Micro-structural Evolution in Metals Subjected to Simple Shear by a Particular Severe Plastic Deformation Method

Simple shear (SS) has been considered an optimal deformation method of severe plastic deformation (SPD). To achieve SS, a particular SPD method known as mutative channel torsion extrusion (MCTE) was designed based on the geometric equivalence of SS, and the cavity parameters of a die were calculated according to strain equivalence. To investigate the characteristics of micro-structural evolution subjected to MCTE, simulated and experimental investigations were conducted. The simulated results indicate that equivalent strain distribution on the cross section is relatively uniform, and the metallographic observations confirm the simulated phenomenon. Transmission electron microscopy investigations show that the process of grain refinement undergoes the formation of shear bands, dislocation cells, dislocation forests, large-angle grain boundaries, and recrystallization nuclei. Two types of mechanisms are proposed in view of the different effects of SS on grain refinement. Eventually, MCTE is ensured as an effective method for grain refinement.