Effect of strain rate in severe plastic deformation on microstructure refinement and stored energies

The interplay of large strain and large strain rate during high-rate severe plastic deformation (HR-SPD) lead to dynamic temperature rise in situ that engenders a recovered microstructure whose characteristics are not just a function of the strain, but also of the strain rate and the coupled temperature rise during the deformation. In this work, we identify three classes of microstructures characterized by multistage recovery phenomena that take place during the high strain rate SPD of Cu. It is found that the first stage of this recovery is similar to the first stage of static recovery, which is characterized mainly by annihilation of dislocations. The second stage starts around 360 K and was characterized by dislocations getting arranged in tight cell boundaries and eventually into subgrain. Recovery stages were found to be followed by a stage of grain growth and recrystallization when the temperature in the deformation zone approaches 480 K.