The influence of aluminum on hot deformation behavior and tensile properties of high-Mn TWIP steels

The influence of aluminum (0–3 wt.%) on the high-temperature flow stress and recrystallization kinetics of two austenitic 25 wt.% Mn-bearing TWIP steels were investigated and compared with the behavior of a low-carbon steel. In addition, tensile properties were determined over the temperature range from −80 to 200 °C. It was observed that the hot deformation resistance is slightly higher for the 25Mn3Al than for the 25Mn steel, but in both steels significantly higher than for the low-carbon steel. The static recrystallization kinetics is significantly retarded in both steels compared to the rate in the low-carbon steel. The activation energies of hot deformation and static recrystallization are higher than those for the low-carbon steel. In contrast to the high temperature behavior, below RT, the 25Mn steel possessed a higher tensile strength and a higher work hardening rate than the 25Mn3Al steel due to strain-induced martensite formation. With increasing temperature up to 200 °C, the deformation mode changed gradually to mechanical twinning. In the 25Mn3Al steel, the elongation increased with decreasing temperature as a result of enhanced mechanical twinning.