High-rate Characterization of 304L Stainless Steel at Elevated Temperatures for Recrystallization Investigation

An integrated experimental technique was developed for high-rate mechanical characterization of 304L stainless steel at elevated temperatures by using a modified split Hopkinson pressure bar (SHPB). A sandwich structure consisting of two platens and the specimen in between was heated before mechanical loading while the bars were maintained at room temperature to eliminate the temperature gradient effect on the wave propagation in the bars. Upon contacting the cold bars, temperature gradients form in the platens, leaving the temperature in specimen constant and uniform. Pulse shaping techniques were employed to maintain constant strain-rate deformation and dynamic stress equilibrium in the specimen. Dynamic compressive stress-strain curves at elevated temperatures for the 304L stainless steel were obtained. To relate recrystallization to impact loading, a momentum trapping system was employed to apply a single loading on the specimen during one dynamic experiment. We also controlled the quenching time to study its effect on recrystallization.