Neutron diffraction analysis of atomic arrangements in a maraging steel
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Alloy
Stacking Faults in 3/ Particles After Creep at 1400~
Nominal Chemical Composition, Wt Pct
Low-carbon* MAR-M200
8 Cr, 10 Co, 12.5 W, 2 Ti, 5 AI, 1 Cb, bal. Ni.
Low-carbon* 13-1900
8 Cr, 10 Co, 6 Mo, I Ti, 6 AI, 4.3 Ta, bal. Ni.
Low-carbon* IN-100
10 Cr, 15 Co, 3 Mo, 4.5 Ti, 5.5 AI, I V, bal. Ni.
Yes
Waspaloy4 Udimet 5004
20 Cr, 13 Co, 5 Mo, 2.8 Ti, 1.5 AI, 0.08 C, bal. Ni. 18Cr, 18.5 Co, 4 Mo, 2.9 Ti, 2.9 AI, 0.08 C, bal. Ni.
Yes Yes
Ni-9.5 All Ni-5.3 AI-4.1 Ti Ni-7.5 AI-9.4 Cr Ni-8.5 AI-8.1 Ta Ni-7.3 AI-2.6 Si Ni-5.3 AI-8.5 Cb Ni-7.2 AI-IO.5 W
No
-
Yes Yes
No No No No No No
*10 to 50 p p m c a r b o n . "['Actnal chemical composition for the binary and ternary alloys.
alloys o c c u r s by f o r m a t i o n of stacking faults in the y ' p a r t i c l e s only when the s t a c k i n g fault e n e r g y of the m a t r i x is below some c r i t i c a l value. F u r t h e r m o r e , this c r i t e r i o n is r e s t r i c t e d to i n t e r m e d i a t e t e m p e r a t u r e s (~ 1400~ s i n c e it has been shown tt that at higher t e m p e r a t u r e s (~ 1600~ the p r e d o m i n a t e c r e e p d e f o r m a t i o n mode, even in a highly alloyed s y s t e m such as MAR-M200, is p a r t i c l e s h e a r by a/2 (110) dislocation pairs. 1. B. H. Kear, G. R. Leverant, J. M. Oblak: Am. Soc. Metals, Trang Quart., 1969, vol. 62, p. 639.
Neutron Diffraction Analysis of Atomic Arrangements in a Maraging Steel STEPHEN SPOONER, H . J . RACK, AND DAVID KALISH C O B A L T is known to be a n e s s e n t i a l a l l o y i n g addition for a c h i e v i n g high s t r e n g t h in 18 pct Ni m a r a g i n g s t e e l s . 1 T h e e a r l i e s t s p e c u l a t i o n was that cobalt gives a l o n g - r a n g e o r d e r e d m a t r i x . 2 A l t e r n a t i v e l y , it has been suggested that cobalt l o w e r s the s o l u b i l i t y of m o l y b d e n u m in the m a t r i x and thus i n c r e a s e s the amount of m o l y b d e n u m p r e c i p i t a t e 3'~ o r that cobalt lowers the s t a c k i n g - f a u l t e n e r g y of the m a t r i x , thus i n c r e a s i n g the a v e r a g e d i s l o c a t i o n d e n s i t y and p r o viding m o r e n u c l e a t i o n s i t e s for p r e c i p i t a t i o n to take place. 5 This note d e s c r i b e s the a t o m i c a r r a n g e m e n t s in a 18 pet Ni-12 pct Co m a r a g i n g s t e e l and d i s c u s s e s the STEPHEN S P O O N E R is A s s o c i a t e Professor, Georgia I n s t i t u t e o f T e c h n o l o g y , A t l a n t a , Ga. H. J. R A C K and D A V I D K A L I S H are Scientists w i t h the Lockheed-Georgia Co., Marietta, Ga. Manuscript s u b m i t t e d March 16, 1971. 2 3 0 6 - V O L U M E 2, AUGUST 1971
2. G. R. Leverant and B. H. Kear: Met. Trans., 1970, vol. 1, p. 491. 3. G. R. Leverant and D. N. Duhl: Met. Trans., 1971, vol. 2, p. 907. 4. A. Gumier and J. L. Strudel: Proc. Second lnterrt Conf. on the Strength of Metals and Alloys, p. 1145, Am. Soc. Metals, 1970. 5. P. C. J. GaUagher: Phys. Stat. Solidi, 1966, vol. 32, p. 95. 6. R
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