Characterisation and quantification of microstructural banding in dual phase steels Part 1 – General 2D study

Abstract

In order to quantify the degree of banding in dual phase steel, optical micrographs of various dual phased steel microstructures have been analysed. From the binary images of the micrographs, greyscale profiles are created and used to define the bands within the image. Two parameters are calculated from the defined bands: band continuity index C_b and perpendicular continuity index C_p. The first parameter quantitatively describes the continuity of each band along the direction of banding, while the second parameter quantitatively describes the continuity of the bands perpendicular to the banding direction. Both parameters are bounded on [0,1], with 0 indicating no banding and 1 indicating strong banding.

Keywords:

• Banded structures
• Microstructure
• Dual phase steel
• Banding quantification

The present research was carried out under project no. M41·10·09330 in the framework of the Research Program of the Materials Innovation Institute M2i (www.m2i.nl). Thanks to our industrial partner, Tata Steel Europe (formerly Corus Steel), for the materials and the use of the polishing, etching and microscope labs. Thanks to the Metallography and Surface Analysis group at Tata Steel RT&D for the use of their facilities, for the help with the data acquisition and for the insightful discussions about the present work. K. S. McGarrity would like to thank E. McGarrity for discussion and help with revising the manuscript. The authors thank K. de Moel, K. Lammers and P. Kok for discussions, guidance and valuable insights with this project. K. S. McGarrity extends special thanks to J. Wörmann for the personal help during the data acquisition period and to S. Sengo, P. Kok and J. Gautam for sending the other microstructures to use for this analysis.