Texture and microstructure of ultra low carbon steel processed by equal channel angular extrusion

Grain structure, texture, and mechanical behavior of ultra low carbon steel subjected to severe plastic deformation at room temperature via equal channel angular extrusion (ECAE) were studied. After one pass the grains were elongated in the shear direction, showing microbands at ±30° with respect to grain boundaries. The microbands confined a substructure oriented into 〈1 1 1〉 and 〈1 0 0〉 fibers, whose axis were at ≈70° with respect to the extrusion direction. After four passes using route A the original grain boundaries cannot be distinguished in the deformation-induced microstructure, and a strong fine microbands structure, oriented into 〈1 1 1〉 and 〈1 1 0〉 fibers lying at 45 and 10° from the extrusion direction, respectively, was formed. At room temperature the stress–strain curves of ECAE deformed materials exhibited softening. The tensile strength increased and the elongation fell below 10% with increasing number of passes. However, for annealed ECAE deformed materials the stress–strain curves showed work hardening while the elongation increased up to about ≈40–50%.