Strain Localizations in Ultra Low Carbon Steel: Exploring the Role of Dislocations

Abstract

Ultra low carbon steel samples were near plane strain deformed at different strains, strain rates and temperatures. Density of grain interior strain localizations in γ (ND//<111>) and θ (ND//<100>) fibres were evaluated against micro-stress estimates through X-ray line profile measurements. The patterns were remarkably different between the fibres. The increase in strain localizations were associated with increased dislocation density. This effect was more pronounced in γ-fibre. In θ-fibre, however, the peaks were increasingly more asymmetric and dislocation substructures were stipulated to have lesser recovery. Discrete dislocation dynamics simulations for single crystal pure iron also brought in different behavior for γ and θ fibres: increase in dislocation density in the former was estimated to be ~5 times more. A combination of textural softening and large/positive increase in dislocation density appears to justify the preference for strain localizations in γ-fibre.