Mechanical Stability of Retained Austenite in Tempered 9Ni Steel.
CALIFORNIA UNIV BERKELEY
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The behavior of the thermally stable austenite in the ductile fracture surface layer of a grain-refined and tempered 9Ni steel broken at 77 K was studied through use of Moessbauer spectroscopy and transmission electron microscopy. Thin foils revealing the microstructural profile of the fracture surface layer were prepared by electroplating a thick pure iron layer on the fresh fracture surface, then thinning a profile sample through a combination of conventional twin-jet electropolishing and ion milling techniques. The results of both Moessbauer spectroscopy and TEM studies showed that the thermally stable austenite transforms to a dislocated martensite in the deformed zone adjacent to the ductile fracture surface. This result suggests that transformation of the retained austenite present in tempered 9Ni steel is compatible with low temperature toughness, at least when the transformation product is a ductile martensite. Author
- Properties of Metals and Alloys