5th International High Manganese Steel Conference - HMNS 2022

To increase the yield strength of HMnS and afterwards regain the capability for residual deformation we developed a novel thermomechanical treatment to manufacture a high manganese TRIP steel with excellent mechanical performance by combining the deformation-mechanisms SLIP, TWIP and subsequently activating the TRIP-effect. Our process resulted in ultra-high tensile strength of the high manganese steel. The so-called mechanism-controlled rolling and a subsequent recovery annealing lead to 1.6 GPa, with uniform elongations up to 15%.

The TRIP-steel was warm rolled at 200 °C, to suppress TRIP and activate TWIP as deformation mechanism. Thus, a high density of deformation twins and dislocations was introduced to the microstructure, avoiding martensite formation. A subsequent recovery annealing at elevated temperatures, reduced the dislocation density and while a high density of deformation twins was preserved. This combination of warm rolling and annealing allows the production of a fully austenitic nano-structured microstructure. If then deformed the TRIP effect is predominant in and depending on the tensile direction. The plastic deformation at ambient conditions creates martensite in a highly twinned microstructure which increases work hardening. The anisotropic behavior was analyzed as well as the hydrogen resistivity in slow strain rate tests. The HMnS exhibits an ultra-high yield strength and sufficient ductility, favorable properties for lightweight construction in automotive or aerospace industry.