Work hardening behavior and substructure evolution of a low-density steel during compressive deformation

In the present work, the room temperature work hardening behavior and substructure evolution of Fe–17.5Mn–8.3Al–0.74C-0.14Si lightweight steel were investigated during compressive deformation. A series of compression tests were conducted under strain rates of 0.001s−1, 0.01s−1, and 0.1s−1. In addition, the compression tests were interrupted at strain levels of 0.25, 0.75, and 1.25 under the strain rate of 0.001s−1 to study the evolution of the substructure under compression. The starting and deformed microstructures were characterized through high-resolution electron back scatter diffraction (EBSD) technique. The obtained flow curves indicate the high capability of the experimented material for strain hardening. According to the microstructural observation, the outstanding mechanical properties are attributed to the capability of the alloy in cell structure formation and its progressive evolution to subgrains. Such extended dynamic recovery was followed by continuous dynamic recrystallization (CDRX) and deformation-induced ferrite transformation (DIFT) to accommodate the high amount of compressive strain (∼2.5). These two mechanisms result in a final refined microstructure with ultrafine equiaxed grains which provides a great combination of strength and formability.