Microstructure and texture evolution in high manganese TWIP steels

The mechanical behavior of high manganese TWIP (Twinning Induced Plasticity) steels is characterized by a combination of good formability and high strength. The exceptional work hardening capability of TWIP steels is generally attributed to the gradually proceeding twinning of crystal planes during deformation, forming strong obstacles to dislocation motion. The onset of twinning depends on the orientation of the individual grains with respect to the loading direction and is therefore texture sensitive. In order to get better insight into the active deformation mechanisms resulting in the typical mechanical behavior of fully austenitic TWIP steels, a hot rolled Fe-28wt.%Mn-1.6wt.%Al-0.3wt.%Si-0.08wt.%C TWIP steel was studied by means of electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) after the specimens had been uniaxially deformed to different degrees of plastic deformation. Lowering the deformation temperature to - 50 degrees C resulted in increased strength values and decreased elongation values due to premature twinning and at the same time incomplete texture evolution. An increase in strain rate gave rise to extensive twinning and resulted in increased strength values. In addition to the rather coarse grained grade, a fine grained grade was produced via a recrystallization procedure with the objective to study the effect of grain size on the extent of twinning.