Microtexture, grain boundary character distribution and secondary working embrittlement of high strength IF steels

The batch annealing (BA) and continuous annealing (CA) of high strength interstitial-free (IF) steel sheets have been simulated. Microtexture, grain boundary character distribution (GBCD) and secondary working embrittlement (SWE) were investigated using an electron backscatter diffraction (EBSD) technique. The results show that a crack from SWE occurs preferentially at random boundaries, that low-angle and low-Σ CSL boundaries can offer resistance to the propagation of SWE cracks. It is suggested that an optimum GBCD described as a high frequency of low-angle or low-Σ CSL boundaries and a more discontinuous random boundary network in the microstructure of IF steels can offer the potential for decreasing their ductile-to-brittle transition temperature (DBTT), i.e. reducing their susceptibility to SWE.