Characterization of the deformation substructure of AISI 316 stainless steel after high strain fatigue at elevated tempe
- PDF / 1,345,285 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 29 Downloads / 176 Views
I
O
I
I
I
g r o o v e s . (This c o n t r i b u t i o n can be i n t e r p r e t e d as a p o s i t i v e g r o o v e width at l = 0 as p r o p o s e d in this t r e a t m e n t ) . H o w e v e r , p a s t this i n i t i a l p e r i o d the s u r f a c e c o n t r i b u t i o n would be n e g l i g i b l e . Studies of t h e r m a l g r o o v i n g data on o t h er m e t a l s and c e r a m i c s have been r e v i e w e d . L o g - l o g p l o t s have b e e n u n i v e r s a l l y used to e x t r a c t e x p o n e n t i a l d e p e n d e n c e of the data. T h i s p r a c t i c e m a y be u n s u i t a b l e b e c a u s e of the c o n t r i b u t i o n of v a r i o u s p r o c e s s e s to the i n i t i a l g r o o v e f o r m a t i o n . T h e s e can be i n t e r p r e t e d as c o n t r i b u t i n g to a n o n z e r o i n i t i a l condition. R e i n t e r p r e t a t i o n with the c o n c l u s i o n that, o v e r the t e m p e r a t u r e r a n g e s , g r o o v e w i d t h s , and m a t e r i a l s i n v e s t i g a t e d , v o l u m e diffusion is the p r e d o m i n a n t m e c h a n i s m f o r m a s s t r a n s p o r t p r o d u c e s r e s u l t s which a r e in h a r m o n y with t r a c e r diffusion d at a. T h e high l e v e l of a g r e e m e n t i n d i c a t e s that t h e r m a l g r o o v i n g s t u d i e s m a y be s u i t a b l e f o r the d e t e r m i n a t i o n of a c c u r a t e v a l u e s f o r v o l u m e diffusion c o e f f i c i e n t s .
1
Experimentol Kuper et ol. Dv
30
25~-
[
....
Russion Ds = 0 0 7 exp-I~TO0
--'--
GJ0stein DS " 6"5 ~' I O ' e l t p - 4 0 8 0 0
2O "I" lID
5
31~ ~ 2
o
SHORT TIME INSERT
o
I 0.5
I 20
I 40
I I.O
I 60 TIME (hrs)
I I.•
I 2.0
I
I I00
80
_~
II
I 120
Fig. 4--Comparison of experimental and calculated copper groove widths at 960~ would be e x p e c t e d . T h e Z e i s s I n t e r f e r e n c e M i c r o s c o p e did not have s u f f i c i e n t m a g n i f i c a t i o n c a p a b i l i t y to p e r m i t e x a m i n a t i o n of the v e r y s m a l l , s h o r t - t i m e g r o o v e s . As additional v e r i f i c a t i o n of the v o l u m e diffusion m e c h a n i s m , the f o r m u l a (Dv = 0.47 exp ~ 9 , 1 4 0 / R T ) d e r i v e d by Ku p er e t al. 3 f r o m t r a c e r s t u d i e s was u s e d to c a l c u l a t e the g r o o v e width which would f o r m at v a r i o u s t i m e s a s s u m i n g that v o l u m e diffusion w e r e the only c o n t r i b u t i n g m e c h a n i s m . A s a m p l e plot of this data at T = 960~ is shown in F i g . 4. E x p e r i m e n t a l data taken at 960~ a r e plotted on the s a m e f i g u r e and c o r r e s p o n d v e r y c l o s e l y with the c a l c u l a t e d data. F o r c o n t r a s t , two d i f f e r e n t c a l c u l a t e d s e t s of s u r f a c e d i f f u s i o n data a r e p l o t t e d . S u r f a c e diffusion should have p r o d u c e d m u c h l a r g e r g r o o v e s than w e r e m e a s u r e d at the s h o r t t i m e e x p o s u r e s . Th e
