Implications of microstructure, Taylor factor distribution and texture on tensile properties in a Ti-added Fe-Mn-Al-Si-C steel

Abstract

Structure-property relationship in a Ti-added medium Mn multicomponent steel has been studied and compared with a Ti-free variant of same composition. Both the steels with initial ferrite-austenite microstructure were subjected to cold rolling, followed by annealing treatment at 1073K for 3 and 50 min. The Ti-modified steel shows good strength-ductility combination after 50 min of annealing. In contrast, a reverse trend is observed in the Ti-free variant where strength-ductility relationship ameliorates after 3 min annealing. The remarkable strength in the Ti-free variant originates from the higher volume fraction of Mn5(Al,Si)C precipitates having larger lattice misfit, higher fraction of deformed grains and finer ferrite grain size. The presence of Ti as a microalloying element in the Ti-modified steel instigates the formation of Ti-rich intermetallic carbide precipitates which refine the ferrite grain size during extended annealing. However, the evolution of such precipitates and refinement of ferrite grains do not significantly improve its tensile strength owing to the coarser size and lower lattice misfit of the precipitates, lesser fraction of deformed grains and predominant presence of cube fibers. The Taylor factor distribution within the range of (~2–5) is also studied to understand its implications on the texture-property relationship of the developed steels. It is observed that the γ-fiber fraction of ferrite phase increases due to higher number of grains within the Taylor factor range of (~3–4) and this, in turn, enhances the elongation in both the Ti-free (3 min annealed) and Ti-added (50 min annealed) steels.