Evolution of microstructure, texture and mechanical properties of Fe–30Mn–11Al–1.2C low-density steel during cold rolling

Abstract

In the past decades, the microstructure and properties of tensile deformed high Mn–Al–C lightweight steels were extensively studied due to their excellent combination of strength, ductility and low-density. However, the effects of cold rolling were barely reported. This study systematically investigated the evolution of microstructure and texture as well as mechanical properties during cold rolling of Fe–30Mn–11Al–1.2C (wt%) steel. The stacking fault energy (SFE) of the steel was estimated as ~108 mJ/m2. With cold rolling, the yield strength of the steel was significantly enhanced and exceeding 2.0 GPa after 90% rolling reduction, which is attributed to the gradual refinement of the microstructure. Different deformation substructures were formed approximately in the sequence of Taylor lattice, microbands, nano-twins, shear bands and dislocation cells. This means the dislocation glide mode changes from planar to wavy glide with increasing rolling reduction. Among these structures, twining is widely believed to be impossible by tensile deformation due to the high SFE. But it happened during cold rolling with relatively low resolved shear stress, which may be attributed to the occurrence of short range order (SRO) in austenitic matrix and local stress concentration. The rolling texture of the steel was weak and characterized by the transition from “copper-type” to “brass-type” after 50% rolling reduction. The dislocation planar glide and deformation twining play an important role in texture evolution.