Work Hardening and Microstructural Development during High-Pressure Torsion in Pure Iron

Abstract

The work hardening behavior and the developments of microstructure and crystallographic texture during high-pressure torsion (HPT) in pure iron were investigated. A set of the 3D electron backscatter diffraction (EBSD) measurements were also performed to characterize the microstructure in 3D using an orthogonally arranged focused ion beam-scanning electron microscope (FIB-SEM) instrument. It was found that the image quality (IQ) values of the EBSD data obtained by the FIB-SEM are better compared to the conventional mechanical polishing procedure. A detailed analysis on the distribution of misorientation angle was performed, being fitted with the Mackenzie plot. The use of the Hencky equivalent strain made it possible to compare the work hardening behaviors and the microstructural evolutions observed in the current investigation with those reported for accumulative roll bonding (ARB). This comparison has revealed that the Hall–Petch coefficient k obtained by HPT deformation drastically increases with the grain refinement by HPT deformation.