[en] A Transmission Electron Microscope (TEM) was used to establish that the substructure of press formed (PF) 21-6-9 stainless steel toroids was characterized by a dislocation cell size finer, about 0.16 μm, than that of about 0.29 μm, of high-energy-rate-formed (HERF) processed toroids. In addition, HERF processed material showed areas of a coarser, well-developed subgrain structure characteristic of hot work deformation. The formation of the substructures, as-well-as the grain size and carbide distributions of the toroids produced by the two processing techniques, are discussed in terms of the various operations, temperatures, and strain rates associated with the two different processing schedules. The Press-Formed toroid had a higher yield strength than the HERF processed toroid which was attributed to the finer cell size of the PF processed toroid