Realization of the innovative potential of radial-shear rolling for forming the structure and mechanical properties of AISI-321 austenitic stainless steel

In this paper the grain structure and mechanical properties of AISI-321 austenitic stainless steel subjected to 7 passes of radial-shear rolling at 1000 °С were investigated. The tensile strength (1076 MPa) and Vickers microhardness (322 HV) after 7 passes increased by 2.2 times and 2 times, respectively, relative to the initial annealed state (480 MPa, 160 HV). Ultra-fine grained structure (200-700 nm) formed in the bar section area from its surface to a depth of 0.25 of the radius. The transition zone is located in the area between 0.5 R and 0.25 R of the bar section. Anything deeper is a rolling texture. The 7-pass radial-shear rolling process is an effective way to form UFG structure and improved mechanical properties in AISI-321 austenitic stainless steel.Keywords: severe plastic deformation, ultra-fine grained structure, radial-shear rolling, microstructure, mechanical properties.

Development and Computer Simulation of the New Combined Process for Producing a Rebar Profile

The study presents results of computer simulation by finite elements method of a new metal forming process combining the deformation of a billet with round cross-section on a radial-shear rolling mill and subsequent billet twisting in a forming die with a specific design. To analyze the efficiency of metal processing, the main parameters of the stress–strain state are considered: effective strain, effective stress, average hydrostatic pressure, and Lode–Nadai coefficient. The maximum value of effective strain up to 13.5 is achieved when a screw profile on the billet in the die is forming, which indicates an intensive refinement of the initial structure of the billet. During combined process, the nature of the deformation changes in the transverse direction from the axis of rotation to the surface. The central area of the billet is under the action of tensile stresses. In the peripheral part, compressive stresses grow. In the surface area, Lode–Nadai coefficient is 0.1 approximately, which indicates the high level of shear strain