Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 528, Issue 24, Pages 7257-7266Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.msea.2011.06.025
Keywords
High-nitrogen austenitic steels; Ductile-to-brittle transition; Austenite stability; Deformation-induced martensite; Brittle fracture
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Funding
- Ministry of Knowledge Economy, Korea
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Ductile-to-brittle transition behavior of high-nitrogen 18Cr-10Mn austenitic steels containing different contents of Ni, Mo, Cu as well as nitrogen is discussed in terms of austenite stability and associated deformation-induced martensitic transformation (DIMT). Electron back-scattered diffraction and transmission electron microscopy analyses of cross-sectional area of the Charpy impact specimens fractured at -196 degrees C indicated that the brittle fracture planes were almost parallel to one of {1 1 1} slip planes and some metastable austenites near the fracture surface were transformed to alpha'-martensite by localized plastic deformation occurring during crack propagation. Quantitative evaluation of deformation-induced martensite together with characteristics of true stress-strain and load-displacement curves obtained from tensile and Charpy impact tests, respectively, supported that DIMT might take place in high-nitrogen austenitic steels with relatively low austenite stability. The occurrence of DIMT decreased low-temperature toughness and thus increased largely ductile-to-brittle transition temperature (DBTT), as compared to that predicted by empirical equations strongly depending on nitrogen content. As a result, the increased DBTT could be reasonably correlated with austenite stability against DIMT. (C) 2011 Elsevier B.V. All rights reserved.
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