Investigation of nanoscale twinning in an advanced high manganese twinning-induced plasticity steel

A twinning induced plasticity (TWIP) steel, developed for automotive applications, was characterized down to the nanoscale to investigate the nature of the strengthening mechanisms. Both tensile-deformed and non-deformed materials were studied by light optical microscopy, X-ray diffraction, electron backscatter diffraction, and transmission electron microscopy. The investigated TWIP steel showed extensive twinning upon deformation. With high-resolution transmission electron microscopy, nano-twins as small as 3 nm in width were observed, and large-angle convergent-beam electron diffraction identified the pole mechanism as one of the twinning mechanisms in this TWIP steel. This study emphasizes that a thoughtful combination of techniques is necessary to fully capture the microstructure of this TWIP steel and explain the origin of superior mechanical properties compared to other TWIP steel grades.