Evaluation of Dislocation Density in Cold Worked Low Carbon Ferritic Steel

Abstract

A low carbon ferritic steel (Fe-0.0056%C) was used for the estimation of dislocation density. Annealed steel sheet with the ferrite grain size of 50 μm was subjected to cold rolling up to 80% thickness reduction and then provided to the X-ray diffraction analysis. Dislocation density was evaluated by the Modified Williamson-Hall / Warren-Averbach method. It was confirmed in cold rolled specimens that the equation; σ_y [GPa] = 0.05+18 ρ /10⁹ stands up in the relation between yield stress σ_y and dislocation density ρ [m^–2]. On the other hand, the values of parameter φ in the Modified Williamson-Hall equation were accurately estimated in each cold rolled specimen and it was found that the equation ρ[m^–2] = 4.5×10¹⁹φ² stands up between φ and ρ. In addition, it is suggested that the screw dislocation component decreases with cold rolling and, in specimens with cold rolling more than 40%, dislocations are of almost full edge dislocation.