Bimodal grain size and mechanical properties enhancement in low carbon steel by ultra-rapid annealing

Different heating rates of 200-1200 deg;C/s were utilized during ultra-rapid annealing (URA) up to the temperatures of 730 and 760 degrees C on the severely deformed low carbon steel. Higher hardness, strength and ductility achieved for the sample heated at 730 degrees C with 600 degrees C/s due to formation of bimodal grain size (BGS) microstructure than them for nonBGS samples. The BGS enhancement for the hardness, strength and ductility with respect to those of as received sample was 67%, 80% and 7%, respectively, and, with respect to those of severely deformed one was 16%, 44% and 24%, respectively. URA with the heating rate of 200 degrees C/s and 1000 degrees C/s leads to fully recrystallized and non-recrystallized microstructures, respectively. Also, BGS microstructure in heating rate of 1200 degrees C/s can be formed if the peak temperature of URA is increased proportionally to the increased heating rate. (c) 2022 The Author(s). Published by Elsevier B.V.

Automated summary

Different heating rates were used during ultra-rapid annealing of severely deformed low carbon steel, resulting in improved hardness, strength, and ductility. The formation of a bimodal grain size (BGS) microstructure at a heating rate of 600 degrees C/s and a temperature of 730 degrees C led to the best performance.