3d/4d Characterization Of Microstructural Heterogeneity In Bainitic Steels

A quantitative understanding of the microstructure of steel and its relationship to mechanical properties has been investigated in order to develop effective processing techniques and higher performance steel products. With strong demand from commercial markets to decrease energy usage and CO2 emissions, recent steel microstructures have dramatically changed from a ferrite single phase to a complex phase consisting of bainite, martensite and other residual phases. The heterogeneity of the microstructure in the range of several micrometers is considered to mostly affected to the mechanical properties, and a new approach using recent 3D characterization techniques has been performed. By a serial-sectioning method using a conventional FIB system, the morphology of bainite and the M-A constituent, along with a very different 3D morphology from that reported by previous two-dimensional observations, will be revealed. A new characterization technique using the FIB system equipped with a heating stage has also been developed to clarify the actual transformation behavior in the bainite forward and reverse transformations at high temperature.