Tensile deformation of low density duplex Fe-Mn-Al-C steel

In situ scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis were performed on the duplex Fe-27Mn-11.5Al-0.95C steel at room temperature to examine the tensile deformation behavior. The steel consisting of stable austenite matrix and a small amount of ferrite exhibited excellent combination of high strength and ductility (46.5 GPa%) in solid solution state due to the continuous strain hardening behavior. In situ SEM revealed that slip bands appeared in the austenite grain at the early deformation stage, and different slip systems intersected with higher density as the displacement increased. The deformation strains of austenite were obviously larger than that of ferrite, which resulted into the ferrite crack propagation at the later stage. With the stack fault energy (SFE) of similar to 80 mJ/m(2), the evolution of dislocation substructure with increasing strain shows typical planar glide characteristics, namely, dislocation pile-ups, Taylor lattice, high density dislocation walls, domain boundary and intersected microbands. Grain subdivision by microband intersection at high strains results in stable work hardening rate and continuous strain hardening behavior. (C) 2015 Elsevier Ltd. All rights reserved.