Characterization of Twin-Like Structure in a Ferrite-Based Lightweight Steel

Abstract

The present study examined cold to warm compressive deformation behavior of a ferrite-based lightweight steel through characterization of the banded structures. Compression tests were carried out at 25 to 500 degrees C at a strain rate of 0.01 s(-1) up to true strain of 0.6. Analysis of the microstructural evolution using electron back scatter diffraction indicated that the twin-like bands in the large ferrite grains occurred with the {112}[ 111] system at a 60 degrees misorientation. Density of the twin-like bands is increased by raising the deformation temperature. EBSD results showed that the primary and secondary twins occurred in the [-11-1] and [ 1-1-1] directions. In addition, the strain at 500 degrees C distorted the twin-like bands and resulted in wavy boundaries. The strain hardening behavior was also examined using the Crussard-Jaoul (C-J) model and the n-values were calculated for each stage of imposing strain. The results showed high dislocation density in the adjacent of twin-like boundaries intersections which resulted in the n-value increment.