Effect of B on Growth of Recrystallized Grain of Ti-added Ultra-low Carbon Cold-rolled Steel Sheets

The effect of boron (B) on the recrystallization behavior, in particular the growth of the recrystallized grain into the unrecrystallized grain, of titanium (Ti) added interstitial atom free (IF) steel sheets was studied from the viewpoint of the solute-drag effect considering the interaction between B and Ti atoms. The growth rate of the recrystallized grain at 5% fraction recrystallized decreased with increasing the B content. Furthermore, the decrease became more pronounced in the B added steels with the higher Ti content. The interaction energy between B and Ti atoms at the grain boundary was evaluated by the first-principles calculation in the bcc-Fe(111)Sigma 3[1 (1) over bar0] symmetrical tilt grain boundary. The attractive interaction between B and Ti atoms was obtained in most of the grain boundary atom sites examined. B segregation at the interface between recrystallized and unrecrystallized grains was concluded to induce Ti segregation through the attractive interaction between B and Ti atoms during interface migration. The mechanism for the suppression in the growth of the recrystallized grains was proposed to be caused by the decrease in the interface mobility caused by the enhanced Ti segregation.