Experimental observation of microstructure evolution under strain-path changes in low-carbon IF steel

The microstructure of a Ti-killed interstitial free (IF) steel has been examined through TEM observations after simple-shear/simple-shear strain-path changes, in connection with the crystallographic orientation of the examined grains. A partial disappearance of prestrain microstructures is shown to cause the stagnation of work hardening at earlier stages of reversed loading during Bauschinger simple shear sequences. Under progressing reversed deformation, a fragmentation of the grains of unstable orientations still slows down the work-hardening rate. A strong localization of plastic flow within microbands following an orthogonal strain-path change is shown to occur within the grains containing well-developed prestrain dislocation boundaries and belonging to certain orientation groups.