The fatigue behavior of fine grained two-phase alloys
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PROCEDURE
In o r d e r to s c r e e n t h e f a t i g u e p r o p e r t i e s of a n u m b e r of m i c r o d u p l e x a l l o y s s e v e r a l s e r i e s of h e a t s w e r e studied. These alloys were prepared as 30-lb. vacuum i n d u c t i o n m e l t s t h a t w e r e h o t w o r k e d to ~ i n . d i a m b a r s t o c k . T h e c h e m i c a l c o m p o s i t i o n s a r e g i v e n i n T a b l e I. T h e f o l l o w i n g f o u r s e r i e s of a l l o y s w e r e u s e d : Tie-Line
Series
These alloys lay along a tie-line in the Fe-rich corner of t h e F e - N i - C r t e r n a r y d i a g r a m . T h e t i e - l i n e g o e s t h r o u g h t h e I N - 7 4 4 c o m p o s i t i o n a n d o n e h e a t , n u m b e r 5, w a s m a d e to t h i s c o m p o s i t i o n . T h e s i n g l e p h a s e a l l o y s a t t h e e n d s of t h e t i e - l i n e w e r e a l s o p r e p a r e d . T h e s e w e r e a n a u s t e n i t i c a l l o y , h e a t 1, a n d a h i g h c h r o m i u m f e r r i t e , h e a t 7. H. W. HAYDEN, formerly with the International Nickel Company, Inc., is now with the Research Institute for Advanced Studies, Martin Marietta Corp., Baltimore, Md. 21227. S. FLOREEN is with the International Nickel Company, Inc., Paul D. Merica Research Laboratory, Sterling Forest, Suffern, N. Y. 10901. Manuscript submitted April 11, 1972. METALLURGICAL TRANSACTIONS
Table I. Chemical Compositions of Alloys (Wt Pct)
Heat No.
Structure
1 2 3 4 5 6 7 C
100 pet 7 7-7 pet a 7-10 pet a 7-29 pet a 7-57 pet a 7-79 pet a 100 pet a 100pet a
C
AI
Ti
Ni
Cr
Fe
Other
16.5 18.2 20.2 22.5 25.5 27.2 29.4 30.1
Bal Bal Bal Bal Bal Bal Bal Bal
-
8 9 10 11
100 pet a M-8 pet a M-63 pet a lO0 pet a
Martensite-FerriteTie-LineSeries 0.020 0.02 0.12 6.3 15.0 0.003 0.04 0.17 5.9 16.3 0.011 0.05 0.16 4.1 20.2 0.025 0.06 0.16 2.2 25.5 Fe-Cu Tie-Line Series
Bal Bal Bal Bal
-
12 13 14 15 16
100 pet a a+Cu a+Cu a+Cu Cu
0.008 0.04 0.07 0.010 0.04 0.18 0.007 0.04 0.18 0.005 0.05 0.05 0.006 0.06 0.07 Ni-Cr Binary Alloys
17 18 19 20
7 7+aCr 7+aCr 7+aCr
0.059 0.011 0.015 0.021
Austenite-FerriteTie-LineSeries
AND RESULTS
Alloy Preparation
a) A u s t e n i t e - F e r r i t e
T h e s e h e a t s w e r e f o r g e d a t 2 1 0 0 ~ to a 2 - i n . s q u a r e cross-section and then hot rolled at 1900~ to ~ in. bar stock. Tensile and R. R. Moore rotating beam fatigue specimen blanks were annealed one hour at 1700~ a n d a i r c o o l e d . A n o t h e r s e t of s a m p l e s f r o m h e a t 5 w e r e a n n e a l e d o n e w e e k a t 1 7 0 0 ~ to p r o d u c e a c o a r s e r microstructure. The mechanical properties and micros t r u c t u r e s of a l l o y s of t h i s k i n d a r e d e s c r i b e d in R e f . 3. T h e t w o - p h a s e a l l o y s h a d f i b r o u s m i c r o s t r u c t u r e s e l o n g a t e d p a r a l l e l to t h e b a r a x i s . T h e g r a i n s i z e s of e a c h p h a s e w e r e on t h e o r d e r of s e v e r a l m i c r o n s . T h e two single phase heats had equiaxed structures with
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