New information on the mechanism of temper embrittlement of alloy steels
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C ONC LUSION The s e l e c t i v e s u b l i m a t i o n of s y s t e m s s u c h a s C d CuCd 3 a p p e a r s to be a p r o m i s i n g tool f o r the o b s e r v a tion of t h r e e - d i m e n s i o n a l s t r u c t u r e s , s i n c e it p e r m i t s r e m o v a l of one p h a s e without a f f e c t i n g the o t h e r .
Fig. 3 - - F i b e r - t e r m i n a t i o n in CuCd 3 p h a s e . Magnification 16,000 t i m e s .
New Information on the Mechanism of Temper Embrittlement of Alloy Steels H. OHTANI, H. C. FENG, AND C. J. McMAHON, JR.
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is a r e p o r t on r e c e n t r e s e a r c h which h a s l e d to new u n d e r s t a n d i n g of the p h e n o m e n o n of e m b r i t t l e m e n t of a l l o y s t e e l s by r e s i d u a l i m p u r i t i e s . This p h e n o m e non is m o s t w i d e l y r e c o g n i z e d in the p r o b l e m of t e m p e r e m b r l t t l e m e n t , in which a buildup of e l e m e n t s such a s p h o s p h o r u s , tin, a n t i m o n y , a r s e n i c , and so forth, o c c u r s at g r a i n b o u n d a r i e s when a c o m m e r c i a l - p u r i t y s t e e l is h e a t e d in, o r c o o l e d s l o w l y through, the r a n g e ~ 620 to 820K (350 to 550~ 1'2 Such a buildup p r o d u c e s a t e n dency f o r b r i t t l e f r a c t u r e along the g r a i n b o u n d a r i e s and is a s e r i o u s l i m i t a t i o n to the use of a l l o y s t e e l s in h e a v y s e c t i o n s , such a s in p r e s s u r e v e s s e l s and s t e a m t u r b i n e r o t o r s . S e r i o u s s e r v i c e f a i l u r e s have b e e n a t t r i b u t e d to t h i s p r o b l e m , p e r h a p s the b e s t known b e i n g the d i s i n t e g r a t i o n of the low p r e s s u r e t u r b i n e at the Htnckley Point p o w e r s t a t i o n in England in 1969. 3 E l i m i n a t i o n of the p r o b l e m would p e r m i t an i n c r e a s e in the inlet s t e a m t e m p e r a t u r e in low p r e s s u r e t u r b i n e s in a g r e a t n u m b e r of i n s t a l l a t i o n s and would p r o d u c e s i g n i f i c a n t i n c r e a s e s in g e n e r a t i n g e f f i c i e n c y and d e c r e a s e s in fuel c o n s u m p t i o n . It is g e n e r a l l y b e l i e v e d that e q u i l i b r i u m s e g r e g a t i o n
H. OHTANI and H. C. FENG are Post Doctoral Fellows, and C. J. McMAHON, JR. is Associate Professor, Department of Metallurgy and Materials Science, University of Pennsylvania, Philadelphia, Pa. 19174. Manuscript submitted June 12, 1973. 516-VOLUME 5, FEBRUARY 1974
1. H. E. Cline, J. L. Walter, E. Lifshin, and R. R. Russell.Met. Trans., 1971,vol. 2, p. 189. 2. M. F. X. Gigliotti and G. A. Colligan: Met. Trans., 1972, vol. 3, p. 933. 3. J. L. Walter and H. E. Cline: Met. Trans., 1973, vol. 4, p. 33. 4. M. F. X. Gigliotti and G. A. Colligan: Met. Trans., 1972, vol. 3, p. 935. 5. L. M. Hogan, R. W. Kraft, and F. D. Lemkey: in Advances in Materials Research, H. Herman Ed., p. 154, Wiley, New York, 1971.
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