Effect of austenite deformation in non-recrystallization region on microstructure development in low-silicon content TRIP-assisted steels

The influence of austenite deformation in non-recrystallization region on microstructural development in low-silicon content TRIP-assisted steels was investigated. Laboratory simulation of a typical thermomechanical control processing was carried out in an automated hot-compression testing machine. Specimens subjected to a typical multi-stage isothermal deformation/cooling program were deformed to true strains of 0, -0.15, -0.25 and -0.35 at various temperatures in austenite non-recrystallization region. Mossbauer spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and a novel tint-etching method were used to investigate the microstructure of deformed specimens. The results indicated that the maximum volume fraction (V-RA) and carbon content (C-RA%) of retained austenite can be obtained by deforming samples to some intermediate strains (epsilon =-0.15 for V-RA and epsilon=-0.25 for C-RA%). However, further straining of samples to epsilon=-0.35 resulted in a drastic reduction of both parameters due to formation of pearlite. It was found that a decrease in deformation temperature resulted in increasing V-RA and C-RA%. Moreover, deformation of austenite was associated with morphology changes in retained austenite particles from interlath film-like type in undeformed specimens to blocky and encapsulated types in the deformed specimens. (C) 2014 Elsevier B.V. All rights reserved.