In Situ High Energy X‐Ray Diffraction for Investigating the Phase Transformation in Hot Rolled TRIP‐Aided Steels

The phase transformation kinetics of a hot rolled transformation induced plasticity (TRIP) steel is investigated by means of in situ high energy X-ray diffraction. The samples are deformed and annealed according to the parameters of a hot rolling process in a deformation dilatometer installed in the synchrotron beamline. Simultaneously, the phase fraction and the carbon content in the remaining austenite were measured by X-ray diffraction. It is advantageous that the retained austenite (RA) can be measured without sample preparation, which usually results in unwanted strain-induced martensite transformation. This study shows that enough carbon enrichment of austenite can be achieved by forming carbide free bainite. However, too little fraction of the RA for the TRIP effect can be formed without the pre-deformation. The pre-deformation also promotes the decarburization of the bainitic ferrite especially at high temperature.