r a c t u r e , and it is the p u r p o s e of the p r e s e n t work to study the effect of t e m p e r a t u r e on gbs in a low alloy f e r r i t i c s t e e l . T h e r e is much i n f o r m a t i o n a v a i l a b l e c o n c e r n i n g the effects of gbs within r e l a t i v e l y s i m p l e m e t a l s y s t e m s , 2,a but it is only r e c e n t l y that s t u d i e s have b e e n extended to a u s t e n i t i c s t e e l s , 4-~ and t h e r e is s t i l l a p p a r e n t l y no i n f o r m a t i o n for low alloy f e r r i t i c s t e e l s . Due to the complex n a t u r e of the p o s s i b l e m i c r o s t r u c t u r e s a v a i l a b l e in t r a n s f o r m a b l e s t e e l s , a f i r s t step m u s t be to attempt to s t a b i l i z e as m a n y v a r i a b l e s as p o s s i b l e and thus the p r e s e n t work has studied the effect of change in t e m p e r a t u r e on the int e r g r a n u l a r f r a c t u r e m e c h a n i s m s for a v a c u u m m e l t e d low alloy s t e e l in two m i c r o s t r u c t u r a l conditions. EXPERIMENTAL 1 ~2 pct C r 9~2 pct V f e r r i t i c s t e e l c o n t a i n i n g e i t h e r 0.2 wt pct C (Batch A.1) or 0.09 wt pct C (Batch A.2) was r e c e i v e d in s t r i p f o r m , given a solution t r e a t m e n t of 1 h at 1533 K, f u r n a c e cooled, and then t e m p e r e d at 953 K for 24 h. (Detailed c o m p o s i t i o n s a r e given in T a b l e I.) F l a t t e n s i l e s p e c i m e n s were m a c h i n e d to a gage length of 25.4 • 5 m m and then m e c h a n i c a l l y polished to 1~4 yaza finish. The s p e c i m e n s were s c r a t c h e d with 6 /an d i a m o n d paste longitudinally along the outside D. A. MILLER, formerly of the Department of Metallurgy, University of Manchester, is now at the Department of Materials Science, University of Southern California, Los Angeles,CA 90007, and R. PILKINGTONis at the Department of Metallurgy,University of Manchester, Manchester M1 7HS, England Manuscript submitted December 14, 1977. METALLURGICALTRANSACTIONSA
of the gage length and on the other side a photo r e s i s t technique was used to p r i n t a grid 2 c m long on the s p e c i m e n gage length. The s t r a i n due to gbs, s was d e t e r m i n e d by m e a s u r i n g the s u r f a c e offsets p r o duced at the i n t e r s e c t i o n of g r a i n b o u n d a r i e s with a longitudinal line p a r a l l e l with s t r e s s axis. D i s p l a c e m e n t s of the line (w)
Data Loading...
