A novel top-down approach to make bulk nanostructured metal with low stacking fault energy

Abstract

We report a novel method, named as stepping refining (STR) processing, to prepare three-dimensional nanograined bulk of high-Mn twinning-induced plasticity (TWIP) steel for the first time. After STR processing, the average grain size reduces to 20 nm—which is smaller than any reported grain size of TWIP steel—and the hardness reaches to 5.8 GPa, approximately 0.9 GPa above that of its nanotwinned counterpart with average twin-boundary spacing of 14 nm. The coarsening temperature of both nanograined and nanotwinned TWIP steels exceeds 350 °C, due to the low energy stored at grain/twin boundaries.