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. Mössbauer 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 (VRA) and carbon content (CRA%) of retained austenite can be obtained by deforming samples to some intermediate strains (ε=−0.15 for VRA and ε=−0.25 for CRA%). However, further straining of samples to ε=−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 VRA and CRA%. 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.