Microstructure Evolution and Mechanical Properties of Light Medium Manganese Steel: Different Rolling Directions during Warm Stamping

We address here the factors affecting the stability of austenite and studied the mechanical properties of Fe-0.2C-8.5Mn-1.5Al light medium manganese steel after stamping in parallel and vertical rolling directions. The results show that the ferrite and austenite dual-phase was obtained after the experimental steel was heated in Ac1-Ac3 in the parallel rolling and vertical rolling directions. Quenched martensite organization is also generated with the increase in temperature. The experimental steel attained the best mechanical properties after being stamped in the parallel rolling direction and quenched at 710 °C, while the steel after being stamped in the vertical rolling direction and quenched at 730 °C reached optimum mechanical properties. The grain orientation of experimental steel is obviously distributed along the strip in the rolling direction. Internal mechanical properties of the material tend to be consistent, and the grain orientation perpendicular to the rolling direction is relatively dispersed. And the grain size is uneven, so that the austenite forms an unequal mechanical stability gradient, and the material has a discontinuous TRIP effect during deformation. The mechanical properties of the formed parts after stamping in the parallel rolling direction are higher than those after stamping in the vertical rolling direction. Mechanical properties of sample stamping in vertical rolling direction at 730 °C are attributed to the cumulative contribution of TRIP effect and TWIP effect.