Processing ultrafine grained non-circular cross-section profiles via severe plastic deformation

In this study, a new technique is presented for processing ultrafine-grained noncircular thin section profiles via severe plastic deformation. For the first time, a noncircular thin section profiles can be severe plastic deformation processed by this method entitled the noncircular thin section cyclic extrusion–compression (NCTS-CEC). In this technique, the whole length of the profile is passed through a neck zone while it is fully enclosed by the tools set. Therefore, the whole length of the specimen experiences a cyclic extrusion and compression, which accumulates a high level of strain in the material. The feasibility of the NCTS-CEC was successfully examined on aluminum profiles with L, U, and hollow square cross-sections. The microstructure evolution of the processed specimens was investigated by metallographic observations and X-ray diffraction analysis, which demonstrate the formation of a ultrafine-grained microstructure after processing by two cycles of the NCTS-CEC. Moreover, evaluations of the mechanical properties of the processed profiles show remarkable improvements in the yield and ultimate strengths. The microhardness of the processed specimens was also increased after the second cycle to ∼55 Hv from the initial value of 30 Hv. The deformation behavior of the material during processing by the NCTS-CEC method was also numerically simulated by the commercial finite element software DEFORM TM-3D V11.