Characterization of transformed and deformed microstructures in transformation induced plasticity steels using electron backscattering diffraction

The microstructure of transformation induced plasticity (TRIP) steels was characterized by means of electron backscattering diffraction (EBSD) technique to identify and quantify their different microstructures such as ferrite, bainite, and retained austenite. Further, the strain distribution in ferrite and retained austenite was analyzed during deformation. The TRIP steels were annealed by austempering for different durations to investigate the effect of the austempering time on the volume fraction change of the microstructural constituents. The quantitative analysis by EBSD coupled with an image contrast analysis revealed that the amount of retained austenite decreased and the amount of bainite increased with increasing austempering time. The mechanical properties of the TRIP steels were also affected by the austempering time. The maximum elongation was obtained in the sample austempered for 5 min, probably because of the good stability of retained austenite. The strain distribution in bcc and fcc phases during tensile deformation was characterized by evaluating the changes in the average local misorientation of the phases.

► Different austempering durations result in change in the microstructural features and mechanical properties of TRIP steels. ► Quantitative analysis using band slope allows the estimation of the change in the constituent phases with increasing austempering time. ► Mechanical stability of retained austenite deteriorates when sample is austempered for more than 5 min.