Mechanical behavior of a microsized pillar fabricated from ultrafine-grained ferrite evaluated by a microcompression test

This paper studied the local mechanical properties of ferrite processed by high-pressure torsion (HPT). The evaluation was conducted by a microcompression test using a non-tapered microsized pillar as the specimen. Electron backscattering diffraction analysis was conducted to investigate the structural changes with different amounts of HPT strain. While the crystal orientation and grain size did not change with increasing strain in the HPT process beyond the structural saturation point, the grain boundary misorientation angle distribution tended towards a random distribution, which indicates dynamic recrystallization. The microcompression test revealed site-specific mechanical properties of ultrafine-grained ferrite. The strength was increased with decreasing grain size and reached 1.5 GPa, accompanied by a decrease in elongation. Further increasing the amount of HPT strain did not change the strength, but the elongation increased slightly. These improvements in the mechanical properties are discussed based on the nature of the grain boundary.