Effect of Carbon Fraction on Stacking Fault Energy of Austenitic Stainless Steels
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(fcc) materials, stacking fault energy (SFE) has received a great deal of attention since their deformation modes are closely related to the change in SFE.[1–5] Owing to the recent advances in theoretical calculation[2,3] and high-resolution experimental methodologies,[4,5] the alloy design based on the SFE control has been attempted, and notable accomplishments have been made in austenitic steels such as twinning-induced plasticity (TWIP) steels[3] and transformation-induced plasticity (TRIP)-aided stainless steels.[5] Among several factors affecting SFE, the compositional dependence is an important matter of concern, and a systematic discussion on the topic is due to
TAE-HO LEE, Principal Researcher, and HEON-YOUNG HA and BYOUNGCHUL HWANG, Senior Researchers, are with the Ferrous Alloy Department, Korea Institute of Materials Science, Changwon 642-831, South Korea. Corresponding e-mail: lth@kims. re.kr SUNG-JOON KIM, Professor, is with the Graduate Institute of Ferrous Technology, Pohang University of Science & Technology, Pohang 790-784, South Korea. EUNJOO SHIN, Senior Researcher, is with the Neutron Physics Department, Korea Atomic Energy Research Institute, Daejeon 305-600, South Korea.. Manuscript submitted April 25, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS A
Schramm and Reed.[1] They compiled the SFE values reported in the literature and proposed empirical equations reflecting the relative contributions of alloying elements. Although some quantitative descriptions on compositional correlations could be made referring to their equation, the measured SFE values even in the same alloy showed a disparity in some cases. Several questions have been raised associated with the methodology, linear correlations, and compositional range,[5–8] and modified relations adjusted to specific alloy system were proposed.[6,7] In particular, the high coefficient assigned to C in Schramm and Reed’s equation required some comments in that the maximum C content used in their analyses was as small as 0.036 wt pct. Since C has rarely been used as a major alloying element in austenitic stainless steels due to its deleterious effects on corrosion resistance (the amount of alloyed C has usually been restricted to less than 0.1 wt pct), not much is known about the effect of C on SFE of austenitic stainless steels. Our previous investigation[5] showed that the SFE of austenitic stainless steels measured by neutron diffraction showed almost linear dependence on C + N and was well correlated with deformation modes (straininduced martensitic transformation and deformation twinning). However, there has been ongoing question as to the role of C in comparison with N. In an effort to understand the relative role of C, the SFEs of the Fe-18Cr-10Mn alloys with a fixed amount of C + N but varying C fraction (C/N) were evaluated using neutron diffraction, and the relative change in deformation microstructure depending on C fraction was discussed. To evaluate the effect of C on SFE in comparison with that of N, the alloys with almost the same amount of C
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