Synergetic strengthening from dynamic slip band-grain boundary interaction in a low-density FeMnAlC steel

The deformation response of a (Nb, V) micro-alloyed FeMnAlC low density steel has been investigated as a function grain size using samples subjected to different solution-treatment conditions. Mechanical properties have been characterized by tensile testing, and the microstructure before after tensile deformation has been quantified using electron back scattered diffraction and transmission electron microscopy. The deformation microstructure evolution during tensile deformation was dominated by a planar slip mode, leading to slip-band formation and a rapid refinement in microstructural scale. A detailed analysis of the relationship between microstructure and mechanical properties reveals a strong dependence of the yield stress on the initial grain size, as well as a variation of the friction stress and Hall-Petch slope on the level of applied tensile strain. The results suggest that the flow stress in the investigated low-density steel is strongly coupled with the dynamic nature of the increased Hall-Petch slope and the increased friction stress for dislocation movement. Based on this a model is proposed to simulate the stress-strain curves during tensile deformation of the low-density steel over a wide range of strain.