Microstructure and mechanical behavior of martensitic steel severely deformed by the novel technique of repetitive corrugation and straightening by rolling

The method of severe plastic deformation (SPD) is often used to produce bulk ultrafine grained (UFG) metallic materials. SPD is a procedure, whereby the initial coarse grained structure of the material usually changes to deformed and UFG state. In the present study, a new SPD process called repetitive corrugation and straightening by rolling (RCSR) is introduced. A strain calculation method is then reported for inducing high strains after repetitive cycles in order to fabricate UFG metallic materials. RCSR consists of corrugated and flattened rolls. Changeable position of the workpieces during different routes, is of substantial capabilities of this procedure. Fe-10Ni-7Mn martensitic steel sheets were subjected to RCSR process. Optical and scanning electron microscopy along with mechanical testing investigation was used to systematically study the microstructure and mechanical properties of the workpieces. Microstructural study depicts micro-voids formation with average size of 100-150 nm. The spherical morphology appeared mostly along the laths, resulted from the non-equilibrium grain boundaries. (C) 2012 Elsevier B.V. All rights reserved.