ND//< 111 > Recrystallization in Interstitial Free Steel: The Defining Role of Growth Inhibition

Hot band, fully recrystallized, interstitial free (IF) steel samples were cold rolled to 10-80% thickness reductions. After characterizing the developments in deformed microstructures, 50-80% deformed samples were fully recrystallized at 650 degrees C. Though different annealing times were used, use of a relatively lower annealing temperature and repeated trials ascertained absence of significant post-recrystallization grain coarsening. Recrystallization brought in a steady improvement in gamma-fibre (ND//) and drop in theta-fibre (ND//). The only exception was 80% prior deformed microstructure, where the trend was reversed: enforcing a drop in texture estimated normal anisotropy or (r) over bar value. The study brought out growth inhibition of recrystallized gamma-fibre grains, caused by non-gamma fibre bands and by orientation pinning of recrystallized gamma-gamma boundaries, as the mechanism behind the observed trend reversal

Orientation Dependent Recovery in Interstitial Free Steel

Cold rolled (40, 60 and 80% thickness reductions from hot-band) interstitial free (IF) steel samples were recovered at 500 degrees C for different times (15 min to 32 h). The recovery kinetics, studied through a combination of X-ray line profile analysis and high resolution electron diffraction, were best represented by logarithmic relationship. Though the kinetics was dependent on the prior deformation, gamma(ND//) fibre clearly had stronger recovery than theta(ND/) fibre. Recovery was observed, statistically to create grain interior strain localizations: an orientation independent phenomenon. Increase in misorientation across such strain localizations was, however, orientation dependent. This was responsible for enhanced in-grain misorientation in recovered gamma-fibre grains/bands. Extended recovery of 80% pre-deformed samples also led to coarsening of gamma-fibre bands: strain induced boundary migration (SIBM) or uniform movement of gamma-fibre boundaries into neighbouring non gamma-fibre orientations

Magnetic Properties in Deformed Grain Oriented Electrical Steel: On the Role of Strain Hardening Exponent and Microstructural Developments

High permeability commercial CRGO, cold rolled grain oriented steel was subjected to uni-axial tensile strain in three principal orientations: (110) , (110) and (110). The samples exhibited remarkably different stress-strain behavior. The numerical values of the strain hardening exponent, n, largely determined the degradation in magnetic properties: namely increase in Hysteresis loss (H) and drop in Permeability (mu). Changes in magnetic properties were also correlated with microstructural observations: misorientation and dislocation density developments, relative recovery, residual strain and deviation from ideal . The study established constitutive relationships between degradation in magnetic properties and various parameters of the deformed microstructures