The influence of reverted austenite on torsional behavior of 18 Ni (200) maraging steel
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Table I. Chemical Composition
44,800 + 39.9 T ( c a l / m o l e )
L i n e a r a p p r o x i m a t i o n s of this type often d e m o n s t r a t e good a g r e e m e n t with m o r e complex equations. ~ For e x a m p l e , the f r e e e n e r g y data c a l c u l a t e d f r o m ZXH~,a and S,~ for Na2SO4, PbSO 4 and CaSO a have shown an a g r e e m e n t with the a c c u r a t e equations within +3 k c a l / mole. The f r e e e n e r g y data used for CuO (s), Cu,O(s), Cu,S(s), SO,(g), and SOs(g) were cited f r o m Kubaschewski et al., 7 those for CuS(s) were f r o m E l l i o t t et al." and those for CuSO4(s) and CuO. CuSO4 (s) w e r e f r o m Kellogg." Based on t h e s e f r e e e n e r g y equations the e q u i l i b r i u m c o n s t a n t s were c a l c u l a t e d for the r e a c t i o n s d e t e r m i n i n g the p r e d o m i n a n t zones, as shown in Table I. Using those values, the predominance diagram for the Cu-S-O system at 350~ was constructed as shown in Fig. I. It is evident that Cu2SO4 can exist as a stable phase under the designated conditions. The variation of the Cu~SO4-stablezone with temperature is shown in Fig. 2. The stability zone for Cu~SO4 disappears below about 300~ whereas a more than atmospheric SOs pressure is required to render Cu2SO4 stable at about 400~ Fig. 1 readily provides an explanation for the possible appearance of the stable Cu~SO4 phase during reduction of CuSO4 to Cu, The present data are also helpful in synthesizing pure solid Cu~SO4. 1. F.Habashiand 1LDugdale:Met. Trans., i973, vol.4, pp. 1429-30. 2. K. Vo Van and F. Habashi:Can. J. Chem., 1972,vol.23, pp. 3872-75. 3. K. lto: Nippon Kogyo Kaishi, 1964,vol. 80, pp. 28-34. 4. T. R. Ingraham:Trans. TMS-A1ME, 1965,vol.233, pp. 359-63. 5. J. L. Woolfreyand B. Russell:Prec. Commonwealth Conf., 1967,vol.6, pp. 49-59. 6. A. Recoura:CR. Acad Sci. Paris, 1909,vol. 148, pp. 1105-08. 7. O. Kubaschewski,E. LL. Evans,and C. B. Alcock:Metallurgical Thermochemistry, Pergamon,London,1967. 8. J. F. Elliottand M. Gleiser:ThermochemistryforSteelmaking, AddisonWesley,Reading,Mass., 1960. 9. H. H. Kellogg:Tram. TMS-AIME, 1964,vol.230, pp. 1622-34.
The Influence of Reverted Austenite on Torsional Behavior of 18 Ni (200)Maraging Steel R. C H A I T A N D P. T. L U M It has b e e n shown that p l a s t i c i n s t a b i l i t y which leads to l o c a l i z e d d e f o r m a t i o n l i m i t s t o r s i o n a l ductility, h~ P a r t i c u l a r effort has b e e n d i r e c t e d t o w a r d s AISI 4340 s t e e l in the quenched and t e m p e r e d condition, z-s A r e c e n t study 4 has shown that in t o r s i o n , v a r i o u s g r a d e s of c o n v e n t i o n a l l y aged (~ 3 h at 900~176 18 Ni m a r a g i n g s t e e l also e x h i b i t a s t r o n g t e n d e n c y for l o c a l i z e d p l a s t i c flow. If not c o m p e n s a t e d by sufficient s t r a i n r a t e R. CHAITand P. T. LUM are Chief and Materials Engineer, respectively, Materials Properties Branch, Materials Manufacturingand Testing Technology Division,Army
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