Constrained groove pressing of low carbon steel: Nano-structure and mechanical properties

In this study a severe plastic deformation method called constrained groove pressing (CGP) is used for imposing a high magnitude of strain into the low carbon steel sheets. Microstructural changes during process are examined by X-ray diffraction and optical observations. The grain size evolution during severe plastic deformation is studied using Williamson-Hall analysis on XRD pattern of the deformed samples. In effective strain of 4.64, ferrite grains with a submicron size of 200-300 nm are achieved. The results show that constrained groove pressing can effectively refine the coarse-grained structure to an ultra fine grain range. Mechanical properties changes due to microstructure evolution are measured by tensile and hardness tests. The results show that the constrained groove pressing process leads to decrease of work hardening rate and increase of strain rate sensitivity of the sheets material. Finally, in cumulative strain of 4.64, a deformed sheet with grain size of 230 nm and ultimate tensile strength of 400 MPa is obtained. (C) 2010 Elsevier B.V. All rights reserved.