Grain Boundary Engineering of Medium Mn TWIP Steels: A Novel Method to Enhance the Mechanical Properties

The grain boundary engineering (GBE) approach was employed on a medium manganese (Mn) based twinning induced plasticity (TWIP) steel to improve its mechanical properties. Two specially designed thermo-mechanical processing (TMP) routes, one involving unidirectional rolling (UDR) and the other one employing multi-step cross rolling (MSCR), with intermediate short term annealing treatment have been used. The annealing temperatures are chosen considering recrystallization and grain growth. Of the two routes, the one involving MSCR, has shown a higher fraction of special or coincident lattice site (CSL) grain boundaries. A detailed grain boundary microstructural analysis has been carried out by electron backscatter diffraction (EBSD) for differently processed samples. A significant improvement in ductility is observed in MSCR processed samples due to increase of CSL boundary fraction