Large and Severe Plastic Deformation of Metals: Similarities and Differences in Flow Mechanics and Structure Formation

Large and severe plastic deformations (SPD) are two widely known approaches for the processing of metallic billets that have a different effect on the microstructure and physico−mechanical properties of materials. After a large deformation is implemented, for example, by longitudinal rolling or drawing, dislocation substructure cells and microbands are formed in billets. As a result of SPD, in particular, after equal‐channel angular pressing (ECAP), ultrafine nanoscale grains are formed in metals,^[1,2] which provides their high mechanical and functional properties. Herein, in both cases, structure formation is largely conditioned by the patterns in the mechanics of plastic deformation. The difference in the produced microstructures is determined by different scalar and vector characteristics of large and severe strains. In the former case, monotonic strain accumulation takes place in a billet. In the latter case, due to the active nonmonotonic deformation of a billet, heavy strain is accumulated, and rotational modes are realized, which, as a result, produces shear bands with further formation of ultrafine grains with high‐angle grain boundaries. As a conclusion, a more precise definition of SPD is introduced, and recommendations are given for increasing the efficiency of the process of UFG structure formation in metals.