A Transmission Electron Microscopy Investigation of Reaustenitized-and-Cooled HSLA-100 Steel

Abstract

A continuous-cooling-transformation diagram for 0. 06% C HSLA-100 steel (austenite grain size of about 10 μm) was reexamined in combination with hardness data and light-microscope images. Data suggested the presence of a martensitic microstructure over a wide range of cooling rates. A specimen cooled at approximately 17 °C/s was chosen for detailed microstructural investigation. Transmission electron microscopy revealed a microstructure consisting primarily of martensite laths with a moderate-to-high dislocation density. About 5% of retained austenite was present as interlath films. An orientation relationship close to Kurdjumov-Sachs was verified for martensite and austenite, and adjacent laths exhibited an axis/angle pair consistent with two variants of this relationship. Some regions of twinned martensite were observed, and multi-variant cementite precipitation was observed within large autotempered martensite laths. All results are consistent with this steel in its as-received mill-processed condition. © 2012 Springer Science+Business Media, LLC and ASM International.