A method for dry-stripping single stage replicas from deformed surfaces
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Material Aluminum Lithium Fluoride
Dislocation Type
X
T, dynes per sq cm
3~, per sec
(AT)m~
Edge Screw Edge Screw
0.15 1.00 0.50 0.95
4.2 X 10a 4.2 X 10a 29.4 • 10a 29.4 • 108
1.05 X 104 1.05 X 104 20 X 104 20 • 104
6.23 X 10-6 4.15 • 10"s 6.48 X 10-2 1.23 X 10"1
e x t r a p o l a t e d d a t a f r o m F e r g u s o n et a l . 1~ w e r e a n o r d e r of m a g n i t u d e l a r g e r b u t h a r d l y s i g n i f i c a n t . The temperature increase values calculated by Freudenthal and Weiner 5 and Eshelby and Pratt 6 are s t r o n g l y d e p e n d e n t u p o n t h e n u m b e r of d i s l o c a t i o n s p a s s i n g t h r o u g h t h e s l i p p l a n e s . T h e i r e s t i m a t i o n of the slip plane temperature increase is several ord e r s of m a g n i t u d e h i g h e r t h a n t h e v a l u e s s h o w n i n T a b l e I. T h i s o v e r e s t i m a t i o n i s l a r g e l y d u e to t h e i r f a i l u r e to c o n s i d e r t h e s i m u l t a n e o u s h e a t d i s s i p a t i o n d u r i n g a n d a f t e r t h e h e a t i n g of t h e s l i p p l a n e s b y d i s location motion. 1. P. J. E. Forsyth: Proc. Roy. Soc., 1957, vol. A242, p. 198.
A Method for Dry-Stripping Single Stage Replicas from Deformed Surfaces CLARENCE
R. BARNES
As p a r t of a c o m b i n e d e x p e r i m e n t a l a n d t h e o r e t i c a l p r o g r a m on d e f o r m a t i o n in b c c m e t a l s , s o m e d e t a i l e d surface slip line observations have been undertaken. I n o r d e r to o b t a i n the h i g h e s t p o s s i b l e r e s o l u t i o n , single-stage replicas have been prepared for examina t i o n in t h e e l e c t r o n m i c r o s c o p e . W i t h u s e of t h e technique described in this note, the reported' singles t a g e l i m i t of r e s o l u t i o n (10 t o 20/~) h a s b e e n a p p r o a c h e d a n d , u n l i k e in a l m o s t a l l o t h e r s i n g l e s t a g e techniques, the specimen surface has been preserved. In a d d i t i o n , t h e p r o c e d u r e i s r e l a t i v e l y s i m p l e a n d a p p l i c a b l e to a v a r i e t y of a l l o y s . Our technique involves dry-stripping a Pt-C replica f r o m a d e f o r m e d s p e c i m e n s u r f a c e . It w a s d e v e l o p e d using a molybdenum polycrystal tensile specimen def o r m e d i n 4 p c t i n c r e m e n t s of s t r a i n . * At e a c h s t a g e *This experiment extended over a period of 2 months. Since the surface needed be preserved, the specimen was placed in a dessicator immediately after replication at each stage of deformation. to
of d e f o r m a t i o n , t h e r e p l i c a s s t r i p p e d e a s i l y , F i g . 1. E v e n t h o u g h the e x p e r i m e n t w a s t e r m i n a t e d a t t o t a l s t r a i n of 20 p c t , t h e r e i s n o r e a s o n to b e l i e v e t h a t t h e replicas wouldn't have stripped just as easily at even higher strains. CLARENCE R. BARNES is Engineering Technician, Metal Science Group, Battelle Memorial Institute, Columbus, Ohio. Manuscript submitted
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