Improved hot ductility of an as-cast high Mn TWIP steel by direct implementation of an MnS-containing master alloy

Transverse cracking is the main issue during continuous casting of TWIP steels due to degraded hot ductility at 700–950 °C. In this study, we improve the hot ductility of an 18.1Mn-0.68C-1.5Al (wt.%) TWIP steel by refining the as-cast structure via inoculation . Inoculation was implemented by direct addition of MnS-containing master alloy to the melt. Since MnS did not dissolve in the melt, they acted as heterogeneous nucleation sites for austenite nucleation. Consequently, MnS-inoculated steel shows finer grain sizes than reference steel. Additionally, MnS particles are found to have a polygonal shape, randomly distribute, and share a cube-on-cube orientation relationship with austenite; both habit planes are parallel to {111}. A periodic array of b = 1/6<112> edge dislocations at every fourth {222} planes of MnS is necessary to accommodate the large lattice misfit of the cube-cube relationship. The MnS-inoculated TWIP steel shows significantly improved hot ductility compared to previously reported TWIP steels.