Microstructure and Mechanical Behavior of ARMCO Fe Severely Plastically Deformed by Combination of Constrained Groove Pressing and Cold Rolling

In the present work, the combined effect of constrained groove pressing (CGP) followed by cold rolling on the microstructural and mechanical behavior of ARMCO Fe is investigated. Annealed ARMCO Fe sheets are CGP processed up to 3 cycles and 4 cycles followed by cold rolling reduction up to 60%, 75% and 90%, thereby imposing strain up to similar to 7. Backscattered scanning electron microscope (BSE-SEM) studies complemented by transmission electron microscope analysis indicated significant grain refinement resulting in similar to 0.5-0.7 mu m sized structure after CGP processing. Microstructural evolution studied employing electron backscattered diffraction, divulged continuous dynamic recrystallization-driven grain refinement manifested by low-angle grain boundaries bounded cell structures and highly misoriented high-angle boundary bounded grains after CGP processing. Combining cold rolling followed by CGP revealed further grain refinement up to similar to 0.3 mu m characterized by elongated grain structure. Tensile behavior indicates substantial improvement in yield strength by nearly similar to 3 times after CGP processing corroborating to the observed grain refinement with a concomitant decrease in ductility. Combined with cold rolling, the yield strength further improved with increasing cold rolling reduction and maximized to similar to 483 MPa from an initial strength of 90 MPa in the annealed condition.