Interrupted Quasi-static and Dynamic Tensile Experiments of Fully Annealed 301 Stainless Steel

This research examined the evolving microstructure of quasi-static and dynamically loaded fully annealed metastable 301 austenitic stainless steel (SS). Experiments were performed to an interrupted strain value of 20% and to failure using a tension Kolsky bar (1000/s) and an electromechanical load frame (0.001/s). Electron Backscatter Diffraction (EBSD) identified the microstructural evolution from the as-received condition to the 20% strain level for the high and low rate interrupted samples. This material achieved over 60% elongation to failure with increasing strength as strain rate increased, as expected. Fractography analysis using SEM showed particles in the microstructure and a ductile failure mode. The 301 SS exhibited a greater amount of phase transformation from parent austenite to α’-martensite at the dynamic strain rate when compared to the quasi-static strain rate during the interrupted experiments. This result is indicative of the increased propensity for austenite to α’-martensite phase transformations at the high strain rate.